US20050022358A1 - Housing with functional overmold - Google Patents

Abstract

An article having a first structure and a second structure. The first structure includes a structural portion and an overmold portion, which is formed from a resilient material and molded onto the structural portion. The overmold portion is configured to perform an auxiliary function, such as creating a seal portion that is configured to sealing engage the second structure, an isolator portion that is configured to contact the second structure and dampen vibrations that are transmitted thereto and/or an auxiliary gripping surface.

Description

PRIORITY & CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation application of U.S. application Ser. No. 09/963,905 field Sep. 26, 2001 entitled “Housing With Functional Overmold”, which claims the benefit of U.S. Provisional Application No. 60/263,379, filed Jan. 23, 2001. Other features of the present invention are discussed and claimed in commonly assigned: copending U.S. application Ser. No. 10/384,809 entitled “Multispeed Power Tool Transmission”; copending U.S. application Ser. No. 10/792,659 entitled “Multispeed Power Tool Transmission”; copending U.S. application Ser. No. 10/755,250 entitled “First Stage Clutch”; U.S. Pat. No. 6,676,557 entitled “First Stage Clutch”, U.S. Pat. No. 6,431,289 entitled “Multispeed Power Tool Transmission”; and U.S. Pat. No. 6,502,648 entitled 360 Degree Clutch Collar.
BACKGROUND OF THE INVENTION
• 1. Technical Field
• The present invention relates generally to housings for devises such as power tools, including rotatable drills, power screwdrivers and cutting tools. More particularly, the present invention relates to a housing having an overmold portion in which the overmold portion performs an auxiliary function.
• 2. Discussion
• Modern manufactures of power tools typically seek to provide powerful and robust tools that are both ergonomically configured and which offer exceptionally high value at a relatively inexpensive price. Often times, however, the goal of a robust, ergonomic configuration seems to be at odds with the offering of the tool at a relatively inexpensive price as additional processes, such as overmolding, or a multiplicity of parts that do not appear to add significant value, such as vibration isolators and seals, are required.
• The overmolding of the grip of a hand tool is known in the art for purposes of reducing the transmission of vibration to the user's hand. In these situations, the outer surface of the grip of the tool is overmolded with a resilient material; the overmolded portion tends to damp the vibrations that are transmitted between the housing of the tool and the user's hand. The overmolded portion does not effect the operation of the tool per se, and as such, the use of overmolding tends to be limited to a relatively small area on the exterior of the tool so as to minimize the cost of the tool. More specifically, the overmolding operation is typically employed in a non-functional manner which adds cost to the article of manufacture without adding a commensurate amount of value.
• While parts, such as isolators and even seals, may be necessary for the proper operation of the power tool, their discrete nature nonetheless increases the cost of the power tool, both in terms of materials and in assembly labor. Furthermore, the proliferation of component parts is known to have a- detrimental on defect rates and warranty costs.- Accordingly, there remains a need in the art for a functional overmold which adds value to the article of manufacture in an amount commensurate with its cost.
SUMMARY OF THE INVENTION
• In one form, the present teachings provide an article having a first structure and a second structure. The first structure includes a structural portion and an overmold portion, which is formed from a resilient material and molded onto the structural portion. The overmold portion is configured to perform an auxiliary function, such as creating a seal portion that is configured to sealing engage the second structure, an isolator portion that is configured to contact the second structure and dampen vibrations that are transmitted thereto and/or an auxiliary gripping surface.
BRIEF DESCRIPTION OF THE DRAWINGS
• Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein:
• FIG. 1 is a side view of a power tool constructed in accordance with the teaching of the present invention;
• FIG. 2 is an exploded perspective view of a portion of the power tool ofFIG. 1;
• FIG. 3 is a perspective view of a portion of the housing of the power tool ofFIG. 1 illustrating the rear of the end cap assembly;
• FIG. 4 is a front view of the end cap assembly;
• FIG. 5 is a section view taken along the line5-5 ofFIG. 4;
• FIG. 6 is a rear view of a portion of the power tool ofFIG. 1 with the end cap assembly removed;
• FIG. 7 is a side view of a portion of the power tool ofFIG. 1 with the end cap assembly removed;
• FIG. 8 is a view similar to that ofFIG. 4, but illustrating the end cap shell prior to the overmolding operation;
• FIG. 9 is a view similar to that ofFIG. 5, but illustrating the end cap shell prior to the overmolding operation;
• FIG. 10 is a view similar to that ofFIG. 4, but illustrating an alternate construction of the overmold member;
• FIG. 11 is a partial sectional view of a portion of a power tool that employs an end cap assembly having an overmold member constructed in the manner illustrated inFIG. 10;
• FIG. 12 is an exploded perspective view of a portion of the power tool ofFIG. 1, illustrating the transmission assembly in greater detail;
• FIG. 13 is an exploded perspective view of a portion of the power tool ofFIG. 1, illustrating the reduction gearset assembly, the transmission sleeve, a portion of the housing and a portion of the clutch mechanism in greater detail;
• FIG. 13ais a sectional view taken along a longitudinal axis of the second ring gear;
• FIG. 13bis a sectional view taken along a longitudinal axis of the third ring gear;
• FIG. 14 is a side view of the transmission sleeve;
• FIG. 15 is a rear view of the transmission sleeve;
• FIG. 16 is a sectional view taken along the line16-16 ofFIG. 15;
• FIG. 17 is a sectional view taken along the line17-17 ofFIG. 15;
• FIG. 18 is an exploded view of the reduction gearset assembly;
• FIG. 19 is a sectional view taken along a longitudinal axis of the power tool ofFIG. 1 illustrating a portion of the reduction gearset assembly in greater detail;
• FIG. 20 is a front view of a portion of the first reduction carrier;
• FIG. 21 is a sectional view taken along a longitudinal axis of the power tool ofFIG. 1 illustrating a portion of the reduction gearset assembly in greater detail;
• FIG. 22 is a rear view of a portion of the third reduction carrier;
• FIG. 23 is an sectional view taken along the longitudinal axis of the power tool ofFIG. 1 and illustrating the transmission assembly as positioned in the first speed ratio;
• FIG. 24 is a sectional view similar to that ofFIG. 23 but illustrating the transmission assembly as positioned in the second speed ratio;
• FIG. 25 is a sectional view similar to that ofFIG. 23 but illustrating the transmission assembly as positioned in the third speed ratio;
• FIG. 26 is a top view of a portion of the power tool ofFIG. 1 illustrating the speed selector mechanism in greater detail;
• FIG. 27ais a side view of the rotary selector cam;
• FIG. 27bis a top view of the rotary selector cam;
• FIG. 27cis a sectional view taken through along the central axis of the speed selector mechanism;
• FIG. 28 is a rear view of the output spindle assembly;
• FIG. 29 is an exploded perspective view of the clutch mechanism;
• FIG. 29ais a perspective view of a portion of the clutch mechanism illustrating another configuration of the clutch member;
• FIG. 29bis an exploded perspective view illustrating a multi-piece construction for the first ring gear and clutch member;
• FIG. 30 is a schematic illustration of the adjustment structure in an “unwrapped” state;
• FIG. 31 is a schematic illustration similar to that ofFIG. 30 but showing an alternate construction of the adjustment profile; and
• FIG. 32 is a schematic illustration similar to that ofFIG. 30 but showing a portion of another alternate construction of the adjustment profile;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• Overview
• With reference toFIGS. 1 and 2 of the drawings, a power tool constructed in accordance with the teachings of the present invention is generally indicated byreference numeral10. As those skilled in the art will appreciate, the preferred embodiment of the present invention may be either a cord or cordless (battery operated) device, such as a portable screwdriver or drill. In the particular embodiment illustrated,power tool10 is a cordless drill having ahousing12, amotor assembly14, amulti-speed transmission assembly16, aclutch mechanism18, anoutput spindle assembly20, achuck22, atrigger assembly24 and abattery pack26. Those skilled in the art will understand that several of the components ofpower tool10, such as thechuck22, thetrigger assembly24 and thebattery pack26, are conventional in nature and need not be described in significant detail in this application. Reference may be made to a variety of publications for a more complete understanding of the operation of the conventional features ofpower tool10. One example of such publications is commonly assigned U.S. Pat. No. 5,897,454 issued Apr. 27, 1999, the disclosure of which is hereby incorporated by reference as if fully set forth herein.
• Housing12 includes anend cap assembly30 and ahandle shell assembly32 that includes a pair ofmating handle shells34. Handleshell assembly32 includes ahandle portion36 and a drive train orbody portion38.Trigger assembly24 andbattery pack26 are mechanically coupled to handleportion36 and electrically coupled tomotor assembly14.Body portion38 includes amotor cavity40 and a transmission cavity42.Motor assembly14 is housed inmotor cavity40 and includes arotatable output shaft44, which extends into transmission cavity42. Amotor pinion46 having a plurality of gear. teeth48 is coupled for rotation withoutput shaft44.Trigger assembly24 andbattery pack26 cooperate to selectively provide electric power tomotor assembly14 in a manner that is generally well known in the art so as to control the speed and direction with whichoutput shaft44 rotates.
• Transmission assembly16 is housed in transmission cavity42 and includes aspeed selector mechanism60.Motor pinion46couples transmission assembly16 tooutput shaft44, transmitting a relatively high speed, low torque drive input totransmission assembly16.Transmission assembly16 includes a plurality of reduction elements that are selectively engaged byspeed selector mechanism60 to provide a plurality of speed ratios. Each of the speed ratios multiplies the speed and torque of the drive input in a predetermined manner, permitting the output speed and torque of thetransmission assembly16 to be varied in a desired manner between a relatively low speed, high torque output and a relatively high speed, low torque output. The transmission output is delivered theoutput spindle assembly20, to which thechuck22 is coupled for rotation, to permit torque to be transmitted to a tool bit (not shown). Theclutch mechanism18 is coupled totransmission assembly16 and is operable for limiting the magnitude of the torque associated with the drive input to a predetermined, selectable torque limit. Functional Overmold
• With specific reference toFIGS. 2 through 9,end cap assembly30 is shown to include anend cap shell100 and anovermold member102. In the example provided, theend cap shell100 is injection molded from a plastic material, such as ABS. Theend cap shell100 defines anend cap cavity104 that is sized to receive the portion of themotor assembly14 that extends rearwardly of thehandle shell assembly32. A plurality of first and secondradial tab apertures108 and110 and theabutting face128 are formed into theforward face114 of theend cap shell100 and a plurality ofscrew bosses116 are formed into the perimeter of theend cap shell100. Each of the first and secondradial tab apertures108 and110 is sized to receive one of the firstradial tabs120 and secondradial tabs122, respectively, that are formed into therearward face124 of thehandle shells34. The first and secondradial tab apertures108 and110 cooperate with the first and secondradial tabs122 to properly align theend cap shell100 to thehandle shell assembly32, as well as to inhibit relative rotation therebetween. Anarcuate portion128 of theforward face114 of theend cap shell100 is angled to match the abuttingface132 of therearward face124 of thehandle shells34. Thescrew bosses116 permit theend cap shell100 to be fixedly coupled to themotor cover136 via a plurality ofscrews138. The geometry of themotor cover136 is such that it is constrained to thehandle shells34. As such, fastening of theend cap shell100 to themotor cover136 operates to fixedly retain theend cap shell100 against therearward face124 of thehandle shell assembly32, as well as to close off therear handle aperture139 in thehandle shell assembly32.
• A plurality ofside apertures140 are formed into the sides of theend cap shell100 to permit air to flow through thehandle shell assembly32 and cool themotor assembly14 in a manner that is well known in the art. A plurality ofrear apertures144 are formed into the rear of theend cap shell100, with each of therear apertures144 including a recessedportion146 that extends only partially into theouter surface148 of theend cap shell100 and a through-portion150 that extends completely through theend cap shell100. A pair of retainingtabs152 are formed to extend from theinterior surface154 of theend cap shell100 inwardly into theend cap cavity104. Achannel156 is formed into theinterior surface154 of theend cap shell100 and intersects each of therear apertures144 and the retainingtabs152.
• Theovermold member102 is formed from a resilient material, such as thermoplastic elastomer (e.g., HYTREL® manufactured by E. I. du Pont de Nemours and Company) and is simultaneously formed and coupled to theend cap shell100 in an injection molding operation. In the particular example provided, theovermold member102 includes a plurality ofbumper members170, a pair ofisolators172 and a linkingmember174. Each of thebumper members170 extends from a point roughly coincident with theinterior surface154 of theend cap shell100 to a point rearwardly of theouter surface148 of theend cap shell100 by about 0.5 mm to about 1.5 mm and preferably about 0.75 mm. Construction in this manner permits thebumper members170 to provide a degree of shock absorption which reduces the likelihood of damaging theend cap shell100 in the event that thetool10 is dropped. Furthermore, it is sometimes necessary for an operator to apply a relatively high force to thetool10, as when employing a hole saw to drill large diameter holes. In such situations, the operator is inclined to press onto the rear of thetool10 to apply a force that is in-line with the axis of thechuck22. In such situations, thebumper members170 provide the operator with a relatively soft and comfortable surface which tends to resist slipping as well as attenuate the vibrations that are transmitted to the operator.
• Theisolators172 are formed about the retainingtabs152 on theinterior surface154 of theend cap shell100. In the example provided, each of theisolators172 includes anannular member180 that extends forwardly of theinterior surface154 of theend cap shell100. Construction in this manner permits theend cap shell100 to engage theisolators172 to theouter diameter14aand therear surface14bof themotor housing14cto fixedly retain themotor14dwithin themotor cover136. This prevents the components of themotor assembly14 from moving along the longitudinal axis of thetool10, as well as dampens vibrations that are created during the operation of themotor assembly14. The linkingmember174 is fixedly coupled to each of thebumper members170 and theisolators172. The linkingmember174 provides a flow path through which the resilient material flows during the formation of thebumper members170 and theisolators172. The linkingmember174 also interconnects thebumper members170 and theisolators172, thereby rendering their removal from theend cap shell100 more difficult.
• Those skilled in the art will appreciate that this aspect of the present invention may be incorporated into various other positions within thehandle assembly32 for sealing between two or more components, dampening vibrations or positioning one component relative to another. One such example is illustrated inFIGS. 10 and 11 where theisolators172 are modified to extend around the perimeter of a portion of theend cap cavity104 and sealingly contact therear surface14bof themotor14d. Theisolators172 seal the interface between theend cap shell100 and themotor assembly14, while thebumper members170 seal therear apertures144 in theend cap shell100. Thespace188 defined by theisolators172 is then filled with grease or another suitable lubricant, which lubricates amotor armature bearing190.
• Transmission Assembly
• With reference toFIG. 12, thetransmission assembly16 is shown to be a three-stage, three-speed transmission that includes atransmission sleeve200, areduction gearset assembly202 and thespeed selector mechanism60. With additional reference toFIGS. 13 through 17, thetransmission sleeve200 includes awall member210 that defines a generally transmission bore orhollow cavity212 into which thereduction gearset assembly202 is disposed. Thetransmission sleeve200 includes abody214 and abase216. Thebody214 of thetransmission sleeve200 is fairly uniform in diameter and generally smaller in diameter than thebase216. The inside diameter of thebase216 is sized to receive thecylindrical nose portion220 of themotor cover136.
• A plurality of raisedlands226 are formed into thebase216. The raised lands226 define a plurality offirst grooves228 in theouter surface230 of thebase216 and a plurality ofsecond grooves232 in theinner surface234 of thebase216. Thefirst grooves228 are configured to receive thealignment ribs238 that are formed into theinner surface242 of thehandle shells34 to align thetransmission sleeve200 to thehandle shells34 and inhibit relative rotation between thetransmission sleeve200 and thehousing12. Preferably, thefirst grooves228 andalignment ribs238 are configured in a manner that thetransmission sleeve200 can only be assembled to thehandle shells34 in one orientation (i.e., the configuration of thefirst grooves228 andalignment ribs238 prevents thetransmission sleeve200 from being rotated 180° out of position relative to the handle shells34). Thesecond grooves232 will be discussed in greater detail, below.
• Thebody214 of thetransmission sleeve200 is shown to include acylindrical body portion246 and apin housing portion248. In the particular embodiment illustrated, thecylindrical body portion246 includes aselector cam guide250, a plurality oflubricant grooves252 and first and second sets ofring engagement teeth254 and256, respectively. Theselector cam guide250 is generally rectangular in cross section, extending outwardly from the top of theouter surface258 of thebody portion246. Thelubricant grooves252 are formed concentrically around the upper half of the perimeter of thebody portion246. Thelubricant grooves252 have a depth of about 0.01 inch to about 0.030 inch to hold a lubricant, such as grease, on the upper half of the perimeter of thebody portion246. The operation of theselector cam guide250 and thelubricant grooves252 will be discussed in detail, below.
• A raisedbead264 segregates the interior of thebody portion246 into first andsecond housing portions260 and262, respectively. The first set ofring engagement teeth254 are formed onto theinner surface266 of thebody portion246 and extend rearwardly from the raisedbead264 toward thebase216. The second set ofring engagement teeth256 are also formed into the inner surface of thebody portion246 but extend forwardly from the raisedbead264. The teeth268 of the first and second sets ofring engagement teeth254 and256 are uniformly spaced around theinner surface266 of thebody portion246. The configuration of each tooth268 in the first and second sets ofring engagement teeth254 and256 is similar in that each tooth extends from the raisedbead264, has a pair of parallel engagement surfaces270 and terminates at atip portion272. Thetip portion272 of each tooth268 is both rounded and tapered to enhance the ability with which it will mesh with a portion of thereduction gearset assembly202 as will be described in detail, below.
• Thepin housing portion248 extends downwardly from thebody portion246 over a significant portion of the length of thebody portion246. Anactuator aperture274 is formed into thepin housing portion248 and extends rearwardly through thebase216 of thetransmission sleeve200. In the particular embodiment illustrated, theactuator aperture274 is stepped, having afirst portion276 with a first diameter at the rear of thetransmission sleeve200 and asecond portion278 with a smaller second diameter at the front of thetransmission sleeve200. In the example shown, thefirst portion276 of theactuator aperture274 breaks through the wall of thefirst housing portion260 and forms agroove280 into theinner surface234 of thebase216. Thepin housing portion248 will be discussed in further detail, below.
• A pair offirst clip slots284 and a pair ofsecond clip slots286 are formed into thetransmission sleeve200, extending along the sides of thetransmission sleeve200 in a manner that is parallel the longitudinal axis of thetransmission sleeve200. The first pair ofclip slots284 is formed through the sides of thebody portion246 rearwardly of the raisedbead264 and extends rearwardly toward thebase216. The depth of the first pair ofclip slots284 is such that they do not extend through the portion of thewall member210 that defines thebase216. The second pair ofclip slots286 are also formed through the sides of thebody portion246 beginning forwardly of the raisedbead264 and extending through thefront face288 of thetransmission sleeve200.
• With reference toFIGS. 12, 13,18 and23, thereduction gearset assembly202 includes a first reduction gear set302, a second reduction gear set304 and a third reduction gear set306. The second and third reduction gear sets304 and306 are operable in an active mode and an inactive mode. Operation in the active mode causes the reduction gear set to perform a speed reduction and torque multiplication operation, while operation of the reduction gear set in an inactive mode for causes the reduction gear set to provide an output having a speed and torque that is about equal to the speed and torque of the rotary input provided to that reduction gear set. In the particular embodiment illustrated, each of the first, second and third reduction gear sets302,304 and306 are planetary gear sets. Those skilled in the art will understand, however, that various other types of reduction gear sets that are well known in the art may be substituted for one or more of the reduction gear sets forming thereduction gearset assembly202.
• As shown, the first reduction gear set302 includes a first reduction element orring gear310, a first set of planet gears312 and afirst reduction carrier314. Thefirst ring gear310 is an annular structure, having a plurality ofgear teeth310aformed along its interior diameter. Aclutch face316 is formed into the outer perimeter of thefront face318 of thefirst ring gear310 and will be discussed in greater detail, below. Thefirst ring gear310 is disposed within the portion of thehollow cavity212 defined by thebase216; thefront face318 of thefirst ring gear310 contacts astep320 formed into thetransmission sleeve200, thereby limiting the ability of thefirst ring gear310 to move forwardly into thehollow cavity212.
• Thefirst reduction carrier314 is formed in the shape of a flat cylinder, having plurality ofpins322 that extend from itsrearward face324. A plurality ofgear teeth314aare formed into almost the entire outer perimeter of thefirst reduction carrier314, with avalley314bbeing formed between each pair ofadjacent gear teeth314a. Due to the spacing of thegear teeth314a, one of the valleys (i.e.,valley314b′) is relatively larger than the remainingvalleys314bdue to the omission of atooth314ain the outer perimeter of thefirst reduction carrier314. In the particular embodiment illustrated, thegear teeth314aof thefirst reduction carrier314 are configured so as not to be meshingly engagable with thegear teeth310aof thefirst ring gear310.
• With specific reference toFIGS. 19 and 20, the profile of thegear teeth314ais illustrated in greater detail. As shown, eachgear tooth314aterminates at agradual radius326 at theforward face328 of thefirst reduction carrier314 but terminates abruptly at therearward face324 of thefirst reduction carrier314. Aradius330 is also formed on thevalleys314bbetween thegear teeth314a.
• Returning to FIGS.12,13,15,18 and23, afirst thrust washer332 having a firstannular portion334, a secondannular portion336 and a plurality of retainingtabs338 is positioned rearwardly of the first reduction gear set302. The retainingtabs338 engage thesecond grooves232 in thebase216 of thetransmission sleeve200 and as such, relative rotation between thefirst thrust washer332 and thetransmission sleeve200 is inhibited. The inside diameter of thebase216 is sized to receive themotor cover136 and as such, the front face340 of themotor cover136 inhibits the axial movement of thefirst thrust washer332. The firstannular portion334 contacts therear face342 of thefirst ring gear310, providing a wear surface and controlling the amount by which thefirst ring gear310 is able to move in an axial direction. The secondannular portion336 is spaced axially apart from the firstannular portion334, extending forwardly of the firstannular portion334 to provide a wear surface for the first set of planet gears312 that also controls the amount by which they can move in an axial direction.
• The first set of planet gears312 includes a plurality of planet gears344, each of which being generally cylindrical in shape, having a plurality ofgear teeth344aformed into its outer perimeter and apin aperture346 formed its their center. Eachplanet gear344 is rotatably supported on an associated one of thepins322 and thefirst reduction carrier314 and is positioned such that itsteeth344ameshingly engage theteeth314aof thefirst ring gear310. A raisedportion348 is formed into the front and rear face350 and352 of eachplanet gear344 that inhibits theteeth344afrom rubbing on thefirst reduction carrier314 and thefirst thrust washer332 and creating dust or chips that would impair the performance of thetransmission assembly16 and reduce its operating life. As theteeth46aof themotor pinion46 on theoutput shaft44 are also meshingly engaged with theteeth344aof the planet gears344, themotor pinion46 serves as a sun gear for the first reduction gear set302.
• The second reduction gear set304 is disposed within the portion of thehollow cavity212 defined by thefirst housing portion260 and includes asecond sun gear358, a second reduction element orring gear360, a second set of planet gears362 and asecond reduction carrier364. Thesecond sun gear358 is fixed for rotation with thefirst reduction carrier314. Thesecond sun gear358 includes a plurality ofgear teeth358athat extend forwardly of theforward face328 of thefirst reduction carrier314.
• Thesecond ring gear360 is an annular structure, having a plurality ofgear teeth360aformed along its interior diameter. Thegear teeth360amay be heavily chamfered at therear face366 of thesecond ring gear360 but terminate abruptly at thefront face368. More preferably, aheavy radius369 is formed onto therear face366 and the sides of each of thegear teeth360a, with theheavy radius369 being employed rather than the heavy chamfer as theheavy radius369 on thegear teeth360aprovides for better engagement between thesecond ring gear360 and thefirst reduction carrier314.
• A plurality ofsleeve engagement teeth370 are formed into the outer perimeter of thesecond ring gear360; thesleeve engagement teeth370 extend forwardly toward thefront face368 of thesecond ring gear360 and terminate at atip portion372 that is rounded and tapers forwardly and inwardly. Anannular clip groove374 is also formed into the outer perimeter of thesecond ring gear360. In the example illustrated, theclip groove374 is a rectangular slot having a pair ofsidewalls376. Theclip groove374 will be discussed in greater detail, below.
• Thesecond reduction carrier364 is formed in the shape of a flat cylinder, having plurality ofpins378 that extend from itsrearward face380. The second set of planet gears362 is shown to include a plurality of planet gears382. Eachplanet gear382 is generally cylindrical in shape, having a plurality ofgear teeth382aformed into its outer perimeter and apin aperture384 formed its center. Eachplanet gear382 is rotatably supported on an associated one of thepins378 and thesecond reduction carrier364 is positioned such that thegear teeth382aof the planet gears382 meshingly engage thegear teeth360aof thesecond ring gear360. Thegear teeth358aof thesecond sun gear358 are also meshingly engaged with thegear teeth382aof the planet gears382.
• The third reduction gear set306 is disposed within the portion of thehollow cavity212 defined by thesecond housing portion262 and includes athird sun gear398, a third reduction element orring gear400, a third set of planet gears402 and athird reduction carrier404. Thethird sun gear398 is fixed for rotation with thesecond reduction carrier364. Thethird sun gear398 includes a plurality ofgear teeth398athat extend forwardly of the front face406 of thesecond reduction carrier364.
• Thethird ring gear400 is an annular structure, having a plurality ofgear teeth400aformed along its interior diameter. Thegear teeth400amay be heavily chamfered at thefront face412 of thethird ring gear400, but terminate abruptly at therear face414. More preferably, aheavy radius407 is formed onto thefront face412 and the sides of each of thegear teeth400a, with theheavy radius407 being employed rather than the heavy chamfer as theheavy radius407 on thegear teeth400aprovides for better engagement between thethird ring gear400 and thethird reduction carrier404. A plurality ofsleeve engagement teeth418 are formed into the outer perimeter of thethird ring gear400; thesleeve engagement teeth418 extend rearward toward therear face414 of thethird ring gear400 and terminate at atip portion420 that is rounded and tapers rearwardly and inwardly. Anannular clip groove422 is also formed into the outer perimeter of thethird ring gear400. In the example illustrated, theclip groove422 is a rectangular slot having a pair ofsidewalls424. Theclip groove422 will be discussed in greater detail, below.
• Thethird reduction carrier404 is formed in the shape of a flat cylinder, having plurality ofpins428 that extend from itsrearward face430. A plurality ofgear teeth404aare formed into almost the entire outer perimeter of thethird reduction carrier404, with avalley404bbeing formed between each pair ofadjacent teeth404a. Due to the spacing of theteeth404a, one of thevalleys404b(i.e.,valley404b′) is relatively larger than the remainingvalleys404bdue to the omission of atooth404ain the outer perimeter of thethird reduction carrier404. In the particular embodiment illustrated, thegear teeth404aof thethird reduction carrier404 are configured so as not to be meshingly engagable with thegear teeth382aof the second planet gears382.
• With brief additional reference toFIGS. 21 and 22, the profile of thegear teeth404ais illustrated in greater detail. As shown, therear face430 of thethird reduction carrier404 is chamfered and aheavy radius434 is formed into each of sides of theteeth404aandvalleys404b. Eachgear tooth404aterminates abruptly at theforward face436 of thethird reduction carrier404.
• Returning back toFIGS. 12, 13,15,18 and23, the third set of planet gears402 is shown to include a plurality of planet gears438. Eachplanet gear438 is generally cylindrical in shape, having a plurality ofgear teeth438aformed into its outer perimeter and a pin aperture440 formed through its center. Eachplanet gear438 is rotatably supported on an associated one of thepins428 and thethird reduction carrier404 is positioned such that thegear teeth438aof the planet gears438 meshingly engage thegear teeth400aof thethird ring gear400. A raisedportion442 is formed into each of the front and rear faces of the planet gears438 which inhibits thegear teeth438afrom rubbing on thethird reduction carrier404 and creating dust or chips that would impair the performance of thetransmission assembly12 and reduce its operating life. Asecond thrust washer450 is disposed around thethird sun gear398 and theteeth398aof thethird sun gear398 are meshingly engaged with thegear teeth438aof the planet gears438. Thesecond thrust washer450 includes a plurality of retainingtabs452 that are configured to engage correspondingtab grooves454; (FIG. 13) that are formed in theinner surface266 ofbody portion246 of thetransmission sleeve200. The retainingtabs452 and thetab grooves454 cooperate to inhibit relative rotation between thesecond thrust washer450 and thetransmission sleeve200.
• Theoutput spindle assembly20 includes a transmitting means458 for coupling aspindle460 for rotation with thethird reduction carrier404 so as to transmit drive torque from thereduction gearset assembly202 to thechuck22. Such transmitting means458 are well known in the art and easily adapted to the transmission assembly of the present invention. Accordingly, a detailed discussion of the transmitting means458 need not be included herein.
• With reference toFIGS. 13, 13a,13b,16,17,18 and23 through28, thespeed selector mechanism60 is movable between afirst position500, asecond position502 and athird position504 and includes aswitch portion510 for receiving a speed change input and anactuator portion512 for manipulating thereduction gearset assembly202 in accordance with the speed change input. Theactuator portion512 is operatively coupled to thereduction gearset assembly202 and moves the second and third reduction gear sets304 and306 between the active and inactive modes in response to movement of theswitch portion510 between the first, second andthird positions500,502 and504. In the particular embodiment illustrated, theactuator portion512 includes arotary selector cam520, a plurality ofwire clips522 and aspring member523. Each of the wire clips522 is formed from a round wire which is bent in the shape of a semi-circle524 with a pair oftabs526 extending outwardly from the semi-circle524 and positioned on about the centerline of the semi-circle524. The semi-circle524 is sized to fit within theclip grooves374 and422 in the second and third ring gears360 and400, respectively. In this regard, the semi-circle524 neither extends radially outwardly of an associated one of the ring gears (360,400), nor binds against the sidewalls (376,424) of the clip grooves (374,422). In the example provided, the sidewalls (376,424) of the clip grooves (374,422). are spaced apart about 0.05 inch and the diameter of the wire forming the wire clips522 is about 0.04 inch.
• Thetabs526 of the wire clips522 extend outwardly of thehollow cavity212 into an associated one of the clip slots (284,286) that is formed into thetransmission sleeve200. Thetabs526 are long enough so that they extend outwardly of theouter surface258 of thebody214 of thetransmission sleeve200, but not so far as to extend radially outwardly of the portion of thefirst clip slots284 in thebase216 of thetransmission sleeve200. Configuration of the wire clips522 in this manner facilitates the assembly of thetransmission assembly16, permitting the wire clips522 to be installed to the second and third ring gears360 and400, after which these assemblies are inserted into thehollow cavity212 along the longitudinal axis of thetransmission sleeve200.
• With specific reference toFIGS. 13 and 27athrough27c, therotary selector cam520 is illustrated to include anarcuate selector body530, aswitch tab532 and a plurality of spacing members534. A pair offirst cam slots540aand540b, a pair ofsecond cam slots544aand544b, aspring aperture546 and aguide aperture548 are formed through theselector body530. Theselector body530 is sized to engage the outside diameter of thebody portion246 of thetransmission sleeve200 in a slip-fit manner. Theguide aperture548 is generally rectangular in shape and sized to engage the front and rear surfaces of theselector cam guide250. Theguide aperture548 is considerably wider than the width of theselector cam guide250, being sized in this manner to permit therotary selector cam520 to be rotated on thetransmission sleeve200 between a first rotational position, a second rotational position and a third rotational position. Theselector cam guide250 and cooperates with theguide aperture548 to limit the amount by which therotary selector cam520 can be rotated on thetransmission sleeve200, with a first lateral side of theselector cam guide250 contacting a first lateral side of theguide aperture548 when therotary selector cam520 is positioned in the first rotational position, and a second lateral side of theselector cam guide250 contacting a second lateral side of theguide aperture548 when therotary selector cam520 is positioned in the third rotational position.
• Each of thefirst cam slots540aand540bis sized to receive one of thetabs526 of thewire clip522 that is engaged to thesecond ring gear360. In the particular embodiment illustrated,first cam slot540aincludes afirst segment550, asecond segment552 and anintermediate segment554. Thefirst segment550 is located a first predetermined distance away from areference plane558 that is perpendicular to the longitudinal axis of therotary selector cam520 and thesecond segment552 is located a second distance away from thereference plane558. Theintermediate segment554 couples the first andsecond segments550 and552 to one another. The configuration offirst cam slot540bis identical to that offirst cam slot540a, except that it is rotated relative to therotary selector cam520 such that each of the first, second andintermediate segments550,552 and554 in thefirst cam slot540bare located 180° apart from the first, second andintermediate segments550,552 and554 in thefirst cam slot540a.
• Each of thesecond cam slots544aand544bis sized to receive one of thetabs526 of a corresponding one of the wire clips522. In the particular embodiment illustrated,second cam slot544aincludes afirst segment560, asecond segment562, athird segment564 and a pair ofintermediate segments566 and568. The first andthird segments560 and564 are located a third predetermined distance away from the reference plane and thesecond segment562 is located a fourth distance away from thereference plane558. The intermediate segment566acouples the first andsecond segments560 and562 to one another and theintermediate segment568 couples the second andthird segments562 and566 together. The configuration ofsecond cam slot544bis identical to that ofsecond cam slot544a, except that it is rotated relative to therotary selector cam520 such that each of the first, second, third andintermediate segments560,562,564 and566 and568 in thesecond cam slot544bare located 180° apart from the first, second, third andintermediate segments560,562,564 and566 and568 in thesecond cam slot544a.
• With thetabs526 of the wire clips522 engaged to thefirst cam slots540aand540band thesecond cam slots544aand544b, therotary selector cam520 may be rotated on thetransmission sleeve200 between the first, second andthird positions500,502 and504 to selectively engage and disengage the second and third ring gears360 and400 from the first andthird reduction carriers314 and404, respectively. During the rotation of therotary selector cam520, thefirst cam slots540aand540band thesecond cam slots544aand544bconfine thewire tabs526 of their associatedwire clip522 and cause thewire tabs526 to travel along the longitudinal axis of thetransmission sleeve200 in an associated one of the first andsecond clip slots284 and286. Accordingly, the rotary.selector cam520 is operative for converting a rotational input to an axial output that causes the wire clips522 to move axially in a predetermined manner. A lubricant (not specifically shown) is applied to thelubricant grooves252 formed intobody portion246 of thetransmission sleeve200 is employed to lubricate the interface between thetransmission sleeve200 and therotary selector cam520.
• Positioning therotary selector cam520 in the firstrotational position500 causes thetabs526 of thewire clip522 that is engaged to thesecond ring gear360 to be positioned in thefirst segment550 of thefirst cam slots540aand540band thetabs526 of thewire clip522 that is engaged to thethird ring gear400 to be positioned in thefirst segment560 of thesecond cam slots544aand544b. Accordingly, positioning of therotary selector cam520 in the first rotational position causes the second and third ring gears360 and400 to be positioned in meshing engagement with the second and third planet gears362 and402, respectively. Simultaneously with the meshing engagement of the second and third ring gears360 and400 with the second and third planet gears362 and402, thesleeve engagement teeth370 and418 of the second and third ring gears360 and400, respectively, are positioned in meshing engagement with the first and second sets ofring engagement teeth254 and256, respectively, to inhibit relative rotation between the second and third ring gears360 and400 and thetransmission sleeve200 to thereby providing thetransmission assembly16 with a first overall gear reduction orspeed ratio570 as shown inFIG. 23. Those skilled in the art will understand that thetip portion272 of the teeth268 of the first and second sets ofring engagement teeth254 and256 and thetip portions372 and420 of thesleeve engagement teeth370 and418, respectively, are rounded and tapered so as to improve their capability for meshing engagement in response to axial repositioning along a longitudinal axis of thetransmission assembly16.
• Positioning therotary selector cam520 in the secondrotational position502 causes thetabs526 of thewire clip522 that is engaged to thesecond ring gear360 to be positioned in thefirst segment550 of thefirst cam slots540aand540band thetabs526 of thewire clip522 that is engaged to thethird ring gear400 to be positioned in thesecond segment562 of thesecond cam slots544aand544b. Accordingly, positioning of therotary selector cam520 in second rotational position causes thesecond ring gear360 to be in meshing engagement with the second planet gears362 and thethird ring gear400 in meshing engagement with both the third planet gears402 and thethird reduction carrier404. Positioning of therotary selector cam520 in the secondrotational position502 also positions thesleeve engagement teeth370 of thesecond ring gear360 in meshing engagement with the first set ofring engagement teeth254 while thesleeve engagement teeth418 of thethird ring gear400 are not meshingly engaged with the second set ofring engagement teeth256. As such, relative rotation between thesecond ring gear360 and thetransmission sleeve200 is inhibited, while relative rotation between thethird ring gear400 and thetransmission sleeve200 is permitted to thereby provide thetransmission assembly16 with a second overall gear reduction orspeed ratio572 as illustrated inFIG. 24.
• Positioning therotary selector cam520 in the thirdrotational position504 causes thetabs526 of thewire clip522 that is engaged to thesecond ring gear360 to be positioned in thesecond segment552 of thefirst cam slots540aand540band thetabs526 of thewire clip522 that is engaged to thethird ring gear400 to be positioned in thethird segment564 of thesecond cam slots544aand544b. Accordingly, positioning of therotary selector cam520 in the third rotational position causes thesecond ring gear360 to be in meshing engagement with both the second planet gears362 and thefirst reduction carrier314 while thethird ring gear400 in meshing engagement with only the third planet gears402. Positioning therotary selector cam520 in thethird rotation position504 also positions thesleeve engagement teeth370 on thesecond ring gear360 out of meshing engagement with the first set ofring engagement teeth254 and thesleeve engagement teeth418 on thethird ring gear400 in meshing engagement with the second sets ofring engagement teeth256 to inhibit relative rotation between thesecond ring gear360 and thetransmission sleeve200 and permit relative rotation between thethird ring gear400 and thetransmission sleeve200 to provide thetransmission assembly16 with a third overall gear reduction orspeed ratio574.
• In the example shown inFIGS. 13, 27band28, thespring member523 is formed from a flat rectangular piece of spring steel and includes a flattened Z-shapedportion580 and a raisedportion584. The flattened Z-shapedportion580 is configured to wrap around tworeinforcement bars586 that extend into thespring aperture546, thereby permitting the raisedportion584 to be maintained at a predetermined position and also to transmit a spring force between therotary selector cam520 and thespring member523. With additional reference toFIG. 28, the raisedportion584 of thespring member523 is sized to engageinternal notches590 formed in thehousing592 of theoutput spindle assembly20.Lands594 that are circumferentially spaced from therotary selector cam520 are formed between thenotches590. When theoutput spindle assembly20 is positioned over thetransmission assembly16 and thespeed selector mechanism60 is positioned in one of the first, second and thirdrotational positions500,502 and504, the raisedportion584 of thespring member523 engages an associated one of thenotches590. The force that is generated by thespring member523 when the raisedportion584 is moved downwardly toward therotary selector cam520 in response to contact between the raisedportion584 and theland594 acts to inhibit unintended rotation of thespeed selector mechanism60. Furthermore, placement of the raisedportion584 in anotch590 provides the user with a tactile indication of the positioning of therotary selector cam520.
• In the particular embodiment illustrated inFIGS. 13 and 27c,switch portion510 is shown to include anarcuate band600 having a raised hollow andrectangular selector button602 formed therein. Thearcuate band600 is formed from a plastic material and is configured to conform to the outer diameter of therotary selector cam520. The open end of theselector button602 is configured to receive theswitch tab532, thereby permitting theswitch portion510 and therotary selector cam520 to be coupled to one another in a fastenerless manner. The plurality of spacing members534 are raised portions formed into therotary selector cam520 that are concentric to and extend radially outwardly from theselector body530. The spacing members534 elevate thearcuate band600 to prevent the arcuate band from contacting thewire tabs526 in thefirst cam slots540aand540b. The spacing members534 may also be employed to selectively strengthen areas of therotary selector cam520, such as in the areas adjacent thefirst cam slots540aand540b.
• Those skilled in the art will understand that the rotary selector cam520 (i.e., thefirst cam slots540aand540band thesecond cam slots544aand544b) could be configured somewhat differently so as to cause thesecond ring gear360 meshingiy engages both the second planet gears362 and thefirst reduction carrier314 while thethird ring gear400 meshingly engages both the third planet gears402 and thethird reduction carrier404 to thereby providing thetransmission assembly16 with a fourth overall gear reduction or speed ratio.
• Those skilled in the art will also understand that selector mechanisms of other configurations may be substituted for theselector mechanism60 illustrated herein. These selector mechanisms may include actuators that are actuated via rotary or sliding motion and may include linkages, cams or other devices that are well known in the art to slide the second and third ring gears360 and400 relative to thetransmission sleeve200. Those skilled in the art will also understand that as the second and third ring gears360 and400 are independently movable between the active and inactive modes (i.e., the placement of one of the second and third ring gears360 and400 does not dictate the positioning of the other one of the second and third ring gears360 and400), theswitch mechanism60 could also be configured to position the second and third ring gears360 and400 independently of one another.
• Clutch Mechanism
• InFIGS. 23, 26 and28 through30, theclutch mechanism18 is shown to include aclutch member700, anengagement assembly702 and anadjustment mechanism704. Theclutch member700 is shown to be an annular structure that is fixed to the outer diameter of thefirst ring gear310 and which extends radially outwardly therefrom. Theclutch member700 includes an arcuateclutch face316 that is formed into thefront face318 of thefirst ring gear310. The outer diameter of theclutch member700 is sized to rotate within the portion of thehollow cavity212 that is defined by thebase216 of thetransmission sleeve200. With specific brief reference toFIG. 29, theclutch face316 of the example illustrated is shown to be defined by a plurality ofpeaks710 andvalleys712 that are arranged relative to one another to form a series of ramps that are defined by an angle of about 18°. Those skilled in the art will understand, however, that other clutch face configurations may also be employed, such as a sinusoidally shapedclutch face316′ (FIG. 29a).
• While thefirst ring gear310 and theclutch member700 have been illustrated as a one piece (i.e., unitarily formed) construction, those skilled in the art will understand that they may be constructed otherwise. One such embodiment is illustrated inFIG. 29bwherein thefirst ring gear310′ is shown to include anannular collar1000 and a plurality oftab apertures1002. Theannular collar1000 is illustrated to include a plurality oframps1004 that have dual sloping sides, but is otherwise flat. Thefirst ring gear310′ is otherwise identical to thefirst ring gear310. Anannular damper1008 abuts theannular collar1000 and includes a plurality oftab members1010 that engage thetab apertures1002 in thefirst ring gear310′ to prevent thedamper1008 from rotating relative to thefirst ring gear310′. Thedamper1008 includes abody portion1012 that is configured to match the contour of theannular collar1000 and as such, includes a plurality of mating rampedportions1014 that are configured to engage each of theramps1004. Thedamper1008 is formed from a suitable impact dampening material, such as acetyl. Theclutch member700′, which is an annular member that is formed from a wear resistant material, such as hardened8620 steel, is disposed over thedamper1008. Like thedamper1008, theclutch member700′ includes a plurality oftab members1020, which lock into thetab apertures1002 to prevent rotation relative to thefirst ring gear310′, and a plurality of mating rampedportions1022. The mating rampedportions1022 of theclutch member700′, however, matingly engage the mating rampedportions1014 of thedamper1008. While the construction in this manner is more expensive relative to the previously described embodiment, it is more tolerant of high impact forces that are associated with the operation of theclutch mechanism18.
• In the particular embodiment illustrated, theengagement assembly702 includes apin member720, afollower spring722 and afollower724. Thepin member720 includes acylindrical body portion730 having an outer diameter that is sized to slip-fit within thesecond portion278 of theactuator aperture274 that is formed into thepin housing portion248 of thetransmission sleeve200. Thepin member720 also includes atip portion732 and ahead portion734. Thetip portion732 is configured to engage theadjustment mechanism704 and in the example shown, is formed into the end of thebody portion730 of thepin member720 and defined by a spherical radius. Thehead portion734 is coupled to the end of thebody portion730 opposite thetip portion732 and is shaped in the form of a flat cylinder or barrel that is sized to slip fit within thefirst portion276 of theactuator aperture274. Accordingly, thehead portion734 prevents thepin member720 from being urged forwardly out of theactuator aperture274.
• Thefollower spring722 is a compression spring whose outside diameter is sized to slip fit within thefirst portion276 of theactuator aperture274. The forward end of thefollower spring722 contacts thehead portion734 of thepin member720, while the opposite end of thefollower spring722 contacts thefollower724. Theend portion740 of thefollower724 is cylindrical in shape and sized to slip fit within the inside diameter of thefollower spring722. In this regard, theend portion740 of the follower acts as a spring follower to prevent thefollower spring722 from bending over when it is compressed. Thefollower724 also includes afollower portion744 having a cylindrically shapedbody portion746, atip portion748 and aflange portion750. Thebody portion746 is sized to slip fit within thefirst portion276 of theactuator aperture274. Thetip portion748 is configured to engage theclutch face316 and in the example shown, is formed into the end of thebody portion746 of thefollower724 and defined by a spherical radius. Theflange portion750 is formed at the intersection between thebody portion746 and theend portion740. Theflange portion750 is generally flat and configured to receive a biasing force that is exerted by thefollower spring722.
• Theadjustment mechanism704 is also shown to include anadjustment structure760 and asetting collar762. Theadjustment structure760 is shaped in the form of a generally hollow cylinder that is sized to fit ahousing portion766 of theoutput spindle assembly20. Theadjustment structure760 includes anannular face768 into which anadjustment profile770 is formed. Theadjustment profile770 includes afirst adjustment segment772, alast adjustment segment774, a plurality ofintermediate adjustment segments776 and aramp section778 between the first andlast adjustment segments772 and774. In the embodiment illustrated, asecond ramp section779 is included between the lastintermediate adjustment segment776zand thelast adjustment segment774. Also in the particular embodiment illustrated, the portion of theadjustment profile770 from thefirst adjustment segment772 through the last one of theintermediate adjustment segments776zis formed as a ramp having a constant slope. Accordingly, afollower780 that is coupled to thehousing portion766 of theoutput spindle assembly20 is biased radially outwardly toward the inside diameter of theadjustment structure760 where it acts against the plurality ofdetents782 that are formed into the adjustment mechanism704 (e.g., in the setting collar762). Thefollower724 and plurality ofdetents782 cooperate to provide the user oftool10 with a tactile indication of the position of theadjustment profile770 as well as inhibit the free rotation of theadjustment structure760 so as to maintain the position of theadjustment profile770 at a desired one of theadjustment segments772,774 and776.
• Thesetting collar762 is coupled to the exterior of theadjustment structure760 and includes a plurality of raisedgripping surfaces790 that permit the user of thetool10 to comfortably rotate both thesetting collar762 and theadjustment structure760 to set theadjustment profile770 at a desired one of theadjustment segments772,774 and776. A settingindicator792 is employed to indicate the position of theadjustment profile770 relative to thehousing portion766 of theoutput spindle assembly20. In the example provided, the settingindicator792 includes anarrow794 formed into thehousing portion766 of theoutput spindle assembly20 and ascale796 that is marked into the circumference of thesetting collar762.
• During the operation of thetool10, an initial drive torque is transmitted by themotor pinion46 from themotor assembly14 to the first set of planet gears312 causing the first set of planet gears312 to rotate. In response to the rotation of the first set of planet gears312, a first intermediate torque is applied against thefirst ring gear310. Resisting this torque is a clutch torque that is applied through theclutch mechanism18. The clutch torque inhibits the free rotation of thefirst ring gear310, causing the first intermediate torque to be applied to thefirst reduction carrier314 and the remainder of thereduction gearset assembly202 so as to multiply the first intermediate torque in a predetermined manner according to the setting of theswitch mechanism60. In this regard, theclutch mechanism18 biases thefirst reduction gearset302 into a mode that permits torque multiplication and speed reduction.
• The magnitude of the clutch torque is dictated by theadjustment mechanism704, and more specifically, the relative height of theadjustment segment772,774 or776 that is in contact with thetip portion732 of thepin member720. Positioning of theadjustment mechanism704 at a predetermined one of theadjustment segments772,774 or776 pushes thepin member720 rearwardly in theactuator aperture274, thereby compressing thefollower spring722 and producing the a clutch force. The clutch force is transmitted to theflange portion750 of thefollower724, causing thetip portion748 of thefollower724 to engage theclutch face316 and generating the clutch torque. Positioning of thetip portion748 of thefollower724 in one of thevalleys712 in theclutch face316 operates to inhibit rotation of thefirst ring gear310 relative to thetransmission sleeve200 when the magnitude of the clutch torque exceeds the first intermediate torque. When the first intermediate torque exceeds the clutch torque, however, thefirst ring gear310 is permitted to rotate relative to thetransmission sleeve200. Depending upon the configuration of theclutch face316, rotation of thefirst ring gear310 may cause the clutch force to increase a sufficient amount to resist further rotation. In such situations, thefirst ring gear310 will rotate in an opposite direction when the magnitude of the first intermediate torque diminishes, permitting thetip portion748 of thefollower724 to align in one of thevalleys712 in theclutch face316. If rotation of thefirst ring gear310 does not cause the clutch force to increase sufficiently so as to fully resist rotation of thefirst ring gear310, thefirst reduction gearset302 will rotate so as to limit the transmission of torque to thefirst reduction carrier314.
• Configuration of theclutch mechanism18 in this manner is highly advantageous in that the clutch torque is sized to resist the first intermediate torque, as opposed to the output torque of thetool10 that is generated by themulti-reduction transmission assembly16 and transmitted through thechuck22. In this regard, theclutch mechanism18 may be sized in a relatively small manner, thereby improving the ability with which it can be incorporated or packaged into thetool10. Furthermore, as the speed or gear ratios are changed after or down stream of thefirst ring gear310, theclutch mechanism18 is operable over a relatively large span of output torques. In comparison with conventional clutch mechanisms that operate to limit the output torque of a transmission, these devices are typically operable over a relatively narrow torque band, necessitating a change in their clutch spring if a considerable shift in the magnitude of the output torque is desired. In contrast, theclutch mechanism18 of the present invention can accommodate a considerable shift in the magnitude of the output torque of thetool10 by simply operating thetransmission assembly16 in a different (i.e., lower or higher) gear ratio.
• In the operation of rotary power tools such astool10, it is frequently desirable to change between two clutch settings, as when thetool10 is used to both drill a hole and thereafter install a screw in that hole. Accordingly, theadjustment mechanism704 may be rotated relative to theoutput spindle assembly20 to position theadjustment mechanism704 at a desired one of theadjustment segments772,774 and776 to perform the first operation and thereafter rotated to a second one of theadjustment segments772,774 and776 to perform the second operation. In contrast to the known clutch arrangements, theadjustment mechanism704 of the present invention is configured such that theadjustment structure760 and thesetting collar762 are rotatable through an angle of 360°. Assuming theadjustment structure760 to be positioned at anintermediate adjustment segment776x, rotation of theadjustment mechanism704 through an angle of 360° would rotate theadjustment structure760 past the otherintermediate adjustment segments776, as well as the first andlast adjustment segments772 and774 and theramp section778 such that theadjustment structure760 would again be positioned at theintermediate adjustment segment776x. The feature is especially convenient when it is necessary to change the clutch setting between a relatively high clutch setting and a relatively low clutch setting. In this regard, theramp section778 permits the setting collar762 (and adjustment structure760) to be rotated from highest clutch setting, corresponding to the last adjustment segment, to the lowest clutch setting, corresponding to the first clutch setting, without positioning theclutch mechanism18 in one of the intermediate clutch settings. Accordingly, the user of thetool10 is able to vary the clutch setting from its maximum setting to its minimum setting (and vice versa) by rotating the setting collar762 a relatively small amount.
• While theadjustment profile770 has been described thus far as having a constant slope, those skilled in the art will appreciate that the invention, in its broader aspects, may be constructed somewhat differently. For example, theadjustment profile770′ may be formed such that each of the first, last andintermediate adjustment segments772′,774′ and776′ is detented as illustrated inFIG. 31. In this arrangement, thedetents782 in theadjustment structure760 and thefollower780 in thehousing portion766 of theoutput spindle assembly20 are unnecessary as theadjustment segments772′,774′ and776′ will cooperate with theengagement702 to provide the user of thetool10 with a tactile indication of the position of theadjustment profile770′, as well as inhibit the free rotation of theadjustment structure760.
• Another example is illustrated inFIG. 32 wherein theadjustment profile770″ is generally similar to theadjustment profile770 except that theramp section779 has been omitted so that the lastintermediate adjustment segment776zis immediately adjacent thelast adjustment segment774.
• While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the description of the appended claims.

Claims (22)

1. An article comprising a housing structure and a secondary structure that are fixedly but removably coupled to one another, one of the housing structure and the secondary structure having a structural portion and an overmold portion that is formed from a resilient material and molded onto at least a portion of the structural portion such that the overmold portion is permanently and fixedly coupled to the structural portion, the overmold portion defining a seal portion that is configured to engage the other one of the housing structure and the secondary structure to form a seal between the structural portion and the other one of the housing structure and the secondary structure when the housing structure and the secondary structure are coupled to one another.

2. The article ofclaim 1, wherein the resilient material is a thermoplastic.

3. The article ofclaim 2, wherein the thermoplastic is a thermoplastic elastomer.

4. The article ofclaim 1, wherein the one of the housing structure and the secondary structure is an end cap.

5. The article ofclaim 1, wherein the overmold portion further includes a bumper member that is coupled to an exterior surface of the structural portion, the bumper member being configured to abut the other one of the housing structure and the secondary structure to limit movement of the other one of the housing structure and the secondary structure relative to the structural portion in a predetermined direction.

6. The article ofclaim 5, wherein the bumper member is raised from the exterior surface of the molded portion but otherwise conforms to the shape of the structural portion in an area in which the bumper member and the other one of the housing structure and the secondary structure abut.

7. The article ofclaim 6, wherein the overmold portion includes a linking member that couples the seal portion to the bumper member.

8. The article ofclaim 1, wherein the article is a power tool.

9. The article ofclaim 8, wherein the power tool is a drill.

10. An article comprising a first structure and a second structure, at least one of the first and second structures having a structural portion and an overmold portion that is formed from a resilient material and at least partially molded onto the structural portion so as to be substantially permanently fixedly coupled thereto, the overmold portion defining an isolator portion that is configured to contact the other one of the first and second structures and dampen vibrations that are transmitted between the structural portion and the other one of the first and second structures.

11. The article ofclaim 10, wherein the first structure is an end cap shell and the second structure is a motor.

12. The article ofclaim 10, wherein the overmold portion also retains the other one of the first and second structures in a predetermined location relative to the structural portion.

13. The article ofclaim 10, wherein the resilient material is a thermoplastic.

14. The article ofclaim 13, wherein the thermoplastic is a thermoplastic elastomer.

15. The article ofclaim 10, wherein the overmold portion further includes a bumper member that is coupled to an exterior surface of the structural portion, the bumper member being configured to abut the other one of the first and second structures to limit movement of the other one of the first and second structures relative to the structural portion in a predetermined direction.

16. The article ofclaim 15, wherein the overmold portion includes a linking member that couples the isolator portion to the bumper member.

17. The article ofclaim 15, wherein the bumper member is raised from the exterior surface of the structural portion but otherwise conforms to the shape of the structural portion in an area in which the bumper member and the other one of the first and second structures abut.

18. The article ofclaim 10, wherein the article is a power tool.

19. The article ofclaim 18, wherein the power tool is a drill.

20. An article comprising:

a first structure;

a second structure, the second structure including a structural portion and an overmold portion that is overmolded onto the structural portion, the overmold portion resiliently deflecting to accommodate the first structure when the first and second structures are coupled to one another.

21. A method comprising:

providing a first structure;

forming an overmold onto the first structure;

coupling a second structure to the first structure such that the overmold resiliently deflects to accommodate the second structure.

22. A method comprising:

providing a first structure;

forming an overmold onto the first structure;

coupling a second structure to the first structure such that the overmold sealingly engages the second structure to thereby form a seal between the first and second structures.

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