US20030104767A1 - Extensible dust-collecting shroud for grinders - Google Patents

Abstract

A rotary abrading tool has a dust removal accessory that accommodates for wearing of the abrading member. The tool has a portable housing having a handgrip portion and a rotatably driven shaft extending from the housing. A backing plate is mounted to an end of the shaft for rotation therewith, An abrading member mounted to the backing plate. A shroud base is stationarily mounted to the housing around the backing plate. A plurality of concentric rings of successively smaller diameters are carried by the base, each of the rings having an outer diameter that frictionally engages an inner diameter of another one of the rings. The rings are movable relative to the base from a contracted position to an extended position, defining a generally conical enclosure that surrounds the abrading member. An exhaust tube extending from the base for creating a suction within the base and the conical enclosure to collect dust particles.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application claims the benefit of provisional application No. 60/334,467, filed Nov. 30, 2001.[0001]
FIELD OF THE INVENTION
• This invention deals with dust collecting shrouds for rotary abrasive tools such as grinders.[0002]
BACKGROUND OF THE INVENTION
• The dust created by abrasive tools as they abrade a workpiece can be hazardous to the workers health. While masks are commonly worn, it is also desirable to prevent as much dust as possible from dispersing into the air around the worker. Dust collecting shrouds are employed around the tool. Typically, the shroud is connected through a vacuum tube to a vacuum source. The shroud is secured by a bracket to the tool and is of a fixed length that extends to the abrading member.[0003]
• Shrouds of this nature work well enough for grinders employing sand paper. When the sand paper is worn sufficiently for replacement, the shroud distal end will still be approximately aligned with the sand paper because the difference in thickness between new sand paper and worn sand paper is small. Other types of abrading members, however, are much thicker when new than when worn. One type comprises a disk with a plurality of resilient fingers or bristles extending from the disk. The bristles are used to remove paint, particularly in marine applications. The bristles wear down with use. Abrasive stones also wear in thickness. Hole cutters of a type using a circular sawtooth band don't wear in thickness, however, the distance between the workpiece and the tool decreases as the hole is being cut. In all of these instances a rigidly mounted shroud of fixed length will not accommodate the decreasing distance from the tool to the workpiece.[0004]
SUMMARY
• A rotary abrading tool accessory attaches to a rotary abrading tool having a shaft that rotates a backing plate that has an abrading member attached thereto. The accessory has a shroud base that fits around the backing plate. A telescoping enclosure section extends from the base for enclosing the abrading member. The telescoping enclosure section has a length that is axially variable. An exhaust tube extends from the base for creating a suction within the enclosure section and the base to collect dust particles.[0005]
• In the preferred embodiment, the telescoping section is made up of a plurality of concentric rings that overlap and frictionally engage each other to create an enclosure. The rings are of successively smaller diameters in a direction away from the base. Preferably, the rings are formed by coiling a resilient metal band, with each turn of the coil creating another ring.[0006]
BRIEF DESCRIPTION OF THE DRAWINGS
• The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:[0007]
• FIG. 1 is a perspective view of a portable abrasive grinder of the invention showing the shroud surrounding the backing plate and abrasive disk with portions of the shroud broken away for ease of illustration;[0008]
• FIG. 2 is a sectional view of the shroud, backing plate and abrasive disk used with the grinder of FIG. 1; and[0009]
• FIG. 3 is a plan view of the bottom surface of the abrasive disk.[0010]
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 shows a portable abrading tool, which is an[0011]abrasive grinder11. Grinder11 has ahandgrip12 and acontrol valve13.Control valve13 is coupled to a remote air source through aconduit15 in order to power amotor17 having a verticallyoriented output shaft19. Grinder11 can be, for instance, a DOTCO Sander Model No. 10L1280-36, right angle, air powered, rear exhaust, 12,000 rpm, 3 inch sanding disk capacity, available from DCM Clean-Air Products, Inc., Fort Worth, Tex. Grinders of the type under consideration typically operate at speeds on the order of 12,000-20,000 rpm for driving a 3 inch disk.
• Referring to FIG. 2,[0012]output shaft19 ofmotor17 is joined by acoupling21 to abacking plate23 for driving thebacking plate23 in rotary fashion about the vertical axis defined by theoutput shaft19. Grinder11 may be used to drive any rotary implements adapted for use on high-speed grinders.
• [0013]Backing plate23 has anupper surface25, alower surface27 and a plurality ofholes29 which communicate the upper andlower surfaces25,27. As shown also in FIG. 3,lower surface27 of thebacking plate23 has a circular periphery, and a plurality ofholes29 are circumferentially spaced a radial distance from the vertical axis at regular angular intervals.Lower surface27 has an internal threadedfemale connector31 that is coaxial with the vertical axis and used for securing anabrasive member33 to the plate.Backing plate23 may be formed of any appropriate material which is sufficiently resilient to pressabrasive member33 against awork surface35 and returnbacking plate23 to an approximately planar condition whenabrasive member33 is out of contact withwork surface35. For instance,backing plate23 can be formed of an appropriate fabric-reinforced resinous plastic material, such as a suitable phenolic. Alternatively,backing plate23 could be made of a hard rubber.
• An[0014]extensible shroud37encircles backing plate23 and is connected by means of aconduit39 to a commercially-available vacuum source (not shown) for removing dust particles fromwork surface35. The term “dust particles” means spent abrasive particles and other particulate matter created by the abrading operation and which are entrained in the air flowing throughshroud37 and throughconduit39 to the dust collection point. Shroud37 is designed to be used with any type of rotary grinding or cutting implement that is attached tooutput shaft19 and fits withinshroud37.
• Referring to FIG. 2,[0015]shroud37 has ashroud base38 that is a cylindrical member with a closed proximal end, the proximal end being the closer end tohandgrip12. The distal end ofshroud base38 is open. Shroudbase38 is retained in position by securing it to a support arm43 (FIG. 1) having an appropriate opening to receiveoutput shaft19 of themotor17.
• Shroud[0016]37 also has a telescoping enclosure section comprising athin band40 of resilient metal wound in a plurality of turns to create a helix. The helix is coaxial with theoutput shaft19, and each 360 degree turn decreases in diameter by the horizontal thickness of the band, creating a plurality ofrings41 of progressively smaller diameter. Each ring ofband40 overlaps bears frictionally against another of the rings. Thelargest diameter ring41 has one end attached toshroud base38, and the smallest diameter ring has the opposite end ofband40 attached within.Rings41 ofshroud37 can translate in a direction parallel to the axis ofoutput shaft19 and can tilt slightly relative to the axis ofoutput shaft19. Grasping thesmallest diameter ring41 and pulling it away fromshroud base38 causesrings41 to move to an extended position, defining a conical enclosure. An outward facinglip45 is preferably formed on the proximal edge ofband40. An inward facinglip47 is preferably formed on the distal edge ofband40.Lips45, will engage each other when in the fully extended position to retainrings41 in the coiled configuration. Eachlip45,47 engages a surface of anadjacent ring41, providing a substantially air tight seal for the telescoping enclosure defined byrings41.
• The inner surface of the innermost and most[0017]distal ring41 has a radius approximately ¼″ larger than that of thebacking plate23. The space permits the intake of dust particles fromwork surface35 about the periphery of thebacking plate23. Preferably,shroud37 has an extended length that is selected so that the distal end ofband40 is approximately flush with the distal end of an unwornabrasive member33.Rings41 allow the length ofshroud37 to decrease as it is pushed against thework surface35.
• Alternatively, though not shown in the figures,[0018]shroud37 may be formed from a plurality of nested cones. The cones are coaxial withoutput shaft19, each having a slightly larger upper diameter than lower diameter. The diameter of each subsequent inner cone decreases by the horizontal thickness of the cones, and the cones frictionally engage each other. The outer cone is secured to thesupport arm43, but the inner cones can translate in a direction parallel to the axis of theoutput shaft19. The inner cones move independently of and relative to each other. Any two adjacent cones can move relative to each other any distance less than the vertical height of the cones.
• FIGS. 2 and 3 show one type of[0019]abrasive member33 that secures to backingplate23.Abrasive member33 is circular in shape and has abottom surface51, a top surface ordisk53 and a plurality of circumferentially-spacedholes55. The number ofholes55 is equal to the number ofholes29 inbacking plate23 to permit alignment of theholes29,55.Top surface53 ofmember33 has a threadedmale connector57 for securingmember33 tobacking plate23.
• [0020]Member33 has a plurality of resilient bristles orfingers59 depending from thebottom surface51 and extending parallel to the vertical axis. A clearance betweenrings41 andfingers59 allowsfingers59 to flare outwardly without contacting the inner surface of theinnermost ring41. The lower ends offingers59 are applied towork surface35 whilemember33 is rotating to remove material fromwork surface35. As thework surface35 abrasion process continues, the ends offingers59 are also abraded, and the lengths offingers59 decrease.Extensible shroud37 accounts for this decrease in length by allowinginner bands41 to move axially relative to each other to decrease the extended length ofshroud37.
• The proper use of the[0021]grinder11 is shown in FIG. 2.Grinder11 is held at a 3-5 degree angle relative towork surface35, and the rear portion of the lower edge of the innermost turn orring41 is placed againstwork surface35.Fingers59 near the rear ofshroud37contact work surface35, but the front edge ofinnermost ring41 and fingers at the front are held abovework surface35. Asfingers59 rotate and brush againstwork surface35,fingers59 remove particles fromwork surface35. The tips offingers59 are also abraded during this process, and this decreases the lengths of thefingers59. To account for this decrease, the grinder assembly is moved toward thework surface35 while maintaining the 3-5 degree tool angle, and theinnermost ring41 moves toward thesupport arm43 untilfingers59 contact thework surface35.
• The invention has significant advantages. The shroud provides efficient dust collection for abrading tools that cause the tool to become nearer to the workpiece during use. The shroud is particularly useful for abrasive members that wear significantly in thickness.[0022]
• Although the invention has been described with respect to a threaded connector between the[0023]backing plate23 andabrasive member33, other arrangements could be used as well, as long as the particular engagement means provides for themale connector57 to fit loosely in a first rotary position and to be turned through a predetermined degree of rotation to a second binding position, the degree of rotation being calculated to cause alignment of the member holes55 with theholes29 of thebacking plate23.
• While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.[0024]

Claims (16)

1. A rotary abrading tool accessory for attachment to a rotary abrading tool having a shaft that rotates a backing plate that has an abrading member attached thereto, the accessory comprising:

a shroud base adapted to fit around the backing plate, the base having an axis that is adapted to coincide with an axis of the shaft;

a telescoping enclosure section extending from the base for enclosing the abrading member, the telescoping enclosure section having a length that is axially variable; and

an exhaust tube extending from the base for creating a suction within the enclosure section and the base to collect dust particles.

2. The abrading tool accessory according toclaim 1, wherein the base has an enclosed proximal end into which the exhaust tube extends.

3. The abrading tool accessory according toclaim 1, wherein the telescoping section comprises a plurality of rings of successively smaller diameters.

4. The abrading tool accessory according toclaim 1, wherein the telescoping section comprises a band that is helically wound in a plurality of rings, with each successive ring being farther from the base and of a smaller diameter.

5. The abrading tool accessory according toclaim 1, wherein the telescoping section comprises a resilient metal band that is helically wound in a plurality of rings, with each successive ring exerting a radially outward directed frictional force against a preceding ring.

6. The abrading tool accessory according toclaim 1, wherein the telescoping section comprises a resilient metal band having an outward protruding lip at a proximal edge of the band and an inward protruding lip at a distal edge of the band, the band being helically wound to define a plurality of rings, with the lips of each successive ring engaging each other as the telescoping section is moved to the fully extended position.

7. The abrading tool accessory according toclaim 1, further comprising a bracket for mounting the base stationarily to the abrading tool.

8. A rotary abrading tool, comprising:

a portable housing having a handgrip portion;

a rotatably driven shaft extending from the housing;

a backing plate mount to an end of the shaft for rotation therewith;

an abrading member mounted to the backing plate;

a shroud base stationarily mounted to the housing around the backing plate;

a plurality of concentric rings of successively smaller diameters carried by the base, each of the rings having an outer diameter that frictionally engages an inner diameter of another one of the rings, the rings being movable relative to the base from a contracted position to an extended position, defining a generally conical enclosure that surrounds the abrading member; and

an exhaust tube extending from the base for creating a suction within the base and the conical enclosure to collect dust particles.

9. The rotary abrading tool according toclaim 8, wherein the rings comprise flat metallic bands.

10. The rotary abrading tool according toclaim 8, wherein the rings are formed from a single, resilient metallic band that is wrapped helically in a plurality of turns, with each of the turns defining one of the rings.

11. The rotary abrading tool according toclaim 8, wherein the rings are formed from a single, resilient metallic band that is wrapped helically in a plurality of turns, with each of the turns defining one of the rings, the band having an outward protruding lip on a proximal edge and an inward protruding lip on a distal edge, the lips engaging each other when the band is in the extended position.

12. The rotary abrading tool according toclaim 8, wherein the abrading member comprises:

a disk secured to the backing plate;

a plurality of resilient fingers extending from the disk for abrading a workpiece; and

a plurality of holes extending through the disk that register with holes provided in the backing plate.

13. The rotary abrading tool according toclaim 8, further comprising a bracket connecting the shroud base to the housing.

14. A rotary abrading tool accessory for attachment to a rotary abrading tool having a shaft that rotates a backing plate that has an abrading member attached thereto, the accessory comprising:

a shroud base adapted to fit around the backing plate, the base having an axis that is adapted to coincide with an axis of the shaft;

a flat, resilient metallic band having one end attached to the shroud base and coiled in a plurality of turns that overlap and frictionally engage one another to define a telescoping enclosure of variable length for extending around the abrading member; and

an exhaust tube extending from the base for creating a suction within the enclosure section and the base to collect dust particles.

15. The abrading tool accessory according toclaim 14, wherein the band has an outward protruding lip on a proximal edge and an inward protruding lip on a distal edge, the lips engaging each other when the band is in an extended position.

16. A method for abrading a workpiece, comprising:

mounting an abrading member to a backing plate, the backing plate being attached to a shaft of a rotary abrading tool;

mounting a shroud around the backing plate, the shroud having a telescoping section that encloses the abrading member;

connecting an exhaust tube to the shroud;

gripping the rotary abrading tool, rotating the shaft, placing the abrading member and the telescoping section against a workpiece and creating a suction within the shroud to collect dust particles created by the abrading member; and

as the abrading member wears, causing the telescoping section to reduce in length.

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