US3905276A - Multiple spool power pack unit - Google Patents

Abstract

A power pack for converting gas pressure into rectilinear movement of a drive shaft. The power pack is actuated by unseating the primary spool of a spool mechanism having a primary spool and a secondary spool releasing a volume of pressurized gas and thereby driving a shaft adapted to be associated with a mechanism requiring an input of rectilinear movement. Differential pressures cause the spool mechanism to be reseated, thus allowing the drive shaft, biased toward the spool, to return to its rest position. The operation of the power unit depends upon the formation of pressure-tight chambers by the spool mechanism and associated O-rings and the sealing ability of the primary spool to slidably seal the flow of pressurized gas.

Description

United States Patent [191 Noiles et al.

[ 1 Sept. 16, 1975 MULTIPLE SPOOL POWER PACK UNIT [73] Assignee: United States Surgical Corporation,

Baltimore, Md.

[22] Filed: Sept. 29, 1972 21 Appl. No.: 293,469

3,583,426 6/1971 Feres 251/174 X 3,613,507 10/1971 Smith, Jr 91/433 X FOREIGN PATENTS OR APPLICATIONS 1,257,410 2/1961 France 91/465 1,002,091 8/1965 United Kingdom 137/59614 Primary Examinerlrwin C. Cohen Attorney, Agent, or FirmFleit & Jacobson 57 ABSTRACT A power pack for converting gas pressure into rectilinear movement of a drive shaft. The power pack is actuated by unseating the primary spool of a spool mechanism having a primary spool and a secondary spool releasing a volume of pressurized gas and thereby driving a shaft adapted to be associated with a mechanism requiring an input of rectilinear movement. Differential pressures cause the spool mechanism to be reseated, thus allowing the drive shaft, biased toward the spool, to return to its rest position. The operation of the power unit depends upon the formation of pressure-tight chambers by the spool mechanism and associated O-rings and the sealing ability of the primary spool to slidably seal the flow of pressurized gas.

14 Claims, 14 Drawing Figures mamas E 1 :915 9sum 2 OF 3 052 {6 MULTIPLE SPOOL POWER PACK UNIT BACKGROUND OF THE INVENTION The general concept of a gas powered driving unit as disclosed by the present application is not new. See for example, U.S. Pat. Nos. 3,613,507, issued Oct. 19, 1971; 3,618,842, issued Nov. 9, 1971 and 3,643,851, issued Feb. 22, 1972, all of which are assigned to the present Assignee. Additional prior art of interest can be found in the art cited by the Patent Office during the prosecution of the above-identified patents.

The power unit described in each of the above-noted patents functions capably. However, each of the abovementioned power units suffers from certain disadvantages. For example, the power unit described in US. Pat. No. 3,613,507 has a small seal area which with repeated seatings may become damaged thus preventing good contact between mating surfaces. Consequently, the sealing area increases because of plastic deformation and can ultimately create an area large enough for pressure forces to exceed spring forces in the other direction and hence the power unit could fail due to leakage.

In the power unit described in US. Pat. No. 3,618,842, the pressure chambers are defined by a se ries of O-rings which after long periods of wear may result in leakage between one chamber and the next.

In the third US. Pat, No. 3,643,851, the gas chamber is defined by a plurality of sliding diaphragms. These diaphragms were found to be somewhat Weak and, in time, often developed leaks.

It is towards the elimination of the above-noted disadvantages and the simplification of known power pack units that the present invention is directed.

SUMMARY OF THE INVENTION The present invention relates to a power pack capable of converting gas pressure into rectilinear movement, using a minimum amount of pressurized gas and with a minimum of moving parts. Pressurized gas is fed into the inventive power pack and when the power pack is idle the spool mechanism of the power pack is sealed off from the gas pressure. The two-part movable spool mechanism is maintained in constant contact with the gas pressure through the action of a pilot valve which has a gas port through its center. The contact between the rear of the spool mechanism and the pilot valve seals off the pressurized gas with the flat surface of the outer end of the valve abutting the flat surface of the inlet valve body allowing the pilot valve to have random orientation contact without damaging the seal.

The power pack of the present invention is fired when the driving piston and integral drive shaft are moved against the force of the piston return biasing spring. This movement allows the spool mechanism to become unsealed from the pilot valve and held in its unseated position through the action of pressurized gas acting upon the surfaces of the spool mechanism. When the spool is unseated the source of pressurized gas acts upon the piston integral with the drive shaft. The drive shaft is then driven by the pressurized gas through a firing cycle.

During the return movement of the piston, the force on the face of the spool mechanism remote from the gas port becomes greater than the force on the face of the spool mechanism adjacent the gas port, so that the spool mechanism is driven toward the gas port seating it against the pilot valve to seal the source of gas pressure. When the drive shaft is returned by its biasing spring, the gas in the piston chamber is exhausted, and the piston is brought into contact with the spool mechanism. At this time the power unit is ready for another drive cycle.

The operation of the inventive power pack is dependent upon the self energizing seal of the pilot valve, and the two-part spool mechanism with its sealing O-rings. Furthermore, the total area of the pilot valve sealing surface is such that it cannot become enlarged enough to misfire as there is always a sealing contact between the flat surfaces of the valve lip and the flat end surface primary spool projecting tip allowing a random orientation contact of the pilot valve body without damaging the seal. In addition, the unit provides for a cushioning effect on its various component parts. The rearward thrust of the spool mechanism causing contact with the pilot valve body is cushioned by two independent forces. The first force, and the lesser of the two, originates in the pilot valve biasing spring which at all times urges the pilot valve toward the spool mechanism and thus absorbs the contact force when the spool mechanism strikes the pilot valve body. The second force originates in the pressure of the inlet acting on the net cross-sectional areaof the pilot valve body.

Also, the forward unit of the drive shaft is against the biasing spring which at all times urges the drive shaft and integral piston toward the spool mechanism.

As constructed, the power pack forming the present invention has two major moving elements comprising a spool mechanism having two movable parts and a movable pilot valve body. The life of the power pack is substantial because of the minimal amount of wear on the apparatus so that it has great reliability for long periods of use. Furthermore, the apparatus also provides a means of transforming pressure forces into rectilinear motion in an efficient and reliable manner.

By utilizing the present invention, whose parts have tolerances that are relatively loose, the need for high precision machinery is eliminated as the manufacturing tolerances do not have to be so precise. Even without close tolerance of the parts as compared with similar units of the prior art, substantial thrust is able to be developed in the drive shaft with the effect that the moving parts are returned to their prefiring positions by combining the effects of the gas pressure and a single biasing spring.

Other features and advantages of the invention will be apparent from the following description of the embodiments of the invention as shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross section through a power pack constructed in accordance with the teachings of the present invention.

FIG. 2 is a cross section view of the inlet valve body shown in FIG. I in relation to the piston.

FIG. 3 is the right end elevation view of the inlet valve body of FIG. 2.

FIG. 4 is a cross section view of the secondary spool body shown in FIG. 1.

FIG. 5 is the left end elevation view of the secondary spool body of FIG. 4.

FIG. 6 is a cross section view of the primary spool body shown in FIG. 1.

FIG. 7 is the left end elevation view of the primary spool body shown in FIG. 6.

FIG. 8 is a cross section view of the pilot plug housing shown in FIG. 1.

FIG. 9 is plan view of the pilot plug housing shown in FIG. 8.

FIG. 10 is the right end elevation view of the pilot plug housing of FIG. 8.

FIG. 11 is an enlarged cross section view of the pilot valve body shown in FIG. 1.

FIG. 12 is the left end elevation view of the pilot valve body of FIG. 11.

FIG. 13 is a side view of the filter shown in FIG. 1.

FIG. 14 is a plan view of the filter illustrated in FIG. 13.

DETAILED DESCRIPTION OF THE DRAWINGS:

As shown in FIGS. 114 the inventive power pack generally discloses anouter casing 22 in which is mounted aninlet valve body 30 containing aprimary spool body 62, asecondary spool body 79, apilot housing 46 and apilot valve body 54. Adrive shaft 24 is slidably mounted in the outer casing with the foremost end of the drive shaft (not shown) being the output side of the power pack and serving to operate any device depending upon a rectilinear motion input for its performance.

The rearwardmost end of the drive shaft takes the form of apiston 26 slidably mounted in apiston chamber 28 defined by aninner casing member 29. Thepiston 26 is held in position by a piston return Spring which exerts a force on thepiston 26 of approximately 11 to 12 pounds. Theinner casing member 29 is mounted in a fixed position within theouter casing 22.

Mounted in theouter casing 22 adjacent theinner casing member 29 is aninlet valve body 30. Theinlet valve body 30 as shown in FIGS. 2 and 3 defines two centrally located interconnected chambers; a steppedspool chamber 58 and apilot housing chamber 45 which are interconnected byport 56 and vents 47. The steppedspool chamber 58 preferably comprises two sections or steps each of which has a different diameter, thelarger section 57 being of sufficient diameter to hold theprimary spool body 62, the other 59 being of sufficient diameter to hold thesecond spool body 79. The outer surface of theinlet valve body 30 defines a plurality ofannular channels 36, 94, 124 and 126. Anexhaust port 92 is cut through theinlet valve body 30 to connectchamber section 57 with an annular exhaust channel orring 94. The inlet valve body also defines afilter chamber 37 which is connected to thepilot housing chamber 45 byinlet passageway 42.

A stainlesssteel capillary tubing 32 leads from the gas pressure source (not shown) through theouter casing 22 into thegas feed channel 36 of the inlet valve body so that the source of pressurized gas can operate the working mechanism of thepower pack 20. The pressurized gas enterschannel 36 from thecapillary tubing 32 at 34 and travels into the inlet valvebody filter chamber 37. The gas is filtered byfilter 38 on its way intopassageway 42 which communicates with annulus 48 inhousing chamber 45. The annulus 48 is defined by theinlet valve body 30, the outer surface of thepilot housing 46 and O-ring 50 seated inside thehousing chamber 45 and abutting the housing body shoulders 43. Thepilot housing 46 as shown in FIGS. 1, 8 and 9, is preferably threaded so that it can be screwed into theinlet valve body 30 by means of adriv ing slot 110. A blind hole is drilled in the pilot housing to form thepilot valve chamber 44. The blind end ofchamber 44 is used as a spring seat for the pilotvalve biasing spring 108. Thechamber 44 is preferably stepped to allow clearance forshoulder 103 onpilot valve body 54. Afilter chamber 53 holdsfilter 55. Thefilter chamber 53 communicates with thepilot chamber 44 by means of aport 57 cut through thepilot housing 46.Filter chamber 53 also communicates with feed chamber 48 bypassageway 51. Apilot valve body 54 is slidably fitted intopilot housing chamber 44 in a gas tight relationship by means of O-ring 100.

Thepilot valve body 54 as shown in FIGS. 11 and 12 is constructed with abore 96 which allowsgas entering port 56 to flow through it. Anannular channel 98 is cut into the valve body to hold O-ring so that the O-ring 100 will form a gas-tight seal between the wall ofchamber 44 and the outer surface of thevalve body 54. The biasingspring 108 has one end seated in the blind end ofchamber 44 and the other end surrounding the pilot valve body at thespring rest 99 where it abuts against the pilot valve body to urge the pilot valve body away from the blind end ofchamber 44 toward the spool mechanism. The other end of the pilot valve body which performs the sealing functions comprises ashoulder portion 103, the front surface of which has a flat surface to contact the flat surface of the inlet valvebody contact area 60.Counterbore 41 in the pilot housing provides clearance forshoulder 103. The forward edge of the pilot valve body slopes upward from the flat surface ofshoulder 103 to form anannular ring 102 which has a flat sealing surface surrounding thebore 97. Thus there is formed on the forward edge of the pilot valve body a geometric surface which does not have to hit the same point repeatedly and therefore never spreads the seal area. When the valve is closed,ring 102 abutsfiat surface 68 onprimary spool 62. Inlet gas pressure works on an area created by diameter ofbody 54 less diameter ofbore 96 to hold the valve closed. The same pressure also works on the much smaller area ofring 102 less that ofbore 96. The net effect is that the inlet gas pressure holds the valve closed providing that the bias ofspring 25 is strong enough to prevent the gas pressure onbody 54 from movingprimary spool 62.

Adjacent thepilot valve chamber 44 isspool port 56 cut through the inlet valvebody contact area 60. Thespool port 56 allows the pressurzed gas passing though the pilot valve bore 96 to pass into the steppedspool chamber 58. A plurality ofvents 47 are also cut through the inlet valvebody contact area 60 substantially parallel to thespool port 56 and located approximately adjacent the flat forward surface of the pilotvalve body shoulder 103. As thepilot valve body 54 moves forward itsshoulder 103 hits thecontact area 60 thus stopping the pilot body and keeping it in position until its return.

Mounted in the inletvalve spool chamber 58 is aprimary spool body 62 as shown in FIGS. 6 and 7 having a centrally positioned bore 64 connected to the spool chamber by afeed port 66. Thefeed port 66 serves to admit gas to the working surface ofpiston 26 from the pilot valve bore 96 against thepiston head 26. The rearward end ofprimary spool body 62 forms a projectingtip 68 which is adapted to seat against thepilot valve body 54 forming a gas-tight seal and preventing gas from entering intospool chamber 58, except when the unit is actuated. The end of projectingtip 68 has a flat surface and a greater total area than the area of thepilot valve lip 102. In addition, sealing contact is always between flat surfaces, so that there can be random orientation contact without damaging the seal. Theprimary spool body 62 also defines anannular rib 70 having ashoulder 72 upon which is seated a free floating O-ring 74. Theannular rib 70 preferably fits within bore 80 of thesecondary spool body 79 to guide the primary spool body along theinner surface 81 of the secondary spool body. The other end of theprimary spool body 62 defines aforward head 63 which is adapted to engagepiston head 26. The outer circumference of the forward head terminates in anouter rib 76 having ashoulder 77 cut therein. Anescape port 75 is cut through theouter rib 76 so that gases exhausted by the returningpiston 26 escape throughport 75 in theforward head 63 intochamber 83 fonned by the primary spool body and secondary spool body in thespool chamber 58. Theshoulder 77 is adapted to form a channel or seat in cooperation with the secondary spool to hold O-ring 78. Theshoulder 77 in cooperation with the secondary spool body places the O-ring 78 under compression so that the O-ring will expand toward thepiston 26 thus forcing theprimary spool body 62 forward when the compressive forces of thepiston 26 on theforward head 63 of the primary spool body are lessened.

As shown in FIGS. 1, 4 and 5, asecondary spool body 79 having abore 80 therethrough surrounds theannular rib 70 of theprimary spool body 62 to form the O- ring seat for O-ring 74. The rear of thesecondary spool body 79 has a plurality ofradial slots 82 cut from the outer surface of thespool body 79 to thebore 80 so that when the rear end wall of thesecondary spool body 79 engages the rear wall ofbody chamber section 59, theannulus 87 is in communication withbore 80. The outer surface of thespool body 79 is stepped outward from the end wall to define ashoulder 84 and aseat 85 which are adapted to seat and hold a free floating O-ring 86. The forward portion of thesecondary spool body 79 takes the form of anannular ring 88. Thering 88 has anannular notch 89 cut into it to form the other part of the seat for O-ring 78, in cooperation with the abuttingshoulder 77 of the primary spool body. It should be noted that the abuttingshoulder 77 of the primary spool body does not form a level seat for O-ring 78 when it abutsnotch 89.Exhaust channels 90 are provided through thering 88 so that the exhaust gas moved by the return of thepiston 26 can pass fromexhaust area 87 through primaryspool exhaust port 75 intochamber 83. Fromchamber 83 the gas passes throughchannels 90 intoexit port 92 and theexhaust ring 94 of the inlet valve body. The gas is carried by theexhaust ring 94 to exhaustconduit 95 in theouter body 22 where the gases are vented to the atmosphere.

In the unit, awasher 116 is preferably placed under the head of the plug housing in contact the-inlet valve body surrounding O-ring 118 to provide a suitable gas seal. In addition, inlet valve body O-rings 120 and 122 are placed inrespective channels 124 and 126 of the inlet valve body so that the inlet gas is sealed between these O-rings.

The unit is maintained in its readiness condition by means of acoil spring 25 acting on thepiston 26, which spring exerts a force greater than that developed by thespring 108, plus the gas pressure acting on the area of the diameter of thebody 54. A trigger notch (not shown) is located in anoutput shaft 24 integral with thepiston 26. Upon activation of atrigger 27 theoutput shaft 24 and itsintegral piston 26 move in the direction of arrow A. Then, under the force ofspring 108 and that developed by the pressurized gas, thepilot valve body 54, thespool bodies 62, 79 and thepiston 26 move in unison until the front face of thepilot valve body 54 abutssurface 60 of theinlet valve body 30.

The piston is pulled further forward by the trigger to allow the force of the gas pressure passing throughbore 97 of the pilot valve body to act against the rearward surface of theprimary spool 62 in combination with the resilient action of O-ring 78 againstshoulder 77 to move theprimary spool body 62 until the drivinghead 63 of the primary spool body abuts against thepiston chamber walls 29 creating a seal therewith. Thepilot valve body 54 cannot follow theprimary spool body 62 becauseport 56 is smaller than theshoulder 103 of the pilot valve body. Thus, after projectingtip 102 of thepilot valve body 54 projects intoport 56 the pilot valve body shoulders 103 strike the flat surface of thecontact area 60 stopping movement of the pilot valve body. Pressurized gas pours through thebore 96 of the pilot valve body into thespool chamber 58 to seat O-ring 74 againstshoulder 72, guide ring and theinner surface 81 of the secondary spool body to form a gas-tight seal. As theprimary spool body 62 is moved forward, gas continues to pass throughorifice 66 in theprimary spool body 62 into the lesser pressure ofchamber 64 of the primary spool to drivepiston 26 forward. At the same time that pressurized gas begins to enter thespool chamber 58 the gas travels throughradial slots 82 of the secondary spool body causing the O-ring 86 to seat against theshoulder 84, end wall and the inner surface of thespool chamber 58 to form a gas-tight seal. When theprimary spool body 62 has traveled forward, the gas pressure pushes the secondary spool body forward until its forwardedge contacts shoulder 77 of the primary spool body. The contact between theprimary spool shoulder 77 and the secondary spool seats O-ring 78 in a state of compression so that it can act on the primary spool body when thepiston 26 is removed from contact with the primary spool body.

When thepiston chamber 59 is filled with gas, the pressure ratios become such that the spool mechanism is returned rearward to its initial position. As a greater area of pressure is formed on the face of the primary spool body on the piston side as opposed to the lesser area of pressure formed on the rear surfaces of the primary spool body and secondary spool body, the greater force pushes the primary spool body rearward by carrying both spool bodies back until the flat end surface of thetip projection 68 is seated against the pilotspool body lip 102 to seal the pilot valve body bore 96 and close the valve. As the spool mechanism is returned, gas pressure acting on the diameter of thepilot valve body 54 serves along withspring 108 to absorb the effect of thetip projection 68 striking thelip 102. This cushioned action eliminates impact onlip 102 so that the surfaces will continue to form a gas-tight seal after repeated use.

Functionally, the pilot valve works fully well withoutspring 108. The purpose ofspring 108 is to insure that the valve is in the closed position when initially pressurized. The force due to pressure acting on pilot valve body is several times greater than that ofspring 108. For example, in the preferred embodiment the pressure force on thespring 108 is less than one pound with the pressure force acting on the pilot valve body being equal to to 6 pounds.

A gas exhaust is provided in the apparatus as the pressurized gas returned by the returningpiston head 26 acted on byspring 25, is forced into theannular channel 87 formed by the forward face of the primary spool and theinner casing 29, theinlet valve body 30 and O-ring 78. The O-ring 78 forms a gas-tight seal so that the gas passes fromannular channel 87 through the primary spool body atport 75 into anannular chamber 83 formed by theprimary spool body 62 and thesecondary spool body 79. The gas exits fromchamber 83 throughpassage 90 andport 92 into an annular exhaust ring orchannel 94 which is connected to the atmosphere byexhaust channel 95. At this time, the apparatus is ready to begin a repeat cycle of operation.

While the preferred embodiment of the invention has been disclosed, it is understood that the invention is not limited to such an embodiment since it may be otherwise embodied in the scope of the appended claims.

What is claimed is:

1. A gas powered driving unit for converting gas pressure into rectilinear motion in a drive shaft, the unit comprising a main casing, a piston chamber having an abutment surface at one end thereof, piston means including a drive shaft mounted for reciprocation in said piston chamber, an inlet valve body mounted in said main casing adjacent said piston means, said inlet valve body defining a spool chamber and a valve chamber interconnected by a port, spool means slidably mounted in said spool chamber, said spool means comprising a primary spool body and a secondary spool body, each said body being capable of independent movement within said spool chamber, valve means mounted in said valve chamber, gas feed means leading to said valve means for the introduction of pressurized gas, said valve means being constructed to convey gas from said gas feed means into said spool chamber, said pri mary spool body being slidably mounted in said spool chamber and in one position sealing against said valve means to effect the sealing of said valve means stopping gas conveyance of said valve means, means biasing said primary spool body into said one position trigger means for unseating said primary spool body from said valve means and for enabling said pressurized gas to initially thrust said primary spool body and then said secondary spool body in the direction of said piston means until in contact with said abutment surface, and for introducing said pressurized gas to said piston chamber to thrust said piston means away from said spool means, said primary and secondary spool bodies being together returned by gas pressure into positions wherein said primary spool body seats against said valve means to intercept the passage of pressurized gas therethrough, and exhaust means disenabled when said piston means is thrust away from said spool means by said pressurized gas, and enabled to exhaust the gas from said piston chamber, whereby said piston means moves towards said spool means.

2. A gas powered driving unit for converting gas pressure into rectilinear motion in a drive shaft, the unit comprising a main casing, piston means including a drive shaft reciprocally mounted in said casing, an inlet valve body mounted in said main casing, said inlet valve body defining a spool chamber and a valve chamber interconnected by a port, spool means slidably mounted in said spool chamber, said spool means comprising a moveable primary spool body and an independently moveable secondary spool body, means biasing said piston means against said primary spool body said primary spool body abutting said secondary spool body to form a substantially ring shaped seat, a first O-ring housed within said seat, said O-ring providing a gastight seal between the inlet valve body and said spool means and adapted to urge said primary spool away from said secondary spool when pressure from said piston means acting on said primary spool body is lessened, valve means mounted in said valve chamber, gas feed means connected to said valve means for the introduction of pressurized gas, said valve means being adapted to convey pressurized gas from said feed means into said spool chamber to move said spool means, said primary spool body being slidably mounted in said spool chamber to assume a position in repose seating against said valve means to effect the sealing of said valve means and stop the conveyance of gas by said valve means, trigger means for unseating said primary spool body from said valve means, and for enabling said pressurized gas to be conveyed into said spool chamber, and exhaust means disenabled when said piston means is thrust away from said spool means by said pressurized gas, and enabled for exhausting gas from said main casing, whereby said piston means moves towards said spool means.

3. A driving unit as claimed inclaim 2 wherein the depth of the substantially ring shaped seat section formed by the primary spool body is less that the depth of the seat section formed by the secondary spool body.

4. A driving unit as claimed inclaim 2, wherein said valve means has a throughgoing passage allowing gas to pass therethrough into said spool chamber.

5. A driving unit as claimed inclaim 2, wherein said inlet valve body defines a stepped spool chamber and the outer surface of the valve body defines a plurality of annular rings carved into the inlet valve body with feed means being provided in said inlet valve body to connect said valve chamber with a source of gas.

6. An inlet valve body as claimed in claim 5, wherein said inlet valve body includes a filter chamber therein, said filter chamber being connected to said valve chamber by a passageway.

7. An inlet valve body as claimed in claim 5, wherein each of said spool chamber steps has a different diameter, the larger step chamber section being of sufficient diameter to hold the primary spool and the other stepped section being of sufficient diameter to hold at least a portion of the secondary spool body.

8. A driving unit as claimed inclaim 2, wherein said primary spool body has a forward head, said forward head being adapted to engage said piston means, with the other end terminating in a projecting tip, said projecting tip being adapted to engage said valve means to effect the sealing of gas passing through said valve means.

9. A primary spool body as claimed in claim 8, wherein said forward heads outer edge forms a rib with a shoulder cut therein, said shouldered rib forming a substantially ring shaped seat in cooperation with the second spool to hold an O-ring, said shoulder cooperating with said secondary spool body to place said O-ring under compression so that the O-ring will expand toward the piston means forcing the primary spool body away from the secondary spool body when the compressive forces of the piston means are removed from the forward head of the primary spool body.

10. The primary spool body as claimed in claim 9, wherein a port is cut through the outer rib of said forward head.

11. A gas powered drive unit as claimed inclaim 2, wherein said secondary spool body has a substantially annular body configuration with a bore out therethrough and a primary spool engaging rib projecting from said annular body.

12. A secondary spool body as claimed in claim 11, wherein said secondary body rib has a shoulder cut therein, said shoulder being adapted to engage against the primary spool body to form a seat for an O-ring.

13. A secondary spool body as claimed in claim 11, wherein one end of said secondary spool body has a plurality of radial slots formed therein.

14. A gas-powered driving unit for converting gas pressure into rectilinear motion in a drive shaft, the unit comprising a main casing, an inner casing mounted in said main casing, said inner casing defining a piston chamber, piston means slidably mounted in said piston chamber, said piston means comprising a drive shaft, a piston head connected to said drive shaft, said piston head having a ring out therein, an O-ring mounted in said ring, and spring means surrounding said drive shaft and biasing said piston head, an inlet valve body mounted in said main casing adjacent said inner casing, said inlet valve body defining an interconnected stepped spool chamber and a valve chamber, a plurality of channels cut in the outer surface of said inlet valve body and gas feed means provided in said inlet valve body to connect said valve chamber with a source of gas for the introduction of pressurized gas, spool means slidably mounted in said spool chamber, said spool means comprising a moveable primary spool body and an independently moveable secondary spool body mounted on said primary spool body, said primary spool body comprising a forward head at one end adjacent said piston means, with the other end terminating in a projecting tip and an annular rib projecting from said body, said secondary spool body having a substantially annular configuration with a throughgoing bore, a rib projecting from said annular body to engage said primary spool, said engaging rib abutting said primary spool forward head to form a substantially ring-shaped seat, a first O-ring mounted in said seat to provide a gas tight seal between the inlet valve body and said spool means, a second O-ring mounted around said primary spool body to provide a gas tight seal between said primary spool body and said secondary spool body, a third O-ring mounted around said secondary spool body to provide a gas tight seal between said secondary spool body and said inlet valve body, valve means mounted in said valve chamber for enabling the passage of pressurized gas, said valve means being adapted to engage the projecting tip of said primary spool body to seal gas conveyed by said valve means, trigger means to unseat the projecting tip of said primary spool body from said valve means, and gas exhaust means defined by said spool means and said inlet valve body.

Claims (14)

1. A gas powered driving unit for converting gas pressure into rectilinear motion in a drive shaft, the unit comprising a main casing, a piston chamber having an abutment surface at one end thereof, piston means including a drive shaft mounted for reciprocation in said piston chamber, an inlet valve body mounted in said main casing adjacent said piston means, said inlet valve body defining a spool chamber and a valve chamber interconnected by a port, spool means slidably mounted in said spool chamber, said spool means comprising a primary spool body and a secondary spool body, each said body being capable of independent movement within said spool chamber, valve means mounted in said valve chamber, gas feed means leading to said valve means for the introduction of pressurized gas, said valve means being constructed to convey gas from said gas feed means into said spool chamber, said primary spool body being slidably mounted in said spool chamber and in one position sealing against said valve means to effect the sealing of said valve means stopping gas conveyance of said valve means, means biasing said primary spool body into said one position trigger means for unseating said primary spool body from said valve means and for enabling said pressurized gas to initially thrust said primary spool body and then said secondary spool body in the direction of said piston means until in contact with said abutment surface, and for introducing said pressurized gas to said piston chamber to thrust said piston means away from said spool means, said primary and secondary spool bodies being together returned by gas pressure into positions wherein said primary spool body seats against said valve means to intercept the passage of pressurized gas therethrough, and exhaust means disenabled when said piston means is thrust away from said spool means by said pressurized gas, and enabled to exhaust the gas from said piston chamber, whereby said piston means moves towards said spool means.

2. A gas powered driving unit for converting gas pressure into rectilinear motion in a drive shaft, the unit comprising a main casing, piston means including a drive shaft reciprocally mounted in said casing, an inlet valve body mounted in said main casing, said inlet valve body defining a spool chamber and a valve chamber interconnected by a port, spool means slidably mounted in said spool chamber, said spool means comprising a moveable primary spool body and an independently moveable secondary spool body, means biasing said piston means against said primary spool body said primary spool body abutting said secondary spool body to form a substantially ring shaped seat, a first O-ring housed within said seat, said O-ring providing a gas-tight seal between the inlet valve body and said spool means and adapted to urge said primary spool away from said secondary spool when pressure from said piston means acting on said primary spool body is lessened, valve means mounted in said valve chamber, gas feed means connected to said valve means for the introduction of pressurized gas, said valve means being adapted to convey pressurized gas from said feed means into said spool chamber to move said spool means, said primary spool body being slidably mounted in said spool chamber to assume a position in repose seating against said valve means to effect the sealing of said valve means and stop the conveyance of gas by said valve means, trigger means for unseating said primary spool body from said valve means, and for enabling said pressurized gas to be conveyed into said spool chamber, and exhaust means disenabled when said piston means is thrust away from said spool means by said pressurized gas, and enabled for exhausting gas from said main casing, whereby said piston means moves towards said spool means.

3. A driving unit as claimed in claim 2 wherein the depth of the substantially ring shaped seat section formed by the primary spool body is less that the depth of the seat section formed by the secondary spool body.

4. A driving unit as claimed in claim 2, wherein said valve means has a throughgoing passage allowing gas to pass therethrough into said spool chamber.

5. A driving unit as claimed in claim 2, wherein said inlet valve body defines a stepped spool chamber and the outer surface of the valve body defines a plurality of annular rings carved into the inlet valve body with feed means being provided in said inlet valve body to connect said valve chamber with a source of gas.

6. An inlet valve body as claimed in claim 5, wherein said inlet valve body includes a filter chamber therein, said filter chamber being connected to said valve chamber by a passageway.

7. An inlet valve body as claimed in claim 5, wherein each of said spool chamber steps has a different diameter, the larger step chamber section being of sufficient diameter to hold the primary spool and the other stepped section being of sufficient diameter to hold at least a portion of the secondary spool body.

8. A driving unit as claimed in claim 2, wherein said primary spool body has a forward head, said forward head being adapted to engage said piston means, with the other end terminating in a projecting tip, said projecting tip being adapted to engage said valve means to effect the sealing of gas passing through said valve means.

9. A primary spool body as claimed in claim 8, wherein said forward head''s outer edge forms a rib with a shoulder cut therein, said shouldered rib forming a substantially ring shaped seat in cooperation with the second spool to hold an O-ring, said shoulder cooperating with said secondary spool body to place said O-ring under compression so that the O-ring will expand toward the piston means forcing the primary spool body away from the secondary spool body when the compressive forces of the piston means are removed from the forward head of the primary spool body.

10. The primary spool body as claimed in claim 9, wherein a port is cut through the outer rib of said forward head.

11. A gas powered drive unit as claimed in claim 2, wherein said secondary spool body has a substantially annular body configuration with a bore cut therethrough and a primary spool engaging rib projecting from said annular body.

12. A secondary spool body as claimed in claim 11, wherein said secondary body rib has a shoulder cut therein, said shoulder being adapted to engage against the primary spool body to form a seat for an O-ring.

13. A secondary spool body as claimed in claim 11, wherein one end of said secondary spool body has a plurality of radial slots formed therein.

14. A gas-powered driving unit for converting gas pressure into rectilinear motion in a drive shaft, the unit comprising a main casing, an inner casing mounted in said main casing, said inner casing defining a piston chamber, piston means slidably mounted in said piston chamber, said piston means comprising a drive shaft, a piston head connected to said drive shaft, said piston head having a ring cut therein, an O-ring mounted in said ring, and spring means surrounding said drive shaft and biasing said piston head, an inlet valve body mounted in said main casing adjacent said inner casing, said inlet valve body defining an interconnected stepped spool chamber and a valve chamber, a plurality of channels cut in the outer surface of said inlet valve body and gas feed means provided in said inlet valve body to connect said valve chamber with a source of gas for the introduction of pressurized gas, spool means slidably mounted in said spool chamber, said spool means comprising a moveable primary spool body and an independently moveable secondary spool body mounted on said primary spool body, said primary spool body comprising a forward head at one end adjacent said piston means, with the other end terminating in a projecting tip and an annular rib projecting from said body, said secondary spool body having a substantially annular configuration with a throughgoing bore, a rib projecting from said annular body to engage said primary spool, said engaging rib abutting said primary spool forward head to form a substantially ring-shaped seat, a first O-ring mounted in said seat to provide a gas tight seal between the inlet valve body and said spool means, a second O-ring mounted around said primary spool body to provide a gas tight seal between said primary spool body and said secondary spool body, a third O-ring mounted around said secondary spool body to provide a gas tight seal between said secondary spool body and said inlet valve body, valve means mounted in said valve chamber for enabling the passage of pressurized gas, said valve means being adapted to engage the projecting tip of said primary spool body to seal gas conveYed by said valve means, trigger means to unseat the projecting tip of said primary spool body from said valve means, and gas exhaust means defined by said spool means and said inlet valve body.

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