US2959155A

US2959155A - Drive piston for a fluid operated motor

Info

Publication number: US2959155A
Application number: US714412A
Authority: US
Inventors: Richard E Powers; Charles W Weis
Original assignee: POWERS WIRE PRODUCTS Co I
Current assignee: SPENAX Corp A CORP OF INDIANA; POWERS WIRE PRODUCTS Co I; POWERS WIRE PRODUCTS COMPANY Inc
Priority date: 1958-02-10
Filing date: 1958-02-10
Publication date: 1960-11-08
Anticipated expiration: 1977-11-08

Description

2 Sheets-Sheet 1 R. E. POWERS ErAL DRIVE PISTON FOR A FLUID OPERATED MOTOR- Nov. 8, 1960 Filed Feb. 10, 1958 IP/c/MRD Nov. 8, 1960 R. E. POWERS ETAL DRIVE PISTON FOR A FLUID OPERATED MOTOR 2 Sheets-Sheet 2 FIG. 6.

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5 a m m T m w E N v M m w 7 A M D s PM r M m M Raw I I/// /r///// ///7//////// Unite DRIVE PISTON FOR A FLUID OPERATED MOTOR Filed Feb. 10, 1958, Ser. No. 714,412

14 Claims. (Cl. 121--13) This invention is concerned with a drive piston for a fluid operated motor and particularly relates to a self returning piston that is coupled to an elongate driver blade, such as, for example, a blade in a fastener driving tool, it being a general object of this invention to provide an extremely simple and practical drive piston that is reliably coupled to the driving blade and which also returns to a retracted position at the end of each work stroke.

The manufacture of a tool for driving fasteners is complicated by the construction of a satisfactory drive motor, that is, a motor that not only provides the desired functions but which is also reliable in its operation. This invention relates to fluid operated tools and more specifically to a pneumatic tool wherein an elastic fluid is relied upon to power the tool. In this case, a cylinder and piston type motor is employed, and for the purpose of illustration such a motor is shown employed in a staple driving tool.

In a tool of the type under consideration, wherein a piston is employed to drive a blade, the work stroke of the piston is effected by applying fluid under pressure to one end of the cylinder, after which a return stroke of the piston must be effected. In order to effect a forceful work stroke, a latching means is adapted to restrain the piston until sufficient volume of fluid under pressure is contained within the cylinder for effecting said stroke. In order to effect a return stroke, a spring may he employed, but it is preferred that a fluid operated means be employed thus eliminating said spring. However, the cylinder and piston motor is not double acting in the common sense since one end of the cylinder remains open to atmosphere allowing for rapid movement of the piston toward that end of the cylinder.

In addition to the operational functions above referred to, the driving blade must be satisfactorily coupled to the piston, and both the piston and the driver blade must be arrested or damped at the end of the work stroke. In tools of the type under consideration the driver blade is long and flexible, and under operating conditions it warps or bends and creates undue strain at the upper end portion thereof which is ordinarily anchored directly to the piston. Said strains result in breakage of the blades and general damage to the piston and cylinder. A damper, in the form of a bumper, is ordinarily carried at the end of the cylinder to arrest the piston, and in some cases the driver blade is shiftably carried by the piston and damped relative to the piston. In the structure herein disclosed, the above mentioned functions of coupling the driver blade to the piston, and the independent damping of the driver blade and of the piston are all satisfied by one simple coupler construction as hereinafter described.

An object of this invention is to provide a piston for operation in a tool of the type under consideration wherein the driver blade is universally coupled to the piston, within limits, in order to avoid undue strains on the blade. With the structure provided, the flexible States Patent "ice blade can deflect and bend from normal alignment without affecting the anchoring thereof.

It is an object of this invention to provide a piston for operation in a tool of the type under consideration wherein the driver blade is arrested or damped at the end of the work stroke independently of the. piston. The coupler that is provided includes means to damp the driver blade.

It is still another object of this invention to provide a piston for operation in a tool of the type under consideration wherein the piston is arrested or damped at the end of the work stroke independently of the driver blade. The coupler that is provided includes means to damp the piston.

Another object of this invention is to provide a piston for operation in a tool of the type under consideration wherein a single coupling device is employed to join the driver blade and piston and to independently damp both the driver blade and piston. With the structure provided, the coupling device is a single unit or part that universally, or flexibly, joins the driver blade and piston and which is carried by the piston to snub movement of both the driver blade and piston at the end of the work stroke.

Further, it is an object of this invention to provide a piston for operation in a tool of the type under consideration wherein a simple and improved valve element controls fluid flow through the piston in order to effect a return stroke to complete the cycle of operation of the tool.

It is still a further object of this invention to provide a piston for operation in a tool of the type under consideration wherein a minimum of parts and elements are involved and wherein the operation of the tool is highly improved and made more reliable. With the structure herein disclosed there are essentially but three simple ruggedly formed parts involving the piston, the coupler anda head thatis anchored to the driver blade. In addition, there is a single element operating as a valve.

The various objects and features of our invention will be fully understood from the following detailed description of a typical preferred form and application of our invention, throughout which description reference is made to the accompanying drawings in which:

Fig. l is a side sectional view of a fastener driving tool incorporating the piston construction of the present invention. Fig. 2 is an enlarged detailed sectional view of a portion of the structure shown in Fig. 1. Fig. 3 is an enlarged detailed view of a portion of Fig. 1 and showing the parts in a different operational position. Fig. 4 is a sectional view taken as indicated by line 44 on Fig. 1. Figs. 5 and 6 are enlarged detailed sectional views of a portion of the structure, Fig. 5 showing the moving parts in an up position and Fig. 6 showing the parts in a down position. Fig. 7 is a sectional view taken through the piston and as indicated by line 7-7 on Fig. 5, and Fig. 8 is an enlarged detailed view of a portion of the piston and taken as indicated by line 88 on Fig. 7.

The cylinder and piston mechanism of the present invention is shown incorporated in a pneumatic or air 0perated tool or fastener driving device. The drive piston for fluid operated motors that we have provided may be used in connection with a stapling gun and, therefore, in the drawings we have illustrated this type of tool. It is to be understood, however, that the present invention is not limited to this particular kind of tool and may be employed in connection with various tools having a cylinder and piston driving means. I s v The tool, as illustrated in the drawings, is adapted to be handled manually and involves, generally, a frame A having a body portion and a handle or grip portion 11, a head B carried by the frame A and adapted to direct fasteners into a piece of work, a magazine C for handling a supply of fasteners such as staples are receiv'ed and handled by the head, a driver blade D a latching means F adapted to cooperate with and control operation of the driver blade D, a piston G having differentially formed portions X and Y operable in a cylinder 12 in the frarne A and adapted to drive the blade D, a coupler H operatively joining the driver blade D and piston G, fluid pressure handling means Z carried by the piston G, and valve means I adapted to control the supply of fluid under pressure to actuate the piston G through a work stroke and to be handled by the means Z to effect a return stroke.

The frame A carries the various elements of the tool, and is shaped to be conveniently handled by a person. The frame A involves, generally, the body portion 10 and the handle or grip portion 11. The body portion 10 is a simple elongate part having a cylinder 12 extending longitudinally thereof and having an opening or passage 17 extending longitudinally through the head thereof at the lower end of the cylinder 12, and has a recess 14 at the opening 17 for receiving and positioning the head B.

The handle or grip portion 11 is provided to give the person handling the tool a convenient means to hold the tool and is a simple grip of ordinary construction that projects from the body 10. In practice, the grip 11 may be substantially normal to the axis of the body and may project therefrom as clearly shown in Fig. 1 of the drawings.

In structures of the type under consideration, it is common practice to provide a fluid pressure supply connection 18 at the grip 11, such as a pneumatic hose or the like, and also to include a control means at the grip 11. It is to be understood that any suitable fluid pressure supply can be provided without aflecting the present invention. In the case illustrated the hose of the power connection 18 is attached to the grip 11 through a quick disconnect and the valve means I is under control of a finger operated trigger 21.

The head B is, in effect, an extension of the body 10 of the frame A and is provided to receive and deliver fasteners such as staples to the Work being acted upon by the tool. The head B is carried by the body in the recess 14 and is provided with a longitudinal guideway 22 that extends through and opens at the ends of the head B. The head B has a bottom face 23 engaged with the recess 14 and it has a front end face 25 engageable with the work.

In the particular form of the invention shown, the guideway 22 is adapted to handle fasteners or staples S that are U-shaped and formed of wire, or the like, having a pair of sharpened ends (see Fig. 4). The staples referred to are substantially elongate with straight parallel shanks joined by a curved back. It will be apparent how the guideway 22 can be proportioned so that it will readily pass the staples with clearance and will act upon the staples to guide them as they are delivered through the head B and from the tool. The guideway 22 is a continuation of the passage 17 above described and guides the driver blade D of the tool as Well as the staples S that are handled thereby.

A fastener or staple receiving opening 32 extends laterally through the head B, which opening enters the bottom face 23 of the head and opens into the passage 22 so that the staples S fed to the head B are properly guided and aligned with the passage 22 before they are engaged by the driver blade D of the mechanism.

The magazine C is adapted to handle a supply or stack of fasteners or U-shaped staples S and involves, generally, a case 35 carried by the frame A, a guide 36 within the case 35, a follower 37 adapted to advance the fasteners or staples, and a feed spring 38 yieldingly urging the follower toward the head B. The case 35 is carried by the body 10 and is an elongate part that projects laterally therefrom. The case is shell like in form and the guide 36 is a core like part that is coextensive with the case 35 and is carried between the side walls thereof. As shown in Fig. 4 of the drawings, the case 35 and guide 36 are shaped so that a longitudinal passage 40 is formed, which passage conforms in general configuration to the U-shaped staples S which are handled by the head.

The guide 36 enters the fastener or staple receiving opening 32 and terminates in a flat end 39 that occurs in the plane of the bottom wall of the guideway 22. The follower 37 conforms with the configuration of and is slidably carried in the passage 40 and is yieldingly urged toward the head B by the feed spring 38. Means is provided to prevent the follower 37 from entering the guideway 22. The fasteners or staples S are inserted into the magazine C through the open top thereof by simply engaging them over the guide 36 ahead of the follower 3'7 tensioning the spring 38. As clearly shown in Fig. l, a spring biased latch 30 secures the follower 37 in a retracted position when desired, thus facilitating insertion of the fasteners.

The driver blade D is essentially a slender elongate part rectangular in cross sectional configuration and terminates at its forward end in a flat fastener or staple driving face 45. The blade D has a lower staple driving portion at the forward end thereof which occupies the guideway 22 of the head B, and the blade D has an upper driven portion 46 at the rear end thereof which couples to a head E to have driving engagement with the piston G.

That latching means F that may be employed in tools of the type under consideration is adapted to cooperate with and control operation of the piston G, later described. The means F is provided to couple with and to hold the piston G at the upper end of the cylinder 12 and to release the piston G when sufiicient fluid pressure has been established in the cylinder to effect the desired work stroke. 7 The latching means F may involve suitable mechanism to carry out the function referred to without affecting the present invention. For example, the latching means =F may involve means adapted to releasably couple to a head 57 that projects from the top of the piston G, and 'a pressure responsive release means 58 adapted to release the head 57. from the upper end of the cylinder 12. The upper end of the cylinder 12 remote from the head B is closed by a cap 59, the latching means F being threadedly engaged through an opening in the cap for adjustment.

The piston G that we provide operates in the cylinder 12 andhas driving engagement with the driver blade D. The piston G is adapted to drive or move the driver blade D forwardly or downwardly and is adapted to be damped or snubbed separately from the driver blade D. The cylinder 12 is incorporated in the body 143 of the frame A on the longitudinal axis thereof, and is supplied with fluid under pressure by the valve means I, as hereinafter described. The piston G is freely carried in the cylinder 12 and is actuated to retract and to advance in the cylinder. In the particular tool illustrated throughout the drawings the ordinary compression return spring is eliminated which is usually provided within the cylinder 12 ahead of the piston G to return the piston to a retracted position. The tool illustrated is operated entirely by fluid pressure so that when the trigger 21 of the tool is operatedthe piston G is moved to the bottom of the cylinder 12, and so that when the trigger 21 is released the piston G is moved to the top of the cylinder 12. The trigger 21 controls the valve means I later described.

In accordance with the present invention the piston G is light in weight, preferably of magnesium, or the like, to provide minimum inertia therein and is characterized by upper and lower portions X and Y of'dilferent diameter establishing a chamber 60 therebetween. The piston G occupies the interior of the cylinder 12 in which case the cylinder 12 is also characterized by upper and

lower bores

62 and 63 of different diameters. The return means that we have provided involves the provision of said differing diameters in connection with the cylinder 12 and piston B, and further involves the provision of a pressure supply means Z in communication with the-cylinder 12 between the portions X and Y of the piston G. As illustrated, the lower bore 63 is somewhat smaller in diameter than the upper bore 62. Thus, there is a diiferential between the eflective diameters of the two

bores

62 and 63.

The piston G is a shell-like body 64 of material, for example light weight material as above specified, and has upper and lower piston heads 65 and 66 at the upper and lower portions X and Y respectively. The head 65 is slidably operable in the bore 62 of the cylinder 12 while the head 66 is slidably operable in the bore 63 of the cylinder 12. As shown, suitable sealing rings 67 and 68 are provided at the two

heads

65 and 66, and are preferably O ring type sealing rings carried in annular grooves provided in the peripheries of the heads, respectively. As shown, a turned portion 69 extends between the

heads

65 and 66, preferably of a diameter slightly smaller than the lower head 66.

The valve means I is a fluid pressure supply and exhaust means that admits and exhausts operating fluid to and from the top end of the cylinder 12 hereinabove described. The valve means I is preferably formed in and carried by the frame A of the tool and, as shown, is housed in the grip 11. In the case illustrated, the valve means I involves a valve chest 85 formed or machined in the grip 11, and a slide 86 that is shiftably carried in the chest to control flow of fluid. As shown, the chest 85 extends through the grip 11 to open at both the front and back thereof, there being a recess 87 at the back of the chest and a recess 88 at the front of the chest. The recesses 87 and 88'are in the form of counterbores, the recess 87 handling the inlet of fluid under pressure and the recess 88 handling the exhaust of fluid. A pressure supply passage 89 connects 18 while the recess 88 simply opens to the outside atmosphere at the exterior of the grip 11.

The slide 86 of the valve means I is freely shiftable in the chest 85 and involves a plunger 90 that is operable in the recess 88 and a valve disc Q1 that is operable in the recess 87. A spring 92 is seated in a cap 93 that confines the spring to the recess 87, the spring engaging and yieldingly urging the disc 91 into contact with a seat in the recess. An extension 94 projects from the plunger 90 and is engaged by and is operated by the trigger 21. When the valve means I is actuated to the position shown in Fig. 3 the disc 91 is lifted from the seat allowing passage of fluid under pressure to a passage 100 that is in communication With the upper end of the cylinder 12, while the plunger 90 enters the chest 85 to close the exhaust recess 88. When the valve means I is released to the position shown in Fig. l the disc 91 is seated to close the recess 87 while the plunger 90 opens the recess 88 to exhaust fluid from the upper end of the cylinder 12.

. In accordance with the invention we have provided the fluid pressure handling means Z that is incorporated in the piston G between the upper and lower portions X and Y thereof. The means Z is a valve means that allows fluid to flow in one direction only and checks the flow of fluid in the other direction so that fluid pressure applied to the cylinder 12 above the piston G :is directed to the chamber 60 and is retained in the chamber 60 by action of the valve of the means Z. As

shown, the means Z is incorporated in the construction of the piston G (see Figs. 7 and 8) and involves a valve .seat 100, a port 101 opening at the seat, and a valve element 102 engaged with the seat to close the port. The valve seat 100 is a circumferentially formed seat at the exterior of the piston G and formed in the intermediate cylindrical portion 69 of the piston between the portions X and Y. The port 101, or ports as shown, extends from the interior of the piston G in communication with the upper end thereof and opens at the seat 100. The valve element 102 is a circular element, preferably a band or the like, of elastic material. In the case illustrated, the valve element 102 is an elastic band of rubber that encircles the piston G and which is contricted onto the seat 100. As shown, the valve element 102 normally closes the port 101 so that external fluid pressure will not enter the piston G, but so that internal fluid pressure is free to pass into the chamber 60. In practice the band forming the valve element 102 is circular in cross section and in the form of an O ring sealing ring, and in which case the seat is arcuate in form to cooperate with the inner diameter of the element 102. It will be apparent how the O ring shaped valve element 102 seals fluid under pressure in the chamber 60.

When fluid under pressure is applied to the upper end of the cylinder 12 the piston G moves downwardly and the chamber 60 is charged with fluid under pressure. Upon release of fluid from the upper end of the cylinder 12 the valve 102 of the means Z operates to retain fluid under pressure in the chamber 60. The fluid that is employed to operate the piston G is air, or the like, which is elastic or compressible. The compressed fluid that is captured in the chamber 60 tends to expand and acts against the larger piston head 65 to move it upwardly to the position shown in Fig. 5.

In accordance with the invention we have provided a coupler H that universally couples the driver blade D to the piston G and which also involves means to arrest or damp the piston G and blade D independently of each other. The coupler H cooperates a head E at the upper end of the driver blade D and is characterized by a single body 99 of resilient or elastic material, preferably of rubber or the like, that flexibly joins the piston G to the blade D and which engages the bottom 12 of the cylinder 12 to arrest the piston G and blade D.

The driving head E is rigidly coupled to the driver blade D and is free of the piston body 64 of the piston G. In accordance with the invention the head E is formed of a light weight material, for example of aluminum or the like, to provide minimum inertia in the driver blade D. In practice, the head E is carried within a recess 105 entering the lower end 66' of the piston G and is positioned and guided therein by the coupler H, as hereinafter described. As shown, the recess has a flat bottom 106 in a plane normal to the central longitudinal axis of the piston G, and the recess has a smooth cylindrical wall 107 turned concentric with said axis. The head E has driving engagement with the piston body through the bottom 106 and has clearance with the wall 107.

The head E is characterized by a radially projecting flange 110 and a center portion 111 that is coupled to the driver blade D. The flange 110 forms a disc-shaped element that has an upper face 112 for engagement with the bottom 106 and has a lower face 113 for engagement with the coupler H. The upper face 112 is spherically shaped to have a point of engagement with the bottom 106, that is, the face 112 is convexly formed concentrically with the axis of the blade D. The center portion 111 is in theform of 21 depending extension substantially smaller in diameter than the flange 110 and of substantial longitudinal extent. Said center portion 111 is round in cross sectional configuration and has centering engagement with the coupler H.

The center portion 111 is provided for coupling the driver blade D to the head E establishing a positive connection between these two elements so that they operate together as a unit. In the case illustrated, the head E has a slot 115 provided therein and entering the center portion from the lower end thereof. The slot 115 is vertically disposed and extends diametrically of the head intersecting the central axis thereof. As shown, the slot 115 terminates in a flat bottom adapted to have flat driving engagement with the top end of the blade D. The driver blade D slidably enters the slot 115 and a pin 117 is passed diametrically through the head and blade coupling the two elements together.

The coupler H of resilient or elastic material retains the head E within the recess 105 and centered with the piston G. Further, the coupler H holds the head E in working position relative to the bottom 1%. The body 99 of material forming the coupler H has a central bore 120 extending therethrough to receive the central portion 111 of the head E, and it has a flat top 121 adapted to have flat engagement with the bottom face 113 of the flange 110. The outer diameter of the center portion 111 has frictional engagement with the bore 120, the coefficient of friction between the head E and bore being substantial due to the particular materials involved, as described.

The coupler H of resilient or elastic material is retained in the recess 105 and centered with the piston G. The body 9 of material forming the coupler H is carried by the piston G and has a cylindrical outer wall 122 that is received within the recess 105 to have frictional engagement therewith. That is, the wall 122 has engagement with the cylindrical wall 107, the coefiicient of friction between the body 99 and piston G being substantial due to the particular materials involved, as described.

The coupler H is characterized by means to arrest or damp the piston G and blade D independently of each other. That is, means is provided in the coupler H to individually damp the piston G and/or the blade, to the end that the piston alone can be damped, and to the end that the blade D can be damped, all as circumstances require. As shown, the coupler H is characterized by a buffer portion 125 that underlies the piston G and/or head E, said buffer portion 125 being a circular ringshaped part having an outer peripheral portion underlying the bottom 66 of the piston G, and/or an inner peripheral portion underlying the face 113 of the head E. The buffer portion 125 has a bottom 126 and an outer wall 127, the bore 120 forming the inner wall thereof.

The outer peripheral portion of the buffer portion 125 has an upper face 128 projecting radially from the wall 122, while the inner peripheral portion is joined integrally with the central portion of the body 99 that is secured in the recess 105. The face 128 has fiat engagement with the bottom 66 of the piston G so that the outer peripheral portion of the buffer portion 125 acts beneath the piston G to arrest it. The top 121 has flat engagement with the face 113 so that the inner peripheral portion of the buffer portion 125 acts beneath the head E to arrest the blade D. As illustrated, the buffer portion 125 is preferably formed with both outer and inner peripheral portions so that both the piston G and blade D are arrested simultaneously and independently by compression of said individual portions of the buffer against the bottom 12 of the cylinder 12.

From the foregoing, it will be apparent that the coupler H is carried by the piston G to reciprocate therewith in the cylinder 12. The elements of the coupler are proportioned as shown and the hardness of the body 99 of resilient material is selected in order to gain the best re- :sults, as circumstances require. In the case illustrated the piston G and head E are made of light weight materials, as specified, with the result that low inertia values are involved in said moving parts. Therefore, the driving 'forces in the tool are obtained by introducing a substantial charge of fluid under pressure, and with the re- :sult that a very quick and forceful work stroke is effected.

At the end of the stroke the piston G and/ or the head E are arrested independently of each other through compression of the body 99 of resilient material. Further,

at the end of each work stroke the coupler H is driven into the recess thus maintaining all of the parts in working position relative to each other, said parts remaining in working position due to the frictional engagement therebetween. In addition to the foregoing, the top 112 of the head E is adapted to rock, or roll, upon the bottom 106 of the recess as permitted by the body 99 of elastic material, to the end that the head E and driver blade D seek alignment without undue strain between the blade D and piston G.

Having described only a typical preferred form and application of our invention, we do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to ourselves any variation or modifications that may appear to those skilled in the art and fall within the scope of the following claims.

Having described our invention, we claim:

1. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess with an inner diameter wall, and a buffer means to move with the piston and comprising a body of resilient material with a portion frictionally engaged within said inner diameter Wall in the recess and with a portion projecting from the piston body to engage the end of the cylinder to arrest the piston, there being a bore extending through the body of resilient material and freely passing the driver element.

2. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess with a substantially smooth cylindrical inner diameter wall, and

a buffer means to move with the piston and comprising a body of resilient material with a portion carried in the recess and frictionally engaged with the said inner diameter wall thereof and with a portion projecting from the piston body to underlie the same and to engage the end of the cylinder to arrest the piston, there being a bore extending through the body of resilient material and freely passing the driver element.

3. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder, and a coupler and buffer means comprising a body of resilient material frictionally carried by the piston body and frictionally engaged with the driver element to position it relative to the piston body and with a portion adapted to engage the end of the cylinder to arrest the piston body and driver element.

4. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein, and a coupler and buffer means comprising a body of resilient material with a part frictionally engaged in the recess and with a part projecting from the piston body, there being a bore extending through said parts and frictionally passing and centering the driver element, said body of material being adapted to engage the end of the cylinder to arrest the piston body and driver element.

5. A drive piston fora fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and with a bottom having an axially disposed recess entering therein, and a coupler and bufier means comprising a body of resilient material with a part frictionally engaged in the :recess and with ,a part projecting from and underlying the bottom of the piston body, there being a bore extending through said parts and frictionally passing and centering the driver element, said body of material being adapted to engage the end of the cylinder to arrest the piston body and driver element.

6. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein, a head on the driver element and entering said recess, and a coupling means comprising a body of resilient material frictionally carried in the recess and frictionally engaged with the head of the driver element to solely retain it within said recess.

7. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein, a head on the driver element and carried within the said recess and engageable with the bottom thereof, and a coupling means comprising a body of resilient material frictionally carried in the recess and with an opening passing and frictionally engaged with the head of the driver element to retain it within said recess.

8. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein, a head on the driver element and carried within the said recess and engageable with the bottom thereof, and a coupling means comprising a body of resilient material frictionally carried in the recess and with a bore extending through the body of resilient material and frictionally passing and centering the driver element to retain it within the recess.

9. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein, a head on the driver element and carried within the said recess and having an upper face engageable with the bottom thereof and having a lower face, and a coupling means comprising a body of resilient material frictionally carried in the recess and with a portion projecting from and underlying the piston body and said head, there being a bore extending through the body of resilient material and frictionally passing and centering the driver element to retain it within the recess and the body being adapted to engage the end of the cylinder to arrest the piston body and driver element.

10. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindically shaped body slidably engaged in the cylinder and having an axially disposed recess therein with a fiat bottom, a disc-shaped head joined to the driver element and carried within the said recess and engageable with the bottom thereof, and a coupler and bufler means comprising a body of resilient material with a portion frictionally engaged in the recess and with a portion projecting from the piston and underlying said head and adapted to engage the end of the cylinder to arrest the head.

11. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein with a flat bottom, a disc-shaped head joined to the driver element and carried within the said recess and engageable with the bottom thereof, and a coupler and bufler means comprising a body of resilient material with a portion frictionally engaged in the recess and with a portion projecting from the piston and underlying the said head, there being a bore extending through the body of resilient material and frictionally passing and centering the driver element and the body being adapted to engage the end of the cylinder to arrest the head.

12. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body slidably engaged in the cylinder and having an axially disposed recess therein with a flat bottom, a disc-shaped head joined to the driver element and carried Within the said recess and having an upper face engageable with the bottom thereof and having a lower face, and a coupler and buffer means comprising a body of resilient material with a portion frictionally engaged in the recess to engage the lower face of the head and with a portion projecting from the piston body and underlying the said head, there being a bore extending through the body of resilient material and frictionally passing and centering the driver element and the body being adapted to engage the end of the cylinder to arrest the head.

13. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including a cylindrically shaped body with a bottom and slidingly engaged in the cylinder and having an axially disposed recess therein with a bottom and a cylindrical wall and opening at the bottom of the piston body, a disc-shaped head joined to the driver element and carried in the recess to engage the bottom thereof, and a bufler means comprising a body of resilient material with a cylindrical portion frictionally engaged with the wall of the recess and frictionally passing the head of the driver element and with a butler portion underlying the head of the driver element and the bottom of the piston and adapted to engage the end of the cylinder to arrest the said head and piston.

14. A drive piston for a fluid operated motor and operable in a cylinder to reciprocate a driver element, and including, a cylindrically shaped body with a bottom and slidably engaged in the cylinder and having an axially disposed recess therein with a bottom and a cylindrical wall and opening at the bottom of the piston body, a discshaped head joined to the driver element and carried within the recess to engage with the bottom thereof, and a coupler and bufler means comprising a body of resilient material with a cylindrical portion underlying the head and frictionally engaged with the wall of the recess and with a buffer portion underlying the cylindrical portion and the bottom of the piston, there being a bore extending through the body of resilient material to frictionally pass the driver element and center the head, said buffer portion being adapted to engage the end of the cylinder to arrest the piston body and the driver element.

References Cited in the file of this patent UNITED STATES PATENTS