US3547003A

US3547003A - Fastener driving tool

Info

Publication number: US3547003A
Application number: US737649A
Authority: US
Inventors: Howard B Ramspeck
Original assignee: Duo Fast Corp
Current assignee: Duo Fast Corp
Priority date: 1968-06-17
Filing date: 1968-06-17
Publication date: 1970-12-15
Anticipated expiration: 1987-12-15

Description

United States Patent (Cursory). 308(Cursory), 304(Cursory), 281(Cursory), 290(Cursory), 220, 252, 300, 305(Curs0ry). 207(Curs0ry), 309(Cursory),

[56] References Cited UNITED STATES PATENTS 3,427,928 2/1969 Bade 91/305 3,278,103 10/1966 Juilfs et al.... 91/220 3,278,104 10/1966 Bechtet al... 91/220 3,278,105 10/1966 Juilfs et al.... 91/220 3,405,602 10/1968 Novak 91/281 Primary Examiner-Paul E. Maslousky I Attorne vMason, Kolehmainen, Rathburn & Wyss ABSTRACT: There is provided a pneumatic fastener driving toolhaving control means providing for successive fastener driving operations upon a single depression of the tool trigger. The operating cycle is controlled by the tool piston closing a valve passageway connected sequentially to the atmosphere and to the fluid in the pneumatic return system of the tool driver. The tool is readily adaptable for multiblow operation of a single fastener by the addition of a control valve or element. Additionally a shuttle valve is provided so that the tool may selectively be fired automatically or used as a single- PATENIEDDEBISIQYU I I 3547003 I 2 OF 5 3,. INVENTOR: 3 w 9 Q HowARo B. RAMSPECK N c3 2 BY.-

PATENTEU 08:1 5 I978 saw u 0F 6 INVENTOR:

H WARD B. RAMSPECK m o E g 5.

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, 1 FASTENER muvnvc TOOL- This invention relates to a fastener-driving tool, particularly to a fastener-driving tool including new and improved control means providing for successive fastener driving operations upon a single depression of the tool trigger. A multiple-stroke fastener-driving tool similar to that shown in this application is described and claimed in a copending 115. Pat. application of Howard B. Ramspeck, US. Pat. Ser.N o. 708,330, filed Feb. 26, 1968, now abandoned.

Commercially available pneumatic fastener-driving tools more generally provide a single fastener-driving stroke upon each depression of the tool trigger. However more recently situations have arisen wherein it is desirable .to drive a'plurality of fasteners in successive fastener-driving operations at suitable short intervals upon a single depression of the tool trigger. One such automatic tool isdescribed and-claimed in the U.S. Pat. application Ser. No. 629,244 of Allen R. Obergfell filed Apr. 7, 1967, now abandoned.

Additionally situations have also arisen where it is desirable to drive larger and longer fasteners and therefore the fastenerdriving tool is unable to complete the driving of the fastener in a single stroke. In these situations it would be desirable to provide a fastener-driving tool which will. cycle repetitively until such time as a single fastener has been fully driven, and thereafter will return to its normal position in preparation for the next fastener driving operation. 5,

Additionally it may be sometimes desirable to prevent repetitive cycling of the-tool, so thatbut a single fastener will be driven by each depression of the'trigger. Moreover in the automatic firing or cycling of ,a fastener-drivingtool it' may become desirable to drive one fastener, and thereafter for the tool to return automatically to theautomatic or multifire position. j

An object of the present invention, therefore, is to provide a new and. improved pneumatically actuated fastener-driving tool of the type. to continuously and repetitively operate through its working cycle for a selected interval.

Anobject of the present invention is toprovide a new and improved pneumatically actuated fastener-driving tool of the. type to continuously and repetitively "operate through its working cycle so long as the trigger thereof is depressed.

Another object of the present invention is to provide a new f and improved pneumatically actuated fastener-driving tool of the type to continuously and repetitively cycle during the driving of a single fastener, and to stop cycling upon completion of the driving of the fastener.

Yet another object of the presentinvention is to provide a new and improved pneumatically actuated fastener=driving tool which may be selectively set to automatically cycle so long as the trigger thereof is depressed,'or selectively set to complete a single stroke upon each depression of the trigger.

Another object of the present invention is to provide a newv and improved pneumatically actuated fastener-driving tool which may be selectivelyset to complete a single stroke of which the connection to the atmosphere 'is closed and the passageway is connected to the reservoir through the other 1 port to supply compressed air to the cylinder. This air drives a piston which is slideably mounted in the cylinder and which is connected to a fastener-driving blade downwardly from a normal position adjacent its open upper end to a lower position. During this power stroke of the piston, the air disposed in the cylinder below the piston is discharged. One such control valve for a fastener-driving tool is more fully described in US. Pat. No. 3,173,340 granted on Mar. 16,1965 to Richard H. Doyle et all i In accordance with the present invention, the fastener-driving tool is provided with a pneumatic piston return means for returning the piston to the upper end of the cylinder. A port in I the wall of the cylinder intermediate the stroke of the piston is controlled or closed by movement of the piston or piston ring past the port so as to alternately connect the return air chamber to the control valve, and exhaust the control valve to atmosphere, thereby to cycle the control valve in sequence with the stroke of the piston.

In accordance with another feature of the present invention, the fastener-driving tool is adapted for a multiblow cycling arrangement whereby the fastener-driving tool will repetitively cycle until such time as a fastener is fullydriven, and then the cycling of the tool piston will automatically terminate.

In accordance with yet another feature of the present invention,-a shuttle valve is provided for altering the operation of the tool from-an automatic-fire tool to a single-fire tool, and

for adjusting-the time rate of recycling of the tool. In one embodiment the shuttle valve will return to an automatic-fire position automatically after completion of a single-fire operaoperation upon depressionof the trigger-and which will 7 thereafter automatically return to-the automatic or multifire position.

7 Further objects and advantages ofthe present invention, will become apparentas the following description proceeds and.

the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with these and many other objects, an embodiment of the invention comprises a pneumatically operated fastener-driving tool or apparatus having a housing defining a cylinder and a fluid reservoirfor compressed medium. The cylinder has an openupper end, and the lower end of the cylinder exhausts to the atmosphere. A passageway in the housing communicating with the open upper end of the cylinder includes a first port opening to the atmosphere and a second port communicating with thereservoir. A manuallycontrolled valve normally connects the passageway to the attion.

Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the drawings in which:

FIG. 1 is a fragmentary sectional view of a fastener-driving tool according to the present invention illustrated in its normal position;

FIG. 2 is a fragmentary sectional view of the fastener-driving tool of FIG. 1, illustrated with thepiston moving through its power stroke',

' FIG. 3 is a fragmentary sectional view ofthe fastener-driving tool of FIG. 1, illustrated with the drive piston at the end of its power stroke;

FIG. 4 is a fragmentary sectional view of a fastener-driving tool according to another embodiment of the present invention wherein the tool will repetitively cycle to drive a single fastener until such time as the fastener is fully driven;

FIG. 5 is a fragmentary sectional view of the fastener-driv- FIG; 8 is a fragmentary sectional view of a fastener-driving tool according to yet another embodiment of the present invention illustrating a shuttle valve providing for selective settingofthe fastener-driving tool between an automatic-fire position and a single-stroke position;

FIG. 9 is a cross-sectional view of the fastener-driving tool of FIG. 8, illustrating the shuttle valve in the single-fire position;

FIG. 10 is a cross-sectional view of the fastener-driving tool of FIG. 9, illustrating the shuttle valve in the autofire position;

FIG. 11 is a fragmentary sectional view of yet another fastener-driving tool according to the present invention illustrating a modified form of shuttle valve which will automatically return to the multifire or autofire position after a singlefire operation; I

FIG. 12 is a cross-sectional view of the fastener-driving tool of FlG.-1l, illustrating the shuttle valve of FIG. 11 in the sinmosphere through one port and is operable to a position in gle-fire position;

FIG. 13 is a cross-sectional view of the shuttle valve of FIG. 12, illustrated in the autofire position;

FIG. 14 is a cross-sectional view of the shuttle valve of FIG. 12, illustrated with a restricted speed adjustment;

FIG. 15 is a fragmentary sectional view of yet another fastener-driving tool according to the present invention illustrating a modified form of shuttle valve which will automatically return to the autofire position after a single-fire operation;

FIG. 16 is cross-sectional view of the modified shuttle valve taken along line 16-16 of FIG. 15, illustrated in the autofire position; and

FIG. 17 is a cross-sectional view of the shuttle valve of FIG. 15, illustrated in the single-fire position.

Referring now to the drawings. specifically to the embodiment of FIGS. 1, 2 and 3, there is illustrated a fastener-driving tool generally as 10 which embodies the present invention. The tool 10 includes a housing 12 having a forward and generally vertically extending head portion 120 and a rearwardly extending hollow handle portion 12b forming a reservoir 14 to which is supplied pressurized fluid, such as compressed air, in any suitable manner'as by a flexible air line. The head portion 12a of the housing 12 includes the cavity 16 in which is mounted a differential-diameter cylinder 18 having its lower end in communication with the atmosphere through suitable ports 19, and an open upper end 18a in continuous communication with a passageway 20 formed in the housing.

A manually-actuated control valve assembly indicated generally as 22 normally connects the passageway 20 to the atmosphere through a passageway 24 formed in the hollow handle portion 12b and is operable toa position in which it connects the passageway 20 to the fluid in the reservoir 14. The fluid admitted to the passageway 20 enters the open upper end of the cylinder 18 and drives a differential-diameter piston or piston assembly 26 which is slideably mounted within the cylinder 18 and to which is secured the upper end of a fastener-driving blade 28. The lower end of the driver blade 28 is adapted to engage and drive a fastener 30 through a drive track 32 in a nosepiece assembly 34 by a magazine assembly indicated generally as 36.

During the downward movement of the piston assembly 26, the air disposed within the cylinder 18 below the piston 26 is discharged to the atmosphere through-the lower end of the cylinder 18 through the ports 19.

To provide for the pneumatic return of the piston chamber 38 formed between upper and intermediate O-

rings

40 and 42 between the cylinder 18 and the cavity 16, continuously in communication with the reservoir 14 through a passageway 44. The return air chamber 38 communicates with the cylinder 18 through a return air port 46. Since the cylinder 18 and the piston 26 are of the differential-diameter type, with a large cylinder portion 18a and a small cylinder portion 18b receiving a large piston element 260 defined by an O-ring and a small piston element 26b also defined by an O-ring, the return air port 46 continuously opening between the

piston elements

26a and 26b provides for the exertion of a greater upward force on the piston 26 than the downward force, and the differential force will continuously bias the piston 26 upwardly. However the upward bias of the piston 26 is small enough to become negligible compared to the driving force of the piston during its drive stroke. The piston 26 has substantial length so that the port 46 is always between the

piston elements

26a and 26b throughout the stroke of the piston. Thus when the piston 26 is to be pneumatically returned to its normal position, the control valve assembly 22 operates so that the passageway 20 is again connected to the atmosphere through the passageway 24 and the compressed air in the return air chamber 38 acting on the differential diameters of the piston 26 will drive the piston-'26 upwardly to its normal position as indicated in FIG. 1.

The mechanical construction of the housing 12 and the magazine assembly 36 is disclosed in detail in U.S. Pat. No. 3.2l5.324 granted May 2, 1965 to Thomas H. Dorney and assigned to the assignee of the present invention. However, in

general, the head portion 120 of the housing 12 is closed by a closure cap 47 secured to the housing 12 by a plurality of machine screws 48 with a resilient sealing gasket 49 interposed therebetween. An opening 50 in a depending portion 47a on the closure cap 47 carries a block or bumper 52 of resilient material that engages the upper end of the piston 26, and an annular resilient bumper 54 is disposed in the lower end of the cavity 16 to cushion the termination of the power stroke of the piston 26. The bumper 54 is held in position at the bottom of the cylinder 18 by engagement with a shouldered portion 18c formed on the cylinder 18. The lower end of the interior of the cylinder 18 is placed in communication with the atmosphere through the ports 19 extending through the housing 12. The interface between the outer wall of the cylinder 18 and the inner wall of the cavity 16 is sealed by an additional O-ring 56 which further defines, along with the O- ring 46, a delay chamber 58.

The connection of the open upper end of the cylinder 18 to either the atmosphere or the fluid reservoir 14 is controlled by a pneumatically controlled main valve portion 60 of the manually actuated control valve assembly 22. The valve portion 60 includes an exhaust valve seat 62 carried on the housing 12 having downwardly and inwardly tapered openings 64 through which the passageway 20 is normally placed in com munication with the exhaust passageway 24. The openings 64 can be closed by a resilient O-ring 66 defining a valve element carried on the upper end of a valve stem 68. A resilient valve element 70 defining a control valve is also carried on the valve stem 68 disposed between a shouldered portion 68a on the valve stem 68 and a piston 72 that is secured to the lower end of the stem 68. The resilient valve-element 70 normally closes a port or passageway 74 interposed between the reservoir 14 and the passageway 20. The piston 72 carries and O-ring 76 and is slideably mounted within'a valve cylinder 78 formed in a valve body 80 received within an opening 82 in the housing 12.

A trigger or pilot valve portion 77 is included in the control valve assembly 22 to control the operation thereof and to permit the assembly 22 to be operated witha minimum manually applied force. This trigger valve portion 77 includes an operating pin 84 that is slideably mounted within an axial bore formed in a valve body member 86 that is threadedly received within an opening 88 in the housing 12. An O-ring 90 seals the interface between the valve body member 86 and the opening 88. The upper end of the operating pin 84 is tapered and carries an O-ring 92 that operates as a valve element to control communication between the reservoir 14 and a valve chamber 93 through a passageway 94. In the normal condition or released state of the control valve assembly 22, compressed air flows from the reservoir 14 through the passageway 94 to deflect or bias the O-ring 92 downwardly to permit the compressed air to build up within the upper end of the valve chamber 93. This compressed air flows through a passageway 96 in the valve body 80 to enter the lower end of the cylinder 78. This compressed air, which isat the same pressure as the fluid within the reservoir 14, operates on the greater area lower surface of the piston 72 and overcomes the force of the compressed air in the reservoir 14 acting on the upper effective surface of the piston 72 to provide an upwardly directed force that holds the resilient valve element 70 in engagement with the housing 12 to close the port 74 and holds the valve element 66 spaced from the valve seat 62 so that the passageway 20 normally communicates with the atmosphere through the opening or port 64 and exhaust passageway 24.

When the tool 10 is to be operated, a trigger or actuating element 98 pivotably mounted on the housing 12 is pivoted in a counterclockwise direction to engage the lower end of the operating pin 84. This moves the pin 84 upwardly so that the O-ring 92 engages the adjacent portion of the valve body 80 to seal the passageway 94. At the same time the O-ring is moved away from the member 86 so that the upper end of an annular passageway or groove 102 is uncovered. The passageway 102 connects with a passageway 106 in the valve body member 86 and further communicates through a passageway 108 with the delay chamber 58 defined between the cylinder 18 and cavity 16. The delay chamber 58 communicates with the cylinder 18 through a port or valve opening 110 in the wall of the cylinder 18 located below the piston 26 intermediate the travel of the piston element 26b so that the piston portion 26b passes across the port 110 during the stroke of the piston 26. Thus the compressed air within the lower portion of the cylinder 78 is discharged to atmosphere around the annular groove 102,

passageways

106 and 108, delay chamber 58, port 110, and through the exhaust ports 19 from the lower end of the cylinder 18. When the compressed air is discharged from within the lower end of the cylinder 78, the compressed air acting on the effective upper surface of the piston 72 moves this piston and the connectedvalve stem 68 downwardly. In moving downwardly, the O ring 66 moves into engagement with the tapered wall of the valve sea't 62 to close the exhaust port or opening 64. This also moves the upper surface of the resilient valve element 70 out of engagement with the housing 12 to open the port or passageway 74. The passageway 20 and the upper end of the cylinder 18 are now placed in direct communication with the fluid in the reservoir 14 so that the piston 26 and the connected driver blade 28;areldriven downwardly.

to engage and drive the fastener 30 supplied through the drive track 32 by the magazine assembly 36.,Compressed fluid also enters thecylinder 18 between the differential portions thereof through the passageway 44, return air chamber 38, and return air port 46; However the net upward bias of this compressed air is negligible compared to the driving force on the piston,26 due to the air in the upper end of the cylinder 18. The flow of pressurized air to the return air chamber is indicated by the arrows A, while the exhaust of air from the cylinder78 after depression of the trigger 98 is indicated by I the arrows B, FIG. 1.

As soon as the small piston element 26b on the piston 26 passes over the port 110 during its driving stroke, pressurized fluid from the reservoir 14 will now enter the lower portion of the cylinder 78 through the passageway 44, port 46, return air chamber 38, valve opening 110, and passageway 108, around the annular groove 102 and into the valve chamber 93 as indicated by the arrows C in FIG. 2. T he lower end of the cylinder 18 is, of course, vented to theatmosphere through the ports 19 as indicated by the arrowsD. As soon as the pres sure in the lower end of the cylinder 78 builds up sufficiently to overcome the differential force acting downwardly on the valveelement 70, the'valve element 70will be forced upwardly until it seats to close the port 74 and exhausts the upper end of the cylinder to the atmosphere as indicated in FIG. 3. At this time the return air will build up within the return air chamber 38, arrows A, to effect return of the piston 26 to its uppermost position. s

The operation of the improved fastener-driving tool is be lieved clear from' the above description. However, briefly, it will be understood that with the tool at rest and the trigger released, as illustrated in FIG. I, the pressure'of the fluid in the return air chamber 38, which is always in communication with the reservoir 14, willmaintain the piston 26 in its uppermost or normal position. As soon as the trigger 98 is depressed the fluid will exhaust from the lower end of the cylinder 78 through the passageway 96, valve chamber 93, around the an-- nular groove 102, through the

passageways

106 and 108, through the delay chamber 58, port 110, lower end of the cylinder 18, and through the exhaust ports 19 as indicated by the arrows B in FIG. 1. This will permit the fluid in reservoir 14 acting on top of the piston 72 to drive the piston 72 downwardly, seating the valve member 66 against the valve seat 62 and closing the exhaust port or opening 64, whileat thesame time coSonecting the reservoir 14 to the upper end of the cylinder 18 through the port 74 and passageway 20. Thus the piston 26 will be driven downwardly through a power stroke. As the piston 26 moves downwardly, the O-ring 26b closes the valve opening 110 from the lower end of the cylinder 18, and the exhaust of air from the cylinder 78 will end and pressurized fluid from the reservoir 14 will be directed into the lower end of the cylinder 78 through the passageway 44, the return air chamber 38, port 46, valve opening 110, delay chamber 58, passageway 108, passageway 106, around the annular groove 102, valve chamber 93, and passageway 96. The flow of air to the cylinder 78 will be metered by the size of the port openings, by the clearance of the piston 26 with the cylinder 18, and by the size of the delay chamber 58 so that the piston 26 will, have sufficient time to complete its drive stroke substantially unhindered prior to the actuation of the piston 72. The size of the chamber 58, along with the restrictions in the fluid flow, will determine the rate of pressure buildup within the cylinder 78.

As soon as the pressure in the cylinder 78 is sufficient to overcome the differential pressure acting on the piston 72, the piston 72 will be driven upwardly from the position indicated in FIG. 2 to the position indicated in FIG. 3. At this time the upper end of the cylinder 18 is exhausted to the atmosphere and the return air in the return air chamber 38 will drive the piston 26 back to its normal position.

After the piston 26 is returned to its normal position, and as long as the trigger 98 remains depressed; the piston 26 will immediately recycle since the movement of O-ring 26b past the valve opening now permits exhaust of the air from the cylinder 78, in the manner previously described, as indicated by the arrows B of FIG. 1. Thus the fastener-driving tool 10 will continue to cycle through a drive and return stroke so long as the trigger 98 is maintained depressed.

If desired the fastener-driving tool heretofore described may readily be modified to provide for multiblow operation of a single fastener. Thus when it is desired to drive a fastener which cannot be driven with a single blow, the drive piston of the tool will continue to recycle until such time as the fastener is fully driven, and then the piston will return to its static or normal position until such time as the fastener-driving tool is again activated to drive another fastener. A tool modified for multiblow operation is illustrated in the embodiments of FIGS. 4 through 7.' As therein illustrated there is provided a fastenerdriving too] 120, similar to the fastener-driving tool 10 heretofore described but modified by the inclusion of a shutoff valve 121. Accordingly the fastener-driving tool will-not be described in detail except wherein it differs from the fastenerdriving tool 10.

However, briefly, it will be understood that the fastenerdriving tool 120 includes a housing 122 defining a fluid reservoir 124 and a forward cavity 126. A cylinder 128 is mounted within the cavity 126. As heretofore described the cylinder 128 has its lower end in communication with the cavity 126 and has an open upper end in continuous communication with the passageway 20 formed in the housing. The operation of the fastener-driving tool 120 is under the control of the manually actuated control valve assembly 22, identical with that described in the embodiment of FIGS. 1 through 3. The control valve 22 is operable to alternately connect the passageway 20 to the atmosphere through the passageway 24 and connect the passageway 20 to the fluid in the reservoir 124. The fluid admitted to the passageway 20 enters the upper of the cylinder 128 and drives the piston 26 downwardly so that the lower end of the drive blade 28 engages and drives the fastener 30 supplied to the drive track 32 in the nosepiece assembly 34 by the magazine assembly indicated generally as 36.

To provide for the return stroke of the piston 26, the fastener-driving tool 120 is provided with the pneumatic return system including the return air chamber 38 defined between the cylinder 128, the cavity 126, and the O-

rings

40 and 42, which is in communication with the reservoir 124 through the passageway 44 and which communicates with the cylinder 18 through the return air port 46. The lower end of the cylinder 128 exhausts to the atmosphere through the plurality of exhaust ports 19.

For providing repetitive motion of the piston 26, the control I valve 22 is provided with a signal pressure from passageway means 108a, 108b, connected to the return air chamber 38.

Pressurized fluid which is received by the control valve 22 after the lower O-ring 26b clears the delay port or valve opening 110 will be effective to create a return stroke of the piston 26 so long as the passageway means 108a and 10812 are unobstructed.

To provide for termination or shutoff of the cycling of the tool 120 upon completion of the driving of the fastener 30, there is provided the shutoff valve 121 positioned within a differential diameter valve chamber 130 formed within the housing 122. The shutoff valve 121 is adapted to block or close the passageway means 108a, 108b upon complete driving of the fastener 30. More specifically the shutoff valve 121 includes a valve element 132 slideably mounted within the valve chamber 130 and includes an enlarged lower end defining a piston 134. The valve chamber 130 has an open end closed by a valve cap or cylinder head 136. When the valve element 130 is in its normal or at-rest position, as illustrated in FIG. 4, the valve element 132 is biased toward the larger or cap end ofthe valve chamber 130. Moreover the passageway means 108k has a port 138 opening into the inner side wall of the valve chamber 130, and the passageway means 108a has a port 140 opening into the inner end of the valve chamber 130. The port 138 is closeable by the movement of the valve element 132, and more specifically by the movement of an O-ring 142 to a position intermediate the

ports

138 and 140.

During the multiblow operation of the fastener-driving tool 120, the passageway means l08b and 108a are in communication through the valve chamber 130, with the valve element 132 in its lowermost position as indicated in FIGS. 1 and 2. During this cycling of the fastener-driving tool 120, the tool functions in like manner as the fastener-driving tool described in the embodiment of FIGS. 1 through 3.

To provide for termination of the cycling of the fastenerdriving tool 120 upon completion of the driving of a single staple 30, means are provided for shifting the valve element 132 upwardly to cause the O-ring 142 thereof to block the port 138. More specifically there is provided signal port means 144 in the lower end of the cylinder 128 communicating through a passageway 146 with the head or large end of the valve chamber 130. The signal port means 144 is positioned to be covered by the lower O-ring 26b when the piston 26 reaches the bottom or end of its driving stroke. Thus when the stroke of piston 26 is sufficiently long so that the O-ring 26b moves past the signal port 144, pressurized fluid from the reservoir 124 will enter the port 144, pass throughpassageway 146 and enter the lower end of the valve chamber 130 so as to move the valve element 132 upwardly. At this time the O-ring 142 on the valve element 132 will move past the port 138 preventing the return signal in passageway means 108b from reaching the valve chamber 93 and preventing further automatic cycling of the piston 26 through a subsequent stroke.

So long as the trigger 98 is maintained depressed, air from the cylinder 78 will continue to exhaust to atmosphere through the passageway means 108a and a passageway 148 formed in the valve element 132, best illustrated in FIG. 7, which mates with the port 140 and which exhausts to atmosphere through a passageway 150 in the tool housing 122. A vent 152 through the differential portion of the valve chamber 130 permits free movement of the valve element 132 within the valve chamber 130. Thus the piston 26 will not return after it has completely driven the fastener 30 until such time as the trigger 98 is released. Upon release of the trigger 98 and movement of the O-ring 92 from the seat in the passageway 94, pressurized fluid will once again enter the cylinder 78 from the reservoir 124 and will return the

valve elements

66 and 70 to their normal position as indicated in FIG. 1, permitting return of the piston 26 to its normal position. As soon as the O-ring 26b clears the port 144, pressurized fluid from below the piston 134 will exhaust to atmosphere through the cylinder 128 and the exhaust ports 19.

Thus it will be understood that the addition of the shutoff valve 121 into the signal passageway means 108a and I08b is effective to permit multiblow firing of the piston 26 so as to completely drive a single fastener 30, and the shutoff valve 121 is effective to end the automatic cycling of the piston 26 upon completion of the driving of the fastener 30 until such time as the trigger 98 is released and once again activated by depression thereof.

FIGS. 8, 9 and 10 illustrate a modification of the fastenerdriving tool of FIGS. 1 through 3 wherein a shuttle valve is added to the signal line 108 thereby permitting the fastenerdn'ving tool to be set to either an autofire position or to a single-fire position, and further to provide for adjustment of the cycling rate of the tool. More specifically there is illustrated a fastener-driving tool 160, identical with the fastener-driving tool 10 except for the addition of a shuttle valve assembly 162 in the signal passageway. The shuttle valve assembly 162 includes a valve body or valve sleeve 164 positioned within an opening 166 within the tool housing 12. The valve body 164 is provided with

ports

168 and 170 forming a part of the signal passageway, herein identified as 108c and 108d and interconnecting the delay chamber 58 with the control valve 22. The valve assembly 162 includes a spool valve element or valve stem 172 slideably received within the valve body 164 and provided with a projection 174 extending through one end of the valve body 164, and further including a button portion 176 at the other end thereof so that the valve element 172 may be manually shifted between its single-fire position, illustrated in FIG. 9, to its autofire position, illustrated in FIG. 10, by the depression of projection 174, and may be returned to the single-fire position by depression of the button portion 176 thereof.

To provide for single-firing of the fastener-driving tool 160, the valve element 172 is provided with an annular groove or reduced diameter portion 178 so that in the position illustrated in FIG. 9 the control valve 22 exhausts through the passageway 108d, the port 170, along a passageway 180 defined by the annular groove 178 and past the open end of the valve body as defined by a passageway 182.

To provide for autofiring of the fastener-driving too] 160 so long as the trigger 98 is depressed, movement of the valve element 172 to the position illustrated in FIG. 10 will permit flow of the necessary signal through the

passageways

108b and 108d to provide for the operation in like manner as described in the embodiment of FIGS. 1 through 3. More specifically, as therein illustrated, the valve element 172 is provided with a pair of

circumferential grooves

184 and 186 interconnected by an inner bore 188 and aligned in the autofire position with the

ports

168 and 170 respectively to provide for communication between the

passageways

108a and 108d. The fastenerdriving tool 160 will now function in an autofire condition.

To adjust the rate of cycling of the tool, the recycling of the piston 26 is dependent on the restriction within the signal passageways and the size of the delay chamber 58. The desired restriction may be adjustably selected by the provision of a needle valve 190 which extends into the inner bore 188 of the valve element 172 and meters the rate of fluid flow between the

grooves

184 and 186.

It is understood that with the shuttle valve assembly 162 in the autofire position, the operation of the fastener-driving tool 160 is identical with that in the embodiment of FIGS. 1 through 3, except for the adjustable metering of the rate of flow in the signal passageway which controls the selective setting of the recycling rate.

FIGS. 11 through 14 illustrate a modification of the fastener-driving tool of FIGS. 1 through 3 wherein the shuttle valve is arranged to return to the autofire position upon completion of a single-firing operation. More specifically there is illustrated a fastener-driving tool 200, which may be identical with the fastener-driving tool 10 heretofore described, but in the illustrated embodiment is of the type having valve means around the upper piston to provide for flow of air to the air return chamber as more fully described and claimed in the US. Pat. No. 3,040,709 granted to O. A. Wandel on June 26, 1962. As therein more fully described, the tool 200 includes a housing 202 having a forward and generally vertically extending head portion 202a and a rearwardly extending hollow handle portion 202b forming a reservoir 204 to which is supplied pressurized fluid, such as compressed air, in any suitable manner as by a flexible airline. The head portion 202a of the housing 202 includes a cavity 206 in which is mounted a differential-diameter cylinder 208 having a large cylinder portion 208a and a small cylinder portion 20812. The lower end of the cylinder 208 is in communication with the atmosphere, and the open upper end 208a is in continuous communication with a passageway 210 formed in the housing.

A manually actuated control valve assembly indicated generally at 212 normally connects the passageway 210 to the atmosphere through a passageway 214 formed in the hollow handle portion 202b and is operable to a position in which it connects the passageway 210 to the fluid in the reservoir 204. The fluid admitted to the passageway 210 enters the open upper end of the cylinder 208 and drives a differential-diameter piston 216 which is slideably mounted within the cylinder 208 and to which is secured the upper end of a fastener-driving blade 218. The piston 216 includes a large diameter element 206a defined by an O-ring 224 and a small diameter element 206b defined by an O-ring 230. The lower end of the drive blade 218 is adapted to engage and drive a fastener through a drive track in a nosepiece assembly'in like manner as the embodiment of FIGS. 1, 2 and 3.

During the downward movement of the piston assembly, the air disposed within the cylinder 208 below the piston 216 is discharged to the atmosphere through the lower end of the cylinder 208. I v

To provide for the pneumatic return of the piston 216 to its normal position, there is provided a return air chamber 220 formed between the vdifferential-diameter portions of the piston 216 and cylinder 218. The air return chamber 220 may be placed in communication with the reservoir 204 through suitable valve or port means 222 located in the upper portion of the piston assembly 216. The valve means 222 includes the resilient O ring 224 mounted within an elongated groove 226 slideably engaging the inner wall of the upper portion of the cylinder 208. To provide means for selectively supplying compressed air to the air return chamber 220, the bottom wall of the groove 226 and a portion of the lower lip of this groove are recessed to provide a slot 228 which places the air return chamber 220 in communication with the annular groove 226. Thus when compressed air is supplied to the upper end of the cylinder 208, the air passing through the interface between the upper flange and the inner wall of the upper portion of the cylinder 208 enters the groove 226 and passes through the slot 228 to be accumulated in the air returnchamber 220. Since the cylinder 208 and the piston 216 are of the differentialdiameter type pressurized fluid in the air return chamber 220 provides for the exertion of a greater upward force on the piston 216 than the downward force, and the differential force will bias the piston 216 upwardly.

When the piston 216 is to be pneumatically returned to its normal position, the control valve assembly 212 operates so that the passageway 210 is again connectedto the atmosphere through the passageway 214 and the compressed air in the air return chamber 220 acting on the upper O-ring 224 is effective to slide the O-ring 224 upwardly, to the position illustrated in FIG. 11, thereby sealing the passageway defined by the slot 228 and the differential force acting on the differential diameters of the piston 216 will drive the piston 216 upwardly to its normal position as indicated in FIG. 1.

The valve assembly 212 is identical to the valve assembly 22 described in the embodiment of FIGS. 1 through 3 and, briefly, includes a pneumatically controlled main valve portion 232 controlling the connection of the open upper end of the cylinder 208 to either the atmosphere or to the fluid reservoir 204. The valve portion 232 includes an exhaust valve seat 234 carried on the housing 202 having a downwardly and inwardly tapered opening 236 through which the passageway 210 is normally placed in communication with the exhaust passageway 214. The opening 236 can be closed by a resilient O-ring 238 defining a valve element carried on the upper end of a valve stem 240. A resilient valve element 242, here shown in the form of an O-ring, is also carried on the valve stem 240 disposed between a shouldered portion 240a on the lower end of the valve stem 240 and a control valve or piston 244. The resilient valve element 242 normally closes a port or passageway 246 interposed between the reservoir 204 and the passageway 210. The piston 244 carries an O-ring 248 and is slideably mounted within a control valve cylinder 250 formed in a control valve body 252 received within an opening 254 in the housing 202.

A trigger or pilot valve'portion 256 is included in the valve assembly 212 to be operated with a minimum manually applied force. This trigger valve portion 256 includes an operat ing pin 258 that is slideably mounted within an axial bore formed in a valve body member 260 that is threadably received within an opening 262 in the valve body 252. The upper end of the operating pin 258 is tapered and carries an O-ring 264 that operates as a valve element to control communication between the reservoir 204 and a valve chamber 266 through a passageway 268. In the normal condition or released state of the control valve assembly 212, compressed air flows from the reservoir 204 through the passageway 268 to deflect or bias the O-ring 264 downwardly to permit the compressed air to build up within the upper end of the valve chamber 266. This compressed air flows through a passageway 270 in the valve body 252 to enter the lower end of the cylinder 250. This compressed air, which is at the same pressure as the fluid within the reservoir 204, operates on a greater area lower surface of the piston 244 and overcomes the force of the compressed air in the reservoir 204 acting on the upper effective surface of the piston 244 to provide an upwardly directed force that holds the resilient valve element 242 in engagement with the housing 202 to close the port 246 and holds the valve element 238 spaced from the valve seat 236 so that the passageway 2 10 normally communicates with the atmosphere through the opening or port 236 and exhaust passageway 214.

When the tool 200 is to be operated, a trigger or actuating element 272 pivotally mounted on the housing 202 is pivoted in a counterclockwise direction to engage the lower end of the operating pin 258. This moves the pin 258 upwardly so that the O-ring 264 engages the adjacent portion of the valve body 252 to seal the passageway 268. At the same time the O-ring 238 is moved away from the member 234 so that the upper end of an annular passageway or groove 274 is uncovered. The passageway 274 connects with a passageway 276 in the valve body 252 and further communicates through a passageway 278 with a delay chamber 280 defined between the cylinder 208 and the cavity 206. The delay chamber communicates with the cylinder 208 through a port or valve opening'282 in the wall of the cylinder 208 located below the piston 216 intennediate the travel of the lower piston element 216b so that the piston portion 126b passes across the port 282 during the stroke of the piston 216. Thus when the tool 200 is in its rest position the compressed air within the lower portion of the cylinder 250 is discharged to atmosphere around the annular groove 274,

passageways

276 and 278, delay chamber 280, and port 282 to be exhausted from the lower end of the cylinder 208. If the compressed air is discharged from within the lower end of the cylinder 250, the compressed air acting on the effective upper surface of the piston 244 moves this piston and the connected valve stem 240 downwardly. In moving downwardly, the O-ring 238 moves into engagement with the tapered wall of the valve seat 234 to close the exhaust port or opening 236. This also moves the upper surface of the resilient valve element 242 out of engag'ement with the housing 202 to open the port or passageway 246. The passageway 210 and the upper end of v the cylinder 208 are now placed in direct communication with the fluid in the reservoir 204 so that the. piston 216 and the connected driver blade 218 are driven downwardly through a fastener-driving stroke. Compressed air also enters the fluid from the reservoir 204 will enter the lower portion of the cylinder 250 through the delay chamber 280,

passageways

278 and 276, annular groove 274, and passageway 270. As

soon as the pressure in the lower end of the valve cylinder 250 builds up sufficiently to overcome the differential force acting downwardly on the valve element 242, the valve element 242 will be forced upwardly until it seats to close the port 246 and exhaust the upper end of the cylinder to the atmosphere. At this time the return air builds up within the air return chamber 220 to effect return of the piston 216 to its uppermost position.

To provide for the selective single-stroke operation of the tool 200, and to provide for speed regulation of the repetitive cycling thereof, there is provided a shuttle valve assembly 290 in the passageway 278. The shuttle valve assembly 290 includes a valve cylinder 292 defined within the housing 202 of the tool 200, FIGS. 12 through 14, of a differential type, having an intermediate small diameter portion 292a, a larger end portion 929b, and additionally a counterbore 292C outwardly of the intermediate portion 292a to define a stop. A spool or valve stem 294 is mounted for reciprocal or sliding movement within the valve cylinder 292. The valve stem 294 includes a small piston 296 containing an O-ring 298 for slideable movement within the small diameter portion 292a of the valve cylinder 292, and a large piston 300 having an O-ring 302 for sliding movement within the large diameter portion 292b of the valve cylinder 292. The valve stem 294 is longitudinally movable within the valve cylinder in a single-fire direction, as illustrated in FIG. 12, until the O-ring 302 seats against a shoulder 304 formed between the intermediate and

large diameter portions

292a and 292b of the valve cylinder 292, and into an autofire position, illustrated in FIGS. 13 and 14, until a nut 306 adjustably threaded on the end of the valve stem 294 strikes against the bottom of the counterbore 292C. The adjustable threading of the nut 306 onto the valve stem 294 provides for selective positioning of the stem in the autofire position longitudinally of the valve cylinder 292.

To provide for control of the fluid flow between the delay chamber 280 and the valve means 222, the passageway 278 has a first port 278a opening into the small diameter portion 292a of the valvecylinder 292 beyond the longitudinal movement of the O-ring 298 on the small piston 296. However the small piston 296 may be adjusted to move longitudinally to a position partially obstructing the flow from the port 2780 by adjusting or backing off the nut 306, as illustrated in FIG. 14. Moreover the passageway 278 has a continuing port 278b intermediate the stoke of the large piston 300 so as to be blocked from communication with the signal air received from port 278a, as illustrated in FIG. 12, exhausting to the atmosphere through a passageway 308 formed between a head 2940 of the valve stem 294 and the edge of the valve cylinder 292. Moreover when the valve stem 294 is moved longitudinally to its autofire position, as illustrated in FIGS. 13 and 14, the port 2781; is placed in communication with the port 2780.

From the above brief description, the operation of the improved shutter valve is believed clear. However, briefly, it will be understood that the tool 200 employs a signal taken from the delay chamber 280 to control the actuation of the valve assembly 212 so long as the trigger 272 is maintained depressed. Assuming first that the shuttle valve assembly 290 is in the autofire position illustrated in FIG. 13; the passageway 278 is unobstructed and the tool 200 will cycle in a manner identical with that described in the embodiment of FIGS. 8 through 10. However if it is desired to reduce the cycling speed of the tool, it'is merely necessary to .adjust the longitudinal position of the valve stem 294 by backing off the nut 306 to the position, for

example, as illustrated in FIG. 14. In this position the edge of the small diameter piston 296 partially obstructs flow of fluid passing through the passageway 278 by partially blocking the 5 port 278a. Thus the signal fluid is retarded and the tool 200 will fire at a slower rate.

If it is desired to fire the tool 200 as a single-fire tool. it is merely necessary to depress the head end of 294a of the valve stem 294 to the position illustrated in FIG. 12. In this position the passageway 278 is blocked by the large diameter piston 300 and the O-ring 302 and no signal air will be received from the delay chamber 280 by the valve means 222. Moreover the valve means 222 will exhaust to the port 2781) and the passageway 308 to provide for single-fire cycling of the tool. Thus the operator needs merely to move the valve stem 294 to the single-fire position, drive a fastener, and release his finger from the shuttle valve. The shuttle valve assembly 290 will automatically return to the multifire position since the diameter of the large piston 300 is greater than the diameter of the small piston 296 and the differential pressure entering through the passageway 278 will be effective to move the valve stem 294 from the single-fire to the multifire position. If it is desired to drive more than one fastener on a single-fire arrangement, the valve stem 294 may be held to the single-fire position manually.

Referring now to the embodiment of FIGS. 15, 16 and 17, there is illustrated a modification of the fastenerdriving tool having an improved shuttle valve in the signal line 108 providing' improved operation of the fastener-driving tool as either an autofire or a single-fire tool. More specifically there is illust-rdted a fastener-driving tool 310, identical with the fastenerdriving tool 160 heretofore described, except for a modified shuttle valve assembly 312 in the signal passageway 108. Ac-

'cordingly similar parts of FIG. 15 and of FIGS. 8 through 10 are represented by the same reference numeral and are not again described in detail. The shuttle valve assembly 312 includes a valve cylinder 314 defined in the housing 12. The

valve cylinder 314 includes a threaded portion 314a at one 9 end and a reduced diameter portion 314b at the other end.

For regulating the rate of flow in the passageway 108, there is provided a needle valve assembly 316 including a needle valve body 318 threadedly received in the threaded portion 314a and provided with a longitudinal bore 320 receiving a stern member 322. The stem member 322 has a threaded portion 322a threadedly received within a threaded portion 320a of the longitudinal bore 320 providing adjustment of the stem member 322. Additionally the stem member 322 includes a tapered stem portion 322b extending through a port 324 formed by the longitudinal bore 320 to meter the rate of flow therethrough. A port 326 in the side wall of the needle valve body 318 provides communication between the passageway portion 1080 and the metering port 324, and in the normal or autofire position as illustrated in FIG. 16, the metering port 324 is in communication with the passageway portion 108d.

Thus it will be understood that during the autofiring of the fastener-driving tool 310 so long as the trigger 98 is depressed,

" a signal flow will occur through the passageway 108 between the portions 108s and 108d to provide for the operation of the tool in like manner as in the embodiment of FIGS. 8 through 10.

To adjust the rate of cycling of the tool, the recycling of the piston 26 is dependent on the restriction within the signal passageways and the rate of flow through the metering port 324. The desired rate may be adjustably set by the adjustment of the threaded stern member 322 within the needle valve body 318.

To provide for firing ofthe tool 310 as a single-fire tool, the

passageway 1080 may be selectively blocked by a single-fire valve member 328. More specifically the single-fire valve member 328 includes a ball valve member 330 within a valve chamber 332 and integrally formed with a manually operable stern 334 extending through the reduced-diameter portion 314b. The ball valve member 330 is provided with an inwardly extending recess 336 providing clearance with the stem portion 322b of the stem member 322 preventing interference between the stem member 322 and the valve member 328. The stem 334 of the-valve member 328 is somewhat smaller than the port 326 so that an exhaust passageway 338 is defined around the stem 334. The exhaust passageway 338 is normally closed, in the autofire position, by the seating of the ball valve member 330 against a valve seat member 340, here shown as an O-ring. When depressed, the ball valve member 330 will unseat from the valve seat member 340 and will move against an edge of the needle valve body 318 defining a valve seat member 342 around the metering port'324. Thus when the ball valve member 330 is seated against the valve seat member 342, the passageway l08c is blocked, and the passageway 108d is exhausted to the atmosphere. I

In operation it will be understood that when the tool 310 is i to be firedin the autofire position, the single-fire valve member 328 will be released, so that the, passageway 108 is open and fluid flow can occur therethrough. However when it is desired to fire the tool 310 as a single-fire tool, the operator will depress the single-fire valve member 328, unseating the ball valve member 330 .from the valve .seat member 340 and closing the metering port 324 by the seating of the ball valve member 330 against the valve seat member 342. In this position, with the depression of the trigger 98, the tool will fire in the manner heretofore described. A signalflow cannot take place through the passageway 108 since the passageway 108 is now obstructed by the seating of the ball valve 330 against the valve seat member 342. Moreover the valve cylinder 78 will now be exhausted to the atmosphere through'the passageway 94, valve chamber 93, passageway 96, and passageway 108d into the valve chamber 332 of the shuttle valve assembly 312 and through the exhaust passageway 338'. Thus so long as the single-fire valve member 328 is depressed, and so long as the trigger 98 is not released, the piston 26 and associated driver blade 28 will remain at the end of its driving stroke. Of course as soon as the trigger 98 is released, fluidfrom the reservoir 14 will once again enter into the valve cylinder 78 and will close the valve element 70 against the port 74, lifting the valve element 66 from the exhaust valve seat 62. Thereservoir air from above the piston 26 is shut off, and the upper open end of the cylinder 18 is exhausted to the atmosphere. The reservoir air entering the return air chamber 38 and communicating with the cylinder 18 through the return air port 46will be effective, acting on the

differential diameter elements

26a and 26b, to return the piston 26 and associated driver blade 28 to its static or at rest position as illustrated in FIG. 15. p

Advantageously a fastener-driving tool according to the present invention provides for a high speed or cycling of the fastener-driving tool so that fasteners may be rapidly driven in a continuous manner. Moreover in a particular embodiment thereof the desired rate of cycling may bevaried as desired by the operator. The easy-trip pilot valve may be operated by minimum efi'ort on the part of the operator, and the operator is subjected to a minimum fatigue since it is not necessary that he operate or depress the trigger for each'cycle of operation. Moreover, in accordance with another embodiment of the present invention, the fastener-driving tool is readily adapted to drive a large fastener with a relatively small tool which in turn would be a less expensive tool, and to shut ofi' the v recycling of the tool once the fastener has been fully driven.

fluid under pressure; fastener-driving means including a piston slideably mounted in the cylinder;

a housing including'a cylinder and a reservoir supplied with valve means operable between a normal position connecting one end of the cylinderto the atmosphere to an operated position connecting the oneend of the cylinder to the reservoir;

pneumatic piston return means forreturning said piston to said one end of said cylinder including an air return chamber; and Q 7 means controlled by movement of said piston sequentially connecting said return air chamber to said valve means to cycle said valve means in response to the stroke of said piston and thereby provide for automatic cycling of said piston.

2. A fastener-driving tool as set forth in claim 1 wherein said last-mentioned means includes a passage means connected to said valve means having a port opening in said cylinder sequentially connected to said return air chamber by the movement of said piston.

3. A fastener-driving tool as set forth in claim 2 including shutoff means for blocking said passage means when said piston completes a full drive stroke.

4. A fastener-driving tool as set forth in claim 3 wherein said shutoff means includes a shutoff valve and passage means connecting said shutoff valve with a port opening in the other end of said cylinder to provide a signal when said piston moves past said port.

5. A fastener-driving tool as set forth in claim 4 wherein said signal is provided by the connection of said port with said return air reservoir.

6. A fastener-driving tool as set forth in claim 2 including a shuttle valve in said passage means operable to exhaust said valve means to atmosphere.

7. A fastener-driving tool as set forth in claim 2 including throttling valve means in said passageway.

8. A fastener-driving tool as set forth in claim 2 including adjustable throttling means operatively connected to delay recycling of said valve means to provide for speed control of the automatic cycling of said tool.

9. An automatically cycling fastener-driving tool comprising:

a housing including a differential-diameter cylinder and a reservoir supplied with fluid under pressure;

fastener-driving means including a differential-diameter piston slideably mounted in the cylinder;

an air return chamber being defined by the space formed between the differential-diameter portions of said cylinder and piston;

means continuously connecting said-air return chamber to said reservoir; valve means operable between a normal position connecting one end of the cylinder to the atmosphere to an operated position-connecting the one end of the cylinder to the reservoir; pneumatic piston return means including an air return chamber; and 1 means controlled by movement of said piston selectively connecting said return air chamber to said valve means to cycle said valve means in sequence with the stroke of said piston and thereby provide for automaticcycling of said piston and including a port in the'wall of said cylinder intermediate the movement of one of said portions of said piston to connect said valve means to said air return chamber upon a predetermined movement of said piston. 10. An automatically cycling fastener-driving tool comprising:

fastener-driving means including a' differential-diameter piston means with larger and smaller diameter pistons slideably mounted in the cylinder;

pneumatically controlled valve means operable between a normal position connecting the larger end of said cylinder to the atmosphere and an operated position connecting said larger end of the cylinder to the reservoir;

pneumatic piston return means for returning said piston means to said larger end of said cylinder including a return air chamber and first port means for connecting said return air chamber to said reservoir; exhaust means connecting the other end of said cylinder to the atmosphere; a

second port means in said cylinder intermediate the stroke of the smaller diameter piston, said second port means normally being in communication with said exhaust means and communicating with said first port means when said smaller diameter piston moves between said second port means and said exhaust means;

passage means communicating with said second port means;

and

pilot valve means movable between a released position placing said pneumatically controlled valve means in communication with said reservoir and an operated position placing said pneumatically controlled valve means in communication with said passage means. whereby pressure from said return air chamber through said passage means is effective to move said pneumatically controlled valve means to said normal position.

11. A fastener-driving tool as set forth in claim including a shuttle valve means connected in said passage means selectively movable between a first position permitting flow through said passage means and a second position bypassing said pneumatically controlled valve means to exhaust to selectively set said tool for automatic recycling thereof and for single firing thereof.

12. A fastener-driving tool as set forth in claim 11 wherein means are provided for throttling the fluid flow in said passage means when said shuttle valve is in said autofire position to regulate the speed of recycling of said tool.

13. A fastener-driving tool as set forth in claim 12 wherein said shuttle valve comprises a differential diameter valve cylinder defined in said housing open at both ends, and a spool valve of differential diameters slideable therein, said valve cylinder having a first port opening into the smaller diameter portion for receiving a signal flow and a second port intermediate the stroke of the smaller diameter portion of said spool valve communicating with said pilot valve.

14. A fastener-driving tool as set forth in claim 13 including means adjustably positioning said spool valve in its said autofire position to provide for throttling the flow therethrough.

15. A fastener-driving tool as set forth in claim 10 including throttling valve means for adjustably metering the rate of fluid flow in said passage means.

16. A fastener-driving tool as set forth in claim 10 including shutoff means for closing said passage means upon completion ofa full drive stroke by said piston.

17. A fastener-driving tool as set forth in claim 16 wherein said-shutoff means includes a shutoff valve having a valve element movable between a first position wherein said passage means is unobstructed and a second position in which said pneumatically controlled valve means is connected to exhaust thereby shutting off the automatic recycling of said piston.

18. a Fastener-driving tool as set forth in claim 17 including passage means having a shutoff port opening near said lower end of said cylinder connected to said shutoff valve to provide a signal whenever said smaller diameter piston moves past said shutoff port in its drive stroke.

19. An automatically cycling fastener-driving tool comprismg:

a housing including a cylinder and a reservoir supplied with fluid under pressure;

fastener-driving means including a piston slideably mounted in the cylinder; main valve means operable between a normal position and an operated position connecting one end of said cylinder to the reservoir to provide a powerstroke for said piston;

pneumatic piston return means operatively associated with said piston;

means for exhausting said one end of said cylinder to atmosphere to provide a return stroke of said piston under the force developed by said pneumatic piston return means;

control valve means connected to control said main valve;

trigger valve means pneumatically connected to said control valve;

passage means communicating with said cylinder for supplying a control signal to said control valve; and

means sequentially connecting said pneumatic piston return means and said passage means to automatically cycle said tool.

20. An automatically cycling fastener-driving tool as set forth in claim 19 including adjustable metering means in said passage means metering the flow of fluid through said passage means to regulate the rate of recycling of said tool.

21. An automatically cycling fastener-driving tool comprismg:

fastener-driving means including a piston slideably mounted in the cylinder;

valve means operable between a normal position connecting one end of the cylinder to the atmosphere to an operated position connecting the one end of the cylinder to the reservoir;

pneumatic piston return means including a return chamber;

means responsive to the pressure in said return chamber to control the movement of said valve means between said normal and said operated positions;

shuttle valve means selectively operable between an autofire position and a single-fire position; and

pneumatic means for automatically shifting said shuttle valve means to an autofire position upon completion of a single-fire operation.

22. An automatically cycling fastener-driving tool comprismg:

fastener-driving means including a piston slideably mounted in the cylinder;

means automatically shifting said shuttle valve means to an autofire position upon completion of a single-fire operation.