Fastener Driving Tool

Abstract

There is provided a fastener driving tool having a control valve arrangement including a trigger valve, a cycling valve and a safety valve. The cycling valve is adapted to repetitively cycle the driving piston of the fastener driving tool through power and return strokes or to provide for single-cycling of the piston through a drive and return stroke in response to the position of the trigger. In addition there is provided an arrangement wherein the operation of the piston is arrested when the bumper cushioning the power stroke of the piston is excessively worn.

Description

This invention relates to a fastener driving tool, and more particularly to a fastener driving tool including new and improved control and cycling means therefor.

Pneumatic fastener driving tools on the market today may be of the type that, when the trigger is depressed, the drive piston and connected fastener driving blade move through a power or drive stroke of a fastener driving operation and are returned upon completion thereof by a suitable piston return means. Such piston and driving blade are cycled through a single cycle of power and return strokes upon depression of the trigger, whether or not the trigger has been released to provide for single-cycle operation of the tool.

Fastener driving tools also are known which are provided with means for repetitively cycling the driving piston and driving blade through its cycle of power and return strokes so long as a trigger valve is maintained depressed, to provide for auto-firing or multiple-firing of the tool. Means may be provided in such a multiple-fire tool to provide for single-firing thereof if desired.

Heretofore it has been known to provide means for adjusting the autofiring rate of the tool. However such autofiring adjusting means in commercially known tools has adjusted or restricted the single-firing rate of the tool. Such tools are restricted to the autofire repetitive rate which may be a handicap when a few fasteners are required to be fired at a higher rate of speed into a particular area of the workpiece.

Moreover it has been customary to provide a bumper or cushion for the drive piston at the end of its drive stroke. However when the fastener driving tool is operated in the autofire position for long periods of time, the bumper becomes hot and deteriorates rapidly.

Accordingly one object of the present invention is to provide a new and improved pneumatically actuated fastener driving tool wherein the autofire rate thereof may be adjusted without affecting the single-fire rate of the tool.

Another object of the present invention is to provide a new and improved fastener driving tool wherein the tool is rendered inoperative if the piston bumper has deteriorated beyond useful limits.

Another object of the present invention is to provide a new and improved pneumatically actuated fastener driving tool.

Yet a further object of the present invention is the provision of a fastener driving tool having a new and improved control valve permitting ease of autofire selection or single-fire selection by the operator.

In accordance with the present invention there is provided a new and improved fastener driving tool of the general type including a housing having a cavity defining a fluid reservoir and a cylinder in the housing. A driving piston having a driving blade is slidably mounted in the cylinder. A main valve of known type is provided for controlling the admission of fluid to and the exhaust of fluid from one end of the cylinder so as to drive the piston through a power or drive stroke and to permit the return of the piston through a return stroke.

In accordance with the present invention there is provided an improved control valve including a safety valve, a trigger valve, and a cycling valve. The cycling valve is movable between a first position permitting control of the driving piston through a driving stroke by the trigger valve and safety valve, to a second position providing for the return of the piston upon completion of a driving stroke. To this end a signal is received by the cycling valve representative of the completion of a driving stroke. When the tool is operatively selected for autofire, a back pressure on the cycling valve prevents shifting of the cycling valve until the signal fluid builds up to an amount sufficient to overcome the back pressure. Thus throttling of the signal fluid passageway will vary the repetitive firing rate of the tool. When it is desired to fire the tool as a single-fire tool, the back pressure on the cycling valve is removed and the cycling valve will shift upon the first pressure buildup to the valve. Thus throttling or restriction of the signal fluid passageway is ineffective to alter the cycling of the tool through the single-fire cycle.

In accordance with another feature of the present invention, the driving piston is returned through its return stroke by a pressure buildup of fluid within a return air chamber. The pressure buildup in the chamber results when passages in the piston line up with passages through the cylinder wall leading into the return air chamber. However, in the event that the bumper at the end of the power stroke has deteriorated, air from the return air chamber will discharge through the same passageway into the cylinder above the piston and exhaust to the atmosphere through an exhaust valve in the cylinder preventing return cycle of piston to take place. Thus the operator will be apprised of the fact that the tool requires servicing or maintenance before it can be further operated.

For a better understanding of the present invention, reference may be had to the accompanying drawings wherein:

FIG. 1 is a fragmentary elevational view of a fastener driving tool according to the present invention illustrated in its normal or at rest position;

FIG. 2 is a fragmentary view of the improved fastener driving tool shown with the driving piston at the end of a driving stroke;

FIG. 3 is a fragmentary view of the improved fastener driving tool similar to that shown in FIG. 2 but illustrating a deteriorated cushioning bumper;

FIG. 4 is a fragmentary view of the valve arrangement taken along line 4--4 of FIG. 1;

FIG. 5 is a cross-sectional view of the valve arrangement according to the present invention, taken along lines 5--5 of FIG. 1;

FIG. 6 is a cross-sectional view of the trigger valve of the improved fastener driving tool taken along line 6--6 of FIG. 5;

FIG. 7 is a cross-sectional view of the cycling valve of the improved fastener driving tool taken along line 7--7 of FIG. 5;

FIG. 8 is a cross-sectional view of the control valve housing of FIG. 1, illustrating the throttling mechanism, taken along line 808 of FIG. 5;

FIG. 9 is a cross-sectional view of the control valve mechanism of the fastener driving tool of FIG. 1, illustrated in the single-fire arrangement;

FIG. 10 is a fragmentary cross-sectional view of the control valve arrangement of FIG. 9, illustrating the cycling valve in its position for the return of the piston through a return stroke;

FIG. 11 is a cross-sectional view of the control valve of the improved fastener driving tool illustrated in the autofire position; and

FIG. 12 is a perspective view of the control valve housing of the improved fastener driving tool.

Referring now to the drawings, particularly to FIG. 1, there is fragmentarily illustrated a fastener driving tool, generally illustrated as 10, which embodies the control valve assembly and bumper arrangement according to the present invention. The tool 10 may be of known construction, and, as illustrated, comprises a housing 12 including a generally vertically extending head or forward portion and a rearwardly extending hollow handle portion having a cavity defining a fluid reservoir 16. Pressurized fluid such as compressed air is supplied to the fluid reservoir 16 of the tool by a suitable flexible line. The drive system for the tool 10 includes a main or power cylinder 18 mounted within the head portion of the housing 12 and having an open upper end 18a that is adapted to be selectively connected to the reservoir 16. The open upper end of the cylinder 18 is in engagement with a main or cylinder valve assembly 20 of a known type, under the control of a control valve assembly 22 according to the present invention. A fastener driving assembly 24 slidably mounted in the cylinder 18 includes a main or drive piston 26 and has connected thereto a depending drive blade member 28. The fastener driving assembly 24 is normally biased to a position with the piston 26 adjacent the cylinder valve assembly 20. An exhaust valve assembly indicated generally as 32 is provided for controlling the selective connection of the upper end of the cylinder 18 to the atmosphere.

When the tool 10 is to be operated, compressed fluid from the reservoir 16 enters the upper open end 18a of the cylinder 18 and drives the fastener driving assembly 24 downwardly to engage and set a fastener or nail 34 supplied to a drive track 36 in a nosepiece or nosepiece structure 38. The flow of compressed fluid in the upper end of the cylinder 18 is controlled by the main valve assembly 20, which includes a vertically movable ring member 40 defining a valve element, and having a sealing ring 42 engageable with the upper open end 18a of the cylinder 18. The cylinder side of the ring member 40 is continuously in communication with the fluid reservoir 16 through a suitable passageway 44 so that pressurized fluid continuously acts against the cylinder side of the ring member 40 tending to displace the ring member 40 from the edge 18a of the cylinder 18. However pressurized fluid is also introduced to the opposite side of the ring member 40 through a passageway 48 while the fastener driving tool 10 is in a static or at rest position. The differential pressure acting on the ring member 40 is effective to maintain the ring member 40 down, in a closed position, with the sealing ring 42 against the top 18a of the cylinder 18. However if the pressurized fluid above the ring member 40 is discharged, the pressurized fluid acting through the passageway 44 is effective to unseat the ring member 40 from the edge 18a of the cylinder 18 to dump pressurized fluid into the top of the main cylinder 18 and to drive the drive piston 26 through the drive stroke.

When the fastener driving tool is at rest, or during the return stroke of the drive piston, the upper open end of the cylinder 18 is exhausted to the atmosphere through the exhaust valve assembly 32. In the illustrated embodiment the exhaust valve assembly includes a disc-shaped valve member 50 having a resilient valve element 52, one edge 52a of which is engageable with an inwardly projecting lip 40a of the ring member 40 when the ring member is displaced upwardly to provide a seal therebetween. The valve element 52 is spaced below the inner surface of a downwardly projecting boss 54 defined in a cap 56 of the tool 10. The downwardly projecting boss has a plurality of exhaust passageways 58 providing for the exhaust of the fluid when the ring member 40 is in its downward position.

To provide for the return stroke of the fastener driving assembly 24, there is provided a return air chamber 60 communicating with the lower end of the cylinder 18 through a plurality of fluid inlet ports 62 and a plurality of fluid outlet ports 64. Moreover the drive piston 26 is provided with a pair of spaced O-rings 66 and 68, and a passageway 70 that communicates from the upper surface of the piston 26 opening between the O-rings 66 and 68. The smaller passageway 70 defines a valve or passage for the flow of return fluid from above the piston 26 into the return air chamber 60 whenever the passageway 70 is aligned with the fluid inlet ports 62, as illustrated in FIG. 2. Thus it will be understood that in the normal operation of the fastener driving tool 10, the working fluid above the piston 26 will flow through the passageway 70 and fluid inlet ports 62 into the return air chamber 60, and will thereafter flow through the fluid outlet ports 64 below the piston 26 to drive the piston 26 back through its return stroke. For efficient piston return, restricting passage 70 should be smaller than passage through ports 64. The fluid pressure drop through port 64 should be appreciably less than that through port 70, otherwise, fluid will escape from this port rapidly to atmosphere when the poppet is closed and the exhaust valve 52 is open. In this event the piston will not shift initially blocking passage between ports 62 to 70, thereby allowing escape of fluid from the storage chamber 60 until it is depleted. The fluid pressure drop should be less through the port beneath the piston than above, otherwise it will not be displaced sufficiently, blocking ports 62 and 70 and allowing the full return stroke. A greater volume of fluid will exit from chamber 60 to the bottom of the driver thus shifting it upwardly and closing off flow from passage 62 to above the driver and to atmosphere. Residual return fluid below the piston 26 will be dissipated to atmosphere by bleeding through a bleed opening 71 formed between the drive blade 28 and a washer 72.

In accordance with the customary practice, there is provided a resilient cushioning member or bumper 74 in the lower end of the cylinder 18, defining a stop for the piston 26 when it is at the end of its drive stroke. At this time the passageway 70 will be aligned with the fluid inlet port 62 as indicated in FIG. 2.

In the event that the bumper 74 has deteriorated, so that the piston 26 moves down the cylinder 18 further than desired, to the position illustrated in FIG. 3, the passageway 70 will no longer align with the fluid ports 62; the O-ring 66 of piston 26 will have cleared past the fluid ports 62. Thus any pressurized fluid entering the return air chamber 60 as the piston 26 travels past the ports 62 will be discharged into the cylinder 18 above the piston 26 and exhausted to atmosphere through the exhaust valve assembly 32, and the piston 26 will not return upon completion of a drive stroke. Under normal conditions, fluid will leak only momentarily through the small port 70, until the fluid pressure beneath the piston discharging through the least resistant port 64, raises the piston to its fully retracted position. When the piston is displaced below the larger port 64, as caused by deterioration of the bumper, a much higher proportion of the stored fluid will escape above the piston as this flow is no longer restricted through the small passage 70. A substantial decrease in chamber 60 fluid pressure will result, preventing the full return of the piston. The tradesmen will be required to replace the fastener driving tool and to have the tool serviced so that the bumper 74 may be replaced.

The control valve assembly 22 includes a trigger valve 78, a safety valve 80, and a cycling valve 82. As is known in the art, the safety valve 80 includes an actuator rod 84 connected by linkage to move down when the nosepiece 38 of the fastener driving tool is in engagement with the workpiece, and is programmed to prevent firing or cycling of the tool when the nosepiece 38 is not in engagement with the workpiece. The trigger valve 78 includes a trigger 86 which may be depressed to a first position, illustrated in phantom as 86' in FIG. 6, and represented in FIGS. 9 and 10 to provide for single-fire operation of the tool 10, and further depressible to a second position illustrated in phantom in FIG. 6 as 86", represented in FIG. 11 wherein there is provided autofire operation of the tool 10 so long as the trigger is held in the depressed position. Any suitable means may be provided for positioning the trigger depression into its intermediate position; however in the illustrated embodiment there is provided a pneumatic bias to the trigger 86 such that for depression of the trigger 86 to its intermediate position 86' the trigger 86 is brought to bear against an outwardly biased piston 90 riding within a cylinder 92 communicating with the fluid reservoir 16 through a passageway 94. In order to further depress the trigger 68 into its position 86", the trigger 86 must overcome the resisting bias of the piston 90, depressing the piston 90 to the position illustrated in phantom in FIG. 6. The cycling valve 82 is effective to control the return movement of the fastener driving assembly 24 through its return stroke and will control the return thereof through a single cycle or through multiple repetitive cycles as called for by the function of the trigger 86.

Advantageously the control valve assembly 22 including the trigger valve 78, safety valve 80 and cycling valve 82 is housed within one compact removable valve housing 98, best illustrated in FIG. 12. Passageways may be die cast into the housing 98 and the housing 98 is readily secured to the housing 12 with the upper end thereof retained by a suitable pin 100 and the lower end thereof fastened by suitable screws or bolts 102. Advantageously the valve housing 98 may be readily removed for repair and replacement.

Referring now to the valves in the control valve assembly 22, the cycling valve 82 includes a differential cycling valve cylinder 108 defined within the valve housing 98, closed at both ends, and slideably receiving a cycling valve spool or element 110 of a differential diameter type. The cycling valve cylinder 108 has an upper large diameter portion 108a and a lower small diameter portion 108b. The cycling valve spool 110 has an enlarged upper portion 110a received within the large diameter portion 108a, and a lower small diameter portion 110b slideably receivable within the small diameter portion 108b. Additionally the cycling valve spool 110 is provided with a large sealing ring 112 defining a valve piston and a pair of spaced small diameter O-rings 114 and 116 spaced apart from the O-ring 112 and carried on the small diameter portion 110b. A first cycling port 118 opens into the end of the small diameter portion 108b of the valve cylinder 108. A second cycling port 48a opens into the lower end of the small diameter portion 108b of the valve cylinder 108 intermediate the stroke of the O-ring 116, and connects through passageway 48 to the upper surface of the ring member 40 of the cylinder valve assembly 20. A third cycling port 122 opens into the small diameter portion 108b of the valve cylinder 108 intermediate the stroke of the small diameter O-rings 114 and 116. A fourth cycling port 124 opens into the valve cylinder 108 intermediate the large O-ring 112 and the spaced small O-ring 114 throughout their travel. A fifth cycling port 126 opens into the end of the large diameter portion 108a of the valve cylinder 108 and is connected by a signal passageway 128 (FIG. 8) to a source of signal fluid, here shown as connected to the return air chamber 60.

The trigger valve 78 includes a valve cylinder 140, open to the atmosphere at its upper end, and slideably receiving a trigger spool valve 142, the upper end of which is engaged by a projecting finger 86a of the trigger 86 to be actuated thereby. The trigger spool valve 142 contains three spaced O-rings 144, 146 and 148. The trigger spool valve 142 is movable from a normal position, with the tool at rest, as illustrated in FIGS. 5 and 6, to an intermediate or single-fire position as illustrated in FIGS. 9 and 10, to a fully depressed or autofire position as illustrated in FIG. 11. The valve cylinder 140 is provided with an annular exhaust passageway 150 formed around the upper protruding end of the valve spool 142. A first trigger port 152 opens into the valve cylinder 140 intermediate the normal and displaced positions of the valve O-ring 144. A second trigger port 154 opens into the valve cylinder 140 intermediate the stroke of the trigger spool valve 142 between the valve O-rings 144 and 146. A third trigger port 156 opens into the valve cylinder 140 intermediate the travel of the valve O-ring 146 from the single-fire position to the autofire position and is connected to the fourth port 124 of the cycling valve 82 by a passageway 158. A fourth trigger or exhaust port 160 opens into the valve cylinder 140 intermediate the travel of the valve O-rings 146 and 148, and exhausts to the atmosphere. A fifth trigger port 162 opens into the closed lower end of the valve cylinder 140, and is connected to the second trigger port 154 by a passageway 164, and to the reservoir by a passageway 165.

Referring now to the safety valve 80, the safety valve 80 is defined by a safety valve cylinder 172 containing a safety spool valve 174 joined to the actuating rod 84 for movement therewith. The safety spool valve 174 carries three spaced O-rings 176, 178 and 180 defining or forming a pair of annular passageways 182 and 184 therebetween. A first safety port 186 opens into the annular passageway 182 formed by the O-rings 176 and 178, and is connected to the first trigger port 152 by a passageway 188. A second safety port 190 opens into the valve cylinder 172 intermediate the travel of the O-ring 178, and is connected to the first port 118 of the cycling valve 82 by a passageway 192. A third safety port 194 opens into the valve cylinder 172 into the annular passageway 184, and is connected to the trigger ports 154 and 162 by a passageway 196, and further interconnects these trigger ports with the third port of the cycling valve 82 through a passageway 198. An adjustable needle valve 204, FIG. 8, restricts the fluid flow through the signal passageway 128, thereby providing the regulation of the repetitive cycling rate of the tool 10 when in the autofire position.

From the above detailed description, the operation of the control valve assembly 22 is believed clear. However, briefly, it will be understood that the control valve assembly has three operable positions; namely a normal position, with the valve elements as illustrated in FIG. 5; a single-fire position with the trigger and safety valve as shown in FIGS. 9 and 10, and the cycling valve cycling between the positions also therein indicated; and an autofire position, with the safety and trigger valves in the position illustrated in FIG. 11 and the cycling valve movable between the position illustrated in FIG. 11 and the position illustrated in FIG. 10 repetitively so long as the trigger 86 is maintained in the fully depressed position.

More specifically, and referring to the normal or at rest position of the tool, in this position the upper surface of the ring member 40 is maintained at reservoir pressure through the trigger port 162, passageway 196, safety port 194, annular passageway 184, safety port 190, passageway 192, port 118 in the cycling valve, port 48a, and passageway 48 to maintain the ring member 40 down and closed against the top 18a of the cylinder 18.

The tool 10 will not operate unless both the trigger valve 78 and safety valve 80 are actuated. Thus if the safety valve 80 alone is actuated, then the flow of pressurized fluid between the safety ports 190 and 194 will be blocked by the O-ring 178, but the upper surface of the ring member 40 will not be exhausted to atmosphere and thus the tool 10 will not fire. More specifically, the upper surface of the ring member 40 remains pressurized by the fluid supplied to the port 190 over the fluid conveying system including the passages 196, 164, the port 154, the clearance between the O-rings 144 and 146, the port 152, the passage 188, the port 186, and the clearance between the O-rings 176 and 178.

When it is desired to operate the tool 10 as a single-fire tool, it is necessary that the safety valve 80 be actuated to the operative position, as illustrated in FIG. 9, and that the trigger valve 78 be actuated to its intermediate position as also therein illustrated. In this position the upper surface of the ring valve 40 will be exhausted to atmosphere through the passageway 48, cycling ports 48a and 118, passageway 192, safety ports 190 and 186, passageway 188, trigger port 152, and through the exhaust passageway 150 thus opening the cylinder valve assembly 20 and driving the fastener driving member 24 through a fastener driving cycle. At the same time the differential portion of the cycling valve 82, intermediate the large and small O-rings 112 and 114, will be exhausted to atmosphere through the cycling port 124, passageway 158, trigger port 156, and trigger port 190. As soon as the drive piston 26 reaches the end of its drive stroke, the return air chamber 60 will be pressurized by the flow of pressurized fluid through the passageway 70 and fluid inlet port 62. The pressure will instantly act on the upper large diameter portion of the cycling valve 82 through the passageway 128 and cycling port 126. Since there is no counter bias to the cycling valve 174, the cycling valve 82 will instantly shift from the position illustrated in FIG. 9 to the position illustrated in FIG. 10. At this time pressurized fluid will flow from the reservoir by means of the trigger port 162, passageway 198, and cycling ports 122 and 48a through passageway 48 to the upper surface of the ring member 40 to close the ring member 40 against the open upper end 18a of the cylinder 18. This permits exhaust of the upper end of the cylinder 18 and the pressurized fluid which has now built up in the return air chamber 60 will be effective to return the piston 26 to its normal or at rest position. Moreover since there is no force on the cycling valve 82 tending to return the cycling valve 82 back to its original position, it will remain in its displaced position so long as the trigger is held in the single-fire condition. Upon release of the safety and/or the trigger from the single-fire position, pressurized fluid will be admitted to the closed lower end of the cycling valve to the port 118, in like manner as described in connection with FIG. 5, and the cycling valve 82 will be returned to its normal position.

When it is desired to operate the tool 10 in the autofire position, it is necessary that the trigger 86 be fully depressed against the resisting bias of the piston 90, depressing the trigger spool valve 142 to the position illustrated in FIG. 11. Under these conditions there is provided a return bias to the cycling valve 82; specifically the differential portion of the cycling valve spool 110 will be connected to reservoir pressure through the port 124, passageway 158, trigger ports 156 and 154, passageway 164, and trigger port 162 which is connected to the reservoir through the passageway 165. As soon as the piston 26 reaches the end of its driving stroke, as illustrated in FIG. 2, fluid pressure will build up within the return air chamber 60. This pressure will be transmitted through the signal passageway 128, past the needle valve 204, and into the upper closed end of the portion 108a of the cycling valve cylinder 108. As soon as the pressure in this end of the valve cylinder 108 builds up to a sufficient magnitude to overcome the return bias on the differential diameter portion of the valve spool 110, the cycling valve spool 110 will shift to its down position, as illustrated in FIG. 10. Because the rate of pressure buildup in the valve cylinder 108 from the signal passageway 128 may be regulated by adjusting the needle valve 204, the speed at which the cycling valve spool 110 shifts can be controlled, and thus the cycling rate of the tool is selectively controlled. As soon as the cycling valve spool 110 is shifted to its downward position, pressure will once again be applied to the upper surface of the ring valve 40 in like manner as described in connection with FIG. 10. Specifically the reservoir fluid from the trigger port 162 will flow through passageway 198 and cycling passageways 122 and 48a, through passageway 48 to the upper surface of the ring member 40. At the same time the air pressure below the piston 26, effective to return the drive piston 26 upwardly through a return stroke, will be depleted by leakage through the bleed opening 71. The pressure of the fluid in the closed upper end of the portion 108a of the cycling valve cylinder 108 will be bled off the atmosphere and the return bias pressure acting on the differential diameter portion of the cycling valve spool 110, applied through the trigger port 162, passageway 164, trigger ports 154 and 156, passageway 158, and safety port 124, will be effective to more or shift the cycling valve spool 110 back to its upper position, to the position illustrated in FIG. 9. At this point the cycling valve 82 is reset to exhaust the cylinder valve assembly 20 and to repeat the cycling operation of the tool.

Although the present invention has been described by reference to only a single embodiment, it will become apparent that numerous modifications and embodiments may be devised by those skilled in the art, and it is intended by the appended claims to cover all modifications and embodiments which will fall within the true spirit and scope of the present invention.

Claims

What is claimed and desired to be secured by Letters Patent of The United States is:

1. A pneumatically operated fastener driving tool including a housing having a cavity defining a fluid reservoir; a cylinder in said housing; a piston slideably mounted in the cylinder; main valve means controlling admission of fluid to and the exhaustion of fluid from one end of the cylinder; pneumatic piston return means including a return air chamber, a cycling valve having a body defining a cycling valve cylinder of the differential type having a small and a large diameter portion and a spool valve element in said cylinder movable through a stroke from a first to a second position, said spool valve element having large and small diameter portions slideable in the corresponding portions of the cycling valve cylinder and having a first sealing means on the large diameter portion of the spool valve element and a pair of spaced second and third sealing means on the small diameter portion of the spool valve element, said body having means defining a first port in the end of said small diameter portion of the cycling valve cylinder, first passageway means extending from said first port, a second port intermediate the stroke of the third sealing means, second passageway means connecting said second port to said main valve means, a third port opening between the second and third sealing means, throughout their stroke, third passageway means connecting said third port to said fluid reservoir, a fourth port opening between the first sealing means and the second sealing means throughout their travel, fourth passageway means extending from said fourth port, a fifth port in the end of said large diameter portion of the cycling valve cylinder, fifth passageway means extending from said fifth port to a source of signal fluid, and control means for selectively connecting said first and fourth passageways to said reservoir and to exhaust.

2. A fastener driving tool as set forth in claim 1 wherein said control means includes a trigger valve movable between a first position exhausting said fourth port, a second position exhausting said first port to provide single-fire operation of said tool, and a third position connecting said fourth port to the reservoir to provide multiple-fire operation of said tool.

3. A fastener driving tool as set forth in claim 2 and including a safety valve in said first passageway movable between a safety position connecting said first port to said reservoir and a second position connecting said first port to said trigger valve for exhaust thereby.

4. A pneumatically operated fastener driving tool as set forth in claim 1 and including metering means in said fifth passageway regulating the repetitive firing rate of said tool without affecting the single-fire rate thereof.

5. A pneumatically operated fastener driving tool as set forth in claim 1 wherein said fifth passageway opens into said return air chamber.

6. A pneumatically operated fastener driving tool including a piston slideably mounted in a cylinder and movable through a driving and return stroke, control means including manually operable means operable from a normal position to a first operated position for selectively operating said tool through a single-fire operation, wherein said piston automatically moves through a single driving and return cycle while said manually operable means remains in said first operated position, said manually operable means being movable to a second operated position to effect a multiple-fire operation wherein said piston automatically and continuously moves through repetitive cycles of driving and return strokes, and means for adjustably regulating the repetitive cycling rate of said tool during said multiple-fire operation without altering the single firing cycling speed thereof.

7. A pneumatically operated fastener driving tool as set forth in claim 6 wherein said tool includes a cycling valve movable between a normal position controlling a power stroke and an actuated position providing the return stroke, and means selectively providing for retention of said cycling valve in said actuated position and for cycling said cycling valve in response to a cycling signal.

8. A pneumatically operated fastener driving tool comprising a driving member operable through cycles of power and return strokes, control means selectively positionable to a first position to automatically operate said driving member through a single cycle with the control means held in the first position and to a second position to automatically operate said driving member through repetitive cycles with the control means held in the second position, and means for adjustably regulating the repetitive cycling rate without altering the single cycle speed thereof.

9. A fastener driving tool as set forth in claim 8 and including a cycling valve controlling the movement of said driving member through its strokes, said cycling valve having a differential diameter portion defining first and second surfaces of different area, first passage means connecting said first surface area to a source of signal fluid, and second passage means connecting said second surface area selectively to the atmosphere and to a source of pressurized fluid in response to the selective setting of said control means to said first and second positions for single-cycle operation and multifire operation.

10. A fastener driving tool as set forth in claim 9 and including adjustable means for throttling the fluid flow in said first passage.

11. A fluid-operated fastener driving tool comprising a driving member operable through a cycle of a power stroke and a return stroke, a main valve assembly operable to apply fluid to and to exhaust fluid from the driving member to move the driving member through its power and return strokes, a cycling valve operable between spaced positions to control the operation of the main valve assembly, and manually operable control means operable from a normal position to a single cycle position to control the main valve and the cycling valve to effect a single cycle of the driving member while the manually operable control means remains in said single cycle position, said manually operable control means being operable to a second position to control the main valve assembly and the cycling valve to automatically and continually move said driving member through successive and repeated cycles so long as the manually controlled means remains in said second position.

12. The tool set forth in claim 11 in which the manually operable control means includes means operable in one of said first and second positions for applying a bias to the cycling valve and operable in the other of said first and second positions to prevent the application of a bias to the cycling valve.

13. A fluid-actuated fastener driving tool operable through a single cycle of a power stroke and a return stroke or a number of cycles each including a power stroke and a return stroke, said tool comprising a cylinder, a piston slideable in the cylinder, fluid-actuated main valve means for alternately supplying fluid to and exhausting fluid from the cylinder to move the piston through the power stroke and a return stroke, respectively, a cycling valve operable between two spaced positions and coupled to the main valve means for selectively controlling the connection of the main valve means to fluid and the atmosphere, said cycling valve being coupled to receive fluid admitted to the cylinder by the main valve means and operable to one of its two spaced positions thereby on each tool operation to institute the return stroke of the piston, and manual control means operable from a normal position to a first position to control the cycling valve to remain in said one position until the manual control means is returned to its normal position so that the tool automatically operates through a single cycle, said manual control means also being operable from a normal position to a second position to control the cycling valve to move from said one position to the other of its positions on each return stroke so long as the manual control means is held in its second position so that the tool automatically operates through a number of cycles.

14. The tool set forth in claim 13 in which the cycling valve includes a differential piston operator and the manual control means includes a valve for selectively connecting the differential piston to the atmosphere and fluid.

15. A pneumatically operated fastener driving tool including a housing, a cylinder in said housing, a piston slidably mounted in said cylinder for movement through power and return strokes, cylinder valve means for controlling the admission and exhaust of fluid from one end of said cylinder to drive said piston through a power stroke and permit return thereof, cushioning means positioned in the other end of said cylinder in the path of said piston to stop and cushion power strokes thereof at a normal piston stopping point, an air return chamber, first port means adjacent the cushioning means for supplying air from the chamber beneath the piston to move the piston through a return stroke, means for supplying pressurized air to the chamber incident to each power stroke, and second port means spaced above the first port means and placing the chamber in communication with the cylinder, said second port means being so spaced relative to the cushioning means that when the cushioning means deteriorates a given amount, the piston moves downwardly beyond the normal piston stopping point and the second port means become opened to discharge pressurized air from the chamber into the cylinder above the piston, the second port means being of such size that the air discharged renders the air in the chamber ineffective to move the piston through a return stroke.

16. The fastener driving tool set forth in claim 15 in which the piston carries a sealing means disposed between said one end of the cylinder and the second port means when the piston is at its normal stopping point and disposed between said first and second port means when the cushioning means deteriorates said given amount.

17. The fastener driving tool set forth in claim 16 in which the means for supplying pressurized air to the chamber includes a passage through the piston and opening into the cylinder between said sealing means and said other end of the cylinder.

18. A fluid-actuated fastener driving tool operable through a single cycle of a power stroke and a return stroke or a number of cycles each including a power stroke and a return stroke, said tool comprising a cylinder, a piston slideable in the cylinder, fluid-actuated main valve means for alternately supplying fluid to and exhausting fluid from the cylinder to move the piston through the power stroke and the return stroke, respectively, a cycling valve operable between two spaced positions and coupled to the main valve means for selectively controlling the connection of the main valve means to fluid and the atmosphere, said cycling valve being coupled to receive fluid admitted to the cylinder by the main valve means and operable to one of its two spaced positions thereby on each tool operation to institute the return stroke of the piston, and manual means coupled to the cycling valve and the main valve means for selectively controlling operation of the tool through a single cycle or a number of cycles, said control means including first valve means operable between operated and released positions for selectively supplying a connection to fluid and the atmosphere to operate the tool, said manual control means also including a second valve means, said second valve means being operable to a first position to control the cycling valve to remain in said one position until the first valve means is returned to its released position so that the tool automatically operates through only a single cycle, said second valve means also being operable to a second position to control the cycling valve to move from said one position to the other of its positions on each return stroke so long as the first valve means is in its operated position so that the tool operates through a number of cycles.

19. The tool set forth in claim 18 in which the cycling valve includes a differential piston operator with two fluid surfaces, one of said surfaces receiving fluid admitted to the cylinder by the main valve means, and in which the second valve means selectively connects the other of said surfaces to the atmosphere and fluid.