US3837556A

US3837556A - Pneumatic nailing machine

Info

Publication number: US3837556A
Application number: US00287687A
Authority: US
Inventors: R Doyle; A Obergfell
Original assignee: Duo Fast Corp
Current assignee: Duo Fast Corp
Priority date: 1972-09-11
Filing date: 1972-09-11
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24

Abstract

A pneumatic nailer for driving nails from a flexible belt thereof into a workpiece includes an index cylinder for feeding successive nails into a drive track defined by the cylinder and a nosepiece structure. A sensor engaging flutes or recesses in the cylinder wall controls a control valve assembly to inhibit operation of a driver when the cylinder is not properly positioned. The control valve assembly includes a single cycle valve controlled by a control valve for controlling a pneumatic motor for the driver so that the driver is automatically retracted after a power stroke. This permits the use of the nailer in assembly machines wherein the nailer and the workpieces are moved relative to each other by preventing the driver ''''follow-through'''' from locking the nailer and the workpiece together. The sensor disables the control valve when the cylinder is not properly positioned.

Description

United States Patent Doyle et al.

[ 1 Sept. 24, 1974 PNEUMATIC NAILING MACHINE Primary Examiner-Granville Y. Custer, Jr. 7 A ttoiiitv'f Age/1'1. or Firm-Mason. Kolehmainen. 4 Rathburn & Wyss [57] ABSTRACT A pneumatic nailer for driving nails from a flexible belt thereof into a workpiece includes an index cylinder for feeding successive nails into a drive track defined by the cylinder and a nosepiece structure. A sensor engaging flutes or recesses in the cylinder wall controls a control valve assembly to inhibit operation of a driver when the cylinder is not properly positioned. The control valve assembly includes a single cycle valve controlled by a control valve for controlling a pneumatic motor for the driver so that the driver is automatically retracted after a power stroke. This permits the use of the nailer in assembly machines wherin the nailer and the workpieces are moved relative to each other by preventing the driver follow-through from locking the nailer and the workpiece together. The sensor disables the control valve when the cylinder is not properly positioned.

5 Claims, 8 Drawing Figures PNEUMATIC NAILING MACHINE This invention relates to a new and improved fluid powered fastener driving apparatus and, more particularly, to an improved pneumatic nailer using a cylinder feed for flexible belts of nails and having an improved control and safety valve assembly.

Pneumatic nailers are frequently used in structural assembly machines to construct such items as wall frame sections. These machines have a greater production rate if the nailer and the workpieces can be moved almost continuously relative to each other. This can be frustrated by the follow-through of the nail driving blade into the wood if the blade is not immediately retracted following a power stroke. Further, the production rate of these machines is increased by feeding nails from flexible belts of great length. One common way of feeding such belts is an indexed rotary cylinder having nail receiving grooves which may define at least a part of the nail drive track. Thus, it is necessary to insure that the cylinder is accurately positioned to insure that it is not struck by the driver blade or element. In addition, any sensor means for detecting proper cylinder position should be kept away from the drive track to avoid possible damage to the sensor.

Accordingly, one object of the present invention is to provide a new and improved fastener driving tool.

Another object is to provide a pneumatic nailer in which the nail driver is automatically operated through a return stroke at the conclusion of a power stroke, and a cycle of a power stroke and a return stroke cannot be initiated whenever a nail feeding cylinder is not properly positioned.

A further object is to provide a fluid actuated nailer including a new and improved control valve assembly responsive to the position of a nail feeding cylinder and a control for initiating tool operation, the control valve assembly also including a single cycle valve.

In accordance with these and many other objects, an embodiment of the invention comprises a pneumatic fastener driving tool with a pneumatic motor for reciprocating a nail driving element within a drive track formed in a nosepiece structure. A rotatably mounted cylinder with axially extending and peripherally spaced grooves for receiving successive nails is indexed to successive predetermined positions in which the cylinder forms at least a part of the drive track and in which positions a nail is disposed within the drive track. A sensor controlled by an actuator or element bearing against the peripheral wall of the cylinder detects the proper positioning of the cylinder. An improved control valve assembly includes a single cycle valve for automatically operating a pneumatic motor for the driver blade through a cycle comprising a power stroke and a return stroke. The single cycle valve is controlled by a shuttle valve which is actuated, for instance, when the nailer and a workpiece are moved into a nail driving relation. A further pneumatic valve controlled by the sensor disables the shuttle valve whenever the cylinder is improperly positioned so as to prevent possible damage to either the cylinder or the nail driver.

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

FIG. 1 is a side elevational view of a pneumatic nailer embodying the invention;

FIG. 2 is a side elevational view taken from the opposite side from FIG. 1 and in partial section to illustrate a pneumatic motor and a nail driving blade actuated thereby;

FIG. 3 is a fragmentary bottom view in partial section taken along line 3-3 in FIG. 1;

FIG. 4 is an enlarged sectional view of a sensor for a nail feeding cylinder taken along line 4-4 in FIG. 1;

FIG. 5 is a partially schematic sectional view of a control valve assembly for the nailer shown in FIGS. 1 and 2 illustrating the control valve assembly in a normal condition;

FIG. 6 is a schematic view similar to FIG. 5 illustrating the condition of the tool following operation and at the initiation of a power stroke of the tool;

FIG. 7 is a schematic view similar to FIGS. 5 and 6 illustrating the control valve assembly at the beginning of a return stroke; and

FIG. 8 is a schematic view similar to FIGS. 5-7 illustrating the control valve assembly in a normal state but disabled from operation because of improper cylinder positioning.

Referring now more specifically to FIGS. 1-4 of the drawings, therein is illustrated a pneumatic nailer which is indicated generally as 10 and which embodies the present invention. The tool 10 includes a housing indicated generally as 12 including a head portion 12A containing a pneumatic motor and a reservoir portion 128 providing a large capacity reservoir of compressed air in immediate proximity to the driving components so as to permit high speed operation of the tool without reduction in operating air pressure. A fastener feeding assembly indicated generally as 14 (FIG. 1) including a rotatably mounted cylinder 16 feeds successive fasteners or nails 18 (FIG. 3) into a drive track 20 partially defined by the cylinder 16 and the nose-piece structure 22 secured to, depending from, and forming a part of the housing 12. A pneumatic motor indicated generally as 24 (FIG. 2) automatically reciprocates a nail driver 26 through a power and a return stroke through the drive track 20 to drive a fastener or nail 18 into a workpiece under the control of a control valve assembly indicated generally as 28 (FIGS. 5-8). The control valve assembly 28 is connected to and controlled by a sensor assembly 30 (FIG. 3) responsive to the position of the cylinder 16 to prevent operation of the tool 10 when the cylinder 16 is not properly positioned.

The constructions of the pneumatic motor 24 and the fastener feeding assembly 14 are conventional in the art, and the details are not set forth herein. As an example, the pneumatic motor 24 can comprise the drive means shown and described in detail in US. Pat. Nos. 3,253,760 (Doyle et al.) and 3,434,643 (Wandel). In general, compressed air supplied through a fitting 32 (FIGS. 1 and 2) to the reservoir formed by the housing portion 128 is supplied through the control valve assembly 28 to a passage 34 (FIG. 2). This passage communicates with a space 36 to normally supply a continuously upwardly directed force to a slidably mounted cylinder 38. This biases the upper edge of the cylinder 38 against a resilient main valve element 40 to seal off communication between the interior of the cylinder 38 and the compressed air in the reservoir which surrounds the upper end of the slidably mounted cylinder 38. When the passageway 34 is connected to or vented to the atmosphere, the compressed air acting on exposed surfaces of the cylinder 38 moves this cylinder downwardly away from the resilient valve member 40 so that compressed air enters the open upper end of the cylinder 38. This air acts on a piston 42 which is connected to the upper end of the driver blade 26 to drive this piston 42 downardly through a power stroke during which the driver blade 26 moves downwardly through the drive track 20 (FIG. 3) to drive the nail 18 into a workpiece. When pressurized fluid or compressed air is again supplied to the passageway 34 and the chamber or space 36, the cylinder 38 is moved upwardly to engage the main valve element 40, and the upper interior of the cylinder 38 is vented to the atmosphere. A control valve assembly indicated generally as 44 controls the supply of pressurized fluid to the cylinder 38 beneath the piston 42 to return the piston to its normal position. These operations of the pneumatic motor 28 and the construction thereof are set forth in detail in the two above-identified patents.

The tool is designed particularly for use in stationary applications or structural assembling machine applications in which repetitive identical fastening operations are performed. To increase the production of structural machines using the pneumatic nailers 10, it is desirable to use long lengths of flexibly joined or belted nails including a large number of individual nails 18 joined by a flexible tape such as a tape 45 (FIG. 3). This permits operation of the pneumatic nailer 10 for longer periods of time without requiring the replacement of the nail supply. A suitable strip of flexibly joined or belted nails 18 as well as the method of making such nail belts is shown and described in detail in a copending application of Ronald J. Mosetich et al., Ser. No. 90,688, filed Nov. 18, I970, which application is assigned to the same assignee as the present invention.

The assembly 14 for feeding successive nails 18 into the drive track 10 is conventional in the art and includes the cylinder 16 which is rotatably mounted on the nosepiece structure 22. The cylinder 16 is provided with a plurality of axially extending and peripherally spaced grooves, recesses, or flutes 16A (FIGS. 1-3) for receiving successive nails 18. These grooves 16A are defined by intervening teeth or ribs 168. A belt or strip of nails 18 is fed to the cylinder through a raceway or guiding structure 46 from a suitable receptacle in which the belt is fan-folded to provide a large capacity supply. To permit access to the cylinder 16, there is mounted on the nosepiece structure 22 a gate assembly indicated generally as 48 including two

arms

50 and 52 joined by a central post 54 and pivoted on the nosepiece structure 22 by a pivot pin 56. The gate assembly 48 can be pivoted in a counterclockwise direction (FIG. 3) to obtain access to the outer surface of the cylinder 16 so as to bring the leading edge of a new strip of nails 18 into a position with the nails 18 located within the grooves 16A.

The cylinder 16 is indexed by a conventional piston actuated pawl including a pawl member 58 (FIG. 1) with the pawl portion engaging the teeth 16B adjacent the upper end of the cylinder and resiliently guided and biased into engagement therewith by an assembly 60 carried on the nosepiece 22. The other end of the pawl 58 is pivotally connected to a piston operator 62, the piston portion of which (not shown) is received within a cylinder assembly 64 carried on the housing 12. The piston is resiliently biased to a normal extreme lefthand position as shown in FIG. 1 by a compression spring (not shown) interposed between the right-hand surface of the piston and a wall of the cylinder assembly 64. When compressed air is supplied to the upper interior of the cylinder 38 in the manner described above, a portion of this air passes through a flexible line or conduit 66 and shifts the piston and the pawl 58 to the right (FIG. 1) during which the pawl slides idly over one tooth 163 on the cylinder 16. When the piston 42 is returned by the pneumatic motor 24 in the manner described above and the upper interior of the cylinder 38 is placed in communication with the atmosphere, the line 66 is also placed in communication with the atmosphere, and the compression spring moves the pawl 58 to the left as shown in FIG. 1. The pawl now engages the tooth 16B and rotates the cylinder 16 one increment of movement in a counterclockwise direction (FIG. 3) to advance the next nail 18 into the drive track 20.

As shown in FIG. 3, the walls defining each slot or groove 16A in the cylinder 16 sequentially form a portion of the drive track 20. Thus, to avoid damage to the cylinder 16 and to the drive blade 26, it is necessary to insure that the cylinder 16 is properly positioned in a predetermined location following each indexing movement of the feeding assembly 14. To accomplish this, the detector assembly 30 is provided. This assembly (FIGS. 14) includes a housing or supporting member 70 with a generally centrally disposed slot 70A (FIGS. 1 and 4) in which is pivotally mounted by a pivot pin 72 a sensor lever 74. One end 74A of the lever is slightly offset and adapted to be received within successive grooves 16A on the cylinder. Another end 74B of the lever 74 is disposed within an opening 76 into a valve chamber 78 closed at one end by a threaded plug 80. Disposed within the valve chamber 78 is a valve 0- ring 82, a ball valve element 84, and a compression spring 86 interposed between the ball valve element 84 and the sealing plug 80. The compression spring 86 normally biases the ball valve 84 into engagement with the valve member 82 to close the opening 76 so that the valve chamber 78 is normally sealed off from communication with the atmosphere.

During the indexing movement of the cylinder 16 and whenever the cylinder 16 is not in a proper position, the engagement of a portion of the tooth 168 with the end portion 74A of the lever 74 pivots this lever in a clockwise direction (FIG. 4) so that the end portion 74B thereon moves through the opening 76 and displaces the ball valve 84 downwardly against the force of the compression spring 86. This places the valve chamber 78 in communication with the atmosphere through the port or opening 76. When, however, the cylinder 16 has been advanced to a proper position, the detector assembly 30 is in the state shown in FIGS. 3 and 4, and the valve chamber 78 is sealed off from communication with the atmosphere.

To provide means for using the detector assembly 30 to control the operation of the valve assembly 28, the housing 70 is provided with a perpendicular passage 88 communicating with a fitting 90 to which a flexible conduit 92 is connected. The flexible conduit 92 extends to the control valve assembly 28. Whenever the valve chamber 78 and thus the conduit 92 is placed at atmospheric pressure, an indication is provided that the cylinder 16 is not in the proper position, and operation of the tool 10 should not be initiated.

The control valve assembly 28 is shown in its normal state in FIG. 5 of the drawings and includes a housing 100. The housing 100 carries a main valve assembly indicated generally as 102, a single cycle valve assembly indicated generally as 104, a shuttle valve assembly indicated generally as 106, and a safety valve assembly which is indicated generally as 108 and which is controlled by the sensor or detecting assembly 30. The main valve assembly includes an inlet line 110 connected to the reservoir of compressed air provided by the housing portion 12B. This pressurized air normally flows from the passage 110 to the passage 34 so as to maintain the cylinder 38 in its elevated position as described above. The main valve assembly 102 also includes a two-diameter bore 112 in which is slidably mounted a smaller diameter valve 114 carrying a pair of sealing O-

rings

116 and 118 and to which is integrally formed or connected a piston portion 114A carrying an O-ring 120.

The single cycle valve assembly 104 includes a single diameter bore or valve chamber 122 in the upper end of which is mounted a throttle valve assembly 124. A valve piston 126 is disposed in the lower end of the cylindrical bore 122 biased against a resilient O-ring .128 by a compression spring 130 interposed between the throttle assembly 124 and the piston 126. The piston 126 carries three spaced O-

rings

132, 134, and 136.

The shuttle valve assembly 106 includes a twodiameter bore 140, in the smaller diameter portion of which is slidably mounted a valve member 142 carrying a pair of spaced O-

rings

144 and 146. The larger diameter portion of the bore 140 receives an integrally formed piston or operator portion 142A carrying a single O-ring 148 and normally biased against a resilient O-ring 150 disposed within the upper end of the bore 140.

The safety valve assembly 108 includes a twodiameter bore 152 connected to the passage 92. A resilient O-ring 154 rests in the bottom of the bore 152. Slidably mounted within the small diameter portion of the bore 152 is a valve member 156 carrying a pair of spaced O-

rings

158 and 160. An integrally formed piston or operator portion 156A is slidably mounted within the large diameter portion of the bore 152 and carries a single O-ring 162. The member 156 includes a passage 156B passing therethrough. The pressurized fluid from the inlet line 110 passes through a pair of

passageways

164 and 166 to be supplied to the passageway 156B in the piston portion 156A of the valve member 156 in the safety valve assembly 108. This supplies pressurized fluid to the lower end of the bore 152 to maintain the valve member 156 in the illustrated position. In addition, this pressurized fluid passes over the line 92 to be accumulated within the valve chamber 78 (FIG. 4) in the detector assembly 30.

A vent line 168 extending to the atmosphere normally connects the inner ends of the small diameter portions of the

bores

140 and 152 to the atmosphere.

This vent line is also effective over a passageway 170 to connect the area on the valve element 126 bounded by the O-

rings

132 and 134 to the atmosphere. Thus, a passageway 172 communicating with the closed end of the large diameter portion of the bore 112 is also normally connected to the atmosphere. In addition, the vent passageway 168 connects the lower end of the bore 122 to the atmosphere over a pair of

passageways

174 and 176 and connects the inlet to the throttle valve 124 to the atmosphere over the passageway 174 and an additional passageway 178.

To provide means for controlling the control valve assembly 28, a three-way valve shown schematically as 180 is provided. This valve can either be manually controlled as by actuating a trigger or preferably when the tool 10 is to be used in, for example, a frame assembling machine can be actuated by a lever responsive to the presence of a 2 X 4 stud. The valve 180 normally connects an inlet line 182 communicating with the upper end of the larger diameter portion of the bore to the atmosphere. When, however, the nailer 10 and a stud or workpiece are moved into a position for driving a nail 18, the valve 180 is operated to its alternate position shown in FIG. 6 to supply pressurized fluid from the reservoir in the housing portion 128 to the line 182. This pressure acts on the greater upper area of the piston portion 142A against the upwardly directed bias supplied through a passage 184 from the bore 152 to move the valve member 142 downwardly to the position shown in FIG. 6. In this position, the lower O-ring 146 cuts off communication between the

passages

174 and 168 and places the passage 174 in communication with a passage 186 that is supplied with pressurized fluid from the bore 152. The pressurized fluid supplied to the passageway 174 passes over the passageway 176 to accumulate within the lower end of the bore 122 beneath the valve member 126. This moves the valve member 126 upwardly against the bias of the compression spring 130 until the upper end of the valve member 126 abuts the lower end of the throttle valve 124, as shown in FIG. 6. In this position, the O-ring 134 on the valve element 126 in the single cycle valve assembly 104 closes off communication between the passageway 172 and the exhaust passage and connects the passageway 172 to the pressurized fluid supplied by the passage 164. Thus, pressurized fluid accumulates within the large diameter portion of the bore 112 to the right of the O-ring 120 on the piston operator 114A.

When sufficient compressed air accumulates within the bore 112 operating on the large area right-hand surface of the piston portion 114, the bias applied to the left-hand or small area portion of the piston 114A is overcome, and the valve member 114 shifts to the left to the position shown in FIG. 6. In this position, the O- ring 118 closes off communication between the

passageways

110 and 34 so that pressurized fluid is no longer supplied to the passage 34. In addition, the O- ring 116 on the valve member 114 moves into a recessed area 112A in the bore 112 so that the passageway 34 is connected to the atmosphere through a fairly large area opening. This dumps the air within the space or volume 36 beneath the cylinder 38 so that this cylinder moves downwardly in the manner described above to initiate a power stroke of the piston 42 and the connected driver blade 26. During this power stroke, the fastener 18 in the drive track 20 is driven into the workpiece, and the pawl 58 is advanced by the cylinder assembly 64.

When pressurized air is supplied to the passage 174 in the manner described above, it also passes through the passageway 178 and the throttle valve assembly 124 to begin accumulation within the bore 122 above the valve member 126 at a rate determined by the size of the orifices in the throttle valve 124. After a predetermined period of time sufficient to complete the driving operation, the pressure of the compressed air above the member 126 considered with regard to the effective surface thereof combined with the force of the com pression spring 130 overcomes the pneumatic bias applied to the lower surface of the valve member 126 and moves this valve member to the position shown in FIG. 7 of the drawings. The valve member 126 will remain in the position shown in FIG. 7 even though pressurized fluid of substantially the same pressure is acting on the approximately equal upper and lower exposed surfaces of the valve member 126 because of the overbalancing downwardly directed force provided by the compression spring 130. This return of the valve element 126 to the position shown in FIG. 7 initiates the return stroke of the pneumatic motor 24 during which the piston 42 returns to its normal position to retract the driver blade 26, and the spring bias in the cylinder assembly 64 retracts the piston and pawl 58 to index the feed cylinder 16 a single step, thereby placing the next nail 18 in the drive track 20 beneath the lower end of the retracted driver blade 26.

More specifically, when the valve element 126 moves downwardly from the position shown in FIG. 6 to the position shown in FIG. 7, the O-ring 134 on the valve member 126 seals off communication between the

passageways

164 and 172 to interrupt the connection of pressurized fluid to the large diameter portion of the cylinder 112. The O-ring 134 also places the passageway 172 in communication with the

exhaust passageways

168, 170 through the portion of the cylinder 122 bounded by the O-

rings

132 and 134. Thus, the pres surized air in the right-hand portion of the large diameter portion of the cylinder bore 112 is exhausted to the atmosphere, and the pressurized fluid supplied from the reservoir through the line 110 acting on the smaller area surface of the piston portion 114A shifts this piston portion to the right to the position shown in FIG. 7. In this position, the O-ring 116 moves out of the clearance 112A and closes off the connection of the passageway or line 34 to the atmosphere. Further, the O-ring 118 on the valve member 114 places the

passageways

34 and 110 in communication so that pressurized fluid is again supplied to the area or volume 36 beneath the cylinder 38. This moves the cylinder 38 upwardly against the resilient main valve element 40 (FIG. 2) so as to seal off connection between the interior of the cylinder 38 and the pressurized fluid supplied by the reservoir in the housing portion 128. In addition, the upper end of the cylinder 38 is connected to the atmosphere so that the piston 42 can be returned under the control of the valve 44 and so that the cylinder assembly 64 actuates the pawl to advance the nail feed cylinder 16. The control valve assembly 28 remains in this position until such time as the control valve 180 is returned to normal position.

Because of the fact that the driver blade 26 is automatically retracted by the cycle valve assembly 104 at the end of its power stroke, it is possible to either produce continuous relative movement between the nailer and the workpiece or to provide only a momentary stop in this relative movement. In most nailing tools of the type represented by the nailer 10, the driver blade 26 is frequently provided with a certain amount of overtravel or follow-through by which the lower end of the driver blade 26 protrudes beyond the lower surface of the nosepiece structure 22 at the end of its power stroke so as to countersink the driven nail 18. If

the driver blade 26 remains in this position occupied at the end of its power stroke until such time as the control valve 180 is released, the nailer 10 is more or less locked to the workpiece, and continuous relative movement between the workpiece and the nailer 10 cannot be achieved. However, with the provision of the single cycle valve assembly 104 in the control valve as sembly 28, the blade 26 is immediately retracted after its power stroke, and continuous or substantially continuous relative movement is accomplished with the consequent increase in the production rate of the structural assembling machine.

Thus, when the nailer 10 moves away from the workpiece previously nailed, the mechanical operator for the valve 180 shifts to its normal position shown in FIG. 5 so that the passageway or conduit 182 is connected to the atmosphere. This exhausts pressurized fluid behind the piston portion 142A in the large diamter portion of the cylinder or bore 140. This permits the pressurized fluid supplied to the other end of the large diameter portion of the cylinder below the O-ring 148 to move the piston portion 142A of the valve member 142 upwardly from the position shown in FIG. 7 to the normal position shown in FIG. 5. In this position, the O-ring 146 on the valve element 142 closes off the communication between the passageways and 174 and the passageway 186 supplying pressurized fluid. This movement of the valve element 142 also connects the

passageways

170 and 174 to the exhaust passage 168 so that the pressurized fluid trapped below the lower end of the valve element 126 is discharged to the atmosphere together with the pressurized fluid trapped above the upper surface of the valve element 126 which reaches the atmosphere through the throttle valve 124 and the

passageways

174 and 178. The tool 10 is now in condition for a further cycle of operation which will be initiated when the triggering valve is next actuated as by engagement of its operator with the next stud to be nailed.

Assuming that during one cycle of operation of the tool 10 a bent nail or an accumulation of foreign material prevents the cylinder 16 from moving to one of its predetermined index positions, one of the teeth or ribs 163 on the cylinder bears against the portion 74A of the operator arm 74 for the detector assembly 30 to pivot this arm in a clockwise direction (FIGS. 3 and 4) about the pivot pin 72. When this happens, the portion 748 of the arm enters the opening or port 76 and depresses the ball valve 84 against the force of the compression spring 86 so that it moves out of engagement with the O-ring 82. This vents the valve cylinder or cavity 78 to the atmosphere and is also effective through the port or passage 88 and the passageway 92 to supply an exhaust connection to the lower end of the large diameter portion of the bore or cylinder 152 in the safety valve assembly 108 of the control valve assembly 28 (FIG. 8).

In the normal condition of the safety valve assembly 108, the lower end of the larger diameter portion of the cylinder 152 is supplied with pressurized fluid through the passageway 1568 so as to maintain the valve member 156 in the upper position illustrated in FIGS. 5-7. When, however, the passageway 92 is connected to the atmosphere, the pressure in the lower end of the larger diameter portion of the cylinder 152 drops appreciably. This is true because even though the passageway 156B remains continuously open, an inlet port or orifice 156C is restricted and the passageway 92 dumps compressed air to the atmosphere faster than it can be replenished through the restricted orifice 156C. Since pressurized fluid is supplied by the passageway 166 to the upper effective surface on the piston portion 156A and since the lower effective surface of this piston portion is at a reduced pressure, the valve member 156 moves downwardly from the position shown in FIGS. -7 to the position illustrated in FIG. 8. When the valve element 156 moves to this position, the O-ring 160 closes off communication between the passageway 166 supplying pressurized air and the inlet to the passageway 186. The O-ring 158 maintains the passageway 186 out of communication with the exhaust passage 168 through the upper portion of the bore 152. Since the passageway 186 supplies the pressurized fluid used to effect operation of the valve assembly 102 under the control of the control valve assembly 106, the interruption in the supply of compressed air to the passage 186 by the safety valve assembly 108 prevents operation of the pneumatic nailer 10. In other words, if the valve assembly 180 is now actuated, the valve element 142 can be moved to its actuated position shown in FIGS. 6 and 7. Since, however, the passageway 186 is closed off from communication with the source of pressurized fluid by the O-ring 160 on the valve element 156, the passageway 186 cannot supply pressurized fluid to the passageway 174 and the nailer 10 cannot be operated.

The safety valve assembly 108 remains in the position shown in FIG. 8 until such time as the malfunctioning in the fastener feeding assembly is corrected by moving the cylinder 16 to a proper index position. When this happens, the lever 74 is shifted in a counterclockwise position (FIGS. 3 and 4) to its illustrated position by the compression spring 86, and the ball valve 84 again seats on the O-ring 82. This permits pressurized fluid passing through the bleeder orifice 156C to pass through the

passageways

156B, 92, and 88 to pressurize both the valve chamber 78 (FIG. 4) and the lower end of the larger diameter portion of the cylinder 152'. When the pressure acting on the lower effective surface of the piston portion 156A of the valve element 156 becomes great enough to overbalance pressurized fluid acting on the smaller upper effective surface on the piston portion 156A, the valve element 156 is moved upwardly to the position shown in FIGS. 5-7, and the control valve assembly 28 is enabled for operation under the control of the valve 180 in the manner described above.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments may be devised by those skilled in the art which will fall within the spirit and scope of the principles of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A fluid actuated tool for driving fasteners from a strip thereof into a workpiece comprising a fluid actuated driving means including a fluid motor and a fastener driver actuated by the fluid motor,

a first valve means for controlling the operation of the fluid motor,

a single cycle valve means coupled to the first valve means to control the first valve means to automatically operate the fluid motor through a cycle of operation including a power stroke and a return stroke,

a second valve means coupled to the single cycle valve means for initiating the operation of the single cycle valve means,

a fastener feeding means for advancing successive fasteners to a position to be driven into the workpiece by the fastener driver,

detecting means for detecting whether a fastener has been advanced by the fastener feeding means to a position to be driven,

third valve means controlled by the detecting means and coupled to the second valve means for inhibiting operation of the single cycle valve means by the second valve means when the fastener feeding means has not been properly positioned and the detecting means includes a fourth valve means coupled to the third valve means for controlling the operation of said third valve means.

2. The fluid actuated tool set forth in claim 1 in which the third valve means includes a piston portion for operating the third valve means.

3. The fluid actuated tool set forth in claim 1 in which the fastener feeding means includes a rotatable cylinder,

and the detecting means includes a fourth valve means actuated in dependence on the position of the cylinder and coupled to the third valve means.

4. The fluid actuated tool set forth in claim 1 in which the second valve means includes passage means coupled between the third valve means and the single cycle valve means, a valve element for controlling the passage means, and a piston portion for moving the valve element.

5. The fluid actuated tool set forth in claim 4 in which the second valve means also includes a valve for selectively connecting the piston portion to pressurized fluid and the atmosphere to control the movement of the piston portion.

Claims

1. A fluid actuated tool for driving fasteners from a strip thereof into a workpiece comprising a fluid actuated driving means including a fluid motor and a fastener driver actuated by the fluid motor, a first valve means for controlling the operation of the fluid motor, a single cycle valve means coupled to the first valve means to control the first valve means to automatically operate the fluid motor through a cycle of operation including a power stroke and a return stroke, a second valve means coupled to the single cycle valve means for initiating the operation of the single cycle valve means, a fastener feeding means for advancing successive fasteners to a position to be driven into the workpiece by the fastener driver, detecting means for detecting whether a fastener has been advanced by the fastener feeding means to a position to be driven, third valve means controlled by the detecting means and coupled to the second valve means for inhibiting operation of the single cycle valve means by the second valve means when the fastener feeding means has not been properly positioned and the detecting means includes a fourth valve means coupled to the third valve means for controlling the operation of said third valve means.

3. The fluid actuated tool set forth in claim 1 in which the fastener feeding means includes a rotatable cylinder, and the detecting means includes a fourth valve means actuated in dependence on the position of the cylinder and coupled to the third valve means.