Safety For Fastener Driving Tool

Abstract

A pneumatic fastener driving tool includes a safety arrangement that requires the tool to be placed against a workpiece before a manual trigger valve is operated in order to permit the tool to fire. Once the tool is placed against the workpiece the safety arrangement prevents "touch" firing by moving the tool toward and away from the workpiece. In one embodiment, the safety arrangement includes a fluid controlled piston which is operated to mechanically latch a workpiece actuated safety in its normal position to prevent tool operation whenever the trigger is operated before the tool is placed against a workpiece and whenever an attempt is made to "touch" fire the tool with the trigger held operated. In a second embodiment, a fluid controlled piston mechanically latches the trigger valve in normal position until after the workpiece actuated safety has been operated.

Description

The present invention relates to a fastener driving tool and more particularly to a safety arrangement for a fastener driving tool which prevents accidental or inadvertent firing of the tool.

Pneumatic fastener driving tools, particularly those adapted to drive large fasteners in certain industrial working conditions, have long included safety devices effective to prevent the tool from being fired or operated by trigger actuation unless or until the tool is adjacent the workpiece. These safety devices have included both pneumatic and mechanical interlocks. Some of these safety devices are such that the safety and trigger can be operated in any sequence, and others require the operation of the safety prior to the operation of the trigger. Some of these safety devices, generally those that are indifferent to the sequence of the trigger and safety operation, are capable of "touch" firing, i.e., the tool can be operated by moving the tool toward and away from the workpiece while holding the trigger operated. This "touch" firing is quite desirable in a number of applications because it increases the speed at which the fasteners can be driven.

As an example, the mechanical safety arrangement shown and described in U. S. Pat. No. 3,198,412 and shown in FIGS. 1-5 of U. S. Pat. No. 3,056,965 are ones in which the usual trigger control is mechanically locked in a released state until a mechanical latch is released by placing the tool against a workpiece. This mechanical latch is, however, incapable of "touch" firing. In the mechanical arrangement shown, for example, in FIGS. 6-11 of U. S. Pat. No. 3,056,965 and in U. S. Pat. No. 3,194,324, the safety arrangements include differential levers or shifting lever fulcrums to achieve "touch" firing of the tool using the safety. However, these tools are not disabled when the trigger is actuated prior to the safety. The natures of these mechanical interlocks used to achieve either control over the sequence of safety-trigger operation or "touch" firing using the safety are not such that a single basic tool design can be used in the factory to construct either of the two types of controls. Further, the mechanical linkages are often capable of being "teased" with the result that undesired multiple firing may occur due to tool recoil.

Pneumatic safety arrangements are known which require the tool to be adjacent the workpiece before the tool can be fired. Examples of this type of safety are shown and described in U. S. Pat. Nos. 2,979,725; 3,112,489; and 3,252,641. In this type of safety, the tool is operated by the last to be operated of the trigger and safety, and there is no control requiring the safety to be operated first in order to fire the tool. These tools are, however, capable of "touch" firing.

There is a growing tendency to establish more demanding safety standards for pneumatic fastener driving tools, particularly those tools using larger fasteners and particularly in those industrial applications in which working conditions are such that accidental operation of a tool may cause injury. These standards can require two separate and distinct operations to cause the operation of the tool, or that the tool cannot be operated unless the tool is placed against a workpiece before the trigger is operated, or that the tool is disabled if the tool is lifted from the workpiece, thus preventing "touch" firing. It would be desirable to satisfy all of these standards with a pneumatic or fluid controlled safety because of the advantages in this type of control. Further, because the safety standards are not universally applicable, it would be desirable to provide a basic tool that could be factory constructed to either meet these standards or provide the old safety arrangement providing "touch" firing.

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

Another object is to provide a fastener driving tool including a new and improved safety arrangement.

A further object is to provide a new and improved fluid controlled safety arrangement for fastener driving tools which requires the operation of the safety prior to the manual or trigger operation of the tool in order to achieve tool operation.

A further object is to provide a new and improved fluid controlled safety for a fastener driving tool which prevents "touch" firing of the tool.

A further object is to provide a pneumatically controlled mechanical interlock for a fastener driving tool which positively controls the sequence of trigger and safety actuation to permit these to be actuated in only a proper sequence.

In accordance with these and many other objects, an embodiment of the present invention comprises a pneumatically actuated tool for driving fasteners such as staples and nails which includes a housing defining a pressurized fluid reservoir and including a cylinder in which is slidably mounted a piston actuated fastener driving means. A main valve assembly and an exhaust valve assembly for the top of the cylinder are provided by which the upper end of the interior of the cylinder is selectively connected to the reservoir or to the atmosphere to drive the fastener driving means through power and return strokes. The main and exhaust valve means are selectively controlled by a trigger actuated valve means and a safety means actuated by engagement between the tool and the workpiece in which the fastener is to be driven. A pneumatically controlled mechanical interlock is provided coupling the safety means and the trigger valve means to insure that the trigger and safety cannot be operated in an improper sequence and to further insure that, once the tool has been removed from the workpiece, the tool cannot be again actuated without releasing and reoperating the trigger in a proper sequence with the safety means.

In one embodiment, a fluid controlled piston mechanically latches the safety means in a normal position when the trigger is operated before the safety. In this embodiment, the release of the safety while the trigger is held operated also causes the piston to latch the safety in its normal or released position to prevent "touch" firing. In a second embodiment, a fluid controlled piston mechanically latches the trigger in its normal or released position until after the safety has been operated. In this embodiment, the release of the safety controls the piston to latch the trigger in its normal position any time that the trigger is released with the safety also released.

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 pneumatic fastener driving tool including a safety control assembly forming a first embodiment of the invention;

FIG. 2 is a fragmentary sectional view taken along line 2--2 in FIG. 1 showing the safety control assembly in a normal position;

FIG. 3 is a fragmentary sectional view similar to FIG. 1 and illustrating an improper tool operation;

FIG. 4 is a fragmentary sectional view taken along line 4--4 in FIG. 3 illustrating the safety control assembly in an actuated position;

FIG. 5 is a fragmentary sectional view of another pneumatic fastener driving tool including a safety control assembly forming a second embodiment of the invention;

FIG. 6 is a sectional view taken along line 6--6 in FIG. 5;

FIG. 7 is an enlarged fragmentary sectional view partially in schematic form taken along line 7--7 in FIG. 5 and illustrating the safety control assembly in a normal position; and

FIG. 8 is a fragmentary sectional view similar to FIG. 7 showing the safety control assembly in an operated position.

Referring now more specifically to FIG. 1 of the drawings, therein is illustrated a fastener driving tool which is indicated generally as 20 and which embodies the present invention. The tool 20 includes a housing 22 with a hollow handle portion 22A forming a reservoir 24 continuously supplied with a pressurized fluid such as compressed air. Disposed within the housing is a cylinder 26 containing a slidably mounted piston (not shown) to which the upper end of a fastener driving blade or element 30 is secured. The lower end of the blade 30 is slidably received within a drive track 32 formed within a nosepiece structure 34 to which fasteners such as individual staples 36 are successively supplied by a magazine assembly indicated generally as 38. The open upper end of the cylinder 26 is normally closed by a combined main valve and exhaust assembly (not shown).

The operation of the tool 20 or more specifically of the fluid motor provided by the cylinder 26 and the piston is controlled by a safety valve assembly indicated generally as 46 and a trigger valve means or assembly indicated generally as 48. A safety control assembly indicated generally as 50 including the valve means 46 and 48 permits the operation of the main valve 40 to admit pressurized air from the reservoir 24 into the cylinder 26 to drive the blade 30 through a fastener driving stroke only when the safety valve assembly 46 is actuated by placing the nosepiece 34 adjacent a workpiece and thereafter actuating the trigger valve assembly 48. If the tool 20 is lifted away from the workpiece so as to release the safety valve assembly 46 following an initial operation of the tool and during a period in which the trigger valve means 48 is maintained operated, as in an effort to achieve "touch" firing, the assembly 50 disables the tool 20 from further operation until the trigger 48 has been released and again operated following movement of the nosepiece 34 against the workpiece.

The construction and operation of the tool 20 except for the safety control arrangement or assembly 50 is shown and described in U. S. Pat. No. 2,979,725 and in a contemporaneously filed application, Ser. No. 55,178. Accordingly, only a brief summary of the construction and operation of this tool is set forth herein. It should be understood that many other arrangements using fluid actuated piston or diaphragm main valve and exhaust assemblies that are well known in the art can be used with the safety control assembly 50 of the present invention.

The cylinder 26 includes a piston portion 26A slidably mounted within a cylindrical insert 52 in the housing 22 with the upper surface of the piston portion 26A continuously exposed to the pressurized fluid or compressed air in the reservoir 24. In the normal condition of the tool 20 shown in FIG. 1, the area beneath the piston 26A and a similar shouldered portion on the lower end of the cylinder 26 are disposed within a chamber 54 supplied with pressurized fluid through an inlet passage 56 so that the upper edge of the cylinder 26 is pneumatically biased upwardly by a net upwardly directed force against the main valve assembly.

When the tool 20 is to be operated, the passage 56 is connected to the atmosphere under the control of the assemblies 46, 48, and 50, and the pressurized fluid acting on the upper surface of the piston portion 26A moves the cylinder 26 downwardly to separate its upper edge from the main valve. This opens the main valve and closes the exhaust valve so that the piston actuated blade 30 is driven downwardly by the pressurized fluid admitted to the cylinder 26 from the reservoir 24. As the cylinder 26 moves downwardly, an opening 64 therein moves into alignment with an opening 66 in the housing 22 to provide a vent or exhaust connection for the air trapped beneath the piston. During this downward movement, the lower end of the blade 30 strikes a staple 36 and drives it through the drive track 32 into the workpiece.

When the tool 20 is to be released, the assemblies 46, 48, and 50 again supply compressed air to the passage 56 in the chamber 54 so that the cylinder 26 is moved upwardly to cause closure of the main valve and opening of the exhaust valve. Further, the opening 64 is moved out of alignment with the opening 66 to seal off the lower end of the interior of the cylinder 26, and another opening or passage 68 in the lower end of the cylinder 26 is moved into alignment with a discharge opening from a passage 70 in the housing 22. Whenever the piston 28 is displaced from its normal position, a valve assembly indicated generally as 72 is opened to interconnect the passage 70 with a passage 74 that is continuously supplied with pressurized fluid from the reservoir 24. Accordingly, pressurized piston return air from the reservoir 24 is now supplied beneath the piston to restore it and the blade 30 to their normal positions. When the blade 30 reaches this position, a depression in its lower end releases the valve 72 so that compressed air is no longer supplied to the interior of the cylinder 26. This completes the power and return strokes of the fastener driving blade 30 under the control of the fluid motor.

The safety control assembly 50 including the safety valve assembly or safety means 46 and the trigger valve means 48 selectively control the alternate connection of the passage 56 to the atmosphere and to the pressurized fluid in the reservoir 24 in accordance with the conditions under which the tool 20 can be operated. The safety valve assembly 46 is substantially identical to that shown and described in the above-identified U.S. Pat. No. 2,979,725 and includes a valve stem 80 slidably mounted within a sleeve 82 in the housing 22. A somewhat U-shaped element 84 connected to an intermediate portion of the valve stem 80 carries a wire frame or actuating element 86 which protrudes slightly below the lower end of the nosepiece structure 34 and is adapted to be moved upwardly and to produce a corresponding upward movement of the valve stem 80 when the tool 20 is placed against a workpiece, this movement taking place against the resilient bias of a compression spring 88 coupled to the lower end of the valve stem 80.

In the normal position of the safety valve 46 shown in FIG. 1, compressed air is supplied directly from the reservoir 24 to the passage 56 through a bore 90 and an opening 92 from the bore 90 through the wall of the stem 80. When the operator 86 engages the workpiece to move the valve stem 80 upwardly against the resilient bias provided by the spring 88, the passage 92 is sealed off by the sleeve 82 and a reduced diameter portion 80A on the valve stem 80 places the passage 56 in communication with a passage 94. Whenever the tool 20 is moved away from the workpiece, the bias provided by the spring 88 coupled with pneumatic bias applied to the exposed upper surfaces of the stem 80 move the stem from the actuated position to the normal position shown in FIG. 1.

The trigger valve assembly 48 is substantially identical to that shown and described in detail in the above-identified U.S. Pat. No. 2,979,725. In general, the assembly 48 includes a ball valve 96 resting on an O-ring 98 within a valve chamber 100 in the housing 22. The upper end of the chamber 100 is placed in direct communication with the reservoir 24 through a passage or opening 102. In the normal position of the valve assembly 48, compressed air is supplied through the passage 102 in the chamber 100 to the passage 94. When a trigger element 106 pivotally mounted on the housing 22 is actuated or pivoted in a counterclockwise direction, a fluted or ribbed valve stem 108 is moved upwardly to engage the ball valve 96 and move it upwardly to the position shown, for example, in FIG. 3 in which the passage 102 is closed. In this position, the ball valve 96 no longer rests on the resilient O-ring 98, and the chamber 100 as well as the passage 94 is connected to the atmosphere through the recesses in the fluted valve stem 108. When the trigger 106 is released, the pneumatic bias applied to the ball 96 by the pressurized fluid in the reservoir 24 restores the trigger valve assembly 48 to the condition shown in FIG. 1.

To mechanically interlock the actuation of the safety means or assembly 46 and the trigger assembly 48, the safety control assembly 50 is provided. This assembly includes a fluid actuated latch or piston 110 having a small diameter portion 110A and a large diameter portion 110B. The fluid controlled piston 110 is slidably mounted within a corresponding two diameter cylinder 112 extending generally transverse to the direction of elongation of the housing 22. The interface between the piston 110 and the cylinder 112 is sealed by a pair of O-rings carried on the piston portions 110A and 110B. The piston 110 is normally held in the position shown in FIG. 2 by pressurized fluid supplied to the cylinder 112 from the passage 94 through a passage 113. The pneumatic bias supplied to the exposed face of the large diameter portion 110B of the piston 110 is greater than the oppositely directed bias provided by a compression spring 114 received within a recess in the larger diameter piston portion 110B and acting between a wall of the piston 110 and the inner wall of a closure cap 115 threadedly mounted on the housing 22 to close one end of the cylinder 112.

To permit the piston 110 to control the selective actuation or freedom of movement of the safety means 46, the coupling element 84 for the safety means 46 includes an offset arm 84A, the free end of which slidably engages one side wall of the housing 22. A threaded fastener 116 cooperating with a slot 117 in the free end of the operator extension 84A mounts the extension 84A for sliding movement relative to the handle. In the normal position of the safety means 46, an opening 118 is aligned with and adapted to receive the outer end of the small diameter portion 110A on the piston 110. This portion 110A engages a locking surface defined by the edges of the opening 118 to provide a lock for preventing movement or operation of the safety means 46 when the piston 110 is in the position shown in FIG. 4.

Assuming that the tool 20 is to be operated in the proper sequence by first actuating the safety means 46 followed by the actuation of the trigger valve assembly 48, the operator places the nosepiece 34 of the tool 20 against the workpiece and moves the actuating element 86 upwardly. This movement of the element 86 moves the element 84 and the connected valve stem 80 upwardly so that the passage 92 is closed by the sleeve 82, and the reduced diameter portion 80A moves into alignment with the passages 56 and 94 to place these passages in communication. Since compressed air is supplied to these passages by the passage 102, the chamber 54 remains filled with pressurized fluid, and the tool 20 is not operated. The upward movement of the element 84 moves the extension or arm 84A upwardly to move the opening 118 out of alignment with the small diameter portion 110A of the piston 110.

The operator now actuates the trigger valve assembly 48 by pivoting the trigger 106 in a counterclockwise direction to move the valve stem 108 upwardly. The upper end of the valve stem 108 lifts the ball valve 96 out of engagement with the O-ring 98 and into a position in which the ball valve 96 closes the passage or opening 102. The passages 56 and 94 are now connected to the atmosphere along the flutes on the valve stem 108, and the pressurized fluid is discharged from the chamber 54. This permits the operation of the tool in the manner describe above.

When the passage 94 is connected to the atmosphere, pressurized fluid within the cylinder 112 is also discharged to the atmosphere through the passage 113 (FIG. 2). This permits the bias spring 114 to attempt to shift the piston 110 to the left. Since the opening 118 is no longer aligned with the small diameter portion 110A of the piston 110, the end of the small diameter piston portion 110A bears against the adjacent wall of the extension 84A of the operator 84, and the piston 110 remains in its normal position.

Assuming that the operator now attempts to "touch" fire the tool 20 while operating the trigger valve means assembly 48, the safety control assembly 50 is moved to the position shown in FIG. 3 when the operator lifts the nosepiece 34 of the tool 20 off of the workpiece. In this position the valve stem 80 and the operator 84 are moved downwardly by the compression spring 88 and the fluid bias from the reservoir 24 so that the passage 92 again communicates with the passage 56 and supplies pressurized fluid from the reservoir 24 through the bore 90 to pressurize the chamber 54. This moves the cylinder 26 upwardly and restores the tool 20 to its normal condition. However, when the valve stem 80 and the operator 84 move to the position shown in FIG. 3, the opening 118 is moved into alignment with the small diameter portion 110A of the piston and the small diameter portion 110A moves into the opening 118 (FIG. 4) under the resilient bias of the compression spring 114. This movement is permitted because the passageway 94 and thus the cylinder 112 through the passage 113 are maintained at atmospheric pressure because of the actuated state of the valve 48. When the small diameter portion 110A moves into the opening 118, the operator linkage 84 is positively locked in its normal position. Thus, if the operator makes an attempt to reactuate the tool by again pressing the nosepiece 34 of this tool against the workpiece, the actuator 86 cannot be moved upwardly, and the safety valve means 46 cannot be moved from its normal position in which the opening 92 continuously supplies pressurized fluid to the chamber 54. Thus, the tool 20 cannot be operated.

The tool can be reoperated only by releasing the trigger valve assembly 48. When this happens, pressurized fluid from the reservoir 24 flows through the opening 102 into the passage 94 and from this passage through the passage 113 to the cylinder 112. The pneumatic bias provided by this fluid exceeds the resilient bias provided by the spring 114 and forces the piston 110 from the position shown in FIG. 4 to the position shown in FIG. 2. This withdraws the small diameter portion 110A of the piston from the opening 118 and permits actuation of the safety assembly 46.

Assuming that the operator attempts to operate the tool 20 from its normal position (FIG. 1) by first actuating the trigger valve assembly 48, the actuation of the trigger valve assembly 48 places the control assembly 50 in the position shown in FIG. 3. The ball valve 96 closes off the passageway 94 from the reservoir 24 and connects this passage to the atmosphere along the flutes on the valve stem 108. This discharges the air from the cylinder 112, and the piston 110 is moved to the position shown in FIG. 4 by the resilient bias provided by the compression spring 114. In this position the small diameter portion 110A of the piston 110 enters the opening 118 on the extension 84A of the operator 84 and positively locks the safety means 46 in its normal condition. Thus, when the operator makes an attempt to complete the sequence for operating the tool 20, the actuator 86 cannot be elevated, the safety means 46 cannot be operated, and the tool 20 cannot be operated. The tool can be operated only by releasing the trigger valve assembly 48 to again pressurize the cylinder 102 so that the piston 110 is retracted to its normal position.

Referring now more specifically to FIGS. 5-8 of the drawings, therein is illustrated a fastener driving tool which is indicated generally as 120 and which forms a second embodiment of the present invention. The tool 120 includes a housing 122 with a hollow handle portion 122A forming a reservoir 124 continuously supplied with a pressurized fluid such as compressed air. Disposed within the housing is a cylinder 126 containing a slidably mounted piston 128 to which the upper end of a fastener driving blade or element 130 is secured. The lower end of the blade 130 is slidably received within a drive track 132 formed within a nosepiece structure 134 to which fasteners, such as individual staples 136, are successively supplied by a magazine assembly indicted generally as 138. The open upper end of the cylinder 126 is normally closed by a main valve and exhaust assembly indicated generally as 140 and which is slidably mounted on a closure gap 144 which closes and forms part of the housing 122.

The operation of the tool 120 is controlled by a safety assembly indicated generally as 146 and a trigger valve means or assembly indicated generally as 148. A safety control assembly indicated generally as 150 including the assemblies 148 and 148 permits the operation of the main valve means 140 to admit pressurized air from the reservoir 124 into the cylinder 126 to drive the piston 128 through a fastener driving stroke only when the safety assembly 146 is actuated by placing the nosepiece 134 adjacent a workpiece and thereafter actuating the trigger valve assembly 148.

The construction and operation of the tool 120 except for the safety control assembly 150 is shown and described in detail in a copending application of Raymond F. Novak, Ser. No. 837,696, filed June 30, 1969. Accordingly, only a brief summary of the construction and operation of this tool is set forth herein.

In the normal condition of the tool 120, the trigger valve assembly 148 normally supplies compressed air over a passage 152 to a chamber or cylinder 154 in which is slidably mounted a generally annular body of the combined main and exhaust valve 140, and the pressurized fluid supplied to the cylinder 154 biases the valve means 140 downwardly to seat on the open upper end of the cylinder 126. When the passageway 152 is connected to the atmosphere, the compressed air in the reservoir 124 moves the main valve 140 upwardly to admit pressurized fluid from the reservoir 124 to the top of the cylinder 126. In moving upwardly, a surface 140A on the main valve 140 seats against the edge of a generally circular resilient member 156 to seal off an exhaust system for the cylinder 126 including an exhaust passage 158. In this connection, upward movement of the main valve 140 is arrested short of contact with the illustrated portion of the top wall of the cylinder 154 by stops (not shown) with the surface 140A in sealing engagement with the member 156.

The compressed air admitted to the cylinder 126 drives the piston 128 downwardly so that the lower end of the fastener driving blade 130 engages and drives a staple 136 supplied to the drive track 132. When the piston 128 strikes a resilient bumper 160 disposed within the lower end of the cylinder 126, compressed air passes through a passageway 162 in the piston and through an opening 164 in the wall of the cylinder 26 to be accumulated within a piston return air reservoir 166.

To return the tool 120 to a normal position, pressurized fluid is again supplied over the passageway 152 to the cylinder 154. This pneumatic bias coupled with the resilient bias provided by compression springs (not shown) acting on the top surface of the main valve 140 moves the valve downwardly to the normal position shown in FIG. 5. At the same time the exhaust passageway 158 is opened so that a portion of the interior of the cylinder 126 disposed above the piston 128 is exhausted to the atmosphere. At this time compressed air in the storage or return reservoir 166 flows into the lower end of the cylinder 126 below the piston 128 through a series of ports 168. This compressed air restores the piston 128 to its normal position shown in FIG. 5.

The safety assembly including the trigger valve means 148 and the safety means 146 is formed as a separate subassembly which is secured to an outer surface of the housing 122 to facilitate the construction of the tool 120. This unitary subassembly includes, for example, a housing 170 secured to the housing 122 of the tool 120 by a plurality of removable or threaded fasteners 172. The only interconnection between this subassembly and the tool 122 except for linkages forming a part of the safety means 146 are a group of passageways, one of which forms a termination of the passageway 152 and the other of which communicates with a passageway 174 extending to the reservoir 124.

The safety means 146 includes a rod 176 slidably mounted within a vertically extending opening in the housing 170 and resiliently biased to an upper position determined by engagement with the wall of the housing 122 by a compression spring 178. To provide a means for shifting the position of the rod 176, a linkage is provided including a toggle plate 180 pivotally mounted about a shift 182. One end of the plate 180 is coupled to the lower end of the rod 176 by an actuator element 184 pivotally coupled to one end of the plate 180. An additional actuator element 186 whose lower end is disposed adjacent the lower end of the nosepiece structure 134 and is adapted to engage the workpiece is pivotally coupled to the other end of the plate 180. Thus, the compression spring 178 in addition to biasing the rod 176 against the stop formed by the housing 122 also resiliently biases the linkage to a position in which the lower end of the actuating element 186 projects slightly beyond or below the lower end of the nosepiece structure 134.

When the tool 120 is placed adjacent a workpiece, the lower end of the actuator 186 engages the workpiece and moves upwardly to pivot the plate 180 in a clockwise direction about the shaft 182 to the position shown in FIG. 8. This movement of the plate 180 is effective through the actuator 184 to move the rod 176 downwardly against the bias afforded by the spring 178 to the position shown in FIG. 8. When the tool 120 is moved away from the workpiece, the compression spring 178 restores the rod 176 and the linkage coupled thereto to its normal position determined by engagement of the upper end of the rod 176 with the aligned portion of the wall of the housing 122.

The trigger valve assembly 148 includes a valve element 188 slidably mounted within a cylinder or bore 190 in the housing 170 and carrying a pair of spaced O-rings 192 and 194. The cylinder 190 includes two ports or passages 196 and 198 (FIGS. 5 and 7) that are placed in continuous communication with the pressurized fluid in the reservoir 124 through the passage 174 and a connecting recessed surface on the rear wall of the housing 170. The compressed air supplied by the port 198 continuously biases the valve element or valve piston 188 upwardly to the normal position shown in FIGS. 5 and 7 so that the upper end of the valve element 188 bears against a nose on a trigger 200 which is pivotally mounted on the housing 170 by a pivot pin 202. In this position compressed air supplied from the port 196 passes within the cylinder 190 in the area bounded by the two O-rings 192 and 194 to be supplied to the inlet to the passage 152. Thus, in the normal condition of the trigger valve assembly 148, pressurized fluid is continuously supplied over the passage 152 to the cylinder or chamber 154 (FIG. 5).

To provide means for interlocking or relating the operations of the trigger valve assembly 148 and the safety means 146, a fluid actuated piston 204 is provided carrying an O-ring 206 and slidable within a cylinder 208 extending transverse to and interconnecting the cylinder 190 and the cylinder in which the rod 176 is slidably mounted. The compressed air continuously supplied to the lower end of the cylinder or bore 190 by the passage 198 continuously biases the piston 204 toward the right (FIG. 7) so that one end of the piston 204 bears against the rod 176. In this position the left-hand end of the piston 204 underlies the valve element 188 within the bore 190 and prevents downward movement of the valve element 188.

Accordingly, the valve element 188 and thus the trigger valve assembly 148 is positively and mechanically locked in its normal position in the normal condition of the tool 120. If the tool 120 is to be operated, the operator must first place the nosepiece structure 134 against the workpiece so that the linkage described above moves the rod 176 downwardly against the bias of the spring 178 to the position shown in FIG. 8. As the rod 176 moves downwardly to this position, a recessed portion 176A having an inclined or cammed surface forming a part thereof moves into alignment with the piston 204 and permits the piston 204 to move to the right under pneumatic bias from the position shown in FIG. 7 to the position shown in FIG. 8. The recess 176A is of sufficient extent to permit the left-hand end of the piston 204 to move beyond and out of an interfering relation with the lower wall of the valve element 188 when the rod 176 is fully lowered.

The trigger valve assembly 148 can then be manually actuated by the operator by pivoting the trigger 200 in a counterclockwise direction about the shaft 202. The nose of the trigger 200 moves the valve element 188 downwardly against the resilient bias provided by the pressurized fluid supplied through the passageway 198 to the fully depressed position shown in FIG. 8. In this position the upper O-ring 192 closes off communication between the passageway 196 and the entrance to the passageway 152 so that pressurized fluid is no longer supplied to the passageway 152. Further, the upper O-ring 192 moves below the port terminating the passageway 152 so that this passageway is connected to the atmosphere by passing around the upper end of the valve element 188. This causes the operation of the tool 120 in the manner described above.

If the trigger 200 is now released, the pneumatic bias acting on the lower end of the valve element 188 pivots the trigger 200 in a clockwise direction about the shaft 202 to the normal position shown in FIGS. 5 and 7. As the valve element 188 moves upwardly, the upper O-ring 192 closes off communication between the port terminating the passage 152 and places this port in communication with the port terminating the passage 196 in the portion of the interior of the cylinder 190 bounded by the O-rings 192 and 194. This returns the flow of pressurized fluid over the passageway 152 to the cylinder 154 to close the combined main-exhaust valve means 140 and completes the operating cycle of the tool 120. The tool 120 can be reoperated by manually actuating the trigger 200 and the trigger valve assembly 148 so long as the safety means 146 is held actuated by a maintaining engagement between the nosepiece structure 134 and the workpiece. If, however, the tool 120 is lifted off the workpiece during the interval in which the trigger is released, the resilient bias provided by the spring 178 exceeds the pneumatic bias provided by the air within the cylinder 208, and the inclined surface on the recessed portion 176A is effective as the rod 176 is elevated to cam the piston 204 to its normal position (FIG. 7) disposed below the lower end of the valve element 188. This prevents reoperation of the tool 120 under the control of the trigger valve assembly 148 until the safety means 146 is again actuated. If the safety means 146 is released by lifting the tool 120 from the workpiece during the time in which the valve element 188 is held in its lower position (FIG. 8), the compression spring 178 biases the left-hand surface of the piston 204 against the side surface of the valve element 188, and the piston 204 will move beneath the valve element 188 as soon as the trigger valve assembly 148 is released. This prevents any further operation of the tool until the safety means 146 is next operated.

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

Claims

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

1. In a tool for driving fasteners into a workpiece using a fluid motor to actuate a fastener driver,

a reservoir of pressurized fluid in the tool,

trigger valve means for controlling the application of fluid from the reservoir to the motor, the actuation of the trigger valve means from a normal position to an operated position being effective to cause the operation of the fluid motor,

safety means actuated from a normal position to an operated position when the tool is disposed adjacent a workpiece,

a movably mounted interlock member interconnecting the trigger valve means and the safety means and movable in opposite directions between normal and displaced positions,

separate biasing means for biasing the interlock member in opposite directions,

and control means responsive to actuation of the one of trigger valve means and the safety means for controlling the forces of the biasing means to permit movement of the interlock member so that the safety means must be actuated to its operated position before the trigger valve means can be actuated to its operated position.

2. The fastener driving tool set forth in claim 1 in which

one of the separate biasing means is fluid pressure.

3. The fastener driving tool set forth in claim 1 in which

one of the separate biasing means is a resilient means.

4. The fastener driving tool set forth in claim 1 in which

the interlock member is resiliently biased to a normal position mechanically blocking movement of the trigger valve means to its operated position,

the interlock member is continuously fluid biased toward a displaced position freeing the trigger valve means for movement to its operated position,

and the control means includes means for relieving the resilient bias when the safety means is actuated to its operated position to permit the interlock member to be moved to its displaced position.

5. The tool set forth in claim 4 in which

the trigger valve means includes a valve stem slidably mounted for movement along a given line,

and the interlock member is slidably mounted for movement generally perpendicular to said given line to engage said valve stem.

6. The tool set forth in claim 5 in which

the valve stem is disposed in a cylinder and includes a fluid pressure receiving surface in the cylinder,

the interlock member includes a fluid pressure receiving surface communicating with the cylinder,

and means coupling the cylinder to the reservoir so that the fluid provided to the cylinder biases both the valve stem and the interlock member.

7. The tool set forth in claim 5 in which

the safety means is movable in a direction generally parallel to said given line and includes a control surface engaging one end of the interlock member.

8. The tool set forth in claim 7 in which

a common resilient means biases the safety means to its normal position and the interlock member to its normal position.

9. The fastener driving tool set forth in claim 1 in which

the interlock member is fluid biased to a normal position freeing the safety means for movement to its operated position,

the interlock member is continuously resiliently biased to its displaced position in which the safety means is locked in its normal position,

and control means includes means responsive to the position of the trigger valve means for controlling the fluid bias applied to the interlock member to permit the interlock member to move to its displaced position when the trigger valve means is actuated to its operated position prior to the operation of the safety means.

10. The fastener driving tool set forth in claim 9 in which

the interlock member is a piston slidable in a cylinder,

and the control means includes a passage for supplying fluid from the reservoir to the piston through the trigger valve means.

11. The fastener driving tool set forth in claim 9 in which

the safety means includes a movable structure with a locking surface thereon aligned with and adapted to be engaged by the interlock member to prevent movement of the safety means from its normal position when the interlock member is in its displaced position.

12. In a tool for driving fasteners into a workpiece using a fluid motor having a main valve for admitting fluid to actuate a fastener driver and a fluid control for the main valve,

a reservoir of pressurized fluid in the tool,

trigger valve means having an outlet normally coupled to the reservoir when the trigger valve means is in a normal position, the trigger valve means being operable to an operated position to couple the outlet to the atmosphere,

passage means coupling the outlet to the fluid control for the main valve to control the operation of the main valve,

a cylinder coupled to said outlet,

a piston slidably mounted in the cylinder,

bias means acting on the piston to bias the piston in one direction, the fluid provided to the cylinder from the outlet acting on the piston to bias the piston in a direction opposite to the one direction,

workpiece engaging means having a normal position and operable to an operated position when the tool is placed adjacent a workpiece,

and cooperating latching means on the piston and workpiece engaging means movable into latching relation when the workpiece engaging means is in its normal position and the piston is moved by said bias means.

13. The tool set forth in claim 12 in which

the workpiece engaging means includes a retaining structure for retaining the piston against movement by the bias means when the workpiece engaging means is moved away from its normal position.

14. The tool set forth in claim 12 including

safety valve means actuated by the workpiece engaging means and coupled to the passage means.