Pneumatic powered fastener device

Abstract: A fastener driving device of pneumatic type comprises a piston, 20, within a cylinder, 49, and a driver, 21, connected to the piston, 20, and movable through a fastener driving throat, 26, formed by the housing of the device. A pressure amplifier, 14, is removably inserted within an enlarged portion of the air inlet body portion, 12.

Description: This invention relates to a pneumatic device for driving fasteners and in particular to an improvement in the pneumatic operation of the device. Powered operated devices for driving fasteners, such as nails, staples, pins and the like, have been used in industrial applications for several years. The fastener range varies from small pins used in furniture to large nails driven into concrete. In some applications it is possible to mount the device stationary and bring the material to be fastened to the device but in most applications it is required that the driving device be portable. Portable tools for driving small fasteners are in general rather small since the power needed for driving is not great. Both electric and pneumatic power sources have been utilized in these smaller tools, as the fastener increased in size the power needed to properly drive the fastener also increased thus making the tool larger and heavier. When designing portable devices human fatigue has to be considered, therefore weight and size becomes a negative feature in such tools. The use of pressurized air in connection with proper valving can be sized in a much smaller and lighter housing than can an equivalent electrical device, thus compressed air operated portable tools have become dominant in industrial fastener driving devices. There have also been tools designed to use powder or gas filled cartridges but in general these power sources have a much greater cost per fastener ratio, than that of compressed air. These cartridge system tools have been successful in applications where the maximum air pressure produced by the available air compressor is limited below that which will properly drive a selected fastener using a conventional pneumatic tool. Recent developments in pneumatic operated portable tools have lead to providing an air pressure booster built into such tools, as shown in DE-A-3 347 605, upon which the preamble of claim 1 is based. The system allows a readily available air pressure supply to be connected to the tool inlet and the air pressure booster increases the air pressure within the tool to a level necessary for properly driving the fastener. The consumption of air increases of course as the pressure is increased and the driving cost per fastener increases. It is the object of the invention to provide a portable pneumatic fastener device that can be quickly and easily converted from a conventional air powered tool to a device that increases the internal air pressure above that of the air inlet source. According to the present invention there is provided a portable pneumatic device according to claim 1. The portion of the body where the air inlet is connected has been enlarged. A plug is inserted that has an air connector for attaching the air inlet. If the application requires an air pressure higher than that of the inlet source then the plug can be removed and a self-contained air amplifier can be inserted. By having the air amplifier as a self-contained unit servicing and tool downtime can be held to a minimum. Should there be a malfunction in an air amplifier component the unit can be removed and a spare inserted into the tool thereby keeping the tool in use and the malfunction component can be repaired when time is available. A second advantage is there is no wear on tool components such as the body that would require a major repair and possible expensive replacement and long downtime. The invention will now be further described by way of the accompanying illustration of which: FIGURE 1 is a cross section view along the center line of a typical pneumatic fastener driving device with components at a normal rest position. FIGURE 2 is an end view of the pressure amplifier. FIGURE 3 is a cross-sectional view of a preferred embodiment of the pressure amplifier along line C-C when air inlet source is first connected to the tool. FIGURE 4 is the same as FIGURE 3 with piston at full stroke and valve shifted to start the piston return stroke. FIGURE 5 is the same as FIGURE 4 with the piston at full return stroke. Referring now to FIGURE 1 a pneumatic fastener driving tool, 11, is shown containing all aspects of the present invention. The body, 12, has an enlarged section, 13, in which is inserted a pressure amplifier, 14, to increase the inlet pressure; a valve means, 15, for controlling the return stroke pressure at a reduced pressure than that of the drive stroke, a valve means, 16, to assure the pressure under the piston is exhausted before allowing a drive stroke, and a control means, 17, to prevent the tool from operating without fasteners. The tool, 11, has certain components that are wholly conventional in present pneumatic fastener driving devices and are not restrictive upon the, present invention. The body, 12, contains a hollow section to be used as an air reservoir, 18. Within the body is mounted a cylinder, 19, in which a piston, 20, can slide. The driver, 21, is attached to the piston, 20, to enable both to function as a unit. An O-Ring, 22, is used to provide an air seal between the upper, 23, and lower, 24, sides of the piston, 20. In the lower section of the tool, 11, below the cylinder, 19, there is mounted a guide piece, 25, containing a driving throat, 26, through which the driver, 21, can freely move. The throat, 26, is sized according to the shape of the fasteners, 27, to be driven and one side open for entry of the leading fastener, 28. The upper section of the guide piece, 25, has a bushing, 29, to center the driver, 21, on the drive throat, 26. A piston bumper, 30, is used to cushion the shock that would occur if the piston, 20, was allowed to strike directly on the lower section of the tool. Directly above the top of the cylinder, 19, is located a driving stroke valve means, 31, that is shiftable between a closed and open position. In the closed postion, as shown in FIGURE 1, a seal, 32, blocks the air in the reservoir, 18, from entering the upper section of the cylinder, 19. At the same time the upper, 23, side of the piston is in communication with atmosphere through passageway, 33, located in a cap, 34, attached to the body, 12. An exhaust air deflector, 35, is provided to direct the exhaust forward away from the operator when the tool is cycled. Top of the valve, 31, is pressurized by way of passageway, 36, in communication with valve means, 16. The lower portion of valve, 31, is in continuous communication with the reservoir, 18, but since the top is larger than the area of the lower portion, the valve, 31, remains in the closed position. A manually operated trigger, 37, pivots on the body, 12, and when pulled upward lifts the trigger valve, 38, to start the driving sequence. The fasteners, 27, are normally collated in strip form and guided into the drive throat, 26, by way of a fastener magazine, 39. A pusher, 40, is biased forward to force each consecutive fastener into the drive throat, 26, as the leading fastener, 28, is driven therefrom. The magazine, 39, as shown in FIGURE 1, has been positioned at an inclination to allow clearance above the workpiece but many forms of magazines can be utilized including that designed for fasteners collated in coils. A workpiece contact element, 41, extends below the guidepiece, 25, and must be depressed against the workpiece before the tool, 11, will function. A tool as hereabove described is disclosed in EP-A-0336021. Although the above described embodiment is preferred the components could be modified considerable depending on the application in which the tool is to be used. Referring now to FIGURE 3 and FIGURE 4 the internal construction of the amplifier, 14, will be described. The amplifier, 14, consists of a housing, 127, and an insert, 127a, attached by thread, 127b, to form a unit in which the components are contained needed to increase the inlet pressure. The O-Rings shown as black circles are used as static seals to isolate the passageways. The amplifier, 14, is a self contained unit without need of any external components other than the inlet source connected to inlet, 43, and a sealed reservoir, 18, in which to hold the increased air pressure. The piston, 130, and valve, 132, and the respective chamber, 131, and chamber, 133, in which they have reciprocal motion, are all cylindrical about the centerline of the unit. Piston, 130, contains an external O-Ring, 134, that seals against the outer wall of the chamber, 131, and an internal O-Ring, 135, that seals against the inner wall of chamber, 131. Chamber, 136, is an extension of chamber, 131, but having a considerable reduction in volume. The piston, 130, has a cylindrical extension, 137, sized to be able to move within chamber, 136. An O-Ring, 138, seals on both walls of chamber, 136, thus when pressure is applied to the top of piston, 130, and moves the O-Ring, 138, to reduce the volume in chamber, 136, the air within will increase in pressure. The end of the unit exposed to reservoir, 18, contains a ball type check valve means in which a ball, 139, seals against port, 128, that is in communication with the end of chamber, 136, when the pressure within reservoir, 18, is greater than the pressure within chamber, 136. As the pressure within chamber, 136, is increased, by movement of the piston, 130, the ball, 139, will be forced away from port, 128, and the high pressure air within chamber, 136, will flow into the reservoir, 18, thus increasing the air pressure within reservoir, 18. As the piston, 130, returns and the volume of chamber, 136, increases, the pressure within chamber, 136, is the same as the inlet pressure and the ball, 139, reseats closing port, 128, to prevent the flow of air from the reservoir, 18, back into chamber, 136. A retaining pin, 140, limits the movement of ball, 139, away from to assure proper sealing. The lower end of chamber, 136, has a second type ball check valve means in which a second port, 141, intersects a cavity, 142. Passageway, 143, also intersects cavity, 142, and an extension, 143a, of passageway, 143, provides communication with air inlet source. A ball, 144, is contained within cavity, 142, and seals against the end of passageway, 143, when air pressure within chamber, 136, is greater than inlet source. A seal, 145, and retaining pin, 146, keeps ball, 144, within cavity, 142, and prevents flow of air within reservoir, 18, into cavity, 142. The valve, 132, contains an external O-Ring, 147, that seals against the outer wall of chamber, 133, and an internal O-Ring, 148, that seals against the inner wall of chamber, 133. Chamber, 149, is an extension of chamber, 133, along the inner wall but has a lesser outside diameter. A portion, 150, of valve, 132, also has a lesser outside diameter to allow movement of portion, 150, within chamber, 149. The inner wall of chambers, 133 and 149, has 3 ports, with first port, 151, intersecting chamber, 136, below O-Ring, 138, when O-Ring, 138, is in retracted position (FIG. 3). The second port, 152, intersects chamber, 131, at a position above O-Ring, 135, when piston, 130, is in compressed position as shown in Figure 12. The third port, 153, intersects chamber, 131, above O-Ring, 135, when piston, 130, is in retracted position (FIG. 3). The outer wall of chamber, 149, has a port, 155, intermediate the ends communicating with air inlet source by way of passageways, 156 and 157. An undercut in the outer wall of chamber, 149, in the area of port, 155, is isolated by O-Rings, 154. The valve, 132, has a second internal O-Ring, 158, located on the opposite end of O-Ring, 148. A third O-Ring, 159, is located intermediate O-Rings, 148 and 158. The portion, 150, of valve, 132, has a first port, 160, between O-Rings, 148 and 159, and a second port, 161, between O-Rings, 159 and 158. Only ports, 151, 152 and 153, are crossed by O-Rings and all other ports, 155, 160 and 161, serve only as a passageways. The portion of the chamber, 131, under the piston, 130, is in continuous communication with atmosphere, by way of port, 162, passageways, 163, 164 and 165. To provide a means to exhaust the reservoir, 18, when the air inlet source is removed from the tool, a cavity, 166, is located between, and intersected by, passageway, 143a, and port, 129. Located within the cavity, 166, is a small piston, 167, and O-Ring, 168, acted upon by inlet pressure. Also located in cavity, 166, between piston, 167, and port, 129, is a ball, 169, which is forced in a sealing position against port, 129, by the piston, 167. When the air inlet source is removed from the tool the ball, 169, is forced to a non seal position with port, 129, and reservoir, 18, is in communication with chamber, 131, under the piston, 130, by way of passageway, 170, and in turn communicates with atmosphere to exhaust the air within reservoir, 18. Referring to FIG. 3, when the air inlet is first connected to the tool at inlet, 43, passageways, 143a and 143, are pressurized forcing ball, 144, away from end of passageway, 143. Cavity, 142, and the chamber, 136, are also pressurized. Since reservoir, 18, has only atmosphere pressure at this time ball, 139, moves away from port, 128, allowing air to enter reservoir, 18, thus increasing the pressure within reservoir, 18, to that of the inlet source very rapidly. Pressure on small piston, 167, holds ball, 169, in a sealing position against port, 129. Chamber, 133, is also pressurized by way of port, 151, holding valve, 131, in a retracted position. The internal surface of valve, 132, between O-Rings, 158 and 159, is continuously pressurized by way of ports, 161, 155, and passageways, 156, 157. Air enters the chamber, 131, above piston, 130, through port, 153, and piston, 130, moves forward causing extension, 137, to push O-Ring, 138, forward reducing the volume in chamber, 136. As the volume in chamber, 136, decreases the air within will increase in pressure to resist the movement of the piston, 130. Since the area of chamber, 130, is greater than the area of chamber, 136, the pressure within chamber, 136, will increase to the same ratio above the inlet pressure as the inverted ratio of the areas of piston, 130, to piston, 136. By example: if the area of piston, 130, is 2.5 time that of chamber, 136, then the pressure within chamber, 136, will reach 2.5 times that of the inlet pressure before the piston, 130, will stall out in a balanced state. Referring now to Figure 4 it can be seen as an O-Ring, 138, passes port, 151, the chamber, 133, exhausts through a port, 170, in the extended portion, 137, of piston, 130, but no shifting of valve, 132, takes place since the end of portion, 150, is also open to exhaust. When the pressure increases within chamber, 136, to that within reservoir, 18, the ball, 139, will no longer form a seal against port, 128, and the air within chamber, 136, can be forced into the reservoir, 18. As the piston, 130, moves the external O-Ring, 134, passes the port, 152, in external wall of chamber, 131, pressurized air enters chamber, 133, between O-Rings, 147, 148, 154 and 159. Since O-Rings, 148 and 159, seal against the same surface the opposite forces are equal, but O-Ring, 147, seals against outer surface of chamber, 133 and O-Ring, 154 seals against a surface having a lesser diameter, there is a resulting force to shift the valve, 132. The O-Ring, 158, passes port, 153, providing a passageway to exhaust the air within chamber, 131. The force against O-Ring, 138, starts the piston, 130, return and since the air within cavity, 142, is now the same as the inlet source the ball, 144, breaks the seal with the end of passageway, 143. Inlet air will fill chamber, 136, as the piston, 130, and O-Ring, 138, continue the return stroke. As O-Ring, 134, passes port, 152, on the return stroke, the chamber, 133, between O-Rings, 147, 148, 154 and 159, exhaust by way of port, 170, in the piston extension, 137, port, 162 and passageways, 163, 164, 165. Referring now to FIGURE 5 the piston, 130, has completed the full return stroke and O-Ring, 138, has passed port, 151. Air enters chamber, 133, and forces the valve, 132, to the retracted position as shown in FIGURE 3. The top of the piston, 130, is again pressurized and the cycle is repeated. The cycling will continue until the air pressure within reservoir, 18, increases to the maximum that can be created within chamber, 136. Upon each operation of the driving cycle of the tool the consumption of air needed to produce the driving stroke will cause a reduction in pressure within reservoir, 18, permitting the piston, 130, to advance for enough to allow O-Ring, 134, to pass port, 152, which will start again the amplifier, 14, functioning, thus building the pressure within reservoir, 18.

Claims: A pneumatic fastener driving device comprising in combination a body (12), a cylinder (19) within said body (12), a piston (20) within said cylinder (19), a driver (21) connected to said piston (20), a valve means (15,16) for providing reciprocal movement of said piston (20), and said driver, a chamber (18) within said body (12) to function as an air pressure reservoir, a cavity (13) of said chamber (18) within said body (12), a self-contained air pressure amplifier (14) positioned in said cavity (13) for the purpose of increasing the air pressure within said chamber (18) above an air pressure source connected to said device (11), characterised in that said air pressure amplifier (14) is removably inserted in said cavity (13), such removal affecting the air pressure, but not affecting the pneumatic operation of said device in any other ways. A fastener driving device as defined in claim 1, characterised in that said valve means (15,16) comprises a driving stroke operating means (16,31,37,38) providing pressurised air to an upper side (23) of said piston (20) and a return stroke operating means (15,17) providing lower pressurised air to a lower side (24) of said piston (20). A pneumatic fastener driving device as defined in claim 1, in which said air amplifier (14) further comprises a housing unit (127), a means (43) for connecting an air inlet source, said housing unit containing a first chamber (131), a piston (130) having reciprocal movement within said first chamber (131), a second cylindrical chamber (136) concentrical to said first chamber (131), a cylindrical tube (137) slidable within said second chamber (136), a first valve means (132, 133) providing said reciprocal movement of said piston (130) and said tube (137), a second valve means (128, 139, 140) providing an enclosed volume within second chamber (136), movement of said cylindrical tube (137) in one direction within said second chamber (136) reduces said enclosed volume thus increasing the air pressure therein, said second valve means (128, 139, 140) providing communication between said second chamber (136) and said reservoir (18) whenever said air pressure within said second chamber (136) becomes greater than the air pressure within said reservoir (18) and blocks said communication when pressure within said second chamber (136) is less than pressure within said reservoir (18). A pneumatic fastener driving device as defined in claim 3 wherein said cylindrical tube (137) and said piston (130) are integral. A pneumatic fastener driving device as defined in claim 3 wherein said first valve means further comprises a third cylindrical chamber (133) concentrical to said first chamber (131), a shiftable valve sleeve (132) within said third chamber (133) when in a first position providing communication between said inlet source (43) and the upper side of said piston (130) providing a power stroke of said piston (130) and said tube (137) in said volume reducing direction, means to shift said valve sleeve (132) to a second position that provides communication between said upper side of said piston and atmosphere providing a return stroke, a third valve (141, 142, 144, 145) providing communication between said inlet source (43) and said second chamber (136) when air pressure within said second chamber (136) is less than air pressure of said inlet source. A pneumatic fastener driving device as defined in claim 5 wherein said means for shifting said valve sleeve (132) to said second position comprises a first port (152) in said first chamber (131)to pressurize a first surface of said sleeve (132) when said piston (130) passes thereby during said power stoke, a second port (151) in said second chamber (136) pressurizes a second surface of said sleeve (132) to return said sleeve (132) to said first position when said cylindrical tube (137) passes thereby during said return stoke. A pneumatic fastener driving device as defined in claim 3, 4, 5 or 6 wherein a fourth valve means (166, 167, 168, 169) is held closed when said air inlet source is connected to said device and opens to provide communication between said reservoir (18) and atmosphere when said air inlet source is disconnected from said device.

Inventors: MONACELLI UMBERTO, MONACELLI, UMBERTO
Applicants: PITTINI ALESSANDRA, PITTINI, ALESSANDRA
Application year: 1988
Main classification: B25C1
IPC codes: B25C1, F15B15