US 3657968 A
A pneumatic stapler of the type having a working cylinder communicating with a surrounding air chamber by means of ports in the cylinder wall is provided with an annular valve means movable on the external surface of the cylinder wall. During the driving stroke of the piston said valve means closes the ports in the cylinder wall and opens an outlet passage for venting the air from the cylinder displaced by the piston and from the air chamber to the atmosphere. When the piston reaches the end of its driving stroke, said valve means opens the ports in the cylinder wall and connects the air chamber with a space beneath the piston and closes the outlet passage, whereby the piston is exposed to air pressure from the chamber for returning the piston to its initial position.
Claims available in
Description (OCR text may contain errors)
[4 1 Apr. 25, 1972  PNEUMATIC STAPLING DEVICE Wilfried Lange, 1 Brockhold, 3101, A1- tenhagen, Germany  Filed: Feb. 12,1970
 Appl.No.: 10,929
 Foreign Application Priority Data Feb. 13, 1969 Germany ..P 19 07 069.0
 US. Cl ..9l/398, 91/399, 91/404, 91/461  Int. Cl ..F15b 15/22, F15b l3/042  Field of Search ..91/399, 404, 461, 398; 92/85  References Cited UNITED STATES PATENTS 3,396,636 8/1968 Bade ..9l/399 3,479,926 11/1969 Hillier ..91/404 3,512,454 5/1970 Perkins ..92/85 Primary Examiner-Paul E. Maslousky Attorney-Hibben, Noyes & Bicknell ABSTRACT A pneumatic stapler of the type having a working cylinder communicating with a surrounding air chamber by means of ports in the cylinder wall is provided with an annular valve means movable on the external surface of the cylinder wall. During the driving stroke of the piston said valve means closes the ports in the cylinder wall and opens an outlet passage for venting the air from the cylinder displaced by the piston and from the air chamber to the atmosphere. When the piston reaches the end of its driving stroke, said valve means opens the ports in the cylinder wall and connects the air chamber with a space beneath the piston and closes the outlet passage, whereby the piston is exposed to air pressure from the chamber for returning the piston to its initial position.
5 Claims, 2 Drawing Figures PATEHTEDAPR 25 m2 3, 557, 96a
SHEET 1 UF 2 ATTORNEYS PNEUMATIC STAPLING DEVICE DESCRIPTION The present invention relates to a pneumatic stapling device and especially to a portable device operable by compressed air and serving to drive fastening means such as staples and the like into a work piece by means of a driver which is actuated by a piston operated by compressed air, which piston is returned to its initial position by pneumatic operation.
The prior art devices providing for a pneumatic return of the piston to its initial position have an additional storage chamber receiving the air which is necessary for moving the piston to its initial or retracted position. Said storage chamber encloses the working cylinder and communicates with said cylinder by means of ports arranged in its side wall. A first group of said ports is provided for admitting compressed air to the storage chamber from the interior of the working cylinder toward the end of the driving stroke of the piston. A second group of ports for admitting compressed air from the storage chamber to the interior of the cylinder for effecting return of the piston from its terminal position to its initial position provided adjacent the lower end of the cylinder. Practical experience has shown that after each working stroke of the piston more compressed air is passed from the interior of the cylinder into the storage chamber than is needed for returning the piston. If the piston performs at very high speeds, the air displaced by the piston is pumped into the storage chamber whereby a counterpressure is produced which reduces the efficiency ofthe stapling device.
It is an important object of the present invention to provide a compressed air operated stapling device of the above type the piston of which during its working stroke is not exposed to any counterpressure resulting from the air which is displaced by said piston.
Another object of the invention is the provision of a pneumatic stapler with the interior of its working cylinder beneath the piston vented during the working stroke of said piston.
A further object of the invention is to provide a portable stapler with a piston pneumatically returned to its initial position, and the storage chamber of which receives no increase of air pressure during a rapid sequence of working strokes.
These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings in which an embodiment of the invention is illustrated by way of an example. In the drawings FIG. 1 is a fragmentary sectional view of a pneumatic stapler embodying this invention with the piston in its initial position, and
FIG. 2 is a similar view with the piston in its terminal position after completion of its working stroke.
The invention comprises a pneumatic valve means for directly exhausting the storage chamber and the interior of the working cylinder beneath the piston to the atmosphere during its working stroke. Preferably an annular slide valve is provided with pressure faces which are of different size and are directed opposite one another. Said slide valve comprises a check valve for the admission of compressed air. Said annular slide valve encloses the lower end of the working cylinder and has transverse ports for venting the air contained in the storage chamber. These transverse ports together with venting openings of the working cylinder open in an annular passage formed between said annular slide valve and the working cylinder. Said cylinder communicates with venting openings leading to the atmosphere. The pressure face of the annular slide valve effecting its descending motion is greater than the pressure face which effects its upward motion. The face effecting the upward motion is always acted on by compressed air.
The provision of the pneumatic valve means according to the invention provides during each working stroke of the piston an intense venting of the storage chamber and of the interior of the working stroke beneath the piston. Thus when the working strokes are repeated very rapidly, air from the interior of the cylinder cannot be pumped into the storage chamber. Therefore, the staplers embodying the invention are especially adapted for a rapid sequence of working strokes as is the case with automatic devices.
Referring now to the drawings, a body casing l of a portable pneumatic stapler encloses a working cylinder 2 with a side wall and a bottom end wall having a. storage chamber 3 surrounding the cylinder. In the cylinder 2 a piston 4 is reciprocable and is secured to a driver 5. In the lower portion of the working cylinder 2 transverse ports 14 and 18 are arranged, which connect the cylinder with the atmosphere and the storage chamber 3, respectively. A step shaped annular slide valve member 6 surrounds the lower portion of the working cylinder which is provided with said transverse ports 14 adjacent the end of the cylinder and ports 18 intermediate the ends of the cylinder. The slide valve member 6 has two opposed pressure faces 7 and8. Pressure face 8 is greater than the other pressure face 7. First passage means including trans verse bores 10 in the slide valve member 6 communicate the interior of the cylinder with the storage chamber 3 by means of the intermediate ports 18 in the side wall of the cylinder 2. The slide valve member 6 is provided with a second passage means including transverse ports 11 which open into an annular chamber 12 which communicates with ports 14 on the lower end of the cylinder side wall. The annular chamber 12 communicates with outletpassages 13 adjacent the bottom wall of the body casing and connects said annular chamber 12 directly with the atmosphere when the slide valve 6 is in the position shown in FIG. 1.
In the upper terminal position of the annular slide valve member 6 as is shown in FIG. 1 of the drawings the upper pressure face 8 is adjacent a shoulder 15 of the side wall of the working cylinder, the shoulder 15 limiting the travel of the valve 6. The lower face 7 of the slide valve member 6 is permanently exposed to the pressure of the compressed air contained in an air reservoir :19 which communicates by means of a passage 16 with the space7 beneath the pressure face 7. The annular slide valve member 6 by sealing rings 20 is closed off against the external surface of the working cylinder 2. An elastic ring 9 inserted in an annular recess 17 encircling the bores 10 serves as a check valve for the slide valve member 6 to permit air to pass only into the chamber 3.
The air reservoir 19 communicates by means of a control valve 21 manually actuated by a trigger level 22 with a firing valve 23, which in its initial position as shown in FIG. 1 is exposed to the pressure of the air contained in the air reservoir 19 via control valve 21. When control valve 21 is lifted to its upper terminal position by means of trigger level 22, the air acting on the firing valve 23 can escape to the atmosphere via the venting openings 24 and 25, as is illustrated in FIG. 2. The air under pressure contained in reservoir 19 moves the firing valve 23 upward, enters the working space 2' of the cylinder and acts upon the upper face of the piston 4 and moves it in its working direction. Beneath piston 4 the interior of the working cylinder via the ports 14, the annular chamber 12 and the openings 13 is completely vented. Also the storage chamber 3 at this moment is also connected to the chamber 12 by the ports 11 and contains no air under pressure, so that the annular slide valve member 6 by means of the lower pressure face 7 is held in its upper position.
When the piston 4 has proceeded the largest part of its working stroke and has passed the ports 18, it opens the ports 18 in the cylinder side wall for admission of air under pressure from the interior of the working cylinder into the storage chamber 3. First the annular slide valve member 6 is moved downward to its lower terminal position. by the air acting on its upper face 8, whereby the openings 113 are closed. The air under pressure has free access to the storage chamber 3 and in addition flows beneath the piston 4 via the ports 11 of the slide valve member 6 and the transverse ports 14 of the cylinder side wall.
When the control valve 21 returns to its lower terminal position upon release of the trigger 22, air under pressure acts again on the upper surface of the upper end of the firing valve 23 and moves it downward, whereby the connection of the working cylinder 2 with the air reservoir 19 is blocked. Simultaneously a connection to the venting openings 25 is produced and the air contained in the working cylinder 2 above the piston 4 escapes to the atmosphere. The air from the storage chamber 3 enters the return space 2" of the working cylinder beneath the piston 4 and moves it in a return stroke to its initial or retracted position as is illustrated in FIG. 1.
The upper frontal face 26 of the annular slide valve member 6 (see FIG. 2) is so dimensioned that the air contained in the storage chamber 3 can hold the valve member 6 in its lower terminal position till the piston has reached its upper terminal position.
The present invention is of considerable advantage for pneumatic equipment of all kinds, and in particular for portable pneumatic percussion devices having a rapid series of working strokes. This is of particular importance where the percussion device is concerned for driving in staples, nails and other fasteners, so widely used in mass production. The invention is also of importance for pliers and packing devices for stapling the lids of cardboard boxes.
What i claim is:
1. In a pneumatic stapling device including a body portion containing an air reservoir, a cylinder having a side wall and a wall at one end thereof, an air storage chamber surrounding said cylinder, a piston reciprocable in a working stroke and a return stroke in said cylinder and separating said cylinder into a working space on one side of said piston and a return space on the other side of said piston, and outlet passage means for venting said return space and said air storage chamber during said working stroke, said cylinder having valve means at the other end thereof for admitting compressed air from said air reservoir into said working space of said cylinder for moving said piston in said working stroke, said cylinder having first port means in said side wall of said cylinder to connect said working space to said air storage chamber to fill said air storage chamber and second port means in said cylinder to connect said air storage chamber to said return space for moving said piston in said return stroke and for venting said return space; the improvement comprising a pneumatic valve for exhausting said return space of said cylinder and said air storage chamber through said outlet passage means, said pneumatic valve having first passage means communicating said air storage chamber with said first port means and second passage means communicating said air storage chamber with said second port means, said first passage means including a check valve permitting air to flow only from said working space into said air storage chamber, said pneumatic valve having two opposed faces, one of said faces being in communication with said cylinder and the other of said faces being in permanent communication with said air reservoir, said one face being larger than said other face, said pneumatic valve being slidable on said cylinder to an open position by compressed air from said air reservoir acting on said other face and to a closed position by compressed air from said working space of said cylinder acting on said one face, in said open position said pneumatic valve connecting said return space of said cylinder and said air storage chamber to said outlet passage means during the working stroke, and in said closed position said pneumatic valve closing ofi said return space and said air storage chamber from said outlet passage means during the return stroke.
2. The device of claim 1, wherein said cylinder has a shoulder engageable by said one face to limit the movement of said pneumatic valve to its open position.
3. The device of claim 1, wherein said body portion includes a passage permanently communicating said other face of said pneumatic valve with said air reservoir.
4. The device of claim 1, wherein said check valve comprises an elastic ring and said first passage means includes at east one transverse bore in said pneumatic valve, said elastic ring covering said bore.
5. The device of claim 4, wherein said first passage means further includes an annular recess on said pneumatic valve, said elastic ring being located in said recess.