US3392632A - Valve means for an air-operated fastener device - Google Patents

Description

4 Sheets-Sheet 1 July 16, 196s VALVE MEANS FOR AN AIR-OPERATED FASTENER DEVICE Filed Feb.

July 16, 1968 l D. VOLKMANN 3,392,632

VALVE MEANS FOR AN AIR-OPERATED FASTENER DEVICE Filed Feb. 3, 1966 4 Sheets-Sheet 2 )NVE/vra@ /ETER VOL/(MANN July 16, 1968 D. voLKMANN 3,392,632

n VALVE MEANS FOR AN AIR'OPERATED FSTENER DEVICE Filed Feb. 5, 1966 4 Sheets-Sheet Z5 JSM/W5 July 16, 1968 D. VLKMANN 3,392,532

VALVE MEANS FOR AN AIR*OPERATED FASTENER DEVICE Filed Feb. s, 196e 4 Sheeshee' 4 WXM United States Patent M 3,392,6 32 4VALVE MEANS FOR AN AIR-OPERATED l FASTENER DEVICE Dieter Volkmann, Neustadt am Rubenberge, Germany, assignor to Dieter Haubold'doing business as Dieter Haubold Industrielle Nagelgerate, Westerfeld, Germany Filed Feb. 3, 19.66, Ser. No. 524,902

priority, application Germany, Feb. 4, 1965,

` 'claims :7 Claims. (Cigar-T457) This invention relates to valve means for an airop erated fastener device by which fastening means, such as nails, staples, pins e-tc., are driven into a work piece. In this device, when in its operative position, air under pressure froma source of compressed Iair is admitted to a cylinder by an inlet valve, and when in its inoperative position said cylinder is exhausted. The inlet valve is by a manually actuated control valve moved into operative or inoperative position. v To providesuch devices with great effective power it has to be insured that the full pressure of the operative air is instantly admitted to the driving piston reciprocable in the cylinder as the control valve is actuated.

According to'methods known in the art, the cylinder is surrounded by an air chamber which is in permanent communication with the source of compressed air and against which the interior of the cylinder is sealed off by means of-the inlet valve provided at its upper open end. The area of the upper face of the inlet valve is greater than of its lowerV face so that the air operating on the upper face of the inlet valve pushes it on its seat and closes the cylinder. When the control valve is actuated the upper face of the inlet valve is discharged from the air pressure, and the air' acting on its lower face raises it from its seat to open the cylinder, which causes the compressed air to 4be admitted to the piston. When the inlet valve is opened the air exhaust valve -must simultaneously be closed, which is open during the return travel ofthe piston so that the air displaced by the piston may escape. lThe exhaust valve is mostly constructed as a check valve which in the initial position of the device is open and only closesas the compressed air, whichis introduced into the cylinder after actuating the control valve, is gaining impact on it. As long as the exhaust valve Vis n ot` yet completely closed, part of the compressed a'ir admitted to the cylinder may escape and thus cause a drop` in pressure which results in equivalent loss of eiciency. Y vAn important-object Iof the inventionis to provide valve -means in which the exhaust valve is closed immediately after actuating the control valve and thus to avoid 3,392,632 Patented July 16, v1968 ICAC any losses of compressed air which is intended to be supplied to the opened cylinder without any pressure drop.

Another object vof this `invention is to provide an im proved type of valve means for exhausting the air which is displaced by the driving piston during its return travel.

A further object of this invention is to provide an air operated portable fastener device in which the height of the device is less than of other comparable devices, and which device is substantially trouble free and extremely economical to operate.

According to the invention, the exhaust valve is lactuated by a differential piston, the annular piston face of which is in permanent communication with the air chamber, while its opposite piston face is connected with said chamber via the Vcontrol valve when in its inoperative position. The cylinder space of the differential piston actuating the exhaust valve, at its end adjacent the annular piston face, is connected to a passage,` which is in continuous open communication with the air chamber, and at its other end the cylinder space is connected to a passage Which is in open communication with a cham-ber located 4between the control valve and the inlet valve of the cylinder.

As soon as the control valve is moved from its initial into the operative position in that its actuating trigger is squeezed, the piston face of the differential piston actuating the exhaust valve is connected to lthe open air. The compressed air in the air chamber enters the cylinder space of the differential piston underneath its annular pist0n face and moves the piston towards the piston face which is discharged of air pressure so that the exhaust valve is instantly moved int-o its closed position. Thereupon, the compressed air moves the inlet valve from its inoperative into its working position and releases the open end of the cylinder for admittance of the compressed air operating the device. As the exhaust valve is closed before the operating air flows in there is not any loss in the operating air which is therefore admitted to the driving piston within the cylinder at its full pressure.

The inlet valve and the cylinder are of like cross section while the area of the differential piston actuating the exhaust valve and, along therewith, the cross section of its cylinder space, are substantially smaller. The cylinder space of the differential piston is therefore faster discharged of the compressed air than the space above the inlet valve so that also with this in view, the exhaust valve is assured t-o be closed before the compressed air from the air chamber is fully admitted to the driving piston being at the upper end of the cylinder. The time needed for the discharge of the compressed air from the cylinder space of the differential piston actuating the exhaust valve may be regulated -by the cross section of the duct connecting the space at theface of the differential piston with the chamber between control valve and inlet valve. The larger the cross section of this duct the faster is the space vented and by this the exhaust valve is closed.

In a preferred embodiment of the invention, -the exhaust valve extends across the central axis of the cylinder, which construction results in particularly short connection passageways and, together therewith, short time required for closing the exhaust valve. Besides, the overall height of the device is reduced, Which is of practical importance mainly with hand tools the handling of which is considerably facilitated thereby. y

Other and further important objects of the invention will become apparent by reference to the following detailed description taken in connection with the accompanying drawings, in which drawings the invention, for purposes of illustration, is shown as applied to a portable pneumatic stapler.

In the drawings:

FIG. 1 is `a longitudinal section and partly side elevation of a portable air-driven stapler in its initial position;

FIG. 2 is an enlarged detailed fragmentary sectional view of FIG. 1;

FIG. 3 is a sectional view of FIG. 2 in operative position;

FIG. 4 is an enlarged sectional view taken as indicated by line IV-IV of FIG. 2.

The stapling device, which, by way of example, is designed as a portable hand tool, consists of a casing 1, which may be made of a light metal casting or pressing and is provided with a lateral handle 2 having a conventional connection (not shown) to a suitable supply of air under pressure. The casing 1 encloses a large air chamber 4 which is in open communication with the air supply connection and surrounds the upper portion of a sleeve or main cylinder 5. The main cylinder 5 is inserted into the casing 1 and by a resilient O-ring 6 is sealed oif against an intermediate wall 7 of casing 1. Together with a bottom portion 8, the intermediate wall 7 encloses an air storage chamber 9, which is through a narrow port 10 and a plurality of wider ports 11 in the wall of cylinder 5 in open communication with the interior of cylinder 5. The lower end of cylinder sleeve 5 is supported on lan annular shoulder 12 of an elastic bumper 13, which is inserted in the bottom 8 of the casing and limits the working stroke of driving piston 14.

The piston 14 is slidably mounted within the cylinder sleeve 5 and consists, for example, of light metal with a steel core. Firmly secured to piston 14 is a staple driver 15, which, for instance, is made of steel sheet metal and is in the conventional manner guided in a drive track provided in a nose piece 16, which drive track is not shown in the drawings. Secured to the nose piece 16 is a magazine 17 for handling a supply of fasteners, such as staples, which are joined together as a strip or bar.

Supported on the upper open end of main cylinder 5, by means of a profiled ring 19, which contains an elastic sealing ring 18, is a sleeve or cylinder 20, the upper end of which is adjacent to a cap or top 22, which is by screws 21 (see FIG. 4) secured to the casing 1.

The main cylinder 5, loosely inserted into casing 1 by the cap 22 is rigidly clamped between the annular shoulder 12 of bumper 13 and the sleeve 20. Therefore, if cap 22 is screwed oilc Iand sleeve 20 is pulled out, main cylinder 5 may be replaced in an easy fashion and with a minimum of time when worn out owing to rough working conditions of the device. The easy replacement of the heavily strained main cylinder 5, which is thus enabled, avoids longer periods of break down and therefore is of importance for practical usefulness of the device.

An annular piston-like element 23 is adapted for a slight sliding movement in sleeve 20 and operates as a valve for introducing compressed air to the main cylinder 5. The piston valve 23 is supported by the profiled ring 19 and by air and by springs 24 is pressed on its seat, which is formed by the profiled ring 19. Piston valve 23 may be moved entirely in a pneumatic fashion without the use of any springs if it is constructed as a differential piston. The sealing surface of piston valve 23 consists of an elastic disc 25. By a resilient O-ring 26, piston valve 23 is also sealed ol against sleeve 20, land by a resilient O-ring 27 is sealed against a cylindrical projection 28 of cap 22. Secured into this cylindrical projection 28 is an annular permanent magnet 29 to maintain the piston 14 in its initial upper position Ias shown in FIGURES 1 and 2. The magnet 29 encloses an axially extending exhaust duct 30, the upper angularly bent end 31 of which is closed by an exhaust valve 32.

The valve stem 33 of exhaust valve 32 extends across the central axis of cylinder 5 and at its rear end carries an actuating piston 34 shaped as a dilferential piston, which has an airtight guide within a cylindrical bore 35. The cylindrical bore 35 is closed by a screw 36 and sealed against the valve stem 33 by a resilient disc 37. Besides, valve piston 34 is by a resilient O-ring 38 sealed against the cylindrical bore 35. The area of the annular face of differential pist-on 34, adjacent the exhaust valve 32 is substantially smaller than the area of the opposite face of the piston adjacent the end screw 36. By a passage 39, which is arranged in the neighbourhood of the resilient disc 37 and crosses cap 22 and casing 1 of the device (see FIG. 4), the cylindrical bore 35 permanently communicates with the air chamber 4. The opposite end of cylindrical bore 35 adjacent screw 36, is by a passage 40 connected with a chamber 41 located between cylinder 20 and a control valve 42. By a resilient O-ring 43, valve stem 33 is also sealed against the bore of cap 22, in which it is housed. Sleeve 20 is at its upper edge provided with a plurality of ports 44 and at its lower edge with corresponding ports 45.

The control valve 42 has a valve stem 47, which is actuated by a trigger lever 46, and slides within a valve box 50, which is together wtih interposed sealing rings 51 and 52 inserted into a corresponding recess of casing 1. Valve box 50 is provided with a port 53 and is in open communication with an exhaust duct 54, and an annular chamber enclosed between casing 1 and valve box 50 is in open communication with chamber 41.

The valve assembly operates as follows:

In its inoperative position as shown in FIGURES 1 and 2, main piston 14 is in its uppermost position and cylinder 5 is closed by the annular piston valve 23, which in turn is pressed on its seat 19 by springs 24 and by the compressed air acting on its upper face from within the air chamber 4, chamber 55, chamber 41 and ports 44. The exhaust valve 32 is open because the full pressure of the compressed air kept in storage chamber 41 is via passage 40 admitted to the face of the dierential piston 34. As the area of this face is greater than of the opposite annular face of differential piston 34, exhaust valve 32 is kept in its open position. Magnet 29 holds main piston 14 in its uppermost initial position.

When the trigger 46 is squeezed for carrying out a working stroke, control valve 42 is upwardly shifted into the position shown in FIG. 3 so as to interrupt supply of compressed air from air chamber 4 to chamber 41 as O-ring 48 closes the cylindrical bore of valve casing 50. Chamber 41, being in connection with the space above annular piston 23 through the upper ports 44 of cylinder 20, is via annular chamber 55, ports 53 of valve casing 50 and its annular bore in open communication with exhaust passage 54 and thus allowing the air to escape from the space above annular piston 23.

Due to the open communication formed by passage 40 between the cylindrical space 35 and the chamber 41, the air from the cylindrical space 35 immediately escapes to the atmosphere. The compressed air from air chamber 4 through passage 39 act-s on the annular face of differential piston 34 which piston is at once shifted to the right and moves valve 32 into its closed position, in which it blocks the exhaust duct 30, 31. Because of the small quantity of air prevailing within the cylindrical space 35 and because of the greater volume of air in the cylindrical Space within the sleeve 20 above the piston valve 23, exhaust valve 32 is certainly closed before annular piston 23 is moved into its operative position.

The compressed air streaming in from air chamber 4 via the lower ports 45 of cylinder 20 raises annular piston 23 from its seat 19 as the air is more eiective than the springs 24.

The compressed air may therefore freely stream into main cylinder 5 and be admitted to driving piston 14, As soon asV this compressed air overcomesthe arresting force of magnet 29, driving piston 14 is pushed forward in4 its working direction and with its driver15 drives a staple into the work piece.

The air displaced during the working strokecfdriving piston 14 moves through ports 11 into the storage chamber 9 and is stored therein. When piston 14 has' almost completed its working stroke and abuts bumper 13, the compressed air above it flows through the narrow port 10 into the storage chamber 9 and increases the pressure of the air stored therein, which air moves through the large ports 11 to underneath the lower face of piston 14 when it has hit bumper 13 and in a known manner returns the piston 14 into its initial position.

During this return motion, the space above piston 14 is through the passages 30 and 31 connected with the outside air by means of exhaust valve 32. As soon as piston 14 reaches the top of main cylinder 5 it is held in this position by the magnet 29.

The instant closing of exhaust valve 32 is favored by its arrangement across the central axis of main cylinder 5 and annular piston 23 respectively, as this allows for the passages 39 and 40 to be relatively short. Besides, this across-arrangement of exhaust valve 32 reduces the construction height of the device.

The start of any working stroke thus takes place in two phases: at first exhaust valve 32 is closed after actuation of control valve 42 by trigger 46, and secondly the annular piston 23 is opened so that no loss in compressed air by it being blown out of the then still open exhaust valve can occur before annular piston 23 is opened and effects the working stroke. In this manner, an increase in the performance of the device and a better economy of its operation are obtained as driving devices of the type referred to Work for longer periods without being allowed any pauses.

Although the invention is herein shown and described as applied to a portable pneumatic stapler, it is to be understood that in its broadest aspect the invention is not to be so limited except as particularly set forth in the following claims.

I claim as my invention:

1. In an air-operated fastener device, a casing having a main cylinder, an air storage chamber adjacent said main cylinder and adapted to be connected to a source of compressed air, a piston slidable in said main cylinder, holding means adapted to maintain said piston in an initial position at one end of said main cylinder, pneumatically actuated valve means including a differential piston inlet valve arranged at said one end of said main cylinder and operable to introduce air under pressure from said air storage chamber to said main cylinder, an exhaust valve connecting said one end of said main cylinder with the atmosphere when said piston has completed its working stroke and returns to said initial position, a manual control valve for pneumatically moving said inlet and exhaust valves, an air chamber between said inlet valve and said control valve, said air chamber lbeing exhausted to the atmosphere upon activation of said control valve, a differential piston combined with said exhaust valve, la cylindrical space containing said differential piston, the axis of said cylindrical space extending transversely of the axis of said main cylinder and said inlet valve, a first passage adjacent one face of said differential piston and communicating With said air storage 2. A device in accordance with claim 1,- .wherein said cylindrical space of said4 differential piston contains a smaller quantity of air than said air chamber between said inlet valve and said control valve.

3. A device according to claim 2, wherein the cross section of said second passage is sufficiently large so that said cylindrical space is exhausted to the atmosphere before said air chamber is exhausted to the atmosphere.

-4.v A device according to claim 1, wherein said control valve has a stem extending across said air storage chamber and is guided in a valve box, said box being disposed in a cavity of said casing and being provided with air passages, said air passages in the operative position of said control valve connecting said air chamber with an exhaust port, and said air pas-sages in the inoperative position of said control valve connecting said air chamber with said air storage chamber.

5. In an air-operated fastener driving tool having a main cylinder, a piston and driver movable in said main cylinder through a working stroke and a return stroke, means defining an air storage chamber adapted to be connected to a source of compressed air, means for supplying air under pressure from said air storage chamber to said main cylinder for moving said piston and driver through said working stroke, and exhaust passage means for venting air from said main cylinder to the atmosphere during movement of said piston and driver through said return stroke; the improvement which comprises the combination of an air inlet valve cylinder, a differential piston air inlet valve in said air inle-t valve cylinder movable between open and closed positions by air under pressure from s-aid air storage chamber for controlling the supply of air from said air storage chamber to said main cylinder, an exhaust valve for opening and closing said exhaust passage means, a differential piston cylinder containing a differential piston which is connected to said exhaust Valve for moving the latter between open and closed positions, first air passage means for supplying air under pressure from said air storage chamber to said air inlet valve cylinder and to one portion of said differential piston cylinder at one face of said differential piston, second air passage means in permanent communication with said air storage chamber for supplying air under pressure from said air storage chamber to an opposite portion of said differential piston cylinder at the opposite face of said differential piston, a control valve in said first air passage means movable between operative and inoperative positions, said exhaust valve being held in open position and said air inlet valve being held in closed position by air under pressure from said `air storage chamber and from said first air passage means when said control valve is in its inoperative position, said one portion of said differential piston cylinder and said air inlet valve cylinder being vented to the atmosphere through said first air passage means and said control valve when the l-atter is in its operative position, and said exhaust valve thereupon being movable to closed position by air under pressure from said air storage chamber and from said second air passage means and said inlet valve thereupon being movable to open position by air under pressure from said air storage chamber for admitting air under pressure to said main cylinder, the volume of said one portion of said differential piston cylinder being substantially smaller than the volume of said air inlet valve cylinder whereby said exhaust valve is fully closed before said air inlet valve is opened.

6. The tool of claim 5 further characterized in that said first air passage means includes an air chamber interposed in permanent fluid communication between said -air inlet valve cylinder and said control valve and also being in permanent fiuid communication with said one portion of said differential piston cylinder whereby said -air inlet valve cylinder and said Vone portion of said differential piston cylinder are both vented through said air chamber and thence through said control valve when the latter is in its operative position.

7 7. The tool of claim 5 further characterized in that the axis of said dierential piston cylinder is disposed transversely of the axis of said main cylinder and said air inlet valve cylinder.

References Cited UNITED STATES PATENTS 8 Smith. Lingle 1-44.4 Juilfs 137-625.6 Maynard 227--8 Juilfs 227-130 EDGAR W. GEOGHEGAN, Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

B. L. ADAMS, Assistant Examiner.

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