US3251276A - Stapling machine - Google Patents

Description

y 1966 D. VOLKMANN 3,251,276

STAPLING MACHINE Filed May 25, 1962 5 Sheets-Sheet 1 /NVEN To? TQILNESS May 17, 1966 D. VOLKMANN STAPLING MACHINE 5 Sheets-Sheet 2 Filed May 25, 1962 W wan W QUE RM file fer l/o/K man/7 ATTORNGjS May 17, 1966 D. VOLKMANN STAPLING MACHINE 5 Sheets-Sheet 5 Filed May 25, 1962 WEE Dieter Vo// man/7 GL M gm AT TDLNESS United States Patent 3,251,276 STAPLKNG MACHENE Dieter Volkmaun, Leinstrasse 23, Neustadt, Ruhenberge, Germany Filed May 25, 1962, Ser. No. 199,560 3 Claims. (Cl. 91394) This invention resides in the provision of a stapling machine to actuate, by pneumatic force, a piston on a work performing stroke.

A primary object of the invention is to provide a portable machine adapted to be connected to a supply of compressed air and which will, on' the actuation of the trigger of the machine, cause fastener means, such as wire staples, nails, pins and the like, to be driven into a work piece from a magazine contained in the machine.

More specifically, an object of the invention is to a provide a manually portable pneumatic machine actuated by compressed air in that compressed air causes the working stroke of the piston as well as its return movement into the initial or starting position so that it is not any more necessary to have a return spring for the piston.

In the case of stapling machines with pneumatic return of the piston known in the art, the piston is actuated upon by compressed air on both sides, both during the Working stroke and during the return stroke. In this case, the compressed air is either reversed at the end of the working stroke or it acts continuously on the piston which is constructed as a stepped piston. The constructional length of the machine is however increased by the stepped piston which also exhibits a greater degree of recoil due to the increase in the piston mass, and this is extremely disadvantageous with hand apparatus.

In another compressed air driven stapling machine, the air displaced by the piston during the working stroke is stored, compressed in a special chamber and is used for the return stroke of the piston. This air-storage chamber surrounds the cylinder concentrically an'd'therefore requires an additional amount of space and 11 separate sealing means, thus increasing the dimensions and therewith also the weight and the manufacturing cost of the apparatus. Weight and space requirements must, however, be kept as small as possible with hand appliances in order to permit easy and convenient handling. Furthermore, the manufacturing costs must be kept down. The hitherto known constructional types of compressed air-driven stapling machines do not fulfill these requirements.

According to the invention a compressed air-driven stapling machine for fastening means is designed in such a manner that the disadvantages of the known constructional types of such appliances are obviated. For this purpose, the invention provides the idea whereby whilst avoiding the use of a secondary chamber there is formed directly in the working cylinder on the side of the piston not acted upon by compressed air during the working stroke and in the end position thereof, an air chamber which is sealed oif relatively to the outer air, is connected with the compressed air supply and the pressure of which returns the piston, from the opposite side of which air has been released, into its starting posi- 325L276 Patented May 17, 1966 tion. The construction of the stapling machine according to the invention requires no supplementary space for the return of the piston, on the contrary the space hitherto provided for receiving the return spring is used for the pneumatic return arrangement, so that the constructional height and diameter of the working cylinder does not require to be increased, thus permitting a saving of weight and space which facilitates the handling of the apparatus.

In order that at the end of the working stroke of the piston a space may be formed in the: cylinder which suffices for producing the return force, the invention furthermore provides means whereby the piston is retained in its end position at a specific distance from the cylinder bottom, simultaneously sealing: off the space thus formed relatively to the outer air. This means may consist of an abutment disposed on the driver and impinging on the cylinder bottom in the end position of the piston, thereby sealing ofi" the ejection conduit guiding the driver. This abutment may simultaneously serve to space the piston in its end position sufficently from the cylinder bottom to form a sufficiently large air chamber.

For retaining the piston at the necessary distance from the cylinder bottom and for sealing oil the air chambe formed thereby it is possible, in further development of the invention, also to provide two means which are separate from each other. Thus, a sleeve like abutment having an axial length corresponding to the size of the air chamber can be arranged on the cylinder bottom as a stroke limiting means for the piston whereas the ejection conduit is closed by a valve-like element provided on the driver.

According to a further feature of the invention, there is provided on the underside of the piston a sleeve which, in its end position, ensures the necessary spacing from the cylinder bottom and simultaneously also seals oil. the passage aperture of the driver.

The feed of compressed air into the air chamber formed in the end position of the piston can be efiected in Various ways, for example by means of a passage formed in the end face of the piston, by means of an overflow conduit formed in the inner wall of the cylinder or by means of a clearance provided between the piston and the cylinder wall. By this means, there is produced at the end of the working stroke on the underside of the piston a pressure which generates a return movement displacing the piston back into its starting position.

In order that the piston may have the necessary acceleration during its working stroke for producing a considerable impact force, the air displaced by it must be removed to the greatest possible extent. Since the driver, which generally consists of thin sheet-metal having the thickness of a wire staple hasonly a small degree of play in the ejection conduit, offering a relatively considerable resistance to the escape of the air displaced by the piston it is advisable to keep this resistance as small as possible by special means. For this purpose, the driver can be formed with slots through which the air displaced by the piston is able to escape to the exterior. It is also possible to provide in the vicinity of the cylinder bottom a venting aperture, such as is conventional with apparatus provided, with return springs. This venting aperture must be closed in the end position of the piston, in order that the pressure necessary for generating the recoil force is retained in the air space. For the closing of the venting aperture, according to a further feature of the invention, it is possible to provide a separate element, i.e. a slide member which during the working stroke of the piston frees the venting aperture and closes it in the end position thereof. The said slide member is conveniently provided with a detent device which retains it during operation in a position freeing the venting aperture.

In its starting position, the piston is advantageously retained by a retaining device provided on the cylinder cover and consisting for example of a mechanical locking means or a permanent magnet secured on the cylinder cover and which retains the piston until the air flowing into the compressed air feed conduit after the opening of the hand-actuated control valve has reached a sufficient pressure.

Further features of the invention will be apparent from the drawings, wherein various constructional examples of the subject of the invention are illustrated. In the drawings:

FIGURE 1 shows a partial longitudinal section through a compressed air actuated hand apparatus for the driving ing of U-shaped staples,

FIGURE 2 shows a partial longitudinal section through another embodiment of a device of this kind,

FIGURE 3 shows a partial longitudinal section through still another embodiment, having a venting aperture controlled by a slide member, shown in the starting position of the piston,

FIGURE 4 shows a fragmentary longitudinal section of FIGURE 3 in the position at the end of the working stroke of the piston,

FIGURE 5 shows the section illustrated in FIGURE 4, in a plane displaced through 90,

FIGURE 6 shows a partial longitudinal section through still another staple driving apparatus with a separate spacing and sealing means.

Referring to FIGURE 1, the apparatus consists of a housing body 11 designed as a handle member and provided with a stub pipe 12 for connection to a source of compressed air. Formed in the housing body Ill is a compressed air conduit 13 connected with an inlet valve 15' adapted to be controlled by means of a trigger lever 14. The inlet valve 15 is connected via a conduit 16 with the upper end of a cylinder 17 in which a piston 18 is guided for sliding movement. The piston 18 is dished and through it extends a radial pin 19 upon which an appropriately bored driver 2% is pushed, the central positioning of said driver being assured by spacing sleeves 21 disposed on the pin 1% each of said spacing sleeves bearing against a U-shaped sheet-metal element 22 pushed on the upper end of the driver 29. The two carrier members 22 hear at their upper end against the inside of the dished piston 18 and are connected at their other end with a disc 23.

The driver is guided in an ejection conduit 25 secured on the bottom 24 of the cylinder 17 and con nected in known manner with a staple magazine 26. Arranged on the cylinder bottom 24 is a cushioning means 27 made of a resilient material such as rubber or the like and formed with an aperture 28 for the passage of the driver 20.

The valve 15 is formed in known manner with a venting duct 29 which, when the valve is closed, connects the duct 16 with the outer air.

Formed in the end face of the piston 18 is a bore 30 of small passage cross-section. The piston 18 which may for example be made of steel is retained in the starting position illustrated in the drawings by a disc-shaped permanent magnet 32 secured on the cylinder cover 31.

The mode of operation of the embodiment is as follows:

For driving a staple into a work piece, the trigger lever 14 is pivoted upwardly, whereby the inlet valve 15 is opened and the compressed air conduit 13 is connected with the air conduit 16, whereas the venting conduit 29 is closed. The compressed air flows through the conduit 16 into the upper portion of the cylinder I7 and moves the piston 18 downwardly as soon as the pressure of the compressed air in the conduit 16 overcomes the attraction force of the permanent magnet 32. During the working stroke of the piston 13 a staple disposed in known manner in the ejection conduit 25 is driven by the downwardly travelling striker 20 into the work piece. The air displaced by the piston during its working stroke flows for the greater part through the ejection conduit 25 into the open air, since the driver 26 is guided therein with a certain degree of play, so that the displaced air is practically speaking not compressed and is unable to brake the downward movement of the piston 13.

When the piston 18 has reached the end of its working stroke (this taking place after a short time, of the order of some hundredths of a second) the plate 23 impinges on the annular cushioning means 27 and closes the outlet aperture of the driver 20 in air-tight manner. A small part of the compressed air acting on the upper end face of the piston 18 passes during the working stroke to the lower side of the piston, in the end position of which (the inlet valve 15 still being open) an excess pressure is built up. As soon as the valve 15 reaches its closure position due to cessation of the finger pressure on the trigger lever 14, the venting duct 29 is opened and therewith the space over the piston 18 is connected with the outer air by the conduit 16. Due to the spacing between the abutment plate 23 and the end face of the piston 18, it is possible for a pressure to 'build up under it, since the air chamber is sealed off by the abutment plate 23 at the point at which the driver 20 extends through. This pressure suflices to return the piston 18 out of its end position to the starting position, especially since the piston is not subjected to any counter-pressure during the return stroke due to the fact that the venting conduit 29 is open. The permanent magnet 32 then retains the piston 18 in its starting position until the cycle is repeated on the next opening of the inlet valve 15.

The bore 30 in the end face of the piston 18 requires only to have a small cross-section, since the pressure necessary for the return force below the piston is substantially smaller than the pressure of the compressed air necessary for the working stroke. For this reason, very little or practically speaking no compressed air will flowduring the working stroke through the bore 30 under the piston. If required, the bore 36 can be closed by a nonreturn valve, for example in the form of a plate fitted on the inside of the piston 18.

The embodiment illustrated in FIGURE 2 corresponds substantially to that shown in FIGURE 1, except that in place of the dished piston 18 there is a solid piston 33, the underside of which carries a sleeve 34 connected firmly, for example, by welding, therewith and providing the necessary spacing between the cylinder bottom 24- and the piston at the end of its working stroke. This tubular sleeve has a smaller diameter than the piston 33 and is connected by a pin 35 with the driver 20 between which and the sleeve 34 it is also possible to provide the spacer sleeves 21 as illustrated in FIGURE 1, for retaining the driver in its middle position.

In the path of travel of the piston 33 is a longitudinal conduit 36 shown formed with cylinder wall 17 and connecting in the lower end position of the piston 33 the side of the latter acted upon by compressed air from the conduit 16 with the lower side of the piston 33. Compressed air flows through this return flow conduit 36 at the end of the working stroke into the lower air chamber and subjects the latter to a pressure which produces the recoil force for the return movement of the piston into its starting position.

At the end of the working stroke, the sleeve34 bears against the cushioning means 27 and thereby closes the outlet point of the driver 20 in air-tight manner, so that the compressed air flowing through theoverflow conduit 36 into this air chamber is entirely made use of for producing the return stroke.

In order to enlarge the bearing surface of the sleeve 34 and to dimiish the Wear of the cushioning means 27, there may be provided at its lower end a disc 37, as shown in broken lines in the drawings.

For the purpose of diminishing the recoil, the piston 33 can be manufactured from light metal or plastic instead of from steel, in which case there is disposed on the upper end face, acted upon by compressed air, of the piston a disc of ferro-magnetic metal upon which the permanent magnet 32 arranged in the cylinder cover 31 acts in the starting position of the piston.

Whereas in the previously described constructional forms the air displaced by the piston during its working stroke in the cylinder flows out to the open air through the ejection conduit 25, in the embodiment according to FIGURE 3, there is formed in the lower portion of the cylinder 17 a venting aperture 41 which is closed only for a short time at the end of the working stroke of the piston 33. For this purpose, use is made of a slide plunger 42 which is sealed by an O-ring 43 relatively to the inner wall of the cylinder 17. The slide plunger 42 is retained by a detent device, for example a ball 45 subjected to the action of a compression spring 44 and snapping into an annular groove 46 in the inner wall of the cylinder, at a height such that its lower side is disposed in the same radial plane as the upper edge of the venting aperture 41. The side plunger 42 is formed with a recess 47 having a larger cross-section than the driver 20, so that the air displaced by the piston 33 during the working stroke is able to escapeunhindered through said recess 47 and the venting aperture 41 into the open air. Arranged at the upper side of the slide plunger 42 is a resilient insert 48 against which the sleeve 34 of the piston 33 impinges in the end position thereof, whereby the ball 45 snaps out of its annular groove 46 and the slide plunger 42 is displaced into the end position illustrated in FIGURE 4 wherein it bears closely on the cushioning means 27 of the cylinder bottom 24 and simultaneously its recess 47 is sealed olf by the sleeve 34 of the piston 33. In this position, compressed air which has passed through the inlet valve 15 (still open for a short time) and the air conduit 16 into the cylinder chamber above the piston 33, is able to flow through the overflow conduit 36 into the chamber (now closed) below the piston 33 and there to build up the pressure necessary for the return stroke of the piston, so

that the piston, after the closing of the inlet valve 15 and simultaneously opening of the venting duct 29, again passes back into its starting position.

In order that the slide plunger 42 may move out of the end position illustrated in FIGURE 4 into the operative position illustrated in FIGURE 3, the driver 20 is, as shown in FIGURE 5, formed with a shoulder 49 which lifts the slide plunger 42 during the return stroke of the piston 33 to such an extent that the ball is able to snap into the annular groove 46 under the pressure of the spring 44.

as rubber or the like, serving as an abutment for the piston 33 in its lower end position and enclosing therewith an air chamber 52. The length of the cushioning member 51 in the axial direction is such that there is built up by the compressed air reaching the lower side of the piston 33 through the overflow conduit 36 at the end of the working stroke a pressure which suifices for producing the return stroke of the piston. The said air chamber 52 is sealed off relatively to the ejection conduit 25 by a widened portion 53 which is arranged at the upper end of the driver 20 and the wedge-shaped transmission surfaces 54 of which bear against the recess 55 formed in the bottom of the cushioning member 51 and seal off the said recess 55 in air-tight manner. The compressed air flowing in the end position of the piston 33 through the overflow conduit 36 into the chamber 52 is therefore unable to escape and produces the recoil force necessary for returning the piston 33.

By means of the invention, the piston is reliably returned into its starting position by simple means and without using springs or sensitive reversing devices. In this connection, it is especially advantageous that the cylinder does not require a. supplementary secondary chamber for the air space providing the recoil force, the space otherwise provided for accommodating the return spring now being used for the pneumatic recoil of the piston. Thus, it is unnecessary to increase the dimensions of the apparatus so as to make provision for the pneumatic recoil of the plunger, either in respect of constructional height or of the cylinder diameter.

The invention is of particular importance in connection with compressed air operated hand' appliances for the driving of staples and other fastening means and has, in addition to the advantages of low weight and small dimensions, also that of lower manufacturing costs.

It is apparent that the examples shown above have been given solely by way of illustration and not by way of limitation and that they are subject to many variations and modifications within the scope of the present invention. All such variations and modifications are to be included within the scope of the present invention.

I claim:

1. In a pneumatic stapling machine comprising a cylinder having a bottom and a slot extending through said bottom, a piston slidably supported in said cylinder, a source of compressed air, means for admitting compressed air from said source to one side of said piston, valve means for controlling the flow of air to said one side of said piston and for venting said flow, a staple driver for driving staples connected with the other side of said piston and extending through said slot, said slot communicating with the atmosphere, resilient means limiting the working stroke of said piston and establishing an air chamber at the other side of said piston, said air chamber communicating with said slot and being enclosed by said other side of the piston, said bottom of the cylinder and the adjacent walls of the cylinder; an overflow conduit located in the wall of said cylinder and adapted to connect said air chamber with 'said source at the end of the working stroke of said piston, the top of said resilient means lying adjacent the bottom end of said overflow conduit, and a valve-like device disposed on said driver sealing said slot from the atmosphere when said piston reaches the end of its working stroke.

2. The stapling machine of claim 1 in which said stroke limiting means constitute a sleeve-like cushion which at the end of the working stroke of said piston encloses with the latter said air chamber which is sealed off by said valve-like device disposed on said driver from said slot in which said driver is guided.

3. In a pneumatic stapling machine comprising a cylinder having a top and a bottom having an ejection conduit communicating with the atmosphere, a magnet mounted in the top of the cylinder, a piston reciprocable in said cylinder and adapted to be retained by said magnet adjacent the top of the cylinder, means connected with said cylinder for admitting compressed air into the top of said cylinder to the upper side of said piston, valve means for controlling the flow of compressed air into said cylinder and for venting said flow, a staple driver connected with the lower side of said piston and extending through said ejection conduit for driving staples, said staple driver having a widened portion adapted to engage and seal said ejection conduit from the atmosphere when said piston is in its stroke-end position, a resilient sleeve-like cushion mounted upon the bottom of said cylinder and enclosing with said piston an air chamber when the piston is in its stroke-end position, said cylinder having a Wale conduit interconnecting the upper side of the piston with said air chamber when the piston is in its strokeend position the top of said resilient sleeve-Ike cushion lying adjacent the bottom end of said Wale conduit.

References Cited by the Examiner UNITED STATES PATENTS Slater 91399 Moifett 915 Schafer 9l399 Juilfs 9146l X Wandel 914l6 10 SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner.

Claims (1)

1. IN A PNEUMATIC STAPLING MACHINE COMPRISING A CYLINDER HAVING A BOTTOM AND A SLOT EXTENDING THROUGH SAID BOTTOM, A PISTON SLIDABLY SUPPORTED IN SAID CYLINDER, A SOURCE OF COMPRESSED AIR, MEANS FOR ADMITTING COMPRESSED AIR FROM SAID SOURCE TO ONE SIDE OF SAID PISTON, VALVE MEANS FOR CONTROLLING THE FLOW OF AIR TO SAID ONE SIDE OF SAID PISTON AND FOR VENTING SAID FLOW, A STAPLE DRIVER FOR DRIVING STAPLES CONNECTED WITH THE OTHER SIDE OF SAID PISTON AND EXTENDING THROUGH SAID SLOT, SAID SLOT COMMUNICATING WITH THE ATMOSPHERE, RESILIENT MEANS LIMITING THE WORKING STROKE OF SAID PISTON AND ESTABLISHING AN AIR CHAMBER AT THE OTHER SIDE OF SAID PISTON, SAID AIR CHAMBER COMMUNICATING WITH SAID SLOT AND BEING ENCLOSED BY SAID OTHER SIDE OF THE PISTON, SAID BOTTOM OF THE CYLINDER AND THE ADJACENT WALLS OF THE CYLINDER; OF THE CYLINDER AND LOCATED IN THE WALL OF SAID CYLINDER AND ADAPTED TO CON-

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