US3351257A

US3351257A - Pneumatic nailing machine

Info

Publication number: US3351257A
Application number: US634048A
Authority: US
Inventors: Reich Kurt; Cast Adolf
Original assignee: Karl M Reich Maschinenfabrik GmbH
Current assignee: Karl M Reich Maschinenfabrik GmbH
Priority date: 1964-04-25
Filing date: 1967-04-21
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07
Also published as: NL6504917A; DE1298057B; GB1033870A

Description

NOV. 7, 1967 RElCH ET AL PNEUMATIC NAILING MACHINE 5 Sheets-Sheet 2 Filed April 21, 1967 MN w lnvenior:

NOV. 7, 1967 RElCH ET AL 3,351,257

PNEUMATIC NAILING MACHINE Filed April 21, 1967 5 Sheets-Sheet 3 I I Q I 1 9\ K 256 28/ f 51/ f J 3; t 5/4 257 A 285 255 E49 lm emon' Mark 720 in 1d Adolf CLKL Ev: Wu! MMMLi/ML A'fHJrnu United States Patent 3,351,257 PNEUMATIC NAILING MACHINE Kurt Reich, Nurtingen, Wurttemberg, and Adolf Cast, Oberlenningen, Wurttemberg, Germany, assignors to Karl M. Reich Maschinenfabrik Nurtingen, Wurttemberg, Germany Filed Apr. 21, 1967, Ser. No. 634,048 Claims priority, application Germany, Apr. 25, 1964, R 37,776 14 Claims. (Cl. 227-130) ABSTRACT OF THE DISCLOSURE A pneumatic nailing machine which is provided with a percussion piston driven by compressed air and guided in a working cylinder. The pressure chamber therein is connected through a bore in the wall of the working cylinder and through an air inlet valve with a compressed air supply line. A tubular slide valve surrounds the main cylinder and is movable to an open position which closes a vent line communicating the bore with the outer air and permitting the compressed air to enter the pressure chamber and a closed position shutting olf the compressed air and opening the vent line, respectively.

This is a continuation-in-part application of the copending application, Ser. No. 449,705, filed Apr. 21, 1965, now abandoned.

The present invention relates to a pneumatic nailing machine which is provided with a percussion piston, which may be driven by compressed air and is guided in a working cylinder, the pressure chamber of which is connected through at least one opening in the wall of this cylinder and through an air inlet valve with a compressed-air supply line.

It is an oject of the present invention to provide a pneumatic nailing machine which has an especially compact size and structural design, but still insures that the air inlet valve will be opened very suddenly so that the compressed air will drive the percussion piston forwardly with great force.

According to the invention, this object is attained by providing an annular chamber which surrounds the working chamber and is connected with the latter through a compressed-air inlet opening thereof, and is connected with the compressed-air supply line at a point which is radially spaced from the outer surfaces of the working cylinder, and by providing a tubular slide valve, which surrounds the cylinder and the annular chamber and extends coaxially thereto and is axially slidable along the i1 ner wall of its valve housing, and which in its closed position shuts off the compressed-air supply line from the inlet opening of the working cylinder. By providing the annular chamber around the working cylinder, the advantage is attained, that this chamber may be connected with the inside of the working cylinder through one or more inlet openings in a manner, so as to permit the compressed air to enter the working cylinder very rapidly and without restriction. Since the valve member for shutting olf the supply of compressed air from the inlet opening of the working chamber also consists of a tubular slide valve which surrounds the annular chamber, the further advantage is attained, that the inlet valve also has a very large cross-sectional area of flow. Furthermore, by providing this valve in the form of a tubular slide valve around the working cylinder, it will not increase the length of the nailing machine, while the increase in thickness of the nailing machine due to this tubular slide valve may be utilized for providing the compressed-air supply line in the form of a tubular channel, which like- 3,351,257 Patented Nov. 7, 19 67 wise surrounds the cylinder and forms an axial extension of the outer surface of the slide valve or its housing. This arrangement of a tubular compressed-air supply line also has the advantage that a very large cross-sectional area of flow of the compressed air through this supply line will be attained.

A very valuable feature of one preferred embodiment of the invention further consists in providing the tubular slide valve in the form of a differential piston, in which the piston part with the smaller end surface is movable within a first pressure chamber which is connected directly with the compressed-air supply line for moving the slide valve to its closed position, while the piston part with the larger end surface is movable within a second pressure chamber which is connected with the compressedair supply line via an auxiliary valve for moving the slide valve to its open position.

Another advantageous feature of the invention provides that the tubular slide valve is composed of two sleeves which are screwed together by a tubular connecting member in such a manner, that the mentioned end surfaces form radial surfaces which are axially spaced from each other and face each other, and that the side wall of the housing of the valve is provided with an inwardly projecting flange which extends between the two sleeves and the peripheral surface of which engages with the tubular connecting member between the two sleeves and guides the slide valve, while the end surfaces of this intermediate flange together with the radial surfaces of the two sleeve parts define the mentioned first and second pressure chambers. The tubular slide valve may also be designed such, that one end thereof forms a sealing edge which, in case the valve is in its closed position, engages upon a valve disk of an elastic material and thus insures r that this valve will be tightly closed, when the percussion piston is in its inactive or rest position.

The above-mentioned, as well as numerous other features and advantages of the present invention will become more clearly apparent from the following detailed description thereof, which is to be read with reference to the accompanying drawings, in which:

FIG. 1a shows a longitudinal section of the rear part or head of a pneumatic nailing machine according to the invention, the tubular air inlet valve being in the open position and the percussion piston in the position during its power stroke;

FIG. lb shows a longitudinal section of the rear part or head of a pneumatic nailing machine according to the invention, the air inlet valve being in its closed position and the percussion piston in its inactive or rest position;

FIG. 2 shows a longitudinal section of the main body of the same nailing machine with the auxiliary valve in the actuated position and the pivotal nail feed conduit in the outwardly pivoted position, and with the percussion piston in a position shortly before striking a nail;

FIG. 3 is a fragmentary section of a portion of the body at enlarged scale indicating the piston and the valve; and

FIG. 4 shows a longitudinal section of the rear part or head of another embodiment of the pneumatic nailing machine according to the invention.

Referring now to the drawings,and in particular to FIGS. l3, the rear part of the pneumatic pistol-shaped nailing machine forms a head 1, which is secured to the main body 2 of the machine by means of a working cylinder 3 of steel, which is provided with

external screw threads

4 and 5 on both ends. The screw thread 5 on the front end of cylinder 3 is screwed into the socket-like rear end of a steel tube 6 around which an outer body 7 is cast which consists of a light-metal alloy, preferably an aluminum or magnesium alloy. The front part of the steel tube 6 contains the rear part of a short barrel-like mouthpiece 8 which is axially slidable therein and prevented from falling out of the steel tube 6 by the provision of radial bores in the latter, into which balls 9 are inserted, which engage into axially extending grooves 11 of a short length and are held in this position by a rotatable ring 13 which may be locked by at least one spring-loaded ball 12. An axial movement of the ring 13 is prevented at one end thereof by the light-metal body 7 and at the other end by a ring 14 which is secured on the steel tube 6 by at least one screw 15 and carries a nail catcher 16. The mouthpiece 8 is further provided with radial slots 17 containing clamping jaws 19 which are pivotal about their rear axes 18 and are surrounded by a resilient ring 21 of plastic, so as to grip a nail 23 which is inserted into the axial bore 22 in the mouthpiece 8.

For inserting the nails 23 into the bore 22, a nail feed line 24 is provided which terminates into a separate tubular curved end part 25, which is pivotal back and forth about an axis 27 from a position within the nail channel 22, as shown in FIG. 2 in dot-and-dash lines, through a radial slot 26 in the lower side of the steel tube 6 and the body 7 to the outside position, which is shown in full lines. In this outside position, the mouth of the tubular end part on the end of the nail feed line 24 is located opposite to the nail catcher 16, which is formed by a slot in a projection on the ring 13, so that any nails which are accidentally fed, when the tubular end part 25 is in this outside position, will be caught by the nail catcher 16. In order to hold the mouthpiece 8 in its forwardly advanced position, a spring 28 is provided acting upon a safety sleeve 29, which is mounted between a shoulder 31 in the steel tube 6 and a collar provided on the safety sleeve 29. In its forward side, the front end of this safety sleeve 29 is provided with an axial slot, the bottom of which is inclined, so as to permit the curved tubular end part 25 operating as a nail feed conduit, when pivoted upwardly into the axial bore 22 operating as a nail channel, to engage partly into this slot. For holding this tubular end part 25 in this position, it is provided with two lateral projections 32, which engage into the front end of the sleeve 29, so that tubular end part 25 will then be arrested by the safety sleeve 2-9 in the inwardly pivoted position. If, however, the mouthpiece 8 is pushed back into the steel tube 6 when pressed against a workpiece 33, the safety sleeve 29 will at the same time also be shifted toward the rear against the action of the spring 28, so that the projections 32 will then be released from the front end of the sleeve 29 and the tubular end part 25 can pivot out of the bore 22 in the mouthpiece 8. The movement of the safety sleeve 29 in the axial direction is limited by a pin 35 which engages into an axial groove 34 in the sleeve 29.

For pivoting the tubular end part 25 on the end of the nail feed line 24, a control valve piston 36 in the form of a differential piston is provided in the grip 37 which is secured to the body 2 of the machine. The front end of a piston rod 38 of this valve piston 36 which projects from the grip 37 is provided with a screw thread 39 on which two nuts 41 are screwed between which a sleeve 42 is clamped which engages into a bifurcated end 43 of the pivotal conduit or tubular end part 25. When the control piston 36 is in its forward end position, it is possible to adjust the pivotal conduit or tubular end part 25 very accurately by means of the nuts 41, so as to be located in the proper position wit-bin the mouthpiece bore 22. Piston 36 is slidable within a valve cylinder which is formed by a bore in the grip 37. A working chamber 45 of this cylinder adjacent to the larger end surface 44 of piston 36 is connected by a channel 46 with an auxiliary valve 47, the slide member 48 of which carries on its outer end a push-button 49, while its cylindrical body is provided with a continuous axial groove 51 and with sealing rings 52 and 53 at both ends thereof. Slide member 48 is slidable within a guide bushing 55 which is screwed into a tapped bore 54 in the grip 37 and has a radial aperture 56 therein which communicates with the axial groove 51 and the channel 46 and is adapted to connect the channel 46 either with the inner part of bore 54, when the slide member 48 is in the depressed or rearward position, as shown in FIG. 2, or with the outer air when the slide member is pushed outwardly, as shown in FIG. 3, that is, toward the left of FIG. 2 of the drawing. The inner part of bore 54 communicates through a channel 57 with a compressed-air supply line 58 and through a channel 59 with a resetting chamber 61 of the valve cylinder for the control piston 36, so that in this chamber 61 always the same air pres sure prevails as in the compressed-air line 58.

The resetting chamber 61 is, in turn, connected with a valve chamber 62 of a valve, the ball-shaped valve member 63 of which is normally pressed by a spring upon its seat, so as to close the chamber 62 toward the end of a conduit 64 which connects the

valve

62, 63 with a nailfeed mechanism which is adapted to insert a nail into the nail feed line 24, when the connecting conduit 64 is vented. For lifting the valve ball 63 off its valve seat,

a slide tappet 65 is provided, which projects into the working cylinder 3 and will be depressed by a percussion piston 66, when the latter reaches the end of its power stroke in cylinder 3, so that the compressed air can then pass from the valve chamber 62 into the connecting conduit 64.

The connecting conduit 64 communicates through a bore 67 with a chamber 68 which forms a narrower extension of the cylinder in which the control piston 36 is movable. The chamber 68 is connected at its rear end by a vent channel 69 with the outer air, while its front end is sealed relative to the sesetting chamber 61 by an extension 71 of the control piston 36. This extension 71,

which has a smaller diameter than the control piston 36 itself, is designed such as to close the bore 67 when piston 36 is in its rearward position, as shown in FIG. 2, and it will not open it toward the chamber 68, until the control piston 36 has moved to the position, in which the pivotal nail conduit 25 engages into the mouthpiece bore 22. Thus, when the control piston 36 is in its inactive position, in which the end of the pivotal nail conduit 25 is held within the mouthpiece bore 22, the connecting conduit 64 is vented, so that the nail-feed mechnaism (not shown) will then pass a nail into the nail feed line 24 and feed it through this line and the pivotal conduit 25 into the mouthpiece bore 22. The rear end of the thinner part 71 of the controlpiston 36 carries a rod 72 which engages upon a valve ball 73 which, when the control piston 36 is in its forward end position, is pressed by a spring 74 upon a valve seat 75 and thereby shuts off the communication between a channel 76, which is connected to the compressed-air supply line 58, and a channel 77 which is connected by a line 78 to a pressure chamber 81 of a cylinder bore in the head 1 (FIG. lb), in which the larger side 79 of a tubular slide valve 82 in the form of a differential piston is slidable, which serves as a compressed-air inlet valve and in its closed position shuts off a pressure chamber 83 of the working cylinder 3 from communication with the compressed-air line 58.

When the control piston 36 is located in the position as shown in FIG. 2, the valve ball 73, which forms the valve member of a second auxiliary valve, is lifted off its valve seat 75, so that the compressed air entering through the

auxiliary valve

73, 75 into the pressure chamber 81 of the cylinder containing the tubular slide valve 82 moves the latter to its open position. When the control piston 36 is in the position in which it maintains the end of the pivotal nail conduit 25 within the mouthpiece bore 22, the rod 72 on the rear end of the piston 36 disengages from the valve ball 73 so that the latter will be pressed upon its seat 75. Channel 77 is thereby shut off from the compressed-air line 58 and instead connected with the outer air through an axial bore 84 and a transverse bore 85 in rod 72, the chamber 68, and the venting channel 69.

The nailing machine is further provided with two

more cylinders

86 and 87 which extend concentrically to cylinder 3 and form a tubular chamber 88 and another tubular chamber 89, respectively. Chamber 88 is provided as an air storage chamber in which, through bores 113, the air is stored which is displaced by the percussion piston 66 during its power stroke and the air which has penetrated between the percussion piston and the wall of the work cylinder 3 in which this piston is loosely slidable. Thus, means for returning the percussion piston to its inactive position are provided. In the present instance this stored air serves for returning the percussion piston 66 to its inactive position after it has completed its power stroke and driven a nail 23 into the workpiece 33. The outer tubular channel 89 is directly connected with the compressed-air line 58. The rear end of cylinder 86 is provided with an inwardly directed flange 91 which forms the end wall of the annular chamber 88 and carries a resilient sealing ring 92 upon which a sealing edge 93 on the tubular slide valve 82 is adapted to engage.

Slide valve 82 comprises two

sleeves

94 and 95 which are screwed together and have radial surfaces '96 and 79 facing each other. Slide valve 82 is separated from the work cylinder 3 by an annular chamber 97 and it is slidable along and guided by a flange 99 which projects inwardly from the valve housing 98 and the two end surfaces of which, together with the radial surfaces 96 and 79, respectively, define the first pressure chamber 101 and the second pressure chamber 81. The first pressure chamber 101 is connected 'by grooves 102 and the tubular channel 89 to the compressed-air line 58, so that, in the event that there is no pressure in the working-pressure chamber 81, the tubular slide valve 82 will be forced forwardly by the pressure prevailing in the first pressure chamber 101, so that the sealing edge 93 of the slide valve 82 will be pressed against the sealing ring 91. The radial surface 96 is, however, smaller than the other radial surface 79, so that if the pressure in the second pressure chamber 81 is equal to that in the first pressure chamber 101, the

slide valve 82 will be shifted to its open position, as shown in FIG. 1a.

The percussion piston 66 is locked in its inactive position by a resilient locking member 103 which is shaped somewhat like a mushroom and then engages into a socketrecess 106 is provided for receiving the rear end of the slide valve 82, when it is in its open position. As long as this end of the slide valve 82 is not located within the annular recess 106, this recess communicates through a gap 108 with a channel 109 which, in turn, is connected through an adjustable needle throttle 110 with a channel 111 which leads to the outer air, so that when the slide valve 82 is in its closed position, the pressure chamber 83 of work cylinder 3 communicates through the bores 105, the recess 106, and the channels 109 and 111 with the outer air.

The operation of the nailing machine according to the present invention is as follows:

When in the inactive or rest position of the nailing machine the compressed-air line 58 is connected to a source of compressed air, but the first auxiliary valve 47 is not as yet actuated, the slide member 48 of this valve, as shown in FIGS. 2 and 3, will be held in its left outer position, in which the sealing ring 53 seals off the groove 51 from the compressed air prevailing in the bore 54 and groove 51 communicates with the outer air since the sealing ring 52 is lifted off the guide bushing 55. The work chamber 45 for the control piston 36 is then also connected with the outer air through the channel 46 so that, due to the pressure prevailing in the resetting chamber 61, because of its connection through the channels 59 and 57 with the compressed-air line 58, the control piston 36 will be held in its inactive position in which it maintains the end of the pivotal nail conduit 25 in the position as indicated in FIG. 2 in dot-and-dash lines, in which this end engages into the mouthpiece bore 22. The second

auxiliary valve

73, 75 is then likewise closed, so that the second Working-pressure chamber 81 of slide valve 82 is connected with the outer air through the line 78, bores 84 and in rod 72, and the vent channel 69. However, since the first pressure chamber 101 is connected through the grooves 102 and the tubular channel 89 with the compressed-air line 58, slide valve 82 will be held in its closed position, as shown in FIG. 1b by the pressure which acts upon its smaller radial surface 96.

If the push-button 49 on valve 47 is then depressed by the operator of the machine, groove 51 will no longer be connected with the outer air, since the sealing ring 52 will then engage with the guide bushing 55, but the compressed air in the bore 54 will then penetrate through the groove 51 and the channel 46 into the working chamber 45 of the cylinder of the control piston 36. Since the end surface 44 of the control piston is larger than its other end surface facing the resetting chamber 61, the control piston 36 will then be moved to the position as shown in solid lines in FIG. 2. At the same time, the nail conduit 25 will be pivoted out of the mouthpiece bore 22 and the valve ball 73 will be lifted, off the valve seat 75 by the rod 72. This permits the compressed air to pass through the

channels

76 and 77 and the line 78 into the second pressure chamber 81 of the tubular slide valve 82, so that this valve will be moved to its open position, as shown in FIG. 1a. The compressed air will then pass suddenly from the annular chamber 89 through the annular chamber 97 and the bores into the pressure chamber 83 of the working cylinder 3. and act upon the percussion piston 66, so that the latter will carry out its power stroke and its striker rod 112 will hit upon the head of the nail 23 in the mouthpiece bore 22 into which -it has previously been inserted and will drive it into the workpiece 33. As soon as the percussion piston 66 reaches the end of its power strike, it depresses the tappet 65 of 'valve 63, so that compressed air will then pass through the connecting line 64 to the nail-feed mechanism, whereby the next nail will be moved into a position ready to be fed to the machine.

As soon as the operator of the machine then releases the push-button 49, the pressure in the bore 54 will move the slide member 48 of the auxiliary valve 47 back toward the left to its original position, so that the work chamber 45 of the control piston 36 will be vented and the pressure prevailing in the resetting chamber 61 will move this piston back to its inactive position and thereby pivot the nail conduit 25 into the mouthpiece bore 22 to the .position as indicated in dot-and-dash lines in FIG. 2. At the same time, the valve ball 73 of the second auxiliary valve will be pressed by its spring 74 upon its seat 75. The bores 84 and 85 in rod 72 are then also connected with the vent channel 69, so that the second pressure chamber 81 of the tubular slide valve 82 will be vented through the line 78, the channel 77, the bores 84 and 85, and the vent channel 69 with the result, that the pres sure which then acts upon the radial surface 96 of slide valve 82 and upon its rear surface which is located in the annular recess 106 in the cap 107 will move the slide valve 82 to its closed position, as shown in FIG. 1b. As soon as slide valve 82 reaches its closed position, gap 108 is opened and the pressure chamber 83 of the work cylinder is vented through the needle throttle 110 sothat, since the annular chamber 88 communicates through the bores 113 with the chamber of the working cylinder in .front of the percussion piston, the air which has been 7 stored up in chamber 88 will then drive the percussion piston 66 back to its rest position in which itwill be held by the locking member 103.

Also at the same time, when the control piston 36 moves toward the left, the rear part 71 thereof uncovers the bore 67, so that the connecting line 64 is likewise vented, whereby the nail feed mechanism is actuated to feed the next nail through the nail feed line 24 and the pivotal conduit 25 into the mouthpiece bore 22. As soon as this has occurred, the push-button 49 may again be depressed, whereupon the entire cycle of operations, as above described, will be repeated.

Since the needle throttle 110 is adjustable, it permits the discharge of the air from the pressure chamber 83 to be regulated, so as to prevent the percussion piston 66 from being driven back to its rest position with such a force, that it might rebound from the end wall of the work cylinder 3 and become unlocked from the locking member 103.

Referring now again to the drawings, and more particularly to FIG. 4, in this embodiment, a slide valve 282 is provided in a second annular chamber 281 which is directly adjacent and connected with a control valve 247 via a short channel 278. The channel 278 is as short as possible due to the adjacent location of the second annular chamber 281 and the control valve 247 for venting of the second annular chamber 281 as will hereinafter become apparent. The piston rod 238 of the valve 247 projects from below grip 237 and its outer end abuts a push button 249, the latter being swingable about axis 227. The piston rod 238 carries a piston 236 which is axially displaceable in the bore of a second piston 236 which is axially displaceable within the housing of the valve 247. The piston 236 has two

bores

276 and 277, respectively, which, in the first rest position of the piston 236, connects a compressed air supply line 258 with the channel 278, and thus with the second annular pressure chamber 281. The slide valve 282 is maintained in its closed position by the pressure in the chamber 281. In this position, the sealing edge 293 of the slide valve 282 abuts sealing ring 292 and thus prevents the compressed air from penetrating from a first annular pressure chamber 301 through bores 305 in the main cylinder 203 into pressure chamber 283. In this position of the slide valve 282, the pressure chamber 283 is connected to the outside air via annular chamber 297, bores 208 in the slide valve 282 and bores 209 (or vent line) in the valve housing 298.

Upon pressing the push-button 249, the piston rod 238, and thus the piston 236, is moved to its second position, in which the compressed air channel formed by the

bores

276 and 277, respectively, is sealed and closed by the upper end of the piston 236. Upon further pressing of the push-button 249, the second piston 236' is moved upwardly, so that its lower edge forming sealing edge 310 is lifted from a sealing ring 311. By this arrangement, the channel 27 8, and thus the second annular pressure chamber 281, is connected to the outside air via

annular chambers

312 and 312 as well as

bores

313 and 314. The compressed air thus escapes from the second annular pressure chamber 281, and the slide valve 282 is moved by the compressed air acting on its upper smaller face 296 from the first annular pressure chamber 301 into its open position. In this position, the bore 208 closes so that the compressed air cannot escape from the pressure chamber 283. In order to achieve a tight sealing, the slide valve 282 is equipped at its periphery with an annular projection 316 which abuts a shoulder 317 of the valve housing 298 when the slide valve 282 is in its open position. A tight seal of the bores 208 towards the outside is thus obtained.

The slide valve 282 is preferably made from an acetal resin known by the trade name Delrin or the like. It can be manufactured very economically, since there is no finishing required after the injection molding. In addition, it is very sturdy and has a good resistance against wear and tear and thus a long active life. The sliding properties of the plastic slide valve 283 on the cylinder 203 are very good. Finally, the abutment of the annular projection 316, made from acetal resin, against the metal shoulder 317 provides a very tight seal.

In the percussion piston 266, a bore 315 is provided connecting the pressure chamber 283 with an annular space in the main chamber of the cylinder 203, the annular space being arranged peripherally at the front of the percussion piston 266. The diameter of the bore is so small that the compressed air streaming therethrough during the stroke of the percussion piston 266 does not harnper the movement of the latter. The bore 315 also serves the purpose of feeding additional compressed air through the bore 213 into the annular chamber 288 at the completion of each stroke performed by the percussion piston 266, in addition to the air displaced by the percussion piston. After closing of the slide valve 282 and after venting of the pressure chamber 288, the percussion piton 266 is then moved into its position of rest. In order to prevent a rubber-elastic stopper 318 for the percussion piston 266 from moving into the bore 315 during an idle stroke, the bore is projected radially outwardly at the recessed periphery of the front side 319 of the percussion piston 266.

While we have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

We claim:

1. A pneumatic nailing machine comprising a main cylinder defining a main chamber,

a percussion piston slidable within said main cylinder in the axial direction thereof,

said main cylinder having a pressure chamber behind said piston as a part of said main chamber,

at least one bore in the Wall of said main cylinder opening into said pressure chamber,

a tubular slide valve surrounding said main cylinder,

a compressed air supply line controlled by said tubular slide valve,

means for communication between said compressed air supply line and said bore in response to the position of said tubular slide valve,

a vent line communicating said bore with the outer air for venting said pressure chamber, said tubular slide valve being axially movable along said main cylinder between two positions, from a first position in which said tubular slide valve closes said vent line and compressed air passes into said pressure chamber, thereby acting upon the rear end of said percussion piston to carry out a forward power stroke, to a second position in which said tubular slide valve opens said vent line and interrupts the flow of compressed air to said pressure chamber, and

means for returning said percussion piston to its inactive position.

2. The pneumatic nailing machine, as set forth in claim 1, wherein said means for returning said percussion piston comprises a cylinder surrounding said main cylinder in spaced relation and forming therewith an annular chamber communicating with said main chamber and defining an air storage chamber to receive air from said main chamber to return said percussion piston to its inactive position.

3. The pneumatic nailing machine, as set forth in claim 1, wherein said tubular slide valve has a larger radially extending surface and a smaller radially extending surface, said surfaces are axially spaced apart from each other,

a valve housing radially spaced from said main cylinder for receiving said tubular slide valve and having an inwardly projecting flange thereon,

said flange together with said smaller and said larger radially extending surfaces defines a first and a second annular pressure chamber, respectively,

said first annular pressure chamber being connected to said compressed air supply line,

a control valve connected at one side to said compressed air supply line and at the other side to said second annular pressure chamber, and being movable between a first and a second position,

said control valve in its first position allowing the compressed air to flow into said second annular pressure chamber to act on said tubular slide valve to move it into one of its two positions, and

said control valve in its second position venting said second annular pressure chamber, so as to permit said slide valve to move under the pressure on said smaller surface into the other of its two positions.

4. The pneumatic nailing machine, as set forth in claim 3, wherein 3, wherein said first annular pressure chamber is located at the upper end of said tubular slide Valve surrounding the top of said main cylinder and connected directly with said compressed air supply line.

6. The pneumatic nailing machine, as set forth in claim 3, which includes a main body receiving said control valve, said main cylinder is connected near its front end to said body and projects toward the rear thereof, a barrel-like mouthpiece has a rear part secured within said body and a front part projecting therefrom, said mouthpiece has an axial bore in axial alignment with said main cylinder,

a nail feed channel within said body, and

the rear end of said channel is adapted to be connected to a nail feed mechanism separate from said machine and its forward end is adapted to communicate with said axial bore of said mouthpiece to permit a nail to be conveyed through said nail feed channel into said mouthpiece bore.

7. The pneumatic nailing machine, as set forth in claim 6, further comprising means connected to the front part of said machine for catching a nail, if propelled from said nail feeding channel, if the forward end of the latter is not in communication with said axial bore of said mouthpiece.

8. The pneumatic nailing machine, as set forth in claim 1, wherein said tubular slide valve is disposed in spaced relation from said main cylinder and forms with the latter a first annular chamber, and said first annular chamber constitutes said communication means. 9. The pneumatic nailing machine, as set forth in claim 8, wherein said main cylinder is surrounded by a second annular chamber, said tubular slide valve being disposed in said second annular chamber,

said compressed-air supply line is connected to said second annular chamber at a point radially spaced apart from the outer surface of said main cylinder, and said tubular slide valve divides said second annular chamber into a radial outer part connected with said compressed-air supply line and said first annular chamber connected with said inlet opening. 10. The pneumatic nailing machine, as set forth in Claim 1, further comprising an adjustable throttle member disposed within said vent line.

11. The pneumatic nailing machine, as set forth in claim 1, comprising a main body,

said main cylinder is secured at its front end into said main body and projects toward the rear thereof,

a barrel-like mouthpiece has a rear part secured to and axially slidable within said main body and in axial alignment with said main cylinder, and

spring means acting upon said mouthpiece and tending to press the same forwardly.

12. The pneumatic nailing machine, as set forth in claim 1, wherein said tubular slide valve is made of plastic material.

13. The pneumatic nailing machine, as set forth in claim 1, wherein said plastic material is acetal resin.

14. The pneumatic nailing machine, as set forth in claim 12, wherein 40 said tubular slide valve includes at its periphery an annular rojection, and a valve housing radially spaced about said main cylinder for receiving said tubular slide valve and having an inwardly projecting shoulder thereon adapted to abut said annular projection sealingly when said tubular slide valve is in said first position and providing a tight-seal between said bore and said vent line.

References Cited UNITED STATES PATENTS 3,010,430 11/1961 Allen et al. 3,172,124 3/1965 Kremiller 227- X 3,301,456 1/1967 Schafroth et a1. 227130 X 50 GRANVILLE Y. CUSTER, 1a., Primary Examiner.

Claims

1. A PNEUMATIC NAILING MACHINE COMPRISING A MAIN CYLINDER DEFINING A MAIN CHAMBER, A PERCUSSION PISTON SLIDABLE WITHIN SAID MAIN CYLINDER IN THE AXIAL DIRECTION THEREOF, SAID MAIN CYLINDER HAVING A PRESSURE CHAMBER BEHIND SAID PISTON AS A PART OF SAID MAIN CHAMBER, AT LEAST ONE BORE IN THE WALL OF SAID MAIN CYLINDER OPENING INTO SAID PRESSURE CHAMBER, A TUBULAR SLIDE VALVE SURROUNDING SAID MAIN CYLINDER, A COMPRESSED AIR SUPPLY LINE CONTROLLED BY SAID TUBULAR SLIDE VALVE, MEANS FOR COMMUNICATION BETWEEN SAID COMPRESSED AIR SUPPLY LINE AND SAID BORE IN RESPONSE TO THE POSITION OF SAID TUBULAR SLIDE VALVE, A VENT LINE COMMUNICATING SAID BORE WITH THE OUTER AIR FOR VENTING SAID PRESSURE CHAMBER, SAID TUBULAR SLIDE VALVE BEING AXIALLY MOVABLE ALONG SAID MAIN CYLINDER BETWEEN TWO POSITIONS, FROM A FIRST POSITION IN WHICH SAID TUBULAR SLIDE VALVE CLOSES SAID VENT LINE AND COMPRESSED AIR PASSES INTO SAID PRESSURE CHAMBER, THEREBY ACTING UPON THE REAR END OF SAID PERCUSSION PISTON TO CARRY OUT A FOWARD POWER STROKE, TO A SECOND POSITION IN WHICH SAID TUBULAR SLIDE VALVE OPENS SAID VENT LINE AND INTERRUPTS THE FLOW OF COMPRESSED AIR TO SAID PRESSURE CHAMBER, AND MEANS FOR RETURNING SAID PERCUSSION PISTON TO ITS INACTIVE POSITION.