US3437013A

US3437013A - Valve assembly for a pneumatically actuated fastener driving tool

Info

Publication number: US3437013A
Application number: US597770A
Authority: US
Inventors: Dieter Volkmann
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-12-01
Filing date: 1966-11-29
Publication date: 1969-04-08
Anticipated expiration: 1986-04-08
Also published as: DE1478936A1; GB1156159A

Description

April 8, 1969 D. VOLKMANN 3,437,013

VALVE ASSEMBLY FOR PNEUMATICALLY ACTUATED FASTENER DRIVING TOOL Filed Nov. 29. 1966 sheet of 4 y Jl 25 La# 2 33 A 5 o Uw y Y /'5\ ,/51 ,ggf 55 2f f y f4 F35 i; l la J4 f M l l f/ 5 :l f I/ 1. l i Y ff? WW a f1 x i l wf V i i,

/7ml 3 1 .n l" il!!l 1i l l), i -'@f x1w I kl nii Mum/rop prll 8, 1969 D. VOLKMANN 3,437,013

VALVE ASSEMBLY FOR PNEUMATICALLY ACTUATED FASTENER DRIVING Tool. Filed NOV. 29. 1966 Sheet 2 o`4 April 8, 1969 D. VOLKMANN 3,437,013

VALVE ASSEMBLY FOR PNEUMATICALLY ACTUATED Sheet FASTENER DRIVING TOOL Filed NOV. 29. 1966 nnlmn 50 57 pril 8, 1969 D. VOLKMANN 3,437,013

VALVE ASSEMBLY FOR PNEUMATICALLY ACTUATED FASTENER DRIVING TOOL Filed Nov. 29. 1966 sheet 4 of 4 United States Patent Office 3,437,013 Patented Apr. 8, 1969 U.S. Cl. 91-461 9 Claims ABSTRACT OF THE DISCLOSURE A pneumatically actuated fastener driving tool is provided with an air inlet valve for the working cylinder and an exhaust valve which extends through and supports the air inlet valve when the latter is in its open position. The exhaust valve has an upwardly extending stem which is secured to the central portion of a flexible diaphgram. When the tool is in its inoperative position, air pressure on the upper side of the diaphragm holds the air inlet valve closed and the exhaust valve open. When air pressure above the diaphragm is vented by actuation of a manual control valve, air under pressure within the tool causes the exhaust valve to close and the inlet valve to open. The diaphragm has a normally convex shape which assists in moving the exhaust valve to closed position and insures that the exhaust valve is in closed position before the inlet valve opens.

The present invention relates to a valve assembly for a pneumatically actuated fastener driving tool by which U-shaped staples, nails `and similar fastening means can be driven into a workpiece.

Pneumatically actuated fastener driving tools in gen` eral comprise an air cyclinder in which a piston is slidably disposed powering a fastener driver blade. In the tools known in the art the cylinder is enclosed by a storage chamber, which is in constant communication with a source of compressed air. The upper open end of the air cylinder communicates with the storage chamber by means of a pneumatically operated inlet valve which is combined with an exhaust valve for venting the air cylinder during the upward movement of the piston. The prior art inlet valve comprises a flexible diaphragm which is clamped between the cap and main portion of the casing. This diaphragm engages the upper edge of the air cylinder. Because of its repeated movement against the edge of the air cylinder, the diaphragm is subjected to strong wear and tear, which reduces the working reliability of the tool and necessitates expensive repairs.

Secured to the central portion of the diaphragm is an exhaust valve which is movable in upward and downward direction along a control cylinder which is arranged above the diaphragm coaxial with the air cylinder. The exhaust valve must exactly be sealed in the control cylinder which makes it necessary to provide a plurality of washer packing rings which increase the cost of manufacture of the valve device.

Also it is not possible to make sure that the exhaust valve is always closed in the initial position of the piston before the inlet valve is opened.

The inlet valve generally is controlled by ya hand operated actuation valve. To obtain good working efficiency of the device it is desirable that the full power of the compressed air hits the piston as soon as the actuation valve has been moved. To ensure this the exhaust valve must be closed before the air inlet valve starts to move as otherwise part of the compressed air intended to ow on to the air cylinder is allowed to reach the outside air. The

drop of pressure on the piston caused by this could considerably impair the working power of the device.

It is an important object of the invention to provide an improved valve assembly for pneumatically actuated fastener driving tools which overcomes the shortcomings and disadvantages of the prior art devices and by which it is ensured that the exhaust valve is always closed before the inlet valve ofthe air cylinder is opened to initiate the working stroke.

Another object of the invention is to largely protect the air inlet valve 'of the above mentioned valve assembly against wear and tear.

A further object relates to a valve assembly in which means are provided by which the exhaust valve is kept in its closed position as long as the air inlet valve of the air cylinder is in open position.

Other objects and advantages of the present invention will be described in the following specification in which reference is made to the accompanying drawings showing, by way of example, two preferred embodiments of the invention.

In the drawings,

FIG. 1 is a partial longitudinal section of a fastener driving tool in operative position,

FIG. 2 is a partial longitudinal section of the same tool in inoperative position,

FIG. 3 is a longitudinal section of a modified embodiment of the tool in operative position,

FIG. 4 is a longitudinal section of the embodiment of FIG. 3 in inoperative position.

Briey stated the invention provide a valve assembly for a pneumatically actuated fastener driving tool with an air storage chamber adjacent the piston cylinder and communicating with a source of compressed air, against which the upper open end of the cylinder is sealed by means of a pneumatically operated inlet valve which is combined with an exhaust valve and comprises a diaphragm clamped `into the housing of the tool. The invention further provides for the exhaust valve to have its upwardly directed shaft suspended on the movable central portion of the diaphragm and thereby to be directly shiftable, with respect to the inlet valve, from open position into closed position in which latter position of the exhaust valve the inlet valve is supported on the exhaust valve in an open position due to -pressure relief on the upper side of the diaphragm. The pressure relief on the upper side of the diaphragm at rrst causes the exhaust valve to be moved from below iinto its own closed position to bear against the inlet valve, which initially retains its closed position. The exhaust ducts for the upper portion of the air cylinder are in the closed position of the exhaust valve sealed against the outside. Only then the exhaust valve, in continuing its upward movement, causes the inlet valve to be moved into open position in which it allows a sudden and unimpaired flow of compressed air kept in the air chamber into the now open upper space of the air cylinder to act on the piston. Consequently, the device is operated on a typical two-stroke principle.

With reference to the drawings, the embodiment of a fastener driving tool illustrated in FIGURES 1 and 2 is a portable tool for hand use which has a housing 1 made of a light metal casting or pressing and is provided with a lateral handle portion, which is not shown in the drawing, and a connection nipple for a pipe by which pneumatic air is supplied. The housing 1 contains a chamber 2 for compressed air. Chamber 2 is in constant communication with the air admission pipe and is by a partition wall 3 separated from a cylinder with an The upper end of partition wall 3 is provided with anannular extension 5 which tightly surrounds the cylinder 4 and into which a resilient sealing ring 6 is inserted.

Within the cylinder 4 a driving piston 7 (see FIG. 2)

is movable in upward and downward direction. The pison 7 is sealed against the inside surface of cylinder 4 by a resilient O-ring 8 and at its bottom end has an abutment 9 to receive a driver blade 10 by which the fasteners are in the usual manner driven into workpieces. Together with cylinder 4 and a front wall 11 of housing 1 the partition wall 3 forms a storage chamber 12 for cornpressed air which is to return piston 7, by passage means not shown, into its initial position shown in FIG. 2 when it has `completed its working stroke.

Above cylinder 4 and `coaxial with it a control piston 13 is movable in upward and downward direction within a control cylinder 14 consisting of a bore of housing 1. The control piston 13 is used as an inlet valve for cylinder 4 and in the position of FIG. 2 seals the latter against the air chamber 2, in which position control piston 13 rests with its lower annular surface 15 on sealing ring 6 of the annular extension 5 of partition wall 3.

In the operative position shown in FIG. 1 the control piston 13 is elevated so that the air chamber 2 and an air duct 16, which is provided within housing 1, are made to be in communication with cylinder 4.

The control piston 13 is sealed against the control cylinder 14 in which it is contained by a single elastic O-ring 17 and is provided with a plurality of axial conduits 18 which are controlled by the valve head 19 of an exhaust valve, the stem 20 of which has a relatively large clearance against the bore of control piston 13 in which it is guided, as is shown in the drawings. When the

exhaust valve

19, 20 is in the elevated operational position shown in FIG. 1, in which valve head 19 is adjacent to a resilient gasket 21 of control piston 13, the conduits 18 are closed.

The conduits 18 are terminated in a chamber 22 which is at its top end closed by a resilient diaphragm 23 and via radial passages 24 is in communication with an annular chamber 25. Chamber 25 is through a radial passage 26 provided in housing 1 in open communication with the external air and is of larger diameter than the control cylinder 14 which contains the control piston 13.

The diaphragm 23 is of normally convex shape and at its outside edge is clamped between the housing 1 and a cover plate 27. At its center the diaphragm 23 is clamped between the exhaust valve stem 20 and a disc 28. By a screw 29 coaxial with the central axis of driving piston 7, disc 28 is secured to the exhaust valve stem 20. Disc 28 presses diaphragm 23 against the surface of a supporting ring 28a which encloses valve stem 2 0. A permanent magnet 30 mounted into valve head 19 is arranged below screw 29 to keep driving piston 7 in its initial position shown in FIG. 2.

A space 31 is enclosed between diaphragm 23 and the inside surface of cover plate 27 which space forms an upward continuation of annular chamber 25 and is of like diameter. The space 31, is, through a conduit 32, a port 33 provided in the diaphragm 23 near its edge and a duct 34, connected with the valve chamber 35 of an actuation valve 36, the stem 37 of which passes through the air chamber 2 and is for operation of valve 36 movable in upward and downward direction by a trigger lever which is not shown in the drawings.

Valve chamber 35 through a passage 38 is in communication with the air storage chamber 2 and through an opening 39 is connected with the external air.

In the inoperative or initial position of the tool the parts are in the positions shown in FIG. 2. In this position, space 31 above diaphragm 23 is through conduit 32, port 33, duct 34, valve chamber 35 and passage 38 in communication with air chamber 2. As the upper side of diaphragm 23 has a larger surface than the annular shoulder 40 which outwardly projects over the lower annular surface 15 of control piston 13 and is also pressurized by the compressed air within air chamber 2, control piston 13 is moved downwards so that its lower annular surface 15 rests on the sealing ring 6 and closes the cylinder 4 against air chamber 2. By the pressure of the air bearing on its diaphragm 23 is downwardly deflected against the initial stress caused by its convexity. The exhaust valve head 19 is also pushed downwards so that the space above driving piston 7 is vented through the open axial conduits 18, chamber 22, the radial passages 24, annular chamber 25 and passage 26. The air above driving piston 7 does therefore not slow down the upward movement of driving piston 7 caused by the pressure of the air from storage chamber 12. When driving piston 7 has reached its upper initial position it is kept there by the magnet 30.

The fasteners are joined together into bars kept in the fastener magazine, which is of the conventional type and is not shown in the drawings. For driving a fastener into the workpiece the trigger lever of actuation valve 36 is shifted, which causes valve stem 37 to be moved in upward direction to assume the position shown in FIG. l, in which the space 31 above diaphragm 23 is through conduit 32, port 33, duct 34, valve chamber 35, and opening 3-9 in communication with the outside air and is therefore free from pressure, while the pressure of the air in air chamber 2 acts upon the annular shoulder 40 of control piston 13. Consequently, control piston 13 and, at the same time, exhaust valve head 19 are moved upwards and valve head 19 is caused to be adjacent to gasket 21. The air from air chamber 2 may now freely reach cylinder 4 above the partition wall 3 and with its full power act on driving piston 7 which then carries out its working stroke at full speed.

The actuation valve 36 rests only for a short time in its position shown in FIG. 1, namely as long as its trigger -lever is being pressed down. As soon as the trigger lever is released the valve stem 37 moves downwards into the position shown in FIG. 2, in which position the space 31 above the diaphragm 23 is pressurized through valve chamber 35 in the manner described. The cylindrical room above driving piston 7 is vented by the opened exhaust valve head 19, conduits 18, passages 24, annular chamber 25, and passage 26. This causes driving piston -7 to be under the inuence ofthe air from storage chamber `12 returned into its initial position.

-By its convexity, which is apparent from FIG. l, diaphragm 23 has such an initial stress that exhaust valve l19, the stem 20 of which is secured to diaphragm 23, is 1kept in its closed position. This is important for generation of a good striking performance as all the air liow- Ling into the cylinder 4 when control piston 13 is raised is used to act on driving piston 7 without it being possible that part of the air streams to the outside due to not yet completed closing of the exhaust valve, as is often the case in conventional constructions.

As is to be noted from the drawings, the shaft 20 of the exhaust valve has a relatively large clearance in the bore of control piston 13 by which it is enclosed; this is, however, of no effect on the functioning of the valve assembly. The assembly moreover only requires one O- ring 17 to seal control piston 13 against the inside surface of the control cylinder 14, which makes the manufacture of the device substantially cheaper.

The embodiment of FIGURES .3 and 4 mainly differs from the afore-described embodiment in that the diaphragm on which the exhaust valve is supported is at its outer edge clamped to, instead of a rigid part of the housing, an auxiliary piston which is mounted above the diaphragm and is used to actuate the exhaust valve.

The stem 20 of exhaust valve 19 is again guided with clearance inside an axial bore of control piston 13 and is via the screw 29, disc 28, and the supporting ring 28a connected with a diaphragm 43, the outer edge of which is by means of a plurality of screws 44 clamped between a ring 45 and a bell shaped auxiliary piston 46. The piston 46 has a central bore 47 and is movable in upward and downward direction inside a cylindrical bore 48 of housing 1 of the device against which is is sealed by an O- ring 49. The heads of the screws 44 are provided with a resilient annular disc `Si) which is secured to the upper side of the auxiliary piston 46. The cylindrical bore 48 is firmly sealed by a cover plate 51 which, together with the upper face of the auxiliary piston 46, includes a cylindrical space 52, the diameter of which is larger than the diameter of the cylindrical bore 14 in which the control piston 13 is contained. The space 52 via a passage 53 is in communication with the chamber of an actuation valve 54 which connects passage 53 either with the air chamber 2 or with the outside air, depending upon the position of its valve stem 55.

The lower end of control piston 13 is in the shape of a sleeve 57 which is similar to the shoulder 40 of the embodiment of FIGS. 1 and 2 and is provided with an annular shoulder 59. The sleeve 57 moves over a plurality of air entrance slots 56 provided at the upper end of cylinder 4. The -bell shaped auxiliary piston 46 encloses a chamber 58 which is arranged above diaphragm 43 and is via the central bore 47 in communication with the cylindrical space 52. The annular disc 50 which covers the heads of the screw bolts 44 in the operative position shown in FIG. 3 leaves the narrow gap or space 52 between the upper face of auxiliary piston 46 and the lower side of cover plate 51, which at the beginning of the working stroke admits the compressed air from air chamber 2 via actuation valve 54 and passage 53 to the upper surface of auxiliary piston 46.

The auxiliary piston 46 has a larger upper surface than control piston 13 and is therefore moved downwards by the air bearing on it. In its downward motion piston 46 moves exhaust valve 19 from control piston 13, this also because the air above the central bore 47 and the chamber 58 bears directly on the diaphragm 43 and thus causes an additional downward pressure on exhaust valve head 19.

In the inoperative position shown in FIG. 4, the sleeve 57 rests on the sealing ring 6 of partition wall 3 at the lower end of control piston 13 and seals working cylinder 4 against the air chamber 2. The space above auxiliary piston 46 is via passage 53 and actuation valve 54 connected with air chamber 2. The air pressure bears via the central bore 47 of auxiliary piston 46 on the diaphragm 43 and moves exhaust valve head 19 downwards so that the space above driving piston 7 is, in the same manner as in the first embodiment via the conduits 18, passages 24 and the passage 26, vented and communicates with the atmosphere.

If a fastener is to be driven into a workpiece the stem 55 of actuation valve 54 is moved upwards, thus causing space 52 above auxiliary piston 46 to be vented. As the control piston 13 is at its lower end 57 provided with a shoulder 59 the pressure ot the air from chamber 2 acts upon this shoulder and causes control piston 13 and thereby also auxiliary piston 46 to be moved in upward direction, whereby the exhaust valve head 19 is closed and the lower end 57 of control piston 13 releases the air entrance slots 56 of cylinder 4. The compressed air from chamber 2 may now freely liow into the cylinder 7 and move the driving piston 7 downward-s.

While two particular embodiments of the invention have been shown and described it will be obvious that changes and modifications may be made without departing from the invention in its broader aspects. Accordingly, the appended claims cover all such changes and modifications as fall wtihin the true spirit and scope of the invention.

What is claimed is:

1. A Valve assembly for a pneumatically actuated fastener driving tool comprising a housing adapted to receive air under pressure, `a working cylinder in said housing, a driving piston slidably disposed in said cylinder, lirst valve means for controlling the admission of air under pressure to said cylinder, second valve means for venting said cylinder after said piston has been driven, the body of said second valve means comprising a lower valve disc and an upper stem portion, a diaphragm, means providing a sealing relation between the edge of said diaphragm and said housing, said stem portion of said second valve means being carried by the central portion of said diaphragm and said diaphragm having a normally convex shape causing an initial stress for keeping said second valve means in its closed position, and means for pneumatically actuating said diaphragm K.whereby said first valve means in its operative open position is supported by said second valve means and in its inoperative closed position said second valve means is opened to exhaust the air from the upper Side of said piston.

2. A valve assembly according to claim 1 wherein the edge of said diaphragm is secured to said housing.

3. A valve assembly according to claim 1 wherein said first valve means comprises a control piston carrying the operative valve body and adapted to be retained in closed position by air pressure acting on the upper surface of the diaphragm.

4. A valve assembly as claimed in claim 3, wherein said control piston has an axial bore for guiding the stem porti-on of said second valve means.

5. A valve assembly as claimed in claim 3 wherein the diaphragm encloses an annular space which communicates with the atmosphere and is of larger diameter than the control piston of the irst valve means.

6. A valve assembly as claimed in claim 3 wherein the edge of said diaphragm is clamped to an auxiliary piston which is movable in upward and downward direction within ya cylindrical space arranged in the housing above the working cylinder, the diameter of said cylindrical space being larger than the diameter of the cylindrical bore in which the control piston is disposed.

7. A valve assembly according to claim 6 wherein the control piston has a depending sleeve portion which moves over inlet slots provided at the upper end of the working cylinder.

8. A valve assembly according to cl-aim 6 wherein the auxiliary piston is provided with a chamber which is closed from below by the diaphragm and is in open communication with the cylindrical space said cylindrical space being in communication with an actuation valve which controls the passage of air from `said housing to said cylindrical space.

9. A valve assembly according to claim 1 wherein the valve body of said first valve means comprises an annular end portion which cooperates with a sealing ring of a partition wall which encloses the working cylinder and separates the latter from a storage chamber for compressed air enclosed by said housing.

References Cited UNITED STATES PATENTS 2,944,522 7/ 1960 Doyle. 3,056,964 10/ 1962 Beckman et al. 3,087,162 4/ 1963 Saurenman et al. 3,170,487 2/1965 Juilfs et al. 3,205,787 9/ 1965 Volkmunn.

PAUL E. MASLOUSKY, Primary Examiner.