EP0326639B1 - Control valve device for a pneumatically operated fastener driving tool - Google Patents

Description

The innovation relates to a control valve device on a device operated with compressed air for driving in fasteners according to the preamble of claim 1.

Known devices (see e.g. DE-A-2 704 949) of this type are used for the removal of nails, staples or the like. The driving piston for actuating the driving plunger is operated pneumatically. The release takes place with the help of a pusher or a release lever that actuates a release valve. The release valve in turn controls a control valve which, in its open position, connects the displacement of the working piston to a compressed air source, while in the closed position it vents the working stroke space.

In devices of this type, a single driving stroke usually occurs when the trigger valve is actuated by hand. The driving piston does not return to the top dead center position until the triggering is ended. In many cases, continuous automatic driving of fasteners is desired without the need for actuation per driving process. This requires a control valve device which automatically brings the control valve into the closed position and thus initiates the piston return process when the driving-in process has ended in order to start a new work cycle.

From DE-PS 16 03 979 a control valve device has become known in which a control piston is constantly biased by a spring in the closed position. A control valve piston is provided coaxially with the control piston and pushes the control piston into the open position when the pressure is applied accordingly. The pressurized air supply to the control piston is controlled by a reversing valve, which optionally applies an atmosphere or compressed air to an active surface of the control valve. A disadvantage of the known device is that the return spring on the control piston is a pronounced wear part that tires after a certain number of driving operations. Another disadvantage is that the control piston is brought into the open position with the aid of the control valve piston. As a result, the control valve piston and the control piston are subjected to high mechanical loads. There are also unpleasant noises. However, it is particularly disadvantageous that there is no synchronization of the reversing of the automatic valve with the sequence of movements of the driving piston. There is a risk that the reversal process is initiated before the driving piston has completed its stroke. The fastener may therefore not be subjected to sufficient energy and may not be driven far enough. There is also the danger that the working piston space of the driving piston is already pressurized with compressed air before it has reached its top dead center position. The driving piston is also not driven with sufficient energy. It can also happen that the driving piston does not drive out any fastening means at all, since it does not approach the top dead center position sufficiently far. The driving plunger thereby prevents a fastener from entering the ejection channel.

A control valve device has also become known from DE-PS 1 603 839, in which the control chamber facing a main control valve slide is connected to the piston return chamber via an additional pressure-sensitive valve, this connection being controlled by an auxiliary valve slide. As is known, the piston return chamber serves to move the piston from the bottom dead center position back to the top dead center position by filling it with compressed air when the driving piston has approximately reached its bottom dead center position. The return chamber is connected to a bore below the piston in the bottom dead center position with the cylinder, so that the air stored in the return chamber can now accomplish the return stroke. In the known control valve device, part of the compressed air is now branched off from the piston return chamber in order to move the main valve slide back into the closed position. However, the pressure conditions in the piston return chamber are dependent on various factors, such as the friction of the working piston, the seals, etc., so that reproducible pressures are not always achieved. The additional valve therefore does not open reproducibly at a certain position of the working piston. There is therefore no exact synchronization between the movement of the driving piston and the switching operations of the control valve device in this valve device. Moving the main valve spool to the closed position requires a certain pressure and a certain volume, which may not be available for piston return. There is also a risk with the known valve that the reversing process takes place too quickly and the driving piston does not reach its top dead center position reached before the working displacement is reconnected to the compressed air source. Finally, the known valve requires a large number of dynamically stressed sealing rings as well as a return spring in the additional valve. However, sealing rings and springs are wear parts that need to be replaced from time to time.

The same difficulties as the one above Valve arrangement described result in the known valve arrangement according to DE-PS 3 222 949, in which the return space of the driving device is connected directly to an active surface of the main valve, which is arranged as a so-called head valve coaxially to the driving piston above the working cylinder. Although such a valve arrangement is mechanically simple because it works without an auxiliary valve, it has poor controllability of the repetition frequency. Furthermore, a relatively long air path is arranged between the return chamber and the corresponding effective area of the main valve, which is disadvantageous for rapid reversal. With the known valve, therefore, only relatively low repetition frequencies can be achieved. Finally, a reversal only takes place when the pressure has increased almost completely, since the difference areas are very small.

From US-PS 3 808 620 a complex valve has become known, the main valve is also designed as a head valve. The auxiliary valve slide is slidably arranged in a sleeve, which in turn is slidably mounted in the housing of the driving tool. In single-shot mode, the sleeve remains in a predetermined end position. In repeating operation, the sleeve is acted upon by the pressure in the piston return space and adjusted relative to the auxiliary valve spool. This brings it back to its original position and the main valve is reversed in this way. This known valve arrangement also has some disadvantages. The sleeve, which oscillates in repetition mode, is of relatively large design and therefore has a relatively large mass, which is disadvantageous for high repetition frequencies. Like the auxiliary valve spool, the oscillating sleeve is provided with a large number of dynamically loaded O-rings that are subject to relatively heavy wear. In addition, a higher reversing force is required for O-rings. In the known valve arrangement, the difference areas are also relatively small. A reversal therefore only takes place after almost complete pressure build-up or reduction. At higher repetition frequencies there is therefore a risk that the working piston is already pressurized with compressed air while it is still in the return stroke.

A control valve device of the type mentioned has become known from DE-PS 19 08 150. An auxiliary valve spool is also designed in the form of a stepped piston, which delimits its own control space with a piston step, which can be connected to the pressure line in the open valve position and to a vent line in the closed valve position via a line controllable by the main valve spool. The auxiliary valve spool in turn controls the pressurization of the main valve spool. The reversal of the main valve spool only begins when the main valve spool has fully reached the open position so that sufficient pressure can build up in the working stroke space to drive the driving piston. Another working cycle is only initiated when almost no air flows out of the working cylinder during the piston return stroke. In the known valve device, the outflowing air is introduced into the further control chamber via a controllable line, so that its ventilation can only occur when the countercurrent air has almost or completely escaped from the working stroke space. With the aid of these measures, an adaptation to the movement sequence of the driving piston is to be achieved in such a way that the driving piston always executes a full working and a full return stroke. However, it has been shown that, above all, the intended synchronization is no longer achieved at higher drive frequencies. The time that elapses between the reversal processes is essentially predetermined by the connecting channels, which may have throttling points. If the flow cross-sections are too small or too large, it can therefore happen that the driving piston is already relieved of pressure before bottom dead center or that pressure is already applied again before top dead center. Another disadvantage of the known control valve device is that a large number of dynamic sealing rings are required, which are known to be regarded as wearing parts.

The innovation is therefore based on the task of creating a control valve device on a device operated with compressed air for driving in fasteners, which has a minimum of wearing parts and, above all, an exact adaptation of the switching processes to the movement of the driving piston even at high driving frequencies in the so-called repeating mode guaranteed.

This object is achieved by the features of the characterizing part of claim 1.

The new control valve device, like the generic valve device, does not require any dynamically loaded springs. A compression spring can be provided for the release valve or its stem, but is not dynamically loaded. The new control valve device also comes with a very small number of dynamically loaded sealing rings, so that it has minimal susceptibility to wear and allows longer maintenance intervals.

As is also the case with the generic control valve device, the new one comes direction with only two valve spools, with the main valve spool controlling the channel to the working drawer, while the auxiliary valve spool controls the pressurization of the larger effective area of the main valve spool. It is now essential for the innovation that the second active surface of the auxiliary valve slide is directly connected to the piston return space. This connection, which can be formed by a simple transverse bore, preferably contains a throttle, for example in the form of an adjusting screw or a needle for adjusting the flow cross section. If the hole is completely closed, the new device works in single-shot mode. The flow cross-section in the bore set by the throttle, however, determines the repetition frequency of the automatically operating control valve.

The release valve ensures, in the relaxed or non-actuated state, that the larger effective area of the main valve spool is acted upon by the pressure of the compressed air source, for example the reservoir in the handle of the driving tool. As a result, the main valve spool remains in the closed position and blocks the connection of the compressed air source to the working drawer. By actuating the trigger valve, however, the larger effective area of the main valve spool is vented. The auxiliary valve slide can keep its position. For example, a space connected to the atmosphere by actuation of the trigger valve in the starting position of the auxiliary valve spool can be permanently connected via a connection to the larger effective area of the main valve spool. The pressure on the smaller effective area of the main valve slide therefore leads to an adjustment to its open position, in which it releases the connecting channel between the compressed air source and the working push chamber. The driving piston is driven down and drives the fastener into a workpiece. When the driving piston has reached its lower position (bottom dead center), the compressed air can flow into a return space surrounding the cylinder via a hole in the cylinder. Some air flows out of the return space via the described bore and the throttle arranged therein to the second active surface of the auxiliary valve spool. This is then adjusted to its second position, in which it now connects the larger effective area of the main valve spool with the compressed air source. The main valve slide is then moved back to the closed position, therefore separates the connection between the compressed air source and the working push room and instead puts the working push room in the atmosphere. The air stored in the return space now pushes the piston towards the top dead center position. During the entire return time, the return chamber is under a certain pressure until the end, so that this pressure is applied to the second active surface of the auxiliary valve spool and prevents the auxiliary valve spool from returning to the initial position. When the sign of the pressure difference is reversed, the air flows under pressure from the second active surface of the auxiliary valve spool to the return space and thereby supports its return effect. If the second effective area of the auxiliary valve spool is designed to be large, it can easily be achieved that the auxiliary valve spool only returns to its first or initial position when the driving piston has reached its top dead center position with certainty. At some point the auxiliary valve spool is returned to the initial position by the pressure of the compressed air source, so that it connects the larger effective area of the main valve spool with atmosphere again and a new work cycle can begin.

As can be seen, the automatic valve according to the invention can only be switched over when the driving piston has actually reached its bottom dead center position. Conversely, the working stroke of the driving piston is only connected to the pressure source when it has reached its top dead center position. In the control valve according to the innovation, the maximum available energy is therefore used to drive in fasteners effectively, and above all in repeating operation.

Similar to the control valve device described at the outset, the valve according to the innovation has a fixed control sleeve, which cooperates in a sealing manner with a central bore in the main valve spool. According to the innovation, the control sleeve can have a radial flange through which the main control space, to which the larger effective area of the main valve spool faces, delimits. According to the innovation, the auxiliary valve slide is displaceably guided in the bore of the control sleeve.

The second effective area of the auxiliary valve slide, which is optionally exposed to the pressure of the piston return space, is preferably designed to be much larger than the first effective area. If the auxiliary valve slide is also provided with an active surface that is constantly exposed to the pressure of the compressed air source, the second active surface is chosen to be large enough that it is at least twice as large as the active surface that is constantly exposed to the pressure of the compressed air source. In this way it is ensured that during the return stroke of the piston the auxiliary valve spool remains in a position in which the control chamber of the main valve spool is connected to the compressed air source. Only when the pressure in the piston return space is almost completely reduced to a fraction of the Maximum pressure, the auxiliary valve slide returns to its first position and thus initiates the opening of the main valve so that the working piston can be pressurized to perform a new working stroke. In this way it is ensured that the piston has reached its top dead center position before a new working stroke is carried out.

The first active surface of the auxiliary valve slide is preferably formed by a piston section. Another piston section of the auxiliary valve spool is sealingly arranged in the bore of the control sleeve. However, the piston sections described are such that only one of the two cooperates in a sealing manner with the bore of the control sleeve. The piston sections are of smooth cylindrical design without sealing elements, so that seals susceptible to wear are largely eliminated in the auxiliary valve slide. Only the piston section, which forms the second active surface, is preferably sealed in the associated housing bore via an O-ring. The auxiliary valve spool is therefore extremely smooth-moving, which is of considerable advantage for achieving high repetition frequencies of up to 2000 per minute.

According to a further embodiment of the innovation, the auxiliary valve slide can consist of two parts, one of which has the cylindrical sections interacting with the control sleeve and the other has the second active surface. This subdivision is advantageous since the lower part does not have to be arranged exactly coaxially with the upper part and thus different, offset positions of the valve bores in the housing and in the valve cover can be realized. This means that the position tolerances for production can be relatively rough.

In the valve arrangement described, the frequency can be continuously adjusted in automatic mode by changing the throttle between the piston return chamber and the auxiliary valve slide until finally only individual shots are fired. In practice, e.g. in upholstery, it often happens that a so-called mixed operation is required, i.e. First, in single-shot mode, a few clips are specifically driven in to fix the fabric. Then the work continues in automatic mode with a high firing order. To switch from single-shot to automatic mode, for example, a screw has to be actuated by about three to four turns. This may take too long. Therefore, an embodiment of the invention provides that a bore directed toward the trigger of the trigger valve is provided for the second active surface and is connected to the atmosphere when the trigger is not actuated. A section of the trigger carries a sealing element which seals the bore when the trigger is actuated. The relationship of the trigger valve to the trigger is such that although the trigger valve is activated from a first distance of the trigger to trigger a shot, the bore below the second active surface remains open. Despite the automatic setting of the throttle in the channel to the second active surface, the automatic mode is suppressed, and a new single shot can only be triggered when the trigger is released and actuated again. If, on the other hand, the trigger is adjusted a second distance following the first distance, the sealing element closes the hole and the driving tool works in automatic mode. The arrangement described is preferably chosen so that the operator feels two pressure points when the trigger, for example a trigger, is actuated, the first being relatively easy to overcome, while the second can be felt to a greater or lesser extent.

In summary, it can be stated that the valve according to the innovation manages with a minimum number of moving parts or ensures an exact adaptation to the movement sequence of the driving piston. Even at the highest repetition frequencies, there is no loss of impact energy due to the fact that the valve switches over during the up and down movement. Rather, the piston return is only initiated when the impact has been carried out. The next stroke is only switched over when the piston has reached its top dead center position. The valve according to the invention also works with a minimum of wear parts or only those parts which have a very long service life, so as not to cause a failure over a longer period even at the highest repetition frequencies. In particular, loaded springs and dynamically highly loaded sealing elements (O-rings) are eliminated. The valve according to the invention is infinitely variable in a very wide control range from single shot to a maximum limit of 30 Hz, for example. In addition, the valve according to the innovation is designed so that it can be installed in the existing housing of driving tools, without special adaptation measures having to be provided.

The innovation is explained in more detail below with the aid of drawings.

The driving tool shown partially in section in FIGS. 1 to 5 has a housing 10 and a working cylinder 11 which receives a driving piston 12 to which a driving plunger 13 is connected. At the lower end of the working cylinder 11, a brake ring 14 is arranged. The working cylinder 11 is surrounded by a piston return chamber 15 which is connected to the working cylinder 11 via first radial bores 16 and second radial bores 17, the bores 16 on the side of the return chamber 15 being closed by an O-ring 18 which forms a check valve .

The housing 11 has a handle part 20, in which a reservoir 21 for compressed air is formed, which can be connected to a compressed air source (not shown), for example via a compressed air hose. In addition, a ventilation channel 22 is formed in the handle part 20. At the cylinder-side end, a valve plate 23 is attached to the underside of the grip part 20, which engages with a projection in a corresponding recess in the housing 10. The valve plate 23 is screwed to the handle 20 by means of a screw 25 which is arranged countersunk in the valve plate 23. On the underside, the valve plate 23 supports a release lever 26 which is pivotably mounted at 27.

A bore 30 in the grip part 20 is connected to a channel 31, which leads to the working space 32 of the cylinder 11. Above, the working drawer 32 is closed by a cover plug 33. A control valve device 36 is received in the bore 30. It has a main valve spool 37 and an auxiliary valve spool 38. The main valve spool 37 is designed as a stepped piston with an end-side active surface 37a facing the reservoir 21 and an oppositely directed larger active surface facing a main control chamber 39. The piston section of the main valve spool 37 which has the active surface 37a has two axially spaced O-rings 41, 42, the O-ring 41 cooperating with an upper valve seat, as a result of which the connection between the channel 31 and the reservoir 21 is interrupted. The lower O-ring 42 interacts with a stepped bush 43 which is sealingly received by the bore 30. The bushing bore guides the piston section of the main valve spool 37 in a sliding and sealing manner. In the position of the main valve spool 37 shown in FIG. 1, the channel 31 is connected to an annular space 45 surrounding the main valve spool 37, which is connected to an annular space 46 surrounding the bush 43 via radial bores in the bush 43, which is in constant communication with the ventilation duct 22. The working stroke space 32 is therefore under atmospheric pressure.

The central bore of the main valve spool 37 slidably and sealingly receives the upper end of a control sleeve 48 which has a radial flange 49 which is seated in an enlarged section of the bore 30. The control sleeve 48 has a plurality of radial bores 50 which connect the bore of the control sleeve 48 to the main control chamber 39.

The radial flange 49 bears against the bush 43 from below and is in turn held by the valve plate 23 from below. The bore of the control sleeve 48 receives the upper part of the two-part auxiliary valve spool 38. This consists of an upper smooth cylindrical section 51 with an active surface 52 which faces the reservoir 21 via the bore 47 of the main valve slide 37. The upper part of the auxiliary valve slide also has a smooth cylindrical section 53. The intermediate rod is triangular in cross section in the central region, as shown at 54. A passage is thereby formed between the sections 51 and 53 between the rod 54 and the bore wall of the control sleeve 48. The bore of the control sleeve 48 has an enlarged section 55 in the region of the flange 49, into which the smooth cylindrical section 53 can be inserted in a sealing manner. The distance between the smooth cylindrical sections 51, 53 is such that either the upper smooth cylindrical section 51 sits sealingly in the bore of the control sleeve 48, while the section 53 releases the bore section 55, or the smooth cylindrical section 53 sits in the bore section 55, in which case the smooth cylindrical Section 51 projects upwards so far from the control sleeve 48 that the passage around the valve rod 54 is connected to the bore 47 of the main valve spool and thus to the reservoir 21 (FIG. 4).

The lower part of the auxiliary valve spool 38 is arranged in a bore 56a of the valve plate 23. It has a valve piston section 56 which can be moved in a sealed manner in the bore 56a. A piston section 57 with a polygonal cross section - preferably triangular - is seated in a corresponding bore in the valve plate 23. The lower part of the auxiliary valve slide 38 has an active surface 57a and a polygonal active surface 66 which is connected to the return chamber 15 together via an oblique bore 58 in the valve plate 23.

A plunger 60 of a release valve 61 interacts with the release lever 26. It is pressed by the air pressure in the grip space 21 and in a bore 63a of an insert 63 supported by a spring 62 in the direction of the release lever 26. An O-ring 62a closes the bore in the valve plate 23 downwards. The plunger 60, which is triangular in cross-section in the lower region, has a further sealing ring 64 at the upper end, which sealingly cooperates with the bore 63a in the insert 63 when the plunger is lifted upwards using the release lever 26. As a result, a control chamber 65 is separated from the reservoir 21, which is connected to the bore 56a in the position of the auxiliary valve slide 38 shown in FIG. 1.

The control valve device described operates as follows.

Fig. 1 shows the unactuated state again. The release lever 26 is shown in its unactuated position, this position of the release valve 61 prevails in the chamber 65 at the same pressure as in the reservoir 21, since a connection is made via the bore 63a. As a result, the pressure of the reservoir 21 is also located in the bore 56a and in the bore section 55, and can also spread into the main control chamber 39 via the radial bores 50. Since the effective area 40 of the main valve slide 37 is larger than the effective area 37a facing the reservoir 21, the main valve slide is held in the closed position shown in FIG. 1, in which it blocks the connecting channel 31 from the compressed air and via the annular space 45 to the outlet channel 22 connects. The piston 12 is in its top dead center position. However, as can be readily seen, the main valve spool 37 is held in the closed position even when the upper part of the auxiliary valve spool 38 is in its upper position (which is shown approximately in FIG. 4). The cylindrical portion 51 is then outside the bore of the control sleeve 48, so that the passage between the connecting rod 54 and the control sleeve 48 is also connected via the bore 47 of the main valve spool 37 with compressed air, which then also via the radial bores 50 in the Main control chamber 39 can enter.

If the trigger lever 26 is actuated in the direction of the arrow (FIG. 3), the valve tappet of the trigger valve 61 is raised and the sealing ring 64 connected to the valve tappet enters the lower section of the bore 63a of the insert 63, so that the compressed air is shut off At the same time, the sealing ring 62a emerges from the associated bore in the valve plate 23. Since the valve tappet is polygonal, preferably triangular in cross section in the lower region, a connection of the control chamber 65 to the atmosphere is established. The bores 56a, 55 and the radial bores 50 now also connect the main control chamber 39 to the atmosphere. The pressure acting on the smaller effective surface 37a of the main valve spool 37 therefore moves the main valve spool 37 into the open position shown in FIG. 3, in which the O-rings 41, 42 cooperate with the bore of the bush-shaped insert 43 and thereby connect the connecting channel 31 to Shut off outlet duct 22. As a result, the compressed air enters the working stroke space 32 and drives the driving piston 12 downward so that a driving impact is carried out on a fastening means.

In its bottom dead center position, the driving piston 12 strikes the brake ring 14 with its lower end face. Its upper end face exposes the bores 16, and the compressed air can flow from the working space 32 through the bores 16 and the sealing ring 18 acting as a check valve into the return chamber 15 . As already mentioned, the return chamber 15 is connected to the bore 56a via the bores 58 and 58a. If this bore is closed (the throttling of bore 58 will be described further below), the control valve device described operates as a single-shot device. As long as the trigger lever 26 is actuated, the driving piston 12 remains in the bottom dead center position. When the release lever 26 is released, the valve pin 60 is pushed down again by the compression spring 62 and the air pressure. This separates the auxiliary control chamber 65 from the atmosphere. At the same time, the auxiliary control chamber 65 is pressure-connected to the reservoir 21, so that a pressure can build up again in the main control chamber 39, which adjusts the main valve slide 37 back to the closed position. As a result, the working stroke space 32 is reconnected to the atmosphere, and the compressed air stored in the return space 15 drives the driving piston 12 back to the top dead center position. A state as shown in FIG. 1 is thereby obtained again.

If, on the other hand, the trigger lever 26 remains actuated and the bore 58 clears a flow cross section, the control valve device described operates as an automatic valve. If the compressed air from the return chamber 15 passes through the bore 58 and 58a into the bore 56a, it acts on the lower active surface 57a and on the polygonal lower active surface 66 of the lower part of the auxiliary valve spool 38 and pushes it upwards, while at the same time pressing the upper one Takes part and reached the position shown in Fig. 4. This can a pressure in the main control chamber 39 builds up again via the bore 47 in the main valve slide 37 and the passage between the valve rod 54 and the control sleeve 48 and the radial bores 50, through which the main valve slide 37 is returned to the closed position shown in FIG. 4. At the same time, the working drawer 32 is placed on the outlet duct 22 via the connecting duct 31. The driving piston 12 can therefore be moved back to the top dead center position with the aid of the air stored in the return chamber 15. During the return stroke of the driving piston 12, the pressure in the return chamber 15 relaxes gradually, so that the compressed air from the bore 56a below the active surface 57a and the polygonal active surface 66 of the piston section 56 flows back into the return chamber 15 via the bores 58 and 58a and thereby Return stroke of the piston 12 is supported (excess air is guided past the driving plunger 13 into the atmosphere).

Due to the pressure drop in the return chamber 15, the force that holds the piston portion 56 in the upper position gradually decreases until the pressure acting on the cylindrical portion 53 of the upper part of the auxiliary valve spool 38 is sufficient, the upper part together with the lower to move down. As soon as the cylindrical section 53 emerges from the bore 55, it is at atmospheric pressure, since the auxiliary control chamber 65 is still connected to the atmosphere. The main control chamber 39 is therefore relieved of pressure, so that the main valve spool 37 can move down again. A new work cycle begins.

As can be seen, the plate 23 has a connection bore 102 below the bore 56a, in which the second part of the auxiliary valve spool is arranged, which normally goes into the atmosphere. In a threaded bore of the release lever 26 sits a screw or threaded sleeve 100, the bore of which receives a cylindrical sealing element 101 made of elastomeric material, which is provided with a conical tip 105 at the upper end. In the unactuated state of the release lever 26, the bore 102 remains free. If, as shown in Fig. 2, the trigger lever 26 is raised so that the trigger valve 61 responds by immersing the sealing ring 64 in the corresponding bore 63a, but not so far that the cone tip 105 cooperates sealingly with the bore 102, this takes place Triggering of the driving tool described above, but only in single-shot operation, even if the throttle 59 in the connecting channel between the return chamber 15 and the second active surface 57a is open. The connection of the second active surface 57a to the atmosphere has the effect that the auxiliary valve slide cannot initiate automatic reversal of the main valve as long as the bore 102 is connected to the atmosphere. Only when the trigger lever 26 is raised further, as shown in FIG. 3, can the automatic mode be implemented. In this way it is possible, in the "automatic" operating position, which is specified by the throttle, to also selectively operate single-shot and automatic mode. The operating mode depends on the actuation position of the release lever 26.

It is understood that sealing element other than the one shown can also effect a bore 102 seal, for example an annular seal.

6 shows a section through the housing 10 and part of the valve plate 23 in the region of a seal 70, by means of which the attachment 24 is sealed off from the housing 10. The bore 58a can be seen, which connects the return chamber 15 to the bore 56a via the bore 58. Furthermore, the throttle 59 can be seen, which cooperates with the bore 58. It consists of a screw which has a knurled head 71, a threaded section 72 and a throttle section 73, which is conical at 74 at the end. With the help of the throttle screw, the size of the flow cross-section through the bore 58 can be set as desired. It determines the repetition frequency of the control valve device.

The control valve device shown has the following advantages. It works without dynamically loaded springs. The only spring provided is the compression spring 62 for the trigger valve. However, it is not dynamically loaded. Furthermore, the control valve device shown is provided with very little dynamically loaded O-rings. In the embodiment shown, only five O-rings dynamically loaded with the stroke frequency are required, a number that is far exceeded by known control valve devices. For example, the upper part of the auxiliary valve spool 38 works completely without O-rings and the lower part has only one O-ring.

The control valve device described can be used equally for single-shot and repeating operation. In single-shot operation, the lower part of the auxiliary valve slide remains in its lower position shown in FIG. 1. However, it is particularly important that the control valve device shown provides an adaptation to the movement of the driving piston 12. The main valve spool is not switched to the closed position until the driving piston 12 has actually reached the bottom. As a result, the entire available driving energy can be used. Conversely, the working stroke space 32 is only pressurized from the reservoir 21 when the driving piston 12 is actually its upper one Has reached dead center.

In relation to the active surface 52 of the upper part of the auxiliary valve slide 38, the piston sections 56 and 57 of the lower part have a particularly large active surface 57a and 66. It is therefore sufficient to hold the auxiliary valve slide 38 in the upper position, so that a reversal only takes place when the driving piston 12 has actually assumed its top dead center position.

As can be easily recognized, the control valve device described can be installed in conventional nailers which are already in operation. Only the hole 58a has to be made additionally.

Claims (14)

1. Control valve means for a pressurized air-operated device for driving-in fasteners, by which single or continuous working cycles of a working piston (12) are effected which return stroke is effected by a return chamber (15) (a working cycle comprises a single working stroke of the piston (12) for driving-in a fastener followed by a return stroke), comprising a pressure-controlled stepped main valve spool (37) located in a pressure and vent passage (31) for the working stroke chamber and having a smaller piston area facing a compressed air reservoir (21) and having a larger piston area facing a main control space (39) which can be pressurized or vented for controlling subsequent working cycles, a stepped auxiliary valve spool (38) mounted for movement coaxial of the main valve spool (37), including a first effective area which is selectively connectable to the compressed air reservoir (21) or the atmosphere by means of a trigger valve (61) and including an opposedly facing second effective area (57a) which is connected to a passage (58) connected to the return chamber (15) through which passage a reverse pulse is supplied in order to displace the auxiliary valve spool (38) into a second axial position in which the main control chamber (39) is connected to the compressed air reservoir (21) to displace the main valve spool (37) into its closed position, wherein the auxiliary valve spool (38) is returned into its first position by the pressure of the compressed air reservoir if the pressure on said second effective area falls below a predetermined value, characterized in that the second effective area (57a) of the auxiliary valve spool (38) is connected to a bore (102) facing towards the trigger level (26) of the trigger valve (61) which bore is connected to atmosphere in the non-actuated position of the trigger (26), that a portion of the trigger (26) supports a sealing element (101) which sealingly closes the bore (102) when the trigger (26) is actuated, and that the sealing element (101) and the trigger valve (61) are designed such that to actuate the trigger valve (61) the trigger (26) is actuated from its rest position by a first length of travel and that after a second length of travel following the first length the sealing element (101) seals the bore (102) while the trigger valve (61) is maintained to be actuated.

2. The control valve means of claim 1 characterized in that a throttle screw (59) or the like is located in said passage (58).

3. The control valve means of claim 1 or 2, characterized in that a fixedly located control sleeve (48) sealingly engages a central bore (47) of the main valve spool (37) which sleeve preferrably confines the main control space (39) by means of a radial flange (49) and that the auxiliary valve spool (38) is guided in a bore of said sleeve.

4. The control valve means of claim 3, characterized in that the second effective area (57a) of the auxiliary valve spool (38) is defined by a piston portion (56) of the auxiliary valve spool (38) which is sealingly guided in a cylindrical bore beyond the control sleeve (49) and which is significantly larger than the first effective area, preferrably at least twice of the first effective area.

5. The control valve means of claims 3 or 4, characterized in that the first effective area of the auxiliary valve spool (38) is defined by a piston portion (53) sealingly cooperating with the bore (55) of the control sleeve (48) when another piston portion (51) subjected to the pressure of the compressed air reservoir is located with respect to a third effective area (52) beyond the control sleeve bore, that an auxiliary control space (65) is connected to the first effective area when the piston portion is beyond the bore (55), wherein the auxiliary control space (65) is connected with compressed air when the trigger valve is non-actuated and connected to atmosphere when the trigger valve (61) is actuated and that both piston portions (51, 63) are smooth cylindrical portions without sealing elements which exclusively metallically seal in said control sleeve bore.

6. The control valve means of claim 5, characterized in that the piston portion (53) between said effective areas (52, 57a) and the associated bore portion (55) of the control sleeve (48) have a larger diameter than said bore portion having said third effective area.

7. The control valve means of claims 3 and 5, characterized in that the portion (54) between the piston portions (51, 53) of the auxiliary valve spool (38) defines an annular space with the control sleeve (48) which annular space is connected to the main control space (39) through at least a radial bore (50) in the control sleeve (48).

8. The control valve means of claim 7, characterized in that the auxiliary valve spool (38) in the area of said passage is polygonal in cross- section, preferrably triangular.

9. The control valve means of one of claims 4 to 8, characterized in that a third effective area (52) of the auxiliary valve spool is many times smaller than the second effective area (57a).

10. The control valve means of one of claims 5 to 9, characterized in that the auxiliary valve spool (38) comprises two parts, one part having said cylindrical piston portions (51, 53) cooperating with the control sleeve and the other part having the second effective area (57a), wherein the piston portion (56) having the second effective area faces an opposite effective area of the auxiliary control space (65).

11. The control valve means of one of claims 1 to 10, characterized in that a separate valve plate (23) is provided supporting the trigger lever (26) for the trigger valve (61), said valve plate including said passage (58) for the connection through said passage (58a) from the return space (15) and said second effective area (57a), said valve plate sealingly and slidably supporting said piston portion (56) having the second effective area (57) of the auxiliary valve spool (38) in a bore (56a) and which further supports a pin (60) for the trigger valve in a further bore.

12. The control valve means of claim 1, characterized in that an elastomeric sealing element (101) is provided.

13. The control valve means of claim 12, characterized in that a plug-like sealing element (101) is provided having a conical tip (105) at its end.

14. The control valve means of claims 12 or 13, characterized in that the sealing element (101) sits in a bore of a screw (100) which in turn is arranged in a threaded bore of said trigger (26).

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