DE29812477U1 - Actuator valve assembly for a pneumatic tool - Google Patents

Description

PALGEN, SCHUMACHER & KUJIN* \.· : ..*\. ^:

DÜSSELDORF ESSEN PATENT ATTORNEYS

OUR SIGN: 98 486 P/rm Düsseldorf .15 July 1998

FILE NO. 4

Mr

ECKHARD POLMAN Hufstrasse 6a

D - 46562 Voerde-Spellen Actuating valve arrangement for a pneumatic tool

The invention relates to an actuating valve arrangement of the type corresponding to the preamble of claim 1.

Such actuating valve arrangements are present on practically every pneumatic tool in order to put it into operation. The "force pulses" exerted by the pneumatic tool can either be linear, in which case it is a pneumatic hammer. In the case of a pneumatic screwdriver, however, the force pulses occur in the circumferential direction as torque pulses. And the invention is suitable for both types of pneumatic tools.

The purpose of executing a sequence of power impulses is to distribute the energy input required for a specific task, usually by overcoming friction, in order to make it easier to control. For example, with a pneumatic hammer, this could involve driving parts into a recess, while with a pneumatic screwdriver, it could involve tightening screws up to a certain limit torque.

D-40239 DÜSSELDORF MULVANYSTRASSE 2 TELEPHONE 49 / 211 / 96 145 - 0 TELEFAX 49 / 211 / 96 145 - 20

D45133 ESSEN FRÜHLINGSTRASSE 43 A TELEPHONE 49 / 201 / 84 230 - 0 ■ FAX 49 /201/84 230 - 20

POSTBANK COLOGNE &Ggr;&Bgr;&Igr;.7. 370 100 50&Idigr; 115 211 - 504

With conventional pneumatic tools of the type in question, the operator activates the release valve, whereupon the pneumatic tool carries out a series of force impulses. When the operating lever is released, the release valve shuts off the compressed air supply and the series of force impulses is interrupted. However, when this happens can vary from operator to operator. A certain tolerance range in the number of force impulses applied cannot be avoided for different operators. This means that, for example, parts to be fastened are driven in with different degrees of force and screws to be tightened with different degrees of force.

This tolerance range is undesirable in some applications. For example, the automotive industry has high requirements for a defined energy input, i.e. for a certain number of force pulses to be maintained as precisely as possible.

The invention is based on the object of creating an actuating valve arrangement for pneumatic tools of this type which is independent of individual differences in actuation with regard to the number of force pulses triggered.

This object is solved by the invention set out in claim 1.

The number of power strokes applied, whether with a pneumatic hammer or a pneumatic screwdriver, is determined by the upstream control valve, no longer by the actuation of the trigger valve, which only serves to determine the starting point of the pneumatic tool's operation and thereby activates the control valve. The control valve then allows the pneumatic tool to execute a number of power strokes during a specific short time, e.g. a few seconds, after which the compressed air supply is shut off again. In this way, the number of

The number of force pulses per activation can be maintained much more precisely.

According to the embodiment according to claim 2, the barrier can be automatically released after the specified time has elapsed, so that a new activation can then be carried out for the same number of force impulses without a separate actuation step being necessary for the release itself.

In the preferred embodiment of the invention, the pneumatic tool is a hand-held tool which can be moved back and forth as desired by the operator in his work area. The control valve is arranged in a fixed position and a flexible hose line leads from the control valve to the trigger valve arranged on the pneumatic tool.

In this design, there is a gap between the control valve and the release valve. Even after the control valve has been shut off, there is still air under pressure in the corresponding length of the flexible hose, which allows the pneumatic tool to continue working for a certain time after it has been shut off, which must be taken into account when setting the operating mode of the control valve.

In the preferred embodiment of the invention, which includes such a flexible hose line, the control valve according to claim 4 shuts off the compressed air supply immediately after the trigger valve is actuated.

The "specific short time" is therefore practically zero. The force of the impulses exerted by the pneumatic tool is determined entirely by the compressed air contained in the flexible hose. If the pressure in the hose is no longer sufficient to generate the impulses of the pneumatic tool, the tool stops working.

In one embodiment, the control valve of the actuating valve arrangement can be designed according to claim 5.

An embodiment of the invention is shown in the drawing.

Fig. 1 shows schematically a pneumatic tool with the actuating valve arrangement;

Fig. 2 shows a section through the control valve.

Fig. 1 shows a hand-held pneumatic tool, designated as a whole by 10, which can be a pneumatic hammer or a pneumatic screwdriver. The pneumatic tool 10 comprises a pistol grip-like handle 1, from which the drive part 2 projects at an angle like a pistol barrel. 3 is the actual tool, e.g. the hammer head or the screwing tool. In the handle 1 there is a trigger valve 4 which can be operated with the finger and which interrupts or releases the flow of compressed air supplied via the flexible hose line 5 to the drive part 2. The compressed air is supplied from a compressed air source 6 and passes via a compressed air supply line 7, in which a throttle valve 8 is arranged for adjustment purposes, to a branching point 9, from which it splits into two lines 11, 12 which lead to a control valve 20, the output line 13 of which merges into the flexible hose line 5. An adjusting element 21 is provided on the control valve 20.

When the pneumatic tool 10 is not in operation, the pressure of the compressed air source 6 is present at the compressed air supply 7,13,5. If the trigger valve 4 is now actuated and the pneumatic tool 10 is thereby put into operation, whereupon this exerts a series of rapidly successive force impulses on the actual tool 3, compressed air flows through the arrangement and there is therefore a pressure drop in the compressed air supply 7,13,5, which results in the pressure supplied to the trigger valve 4 in the pressure

The control valve 20 connected upstream of the air supply 7,13,5 shuts off the compressed air flow for a short time. The pneumatic tool 10 therefore only remains in operation during this short time and during an additional time which is determined by the fact that the pressure of the compressed air remaining in the part 13,5 of the compressed air supply line 7,13,5 has fallen below the minimum working pressure of the pneumatic tool 10.

In the preferred embodiment of the invention, the specific short period of time is practically zero, i.e. the compressed air flow is only briefly interrupted and the shut-off is immediately removed. However, since the release valve 4 is then released again and the compressed air flow is thereby interrupted, the pressure in the compressed air supply 7, 13, 5 rises again to the pressure of the compressed air source 6, after which the process described above starts again when the release valve 4 is actuated again.

The control valve 20 can have the design shown in Fig. 2 in an arrangement in which the shut-off caused by the actuation of the release valve 4 is immediately released. In the upper part 14 of the valve housing there is a flat membrane 15 against which a helical compression spring 19 acts from above, the force of which can be adjusted using the adjusting element 21 designed as an adjusting screw. On the other side of the membrane 15 there is a chamber 16 which is under the pressure of the compressed air via the line 11. In the chamber 16 there is a flat valve plate 17 on the membrane 15 which interacts with a valve seat 18 which is closed under the pressure of the spring 19 in the pressure-free position shown. The valve seat 17 surrounds a passage 29 to a chamber 21 which is closed by a membrane 22 which acts on the other side via a plate 23 against a tappet 25 which is displaceable in the lower housing part 24

and a valve slide 27 which is pressed up against a valve seat 28 under the force of a spring 26. In the pressure-free position shown, the valve slide 27 rests against the valve seat 28 so that the passage of compressed air from the line 12 into the line 13 is blocked.

If pressure is now applied to the lines 11, 12, the diaphragm 15 is pressed upwards relative to the position shown, so that compressed air from the chamber 16 can pass through the passage 29 into the chamber 21 and press the diaphragm 22 downwards, whereby the tappet 25 lifts the valve slide 27 from its seat 28 and opens the passage from 12 to 13.

However, compressed air only flows from 12 to 13 when the release valve 4 is actuated. This leads to a drop in pressure in the lines 11, 12 and in the chamber 16, whereby the helical compression spring 19 can press the valve plate 17 down onto the valve seat 18. This also causes the pressure in the chamber 21 to drop and the spring 26 can push the valve slide 27 up against the tappet and block the passage from 11 to 13. As soon as the release valve 4 is actuated, the further supply of compressed air is interrupted.

The pneumatic tool 10 works with the pressure in the flexible hose line for a short time and carries out a certain number of power pulses. However, the pressure in the chamber 16 has risen again in the meantime because the flow has been blocked, so that the blockage between 12 and 13 is removed again. When the release valve 4 is actuated again, the pneumatic tool 10 can be started again with a certain number of power pulses.

Claims (5)

1. Actuating valve arrangement for a pneumatic tool ( 10 ) executing a sequence of force pulses,
with a compressed air supply ( 7 , 13 , 5 ) leading to the pneumatic tool ( 10 ),
with a trigger valve ( 4 ) arranged in the compressed air supply ( 7 , 13 , 5 ) on the pneumatic tool ( 10 ) for the sequence of power impulses, characterized in that
that a control valve ( 20 ) which can be activated by the pressure drop when the release valve ( 4 ) is actuated is connected upstream of the release valve ( 4 ) in the compressed air supply ( 7 , 13 , 5 ), which shuts off the compressed air supply to the pneumatic tool ( 10 ) again after a certain short time after activation. 2. Actuating valve arrangement according to claim 1, characterized in that the shut-off can be automatically released when the pressure in the compressed air supply ( 7 , 13 , 5 ) drops. 3. Actuating valve arrangement according to claim 1 or 2, characterized in that the pneumatic tool ( 10 ) is a hand-held tool, that the control valve ( 20 ) is arranged in a fixed position and that a flexible hose line 5 leads from the control valve ( 20 ) to the release valve ( 4 ) arranged on the pneumatic tool ( 10 ). 4. Actuating valve arrangement according to claim 3, characterized in that the control valve ( 20 ) shuts off the compressed air supply immediately after the actuation of the release valve ( 4 ). 5. Actuating valve arrangement according to one of claims 1 to 4, characterized in that the control valve ( 20 ) comprises a spring-loaded membrane ( 15 ) against which the pressure of the compressed air supply line ( 7 ) is applied in a chamber ( 16 ) opposite the spring ( 19 ) and which actuates a valve arrangement ( 17 , 18 ; 27 , 28 ) in such a way that when the compressed air supply line ( 7 ) is at full pressure, it is connected to the trigger valve ( 4 ), but when the pressure in the compressed air supply line ( 7 ) drops, the connection from this to the trigger valve ( 4 ) is blocked.