DE20002061U1 - Control device for a fluid-operated drive - Google Patents

Description

G 19023 - 05.01.2000

FESTO AG & Co, 73734 Esslingen Control device for a fluid-operated drive

The invention relates to a control device for a fluid-operated drive, which has a base block which contains a base plate equipped with two main valves located next to one another and which is equipped with electrically activated pilot valves for actuating the main valves.

A control device of this type known under the name "control block for welding gun" is shown in the applicant's "Automobile Body Shop" brochure. It is used to control the welding gun of a spot welding device, with one main valve controlling the feed movement and the other main valve controlling the actual working movement. In order to achieve different speeds for the feed movement and the working movement, so-called throttle plates can be mounted between the base plate and the valves.

The known control device works very reliably, but due to its complex structure it is not very service-friendly and can be used for different purposes.

The operating specifications of the connected welding gun drive can only be changed with great difficulty.

It is therefore the object of the present invention to provide a control device which, with a service-friendly design, allows the possibility of easily influencing the pressure medium to be supplied to the drive.

This object is achieved by a control device for a fluid-operated drive, with a base block which has a base plate equipped with two main valves lying next to one another and a connection plate extending over the two main valves on the side opposite the base plate and which is equipped with pilot valves for actuating the main valves, wherein a base block feed channel which communicates with the two main valves and serves to feed in the pressure medium used to actuate the drive, as well as several first base block working channels which are controlled by the main valves and connected to first working openings used to connect the drive, run in the connection plate, and wherein the connection plate has a connection surface facing away from the main valves, to which a control block which serves to influence the pressure medium present at the first working openings is or can be attached with a mounting surface.

This results in a control device whose base block alone offers the possibility of controlling a fluidic drive, but the connection plate provided in addition to the base plate creates an interface that allows the installation of an additional control block, through which the pressure medium to be fed to the drive can be influenced in a manner that corresponds to the operational requirements. Since the control block is only attached or is

and its assembly can be carried out without dismantling the base block, the control device is very service-friendly and can be quickly converted if necessary.

The control block, which can be attached with its mounting surface to the connection surface of the connection plate of the base block, can be designed in particular to specify different working pressures that can be tapped at the first working openings and preferably have a switching device for at least one and preferably for each first working opening, which causes a working pressure switchover depending on control signals oriented towards the operating sequence of the drive to be actuated. This enables optimal stroke control, especially in connection with the control of a welding gun drive. The fluid-operated drive that moves a welding electrode can thus, for example, be controlled in such a way that, after positioning in the area of the workpieces to be welded, a

A fast pre-stroke feed movement takes place until shortly before the workpieces are reached, followed by a slower pre-stroke working movement until the electrode has touched the associated workpiece, whereupon a higher pressure can be applied again in order to achieve the application force required for the welding process. The control signals used for switching the working pressure can be generated in a position-dependent manner, but preferably in a time-dependent manner, the latter using at least one timer provided on the control block, which can be based on a fluidic or electrical operating principle.

The first working openings that can be connected to the fluid-operated drive are preferably provided on the control block and are connected to the first base block working channels via control block working channels running in the control block, wherein the interface is located in the region of the connection surface of the base plate and the mounting surface of the control block.

It is particularly advantageous in connection with the generation of different stroke phases of the drive to be operated if there are second base block working channels controlled by the two main valves, which run in the base plate and lead to second working openings provided on the base plate, which, like the first working openings, enable a connection to the drive to be controlled. This makes it possible to provide the drive with a control :**::::'·":*:"::"::":·"::"::!:. ·: : : ·:

block influenced pressure medium, which can be tapped at the first working openings, and also to supply pressure medium not influenced by the control block, which can be tapped at the second working openings of the base plate.

In order to achieve a particularly good level of efficiency, the main valves expediently have valve channels that open out onto opposite outer surfaces and communicate with the first and second base block working channels running in the connecting plate and the base plate. This allows a largely straight flow through the main valves with low flow losses.

It is expedient for not only the main valves but also the control block to be supplied with pressure medium from the base block feed channel. For this purpose, at least one connection opening connected to the base block feed channel can be provided on the connection surface of the connection plate, via which, when the control block is attached, there is a fluid connection to at least one control block feed channel running in the control block, which can help to influence the pressure medium present at the first working openings. The pressure medium provided in the control block feed channel can in particular be passed through a pressure regulator in order to provide different working pressures at the first working openings if required.

The invention is explained in more detail below with reference to the accompanying drawing, whereby additional advantages of the control device become apparent. In the drawing:

Fig. 1 shows a preferred design of the control device according to the invention in a perspective exploded view in an oblique view from the front,

Fig. 2 the control device from Fig. 1 in reverse view from the rear,

Fig. 3 shows a preferred circuit diagram of the control device according to Figs. 1 and 2, wherein a fluid-operated drive to be controlled is additionally indicated, and

Fig. 4 shows a section of the control device in the region of a main valve of the base block in the region IV indicated by dash-dot lines in Fig. 1 and 3.

The control device, designated overall by reference number 1, is of modular construction and includes a base block 2 as the first module and a control block 3 as the second module. It is suitable for the fluidic control of a fluid-operated drive 4, indicated schematically in Fig. 3, preferably in the design of a linear drive.

The embodiment shows the control device 1 in a design in which it forms a welding tongs control device which is designed to actuate the drive of a welding tongs 5 which can be used for spot welding. Such welding tongs are used in particular in bodywork production in the automotive sector in order to weld body panels together at specific points. The movable output part 6 of the drive 4 to be actuated carries a first welding electrode 7, opposite which a second welding electrode 8 is located at a distance, with the workpieces to be welded being placed in the area between the two welding electrodes 7, 8. As part of a controlled linear movement, the first welding electrode 7 can be displaced relative to the second welding electrode 8 in order to bring both welding electrodes into contact with the workpieces to be welded from opposite sides with a desired force, after which the spot welding process can take place.

The control device 1 can cause the output part 6 of the drive 4 to perform a stroke movement divided into several operating phases. In the present case, these operating phases are a feed movement and a working movement. The feed movement serves to open and close the welding gun 5 between a basic position with the welding electrodes 7, 8 spaced as far apart as possible and an intermediate position with the welding electrodes 7, 8 brought so close to one another that the workpieces to be welded are not yet exposed to the pressure. During the working stroke, the welding electrodes 7, 8

between the intermediate position and the welding position adjacent to the workpieces to be welded, whereby the stroke distance covered here is less than that of the feed movement.

The control device 1 is also designed so that the forward stroke feed movement starting in the basic position initially runs at high speed and is slowed down as the intermediate position is approached. The subsequent forward stroke working movement in the same direction is carried out at a corresponding speed. This is achieved by controlling the drive 4, which can be referred to as a positioning cylinder, with different working pressures. The advantage of this control is that the first welding electrode 7 can be positioned relatively gently in the intermediate position and in the welding position without the components of the welding gun being subjected to strong vibrations or to a hard impact, which would require a disadvantageous break in operation until the vibrations subside or could cause damage.

The base block 2 contains an elongated base plate 12, which is equipped with two main valves 14, 15 arranged next to one another on a longitudinally arranged mounting surface 13. The main valves 15 are preferably aligned so that they follow one another axially, with their longitudinal axes coinciding and running parallel to the longitudinal axis of the base plate 12. They are placed face to face.

decorated.

On the upper side of the two main valves 14, 15 opposite the base plate 12, an elongated connecting plate 16 is provided and fastened to the main valves 14, 15.

The connection plate 16 extends continuously over both main valves 14, 15, which are thus flanked on opposite longitudinal sides by the base plate 12 on the one hand and the connection plate 16 on the other.

The main valves 14, 15 are multi-way valves that can be actuated by fluid power, in this case in a 5/2-way design. Inside each valve there is a valve slide 17, shown schematically in Fig. 4, which can be positioned in one of two possible positions by a pressure medium that can be supplied via pilot channels 18. The corresponding actuating movement is effected by electrically actuated pilot valves 22, two of which are provided for each main valve 14, 15 and are designed as an immediate component of the base block 2. Their electrical actuators are expediently made up of electromagnets, but in principle piezo actuators could also be provided, for example.

The pilot valves 22 are provided on the connection plate 16, i.e. they are not located directly on the main valves 14, 15, but can at least partially overlap them.

Accordingly, the connection plate 16 contains fluid channels 21 controlled by the pilot valves 22, which are connected to the pilot channels 18 of the main valves 14, 15.

A base block feed channel 23 runs in the connection plate 16 and opens out to a front side of the connection plate 16 via a feed opening 24. A pressure medium, preferably compressed air, which is supplied by a pressure source P and is used to actuate the drive 4 can be fed in there.

The fluid channels 21 controlled by the pilot valves 22 are branched off from the base block feed channel 23, which consequently supplies the pressurizing medium for switching the valve spool 17.

The base block feed channel 23 also communicates with each main valve 14, 15, whereby the main valves 14, 15 each enable a controlled forwarding of the supplied pressure medium to a first base block working channel or to a second base block working channel 26. While the first base block working channels 25 run in the connection plate 16 and open out at a connection surface 27 facing away from the main valves 14, 15 with working channel connection openings 28, the second base block working channels 26 pass through the base plate 12 and open out at this with second working openings 33.

The base block feed channel 23 leads within the connection plate 16 not only to the main valves 14, 15, but also opens with a first feed channel connection opening 29 to the connection surface 27 of the connection plate 16.

The control block 3 mentioned at the beginning is detachably attached to the connection surface 27 of the base block 2 with a mounting surface 34 with the interposition of a one- or multi-part seal 35 which is plate-shaped in the embodiment. The control block can be used to change the state of the pressure medium which can be tapped at the first working openings 32 which are connected to the base block working channels 25. The first working openings 32 are located on the control block 3 and are connected to control block working channels 36 which run in the control block 3 and which lead to control block connection openings 37 located on the mounting surface 34 which, when the control block 3 is mounted, are connected to the working channel connection openings 28 of the base block 2.

In the control block 3, there are also two control block feed channels 38, which are connected to a second feed channel connection opening 30 provided on the mounting surface 34, which, when the control block 3 is mounted, is connected to the first feed channel connection opening 29 provided on the connection surface 27. In this way, the pressure medium supplied via the feed opening 24 is not only

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on the two main valves 14, 15, but also inside the control block 3.

The control device 1 is constructed overall in such a way that two pairs of first and second working openings 32, 33 result, the working openings belonging to the first pair being additionally provided with the reference number 42 in the drawing for better understanding and the working openings belonging to the second pair being additionally provided with the reference number 43. Each main valve 14, 15 controls one of these working opening pairs 42, 43, which serve to control two drive units of the drive 4, the first connection opening pair 42 being used to control a feed unit 44 and the second connection opening pair 43 being used to control a work unit 45, which are responsible for generating the feed movements and work movements explained at the beginning. The two main valves 14, 15 allow the feed unit 44 and the work unit 45 to be operated individually in any coordinated manner.

The first and second working openings 32, 33 are each connected to the feed or working unit 44, 45 of the drive 4 via fluid channels 46, 47 indicated by dash-dotted lines, whereby the fluid channels 46, 47 can be formed by hose- or tube-like pressure medium lines or by channels inside the housing. The latter applies in particular when the control device 1 is advantageously mounted directly on the drive 4 and is connected to it by a

structural unit.

The connection diagram is expediently designed in such a way that the pressure medium that can be tapped at the second working openings 33 is used for the return stroke of the respectively assigned feed unit 44 and working unit 45. The pressure present corresponds to the pressure fed into the feed opening 24, for example in the order of 10 bar. This enables high return stroke speeds that ensure a fast work sequence.

On the other hand, the control block 3 can be used to ensure that different operating pressures for the preliminary strokes of the output part 6 can be tapped at the first working openings 32 assigned to it, depending on the activation state of the control block 3.

For this purpose, each of the two control block working channels 36 is assigned a switching device 48, which in the embodiment is formed by a switching valve, through which a respective first working opening 32 can be connected optionally to one of the control block working channels 36 or to one of the control block feed channels 38, wherein a pressure control valve 52 is inserted in the course of the control block feed channels 38. When a first working opening 32 is connected to the assigned control block working channel 36 by corresponding actuation of the switching device 48, a pressure control valve 52 can be connected to the first working opening

32 an operating pressure corresponding to the feed pressure, in this case the aforementioned 10 bar. In the other position of the switching device 48, an operating pressure which is lower than the feed pressure is present at the first working openings 32, which is determined by the setting of the associated pressure control valve 52 as required.

It is therefore possible to initially carry out both the forward stroke of the feed movement and the forward stroke of the working movement of the drive 4 at a high speed using the higher operating pressure and only towards the end of the respective movement to carry out it at a slower speed by switching to the lower operating pressure, so that the output part 6 or the first welding electrode 7 coupled to it is gently braked when the intermediate position and the welding position are reached in order to largely exclude vibrations of the welding gun. After the welding position has been reached, the switching device can be switched back so that the higher operating pressure is again applied for the actual welding process, which provides the necessary application force.

The switching state of the switching device 48 is therefore based on the operating sequence of the drive 4 to be operated, whereby the control signals could in principle be generated depending on the position, but preferably by a time control

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In the exemplary embodiment, each switching device 48 is assigned two time elements 53, 54 arranged on the control block 3, which cause the time-dependent actuation of the switching device 48 and which, in the exemplary embodiment, are based on a fluidic functional principle. One of these time elements 53, 54 is responsible for switching from the higher to the lower or from the lower to the higher operating pressure.

In the specific case, each timing element 53, 54 contains a control valve 55, preferably designed as a 3/2-way valve, which is actuated by fluid power, the actuating pressure being supplied by an upstream pressure accumulator 56, which is fed from the associated control block working channel 36 by an upstream throttle check valve 57. The two control valves 55 of the timing elements 53, 54 assigned to a respective switching device 48 are connected in series in a switching channel 58, which is responsible for the actuation of the switching device 48 caused by fluid power and is also connected to the associated control block working channel 36.

A preferred mode of operation of the control device is as follows:

Starting from the basic position of the output part 6, one main valve 14 is actuated so that pressure medium flows from the base block feed channel 23 into the associated control block working channel 36 and from there via the first working opening 32

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to the feed unit 44. This triggers the forward stroke feed movement, whereby the necessary ventilation of the feed unit 44 takes place via the second working opening 33.

During the pre-stroke feed movement, the pressure accumulators 56 of the associated time elements 53, 54 are gradually filled with pressure medium, whereby the filling rate is predetermined by the variably predeterminable setting of the throttle device of the throttle check valves 57.

After a certain predetermined time, the pressure built up in the pressure accumulator 56 of the first timer 53 is sufficient to switch the associated control valve 55, so that the previously closed switching channel 58 is opened and the associated switching device 48 is actuated. As a result, the control block working channel 36 is separated from the first working opening 32 and instead the first working opening 32 is connected to the control block feed channel 38, so that the lower operating pressure predetermined by the switched-on pressure control valve 52 is applied to the first working opening 32. Accordingly, the forward stroke feed movement slows down until the end of the feed movement.

This is followed by activation of the control valve 55 of the second timing element 54, whereby the switching channel 58 is shut off again so that the switching device 48 switches back and the higher operating pressure is again applied.

Already during or at the end of the pre-stroke feed movement, a comparable multi-phase pre-stroke working movement is triggered by corresponding control of the second main valve 15 with respect to the working unit 45. The venting of the working unit 45 takes place via the second working opening 33 assigned to the second main valve 15.

When spot welding workpieces, several welding spots are usually placed next to one another. During this process, it is advisable to cause only the working unit 45 to alternate between forward and return strokes. The return stroke of the feed movement is only carried out when the workpieces to be welded are changed.

Instead of timing elements based on a fluidic operating principle, timing elements with an electrical operating principle could also be used in order to reduce the fluidic wiring effort.

In order to be able to carry out a rapid venting of the associated feed or working unit 44, 45 during the return stroke movements, a quick vent valve 62 is expediently assigned to each of the first working openings 32. In this way, the venting flow does not have to be passed completely through the main valves 14, 15. The latter also communicate with the valves 14, 15 in the base plate for venting.

te 12 extending ventilation channels 63, which open out to the outer surface of the base plate 12, wherein the openings are expediently assigned silencers 64.

In the exemplary embodiment, each feed or working unit 44, 45 contains a piston 66 which separates two application chambers from each other and acts on the output part 6, the application chambers being connected to the control device 1 via the aforementioned fluid channels 46, 47. In the exemplary embodiment, it is now provided that a pressure switch 65 is connected between the first and second base block working channels 25, 26 used to control the working movement, which switches the welding current depending on the pressure difference when the welding electrodes assume the welding position.

The fluid channels 23, 25, 26, 63 running in the connection plate 16 and in the base plate 12 communicate with valve channels 66 of the respective associated main valve 14, 15, which open out on opposite longitudinal sides. This arrangement of the valve channels 66 ensures that the pressure medium, preferably compressed air, flows through the relevant main valve with as little deflection as possible, so that a high degree of efficiency is achieved.

Regarding the control block 3, it should be added that this expediently contains an elongated mounting plate 67 on which the mounting surface 34 is provided and which is connected to the individual

equipped with the components explained above.

For detachable fixing of the control block 3 to the base block 2
Suitable removable fastening devices are provided, which
in the embodiment of the control block 3 attacking
Fastening screws 68 and with these in screw engagement
threaded holes 69 on the connecting plate 16 of the base block 2. In this way, the mounting plate 67 and the connecting plate 16 can be firmly clamped against each other and against the seal 35 inserted therebetween, the seal 35 ensuring a leak-free connection of the channel openings assigned to each other in the area of the interface.

With regard to the base block 2, it should also be mentioned that the connection openings 28, 29 provided on the connection surface 27 are expediently equipped with internal threads or other suitable fastening means which, when the control block 3 is removed, allow the direct connection of further lines or the attachment of closure means in order to be able to operate the base block 2 as an independent unit.

Claims (12)

1. Control device for a fluid-operated drive, with a base block ( 2 ) which has a base plate ( 12 ) equipped with two main valves lying next to one another and a connecting plate ( 16 ) extending beyond the two main valves ( 14 , 15 ) on the side opposite the base plate and which is equipped with pilot valves ( 22 ) for actuating the main valves ( 14 , 15 ), wherein in the connecting plate ( 16 ) there is a base block feed channel ( 23 ) which communicates with the two main valves ( 14 , 15 ) and serves to feed in the pressure medium used to actuate the drive ( 4 ), as well as a plurality of first base block working channels (32) which are controlled by the main valves ( 14 , 15 ) and connected to first working openings ( 32 ) used to connect the drive ( 4 ). 25 ), and wherein the connection plate ( 16 ) has a connection surface ( 27 ) pointing away from the main valves ( 14 , 15 ), to which a control block serving to influence the pressure medium present at the first working openings ( 32 ) is or can be attached with a mounting surface ( 34 ). 2. Control device according to claim 1, characterized in that the first working openings ( 32 ) are provided on the control block ( 3 ) and are connected to working channel connection openings ( 28 ) of the first base block working channels ( 25 ) provided on the connection surface ( 27 ) of the connection plate ( 16 ) via control block working channels ( 36 ) of the control block ( 3 ) leading to the mounting surface ( 34 ). 3. Control device according to claim 1 or 2, characterized in that second base block working channels ( 26 ) controlled by the two main valves ( 14 , 15 ) run in the base plate ( 12 ) and lead to second working openings ( 33 ) provided on the base plate ( 12 ) for connecting the drive ( 4 ). 4. Control device according to claim 3, characterized in that the main valves ( 14 , 15 ) each have valve channels (66 ) which open out to opposite outer surfaces and communicate with the first and second base block working channels ( 25 , 26 ) running in the connection plate ( 16 ) and in the base plate ( 12 ). 5. Control device according to one of claims 1 to 4, characterized in that at least one first feed channel connection opening ( 29 ) connected to the base block feed channel ( 23 ) is provided on the connection surface ( 27 ) of the connection plate ( 16 ), via which, when the control block ( 3 ) is attached, there is a fluid connection to at least one control block feed channel ( 38 ) running in the control block ( 3 ), which helps to influence the pressure medium present at the first working openings ( 32 ). 6. Control device according to one of claims 1 to 5, characterized in that the control block ( 3 ) is designed to specify different operating pressures which can be tapped at the first working openings ( 32 ). 7. Control device according to claim 6, characterized in that the control block ( 3 ) for one or each first working opening ( 32 ) contains a switching device ( 48 ) which can bring about an operating pressure switchover depending on control signals oriented towards the operating sequence of the drive ( 4 ) to be actuated. 8. Control device according to claim 7, characterized in that the control signals for the operating pressure changeover are each supplied by at least one timing element ( 53 , 54 ) provided on the control block ( 3 ), which is based on a fluidic and/or electrical operating principle. 9. Control device according to one of claims 1 to 8, characterized in that the connection surface ( 27 ) is located on the side of the connection plate ( 16 ) facing away from the main valves ( 14 , 15 ). 10. Control device according to one of claims 1 to 9, characterized in that it is designed as a welding tongs control device for actuating the drive ( 4 ) of a welding tongs ( 5 ) which can be used for spot welding. 11. Control device according to claim 10, characterized by two pairs ( 42 , 43 ) of first and second working openings ( 32 , 33 ), each of which can be connected to one of two drive units ( 44 , 45 ) of the fluid-operated drive ( 4 ) to be actuated. 12. Control device according to one of claims 1 to 11, characterized in that the openings ( 28 , 29 ) of the first base block working channels ( 25 ) and/or the base block feed channel ( 23 ) provided on the connection surface ( 27 ) of the connection plate ( 16 ) are equipped with fastening means formed, for example, by internal threads, which enable the connection of further fluid lines and/or closure means when the control block ( 3 ) is removed.