GB2326696A

GB2326696A - Valve/vacuum producing unit

Info

Publication number: GB2326696A
Application number: GB9810466A
Authority: GB
Inventors: Kurt Stoll; Grzegorz Bogdanowicz
Original assignee: Festo SE and Co KG
Current assignee: Festo SE and Co KG
Priority date: 1997-06-26
Filing date: 1998-05-18
Publication date: 1998-12-30
Anticipated expiration: 2018-05-18
Also published as: FR2765277B1; GB9810466D0; GB2326696B; DE19727158A1; DE19727158C2; FR2765277A1

Description

A 1 A control Device 2326696 The invention relates to a control device for

the control of the air flow in a fluid power duct adapted to be connected with a fluid power device, comprising a control unit, which is able to be switched over among different switching positions, in which the fluid power duct, a feed duct adapted to be connected with a source of compressed air and a venting duct are linked together in different manners fluidwise, said control unit being set in a housing recess which communicates with the above mentioned fluid ducts.

Such a control device, which is designed as a valve arrangement, is disclosed in the German patent publication Cl 4,413,657. In the case of this valve arrangement one or more base plates are present, which respectively comprise a housing recess, in which a control unit designed in the form of a valve unit and comprising essentially a valve spool is set. Dependent on the position of the valve unit a fluid power duct is supplied with compressed air or vented in order to operate a fluid power device connected therewith.

It is more especially in manufacturing and assembly technology that a multiplicity of different working steps occur, which require the handling of objects, vacuum handling equipment being frequently employed, which holds the objects to be handled by suction. The necessary vacuum can be produced by a control device as disclosed in the US patent 4,861,232 and containing a vacuum producing means, which is able to be connected with a suitable fluid power means, as for example a suction cup.

In the case of hybrid pneumatic applications, as frequently occur, which call for the use of both a valve arrangement and also a vacuum producing means, there would in principal be the possibility of combining control means of the type in accordance with the said prior art. Owing to the differences in the rationale of design there-is an extremely different structure, involving correspondingly high. manufacturing costs for the various different control means. Accordingly one object of the invention is to adopt measures

2 which render possible a reduction in manufacturing costs for valve arrangements and vacuum producing means more particularly in the case of combined or hybrid applications as well.

In order to attain this objective in connection with a control device of the type initially mentioned the invention contemplates a design in which the housing recess is designed for the selective accommodation of a control unit designed as a valve unit or as a vacuum producing unit, the effect of the vacuum producing unit so accommodated being such that given a suitable switching position in the fluid power duct a vacuum- engendered air current may be produced.

It is in this manner that there is the possibility, on the basis of a uniform basic structure, of providing a control device, which may be employed selectively as a valve arrangement or as a vacuum producing means, it being possible in certain cases to even have a combination of both manners of operation. Thus it is readily possible to obtain a control device in the form of a vacuum producing means by mounting a suitably adapted vacuum producing unit in the housing recess instead of a valve unit. If the control device comprises a plurality of housing recesses, it is furthermore possible to provide a combined arrangement of a valve unit and a vacuum producing means, something which leads to a further reduction in structural complexity, if hybrid gage pressure and vacuum applications are to be provided for.

Further advantageous developments of the invention are defined in the claims.

It is convenient for the vacuum producing unit to comprise a control member, which is able to be switched over between an open position and a closed one, a suction effect being produced in the open position in the fluid power duct because the compressed air coming from the feed duct is conducted through a nozzle arrangement belonging to the vacuum producing unit, such nozzle arrangement being connected with the fluid power duct in accordance with the ejector principle.

In a particularly convenient embodiment the nozzle 1 p arrangement is provided on the control member and connected with same for ganged movement so that it partakes in the switching over movement.

As an alternative to this it is possible for the vacuum producing unit to comprise a housing adapted to be placed in the respective housing recess in a immobile manner, such housing then comprising for its part a fixedly positioned nozzle arrangement and a moving control member.

In order to produce the sealing separation of the fluid ducts from each other, between the peripheral wall of the housing recess and the control unit mounted therein there is best a multiple arrangement of axially consecutive annular sealing units. Same are conveniently fixedly connected with the housing recess and arranged in an identical fashion, irrespectively of whether a valve unit or a vacuum producing unit is inserted. It is a question in the case of the sealing units preferably of a cartridge-like units, which respectively comprise at least one rubberelastic sealing ring and furthermore a holding ring holding the at least one sealing ring, the same being positioned and fixed in place in the housing recess with the aid of the holding ring particularly by there being a press fit.

If at least two housing recesses are present in the control device, it is possible, if required, for each housing recess to be provided with a vacuum producing unit in order to operate two separate fluid power devices. It would be also be possible to have a combined design with on the one hand a vacuum producing unit and on the other hand a valve unit, the valve unit being able to be employed either for control of an associated fluid power device or for the operation of the vacuum producing unit present. The latter would be more particularly so designed that a vacuum connection would be provided, which renders it possible to supply an over-pressure signal to the fluid power duct associated with the vacuum producing unit in order to terminate the vacuum obtaining and accordingly to cause the release or ejection of an object suction-held on a fluid power device.

If required the over-pressure signal may be influenced 1 4 - if a choke means is provided in the associated duct connection.

In what follows the invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows a longitudinal section taken through a preferred embodiment of the control device of the invention, same having two housing recesses, which in figure 1 are respectively provided with a valve unit.

Figure 2 shows the region II as marked in chained lines in figure 1 on a larger scale, a preferred design of a vacuum producing unit being illustrated instead of a valve unit.

Figure 3 shows in the same manner of representation as in figure 2, a further embodiment of the vacuum producing unit adapted to be inserted in the housing recess.

Figure 4 shows a region IV as marked in chained lines in figure 1, on a larger scale, the valve unit present, unlike the 3/2 valve type illustrated in figure 1, being designed in the form of a 2/2 type valve and serving to supply an over-pressure signal for a short time as an ejection pulse to the vacuum producing unit also present.

Figure 1 shows an electromagnetically operated control device 1 having a preferably multiple part tabular device housing 2. Owing to the subdivision arranged for the device housing 2 has a central part 3 and two releasably mounted terminal parts 5 and 5' on the mutually opposite axial end faces 4 of the central part 3.

The device housing 2 has a plurality of fluid ducts 6 extending therethrough, which are preferably formed in the central part 3. Among the fluid ducts 6 there is a generally centrally arranged venting duct R, which is followed axially 1 by a respective fluid power duct A and B at either end. On the axial end opposite to the venting duct R of each fluid power duct A and B there is furthermore a feed duct Pi and P2.

The control device 1 is so designed that it may be joined together with a plurality of control devices all possessing a common basic design to form a parcel-like unit, this being achieved because the individual tabular or platelike device housings 2 are placed in a row against each other and securely fixed together. The fluid ducts 6 of the various different control devices 1 thus complement each other to form parts of common through ducts. Accordingly there is the possibility of assembling together battery-like arrangements of control devices 1 in a modular fashion for each specific application.

In the interior of the device housing 2 a linearly extending and generally cylindrically designed well 7 is formed. The 'Live fluid ducts 6 mentioned open with an axial spacing between them into this well 7. In this respect the middle venting duct R acts as a sort of axial partition for the well 7 so that two housing recesses 8 and 9 are produced which merge with each other at an intermediately placed region of the venting duct R and are coaxially arranged.

The first housing recess 8 on the left in terms of figure 1 communicates with the first feed duct P, and the first fluid power duct A, which also opens peripherally into same, and, atL the end, with the venting duct R.

The same simultaneously communicates via the associated end face with the second housing recess 9, into which the second fluid power duct B and the second feed duct P2 open peripherally as well.

The two feed ducts P, and P2 are able to be connected with a source of compressed air, not illustrated in detail, it possibly being one and the same source of compressed air.

The venting duct R is best held at atmospheric pressure by opening into the surroundings on the outer side of the control device 1. In the arrangement in accordance with figure 1 the two fluid power ducts A and B are suitable for the connection of a fluid power means operated pneumatically at a gage pressure, as for instance a double acting pneumatic 1 6 cylinder. The fluid power ducts A and B may in this case be connected with the two cylinder chambers of the fluid power cylinder.

The two housing recesses 8 and 9 extend in the embodiment for the most part in the central part 3, although, as illustrated, they may also extend somewhat into the respectively associated terminal part 5 and 5'. When the terminal parts 5 and 5' are removed the associated housing recess 8 and 9 is accordingly open to the outside so that insertion of any components required is possible.

In the illustrated working embodiment the above mentioned components will include for example a plurality of annular sealing units 12. They are arranged coaxially and secured in the housing recesses 8 and 9 with an axial clearance between them. They are best secured in place by a purely frictional press fit, each sealing unit 12 having a holding ring 13 which is U-like in cross section, such holding ring 13 being press-fitted in the associated housing recess 8 and 9. The cylindrical external face 14 directed radially outward of the holding rings 13 is in this case seated against the internal peripheral face 15 of the associated housing recess 8 and 9 with a press fit. An additional intermediately placed seal is not required.

The holding ring 13 serves not only for fixing the sealing unit 12 in place axially, but also at the same time for holding at least one rubberelastic sealing ring 16, which is held within the U-like cross section. It has an annular sealing part 17 projecting radially inward past the holding ring 13.

The sealing units 12 are respectively positioned axially between the aperture regions of the fluid ducts 6, there being a further sealing unit 12 adjoining the opening of each respective feed duct P, and P2 in addition axially on the outside.

In each housing recess 8 and 9 there is seated a valve unit 18 surrounded by the associated sealing units 12. Such valve unit 18 respectively comprises a cylindrical valve spool 22 having multiple steps with an axial alignment, on whose end part which is opposite to the venting duct R and is axially to the outside, an actuating piston 23 is arranged having an encircling seal 24. The valve spool 22 and the associated actuating piston 23 are preferably connected together in an axially fixed fashion and may also be manufactured integrally.

Owing to the above mentioned stepped shape of the valve spool 22 there is a a groove 25, which on either side is flanked by a cylindrically shaped control region 26 and 27.

Owing to the fluid action, still to be explained, the valve unit 18 is able to be switched over between two positions of switching, which are represented in figure 1 above and below the common axis of symmetry or, respectively, longitudinal axis 28 of the housing recesses 8 and 9. The position illustrated above the longitudinal axis 28 is the operating position, in which the groove 25 is generally at the same level as the central sealing unit 12 so that a gap for flow is made available rendering possible the flow of compressed air from the feed duct P, or, respectively, P2 into the associated fluid power duct A and, respectively, B and for such compressed air to act on the connected fluid power device. Simultaneously the control region 26, which is on the opposite side of the actuating piston 23, is at the same level as the sealing unit 12 placed between the fluid power duct A and B and the venting duct R, such sealing unit having its sealing part 17 surrounding the region 26 in a sealing manner. Accordingly the venting duct R is cut off from the fluid power ducts A and B. In the venting position depicted underneath the longitudinal axis 28 the valve 18 is displaced axially to the outside so that the two control regions 26 and 27 are surrounded by the sealing units 12 flanking the feed duct P, and, respectively, P2 in a sealing fashion and the ducts P, and P2 are shut off. At the same time there is a fluid connection between the fluid power ducts A and B and the venting duct R, since the overall length of the valve spools 22 is so small that in the venting position the valve spools 22 end in the intermediate region between the sealing units 12 flanking the fluid power ducts A and B. The two switching positions are preferably pre-set by 1 8 - abutments 32 and 33, which are provided on mutually axial limiting faces of a piston space 34 formed in the associated housing recess 8 and 9, in which space the actuating piston 23 is located. Thus the actuating piston 23 cooperates with the abutments 32 and 33 and sets the stroke of the valve unit 18.

Since the piston space 34 extends past the separating region between the central part 3 and the respectively adjoining terminal part 5 and 5', it is lined by a guide sleeve 35, whose internal face constitutes the running face for the actuating piston 23 and, respectively, the seal 24 thereof. A securing projection 36 extending out from the guide sleeve 35 radially, fits into a complementary recess 37 in the above mentioned separating region so that the guide sleeve 35 is fixedly secured in place. The abutment 32, which is axially to the inside, is preferably provided directly on the guide sleeve 35 and may be constituted by an annular projection extending inward radially.

The axial motion of the valve units 18 is caused by fluid force. Each actuating piston 23 divides up the associated piston space 34 axially into an axially inner and an axially outer actuating space 39 and 38 and each actuating space 38 and 39 is connected with the aid of a control duct 42 and 43 with a control feed duct Ps, which receives compressed air subject to a control pressure. In the first control duct 42 a pilot valve 44 is intermediately placed, which is in the position of preventing or allowing flow through first control duct 42 in a manner dependent on the state of actuation. Via the second control duct 43, which is only indicated in chained lines, the inner actuating space 39 is in constant communication with said control feed duct Ps.

Each valve unit 18 may have its own associated control feed duct Ps, as is in fact the case with the embodiment.

The pilot valves 44 are best solenoid valves, which are designed in the form of 3/2 valves and also communicate with a preferably common control venting duct Rs as well.

When the pilot valves 44 are in the un-actuated state the passage through the first control ducts 42 is shut off and simultaneously the duct region communicating with the il 1 outer actuating space 38 is connected with the control venting duct Rs. Owing to the control pressure continuously obtaining in the inner actuating space 39 the valve unit 18 will consequently assume the venting position.

Because of the electrical operation of the pilot valves 44 same permit flow through the first control ducts 42 and simultaneously shut off the connection with the control venting duct Ps. Thus the control pressure is present in full in the outer actuating space 38, something which leads to an axial displacement of the valve unit 18 into the operating position, because the actuating face, turned toward the outer actuating space 38, of the actuating piston 23 is larger than its actuating face, turned toward the inner actuating space 39 and continuously subject to pressure via the second control duct 43.

The constant connection of the inner actuating space 39 with the control pressure feed duct Ps leads to a pneumatic spring effect, which however could also be replaced by a mechanical spring means.

Owing to the two valve units 18 the control device 1 all in all constitutes a valve arrangement, which comorises two independently operable valve means 45 and 45', which in the present case are a 3/2 way valve means.

The control device 1 is characterized furthermore in that at least one of the valve units 18 may be readily replaced by a vacuum producing unit 46 and 46' in order to have a vacuum producing means 47 - as is for instance illustrated in figures 2 and 3, instead of a valve means 45 and 45'. Figures 2 and 3 show a design, in which the valve unit 18 on the left in terms of figure 1 is replaced by two possible alternative designs of vacuum producing units 46 and 46'. Given a suitable switching setting in the associated fluid power duct A, these units render possible the production of an air current caused by vacuum, in the associated fluid power duct A, such air current meaning that in a fluid power device connected with the fluid power duct A, a suction effect is caused. The fluid power device may for example be a vacuum-driven materials handling means, which has one or more suction chambers or suction cups, which can be applied to the objects to be handled in order to produce a holding effect caused by suction, this making it possible to displace the respective object.

Since the housing recesses 8 and 9 are thus designed for selective reception of a control unit in the form of a valve unit 18 or a vacuum producing unit 46 and 46', using all other remaining components of the control device 1 the desired valve means 45 and 45' or vacuum producing means 47 can be obtained simply by insertion of the desired unit 18, 46 and 46'. Accordingly there is a sort of modular system, in which different means may be produced using a large number of identical parts, something which leads to extremely economical manufacture coupled with only a small need for stockholding of parts.

In order to obtain the vacuum producing means 47 indicated in figure 2, there is the departure from the embodiment of figure 1 that the valve unit 18 consisting of the valve spool 22 and the actuating piston 23 is replaced by a vacuum producing unit 46. The latter comprises a control member 48 similar in design to a valve spool and which like the valve spool 22 plunges coaxially into the sealing units 12 and at an axial end bears a setting piston 52, which may have a structure as described in connection with the above mentioned actuating piston 23. Accordingly it is provided with a sealing ring 24', which runs on the inner face of the guide sleeve 35, which is present here as well and is not replaced. The action of pressure on the setting piston 52 takes place in the same manner as with the actuating piston 23. Consequently the control member 48 is able to be displaced between the closed position indicated in full lines, which is the home position, and the open position 53 shown in chained lines.

In its interior the elongated control member 48 possesses a cavity 54 extending in the longitudinal direction, wherein a nozzle arrangement 55 is accommodated and is more particularly press fitted in place. Such arrangement comprises a nozzle body 56 more especially in the form of a Laval nozzle having an axially directed nozzle passage 57 therein having an inlet 58 turned toward the - 1 1 - setting piston 52 and an outlet 59 pointing in the opposite direction.

On the side with the outlet 59 a receiving tubular body 62 is coaxially arranged at an axial distance from the nozzle body 56, such tubular body also being press fitted in the cavity 54 if desired and having an axial through duct 63. The aperture 64 thereof on the inlet side is opposite to the outlet 59, whereas the aperture 65 is set on the terminal region of the control member 48 turned toward the venting duct 48.

The intermediate space 66 between the outlet 59 and the aperture 64 on the input side is connected with a transverse duct 67, which opens at a duct aperture 68 at the peripheral face of the control member 48. The fluid connection between the intermediate space 66 and the transverse duct 67 may be in the interior of the control member 48 via an annular space 72, which extends between the receiving tubular member 62 and a tubular region 73, surrounding the same, of the setting member 48.

The transverse duct 67 is so positioned that it is in communication with the first fluid power duct A in both possible switching positions of the control member 48.

A further transverse duct, in the following termed the input duct 74, also opens at the peripheral face of the control member 48 and on the other hand communicates via a region of the cavity 54 with the inlet 58 of the nozzle opening 57. The arrangement is such that in the open position 53 the input duct 74 communicates with the first feed duct P,, from which it is separated in the closed position by the cooperation of the axially outer sensor unit 12 with the control member 48. In this respect the aperture of the input duct 74 is in the closed position in the inner actuating space 39, which in this case is not connected via a second control duct 43 with a control feed duct Ps, since the setting force holding the vacuum producing means 47 in the closed position is supplied by a spring means 75 located in the inner actuating space 39. The relevant setting force for switching over the control member 48 into the closed position is however still produced by fluid power, that is to say 1 12 - using the pressure medium supplied via P,, which not only passes into the input duct 74 but also into the inner actuating space 39. A further second control duct 43, which may be present, is closed as desired and thus is incapable of functioning.

In the home position of the vacuum producing unit 46, which corresponds to the closed position, the first fluid power duct A is connected via the transverse duct 67 and the through duct 63 with the venting duct R so that there is no effective suction effect. By operation of the pilot valve 44 the setting piston 52 may be acted upon on the side opposite to the spring means 75 so that together with the control member 48 it is displaced into the open position 53 as indicated in chained lines. The nozzle arrangement 55 is then moved with it.

Since the control member 48 has a reduced external diameter in the input duct 74 and is arranged with a radial clearance between it and the associated external sealing unit 12, in the open position there will be a fluid connection between the first feed duct P, and the input duct 74 so that compressed air subject to the operating pressure may flow in, such compressed air then flowing through the nozzle opening 57 and flowing out via the following through duct 63 to the venting duct R. Owing to the ejector effect in the intermediate space 66 a vacuum will be produced, which extends into the first fluid power duct A via the transverse duct 67 with the effect that the fluid power duct A is cleared by suction or is evacuated. It is consequently possible for vacuum to be produced in a fluid power device connected with these parts and such suction or vacuum may be employed for holding an object to be moved.

It is naturally possible for the vacuum producing unit 46 to be employed as well in cases, in which the force urging the control member 48 in the closing direction is produced by a control fluid supplied via a second control duct 43 in analogy with the design of figure 1. For this purpose it would be merely necessary for the side, turned toward the setting piston 52, of the axially outer sealing unit 12 to have a further sealing unit thereon so that the input duct 74 p is always separated from the inner actuating space 39.

In the design of figure 3 parts corresponding to parts in figure 2 are given the same reference numerals. The design differs on the one hand from the previously described embodiment to the extent that the control member 48' is able to be moved in relation to the nozzle arrangement 55, which latter is accommodated in an immobile manner in the housing recess 8.

Furthermore in the case of the embodiment of figure 3 the guide sleeve 35 is a fixed component of the vacuum producing unit 46' and belongs to a more especially integrally designed housing insert 76 of the vacuum producing unit 4P, which is axially fixed in position in the first housing recess 8 immovably.

The housing insert 76 comprises a first housing region 77 constituting the guide sleeve 35, said region 77 being adjoined integrally by a second housing region 78 which is slimmer and more elongated than the control member 48 of figure 2, said region 78 extending coaxially in the first housing recess 8 and thereby extending through the sealing units 12 present. It is so designed that it is in constant sealing contact with the two sealing units 12 flanking the first fluid power duct A, whereas between it and the axially outer sealing unit 12 a more especially annular transfer gap 82 is present, which ensures a constant connection between the first feed duct P1 and a recess region 83, placed on the other axial side of the sealing unit 12, of the first housing recess 8. The latter is connected via one or more input ducts 74' with an input space 84, formed in the first housing region 77, which space 84 is a component of a cavity 54 extending coaxially through the housing insert 76. In the cavity 54 a nozzle body 56 with a nozzle opening 57 similar to that of figure 2 is provided, said nozzle body possessing a receiving tubular body 62 with a through duct 63 open toward the venting duct R.

Axially between the input flow space 84 and a cavity region 85 placed in front of the inlet 58 of the nozzle opening 57 the axially movable control member 48' is arranged, which is urged by a return spring arrangement 86 14 (arranged in the cavity portion 85 and bearing against the nozzle body 56), into a closing position as indicated in figure 3, in which closing position the control member 48' rests against an annular valve seat 87, which surrounds a connection opening 88 between the input form space 84 and the cavity region 85.

In the input flow space 84 there furthermore axially extends an actuating tailpiece 89, which is arranged on the setting piston 52, which within the guide sleeve 35 divides the two actuating spaces 38 and 39 from one another. The actuating tailpiece 89 in this respect extends through the inner actuating space 39, which is sealed off from the input flow space 84. In the radial direction the sealing action between a piston region 89' of the actuating tail-piece 89 and the region, adjoining the input flowspace 84, of the cavity 54 is produced because an annular seal 92 is arranged on the piston region 89', such seal 92 cooperating with the inner periphery of the cavity 54.

A second control duct 43 as in figure 2 is not required here and if in fact present will be closed by a seal for example. The inner actuating space 39 preferably communicates with the atmosphere only via ducts formed in the first housing region 77 and a duct, not illustrated, in the housing of the device. The return force is supplied by the pressure medium supplied from P, via the transfer gap and present in the input flow space 84, such force preferably being reinforced by the return spring arrangement 86 acting via the control member 48' on the acting tailpiece 89.

With the first control duct 42 vented the setting piston 52 will assume the home position thereof depicted in figure 3, in which it rests against the axially outer abutment 33. Simultaneously the control member 48' will be in the closed position, in which the connection between the input flow space 84 and the adjoining cavity portion 85 is interrupted.

In order to produce vacuum at the first fluid power duct A the associated pilot valve 44 is actuated so that the outer actuating space 38 is supplied with control compressed air from the control and feed duct Ps and so that the setting piston 52 is displaced axially as far as the opposite 1 - 15 abutment 32, the actuating tailpiece 89 acting on the control member 48' and lifting it from the valve seat 87. Accordingly compressed air may flow from the first feed duct P, via the transfer gap 82, the recess region 83, the input flow ducts 74, the input flow space 84, the connecting opening 88 and the adjoining cavity region 85 as far as the inlet 58 of the nozzle arrangement 55. The effect resulting from this is the same as in the design of figure 2, since in the intermediate space 66 vacuum is produced, which takes effect via the annular space 72 and one or more transverse ducts 67 in the second housing region 78 in the -first fluid power duct A. The transverse ducts 67 open into the first fluid power duct A.

In order to reduce the consumption of air it is possible for the connection between the intermediate space 66 and the first fluid power duct A to have a check valve 94 in it. In the closed position of the control member 48' it prevents return flow of air from the venting duct R into the first fluid power duct A. Once it has been produced in the first fluid power duct A vacuum will consequently remain even when the control member 48' is switched over into the closed position so that the vacuum producing unit does not have to be in operation at all times.

In the illustrated working embodiment the check valve 94 comprises a rubber-elastic cuff, which is arranged in the annular space 72 and covers over the transverse ducts 67 from the inside. Flow of air from the first fluid power duct A to the intermediate space 66 is possible with radially inwardly directed deformation of the cuff region.

More particularly when a check valve 94 is present it is to be recommended to provide means to supply an over-pressure signal to the evacuated first fluid power duct A when vacuum is to be terminated in order to deposit an object held by the associated handling equipment. This over-pressure signal can be supplied to the first fluid power duct A by means of a signal duct 95 as indicated in chained lines in figures 2 and 3, such signal duct 95 best being formed in the housing 2 of the device and more particularly in the central part 3. It is an advantage if a valve unit 181, arranged in the second - 16 housing recess 9, is employed for the production as necessary of the over- pressure signal, as is indicated by way of example in figure 4.

In the arrangement of figure 4 the valve unit 18' forms a valve means 45'', which possesses a 2/2 way switching function. To this extent it differs from the corresponding valve means 45' of figure 1, which possesses a 3/2 way switching function in order to supply with compressed air, or to vent a further fluid power duct B as may be required. Unlike the design of figure 1 the second fluid power duct B does not lead to a further fluid power device but is connected with the first signal duct 95, same communicating with the fluid power duct A. In other respects the components illustrated in figure 4 have the same reference numerals as in figure 1.

In order to to produce a 2/2 way function differing from the valve means 451 it is merely necessary to have a slightly modified valve spool 22', whose front control region 26 is made somewhat longer so that in the home position it is sealingly surrounded by both seal units 12 which delimit the second fluid power duct B. In this home position illustrated underneath the longitudinal axis 28 in figure 4, the signal duct 95 is consequently connected neither with the venting duct R nor with the second f eed duct P2 so that a vacuum may be established and maintained in it.

For the production of the over-pressure signal the pilot valve 44 on the right in terms of figure 1 is operated so that the valve unit 18' is switched over into the working position illustrated above the longitudinal axis 28, in which position the second feed duct P2 will be joined with the second fluid power duct B and hence with the signal duct 95 connected with it.

In accordance with figure 4 a more particularly adjustable choke means 96 may be arranged in the connection between the second and the first fluid power duct B and A in order to modify the over-pressure signal to be produced.

It would be readily feasible to replace the valve means 4511 employed for producing the over-pressure signal by a valve means 45', which renders it possible to control a fluid power connected with the second fluid power duct B. Furthermore there is the possibility of arranging a vacuum producing unit 46 and 261 in both housing recesses in order to operate separate fluid power device or by linking the fluid power ducts A and B to obtain an enhanced suction effect.

It is furthermore to be mentioned that the sealing units 12 solid with the housing may have a design different to that illustrated and for example could be constituted by sealing rings fixed in relation to the device housing 2 by being seated in the grooves in the housing or between ring-like holding elements inserted in the receiving well 7. Furthermore it is possible for the arrangement to be reversed so that the sealing units are arranged on the movable member and cooperate with sealing faces on the housing side.

The control device furthermore possesses the quite substantial advantage that independently of being fitted with a valve unit or vacuum producing unit as a rule the same electrical and/or electronic and fluid drive technology may be utilized so that the customer does not have to perform any substantial refitting or upgrading.

r 1 18

Claims

1. A control device for the control of the air flow in a fluid power duct adapted to be connected with a fluid power device, comprising a control unit, which is able to be switched over among different switching positions, in which the fluid power duct, a feed duct adapted to be connected with a source of compressed air and a venting duct are linked together in different manners fluidwise, said control unit being set in a housing recess which communicates with the above mentioned fluid ducts, wherein the housing recess is designed for the selective accommodation of a control unit designed as a valve unit or as a vacuum producing unit, the effect of the vacuum producing unit so accommodated being such that given a suitable switching position in the fluid power duct a vacuum- engendered air current may be produced.

2. A control device as claimed in claim 1, wherein the vacuum producing unit comprises a control member adapted to be switched over between an open position and a closed position, such that in the open position compressed air may flow from the feed duct through a nozzle arrangement of the vacuum producing unit to the venting duct to be drawn off from the fluid power duct communicating with the nozzle arrangement.

3. A control device as claimed in claim 2, wherein the vacuum producing unit comprises a setting piston adapted for cooperation with the control member, such setting piston being adapted to be acted upon by control air, which is under pressure, for switching over the control member.

4. A control device as claimed in claim 2 or in claim 3, t - 19 wherein the nozzle arrangement is provided on the control member to be entrained on switching over of the control member with same.

5. A control device as claimed in claim 4, wherein the nozzle arrangement is provided in the interior of the control member.

6. A control device as claimed in any of the claims 2 through 5, wherein the control member is designed like a valve spool.

7. A control device as claimed in claim 2 or in claim 3, wherein the vacuum producing unit possesses a housing insert adapted to be placed in the housing recess immovably, such housing insert comprising the movable control member and furthermore the nozzle arrangement.

8. A control device as claimed in any of the claims 1 through 7, comprising a plurality of coaxial annular sealing units secured in place within the housing recess in a sequence with a spacing between them, such sealing units surrounding the respectively inserted control unit at least in partial sealing contact with same.

9. A control device as claimed in claim 8, wherein said sealing units respectively comprise at least one rubberelastic sealing ring and a holding ring holding said at least one sealing ring, said sealing unit being held in position using the holding ring in the housing recess more especially with a press fit.

10. A control device as claimed in any of the claims 1 through 9, having a second housing recess wherein either a valve unit or a vacuum producing unit is located.

11. A control device as claimed in claim 10 comprising in the first housing recess a vacuum producing unit and in the second housing recess a valve unit.

1 -

12. A control device as claimed in claim 11, wherein a second fluid power duct, associated with the valve unit arranged in the second housing recess, is connected with the first fluid power duct associated with the vacuum producing unit arranged in the first housing recess, the second fluid power duct communicating in one working position of the associated valve unit, with a source of compressed air so that an over-pressure signal is supplied to the first fluid power duct for the purpose of terminating the vacuum obtaining therein.

13. A control device as claimed in claim 12, comprising a preferably adjustable choke means is placed in the connection between the first and the second fluid power duct.

14. A control device as claimed in any of the claims through 13, wherein the two housing recesses are arranged coaxially in sequence.

as

15. A control device as claimed in claim 1 substantially described hereinbefore with reference to and as illustrated in figure 1 of the accompanying drawings.

16. A control device as claimed in claim 1 substantially as described hereinbefore with reference to and as illustrated in figure 2 of the accompanying drawings.

17. A control device as claimed in claim 1 substantially as described hereinbefore with reference to and as illustrated in figure 3 of the accompanying drawings.

18. A control device as claimed in claim 1 substantially as described hereinbefore with reference to and as illustrated in figure 4 of the accompanying drawings.

1 A

19. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.