DE1600837A1 - Control system for several hydraulically operated organs - Google Patents

Description

> R. ING. F. WUBSTHOFF, β MUNICH 90

DIPIKIN-G ₁ G-PtTLS SCHWEIQERSTRASSE 2 DR.E.T.PEOHMANN Txtxroir 22 08 31 PATENTANWÄLTE TKI-KaBAHUASnEBaEt PBOTKOTPATKNT MÜKOHlCSr

Skin friction to the patent application

KEEIAVITE HYDRAULICS LIMITED, Allesley, Coventry, Warwickshire, England

concerning
Control system for several hydraulically operated organs.

The invention relates to control systems for with Devices to be operated with the aid of a pressure medium, whereby the working medium used is either gaseous or liquid is; for the sake of simplicity, it is assumed in the following that a liquid working medium is used; therefore be the systems as hydraulic control systems and the organs operated with the aid of a pressure medium as hydraulically operated Organs, whereby appropriate terminology is used throughout the description. More precisely, The invention relates to hydraulic control systems for hydraulically operated members, for example hydraulically operated ones Flow control valves as used to control the flow to control of liquid to and / or from and / or between the different chambers of containers, e.g. in tankers, it is desirable that one not only be able to control the position from a common control station or control room to influence several hydraulically operated organs, possibly at different ones far away from the control room

009817/0234

Points are arranged, but also at the control station at any time a display of the positions of the various hydraulic to have operated organs available.

In the previously known, the above-mentioned purpose serving remote controllable hydraulic control system for the hydraulically operated valves that are used on tankers and are referred to below as tank valves for short the hydraulic control of the position of each hydraulically operated tank valve is effected in some cases by each hydraulically operated tank valve with a hydraulic actuator equipped or designed as such a device, the device having an actuating piston or comprises two actuating pistons which have mutually facing surfaces which are the prevailing in two working chambers Pressures are exposed, with the flow of working fluid to and from the working chambers via feed and Buckline ducts with the help of a hydraulic control valve is regulated at the control station in such a way that the actuating piston of the hydraulic actuating device moves becomes, as required, or that the actuating piston being held in his position; In addition, it is common to provide a hydraulic or other display line, by means of which a signal can be fed to the control station to determine the position of the hydraulically operated tank valves display at any point in time. This arrangement requires the use of several drilling lines, which are connected to each hydraulic Guide actuating device, so that numerous drilling

000817/021%

there are lines that extend from the control station Extend over the entire area over which the, various hydraulic actuators are distributed; therefore, such a system has an undesirably complicated structure.

Another arrangement, also already known, dispenses with the convenience offered by the use of a common control station, and the supply and bypass lines form a "main ring line ¹¹ for the working fluid, these lines being laid to each of the hydraulic actuators; moreover, near each one is hydraulic When the tank valve is operated, a separate, manually operated hydraulic control valve is provided, by means of which the flow of the working fluid to and from the working chambers of the hydraulic operating device can be regulated; display lines can also be laid from the hydraulically operated tank valves to a common display point so that the position of all valves at this display station can be "read" but not influenced.

The invention now provides an improved control system for numerous hydraulically operated organs, which comprises a smaller number of pipelines than the one just mentioned known remotely controllable hydraulic control system, the system according to the invention comprising both means for controlling the positions several hydraulic actuation devices from one common Tax status. from to rule ::, as well as means to participate in the

009817/0231

common control station at any point in time the position of the Display actuating devices and thus also the valves or other organs operated by them.

To this end, in a control system according to the invention for numerous hydraulically operated organs, of which each operated by a different hydraulic actuator, the flow of working fluid from one

Working medium source from to the actuating device and the simultaneous flow of the working medium to a return line the actuator is controlled by a hydraulic control valve, each hydraulic control valve in the form of a spring-centered valve, e.g. a piston or slide valve, the piston being opposite has directed pressure application surfaces on which the fluid pressures prevailing in two control pressure chambers act, and the pressure in such a control pressure chamber, which is described below is referred to as the local control pressure chamber for simplicity, is taken from the working fluid supply line, namely via an adjustable pressure reducing valve, its position automatically depends on the position of the hydraulic actuator, while the pressure in the other Control pressure chamber, hereinafter referred to as the remote control pressure chamber is referred to, is taken from a Fernsteuerurigs pressure line, which is in communication with control means, which are arranged at a common control station, and which make it possible to determine and vary the pressure mentioned.

009817 / ailft

The control means by means of which the pressure in the remote control pressure line can be determined and varied, two-way include an adjustable pressure reducing valve.

The display devices, which are located at the common control station and each respond to the pressures in the remote control pressure chambers, and / or display devices, which respond to the pressure in the local control pressure chambers, are provided in two ways to control the position of the various hydraulic actuation devices and also display the position of the various tank valves or other actuated devices in the event of proper operation. It can thus be seen that the Druok in any remote control pressure chamber and the pressure in the associated local control pressure chamber under stable conditions and under the assumption of proper operation provides an indication of the position of the associated hydraulic actuation device, because only if the pressure in the local Control pressure chamber is essentially the same as the pressure in the remote control pressure chamber, the springs acting on the hydraulic control valve in question will be able to center this hydraulic control valve and thus interrupt the movement of the hydraulic actuating device, ^ eiw. the control valve is brought out of its centered position or the middle position into another position, since the pressure in the local control pressure chamber exceeds the pressure in the remote control pressure chamber, or vice versa, ai ©? © ratel-

009817/033%

ment of the valve with respect to its central position in such a Direction that movement of the hydraulic actuator is effected in sighting the position at which the pressures in the remote control pressure chamber and exactly equalize in the local control pressure chamber.

Furthermore, when the control valve of each hydraulic actuator a display device of the type mentioned is associated with the pressure in the remote control pressure chamber responds, as well as one on the Druok in the local Control pressure chamber responsive display device, it is possible for an operator to monitor the pressure in the remote Adjust the control pressure chamber according to a desired position of the associated hydraulic actuator and then with the help of the pressure in the local control pressure chamber Appealing display device to determine if and when the hydraulic actuator is the desired one Position.

According to the invention it is thus possible to use a common "main ring line" which is a feed line to the , Supplying the pressurized working fluid from a Pressurized fluid source off to all hydraulic actuators and a bypass line to return the work » liquid from these valves to the liquid container, and it is only necessary to have a single pipeline, which can be relatively small »to be provided, which differs from

009817/023%

the control station extends out to a point near each hydraulically operated device.

It should also be noted that the dimensions of the control pressure application surfaces of the hydraulic control valves and / or the forces applied by the centering springs that you;} © the desired range of control pressures and achieve various degrees of accuracy and the desired sensitivity of the control system.

Dia used in a control system according to the invention Pressure reducing valves can be of any suitable adjustable construction, but are preferably So-called direct-acting three-way valves, i.e. valves of the type with a valve piston or piston slide} in one Cylinder is arranged, one end of which is in direct connection with the channel or the line in which a certain, however, controllably reduced pressure should be maintained, BO that this reduced pressure on one end of the piston valve acts while an adjustable spring acts on other sins the piston adjuster acts; here the valve is set up so that that there is the connection between a "port for a reduced pressure" which is in communication with the line, in which the reduced pressure is to be maintained, and on the one hand a pressure port which is connected to a source which supplies a liquid pressure which is higher than the minimum pressure in the line for the reduced

009817/0234 ^{BAD mmHkL}

-6-

Pressure is required, and on the other hand with a relief channel controls so that when the on one end of the The reduced pressure acting on the piston slide exactly balances the force of the spring acting on the other end of the piston slide, the valve or the piston slide assumes a neutral position in which it opens the opening for the reduced Pressure closes, while when the force due to the reduced pressure exerted on one end of the The piston valve acts larger or smaller than it is necessary to exactly balance the force of the spring when it is the piston valve is in its central position, so that the piston valve has a position on one or the other side When it assumes its neutral position, the valve either connects to the relief duct or the opening for the reduced pressure connects to the pressure channel, so that in the channel for the reduced Pressure and therefore also at the opposite end of the piston valve a pressure is produced, which the spring force exactly compensates, so that the piston valve is caused to assume its neutral position. Thus the degraded Pressure always determined by the position of the adjustable spring.

In some cases it may be desirable to prevent inadvertent actuation of the hydraulically actuated devices when the actuation pressure is in the vicinity of a hydraulic one. Z ^- Ji actuating or & ans is available before the correct remote control pressure is similarly available, or vice versa, wa ^ eg on the longer one. Routes

0098 17/0234 _B AD OKlCWNAl

can, over which the drilling lines extend in some cases, by means of which the remote control pressure and / or the actuation pressure su is transferred to the hydraulically operated organs. To this end, according to a further feature of the invention, means can be provided by means of which each of the hydraulic activated organs is locked against any movement until both pressures are available in its vicinity. This can be done by the use of appropriately operated control devices can be achieved based on the in question Address pressures? in one embodiment, this control device e.g. comprise one or more shut-off valves, one of which is assigned to each hydraulically operated element, so that it is possible to hydraulically lock the organ in question against any movement until the actuation pressure and the Remote control pressure, by means of which the position of the organ is to be determined, are both available. With a typical SoKen arrangement according to the invention can the shut-off valves are operated by electromagnets, the circuit of the or each electromagnet associated with a hydraulically operated element controlled by pressure sensitive switches that respond to the actuation pressure at a point near the hydraulic actuator and on the Pern control pressure also respond in the associated control pressure lines at a point near the hydraulic actuation device, these pressure sensitive switches are set up so that the circuit of the or each electromagnet remains open, until both pressure-sensitive switches are closed by the correct

009817/0234 _β

GWONAL H «

Pressures prevail. Thus every hydraulic actuator remains hydraulically locked in their respective position, regardless of the position which the associated Control valve can take until the correct pressures are available at the points in question to ensure that the actuating device can only then be brought into the position which is determined by the position of the means for controlling the remote control pressure is determined.

In connection with a pressure reducing valve, the term "setting" is used in its usual sense in the following, i.e. it denotes that characteristic or setting which determines the "reduced" pressure at any point in time, the maintains the valve and / or operates in the chamber or conduit concerned j the expression "spring-centered Valve "refers here in the usual way to a valve or valve system on which opposing spring forces act, which are constantly striving to bring the valve or valve system in a central position or to bring it to a central position hold, in which the channels or lines to be controlled are kept closed.

The invention is explained in more detail below with reference to the schematic drawings using an exemplary embodiment. _f

Fig. 1 is a schematic representation of a complete gen control system according to the invention, in which for simplification it is assumed that only four hydraulically operated flow control valves are provided, but it should be noted that daa -.

0098177023 *

-11-Syatem also any other number of such valves in

may include a corresponding arrangement.

Fig. 2 shows on a larger scale schematiach one of the hydraulically "operated valves, the associated hydraulic control valve, valves for controlling the remote control pressure and the Local control pressure and other associated parts.

Fig. 3 shows schematically in longitudinal section one of the in valves used in the system to control local control pressure.

FIG. 4 is similar to FIG. 3, but shows one in longitudinal section the valves used in the system to control the remote control

Fig. 5 shows in section an embodiment of a pressure sensitive device Switch that can be used in the system.

Fig. 6 shows an embodiment in a longitudinal section a shut-off valve that can be used with the system.

The ^ε in Fig 1'gezeigte. hydraulically actuated system comprises four bodies 1 from which it is assumed that it is four control valves, which serve the connection. between the various individual containers of a tanker, the division of each of these valves being determined by a hydraulic actuation device and an associated control valve, the latter of which is shown schematically in FIG.

817/0234 ^SAD

According to Fig. 2, the valve 1 is controlled via a rod 1A by a hydraulic actuator comprising an actuating piston 2; the piston 2 works in a hydraulic cylinder 2A with working chambers 3 and 4. The control valve 5-6 is designed in a known manner so that the piston slide 5, when it assumes its central position as shown in FIG. is removed} in the case just described, the piston 2 is thus held firmly in its position; however, if the piston valve 5 moves in one direction or the other with respect to its central position, it causes working fluid to be fed from a pressure line 9, which is connected to a pressure medium source, to one of the working chambers 3 and 4, v / obei in each case the relevant other chamber is brought into communication with a main return line so that the piston 2 is caused to move in the desired direction. Furthermore, springs 11 are provided UIu to always pretension the piston valve 5 in the direction of its central position; the two ends of the cylinder 6 form a local control pressure box 12 or a remote control pressure-i-er Ί3 »and the pressures prevailing in this box act on control jerk signals c": .lag-indication areas 14 or 15 of the piston 33i: i'3cer3 5. The ir of the local 3teu3rdr ^- ickka; .. i.:er 12 upright-

009817/0236 BAD

pressure obtained depends on the setting of an adjustable Pressure reducing valve 16, the position of which is in turn determined by the position of the piston 2, since between the Piston 2 'and the adjusting element 17 of the pressure reducing valve 16 a connection is provided; this connection is in jig. shown schematically it comprises one with the piston rod 2C connected cam 18, which is connected to the Einatell member 17 of the Pressure reducing valve cooperates. The pressure maintained in the remote control pressure chamber 15 depends on the adjusting ring a manually adjustable pressure reducing valve '19' with which the chamber 13 is controlled by a Pernsteuerdruckleitung 13A connected is. According to Fig. 1, each of the valves' 19 is arranged at a common control station in any appropriate distance from the associated valve 1 can be provided; the control station can also have other similar hand-operated Include control valves 19 which are each assigned to the remaining valves 1.

Display devices 20 are provided at the control station, by means of which the pressures in the various control pressure chambers are provided 15 of the various control valves 5-6 are displayed; under stable conditions if you have a flawless Assuming that the system is working, it can be seen that this pressure will be the same as the pressures in the various local control pressure chambers 12 when the piston valve 5 their Assume central position in which the associated channels are closed are.

bathroom 009817/023 4

If there is any piston valve 5 in the central position or the closed position, the pressure in the associated chamber 12 is thus based on the position of the piston 2 and therefore also after the position of the hydraulically operated valve 1, so that the pressure in the pressure chamber 13 is also after 'the position of the valve 1 and this position indicates. Each of the pressure-sensitive display devices 20 therefore displays the position of the associated valve 1. if the position of the valve 19 is changed to reduce the pressure in the To increase or decrease chamber 13, the piston slide 5 thus moves out of its closed position in one or both of them other direction to cause the piston 2 to move in the desired direction until it reaches a new position, in which the change in the position of the valve 16 effected in this way has brought the pressure in the chamber 12 to the same value as the pressure in the chamber 13, so that the piston valve 5 resumes its central or closed position.

As an alternative or in addition, pressure transmission lines can therefore be used provide, which extend between the local control pressure chamber 12 and other pressure-sensitive display devices on the control station, these additional Display devices then show whether and when the piston 2 of a specific hydraulic actuation device is in a Has moved position or assumes a position that corresponds to the position of the associated adjustable pressure reducing valve. 19 corresponds.

■■■■ - * ■ 009817 / 02-3 *

If one assumes that the system is working properly, Thus, each pressure sensitive display device 20 has the Shutdown of the associated valves 1, while the given

foreseen additional pressure-sensitive display »Which preeohe the pressure in the pressure chambers 12, give the opportunity to »check whether the approved valve 1 is in the relevant position.

fecner let it be seen that the dimensions of the pressure relief areas 14 and 15, those of equal or ver-sohledener Can be size, the forces applied by the springs 11 and / or the characteristics of the connection «Between the piston 2 and the adjusting member 17 of the valve can be varied within wide limits, so that a system is obtained that has the desired properties overall,

The main printing line »with that of the various people Control valves leading pressure lines 9 are connected, iilt In iig. 1 denoted by 9A =, while the main return line is shown at 10} a 'fcr * ft-driven pump 9B sucks the ArbeitsflÜaSigkeit «from a container 21 and conveys it the main pressure line 9A4 for returning the working fluid A main oil duct 10A serves to the container 21. 331 e Main lines 9 and 10 thus form a line that EUeasußen can be referred to as the main ring line.

According to Fig. 3, the pressure reducing valve 16 is as direct acting three-way valve formed; it includes a housing

009817/023%

16pO837 , 1

with a cylindrical valve chamber in which a piston valve 23 is slidably mounted; the pressure in a pressure chamber 24 acts on one end of the piston valve 23 while on the other end one end of a spring 25 acts, the other end of which is supported on a stop 26, which on the adjacent End of the adjusting member 17 is formed, the position of which is according to the above description after the axial position of the cam 18 and eoinit also after the position of the piston 2 and the valve 1 directs. The cylindrical housing is provided with an insertion groove 27, which is provided with a bore in Is in communication with a line 28, which leads both to the line 12A and to the pressure chamber 24j in the wall of the cylindrical housing 22 are a pressure port 29, the with part 9A. the bing line 9A-10A is connected, and one Pressure relief opening 30 is formed, which leads to the part 10A the main ring line leads. The piston slide 23 has two annular grooves 31 and 32, each in constant connection with the openings 29 and 30 respectively and through a web 33

separated aind, which then, when the piston valve is in his from Jig * 3 evident neutral position, the connection between the insertion groove 27 on the one hand and the two openings 29 and 50 is interrupted.

When the spool 23 is in its neutral position 3, it prevents the flow of liquid to or vcr. the line 28 so that it maintains the pressure in the line 12A and the Iruckkamsier 24, respectively, the

009817/023 * _B AD

in it prevails at the relevant point in time. It can also be seen that the piston valve 23 assumes this neutral position only when the pressure in the pressure chamber 24 is accurate compensates for the force applied by the spring 25 to the piston valve. Assuming that the piston valve 23 is in the position shown, and that then the adjusting member 17 in a movement of the piston rod 2E in one od * the other sighting is moved up or down, the piston slide 23 also moves up or down; while an upward movement causes the hanging groove 27 to be brought into communication with the pressure port 29, causes a Downward movement that the annular groove 27 with the Druckentlastungsö'ffmmg 30 is connected; in the first case it becomes a Increasing the pressure in the pressure chamber 24 and line 12A causes the spool valve 23 to be in its neutral position to be returned; in the latter case the pressure in the pressure chamber becomes 24 and line 12A to similarly cause the spool to be in its neutral position Position is returned. It can thus be seen that the pressure prevailing in line 12A at any point in time of the Position of the adjusting member 17 and thus also the piston rod 2E and the actuating piston 2 de3 valve 1 depends.

The general structure of the pressure reducing valve shown in Fig. 4 is the same as that of the valve of Fig. 3, however, the valve 19 is shown in FIG. 4 in an inverted position in order to better match the schematic representation

009817/0234 ^BAD ° * ^lelNAL

± n Fig. 1 and 2 to achieve. The parts of the valve according to FIG. 4, which correspond to parts of the valve according to FIG. 3, are each designated with the same reference numbers, so that a renewed description is unnecessary. According to Fig. 4, the setting of the effective force of the spring 25 is not based on the position of the actuating piston 2, but the spring 25 can be adjusted with the help of a manually operated stop 34 which is connected to a threaded spindle 35, the one Adjusting knob 36 carries. In addition, in this case the pressure opening 29 is connected to a pressure line 37 to which the pressurized liquid can be supplied by a pump 38 which sucks liquid from a container 39 to which the liquid escaping via the opening 30 is fed back via a return line 40 .

A shut-off valve is switched on in each of the lines 7 and 8, which is indicated in Fig. 2 at 47, but is omitted in Fig. 1 for simplicity; each of these shut-off valves is arranged to be normally closed, but by means of FIG. 6 in a manner yet to be explained an electromagnet 48 can be opened, and only when two indicated in Fig. 2 at 50 and 51 pressure-actuated Switches have been closed to indicate that a sufficient fluid pressure in the "local" parts of the Lines 9 and 13A prevail, i.e. in those parts of these lines which are adjacent to the plunger device, which the two shut-off valves are assigned. As in Fig. 2 schematically indicated, the two pressure-actuated switches 50,

009817/0236

'IIad the electromagnets in all fieihe connected, ie they

j »
are in a circuit 52 which includes a current source 53; JFig. 5 apparently shows a suitable construction of a single switch, while FIG. 6 schematically shows a suitable construction of a shut-off valve of the type described.

The schematic in Fig. 5 !! switch shown includes a Housing 54 »in which part of its wall is covered by a flexible Hembrane 55 is formed} the interior of the housing 54 protrudes tin tubular connector 54A in conjunction with the Line 9 or line 13A »The membrane 55 is therefore open 4er exposed on one side to the pressure of the atmosphere and on the other side to the bridge in the line 9 or the line 13A prevails.

The membrane 5 $ i carries a contact 56 which dureh the lembran conductively connected to a. Is line-connected 57, which forms a part 4es Stroifikreises 52 »The contact 56", which thus moving the ^"11 forms Eontakt of the switch, a normally fixed but adjustable contact 56 2ugeordnet _T of FIG. 5 duroh a, Mnäe -eiaea Metallstreifeixs is unteretütst 59 'whose other end ^ lint to -this first etching. j "is -fcefestigt 60 also is a. ; .8: tel3, very £ ube: 61- yorgeseiienj by means of which the normal Äbötärid ^ wiaohen "de.ii" fce.iäeii "-56 and 'SS.eingeoielAt-; k ^ mi *; 1) sf Sisntakt-" 5 metal strips 59 elekUrise !? sxi to an Iieitiing 62-connected, which forms part of the circuit 52 .

That in Fi ^. 6 .soiisiäischem dar ^ esteliue Abspsrrv * :; til

includes a ;: Zvli :: - äer 65, cLesse :: ^ aiid ö- ^ yjxnx ^ xi ^ '5A av ^ eist

009817 / 023Λ

which are in communication with the two parts of the line 7 and the line 8 on both sides of the shut-off valve. A piston valve 64 is slidably mounted in the cylinder and carries piston rods 65 and 66 which protrude through seals built into the ends of the cylinder 63. The ends of the cylinder 63 are over a channel. 67 in the piston slide 64 in free connection with one another, and the piston rod 65 can be actuated by a -suitable electromagnet 48 which, according to FIG. 2, is in the circuit 52 * while the piston rod 66 carries a head 67 on which a compression spring 68 acts to set the spool 64 normally in the Pig. 6, in which the connection between the openings 65A is interrupted. The spool or the valve member 64 has a fiingnut 69, and the arrangement is such that when the solenoid 48 is turned on, the spool of Fig. 6 is rightward moved so that the Bingnut 69 a connection between & en openings 63A manufactures.

During the operation of the system described, the piston 2 of each hydraulic actuation device is hydraulically locked in its respective position until sufficient pressure is available in the lines 9A and 13A If there is no pressure in the local line of one of these lines, while pressure is available in the local line of the other line, scmi-t is prevented; on the other hand there is sufficient pruok in the local parts azr suffer ;! Le-, ignite available,

BAD-Q09817 / 023 &

can use any hydraulic actuation device in the bssciirebenen Manner, and when stable conditions exist, the associated display device 20 shows in FIG each point in time the position of the piston 2 and therefore also that of the associated valve 1.

Patent claims:

009817/023%

Claims (1)

'SCHWEIOEllSTRASSE 3 TKLKFON IT. 08 31 TILZOUHHiDIIXBBKt PBOTBOTPATKMT HtMC -3> 417 PATENT CLAIMS 1. Control system for several hydraulically operated Organs, each of which could be operated by a different hydraulic actuator, with the flow of the Working medium from a working medium supply line to the actuating devices and to a pressure relief or bypass line is controlled by a hydraulic control valve, characterized in that each hydraulic Control valve (6) is designed as a valve centered by springs, which has oppositely directed control pressure application surfaces (14, 15), soften the positive pressures in a local control pressure chamber and the pressure in a remote control pressure camera, the pressure in the local control pressure chamber of the work medium supply line is removed via an adjustable pressure reducing valve (16), the position of which changes automatically according to the position the hydraulic actuator changes while the 'pressure in the remote control pressure carriage via a remote control pressure line Control means is taken, which are arranged at a common control station, and by means of which the mentioned Pressure can be determined and varied. 009817 / Q234 2. Control system for several hydraulically operated organs according to claim 1, characterized in that that the control means «by means of which the pressure in the remote • pressure chamber can be determined and varied, a ; ! Include separable pressure reducing valve (19). j 3, control system according to claim 2, characterized in that g e k e η η j draws that each of the pressure reducing valves as direct Acting valve is designed with three openings. {4 * statter system according to claim 1 to 5, g ek e η η - ; ; ■ Rewarded by arranged at the common control station Display devices (20), each of which is based on the Ferneteuerdruekkauninern address the prevailing pressures to the Positions indicating the hydraulic actuation i .. Torriohtungen einnelufien * o4 # r ** Treichen eolleu, if the system , 'works perfectly. 5 "control system according to claim 1 to 4, characterized in that in the common control station is" - - _t AnreigevorrichtungeE arranged, each & onto the bridge in the local stsuer jerk karl numbers. $ Ötei * ersy8ter> according to claim 1 to 5 »; g e-ifc., e'Ji η * - Everyone "kneads" through printing fluffy smocks hydraulic actuation device are sugeerdne / t and on the pressures on beatiiainten points ar.spreeher. «namely ir. der something in the line in the cage of every hydraulic bed BATH * α if and by means of locking bolts that run through the pressure-sensitive Means will be controlled: -, uiu every movement; the hydraulic Prevent actuating devices as long as they are not sufficient Pressures are available in the two lines at the points mentioned, 7. Control system according to claim 6, characterized in that the pressure sensitive means are two comprise pressure-sensitive electrical switches (50, 51), each responding to the pressures at the two points mentioned, and at least one electromagnetically operated shut-off valve (47), which is set up so that it-normally closed cleifct and therefore the hydraulic actuator hydraulically locked, v / ocei the electromagnet only can then be switched on when both pressure-sensitive switches are closed. . BAD OHSQiNAL 009817/0236