US3830137A

US3830137A - Safety control system for a pneumatic or hydraulic control circuit

Info

Publication number: US3830137A
Authority: US
Inventors: H Wurth; G Freund
Original assignee: KNORR BREMSE GmbH
Current assignee: Knorr Bremse AG
Priority date: 1972-01-31
Filing date: 1973-01-31
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20
Also published as: FR2169933B1; DE2204478A1; BE794710A; GB1415933A; DD103744A5; FR2169933A1; NL7300891A

Abstract

A safety control system for a pneumatic or hydraulic control circuit has at least one control valve arrangement connected to at least one pickup for monitoring or sensing at least one specific operational condition and for releasing at least one measurement signal, as a function of the operational condition, to the control valve arrangement, which releases a control signal for the actuation of at least one pneumatic or hydraulic correcting element. An indicator circuit is connected to the control valve arrangement for releasing warning signals indicating a disorder, at least in the case of a defect in the control valve arrangement. A control valve is provided between the pickup and the control valve arrangement to simulate briefly the operational condition for the purpose of testing the operational capability of the control valve arrangement.

Description

United States Patent Wiirth et al.

SAFETY CONTROL SYSTEM FOR A PNEUMATIC OR HYDRAULIC CONTROL CIRCUIT Inventors: Hans-Jiirg Wiirth; Georg Freund,

both of Munich, Germany Assignee: Knorr-Bremse GmbH, Munich,

Germany Filed: Jan. 31, 1973 Appl. No.: 328,282

Foreign Application Priority Data Jan. 31, 1973 Germany 2204478 US. Cl 91/1, 137/558, 91/35 Int. Cl. F0lb 1/00 Field of Search 9l/l, 35; 137/558 References Cited UNITED STATES PATENTS 6/1971 Mastroianni 137/558 Primary Examiner-l-lenry T. Klinksiek Attorney, Agent, or Firm-Edmund M. Jaskiewicz [57] ABSTRACT A safety control system for a pneumatic or hydraulic control circuit has at least one control valve arrangement connected to at least one pickup for monitoring or sensing at least one specific operational condition and for releasing at least one measurement signal, as a function of the operational condition, to the control valve arrangement, which releases a control signal for the actuation of at least one pneumatic or hydraulic correcting element. An indicator circuit is connected to the control valve arrangement for releasing warning signals indicating a disorder, at least in the case of a defect in the control valve arrangement. A control valve is provided between the pickup and the control valve arrangement to simulate briefly the operational condition for the purpose of testing the operational capability of the control valve arrangement.

10 Claims, 2 Drawing Figures liar The present invention relates to a safety control system for a pneumatic or hydraulic control circuit having a sensor for indicating an operational condition and for releasing a signal responsive to said condition, more particularly, to such a circuit that gives an indication of any defect in the circuit or shuts off the control circuit with respect to a source of flow medium should for any reason the control valve circuit not be capable of operation.

The control should be particularly suitable for filling and/or emptying containers for liquid, for example, tank cars or trucks containing in each case an overpressure valve and a bottom valve, through which the liquid flows in or out. This means that the bottom valve should be closed when the device for sensing the level of the liquid is not capable of operation or when the container or containers are full or empty, depending on whether the question is of a filling or of an emptying operation. If one deals with such a device for sensing the level of liquid, one should preferably be able to employ sensing pipes that can be connected to a source of pressure medium and in which accumulation pressures are formed when the openings of the sensing pipes are closed by the liquid, the presence or absence of such pressures exerting an effect on the connected control valve arrangement. In this connection, in addition to the testing of the control valve arrangement, the safety control system should provide a simple possibility of testing also the pickups in regard to their operational capability. Finally, it should be possible to connect the control valve arrangement combined to at least one pickup together with the correcting element, e.g., for opening or closing the valves of the container, to a common source of compressed air.

The object of the invention is to have available a safety control system which automatically always checks its operational capability prior to the occurrence of a specific operational condition to be measured which condition must be followed, e.g., by the switching-off or on of a correcting element, and disconnects the control as soon as a disturbance or defect is present. In this manner it should be made certain, for example, in the case of emptying containers for liquid, that the emptying is stopped at the proper time so that no air is drawn in through the emptying pipes, which condition must be fulfilled, for example, in the case of emptying tank cars filled with liquid fuel, that are emptied separately or combined in groups.

The invention solves the problem in such a manner that a control valve controlled by the control valve arrangement is arranged between the pickup and the control valve arrangement, which control valve for the purpose of testing the operational capability of the control valve arrangement simulates briefly the operational conditions to be measured during a sequence of operation, in each case prior to the occurrence of such conditions, a disturbance or defect indication being released and/or the correctingelement (20) is not actuated when a control signal corresponding to the simulated condition does not appear.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings, which are merely exemplary, wherein;

FIG. 1a is the left hand portion of a schematic circuit diagram of the control circuit incorporating the present invention; and,

FIG. lb is the right hand portion of the same circuit.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views, a specific embodiment of the present invention will be described in detail.

It should be borne in mind that we are dealing in this connection with'a safety control system for filling and emptying the containers for liquid. To one skilled in the art, it will be immediately clear that on the basis of the teaching indicated for constructing the specific safety control system one can readily build corresponding systems within the scope of the invention that can be employed for similar control purposes.

A supply main 1 communicating with a source of compressed air is connected by means of coupling 2 to an air line 3 of the safety control system of the invention. An air filter 4 and a pressure regulator 5 are connected in air main 3. The air regulated at a predetermined pressure arrives through a main stopcock 6 in a pipe 7 to a spring-loaded valve 8. When the supply of compressed air is switched on, valve 8 is in the illustrated, opened position and connects pipe 7 to a pipe 9, through which a pulse valve 10 can be switched from the particular position illustrated into another position still to be described. For the purpose of switching, a

pipe 11 branching off pipe 7 is connected over an adjustable throttle valve 12 and a timing element 13 to valve 8, that can be switched from its illustrated stable position into its unstable position, wherein the connection between pipes 7 and 9 is interrupted. Throttle 12 is bridged over by a check valve 14 in the manner illustrated. When the supply of compressed air is switched on in the example, valve 8 is switched into its blocking position after 5 seconds. From this position it is switched back .automatically through spring power again into the position of opening (which is illustrated), after the supply of compressed air is disconnected.

In front of main stopcock 6, a pipe 15 branches off to pulse valve 10. In the particular illustrated stable position of pulse valve 10, pipe 15 is connected to a pipe 16 that is led for the purpose of switching to a further pulse valve 17. In the illustrated position of pulse valve 10, a connected pipe 18, led through an adjustable throttle valve 19 to a cylinder 20, is vented. With cylin der 20 vented, a piston 21 is disposed through the power of its spring 22 in its particular position which is illustrated. A piston rod 23 is connected to a suitable linkage, e.g., for connecting a liquid container or containers to emptying valves. In the position illustrated, throttle 19 is bypassed by a check valve 24.

In front of throttle 19, a pipe 25 branches of? to a spring-loaded valve 26 which, in its particular illustrated stable position interrupts the connection to an justed that, after pulse valve is switched and pipe connected to pipe 18 for applying pressure to cylinder 20 after 20 seconds in the example, valve 26 is switched for connecting pipe to pipe 27.

From pipe 27, a pipe 27 branches off to pulse valve 17 which, in the position illustrated, connects pipe 27 to a pipe 29' that is led through an adjustable throttle 30' and a timing element 31 for the purpose of switching to a valve 32. In the position illustrated, valve 32 blocks a pipe 33 branching off air main 3 and leading to a horn 34, that releases an audible warning signal when connected to pipe 33 in the other position of valve 32. From this position, valve 32 can be pressed back into the position illustrated by applying pressure to a spring-loaded button 32. 7

From pipe 27, there branches off a further pipe 35, that is led for the purpose of switching to two springloaded valves 36, 37. In the illustrated stable positions of valves 36, 37, these valves block

respective sensing pipes

38 and 39 in relation to pipes 40 and 41. Pipe 29' is connected to pipes 40 and 41 by means of parallel pipes 43 and 44. Pipes 43, 44 contain in this connection respective valves 45, 46 and throttles valves 47, 48. Sensing

pipes

38, 39 are situated in a container for liquid. Longer sensing'pipe 38 triggers a circuit when the level of the liquid in the container drops below an open end 49 of the pipe. Shorter sensing pipe 39 triggers a circuit when an end 50 of the sensing pipe is closed by the level of the liquid in the container.

In its illustrated stable position, pipe 40 is blocked by a spring-loaded valve 51 in relation to a pipe 52, which is vented in this connection through valve 51. Pipe 52 branches off pipe 27. An air filter 54, as required for a disturbance-free operation of fluid flow elements, precedes a connection point 53. Two

throttles

55, 56 are situated in pipe 52. Subsequently to first throttle 55, a pipe 57 branches off pipe 52 for the purpose of a parallel compressed air supply of two

fiuidic negators

58, 59 connected in series. From pipe 57, there branches off a pipe 60, which is led through a throttle 61 and connecting

pipes

62, 63 to the control inlet of negator 58 and to a spring-loaded valve 64 which, in the position illustrated, shuts off pipe 41 in relation to pipe 63.

An outlet 65 of first negator 58 is connected through a valve 66 to the inlet of second negator 59 in accordance with the position as illustrated. Subsequently to second throttle 56, a pipe 67 branches off pipe 52, pipe 67 being connected to valve 66 which, in the position illustrated, interrupts a connection of pipe 67 to the control inlet of negator 59, which is disconnected from the outlet of negator 58 when valve.66 is switched in corresponding manner. In the example, valve 66 is switched manually from its position illustrated into its other position inversely; valve66 is switched into the position illustrated when the container is to be filled and sensing pipe 39 should sense the level of liquid in the filled container. Valve 66 must be switched into the other position when the container is emptied and sensing pipe 38 should indicate the level of liquid dropped below end 49 of the sensing pipe.

Pipe 52 and connected pipe 67 are vented through spring-loaded valve 51 in the illustrated stable position thereof. Besides, pipe 40 is shut off in relation to pipe 52. In its other unstable position, there is produced a connection between pipe 52 and pipe 40. In the corresponding manner, in the other unstable position of valve 64, pipe 63 is connected to pipe 41. In order to switch

valves

51 and 64 into their unstable positions, pulse valve 17 can be switched from its stable position illustrated into its other stable position, wherein pipe 28 is separated from pipe 29 and, instead, connected to a pipe 68. Pipe 68 is thus led in parallel manner to

valves

51 and 64 for the purpose of switching the valves. Besides, pipe 68 is led through an adjustable throttle 69, for the purpose of switching, to a springloaded valve 70 which, in its position illustrated, shuts off a pipe 71, leading to the outlet of an amplifier 72, in relation to a pipe 73 which, in the direction illustrated, is connected through a check valve 74 to

pipes

77 and 78. Through pipe 77, valve 32 can be switched from its position which is illustrated into the position for releasing a warning signal and, through pipe 78, pulse valve 10 can be switched from its stable position illustrated into its other stable position. Amplifier 72 is supplied with air through pipe 27 through filter 54. An outlet 59 of negator 59 is connected to the control inlet of amplifier 72 that releases a flow signal into pipe 71 when a signal appears on the outlet of negator 59. From pipe 71, there branches off a pipe 74, that is led through an adjustable throttle 75 and a timing element 76 to pulse valve 17 for switching the said valve into its 8 other stable position. If a flow pulse is released by amplifier 72 into pipe 71, the pipe switches pulse valve 17 after 3 seconds in the example, owing to throttle valve 75 and timing element 76, in which position pipe 28 is connected to pipe 68 for. switching

valves

51, 64 and 70. While with the connection of pipe 68 to pipe 28

valves

51 and 64 are switched from their stable positions intotheir unstable positions substantially without delay, valve 70 is switched only after an adjustable time, after 2 seconds in the example, because of throttle 69.

The safety control system of the invention, employed according to the example for filling and emptying a container for liquid or a plurality of such containers connected in parallel, operates in the following manner:

When coupling 2 is connected to supply main 1, main 2 and connected pipes 33 and 15 are under compressed air. Valve 32 is situated in its position which is illustrated, wherein pipe 33 is blocked off in relation to signal horn 34. At the start of a control cycle, also pulse valve 10 is in the position illustrated, so that cylinder 20 is vented and pipe 15 is connected to pipe 16. Accordingly, valve '17 is pressed into its position which is illustrated, wherein

pipes

27, 28 are connected to pipe 29', leading to valve 32, and to pipes 43 and 44 associated with pipes 40 and 41.

When stopcock 6,is opened, compressed air passes into pipe 7 and through valve 8, held in the position illustrated by the spring power, also into pipe 9, in order to switch pulse valve 10 from its position which is illustrated into its other position, wherein cylinder 20 is subjected to the action of compressed air through pipes 3, l5 and 18. At the same time, pipe 16 is vented through the switched pulse valve 10 so that pulse valve 17 can be switched into its other position through a signal from amplifier 72. As described above, valve 8 is held pressed in its unstable position after a set time (5 seconds in the example) during the control cycle, in which unstable position pipe 7 is separated from pipe 9 and the latter pipe is vented, so that pulse valve 10 can be switched back into its position which is illustrated by a signal arriving through pipe 78.

As cylinder is subjected to pressure, required movements are performed, e.g., to open mechanically the bottom valves and the overpressure valve during the filling of containers. As described above, on connection of pipe 18 to pipe 15, valve 26 is switched into its unstable position after an adjustable time, e.g. after 20 seconds, in which unstable position pipes 2, 15, 18 and are connected to pipe 27. Because of this, compressed air passes into

pipes

28, 29, 43, 44 and as well as into pipes situated in the connections to

fluidic negators

58, 59, amplifier 72 and

valves

51, 64. Through pipe 35, valves 36 and 37 are pressed into their unstable positions, wherein pipe 41 is connected to sensing pipe 39 and pipe 40 is connected to sensing pipe 38. Air then passes through

pipes

27, 28, 43, 44, check valves 45, 46 and throttles 47, 48 into pipes 40 and 41 and, further, into

sensing pipes

38 and 39, in order to blow out these pipes before they are to become operative.

If the container is to be filled, valve 66 is switched into the position illustrated. Since valve 64 is in its stable blocking position, wherein pipe 63 is separated from pipe 41 and, in addition, sealed in relation to the atmosphere, a pressure is built up at the inlet of negator 58. As a result the filled state of the container is simulated at the start of a filling control cycle. Because, if later, after completed testing of the control system, sensing pipe 39 is connected to

pipes

41 and 63, a pressure likewise builds up at the inlet of negator 58, when the sensing pipe is closed at its end 50 by the level of the liquid, i.e., the container is filled.

If a pressure is built up at the inlet of negator 58, no pressure signal appears at the outlet of negator 58 and, therefore, likewise at the inlet of negator 59. Consequently, a pressure signal appears at the outlet of negator 59 to cause amplifier 72 to release a pressure signal into pipe 71. After an adjustable time, after 3 seconds in the example, through pipe 74 the pressure signal in pipe 71 switches pulse valve 17 from its position which is illustrated into the other position, wherein pipe 28 is blocked off in relation to pipes 29, 43 and 44 and the latter are vented. Through this, the blowing-out of the sensing pipes is completed. Valve 32 has not yet been switched into the position for the release of a warning signal, because the delay period for switching the valve 32, selected through throttle 30' and

timing element

31, 6 seconds in the example, is longer than the delay period of 3 seconds for switching pulse valve 17, set by means of throttle 75 and timing element'76.

When pulse valve 17 is suitably switched, pipe 68 is subjected to the action of compressed air, owing to i which

valves

51 and 64 and, after a time delay, also valve 70 are pressed into their unstable positions, wherein pipe 63 is connected to pipe 41 and pipe 52 to pipe 40 as well as pipe 71 to pipes 73, 78. With this, the simulation of the filled container is completed and

sensing pipes

38 and 39 are connected to

pipes

52 and 63 respectively.

Through this, the pressure buildup at the inlet of negator 58 disappears. Consequently, a signal appears at the outlet of negator 58 and, therewith, also at the inlet of negator 59, so that the signal at the outlet of negator 59 disappears. However, with this, the signal delivered by amplifier 72 also dispappears and, indeed, the signal disappears before valve 70 is switched from its position which is illustrated into its other position through the time delay of, e.g., 2 seconds set on throttle 69, so that pulse valve 10 is not switched back into its starting position.

Now, the various delay periods are so selected that, in the case where the control is in proper order, the signal of amplifier 72 again disappers before the container is filled. lf opening 50 of the sensing pipe is then closed by the level of the liquid when the container is filled, a pressure again builds up at the inlet of negator 58, which pressure leads to the release of a signal by amplifier 72, as explained above. The signal passes again through pipe 71 and valve (switched in the meantime) into pipe 78, in order to switch pulse valve 10 back into its starting position which is illustrated, wherein the cylinder is vented in the manner described above and the filling operation is thus completed. At the same time, valve 32 is switched through pipe 77 for the purpose of connecting pipe 33 to the signal born This sequence takes place when the safety control device of the invention does not exhibit any defects or disturbances. However, if one of

negators

58, 59 or amplifier 72 is defective, so that no signal appears on amplifier 72 during the simulation procedure, pulse valve 17 is not switched from its position which is illustrated and, after a time period which can be set on throttle valve 30 and time element 31 and which amounts, e. g., to 6 seconds (Le, a time which is greater than the time of, e.g., 3 seconds which can be set on throttle 76 and timing element valve 32 is switched in order to connect pipe 33 to horn 34 for the purpose of releasing a warning signal. If the stopcock is closed thereafter, the various spring-loaded valves are returned automatically into their starting position. If stopcock 6 is then opened again, a control cycle can be'started again.

Should the container be emptied, valve 66 must be switched into its other position, wherein two

negators

58, 59 are separated from each other and pipe 67 is applied to the control inlet of negator 59. If the control is then switched on, it runs initially in the same manner as in the above-mentioned filling control, until pipe 27 is subjected to pressure. Since valve 51 is in its starting position which is illustrated, pipe 52 is vented through valve 51. In this manner, no pressure is built up at the inlet of the negator, which is also the case when the air can flow off through sensing pipe 38 while pipes 52 and 40 are connected to the sensing pipe, when the container is empty. In its position which is illustrated, valve 51 thus simulates an empty container. If the control is in proper order, a signal appears on the amplifier during such a simulation, through which the blowing of sensing pipes 37, 38 is completed and

valves

51 and 64 are switched, as in the case described above. Also here the delay periods are so selected that

valves

51 and 64 can be switched before the container is emptied.

Accordingly, since sensing pipe 38 is submerged in the liquid during the emptying operation, a pressure builds up in sensing pipe 38 and connected pipes 40, 52, and 67 after

valves

51 and 64 are switched, which pressure leads to the fact that no signal is released at the outlet of negator 59. With this, the signal on the amplifier disappears and it appears only after the level of the liquid drops to such an extent that the opening of the sensing pipe is released. As in the case described above, a signal is then released to pulse valve 10. However, if owing to a defect in negator 59 or amplifier 72 no signal appears at the outlet thereof during the simulation of the emptied container, a warning signal is released likewise after a certain time by born 34 in the same manner as described above.

In the example, the simulation of the operational conditions to be measured (wherein a switching must take place) is effected already during the course of the .filling or emptying operation. This is possible because in the example the filling and emptying certainly last longer than the time for testing the control system. It is clear that the circuit of the invention can also be constructed in such a manner that cylinder 20 is subjected to pressure only after the completion of the testing time.

The circuit of the invention can also be readily modified in such a manner that a warning signal is released also in the case where sensing

pipes

38, 39 cannot be blown through for any reason and, accordingly, a high stagnation accumulation pressure builds up in pipes 43, 44. In this case, pipes 43, 44 could be connected to pipes 71 and 29 by means of valves and throttles, so that pulse valve 10 is switched and a warning signal produced also in the case where pulse valve 17 was switched while the logical circuit and amplifier were intact.

Moreover, the invention is not limited to the exemplified embodiment illustrated and described or to similar examples for filling or emptying the containers. It can be applied in similar manner and with advantage in any case where, owing to certain operational conditions that must be sensed by pneumatic or hydraulic pickups, logical switching operations must be carried out, which operations can be tested in a simple manner according to the invention in regard to operational capability by a preliminary simulation of the operational conditions to be measured.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is: I

1. In a safety control system for a pneumatic or bydraulic control circuit, the combination of control valve circuit means, means for sensing an operational condition, means responsive to said sensing means for releasing a signal indicative of said condition to said control valve circuit means, means in said control valve circuit means for releasing a control signal, a flow correction element actuated by said control signal, indicator circuit means connected to said control valve circuit means for releasing warning signals in response to an abnormal state in said control valve circuit means, and control valve means controlled by said control valve circuit means connected between said sensing means and said control valve circuit means for simulating briefly the operational condition which is to be sensed in order to test the operative capability of the control valve circuit means prior to an occurrence of 'the actual operational condition, a warning signal being released or said correction element not being actuated when a control signal corresponding to the simulated condition does not appear.

2. In a control system as in claim 1 wherein said sensing means comprises an open pipe connected through said control valve means to a flow medium circuitand in which pressure accumulates when said pipe is closed,

said control valve means interrupting or releasing the admission of fluid into said pipe in response to a control signal released by said control valve circuit means upon the closing or opening of said pipe open end.

3. In a control system as in claim 1 wherein said control valve circuit means comprises a flow medium logic element having a control inlet connected to the inlet of said control valve means and an outlet, a flow amplifier having a control inlet connected to said outlet of said logic element and having an outlet, and an actuation valve connected to said correction element and having a control inlet connected to said outlet of said amplifier, said amplifier releasing a signal on the occurrence of an actual or simulated condition.

4. In a control system as in claim 1 wherein a valve (17) controlled by amplifier (72) is connected between a source of flow medium (1,2,27) and an indicator circuit (34), on the one hand, and a valve (10) for the connection of pressure-flow medium to cylinder (20), on the other hand, which valve in its first switching position and in connection with the starting of the control system, connects source of flow medium (27) through a first timing element (30,31) having a delay t to the indicator circuit means and a signal of amplifier (72) switches the valve into its second switching position after a time t t in which second position the source of the flow medium is blocked in relation to the indicator circuit means and is connected through a timing element (69) with a delay t to the control inlet of a valve (70), which valve, when subjected to the action of the flow medium, releases the signal path from amplifier (72) to the control inlet of valve (10) for the actuation of cylinder (20).

'5. In a control system as in claim 1 wherein a valve (17) is connected'between source of flow medium (27) and the control inlet of control valve means (51,64), said valve (17 interrupting a connection between the source of the flow medium and the control valve when the system is set into motion, and releasing through a signal of the amplifier after a time t the connection for switching the control valve means.

6. In a-control system as in claim 5 wherein said valve (17 is connected between sensing means (38,39) and source of flow medium (27 said valve connecting the sensing means to the source of flow medium when the system is started for the purpose of testing the pickup, and a signal of amplifier (7 2) switches said valve for the purpose of interrupting the connection between the sensing means and the source of the flow medium.

7. In a control system as in claim 6 wherein the valves for effecting the connection of the source of flow medium to indicator device (34), control valve means (51,64) as well as the valve for testing the sensing means are replaced by a single pulse valve (17) which is switched by a control signal of the control system into one of its positions and by an amplifier signal into the other position when the system is started.

8, In a control system as in claim 1 wherein at least two pickups (38,39) are provided for sensing two boundary conditions, a control valve (51,64) preceding each pickup, the control valve simulating the operational conditionto be measured at the start of an operational sequence whereby first control valve (64) connected to the first pickup (39) interrupts the connection of a source of flow medium (27) to the first pickup for the purpose of simulating a boundary condition, and second control valve (51) connected to second pickup (38) releases the connection of source of flow medium (27) for the purpose of simulating the other boundary condition, the inlet of first control valve (64) together with the control inlet of a first negator (S8) is connected to the source of flow medium via throttles, and the outlet of the first negator is connected through a switch-over valve (66) in one of its positions to the control inlet of a second negator (59) whose outlet is connected to the control inlet of amplifier (72), the inlet of second control valve (51) is connected through reversing valve (66) in its other position together with the control inlet of the second negator and via throttles to a source of flow medium (87).

9. In a control system as in claim 1 in particular for filling and/or emptying containers for liquids, e.g., tank cars provided in each case with an overpressure valve and a bottom valve, wherein a common source of pressure medium (1) is provided for supplying the control system and for actuating the cylinder or cylinders (20) for actuating the overpressure and bottom valves, a pulse valve (10) connected between the source of pressure medium on the one hand, and the control valve circuit means and the cylinder or cylinders on the other hand, said valve (10) is connected to the source of pressure medium through a pulse limiter (8,12,13) for controlling movement into its switched-on position, and said valve 10) is connected to the outlet of amplifier (72) or to indicator circuit means (32,33,34) for the purpose of the control movement into its switchedoff position.

10. In a control system as in claim 9 wherein a valve (26) is connected between pulse valve (10) and control valve circuit means (58,59,72), said valve 26) is held in its open position by the pressure of source of pressure medium (1,3) through timing element (29,30)

when pulse valve (10) is opened.

Claims

1. In a safety control system for a pneumatic or hydraulic control circuit, the combination of control valve circuit means, means for sensing an operational condition, means responsive to said sensing means for releasing a signal indicative of said condition to said control valve circuit means, means in said control valve circuit means for releasing a control signal, a flow correction element actuated by said control signal, indicator circuit means connected to said control valve circuit means for releasing warning signals in response to an abnormal state in said control valve circuit means, and control valve means controlled by said control valve circuit means connected between said sensing means and said control valve circuit means for simulating briefly the operational condition which is to be sensed in order to test the operative capability of the control valve circuit means prior to an occurrence of the actual operational condition, a warning signal being released or said correction element not being actuated when a control signal corresponding to the simulated condition does not appear.

2. In a control system as in claim 1 wherein said sensing means comprises an open pipe connected through said control valve means to a flow medium circuit and in which pressure accumulates when said pipe is closed, said control valve means interrupting or releasing the admission of fluid into said pipe in response to a control signal released by said control valve circuit means upon the closing or opening of said pipe open end.

4. In a control system as in claim 1 wherein a valve (17) controlled by amplifier (72) is connected between a source of flow medium (1,2,27) and an indicator circuit (34), on the one hand, and a valve (10) for the connection of pressure-flow medium to cylinder (20), on the other hand, which valve in its first switching position and in connection with the starting of the control system, connects source of flow medium (27) through a first timing element (30,31) having a delay t1 to the indicator circuit means and a signal of amplifier (72) switches the valve into its second switching position after a time t2<t1, in which second position the source of the flow medium is blocked in relation to the indicator circuit means and is connected through a timing element (69) with a delay t3 to the control inlet of a valve (70), which valve, when subjected to the action of the flow medium, releases the signal path from amplifier (72) to the control inlet of valve (10) for the actuation of cylinder (20).

5. In a control system as in claim 1 wherein a valve (17) is connected between source of flow medium (27) and the control inlet of control valve means (51,64), said valve (17) interrupting a connection between the source of the flow medium and the control valve when the system is set into motion, and releasing through a signal of the amplifier after a time t2 the connection for switching the control valve means.

6. In a control system as in claim 5 wherein said valve (17) is connected between sensing means (38,39) and source of flow medium (27), said valve connecting the sensing means to the source of flow medium when the system is started for the purpose of testing the pickup, and a signal of amplifier (72) switches said valve for the purpose of interrupting the connection between the sensing means and the source of the flow medium.

8. In a control system as in claim 1 wherein at least two pickups (38,39) are provided for sensing two boundary conditions, a control valve (51,64) preceding each pickup, the control valve simulating the operational condition to be measured at the start of an operational sequence whereby first control valve (64) connected to the first pickup (39) interrupts the connection of a source of flow medium (27) to the first pickup for the purpose of simulating a boundary condition, and second control valve (51) connected to second pickup (38) releases the connection of source of flow medium (27) for the purpose of simulating the other boundary condition, the inlet of first control valve (64) together with the control inlet of a first negator (58) is connected to the source of flow medium via throttles, and the outlet of the first negator is connected through a switch-over valve (66) in one of its positions to the control inlet of a second negator (59) whose outlet is connected to the control inlet of amplifier (72), the inlet of second control valve (51) is connected through reversing valve (66) in its other position together with the control inlet of the second negator and via throttles to a source of flow medium (87).

9. In a control system as in claim 1 in particular for filling and/or emptying containers for liquids, e.g., tank cars provided in each case with an overpressure valve and a bottom valve, wherein a common source of pressure medium (1) is provided for supplying the control system and for actuating the cylinder (20) or cylinders (20) for actuating the overpressure and bottom valves, a pulse valve (10) connected between the source of pressure medium on the one hand, and the control valve circuit means and the cylinder or cylinders on the other hand, said valve (10) is connected to the source of pressure medium through a pulse limiter (8,12,13) for controlling movement into its switched-on position, and said valve (10) is connected to the outlet of amplifier (72) or to indicator circuit means (32,33,34) for the purpose of the control movement into its switched-off position.

10. In a control system as in claim 9 wherein a valve (26) is connected between pulse valve (10) and control valve circuit means (58,59,72), said valve (26) is held in its open position by the pressure of source of pressure medium (1,3) through timing element (29,30) when pulse valve (10) is opened.