SK136898A3 - Safety circuit - Google Patents

Abstract

The invention relates to a safety circuit for controlling a hydraulic drive (10) with a drive part (12) movable in at least two different directions of movement and controllable for any movement by a control switching circuit. A safety circuit which ensures the required safety function in an absolutely safe manner, even in the event of a power failure, is obtained in that at least one safety switching circuit is hydraulically combined with the control switching circuit in such a manner that when the latter is switched off the drive part (12) can only be controlled by the respective safety switching circuit. Consequently, the highest-priority operation provided in an emergency, for example in the form of the defined closing or opening of a vapour control valve, is safely executed and the otherwise usual control process is interrupted by the control switching circuit.

Description

Safety circuit

Technical field

The invention relates to a safety circuit for activating a hydraulic drive with a drive member movable in at least two different directions of travel.

BACKGROUND OF THE INVENTION

Hydraulic actuators with a drive member movable in two mutually different directions of travel may, for example, consist of a hydraulic differential cylinder or a synchronous cylinder whose working pistons as actuators perform adjusting movements to actuate the steam valve, for example, or to create it themselves. As a rule, the fluid or oil supply is carried out via a pressure accumulator, whereby separately arranged safety pressure accumulators are also used. In normal control mode, the steam valve can be moved to any position.

The steam setting valve can be designed as a shut-off and control valve with a quick-opening priority or a quick-closing as a so-called quick-opening safety valve. In particular, these priorities play a role when the steam adjusting valve is used in safety-relevant areas, such as power plant technology, and in emergency operation it must be ensured that the steam adjusting valve assumes adjustable, defined end positions as quickly as possible. In known safety circuits, such as for example for a hydraulic press described in DE 36 31 104 A1, the respective safety functions are often checked and carried out by electronic circuits which are susceptible to failure and failures and do not produce the necessary switching process with absolute certainty.

GB-A-2 057 718 discloses a safety circuit for activating a hydraulic drive with a drive member movable in two different ways

2-directional displacements which can be activated for any displacement by the control circuit in the form of a servo system, the safety circuit being hydraulically superior to the control circuit in such a way that when the actuator is switched off, the actuator can be activated exclusively by the safety circuit. This known safety circuit is mainly used to control rotor blades in helicopters.

However, the triggering of the safety function is not defined by activating the control valve of the control switch via the safety switch, but rather the switch valve is activated via the hydraulic pump of the safety switch circuit of the control switch circuit. The pressure transmitting the connection to the hydraulic drive by the same hydraulic pump is then also activated via this switching valve by the safety switch. By combining a number of safety-relevant functions per switch valve of the control circuit, it is not possible to achieve an absolutely safe function in this known solution.

Based on this prior art, the present invention aims to provide a safety circuit for actuating a hydraulic drive that is not prone to failure and offers a high degree of safety.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides a safety circuit for activating a hydraulic drive with a drive member movable in at least two different feed directions which can be actuated for arbitrary shifting by a control circuit, wherein the at least one safety circuit is hydraulically superior to the control circuit. the switching part, whose fluid conducting outlets are each connected to a first switching valve which generates or closes the pressure-transmitting connection to the driving part and which can be activated for this by the safety switching part of the safety switching circuit; The part activates the first switch valve to close the pressure

The pressure transmitting connection to the hydraulic actuator is formed by the pressure transfer connection and at least one second switching valve.

A second safety switch circuit of the safety circuit may also be provided which, together with the first safety switch element, activates at least one third switch valve which creates a pressure transferring connection to the movement of the actuator opposite to the first safety function.

The hydraulic drive is an adjusting cylinder whose double-acting piston forms the actuating part, and that the regulating switching part is a 4/3 distributor valve or includes pulse control.

Each safety switching part is a 4/2 directional control valve which assumes the same switching position in the energized or idle state.

Each switch valve constitutes a cartridge valve whose respective control connection cooperates with at least one outlet of at least one of the safety switch components.

The switch valves are at least partially interposed between the respective output of the respective safety switch and the associated cartridge valve.

For the quick-closing process, the first safety switch is unpowered, and for the quick-opening process, the first safety switch and the second safety switch are provided, and for the controlled opening and closing of the drive part, the first safety switch cooperates with the control switch in each displacement position.

In order to activate the safety function by the actuator, the first safety switch activates the first switch valve to close the pressure transfer connection and creates a pressure transfer connection to the hydraulic drive via the at least one second switching valve, which ensures that the safety circuit fulfills the required voltage even in the event of a power failure. security function with absolute certainty. Because of the fact that, for different functions, there are two independently operating switching valves, which are always activated by the first safety switch, the safety-relevant functions are technically disconnected from each other and thus more safe to operate. Due to this arrangement, it is in any case guaranteed that the hydraulic switching function

-4 is defined by stop independently of the status of the rest of the hydraulic circuit system and its individual controls. In any case, the hydraulic safety circuits according to the invention prevent failures and faulty connections with certainty.

Further advantageous embodiments of the safety circuit are the subject of the dependent claims.

Overview of the figures in the drawing

In FIG. the wiring diagram is shown and a function table is shown at the top left.

DETAILED DESCRIPTION OF THE INVENTION

The safety circuit serves to activate the hydraulic actuator W, which consists of an adjusting cylinder, a dual acting piston as a driving part 12, which has movable back and forth movable on both sides, in particular in the direction of viewing the periphery of the reciprocating piston rods. (adjusting cylinder) 10, formed as a steam adjusting valve, can change the free cross-sections of the pipe opening (not shown), completely release or close them, or said piston rods 14 can in turn act on other adjusting valves (not shown). Possible directions of movement of the actuator (piston) 12 are indicated by arrows in the circumference as well as the insertion and withdrawal data. Instead of the adjusting roller 10, another hydraulic drive can also be used depending on the application, for example in the manner of a hydraulic motor (not shown).

Through its connection points A and B, the adjusting roller 10 can be connected to the hydraulic pump P 'and the tank T' via the corresponding fluid-guiding connecting lines. Depending on whether the pressure transfer connection abuts the hydraulic pump P 'via port A or port B, the piston 12 moves with both of its piston rods 14 downwards in the wiring diagram. respectively. up. To activate the respective movement, the adjusting roller 10 is connected to a hydraulic actuator

-5block, marked as a whole with W, as well as hydraulic pump P 'and tank Γ. Particularly on the tank side, the respective connecting lines may be provided with adjustable throttle valves 18. For the sake of clarity, not all fluid conducting connecting lines passing through the control block 16 are drawn with continuous lines. Also, the ducts, which are dotted and intermittent, represent possible fluid conducting connections.

The actual regulating function of the adjusting cylinder 10, i.e., depending on the state of the system, the substantially continuous opening and closing movements of the piston 12 is carried out via a 4/3 valve (control switch) MV3 with magnets Y3 and Y4. In the present embodiment, said control is performed via a 3-point pulse controller, but can also be performed by pure pulse control or by a fully continuous control. However, in the case of a fully continuous control, a proportional valve or servo valve is used instead of the slider valve shown. The 4/3-way valve MV3 is connected to the first cartridge valve LERA and LERB via both connections A, B at the outlet side. These cartridge valves as well as the switch valves described below with respect to the cartridge valves open essentially when there is no fluid pressure at their respective control port X, that is, the control port X is depressurized.

The two control terminals X of the first switching valves LERA and LERB are connected via a change-over valve W3 to the fluid-conducting output A of the first safety switching component (solenoid valve) MV1 of the safety switching circuit in the form of a 4/2 distribution valve. In addition, the connection line from the change-over valve W3 leads to the fluid-conducting outlet B of the second safety switching part (solenoid valve) MV2 in the form of a 4/2 distribution valve which is actuable via the magnet Y2. Both solenoid valves MV1 and MV2 are shown in their energized, ie no-current, position in the wiring diagram. As soon as the magnet Y1 activates the solenoid valve MV1, it is energized and assumes the left switching position in the wiring diagram. As a result, the supply to the change-over valve W3 is switched to the tank T and thus to the depressurized state, and both control connections X of the cartridge cartridges LERA and LERB

They will also be depressurized, with the result that said cartridge valves are opened. Depending on whether the magnet Y3 or Y4 of the MV3 control switch is energized, the adjusting roller 10 is retracted. ejected. The corresponding activation is shown in the table above the wiring diagram.

A defined or fast-closing process of the adjusting roller 10 is to be assumed as a safety function. This function of highest priority is performed via the two cartridge valves LEPA and LETB. In doing so, LETB connects the cylinder chamber B with the control port T to the tank, while LEPA connects the chamber A with the pressure transfer port P, with the result that the piston 12 is fully extended. The corresponding activation of the cartridge valves takes place again via the first safety switch-on part MV1. In the energized state shown, both the X cartridge control valves LEPA and LETB are switched to a depressurized state so that the LEPA cartridge cartridges and the LETB can be opened to activate the adjusting cylinder 10. In contrast, the two control connections X of the first LERA and Lerby. this time through the switch valve W3, under pressure, with the result that the first switch valves LERA and LERB remain closed and the control function is bypassed.

The corresponding closing safety function is again shown in the table below, leaving the current Y1 free. Upon corresponding activation, additional switch valves W1 and W2 are also actuated, which are connected to the fluid conducting connection between switch valve W3 and solenoid valve MV1, with the result that both control connections X of the third switch valves (cartridges) LETA and LEPB, which we will further clarify, they will also remain closed because the pressure of the pump persists. The hydraulically superior safety function is set independently of the other switching state of the control block 16, i.e. irrespective of the state of excitation of the second magnets Y2, Y3 and Y4.

Further, the quick-opening switching function achievable by the safety circuit is effected through the activation of the second safety switching part MV2. This function is enabled by energizing the magnet Y1 of the solenoid valve MV1. By actuating the solenoid valve Y2 of the solenoid valve MV2, the associated control connections X of the cartridge cartridges LETA and LEPB are released and are thus depressurized. The cartridge-valve LETA can then connect the cylinder chamber A with the control port to the tank, and the cartridge-valve LEPB will connect the chamber B of the adjusting cylinder 10 to the control port P. In port B of the solenoid valve MV2, the lasting pressure brings the closing part of the change-over valve W3 to its right closing position and, due to the fluid pressure in the control ports X, the cartridge valves LERA and LERB are closed. Likewise, the control ports X of the LEPA and LETB cartridge valves are pressurized via the outlet B of the solenoid valve MV1 and the LEPA and LETB cartridge valves remain closed.

On the other hand, the change-over valves W1 and W2 are depressurized via port A of the solenoid valve MV1 to the tank T, so that the control ports X without the pressure of the LETA and LEPB cartridges cause them to open, thereby connecting port B of the adjusting cylinder 10 to the hydraulic pump. P 'and port A to tank T'. This leads to a quick-opening or retracting process, whereby the adjusting roller 10 re-assumes its position shown in the wiring diagram. Thus, the fast-opening process can be initiated as soon as the magnets Y1, Y2 are energized and assigned to the solenoid valves MV1 and Y1, respectively. The MV2 is brought in the wiring diagram to their left switching position.

Depending on the connection, the opening process can also be triggered as a safety function in the opposite sense. Even in this case, this highest priority would be superior to the normal regulatory and closing function with a safe execution.

ri / mm

Claims (6)

PATENT CLAIMS A safety circuit for activating a hydraulic drive (10) with a drive member (12) movable in at least two different displacement directions, which can be actuated for arbitrary shifting by a control circuit, wherein at least one safety circuit (MV1, LEPA, LETB; MV2, LETA, LEPB) is hydraulically superior to the control circuit (MV3, LERA, LERB), which has a control switch part (MV3), whose fluid conducting outlets (A, B) are always connected to the first switch valve (LERA, LERB), which generates or closes the pressure-transmitting connection to the actuator (12) and which can be activated for this by a safety switch (MV1) of the safety circuit, characterized in that the first safety switch part (MV1) activates the first switch valve (LERA, LERB) to close the pressure transfer connection and through at least one type off valve (LEPA, LETB) form a pressure-carrying connection (P) to the hydraulic actuator (10). The safety circuit according to claim 1, characterized in that a second safety switching part (MV2) of the safety switching circuit is provided which, together with the first safety switching part (MV1), activates at least one third switching valve (LETA, LEPB) which creates a pressure transferring connection to the movement of the actuator (12), opposite to the first safety function. The safety circuit according to claim 1 or 2, characterized in that the hydraulic drive (10) is an adjusting cylinder whose double-acting piston forms the drive part (12) and that the control switching part (MV3) is 4/3 of the switchgear. valve, or includes pulse control. Safety circuit according to claim 2 or 3, characterized in that each safety switching part (MV1, MV2) is a 4/2 directional valve, which in the energized or non-energized state assumes the same switching position. -95. Safety circuit according to any one of claims 2 to 4, characterized in that each switching valve (LERA, LERB, LEPA, LETB, LETA, LEPB) forms a cartridge valve, whose respective control connection (X) cooperates with at least one output (A, B) of at least one of the safety switch components (MV1, MV2). The safety circuit according to claim 5, characterized in that switch valves (W1, W2, W3) are at least partially inserted between the respective output (A, B) of the respective safety switch (MV1, MV2) and the associated cartridge-valve. Safety circuit according to any one of claims 4 to 6, characterized in that for the quick-closing process the first safety switch (MV1) is current-free, that for the quick-opening process the first safety switch (MV1) and the second safety switch The first safety switch (MV1) cooperates with the control switch (MV3) in each displacement position for controlled opening and closing by the drive part (12). ^{? ν}