SE465478B - Primary release valve - Google Patents

Abstract

A hydraulic valve constructed as a multi-way valve with pressure medium feed through the valve in two parallel ducts. Closing and opening of ports 1, 2, 3, 4, T to the various ducts is performed by a combined piston/slide 6. The piston 6 is provided with cams 7, 8, 9 which, in interaction with throttling edges A, B, C, D, E inside the valve space, where the piston 6 runs, open or close the ducts and connections to the valve. Operation of the piston 6 is brought about by applying a control pressure at one end of the piston, where the piston is provided with a pressure area. The control pressure can be produced in any way. At the opposite end of the piston, the piston bears against a valve seat F when control pressure is applied to the piston. This valve seat seals effectively between a duct inside the valve seat and a port outside. At the same end of the piston, there is also a return spring 10 which returns the piston to the starting position when control pressure is not applied to the piston. The object of the valve is to produce a valve in which two ducts through the valve are fed in parallel with pressure medium in separate ducts with the same pressure in the two ducts and in which one of the outputs from the two ducts of the valve retains the same pressure medium pressure even when the position of the valve is changed without any pressure drop occurring during the change. This is achieved by means of a change procedure which is accurately regulated in terms of position. Fig. 1. <IMAGE>

Description

j4e5 478 2 'faults in the signaling systems that control and monitor the triggering of the safety system. Unnecessary tripping of the kind mentioned can cause very costly downtime at, for example, a nuclear power plant. In addition, there is a certain tendency not to test the function of the valves during long operating times due to the risk of secondary fault changes, such as that a tested valve does not want to return to its normal position correctly, or that a control signal does not confirm the valve's return to normal after a test under operating conditions.

The Swedish patent application with number 9000301-3 describes a method of achieving a rapid release of a hydraulic safety system with a system of hydraulic valves. Triggering of this hydraulic safety system is caused by at least two valves being operated simultaneously to shift from a first to a second shift position, whereby the safety system drains and loses its fluid pressure and thereby affects a turbine with a predetermined action. Furthermore, the function is such that shifting from the corresponding first to second shift position in a single valve, effected during testing of this valve or caused by a malfunction of, for example, a control system for the release device, does not affect the state of the hydraulic safety system by pressure changes.

In addition, the said patent application discloses an embodiment in which the number of valves has been increased in order to increase the functional safety of a turbine plant by reducing the risk of failure in the event of a required need and reducing the risk of an incorrect signal to a valve triggering the system and causing costly downtime. The described device uses a so-called "2 of fl era" function, which means that at least two valves included in a system comprising at least two valves in a release device must be actuated to change position for the safety system to be triggered.

In the safety system described above, a valve is required which can convey pressure medium via the valve to receiver equipment through at least two channels, where the pressure in one channel remains unaffected during a position change of the valve. Furthermore, it must be possible to drain the outlet side of the second duct via a valve port. This valve port must have a very good seal against the two mentioned channels, at the same time as it is desirable that the two adjacent channels are sealed to each other in order to reduce leakage and to obtain increased operational safety.

For example, patent patents FR 1553022, US 3195574 and US 4234015 disclose way valves which in principle function with respect to the number of channels and ports are reminiscent of the present invention. These devices described in the patents are not otherwise relevant. ßl 465 478 DESCRIPTION OF THE INVENTION In the following, the construction of a hydraulic valve that meets the set requirements for use in a hydraulic release system as described above is described. Of course, there is nothing to prevent the valve from being used in other contexts in hydraulic technology.

The valve is constructed as a multi-way valve with the possibility of feeding pressure medium through the valve in fl your parallel channels, preferably two parallel channels. Closing and opening of doors to the various channels is provided by a combined piston / slide. This piston / slide which in some functions functions as a slide and in others as a piston is hereinafter referred to only as a piston. The piston is provided with cams which in cooperation with throttle edges inside the valve chamber, where the piston runs, opens or closes channels and connections to the valve.

Operation of the piston is accomplished by applying a guide pressure to one end of the piston, where the piston is provided with a pressure area. Control pressure can be realized in any way. At the opposite end of the piston, the piston, when control pressure is applied to the piston, abuts a valve seat. This valve seat effectively seals between a channel inside the valve seat and a port outside. At the same end of the piston there is also a return spring, which returns the piston to the initial position when control pressure is not applied to the piston.

The purpose of the valve is to provide a valve, where two channels are fed in parallel through the valve with pressure medium in separate channels with the same pressure in the two channels and where one of the outlets from both valves maintains the same pressure on the pressure medium even during a change of position of the valve , without any pressure drop occurring during shifting. This is achieved through a carefully positioned changeover process. In order to avoid disturbances which could adversely affect the function and functional safety of the valve, the same pressure is used on the medium in the two mentioned channels and preferably the same pressure medium is also used when applying control pressure to the piston. The advantage of this method is that the same pressure in the pressure medium occurs on different sides of the piston chambers, which separate the valve channels and also the space with control pressure from each other. In this case, no leakage problems arise at all over said cams of the piston. Another advantage of this is that the risk of clogging, dirt accumulation and pressure drop is avoided, thereby reducing the risk of malfunctions.

In the event of a valve change, one of the ducts on the outlet side must be drained of pressure medium. This is done by draining to the said port at the seat valve. In operating mode, this port is normally depressurized. As a result, a pressure difference is found between this port and the adjacent channel.

By designing the separation of this pressureless port and adjacent duct with both a seat function and a slide function, a good seal is obtained between said spaces, whereby leakage problems are eliminated, which at the same time increases functional safety and service life of the valve. Because the seal is made with both seat and slide function, this seal can also withstand short-term pressure drops in the control pressure to the piston, since the piston must be returned a short distance by means of the return spring before the door at the seat valve is opened.

The described valve can be used as a separate valve in all technical contexts, where a valve with the described function is desired. As previously mentioned, however, the intention is that the invention is used in a system of valves, where the valves are connected in series with each other. If the valve is made with two parallel pressure medium channels as above, at least two valves connected in series are required to, for example, set both channels running through the valves depressurized on the output side of the valve system and thereby activate other equipment connected to the system by valves. If for some reason a system of your valves is desired, there is nothing to prevent a valve from being manufactured according to the principle described here, where more than two parallel channels are arranged through the valve with the same function of the valve as is otherwise stated in this description. With, for example, three parallel channels through the valve, three valves must be connected in series in order for a trip of all three continuous channels to be effected. f1 - DESCRIPTION OF THE DRAWINGS Fig. 1 shows a cross section through a valve according to the invention: Fig. 2 schematically shows the changeover process in 5 steps during position change of the valve.

Fig. 3 shows a cross section of the valve piston.

EMBODIMENTS Function and construction of the preferred embodiment of the valve of the present invention are presented herein with the aid of the accompanying figures.

Figure 1 illustrates inlet ports 1, 3 and outlet ports 2, 4 for a pressure medium at a valve housing 5 for a valve according to the invention. Along the center through the valve housing 5 extends a chamber, in which a combined piston / slide 6, hereinafter referred to as piston only, can run back and forth guided by throttle edges A, B, C, D, E, which tightly enclose cams 7, 8, 9 on the piston, at least when these combs are located at the level of the throttle edges.

At the same time, the choke edge E forms an opening Y outwards in the valve housing at the opening of which the piston has a arranged pressure area 6a, whereupon a pressure can be applied for insertion of the piston 6 into the valve space. For return of the piston, a return spring 10 mounted at the opposite end of the piston is responsible. When no pressure rests on the pressure area 6a of the piston at opening Y, the piston 6 assumes a rest position, here called the second shifting position. The first shift position is assumed when the piston is fully inserted. This is the normal operating mode of the valve. When entering the second shift position, the valve is triggered. 5 '465 478 When the piston 6 is fully inserted, the annular front of the piston abuts a seat F. This piston abutment against the valve seat F effectively seals port 4 against an opening T, a fifth port, which is normally connected to the tank, to which at port 4 pressure medium is drained during change of position.

Through opening T, a return spring 10 for its contact with and action on the piston 6 also runs in through the annular front of the piston 6.

Said seal at valve seat F is further improved by the piston cam 9 with slide function sealing against throttle edge A. This also makes the seal between opening T and port 4 insensitive to short-term pressure drops in the guide pressure of the piston, in that there is no leakage over throttle edge A if possible the piston temporarily leaves seat F a limited part of the width of the throttle edge A.

Normally, during operation, a first channel is open for pressure medium through port 1 between the pistons 7, 8 of the piston and over the throttle edge D to port 2.

In the same way a second channel is open for a pressure medium through port 3 to port 4 between the pistons 8, 9 of the piston and over the throttle edge B. Both of these channels are fed with pressure medium of the same pressure in the intended application, whereby leakage between the separate channels does not occur .

Preferably, the piston is also provided with guide pressure at opening Y with pressure medium from the same source, which means that no pressure difference occurs between opening Y and adjacent channel over throttle edge E.

When changing position of the valve, it is important that no pressure drop can be noted at port 2. For this reason, special care has been taken to avoid such a pressure drop during a position change. This has been achieved by carefully controlling the changeover process. The change process has been schematized in Fig. 2, where this is reported in 5 steps.

During a change of the valve from a first to a second changeover position, it is illustrated in Fig. 2 that as a first step in the process the first and second channels inside the valve are connected to each other, so that these are joined.

This is realized by first reducing the control pressure to a certain set level, whereby the return spring moves the piston towards its rest position. In this case, a connection is first opened between the first and the second channel over the throttle edge C. Since the pressure medium to both port 1 and port 3 is fed from the same source, no pressure changes are noted at port 2 during the interconnection of the two channels. In the next phase, throttle edge B closes the connection over throttle edge B between ports 3 and 4. In this position, gate 4 is thus blocked, while ports 1, 2, 3 are connected to each other. During the progressive movement of the piston, a connection is now opened over the throttle edge A between the fifth port, tank port T, and port 4, which means that pressure medium connected to port 4 is drained to tank. Finally, the connection between port 1 and port 2 is broken, which means that port 1 is blocked, while a new channel has been opened between port 3 and port 2, which channel now supplies port 2 with pressure medium of the same pressure as before but from another input port.

The control of the movement of the piston 6 inside the space of the valve housing is realized by means of longitudinal ridges 11, which run unbroken along the entire outside of the piston also.

Claims (1)

465 478 ES 'between the chambers of the piston. See Fig. 3. These longitudinal ridges abut during the entire piston movement the throttle edges B, C, D, E, which at the same time function as guides for the piston. Throttle edge A also acts as a guide during the time that the piston penetrates this throttle edge. When the cam 9 on the piston is no longer controlled in its piston movement when exiting the throttle edge A, the throttle edge B has already taken over control of the cam 9 on the piston. In the figures, the piston has been depicted with a round cross section. This is not a necessary design as the piston 6 may very well have a different cross-sectional appearance, for example a square cross-section on the outside. CLAIMS 1. A 1. road type valve with two gear positions for hydraulic or pneumatic applications comprising a valve housing (5) with a number of valve ports (1, 2, 3, 4, T) and an interior space for a slide / piston (6) running therein operated by means of applied guide pressure on the slide / piston (6) and with return under the influence of return spring (10), characterized in that between the valve ports (1, 2, 3, 4), in the valve's first shift position, parallel channels are arranged by cooperation between the valve space throttle edges (A, B, C, D, E) and the chambers (7, 8, 9) of the slide (6), through which channels flow pressure medium of the same pressure to eliminate leakage of pressure medium between the channels and that the valve is provided with a port ( T) with seat valve for completely leak-free seal between port (T) and adjacent pressurized duct, Valve according to claim 1, characterized in that when changing from first to second changeover position the sequence for opening and closing the various ducts are one such that one of the outgoing ports (4) in the parallel channels is connected to the port (T) at the seat valve and that the other outgoing ports (2) in the previously parallel channels switch over to new connections with other input ports (3) with the same prevailing pressure on the input pressure medium, no pressure drop occurring at the last-mentioned outgoing ports (2) during the weighing and that the remaining input port (1) which previously provided one of the last-mentioned outgoing ports (2) with pressure medium is closed. Valve according to patent 1 is preferably used in two-of-a-kind systems, ie the valve is arranged in a system of at least two valves, where at least two valves must change position for the valve system to activate other equipment outwards. Valve according to claim 2, characterized in that the valve is provided with, in a first switching position, a channel through a first (1) and a second port (2) connected over a choke edge D and a second G ». 1. * 465 478 channel through a third (3) and a fourth port (4) connected over a throttling edge B, both channels being fed with pressure medium of the same pressure at the first (1) and third port (3) of the channels, respectively, to avoid leakage. of pressure medium between the two channels, which are separated by a throttle edge (C), and that the second channel is leak-proof sealed against a fifth port (T) by means of a seat valve with sealing by both an abutment of piston (6) against seat (F ) and slide (6) abutting against the throttle edge (A) and that, in a second shift position, during the movement of the piston / slide (6) the two channels are first joined together over a throttle edge (C), after which the fourth port (4) closed at a throttle edge (B) and then opened towards the fifth port (T) over throttle edge A, after which throttle edge D finally blocks the connection of the first port (1) to the now only existing channel, which channel is now fed through the third port ( 3) and is connected to the second port (2) over the throttle edge C, thus the second port (2) has changed input port without pressure drop during switching being announced at this second port (2). Valve according to claim 4, characterized in that the piston / slide (6) is provided with longitudinal ridges (11), which during a piston stroke during the entire stroke control the movement of the piston / slide through the abutment of the ridges (11) against the throttle edges (A, B, C , D, E). Valve according to Claim 5, characterized in that the valve is insensitive to short-term pressure drops in the control pressure, since the port (T) at the seat (F) is also sealed by means of a slide function between the cam (9) and the throttle edge (A).