WO2005017367A1

WO2005017367A1 - Device and process for circulation of pressurized fluid in an actuator system

Info

Publication number: WO2005017367A1
Application number: PCT/NO2004/000232
Authority: WO
Inventors: Jørgen GRØNFUR
Original assignee: Imenco Engineering As
Priority date: 2003-08-19
Filing date: 2004-07-30
Publication date: 2005-02-24
Also published as: CN100404884C; KR20060064656A; KR101023796B1; NO20033661D0; NO328098B1; NO20033661L; CN1836111A

Abstract

A device and method for a circulating valve for an actuator (1) supplied with pressurized fluid via a directional valve (10) and a first connecting pipe (A) to a first pressurized fluid chamber (4) and a second connecting pipe (B) to a second pressurized chamber (8), respectively, where the introduction of pressurized fluid in one of the pressurized fluid chambers (4, 8) causes the operative member (6) of the actuator (1) to be displaced towards a corresponding extreme position, and where a bypass valve (12, 14) controlled by the operative member (6) is connected in a communicating manner between the connecting pipes (A, B), the bypass valve (12, 14) being arranged so as automatically to open a connection between the connecting pipes (A, B) when the operative member (6) is in a specific position.

Description

DEVICE AND PROCESS FOR CIRCULATION OF PRESSURIZED FLUID IN AN ACTUATOR SYSTEM

This invention regards circulation of pressurized fluid in an actuator system. More particularly, it regards a hydraulic circulation valve that is particularly suited for use in hydraulic systems where the hydraulic fluid is of nature such that it requires periodic circulation in order to avoid degradation. The invention also regards a method of circulating the pressurized fluid in the actuator system.

It has become apparent that when using so-called environmental oils in hydraulic systems, the oil, if left stationary in e.g. a pipe for a period of time, may undergo self-degradation. The products of this process include, among other things, glucose and acid reaction materials that may damage the hydraulic system.

Small hydraulic systems such as control systems for valve actuators, with low flow rates and possibly irregular use, have proven to be particularly susceptible to this type of damage .

I most cases, periodic actuation of the actuator is not possible without first disconnecting the actuator mechanically from its respective valve. In order to overcome this problem, prior art describes the provision of one or more pressure relief valves designed to open after the actuator has assumed one extreme position, by the hydraulic pressure being increased to the set pressure of the pressure relief valve, whereupon the hydraulic fluid is circulated around the actuator. However, this solution involves uncertainty as to whether the actuator has reached its extreme position before the opening of the pressure relief valve, and the solution presupposes the existence of equipment connected with the valve, which equipment indicates the valve position by means of either local or remote reading .

It is also known to equip the actuator with a manually operated bypass valve. Access to the actuator may be difficult, thus this method has only been put to limited use.

The object of the invention is to remedy the disadvantages of prior art .

The object is achieved in accordance with the invention, by the characteristics given in the description below and in the following claims.

By equipping an actuator with a controlled bypass valve designed to be operated, directly or indirectly, by the actuator when the operative member of the actuator is in a specific position, usually an extreme position, it is possible to ensure that the operative member of the actuator reaches its specific position before the circulation of hydraulic fluid commences. The circulation will generally take place without the initiation of special steps and may be carried out at intervals without the operative member of the actuator changing position. In a preferred embodiment the actuator is equipped with cooperating bypass valves arranged to be activated at either of the respective extreme positions of the operative member. Preferably the valves are mechanically controlled one-way valves with a relatively large flow area. The spring force of the one-way valve that must be opened by the fluid pressure contributes to the force acting on the operative member of the actuator in the direction of the extreme position in which the operative member is located, making this greater than the force acting in the opposite direction. This feature is explained in greater detail in the specific part of the application.

A further advantageous feature of the device and the method according to the invention is that a readjustment of the bypass valve will cause a significant change in the differential pressure in the fluid circuit. This change in differential pressure can be used to indicate that the operative member of the actuator is in a specific position.

The invention is suitable for any fluid system in which there is a requirement for circulation of fluid after completion of an operation.

The following describes a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which:

Figure 1 shows a hydraulic diagram for a valve actuator having a control valve and circulation valves;

Figure 2 shows the same as figure 1, but here the operative member of the actuator is in one extreme position, a circulation valve is open and the circulation is running; and Figure 3 shows an alternative embodiment in which the hydraulic fluid chamber of the actuator is also circulated out .

In the drawings, reference number 1 denotes an actuator for a valve 2. The actuator 1 comprises a first hydraulic fluid chamber 4, an operative member in the form of a piston 6 and a second hydraulic fluid chamber 8, together with other necessary components (not shown) that are known per se.

Pressurized hydraulic fluid is supplied via a feed pipe P from a hydraulic unit to a directional valve 10. The hydraulic fluid is returned from the directional valve 10 via a return pipe T to the hydraulic unit (not shown) .

A first connecting pipe A connects one work port of the directional valve 10 with the first hydraulic chamber 4. A second connecting pipe B connects the second work port of the directional valve 10 with the second hydraulic chamber 8.

The actuator 1 is equipped with a first controlled one-way valve 12, which, for illustrative purposes, in the drawings has been shown as being operated by the actuator 1 piston 6 when the piston 6 is near its first extreme position. The one-way valve 12 is normally activated by e.g. a cam (not shown) on the shaft (not shown) of the valve 2.

A second controlled one-way valve 14 is arranged so as to be activated when the piston 6 is near its second extreme position.

The first controlled one-way valve 12 is connected at its inlet port to the second connecting pipe B, thus communicating with the second hydraulic fluid chamber 8, see figure 1. The second controlled one-way valve 14 is connected at its inlet port to the connecting pipe A, thus communicating with the first hydraulic chamber 4.

The outlet ports of the controlled one-way valves 12, 14 communicate by means of a circulating pipe 16.

When the directional valve 10 is displaced so as to allow hydraulic fluid to flow from the feed pipe P via the first connecting pipe A to the first hydraulic fluid chamber 4, the piston 6 is displaced towards its first extreme position, Hydraulic fluid can flow through the second one-way valve 14 and the circulating pipe 16 but not onwards through the first one-way valve 12.

When the piston 6 is displaced so as to be in its first extreme position, see figure 2, the first one-way valve 12 is activated, so that hydraulic fluid can flow from the circulating pipe 16 via the second connecting pipe B, the directional valve 10 and the return pipe T to the hydraulic unit (not shown) .

Thus the piping and valves of the system can be circulated out without moving the piston 6 of the actuator 1.

As the hydraulic fluid in the first connecting pipe A must overcome among other things the spring force in the second one-way valve 14, a slightly higher pressure is maintained in the first hydraulic fluid chamber 4 during the circulation than in the second hydraulic fluid chamber 8. This feature causes the piston to remain in its first extreme position. If the piston 6 were to be displaced from its first extreme position, the first one-way valve will close, whereby the hydraulic fluid pressure will again move the piston towards its first extreme position. In an alternative embodiment, see figure 3, the one-way valves 12 , 14 are arranged in a manner such that the hydraulic fluid chambers 4, 8 of the actuator 1 are also circulated out.

Claims

C l a i s

1. A circulating valve device for an actuator (1) supplied with pressurized fluid via a directional valve (10) and a first connecting pipe (A) to a first pressurized fluid chamber (4) and a second connecting pipe (B) to a second pressurized chamber (8), respectively, whereby the introduction of pressurized fluid in one of the pressurized fluid chambers (4, 8) causes the operative member (6) of the actuator (1) to be displaced towards a corresponding extreme position, c h a r a c t e r i z e d i n that a bypass valve (12, 14) controlled by the operative member (6) is connected in a communicating manner between the connecting pipes (A, B) , the bypass valve (12, 14) being arranged so as automatically to open a connection between the connecting pipes (A, B) when the operative member (6) is in a specific position.

2. A device in accordance with Claim 1, c h a r a c t e r i z e d i n that the bypass valve (12, 14) is constituted by a first controlled oneway valve (12) and a second controlled one-way valve (14) .

3. A device in accordance with Claim 2, c h a r a c t e r i z e d i n that an inlet port of the first controlled one-way valve (12) communicates with the second connecting pipe (B) and an inlet port of the second controlled one-way valve (14) communicates with the first connecting pipe (A) , outlet ports of the one-way valves (12, 14) being connected by a circulating pipe (16) .

4. A method of circulating pressurized fluid in an actuator system, in which an actuator (1) receives pressurized fluid via a directional valve (10) and a first connecting pipe (A) to a first pressurized fluid chamber (4) and a second connecting pipe (B) to a second pressurized fluid chamber (8) , respectively, the introduction of hydraulic fluid in one of the pressurized fluid chambers (4, 8) causing the operative member (6) of the actuator (1) to be displaced towards a corresponding extreme position, c h a r a c t e r i z e d i n that a bypass valve (12, 14) connected between the connecting pipes (A, B) is controlled by the operative member (6) , the bypass valve (12, 14) automatically opening a connection between the connecting pipes (A, B) when the operative member (6) is in a specific position.