EP0605425B1

EP0605425B1 - A position indicator for a hydraulic type setting motor

Info

Publication number: EP0605425B1
Application number: EP92910183A
Authority: EP
Inventors: Peter Gamborg Gr N
Original assignee: NORDISK MARINE HYDRAULIK DANMARK AS
Current assignee: NORDISK MARINE HYDRAULIK DANMARK AS
Priority date: 1991-04-29
Filing date: 1992-04-27
Publication date: 1995-08-09
Anticipated expiration: 2012-04-27
Also published as: ATE126326T1; NO933698L; EP0605425A1; WO1992019871A1; DK78291D0; FI934776A; NO933698D0; FI934776A0; DE69204072D1; JPH06507467A

Abstract

For remote indication of the position of the movable member (7) of a double-acting, fluid-pressurized hydraulic setting motor (6) communicating with two control conduits (A2, B2) for the supply and removal of pressure fluid to actuate the movable element (7) for movement in an opening direction or in a closing direction, use is made of a volumeter (3) having a capacity corresponding to the stroke volume of the setting motor (6). The two control conduits (A2, B2) may be connected through a multi-way valve (2) with a pressure line (P) and a tank line (T) or, in a neutral state both of them may be connected with the tank line (T). The volumeter (3) is coupled to the multi-way valve (2) in such a manner that in both operating positions it is connected into the control line connected with the tank line (T), whereas it is barred in the neutral condition. The two control conduits are connected with the setting motor over pilot controlled non-return valve arrangements (4) each of which in the neutral state prevents pressure fluid from passing from the setting motor to the control conduits, whereas in the operating position return of pressure fluid to tank is being opened only after a sufficient working pressure has been established in the pressurized control conduit.

Description

The invention relates to a hydraulically operating position indicator for remote indication of the position of the movable member in a double-acting, fluid-pressurized hydraulic setting motor having the same stroke volume in both directions and being connected with two control conduits for the supply and removal of pressure fluid to actuate the movable member for movement in an opening direction or in a closing direction, the position indication being performed by a volumeter positioned remote from the setting motor and having a measuring volume corresponding to the stroke volume of the setting motor.
It is known to implement such a remote indicating system in which the volumeter is coupled directly into one of the control conduits. In prior art designs, however, such a system has suffered from the weakness that at the same time the volumeter measures the compression and the decompression in the conduits extending to the setting motor which at a small stroke volume of the setting motor and long pipe connections may cause very severe indication errors. Moreover, thermal expansion of the pressure fluid by heating of the setting motor and the pipe system results in pressure fluid being passed through the volumeter, thereby also entailing indication errors.
In a hydraulic, remote control system known from DE-A-1 601 755 for valve setting, e.g. onboard tankers, in which use is made of two setting motors with different piston area, it has been suggested in order to counteract indication errors to disconnect the position indicator from the control conduits in the neutral state, in which both control conduits in this system are pressurized, by connecting the position indicator into a bypass conduit to one control conduit.
While preserving the advantages related to direct connection of the position indicator designed as a volumeter in one of the control conduits, thereby avoiding a supplementary electric, pneumatic or hydraulic measuring conduit, the invention aims at providing a remote indicator system eliminating or considerably diminishing the above mentioned problems of indication errors.
For that purpose a hydralically operating position indicator of the above type according to the invention is characterized in that a multi-way valve is provided for connecting the two control conduits, in one and the other of two operating positions corresponding to opening and closing, respectively, with a pressure conduit and a tank conduit or, in a neutral state, connecting both of said control conduits with the tank conduit in a free flow communication therewith, the volumeter being coupled to said multi-way valve in such a manner that in both operating positions the volumeter is connected into the control conduit connected with the tank conduit, means being provided for firmly retaining the volumeter in its latest occupied position in said neutal state, and the two control conduits being connected with the working chamber of the setting motor on either side of the movable element member over pilot controlled non-return valve arrangements which in the neutral state prevent pressure fluid from passing from the setting motor to the control conduits which are unpressurized in this position, whereas each of these non-return valve arrangements in the operating position in which the control conduit associated with the other non-return valve arrangement is fluid-pressurized, is being opened for return of pressure fluid from the setting motor only after a sufficient working pressure has been established in the actual control conduit.
By allowing the volumeter to always be connected with the return line extending to tank in the two operating positions, a substantially exact measurement is obtained of the volume in the setting motor at the rear side of the piston which is urged back to tank. This eliminates the indication error which otherwise occurs in prior art systems due to the compression of oil built up in the fluid-pressurized control conduit to obtain the necessary working pressure. The system may thus be said to be pressure-compensated.
When a motion of the movable member of the setting motor in the opening and closing direction is completed and the movable element has occupied the desired position, the system is brought into a neutral state in which both control conduits are coupled to tank and the volumeter is retained in the latest occupied position. Due to the above non-return valve arrangements the setting motor is likewise firmly retained in the occupied position by the movable element. As the volumeter is securely retained in the occupied position, oil flowing through the control conduits due to thermal expansion in the setting motor are unable to influence the volumeter, but are passed directly to tank to which the control conduits have free access in the neutral state. Thus, the system is also temperature-compensated.
The retainment of the volumeter in the indicator position may advantageously be obtained by a connection with said multi-way valve such that in the neutral state the volumeter is disconnected from both control conduits.
In order to ensure that prior to such a disconnection the volumeter is allowed to occupy a position corresponding to the position of the movable member of the setting motor, throttle valve arrangements causing some time delay of the disconnection may be associated with said multi-way valve to which the volumeter is connected.
Due to the elimination of the above mentioned indication error the invention offers an advantageous possibility of positioning the pilot operated non-return valve arrangements in the vicinity of the setting motor so that the retainment of the setting motor and thus of a valve operated by it, may be effected immediately at the setting motor and the valve, thereby fulfilling the demands increasingly made by classification societies.
The invention will now be explained in detail with reference to the schematical drawings, in which

Figs 1 to 3 are charts of a hydraulic setting motor with remote indication by means of an embodiment of a position indicator according to the invention, upon activation of the setting motor in the closing direction, in the neutral condition and upon activation of the setting motor in the opening direction, respectively, and
Figs 4 to 6 corresponding charts of a second embodiment.

In the embodiment illustrated in Figs 1 to 3 a setting motor 6 with a working piston 7 is connected through control conduits A₂ and B₂ connected with a six-way valve 2 over which the conduits lines A₂ and B₂ may be connected with control strings A₁ and B₁ which by means of a solenoid-controlled three-way operating valve 1 may be coupled to a pressure conduit P, and a tank conduit T. In the rest position shown in Fig. 2 the three-way valve 1 is de-energized and brought into a centre-position by springs, not shown. The control strings A₁ and B₁ are connected with the tank conduit T, thereby likewise causing the six-way valve 2 to occupy a centre position by bias stress from springs 11 and 12 therein, so that also the control conduits A₂ and B₂ are unpressurized. In the illustrated embodiment the volumeter 3 is locked in its position in this condition by barring the oil inlets, but such a retainment may also be obtained in another way, e.g. by means of a mechanical locking device which is activated when the control strings by the change-over of the valve 1 to the neutral condition become unpressurized or assume a very low pressure. The valve 2 may thus be a four-way valve instead of the illustrated six-way valve.
The working piston 7 of the setting motor 6 is locked in this position due to the pilot controlled non-return valves 4 confining the oil at both sides of piston 7. Safety or release valves 5 serve to ensure that an excess pressure encouraged by heating may escape.
At a desired movement of the piston 7 of setting motor 6 towards the closed position as shown in Fig. 1, one magnet 13 of the three-way valve is electrically activated, following which valve 1 changes over to the illustrated position. The pressure from conduit P will actuate one of two activation pistons 15, 16 of the six-way valve 2 so that this valve too shifts. The pressure fluid will now be compressed in the B₂ conduit until it attains a magnitude capable of moving the piston 7 towards closing. During this pressure build-up no flow is taking place in A₂ as piston 7 has not moved. When piston 7 moves, the oil A₂ flows to the six-way valve 2 from which the oil is directed through the volumeter 3 which then indicates the actual position of piston 7. When the desired position of piston 7 corresponding to a desired setting of a valve operated by the setting motor has been attained, the system is brought into the neutral state shown in Fig. 2, thereby connecting both control conduits A₂ and B₂ with tank. Throttle valve arrangements 8 and 9 between the control strings A₁ and B₁ and the activation pistons 15, 16 of the six-way valve 2 entail some time delay of the disconnection of volumeter 3 to ensure that it occupies a position corresponding to the position occupied by piston 7 prior to disengagement.
In a desired movement of piston 7 towards open position as illustrated in Fig. 3, the other magnet 14 of valve 1 actuated and valve 1 changes its position con-currently with shifting of the six-way valve 2, thereby causing conduit A₂ to be connected with pressure conduit P.
The piston 7 is moved and return oil is passed through the B₂ conduit to volumeter 3 in the reverse direction in relation to the closing movement. When piston 7 is in the desired position, the system is again brought into the rest position shown in Fig. 2.
In the embodiment illustrated in Figs 4 to 6, two four- way valves 17 and 18 are substituted for the six-way valve 2, but the system and the position indication operate actually in the same manner as described above.
In the operating situation illustrated in Figs 1 and 3 and in Figs 4 and 6, respectively, it is incidentally not necessary that the connection of the unpressurized control conduits A₂ and B₂, respectively, with the tank conduit T is effected over the operating valve 1, because the connection may be established directly from the multi-way valve 2, and 17, 18, respectively.

Claims

A hydraulically operating position indicator for remote indication of the position of the movable member (7) in a double-acting, fluid-pressurized hydraulic setting motor (6) having the same stroke volume in both directions and being connected with two control conduits (A, B) for the supply and removal of pressure fluid to actuate the movable element (7) for movement in an opening direction or a closing direction, the position indication being performed by a volumeter (3) positioned remote from the setting motor and having a measuring volume corresponding to the stroke volume of the setting motor, characterized in that a multi-way valve (2; 17,18) is provided for connecting the two control conduits (A₂, B₂), in one and the other of two operating positions corresponding to opening and closing, respectively, with a pressure conduit (P) and a tank conduit (T) or, in a neutral state, connecting both of said control conduits (A₂, B₂) with the tank conduit (T) in a free flow communication therewith, the volumeter (3) being coupled to said multi-way valve (2) in such a manner that in both operating positions the volumeter is connected into the control conduit connected with the tank conduit (T), means being provided for firmly retaining the volumeter in its latest occupied position in said neutal state, and that the two control conduits (A₂, B₂) being connected with the working chamber of the setting motor (6) on either side of the movable member (7) over pilot controlled non-return valve arrangements (4) which in the neutral state prevent pressure fluid from passing from the setting motor (6) to the control conduits (A₂, B₂) which are unpressurized in this position, whereas each of these non-return valve arrangements (4) in the operating position in which the control conduit associated with the other non-return valve arrangement is fluid-pressurized, is being opened for return of pressure fluid from the setting motor (6) only after a sufficient working pressure has been established in the actual control conduit.
A position indicator as claimed in claim 1, characterized in that a safety valve (5) is provided in association with each of said non-return valve arrangements (4), said safety valve (5) allowing in said neutral state pressure fluid to escape from the setting motor (6) to the associated control conduit upon occurrence of a thermally based overpressure in the setting motor on one or the other side of the movable member.
A position indicator as claimed in claim 1, characterized in that said multi-way valve (2; 17,18) is accommodated within a control panel remote from the setting motor (6) and is coupled in series with a three-way operating valve (1) through which the pressure line (P) and tank line (T) may be connected with one or the other of said two control conduits and vice versa, or the two control conduits (A₂, B₂) may be coupled together and connected with the tank line (T).
A position indicator as claimed in claim 1, 2 or 3, characterized in that the volumeter (3) is coupled to said multi-way valve (2) in such a manner as to become disconnected from both control conduits (A₂, B₂) in the neutral state.
A position indicator as claimed in claim 4, characterized in that throttle valve arrangements (8, 9) are associated with said multi-way valve for time delay of the disconnection of the volumeter (3) from the control conduits (A₂, B₂).
A position indicator as claimed in any of the preceding claims, characterized in that the pilot controlled non-return valve arrangements (4) are located in the vicinity of the setting motor (6).