GB2245313A - Actuator control means - Google Patents

Abstract

A fluid-operated actuator (2) (Fig 1) is controlled through a pumping unit (12) providing operating pressure fluid and a control unit (10) directing the fluid flow to and from the actuator. The pumping unit and the control unit have respective passages (44, 46 and 40, 42) which are put in communication when the units are attached together. The passages communicating with concentrically disposed channels (124, 126) at the interface of the units which allow the units to be attached together in different relative angular orientations with respect to the common centre of the openings. <IMAGE>

Description

ACTUATOR CONTROL MEANS This invention relates to means for the control of fluid-powered actuators.

Such actuators have a wide range of applications in many fields. In the interests of economy in the manufacture and stocking of parts, it is desirable to standardise many of their features. However, users may want to install an actuator in any of a number of different orientations, which can require different configurations of the control set-up. For example, independently of the position in which the actuator must be placed, if there is a motor-driven hydraulic pump, it may be important to keep the pump below its driving member in order to ensure that the motor cannot be affected by leakage from the pump. This also is a reason for multiplication of the versions of a particular form of control means.

According to the invention, a control means for a fluid-operated actuator comprises a fluid power source and a control unit for attachment to the actuator to connect with an operating mechanism of the actuator, the fluid power source being provided by a pumping unit releasably securable to the control unit, the two units having porting that is put in communication, when they are secured together, through a plurality of concentrically disposed openings on at least one of the units and said securing means being adapted to attach the units together in a plurality of different angular positions with respect to the common centre of said openings, thereby to permit selection of the relative orientation of the two units attached together.

By way of example, an embodiment of the invention will be described in more detail with reference to the accompanying drawings, which also illustrate a further invention that is the subject of our earlier application 8823837.3. In the drawings: Fig. 1 is an outline front view of a fluidpowered actuator provided with control means according to the invention, Fig. 2 is a plan view illustrating the fluid connections within the control unit of Fig. 1, Figs. 3 and 4 are end views of the control unit and the pumping unit of the control means sho.:-r. the mating faces through which they are secured together, Fig. 5 illustrates one of the non-return valves in the control unit, Fig. 6 illustrates the delay valve of the pump unit, and Fig. 7 is a plan view of the spring plate of the delay valve of Fig. 6.

Fig. 1 illustrates a swinging vane actuator 2 of conventional construction, having a main casing 4 the interior of which is divided into mutually sealed chambers by a vane (not shown) pivoting on a shaft 6 through angular movement of perhaps 90 by the application of fluid pressure to one or other of the chambers, the actuator thereby operating a device such as a valve (not shown) connected to the shaft. Fig. 1 also shows an optional return spring unit 8 which biases the actuator shaft 6 to one end position. An example of this form of actuator is described in more detail in GB 1270941. Mounted on the top of the actuator casing is a control unit 10 which has bolted to it a pumping unit 12 supplying, through the control unit, pressure fluid for driving the actuator.

The control unit comprises a dished casing 22 and a cover 24 which together provide an enclosed chamber in which a series of control devices for the fluid flows are mounted. These devices include first and second nonreturn valves 26,28, first and second solenoid-operated valves 30,32, flow control screws 34, as well as such electrical control means as limit switches and pos,tioning means (not shown) comprising an electronic positioner circuit of a kind known in the art. The solenoid-operated valves may be proprietary units such as Webber 18-series sub-base mounted valves, 3/2 normally open type. The casing has a mounting flange 38 for the pumping unit 12.

Inlet and return conduits 40,42 in the casing walls open into the flange 38 and communicate directly with corresponding conduits 44,46 opening into mounting face 48 of the pumping unit that seats against the flange 38.

Under the control of the devices in the control unit, as will be described below, fluid can flow between the inlet and return conduits 40,42 and a further pair of conduits 50,52 in the casing bottom wall that connect with respective openings 54,56 in the casing bottom face communicating directly with the two sealed chambers of the actuator on opposite sides of the swinging vane, so as to drive the actuator.

The heads of screws 58 bear on the bases of the valves 30,32 and the screws are threaded into the casing bottom wall to secure the valves in position over a region of the casing floor into which the conduits 42,50,52,62,64 open. The fluid flow in the control unit between the inlet and return conduits 40,42 and the conduits 50,52 connected to the actuator is channelled through a replaceable adaptor plate 60 which is sandwiched by the screws 58 between the solenoid-operated valves 30,32 and the casing interior floor over the conduits 42,50,52,62,64. The adaptor plate has internal conduits that determine how the casing conduits communicate with inlet and outlet porting in the bases of the valves.

More specifically, the pressure inlet conduit 4u communicating with the pumping unit extends to ports 40a,40b that open onto the inlets of the two non-return valves 26,28. From outlet 62a of the first non-return valve the conduit 62 extends through the casing to a port 62b within the area of the adaptor plate and below the first valve 30, while the conduit 64 similarly connects the outlet 64a from the second non-return valve 28 to a port 64b within the area of the adaptor plate below the second valve. The return conduit 42 to the pumping unit leads from a port 42a within the area of the adaptor plate under the second valve 32. The conduits 50,52 to the actuator porting 54,56 run from respective ports 50a and 52a in the area of the adaptor plate under the first valve.

The base of each solenoid-operated valve 30,32 has corresponding porting consisting of two elongate ports 72,74 extending along a common diagonal and, on opposite sides of that diagonal a further pair of ports 76,78. In each valve the internal passages are so arranged that, when its solenoid is energised, the elongate port 74 communicates with both smaller ports 76,78 and the other elongate port 72 is isolated, whereas when the solenoid is de-energised, the other elongate port 72 communicates with both smaller ports 76,78 and the elongate port 74 is isol ted. The ports in the bases of the valves 30,32 communicates with the internal conduits in the adaptor plate 60. The configuration of these conduits accordingly determines the fluid circuit connections to and from the solenoid-operated valves and the actuator.

As is described in more detail in our co-pending application 8823837.3, the adaptor plate illustrated in Fig. 2 serves to drive the actuator vane clockwise (as seen in the figure) and allow the vane to return in the anti-clockwise direction under the action of the spring return unit 8, while other modes of operation are obtained by alternative adaptor plates with different configurations of conduits.

In each case, control of the flow rate can be obtained by the use of adjustable flow control screws 34.

Each screw is held in a threaded boss on the respective adaptor plate, between the valves, and its tip 34a projects into the pressure supply conduit in the adaptor plate to act as a variable restrictor for that condu+.

The pumping unit 12 comprises a pump section 102, in which is located a gear pump 104 producing a supply pressure of about 10 bar, and a reservoir section 106 for the hydraulic fluid. The pump is driven, through a dog coupling 108, by an electric motor 110 mounted on top of the unit casing. Within the pump section of the pumping casing there is also shown a pressure release valve 112 connected between the pump pressure outlet line and the reservoir. This section also contains a delay valve 113, shown in more detail in Figs. 6 and 7, connected to the outlet line which allows the motor to accelerate to high speed before full hydraulic pressure is generated, this providing a load characteristic more suited to an induction motor.The filler 114 of the pumping unit reservoir is so arranged that there is also an air space 116 left in the top of the reservoir which can be vented through a conventional fluid trap and filter (not shown) in the casing of the motor 110.

Figs. 3 and 4 illustrate the connections between the control and pumping units. For these connections the control unit mounting flange 38 carries a series of three concentric O-rings 118,120,122. The sealing rings bear against the mating face 48 of the pumping unit casing in which there are two annular channels 124,126 concentric with the O-rings, which seal the channels from each other and from the centre and outermost regions of the mating faces. Opening into the inner of the two channels in the pumo casing face is the pressure line 46 from the pump 104. The fluid return line 44 to the reservoir section 106 leads from a pair of openings in the outer of the channels, this arrangement with its two openings providing for a symmetrical flow from the pressure release valve 112 when it is opened, to avoid disturbing the operation of that valve.At the centre of the face 48 within the area sealed by the innermost O-ring 122, there is a passage 128 for electrical power supply leads (not shown) to the pump.

Ancillary electrical equipment associated with the pump, such as a capacitor 130 (if a single phase induction motor is used) and a control circuit (not shown) can be located in the control unit through which the power supply leads pass. The control and pumping units are secured together by bolts through four bores 132 equally spaced along a circular locus concentric with the channels 124,126. The pumping unit can, therefore, be secured in place in any of four rotational positions of adjustment to obtain the connections described.

The positioning of the motor 110 above the pump and reservoir ensures that hydraulic fluid will not seep into the motor by gravity. If in a particular installation the actuator axis is required to be horizontal rather than vertical as shown in Fig. 1, the construction of the connection between the control and pumping units allows the pumping unit still to be secured with its orientation unchanged so that the advantage of placing the motor uppermost can be retained.

A preferred construction for thn non-retur valves 26,28 is illustrated in Fig. 5. The valve body 140 has a central inlet 142 and an outlet 143 radially offset, and is secured in place by a series of bolts inserted through the control unit casing from below. A threaded cap 144 encloses the main bore of the body and bears on two biasing springs 146,148, the first holding down a valve seat 150 surrounding the top of the inlet opening and the other urging a valve ball 152 against that seat if there is not a positive pressure difference between the inlet and outlet of the valve.It may be noted that in the first two modes of operation described above, where spring-return actuators are employed, biased to one end position, only one of the non-return valves carries a flow of fluid and in such cases it is possible to dispense with the other valve and blank off its mating ports in the casing.

The delay valve 113 of the pump section, as shown in Figs. 6 and 7 comprises a chamber 160 having ports 162,164 communicating directly with the pump output side and the pump return side respectively and a further port 166 to the pressure release valve 112. The chamber has a valve seat 168 against which a valve ball 170 can seal to block flow from the port 162 to the port 164.

start-up, before the flow rate from the pump picks up, the ball rests at the bottom of the chamber and the initial outlet flow is therefore bypassed to the reservoir on the pump return side, via the port 164, so that there is a minimal load on the pump motor. As the flow upwards through the chamber increases it lifts the valve ball 170 until the ball reaches its seat 168 and is then held in sealing engagement with the seat by the static fluid pressure in the chamber. The pump outlet flow can now only be bypassed to the reservoir via the pressure release valve 112 and it therefore flows at normal operating pressure to the control unit.

When the pump is stopped, to ensure that any residual pressure in the chamber does not retain the valve ball sealed against its seating, a spring plate 172 is provided comprising a centre ring 174 connected to an outer rim 176 through radial arms 178. The spring plate is formed with a monostable action in which the centre ring is in a lower position from which it is forced upwards by the valve ball as it reaches the seat 168.

While the ball is pressed against the seat the spring plate exerts a downwards pressure on it which is sufficient to dislodge the ball from the seat when the pump is stopped and the pressure on its output side drops.

Claims (8)

1. Control means for a fluid-operated actuator comprising a fluid power source and a control unit for attachment to the actuator to connect with an operating mechanism of the actuator, the fluid power source being provided by a pumping unit releasably securable to the control unit, the two units having porting that is put in communication, when they are secured together, through a plurality of concentrically disposed openings on at least one of the units and said securing means being adapted to attach the units together in a plurality of different angular positions with respect to the common centre of said openings, thereby to permit selection of the relative orientation of the two units.

2. Control means according to claim 1 wherein securing means between the pumping and control units provide four alternative relative positions of rotation at which the units may be secured together at 90C intervals of rotation about said common centre.

3. Control means according to claim 1 or claim 2 wherein conduits open into said common centre for electrical leads extending between the units.

4. Control means according to any one of claims 1 to 3 wherein the pumping unit comprises a pump and an electrical motor arranged so as to be disposed with the pump below the motor, and said disposition being available with different orientations of the control unit on the fluid-operated actuator.

5. Control means according to claim 4 comprising means for limiting the pump outlet pressure on start-up, said means comprising a bypass passage and means responsive to the rate of flow from the pump to block said bypass passage with increase of flow rate after start-up.

6. Control means according to claim 5 wherein said blocking means is maintained in its operative blocking position by the pump outlet pressure during continuing operation of the pump.

7. Control means according to claim 6 wherein biasing me- urge the blocking means away from its operative position, whereby to reopen the bypass when the pump outlet pressure falls below a predetermined level.

8. A pumping unit and a control unit for a control means for a fluid-operated actuator and being constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.