GB2114741A

GB2114741A - Actuators

Info

Publication number: GB2114741A
Application number: GB08203813A
Authority: GB
Inventors: Raymond Keith Fear
Original assignee: Loomhurst Ltd
Current assignee: Loomhurst Ltd
Priority date: 1982-02-10
Filing date: 1982-02-10
Publication date: 1983-08-24
Also published as: DK52283A; IT1161616B; IT8319524A0; JPS58149407A; FR2521319A1; DK52283D0; DE3304585A1

Abstract

An actuator comprises a variable volume bellows (16) that is connected with an operating rod (18) to move this rod in dependence upon changes in volume of the bellows. The bellows is part of a temperature responsive means (16/20/22) and the actuator further comprises a Peltier thermo- electric assembly (24) selectively operable to apply a heating or a cooling effect to the temperature responsive means to vary the volume of the bellows and thus move the rod. As described a valve (1) is operated and the temperature responsive means is insulated from hot flow line fluid by a further bellows (12) disposed between the valve and the temperature responsive means and through which the rod passes. The actuator is connected to a remote controller (26) by simple wiring (25) merely sufficient to supply operating current to the Peltier thermo-electric assembly (24). <IMAGE>

Description

SPECIFICATION Actuators This invention relates to actuators for operating mechanisms such as valves. If it is desired to operate a mechanism from a control location remote from the mechanism, or to operate from a single control location several mechanisms that are remote from one another, it is desirable that lines of communication between the control location and the or each mechanism be as simple as possible, and likewise that an actuator for the or each mechanism be of simple but reliable construction.

According to the present invention there is provided an actuator comprising a variable volume member that is connected with an operating member of the actuator to move this operating member in dependence upon changes in volume of the variable volume member, the variable volume member being part of a temperature responsive means and the actuator further comprising a Peltier thermoelectric assembly selectively operable to apply a heating or a cooling effect to the temperature responsive means to vary the volume of the variable volume member and thereby bring about movement of the operating member.Such an actuator can be connected to a remote control location by a simple wiring merely sufficient to supply operating current to the Peltier thermo-electric assembly, and the actuator is of simple but reliable construction as it is a Peltier thermoelectric assembly that is used as a motivating means.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing in which the single Figure is a sectional side view, partly diagrammatic, of a valve equipped with an actuator connected to a controller remote therefrom.

In the Figure the valve 1 has its valve member 2 held off its valve seat 3 by a compression spring 4 so that the valve is normally open. The body of the valve includes a housing 5 for the spring 4.

The spring 4 is mounted on the stem 6 of the valve member, this stem projecting into the housing 5 and terminating therein.

The valve stem 6 enters the housing 5 at one end and at the other end the housing 5 has secured to it by a nut 7 the actuator 8, the nut 7 clamping fast to the housing end a shoulder 9A of a bush 9 that is fast with one end of a first housing 10 of the actuator. Within this end of the first housing 10, and also fast therewith, is a shouldered member 11.

The shouldered member 11 has one end of a variable volume member in the form of a first bellows 12 fast with it, this bellows being housed in the first housing 10 and being fast at its other end with a plug 13. Adjacent this other end of the bellows 12 the first housing 10 is closed by a bush 14 which is fast in one end of a second housing 1 5. Within this second housing 1 5 there is another variable volume member in the form of a second bellows 1 6 which has one end fast with a shouldered portion 1 4A of the bush 14, and which has its other end closed by a plug 17.

An operating member of the actuator is constituted by a rod 1 8 which at one end is in abutment with the end of the valve stem 6 remote from the valve member 2. This rod extends through the bush 9, the shouldered member 11, the plug 13 and the bush 14 to the plug 17. The rod 18 is a sliding fit in the bush 9 and in the shouldered member 11; is fast in fluid-tight manner with the plug 13; is a sliding fit in the bush 14; and is fast in fluid-tight manner with the plug 17. The interior of the bellows 12 is sealed by the connection of this bellows to the shouldered member 11 and the plug 13. Likewise the interior of the bellows 1 6 is sealed by the connection thereof to the plugs 13 and 17.

The rod 1 8 passes through each of the bellows with clearance so that between the rod and the interior wall of the first bellows 12 there is defined a variable volume chamber 19, and between the rod and the interior of the second bellows 1 6 there is defined a variable volume chamber 20. Further variable volume chambers 21 and 22 are defined between the exterior of the bellows 12 and the interior wall of the housing 10 (chamber 21), and between the exterior of the bellows 1 6 and the interior wall of the housing 1 5 (chamber 22).The chamber 22 contains an expansible fill of temperature responsive medium such as oil which will expand with rise in temperature, the bellows 16 and this fill in the chamber 22 constituting a temperature responsive means for moving the rod 1 8 in dependence upon changes in volume of the bellows 16.

Associated with the chamber 22 is a heat pump 23 consisting of a Peltier thermo-electric assembly mounted on the housing 16 and including a heat sink 24. This heat pump is connected by electrical leads 25 to a control box 26 having electrical power supply leads 27.

In use the valve 1 is connected in a fluid flow line, for example a steam line. In the open condition illustrated line fluid will be on both sides of the valve member, and is able to enter the first housing 5 and the interior (chamber 19) of the first bellows 12. This bellows, however, acts as a seal and serves to isolate the expansible fill in the chamber 22 in the second housing 1 5 from the line fluid. In particular, therefore, where the line fluid is a hot fluid such as steam, the expansible fill is insulated from the effects of the heat of the line fluid.

The valve 1 can be operated, that is caused to close or permitted to open, from the control box 26 by setting the control box to supply current to the Peltier thermo-elctric assembly 23.

Dependent upon the selected direction of current flow either a heating or cooling effect is obtained at the Peltier thermo-electric assembly 23. If heat is generated, the expansible fill in the chamber 22 increases in volume. This causes the bellows 16 to contract, which drives the rod 18 in the direction to act on the valve stem 6 to close the valve against the action of the spring 4. The bellows 12 also contracts to accommodate this movement of the rod 18. By subsequently reversing the current flow to the Peltier thermo electric assembly 23, a cooling effect can be obtained to reduce the volume of the expansible fill, whereby the spring 4 is permitted to assert itself to open the valve.

As a Peltier thermo-electric assembly is of inherentiy simple construction, requiring no moving parts, there is included in the actuator a source of motivating power that is of simple but reliable construction. The remainder of the actuator is also of simple construction with a minimum of moving parts. Because of the cooling effect that can be obtained, the provision of the Peltier thermo-electric assembly also enables rapid response to be obtained in both directions of operation of the actuator. Furthermore stepless operation is achieved by virtue of using such an assembly as the source of motivating power.

The bellows 12 constitutes a seal of conveniently simple construction that by its size, elongated in the direction away from the valve, serves well to insulate the expansible fill from hot flow line fluid. In situations where heat associated with the mechanism to be operated is not a problem, the bellows 12 can be replaced by some other form of seal comparatively compact in the direction away from the valve, for example one or more O-ring seal(s). It is also to be understood that the mechanism to be operated can be other than a valve, and that more than one mechanism can be operated from a single control box. The connection of the control box to the or each actuator requires only a minimum of simple electrical leads.

Claims

1. An actuator comprising a variable volume member that is connected with an operating member of the actuator to move this operating member in dependence upon changes in volume of the variable volume member, the variable volume member being part of a temperature responsive means and the actuator further comprising a Peltier thermo-electric assembly selectively operable to apply a heating or a cooling effect to the temperature responsive means to vary the volume of the variable volume member and thereby bring about movement of the operating member.

2. An actuator as claimed in claim 1, wherein the variable volume member is a bellows, wherein the temperature responsive means further includes a housing in which this bellows is disposed with its interior sealed from the interior of the housing, and wherein a chamber defined between the inner wall of the housing and the outer wall of the bellows contains an expansible fill of temperature responsive medium that expands with rise in temperature.

3. An actuator as claimed in Claim 2, wherein the operating member is a rod which is fast with the bellows so as to be moved by change in volume of the bellows, and wherein this rod extends from the remainder of the actuator through an elongated seal that serves to insulate the temperature responsive means from hot medium if present in the mechanism to be operated by the actuator.

4. An actuator as claimed in claim 3, wherein the elongated seal is a bellows through which the rod extends, the interior of this bellows being sealed to the rod at the end of this bellows that is adjacent the temperature responsive means.

5. An actuator as claimed in claim 4, wherein the elongated seal forming bellows is disposed in a housing, the interior of this bellows being sealed from the interior of this housing.

6. An actuator as claimed in any one of the preceding claims and further comprising a controller electrically connected to the Peltier thermo-electric assembly for operating this assembly to apply said heating or said cooling effect to the temperature responsive means.

7. An actuator substantially as hereinbefore described with reference to the accompanying drawing.