GB2047472A - Improvements relating to intrinsically safe electromagnetic actuators - Google Patents

Abstract

An intrinsically safe electromagnetic valve actuator (5) is formed with two independent operating windings (9a, 9b) side by side or one above the other, and separated by a protective earthed winding 10. Each winding 9a, 9b is independently connected to the mains supply via a respective intrinsically safe power pack. Thus the actuating force is approximately doubled without affecting the electrical safety of the actuator. <IMAGE>

Description

SPECIFICATION Improvements relating to intrinsically safe electromagnetic actuators The invention relates to an intrinsically safe electromagnetic actuator for final control elements such as solenoids valves, in particular.

Devices are known for detecting the switching state of the circuits of magnetically operated final control elements, especially solenoid valves, such devices embodying a warning or signalling system, and it is common for facilities of this kind to be intrinsically safe. Intrinsically safe devices have a power rating of 1 2 VA or less and therefore produce correspondingly low outputs which are usually inadequate to overcome the resistances to movement caused by dirt or high temperature, for instance, in the case of solenoid valves.

It is the object of this invention to provide an intrinsically safe electromagnetic actuator for final control elements, more particularly for solenoid valves, which has a considerably increased actuating force.

Accordingly this invention provides an electromagnetic actuator having at least two separate windings, the windings being disposed one above another or one beside another, being separated from one another by a protective winding, and each being independently connected to the electricity supply mains by a respective intrinsically safe power pack.

While still being intrinsically safe, an electromagnetic actuator of this kind has at least twice the output of the known intrinsically safe magnetic actuators. The magnetic actuator in accordance with the invention is therefore much more able to overcome increases in resistance arising in operation as a result of dirt, high temperature and so on. Thus the operating reliability of such elements, e.g., magnetic actuators is improved.

The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through an electromagnetic actuator associated with a solenoid valve, Figure 2 is a view similar to Fig. 1 of another embodiment of the invention, and Figure 3 is a basic circuit diagram for use with the devices of Figs. 1 or 2.

In each of Figs. 1 and 2 there is shown a solenoid valve whose plunger 2 controls a hydraulic circuit (not shown), is retained in a normal position (as shown in the drawing) by a spring 4 bearing on a disc 3, and is moved into its opposite dead position (towards the right as shown in the drawings), against the force of spring 4, by means of electromagnetic actuator 5. The actuator 5 basically comprises an armature 6 and a winding 9 therearound, the armature 6 being fixedly disposed on a pin 8 which is guided for longitudinal movement in bushes 7.

The winding 9 comprises two independent separate component windings 9a, 9b separated from one another by a protective winding 10. In the embodiment shown in Fig. 1 the component windings 9a, 9b are in the form of windings which are disposed concentrically one inside another, and are separated from one another by an earthed protective winding 10 which extends over the whole length of the winding and extend concentrically around the armature 6. In the embodiment shown in Fig. 2 the component windings 9a, 9b are in the form of two windings which extend concentrically around the armature 6, are disposed one beside the other and are separated longitudinally from one another by the protec tivewinding 10.

As can be seen from Fig. 3, the two component windings 9a, 9b, are each able to be connected to electricity supply mains 1 3 via an individual intrinsically safe power pack 11, 1 2 respectively and are operative in the same sense. With the respective switch 16, 1 7 on, the mains supply 1 3 is connected to the respective component winding 9a, 9b by way of lines 14 or 15. The two switches 16, 17 are interconnected and are actuated together by way of a relay 1 8 which can also be connected to the mains 13, through the agency of a switch 20 and line 1 9.

1. An intrinsically safe electromagnetic actuator for final control elements, such as solenoid valves, and having at least two separate windings, the windings being disposed one above another or one beside another, being separated from one another by a protective winding, and each being independently connected to the electricity supply mains by a respective intrinsically safe power pack.

2. An intrinsically safe electromagnetic acturator substantially as herein described with reference to Figs. 1 and 3 or Figs. 2 and 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to intrinsically safe electromagnetic actuators The invention relates to an intrinsically safe electromagnetic actuator for final control elements such as solenoids valves, in particular. Devices are known for detecting the switching state of the circuits of magnetically operated final control elements, especially solenoid valves, such devices embodying a warning or signalling system, and it is common for facilities of this kind to be intrinsically safe. Intrinsically safe devices have a power rating of 1 2 VA or less and therefore produce correspondingly low outputs which are usually inadequate to overcome the resistances to movement caused by dirt or high temperature, for instance, in the case of solenoid valves. It is the object of this invention to provide an intrinsically safe electromagnetic actuator for final control elements, more particularly for solenoid valves, which has a considerably increased actuating force. Accordingly this invention provides an electromagnetic actuator having at least two separate windings, the windings being disposed one above another or one beside another, being separated from one another by a protective winding, and each being independently connected to the electricity supply mains by a respective intrinsically safe power pack. While still being intrinsically safe, an electromagnetic actuator of this kind has at least twice the output of the known intrinsically safe magnetic actuators. The magnetic actuator in accordance with the invention is therefore much more able to overcome increases in resistance arising in operation as a result of dirt, high temperature and so on. Thus the operating reliability of such elements, e.g., magnetic actuators is improved. The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through an electromagnetic actuator associated with a solenoid valve, Figure 2 is a view similar to Fig. 1 of another embodiment of the invention, and Figure 3 is a basic circuit diagram for use with the devices of Figs. 1 or 2. In each of Figs. 1 and 2 there is shown a solenoid valve whose plunger 2 controls a hydraulic circuit (not shown), is retained in a normal position (as shown in the drawing) by a spring 4 bearing on a disc 3, and is moved into its opposite dead position (towards the right as shown in the drawings), against the force of spring 4, by means of electromagnetic actuator 5. The actuator 5 basically comprises an armature 6 and a winding 9 therearound, the armature 6 being fixedly disposed on a pin 8 which is guided for longitudinal movement in bushes 7. The winding 9 comprises two independent separate component windings 9a, 9b separated from one another by a protective winding 10. In the embodiment shown in Fig. 1 the component windings 9a, 9b are in the form of windings which are disposed concentrically one inside another, and are separated from one another by an earthed protective winding 10 which extends over the whole length of the winding and extend concentrically around the armature 6. In the embodiment shown in Fig. 2 the component windings 9a, 9b are in the form of two windings which extend concentrically around the armature 6, are disposed one beside the other and are separated longitudinally from one another by the protec tivewinding 10. As can be seen from Fig. 3, the two component windings 9a, 9b, are each able to be connected to electricity supply mains 1 3 via an individual intrinsically safe power pack 11, 1 2 respectively and are operative in the same sense. With the respective switch 16, 1 7 on, the mains supply 1 3 is connected to the respective component winding 9a, 9b by way of lines 14 or 15. The two switches 16, 17 are interconnected and are actuated together by way of a relay 1 8 which can also be connected to the mains 13, through the agency of a switch 20 and line 1 9. CLAIMS

1. An intrinsically safe electromagnetic actuator for final control elements, such as solenoid valves, and having at least two separate windings, the windings being disposed one above another or one beside another, being separated from one another by a protective winding, and each being independently connected to the electricity supply mains by a respective intrinsically safe power pack.

2. An intrinsically safe electromagnetic acturator substantially as herein described with reference to Figs. 1 and 3 or Figs. 2 and 3 of the accompanying drawings.