GB2365948A

GB2365948A - Gas valve mechanism

Info

Publication number: GB2365948A
Application number: GB0020104A
Authority: GB
Inventors: William Bond; Adrian Dickerson
Original assignee: Schlumberger Industries Ltd
Current assignee: Gemalto Terminals Ltd
Priority date: 2000-08-15
Filing date: 2000-08-15
Publication date: 2002-02-27
Also published as: GB0020104D0; WO2002014725A1; AU2001291751A1

Abstract

An operating mechanism for a gas valve e.g. for use in a pre-payment gas meter or other gas supply system includes a cam (20), a cam follower (22) and an operating arm (26) mounted for movement with the gas valve mechanism so that movement of the operating arm (26) operates the gas valve mechanism to control the flow of gas. The cam follower (22) is coupled to the operating arm (26) by means of a solenoid actuator (28) operable to move the cam follower (22) from a first position relative to the operating arm to a second position relative thereto. In the first position, the cam follower (22) does not contact the cam (20). In the second position, the cam follower (22) engages the cam (20). The cam (20) is rotatable manually and when the cam follower (22) is in the second position causes the cam follower (22) and, hence, the operating arm to move to operate the gas valve mechanism. When the cam follower (22) is in the first position, rotation of the cam is ineffective. A pull-action or push-action solenoid actuator may be used.

Description

21365948 IMPROVED GAS VALVE MECHANISM The invention relates to a gas valve

mechanism intended for use in a pre- payment meter or other pre-payment gas supply system.

5 It would, ideally, be desirable to provide a valve mechanism in pre-payment gas supply systems capable of being operated, say, 1000 times over a ten year period while powering the mechanism with as small a battery as possible. Traditional mechanisms have used either motors or solenoids to operate the valve mechanism, which requires significant power, and makes it difficult to meet the ten-year lifespan requirement.

It is also important to ensure that the valve will not open accidentally.

15 In accordance with the invention, there is provided an operating mechanism for a gas valve, the mechanism - comprising a cam,- a cam follower and an operating arm mounted for movement with a gas valve mechanism so that movement of the operating arm operates the gas valve 20 mechanism to control the flow of gas therethrough; the cam follower being coupled to the operating arm by means of a solenoid actuator operable to move the cam follower from a first position relative to the operating arm in which the cam does not contact the cam and a second position 25 relative to the operating arm in which the cam follower engages the cam; the cam being rotatable when the cam follower is in the second position to cause the cam follower and, hence, the operating arm to move therewith to operate the gas valve mechanism.

30 Preferred embodiments of valve mechanisms in accordance with the invention will now be described in detail, by way of example, with reference to the drawings, in which:

Figure 1 is a first schematic view of a first 'pullaction' solenoid latched mechanism in accordance with the invention; Figure 2 is a second schematic view of the mechanism 5 of Figure 1; Figure 3 is a first schematic view of a second 'pushaction' solenoid latched mechanism in accordance with the invention; and 10 Figure 4 is a second schematic view of the mechanism of Figure 3.

Both mechanisms shown in the drawings Utili3e, a cam and a cam follower mechanism to operate the valve.

The cam 20 is fixed in position but mounted for rotation is about a central axis by means of an operating knob (not shown) on the outside of the meter or other supply arrangement. The cam 20 is biassed into the 'closed' position shown in Figure 1 by suitable spring means (not shown).

20 The cam follower 22 is mounted on a support arm 24 coupled to an operating arm 26 which is pivotable about one of its ends to operate the actual gas valve mechanism (not shown) to permit or restrict the flow of gas. The operating arm 26 is biassed into the position it occupies when the gas 25 valve mechanism is closed by means of a suitable spring arrangement (not shown).

Any appropriate form of gas valve mechanism may be used provided that it is operable by means of the rotary motion imparted by pivoting movement of the operating arm 26 30 about its pivot axis.

The cam follower 22 arm is coupled to the operating arm 26 by means of a solenoid actuator 28 which is operable to move the support arm 24 between two positions which it can occupy relative to the operating arm 26.

The mechanism shown in Figures 1 and 2 uses a 'pull action' solenoid actuator 28. The solenoid is mounted on the operating arm 26 and is connected to the cam follower support arm 24 by means of a rigid link 30 which is pivotably coupled to the support arm 24 mid way along the 10 latter so that the operating arm 26, rigid link 30 and support arm 24 form a generally triangular linkage. The solenoid utilises a permanent magnet to hold the rigid link 30 and, hence, the support arm 24 in the latched state but requires only a short electrical pulse, 15 typically, of 50 ms duration, to change its state. Simply reversing the polarity of the pulse changes the state of the solenoid. The solenoid actuator 28 is, preferably, operated by the electronic circuitry which permits the depositing of credit by the user, for example, by the 20 insertion of a smart card or the like. The circuit applies the required pulse to change the state of the solenoid actuator when credit is deposited to permit gas to be supplied. As can be seen from Figure 1, the solenoid actuator 28 is operable to move the support arm 24 and, 25 hence, the cam follower 22 from a retracted position in which it does not contact the cam 20, shown in dotted lines in Figure 1, to a cam contacting position (shown in solid outline in Figure 1). During this movement, the operating arm 26 remains stationary.

30 The gas valve mechanism is opened by the credit registering circuitry which operates the solenoid actuator 28. This causes the cam follower 22 to be brought into contact with the cam 20 but does not, of itself, open the gas valve mechanism, because there is no movement of the 35 operating arm 26. The gas valve mechanism is then opened by rotating the cam 20 by means of the external knob; engagement of the cam 20 and cam follower 22 causes the triangular linkage formed by the operating arm 26, rigid link 30 and support arm 24 to pivot about the operating 3 arm's pivot point, opening the valve. In the fully open position, the cam follower 22 drops into a notch 32 in the periphery of the cam 20, to prevent further rotation and to retain the valve in the open position.

When the state of the solenoid actuator 28 is subsequently 10 changed, the cam follower 22 is retracted, bringing it out of contact with the cam 20, the valve is closed as the operating arm 26 returns to its 'closed' position and the knob is returned to the position shown in Figure 1 by the action of the biassing spring referred to above. The state 15 of the valve may be monitored by the use of sensors and/or micro switches built into the mechanism.

This arrangement has the advantage that the solenoid actuator 28 has very low power usage; the customer provides the energy to open the valve by rotating the knob 20 manually and springs are used to close the gas valve mechanism when necessary. Battery power is only used to change the state of the solenoid actuator 28 so as to enable/disable the mechanism by moving the cam follower 22 into or out of contact with the cam 20. As described 25 above, power is supplied to the solenoid actuator 28 in the form of a 50 ms pulse supplied via a capacitor. The main electronic circuit in the meter or supply installation controls this pulse when credit has either been inserted or has run out.

30 The mechanism has the additional advantage that if the solenoid actuator 28 is operated by mistake, for example, due toa malfunction of the electronic circuitry, the gas valve mechanism is not opened until the knob has been turned to rotate the cam 20. Similarly, if the knob is accidentally rotated, the gas valve mechanism will not open unless the mechanism has been enabled by operation of the solenoid actuator 28 to bring the cam 20 and cam follower 22 into contact with one another. The mechanism 5 of the invention thus helps to avoid accidental opening of the gas valve mechanism.

The mechanism shown in Figures 3 and 4 is similar in principle to that of Figures 1 and 2 but utilises a differently arranged solenoid actuator 48, a 'push action' 10 actuator.

Again, the solenoid actuator 48 is mounted on the operating arm 26 but in this embodiment the support arm 44 which carries the cam follower 22 is coupled directly to the solenoid so that operation of the solenoid actuator 48 15 causes the support arm 44 to extend or retract so that it occupies one of the two positions shown in Figure 3. In the retracted position, shown in dotted outline, the cam follower 22 does not contact the cam 20. In the extended position, shown in solid outline, the cam follower 22 20 contacts the cam 20 and rotation of the cam 20 to the position shown in Figure 4 causes the operating arm 26 to rotate about its pivot point to open the gas valve mechanism.

Other than utilising a slightly simpler operating 25 arrangement, the mechanism is in all other respects similar to that of Figures 1 and 2.

Claims

An operating mechanism for a gas valve, the mechanism comprising a cam, a cam follower and an operating arm mounted for movement with a gas valve mechanism so that movement of the operating arm operates the gas valve mechanism to control the flow of gas therethrough; the cam follower being coupled to the operating arm by means of a solenoid actuator operable to move the cam follower from a first position relative to the operating arm in which the cam does not contact the cam and a second position relative to the operating arm in which the cam follower engages the cam; the cam being rotatable when the cam follower is in the second position to is cause the cam follower and, hence, the operating arm to move therewith to operate the gas valve mechanism.
2. A mechanism according to claim 1 in which the solenoid actuator is capable of moving the cam follower from its first position to its second position on application of an electrical pulse.
3. A mechanism according to any preceding claim in which the operating arm is biassed towards a position in which the gas valve mechanism prevents the flow of gas therethrough.

25
4. A mechanism according to any preceding claim in which the cam is biassed into a position in which, when engaged by the cam follower, the operating arm occupies a position in which the gas valve mechanism prevents the flow of gas therethrough.

30
5. A mechanism according to any preceding claim comprising means to permit manual rotation of the cam.