GB2173621A

GB2173621A - Safety devices for burners

Info

Publication number: GB2173621A
Application number: GB08605823A
Authority: GB
Inventors: Donald Paton Mcculloch
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-03-09
Filing date: 1986-03-10
Publication date: 1986-10-15
Also published as: GB8605823D0; GB2173621B

Abstract

A fuel supply shut off system for a burner comprises a thermomechanically actuated diaphragm valve 52 in the fuel supply line. A cable 42 is connected via spring loaded diaphragm 48 to a plunger 50 that controls the amount of gas passing through its valve. The cable 42 is connected to a thermomechanical mechanism located in a position which only gets hot if a malfunction occurs. <IMAGE>

Description

SPECIFICATION Warning or shut off systems This invention concerns warning or shut off systems in particular for use in conjunction with gas fired heating appliances.

One problem with gas fired appliances is that an inadequate air supply results in incomplete combustion of the gas and hence the formation of carbon monoxide as a combustion product. Carbon monoxide has no detectable smell but is extremely poisonous. Often an inadequate air supply is caused because the flue of the appliance is blocked. Airflow through the appliance is not, therefore, as it should be and so incomplete combustion occurs. Other causes of inadequate combustion may be a blockage in the appliance itself or just even inadequate room ventilation.

When the hot combustion products of the gas cannot escape properly through the flue there is an increase in temperature in the appliance and I have made proposals in my patent application No.

21 3441A for utilising the heat from the hot combustion products to operate a warning system comprising a mechanism sensitive to temperature increase, which mechanism can actuate a warning means. The warning means can be an alarm, such as a bell, or can merely shut off gas supply. Preferably the warning system comprises a temperature change detection device which has a part sensitive to temperature change such that at a desired temperature the part changes configuration, for example, lengthens or shortens, sufficiently to allow or cause movement of a member adjacent or connected thereto, movement of that member actuating a warning means. The part sensitive to temperature change is preferably a shape memory alloy member, say in the form of a coil.

Various warning/shut off systems were proposed in my application but I have now developed what may be more efficient and effective systems which are the subject of the present application.

In my earlier application I proposed incorporating in the gas supply line a shut off valve biassed to closing but held open by a mechanism including a shape memory alloy coil. A rise in temperature would cause the coil to expand and release that part of the mechanism holding the valve open. Alternatively the valve was biassed to closing but the shape memory alloy coil released a weight that acted on the valve to close it.

Reliance on a valve biassed by a spring to closing is not entirely satisfactory especially as it is likely to be several years after installation that the warning system is needed to operate. The valve could by then have become stuck in an open position or the spring may have weakened so that closing of the valve is not entirely effective.

The use of a weighted system to close a valve is unfortunately rather cumbersome and could actually operate because of strain. Also, a gas appliance including such a system would be unduly heavy.

I now propose that a fuel shut off system include a diaphragm type valve, wherein change of configuration of a heat sensitive member can act on the diaphragm to close the valve.

In such a system for a gas fire, the heat sensitive member may be positioned in a part of the fire that will become hotter if exhaust gases are not escaping properly, such as in front of the canopy above the gas fire radiants, or may be positioned in generally cool areas of the fire but have heat transferred or conducted thereto from a part of the fire that becomes hotter if exhaust gases are not escaping properly. For the former, it is advantageous to shield the heat sensitive member against contact with metal parts of the fire, which will usually always be hot. For the latter a rod or strip of conductive material, such as copper, may be situated in the fire so that one end is in such hotter situation and its other end is adjacent the heat sensitive member.

Alternatively, some of the hot exhaust gases not escaping from the flue may be directed to the heat sensitive member via a tube which is preferably wholly or partly of a relatively low conductivity material, such as stainless steel.

As well as being shielded say by reflective sheeting, the heat sensitive member may advantageously be in a ventilated position say provided by louvred openings in a side of the gas fire.

Preferably the heat sensitive member is a shape memory alloy member, such as coil. Such a coil could be held on the end of a conductive rod or bar so that heat conducted to the coil will cause it to expand or lengthen. That expansion can be used to release a cable that holds a diaphragm valve open.

A suitable mechanism for releasing the cable comprises a sleeve about the coil which sleeve when the coil is unexpanded holds the end of the cable by a detent type system but when the coil expands releases the detent system and hence the cable.

The cable in turn can in its normal state be used to hold a diaphragm of a diaphragm valve so that gas flow through the valve is allowed. In diaphragm valves gas flow can be controlled by a plunger connected to the diaphragm, which plunger can seat in a passage through the valve to stop gas flow, the position of the plunger depending upon the position of the diaphragm . The position of the diaphragm is usually spring controlled so that more or less gas is allowed through depending upon the pressure in order to even out the flow of gas.

Thus in its normal state the intermediate mechanism will permit the normal function of the diaphragm valve to continue but upon release of the cable that mechanism operates to seat the plunger in the valve passage to prevent further gas flow.

The diaphragm shut off system described herein may have more general application than in connection with gas fires but in any situation where fuel supply shut off or control may be required. Thus, the system may be used in connection with oil fired systems for controlling or shutting off oil supply.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows the first part of a gas supply shut offsystem suitablefora gas fire; Figure 2 shows the second part of the system; and Figure 3 shows the third part of the system.

Referring to the drawings, a gas fire has a bar 12 of copper positioned in its canopy above the radiants and extending across to one side of the radiants where it bends downwards and ends in a narrower portion 14. Aboutthe narrower portion 14 is a shape memory alloy coil 16 enclosed within a sleeve 18.

The coil 16 is prevented from moving downwards by a pin 20 through the end of bar 12.

The sleeve 18 has indents 22 in its inside surface to receive balls 24. These balls 24 also sit in indents 26 of a member 28 secured on the end of a cable 30.

That member 28 is also free to slide in a sleeve 32 screw threadedly held in a cable guide 34.

The cable 30 is connected to the upper end of a lever 36 pivotally mounted at its other end in a vertical position. The lever 36 has lug 38 that holds down a ring 40 fixed about another cable 42. The ring 40 presses on a spring 44 that tends to urge the ring 40 upwards. The lever 36 is also connected at its upper end to a coil spring 46 that acts against the cable 30 tending to pivot the lever so that the lug 38 releases the ring 40.

The cable 42 is connected via spring (53) loaded diaphragm 48 to plunger 50 of diaphragm valve 52.

The plunger 50 controls the amount of gas passing through the valve according to its position relative to seating 54. The usual operation of the diaphragm is to move the plunger according to the pressure of gas flowing through the valve so that an even pressure is attained.

However, if the gas fire has its flue blocked or escape of exhaust gases is hampered in some way so that the temperature within the fire rises, the bar 12 will become hot. The heat is conducted along the bar to the shape memory alloy coil 16. The coil 16 expands and moves the sleeve 18 so that the balls 24 are released. The member 28 and cable 30 are thus released and in turn the lever 36 pivots so that the ring 40 is no longer held down by the lug 38. The spring 44 urges the ring 40 upwards and hence pulls the plunger 50 into its seating to preventfurther passage of gas.

In this way the gas supply for a gas fire or any other gas fired appliance can be stopped to prevent release to a room of poisonous fumes that occurs when the escape of combustion products is hampered.

Whilst the invention has been described with reference to gas fires, it may also be applicable to any gas fired appliance.

Claims

1. Afuel supply shut off system comprising a diaphragm type valve and a heat sensitive member, wherein change of configuration of the heatsensi- tive member acts on the diaphragm to close the valve.

2. A system as claimed in claim 1, wherein the heat sensitive member is a shape memory alloy member.

3. A system as claimed in claim 2, wherein the heat sensitive member is a shape memory alloy coil.

4. A system as claimed in claim 1,2 or 3, wherein the valve has a plunger connected to the diaphragm, which plunger can seat in a passage through the valve to stop fuel flow, the position of the plunger depending upon the position of the diaphragm.

5. A system as claimed in claim 4, wherein the position of the diaphragm is usually spring controlled so that more or less fuel is allowed through depending upon thepressure thereof in order to even out fuel flow.

6. A fuel supply shut off system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A gas fire incorporating in its fuel supply line a a fuel supply shut off system as claimed in any one of claims 1 to 6.

8. A gas fire as claimed in claim 7, wherein the heat sensitive member is positioned in a part of the fire that will become hotter if exhaust gases are not escaping properly.

9. A gas fire as claimed in claim 8, wherein the heat sensitive member is in front of a canopy above the gas fire radiants.

10. A gas fire as claimed in claim 8 or 9, wherein the heat sensitive member is shielded against contact with metal parts of the fire.

11. A gas fire as claimed in claim 10, wherein said shieiding comprises reflective sheeting.

12. A gas fire as claimed in claim 10 or 11, wherein the heat sensitive member is also in a ventilated position.

13. A gas fire as claimed in claim 7, wherein the heat sensitive member is positioned in a generally cool area of the gas fire but has heat transferred or conducted thereto from a part of the fire that becomes hotter if exhaust gases are not escaping properly.

14. A gas fire as claimed in claim 13, wherein a rod or strip of conductive material has one end in said part of the fire that becomes hotter and the other end adjacenttothe heat sensitive member.

15. A gas fire as claimed in any one of claim 7 to 14, wherein expansion of the heat sensitive member causes release of a cable that holds the diaphragm valve open.

16. A gas fire as claimed ih claim 15, wherein the mechanism for releasing the cable comprises a sleeve about the heat sensitive member, which sleeve when the member is unexpanded holds the end of the cable by a detent system but when the member expands releases the detent system and hence the cable.