WO1998038460A1

WO1998038460A1 - Improvements in and relating to catalytic gas burners

Info

Publication number: WO1998038460A1
Application number: PCT/IE1998/000014
Authority: WO
Inventors: Derek William Butler
Original assignee: B S TECHNOLOGY Ltd
Current assignee: B S TECHNOLOGY Ltd
Priority date: 1997-02-27
Filing date: 1998-02-23
Publication date: 1998-09-03
Anticipated expiration: 1999-08-27
Also published as: AU6633098A

Abstract

A thermostat (15) for a catalytic gas burner (1) where the thermostat is an in-line device controlling delivery of gas from a gas storage chamber to a discharge nozzle (3, 4) without the use of linkages, through a piston-valve assembly (20, 23).

Description

"Improvements in and relating to catalytic σas burners"

The present invention relates to catalytic gas burners and in particular to ignition control for such gas burners.

Such catalytic gas burners are generally of the type comprising: -

a gas storage chamber;

a gas delivery valve in the gas storage chamber;

an air inlet;

a gas/air discharge nozzle;

an ignition device downstream of the nozzle;

a thermostat connected to the gas delivery valve and adjacent the nozzle; and

a catalyst downstream of the nozzle.

Such catalytic gas burners are used extensively for soldering irons, glue guns, hair curling tongs, lamps, heaters, etc. Generally, the thermostat is some form of bi-metallic strip which is connected by means of linkages to the gas delivery valve. Known thermostats have a considerable number of moving parts and linkages and are not particularly accurate. A problem thus arises due to the need to provide a relatively simple and inexpensive thermostatic valve. This is particularly problematic in that the unit must be robust and produced with sufficient tight tolerances for accuracy. A further problem arises during use in that, due to the number of levers and other connectors used, distortion and wear further reduces accuracy. A further problem is that during use it can be difficult to accurately adjust the thermostat to take account of wear.

The present invention is directed towards providing an improved construction of thermostat for such gas burners, a better construction of thermostatically controlled shut off valve for such gas burners and finally a more efficient construction of gas burner.

The invention is characterised in that the thermostat is an in-line device directly connected to the gas delivery valve.

The advantage of this is that linear movement of the thermostat acts directly on the gas delivery valve thus obviating the need for linkages and providing the minimum number of moving parts, namely, the movement of the thermostatic valve itself and the movement of the valve, both of which occur in all other forms of gas burner. The invention thus eliminates all other linkages and moving parts .

Ideally the thermostat incorporates a bi-metallic strip in the form of a composite disc for surrounding portion of the gas/air discharge nozzle. This is a particularly suitable way of sensing directly the heat and at the same time allowing the bi-metallic strip to move linearly in line with the nozzle and once the gas delivery valve is in line with the nozzle then linear movement of the bimetallic strip in the form of a disc moves the valve.

Ideally in this latter embodiment, the valve is in the form of a piston directly movable by the disc into and out of engagement with an orifice forming a gas exit from the gas storage chamber.

Further, the invention provides a thermostatically controlled shut-off valve for a gas burner of the type hereinbefore described, comprising:

a valve linearly movable between an open and closed position; and

a bi-metallic strip directly connected in line with the valve.

Additionally, the invention provides a catalytic gas burner comprising:

an elongated hollow gas burner body, closed at one end by a gas nozzle assembly feeding a catalyst and at its other end closed by an end plate carrying an inlet orifice communicating with the gas storage chamber;

a piston having a bore and at one end slidably engaging portion of the nozzle assembly within the gas burner body with its bore communicating with the nozzle assembly and at its other end slidably engaging in a gas type manner with a chamber communicating with the inlet orifice, the piston carrying an end face seal covering its bore and engagable with the orifice and the bore having a radially arranged hole, connecting the bore to the interior of the chamber; and

a bi-metallic strip in the form of a washer-like disc mounted on the nozzle assembly between it and the other end face of the piston. This is a particularly suitable form of gas burner, it has the minimum number of moving parts and it can be manufactured relatively cheaply and in particular requires the minimum modification to existing equipment to provide it since many of the parts at present used in such gas burners, may be readily easily adapted to provide this gas burner.

The invention will be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings in which :-

Fig. 1 is a cross-sectional view of portion of a gas burner in a working position;

Fig. 2 is a sectional view similar to Fig. 1 showing gas cut-off by its thermostatic valve;

Fig. 3 is a cross-sectional view, in which sectional lines are omitted and which shows in more detail most of the gas burner according to the invention in the totally shut-off position;

Fig. 4 is a view similar to Fig. 3 showing the gas burner in the normal operating position;

Fig. 5 is a view similar to Figs. 3 and 4 showing the gas burner in the initial ignition position;

Fig. 6 is a view similar to Figs. 3 to 5 showing the gas burner operating with the gas cut-off by the thermostatic; Fig. 7 is a view of the total gas burner illustrated in Figs. 1 to 6 forming part of a glue gun; and

Fig. 8 is a view of another glue gun incorporating an alternative gas burner in accordance with the invention.

While springs, levers, knobs, catalysts, etc. all form part of the burner for a clear understanding of the major features of the burner reference is first made to Figs. 1 and 2 where there is illustrated portion of a catalytic gas burner indicated generally by the reference numeral 1 having an elongated hollow gas burner body 2 closed at one end by a gas nozzle assembly 3 incorporating a conventional gas jet 4. The gas nozzle assembly 3 incorporates a bore 4a which communicates between the gas jet 4 and the interior of the gas burner body 2. The gas jet 4 feeds the catalyst as will be described hereinafter. The gas burner body 2 is closed at its other end by an end plate 5 carrying a plug 6 which in turn carries a spigot 7 for engagement with a gas storage chamber formed by a gas cylinder. The plug 6 is threaded to engage a corresponding internal thread on the plate 5. Radial rotation of the plug 6 is used to vary the temperature of the burner. The spigot 7 is of conventional construction. The plug 6 has a conduit 8 terminating in an inlet orifice 9 which communicates with a chamber 10 in the plug 6. The gas nozzle assembly 3 carries a bi-metallic strip in the form of a bi-metallic disc 15, a two-part piston indicated generally by the reference numeral 20 is mounted within the gas burner body 2.

The piston 20 has a bore 21 and the piston 20 slidably engages over the gas nozzle assembly 3 and against the bimetallic disc 15, the bore 21 communicating directly with the bore 4a in the gas nozzle assembly 3. The other end of the piston 20 slidably engages within the chamber 10. An O-ring 22 ensures that the piston 20 engages within the chamber 10 in a gas-tight manner.

An end face seal formed by a nitrile plug 23 is formed in the bore 21 within the chamber 10. The chamber 10 communicates with the bore 21 through a radial hole 24. An air intake formed by a venturi 25 is provided in the bore 21.

While the remainder of the catalytic gas burner 1 and its operation will be described in more detail, it is useful to consider briefly the operation of this portion of the catalytic gas burner 1.

In the normal operating position as illustrated in Fig. 1, the bi-metallic disc 15 is in the retracted position and the piston 20 is lying such that the nitrile plug 23 is spaced apart from the inlet orifice 9 and thus gas will flow through the conduit 8 into the chamber 10 through the holes 24 and down the bore 21 where air will be drawn through the venturi 25 such that an air/gas mix is then delivered down the remainder of the bore 21 into the bore 4a and out the gas nozzle assembly 3.

As the temperature rises the bi-metallic disc 15 will begin to move forcing the piston 20 to the right in Figs. 1 and 2 initially restricting somewhat the flow of gas out the conduit 8 until it fully seals against the inlet orifice 9 shutting off the gas as illustrated in Fig. 2.

It will be appreciated that flow of gas may not be always completely halted but significantly reduced. The operation being more easily equated with an analogue temperature sensing device. Referring now to Figs. 3 to 6 , more of the catalytic gas burner 1 is illustrated. Mounted between the gas burner body 2 and the plug 6 is an adjustment ring 30 which can move the plug 6 into and out of the gas burner body 2. This may be achieved by, for example, having interengagable threads on the end plate 5 and plug 6 to control the distance between the inlet orifice 9 and the nitrile plug 23, thus controlling flow of gas from the conduit 8. A gas storage chamber formed by a conventional pressurised gas cylinder 31 is shown mounted on the spigot 7. A conventional piezo igniter unit 35 is mounted on the gas burner body 2 and is operated in conventional manner by an operating plunger 36. An on-spring 40 is mounted between the plug 6 and the piston 20 to bias the nitrile plug 23 away from the inlet orifice 9. An off-spring 41 is mounted between the gas nozzle assembly 3 and the piston 20, through a lever 42. The off-spring 41 is stronger than the on-spring 40 and thus naturally keeps the gas shut-off. A rocker arm 45 is mounted off and around the gas burner body 2 and is operated by a conventional switch 46. The switch 46 has three positions, namely an OFF position, an ON position and a fully forward ignition position.

In operation, Fig. 3 illustrates the switch 46 totally retracted in the OFF position and the off spring 41 acting to force the nitrile plug 23 hard against the inlet orifice 9 to shut off all gas. The switch 46 is then moved to the position illustrated in Fig. 4 and the lever 42 is moved against the off-spring 41 so that the piston 20 lifts under the influence of the on-spring 40 off the inlet orifice 9. It should be noted that the on-spring 40 is probably unnecessary in that the pressure of gas within the gas cylinder 31 would probably be sufficient to lift the piston 20. For ignition the switch 46 is pushed to its third position so that the rocker arm 45 engages the plunger 36 and the piezo igniter unit will ignite the gas being delivered out the gas nozzle assembly 3 through the gas jet 4. This is illustrated in Fig. 5. Once the ignition takes place, the switch 46 is retracted to the position illustrated in Fig. 4 and the catalytic gas burner 1 will continue to operate as long as the catalyst temperature does not fall below "light off" temperature.

As ignition continues, the bi-metallic disc 15 will expand and gradually push the piston 20 towards the inlet orifice 9 until the critical temperature is reached as illustrated in Fig. 6 when the bi-metallic disc 15 has expanded sufficiently to force the nitrile plug 23 toward the inlet orifice 9 restricting the flow of gas until the temperature falls sufficiently for the bi-metallic disc to contract somewhat and allow the nitrile plug 23 to move away from the inlet orifice 9. Thus, the catalytic gas burner 1 will operate generally intermediate the positions illustrated in Figs. 4 and 6. Obviously the nitrile plug 23 may be used to partially restrict the flow of gas or to prevent all gas flowing depending the expansion of the bimetallic disc 15 and its position as dictated by the adjustment ring 30.

When it is desired to increase or decrease somewhat the temperature the adjustment ring 30 may be used. It will be noted that the bi-metallic disc 15 in this way operates as a heat sensitive spring.

Referring to Fig. 7 the catalytic gas burner 1 is illustrated mounted in a glue gun 50 having a glue heating chamber 51, a catalyst 52 and a conventional glue stick dispenser 53. Referring to Fig. 8, there is illustrated another glue gun 60 in which similar parts are identified by the same reference numerals generally. In this embodiment, the igniter unit 35 is reversed but operates generally as previously described. The spigot 7 and conduit 8 are connected to an outlet nozzle 61 of the gas cylinder 31 with a flexible hose 62. This arrangement beneficially allows the through flow of gas without the need for a direct connection, thereby improving the robustness of the unit as the connection cannot be broken or damaged if the unit is dropped.

It will be appreciated that the functions of the on-spring 40 and the off-spring 41 may be achieved in many ways including using the pressure of the gas housed in the cylinder 31.

It will be appreciated that while specific reference is made throughout to the use of the invention with gas burners using a catalyst it may be used in any application where thermostatic control of a burner using gas is required. For example, in the manufacture of soldering irons, hair curlers or any other similar device. As a result of the improved accuracy and reliability of the controls described it is possible to restrict gas flow to control burning temperature in such devices.

It will further be appreciated that the plug may be tapered to a needle point for interaction with the inlet orifice or otherwise shaped to improve control of the volume of gas supplied.

The invention is not limited to the embodiment hereinbefore described which may be varied in both construction and detail.

Claims

1. A thermostat for a catalytic gas burner of the type comprising:

a gas storage chamber;

a gas delivery valve in the gas storage chamber;

an air inlet;

a gas/air discharge nozzle;

an ignition device downstream of the nozzle;

a thermostat connected to the gas delivery valve and adjacent the nozzle; and

a catalyst downstream of the nozzle:

characterised in that the thermostat is an in-line device directly connected to the gas delivery valve.

2. A thermostat as claimed in claim 1, wherein the thermostat incorporates a bi-metallic strip in the form of a composite disc.

3. A thermostat as claimed in claim 2, wherein the composite disc is formed to surround portion of the gas/air discharge nozzle.

4. A thermostat as claimed in claims 2 or 3 , wherein the gas delivery valve is in the form of a piston.

5. A thermostat as claimed in claim 4, wherein the piston is directly movable by the disc into and out of engagement with an orifice forming a gas exit from the gas storage chamber.

6. A thermostatically controlled shut-off valve for a gas burner comprising:-

a valve linearly movable between an open and closed position; and

a bi-metallic strip directly connected in line with the valve.

7. A catalytic gas burner comprising: -

a bi-metallic strip in the form of a washer-like disc mounted on the nozzle assembly between it and the other end face of the piston.