WO1994001722A1

WO1994001722A1 - Fail-safe valve responsive to flame failure and flaring

Info

Publication number: WO1994001722A1
Application number: PCT/AU1993/000348
Authority: WO
Inventors: Joseph Patric Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-07-13
Filing date: 1993-07-13
Publication date: 1994-01-20
Anticipated expiration: 1995-01-13

Abstract

The present invention relates to a fluid flow control device which is particularly adapted for use with domestic gas appliances, such as domestic gas cookers. In a fluid flow control device in accordance with the present invention, an excess flame sensor is provided positioned proximate to a fluid burner and arranged to determine whether 'flaring' of the burner flame is occurring (such as may occur due to hot oil spillage, for example). On the occurrence of excess flame, a safety valve in the device is actuated to cut off fluid flow to the burner. Further, a heat sensor is also provided to detect the existence of flame at the burner. In the absence of flame, the safety valve is also actuated to cut off fluid flow to the burner.

Description

FAIL-SAFEVALVERESPONSIVETOFLAMEFAILUREANDFLARING

The present invention relates to a fluid flow device, particularly, but not exclusively, for control of fluid flow to gas burners and gas burning appliances, domestic or otherwise.

In any fluid burning appliance a dangerous situation will arise if the flame is extinguished and fluid flow is maintained. For example, subsequent attempted re-ignition of the flame following a long period of fluid flow could result in an explosion.

Another type of dangerous situation arises if "excess flaming" occurs from the fluid burner. This can be a fire hazard.

In domestic appliances, for example, such as home gas cookers, the gas flame can be extinguished due to boiling over of fluid from a utensil, for example. If fluid flow is subsequently maintained, the dangerous condition discussed above arises. Further, excess flaming can occur due to spillage of hot oil, for example, leading to a possible fire hazard.

Prior art attempts have been made to provide safety mechanisms to cause gas flow to be terminated in the absence of a flame from a gas burner. One such safety mechanism is disclosed in U.S. Patent 5094259 (Hsu) . This mechanism incorporates a safety valve and an electromagnetically operated armature. In the absence of flame and the presence of gas flow, the armature is actuated to enable the safety valve to close, cutting off gas flow. This mechanism is, however, unsatisfactory, as it is the absence of flame condition which causes actuation of the electromagnetic armature. If, for some reason, the electromagnetic circuit fails, then the safety valve mechanism will not operate and fluid flow will continue even in the absence of flame. Further, this safety mechanism has no facility for preventing danger due to an excess flame condition.

The present invention provides a fluid flow control device, comprising a valve assembly for controlling fluid flow from a fluid source to a fluid burner, manually operable control means for operating the valve assembly to enable fluid flow to the burner, and detection and control means for monitoring operation of the fluid burner, wherein the valve assembly comprises a safety valve mechanism which is responsive to the detection and control means determining non-optimum operation of the burner to cause fluid flow to the burner to be discontinued, the safety valve mechanism being a fail-safe mechanism.

By "optimum" operation is meant operation where a flame is burning within safe limits, i.e. the flame is not absent and it is not "flaring" (excess flame) and creating a fire hazard.

By "fail-safe" operation is meant that the safety valve mechanism fails in a safe position, i.e. should the mechanism or associated control arrangements fail, then fluid flow will automatically be discontinued. The safety valve mechanism preferably comprises a safety valve movable between an OPEN position, in which fluid flow to the fluid burner may occur, and a CLOSED position in which fluid flow to the burner will not occur. Preferably, as long as a flame is burning and is not an excess flame, the safety valve will remain in its OPEN position. The safety valve is preferably associated with electromagnetic control means arranged to be energised as long as a flame is present and no excess flaming is occurring, to maintain the valve OPEN. De-energisation of the electromagnetic control means results in closure of the safety valve. Alternative means may be used to control the safety valve, other than electromagnetic control means. The detection and control means preferably comprises a heat sensor for detecting the existence of a flame at the fluid burner or a thermocouple which is responsive to flame to energise the electromagnetic control means to maintain the safety valve in its OPEN position.

To detect excess flaming, the detection and control means preferably comprises a heat sensitive switch, arranged to cause de-energisation of the electromagnetic control means on the detection of excess flame, to cause the safety valve to CLOSE. Whether or not an "excess flame condition" has occurred is preferably determined by an adjustable threshold of the excess flame switch. One way of adjusting the threshold is to have the excess flame switch on a mobile mounting so that it can be moved to a predetermined distance from the fluid burner. For example, the further away from the fluid burner the excess flame switch is, the higher the threshold and the more excess flame will be necessary to cause the safety valve to be closed. In one embodiment of the invention, directed to a gas cooker, the excess flame switch is mounted to an adjustable slide and a projecting member is provided, arranged to abut against a pan or other implement placed on the fluid burner. The larger the diameter of the pan or of the implement, the further away from the fluid burner would be the position of the heat sensitive switch.

The manually operable control means preferably comprises a manually operable switch, in the form of either a push button switch or a push and rotate switch (of the type generally used on conventional gas ovens, for example) .

In one embodiment of the invention, where the manually operable control is a push button, actuation of the control (e.g. pushing the button in) operates a mechanical linkage which causes the safety valve to be opened. In this simple arrangement, the safety valve also acts as a main valve for enabling fluid flow to the burner, i.e. operation comprises a simple ON/OFF step. There is no facility enabling adjustment of the valve between the OPEN and CLOSED positions to enable regulation of fluid flow. The push button, on operation, actuates a flame rectification switch to cause ignition of the burner. A heat sensor proximate the burner and associated control circuit is responsive to the existence of flame to maintain the safety valve in the OPEN position (e.g. by energising an electromagnetic control means) .

In alternative embodiments, the valve assembly preferably includes a pair of valves, being the safety valve and a main fluid flow control valve. A rotatable control knob is provided as the manually operable control means. In some embodiments, a mechanical linkage is provided between the control knob and the safety valve. The control knob is movable between a first and a second position (usually pushing the control knob in from an extended position) to actuate the mechanical linkage to cause the safety valve to be opened. Subsequent movement of the knob from the second position towards a third position (e.g. rotation of the knob) opens the main fluid flow control valve to enable fluid to flow to the fluid burner. At the same time, a heat rectification switch is actuated to cause ignition of the burner. A heat sensor proximate the fluid burner and associated electromagnetic control means is responsive to the existence of flame to maintain the safety valve in the OPEN position. In other embodiments, no mechanical linkage is provided between the control knob and safety valve. In these embodiments, the action of fluid pressure following opening of the main fluid control valve operates the safety valve to move it to the OPEN position. The OPEN valve is then maintained in the OPEN position responsive to the detection and control means.

In some arrangements, a problem may arise if it is possible to re-open the safety valve following operation due to a fault, while the main valve is still open. If there is high pressure in the fluid line this could lead to a rush of fluid to the burner, resulting in a possibly dangerous situation. To avoid this danger, in preferred embodiments, precautions are taken to ensure that, following operation of the safety valve, the main fluid flow valve must first be closed before the safety valve can be re-opened. In one embodiment, the arrangement is such that, following operation of the safety valve, fluid pressure on the safety valve maintains the safety valve, in the closed position notwithstanding any operation of a mechanical linkage between the control valve and the safety valve, until the main valve is first returned to a closed position, enabling release of the "back" fluid pressure on the safety valve. In other embodiments, the safety valve is fluid-operated (as discussed in the preceding paragraph) and cannot be opened until the main valve is first closed.

From a further aspect, the present invention provides a fluid flow control device, comprising a valve assembly for controlling fluid flow from a fluid source to a fluid burner, manually operable control means for operating the valve assembly to enable fluid flow to the burner, and excess flame detection and control means for detecting the occurrence of excess flame from the fluid burner, wherein the valve assembly comprises a safety valve mechanism, the safety valve mechanism being responsive to the excess flame detection and control means detecting that excess flame is occurring to cause fluid flow to the burner to be discontinued.

In domestic appliances, for example, the excess flame sensor may reduce the possibilities of a fire hazard by operating to cut off fluid flow following "flaring" of a flame due to a hot oil spill, for example. Preferably the safety valve mechanism is fail-safe. Preferably the excess flame sensor has an operating threshold at which it causes the operation of the safety valve mechanism to cut off fluid flow. Preferably, this threshold is adjustable. In one embodiment, the excess flame sensor is mounted on a movable mounting and the threshold is adjusted by varying the distance of the excess flame sensor from the fluid burner. The flame sensor mounting may be provided with a projection for abutting implements placed on the fluid burner, such that the larger the diameter of the implement the further away from the burner is the excess flame sensor. The excess flame detection and control means preferably comprises a heat sensitive switch and associated control circuitry for controlling the safety valve mechanism.

Embodiments of a fluid flow control device in accordance with this aspect of the invention may also include any or all of the features discussed above in relation to the first aspect of this invention.

The present invention yet further provides a fluid flow control device, comprising a valve assembly for controlling fluid flow from a fluid source to a fluid burner, a manually operable control means for operating the valve assembly to enable fluid flow to the fluid burner, a flame sensor for detecting the existence of flame at the fluid burner, an excess flame sensor for detecting the occurrence of excess flame from the burner, the valve assembly comprising a safety valve mechanism which is responsive to the flame sensor detecting the absence of flame to cause fluid flow to the burner to be cut off and is responsive to the excess flame sensor determining excess flame to cause fluid flow to the burner to be cut off, a manually operable control means comprising a single manually operable control operable to initiate the safety valve mechanism to move a safety valve of the safety valve mechanism from a CLOSED to an OPEN position, to cause fluid flow to the fluid burner and to initiate flame ignition by means of a heat rectification switch actuated by the manually operable control, the flame sensor being responsive to the existence of flame to operate a control circuit to maintain the safety valve in the OPEN position until such time as there is an absence of flame or excess flame. Embodiments of this aspect of the invention may include any or all of the features discussed above in relation to the first two aspects of the present invention.

Features and advantages of the present invention will become apparent from the following description of embodiments thereof, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a generalised embodiment of the present invention intended for application in a domestic gas appliance; Figure 2 is a section through a valve and manual control assembly for a fluid flow control device in accordance with an embodiment of the present invention;

Figure 3 is a section through a safety valve mechanism of the assembly of Figure 2, showing a safety valve in a closed position and also showing a variation of an outlet of the assembly from that of Figure 2;

Figure 4 is a section through a valve and manual control assembly in accordance with a further embodiment of the present invention; Figure 5 is a section through a safety valve mechanism of the assembly of Figure 4, showing a safety valve in a closed position and showing a variation of the fluid outlet of the assembly from that of Figure 4;

Figure 6 is a side elevation of a fluid burner for embodiments of the fluid flow control device in accordance with the present invention, illustrating the fluid burner in association with ignition and sensor devices;

Figure 7 is a further side elevation of a fluid burner for use with embodiments of the present invention, illustrating alternative ignition and sensor devices;

Figure 8 is a diagram for illustrating operation of a cam arrangement for a mechanical linkage between a manually operable control and valve assembly, which is used in embodiments of the present invention;

Figure 9 is a diagram for illustrating operation of a manually operable rotary main valve means used in embodiments of the present invention; Figure 10 is a section through a valve and manual control assembly for a fluid flow control device in accordance with a further embodiment of the present invention; Figure 11 is a section through a valve assembly which may be used in embodiments of the present invention;

Figure 12 is a section through a further valve assembly which may be used in embodiments of the present invention;

Figure 13 is a section through a valve and manual control assembly for a fluid flow control device in accordance with yet a further embodiment of the present invention; Figure 14 is a section through a safety valve mechanism of the assembly of Figure 13, illustrating a safety valve in an open position and illustrating a variation of the fluid outlet of the assembly from that of Figure 13; Figure 15 is a plan view of the valve and manual control assembly of Figure 13;

Figure 16 is a section through a part of the assembly shown in Figure 15;

Figure 17 is a diagram for illustrating the operation of a rotary main valve means of the embodiment of Figure 13;

Figure 18 is a detail view of a safety valve for use with the embodiment of Figure 13;

Figures 19-25 are schematic circuit diagrams of electrical circuits employed in embodiments of the present invention;

Figure 26 is a section through a valve and manual control assembly for use with a fluid control device in accordance with yet a further embodiment of the present invention;

Figure 27 is a section through a valve and manual control assembly for use with a fluid control device in accordance with yet a further embodiment of the present invention;

Figure 28 is a section through a valve and manual control assembly for use with a fluid control device in accordance with yet a further embodiment of the present invention;

Figure 29 is a detailed section of a gear arrangement for operation of a valve assembly in accordance with a further embodiment of the present invention; Figure 30 shows details of a safety valve for use with an embodiment of the present invention illustrating operation of the safety valve;

Figure 31 is a cross-section through the safety valve of Figure 31; Figure 32 is a section of a valve and manual control assembly for use with a fluid control device in accordance with yet a further embodiment of the present invention;

Figures 33 and 34 are diagrams illustrating operation of a safety valve mechanism of the embodiment of Figure 32;

Figure 35 is a detail of a safety valve which may be used -in embodiments of the present invention;

Figure 36 is a diagram of a four-burner top-plate for a domestic stove, indicating the positions of sensor mounts;

Figure 37 shows a first embodiment of an excess flame sensor mount in accordance with the present invention; and Figure 38 shows a second embodiment of an excess flame sensor mount in accordance with the present invention.

Referring firstly to Figure 1, description will be given of a generalised embodiment of a fluid flow device in accordance with the present invention. Figure 1 schematically illustrates a fluid flow device intended for use with a domestic gas appliance, such as a gas cooker, for example. Conduits 10 and 11 are gas flow conduits for providing gas from a gas source 15 (such as the domestic "mains", for example) to a gas burner 2. A main valve/safety valve assembly 1 is arranged to govern the flow of gas to the burner 2. The main valve/safety valve assembly 1 is controlled by way of controlling linkage 4 and manually operable control means 5 (e.g. comprising the "knob" of a domestic gas stove) . Also provided are a heat rectification switch 6 which is connected to a power supply 12, and which is arranged to initiate operation of the igniter 7 in response to operation of the control switch 5. A heat sensor 13 and excess flame sensor 9 are also provided connected to power supply 13 and safety valve control unit 3.

In operation, a user of the appliance operates means 5 to actuate linkage 4 to operate the main valve/safety valve assembly to open the valves and allow flow of fluid from conduit 10 through conduit 11 to burner 2. At the same time, operation of means 5 causes heat rectification switch 6 to operate the igniter 7 to cause a spark to ignite gas flowing from burner 2. On ignition, heat sensor 13 detects the existence of a flame and safety valve control unit 3 is responsive thereto to maintain a safety valve in the assembly 1 in an OPEN position to maintain fluid flow to the burner 2. Should flame from the burner 2 be extinguished, for example if a utensil boils over, sensor 13 will detect there is no flame and unit 3 will respond to that information to cause the safety valve in the assembly 1 to close, cutting off fluid supply. It will be appreciated that this is a feedback mechanism. Fluid supply to the burner is only maintained as long as the flame exists at the burner 2.

Further, should "flaring" of the burner 2 flame occur, due to a hot oil spill, for example, this excess flame will be detected by the excess flame sensor 9, which will cause unit 3 to cause the safety valve to close.

This embodiment therefore operates to ensure, that firstly, gas flow to the burner is only maintained when a flame exists and, secondly, gas flow to the burner is cut off should excess flame occur.

Figure 2 is a sectional view of a valve assembly generally designated by reference numeral 20 and a control knob and linkage assembly 21 for operating the valve assembly 20. The valve assembly 20 comprises a unitary valve assembly body 22 which mounts a safety valve mechanism 23 and a main valve assembly 24. The valve assembly 20 controls the flow of fluid (e.g. domestic gas) from fluid supply 25 through conduit 26, main valve assembly 24, conduit 27, safety valve assembly 23, conduit 28, and through to exit conduit 29. The "arrows" in the figure illustrate the fluid flow path when the valve assembly 20 is open.

In Figure 2, the main valve assembly 24 is open, allowing fluid flow to conduit 20. Valve body 30 has been rotated to such a position that passage 31 is open and communicates with conduit 26 and conduit 27. Rotation of the valve body 30 away from this position, it will be appreciated, will tend to close valve passageway 31 off from passageway 26 and therefore shut off the fluid flow. This is a conventional arrangement for fluid flow appliances. Further, safety valve 32 is shown in the OPEN position such that conduit 27 communicates with passage 28.

Conduit 29 is, in operation, connected to a fluid burner such as shown in Figure 6 or Figure 7. In operation, therefore, when valve assembly 20 is open, fluid will flow to burner 40.

Figure 3 shows a partial view of Figure 2 showing the valve assembly 23 with the valve 32 in the CLOSED position. Figure 3 also shows a variation of the conduit 29. A "jet nozzle" 33 is provided in this variation.

Manual control and linkage assembly 21 comprise a manual control knob 34 which, in operation, is arranged to be moved inwards from an extended position (as shown in "ghost" outline) to an "inward" position and rotated to operate the valve assembly 20. The knob 34 is shown in the inward position in Figure 2. Such control knobs are conventional and are known on conventional gas cookers. A cam follower 35 is pushed inwardly against the force of spring 36 when the knob 34 is pushed in. These elements are conventional . When the cam follower 35 is pushed inwards it connects with extension portion 37 of main valve body 30 and subsequent rotation of knob 35 will cause the main valve body 30 also to rotate. The cam profile of the extension portion 37 is illustrated diagrammatically in Figure 8, which shows the cam profile in a linear diagrammatic form in relation to degrees of anticlockwise rotation of the knob 35.

The return spring 36 holds the cam follower 35 in an outward position against the cam profile. The cam profile has a safety and positioning function, i.e. if you bump it, it won't turn on. The knob 70 needs to be pressed to get over the cam.

Figure 9 is a diagram which illustrates the operating positions of the main valve 24 on anticlockwise rotation of the knob 34. After rotation of 30° passageway 31 becomes open to conduit 26 and gas flows through to passageway 29 and burner 40 is enabled (as long as safety valve mechanism 23 is opened - see later) . The area between 30° and 90° rotation of knob 34 is termed "flow 1". As in conventional domestic appliance gas control valves, the amount of passageway 31 opened to passageway 26 is adjustable depending upon the angle at which the knob 34 is set. At 90°, the valve 24 is fully opened allowing the maximum pressure of gas through to burner 40. Past 90°, gas flow through the main passage 31 and valve body 30 is cut off and a further, narrower passageway (not shown) , is opened to passageway 26 to provide a "simmer" function from burner 40. This narrow passageway is not shown in the drawing. It is conventional in the prior art. It should be noted that the cam operation of the knob 34 is such that after the knob has been pushed in and rotated to the desired position, on release it will return to the outward position, as shown in ghost outline.

Operation of the safety valve mechanism 23 is as follows. A push rod 50 is slidably mounted through the main valve body 30 and cam follower 35. "0" rings 51 mounted in the valve body 30 prevent fluid escaping along the push rod 50.

A knob 34 is slidably mounted on the cam follower 35. A first movement of the knob 34 towards the inward position drives the end of the cam follower 35 to contact the cam profile on extension portion 37. The end of the cam follower 35 is halted and a second consecutive movement to the inward position of knob 34 drives push rod 50 further into the valve assembly 20, against the action of spring 70 as the knob 34 slides over the outside of cam follower 35. A cam 52 on the end of push rod 50 engages a cam follower 53 on valve 32, raising the valve 32 to the OPEN position against the action of spring 54. When knob 34 has been turned to the desired position to open main valve 24 and has returned to the position indicated by the inner ghost outline, cam 52 disengages from cam 53 and, unless the valve 32 is maintained in the OPEN position, spring 54 will cause valve 32 to close.

Safety valve mechanism 23 further comprises an electromagnet arrangement 55 and armature 56 connected to valve 32. When the electromagnet 55 is energised, the armature 56 is attracted upwards and maintains the safety valve 32 in the OPEN position. Electromagnet 55 is connected by means of cable 57 to a heat sensor 58 (Figure 6) or thermocouple 59 (Figure 7) , excess flame sensor 60 (Figure 6) and associated power supply

(complete schematic diagrams of electrical circuits are shown in Figures 19 to 25 and will be referred to in more detail later) . In operation, therefore, knob 34 is initially pushed in so that safety valve 32 is raised against the action of spring 54. At the same time, heat rectification switch 61 is actuated by projecting rim 62 on knob 34. Switch 61 is connected by cables 63 to a power supply and 64 to an igniter 65 (Figure 6) . Igniter 65 is therefore activated. Whilst maintaining the knob 34 in its most inward position it is then rotated to open main valve 24 and thus enable fluid flow to burner 40. When fluid reaches the burner 40 it will be ignited. The appearance of a flame at burner 40 is detected by heat sensor 58. Circuit means 69 are responsive to the detection of flame by heat sensor 50 to energise electromagnet 55 to maintain the valve 32 in the OPEN position. When the knob 34 has been turned to the desired position, it is released and will return to the outward position. Cam 52 will then disengage cam follower 53.

In the burner illustrated in Figure 7, a pilot 66 is ignited at the same time as the burner.

An alternative to heat sensor 65 is thermocouple 59 (Figure 7) . This is heat responsive to cause electromagnet 55 to be de-energised. The pilot burner 66, is used to heat thermocouple 59 to its operating temperature. The use of a pilot burner means that the thermocouple 59 can be placed away from the burner 40, preventing damage to the thermocouple 59. An igniter 65 (not shown in Figure 7) would still be necessary to light both the pilot 66 and burner 40. The use of a pilot burner 66 to maintain the thermocouple 59 at its operating temperature, preferably results in an extension of the lifetime of the thermocouple 59.

Should the flame from burner 40 be extinguished, due to spillage or boiling over of liquid, for example, this will be detected by heat sensor 58 or thermocouple 59 and electromagnet 55 will be de-energised, causing valve 32 to close and shut off gas flow to burner 40. Further, should flaring of the flame occur due to, for example, spillage of hot-oil flame sensor 60 will be activated and electromagnet will be de-energised. As in the generalised embodiment of Figure 1, the excess flame sensor 60 may be placed in a mobile mounting to enable its distance from the burner 40 to be varied (and to thereby determine a "threshold" for excess flame) .

The fluid control device of Figure 2 is arranged so that it is not possible to reopen the safety valve 32, after it has closed in response to a fault condition, without first closing the main valve 24. Particularly in high pressure systems, there is the danger that if this were allowed it could lead to a fire hazard due to high pressure fluid suddenly reaching burner 40 with igniter 65 in operation (for example, where it is possible to press knob 34 inwards to lift safety valve 32 while main valve 24 is still open) . Fire hazard or even an explosion hazard could exist.

To avoid this danger, the embodiment of Figures 2 and 3 is arranged such that it is not possible to lift the safety valve 32 following its operation until knob 34 is returned to the 0° position and main valve 24 is therefore closed.

This is .achieved by utilising gas pressure present in passage 27 following operation of the safety valve 32 to maintain the safety valve 32 in the closed position. Following operation of the safety valve mechanism 23, if the user subsequently attempts to push knob 34 inwards to raise the safety valve without first returning the knob 34 to the 0° position, if the fluid pressure in passage 27 is high enough, valve 32 will be maintained in the

CLOSED position and it will not be possible to move the push rod further inwards.

To release the back pressure on the valve 32 and to enable its reactivation, a fluid bleed mechanism is provided. This comprises a bleed hole 71 in main valve body 30 which communicates with bleed pipe 72 which communicates with conduit 29 (bleed mechanism is not shown in Figure 3, but it is present) . Bleed hole 30 only communicates with bleed pipe 72 when the knob 34 is in the 0° position, (see Fig. 9) .

When knob 34 is returned to 0°, therefore, fluid pressure from passage 27 will be bled to passage 29 and the back pressure on the valve 32 will be released. The safety valve 32 may then be operated as normal, as discussed in the preceding sections.

A number of alternative embodiments of the present invention are illustrated in the other figures and are discussed in the following sections of this description. Where components of the alternative arrangements are, however, considered to be equivalent to components in the embodiments of Figures 2 and 3 , the same reference numerals have been used and their operation will not be described further. Only the operation of components which have important structural and/or functional differences will be referred to and described.

All the valve and manual control assemblies described are intended to be used with the burner, sensor and ignition assemblies of Figures 6 or 7. As well as the components described previously with respect to those Figures, the gas burners of Figure 6 and 7 also include a burner mount 80, a connecting nut 89, connect conduit 29, a main gas jet and air intake 81. Figures 19 through 25 illustrate schematically a number of electrical circuits for use with embodiments of the present invention. In all cases, reference number 40 indicates a fluid burner; reference numeral 65 indicates an igniter; reference numeral 61 is a flame rectification switch; reference numeral 63 indicates a cable leading to a power supply; reference numeral 59 is a thermocouple; reference numeral 60 is an excess flame sensor; reference numeral 55 is an electromagnet means; and reference numeral 90 is an electrical switch for operation of the solenoid by means of a manual control.

Figure 19 illustrates schematically an ignition circuit for embodiments of the present invention incorporating a heat rectification switch 61 connected to power supply 63 and operated by control knob 34 (or in some embodiments by a control button or switch - see later) and igniter 65 responsive to the switch 61 to create a spark. Figure 20 shows a circuit for operation of an electromagnet 55. Thermocouple 59 maintains energisation of electromagnetic means 55 as long as a flame exists at burner 40.

Figure 21 is similar to Figure 20, but a heat sensor 58 connected to power source 63 is used for control of electromagnet means 55.

Figures 22 and 23 are the same Figures 20 and 21 with the addition of excess flame sensor 60.

Figures 24 and 25 are the same circuit as Figures 22 and 23 with the addition of an electrical switch 90 for activating electromagnet means 55.

The operation of the embodiment of Figures 4 and 5 is similar to that of the embodiment of Figures 2 and 3, with the exception that the gas bleed mechanism is different and the shape of the safety valve is different. In Figure 4, the safety valve 100 comprises an elongate armature 101 for electromagnet 55. On initial operation from turn off of the valve assembly 20 to turn on, cam 52 and cam follower 102 operate to raise the valve 100 against the action of spring 103. Subsequent operation is the same as for the embodiment of Figures 2 and 3, apart from operation of the gas bleed mechanism. Figure 5 shows a further variation for the safety valve. Safety valve 110 is a ball valve and a ball valve seat 111 is provided in the assembly 23. Valve 110 is shown in the CLOSED position.

The gas bleed mechanism of the embodiment of Figures 4 and 5 will now be explained with reference to those Figures and the valves illustrated in Figures 30 and 31. In these embodiments, it is actually possible to raise the safety valve 100 with the main valve 30a still in the OPEN position. Valve 100 has a movable membrane 500 (not shown in Figures 4 and 5) which, when the valve 100 is in the CLOSED position, seals a central bleed hole 501 in the nose of the valve 100. Figure 30a shows the position of the valve 100 where the bleed hole 501 is closed by the membrane 500. When the valve is raised by action of push rod 50, membrane 500 moves to open bleed hole 501 to allow escape of high pressure gas in chamber 27 to enable the valve 100 to continue to be open. Arrow 502 indicates the direction of the escape of high pressure gas when the bleed hole 501 is open (Figure 30b) .

The safety valve arrangement 23 of the embodiments of Figures 13 through 16 is of a different construction and operates in a different manner from the embodiments of Figures 2 to 5. A mechanical linkage in the form of a push rod, used in the embodiments of Figures 2 through 5 has been dispensed with. The safety valve is, instead, operated by means of fluid pressure.

The valve assembly 23 of Figures 13 through 16 comprises a valve 120 and body portion 121 connected to valve 120 by means of spindle 122. Figure 18 shows a detail of a valve 120. Valve body 121 is slidably mounted within cylinder 124. Passageway 125 connects the cylinder 124 to a housing 126 containing a resilient bladder 127. Passageway 125 opens into the cylinder 124 on the underside of valve body 121. A further passageway 128 communicates between passageway 27 and cylinder 124.

Operation of valve 120 is as follows. Manual control knob 34 is pushed to the inward position (shown in ghost outline - note that this knob only has two positions, inner and outer, and no intermediate position. This is also a conventional arrangement.) and rotated anticlockwise to the 90° position. This allows conduit 26 to communicate with passageway 27 via passageway 31 and main valve body 30b. Due to back pressure in cylinder 124, via passageway 128, however, and due to the force of spring 130 on valve 120, valve 120 remains closed and fluid does not, therefore, reach passageway 29. Passageway 131 in valve body 31, at the 90° angle, communicates with passageway 132 leading to bladder 127. Figure 17 is a diagram illustrating rotation of valve body 30b and showing the OPEN and CLOSED positions of passageway 131 in relation to rotation of body 30b.

Passageway 131 is only open at the 90° angle. Fluid pressure from passageway 132 causes bladder 127 to expand. Subsequently, the manual control knob 34 is returned to 0°, closing off passageway 31 from conduit 26 and also closing off passageway 132. Because of the pressure in bladder 127, the differential pressure created across valve body 121 via passageway 125 and passageway 128 (passageway 128 communicating with passageway 27 to release the back pressure on the valve body 121) is enough to raise valve 120 to the OPEN position against the force of spring 130. As the valve body 121 nears the top of its throw it is attracted by a magnetic hollow cylinder head 133 and held in place in the OPEN position. Subsequent rotation of control knob 34 to open passageway 31 in main valve body 30b enables fluid to flow through to passageway 28 and conduit 29, to burner 40. The valve 120 is shown in its OPEN position in Figure 14 (also shows conduit 29 including jet nozzle 33, as a variation from Figure 13) . When knob 34 is pushed to the inward position, it actuates the heat rectification switch 61 to actuate igniter 65 to cause flame at burner 40. As per the embodiments of Figures 2 to 5, the existence of a flame activates the electrical circuit to energise electromagnetic means 55. Armature 136 is then raised against the biasing force of spring 137. Should the flame from burner 40 be extinguished, or should an excess flame situation be sensed, as in other embodiments electromagnetic means 55 becomes de-energised. Spring 137 forces armature 136 downwards and extension portion 138 of armature 136 is forced through hole 139 against the force. of spring 140. Projection 138 strikes the valve body 121 and forces it away from magnet 133 to the CLOSED position. It is not possible to re-open the valve 120 without first returning the knob 34 to 0°.

Referring to Figure 18, a small passageway 125a is provided in valvehead/piston 121. When differential pressure forces the piston head 121 upwards, a small ball bearing 125b is raised by the pressure to close passageway 125a. The ball bearing 125b subsequently drops away, to enable subsequent closure of the valve. Figure 10 shows a further valve and manual control assembly for use with an embodiment of the present invention. As for the other embodiments, it is intended to be used with the burner arrangement of Figure 6 or 7 and the electrical circuits of Figures 19 to 23. Heat rectification switch 61 is not shown but would be present in operation. Further, although a projecting rim 62 is not shown on knob 34 it would be present in operation in order to actuate heat rectification switch 61. The valve and manual control assembly of Figure 10 is designed for low pressure operation. The valve assembly 23 comprises horizontally aligned valve member 140, comprising valve 141 and armature 142. Push rod 50a, which is operated in the same manner as the push rod of the embodiments of Figures 2 to 4, has a projecting portion 143. In operation, projecting portion 143 operates to push the valve 141 away from valve seat 144, in order to open the valve to allow the flow of fluid to conduit 29. Subsequent operation of valve mechanism 23 is the same as for the embodiments of Figures 2 to 4. The existence of a flame at burner 40 results in the circuit energising the electromagnet 55 to maintain the valve in the OPEN position against the force of spring 145.

Valve body 30b is the same as valve body 30 of the embodiment of Figure 2 but there is no port for release of back pressure. This assembly should only be used with low pressure systems.

Figures 11 and 12 show two different types of safety valve arrangements which can be used in the present invention. The arrangement of Figure 11 comprises an electromagnetic means 55 mounted around a conduit 400 for the passage of fluid. A spindle 401 which moves in response to energisation of an electromagnetic means 55 is slidable within conduit 400. Passageway 402 lies within the spindle 401, for the passage of fluid. Passageway 402 communicates with passageway 403 containing a ball valve 404 and ball valve seat 405. The ball valve seat 405 is movable within the spindle 401 against the action of spring 406. Ball valve 404 is maintained against a stop 407 by a biasing spring 408. Stop 407 has slots in its side to enable communication of passage 403 with passage 408 in stop 407. The slots in stop 407 are not shown. When the valve is closed the slots are covered by valve seat 405. When valve seat 405 is moved to the left in the drawing, the slots are open and fluid may flow into passageway 408.

In operation, when push rod 50 is moved to the left U-shape projection 409 pushes spindle 401 to the left against the action of spring 406. This allows fluid to enter passageway 402. At the same time the valve seat 405 is moved to the left to uncover the slots to allow fluid flow into passageway 408 and through to burner 40. On activation of the electromagnetic means 55, spindle 401 is maintained in the leftmost position against the action of spring 406, keeping the valve open.

An advantage of this valve is that it can be made very small.

The valve of Figure 12 has similar advantages to that of Figure 11, although the operation is somewhat different.

Electromagnetic means 55 is mounted around conduit 400. Conduit 400 mounts therein a slidable sleeve 420 which mounts within it a slidable spindle 421 which is responsive to energisation of electromagnetic means 55 to move to the right against the action of spring 422. Passageway 423 in spindle 421 allows for flow of fluid past valve 424 and valve seat 425 (when open) through to passageway 426 in stop 427 (which has a similar stop to the slot 407 of Figure 11, having slots to enable gas flow) . In operation, when push rod 50 is moved to the left, the "U"-shaped portion 409 moves sleeve 420 to the left against the action of spring 430. This has the effect of moving the valve seat 425 down past the stop 427 to open the slots to allow the passage of fluid, and at the same time that ball valve 424 contacts stop 427. Subsequently, on energisation of electromagnet 55 spindle 421 moves to the right against the action of spring 422 to move the ball valve 424 away from stop 427. Sleeve

420 returns to its rightmost position on release of the push rod, the effect of the electromagnet 55 on spindle

421 is such that the valve 424 remains open as valve 424 is pushed to the right away from the seat 425.

Figure 26 shows a further variation of a valve assembly and control assembly for use in the present invention. In this embodiment, the safety valve mechanism 23 is arranged such that the valve 150 is in front of the main valve 30b in the fluid flow path. The valve 150 is initially operated by push rod 151, responsive to inward movement of knob 34. In this embodiment, push rod 151 runs separately from cam follower 35, against the action of spring 152. A further projecting rim 153 on knob 34 is positioned to actuate push rod 151. On the appearance of a flame, the electrical circuit is operated to attract valve body 155 to maintain the valve 150 in the OPEN position, against the action of spring 156. Main valve assembly 24 operates in a similar manner to that of previous embodiments.

Figure 27 shows an embodiment which is similar to Figure 26, except that valve 160 is electromagnetically operated in entirety and no push rod is provided for mechanical operation. It will also be noted that no rim is necessary on knob 34 to actuate the switches 61 (heat rectification) and 165 (reference numeral 90 of Figures 24 or Figure 25) . Switch 165 is connected to a power supply by lead 166 and to the rest of the electrical circuit by lead 167. In operation, as will be seen from the circuit diagrams, inward motion of the switch 34 actuates switch 165 which in turn causes actuation of electromagnetic means 55 to draw back valve 160 against the force of spring 166. Subsequent rotation of main valve body 30b enables fluid flow to burner 40. The appearance of a flame has the same feedback effect as in previous embodiments, by virtue of an electrical circuit, to maintain energisation of electromagnetic means 55 whether or not switch 165 is being actuated.

The valve 160 of the embodiment of Figure 27 may have the same structure and operation of the valve of Figures 30 and 31, in order to enable gas bleed. Figure 28 shows an alternative arrangement for a safety valve mechanism 23 for use with the arrangement of Figure 26. A different shaped valve 236 is provided which is movable against the action of spring 237 in response to the action of a crank push rod 235 moving against the action of spring 240. The crank 241 on the push rod enables a smaller diameter manual control knob 34 (not shown) to be used. Side supports 234 are provided for the push rod 241.

Figure 29 shows a gearing arrangement which can be used in accordance with the present invention to actuate a safety valve by means of push rod. The arrangement includes a linkage 300 pivotally mounted on plate 301 for the actuation of a further push rod 302 which is arranged to push open a valve (not shown) . The further push rod 302 may operate a safety valve in a similar manner to the push rod operation already described herein in relation to other embodiments. The effect of the gearing arrangement is to increase the throw of push rod 302 over that of push rod 50. It is therefore possible to move the safety valve by a greater distance than the movement of a control knob actuating push rod 50. This means that a large throw can be given to a safety valve.

Figure 33 shows yet another arrangement in which the safety valve 23 is in front of the main valve 24 in the fluid path. Push rod 300 is arranged to actuate the safety valve 201 to push it to the OPEN position against the action of spring 202. This interrupts the rotation of knob 34 and allows fluid flow through to passage 29 and burner 40. On the existence of a flame, the electrical circuit operates to energise electromagnetic means 55 which retracts the armature 203 against the action of spring 204. The armature 203 has a specially shaped foot 204 which moves in a slot 205 in push rod 200. As will be seen from Figure 33 (a) , as long as electromagnetic means 55 is energised and ^'armature 203 is raised against spring 204a, projecting portion 210 of foot 204 abuts the push rod 200 to maintain it in the inward position and therefore maintain safety valve 202 OPEN. Should the electromagnetic means 55 become de-energised, spring 204a will force armature 203 to drop, releasing push rod 200 to allow safety valve 202 to close, as shown in Figure (c) . Initial inward motion of push rod 200 due to force from handle 34 causes the armature 203 to be mechanically raised by virtue of cam 211 and cam follower 212.

Referring to Figure 35, an alternative arrangement for a safety valve, similar to that of Figure 11, is illustrated. In this embodiment, an element 410 is provided instead of the solenoid type arrangement 55. Element 410 can be attracted by a magnetisable element (not shown) at the same end as element 410 and spaced therefrom to maintain the valve in the OPEN position. This arrangement is suitable for use with a thermocouple driven electromagnetic means.

Referring to Figures 36 through 38, a novel mounting for an excess flame sensor to be used in accordance with the present invention will now be described. Figure 36 is a schematic plan view of a four-hob gas cooker. Hobs 601, 602, 603, 604 each have associated therewith excess flame sensors 605 through 608 respectively. Excess flame sensors 605 to 608 are mounted movably, so that their positions can be changed depending upon the size of any cooking utensil being placed on hobs 601 to 604. Excess flame sensors 605 and 606 are respectively mounted on pivoting mounts 609, 610. Mounts 609, 610 are pivotable about pivot points 611 and 612 in the direction of arrows 613 and 614. Respective lugs 615 and 616 are provided at corners of mounts 609 and 610. These lugs as is more clearly shown in Figure 37 (view along line BB) are arranged to be brought up against any utensil resting on pot support 620 (or 621) on hob 602. Depending upon the size of the utensil on pot support 620, the lug 615 will be moved outwards about the pivot point 611 (which will be spring biased against the motion) . Excess flame sensor 605, 606 therefore is moved to an appropriate distance away from the hob 601 depending upon the size of the utensil.

On hobs 603 and 604, the excess flame sensor 607, 608 is slidably mounted on slide 632, 633. Lug 634, 635 operates to abut a pot on pot support 640 and, depending on pot size, the excess flame sensor 607, 608 is moved away from the hob 601, 602.

The cooker is shown with a glass top 650. Any available types of sensors may be used, for the excess flame sensor and for the flame sensor. Preferably, for the excess flame sensor, an electrical switch is used, such as a bi-metallic strip or a mechanical switch using invar steel and brass. The flame sensor may be electronic, solid state or thermocouple.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

THE CLAIMS :

1. A fluid flow control device, comprising a valve assembly for controlling fluid flow from a fluid source to a fluid burner, manually operable control means for operating the valve assembly to enable fluid flow to the burner, and excess flame detection and control means for detecting the occurrence of excess flame from the fluid burner, wherein the valve assembly comprises a safety valve mechanism, the safety valve mechanism being responsive to the excess flame detection and control means detecting that excess flame is occurring to cause fluid flow to be discontinued.

2. A fluid flow control device in accordance with claim 1, wherein the safety valve mechanism is fail-safe.

3. A fluid flow control device in accordance with claims 1 or 2, wherein the excess flame sensor has an adjustable threshold, whereby the safety valve may be actuated by varying amounts of excess flame.

4. A fluid flow control device in accordance with claim 3, wherein the excess flame sensor is mounted movably, to enable it to be moved towards and away from the fluid burner whereby to set the threshold.

5. A fluid flow control device, comprising a valve assembly for controlling fluid flow from a fluid source to a fluid burner, a manually operable control means for operating the valve assembly to enable fluid flow to the fluid burner, a heat sensor for detecting the existence of flame at the fluid burner, an excess flame sensor for detecting the occurrence of excess flame from the burner, the valve assembly comprising a safety valve mechanism which is responsive to the heat sensor detecting the absence of flame to cause fluid flow to the burner to be cut off and is responsive to the excess flame sensor determining excess flame to cause fluid flow to the burner to be cut off, a manually operable control means comprising a single manually operable control operable to initiate the safety valve mechanism to move a safety valve of the safety valve mechanism from a CLOSED to an OPEN position, to cause fluid flow to the fluid burner and to initiate flame ignition by means of a heat rectification switch actuated by the manually operable control, the heat sensor being responsive to the existence of flame to operate control circuit to maintain the safety valve in the OPEN position until such time as there is an absence of flame or excess flame.

6. A fluid flow control device, comprising a valve assembly for controlling fluid flow from a fluid source to a fluid burner, and manually operable control means for operating the valve assembly to enable fluid flow to the burner, and detection and control means for monitoring operation of the fluid burner, wherein the valve assembly comprises a safety valve mechanism which is responsive to the detection and control means determining non-optimum operation of the burner to cause fluid flow to the burner to be discontinued, the safety valve mechanism being a fail-safe mechanism.

7. A fluid flow control device in accordance with claim 6, the safety valve mechanism comprising a safety valve movable between a first, open position in which fluid flow to the burner is enabled and a second, closed position in which fluid flow to the burner is disabled.

8. A fluid flow control device in accordance with claim 7, the safety valve mechanism further comprising an electromagnet which maintains the safety valve in the open position in response to the detection and control means determining that fluid burner operation is optimum, the electromagnet being arranged to be disengaged when non-optimum operation of the fluid burner is determined.

9. A fluid flow control device in accordance with claims 6, 7 or 8, wherein the detection and control means is responsive to the absence of flame from the fluid burner to actuate the safety valve mechanism to cause fluid flow to be discontinued.

10. A fluid flow control device in accordance with any one of claims 6 to 9, wherein the detection and control means is responsive to the occurrence of excess flame from the fluid burner to actuate the safety valve mechanism to cause fluid flow to be discontinued.

11. A fluid flow control device in accordance with claim 10, wherein the detection and control means comprises a heat responsive sensor mounted at a predetermined distance from the fluid burner and settable to a predetermined threshold whereby to enable it to be preset to determine when excess flame has occurred.

12. A fluid flow control device in accordance with claim 11, wherein the distance of the mounting of the heat responsive sensor from the fluid burner is adjustable, whereby to determine the threshold.

13. A fluid flow control device in accordance with any one of claims 7 to 12, wherein the manually operable control means comprises a manually operable control movable between OFF and ON positions, movement between the OFF to the ON position being arranged to actuate the valve assembly and to position the safety valve in the OPEN position whereby to enable fluid flow to the fluid burner, and also to initiate flame ignition.

14. A fluid flow control device in accordance with claim 13, wherein movement of the manually operable control actuates a push rod mechanically connected to the safety valve to cause movement of the safety valve from the CLOSED to the OPEN position.

15. A fluid flow control device in accordance with claim 14, wherein the push rod is actuated by means of a gear mechanism arranged to move the safety valve by a large distance than the manually operable switches moved to actuate the push rod, whereby the distance between the CLOSED and OPEN position of the safety valve can be chosen to reduce the chances of blockage of the safety valve.

16. A fluid flow control device in accordance with claim 13, wherein the safety valve is arranged to be actuated in response to fluid pressure caused by movement of the manually operable control between the OFF and ON positions.

17. A fluid flow control device in accordance with claim 13, wherein the movement of the manually operable control from the OFF position being arranged to actuate an electrolmagnetic means which operates to put the safety valve into the OPEN position.

18. A fluid flow control device in accordance with any preceding claim, the arrangement being such that, following operation of the safety valve mechanism to cut off gas flow, gas flow cannot be reinstituted until the manually operable control means has been returned to an OFF position, whereby to avoid the occurrence of high pressure fluid flow to the fluid burner.

19. A fluid flow control device in accordance with claim 18 when read on to claim 14, the arrangement being such that following operation of the safety valve to cut off gas flow, fluid pressure acts on the safety valve to maintain it in the CLOSED position notwithstanding actuation of the push rod, until the fluid pressure is released by returning the manually operable control to an OFF position.

20. A fluid flow control device in accordance with claim 19, wherein a fluid flow path is provided to cause release of the fluid pressure on the valve maintaining it in the CLOSED position, the fluid flow path only being opened when the manually operable control is in an OFF position.