GB2186720A - Gas-fired cooking appliance - Google Patents

Abstract

A gas fired cooking appliance is provided with a pivotable cover (1) and is controlled by a user operated gas tap. Provision is made to cut off the gas supply whenever the cover is closed, and further provision is made to prevent escape of gas when the cover is reopened when the gas tap is turned on. In a gas fired cooking appliance of the kind in which a cover (1) is linked to a safety cut off valve so that the gas is turned off whenever the cover is closed, provision is made to prevent the escape of gas if the cover is reopened after having been closed while a user operated gas tap has been left on. The safety cut off valve (10) is controlled in response to movement of a lever (13) on switch (11). The lever (13) is moved in response to a linkage connected to the cover, and is latchable in the 'gas off' position by means responsive to the open condition of the gas tap. As shown (Fig. 1) the latch comprises a magnetic retainer (35) on a solenoid plunger (34) whose position is governed by the condition of a switch (33) associated with the gas tap. <IMAGE>

Description

SPECIFICATION Gas-fired cooking appliance This invention relates to a gas-fired cooking appliance and it relates particularly, though not exclusively, to a gas-fired hob fitted with a pivoted cover, displaceable by a user between open and closed positions.

A gas-fired hob forming part of a standalone cooking appliance, or mounted in an existing worktop, is commonly provided with a pivoted cover, sometimes referred to as a "shut-down" cover. Such covers, which are usually made of toughened glass, or ceramic or metal, have a aesthetically pleasing appearance and, in the closed position, provide an additional work surface.

A hob provided with a cover of this kind is usually fitted with a safety cut-off valve effective to interrupt a supply of gas to the burners whenever the cover approaches or attains the closed position. This valve ensures that the burners are extinguished even if a user forgets to shut off the supply at a gas tap, and so prevents the cover from being damaged. In some arrangements the safety cut-off valve is returned to the open condition whenever the cover is raised. This arrangement could, however, lead to a potentially hazardous situation, particularly if a user leaves a gas tap open inadvertently and then raises the cover so allowing gas to escape unlit.

It is an object of the present invention to provide a gas-fired cooking appliance in which the above-described problems are at least alleviated.

Accordingly there is provided a gas-fired cooking appliance including at least one gas burner; a cover for said at least one gas burner displaceable by a user between open and closed positions; a user-operable valve and a safety cut-off valve for controlling a supply of gas to said at least one burner; an actuator displaceable, in response to closure of the cover, to a first position to initate closure of the safety cut-off valve and so block a flow of gas to the at least one gas burner and being returnable, in response to opening of the cover, to a second position to allow a flow of gas to the burner; and means to releasably latch the actuator in the first position, to prevent its return to the second position, whenever both the cover is in the closed position and the user-operable valve is open and until the user-operable valve is closed.

In order that the invention may be carried readily into effect an embodiment thereof is now described, by way of example only, by reference to the accompanying drawings of which, Figure 1 shows a schematic representation of an arrangement in accordance with the present invention, and Figure 2 shows an alternative form of mechanical linkage used in the arrangement of Fig. 1.

In one application of the invention a standalone cooking appliance includes a gas-fired hob fitted with a "shut-down" cover, typically made of toughened glass, ceramic or metal.

The cover is mounted pivotally on the hob and is displaceable by a user, about a horizontal axis, between a raised, open position and a lowered, closed position.

The hob has a number (e.g. four) of gas burners, the gas supply to each being control lable by a respective user-operable valve and by a safety-cut-off valve, common to all the burners, positioned on the upstream side of the user-operable valves. The cover is coupled operatively to the safety cut-off valve so as to interrupt a flow of gas to the burners whenever the cover approaches or attains the closed position, this arrangement being effective to significantly reduce the risk that the cover is damaged if it is lowered before all the burners have been turned off by a user.

As will be described in greater detaii hereinafter the coupling between the safety cut-off valve and the cover is arranged so that the supply to the burners cannot be restored, as a result of the cover being raised, if any one of the user-operable valves has been left open.

In this example, the cover and the safety cut-off valve are coupled by means of an electro-mechanical arrangement of the form shown schematically in Fig. 1.

The safety cut-off valve comprises a solenoid valve 10 connected electrically in series with a microswitch 11 and a source 12 of rectified ac, or alternatively dc, power. The microswitch is fitted with an actuator in the form of a lever arm 13 coupled to the cover by means of a mechanical linkage, shown generally at 20. If, in use, the cover is lowered to the closed position the linkage acts to urge arm 13 against a control button on the microswitch causing it to open. This, in turn, terminates a supply of power to the solenoid valve which, in response, assumes a closed condition blocking a flow of gas to the burners. It, would, of course, be possible alternatively to use a solenoid valve which is normally open. In this case it would be necessary to close microswitch 11 in order to block a flow of gas to the burners.

As shown in Fig. 1, cover 1 is coupled to a control rod 21 through a hinge 22. If the cover is lowered, the control rod is urged upwardly and outwardly, as illustrated by the full arrows, in opposition to the resilience of a coil spring 23. The control rod is connected to a first push rod 24, linked by means of a toggle 25, to a second push rod 26 which, in turn, acts on arm 13 directly. Thus, whenever the cover is lowered the second push rod urges the arm towards the microswitch causing it to assume an open condition and so preventing a flow of gas to the burners.

If the cover is raised, the control and push rods are displaced in the reverse direction, as illustrated by chain-dotted arrows. Provided none of the user-operable valves is open, arm 13, which is biased resiliently, is free to pivot away from the microswitch which can then assume a closed condition. In these circumstances power passes to the solenoid valve and the valve is held open. If, however, one or more of the user-operable valves has been left open, and the cover is in the closed position, a latching arrangement, shown generally at 30, functions to hold arm 13 against microswitch 11 returning it in the open condition, even if the cover is subsequently raised. It will be appreciated that this arrangement eleminates the risk that gas could escape unlit from a burner solely as a consequence of a user raising the cover when a user-operable valve has been left open inadvertently.

Latching arrangement 30 comprises a solenoid 31 connected electrically in series with a second source 32 of power and a number of further microswitches, connected together is parallel. Each such further microswitch is associated with a respective user-operable valve, though only one of them (i.e. 33) has been shown in Fig. 1. The solenoid has a plunger 34, preferably of a non-magnetic metal, which is fitted with a magnetic disc 35 at the end thereof closest to arm 13. If any user-operable valve is left open then the associated microswitch 33 assumes the closed condition causing power to be supplied to solenoid 31.

In these circumstances plunger 34 is displaced towards arm 13 to a fully extended position, as shown in chain-dotted outline in Fig. 1, and if the cover is then closed, arm 13, urged by push rod 26, comes to bear against magnetic disc 35. The armature is also made of a magnetic material and is therefore held magnetically by the disc in a latched condition. Thus, if any user-operable valve is left open and the cover is closed, microswitch 11 is retained in an open condition causing solenoid valve 10 to be held closed, and so blocking a flow of gas to the burners, even if the cover is subsequently raised. The arm may only be released if all the user-operable valves are closed; this terminates a supply of power to solenoid 31 allowing plunger 34 to return, by the action of a coil spring 36, to a retracted position (shown in full outline).

It will be appreciated that the mechanical linkage 20 need not necessarily be of the form shown in Fig. 1. Alternatively a relatively simple construction of the form shown in Fig.

2 could be used. In this case, cover 1 is coupled, through hinge 22, to be pivoted lever 27 which acts directly on arm 13. Alternative forms of latching arrangement 30 are also possible. For example, lever arm 13 could be held in the shown, iatched position by means of an electromagnet, energisable on opening a user-operable valve. Alternatively a mechanical latch could be used.

It will be appreciated that although the present invention has be described with reference to a stand-alone cooking appliance having a hob, the invention is also applicable in other, similar situations in which a gas burner has a user-displaceable cover and in which it is desirable to prevent gas escaping unlit; for example, in the case of a hob-only appliance or a grill compartment fitted with a fold-down door.

Claims (5)

1. A gas-fired cooking appliance including at least one gas burner; a cover for said at least one burner displaceable by a user between open and closed positions; a user-operable valve and a safety cut-off valve for controlling a supply of gas to said at least one burner; an actuator displaceable, in response to closure of the cover, to a first position to initate closure of the safety cut-off valve and so block a flow of gas to the at least one burner and being returnable, in response to opening of the cover, to a second position to allow a flow of gas to the burner and means to releasably latch the actuator in said first position, to prevent its return to the second position, whenever both the cover is in the closed position and said user-operable valve is open, and until the user-operable valve is closed.

2. A gas-fired cooking appliance according to claim 1 wherein said actuator is made of, and includes, a magnetic material and said latching means is effective to hold the actuator magnetically in said first position.

3. A gas-fired cooking appliance according to Claim 2 wherein said latching means comprises a solenoid arranged to be energised whenever the user-operabie valve is open and a plunger including a magnetic material and displaceable to a latching position in response to energisation of the solenoid.

4. A gas-fired cooking appliance according to Claims 1 to 3 wherein said actuator comprises a lever arranged to act directly on a microswitch connected in series with said safety cut-off valve and a source of power for the valve.

5. A gas-fired cooking appliance substantially as hereinbefore described by reference to the accompanying drawings.