GB2213914A

GB2213914A - Safety control knob for a gas or electrical appliance

Info

Publication number: GB2213914A
Application number: GB8729817A
Authority: GB
Inventors: Anthony Roger Worsfold; Roy Leslie Johnson
Original assignee: Glynwed Consumer and Building Products Ltd
Current assignee: Glynwed Consumer and Building Products Ltd
Priority date: 1987-12-22
Filing date: 1987-12-22
Publication date: 1989-08-23
Anticipated expiration: 2007-12-22
Also published as: GB2213914B; GB8729817D0

Abstract

A control knob, for deterring manipulation by young children, for example, comprises a grip component 5 for turning the operating spindle 2 of a gas tap or electrical switch, and a shroud component 6 at least partially surrounding the grip component is movable relative thereto between a forward active position, to which it is spring-loaded, in which it prevents manipulation of the grip component and a rearward release position allowing the grip component to be gripped for turning the spindle. In the active position the grip component 5 is received into a channel 12 in the shroud component and front faces of the components lie on, or substantially on, a common notional surface. A surround 35 around the shroud component 6 is fixed in use against movement with the components and has a cam profile with which followers 19 on the shroud component can co-operate to retain the component in the released position. <IMAGE>

Description

Improvements Relating to Control Knobs for Gas and Electrical Appliances This invention relates to control knobs for gas and electrical appliances, such as cookers and fires.

It is a safety requirement that control knobs of gas and electrical cookers and fires should not be able to be manipulated readily by young children in order to deter them from putting the appliances into operation or in the case of a gas cooker or fire from turning on the gas supply.

According to a first aspect of the present invention a control knob is provided adapted for application to a gas or electrical appliance and comprising a grip component adapted to be connected operatively to a rotatable operating spindle of a gas tap or electrical switch, a shroud component which at least partially surrounds the grip component and is moveable relative to the grip component between a forward, active, position in which it prevents manipulation of the grip component and a rearward, release position in which it allows the grip component to be manipulated, and means whereby spring loading is exerted on the shroud component normally to urge that component to its active position.

According to a second aspect of the present invention a gas tap or electrical switch is provided having a rotatable operating spindle fitted with a control knob which comprises a grip component connected operatively to the spindle for turning the spindle, a shroud component which at least partially surrounds the grip component and is moveable relative to the grip component longitudinally of the spindle between a forward, active, position in which it prevents manipulation of the grip component for operating the spindle and a rearward, release, position in which it allows the grip component to be manipulated, and means located on the spindle whereby spring loading is exerted on the shroud component normally to urge that component to its active position.

According to yet a third aspect of the present invention there is provided a gas or electrical appliance which includes a gas tap or electrical switch, as the case may be, in accordance with the second aspect of the invention herein set forth.

Preferably the shroud component has a front face which at least adjacent to the grip component is disposed, when the shroud component is in its active position, at or in front of forward extremities of -a part of the grip component which must be held in order to enable that component to be manipulated. The shroud and grip components may have front faces which lie on, or substantially on, a common notional surface, and preferably are closely contiguous, when the shroud is in the active position. It is not essential, of course, for the front faces to be of conforming contours.

A surround may be provided around the shroud component which mounts, or is mounted, on a fixed part of the gas or electrical appliance so that the surround is restrained at least from movement in the directions in which the shroud component is movable relative to the grip component. An interconnection may be provided between the shroud component and the surround whereby when the shroud component is moved to the rearward, release, position it can be retained in that position by relative angular movement between it and the surround. For example the surround may have a cam profile with which one or more followers carried by the shroud component engage.

In the second aspect of the invention applied to a gas tap niting means may be operative between the operating spindle and a fixed part of the tap to lock the spindle in its "OFF" position, and which requires the spindle to be pushed inwardly to release the niting means before the spindle can be turned to operate the valve member. With such an arrangement the shroud component is preferably arranged to co-operate with the spindle, or means carried by the spindle, as the component is moved towards its release position and cause the spindle to be pushed inwardly to release the niting means.If a surround is provided around the shroud component and there is an interconnection between the shroud component and surround, as described, the co-operation between the shroud component and the spindle to release the niting means preferably occurs before the interconnection becomes effective for retaining the shroud component in the release position.

The means located on the spindle by which spring loading is exerted on the shroud component may comprise a helical compression spring which acts between an abutment on the spindle and the shroud component. The abutment may be formed on the spindle or be provided by an element attached to the spindle, for example a plate or a disc fitted on, and rotatable with, the spindle and retained in a required position longitudinally of the spindle by a circlip or the like. The plate or disc may carry markings to indicate settings of the gas tap or electrical switch.

It will generally be desirable for a gas or electrical appliance in accordance with the third aspect of the invention to have the gas tap or electrical switch located for the control knob to be accessible at a body panel or facia of the appliance.

Preferably the control knob is positioned so that the grip and shroud components do not protrude, or protrude only very slightly, for example approximately imam, from an outer face of the body panel or facia, and are thus protected from being knocked and purchase cannot be gained on the knob.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a fragmentary sectioned view of part of a gas cooker hob at which a gas tap having -a control knob in accordance with the invention is provided; Figure 2 and 3 are respectively a front view of, and a central longitudinal section through, a grip component of the control knob; Figure 4 is a front view of a shroud component of the control knob, and Figure 5 is a side view of a surround of the knob.

Referring to Figure 1 of the drawings, a control knob 1 is mounted on the forward end of an operating spindle 2 of a gas tap 3 in a gas rail 4. The gas tap 3 may control the gas supply to an oven, hob or grill burner and may have associated thermostatic control and/or flame failure devices, which may be of known kinds. If there is an associated thermostatic control the spindle will be operated to pre-set the temperature at which the thermostatic control will operate, in addition to turning the gas tap 3 "ON" and "OFF".

The control knob 1 comprises a grip component 5 and a shroud component 6. Both components are conveniently made as plastics mouldings but they may be made of any suitable mouldable or machinable material.

The grip component 5, Figures 2 and 3, is oblong, of a laterally elongated generally T-shape in side elevation, the cross portion of the T presenting a flat front face 7 of the component and the sides of the cross portion and stem portion of the T together presenting parallel flanks 8 of the grip component by which the component can be held by hand for turning.

The grip component fits centrally on the forward, free end of the spindle 2 which is of a non-circular cross-section, for example the usual D-section. The spindle is received as a tight push fit in a complementary socket 9 extending axially of the stem portion of the grip component from its rear face 10.

At either side of the socket 9 are two parallel blind bores 11 in the stem portion which also extend from the rear face 10. The shroud component 6 is generally circular as viewed from the front, Figure 4, with a central, rearwardly-projecting, diametrical channel portion 12 in which the grip component 5 is accommodated. The spindle 2 passes with clearance through a circular aperture 13 in a bottom wall 14 of the channel portion 12. A pair of upstanding guide pegs 15 integral with the bottom wall 14 engage slidably in the blind bores 11 in the grip component and allow the shroud component to be moved relative to the grip component longitudinally of the spindle.

Channel portion 12 is complementary in depth to the grip component between its front and rear faces, 7,10, and in width to the width of the component between the parallel flanks 8. The cross portion of the grip component completes the circular frontal shape of the shroud component. The engagement of the guide pegs 15 in the blind bores 11 and the location of the grip component in the channel portion 12 constrains the shroud component to be rotatable with the grip component Two segmental portions 16 of the shroud component at either side of the channel portion 12 present a flat front face 17 of the component. When the grip component is fully accommodated in the channel portion, as shown in Figure 1, its front face 7 and the front face 17 of the shroud component are co-planar.

Each of the segmental portions 16 has a shallow, rearwardly-turned rim 18 which projects rearwardly substantially less than does the channel portion 12.

Two diametrically opposite follower pins 19 are formed integrally with and project outwards from the rims 18 at right-angles to the length of the channel portion.

Mounted on the spindle behind the control knob is a cup-shaped carrier disc 20 having a plain central hole 21 through which the spindle passes with clearance. A forwardly-extending skirt 22 of the disc 20 surrounds the control knob to a plane intermediate the stem portion and the front face 7 of the grip component. The disc abuts against a circlip 23 attached to the spindle behind the disc.

Inside the skirt 22 a helical compression spring 24 is located between, and bears on, the disc 20 and the bottom wall 14 of the channel portion 12 of the shroud component so as to urge that component forwards to a normal, active, position in which the bottom wall bears on the rear face 10 of the grip component, and the grip component is fully accommodated within the channel portion. An annular protrusion 25 of the disc fits inside the adjacent end of the spring to locate it, and the opposite end of the spring 24 engages in locating grooves 26 in the bottom wall 14. The force of the spring 24 urging the disc against the circlip 23 constrains the disc to rotate with the spindle.Around its rim the skirt 22 has a rearwardly and outwardly inclined peripheral flange 27 on which an identification ring 28 is carried having marking to show settings of the gas tap in different angular positions of the spindle.

As shown in Figure 1 of the accompanying drawings, the gas tap is mounted inside the casing 29 of a gas cooker hob, behind a facia 30 of the casing which has a vertical front wall 31 and a rearwardly and upwardly inclined wall 32. A window 33 is provided in the inclined wall 32 through which the identification ring 28 is visible. If desired, the window 33 may be in the vertical front wall 31. The gas tap is located such that the front face 7 of the grip component of the control knob lies in the plane of the front surface of the front wall 31 of the facia 30, within an opening 34 in that wall, co-axial with the spindle, of larger diameter than the shroud component and slightly smaller than the internal diameter of the rim of the skirt 22.

Around the shroud component 6 an annular surround 35 is fixed in the opening 34 of the facia, for example by means of adhesive or by retaining ribs on the surround which engage behind the edge of the opening. The surround 35, Figure 5, has an annular flange 36 which overlies the front wall 31 of the facia around the opening 34, and a cylindrical body 37 which extends rearwards from the flange 36, co-axially of the spindle, through the opening and, with good clearance, between the rims 18 of the sequential portions 16 of the shroud component and the skirt 22 of the carrier disc 20. The rear end edge of the cylindrical body 37 contains two diametrically-opposed, generally V-shaped notches 38 and forms a cam profile with which the follower pins 19 engage.

The notches 38 are so positioned that the follower pins 19 register with them when the spindle 2 is in its inoperative angular position. With the follower pins in register with the notches, the compression spring 24 urges the shroud component to its forwardmost, active, position, determined by engagement of the follower pins with the inner, apex, ends of the notches, as shown in Figure 1. In that position of the shroud component its front face 17 is co-planar with the front face 7 of the grip component, and those faces are inset slightly from the front surface of the annular flange 36 of the surround 35. Thus, the control knob does not protrude from the facia 30 and is contained within the casing 29 of the cooker hob. The flat front of the control knob presented by the co-planar front faces 7,17 provides no means of obtaining a positive hold on the knob for turning the spindle.Young children, for example, are therefore deterred from trying to operate the knob.

In order to operate the spindle to turn the gas tap "ON" the shroud component has first to be pushed rearwards, against the spring loading, to enable access to be gained to the flanks 8 of the grip component for gripping the component to turn the spindle. Until the shroud component has been pushed rearwards sufficiently to move the follower pins 19 out of the notches, and the grip component has then been turned to operate the spindle sufficiently to take the follower pins out of angular register with the notches, the compression spring 24 will be acting against the hand of the person manipulating the knob and will restore the shroud component to its active position as soon as the hand is removed.Once the follower pins are out of angular register with the notches, of course, they can engage the rear edge of the surround and the shroud component will be held depressed for ready manipulation of the grip component.

Were the gas tap to be associated with a thermostatic control and the usual niting provision is made which requires the spindle to be pushed inwards from its "OFF" position to release the niting engagement before it can be rotated to turn the gas tap "ON" and set the thermostatic control, the inward pushing of the shroud component from its active position can be instrumental in pushing the spindle inwards before the follower pins move out of register with the notches. For example, the shroud component may be arranged to abut against the annular protrusion 25 of the carrier disc 20 just before it reaches its fully depressed position relative to the grip component, so that the disc, and thereby, the spindle are urged, by way of the circlip 23, rearwards with the shroud component to release the niting engagement. As the notches are V-shaped they allow some turning of the grip component before the follower pins are fully disengaged from the notches. With this permitted turning and releasing of the niting engagement, the gas tap can be put into a fully operational condition before the first gas mark setting is reached indicated by the identification ring 28 on the carrier disc.

Instead of having the control knob presented at the front wall 31 of the facia 30, as in Figure 1, the gas tap may be located for the control knob to be presented at the inclined wall 32 of the facia.

A control knob substantially similar to that described and illustrated may be applied to a rotary operating spindle of various types of gas valves and electric switches, including those having a timer.

Claims

1. A control knob adapted for application to a gas or electrical appliance, comprising a grip component adapted to be connected operatively to a rotatable operating spindle of a gas tap or electrical switch, a shroud component which at least partially surrounds the grip component and is movable relative to the grip component between a forward, active, position in which it prevents manipulation of the grip component and a rearward, release, position in which it allows the grip component to be manipulated, and means whereby spring loading is exerted on the shroud component normally to urge that component to its active position.

2. A control knob according to claim 1 wherein the shroud component has a front face which at least adjacent to the grip component is disposed, when the shroud component is in its active position, at or in front of forward extremities of a part of the grip component which must be held in order to enable that component to be manipulated.

3. A control knob according to claim 2 wherein the grip component has a front face, and the front face of the shroud component and the grip component lie on, or substantially on, a common notional surface when the shroud component is in the active position.

4. A control knob according to claim 3 wherein the front faces of the grip component and the shroud component are closely contiguous.

5. A control knob according to any of claims 2 to 4 wherein the grip component has opposed flanks b which the grip component is held by hand for turning, and the shroud component has a forwardly presented channel which in the active position of the shroud component accommodates the grip component such that the flanks of the grip component are contained in the channel respectively adjacent to the opposed sides of the channel.

6. A control knob according to claim 5 wherein guide members project from the bottom of the channel and engage slidably in bores in the grip component to guide the shroud component in its movement relative to the grip component between the active and release positions.

7. A control knob according to any preceding claim wherein a surround is provided around the shroud component which mounts on a fixed part of the gas or electrical appliance to be restrained in use at least from movement in the direction in which the shroud component is movable relative to the grip component.

8. A control knob according to claim 7 wherein there is an interconnection between the shroud component and the surround whereby when the shroud component is moved to the release position it can be retained in that position by relative angular movement between it and the surround.

9. A control knob according to claim 8 wherein said interconnection comprises a cam profile on the surround and one or more followers carried by the shroud component which engage with the cam profile.

10. A control knob according to claim 9 wherein the surround has a cylindrical body co-axial with the axis about which the grip component turns the operating spindle, the cam profile is formed on an end edge of the cylindrical body and contains diametrically opposed generally V-shaped notches, and the shroud component has diametrically opposed followers engageable with the cam profile and which register with the notches when the shroud component is in the active position, thereby to restrain the shroud component from turning relative to the shroud component, the followers being releasable from the notches by movement of the shroud component to its release position and being engageable with the cam profile to retain the shroud component in the release position by turning the shroud component relative to the surround.

11. A control knob according to claim 10 as dependent from claim 3 wherein the surround has an annular flange by which the surround is mounted on the fixed part of the gas or electrical appliance, the cylindrical body extends rearwards from the annular flange, the cam profile and notches are at the rear end edge of the body, and the front faces of the grip component and the shroud component are inset slightly from a front face of the annular flange when the shroud component is in the active position.

12. A gas tap or electrical switch having a rotatable operating spindle fitted with a control knob as claimed in any preceding claim, the grip component being connected operatively to the spindle for turning the spindle, the shroud component being movable longitudinally of the spindle between its active and release positions, and the spring loading means being located on the spindle.

13. A gas tap or electrical switch according to claim 12 wherein the spindle has an abutment and the spring loading means comprises a helical compression spring which acts between the abutment and the shroud component to urge the shroud component to the active position.

14. A gas tap or electrical switch according to claim 13 wherein the abutment comprises an element attached to the spindle.

15. A gas tap or electrical switch according to claim 14 wherein the element comprises a plate or disc rotatable with the spindle and carrying markings to indicate settings of the gas tap or electrical switch according to the rotational position of the spindle.

16. A gas tap or electrical switch according to claim 15 wherein the element has a skirt portion which extends forwards about the spindle over the helical compression spring and surrounds the shroud component.

17. A gas tap according to any of claims 12 to 16 having niting means operative between the operating spindle and a fixed part of the tap to lock the spindle in an "OFF" position and requiring inward pushing of the spindle for release before the spindle can be turned to open valve means, and wherein the shroud component is arranged to co-operate with the spindle, or means carried by the spindle, as that component is moved towards the release position and cause the spindle to be pushed inwardly to release the uniting means.

18. A gas tap according to claim 17 wherein the control tap is in accordance with any of claims 8 to 11 and the co-operation between the shroud component and the spindle to release the niting means is arranged to occur in the movement of the shroud component towards the release position before the interconnection between the shroud component and the surround becomes effective for retaining the shroud component in the release position.

19. A gas or electrical appliance including a gas tap or electrical switch as claimed in any of claims 12 to 18.

20. A gas or electrical appliance according to claim 19 in which the gas tap or electrical switch is located behind a body panel or facia of the appliance, and the control knob of the gas tap or electrical switch is accessible at the body panel or facia and positioned such that there is no protrusion, or substantially no protrusion, of the grip and shroud components from an outer face of the body panel or facia.

21. A control knob substantially as described herein with reference to the accompanying drawings.

22. A gas tap substantially as described herein with reference to the accompanying drawings.

23. A gas appliance substantially as described herein with reference to the accompanying drawings.