GB2342685A

GB2342685A - Twist-tab fastening, eg for electrical devices

Info

Publication number: GB2342685A
Application number: GB9822350A
Authority: GB
Inventors: Robert Andrew O'neill
Original assignee: Otter Controls Ltd
Current assignee: Otter Controls Ltd
Priority date: 1998-10-13
Filing date: 1998-10-13
Publication date: 2000-04-19
Anticipated expiration: 2018-10-13
Also published as: GB9822350D0; GB2342685B; HK1027710A1

Abstract

An electrical device, such as a heating element overtemperature protector and/or a power supply input connector is coupled to a planar electric heating element of the underfloor or thick film type by a mounting bracket secured to the heating element and the device being releasably secured by twist-tabs on the mounting bracket engaging slots on the device. The arrangement enables ready replacement of a faulty device and avoids the necessity of scrapping an otherwise operable heating element.

Description

IMPROVEMENTS RELATING TO THE CONTROL OF ELECTRIC HEATING ELEMENTS Field of the : This invention concerns improvements relating to the control of electric heating elements and the supply of electricity thereto. More particularly, though not exclusively, the invention is concerned with overtemperature controls for switchin, off the supply of electricity to an electric heating element in the event of the heating element temperature rising above a safe level, such controls commonly being referred to as element protector controls and being utilized in domestic water heating appliances, for example, such as electric kettles and hot water jugs. As will become apparent hereafter, the invention is even more particularly, though not exclusively, concerned with the attachment of such controls and other electrical devices to electric heating elements.

Background of the Invention Conventional immersion heating elements of the metal sheathed wire wound resistance heating type have conventionally had an element head portion in the form of a more or less flat metal plate which served not only for the attachment of the heating element into an associated vessel but also for the attachment of an element protector control and a power supply inlet connector to the heating element. The heating element head plate conventionally carried a plurality of screw-threaded mounting studs which served this purpose.

Planar heating elements of the underfloor and thick film types are also know, the former having been popular in the European mainland for many years and the latter more recently appearin,, in domestic appliances. An underfloor heating element conventionally comprises a metal plate having a metal sheathed wire wound resistance type of heating element proper affixed to its undersurface. For affixing element protector controls and power supply inlet connectors to such underfloor heating elements it has been conventional to provide mounting studs on the underside of the metal plate of the heating element, the studs either being screw-threaded or being adapted to be deformed in the manner of a rivet. Deformable studs are preferred over screw-threaded studs, since they can be formed integrally with the heating element, whereas screw-threaded studs have to be welded on as a separate step. Similarly, thick film heating elements, comprising an insulated metal plate substrate, commonly stainless steel with a layer of glass insulation, have been provided with studs for the attachment of element protector controls etc and also have been arrange for the direct attachment to the metal substrate by welding of mounting rackets for the controls. Examples of such arrangements are shown in WO-A-9738557 and in our British Patent Application No. 9808484. 1 filed 21 April 1998.

When a screw-threaded stud is employed for attachment to the heating element of element protector controls and other facilities, replacement of a faulty control clearly is a simple matter. When the control, or whatever, is attached to the heating element by means of deformable studs or by direct welding, replacement of a faulty component is not so easy and it may be that the entire heating element has to be replaced, together with its attachments, even though there is in fact nothing wrong with the heating element. As an approach to solving this problem we have proposed in WO-A-9738557 to provide additional, redundant studs on the heating element which will be utilized only in the event that an attached control or whatever becomes faulty and has to be replaced, the redundant studs then coming into their own and serving for the attachment of the replacement control to the heating element.

Whilst the above proposal meets its objectives, it clearly is not convenient or possible to provide targe numbers of redundant fixing studs on a heating element. It would be possible to use long studs in combination with different sizes of spacers so that the same studs could be reutilized with a different spacer in the replacement of a faulty control, but such a solution is open to accidental abuse leading to improperly fixed heating element attachments if the wrong size spacers are employed.

Objects and Summary of the Invention : Accordingly, it is the object of the present invention to provide an alternative solution to the problem of facilitating the removal of faulty attachments from electric heating elements and their replacement.

According to the present invention, the heating element has attached thereto a mounting bracket or carrier for the facility that is to be attached to the heating element, and the mounting bracket or carrier has twist tabs designed to co-operate with the facility that is to be attached to enable its attachment to the bracket in a removable manner.

By providing camming surfaces on the twist tabs and/or on the co-operating parts of the facility that is to be attached, a secure and firm attachment of the facility to the heating element can be assured. By providing stop surfaces on the co-operating parts of the facility that is to be attached, it can be ensured that the twist tabs are not over-twisted and can readily withstand a reasonable number of repeated twisting and un-twisting operations.

The invention will best be understood from consideration of the following description given with reference to the accompanying drawings which illustrate an exemplary embodiment of the invention.

Description of the Drawings : Figure 1 shows an exemplary mounting bracket for attachment to a heating element of the underfloor or thick film type, the bracket having plural twist tabs enabling the attachment thereto of an element protector control cum 360 power input connector as described in our British Patent Application No. 9808484.1 filed 21 April 199S the disclosure whereof is incorporated herein by reference ; and Figures 2A, 2B and 2C illustrate stages in the attachment of the control by use of the twist tabs shown in Figure 1.

Detailed Description of the Embodiment : Described in British Patent Application No. 9808484.1 abovementioned is a combined element protector cum power supply input connector wherein a 360 cordless power input connector, based upon the CP7 360 connector manufactured by and available from us and adapted for use with our CS4 360 power outlet connector in cordless appliances, is integrated with first and second heating element protector controls, the whole arrangement being fixedly secured to a mounting bracket which in turn is provided with plural feet enabling it to be attached to a heating element by any convenient means. Figures) to 4D of the drawin, s accompanying British Patent Application No, 9808484.1 illustrate such arrangements and in these arrangements no provision is made for removal of the element protectors cum power input connector from the bracket, though the bracket may be removable for servicing or repair of either the heating element or the cordless connector cum overtemperature controls combination. In Figure 5 of the drawings accompanying British patent Application No. 9S08484. 1, however, an alternative mounting bracket is shown which is adapted to be permanently affixed to the heating element, and the bracket in question has plural screw receptacles which enable the cordless connector cum overtemperature controls combination to be affixed to the bracket in a removable manner by means of plural fixing screws. The arrangement hereinafter described provides a cost-effective alternative to the Figure 5 arrangement of British Patent Application No. 9808484.1.

Referring to Figure 1 of the accompanying drawings, shown therein is a mounting bracket 60 formed as a sheet metal stamping and having three feet 61 enabling the bracket to be secured to the underside of a planar heating element of the underfloor or thick film type by any convenient means, such as by riveting, welding or by nut and screw connections for example. The bracket may or may not be readily removable from the heating element, depending upon its method of fixing thereto. The bracket 60 is further formed with an integral earth (ground) connection tab 62 and with three twist-tabs 63 which, as shown, comprise a head portion 64 and a thinner neck portion 65.

Figure 2A shows on the left-hand side thereof a perspective view of a portion only of the moulded-plastics body part of a 360 cordless appliance power input connector cum element protector control substantially as described in our British Patent Application No. 9808484. 1 aforementioned. Of course, the present invention is not limited to the attachment of such devices to electric heating elements and could be utilized for the attachment of any kind of device to an electric heating element. As shown in Figure 2A, the device body 70 is formed with integrally moulded receptacles 71 for receiving the upstanding twist-tabs 63 when the device is appropriately located on the bracket 60. The receptacles 71 have internal camming surfaces 72 and stops 73.

As shown in Figure 2A, a twist-tab 62 is received in receptacle 71 and awaits a twisting operation. A twisting tool 74 having a slot 75 in its tip is shown being advanced towards the twist-tab. Figure 2B shows the slotted end 75 of the tool 74 engaged with the head of twist-tab 63 and illustrates that the tool should then be turned in a clockwise direction to twist the head 64 of the twist-tab 63 into the position shown in Figure 2C. During this twisting movement, the bottom surface of the head 64 of the twist-tab 63 rides up the camming surface 72, which causes the device body 70 to be pulled firmly into contact with the mounting bracket 60, until it contacts the stop 73. By repeating this operation for the three twist-tabs 63, the device is reliably secured to the mounting bracket 60.

The receptacles 71 have key-hole type through openings for receiving the twist tabs 63, that is to say they have a circular portion 76 for accommodating the neck portions 65 of the twist tabs and ensuring that they are not significantly displaced laterally when the tabs are twisted and a slotted portion 77 extending from one side of the circular portion 76 for accommodating the larger head portion 64 of the tab 63. The anti-clockwise oriented wall of the slotted portion 77 serves as a stop 78 when the tabs are un-twisted for removal of the device 70 from the bracket 60, as best seen in Figure 2C.

The invention thus provides a simple and convenient means of attaching an element protector control or any other device to an electric heating element, the described means being advantageous over the arrangement of Figure 5 of our British Patent Application No. 9808484.1 in that screw-threaded receptacles do not have to be provided on the mounting bracket and separate fixing screws are not required. In the practice of the present invention, both the mounting brackets and the co-operating moulded plastics body parts of the device being affixed can be precisely formed and, by virtue of the form of the twist tabs and their accommodating receptacles in the device, assured and precise fixing of the device to its mounting bracket is readily achieved. Furthermore, removal of the device from the bracket is likewise a simple and well defined operation. The described arrangement will readily withstand at least 30 assembly and dis-assembly operations before showing any signs of failure, which is well above the number of operations it is ever likely to be called upon to withstand in practice.

Claims

CLAIMS 1. A method of securing a device to an electric heating element, said method comprising securing a mounting bracket to the heating element, the mounting bracket being formed with one or more twist-tabs adapted for engagement with the device and the device having one or more parts adapted for co-operation with the twist-tab (s), assembling the device to the mounting bracket with the twist-tab (s), assembling the device to the mounting bracket with the twist-tab (s) in registry with said device part (s), and twisting the twist-tabs (s) to secure the device to the mounting bracket.
2. A method as claimed in claim I wherein the part (s) of the device adapted for co-operation with the twist-tab (s) of the mounting bracket are such as to enable the twist-tab (s) once twisted to be un-twisted for releasing the device from the bracket.
3. A method as claimed in claim 1 or 2 wherein the part (s) of the device adapted for co-operation with the twist-tab (s) of the mounting bracket include stop formations limiting the degree of twisting of the tab (s) in a device-fixing and/or a device-releasing direction.
4. A method as claimed in any of the preceding claims wherein the part (s) of the device adapted for co-operation with the twist-tab (s) of the mounting bracket include cam means adapted to pull the device towards the mounting bracket when the tab (s) are turned in a device-fixing direction.
5. A method as claimed in any of the preceding claims wherein the part (s) of the device adapted for co-operation with the twist-tab (s) and the twist-tab (s) are adapted and arrange so that the device is not subject to significant lateral displacement relative to the mounting bracket when the tab (s) are being twisted.
6. A method as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings
7. A mounting bracket adapted and arrange for use in a method as claimed in any of the preceding claims.
8. A device adapted and arrange for use in a method as claimed in any of the preceding claims.
9. An electrically powered water heating vessel having an electric heating element of the underfloor or thick film type and wherein a heating element overtemperature protection device is removably assembled with the heating element by virtue of a mounting bracket for the device being secured to the heating element and the device being secured to the mounting bracket by means of the engagement of one or more twist-tabs of the mounting bracket releasably with the device.
10. An electrically powered water heating vessel having an electric heating element of the underfloor or thick film type and wherein a power supply input connector for the heating element is removably assembled with the heating element by virtue of a mounting bracket for the connector being secured to the heating element and the connector being secured to the mounting bracket by means of the engagement of one or more twist-tabs of the mounting bracket with the connector.
11. An electrically powered water heating vessel as claimed in claims 9 and 10 wherein the same bracket serves for mounting the device and the power supply input connector to the heating element.
12. An electrically powered water heating vessel as claimed in claim 11 wherein the power supply input connector and the heating element overtemperature protection device are integrally formed.

12. An electrically powered water heating vessel as claimed in claim I1 wherein the power supply input connector and the heating element overtemperature protection device are integrally formed.

Amendments to the claims have been filed as follows CLAIMS: 1. A method of securing a device to an electric heating element, said method comprising securing a mounting bracket to the heating element, the mounting bracket being formed with one or more twist-tabs adapted for engagement with the device and the device having one or more parts adapted for co-operation with the twist-tab (s), assembling the device to the mounting bracket with the twist-tab (s) in registry with said device part (s), and twisting the twist-tabs (s) to secure the device to the mounting bracket.

2. A method as claimed in claim 1 wherein the part (s) of the device adapted for co-operation with the twist-tab (s) of the mounting bracket are such as to enable the twist-tab (s) once twisted to be un-twisted for releasing the device from the bracket.

3. A method as claimed in claim 1 or 2 wherein the part (s) of the device adapted for co-operation with the twist-tab (s) of the mounting bracket include stop formations limiting the degree of twisting of the tab (s) in a device-fixing and/or a device-releasing direction.

4. A method as claimed in any of the preceding claims wherein the part (s) of the device adapted for co-operation with the twist-tab (s) of the mounting bracket include cam means adapted to pull the device towards the mounting bracket when the tab (s) are turned in a device-fixing direction.

5. A method as claimed in any of the preceding claims wherein the part (s) of the device adapted for co-operation with the twist-tab (s) and the twist-tab (s) are adapted and arrange so that the device is not subject to significant lateral displacement relative to the mounting bracket when the tab (s) are being twisted.

6. A method as claimed in claim I and substantially as herein described with reference to the accompanying drawings.

7. A mounting bracket adapted and arrange for use in a method as claimed in any of the preceding claims.

8. A device adapted and arrange for use in a method as claimed in any of the preceding claims.

9. An electrically powered water heating vessel having an electric heating element of the underfloor or thick film type and wherein a heating element overtemperature protection device is removably assembled with the heating element by virtue of a mounting bracket for the device being secured to the heating element and the device being secured to the mounting bracket by means of the engagement of one or more twist-tabs of the mounting bracket releasably with the device.

10. An electrically powered water heating vessel having an electric heating element of the underfloor or thick film type and wherein a power supply input connector for the heating element is removably assembled with the heating element by virtue of a mounting bracket for the connector being secured to the heating element and the connector being secured to the mounting bracket by means of the engagement of one or more twist-tabs of the mounting bracket with the connector.

11. An electrically powered water heating vessel as claimed in claims 9 and 10 wherein the same bracket serves for mounting the device and the power supply input connector to the heating element.