GB2340714A

GB2340714A - Securing insulation in support dish

Info

Publication number: GB2340714A
Application number: GB9817644A
Authority: GB
Inventors: David Aubrey Plumptre
Original assignee: Ceramaspeed Ltd
Current assignee: Ceramaspeed Ltd
Priority date: 1998-08-14
Filing date: 1998-08-14
Publication date: 2000-02-23
Also published as: EP0981264A2; GB9817644D0; EP0981264A3

Abstract

An electric heater comprises a metal support dish (1) having a base (1A) and an upstanding peripheral rim (1B), and a layer (2) of insulation material in the dish with at least one heating element (3) disposed relative thereto. A ring-shaped insulation member (6) is arranged within the dish adjacent to the peripheral rim and supported at least in part on the layer of insulation material. Securing means is provided for the ring-shaped insulation member comprising at least one narrow strip (5) of dish material at the edge of the rim, formed by a slit section (4) of the dish, the or each narrow strip (5) being deformed to overlying engage a portion (9, 10) of the ring-shaped insulation member.

Description

2340714 Electric Heater This invention relates to electric heaters

particularly, but not exclusively, for use in cooking appliances behind a sheet of a material such as glass-ceramic. In particular, the sheet of material such as glass-ceramic may be a cooking surface.

Electric heaters are well known for use behind glass-ceramic cooking surfaces. Such heaters can comprise a metal support dish, having a base and an upstanding peripheral rim and having therein a base layer of insulation material, such as microporous thermal and electrical insulation material. At least one electrical heating element is provided, supported on or adjacent to the surface of the base layer. A ring-shaped insulation member is known to be arranged within the dish adjacent to the peripheral rim and supported at least in part on the layer of insulation material. Stich ring-shaped insulation member may have a top surface arranged to contact the rear surface of a glass-ceramic cooking plate.

It is known for such a ring-shaped insulation member to comprise a material such as bound vermiculite, although other materials are also well known to be used.

The ring-shaped insulation member may be secured in the dish by frictional engagement with the rim, or with a stepped and/or tapered shim of insulation material of the base layer provided between the ring-shaped member and the rim. In practice, however, such frictional engagement can be inadequate, particularly since some softening or shrinkage of the ring-shaped member may occur at elevated temperatures when the heater is subsequently operated. As a result. undesirable detachment of the ring-shaped member from the dish may occur.

2 It is an object of the present invention to overcome or minimise this problem.

The present invention provides an electric heater comprising a metal support dish having a base and an upstanding peripheral rim, a layer of insulation material in the dish with at least one heating element disposed relative thereto, a ring-shaped insulation member arranged within the dish adjacent to the peripheral rim and supported at least in part on the layer of insulation material, securing means being provided for the ring-shaped insulation member comprising at least one narrow strip of dish material at the edge of the rim, formed by a slit section of the dish, the or each narrow strip being deformed to overlyingly engage a portion of the ring shaped insulation member.

The portion of the ring-shaped insulation member overlyingly engaged by the or each deformed narrow strip may comprise a protrusion on the member or may comprise a slot, rebate. groove or ledge on or in a section of the member.

is The or each narrow strip may be deformed into a loop shape within the dish and which overlyingly engages a portion of the ring-shaped insulation member. The loop shape may be continuous or discontinuous. that is, broken.

Alternatively the or each narrow strip may be cut to form a tine which is shaped to overlyingly engage a portion of the ring-shaped insulation member.

A plurality of spaced apart narrow strips of dish material may be provided, formed by a plurality of slit sections of the dish. the narrow strips being deformed to overlyingly engage associated portions of the ring-shaped insulation member.

3 The associated portions of the ring-shaped insulation member may comprise a plurality of outwardly-directed protrusions provided on and spaced apart around the member, the protrusions having top surfaces overlyingly engaged by the deformed narrow strips. In this embodiment, the protrusions may be integral with the member.

The protrusions may be of higher density than the remainder of the member.

The ring-shaped insulation member may comprise bound vermiculite.

The layer of insulation material may comprise microporous thermal and electrical insulation material.

A shim of the insulation material of the layer may be provided between at least a portion of the ring-shaped insulation member and the peripheral rim of the dish. Such shim may be of stepped or tapered form, reducing in width towards the top of the peripheral rim of the dish.

The ring-shaped insulation member may be of suitably complementary stepped or tapered form for contact with the shim of insulation material.

The invention is now described by way of example with reference to the accompanying drawings, in which:

Figure I is a perspective view of part of an electric heater according to the invention:

Figure 2 is an exploded perspective view of an electric heater according to the invention.- 4 Figure 3 is a perspective view of part of an alternative arrangement for the heater of Figure I and Figure 4 is a perspective view of part of a further alternative arrangement for the heater of Figure 2. An electric heater comprises a metal support dish I having a base IA and an upstanding peripheral rim 113. A layer 2 of microporous insulation material is provided in the dish I with 10 at least one heating element 3, such as of corrugated ribbon or coiled wire form, disposed thereon or adjacent thereto. The dish is slit at regions 4 to provide narrow strips 5 of dish material spaced apart around the rim at the edge thereof 15 A ring-shaped insulation member 6. comprising bound vermiculite, is arranged to be located within the dish I adjacent to the peripheral rim I B and supported at least in part on the layer 2 of insulation material. 20 To reduce the temperature of the peripheral rim I B of the dish, a shim 7 of insulation material of the layer 2, of lower thermal conductivity than the ring-shaped insulation member 6, is optionally provided between the ring-shaped member 6 and the peripheral rim IB of the dish. This shim 7 may be of stepped or tapered form, reducing in width towards the top of the peripheral rim IB of the dish. The ring-shaped insulation member 6 is of suitably 25 complementary stepped or tapered form for contact with the shim 7 of insulation material.

A plurality of outwardly-directed protrusions 8 are provided integral with the ring-shaped member 6 and spaced apart around the member. Such protrusions have top surfaces 9 and arc preferably formed of a higher density than the ring-shaped member 6 itself This is achieved by compacting the ven-niculite material of the protrusions 8 to a greater extent than the material of the remainder of the ring-shaped member 6, during formation of the ring-shaped member 6.

The ring-shaped member 6 is located in the heater with the protrusions 8 on the member 6 10 aligned with the narrow strips 5 of dish material.

The narrow strips 5 are deformed into loop shapes within the dish which overlie and engage the top surfaces 9 of the protrusions 8 and secure the ring-shaped member 6 in position in the heater. Partial deforrilation of the narrow strips may be effected prior to locating tile ring15 shaped member in the heater.

The loop shapes of the narrow strips 5 can be continuous, as shown in Figure 2. They could however be discontinuous (i.e. broken), as shown by reference numeral 5A in Figure 3. by breaking or cutting the narrow strips prior to or during deformation thereof Instead of the narrow strips 5 being deformed into loop shapes, they could, as shown in Figure 4. be cut to form tines 5B which are shaped to overlie and engage the top surfaces 9 of the protrusions 8 and secure the ring-shaped member 6 in position in the heater, 6 Instead of protrusions 8 being provided on the ring-shaped member 6, slots, rebates, grooves or ledges 10 could be provided in the member 6, facing the upstanding peripheral rim lB of the dish, the deformed narrow strips 5, 5A, 5B, either as loop shapes or tines. engaging with such slots. rebates, grooves or ledges 10 to secure the ring-shaped member 6 in position in the 5 heater.

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Claims

1. An electric heater comprising a metal support dish having a base and an upstanding peripheral rim, a layer of insulation material in the dish with at least one heating element disposed relative thereto, a ring-shaped insulation member arranged within the dish adjacent to the peripheral rim and supported at least in part on the layer of insulation material. securing means being provided for the ring-shaped insulation member comprising at least one narrow strip of dish material at the edge of the rim, formed by a slit section of the dish. the or each narrow strip being deformed to overlyingly engage a portion of the ring-shaped insulation member.

2. A heater according to claim 1, in which the portion of the ring-shaped insulation member overlyingly engaged by the or each deformed narrow strip comprises a protrusion on the member or comprises a slot, rebate, groove or ledge on or in a section of the member.

3. A heater according to claim 1 or 2. in which the or each narrow strip is deformed into a loop shape within the dish and which overlyingly engages a portion of the ring-shaped insulation member.

4. A heater according to claim 3, in which the loop shape is continuous or discontinuous.

5. A heater according to claim 1 or 2, in which the or each narrow strip is cut to form a tine which is shaped to overlyingly engage a portion of the ring shaped insulation member.

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6. A heater according to any preceding claim, in which a plurality of spaced apart narrow strips of dish material are provided, formed by a plurality of slit sections of the dish. the narrow strips being deformed to overlyingly engage associated portions of the ring-shaped insulation member.

7. A heater according to claim 6, in which the associated portions of the ring-shaped insulation member comprise a plurality of outwardly directed protrusions provided on and spaced apart around the member, the protrusions having top surfaces overlyingly engaged by the deformed narrow strips.

8. A heater according to claim 7. in which the protrusions are integral with the member.

9. A heater according to claim 8. in which the protrusions are of higher density than the remainder of the member.

10. A heater according to any preceding claim, in which the ring-shaped insulation member comprises bound vermiculite.

11. A heater according to any preceding claim, in which the layer of insulation material comprises microporous thermal and electrical insulation material.

12. A heater according to any preceding claim, in which a shim of the insulation material of the layer is provided between at least a portion of the ring-shaped insulation member and the upstanding peripheral rim of the dish.

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13. A heater according to claim 12. in which the shim is of stepped or tapered form. reducing in width towards the top of the peripheral rim of the dish.

14. A heater according to claim 13, in which the ring-shaped insulation member is of suitably complementary stepped or tapered form for contact with the shim of insulation material.

15. An electric heater constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.