GB2392598A

GB2392598A - Metal to frangible component sealing and securing system

Info

Publication number: GB2392598A
Application number: GB0220358A
Authority: GB
Inventors: Peter Hallam Wright
Original assignee: Otter Controls Ltd
Current assignee: Otter Controls Ltd
Priority date: 2002-09-02
Filing date: 2002-09-02
Publication date: 2004-03-03
Anticipated expiration: 2022-09-02
Also published as: CN1495368A; GB2392598B; GB0220358D0

Abstract

An electric beating element 1, having a depending flange around which is placing an elastomeric spacer ring 14, is inserting into a vessel bottom where the compressed spacer ring and serves to hold the heating element in predetermined spaced-apart relation to the vessel bottom while a curable adhesive sealant is introduced 13,15 and allowed to cure so as to hold the two parts together ensuring that thermal movements of the heating element cannot crack the vessel.. The spacer ring can be removed for re-use or can be left in place. The sealant and the spacer may be silicone and the vessel may be, for example, glass, glass ceramic or porcelain

Description

IMPROVED METAL TO GLASS SEALING SYSTEM

Field of the Invention:

This invention concerns an improved metal to glass sealing system 5 and more particularly, though not exclusively, concerns the sealing of electric heating elements into glass vessels.

Background of the Invention:

Figure 1 of the accompanying drawings illustrates a widely used 10 conventional method for sealing an electric heating element into the bottom of a glass vessel. Referring to the figure, the heating element 1 is formed with an upwardly-facing circumferential groove 2, and the lower edge 3 of the glass vessel 4 is formed with a slight bulge as shown. This bulge tends to form naturally as part of the process for forming the vessel 4 involves heating 15 of its lower edge to remove sharp edges.

To seal the heating element 1 to the vessel 4, the lower edge 3 of the vessel is located in the element groove 2 with the glass spaced apart from the metal heating element, appropriate jigs being used for this purpose. A suitable silicone sealant is then poured into the groove 2 to surround the bulge 20 in the lower edge 3 of the glass vessel 4 and the assembly is left for about 24 hours to cure, the curing process being triggered by natural air humidity.

It is necessary that the glass does not contact the metal heating element at any point since the ensures that thermal movements of the heating

element in use are isolated from the glass vessel and do not risk cracking the vessel such as to cause it to leak. To ensure that this cannot happen, the assembly has to be precisely controlled with jigs supporting and locating the glass vessel relative to the heating element. This leads to increased 5 manufacturing expense, not only as regards assembly time but also as regards the cost of the number of jigs to support 24 hours production. It is a common problem with appliances that use this form of construction that manufacture is not sufficiently precisely controlled, leading to appliance failure in use.

10 Objects and Summary of the Invention:

It is the principal object of the present invention to overcome or substantially reduce the abovementioned problem.

According to the present invention, a metal member, an electric heating element for example, is secured into a vessel formed of glass or 1 S porcelain or any like readily-breakable material by forming the metal member so that it can be fitted into the open bottom of the vessel with an all round spacing therefrom and has a surface facing the internal wall surface of the vessel, providing a spacer of resilient material which surrounds the said surface of the metal member and locates it within the vessel, and introducing 20 a curable adhesive material into the spacing between the metal member and the internal wall of the vessel.

As will be explained in more detail hereinafter, the present invention can accurately locate the respective parts during introduction of the adhesive

and during curing and requires no accurate jigs. The assemblies can simply be placed on a flat surface for curing to take place, and access to the adhesive for sufficient air to ensure full curing is assured.

The above and further aspects of the present invention are set forth in 5 the expanded claims and will be explained hereinafter by reference to specific embodiments which are illustrated in Figures 2 and 3 of the accompanying drawings. Description of the Drawings;

10 Figure 1 illustrates a prior art method of securing a heating element in

a glass vessel; Figure 2 is a view similar to Figure 1, but inverted, illustrating an embodiment of the present invention; and Figure 3 is a view similar to Figure 1 illustrating a second embodiment 15 of the present invention.

Detailed Description of the Embodiments:

Refernng to Figure 2, the vessel 4 is identical to that described hereinbefore with reference to Figure 1, except that it is no longer necessary 20 to form a bulge on the lower edge 3 of the vessel since the heating element 1 is fitted into the bottom of the vessel, rather than the vessel edge fitting into a groove formed in the heating element as in Figure 1. The heating element 1 has a downwardly-depending flange 10 (remember, Figure 2 shows the vessel

inverted) which is stepped at 11 to accommodate an elastomeric spacer 12 which fits around the heating element circumference and projects radially outwardly therefrom.

With the spacer 12 fitted to the heating element 1, the heating element 5 is inserted into the open bottom of the vessel 4. The spacer 12 takes up the gap between the heating element flange 10 and the inner wall of the vessel 4 and properly locates the heating element within the vessel as the heating element is adjusted to its correct position within the vessel. Silicone adhesive material may then be poured into the groove 13 between the element flange 10 10 and the vessel wall and allowed to cure, the surface of the adhesive being fully exposed to the air humidity to ensure a full cure, there being no obstructing features. After curing, the elastomeric spacer 12 may be removed via the inside of the vessel and may be reused.

Figure 3 shows an alternative embodiment wherein the intention is not 15 to re-use the resilient elastomeric spacer 12, but rather leave it in place. As shown, the heating element flange 10 in this embodiment is formed with a spacer-retaining groove 14. As in the Figure 2 embodiment, with an elastomeric spacer 12 installed in the groove 14, the heating element 1 may be introduced into the bottom of the vessel. The assembly may then be placed, 20 the right way up, onto a flat surface, which serves to align and straighten the heating element within the vessel and provides additional support indirectly to the spacer 12. Adhesive may then be introduced into the groove 15 formed between the glass vessel wall and the heating element flange, from inside the

s vessel. The top surface of the adhesive may be suitably smoothed to give a good cosmetic appearance. The assembly is then simply left to cure. As in the Figure 2 embodiment, the surface of the adhesive is well exposed to the air for efficient curing.

5 The invention as hereinabove described has the advantage that the lower edge of the glass vessel does not require any special form, such as the bulge mentioned above, and may be prepared in the most economical fashion.

The edge of the heating element has a downwardly depending flange, which has a length to suit the style of the appliance, and has an outer diameter which 10 gives a clearance between the plate and the glass vessel inside diameter under all conditions of manufacturing tolerances. The flange has also a feature which locates an elastomeric spacer which fits around the flange, and presses against the inner surface of the glass vessel. The spacer is made of a suitable material, depending on whether it is intended to leave it in place, in which 15 case a silicone elastomer would be appropriate, or if it is intended to be removed after completion, in which case a cheaper material could be used.

The assembly of the plate into the glass vessel, with the spacer in place, ensures that a gap exists all round the flange of the element, and the resilience of the seal holds the parts together in the correct relative position. The gap 20 between the flange and the glass vessel forms a groove, with an outer glass wall, an inner metal (eg stainless steel) wall and an elastomer bottom. This groove is filled with adhesive which can simply be left to cure. After curing

the spacer may be removed if desired as it no longer has any function and may be reused, or alternatively it can be left in situ.

A further advantage is that the element plate is entirely within the glass vessel and there is no part that projects beyond the outside diameter of 5 the glass. In the prior construction, this projection normally necessitated a step reduction in diameter at the lower edge of the periphery of the glass (similar to the top edge of the vessel shown in Figure 1) to allow a moulding to conceal the edge of the element. The form of the glass is thus simpler to manufacture and the appliance designer is given greater freedom.

10 The invention having been described in the foregoing by reference to specific embodiments, it is to be appreciated that the embodiments are in all respects exemplary and that modifications and variations thereto could be made without departure from the scope of the invention as set forth in the appended claims. For example, whereas the embodiments concern the fixing 15 of an electric heating element to the bottom of a glass vessel, the invention is also applicable to other applications wherein a metal plate or other member which is not a heating element is to be secured to the base of a glass, glass ceramic or other frangible material vessel. Furthemmore, whereas the embodiments concern the fitting of a metal member into a larger diameter 20 glass or other vessel, the same technique, namely the use of a resilient spacer to predetermine the relative positions of the parts, could be employed to fix the bottom of a frangible vessel into a larger-diameter metal member.

The heating element 1 is schematically illustrated and could be of the thick film type having a printed circuit type heating element on the underside of the element plate shown, or could just as well be of the underfloor type in which the plate shown provides support for a more convention resistance wire 5 type of heating element secured in known manner to the plate.

Claims

CLAIMS:

1. A method of securing a metal member to an open frangible component, said method comprising the use of a resilient spacer 5 between opposed surfaces of the two parts so as to hold them in predetermined spacedapart relationship whilst an adhesive sealant is introduced between the two parts and allowed to cure.

2. A method as claimed in claim 1 wherein the metal member has a 10 lesser diameter than the frangible component and is fitted into the opening thereof.

3. A method as claimed in claim 1 or 2 wherein the metal member is an electric heating element, or a mounting therefor, and the frangible 15 component is a vessel body.

4. A method as claimed in claim 3 wherein the vessel body is fommed of glass, glass ceramic, porcelain or the like.

20 5. A method as claimed in any of the preceding claims wherein the metal member is formed on its said surface with a seating for said resilient spacer.

6. A method as claimed in any of the preceding claims wherein the resilient spacer comprises an elastomeric material.

7. A method as claimed in claim 6 wherein said elastomeric material is a 5 silicone material.

8. A method as claimed in any of the preceding claims wherein said sealant is a silicone material., 10 9. A method as claimed in any of the preceding claims comprising removing and re-using the resilient spacer after the adhesive sealant has cured.

10. A method as claimed in any of claims 1 to 8 wherein the resilient 15 spacer is retained in the construction after the adhesive sealant has cured. A structure formed by a method as claimed in any of the preceding claims. 12. In the manufacture of an electrically heated vessel, a structure comprising an open-ended vessel body formed of glass or of a similar frangible material and an electric heating element or support therefor

fitted into the open end of the vessel body, the heating element/support comprising a metal plate having a circumferential flange and dimensioned to fit into the open end of the vessel body with an all round spacing therefrom, a resilient spacer surrounding the said flange 5 and compressed into said spacing, and a curable or cured adhesive sealant introduced into said spacing.

13. An electrically heated vessel comprising a vessel body formed of glass or of a similar frangible material and an electric heating element or 10 support therefor secured into an otherwise open end of the vessel body, the heating element/support comprising a circumferential flange dimensioned to fit into the vessel body with an all-round uniform spacing therefrom, and a cured adhesive sealant material between the external surface of said flange and the internal surface of the vessel 15 wall and retaining the heating element/support with said uniform spacing from the internal surface of the vessel wall.

14. A vessel as claimed in claim 13 wherein a spacer of resilient material is disposed within said spacing.

15. A method or an electrically heated vessel substantially as hereindescribed with reference to Figure 2 or Figure 3 of the accompanying drawings.