IMPROVEMENTS RELATING TO ELECTRICALLY HEATED VESSELS

Abstract: For assembling a planar heating element to a glass bodied vessel, the heating element forming the bottom of the vessel, the heating element (or a carrier therefor) is formed with an upwardly extending flange which extends, with spacing, around the rim of a necked-in part of the lower end of the vessel body and a sealing ring is interposed between the flange and the vessel body. The heating element is supported by a base part of the vessel which is attached to the glass body part by virtue of being attached to a separate handle which extends up the side of the glass body of the vessel and hooks over its top edge. Other means of securing the base to the glass vessel body are described including a base-to-spout attachment, the provision of a band encircling the vessel body and attached to the handle which in turn is attached to the base, and adhesive. The problem of dimensional variations in mass produced blow moulded glass vessel bodies is overcome since the seal takes up any dimensional variations.

Description: IMPROVEMENTS RELATING TO ELECTRICALLY HEATED VESSELS Field of the Invention: This invention concerns improvements relating to electrically heated vessels, particularly electrically powered water heating vessels such as kettles, hot water jugs, pots, pans, urns, laboratory equipment and the like. Background of the Invention: Our British Patent Application No. 9821862.1 concerns the assembly of planar electric heating elements into the bodies of electrically heated vessels, particularly plastics material vessel bodies which exhibit substantial dimensional changes as the temperature of water within the vessel is brought from cold to boiling. Planar heating elements are commonly of two different types, namely the underfloor heating element which comprises a metal plate having a sheathed heating element clamped or clenched to the underside thereof and the thick film heating element which comprises a resistance heating track or layer formed on the underside of an electrically insulating substrate. A sheathed heating element comprises an electrical resistance wire mounted with mineral insulation within a tubular metal sheath. The substrates used for thick film heating elements commonly comprise a stainless steel plate which is coated with glass or other electrically insulating material, the resistance heating track or layer being formed on the surface of the glass and then a further, protective, electrically insulating layer being formed over the resistance heating track or layer. Described in our British Patent Application No. 9821862.1 abovementioned are proposals for the attachment of planar heating elements of both types abovementioned in water heating vessels by provision of abutments within the vessel body against which the heating element is urged and retained by means of a circlip arrangement interacting with formations provided in the wall of the moulded plastics vessel body, the spacing between the periphery of the heating element and the internal surface of the vessel wall being closed by means of a resilient seal formed of an elastomeric and advantageously thermally-insulating material. A preferred form of seal comprises a ring shaped to locate positively around the periphery of the heating element and having a plurality of outwardly-extending, vertically spaced-apart fins which are deformed by contact with the vessel wall as the heating element and seal are assembled into the vessel. Whereas the invention of our British Patent Application No. 9821862.1 is primarily directed to the problems of assembling planar heating elements into plastics bodied vessels, the present invention is concerned with the different problems that arise when the vessel body is formed of glass. Glass vessels are generally blown and formed into a mould and this controls the outer dimensions fairly accurately. However, the internal dimensions, in addition to whatever tolerances affect the external dimensions, exhibit dimensional variations due to variations in the thickness of the glass. Further inaccuracy is introduced when the vessel is annealed for stress relief after it is initially formed. As a result, the outer diameter of a mass-produced glass-bodied vessel may exhibit a dimensional tolerance of +/- 2mm and the internal diameter may be somewhat worse. On account of these levels of tolerance variation, the sealing of a heating element into a glass-bodied vessel by a technique as taught in our British Patent Application No. 9821862.1 may not be satisfactory. Object and Summary of the Invention: The principal object of the present invention is to overcome or substantially reduce the abovementioned problem of assembling planar heating elements into glass-bodied vessels. The present invention resides in the concept of utilizing a seal arrangement which is similar in principle to the arrangement disclosed in our British Patent Application No. 9821862.1 , but differs therefrom in that the arrangement is modified so that the seal acts between the periphery of the heating element and the external surface of the glass vessel, rather than the internal surface as in the arrangement taught in British Patent Application No. 9821862.1 According to the present invention, an electrically heated vessel, particularly though not exclusively a glass bodied vessel, has a planar heating element assembled therewith by virtue of the heating element having a part formed to extend around the outside of the πm of an opening in the vessel with a spacing therefrom, and a resilient seal is provided between said part and said rim so as to seal said spacing. The planar heating element itself may have an upturned flange constituting the said part formed to extend around the outside of the rim of the vessel opening. Alternatively, and as in some of the embodiments described in British Patent Application No. 9821862.1 (the embodiment of Figure 4 for example), the heating element proper may be arranged to sit within a mounting flange which is provided with a part formed to extend around the outside of the rim of the vessel opening as aforesaid. The seal can comprise an annular member having an external surface adapted to coact with the inner surface of said heating element part and an internal plurality of vertically-spaced inwardly-directed fins adapted to contact the external surface of the said rim. As such, the seal is the inverse of the preferred seal configuration described in British Patent Application No. 9821862.1 aforementioned. The seal may be shaped to positively locate with the upstanding part of the heating element. In order to retain the heating element in place, it is proposed in accordance with an exemplary embodiment to provide the vessel with a base securely affixed to the glass bodied vessel and bearing upon the heating element so as to keep it in place. The base can conveniently form part of a handle moulding for the vessel, for example, the glass body of the vessel being captured within the base and handle moulding for example by virtue of the handle moulding providing a top mounting for a lid for the vessel and/or by virtue of the vessel body including an integrally formed pouring spout which serves additionally as an anchorage for the base. The above and further features of the present invention are set forth in the appended claims and, together with advantages thereof, will be made clear in the following detailed description given with reference to the accompanying drawings. Description of the Drawings: Figures 1A, IB, 1C and ID are, respectively, top plan, side elevation, cross-sectional and enlarged fragmentary cross-section views of a sealing ring which is utilized in the practice of the present invention as hereinafter described; Figure 2 is an exploded perspective view showing an exemplary embodiment of glass-bodied water heating vessel according to the present invention; Figure 3 is a cross-sectional side elevation view of the embodiment of Figure 2, showing in addition an exemplary handle moulding and base-to-spout attachment; Figure 4 is a perspective view of the vessel shown in Figure 3; Figure 5 is a side-elevation view showing an alternative to the base-to-spout attachment of Figure 3; and Figure 6 is a cross-sectional view similar to Figure 3, but without the base-to-spout attachment and including a modification of the heating element and of the glass-bodied vessel for effecting positive engagement therebetween. Detailed Description of the Embodiments: Referring first to the exploded view of Figure 2, shown therein is an open ended blow-moulded, glass vessel body 1 of generally cylindrical form provided with an integral pouring spout 2 at its upper rim 3 and, at its other (bottom) end, with a necked-in portion 4 of reduced diameter. An O-ring elastomer seal 5, which is shown in more detail in the several views of Figure 1 and will be described more fully hereinafter, is adapted to sealingly engage the external surface 6 of the reduced-diameter portion 4 of the vessel body 1. The seal 5 is also adapted to make positive engagement with an upturned flange part 7 of a schematically-shown planar heating element 8 and to seal the gap between the internal surface of flange part 7 and the external surface 6 of the necked-in vessel body portion 4 when, as hereinafter described, the heating element 8 is fitted to the bottom of the vessel body 1. Finally, there is also shown in Figure 2 a base 9 provided with internal ribs 10 which, in the assembled vessel, serve to keep the heating element 8 in place. Figure 3 is a cross-sectional view of a vessel assembly substantially as shown in Figure 1 save for the showing additionally of a handle moulding 11 and a base-to-spout attachment moulding 12. Referring to Figure 3 and also to the several views of Figure 1 showing the detailed form of the seal 5, it can be seen that the seal 5 has a slot formation 13 which is adapted to receive the upturned flange part 7 of the heating element 8 so as positively to engage the seal 5 with the flange part 7. With the seal 5 thus positively engaged with the upturned flange part 7 of the heating element 8, the heating element 8 can be pushed onto the reduced diameter part 4 of the vessel body 1. The seal 5 has three internal horizontal fins 14 which are vertically spaced apart from each other (see Figure ID), the lowermost fin being longer than the other two. As shown in Figure 3, the bottom rim 15 of the reduced diameter part 4 of the vessel body 1 seats down upon the longest fin 14 when the heating element 8 is pushed into place on the bottom of the vessel body 1, and the other two fins 14 are deformed downwardly by engagement with the surface 6 at the bottom of the vessel body 1. The seal 5 thus renders watertight the gap that otherwise would exist between the internal surface of the heating element flange part 7 and the external surface 6 at the bottom of the vessel body. The base 9 is formed of moulded plastics material and the internal ribs 10 are shaped and dimensioned as shown to provide support for the underside of the planar heating element 8 around the periphery thereof. The handle moulding 1 1 , which may be formed integrally with the base moulding 9 or may be attached thereto by means of screws or clips for example, is arranged as shown to hook over the top rim 3 of the vessel 1 so as to secure the handle 1 1 to the vessel and at the same time maintain the glass body 1 of the vessel securely in place. There may be a separate moulding to secure the top of the handle to the rim of the vessel and take up assembly tolerances, but this is not shown. The handle, as shown, incorporates a steam duct 15 for directing steam from within the top of the vessel to a thermally-responsive control (not shown) provided for automatically switching off the heating element when water boils in the vessel. Also not shown is a lid for the vessel, which may be pivoted from the top of the handle moulding or from the separate securing moulding or may be fixed if the vessel is to be filled via the spout 2. On the spout side of the vessel, opposite the handle moulding, there is provided a base-to-spout attachment moulding 12 which can be formed integrally with the base moulding 9 or may be attached thereto by any convenient means. The base-to-spout attachment moulding 12, as shown more clearly in Figure 4, ties the upper rim 3 of the vessel to the base moulding 9 by virtue of having a loop formation 16 at its upper end which fits around and over the spout 2. Alternatively, or additionally, as shown in Figure 5, a metal or plastics material band or strap 17 could be provided around the vessel body 1 so as to retain the vessel body and handle moulding together; such a band could be moulded integrally with the base-to-spout attachment moulding 12 and/or with the handle moulding 11 , though this obviously would complicate the respective mouldings. Further, an adhesive such as an adhesive silicone rubber (for example Silicoset RTV Adhesive Sealant manufactured by Ambersil Limited) could be used for fixing the glass body part 1 of the vessel into its base moulding 9. Figure 6 shows a modification of the above-described embodiment wherein the bottom rim 15 of the glass body 1 of the vessel has a protrusion 18 aligned vertically with the spout 2 and the vertically-extending flange part 7 of the heating element 8 is formed with a detent 19 adapted to hook over the protrusion 18 so as to assist in retaining the heating element to the vessel body. The protrusion 18 is designed so as not to interfere with the operation of the seal 5 and/or the seal 5 may be modified to accommodate the detent 19 without distortion of the seal which might cause leakage. Plural protrusions could be provided spaced around the bottom rim 15 of the vessel body 1, or the protrusion could be formed continuously about the rim 15. Having thus described the present invention by reference to specific embodiments, it is to be well understood that the embodiments are in all respects exemplary and that modifications and variations thereto are possible without departure from the spirit and scope of the invention as set forth in the appended claims. For example, as previously mentioned herein, the part 8 shown in Figure 2 could be formed as a separate carrier for a planar heating element rather being an integral part of the heating element itself. Additionally, the juncture between the base moulding and the glass jug body 1 could be concealed and reinforced by means of an encircling band similar to the band 17 shown in Figure 5. Finally, while the invention is particularly concerned with the assembly of planar electric heating elements to glass bodied vessels, the invention clearly is equally applicable to vessel bodies formed of moulded plastics materials or of other materials such as ceramics, porcelain or china for example.

Claims: CLAIMS: 1. An electrically heated vessel wherein a planar heating element is assembled with the body of the vessel by virtue of the heating element, or a carrier therefor, having a part formed to extend around the outside of the rim of an opening in the vessel body with a spacing therefrom, and a resilient seal is provided to seal said spacing. 2. An electrically heated vessel as claimed in claim 1 wherein the vessel body is formed of glass. 3. An electrically heated vessel as claimed in claim 1 or 2 wherein said part comprises an upstanding flange. 4. An electrically heated vessel as claimed in claim 3 wherein said flange has one or more detents formed therein for positive engagement with complementary formations provided on said rim. 5. An electrically heated vessel as claimed in any of the preceding claims including a base arranged to support the heating element relative to the vessel body. 6. An electrically heated vessel as claimed in claim 5 wherein the base is adhesively secured to the vessel body. 7. An electrically heated vessel as claimed in claim 5 or 6 wherein the base is secured to the vessel body, at least in part, by means of the vessel including one or more structural parts which connect at one end to the base and at their other end engage with the top of the vessel body or an upper part thereof. 8. An electrically heated vessel as claimed in claim 7 wherein said one or more structural parts comprises a handle of the vessel. 9. An electrically heated vessel as claimed in claim 7 or 8 wherein the vessel body is formed with a spout and said one or more structural parts comprises a base-to-spout attachment. 10. An electrically heated vessel as claimed in any preceding claim wherein one or more bands are provided securing the vessel body to a separately formed handle of the vessel. 1 1. An electrically heated vessel as claimed in any of the preceding claims wherein said planar heating element comprises a metal plate having a sheathed heating element affixed to the underside thereof. 12. An electrically heated vessel as claimed in any of claims 1 to 10 wherein said planar heating element comprises a thick film heating element. 13. An electrically heated vessel as claimed in any of the preceding claims wherein said seal comprises an annular member shaped on its external periphery complementarily to the internal surface of said part and having on its internal surface a plurality of vertically spaced-apart horizontal fins. 14. An electrically heated vessel as claimed in claim 13 and wherein the seal is substantially as hereinbefore described with reference to Figures 1A, IB, 1C and ID of the accompanying drawings. 15. An electrically heated vessel substantially as hereinbefore described with reference to any of Figures 2 to 6 of the accompanying drawings. 16. A seal adapted and arranged for use in an electrically heated vessel as claimed in any of the preceding claims. 17. A planar heating element adapted and arranged for use in an electrically heated vessel as claimed in any of claims 1 to 15.

Inventors: HOWARTH JOHN ANTHONY, LINDSTROM JOHN JEFFREY, O'NEILL ROBERT ANDREW, HOWARTH, JOHN, ANTHONY, LINDSTROM, JOHN, JEFFREY, O'NEILL, ROBERT, ANDREW
Applicants: HOWARTH JOHN ANTHONY, LINDSTROM JOHN JEFFREY, ONEILL ROBERT ANDREW, OTTER CONTROLS LTD, HOWARTH, JOHN, ANTHONY, LINDSTROM, JOHN, JEFFREY, O'NEILL, ROBERT, ANDREW, OTTER CONTROLS LIMITED
Application year: 1999
Main classification: A47J27
IPC codes: A47J27