GB2186168A

GB2186168A - Electric immersion heaters

Info

Publication number: GB2186168A
Application number: GB08629706A
Authority: GB
Inventors: George Purvis
Original assignee: Redring Electric Ltd
Current assignee: Redring Electric Ltd
Priority date: 1986-01-29
Filing date: 1986-12-12
Publication date: 1987-08-05
Also published as: GB8629706D0; GB8602191D0

Abstract

A mounting head for an immersion heater has a flanged and threaded first part 1 of sheet metal carrying a sheathed wire heating element 17 designed to be fitted in a liquid tight manner into an opening in a tank, a second part 2, also preferably of sheet metal, having at least one pair of flattened regions to enable it to be held by a spanner or wrench, and means, eg tongues 7 and slots 12, for connecting the two parts together in a manner that secures them against relative rotation. The two parts can be made relatively cheaply by stamping and pressing to shape, and can be formed of dissimilar metals eg part 1 of brass and part 2 of steel. <IMAGE>

Description

SPECIFICATION Electric immersion heaters This invention relates to electric immersion heaters of the kind comprising a mounting head designed to be fitted in a liquid tight manner across an opening in the wall of a vessel, such as a water tank, and carrying a sheathed wire electric heating element such that the latter extends into the interior of the vessel.

The mounting heads of such immersion heaters are commonly formed of solid brass by hot pressing and subsequent machining, and have a threaded portion designed to be inserted into the opening from outside the vessel and on to which is arranged to be screwed a flanged nut for compressing a gasket between a flanged part of the mounting head and the external surface of the vessel to provide a liquid tight seal. The periphery of the flange is usually provided with at least one pair of opposed flattened regions to enable the mounting head to be held firmly, as by a spanner or wrench, when tightening the nut.

However immersion heater mounting heads of solid brass are expensive and an object of the invention is to provide an alternative, less expensive construction of mounting head.

According to the invention a mounting head for an immersion heater of the kind referred to comprises a flanged and threaded first part formed of sheet metal arranged to carry a sheathed wire electric heating element and to be fitted into an opening in the wall of a vessel and to be secured in position by means of a nut screwing on to the threaded part to compress a gasket between the flange and the exterior surface of the wall to form a liquid tight seal, and a second part having at its periphery at least one pair of opposed flattened regions, and means connecting the first and second parts together in a manner which secures them against relative rotation.

The second part is preferably also of sheet metal, the use of sheet metal (which term includes metal alloys) for forming the parts of the mounting head enables them to be fabricated comparatively cheaply by stamping and pressing to shape. Moreover the first part can be formed of a relatively corrosion resistant metal, such as brass, and the second part to be formed of a stronger metal, such as steel giving adequate strength for resisting deformation when it is being held by a spanner or wrench when tightening the securing nut, the latter conveniently including an integral flange in the usual way.

In addition the use of sheet metal enables the second part to be readily formed with an integral earthing tag, as well as a bracket for the attachment of a cover.

The first part is preferably substantially dish shaped having a base carrying the heating element and possibly a pocket for a thermostat, and a cylindrical externally-threaded side wall with an outwardly extending flange around its periphery, the flange having a plurality of lugs spaced around its edge which fit within cooperating slots in the second part and are bent over to secure the parts together. The second part is preferably provided with a continuous side wall of hexagonal or octagonal shape.

It will be understood that the invention includes within its scope immersion heaters incorporating two part mounting heads as above described.

One electric immersion heater and mounting head therefor, in accordance with the invention, for a hot water tank will now be described by way of example with reference to Figs. 1 and 2 of the accompanying drawing, in which Figure 1 represents an exploded perspective view of the main parts of the immersion heater, and Figure 2 represents a transverse section through the assembled mounting head.

Referring to the drawing the immersion heater comprises a mounting head consisting of two main parts 1 and 2, the first part 1 being formed of sheet brass stamped to shape and being generally dish-shaped, having a flat base 4 and a surrounding cylindrical side wall 5, the latter terminating in an outwardly directed flange 6, around which are spaced eight forwardly directed lugs 7. The second part 2 of the mounting head is formed as a steel stamping, and comprises a flat octagonal base 8 formed with a central substantially circular aperture 9, and a surrounding side wall 11. Around the central aperture 9, the base 8 is formed with eight spaced slots 12 positioned to receive the lugs 7 of the first part 1 of the mounting head, which lugs are then arranged to be bent over to secure the parts together as shown in Fig. 2.

The second part 2 of the mounting head is also formed with a projection 13 within the central opening 9 which provides a tag for an earth terminal, and a further, longer projection 14 bent to form a bracket for securing a cover to the mounting head. Thus this further projection is bent so that it extends outwards at right angles to the base 8 and terminates in an inwardly turned end part 1 5 formed with a hole 16 by which the cover (not shown) can be secured to the assembly by means of a self-tapping screw.

The base of the first part 1 of the mounting head carries a sheathed wire electric heating element 17, the ends of which project through openings in its base 4 and are secured in position as by soldering. A cylindrical pocket 18 of known kind, for accommodating a thermostat is also fixed by soldering into a respective opening in the base 4. The exterior surface of the side wall 5 of the part 1 of the mounting head carries a screw thread 19, and is designed to be fitted into an opening in the wall of a hot water tank with the flange 6 outside of the tank, a flanged securing nut being arranged to be screwed on to the threaded part 19 so as to cause the flange 6 to compress a gasket (not shown) against the outer surface of the wall, so as to form a water-tight seal.

The shape of the part 2 of the mounting head enables a spanner or wrench to hold it firmly when tightening the flanged nut, the use of steel for this part giving adequate strength for this purpose, whereas the use of brass for the first part, which will be in contact with water in use of the immersion heater, will ensure adequate resistance to corrosion.

Claims

1. A mounting head for an immersion heater comprises a flanged and threaded first part of sheet metal arranged to carry a sheathed wire heating element, designed to be fitted in a liquid-tight manner into an opening in a vessel and to be secured by means of a nut screwing onto the threaded part to compress a gasket between the flange and the exterior surface of the wall to form a seal, a second part having at its periphery at least one pair of opposed flattened regions and means for connecting said two parts together to secure them against relative rotation.

2. A mounting head as claimed in Claim 1 wherein the second part of the mounting head is formed from sheet metal.

3. A mounting head as claimed in Claim 2 wherein the second part of the mounting head is formed from a relatively strong metal compared with that of the first part.

4. A mounting head as claimed in any preceding claim wherein the first part of the mounting head is formed from a relatively corrosion resistant metal compared with that of the second part.

5. A mounting head as claimed in any preceding claim wherein the first part is formed of brass and the second part is formed of steel.

6. A mounting head as claimed in any preceding claim wherein the second part is formed with a projection to provide an integral earthing tag and a further projection, bent to form a bracket for the attachment of a cover to the mounting head.

7. A mounting head as claimed in any preceding claim wherein the first part of the mounting head is substantially disk-shaped, having a base carrying a heating element and a cylindrical externally threaded side wall with an outwardly extending flange around its periphery, the flange having a plurality of lugs spaced around it which fit within co-operating slots in the second part and are bent over to secure the parts together.

8. A mounting head as claimed in Claim 7 wherein the first part of the mounting head has a base carrying a pocket for a thermostat.

9. A mounting head as claimed in any preceding claim wherein the second part of the mounting head is provided with a continuous side wall of hexagonal or octagonal shape.

10. A mounting head as hereinbefore described and illustrated in the accompanying drawing.

11. An immersion heater incorporating a two part mounting head as hereinbefore described.