AU662463B2

AU662463B2 - Heating element

Info

Publication number: AU662463B2
Application number: AU57761/94A
Authority: AU
Inventors: Gheorghe Dragoi
Original assignee: Email Ltd
Current assignee: Email Ltd
Priority date: 1993-04-20
Filing date: 1994-03-11
Publication date: 1995-08-31
Anticipated expiration: 2014-03-11
Also published as: AU5776194A

Description

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT "Heating Element" The following statement is a full description of this invention, including the best method of performing it known to us *00000 0 0.

0 0*0* 0000 0 0 00. *00@ 04 0 0d *J 00 0 0 0008 0 0000 0 I S -1- This invention relates to heating element assemblies for electric water heaters.

In Australian patent 626,359 there is described a water heater element assembly in which the tubular element sheaths pass through and are brazed to a copper cup which is separated from a metal clamping plate by an electrically insulating disc. A leakage current regulating resistor is mounted on the disc, and has leads which are pressed respectively between the disc and the cup and between the disc and the clamping plate to connect the resistor: between the cup and the clamping plate. Reference is directed to the description contained in that specification, the contents of which are incorporated herein by reference to avoid unnecessary duplication.

Although a primary seal against the entry of water is provided in such assemblies by a rubber boot with a S' 20 flange which is clamped between the rear face of the 4t t€ cup flange and the wall of the tank, it has been found that in rare instances leakage of water may occur, apparentl 1 by the passage of water between the cup and the insulating disc, and thence to the element terminals where flashover may occur.

V In a first embodiment of the present invention this problem is addressed by adding an elastomeric sealing 1 r °gasket between the cup and the disc. A second 30 embodiment of the invention also employs such a sealing gasket, and also introduces other improvements in the design.

9 The invention broadly resides in an element assembly for an electric water heater, the assembly including a heating element having electrically conductive sheath means, an electrically conductive inner cover through c Is I -I

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-2which said sheath means extend and to which said sheath means are affixed, an insulating body engaged by said inner cover and receiving said sheath means, characterised in that sealing gasket means are interposed between said inner cover and said insulating body.

Preferably, the insulating body forms a mounting plate and includes means for mounting the assembly to the water heater.

The invention will be described by reference to these two embodiments, shown in the accompanying drawings.

The embodiments are given, of course, by way of -example only, and it is to be understood that the invention is capable of embodiment in other forms.

'ft *4(444 *t a 1 4 1 4~ 4 In the drawings: Fig. 1 illustrates in cross-section, otherwise 20 corresponding to Fig. 9 of 626,359, a first embodiment of the invention; Fig. 2 shows a second embodiment of the invention in cross-section; Fig. 3 is an end elevation of the assembly of Fig. 1; Fig. 4 is a partly sectioned exploded view of the assembly; Fig. 5 is an end elevation of the unitary mounting head in the direction 5 of Fig. 8; Fig. 6 is an end elevation of the unitary mounting 30 head in the direction 6 of Fig. 8; Fig. 7 is a section taken on the line 7-7 in Fig. 6; Fig. 8 is a section taken on the line 8-8 in Fig. 6; Fig. 9 is a side elevation in the direction 9 in Fig.

6; i3 14(C (IrI 4., 4 Fig.

Fig.

10 is an elevation of a gasket; and 11 is an elevation of an upper cover plate.

L _i ii I~ -3- In the embodiment illustrated in Fig. 1, the assembly of 626,359 is modified by the addition of a gasket of elastomeric material, preferably rubber, interposed between the copper cup 12 and the insulating disc 14.

As described in 626,359, one lead of the current limiting resistor 32 passes through the disc 14 and is trapped between the disc and the clamping plate 16, while the other lead is trapped agaiAnst the copper cup 12, but in this case by means of the rubber gasket 50. It is believed that this will increase the reliability of this electrical contact.

When the mounting assembly is compressed by bolting the heating element against the tank flange o the hot water service, the gasket 50 provides the assembly with a degree of flexibility and will increase the security of the sealing of the element *4*SSS mounting and termination assembly against secondary i ingress of water.

In the second illustrated embodiment of the present invention, there is still utilised the elastomeric gasket described above, but the embodiment also incorporates other substantial departures from prior M art designs exemplified by 626,359.

In the second embodiment, the insulating disc 14 and clamping plate 16 of the previous example are replaced by a unitary mounting head 51 of electrically insulating material such as glass fibre reinforced nylon, which combines the functions of providing supplementary support for the element sheath ends, mounting of the assembly to the water tank, nesting for the current limiting resistor and for element connector terminals, and also provides nesting and

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-4location of a metal upper cover plate which itself represents an innovation in heating element assemblies.

The element sheaths 52 are silver soldered to a cup 53 of conventional configuration, and pass with an interference fit through apertures 54 in the mounting head 51. These apertures are partially blind at their upper end, with a small aperture 55 allowing for the passage of the element conductor only. The apertures 54 are continued in protruding skirt portions 56 of the head 51 and have a depth sufficient to give useful support to the element sheaths during transport and installation of the assembly. Slits 56a in the skirt portions 56 provide some resiliency to facilitate insertion of the sheaths 52.

Adjacent the portion 56 a bifurcated post 57 is provided for the reception of the current limiting $too#: t 20 resistor 58, one lead of which is passed through an aperture 58a in the head as later referred to.

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As shown in Fig. 10, the elastomeric gasket 50, which has an outside diameter corresponding to that of the cup 53, is cut out to fit over the skirt portion 56a, the post 57 and the region between the post and the Saperture 59 through which the resistor lead passes to Sthe upper side of the head 51. The resistor 58 is installed after the gasket 50, and the other resistor 30 lead is laid against the outer surface of the gasket to be caught, in assembly, between the gasket and the outer flange of the cup 53, whereupon the gasket provides resilient clamping of the lead against the cup as described in relation to the first embodiment of the invention.

The upper side of the head 51 is provided with a p 9rN W- protruding portion 59 which provides for the termination of the element conductors, and for captive mounting of an upper cover plate.

Adjacent each of the apertures 55 is a blind hole for the reception of the end of a terminal screw 64, and the respective pairs of apertures 55 and holes are bridged by recesses 61. In to these recesses 61 are placed connector straps 62 apertured for the reception of the element conductor ends 63 and terminal screws 64 respectively. The conductor ends are mechanically and electrically fixed to the straps 62 by, for example, fusion welding, and flexible silicone insulated cable pieces 66 provided with spade terminals may then be connected.

The head 51 has mounting holes 67 for the clamping of the assembly to the heater wall, but rather than mounting the head directly, there is provided, in 20 accordance with a further preferred feature of the invention, a metal upper cover plate 68. This plate, Si', which may be of galvanised steel, has the same external dimensions as the head 51, and is provided with holes 69 for the reception of fixing bolts, in T registry with the holes 67 of the head 51. The plate 68 is made from thin sheet, suitably 0.9mm thick, as it is not required to have any rigidity, unlike the metal clamping plates used in the prior art.

S S The plate 68 is provided with a punched out section dimensioned to fit over the protruding portion 59 of the mounting head 51. This portion 59 is provided at four points, two on each of a pair of opposite sides, with ribs 71 which do not extend over the full height of the protrusion, so as to leave a gap between their inner ends and the underlying surface of the head 51, as shown at 72. The corresponding sides of the cutout -6are provided with recessed portions 73 shaped and dimensioned to fit over the ribs 71. A third side of the portion 59 is extended in its central region with a small shoulder 74, and in the direction of that shoulder the width of the cutout 70 is equal to the width of the portion 59 plus that of the shoulder.

The height of the shoulder above the underlying surface of the head 51 is small, and is of the order of the thickness of the plate 68 and the gaps 72.

The upper cover plate is assembled with the unitary head 51 by passing the cutout 70 over the protruding portion 59 with the ribs 71 and the recesses 73 in registration. In this position the edge of the cutout 70 opposite the shoulder 74 will be clear of the adjacent side of the portion 59, and the opposite edge of the cutout will be against the adjacent side of the portion 59. When the plate approaches the surface of the head 51, the last-mentioned cutout edge comes up against the shoulder 74. The plate is pressed down in C l. the region of the ribs 71 so that it can pass beneath those ribs, and the edge of the cutout adjacent to the shoulder 74 snaps into contact with the surface of the head 51 and engages against the shoulder to lock the plate against removal, with the recesses 73 no longer in register with the ribs 71.

The plate 68 presses against the resistor lead which **has been passed through the aperture 58a to complete 30. the connection of that lead with the tank upon installation of the assembly.

In this way the head 51 is provided with a metal surface which provides the necessa-y electrical continuity with the current limiting resistor, and acts as a wear plate preventing the mounting bolts from embedding in the plastics mounting head. The tmi-.

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-7plate may be stamped with wattage, voltage, part numbers and other information enabling product differentiation to be achieved by simple stamping or printing on a metal plate only.

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Claims

1. An element assembly for an electric water heater, the assembly including a heating element having electrically conductive sheath means, an electrically conductive inner cover through which said sheath means extend and to which said sheath means are affiX.d, an insulating body engaged by said inner cover and receiving said sheath means, characterised in that sealing gasket means are interposed between said inner cover and said insulating body.

2. An assembly according to claim 1 wherein the gasket means includes a gasket of elastomeric material compressed between said inner cover and said insulating body.

3. An assembly according to claim 1 or claim 2 wherein said insulating body forms a mounting plate and includes means for mounting the assembly to said water heater.

4. An assembly according to claim 2 wherein said insulating body further includes means for the reception of free ends of said sheath means, means for the passage of element conductors through said body, and means on the side of said body remote from said inner cover for the termination of said conductors.

5. An assembly according to claim 3 further including an electrically conductive outer cover plate mounted on the face of said body remote from the heating IL I I element.

6. An assembly according to claim 1 or claim 2 wherein said insulating body comprises a disc having i~,i~j 1 -9- a rearward face, said inner cover being provided with a flange facing said rearward face, said gasket being pressed between said flange and said rearward face.

7. An element assembly substantially as described i herein with reference to Fig. 1 of the accompanying drawings.

8. An element assembly substantially as herein described with reference to Figs. 2 to 9 of the accompanying drawings. DATED this 10th day of March 1994 EMAIL LIMITED Patent Attorneys for the Applicant: HALFORD CO. 4449* I 1* i4 ,ii I «1 44;c ((II L L- ~U a i\ n i ij ii. i i i-iii-iiiiiiii "i ABSTRACT A water heater element assembly of the kind in which tubular element sheath ends (52) brazed to a cup (53) are terminated beyond a mounting plate (16, 68) with an insulating body (14, 51) separating the cup .from the plate, in which a sealing gasket (50) is provided between the cup and the insulating body to provide an additional seal against the entry of water. II (i S,. i -1 I i i LI~Y I