AU626359B2

AU626359B2 - Water heater element assembly

Info

Publication number: AU626359B2
Application number: AU46472/89A
Authority: AU
Inventors: Kevin Fahey
Original assignee: Email Ltd
Current assignee: Email Ltd
Priority date: 1988-12-08
Filing date: 1989-12-05
Publication date: 1992-07-30
Anticipated expiration: 2009-12-05
Also published as: AU4647289A

Description

WATER HEATER ELEMENT ASSEMBLY

FIELD OF THE INVENTION

The current invention relates to a water heater element and in particular to a method of assembling a water heater element.

BACKGROUND OF THE INVENTION

In the prior art water heater elements are normally bolted on by way of a flange to the body of the water heater. In domestic and commercial hot water heating systems sacrificial anodes are often employed particularly in glass lined steel tanks to increase the life of the system in adverse environments. The use of such sacrificial anodes requires the clamping plate and element assembly be insulated from each other. A bridging resistor is often fitted between the element assembly and the clamping plate to regulate the leakage current flowing to the clamping plate, which is normally earthed, to extend the anode life.

In such prior art assemblies the clamping plate is generally secured to the copper flange of the sheathed element by suitable fixing means such as insulated nuts and washers. A separate assembly insulates the clamping plate from the element assembly. This procedure necessitates two separate assemblies and steps to produce the water heater element.

STATEMENT OF THE INVENTION

The present invention seeks to overcome these disadvantages in the prior art and to in particular improve the manufacture and assembly of water heater elements of the above type.

According to a first aspect of the invention there is provided an insulating gasket for a water heater element assembly including a disc having a front and a rear face, apertures extending through said disc to accommodate ends of a water heater element and sleeve means extending from the rear face of said disc about said apertures.

According to a second aspect of the invention there is provided a water heater element assembly of the type including a sheathed heating element having first and second tube ends, a flange of a conductive material in electrical contact with the sheath of said element, a clamping plate for attaching the assembly within a heater housing and an insulating gasket to insulate said plate from said flange, the improvement comprising insulating means for accommodating said tube ends through said plate, said plate having apertures therein through which said insulating means and said ends extend, with said insulating means fixing said insulating gasket to said clamping plate, and said plate to said ends whereby said flange, plate and tube ends form an assembly.

According to another aspect of the invention there is provided a method of manufacture for a water heater element assembly, with the assembly of the type including a sheathed heating element having first and second tube ends, a flange in electrical contact with the sheath of said element, a clamping plate for attaching the assembly within a heater housing, and a insulating gasket to insulate said plate from said flange, with the improvement comprising insulating means for accommodating said tube ends through said plate, said plate having apertures through which said insulating means and said tube ends can extend, including the steps of:

sliding in sequence said flange, said insulating gasket, said insulating means and said clamping plate over said tube ends; and bonding said insulating means between said tube ends and said clamping plate. BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment will now be described with respect to the following figures in which:

Figure 1 shows a water heater element assembly according to the invention in exploded schematic form;

Figure 2 and Figure 3 show respectively a front elevation and a side elevation of the insulator gasket of Figure 1;

Figure 4-6 show end and cross-sectional views of the insulator gasket of the assembly of Figure 1; and

Figures 7-9 show respectively side, end and cross-sectional schematics of the assembly of Figure 1 in an assembled form.

PREFERRED MODES OF THE INVENTION

As shown in Figure 1 the water heater element assembly comprises a water heater element 10, flange 12, insulating gasket 14 and clamping plate 16. The assembly, in use, is secured to support 20 within the housing (not shown) of the water heater through fixing holes 22 of the clamping plate 16. The heater element 10 comprises an outer conductive sheath 24, normally of copper, separated by an insulator 26 from resistance heating filament (not shown) having external end leads 28. Terminal lugs 30 are secured (for example, soldered, spot welded., or crimped) to end leads 28 to allow element 10 to be connected to a suitable power supply for operating the element 10. The element 10 can have a variety of physical shapes and power ratings depending on its application.

The flange 12 is electrically connected to the sheath 24 of the element 10, for example by brazing. The clamping plate 16 is normally of a dissimilar metal to the flange 12, for example mild steel. To increase the life of the assembly a current limiting resistor 32 (see Figure 9) is connected as is well known in the prior art, between the flange 12 and the clamping plate 16 which is normally earthed, to control the leakage of the electrochemically generated charge.

As shown more clearly in Figures 2 and 3 the insulating gasket 14 comprises a disc 34 having a lip 36 around its perimeter. On one face 38, the front face, of the disc 34 a post 40 is formed. On the other face 42, the rear face, of the disc 34, two sleeves 44 are provided. Sleeves 44 are more clearly shown in Figures 4-6 to have projections 46 and 48 on the outer and inner surfaces respectively of the sleeves 44. Though projections are shown both on the inner and outer surfaces of the sleeves 44 it is also contemplated that projections may only be formed on the inner or the outer surfaces alone. It is preferred that the projections be formed on at least the inside surface of each sleeve 44. The outer diameter of the sleeves 44 is dimensioned to fit firmly through holes 50 in clamping plate 16, while the internal diameter is chosen to be a snug fit about the sheath 24 of the element 10.

As shown more clearly in Figure 9 insulating gasket 14 accommodates the flange 12 within the space defined by the lip 36 and the front face 38 of the gasket 14 supported on post 40. This insulates the body of the flange 12 from -the clamping plate 16 while the sleeves 44 insulate the flange 12 and the sheath 24, to which it is connected, also from the clamping plate 16.

Post 40 is provided with a slot 52 to act as a suppport for resistor 32. A hole or slot 54 extends through the disc 34 of the gasket 14 to enable a lead of the resistor 32 to extend rearward to connect with the clamping plate 16 in a manner to be described below. Equally the other lead of the resistor projects forward of the gasket 14 to connect with the body of the flange 12. To manufacture the assembly the ends of element 10 are inserted through the holes 51 in the flange 12 and flange 12 brazed to the sheath 24. Insulating gasket 14, with resistor 32 cradled in the slot 52 and with its leads suitably disposed forward, and rearwardly through the slot 54, is then pressed over the ends of element 10 up against the flange 12, with the tube ends of the element 10 extending through the sleeves 44. The clamping plate 16 is then fitted over the sleeves 44 through holes 50. Sleeves 44 extend rearward of surface 42 of gasket 14 sufficient to clear and adequately insulate plate 16 from sheath 24 of the tube ends. The sleeves 44 are now collapsed by means of riveting (hot or cold), ultrasonic welding, melting, welding or any other suitable method which can be used to create a fillet between the sheath 24 of element 10 and the mild steel plate 16. For example, another method may involve the use of a suitable adhesive to fill the gaps and to bond the components together. The assembly of the components together also results in the leads of the resistor 32 being electrically connected respectively to the flange 12 and the clamping plate 16 either due to the pressure with which the components are assembled or due to the method, for example ultrasonic welding, employed to create the fillet between the sheath 24 and the clamping plate 16. It is preferred as described above that the sleeves 44 are made integral with the gasket 14. However, it is also contemplated that the sleeves 44 may be separate elements for example, as shown in Figures 5(a) and 6(a) which are secured by a method as described above, for example melting, ultrasonic welding to the rear surface 42 of the gasket 14.

In this manner the sleeves 44 join together the insulating gasket 14, flange 12 and plate 16 to the heater element 10 while at the same time providing the necessary electrical insulation between the flange 12 and the clamping plate 16. Thus a water heater element can be assembled more simply than hitherto. This results in savings in time, cost and material.

The insulating gasket 14 and sleeves 44 can be made of any appropriate material, for example polypropylene.

Though the invention has been described above with respect to a preferred embodiment thereof variations of the invention are possible within the knowledge of a person skilled in the art.

Claims

1. A water heater element assembly of the type including a sheathed heating element having first and second tube ends, a flange of a conductive material in electrical contact with the sheath of said element, a clamping plate for attaching the assembly within a heater housing and an insulating gasket to insulate said plate from said flange, the improvement comprising insulating means for accommodating said tube ends through said plate, said plate having apertures therein through which said insulating means and said ends extend, with said insulating means fixing said insulating gasket to said clamping plate, and said plate to said ends whereby said flange, plate and tube ends form an assembly.

2. An assembly as claimed in claim 1 wherein said insulating means comprises sleeve means extending about said tube ends.

3. An assembly as claimed in claim 2 wherein said insulating means are formed integral with said insulating gasket.

4. An assembly as claimed in claim 3 wherein said insulating gasket is further characterised in that it includes a disc with a perimeter lip, said lip is accommodated within said perimeter lip upon a front face of said disc, and said insulating means are attached to a rear face of said disc.

5. An assembly as claimed in claim 4 wherein said insulating gasket and said insulating means are made of polypropylene.

6. A method of manufacture for a water heater element assembly, with the assembly of the type including a sheathed heating element having first and second tube ends, a flange in electrical contace with the sheath of said element, a clamping plate for attaching the assembly within a heater housing, and an insulating gasket to insulate said plate from said flange, with the improvement comprising insulating means for accommodating said tube ends through said plate, said plate having apertures through which said insulating means and said tube ends can extend including the steps of:

sliding in sequence said flange, said insulating gasket, said insulating means and said clamping plate over said tube ends; and bonding said insulating means between said tube ends and said clamping plate.

7. A method of manufacture as claimed in claim 6 wherein said bonding step comprises ultrasonic welding.

8. A method of manufacture as claimed in claim 5 wherein said bonding step comprises hot or cold riveting, melting, welding, or adhesive bonding.

9. An insulating gasket for a water heater element assembly including a disc having a front and a rear face, apertures extending through said disc to accommodate ends of a water heater element and sleeve means extending from the rear face of said disc about said apertures.

10. An insulating gasket as claimed in claim 9 further including a lip extending about the perimeter and forwardly of said disc, a post formed on said front face, a slot formed in said post for supporting a resistor, and a hole in said disc for accommodating a lead of a resistor when cradled in said slot.

11. An insulating gasket as claimed in claim 10 made of polypropylene.