Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WATER HEATER ELEMENT ASSEMBLY
FI~LD OF THE INVENTION
The current invention relates to a water heatex
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
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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.
A~cording 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
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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.
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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,
însulating 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.
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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
aLe 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, ~he 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
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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 S0 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.
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To manufacture the assembly the ends of elemen~ 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.
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lt 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, flanqe 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.
