Note: Descriptions are shown in the official language in which they were submitted.
20~9061
BACKGROUND OF INVENTION:
Field of Invention
~ The present invention relates to an insulating
- support base for a cylindrical electric hot water tank.
Description of Prior Art
Hot water tanks are constructed with dome shaped
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bottom walls to withstand the load pressure within the
tanks. These hot water tanks contain one, two or three
electrodes which are spaced apart along the length of the
tank. The bottom electrode is usually positioned about
six inches above this dome shaped bottom wall and warms
-~ the water in that area to about 130F. However, the water
at the bottom of the tank about the dome shaped bottom
wall can fluctuate usually between 90-100F as the water
rises to the top of the tank. At these lower temperatures
in the bottom of the tank, it has been found that bacteria
growth can take place, and in fact the growth of bacteria
legionella, and which is harmful to humans, has been
attributed to this heat problem in the bottom of the
tanks.
~ In order to resolve the above problem it is
-~ known in the prior art to provide an additional heating
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element on the dome shaped bottom wall to raise the tempe-
rature of the water within the tank at the bottom region
thereof. However, because the bottom wall is exposed to
air in the cavity adjacent its outer surface, the provi-
sion of that heating element has not been found efficient,
as it also heats air and the metal of the tank as well as
the water. The result is that the tank consumes much more
electricity and the solution is costly.
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Another cause of large temperature differentials
within hot water heating tanks is the efficiency of the
insulation between the inner and outer casings of the
tank. Inproper insulation has results in excessive heat
loss in certain regions of the tank. Proper insulation is
particularly important in the lower regions of the tank to
.
maintain the water temperature as high as possible to
,~ prevent bacterial growth.
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SUMMARY OF INVENTION:
' It is therefore a feature of the present inven-
- tion to provide an insulating support base for a cylin-
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- drical electric water heater tank and which substantially
reduces the above-mentioned disadvantages of the prior
art.
.
A further feature of the present invention is to
provide an insulating support base for a cylindrical
electric water heater tank which permits the inner casing
and the outer casing to be perfectly concentrically
positioned equidistantly from one another whereby an even
layer of insulation may be disposed between the inner and
outer casings and wherein the insulation is not damaged or
modified by the misalignment of the casings. This feature
is needed in the robotic advanced assembly production
line.
Another feature of the present invention is to
provide an insulating support for a cylindrical electric
water heater tank and wherein a plate-like electrode is
trapped to the lower region of the inner casing adjacent
the dome wall, with the dome wall being insulated by the
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support base to maintain the temperature in the lower region
inside the inner tank and about the dome wall, above that of
bacteria growth, to prevent formation of bacteria legionella.
According to the above features, from a broad
aspect, the present invention provides an insulating support
base for supporting a cylindrical electric water heater tank.
The base is formed of a rigid molded foam material and
defines a circular base having a flat bottom wall with a
concentrically disposed support dome on a top face thereof
and shaped for close fit within a bottom cavity of the tank
for support engagement with a dome shaped bottom wall of a
casing of the tank. The support dome has an angulated outer
side wall for guiding a lower flange edge of the inner casing
to permit same to be automatically centered on the support
base in sealing engagement therewith. A spacer ledge is
defined about the support dome and extends to an outer edge
of the flat circular base. The spacer ledge accommodates an
insulating jacket positioned about the inner tank casing with
the outer edge of the flat circular base being disposed in
close fit within a lower marginal edge portion of an outer
cylindrical casing of the tank to position the outer casing
equidistantly spaced about the inner casing with the
insulating jacket therebetween.
According to a still further aspect of the present
invention, the support dome is defined by a plurality of
equidistantly spaced radiating support ribs formed integrally
with the support base whereby the load in the dome shaped
bottom wall of the casing is transferred directly to the
base.
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BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention is
described with reference to the accompanying drawings in
which:
FIG. 1 is a fragmented view of a cylindrical
electric water heater tank incorporating the insulating
support base of the present invention;
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FIG. 2 is a section view of the bottom section
of a cylindrical electric water heater of the prior art;
FIG. 3 is a side side view of the insulating
- support base of the present invention;
FIG. 4 is a top view of Fig. 3;
FIG. 5 is a section view through section lines
V-V of Fig. 4; and
FIG. 6 is an enlarged fragmented section view
illustrating the position of the locating channel disposed
,
in the top face of the spacer ledge and about the support
dome.
DESCRIPTION OF PREFERRED EMBODIMENTS:
Referring now to the drawings and more particu-
larly to Fig. 1, there is shown schematically at 10 a
cylindrical electric hot water tank. The tank is
constructed of an inner metal tank casing 11 and an outer
metal tank casing 12 positioned thereabout with a thermal
insulating jacket 13 disposed therebetween. The tank is
provided with fittings 14 to admit water in an out of the
tank in order to maintain a constant supply of water ~ ~-
.:
- therewithin. Two or more resistive heating elements 15 `~
are disposed at various levels within the tank. As herein
shown, the lower electrode 15' is disposed approximately ~;;
- six inches above the dome shaped bottom wall 16 of the
-~ inner casing. The bottom wall is dome shaped to withstand
;~ the load in the tank.
; Fig. 2 shows a tank bottom section as formed in
the prior art. As herein shown, a further resistive
heating element 17 is secured to the outer face 16' of the
- dome shaped bottom wall 16 to heat the water in the lower
section of the tank to raise the temperature of the water
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to prevent the formation of bacteria legionella. As
previously described, the position of the electrode 17 on the
outer face of the dome shaped bottom wall 16 results in a
substantial heat loss within the space 18 under the dome wall
with some of the heat being lost through the metal base 19 of
the tank. Also, it has been found difficult with the prior
art to perfectly position the outer tank casing 12
concentrically about the inner tank casing 11 on the base 19.
Consequently, the insulating jacket 13 may be damaged or
compressed in certain portions of the tank and form spaces
13' in other portions resulting in uneven insulation and
consequently heat loss. These problematic factors have made
it difficult to resolve the problem of maintaining the
temperature in the lower portion of the tank sufficiently
high to prevent bacteria growth and in an economically
efficient manner.
Referring now additionally to Figs. 4 to 6, there
will be described the construction and function of the
insulating support base 20 of the present invention. As
herein shown the support base 20 is formed of a rigid molded
foam material, such as polystyrene foam which is a good
thermal insulation. The base defines a flat circular base
portion 21 having a concentrically disposed support dome 22
integrally molded on a top face 23 of the base portion 21.
This support dome 22 is shaped for close fit within the
bottom cavity 18 of the inner casing 11 so that the support
dome provides support engagement with the dome shaped bottom
wall 16 to provide distributed support of the load within the
tank and distribute it across the flat bottom surface 21' of
the base 20. The support dome 22 also has a cylindrical
inwardly curved side edge 24' to
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guide the inner casing 11 to permit it to be automatically
centered on the support base 20 by guiding the lower
flange edge 25 of the inner tank casing 11 into a circum-
ferential locating channel 28 disposed in the top face 23
of a spacer ledge 24 of the flat wall 21. Pilot hole 33
is the guide on the automatic production line.
The spacer ledge 24 extends to an outer edge 26
of the flat circular base 21. This outer edge 26 may have
a slight inner inclination of about 5 to facilitate the
placement of the outer tank casing 12 about the base. The
.
spacer ledge 24 is dimensioned to accommodate the insulat-
ing jacket 13 position about the tank inner casing with
the outer casing heing maintained spaced substantially
equidistantly about the inner casing not to damage the
insulating jacket by accidental shifting of the inner and
outer casings during assembly.
As more clearly seen in Figs. 3 to 5, the
support dome 22 is herein defined by a plurality of equi-
distantly spaced radiating support ribs 27 formed
integrally with the support base 21. The ribs have a
curved convex shape and a curved top face to fit flush
,
~ - with the outer face 16' of the dome shaped bottom wall of
- the inner tank casing, and to transmit the load inside the
.
-- tank on the flat bottom surface 21' of the circular base
21.
- As shown in Fig. 6, the lower flange edge 25 of
the inner casing 11 is snugly received within the circum-
- ferential channel 28 and provides a seal therewith. The
insulating support base also has a thick bottom wall
section 29 which provides good insulation to substantially
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reduce heat loss from the bottom dome shaped wall 16 of
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the tank. Accordingly, the support base provides both
load support, good thermal insulation of the dome shaped
bottom wall to increase heat retention within the lower
inner section of the inner casing of the hot water tank,
and furthermore is adapted to an automated assembly line
by pilot 33.
Additionally and as shown in Fig. 1, the lower
section of the tank is further heated by a resistive
heating plate 30 formed of pliable material and shaped to ~-
the curve of the inner casing outer wall and secured
thereto by a detachable strap attachment 31. A thermostat --
32 is positioned between the resistive heating plate 30 ~ -
and the outer wall of the inner casing 11 to regulate the
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temperature of the resistive heating plate, and to assure
that the water temperature at the bottom of the inner
casing is at a temperature sufficiently high to prevent
harmful bacteria growth.
It is within the ambit of the present invention
to cover any obvious modifications of the preferred
embodiment described herein, provided such modifications
fall within the scope of the appended claims.
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