Method of water heater construction

A method of insulating a water heater of the type including an inner water tank and a surrounding outer shell which is spaced apart from the inner tank so as to define an annular clearance space therebetween includes the steps of providing a flexible envelope of insulation material which begins as a generally cylindrical member which is placed at the bottom of the outer shell on its interior generally centered within the side walls of the outer shell. The next step is to lower the inner water tank into position down onto the insulation-filled flexible envelope. The weight of the inner water tank which has a concave bottom surface shapes the flexible envelope so as to create a first portion or pouch beneath the bottom surface of the tank and a surrounding collar which although connected to the inner pouch is pushed outwardly so as to be disposed between the outer wall of the inner tank and the inner wall of the outer shell.

BACKGROUND OF THE INVENTION 
The present invention relates to water heater devices and more particularly 
to a thermally insulated water heater device. It is becoming more 
important to improve the insulation of hot water heaters to conserve 
energy, and the present invention is directed to improve insulation 
concepts. 
Typically, water heater devices are constructed of an inner water tank with 
an outer shell located concentrically over the inner tank defining an 
annular space therebetween, a cap closing the top end of the water heater 
device, and a floor closing the bottom end of the water heater device. The 
space between the inner tank and outer shell is filled with a thermal 
insulation. For many years fiberglass mats have been used as the 
insulation material between the inner tank and outer shell. More recently 
a foam, such as urethane, has been used as the thermal insulation material 
in place of fiberglass between the inner tank and outer shell. Typically, 
a foamable material is injected into the annular space between the inner 
tank and outer shell, and is allowed to foam in situ. However, there is a 
problem in restraining the expanding foam within the annular space and 
more particularly within a predetermined location or region within the 
annular space. Further, it is a problem during manufacture of the water 
heater device to insulate the bottom end of the water tank. Various 
proposals have been made to solve this problem. 
U.S. Pat. No. 4,372,028 issued on Feb. 8, 1983 to Clark et al. shows a 
water heater having a foam-filled closed bag located in the annular space 
between the inner tank and outer shell at the bottom of the inner tank, 
with the annular space above the annular bag filled with expanded foam. 
The collar functions as a stop to the expanded foam in the annular space 
thereabove. In the manufacture of the water heater a flexible, expandable 
closed elongated bag having a hole therein is filled with a foam material 
which expands the bag, and before the foam material has had sufficient 
time to fully expand, the bag opening is sealed and the bag is 
circumferentially wrapped around the lower end of the tank with the bag 
ends overlapping each other. Still, before the foam material in the bag 
has had sufficient time to expand, the outer shell is positioned over the 
inner tank and bag. The foam in the bag expands to a size so as to be in 
compression between the inner tank and outer shell. The annular space 
above the collar is then filled with expandable foam material. 
U.S. Pat. No. 4,447,377 issued on May 8, 1977 to Denton shows a gas-fired 
water heater wherein a layer of fiberglass batt insulation material is 
wrapped around the bottom portion of the inner water tank around the 
combustion chamber and a plastic envelope is wrapped around the inner tank 
above the fiberglass insulation. The envelope is in the form of an 
elongated thin tube having an inner wall, an outer wall, a bottom wall, 
two end walls and an open top. When wrapped around the inner tank, the end 
walls of the envelope abut each other. The outer shell is positioned over 
the inner tank such that the envelope is in the annular space 
therebetween. Expandable foam is injected through tthe open envelope top 
into the envelope and allowed to expand therein. The fiberglass batt does 
not form a seal between itself and the inner water tank and the outer 
shell. 
U.S. Pat. No. 4,477,399 issued on Oct. 16, 1984 to Tilton shows a water 
heater having an inflatable toroidally shaped tube located around the 
bottom end of the inner tank such that when the toroidal tube is inflated 
with air, it seals the bottom end of the annular space between the inner 
tank and outer shell. A foamable material is then injected into the 
annular space above the toroidal tube to fill the annular space. 
It is also known to position a layer of insulation batting, such as a layer 
of fiberglass batt, over the bottom end of the water tank. 
Each of the above-discussed water heater constructions present numerous 
problems in manufacture such as, for example, a large number of steps, 
critically timed steps, and time-consuming steps which add to the cost and 
present potential for defects in the final product. In contrast, the 
present invention provides a simple and efficient method of constructing a 
hot water heater wherein the area below the tank as well as the sides of 
the tank are thermally insulated. 
SUMMARY OF THE INVENTION 
A method of insulating a water heater device of the type including an inner 
water tank and a surrounding outer shell spaced apart from the tank so as 
to define an annular clearance space therebetween according to a typical 
embodiment of the present invention comprises the steps of providing a 
flexible envelope with insulation material disposed therein, placing the 
envelope at the bottom of the outer shell and lowering the tank down into 
the outer shell in the direction of and onto the envelope whereby the 
envelope changes shape in response to the weight of the tank so as to 
create a disc portion below the tank. 
One object of the present invention is to provide an improved method of 
water heater construction. 
Related objects and advantages of the present invention will be apparent 
from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations and further modifications 
in the illustrated device, and such further applications of the principles 
of the invention as illustrated therein being contemplated as would 
normally occur to one skilled in the art to which the invention relates. 
FIG. 1 schematically illustrates, in longitudinal cross section, a water 
heater device generally denoted by reference numeral 10, having a 
generally cylindrical inner water tank 12 for containing water and a 
generally cylindrical outer shell 14 concentrically surrounding the inner 
water tank 12. The outer shell 14 is of a larger diameter than the water 
tank 12 and they cooperate to define an annular space 16 therebetween. As 
illustrated, the water heater device 10 is of the electrically heated type 
having, for example, an electrical resistance unit (not shown) projecting 
into the interior of the water tank 12 to heat the water therein. The 
bottom end of the inner water tank 12 is formed with a concavity 18. The 
top end of the water heater device 12 is closed by a cap 20, which may be 
a separate component or may be unitary with the outer shell 14. The bottom 
end of the water heater device 10 is typically closed by a floor 12. 
With further reference to FIG. 1, an insulating thermal collar 24 is 
located in the annular space 16. The collar 24 includes an enclosing 
envelope 26 filled with a thermal insulation material 28. The enclosing 
envelope 26 is fabricated of a fluid impermeable, pliable material such 
as, for example, polyethylene film, vinyl film, metalized polyester, metal 
foil, and the like. The thermal insulation material 28 can be a fibrous 
batt, such as interwoven fiberglass, or a loose, discrete, divided 
material, such as for example noninterengaged fiberglass, mineral wool, 
steel wool, cellulose, ceramic fiber, discrete particles or beads of 
plastic foam, and the like. It is contemplated that in some applications 
it may be necessary to cohesively hold the loose, discrete, divided 
insulation material together inside the envelope 26 to prevent the 
insulation material from shifting or settling within the enclosing 
envelope 26. In this event, a binder material is homogeneously dispersed 
throughout the mass of the insulation material 28 to cohesively hold the 
insulation material together, and possibly adhesively affix the insulation 
material to the wall of the envelope 26, to prevent the insulation 
material 28 from shifting or settling within the envelope 26. The binding 
material used is a function of the type of insulation material 28 and can 
be a thermosetting adhesive, thermoplastic adhesive, cold setting 
adhesive, ambient setting adhesive, or hot setting adhesive. For example, 
a suitable adhesive for use with fiberglass and mineral wool is a phenolic 
or sodium silicate, and a suitable adhesive for cellulose is polyvinyl 
acetate. 
The collar 24 extends circumferentially around the inner water tank 12 in 
the annular space 16 proximate the bottom end of the water heater device 
10. The collar 24 has a width greater than the radial width of the annular 
space 16 so that the collar 24 is radially compressed between the interior 
wall surface of the outer shell 14 and the exterior wall surface of the 
inner water tank 12 to a sufficient degree in order to tightly seal the 
interface of the collar 24 and inner wall surface of the outer shell 14 
and to tightly seal the interface of the collar 24 and exterior wall 
surface of the inner water tank 12. In addition, the collar 24 is in 
abutment with the water heater device floor 22. 
With reference to FIG. 2, the enclosing envelope 26 of the collar 24 is in 
the form of an elongated generally cylindrical tube closed at both of its 
ends 27 and 29. The tubular collar 24 is circumferentially wrapped around 
the perimeter of the water tank 12 with the ends 27 and 29 thereof brought 
together into mutual abutment. The abutting ends 27 an 29 can be secured 
together by, for example, adhesive tape if necessary. 
With reference to FIG. 3, an alternative construction for the enclosing 
envelope 26 of the collar 24 is illustrated. Envelope 126 is in the form 
of an elongated generally cylindrical tube having one of its ends 127 
closed and the other of its ends 129 open. The tubular collar 124 formed 
in party by envelope 126 is circumferentially wrapped around the perimeter 
of the water tank 12 and the closed end 127 is inserted into the open end 
129. The ends 127 and 129 can be secured together by, for example, 
adhesive tape, if necessary. 
With reference to FIG. 4, a further alternative construction is 
illustrated. The enclosing envelope 226 of the collar 224 is in the form 
of an elongated generally cylindrical tube having both of its ends 227 and 
229 open. The tubular collar 224 is circumferentially wrapped around the 
perimeter of the water tank 12 and one of the open ends 227 is inserted in 
to the other of the open ends 229. The ends 227 and 229 can be secured 
together by, for example, adhesive tape, if necessary. 
With reference to FIG. 5, a still further alternative construction is 
illustrated. The enclosing envelope 326 of the collar 324 is in the form 
of a closed toroid. The envelope 326 is filled with a suitable insulation 
material as previously described relative to collar 24. The toroid collar 
324 is concentrically slid over the water tank 12. 
With reference once again to FIG. 1, the annular space 16 above the collar 
24 is filled wwith an expanded foam thermal insulation material 30 such as 
urethane, polyethylene, polystyrene and the like, which functions as a 
thermal insulation surrounding the inner water tank 12. 
With reference to FIG. 1, an insulating disc 32 is located at the bottom 
end of the inner water tank 12. The insulating disc 32 includes an 
enclosing envelope 34 filled with a thermal insulation material 36. The 
enclosing envelope 34 has a peripheral configuration matching that of the 
bottom end of the water heater 12 and a thickness preferably at least as 
great as the depth of the concavity 18. As shown, the envelope 34 has a 
generally circular perimeter to correspond to the perimeter of the bottom 
end of the inner water tank 12 so that the disc 34 overlays the bottom end 
of the tank. The enclosing envelope 34 is fabricated of a 
fluid-impermeable, pliable material such as, for example, polyethylene 
film, vinyl film, metalized polyester, metal foil, and the like. The 
thermal insulation material 36 is either a fibrous batt such as interwoven 
fiberglass, or a loose, discrete, divided material such as, for example, 
noninterengaged fiberglass, steel wool, mineral wool, cellulose fibers, 
ceramic fibers, discrete particles or beads of plastic foam, and the like. 
It is contemplated that in some applications it may be necessary to 
cohesively hold the loose, discrete, divided insulation material together 
inside the envelope 34, and possibly adhesively affix the insulation 
material to the wall of the envelope 34, to prevent the insulation 
material from shifting or settling within the enclosing envelope 34. In 
this event, a binder material is homogeneously dispersed throughout the 
mass of insulation material 36 to cohesively hold the insulation material 
together and prevent the insulation material from shifting or settling 
within the envelope 34. The binder material used will be a function of the 
type of insulation material 36 and can be a thermosetting adhesive, 
thermoplastic adhesive, cold setting adhesive, ambient setting adhesive, 
or hot setting adhesive. For example, a suitable adhesive for use with 
fiberglass and mineral wool is phenolic or sodium silicate, and a suitable 
adhesive for cellulose is polyvinyl acetate. 
With reference to FIG. 7, an alternative construction for disc 32 is 
illustrated. The insulating disc 132 includes an enclosing envelope 134 
having a peripheral configuration generally matching that of the bottom 
end of the water tank and a thickness preferably at least as great as the 
depth of the cavity 18. The envelope 134 includes a central inner circular 
pocket 138 concentrically surrounded by a perimeter outer pocket 140. The 
envelope 134 is fabricated of a fluid-impermeable, pliable material such 
as, for example, polyethylene film, vinyl film, metalized polyester, metal 
foil and the like. The central circular pocket 138 is separated from the 
perimeter pocket 140 by a circular seal 142. The central circular pocket 
138 is filled with a fibrous batt of insulation material, such as 
interwoven or interengaged fiberglass, and the perimeter pocket 140 is 
filled with a loose, discrete, divided insulation material such as, for 
example, noninterengaged fiberglass, mineral wool, steel wool, cellulose 
fibers, ceramic fibers, discrete particles of beads of plastic foam, and 
the like. However, it is contemplated that the central circular packet 138 
be filled with the loose, discrete, divided insulation material and the 
perimeter pocket 140 be filled with the fibrous batt. It is contemplated 
that in some applications, it may be necessary to cohesively hold the 
loose, discrete, divided insulation together inside of the pocket. In this 
event, a binder material is homogeneously dispersed throughout the mass of 
insulation material within the pocket to cohesively hold the insulation 
material together, and possibly adhesively affix the insulation material 
to the wall of the pocket to prevent the insulation material from shifting 
or settling within the pocket. The binder material used will be a function 
of the type of insulation material used within the pocket and can be 
thermosetting adhesive, thermoplastic adhesive, cold setting adhesive, 
ambient setting adhesive, or hot setting adhesive. For example, a suitable 
adhesive for use with fiberglass and mineral wool is phenolic or sodium 
silicate, and a suitable adhesive for cellulose is polyvinyl acetate. 
With reference to FIGS. 8 and 9, there is illustrated, in schematic format, 
the results of various steps for manufacturing the water heater 10. The 
insulation collar 124 (or one of the alternative constructions) is 
circumferentially fitted around the perimeter of the inner water tank 12 
proximate the bottom end thereof. The collar 124 can be secured to the 
wall of the water tank 12 by an adhesive, or tape. The insulating disc 32 
(or one of the alternative constructions) is disposed in overlaying 
relationship to the bottom end of the water tank 12, and can be secured in 
place by an adhesive or a tape. The outer shell 14 is coaxially moved over 
the inner water tank 12, the floor 22 is positioned over the bottom of the 
water tank 12 and the outer shell 14 assembly to close the bottom of the 
water heater device 10l. An expandable foam insulation material 30 is 
injected into the annular space 16 between the inner water tank 12 and 
outer shell 14 above the collar 124 and allowed to expand in situ filling 
the annular space 16 above the collar 124. The collar 124 is radially 
compressed between the inner wall surface of the outer shell 14 and outer 
wall surface of the inner water tank 12 to form a seal at the interface of 
the collar 124 and outer shell 14 and a seal at the interface of the 
collar 124 and inner water tank 12, and functions as a stop or block to 
the expanding foam. 
With reference to FIG. 10, there is illustrated another embodiment of the 
invention wherein insulating member 400 is disposed beneath tank 401 and 
around the lower periphery of the tank in the annular space 402 which is 
defined by the tank and shell 403. Although member 400 begins as a single, 
generally cylindrical envelope which is filled with insulation material, 
it is ultimately configured into the shape and arrangement of FIG. 8. One 
way to view member 400 (see FIG. 11) is to see it as comprising a center 
pouch 404 which is disc-shaped and disposed beneath the tank and a 
surrounding annular ring pouch 405 which fits snugly between the outer 
surface of the tank and the inner surface of the shell. 
The circular line of intersection 406 between center pouch 404 and annular 
ring pouch 405 may be heat sealed closed (as in FIG. 7) or left open such 
that there is communication between the two pouches. By sealing the 
interface between the two pouches different insulating materials can be 
placed in the two pouches. If sealing is to be done, it must be performed 
before the tank is positioned over member 400 and thus the circumferential 
size of the tank must be considered in order to properly size the two 
pouches. It is also important that the radial width of the annular ring 
pouch be greater than the width of the clearance space so that enough 
compression of the pouch can be obtained in order to establish the desired 
seal between the tank and the shell. 
The two pouches 404 and 405 are constructed of a flexible, 
fluid-impermeable material which is sufficiently pliable to conform to the 
desired shapes. This pliable material envelope may be the same as any of 
the material options given for envelope 26. Each pouch envelope is filled 
with an insulation material which may be the same as any of the material 
options given for insulation material 28. 
If the insulating member 400 is not preshaped and configured and heat 
sealed along the line of intersection 406, then it begins as a single 
envelope of a generally cylindrical shape, see FIG. 12. Member 400 is 
initially placed within the shell 403 at its base and is centered as much 
as possible within the shell. A tight fit initially is not required 
because as the tank 401 is lowered onto the insulating member (arrows 
407), the weight of the tank causes the center of the member to compress 
and conform to the contour of the bottom of the tank. As this occurs, some 
of the insulation pushes outwardly (arrows 408) shaping and orienting 
member 400 into the form illustrated in FIG. 10. The shift in the 
insulation and the pliable shaping of the enclosing envelope into the FIG. 
10 form creates the annular ring pouch 405 in the form of a collar which 
seals off the space 402. 
As a further variation to the construction member 400, it is possible to 
mold the entire envelope into the shape illustrated in FIG. 11 prior to 
filling the envelope with insulation material. The envelope is then filled 
with a sufficient amount of insulation material in order to support the 
walls of the envelope and in order to maintain the desired shape. The 
molded configuration of the envelope is sized and shaped according to the 
size and contour of the tank 401 and the annular clearance space 402. If 
it is only desired to provide a conforming disc of insulation material 
below the tank and not include the collar as a connected portion, the size 
of the starting envelope of material is reduced such that the weight of 
the tank creates only a conformed disc. The collar can be added as a 
separate component piece. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.