Fully submersible immersion heater

Details Fully submersible immersion heater Fully submersible immersion heater

2001-01-25

2003-04-29

Pelham, Joseph (Department: 3742)

Electric heating

Heating devices

With power supply and voltage or current regulation or...

C219S523000

Reexamination Certificate

active

06555797

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is based on and claims the benefit of U.S. Provisional Application Serial No. 60/178,091, filed Jan. 26, 2000, entitled “FULLY SUBMERSIBLE IMMERSION HEATER.”
BACKGROUND OF THE INVENTION
The present invention relates to the field of immersion heaters. More particularly, the present invention relates to a fully submersible immersion heater having reduced dimensions that is used primarily, but not exclusively, for heating and maintaining the water temperature of an aquarium.
Immersion heaters are known for various purposes, including heating and maintaining the temperature of water in aquariums. As shown in
FIG. 1
, a typical immersion heater
10
is made up of a heating element
12
, a thermostat
14
, a power supply cable
16
, a waterproof housing
18
, an end cap
20
, and a temperature control
22
. The heating element
12
, which is usually a thermal resistance, is electrically connected by one or more wires
13
to the thermostat
14
. The thermostat
14
, which is typically a thermostatic bimetal camber, is used to regulate the heat output of the heating element
12
. The thermostat
14
is in turn electrically connected to the supply cable
16
, which supplies power to the heating element
12
. The heating element
12
, the wires
13
, the thermostat
14
and a portion of the supply cable
16
are placed inside the waterproof housing
18
, which has an opening (not shown) at one end. The waterproof housing
18
usually comprises a glass tube. The opening in the waterproof housing
18
is sealed with the end cap
20
, which is typically made from a rubber material. The end cap
20
has a first conduit
38
(shown in
FIG. 4A
) and a second conduit
40
(shown in
FIG. 4A
) that both extend through the end cap
20
. The supply cable
16
passes through the first conduit
38
in the end cap
20
, allowing the supply cable
16
to be electrically connected to an external power source (not shown). The temperature control
22
, typically a knob, dial or button, is seated adjacent to the second conduit
40
in the end cap
20
. The temperature control
22
is usually mechanically connected, by a plastic or metallic shaft
24
that passes through the second conduit
40
in the end cap
20
, to the thermostat
14
. The temperature control
22
allows a user to select or adjust the temperature the immersion heater
10
should maintain. For example, when the user turns or presses the temperature control
22
, the shaft
24
respectively rotates or moves vertically to modify the thermostat
14
. It will be understood by those of skill in the art that the temperature control
22
could alternatively be electrically connected to the thermostat
14
, by replacing the shaft
24
with an electrical cable (not shown).
There are two general designs of conventional immersion heaters for use in heating and maintaining the temperature of water in aquariums. The first such design is illustrated in
FIG. 2
, in which like numerals are used to indicate like elements without a repeat of the description of the like elements for purposes of brevity. In this design, the upper part of the immersion heater
10
is not watertight because there is no watertight seal between the supply cable
16
and the first conduit
38
in the end cap
22
through which the supply cable
16
passes. The supply cable
16
is usually an SPT1 or SPT2 type cable, because such cables are pliable and relatively thin in cross-section. Even though this design is somewhat resistant to water splashes onto the top of the end cap
22
, if the end cap
22
were submerged, water would seep through the first conduit
38
in the end cap
22
and inside the waterproof housing
18
. This would create an obvious danger of electrocution to both the fish in the aquarium and the owner, who often has to place his hands in the aquarium water. To obviate this danger, the upper part of the immersion heater
10
is held above the maximum water level
28
of an aquarium
30
by a support
26
. This design is disadvantageous in that the immersion heater
10
is only partially submersible and it is not aesthetically pleasing. This design also poses a safety risk in that the support
26
is rarely 100% dependable and it is therefore possible that the end cap
20
may touch the aquarium water.
The second conventional design is illustrated in
FIG. 3
, in which like numerals are again used to indicate like elements without a repeat of the description of the like elements for purposes of brevity. The immersion heater
10
of
FIG. 3
is fully submersible. The supply cable
16
is a relatively large diameter, water-resistant cable having a circular cross section, such as an ST or SJT type cable. Those of skill in the art will appreciate that the circular cross section of the supply cable
16
allows a reliable watertight seal to be achieved between the supply cable
16
and the first conduit
38
in the end cap
20
. A watertight seal is also formed between the shaft
24
attached to the temperature control
22
and the second conduit
40
of the end cap
20
in a manner well understood by those of ordinary skill in the art. For example, as shown in
FIG. 4B
, one or more raised sealing rings
41
can be formed on the interior surface of the second conduit
40
. Then, when the shaft
24
, which has a diameter that is approximately the same as the diameter of the second conduit
40
, is inserted into and through the second conduit
40
, an interference fit is formed between the shaft
24
and each of the sealing rings
41
creating a reliable watertight seal.
Even though the immersion heater
10
of
FIG. 3
is fully submersible, the design is disadvantageous because the large diameter of the supply cable
16
requires a large end cap and thus a large diameter glass tube to be used as the waterproof housing
18
. Such a design is not practical or aesthetically pleasing. Consumers of this type of product like immersion heaters to be discreet in the aquarium. Thus, the waterproof housing
18
should be as small as possible and also the supply cable
16
should be unobtrusive. Neither of these requirements is met by the design of FIG.
3
. This design is also disadvantageous because large cables such as the ST or SJT type cables used for the supply cable
16
are rigid and hard to manipulate. For example, a water-resistant ST or SJT type cable can only be bent to produce a curve with a radius of approximately two centimeters. By contrast, a water-resistant SPT1 or SPT2 type cable can be bent to produce a curve with a radius of only three millimeters. The immersion heater
10
of this design is therefore difficult to position or move in an aquarium.
There is a need in the art for an immersion heater, and particularly those for heating and maintaining the temperature of water in aquariums, that is completely submersible but also has reduced dimensions and is thus practical and aesthetically pleasing to consumers. There is also a need for a completely submersible immersion heater that uses a thin, flexible supply cable that is both unobtrusive and easy to manipulate.
BRIEF SUMMARY OF THE INVENTION
Briefly stated, the present invention provides an immersion heater. The immersion heater includes a waterproof housing, an electric heating element, a thermostat, an end cap, a temperature control, a flexible, water-resistant power cable and a sheath. The waterproof housing has an opening at one end. The electric heating element is placed inside of the housing and generates a heat output. The thermostat is placed inside of the housing and is electrically connected to the heating element for regulating the heat output of the heating element. The end cap sealingly engages the opening in the housing to form a watertight seal between the end cap and the opening in the housing. The end cap has a first conduit and a second conduit that extend through the end cap from a first surface of the end cap outside of the housing to a second surface of the end cap inside of the housing. The temperature control is sea

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