US 3859504 A
A panel heater comprising a heat-generating element formed of a sheet of carbon fiber-containing paper and electrodes at both ends, layers of a synthetic resin and then aluminum foils laminated successively on both surfaces of said sheet of paper, and sheets of a synthetic resin further laminated on both surfaces of the aluminum foils. Electricity can be passed to the electrodes of the heat-generating element with good insulation.
Description (OCR text may contain errors)
United States Patent 1 1 1111 3,859,504 Motokawa et al. Jan. 7, 1975 [5 MOISTURE RESISTANT PANEL HEATER 3,584,198 6/1971 Doi et al. 1. 338/212 X 3,627,981 12/1971 Kuhn .1 338/210 X [751 Invemorsi 3,657,516 4/1972 Fujihara 219/345 9 1 Japan FOREIGN PATENTS OR APPLICATIONS 731 Assignees; Kureha Kagaku Kogyo Kabushiki 1,267,248 6/1961 France... 219/345 i y ki 866,938 4/l958 Great Br1ta1n 2l9/345 Kabushiki Kaisha, Osaka, Japan Primary ExaminerJ, V. Truhe  Flled 1973 Assistant Examiner-Clifford C. Shaw  Appl. No.: 348,786 Attorney, Agent, or FirmSughrue, Rothwell, Mion,
Zinn & Macpeak  Foreign Application Priority Data Apr. 6, 1972 Japan 47-34698 ABSTRACT A panel heater comprising a heat-generating element  CI 4 4 5 formed of a sheet of carbon fiber-containing paper I 3 8/212 33 ,25 3 B g 28 and electrodes at ,both ends, layers ofa synthetic resin g i and then aluminum foils laminated successively 0n [5 1 g both surfaces of said sheet of paper, and sheets of a 3 lzlz 3 3 synthetic resin further laminated on both surfaces of 219/528 541 the aluminum foils. Electricity can be passed to the electrodes of the heat-generating element with good  References CIted insulation.
UNITED STATES PATENTS 1,422,130 7/1922 Reynolds 338/329 x 3 Clam, 3 Drawmg Flgures ,fish culture.
MOISTURE rdtsrsrANr PANEL HEATER BACKGROIIND or THE INVENTION l. Fieldof the Invention This invention relates to a panel heater for use in water or in a wet condition, especially in a fish tank for 2. Description of the Prior Art The panel heater for such purposes must meet a number of requirements, among which are;
I. It shouldhave an output suited for the particular size of the water tank, and be free from current leakage.
2.,Its surfacetemperature should not be too high (watt density).
3. It should not be corroded by sea water.
4'. There should be no change in the resistance of the heat-generating element with the passage of time, and the element should generate a constant amount of heat.
5. The outer sheath of the heater should not burn when exposed to air. I
6. The size of the heater should be moderate and easy to withdraw from the tank.
The conventional underwater heater which has a metal surface-has a high watt density and a surface temperature of more than 200C, and its temperature gradient in a water tank is steep.,Therefore, it is unsuitable for fish culture. Furthermore, the metal coating on the surface is especially heavily corroded in a fish tank for sea fish, and can be used only for a short duration of time. I
Commercially available vinyl resin coated wires are sometimes used as a heater for a fish tank. Officially,
with laminated layers of synthetic resin films on both sides suffer from an increase in the resistance of the heating element by the influence of moisture which has permeated through the films as time passes, and a decrease in output cannot be avoided. Furthermore, when the heaters of this type are connected in water to an alternating current source, the worker standing on the ground feels leaked current when putting his hand into the water, although the leakage does not affect the fish in the tank. According to the Law for Regulating Electric Appliances, the leaked current should be less than 1 mA. Experiments show that in order to adjust the leaked current to less lmA, the maximum area of the panel heater should be restricted to 700cm and its output should be adjusted to less than 140 W. With such a panel heater, it is impossible to maintain a water tank having a capacity of 300 to 500 liters at a moderate temperature of to 28C.
SUMMARY. OF THE INVENTION The present invention Provides a panel heater containing a carbon fiber-containing paper as a heating element, which is free from the above-mentioned defects as an underwater heater.
The main object of this invention is to provide an underwater heater for maintaining a fish tank for sea fish culture at a moderate temperature, which is safe and usable for prolonged periods of time, that is, to reduce leakage of current by incorporating aluminum foil in a panel heater, and to prevent a change of the resistance of the heating element with the passage of time.
Still another object is to prevent the leakage of current at the current passing part of a panel heater.
- BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing the structure ofa moisture resistant panel heater of this invention;
FIG. 2 is an enlarged sectional view of a part of the panel heater shown in FIG. 1; and
FIG. 3 is a partly sectional plan view showing the current passing part of the panel heater of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT The structure of the panel heater of this invention will be described by reference to the accompanying drawings.
Referring to FIGS. 1 and 2, there is shown a panel heater consisting of a heating element 1, layers 2 and 2' of a synthetic resin such as polyethylene, aluminum foils 3 and 3', layers 4 and 4' of the above-mentioned synthetic resin, outer layers 5 and 5 of a synthetic resin such as a polyester, electrodes 6 and 6, and conducting wires 7 and 7' for passing electricity. Specifically. on both surfaces of the heating element 1 consisting of a sheet of carbon fiber-containing paper and electrodes 6 and 6 made, for example, of a copper wire gauze I connected to both ends of the paper sheet are laminated the synthetic resin layers 2 and 2. On both surfaces of the resin layers, the aluminum foils 3 and 3' are then laminated. Furthermore, on both surfaces of the.
aluminum foils, the synthetic resin layers such as polyethylene 4 and 4 and then the synthetic resin sheets such as polyester 5 and 5' are laminated successively. The heating element 1 is adapted to be heated by passing electricity through the electrodes 6 and 6.
For example, when the panel heater is used in water or in a wet condition, it is necessary to take measures for preventing current leakage at terminals leading to the heating element in water or in a wet condition, as shown in FIG. 3. An extension of the electrode 6 of the panel heater is soldered to a core 10 of an exteriorly insulated conductor, and a polyethylene insulating layer ll of the conductor is laminated by hot pressing to the polyethylene layer2 and 2 which is an interlayer of the synthetic resinportion of the above-heating element. Then, a part of a polyvinyl chloride sheath 8 of the conductor is brought into contact with the edge 12 of the above laminated synthetic resin Sand 5, and then, both of them are wrapped in contact with each other in a cloth, such as a felt or flannel I3, impregnated with an epoxy resin, and by curing the epoxy resin the, terminal portions of thepanel heater are completed.
By this construction, the impermeability of the aluminum foils serves to avoid an increase in the resistance of the carbon fiber-containing paper, and hence a decrease inoutput. Furthermore, the presence of the aluminum foils contributes to the reduction of leaked current to about one-third as compared with a panel heater which does not include aluminum foils. Thus, the area of the panel heater can be increased by about three times.
The panel heater of this invention produces output suitable for a given fish culture tank, and is free from current leakage and corrosion by sea water. It also prevents changes in the resistance of the heating element with the passage of time, and also burning of the outer layer during heat generation in air. It is flexible and can be formed into any desired shape, and moreover, a suitable temperature gradient in the fish tank can be provided by its suitable surface temperature. Thus, the panel heater of this invention can be effectively used with safety not only in water but also ina wet environment. v
What we claim is: g
l. A moisture resistant panel heater comprisinga heating element consisting of a carbon fiber-containing paper sheet and electrodes on two opposite ends thereof, a layer of polyethylene laminated to both surfaces of said heating element, a layer of aluminum foil laminated to both outer surfaces of the polyethylene layers, sheets of a synthetic resin laminated to both outer surfaces of said aluminum foils, and further comprising extended portions of said electrodes soldered to a core of an insulated conductor having a polyethylene vlaminated to both outer surfaces of the polyethylene layers, .a polyethylene layer laminated to both outer surfaces of said aluminum foils, and polyester sheets laminated to both outer surfaces of the last-mentioned polyethylene layers, and further comprising extended portions of said electrodes soldered to a core of an insulated conductor having a polyethylene insulating layer and an outer sheath, said polyethylene insulating layer of said conductor being melt-bonded to said firstmentioned polyethylene layers, and a felt impregnated insulating layer and an outer sheath, said polyethylene insulating layer of said conductor melt-bonded to said polyethylene layers, and a felt impregnated with an with an epoxy resin which is cured, said felt holding an edge of the outer synthetic resin layers of said heater and the outer sheath of said conductor.
3. The panel heater of claim 1 wherein said electrodes are made of a copper wire guaze.