US 3621566 A
Description (OCR text may contain errors)
Nov. 23, 1971 J. w. WELSH 3,621,566
METHOD OF MAKING AN ELECTRICAL HEATING ELEMENT Filed May '7, 1969 2 Sheets-Sheet 1 FIG.|
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26 25 INVENTOR.
JAMES W. WE L SH BY J my /3 (A ATTORNEY NOV. 23, 1971 w WELSH I 3,621,566
METHOD OF MAKING AN ELECTRICAL HEATING ELEMENT Filed May 7, 1969 2 Shoots-Shoot 2 g INVHNTOR.
JAMES w. WELSH BY ATTORNEY United States Patent 3,621,566 METHOD OF MAKING AN ELECTRICAL HEATING ELEMENT James W. Welsh, Summit, 'N.J., assignor to Standard Motor Products, Inc., Long Island City, N.Y.
Filed May 7, 1969, Ser. No. 822,575 Int. Cl. H01c 17/00 US. Cl. 29-610 6 Claims ABSTRACT OF THE DISCLOSURE Method of making an electrical heating element which 'includes cutting a planar resistance member into a plurality of laterally interconnected strips and bonding insulating material about the strips. The insulating material is preferably a thermoplastic material and is preferably affixed by dipping the strip into liquified material. The insulating material has a thickness of from .0025- .006 inch with preferred thickness being .001 inch.
An electrical heating element is also described which comprises a resistance member having insulation bonded thereto. The resistance member is formed of an integral interconnected plurality of laterally disposed members with each member connected to the adjacent member at an opposite side portion.
A water heater is shown which includes a water-containing tank having inlet and outlet conduits. An electrically operated heater member is disposed within the tank and a pressure-controlled switch is provided to render the heater member inoperative when the water within the tank falls below a predetermined level.
DESCRIPTION OF THE INVENTION This invention relates to a method of making an electrical heating element, to the electrical heating element itself, and to a water heater which includes the electrical heating element of this invention.
conventionally, electrical heating elements which are utilized in various types of heating devices are made of a resistance member, preferably a resistance wire, which resistance member is surrounded by insulation and generally encased in a metallic housing. Conventional resistance members are rather costly to manufacture and, by reason of deposits which form on the outside housing tend to burn out under even moderate load. Also, where such conventional resistance members are used in water heaters, a galvanic action occurred between the outside housing and the heater jacket which caused premature failure.
I have discovered a novel method of making such electrical heating element which avoids the disadvantages of the prior devices.
In the first place, the electrical heating element is made of a single planar resistance member. This resistance member can be of relatively low cost material such as, for example, nickel-chrome alloy, iron or steel. The resistance member is then cut into a plurality of interconnected strips. This step can be performed extremely rapidly by means of the conventional cutting die. Thereafter, insulating material is bonded to the cut resistance member. This step is also rapid since the preferable method of performing the operation is to merely dip the cut resistance member into liquified thermoplastic insulating material, and then squeeze the resistance member between heated plates.
The interconnected insulating strips can then be utilized in various ways as heating elements. The strips can be partially separated and secured to a stem member and lead-in wires then attached. Alternatively, the strip Patented Nov. 23, 1971 Ice material formed can be elongated and wrapped about a form. Removal of the form will produce a relatively strong and stable heating element.
The heating element made by the method of this invention can be disposed into a heating device such as, a water heater. When the heating element structure of this invention is utilized in a water heater, the insulation on the heating element is of a non-stick type. Therefore, deposits normally do not build up on this structure. However, a self-cleaning action is also produced since the heated wire is free to expand within the insulation, which is flexible. In the water heater shown in this invention, additional novel structure is provided which includes a pressure control switch member which can be utilized to render the heater inoperative when the water in the device falls below a predetermined level. The leadin plug of the heating element of this invention, when utilized in connection with a water heater, can be molded because the heating element does not produce the large quantities of unusable heat which are normally produced by conventional methods.
The above constitutes a brief description of this invention and some of the objects and advantages thereof. Other objects and advantages of this invention will become apparent to the reader of this specification as the description proceeds.
The invention will be further described by reference to the accompanying drawing which is made a part of this specification.
FIG. 1 is a longitudinal cross-sectional view of a water heater made in accordance with this invention.
FIG. 2 is a detailed side elevational view on a large scale of one form of the electrical heating element made in accordance with this invention.
FIG. 3(a) is a plan view of the resistance member prior to its formation into an electrical heating element.
FIG. 3(b) is a view similar to that of FIG. 3(a) but showing the form assumed by the resistance member after being cut into a plurality of interconnected strips.
FIG. 3(a) is a view similar to that of FIG. 3(b) but showing the manner of afiixing the steel member to the device after the resistance member has been insulated.
FIG. 4 is a fragmentary side elevational view of the heating element formed by the method described in this invention.
FIG. 4(a) is an end view of the electrical heating element shown in FIG. 4.
FIG. 5 is a fragmentary front elevational view showing the manner in which a resistance member can be formed by an alternative method described in this invention. In this figure the removable forming member is shown in fragmentary form about the formed resistance member.
FIG. 6 is a cross-sectional view taken along line .66 of FIG. 5.
FIG. 7 is a front elevational view of the electrical heating element formed utilizing the method described.
FIG. 7(a) is an end view of the form of electrical heating element shown in FIG. 7.
FIG. 8 is a detailed view of one form of lead-in element that can be used in connection with the electrical heating device of this invention.
The invention will now be further described by reference to the specific forms thereof as shown in the accompanying drawings. However, the reader is cautioned to note that the specific forms of this invention as illustrated herein are merely for illustrative purposes and purposes of example only. Various changes and modifications may, obviously, be made within the spirit and scope of this invention.
The method of manufacture of the electrical heating element of this invention is illustrated in FIGS. 3(a), 3(b), 3(0), 4, 4(a), 5, 6, 7 and 7(a). The first step of constructing such an electrical heating element is the obtaining of a resistance member 11 shown in FIG. 3(a). This resistance member may be iron, steel, nickel-iron, nickel-chromium, or any other conducting material. The material should be relatively thick and preferably from about .001 to .010 inch. The thickness of the material is, of course, not material and any suitable thickness can be used. However, of course, the resistance of the element will depend upon the thickness of the material and the material used.
The resistance member 11 is then cut into a plurality of interconnected laterally disposed strips 12 by means of a forming die into the configuration shown in FIG. 3(b). Insulating material is then bonded to the cut resistance member preferably by dipping the resistance member into a liquified thermoplasticsuch as Teflon made by E. I. du Font and Co., nylon or Kel-F made by Minnesota Mining and Manufacturing Company. The resistance member is then removed from the thermoplastic insulating material and allowed to cool. Normally, the insulating material must then be baked to produce a proper bond to the resistance member. However, such baking normally produces shrinkage and capillary action which tends to expose the end portions of the resistance member. Therefore, after the baking step, it is preferable to place the insulated resistance member between a pair of heated plates which causes the insulating material to flow gutwardly around the outer portions of the resistance member. Thereafter, a stem member 13 may be secured to the resistance member as shown in FIG. 3(c) and FIG. 4 by sliding the stern member through the resistance member and then securing the stern member to the resistance member by rivets 14. It is to be noted that in the form of invention shown in FIG. 4 the stem member is secured to the resistance member at only a single point so that the resistance member may move downwardly and thus become a part of an automatic shutofi device as will be subsequently explained.
Alternatively, the insulated resistance element may be separated and the strip so produced wound about a form 15 thereby producing the configuration shown in FIG. 5. This may then be optionally secured to a stem member 13 as shown in FIG. 7.
The heating element of this invention can be utilized in various electrical heating devices. FIGS. 1, 2 and 8 show the method of utilizing the heating element of this invention in a Water heater. The water heater consists of a tank 15 which preferably is insulated by an insulating jacket (not shown). Operatively connected to the tank is a water inward conduit 17 and a water outlet 18. A thermostat 19 is disposed between wires 20 and 21 and a switch 22 is disposed between wires 20 and 23. Wire 24 is also provided. Wires 23 and 24 are connected to a source of electrical power. Wires 25 and 26 are embedded in a connector 27 which bears a threaded portion 28 on the outside thereof. Wire 26 is in turn connected to stem 13 (FIG. 2).
Wire 25 is normally disconnected from plunger 27. Plunger 27 is normally maintained in the disconnected position by coil spring 28 which is disposed about plunger 27 and which is disposed within recess 29. Plunger 27 is movable within recess 29 and water is kept out of this recess by seal 30. Plunger 27 bears a pressure portion 31 thereupon and is in turn connected to resistance member 11. Wire 25 is connected to wire 24 and wire 26 connected to wire 21.
With the foregoing specific description the operation of this invention can now be explained.
In the normal condition, where no water is present within tank 16, plunger 27 is in the up (disconnected) position. At this point no power flows into resistance member 11.
When water 35 rises within tank 16 above a predetermined level it applies pressure to seat 31 which in turn moves plunger 27 in a downward position thereby causing plunger 27 to make electrical contact with wire 25. If switch 22 is now closed and thermostat 19 at a temperature below the temperature that the water is to assume, power will now flow into resistance element 11 and cause water 35 to be heated. Power can be manually disconnected at any time by opening switch 22 or power will be disconnected if the temperature of the water reaches the predetermined temperature and thermostat 19 opens. Power will also be disconnected if water 35 falls below a predetermined level and pressure is no longer applied to seat 35.
The foregoing sets forth the manner in which the objects of this invention are achieved.
1. A method of making an electrical heating element comprising the steps of obtaining a planar metallic member of relatively high resistance having a thickness of from .001 to .010 inch, cutting said member into a plurality of laterally interconnected parallel strips having alternately cut-out lateral portions, dipping said formed member into a heated liquified thermoplastic insulating material, removing said formed member from said liquified insulating material and allowing it to cool, baking said formed member until the insulating material bonds firmly to the resistance member, and thence placing said resulting product between a pair of heated plates until the insulating material flows outwardly around the outer portions of the resistance member.
2. A method as described in claim 1 including the additional step of placing a stem member within said completed formed member with said stern member passing alternately above and below adjacent interconnected parallel strips.
3. A method as described in claim 2, said stern member being substantially centrally disposed with respect to said strips.
4. A method as described in claim 3, said stem member being secured to said resistance member.
5. A method as described in claim 4, said stem member being secured to said resistance member at a single point onl g A method as described in claim 5, the said single point of securement of said stern member to said strip being at the upper end thereof.
References Cited UNITED STATES PATENTS 953,393 3/1910 Parkhurst 29610 X 2,357,906 9/1944 Osterheld 338-244 2,432,800 12/ 1947 Reichold 296 10 X 2,865,795 12/1958 Morrison, Jr 1l7230 3,028,265 4/1962 Wareham 117128.4 X 3,340,216 9/l967 Mack 117132 X 3,408,735 11/1968 Eisler 29-610 3,516,154 6/1970 Cooper et al. 29611 JOHN F. CAMPBELL, Primary Examiner V. A. DI PALMA, Assistant Examiner U.S. Cl. X.R.