US 3387364 A
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Description (OCR text may contain errors)
June 11, 1968 A. c. BoGGs y 3,387,364
METHOD OF TERMINATING RESISTORS Filed July 30, 19625 Pg. Z j] f7 j f5 fi j laf-g5 j ff INVENTOR. ALBEN C1. Bossa A fromm/5 United States Patent O 3,387,364 METHOD F TERMINATING RESISTORS Alben C. Boggs, Pittsburgh, Pa., assignorto Edwin L. Wiegand Company, Pittsburgh, Pa. Filed July 30, 1963, Ser. No. 298,679 3 Claims. (Cl. 29-621) The present invention relates to metallic sheathed electric resistance heaters, more particularly to such heaters which are hermetically sealed against entrance of moisture or other deleterious substances, and the principal object of the invention is to provide new and improved heaters of the character described, and new and improved methods of making the same.
Electric heaters of the type wherein a tubular metallic sheath encloses a resistor conductor, wherein a terminal conductor is connected to said resistor conductor within the sheath and projects axially outwardly of an open end thereof, wherein a flexible, insulated lead wire is electrically connected to said terminal conductor, and wherein a molded body of cured-in-position, rubber-like material extends between and is bonded to the sheath and the lead wire insulation and embeds the connection between the lead wire and the terminal conductor have long been known and used. Such a heater assembly is shown and described in Letters Patent No. 2,659,795, assigned to the same assignee as is the instant case.
While heaters of the type disclosed in the above patent have been widely used, relatively high manufacturing costs have restricted even more widespread use. These high costs have largely resulted from the necessity of curing the rubber-like material body in a heated mold. Such molds are expensive, large numbers of molds are required in high volume production, and disposition of the assembly in the mold and its removal therefrom is time-consuming.
While the present invention provides a finished assembly which may not be superior to that 'heretofore provided, such assembly may be produced at markedly lower costs because of the elimination of the previously required molds. Other advantages will become apparent from a study of the following description and from the drawing appended hereto.
In the drawing accompanying this specification and forming a part of this application there is shown, for purpose of illustration, an embodiment which the invention may assume, and in this drawing:
FIGURE 1 is a fragmentary elevational view of a completed heater assembly constructed in accordance with the present invention,
FIGURE 2 is a view in longitudinal section of the as- 'y sembly seen in FIGURE l, and
FIGURES 3, 4 and 5 are views similar to FIGURE 2 but showing successive stages of manufacture.
With reference to FIGURES l and 2, there is illustrated a conventional electric resistance heating element of the type having a coiled resistor conductor 11 disposed -within a tubular metallic sheath 12 which is filled with electric-insulating, heat-conductive material 13 preferably compacted to a rock-like hardness. Resistor conductor 11 preferably terminates short of the sheath end and a terminal conductor pin 14 is welded or otherwise electrically secured to the conductor 11 within the sheath and projects beyond the sheath end to provide for making an electrical lpower connection to the heating element.
The bared end of a flexible, insulated lead Wire 15 is electrically connected to the protruding portion of the terminal pin 14 in any suitable manner and as herein disclosed, a connector 16 is crimped about their juncture for such purpose.
Embedding the juncture aforesaid of the wire and the terminal pin is a mass of cured, rubber-like material 17 3,387,364 Patented June 11, 1968 ICC which extends over both the adjoining end of the shea-th 12 and the insulating covering of the wire 15 and is bonded thereto. Enclosing the mass of material 17 is a rubber-like sleeve 18 bonded to the material mass, the sheath and the wire covering.
Turning now to the novel mode of manufacture of the assembly hereinabove described and with reference first to FIGURE 3, the bared end of the lead wire 15 will be secured to the terminal pin 14 as by means of a suitable connector 16. Next, the adjoining ends of the sheath 12 and the insulation of the lead wire will be suitably treated to ensure a good bond with the mass of material 17. Such treatment may, if desired, take place before the wire is secured to the terminal pin and may include sand blasting or pickling of the sheath end and the coating of the sheath end and the wire insulation with a suitable adhesive. One such adhesive found suitable for the present purpose is known as Ty-Ply-Up, supplied by the Marbon Corporation of Gary, Ind.
With the wire secured to the terminal pin as above described and with the adjoining ends of the element sheath and the wire covering suitably treated, when necessary, an uncured body of rubber 17 ywill be deposited over the juncture of the wire and the pin and preferably spanning the element sheath and the wire covering as shown in FIG- URE 4. Next, a sleeve of dielectric, iiexible, heat-shrinkable material 18 will be slid over the material mass 17, such sleeve preferably being somewhat greater in length than the material mass as illustrated in FIGURE 5.
Sleeve 18 is a product of Rayclad Tubes, Incorporated, and is known as Thermofit NT. Such sleeve is formed of a flexible, dielectric, neoprene material which has been so modified in chemical structure that it will shrink in diameter as much as upon subjection to a temperature in excess of 175 C.
With the various parts assembled as seen in FIGURE 5, they will be placed in an oven or otherwise subjected to a temperature suicient to cause contraction of the sleeve 18. As the latter contracts, it functions in a manner similar to a mold to compress the flowable, uncured rubber mass 17 into intimate relation with the element sheath, the ter minal pin, the bared portion of the lead wire and the covering thereof. The assembly will thereafter be maintained at a temperature sufficiently high and for a long enough period of time to cause the rubber mass to cure and form a tight bond with the element sheath and the lead wire covering. A bond may also be effected between the rubber mass and the sleeve 18 and between the latter and the element sheath and 'wire covering.
In view of the foregoing it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.
1. The method of making a hermetically sealed electrical connection to a metallic sheathed, electric heating element having a terminal conductor protruding therefrom, which comprises electrically connecting the bared end of an insulated lead wire to the protruding portion of said terminal conductor,
depositing a mass of flowable, uncured, rubber-like material about the connection between said wire and said conductor,
disposing a heat-shrinkable, flexible `dielectric sleeve over said mass of material and with respective ends of such sleeve extending beyond said material and over the adjoining end of the element sheath and the insulation of the lead Wire,
radially shrinking the intermediate portion of said sleeve about said mass of material by the application of heat thus compressing such mass about the electrical vconnection aforesaid and at the same time radially shrinking the opposite ends of said sleeve about the element sheath and the Wire insulation respectively,
and curing said rubber-like mass of material in position by the application of heat aforesaid.
2. The method of cliam 1 wherein said rubber-like mass of material extends over the adjoining end of the element sheath,
and further comprising the step of treating the adjoining element sheath end prior to deposit of said material about said connection to insure a good bond between said element sheath end and the cured mass of material.
References Cited UNITED STATES PATENTS 3. The method of claim 1 wherein said rubber-like mass of material extends between adjoining ends ofthe element sheath and the insulation of the lead Wire,
and further comprising the step of treating the adjoining element sheath end and the insulation of the lead wire prior to deposit of said material about said connection to insure a good bond between said element sheath end and the cured mass of material and between the latter and the insulation of said wire.
2,790,285 4/1957 Pike etal 53-42X 5 2,898,714 8/1959- Keith 53--30 3,040,385 6/1962 Folia Z9-613x 3,226,807 1/1966 oir. 3,243,211 3/1966 Wetmore 287-718 3,276,929 10/1966 Perch. 3,026,604 3/1962 Boggs 294-15563 10 3,085,316 4/1963 Nelson 29-155.63 2,063,826 12/1936 Bender 338-274 3,102,248 8/1963 Temple 338-274 2,727,120 12/1955 Boggs 338-274x 15 2,942,222 6/1960 Nelson 338-243 2,659,795 11/1953 Boggs sas- 274x 2,876,322 3/1959 Boggs 338-274X 2,989,785 I6/1961 stahl 264-2302( 3,113,284 12/1963 van1n1i1oudt 338-274 3,131,240 4/1964 Kirkpatrick 264-230 3,187,088 6/1965 Warner 174-76X FOREIGN PATENTS 1,054,527 4/1959 Germany.
q JOHN F. CAMPBELL, Primary Examiner.
RICHARD M. WOOD, CHARLIE T. MOON,
V. Y. MAYEWSKY, I. CLINE, Assistant Examiners.