US2489998A

US2489998A - Electric tubular heater terminal seal

Info

Publication number: US2489998A
Application number: US1146A
Authority: US
Inventors: Allan P Charbonneau; Edwin W Seeger
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1948-01-08
Filing date: 1948-01-08
Publication date: 1949-11-29
Anticipated expiration: 1966-11-29

Description

Nov. 29, 1949 A. P. CHARBONNEAU ETYAL 2,489,998

ELECTRIC TUBULAR HEATER TERMINAL SEAL Filed Jan. 8, 1948 GU/g3: Z,

l2, W W

FUSLON H F WELD USION m 1 v WELD w i 6 w in 1' I5- I I1 ll 1 2- l Patented Nov. 29,1949

UNITED STATES PATENT OFFICE ELECTRIC TUBULQR HEATER TERMINAL ware Application January 8, 1948, Serlal No. 1,146

This invention relates to electric heaters and more particularly to an improved method of and means for sealing terminals of heaters having tubular enclosing sheaths.

An object of the present invention is to provide for making a highly satisfactory terminal seal for tubular sheathed heaters in a simple and expeditious manner.

Another object is to provide a terminal seal which is impervious to moisture and of a nonbreakable character;

Another object is to provide a terminal seal of the aforementioned character without the application of heat or introduction of fusible sealing materials.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of the invention which will now be described. r

In the drawings:

Figure 1 is a view in longitudinal section of a portion of a tubular type heater prior to the application of a terminal seal.

Fig. 2 is like Fig. 1, but shows the terminal seal in a completed state, and

Fig. 3 is like Fig. 2, but modified in respect of the terminal seal retaining member.

Referring to Fig. 1 it shows a tubular type electric heater comprising a helical resistor 5 which 4; Claims. (CL 201-41) so that its inner end engages the insulating material I. Then a locking member II, which in one preferred form is a blade-dike terminal device shown in Fig. 2, is attached to the extended end of terminal lead 8 as by fusion welding. To aii'ord proper sealing action by the plug I0 it is necessary that member l2, during and following its attachment to the terminal lead 8 in any preferred manner compress the plug Ill inwardly of the recess 9 to effect longitudinal compression of the plug. Such compression Of the plug Io provides for lateral expansion of the same within recess 9 to eflect intimate and tightly fitting engagement is embedded in a compacted mass of refractory insulating material 6 and incased by a tubular metal sheath 1 of any preferred cross sectional form. The resistor 5 is connected in any preferred manner to a terminal lead 8 which extends outwardly of the sheath 1. The sheath adjacent its end is unfilled and provides a recess 9 to receive the terminal seal.

Prior to applying the terminal seal, it is assumed that the heater has been worked as by swaging to the desired cross sectional form and dimensions.

A plug i0 composed of silicone rubber of elastic character, such as, for example, Dow Corning Silastic No. 180, is used for effecting a terminal seal. Preferably plug I0 is externally formed to match the cross sectional form of the recess 9 but with slightly smaller dimensions to facilitate its insertion within recess 9. It is also provided with a central longitudinal perforation H to provide clearance for terminal lead 8. The length of plug in is preferably somewhat in excess of the depth of recess 9.

To effect the terminal seal, plug I0 is slipped onto terminal lead 8 and is inserted into re$$ 9 66 1.

of the plug with the inner walls of sheath I and with the terminal lead 8.

As shown in Fig. 2, a washer i3 is preferably interposed between the adjacent ends of plug iii and member I! to insure that when the latter is attached to terminal lead 8 it will exert pressure on plug Ill substantially uniformly about the outer end of the latter. However, washer is may be dispensed with as desired when-other preferred locking members or terminal devices are used which are provided with abutting end portions that substantially overlie the end of the plug; such as for example another preferred type of terminal device I shown in Fig. 3.

If the terminal seal has been eflected as hereinbefore described a finished terminal such as shown in Figs. 2 and 3 will be had. The terminal seal will be moisture impervious and of a nonbreakable character. The use of a silicone rubber plug as the sealing medium insures that the seal will not disintegrate unless the temperature of the terminal end of the heater exceeds 500' Fahrenheit. The terminal end temperatures of properly designed and constructed tubular sheathed heaters such as used in the cooking art are substantially below 500 Fahrenheit even when subjected to their maximum rated wattages. The danger of seal disintegration due to heat is therefore remote.

It will be apparent that the terminal seal described herein has numerous advantages. The use of fusible sealing materials is obviated, and several steps heretofore used in providing a finished terminal seal are eliminated. Consequently there is a saving in time and cost. Because of the elastic character of the seal it is not subject to breakage which is ordinarily associated with many types of terminal seals heretofore used.

What we claim as new and desire to secure by Letters Patent is:

The method of sealing the terminal end of an electric heater wherein a resistor enclosed in an open end tubular sheath is embedded in in sulation at a distance from the end of the sheath to leave the sheath with an open end recess, and wherein the resistor has a terminal portion projecting through such recess to a point beyond the sheath, comprising the step of inserting a perforated heat resistant plug of elastic character into the open end recess of said heater, compressing said plug inwardly of said recess to cause lateral expansion of said plug for engagement with the inner walls of said sheath and with said terminal portion of said resistor, and locking a member to said terminal portion of said resistor toretain said plug in compressed condition.

2. The method of sealing the terminal end of an electric heater wherein a resistor enclosed in an open end tubular sheath is embedded in insulation at a distance from the end of the sheath to leave the sheath with an open end recess, and wherein the resistor has a terminal portion projecting through such recess to a point beyond the sheath, comprising the steps of slipping onto the terminal portion of said resistor a perforated silicone rubber plug of elastic character, inserting said plug into the open end recess of said heater, compressing said plug inwardly of said recess to cause lateral expansion of said plug for engagement with the inner walls of said sheath and with said terminal portion of said resistor, and looking a member to said terminal portion of said resistor to retain said plug in compressed condition.

3. The combination with a tubular heater comprising a resistor having a terminal portion, an open end tubular sheath surrounding said resistor and also its terminal portion in part, and insulation in said sheath retaining said resistor in spaced relation to said sheath, said insulation terminating at a distance from the end of said sheath leaving said sheath with an open end recess through which said terminal portion projects, of a perforated elastic plug formed of heat resistant material compressed in situ to tightly engage said insulation, the inner walls of said sheath and the terminal portion of said resistor projecting through said recess, and a member locked to said terminal portion of said resistor to maintain said plug in such compressed state.

4. The combination with a tubular heater comprising a resistor having a terminal portion, an open end tubular sheath surrounding said resistor and also its terminal portion in part, and insulation in said sheath retaining said resistor in spaced relation to said sheath, said insulation terminating at a distance from the end of said sheath, leaving said sheath with an open end recess through which said terminal portion projects, of a perforated silicone rubber plug of elastic character compressed in situ to tightly engage said insulation, the inner walls of said sheath and the terminal portion of said resistor projecting through said recess, and a member locked to said terminal portion of said resistor to maintain said plug in such compressed state.

ALLAN P. CHARBONNEAU. EDWIN SEEGER.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,003,175 Daly May 28, 1935 2,369,045 Hampton et a1 Feb. 6, 1945 2,375,058 Wiegancl May 1, 1945 2,397,568 Seaman Apr. 2, 1946 2,428,053 Vasileff Sept. 30, 1947 A FOREGN' PATENTS Number Country Date 495,212 Great Britain Nov. 9, 1938 OTHER. REFERENCES Knight, Silicones, October 1945, pages 1069- 1073 of Materials And Methods.

Silicones, April 22, 1946, pages 121-122, Steel.