US1735168A - Terminal for heating units - Google Patents

Description

NOV. 12, W R KgNG TERMINAL FOR HEATING UNITS Filed March 28, 1927 ATTQRNEY L Patented Nov. 12, 1929 i UNITED sTATEs WILLIAM R. KING, F CMANSFIELD, OHIO,

ASSIGNOR, T0 fESTINGI-IO'USE ELECTRIC &

MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA TERMINAL FOR HEATING UNITS Application led March 28, 1927. Serial No. 178,872.

My invention relates to electric heaters and particularly to encased tubular heating units. An object of my invention is to provide an encased vtubular heating unit embodying a particularly simple and etlicient terminal construction.

Inpracticing my invention, I provide a tubular metal casing that may be bentlinto any desired shape, a helically-Wound resistor member therein that is held tightly therein by expansively-oxidized lelectric-insulating material, and resilient pre-shaped terminal members at each end of the tubular casing, an electric insulating bushing, and a cable ter- 1'5 minal securedv to the projecting end of the resilient terminal wire.

In the drawings,

Fig. 1 is a view, partially in side elevation and partially in longitudinal section, of an electric heater embodying my invention.

F ig. 2 is aview of an end portion, on an enlarged' scale, of an unfinished electric heater em odying my invention.

Fig. 3 is a View, in longitudinal sectiompf an end portion of Ia completed heater embodying my invention. p y v Figs. 4 and 5 are views, in side elevation and in front elevation, respectively, of an end bushing, and p A 30` Fig. 6 is a view in section of the tubular heater taken on line VI-VI of Fig. 1.

' An electric heater 11 comprises an outer tubular metal casing 12 which may be` of any kind of metal suitable for the temperature at' which it is to be operated. Thus, if the heater unit is to be operated at relatively low temperatures a copper tube may bey used,

while a steel tube or a tube made of an alloy steel must be used if the temperature is to be much higher.

A helically-wound resistor wire 13 is located withi'n thectubular casing 12 and the respective turns thereof are slightly separated from each other, as shown more particularly in Fig. 1 of the drawing.' The resistor wire is held tightly Within the casing '12 by means of a mass 14 of eXpansively-oxidized electric-insulating material consisting .of magnesium hydroxide or, oxide. The'V method of making or producingthe crystalline mass of electric-insulatng material is more particularly disclosed and claimed in re-issued Patent No. 16,340 to C. B. Backer. Briefly, the method is'that of providing a helix of resistor wire located within an open helix 15 of a strip of initially-metallic magnesium and the location of these parts within a tubular casing, such as the casing 12, or a bundle of bars or wires of magnesium may be located within the helix. The assembly is then subjected, for a predetermined length of time, to the action of high-temperature steam which effects a change of the metallic magnesium into magnesium hydroxide or oxide, the material expanding to substantially 200% of its initial volume, whereby theresistor wire is tightly held within the tubular' casing. The mass 14 of electricinsulating material thus produced 1s composed more particularly of a substantially solid crystalline structure, whereby a highly efficient heat path from the resistor Wire to the casing is provided, in addition to holding Ythe wire iirml-y within the casing. p

I prefer to make the longitudinal extent of the resistor helix 13 much less than that of the casing 12, and I provide a resilient terminal conductor 16 for each end of the casing.

The outer-end portion of each of the terminal conductors 16 is substantially straight, while the inner-'end portion is wavy or sinuous and is suitably connected to'an end of the resistor wire 13. The helix 15 of initially-metallic magnesium extends to substantially the end \of the casing at each end thereof so as to surround both end portions of the respective resilient terminal conductors 1G. Upon treatment thereof, as hereinbefore described, the 'resilient terminal wire is tightly held by the yeXpansively-oxidized magnesium hydroxide or oxide, substantially as shown in Fig. 1 of the drawing.

An'insulating bushing 17, of some suitable refractory material and having a (2o-'axial opening 18 therethrough, is provided at each end of the casing, the inner portion thereof being such as to closely fit within the casing 12, substantially as shown in Figs. 2 and 3 of the drawings.

A cable terminal. l9fis provided at each end of the heaterand embodies anouter portion to which a slpply-circuit conductor may be connected an an inner portion which may be folded over and around the end of the ters minal conductor 16 and soldered thereto. The inner` end of the cable terminal -19 abuts against the outer face of the bushing 17 in order to hold it securely in its operative poto crush the mass 14 of expansivel oxidized' magnesium h droxide or oxide uring the 20 final steps o manufacture of the heating units. The device embodying my invention provides a terminal wire that is heavier in lateral section than the resistor wire 13 and embodies two portions, one of these bein sinuous or bent, in order that the expande vmass of electric insulating material may hold the same and prevent longitudinal movement thereof relatively to the casin 12. The outer-end portion thereofvis straight and exao tends through an opening in an end bushing, which bushing is effective .to prevent lateral movement ofthe terminal lead and also to retain th'ejmass 1414 within the casing. As the cable terminal 19 is securely mounted on the outer end of the terminal conductor 16, it

holds the bushing 17 in. its proper operative position and prevents any leakage of the mass 14l of `'electric-insulating'material from /the'casing in case it becomes disintegrated to -magnesium t0 magnesium Ioxide in situ,

whereby the sinuous terminal conductor is secured 1n. place and provides an openingl through the oxide at the ends of the tube through which the oxidizing medium may pass until all of the metal about the resistor element has been converted to magnesium oxide.

[2. A terminal for a tubular heating unit 'having a `tubular casin and a resistor therein, said terminal inclu ing an extended resillent terminal wlre havmgvan inner sinuous portion electrically connected to the resistor,

and a substantially straight outer portion, a mass of electric-insulating material expansively oxidized in situ in the casing and holding the resistor and the sinuous portion of the terminal wire thereinz a bushing of electric-insulating material 1n the' end of the tubular casing and having the straight` portion of the terminal wire extending therethrough, and a terminal secured to the terminal wire for holding the bushing in the cas- 1ng w In testimony whereof, I have hereunto subscribed my name this 22d da Iof March, 1927.

' WILLI R. KING.

6 a slight extent during the handling or the use thereof.

Since a portion of the lterminal conductor 16 is sinuous, a tortuous passageway is rovided about and around the conductor w ich i" l 45 extends through a portion of the magnesium oxide for a distance substantially coextensive Y with the length of the conductor (see Figs. 1, 3 and 6). This passageway insures that steam will be permitted to flow through the 50 tube to convert the portion magnesium metal helix 15 located in the middle portion of the i v tube 12 to the oxideof magnesium in the event that the metal located in the ends of the tube has been converted rst,which is usul 55 ally the'case.

Various modifications may be madel in the device embodying my invention without departin from the spirit and. scope thereof and I esire, therefore, that only such limit, o0 tions shall be-A placed thereon as are imposed 1. The method of'making` a terminal strucl 4t -ture for a resistance element located in a. f

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