US1614168A - Electric heater - Google Patents

Description

1927. Jan 11 c. c. ABBOTT ELEGTRIC'HEATER Filed April 8. 1925 F1 5 //a t 3 la 54 2a 2 Invenfor: Charles QAbbol'E H isArlor'neu.

'rseaauaau, 1927.

UNITED STATES m 0. ABBOTT, OI iussacnum'ra, ABSIGI'Q B T I'D-1C comm, A OOBPOBQAIOI O! m roan.

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M inventionv relates to electric heaters and as for its object the provision of means for dissipating heat therefrom and for preventing overheating of a certain part. or parts of the heater.

My invention relates more particularl to electric space heaters or air heaters suc as may be used in heating rooms, street cars, etc. One form of this type of heater is described and claimed in my-Patent No. 1,494,- 939, dated May 20, 1924, of which this invention is an improvement. In certain cases it is desirable to maintain the terminal ends of electric heaters at a comparatively low temperature, 'for example, where the terminalends are sealed with a material having a comparatively low melting int.

In"earrying out my invention I provide heating means for a central section of the heater, and heat dissipating vanes extending lengthwise of the heater provided with slots near their ends whereby conduction of heat to the ends of the heater is prevented. For a more complete understanding of my, invention reference should be had to the accompanying drawing in which Figure 1 is 1. side view partially in section of an electric heater embodying my invention; Fig. 2 is a sectional view alongthe line 2-2 of Fig. 1 looking in the direction of the arrows, while Figs. 3 and 4 are views similar to Figs. 1 and 2 showing a modified form of my invention.

Referring to Figs. 1 and 20f the drawing, I have shown my invention in one form as comprising a helical coil, sheathed wire heating unit of convenient length, such as described and claimed in my Patent No. 1,367 ,341, dated February 1, 1921. Briefly, this heating unit comprises an outer metallic sheath 11 in which a helical resistance conductor 12 is embedded in acompacted mass of powdered-heat refractory insulating m terial 13. The insulating material 13 mag .be compacted to a hard dense mass. having good heat conductivity by reducing the di; ameter ofthe sheath after the unit has been assembled. Suchheating units can be bent easily into any desired shape and asshowh the unit 10 is bent in form of a hairpin.

1 The resistance" conductor 12 extends throughout a central or body section 11' only of the sheath, and-has its ends connected to terminalmembers 14 and 15 which are also PATENT OFFICE.

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The terminal mem extend thro the end portions 11" and 11 of the and project from the sheathjor connection with a suitable source of electric supply.

' For convenience in securing the terminals to theresistance conductor, the" ends of the terminals may be suitably threaded as indi} I cated by reference characters 16 and 17 and the turns of the resistance. conductor screwed on'these threaded portions. This forms a good mechanical as well as electrical connec ion. Y As shown, each end of the sheath is sealed to prevent the entrance of moisture. For exam le, each end of the sheath 11 may be thre ed at 18 for a short.'distance,"and a cup-like member or receptacle 19. having a threaded bore screwed on the threaded end 18. The member 19 is filled with a suitable sealin material 20 such as bakelite or an aspha tic compound. This sealing material is poured into the member 19, the unit being d-upright with the member 19 uppermost,

while heated to thinly liquefy 1t; The threaded end of the sheath extends into the interior of the cupv a slight distance only. Suitably connected to the ends of the terminal members 14 and-15, as by brazing, are copper connectors. 14 and 15'. These connectors extend into the cup members in close proximity to the ends of the sheath, a short gap being left between the inner end of each connector and the end of the sheath, which gap is filled with the sealing material 20. The inner ends of the connectors are beveled to allow the sealing material to flow readily into these sealing material fill e gaps thoro y and make a good firm connection with e insulating material 13, which is exposed at the ends of the unit, so that there will be no air gaps and otheroveak points in the formed by the sealin material between the terminal members and the ends of the sheath. The sealing material surrounds the connectorsto the level ,of the cup members which have their inner edgesbleveledllzlo provide ter cree age space tween t e connect dr and this sheath. provided with vrtions 14" and 15 gaps. It is essential that the- The connectors arewhich' are embedded in esealing material embedded the 118. For the purpose f-dissipating the heat nerated by the unit 10, the unit is clamped tween two metallic plates 21 and 22 extending lon itudinally thereof and forming together a eat dissipating member. The plates are formed with registering hairpinshaped grooves or recesses 23 and 24 respective y in which the heatin unit 10 is placed and secured by welding the plates together as near the heatingumt as ossible in such manner as to clamp the heating unit tightly and form a and thermal contact with the sheath 11. e welding of-the plates ma be carried out in any suitable manner, sue as by a line welding or spot welding process.

The clamping plates 21 and 22 extend throughout the entire length of the hairpinshaped unit 10, covering the central portion 11 and the two end portions 11 and 11. In order to interrupt the conduction of heat from the central portion 11 to the ends of the unit, slots are formed in the plates. As shown in Fig. l'an internal slot 25 is formed in the plates substantially at the junction of the resistance conductor and the terminal members. This slot -25 terminates at each end a short distance from the edge of the plates and serves to interrupt the continuity of the plates in a region adjacent the heating unit. .Two additional internal ' slots 26 and 27, similar to slot 25, are provided at suitable intervals between the slot25 and the ends of the heating unit. Between slots 25 and 26 are two aligned external slots 28 and 29 which are cut in toward each other from opposite edges of the plates.

These slots extend toward each other far enough to break away the metal of the plates around the heatingunit. Slots 30 and 31, imilar to slots 28 and 29, are provided between slots 26 and 27 Bymeans of the slots'25 t0 31 inclusive, it will be observed that the metal of the, plates is broken away adjacent the heatingfiinit- 1n such manner as to interrupt the condu tion of heat through the lates, but witnput materially impairing t e'heat dissipatmg'characteristics of the plates. It will also I be observed that any heat which is conducted 14 and 15. It is for this reason that the inner ends-of the connectors fare brought own near the bottomsof the cup toward theend of the heating unit must follow a zigzag course through the plates. This construction-plays an important part in maintaining the ends of the heating unit at a comparatively low temperature at which the sealing material 20 is not melted .or appreciablysoftened. The ends of the heating unit are also cooled by'conduction through the connectors down as near as possible to theends of the sheath. Furthermore-by terminating the 'ends of the sheath near the bottoms of the 1p members, the connectors are brought members so that lower temperatures are mamtained at of the heating unit.

heat will be conducted through the sheath 90 these points, and therefore any tendency for the sealing material to be melted at the bottoms of the cup members is ove come.

In order to provide for more effective dissipation of heat by the plates 21 and 22,

the plates are cut or slit from the slot 25 in a direction parallel with the two branches of the heating unit-to a point near the bend of the heating unit. As indi ated in Fig. i

2, this cut in the plate 21. is near the lower branch of the heating unit, while the cut in the plate 22 is near the uppenbranch 'of the heating unit. The two overlapping vanes 32 and 33 thus formed are bent apart to provide for the circulation of air between adjacent the central portion 11 of the heat- 86 ing unit substantially independently of the dissipation of heat by the ortions of the plates adjacent the end ortions 11" and 11 small amount of 11', the terminal members 14 and 15 and other parts toward the ends of the heater,

but this heat will be rapidly dissipated.

In .the modified form of my invention shown in Figs. 3 and 4.- the heating unit 35,

which is similar in construction to the heating unit 10, is shown as a straight length clamped between two metallic strips 36 and 37-. Since the ends of the heater are identical in construction, only one end will be described in detail. Slots 38 and 39 are cut in the plates from opposite edges toward the heating unit at the junction betweenthe resistanceronductor and the terminal. mernber 40. Similar slots 41 and 12 are pro- 106 however, a difierent form of connector,

shown. as a binding post 47, is secured, as by brazing, to the end of the terminal member 40 in place of the connector of Fi 1. This binding post. serves to conduct heat away-from the-eiiil oftheheating unit in the manner previously described in connec- }tion with Fig. 1. The binding post receives heat by conduction from the end of the heating unit, which heat is dissipated intothe surrounding air, and has an appreciable effect in cooling the end of the heating unit.

While I have described my invention ge embodied in concrete form and as operatingin a specific manner in accordance with the througha section of said sheath, a terminal for said resistance conductor extending through an end section of said sheath, and heat dissipating means extending lengthwise of said sheath in heat conducting rela- "tion therewith,the continuity of said heat is dissipated from said sections independ-' dissipating means being interrupted substantially at the junction of said resistance conductor and said terminal, whereby heat ently o eachother.

2. An electric heater comprising a metal lic sheath, a resistance conductor extending through a section of said sheath, a terminal for said resistance conductor extending through an end section of said sheath, and a heat dissipating member extending lengths wise of said sheath provided with a slot at the junction of said resistance conductor. and said terminal for interrupting the conduction of heat through said member to the said end section.

3, An' electric heater comprising a metal- --lic sheath, a resistance conductor in a body section of said sheath,- a' terminal for said resistance conductor extending through an end section'of saidsheath, powdered heat refractory insulating material, surrounding said resistance conductor and terminal, and a heat dissipating member extending length wise in heat conducting relation with said sheath, said member being provided with a slot adjacent the 'unction of said sect ons whereby heat is dissipated from said tody section substantially independently'of said end section.

4. 'An electric heater comprising a metallic sheath, a resistance conductor located in a central section of said sheath, terminals for said resistance conductor extending through the end sections of said sheath, powdered heat refracto insulating material compacted aroun said resistance conductor and terminals, and a pair of metallic plates forming heat dissipating means between which said sheath clamped, said plates being provided with slots at the junctions of said central section with said end sections whereby heat is dissipatedfrom said end sections independently of said central section.

5. An electric heater comprising a U- shaped heating unit, a pair of metallic plates forming heat dissipating means be-- tween which said unit is clamped, said plates being slit and shaped to allow circulation of air between the branches of said U-shaped unit and provided with a series of internal-and external slots for interrupting the conduction of heat to the ends of said unit.

6. An electric heater comprising a metal- 1 lie sheath, a resistance conductor secured in said sheath in electrically insulating relation therewith, a receptacle securedto the end of said sheath, a sealing material in said receptacle, and a'relatively heavy heat conducting member electrically connected to said resistance conductor extending into said sealing material in close proximity to said sheath.

7. An electric heater comprising a metallic sheath, a resistance conductor secured in said sheath, a terminal member for said resistance conductor projecting from said sheath, powdered heat refractory material in said sheath surrounding said resistance conductor and terminal, a relatively heavy heat dissipating connector secured to said terminal near the end of said sheath, a receptacle secured to the end of said sheath,

and a sealing material in said rece tacle

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