US1763117A - House electric - Google Patents

Description

June 10, 1930. J. c. wooDsoN `1,763,117

ELECTRIC HEATING UNIT Filed Oct. 10, 1925 //IIIIIIIIIIIII v. v agg N V ENTOR V/'mes C MM50@ UM'IED "STATES Patented `lune 10, 1930 iwi'rlala'l"v OFFICE JAMES C. wooDSoN, OE EAST PITTSBURGH, PENNSYLVANIA, ASSI''LNoR To WESTING- HOUSE ELECTRIC 'sa MANUFACTURING COMPANY, A CORPORATION OE PENNSYL- 4 vANIA ELECTRIC HEATING UNIT Application sled october 1o, 1925. serialfNo. 61,683.

' My invention relates to electric heating units :and particularly to units in whichthe resistor member is entirely inclosed.

An object of my inventionis to provide a heating unit that Shall have its heating element inclosed and protectedfrom the air and which shall have high-thermal conductivity, thereby prolonging the lift of the heating element. 'Y y Another object' of my inventionl isto prol vide a heating unit that-may be easily manufactured, which shallbe durable and which shall have its heating element protected from en agement with foreign'A bodies or fluids.

n the accompanying drawings,

Figure 1 is a view, in longitudinal section, of a vheating unit embodying my invention,

Fig. 2 is a view in longitudinal section of a device embodying amodfied form of my invention, 2 1

Fig. 3 is a view incross' section of fthe device, illustrated in Fig.l2,-and Y Fig. 4 is a view in longitudinal sectionof a further modification Of the device embodyinglmy'invention. y eferring more -particularly lto`fF-ig.1,'fa heating unit 11 comprises a presbaped resistor element'12 disposed within pulverulent, electrically non-conducting material 13. The material 13 is surrounded vby a sheet 14 bent in the form of a cylinder or tube, of expan- Sively oXidiZable metal'which, in turn, is in-A closed within a cylinder of suitable metal 15,

. The ends of the resistor element 12 'are attached to terminals 16, only one of which is shown, which, in turn, is registered with a closure member 17 that is of suitable dimensions to fit snugly within thetubular mem ber 14.

The Dulverulent material 13 which is sub# stantially electrically non-conducting, may be, for example, magnesium oxide in powderedf'orm or alundum powder. v In constructing the heating unit'illustrated in 1, it is desirable to place the cylinder 14` ofexpansively oxidizable material, such as magnesium, within the cylinder 15 and then to locate the preshaped resistor'element 12 centrally within the enclosure-thus formed. The alundum powder or the magnesium Oxide powder may then be poured into the tube so as to completely -surround the resistor element 12 therebysupporting the same in its pre-shaped form. The oxide or alundum powder 13 Amay be compacted inplace, whereby good mechanical contactis made between the material 13 and the element 12.

The provisionof thevsleeve or'cylinder 14 insures-that the heat will be conducted away from the resistor element' 12 to the'surface of the tube 15 by reason of the eliicient thermally conductive relation between the associated parts when' the sleevehas` been expanded by oxidation in themann'er described below. i f

A small clearance is left between the inner diameter of thecylinder 15 and the outer diameter ofthe Acylinder 14, whereby'steamat a suitable-.pressure may l'be forced through to change the magnesium metal ofthe tube 14 to magnesium'o'xide. "It is characteristic of magnesiummeta'l, when thus 'treated with 'steam to'= changeto magnesium oxide and to expand substantially to'200'% of its original dimensions. Since the magnesium is located within-a' strong tube, as illustrated by the member 15 in Fig. 1, a very high radial pressure will-result between the granular material 13 and the outer Vtube 15, thereby effecting high thermal conductivity from the element 12 to the surface of the member 15. As the magnesium oxide is an electric insulator, the resistor 12 is effectively insulated from the tube 1 5.

The closure member 17, which is made of an electric-insulating material, is located within the magnesium tube 14 before the oXidation thereof takes lace. Since the material 14 expands on belngoxidized, the member 17 is held firmly in position in the heating unit 11l- In order that complete oxidation of the metal tube v14* may take place, I mayernploy the construction of Figs. 2 and 3 in which an oxidizing agent 18,`such as red lead, is in serted between the granular material 13 and a magnesium tube 19 having longitudinal slots or grooves 21 therein. On heating with steam the magnesium nearest the inner surface of the cylinder 15 will be in more direct Contact with the steam than the inner surface of the magnesium tube 19, but as the temperature of the magnesium is raised to a high degree as a result of the temperature 5 of the steam, oxygen will he liberated from the oxidizin agent 18 to oxidize the inner surface of t e magnesium tube 19, thereby causing a complete transformation of magnesiumvmetal to magnesium oxide.

lAsshown in Fig. 3 which shows the initial positionsof the va rious elements before treatment, the tube 19 has a plurality of projections 20 on its outer circumference that form longitudinal slots therein. These projections may be produced by drawinvf a tube of magnesium metal through a suitable die. The grooves 21 intervening between the projections'20 extend longitudinally of the heating unit so as to facilitate -the passage of steam therethrough. These .grooves need not necessarily extend longitudinally of the heating unit 11, as they may extend helically -along the outer surface of the member 14.

Although I have not illustrated all of the methods by which the magnesium metal 14 may be inserted within the tube l5, there are other methods by which the metal 14 may be disposed therein. 'F or example, magnesium metal in the form of narrow ribbon of suitable thickness niay be wound in the form of a helixv22 -as illustrated .in Fig. 4, and then inserted within the tube 15, whereby substantially the same result is obtained.

The Idevice embodying my invention pro- 5 ductor inclosed within two cylinders, the

innercylinder being an expansively oxidizable material. The conductor is centrally located in the opening withinthe cylinders and pulverulent or granular material is compacted therearound. On oxidizing the expansively oxidizable material, the granular material is compacted and the outer cylinder is firmly held in operative position and in good thermal conductive relation with the conductor by reason of the expansion of the oxidizable material.

The device embodying my invention may be manufactured in various sizes and shapes, as for. instance in substantially circular tubes having an outer diameter of about 3/8 inches and of any desired length. Larger sizes may employ outer cylindrical members of other than circular shape in cross-section such as rectangular or oval.

Various modifications of my invention may be .made without departing from the spirit and the scope thereof. I desire, therefore, that only such limitations shall be placed thereon as shall be imposed by the prior `art and the appended claims.

I claim as my invention:

1. In an electric-heating unit, in combination, an electric-resistance conductor having 65 terminals at the ends thereof, granular elecvides a heating unit which comprises a con,

trically non-conducting material disposed therearound, a casing inclosing said granular material, and electric-insulating material disposed between said casing and the granular material comprising expansively oxidized magnesium oxidefor tightly compacting the granular material, for maintaining the terminals firmly in operative relation within the casing and for effecting high thermally-.conductive relation between 'said .electric con-v ductor and said casing.

2. In an electric-heating device, in combination,"a helically-wound electric resistor .having terminals at. the ends thereof, pulverulent electrically non-conducting material disposed -therearound to, firmly support said conductor and to be in thermal contact therewith, a metal casing inclosing said pulverulent material, and electric-insulating'material disposed between said-:casing and-the pulverulent material com risingexpansively oxidized-magnesium =oXi e 'for tightlyxcomn pacting the pulverulent material within the casing, for maintaining the terminals firmly in operative relation within the c linder and for effecting high thermal conduction vbeween said electric conductorv .and said cylin 3. The method of making a Atubularzheati ing unit, which .comprises locating asubstantially-tubular memberiof metallic magnesium within a metal casing, locatinga Aresistor element ywithin said :tubular member, filling the space with pulverulent electricinsulating material, and then subjecting the assembled elements lto. the action of steam lto expansively oxidize the magnesium into magnesium 0X- ide to .tightlycompact the lling within the outer casing.

'4. The method of making a .tubular heating unit which comprises locating -an exten nally longitudinally grooved cylinder of metallic magnesium in .an outer metal casing, locating a .resistor member in. theoylinder, filling the vspace within the cylinderwith a pulverulent electric-insulating material and subjecting said elements to the action of steam to expansivelyoxidize the magnesium into magnesium oxide-to tightly compact the filling in the casing.

5. The method of making a tubular heating unit, which comprises locating a cylinn drical member of metallic magnesium in an outer metal casing, locating a preformed resistor member having a terminal member connected theretoin said cylindrical member, locating a bushing-of electric-insulating material within the cylindrical member and around the terminal member,lling the cylindrical member with a pulverulent -electric-insulating material, and then subject ing the assembled elements to the action of steam to compact the pulverulent .material and tightly -hold the bushing in the metal casing.

6. The method of making a tubular heating unit, which comprises locating a substantially tubular member of metallic magnesium Within a substantially co-eXtensive metal casing, locating a preformed resistor member centrally of said tubular member of magnesium, placing a filling of pulverulent electric-insulating material in the tubular member, compacting said filling, and then subjecting the assembled elements to the action of steam to expansively oxidize the magnesium into magnesium oxide to tightly compact the filling Within the casing.

In testimony whereof, I have hereunto subscribed my name this 28th day of September,

JAMES C. WOODSON.

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