US1706014A - Resistance unit - Google Patents

Description

March 19, 1929. G. H. WHITTINGHAM RESISTANCE UNIT Filed June 22, 1926 Zlwuentoo Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

GEORGE E. WHITTINGHAM, OF BALTIMORE, MARYLAND, ASSIGNOR TO MONITOR CON TROLLER COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

RESISTANCE UNIT.

Application filed June 22, 1926. Serial No. 117,763.

This invention relates to resistance units composed of wire coils wound on bodies of refractory material, such as porcelain. Porcelain is desirable as a support for the windings because of its high heat-resisting and electrical insulating properties, but difficulty is experienced in satisfactorily securing terminals and other connectors to the porcelain because of its hard and brittle nature. The purpose of the present invention is to provide a resistance unit of this character in which connectors can be readily applied to the unit at any desired points, the connectors and insulator being formed so that the former will interlock with the latter, and the connectors are held in such interlocking engagement by the coil itself.

In carrying out the invention, a metal supporting bar is provided with a covering of refractory material having a plurality of toothed ribs for supporting the coils of resistance wire, the convolutions of which are wound between and spaced apart by the teeth of the ribs. The refractory material is formed with one or more channels extending longitudinally of the bar, and connectors are provided, each having an angular base adapted to fit between the side walls of the channel, whereby the connectors will be prevented from turning when their bases are within the channels. The bases of the connectors are formed so that they may be inserted into a channel between adjacent convolutions of'the coil, and each connector is provided with clamping means whereby it may be clamped directly to the coil. Thus, the coil serves to hold the connector in the channel with itsbase on the bottom wall thereof, and prevents movement of the connector longitudinally of the channel, and the interlocking engagement of the base or foot of the connector with the side walls of the channel prevents any twisting or turning movement of the connector.

In the accompanying drawing,

Fig. 1 is a side elevation, partly broken away, of a resistance unit made in accordance with my invention, several forms of connector being shown on the unit;

Fig. 2 is a section on the line 22 of Fig. 1;

Fig. 3 is a top plan view of the right hand end of the unit shown in Fig. 1;

Fig. 4 is a detail perspective view of one form of connector; and,

The covering 7) is preferably of porcelain,

because of its high insulating and heat-resisting properties, and it iscomposed of a series 0t relatively short sections 3, 4, and 5, fitting over the upper half of the bar, and a complementary series of similar sections 3", 4 and 5 fitting over the lower half of the bar. These sections are slotted longitudinally to fit over the bar, as clearly shown at 6 in Fig. 2. The covering has a plurality of toothed ribs 7, 8, 9, 10, 11 and 12, and the resistance coil 0 is Wound over these ribs and its convolutions are spaced apart by the teeth of the ribs. Between the ribs '1 and 8 is a channel 13, and between the ribs 10 and 11 is a similar channel 13. These channels have relatively fiat bottom walls and parallel sides and extend throughout the len th of the covering and are open at their en s.

In the channel 13 are shown terminals (l, of the type shown in detail in Fig. 4, each terminal formed from a sheet metal strip and composed of a body portion 14, constituting a binding post, and a part 14' bent over at right angles to the body portion to form a base or foot. The end of the base is turned downwardly, forming a flange 14 As shown, the bases of the terminals d are arranged within the channel 13, in Fig. 1, beneath the wire coil, and the bases of the terminals rest upon nuts 15, which fit within the channel. A clamping screw 16 extends through the base 14 and into the nut 15, and a washer 17, under the head of the clamping screw, clamps two convolutions of the coil between said washer and the foot 01" the binding post. Thus, the binding post is secured to the insulator by the coil and is prevented from turning by the side walls of the channel. The terminals (5 may be applied While the coil is being wound upon the insulator, and the ends of the coil are secured to the binding posts by screws 18.

The connector d is the same as the terminal connectors cl except that the nut is not shown associated with the base of the connector d. The form of the connector is such that the base or foot may be inserted into a channel through the space between two adjacent convolutions of the coil, and when the base of the connector is turned parallel with the channel, it may be secured to the coil by the clamping screw and the nut may or may not be used, as desired. If it is desired to place a nut under'the base of the connector 03, the nut may be inserted into the channel through one of its open ends and pushed along the channel until it is stopped by the flange on the connector base, and the clamping screw may then be inserted through the base and into the nut.

It will be evident that a connector such as d or d may be readily attached to the unit at any desired point. With this form of connector, the clamping screw passes between two adjacent convolutions of the coil and these two convolutions are directly connected electrically to the connector. This is an advantage where the current taken off through the connector is heavy, but it may be a disadvantage in some instances, especially where numerous connectors are applied to a coil because each connector short circuits one convolution of the coil. A form of connector is shown at e and e which engages only one convolution of the coil. This connector is made from a sheet metal strip and comprises the body portion 19, having one end turned over to form a foot or base 19 (Fig. 3) and a clamping member 20, made from a strip of metal of the same width as that of the post 19 and having a part 20 turned outwardly at right angles to the body portion to form a foot, and having a flange 20 at its upper end, adapted to bear against the post 19 and space the part 20 from said post. A clamping screw 21is provided for clamping the parts together. This connector may be secured to the coil at any point by inserting the base of each part separately into a channel at opposite sides of a convolution of the coil, and by then inserting the clamping screw through the parts and drawing them tightly together the connector will be secured to the convolution of the coil and will be held in place within the channel by said convolution.

In the several forms of connector shown,

the insulator, connectors may be applied at points close together in the length of the coil and at diiferent angles with respect to the body of the resistance unit.

For convenience in connecting the terminal of one unit to the opposite terminal of another unit, and for connecting the units in various ways, each section of insulating material is formed with semi-circular grooves 22 (Fig. 2) on its inner face, and when the sections are brought together on the supporting bar these grooves form circular openings through the insulator and the connecting wires may be extended through these openings.

What I claim is 1. A resistance unit comprising a metal supporting bar, an insulating covering of refractory material thereon, said covering comprising two series of opposed complementary sections, grooved to fit the bar, each sect-ion having toothed ribs and a channel between said ribs extending longitudinally of the bar, said channel having substantially parallel side walls and a relatively fiat bottom wall, a wire coil-wound over said ribs, and a connector comprising a post having a fiat metal foot insertable into said channel between convolutions of the coil, the foot of said post fitting within the channel and held against turning movement by the side walls thereof, and means for clamping said connector to the coil.

2. A resistance unit comprising a metal supporting bar, an insulating covering of refractory material thereon, said covering comprising two series of opposed complementary sections, grooved to fit the bar, each section having toothed ribs and a channel between said ribs extending longitudinally of the bar, said channel having substantially parallel side walls and a relatively flat bottom wall, a wire coil wound over said ribs, and a connector comprising, two metal strips arranged at opposite sides of a convolution of the coil and each having a foot insertable through the space between adjacent coils and fitting between the walls of a channel, and means for clamping said strips against said convolution of the coil.

3. A resistance unit comprising a metal supporting bar, an insulating covering of refraotory material thereon, said covering comprising a plurality of complementary sections arranged on opposite sides of the bar, said sections having opposed slots through which the bar extends and having opposed channels spaced from said slots and forming a longitudinal passageway through the covering at one side of the bar and a resistance coil on said covering.

In testimony whereof I hereunto afiix my signature.

GEORGE H. WHITTINGHAM.

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