US2868937A - Grid-type resistance units - Google Patents

Description

Jan. 13, 1959 A. P. CHARBONNEAU GRID-TYPE RESISTANCE UNITS Original Filed May 9, 1955 3m MEG/MW United States Patent GRID-TYPE RESISTANCE UNITS Allan P. Charbonneau, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Continuation of abandoned application Serial No. 506,802, May 9, 1955. This application February 12, 1958, Serial No. 714,927

2 Claims. (Cl. 20169) This invention relates to improvements in connector terminal means for punched sheet metal grid-type resistance units.

This application is a continuation of my application, Serial No. 506,802, filed May 9, 1955, now abandoned.

A grid-type resistor unit comprises a plurality of punched sheet metal resistor grids and insulating washers which are stacked on parallel support rods so that a resistance path is formed through the grids in series. It is common in such units to insert connector plates in the stack at various points in juxtaposition to the grids to provide end terminals and taps for the resistor. Lead wires are connected to these connected terminals by nut and bolt sets. In prior art resistor units the grids are often buckled when the nuts are turned down tightly. This problem is especially troublesome when the grids are formed of thin material and when they are welded together to the connector terminals. It is an object of this invention to provide a resistor unit and terminal connector structure which overcomes this problem.

This object and certain of the other objects and advantages of the invention which will hereinafter appear, are realized by the provision of an elongated terminal member and means by which it can be stacked on the parallel support rods so that it is connected to the resistor grids at one end and is insulated therefrom at the other end.

One embodiment of the invention is shown in the accompanying drawing, it being understood that certain modifications are possible to be made in the embodiment illustrated and that other embodiments are possible without departing from the spirit of the invention or the scope of the appended claims.

In the drawing, Figure 1 is a fragmentary top plan view of a resistance unit in which the invention is embodied.

Fig. 2 is a view in front elevation of the unit of Fig. 1, and

Fig. 3 is a view in front elevation of a connector terminal embodying the invention.

The assembled unit of Figs. 1 and 2, comprises a pair of parallel spaced support rods and 12 having insulating coverings 14 and 16, respectively. Spacers 18, insulating washers 2t), resistor grids 22 and terminal connectors 24 are stacked upon the support rods 10 and 12; so that the intermediate or main body portions of adjacent grids extend upwardly and downwardly, respectively, with respect to a median line therebetween, as shown. For the sake of clarity only a few of the washers, spacers, etc., are shown numbered.

The stacked elements are compressed between suitable fastening members at the ends of the rods 10 and 12 so that the grids 22 are arranged in zigzag fashion.

The connector elements 24, as best illustrated in Figs. 1 and 3, are formed from flat sheet metal and consist of a pairof end lugs 26 and 28 having perforations or cutouts 30 and 32, respectively, for accommodation of the element on both of rods 10 and 12. Lugs 26 and 28 are connected by a strap portion 34 which extends between them. The connector piece or wiring terminal portion 36 extends laterally fromthat side of lug 28 which is opposite to strap 34.

A square perforation 38 (Fig. 3) in the piece 36 is adapted to accommodate a square shoulder under the head of a bolt 40 so that the bolt 40 will not turn when nut 41 is tightened down to eifect clamping by member 42 of a circuit wire lead or leads brought to the terminal portion 36. When the nut 41 is turned, any tendency for the connnector member 24 to rotate on rod 12 is opposed and prevented by strap 34 and the connection to rod it). Since member 24 cannot rotate, the portion 28 thereof is likewise restrained against rotation, thus preventing rotation and buckling of the resistor grid 22 to an end portion of which it is connected, as by spot-welding.

Strap 34 could be fully as wide as lugs 26 and 28, but the narrower width shown in the drawing will usually provide adequate strength. The upper and lower edges of the connector members 24 have complementary contours to permit their being punched from sheet stock with a minimum of waste material.

Lugs 26 and 28 are slida ble onto the tubular insulators or coverings 14 and 16 on the rods 10 and 12, respectively. Lug 26 (Fig. 1) is insulated from the left-hand end of the lowermost grid 22 by an insulating washer 20. The other lug 28 is arranged in juxtaposition to the righthand end of the lowermost grid 22 and may be welded to it to decrease any contact resistance that might otherwise exist between them. When used as a tap, the connector terminal 24 has its lug end 28 arranged in juxtaposition to and between two resistor grids 22, as shown at the upper right-hand side of Fig. 1.

The perforation 30 in each connector terminal 24 is enlarged to provide clearance between lug 26 and the insulated rod 10 whereby to prevent buckling of the con nector terminals. Buckling might otherwise occur if the connector terminals and the grids were expanded in different amounts as an incident to resistor heating.

Another advantage of the invention is that it is adapted for use with various types of zigzag grid constructions.

Thus, it may be employed with formed grids with offset lugs arranged with the body portions of the grids lying parallel; with the grid construction illustrated in the drawing, and others.

I claim:

1. Connector terminal means for a grid-type resistor unit comprising a multiplicity of like, one-piece, punched sheet metal resistor grids and a multiplicity of insulating spacers stacked in predetermined relationship upon parallel support rods so that the adjacent grids are arranged in zigzag fashion in electrically conductive relationship with each other to form a series conducting path, a plurality of wiring terminal connectors each comprising an elongated, one-piece, flat, punched sheet metal member including an integral, intermediate strap portion electrically connected directly with one or more of said grid lugs at one end only of said sheet metal member, a wiring terminal lug portion formed integrally with and extending laterally from one end of each of said metal members in a direction away from the strap portion thereof, said lugs being formed to permit accommodation of the wiring terminal connector member upon the support rods with the strap portion extending therebetween, said one of said lugs being held in electrically conducting relationship to a resistor grid, and the other lug of said pair being supported against rotation about the first of said rods and in insulated relationship to all of the resistor grids.

2. A resistor unit of the character defined by claim 1, wherein said lugs are respectively provided with openings therethrough whereby the same may be accommodated jointly upon said support rods, and wherein the opening a 4 in the lug remote from said Wiring terminal portion is References Cited in the file of this patent elongated in a direction to permit relative movement in UNITED STATES PATENTS one direction only between the same and its associated 1 501 638 W r t l Jun/15 1924 t d a 'de t t th 1 and/o1 e e a PP To as n Incl I1 0 Erma expanslon 2,533,673 Lassfire Dec- 12,1950

contractlon of the revslstor grlds- 2,639,360 Widdow M ay 19, 1953

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