US2736785A - Electric resistor structure - Google Patents

Description

ELECTRIC RESISTOR STRUCTURE 2 Sheets-Sheet 1 Filed Nov. 12, 1955 ATTORNEY Feb. 28, 1956 R. E. DU BOlS ELECTRIC RESISTOR STRUCTURE 2 Sheets-Sheet 2 INVENTOR ATTORNEY Filed Nov. 12, 1953 United States Patent 2,736,785 ELECTRIC RESISTOR STRUCTURE Robert E. Du Bois, Hammond, Ind. Application November 12, 1953, Serial No. 391,568 4 Claims. (Cl. 201--69) This invention relates to an improved resistor element and to the assembly thereof in a resistor bank struc- 'ture.

The primary object of this invention is to provide a resistor element which may be formed from a sheet of resistor material with substantially no loss of resistor material in the form of scrap.

An important object of this invention is to provide a Zig-zag grid resistor element in which the dissipated heat from the resistor will be constant over the whole element due to the structural formation of the element.

A further object of this invention is to provide a resistor grid element which, when mounted between two fixed points, will expand and contract without warping or buckling.

Another important object of this invention is to provide a zig-zag resistor grid which is adaptable to center axis mounting at either end of the grid.

A still further object of this invention is to provide an improved zig-zag resistor grid element having complementary continuous sections extending on either side of the terminal point to a terminal point axis of the grid.

A more specific object of this invention is to provide an improved Zig-zag resistor grid having identical continuous sections disposed angularly with respect to and extending equidistantly from either side of a center line between the two terminal mounting holes at either end of the grid.

A further object of this invention is to provide an improved resistor grid of such construction that it may be compactly arranged in a multiple or stacked type grid structure assembly.

A still further object of this invention is to provide an improved resistor structure composed of a plurality of identically formed and oppositely disposed grids within the structure in order that the overall dimensions of the resistor structure will be substantially at a minimum for the amount of resistance required in a given application.

Another object is to provide an improved resistor grid structure which is well adapted to forced air cooling due to the arrangement and construction of the grid elements therein.

Another object of this invention is to provide an improved die construction for stamping resistors from sheet resistor material with substantially no loss of resistor material.

A still further object of this invention is to provide an improved adjustable die construction which is operative to stamp resistor grids from sheet material without scrap and which may be readily adapted to stamp out resistor grids of varying dimensions.

With the foregoing and other objects in view, the invention resides in the following specification and appended claims, certain embodiments and details of construction of which are shown in the accompanying drawings, in which:

Figure 1 is a partial view in side elevation of the as sembler resistor structure;

Figure 2 is a plan view of a single grid element of the resistor structure, the dotted line and the dot-dashed line indicating such grid elements of varying area as may readily be produced;

Figure 3 is a View taken along the lines 33 of Figure 1;

Figure 4 is a plan view of a plurality of grid elements illustrating the stacking feature of the invention; and

Figure 5 is a partially sectioned perspective view of the novel die for forming the resistor grid elements of the invention.

Referring more particularly to Figure 1, end frame elements 1 and 2, which are preferably of channeled metal construction are connected firmly together by through bolts 3 and 4. Insulating washers .5 are provided between each locking nut 6 of the bolts and the frame elements 1 and 2. Surrounding bolts 3 and 4 are sleeves 7 and 8 respectively, which are formed of any suitable insulating material.

Mounted about the insulating sleeves 7 and 3 are a plurality of spacing washers 9 made of electrically conductive material. Between the end washer at either end of the structure and the corresponding end frame element are insulating washers 10. Resistor grid elements 11, which will be later described in detail, are carried by the bolts 3 and 4 with the sleeves 7 and '8 insulating the bolts from the grid. Between adjacent grids 11 are the conducting spacing washers 9. Obviously in order to make a continuous circuit through the grids of the structure it is necessary to provide alternately placed insulating washers 12. Terminals 13 may be provided at any point along the grid structure, but as shown in Fig. 1 are located at each end of the structure. These terminals may be clamped between a conducting washer and a grid or may be secured to the grid by any suitable means such as welding.

Following the circuitry of the structure 1 from the left side of Figure 1, it will be seen that current entering through terminal 13 passes through grid 14 and washer 15 to grid 16, through washer 18 on the far side of insulating washer 17 through grid 10, past insulating washer 20, and so on until the terminal 13 at the opposite end of the structure is reached.

The grid elements 11 are best illustrated in Figures 2 and 4. It is highly desirable to provide a zigzag grid element in which the overhang or lateral dimension from either side of the center line through the element is equal. It is also highly desirable, for obvious reasons, that as little scrap as possible result in the manufacture of grid elements. For these and other reasons, the elements 11 are stamped out of the resistor sheet material with identical angular sections as will be obvious from Figure 4. In describing the sections so formed as angles, it must be assumed that the base of each of the angles is formed by a center line through the grid terminals about to be described.

Each element 11 is provided with terminal portions 21, each of the terminals being suitably perforated at 22 to accommodate the bolts 3 and 4 of the structure illustrated in Figures 1 and 3. The transverse dimension of the grid 11 at the terminal portion 21 is substantially less than the lateral or transverse dimension of the grid taken on a line through overhung angular sections of the grid. Referring particularly to Figure 2, the solid line depicts a grid element of a given resistance characteristic. If an element of less resistant material is desired, the dotted line 23 will represent the lower extremity of such a grid and mounting hole 22' will be located slightly above hole 22. If a grid of greater material is desired, then the dash-dot line 24 will represent the lower extremity of such a grid and mounting hole 22" will be located slightly below hole 22. The purpose in properly centering the mounting hole in the terminal elements 21 is so that the pointed extremities 25 of the grids will always be equidistant on either side of a center line drawn through the center of the mounting holes 22. In assembling then, the grids will appear as in Figure 3, with the extremities 25 of elements 11 positioned equidistantly from a line drawn between the centers of the mounting bolts 3 and 4. It is desirable to have adjacent grids in such a structure oppositely disposed as shown so that the extremities 25 of adjacent grids 11 are in staggered relationship. In the prior art it has been necessary to have left and right hand elements. The grids of the present invention may be alternately arranged in staggered relationship without any regard to right or left hand mounting, due to the fact that all elements are identically constructed.

In considering the construction or formation of the grid, it is well to note that the angle of the apex 26 of one grid perfectly coincides with the included angle 27 of the grid below it, as illustrated in Figure 4. This is an extremely desirable feature in the manufacture of compact-type resistors.

Referring to Figure a pair of dies 28 and 29 are carried by the moving member 30 and the stationary member 31 of a stamping machine, not illustrated by the drawings. The grids 11 are formed by feeding the sheet resistor material in the direction of the arrow against the adjustable stops 32 and 33, and then reciprocating the upper die member 30 in the well known manner. The novelty of the die, however, lies in the fact that the angular sections 34 thereof cooperate to stamp or shear off successive grids without loss of material. Thus, by merely adjusting the stops 32, grids such as represented by the fully dotted and dot-dash lines in Figure 2, may readily be produced with no resulting scrap. The terminal holes 22 are punched out in a separate operation and give rise to the only scrap in the manufacture of the grids.

When the resistor structure of Figures 1 and 3 is utilized with a forced draft cooling means to dissipate the generated heat, the air will flow across the resistor grids in the plane of the grid elements as shown by the arrows in Figures 2 and 3. Due to the fact that the length of any section through a grid element is the same when taken normally with respect to the longitudinal axis of the resistor, the air path at any point crossing the face of a grid will be of the same length as at any other point. This is important in providing greater uniformity in the cooling of such resistors.

In summary, the improvements in the resistor construction are primarily brought out when assembled in the type of structure illustrated in Figure 3. The very design of the grids permits expansion and contraction without buckling. Also the design permits a so-called flip-over grid as distinguished from the former left and 4 right hand types for alternately assembly in a resistor structure.

Further, the structure of the grid elements provides for equal cooling throughout a structure such as illustrated in Figure 3, by having equal length air paths through the structure relative to the grid surfaces at any location in the resistor structure. Also the overall compactness of a resistor structure of a given capacity is facilitated by the equal overhang of the extremities 25 of the elements 11. Also, the die construction of Figure 5 is provided to simplify the manufacture as well as to eliminate the heretofore wasted resistor material in the form of scrap.

I claim:

1. A resistor grid comprising a single strip of resistor material and a terminal portion at either end of said strip, said strip, between the terminals, being formed into identical angular sections with pointed extremities extending alternately to either side of a center line through the terminal portions of the grids the transverse dimension of the grid through the angular sections being substantially greater than the transverse dimension of the grid at said terminal portions.

2. A resistor structure comprising a plurality of grids, and mounting means for said grids, each of said grids including a pair of terminals connected to the mounting means and being formed between the terminals into coextensive, identical sections lying alternately of a center line through the grid terminal portions of the grid so that when said grids are mounted on the mounting means the adjacent grids may be oppositely disposed with the identical sections or" each grid being staggered relative to each adjacent oppositely disposed grid.

3. A resistor structure comprising a plurality of grids, and mounting means for said grids, each of said grids including a pair of terminals connected to the mounting means and being formed, between the terminals, into coextensive identical angular sections with pointed extremities lying alternately of a center line through the grid terminal portions of the grid so that when the grids are mounted on the mounting means the adjacent grids may be oppositely disposed with the pointed extremities of adjacent grids being in staggered relationship.

4. A resistor grid structure comprising a mounting means and a plurality of identical zig-zag grids carried by and connected to said mounting means, along the longitudinal axes through the zig-zag position of the grids, adjacent grids being oppositely disposed on said mounting means with the Zigzag portions of adjacent sections being in staggered relationship.

References Cited in the file of this patent UNITED STATES PATENTS 443,353 Bristol Dec. 23, 1890 846,153 Souther Mar. 5, 1907 1,860,493 Campbell May 31, 1932 2,421,731 Williams June 3, 1947 2,518,941 Satchwell et al Aug. 15, 1950

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