US2662958A

US2662958A - Electrical resistance unit

Info

Publication number: US2662958A
Authority: US
Priority date: 1950-02-20
Filing date: 1951-02-20
Publication date: 1953-12-15
Anticipated expiration: 1970-12-15
Also published as: CH291024A; FR1013067A

Description

'Dec. -15, 1953 T. N. FLIGHT ETAL 2,662,958

ELECTRICAL RESISTANCE UNIT Filed Feb. 20, 1951 2 Sheets-Sheet 1 Q 1) 3''(L j 7 2 s i 4 ,i I p 6 FIG. 2. 7*

Dec. 15, 1953 T, FLI ET AL 2,662,958

ELECTRICAL RESISTANCE UNIT Filed Feb. 20, 1951 2 Sheets-Sheet 2 23 [jl ll Tl"Tl ll 'll j 23 I I I] I U l] U Fl L T fi Patented Dec. 15, 1953 ELECTRICAL RESISTANCE UNIT Theodore Nicholas Flight, Farnham Common, and William Harry Wilson, Camberley, England, assignors to The Rheostatic Company Limited, Slough, England, a British company Application February 20, 1951, Serial No. 211,866

Claims priority, application France February 20, 1950 Claims. (Cl. 201-74) This invention relates to electrical resistances formed from strip material.

An object of this invention is to provide an electrical. resistance unit with a strip resistance form which will enable variations of resistance value and current carrying capacity to be made economically in various steps of a resi tance and to provide a maximum number of adjustment tappings.

Another object is to form a strip by simple bending operations into convenient, easily handle,- elements capable of being welded to" gether to form a continuous resistance grid.

Another object is to provide a strip resistance bank as a compact easily replaceable unit.

The improved resistance unit of the invention comprises a plurality of resistance elements of strip material bent to e form, each element having a support strip welded thereto and each element being welded to its neighbour to form a continuous electrical path and interlocking ceramic bobbins on a pair of metal tie rods to support the resistance elements, with flanges on the ceramic bobbins projecting between the convolutions of the elements to give support against vibration.

The invention is illustrated in the accompanying drawings in which Figures 1 and 2 show one strip element, Figure 3 is the elevation of an assembly of 12 such elements into a bank, Figure 4 is a sectional plan of a part of one bank (enlarged), and Figure 5 is an elevation of one bank in the resistance frame of Figure 6 cut across line AA. Figure 8 shows three such banks mounted into a complete resistance frame.

Referring to Figure 1, a strip of resistance material l is bent twice at 2 and 3 so as to leave the ends t and 5 pointing in opposite directions. One end i is left straight while end 5 is cranked to the same dimension as the Width of

bends

2 and 3. The end 5 is then in line with the straight end 01' the commencement to the next element, Each end of the strip element is pierced by a tap ping or terminal hole (3. Strip l is attached to the resistance strip by spot welding and forms in known manner the support for the element.

Referring to Figs. 3 and 4 two tie rods 8, 9 pass through the centre of cylindrical insulators it, i I, on each of which flanges 12 are formed. Each insulator interlocks with the next on the rod by projecting pieces :13 locating in recesses i l in the opposite end of the next insulator. This is shown in section in Figure 4 which also shows the bank arrangement of two groups of elements one on each side or" the pair of tie rods.

This sectioned view also illustrates the fixing means for each element by strip '1 clamped between adjacent insulators and supported out of contact with tie rod 6 by the projecting portion i3 of the insulator which passes through the hole l5 in the support strip i. Terminals or tapping points I? occur at each element junction, each element being spot welded to the next adjacent element at this point thus making each grid a continuous unit from end to end.

The flanges I2 formed on insulator it project slightly into the bends of the strip element as shown at It and give support against vibration to the individual turns of the element at these points.

For mounting into a complete resistance frame, Figs. 5 and 6, the two tie rods 3, s are joined by a strip [9 which is cranked at one end as shown. In the cranked end is a fixing hole which aligns with the corresponding hole in the frame member 20. This frame has a turned over flange 2i formed with recesses 22 shaped to pass the fixing nut on the tie rod end and to give support to the strip I9 as shown.

Any one bank can thus be removed from a complete resistance frame by first disconnecting any electrical connection, removing the fixing bolts 23 and dropping the complete bank out of the supporting frame 28.

We claim:

1. An electrical resistance unit comprising a series of interconnected resistance elements forming a resistance grid, each element formed from a strip of resistance material bent natwise so as to form an 8-shaped strip viewed edgewise of this strip, the adjacent ends of adjacent S- shaped resistance elements being welded together to provide a continuous electrical path, a support strip Welded to each element and projecting from the plane of the grid, a metal ti rod extending through the support strips, inte cking cylindri-- cal insulators mounted on the tie-rod for insulating the rod from the support strips associated therewith, and spaced flanges on the insulators between which the convolutions of the resistance elements extend for supporting said elements against vibration, said tie-rod extending parallel to the resistance grid in a direction opposite to that of the convolutions of the elements.

2. An electrical resistance unit comprising a series of interconnected resistance elements forming a resistance grid, each element formed from a strip of resistance material bent fiatwise so as to form an S-shaped strip viewed edgewise of this strip, each s-shaped element being reversed with respect to adjacent S-shaped elements so that adjacent ends of adjacent elements are on the same side of the grid, said ends being Welded together to provide a continuous electrical path, two rows of support strips on one side of the unit projecting from the plane of the grid, one support strip being welded to each element, a metal tie-rod extending through each row of support strips, and interlocking cylindrical insulators mounted on said rods for insulating the rods from the support strips associated therewith, said tie-rods extending parallel to each other and to the resistance grid in a direction opposite to that of the convolutions of the elements.

3. An electrical resistance unit as claimed in claim 2, in which the ends of each S sha-pad element extend beyond the bends of the element, and in which the-adjacent welded ends of adjacent elements are formed to provide electrical taps.

4. An electrical resistance unit comprising a series of interconnected resistance elements iorming a resistance grid, each element comprising a flattened S-shaped member formed irom a strip of resistance material bent fiatwise and having two bends, the adjacent ends 10:" adjacent s-shaped resistance elements being welded together to provide a continuous electrical path, a support strip welded't-o each'elementand projecting from the plane of the grid, a metal tie-rod extending through at least-some of said supper strips, and a-series of interlocking cylindrical insulators mounted on the rod :for insulating the rod from thesupport strips associated therewith, each insulator including an axial recess on one side and an axial projection on its other side fitting in the recess of the adjacent insulator, each support strip having an opening through which an insulator projection extends, said tierod extending parallel to the resistance grid in a direction opposite to that of the convolutions of the elements.

5. An electrical resistance unit comprising a series of interconnected resistance elements forming a resistance grid, each element formed from a strip of resistance material bent flatwise so as to form an S-shaped strip viewed edgewise of this strip, each S-shaped element being reversed with respect to adjacent $-shaped elements so that adjacent ends of adjacent elements are on the same side of the grid, said ends being welded together to provide a continuous electrical path, two rows of support strips on one side of the unit projecting from the plane of the grid, one support strip being Welded to each element, a metal tierod extending through each row of support strips, interlocking cylindrical insulators mounted on said rods for insulating the rods from the support strips associated therewith, said tie-rods extending parallel to each other and to the resistance grid in a direction opposite to that of the convolutions of the elements, a main frame for supporting the resistance unit, a stripon the main frame, and a flat strip extending from the main frame and connected to the two tie-rods, said fiat strip also engaging with said strip on the main frame.

THEODORE NICHOLAS FLIGHT. WILLIAM HARRY WILSON.

References Gited in the file of this patent UNITED STATES PATENTS Number Name Date 2,277,912 Johnson et a1 Mar. 31, 1942 2,378,056 Wright 7. June 12, 1945 FOREIGN PATENTS Number Country Date 153,908 GreatBritain Nov. 10, 1921