US2457399A - Resistance grid and method of assembling - Google Patents

Description

Dec. 28, 1948.

c. H. ROCKWOOD ETAL 2,457,399 RESISTANCE GRID AND METHOD OF ASSEMBLING v Filed April 21, 1944 Patented Dec. 28, 1948 RESISTANCE GRID AND METHOD OF ASSEMBLING Charles H. Rockwood, West Allis, and Daniel J. Sikorra, Milwaukee, Wis., assignors t Allis Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application April 21, 1944, Serial No. 532,090

9 Claims.

This invention relates in general to resistance grid assemblies and to the resistance grid sections forming a part thereof and to the method of assembling such grid sections to form an assembly.

rior art resistance grid assemblies have utilized a plurality of grid sections supported in spaced relation on two insulated studs passing through supporting portions of each section. These grid sections are usually thin stampings or castings of a modified wave shape and the sections are identical in order to reduce manufacturing expense. As the grid sections are identical, each heat dissipatingportion is directly opposite a similar-heat dissipation portion of the adjacent grids, and the heat dissipating capacity is limited by the spacing between grid sections. Attempts have been made to support grid sections so that the heat dissipating portions were not opposite similar portions of adjacent grids, but this has been done only at the expense of additional supporting studs or at the expense of using diiierently shaped sections in the same assembly, or at the expense of increased space for the assembly.

It is therefore an object of the present invention to provide a new and improved resistance grid and a new and improved method of assembling the same to provide a new and improved grid assembly avoiding the above disadvantages.

It is also an object of the present invention to provide a resistance grid assembly of similar resistance grid sections utilizing only two supporting members and in which the heat dissipating portions of alternate grid sections are adjacent but are not directly opposite each other.

It is also an object of the present invention to provide a grid assembly of similar grid sections in which the heat dissipating capacity is improved Without increasing the number of supporting members and without increasing the cross sectional area necessary for the assembly.

It is also an object of the present invention to provide a resistance grid with a heat dissipating portion and with two supporting portions one of which is offset from the longitudinal center line of the heat dissipating portion a distance greater than the distance from such center line to the other supporting portion.

It is also an object of the present invention to provide a new method for assembling identical grid sections without increasing the number of supporting members nor the cross-sectional area of the assembly but providin for improved heat dissipation.

Objects and advantages other than those above set forth will be apparent from the following de- 2 scription when read in connection with the ac-. companying drawing, in which:

Fig. l is a top View of a resistance grid assembly embodying the present invention; and

Fig. 2 is a sectional view taken on the line II--II of Fig. 1. i

The grid assembly shown in the drawing is made up of a plurality of substantially plane grid sections 4 having a central heat dissipating portion of irregular shape and ing portions 5 and 6. The grid sections are preferably identical stampings of sheet metal. As shown more clearly in Fig. 2, the distance a from the supporting portion 5 to the center line through the heat dissipating portion is greater than the distance b from the supporting'portion 6 to such center line. In other words, the grid section is unsymmetrical about a line in the plane of the grid section and midway between the supporting studs 1. This unsymmetrical arrangement or the oiisetting of one supporting portion permits the reversal of alternate identical sections 4, whereby the heat dissipating portions of alternate sections are not directly opposite each other, but are displaced laterally relative to heat dissipating portions of adjacent grid sections.

The offsetting of alternate sections permits increased current capacity for a given spacing of the grid sections 4 or permits a closer spacing of the sections 4 for a given current capacity, thereby permitting a shorter overall length of an assembly. It has been found on comparable tests between an assembly formed as shown in Figs. 1 and 2 and an assembly formed without reversing alternate grids that the heat dissipating capacity is increased in the new and improved structure by as much as 30%. I

The grids 4 are assembled on two steel studs 1 covered with tubes 9 of suitable insulatin material such as mica. Steel spacers l2 and insulating spacers [3 space the grids 1 between the end plates 8 and the assembly elements are held in assembled relation by nuts 10 on threaded end portions of the studs 1. Terminal conductors II are provided as shown in Fig. l which illustrates the assembly when the grids 4 are all connected in series. By varying the relation of the conductive and insulating spacers, the grids 4 may be connected in varying parallel or series parallel arrangements.

The distance by which the supporting portion 5 is offset is determined so that the greatest surface of the heat dissipatin portion of one grid 4 is not directly opposite to the heat dissipating portion of the adjacent grids.

provided with two support Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A resistance grid comprising a heat dissipating portion having an irregular shape in a given plane, a first supporting portion positioned in said plane a predetermined lateral distance in one direction from the longitudinal center line through said heat dissipating portion, and a second supporting portion position in said plane a lateral dstance greater than said predetermined distance in the opposite direction from said center line through said heat dissipating portion.

2. A new article of manufacture comprising a conductor provided with a portion formed in a wave shape, and extensions on the ends of said conductor provided with apertures therein, the distances between said apertures and the center of said wave shaped portion being unequal.

3. A resistance grid assembly comprising a plurality of similar grid sections of Wave shape, each of said grid sections comprising a central heat dissipating portion and further comprising supporting portions positioned on either side oi said central portion and provided with apertures therein, supporting members extending through said apertures, and means comprising the positioning of said apertures difierent distances from the center of said central portion, for oifsetting said central portions of adjacent grid sections.

4. In a resistance grid assembly of similar grid. sections each provided with a plurality of supporting portions, one of which is ofiset a distance greater than another from the center of said section, the method of assembling said sections adjacent one another comprising the reversal of alternate sections whereby the offset supporting portions of adjacent sections are on opposite sides of said assembly.

5. In a resistance grid assembly of similar grid sections each provided with a heat dissipating portion and a plurality of supporting portions for supporting said grid sections in spaced relation on only two supporting members, the method of assembling said sections adjacent one another in a space having a cross-sectional area substantially equaling the area of one of said sections comprising the reversal of alternate sections whereby said heat dissipating portions of adjacent sections are offset relative to each other.

6. A new article of manufacture comprising a conductor provided with a heat dissipating portion formed in an irregular shape, and extensions on the ends of said conductor provided with apertures therein, the distances between said apertures and the center of said heat dissipating portion being unequal.

'7. A new article of manufacture comprising a conductor provided with a heat dissipating portion formed in an irregular shape, and extensions on the ends of said conductor provided with supporting portions thereon, the distance between said supporting portions and the center of said heat dissipating portion being unequal.

8. An electric resistance grid assembly comprising a pair of parallel supporting members disposed at equal distances from a plane of symmetry therefor and a plurality of electrical resistance grid sections, each said section comprising a first terminal portion mounted on one of said supporting members and a second terminal portion mounted on the other of said supporting members, said portions being connected by a conductor having a dissymmetrical configuration with respect to said plane, adjacent said sections being reversed relative to said supporting members to bring said conductors of adjacent said sections out of alignment in a direction parallel to said supporting members.

9. An electric resistance grid assembly comprising a pair of parallel supporting members disposed at equal distances from a plane of symmetry therefor and a plurality of identical electrical resistance grid sections, each of said sections hav- .ing a predetermined length in a direction joining said supporting members and having a. predetermined width, each said section comprising a first terminal portion mounted on one of said supporting members and a second terminal portion mounted on the other of said supporting members, said terminal portions being connected by a conductor having a dissymmetrical configuration with respect to said plane, each of said sections being reversed relative to the next adjacent section to bring said conductors of adjacent said sections out of alignment in a direction parallel to said supports, whereby said grid assembly has the same width as each of said sections.

CHARLES H. ROCKWOOD. DANIEL J. SIKORRA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,455,903 Clark May 22, 1923 1,860,493 Campbell May 31, 1932 1,861,434 Campbell June 7, 1932 2,128,222 Du Bois Aug. 30, 1938 FOREIGN PATENTS Number Country Date 841,327 France Feb. 1, 1939 Certificate of Correction Patent N 0. 2,457,399. December 28, 1948. CHARLES H. ROCKWOOD ET AL. It is hereby certified that errors appear in the printed specification of the above numbered patent requu'ing correction as follows:

Column 3, line 16, claim 1, for position read positioned; line 17, for dstance read distance;

and thatsaid Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant aommz'asioner of Patents.

Certificate of Correction Patent N 0. 2,457,399. December 28, 1948. CHARLES H. ROOKWOOD ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 16, claim 1, for position read positioned; line 17, for dstance" read distance;

and that'said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents.

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