US2647978A - Resistance unit and element thereof - Google Patents

Resistance unit and element thereof Download PDF

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US2647978A
US2647978A US241408A US24140851A US2647978A US 2647978 A US2647978 A US 2647978A US 241408 A US241408 A US 241408A US 24140851 A US24140851 A US 24140851A US 2647978 A US2647978 A US 2647978A
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resistor
portions
grids
resistance
members
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US241408A
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Alvin C Dyer
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Electric Controller and Manufacturing Co LLC
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Electric Controller and Manufacturing Co LLC
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C3/00—Non-adjustable metal resistors made of wire or ribbon, e.g. coiled, woven or formed as grids
    • H01C3/10—Non-adjustable metal resistors made of wire or ribbon, e.g. coiled, woven or formed as grids the resistive element having zig-zag or sinusoidal configuration

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  • This invention relates to electric resistance elements and electric resistance units containing the same, and more particularly to composite resistance elements formed by attaching a pair of individual resistance grids, preferably stamped from sheet metal, to a common supporting member which also serves as a wiring terminal and to resistance units which comprise an assemblage of such composite resistance elements and which are suitable for various purposes such as, for example, the control of electric motors of the smaller integral horsepower sizes.
  • a general object of this invention is to provide a resistance unit or resistor possessing the advantages of the resistor disclosed and claimed in David C. Wright Patent No. 2,378,056 issued on June 12, 1945, but capable of having a wider range of resistance per unit volume, particularly a greater resistance per unit volume, and of having a larger number of intermediate taps.
  • lug portions at opposite ends of a sheet metal resistance element shaped in the form of a grid are oiTs-et in opposite directions from the plane of the intermediate portion of the grid and lie in respec- 17 Claims. (Cl. 201-459) tive planes which are spaced from but parallel to v the plane of the intermediate portion.
  • Resistors such as disclosed in the Wright patent and using grids stamped from a chromiumaluminum-steel alloy of high specific resistance are currently being manufactured with a minimum continuous rating of 32 amperes at a temperature rise of 375 degrees centigrade.
  • the resistors of this rating with forty-eight grids have a resistance of approximately seven ohms.
  • a more specific object of this invention is to provide a resistor of the same or similar outline dimensions which has a resistance considerably in excess of seven ohms and which is capable of having a larger number of intermediate taps than the resistor of the Wright patent, thus enabling more precise selection of increments of the total resistance of the resistor for utilization in an external circuit.
  • the resistance of a resistor built in accordance with the disclosure of the Wright patent can be increased only by decreasing the crosssectional area of the current path through the grids, using more grids, making the current path of each grid longer, or by a combination of any two or all three of these expedients.
  • another object of the present invention is to provide an improvement of the resistor of the Wright patent capable of being manufactured economically with a much larger resistance per unit volume and without deviation from standard outline dimensions for such resistors.
  • a further object is to obtain the increased resistance to volume ratio by the provision of a novel composite resistance element formed by spot welding a pair of identical sheet metal grids to a common combined terminal and supporting member.
  • the composite resistance element in accordance with this invention has a longer current path for a given area than prior resistance elements, and the individual grids thereof are so proportioned and arranged in cooperation with novel combined terminal and supporting members that they can be made of relatively thin metal and have relatively narrow grid bars and still be conveniently supported for operation at elevated temperatures
  • the cooperative relation between the individual grids and the combined terminal and supporting members is such that taps to which lead-in conductors can be secured are provided at opposite ends of each of the individual identical grids thereby to provide the desired large number of intermediate taps.
  • the principal advantages of the off-set end portions of the grids vof the .prior resistor are retained in the improved resistor.
  • Additional objects are to provide an improved composite resistance element, to provide a composite resistance element :comprising a :pair :of substantially coplanar identical sheet metal resistance elements secured to and extending in the same direction from a common :combined terminal and supporting member, to provide an improved electric resistor comprising .a plurality of composite resistance elements arranged inflatwise spaced relation and having a relatively'large number of intermediate taps, to provide an improved resistor comprising an assemblage of fiatwise spaced resistance elements than can be economically manufactured with a relatively large resistance per unit volume, to provide a resistor comprising a spot-welded assemblage of composite resistance elements of improved design, and to provide an electric resistor in which a plurality of complementary composite resistance elements are supported in flatwise spaced relation with an offset portion of each of the elements extending toward and engaging a portion of an adjacent element at an area accessible for spot-welding therebetween.
  • An individual resistance element of the composite resistance element of this invention preferably is stamped from resistive sheet metal in the form of a relatively long and narrow substantially uniplanular grid having a plurality of relatively narrow transverse grid bars of substantially the same width.
  • the bars at opposite ends of the grid constitute respective lug portions one of which is in the plane of the grid and the other of which is offset so that its terminal portion is spaced from and parallel to the plane of the remainder of the grid.
  • Apair of the individual grids are assembled into a composite resistance element by spot-welding the respective end bars thereof that are not offset to respective tongue portions of a common combined terminal and supporting member.
  • the pair of individual grids are arranged in edgewise spaced relation in a common plane with their respective longitudinal axes parallel to each other and with the respective offset end bars of the two individual grids offset in opposite directions from the plane of the remainder of the composite resistance element.
  • the composite resistance element is completed by spot-welding another of the combined terminal and supporting members to one of the two offset end bars.
  • a resistor in accordance with this invention comprises an assemblage of such composite resistance elements held in fiatwise spaced relation by a supporting means with those of the respective terminal members which are spot welded to the ofi-set end bars extending toward and in engagement with the respective oppositely off-set end bars of adjacent composite resistance elements which do not have terminal members welded to them. After the resistor is assembled on the supportingmeans, spot Welds are made between these terminal members and these oppositely oif-set end bars engaged thereby. Alternate ones of the composite resistance ele- When asments have terminal members of slightly different configuration from each other so that extending portions of adjacent terminal members are spaced apart to provide adequate electrical clearance and to facilitate accessibility and the connection of lead-in conductors thereto.
  • Fig. l is an exploded perspective view showing how a pair of the composite resistance elements of this invention are complementary to each other when arranged side by side on a pair of supporting bolts,
  • Fig. 2 is a sectional view taken generally along :thedine 2-2-of Fig, 3,
  • Fig. 3 is a front elevation of a resistance unit, embodying an assemblage of the resistance elements of Fig. l, with an intermediate portion having parts at the rear of the unit omitted, and partly in section as indicated by the line 3-3 of Fig. 4,
  • Fig. l is a top plan View with an intermediate portion having parts at the bottom of the unit omitted and partly in section along the line 4-4 of Fig. 2,
  • Figs. 5 and 6 are perspective views of the combined terminal and supporting members of the unit of Figs. 2, 3, and 4,
  • Fig. '7 is a fragmentary front elevation of a modified resistance unit with parts at the rear omitted, and
  • Fig. 8 is a fragmentary rear elevation of the unit of Fig. '7 with parts at the front omitted.
  • resistance unit or resistor may be used in any turned position as well as in the position in which shown, such positionally descriptive words as front and rear, upper and lower, and the like as used herein are used for convenience in describing relative positions only.
  • one of a pair of complementary composite resistance elements in accordance with this invention comprises a pair of identical individual resistance elements H suitably fastened to a common combined terminal and supporting member 52 as by spotwelding, and another one of the pair of composite resistance elements, indicated by the reference numeral M, comprises a pair of the individual resistance elements H similarly fastened to a common combined terminal and supporting member l5.
  • Each of the individual resistance elements I i is preferably an integral. piece of sheet metal of suitable thermal, mechanical and electrical characteristics, such a high resistance alloy of chromium, aluminum, and steel, and is preferably shaped in the form of an elongated grid having a plurality of parallel spaced intermediate leg portions 16 transverse to its longitudinal axis and interconnected alternately at opposite ends by connecting portions IE to form a uniplanular circuitous current path between opposite end leg portions I9 and 29 which are preferably parallel to the intermediate leg portions l6 and which constitute supporting lugs for the individual resistance elements or grids.
  • An adjacent pair of the intermediate leg portions IS preferably a pair iSa midway between the end leg portions l9 and 2B, are of reduced length and are connected by a connecting portion !8a of correspondingly increased width to provide space for a circular opening 2
  • the grids I I may be formed directly from sheet metal by a stamping operation or may be formed by edgewise bending of a long straight strip, and may be of any suitable configuration, the convolutions defined by the leg portions I6 and connecting portions I8 being merely illustrative of a preferred embodiment which provides a relatively long current path Within a relatively small area with only a small amount of metal being wasted in the stamping operation.
  • the leg portions I5 are relatively short as shown so as to impart sufficient rigidity to the grids I I to enable them to be relatively long and to be formed of relatively thin sheet metal and still not vibrate excessively or warp at elevated temperatures.
  • each of the grids II is bent intermediate of its length to define an angularly disposed portion 22 between an inner end portion of the leg 29 which remains in the plane of grid and an outer end portion 24 which is bent so that it lies in a plane spaced from but parallel to the plane of the remainder of the grid.
  • the end legs are made slightly longer than the legs I9 so that, after the bending operation, the end edges of the end legs I9 and 20 are substantially equidistant from the longitudinal center-line of the grid,
  • the opening 2I is on the 0pmsite side of the longitudinal center-line of the grid from the end edges of the legs I9 and 2B.
  • the combined, terminal and supporting member I2 comprises a piece of sheet metal, preferably coldrolled steel, having a body portion 25 provide with a centrally disposed circular opening 25.
  • A. pair of aligned tongue portions 28 and 29 extend from the top and. bottom, respectively, of the body portion 25 in the plane thereof and preferably have their respective outer side edges aligned with a side edge 30 of the body portion 25.
  • a bracket portion 3I which extends from the top of the body portion 25 is spaced a short distance from the tongue portion 28 and has a portion 32 overhanging a side edge 33 of the body portion 25 opposite the side edge 30.
  • the bracket portion BI is bent at right angles to the plane of the body portion 25, to the left as viewed in Fig. 5, and the overhanging portion 32 is formed to define a downwardly directed wire receiving channel 34.
  • Notches 35 (Fig. 1) formed in opposite side edges of the portion 32 define an intermediate portion 35 of reduced width between pairs of opposing shoulders 31.
  • the combined terminal. and supporting member I5 which is similar to the terminal and supporting memher I 2, has a body portion 38 provided with a centrally disposed circular opening 39, a pair of tongue portions 44! and 4
  • A. wire receiving channel 44 formed in an overhanging portion 45 of the bracket portion 42 opens upwardly, as viewed in Fig. 6, and notches 46 (Fig. 1) in opposite side edges of the overhanging portion 45 define an intermediate portion 41 of reduced width between pairs of opposing shoulders 48.
  • a pentagonal collar 49 which may be received on the overhanging portion 32 of the bracket 3! of the terminal member I2 between the shoulders 37, has a set screw 58 threaded through an openinggin a relatively short side wall 5I.
  • the set screw 50 may be turned to engage the upper surrace of the intermediate portion 36 thereby to force a pair of side walls 52 of the collar 45, which intersect at an acute angle opposite from the lower end of the set screw 50, against a leadin conductor (not shown) received in the channel 34 thereby to hold the lead-in conductor in good electrical contacting engagement with the terminal member I2.
  • a collar 48 may be received on the overhanging portion 45 of the bracket 42 of the terminal member I5 between the shoulders 48 so that its set screw 59 may be turned to engage the lower surface (Fig. 6) of the intermediate reduced portion 41 to cause a lead-in conductor (not shown) to be gripped between the acutely intersecting side walls 52 and the channel 44.
  • terminal members I2 and I5 are shaped to accommodate a specific form of wire securing means, it is to be understood that they may be arranged in other suitable ways to facilitate the attachment of conductors thereto.
  • the collars 49 have been omitted from the resistor shown in. Figs. 1, 2, 3, and 4, it being understood that they may be placed either on all or selected ones of the mem bers I2 and I5 thereof.
  • each of the composite resistance elements I 0 is assembled by overlapping the outer end portion of the end leg I9 of one of the grids II on the tongue portion 28 of one of the terminal members I2 and securing it thereto as by a pair of spot welds 54, and by overlapping the outer end portion of the end leg I9 of another one of the grids II on the other tongue portion 29 of the same one of the members I2 and securing it thereto as by a pair of spot welds 55.
  • the two grids I I of the resistance element I I] lie in a common plane and extend in edgewise spaced relation from the terminal member I 2 in the same direction with their longitudinal axes parallel and, as viewed in Fig. l, with the offset portion 24 of the leg 26 of the uppermost grid II offset in a direction away from the resistance element I4, and the offset portion 24 of the leg 20 of the lowermost grid II oifset in a direction toward the resistance element I4.
  • the offset portion 24 of the uppermost grid II overlaps the tongue portion 28 of another of the terminal members I2 and is secured thereto as by a, pair of spot Welds 56.
  • the terminal members I2 of each of resistance elements II! overlap the grids II thereof on the side facing in the direction of offset of the portion 24 of the uppermost one of the grids.
  • Each of the composite resistance elements I4 is assembled in a similar manner by overlapping the outer end portion of the end leg I9 of one of the grids II on the tongue portion 4
  • the two grids II of the resistance element I4 are so positioned that they lie in a common plane and extend from the terminal member I5 in edgewise spaced relation in the same direction with their longitudinal axes parallel and, as viewed in Fig. 1, with the oIT-set portion 24 of the leg 20 of the uppermost grid II oil-set in a direction toward the resistance element I0, and the oifset portion 24 of the lowermost grid H offset in a direction away from the resistance element. in.
  • the offset portion 24 of the uppermost grid. ll of each of the resistance elements l4 overlaps and is secured as by a pair of spot welds B to the tongue portion 4! of another of the terminal members l5.
  • the composite resistance elements If) and [4- are complementary to each other and a complete resistor in accordance with this invention and shown in Figs. 2, 3, and 4 comprises a plurality of the elements in and I4 arranged alternately in fiatwise spaced relation along a pair of elongated main supporting bolts 54 and 65 held in parallel spaced relation in a manner to be described and surrounded throughout most of their length by respective insulating tubes 66 and 51.
  • the resistor is assembled by slipping the openings 25 in the terminal members l2 of one of the resistance elements 12 over the tubes 66 and 61, respectively, with the brackets 3
  • of the terminal members 12 are above the longitudinal center line of the resistor, their respective channels 34 open downwardly, and since the brackets 42 of the terminal members l5 are below the longitudinal center line of the resistor, their res ective channels 44 also open downwardly.
  • the uppermost grids H of the resistance elements Hi and !4 are in an upper row with their respective intermediate openings 2
  • the brackets 31 and 42 at the rear of the resister all extend from their respective terminal members i2 and 15 in the same direction or toward the right as viewed in Figs. 3 and 4, and the brackets 3
  • the brackets 34 and 42 of adjacent ones of the resistance elements Hi and M, respectively, are thereby spaced apart from each other both horizontally and vertically of the resistor thereby to provide adequate electrical clearance therebetween and between lead-in conductors (not shown) connected thereto.
  • the upper offset portions 24 of the resistance element [0 and I4 all extend in one direction endwise of the row from the plane of their respective elements, and the lower ofiset portions 24 all extend in the opposite direction. As. seen from the. front of the resistor as in Fig. 3, the upper offset portions 24 extend to the left and the lower offset portions 24 extend to the right.
  • the terminal members l2 and I5 which depend from respective ones of the upper offset portions 24 at the front of the resistor are disposed alternately along the row, and their respective tongue portions 29 and 40 engage the lower offset portions 24, respectively.
  • the offset portion 24 of the lowermost grid ll of each of the resistance elements 10 extends toward and engages in overlapping relation the tongue portion 40 of the front terminal member l5 of the next adjacent resistance element 14, and the offset portion 24 of the lowermost grid ll of each of the resistance elements l4, except the one nearest an end frame 68 at the right-hand end of the row, extends toward and engages in overlapping relation the tongue portion 29 of the front terminal member l2 of the next adjacent resistance element In.
  • the offset portions 24 engage the respective tongue portions 29 and 40 at respective areas accessible by the electrodes of a spot-welding machine (not shown) and, after the resistor is assembled, pairs of spot-welds (not shown) may be made between the abutting portions 24 and tongue portions 29 and 40, respectively.
  • the adjacent resistance elements [0 and 14 are thus held in flatwise spaced relation at the front of the resistor and an electric circuit is completed from element to element through spot-welds.
  • the main supporting bolts 64 and 65 are received at one end in respective horizontally spaced openings in the end frame 68 and at the other end in similar respective openings in an end frame 69.
  • the openings in the end frames 68 and 69 are elongated horizontally, as indicated in Fig. 4, so as to provide space for thermal expansion of the resistance elements [0 and 14 carried by the bolts 64 and
  • Each of the bolts 64 and 65 is preferably insulated from the end frame 68 by an outer insulating washer 10 having a centrally disposed annular boss H (Fig.
  • each of the bolts 64 and 65 is similarly insulated from and secured to the end frame 69.
  • the resistance elements l0 and I4 are arranged alternately in a row or stack along the bolts 64 and 65 with the insulating tubes 66 and 61 passing through the respective openings 26 and 39 in the terminal members 12 and I5.
  • the respective end portions of the resistance elements I0 and I4 at the front of the resistor or in the region of the bolt 64 are additionally held in flatwise spaced relation by suitable heat resisting insulating washers 16 received over the insulating tube 66 and interposed respectively in the spaces between adjacent ones of the terminal members l2 and I5 disposed along the tube 66.
  • Additional washers 16 may be placed on the insulating tubes 66 and 61, respectively, at opposite ends of the row of resistance elements, the outermost ones of the washers 16 at each end of the row preferably extending slightly beyond the end of their respective tubes as shown in Fig. 4.
  • the row of resistance elements I0 and I4 is held together by nuts 18 threaded on the end portions of the bolts 64 and 65, respectively, suitable lock washers 19 and plain metal washers 89 being disposed between the nuts 18 and the outermost of the insulating washers 16, respectively.
  • the uppermost ones of the individual grids II are supported intermediate of their respective end portions by a supporting means comprising an elongated bolt 8
  • a supporting means for the intermediate portions of the lowermost ones of the individual grids comprises a similar bolt 82 passing through the aligned openings 2
  • and 82 is preferably secured to and insulated from its associated one of the end frames 68 and 69 by a pair of telescoping insulating washers 84 and 85, similar to the washers and 12, respectively, and outer and inner nuts 86 and 81.
  • the upper and lower intermediate supporting means also comprise respective groups of insulating washers 89 to bedescribed and received on the respective bolts 8
  • each of the washers 89 has a central annular boss 90 on one side, and, on the other side, a central cylindrical recess 9
  • are interposed respectively in the spaces between adjacent ones of the uppermost grids H with the bosses 90 thereof fitting snugly into the next adjacent ones ofthe openings 2
  • the washers 89 of the group disposed along the bolt 82 are interposed respectively in the spaces between the adjacent ones of the lowermost grids Additional washers 89 may be placed on the bolts 8
  • of each of the grids H is thus disposed between an annular surface around the boss of one of the washers 89 and an annular surface around the recess 9
  • and 82 are held in position by nuts 92 threaded on respective opposite end portions of the bolts.
  • a suitable lock washer 94 and a plain washer 95 are interposed between the nut 92 and the outermost one of the washers, 8.9- on the bolt 8
  • Similar lock washer-s 94 and plain washers 95 are used respectively on the end portions of the bolts 8
  • the circuit is from the bracket portion 3
  • the circuit continues from the uppermost grid ll of the first of the resistance elements In downwardly through the spot welds 54 (Fig. 1) into the tongue portion'28 of the other or rear terminal member I2 of the first resistance element l0 and from the tongue portion 29 thereof through the spot welds 55 (Fig.
  • this member l5 through a pair of the spot welds 59 (Fig. 1) intothe lowermost of the grids H of the first of the resistance elements M.
  • the circuit then extends through this lowermost grid H across the bottom portion of the resistor towards the front and into its offset portion 24 which is spot Welded to the tongue portion 29 of: the front terminal member I22 of the next adjacent one. oftheresistance elements.- I0.
  • the circuit continues in likemanner back and for-th-v across the I resistor until. the resistance element L L nearest the. end frame. 68; is reached.
  • lead-in conductors may be secured to any of. the terminal members I21 and I5 atthe front: and. rear of the resistor to select increments of the total resistance of the resistor for use in an external electric circuit.
  • all of theresistance elements I and I4 in the row are connected to form a continuous series circuit from one end. of the resistor to the other, it will be understood that groups of series-connected resistance elements I0 and I4 may-be disposed along the supporting bolts 64 and 05 andlelectrically isolated from each other.
  • complementary composite resistance elements I00 and I0,I each comprising a pair of. individual grids I02v similar to the grids II but not having ofi-set portions, are arranged alternately in a row along the main supporting bolts 64 and 65-.and the bolts SI and 82 are used to support intermediate portions of the grids I02.
  • Theinsulating washersllfiland 89 may beused asin the resistor of Figs 2, 3, and 4v to hold the elements I00 and, IOI in fiat-wise spaced relation.
  • Each of the composite resistance elements I00 is assembled by overlapping the outer end portion of an end leg I04 (Fig. 8) of one of the individual grids I02 on the tongue portion 28 of one of the terminal members I2. and securing it thereto asby a pair of spot welds I09, and by overlapping the outer end portion of the end leg I04, of another one of the grids. I02 on the tongue portion 29 of. the same one of the terminal members I2. and securing it thereto as by a pair of spot welds I05. When so welded to the tongue portions 28 and 29, the two grids I02 lie in the same plane and extendifrom the terminal member I2 in the same direction with their longitudinal axes parallel to each other.
  • Each of the resistance elements I00 also comprises aterminal member IIO (Fig. '7), similar to the terminal members I2, but having its tongue portions bent, in opposite directions from its body portion to define respective angularly disposed portions IIIand II2, between its body portion and respective o ter end portions H4 and N5 of the tongues.
  • the end portions. [I4 and H5 are bent so that they lie in respective planes which are spaced from but parallel to the plane of the body portion.
  • Each of the resistance elements I00 is completed by overlapping the ofiset end portion II4 of one of the terminal members IID on an end leg IIG opposite from the end leg I04 of the uppermost one of the grids I02 thereof and securing it thereto as by a pair ofspot welds II8.
  • Each of the composite resistance'elements IOI is assembled by overlapping the outer end portion ofthe end leg I04 (Fig. 8) clone of the grids I02 on the tongue portion 4
  • Each of theresistance elements: I 0I also comprises a terminal-member I2 (Fig. '7) similar to the terminal members I5; but havingitstongue portionsbent in opposite directions fromits bodyportion'.
  • each of the resistance elements MI iscompleted v by'overlappingthe offset end portion- IzZfiof; onesof"theterminall members I-2 I on the endlegr I I001 the uppermost-one of -the grids: I02 thereof-and securing-it thereto as by a pair of: spot welds I30.
  • ele tric e isto o pris n a. g o p. i eenel'allv la anmeta lic id emh sar anse pairssw hs e in iv dual l gr s l lfn ach pair in generally, deewisesnacedl ande n rallypaialie relation, andithe sev al; pai s ar an ed; n l k pa ed; nd eenera y arallel elation; o. a h heinvhereby adjac nt on sh pairs s? l ett s era lyl One from.
  • each f the grid members of each having, at one n l he. ir afi stnt e a ue ortlonlele trical y ond cti e i id upp rt nem mbers 're t ve o the. a t nd. h .elec r cally terronnectin dr ma n m onded to. he-firsts g. t 0n i. s scr mma e. and hereby hol in 7 he. id 0 members) f s. ssociated pair fix l n said.
  • each of said first lug portions is substantially coplanar with the major portion of its associated grid member.
  • each of said grid members comprises a row of spaced bar portions and integral connecting portions at the ends of adjacent bar portions and forming therewith a sinuous electrical path extending endwise of the row, and said lug portions are the respective end ones of said bar portions.
  • eachof the two grid members connected together by an additional supporting member are also offset edgewise from each other.
  • each of said second lug portions is oiTset laterally from the plane of the major portion of its associated grid member.
  • each additional supporting member has a planar portion and the connected portions of each of said additional supporting members are offset laterally of the planes of the pairs in opposite directions, respectively, .from its planar portion.
  • the resistor of claim 1 characterized in that at least some of said supporting members, and at least some of said additional supporting members, have extending portions, respectively, and each of said extending portions is arranged for connection with a Wire.
  • the resistor of claim characterized in that the extending portions of adjacent ones of the supporting members extend laterally of the planes of the members, each in the same direction from its associated member at least close to the plane of the next adjacent member, and said extending portions on said adjacent ones of said supporting members are spaced from each other in the general direction of the edgewise spacing of the grids of each pair.
  • An electric resistor comprising a plurality of generally planar U-shaped metallic resistance elements each having a rigid base portion and a pair of arm portions extending therefrom and fixedly held in generally endwise spaced relation to each other thereby, each of said elements having a first mounting means at its base portion and a second mounting means electrically connected to, and permanently bonded to, the free end portion of one of said arm portions, said second mounting means being ofiset from the plane of the remainder of said element and lying in a plane spaced from and generally parallel to the plane of said element, and supporting means for said resistance elements cooperating with said first and second mounting means, respectively, of each element, and thereby supporting said elements in substantially parallel and flatwise 14 spaced relationship with respect to each other with each of said second mounting means extending toward, and being in electric contact with, and permanently bonded to, the free end portion of an arm portion of an adjacent element.
  • one of said arm portions comprises a metal strip forming a circuitous current path including a succession of parallel legged loops alternately extending in opposite directions from the longitudinal axis of their associated arm portion and including an elongated portion at the free end of the strip and extending toward but not intersecting the longitudinal axis of the resistance element as a whole, and said second mounting means are electrically connected to, and permanently bonded to, said strip portions, respectively.
  • each of said arm portions of each element is a separate strip of electric resistance material and each base portion of each element is a separate electric conductive member electrically connected to, and permanently bonded to, the strips of the element of which it forms a part, and, constitutes said first mounting means.
  • each of said conductive members is spot welded to the strip of the element of which it forms a part.
  • An electric resistance element adapted to be assembled in a resistance unit which includes a plurality of said resistance elements arranged in fiatwise and generally parallel spaced relationship, said element comprising a pair of metal supporting members permanently bonded to, and supported in fixed position by, and electrically connected by, a generally planar intermediate metallic resistive portion, one of said supporting members lying substantially in the plane of said resistive portion and the other of said supporting members being ofiset from the general plane of said resistive portion and lying in a plane which is generally parallel to the general plane of said resistive portion, a second substantially planar resistive portion permanently bonded to, and supported in fixed position by, and electrically connected to, said one of said supporting members and disposed in edgewise spaced and generally parallel relation to said first resistive portion and generally coplanar therewith.

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Description

4, 1953 A. c. DYER 2,647,978
RESISTANCE UNIT AND ELEMENT THEREOF Filed Aug. 11, 1951 5 Sheets-Sheet 1 IN V EN TOR.
Aug. 4, 1953 A. c. DYER RESISTANCE UNIT AND ELEMENT THEREOF Filed Aug. 11, 1951 5 Sheets-Sheet 2 INVENTOR.
ALVIN G. DYER' Aug. 4, 1953 A. c. DYER RESISTANCE UNIT AND ELEMENT THEREOF 5 Sheets-Sheet 5 Filed Aug. 11 1951 INVENTOR.
5 v, R g E? p m 6% a M L A B A 1953 A. c. DYER, 2,647,978
RESISTANCE UNIT AND ELEMENT THEREOF Filed Aug. 11, 1951 5 Sheets-Sheet 4 IN VEN TOR.
Aug. 1953 A. c. DYER 2,647,978
RESISTANCE UNIT AND ELEMENT THEREOF Filed Aug. 11, 1951 5 Sheets-Sheet 5 laz mm m 'w Patented Aug. 4, 1953 RESISTANCE UNIT AND ELEMENT THEREOF Alvin C. Dyer, Shaker Heights, Ohio, assignor to The Electric Controller & Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application August 11, 1951, Serial No. 241,408
This invention relates to electric resistance elements and electric resistance units containing the same, and more particularly to composite resistance elements formed by attaching a pair of individual resistance grids, preferably stamped from sheet metal, to a common supporting member which also serves as a wiring terminal and to resistance units which comprise an assemblage of such composite resistance elements and which are suitable for various purposes such as, for example, the control of electric motors of the smaller integral horsepower sizes.
A general object of this invention is to provide a resistance unit or resistor possessing the advantages of the resistor disclosed and claimed in David C. Wright Patent No. 2,378,056 issued on June 12, 1945, but capable of having a wider range of resistance per unit volume, particularly a greater resistance per unit volume, and of having a larger number of intermediate taps.
In the resistor of the Wright patent, lug portions at opposite ends of a sheet metal resistance element shaped in the form of a grid are oiTs-et in opposite directions from the plane of the intermediate portion of the grid and lie in respec- 17 Claims. (Cl. 201-459) tive planes which are spaced from but parallel to v the plane of the intermediate portion. When a plurality of the grids of the patent are properly assembled in fiatwise spaced relation on a supporting means to form a resistor, the lug portions at a given end of a pair of adjacent grids extend away from each other and the lug portions at the other end of the same adjacent grids extend toward and engage each other. The lug portions in engagement with each other are spot welded together after the resistor is assembled.
Resistors such as disclosed in the Wright patent and using grids stamped from a chromiumaluminum-steel alloy of high specific resistance are currently being manufactured with a minimum continuous rating of 32 amperes at a temperature rise of 375 degrees centigrade. The resistors of this rating with forty-eight grids have a resistance of approximately seven ohms.
A more specific object of this invention is to provide a resistor of the same or similar outline dimensions which has a resistance considerably in excess of seven ohms and which is capable of having a larger number of intermediate taps than the resistor of the Wright patent, thus enabling more precise selection of increments of the total resistance of the resistor for utilization in an external circuit.
Since suitable metals or alloys of higher specific resistance than the alloy described above are not available, the resistance of a resistor built in accordance with the disclosure of the Wright patent can be increased only by decreasing the crosssectional area of the current path through the grids, using more grids, making the current path of each grid longer, or by a combination of any two or all three of these expedients. To provide the desired higher resistance by reducing the cross-sectional area of the current path through grids proportioned and supported like those of the Wright patent, either by using thinner metal or narrowing the width of the grid bars, or both, is not a satisfactory solution of the problem beyond a limited range because the grids become too flexible and have to be supported at so many intermediate locations that the cost of the resistor is materially increased and its heat dissipating ability is seriously impaired. Increasing the length of the grids or using more grids in flatwise spaced relation likewsie are not adequate solutions of the problem because the ratio of resistance to unit volume is either lessened or not materially increased and the shape and outline dimensions of the resistor deviate too much from standard practice. Furthermore, none of these expedients, or any combination of them, results in a resistor which can be provided conveniently with the desired large number of intermediate taps. For these and other reasons it is not practicable economically to manufacture resistors such as disclosed in the Wright patent which have the desired higher resistance or the'greater number of taps.
Accordingly, another object of the present invention is to provide an improvement of the resistor of the Wright patent capable of being manufactured economically with a much larger resistance per unit volume and without deviation from standard outline dimensions for such resistors.
A further object is to obtain the increased resistance to volume ratio by the provision of a novel composite resistance element formed by spot welding a pair of identical sheet metal grids to a common combined terminal and supporting member. The composite resistance element in accordance with this invention has a longer current path for a given area than prior resistance elements, and the individual grids thereof are so proportioned and arranged in cooperation with novel combined terminal and supporting members that they can be made of relatively thin metal and have relatively narrow grid bars and still be conveniently supported for operation at elevated temperatures The cooperative relation between the individual grids and the combined terminal and supporting members is such that taps to which lead-in conductors can be secured are provided at opposite ends of each of the individual identical grids thereby to provide the desired large number of intermediate taps. The principal advantages of the off-set end portions of the grids vof the .prior resistor are retained in the improved resistor.
Additional objects are to provide an improved composite resistance element, to provide a composite resistance element :comprising a :pair :of substantially coplanar identical sheet metal resistance elements secured to and extending in the same direction from a common :combined terminal and supporting member, to provide an improved electric resistor comprising .a plurality of composite resistance elements arranged inflatwise spaced relation and having a relatively'large number of intermediate taps, to provide an improved resistor comprising an assemblage of fiatwise spaced resistance elements than can be economically manufactured with a relatively large resistance per unit volume, to provide a resistor comprising a spot-welded assemblage of composite resistance elements of improved design, and to provide an electric resistor in which a plurality of complementary composite resistance elements are supported in flatwise spaced relation with an offset portion of each of the elements extending toward and engaging a portion of an adjacent element at an area accessible for spot-welding therebetween.
An individual resistance element of the composite resistance element of this invention preferably is stamped from resistive sheet metal in the form of a relatively long and narrow substantially uniplanular grid having a plurality of relatively narrow transverse grid bars of substantially the same width. The bars at opposite ends of the grid constitute respective lug portions one of which is in the plane of the grid and the other of which is offset so that its terminal portion is spaced from and parallel to the plane of the remainder of the grid. Apair of the individual grids are assembled into a composite resistance element by spot-welding the respective end bars thereof that are not offset to respective tongue portions of a common combined terminal and supporting member. sembled into acomposite resistance element, the pair of individual grids are arranged in edgewise spaced relation in a common plane with their respective longitudinal axes parallel to each other and with the respective offset end bars of the two individual grids offset in opposite directions from the plane of the remainder of the composite resistance element. The composite resistance element is completed by spot-welding another of the combined terminal and supporting members to one of the two offset end bars.
A resistor in accordance with this invention comprises an assemblage of such composite resistance elements held in fiatwise spaced relation by a supporting means with those of the respective terminal members which are spot welded to the ofi-set end bars extending toward and in engagement with the respective oppositely off-set end bars of adjacent composite resistance elements which do not have terminal members welded to them. After the resistor is assembled on the supportingmeans, spot Welds are made between these terminal members and these oppositely oif-set end bars engaged thereby. Alternate ones of the composite resistance ele- When asments have terminal members of slightly different configuration from each other so that extending portions of adjacent terminal members are spaced apart to provide adequate electrical clearance and to facilitate accessibility and the connection of lead-in conductors thereto.
Other objects and advantages of this invention will become apparent from the following specification wherein reference is made to the accompanying drawings, in which Fig. l is an exploded perspective view showing how a pair of the composite resistance elements of this invention are complementary to each other when arranged side by side on a pair of supporting bolts,
Fig. 2 is a sectional view taken generally along :thedine 2-2-of Fig, 3,
Fig. 3 is a front elevation of a resistance unit, embodying an assemblage of the resistance elements of Fig. l, with an intermediate portion having parts at the rear of the unit omitted, and partly in section as indicated by the line 3-3 of Fig. 4,
Fig. l is a top plan View with an intermediate portion having parts at the bottom of the unit omitted and partly in section along the line 4-4 of Fig. 2,
Figs. 5 and 6 are perspective views of the combined terminal and supporting members of the unit of Figs. 2, 3, and 4,
Fig. '7 is a fragmentary front elevation of a modified resistance unit with parts at the rear omitted, and
Fig. 8 is a fragmentary rear elevation of the unit of Fig. '7 with parts at the front omitted.
Since the resistance unit or resistor may be used in any turned position as well as in the position in which shown, such positionally descriptive words as front and rear, upper and lower, and the like as used herein are used for convenience in describing relative positions only.
Referring principally to Figs. 1 and 2, one of a pair of complementary composite resistance elements in accordance with this invention, indicated by the reference numeral I0, comprises a pair of identical individual resistance elements H suitably fastened to a common combined terminal and supporting member 52 as by spotwelding, and another one of the pair of composite resistance elements, indicated by the reference numeral M, comprises a pair of the individual resistance elements H similarly fastened to a common combined terminal and supporting member l5.
Each of the individual resistance elements I i is preferably an integral. piece of sheet metal of suitable thermal, mechanical and electrical characteristics, such a high resistance alloy of chromium, aluminum, and steel, and is preferably shaped in the form of an elongated grid having a plurality of parallel spaced intermediate leg portions 16 transverse to its longitudinal axis and interconnected alternately at opposite ends by connecting portions IE to form a uniplanular circuitous current path between opposite end leg portions I9 and 29 which are preferably parallel to the intermediate leg portions l6 and which constitute supporting lugs for the individual resistance elements or grids. An adjacent pair of the intermediate leg portions IS, preferably a pair iSa midway between the end leg portions l9 and 2B, are of reduced length and are connected by a connecting portion !8a of correspondingly increased width to provide space for a circular opening 2| which cooperates with an intermediate supporting means to be described.
The grids I I may be formed directly from sheet metal by a stamping operation or may be formed by edgewise bending of a long straight strip, and may be of any suitable configuration, the convolutions defined by the leg portions I6 and connecting portions I8 being merely illustrative of a preferred embodiment which provides a relatively long current path Within a relatively small area with only a small amount of metal being wasted in the stamping operation. Preferably, the leg portions I5 are relatively short as shown so as to impart sufficient rigidity to the grids I I to enable them to be relatively long and to be formed of relatively thin sheet metal and still not vibrate excessively or warp at elevated temperatures.
The end leg 29 of each of the grids II is bent intermediate of its length to define an angularly disposed portion 22 between an inner end portion of the leg 29 which remains in the plane of grid and an outer end portion 24 which is bent so that it lies in a plane spaced from but parallel to the plane of the remainder of the grid. The end legs are made slightly longer than the legs I9 so that, after the bending operation, the end edges of the end legs I9 and 20 are substantially equidistant from the longitudinal center-line of the grid, Preferably, the opening 2I is on the 0pmsite side of the longitudinal center-line of the grid from the end edges of the legs I9 and 2B.
As shown most clearly in Figs. 1 and 5, the combined, terminal and supporting member I2 comprises a piece of sheet metal, preferably coldrolled steel, having a body portion 25 provide with a centrally disposed circular opening 25. A. pair of aligned tongue portions 28 and 29 extend from the top and. bottom, respectively, of the body portion 25 in the plane thereof and preferably have their respective outer side edges aligned with a side edge 30 of the body portion 25. A bracket portion 3I which extends from the top of the body portion 25 is spaced a short distance from the tongue portion 28 and has a portion 32 overhanging a side edge 33 of the body portion 25 opposite the side edge 30. The bracket portion BI is bent at right angles to the plane of the body portion 25, to the left as viewed in Fig. 5, and the overhanging portion 32 is formed to define a downwardly directed wire receiving channel 34. Notches 35 (Fig. 1) formed in opposite side edges of the portion 32 define an intermediate portion 35 of reduced width between pairs of opposing shoulders 31.
As shown. most clearly in Figs. 1 and 6, the combined terminal. and supporting member I5, which is similar to the terminal and supporting memher I 2, has a body portion 38 provided with a centrally disposed circular opening 39, a pair of tongue portions 44! and 4| corresponding to the tongue portions 23 and 29 of the member I2, and a bracket portion 42 similar to the bracket portion 3| but bent in the opposite direction or to the right as viewed in Fig. 6. A. wire receiving channel 44 formed in an overhanging portion 45 of the bracket portion 42 opens upwardly, as viewed in Fig. 6, and notches 46 (Fig. 1) in opposite side edges of the overhanging portion 45 define an intermediate portion 41 of reduced width between pairs of opposing shoulders 48.
A pentagonal collar 49, which may be received on the overhanging portion 32 of the bracket 3! of the terminal member I2 between the shoulders 37, has a set screw 58 threaded through an openinggin a relatively short side wall 5I. The set screw 50 may be turned to engage the upper surrace of the intermediate portion 36 thereby to force a pair of side walls 52 of the collar 45, which intersect at an acute angle opposite from the lower end of the set screw 50, against a leadin conductor (not shown) received in the channel 34 thereby to hold the lead-in conductor in good electrical contacting engagement with the terminal member I2. Similarly, a collar 48 may be received on the overhanging portion 45 of the bracket 42 of the terminal member I5 between the shoulders 48 so that its set screw 59 may be turned to engage the lower surface (Fig. 6) of the intermediate reduced portion 41 to cause a lead-in conductor (not shown) to be gripped between the acutely intersecting side walls 52 and the channel 44.
Although the terminal members I2 and I5 are shaped to accommodate a specific form of wire securing means, it is to be understood that they may be arranged in other suitable ways to facilitate the attachment of conductors thereto. For clarity of illustration, the collars 49 have been omitted from the resistor shown in. Figs. 1, 2, 3, and 4, it being understood that they may be placed either on all or selected ones of the mem bers I2 and I5 thereof.
Again referring principally to Figs. 1 and 2, each of the composite resistance elements I 0 is assembled by overlapping the outer end portion of the end leg I9 of one of the grids II on the tongue portion 28 of one of the terminal members I2 and securing it thereto as by a pair of spot welds 54, and by overlapping the outer end portion of the end leg I9 of another one of the grids II on the other tongue portion 29 of the same one of the members I2 and securing it thereto as by a pair of spot welds 55. When so welded to the tongue portions 28 and 29, the two grids I I of the resistance element I I] lie in a common plane and extend in edgewise spaced relation from the terminal member I 2 in the same direction with their longitudinal axes parallel and, as viewed in Fig. l, with the offset portion 24 of the leg 26 of the uppermost grid II offset in a direction away from the resistance element I4, and the offset portion 24 of the leg 20 of the lowermost grid II oifset in a direction toward the resistance element I4. The offset portion 24 of the uppermost grid II overlaps the tongue portion 28 of another of the terminal members I2 and is secured thereto as by a, pair of spot Welds 56. It should be noted that the terminal members I2 of each of resistance elements II! overlap the grids II thereof on the side facing in the direction of offset of the portion 24 of the uppermost one of the grids.
Each of the composite resistance elements I4 is assembled in a similar manner by overlapping the outer end portion of the end leg I9 of one of the grids II on the tongue portion 4| of one of the terminal members I5 and securing it thereto as by a pair of spot welds 53, and by overlapping the outer end portion of the end leg I9 of another one of the grids II on the other tongue portion 40 of the same one of the members I5 and securing it thereto as by a pair of spot welds 59. When so welded to the tongue portions 40 and M, the two grids II of the resistance element I4 are so positioned that they lie in a common plane and extend from the terminal member I5 in edgewise spaced relation in the same direction with their longitudinal axes parallel and, as viewed in Fig. 1, with the oIT-set portion 24 of the leg 20 of the uppermost grid II oil-set in a direction toward the resistance element I0, and the oifset portion 24 of the lowermost grid H offset in a direction away from the resistance element. in. The offset portion 24 of the uppermost grid. ll of each of the resistance elements l4 overlaps and is secured as by a pair of spot welds B to the tongue portion 4! of another of the terminal members l5. It should be noted that the terminal members E5 of each of the resistance elements 14, like the terminal members I2 of each of the resistance elements l9, overlap the grids H thereof on the side facing in the direction of off-set of the portion 24 of the uppermost one of the grids.
The composite resistance elements If) and [4- are complementary to each other and a complete resistor in accordance with this invention and shown in Figs. 2, 3, and 4 comprises a plurality of the elements in and I4 arranged alternately in fiatwise spaced relation along a pair of elongated main supporting bolts 54 and 65 held in parallel spaced relation in a manner to be described and surrounded throughout most of their length by respective insulating tubes 66 and 51. The resistor is assembled by slipping the openings 25 in the terminal members l2 of one of the resistance elements 12 over the tubes 66 and 61, respectively, with the brackets 3| above the bolts 64 and 65, and then slipping the openings 39 in the terminal members of one of the resistance elements l4 over the tubes 65 and 61', respectively, with the brackets 42 below the bolts 84 and 55. Additional resistance elements to and 14 are received alternately in like manner on the bolts 64 and 55- until the desired number of elements have been assembled to form a row or stack. Since, when so assembled, the brackets 3| of the terminal members 12 are above the longitudinal center line of the resistor, their respective channels 34 open downwardly, and since the brackets 42 of the terminal members l5 are below the longitudinal center line of the resistor, their res ective channels 44 also open downwardly.
The uppermost grids H of the resistance elements Hi and !4 are in an upper row with their respective intermediate openings 2| in alignment and the lowermost grids H of the resistance elements are in a lower row with their respective intermediate openings 2i in alignment.
The brackets 31 and 42 at the rear of the resister all extend from their respective terminal members i2 and 15 in the same direction or toward the right as viewed in Figs. 3 and 4, and the brackets 3| and 42 at the front of the resistor all extend in the same direction from their respective terminal members 12 and I5 or to the left as viewed in Figs. 3 and 4. The brackets 34 and 42 of adjacent ones of the resistance elements Hi and M, respectively, are thereby spaced apart from each other both horizontally and vertically of the resistor thereby to provide adequate electrical clearance therebetween and between lead-in conductors (not shown) connected thereto.
Since the channels 34 and 44 open downwardly, the set screws 5b of the collars 45 when received on the brackets 3i and 42 have their respective heads facing upwardly, and since the brackets 3| and 42 on the same side of the resistor extend in the same direction, clearance is provided for a screw-driver to reach the set screws 52 of the collars 49 when received on the brackets 4-2 as clearly seen in Figs. 3 and 4.
Referrin particularly to Fig. 3, it will be noted that the upper offset portions 24 of the resistance element [0 and I4 all extend in one direction endwise of the row from the plane of their respective elements, and the lower ofiset portions 24 all extend in the opposite direction. As. seen from the. front of the resistor as in Fig. 3, the upper offset portions 24 extend to the left and the lower offset portions 24 extend to the right.
Because the elements I0 and 14 are disposed alternately in the row or stack along the bolts.
64 and 65, the terminal members l2 and I5 which depend from respective ones of the upper offset portions 24 at the front of the resistor are disposed alternately along the row, and their respective tongue portions 29 and 40 engage the lower offset portions 24, respectively. Thus the offset portion 24 of the lowermost grid ll of each of the resistance elements 10 extends toward and engages in overlapping relation the tongue portion 40 of the front terminal member l5 of the next adjacent resistance element 14, and the offset portion 24 of the lowermost grid ll of each of the resistance elements l4, except the one nearest an end frame 68 at the right-hand end of the row, extends toward and engages in overlapping relation the tongue portion 29 of the front terminal member l2 of the next adjacent resistance element In. The offset portions 24 engage the respective tongue portions 29 and 40 at respective areas accessible by the electrodes of a spot-welding machine (not shown) and, after the resistor is assembled, pairs of spot-welds (not shown) may be made between the abutting portions 24 and tongue portions 29 and 40, respectively. The adjacent resistance elements [0 and 14 are thus held in flatwise spaced relation at the front of the resistor and an electric circuit is completed from element to element through spot-welds.
The main supporting bolts 64 and 65, each of which is threaded at its opposite end portions, are received at one end in respective horizontally spaced openings in the end frame 68 and at the other end in similar respective openings in an end frame 69. Preferably, the openings in the end frames 68 and 69 are elongated horizontally, as indicated in Fig. 4, so as to provide space for thermal expansion of the resistance elements [0 and 14 carried by the bolts 64 and Each of the bolts 64 and 65 is preferably insulated from the end frame 68 by an outer insulating washer 10 having a centrally disposed annular boss H (Fig. 4) which extends through its associated opening in the end frame 68 into a complementary centrally disposed cylindrical recess in an inner insulating washer l2, and each is retained in position with respect to the end frame 68 by inner and outer nuts 14 and 15 tightened against the washers l2 and I0, respectively, metal washers l3 performing their usual function as indicated. The opposite end portion of each of the bolts 64 and 65 is similarly insulated from and secured to the end frame 69.
As mentioned, the resistance elements l0 and I4 are arranged alternately in a row or stack along the bolts 64 and 65 with the insulating tubes 66 and 61 passing through the respective openings 26 and 39 in the terminal members 12 and I5. The respective end portions of the resistance elements I0 and I4 at the front of the resistor or in the region of the bolt 64 are additionally held in flatwise spaced relation by suitable heat resisting insulating washers 16 received over the insulating tube 66 and interposed respectively in the spaces between adjacent ones of the terminal members l2 and I5 disposed along the tube 66. Similarly, the respective end portions of the elements and M at the rear of the resistor or in the region of the bolt 65 are held in fiatwise spaced relation by additional insulating washers 16 received over the insulating tube 61 and interposed respectively in the spaces between adjacent ones ofthe terminal members 2 and I5 disposed along the tube 61. In other words, both at the front and rear of the resistor adjacent ones of the terminal members l2 and I5 are spaced apart by engagement of the margin of the metal around the respective openings .26 and 39 with the planular side faces of one of the washers 16. Additional washers 16 may be placed on the insulating tubes 66 and 61, respectively, at opposite ends of the row of resistance elements, the outermost ones of the washers 16 at each end of the row preferably extending slightly beyond the end of their respective tubes as shown in Fig. 4. The row of resistance elements I0 and I4 is held together by nuts 18 threaded on the end portions of the bolts 64 and 65, respectively, suitable lock washers 19 and plain metal washers 89 being disposed between the nuts 18 and the outermost of the insulating washers 16, respectively.
The uppermost ones of the individual grids II are supported intermediate of their respective end portions by a supporting means comprising an elongated bolt 8| passing through the aligned openings 2| in the upper row of grids and having its opposite end portions threaded and received in horizontally elongated openings near the top of the respective end frames 68 and 69.
A supporting means for the intermediate portions of the lowermost ones of the individual grids comprises a similar bolt 82 passing through the aligned openings 2| in the lower row of grids and having its opposite end portions received in respective horizontally elongated openings near the bottom of the respective end frames 68 and 69. Fach of the end portions of the bolts 8| and 82 is preferably secured to and insulated from its associated one of the end frames 68 and 69 by a pair of telescoping insulating washers 84 and 85, similar to the washers and 12, respectively, and outer and inner nuts 86 and 81. The upper and lower intermediate supporting means also comprise respective groups of insulating washers 89 to bedescribed and received on the respective bolts 8| and 82 thereof.
The intermediate portions of the grids I in the upper row are held in fiatwise spaced relation by the group of the insulating washers 89 received on the bolt 8|, and the intermediate portions of the grids II in the lower row are held in fiatwise spaced relation by the group of the insulating washers 89 received on the bolt 82. As shown most clearly in Fig. 4, each of the washers 89 has a central annular boss 90 on one side, and, on the other side, a central cylindrical recess 9| of slightly larger diameter than the boss 90 and slightly deeper than the height of the boss 99. Washers 89 of the group disposed along the bolt 8| are interposed respectively in the spaces between adjacent ones of the uppermost grids H with the bosses 90 thereof fitting snugly into the next adjacent ones ofthe openings 2|, respectively, and extending respectively therethrough into the recesses 9| of the "next adjacent ones of the washers 89. Similarly-the washers 89 of the group disposed along the bolt 82 are interposed respectively in the spaces between the adjacent ones of the lowermost grids Additional washers 89 may be placed on the bolts 8| and 82 at opposite ends of the row of resistance elements. The margin of metal around the opening2| of each of the grids H is thus disposed between an annular surface around the boss of one of the washers 89 and an annular surface around the recess 9| of the next adjacent one of the washers 89.
The respective groups of the washers 89. on the bolts 8| and 82 are held in position by nuts 92 threaded on respective opposite end portions of the bolts. At the end portion of the bolt 8| nearest the end frame 69, a suitable lock washer 94 and a plain washer 95 are interposed between the nut 92 and the outermost one of the washers, 8.9- on the bolt 8| and, at the end portion of the bolt 82 nearest theend frame 69, a lock washer 94 and a plain washer 95 are alsointerposed between the nut. 92 and the outermost one of the *washers 89 on the bolt 82. Similar lock washer-s 94 and plain washers 95 are used respectively on the end portions of the bolts 8| and 82 nearest. the end. frame 69. At-the end nearest the end frame 68, however, the respective bosses 99 of the outermost ones of the insulating washers 89 are received respectively in recesses 96 (Fig. 4) of insulating washers 91 received on the respective bolts 8| and 82 and having planular outer surfaces in engagement with the respective washers 95.
An electric circuit through the resistor of Figs; 2, 3, and 4 can be traced'as follows:
Starting at the terminal member |2 at the front ofthe resistor and which forms part of the resistance element loclosest to the end. frame 69, the circuit is from the bracket portion 3| thereof through its tongue portion 28 and the spot welds 56 (Fig. *1) into the offset portion 24 of the uppermost grid ll of this first one of the resistance elements I 9 and thence through this grid across the upper portion of the resistor. 'Atlthe rear. of the resistor, the circuit continues from the uppermost grid ll of the first of the resistance elements In downwardly through the spot welds 54 (Fig. 1) into the tongue portion'28 of the other or rear terminal member I2 of the first resistance element l0 and from the tongue portion 29 thereof through the spot welds 55 (Fig. 1) into the lowermost grid I I of the first resistance element It]. The circuit is then through this lowermost grid back across the bottom portion of the resistor to its offset portion 24 which is spot welded to the tongue portion 49 of the front terminal member 5 of the first of the resistance elements l4 nearest the end frame 69. From the tongue portion 4| of this terminal member I5 the circult is through a pair of the spot welds 68 (Fig. 1) into the offset portion 24 of the uppermost grid ll of the first of the resistance elements i4 and thence through this grid across the top portion of the resistor. At the rear of the resistor, the circuit continues downwardly througha pair of thespot welds 58 into the other or rear terminal member l5 of the first of the resistance elements l4 and from. this member l5 through a pair of the spot welds 59 (Fig. 1) intothe lowermost of the grids H of the first of the resistance elements M. The circuit then extends through this lowermost grid H across the bottom portion of the resistor towards the front and into its offset portion 24 which is spot Welded to the tongue portion 29 of: the front terminal member I22 of the next adjacent one. oftheresistance elements.- I0.
The circuit continues in likemanner back and for-th-v across the I resistor until. the resistance element L L nearest the. end frame. 68; is reached.
It will be understood. that lead-in conductors may be secured to any of. the terminal members I21 and I5 atthe front: and. rear of the resistor to select increments of the total resistance of the resistor for use in an external electric circuit. Although in the resistor as shown. all of theresistance elements I and I4 in the row are connected to form a continuous series circuit from one end. of the resistor to the other, it will be understood that groups of series-connected resistance elements I0 and I4 may-be disposed along the supporting bolts 64 and 05 andlelectrically isolated from each other.
In the modified resistor of Figs. 7 and 8, complementary composite resistance elements I00 and I0,I, each comprising a pair of. individual grids I02v similar to the grids II but not having ofi-set portions, are arranged alternately in a row along the main supporting bolts 64 and 65-.and the bolts SI and 82 are used to support intermediate portions of the grids I02. Theinsulating washersllfiland 89 may beused asin the resistor of Figs 2, 3, and 4v to hold the elements I00 and, IOI in fiat-wise spaced relation.
Each of the composite resistance elements I00 is assembled by overlapping the outer end portion of an end leg I04 (Fig. 8) of one of the individual grids I02 on the tongue portion 28 of one of the terminal members I2. and securing it thereto asby a pair of spot welds I09, and by overlapping the outer end portion of the end leg I04, of another one of the grids. I02 on the tongue portion 29 of. the same one of the terminal members I2. and securing it thereto as by a pair of spot welds I05. When so welded to the tongue portions 28 and 29, the two grids I02 lie in the same plane and extendifrom the terminal member I2 in the same direction with their longitudinal axes parallel to each other.
Each of the resistance elements I00 also comprises aterminal member IIO (Fig. '7), similar to the terminal members I2, but having its tongue portions bent, in opposite directions from its body portion to define respective angularly disposed portions IIIand II2, between its body portion and respective o ter end portions H4 and N5 of the tongues. The end portions. [I4 and H5 are bent so that they lie in respective planes which are spaced from but parallel to the plane of the body portion. Each of the resistance elements I00 is completed by overlapping the ofiset end portion II4 of one of the terminal members IID on an end leg IIG opposite from the end leg I04 of the uppermost one of the grids I02 thereof and securing it thereto as by a pair ofspot welds II8.
Each of the composite resistance'elements IOI is assembled by overlapping the outer end portion ofthe end leg I04 (Fig. 8) clone of the grids I02 on the tongue portion 4| of one of the terminal members I5 and securing itthereto as by apair of spot welds I I9; and .byoverlapping the outer end portionof the end leg I0 4' of another one of the grids I02 on the tongue portion 400i the same one'of the terminal members I5 and securing it thereto as by a pair of spot Welds I Each of theresistance elements: I 0I also comprises a terminal-member I2 (Fig. '7) similar to the terminal members I5; but havingitstongue portionsbent in opposite directions fromits bodyportion'. to define respective angularly disposed portions: I24 and I25 between its body port-iomand respectivelouter endportions I20 and I29 of the tongues. The ends portions. I28: and I2t are bent so. that: they lie in respective planes which arespaced' frombut parallel to the: plane of the body portion. Each of the resistance elements MI iscompleted v by'overlappingthe offset end portion- IzZfiof; onesof"theterminall members I-2 I on the endlegr I I001 the uppermost-one of -the grids: I02 thereof-and securing-it thereto as by a pair of: spot welds I30.
Ilhe resistance elements. I01 and I02 are asa sembled:alternatelydn a row on the bolts 64 and 05-110 forms a resistor with the bracket portions 3d: and 42; of the terminal members I2 and I5 respectively; at: therear of the resistor: extending: in-the same direction, on to the=lef-tas viewed in- Fig; 8; andawith bracket portions I3 I and Iz32 of theiterminal members LID-and I-M at thefront of: the; resistor extending in: thesamedirection orlto theleftas-viewed in- Fig. '7:
Except for the offset end portion I' IS'nearest' thealef t hand end of'the resistor (F-ig; 7 the-end portions lllfi otthe terminal members H0 ex -l tend toward and engage the end leg: HIS of the lowermost grid I 02- of' the-next adj acent resistance element: I0 I to which theyareelectricallyconneoted after the resistor is-.assembled=as by a pair of= spot welds- I-3'4l Likewise, the-offset endportions; I29 Ofthe term-inal members I-2I extendj toward and engage the end leg-I IQ of the lowermost grid; I02" of; the next adjacent: resistance element I00"to which; they are electrically connectedafter the'resistor is assembledasbya pair; of spotwelds I35; Thus an electric circuit through the resistor of'Figs. 7-and'8*is compl ete d through spot welded joints as the resistor of, Figs; 2; 3, and t and the ofiset'. tongue portion j le. t rmina memb s, I I t nd I 2| p ovi e. th dvan e sp fiheo s t porti ns .4, I
Ha insfihis d sc ibed my. invention. laim.
ele tric e isto o pris n a. g o p. i eenel'allv la anmeta lic id emh sar anse pairssw hs e in iv dual l gr s l lfn ach pair in generally, deewisesnacedl ande n rallypaialie relation, andithe sev al; pai s ar an ed; n l k pa ed; nd eenera y arallel elation; o. a h heinvhereby adjac nt on sh pairs s? l ett s era lyl One from. the Other,- I each f; the grid members of each having, at one n l he. ir afi stnt e a ue ortlonlele trical y ond cti e i id upp rt nem mbers 're t ve o the. a t nd. h .elec r cally terronnectin dr ma n m onded to. he-firsts g. t 0n i. s scr mma e. and hereby hol in 7 he. id 0 members) f s. ssociated pair fix l n said. enerally deewi e paced" and: r-ll l fi-ner ll l e ti nr ach er dsmember o ac pair; hav n I a ficchdilltesml ,lug po tion. at ts pposite; ect. dditio al l tri al y conduc: i e igid upportin mem ers ion the ha sp apastic 1y, ach additional supporting m mber i e lect ically-1 onne te and.- permanently bonded at oner portion .to ,thesecOBd lug portion ne. el'i member ts. ass c ated par. atanothgzrportion, tovthelsecond.lug portion or gridme nb i anext .adiacentpair and meanscooperating withisaid suppo ting; members and said .4 additional supporting, members (for holding aid eirsl n id. flatwis spa d andt enerally para lel elatlonl.
Theesist nof. lalln.rll h racterized; inthat each of said first lug portions is substantially coplanar with the major portion of its associated grid member.
3. The resistor of claim 1 characterized in that each of said grid members comprises a row of spaced bar portions and integral connecting portions at the ends of adjacent bar portions and forming therewith a sinuous electrical path extending endwise of the row, and said lug portions are the respective end ones of said bar portions.
4. The resistor of claim 1 characterized in that all of the grid members are substantially identical.
5. The resistor of claim 1 characterized in that eachof the two grid members connected together by an additional supporting member are also offset edgewise from each other.
6. The resistor of claim 1 characterized in that each of said second lug portions is oiTset laterally from the plane of the major portion of its associated grid member.
7. The resistor of claim 1 characterized in that said second lug portions of each pair of grid members are offset laterally from, and in opposite directions respectively from, the plane of their associated pair.
8. The resistor of claim 1 characterized in that each additional supporting member has a planar portion and the connected portions of each of said additional supporting members are offset laterally of the planes of the pairs in opposite directions, respectively, .from its planar portion.
9. The resistor of claim 1 characterized in that said supporting members and additional supporting members have mounting holes, respectively, and said last mentioned means comprises a pair of bolts passing through the mounting holes in said supporting members and in said additional supporting members, respectively.
10. The resistor of claim 1 characterized in that at least some of said supporting members, and at least some of said additional supporting members, have extending portions, respectively, and each of said extending portions is arranged for connection with a Wire.
11. The resistor of claim characterized in that the extending portions of adjacent ones of the supporting members extend laterally of the planes of the members, each in the same direction from its associated member at least close to the plane of the next adjacent member, and said extending portions on said adjacent ones of said supporting members are spaced from each other in the general direction of the edgewise spacing of the grids of each pair.
12. An electric resistor comprising a plurality of generally planar U-shaped metallic resistance elements each having a rigid base portion and a pair of arm portions extending therefrom and fixedly held in generally endwise spaced relation to each other thereby, each of said elements having a first mounting means at its base portion and a second mounting means electrically connected to, and permanently bonded to, the free end portion of one of said arm portions, said second mounting means being ofiset from the plane of the remainder of said element and lying in a plane spaced from and generally parallel to the plane of said element, and supporting means for said resistance elements cooperating with said first and second mounting means, respectively, of each element, and thereby supporting said elements in substantially parallel and flatwise 14 spaced relationship with respect to each other with each of said second mounting means extending toward, and being in electric contact with, and permanently bonded to, the free end portion of an arm portion of an adjacent element.
13. The resistor of claim 12 characterized in that one of said arm portions comprises a metal strip forming a circuitous current path including a succession of parallel legged loops alternately extending in opposite directions from the longitudinal axis of their associated arm portion and including an elongated portion at the free end of the strip and extending toward but not intersecting the longitudinal axis of the resistance element as a whole, and said second mounting means are electrically connected to, and permanently bonded to, said strip portions, respectively.
14. The resistor of claim 12 characterized in that each of said arm portions of each element is a separate strip of electric resistance material and each base portion of each element is a separate electric conductive member electrically connected to, and permanently bonded to, the strips of the element of which it forms a part, and, constitutes said first mounting means.
15. The resistor of claim 14 characterized in that each of said conductive members is spot welded to the strip of the element of which it forms a part.
16. The resistor of claim 12 characterized in that both of said free end portions of each of the U-shaped resistance elements are offset in opposite directions, respectively, from the plane of the remainder of their associated element.
17. An electric resistance element adapted to be assembled in a resistance unit which includes a plurality of said resistance elements arranged in fiatwise and generally parallel spaced relationship, said element comprising a pair of metal supporting members permanently bonded to, and supported in fixed position by, and electrically connected by, a generally planar intermediate metallic resistive portion, one of said supporting members lying substantially in the plane of said resistive portion and the other of said supporting members being ofiset from the general plane of said resistive portion and lying in a plane which is generally parallel to the general plane of said resistive portion, a second substantially planar resistive portion permanently bonded to, and supported in fixed position by, and electrically connected to, said one of said supporting members and disposed in edgewise spaced and generally parallel relation to said first resistive portion and generally coplanar therewith.
ALVIN C. DYER.
References Cited in the file of this patent UNITED LTATES PATENTS Number Name Date 1,501,638 Weimer et a1. July 15, 1924 1,525,460 Miller Feb. 10, 1925 2,378,056 Wright June 12, 1945 FOREIGN PATENTS Number Country Date 361,986 Great Britain Dec. 3, 1931 OTHER REFERENCES Kutcher et al., The Welding Journal, Oct. 1948, Des. 827-830.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2977107A (en) * 1957-10-08 1961-03-28 Pacific Scientific Co Heat treating furnace
DE1136768B (en) * 1960-07-07 1962-09-20 Siemens Ag Cast resistance element with a multiple meander
US3666924A (en) * 1970-11-16 1972-05-30 Westinghouse Electric Corp Electric resistance convection heater
DE19542162A1 (en) * 1995-11-11 1997-05-15 Abb Research Ltd Current limiter
DE102004033680A1 (en) * 2004-07-09 2006-01-26 Wobben, Aloys, Dipl.-Ing. load resistance

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1501638A (en) * 1921-05-06 1924-07-15 Weimer Warren Company Rheostat
US1525460A (en) * 1922-02-13 1925-02-10 Cutler Hammer Mfg Co Resistance
GB361986A (en) * 1931-04-29 1931-12-03 Igranic Electric Co Ltd Improvements in and relating to electrical resistances
US2378056A (en) * 1943-01-23 1945-06-12 Electric Controller & Mfg Co Resistance unit and element thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1501638A (en) * 1921-05-06 1924-07-15 Weimer Warren Company Rheostat
US1525460A (en) * 1922-02-13 1925-02-10 Cutler Hammer Mfg Co Resistance
GB361986A (en) * 1931-04-29 1931-12-03 Igranic Electric Co Ltd Improvements in and relating to electrical resistances
US2378056A (en) * 1943-01-23 1945-06-12 Electric Controller & Mfg Co Resistance unit and element thereof

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2977107A (en) * 1957-10-08 1961-03-28 Pacific Scientific Co Heat treating furnace
DE1136768B (en) * 1960-07-07 1962-09-20 Siemens Ag Cast resistance element with a multiple meander
US3666924A (en) * 1970-11-16 1972-05-30 Westinghouse Electric Corp Electric resistance convection heater
DE19542162A1 (en) * 1995-11-11 1997-05-15 Abb Research Ltd Current limiter
DE19542162C2 (en) * 1995-11-11 2000-11-23 Abb Research Ltd Overcurrent limiter
US6166619A (en) * 1995-11-11 2000-12-26 Daimlerchrysler Ag Overcurrent limiter having inductive compensation
DE102004033680A1 (en) * 2004-07-09 2006-01-26 Wobben, Aloys, Dipl.-Ing. load resistance
US20080191836A1 (en) * 2004-07-09 2008-08-14 Aloys Wobben Load Resistor
DE102004033680B4 (en) * 2004-07-09 2009-03-12 Wobben, Aloys, Dipl.-Ing. load resistance
EP2270821A2 (en) 2004-07-09 2011-01-05 Aloys Wobben Wind energy system with a converter and at least one high performance resistor

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