US1894327A - Fixed clamp - Google Patents

Description

Jan. 17, 1933. N. c. SCHELLENGER FIXED CLAMP Filed April 2. 1930 2 Sheets-Sheet 1 Jan. 17, 1933. N. c. SCHELLENGER 1,894,327

FIXED CLAMP Filed April 2. 1930 2 sheets sheet 2 32 HOB .Qu H

llll I m WW J Patented Jan. 17, 1933 UNITED STATES NEWTON C. SCHELLENGER, OF ELCKHAR'I, PHONE SUPPLY COMPANY, OF ELKHART,

INDIANA, ASSIGNOR TO CHICAGO TELE- INDIANA, A CORPORATION OF INDIANA.

FIXED CLAMP Application filed April 2, 1930. Serial No. 440,984.

My invention which I shall describe and explain in the following specification relates, broadly speaking, to clamps but is more especially concerned with fixed clamps for resistance elements, that is to say, with a novel and improved clamp for permanent transverse attachment to longitudinal resistance elements which comprise, in one embodiment a longitudinal support of insulating material provided with longitudinally progressive transverse coils or convolutions of resistance wire on which the clamp is placed transversely to the insulating support,

Prior constructions of clamps of this type and the manner of attachment of these clamps to resistances occasioned various objections which I shall discuss briefly so that the description of my invention which is to follow may be readily understood and appreciated.

Such a clamp as constructed in the past consists usually of a suitably shaped fiat metal strip formed and clamped permanently in place transversely to and around the wire coiled on a flat insulating support. One or more such clamps may be placed on a resistance element together with terminal provisions for connecting conductors to the clamps. A so-called staking operation is necessary as a step in the production ot resistance elements having such clamps attached thereto, in e., provisions for arranging orstaking the clamps on the resistance in accurate relation to each other and then tprming the clamps around the resistance element.

The contact actually established between such clamp and the resistance wire on an insulating support is located at some point between the lateral edges of the clamp, due to the staking operation which causes bending ot'the transversal contacting surface of the clamp, producing a convex contacting surface which "faces the resistance wire Any twisting or hcnding oi: the resistance element due to heating moisture absorption or any other reason will cause a change in resistance between the terminals of the clamps on a resistance element, because the clamps maintain contact with. the resistance wire by diiferent turns of the wire due to the convex contacting surface, and, accordingly, such bending and twisting will cause a shifting of the contacting surface of the clamps on the wire longitudinally to the element. Slight variations in the metal or in the forming and staking operations will cause variations in the curvature of the contacting portion of the clamps and difliculties will be encountered in holding a close resistance tolerance due to the fact that the effective length of the resistance wire between two clamps varies considerably since contact with certain turns of the winding cannot be made accurately by each clamp at the place of its location on the element. In other words, two such clamps of known construction located on a resistance element in certain longitudinal distance from each other will establish contact with wire turns depending on thecurvature I of the contacting surface of each clamp, and this contacting point of each clamp is diiiicult of controlu Very severe strains and stresses are imposed on a resistance element by such staking operation which usually causes considerable loss from breakage of winding strips as this operation includes attaching the clamps on the element so as to prevent their slipping which requires relatively great force in bending the wings of a staked clamp around the element.

Clamps of old construction crush into the resistance wire and into the insulating support dislocating the wire turns and streoyuently cutting the wire and thereby occasioning further damage and loss,

The wire may be loosened on the insulating support because agreat part or the stresses exteriorly imposed on a clamp is directly transmitted to the wire turns and is carried by the wire.

The clamps of old construction are, in some cases soldered to the wire in order to produce a strong and enduring con; nection between the clamps the wire a in order to locate the clamps definitely with respect to the wire and against displacement on the element.

.erous other objectionable which I have not enumerated above are presented by the old type of clamp. These features will appear by contrast with my 1nvention as the description progresses.

Generally stated, it is the aim of my invention to furnish a clamp for permanent transversal attachment to longitudinal resistances, which is simple in production and application, reliable in use, and which eliminates in production as well as in use all objections presented by prior constructions.

The clamp of my invention consists of a blank which can be conveniently punched in one stroke of the punching press, and which is provided with two oppositely disposed projecting wings for transversely embracing a resistance element, and with suitable projectionsdisposed at right angles to these embracing wings for serving as terminal lugs and as mounting lugs. Each of the embracing wings is provided with a longitudinal slot which is disposed transversely to the resistance element when the clamp is attached thereto. The longer sides of these slots are provided with heavy wedges or burrs for cutting between wire turns into the insulating support. No burr is provided on the ends of the slots in order to prevent cutting of the resistance wire when the clamp is attached to the resistance element. The center section of the clamp is slightly curved to provide a concave surface facing the resistance element longitudinally when the clamp is attached to the element, and the curvature in this section of the clamp remaining after forming the wings, which are left fiat, around the resistance support, will produce a slight spring tension in the clamp body, forcing the outer longitudinal edges of the clamp wings down and into accurate contact with certain wire turns on the insulating support. This simple structure inhibits resistance variations between clamps when the resistance element is bent or twisted, since each clamp attached to the resistance unit has established firm and definite contact with certain wire turns at the longitudinal edges of its embracing wings.

For convenience of definition, I will enumerate the various structural and functional features of my invention in the following brief statements of objects It is one object of my invention to provide a clamp having a curved center section to present a. concave surface to the resistance wire on a flat longitudinal insulating support for the-purpose of forcing the outer longi tudinal edges of the clamp to engage the transversely disposed Wire turns located there.

Another object relates to the provision of a curved center section together with flat wings laterally projectingfrom the curved center section and provided for embracing the resistance element transversely thereto.

neeaeav A third object relates to the provision of longitudinal slots in the laterally projecting embracing wings of the clamp and'to the provision of burrs drawn alongside the longitudinal sides of the slots in each wing for the purpose of furnishing a firm engagement with the resistance support by cutting into said support between the transverse convolutions of the resistance wire wound thereon.

A further object has to do with provision of suitable terminal and mounting lugs integral with the clamps attached to the resistance element and proportioning and shaping these lugs in such manner as to effect a saving in space and better adjustability of'the element as contrasted with .elements using clamps of prior constructions.

My invention may be said to incorporate numerous novel features which avoid the defects of, and furnish considerable advantages over, prior constructions. The wire turns are securely clamped and held by my novel clamps, due to the features intimated previously; loosening of the wire is avoided, since any strains and stresses imposed upon the clamp are transferred to the insulating ,support instead of to the wire turns; changes in resistance between'clamps when the insulating support is bent or twisted relative to the clamps are avoided due to the firm grip of the clamps on definite wire turns; staking and soldering operations are eliminated from the production process; at least one assem-' bling operation can be eliminated over the present practice, since as many clamps as desired can be fastened to a resistance unit in one stroke of the punching press. and other advantages are presented'by my invention as a result of functional and structural features not defined in the statements of objects, which will appear clear as the description progresses.

ll have illustrated the invention in the accompanying two sheets of drawings which show certain embodiments of the invention in various views, and which contain explana tory figures for describing the functions of my invention as contrasted with what is known in the art.

Figure 1 of the drawings shows a perspective view of my invention in one embodiment, i. e, it shows a clamp having a soldering lug as attached to a Hat resistance ele ment;

Figure 2 illustrates an enlarged cross-section of the. clamp taken on line 2-2 ofFigure 1;

Figure 3 presents a similar enlarged crosssection of aclump of prior eonstruetionto demonstrate one of the functions of my novel till) Cit? tion of one of the embracing wings as taken on line 5 of Figure 4;

Figure 6 shows an enlarged cross-section of the center section of the clamp taken on line 6-6 of Figure 4;

Figures 7 and 8 represent one stage of forming the clamp around a resistance element; and

Figures 9, and 11 show three elevations of a completely assembled resistance unit provided with two mounting clamps and one intermediate clamp.

Referring now to Figure 1, numeral 1 designates a fiat longitudinal strip of suitable insulating material such as fiber around which is coiled a resistance wire 2. The clamp of my invention, formed on the re sistance wire comprises a center section 3, a solderin lug 4 and two embracing wings 5 and 6. lots 7 and 8 are provided in these wings, separating the wings in two longitudinal sections 9-16 and 1112, respectively. The wings are formed around the resistance unit as illustrated in the drawings.

As will be seen from Figure 2, which is an enlarged cross-section of wing 5 taken on line 2-2 of Figure 1, the sides of slot 8 are provided with wedges or burrs l3 and let which extend hetween the wire turns and out into the insulating support, fastening the clamp definitely on the support and preventing longitudinal displacement. All strains stresses imposed on the clamp will, therefore, he transferred to the insulating and will not loosen the wire. will also he seen from the drawings that the center section 3 or the clamp is curved slight ly, presentng a concave contacting surface to the resi. ounce element, while the wings 5 6 l low, when the clamp is termed round the element as shown, the upper part of clamp, due to the curvature, wi ngage the wire turns at the edges, maintaining definite and lined line of corn The curvature remaining after the clamp is formed around the resistance elenient provide a slight spring tension, always ten ing to exert a force on the wire turns at the edges of the clamp.

- Should the insulating support he subjectedto bending or twisting, such action will not he detrimental and will not alter the re sistance values between the terminals of the clamps, hecause the wire turns are held lirmly by each clamp, as explained above, and are prevented from sl pping and shifting lon gitudinally to the element. A permanent connection is thus secured hetween the clamp and the resistance element.

Figure 8 illustrates by way of contrast the manner in which contact is maintained hetween a resistance element and the ordinary type of clamp. The cross-section shown in Figure 3 represents an ordinary clamp of prior construction as viewed in a manner corresponding to the view presented in Figure 2 of the clamp of my invention. Numeral 15 designates the insulating support carrying turns of resistance wire indicated by numeral 16. Formed around this resistance unit is the clamp of prior construction designated by numerals 17 and 18 which are part of this clamp hearing at the turns of the resistance wire as shown. The staking operation mentioned previously causes the clamp to bend so that the clamp, after forming, presents a convex contacting surface to the wire turns on the insulating support. It will be readily seen that any bending or twisting of the insulating support relative to the clamp will cause a slipping and displacing of the clamp on the wire turns and, consequently, a variation of the resistance values between clamps disposed on such an element.

This difficulty does not arise with the type of clamp which l have invented, since definite and reliable contact is estahlished with the wire turns located at the edges of the clamp and, accordingly, the efi'ective resistance loctween terminals will be substantially the resistance ot' the wire hetween the edges of the clamps connected to these terminals. The staking operation required for obtaining a secure connection in the ordinary clamp is eliminated, thereby avoiding loss from breal age of winding supports. The clamp is also prevented from slipping, due to the wedges or burrs on the wings which cut ir-To the insulating support as the wings are formed around the same. The operation oi attach ing the clamp to the element does not pro duce any strains and stresses because the burrs cut rather than crush into the insulating support as is the case with the ordinary clamp. All external strains and stresses imposed upon the clamp will he transferred to the insulating support, therehy preventing loosening of the wire turns.

in Figure 4- is shown the hlanlr of a clamp made in accordance my invention. This particular hlanlr is for a clamp having a soldering lug and a mounting lug as may he convenient when the clamp is used an end clamp. The hlanl: comprises two oppositely disposed ernhracing wings 19 and 20. Each of these wings is provided with a longitudinal slot designated by numerals 21 and 912, respectively. The hurrs on the edges of these slots are indicated by dotted lines. designated by numerals 23, 2d, 25 and 26. The ends of the slots, as will he remembered, are not provided with hurrs in order to prevent cutting the resistance wires when "the clamp is formed on the resistance unit, as these burrs, if provided, would be located transversely to the wire turns. However, it may he men tioned at this point that no troulole will result in case a wire is actually out in forming the clamp on a resistance unit. The edges of the clamp will hold the wire securely and is secured.

will prevent trouble and damage. The soldering lug 26 'is provided with a hole 27 for receiving a terminal wire, and the mounting lug 28 is provided with an elongated hole 529 for conveniently adjusting a completely assembled resistance unit provided with two endterminals formed of the blank shown in Figure 4.

Figure 5 is an enlarged cross-section of the clamp wing taken on line 55of Figure l, and illustrates particularly that the wing is fiat and that the sides of the slot 21 in the wing are provided with wedges or burrs 23 and 24. v

Figure 6 is an enlarged cross-section of the clamp body taken on line 6-6 of Figure 4:

for illustrating the curvature of this section of the clamp body, the purpose of which has been discussed previously.

The manner of forming the blank around a resistance unit is particularly shown in the two enlarged views presented in Figures 7 and 8. llhe blank is placed on a resistance element shown in dotted lines in these figures, and the wings l9 and 20 are bent over the resistance element. The bending of the wings l9 and 20 about the edges of the strip 1 occurs on a relatively sharp radius. The grip of the clamp at these edges is peculiarly great and it is here that the greatest hold of the clamp upon the bar is secured. will be observed that the burr '2425 will bite into the corners and adjacent margins of the bar and because these points are spaced a maximum distance apart a solid and permanent hold of the clamp upon the body oi: the bar The burrs need not be continuous, but preferably are so made. They should, for best results, be long enough to reach between the turns of the wire and embed themselves in the body of the bar. llhe soldering lug 26 and the mounting lug 28 are suitably'bent as shown.

'lhe completely assembled resistance element provided with two end terminals for mounting the element and with an intermediate terminal r"or tapping the resistance or dividing the resistance between the end terminals is shown in Figures 9, 10and 11. hi these figures, numeral 31 designates the resistance element, 32 and 33 are the end terminals, and 34: is the intermediate terminal. A more detailed description of these figures is thought superfluous in view of explanations given previously.

The terminals are positioned and formed around the resistance element by dies so that the variations in spacing between terminals is .very small, i. e., less than the spacing between consecutive turns of the resistance winding in practically all cases; Production costs may be materially reduced by the elimination of operations required in the assembly of. resistors using ordinary clamps. The costs may be further reduced and the uniformity oi the product insured by winding long strips of resistances and then cutting these strips into sections of desired unit length and attaching the clamps to these units without trimming the ends of the sections, thereby eliminating the difficulties which are encountered in winding short strips. Further cost reductions may be effected by the use of a nest for accurately positioning and securely holding as many clamps as may be required on a resistance element. lhis assembly nest is then employed incooperation with a punch press which folds all the wings of all clamps and forms them around a resistance element in one stroke.

llhe use of a terminal carrying a soldering lug and a mounting lug, as shown in Figures 4 to 11, inclusive, also effects a considerable saving in space over ordinary types of clamps. There are, for example, clamps provided with a lateral projection or having separate tail washers'for attachment to the mounting screws. All these types of clamps are more or less inconvenient in use and expensive; they waste space and present other objections already discussed.

1 have shown and described two embodiments of my invention, i. e., an and clamp having a soldering lug and a mounting lug, and an intermediate clamp having only a soldering lug for tapping a resistance element. It will be obvious, of course, that many other forms can be devised within the scope oi": my invention, that is to say, lugs projecting from the clamp body in different angles thereto, disposed either in the plane of the clamp body or of the resistance element, or suitably deviating therefrom as desired, and various combinations of mounting lugs and terminal lugs of various suitable shapes and formations demanded by individual requirements.

lit will therefore be understood that l have shown and explained certain embodiments of my invention merely for descriptive purposes and that I do not desire to be limited in the application of the invention to the precise structures of the embodiments which I have shown and explained, but only to the scope of the claims in which I have particularly defined my invention as it distinguishes from prior constructions.

What is claimed is 1. In, combination, a bar shaped insulating member, a conductor disposed upon the lateral surface of the member and supported thereby, and a clamp embracing the member and engaging the conductor. said clamp having an edge disposed circumferentially of the bar, said edge comprising an integral flange extending inwardly and projecting into the body of the insulating member.

2. in combination, a rodlike insulating member, a conducting member disposed upon the surface oi the member and supported its thereby, and a sheet metal clamp externally encompassing and gripping the conductor and substantially the full cross section of the member, said clamp having relatively sharp, circumferentially extending projections biting into the body of the insulating member.

3. In combination, a bar of insulation, a conductor wound upon and supported by the bar, a sheet metal clamp deformed into gripping engagement with the conductor and the bar, said clamp having an edge thereof provided with a sharp flange which engages and bites into the bar between turns of the conductor.

4. In combination, a bar of insulation, a conductor wound thereupon and supported thereby, and a clamp embracing the bar and conductor and being deformed into gripping engagement therewith, said clamp having a slot extending circumferentially of the bar, an edge of the slot having a sharp flange biting into the surface of thebar.

5. In combination, a bar of insulation, a conductor wound thereupon and supported thereby, and a clamp embracing'the bar and conductor and being deformed into gripping engagement therewith, said clamp having a slot extending circumferentially of the bar, an edge of the slot having a sharp flange biting into the surface of the bar, the unslotted portion of the clamp being arched in crosssection, the edges of the arched portion fixed- 1y engaging the conductor to maintain definite contact therewith.

6. In combination, a bar of insulation, a conductor supported upon the surface thereof, a C-shaped clamp embracing the bar and conductor and'being deformed into gripping engagement therewith, said clamp having an arched central portion, the edges of the arched portion defining fixed contact with the conductor, and circumferentially disposed slots on each side of the central portion, said slots having projections along their edges biting into the body of the bar.

7 In combination, a flat strip of insulation, a resistance wire coiled upon the same, and

a sheet metal clamp of C-shape pinched upon the same, said clamp havingslots parallel to its longer edges, the longitudinal edges of the slots having projections for biting into the strip, the body of the clamp being arched, thereby bringing its edges sharply and fixedly into engagement with the resistance wire.

8. In combination, a flat strip of insulation, a resistance wire coiled upon the same, and a sheet metal clamp of C-shape pinched upon the same, said clamp having slots parallel to its longer edges, the longitudinal edges of the slots having projections for biting into the strip, the body of the clamp being arched, thereby bringing its edges sharply and fixedly into engagement with the resistance wire, the body of the clamp having an integral lug extending clear of the active part of the winding for supporting the strip and winding.

9. In combination, aresistance element portion disposed on one fiat side and having end portions folded around the edges of the bar and into contact with the other flat side, the end portions where they fold about the edges of the bar having sharp burrs projecting between turns of the coil and biting into the bar to anchor the clamp upon the bar.

11. In combination with a resistor comprising a strip of insulation and a resistance conductor wound upon the same, a clamp having a body member extending across the width of one side of the strip and wing members wrapped around the edges and deformed to grip the resistor, the body member being wider than the win s and having a concaved face, the edges of t e concaved face fixedly engaging the resistance conductor and providing definite points of contact with the said conductor.

In witness whereof, I hereunto subscribe my name this 29th day of March, 1930.

NEWTON C. SCHELLENGER.

Images