US2604275A - Resistor spool - Google Patents

Description

July 22, 1952 w, HULL 2,604,275

RESISTOR SPOOL Filed Sept. 28, 1946 INVENTOR. RICHARD W HULL avib [@77 0 NEW Patented July 22, l952 RESISTOR SPOOL Richard W. Hull, Pasadena; Calif., assignonto Consolidated Engineering Corporation, Pasadena, Calif., a corporation of California Application September 28, 1946, Serial No. 699,982

'1 This invention relates to electrical coil devices of the type woundcn spools such as inductances and resistances.

The principal object is to provide a spool construction for such wire-wound structures as will minimize the likelihood of damage tothe wire coil and its insulation.

It is a commonpractice to wind coils of insulated wire on a spool to provide inductance or resistance elements. In the case of resistance elements, it isoften desired to make them of the non-inductive type, and this requires reversal of the direction ofwinding at relatively short intervals, according "to a well-known practice. The reversals of direction are frequently performed by the provision-of a spool having a number of winding spaces or sections arranged around the longitudinal axis of the spool; and slots are cut in the partitions between the sections to enable the wire to be carried through from one section to the next. Itordinarily happens that when the wire is carried through a slot from one spool section to the next, it will be carried down around the inside circumference of the spool, so that subsequent layers of the wire will be wound around and rub alongthe strand which has first been carried down. This will frequently wearofi the insulation from the strand and sometimes produces short circuits.

In accordance withmy invention, I provide a spool construction which minimizes the undesired scraping-and wearing off of the Wire insulation.

- I carry out my invention by the provision of a spool having through its end member and/or partitions a slot which is off center, that is, extends along a segment of the spool section rather than through its center. g

A feature of my invention is theprovision of a pair of slots at the partition, and preferably the slots are tangentialto the core of the spool. According to one embodiment, for example, the slots are parallel to each other and'on either side of the center line. According to another embodiment, th slots are non-parallel and converge toward each other.

When the wire is carried through such slots, the wire comes down approximately tangential to the core of the spool 50 that subsequent turns of the wire do not rub against the original strand which has been carried through, and this minimizes the tendency toward damage to theinsulation. 1 i

The foregoing and other features of my invention will be better understood from thel'following detailed description. andthe accompanying drawings of which: I

hold the insulated wire winding. spool partitions 4 is in the form of a member 1 Claim. (01142 -113) Fig. '1 is a side view of a. spool inaccordance with my invention; I i- Fig. 2is an end view of the spool; Fig. 3 is an enlarged view showing partoi the spoolwith windings represented on it; Fig. 4 is a cross-section view taken at line tl ofFigpS; v

Fig. 5: is another enlarged view of. part of the spool showing a difierent arrangement of windings on'it;

Fig. 6 is a cross-section view taken at line 6-4; ofFig. 5;

Fig. '7 is a side view of a modification accordillg to my invention; and

. Fig.8 is a cross-section view taken at line 8.3 of Fig. 7. 1

Referring to Fig: l, the spool l comprises a pair of circular end members 2 and 3 between which arelocatedanumber ofpartitions d at spaced intervals apart, dividing the spool'into a number of winding-sections 5. .The spool may be of. any suitable material, for example bake lite or a rubber composition which will serve to Each of the having conical sides tapering to a narrower thickness at the outside, as shown in Fig. .1', so that each spool is provided with a central core 8 and outwardly tapering sides, this configuration being well adapted to receive a wire winding.

It is desired that a single continuous winding be carried from ,one spool section ,to another, and for this purpose each partition is provided with a pair of slots l and 8, the slots bein paralleLto each other and extending from the circumference of the partition-to the core 6 of .the spool. The slots are not arranged along a; d1? ameter oi the partition, but instead, are arranged alonga line forming a segment of the partition, and are spaced so that the direction of the slot is substantiallytangential to the circular corefi where the slots meet the core. This arrangement is illustrated in Fig. 2;

To form a coil for a resistor winding, an insulated wirewill be Wound in the sections 5' of the spool. Fig. 3'showssuch a winding, which is wound as a non-inductiveKresistance. The windingis formed byanv insulated wire 9 which may be a well known type or covered wiresuch as an enamel-coated wire. The windingis started by inserting the wire into the slot l of the end, piece -2, where .it will be suitably fastened or attached to aterminal memben. This'attachmentismade in the embodiment illustrated-by the provision of a terminal wire .lil whichr-is in sorted in a peripheral groove ll around terminal piece 2, the wire In being suitably twisted at l2 to hold a loop of the terminal wire tightly in the groove while allowing a convenient length of the terminal portion to protrude from the spool. The insulation will be scraped from wire 9 where it meets terminal wire I at groove H of the end piece, and it may be looped over the wire In and fastened by solder l3.

The wire 9 from the slot 1 is carried down into the winding section and wound on the spool in a counterclockwise direction (as viewed from the left end of the spool in Fig. 3) until a sufileient amount of the winding has been put into the section. Then the outermost strand of the winding is carried through the slot 8 of the first partition member nearest the end member 2, and the wire is brought down to the cylindrical base of the spool in the second section, and the winding is formed in the second section in the clockwise direction, that is, opposite to the direction of winding in the first section.

In passing through the next partition, the wire will be brought through the slot 8 on the other side of the axis of the spool, and the winding in the following section will be reversed, that is, wound counterclockwise like in the first section. In this way, the wire is brought through successive partitions through the alternate slots 1 and 8, and the windings in the successive sections are alternately clockwise and counterclockwise. It will be recognized that this change of direction of the winding will create a substantially noninductive type of resistance. At the end member 3, the end of the winding may be connected to a terminal wire such as the wire I5 which may be attached similarly to the attachment of terminal wire Hi.

It may. under some circumstances, be desired to wind all of the sections of the spool in the same direction. This can be done just as well as winding them in opposite directions as in Fig. 3. Fig. 5 shows an arrangement in which the sections are wound in the same direction. In Fig. 5, the

winding is carried down from the terminal wire [0 and wound in a clockwise direction in the first section of the spool, in a manner similar to the winding in the first section of Fig. 3. Then when the first section has received its full winding, the wire instead of being brought down through the opposite slot 1 is carried through slot 8 of the first partition; and in starting the winding in the second section, its direction is continued in the clockwise direction. The wire is carried through all subsequent partitions through the slot 8 on the same side of the axis of the spool, and the windings are all in the same direction.

The tapered shape of the spool partitions 4 is especially advantageous when shrinkable material for the spool is used. Bakelite and some other spool materials, for example, shrink with age so that the length of the spool tends to decrease somewhat. This has the effect of tending to compress and squeeze the windings in the sections. By reason of the tapered sides to the partitions, however, the winding is enabled to be squeezed outwardly somewhat if and when such shrinkage occurs, without the attendant danger of damage to the winding and its insulation if no room for squeezing out were permitted.

Another modification of a spool made according to my invention is illustrated in Figs. 7 and 8. In this embodiment there is provided the central cylindrical core IS with its two end members l1 and I8 and partitions l9 separating the spool into sections. The end members and the partitions diiier somewhat from those in Figs. 1 to 6, in that they do not taper toward the core of the spool, but instead, are in planes perpendicular to the longitudinal axis of the core. The slots 20 and. 2| through the end sections and partitions, instead of being parallel to each other as in the preceding embodiments, are at an angle to each other as shown in Fig. 8. In Fig. 8, the angle between slots 28 and 2| is shown as being substantially although it will be understood that some other angle might be used instead if desired. The slots, although at an angle to each other are arranged to be substantially tangential to the core where they meet the core.

Except for the difference in angularity of the slots, and other details such as the taper of the partitions, the windings in the spool may be made the same as the embodiments in Figs. 1 to 6, and the windings may be made the same way. The construction of Figs. '7 and 8 may have advantages over that of Figs. 1 to 6 in specific instances, for example, where the spool material is more brittle than is being used in the embodiments of Figs. 1 to 6. Where a brittle material is bein used, for example a ceramic or the like, it may be undesirable to space the slots close together and parallel to each other as in Figs. 1 to 6, and instead to space them somewhat further apart as shown in Figs. 7 and 8, to provide additional strength. Moreover, it may in some instances be undesirable to use tapered partition sections as shown in Figs. 1 to 6, and instead to use the straight-sided sections as shown in Figs. '7 and 8.

When straight-sided partitions are used such as is shown in Fig. 7, a spool material will usually be selected which does not shrink appreciably with age. A ceramic or porcelain material, for example, does not shrink much, and the coefficient of expansion of a ceramicis usually even less than that of the wire.

By my novel forms of spool provided with slots arranged accordin to my invention, it will be recognized that I have provided means whereby the windings in a spool may be made without such serious risk of injury to the insulation on the wire as if only a single centrally located slot were used, as has heretofore been the practice. By carrying theinitial lead of a spool section down through the slot which is substantially tangential to the inner cylindrical core of the spool on which the winding is to be carried, there is very little scraping of subsequent lays of the winding over the initial wire which is carried through.

It will be recognized that if a single slot were used and the wire carried down through the single slot, it would be bent in direction at the position where the slot meets the spool; that is, it will turn at almost a right angle in the direction of the tangent to the spool cylinder at the base of the slot. This will result in the subsequent turns of the wire striking the right angle bend and scraping the insulation ofi. If it should happen that the insulation should similarly be scraped off one of the subsequent turns, there would be a resulting short circuit of the turns.

By using the slot which is substantially tangential to the spool, in accordance with my invention, there will be no bend of the Wire at the point where the slot lets the entrance wireinto the base of the spool, and accordingly less likelihood of damage to the insulation.

It will be recognized that my invention is not limited to the particular embodiments shown in the drawing, which are given for illustration purposes rather than for purposes of limitation. Other modifications within the scope of my invention will suggest themselves to those skilled in the art. For example, the advantage of my invention will be obtained even though the spool has only a single section for winding. In such a case, the advantage will be had on the carrying down of the initial length or strand of wire from the terminal position to the base of the spool.

I claim:

A spool having a core for holding an electrical winding comprising a section in which the winding is placed and a boundary wall at each end 01! the section, at least one of the boundary walls having a pair of slots oiI center with reference to the plane which passes through the longitudinal axis of the spool and extending from the periphery of the partition to the core of the spool for passage of the lead in wire to the section, said slots being at substantially a ninety degree angle with respect to each other and lying in planes which are substantially tangential to the core of the spool where the slot meets the core.

RICHARD W. HULL.

REFERENCES CITED "I he following references are of record in the file o! this patent:

UNITED STATES PATENTS

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