US1527484A - Variable inductance coil - Google Patents

Description

2 Sheets-Sheet l Feb 24, 1925.

R. E. MBCDOWELL VARIABLE INDUCTANGE COIL Filed May 18, 1925 Feb. 24, 1925. 1,527,484

R. E. MacDowl-:LL

VARIABLE INDUCTANCE COIL FiledA May 18, 1923 2 Sheets-Sheet 2 I ozb?. ,3

V/Zf,

i: mmm

I vemar Patented Feb. 24, 1925.

UNITED STATES PATENT OFFICE.

ROBERT E. MAODOWELL, OF CLEVELAND, OHIO, ASSIGNOR TO THE WOR-KRITE MANUA FACTURING COMPANY, OF CLEVELAND, OHIO, A CORPORATION.

VARIABLE INDUCTANCE COIL.

Application filed May 18,

T 0 all whom t may concern:

Be it known that I, ROBERT E. MAoDow- ELL, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in Variable Inductance Coils, of which the following is a specification.

This invention relates to inductance coils and has particular reference to an improved form of variable inductance coil for use in radio circuits.

Heretofore it has been customary to vary the number of turns of wire of an inductance coil either by providing a movable contact finger or slider which is movable along the coil to engage separate turns of the wire, or by tapping the coil at certain definite intervals and connecting each tapI with one of a series of contact points over which a switch arm is movable to vary the number of turns in the circuit. These arrangements are each open to many objections, the most important of which is that the unused portion 'of the coil is always connected with the circuit and hence absorbs energy. This loss of energy is usually referred to as dead end loss and becomes an important factor i in radio circuits wherein the currents handled are of a very small value and each instrument must be designed and constructed for maximum efficiency,

It is the general object of the present invention to provide an improved manner of varying the number of turns of an inductance coil wherein the unused portion of the unit as a whole, greatly increased.

Another object is to provide an improved manner of varying the number of turns of an inductance coil which sha-ll be applicable with equal success to stationary or stator windings, and to movable or rotor windings.

Another object is to provide an inductance coil of the aforesaid character wherein the inductance may be varied progressively by small values.

A further object of the invention is to permit 100% inductive relationship by bringing portion of coil in use in a direct inductive couple.

1923. Serial No. 638,862.

A still further obj ect is to provide an improved inductance unit which shall be simple in construction, easy to operate, and which shall be inexpensive to manufacture.

lVith these and other objects in view, the invention consists in the various novel features of construction and arrangement or combination, all of which will be fully described hereinafter and pointed out in the appended claims.

In the accompanying drawings wherein I have shown certain illustrative embodiments of my invention but without intent to limit myself thereto, Fig. 1 is a vertical sectional view through a portion of a variocoupler employing my invention; Fig. 2 is a sectional view taken on the line 2 2 of Fig. 1; Fig. 3 is a vertical sectional view through the rotor of the inductance unit; and Fig. t is a similar view taken at right angles to Fig 3.

Describing by reference ycharacters the various parts illustrated 1 denotes a suitable insulated form over which the stator winding 2 of the inductance unit is wound. This form is preferably spherical in shape so that the rotorI winding, to be referred to more fully hereinafter, may be varied with respect to the stator winding by means of a rotary motion and thus occupy a minimum space. Rising from the form 1 is a substantially rectangular housing 3 also formed from insulating material and the upper end of this housing is normally closed by means of a. cap l which is conveniently secured thereto at each side by a. binding post 5. coil shall be eliminated from the circuit and hence the aforesaid dead end'losses shall be avoided and the efficiency of the inductance Journalled within the housing are a pair of shafts 6 which are arranged in spaced parallel relation and each shaft has mounted thereon a pawl 7. These pawls are each provided with suitable gear teeth 8 which are intermeshed so that movement of one pawl will cause a corresponding movement of the other in a reverse direction. One of the shafts 6 also has mounted thereon a segmental gear 9 which is pinned to the pawl as indicated at 10. This gear is ineshed with a pinion 11 which is mounted on a shaft 12 that 'is journalled in the cap 4. As shown in F ig. 2, shaft 12 projects through each side of the cap and is adapted to receive an operating lever such as a dial (not shown), while the opposite end is reduced Cil and housing is a. fiat or leaf spring 18 which" extends downwardly valongeach sideofthe housing and inwardly betnf'eensaid housing and the stator form 1, and then upwardly into engagement with its respectivepawl' 7.

These metallic springs serve as conductors,

as will be more fully explained hereinafter,

and in order to insure good electrical contact with their respective binding posts 5, I preferably surround the stein of each post with a metallic bushing 19 which offers an increased `area 'of contact between sa'id spring and post.'

In operation, the binding posts are connected in the circuit in any desired {man-ner, as for example, one to the aerial iand the other to the ground. Shaft ,12 is Vthen rotated which rotates pinion 11 and segmental gear 9 and this inlturn rotates the pawls 7 in opposite directions which serves to urge the fiat 'springs 18 progressively into lcontact with the previously bared turns of the stator .vinding.V It 'will be obvious that'the springs contacting withthe stator winding will short circuit the turns thereof with which they are in contact and hence these unused turns will Vin :effect be eliminated from the cicuit as a direct electrical path will be provided, through thel medium of the springs, direct to the binding posts. It y'will be 'noted that thesprings are preferably arranged'so that they -will normally fbe in'con# tact with the outer or Tfirst `and last turns of the stator winding-and in this position maximum inductance will be obtained. The inductance is gradually reduced as the springs progressively short circuit the turns of the winding and minimum inductance is obtained whenthe springs are in contact along their entireV length with the previously fbared paths on the stator winding In Figs. 3 and t I haveshown my invention applied to a movable or rotary winding. In these views, 25 denotes the rotor form which is made of a suitable insulating material and is provided with a winding 26. A hollow shaft or'sleeve 27 is secured to and projects from Vdiametrically opposite points of the rotor form, and these sleeves `serve as axes about which the. rotor revolves with respect to the stator winding to vary Vthe coupling between these windings. *One of these sleeves is preferably projected beyond thev stator form so that ali-operating handle such as a dial' (not shown) maybe conveniently applied thereto. Journalled wit-hin'each'sleeve 27 is a shaftv 28,and the inner opposing ends of these shafts are connected by means of Van insulatingftube 29 so that rotation of one of said shafts will cause a corresponding movement of the anglesthereto sol that said fingers lie in the saine' planeof rotation. The outer end-"of each iingeris bent to defin'eacontact shoe 3Q which is in the shape of a segment of a circleV andthes'e shoes extend in opposite directions as clearly shown in Fig. 3. The shoes areadapted'to'move thro-ugh diametrically opposite slots 33 formed in the rotor and thus contact progressively with the iniV ner surface of the previously bared turn'sof wire forming the rotor'w'inding. In'this manner theftur'ns of the rotorl windingare progressively short circuited from the outer edges rtoward the-center and hence a direct' electrical circuitv is obtained through the contact lingers and respectiveshafts-andthe short 'circuitedl' 4turns or 'unused portion? of the Winding .is eliminated Jfrom' the circuit.

In some instances it might be desirablej'to have both the primary or stator'winding andthe secondary or rotor ,winding variable, while in other'instances it might be desir able to haveV only the Ystatoror onlyv the rotor winding variable and such modifications are deemed'w'ithin tlie'scope'of the presentinvention. Y

While I havesliown and, described my in{ vention as applied' to whatV 4is commonly known as a variocoupler, it will be under# stood thatit'm'ay be applied with equal success to variometers or other form of inductance units employingv a single coil or j posite ends thereof toward the middle, to

short circuit successive turns in said sections, and means for operating?vv said' conv tacts simultaneously andA uniformly.-

2. VThe combination Awith an" inductance coil, of la pair of conductors arranged one 'adjacent eachend of the coil,and means for placing said conductors into contact with the l Vcoil toshort circuit succeeding turns from oppositev ends thereof, -to vary the inducta'nce'of the coilf 3.* The combination with an inductance -coil,'of a. pair-of conductors arranged one adj acent' eachend of the coil, andl meansY for s1 multaneously v'placing saldconductors yinto contact. with the coil to short circuit succeeding turns from opposite ends`thereof, to varythe nductance of the coil.

4f. The combination with anfinductance coil, of a pair of conductors arranged one adjacent each end of the coil, a shaft1 and means connecting said shaft Witheach of said conductors whereby rotation of the former will urge the latter simultaneously into Contact with succeeding turns of the coil from opposite ends thereof, to Vary the induetance thereof.

5. The combination with an inductance ooil7 of a pair of conductors arranged adjacent each end of the coil, a shaft and a pawl connected to each of said conductors and to said shaft whereby rotation of said of a coil wrapped around said surface and defining a segment of a sphere, flexible strip conductors adapted to engage successive turns of the coil from opposite ends thereof7 said strip conductors being adapted to uniformly short circuit successive turns of the coil from the ends toward the middle of the winding, and means for operating said strip conductors simultaneously and uniformly.

In testimony whereof I affix my signature in presence of two witnesses.

ROBERT E. MACDOWELL.

Witnesses:

B. VHITLEY, H. RODINE.

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