US1639044A - Variable inductance - Google Patents

Description

Aug. 16,1927. 1,639,044

, G. F. MANSBRIDGE VARIABLE INDUCTANCE Filed Auml@ i924 George /l idge Patented Aug. 16, 1927.

UNITED STATES 1,639,04@ PATENT oFFl'cE.

GEORGE FREDERICK MANSBRIDG, F NEW BRNET, ENGLAND.

VARIABLE INDUCTANGE.

Application led August 16, 1924, Serial No. 732,531, and in Great Britain August 27, 1923;

This invention relates to variable inductances similar to those shown and described in the specification of United States Letters Patent No. 893,340 of 1908k granted to me.

Variable inductances as heretofore proposed possess certain defects, chief among),- which are (a) their restricted range of variation, (o) their electrostatic capacity and (c) their bulkiness and inconvenient shape. Now, it

is the object of this invention to remove these defects and to obtain in a small and convenient form a variable inductance having a large vrangev ofvariation and a small electrostatic capacity. v

According to this invention the inductance elements are `made of D-form, or substantially so, as explained in the aforesaid patent specification andwound so that their self Capacity is minimized. This I do by winding in a single layer with space between each convolution and the next or by one of the well known anti-capacity methods e. g.

that known as basket winding or I may employ two-layer or multi-layer windings wound in cellular, openwork, or other well known anti-capacity form. The inductance elements so prepared are mounted on discs in such manner that the mountings and their inductance elements can be rotated relatively to one another in order to vary the inductance.

In order that this invention may be the more clearly understood and readily carried into effect, I will proceed to 'describe the same with reference to the accompanying drawings, which illustrate by way of example, and not of limitation, the preferred embodiment of this invention, and wherein- Figure l is a plan of the bottom disc 40 showing the inductance elements mounted therein, and

Figure 2 is an under plan of the top disc also showing the inductance elements mounted therein.

Figures 3 and 4 are under plan and plan respectively of the parts of the instrument as assembled.

Figure 5 is a section on line 5-5 of Figure 3.

Figure 6 is an elevation of the instrument.

Referring to the drawings, the instrument comprises two discs a and b, preferably of ebonite or like insulating material. Mounted in the disc a are two kidney-shaped inse ductance elements c and d sunk slightly be-` low the outer vedge of the dise a and wound so as to have a low self-capacity. These elements are wound in opposite directions and theouter end of element c is joined to the inner end of the element d. The inner end of the element c is connected to a terminal c1 mounted on the underside of the disc a, and the outer end of element d is connected to a like terminal (Z1. The disc a is provided ywith supporting legs al.

In thedisc o are arranged two inductance elements e and f which are shaped, wound and arranged similarly to the inductance elements c and CZ which have their inner ends joined together. The outer ends of these elements are joined ate1 and f1 to flexible leads c2 'and f2 respectively. The leads pass through a Vmetal plug g fixed to the disc o and the saidy plug is insulated from the inductance'elements'by an insulating sleeve g1. The lower portion of the plug is rotatably mounted in a bushing a2 fixed in the disc a, and a nut g2 is screwed on to the lower extremity of the plug to 'keep the discs together.

The free ends of the flexible leads e and f2 are attached to terminals e3 and f3 mounted on the underside of the disc a.

By sinking in the inductance elements, as above described, I obtain the optimum position of thebest balance between maximum inductive effect and minimum capacity between the inductance elements on one dise and those on the other.

The upper edge of the disc a is provided with an upstanding lip a3 adapted to take into a circumferential recess, o1, formed in the lower edge of the disc o. vThe recess b1 is of such length that, in conjunction with the lip a3, it limits the rotary movement of one disc relatively to the other to 180".

To the top of the disc o is vulcanized or otherwise secured a boss b2 having a bevelled edge whereon is inscribed a scale of 180o which, in conjunction with a line marked on a pointer 7L, secured to the disc a, indicates the angle through which the top disc has been rotated in order to vary the inductance. The rotation of the disc b is effectedby means of a knob o3 which is fixed on a rod o", screwed into the plug Strips of metal may be provided to form connections between the terminals 01, d1, e3 and f3 so as to connect the inductance elements c and d and e and f either in series for high values or in parallel for low valuesu will be readily 'understoodthat by' ro-f any other suitable known method designed to give low self-capacity.

According to a modiieation, the induetance elements areembetlded in any suitable known substance having a low dielectric con- '7 stant.

To increase the range of variation the in duotanee elements may be Wound in two or more sections and. means may be provided Whereb one or more of the sections may conveniently be cut out of circuit(l In some eases the inductance elements may be of D-shape having the straight sides of each pair arranged contiguously, or they may be of circular or other than kidney shape.

Thus',A by this invention the advantages o f large range variability ofv inductance, conjointly with eornpactness of construction and, low electrostatic capacity are obtained.

I claim:-

In ai variable induo'tance, an u )per (lise having a partially oircumferentia 'groove, a lower dise having terminals on its underside and an unstanding stop, tivo substantialIy kidney-Shaped inductance elements in each disc, a bushing in the lower disc, a metal plug carried by the upper dise and passingr through the bushing in the lower dise, Hexible connections from the induetanee elements in the upper dise passing through the said plug to eert-ain of the terminals on the vunderside of the lower dise, connections from the inductance elements in the lower dise te other of the said terminals, temporary switch members to bridge the said terminals so as to Connect the said induetanceelement-s either in series or in parallel at Will, the arrangement beinU` such that the said stop abuts against the end of the groove in the upper dise and limits the relative rotar movement of the two discs to 180.

n testimony whereof I have signed my name to this specification.

GEUKGE FREDERICK MANSBRIDGE.

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