US1550277A - Inductance coil - Google Patents

Description

Aug. 18, 1925.

. A. ONWOOD INDUCTANCE COIL Filed Feb. 19,- 1923 Famed Aug. 18, 1925.

UNITED STATES res-am PATENT ,oFFicE.

ANDRE ONWOOD, OF LONDON, ENGLAND.

INDUCTANGE COIL.

Application filed February 19, 1923. Serial No. 620,095.

This invention relates to inductance coils and more particularly to inductance coils suitable for use in instruments for wireless signalling. An object of the present invention is to enable inductance coils to be produced. at a cheap rate with increased mechanical strength and, at the same time, with reduced high frequency resistance and self capacity. Another object of this invention is the provision of a set of such inducttance coils, the coils of the set having substantially the same winding volume and being readily interchangeable in use in the same radio (or wireless) instrument and progressively increasing in number of turns (and consequently in inductance) so as to permit different ranges of wave-lengths to be dealt with by the same instrument.

With these objects in view, according to the present invention, a set of inductance coils are constructed, each without any magnetic core and each designed for one range of a series of ranges of wave-lengths for use, for example, in a wireless receiving instrument and constructed so that the spacing between successive turns of a layer and the spacing between successive layers are different for each coil of the set. The spacing is, in fact, less the higher the wave lengths are over which the particular coil is designed to be employed. This results in lower self-capacity and greater efficiency. By this means the set of coils may be designed such that the windings for all the coilsof the set are of substantially the same volume so that the coils are interchangeable for use in the same radio receiving instrument, the coils being capable of being readily substituted therein for'one another-and affording a wide range of tuning with a single instrument.

Such coils are wound on formers, the

cheeks of which are connected together wholly by means of insulating material. The members which space the cheeks apart and hold, them together may also serve to space apart successive layers of the winding. A convenient form of such a spacing member is a rectangular strip with a reduced portion or neck near each end. The heads of said strips are pushed through narrow radial slots in the cheeks of a width suiticient to allow the smaller dimension of the rectangle to pass; then the strip is turned through a right angle so that the neck portion of the strip remains in the radial slots and holds the cheeks firmly together.

Two inductance coils constructed in accordance with the present invention'are illustrated' in the accompanying drawings in which M Figure 1 is a front view of a coil partly in section and with part of one cheek broken away;

Figure 2 is an edge elevation with part of the external wrapping removed; Y

Figure 3 is a detailed view in perspective of a spacing piece; and

Figure 4 is similar to Figure 1 and shows a modified coil, the inductance of which differs from that of the coil illustrated in Figs. 1 and 2 and which may be made to serve as one of a set of inductance coils of which the coil shown in Figs. 1 and 2' may formanother.

As shown in the drawings, each inductance coil consists substantially of a pair of cheeks a, b which may, for example, be

stamped from vulcanized fibre. The cheeks are substantially circular with an extension 0 at one part of the circumference. Each of the cheeks, as shown, has stamped in it nine radial slots but, of course, this number of slots may be varied. The radial slots extend down to a centre piece d consisting of a tubular piece of insulating material serving to hold together the cheeks during winding. A. layer of wire with the turns suitably spaced is wound upon the centre piece (I and then one by one spacers suchas e are placed in position.

The spacer e is a rectangular strip also of vulcanized fibre with a head f, g at each end separated from the main part of the strip 6 by narrow necks h, is. The radial slots are wide enough to allow the strips 6 to be passed through them when the latter are turned so that their larger dimension lies along the'slot. When the head portions 7', g are passed through corresponding slots in the two checks (1, b the strip e is turned commodate the neck portions 7t, 70 and thestrip 6 therefore holds the cheeks firmly spaced apart and also holds them together,

preventing them from spreading.

When a complete ring of such spacers is placed in position, the winding goes on to form a second layer around these spacers; then a second ring of spacers is placed in position and another layer wound. The winding is clearly seen at Z in Figures 1 and 4:. This method of winding goes on until the inductance of the coil has reached the desired value, the two ends of the winding being connected to terminals and the coil completed by a covering of waterproof tape m.

The terminals in the "form illustrated com prise a pair of split pins n,'0 which are screwed into a block p of insulating material. The block g) has a width equal to the distance between the cheeks and is of a size to fill in the spaces between the two extensions dot the cheeks. It is held in position there by screws 0". The split pins are screwed through the block p until shoulders s abut against the outer surface of the block p. The ends of the coil are soldered to the inside ends of the pins n, 0, the inner end of the wire being brought up outside the cheek at around spacing strips as seen clearly at t. It is worthy f note that apart from the conductor Z of the coil, the only metal parts used are the terminal ins a, 0' and the screws 1". These are place apart from the winding and thus produce practically no losses in the coil." Of course,-it is quite easy to take any number of tappings from intermediate points in the winding and then, of course, more than two terminals will be necessary. It will be noted that when the coil is complete, all the spacing pieces engaging with the side cheeks a, I) give great rigidity which ensures constant values for the electrical constants of the coil. It is convenient from the manufacturing point of view, for all the spacers to be of one size. They may be, for example, of a cross-section one-eighth of an inch by one-sixteenth of an inch and then whenmore than one-sixteenth of an inch is desired between successive layers, two or more spacers can be used together. The only difference, in this respect, between the coils shown in Figures 1 and 4 is that in Figure 1, as can be seen, there are two spacers between, successive layers of the coil and in Figure 4 there are three, spacers between successive layers.

In making a set of inductance coils of this pattern for a wireless receiver, for example, it is clear that the inductance coils for the lower ranges of wave length will have a ma am comparatively few turns and both the turns and successive layers will be spaced well apart; thus a number of spacing pieces 6 will be used between successive layers. For the higher ranges of wave length, however, with a greater number of turns in each coil, less spacers will be used between successive coils and b this arrangement a set of coils esigned sothat the total volume can be so of the winding. is substantially the same for all the coils (as will be observed upon comparing the windings shown in Figs. 1 and 4) .This, of course, has the advantage of standsults the still further advantage that the several coils of the set are interchangeable for one another in use in a radio receiving set (or instrument) that is, in the eveiitthat the set of coils is used in conjunction with a Wireless receiving instrument wherein the tuning is effected by one or more variable condensers, and it be desired to listen in to signals on a comparatively low wavelength, there is selected from the set of coils one of the coils that is formed with a relatively small number of turns and the pins 11, 0, of this selected coil are inserted in the sockets provided in the Wireless receiving set, this pin-and-socket connection being the only switching connection required. Tuning is now sought t be effected by means of the condenser. If itshould appear that the signals are being transmitted on a wavelength that is higher than any included within the range of the chosen coil, the chosen coil is removed from the radio instrument and is replaced therein by an appropriate coil from the same set of coils, the substituted coil having, of course, a larger number of turns to permit tuning for the higher wave-length on which the signal is apparently being sent. This replacement manoeuvre or substitution of one coil for another of the same set of coils in the same radio instrument makes the apparatus capable of receiving signals over a wide range of wave-lengths and is practicable to be effected for the reason that the coils, although varying widely in number of turns and so in inductance, are formed on mountings that "are entirely similar in shape and dimensions and are so wound that their winding-volumes are substantially identical or the same, as herein shown and described. Moreover, the winding-volumes being the same, the air-spaces between the relatively few turns of the coils designed for use where the signals are being transmitted on a comparafrequency currents.

tivelylow wave-length, are wide, and this results in the reduction of the self-capacity of such coils to almost the vanishing point and in the avoidance of an increase of the natural wave-lengths of such coils due to coils designed for use with relatively high wave-lengths and it is practicable to place the turns of fine wire quite close together so thatthe air-spaces therebetween are relatively narrow and the windingwolumes of these coils may be made the same as the winding-volumes of the coils of few turns of coarse wire.

If desired, of course, a space may be left through the windings, so that a rod could be passed completely through the winding along a diameter and would then serve to rotate the coil.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. An inductance coil comprising a pair of cheeks of insulating material formed with However, the objec tions based on the ground of self-capacity are by no means so important in the case of a plurality ofradial slots, a pluralityof insulating strips engaging said slots to space said cheeks apart and to hold them together,

and a winding wound in spaced layers, each layer being wound over a ring of said insulating straps.

2. A former for an inductance coil comprising a pair of cheeks formed with a plurality of radial slots and a plurality of 40 headed spacing strips adapted to protrude through corresponding radial slots of said two cheeks and engage the latter to maintain them in spaced relationship.

l 3. A former for an lnductance co1l,com-

prising a pair of cheeks of insulating mate rial formed with a pluralityof radial slots and a plurality of headed spacing strips of rectangular sections and of dimensions enabling the strips to be passed through the 5 slots and to be turned to lock the said cheeks in spaced relationship.

4.- A11 inductance coil comprising a pair of cheeks of insulating material formed with a plurality of radial slots, a winding wound in spaced layers and a plurality of rings of insulating spacing strips introduced between each pair of adjacent layers to engage corresponding slots in said cheeks to maintain said cheeks in spaced relationship.

ANDRE o-Nwoon.

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