Патент USA US2406720код для вставки
Aug. 27, 1-946. c, JAN VAN LQON 2,406,720 INDUCTANCE DEVICE Filed March 1'7’, 1943 Fly. H04 g. #4 * r/'9.'32 2% 3 BY "22m T’atented Aug. 27, 19746 ' 2,406,720 UNITED STATES PATENT OFFICE 2,406,720 INDUCTANCE DEVICE Carol Jan van Loon, Eindhoven, Netherlands, as signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application March 1'7, 1943, Serial No. 479,465 In the Netherlands March 8, 1941 1 Claim. 1 (Cl. 171-242) The invention relates to self-induction coils whose self-induction may be adjusted by a core of magnetic material which is slidable in the ?eld of the coil, said coils being referred to herein after as “slidable~core coils.” These slidable core coils are utilized inter alia in radio-receiv ing sets in which they may form part of the tuning means. In practice it is often desirable that the value 2 frequency difference will be obtained not only at the limits of the respective frequency ranges of said circuits but also at one or more interme diate points. In the drawing: Figs. 1 and 2 are curves showing conditions of tracking and mistracking between a pair of per meability tuned circuits at various positions of adjustment of the tuning cores. Fig. 3 discloses of the self-induction of the slidable-core coil as 10 a known construction for effecting inductance a function of the position of the iron core should variation in coils. Fig. 4 discloses a coil and core have a predetermined course. Such is the case combination, in accordance with the present in inter alia in superheterodyne receivers if in the vention for effecting a predetermined inductance tuning circuits use is made of slidable-core coils. variation. Figs. 4a and 4b are cross-sectional As is well-known, with a superheterodyne re 1 ceiver there must exist over the whole of the wave range a constant difference in frequency views taken respectively, on the lines a,—a and and a capacity in parallel with the variable con whereas the curve 11 indicates the course which really occurs if no particular steps are taken. In order to obtain the desired course it is necessary, b—~b of Fig. 4 and Fig. 5 discloses curves showing the improved tracking relation obtained with the between the tuning of the oscillator circuit and present invention. that of the preceding circuits so that, given a Figure 1 shows the course of the divergence d determined course of the tuning of the preceding 20 in kilocycles as a function of the stroke S in milli circuit, a determined course of the tuning of the meters of the slidable core in the absence of pre oscillator circuit is ?xed. cautionary measures for effecting tracking at If the tuning is effected by means of a ?xed an intermediate point. inductance and a variable condenser, a substan In Figure 2 the curve I indicates the desired tially constant difference in frequency may be ' course of the self-induction L of the coil as a obtained by connecting a capacity in series with function of the stroke of the core in millimeters denser. These additional capacities should pref erably be formed as trimmers in order to ensure that adjustment is possible. If, however, the tuning is effected by means of as ensues from Figure 2, to increase the slope of the self-induction variation at the beginning of the stroke and to decrease this slope at the end of the stroke. a variable inductance and a ?xed capacity, as is the case with the use of slidable-core coils, it would be necessary to try in a similar manner to According to British patent speci?cation 410,217 obtain the desired result by connecting an addi 85 it is known to increase the slope of the variation tional inductance in series with and an addi of the self-induction of a slidable core by caus tional inductance in parallel with the variable ing a core of copper and a high-frequency iron inductance. This leads, however, to an expen core to slide, the one after the other, through sive and complicated system of connections. the coil. A construction suitable thereto is shown If these additional inductances are omitted, it 40 in Figure 3. is possible to obtain the correct difference in fre In this ?gure l represents a coil, 2 is a core of quency between the oscillator circuit and the pre high-frequency iron and 3 is a rod or tube of ceding circuits only at two points of the wave conductive material, for example, copper. Upon range, for example in the neighborhood of the assuming that the initial position is that in which highest and of the lowest frequencies; in the in the whole of the core 3 is within the‘ coil and the termediate region there is produced in this case, whole of the core .2 is outside the coil, the self however, an inadmissibly large divergence from induction of the coil increases, when both cores the desired difference in wave-length, which di are caused to slide from the right to the left, to vergence may amount in the middle of the inter a higher extent than would be the case with the mediate wave-length range up to 60 or 70 kilo 50 use of a slidable core since the iron core exerts cycles. its action in a coil portion which steadily in It is, therefore, the main object of the present creases and, in addition, the copper core 3, which invention to improve the tracking relation be acts as a short-circuited winding, encloses a tween the signal frequency and oscillator circuits steadily decreasing number of lines of force. of a superheterodyne receiver so that the correct 55 Since, however, by utilizing this construction it aicavao 4 is possible to increase the slope of the increase of the self-induction but impossible to decrease this mentally and may have in a determined case the shape indicated in Figure 4 which diminishes in slope, the use of this form of construction cannot cross-section from each end inwardly toward give here the desired result. According to the present invention, in order to body of to slide, the coil, material the center. Otherwise, in constructing such a slidable-core coil the fact has to be taken into account that the presence of the copper body 4 necessitates an increase of the number of turns or again an in crease of the permeability of the slidable core in order to be able to obtain the same value of the maximum self-induction. Care should be taken being so chosen that the desired course of the in this case to ensure that the minimum value of self-induction is obtained. the self-induction does not increase, which may be effected by increasing the permeability of the core. In the absence of the copper strip accord ing to invention the course of the self-induc obtain with slidable-core coils a predetermined course of the self-induction as a function of the stroke of the core there is provided a conductive material which is caused jointly with the core, into the ?eld of the shape of the body of conductive In one form of construction according to the invention the body of conductive material is preferably provided on the core itself or, if the core is made of pressed material, it is pressed jointly with the core to form a mechanic unit. The invention will be explained more fully with reference to Figures ll and 5 of the accompany 20 ing drawing. Figure 4 shows a slidable-core coil of cylindri tion curve would become steeper over the whole of the range; by providing the copper body the course of the curve on the desired portions is restored to the desired slope. What I claim is: A. variable inductance device comprising a coil of the solenoid type, a core movable axially cal shape wherein the coil body is denoted by I, the turns of the coil by 2 and the slidable core by within the coil and adapted upon movement from In Figure 5 the course of the self-induction L 25 a position outside the coil to a position fully as a function of the stroke of the slidable core contained within the coil to vary the inductance is shown by curve I. of the coil in a predetermined manner as a func If for some reason or other it is desired that tion of the core‘travel, said core consisting of a the curve indicating the course of the self-induc substantially cylindrical body of magnetic mate tion should have a more horizontal course at the 30 rial and an insert of non-magnetic conductive beginning and at the end but a steeper course in the middle, this may be achieved, in accordance with the invention, by providing on the core 3 a body or insert 4 of conductive material which has a determined shape. The conductive mate rial may be for example, copper. The shape of this body or insert may be determined experi material embedded in the surface of said body, the surface of the insert being coextensive with that the body, and said insert diminishing in cross~section from each end inwardly toward the center. CAREL JAN VAN LOON.