US 2873336 A
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Description (OCR text may contain errors)
Feb 1959 L. TASSARA 2,873,336
CONTINUOUS VARIATION POTENTIOMETER Filed Dec. 13, 1955 2 Sheets-Sheet 1 aia INVEN TOR.
L U16 I 73557930 BY Feb. 10, 1959 L. TASSARA CONTINUOUS VARIATION POTENTIOMETER 2 Sheets-Sheet 2 Filed Dec. 13, 1955 INVENTOR. L we I TASSARA BY 1 A) 1' wey 2,873,336 CONTINUOUS VARIATION POTENTIOMETER I "Luigi Tassara,'Milan, Italy, assignor to Metal-Lux S. r. 1.,
The present invention concerns a continuous variation potentiometer with linear and logarithmic variationof resistance, having two or more adjacent layers one of which has e. g. the function of acting asa resistor and the other as a collector or supplemental variable resistor, or the resistor or collecting layers maybe arranged in such a manner as to have one ormore elements in common and one or more independent'elements.
It is well-known that the most common inconveniences of potentiometers are:
(b) Parasitic capacities between the lector;
(c) Non-continuous variation;
The potentiometer according to the present invention has .been developed and embodied in such a way as to be, able to reduce and, in many cases, to eliminate the above mentioned inconveniences.
This potentiometer consists of a support of insulating material, preferably of ceramic or vitreous material, upon which by means of any physical, chemical or mechanical process there are deposited two or more layers of which one has for instance the task of acting as a variable potentiometric resistor while one of the others has the task of acting as a cursor collector.
One of the particular characteristics of this potentiometer is that it enables the cursor collecting layer to act secondarily as a potentiometer or as a variable resistance together with the main potentiometric variation and to obtain secondary potentiometric variations.
For many applications, the collecting layer has closed annular shape with a resistivity value sensibly lower than that of the main resistant layer. For some special applications, the collecting layer has open annular shape with a smaller, equal or greater resistivity value as compared with that of the main resistant layer.
In some cases the potentiometer may have a number of resistivity layers and a number of collecting layers of different value; continuous or not, conveniently connected to obtain, with one single operation, multiple effects even independent of the main variation.
In this latter embodiment, the potentiometer offers one or more additional resistances, one-or more potentiometric resistivity values, variable depending on the angle of rotation of the shaft put in series with the cursor. These variations may follow a course in agreement or in contrast with the variations of the main poshaft and coltentiometric resistivity layer.
A particular arrangement of the potentiometer permits to solve the problem of the simultaneous variation of the output volume and of the timbre of the electronic audition instruments. It is known in fact that volume reduction is accompanied by the physiological effect of the attenuation of the lower frequencies of the acoustic band. In order to make up for this effect generally a second potentiometer is resorted to, which is mono-con- United States Patent "ice 2. trolled with the volume regulating potentiometer, and which in connection with convenient capacities operates a correction of the response curve tending to attenuate the higher frequencies of the acoustic band.
'The potentiometer according to the present invention permits to utilize the potentiometric resistant layer for the volume variation and the collecting resistant layer we device for varying the acoustic timbre and, there fore; with one single potentiometer and one single operation,;there are obtained the two aforesaid variations for which two distinct potentiometers appeared to be necessary heretofore.
Hence. it is an object of the present invention to provide acontinuous variation potentiometer having one or more resistant layers and one or more collecting lay ers-deposited and adjacent, connected, for instance, with a small bridge with brushes to obtain a direct electric contact'between the resistant layer or layers and the collecting layer or layers. One or more collecting layers .or resistant layers may be interrupted with the task of opening or closing supplemental circuits. The potentiometer with the interrupted collecting layer and, in this case, with an appropriated resistivity value, may be employed as a potentiometer with a number of resistant layers having a greater ratio between the length of path on the resistant layer andthe respective angle of rotation, utilizahle'in various ways and also for the purposes of a non-linear variation, or, as a potentiometricvariator with variable additional resistance, linear or not, in direct .01. inverse ratio as compared with that of the potentiometer and also astwo potentiometers with single control. Such a. potentiometer can be easily built with a structureenablingcontinuous rotation over 360.
To makethe invention more fully clear, a preferred embodiment will be referred to hereinafter, as illustrated diagrammatically by way of example in the accompanying drawings wherein:
Fig. 1 represents a diametral section of the potentiometer according to the invention;
Fig. 2 represents a plan view of the same potentiometer;
Figures 3 and 4 represent in plan two variants in the connections of the collecting layer.
With reference to Figures 1-2 it will be noted that with 1 there is indicated a support of insulating material, e. g. steatite, on which there have been deposited two metal layers, or two layers of a compound of oxides and of metals, marked with numerals 2-3.
In the structure which is described hereinafter, to deposit the layers 2 and 3 there has been preferred the method of evaporation under vacuo. In pursuance of the description, it is pointed out that with 4 there is designated a protecting cover fixed or Welded to the support 1, and this is to obtain dustand gas-proof sealing. The layers 2 and 3 have the shape of sectors of concentric circular annuli to the free ends of which there are welded the terminals 5, 5' and 6 (see Fig. 2). The annulus sector 3, called hereinabove collecting layer, is in many cases closed in itself and, therefore, it becomes a ring concentric with the annulus sector 2 (see 3), and has, in this case, the only task of acting as a cursor collecting layer.
Fig. 2 represents the interrupted annulus sector 3 with the terminal 6 welded at only one end. in this case the layer 3 has the task of acting as a cursor collector and as a variable resistance in the main potentiometric circuit with direct or inverse continuous variation.
Fig. 4 represents the interrupted annulus sector 3, with the terminals 6-6 welded to the two ends. In this case the layer 3, in addition to the task as a collector, has that as an independent secondary variator. Moreover, by connecting together the two terminals 6-6 there is obtained a solution analogous to Fig. 3, while if connectspect to the support 1, is destined to receive the control member (not represented in the drawing) while to the opposed end there is fitted the arm 14 built of insulating material at the free end of which there is provided a pressure contact which connects the circular annulus sectors 2 and 3. 1
In Fig. l, the pressure contact is represented in a simplified way by a small bridge with two brushes 15-;l5' electrically connected with each other and destined to slide respectively on the metal layers 2 and 3.
A potentiometer built in accordance with the principles described has proved to be:
(a) Affected only by extremely reduced parasitic capacities; (b) Anti-inductive; (c) Non-hygroscopic; (d) Noiseless;
with a highly appreciated continuous variation and with manifold possibilities of use in electronic circuits.
I claim: Y
1. A potentiometer comprising an insulating support member, at least one layer of electrically resistant material on said support member in the form of a first elongated band having its opposite ends spaced from each other to define a resistance element, a collector element "asrasae defined by at least one layer of electrically resistant material on said support member in the form of a second elongated band extending parallel to said first band and also having its opposite ends spaced from each other, contact means simultaneously engaging in a conductive relationship said resistance and collector elements, means supporting said contact means for movement along said first and second bands, first and second terminals connected to the opposite ends of said first elongated band of the resistance element, and at least a third terminal connected to one of the ends of said second elongated band of the collector element so that the latter can act as both a collector for current conducted from said resistance element by said contact means and as an addi tional variable resistance in series with the variable resistance of said resistance element.
2. A potentiometer as in claim 1; wherein at least one of said ends of the second elongated band extends beyond the adjacent end of said first band in the direction of movement of said contact means along said bands.
3. A potentiometer as in claim 1; further comprising a fourth terminal connected to the other of said ends of the second hand forming the collector element so that said second band can be adapted to function solely as acollector, by connection of said third and fourth terminals to each other, and connection to a selected one of said third and fourth terminals causes said second hand to add resistance in the circuit as a corresponding function of the position of said contact supporting means.
4. A potentiometer as in claim 1; wherein said first and second bands have difierent resistivities.
Tellkamp Jan. 6, 1942 Tellkamp July 11, 1956