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Publication numberUS3764953 A
Publication typeGrant
Publication dateOct 9, 1973
Filing dateSep 18, 1972
Priority dateSep 18, 1972
Publication numberUS 3764953 A, US 3764953A, US-A-3764953, US3764953 A, US3764953A
InventorsLehnert G
Original AssigneeGen Motors Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Rheostats
US 3764953 A
Abstract
An encapsulated rheostat, particularly for data transmitters of filling level indicators in motor vehicle fuel tanks, has its resistive element enveloped in a resilient sheet of plastics material. A conductive inner layer is carried by the plastics sheet, and an adjustable contact pin presses against the sheet to establish localised contact between the conductive inner layer and the resistive element. The value of the electrical resistance of the rheostat is thereby variable by adjustment of the position of the contact pin. Air or other gas, or a liquid, confined within the encapsulating resilient plastics sheet tends to separate the resistive element and the conductive inner layer except at the region of localised contact provided by the adjustable contact pin.
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Description  (OCR text may contain errors)

United States Patent [191 Lehnert [451 Oct. 9, 1973 RHEOSTATS [75] Inventor: Gunter Lehnert, Russelsheim, Main,

Germany [7 3] Assignee: General Motors Corporation,

Detroit, Mich.

22 Filed: Sept. 18,1972

21 Appl. No.: 290,266

[52] U.S. Cl. 338/154, 338/199 [51] Int. Cl. H01c 5/00 [58] Field of Search 338/69, 154, 199

[56] References Cited UNITED STATES PATENTS 3,624,584 ll/l97l Ohno 338/154 X 3,699,492 10/1972 Yoshihara 338/69 Primary Examiner-Bernard A. Gilheany Assistant Examiner-4). A. Tone Attorney-dean L. Carpenter et a1.

[5 7] ABSTRACT uid, confined within the encapsulating resilient plastics sheet tends to separate the resistive element and the conductive inner layer except at the region of localised contact provided by the adjustable contact pin.

The resistive element may be of wire-wound construction, or may be resistive inner layer, possibly of strip form, carried by the plastics sheet.

7 Claims, 7 Drawing Figures RI-IEOSTATS This invention relates generally to rheostats, and is particularly concerned with rheostat constructions usable as data transmitters for filling-level indicators of fuel tanks in motor vehicles and aircraft.

Rheostats are used for a great diversity of purposes, such that there is frequently a need to encapsulate the resistances thereof in order to protect them from the effects of surrounding vapours or liquids, for example. In particular, data transmitters which are fitted into fuel tanks are exposed to such external influences, since they come directly into contact with the fuel or fuel vapours.

Objects of the present invention are to provide a rheostat construction which gives protection from harmful external influences, is simple and inexpensive to produce, operates reliably, and has a long working life.

In accordance with the present invention, such objects may be achieved by a construction in which the rheostat is encapsulated by a resilient sheet of plastics material having an' inner conductive layer against which an adjustable contact pin is arranged to press, whereby adjustment of the contact pin establishes different values of electrical resistance.

In one form of such an arrangement, a winding of resistance wire is applied to a flat insulating plate which is placed between two sheets of plastics material welded together at the edges.

In another form of arrangement, a conductive layer is carried by one half of the sheet, and a resistive layer is carried by the other half, and the two layers overlie each other. I

By encapsulating the resistance wire or the resistance layer by enveloping it in the plastics sheet, an advantageous and effective protection against external influences may be attained. Since such sheets can easily be welded together, a simple and cost-saving production is ensured. Air, or other gas, or a liquid, enclosed between the sheets ensures that when the position of the contact pin changes, the places previously pressed together by the contact pin are separated with certainty, so that the resistance values are faultlessly reproducible, and exact measurement values are assured for the entire working life. It is possible to employ thin, nonabrasive resistance layers and conductive layers which, in order to simplify production, may be applied by sputtering.

The encapsulated rheostat may be connected as a voltage divider if the construction is such that a conductive layer and a resistive layer are located side by side on the front half of the sheet, and a conductive layer overlying both of the said two layers is located on the rear half of the sheet, the contact pin being made so wide that it permits bridging of the two mutually adjacent layers.

Appropriately, the ends of the layers or strips are provided with metal supports for the attachment of leads or contact pins, for example by soldering.

In the drawing:

FIG. 1 is a plan of one embodiment of a rheostat in accordance with the invention, in the form of an encapsulated wire-type rheostat;

FIG. 2 is a longitudinal section through the rheostat shown in FIG. 1, along the line Il-Il;

FIG. 3 is a cross-section through the rheostat shown in FIG. 1, along the line IIIIII;

FIG. 4 is a plan of a second embodiment of a rheostat in accordance with the invention, in the form of an encapsulated layer-type rheostat;

FIG. 5 shows folded half-sheets of the rheostat embodiment shown in FIG. 4;

FIG. 6 is a cross-section along the line VI-VI of FIG. 4; and

FIG. 7 is a plan of a third embodiment of a rheostat in accordance with the invention, in the form of a rheostat designed as a voltage divider.

In the embodiment shown in FIGS. 1 to 3, the rheostat consists of a plastics plate 1 serving as a support for a wire winding 2, two sheets of plastic 3 and 4, and a contact pin 5 which presses the conducting layer 6 at the inside of the sheet 4 against the winding 2 in order to make localised contact, as will be seen from FIG. 2. The two sheets 3' and 4 are welded together at their edges at 7 so that the enclosed resistance 1, 2 cannot slip. The two leads 8 and 9 for the electric current are hermetically embedded in the edge 7. The contact pin 5 is displaceable: reference numeral 10 designates its path. The air enclosed between the resilient sheets 3 and 4 ensures that, during movement of contact pin 5, the conductive layer 6 tends to be separated from the winding 2 of the resistance, so that contact is made only at the place at which the contact pin 5 is currently situated.

In the embodiment shown in FIGS. 4 to 6, two layers, of metal and resistance material respectively, are applied to two associated sheet half-portions 15 and 16. A conductive metallic layer 17 is carried by the upper half 15 and a resistive layer 18 is carried by the lower half 16. Located at the ends of the layers 17 and 18 are metal electrodes 19 and 20 to which lead-in conductors in the form of contact pins 21 and 22 are secured by soldering. Following application of the layers, the sheet half-portions 15 and 16 are folded and welded together at their common edge 23, with the layers 17 and 18 inside, as will be seen in FIGS. 4 and 6. The bottom edge 24 is formed by the fold which arises when the two halves 15 and 16 are closed together.

The mode of operation of this embodiment is the same as for the embodiment shown in FIGS. 1 to 3. Here again, the enclosed air (or other enclosed gas, or liquid) ensures the separation of the two layers 17 and 18 during the movement of the contact pin 5 (here omitted for simplicity).

In the embodiment shown in FIG. 7, two layers are applied side by side to the front plastics sheet, namely a conductive layer 30 and a resistive layer 31, these two layers being bridged by an oval contact pin 32. A conductive layer overlying both these layers 30 and 31 is applied to the rear sheet. This embodiment is intended for use as a voltage divider, and has three connecting leads 33, 34 and 35.

The present invention is not limited to constructions corresponding to those of the above-described embodiments illustrated in the drawing. Many possibilities of modification exist as regards the construction and design of the rheostat and the arrangement of its individual components, without departing from the scope of the present invention. As has already been mentioned, instead of air, a different gas, or a liquid, may be enclosed in the interior space between the two sheets such as 3 and 4.

3 If required, several resistance strips may be provided on one sheet in place of a resistance layer, whereby the rheostat construction may be adapted to a great number of operating conditions.

If, for example, in the FIG. 7 embodiment, the conductive layer applied to the rear sheet is reduced to the width of the resistance layer 31 over its entire length, and if the connection 34 is joined to this rear layer, then in the lowermost position of the contact pin 32 a pilot light, for example, can be additionally controlled, by way of the connection 33. i

I claim:

I. A rheostat comprising a resistive element,

a resilient plastics sheet encapsulating the resistive element,

a conductive inner layer carried by the plastics sheet,

first contact means extending from the resistive element to the exterior of the encapsulating plastics sheet,

second contact means extending from the conductive inner layer to the exterior of the encapsulating plastics sheet, and

a contact pin arranged to press on the encapsulating plastics sheet and adjustable to establish different values of electrical resistance between the first and second contact means.

2. A rheostat comprising a resistive element,

a resilient plastics sheet encapsulating the resistive element,

a conductive inner layer carried by the plastics sheet,

first contact means extending from the resistive element to the exterior of the encapsulating plastics sheet,

second contact means extending from the conductive inner layer to the exterior of the encapsulating plastics sheet,

fluid interposed between the resistive element and the conductive inner layer and tending to separate same, and

a contact pin that is arranged to press on the encapsulating plastics sheet to thereby establish localised contact between the conductive inner layer and the resistive element, and is adjustable to establish different value of electrical resistance between the first and second contact means.

3. A rheostat comprising a resistive element comprised of a flat insulating plate I carrying a winding of resistance wire,

a resilient plastics sheet encapsulating the resistive element, said plastics sheet being comprised of first and second sheet portions welded together at their edges,

a conductive inner layer carried by the plastics sheet,

and

a contact pin that is arranged to press on the plastics sheet to' thereby establishv localised contact between the conductive inner layer and the resistive element, and is adjustable to establish different values of electrical resistance.

4. A rheostat comprising an encapsulating resilient plastics sheet comprised of first and second sheet portions folded against one another about a common edge and welded together at their other edges,

a resistive element comprised of a resistive inner layer carried by the first sheet portion of the encapsulating plastics sheet,

a conductive inner layer carried by the second sheet portion of the plastics sheet and arranged to overlie the resistive element when the first and second sheet portions are folded against one another,

fluid interposed between the resistive element and the conductive inner layer and tending to separate same, and

a contact pin that is arranged to press on the encapsulating plastics sheet to thereby establish localised contact between the conductive inner layer and the resistive element, and is adjustable to establish different values of electrical resistance.

5. A rheostat comprising an encapsulating resilient plastics sheet comprised of first and second sheet portions hermetically secured together at their edges,

a resistive element comprised of a resistive inner layer carried by the first sheet portion of the encapsulating plastics sheet,

a first conductive inner layer carried by the first sheet portion of the encapsulating plastics sheet at a location alongside the resistive inner layer thereof,

a second conductive inner layer carried by the second sheet portion of the encapsulating plastics sheet and overlying both the resistive element and the first conductive inner layer, and

a contact pin that is arranged to press on the encapsulating plastics sheet to thereby establish localised contact between the second conductive inner layer and both the resistive element and the first conductive inner layer, and is adjustable to establish different values of electrical resistance.

6. A rheostat according to claim 5, in which first contact means extends from the first conductive inner layer of the encapsulating plastics sheet to the exterior of the encapsulating plastics sheet, and second and third contact means extend respectively from opposite ends of the resistive element to the exterior of the encapsulating plastics sheet, for connection of the rheostat as a voltage divider.

7. A rheostat comprising an encapsulating resilient plasticssheet comprised of first and second sheet portions sealed together at their edges,

a resistive element comprised of a resistive inner layer carried by the first sheet portion of the encapsulating plastics sheet,

a first conductive inner layer carried by the first sheet portion of the encapsulating plastics sheet at a location alongside the resistive inner layer thereof,

a second conductive inner layer carried by the second sheet portion of the encapsulating plastics sheet and overlying the resistive element,

first contact means extending from the first conductive inner layer of the encapsulating plastics sheet to the exterior of the encapsulating plastics sheet, and second and third contact means extending respectively from opposite ends of the resistive e element to the exterior of the encapsulating plastics sheet, the second contact means also being connected to the second conductive inner layer,

a contact pin that is arranged to press on the encapsulating plastics sheet to thereby establish localised contact between the second conductive inner layer and both the resistive element and the first conductive inner layer, and is adjustable to establish different values of electrical resistance, and a pilot light connected to, and controlled by, the first contact means.

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Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3624584 *Feb 13, 1970Nov 30, 1971Nippon Musical Instruments MfgVariable resistance device for an electronic musical instrument
US3699492 *Nov 9, 1971Oct 17, 1972Nippon Musical Instruments MfgVariable resistance device for a portamento performance on an electronic musical instrument
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4333068 *Jul 28, 1980Jun 1, 1982Sangamo Weston, Inc.Position transducer
US4573106 *Aug 1, 1984Feb 25, 1986Alps Electric Co., Ltd.Illuminated slide rheostat
US4644893 *Aug 6, 1984Feb 24, 1987International Hydraulic Systems, Inc.Position indicating apparatus for use in a boat leveling system
US4651123 *Aug 6, 1984Mar 17, 1987International Hydraulic Systems, IncLinear potentiometer
US4928392 *Feb 16, 1988May 29, 1990General Electric CompanyDiameter gauge
US5334967 *Jun 29, 1993Aug 2, 1994Illinois Tool Works Inc.Voltage divider
Classifications
U.S. Classification338/154, 338/199
International ClassificationH01H13/702, H01H13/70, H01H13/703, H01C10/00
Cooperative ClassificationH01C10/00, H01H13/703, H01H2231/038, H01H2221/014, H01H2211/002, H01H13/702
European ClassificationH01C10/00, H01H13/702