GB2349986A - Linear potentiometer - Google Patents
Linear potentiometer Download PDFInfo
- Publication number
- GB2349986A GB2349986A GB9907709A GB9907709A GB2349986A GB 2349986 A GB2349986 A GB 2349986A GB 9907709 A GB9907709 A GB 9907709A GB 9907709 A GB9907709 A GB 9907709A GB 2349986 A GB2349986 A GB 2349986A
- Authority
- GB
- United Kingdom
- Prior art keywords
- groove
- pickup
- casing
- potentiometer
- wound element
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C10/00—Adjustable resistors
- H01C10/30—Adjustable resistors the contact sliding along resistive element
- H01C10/38—Adjustable resistors the contact sliding along resistive element the contact moving along a straight path
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/02—Housing; Enclosing; Embedding; Filling the housing or enclosure
- H01C1/022—Housing; Enclosing; Embedding; Filling the housing or enclosure the housing or enclosure being openable or separable from the resistive element
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C10/00—Adjustable resistors
- H01C10/24—Adjustable resistors the contact moving along turns of a helical resistive element, or vica versa
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C10/00—Adjustable resistors
- H01C10/30—Adjustable resistors the contact sliding along resistive element
- H01C10/38—Adjustable resistors the contact sliding along resistive element the contact moving along a straight path
- H01C10/44—Adjustable resistors the contact sliding along resistive element the contact moving along a straight path the contact bridging and sliding along resistive element and parallel conducting bar or collector
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Adjustable Resistors (AREA)
Abstract
A linear potentiometer has a casing 1 with end fittings 2, 3, and has a shaft 6 extending through one of the end fittings 3, and mounting a slider block 7 on which electrical contacts are mounted to make sliding contact with a wound element and a longitudinal pick-up element. The end fitting 3 is formed from two axially juxtaposed parts 3a, 3b, with the outer one 3b of those parts snap-fitted into a recess (16, 17 figure 2) in the inner wall of the casing 1 such that the end fitting can be readily removed from the shaft 6, and the seals 19, 21 contained therein can be serviced. Furthermore, the slider block 7 has a face angled at an acute angle (figure 5), and has electrical contact springs clamped to the face, which make sliding contact with the wound element or pick-up element. A design for the plastic former which receives the wound element or pick-up is also disclosed (figure 3).
Description
2349986 POTENTIOMETER The invention relates to a potentiometer.
Potentiometers are widely used to provide a voltage signal which is proportional to physical displacement of a member and the invention is concerned with linear potentiometers where the voltage signal is proportional to the axial displacement of a shaft. In previously proposed potentiometers of this kind a wound element and a pickup extend longitudinally within a cylindrical housing, a voltage is placed across the length of the winding, the pickup has negligible electrical resistance and a slider block is connected to the shaft and mounts electrical contacts which resiliently engage the wound element and the pickup, the voltage existing between the zero potential end of the wound element and the corresponding end of the pickup being proportional to the axial displacement of the slider block and thus the shaft from the zero end of the wound element.
Sealing the potentiometer, particularly around the shaft entry, is always a problem, seal life is generally quite low and for example, five or six seal changes may be required during the life of a potentiometer.
Forming of the resilient electrical contacts for the slider block is an expensive and highly skilled operation.
Mounting of the wound element and the pickup in a plastics former so that they are maintained parallel is again an expensive and skilled operation.
Mounting of electrical connection pressure taps to connect the ends of the wound element and the pickup to wires to extend out of the casing again has caused troubles in the past as has the passage of the wires through end portions of the casing.
According to one aspect of the invention, a linear potentiometer comprises a tubular casing with a front end fitting in one end thereof through which a shaft extends wherein the front end fitting comprises two juxtaposed members each having a shaft seal therein and with an outer one of the said members provided as a moulding which can be snap fitted into a recess in the casing to retain the end fitting within the casing.
By unsnapping the outer member from the casing and removing the end fitting from the casing and front the shaft, the seals can be serviced to extend the life of the potentiometer. Preferably the recess in the casing is a circumferential groove and the outer member includes flexible portions mounting projections which can engage in the groove and be disengaged therefrom by defeeding the flexible portions towards the 5 axis of the casing.
According to another aspect of the invention, a slider block mounted on a shaft of a linear potentiometer has a face angled at an acute angle to the axis of the potentiometer, to which face are clamped electrical contact springs which make sliding electrical contact with a wound element or a pickup extending longitudinally within the potentiometer.
The contact springs can be clamped in a linear extending position but due to the angle of the mounting face are automatically curved to a desired curvature when engaged with the wound element or pickup thereby obviating the need for a "stroking" operation to preform a curve into the contact spring.
According to a further aspect of the invention, a groove in a plastics former of a linear potentiometer, which former extends longitudinally of the potentiometer, to receive a wound element or a pickup, is provided with a cross section which is greater than a semicircle such that the wound element or pickup can be snapped into the groove and retained therein by the edges of the groove due to the form of the groove.
Twin grooves for the wound element and the pickup are advantageously provided in one face of the former and in a middle portion of an opposite face a further groove is provided into which pressure taps can be clipped to make electrical contact between an electrical wire and the wound element or the pickup, the wires extending through an end fitting of the potentiometer to make external connection.
Preferably the end fitting is injection moulded in a mould through which the wires extend such that they are permanently sealed therein.
The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:
Figure 1 is a schematic cutaway view of a linear potentiometer according to the invention; 3 Figure 2 is a greatly enlarged version of the righthand end of Figure 1; Figure 3 is an end view of a former of Figure 1; Figure 4 is an enlarged view of the lefthand end of Figure 1; Figure 5 is a side view of a slider block shown in Figure 4; Figure 6 is a schematic sectional end view corresponding to Figure 4; and Figures 7, 8 and 9 show a plan view, side view and end view respectively of a pressure tap of a linear potentiometer according to the invention.
Referring to the drawings, and firstly to Figure 1, a linear potentiometer generally includes a cylindrical casing 1 which at one end receives a rear end fitting 2 and at the other end receives a front end fitting 3. A front end rod 4 with a connecting eye 5 is coupled to a shaft 6 which extends through the front end fitting 3 and at its rear end is connected to a slider block 7. The rear end fitting 2 has a connection eye 8 and is sealed in the cylindrical casing 1 by means of an O-ring 9 which is provided in an O-ring groove 9a. A former 10, shown in Figure 3, extends longitudinally within the casing 1, is mounted on the rear end fitting 2 and mounts in grooves 11 and 12 therein a wound element and a pickup rod respectively.
As can be seen in Figure 2, the front end fitting 3 comprises two juxtaposed members 3a and 3b each having a centre bore 13 to receive the shaft 6 and an external generally cylindrical surface to engage a counter-bore 14 provided at the end of the casing 1. A step 15 is provided at the end of the counter bore 14 and a further counter bored recess 16 is provided adjacent the extreme end of the casing 1 into which engage outwardly extending projections 17 on the end fitting member 3b. The member 3a includes an exterior groove 18a for an O-ring 18 and an interior recess 19a to receive a quad-seal 19, of known kind. Between the members 3a and 3b of the end fitting is a washer 20 and an inner recess 21a in the member 3b receives a felt seal 21. Transverse slots 22 in the member 3b provide flexibility for outer portions of the member 3b which mount the projections 17 to allow the projections 17 to snap into the groove 16 or be disengaged therefrom. By means of the division of the end member 3 into the members 3a and 3b, and as shown provided with the washer 20 therebetween, and the disengageable projections 17 and the recess 16, the life of the potentiometer can be greatly extended since it is possible readily to 4 disengage the front end fitting 3 from the casing 1 and replace the quad- seal 19 in the recess 19a and the felt seal 21 in the recess 21a. The leftward extending portion 23 of the member 3a, as viewed in Figure 2, forms a bearing for the shaft 6.
Referring to Figure 5 the slider block 7 shown therein is provided with a face 7a which is at an acute angle to the axis of the casing 1 and onto which face 7a a phosphor bronze electrical contact spring 24 is clamped to mount the spring 24 on the slider block 7. In fact the spring 24 is one of a pair of springs, one of which engages the wound element and the other of which engages the pickup rod. By providing the mounting face 7a of the slider block 7 for the pickup springs 24 to be at an acute angle to the axis of the casing 1, a previously necessary highly skilled operation of "stroking" the phosphor bronze spring to pre-set a curve thereinto can be avoided.
Referring to Figure 3, it can be seen that the grooves 11 and 12 for the wound element and the pickup rod respectively provided in one face of the former 10, which former 10 is a plastics extrusion, are formed with a section which basically comprises more than a half circle with the mouth of each recess formed by projections which due to their shape have some flexibility. Accordingly the wound element and pickup can be snapped into the grooves 11, 12 and retained therein by the form of the grooves. Previously grooves provided to receive such members were generally of square section and glue was provided beneath the members and subsequently cooked in an oven to cure it.
Figure 6 shows a pressure tap 25 to be engaged in a groove 30 provided in the former 10 on an opposite face thereof to the grooves 11 and 12.
As shown in Figures 7, 8 and 9 the pressure tap 25, which is formed of beryllium cooper sheet with a gold plate finish, is formed by pressing from a blank so as to have a tongue 26 at a mid position, two almost circular portions 27 and upturned portions in a V-formation 28 spaced along the length. The pressure tap 25 can be engaged in the groove 30 provided in an opposite face of the former 10 to the grooves 11 and 12 to connect a connection wire to the wire wound element or the pickup. Projections 31 at the mouth of the groove 30 can deflect to enable the circular portions 27 which are connected to contact wires to be engaged in the groove 30, the end portions of the V-formation 28 engaging the projections 31 which are restored by their own resilience to retain the circular portions 27 in the groove 30. The arm 26 projects through a slot in the former 10 to make electrical connection with the wound element or the pickup.
The end fitting 2 is moulded in a mould through which the electrical contact wires extend such that when the end fitting 2 is removed from the mould the wires extend therethrough from a position which will be within the casing 1 inboard of the O-ring slot 9 and out through a projecting portion 32 for external connection.
6
Claims (8)
1. A linear potentiometer comprising a tubular casing with a front end fitting in one end thereof through which a shaft extends wherein the front end fitting comprises two juxtaposed members each having a shaft seal therein and with an outer one of the said members provided as a moulding which can be snap fitted into a recess in the casing to retain the end fitting within the casing.
2. A linear potentiometer according to claim 1, in which the recess in the casing is a circumferential groove and the outer member includes flexible portions mounting projections which can engage in the groove and be disengaged therefrom by defeeding the flexible portions towards the axis of the casing.
3. A linear potentiometer in which a slider block is mounted on a shaft and has a face angled at an acute angle to the axis of the potentiometer, to which face are clamped electrical contact springs which make sliding electrical contact with a wound element or a pickup extending longitudinally within the potentiometer.
4. A linear potentiometer according to claim 3, in which the contact springs clamped in a linear extending position but due to the angle of the mounting face are automatically curved to a desired curvature when engaged with the wound element or pickup.
5. A linear potentiometer in which a groove in a plastics former which extends longitudinally of the potentiometer, which groove receives a wound element or a pickup, is provided with a cross section which is greater than a semicircle such that the wound element or pickup can be snapped into the groove and retained therein by the edges of the groove due to the form of the groove.
6. A linear potentiometer according to claim 5, in which twin grooves for the wound element and the pickup are provided in one face of the former and in a middle
7 portion of an opposite face a further groove is provided into which pressure taps can be clipped to make electrical contact between an electrical wire and the wound element or the pickup, the wires extending through an end fitting of the potentiometer to make external connection. 5 7. A linear potentiometer according to claim 6, in which the end fitting is injection moulded in a mould through which the wires extend such that they are permanently sealed therein.
8. A linear potentiometer substantially as hereinbefore described and illustrated with reference to the accompanying drawings.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9907709A GB2349986B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
GB0200407A GB2370696B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
GB0200405A GB2370695B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9907709A GB2349986B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
Publications (3)
Publication Number | Publication Date |
---|---|
GB9907709D0 GB9907709D0 (en) | 1999-05-26 |
GB2349986A true GB2349986A (en) | 2000-11-15 |
GB2349986B GB2349986B (en) | 2002-05-29 |
Family
ID=10850943
Family Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB9907709A Expired - Lifetime GB2349986B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
GB0200407A Expired - Lifetime GB2370696B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
GB0200405A Expired - Lifetime GB2370695B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
Family Applications After (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB0200407A Expired - Lifetime GB2370696B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
GB0200405A Expired - Lifetime GB2370695B (en) | 1999-04-01 | 1999-04-01 | Potentiometer |
Country Status (1)
Country | Link |
---|---|
GB (3) | GB2349986B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2917177A1 (en) * | 2007-06-06 | 2008-12-12 | Renault Sas | Starter battery connection wiring resistance simulation device for motor vehicle, has cables respectively connected to end of bar and cursor, where cursor is slidably mounted on bar, and device is mounted in series on starter circuit |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4165622A (en) * | 1976-04-30 | 1979-08-28 | Bourns, Inc. | Releasable locking and sealing assembly |
US4400687A (en) * | 1980-10-14 | 1983-08-23 | Sakae Tsushin Kogyo Co. Ltd. | Housing for use with a variable resistor |
US4712084A (en) * | 1985-03-22 | 1987-12-08 | Copal Electronics Co., Ltd. | Potentiometer |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2863031A (en) * | 1956-03-23 | 1958-12-02 | Myron A Coler | Precision potentiometers |
US2976508A (en) * | 1958-10-30 | 1961-03-21 | Waters Mfg Inc | Rectilinear potentiometer |
DE1790163C3 (en) * | 1968-09-20 | 1973-12-06 | Dale Electronics, Inc., Columbus, Nebr. (V.St.A.) | Small potentiometer with an elongated cuboid housing that can be closed by a housing cover |
US3703699A (en) * | 1971-11-12 | 1972-11-21 | Spectrol Electronics Corp | Trimmer potentiometer having means for lead screw misalignment compensation |
DE8908984U1 (en) * | 1989-07-24 | 1989-09-14 | Wilhelm Ruf Kg, 8000 Muenchen, De |
-
1999
- 1999-04-01 GB GB9907709A patent/GB2349986B/en not_active Expired - Lifetime
- 1999-04-01 GB GB0200407A patent/GB2370696B/en not_active Expired - Lifetime
- 1999-04-01 GB GB0200405A patent/GB2370695B/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4165622A (en) * | 1976-04-30 | 1979-08-28 | Bourns, Inc. | Releasable locking and sealing assembly |
US4400687A (en) * | 1980-10-14 | 1983-08-23 | Sakae Tsushin Kogyo Co. Ltd. | Housing for use with a variable resistor |
US4712084A (en) * | 1985-03-22 | 1987-12-08 | Copal Electronics Co., Ltd. | Potentiometer |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2917177A1 (en) * | 2007-06-06 | 2008-12-12 | Renault Sas | Starter battery connection wiring resistance simulation device for motor vehicle, has cables respectively connected to end of bar and cursor, where cursor is slidably mounted on bar, and device is mounted in series on starter circuit |
Also Published As
Publication number | Publication date |
---|---|
GB2370696B (en) | 2002-12-18 |
GB9907709D0 (en) | 1999-05-26 |
GB2349986B (en) | 2002-05-29 |
GB2370696A (en) | 2002-07-03 |
GB0200405D0 (en) | 2002-02-27 |
GB2370695A (en) | 2002-07-03 |
GB2370695B (en) | 2002-12-18 |
GB0200407D0 (en) | 2002-02-27 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PE20 | Patent expired after termination of 20 years |
Expiry date: 20190331 |