US3676819A

US3676819A - Contact-free potentiometer

Info

Publication number: US3676819A
Application number: US884167A
Authority: US
Inventors: Werner Keller
Original assignee: Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 1968-12-17
Filing date: 1969-12-11
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11
Also published as: GB1225890A; DE1815160A1; CH510322A; AT295662B; FR2026334A1; NL6918264A; DE1815160C3; SE345545B; DE1815160B2

Abstract

A stationary elongated armature body and a permanent magnet are connected in a magnetic circuit. A guide plate of non-magnetic material is interposed between the armature body and the magnet. The guide plate is adjacent the armature body and has a recess formed therethrough and a galvanomagnetic resistor is embedded in the recess. The guide plate guides the magnet in gliding relation.

Description

United States Patent Keller 51 July 11,1972

[54] CONTACT-FREE POTENTIOMETER 72] Inventor: Werner Keller, Olching, Germany [73] Assignee: Siemens Aktiengesellschalt, Berlin and Munich, Germany [22] Filed: Dec. 11, 1969 [21] Appl. No.: 884,167

[30] Foreign Application Priority Data Dec. 17, 1968 Germany ..P l8 15 160.5

[5 2] US. Cl. ..338/32 R, 323/94 H [51] Int. Cl. ..H0lc 7/16 [58] Field ofSearch ..338/32, 32 H; 323/941-1 [56] References Cited UNITED STATES PATENTS 3,571,774 3/1971 l-luhvich ..338/32 R 2,752,434 6/1956 Dunlap, Jr.

3,359,522 11/1967 Albrecht et al. ..323/94 H 3,366,908 l/l968 Weiss et al ..323/94 11 FOREIGN PATENTS OR APPLICATIONS 1,185,557 3/1970 Great Britain ..338/22 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-41. Kinberg Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick [57] ABSTRACT A stationary elongated armature body and a permanent magnet are connected in a magnetic circuit. A guide plate of nonmagnetic material is interposed between the armature body and the magnet. The guide plate is adjacent the armature body and has a recess formed therethrough and a galvanomagnetic resistor is embedded in the recess. The guide plate guides the magnet in gliding relation.

13 Claims, 7 Drawing Figures Patented July 11, 1972 CONTACT-FREE POTEN'IIOMEI'ER DESCRIPTION OF THE INVENTION The invention relates to a potentiometer. More particularly, the invention relates to a contact-free potentiometer.

The contact-free potentiometer of the invention comprises a permanent magnet which may be removed across a stationary armature body, and a galvanomagnetic resistor or field plate. Field plates are bodies having electrical resistance which may be magnetically controlled.

The principal object of the invention is to provide a new and improved contact-free potentiometer.

An object of the invention is to provide a contact-free potentiometer which includes a field plate adjustable to provide a desired resistance magnitude which may be reproduced at any time.

An object of the invention is to provide a contactfree potentiometer having a resistance magnitude which, once adjusted, may be maintained without variation for a long period of time.

An object of the invention is to provide a contact-free potentiometer having a resistance magnitude which, once adjusted, may be maintained without variation for more than fifteen years.

An object of the invention is to provide a contact-free potentiometer which is sealed dust tight and is shielded against outside magnetic fields.

An object of the invention is to provide a contact-free potentiometer which is almost completely insensitive to production tolerances.

An object of the invention is to provide a contact-free potentiometer in which a layer of non-magnetic material interposed between the armature body and the magnet creates a space between said armature body and said magnet, which remains constant in each position of the magnet, thereby preventing the accumulation of foreign bodies between said armature body and said magnet, so that the potentiometer remains almost completely insensitive to production tolerances.

An object of the invention is to provide a contact-free potentiometer which functions with efficiency, effectiveness and reliability.

In accordance with the invention, a contact-free adjustable semiconductor potentiometer has a plate-shaped galvanomagnetic semiconductor resistor whose resistance may be determined by shifting a magnetic field in operative proximity therewith. The magnetic field is produced by a magnetic circuit having a permanent magnet and a stationary elongated armature. The potentiometer comprises a guide plate of nonmagnetic material interposed between the magnet and the armature body. The guide plate has a recess formed therein and the galvanomagnetic resistor is embedded in the recess. The guide plate guides the magnet in gliding relation.

The guide plate comprises a U-shaped frame aflixed to the armature body and forming a tunnel-like housing therewith enclosing the area of the magnet.

The guide plate comprises a brass sheet and is cemented to the armature body. The magnet comprises a permanently magnetic cylindrical rod having a pair of wafer-like poleshoes.

The guide plate further comprises a spring bolt mounted between the magnet and abutting against the frame. The guide plate further comprises a spiral spring in the area enclosed by the frame and abutting an axial end of the magnet whereby the magnet is movable relative to the spiral spring.

A container of substantially hollow cylindrical configuration has a closed bottom base and an open top base and encloses the potentiometer with the spiral spring adjacent the bottom. A cover of substantially hollow cylindrical configuration has an open bottom base and a closed top base and is adapted to engage the container in a threadlike manner as a micrometer screw.

The guide plate further comprises a spherical member mounted on the opposite axial end of the magnet between the magnet and the cover and abutting the magnet and the cover. The container has a groove formed therein and the cover has at least one bolt engaging the groove.

The cover has a border area on its cylindrical surface. The cover has a recess formed in its top surface adapted to receive an adjusting tool. The cover has a ring shiftably mounted on its cylindrical surface and having a scale division thereon.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing wherein:

FIG. 1 is a view, partly in section, of an embodiment of the contact-free potentiometer of the invention;

FIG. 2 is a side view of the enclosed contact-free potentiometer of the invention;

FIG. 3 is a top view of the embodiment of FIGS. 1 and 2, with the cover removed;

FIGS. 4 and 4a illustrate the two extreme positions of the magnet and armature body relative to each other; and

FIGS. 5 and 5a are two views of the layer of non-magnetic material illustrating the position of the galvanomagnetic resistor.

In the FIGS, the same components are identified by the same reference numerals.

As shown in FIGS. 1, 2 and 3, an armature body 4 is formed of a non-ferrous, substantially planar, iron rod. The armature body 4 is aflixed to a U-shaped metal frame 8 and defines with said frame a housing which encloses the area of a magnet l, 2, 3.

The magnet l, 2, 3 is a permanent magnet mounted for movement in axial directions alongside the armature body 4 within the housing formed by said armature body and the U- shaped frame 8. The magnet comprises a permanently mag netic cylindrical rod 1 having a first wafer-like poleshoe 2 at the upper end thereof and a second wafer-like poleshoe 3 at the lower end thereof.

A spring bolt or buckle 9 is affixed to the

poleshoes

2 and 3 of the

magnet

1, 2, 3 and abuts the inside surface of the U- shaped frame 8. The spring bolt 9 thereby urges the

magnet

1, 2, 3, in addition to the magnetic force at the areas of the

poleshoes

2 and 3 of said magnet, against a layer of non-magnetic material 5. The layer of non-magnetic material 5 is interposed between the annature body 4 and the magnet l, 2, 3 and comprises a thin brass sheet cemented to said armature body.

A recess 6 (FIGS. 5 and 5a) is formed through the layer 5 of non-magnetic material. A galvanomagnetic resistor or field plate 7 (FIGS. 4 and 4a and 5 and 5a) is embedded in the recess 6 formed in the layer 5 of non-magnetic material.

The magnet l, 2, 3 and the metal frame 8 are housed in a steel container 13 of substantially hollow cylindrical configuration having a closed bottom base and an open top base. The magnet l, 2, 3 is movable in the container 13 in axial directions thereof and in gliding relation on the non-magnetic layer 5. The magnet l, 2, 3 is thus movable between a position in which it is at a minimum or maximum distance from the galvanomagnetic resistor 7 positioned in the recess 6 of the nonmagnetic layer 5 and the maximum or minimum distance from said galvanomagnetic resistor.

A spiral spring 14 is positioned around the lower end of the magnet l, 2, 3 between the second poleshoe 3 of said magnet and the inside surface of the container 13 and abuts said poleshoe and said container. A steel cover 10 covers and seals the container 13. The cover 10 is of substantially hollow cylindrical configuration having an open bottom base and a closed top base and adapted to engage the container 13 in a threadlike manner as a micrometer screw.

The edge of the cover 10 which partly surrounds the container 13 is joined by bolts with said container. The housing provided by the container 13 and the cover 10 provides, without additional measures, and in an advantageous manner, a dusttight sealing of the potentiometer and complete protection against interfering magnetic fields.

manually rotated, with the assistance of a milled or border area 31 (FIG. 2) on its cylindrical surface, or with the assitance of a screwdriver or other suitable tool. The screwdriver is accommodated by a recess 30 formed in the outer top surface of the cover 10.

The rotating movement of the cover is translated into an axial movement of the

magnet

1, 2, 3 via the spherical member 1 1. A specific threading pitch between the container 13 and the cover 10 is selected to enable the adjustment and setting of the potentiometer at a desired precision, without the requirement for additional measures such as, for example, gears. The rotation of the cover 10 is limited by bolts 12 provided in the engaging edge of the cover 10 and functioning as stops for engaging a groove 25 formed in the container 13. The bolts 12 also prevent the housing from being unintentionally disturbed by preventing the cover 10 from being unintentionally removed from the container 13. The tightening of at least one bolt at the surface of the container may prevent an adjusted resistance value from undesired variation.

In the final positions of movement determined in this manner, the

magnet

1, 2, 3 is positioned at a maximum and a minimum distance from the galvanomagnetic resistor 7 positioned in the recess 6 of the non-magnetic layer 5. The maximum position of the cover 10 is illustrated by broken lines in FIG. 2.

The left-hand view of FIGS. and 4a illustrates the minimum position in which the

magnet

1, 2, 3 is a minimum distance from the galvanomagnetic resistor 7. In the minimum position, the second poleshoe 3 of the magnet l, 2, 3 covers the field plate 7 completely, so that said field plate is subjected to a maximum flux. The right-hand view of FIGS. 4 and 4a illustrates the maximum position in which the magnet l, 2, 3 is a maximum distance from the galvanomagnetic resistor 7 positioned in the recess 6 of the non-magnetic layer 5. In the maximum position, the second poleshoe 3 is a maximum distance from the field plate 7, so that the magnetic flux to which said field plate is subjected is almost zero.

The play or clearance in the threading between the container l3 and the cover 10 of the housing of the potentiometer of the invention is canceled out or compensated for in a preferred manner by the spiral spring 14. The setting or reading of a specific resistance value is provided with the assistance of two scale marks and 16 provided on the outside of the potentiometer housing in the same manner as for a micrometer screw. One scale mark 15 is positioned on a ring 17 around the cylindrical surface of the cover 10 and may be shifted thereon. The distance between the scale marks may be selected in a manner whereby any desired exact adjustment may be effected for desired resistance values. After adjustment, the ring 17 may be cemented to the cover 10.

Electrically conductive leads 18 extend from the potentiometer housing, through the bottom of the container 13 thereof, to the outside. A winding 19 is positioned around the permanent magnet rod 1 in order to adjust the magnetic field. The two ends of the winding 19 are connected to electrically conductive leads which extend from the potentiometer housing through the bottom of the container 13 thereof via electrical contacts 21. One of the leads 20 from one of the ends of the winding 19 is shown in FIG. 3. The bottom of the container 13, as shown in FIG. 3, is provided with bolts or screws 22, 23 and 24 for fixing the various components of the potentiometer of the invention in position in the potentiometer housing.

While the invention has been described by means of a specific example and in a specific embodiment, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

I claim: 1. A contact-free, adjustable semiconductor potentiometer having a plate-shaped, galvanomagnetic semiconductor resistor whose resistance may be determined by shifting a magnetic field in operative proximity therewith, the magnetic field being produced by a magnetic circuit having a permanent magnet and a stationary elongated armature body, said potentiometer comprising a guide plate of non-magnetic material interposed between the magnet and the armature body of the magnetic circuit, said guide plate being adjacent to the armature body and having a recess formed therein and said galvanomagnetic resistor being embedded in said recess, said guide plate guiding the magnet in gliding relation.

2. A contact-free potentiometer as claimed in claim 1, wherein said guide plate comprises a U-shaped frame affixed to said armature body and forming a tunnel-like housing therewith enclosing the area of said magnet.

3. A contact-free potentiometer as claimed in claim 1, wherein said guide plate comprises a brass sheet and is cemented to said armature body.

4. A contact-free potentiometer as claimed in claim 1, wherein said magnet comprises a permanently magnetic cylindrical rod having a pair of wafer-like poleshoes.

5. A contact-free potentiometer as claimed in claim 2, wherein said guide plate further comprises a spring bolt mounted between said magnet and abutting against said frame.

6. A contact-free potentiometer as claimed in claim 2, further comprising a spiral spring in the area enclosed by said frame and abutting an axial end of said magnet whereby the magnet is movable relative to the spiral spring.

7. A contact-free potentiometer as claimed in claim 6, further comprising a container of substantially hollow cylindrical configuration having a closed bottom base and an open top base and enclosing said potentiometer with said spiral spring adjacent said bottom.

8. A contact-free potentiometer as claimed in claim 7, further comprising a cover of substantially hollow cylindrical configuration having an open bottom base and a closed top base and adapted to engage said container in a threadlike manner as a micrometer screw.

9. A contact-free potentiometer as claimed in claim 8, wherein said guide means further comprises a spherical member mounted on the opposite axial end of said magnet between said magnet and said cover and abutting said magnet and said cover.

10. A contact-free potentiometer as claimed in claim 8, wherein said container has a groove formed therein and said cover has at least one bolt engaging said groove.

11. A contact-free potentiometer as claimed in claim 8, wherein said cover has a border area on its cylindrical surface.

12. A contact-free potentiometer as claimed in claim 8, wherein said cover has a recess formed in its top surface adapted to receive an adjusting tool.

13. A contact-free potentiometer as claimed in claim 8, wherein said cover has a ring shiftably mounted on its cylindrical surface and having a scale division thereon.

Claims

1. A contact-free, adjustable semiconductor potentiometer having a plate-shaped, galvanomagnetic semiconductor resistor whose resistance may be determined by shifting a magnetic field in operative proximity therewith, the magnetic field being produced by a magnetic circuit having a permanent magnet and a stationary elongated armature body, said potentiometer comprising a guide plate of non-magnetic material interposed between the magnet and the armature body of the magnetic circuit, said guide plate being adjacent to the armature body and having a recess formed therein and said galvanomagnetic resistor being embedded in said recess, said guide plate guiding the magnet in gliding relation.