Magnetoelectric Indicating Device With A Great Scale Range

Abstract

The device comprises a magnetic circuit formed by an annular permanent magnet secured between the peripheral rims of two cheek members of which one is divided into two equal parts, the frame of a mobile assembly being engaged on one of the rims and the device being provided with an adjustable magnetic shunt.

Description

The present invention relates to a magnetoelectric indicating device with a wide scale range composed of a plurality of simple parts.

Conventional magnetoelectric devices generally comprise a magnetic circuit obtained by assembling a permanent annular magnet secured between two concentrical cheek members which are cut and formed to receive the mobile assembly of the device. One of the cheeks is either apertured or formed with two separate parts for introducing the coil of the mobile assembly. There exist several variants in the shape of the elementary parts as well as in the method of assembling said parts. Namely, the assembling may be made by moulding of plastic material which makes difficult the disassembly of the device.

The present invention makes it possible to combine accuracy of the indicating device with disassembly at competitive prices.

According to the invention, the device comprises a mobile assembly and a magnetic circuit obtained by assembling a permanent annular magnet secured between two cheek members provided with peripheral annular portions and shaped to receive the coil of the mobile assembly and providing the free displacement thereof, and wherein the magnetic circuit is formed by an annular permanent magnet secured between the respective peripheral portions of the two cheeks, the first cheek being, moreover, divided into two equal parts according to a symmetry plane separating magnetic bridges connecting the peripheral annulus to a central annulus of the first cheek, the mobile assembly being provided with a spindle placed in said symmetry plane, the frame of the mobile assembly being engaged to the first cheek, the first cheek and the magnet being fitted at the outside of a structure centered on a concentric shoulder of the second cheek and maintained by fixing means, and an adjustable magnetic shunt being interposed between the magnetic bridges.

According to another embodiment of the invention, the first cheek is made by two identical elementary parts whose adjoining surfaces constitute a plane passing through the symmetry plane.

According to another embodiment of the invention, an elementary part of the first cheek is made by a central annulus and a peripheral annulus concentrically placed, and connected together by radial magnetic bridges adjacent the symmetry plane.

According to another embodiment of the invention, the magnetic shunt comprises a steel core, interposed between the magnetic bridges and having the axis thereof disposed in the symmetry plane, and means for adjusting the core perpendicularly to the plane of the first cheek.

According to a further embodiment of the invention, the spindle of the mobile assembly is placed between an extension of a structure and the center of the second cheek.

Other characteristics of the invention will become apparent from the following description and the annexed drawings which are given by way of nonrestrictive example.

Referring now to the drawings:

FIG. 1 diagrammatically shows in elevation a section of the device of the invention taken on line I--I of FIG. 2.

FIG. 2 is a plan-section taken on line II--II of FIG. 1.

FIG. 3 is a plan-section of one element taken on line III--III of FIG. 1.

The device of the invention is described in the following:

A magnetic circuit 1 (FIG. 1) comprises a permanent annular magnet 2, a first cheek 3 and a second cheek 4.

The magnet 2 and the first cheek 3 are centered on a cylindrical body 5 of a structure 6, an inner shoulder 7 of which centers also the cup shaped recess 8 formed in the second cheek 4.

A mobile assembly is carried by a spindle 9 which is pivotally mounted between two step-bearings 10 and 11, the first bearing being housed in an extension 12 of the structure 6, the second bearing being placed in the center of the recess 8 of the second cheek 4.

The mobile assembly 40 comprises a coil 13 wound on a yoke 13a which is keyed on said spindle 9, a needle 14 being also carried by the yoke 13a and an balancing plate 15 as well as spiral springs 16 and 17. The coil 13 surrounds the radial section 20 of the central annulus 23 or 23' (FIG. 2) of the first cheek 3 and may rotate at least 250.degree. together with the spindle 9, thereby causing a rotation of the same amplitude of the needle 14 in front of a dial 14a and providing a device with a wide scale range.

FIG. 2 shows the first cheek 3 and the magnet 2 which is ring-shaped and of the same diameter as said cheek 3 (the magnet 2 is shown limited by a dash line). Both the magnet and cheek 3 are centered on the cylindrical body 5 of the structure 6. The assembly of the structure 6, the magnet 2, the first cheek 3, on the one hand, and the second cheek 4, on the other hand, is made by means of screws 18, 19.

FIG. 3 shows an embodiment of the first cheek 3 which is made by joining two identical elements 21, 21', each comprising a peripheral half annular rim 22, 22' and a central half annular rim 23, 23', which are connected together by means of magnetic bridges, respectively 24 and 24'.

The junction of the elements 21, 21' is made by adjoining surfaces such as 31, 32, 33, 34 and 31', 32', 33', 34'.

Said adjoining surfaces determine a joint plane like a plane of symmetry passing through the axis yy' (FIG. 3) and by the center 0 of the cheek 3 (FIG. 3), i.e. passing through the spindle 9 of the mobile assembly of the indicating device.

A magnetic shunt for accurate loading of the device is placed in the first cheek 3 between the bridges 24, 24' in an aperture that they define. This shunt is made by a steel core 27 which may be displaced perpendicularly to the plane of the first cheek 3 by means of a screw 28 (FIG. 1) mounted in order to freely turn in a hole provided on the second cheek 4. A return spring 29 is placed between a shoulder 30 of the screw 28 and the bottom of the core 27 which is prevented from turning because of the polygonal shape of said core 27. It is thus possible to have access to the screw 28 from the bottom of the second cheek 4 constituting the rear face of the device.

The core 27 is advantageously triangular in section so as to be perfectly adapted to the arrangement of the magnetic bridges 24, 24'. A different section-shape of the core 27 would not alter the scope of the invention.

To make the indicating device of the invention one has only to introduce a central half annular rim 23 or 23' in the frame 13a, and then to connect the elements 21, 21' by their adjoining surfaces 30 to 33 and 30' to 33' in order to form the first cheek 3 which one may then place on the cylindrical body 5 and lock by the turned-down edge 35 of the structure 6. The magnet 2 is then placed on the cylindrical body 5, against the first cheek 3. The mounting is then secured to the second cheek 4 centered on the shoulder 7 of the structure 6, with known fixing means, for example with screws 18, 19. The mounting of the mobile assembly between the step-bearings 10 and 11 of the spindle 9 is then a conventional operation which may be done in various known ways. The disassembly is made inversely and quite easily.

The mounting of the mobile assembly between the step-bearings has been given only as an example, but without altering the scope of the invention, this mounting could be made as well by different suspension as, for example by a stretched thread-suspension.

Claims

We claim:

1. A magnetoelectric indicating device having a wide range comprising a magnetic circuit assembly and a mobile assembly mounted therein to be responsive thereto, said magnetic assembly comprising an annular permanent magnet, a first circular cheek member and a second circular cheek member engaging opposite faces of the magnet for retaining said magnet between the peripheral portions thereof, said first cheek member being formed as two radially spaced concentric annuluses having two magnetic bridges adjoining them and being divided across a diameter between the two bridges and said mobile assembly comprising a spindle passing through the center of the inner concentric annulus of said first cheek member, an indicator connected to said spindle, a coil surrounding the inner concentric annulus of the first cheek member and connected to said spindle, means for rotatably supporting said spindle to rotate as said coil moves about the axis thereof in response to magnetic flux, said annular magnet being removably secured between the outer annulus of the first cheek member and the second cheek member and an adjustable magnetic shunt interposed between the magnetic bridges.

2. A magnetoelectric indicating device as claimed in claim 1 wherein the divided portions of said first cheek member across a diameter thereof are reciprocals of each other and the surfaces when adjoined are in magnetic contact.

3. A magnetoelectric indicating device as claimed in claim 1 wherein said magnetic bridges are located adjacent the line of division across the diameter of said first cheek member on either side of said line.

4. A magnetoelectric indicating device as claimed in claim 1 wherein said magnetic shunt comprises a steel core disposed between the magnetic bridges, the axis of said core lying in the line of division across the diameter and further comprising means for adjustably moving the core perpendicular to the plane of the first cheek member.

5. A magnetoelectric indicating device as claimed in claim 1 and further comprising structure means engaging said first cheek member, said means for rotatably supporting said spindle comprising means supported by said structure means and means at the center of said second cheek member.