GB2129221A

GB2129221A - Indexing mechanism, in particular for a multistate rotary switch

Info

Publication number: GB2129221A
Application number: GB8325785A
Authority: GB
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1982-10-19
Filing date: 1983-09-27
Publication date: 1984-05-10
Also published as: FR2534711A1; DE3238660C2; GB8325785D0; DE3238660A1; FR2534711B1; GB2129221B

Abstract

In an indexing mechanism which is particularly suitable for a multistage rotary switch, there is provided a coarse-division type of indexing cam member (5) having an indexing angle alpha . A fine division with more than a triple division and an indexing angle alpha ', is achieved in that at least n indexing elements (7, 8, 9, 10) are provided of which each one, referred to a common initial value, is arranged at a different angular indexing ratio m-1 DIVIDED n, with m indicating the number of positions of one indexing element (7, 8, 9, 10) and being an integer between 1 and n inclusive, and with n indicating the total number of required indexing elements (7, 8, 9, 10) and being an integer greater than 3. There are consequently a greater number of indexed positions than the number of depressions since not all of the indexing elements are simultaneously engaged in depressions. <IMAGE>

Description

SPECIFICATION Indexing mechanism, in particular for a multistage rotary switch This invention relates to an indexing mechanism, in particular for a multistage rotary switch of the kind having switch positions spaced apart by equal angular amounts, and with an indexing cam member alternateiy comprising high points and depressions, and several indexing elements capable of rotating in relation to the indexing cam member, which are arranged in such a way that one or more indexing elements lockingly engage into one depression with the remaining one or more indexing elements not engaging into a depression so that there will result a greater number of indexing steps than high points or depressions.

One such indexing mechanism is known from U.S. Patent Specification No. 2,399,906. In this indexing mechanism, there is attached to the main switch shaft a disc with eight circular segment sections provided for along the circumferential edge in equaliy spaced relation. Four indexing balls cooperate with the series of cam members thus formed. Neighbouring indexing balls are each spaced apart by 90 angular degrees and each simultaneously engage into one of the eight circular segment sections. This arrangement, therefore, has eight positions which the switch may occupy.In order to double the number of positions that the switch may occupy, two diagonally opposite indexing balls may be staggered by half the angular amount, so that in each position that the switch may occupy, one pair of the indexing balls will each engage one indexing circular segment section while the other pair presses against the circumference of the disc lying therebetween and assumes an unstable position.

Moreover it is known from the German Patent No. 2,230,856 to achieve a division of the angular amount as defined by an indexing disc, in that two identical indexing discs are arranged one above the other and staggered by half an indexing step with respect to one another. The indexing balls lying diagonally opposite each other, in response to a turning in the axial direction, hence vertically in relation to the disc plane, jump from one indexing disc to the other. Accordingly, this also requires a longer axial construction.

It is an object of the invention, also with a view to an extensive miniaturisation of indexing mechanisms for rotary switches, coder switches, indexable rotary potentiometers, etc., to achieve a very high number of switch positions by maintaining a high angular accuracy and a sufficient position-locating characteristic.

According to the invention in its broadest aspect, an indexing mechanism of the kind referred to is characterised in that at least n indexing elements are provided, of which each with respect to a common initial position, is arranged at a different angular indexing ratio m-1 n with m indicating the respective position number of an indexing element and an integer number 2 1 < n, and n indicating the total number of the required indexing elements and being an integer > 3.

An embodiment of the invention will now be described by way of example with reference to Figures 1 and 2 of the accompanying drawings, in which: Figure 1 shows an indexing mechanism according to the invention in a section taken along the line C-D of Figure 2, and Figure 2 shows the indexing mechanism in a section taken along the line A-B of Figure 1.

The reference numeral 1 indicates a control knob in which an indexing ring member 2 is arranged, The iatter is provided on its inside with an indexing cam member 5 providing high points 3 and depressions 4. Preferably, the connecting sliding surfaces 6 for the indexing elements which have the shape of indexing balls 7, 8, 9, 10, are at least approximately straight and inclined in such a way that the angle between two adjoining sliding surfaces 6 in the depression 4 ranges between 70 and 1100, and preferably amounts to about 900.

In the embodiment shown there are provided twelve such indexing depressions 4.

A carrier for the indexing balls 7, 8, 9, 10, which is designed as a disc 12, is rotatably supported on a journal portion 11 which, for example, forms a structural unit with the indexing ring member 2. This disc is provided with an inner flange 13 which rests on a projection of the journal portion 11. The fixing in position of the disc 12 is effected via two hold members 14 extending through the inner flange 1 3, and over which a washer 1 5 is slipped. The ends of the hold members 14 are bent over, thus securing the disc 12 with a small axial play. Indexing elements 7, 8, 9, 10 and the indexing cam member 5 are thus capable of being turned relative to one another.

The indexing balls 7, 8, 9, 10 rest in correspondingly designed blind holes (ball cages) 1 6 as provided for in the disc 1 2 and preferably pointing towards the centre of the disc 12, and are pressed outwardly against the indexing cam member 5 by the action of compression springs 17.

When providing on the indexing ring member 5 twelve positions that the switch may occupy, each position includes an angle a = 300. By the arrangement according to the invention of the four indexing balls 7, 8, 9, 10 shown there is achieved an angle a' of 7.5a. This angle is obtained in that the indexing balls 7, 8, 9, 10 or the blind hoies (ball cages) 1 6 are so arranged that each of the indexing balls 7, 8, 9, 10, with respect to the next following one, referred to a common starting position, for example, the position of the indexing ball 7, is staggered by an angle which corresponds to the angle a of the indexing ring member 5 or to an integer multiple thereof plus (or minus) an angular amount ' corresponding to the angle divided by the number of indexing balls.

In the example, this reads as follows: 300:4 = 7 50 Therefore, the angular indexing ratio is 1:4=-, n in cases where n is the amount of those indexing balls 7, 8, 9, 10 which are to effect the fine indexing. Therefore, n must be an integer and greater than three.

In that case, the indexing balls 7, 8, 9, 10 are displaced with respect to the aforementioned reference point 0 and, when actuated in the clockwise direction, in the example of indexing ball 7, by Oa', in the case of the indexing ball 8 by a - 1 la', in the case of the indexing ball 9 by Y.- 2.a', and in the case of the indexing ball 10byZ-cg3cg'.

If, in general, for each indexing ball 7, 8, 9, 1 0, there is inserted one number m of the sequence of numbers 1 through n, there will generally be obtained the indexing ball displacement m-1 V= n with respect to the individual indexing balls. This then indicates by how many fine indexing angles a1 an indexing ball is displaced with respect to a given reference value. Thus, in the example, the third indexing ball 9 with m = 3 and with n = 4 is displaced by 3-1 1 4 2 of the indexing angle a, hence by 1 1 2-=2- --cL=2d, n 4 with the expression 1 n resulting in the indexing angle a'.

According to this embodiment of the invention each indexing ball 7, 8, 9, 10 engages one depression 4 while the remaining balls are lying on the slanting sliding surfaces 6 or possibly on a high point 3. At first it will not be immediately recognised that in spite of the unstable position of the last-mentioned indexing balls there is still obtained an unobjectionable engagement also in cases where it is intended to obtain a very fine sub-division, that is, a very small angle cut'. When taking a closer look, however, it will be seen that the restoring forces occurring owing to the instable state, almost cancel each other. Up to now, obviously, the development of such types of indexing mechanisms has been prejudiced although, owing to the miniaturisation of component parts, indexing mechanisms with a very fine division have been long-felt need.

Moreover, the good locking effect of the indexing mechanism according to the invention is based on the fact that one indexing ball 7, 8, 9, 10 in spite of the small indexing angle ', from its locking position in the depression 4 to the next fine-indexing position, performs a much greater travel than in the case of a corresponding division or indexing of the indexing cam member 5 of the indexing ring member 6.

By way of example, this relationship is shown in Figure 1 above the indexing ball 7 in the form of a small-indented indexing cam member. In the case of the shown indexing angle a', owing to the small teeth 18 and with the corresponding smalldiameter indexing ball 19, the travel of the indexing ball 19 in the maximum amounts to 40 to 45% of the space depth of the teeth. This percentage travel is almost also achieved with the arrangement according to the invention as is evident from the position of the indexing balls 8 and 10 compared with that of the indexing ball 7.

However, since the space depth of the teeth in this embodiment of the invention is much greater, the travel for the indexing balls 7, 8, 9, 10 is correspondingly also enlarged.

It has still to be emphasised that an indexing cam member 5 having a coarse division, of the type as employed with the invention, can be more easily manufactured with a high accuracy than a fine-division type of indexing cam member.

In the manner known per se, in addition to the four indexing balls 7, 8, 9, 10 shown in the example, it is possible to provide further indexing balls which are arranged in the same way but staggered or displaced by an angular amount, so that it is possible to increase the locking effect.

Instead of the indexing balls 7, 8, 9, 10 it is also possible to provide other types of indexing elements, such as indexing fingers or discs, etc., and instead of the indexing ring member 2, it is possible to use a disc with high points and/or depressions, etc. provided for along the circumference thereof or on the top surface of the disc.

According to an advantageous embodiment of the invention, the angular spacing between two indexing elements 7, 8, 9, 10 ranges between 30 and 900, with this corresponding to an indexing angle a or to an integer multiple thereof plus/minus m-1 n hence + (n-1).a'.

Moreover, the disc 12 may be provided with a screw socket 20 so that the indexing mechanism can be easily inserted and secured in a borehole, and actuated via the control knob 1. For being coupled to a main switch shaft or any other switch spindle, etc., the journal portion 11 is provided with a non-circular central recess 21, such as a slot. A correspondingly adapted part to be turned, may be inserted into this recess 21.

Claims

1.An indexing mechanism, in particular for a multistage rotary switch of the kind having switch positions spaced apart by equal angular amounts, and with an indexing cam member alternately comprising high points and depressions, and several indexing elements capable of rotating in relation to the indexing cam member, which are arranged in such a way that one or more indexing elements lockingly engage into one depression with the remaining one or more indexing elements not engaging into a depression so that there will result a greater number of indexing steps than high points or depressions, characterised in that at least n indexing elements (7, 8, 9, 10) are provided of which each with respect to a common initial position, is arranged at a different angular indexing ratio m-1 n with m indicating the respective position number of an indexing element (7, 8, 9, 10) and an integer number 2 1 < n n, and n indicating the total number of the required indexing elements (7, 8, 9, 10) and being an integer > 3.

2. An indexing mechanism as claimed in claim 1, characterised in that the indexing cam member (5) is arranged on an indexing ring member (2) surrounding the indexing elements (7, 8, 9, 10).

3. An indexing mechanism as claimed in claim 1 or 2, characterised in that the indexing elements are designed as indexing balls (7, 8, 9, 10) resiliently pressing against the indexing cam member (5).

4. An indexing mechanism as claimed in any one of claims 1 to 3, characterised in that the indexing elements (7, 8, 9, 10) are arranged on or in a disc (12) which is surrounded by the indexing ring member (2) and that both the disc (12) and the indexing ring member (2) are capable of being turned in relation to one another.

5. An indexing mechanism as claimed in any one of claims 1 to 4, characterised in that neighbouring indexing elements (7, 8, 9, 10) have a mutual angular spacing ranging between 30 and 900 which, however, corresponds to the angular amount (m) or an integer multiple of the angular amount (a) plus or minus m-1 m

6. An indexing mechanism as claimed in any one of claims 1 to 5, characterised in that the indexing cam member (5) is provided with slanting run-up surfaces (6) and that neighbouring sliding surfaces (6) in the depression (4) occupy an angle ranging between 70 and 1100.

7. An indexing mechanism as claimed in any one of claims 1 to 6, characterised in that the indexing ring member (2) is provided with a journal portion (11) for the part (12) bearing the indexing elements (7,8, 9, 10).

8. An indexing mechanism as claimed in any one of claims 1 to 7, characterised in that the part (12) bearing the indexing elements (7, 8, 9, 10) is provided with a screw socket or sleeve (20).

9. An indexing mechanism as claimed in any one of claims 1 to 8, characterised in that the indexing ring member (2) is provided with an actuating part (1).

1 0. An indexing mechanism as claimed in any one of claims 1 to 9, characterised in that the journal portion (1 1 ) is designed as a driver for a part to be driven.

11. An indexing mechanism as claimed in any one of claims 1 to 10, characterised in that the journal portion (11) is provided with a recess (21) of non-circular cross section.

12. An indexing mechanism substantially as described with reference to the accompanying drawings.