GB2059542A

GB2059542A - Indexing Mechanism

Info

Publication number: GB2059542A
Application number: GB8029497A
Authority: GB
Original assignee: Elms Lightning Tools & Fastene
Current assignee: Elms Lightning Tools & Fastene
Priority date: 1979-09-25
Filing date: 1980-09-12
Publication date: 1981-04-23

Abstract

An indexing mechanism comprises a linearly reciprocated driving rack member (10) having localised teeth which mesh with a rotatable toothed wheel (13) coupled to the apparatus to be indexed. The teeth of the driving member (10) are localised in one, or in two opposed quadrants considered about the axis of elongation of the member. The driving member (10) is moved linearly and then rotated to bring the teeth out of mesh at the end of the driving stroke, this rotational movement being coupled via a yoke and slide (19, 20), carrying cam surfaces (22), to a locking member which is forced between the teeth of the toothed wheel at the instant that the driving member (10) disengages. The locking member (17) ensures precise stopping of the toothed wheel (13). It is withdrawn simultaneously with further rotation of the driving member (10) to bring the rack teeth back into mesh with the wheel (13) for a further indexing stroke. <IMAGE>

Description

SPECIFICATION Indexing Mechanism This invention relates to an indexing mechanism for producing rotary indexing movement of a member.

Such indexing movement may be in one or both directions of rotation.

Previously known forms of indexing mechanism have had certain disadvantages in that, for example, the degree of rotation available in the indexing movement was predetermined and fixed by the configuration of the apparatus and could not be varied at will. Furthermore, most conventional indexing mechanisms have insufficient precision in positioning of the indexed member for the dwell period between indexing movements.

It is an object of the present invention to provide an indexing mechanism of a new or improved type compared with previously known indexing mechanisms.

According to the invention there is provided an indexing mechanism comprising an elongate driving member which is arranged for limited linear sliding movement between two abutment means and for limited rotation about its axis of elongation, the driving member being toothed along at least a portion of its length, a toothed wheel being rotatably mounted in a position such that its teeth are enabled to mesh with those of the driving member whereby linear sliding movement of the driving member may rotate the wheel, the teeth of the driving member being localised circumferentially of the axis of elongation of the driving member so that rotation of the driving member rotates the localised teeth thereon into and out of mesh with those of the toothed wheel, a locking member being provided, movable into and out of locking engagement with the toothed wheel, such engagement positively preventing rotation of the wheel, and operating means being provided for the locking member, causing it to move into locking engagement with the wheel simultaneously with the driving member being rotated to move the localised teeth thereon out of mesh with the teeth of the wheel.

The abutment means may be relatively adjustable in position so as to adjust the linear sliding stroke of the driving member and hence the rotation of the driven toothed wheel.

Means may be provided to prevent rotation of the driving member except at the ends of its stroke.

The rotation of the driving member may be positively coupled to a linearly reciprocable slide forming part of the operating means.

The slide may be coupled for driving movement to the locking member, for example by a cam mechanism.

The elcngate driving member may be operatively connected to power means capable of causing its linear sliding movement and rotation.

Preferably, such power means are hydraulic or pneumatic. Control means for the power means may be programmed to operate the mechanism in a predetermined sequence of movements.

The driving member may have its teeth localised in one quadrant defined about its axis of elongation or in two opposed such quadrants separated by portions which are devoid of teeth capable of meshing with the toothed wheel.

One or more alternative wheels may be provided, having a closely similar but not identical number of teeth to said toothed wheel and being selectively movable into position to substitute for said toothed wheel.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings in which: Figure 1 is a diagrammatic plan view of an indexing mechanism at the commencement of an indexing stroke; Figure 2 is a similar diagrammatic view of the indexing mechanism at the end of the stroke; Figure 3 is a similar view of the commencement of a free return stroke of the driving member showing the driven member locked in position.

Figure 4 is a detail view of a yoke.

Referring to the drawings, the indexing mechanism comprises a driving member 10 which is in the form of an elongate bar having teeth 11 provided along at least part of its length, these teeth being localised around part of the periphery only of the member. This can be seen by comparing Figure 2 with Figure 3 which shows the driving member in a position where it has been rotated through an arc of 90C from the Figure 2 position.

The teeth 1 1 of the driving member 10 are suitably sized to mesh with teeth 12 on a rotatably mounted wheel 13. Linear sliding movement of the driving member 10 can therefore drive the wheel 13 for rotational movement about its axis, owing to the meshing engagement of the teeth 1 1 and 12.

In Figure 1, the driving member is shown at one end of its stroke at the commencement of an indexing movement of the wheel 1 2. The end of the driving member abuts an adjustable stop 14 which may for example be arranged to be moved linearly to the left or right as shown in the drawings, which are purely diagrammatic. It will be appreciated that the driving member is constrained for linear sliding movement towards and away from this adjustable stop 14.

At the other end of the stroke of the driving member 10, a projection 15 of the driving member can abut against a further stop 16 which may be adjustable or may be fixed. Thus, the stroke of the driving member can be adjusted to suit the degree of rotational movement required in each indexing movement of the wheel 13.

At the end of the indexing stroke, when the driving member 10 has moved from the Figure 1 to the Figure 2 position, it is released from driving engagement with the wheel 13 by rotation of the driving member about its axis of elongation, through 900 to the condition shown in Figure 3.

In this condition, the teeth 1 1 can be seen facing out of the paper and there is a clearance between the teeth 11 and the teeth 12 of the wheel 13.

Suitable means (not shown) may prevent rotation of the driving member except at the ends of its stroke.

By comparison of Figures 1 and 2 with Figure 3 of the drawings, it will be seen that a locking member 17 has been moved from a withdrawn condition in which it is clear of the toothed wheel 13, as seen in Figures 1 and 2, to a locking position shown in Figure 3, in which it engages between the teeth 12 of the wheel 13.

Reference to the left hand side of Figures 2 and 3 illustrates a form of operating means for the locking member 17, also illustrated in the detail view Figure 4.

An extension of the driving member 10 is formed as a flat strip 18 which is received in a yoke 19 of a slide 20 which is constrained for sliding movement in a direction generally perpendicular to the axis of the driving member 10, between a pair of fixed abutments 21. The slide 20 has a cranked end which provides cam surface 22 projecting into an aperture 23 of the locking member 17. The locking member is constrained for sliding movement by any suitable means. The yoke 19 has the shape shown in Figure 4.

In operation, when the driving member occupies the condition shown in Figure 2, the slide 20 is in its uppermost position and the cam surfaces 22 tend to force the locking member 17 to the left hand side. The expressions "upper", "lower", and so on, refer to the drawings.

Rotation of the driving member 10 about its axis of elongation brings the strip 18 into a condition in which it bears down on the slide 20 and forces it into a lower position. The cam surfaces 22 force the locking member 17 to the right hand side and it moves into engagement with the teeth 12 of the wheel 13.

The position of the driving member 10 in the Figures 1 and 2 conditions is shown on Figure 4 at 1 ova. The position occupied when the driving member rotates to the Figure 3 condition is shown at 1 Ob.

The operating means are so arranged that there is a rapid transfer between a condition in which the wheel is in mesh with the teeth 11 of the driving member but is free from the locking member 17, and a condition in which the locking member 17 is locking the wheel against rotation but the wheel is entirely free from the teeth 1 1 of the driving member. It is intended that the wheel is momentarily held by the locking member 17 as the teeth 1 1 of the driving member disengage from the teeth 12 of the wheel 13, and also during re-engagement for the next driving stroke.

After the driving stroke has been completed and the driving member disengaged from the wheel by rotation of the driving member, a linear sliding movement returns the driving member 10 to its position adjacent the first stop 14, ready for another driving stroke. During this return movement, the wheel is held by the locking member 17.

To start another driving stroke, the driving member is again rotated, this time in the opposite sense of rotation, to withdraw the yoke 19 and hence the slide 20. The locking member 17 is thereby withdrawn from the Figure 3 condition to the Figure 2 condition, while the teeth 1 1 reengage the teeth 12. Again, the wheel 13 is at all times held in engagement either by the locking member 17 or by the driving member 10.

In the example illustrated in the drawings, the driving member has teeth on only one quadrant considered about its axis of elongation. It is possible to have teeth on two opposed quadrants if desired. This may enable the control means for the driving member to operate to reciprocate the driving member linearly and to rotate it in one sense of rotation only. If the teeth are localised to one quadrant only of the driving member, it would normally be necessary to rotate the driving member in both senses of rotation.

The movement of the driving member can be carried out manually or by operator controlled power means. However, it is envisaged that a completely automatic cycle of operations could be carried out by the use of suitable hydraulic or pneumatic power control means arranged to cycle in such a manner that the driving member was moved linearly and rotated as appropriate to drive the wheel 13 for indexing movement. It will be seen from a consideration of the drawings that the driving stroke illustrated is from right to left as shown. However, the driving stroke could equally well be from the left to right. No structural modifications of the apparatus are required to cause it to index the wheel in the reverse sense of rotation or to index the wheel in alternate senses of rotation.The control means can be programmed to drive the driving member in the appropriate manner for any selected pattern of indexing movement.

To give additional flexibility, the single toothed wheel 13 can be replaced by a pair of wheels having similar, but not identical numbers of teeth.

For example, there may be 35 teeth on-one wheel and 36 on another. The wheels may be mounted one above the other on a common axis and may be movable selectively into alignment with the driving member 10.

Each indexed movement of the wheel must be equivalent to the passage of an internal number of teeth past the locking member. For example, where a wheel having 36 teeth is used, the passage of 18 teeth past the locking member represents a rotation of the wheel through 1 800 whilst the passage of 12 teeth represents a rotation of 1200 and so on. These rotations are equivalent to two and three indexing movements respectively of the wheel per complete revolution.

If a wheel having 35 teeth is also provided, the full revolution may also be divided up into five or seven equal indexing movements for example.

It will be appreciated that the number of teeth and the difference in the number of teeth between the two wheels will be selected so that each will mesh comfortably with the teeth 1 1 of the driving member 10. It will be seen that only a few of the teeth of the wheel and driving member are in engagement at any given time and of course adequate play must be provided to allow for the slight mis-match between the teeth.

Various modifications of the apparatus can be made without departing from the scope of the invention. The wheel can be arranged to drive some part of a machine, an indexing table or the like, either directly or indirectly.

Claims

1. An indexing mechanism comprising an elongate driving member which is arranged for limited linear sliding movement between two abutment means and for limited rotation about its axis of elongation, the driving member being toothed along at least a portion of its length, a toothed wheel being rotatably mounted in a position such that its teeth are enabled to mesh with those of the driving member whereby linear sliding movement of the driving member may rotate the wheel, the teeth of the driving member being localised circumferentially of the axis of elongation of the driving member so that rotation of the driving member rotates the localised teeth thereon into and out of mesh with those of the toothed wheel, a locking member being provided, movable into and out of locking engagement with the toothed wheel, such engagement positively preventing rotation of the wheel, and operating means being provided for the locking member, causing it to move into locking engagement with the wheel simultaneously with the driving member being rotated to move the localised teeth thereon out of mesh with the teeth of the wheel.

2. An indexing mechanism according to Claim 1 wherein the abutment means are relatively adjustable in position so as to adjust the linear sliding stroke of the driving member and hence the rotation of the driven toothed wheel.

3. An indexing mechanism according to Claim 1 or Claim 2 wherein means are provided to prevent rotation of the driving member except at the ends of its stroke.

4. An indexing mechanism according to any preceding claim wherein the rotation of the driving member is positively coupled to a linearly reciprocable slide forming part of the operating means.

5. An indexing mechanism according to Claim 4 wherein the slide is coupled for driving movement to the locking member by a cam mechanism.

6. An indexing mechanism according to any preceding claim wherein the elongate driving member is operatively connected to power means capable of causing its linear sliding movement and rotation.

7. An indexing mechanism according to Claim 6 wherein the power means are hydraulic or pneumatic.

8. An indexing mechanism according to Claim 6 or Claim 7 and provided with control means for the power means, programmed to operate the indexing mechanism in a predetermined sequence of movement.

9. An indexing mechanism according to any preceding claim wherein the driving member has its teeth localised in one quadrant defined about its axis of elongation.

10. An indexing mechanism according to any one of Claims 1 to 8 wherein the driving member has its teeth localised in two opposed quadrants defined about its axis of elongation and separated by portions which are devoid of teeth capable of meshing with the toothed wheel.

11. An indexing mechanism according to any preceding claim wherein one or more alternative wheels are provided, having a closely similar but not identical number of teeth to said toothed wheel and being selectively movable into position to substitute for said toothed wheel.

12. An indexing mechanism substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.