GB2053748A - Locking device for indexing mechanism for a machine tool - Google Patents

Abstract

A device for locking an indexable turret comprising a part (61) being fixed to the turret and having teeth (63), a part (15) having teeth (17) and fixed to the structure on which the turret is mounted and relatively to which it is indexable, and a movable part (38) having sets of teeth (39 and 41) which can engage simultaneously with the teeth (63 and 17) on the parts (61 and 15) on the turret and structure respectively, and fluid pressure means arranged to move the movable parts (38) between a position in which the teeth are in engagement and a further position in which they are out of engagement but in which the set of teeth (39) are in engagement with a member (42) forming part of means for indexing the turret. <IMAGE>

Description

SPECIFICATION Locking device for indexing mechanism for a machine tool This invention relates to indexing mechanisms for machine tools and to devices whereby locking is achieved in selected indexed positions.

Indexing mechanisms are applicable to machine tools such as lathes and are used on such apparatus as tool turrets to rotate them through predetermined angles and at required intervals. On a tool turret, indexing usually takes place between successive machining operations and is frequently automatically controlled in accordance with the operating cycle of the machine.

It is important that indexing between successive positions should take place very accurately so that tools or other items carried on the indexed component are accurately aligned. To achieve accurate indexing it is necessary not only to ensure that, when indexing has taken place, the component is in exactly the correct position but also that the component is sufficiently firmly fixed to guard against movement or deflection under load, resulting, for example, from machining operations.

There are in existence several devices for locking indexable components. One of these employs a plunger which is locked in a hole and which can be withdrawn to allow indexing to take place. This system requires some clearance for plunger engagement but it suffers from the disadvantage that this clearance is translated into some lack of stiffness and consequent inaccuracy of alignment when it should be locked firmly.

Another known system employs interengaging gear rings or part rings. These are engaged and disengaged by axial movement to lock and to allow for indexing and such axial movement is not only complicated but can give rise to ingress of dirt to precision parts. It also required withdrawal of certain types of tooling because of clearance needed during indexing.

The object of the invention is to provide a device for locking an indexable component which is accurate in its location of the component, in indexed positions, and which is capable of holding the component securely in position.

According to the invention there is provided a device for locking an indexable component comprising a part fixed to the component to be indexed, having teeth thereon, a part secured to the fixed structure relatively to which the component is indexable and a movable part non-rotatably connected to said component and having sets of teeth simultaneously inter-engageable with the teeth on said parts fixed to the component and to the structure respectively, and means for moving said movable part between a first position in which interengagement with said respective teeth takes place, and a second position in which the sets of teeth are out of engagement, one of the sets of teeth on said movable part being arranged to interengage, when said movable part is in said second position, with teeth on a member forming part of means for indexing said component.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a plan view of a tool support turret incorporating a turret locking mechanism constructed in accordance with the invention; Figure 2 is a cross-sectional view of the turret.

Figure 3 is a fragmentary cross-sectional view on the line 3-3 in Figure 1, and Figure 4 is a fragmentary cross-sectional view on the line 4-4 in Figure 3.

The drawings showing a turret having means for indexing about a vertical axis. Such indexing means is the subject of co-pending Patent Application No.

7923791 and incorporating a tool clamp arrange mentforming the subject of co-pending Patent Application No. 7923789.

The turret is supported on a slide indicated generally at 10 engaging a slideway 11 on a machine such as a lathe. The slide is movable relatively to the slideway by any conventional mechanism (not shown). Although the slide is itself movable on the slideway as described it can be regarded as fixed structure relatively to which the turret is indexable.

The slide has an upstanding portion 12 of circular section on which the turret is mounted as will be described. This portion 12 is of generally stepped cylindrical form. In the centre base of the portion 12 at which its joins the slide 10 is a collar 13 secured in place by screws 14. Mounted on the highest internal step within the portion 12 is mounted a gear ring 15 fixed on its shoulder of the portion 12 by screws 16.

This has straight cut teeth 17 which extend radially inwardly.

Located by the collar 13 is a spindle 18 on which the turret is carried. The lower end of the spindle is located by an inward annular projection of the collar 13 the spindle at this end having an integral annular projection 19 for this purpose. The adjacent portion of the spindle 18 has two spaced annular grooves 21, 22to accept respective sealing rings. This portion of the spindle is otherwise cylindrical and joins the upper cylindrical portion of the spindle through a narrow neck portion defining an additional annular groove 23 to accommodate a further sealing ring.

At its upper end, the spindle is screw threaded at 24 to accept a nut 25.

Within the lower end of the spindle and communicating with the end at which the annular projection 19 is provided are two internal longitudinal drillings 26, 27. One of these communications at its inner end with a cross drilling 26a to the outside of the spindle adjacent to the narrow neck at which the groove 23 is provided. This drilling 26a opens onto an annular shoulder of the spindle at this position.

The other drilling 27 communicates with a cross drilling 27a which opens to the outside of the spindle 18 between the two annular grooves 21 and 22 on the intervening cylindrical surface of the spindle.

Slidably engaged on the portion of the spindle having the two annular grooves 21,22 is an annular piston 29. About the annular piston 29 is an upper ring 31 secured on the spindle 18. Secured to the exterior of the annular piston 29 is a ring 32. This is secured to the annular piston 29 through washers 33 and 34 by pegs 35 and 36. On its upper face, the ring 32 has an annular projection with an externally present part-conical face 37. Engaged with this face are a number of segments 38 forming together a floating gear ring. The segments forming the gear ring has external straight cut gear teeth 39 and internal bevel gear teeth 41.

The piston 29 together with the ring 32 and the segments 38 can be moved vertically relatively to the spindle 18. This is achieved by admitting fluid under pressure, through the internal spindle drilling 26 or 27. If such fluid is admitted through the spindle drilling 26 and the cross-drilling 28a the piston 29 and the segments 38 are moved downwardly. Such downward movement causes engagement of the teeth 39 on the segments 38 with the teeth 17 on the fixed ring 15 on the portion 12 of the slide. In such position, the segments 38 become rotationally immovable with respect to that portion 12 of the slide.

When, however, the piston 29 is moved upwardly, by exhaust of the fluid through the drilling 26 and admission of fluid under pressure through the drilling 27, engagement between the teeth 39 and 17 is released. However, when the piston and therefore the segments 38 are in such position (as shown) the teeth 39 on the segments 38 are instead in engagement with a gear 42 mounted on a spindle 43 on the portion 12 of the slide. This spindle 43 is mounted in needle roller bearings 44 in said portion and is also mounted by means of further needle roller bearings 45 in a part 46 secured to the portion 12 ofthe slide.

Also mounted in the portion 12 as well as in the member 46 is a further spindle 48 carrying a gear 49 in mesh with the gear 42. The upper end of the spindle 48 is mounted in needle roller bearings 51 in the member 46. The lower end of the spindle 48 is engaged in a needle roller bearing 52 in the portion 12 of the slide. The spindle 48 also has a toothed pinion 53 secured to it. This pinion engages a rack indicated generally at 54 forming part of the indexing mechanism referred to and not forming part of this invention.

The turret has a multi-part body and is intended to carry tooling of any appropriate kind. Two forms of such tooling are indicated generally at 55 and 56, the former, being shown mounted in the turret by means of a tool clamp arrangement of the kind already referred to and again not forming part of this invention. By means of this clamp, the tool having a tapered shank 57 is secured in a part of the turret with its longitudinal axis extending radially with respect to the vertical axis of the spindle 18.

The main part of the body of the turret is a stepped disc 58 mounted on a sleeve 59 surrounding the smaller diameter portion of the spindle 18. The disc 58 has secured to its lower face a gear ring 61.

Screws 62 secure these parts together. The gear ring 61 has external upwardly facing bevel gear teeth 63 arranged to engage with the teeth 41 on the floating ring formed by the segments 38. Also on the underneath surface of the disc 58 are a number of spaced cylindrical bosses 64 each secured to the disc by a screw 65 and engaging in respective cylindrical recesses in the upwardly presented faces of the segments 38. The purpose of these is to hold the segments 38 against radial or circumferential movement while allowing the segments to move in a vertical direction under the control of the piston 29 as already described.

The gear ring 61 is mounted on its sleeve 59 through a ball bearing 66. At its upper end the disc 58 forming the main body portion of the turret has a stepped bore occupied by a further ball bearing 67.

This is situated adjacent to the nut 25 on the top of the spindle 18 and is enclosed by a removable cover 68 in the centre of the top of the turret. Removal of the cover 68 followed by removal of the nut 25 allows the whole of the turret to be removed from the slide. When such removal occurs the whole assembly including the piston 29, the ring 32, the segments 38, the gear ring 61 as well as the turret disc 28 and the sleeve 59 can be removed from the spindle 18. When re-inserting the assembly seals on the spindle must be engaged.

It has already been described that movement of the piston 29 as a result of introduction of fluid under pressure through the spindle drilling 26 causes the segments 38 to move downwardly so that engagement occurs between the teeth 39 thereon and the teeth 17 on the fixed ring 15. Simultaneously with such engagement there is engagement between the teeth 41 on the segments 38 and the teeth 63 on the gear ring 61 attached to the turret disc 58. Thus, when the segments 38 are prevented from rotating, the turret is also held by this means against rotation.

The shapes and match of the teeth is such as to remove any backlash. The bevel forms of the teeth 41 and 63 ensure this. It is also apparent that the bevel gear teeth must be straight cut.

When the piston 29 has been moved to disengage the segments 38 from the teeth 17 and from the teeth 63 engagement takes place as already described with the teeth of the gear 42 forming part of the indexing mechanism. When the indexing mechanism is actuated therefor, under these conditions the turret can be rotated because the segments 38 are non-rotatable with respect to the turret being engaged therewith through the bosses 64. Thus, in use, indexing can take place when required without the necessity for movement of the whole turret but only of the piston 29 and the parts attached to it and when locking is required the piston 29 is again moved so that the segments are locked not only to the fixed ring 15 but also to the gear ring 61 of the turret.

In order to allow dismantling as already described by the removal of the nut 25 from the top of the spindle 18 it is necessary to support the segments 38 during the process of removing the turret from the slide. For this purpose, drillings 71 through the turret and aligned with threaded holes 72 in the segments 38 are fitted with screws 73, the purpose of which is to secure the segments to the underneath surface of the turret disc 58.

Figure 3 and Figure 4 show means for indicating the condition of the turret with respect to indexing movement thereof.

On each of four faces of the turret is a plate 24 in the centre of which is the opening to accept the tool shank 57. The plates of which three are shown in Figure 1 are identified by numerals 74 and 76, and 76 respectively. Figures 3 and 4 show the plate 74 and the securing screws 77 whereby it is attached to the turret disc 58. Each plate 74, 75,76 and the fourth one which is now shown has blind drillings in its underneath edge. Such drillings in the plate 74 are indicated at 78 and 79 respectively. The plate 74 has two such holes as shown but the other plates 75, 76 and that which is not shown have other numbers of such holes. There are three positions for such holes and in one plate there are two holes in two other plates there are single holes but in different locations and in the fourth position there are no holes at all.

Adjacent to the position of the plates when the turret is in an indexed position is the mechanism shown in Figures 3 and 4. This includes three proximity switches 81, 82, 83 which are situated adjacent to the positions at which the holes in the plates 74, 75,76 etc. can register. Thus it is possible in accordance with the signals received from the proximity switches to determine which indexed position of the turret has been reached. The proximity switches 81,82, 83 are therefore electrically connected with a control unit which provides a signal to a central control for the cycling of the machine.

To determine whether the index lock for the turret is operative, a further mechanism is provided.

This mechanism comprises a lever 84 pivoted about a horizontal axis 85 and occupying a slot 86 in the portion 12 of the slide 10. The ring 32 attached to the annular piston 29 has an annular external groove 87 in which a projection on the end of the lever 84 engages. Vertical movement of the piston 29 causes the lever 84 to pivot about the axis 85 between two extreme positions within the slot 86.

The other end of the lever 34 has a head 88.

Attached to the head is a plate 89. In one position of the lever 84 the plate 89 is in close proximity to a horizontally mounted proximity switch 91 and in the other position the head is situated close to a further vertically mounted proximity switch 92. Electrical signals produced from the two proximity switches allow determination of the condition of the indexing lock for the turret.

A cover 92 encloses the mechanism including the proximity switches 81,82,83,91 and 92 and the lever head 88 with its plate 89.

Figure 2 also shows in the portion 12 of the slide 10 a passageway 93 for lubrication and/or cooling fluid to the tooling 55. This passage communicates through a running joint 94 between the said portion 12 of the sleeve and the turret disc 58 so that communication is made with an appropriate gallery 95 in the turret at each indexed position.

Claims (11)

1. A device for locking an indexable component comprising a part fixed to the component which is accurate in its location of the component, in indexed positions, and which is capable of holding the component securely in position.

2. A device as claimed in claim 1 in which the movable part is a number of segments forming a ring having teeth for engagement with the component and fixed part respectively.

3. A device as claimed in claim 1 or claim 2 in which the movable part is mounted for movement under the influence offluid under pressure.

4. A device as claimed in any one of the preceding claims wherein the teeth by means of which the movable part can engage with the component be indexed, are bevel gear teeth.

5. A device as claimed in any one of the preceding claims in which the movable part has teeth for alternative engagement between said fixed structure and a rotatable part of said means for indexing the component.

6. A device as claimed in any one of the preceding claims wherein the index position of the component is monitored by signal producing means.

7. A device as claimed in claim 6 in which the signal producing means includes different recognition elements for the different index positions of the component.

8. A device as claimed in claim 7 in which the recognition elements are groups of holes which can be aligned with proximity switches for signal production. The groups of holes co-operating with the proximity switches to produce different signals at each index position of the component.

9. A device as claimed in any one of the preceding claims in which the position of said movable part is monitored by signal producing means.

10. A device as claimed in claim 10 in which the signal producing means is a proximity switch which is arranged to produce a signal related to the position of the movable part.

11. A device for locking an indexable component substantially as hereinbefore described with reference to and as shown in the accompanying drawings.