GB1600118A

GB1600118A - Machine tool

Info

Publication number: GB1600118A
Application number: GB4606676A
Authority: GB
Original assignee: HERBERT Ltd ALFRED
Current assignee: HERBERT Ltd ALFRED
Priority date: 1978-02-03
Filing date: 1978-02-03
Publication date: 1981-10-14

Description

(54) MACHINE TOOL (71) We, ALFRED HERBERT LIMITED, a British Company located at P.O.

Box 30, Edgwick Works, Coventry, CV6 5GT, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it Is to be performed to be particularly described in and by the following statement: This invention relates to machine tools, and particularly to an automatic machine tool having a turret which is normally held against rotational movement but is releasable for such movement when indexing is required.

According to the invention, a machine tool comprises a turret adapted to support one or more tools and being indexible to bring the or each tool selectively into a working position, axially facing opposed surfaces of said turret and of a relatively rotationally fixed member being provided respectively with coupling formations, coupling means selectively operable to move generally radially between a first position in which it engages one or more formations on each of said turret and member to couple the turret and member together for normal use, and a second position in which it is disengaged from said formations to permit indexing movement of the turret, and clamping means operable to clamp the coupling means between the turret and fixed member.

Preferably, said coupling means is at least one plunger which may conveniently be moved into and out of coupling engagement with the formations by selectively operable actuating means which are preferably fluid pressure-operated.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross-section along the line 1-1 of Figure 2 in the direction of the arrows of part of an automatic machine tool showing a multi-station turret mounted for indexing movement; Figure 2 is a cross-section along the line 2-2 of Figure 1 in the direction of the arrows; Figure 3 is a part-sectional view, to an enlarged scale, of part of the machine tool of Figures 1 and 2; Figure 4 is a scrap view from above of part of Figure 3, and Figure 5 is a part-sectional side elevation of an indexing drive and control mechanism for the turret.

Referring to the drawings, these show a carrier 1, forming part of a machine tool (not shown) and having mounted thereon a multi-station turret 2 indexable, in this embodiment, over a range of twelve tool positions. The turret is mounted for rotational indexing movement on a spindle 3 supported in the carrier on roller bearings 4 and 5 and is retained axially on the spindle 3 between a shoulder 6 formed on the spindle and a nut 7 screwed onto a threaded end portion 8 of the spindle.

An annular piston member 9 surrounds the spindle 3 for axial sliding movement thereon and a Belleville washer 10 urges the piston member against the shoulder 6. The piston member carries an annular piston 11 slidable in an annular cylinder 12 defined between a pair of members 13, 14 secured to the carrier. The piston 11 divides the cylinder 12 into a pair of cylinder spaces 12A, 12B.

An indexing gear 15 is mounted on the spindle 3 so as to be fast for rotation therewith and meshes with a worm 16 journalled in the carrier and drivable in rotation by a motor 17 secured to a motor carrying bracket 18 fixed to the carrier (Figure 2). Indexing of the turret can be effected via the worm 16 and indexing gear 15 by rotation of the motor 17. In order to protect the indexing mechanism from the effect of rotational momentum of the large mass of the turret and to compensate for indexing discrepancies, the worm is capable of some axial movement and is driven by the motor via a shock absorbing device shown generally at 19 which will be described in more detail hereinafter.

The turret 2 is mounted on the shaft 3 by way of a coupling 20 to which it is rigidly secured, the coupling having a splined con nection 21 with the shaft. The turret is normally non-rotatably coupled to the carrier, by means of a series of mechanisms indicated generally at 22 which are operable to release the turret when it is desired to index the latter. In this embodiment, six mechanisms 22 are provided, equi-angularly disposed around the axis of the shaft 3.

One of the mechanisms 22 is shown in more detail in Figure 3. A ring 23 housed partly within an annular recess of the carrier and partly within a similar annular recess in the coupling member 20, is secured to the carrier by means of bolts 23A (Figure 1).

The ring has six equi-spaced radial bores formed therein, into each of which is pressfitted a bush 24 within which is mounted one end portion 25A of a piston 25 for sliding reciprocatory movement. A pair of lands 25C divide the interior of the bush into a pair of pressure chambers 25D, 25E respectively above and below the lands. The other end 25B of the piston 25 slides within a bore 26 of the body member 23 and sealing between the piston portions 25A, 25B and their co-operating surfaces is effected by O-rings 27, 28. Other seals are located between the bush 24 and body member 23 and between the carrier and body member 23. A plunger 29, cylindrical in this embodiment, projects radially outwardly from the piston 25 and has an extension 30 disposed with peripheral clearance within an axial recess of the piston and loosely pinned therein by means of a pin 31 so as to be capable of a limited floating action. Each plunger, when in its position as shown, co-operates with pairs of opposed coupling formations 32, 33 carried respectively by the carrier and turret and acts to locate these two components one with respect to the other. Each formation is, in this embodiment, a slot of generally halftrapezoidal section and the carrier has six equi-angularly spaced slots (Figure 2) formed in an axially facing surface thereof, each plunger 29 being at least partially engaged with a respective one of these slots at all times. The corresponding slots in the turret are also equi-angularly spaced and formed in an axially facing surface of the turret which is opposed to the slotted carrier surface. The formations 33 are radially foreshortened at their ends nearer to the piston 25.

As shown in Figure 1, the turret 2 is rendered non-rotatable with respect to the carrier 1 by means of the plungers 29, enabling a desired working operation to be performed upon a workpiece carried in conventional manner, for example in a chuck of the machine tool (not shown). During this time, the plungers 29 are urged into their positions engaged with the formations 32, 33 as shown by hydraulic pressure applied via a passage 34 to the underside of the lower piston land 25C. The piston member 9 is urged against the shoulder 6 by hydraulic pressure supplied to the clearance 12B, which assists the Belleville washer 10 in applying a clamping force via the spindle 3 and nut 7 to the coupling 20, thereby urging the plungers 29 tightly into engagement within their recesses. The floating action of the plungers on the pins 31 facilitates their accurate engagement in the recesses.

Moreover, the inclined angle at the trapezoidal slots, preferably 40 as shown, is chosen to provide a considerable wedging action between the plungers and the sides of the formations 32 and 33 with which they are engaged.

When it is desired to index the turret, pressure is removed from the space 12B and applied to the space 12A at the opposite side of the piston 11. This pressure is such as to overcome the force of the Belleville washer and permit the piston to move to the right as seen in Figure 1 by a distance defined by the space 12B, which is typically between .005 inches and .010 inches. This movement of the piston relieves the clamping pressure on the spindle and consequently on the plungers 29 and by interruping the pressure supply via the passage 34 to the underside of land 25C and applying pressure via passage 35 to the upper side of land 25C, the plungers 29 may be retracted into the bushes 24 to positions in which they are clear of the radially inner surfaces 33A of the formations 33, thereby freeing the turret for rotation with the spindle 3.

Indexing of the turret may now be effected by the motor 17 via the worm 16 and indexing gear 15, the motor being controlled in known manner by slotted discs 37, 38 fast for rotation with the left hand end portion 39 of the spindle 3. The slots in the disc 37 are equi-angularly spaced and equal in number to the number of turret tool positions, in this case twelve and the disc 38 has a single slot providing a datum position. The slots interrupt infra-red beams, during rotation of the spindle, and this information is converted into electrical signals by conventional means to control operation of the motor for indexing. The disc and beam arrangement operates a damping circuit for the motor to slow the latter and performs a further function to which reference will be made hereinafter.

Referring more specifically to Figure 5, the motor shaft 40 has a splined connection with a sleeve 41 which is in turn nonrotatably connected by a pin 42 to a shaft 43 of the shock absorber device 19. Also fast for rotation with the shaft 43 is an indexing disc 44 having a notch 44A in the periphery thereof into which a plunger 45 is normally urged by spring or other suitable means (not shown). Only one slot is required since the worm ratio is 12:1, which corresponds to the number of turret tool positions provided.

The plunger 45 is controlled by the infra-red beam and disc arrangement referred to above and is withdrawn from the slot to enable the motor 17 to drive the worm 16.

Once the motor starts to operate, as a result of the production of a timed impulse from a timing device, which may conveniently be in or actuated by an N.C. control system of the machine, the plunger 45 is urged towards its engaged position and rides over the peripheral edge of the disc 44 until it becomes aligned with the notch which it then engages to set a new indexing position of the turret. This action of engagement also switches off the supply to the motor and initiates the outward movement of the plun gers to re-engage the turret.

The shock absorber 19, which will now be described, acts to absorb any over-rotation of the turret resulting from the momentum thereof, which produces a racking action of the axially floating worm 16. The plungers 29 also aid in correcting any misalignment of the slots into which they return after indexing. Such return of the plungers is effected by reversing the pressure supply at passages 34 and 35.

The shock absorber device 19 comprises a casing 46 secured to a fixed part of the machine and having at one end an annulus 47 retained in the casing by a circlip or any other convenient means (not shown) and housing a bearing 49 for rotatably support ing one end of the shaft 43. A pair of Belleville washer packs 50 and 51 are located to either side of a common annular abutment 52 and bear against respective sleeves 53, 54 slidable axially within the casing 46.

Each sleeve engages a respective roller thrust bearing 55, 56, the former of which is preloaded by a nut 57 engaged on a threaded portion 58 of the shaft 43. The shock absorber 19 is able to absorb axial thrust applied in either direction as a result of racking of the worm 16, by compression of either pack of Belleville washers.

As seen from Figure 4, the slots provided in this embodiment in the turret and carrier are half-hexagonal when viewed from an end thereof and co-operate to form substantially hexagonal openings which receive the cylindrical plungers. It is of course possible to vary the shapes of slots and plungers as desired using, for example, rectangular or triangular slots with plungers of any convenient cross-section. The means for controlling actuation of the plungers and other components in timed relationship may be of any convenient kind selected from a wide variety of electrical, fluid operated and mechanical controls known in the art. When the machine tool of the invention is N.C.

controlled, the control means would conveniently form part of or be controlled by, the N.C. control system.

WHAT WE CLAIM IS: 1. A machine tool comprising a turret adapted to support one or more tools and being indexible to bring the or each tool selectively into a working position, axially facing opposed surfaces of said turret and of a relatively rotationally fixed member being provided respectively with coupling formations, coupling means selectively operable to move generally radially between a first position in which it engages one or more formations on each of said turret and member to couple the turret and member together for normal use, and a second position in which it is disengaged from said formations to permit indexing movement of the turret, and clamping means operable to clamp the coupling means between the turret and fixed member.

2. A machine tool according to Claim 1, wherein the coupling means is at least one plunger movable by selectively operable actuating means into and out of coupling engagement with the formations.

3. A machine tool according to Claim 1 or Claim 2 wherein the or each plunger is fluid pressure-operated.

4. A machine tool according to any one of the preceding claims wherein a plurality of coupling means is provided.

5. A machine tool according to Claim 4, wherein the coupling means are equiangularly disposed around the turret axis.

6. A machine tool according to Claim 2, wherein the actuating means for the or each plunger is a respective double acting radial piston slidable in a corresponding bore in said relatively fixed member, the or each piston being floatingly mounted on its associated plunger so as to be freely movable in a direction generally axially of the turret.

7. A machine tool according to any one of the preceding claims wherein the formations on the turret are of less radial extent in a direction towards the turret centre than the formations on the relatively fixed member whereby the coupling means may be fully disengaged from the turret formations whilst remaining engaged with the fixed member formations.

8. A machine tool according to any one of the preceding claims wherein the turret is mounted on a shaft which is rotatable by drive means to index the turret, the shaft being operatively connected to a shockabsorbing device which yields to absorb any rotation of the turret beyond a desired one of said working positions.

9. A machine tool according to Claim 8, wherein the shock-absorbing device includes a pair of resilient means which yield respectively for excessive rotation of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. worm ratio is 12:1, which corresponds to the number of turret tool positions provided. The plunger 45 is controlled by the infra-red beam and disc arrangement referred to above and is withdrawn from the slot to enable the motor 17 to drive the worm 16. Once the motor starts to operate, as a result of the production of a timed impulse from a timing device, which may conveniently be in or actuated by an N.C. control system of the machine, the plunger 45 is urged towards its engaged position and rides over the peripheral edge of the disc 44 until it becomes aligned with the notch which it then engages to set a new indexing position of the turret. This action of engagement also switches off the supply to the motor and initiates the outward movement of the plun gers to re-engage the turret. The shock absorber 19, which will now be described, acts to absorb any over-rotation of the turret resulting from the momentum thereof, which produces a racking action of the axially floating worm 16. The plungers 29 also aid in correcting any misalignment of the slots into which they return after indexing. Such return of the plungers is effected by reversing the pressure supply at passages 34 and 35. The shock absorber device 19 comprises a casing 46 secured to a fixed part of the machine and having at one end an annulus 47 retained in the casing by a circlip or any other convenient means (not shown) and housing a bearing 49 for rotatably support ing one end of the shaft 43. A pair of Belleville washer packs 50 and 51 are located to either side of a common annular abutment 52 and bear against respective sleeves 53, 54 slidable axially within the casing 46. Each sleeve engages a respective roller thrust bearing 55, 56, the former of which is preloaded by a nut 57 engaged on a threaded portion 58 of the shaft 43. The shock absorber 19 is able to absorb axial thrust applied in either direction as a result of racking of the worm 16, by compression of either pack of Belleville washers. As seen from Figure 4, the slots provided in this embodiment in the turret and carrier are half-hexagonal when viewed from an end thereof and co-operate to form substantially hexagonal openings which receive the cylindrical plungers. It is of course possible to vary the shapes of slots and plungers as desired using, for example, rectangular or triangular slots with plungers of any convenient cross-section. The means for controlling actuation of the plungers and other components in timed relationship may be of any convenient kind selected from a wide variety of electrical, fluid operated and mechanical controls known in the art. When the machine tool of the invention is N.C. controlled, the control means would conveniently form part of or be controlled by, the N.C. control system. WHAT WE CLAIM IS:

1. A machine tool comprising a turret adapted to support one or more tools and being indexible to bring the or each tool selectively into a working position, axially facing opposed surfaces of said turret and of a relatively rotationally fixed member being provided respectively with coupling formations, coupling means selectively operable to move generally radially between a first position in which it engages one or more formations on each of said turret and member to couple the turret and member together for normal use, and a second position in which it is disengaged from said formations to permit indexing movement of the turret, and clamping means operable to clamp the coupling means between the turret and fixed member.

turret in two opposed directions.

10. A machine tool according to any one of the preceding claims wherein the coupling formations are so shaped as to provide a wedging action on the associated plunger under the action of the clamping means.

11. A machine tool according to any one of the preceding claims wherein each of the coupling formations is of generally trapezoidal configuration when viewed in a direction radially of the turret, and the associated plunger engages the non-parallel sides thereof.

12. A machine tool according to Claim 8 wherein the turret is located in its working positions prior to actuation of the coupling means by locking means fixed with respect to the shaft engaging co-operating means rotatable with the shaft, the locking means being actuated by control means to lock the turret in a selected working position.

13. A machine tool according to Claim 12, wherein the locking means is a plunger and the co-operating means is a series of slots in the shaft or in means fixed to the shaft.

14. A machine tool according to any one of the preceding claims wherein the or each plunger has a formation of the turret and a formation of the fixed member arranged in diametrically opposed relationship thereto.

15. A machine tool according to any one of the preceding claims wherein said clamping means is a fluid pressure-operated device operable to apply an axial clamping force to the turret.

16. A machine tool according to Claim 15 wherein the clamping means acts on a spindle upon which the turret is mounted for rotation.

17. A machine tool substantially as hereinbefore described with reference to the accompanying drawings.