GB2048133A

GB2048133A - A supporting and actuating device for a rotatable turntable for a machine tool

Info

Publication number: GB2048133A
Application number: GB8012288A
Authority: GB
Original assignee: IDROMA SpA
Current assignee: IDROMA SpA
Priority date: 1979-04-17
Filing date: 1980-04-15
Publication date: 1980-12-10
Also published as: IT7921921A0; ES490567A0; GB2048133B; ES8103556A1; DE3014666A1; IT1112308B; FR2454353A1

Abstract

A device for supporting and actuating a turntable 2 for a machine tool comprises a base member 3, a member 5 fitted for supporting the turntable 2 and mounted on the member 3 for rotation about a vertical axis and movement along said axis. The member 5 is fixed to a screw 13 which is screwed into a central threaded bore in an actuating member in the form of a gear 11 drivable in either direction about said axis. A dog clutch 8 engageable and disengageable by axial movement of the member 5 is provided between member 5 and member 3. A first one- way clutch arrangement 16 acts between the base member and the turntable supporting member and a second one-way clutch arrangement 21 acts between member 11 and member 5. The direction of rotation of said actuating member relative to the turntable supporting member in which the clutch 21 arrangement is freewheeling is opposite to the direction of rotation of the member 5 relative to the member 3 in which the clutch arrangement 16 is freewheeling, and the screw threaded engagement between screw 13 and gear 11 operates to move the member 5 axially relative to the member 11 and member 3, in consequence of rotational movement of the member 11 relative to the member 5 in order to effect engagement and disengagement of the dog clutch 8. <IMAGE>

Description

SPECIFICATION A supporting and actuating device for a rotatable turntable for a machine tool DESCRIPTION OF INVENTION This invention relates to a device for supporting and actuating a turntable for a machine tool, the device being of the kind comprising: a stationary base member fitted with reversible drive means, a turn-table supporting member fitted with turntable securing means and mounted on the base member so that said turn-table supporting member can rotate about an axis and move along said axis, so as to make angular movements for positioning the turn-table and axial movements for locking and unlocking it, an actuating member for actuating the turn-table supporting member so that it can make the aforementioned angular and axial movements, the means being rotatably mounted on the base member and actuable by said drive means, a locking and unlocking clutch arrangement, as hereinbefore defined, engageable and disengageable by axial movement of the turntable supporting member relative to the base member in respective opposite directions, respectively to prevent rotational movement of the turntable supporting member relative to the base member in either sense about said axis and to permit such relative movement in either sense, a first one-way clutch arrangement acting between the base member and the turn-table supporting member, said one-way clutch arrangement comprising recesses and a spring catch, a screw and nut coupling and a second one-way clutch arrangement both acting between said actuating member and the turn-table-supporting member, said second one-way clutch arrangement including recesses and a spring catch.

A turntable supporting and actuating device of the aforementioned kind must support the turntable in a rigid manner because machine-tool turntables are subjected to the forces, usually high, arising in machining operations from the action between the workpieces and tools, whether such turntables are used to bear a plurality of workpieces or a plurality of tools.

The known devices in present use have considerable height, i.e. a considerable distance between the base surfaces via which they are secured to the respective machine tools, and their top surfaces to which the respective turn-tables are secured.

Because of their height, these known devices suffer considerable tilting moments under the action of the forces arising in machining operations, more particularly the transverse components of such forces resulting in high mechanical stresses on the device and considerable elastic strain thereof. The result is that the turn-table is not supported with the required rigidity.

In order to reduce the height, it has been proposed to form the turn-table bearing member integrally with the turn-table. This would reduce bulk but of course has practical and economic disadvantages e.g. the impossibility of massproducing supporting and actuating devices as independent units.

It is an object of the invention to provide a turntable supporting and actuating device having structural and operating characteristics such that it can bear a turn-table with the necessary rigidity.

To this end, according to the invention there is provided a device for supporting and actuating a turn-table for a machine tool, of the kind comprising; a stationary base member fitted with reversible drive means, a turn-table supporting member fitted with turn-table securing means and mounted on the base member so that said turntable supporting member can rotate about an axis and move along said axis, so as to make angular movements for positioning the turn-table and axial movements for locking and unlocking it, an actuating member for actuating the turn-table supporting member so that the turn-table supporting member can make the aforementioned angular and axial movements, the actuating member being rotatably mounted on the base member and actuable by said drive means, a locking and unlocking clutch arrangement, as hereinbefore defined, engageable and disengageable by axial movement of the turntable supporting member relative to the base member in respective opposite directions, respectively to prevent rotational movement of the turn-table supporting member relative to the base member in either sense about said axis and to permit such relative movement in either sense, a first one-way clutch arrangement acting between the base member and the turn-table supporting member, said one-way clutch arrangement comprising recess and a spring catch, a screw and nut coupling and a second one-way clutch arrangement both acting between said actuating member and the turn-table supporting member, said second one-way clutch arrangement including recesses and a spring catch and being so arranged that the direction of rotation of said actuating member relative to the turn-table supporting member in which said second one-way clutch arrangement is freewheeling is opposite to the direction of rotation of the turn-table supporting member relative to the base member in which the first one-way clutch arrangement is freewheeling, said screw and nut coupling operating to move the turntable supporting member axially relative to the actuating member and the base member, in consequence of rotational movement of the actuating member relative to the turn-table supporting member in order to effect locking of the turn-table supporting member against, and unlocking of the turntable supporting member for, rotational movement relative to the base member, and wherein the screw of the screw and nut coupling is fixed with respect to the turn-table supporting member and extends through the base member, and the actuating member comprises a wheel having an internal thread engaging said screw so that said wheel forms the nut of the screw and nut coupling, said wheel also having external teeth engaging the drive means. Preferably the catches of first and second one way clutch arrangements are aligned, the axis of such alignment being perpendicular to the axis around which the turn-table supporting member can rotate.

An embodiment of the invention is described below by way of non-limitative examples with reference to the accompanying drawings in which: Figure 1 is a view in section of a device embodying the invention and Figure 2 is another view in section of the device according to the invention, along line Il-Il of Figure 1.

With reference to the accompanying drawings, the general reference 1 denotes a device embodying the invention adapted to be secured to a machine tool and to support and actuate a turntable 2, diagrammatically indicated by chaindotted lines.

Device 1 comprises a stationary base member 3, having a bottom surface 3a adapted to be secured to a machine tool (conventional and therefore not shown).

The stationary base member 3 has known drive means 4 comprising a driving worm 4a. The direction of rotation of the worm 4a can be reversed.

A turntable supporting member 5 is mounted on the base member 3 for rotation about an axis x-x and for movement along the axis x-x. The turn-table bearing member 5 has an upper planar supporting surface 6a, and a cylindrical centering surface 6b, for turn-table 2, and a locating spigot 7a and screws 7b for securing the turn-table A locking and unlocking clutch arrangement 8 is provided between member 5 and comprises a toothed ring 9 secured to member 3 and a toothed ring 10 secured to member 5, by screws 8a and pins 8b respectively.The clutch 8 is, in effect, a dog clutch, the teeth of rings 9 and 10 constituting the clutch dogs and interengaging with one another to prevent relative rotation of the member 5 relative to member 3 when the member 5 is in the axial position relative to member 3 which is shown in Figure 1. The teeth of ring 10 are, however, disengageable from the teeth of ring 9, to allow rotation of member 5 relative to member 3, by moving the member 5 axially upwardly from the position shown in Figure 1.

Device 1 also comprises an actuating member 11 rotatably mounted in member 3 and rotatable about axis x-x by the drive worm 4a. Member 1 1 is adapted to produce angular motion for positioning the turn-table and axially locking and releasing it.

A screw and nut coupling 12 is provided between the actuating member 11 and the turntable supporting means 5. Coupling 12 comprises an externally threaded screw 13 fixed with respect to member 5 and extending through member 3, and engaged in an internal thread 14 fixed with respect to the actuating member 11.

The actuating member 1 1 is in the form of an annular member having the internal thread 14 formed therein and having its periphery formed as the periphery of a worm gear having teeth 15 engaging the threads of the worm 4a of the drive means 4.

A one-way clutch or ratchet clutch 16 is interposed between member 5 and member 3.

The clutch 16 comprises a spring catch 17 carried by the screw 13 and able to cooperate with a number of recesses 1 Ba, 1 Bh, 1 Bc, 1 Bd, formed in a ring 19 encircling screw 13 and secured by screws 20 to the base member 3. The respective recesses 1 Ba, 1 Bb, 1 Bc, and 1 8d each define a respective angular position of the member 5 relative to the member 3.

A second one-way or ratchet clutch 21 is provided acting between member 5 and member 11. Clutch 21. comprises a spring catch 22 mounted in screw 13 and a recess 23 formed in a ring 24 encircling screw 13 and secured by screws 25 to the actuating member 11.

The spring catches 17 and 22 are slidably disposed in a common passage extending diametrically through screw 13 perpendicular to axis x-x.

The catches 17 and 22 have at their radially outer ends respective detents 1 7a, 23a, of sawtooth form (Figure 2) which are offset axially from one another, as are the respective rings 19, 24.

The radially inner ends of catches 17, 22 face towards one another and are acted upon by a single spring 23 disposed between them to urge the catches 17, 22 radially outwardly. The catches 17, 22 are so dimensioned radially that their radially inner ends abut when either catch is fully engaged in the or a respective recess and the other is retracted to the extent that the free end of its detent lies just at the cylindrical internal surface of the respective ring 19 or 24.

The catches are aligned along the axis perpendicular to the axis x-x.

The actuating means 11 is rotatably supported in base member 3 by known rolling element bearings 40,41 and a plain bearing 42 having cylindrical surfaces.

The screw 13, and thus the member 5 secured thereto, is supported for rotation about axis x-x and for reciprocating movement along axis x-x by a plain bearing comprising a cylindrical bore in ring 19 receiving a cylindrical journal 27 on screw 13 and by a plain cylindrical bearing surface farmed in a ring 29 secured to member 11, receiving a cylindrical journal 28 formed on screw 13.

Members 5 and 3 have rings 30,31 respectively, fitted with gaskets 32, 33, 34 for sealing.

Screw 13 is rigidly secured to member 5 by a key 35 and a locking bush 36.

The operation of the device will now be described with reference to the initial state, wherethe device is locked as shown in Figures 1 and 2.

To unlock and adjust the angular position of the member 5, wheel 11 and ring 24 are rotated in the direction of arrow F (Figure 2), under the action of drive means 4. Coupling 12 thus moves member 5 axially, (as member 11 is unscrewed on screw 13) so that clutch 8 disengages and releases the member 5, and with it screw 13 for rotation. When recess 23 is opposite catch 22 and the active detent 22a engages in the recess, continued rotation of ring 24 drives screw 13 and member 5 in rotation.

During the aforementioned rotation, catch 17 is ejected from (i.e. cammed out of) recess 18a, in which it had previously been engaged, and is ready to engage the next recess 1 bob. When catch 17 has engaged in recess 18a, the drive means reverse the direction of rotation. Screw 13 is prevented from reversing the rotation of joint 1 6, since catch 17 has engaged in recess 1 bob.

Consequently, when ring 24 rotates in the direction opposite to that shown by arrow F, it axially moves member 5, via coupling 12, towards the base member 3 until the clutch 8 engages and thus locks the device.

At the end of the period of rotation of ring 24 in the direction of arrow F, the turn-table supporting member, as a result of inertial torques if any, may rotate an extra distance the limit of such distance being a distance which is sufficient to take up entirely the distance between the tail ends 1 7b, 22b of catches 17 and 22, so that the catches abut one another.

When ring 24 reverses its direction of rotation, the aforementioned extra rotation is completely recovered since catch 22 is ejected from recess 23 and forces catch 17 to re-engage the proper recess 18b after partly coming out of it during the aforementioned excess rotation.

The main advantage of the bearing and actuating device described with reference to the drawings is that its height is limited, so that it supports the turntable with adequate rigidity.

Another advantage is that the device can be applied to machine tools even when the available space is limited, e.g. on lathes having a reduced centre height. In such cases the device and turntable can be directly secured to the top surface of the carriage without expensive operations such as forming the carriages with seats for receiving and holding a portion of the device.

Claims

1. A device for supporting and actuating a turntable for a machine tool, of the kind comprising; a stationary base member fitted with reversible drive means, a turn-table supporting member fitted with turn-table securing means and mounted on the base member so that said turntable supporting member can rotate about an axis and move along said axis, so as to make angular movements for positioning the turn-table and axial movements for locking and unlocking it, an actuating member for actuating the turntable supporting member so that the turn-table supporting member can make the aforementioned angular and axial movements, the actuating member being rotatably mounted on the base member and actuable by said drive means, a locking and unlocking clutch arrangement, as hereinbefore defined, engageable and disengageable by axial movement of the turntable supporting member relative to the base member in respective opposite directions, respectively to prevent rotational movement of the turn-table supporting member relative to the base member in either sense about said axis and to permit such relative movement in either sense, a first one-way clutch arrangement acting between the base member and the turn-table supporting member, said one-way clutch arrangement comprising recesses and a spring catch, a screw and nut coupling and a second one-way clutch arrangement both acting between said actuating member and the turn table supporting member, said second one-way clutch arrangement including recesses and a spring catch and being so arranged that the direction of rotation of said actuating member relative to the turn-table supporting member in which said second one-way clutch arrangement is freewheeling is opposite to the direction of rotation of the turn-table supporting member relative to the base member in which the first one-way clutch arrangement is freewheeling, said screw and nut coupling operating to move the turntable supporting member axially relative to the actuating member and the base member, in consequence of rotational movement of the actuating member relative to the turn-table supporting member in order to effect locking of the turn-table supporting member against, and unlocking of the turn-table supporting member for, rotational movement relative to the base member, and wherein the screw of the screw and nut coupling is fixed with respect to the turn-table supporting member and extends through the base member, and the actuating member comprises a wheel having an internal thread engaging said screw so that said wheel forms the nut of the screw and nut coupling, said wheel also having external teeth engaging the drive means.

2. A device according to claim 1 wherein the catches of the first and second one-way clutch arrangements are aligned, the axis of such alignment being perpendicular to the axis around which the turn-table supporting member can rotate.

3. A device for supporting and actuating a turntable for a machine tool, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

4. Any novel feature or combination of features described herein.