GB2364661A

GB2364661A - Rotating table transfer machine

Info

Publication number: GB2364661A
Application number: GB0113441A
Authority: GB
Inventors: Federico Gozio
Original assignee: GOZIO FEDERICO Srl COSTRUZIO
Current assignee: GOZIO FEDERICO Srl COSTRUZIO
Priority date: 2000-06-02
Filing date: 2001-06-01
Publication date: 2002-02-06
Also published as: ITBS20000054A0; GB0113441D0; FR2809649A1; FR2809649B3; DE10126004A1; ITBS20000054A1; IT1314735B1

Abstract

The invention relates to a transfer machine with multiple workstations, of which at least one is for loading/discharge of the workpieces being machined, having a rotary table bearing as many workpiece-holding supports as there are workstations. Each support can be positioned in sequence opposite each workstation through stepwise rotation of the table, and the latter is controlled by means for stepwise rotation in one direction and continuous rotation without stopping in the opposite direction, through an angle of less than 360{C which is equal to the sum of the angles between the initial loading/discharge station and the final workstation.

Description

2364661 SYSTEM FOR ROTATING THE TABLE OF TRANSFER MACHINES This invention

relates to transfer machines in general and more particularly to a new system for rotating the workpiece-holding table of a transfer machine having multiple stations.

As is known, a transfer machine is a machine tool provided with multiple working stations and a rotary table, with a horizontal or vertical axis, which has the task of transferring the workpiece requiring machining from one station to the next by performing stepwise movements. One or two of the said stations are the so-called loading and discharge stations, where the machined workpiece is removed or discharged and a new unmachined workpiece requiring processing is added or loaded. These loading and discharge operations can be performed either manually or through the help of appropriate servo devices. One or more working units such as drills, taps, milling machines, etc., or detection units capable of performing tests and measurements to certify the quality of the machined pieces are however located at the other stations.

In a transfer machine of the conventional type workpiece-holding supports essentially comprising clamps are located on the table, while the working units are located around the table facing the parts. In this way, and as is generally the case, the table, starting from the loading position, can always rotate in the same direction bringing the finished part to the discharge station after rotating through 3600. In addition to this, in order to avoid collisions, the, working units have to be in a position which does not interfere with the moving workpieces while the table is in rotation, and the workpiece must remain immobilised on the corresponding supports. It is not therefore usually possible for the workpiece to move in any way when being transferred from one station to the next. This brings about an increase in processing I times, in that once the workpiece has come to face each working unit, it has to be rotated before being machined so that the correct side on which the specified operation has to be performed faces the tool.

A transfer machine in which each or any workpiece-holding support comprises a clamp and a swivel, which can rotate about two vertical and horizontal axes at right angles to achieve corresponding rotation of the workpieces as necessary, is however known from a previous patent application by the same applicant. The means for controlling such rotation, of reduced size, are located beneath and within the outline of the support, and are orientated along the vertical axis of rotation. These may be represented, for example, by two brushless motors which are independently and digitally controlled by a suitable digital control unit through which they can intervene. The motors are stably secured to the table, thus permitting the clamp to rotate even as the table is rotating, achieving an appreciable saving in time. However, this system prevents the table from rotating completely unless a special and sophisticated system for engaging and disengaging the units controlling rotation of the clamp and the swivel, or special rotating connectors, such as those based on mercury contacts, which are delicate and subject to early aging, and therefore not very.-reliable, are used. The operation of engaging and disengaging the clamps from the rotating units can also be a cause of errors.

The purpose of this invention is to overcome the abovementioned disadvantages, and therefore to allow the workpiece-holding clamps and with them the workpieces to rotate during the stepwise rotation of the tables from one workstation to another without having to make use of special connectors or sophisticated systems for engaging/disengaging control for the rotation of such clamps and eliminating any errors deriving from engaging/disengaging the clamp rotation units.

According to the invention there is provided a transfer machine having a plurality of workstations in which at least one is a station for loading/unloading workpieces for machining, a rotary table bearing as many workpiece-holding supports as there are said workstations, and in which each support can be positioned in sequence opposite each workstation through stepwise rotation of the table, characterised by control means for stepwise rotation of the table in one direction and continuous rotation of the table without stopping in the other direction.

According to a further aspect of the invention there is provided a method for control of a rotary table in a transfer machine with multiple workstations, of which at least one is for load ing/d ischarge of the workpieces on the workpiece-holder supports provided on the said table, characterised in that the table moves stepwise in one direction from the loading/discharge station to the final workstation without reaching the load ing/discharge station in the same direction of rotation and the table is returned to the starting position through rotation without stopping in the opposite direction.

Thus the workpiece-holding table may be caused to rotate first in one direction, from the initial station at which a workpiece is loaded onto the workpiece-holding clamp, to the final station at which the workpiece is machined on the same clamp, and then in an opposite direction so as to return the said clamp bearing the finished workpiece, without any intermediate stop, back to the initial station for discharge of the workpiece and loading a new workpiece. The machine repeats the operation in succession for each clamp mounted on the rotary table.

The table may rotate alternately in one direction and the other through less than 3600C, more specifically, may rotate in the outward direction, through an angle of rotation of as many steps as there are load i ng/d ischarge and workstations, less one step.

This innovation makes it possible to rotate the part as it is being transferred from one station to another, and therefore achieves an appreciable time saving without any special problems associated with control of the rotation of the clamps. Also, even though the table is caused to rotate further in this way in order to bring the workpiece from the last station to the first one, the difference in positioning time due to the greater rotation is minimised. In fact table positioning time is primarily governed by the stages of acceleration and deceleration and the stages of immobilisation and release, and is minimally dependent on the stage of rotation at constant speed.

The present invention will now be described further, by way of example, with reference to the appended drawing in which the single figure shows a diagrammatical view of a four-station transfer machine seen from above.

The transfer machine illustrated comprises a workpiece-holding rotary table 10 around which are several workstations S1, S2, S3... starting from a station C/S for loading the workpieces requiring machining and discharging the machined workpieces (if these two stations coincide).

The rotary table is controlled in order to rotate in steps in one direction (arrow A) and carry each workpiece in succession from the loading station to each workstation S1, S2, S3... where operating or detection units 11, 12, 13 respectively are provided, and in an opposite direction (arrow R) without stopping.

The stepwise rotation of the table in its outward travel does not reach 3600C and stops when it reaches the last workstation S3, starting from initial loading station C/S.

Because this rotation is less than 3600C the step between the last station and the load i ng/d ischarge station is no longer provided.

Thus, in a four-station machine of which one is a workpiece load ing/d ischarge station as shown in the drawing, and in which the stations are equally spaced at 900C, the table rotates through 2700C in the outward direction in a stepwise fashion, and likewise on returning but without stopping at the intermediate stations, only stopping at station C/S.

Obviously in a 6-station machine the rotation of the table will be limited to 3000C.

In practice, and with reference to the embodiment of a 4-station machine illustrated in the drawing, initially a first workpiece is loaded onto a support 14 at load ing/unloading station C/S. The rotary table then performs a first movement in a clockwise direction carrying the first workpiece to workstation S1, and the next support is moved to station C/S where a second workpiece is loaded.

On the second movement of the rotary table the first workpiece is carried to station S2, the second workpiece to station S1 and a third workpiece is loaded at station C/S on a subsequent support. On the third movement of the rotary table the first workpiece is positioned opposite station S3, where its machining is completed. The second workpiece is positioned opposite station S1, while a fourth workpiece is loaded on to the last support at C/S. The rotary table then performs a rotation in the anticlockwise direction without stopping, carrying the first finished workpiece to C/S for discharge, while the other workpieces are carried to the correct stations for the machining which they require. After a further workpiece has been loaded onto the support at C/S, the table resumes its stepwise rotation in a clockwise direction for a new operating cycle.

Claims

1 A transfer machine having a plurality of workstations in which at least one is a station for load ing/u nload ing workpieces for machining, a rotary table bearing as many workpiece-holding supports as there are said workstations, and in which each support can be positioned in sequence opposite each workstation through stepwise rotation of the table, characterised by control means for stepwise rotation of the table in one direction and continuous rotation of the table without stopping in the other direction.

2. A machine according to claim 1, in which the rotary table is caused to rotate stepwise in one direction between at least one initial load ing/u nloading station and a last workstation and continuously in the opposite direction between the last workstation and the initial load ing/d ischarge station.

3. A machine according to claim 2, in which the table is caused to rotate alternately in one direction and the other through an angle of less than 3600C.

4. A machine according to claim 3, in which the table is caused to rotate in one direction through an angle equal to the sum of the angles between the initial load ing/discharge station and the final workstation.

5. A machine according to claim 4, in which the table is caused to rotate stepwise through an angle of rotation in one direction of as many steps as there are workstations, less one step.

6. A method for control of a rotary table in a transfer machine with multiple workstations, of which at least one is for load ing/d ischarge of the workpieces on the workpiece-holder supports provided on the said table, characterised in that the table moves stepwise in one direction from the load ing/d ischarge station to the final workstation without reaching the load ing/d ischarge station in the same direction of rotation and the table is returned to the starting position through rotation without stopping in the opposite direction.

7. A method according to claim 6, in which the table is caused to rotate in one direction and the other through an angle of less than 3600C.

8. A machine substantially as described herein with reference to the accompanying drawing.

9. A method substantially as described herein with reference to the accompanying drawing.