GB2049505A - Automatic tool changing arrangement on a machine tool - Google Patents

Abstract

For the purpose of a tool change a work spindle (6) is moved along a tool axis (z) out of a work position into a tool changing position and a tool changing device (9) is brought alternately into a transfer position relative to the work spindle (6) and relative to a tool magazine (7). The movement of the work spindle (6) into the tool changing position is correlated with the movement of the tool changing device (9) into the transfer position relative to the work spindle (6), a positive association existing between the two movements. A support arm (11) of the changing device is pivotally supported on a frame (10) of the machine and guides a carriage (13) which accommodates a double arm gripper (14). A follower (15) on the support arm interacts with a cam (16) on an upright (3) during axial movement of the upright with a spindle head (5) to pivot the arm into a tool changing position. <IMAGE>

Description

SPECIFICATION Automatic tool changing arrangement on a machine tool The invention relates to an automatic tool changing arrangement on a machine tool, more particularly on a machining centre.

Machining centres are known, in which in preparation for a tool change the sliding of an upright carriage out of its work position into a toci changing position occurs, and then a tool changing device, which pivots alternatively into a transfer position relative to the work spindle and relative to a tool magazine arranged at the side of the upright carriage, performs the tool change (Federal German Offenlegungschrift 26 13736, DT-Zeitschrift fur industrielle Fertigung (German Journal of Industrial Production) 60 (1970) No. 11 P. 660-661, Prospectus MM 800127615 M JMP of Messrs, Kearney & BR< Trecker Corp. USA).

The functional cycle which underlies the known devices in conjunction with the preparation of the tool change is characterised by the fact that the tool changing device is brought into the transfer position to the work spindle only when the upright carriage has reached the tool changing position. This causes a lengthening of the tool changing times, which leads to longer non productive times and hence to a reduction in productivity, more particularly in the case of machining centres in which a tool change is performed frequently.

A further disadvantage of the known arrangements lies in the fact that more particularly the feed movement of the tool changing device, whereby it is brought into the transfer position relative to the work spindle, must be braked at its extreme point. This limit position braking, the necessity for which results from the relatively high speed at which it is necessary for the tool changing device to execute this movement in order to achieve short changing times in these devices, necessitates a greater outlay.

It is an object of the invention to achieve a reduction of the tool changing times and to reduce the outlay for the execution of the movement of the tool changing device into the transfer position to the work spindle.

The technical reasons for the disadvantages of the known solutions mentioned are due substantially to the fact that the functional cycles for the movement of the work spindle out of the work position into the tool changing position, and of the tool changing device into the transfer position relative to the work spindle, are performed mutually separately and at different times.

In order to eliminate these causes, the underlying aim of the invention is to produce an arrangement wherein the two functional cycles are given such a configuration that, as soon as the work spindle has attained the tool changing position, the tool changing device assumes the transfer position relative to the work spindle and a limit position braking for this movement of the tool changing device is unnecessary.

The invention consists in an automatic tool chang ing arrangement on a machine tool, wherein in order to prepare for a tool change the work spindle is moved in the tool axis (z axis) out of the work position into a tool changing position and a tool changing device is brought alternately into a transfer position relative to the work spindle and relative to the tool magazine, the said arrangement comprising means by which the movement of the work spindle into the tool changing position is correlated with the movement of the tool changing device into the transfer position relative to the work spindle, a positive association existing between the two movements.

According to further features of the invention, the tool changing device stands in positive relationship to the upright carriage of the machine. The upright carriage has a cam piece with a bracing cam, whilst in the movement path of the cam piece which extends in the z axis there is arranged a bracing follower firmly attached to the tool changing device, which is operatively associated with the bracing cam. The bracing cam has a region extending parallel to the z axis, which is complemented by a cam configuration analogous to the movement of the tool changing device into the transfer position relative to the work spindle. The bracing follower is fixed to the pivotally movable support arm of the tool changing device.

In order to make the invention clearly understood reference will now be made to the accompanying drawings which are given by way of example and in which Figure 1 is a plan view of parts of a machining centre; Figure 2 illustrates the essential features of the invention in the deviated position of a tool changing device; and Figure 3 shows the tool changing device according to Figure 2 in the transfer position of the tool changing device to the work spindle.

On an upright foundation 1 there is arranged a cross carriage 2 displacable in the x axis which in turn accommodates an upright 3 movable in the z axis. A tool carriage 4 with spindle head 5 and work spindle 6 are shown, these being displacable vertically on the upright 3. A tool magazine 7 and a tool changing device 9 pivotally mobile about an axis 8 are fixed to a support frame 10 arranged at the side of the upright 3. The support frame 10 is firmly attached to the cross carriage 2 and is additionally retained on the upright 3. The tool changing device 9 comprises a support arm 11 pivotable about the axis 8, and providing a guideway 12 (Figure 2 and 3) on which a carriage 13 is slidably arranged.The carriage 13 accommodates a double armed gripper 14 capable of executing a 180 rotary movement and being axially slidable.

As may be seen from Figures 2 and 3, a bracing follower 15 is fixed to the support arm 11 and is in abutment with the bracing cam 16 of a cam piece firmly attached to the upright 3.

The mode of operation of the device according to the invention will be described in further detail hereinbelow in conjunction with the tool changing operation, the explanation of the relevant functional cycle being given on the assumption that the next tool is held ready in the double armed gripper 14.

In order to prepare for the tool changing, the upright 3 travels back, whereby the work spindle 6 is moved in the tool axis out of its work position towards the tool magazine 7. At the beginning of this sliding movement of the upright 3, the tool changing device 9 occupies a standby position. In this standby position the support arm 11 assumes the position indicated in Figure 2, so that the double armed gripper 14 is swivelled away from the work spindle 6 through 900.

In the course of its backward movement, the upright 3 actuates a limit sensor, not shown, whereby a hydraulic device, likewise not shown, substantially constituted by way valves and work cylinders, initiates a counterclockwise movement of the support arm 11. Due to this movement, the bracing follower 15 comes into abutment with the cam piece 17 in the region of the bracing cam 16 extending parallel to the z axis, which results in the establishment of an operative connection between the upright 3 and the tool changing device 9.Due to this positive association which now exists between the upright 3 and the tool changing device 9, upon the further backward travel of the upright 3 the support arm 11 and hence the double armed gripper 14 commence to pivot into the transfer position to the work spindle 6 as soon as the bracing follower 15 has left that region of the bracing cam 16 extending parallel of the z axis. With the attainment of the position illustrated in Figure 3 the upright 3 completes its backward movement, whilst simultaneous ly the work spindle 6 has been brought into the tool changing position and the tool changing device 9 has been brought into the transfer position to the work spindle 6 (Figure 1).

The reduction in speed of the described upright movement occurs in known mannerthrough a positional control circuit continuously until the tool changing position is reached. Due to the positive association which exists in this phase between the upright 3 and the tool changing device 9, the pivotal movement of the support arm 11 is simultaneously braked analogously, so that a special limit position braking for this movement of the tool changing device 9 can be omitted. Since the further course of the tool change at the work spindle 6 is realised by known functional principles, the operational steps following the above-described functional cycle need not be described in detail.

After the tool change has been effected and a radial sliding of the double armed gripper 14 away from the work spindle 6 has been performed, the work spindle 6 is moved back out of the tool changing position into the required work position.

For this purpose the said hydraulic device pivots the support arm 11 back away from the work spindle 6.

This pivotal movement is complete when the bracing follower 15 has left the region of the bracing cam 16. The support arm 11 has thus reached its position shown in Figure 2, and the actual tool changing operation is complete after the work spindle 6 has attained the prescribed work position.

During the machining, the tool changing device 9 performs an exchange of the used tool for a fresh tool at the tool magazine 7, which need not be described here. Then the tool changing device 9 travels back into the abovementioned standby position.

Claims (5)

1. An automatictoolchanging arrangement on a machine tool, wherein in order to prepare for a tool change the work spindle is moved in the tool axis (z axis) out of the work position into a tool changing position and a tool changing device is brought alternately into a transfer position relative to the work spindle and relative to the tool magazine, the said arrangement comprising means by which the movement of the work spindle into the tool changing position is correlated with the movement of the tool changing device into the transfer position relative to the work spindle, a positive association existing between the two movements.

2. An automatic tool changing arrangement as claimed in claim 1,wherein the tool changing device is positively connected to an upright carriage member.

3. An automatic tool changing arrangement as claimed in claim 2, wherein the upright carriage member carries a cam piece having a bracing cam formation against which acts a bracing follower firmly attached to the changing device, the bracing follower being arranged in the movement path of the cam piece extending in the z axis.

4. An automatic tool changing arrangement as claimed in claim 3, wherein the bracing cam has a region extending parallel to the z axis which is complemented by a cam configuration analogous to the movement of the tool changing device into the transfer position relative to the work spindle.

5. An automatic tool changing arrangement as claimed in claim 3 or 4, wherein the bracing follower is fixed to a pivotally movable support arm of the tool changing device.