Automatic tool changing device

A tool changing device for tool systems in which a tool head and a tool holder are connected with one another by means of an automatic clamping mechanism which includes an integrated clamping screw. The tool changing device includes a lifting carriage which is movable on several axes and a rotatably mounted, motor driven pivot arm which is mounted on the lifting carriage. The pivot arm has a free end which is equipped with a gripper holder having at least four tool locations and an integrated clamping shaft. Both ends of the clamping shaft are provided with profiles which permit transfer of torques. The clamping shaft can be moved axially in such a manner that it can be coupled with the clamping screw of a tool holder either from the left or from the right.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for changing and releasing or 
clamping in the tool in tool systems in which a tool head and a tool 
holder are connected together by means of a clamping unit. The invention 
relates, in particular, to such tool systems in which the clamping screw 
of the clamping unit is integrated in the tool holder. 
For such machine tools, too changing devices are known in which a gripping 
element takes the tool out of the basic tool holder and inserts a new one. 
A clamping unit installed in the machine tool releases and clamps in the 
tool. Releasing and clamping in of the tool are effected manually. 
U.S. Pat. 4,581,811 discloses a tool changing device in which the clamping 
screw is operated by an automatic device stationarily attached to the 
machine tool. The machine tool is provided with a tool holder receptacle 
having a central bore into which a tool holder can be inserted, the tool 
holder being equipped with a cylindrical section for engagement of a 
changing arm. The tool holder is connected with the tool receptacle by 
means of a clamping unit including a clamping screw. The cylindrical 
section of the tool holder is equipped with a radial, threaded bore. At 
the free end of a changing arm which operates independently of the machine 
tool, there is disposed a motor-driven connecting bolt which is provided 
with an external thread matching the threaded bore of the cylindrical 
section of the tool holder. To change the tool, the connecting bolt of the 
changing arm is automatically screwed into the radial, threaded bore of 
the tool holder. The threaded bore and the connecting bolt are connected 
together in the correct position by way of prism-shaped centering recesses 
provided at the outer end of the changing head. A motor-driven screwdriver 
stationarily provided at the machine tool loosens the clamping screw in 
the tool receptacle. The tool is removed by the changing arm and an 
identical changing head disposed on the changing arm diametrally opposite 
the old tool head is attached. Then the screwdriver tightens the clamping 
screw again. 
It is a drawback of this device that the exchange and release or tightening 
of the tool is performed by means of two separate devices. Not all machine 
tools provide sufficient space for a screwdriver to be attached 
stationarily on the machine. Another drawback of the above-described tool 
changing device is that right and left tool arrangements require 
appropriately adapted embodiments of this device. Thus, this tool changing 
device is not universally usable. Finally, it is a further drawback of the 
system that the changing arm provides no more than two locations for 
changing heads. Thus, for machine tools having tool receptacles able to 
accommodate a plurality of exchanging heads, the tool change times are 
lengthened considerably. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a tool 
changing device for a machine tool in which the changing head and the tool 
receptacle are connected together by means of an automatic clamping unit 
equipped with an integrated clamping screw which permits automatic 
releasing and tightening as well as exchanging of tools arranged axially 
or radially to the machine axis by means of a single device which is 
independent of the machine tool, is able to service left-hand and 
right-hand tool arrangements equally well, and provides for more than two 
locations for changing heads. 
The invention solves this problem in that a rotatably mounted pivot arm is 
disposed at a lifting carriage which is movable on several axes. An 
associated drive permits cadenced movement of the pivot arm into any 
desired angle. At the free end of the pivot arm there is disposed a 
gripper holder having at least four tool locations. Additionally, a 
clamping shaft is integrated in the pivot arm and is provided at both its 
ends with a profile able to transmit torques. This clamping shaft can be 
moved axially in such a manner that it can be coupled with the clamping 
screw of a tool holder either on the left or on the right.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The tool changing device shown in FIGS. 1a and 1b is composed of a lifting 
carriage 1 to which is fastened a pivot arm 2. Pivot arm 2 is equipped 
with a gripper holder 4 and is penetrated by a clamping shaft 5. 
The lifting carriage 1, which operates independently of the machine tool 
(not illustrated), may be moved on one, two, or three axes by carriage 
moving mechanism 20. The pivot arm 2 has a square cross section and is 
mounted on lifting carriage 1 so as to be pivotal about an axis 6. The 
drive 21 for pivot arm 2 may advantageously be integrated in the lifting 
carriage 1. Drive 21 rotates pivot arm 2 by angular increments, such as 
180.degree., 90.degree., or any other desired angle. 
At the lower end of pivot arm 2, on one of the four sides, there is 
attached a gripper holder 4 which is rotatable about an axis 7. The 
gripper holder 4 is equipped with at least four tool grippers 8 for 
selectively receiving and releasing tool heads, such as tool head 18 
having a cutting tool 22. In the horizontal plane, perpendicular to axis 
7, the pivot arm 2 is penetrated by a motor driven, axially displaceable 
clamping shaft 5. Each end 9 of the clamping shaft 5 has a profile which 
enables it to transmit torques. 
FIG. 2 is a cross-sectional view of the lower part of pivot arm 2, and 
shows the clamping shaft 5, an associated drive for rotating clamping 
shaft 5, and a mechanism for shifting shaft 5 axially. 
The drive for rotating clamping shaft 5 includes a motor 10 which is 
mounted within pivot arm 2. A gear 23 is mounted on the shaft of motor 10, 
which preferably has a predetermined maximum torque (as by providing a 
built-in clutch which slips when the predetermined maximum torque is 
exceeded) and is rotatable either clockwise or counterclockwise. Gear 23 
meshes with a gear 24 affixed to rotatably mounted shaft 25. Elongated 
gear 11 is also mounted on shaft 25. A gear 26 affixed to clamping shaft 5 
meshes with gear 11. As a result, rotary motion from motor 10 is 
transferred via gears 23, 24, 11, and 26, to shaft 9. 
The mechanism for shifting shaft 5 axially includes a pneumatic connection 
12 and a spring 13 (a portion of which is shown in dot-dash lines). If the 
pneumatic connection 12 is charged with compressed air, chamber 14 is 
filled with air and clamping shaft 5 is moved to the left out of the pivot 
arm 2 against the force of spring 13. Because gear 11 is elongated, it 
remains in meshing relationship with gear 26. Once the flow of compressed 
air ceases, spring 13 pushes bit clamping shaft 5 back into the 
illustrated position. Accordingly, it will be apparent that the shifting 
mechanism permits one end 9 of shaft 5 to be selectively extended from 
side 27 of pivot arm 2, or the other end 9 to be selectively extended from 
the other side 28 of pivot arm 2. End sensors 15 and 16 are used to detect 
the axial position of clamping shaft 5. 
Returning to FIGS. 1a and 1b, it will be seen that the ends 9 are spaced 
apart from the gripper holder 4 but are aligned with the grippers 8 when 
gripper holder 4 is in the position illustrated. Either end 9 can be 
extended to participate in a tool changing operation, depending upon 
whether side 27 or side 28 is moved next to the tool holder (not shown in 
FIGS. 1a and 1b). To conduct a tool changing operation, pivot arm 2 is 
moved so that a tool exchange region on the appropriate side of arm 2 lies 
parallel to the tool holder (the tool exchange region for side 28 is the 
region between dotted lines 29 in FIG. 1a). The tool changing operations 
will be explained in more detail with reference to FIGS. 3 and 4. 
In FIG. 3, pivot arm 2 has been moved so that the appropriate side (side 28 
in this example) lies adjacent the tool holder 17 and so that the tool 
exchange region for that side (corresponding to the region between dotted 
lines 29 in FIG. 1a) is parallel to the tool holder 17. In this position, 
the tool head 18 disposed in tool holder 17 can be seized by gripper 8. 
Furthermore tool holder 17 includes a clamping unit having a clamping 
screw (described below) with a tensioning socket 29 which is positioned to 
receive the end 9 (see FIG. 2) of shaft 5. The end 9 is moved axially into 
socket 29 while shaft 5 is slowly rotated. Socket 29 has a periphery which 
mates with that of end 9, so that the rotation of shaft 5 can be 
transferred to the clamping unit whithin tool holder 17. The clamping unit 
uncouples the tool head 18 from the tool holder 17. 
In the tool holder 17 is integrated a clamping unit having a clamping screw 
30, which is movable in longitudinal direction, and locking pins 31; these 
form an angle with the longitudinal axis 17a of the tool holder 17. 
On the side facing the tool head 18, the clamping screw 30 has a conical 
head 30a which serves to press the locking pins 31 against the wall 18b of 
bore 18a in the tool head 18 (cf. FIG. 4). The connection between tool 
head 18 and tool holder 17 is effected by moving the clamping screw 30 
away from the tool head 18 and thereby shifting the locking pins 31 
radially outwardly, i.e. towards the wall 18b. 
The removal of the tool head 18 is made possible by a movement of clamping 
screw 30 in the reverse direction (i.e. in FIG. 3 downwards). As a result 
of this movement, the locking pins 31 can slide inwardly in the direction 
of the longitudinal axis 17a. 
The structure and functions of the clamping screw 30 and the locking pins 
31 are in detail prescribed in the U.S. Pat. Nos. 4,406,195 and 4,615,244 
(the clamping screw there being designated as locking bar or clamping bar 
respectively), the entire disclosure of which is incorporated herein by 
reference. 
In FIG. 4, the end 9 has been withdrawn and tool head 18 has been separated 
from tool holder 17. This separation can be accomplished either by axial 
displacement of tool holder 17 or by moving gripper holder 4 away from 
tool holder 17. The gripper holder 4 is then rotated and a new tool head 
is inserted into tool holder 17 and clamped-in in the reverse order of 
steps. 
The particular advantage of the present invention is that for tool changing 
devices in which the clamping screw of an automatic clamping mechanism is 
disposed in the tool holder, the exchange of tool heads can be performed 
by a pivot arm in which tool grippers and a system for actuating the 
clamping mechanism are integrated. With this device, the exchange of tools 
or tool heads can be performed fully automatically by means which operate 
independently of the machine tool. 
Another advantage of the device according to the invention is that the 
rotatable mounting of the pivot arm permits a pivoting movement over any 
desired angle, so that tool holder locations disposed axially as well as 
radially with respect to the machine axis can be reached. In conjunction 
with the clamping shaft configured according to the invention, which makes 
it possible, in particular, to actuate left-hand as well as right-hand 
tool holder changing systems, it is possible in practice to operate all 
tool holder systems arranged at different angles in one plane. 
The present disclosure relates to the subject matter disclosed in Federal 
Republic of Germany patent application No. P 37 20 805.5 of June 24th, 
1987, the entire disclosure of which is incorporated herein by reference. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations, and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.