Tool changing – With control means energized in response to activator...
Reexamination Certificate
1999-07-07
2001-02-06
Wellington, A. L. (Department: 3722)
Tool changing
With control means energized in response to activator...
C483S001000, C483S010000, C483S013000, C483S031000, C483S038000, C483S069000, C483S900000
Reexamination Certificate
active
06183404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a machine tool having a spindle for receiving a tool for machining a workpiece, and a mechanism for clamping the workpiece.
2. Related Prior Art
Machine tools of this kind are commonly known from the prior art.
Machine tools of this kind generally have tool changing mechanisms with which tools attached to standardized tool holders can be transferred between a tool receptacle in the spindle and a magazine position. In this manner, with a single workpiece clamping, different machining operations using different tools can be performed in succession on the clamped workpiece before it is replaced with a workpiece yet to be machined.
With machine tools of this kind, a very rapid tool change is desirable so as to minimize the time necessary for the machining occurring in one clamping, so that the machine tool's workpiece throughput is high.
A basic prerequisite for machining a workpiece using a tool clamped in the spindle is of course that the surface to be machined on the workpiece is accessible to the tool. In this connection, problems occur with internally hollow, for example bell-shaped workpieces, whose interior must be machined with a tool that, for reasons relating either to design or to clamping technology, cannot be introduced into the workpiece cavity from above. It is conceivable in the case of a bell-shaped workpiece, for example, that for other reasons related to machining technology it is clamped on the mechanism with the large opening downward, only a small opening being present toward the top, through which a milling cutter cannot penetrate into the workpiece cavity in order to perform the machining required there. To allow this machining in the interior of the workpiece to be accomplished, the workpiece must thus be reclamped, causing valuable machining time to be lost.
As an alternative to such a reclamping of the workpiece, it is also known to use a two-piece tool comprising an adapter tool and machining tool, for example the one that can be obtained from the Bilz company of Esslingen in Germany, under catalog numbers FH111992 and SS111991.
The adapter tool has a relatively thin, long shaft which is attached to the standardized tool holder and has at its free end a kind of bayonet fastener. This adapter tool is then introduced into the workpiece cavity through an opening which faces upward. A large lateral opening must then be provided in the workpiece, through which an operator can introduce the machining tool, i.e. for example the milling cutter, laterally into the workpiece cavity, and there slide it onto the free end of the adapter tool and interlock it by turning it. For this purpose, the machining tool has a retaining bore with pins which coact with the adapter tool in the manner of a bayonet fastener.
The result of this is that the workpiece cavity can be machined with a machining tool that could not have been introduced through the small upper opening, although that opening is large enough to receive the shaft of the adapter tool.
This eliminates the reclamping that would otherwise be necessary; it is now also possible to machine workpiece cavities of workpieces which do not have correspondingly large openings even on their underside, so that even a reclamping would not make it possible to machine the workpiece cavity.
On the other hand, however, it is necessary for the workpiece to have a relatively large lateral opening, which not only must allow the machining tool to be introduced into the workpiece cavity, but additionally must allow enough room for the hand of the operator who must interlock the machining tool with the adapter tool in the workpiece cavity.
Large lateral openings of this kind can cause stability problems in the workpiece, and should therefore be as small as possible. On the other hand, however, these lateral openings should be as large as possible to eliminate any risk of injury to the operator, and moreover so that the difficult task of threading the adapter tool into the machining tool can be performed as easily, quickly, and above all safely as possible.
It is clear that manipulations of this kind with adapter tools and machining tools interfere with the normal machining sequence of an otherwise fully automatic machine tool: they considerably reduce workpiece throughput during the machining of such workpieces, and moreover represent a safety risk to the operator.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to improve the machine tool mentioned at the outset in such a way that with a configuration of simple design, faster machining of workpiece cavities and rapid and safe changing of a “two-piece” tool are possible, with no need for the workpiece to be reclamped or for excessively large lateral openings to be provided.
In the machine tool mentioned at the outset, this object is achieved according to the present invention in that a changing mechanism for a machining tool is provided, which holds the machining tool in a gripper hand which it introduces laterally into a workpiece cavity in such a way that it can be automatically coupled there to an adapter tool carried by the spindle. The object underlying the invention is completely achieved in this fashion.
Specifically, the inventors of the present application have recognized that first of all, a considerably narrower lateral opening is required for a mechanical gripper hand than for manual manipulations. The two-piece tool is now introduced into the workpiece cavity, so to speak, partially from above via the spindle and partially from the side via the changing mechanism, which because of the numerical controller can be accomplished in an extremely reproducible and positionally accurate manner, and considerably more reliably than by hand. Coupling of the machining tool to the adapter tool can be accomplished, for example, by the fact that the machining tool is rotated by or in the gripper hand, so that it is, so to speak, screwed onto the adapter tool, thus interlocking the bayonet fastener. On the other hand, the gripper hand can also have transverse studs or pins with which the machining tool is interlocked onto the shaft of the adapter tool.
It is thus a general advantage of the new machine tool that workpiece cavities can now be machined in completely automatic fashion without large lateral openings in the workpiece, such that the spindle and the new changing mechanism coact for tool changing purposes.
Although the new changing mechanism requires a considerable design outlay and results in appreciable costs, this is, amazingly, more than compensated for by the structural advantages that can be attained in the workpiece being machined, and by the considerably elevated machining rate. Another important advantage that may be mentioned is that the risk of injury to operating personnel is also much reduced.
It is preferred in this context if the gripper hand has two jaws which hold the machining tool in the axial direction.
The advantage here is that the gripper hand can be very narrow, since the two jaws can lie, for example, in two externally open grooves of the machining tool. This means, however, that the lateral space necessary upon introduction of the machining tool through the lateral opening into the workpiece cavity is only slightly greater than that corresponding to the width of the machining tool. This feature is thus structurally advantageous for the workpiece being machined.
It is further preferred in this context if the gripper hand has overrunnable snap-lock means for holding the machining tool, the snap-lock means preferably comprising two ball catches which are arranged opposite one another internally on the jaws.
The advantage here is that the jaws do not need to execute an opening motion in order to grasp or release the machining tool, which saves further space in the workpiece and the lateral opening. This feature is moreover advantageous in terms of design: all that needs to be provided on the gripper hand are two rigid jaws locat
Chiron-Werke GmbH & Co. KG
Cummings & Lockwood
Ergenbright Erica D.
Wellington A. L.
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