Gear cutting – milling – or planing – Milling – Including means to infeed rotary cutter toward work
Reexamination Certificate
2000-08-25
2001-06-05
Briggs, William (Department: 3722)
Gear cutting, milling, or planing
Milling
Including means to infeed rotary cutter toward work
C248S631000, C408S234000, C409S216000, C409S235000, C901S041000
Reexamination Certificate
active
06241437
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hexapodal machining center having a fixed frame and a support which are interconnected via six struts of an adjustable length.
Such hexapodal machining centers are used as machine tools. They are particularly suited for cutting machine tools, e.g., for milling, drilling, turning or grinding or for laser machining.
In principle, hexapodal machining centers consist of a support, which is sometimes designated as a working platform, and of a fixed frame which are interconnected by six struts of an adjustable length. This allows a movement of the working platform in all of the six spatial degrees of freedom, i.e., three translational degrees of freedom and three rotational degrees of freedom.
A first hexapodal machining center is known from U.S. Pat. No. 5,401,128. This known machine tool structure consists of an octahedral framework comprising twelve rigid struts. A machining unit comprising a spindle is arranged in the center of the framework. Furthermore, a fixed workpiece-receiving device is arranged in the lower part of the octahedral machine frame of the fixed workpiece-receiving device. The hexapod, i.e, a support or working platform for the machining unit, e.g., a drilling or milling spindle, is provided above the workpiece receiving device. Two respective struts of the hexapod which can be adjusted in their length are coupled with one end to a corner of a triangular upper frame part of the machine frame, the connecting points of the two struts on the machine frame being only slightly spaced apart with respect to their height. All of the connecting points of the six struts on the working platform are located in a joint plane. Such an arrangement limits the rotational movements. Moreover, the forces cannot be received in the struts in an optimum manner since these do not extend in the directions of the main load.
A further hexapodal machining center is known from U.S. Pat. No. 5,354,158. In the hexapod shown in that document, two neighboring struts are coupled at a comer of an imaginary triangle to the working platform and two other neighboring struts to the comer of a further imaginary triangle on the frame, the two triangles arranged in parallel with each other being rotated relative to each other. The connecting points of the struts on the working platform and on the frame are each arranged in a common plane. Moreover, it is known from U.S. Pat. No. 5,354,158 that the connecting points on the frame are arranged in two spaced-apart planes. Such an arrangement has similar shortcomings as the arrangement according to U.S. Pat. No. 5,401,128 with respect to the movability of the working platform and the force-receiving capacity.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to optimize the movability of the support in all of the six degrees of freedom, in particular in the three rotational degrees of freedom, as well as the force-receiving capacity in a hexapodal machining center of the above-mentioned type.
This object is achieved by a hexapodal machining center having a fixed frame and a support which are interconnected via six struts of an adjustable length, wherein the connecting points of three struts on the support form a first working plane, and the connecting points of the three further struts on the support form a second working plane spaced apart from the first working plane, wherein the connecting points of three struts on the frame form a first working plane and the connecting points of the three further struts on the frame form a second working plane spaced apart from the first working plane of the frame, and wherein the connecting points of the two working planes of the support are superimposed such that the connecting lines of the superimposed pairs of connecting points extend in parallel with each other.
A great freedom of movement of the support and the working platform, respectively, is thereby achieved because the joints of the struts at the connecting points on the support do not interfere with one another. In particular, a greater freedom of movement is thereby achieved with respect to the rotational degrees of freedom. Therefore, the hexapodal machining center can also be used for more compact supports or smaller machines.
Moreover, the superimposed configuration of the connecting points on the support improves the stiffness of the backing of the support, thereby ensuring a greater manufacturing accuracy.
A machining unit and/or sensor system for sensing the position may be mounted on the support. The machining unit may carry a spindle, with a desired spatial position of the spindle being provided depending on the respective requirements, e.g., horizontal or vertical. The structure of the frame is adapted accordingly.
The struts are suspended within the frame in such a manner that the connecting points of three respective struts on the frame form a total of two separate working planes. Such an arrangement of the struts will enhance movability, in particular with respect to the rotational degrees of freedom, and result in a more uniform force-receiving capacity. Moreover, a particularly economic arrangement of the constructional space is thereby made possible because the distribution of the connecting points on the support and on the frame will provide more space for the design of the respective joints at the connecting points. On the whole, the constructional freedom of design is increased and a more compact construction is made possible, so that the ratio of the space available for machining to the space required by the machining center is increased.
REFERENCES:
patent: 5354158 (1994-10-01), Sheldon et al.
patent: 5401128 (1995-03-01), Lindem et al.
patent: 5556242 (1996-09-01), Sheldon et al.
patent: 5832783 (1998-11-01), Sheldon
patent: 5906461 (1999-05-01), Lunz
patent: 6059703 (2000-05-01), Heisel
patent: 6155758 (2000-12-01), Wieland et al.
patent: 196 40 769 A1 (1997-07-01), None
patent: 196 36 099 A1 (1998-03-01), None
5 D.O.F. robots; p. 19 of 37; “Spatial Robots”; internet site at http://www-sop.inria.fr/saga/personnel/merlet/Archi
ode 2, Apr. 25, 2000.
Akin Gump Strauss Hauer & Feld L.L.P.
Briggs William
Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung
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