Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
1999-09-20
2002-06-25
Bryant, David P. (Department: 3726)
Gear cutting, milling, or planing
Milling
Process
C029S03300H, C029S559000, C409S225000, C198S345300, C104S251000, C104S252000
Reexamination Certificate
active
06409438
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and device for positioning a workpiece carrier.
BACKGROUND OF THE INVENTION
With the object of DE 195 32 281, for instance, a workpiece carrier has become known which consists essentially of a base plate on which several traveling shafts are arranged, each connected immovably to a wheel, with at least one drive wheel provided that is driven by an electric motor. The known workpiece carrier can be displaced on a railway and, by means of wirelessly transferred information, it is capable of stopping at defined machining stations with the objective that defined machining processes can be performed on workpieces arranged on the base plate of the workpiece carrier.
From the cited publication, however, it is impossible to discern how the workpiece carrier in the rail system is to be positioned with high precision at a given machining station. This is important, however, for high-precision machining of workpieces fastened to the workpiece carrier. High machining precision is a requisite, particularly in machining and joining processes, with respect to the workpieces arranged on the workpiece carrier. The cited publication thus lacks a high-precision positioning of the workpiece carrier on the railway when the workpiece carrier stops at a machining station and the machining is to take place.
SUMMARY OF THE INVENTION
An aspect of the present invention involves a refined method and device for positioning a workpiece carrier in a machining station such that the workpiece carrier is positioned with high precision in the machining station.
An aspect of the present invention involves an apparatus for positioning a workpiece carrier in a machining station. The workpiece carrier is movable on a rail system and one or more machining stations are arranged along the rail system for machining a workpiece arranged on the workpiece carrier. The apparatus includes at least one positioning device arranged in an area of the machining station. The positioning device has fixtures for positioning and high-precision retention of the workpiece carrier with respect to a stationary reference surface. The positioning device further includes fixtures for decoupling the workpiece carrier from the rail system, and a deceleration and acceleration device for the workpiece carrier.
The essence of the invention is thus that the workpiece carrier is positioned, after entry into the machining station by means of at least one positioning device, with respect to a stationary reference surface, held in place with high precision and decoupled from the rail system and that, after machining of the workpiece, the workpiece carrier is released by the positioning device and can be moved further along the rail system.
With the technical teaching presented, there results the essential advantage that a high-precision positioning of the workpiece carrier in a machining station with respect to a stationary reference is achieved, with the workpiece carrier being decoupled from the rail system, so that the forces impinging from the machining and the mass forces of the workpiece carrier are absorbed exclusively by the positioning device. Thus, high-precision positioning with very good reproducibility is achieved.
This further results in the advantage that high-precision machining of workpieces arranged on the workpiece carrier is possible, because, according to a first preferred embodiment of the invention, the workpiece carrier does not remain in the rail system. The rail system may, after all, feature corresponding inaccuracies (for instance, depressions, curves, bumps or guidance imprecision) and these inaccuracies of the rail system could impair the machining precision. For this reason, the workpiece carrier is lifted off the rail system, pressed against a stationary reference of the positioning device and coupled to this reference surface by what amounts to a form fit.
With the technical teaching presented, there also exists the advantage that there is no more need to take into account an overall height that varies according to each of the different workpiece carriers because, independently of the overall height of the workpiece carrier, it is always raised sufficiently far off the rail system so that each workpiece carrier, independently of its overall height, comes to rest against a stationary upper reference surface, with respect to which the machining processes on the carrier plate of the workpiece carrier take place. Thus, different workpiece carriers of a widely varying construction can be positioned with equal precision in the positioning device, without the size and dimensions of the workpiece carrier mattering at all. There is therefore no need to take account of tolerances in the overall height of the workpiece carrier.
Neither is the positional precision of the positioning device of the invention dependent on the load weight of the workpiece carrier. That is, if the workpiece carrier remained on the rail system with different load weights and were positioned there, then there would exist the danger that the rail system might be pressed down or yield because of differing weights and thereby the machining precision could be impaired.
If, however, the workpiece carrier is lifted off the rail system according to the invention and pressed against a strong, highly loadable reference surface, then the machining of the workpiece arranged on the workpiece carrier is independent of the load weight of the workpiece carrier.
The invention is not restricted to a vertical lifting of the workpiece carrier off the rails of the rail system as above. In another configuration it is provided that the workpiece carrier remains on the rail system and that it is held tight laterally by appropriate form-fitting receptacles and couplings and thereby decoupled from the rail system in regard to active forces, so that a relieving of the rail system is achieved. In this second embodiment as well, the problem of high-precision positioning is solved with a separate positioning device. The latter-mentioned positioning device then acts essentially laterally on the workpiece carrier and fixes it in place on the rail system (without lifting it off the rail system), with the goal that different load weights of the workpiece carrier are no longer passed on to the rail system. These load weights are thus absorbed by the positioning device.
The invention is not limited either to standing workpiece carriers, i.e., workpiece carriers that roll on their running rollers on guide tracks of a rail system. The present invention pertains equally to so-called suspended systems, that is, those in which a workpiece carrier is arranged so as to move suspended on a monorail or multirail system (in the manner of the suspended train in Wuppertal).
In the embodiment of a workpiece carrier arranged so as to move suspended from the rail system as well, the two embodiments for the fixation of the workpiece carrier in the positioning device can come into consideration, namely, the raising of the entire workpiece carrier with the objective of de-suspending it from the track of the rail system and fixing it in place, on the one hand, and, on the other, the second embodiment, in which the workpiece carrier is only locked laterally to the positioning device such that corresponding load changes are no longer passed on to the rail system, but act instead on the positioning device and are absorbed by it.
In a refinement of the invention, it is preferred that a special deceleration and acceleration-device be associated with the positioning device. The aforesaid deceleration device ensures that the workpiece carrier, independently of its load weight, is always braked uniformly upon entry into the machining station. The braking behavior of this deceleration device is preferably independent of the load weight.
The aforesaid acceleration device has the task of releasing the workpiece carrier from the machining station or positioning device onto the rail system, wherein it receives a certain initial acceleration. The assignme
Bryant David P.
Compton Eric
Heron Sondermaschinen und Steuerungen GmbH
Knobbe Martens Olson & Bear LLP
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