Abrading – Abrading process – Gear or worm abrading
Reexamination Certificate
2000-02-22
2001-05-22
Banks, Derris H. (Department: 3723)
Abrading
Abrading process
Gear or worm abrading
Reexamination Certificate
active
06234880
ABSTRACT:
BACKGROUND OF THE INVENTION
Prior Art
One of the well-known and most widespread types of hard finishing of gears is the generation grinding of the tooth flanks by means of a cylindrical grinding wheel profiled in a worm shape at its circumference, the so-called grinding worm. The gear, when being ground, is brought into meshing engagement with the grinding worm, the tooth flanks of the gear being ground by the grinding-worm thread flanks and the tooth root being ground by the tip part of the grinding worm thread. This means that, before the grinding of the gear, the grinding worm thread has to be completely profiled in accordance with the tooth-gap profile of the workpiece.
A whole series of methods is known for the profiling of the grinding worm thread, the most efficient and the most widespread being that in which one dressing profile disc each is used for the dressing of the left-hand flank and the right-hand flank and a forming roll is used for the dressing of the tip of the grinding worm thread. The three tools, which are combined to form a tool set and in which the outside dimensions of the forming roll have to correspond to the root radius and tooth height of the respective workpiece, permit a short dressing time, since all their active abrasive tool surfaces covered with hard-material grains are in use simultaneously during dressing. However, the advantage of the high efficiency of this dressing method is offset by the disadvantage of limited flexibility or a high setting-up cost.
In another method, by means of a rotating dressing tool coated with hard-material grains at the active circumference, the entire active profile of the grinding worm is profiled line by line in point contact, specifically in such a way that line is placed around line right next to each other until the entire active thread profile is dressed. This method requires only a single dressing tool and is exceptionally flexible with regard to the profile of the thread. However, it has the disadvantage of being very slow. This disadvantage partly still exists even if, as in DE-A 196 24 842 A1, the line-by-line profiling is combined with the use of dressing profile discs.
OBJECT AND SUMMARY OF THE INVENTION
The aim of the present invention is to specify a method and a device by means of which, despite the little presetting constructional effort required and despite high flexibility, the profiling of the entire active grinding worm thread profile is possible with short dressing times. According to the invention, this is achieved by the combination of a dressing profile disc, coated with hard material grains on two faces, for profiling the two grinding worm thread flanks and a radius-forming roll, arranged coaxially hereto and coated on the circumference with hard material grains, for profiling the tip of the grinding worm thread, the active zone of the radius-forming roll being geometrically configured and arranged in such a way that it can be brought into use without collision by axial displacement and pivoting of the dressing spindle relative to the grinding worm. Instead of the double tapered dressing disc coated with hard material grains on two sides, the combination of two single tapered dressing discs, for example, may also be used.
A variant of the invention is the dressing of the grinding worm thread tip by means of a hard material radius-forming tool, mounted on the pivoting support of the dressing spindle, instead of the above radius-forming roll, as a result of which the displacement travel of the dressing device between the dressing of the thread and the circumference of the grinding worm can be reduced.
REFERENCES:
patent: 4073281 (1978-02-01), Asaeda et al.
patent: 4557078 (1985-12-01), Brill
patent: 3715271A1 (1987-11-01), None
patent: 19625370C1 (1997-04-01), None
patent: 19624842A1 (1998-01-01), None
patent: 19706867A1 (1998-08-01), None
Banks Derris H.
Browdy & Neimark
Reishauer AG
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