Shaft with a worm formed onto it, and milling machine for manufa

Details Shaft with a worm formed onto it, and milling machine for manufa Shaft with a worm formed onto it, and milling machine for manufa

1994-06-15

1995-11-14

Herrmann, Allan D.

Machine element or mechanism

Gearing

Teeth

2989331, 409 65, 409 76, 409165, F16H 5508, B23F 2114

Patent

active

054656311

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to shafts, and move particularly to a rotor shaft of an electric motor with a worm formed onto it and with the root line diameter of the worm being smaller than the diameter of the shaft or of a part directly adjoining the worm.


BACKGROUND OF THE INVENTION

Shafts having a worm formed onto it are used, for example, where a worm of a worm gear is to be driven by an electric motor, it being absolutely possible that the worm is formed directly onto the rotor shaft of the electric motor. The worm concerned can be an overhung worm as well as a worm mounted at both ends. In the latter case the diameter of the part of the shaft adjoining the one end of the worm can be larger than the part of the shaft adjoining the other end of the worm. However, it is also possible that there is an equal diameter of the shaft at both sides of the worm. Furthermore, the part of the shaft directly adjoining the one end and/or the other end of the shaft can have a diameter equal to the crown circle of the worm, but also can be different herefrom, for example larger.
If the root line diameter of the worm is smaller than the diameter of the part of the shaft adjoining the end, notch tensions can occur at the transition from the beginning of the worm into the adjacent part of the shaft and/or at the end of the worm to the part of the worm adjoined thereto. This can be noticed especially, if the worm is made by milling. In particular, in the latter case, it often happens that the crown circle of the worm corresponds directly to the diameter of the shaft or to the diameter of the part or the parts of the shaft directly adjoining the worm. The reason for this tension is that an abrupt transition occurs from the shaft diameter to the root line diameter. This can be noticed above all, when the worm is made by means of a disk milling machine.


SUMMARY OF THE INVENTION

The present object is, to improve upon a shaft of the type described at the beginning in such a way that no, or only a reduced, notch tension occurs in the transition from the shaft into the worm.
In order to accomplish this object, it is suggested according to the invention that the shaft with the worm formed onto it is developed having a less abrupt transition from the groove bottom of the worm into the neighbouring shaft. In this manner, the complete cross-section does not reduce in one single step from the shaft to the core of the worm, and therefore, it is effectively reduces or eliminates notch tensions in this area.
The manner in which the transition from the complete shaft diameter onto the core diameter of the worm is accomplished depends on the dimensions of the shaft and the worm as well as on the used material and the strain which is to be expected.
It is preferred that, in the area where the depth of the groove is reduced, the depth of the groove is not constant but increases, in axial direction progressing from the beginning of the worm or the end of the worm, respectively. In this way, a constant reduction of the core diameter of the shaft up to the first tooth of the worm can be obtained, preferably starting from the outside diameter of the shaft, consequently the depth of the groove increases from zero.
In principle, the bottom of the groove can be bent in this area and for example can it be conformed to the cylindrical bend of a worm wheel planned for combing with the worm. In view of the manufacturing capabilities of the milling machine, however, a linear increase of the depth of the groove in axial direction seems preferable.
Another object is to develop a disk milling machine for manufacturing a worm formed onto the shaft.
In order to solve this object a disk milling machine is disclosed. This disk milling machine forms the worm onto the shaft like a state-of-the-art disk milling machine. Because of the special shape of the rough milling machine and its assignment to the actual disk milling machine, seen in axial direction of the shaft of the milling machine, the transition from the diameter of the shaft to the co

REFERENCES:
patent: 1329805 (1920-02-01), Schurr

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