Turning – Pattern section
Patent
1985-03-29
1987-03-24
Larson, Lowell A.
Turning
Pattern section
82 13, 51 90, 51 97NC, B23B 100, B23B 544
Patent
active
046515992
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing workpieces having polygonal outer and/or inner contours, preferably by machining, with the workpiece to be processed rotating at a constant rate around a stationary axis while the tool is guided on a closed curved path. The rate of rotation of the workpiece and the circumferential speed of the tool on its curved path are dependent upon one another and moreover the tool is in engagement with the workpiece during the entire revolution.
DE-OS [German Laid-Open Patent Application] No. 2,355,036 discloses a method of the above-mentioned type in which the tool is guided on an elliptical path with respect to the workpiece. By superposing the rotary motion of the workpiece on the movement of the tool which traverses an elliptical path, corresponding polygonal contours can be produced, even those having sharply defined corners. Drawbacks resulted when the prior art method was reduced to practice, for example a considerable reduction of the operating speeds, since the drive mechanisms for producing the elliptical movement of the tool permit only limited numbers of revolution. A further drawback of the known mode of operation is that the drive mechanism required to produce the law of motion must be constructed with relatively large dimensions and accordingly the production of polygons having different diameters requires the provision of a reduction lever arrangement which is difficult to accomplish with the necessary rigidity. The parameters determinative for the curved path are firmly linked with one another so that only the magnitude of the curved path can be varied by a transmission rod while its shape cannot be changed. A further drawback is that the transmission rod imparts additional "elasticity" to the device which adversely affects dimensional accuracy, particularly in mass production.
It is now the object of the invention to provide a method which permits greater operating speeds and better adjustment possibilities for the individual parameters. Moreover, high precision is to be possible so that precise fits can be produced even in mass production, as they are required, for example, for shaft-hub connections. Additionally, a significantly simplified gear structure is to be possible.
This is accomplished according to the invention in that the tool is guided so as to rotate on a closed curved path which deviates from the circular shape, with such curved path being traversed by the tool at a speed which changes during one revolution according to a given law of motion, and that the curved path is oriented eccentrically with respect to the axis of rotation of the workpiece and encloses this axis. This method has the result that the curved path traversed by the tool does not extend, as in the known methods, between the incircle and the circumcircle of the polygonal profile to be produced, but lies on the circumcircle and thereby encloses the incircle of the polygonal profile to be produced. Since this manner of proceeding permits the predetermination of a curved path which approximately lies in the order of magnitude of the diameter of the polygonal profile to be produced, the resulting pressure angles in principle are more favorable for the tool, which is advantageous particularly for machining work, for example turning. Tool movement in the manner of rotary fly cutting work is likewise possible, i.e. discontinuous tool engagement during one revolution. The advantage of the invention lies in the broad range of possible variations for the curved path.
In a preferred embodiment of the method it is provided that the curved path has the shape of an epicycloid, particularly a Pascal curve. By superposing the rotary movement of the workpiece on a Pascal curve traversed by the tool, preferably in the same sense of rotation, with the Pascal curve being placed, according to the method of the invention, so that it encloses the axis of rotation of the workpiece, suitable selection of the Pascal curve and a correspondingly given ratio of the rate of rotation of the workpiece to
REFERENCES:
patent: 3593603 (1971-07-01), Gellert
patent: 3886693 (1975-06-01), Tajnafoi et al.
patent: 3916738 (1975-11-01), Neubrand et al.
patent: 3958471 (1976-05-01), Muller
Kearns Jerry
Larson Lowell A.
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