Machine element or mechanism – Mechanical movements – Rotary to intermittent unidirectional motion
Patent
1998-01-14
1999-06-29
Wright, Dirk
Machine element or mechanism
Mechanical movements
Rotary to intermittent unidirectional motion
74812R, 74820, F16H 2704
Patent
active
059163240
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a stepping gear mechanism such as for motion control of a machine tool turret.
BACKGROUND INFORMATION
In a known stepping gear mechanism such as disclosed in GB 1 260 928 a roller supporting member cooperates with two cam plates which are identical as such but arranged in inverse relationship. Each of them includes a stop zone which is concentric with the axis of rotation of the cam plate and extends continuously through approximately 250.degree. and further includes a motion zone formed at a projection and an indentation, each extending through approximately 55.degree.. A first one of these two cam plates has the stop zone followed first by the projection with the motion zone and then the indentation; and vice versa for the second cam plate. When a common drive wheel causes both cam plates to rotate in the same direction through 360.degree., first the projection of the first cam plate will entrain a first roller of the roller supporting member, while the next roller, the second one, is not touched by a cam plate, the third roller dips into the indentation of the second cam plate, and the fourth roller likewise is not touched by a cam plate. As soon as the third roller has reached the end of the indentation of the second cam plate it will be taken along by the projection, while the first roller is released by the first cam plate and the indentation thereof receives the second roller. Finally, the third roller is released by the second cam plate, and the second and fourth rollers engage a stop zone each of the cam plates so that the roller supporting member having accomplished a quarter of a revolution is prevented from rotating any further until the two cam plates have executed a full revolution.
With this known stepping gear mechanism, therefore, the number of indexing positions which a turret or like element connected to the roller supporting member may occupy is the same as the number of rollers mounted on the roller supporting member. As a consequence, a roller supporting member of given diameter can mount only relatively small rollers for no more than four indexing positions. That applies even more where six or more indexing positions are needed and, therefore, a corresponding elevated number of rollers must be provided. Due to their restricted dimensions, the rollers cannot be loaded by particularly strong forces, such as required in order to securely hold the roller supporting member against the influence of a great external torque. External torques of significant magnitude occur, for example, when the stepping gear mechanism is provided to drive a turret of an automatic lathe in which the turret is prevented from rotating, in each of its indexing positions, by the stepping gear mechanism alone and is not locked by any additional device.
SUMMARY OF THE INVENTION
It is the object of the invention to develop a stepping gear mechanism, suitable especially for motion control of turrets in turning machines, such that it will be able to reliably withstand great torques acting from outside on the roller supporting member, at given dimensions of the cam plates and of the roller supporting member.
The object is met, in accordance with the invention, by the features of the present invention. Advantageous further developments may be gathered from the following description.
By virtue of the invention, the number of rollers required on the roller supporting member need only be half as great as the number of indexing positions at which the roller supporting member--and thus a turret or the like connected to the same--is stopped in the course of each full revolution. For this reason each individual roller may have a rather great diameter and be loaded by equally strong forces.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will be described in greater detail below, with reference to diagrammatic drawings, in which:
FIG. 1 is a perspective view of a stepping gear mechanism, showing the casing open and partly b
REFERENCES:
patent: 2986949 (1961-06-01), Lancaster et al.
patent: 3590661 (1971-07-01), Chaveneaud et al.
patent: 4109548 (1978-08-01), Shinohara et al.
patent: 4416165 (1983-11-01), Kramer et al.
patent: 4860414 (1989-08-01), Bishop et al.
patent: 5386743 (1995-02-01), Su et al.
patent: 5598749 (1997-02-01), Goto
Kwon Peter T.
Traub Drehmaschinen GmbH
Wright Dirk
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