Motors: expansible chamber type – Working member position feedback to motive fluid control – Electrical input and feedback signal means
Patent
1992-11-10
1995-01-10
Look, Edward K.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Electrical input and feedback signal means
91378, 91473, F15B 903
Patent
active
053796780
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a hydraulic drive and, more particularly, to a rotary or swivel drive for a NC or a CNC controlled machine tool, feeding devices for such machine tools, manipulators, or robots with several rotary or swivel joints.
BACKGROUND OF THE INVENTION
A hydraulic drive of the aforementioned type is disclosed in, for example, German Patent Application P 38 27 365.9-15.
In this drive mechanism, a hydraulic motor designed as an axial-piston motor is provided as the power drive, with a conventional follow-up control valve being included for the motion control, namely, direction of rotation and angular velocity. This valve operates with electrically controllable desired value presetting and mechanical actual value acknowledgment of the indicated dynamic parameters. For desired value introduction, a stepping motor or an AC motor is provided which, in turn, can be activated in accordance with direction of rotation and rotary velocity by output signals of an electronic control unit constituting an output stage of an NC or CNC machine control unit.
The electrical control motor, the follow-up control valve and the axial-piston motor are arranged, in this sequence, along the joint central longitudinal axis of the drive in side-by-side and, respectively, series relationship; feeding of pressure medium takes place to the individual linear cylinders of the axial-piston motor by way of a control cam fixedly mounted to the housing and revolving with the rotor of the axial-piston motor. As seen along the central longitudinal axis, this control cam is arranged "between" the follow-up control valve and the drive section of the hydraulic motor, and the rotor of the hydraulic motor is rotatably supported with its output shaft on a housing end section by two inclined ball bearings in order to obtain a maximally large effective axial length of the bearing, required at the high output power of the hydraulic motor, and yet to make do with small axial dimensions.
The drive mechanism according to the aforementioned patent application is somewhat disadvantageous by virtue of the necessary large total structural length, in spite of these insofar quite suitable structural features and additional aspects, such as the specifically provided type of coupling of the output shaft of the electric control motor, permitting the necessary axial relative motions, to a desired value presetting spindle of the follow-up control valve, and the coupling, accommodated within the rotor shaft, of the actual position value aknowledgment spindle of the follow-up control valve to the rotor of the axial-piston motor. Such length is linked also with relatively large lengths of the liquid columns within the drive mechanism and a concomitant loss of rigidity of the drive unit as a whole.
SUMMARY OF THE INVENTION
It is an object of the invention to improve a hydraulic drive mechanism of the type discussed hereinabove in such a way that it can be realized, with a comparable power density of the drive, with markedly smaller axial dimensions and provides a higher "rigidity" of the drive system as a whole.
In accordance with the present invention, an axial-piston hydraulic motor is provided for forming a power drive means with a follow-up control valve being provided for controlling a pressure medium supply which follow-up control valve is electronically controlled by a desired position value presetting and mechanical actual position value acknowledgement. An electric motor is provided for the desired position value presetting, which motor can be activated by output signals of a central CN or CNC control unit. The rotor of the axial-piston hydraulic motor is rotatably supported with a circular-cylindrical-tubular section of an output shaft thereof on an outer casing surface of an axial extension, being, in turn, fashioned in a hollow-tubular shape and forming a pivot pin for the rotor, of a housing section accommodating the electric motor provided for desired value presetting control.
In accordance with the prese
REFERENCES:
patent: 3530764 (1968-09-01), Tomita
patent: 4630528 (1986-12-01), Eickmann
patent: 4646621 (1987-03-01), Maruyama et al.
patent: 4858650 (1989-08-01), Devaud et al.
Look Edward K.
Lopez F. Daniel
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