Power plants – Pressure fluid source and motor – Servo-motor having externally operated control valve sets...
Patent
1998-09-17
2000-07-04
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Servo-motor having externally operated control valve sets...
60452, F16D 3102
Patent
active
060821078
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic controller in particular for the control of the rotating mechanism of an excavator.
2. Discussion of the Prior Art
A hydraulic controller such as for the control of the rotating mechanism of an excavator is known from DE 44 05 472 A1. This publication discloses a hydraulic controller for the control of a rotating mechanism having a brake valve. The brake valve serves for the sensitive braking of the rotating mechanism by means of control of the braking moment. The brake valve connects a pre-control arrangement, controlling the setting arrangement, with the pressure fluid tank. Thereby, the return flow of the pressure fluid, out of the setting pressure chamber acted on upon acceleration of the rotating mechanism, to the pressure fluid tank, is throttled during the braking, and thus the braking procedure is delayed.
Disadvantageous with this known hydraulic rotating mechanism controller is, however, that solely one brake valve is provided and thus the return flow of the pressure fluid out of the two setting pressure chambers of the setting arrangement is not effected independently of each other. This can influence the dependability of the hydraulic controller. Further, with this known hydraulic rotating mechanism controller, it is disadvantageous that the brake valve responds also when the rotation movement of the rotating mechanism encounters a resistance upon braking. Such a resistance is e.g. brought about in that the excavator is located on an inclined plane and the boom of the rotating mechanism moves uphill during the braking procedure. This situation occurs relatively frequently on building sites which naturally have uneven ground. Further, a corresponding resistance arises when the boom of the rotating mechanism swings into a mound of earth or the like.
SUMMARY OF THE INVENTION
It is thus the object of the present invention to so further develop the known rotating mechanism controller that dependability is increased.
The solution in accordance with the invention is based upon the insight that the dependability of the hydraulic controller can be increased in that its own, separate brake valve is associated with each of the two setting pressure chambers of the adjustment arrangement, whereby each of the two brake valves is controlled by means of the force difference between a setting force exercised by the control pressure and a return force exercised by a return member.
A further solution pursuant of the invention is based on the insight that in the working lines connecting the hydraulic pump with the hydraulic motor a pressure reversal occurs when the rotating mechanism can rotate further without resistance during the braking procedure. When, however, during the braking procedure the rotating mechanism is exposed to a resistance, e.g. due to the down-slope force or an impact, this pressure-side reversal does not occur, i.e. the working line acted upon with high pressure during they acceleration phase is also acted upon with high pressure during the braking procedure. The invention exploits this insight in that for each of the setting pressure chambers a respective separate brake valve is provided which in each case is connected with one of the working lines. The brake valves are thereby controlled in dependence upon the pressure difference between the working pressure in the associated working line and the control pressure. Thereby during the braking procedure with substantially pressureless control lines, only that brake valve responds the associated working line of which is acted upon with high pressure.
The brake valves may be constituted as switch-over valves having a throttled and a non-throttled switching position. During the acceleration phase, in which the control lines are acted upon with control pressure, the brake valves are in their non-throttled switching position. During the braking phase, in which the control lines are substantially pressureless, the brake valves are switched into the
REFERENCES:
patent: 3921503 (1975-11-01), Kubik
patent: 4554991 (1985-11-01), Eden
patent: 4571941 (1986-02-01), Aoyagi et al.
Patent Abstracts of Japan, Publication Number 6 1031534 dated 2/14/86.
Adler Bernhard
Schniederjan Reinhold
Brueninghaus Hydromatik GmbH
Lopez F. Daniel
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