Low-loss drive system for a plurality of hydraulic actuators

Details Low-loss drive system for a plurality of hydraulic actuators Low-loss drive system for a plurality of hydraulic actuators

1999-02-16

2001-03-27

Lopez, F. Daniel (Department: 3745)

Power plants

Pressure fluid source and motor

Having condition responsive control in a system of distinct...

C060S423000

Reexamination Certificate

active

06205780

ABSTRACT:

DESCRIPTION
The invention relates to a drive system with at least two hydraulic actuators which are supplied with a hydraulic fluid by means of at least one pump.
From the DE 40 30 950 A1 it is known to provide a hydraulic double-acting actuator with two pumps, wherein in each instance only one of the two pumps is operative with regard to the movement of the actuator. Furthermore, as usual, loss-entailing regulating valves are used to control the actuator, and the pumps are driven at a largely constant speed, in one direction of rotation, by an internal combustion engine.
Machines with several actuators which must perform different operating movements in a completely or partially sequential manner, are usually supplied with hydraulic energy by means of a regulating valve circuit, that of one or several pumps which are driven at a constant speed. The technical disadvantage of these systems is a low efficiency since, due to the principle, the regulating valves convert hydraulic energy into thermal energy.
It is the object of the present invention to create a drive system which has a simple construction, outstanding regulating properties and at the same time avoids the principle-related throttle losses of regulating valves and, accordingly, operates with a very good efficiency.
According to the invention a hydraulic actuator can be controlled or regulated by two bi-directional, speed-regulated pumps without any regulating valve and, accordingly, in an extremely low-loss way in four-quadrant operation. Because the two pumps have one valve circuit, in particular in the case of sequential operations the two pumps can both be assigned to the active actuator or, in the case of single-action operation, to two actuators. The valve arrangement permits in an advantageous manner the use of only two pumps, which via the valve arrangement can be connected to the individual actuators in a low-loss manner. It is possible, therefore, to dispense with a greater number of pumps, which simplifies the construction and makes it more economical. The valve arrangement essentially serves to produce the low-loss connection between the pumps and the actuators, wherein the regulating functions are ensured directly by the pumps.
In an advantageous embodiment of the invention the valve arrangement has several switching positions, in which in each instance one actuator in the double-acting operating mode is connected to both pumps.
In another advantageous embodiment the valve arrangement has switching positions which permit the two pumps to be connected to different actuators, so that, therefore, two actuators can be operated simultaneously.
Preferably, the valve arrangement has switching positions in which the two pumps can be connected in parallel and jointly supply one actuator.
In another advantageous embodiment the valve arrangement can be provided with seat valves so as to fix in a leakage-free manner the actuators which are not being driven at the time.
In another advantageous embodiment the valve arrangement for single-acting actuators can be provided with holding valves.
Preferred is an embodiment of the drive which is characterised in that at least one of the pumps has a constant displacement volume. Such pumps are of a particularly simple construction, resulting in an economical realisation which is not susceptible to problems.
Furthermore preferred is an embodiment of the drive which comprises a control which co-operates with the drive, is designed as a regulating circuit and includes at least one sensor which detects the position, speed and/or acceleration of the actuator and/or the pressure acting on the actuator or the forces exerted by the actuator. In this way it is possible to adapt the drive in a highly variable manner to the actual circumstances.
With the abovementioned advantageous embodiments it is also possible, of course, to use more than two pumps for driving several actuators.


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Patent Abstracts of Japan vol. 96, No. 9 (for Publication 08-133688 May 28, 1996) Sep. 30, 1996.

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