DE1066424B - - Google Patents

Description

eibUottieek

GERMAN

V11709Ia / 60

REGISTRATION DATE: DECEMBER 29, 1956

NOTIFICATION OF REGISTRATION AND ISSUE OF

FROM LEGE WRITING: 1. 0 KTO B E R 1959

The invention relates to a hydraulic device, which consists of a differential piston and a Pump with alternating direction of delivery exists and is used for systems with alternating direction of force is, preferably for the operation of the pulling mechanism of cranes, such as harbor cranes, block pillar cranes and the like

In these systems, one or more hydraulic cylinders are used to move the boom, which are attached on the one hand to the fixed structure and on the other hand to the boom. As it is for housing of the cylinder or cylinders is cheaper and sometimes required, a differential piston with one-sided To use yeast protruding piston rod, one has so far a so-called open circuit between Pump and cylinder selected. The one that is present in luffing cranes and similar facilities A change in the direction of force requires a controlled counterpressure control valve to prevent the rollover to prevent the boom from falling through when changing the direction of force. The disadvantage of such Facilities, however, is that a special reversing device is used to change the direction of movement of the luffing mechanism must be present and that its actuation, since one must avoid impacts, only sensitively and can generally be carried out at a low boom speed. This condition requires complicated control devices without a harmonic inversion being achieved.

For this reason, the closed circuit between pump and cylinder has already been proposed, which is characterized in that the suction oil required by the pump comes directly from the displacement side of the cylinder is removed and thereby at the same time a Braking effect is achieved. Such systems are also reversed in that when they are used a suitable pump with constant drive direction of rotation thereby the conveying direction it is reversed that the adjusting member of the pump by the Xullage in the opposite design is brought. The disadvantage of such a device, however, is that the inflow and outflow side of a cylinder must have volumes of the same size. A piston is therefore generally used for this purpose with protruding piston rods of the same size on both sides.

For the arrangement on a crane, however, this is disadvantageous because of the space required and in part unsightly outer contour as well as the hindrance caused by this when panning. That is why it has already been proposed to use a differential piston and parallel to the application the piston rod side a second cylinder to be-hydraulic device for reciprocating movement with alternating direction of force

Applicant: VEB Centex Leipzig automatic lathe and hydraulic construction, Leipzig N 26, Pittlerstr. 26th

Fritz Berg and Hans-Dieter Hennig, Leipzig, have been named as inventors

send that takes up the volume of the piston rod size. This gives the same volume when drawing in and laying out. However, this design also represents a structural disadvantage.

The object of the invention is therefore to avoid these known disadvantages and based on the advantages of a closed loop system to develop that use a normal differential piston.

For this it is necessary to provide the cylinder special facilities to compensate for the different volumes, without the stability of a uniform motion is impaired despite Kraftrichtungswechscl and the \ "enefits the simple reversal of direction is lost. Therefore, it has the excess oil once that when pumping the pump into the piston rod side, escaping from the large piston side, can be controlled in such a way that the boom cannot go through even when the direction of force changes.

According to the invention, this is achieved by an outlet valve controlled by the forward pressure. On the other hand, a second valve is provided in order to maintain a constant piston speed when the pump is fed into the large cylinder side, even if the direction of force suddenly changes and the piston is pulled in the direction of movement by the boom weight. Here, the second control valve blocks the discharge line from the piston rod side so far that the pressure on the pressure side of the pump is maintained at a certain level. This is necessary to provide the necessary in such circuits booster pump, which is generally limited to a low oil pressure, not in the pump

909 630/110

Claims (2)

To have conveyor ropes also conveyed, thereby increasing the piston speed when the load is rolled over. In this way it is possible to move a differential piston in a closed circuit in both directions of movement at a speed which corresponds to the set pump delivery rate and which is maintained even when the load changes. Tu the drawing is a system - according to the invention - shown; the mode of operation is as follows: The pump 1, which is designed as a pump with a reversible conveying direction, can convey both into the line 2 and into the line 3, depending on the position of its control device. It is connected in the so-called closed circuit with the cylinder 4 via the aforementioned line 2 and the lines 3 and 3 '. While the cylinder 4 is rotatably linked to the structure, for example, the piston 5 is also rotatably attached to the boom. To fill up the entire circuit and to compensate for the different volumes of the cylinder spaces 6 and 7, a special filling pump 8 is provided. The pressure of this pump is chosen to be just high enough to ensure adequate filling and pre-tensioning of the system. This is particularly necessary when changing the direction of force, for example to keep a boom always safely between hydraulic oil columns. A valve 9 is provided to limit this filling pressure. The filling takes place via the check valves 10 and 11, in each case in the line (2 or 3), the pressure of which is lower than the filling pressure. If, for example, oil is now conveyed by the pump 1 into the line 2, it then reaches the cylinder side 7 and moves the piston 5 to the left. Since the amount of oil displaced from the cylinder chamber 6 is less than the requirement of the pump 1, the shortfall is also supplied by the pump 8 via the check valve 10, while the line 3 and the cylinder chamber 6 are kept at the set preload pressure at the same time. As long as the piston 5 has to overcome compressive forces, the pressure in the cylinder chamber 7 will always be higher than in the chamber 6. If the load tipping point now comes, so that a tensile force acts on the piston 5, the pressure in chamber 7 falls and thus also in the line 2. At the same time, however, the pressure in the control line 12 connected to line 2 falls, so that the piston 15 acted upon by the spring 14 on the end face of the valve 13 is displaced to the right. As a result, the outlet cross-section from cylinder space 6 via line 3 'is throttled to such an extent that pump 1 must deliver into cylinder space 7 via line 2 against an active resistance. This also prevents the check valve 11 from opening and the intake pump 8, in addition to the pump 1, from causing an accelerated piston movement of the piston 5. The spring 14 is dimensioned in such a way that the piston 5 or the boom connected to it cannot move faster than the liquid niengc conveyed by the pump, even when the load changes. If the pump 1 now delivers in the opposite direction into the line 3 and into the cylinder ravini 6, a bypass via the check valve 16 is provided to avoid throttling by the valve 13. The piston 5 now moves to the right and displaces more oil from the cylinder cavity 7 into the line 2 than the pump 1 can suck out. FTierzu is provided ίο a slide 17 which allows the excess oil to escape from the space 7 via line 18 into the oil container. This happens because the pressure from line 3 moves the locking piston 20 against the spring 21 via the line 19 when the forward pressure is above the pressure of the filling pump. If one were to use the only spring-loaded overflow valve with the Finstelluiig at a constant pressure, which is common in closed circuits, then the pressure in line 2 would not be above the pressure of valve 9 in the event of a load change. In the present embodiment, however, a pressure is built up in space 7 and line 2 which can rise to the maximum pressure of the system. The device for limiting this maximum pressure has been omitted in the diagram shown, since it does not affect the invention. When the load changes, the valve 17 produces such a strong braking effect that the full pivoting moment of the boom is also available as a braking moment. Claims = 1. Hydraulic device for controlling the reciprocating movement of a hydraulic servomotor with alternating load direction during the stroke using a differential piston and a closed pressure medium circuit with a pump operating with alternating conveying direction, characterized in that in a known manner in the line between the pump (1) and the piston rod side of the cylinder a control valve (13) is switched on, which builds up a braking effect controlled by the forward pressure when the load direction changes, and that there is another control valve (17j) between the pump and the large cylinder side, so that when working in the opposite direction, the Controls the excess amount from the large cylinder side depending on the forward pressure so that a controlled braking process is effected when the load direction changes. 2. Hydraulic device according to claim 1, characterized in that a non-return valve (16) is arranged to bypass the controlled brake valve (13) in the inflow line to the piston rod side of the cylinder (6). Considered publications:
German Patent No. 644 545;
German interpretation document M 27422 XI / 35b (published on September 6, 1956); French patent specification No. 1 081 952. 1 sheet of drawings © 909 630/110 9.59