Abstract:
The invention relates to a drive device, which is used in particular for the closing unit, the injection unit or the ejectors of a plastics injection molding machine and which has a drive element which can be axially moved by an electric motor and a hydraulic unit which, by moving the drive element, can be moved in the same direction as the latter. Drive devices for the stated applications depend on firstly performing a rapid positioning movement and then exerting great forces. In the case of a known drive device with the stated features, the hydraulic unit is a hydraulic cylinder, which is displaced during the positioning movement by the electric motor via a lifting spindle and to which pressure medium is supplied via a valve for the exertion of a great force. In the case of this known drive device, apart from the electrical installation, a complete hydraulic system is also necessary. Furthermore, great forces of reaction act on the lifting spindle. This is avoided if, according to the invention, the hydraulic unit is a force multiplier with two pistons, which can be moved in relation to one another and differ in the size of their effective surface areas, and an intermediate part, which together with the pistons encloses a pressure chamber filled with a pressure fluid, if the small piston, having the smaller effective surface area, is mechanically connected to the drive element, if the hydraulic unit as a whole can be moved for the positioning movement and if the intermediate part can be blocked against displacement in relation to a fixed frame for the exertion of a great force by the large piston, having the greater effective surface area.
Abstract:
A hydraulic unit having a hollow oil container which has a receiving space for oil between an external outer wall and an internal outer wall, and having a pump unit which comprises an electric motor and a pump which can be driven by the electric motor. Such a hydraulic unit is to be further developed in such a manner that it has only a low noise level, in which connection also sufficient cooling of the hydraulic fluid and of the electric motor should be assured. This is achieved in the manner that at least the pump, and preferably the pump unit, is included in an enclosure which is formed by the hollow oil container and at least one sound-damping element.
Abstract:
A hydraulic circuit for supplying a plurality of series-operated consumers of a hydraulically controlled installation, in particular of an injection molding machine, having a pump with feed-flow pressure control, is described. To be able to slow down greater moving masses with very little expenditure in regard to circuitry and devices, only a portion of the consumers, such as the extruder, the injection unit and possibly the ejector are operated in open circulation, while at least one selected further consumer, such as the clamping unit of the injection molding machine, where a greater mass must be moved in alternating directions, is moved in semi-closed or closed circulation.
Abstract:
The invention relates to a safety arrangement for a controlled drive which is connected to a conduit with impressed pressure. When the safety arrangement responds the machine is separated via shutoff valves from the inlet and outlet and a via a switchover valve the pivot angle of the machine is set to the maximum value so that the largest possible braking torque can be automatically set.
Abstract:
The pressure response of a pressure control valve is adjusted by a solenoid valve of which the solenoid is connected to an electrical three point control device. A programmed signal and an actual signal derived from a transformer of the control pressure valve are fed to the input of the three point control device.
Abstract:
A radial piston pump comprises a housing bounding a suction chamber therein and at least one valve piston unit mounted in the housing. The valve piston unit includes a pressure valve defining a pressure chamber, a movable piston having an axial passage operatively communicating the suction chamber with the pressure chamber, and a suction valve located in the axial passage of the piston. The suction valve is operative for opening and closing the axial passage of the piston so as to establish and interrupt the above communication, respectively. The piston performs a suction stroke and a working stroke, and a valve member of the suction valve is open during the suction stroke of the piston. The valve member has such a mass that it is opened by an accelerative force produced during the above suction stroke of the piston. The piston is moved by an eccentric mounted on a rotatable shaft, which eccentric has a circumferential groove operatively communicating the suction chamber with the axial passage of the piston.
Abstract:
The present invention relates to a hydro-transformer including a hydraulic machine, a switching valve and a control means. A work port of the switching valve, which may optionally be connected hydraulically with a pressure port of the switching valve or a drain port of the switching valve, is connected with a first port of the hydraulic machine. The second port of the hydraulic machine is in hydraulic connection with a drive member. The switching valve is driven by the control means in response to a signal characterizing the volume flow into the hydraulic machine. Where the driver member is a cylinder, its extension may be carried out at a constant velocity and independently of a load, and energy may be recovered upon retraction. Due to the provision of a further switching valve between the second part of the hydrostatic motor and the drive member, a higher pressure may be generated at the drive member in the presence of a low pressure at the pressure port of the switching valve.
Abstract:
A hydraulic system comprises an accummulator for supplying hydraulic fluid to a load, a variable displacement pump for charging the accummulator and a valve means for adjusting the pump to deliver a high pressure for charging the accummulator and then to a low pressure when the load is supplied with fluid from the accummulator. By this operation, in which the pump is switched between the zero stroke positions of high and low pressure, the losses of the pump are decreased and the lifetime is increased.
Abstract:
A hydraulic pump of the type in which a cam ring and rotor are mounted within a rotor chamber formed between a cover and housing fixedly mounted together. An adjustment screw extends into the rotor chamber transverse to the axis of rotation for adjusting the level of the cam ring. Two pairs of bolts, and only two pairs, extend parallel to the rotation axis at a given radius from that axis to fix together the housing and cover. The distance between the pair of bolts on either side of the adjustment screw and at the pressure region are less than the distance betwen the bolts of the opposite pair at the suction region. Further the angle .beta. between an x-x axis transverse to both the adjustment axis and the rotation axis and the radii of the pair of bolts on either side of the adjustment screw is between 60.degree. and 75.degree. and the angly .gamma. between the x-x axis and the radii of the other pair of bolts is between 25.degree. and 40.degree. so that each bolt takes up approximately the same amount of force.
Abstract:
A hydrostatic machine having a rotor mounted in a housing and having a leakage oil connection, the leakage oil being conducted before discharge to the tank through predetermined housing portions in order to heat the central part of the housing during the start-up phase of the machine.