Hydraulic system for the mold clamping unit of a plastics injection molding machine
First Claim
1. A hydraulic actuator assembly for use in a mold clamping unit of an injection machine as a rapid-travel drive for mold opening and closing and as a source of elevated mold clamping pressure, which said mold clamping unit includes a movable mold platen guided for mold opening and closing, the hydraulic actuator assembly comprising:
- (a) a power cylinder for exerting elevated die closing pressures, the power cylinder having a power piston and a power piston rod coupled with the movable mold platen, the power piston dividing the power cylinder into a high pressure space on a rear side of the piston and a low pressure space on a forward side of the piston, the power piston rod having a hollow interior;
(b) flow connection canals on the power piston for effecting communication between the low pressure space and the high pressure space, while the power piston is moving for die closing or opening;
(c) a hydraulic valve having a pressure space and an annular piston for controlling said canals, said valve being controlled by a slide valve disposed in a connecting passage connecting the pressure space with a pump of the assembly;
(d) compensating cylinders, each encircling a communicating space communicating with the low pressure space of said power cylinder by passages and further communicating with the high pressure space via the canals in the high pressure piston when the canals are opened;
the compensating cylinders being arranged diametrically to said power cylinder, each compensating cylinder having a piston on a piston rod, each of said piston rods being connected with the movable mold plate for movement in unison with the power piston;
(e) a hydraulic drive cylinder having a stationary hydraulic drive cylinder piston, the hydraulic drive cylinder being for rapid die closing and opening, the hydraulic drive cylinder being partially formed by the hollow interior of the power piston rod;
the stationary hydraulic drive cylinder piston being a double acting piston with a pressure space on the rear side for opening and a pressure space on the forward side for die closing;
(f) a control valve for controlling an opening movement and a closing movement of each of said compensating cylinders via a displacement detector for detecting displacements of the movable mold platen by a quantity program;
a rear side connecting passage having a pressure sensor connecting the control valve with the rear side cylinder space, and a forward side connecting passage having a pressure sensor connecting the control valve with the forward side cylinder space, whereby the control valve communicates with both said low pressure space and said high pressure space for determining the drive speeds of drive cylinder in closing and opening directions, with simultaneous pressure influencing both sides of the drive cylinder piston in accordance with the quantity program via the displacement detector detecting the opening and closing of the movable mold platen and in accordance with a pressure control for selectively overriding the quantity program; and
(g) a first branching connecting passage connecting the forward side connecting passage with the high pressure space for elevating closing pressure, which first branching connecting passage communicates with a first multi-way slide valve for exerting an elevated die closing pressure.
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Abstract
A hydraulic actuator assembly for use in a mold clamping unit of an injection molding machine. The actuator assembly serves as a rapid-travel drive for mold opening and closing movements and as a source of elevated mold clamping pressure. Among the hydraulic elements contributing to the operation of the mold clamping unit are a power piston for effecting elevated mold clamping pressures and a drive piston for effecting rapid die closing movements. With the hydraulic actuator system of the present invention, it is possible to control the operation of the mold clamping unit based on two-sided hydraulic influencing of the power piston and the drive piston.
47 Citations
11 Claims
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1. A hydraulic actuator assembly for use in a mold clamping unit of an injection machine as a rapid-travel drive for mold opening and closing and as a source of elevated mold clamping pressure, which said mold clamping unit includes a movable mold platen guided for mold opening and closing, the hydraulic actuator assembly comprising:
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(a) a power cylinder for exerting elevated die closing pressures, the power cylinder having a power piston and a power piston rod coupled with the movable mold platen, the power piston dividing the power cylinder into a high pressure space on a rear side of the piston and a low pressure space on a forward side of the piston, the power piston rod having a hollow interior; (b) flow connection canals on the power piston for effecting communication between the low pressure space and the high pressure space, while the power piston is moving for die closing or opening; (c) a hydraulic valve having a pressure space and an annular piston for controlling said canals, said valve being controlled by a slide valve disposed in a connecting passage connecting the pressure space with a pump of the assembly; (d) compensating cylinders, each encircling a communicating space communicating with the low pressure space of said power cylinder by passages and further communicating with the high pressure space via the canals in the high pressure piston when the canals are opened;
the compensating cylinders being arranged diametrically to said power cylinder, each compensating cylinder having a piston on a piston rod, each of said piston rods being connected with the movable mold plate for movement in unison with the power piston;(e) a hydraulic drive cylinder having a stationary hydraulic drive cylinder piston, the hydraulic drive cylinder being for rapid die closing and opening, the hydraulic drive cylinder being partially formed by the hollow interior of the power piston rod;
the stationary hydraulic drive cylinder piston being a double acting piston with a pressure space on the rear side for opening and a pressure space on the forward side for die closing;(f) a control valve for controlling an opening movement and a closing movement of each of said compensating cylinders via a displacement detector for detecting displacements of the movable mold platen by a quantity program;
a rear side connecting passage having a pressure sensor connecting the control valve with the rear side cylinder space, and a forward side connecting passage having a pressure sensor connecting the control valve with the forward side cylinder space, whereby the control valve communicates with both said low pressure space and said high pressure space for determining the drive speeds of drive cylinder in closing and opening directions, with simultaneous pressure influencing both sides of the drive cylinder piston in accordance with the quantity program via the displacement detector detecting the opening and closing of the movable mold platen and in accordance with a pressure control for selectively overriding the quantity program; and(g) a first branching connecting passage connecting the forward side connecting passage with the high pressure space for elevating closing pressure, which first branching connecting passage communicates with a first multi-way slide valve for exerting an elevated die closing pressure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification