Time saver plastic draw-back valve assembly
AssigneeFarrell Patent Company
InventorJohn J. Farrell
Life of this patent
Estimating the term…
Abstract
This invention decreases the time of an injection molding machine cycle by cutting off communication between the mold and the source of material as soon as injection is complete, and accumulating material for the next charge during the cooling part of the cycle. Pressure is maintained on the material in the mold, and material is supplied to compensate cooling shrinkage, from an auxiliary cylinder in which a minor amount of hot material is accumulated. After sufficient cooling, runner material is drawn back by suction of the auxiliary cylinder. A three-way valve cuts off the main material supply and puts the auxiliary cylinder in communication with the mold.
Claims16
An injection molding apparatus including a barrel for holding molten plastic material, a first passage connected at one end with the barrel for receiving hot plastic material from the barrel, a second passage connected with the other end of the first passage for receiving molten material from the first passage for supplying the material to a mold, a cylinder, a third passage connected at one end with the cylinder and connected at its other end with the second passage, a piston in the cylinder, movable in one direction to maintain pressure on any molten material in the cylinder, third passage and second passage, and movable in the other direction to exert a suction action in the cylinder, third passage and second passage for drawing molten material in the second passage back into the third passage and cylinder, and valve means, located between the first and second passages and between the second and third passages, movable into different positions including a first position that closes off the third passage from the second passage and that puts the first passage in communication with the second passage, and a second position that shuts off the first passage from the second passage and that puts the second passage in communication with the third passage , said valve means preventing communication between said first and third passages in said two positions .
The injection molding apparatus described in claim [1] 10 characterized by an actuator for the piston including a controller for supplying energy to the piston to urge the piston to move in one direction when the valve means is in [said first] the second position to maintain pressure on any molten material in the [third passage] cylinder and [second passage] mold runner during the cooling portion of a molding cycle [and while the valve means is in position that puts the third passage in communication with the second passage] whereby the piston forces additional material into the mold to compensate for shrinkage of the material in the mold while cooling, and automatic means associated with the controller for reversing the direction of the energy supply to the actuator , when the valve means is in said second position , to move the piston in a direction to draw back material from the runner[s] , [with which the molding apparatus is used] after a predetermined cooling period.
The injection molding apparatus described in claim [4] 10 characterized by a valve operator for moving the valve means between its different positions including an automatic control that shifts the valve means from its first position at the end of an injection operation of said injection molding apparatus.
The injection molding apparatus described in claim [5] 10 characterized by a helically threaded plasticizer screw in the barrel, pressure means for advancing the screw longitudinally toward the first passage on an injection stroke while the valve means is in its first position, said valve means in its second position shutting off flow of material from the first passage, a motor for rotating the screw in a direction to urge material in the barrel toward the first passage after the valve means has moved into its second position whereby the continued rotation of the screw causes it to back away from said first passage, automatic means for stopping further rotation of the screw after it has backed away far enough to accumulate, between the screw and the first passage, enough material for the next mold charging operation.
The injection molding apparatus described in claim [1] 10 [molten] characterized by apparatus for injecting molten material at high temperature and pressure into the first passage and through the valve means to the second passage when the valve means is in its first position, the valve means shutting off all flow of material through the first passage when the valve means is in its second position, and a valve operator for moving the valve means from first position to second position and vice versa.
An injection molding apparatus including a barrel for holding molten plastic material, a first passage connected at one end with the barrel for receiving hot plastic material from the barrel, a runner that supplies molten material to a mold cavity, a second passage connected with the other end of the first passage for receiving molten material from the first passage for supplying the material to the mold runner, a plasticizer including a helically threaded screw in the barrel, with a front end of the screw facing the first passage, pressure means for advancing the screw longitudinally toward the first passage to discharge material from the barrel on an injection stroke, a motor for rotating the screw in a direction to urge material in the barrel toward the first end of the screw during rotation of the screw as it backs away from said first passage, during its recovery stroke, automatic means for stopping further rotation of the screw after it has backed away far enough to accumulate, between the screw and the first passage, enough material for the next mold charging operation, means for regulating the plasticizer cycle to be less than that absent such means including a cylinder for communication at one end with the mold runner, a piston in the cylinder, movable in one direction providing means to maintain pressure on any molten material in the cylinder and in the mold runner during shrinkage of the molten material, the piston being movable in the other direction providing means to exert a suction action in the cylinder for drawing molten material in the runner back toward the cylinder, and valve means, located between the first and second passages and movable into different positions including a first position that puts the first passage in communication with the second passage, and a second position that shuts off the first passage from the second passage and provides communication between the cylinder and the second passage, said valve preventing communication between said cylinder and said first passage so that recovery of the plasticizer can begin before shrinkage of the plastic in the mold and before drawback of plastic from the runner .
Dependencies are inferred from the claim text.