Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1979-04-09
1980-12-23
Pavelko, Thomas P.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
425149, B29F 106
Patent
active
042409969
ABSTRACT:
A process for controlling part density in molding machines in which a charge of material is injected by a ram into the mold cavity in approximatey 1.5 seconds or less as the ram moves between a variable retraction point and a fixed forward point whereat the ram bottoms, i.e., reaches its forwardmost point of travel beyond which further forward motion is precluded by mechanical limits or stops. Means are included to determine the pressure of the material injected into the mold cavity, using a pressure transducer communicating with the cavity, runner or barrel, at the point in time when the ram bottoms. The measured pressure is then compared against a predetermined pressure correlated to a desired part density, and in response thereto an error signal generated. The error signal is utilized to vary the ram traction point such that the next charge will return the cavity pressure, when the ram tip bottoms, toward the predetermined or desired pressure and in turn return the density of the injected charge toward the desired density notwithstanding changes in density from charge-to-charge.
REFERENCES:
patent: 3767339 (1973-10-01), Hunkar
patent: 3860801 (1975-01-01), Hunkar
patent: 3932083 (1976-01-01), Boettner
Hunkar Laboratories, Inc.
Pavelko Thomas P.
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