Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Molding pressure control means responsive to pressure at...
Patent
1989-03-15
1990-10-09
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Molding pressure control means responsive to pressure at...
264 401, 425170, B29C 4577
Patent
active
049616960
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an injection molding machine of a type having a detector which is capable of simply and accurately detecting resin pressure, and is arranged to facilitate assemblage, maintenance and replacement of the detector.
BACKGROUND ART
Conventionally, an injection molding machine has been known, which has a detector for detecting resin pressure, i.e., injection pressure, hold pressure and back pressure, and performs pressure control in accordance with the detected resin pressure so as to produce good molding products. In general, a pressure sensor disposed within a mold cavity has been employed for detection of the resin pressure. However, this type of sensor is high-priced. In this respect, a strain detector, disposed on a housing which axially supports a screw shaft, for receiving the reaction force from the resin material to detect the resin pressure, has been proposed.
As shown in FIG. 5, this type of detector comprises an annular member 1 and a detecting element such as a strain gauge (not shown) affixed thereon. The annular member 1 is disposed between a thrust ball bearing 3 and a stepped portion 5 formed in a metering bearing housing 2 which is axially and radially supported by the bearing 3 and an angular ball bearing 4, respectively. In assembling the above-mentioned arrangement in which the annular member 1 is interposed between the bearing 3 and the stepped portion 5 within the housing 2, lead wires of the strain gauge must be passed through the housing 2, and an axial clamping force is inevitably applied to the annular member 1 upon assemblage thereof and even thereafter. As a consequence, the annular member 1 is deformed at a portion on which the strain gauge is affixed. Thus, an output from the strain gauge is produced even before the resin pressure is actually generated, that is, a shift of zero point in resin pressure detection takes place. In this connection, a required zero adjustment is made by means of an appropriate circuit in the resin pressure control system upon detection of the resin pressure. Moreover, since the annular member 1 is disposed within a hollowed interior of the metering bearing housing 2, it is troublesome or difficult to effect replacement and maintenance of the annular member 1 and wiring of the lead wires of the strain gauge.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide an injection molding machine equipped with a resin pressure detector which is capable of accurately detecting the resin pressure, without the need of correcting the detected resin pressure, and has a construction which facilitates maintenance, replacement, and assemblage, including wiring.
To achieve the above-mentioned object, according to the present invention, there is provided an injection molding machine of a type having an injection unit which includes a metering bearing housing disposed for movement in unison with a metering screw, and a ball screw
ut mechanism for reciprocal movement of the screw through the housing. The injection molding machine comprises an annular member on which a resin pressure detecting element is mounted, a first fixture means for fixing said annular member on an outer face of the metering bearing housing at a side remote from the screw, and a second fixture means for fixing a ball nut of the ball screw
ut mechanism on an outer face of said annular member at a side remote from the metering bearing housing.
As mentioned above, according to the present invention, since the annular member for resin pressure detection is fixed to the outer face of the metering bearing housing, the resin pressure detecting element can be mounted on the annular member after completion of assemblage of the annular member and its peripheral components, to thereby eliminate a detection error resulting from a deformation of the annular member which occurs at the time of assembling. Moreover, since the connection between the annular member and the housing and the connection between the annular member and the ball
REFERENCES:
patent: 4758391 (1988-07-01), Shimizu et al.
Fanuc Ltd.
Mackey James P.
Woo Jay H.
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