Dispensing – With discharge assistant – Motor operated
Reexamination Certificate
2000-09-21
2001-06-19
Derakshani, Philippe (Department: 3754)
Dispensing
With discharge assistant
Motor operated
C222S413000
Reexamination Certificate
active
06247622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric injection apparatus, and more particularly to an electric injection apparatus which carries out back pressure control in metering by means of hydraulic power.
2. Description of the Prior Art
There have been already known some electric injection apparatuses that carries out back pressure control by means of hydraulic pressure. One of the prior art is to couple the rear end of an injection screw to a piston in a cylinder formed at the center of a screw thrust member so that the backward force of the screw is controlled by hydraulic pressure. In such a conventional electric injection apparatus, the injection screw transfers heat to heat the hydraulic fluid in the cylinder easily. Therefore, long-hour use heats up the hydraulic fluid with viscosity decrease, causing a problem of variations in the set pressure. In addition, since the hydraulic cylinder is provided inside, the screw thrust member is troublesome to fabricate. Accordingly, there is also the problem of hard adoption for electric injection apparatuses of ordinary structure.
In another example of the prior art, hydraulic cylinders are arranged across the support and the screw thrust member of the injection apparatus to carry out backpressure control. The cylinders are integrated onto both sides of the screw thrust member, and their piston rods are coupled to the support. Therefore, as in the conventional apparatus described above, it is inevitable that the heat transfer through the injection screw thermally affects the hydraulic fluid in the cylinders. Besides, like the preceding prior art, there is the problem of hard adoption for electric injection apparatuses of ordinary structure.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the foregoing conventional problems, and an object thereof is to provide an electric injection apparatus in which an independent hydraulic cylinder for back pressure control can be arranged without adding any special means to a screw thrust member. Another object of the present invention is to provide an electric injection apparatus having a cylinder that can be spaced away from a heater barrel to eliminate the thermal effects on the hydraulic fluid. Still another object of the present invention is to provide an electric injection apparatus of new configuration in which a hydraulic block can be incorporated according to need so that valve devices as well as a cylinder are installed on a rear support.
To achieve the foregoing objects, the present invention provides an electric injection apparatus comprising a hydraulic cylinder for back pressure control. This electric injection apparatus includes rear and front supports integrally coupled to each other by a tie bar with a predetermined spacing therebetween. A heating barrel having an injection screw arranged therein is attached to the front support. Between the supports, a screw thrust member having an injection screw rotatably coupled to its front center is movably arranged so that the tie bar penetrates therethrough. Besides, the rear support and the screw thrust member are coupled to each other by means of the threaded engagement between a ball screw shaft and a ball nut portion. The hydraulic cylinder for back pressure control is arranged across the rear support and the screw thrust member, in parallel with the ball screw shaft so that its cylinder and piston rod are fixed to the rear-support side and the screw-thrust-member side, respectively. The ball screw shaft and the injection screw are driven by electric driving means.
Such an electric injection apparatus has servomotors as drive sources, whereas the back pressure control in metering is performed by means of hydraulic power. This means a higher precision as compared with the cases where the back pressure control is carried out through servomotor rotation controls. Moreover, the cylinder of the hydraulic cylinder for back pressure control is fixed to the rear-support side isolated away from the heating barrel. This avoids easy heat transfer from the heating barrel to the cylinder, eliminating the resulting thermal effects on the hydraulic fluid in the cylinder. Therefore, stable back pressure control can be maintained even in long-hour use.
REFERENCES:
patent: 4187961 (1980-02-01), Voller
patent: 4708268 (1987-11-01), Wurtz
Suda Masashi
Tokida Satoru
Yamaguchi Issei
Derakshani Philippe
Nissei Plastic Industrial Co. Ltd.
Weingarten, Schurgin Gagnebin & Hayes LLP
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