Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Temperature control
Reexamination Certificate
2000-03-20
2002-05-07
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Temperature control
C425S144000, C425S378100
Reexamination Certificate
active
06382948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling temperature of a proximal portion of a heating cylinder of an injection molding machine.
2. Description of Related Art
An injection molding machine has a mold clamping mechanism, an injection mechanism and an operation panel, all arranged on a frame, and performs injection molding by clamping a mold between stationary and movable plates constituting the mold clamping mechanism, sliding the injection mechanism to press a nozzle at a distal end of a heating cylinder into a center hole of the stationary plate, and injecting molten resin from the nozzle to be molded in a cavity defined in mold halves.
The temperature of an injection screw in the injection molding machine affects the conveyance of the resin in a metering process as well as the hysteresis of the resin. In order to properly convey the resin in the metering process, therefore, the temperature of the injection screw needs to be controlled such that the resin is prevented from adhering to the outer peripheral surface of the injection screw, and that resin introduced from a hopper is melted at the nozzle side, and not at a lower portion of the hopper. For such temperature control, a temperature control device is provided for controlling the temperature of the proximal portion of the heating cylinder.
The temperature control device is designed to control the temperature of the proximal portion of the heating cylinder by simply allowing a temperature control medium to flow downward. The flow rate of the temperature control medium is, conventionally, not controlled at all or is controlled by means of a main tap or a manual flow control valve arranged in the middle of the medium line.
If the flow rate of the temperature control medium is not controlled at all, the temperature of the proximal portion of the heating cylinder becomes unstable and the plasticizing ability of the resin lowers due to excessive removal of heat from the resin, giving rise to a problem that many defective articles are produced because of uneven molding conditions.
Also, even in the case where the temperature control is performed by means of a manual flow control valve, the operation for such temperature control is troublesome because the flow control valve is located on the side of the injection molding machine opposite the operation panel or at a distance from the injection molding machine, and thus a problem arises in that the operator is forced to work in a small dangerous place such as at the back of the machine.
In view of the above problem of low operation efficiency, a method has been proposed in which the control valve is arranged near the operation panel (e.g., in Examined Japanese Utility-Model Publication No. 7-27148). In factories, however, a main tap of the medium is usually fixed in position and it is necessary that piping be installed between the injection molding machine and the main tap. Accordingly, the degree of freedom in installing the piping is low, and in addition, the cost increases because of the use of parts for fixing the piping Ad the flow control valve, and also because of work associated therewith.
Also, a mechanism for preventing the plasticizing ability of resin from being lowered due to excessive removal of heat from the resin has been proposed, in which the temperature control device for controlling the temperature of the proximal portion of the heating cylinder has a two-upper/lower-piece structure (e.g., Unexamined Japanese Patent Publication No. 7-232361).
FIG. 11
is a diagram illustrating such a device with the two-upper/lower-piece structure. In
FIG. 11
, a temperature control device
100
for controlling the temperature of the proximal portion of the heating cylinder comprises two, upper and lower separate jackets
101
and
102
, and a proximal portion
106
of the heating cylinder having an injection screw
104
inside is fixed in position between the jackets
101
and
102
. One of the jackets, that is, a jacket
101
has a communication port
105
formed therethrough for introducing resin.
A portion of this device disposed in contact with the heating cylinder proximal portion has a semicylindrical surface and thus is difficult to machine with high accuracy. Even if the temperature control device is fixed by bolts or the like, it is still associated with a problem that the efficiency of heat transfer and thus the temperature controllability are low because of a small area of contact between the heating cylinder proximal portion and the temperature control device. Also, since the contact area between the proximal portion of the heating cylinder and the temperature control device varies depending upon a skill of a person who installs the temperature control device, molding conditions vary from machine to machine, and in addition, temperature distribution is liable to become uneven between the upper and lower pieces of the temperature control device, which exerts adverse effects on the molding conditions.
An electromagnetic valve may be used to control the flow rate of the temperature control medium. In this case, however, a controller and a temperature sensor are required in addition to the electromagnetic valve, and thus a problem of high cost arises despite the advantage of high-accuracy temperature controllability.
Further, in order to prevent excessive temperature change from being caused by the downflow of a large quantity of the temperature control medium in a short time, a passage through which the temperature control medium flows may be reduced in diameter. In this case, however, impurities contained in industrial water adhere to the inner surface of the passage, and therefore, frequent maintenance is required to eliminate clogging of the passage with waste, rust, water scale, etc.
FIG. 12
is a sectional view illustrating the arrangement of another conventional device for controlling the temperature of the proximal portion of the heating cylinder. In
FIG. 12
, a temperature control device
110
comprises a jacket
111
having a hole
112
into which the proximal portion of the heating cylinder is inserted, a passage
113
is formed in the jacket
111
for passing a temperature control medium therethrough, and a communication port
115
. The conventional passage often has a complex route for the purpose of temperature control, and it is therefore necessary to cut machining holes for forming the passage. Since such machining holes are unnecessary for actual operation of the passage, a large number of plugs
114
are used to close the holes. Accordingly, foreign matter is liable to be deposited inside the passage, and the removal of the deposited matter requires prolonged maintenance work, often necessitating detachment of the heating cylinder.
SUMMARY OF THE INVENTION
An object of the present invention is to improve maintainability and reduce a manufacturing cost of a temperature control device of a proximal portion of a heating cylinder of an injection molding machine. Another object of the present invention is to make it easy to check and control the flow rate of a temperature control medium.
A temperature control device of the present invention introduces improvements in an attaching structure of the device to the proximal portion of the heating cylinder and an arrangement of a passage of heat medium so as to enhance the maintainability and reduce the manufacturing cost. Further, a flow-rate control mechanism and a flow-rate detecting mechanism are arranged such that an operator can check and control the flow rate at a location where an ordinary operation of an injection molding machine is performed, thereby the flow rate of the heat medium can be checked and controlled with ease.
A temperature control device for a heating cylinder of an injection molding machine according to the present invention comprises a jacket to be attached to a proximal portion of the heating cylinder of the injection molding machine. The jacket has at least one pair of through holes for flowing heat medium for
Ishiguro Toshio
Shiraishi Wataru
Takatsugi Satoshi
Fanuc Ltd.
Heitbrink Tim
Staas & Halsey , LLP
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