JP2770595B2 - Injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold having a cavity formed between a pair of mold plates, and a bush provided with a resin passage communicating with the cavity via a gate in one of the mold plates. About.

[0002]

2. Description of the Related Art Conventionally, injection molding dies of this kind include:
A cavity is formed between the fixed mold plate and the movable mold plate, a bush having a resin passage communicating with the cavity via a gate is provided in the fixed mold plate, and a heater is provided on an outer periphery of a tip portion of the bush. There is known a configuration in which a movable rod is mounted so as to be movable in the axial direction in the resin passage while being opened and closed by the tip of the movable rod.

[0003]

Since the bush is heated by a heater provided at the distal end thereof, the bush at the base end of the bush having no heating means is provided. , The temperature tends to be low,
(In general, it is desirable that the temperature of the molten resin in the resin passage be maintained at about 250 ° C. in any place.
To as low as 190 ° C. and easy to vary). When the temperature of the molten resin in the resin passage fluctuates as described above, the properties of the supplied molten resin are not stable when the molten resin is supplied into a large number of cavities in the mold. There is a problem that products cannot be obtained.

The present invention has been made in view of the above circumstances, and has as its object to reduce the temperature of the molten resin in the resin passage (particularly, the temperature of the molten resin in the base end of the bush) to a predetermined temperature. An object of the present invention is to provide an injection mold that can be stably held and can mold a good quality molded product.

[0005]

According to one aspect of the present invention, a cavity is formed between a pair of molds and communicates with the cavity via a gate in one of the molds. Injection molding in which a bush provided with a resin passage is provided, a heater is mounted on the outer periphery of a distal end of the bush, and a brim at a base end of the bush is placed on a receiving plate. In the mold, reduce the volume of the bush
By reducing the heat capacity of the bush,
To efficiently transfer the heat of the resin to the resin in the resin passage
With the fleshy portion formed on the outer surface of the collar
It is.

According to a second aspect of the present invention, in the intermediate portion of the bush, a heat generating portion of the heater is wound with a gap therebetween, and a spacer having good thermal conductivity is provided between the heat generating portions. It is.

[0007]

In the injection mold of the present invention, the bush
The thinned-out part formed on the outer surface of the flange portion, while suppressing the heat escapes to the receiving plate or the like from the proximal end of the bushing, bushings
Reduce bush heat capacity by reducing bush volume
By reducing the amount of heat required to keep the bush warm
In addition to the above, the heat of the heater is efficiently transferred to the resin in the resin passage.
Try to communicate well.

According to a second aspect of the present invention, the temperature of the molten resin in the bush is further made uniform by a spacer having good thermal conductivity provided between the heat-generating portions of the heater at an intermediate portion of the bush. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In these figures, reference numeral 1 denotes a fixed mold plate, and a movable mold plate 2 is provided so as to be able to approach and separate from the fixed mold plate 1, and between these mold plates 1 and 2. A cavity 3 having a shape of a molded product is formed.
The first and second fixed receiving plates 4 are provided on the fixed die plate 1.
5, a fixed mounting plate (not shown) is mounted via a spacer block 6, and a manifold 8 is provided between the second fixed receiving plate 5 and the fixed mounting plate. A bush 9 is mounted inside the second and first fixed receiving plates 5 and 4 and the fixed mold plate 1, and a temperature sensor 10 and a coil-shaped heater 11
Is provided. A heater cover 12 and an annular member 13 are mounted on the outer periphery of the coil-shaped heater 11. Further, a tip member 14 is screwed to a tip of the bush 9. The fixed member 1 is opposed to the tip member 14, the bush 9, the heater cover 12 and the annular member 13.
Is provided with a funnel member 15. A guide member 16 is provided between the bush 9 and the tip member 14. The guide member 16 includes an outer cylinder mounted on the bush 9, an inner cylinder for guiding and supporting the movable rod 17, and And a plurality of support plates for connecting the inner and outer cylinders. Furthermore, the molten resin is supplied to the cavity 3 through the inside of the manifold 8 and the bush 9, between the inner and outer cylinders of the guide member 16, the inside of the tip member 14, and the inside of the tip of the funnel member 15 (gate). It has become. A closing member 18 is provided in the upper part of the bush 9. The movable rod 17 slides along the axis thereof while being supported and guided by the inside of the closing member 18 and the inner cylinder of the guide member 16. It is supposed to.

A flange 9a at the base end of the bush 9 is fitted into and supported by the step 5a of the second fixed receiving plate 5. A ring-shaped groove 9b is formed on the outer periphery of the flange 9a, and a pair of arc-shaped grooves 9c as shown in FIG. It is formed in a character shape (see FIG. 1). Although the groove 9c is formed in an arc shape avoiding the resin passage, a ring shape (annular shape) or a C-shape may be used as long as there is no space limitation.

The above-mentioned coiled heater 11 is usually
The bush 9 is spirally wound around the outer periphery of the bush 9 and
Are wound so as to be dense at both end portions and coarse at the middle portion.
Since the temperature distribution is likely to be non-uniform between the portion where a is wound and the portion where the coil is not wound, as shown in FIG. A spacer 20 having good thermal conductivity may be provided between the heat generating portions 11a to make the temperature distribution more uniform.

In the injection mold having the above-described structure, the movable rod 17 is moved along the axis thereof and the tip of the movable rod 17 is used to move the gate (inside the tip of the funnel member 15) as in the prior art. Opening and closing operations.

In this case, the molten resin flowing through the resin passage in the bush 9 is heated by the heat from the coil-shaped heater 11 and the manifold 8 provided on the outer periphery of the end of the bush 9. In the collar portion 9a at the base end of the bush 9 where the coil-shaped heater 11 is not wound,
Since the grooves 9b and 9c are formed on the outer periphery and the end face on the distal end side, respectively, the contact portion with the second fixed receiving plate 5 supporting the bush 9 is reduced. The heat that can be transmitted and escaped can be restricted, and the volume of the flange 9a at the base end of the bush 9 can be reduced, so that the amount of heat required for heat retention can be reduced.
c prevents the heat transmitted from the distal end side of the bush 9 from being transmitted to the outside of the collar 9a and is guided to the inside of the collar 9a of the bush 9, so that the collar at the base end of the bush 9 is formed. Despite the absence of the heat generating portion in the portion 9a, the portion 9a is efficiently and smoothly heated, so that a temperature drop and a temperature change can be suppressed. In addition, since the area of the flange 9a of the bush 9 that is in contact with the step 5a of the second fixed receiving plate 5 is small, the contact between the two is better than when the contact area is large. Can be accurately installed and fixed at predetermined positions in the second and first fixed receiving plates 5 and 4 and the fixed mold plate 1. Therefore, the movable rod 17 passing through the inside of the bush 9 can also maintain its positional accuracy with good accuracy, and can smoothly open and close the gate without contact interference with the gate portion when opening and closing the gate.

[0015]

As described above, according to the first aspect of the present invention,
A cavity is formed between a pair of molds, a bush having a resin passage communicating with the cavity through a gate is provided in one of the molds, and a heater is mounted on an outer periphery of a tip portion of the bush. In addition, in an injection mold in which the base flange portion of the bush is placed on a receiving plate, the volume of the bush is reduced to reduce the heat capacity of the bush.
By reducing the amount, the heat of the heater
The fleshy portion for efficient transmission to the resin
Because it is formed on the outer surface of the collar,
The corners reduce the volume of the bush and
By reducing the heat capacity, the heat of the heater
The molten resin in the resin passage is efficiently transmitted to the resin in the passage.
Fat temperature (especially the temperature of the molten resin in the base end of the bush)
Moldings of good quality that can stably maintain
Can be molded.

According to the second aspect of the present invention, the temperature of the molten resin in the bush is further made uniform by the spacer having good thermal conductivity provided between the heat generating portions of the heater in the middle portion of the bush. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing an example of a groove.

FIG. 3 is a cross-sectional view showing an example of a coil heater.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fixed mold plate 2 movable mold plate 3 cavity 5 second fixed receiving plate 9 bush 11 coiled heater 20 spacer 9a flange 9b groove (thickened portion) 9c groove (thickened portion) 11a heat generating portion

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 45/26-45/38 B29C 45/73

Claims (2)

(57) [Claims] 1. A cavity is formed between a pair of molds,
A bush having a resin passage communicating with the cavity through a gate is provided in one of the molds. A heater is mounted on the outer periphery of a distal end of the bush, and a flange at a base end of the bush is received. In an injection mold that is mounted on a plate, the volume of the bush
The heat capacity of the heater by reducing the heat capacity of the
Thickness for efficient transmission to the resin in the resin passage
An injection molding die , wherein a part is formed on an outer surface of the collar part . 2. A heat generating portion of a heater is wound around a middle portion of the bush with a gap therebetween, and a spacer having good thermal conductivity is provided between the heat generating portions. Injection molding die as described.