JPH1119992A - Screw-in-plunger type injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel structure for a screw-in-plunger type injection device that can mold high-quality molded pieces continuously and stably by increasing the kneading efficiency of molten material by imparting further twisting to molten material kneaded by a screw. SOLUTION: Fused material flow-in passageways 73 communicating respectively with at least two or more molten material flow-in ports 72 are formed in a back portion 71B of a screw head 71 provided at a leading end 62 of a screw 61, these molten material flow-in passageways 73 are combined together at a combining portion 74, the combining portion 74 is caused to communicate with a valve chamber 76 incorporating therein a check valve via a valve seat portion 75, molten material flow-out passageways 78 respectively leading from the valve chamber 76 to a least three or more molten material flow-out ports 77 in a front portion 71F of the screw head 71 are formed radially, and the molten material is adapted to flow out of the molten material flow-out ports 77 to a forward side of a plunger 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw-in plunger type injection device, and more particularly to a screw-plunger type injection device which is advantageous for rubber injection molding.

[0002]

2. Description of the Related Art In molding rubber or plastic, a screw-in plunger type injection device is used in which a plunger in which a screw is mounted is reciprocally movable within a predetermined stroke in a heating cylinder of the injection device. In the injection apparatus of this type, a large molten material storage zone is formed in the heating cylinder by retreating the plunger, which is advantageous for molding a large volume.

[0003] By the way, in this kind of injection device of the screw-in plunger structure, it is important to enhance the kneading effect of the molten material, knead the material evenly, and make the temperature and viscosity of the material uniform. Not even. Especially,
In the continuous molding of rubber (including a rubber-based resin), there is a problem that if the kneading of the rubber material is not uniform, the incidence of defective products increases due to partial curing (vulcanization). However, with the conventional screw-in plunger type injection device that relies only on screw rotation for material kneading, the mixing efficiency of the molten material is naturally limited, and in rubber molding, if the injection device is temporarily stopped, the melting in the heating cylinder will occur. The material starts to be vulcanized little by little and partially hardens, and this partial hardening causes a phenomenon that molding unevenness and deterioration of physical properties of the molded product are caused.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in view of such a situation. In a screw-in plunger type injection device, a twist is given to a molten material kneaded by a screw. ,
It is an object of the present invention to improve the kneading efficiency of a molten material and to provide a novel structure capable of continuously and stably forming a high-quality molded product.

[0005]

That is, the present invention provides:
In an injection device in which a plunger containing a screw reciprocates a predetermined stroke in a heating cylinder, a molten material inflow passage communicating with at least two or more molten material inflow ports is provided at a rear portion of a screw head provided at a tip of the screw. Are respectively formed, and the molten material inflow passages merge at a merging portion. The merging portion communicates via a valve seat with a valve chamber in which a check valve is housed. From the valve chamber, a front portion of a screw head is formed. The molten material outflow passages leading to at least three or more molten material outlets are formed radially, and the molten material is discharged from the molten material outlet to the front side of the plunger while being twisted by the rotation of the screw head. And a screw-in plunger type injection device.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing a retracted state (during storage) of a plunger of a screw-in plunger type injection apparatus showing one embodiment of the present invention, FIG. 2 is a sectional view showing a plunger advanced (during injection) state, and FIG. Partial sectional view showing a main part of the screw-in plunger type injection device of the embodiment,
4 is a perspective view thereof, FIG. 5 is a sectional view taken along line 5-5 in FIG. 3, FIG. 6 is a sectional view taken along line 6-6 in FIG. 3, and FIG. It is the side view which showed typically the state in which a molten material flows out.

The injection device 10 shown in the drawing represents the entire screw-in plunger type injection device according to the present invention.
And a cylinder head 21 and a plunger 5 at the tip thereof.
1 and a screw 61 and a screw head 71 at the tip thereof. Note that the screw-in plunger type injection device 10 of this embodiment is configured to be particularly suitable for rubber molding using a rubber-based resin such as nitrile rubber or silicone rubber.

The heating cylinder 11 constitutes a cylinder portion of the injection device 10 and controls the temperature of the injection material. A plunger 51 is inserted into the heating cylinder 11 and a front end 12 thereof.
, A cylinder head 21 is attached via a packing P.

The front portion 11a of the heating cylinder 11 and the cylinder head 21 constitute a molten material storage zone Mz when the plunger 51 shown in FIG. 1 is retracted (when the molten material is stored). The inner peripheral surface of the cylinder head 21 is formed such that the front end 52 of the plunger 51 and the screw head 71 abut when the plunger 51 moves forward (injection) as shown in FIG. Is mounted with a nozzle portion 22 which comes into contact with a sprue portion (not shown) of the molding apparatus. The cylinder head 21 is firmly connected to the front end 12 of the heating cylinder 11 by a large number of bolts 23 and the like so as to sufficiently withstand a large injection pressure during injection. Reference numeral 24 in the drawing is a heater for heating the cylinder head 21.

A plurality of passages 32 extending in the cylinder direction from the heating cylinder 11 to the cylinder head 21 are provided in the cylinder head 21 and the front portion 11a of the heating cylinder 11 serving as the storage zone Mz. A front side temperature control flow path 31 which is connected in order at the rear side connection part 34 and is continuous in the circumferential direction is formed. In this embodiment, the number of the passages 32 is six, and the front connection portion 33 is formed in a substantially arc shape on the boundary surface 25 (the mounting surface to the heating cylinder 11) of the cylinder head 21 with the heating cylinder 11, On the other hand, the rear connection part 34 is formed in a substantially arc shape integrally with the passage 32. By circulating the heat medium set to an appropriate temperature in the front temperature control flow path 31, the temperature of the storage zone Mz can be controlled with high accuracy, and the heating cylinder 11 in which a large number of bolts 23 and the like are arranged is provided. A temperature control passage at the boundary portion of the cylinder head 21 can be secured. The heat medium inlet 35 and the heat medium outlet (36) of the front temperature control channel 31 are connected to a pipe connection plug of a temperature control device (not shown).

On the other hand, a rear temperature control flow path 41 that is annularly continuous is formed in a rear portion 11b of the heating cylinder 11 that is located rearward of the storage zone Mz. This rear temperature control channel 41
Is an outer peripheral surface 11c at an appropriate position on the rear portion 11b of the heating cylinder 11.
In addition, a plurality of annular grooves 42 are formed parallel to each other along the circumferential direction of the outer peripheral surface 11c, and are connected to each other by a communicating portion 43 provided in a part of each annular groove 42.
In this embodiment, the communication portion 43 is located at a half-circumferential position (180-degree position) so that the heat medium circulates through each annular groove 42 reliably.
Are provided alternately. A jacket cover 46 is provided on the outer peripheral surface 11c, and a heat medium supply port 47 and a heat medium discharge port 48 provided on the cover 46 are connected to the heat medium inlet 44 and the heat medium outlet 45 of the flow path 41, respectively. Covered to fit. Although not shown, a heating medium supply port 47 and a heat medium discharge port 48 of the jacket cover 46 are connected to a pipe connection plug of a temperature control device.

As described above, the temperature control of the storage zone Mz (the front portion 11a of the heating cylinder) and the temperature control of the other portion (the rear portion 11b of the heating cylinder) are performed in different systems, so that the temperature control is performed in a different system. The temperature can be adjusted to be suitable for each of the part and the rear part.
In particular, it is very effective in a screw-in plunger type injection device used for rubber molding which requires high temperature control accuracy in the storage zone Mz. The rear temperature control flow path 41 has the above-described configuration because it does not require a very high degree of temperature control accuracy as compared with the temperature control in the storage zone Mz. A configuration similar to that of the Mz front temperature control flow path 31 may be employed.

The plunger 51 is for injecting the molten material stored in the storage zone Mz. The plunger 51 is inserted into the heating cylinder 11 and is reciprocated a predetermined stroke S by a hydraulic cylinder device. I have. In the figure, the plunger 51 has a cylindrical shape with a tapered tip 52, and a screw 61 is provided inside. Although not shown, a raw material supply port connected to a raw material hopper is provided at an appropriate position of the plunger 51, and a rubber-based resin raw material is supplied between the plunger 51 and the screw 61.

Further, as shown in FIG.
A step 53 is provided at a predetermined position on the outer peripheral surface of the plunger 51, and the outer peripheral surface of the plunger from the tip 52 of the plunger 51 to the step 53 is a seal portion 54 that slides on the inner surface 13 of the heating cylinder 11. A leakage material escape gap portion 55 is formed between the outer peripheral surface and the outer peripheral surface of the plunger (small diameter outer peripheral surface) behind the step 53 where the outer peripheral surface does not slide. The position of the step 53 is approximately half to 1.5 times the stroke S of the plunger 51 from the plunger tip 52. That is, the contact length between the heating cylinder 11 and the plunger 51, which is the minimum required from the viewpoint of heat conductivity, is set to be not less than half of the stroke S of the plunger 51, and the leakage material does not accumulate in the seal portion 54. This is because the length that can be advanced to the leaked material escape gap 55 is within 1.5 times the stroke S of the plunger 51.

With such a configuration, the plunger 51
Even if the molten material enters the minute sliding space between the heating cylinder 11 and the plunger 51 during forward movement (injection), the leaked material can be escaped by the leaked material escape gap 55. Therefore, the leakage material can be prevented from accumulating and hardening in the sliding space between the plunger 51 and the heating cylinder 11, and the plunger 51 can be moved smoothly. The leaked material that has entered between the heating cylinder 11 and the plunger 51 is discharged to the outside of the injection device 10 through the escape gap 55.

The screw 61 kneads the raw material supplied from the raw material hopper and continuously mixes the raw material with the storage zone M.
z, and is connected to a hydraulic motor or the like to be rotatable. A screw head 71 is fixed to the tip end 62 of the screw 61 by screwing or other appropriate means. The screw 61 can move forward and backward with the movement of the plunger 51.

The screw head 71 is a portion representing a characteristic structure of the present invention, and has a screw head rear portion 71B, a screw head front portion 71F, and a check valve 81 as shown in FIGS. In this embodiment, the screw head rear part 71B and the screw head front part 71B
F is made of a separate member, and both are connected by screwing. As shown in FIGS. 1 and 2, the screw head 71 is fitted into the inner periphery of the distal end 52 of the plunger 51 and rotates with the rotation of the screw 61 with respect to the plunger 51. .

The screw head rear portion 71B is connected to the screw 6
In the screw head rear portion 71B, a molten material inflow passage 73 communicating with at least two or more molten material inflow ports 72 is formed in the portion fixed to 1. In this embodiment, as can be better understood from FIG. 5, three substantially circular molten material inlets are provided at 120 degrees on the outer peripheral surface of the rear portion 71B (the outer peripheral surface not in contact with the inner peripheral surface of the plunger 51). A plurality of substantially cylindrical molten material inflow passages 73 communicating with the molten material inflow port 72 are formed radially. The inflow passage 73 is provided at the junction 74
The junction 74 communicates via a valve seat 75 with a valve chamber 76 in which a check ring 81 described later is provided. The valve chamber 76 includes a rear valve chamber forming portion 76b formed on the distal end side of the screw head rear portion 71B and a front valve chamber forming portion 76f formed on the rear end side of the screw head front portion 71F. .

On the other hand, a screw head front portion 71F is a portion to be a tip portion of the screw head 71. At least three or more substantially circular molten material outlets from the valve chamber 76 are provided in the screw head front portion 71F. Each of the molten material outflow passages 78 reaching 77 is formed radially. In this embodiment, the distal end side outer peripheral surface of the screw head front portion 71F is tapered, and as can be better understood from FIG. 6, the outer peripheral surface of the screw head front portion 71F (the base point portion of the tapered shape). Four molten material outlets 77 are provided at 90 ° positions on the outer peripheral surface of the molten material outlet 7.
Four molten material outflow passages 78 from 7 to the valve chamber 76
Are formed radially.

The check valve 81 is for preventing the molten material M stored in the storage zone Mz from flowing back, has a spherical shape, and is housed in the valve chamber 76. That is, before the storage of the molten material M in the storage zone Mz is completed (at the time of storage), the check ring 81 is separated from the valve seat 75, and is interposed between the check ring 81 and the valve seat 75 via the gap. This allows the molten material M to flow into the valve chamber 76 from the junction 74, and after the storage is completed (at the time of injection), the check valve 81 closes to the valve seat 75, and the molten material M flows backward. To prevent

With the screw head 71 having such a configuration, the molten material M kneaded by the screw 61 flows into the head 71 from the molten material inlet 72 and joins at the joining portion 74. As shown in FIG. 7, while being twisted by the rotation of the screw head 71, the molten material flows out of the molten material outlet 77 into the storage zone Mz on the front side of the plunger 51. Therefore, the kneading efficiency of the molten material M stored in the storage zone Mz is remarkably improved, and the kneading is made uniform.

In the experimental example, rubber packing (product weight 82
g) After a pause of 23 minutes at the 81st shot of the continuous molding and then restarting the molding, the weighing time was slightly observed, but there was no molding failure such as partial curing and the product was not affected. Good product was obtained.

[0023]

As shown and described above, according to the screw-in plunger type injection device of the present invention, the kneading efficiency of the molten material is increased by further twisting the molten material kneaded by the screw. High quality molded products could be continuously and stably formed. Especially,
According to the present invention, by improving the kneading efficiency of the molten material, even if there is a temporary stoppage in continuous molding of rubber or the like, problems such as partial curing after resumption are improved, and continuous molding of good products is possible. Which has a very advantageous effect in this kind of molding.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a screw-in plunger type injection apparatus according to an embodiment of the present invention, showing a plunger retracted (during storage).

FIG. 2 is a sectional view showing the plunger advanced (during injection).

FIG. 3 is a partial sectional view showing a main part of the screw-in plunger type injection device of the embodiment.

FIG. 4 is a perspective view thereof.

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3;

FIG. 6 is a sectional view taken along line 6-6 in FIG. 3;

FIG. 7 is a side view schematically showing a state in which a molten material flows out into a heating cylinder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Injection apparatus 11 Heating cylinder 51 Plunger 61 Screw 62 Screw tip 71 Screw head 71B Rear part of screw head 71F Front part of screw head 72 Molten material inlet 73 Molten material inflow passage 74 Merge part 75 Valve seat part 76 Valve chamber 77 Molten material Outflow port 78 Molten material outflow passage 81 Check valve M Molten material S Plunger stroke

Claims (1)

[Claims] 1. An injection device in which a plunger in which a screw is mounted reciprocates a predetermined stroke in a heating cylinder, wherein a rear portion of a screw head provided at a tip of the screw communicates with at least two or more molten material inlets. Molten material inflow passages are respectively formed, the molten material inflow passages merge at a merging portion, and the merging portion communicates via a valve seat portion with a valve chamber in which a check valve is provided, and from the valve chamber. A molten material outflow passage leading to at least three or more molten material outlets at the front of the screw head is formed radially, and the molten material is twisted by rotation of the screw head from the molten material outlet to the front side of the plunger. A screw-in plunger-type injection device characterized in that it is discharged to a drain.