JP2520672Y2 - Backflow prevention structure of injection device - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backflow prevention structure for an injection device.

[0002]

2. Description of the Related Art Conventionally, in order to prevent backflow of molten resin in injection molding, as shown in FIG. 7, a thin shaft portion 73 formed at a rear portion of a main body 72 of a screw head 71 of an injection device is used. A wear plate 74 is provided, and a ring valve 75 is fitted into the thin shaft portion 73.
Reference numeral 76 is a resin flow path formed on the outer periphery of the main body 72 of the screw head 71.

The ring valve 75 receives the resin pressure toward the screw main body generated when the end surface 75a on the screw head side injects the molding material accumulated at the tip of the screw due to the rotation of the screw, so that the ring valve 75 moves toward the wear-pure 74 side. It moves, and the resin plate is sealed by the wear plate 74 and the end surface 75b of the ring valve 75 to prevent backflow. The ring valve 75 of the embodiment has a substantially tubular main body 7 as can be easily understood from FIGS. 8 and 9.
7, a claw portion 78 reaching the groove portion 76 of the screw head 71,
Further, if desired, a protrusion 79 that can come into contact with the end surface 71a of the screw head 71 is provided.

The ring valve 75 is of a so-called "rotating" type in which a claw 78 of the ring valve 75 is engaged with a groove 76 formed on the outer periphery of the screw head 71 when the screw rotates, and rotates together with the screw. 75
There is an advantage of preventing abrasion of the sliding surfaces of the screw head 71 and the wear plate 74.

By the way, the ring valve 75 moves toward the tip of the screw head when the plasticizing of the molding material is completed, and the projection 79 is in contact with the screw head end surface 71a as shown in FIG. Reference numeral 80 is a contact surface.

However, in this structure, when the injection resin pressure is applied during the injection molding, the effective area A1 of the ring valve end surface 75a which receives the resin pressure is
As shown by the diagonal lines in FIG. 11, the contact surface 80 has an area A2.
There is a problem that it is offset by and becomes smaller.

Therefore, the movement of the ring valve 75 toward the wear plate 74, that is, the force for closing the ring valve is reduced, and the wear plate 74 of the ring valve 75 is reduced.
The pressure contact force with respect to was decreased and the sealing completion time was varied, which was a cause of defective products such as overpack and short shot of the molded product.

[0008]

The present invention has been proposed in view of the above-mentioned problems, and the movement of the ring valve is ensured by increasing the effective area for resin pressure during injection molding as much as possible. The present invention aims to provide a novel backflow prevention structure for an injection device, which can suppress variations in sealing time and avoid product defects such as overpacks and short shots of molded products.

[0009]

[Means for Solving the Problems] That is, this invention is
A ring valve having a groove formed on the outer periphery of the head main body and a ring head having a claw portion reaching the resin flow path is inserted into the thin shaft portion of the screw head to prevent the reverse flow of the molten resin at the time of injection. A plurality of engaging step portions are provided at the rear end of the thin shaft portion of the screw head, and an engaging portion engaging with the engaging step portion is provided on the inner peripheral side of the rear end of the ring valve. A backflow prevention structure of an injection device characterized by being formed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is an exploded perspective view of a main part of an injection device provided with a backflow prevention structure of the present invention, FIG. 2 is a side view showing a cross section of the main part, and FIG. 3 is a ring used in the backflow prevention structure of the present invention. FIG. 4 is a side view of the valve, FIG. 4 is a view taken in the direction of arrow 4, FIG. 5 is a sectional view taken along line 5-5 of FIG. 2, and FIG.

As shown in FIGS. 1 and 2, the backflow prevention structure of the injection device according to the present invention has a screw head 20 provided at the tip of a screw body 10 of the injection device and a thin shaft portion 22 of the screw head 20. And a ring valve 30 fitted in the.

The screw head 20 is a tapered head body 2
1 and a thin shaft portion 22 formed at the rear portion of the main body 21, and the screw main body 10 through the wear plate 14.
It is fixed to.

An outer circumference 21a of the screw head body 21
A groove 23 for hooking a claw portion 32 of the ring valve 30 described later is formed in this. In this embodiment, the screw head body 21 is provided with two groove portions 23, 23.

At the rear end 24 of the thin shaft portion 22, the outer peripheral surface 2 is formed.
A plurality of engaging step portions 25, 25, 25, ... Are provided so as to project in six directions. In this embodiment, the engagement step 25
Are provided in four places. The engagement step portion 25 is formed at a position where it engages with the engagement portion of the ring valve described below.

As described above, the ring valve 30 is composed of a substantially cylindrical main body 31 into which the thin shaft portion 22 of the screw head 20 is inserted, and its tip, that is, the head main body 21 side, is shown in FIG. As described above, the claw portion 32 reaching the groove portion 23 is provided in a protruding manner. In other words, the ring valve 30 is of the "turn around" type described above.

On the other hand, as will be better understood from FIG. 4, a plurality of engaging portions 35 are formed on the rear end 33 of the ring valve body 31, that is, on the wear plate 14 side, in the direction of the inner peripheral surface 34 of the body. ing. The engaging portions 35 are configured to engage with the engaging step portions 25 formed on the thin shaft portion 22 of the screw head 20 when the molding material is plasticized, and are provided at four places in this embodiment.

According to this structure, as shown in FIG. 5, when the plasticization is completed, the screw head 20 and the ring valve 30 are provided at the rear portion, that is, the wear plate 14.
The engagement step portion 25 and the engagement portion 35 formed on the side are in contact with each other. The shaded portion indicated by reference numeral 40 indicates the contact surface.

Therefore, the effective area A3 of the end surface of the ring valve capable of receiving the resin pressure at the time of injection becomes equal to the area of the end surface 36 of the ring valve body 31, as better understood from FIG. To participate,
Not only can the seal be reliably formed, but also the movement time of the ring valve 30 can be shortened to suppress variations in the time.

[0019]

As shown and described above, according to the backflow prevention structure of the injection device of the present invention, the effective area of the ring valve which receives the resin pressure at the time of injection can be made larger than that of the conventional method. The movement of the ring valve is quick and reliable, and the variation in the sealing time can be suppressed. Therefore, it is possible to suppress the occurrence of poor precision of the molded product, and the present invention has a great advantage.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a main part of an injection device provided with a backflow prevention structure of the present invention.

FIG. 2 is a side view showing a cross section of a main part thereof.

FIG. 3 is a side view of a ring valve used in the backflow prevention structure of the present invention.

FIG. 4 is a view as seen from arrow 4 thereof.

5 is a sectional view taken along line 5-5 of FIG.

FIG. 6 is a diagram showing a pressure effective area of a ring valve.

FIG. 7 is a cutaway side view of a main part of a conventional injection device.

FIG. 8 is a side view showing an example of a conventional ring valve.

FIG. 9 is a view taken in the direction of arrow 9.

10 is a sectional view taken along line 10-10 of FIG.

FIG. 11 is a diagram showing a pressure effective area of a conventional ring valve.

[Explanation of symbols]

 21 Head Main Body 22 Thin Shaft Part 23 Groove Part 25 Engagement Step Part 30 Ring Valve 31 Main Body 32 Claw Part 35 Engagement Part

Claims (1)

(57) [Scope of utility model registration request] 1. A ring valve having a groove formed on the outer circumference of a head body and having a claw portion reaching the groove is inserted into a thin shaft portion of a screw head to prevent backflow of molten resin during injection. A plurality of engaging step portions projecting at the rear end of the thin shaft portion of the screw head, and an engaging step portion engaging with the engaging step portion on the inner peripheral side of the rear end of the ring valve. A backflow prevention structure for an injection device, characterized in that an attachment portion is formed.