JPH0558251U - Backflow prevention ring of injection molding machine - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To completely prevent backflow and to prevent seizure and wear by forming a suitable lubricating coating. [Structure] A gap S for a lubricating coating is formed between the inner circumferential surface of the backflow prevention ring 8 and the heating cylinder 1, and a recess is formed on the outer circumferential surface of the ring.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a backflow prevention ring attached to a screw provided in a heating cylinder of an injection molding machine so as to be rotatable and linearly movable.

[0002]

[Prior Art]

 As is well known, the injection molding machine is composed of a heating cylinder and a screw provided in the cylinder so as to be rotatable and linearly movable. Then, in the metering stroke, when the screw is driven to rotate, the synthetic resin material falls from the hopper into the valley of the screw and is pumped toward the nozzle along the valley. During the delivery, it is compressed, heated by the heating cylinder, melted, and accumulated in the nozzle. When the molten resin accumulates, the pressure causes the screw to retreat, but the amount of retreat measures the amount of resin required for one cycle. In the injection stroke, the screw plays the role of a piston and advances the screw in a piston cylinder unit. Then, the molten resin is injected from the nozzle into the mold.

By the way, as described above, in the injection molding machine, the high-pressure molten resin is processed not only by the injection stroke but also by the measuring stroke, so that the resin flows between the heating cylinder and the screw. May flow backwards through. When the back flow occurs, the amount that is measured by the measuring stroke is not injected, and a predetermined injection amount that is important for molding cannot be obtained. Therefore, a backflow prevention ring is provided.

The backflow prevention ring is generally attached to a screw head provided at the tip of the screw, and prevents the backflow of the molten resin as described above. However, in the conventional backflow prevention ring, for example, it is known that the outer peripheral surface of the ring and the inner peripheral surface of the heating cylinder are densely formed in order to completely prevent backflow. As it comes into contact with the inner surface of the cylinder and rotates and slides, metal contact occurs and wear and seizure occur, causing so-called resin burn. Also, as a measure to prevent this seizure, avoiding metal contact, that is, by increasing the distance between the outer peripheral surface of the ring and the inner peripheral surface of the cylinder, the problems of wear and seizure can be solved, but the original function of preventing backflow is essential. However, the stable injection amount could not be obtained.

Therefore, the applicant of the present invention discloses, in Japanese Utility Model Laid-Open No. Sho 63-7513, a plurality of through holes extending from the inner peripheral surface to the outer peripheral surface in the backflow prevention ring to prevent backflow of the molten resin and to prevent baking and A technique to prevent wear was proposed.

[0006]

[Problems to be solved by the device]

 Although the above proposed technique itself is effective, seizure occurs due to insufficient formation of a lubricating coating between the outer circumferential surface of the backflow prevention ring and the inner circumferential surface of the cylinder.

The present invention completely prevents the backflow of molten resin, and forms a suitable lubricating film between the backflow prevention ring and the cylinder to reliably prevent backflow and wear of the injection molding machine. Intended to provide a ring.

[0008]

[Means for Solving the Problems]

 According to the present invention, in the backflow prevention ring attached to the screw head at the tip of the screw rotatably and linearly installed in the heating cylinder of the injection molding machine, the outer peripheral surface of the ring and the heating A sufficient gap is formed between the inner peripheral surface of the cylinder and a molten resin film necessary for lubrication, and a recess is formed on the outer peripheral surface of the ring.

The backflow prevention ring is preferably provided on the screw head so as to be movable in the axial direction.

In addition, it is preferable that a plurality of recesses be formed to facilitate the operation of the molten resin coating and form a uniform coating.

In addition, it is preferable that the bottom of the recess is continuous to the outer peripheral surface of the ring with a smooth curved surface so that an edge is not formed in consideration of the direction of rotation or movement so as to form a uniform lubricating film. ..

[0012]

[Action]

 In the backflow prevention ring of the injection molding machine configured as described above, the backflow prevention ring that rotates together with the screw at the time of the measuring stroke is pressed against the end surface of the screw head by the moving flow of the molten resin toward the nozzle side. At the same time, the molten resin flows into the gap between the outer peripheral surface of the ring and the inner peripheral surface of the cylinder, forming a lubricating coating. In this measuring stroke, the pressure of the molten resin is not high, so the amount of resin flowing in the gap is small, but there is not enough resin to form a film even from the molten resin filled in the recess during the injection stroke. Supplied.

Further, in the injection stroke, the backflow prevention ring is pressed against the end surface of the screw to prevent backflow. At this time, since the pressure is high, molten resin that does not interfere with practical use flows into the gap between the outer circumferential surface of the backflow prevention ring and the inner circumferential surface of the cylinder, constantly forming a new lubricating coating and filling the recess. It

[0014]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, a cylinder 1 heated by a band heater or the like has a cylindrical shape similar to the conventional one, and a nozzle portion 2 is formed at the left end thereof. As is well known, the screw 3 is rotatably driven by an electric motor or a hydraulic motor (not shown) and can be moved forward by a piston cylinder unit or the like. A screw head 4 is screwed to the tip of the screw 3 with a screw 5. The diameter of the screw head 4 is smaller than the diameter of the screw 3. Therefore, the screw 3 is formed with a step or end face 6. An end face 7 is formed on the screw head 4, and the end face presses the backflow prevention ring 8 in the measuring stroke.

The backflow prevention ring 8 is provided so as to be able to move in the axial direction with respect to the screw head 4 by a projection 8a engaging with the plate-shaped portion 4a of the screw head 4 and to rotate together. The end face 8b is caused by the end face 7 of the head during the metering stroke moving to the nozzle 2 side, and the end face 8c is caused by the end face 6 of the screw 3 during the injection stroke moving to the screw 3 side. It is becoming regulated. That is, there is no restriction on the rotation direction, and the screw rotates together with the screw. A gap S sufficient to form a molten resin film is formed between the outer peripheral surface of the backflow prevention ring 8 and the inner peripheral surface of the heating cylinder 1 both in the co-rotation and in the axial movement. ing.

A plurality of recesses 9, 9 are formed on the outer peripheral surface of the backflow prevention ring 8. As shown in FIG. 2, the shape of the recess 9 is such that a bottom surface 9a formed by a partial spherical surface is continuous with the outer peripheral surface of the ring 8 by a smooth curved surface 9b in all directions.

Next, the operation will be described. At the time of the measuring stroke, the end surface 8b of the ring 8 is pressed against the end surface 7 of the screw head 4 by the molten resin flow toward the nozzle portion 2 side, and the molten resin flows into the gap S from between the end surfaces 6 and 8c and lubricates. A film is formed. Since the pressure of the molten resin is not high in this measuring stroke, the amount of resin flowing in the gap S is small, but the lubricating coating is formed from the molten resin filled in the recesses 9, 9 ... During the injection stroke. Is supplied in sufficient quantity to do so.

Further, during the injection stroke, the end surface 8 c of the ring 8 is pressed against the end surface 6 of the screw 3, and the reverse flow of the resin is prevented. At this time, since the pressure is high, a molten resin having a practically no problem flows into the gap S, a new lubricating film is constantly formed, and the recesses 9 and 9 are also filled with the molten resin.

[0020]

[Effect of the device]

 Since the present invention is configured as described above, a suitable lubricating coating is formed in the gap between the outer peripheral surface of the backflow prevention ring and the inner peripheral surface of the cylinder in both the stroke of the metering stroke and the stroke of the injection stroke. However, it is possible to reliably prevent abnormal wear by eliminating metal contact and to completely prevent backflow of the molten resin.

[Brief description of drawings]

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

FIG. 2 is a side sectional view showing the shape of a recess.

[Explanation of symbols]

 S ... Gap 1 ... Cylinder 2 ... Nozzle part 3 ... Screw 4 ... Screw head 4a ... Plate-shaped part 5 ... Screw 6 ... Screw end surface 7 ... End face of screw head 8 ... Backflow prevention ring 8a ... Protrusions 8b, 8c ... End face of backflow prevention ring 9 ... Recess 9a ... Bottom of recess 9b ... Curved surface

Claims (1)

[Scope of utility model registration request] 1. A backflow prevention ring attached to a screw head at the tip of a screw provided in a heating cylinder of an injection molding machine so as to be able to rotate and rectilinearly move, and an outer peripheral surface of the ring and the heating cylinder. An injection molding characterized in that a sufficient gap is formed between the inner surface and the inner surface to form a molten resin coating film necessary for lubrication, and a recess is formed on the outer surface of the ring. Backflow prevention ring of the machine.