JPH045529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a screw head with a check valve located at the tip of a screw used in an injection molding machine or the like.

(Prior art) A screw used in an injection molding machine is fitted into a heating cylinder and rotated to transfer molten resin to the tip of the screw and inject it into a mold. . A backflow prevention valve is provided at the tip of the screw to prevent the resin from flowing back to the rear of the screw when the resin is injected. A ring valve is generally used as a check valve, and one example is a screw head 2 using a ring valve 1 as shown in FIGS. 2 and 3. The tip of this screw head 2 is formed into a pointed shape from the large diameter part,
The diameter becomes smaller from the large diameter point to the proximal end. The base end becomes a screw and the wear plate 3
The screw head 2 and the screw 4 thus connected are fitted into the heating cylinder 5. Screw heads 2
Groove-shaped passages 6 through which the resin passes are formed at regular intervals in the axial direction on the circumference of the large diameter of the screw head 2, and communicate with the small diameter portion of the pointed end of the screw head 2.

In the conventional valve shown in FIG. 2, an annular ring valve 1 having a width smaller than the gap is fitted between the large diameter portion of the screw head 2 and the wear plate 3. And this ring valve 1
One side is adapted to come into contact with the wall formed by the large diameter part and the small diameter part of the screw head 2, and the outer peripheral surface of the ring valve 1 can slide on the inner peripheral surface of the heating cylinder 5.
The inner circumferential surface thereof is designed to have a slight gap between it and the small diameter portion of the screw head 2. With this configuration, the gap between the ring valve 1 and the wear plate 3 is widened, and one side of the ring valve 1 hits the wall surface of the screw head 2, so that the resin between the screw 4 and the heating cylinder 5 is removed. is pushed out from the passage 6 to the front of the screw head 2. On the other hand, in another conventional embodiment shown in FIG. 3, a groove is provided on one side of the ring valve 1 to engage with the screw head 2, so that the ring valve 1 rotates as the screw 4 rotates. I'm trying to make it possible. For this reason, a gap is provided between the outer periphery of the ring valve 1 and the inner periphery of the heating cylinder 5 so that they can rotate. In FIG. 3, the ring valve 1 comes into contact with the wear plate 3, so that the resin in the front part of the screw head 2 is prevented from flowing back from the passage between the screw 4 and the heating cylinder 5.

(Problems to be Solved by the Invention) In the conventional configuration described above, the contact area is reduced because the ring valve 1 is not fixed to the screw 4 and the groove is provided on the end face of the screw head 2. In the case of the structure shown in Fig. 2, the contact area A of the ring valve 1 and the screw head 2 on the opposite side from the side where the ring valve 1 contacts the wear plate 3 has a small contact area, and when the contact surface pressure becomes high. , they are becoming more likely to wear out each other. on the other hand,
In the structure shown in FIG. 3, the screw head 2 and the ring valve 1 are in an engaged state, so the ring valve 1 rotates together with the screw head 2 as the screw 4 rotates, so that the inner peripheral surface of the heating cylinder 5 and the ring valve 1 rotate together. The outer peripheral surface of the ring valve 1 is likely to wear.
In addition, a large gap must be formed at the part of the ring valve 1 that engages with the screw head 2 in order to prevent "galling" with the inner circumferential surface of the heating cylinder 5, which increases the amount of backflow during injection. .

Therefore, the present invention was made to solve the above problems, and combines the advantages of each by dividing the ring valve into a side that engages with the screw head and a side that contacts the wear plate. The purpose of the present invention is to provide a screw head with a check valve that has a long service life.

(Means for Solving the Problems) A feature of the present invention for achieving the above object is that a screw and a screw head are connected and fitted into a heating cylinder, and a screw head is inserted between a large diameter portion and a small diameter portion at the tip of the screw head. In a screw head equipped with a check valve that forms a passage communicating between the screw and the heating cylinder, and an annular ring valve is fitted into the small diameter portion of the passage to freely open and close the passage, the screw valve is the side engages the screw head;
a first ring valve whose outer circumferential surface forms a sufficient gap with the inner circumferential surface of the heating cylinder; the first ring valve contacts the other side of the first ring valve, and the outer circumferential surface slides into contact with the inner circumferential surface of the heating cylinder; This is because the valve is divided into a second ring valve and a second ring valve.

(Function) With the above configuration, the resin passes through the passage between the heating cylinder and the screw by the rotation of the screw,
When injecting in front of the screw head, the first
Then, the second ring valve moves so that one side of the first ring valve engages the screw head and the other side of the first ring valve and one side of the second ring valve contact each other with a large contact area.
At this time, the second ring valve hardly rotates and is not worn against the inner circumferential surface of the heating cylinder.
On the other hand, although the first ring valve rotates, there is a sufficient gap between it and the inner circumferential surface of the heating cylinder, so that a screw head with a check valve with a long life can be realized.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 shows a screw head 7 with a check valve according to the present invention, which has parts common to the structure already explained in the section of the prior art based on FIGS. 2 and 3. These common parts will be designated by the same reference numerals and detailed explanation thereof will be omitted.
The screw head 7 with a check valve of the present invention shown in FIG. 1 is characterized by a ring valve. A ring valve covering the outer periphery of the screw head 2 including the passage 6 at the small diameter portion is divided into a first ring valve 8 and a second ring valve 9 in the longitudinal direction. A claw portion 10 is provided protruding from the annular end surface of the first ring valve 8 . This claw part 10
Correspondingly, the large-diameter portion formed in the screw head 2 fits into the groove-shaped hole 11, and when the screw head 2 rotates around its longitudinal center axis, the screw head 2 also rotates. It is. When the claws 10 are fully fitted into the groove-shaped holes 11, the surfaces between the claws 10 come into contact with the wall surface 12 formed by the large diameter portion and the small diameter portion of the screw head 2, thereby reaching the stop position. It's summery. 1st
The outer peripheral surface of the ring valve 8 and the inner peripheral surface of the heating cylinder 5 are:
A gap 8a of about 0.5 mm is maintained to prevent wear from rubbing against each other. The end surface of the first ring valve 8 opposite to the claw portion 10 is in contact with the end surface of a second ring valve 9, which will be described below. The second ring valve 9 is also annular and has a screwdriver 4.
Since it is not connected in any way with
Even if they rotate, they do not rotate together. Therefore, the first
When the ring valve 8 rotates together with the screw head 2, the end faces of the first ring valve 8 and the second ring valve 9 that are in contact with each other have a relative rotational speed difference, which causes friction and sliding. Due to the contact, the second ring valve 9 hardly rotates.

With the above configuration, first, the inner circumference of the heating cylinder 5,
The resin between the outer circumference of the screw 4
When injected into the front of the screw head 2 through the passage 6 of the screw head 2 by the rotation of the
The first and second ring valves 8, 9 move forward of the screw head 2, and the claw portion 10 of the first ring valve 8 advances deep into the hole 11 and stops, while
The gap between the end face of the second ring valve 9 and the wear plate 3 is opened, and the resin is injected into the front of the screw head 2. At this time, the end faces of the first ring valve 8 and the end faces of the second ring valve 9 are in contact with each other with a sufficiently large contact area, so that the surface pressure is smaller than in the conventional case, and wear on the end faces is also reduced. Also,
Since they are in sliding contact with each other, the second ring valve 9
Since it hardly rotates, there is no worry that the outer peripheral surface of the second ring valve 9 and the inner peripheral surface of the heating cylinder 5 will rub against each other and cause wear. Also,
Since there is a gap 8a between the outer circumferential surface of the first ring valve 8 and the inner circumferential surface of the heating cylinder 5, there is no need to worry about wear as there is no friction between the outer circumferential surface and the inner circumferential surface of the heating cylinder 5 as they rotate.

When the front of the screw head 2 is filled with resin and is subjected to pressure during injection molding, the first and second ring valves 8 and 9 move, and the first ring valve of the second ring valve 9 moves. The end face on the opposite side from 8 comes into contact with the wear plate 3, and the passage 6 is closed. At this time, since a gap 8a of an appropriate size is formed between the outer circumferential surface of the first ring valve 8 and the inner circumferential surface of the heating cylinder 5, backflow of the resin toward the second ring valve 9 side is reduced. can.

(Effects of the Invention) As described above, in the screw head with backflow prevention of the present invention, the ring valve serving as the backflow prevention valve is engaged with the screw head, and is separated from the inner periphery of the heating cylinder by the first ring valve having an appropriately sized gap. By bringing the ring valve and the second ring valve, which slides against the inner periphery of the heating cylinder, into contact with each other at their end faces, we take advantage of the advantages of conventional technology and reduce wear and backflow, resulting in a long service life. The realization of a screw head with a backflow prevention valve helps improve productivity.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a screw head with a check valve according to the present invention, FIG. 2 is a longitudinal sectional view showing an example of a conventional screw head with a check valve, and FIG. 3 is a longitudinal sectional view showing an example of a conventional screw head with a check valve. FIG. 7 is a longitudinal sectional view showing another example of the screw head. 2: Screw head, 4: Screw, 5: Heating tube, 6: Passage, 7: Screw head with check valve, 8: First ring valve, 8a: Gap, 9: Second ring valve.

Claims (1)

[Claims] 1. A screw and a screw head are connected and fitted into a heating cylinder, a passage is formed that communicates between the screw and the heating cylinder from a large diameter part to a small diameter part at the tip of the screw head, and a passage is formed in the small diameter part of the passage. In a screw head equipped with a check valve into which an annular ring valve is fitted to freely open and close the passage, one side of the ring valve is engaged with the screw head, and an outer circumferential surface is between the inner circumferential surface of the heating cylinder and the screw head. A first ring valve with a sufficient gap formed therein, and a second ring valve that abuts the other side of the first ring valve and has an outer circumferential surface in sliding contact with the inner circumferential surface of the heating cylinder. A screw head with a backflow prevention valve.