JPH0592452A - Structure of screw head - Google Patents

Abstract

PURPOSE:To maintain the stopped state of a non-return ring relative to the rotation of a screw head and thereby prevent sharing forces from occurring on resin in the outer periphery of the non-return ring by forming notched grooves at a plurality of places in the peripheral direction and thus forming projections. CONSTITUTION:When a screw rotates and moves rearward, a screw head 21 rotates together therewith. At this time, a non-return ring 22 moves forward with respect to the screw head 21 and then comes into contact with the rear surface of a cylindrical part 21b. On the end surface of the non-return ring 22, notched grooves 25a-25c are formed at a plurality of places in the direction, as a result, projections 26a-26c are formed. Accordingly, the screw head rotates whereas the non-return ring is maintained in the stopped state. with the result that a sliding surface is defined between the projections and the rear end surfaces of the cylindrical part. In this instance, resin existing in the interstices between the non-return ring 22 and the small diameter part 21c extends through the side of the cylindrical part via the notched grooves. In consequence, the occurrence of resin burning can be prevented.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a screw head structure.

[0002]

2. Description of the Related Art Conventionally, a resin heated and fluidized in a heating cylinder is injected under high pressure into a mold, cooled therein, solidified or cured, and then the mold is opened to take out a molded product. In such an injection molding machine, a screw is arranged in a heating cylinder so as to be rotatable and reciprocal, and a resin melted by the screw is injected.

Therefore, a screw head for extruding resin is provided at the tip of the screw, and is attached to the screw by internal screwing. FIG. 2 is a sectional view of a screw head structure of a conventional injection molding machine. In the figure, 1 is a screw head, 2 is a check ring for preventing backflow of resin, 3 is a seal ring which abuts when the check ring 2 retracts, 4 is a screw, 5 is a heating cylinder, and 6 is resin. Is.

When the screw 4 advances and the resin 6 is filled in the mold, the resin 6 is melted and plasticized and stored at the tip of the screw head 1 prior to the next shot.
That is, measurement is performed. In the measuring process, the screw 4 is driven by a drive system (not shown) and retracts, and at this time,
Resin 6 dropped and supplied from the hopper, that is, the material supply port
Is melted in the heating cylinder 5 while moving forward in the groove 4a by the rotation of the screw 4, and is stored at the tip of the screw head 1. The pressure of the resin 6 in the heating cylinder 5 generated by the melting serves as a reaction force against the screw 4, and the reaction force causes the screw 4 to retract.

In this way, the resin 6 stored at the tip of the screw head 1 is subsequently injected into the mold from a nozzle (not shown) by pushing the screw 4 forward by the drive system. Here, a part of the resin 6 flows backward through the groove 4a of the screw 4 due to the reaction force of the pressure applied to the mold during injection. In order to prevent this, the check ring 2 is arranged at the front end of the screw 4. Then, a screw head 1 which is a separate body from the screw 4 is formed so that the check ring 2 does not come off from the screw 4, and a female screw 4b is formed on the screw 4.
A male screw 1a is formed at the rear end of the screw head 1, and both are screwed together. The outer diameter of the screw head 1 is made larger than the inner diameter of the check ring 2 so that the check ring 2
I try not to come out.

In the screw head structure having the above structure, the check ring 2 can freely rotate with respect to the screw head 1 (non-co-rotating check ring). The screw head 1 is provided so as to rotate integrally with the screw head 1 (co-rotating check ring). FIG. 3 is a sectional view of another screw head structure of a conventional injection molding machine.

In the figure, 1 is a screw head, 3 is a seal ring, 4 is a screw, 5 is a heating cylinder, 6 is a resin, and 10 is a check ring. The screw head 1 is formed with locking grooves 11 for restraining the rotation of the check ring 10 at two locations in the circumferential direction thereof. FIG. 4 is an explanatory view of a conventional screw head structure. (A) of the figure is an overall view of the screw head structure, (b) is a front view of the check ring, and (c) is a sectional view of the check ring taken along the line A-A.

In the figure, 1 is a screw head, 1a is a rear end surface of the screw head 1, and 1b is a screw head 1.
Small diameter part, 3 is a seal ring, 10 is a check ring, 10
a is the front end face of the check ring 10 and 10b is the check ring 1.
0 rear end face. The check ring 10 has four claw pieces 12a, 12b, 13a, 13b at the front end. Reference numeral 14 is an annular passage formed between the small diameter portion 1b of the screw head 1 and the check ring 10. The nail piece 1
2a and 12b are longer than the claw pieces 13a and 13b, and are inserted into the locking grooves 11 formed at the corresponding positions of the screw head 1 to prevent the check ring 10 from rotating with the rotation of the screw head 1. is doing.

Further, the claw pieces 13a, 13b are not inserted into the locking groove 11 of the screw head 1, but come into contact with the rear end face 1a when the screw head 1 retracts in a measuring process or the like. At this time, the front end surface 10 of the check ring 10 is
a and the rear end face 1a of the screw head 1 between the claw piece 1
A gap 15 corresponding to the length of 3a and 13b is formed. In the measuring step, as the screw 4 (see FIG. 3) moves backward, the resin 6 in the groove 4a passes through between the seal ring 3 and the rear end face 10b and enters the annular passage 14, and the gap 1
It goes through 5 and moves to the tip of the screw head 1.

[0010]

However, in the above-mentioned conventional screw head structure, in the case of the non-co-rotating check ring (see FIG. 2), the check is performed while the screw 4 is retracted while rotating in the measuring process. The ring 2 retracts together with the screw 4 without rotating. Therefore, the check ring 2
As a result, the screw head 1 may slide to cause resin burning.

That is, during the measuring process, the screw 4 rotates and slides on the check ring 2, and a shearing force is generated in the resin 6 between them. At this time, between the check ring 2 and the seal ring 3, the resin 6 which is about to be burned is washed away. However, between the screw head 1 and the check ring 2,
Both of them are constantly sliding, and the resin 6 which is being burned receives a shearing force to generate heat, which is burned by heat in the case of a resin having poor thermal stability such as PA66 / AS. The burned resin 6 is extruded into the mold as the screw 4 advances during the injection process, and burns out in the molded product.

Further, in the case of the co-rotating check ring (see FIG. 3), not only the heating cylinder 5 and the check ring 10 are worn to shorten the life of the injection device but also the heating cylinder 5 and the check ring. Resin burn may occur in the gap of 10. FIG. 5 is an explanatory diagram when the co-rotating check ring is rotating. (A) of a figure is a longitudinal cross-sectional view of a check ring, (b) is a cross-sectional view of a check ring.

In the figure, 5 is a heating cylinder, 10 is a check ring, 16 is the inner circumference of the heating cylinder 5 and a check ring 1.
It is a gap formed between 0 outer circumferences. The non-return ring 10 rotates together with the screw when the screw (not shown) moves backward while rotating in the measuring process. Therefore, the inner circumference of the heating cylinder 5 and the outer circumference of the check ring 10 slide to cause wear. In addition, the gap 16 (sliding part)
The resin is subjected to a large shearing force inside, causing resin burning. The shearing force increases from the outer circumference of the check ring 10 to the inner circumference of the heating cylinder 5, as shown in FIG.

Further, in the co-rotating check ring, the above-mentioned gap 1
When the resin is partially solidified in 6, the check ring 10 is also prevented from rotating in the same manner as the screw 4 is retracted while rotating in the measuring process, and the screw head 1 (see FIG. 3) Will add a great force to. Therefore, the screw head 1 may be broken. The present invention solves the problems of the conventional screw head structure described above, and prevents the resin from being abnormally heated between the heating cylinder and the check ring and between the screw head and the check ring to cause resin burning. An object is to provide a screw head structure.

[0015]

Therefore, in the screw head structure of the present invention, the screw head is composed of a conical portion, a cylindrical portion adjacent to the conical portion, and a small diameter portion adjacent to the cylindrical portion. A check ring is arranged around the small diameter portion, and a seal ring is arranged adjacent to the small diameter portion.

The check ring has a cylindrical shape having a front end surface and a rear end surface, forms a gap between the small diameter portion of the screw head, and rotates relative to the screw head. Notch grooves and protrusions are formed at a plurality of positions in the circumferential direction on the front end face of the check ring, and a sliding surface is formed between the protrusion and the rear end face of the cylindrical portion. Further, grooves are formed at a plurality of positions in the circumferential direction of the cylindrical portion of the screw head,
The groove communicates with the gap between the small diameter portion of the screw head and the check ring.

[0017]

According to the present invention, as described above, the screw head is composed of the conical portion, the cylindrical portion adjacent to the conical portion, and the small diameter portion adjacent to the cylindrical portion. The ring is arranged and the seal ring is arranged adjacent to the small diameter portion. The check ring has a cylindrical shape having a front end surface and a rear end surface, forms a gap between the small diameter portion of the screw head, and rotates relative to the screw head.

In the screw head structure having the above structure, when the screw is retracted while rotating, the screw head rotates accordingly. At this time, the check ring moves forward with respect to the screw head and contacts the rear end surface of the cylindrical portion. Notch grooves are formed at a plurality of positions in the circumferential direction on the front end face of the check ring, and as a result, protrusions are formed. Therefore, while the screw head rotates, the non-return ring maintains the stopped state, and forms a sliding surface between the protrusion and the rear end surface of the cylindrical portion. In this case, the resin in the gap between the check ring and the small diameter portion escapes to the cylindrical portion side through the cutout groove.

Further, grooves are formed at a plurality of positions in the circumferential direction of the cylindrical portion of the screw head, and the grooves communicate with the gap between the small diameter portion of the screw head and the check ring. Therefore, the resin in the gap between the check ring and the small diameter portion flows not only through the cutout groove but also through the groove of the cylindrical portion and escapes into the conical portion.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an explanatory view of a screw head structure of the present invention. (A) of a figure is a front view of a screw head structure, (b) is a side view of a screw head structure. In the figure, 3 is a seal ring, 4 is a screw, 21 is a screw head, and 22 is a check ring.
The screw head 21 has a conical portion 21a and the conical portion 21.
a cylindrical portion 21b continuing to the rear of a, and a small diameter portion 2 located on the inner peripheral side of the check ring 22 behind the cylindrical portion 21b.
1c, flat portions 23a to 23d are formed at four locations around the cylindrical portion 21b, and grooves 24a to 24d are formed in the flat portions 23a to 23d, respectively. The groove 2
4a to 24d are formed from the cylindrical portion 21b to the vicinity of the front end portion of the small diameter portion 21c, and the small diameter portion 21c and the check ring 22 are provided.
It communicates with the gap between.

The non-return ring 22 has a front end face 22.
It has a hollow cylindrical shape having a and a rear end surface 22b, and the front end surface 22a faces the rear end surface 21d of the cylindrical portion 21b of the screw head 21, and the rear end surface 2
2b faces the seal ring 3. The front end face 22a
Are formed with notch grooves 25a to 25c at three locations in the circumferential direction, and as a result, protrusions 26a to 26c are formed at three locations in the circumferential direction, that is, at an angle of 120 °.

The projections 26a to 26c contact the rear end face 21d of the cylindrical portion 21b of the screw head 21 when the screw 4 is retracted while rotating in the measuring process, but slides by the notch grooves 25a to 25c. The area becomes smaller, and the check ring 22 does not rotate even if the screw head 21 rotates. Therefore, since the resin on the outer peripheral portion of the check ring 22 is hardly subjected to shearing force, the resin does not burn even if a resin having poor thermal stability is used.

In the above embodiment, the protrusion 26a
Three to 26c are formed on the front end surface 22a of the check ring 22, and the height and the number of the protrusions 26a to 26c are determined by the speed of resin removal from the gap between the small diameter portion 21c and the check ring 22. Can be changed according to. FIG. 6 is a diagram showing a resin flow in the screw head structure of the present invention.

In the figure, 3 is a seal ring, 21 is a screw head, and 22 is a check ring. The resin that has flowed forward between the heating cylinder 5 (see FIG. 3) and the screw 4 is the check ring 22 and the small diameter portion 21 of the screw head 21.
c into the gap with the cutout groove 25a to
25c (see FIG. 1) through the cylindrical portion 21b side, it also flows into the grooves 24a-24d, the grooves 24a-24d
And flows in the radial direction from the side to escape to the side of the conical portion 21a.

The rear end surface 21d of the screw head 21 has a protrusion 26 as the screw 4 rotates.
a-26c and the notch grooves 25a-25c are alternately faced.
That is, the rear end face 21d is intermittently provided with the projections 26a to 26.
It will slide with c. Therefore, the rear end face 21d
Even if heat is generated by the shearing force of the resin between the protrusions 26a to 26c, the resin flowing through the cutout grooves 25a to 25c scrapes the high temperature resin, so that the resin burnt occurs on the rear end surface 21d of the screw head 21. Can be prevented.

FIG. 7 is an explanatory view of a screw head structure showing another embodiment of the present invention. (A) of the figure is an overall view of the screw head structure, (b) is a front view of the check ring,
(C) is sectional drawing of a non-return ring. In the figure, 3 is a seal ring, 31 is a screw head, and 22 is a check ring. The screw head 31 includes a conical portion 31a, a cylindrical portion 31b that follows the conical portion 31a, and a cylindrical portion 31a.
It is composed of a small diameter portion 31c located on the inner peripheral side of the check ring 22 behind the b.

The non-return ring 22 has a front end face 22.
It has a hollow cylindrical shape having a and a rear end surface 22b, and the front end surface 22a faces the rear end surface 31d of the cylindrical portion 31b of the screw head 31, and the rear end surface 2
2b faces the seal ring 3. The front end face 22a
Are formed with notch grooves 25a to 25c at three circumferential positions, and as a result, protrusions 26a to 26c are formed at three circumferential positions, that is, at 120 ° angles.

The protrusions 26a to 26c abut on the rear end face 31d of the cylindrical portion 31b of the screw head 31 when the screw retreats while rotating in the measuring process, but the sliding areas are equal to the notch grooves 25a to 25c. Becomes smaller, and even if the screw head 31 rotates, the check ring 2
2 does not rotate. Therefore, since the resin on the outer peripheral portion of the check ring 22 is hardly subjected to shearing force, the resin does not burn even if a resin having poor thermal stability is used. Further, even if heat is generated by the shearing force of the resin between the rear end face 31d and the protrusions 26a to 26c, the resin flowing through the cutout grooves 25a to 25c scrapes the high temperature resin, so that the rear end face 31d of the screw head 31 is removed. In this case, it is possible to prevent the resin burning.

In this case, the outer circumference of the check ring 22 is made of a hard alloy, and a hard alloy is joined to the rear end face 31d of the screw head 31 to improve wear resistance. Further, the rear end surface 22b of the check ring 22 is
In order to prevent chipping and the like, the taper shape is adopted (in the present invention, the angle of intersection of the tapered surfaces is 120 °).

The present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, the front end face of the check ring is formed with the notch grooves at a plurality of positions in the circumferential direction, thereby forming the protrusions. , The non-return ring keeps stopped while the screw head rotates. Therefore, it is possible to prevent the shearing force from being generated in the resin on the outer circumference of the check ring.

A sliding surface is formed between the projection and the rear end surface of the cylindrical portion, and the rear end surface slides intermittently on the sliding surface and is in the gap between the check ring and the small diameter portion. The resin escapes to the cylindrical portion side through the cutout groove. Therefore, the high temperature resin on the rear end face is scraped off by the resin that escapes to the cylindrical portion side through the notch groove, and it is possible to prevent the occurrence of resin burning.

Further, grooves are formed at a plurality of positions in the circumferential direction of the cylindrical portion of the screw head, and the grooves are communicated with the gap between the small diameter portion of the screw head and the check ring. Therefore, the resin in the gap between the check ring and the small diameter portion flows not only through the cutout groove but also through the groove of the cylindrical portion and flows out into the conical portion, so that the resin burn can be further prevented.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a screw head structure of the present invention.

FIG. 2 is a sectional view of a screw head structure of a conventional injection molding machine.

FIG. 3 is a cross-sectional view of another screw head structure of a conventional injection molding machine.

FIG. 4 is an explanatory view of a conventional screw head structure.

FIG. 5 is an explanatory diagram when the co-rotating check ring is rotating.

FIG. 6 is a diagram showing the flow of resin in the screw head structure of the present invention.

FIG. 7 is an explanatory view of a screw head structure showing another embodiment of the present invention.

[Explanation of symbols]

 3 seal ring 21 screw head 21a conical part 21b cylindrical part 21c small diameter part 22 check ring 22a front end face 22b rear end face 24a-24d groove 25a-25c notch groove 26a-26c protrusion

Claims (2)

[Claims] 1. (a) A conical part, a cylindrical part adjacent to the conical part, a screw head composed of a small diameter part adjacent to the conical part, and (b) a cylindrical shape having a front end face and a rear end face. Consists of
Around the small-diameter portion of the screw head, a check ring is provided so as to be rotatable relative to the screw head, and (c) a seal ring is provided so as to face the check ring. (D) Protrusions are formed on the front end face of the check ring at a plurality of circumferential positions to form protrusions, and a sliding surface is formed between the protrusions and the rear end face of the cylindrical portion. A screw head structure characterized by. 2. The screw head according to claim 1, wherein grooves are formed at a plurality of positions in the circumferential direction of the cylindrical portion of the screw head, and the grooves are communicated with a gap between the small diameter portion of the screw head and the check ring. Structure.