JPH01242222A - Backflow prevention device for injection molding machine - Google Patents

Abstract

PURPOSE:To carry out backflow prevention action by a valve accurately and quickly by drawing or blocking a flow channel of resin by means of combination of the actions in the axial direction and revolving direction of a valve generated by the resin pressure at the time of injection in a valve chamber provided between the screw end and a nozzle. CONSTITUTION:A valve chamber 40 is formed between a screw end 16 and a nozzle 32, and a shaft 18 is fixed at the end of the screw 16. A plurality of channels 18c are provided at given intervals on the outer periphery of the shaft 18, and on the other hand, a valve 34 constituted of ring components with a plurality of channels 34a provided at given intervals on the inner periphery is provided. The valve 34 is engaged with part of the shaft 18 and inserted into the shaft 18 revolvably and movably forward and backward. Thus, respective channels 18c and 34a are drawn or blocked by the revolution of the valve 34 generated by the resin pressure at the time of injection. The backflow prevention action of the valve can be carried out accurately and quickly by said arrangement.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention prevents backflow in injection molding machines! ! Regarding the A-neck, especially when injecting and filling the molten resin into the mold after plasticizing and measuring, the resin r
-Injection in which the resin flow path is throttled or blocked by a small amount of momentum of the valve body by a combination of the 1hhh direction movement and the rotational movement of the valve body, thereby preventing the backflow of molten resin from the mold. This invention relates to a backflow prevention device for a molding machine.

[Conventional technology]

Generally, when using an injection molding machine and injecting molten resin into the mold from the inside of the barrel with a screw, it is measured (8)
It is configured to prevent a part of the molten resin from flowing back toward the slurry 1 side so that the molten resin can flow in and out efficiently.

The conventional check valve 14 is fitted into the inner diameter surface of the barrel 24 and attached to the tip of the screen 116. It has a cylindrical shape with a 4i-inner diameter surface so that a sufficient gap 20 is formed between the small diameter part 18a of the screw head 18 and the circular fit part 18a of the screw head 18. A screw is installed on the tip surface of the screw 16 so that it can move forward and backward in the axial direction at a predetermined distance between the spacers 22. The pawl 26 is engaged with the four parts 28 provided on the conical part 18b of the slurry 2 head, and the screw 16 and the check valve 1 are connected to each other.
A plurality of protrusions 14a are provided on the front end of the top surface Q of the protrusions 14a.
/ J The gap 20 formed between the gap 20 and the gap 30 communicate with the gap S formed between the rear end surface R of the check valve 14 and the space 22 to form a resin flow path. .

As the screw 16 rotates during the culm process, the resin material melted and transferred from the right upstream side of the screw 116 passes through the check valve 14 to the left side of the figure. Conical part 18b of the forward pushing screw head
As a result, the resin material flows through the resin flow path as indicated by arrow a and is accumulated in front of the screw head 1B.

Then, when a total of 13 predetermined accumulation fields are applied, plasticization-[closing is
After finishing the process, the 7i yi+ resin material is O4jJ
j? When the screw 16, which is at the 1st retraction limit, moves forward to the left side in the figure, the check valve 14 closes the screw head 18.
The resin that had accumulated in front of
The resin flow path is closed.

[Problem to be solved by the invention]

However, this conventional device does not have a check valve 14 during injection.
The operation of closing the gap S is very unstable and takes a long time, and may be affected by the frictional resistance with the inner diameter surface of the barrel 2/I or the viscosity of the resin, and especially when the gap S is large, the closing operation becomes even more difficult. It is unstable. Therefore, there is a problem that the unstable operation of the check valve 14 causes variations in the amount of resin injected, which often adversely affects the quality of the Ushijiza U molded product.

Therefore, L1 of the present invention is a combination of the axial movement and rotational movement of the valve body due to the resin pressure of υ, 'f injected into the valve chamber provided between the screw tip and the nozzle. To provide a backflow prevention device for an injection molding machine in which the backflow prevention operation by a valve can be performed accurately, reliably, and quickly by constricting or closing a resin flow path.

[Means to solve the problem]

In order to achieve the above object, the backflow prevention device for the injection molding machine according to the present invention prevents backflow in the axial direction of the valve when molten resin is plasticized by the rotation of the screw and then filled (into the mold after being measured). Alternatively, in the backflow prevention device of a 16 injection molding machine closed by movement in the circumferential direction, a valve chamber is formed between the screw tip and the nozzle, and inside this valve chamber, the C screw tip (shaft is fixed and the outside of this shaft body is A plurality of grooves are formed on the circumference at predetermined intervals [), a valve body is made of an annular member and has a plurality of grooves carved at predetermined intervals on its inner circumference, and this valve body is engaged with a part of the shaft body. 3. In this case, the valve body and the lTll1 body are fitted into the sleeve body so as to be rotatable and retractable, and the grooves are narrowed or closed by the rotational movement of the valve body caused by the resin pressure during injection. It is preferable that a gap is formed in the circumferential direction in the engaging portion of the valve body, and the valve body is rotated within this gap to communicate or close the groove of the C-shaft body and the II'4 portion of the valve body, respectively. It is.

Further, the resin contacting surface of the injection side end surface of the eleven-shaped member is a sloped surface (preferably C is 1.4.1).

(Function) According to the backflow prevention device 1 for an injection molding machine according to the present invention, after the molten resin is plasticized and measured by the rotation of the screw, the valve is rotated by the resin pressure when injected and filled into the mold. This allows the resin flow path to be effectively constricted or blocked.

〔Example〕

Next, a backflow prevention device for an injection molding machine according to the present invention will be described in detail with reference to the accompanying drawings.

For convenience of explanation, parts that are the same as the conventional structure shown in FIGS. 8 and 9 are given the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 shows a cross-sectional view of the essential parts of an embodiment of the backflow prevention device for an injection molding machine according to the present invention, with reference numeral 3.
Reference numeral 2 indicates a nozzle provided at the tip of the barrel 24, and a through hole 32a through which molten resin material is injected is bored on the central axis of this nozzle 32.

A screw head 18, which is a shaft body, is attached to the tip of the screw 16 fitted into the inner diameter surface of the barrel 24, with a conical portion 18b facing the through hole 32a of the nozzle 32.

Further, a sufficient distance is formed between the small diameter portion 18a of the screw head 18 and the inner diameter surface of the barrel 24, thereby forming a cylindrical valve body 42.

Roughly speaking, in the valve chamber 40, grooves 18c are carved in the small diameter portion 18a of the screw head 18 attached to the tip of the screw 16 at predetermined intervals in the axial direction, and the grooves 18c are engaged with the stepped portions between the small diameter portion and the small diameter portion. A pair of four portions 28 are removed.

The small diameter portion 18a has a groove 34a carved in the axial direction on the inner peripheral surface with the same gap as the groove 18c, and a pair of claws 38 that can be engaged with the pair of four portions 28 protrudes from the injection side end. A valve body 42 made of an annular member is fitted so as to be rotatable and movable back and forth.

Further, the outer periphery of the valve body 42 is similarly fit into the inner periphery of the barrel 24 so as to be able to pivot, thereby forming a backflow prevention device in a herbal manner.

The valve body 42 can move back and forth within a gap S in the axial direction between the stepped portion of the screw head 18 and the end G of the spacer. In this case, the engagement between the four parts 28 of the screw head 18 and the pawls 26 of the annular member 34 is maintained even if the annular member 34 moves until it comes into contact with the spacer 22 side. Further, the top surface Q of the protrusion 36 of the annular member 34
In a state where the screw head 18 is in contact with the stepped portion of the screw head 18, a gap 30 is formed between the plurality of protrusions 36 of the annular member 34 and the stepped portion of the screw head.

Further, as is clear from FIGS. 2 and 3, the fitting portion between the small diameter portion 18a of the screw head 18 and the annular member 34 fitted therein has a circular cross section in the axial direction. Arc-shaped flow portions 18C and 34a are each carved at predetermined intervals in the circumferential direction. The flow portion 18C on the side of the small diameter portion 18a is carved to be shorter than the entire length of the annular member 34, and this groove portion is completely covered by the annular member 34 when the annular member 34 is located at the front (injection side). Further, the circulation portion 34a on the annular member 34 side opens only on the spacer 22 side, which is the negative end thereof, and communicates with the gap S formed between the spacer 22 and the rear end surface R of the annular member 34. . Therefore, when the annular member 34 is at the forward end position, that is, when the protrusion 36 Q is in contact with the step part of the screw head 18, the gap S side is roughly connected to the protrusion 36 through the flow parts 18c and 34a. It communicates with the through hole 32a side of the nozzle 32 through the cavity 30 to form a resin flow path.

In this case, an inclined surface 36a is formed on one white side surface of the annular portion +434, which is the same as the plurality of protrusions 36. Pressure acts on this slope 36a to rotate the annular member 34 (see FIG. 4).

Before the start of the injection process, the pawl 38 of the annular member 34 is engaged with the recess 28, and in this case, a gap δ is formed between the four parts 28 and the pawl 38 in the circumferential direction (see FIG. 3). , the resin flow passages 18c and 34a are in communication with each other.

In this case, the cross-sectional shape of the groove of the flow path is not limited to an arcuate groove, but may be any positional relationship that allows communication or disconnection after the annular member is rotated by δ in the circumferential direction.

Next, the operation according to the present invention will be explained below. In FIG. 1, the resin plasticized by the rotation of the screen 16 flows into the flow path 34a of the annular member 34 through the gap S, and then flows into the flow path 18C communicating along the arrow a.

Roughly, the resin flows through the cavity 30 (fourth
(see figure) and is deposited in bulk into the nozzle passage hole 32a in front of the screen head 18.

Note that when the screw head 18 rotates in the direction of the arrow Dh along with the screw 16, as shown in FIGS. 2 and 3,
One side of the claw 3ε3 of the annular member 34 is connected to the slurry 1 head 18.
The pawl 38 is engaged with the four portions 28 with play in the circumferential direction δ, and in this case, the flow passages 18c and 34a are in communication with each other. .

Next, when the plasticization process is completed and the 01 exit process begins, the injected resin flows backwards as shown by the arrow C, and the resin pressure P as shown in FIG. It acts on

This resin pressure P causes the annular member 34 to rotate in the circumferential direction due to the circumferential component force pr acting on the inclined surface 36a, and also moves the annular member 34 in the direction of the resultant force (see FIG. 4). ).

Therefore, the cylindrical member 34 rotates by δ J in the circumferential direction (in the opposite direction to the arrow) due to the acting force of the resin pressure, and each of the flow passages 1
8G and 34a are each in a cutoff state after being narrowed down.

Due to the rotation of the annular member 34, each of the grooves 18C, 34
As the flow passage between a narrows, the screw head 18
Since the flow resistance of the resin from the side to the screw 16 side increases, the closing speed of the annular member 34 increases in terms of acceleration.
The valve body is closed in a short time.

In this case, each of the flow passages 18G.

34a is the rear end surface of the annular member 34, as shown in FIG. It is cut off by R and the end face G of the spacer 22.

〔Effect of the invention〕

As explained above, the backflow prevention device for an injection molding machine according to the present invention includes a valve chamber provided between the Scrico tip and the nozzle, a valve body rotatable by resin pressure inside the valve chamber, and a valve body rotatable by the action of resin pressure. The resin flow path can be configured to be constricted or closed by a combination of axial movement and rotational movement, making it possible to accurately control the amount of injected resin, improving injection accuracy and producing precise molded products (( be able to.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the backflow prevention device N according to the present invention.
j A cross-sectional view of main parts, FIG. 2 is a cross-sectional view taken along line B-8 in FIG. 1, FIG. 3 is a view taken along arrow 7 in FIG. 1, and FIG. External view of main parts, Figure 5 is C- in Figure 7
C sectional view, FIG. 6 is a cross-sectional view of FIG. 9 are sectional views of essential parts of a conventional backflow prevention device. 14...Return prevention valve 14a...Protrusion C1;1
6...Scritter' 18...Slurry 1 head 18a...
・Small diameter part 18b...conical part 18c...
Flow path 20...Gap 22...Suberi
24...2 barrels 1. Nail 28・
...Concave 81130...Gap 32...Nozzle 32a...Through hole 34...Annular member 3
4a...Flow path 36...Protrusion 36a...
・Slope 38...Claw 40...Valve chamber
42... Valve body I:... Resultant force G...
・Space + J, QXi surface 1)...Resin pressure
p r...Circumference/J direction component force Q...Protrusion curved surface
R... Rear end surface S... Gap FIo, 1 FIo 4 FIG, 7

Claims (3)

[Claims] (1) A backflow prevention device for an injection molding machine that blocks backflow when molten resin is plasticized by the rotation of a screw, measured, and then injected into a mold by moving the valve in the axial or circumferential direction. A valve chamber is formed between the valve chamber and the nozzle, a shaft is fixed to the tip of the screw in the valve chamber, and a plurality of grooves are provided at predetermined intervals on the outer circumference of the shaft body. A valve body with a groove carved therein is provided, and this valve body engages with a part of the shaft body and is fitted into the shaft body so as to be able to rotate and move forward and backward. A backflow prevention device for an injection molding machine characterized by narrowing or closing a groove. (2) A gap is formed in the circumferential direction at the engagement portion between the valve body and the shaft body, and the valve body is rotated within this gap to communicate or close the groove of the shaft body and the groove of the valve body, respectively. The backflow prevention device for an injection molding machine according to claim 1, wherein the backflow prevention device is configured to restrict the flow. (3) The backflow prevention device for an injection molding machine according to claim 1, wherein the resin contacting surface of the injection side end surface of the annular member is configured to be an inclined surface.