JP3127474B2 - Screw for in-line screw type injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection screw used in an in-line screw injection molding apparatus.
More particularly, the present invention relates to a screw for an in-line screw type injection molding apparatus suitable for injection molding of a mixed liquid mixed resin such as silicone rubber LIM and other mixed liquid reactive resins.

[0002]

2. Description of the Related Art In general, an in-line screw type injection molding apparatus comprises an injection cylinder member having an injection cylinder chamber inside and having a resin injection nozzle at one end, and a rotatable and axial line in the injection cylinder chamber. Injection screw movably arranged in the direction, a hydraulic motor that rotationally drives the injection screw, a rotational drive means such as an electric motor, and a hydraulic injection cylinder device that drives the injection screw in the axial direction When the injection screw is rotated around its own central axis by the rotation drive means, the resin is taken into the injection cylinder chamber by the screw pump action, and the injection screw is driven forward in the axial direction by the injection cylinder device. The resin taken into the injection cylinder chamber is directed from the resin injection nozzle to the cavity of the molding die It is configured to output.

An injection screw used in the above-described in-line screw type injection molding apparatus is generally provided with a screw pump operating portion for performing a screw pump operation and a diameter of a screw groove bottom portion provided in front of the screw pump. And a compound portion whose valley diameter gradually increases as it moves forward. The resin material fed from the screw pump operating portion by rotation is kneaded while being compressed in the compound portion.

[0004]

The injection screw as described above is suitable for injection molding of a thermoplastic resin, and has not been developed for a low-viscosity resin material.
This injection screw simply compresses and mixes the resin material under one flow in the process of feeding the resin material by the screw, and therefore, a good kneading action can be obtained. Absent. This is silicone L
A problem arises in the injection molding of a multi-liquid mixed resin such as IM, and in particular, in the injection molding of a low-viscosity resin material and a multi-liquid mixed resin having a large viscosity difference, sufficient kneading properties cannot be obtained.

[0005] In order to increase the kneading properties, it is necessary to increase the axial length of the injection screw. However, the extension of the axial length of the injection screw causes an increase in the size of the in-line screw type injection molding apparatus.

In addition, since the conventional injection screw compresses the resin material at the compound part, this becomes the resistance of the rotation of the injection screw. This increases the rotational resistance of the injection screw, and in addition to this, when it is necessary to forcibly supply the resin material to the screw portion using a pushing device, such as a low-viscosity liquid resin, this is necessary. This causes an increase in the material supply pressure, and it is necessary to make the material supply pressure of the pushing device higher than the resin material compression pressure of the compound portion.

In order to improve the kneadability of the resin material,
It has been considered that a weir is provided at an intermediate portion of the injection screw to divide the injection screw into a plurality of zones in the axial direction.

However, this also gives a large resistance to the flow of the resin material, resulting in an increase in required material supply pressure. In addition, the weir impairs the flow of the cleaning liquid during cleaning, thereby deteriorating the cleanability of the injection cylinder chamber, thereby preventing the resin material from being washed well.

In the injection molding of a multi-liquid mixed resin such as silicone LIM, a static mixing mechanism may be used for mixing resin materials without using an in-line screw.

[0010] However, in the case of the static mixing mechanism, since a static mixing is performed by mixing, a long mixing head and a high material supply pressure are required. Further, a high material supply pressure is required, and it is difficult to mix resin materials having different viscosities. Further, in the case of the static mixing mechanism, since the residence time of the resin material in the mixing zone is long, there is a restriction that the resin material must have a long pot life. Also in this case, the mixing of the mixed liquid resin having a large viscosity difference is not sufficiently performed.

The present invention has been made in view of the above-mentioned problems in the conventional injection molding apparatus, and has a large viscosity difference, a mixed liquid mixed resin having a large viscosity difference, and a high viscosity range from a low viscosity to a high viscosity. In-line screw-type injection molding machine that performs good mixing and kneading of resin materials without requiring a long shaft length, and that does not increase the required material supply pressure or deteriorate the cleanability of the injection cylinder chamber. It is intended to provide a screw for use.

[0012]

According to the present invention, there is provided a screw pump operating section for performing a screw pump operation in an injection cylinder chamber, and a screw pump operating section provided in front of the screw pump operating section. A mixing screw portion having a small pitch and a small lead angle as compared with the portion, wherein the mixing screw portion is provided with an axial groove in the axial direction, and a tip portion of the mixing screw portion has A seal ring member is movably fitted between the screw head member and an O-ring for sealing between the seal ring member and an inner peripheral surface of the injection cylinder chamber. The screw head member is provided with a cut groove, and the seal ring member is moved to the screw head member side. The inline screw wherein the cut groove and the axial groove communicate with each other with a phase shift, and when moved to the mixing screw portion side, the communication is interrupted by contact between end faces. This is achieved by a screw for an injection molding machine.

[0013]

According to the construction described above, the resin material is sent to the mixing screw part by the rotation of the screw pump action part, and a part of this resin material flows along the screw groove of the mixing screw part and the remaining resin material Travels along the axial groove and the like, whereby a plurality of flows of the resin material are generated, and as they proceed along the mixing screw portion, they are repeatedly joined and divided. As a result, the mixing and kneading of the resin materials are performed with high efficiency and evenness. Furthermore, the sealing ring member moves toward the screw head member side when the resin material is fed and filled, and the axial groove and the cutting groove communicate with the phase shifted, so that the mixing and kneading of the resin material are performed more efficiently. At the same time, at the time of injection molding, it moves to the mixing screw side to cut off the communication, so that backflow is avoided and injection molding is performed efficiently.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 show an example in which an in-line screw type injection molding apparatus having a screw for an in-line screw type injection molding apparatus according to the present invention is applied as an injection apparatus for a multi-liquid reaction-curable resin such as silicone rubber. An example is shown.

The screw type resin injection device for injection molding is
It has a cylinder fixing base 3 fixed on the forward / backward moving board 1, and the cylinder fixing base 3 holds the injection cylinder member 5 in a horizontal posture.

The injection cylinder member 5 forms an injection cylinder chamber 7 inside, and a tapered cylinder head member 9 for holding an injection nozzle is connected to one end on the same axis.

An injection screw 11 is disposed in the injection cylinder chamber 7 of the injection cylinder member 5 so as to be rotatable about its own central axis and movable in the axial direction. As shown in FIGS. 3 to 5, the injection screw 11 has a relatively large pitch, a triangular screw-shaped screw pump operating section 13 having a large lead angle, and is provided in front of the screw pump operating section 13. Screw pump action part 1
And a mixing screw portion 15 having a smaller pitch than that of No. 3 and a small lead angle. The mixing screw portion 15 has an even number of rectangular grooves 17 having a rectangular cross section having a depth equal to the screw height in the entire axial direction thereof, and in this embodiment, four axial grooves 17 at equal intervals in the circumferential direction. It is provided. Specifically, the screw pump action section 13 has a shaft length of about 90 to 120 mm and a pitch of 20 mm.
mm, a tilt angle of about 15 degrees and a depth of about 2.5 to 2.7 mm may be a non-returned triangular screw. The mixing screw part 15 has an axial length of about 30 to 70 mm,
The thread may be a square screw having a pitch of about 4.5 to 6.0 mm and a depth of about 2.2 to 2.4 mm, and the axial groove 17 may have a groove width of about 2.3 to 2.5 mm. .

At the tip of the injection screw 11, FIG.
As shown in FIG. 8, a screw head member 19 is provided.
Are screwed and fixed, and a seal ring member 23 is externally fitted to the shaft portion 21 of the screw head member 19 so as to be movable in the axial direction. The seal ring member 23 is axially movable between a seal seat surface 25 formed by the distal end surface of the injection screw 11 and an end surface 27 of the screw head member 19 opposed thereto, as shown in FIG. By shutting off the communication between the nozzle side and the screw side of the injection cylinder chamber 7 by seating on the seal seating surface 25, the seating surface is seated on the end surface 27 as shown in FIG. 25, the shaft 21
In this embodiment, the nozzle side and the screw side of the injection cylinder chamber 7 are communicated with an odd number of gaps 31 formed in the head 33 of the screw head member 19, and in this embodiment, three cut grooves 35. It is supposed to be. The reason why the number of the axial grooves 17 and the number of the cut grooves 35 are odd and even is to shift the phases of both. Since these are relative relationships, they may be simply arranged so as to shift the phase.

On the outer periphery of the seal ring member 23, two O-rings 37 are axially separated from each other in order to seal between the outer peripheral surface of the seal ring member 23 and the inner peripheral surface of the injection cylinder member 5. It is provided. The provision of two O-rings in parallel is also for preventing the sealing member 23 from tilting, and is effective for preventing galling.

A nozzle device 39 with a valve is attached to the tip of the cylinder head member 9. As shown in FIG. 9, the valved nozzle device 39 includes a nozzle main body 43 inserted into the distal end hole of the cylinder head member 9 so as to be movable in the axial direction, The spool valve ring 47 which is circumscribed to the thin shaft portion 45 so as to be relatively displaceable in the axial direction, the valve seat member 49 fixed to the rear end of the thin shaft portion 45, and the nozzle body 43 are attached to the cylinder head member 9. On the other hand, the cylinder head 43 has a compression coil spring 51 that urges the valve to the valve closing side, that is, the left side in the figure. By moving the valve seat member 49 relative to the right side in FIG.
The valve hole 53 provided in the thin shaft portion 45 in the radial direction at a distance from the contact with the cylinder 7 is exposed to the cylinder chamber 7. The valve hole 53 communicates with the guide hole 55 extending in the axial direction at the center of the nozzle body 43 and the nozzle hole 57 continuous with the guide hole 55. It leads to the hole 57.

An O-ring 59 for sealing is provided on the outer periphery of the nozzle body 43.

As shown in FIGS. 1 and 2, an O-ring 61 is provided near the rear end of the injection screw 11 to prevent the resin from leaking backward.

A plunger shaft 63 is coaxially fixedly connected to the rear end of the injection screw 11. A reverse screw 6 for preventing the resin from leaking rearward is provided on the outer periphery of the portion where the plunger shaft 63 is fitted with the injection cylinder member 5.
The mechanical seal 67 is provided between the plunger shaft 63 and the cylinder fixing base 3.

The plunger shaft 63 is connected to the injection cylinder member 5.
Projecting rearward from the rear end, and this projection is rotatably and axially moved around its own central axis by a linear motion bearing 71 held by a bearing support member 69 fixed to the cylinder fixing base 3. Supported as possible.

A flange 73 is provided near the rear end of the plunger shaft 63.
As shown in FIG. 2, the drive arm 7
One end of 5 is axially connected so as to be relatively rotatable with a needle thrust bearing 79 interposed between an end ring 77 fixedly mounted on the plunger shaft 63 and a flange 73.

As shown in FIG. 2, the drive arm 75 extends in the radial direction of the injection cylinder member 5 and is connected at its distal end to the distal end of the cylinder rod 83 of the pneumatic cylinder device 81. I have. The pneumatic cylinder device 81
It is arranged parallel to the side of the injection cylinder member 5 and is fixed to the side wall of the cylinder fixing base 3.

A shaft receiving hole 85 is formed at the rear end of the plunger shaft 63 so as to extend axially from the center of the plunger shaft 63 and open to the rear end surface of the plunger shaft 63. The rotary drive shaft 89 can be inserted into and removed from the shaft receiving hole 85 by a torque transmission type linear motion bearing 87, in other words, is fitted to the plunger shaft 63 in a telescopic manner in a torque transmitting relationship.

The rotary drive shaft 89 is connected to an output shaft 93 of a motor 91 fixed on the forward / backward moving board 1 by a coupling 95 in a torque transmitting relationship.

A resin supply block 97 is fixed to the cylinder fixing base 3. In this embodiment, as shown in FIG. 10, a resin material supply tube 99 also serving as a measuring cylinder is provided in the resin supply block 97 for injection molding of a two-component reaction-curable resin. Are mounted in parallel with each other. The resin material supply tube 99 has a resin supply block 97 having a resin discharge port 101 at the tip.
Is communicated with the resin passage 103 provided in the first passage. The resin passage 103 is connected to a resin passage 10 of the resin supply block 97 through a rotary valve 105 provided in the resin supply block 97.
7, a resin supply port 111 provided in the resin passage 109 of the cylinder fixing base 3 and an intermediate portion of the injection cylinder member 5
Is selectively communicated with.

The rotary valve 105 is of a manual type which is rotated by a manual lever 113. When the rotary valve 105 is in a rotating position as shown in FIGS. 1 and 11, when it is turned 90 degrees counterclockwise from the turning position as shown in FIGS. 1 and 11, the washing solvent passage 115 formed in the resin supply block 97 is made into resin. The passage 103 and the resin passage 107 are connected to each other, and when they are turned 90 degrees counterclockwise from the turning position as shown in FIGS. 1 and 11, the connection between the resin passage 103 and the resin passage 107 is established. The communication is interrupted to connect the cleaning solvent passage 115 to the resin passage 107, and the communication between the resin passage 103 and the resin passage 107 is interrupted to connect the cleaning solvent passage 115 to the resin passage 103. To have.

As shown in FIG. 11, each of the resin material supply tubes 99 has a resin intake port 117 at the distal end side, and each of the resin intake ports 117 is formed of a liquid resin from an individual resin material tank 119. Resin material is resin supply pipe 1
21, on-off valve 123, and resin supply pipe 125.

The cleaning solvent passage 115 communicates with a cleaning solvent supply port 127 provided in the resin supply block 97 so that the cleaning solvent is supplied from a cleaning solvent tank 129 via a cleaning solvent supply pipe 131. It has become.

A piston 133 is fitted in each of the resin material supply tubes 99, and the resin material in the resin material supply tube 99 is moved from the resin discharge port 101 by moving the piston 133 to the left in the drawing. The liquid is discharged to the passage 103.

In the resin supply block 97, a pneumatic cylinder device 135 for feeding resin material is supplied with a resin material supply tube 99.
It is attached in parallel with. In the pneumatic cylinder device 135 for feeding resin material, a connecting plate 139 is attached to the tip of a piston rod 137, and one end of two push rods 141 is fixedly connected to the connecting plate 139, respectively. A push pad 143 is attached to each end of the push rod 141, and the push pad 143 is connected to the piston 1 of the resin material supply tube 99.
33, and is pressed to the left in the figure.

A U-shaped position detecting rod 145 is attached to the push pad 143, and a switch support rod 147 is attached to the resin supply block 97 in parallel with the resin material supply tube 99. Proximity switches 149 and 151 that perform switching by proximity of a switch sensitive member 153 attached to the tip of the position detection rod 145 are attached to the switch support rod 147 so that the attachment position can be adjusted. Thereby, the push pad 143 and the resin material supply tube 99
The axial position of the piston 133 is monitored.

The forward / backward moving substrate 1 is connected to a moving table 157 of a rodless pneumatic cylinder device 155, and is moved forward and backward by the rodless pneumatic cylinder device 155.

In this embodiment, a cooling jacket 159 is attached to a portion where the injection cylinder member 5 is exposed to the outside on the front side to prevent the resin in the injection cylinder chamber 7 from hardening. ing.

According to the above-described configuration, when the resin is injected into the molding die M, first, the rotary valve 105 is moved to the position shown in FIG.
Alternatively, the pneumatic cylinder device 135 for feeding resin material is driven in the rotating position as shown in FIG.
The piston 133 of each resin material supply tube 99 is pressed leftward in the figure by each of the push rod 141 and the push pad 143, whereby the resin material of each resin material supply tube 99 is pushed to the resin passage 103 and the rotary valve 10.
5. Resin supply port 111 through resin passages 107 and 109
It is further fed into the injection cylinder chamber 7 of the injection cylinder member 5. In addition, the rotary drive shaft 8 is driven by the electric motor 91.
9 is driven to rotate, and the rotation thereof is transmitted to the plunger shaft 63 and the injection screw 11 by a torque transmission type linear motion bearing 87. As a result, they rotate around their own central axis, and the resin material fed into the injection cylinder chamber 7 is moved forward in the injection cylinder chamber 7 by the screw pump action of the screw pump action section 13 of the injection screw 11. That is, it is fed to the mixing screw part 15 by pressure.

Since the mixing screw portion 15 is provided with an axial groove 17 over the entire area in the axial direction, a part of the resin material from each of the resin material supply tubes 99 fed to the mixing screw portion 15 by pressure is partially formed. A plurality of flows are generated by flowing along the screw grooves of the mixing screw portion 15 and the remaining resin material proceeding along the respective axial grooves 17. Then, as they progress through the mixing screw section 15, they merge and separate again. Thus, the mixing and kneading of the resin materials from the respective resin material supply tubes 99 are performed with high efficiency and uniformity.

The mixed and kneaded resin material reaches the tip of the injection screw 11 and presses the seal ring member 23 to the left in the figure.
It flows to the nozzle side of the cylinder chamber 7 through the cutting groove 35 of the screw head member 19 and the screw head member 19.

At this time, the seal ring member 23 does not rotate due to the resistance of the O-ring 37, but only the injection screw 11 and the screw head member 19 rotate.
The seal ring member 23 and the injection screw 11 rotate relative to each other. As a result, the seal ring member 23 is reliably opened, and the gap 29 as the resin passage is reliably secured.

When the resin material is filled in the nozzle side of the injection cylinder chamber 7, the reaction force acts on the injection screw 11 as a rightward force in the drawing, whereby the injection screw 11 and the flanger are connected. The shaft 63 is retracted rightward in the figure. This retreat is performed with low resistance under the guidance of the linear motion bearing 71, and the retreat increases the amount of the rotary drive shaft 89 entering the shaft receiving hole 89,
Even when the flanger shaft 63 and the rotary drive shaft 89 are relatively moved in the axial direction, the rotary drive shaft 8
9 is driven by a torque transmitting linear motion bearing 87 by a drive plunger shaft 63 and an injection screw 1.
1 is transmitted without delay.

Further, at this time, the injection screw 11 may be lightly driven together with the plunger shaft 63 by the pneumatic cylinder device 81 to assist the backward movement of the injection screw 11 to apply a retreat force to the injection screw 11. In this case, the plunger shaft 63 is rotating,
Since the drive arm 75 and the plunger shaft 63 are relatively rotatable by the thrust needle bearing 77, the rotational drive and the axial drive of the plunger shaft 63 are compatible with each other without any trouble.

When a predetermined amount of the resin material is filled in the injection cylinder chamber 7, the injection screw 1
The rotation of 1 and the discharge of the resin material from the resin material supply tube 99 by the pneumatic cylinder device 135 are stopped, and then the forward and backward substrate 1 is moved forward by the rodless pneumatic cylinder device 155. Thereby, the cylinder fixing base 3,
The entirety of the injection cylinder member 5 and the injection screw 11 move forward, and as shown in FIG.
Is in contact with the molding die M, and the nozzle hole 57 is in contact with the molding die M.
Of the sprue S. When the forward / backward moving substrate 1 is further moved forward, the cylinder head member 9 moves forward with respect to the nozzle body 43, whereby the valve seat member 49 is separated from the contact with the spool valve ring 47 and the valve hole is moved. 53 is exposed to the injection cylinder chamber 7, and the injection cylinder chamber 7 communicates with the nozzle hole 57 via the guide hole 55.

Next, the injection screw 11 is driven forward by the pneumatic cylinder device 81. Then, first, due to the pressure of the resin material in the injection cylinder chamber 7, the seal ring member 23 moves backward with respect to the screw head member 19 and is seated on the seal seat surface 25, and the nozzle side and the screw side of the injection cylinder chamber 7 are moved. Communication is interrupted. Further, when the injection screw 11 is driven forward, this acts as a piston, and the forward thrust of the injection screw 11 by the pneumatic cylinder device 81 is converted into a resin material in the injection cylinder chamber 7 into an injection pressure. The resin material in the cylinder chamber 7 is injected from the nozzle hole 57 to the sprue S of the molding die M.

At this time, the resin material in the injection cylinder chamber 7 is filled with the outer periphery of the seal ring member 23 and the injection cylinder member 5.
The backflow leaks backward from the gap between the inner peripheral surface of the injection cylinder and the backflow, but this gap is sealed by the O-ring 37, so that the backflow is avoided. . As a result, pressure loss is eliminated, and a high injection pressure can be obtained. This means
It is particularly useful in the injection molding of a liquid resin having a low viscosity, a high fluidity and a tendency to cause backflow.

In injection molding of a multi-component reaction-curable resin such as silicone rubber, resin passages 107, 109,
If the resin material mixed in the resin supply port 111, the injection cylinder chamber 7, and the like stagnates for a certain period of time or more, this causes a curing reaction. Switching, the washing solvent in the washing solvent tank 129 is flowed from the washing solvent supply port 127 to the resin passages 107 and 109, the resin supply port 111, the injection cylinder chamber 7, and the like, and these are easily washed with the washing solvent. Can be. In this case, since the injection screw 11 is not provided with a dam or the like and has no obstacle,
The cleaning of the injection cylinder chamber 7 with the cleaning solvent is performed well.

[0049]

[0050]

[0051]

In the above, the present invention has been described in detail with reference to specific embodiments. However, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. Some will be apparent to those skilled in the art.

[0053]

As will be understood from the above description, according to the screw for the in-line screw type injection molding apparatus according to the present invention, the resin material is sent to the mixing screw section by the rotation of the screw pump operating section, and the resin material is Some flow along the screw groove of the mixing screw portion, the remaining resin material proceeds along the axial groove, etc., thereby causing a plurality of resin material flows, and they merge as they progress through the mixing screw portion, Since the flow of splitting is repeated, the mixing and kneading of the resin materials are performed efficiently and uniformly without requiring a long screw shaft length irrespective of the mixed liquid mixed resin having a large viscosity difference and the viscosity.

Further, since this screw does not compress and knead the resin material, and has neither a compound portion nor a weir, the required material supply pressure is increased and the cleaning performance in the injection cylinder chamber is deteriorated. Therefore, the required material supply pressure can be reduced as compared with the related art.

These facts make it possible to reduce the size of the in-line screw type injection molding apparatus, and also to make the in-line screw type injection molding apparatus pneumatic by using a fluid pressure cylinder device for pushing in the material. become.

[Brief description of the drawings]

FIG. 1 shows a part of an embodiment in which an in-line screw type injection molding apparatus having a screw for an in-line screw type injection molding apparatus according to the present invention is applied as an injection apparatus for a multi-liquid reaction-curable resin such as silicone rubber. The side view shown by a cross section.

FIG. 2 is a plan sectional view of a screw portion of the in-line screw type injection molding apparatus shown in FIG.

FIG. 3 is a perspective view showing one embodiment of a screw for an in-line screw type injection molding apparatus according to the present invention.

FIG. 4 is a half sectional view showing one embodiment of a screw for an in-line screw type injection molding apparatus according to the present invention.

FIG. 5 is a sectional view taken along the line VV in FIG. 4;

FIG. 6 is an enlarged sectional view showing a closed state of an embodiment of a seal ring portion used in an in-line screw type injection molding apparatus having a screw for an in-line screw type injection molding apparatus according to the present invention.

FIG. 7 is an enlarged cross-sectional view showing the seal ring portion shown in FIG. 6 in an open state.

FIG. 8 is a sectional view taken along the line VII-VII in FIG. 7;

FIG. 9 is a cross-sectional view showing one embodiment of a nozzle device with a valve used in an inline screw type injection molding apparatus having a screw for an inline screw type injection molding apparatus according to the present invention.

FIG. 10 is an enlarged sectional view taken along line XX of FIG. 1;

FIG. 11 is a partial cross-sectional view showing one embodiment of a resin material supply portion used in an inline screw type injection molding apparatus having a screw for an inline screw type injection molding apparatus according to the present invention.

[Explanation of symbols]

 Reference Signs List 7 Injection cylinder chamber 9 Cylinder head member 11 Injection screw 13 Screw pump operating part 15 Mixing screw part 17 Axis groove 19 Screw head member 23 Seal ring member 35 Cut groove 37 O-ring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/17 B29C 45/46-45/63

Claims (1)

(57) [Claims] 1. A screw pump operating section for performing a screw pump operation in an injection cylinder chamber, and a mixing screw section provided forward of the screw pump operating section and having a smaller pitch and a smaller lead angle than the screw pump operating section. An axial groove is provided in the mixing screw portion in the axial direction, and a seal ring member is movable between a tip end of the mixing screw portion and a screw head member attached to the tip end. An O-ring is provided to be fitted and provided on the outer periphery of the seal ring member to seal between the inner peripheral surface of the injection cylinder chamber, and a cut groove is provided on the screw head member, When the seal ring member is moved to the screw head member side, the cut groove and the axial groove are connected with the phase shifted. A screw for an in-line screw type injection molding apparatus, wherein the communication is cut off by contact between end faces when the screw is moved to the mixing screw portion side.