JPS6321394Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to an injection molding machine equipped with a screw that plasticizes and kneads a resin material in a heating cylinder and sends it forward. This relates to a ring valve mechanism that functions as a.

In such a screw-type injection molding machine, the screw serves to plasticize and knead the resin material (hereinafter also referred to as resin) and feed it to the front of the heating cylinder, and also to feed the plasticized resin material to the mold. It also serves as an injection plunger for press-fitting. However, if the screw is used as it is as an injection plunger, a phenomenon occurs in which resin flows backward along the spiral groove of the screw during injection.

In order to prevent this backflow, between the screw body in which the spiral groove is formed and the screw head integrally provided at the tip of the screw body,
A ring valve is installed. Such a ring valve is movable in the direction of the screw axis, and is held on the screw head side by the transfer pressure of the resin due to the rotation of the screw during plasticization, allowing the resin to move forward. At the time of injection, the screw is relatively moved rearward by the injection pressure until it comes into contact with the front end surface of the screw main body, and the spiral groove of the screw serving as the resin passage is closed to prevent the resin from flowing backward.

By the way, the separation distance between the screw body and the ring valve in the screw axis direction when the ring valve is open, in other words, the opening/closing stroke of the ring valve depends on the characteristics of the resin material used in the injection molding machine, especially the plasticity. It should be optimally determined based on the viscosity etc. in the oxidized state. However, in injection molding machines, it is common for the molding resin material to be replaced frequently.

Therefore, in the past, the stroke of the ring valve was selected to match the resin with a medium viscosity. However, the flip side of such flexibility is that the valve stroke is too large for resins with low viscosity. This is because the pressure to move the ring valve to the closed position is generally low for low-viscosity products, so the timing at which the ring valve closes is unstable, which tends to lead to a decrease in the injection amount and a decrease in the injection pressure. On the other hand, it may be possible to set the valve stroke small to be optimal for low-viscosity resin, but this would inhibit the forward movement of plasticized resin against high-viscosity resin even when the valve is open. It becomes easier.

For this reason, it would be very convenient if the stroke of the ring valve could be made smaller in the case of resins with low viscosity, but it would be very convenient to prepare multiple ring valves with different dimensions for this purpose.
It is costly and difficult to replace.

The object of the present invention is to provide a ring valve mechanism that can change the valve stroke depending on the viscosity of the resin material using one ring valve.

In order to achieve this purpose, the present invention has a ring valve provided between the screw body and the screw head of the screw injection molding machine as described above, so that the ring valve is placed in the first phase position with respect to the screw head. and a second phase position, and a screw shaft between the ring valve and the screw body when the ring valve held at each phase position is opened. The distances in the directions were made different.

In this way, by selectively holding the ring valve in either the first phase position or the second phase position depending on the viscosity characteristics of the resin material used for injection molding, different resin materials can be used. A valve stroke suitable for each can be obtained.
For example, the ring valve may be held in a phase position that provides a small valve stroke for low viscosity resin materials.

Being able to select the stroke of the ring valve in this way makes it possible to set the injection amount and injection pressure more stably than in the past, leading to better injection molded products.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In FIG. 1, 2 is a screw, which includes a screw main body 6 in which a spiral groove 4 is formed, and a screw head 8 fixed to the tip of the screw main body 6, and includes a heating cylinder 1.
It is contained within 0. This screw 2 is rotated by a rotary drive device such as a hydraulic motor (not shown), and reciprocated in the front and rear directions by an injection cylinder.
It serves to plasticize and knead the resin material supplied from the hopper while being heated by the external heat source of the heating cylinder 10 and send it out to the front of the heating cylinder 10. It also functions as an injection plunger by forcing the stored plasticized resin into the mold through the nozzle.

A cylindrical ring valve 12 is provided between the screw body 6 and the screw head 8 of the screw 2. This ring valve 12 mainly functions as a backflow prevention valve that prevents the plasticized resin from flowing backward through the spiral groove 4 of the screw 2 during injection.
The screw is fitted onto the inner circumferential surface of the screw body 6 with virtually no gaps, and movement in the axial direction of the screw is allowed, but the limit of backward movement is defined by the front end surface 14 of the screw main body 6. When the rear end surface 16 of the ring valve 12 is in close contact with the ring valve 12, the ring valve 12 has a wall thickness that can close the screw spiral groove 4, which is a resin passage. On the other hand, the limit of forward movement of the ring valve 12 relative to the screw 2 is defined by the screw head 8.

As is clear from FIG. 2, this screw head 8 has a tapered head body 18.
(substantive head) and a small diameter shaft portion 2 concentrically extending rearward from the rear end surface 20 of the head body 18.
2 and a threaded portion 24 following the threaded portion 24, which is screwed into a threaded hole at the front end of the screw body 6. As a result, the head body 18
A wide annular groove is formed with the rear end surface 20 and the front end surface 14 of the screw body 6 as groove side surfaces on both sides, thereby securing a space for arranging the ring valve 12. The width of the annular groove is larger than the width of the ring valve 12 by a certain amount,
Further, the outer diameter of the screw head shaft portion 22 is smaller than the inner diameter of the ring valve 12 by a certain dimension, and the space between the shaft portion 22 and the ring valve 12 forms a part of a resin passage through which resin passes. ing.

Two grooves 26, 26 are formed in the circular outer peripheral surface of the screw head main body 18 in the axial direction. These grooves 26, 26 have groove bottoms on the rear end side facing the shaft portion 22.
The bottom of the groove on the front end side smoothly continues with the outer peripheral surface of the head body 18, as is clear from FIG.
They are placed at symmetrical positions with respect to the axis, that is, at angular intervals of approximately 180 degrees. Note that the grooves 26, 2
The outer circumferential surface of the head between 6 and 6 is flattened to form a spanner engaging surface 28.

Further, the annular rear end surface 20 of the screw head main body 18 is provided with two relatively shallow recesses 30, 30 on one side with respect to the straight line connecting the grooves 26, 26, and another recess 32 on the other side. There are one. The recesses 30, 30 occupy positions equiangularly spaced from each of the grooves 26, 26, and the other recess 32 is located on an extension of a straight line passing through the midpoint between the recesses 30, 30 and intersecting the axis of the screw head 8. It is located. The rear end surface 20, which is symmetrical to the recesses 30, 30 and 32 with respect to the axis of the screw head 8, has a flat surface on one plane. The recesses 30, 30 and 32 having such a positional relationship are
Both have the same depth and are wide enough to reach from the outer circumferential surface of the head body 18 to the outer circumferential surface of the shaft portion 22 inward in the radial direction.

On the other hand, as is clear from FIGS. 4 and 5, the screw head body 18 of the ring valve 12
On the front end surface 34 facing the rear end surface 20, two guide protrusions 36, 36 are protruded at symmetrical positions across the center line. These protrusions 36, 36 can be slidably engaged with the grooves 26, 26, and their engagement defines the phase position of the ring valve 12 around the screw axis, and also allows movement in the axial direction. is allowed. However, even with such engagement, a certain gap is maintained between the inner surfaces of the protrusions 36, 36 and the groove bottoms of the grooves 26, 26, allowing resin to pass therethrough. In other words, the groove bottom sides of the grooves 26, 26 serve as resin passages, and the groove opening sides serve to hold the ring valve 12 substantially only slidably.

Further, on the front end surface 34 of the ring valve 12, protrusions 40, 40 that can fit into the recesses 30, 30 on the screw head 8 side, and a protrusion 42 that can fit into the recess 32 are provided at positions corresponding to the recesses, respectively. It is being These protrusions 40, 4
0 and 42 serve as forward end defining projections that jointly define the forward end position of the ring valve 12 with the screw head 8, and have a length shorter than the guide projections 36 and 36 described above, and are connected to the front end surface 34.
The recesses project from the screw head 8 by the same amount in a direction parallel to the center line, and each recess has a smaller cross-sectional area than the recesses on the screw head 8 side.

As shown in FIG. 6, the projections 36, 36 on the ring valve 12 side are connected to the screw head 8.
The protrusion 4 is engaged with the side grooves 26 , 26 .
The phase positions where 0 and 40 correspond to the recesses 30 and 30, and the protrusion 42 corresponds to the recess 32, respectively, are as follows.
This is the first phase position of the ring valve 12 relative to the screw head 8. In this first phase position, each tip of the protrusions 40, 40 and 42 is in the recess 3.
When the ring valve 12 is in the forward end position and in contact with the bottom surfaces of the screws 0, 30 and 32, the rear end surface 16 of the ring valve 12 and the front end of the screw body 6 are in contact with each other, as shown in FIG. A distance W ₁ exists between the surface 14 and the surface 14 . In other words, this distance W ₁ is the opening/closing stroke of the ring valve 12 at the first phase position.

On the other hand, when the ring valve 12 is at a phase position that is 180 degrees different from the first phase position about the axis of the screw head 8, as shown in FIG. Again, the projections 40, 40 and 42 engage the grooves 26, 26 on the side of the screw head 8, but the protrusions 40, 40 and 42 all fit into the recess 3.
0, 30, and 32, and correspond to the higher flat rear end surface 34 between them, and this position becomes the second phase position of the ring valve 12. When the protrusions 40, 40, and 42 are in contact with the rear end surface 34, and the forward end of the ring valve 12 is defined, as shown in FIG. Rear end surface 1 of 12
6 and the front end surface 14 of the screw main body 6 is
W ₂ , which is the valve opening/closing stroke at the second phase position. That is, the valve stroke (W ₂ ) at this second phase position is smaller than the valve stroke (W ₁ ) at the first phase position.
It becomes smaller by a dimension corresponding to the depth of .

When the plasticizing viscosity of the resin material used for injection molding is medium to high, the ring valve 12 is held at the first phase position where a relatively large valve stroke (W ₁ ) is given. On the other hand, if a resin material with a low plasticizing viscosity is used, it will be used while being held in the second phase position where a small valve stroke (W ₂ ) is obtained. As a result, even when a low viscosity resin material is used, the delay in closing the ring valve 12 when the ring valve 12 should be closed during injection can be improved, making it more accurate and more accurate than before. Stable injection amount,
Injection pressure can be set.

It should be noted that, regardless of whether the ring valve 12 is held in the first or second phase position, in its open state, the plasticized resin flows into the helical groove 4 of the screw body 6.
It passes between the ring valve 12 and the head shaft 22 through the grooves 26, 26, and is allowed to move forward. Forward movement can also be allowed by passing between the screw head 8 and the inner circumferential surface of the heating cylinder.

Furthermore, when exchanging the position of the ring valve 12 between the first phase position and the second phase position,
The engagement between the grooves 26, 26 and the protrusions 36, 36 can be released with the screw head 8 protruding from the heating cylinder 10 and the ring valve 12 brought to the retracted end position as shown in FIG. The screw head 8 may be loosened by the same amount, and then the ring valve 12 may be rotated.

Although one embodiment of the present invention has been described above, it is literally an illustration, and the present invention is by no means to be construed as being limited to this description.

For example, the number, position, shape, etc. of the recess on the screw head 8 side and the corresponding projection on the ring valve 12 side can be selected as appropriate, and when multiple projections are provided, the length of each can be selected as appropriate. Even if the values are different, the depths of the recesses etc. may be made different accordingly.

In addition, the phase difference between the first phase position and the second phase position is not limited to 180 degrees, but can be made smaller. In that case, a third or more phase positions can be further set, and different valve strokes _W1 , _W2 , and
It is also possible to obtain W ₃ ...

On the other hand, in order to make the strokes of the ring valve different, in addition to selectively bringing the protrusion on the ring valve side into contact with the recess on the screw head side or its opening end surface, the relationship can also be reversed, for example. , a plurality of notches extending rearward from the front end surface of the ring valve are formed with mutually different lengths,
On the other hand, it is also possible to provide the screw head with a pin projecting radially outward so that the pin selectively engages with each of the above-mentioned notches.

In addition, it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art, without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an injection molding machine including a ring valve mechanism according to an embodiment of the present invention, showing the valve in the open state at a first phase position. Second
The figure is a partially cutaway side view of the screw head therein, and FIG. 3 is a cross-sectional view taken from FIG. 2. FIG. 4 is a front view of a ring valve that constitutes the main body of the valve mechanism, and FIG. 5 is a sectional view taken along the line -- in FIG. 4. 6 is an explanatory diagram showing the positional relationship between the ring valve and the screw head in the first phase position superimposed on the sectional view of FIG. 3, and FIG. 7 is an explanatory diagram showing the same positional relationship in the second phase position. FIG. FIG. 8 is a diagram showing the valve open state at the second phase position, and is a partial sectional view corresponding to FIG. 1. 9th
The figure shows the valve closed state in the first phase position, and is a partial sectional view corresponding to FIG. 1. 2... Screw, 4... Spiral groove, 6... Screw body, 8... Screw head, 10... Heating tube, 12... Ring valve, 14... Screw main body front end surface, 16... Ring valve rear end surface, 18...
... Head main body, 20 ... Head main body rear end surface, 22
... Shaft portion, 26 ... Groove, 30, 32 ... Recessed portion, 3
4...Front end surface of the ring valve, 36...Guide protrusion, 40, 42...Protrusion for defining the forward end.

Claims (1)

[Scope of utility model registration request] A ring valve is provided between the screw body and the screw head of the screw that plasticizes the resin material and sends it forward, and prevents the plasticized resin material sent forward during injection from flowing backward. The ring valve can be selectively held at a first phase position and a second phase position, and the distance in the screw axis direction between the ring valve held at each phase position and the screw main body is controlled. A ring valve mechanism in an injection molding machine characterized by different features.