JP6862308B2 - Injection molding screw and injection molding machine - Google Patents

Description

The present invention relates to an injection molding screw (feederless screw) capable of injection molding on a certain amount of material without providing a material supply device, and an injection molding machine provided with the screw.

An injection molding machine that performs injection molding without providing a material supply device is known (see, for example, Patent Document 1). In such an injection molding machine, a predetermined amount of material (for example, resin pellets) is put into a cylinder from a hopper, and a plasticized material is injected from a nozzle to perform molding. A screw for injection molding is rotatably arranged on the cylinder. The screw has a fixed quantity transfer unit (starve feed unit), a supply unit (feed unit), a compression unit (compression unit), and a weighing unit (metering unit). Each of these parts is composed of a screw body and a spirally continuous flight along the outer peripheral surface of the screw body. In the screw main body, the fixed quantity transfer unit, the supply unit, the compression unit, and the measuring unit are arranged in order from the base end connected to the rotary moving device to the tip end. The rotary moving device rotates the screw around the axis of the screw body and linearly moves the screw along the axis.

In injection molding, a predetermined amount of material is charged from the hopper to the fixed quantity transfer section. The charged material is transported forward while being plasticized by the rotation of the screw. Then, the screw regresses (regresses) by being pushed by the conveyed material. When the screw retracts to the weighing completion position, the rotation is stopped. In this state, the screw is advanced (advanced). As a result, the plasticizing material is ejected from the nozzle toward the mold.

The material supplied from the hopper needs to be appropriately replaced according to the type and material of the molded product. At the time of replacement of such a material, work (hereinafter, referred to as purging) is performed to remove the material before replacement (hereinafter, referred to as residual material) remaining in the screw (for example, the spiral groove formed in the screw body by flight). There is a need. In purging, while supplying the material to be replaced and the material for cleaning (hereinafter referred to as the replacement material) from the hopper into the cylinder, the screw is continuously rotated to send the plasticized replacement material forward. And discharge from the nozzle. As a result, the residual material adhering to the screw is extruded by the replacement material.

Japanese Unexamined Patent Publication No. 2016-215473

By the way, in a screw having a fixed quantity transfer section behind the supply section (retracting side of the screw), the material input port (hopper port) covers the range of the maximum screw stroke (maximum advancing / retreating distance of the screw). The cylinder is opened so as to always face the fixed quantity transfer unit while advancing and retreating. That is, the material is charged into the fixed quantity transfer unit from the charging port at both the injection molding and the purging. Further, in the screw, the cross-sectional area (in short, the volume) along the axis of the groove formed between flights is smaller in the fixed quantity transfer section than in the supply section. Therefore, the supply unit is not filled with the replacement material transferred from the fixed quantity transfer unit, and is starved. The filled state is a state in which the grooves between flights are filled with the material (replacement material), and the starvation state is a state in which the grooves between the flights are not filled with the material (replacement material).

Therefore, if the supply unit is starved, for example, if residual material is attached to the pull side of the flight (reverse side of the screw) in the supply unit, even if the replacement material is transferred to the supply unit, the replacement material will be used. There may be voids between the residue and the material. In this case, the removability of the residual material (replaceability with a replacement material) is poor, and it may take time to replace the material.

The present invention has been made on the basis of this, and an object of the present invention is to improve the removability of residual material (replaceability with a replacement material) in a supply unit, and to quickly replace a material. It is an object of the present invention to provide an injection molding screw (feederless screw) and an injection molding machine.

In order to achieve such an object, the screw for injection molding of the present invention is rotatably arranged in a cylinder of an injection molding machine that is charged from a hopper and ejects a plasticized material to mold a molded product. It is possible to advance and retreat in the cylinder within a predetermined maximum stroke range. The screws for injection molding are arranged on the advancing side of the first screw portion where the material is input from the hopper and the screw portion of the first screw portion at the time of injection molding of the molded product, and the material after replacement at the time of material replacement. There comprising been turned from a hopper, and a second screw portion that will be filled by the material after substitution and before the replacement material. The first screw portion and the second screw portion rotate around a linear shaft core, and twist the screw body that moves forward and backward along the shaft core and spirally along the outer peripheral surface of the screw body, respectively. It consists of a screw and a flight. The cross-sectional area along the axis per twist pitch of the flight in the spiral groove formed in the screw body by the flight is smaller in the first screw portion than in the second screw portion. The total length of the first screw portion is shorter than the maximum stroke.

According to the present invention, an injection molding screw (feederless screw) and an injection molding machine capable of improving the removability of residual material (replaceability with a replacement material) and rapidly replacing the material are provided. It can be realized.

The cross-sectional view which shows the structure of the injection molding machine which concerns on one Embodiment of this invention. FIG. 5 is a cross-sectional view showing a state in which the screw is retracted to the weighing completion position (a state in which the screw is retracted within the recommended stroke range) in the injection molding machine of FIG. FIG. 5 is a cross-sectional view showing a state in which the screw is retracted over the maximum stroke during purging in the injection molding machine of FIG. FIG. 3 is a plan view showing an aspect of a spiral groove in a starved state in the screw (second screw portion) of FIG. FIG. 3 is a plan view showing an aspect of a spiral groove in a filled state in the screw (second screw portion) of FIG.

Hereinafter, the injection molding screw (hereinafter, appropriately referred to as a screw) 1 and the injection molding machine 10 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 5.

As shown in FIG. 1, the injection molding machine 10 includes a screw 1, a barrel 2, a heating device 3, a cooling device 4, and a vent mechanism 5.

The barrel 2 has a cylinder 20 inside. The cylinder 20 is configured as a columnar space (hollow) extending straight along the barrel 2. A loading port (hopper port) 22 for the material 23 to which the hopper 21 is connected is provided near the base end of the barrel 2. The input port 22 penetrates from the outer surface 2s of the barrel 2 to the inner peripheral surface 20s of the cylinder 20. The input port 22 is provided at a position where it can face the first screw portion 1a and the second screw portion 1b, which will be described later. As a result, the input port 22 faces the first screw portion 1a during injection molding of the molded product, and faces the second screw portion 1b when the material 23 is replaced (during purging) (details will be described later).

A material 23 for molding a molded product is supplied to the hopper 21. The material 23 supplied to the hopper 21 is charged into the cylinder 20 through the charging port 22. A nozzle 24 communicating with the cylinder 20 is provided at the tip of the barrel 2. The nozzle 24 is configured to be capable of injecting the material 23 (plasticized material 25 shown in FIG. 2) plasticized by the screw 1. As a result, the plasticizing material 25 can be injected out of the cylinder 20 (for example, a mold) through the nozzle 24.

A screw 1 is rotatably arranged in the cylinder 20. The screw 1 extends straight from the base end to the tip end. A coupling 11 is provided at the base end of the screw 1. A rotary moving device (not shown) is connected to the coupling 11. The rotary moving device rotates the screw 1 and moves (advances and retreats) along the linear shaft core 12 in a state where the screw 1 is inserted into the cylinder 20. The screw 1 is capable of advancing and retreating in the cylinder 20 within a predetermined maximum stroke Lm (see FIG. 3) (details will be described later). The rotation direction of the screw 1 (left rotation or right rotation) is the rotation direction when viewed from the base end side of the screw 1.

The barrel 2 is provided with a heating device 3 for heating the barrel 2. As the heating device 3, for example, a heater 31 can be applied. The heater 31 is arranged along the outer surface 2s of the barrel 2. The barrel 2 can be heated by heating the heater 31.

Further, the barrel 2 is provided with a cooling device 4 for cooling the barrel 2. As the cooling device 4, for example, a cooling water passage 41 can be applied. The cooling water passage 41 is piped around the cylinder 20. The barrel 2 can be cooled by flowing cooling water through the cooling water passage 41.

By providing the barrel 2 with the heating device 3 and the cooling device 4 in this way, the heater 31 can be controlled to heat the barrel 2 to a set temperature. As a result, the inside of the cylinder 20 can be heated. Then, when the barrel 2 exceeds the set temperature, cooling water is flowed through the cooling water passage 41 to cool the barrel 2. As a result, the inside of the cylinder 20 can be cooled to the set temperature.

Further, the barrel 2 is provided with a vent mechanism 5. The vent mechanism 5 is configured to be able to exhaust gas components (for example, gas, air, other volatile components, etc.) generated in the cylinder 20 to the outside of the cylinder 20. In the present embodiment, the vent mechanism 5 is provided on the barrel 2 to form the injection molding machine 10, but it is also possible to omit the vent mechanism 5 to form the injection molding machine.

In the present embodiment, the screw 1 is configured to include four screw portions 1a, 1b, 1c, and 1d. In the screw 1, the first screw portion 1a, the second screw portion 1b, the third screw portion 1c, and the fourth screw portion 1a, the second screw portion 1b, and the fourth screw portion 1a, the second screw portion 1b, the third screw portion 1c, and the fourth screw portion 1a, the second screw portion 1b, and the fourth screw portion 1a Screw parts 1d are lined up. The screw 1 advances (forwards) in the direction from the base end to the tip of the barrel 2, and regresses (backward) in the opposite direction (direction from the tip to the base end). That is, the second screw portion 1b is arranged on the advancing side of the screw 1 of the first screw portion 1a (the left side in FIG. 1, hereinafter simply referred to as the advancing side). Similarly, the third screw portion 1c is arranged on the advancing side of the second screw portion 1b, and the fourth screw portion 1d is arranged on the advancing side of the third screw portion 1c.

The first screw portion 1a is a quantitative transfer portion (star feed portion) capable of quantitatively transferring the material 23 charged from the charging port 22 of the barrel 2. The second screw portion 1b is a supply portion (feed portion) capable of continuously supplying the material 23 transferred from the first screw portion 1a. The third screw portion 1c is a compression portion (compression portion) capable of plasticizing the material 23 supplied from the second screw portion 1b. The fourth screw portion 1d is a measuring portion (metering portion) capable of measuring the material 23 plasticized by the third screw portion 1c.

The four screw portions 1a, 1b, 1c, and 1d are configured to include screw main bodies 61, 62, 63, 64 and flights 71, 72, 73, 74, respectively.

The screw bodies 61, 62, 63, 64 are formed along a linear axis 12 from the base end (the end on the coupling 11 side of the screw 1) to the tip (the end on the opposite side of the coupling 11). It's growing. Further, the screw bodies 61, 62, 63, 64 are configured concentrically around the shaft core 12. The screw main body 61, 62, 63, 64 can be rotated around the shaft core 12 by a rotary moving device (not shown), and can be moved forward and backward (forward and backward) along the shaft core 12. Has been done.

The screw main bodies 61, 62, 63, 64 are the first screw main body 61 in the first screw portion 1a, the second screw main body 62 in the second screw portion 1b, and the third screw main body 62 in the third screw portion 1c. The screw main body 73 and the fourth screw main body 64 in the fourth screw portion 1d are provided. The first screw main body 61, the second screw main body 62, and the fourth screw main body 64 have outer peripheral surfaces 61s, 62s, 64s having constant delivery dimensions. That is, these screw bodies 61, 62, 64 have a cylindrical shape. The third screw main body 63 has an outer peripheral surface 63s whose transfer dimension increases from the second screw main body 62 toward the fourth screw main body 64. That is, the third screw body 63 has a truncated cone shape (thick tip shape).

The delivery dimensions (for example, diameter) of the first screw main body 61 and the second screw main body 62 are set to be the same. The transfer dimensions of these screw bodies 61 and 62 are set to be smaller than the transfer dimensions (for example, diameter) of the fourth screw body 64. In other words, the delivery dimension of the fourth screw main body 64 is set to be larger than the delivery dimension of the first screw main body 61 and the second screw main body 62. The delivery dimension (for example, diameter) of the third screw main body 63 is set to be continuously increased from the second screw main body 62 side toward the fourth screw main body 64 side.

In flights 71, 72, 73, 74, the material 23 charged into the cylinder 20 is subjected to the first screw portion 1a, the second screw portion 1b, the third screw portion 1c, and the fourth screw portion 1d in this order. , It is configured to carry continuously. The flights 71, 72, 73, 74 are spirally twisted in the same direction as each other. The twisting direction of the flights 71, 72, 73, 74 may be set, for example, clockwise as in the right-handed screw or counterclockwise as in the left-handed screw. The twisting direction (clockwise or counterclockwise) of the flights 71, 72, 73, 74 is the twisting direction when viewed from the base end side of the screw 1.

FIG. 1 shows flights 71, 72, 73, 74 twisted clockwise. In this case, the rotation direction of the screw 1 (screw main body 61, 62, 63, 64) may be set counterclockwise (counterclockwise) about the axis 12. When the flights 71, 72, 73, 74 are twisted counterclockwise, the rotation direction of the screw 1 (screw body 61, 62, 63, 64) is clockwise (clockwise rotation) about the axis 12. ) Should be set.

Specifically, in the first screw portion 1a, the first flight 71 twisted in a spiral shape is provided on the outer peripheral surface 61s of the first screw main body 61. The twisting direction of the first flight 71 is set clockwise like the right-handed screw. In other words, the first flight 71 is twisted in the direction opposite to the rotation direction of the first screw body 61 (screw 1). The twist pitch of the first flight 71 is constant.

In the second screw portion 1b, a second flight 72 twisted in a spiral shape is provided on the outer peripheral surface 62s of the second screw main body 62. The twisting direction of the second flight 72 is set clockwise as in the right-handed screw. In other words, the second flight 72 is twisted in the direction opposite to the rotation direction of the second screw body 62 (screw 1). The twist pitch of the second flight 72 is constant.

In the third screw portion 1c, a third flight 73 twisted in a spiral shape is provided on the outer peripheral surface 63s of the third screw main body 63. The twisting direction of the third flight 73 is set clockwise like the right-handed screw. In other words, the third flight 73 is twisted in the direction opposite to the rotation direction of the third screw body 63 (screw 1). The twist pitch of the third flight 73 increases from the second screw body 62 side toward the fourth screw body 64 side.

In the fourth screw portion 1d, a fourth flight 74 twisted in a spiral shape is provided on the outer peripheral surface 64s of the fourth screw main body 64. The twisting direction of the fourth flight 74 is set clockwise like the right-handed screw. In other words, the fourth flight 74 is twisted in the direction opposite to the rotation direction of the fourth screw body 64 (screw 1). The twist pitch of the fourth flight 74 is constant.

The twist pitches of the first flight 71 and the second flight 72 are set to be the same and smaller than the minimum pitch of the third flight 73. The twist pitch of the fourth flight 74 is set to be larger than the maximum pitch of the third flight 73.

Further, the flights 71, 72, 73, 74 have a flight width in the direction along the axis 12. The flight width is a thickness along the axis 12 direction of flights 71, 72, 73, 74. The flight width may be the same or different for each flight 71, 72, 73, 74. In the present embodiment, as an example, as shown in FIG. 1, the flight widths W72, W73, and W74 of the second flight 72, the third flight 73, and the fourth flight 74 are the same and the first flight 71. The flight width is set smaller than W71. That is, the flight width W71 of the first flight 71 has a size than the flight width W72 of the second flight 72.

With the screw bodies 61, 62, 63, 64 (screw 1) inserted through the cylinder 20, the distance between the outer peripheral surfaces 61s, 62s, 63s, 64s and the inner peripheral surface 20s of the cylinder 20 is as follows. Is set to. The distance between the outer peripheral surface 61s of the first screw main body 61 and the inner peripheral surface 20s of the cylinder 20 is the same as the distance between the outer peripheral surface 62s and the inner peripheral surface 20s of the second screw main body 62. The distance between the outer peripheral surface 62s and the inner peripheral surface 20s is larger than the distance between the outer peripheral surface 64s and the inner peripheral surface 20s of the fourth screw main body 64. The distance between the outer peripheral surface 63s and the inner peripheral surface 20s of the third screw main body 63 is continuously reduced from the second screw main body 62 side toward the fourth screw main body 64 side.

Spiral grooves 61a, 62a, 63a, 64a are formed in the screw bodies 61, 62, 63, 64 by flights 71, 72, 73, 74. In the first screw main body 61, the cross-sectional area (hereinafter, simply referred to as the cross-sectional area of the groove 61a) S61 along the axis 12 of the groove 61a per the twist pitch of the first flight 71 is constant. Further, in the second screw main body 62, the cross-sectional area (hereinafter, simply referred to as the cross-sectional area of the groove 62a) S62 along the axis 12 of the groove 62a per the twist pitch of the second flight 72 is constant. The cross-sectional area S61 of the groove 61a in the first screw main body 61 is smaller than the cross-sectional area S62 of the groove 62a in the second screw main body 62. Thereby, the transfer amount (supply amount) of the material 23 from the first screw portion 1a to the second screw portion 1b can be limited. Therefore, the material 23 remaining in the groove 62a can be reduced, and the degassing path can be secured. As a result, it is possible to reduce defects (burnt, silver, etc.) in the molded product due to the gas component generated from the material 23.

In order to have such a relationship, as an example in the present embodiment, the first screw portion 1a and the second screw portion 1b are configured as follows. That is, the transfer dimensions (for example, diameter) of the first screw main body 61 and the second screw main body 62 are set to be the same. Further, the twist pitches of the first flight 71 and the second flight 72 are set to be the same. The flight width W71 of the first flight 71 is set to be larger than the flight width W72 of the second flight 72.

As a result, the cross-sectional area S61 of the groove 61a of the first screw main body 61 can be made smaller than the cross-sectional area S62 of the groove 62a of the second screw main body 62. That is, the volume per unit length of the grooves 61a and 62a (twisting pitch of the first flight 71) is smaller in the first screw body 61 than in the second screw body 62. Therefore, the material 23 charged into the cylinder 20 can be quantitatively and stably transferred to the second screw section (supply section) 1b by the first screw section (quantitative transfer section) 1a.

Not limited to the configuration of the present embodiment, the first screw portion 1a and the second screw portion 1b have a groove S61 in cross-sectional area of the groove 61a, with at least one of the following three conditions as an essential condition. The configuration may be smaller than the cross-sectional area S62 of 62a. The first condition is that the transfer dimension of the first screw body 61 (in other words, the depth of the groove 61a) is set from the transfer dimension of the second screw body 62 (in other words, the depth of the groove 62a). Is also small (shallow). The second condition is that the width W71 of the first flight 71 is made larger (wider) than the width W72 of the second flight 72. The third condition is that the twist pitch of the first flight 71 is smaller (narrower) than the twist pitch of the second flight 72.

The operation of the injection molding machine 10 using such a screw 1 will be described. In injection molding, the injection molding machine 10 is in a state where the inside of the cylinder 20 is pulled to a negative pressure through the vent mechanism 5. In this state, the injection molding machine 10 rotates the screw 1 by the rotary moving device. At this time, the screw 1 rotates with its tip close to the nozzle 24. Here, when the material 23 (for example, resin pellets) is supplied to the hopper 21, the supplied material 23 is charged into the cylinder 20 through the charging port 22.

The charged material 23 is quantitatively transferred by the first screw portion 1a. The transferred material 23 is continuously supplied to the third screw portion 1c by the second screw portion 1b. The supplied material 23 is plasticized by the third screw portion 1c. That is, in the third screw portion 1c, the material 23 is melted (plasticized) by being compressed while being heated by the heater 31. Then, the plasticized material 23 (plasticized material 25) is conveyed to the tip of the screw 1 through the fourth screw portion 1d.

At this time, as shown in FIG. 2, the screw 1 is pushed back by the plasticizing material 25 conveyed to the tip of the screw 1. During this time, back pressure is applied to the screw 1. Then, when the screw 1 is retracted to the desired measurement completion position, the rotation of the screw 1 is stopped. At this time, the plasticizing material 25 necessary for making one molded product is stored in the cylinder 20. The measurement completion position is set according to the amount of the plasticizing material 25 determined by the type and size of the molded product (as an example, the position P shown in FIG. 2). When the required plasticizing material 25 is stored, a suck back is performed. That is, after the weighing is completed, the screw 1 is slightly retracted. This makes it possible to prevent material leakage from the nozzle 24.

Next, the non-rotating screw 1 is advanced toward the nozzle 24. That is, the screw 1 is displaced from the position shown in FIG. 2 to the position shown in FIG. As a result, the plasticizing material 25 stored in the cylinder 20 can be injected out of the cylinder 20 (for example, a mold). Then, the mold is cooled. After that, the desired molded product can be obtained by demolding.

Here, the screw 1 can be moved forward and backward within the range of the maximum stroke Lm. FIG. 3 shows a state in which the screw 1 is retracted over the maximum stroke Lm from the position (PF) close to the nozzle 24. That is, the maximum stroke Lm is set as a length (range) capable of advancing and retreating the screw 1 to the maximum, based on the specifications of the injection molding machine 10. For example, assuming that the transfer dimension (diameter) of the screw 1 is D, the maximum stroke Lm is set to a length of about 4.0 D or more and 4.5 D or less.

The delivery dimension (D) of the screw 1 is defined as a diameter dimension including the outermost diameters of flights 71, 72, 73, 74. In the present embodiment, the delivery dimension (D) of the screw 1 is set to a constant (same) dimension over the entire area including the four screw portions 1a, 1b, 1c, and 1d.

Further, in the injection molding machine 10, a recommended stroke is set in addition to the maximum stroke Lm. During injection molding, the screw 1 is moved forward and backward within the recommended stroke range. The recommended stroke is set to a predetermined length (range) shorter than the maximum stroke Lm. The recommended stroke is set to, for example, a length of about 70% to 90% of the maximum stroke Lm. The weighing completion position (P) is set within the recommended stroke range. That is, the screw 1 is retracted from the position close to the nozzle 24 to the measurement completion position (P) at the time of injection within the range of the recommended stroke.

On the other hand, at the time of purging, the screw 1 is retracted from a position close to the nozzle 24 over the maximum stroke Lm (see FIG. 3). The purging is an operation of cleaning the screw 1 when the material 23 is replaced in order to mold a molded product having a different type or material. By purging, the material 23 (hereinafter referred to as residual material) before replacement remaining in the grooves 62a, 63a, 64a (flights 72, 73, 74) of the screw 1 is removed. Specifically, while the material after replacement and the material for cleaning (hereinafter, these are referred to as replacement materials) are put into the cylinder 20 from the hopper 21, the screw 1 is continuously rotated to be a plasticized replacement material. Is sent forward and discharged from the nozzle 24. At this time, the screw 1 does not advance or retreat (advance or retreat). Further, the mold is removed from the nozzle 24. As a result, the residual material adhering to the grooves 62a, 63a, 64a (flights 72, 73, 74) is extruded together with the replacement material. That is, by purging, it is possible to prevent the residual material from remaining attached to the screw 1 and to appropriately replace the material with the replacement material.

The relationship between the inlet (hopper opening) 22 of the barrel 2 and the maximum stroke Lm and the recommended stroke of the screw 1 will be described with reference to FIGS. 2 and 3. During injection molding, while the screw 1 is retracted from the position (PF) close to the nozzle 24 to the weighing completion position (P), the input port 22 is the first screw body 61 (first screw portion 1a). It is always positioned in the range where it can face with. The position (PF) at which the screw 1 is brought close to the nozzle 24 corresponds to the position where the material 23 is started to be charged from the charging port 22 during injection molding. That is, within the range of the recommended stroke of the screw 1, the input port 22 is opened toward the inside of the cylinder 20 so that the center position P22 thereof can face the groove 61a of the first screw portion 1a. In this case, the center position P22 may hang on the edge of the flight 71 of the first screw portion 1a. FIG. 2 shows an example of a mode in which the input port 22 is opened within the range of the recommended stroke.

Further, the input port 22 is the second screw main body 62 (the state shown in FIG. 3) at the time of purging, that is, in a state where the screw 1 is retracted over the maximum stroke Lm from a position (PF) close to the nozzle 24. It is positioned so as to face the second screw portion 1b). That is, in such a state, the input port 22 is opened toward the inside of the cylinder 20 so that the center position P22 thereof can face the groove 62a of the second screw portion 1b. In this case, the center position P22 may hang on the edge of the flight 72 of the second screw portion 1b.

The charging port 22 is arranged in the barrel 22 so as to open as described above (the center position P22 is positioned) during injection molding and purging. As a result, during injection molding of the molded product, the material 23 is charged from the hopper 21 into the first screw portion 1a (specifically, the groove 61a). On the other hand, at the time of purging (when the material 23 is replaced), the material 23 (replacement material) is not the first screw portion 1a but the second screw portion 1b (specifically, the groove thereof) from the hopper 21. It is put into 62a).

Therefore, the total length L1 of the first screw portion 1a is set shorter than the maximum stroke Lm. For example, the total length L1 of the first screw portion 1a is set to a length of 50% or more and 90% or less of the maximum stroke Lm (0.5 Lm ≦ L1 ≦ 0.9 Lm). More preferably, the total length L1 of the first screw portion 1a is set to a length of 70% or more and 80% or less of the maximum stroke Lm (0.7 Lm ≦ L1 ≦ 0.8 Lm).

Another way of thinking is that the total length L1 of the first screw portion 1a is set to be 0.5D or more and 2.0D or less shorter than the maximum stroke Lm. More preferably, the total length L1 of the first screw portion 1a is set to a length shorter than the maximum stroke Lm by 1.0D or more and 1.5D or less. The value of D is the transfer dimension of the first screw portion 1a, that is, the transfer dimension of the screw 1.

In the present embodiment, the total length L1 of the first screw portion 1a is defined as follows. That is, the total length L1 of the first screw portion 1a is on the proximal end side of the second screw portion 1b in the screw 1, and the cross-sectional area of the groove is larger than the cross-sectional area S62 of the groove 62a (in the present embodiment, the groove 61a It is defined as the length of the portion where the cross-sectional area S61) is reduced along the axis 12 direction. In short, the axis 12 directions from the start point (base end side of the screw 1) to the end point (continuous point with the second flight 72) of the groove 61a (in another way, the first flight 71). It is the length along.

According to the present embodiment, by setting the first screw portion 1a to such a length, the following effects can be obtained.

At the time of injection molding of the molded product, the material 23 can be charged from the charging port 22 into the groove 61a of the first screw portion 1a, and at the time of purging (when replacing the material 23), the material 23 (replacement material). Can be charged from the charging port 22 into the groove 62a of the second screw portion 1b.

Therefore, at the time of injection molding of the molded product, the charged material 23 can be quantitatively and stably transferred from the first screw portion 1a to the second screw portion 1b. Therefore, for example, injection molding of a fixed amount of material 23 is possible without separately providing a material supply device.

On the other hand, at the time of purging, the material 23 (replacement material) can be directly charged into the groove 62a of the second screw portion 1b instead of the groove 61a of the first screw portion 1a. For example, when the material 23 (replacement material) is put into the groove 61a of the first screw portion 1a at the time of purging, the material 23 (replacement material) is transferred to the second screw portion 1b. Since the cross-sectional area S62 of the groove 62a is larger than the cross-sectional area S61 of the groove 61a, the groove 62a is not filled with the transferred material 23 (replacement material) and is starved (see FIG. 4). In this case, as shown in FIG. 4, the residual material 26 adhering to the pulling side (reverse side of the screw 1) of the flight 72 in the groove 62a is difficult to remove by the material 23 (replacement material).

In the present embodiment, the material 23 (replacement material) is charged into the groove 62a of the second screw portion 1b to perform purging. Therefore, at the time of purging, the material 23 (replacement material) is charged from the charging port 22 until the groove 62a is filled. The replacement material) can be charged into the groove 62a (see FIG. 5). Since the groove 62a can be filled, as shown in FIG. 5, they can be brought into close contact with each other without forming a gap between the material 23 (replacement material) and the residual material 26. That is, the material 23 (replacement material) and the residual material 26 can be integrated. Thereby, the residual material 26 can be easily removed by the material 23 (replacement material). As a result, the removability of the residual material 26 (replaceability with a replacement material) can be improved, and the material 23 can be quickly replaced.

As described above, in the present embodiment, since the purging performance can be improved, it is possible to prevent the residual material 26 from being mixed with the material 23 (replacement material) to form a molded product. Therefore, according to the injection molding machine 10 using the screw 1, it is possible to improve the quality of the molded product.

Although the embodiment of the present invention has been described above, the above-described embodiment is presented as an example and is not intended to limit the scope of the invention. In addition, the above-mentioned novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

In the above-described embodiment, the flights 71, 72, 73, 74 of the screw 1 are defined as one line (single flight), but the configuration of the screw (flight) is not limited to this. For example, the screw may be configured with subflight between the pitches of flights 71, 72, 73, 74. In addition, the flight may have a multi-row structure.

1 ... Injection molding screw (cylinder), 1a ... 1st screw part, 1b ... 2nd screw part, 1c ... 3rd screw part, 1d ... 4th screw part, 2 ... barrel, 3 ... heating device 4, 4 ... Cooling device, 5 ... Vent mechanism, 10 ... Injection molding machine, 11 ... Coupling, 12 ... Shaft core, 20 ... Cylinder, 21 ... Hopper, 22 ... Input port, 23 ... Material, 24 ... Nozzle, 25 ... Plasticized material, 26 ... Residual material, 61, 62, 63, 64 ... Screw body, 61a, 62a, 63a, 64a ... Groove, 61s, 62s, 63s, 64s ... Outer surface, 71, 72, 73, 74 ... Flight , D ... Cylinder delivery size, L1 ... Overall length of first screw, Lm ... Maximum stroke, P ... Weighing completion position, P22 ... Center position of injection port, PF ... Position where screw is close to nozzle, S61 , S62 ... Groove cross-sectional area, W71, W72, W73, W74 ... Flight width.

Claims (7)

For injection molding, which is rotatably arranged in the cylinder of an injection molding machine that injects a plasticized material that is charged from a hopper and molds a molded product, and can advance and retreat in the cylinder within a predetermined maximum stroke range. Cylinder
A first screw portion in which the material is charged from the hopper during injection molding of the molded product, and
Wherein arranged in the traveling side of the first of the screw of the screw portion, wherein the material after the replacement when replacement of the material is charged from the hopper, Ru is filled by said material after the replacement with the material before replacement With a second screw part,
The first screw portion and the second screw portion are respectively.
It is composed of a screw body that rotates around a linear axis and moves back and forth along the axis, and a flight that is spirally twisted along the outer peripheral surface of the screw body.
The cross-sectional area of the spiral groove formed in the screw body by the flight along the axis per the twist pitch of the flight is smaller in the first screw portion than in the second screw portion. ,
The total length of the first screw portion is shorter than the maximum stroke of the injection molding screw. The screw for injection molding according to claim 1, wherein the total length of the first screw portion is set to a length of 50% or more and 90% or less of the maximum stroke. The total length of the first screw portion is set to a length 0.5D or more and 2.0D or less shorter than the maximum stroke, where D is the transfer dimension of the first screw portion. Item 1. The screw for injection molding according to Item 1. The twist pitch of the flight in the first screw portion is constant,
The twist pitch of the flight in the second screw portion is constant, and the twist pitch is constant.
Said first screw portion, said second injection molding screw according to the flight width of the flight is greater claim 2 or 3 than the screw portion. The injection molding screw according to claim 2 or 3, wherein the delivery dimension of the screw main body in the first screw portion is the same as the delivery dimension of the screw main body in the second screw portion. The injection molding screw according to any one of claims 1 to 5.
With a barrel having the cylinder inside,
The barrel has an inlet for charging the material into the cylinder.
An injection molding machine in which the injection port is arranged so as to face the first screw portion when the molded product is injection-molded and to face the second screw portion when the material is replaced. The slot is
In a state where the screw is retracted over the maximum stroke, the center position of the input port is made to face the second screw portion, and
In a state where the screw is retracted over a stroke shorter than the maximum stroke, the center position is made to face the first screw portion.
The injection molding machine according to claim 6, which is open toward the inside of the cylinder.

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