JP2023024049A - Sprue bush and injection molding device - Google Patents

Abstract

To provide a sprue bush in which a sprue piece can be easily removed from the sprue bush.SOLUTION: A sprue bush according to the invention comprises: an outer side member; and an inner side member. In the outer side member, an outer hole extending in a first direction is provided. In the inner side member, an inner hole that is extending in the first direction and becoming inswept in the first direction is provided, and a plurality of divided bodies which are fitted to the outer hole to become possible to get out from the outer hole, which are arranged around the inner hole to form the inner hole, and which can be separated from each other in a direction orthogonal to the first direction are provided.SELECTED DRAWING: Figure 3

Description

Embodiments of the present invention relate to sprue bushings and injection molding apparatus.

An injection molding apparatus is equipped with a sprue bush that introduces resin supplied from a nozzle of the injection apparatus into a cavity inside a mold. Generally, in the sprue bushing, the sprue hole through which the resin passes is formed in a substantially conical shape that tapers toward the nozzle. Therefore, when the injection molding is completed, a substantially conical sprue piece is formed inside the sprue hole.

JP-A-5-261771

After injection molding is completed, the sprue piece is removed from the sprue bushing as the movable mold moves. However, the frictional force generated between the formed sprue piece and the inner peripheral surface of the sprue hole may make it difficult to remove the sprue piece from the sprue bushing.

One example of the problem that the present invention solves is to provide a sprue bushing and an injection molding apparatus in which the sprue piece can be easily removed from the sprue bushing.

A sprue bushing according to one embodiment comprises an outer member and an inner member. The outer member is provided with an outer bore extending in a first direction. The inner member is provided with an inner hole that extends in the first direction and tapers in the first direction, is fitted in the outer hole so as to be able to escape from the outer hole, and is arranged around the inner hole. a plurality of split bodies that are separated from each other in a direction orthogonal to the first direction to form the inner bore.

FIG. 1 is a side view schematically showing an injection molding apparatus according to the first embodiment. FIG. FIG. 2 is a cross-sectional view schematically showing the mold of the first embodiment. FIG. 3 is a cross-sectional view schematically showing the sprue bushing of the first embodiment. FIG. 4 is an exploded perspective view schematically showing the sprue bushing of the first embodiment. FIG. 5 is a cross-sectional view schematically showing the sprue bushing and sprue piece of the first embodiment. Figure 6 is a schematic cross-sectional view of the outer member, the two separate halves and the sprue piece of the first embodiment; FIG. 7 is a cross-sectional view schematically showing a sprue bushing according to the second embodiment. 8 is a cross-sectional view schematically showing the sprue bushing of the second embodiment along line F8-F8 of FIG. 7. FIG. Figure 9 is a schematic cross-sectional view of the outer member, the two separate halves and the sprue piece of the second embodiment; FIG. 10 is a cross-sectional view schematically showing a sprue bushing according to a modification of the second embodiment.

(First embodiment)
A first embodiment will be described below with reference to FIGS. 1 to 6. FIG. In this specification, basically, the vertically upward direction is defined as the upward direction, and the vertically downward direction is defined as the downward direction. In addition, in this specification, a component according to the embodiment and description of the component may be described with a plurality of expressions. The components and their descriptions are examples and are not limited by the expressions herein. Components may also be identified by names different from those herein. Also, components may be described in terms that differ from the terms used herein.

FIG. 1 is a side view schematically showing an injection molding apparatus 10 according to the first embodiment. As shown in FIG. 1, the injection molding device 10 has an injection device 11 and a mold device 12 . It should be noted that the injection molding apparatus 10 may have other components such as a control device.

The injection device 11 has a cylinder 15 and a hopper 16 . The injection device 11 melts the resin pellets supplied to the hopper 16 by the heat of the heater, and injects them from the nozzle 15a of the cylinder 15 using the rotation of the screw. The injection device 11 injects super engineering plastics, for example. Note that the injection device 11 may inject other materials.

FIG. 2 is a cross-sectional view schematically showing the mold device 12 of the first embodiment. As shown in FIG. 2, the mold device 12 has a fixed mold 21, a movable mold 22, a sprue bushing 23, and a locate ring 24. As shown in FIG. Fixed mold 21 may also be referred to as a cavity. The movable mold 22 may also be referred to as a core.

The movable mold 22 can move in a first direction D1 and a second direction D2 with respect to the fixed mold 21 . The second direction D2 is opposite to the first direction D1. When the mold device 12 is open, the movable mold 22 is separated from the fixed mold 21 in the second direction D2. When the mold device 12 is closed, the movable mold 22 moves in the first direction D1 and contacts the fixed mold 21 . When the movable mold 22 abuts against the fixed mold 21 , a cavity 25 is formed between the fixed mold 21 and the movable mold 22 .

A sprue bushing 23 is attached to the stationary mold 21 . The sprue bushing 23 is provided with a sprue (hereinafter referred to as a sprue hole) 26 . The sprue hole 26 tapers in the first direction D1. The sprue hole 26 communicates with the cavity 25 near the end of the sprue hole 26 in the second direction D2. A locate ring 24 holds the sprue bushing 23 .

The nozzle 15a of the cylinder 15 contacts the sprue bushing 23 during injection molding. The nozzle 15a injects resin into the cavity 25 through the sprue hole 26 from the end of the sprue hole 26 in the first direction D1.

The nozzle 15 a injects resin into the cavity 25 to form the molding Ob and the runner Ru inside the cavity 25 . Further, a sprue (hereinafter referred to as a sprue piece) Sp is formed inside the sprue hole 26 . The runner Ru is located between the molded article Ob and the sprue piece Sp and is connected to the molded article Ob and the sprue piece Sp.

FIG. 3 is a cross-sectional view schematically showing the sprue bushing 23 of the first embodiment. As shown in FIG. 3 , the sprue bushing 23 has a substantially cylindrical shape extending along the central axis Ax of the sprue hole 26 . The central axis Ax extends in the first direction D1 and the second direction D2 in which the movable die 22 moves. In other words, the first direction D1 and the second direction D2 are directions along the central axis Ax. Note that the sprue bushing 23 is not limited to this example.

Axial, radial, and circumferential are defined herein for convenience. The axial direction is the direction along the central axis Ax. The first direction D1 and the second direction D2 are included in the axial direction. A radial direction is a direction orthogonal to the central axis Ax. The circumferential direction is the direction of rotation about the central axis Ax.

FIG. 4 is a perspective view schematically showing an exploded sprue bushing 23 of the first embodiment. The sprue bushing 23 has an outer member 31 and an inner member 32 . The outer member 31 and inner member 32 are made of the same metal material such as stainless steel. Note that the material of the outer member 31 and the material of the inner member 32 may be different.

As shown in FIG. 3, the outer member 31 has an outer cylinder 41 and a mounting flange 42 . The outer cylinder 41 is formed in a substantially cylindrical shape extending along the central axis Ax. The mounting flange 42 protrudes radially from the end of the outer cylinder 41 in the first direction D1 and has a substantially disk shape. The outer cylinder 41 and the mounting flange 42 are integrally formed.

A through hole 51 is provided in the outer cylinder 41 . The through hole 51 extends along the central axis Ax and penetrates the outer cylinder 41 in the axial direction. In other words, the through hole 51 is a space inside the substantially cylindrical outer cylinder 41 . The through hole 51 has an outer hole 52 , a depression 53 and a relay hole 54 . Incidentally, the relay hole 54 may be omitted.

The outer hole 52 extends in the first direction D1 from the end face 41a of the outer cylinder 41 in the second direction D2. In other words, the end of the outer hole 52 in the second direction D2 opens to the end surface 41a. The end surface 41a is an example of an outer surface. The outer hole 52 is a substantially conical hole that tapers in the first direction D1. Note that the outer hole 52 is not limited to this example.

The outer hole 52 is provided concentrically with the sprue hole 26 . The diameter of outer bore 52 is greater than the diameter of sprue bore 26 . The apex angle of the substantially conical outer hole 52 is substantially equal to the apex angle of the substantially conical sprue hole 26 . The vertical angle of the outer hole 52 and the vertical angle of the sprue hole 26 may differ.

The recess 53 is recessed in the second direction D2 from the end face 41b of the outer cylinder 41 in the first direction D1. The shape of the depression 53 corresponds to the shape of the nozzle 15 a of the cylinder 15 . The tip of the nozzle 15a is accommodated in the recess 53 during injection molding.

A relay hole 54 is provided between the outer hole 52 and the recess 53 . The end of the relay hole 54 in the second direction D2 communicates with the end of the outer hole 52 in the first direction D1. An end of the relay hole 54 in the first direction D1 communicates with an end of the depression 53 in the second direction D2.

The relay hole 54 is part of the sprue hole 26 . Therefore, the relay hole 54 is a substantially conical hole that tapers in the first direction D1. The maximum diameter of relay hole 54 is shorter than the minimum diameter of outer hole 52 .

A recess 55 is further provided in the outer cylinder 41 . The recess 55 is recessed from the end face 41 a of the outer cylinder 41 . The recess 55 is formed in a substantially circular shape and arranged concentrically with the outer hole 52 . The diameter of the recess 55 is longer than the maximum diameter of the outer hole 52 . The recess 55 communicates with the outer hole 52 .

Outer cylinder 41 further has inner peripheral surface 41 c of outer hole 52 , bottom surface 41 d of outer hole 52 , inner peripheral surface 41 e of recess 55 , and bottom surface 41 f of recess 55 . The inner peripheral surface 41 c is a substantially conical surface that forms (defines, partitions) the outer hole 52 . The inner peripheral surface 41 c faces the inside of the outer hole 52 . The bottom surface 41d forms the end of the outer hole 52 in the first direction D1 and faces in the second direction D2. The inner peripheral surface 41 e is a cylindrical surface that forms the recess 55 and faces the inside of the recess 55 . The bottom surface 41f forms an end of the recess 55 in the first direction D1 and faces in the second direction D2.

A plurality of mounting holes 57 are provided in the mounting flange 42 . The plurality of mounting holes 57 are arranged at intervals in the circumferential direction. The mounting hole 57 axially penetrates the mounting flange 42 . For example, bolts are attached to the stationary mold 21 through the attachment holes 57 . Thereby, the outer member 31 is attached to the fixed mold 21 . Note that the outer member 31 may be attached to the stationary mold 21 by other methods.

The inner member 32 is fitted in the outer hole 52 so that it can be pulled out from the outer hole 52 . In this embodiment, the inner member 32 can be inserted into and removed from the outer hole 52 through the end of the outer hole 52 in the second direction D2. The following description will describe the inner member 32 fitted in the outer bore 52, unless otherwise specified.

The inner member 32 has an inner cylinder 61 and a flange 62 . The inner cylinder 61 is an example of a cylindrical portion. The inner cylinder 61 is formed in a substantially cylindrical shape extending along the central axis Ax. The flange 62 protrudes radially from the end of the inner cylinder 61 in the second direction D2 and is formed in a substantially disc shape. A radial direction is an example of a direction intersecting with the first direction. The inner cylinder 61 and the flange 62 are integrally formed.

An inner hole 65 is provided in the inner cylinder 61 . The inner hole 65 extends in the axial direction (the first direction D1 and the second direction D2) and penetrates the inner cylinder 61 in the axial direction. In other words, the inner hole 65 is a space inside the substantially cylindrical inner cylinder 61 .

The inner hole 65 is a substantially conical hole that tapers in the first direction D1. Bore 65 is part of sprue bore 26 . The apex angle of the substantially conical inner hole 65 is substantially equal to the apex angle of the substantially conical relay hole 54 . Note that the vertical angle of the inner hole 65 and the vertical angle of the relay hole 54 may be different.

The inner hole 65 is arranged concentrically with the relay hole 54 . By fitting the inner member 32 into the outer hole 52, the end of the inner hole 65 in the first direction D1 communicates with the end of the relay hole 54 in the second direction D2. Thereby, the inner hole 65 and the relay hole 54 form the sprue hole 26 . The inner hole 65 communicates with the cavity 25 .

The inner cylinder 61 has an end face 61a in the second direction D2, an end face 61b in the first direction D1, an inner peripheral face 61c, and an outer peripheral face 61d. The end face 61a is arranged at substantially the same position as the end face 41a of the outer cylinder 41 in the axial direction. The end surface 61 b faces the bottom surface 41 d of the outer cylinder 41 . The end surface 61b abuts on the bottom surface 41d or is slightly separated from the bottom surface 41d in the second direction D2.

The inner peripheral surface 61 c is a substantially conical surface that forms the inner hole 65 . The inner peripheral surface 61c faces the inside of the inner hole 65 . The outer peripheral surface 61d is located on the opposite side of the inner peripheral surface 61c and faces radially outward. The outer peripheral surface 61 d faces the inner peripheral surface 41 c of the outer cylinder 41 . The outer peripheral surface 61d abuts on the inner peripheral surface 41c or is slightly separated from the inner peripheral surface 41c.

Flange 62 fits into recess 55 when inner member 32 is fitted into outer hole 52 . The diameter of flange 62 is, for example, equal to or slightly shorter than the diameter of recess 55 . Therefore, the inner peripheral surface 41 e of the outer cylinder 41 is in contact with the flange 62 or is slightly separated from the flange 62 . A bottom surface 41 f of the outer cylinder 41 is in contact with the flange 62 .

As shown in FIG. 4, the inner member 32 is divided into multiple pieces. In this embodiment, the inner member 32 is halved and includes two halves 71 . In addition, the inner member 32 may include three or more divided bodies 71 .

The inner member 32 is divided along the central axis Ax. For example, the inner member 32 is provided with two dividing grooves 72 . The dividing groove 72 extends in the axial direction and is provided from the end of the inner member 32 in the first direction D1 to the end in the second direction D2. In other words, the dividing groove 72 opens to the end surface 61 a and the end surface 61 b of the inner cylinder 61 . Note that the dividing groove 72 may extend in a direction different from the axial direction.

The inner member 32 is divided into a plurality of division bodies 71 by providing the plurality of division grooves 72 in the inner member 32 . The plurality of divided bodies 71 can be separated from each other in the radial direction. A radial direction is an example of a direction perpendicular to the first direction. Note that the plurality of divided bodies 71 may be separated from each other in other directions as long as they can be separated from each other in the radial direction.

The division groove 72 is provided between two adjacent division bodies 71 . The division groove 72 may be closed by two adjacent division bodies 71 contacting each other. In other words, the dividing grooves 72 are not limited to spaces.

The two dividing grooves 72 are provided at approximately equal intervals in the circumferential direction. Therefore, the two dividing grooves 72 spread along one plane along the central axis Ax, dividing the inner member 32 into two divided bodies 71 having substantially the same shape. Note that the interval between the two dividing grooves 72 is not limited to this example. Also, the shapes of the two divided bodies 71 may be different from each other.

Each of the multiple divided bodies 71 has a portion of the inner cylinder 61 and a portion of the flange 62 . That is, each of the plurality of divided bodies 71 has a portion of the end surface 61a, a portion of the end surface 61b, a portion of the inner peripheral surface 61c, and a portion of the outer peripheral surface 61d. A portion of the outer peripheral surface 61d is an example of the outer peripheral surface.

When the inner member 32 is fitted in the outer hole 52 , the split members 71 are combined together to form the inner member 32 . In this case, the width of the division groove 72 is, for example, 30 μm or less. Note that the width of the dividing groove 72 is not limited to this example. The width of the dividing groove 72 is the distance between two adjacent divided bodies 71 .

A plurality of divided bodies 71 combined with each other are arranged circumferentially around the inner hole 65 to form the inner hole 65 . That is, parts of the inner peripheral surface 61c included in the plurality of divided bodies 71 are combined with each other to form the inner peripheral surface 61c of the inner cylinder 61. As shown in FIG. The inner peripheral surface 61 c forms the inner hole 65 .

Injection molding by the injection molding apparatus 10 of this embodiment will be partially described below. Injection molding by the injection molding apparatus 10 is not limited to the method described below. First, a plurality of segments 71 are assembled to form the inner member 32 . The inner member 32 is then fitted into the outer hole 52 .

Next, the movable mold 22 contacts the fixed mold 21 to form the cavity 25 . Cavity 25 communicates with sprue hole 26 of sprue bushing 23 . Note that the divided body 71 may be inserted into the outer hole 52 by being pushed by the movable die 22 and assembled as the inner member 32 inside the outer hole 52 .

The nozzle 15 a of the cylinder 15 of the injection device 11 is then inserted into the recess 53 of the outer member 31 and abuts the sprue bushing 23 . The nozzle 15 a injects resin into the cavity 25 through the sprue hole 26 . Thereby, a sprue piece Sp is formed in the sprue hole 26 .

A holding pressure acts on the sprue piece Sp until the molded article Ob, runner Ru, and sprue piece Sp are solidified. Therefore, the sprue piece Sp pushes the inner peripheral surface 61c of the inner cylinder 61, which is the inner peripheral surface of the sprue hole 26, radially outward. Therefore, the sprue piece Sp pushes the inner cylinder 61 radially outward. The inner peripheral surface 41c of the outer cylinder 41 supports the inner cylinder 61 pushed by the sprue piece Sp, and restricts the separation of the plurality of divided bodies 71 of the inner cylinder 61 from each other.

FIG. 5 is a sectional view schematically showing the sprue bushing 23 and the sprue piece Sp of the first embodiment. Next, the movable mold 22 is separated from the fixed mold 21 and the mold device 12 is opened. Since the sprue piece Sp pushes the inner peripheral surface 61c, a frictional force is generated between the sprue piece Sp and the inner peripheral surface 61c. Furthermore, since the inner cylinder 61 pushed by the sprue piece Sp pushes the inner peripheral surface 41c, a frictional force is generated between the inner cylinder 61 and the inner peripheral surface 41c.

Generally, the coefficient of friction between resin and metal is higher than the coefficient of friction between metal and metal. Also, the sprue piece Sp filled in the sprue hole 26 by injection molding adheres to the inner peripheral surface 61c. On the other hand, between the inner peripheral surface 41c of the outer cylinder 41 and the outer peripheral surface 61d of the inner cylinder 61, a gap may partially occur due to processing accuracy and distortion, for example. Therefore, the coefficient of friction between the sprue piece Sp and the inner peripheral surface 61c is higher than the coefficient of friction between the inner cylinder 61 and the inner peripheral surface 41c.

Furthermore, the inner peripheral surface 41c of the outer cylinder 41 and the outer peripheral surface 61d of the inner cylinder 61 are, for example, surface-treated to reduce the surface roughness, or provided with a substance such as grease or coating that reduces the coefficient of friction. Friction coefficient is reduced. Note that the inner peripheral surface 41c of the outer cylinder 41 and the outer peripheral surface 61d of the inner cylinder 61 are not limited to this example.

Due to the difference in frictional force, the inner cylinder 61 is pulled out from the outer hole 52 in the second direction D2 substantially integrally with the sprue piece Sp. The inner cylinder 61 is separated from the inner peripheral surface 41 c of the outer cylinder 41 by being at least partially removed from the outer hole 52 .

FIG. 6 is a cross-sectional view schematically showing the outer member 31, the two separated split bodies 71, and the sprue piece Sp of the first embodiment. Next, as shown in FIG. 6, the two split bodies 71 are separated from each other substantially in the radial direction. As a result, the inner hole 65 is enlarged to create a gap between the split body 71 and the sprue piece Sp. That is, the two divided bodies 71 are separated from the sprue piece Sp.

When the divided body 71 is separated from the sprue piece Sp in the substantially radial direction, the friction generated between the divided body 71 and the sprue piece Sp is greater than when the divided body 71 moves substantially in the axial direction with respect to the sprue piece Sp. power is small. Therefore, the divided body 71 can be easily separated from the sprue piece Sp.

As described above, the sprue piece Sp is removed from the sprue bushing 23 without remaining inside the sprue bushing 23 . Next, the molded product Ob, runner Ru, and sprue piece Sp are removed from the movable mold 22 . Injection molding by the injection molding apparatus 10 is thus completed. Since the sprue piece Sp does not remain inside the sprue bushing 23, the injection molding apparatus 10 can continuously mold the molded product Ob without interrupting the injection molding.

In the injection molding apparatus 10 according to the first embodiment described above, the outer member 31 is provided with the outer hole 52 extending in the first direction D1. The inner member 32 is provided with an inner hole 65 that extends in the first direction D1 and tapers in the first direction D1, and includes a plurality of divisions 71 . The plurality of divided bodies 71 can be arranged around the inner hole 65 to form the inner hole 65 and can be separated from each other in a direction perpendicular to the first direction D1. For example, in injection molding, resin is supplied to the cavity 25 through the bore 65 of the inner member 32 to form the sprue piece Sp inside the bore 65 . When the holding pressure in injection molding is high, the sprue piece Sp applies pressure to the inner member 32 in a direction crossing the first direction D1. This pressure may generate a strong frictional force between the sprue piece Sp and the inner member 32 when the sprue piece Sp is about to come out of the sprue bushing 23 in the second direction D2. However, in the present embodiment, the inner member 32 can be removed from the outer hole 52 of the outer member 31 and the plurality of divided bodies 71 can be separated from each other in the direction perpendicular to the first direction D1. By separating the plurality of division bodies 71 forming the inner hole 65 from each other in the direction perpendicular to the first direction D1, the plurality of division bodies 71 expand the inner hole 65 and the sprue formed in the inner hole 65. It is separated from the piece Sp. As a result, the sprue bushing 23 of the present embodiment suppresses the generation of frictional force when removing the sprue piece Sp from the sprue bushing 23 , and the sprue piece Sp can be easily removed from the sprue bushing 23 . Moreover, the sprue bushing 23 of the present embodiment eliminates the need to reduce the holding pressure in injection molding, and can suppress quality deterioration of the molded product Ob.

When the inner member 32 is fitted in the outer hole 52, the distance between two adjacent divided bodies 71 is 30 μm or less. As a result, the sprue bushing 23 of the present embodiment can prevent the resin inside the inner hole 65 from entering the gap (dividing groove 72 ) between two adjacent divided bodies 71 .

The outer member 31 has an end face 41a where the end of the outer hole 52 opens in the second direction D2. The outer member 31 is provided with a concave portion 55 recessed from the end surface 41a. The inner member 32 has an inner cylinder 61 and a flange 62 . An inner hole 65 is provided in the inner cylinder 61 . The flange 62 protrudes from the end of the inner cylinder 61 in the second direction D2 in a direction crossing the first direction D1, and fits in the recess 55 when the inner member 32 is fitted in the outer hole 52 . When the fixed mold 21 and the movable mold 22 are combined and clamped, the movable mold 22 pushes the flange 62 , so that the inner member 32 can be easily fitted into the outer hole 52 . Furthermore, each of the plurality of split bodies 71 forming the inner hole 65 has a portion of the inner cylinder 61 and a portion of the flange 62 . By fitting the flange 62 and the concave portion 55, the plurality of divided bodies 71 are brought into close contact with each other, and the inner hole 65 can be stably formed.

The outer member 31 and the inner member 32 are made of metal. As a result, the frictional force generated between the outer member 31 and the inner member 32 is reduced compared to the case where one of the outer member 31 and the inner member 32 is made of resin or ceramic. Therefore, the sprue bushing 23 of this embodiment allows the inner member 32 to be easily removed from the outer hole 52 .

The outer member 31 and inner member 32 are made of the same material. Thereby, the coefficient of thermal expansion of the outer member 31 and the coefficient of thermal expansion of the inner member 32 are substantially the same. Therefore, the sprue bushing 23 of the present embodiment can suppress the occurrence of stress in the outer member 31 and the inner member 32 due to the difference in coefficient of thermal expansion.

(Second embodiment)
A second embodiment will be described below with reference to FIGS. 7 to 10. FIG. In the following description of the embodiments, constituent elements having functions similar to those already explained may be assigned the same reference numerals as the constituent elements already explained, and further explanation may be omitted. In addition, a plurality of components with the same reference numerals may not all have common functions and properties, and may have different functions and properties according to each embodiment.

FIG. 7 is a cross-sectional view schematically showing a sprue bushing 123 according to the second embodiment. FIG. 8 is a cross-sectional view schematically showing the sprue bushing 123 of the second embodiment along line F8-F8 of FIG.

The sprue bushing 123 of the second embodiment has an outer member 131 and an inner member 132 . The inner member 132 includes two split bodies 171 . The sprue bushing 123, the outer member 131, the inner member 132, and the splits 171 are identical to the corresponding sprue bushing 23, the outer member 31, the inner member 32, and the splits of the first embodiment, unless otherwise described below. It has substantially the same shape and function as 71.

As shown in FIG. 8, two grooves 181 are provided on the inner peripheral surface 41c of the outer cylinder 41 of the second embodiment. A cross section of the groove 181 orthogonal to the central axis Ax is formed in a substantially trapezoidal shape that tapers inward in the radial direction. Note that the shape of the groove 181 is not limited to this example.

As shown in FIG. 7, the groove 181 extends substantially axially. The approximate axial direction in which the groove 181 extends is the direction from the end of the outer hole 52 in the first direction D1 toward the end of the outer hole 52 in the second direction D2. In this embodiment, the grooves 181 may extend in other directions as long as they are different from the circumferential direction.

The length of the groove 181 in the axial direction is shorter than the length of the outer cylinder 41 in the axial direction. An end 181a of the groove 181 in the first direction D1 is separated from the end face 41b of the outer cylinder 41 in the first direction D1. Furthermore, the end 181b of the groove 181 in the second direction D2 is separated from the end face 41a of the outer cylinder 41 in the second direction D2. The end of the groove 181 in the first direction D1 may open to the end face 41b of the outer cylinder 41 together with the end of the outer hole 52 in the first direction D1.

A protrusion 182 is provided on each of the two split bodies 171 of the second embodiment. The protrusion 182 is provided on part of the outer peripheral surface 61 d of the inner cylinder 61 included in the split body 171 . The protrusion 182 protrudes radially outward from the outer peripheral surface 61d.

The cross section of the projection 182 orthogonal to the central axis Ax has, for example, a shape similar to the cross section of the groove 181 and is smaller than the cross section of the groove 181 . That is, the cross section of the protrusion 182 perpendicular to the central axis Ax is formed into a substantially trapezoidal shape that tapers inward in the radial direction. Note that the shape of the projection 182 is not limited to this example.

The protrusion 182 fits into the groove 181 . The length of the protrusion 182 in the axial direction is shorter than the length of the groove 181 in the axial direction. Therefore, the protrusion 182 and the divided body 171 provided with the protrusion 182 are movable along the groove 181 .

The minimum width of groove 181 is shorter than the maximum width of protrusion 182 in the circumferential direction. Therefore, the protrusion 182 can be prevented from being removed from the groove 181 in the radial direction. The protrusion 182 is formed in a shape and size that can fit into the groove 181 by being tilted, for example.

The grooves 181 and the projections 182 that fit together limit the separation of the plurality of split bodies 171 from the inner peripheral surface 41 c of the outer cylinder 41 . Note that the divided body 171 can be separated from the inner peripheral surface 41c by a predetermined distance.

FIG. 9 is a cross-sectional view schematically showing the outer member 131, the two separated split bodies 171, and the sprue piece Sp of the second embodiment. The inner member 132 is movable along the groove 181 between a first position P1 shown in FIG. 7 and a second position P2 shown in FIG.

As shown in FIG. 7, the inner member 132 is fitted in the outer hole 52 at the first position P1. Furthermore, the protrusion 182 is spaced apart from the end 181b of the groove 181 in the second direction D2. The protrusion 182 may abut on the end 181a of the groove 181 in the first direction D1, or may be spaced apart from the end 181a.

At the second position P2, the inner member 132 is partially out of the outer hole 52, as shown in FIG. In other words, a portion of inner member 132 is located inside outer bore 52 and another portion of inner member 132 is located outside outer bore 52 .

Furthermore, at the second position P2, the protrusion 182 abuts the end 181b of the groove 181 in the second direction D2. The end 181b restricts further movement of the projection 182 and the divided body 171 provided with the projection 182 in the second direction D2. The protrusion 182 is spaced from the end 181a of the groove 181 in the first direction D1.

Injection molding by the injection molding apparatus 10 of the second embodiment will be partially described below. Injection molding by the injection molding apparatus 10 is not limited to the method described below. First, the movable mold 22 contacts the fixed mold 21 to form the cavity 25 .

Next, the nozzle 15 a of the cylinder 15 of the injection device 11 is inserted into the recess 53 of the outer member 131 and abuts the sprue bushing 123 . The injection device 11 injects resin into the cavity 25 through the sprue hole 26 . Thereby, a sprue piece Sp is formed in the sprue hole 26 .

Next, the movable mold 22 is separated from the fixed mold 21 and the mold device 12 is opened. The inner member 132 moves in the second direction D2 substantially integrally with the sprue piece Sp. However, in the second embodiment, the grooves 181 and the protrusions 182 limit the separation of the split body 171 from the inner peripheral surface 41 c of the outer cylinder 41 . Therefore, the divided bodies 171 are separated from each other in the radial direction while moving along the inner peripheral surface 41c. As a result, the two split bodies 171 enlarge the inner hole 65 by themselves and separate from the sprue piece Sp. The split body 171 is held on the outer member 131 by grooves 181 and projections 182 that fit together.

As described above, the sprue piece Sp is removed from the sprue bushing 123 without remaining in the sprue hole 26 . Next, the molded product Ob, runner Ru, and sprue piece Sp are removed from the movable mold 22 . Injection molding by the injection molding apparatus 10 is thus completed.

When the next injection molding is performed, the movable mold 22 comes into contact with the split body 171 partially removed from the outer member 131 while moving toward the fixed mold 21 . The movable die 22 contacts the flange 62 of the split body 171 and pushes the flange 62 in the first direction D1.

The split body 171 is inserted into the outer hole 52 by being pushed by the movable die 22 . When the divided body 171 reaches the first position P1, the flange 62 comes into contact with the bottom surface 41f of the outer cylinder 41. As shown in FIG. At this time, the two divisions 171 abut each other to form the inner member 132 . In this manner, the movable mold 22 can move the inner member 132 to the first position P1 without the operator having to assemble the two divided bodies 171 . Since the operator does not need to assemble the two divided bodies 171, the injection molding apparatus 10 can continuously mold the molded product Ob without interrupting the injection molding.

FIG. 10 is a cross-sectional view schematically showing a sprue bushing 223 according to a modification of the second embodiment. As shown in FIG. 10, the modified sprue bushing 223 has an outer member 231 and an inner member 232 . The inner member 232 includes multiple divisions 271 . The sprue bushing 223, the outer member 231, the inner member 232, and the splits 271 are identical to the corresponding sprue bushing 23, the outer member 31, the inner member 32, and the splits of the first embodiment, except as otherwise described below. It has substantially the same shape and function as 71.

A groove 281 is provided on each outer peripheral surface 61 d of the two divided bodies 271 . The groove 281 extends from the end of the outer hole 52 in the first direction D1 toward the end of the outer hole 52 in the second direction D2.

The groove 281 has a main groove 281a and two side grooves 281b. The main groove 281a is recessed radially inward from the outer peripheral surface 61d. The side groove 281b is recessed in a substantially circumferential direction from the inner surface of the main groove 281a at a position spaced apart from the outer peripheral surface 61d.

Two protrusions 282 are provided on the inner peripheral surface 41 c of the outer cylinder 41 . The protrusion 282 fits into the groove 281 . The protrusion 282 and the outer member 231 provided with the protrusion 282 are movable along the groove 281 relative to the inner member 232 .

The protrusion 282 has a main portion 282a and two engaging portions 282b. The main portion 282a protrudes radially inward from the inner peripheral surface 41c. The engaging portion 282b protrudes substantially in the circumferential direction from the side surface of the main portion 282a at a position spaced apart from the inner peripheral surface 41c.

The main portion 282 a fits into the main groove 281 a of the groove 281 . The engaging portion 282b fits into the side groove 281b of the groove 281. As shown in FIG. The maximum width of the projections 282 in the circumferential direction is longer than the minimum width of the grooves 281 in the circumferential direction. Therefore, the grooves 281 and the projections 282 that fit together restrict the separation of the plurality of divided bodies 271 from the inner peripheral surface 41 c of the outer cylinder 41 .

As described above, the grooves 181 and 281 of the second embodiment are provided on one of the inner peripheral surface 41c of the outer cylinder 41 and the outer peripheral surface 61d of the divided bodies 171 and 271. As shown in FIG. Moreover, the protrusions 182 and 282 are provided on the other of the inner peripheral surface 41c and the outer peripheral surface 61d.

In the injection molding apparatus 10 of the second embodiment described above, the outer member 131 has an inner peripheral surface 41c facing the inside of the outer hole 52 . Each of the plurality of divided bodies 171 has an outer peripheral surface 61d facing the inner peripheral surface 41c. One of the inner peripheral surface 41c and the outer peripheral surface 61d extends in a direction from the end of the outer hole 52 in the first direction D1 toward the end of the outer hole 52 in the second direction D2 opposite to the first direction D1. A groove 181 is provided. A protrusion 182 is provided on the other of the inner peripheral surface 41 c and the outer peripheral surface 61 d and fits into the groove 181 so as to be movable along the groove 181 . Thereby, the outer member 131 and the plurality of divided bodies 171 can move relatively along the grooves 181 . Therefore, the sprue bushing 123 of this embodiment can stabilize the relative positions of the outer member 131 and the plurality of segments 171 during repeated injection molding.

The outer hole 52 tapers in the first direction D1. The grooves 181 and the projections 182 that fit together limit the separation of the plurality of split bodies 171 from the inner peripheral surface 41c. As a result, the plurality of divided bodies 171 move in the second direction D2, thereby separating from each other along the inner peripheral surface 41c of the outer hole 52 that tapers in the first direction D1. Therefore, the sprue bushing 123 of the present embodiment can automatically separate the plurality of divided bodies 171 from the sprue piece Sp by moving the plurality of divided bodies 171 in the second direction D2. Furthermore, the sprue bushing 123 can prevent the split body 171 from falling off from the outer member 131 .

The inner member 132 is movable between a first position P1 and a second position P2. At the first position P1, the inner member 132 is fitted into the outer hole 52 and the projection 182 is separated from the end 181b of the groove 181 in the second direction D2. At the second position P2, the inner member 132 is partially removed from the outer hole 52, and the projection 182 contacts the end 181b of the groove 181 in the second direction D2. In other words, the end 181b of the groove 181 prevents the inner member 132 from passing beyond the second position P2 and coming out of the outer hole 52. As shown in FIG. Therefore, the sprue bushing 123 of this embodiment can prevent the inner member 132 from completely coming out of the outer hole 52, and thus injection molding can be easily repeated.

In the above description, inhibition is defined as, for example, preventing an event, action or effect from occurring or reducing the degree of an event, action or effect. Also, in the above description, the restriction is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range. .

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Injection molding apparatus 21... Fixed type 22... Movable type 23, 123, 223... Sprue bushing 25... Cavity 31, 131, 231... Outer member 32, 132, 232... Inner member 41a... End surface , 41c... inner peripheral surface 52... outer hole 55... concave portion 61... inner cylinder 61d... outer peripheral surface 65... inner hole 71, 171, 271... divided body 181, 281... groove 182, 282... Protrusion, D1...first direction, D2...second direction, P1...first position, P2...second position.

Claims (9)

an outer member provided with an outer bore extending in a first direction;
An inner hole that extends in the first direction and tapers in the first direction is provided, is fitted in the outer hole so as to be able to escape from the outer hole, and is arranged around the inner hole. and comprising a plurality of segments spaced apart from each other in a direction orthogonal to the first direction;
a sprue bushing comprising a When the inner member is fitted in the outer hole, the distance between two adjacent ones of the plurality of divided bodies is 30 μm or less,
The sprue bushing of Claim 1. The outer member has an inner peripheral surface facing the inside of the outer hole,
Each of the plurality of divided bodies has an outer peripheral surface facing the inner peripheral surface,
A groove extending in one of the inner peripheral surface and the outer peripheral surface in a direction from the end of the outer hole in the first direction toward the end of the outer hole in a second direction opposite to the first direction. is provided,
The other of the inner peripheral surface and the outer peripheral surface is provided with a protrusion that fits into the groove so as to be movable along the groove.
A sprue bushing according to claim 1 or claim 2. the outer hole tapers in the first direction;
The grooves and the protrusions that fit into each other restrict the separation of the plurality of divided bodies from the inner peripheral surface.
The sprue bushing of Claim 3. The inner member is fitted in the outer hole and has a first position where the protrusion is spaced from the end of the groove in the second direction, and a first position where the protrusion is partially removed from the outer hole and the protrusion is positioned at the second position. a second position abutting the end of the groove in the direction of
A sprue bushing according to claim 3 or claim 4. The outer member has an outer surface that opens at the end of the outer hole in a second direction opposite to the first direction, and is provided with a recess recessed from the outer surface,
The inner member includes a tubular portion provided with the inner hole therein, and a portion protruding from an end portion of the tubular portion in the second direction in a direction intersecting the first direction, and the inner member includes: a flange that fits into the recess when fitted into the outer hole;
A sprue bushing according to any one of claims 1 to 5. the outer member is made of metal,
the inner member is made of metal,
A sprue bushing according to any one of claims 1 to 6. 8. The sprue bushing of claim 7, wherein said outer member and said inner member are made from the same material. fixed type and
a movable mold that is movable with respect to the fixed mold and forms a cavity between the fixed mold and the fixed mold by abutting against the fixed mold;
a sprue bushing according to any one of claims 1 to 6;
and
the outer member is attached to the stationary mold;
the inner hole communicates with the cavity;
Injection molding equipment.

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