JP7332370B2 - Injection mold for synthetic resin flange bush - Google Patents

Description

The present invention relates to an injection mold for synthetic resin flange bushings.

Synthetic resin flange bushings have advantages such as no lubrication, light weight, and low cost, and are often used in devices and equipment that are used under relatively loose conditions. As a method for manufacturing a synthetic resin flange bush, for example, a fluororesin flange bush such as BEAREE ARF series (manufactured by NTN) is manufactured by machining a compression molded body. Products manufactured by injection molding such as the BEAREE BRF series (manufactured by NTN) are also commercially available.

As a synthetic resin flange bushing manufactured by injection molding, it is known to form an introduction portion for synthetic resin sent from the introduction gate of the mold below the pressure receiving surface of the flange-shaped receiving surface that receives the thrust load. (See Patent Document 1).

JP 2016-161094 A

The synthetic resin flange bushing of Patent Document 1 has a configuration in which an introduction portion for the synthetic resin sent from the introduction gate is formed below the pressure receiving surface that receives the thrust load of the flange-shaped receiving surface. You don't have to remove the part. For this reason, the area of the pressure receiving surface is not narrowed, and it is possible to suppress an increase in the surface pressure per unit area due to the thrust load on the pressure receiving surface, thereby extending the life of the sliding bearing.

However, with this synthetic resin flange bushing, there is a problem that the precision of the bearing surface must be compromised because a weld, which is an area where the molten resin joins, occurs. Furthermore, there is a concern that the strength of the molded body will be reduced due to the deterioration of the surface smoothness at the weld and the deterioration of the mechanical strength of the weld.

On the other hand, a disk gate is known as an injection molding method that does not generate welds. Since welds do not occur in disk gate injection molding, it is possible to prevent deterioration in strength and surface smoothness due to welds. However, in this injection molding, it is generally necessary to cut the inner diameter of the molding after injection molding. The cutting of the inner diameter part is the removal of the disk gate, and lathe processing is required as a separate process after injection molding, which is a factor in extending the manufacturing time and increasing the cost.

The present invention has been made to address these problems. Injection molding of a synthetic resin flange bushing that can omit the process of removing the disk gate, such as lathe processing after injection molding, while adopting the disk gate. The purpose is to provide molds.

The injection molding die for a synthetic resin flange bushing of the present invention is an injection molding die for a synthetic resin flange bushing in which a flange portion is integrally formed at one end of a tubular portion, the injection molding die being a movable mold. A three-plate mold structure comprising a plate, a fixed mold plate, and a runner stripper plate, wherein the injection mold comprises a cylindrical portion and a flange formed by abutting the fixed mold plate and the movable mold plate. a mold for injection-molding a synthetic resin into a cavity formed by the flange portion through a disk gate provided on the inner periphery of the cavity of the flange portion, and the movable mold plate has a substantially cylindrical shape corresponding to the cavity. The fixed mold plate has a recess and a core pin concentric with the recess and arranged on the center axis of the recess. and a sprue bush disposed on the central axis of the insert and coaxially with the core pin, the outer peripheral shape of the core pin, The sprue bush has the same shape as the outer peripheral shape of the surface facing the core pin, and in a state where the fixed mold plate and the movable mold plate are in contact with each other, the core pin and the sprue bush are interposed between the core pin and the sprue bush. A disc gate is formed, and in the abutting state, the sprue bushing can be retracted from the abutting surface, and the core pin can be advanced to cut the disk gate.

In the abutting state, the core pin advances in the mold closing direction and the sprue bush retreats.

The fixed die plate has limiting means for limiting the retraction distance of the sprue bushing in the abutted state.

The limiting means is a columnar member having a main body portion and a flange portion whose diameter is enlarged from the main body portion, and the fixed mold plate has an accommodating portion for accommodating the limiting means. The limiting means is housed so as to be movable in the mold closing direction in conjunction with the retreat of the sprue bush, and the end surface of the flange portion on the mold closing direction side comes into contact with the housing portion as the limiting means moves. is characterized by limiting the retraction distance of the sprue bushing.

The core pin is advanced at the same time when the runner stripper plate and the stationary mold plate are released.

In the injection mold for the synthetic resin flange bushing of the present invention, a cavity formed by abutting a fixed mold plate and a movable mold plate and comprising a cylindrical portion and a flange portion, and Welding does not occur because it is a mold for injection molding synthetic resin through the provided disk gate. Therefore, it is possible to prevent a decrease in strength and a decrease in surface smoothness due to welding, and the strength uniformity and surface smoothness are excellent. In addition, it is possible to prevent deterioration of the surface smoothness at the gate, which occurs when a limiting gate such as a side gate or a pin gate is used, and the surface smoothness is excellent. Moreover, since it has a 3-plate mold structure, it is possible to separate the molded product and the runner part and take them out, thereby improving the manufacturing efficiency.

Furthermore, the movable mold plate has a substantially cylindrical recess corresponding to the cavity and a core pin arranged on the center axis of the recess, and the fixed mold plate constitutes a part of the cavity facing the recess. An insert having an end face and a sprue bushing arranged on the central axis of the insert and coaxially with the core pin, wherein the outer peripheral shape of the core pin and the outer peripheral shape of the surface of the sprue bushing facing the core pin are the same shape. , in which a disc gate is formed between the core pin and the sprue bushing in the mating state, the sprue bushing can be retracted from the mating surface, and the disc gate can be cut by advancing the core pin. be. That is, since the injection molding die of the present invention can cut the in-mold gate, it is possible to omit the step of removing the disk gate such as lathe processing after injection molding. By omitting the manufacturing process, the manufacturing time can be shortened and the manufacturing cost can be reduced.

The fixed die plate has limiting means for limiting the retraction distance of the sprue bushing in mating conditions. The retreat distance of the sprue bush corresponds to the advance distance of the core pin, and the longer the retreat distance of the sprue bush, the longer the advance distance of the core pin. In this regard, by limiting the retraction distance by the limit means, the forward movement distance of the core pin is also limited, and the load applied to the core pin during forward movement can be reduced.

In addition, the restricting means is accommodated so as to be movable in the mold closing direction in conjunction with the retraction of the sprue bushing. Since the retraction distance of the bush is limited, it is possible to limit the retraction distance while maintaining a simple mold structure.

Moreover, since the core pin is advanced at the same time as the stripper plate and the fixed mold plate are released, it is possible to prevent burrs from being generated at the gate cut portion.

1 is a cross-sectional view showing the structure of an injection mold according to the present invention; FIG. 2 is a partially enlarged view around a disk gate of the mold of FIG. 1. FIG. FIG. 2 is a partially enlarged view around a stop bolt of the mold in FIG. 1; It is a cross-sectional schematic diagram which shows the filling process using the metal mold|die of this invention. It is a cross-sectional schematic diagram which shows the runner part taking-out using the metal mold|die of this invention. It is a cross-sectional schematic diagram which shows the gate cutting process using the metal mold|die of this invention. It is a cross-sectional schematic diagram which shows the mold release process using the metal mold|die of this invention. It is a perspective view which shows one form of a flange bush. FIG. 4 is a perspective view showing another form of a flange bush;

One form of a synthetic resin flange bushing (hereinafter also referred to as a flange bushing) obtained by the injection molding die of the present invention will be described with reference to FIG. FIG. 8 is a perspective view of a flange bush. As shown in FIG. 8, the flange bushing 31 is a substantially cylindrical body having a bearing hole 34 for rotatably supporting a rotating shaft such as a shaft at its radially central portion. The flange bushing 31 includes a cylindrical tubular portion 32 and a flange portion 33 extending radially outward at one end of the tubular portion 32 . An inner peripheral surface 31a forming the bearing hole 34 serves as a radial bearing surface. An end surface 33a of the flange portion 33 (an end surface on the side opposite to the tubular portion 32) contacts an end surface of another member such as a housing and serves as a thrust bearing surface that receives a thrust load.

The size (outer diameter, inner diameter, etc.) of the flange bushing 31 obtained by the injection molding die of the present invention is appropriately set depending on the application. For example, the dimensions of the flange bushing are 10 mm to 60 mm in inner diameter. The outer diameter of the flange portion 33 is 20 mm to 160 mm, and the thickness (length in the axial direction) of the flange portion 33 is 0.2 mm to 8 mm.

The shape of the flange bush is not limited to that shown in FIG. For example, as shown in FIG. 9, a form having a notch portion 35 obtained by notching a part of the outer periphery of the flange portion 33 in a straight line may be employed. The notch 35 has a detent function, and by engaging the notch 35 with the housing or the like, the flange bush can be prevented from rotating relative to the housing. The shape of the outer diameter surface of the flange bushing is not limited to a substantially cylindrical shape, and may be a polygonal shape matching the shape of the housing.

The flange bush injection mold of the present invention is a mold for manufacturing the flange bush. This injection mold will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of the injection mold of the present invention. As shown in FIG. 1, an injection molding die 1 is a three-plate structure die comprising a movable plate 2, a fixed plate 3, and a runner stripper plate 4. As shown in FIG.

In the injection molding die 1, the movable mold plate 2 and the fixed mold plate 3 are brought into contact with each other to form a cavity 5 composed of a cylindrical portion and a flange portion. The cavity 5 has a cylindrical portion cavity 5a (see FIG. 2) corresponding to the cylindrical portion of the flange bushing, and a flange portion cavity 5b (see FIG. 2) corresponding to the flange portion. A disk-shaped disk gate 6 is provided on the inner periphery of the flange cavity, and a synthetic resin is injection-molded through the disk gate 6 . The cavity 5 is formed so that the axial direction of the molded body (flange bush) and the closing/opening direction of the mold are aligned.

In the present invention, the "mold closing direction" is the direction in which the stationary mold plate and the movable mold plate approach the runner stripper plate, which is the right direction in FIG. The "mold opening direction" is the direction in which the stationary mold plate and the movable mold plate separate from the runner stripper plate, and is the leftward direction in FIG. 2 to 7, the right direction in each drawing corresponds to the mold closing direction, and the left direction in each drawing corresponds to the mold opening direction. In this case, the thrust bearing surface of the flange bush is formed by the fixed mold plate 3 and the outer diameter surface of the flange bush is formed by the movable mold plate 2 . The inner diameter surface of the flange bushing is formed by a core pin 7 which is advanceable towards the stationary mold plate 3 .

FIG. 1 shows the injection mold 1 before injection molding, in which each mold is closed. In this case, the movable mold plate 2 and the fixed mold plate 3 are abutted at the parting line PL, and the fixed mold plate 3 and the runner stripper plate 4 are abutted at the abutment surface F. As will be described later, the abutment surface F is open for removal of the runner section after the molding process, and the parting line PL is opened for removal of the flange bushing and disk gate section after the molding process.

In the movable mold plate 2, a substantially cylindrical concave portion corresponding to the cavity is formed in the end face forming the parting line PL. The recess is connected to an annular recess 2a (see FIG. 2) forming part of the flange cavity and a cylindrical recess 2b (see FIG. 2) forming part of the cylindrical cavity. 2). The annular recess 2a forms the flange portion of the flange bush. The movable template 2 also includes a core pin 7 concentric with the recesses (annular recessed portion 2a and cylindrical recessed portion 2b) arranged on the central axis of the recessed portions (annular recessed portion 2a and cylindrical recessed portion 2b), and the core pin 7 7 (on the central axes of the annular recess 2a and the cylindrical recess 2b). The ejector pin 8 is a cylindrical member. A core pin 7 is supported by a core pin plate 20 . The core pin 7 and the core pin plate 20 are in a state in which a load is constantly applied in the mold closing direction to the movable mold side mounting plate (not shown) by the coil spring 21 .

In addition, a plurality of ejector pins 9 are arranged on the movable template 2 for ejecting the molded flange bush (molded body). The ejector pin 9 is housed behind the cylinder cavity (left side in FIG. 1), and an ejector pin 9a whose tip face faces the cylinder cavity and is housed behind the flange cavity (left side in FIG. 1) and its tip and an ejector pin 9b whose face faces the flange cavity. The ejector pins 8 and 9 can be moved forward and backward by an ejector rod of an injection molding machine (not shown). In the present invention, "advance" means advancing in the direction of protruding out of the mold, and "backward" means advancing in the direction of retraction into the mold.

FIG. 2 is a partially enlarged view around the disk gate in the state of FIG. As shown in FIG. 2, the fixed mold plate 3 is arranged flush with the parting line PL, and faces the concave portions (the annular concave portion 2a and the cylindrical concave portion 2b) to form a part of the cavity 5. and a sprue bushing 11 arranged on the central axis of the insert 10 and coaxially with the core pin 7 . The outer diameter of the annular end surface 10a is larger than the outer diameter of the substantially cylindrical recess. That is, part of the end surface 10a contacts the end surface of the movable mold plate 2 in the mold closed state. An end surface 11a of the sprue bushing 11 on the side of the movable template 2 (an end surface facing the core pin 7) and an end surface 10a of the insert 10 are flat surfaces (flush). constitutes part of The end surface 10a forms a thrust bearing surface of the flange bush.

A coil spring 12 is incorporated as an elastic member between the insert 10 and the sprue bushing 11 in the fixed mold plate 3, and the coil spring 12 biases the sprue bushing 11 in the direction away from the parting line PL (mold closing direction). It is That is, the sprue bushing 11 is constantly subjected to a repulsive force against the insert 10 . A runner plate 13 is provided on the fixed template 3 on the side of the runner stripper plate 4 , and the sprue bushing 11 is fixed to the runner plate 13 . The runner plate 13 is provided movably in the mold closing direction with respect to the insert 10 .

As shown in FIG. 1, a first sprue 14 is provided on the runner stripper plate 4 coaxially with the injection direction of the synthetic resin. A runner 15 is provided in the sprue bushing 11 of the fixed mold plate 3 so as to communicate with the first sprue 14 and is provided in the vertical direction of the first sprue 14, and is provided in parallel with the injection direction of the molten resin in communication with the runner 15. A second sprue 16 is provided, respectively. Also, the runner stripper plate 4 is connected to the core pin plate 20 by the side plate 22 .

In the mold closed state of FIG. 2, the tip of the core pin 7 is arranged at a position slightly retracted from the parting line PL. A disk gate 6 is formed between the tip end face 7a of the core pin 7 and the end face 11a of the sprue bushing 11 facing thereto. The outer diameter of the core pin 7 is approximately the same as the outer diameter of the disk gate 6 . The disk gate 6 communicates with the second sprue 16 . Further, the outer peripheral portion of the disk gate 6 communicates with the inner peripheral portion of the cavity 5 over the entire circumference, and the boundary between them serves as the gate port 6a. That is, the disk gate 6 is provided on the inner diameter surface side of the flange portion of the flange bush. In this configuration, the synthetic resin that has flowed into the disk gate 6 spreads radially from the entire circumference of the disk gate 6 and fills the cavity 5 uniformly. Therefore, welds do not occur in molded articles using this injection mold.

In FIG. 2, the position of the tip of the core pin 7 is recessed from PL according to the thickness of the flange portion of the flange bushing, that is, the axial length of the flange portion cavity 5b. The amount of recession of the position of the tip of the core pin 7 from the PL can be equal to or shorter than the thickness of the flange portion. The amount of retreat from PL of the position of the tip surface of core pin 7 is the axial length of gate port 6a.

A flange bushing manufacturing method using the injection mold of the present invention includes at least the following three steps (a) to (c). That is, (a) a molding step of filling a synthetic resin into a cavity formed in an injection molding mold through a disk gate to form a molded body, and (b) a gate cutting step of cutting the gate in the injection molding mold. and (c) a mold release step of opening the mold and taking out the compact.

In the injection mold of the present invention, the outer peripheral shape of the core pin 7 and the outer peripheral shape of the end face 11a of the sprue bushing 11 are the same shape, and when the stationary mold plate 3 and the movable mold plate 2 are in contact with each other, It is characterized in that the sprue bushing 11 can be retracted from the parting line PL, and the disc gate 6 can be cut by advancing the core pin 7 . In this case, since the outer diameter of the core pin 7, the outer diameter of the disk gate 6, and the outer diameter of the end surface 11a of the sprue bushing 11 are substantially the same, the stationary mold plate 3 and the movable mold plate 2 collide with each other. When the core pin 7 is advanced in the mold closing direction in this state, the disk gate 6 is pushed closer to the fixed mold plate 3 than PL, and is fitted to the inner peripheral portion of the insert 10 to be gate cut. In other words, the injection mold of the present invention is a mold capable of gate-cutting the disk gate while the movable mold plate and the fixed mold plate are in contact with each other.

As shown in FIG. 1, the fixed mold plate 3 has stop bolts 17 as limiting means for limiting the retraction distance of the sprue bushing 11 when the fixed mold plate 3 and the movable mold plate 2 are in contact with each other. . The stop bolt 17 will be explained with reference to FIG. FIG. 3 is a partially enlarged view around the stop bolt in the state of FIG. The stop bolt 17 is a columnar member having a body portion 17a and a flange portion 17b having one end enlarged in diameter from the body portion 17a. The stationary template 3 has a housing portion 18 that houses the stop bolt 17 . In this accommodating portion 18, the stop bolt 17 is accommodated so that the flange portion 17b faces the movable mold plate 2 and its axial direction is parallel to the mold closing direction. An end portion 17c opposite to the flange portion 17b is connected to the runner plate 13. As shown in FIG.

In the mold closed state of FIG. 3, the stop bolt 17 is accommodated so as to be movable in the mold closing direction in conjunction with the retraction of the sprue bushing 11 . Specifically, the stop bolt 17 is accommodated with the end surface of the flange portion 17 b on the mold closing direction side separated from the flange surface 18 a of the accommodating portion 18 by a predetermined distance D. That is, the stop bolt 17 is housed in the housing portion 18 with play so that it can move in the mold closing direction. As a result, the stop bolt 17 moves in the mold closing direction in conjunction with the retraction of the sprue bushing 11 and the runner plate 13, and the end surface of the flange portion 17b on the mold closing direction side comes into contact with the flange surface 18a. Retreat is restricted. Note that the predetermined distance D (amount of play) is set to about several millimeters.

Each step of this manufacturing method will be described with reference to FIGS. 4 to 7. FIG. 4 shows the molding process, FIGS. 5 and 6 show the gate cutting process, and FIG. 7 shows the mold releasing process.

(a) Molding process The molding process is a process of filling a molten synthetic resin into a cavity to form a molded body.

The synthetic resin used in the present invention is not particularly limited as long as it is an injection-moldable thermoplastic resin, and can be appropriately employed depending on the conditions of use. Among thermoplastic resins, crystalline resins are preferred. Crystalline resins include, for example, polyamide (PA) resins, polyacetal (POM) resins, polyphenylene sulfide (PPS) resins, polyetheretherketone (PEEK) resins, injection moldable polyimide (PI) resins, and the like. If necessary, the synthetic resin may be blended with a fibrous reinforcing material such as carbon fiber or glass fiber, or a solid lubricant such as PTFE resin or graphite.

As shown in FIG. 4, a molten synthetic resin 19 injected from a nozzle (not shown) of an injection molding machine passes through a first sprue 14, a runner 15, a second sprue 16, and a disk gate 6 into the cavity 5. After filling and holding pressure, the synthetic resin is solidified by cooling for a certain period of time.

(b) Gate cutting process The gate cutting process is a process of cutting the disk gate in the mold. In this step, the disk gate is cut while the movable template 2 and the fixed template 3 are kept in contact with each other.

The gate cutting process will be explained based on FIGS. In this process, the abutment surface F between the runner stripper plate 4 and the fixed mold plate 3 allows the integrally solidified resin of the first sprue, runner, and second sprue (these integrally solidified resins to be collectively referred to as "runner portions") to be taken out. It is opened by a distance (see FIG. 5). As a result, the runner portion 23 is separated from the mold and dropped. At this time, the parting line PL remains closed by a parting lock device (not shown). The structure for separating the runner portion 23 from the mold is based on the general structure of a three-plate mold.

In this step, the core pin 7 is advanced at the same time when the runner stripper plate 4 and the stationary mold plate 3 are released. Specifically, in conjunction with (simultaneously) opening of the abutment surface F between the runner stripper plate 4 and the fixed mold plate 3, the core pin plate 20 is moved by the coil spring 21 to move the core pin 7 in the mold closing direction, that is, in the parting line PL. (See FIG. 6). At this time, the core pin 7 pushes the sprue bush 11 and the runner plate 13 together with the sprue bush 11 and the runner plate 13 in a mold closing direction in a state where the resin filled in the disc gate 6 is sandwiched between the end surfaces 11a of the sprue bush 11 . As a result, the sprue bushing 11 retreats from PL. Further, since the stationary mold plate 3 and the runner stripper plate 4 are released, the space between the runner plate 13 and the insert 10 is opened, and a part of the runner plate 13 protrudes from the end face forming the abutment surface F.

As the sprue bushing 11 and the runner plate 13 retreat, the stop bolt 17 connected to the runner plate 13 also moves in the mold closing direction, and the end surface of the flange portion 17b in the mold closing direction contacts the flange surface 18a. touch. This abutment restricts the retraction of the sprue bushing 11, the opening of the runner plate 13, and the advancement of the core pin 7 by extension. That is, the amount of play of the stop bolt 17 (predetermined distance D in FIG. 3) is substantially the same as the retreat distance of the sprue bushing 11, the release distance of the runner plate 13, and the advance distance of the core pin 7, respectively. It should be noted that the predetermined distance D may be any distance that separates the molded body and the disk gate that are in a connected state, for example, a distance corresponding to the thickness of the cavity 5, or a distance that allows the cavity 5 to be filled with the molten resin. is. If the predetermined distance D is large, a load is applied to the tip portion of the core pin 7 when the gate is cut, and there is a possibility that the core pin will need to be replaced sooner. Therefore, it is desired that the predetermined distance D is several millimeters or less.

In this gate cutting process, the parting line PL is completely constrained by the movable mold plate 2 and the insert 10 having the same inner peripheral dimension as the inner peripheral dimension of the cavity 5, By moving only the disk gate 6 in the mold closing direction by advancing the core pin 7, the compact and the disk gate are moved relative to each other. At this time, a shearing force is applied to the gate opening 6a by the outer peripheral surface of the core pin 7, and as a result, the gate opening 6a is cut from the resin in the cavity 5 by the core pin 7. FIG. The inner diameter surface of the flange bush is formed by cutting the disk gate 6 with the core pin 7 . That is, the inner diameter surface of the flange portion of the flange bushing is formed by the core pin 7 that advances toward the stationary mold plate 3 . In lathe processing, which is a general removal process for disk gates, lathe marks are left along the circumferential direction on the inner diameter surface of the flange or on the end surface near the inner diameter surface. Since the gate is cut by using a lathe, there is no trace left by this lathe processing.

(c) Mold Release Process The mold release process is a process of opening the fixed mold plate and the movable mold plate to take out the compact (see FIG. 7). In this step, the movable mold plate 2 is released from the fixed mold plate 3 in the mold opening direction by releasing the parting lock device. That is, the parting line PL is opened. Immediately after the mold is opened, the ejector pin 8 arranged in the axial center of the core pin 7 and the ejector pin 9 arranged in the movable mold plate 2 are pushed out by the ejector rod and move forward. By this forward movement, the disk gate portion 24 stuck to the tip of the core pin 7 and the flange bushing 31, which is an injection-molded body, are removed from the mold.

After removing the flange bushing 31 and the disk gate portion 24 from the injection mold 1, the space between the movable mold plate 2 and the fixed mold plate 3 and between the fixed mold plate 3 and the runner stripper plate 4 are closed. Injection molding is performed.

Through the steps (a) to (c) described above, the flange bushing 31 as shown in FIG. 8 is manufactured. As described above, the injection mold of the present invention can cut the gate inside the mold, so it is possible to omit the step of removing the disk gate such as lathe processing after injection molding. As a result, the manufacturing process can be simplified, the manufacturing time can be shortened, and the cost can be reduced. In addition, since the disc gate system is used, welds do not occur in the formed flange bushing, preventing deterioration in strength and surface smoothness due to welds.

In the injection mold of the present invention, when the mold is closed, the sprue bushing can be retracted from the parting line PL, and the core pin can be moved forward to cut the disk gate. It is not limited to the mold shown in 3.

In the injection mold for the flange bushing of the present invention, while employing the disk gate, it is possible to omit the process of removing the disk gate such as lathe processing after injection molding, so the manufacturing process is efficient and the manufacturing cost is excellent. It can be widely used as an injection mold for synthetic resin flange bushings.

REFERENCE SIGNS LIST 1 injection mold 2 movable mold plate 2a annular recess 2b cylindrical recess 3 fixed mold plate 4 runner stripper plate 5 cavity 6 disk gate 7 core pin 8 ejector pin (ejection pin)
9 ejector pin (extrusion pin)
REFERENCE SIGNS LIST 10 insert 11 sprue bushing 12 coil spring 13 runner plate 14 first sprue 15 runner 16 second sprue 17 stop bolt (limiting means)
18 housing portion 19 synthetic resin 20 core pin plate 21 coil spring 22 side plate 23 runner portion 24 disk gate portion 31 flange bushing 32 cylinder portion 33 flange portion 34 bearing hole 35 notch portion

Claims (5)

An injection mold for a synthetic resin flange bush in which a flange portion is integrally formed at one end of a cylindrical portion,
The synthetic resin flange bushing has an inner peripheral surface forming a bearing hole as a radial bearing surface, and an axial end surface of the flange portion opposite to the cylindrical portion as a thrust bearing surface that receives a thrust load,
the thrust bearing surface comprises abutting surfaces of the movable mold plate and the fixed mold plate;
The injection mold has a three-plate mold structure comprising the movable mold plate, the fixed mold plate and the runner stripper plate,
The injection molding die includes a cavity formed by abutting the fixed mold plate and the movable mold plate and having a cylindrical portion and a flange portion, and a disk gate provided on the inner peripheral portion of the cavity of the flange portion. It is a mold for injection molding synthetic resin through
The movable mold plate has a cylindrical recess corresponding to the cavity, and a core pin concentric with the recess and arranged on the central axis of the recess,
The fixed mold plate is arranged flush with the abutment surface with the movable mold plate, and has an end face that faces the recess and constitutes a part of the cavity; and a sprue bush coaxially arranged with the core pin,
an outer peripheral shape of the core pin and an outer peripheral shape of a surface of the sprue bushing facing the core pin are the same shape,
The disk gate is formed between the core pin and the sprue bush in the abutting state in which the fixed die plate and the movable die plate are abutted, and in the abutting state, the sprue bushing contacts the abutting surface. can be retracted from, and the disc gate can be cut by advancing the core pin ,
A mold for injection molding of a synthetic resin flange bushing, characterized by having a parting lock device for keeping the abutment surface closed when the disc gate is cut . 2. The mold for injection molding of a synthetic resin flange bushing according to claim 1, wherein said core pin advances in the mold closing direction and said sprue bushing retreats in said contact state. 3. The mold for injection molding of a synthetic resin flange bushing according to claim 2, wherein said fixed mold plate has limiting means for limiting a retraction distance of said sprue bushing in said state of abutment. The restricting means is a columnar member having a body portion and a flange portion having a diameter enlarged from the body portion,
The fixed die plate has an accommodating portion for accommodating the restricting means, and the restricting means is accommodated in the accommodating portion so as to be movable in the mold closing direction in conjunction with the retraction of the sprue bush. 4. The synthetic resin flange bushing according to claim 3, wherein the end surface of the flange portion on the mold closing direction side comes into contact with the accommodating portion as the means moves, thereby limiting the retraction distance of the sprue bushing. injection mold. 5. The injection molding of the synthetic resin flange bushing according to any one of claims 2 to 4, wherein the core pin is advanced at the same time when the runner stripper plate and the fixed mold plate are released. molding die.

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