JPH0586733B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method and mold for molding plastic cylinders, and relates to a method for molding plastic cylinders, and a method for manufacturing cylinders that require high precision, such as camera lens barrels, using synthetic resin. Products manufactured by molding can generally be used.

[Background technology and its problems]

Traditionally, when products are manufactured by synthetic resin molding, there has been a problem that it is difficult to obtain high precision due to insufficient filling of the resin into the details of the mold.In particular, injection molding of synthetic resins has low cost and production efficiency. It has attracted attention due to its high efficiency, and in recent years, significant improvements have been made in synthetic resin materials and injection molding technology, and it is now being used to manufacture products with complex shapes or requiring precision. However, it is still difficult to mold cylindrical bodies such as camera lens barrels with high precision by injection molding of synthetic resin or the like.

That is, when molding a cylindrical object, it is common to clamp a mold having a cylindrical cavity in the axial direction of the cavity, and fill the cavity by injecting resin from one end of the cavity. Insufficient filling tends to occur at the other end, and it is difficult to precisely mold the side surface of the cylinder. For example, when molding a cylindrical object, it is extremely difficult to mold the cylinder to a high degree of accuracy with a roundness of 30 μm or less, and when forming precision threads on the side of the cylinder, there may be insufficient filling in the details. Therefore, the tips of the threads tend to be damaged, making it almost impossible to form them accurately.

In this way, cylinder bodies that require high precision, such as camera lens barrels, are difficult to mold from synthetic resin, so they are manufactured by conventional cutting of metal materials such as aluminum, which is expensive and slows production. The problem was that efficiency could not be improved.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for molding a plastic cylinder and a mold that can produce a cylinder with high precision.

[Means and actions for solving problems]

The present invention molds a high-precision cylindrical body by filling a cylindrical molding cavity with synthetic resin, pressurizing the filled synthetic resin from the side of the cavity, and filling every detail of the cavity with the synthetic resin. It is.

Therefore, in the present invention, an injection mold having a cylindrical molding cavity inside is clamped in the axial direction of the cavity, and after filling the cavity with molten synthetic resin, before the synthetic resin hardens. The working fluid filled along the sides of the cavity is pressurized to bulge the sides of the cavity into the cavity, and the synthetic resin injected into the cavity is compressed in the radial direction of the cavity, creating a highly precise cylinder. Construct the way to form the body.

Furthermore, the mold used in this method includes a plurality of mold members that form a cylindrical molding cavity with the mold clamping direction as an axis during mold clamping, and the inside of any of the mold members is pressurized. The pressurizing means constitutes a mold having a working liquid that is filled in the vicinity of the cavity inside the mold member along the side surface of the cavity and causes the side surface of the cavity to bulge into the cavity when pressurized.

In the method and mold of the present invention, the synthetic resin filled in the cylindrical molding cavity is solidified within the cavity and molded into a cylinder of a predetermined shape. In its molten state, it is pressurized from the side of the cavity and precisely molded. That is, after filling the synthetic resin, the pressure of the working fluid in the pressurizing means is increased to bulge the side surface of the cavity into the molding cavity.
The synthetic resin in the cavity is compressed in the radial direction by the side surfaces of the cavity, and is also stretched in the axial direction, filling the cavity to the smallest detail. Therefore, the molded cylindrical body is formed with high precision in the shape of the side surface, dimensions in the radial direction, the axial direction, and the like.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings.

The injection mold 10 of this embodiment shown in FIG.
It is attached to an injection molding machine (not shown) and injects synthetic resin into an internal molding cavity 11 to mold a camera lens barrel body having a female thread on the inner peripheral surface with high precision. .

This injection molding die 10 includes a plurality of mold members that form a cylindrical molding cavity 11 having a predetermined shape with the mold clamping direction as an axis when the mold is clamped by the injection molding machine. Cavity block 30, runner plate 40, core block 5
0 and a fixed side mold plate 60, the cavity block 30 is further provided with a temperature adjustment means 70 for adjusting the temperature of the cavity 11, and the core block 50 is provided with a synthetic resin injected into the cavity 11. Processing means 80 for compressing
is provided.

In the detailed structural diagram of FIG. 2, the moving side template 20
is attached to a mold clamping mechanism of an injection molding machine (not shown) and is movable up and down, and a cavity block 30 is in contact with the lower surface of the movable mold plate 20.

A plurality of first hanging rods 21 are hung from the side surface of the lower end of the movable mold plate 20, and these rods 21 slidably pass through the collar-shaped portion 30A at the upper end of the cavity block 30. A cavity lock 30 can be locked at the lower end of the rod 21 via a shock absorbing ring 22 made of rubber or the like. Therefore, the cavity block 30 can be suspended from the movable template 20 via the rod 21, and can accurately abut against the lower surface of the movable template 20 along the rod 21 when pressed from below. has been done. In addition, the moving side template 2
There is a rod 2 between 0 and the cavity block 30.
A coil-shaped pressure spring 23 wound around the mold plate 2 is interposed between the cavity block 30 and the movable mold plate 2.
The rod 21 is biased in a direction away from zero, that is, toward the lower end of the rod 21.

The cavity block 30 consists of an outer block 31 and an inner block 3 fitted together by a warm spring.
2, and this inner block 32
A cavity hole 33 is provided in the center of the inner block 3.
2 is formed in a shape corresponding to the outer shape of the lens barrel cylindrical body from the lower surface side.

The cavity block 30 also includes a temperature adjustment means 7 for adjusting the temperature of the cavity hole 33.
0 is set.

That is, two annular groove-shaped fluid passages 71 are formed on the outer peripheral surface of the inner block 32, and O-rings 72 are provided along both sides of each fluid passage 71 to seal between the passages 71. These fluid passages 71 communicate with an injection hole 73 provided on the right side of the outer block 31 in the figure and a discharge hole 74 provided on the left side of the figure, respectively, so that the temperature regulating fluid is supplied and discharged. It is becoming more and more popular. On the other hand, a temperature sensor 75 is inserted into the right side of the inner block 32 in the figure.
The output signal of No. 5 is taken out through a sensor hole 76 provided in the outer block 31, and is input to a fluid supply device (not shown) that supplies temperature regulating fluid to the injection hole 73. This fluid supply device supplies fluid such as steam, air, hot water, etc. at a predetermined temperature to the fluid passage 71, and adjusts the temperature, flow rate, etc. of the fluid as appropriate based on the temperature detected by the temperature sensor 75, and controls the cavity hole 33. It is designed to adjust the temperature. Here, the fluid passage 71, the injection hole 73, the discharge hole 74, and the temperature sensor 75 constitute a temperature adjustment means 70.

A runner plate 40 is in contact with the lower surface of the cavity block 30. A plurality of second hanging rods 41 are erected on the edge of the runner plate 40, and these rods 41 are slidably provided through the collar-shaped portion 30B at the lower end of the cavity block 30. , and at the upper end of this rod 41 is a shock absorbing ring 42 made of rubber or the like.
It can be locked to the cavity lock 30 via. Therefore, the runner plate 40 can be suspended and supported by the cavity block 30 via the rods 41, and when pressed from below, it moves along the rods 41 and is attached to the cavity block 30.
It is possible to accurately contact the lower surface of 0. Also,
A cavity hole 33 is provided on the upper surface of the runner plate 40.
A plurality of pin gates 43 are provided at positions corresponding to the inner periphery of the runner plate 40 , while a runner 44 communicating with each pin gate 43 is provided on the lower surface of the runner plate 40 .

A core block 50 is fixed to the upper surface of the runner plate 40 with bolts 51. A cavity side surface 52 corresponding to the inner shape of the barrel for the lens barrel is formed on the outer peripheral surface of the core block 50, and a male thread corresponding to the female thread of the barrel is formed on the upper end side of the cavity side 52. A section 53 is provided. This core block 50 can be inserted into the cavity hole 33 of the cavity block 30, and the molding cavity 11 is formed by the gap between the inner peripheral surface of the cavity hole 33 and the cavity side surface 52. It is configured.

The core block 50 also has a molding cavity 1 with a cavity side surface 52 bulging outward.
A pressurizing means 80 for compressing the synthetic resin injected into the container 1 is provided.

That is, the core block 50 has a cavity 8 inside.
1, and this cavity 81 extends from the upper end surface of the core block 50 to the core block 50.
It is formed along the bottom surface and the cavity side surface 52. The piston 8 is inserted into this cavity 81 from above.
A sealing member 83 consisting of a rubber seal and a split ring is interposed between the piston 82 and the inner peripheral surface of the upper end of the cavity 81, and the piston 82 is inserted into the cavity 8 through this sealing member 83.
It is possible to move up and down a predetermined stroke while slidingly contacting the inner circumferential surface of the upper end portion of 1. These cavities 81
A pressurized chamber 84 hermetically sealed by a seal member 83 is provided in the gap between the inner circumferential surface of the piston 82 and the outer circumferential surface of the piston 82.
is formed, and this pressurized chamber 84 is filled with hydraulic oil 85, which is a hydraulic fluid.

The piston 82 has a first oil supply hole 86 that communicates from the top end surface to the bottom surface side, and a second oil supply hole 8 that communicates from the top end surface to the side surface facing the pressurizing chamber 84.
7 are provided, and hydraulic oil 85 is filled into the pressurizing chamber 84 from these oil supply holes 86 and 87.
Oil supply holes 86 and 87 on the upper end surface of the piston 82
The pressurized chamber 84 is hermetically sealed by sealing with a blind plug or the like.

Further, on the upper surface of the cavity block 30, a piston insertion hole 88 is provided which communicates with the cavity hole 33 and has a smaller diameter than the outer diameter of the core block 50 and into which the piston 82 can be inserted. The piston can come into contact with the lower surface of the movable mold plate 20 through the piston insertion hole 88.
Therefore, when the runner plate 40, the cavity block 30, and the movable template 20 are brought into contact with each other in sequence, the piston 82 is pressed by the movable template 20, moves downward against the core block 50, and applies pressure. The hydraulic oil 85 in the chamber 84 can be pressurized. Here, the piston 82, the pressurizing chamber 84
A pressurizing means 80 is constituted by the hydraulic oil 85, and this pressurizing means 80 bulges the cavity side surface 52 into the molding cavity 11 by the hydraulic pressure of the hydraulic oil 85, and the hydraulic oil 85 is injected into the molding cavity 11. The synthetic resin is compressed in the radial direction by the cavity side surface 52.

A fixed side template 60 fixed to an injection molding machine (not shown) is in contact with the lower surface of the runner plate 40. This stationary template 60 is provided with a sprue bush 61 passing through the upper and lower surfaces of the central part, the upper end face of this sprue bush 61 faces the runner 44, and the lower end face is used for the injection molding. The sprue 6 is formed so that it can fit closely with the nozzle of the injection device (not shown) of the machine, and the lower end surface side and the upper end surface side are
2. Therefore, if the nozzle is brought into close contact with the sprue bush 61 from below and the molten synthetic resin is force-fed from the injection device to the nozzle, the synthetic resin will be transferred to the sprue bush 61.
2. It is configured to be injected and filled into the molding cavity 11 via the runner 44 and pin gate 43.

Further, a runner lock pin 63 is passed through the fixed side mold plate 60 from the lower surface side, and the upper end side of this runner lock pin 63 protrudes from the upper surface of the fixed side mold plate 60 into the runner 44, and this protruding portion A groove-shaped undercut portion 64 is formed in the circumferential direction of the
The resin solidified within the runner 44 is fixed onto the stationary template 60 and can be peeled off from within the runner 44.

The contact surface 12 between the cavity block 30 and the runner plate 40 is a so-called parting line (dividing surface), and the contact surface 13 between the run-apart plate 40 and the stationary template 60 is a so-called runner take-out surface. be.

In this embodiment configured as described above, the following operations are performed. The standard operations of this example are mold clamping shown in FIGS. 3A to 3C, injection shown in FIGS. 3D and 4A, and
The compression operations shown in FIGS. E and 4B and the extraction operations shown in FIG. 3F are repeated.

In FIG. 3A, the injection mold 10 is attached to an injection molding machine (not shown), and the mold 10 is opened by the mold clamping mechanism of the injection molding machine. At this time, the cavity block 30 is connected to the movable mold plate 20 via the first hanging rod 21, and the runner plate 4 is connected to the cavity block 30 via the second hanging rod 41.
0 are suspended from each other at predetermined intervals, and the runner plate 40 is held at a predetermined height above the stationary template 6.

Here, when the mold clamping mechanism is operated to lower the movable mold plate 20, as shown in FIG. 3B,
The runner plate 40 is brought into contact with the upper surface of the stationary template 60, and a flow path for the synthetic resin from the sprue 62 to the pin gate 43 via the runner 44 is formed.
Further, as the movable template 20 continues to descend, the cavity block 30 approaches the runner plate 40, and the core block 50 approaches the cavity block 30.
is guided into the cavity hole 33 of.

Thereafter, when the cavity block 30 is brought into contact with the upper surface of the runner plate 40, a molding cavity 11 is formed between the cavity block 30 and the core block 50, as shown in FIG. 3C. At this time, the piston 82 protruding from the upper end of the core block 50 is inserted through the piston insertion hole 88 and protruded to the upper surface side of the cavity block 30.

When the movable template 20 is further lowered, the pressure spring 23 interposed between the movable template 20 and the cavity block 30 is compressed, as shown in FIG. 3D. Due to the biasing force, the contact surface 12 (parting line) between the cavity block 30 and the runner plate 40 and the contact surface 13 (runner removal surface) between the runner plate 40 and the stationary template 60 are pressed into close contact with each other. It is kept in the same condition. Here, the inside of the molding cavity 11 is maintained at a predetermined temperature in advance by the temperature control means 70, and the synthetic resin 91 melted by the injection device (not shown) of the injection molding machine is injected from below onto the sprue.
2 and injected into the molding cavity 11 via the runner 44 and pin gate 43.

At this time, in the molding cavity 11,
As shown in detail in FIG. 4A, molten resin 91 is injected into the cavity 11 from the pin gate 43.
There are minute voids 92 in the corners of the upper end of the molding cavity 11 and in the valleys of the male threaded portion 53 due to insufficient filling.
tends to occur. However, the molding cavity 11 is kept at a predetermined temperature by the temperature control means 70,
The solidification speed of the molten resin 91 is slowed down, making it difficult for insufficient filling due to rapid loss of fluidity to occur. Even if voids 92 are formed in the details, the molten resin is By compressing 91, void 92 is quickly removed.

That is, as shown in FIG. 3E, when the movable mold plate 20 is lowered until it comes into contact with the cavity block 30, the piston 82 of the pressurizing means 80 is pressed by the movable mold plate 20, and the pressure chamber is closed. The hydraulic oil 85 filled in the inside of the molding cavity 1 is pressurized, and the hydraulic pressure of the hydraulic oil 85 moves the cavity side surface 52 into the molding cavity 1.
Expand within 1.

At this time, in the molding cavity 11,
As shown in detail in FIG. 4B, when the piston 82 pressurizes and the hydraulic pressure of the hydraulic oil 85 in the pressurizing chamber 84 increases, the cavity side surface 52 bulges toward the molding cavity 11 side. Therefore, the molten resin 91 in the molding cavity 11 is compressed in the thickness direction, that is, in the radial direction, by the cavity side surface 52, and is also stretched in the axial direction with the compression.
3 etc., every corner of the cavity 11 is filled and the small gaps 92 are removed.

Thereafter, the molten resin 91 is cooled in the cavity 11 and solidified into a highly accurate barrel body 94 having a female threaded portion 93 that corresponds faithfully to the male threaded portion 53. The movable mold plate 20 is raised by moving in the same direction, and the injection mold 10 is opened as shown in FIG. 3F to take out the molded lens barrel cylinder 94.

That is, when the movable mold plate 20 rises, the cavity block 30 is latched to the first hanging rod 21 via the shock absorbing ring 22, suspended, and raised. For this reason, the core block 50
The barrel body 94 for the lens barrel, which is formed around the core block 50, is screwed into the male threaded portion 53 at the female threaded portion 93, and is taken out from the cavity hole 33 together with the core block 50. The barrel body 94 is extracted upward from the core block 50 by manual operation or rotation using a suitable rotating jig, and is extracted horizontally from between the upper end of the piston 82 and the cavity block 30.

When the movable mold plate 20 is further raised, the cavity block 30 is latched to the second hanging rod 41 via the shock absorbing ring 42, and the runner plate 40 is suspended and the upper surface of the fixed mold plate 60 is suspended. separate from At this time, the runner resin 95 that has solidified within the runner 44 is locked to the runner lock pin 63 by the undercut portion 64 and is peeled off from the runner 44, and is manually operated from above the fixed side template 60 together with the solidified portion within the sprue 62. Alternatively, it is peeled off and removed by a discharge device or the like.
Thereafter, the series of operations described above are repeated.

According to this embodiment, the following effects can be obtained.

That is, the pressure means 80 presses the cavity side surface 52.
By expanding the molten resin 91 into the molding cavity 11 and compressing the molten resin 91 injected into the cavity 11 in the radial direction, the molten resin 91 is filled to the smallest details of the molding cavity 11. The body 94 can be molded with high precision, and in particular, sufficient precision can be obtained even when molding the internally threaded portion 93 and the like.

In addition, since the pressurizing means 80 is operated by the hydraulic pressure of the hydraulic oil 85 filled in the pressurizing chamber 84 along the cavity side surface 52, the molten resin 91 in the molding cavity 11 is uniformly pressurized. This allows for uniform and accurate molding all the way to the edges. Particularly in this embodiment in which a cylinder is formed, the circularity of the lens barrel cylindrical body 94 can be increased by making the pressure distribution uniform in the circumferential direction.

Furthermore, by maintaining the inside of the molding cavity 11 at a predetermined temperature with the temperature control means 70, the time until the molten resin 91 injected into the cavity 11 solidifies is extended, and fluidity can be maintained. Insufficient filling during injection can be prevented to a certain extent in advance, and the filling effect of small details due to the compression of the pressurizing means 80 can be promoted, so that higher accuracy can be obtained.

On the other hand, the pressurizing means 80 presses the piston 82 with the movable mold plate 20 as the injection mold 10 is clamped.
Because it operates by pressing the mold 10, there is no need for any other drive source or associated piping, wiring, etc., and the structure of the mold 10 can be simplified, making installation to the injection molding machine and maintenance work easier. etc. is easy.

Further, the cavity side surface 52 by the pressurizing means 80
The bulge can be easily caused by adjusting the amount of hydraulic oil 85 in the pressurizing chamber 84 to adjust the height of the piston 82 when it is not pressed, and by adjusting the amount of movement of the piston 82 when it is pressed. can be adjusted to At this time, the amount of hydraulic oil 85 is controlled by the piston 82.
This can be easily accomplished by supplying and discharging the hydraulic oil 85 through oil supply holes 86 and 87, which are opened on the top surface and are usually sealed with blind plugs or the like.

Furthermore, the injection mold 10 has a moving side template 20.
The molten resin 91 is injected into the molding cavity 11 in a state in which the molding cavity 11 is not in contact with the cavity block 30, that is, in a state in which the molding cavity 11 is not completely closed.
Since the pressing spring 23 is inserted, the cavity block 30 is urged downward, and the contact surfaces 12 and 13 are brought into close contact with each other, thereby preventing the resin 91 from leaking.

Although one embodiment of the present invention has been described above,
The present invention is not limited to the above embodiments.

That is, in the above embodiment, the piston 82 of the pressurizing means 80 protrudes from the upper surface of the core block 50, is inserted through the piston insertion hole 88, and is pressed downward by the movable template 20. The runner plate 40 may be protruded through the runner plate 40 and pressed upward by the stationary template 60. With this configuration, the cavity block 30 and the movable template 20 can be integrated into a single structure to simplify the structure. can do.

Furthermore, the number of pistons 82 is not limited to one, but a plurality may be provided, or one piston may be driven by a plurality of piston rods, and the shape, arrangement, etc. may be changed as appropriate in consideration of interference with other devices. It is subject to change.

Furthermore, the driving of the piston 82 is not limited to the pressing of the movable mold plate 20 accompanying the mold clamping operation.
It may be operated by another hydraulic cylinder or motor. In such a case, the structure can be simplified by integrating the cavity block 30 and the movable template 20, and the molten resin 91 can be applied to the molding cavity 11. During injection, the injection mold 10 can be completely clamped like a normal mold.

On the other hand, the pressurizing means 80 increases the hydraulic pressure of the hydraulic oil 85 filled in the pressurizing chamber 84 by moving the piston 82; 52 may be expanded, and the working fluid is not limited to the working oil 85 but may be another liquid.

Further, although the temperature adjusting means 70 is not particularly necessary for the present invention, by keeping the inside of the molding cavity 11 at a predetermined temperature by the temperature adjusting means 70 and maintaining the fluidity of the molten resin 91 inside the cavity 11, The effect of the pressurizing means 80 can be exhibited more effectively.

Further, in the above embodiment, the cylindrical camera lens barrel body 94 having the female threaded portion 93 was molded by injection molding of synthetic resin, but the cylinder body 94 may have a prismatic shape or may have a fine uneven shape or pattern on the side surface. The shape of the cylinder to be molded is not limited to the above embodiments.

Further, although the pressurizing means 80 is provided in the core block 50, it may be provided in the cavity block 30 so that the inner circumferential surface of the cavity hole 33 bulges into the molding cavity 11 as a cavity side surface. For example, a plurality of pressurizing cylinders filled with hydraulic oil may be arranged circumferentially along the inner peripheral surface of the cavity hole 33, or a cylindrical pressurizing chamber surrounding the cavity hole 33 in the circumferential direction may be provided. In short, a pressurizing means equipped with a working liquid filled along the side surface of the cavity is provided near the molding cavity 11, and the side surface of the cavity is configured to compress the synthetic resin filled inside the cavity in the radial direction. That is to say.

Furthermore, the present invention is not limited to injection molding, but can be widely applied to compression molding or other molding processes in which molten resin is hardened and molded in a closed mold, especially when the speed is high or when the fluidity is low. If applied to injection molding or compression molding, it is effective in resolving insufficient filling in details.

〔Effect of the invention〕

As described above, according to the injection molding method and mold for plastic cylinders of the present invention, the cylinders can be manufactured with high precision using synthetic resin.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a sectional view showing the detailed structure of the embodiment, FIGS. 3A to 3F are schematic sectional views showing the operation of the embodiment, and FIGS. 4A and B are schematic sectional views showing the details of the operation of the embodiment. FIG. DESCRIPTION OF SYMBOLS 10... Injection mold, 11... Molding cavity, 20... Movable side template which is a mold member, 30...
... Cavity block which is a mold member, 40... Runner plate which is a mold member, 50... Core block which is a mold member, 52... Cavity side surface, 60
...Fixed side mold plate which is a mold member, 80 ... Pressure means, 82 ... Piston, 84 ... Pressure chamber, 85 ...
...Hydraulic oil as a working fluid, 91... Molten resin as a synthetic resin, 94... A barrel for a lens barrel as a cylinder.

Claims (1)

[Claims] 1. An injection mold having a cylindrical molding cavity inside is clamped in the axial direction of the cavity, and after filling the cavity with molten synthetic resin, the synthetic resin is cured. The working liquid filled along the side of the cavity is pressurized to bulge the side of the cavity into the cavity, and the synthetic resin injected into the cavity is compressed in the radial direction of the cavity to achieve high precision. A method for forming a plastic cylinder, the method comprising forming a cylinder. 2. A plurality of mold members are provided that form a cylindrical molding cavity with the mold clamping direction as an axis during mold clamping, and a pressurizing means is provided inside one of the mold members, and this pressurizing means 1. A mold for forming a plastic cylindrical body, comprising a working liquid that is filled in the vicinity of the cavity inside the mold member along the side surface of the cavity and causes the side surface of the cavity to bulge into the cavity when pressurized. 3. In claim 2, the pressurizing means includes a piston whose one end is inserted into the mold member in which the pressurizing means is provided and which is slidable in the axial direction of the molding cavity, and a piston that is slidable in the axial direction of the molding cavity. A pressurizing chamber is formed along the side of the cavity near the cavity, and a chamber is sealed inside the pressurizing chamber and is pressurized as the piston is inserted into the mold member, expanding the side of the cavity into the molding cavity. A mold for forming a plastic cylinder body, characterized in that it is equipped with a working fluid to be ejected.