JPH0312530B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention involves moving a movable platen using a predetermined hydraulic cylinder to open and close a mold between it and a fixed platen. The present invention relates to an injection compression molding machine that compresses the resin material by injecting and filling a predetermined resin material into a product cavity and then compressing the resin material by compressing the mold.

(Prior technology) By moving the movable platen, the mold is opened and closed between it and the fixed platen, and the mold is pressed with even greater force, and resin material is injected and filled into the product cavity. However, although injection molding machines for molding such resin materials have been widely used,
Such injection molding machines have had the problem that sufficient dimensional accuracy cannot be ensured due to shrinkage due to cooling and solidification of the resin material filled in the product cavity.

Therefore, in anticipation of shrinkage due to cooling and solidification of the resin material, the mold is opened for a predetermined compression stroke, and the resin material is injected and filled into the product cavity.
By tightening the mold and compressing the resin material,
Injection compression molding machines that prevent deformation caused by shrinkage of resin materials and can produce molded products with high dimensional accuracy have been proposed in recent years (for example,
-Refer to Publication No. 167140, etc.).

(Problems to be Solved by the Invention) However, in conventional injection compression molding machines, the device for opening the mold by the compression stroke is generally mechanical, so the device itself is large-scale. When installing this into an injection molding machine that has been widely used in the past, a large-scale design change was required, and this also made the molding machine expensive. Moreover,
There were also problems such as the time required for the action to be long and the production efficiency to be reduced.

Furthermore, as mentioned above, if the resin material is injected and filled with the mold opened by a predetermined compression stroke, the volume of the product cavity is too large, and a large shock pressure is generated during injection, resulting in a high yield. In some cases, distortion occurred around the molded product.

On the other hand, Japanese Unexamined Patent Application Publication No. 148055/1983,
164709, Utility Model Application Publication No. 153213, etc.,
In a mold for injection compression molding, a spring is built into the mold, and by the biasing force of the spring,
A structure is disclosed in which a predetermined compression stroke is prevented from occurring between a fixed mold and a movable mold, but it is difficult to ensure the amount of compression stroke by the biasing force of such a spring. However, depending on the weight of the mold and the arrangement form, etc.
There is a big problem that the amount of deflection of the spring fluctuates, and the amount of compression stroke changes accordingly, resulting in variations in the amount of compression. Only one value can be adopted, and there are inherent problems such as the need to replace the spring itself in order to set the compression stroke amount to various desired values.

(Means for Solving the Problems) The present invention has been made to solve these problems, and its gist is as follows:
The movable platen is moved by the first hydraulic cylinder to open and close the mold between it and the fixed platen, while a predetermined resin material is injected and filled into the product cavity formed in the mold. , an injection compression molding machine that compresses the resin material by compressing the mold, which (a) is fixed to either the movable platen or the fixed platen, and is configured to supply a predetermined liquid from the pressurized liquid supply means; a second hydraulic cylinder that is supplied with pressure fluid to advance a piston and cause an abutment rod connected to the piston to protrude outward by a predetermined length;
a contact member fixed to the other of the movable plate or the fixed plate and brought into contact with the contact rod of the second hydraulic cylinder; and a contact member that is detachable from the corresponding contact member or the second hydraulic cylinder. a spacer member that is removably attached to define a compression stroke of the mold, the resin being injected into the product cavity by supplying pressurized fluid to the second hydraulic cylinder; In cooperation with the mold opening force caused by the material injection pressure, the movable platen is moved through the abutting member and the second hydraulic cylinder against the mold closing force of the first hydraulic cylinder. (b) a push-back means is provided for pushing back in a direction away from the stationary platen to open the mold by a predetermined compression stroke determined by the spacer member; further, (c) based on the detection by the detection means, the movable platen is brought closer to the fixed platen, and the mold is clamped to compress the resin material. The reason is that a compressing means for compressing is provided.

The pressure of the pressure liquid supplied from the pressure liquid supply means to the push-back means varies depending on the pressure-receiving area of the push-back means, but when the injection pressure of the resin material is not acting on the movable platen, The mold is held in a closed state by the mold closing force of the first hydraulic cylinder, but when the injection pressure of the resin material acts on the movable platen, it resists the mold closing force of the first hydraulic cylinder. The size is set to push back the movable platen.

(Operation and Effects of the Invention) In such an injection compression molding machine, while the mold is closed by the first hydraulic cylinder, the resin material is injected into the product cavity formed in the mold. When the injection pressure of the resin material is applied to the movable platen after being injected and filled, the mold opening force due to this injection pressure and the push-back means (which is supplied with pressure liquid at a predetermined pressure from the compression supply means) Due to the action of the push-back force of the second hydraulic cylinder, the contact member, and the spacer member, the movable platen
Via the contact member and the second hydraulic cylinder, it is pushed back in the direction away from the fixed plate against the mold closing force of the first hydraulic cylinder, and is opened in the mold and the product cavity is opened. As the volume increases, more resin material is filled into the product cavity.

And in this way the movable plate is pushed back,
When the closed mold is opened by a predetermined compression stroke by the spacer member of the push-back means in anticipation of contraction as the resin material cools and solidifies, this is detected. The compression means is actuated based on the detection, and the movable platen is brought close to the fixed platen again, compressing the mold in which the product cavity is filled with resin material. , compressing such resin material.

That is, the injection compression molding machine of the present invention has the following features:
By providing a push-back means to which pressure liquid is supplied from the pressure-liquid supply means, the push-back force of the push-back means and the mold opening force due to the injection pressure of the resin material cooperate,
The movable platen is configured to be pushed back from the fixed platen, and compared to the conventional method of mechanically pushing back the movable platen, the device for this purpose is simpler and more compact, making it easier to install on injection molding machines. At the same time, it is possible to significantly reduce the cost of such an injection compression molding machine.

Moreover, the push-back means according to the present invention is composed of a second hydraulic cylinder, an abutment member, and a spacer member, and the compression stroke amount is accurately regulated by the spacer member. , unlike a conventional structure that utilizes the biasing force of a spring, there is no variation in the compression stroke amount, and therefore an effective injection compression molding operation can be realized, and furthermore, such a spacer member can be replaced. This allows the compression stroke amount to be freely and easily set to an appropriate size.

In addition, by injecting and filling the product cavity with resin material, the movable platen is gradually pushed back through the abutment member that abuts each other and the abutment rod of the second hydraulic cylinder. As a result, compared to injecting resin material with the mold open in advance, the shock pressure during injection is relaxed, there is no risk of distortion around the molded product, and dimensional accuracy is improved. Excellent high quality molded products can be obtained.

Moreover, as mentioned above, since there is no need to open the mold prior to injection of the resin material, the resin material can be injected immediately after the mold is closed by the first hydraulic cylinder, and the mold is held in a predetermined position. When the detection means detects that the compression stroke has been opened, the mold is compressed based on this, so the time required for the series of operations in the mold closing process, injection process, and compression process is shortened. becomes shorter, improving production efficiency.

(Example) Next, in order to clarify the present invention more specifically, an example of the present invention will be described in detail based on the drawings.

In FIG. 1, reference numeral 10 denotes a movable platen to which a movable mold 12 is fixed, and is slidably supported by tie bars 14 arranged parallel to each other in the front-rear direction. The front end (the right end in FIG. 1) of the tie bar 14 is fixed to a fixed plate 18 to which a fixed mold 16 is fixed, while the rear end is fixed to a support plate 20. This support plate 20 has
A first hydraulic cylinder 22 is fixed as a main cylinder, and its piston 24 is mounted on a movable platen 10.
is connected to. In addition, such a hydraulic cylinder 2
Liquid chambers 26 and 28 are formed in the interior of the piston 24 before and after the piston 24, and pressure liquid is supplied from passages 30 and 32, respectively, to separate and separate the movable platen 10 from the fixed platen 18. The molds 12 and 16 are opened and closed by moving toward each other.

Further, between the movable platen 10 and the fixed platen 18, a pair of spacing devices 34 are provided as push-back means for pushing back the movable platen 10 in a direction away from the fixed platen 18.
and 36 are arranged. These spacing devices 3
4 and 36 are configured in exactly the same way,
Hereinafter, only the spacing device 34 will be explained, and detailed explanation of the spacing device 36 will be omitted.

The spacing device 34 includes a second hydraulic cylinder 3 fixed to the surface of the fixed platen 18 on the side facing the movable platen 10.
8 and a contact member 40 screwed onto the movable platen 10. As is clear from the enlarged view of FIG. 2, the hydraulic cylinder 38 includes a piston 44 fitted in a housing 42 fixed to the fixed platen 18 so as to be movable in a direction parallel to the moving direction of the movable platen 10. The piston 44 has a
An abutting rod 46 whose tip protrudes from the housing 42 toward the abutting member 40 is integrally provided. Further, liquid chambers 48 and 50 are formed in the housing 42 before and after the piston 44, and by supplying pressurized liquid into the liquid chamber 50 through a passage 52, the contact rod 46 is pushed out, and The liquid in the liquid chamber 48 is discharged to the outside through a passage 54. In addition, the housing 42
A lid body 56 is fixed to the tip of the contact rod 4.
A sealing member 58 for sealing between the housing 42 and the housing 42 is sandwiched between the housing 42 and the housing 42 .

On the other hand, as is clear from the enlarged view of FIG. 3, the abutting member 40 is screwed into a threaded member 60 having a male thread formed on its outer circumferential surface, with a spacer 62 interposed between the distal end surface of the threaded member 60. contact block 64
It is equipped with The screw member 60 is screwed into a screw hole 66 formed at a position facing the abutting rod 46 of the movable platen 10, and can be rotated via a tool engaging portion 68 provided at its rear end. As a result, the bolt 72 of the lock nut 70 is screwed into the movable platen 10, so that it is fixed to the movable platen 10 so as not to be movable. . Further, the abutment block 64 can also be attached to and detached from the screw member 60 by rotationally operating the abutment block 64 through its tool engaging portion 74, and a plurality of types of spacers 62 having different plate thicknesses t can be attached to and detached from the screw member 60.
can be changed to an appropriate one as needed.

The abutment member 40 is attached to the hydraulic cylinder 22 in a state in which the spacer 62 is removed and the abutment block 64 is completely tightened to the screw member 60.
When pressure liquid is supplied to the liquid chamber 28 of the hydraulic cylinder 3 and the movable platen 10 moves forward to close the molds 12 and 16, the front end surface of the contact block 64 contacts the hydraulic cylinder 3.
Pressure fluid is supplied to the liquid chamber 50 of No. 8, and the piston 44 becomes immovable with respect to the movable platen 10 at a position where it just contacts the tip end surface of the contact rod 46 held at the protruding position located at the forward end. Fixed. Therefore, when the spacer 62 is attached to this, when the movable platen 10 is moved forward by the hydraulic cylinder 22, the contact block 64 of the contact member 40
The contact rod 46 of the hydraulic cylinder 38 brings the molds 12 and 16 into contact with each other at a position where the molds 12 and 16 are opened by a thickness of t from the mold closed state.

A hydraulic circuit 76 shown in FIG. 1 is connected to these hydraulic cylinders 22 and 38. The pressure fluid circuit 76 includes a pump 80 that pumps up hydraulic fluid from the tank 78 and pumps it.
Piping 84 connecting the pump 80 and the switching valve 82 ; Piping 86 connecting the switching valve 82 and each passage 30 and 32 of the hydraulic cylinder 22, respectively.
and 88; a pipe 92 connecting the pipe 84 and the switching valve 90; the switching valve 90 and the hydraulic cylinder 3;
The tank 78 is configured to include pipes 94 and 96 that connect the passages 52 and 54 of the tank 78, respectively; and a pipe 98 that connects the switching valves 82 and 90 with the tank 78.

The switching valve 82 operates in a forward drive state in which the movable platen 10 is moved forward by connecting the pipes 84 and 88, 86 and 98, respectively, and in a backward drive state in which the movable platen 10 is moved backward by connecting the pipes 84 and 86 and 88 and 98, respectively. On the other hand, the switching valve 90 can be switched between a pressure fluid supply state in which the pipes 92 and 94, 96 and 98 are connected and the abutting rod 46 is protruded, and a pressure fluid supply state in which the pipes 94, 96 and 98 are connected respectively. When connected, they can be switched to a pressurized fluid discharge state that allows the abutment rod 46 to retreat.

The switching valve 90, pump 80, etc. maintained in this pressure fluid supply state constitute a pressure fluid supply means for supplying pressure fluid to the hydraulic cylinder 38. Note that there is no particular need to provide the piping 96 connected to the passage 54 of the hydraulic cylinder 38, and the liquid chamber 48 may be an atmospheric chamber communicating with the atmosphere. Although not shown, the piston 24 reaches the forward or backward end when pressure fluid is supplied to the hydraulic cylinder 22, and the piston 44 reaches the forward end when pressure fluid is supplied to the hydraulic cylinder 38. A relief valve is provided to return the pressurized liquid to the tank 78 when the hydraulic pressure in the circuit becomes higher than necessary.

In addition, a dial gauge 100 as a detection means is attached to the mold 12, and detects the distance d when the mold 12 and the mold 16 are opened from the closed state, The distance: d
When the pressure reaches a predetermined compression stroke, a confirmation signal is output to a control device (not shown), thereby switching the switching valve 90 from the pressure fluid supply state to the discharge state.

Next, the operation of the injection compression molding machine configured as above will be explained.

First, the switching valve 82 is kept in the backward drive state to keep the movable platen 10 in the retreated position, and the switching valve 90 is kept in the pressure fluid supply state to move the contact rod 46.
is held in the protruding position, the switching valve 8
2 is switched to the forward driving state, the movable platen 10 is moved forward together with the piston 24. When the distance d between the molds 12 and 16 becomes t, the thickness of the spacer 62, the contact block 64 of the contact member 40 fixed to the movable platen 10 is fixed to the fixed platen 18. The hydraulic cylinder 38 abuts against the abutment rod 46, but the closing force of the hydraulic cylinder 22 is greater than the pushing back force of the hydraulic cylinders 38 of the two spacing devices 34 and 36, and the abutment rod 46 presses against the housing 42. As the movable platen 10 is pushed inward, the movable platen 10 further advances and the molds 12 and 16 are closed.
That is, the pressure receiving area of the piston 24 of the hydraulic cylinder 22: S ₁ and the piston 4 of the hydraulic cylinder 38
The pressure-receiving area of 4: S ₂ satisfies the relationship of the following formula: P ₁ S ₁ > 2P ₁ S ₁ ...(1), where P ₁ is the pressure of the pressure fluid pumped from the pump 80. It has been set. In the above equation (1), P ₁ S ₁ represents the mold closing force of the hydraulic cylinder 22, and 2P ₁ S ₂ represents the pushing force of the spacing devices 34 and 36.

Next, with the molds 12 and 16 closed as described above, an injection device (not shown) inserted into the tapered hole 102 formed in the fixed platen 18 causes the molds 12 and 16 to form a A resin material is injected into the product cavity 104 to be manufactured. When the product cavity 104 is almost filled with the resin material, the injection pressure of the resin material is applied to the mold 12.
The mold opening force due to this injection pressure and the pushing back force act on the movable platen 10 through the injection pressure.
The movable platen 10 is pushed back in the direction away from the fixed platen 18 against the mold closing force, and the product cavity 1
As the volume of the product cavity 104 increases, more resin material is filled into the product cavity 104. That is, the injection pressure by the injection device: P ₂ is
If the pressure receiving area of is S ₃ , the setting is made to satisfy the following equation: P ₁ S ₁ <2P ₁ S ₂ +P ₂ S ₃ (2). Note that P ₂ S ₃ in the above equation (2) represents the mold opening force due to the injection pressure of the resin material.

In this way, the movable platen 10 is pushed back in the direction of separating from the fixed platen 18, and the amount of separation between them is: d
When the distance reaches the thickness t of the spacer 62, the piston 44 of the hydraulic cylinder 38 comes into contact with the housing 42, thereby preventing the contact rod 46 from protruding any further. Therefore, from then on, the movable platen 10 will be driven by the force relationship between the mold closing force of the hydraulic cylinder 22: P ₁ S ₁ and the mold opening force due to the injection pressure: P ₂ S ₂ . is set to satisfy the following formula: P ₁ S ₁ > P ₂ S ₃ ...(3), and the movable platen 10 stops accurately at the position where the distance: d matches the plate thickness: t. do. Furthermore, as is clear from the above explanation,
Pressure receiving area of pistons 24, 44: S ₁ , S ₂ , mold 1
The pressure receiving area of 2: S ₃ , the hydraulic pressure of the pressure liquid supplied from the pump 80: P ₁ and the injection pressure of the resin material: P ₂ are as follows:
It is set in advance so that all of the above equations (1) to (3) are satisfied.

Thereafter, when the switching valve 90 is switched to the pressure fluid discharge state, the supply of pressure fluid to the hydraulic cylinder 38 is cut off and its pushing force becomes 0, and the movable platen 1
0 is moved forward again against the mold opening force due to the injection pressure of the resin material, and the molds 12 and 16 are closed (pressed) to compress the resin material filled in the product cavity 104. . That is, the plate thickness of the spacer 62; t means the compression stroke in the compression process, and the spacer 62 has a predetermined thickness preset according to the shrinkage rate of the resin material to be molded. It is installed. Further, the dial gauge 10 outputs a confirmation signal when the separation amount: d matches the plate thickness: t, and based on the confirmation signal, the switching valve 90
is automatically switched. The switching valve 90, the hydraulic cylinder 22, the switching valve 82, the pump 80, and the like constitute compression means for clamping the molds 12 and 16 together. In addition, the switching valve 90
The pump 80 also serves as the pressure fluid supply means for supplying pressure fluid to the hydraulic cylinder 38, and the hydraulic cylinder 22 also serves as a hydraulic cylinder for opening and closing the molds 12 and 16.

As described in detail above, in the injection compression molding machine of this embodiment, the resin material is injected and filled into the product cavity 104 while pressure fluid is supplied to the hydraulic cylinder 38 and a pushing force is applied. The mold opening force caused by the injection pressure is applied to the movable platen 10, thereby pushing the movable platen 10 back in the direction away from the fixed platen 18, opening the molds 12 and 16 by a predetermined compression stroke. Because of this structure, compared to the case where the movable platen 10 is pushed back mechanically, the devices for this purpose, that is, the separating devices 34 and 36, are simpler and more compact, and can be installed in injection molding machines that have been widely used in the past. In addition to being easy to use, it is possible to significantly reduce the cost of the injection compression molding machine. especially,
In this embodiment, the mold 1 is
Since mold opening/closing and clamping of molds 2 and 16 are performed at the same time, the structure of the apparatus is further simplified.

Furthermore, as the resin material is injected and filled into the product cavity 104, the movable platen 10 is gradually pushed back, so the resin material is injected with the molds 12 and 16 open in advance. Compared to the case where the injection molding is forced, the shock pressure at the time of injection is relaxed and no distortion occurs around the molded product, making it possible to obtain a high quality molded product with excellent dimensional accuracy.

Moreover, during its operation, the hydraulic cylinder 2
Immediately after the mold is closed in step 2, the resin material is injected, and the movable platen 10 is pushed back by the injection pressure, and the distance between the molds 12 and 16: d is the plate thickness: t,
That is, when the preset compression stroke is reached, the switching valve 90 is automatically switched to move the movable platen 10 forward again, so that the resin material in the product cavity 104 is compressed. The time required for these series of operations is shortened, and production efficiency is improved.

Furthermore, in this embodiment, the pressure fluid supplied to the hydraulic cylinders 22 and 38 is pumped from a common pump 80, so compared to the case where the pressure fluid is supplied from separate supply sources. Pressure fluid circuit 7
6 has the advantage of being easily constructed.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the embodiment described above, a pair of spacing devices 34 and 36 are provided as push-back means, and each has a hydraulic cylinder 38 fixed to the fixed plate 18;
The spacing device is composed of a contact member 40 disposed on a movable platen 10, and by changing the pressure receiving area of the hydraulic cylinder 38, etc.
There is no problem with having one or three or more.
Further, while the hydraulic cylinder 38 is fixed to the movable platen 10, it is also possible to arrange the abutting member 40 on the fixed platen 18. Furthermore, the axial dimension of the contact rod 46 of the hydraulic cylinder 38 can be changed using a spacer or the like, so that the contact rod 46 directly contacts the movable platen 10 when the molds 12 and 16 are closed. In this case, the movable platen 10 also serves as the contact member 40, and there is no need to provide it.

Further, in the above embodiment, a dial gauge 100 is attached as a detection means, and the molds 12 and 16 are
The compression stroke is detected by detecting the distance d between the hydraulic cylinder 38 and the hydraulic cylinder 38. A flow sensor is provided in the pipes 96, 94, etc. connected to the liquid chambers 48, 50, and when the flow of the pressure liquid stops, the piston 44 reaches the forward end and the molds 12 and 16 are compressed. Detects that only the front stroke is opened,
It is also possible to detect the compression stroke from the amount of protrusion of the abutment rod 46.

Further, in the above embodiment, the hydraulic cylinder 22 that opens and closes the molds 12 and 16 is used as the compression means, and the push-back force of the hydraulic cylinder 38 is released by switching the switching valve 90. However, if the compressive force is not sufficient, the hydraulic pressure of the hydraulic fluid supplied to the hydraulic cylinder 22 may be increased at the same time as the switching of the switching valve 90, or the pressure of the hydraulic fluid supplied to the hydraulic cylinder 22 may be increased. It is also possible to separately provide a mold clamping cylinder.

Furthermore, in the embodiment, the hydraulic cylinder 2
2 and 38, the pressure liquid is supplied from a common pump 80, but the pressure liquid may be supplied from separate supply sources. In that case, the hydraulic pressure of the hydraulic fluid supplied to the hydraulic cylinder 38 is
When the injection pressure of the resin material is not acting on the movable platen 10, the mold closing force of the hydraulic cylinder 22 holds the molds 12 and 16 in a closed state. The size should be set so that the movable platen 10 can be pushed back against the mold closing force if the mold closing force is applied.

Although no other examples are given, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main parts of an injection compression molding machine according to an embodiment of the present invention, together with a hydraulic circuit. FIG. 2 is a sectional view showing the hydraulic cylinder of the push-back means installed in the injection compression molding machine of FIG. 1. FIG. 3 is a sectional view showing an abutment member of the push-back means attached to the injection compression molding machine of FIG. 1. 10: Movable plate, 12: Movable mold, 16: Fixed mold, 18: Fixed plate, 22: First hydraulic cylinder,
34, 36: Separation device (pushing back means), 38: Second hydraulic cylinder, 40: Contact member, 80: Pump, 82, 90: Switching valve, 100: Dial gauge (detection means), 104: Product Cavity.

Claims (1)

[Claims] 1. The movable platen is moved by the first hydraulic cylinder to open and close the mold between it and the fixed platen, while
An injection compression molding machine that injects and fills a predetermined resin material into a product cavity formed in the mold, and then compresses the resin material by compressing the mold, comprising: (a) the above-mentioned The piston is fixed to either the movable plate or the fixed plate and is supplied with a predetermined pressure liquid from the pressure liquid supply means, thereby moving the piston forward and causing the abutment rod connected to the piston to move outward. a second hydraulic cylinder that protrudes by a predetermined length; a contact member that is fixed to the other of the movable plate or the fixed plate and that is brought into contact with the abutment rod of the second hydraulic cylinder; a spacer member which is removably attached to the corresponding contact member or the second hydraulic cylinder and defines the compression stroke amount of the mold, and which controls the flow of pressure fluid to the second hydraulic cylinder. In cooperation with the mold opening force due to the injection pressure of the resin material injected into the product cavity by the supply,
The movable platen is pushed back in a direction away from the fixed platen through the contact member and the second hydraulic cylinder against the mold closing force of the first hydraulic cylinder, and the mold is closed. (b) providing a push-back means for opening the mold by a predetermined compression stroke determined by the spacer member, and (b) providing a detection means for detecting that the mold has been opened by the compression stroke; Furthermore, (c) compression means is provided for causing the movable platen to approach the fixed platen based on the detection by the detection means, and compressing the resin material by compressing the mold. Compression molding machine.