JP7138285B2 - Die lip opening and closing device - Google Patents

Description

The present invention relates to a die lip opening and closing device for opening and closing a die lip of a T-die.

2. Description of the Related Art Conventionally, there has been provided a molding apparatus equipped with a resin feeder for extruding a thermoplastic resin melted and kneaded by an extruder into a sheet form using a T-die, and shaping the sheet-shaped resin using a mold. A resin supply device for such a molding apparatus includes a die lip opening/closing device for opening and closing the die lip of the T-die. The die lip opening/closing device closes the die lip when the T-die is filled with the molten resin from the accumulator. On the other hand, when extruding the molten resin into a sheet, the die lip opening/closing device opens the die lip.

Here, Patent Literature 1 discloses a die lip opening/closing device using a hydraulic cylinder. This die lip opening/closing device has a sliding bar provided with an inclined projection and connected to a hydraulic cylinder, and a driving piece provided with an inclined groove engaging with the projection and having one end fixed to the die lip. This die lip opening/closing device bends a driving piece by linearly moving a sliding bar, bends the die lip via the driving piece, and opens and closes the die lip. When closing the die lip, it is necessary to bend the die lip with a strong force so that the slit of the die lip through which the molten resin is extruded is completely closed.

JP 2017-144630 A

The force to close the die lips may vary depending on the thermoplastic material used for molding. A stronger force is desired when the molten resin has a high fluidity. In order to close the die lip with a strong force, the conventional die lip opening/closing device requires a high-output hydraulic cylinder for driving the die lip opening/closing device. As a result, the hydraulic cylinder becomes large, and large-sized equipment such as a large-sized hydraulic pump that generates high hydraulic pressure and piping with high pressure resistance may be required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a die lip opening and closing device that is more compact than before.

The die lip opening and closing device of the present invention includes a motor having a drive shaft, a pusher provided to be linearly movable, a drive connection portion having a screw structure for converting the rotary motion of the drive shaft into the linear motion of the pusher, and the and an opening/closing structure for opening and closing the die lip of the T-die according to linear movement of the pusher.

According to the present invention, it is possible to provide a compact die lip opening/closing device.

It is a mimetic diagram showing a molding device provided with a die lip opening and closing device concerning an embodiment of the present invention. It is a bottom view showing a cross section of the main part of the die lip opening and closing device according to the embodiment of the present invention. FIG. 3 is a side view showing the essential part of the die lip opening/closing device according to the embodiment of the present invention in cross section AA of FIG. 2;

Embodiments of the present invention will be described below with reference to the drawings. A molding apparatus 10 shown in FIG. 1 includes a resin supply device 12 and a mold clamping device 14 . The resin feeder 12 is provided with an extruder 18 having a hopper 16 and a hydraulic motor 20 . A screw (not shown) connected to a hydraulic motor 20 is provided inside the extruder 18, and the resin charged from the hopper 16 is melted and kneaded.

The extruder 18 is connected with an accumulator 24 with a plunger 26 . Accumulator 24 is connected to T-die 28 via valve 27 . The T-die 28 is provided with a die bolt 46 for adjusting the gap S (see FIGS. 2 and 3) of the slit of the die lip 28a of the T-die 28. As shown in FIG. A die lip 28a of the T die 28 is opened and closed by a die lip opening/closing device 50, the details of which will be described later.

The resin melted and kneaded by the extruder 18 is filled in the accumulator 24 . The resin filled in the accumulator 24 is filled into the T-die 28 under high pressure by the operation of the plunger 26 . The die lip 28a of the T-die 28 is closed while the T-die 28 is being filled with the molten resin. When the accumulator 24 and the T-die 28 are sufficiently filled with the amount of molten resin necessary for molding, the die lip 28a is opened by the die lip opening/closing device 50, and the molten resin sheet P is extruded through the slit of the die lip 28a.

The thermoplastic resin that is the material of the molten resin sheet P can be appropriately selected. Examples thereof include polyolefins such as polypropylene and polyethylene, acrylic derivatives such as polyamide, polystyrene, and polyvinyl chloride, and materials obtained by adding a foaming agent to a mixture of two or more of them. For example, the molten resin sheet P is made of a material containing expanded polystyrene or expanded polypropylene. As the foaming agent, any of physical foaming agents, chemical foaming agents and mixtures thereof may be used. As physical blowing agents, inorganic physical blowing agents such as air, carbon dioxide gas, nitrogen gas, and water, organic physical blowing agents such as butane, pentane, hexane, dichloromethane, and dichloroethane, and supercritical fluids thereof are used. be able to.

The mold clamping device 14 arranged below the T-die 28 includes molds 32A and 32B arranged facing each other. A cavity 116 is formed in the mold 32A. Between the molds 32A, 32B and the T die 28 below the T die 28, rollers 30A, 30B are provided facing each other. After being extruded by the resin supply device 12, the molten resin sheet P passes between the rollers 30A and 30B while being sent downward by the rollers 30A and 30B, and is placed between the molds 32A and 32B. Note that the rollers 30A and 30B may be omitted. It is possible to prevent the expansion ratio from lowering due to the sandwiching of the rollers 30A and 30B. According to the present invention, since the thickness of the molten resin sheet P can be adjusted by adjusting the opening degree of the die lip 28a, the use of the rollers 30A and 30B can be omitted. By continuously changing the opening of the die lip 28a while extruding the molten resin sheet P, the thickness of the molten resin sheet P can be continuously changed without using the rollers 30A and 30B. can. By gradually increasing the die lip opening degree while extruding, drawdown can be suppressed without using the rollers 30A and 30B, and a vertically elongated molten resin sheet P can be formed.

33 A of molds are provided in the outer periphery of the cavity 116 of 32 A of metal mold|dies. A mold 32B is provided with a mold 33B facing the mold 33A. The forms 33A and 33B are formed in a substantially annular shape and are formed so as to be movable in a direction toward each other. The mold frames 33A and 33B are in contact with the molten resin sheet P to sandwich the molten resin sheet P, and the space area surrounded by the mold 32A (cavity 116), the mold frame 33A and the molten resin sheet P is a closed space. is. A space surrounded by the mold 32B, the mold frame 33B, and the molten resin sheet P is also a closed space as required for molding. When the molds 32A and 32B are closed and clamped, the internal air in the closed space formed by the molten resin sheet P, the cavity 116 and the like is decompressed by a vacuum pump (not shown), and the shape of the cavity 116 is reduced. to shape the molten resin sheet P. At this time, a pressurized fluid may be sent into the space surrounded by the mold 32B, the mold frame 33B and the molten resin sheet P. Not limited to the molds (molds 32A and 32B), the pair of cavity surfaces are arranged apart from each other by a predetermined distance larger than the thickness of the molten resin sheet P when the molds are closed. A pair of molds may be used. In this case, in a state in which the molten resin sheet P is sandwiched between a pair of cavities and hermetically sealed, the molten resin sheet P is sucked from minute suction holes provided on the cavity surfaces on both sides. Thereby, the foamed resin sheet P is pulled in the thickness direction, and the foaming ratio is improved. As a result, it is possible to obtain a foamed molded product with a high expansion ratio.

Next, the die lip opening/closing device 50 will be described in detail with reference to FIGS. 2 and 3. FIG. Upper and lower plates 71 and 72 of a frame 70 of the die lip opening/closing device 50 are fixed to the T die 28 via a bracket 73 . Note that the upper and lower plates 71 and 72 of the frame 70 shown in FIG. 3 are omitted in FIG.

A hydraulic motor 51 is provided on the plate 74 of the frame 70 on the opposite side of the T-die 28 . The hydraulic motor 51 is driven by a hydraulic pump (not shown). A drive shaft 53 protrudes from the hydraulic motor 51 via a reduction gear 52, and the driving force of the hydraulic motor 51 is output. A hydraulic motor 51 combined with a speed reducer 52 is fixed to the frame 70 of the die lip opening/closing device 50 .

The rotary motion of the drive shaft 53 is converted by the drive connection R into linear motion of the pusher 60 . The drive connection R comprises a threaded structure Q. As shown in FIG. Specifically, the drive shaft 53 is provided with a rotary shaft 54 formed in a substantially cylindrical shape. The rotating shaft 54 is fixed in the axial direction by a bearing 55 provided on the plate 74 and is rotatably supported around the axis. The drive shaft 53 is inserted into and fixed to the inner diameter portion of one end of the rotating shaft 54, and the inner diameter portion of the other end is formed with a female screw portion 54a. A male threaded portion 61a of a pusher shaft 61, which will be described later, is screwed into the female threaded portion 54a. The drive connection portion R includes a rotary shaft 54 , a screw structure Q in which a female threaded portion 54 a and a male threaded portion 61 a are screwed together, and a pusher shaft 61 .

The female threaded portion 54a and the male threaded portion 61a are formed of trapezoidal threads in this embodiment. In the present embodiment, a trapezoidal thread is used for the threaded structure Q by the male threaded portion 61a that is threadedly engaged with the female threaded portion 54a. Also, various types of threaded structure Q can be employed, for example, a ball screw can be used. However, by using a trapezoidal thread as in the present embodiment, it is possible to obtain a threaded structure Q that can cope with a strong thrust force.

A pusher 60 is provided on the T-die 28 side of the rotating shaft 54 . The pusher 60 is provided with a rectangular pusher base 62 whose longitudinal direction is perpendicular to the axial direction of the rotating shaft 54 . Two guide posts 75 are erected on the hydraulic motor 51 side of the pusher base 62 . Each guide post 75 is supported by a bush 76 provided on the plate 74 so as to be linearly movable in the axial direction of the rotating shaft 54 . The aforementioned pusher shaft 61 is erected from the pusher base 62 . The pusher shaft 61 is fixed to the pusher base 62 via a fixing boss 62a.

A plurality of substantially cylindrical pusher bars 63 are provided on the T-die 28 side of the pusher base 62 . In this embodiment, four pusher bars 63 are provided at regular intervals along the longitudinal direction of the pusher base 62 . Each pusher bar 63 is guided by a bush 73 a provided on the bracket 73 so as to be linearly movable in the axial direction of the rotary shaft 54 . At the tip of each pusher bar 63, there is formed a pusher head 63a whose tip is curved when viewed from the side. The pusher head 63a is elongated along the longitudinal direction of the pusher base 62, and four pusher bars 63 are connected to it.

Thus, the pusher 60 including the pusher shaft 61, the pusher base 62, the pusher bar 63, etc. is guided by the guide post 75 and the bush 76 on the hydraulic motor 51 side, and by the pusher bar 63 and the bush 73a on the T die 28 side. It is formed to be movable in a linear direction. That is, the pusher 60 is guided in the axial direction of the rotating shaft 54 by the frame 70 .

Also, the boss 62 a of the pusher base 62 is connected to the position detection sensor 100 . The position detection sensor 100 is an eddy current displacement sensor and can detect the position of the pusher 60 . As the position detection sensor 100, another type of sensor such as a proximity sensor can be employed.

The T-die 28 is provided with a receiving piece 80 corresponding to the pusher bar 63 . The receiving piece 80 has an inclined surface 80a that rises toward a receiving piece connecting portion 81b of a die lip 28a, which will be described later. The lower side of the pusher head 63a is in sliding contact with the inclined surface 80a. The receiving piece 80 is connected to a die lip piece 81 provided on the die lip 28a. The die lip piece 81 is formed by cutting out a substantially rectangular parallelepiped block to form a thin bending portion 81a, a receiving piece connecting portion 81b to which the receiving piece 80 is attached, and a fixing portion fixed to the main body of the T die 28. and a portion 81c. That is, the receiving piece connecting portion 81b and the fixed portion 81c are connected by the flexible portion 81a. An opening/closing structure W for opening and closing the slit of the die lip 28a indicated by the clearance amount S includes a receiving piece 80 and a die lip piece 81. As shown in FIG.

The die lip opening/closing device 50 operates as follows. When the accumulator 24 and the T-die 28 are filled with molten resin, the slit of the die lip 28a must be closed. In this case, when the drive shaft 53 of the hydraulic motor 51 is rotated in the normal direction, the rotary shaft 54 rotates together with the drive shaft 53 . Then, the pusher shaft 61 having the male threaded portion 61a to be screwed with the female threaded portion 54a of the rotary shaft 54 advances. Therefore, the pusher 60 (pusher bar 63) advances (linearly moves in the direction of the T die 28). When the pusher head 63a moves forward, the pusher head 63a presses downward the inclined surface 80a of the receiving piece 80 with which it is in sliding contact. Then, the receiving piece 80 and the receiving piece connecting portion 81b of the die lip piece 81 move so as to rotate downward around the bending portion 81a as the bending portion 81a bends. Then, the gap amount S of the slit is reduced to zero. In other words, the die lip 28a is closed.

Further, when pushing out the molten resin sheet P, the drive shaft 53 of the hydraulic motor 51 is rotated in the reverse direction to retract the pusher 60 (pusher head 63a). Then, the pressing of the receiving piece 80 by the pusher head 63a is released, and the receiving piece 80 and the receiving piece connecting portion 81b are restored by the restoring force of the bending portion 81a of the die lip piece 81, so that the die lip 28a (slit) can be opened. can.

In this manner, the rotary motion of the hydraulic motor 51 is converted into linear motion by the screw structure Q to linearly move the pusher 60 to close the die lip 28a. The die lip 28a can be firmly closed without loosening of the blockage of the die lip 28a (slit) due to the damper effect of the hydraulic cylinder, as compared with the case where the die lip 28a is closed. Therefore, the die lip opening/closing device 50 can close the die lip 28a with a strong force without using a large-sized driving device having a hydraulic cylinder with a large output.

In addition, since the force for closing the slit of the die lip 28a is improved by the hydraulic motor 51, the driving connection portion R having the screw-engagement structure Q, and the like, the molten resin melts from the slit of the die lip 28a during filling of the T-die 28 and the like. Exudation of the resin is reduced. In particular, when using a highly fluid resin material, it is preferable to use the die lip opening and closing device 50 .

In addition, in the die lip opening/closing device 50, the actuator for driving the pusher 60 can be made small, so the pusher 60 can be easily provided with the position detection sensor 100. FIG. By providing the pusher 60 with the position detection sensor 100, the dimension control of the gap amount S of the slit of the die lip 28a can be performed with high accuracy. Therefore, the thickness of the molten resin sheet P can be controlled with high precision when the molten resin sheet P is extruded. As a result, it is possible to improve the accuracy when molding a large number of products from one molten resin sheet P.

As described above, the present invention is not limited by this embodiment, and can be implemented in various forms. For example, although the hydraulic motor 51 is used in this embodiment, it is not limited to this, and various motors having a rotating drive shaft, such as electric motors, can be used.

10 molding device 12 resin supply device 14 mold clamping device 16 hopper 18 extruder 20 hydraulic motor 24 accumulator 26 plunger 27 valve 28 T die 28a die lip 30A roller 30B roller 32A mold 32B mold 33A mold 33B mold 46 die bolt 50 die lip Switching device 51 Hydraulic motor 52 Reduction gear 53 Drive shaft 54 Rotating shaft 54a Female threaded portion 55 Bearing 60 Pusher 61 Pusher shaft 61a Male threaded portion 62 Pusher base 62a Boss 63 Pusher bar 63a Pusher head 70 Frame 71 Plate 72 Plate 73 Bracket 73a Bush 74 Plate 75 Guide post 76 Bushing 80 Receiving piece 80a Inclined surface 81 Die lip piece 81a Flexible portion 81b Receiving piece connection portion 81c Fixing portion 100 Position detection sensor 116 Cavity P Molten resin sheet Q Threaded structure R Drive connection portion S Slit clearance W Opening and closing structure

Claims (4)

a motor with a drive shaft;
a pusher provided to be linearly movable;
a drive connection portion having a threaded structure for converting rotary motion of the drive shaft into linear motion of the pusher;
an opening and closing structure for opening and closing the die lip of the T-die according to the linear movement of the pusher;
havedeath,
The threaded structure includes a rotary shaft provided on the drive shaft and having a female thread, and a pusher shaft provided on the pusher and provided with a male thread that engages with the female thread. A die lip opening and closing device characterized by: 2. A die lip opening and closing device according to claim 1 , wherein said female threaded portion and said male threaded portion are formed of trapezoidal threads. 3. The die lip opening and closing device according to claim 1 , wherein the motor is a hydraulic motor, and a drive force is output to the drive shaft via a speed reducer. 4. The die lip opening/closing device according to claim 1 , wherein the pusher has a position detection sensor that detects the position of the pusher.

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