JPS61100428A - Clamping apparatus in injection press - Google Patents

Abstract

PURPOSE:To obtain a clamping force against the injected resin pressure, by moving a movable platen according to the forward operation of a male screw member so as to clamp molds. CONSTITUTION:To carry out molding, a motor 34 is rotated forward to move a movable platen 10 forward thereby pressing a movable mold 12 fixed to the movable platen 10 to a fixed mold 16 of a fixed platen 18 and a resin is injected into a cavity definded by the molds 12, 16. Thus, if the injected resin pressure exerted to the mold 12 in the direction to retract the movable platen 10, a shaft 24 is fixed relative to a ball screw 30 since an armature 44 and a field assembly member 42 are attracted magneticaly to each other and a bearing cover 40 is secured by an air cylinder 48, so that the compression force for clamping the molds 12, 16 would not weakened. Therefore, during the injection molding, the molds 12, 16 can be clamped by a sufficiently great clamping force.

Description

TECHNICAL FIELD The present invention relates to a mold clamping device for an injection molding machine, and more particularly to a mold clamping device that employs a ball screw mechanism as a moving mechanism for a movable platen.

The mold clamping device of the conventional injection molding machine requires the function of moving the movable platen, clamping the mold between it and the fixed platen, and further clamping the mold so as to oppose the pressure of the injection resin. be done.

For this reason, conventionally, a direct pressure type mold clamping device in which the movable platen is directly moved by a hydraulic cylinder, a toggle type mold clamping device in which the movable platen is moved via a link mechanism, etc. have been used.

On the other hand, it has been considered to adopt a ball screw mechanism used in machine tools and the like as a moving mechanism for the movable platen in the above-mentioned mold clamping device.

Problems to be Solved by the Invention However, in the mold clamping device of an injection molding machine, in addition to the function of clamping the mold against the injection resin pressure, the function of opening and closing the mold at high speed is required. Since it is common, it has been difficult to employ a ball screw mechanism as a moving mechanism for a movable platen. In other words, when a ball screw mechanism is adopted as a moving mechanism for the movable platen in a mold clamping device, it is possible to increase the opening and closing speed of the mold by increasing the lead angle of the ball screw mechanism. In this case, sufficient clamping force to counter the injection resin pressure cannot be obtained, and conversely, if you try to obtain a large clamping force by reducing the lead angle, the moving speed of the movable platen will decrease and the The problem was that the mold could not be opened and closed at high speed.

Means for Solving the Problems With this background in mind, the present invention employs a ball screw mechanism as a moving mechanism for the movable platen, and also enables high-speed opening/closing of the mold and a sufficiently large pressure to counter the injection resin pressure. This was done in order to provide a mold clamping device for an injection molding machine that can obtain clamping force. ・Tsukuda Summary 2. 6. The movable platen is moved. 1. Between it and the fixed platen. In a mold clamping device in an injection molding machine that clamps a mold and further clamps the mold to counter the injection resin pressure,
The ball screw mechanism includes a nut member that is rotated and a male screw member that is combined with the nut member in a predetermined ball screw structure, and the male screw member is moved forward and backward by the rotation of the nut member, and the male screw While attaching the member to the movable platen, the nut member is connected to a predetermined rotational drive means and rotated by the rotational drive means, thereby moving the movable platen according to the forward movement of the male screw member. to perform the mold clamping operation of the mold, and to prevent the nut member from being reversely rotated by a force in the backward direction of the male threaded member that acts when the rotation of the nut member is stopped. The reason is that a rotation prevention mechanism is provided.

Functions and Effects According to such a mold clamping device, by increasing the lead angle of the ball screw mechanism, the movable platen can be moved at high speed, and the mold can be opened and closed at high speed. Furthermore, during mold clamping when the movable platen is pressed against the fixed platen, the rotation of the NAND member is prevented by the rotation prevention mechanism, so even if the injection resin pressure acts on the movable platen, the movable platen will be moved backwards. The clamping force against the mold is maintained at a sufficient level.

In other words, according to the present invention, a ball screw mechanism is adopted as a moving mechanism for the movable platen, and a mold clamping device is provided which has the function of opening and closing the mold at high speed and the function of obtaining sufficient clamping force during mold clamping. It becomes possible to obtain it.

Examples Below, in order to clarify the present invention more specifically,
One embodiment thereof 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 at its four corners by four tie bars 14. The tie bars 14 are arranged parallel to each other in the front-rear direction, and a fixed platen 18 to which the fixed mold 16 is fixed is provided at the front end (the right end in FIG. 1) of the tie bars 14.
It is fixed at the four corners of the rear end (left end in Figure 1).
is fixed to the flange 22 of the housing 20.

The housing 20 has a cylindrical shape with a flange 22 on its outer peripheral surface, and is fixed to a stationary member (not shown). The housing 20 rotatably supports the front side portion of the shaft 24 on its inner circumferential surface, but immovably in the front-rear direction.

Further, the shaft 24 is rotatably supported at its rear end by a stationary member 26 .

This shaft 24 has a bottomed cylindrical shape with an open front end, and a cylindrical pole screw nut (hereinafter referred to as
28 (simply called Nando) is fixed. A longitudinal cylindrical ball screw 30, which is fixed to the movable platen 10 at the front end thereof, is threaded through the NAND 28 in the front-rear direction and is screwed into the ball screw 30 via a steel ball (not shown). A ball screw structure is adopted between the NAND 28 and the ball screw 30, and the ball screw 30 is a male screw member.

Further, a large gear 3 is provided on the outer peripheral surface of the rear end side of the shaft 24.
2 is fixed, and a small gear 38 fixed to an output shaft 36 of an electric servo motor (hereinafter simply referred to as motor) 34 is meshed with this large gear 32. When the motor 34 is driven to rotate, the rotation is caused by the gear 38.
32 and is transmitted to the shaft 24, so that the nut 28 is rotated. Depending on the direction of rotation of this nut 28, the ball screw 30 and, by extension, the movable platen 10 are moved forward or backward, and the molds 12 and 16 are opened and closed.In this embodiment, the ball screw 30 and the ball screw By making the lead to the movable platen 30 sufficiently large, the movable platen 10 can be moved at a sufficiently high speed, and the molds 12 and 16 can be opened and closed at a sufficiently high speed. Note that, as is clear from the above description, in this embodiment, the electric servo motor 34
is used as a rotational drive means, and the shaft 24 and
The one-pole screw nut 28 constitutes a nut member. In other words, these shafts 24. Bo
A pole screw mechanism is composed of the lune screw 28 and the ball screw 30.

On the other hand, a housing 20 is provided on the outer peripheral surface of the shaft 24.
A bearing cover 40 having a disc shape and closing an opening on the rear end side and being rotatable relative to the housing 20.
is fitted into the bearing cover 40 so as to be rotatable and slidable in the axial direction, and a ring-shaped field assembly member 42 is fixed to this bearing cover 40 . In addition, the shaft 24
A disc-shaped armature 44 is disposed on the outer peripheral surface of the field assembly member 42, facing the field assembly member 42 with a slight gap therebetween.
is fixed. The field assembly member 42 is always separated from the armature 44, but when a coil (not shown) disposed inside the field assembly member 42 is excited, it moves in the axial direction of the shaft 24 and moves the armature 44. It is designed to be fixed by suction.

Further, the bearing cover 40 is formed with an arm portion 46 extending outward in the radial direction.
As shown in FIG. 2, an air cylinder 48 is connected to the tip of the piston rod 50. The air cylinder 48 is disposed substantially perpendicular to the axes of the arm portion 46 and the shaft 24, respectively, and is connected to a stationary member 52 at the end on the cylinder head side, so that the piston 54 is connected to the stationary member 52.

When the piston rod 50 is retracted by retreating toward the cylinder head side, the bearing cover 40 is rotated in a direction that advances the ball screw 30, and conversely, when the piston rod 50 is extended, the ball screw 30 is retracted. The bearing cover 40 is rotated in the direction.

Note that the expansion and contraction of the piston rod 50 of the air cylinder 48 is controlled by a pneumatic circuit 56. That is, the pneumatic circuit 56 includes a 4-point, 2-position electromagnetic switching valve 58, and the compressed air from the pneumatic source 60 is always passed through the filter 62. Regulator 64. Lubricator 66.
Air cylinder 48 via switching valve 58 and check valve 68
While supplying to the head side chamber 70 of the cylinder head example,
Variable throttle valve 74. Air is discharged from the rod side chamber 72 on the piston rod 50 side via the switching valve 58 and the muffler 76 to extend the piston loft 50, and when the solenoid 78 of the switching valve 58 is energized, The compressed air supplied from the air pressure source 6o to the switching valve 58 is supplied to the rod side chamber 72 via the check valve 8o, while the air in the head side chamber 70 is supplied to the variable throttle valve 82. The air is discharged through the switching valve 58 and the muffler 76, and the piston rod 50 is contracted. Note that 84 is a pressure gauge.

In order to mold a mold using such a mold clamping device, first, the motor 34 is rotated in the normal direction to advance the movable platen 1o.
The movable mold 12 fixed on the fixed mold 1 of the fixed platen 18
Press it to 6. In this case, as mentioned above, the movable platen 10
It is possible to move at high speed. This pressing excites the coil within the field assembly member 42,
The field assembly member 42 is magnetically attached to the armature 44. Then, the solenoid 78 of the switching valve 58 of the pneumatic circuit 56 is energized, and the piston rod 50 of the air cylinder 48 is retracted. Then, resin is injected into the cavity formed by the molds 12 and 16. Note that this injection of the resin is performed by an injection device (not shown) inserted into a tapered hole 86 formed in the fixed platen 18.

In this way, even if the injection resin pressure acts on the movable mold 12 in the direction of retracting the movable platen 10, the armature 44
Since the shaft 24 is fixed relative to the ball screw 30 by the magnetic attachment between the shaft 24 and the field assembly member 42 and the fixation of the bearing cover 40 by the air cylinder 48, the clamping force that tightens the molds 12 and 16 is weakened. Never. In addition, the clamping force is determined by the motor 34
rotational torque and the piston rod 50 of the air cylinder 48
Since it is obtained as a result of the contraction force of , it can be obtained as a sufficiently large one. In other words, according to this embodiment, the molds 12 and 16 can be clamped with a sufficiently large clamping force during injection molding. As is clear from the above description, in this embodiment, the air cylinder 48 constitutes a locking means, and this locking means and the armature 44. Field assembly member 42. bearing cover 40
This constitutes an electromagnetic brake mechanism, and this electromagnetic brake mechanism serves as a rotation prevention mechanism.

On the other hand, when the molding is completed, the solenoid 78 of the switching valve 58 in the pneumatic circuit 56 is demagnetized, and the piston rod 5o of the air cylinder 48 is extended.
The coil within the field assembly member 42 is demagnetized and the armature 44 and field assembly member 4 are demagnetized.
2 is released, and rotation of the shaft 24 is allowed. At the same time, the motor 34 is reversely rotated, and the ball screw 30, that is, the movable platen 1o, is moved backward.

In this case as well, it goes without saying that the movable platen 10 can be moved at high speed. After the retreat, the mold is separated from the movable mold 12 by the ejector bin 88 which is projected forward from the movable mold 12, and is removed.
Thereafter, the same molding process as described above for a new mold is repeated again.

Note that the ejector bin 88 protrudes from the movable platen 10, the ball screw 30. This is accomplished by axial movement of an ejector rod 90 disposed through shaft 24 and stationary member 26.

As explained above, according to the mold clamping device of this embodiment, the ball screw mechanism is adopted as the movement mechanism of the movable platen 10, and the movable platen 10 has a high-speed movement function and a sufficient clamping force during mold clamping. It is possible to obtain both the holding function and the holding function.

Further, in this embodiment, as described above, the electric servo motor 34 is used as the rotational drive means, and an electromagnetic brake mechanism is used as the rotation prevention mechanism, and the air cylinder 48 is used as the locking means for the electromagnetic brake mechanism. This has the advantage that the entire device can be easily controlled and the device configuration itself can be compact.

Furthermore, according to this embodiment, the clamping force is, as described above,
Since this is achieved by the synergistic acting force of both the motor 34 and the air cylinder 48, there is an advantage that the output of the motor 34 can be relatively small, and the pressure of the air in the air cylinder 48 is Another advantage is that the clamping force can be easily adjusted by adjusting. Further, for the same reason, there is an advantage that the clamping force can be easily displayed using the pressure gauge 84.

Although one embodiment of the present invention has been described above, this is literally an illustration, and the present invention should not be interpreted as being limited to this specific example.

For example, in the embodiment described above, the air cylinder 48, which is easy to handle, is used as the locking means, but it is also possible to use another fluid pressure cylinder such as a hydraulic cylinder instead of the air cylinder 48. Further, the locking means does not necessarily have to have a function of rotating the ball screw 30 in the forward direction,
It is also possible to provide a structure that simply has the function of preventing rotation of the bearing cover 40 by spline-coupling the bearing cover 40 to the housing 20 or the like. However, in this case, it is necessary to employ a motor with a larger rotational torque than in the above embodiment.

Further, in the embodiment described above, the electric servo motor 34 was employed as the rotational drive means, but it is also possible to employ other rotational drive means such as a hydraulic motor.

Although not listed here, it goes without saying that the present invention can be implemented in various modifications and improvements without departing from the spirit thereof.

[Brief explanation of drawings]

Fig. 1 is a front cross-sectional view showing a mold clamping device of an injection molding machine according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along the line ■-■ along with a pneumatic circuit for driving and controlling an air cylinder. . 10: Movable plate 12.16: Mold 18: Fixed plate
20: Housing, 30: Ball screw (male thread member) 34: Electric servo motor (rotation drive means) 40: Bearing cover 42: Field terra assembly member 44 Near-gusset air 48: Air cylinder (locking means) 56: Pneumatic circuit

Claims (4)

[Claims] (1) A mold clamping device for an injection molding machine that moves a movable platen, clamps the mold between it and a fixed platen, and further clamps the mold to counter the injection resin pressure, It has a ball screw mechanism that includes a nut member that is rotated and a male screw member that is combined with the nut member in a predetermined ball screw structure, and that the male screw member is moved forward and backward by the rotation of the nut member, and the male screw While attaching the member to the movable platen, the nut member is connected to a predetermined rotational drive means and rotated by the rotational drive means, thereby moving the movable platen according to the forward movement of the male threaded member. A rotation prevention device that allows the mold to be clamped and also prevents the nut member from being reversely rotated by a force in the backward direction of the male screw member that is applied when the nut member is stopped rotating. A mold clamping device characterized in that a mechanism is provided to maintain the mold clamping force of the mold after the mold clamping operation. (2) The rotation prevention mechanism includes an armature member fixed to the nut member and rotating together with the nut member, a field assembly member magnetically attached to the armature member, and a locking means for preventing rotation of the field assembly member. The mold clamping device according to claim 1, which is an electromagnetic brake mechanism. (3) The locking means of the electromagnetic brake mechanism is attached to the field assembly member, and a fluid pressure cylinder biases the field assembly member so as to provide rotational movement in a direction in which the male screw member is advanced. A mold clamping device according to claim 2. (4) The mold clamping device according to any one of claims 1 to 3, wherein the rotational drive means is an electric servo motor.