JP2011031450A - Half nut of mold clamping device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems in a mold clamping device of an injection molding machine wherein, as mechanical backlash normally occurs between when moving in the mold clamping direction and when moving in the mold opening direction, an opening amount of molds differs by the amount of backlash when opening the molds by being pressed by foaming pressure due to the high foaming pressure and when opening the molds by the force of the mold clamping device due to the low foaming pressure, causing variation in thickness of molded articles and unstable quality depending on the foaming state of molten resin. <P>SOLUTION: The compound mold clamping device has a spring 32 pressing a half nut to a movable platen 16 between a nut pressing member 23 and the half nut 22. An engaging part of a tie-bar with the half nut is in a serrated state formed of tilted tooth flanks and vertical tooth flanks, the tilted tooth flanks and the vertical tooth flanks of the engaging part come into contact with each other when engaged to eliminate the backlash between the movable platen and the tie-bar. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  Half-size suitable for foam molding in composite mold clamping device of injection molding machine that molds plastic products, after the injection filling of molten resin containing foaming agent, the mold is slightly opened to promote foam expansion and soften the molded product It is a nut device.

  In an injection molding machine for molding a plastic product, a molten resin is filled into a mold cavity to which a mold clamping force is applied by an injection device, and after cooling and solidification, the mold is opened and taken out to obtain a molded product. The mold clamping device of this injection molding machine mainly uses a toggle structure type and a composite structure type. In the toggle structure, a movable platen is moved by operating a crosshead using a link mechanism, and mold opening / closing and clamping are performed in a series of operations. Also, in the composite structure, after closing the mold with a mold opening and closing device, the tie bar and half nut are engaged, and high pressure hydraulic oil is supplied to the mold clamping cylinder containing the piston that is connected to the tie bar. A large clamping force is applied.

  On the other hand, immediately after the foaming agent is mixed in the resin and melted, and the molten resin is fully filled in the cavity, the mold is slowly opened and foamed and expanded to form a flexible plastic product. It is. In the foam molding, it is important to control the opening amount of the mold with high accuracy, and this makes it possible to obtain a foam molded product having a constant thickness and foamed state and stable quality.

  However, the mold clamping device of an injection molding machine usually has a mechanical backlash (backlash) between when it is moved in the mold clamping direction and when it is moved in the mold opening direction. Therefore, when the mold is opened while the foaming pressure is high and pressed by the foaming pressure, and when the mold is opened by the force of the mold clamping device with a low foaming pressure, there is a difference in the amount of mold opening due to backlash. . Therefore, the thickness of the molded product varies depending on the foamed state of the molten resin, and the quality becomes unstable. In particular, since the foaming state is low at the start of the molding operation in the morning, a molded product (defective product) with a thin backlash thickness is produced.

  In the toggle type mold clamping device, there is a gap (backlash) between the toggle pin and the bush of the link mechanism, and there is also a backlash between the tie bar and the tie bar nut. Therefore, Patent Document 1 discloses a toggle type mold clamping device that supports foam molding.

  In this apparatus, a hydraulic cylinder is mounted between the mold mounting surfaces of the fixed platen and the movable platen, and a force is exerted in the direction of opening the mold during mold clamping and mold opening operations. Then, even if the foaming pressure is small, the backlash is formed in the same direction as the mold clamping due to the force of the hydraulic cylinder.Therefore, if the position of the crosshead of the link mechanism is precisely controlled, the foaming pressure may be small or large. Similarly, since the same mold opening amount can be ensured, the thickness and foamed state of the foamed molded product can be made uniform.

  Patent Document 2 discloses a technique corresponding to foam molding in a composite mold clamping device. In the case of a complex type mold clamping device, an accurate mold opening amount can be secured in the same manner by accurately controlling the position of the piston of the mold clamping cylinder. However, the composite mold clamping device has backlash (backlash) at the engaging portions between the movable platen and the half nut and between the half nut and the tie bar. Therefore, Patent Document 2 discloses a method of adding a pair of additional half nuts to an existing half nut and removing the backlash of the engaging portion by the effect of the double nut.

JP 2006-334793 A JP 2009-1332097 A

However, in the toggle type mold clamping device described in Patent Document 1, a link mechanism is indispensable behind the movable platen, and the molding machine itself becomes large. Therefore, a large space is required for installation, and there is a problem that cannot be avoided that the factory is narrow.
In addition, the composite mold clamping device compatible with foam molding disclosed in Patent Document 2 has a problem in that it is necessary to add a pair of expensive and complicated half nuts, which increases costs.

In order to solve the above problems, in the present invention,
In a combined mold clamping device of an injection molding machine, a spring for pressing the half nut against the movable platen is provided between the nut pressing member and the half nut, and the engaging portion of the tie bar and the half nut is formed from an oblique tooth surface and a vertical tooth surface. In the engaging state, the oblique tooth surface and the vertical tooth surface of the engaging portion are in contact with each other, and the backlash (backlash) between the movable platen and the tie bar is removed.
Further, a linear rolling slurder is mounted between the nut pressing member and the half nut to reduce the sliding resistance during the engagement / disengagement operation.
Further, the half nut is processed so that only one oblique tooth surface is in contact with the oblique tooth surface of the tie bar engaging portion and the other oblique tooth surfaces are not in contact with each other when engaged.

(1) In the foam molding, the mold opening amount can be controlled with high accuracy regardless of the foaming pressure of the molten resin, so that the thickness of the molded product and the foamed state are stabilized and the quality can be improved.
(2) The structure is almost the same as that of the conventional half nut, and there is little increase in the manufacturing cost of the injection molding machine for foam molding.

It is an Example which concerns on this invention, and is a figure which shows the cross section of the engaging part of a tie bar and a half nut. It is a figure which shows the whole complex type mold clamping apparatus based on this invention. It is the figure which looked at the half nut of the open (detachment) state from the tie bar support side. It is a figure showing the section of the engaging part (rectangular engagement tooth) of the conventional tie bar and half nut, and showing the state where there is backlash (backlash). It is a figure showing the cross section of the engaging part (sawtooth engagement tooth) of the conventional tie bar and a half nut, and showing a state with backlash (backlash).

  Embodiments according to the present invention will be described below with reference to the drawings.

  First, the entire composite mold clamping apparatus according to the present invention will be described with reference to FIG. A fixed platen 15 is fixedly placed on the machine base 13 via a fixed key 14. The fixed platen 15 is attached with a fixed mold 10 and is provided with an injection hole 15 a so that the tip of a nozzle of an injection device (not shown) can touch the fixed mold 10. On the other hand, a movable mold 11 is attached to the movable platen 16 and is placed on a machine base 13 via a slider 41 so as to be movable in the opening / closing direction of the mold. A ball (steel ball) is incorporated between the slurder rail 41b of the slider 41 and the slider block 41a. The ball can be slid with a very small frictional resistance and can be smoothly opened and closed. A mold clamping cylinder is integrally formed in the fixed platen 15, and a piston 50 connected to the tie bar 20 is incorporated, and a mold clamping side oil chamber 51 and a mold opening side oil chamber 52 are formed on both sides of the piston 50. ing.

  Four tie bars 20 are provided, which pass through the four corners of the movable platen 16 and are connected to each other via a tie bar support 17 and a collar 18. Further, the tie bar 20 is processed with a tie bar engaging portion 20 </ b> A that engages with the half nut 22. The machine base 13 is provided with a moving device so that the movable platen 16 can be moved to open and close the mold. In the moving device, a mold opening / closing motor 43 is fixed on the machine base 13, and is connected to a ball screw shaft 47 via a coupling 44. The die opening / closing motor 43 side of the ball screw shaft 47 is supported by a bearing support member 45 fixed to the machine base 13 while being rotatable but constrained in the axial direction, and the tip side is supported by a tip support member 48. It is supported rotatably. A ball screw nut 46 that is screwed to the ball screw shaft 47 is fixed to the lower side of the movable platen 16 via a nut holder 49. Therefore, when the motor shaft of the mold opening / closing motor 43 is rotated by a command from a control device (not shown), the connected ball screw shaft 47 is rotated, and the ball screw nut 46, the nut holder 49, and the movable platen are rotated by the action of the screw. 16 opens and closes. Even if this ball screw for opening and closing the mold is a trapezoidal screw or the like, there is no problem.

  A half nut 22 is supported by a nut pressing member 23 on the tie bar support 17 side of the movable platen 16, and one of the half nuts 22 is connected to a cylinder rod 25 a of a nut opening / closing cylinder 25 as shown in FIG. 3. . Therefore, when the nut opening / closing cylinder 25 is driven by hydraulic pressure or air pressure, the half nut 22 is configured to be engageable / detachable (open / close) with respect to the tie bar engaging portion 20A.

  In FIG. 1, the cross section of the engaging part of the tie bar 20 and the half nut 22 is shown. The engaging portion is composed of ring-shaped or spiral teeth, and can be engaged when the respective teeth mesh with each other. The tooth has a sawtooth shape composed of an oblique tooth surface and a vertical tooth surface, and both the oblique tooth surface and the vertical tooth surface are in contact with each other in the engaged (closed) state. Therefore, at this time, the nut end face 22d shown in FIG. 3 is not in contact. The backlash (gap) between the half nut 22 and the tie bar 20 is removed by contacting both the oblique tooth surface and the vertical tooth surface. The half nut 22 is attached to the movable platen 16 by a nut pressing member 23 via a linear rolling slider 31 and a spring 32. The roller built in the linear rolling slider 31 may be either spherical or cylindrical. Since it is pressed by the spring 32, the backlash (backlash) between the movable platen 16 and the half nut 22 is removed. The strength (compression force) of the spring 32 may be larger than the force necessary to open the mold even when the foaming force of the molten resin is weak. Further, the linear rolling slider 31 can be replaced with a flat liner with low friction.

  4 and 5 show a cross section of the engaging portion between the tie bar 20 and the half nut 22 in the prior art. The tooth shape in FIG. 4 is a right-angled rectangle. When the half nut 22 is closed, the nut end face 22d abuts, and in the mold-clamped state, only one side of the tooth is in contact, and the one side of the tooth has a size. There is a gap of y. Further, there is a gap x between the nut pressing member 23 and the half nut 22. In FIG. 5, the tooth shape is a sawtooth, but a similar gap exists. Therefore, x + y becomes backlash, and accordingly, the thickness of the foam molded product varies depending on whether the foaming pressure is large or small.

By mounting the linear rolling slurder 31 between the half nut pressing member 23 and the half nut 22, the sliding frictional force generated by the pressing force of the spring 32 can be reduced, and a smooth opening / closing operation of the half nut 22 can be realized.
In addition, when engaged, only one of the oblique tooth surfaces of the half nut 22 is in contact with the oblique slope of the tie bar and the other oblique tooth surfaces are not in contact with each other. As a result, the man-hour required for processing the tooth surface can be reduced. Since the mold release force is considerably smaller than the mold clamping force, even if the force is applied only at one oblique tooth surface, the mold release force can sufficiently withstand.

From here, the foam molding operation | movement using the compound type clamping apparatus of this invention mentioned above is demonstrated.
First, the mold opening / closing motor 43 operates from a state where the mold is opened as shown in FIG. 2, and the movable platen 16 advances to close the mold. Since the mold thickness size differs depending on the mold, the hydraulic pressure (not shown) is placed in the mold clamping side oil chamber 51 or the mold opening side oil chamber 52 of the mold clamping cylinder so that the engaging portion of the half nut 22 and the tie bar 20 is engaged in this state. The hydraulic oil is supplied from the device, and the piston 50 and the tie bar 20 are adjusted to move and mesh with each other. When the piston 50 moves, the four tie bars 20 and the piston 50 move in conjunction with each other by the action of the tie bar support 17. Next, pressure is supplied to the nut opening / closing cylinder 25, and the half nut 22 is closed. At this time, the oblique tooth surfaces are in contact with each other, but the vertical tooth surfaces may be in a state where a gap is slightly opened. When hydraulic oil is further supplied to the mold clamping side oil chamber 51, the piston 50 and the tie bar 20 move in the right direction in the figure. Then, since the closing force is acting on the half nut 22, it further moves in the closing direction, and both the oblique tooth surface and the vertical tooth surface come into contact with each other. When high pressure oil is supplied to the mold clamping side oil chamber 51, the tie bar 20 is pulled with a large force, and a large mold clamping force is applied to the mold.

In this state, the foamed molten resin is injected and filled into the mold from an injection device (not shown). When the inside of the mold cavity is filled with the foamed molten resin, the resin flow path in the nozzle of the injection device is closed, and the pressure of the hydraulic oil in the mold clamping side oil chamber 51 is lowered. At this time, when the foaming pressure of the resin is high, when the mold clamping side oil chamber 51 is lowered, the mold is slightly opened by the foaming pressure. By controlling the hydraulic pressure supply device by the control device and finely controlling the amount of hydraulic oil discharged from the mold clamping side oil chamber 51, the opening amount of the mold can be finely adjusted, and the desired wall thickness at the desired opening speed. The mold can be opened until Therefore, it becomes possible to stably control the thickness and foaming state of the foam molded product. The thickness of the molded product is a value obtained by adding the mold opening amount to the thickness of the mold cavity.
When the foaming pressure is low, the piston 50, the tie bar 20, and the movable platen 16 are moved slightly to the mold opening side by slightly supplying hydraulic oil to the mold opening side oil chamber 52, and the mold opening amount is increased. The accuracy can be controlled. In the case of the present invention, since there is no backlash (backlash), it is possible to stably control the position of the piston 50 so that an equivalent mold opening amount is stable regardless of whether the foaming pressure is high or low. It can be controlled and the thickness of the foamed molded product is stabilized.

  And it hold | maintains for a fixed time with the desired mold opening amount (molded article thickness), and waits for a molded article to cool and solidify. After the cooling time is completed, hydraulic oil is supplied to the mold opening side oil chamber 52 to generate a mold release force in order to separate the molded product from the fixed mold 10 so that the mold can be opened. The releasing force is transmitted to the movable mold 11 through the tie bar 20, the half nut 22, the linear rolling slider 31, the spring 32, the nut pressing member 23, and the movable platen 16. When the release force is large, the spring 32 contracts, so that the linear rolling slider 31 directly contacts the nut holding member 23 and transmits the release force.

  When the mold is released and the mold is slightly opened, the pressure of the clamping cylinder is released, and hydraulic oil is supplied to the nut opening / closing cylinder 25 to open the half nut 22 (detachment). Thereafter, the mold opening / closing motor 43 is driven to greatly open the movable platen 16. Then, the molded product is extruded from the mold and taken out of the machine, and one molding cycle is completed.

  As described above, the piston 50 and the tie bar 20 of the mold clamping cylinder are integrated, there is no backlash at the engaging portion between the tie bar 20 and the half nut 22, and there is no backlash between the half nut 22 and the movable platen 16. Furthermore, the movable mold 11 is integrally attached to the movable platen 16. Therefore, the amount of opening of the mold can be reliably controlled regardless of the foam pressure by simply controlling the position of the piston 50. And the thickness and foaming state of a foam-molded product can be controlled stably.

  The above-described embodiment is an example of the present invention, and the present invention is not limited by the embodiment, and is defined only by matters described in the claims, and other embodiments are also possible. It can be implemented.

  It can be used in production factories where injection molding machines that can mold resin foam molded products operate, and can contribute to improving the quality of foam molded products.

DESCRIPTION OF SYMBOLS 10 Fixed type 11 Movable type 13 Machine base 14 Fixed key 15 Fixed platen 15a Injection hole 16 Movable platen 17 Tie bar support 18 Collar 20 Tie bar 20A Tie bar engaging part 20a Tie bar sawtooth engaging tooth 20b Tie bar rectangular engaging tooth 20c Tie bar saw tooth engaging Teeth 22 Half nut 22a Half nut saw tooth engaging tooth 22b Half nut rectangular engaging tooth 22c Half nut saw tooth engaging tooth 22d Nut end face 23 Nut holding member 25 Nut opening / closing cylinder 25a Cylinder rod 31 Linear rolling slider 32 Spring 41a Slider rail 41b Slider Block 43 Mold opening / closing motor 44 Coupling 45 Bearing support member 46 Ball screw nut 47 Ball screw shaft 48 Tip support member 49 Nut holder 50 Piston 1 Clamping side oil chamber 52 inch open side oil chamber

Claims (3)

A machine base; a fixed platen fixedly mounted on the machine base and having a clamping cylinder; a movable platen mounted on the machine base so as to be movable in a mold opening and closing direction; and the machine base A movable device that is fixed to the movable platen and moves the movable platen; a tie bar that penetrates the movable platen and is coupled to a piston in the clamping cylinder; and a tie bar that is attached to the movable platen via a nut pressing member. A combined mold clamping device of an injection molding machine comprising a joint and a half nut that can be engaged and disengaged,
A spring for pressing the half nut against the movable platen is provided between the nut pressing member and the half nut, and the engaging portion of the tie bar and the half nut has a sawtooth shape composed of an oblique tooth surface and a vertical tooth surface. The oblique tooth surface and the vertical tooth surface of the engaging portion are in contact with each other at the time of engagement, and backlash (backlash) between the movable platen and the tie bar can be removed. Compound mold clamping device for molding machines. 2. The injection molding machine according to claim 1, wherein a linear rolling slurder is mounted between the nut pressing member and the half nut to reduce sliding resistance during the engagement / disengagement operation. Combined mold clamping device. The half nut is processed so that, when engaged, only one oblique tooth surface is in contact with the oblique tooth surface of the tie bar engaging portion and the other oblique tooth surfaces are not in contact with each other. 3. A combined mold clamping device for an injection molding machine according to 1 and 2.

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