JPH0238019A - Mold clamping apparatus for injection molding machine - Google Patents

Abstract

PURPOSE:To improve the accuracy in clamping a mold by providing a set of rails with guide grooves on an upper surface of a bench frame in a confronting manner, and employing a slide mechanism provided with protruding threads to be engaged with said guide grooves at a bottom surface of a movable bed. CONSTITUTION:A slide mechanism is comprised of a set of rails 11 with guide grooves which are rigidity mounted in parallel onto an upper surface of a bench frame 10 and, protruding threads 13 fitted with the guide grooves 12 on the bottom surface of a movable bed 2 and slidable along the guide grooves 12. The movable bed 2 is installed with right angles to the bench frame 10 and moved in a horizontal direction to a fixed bed 1 by the contraction of a mold clamping cylinder 4 and a toggle link 5. A tie-bar 6 is inserted into an insertion hole 21 of the movable bed 2 without a bush intervened therebetween. Therefore, since a clearance is maintained so that the tie-bar 6 is not in touch with the movable bed 2 even if the tie-bar 6 is deflected in general use, the parallelism of the apparatus is never broken by the distortion or deformation of the tie-bar 6 etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold clamping device for an injection molding machine.

[Conventional technology]

As shown in FIG. 4, the toggle-type mold clamping device of an injection molding machine allows both molds, a fixed mold 15 attached to a fixed platen 1 and a movable mold 16 attached to a movable platen 2, to be fully extended by the fully extended toggle link 5. When the tie bars 6 are closed and tightened, the tie bars 6 are pulled, and as a result, the tie bars 6 themselves extend, generating an elastic recovery force as a reaction force against the extension of the tie bars 6 themselves, and this elastic recovery force is used to tighten the mold. It acts as a force and tightly tightens both molds,
With this toggle type mold clamping device, the elongation of the tie bars 6 changes slightly for each tie bar 6 due to the influence of thermal changes in the mold, etc. during operation of the injection molding machine, the load of the mold, etc., and the entire mold The constant mold clamping force no longer acts uniformly on the mold. In addition, the parallel distance between the fixed platen 1 and the movable platen 2, and the parallel movement of the movable platen 2 relative to the fixed platen 1 by the toggle link 5, are controlled by the tie bars 6...
It changes depending on the clearance between the mold and bushings 8, and also due to distortions such as bending of the tie bars 6 due to thermal effects, etc. As shown in Fig. 3, when the movable platen 2 moves to close the mold 8, Although it is slightly inclined, the movable plate 2 is no longer parallel to the fixed plate 1, and the mold closing position of the movable mold 16 relative to the fixed mold 15 changes slightly. Force will no longer act uniformly.

Ru.

Due to the above-mentioned effects of uniformity of mold clamping force and deterioration of parallelism during mold closing movement of the movable platen, dimensional accuracy of minute units in injection molded products becomes inconsistent, and dimensional accuracy is required. This makes it unsuitable for high precision molding. In order to solve these problems, conventionally, as described in Japanese Patent Application Laid-Open No. 62-227717 and shown in FIG. ′
Detects the extension of the tie bar 6' hair, that is, the tightening force, and switches the toggle support 3.
Each tie bar 6' is expanded and contracted using the adjustment cylinder 8' formed between the mold clamping force adjustment nand 9' locked to the toggle support 3', and the extension force applied to the tie bar, that is, the mold clamping force, is preliminarily adjusted. Feedback control is applied to the value within a predetermined range, and it is possible to absorb minute changes in mold clamping force due to heat effects, etc., to obtain a uniform mold clamping force, and to mold high precision molded products. To prevent misalignment, the bushings 8 attached to the movable platen 2 should be tightly fitted to the tie bars 6... to reduce the clearance between the tie bars and the bushings, or the bottom of the movable platen 2 may be By attaching rollers 19 to the mold, or by bringing the bottom of the movable platen 2 into contact with the base plate frame 10 as shown in Fig. 6, the amount of distortion and deformation due to the weight of the mold guided by the tie bars 6 is reduced. There are ways to do this.

[Problems to be Solved by the Invention] Among the above-mentioned conventional methods, the one described in Japanese Patent Application Laid-Open No. 62-227717 adjusts minute changes in mold clamping force due to thermal effects or mold loads, etc. to maintain a constant mold clamping force. The mold clamping force is obtained and corresponds to high-precision product molding, but the means to achieve this requires a complicated mechanism such as a feedback control means, and the conventional means for adjusting the parallelism of the movable platen does not require the use of rollers 19. The friction between the base plate frame 10 and the bottom of the movable platen 2 and the base plate frame 10 increases due to the bending of the tie bars, and the sliding resistance during parallel movement of the movable platen 2 increases, making it difficult to open and close the mold. It will have an impact. In addition, if the clearance between the tie bar 6 and the bushing 8 is made small, the wear of the bushings of that length will be severe and clearance between the tie bar and the bushing will easily occur, so the number of times the bushings must be replaced and the number of times lubricating oil must be supplied to the bushings is increased. This is a problem that requires a lot of attention, and is not an essential solution.

The present invention uses a simple mechanism based on a novel idea that is completely different from the prior art as described above, and ensures clear run of tie bars and bushings. This ensures that the parallelism of the movable platen to the fixed platen is not affected in any way and the clamping force is always applied evenly, providing a mold clamping device for injection molding machines that is suitable for high-precision product molding. It is something to do.

[Means to solve the problem]

The mold clamping device for an injection molding machine of the present invention includes a hole 21 of a movable platen 2.
The tie bars 6... are pushed through to eliminate contact between the movable platen 2 and the tie bars 6..., so that distortion of the tie bars does not affect the movable platen, and the parallel movement of the movable platen 2 is guided by the upper surface of the base plate frame 10. A rail 11 having a groove 12 is fixed oppositely, the rail 11 is used as a guide, a protrusion 13 is provided on the bottom of the movable platen 2 to fit into the guide groove 12, and the protrusion 13 is arranged along the guide groove 12. The diameter of the hole 21 is preferably made larger than the diameter of the tie bar so that a required clearance is formed between the inner periphery of the hole 21 and the outer periphery of the tie bar 6. In addition, the guide groove 12 and the protrusion 1
The cross-sectional shape of No. 3 is an inverted triangle or a quadrilateral.

be.

[Function] The present invention does not move the movable plate in parallel using tie bars as guides when opening and closing the mold as in the conventional example, but instead provides a slide mechanism between the top surface of the base plate frame and the bottom surface of the movable plate. The movable platen is configured to move in parallel using a guide grooved rail fixed to the platen frame forming one of the slide mechanisms as a guide. In other words, the movable platen moves to close and open the mold in accordance with the expansion and contraction of the toggle link by the mold clamping cylinder, but the load of the movable platen and the movable mold is received by the rail, that is, the platen frame.
Since there are no bushings interposed between the tie bars and the movable platen, their loads do not affect the deflection of the tie bars, and the deflection of the tie bars due to thermal effects, for example, is minimal, and because of the clearance, the movable platen It does not act as frictional resistance. Therefore, the number of tons of movable platen and tie bar required for the parallel movement of the movable platen during the opening and closing action of the mold is
As shown in Figure 4 (the movable platen is not tilted), the protrusion provided on the bottom of the movable platen is closed as a guide groove of the rail opposite to the base frame. It occurs equally on each tie bar when

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

The present invention is an optimal embodiment of a toggle type mold clamping device in an injection molding machine as shown in FIG. A toggle link 5 placed between the movable plates 2 expands and contracts by operating the mold clamping cylinder 4, moving the movable plate 2 to the fixed plate 1.
By moving the movable mold 16 toward and away from the stationary mold 15, the movable mold 16 of the mold is opened and closed by the fixed mold 15, that is, the mold is closed and opened. Then, when closing the mold, the tie bars 6 are extended, and the elastic recovery force is used as a reaction force to clamp the mold, and one end of the tie bars 6 is connected to the fixed platen l via the fixing nut 7. However, the other end of the tie bar 6 is attached to the toggle support 3 via an adjustment nut 9 so that the extension force of the tie bar, that is, the mold clamping force, can be adjusted according to the type, thickness, etc. of the mold. ing. The above mechanism is the same as the conventional toggle type mold clamping device, but
The present invention is different from the conventional one in that the guide function for parallel movement of the movable platen 2 is not performed by the tie bars 6, but by a slide mechanism attached to the base plate frame 10. The slide mechanism includes a pair of guide grooved rails 11 fixedly fixed in parallel on the upper surface of the base plate frame 10 and a protrusion that fits into a guide groove 12 attached to the bottom surface of the movable platen 2 and is slidable along the guide grooves 12. 13, the movable platen 2 is mounted perpendicularly to the base plate frame 10, and moves parallel to the fixed platen 1 in the distance direction by expansion and contraction of the mold clamping cylinder 4 and toggle link 5.

In addition, the tie bar 6 in the movable platen 2...the insertion hole 21...
Since the tie bar 6 is inserted without interposing a bushing, the clearance is formed so that the tie bar and the movable plate do not come into contact even if the tie bar is bent within the range of use, so distortions such as one tie bar may occur. The parallelism of the movable plate does not go out of order due to the influence of the movable plate, and the parallel movement and parallelism of the movable plate have no relationship with the tie bar, and are simply carried out by the sliding mechanism.

In addition, in the embodiment, the cross-sectional shapes of the guide groove 12 and the protrusion 13 are illustrated as having an inverted triangular shape as shown in FIG. 2, and a rectangular uneven trapezoid shape as shown in FIG. 3. There is no particular limitation, and the point is that any shape that fits together and does not allow the guide groove and the protrusion to separate easily may be used.

Although not shown, if the rail 11 provided on the base frame 10 can be finely adjusted in the left and right direction as shown in FIG. In other words, the fixed movable mold 16 of the mold is 15
The position, fitting relationship, etc. can be finely adjusted, making it a mechanism that can be used to manufacture highly accurate molded products.

〔Effect of the invention〕

The present invention has a simple structure by employing a slide mechanism in which rails having guide grooves are provided on the top surface of the base plate frame, and protrusions that fit into the guide grooves are attached to the bottom surface of the movable platen. Not only that, but the weight of the mold attached to the movable platen and the movable platen is not received by the tie bars but by the base frame, so it has nothing to do with the size and weight of the mold. Since there is no bushing in the tie bar insertion hole of the movable platen, the movable platen and the tie bar are formed with a clearance that practically does not have mechanical contact, and the bending of the tie bar is caused by the bending of the movable platen. It does not affect the parallel movement, and conversely, the load of the movable platen and mold does not affect the tie bars and cause strain deformation of the tie bars, so the movable platen moves as shown in Figure 4. The tie bars do not tilt, and parallelism is stably maintained. On the other hand, since a major cause of distortion and deformation of the tie bars is eliminated, distortion and deformation are also minimal, and the clamping force is applied equally to each tie bar. ,
This improves mold clamping accuracy, and as a result, it can be fully used as an apparatus for manufacturing high-precision injection molded products.

In addition, in the past, an appropriate amount of lubricating oil was supplied to the bushing, which caused the molded product to become dirty due to the lubricating oil, but in the present invention, since the bushing is not used on the movable platen, the lubricating oil can be lubricated. There is no need to supply oil, the molded product is not contaminated by lubricating oil, and the product yield is improved.

[Brief explanation of the drawing]

Fig. 1 shows the general structure of a mold clamping device for an injection molding machine according to an embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A' in Fig. 1, and Fig. 3 shows a rail and This shows another embodiment of the cross-sectional shape of the protrusion, and FIGS. 4 to 7 show examples of conventional mold clamping devices for injection molding. 2... Movable plate, 21... Hole, 8... Bush, 6... Tie bar, 10... Base plate frame, 11... Rail, 12... Guide groove,
13...Protrusion inner groove, 13...Protrusion

Claims (4)

[Claims] (1) Insert the tie bars 6 into the holes 21 of the movable platen 2, fix the rails 11 having the guide grooves 12 on the upper surface of the base plate frame 10, and fit the rails 11 into the guide grooves 12 on the bottom of the movable platen 2. A mold clamping device for an injection molding machine, which is provided with matching protrusions 13. (2) The diameter of the hole 21 is made larger than the diameter of the tie bar to the extent that a required clearance is formed between the inner periphery of the hole 21 and the outer periphery of the tie bar 6. 1. The mold clamping device for an injection molding machine according to 1. (3) The mold clamping device for an injection molding machine according to claim 1, wherein the guide groove 12 and the protrusion 13 have an inverted triangular cross-sectional shape. (4) The mold clamping device for an injection molding machine according to claim 1, wherein the guide groove 12 and the protrusion 13 have a rectangular cross-sectional shape.