Mold mounting platen for injection molding machine

In a mold mounting platen for an injection molding machine, at least one of a mold mounting member and a clamping force transmission member constituting the mold mounting platen has a central bearing surface in a central portion thereof and a peripheral bearing surface outside the central bearing surface. The amount of protrusion of the central bearing surface is larger than that of the peripheral bearing surface.

RELATED APPLICATIONS

The present application claims priority to Japanese Application Number 2013-230556, filed Nov. 6, 2013, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mold mounting platen for use in an injection molding machine.

2. Description of the Related Art

An injection molding machine includes a movable platen which moves along several tie rods disposed perpendicularly to a stationary platen fixed to a base frame. Moreover, in a clamping mechanism of the injection molding machine, the movable platen and a rear platen are connected by a toggle mechanism. The extension of links of the toggle mechanism causes the tie rods to extend and generates clamping force.

FIG. 10is a view showing a toggle clamping mechanism of a general prior art injection molding machine. Reference numeral1denotes a movable platen, and reference numeral2denotes a stationary platen. Moreover, reference numerals3denote tie rods. The movable platen1is configured to move along the tie rods3in the lateral direction inFIG. 10. The tie rods3are fixed to tie rod fixing portions6on a surface of the stationary platen2which is opposite from the movable platen1side.

A movable-side mold half5and a stationary-side mold half4are respectively provided on the movable platen1and the stationary platen2to face each other. Moreover, a toggle link mechanism71is provided on a side of the movable platen1which is opposite from the stationary platen2. The toggle link mechanism71transmits the clamping force of the movable platen1side to the movable-side mold half5.

As shown inFIG. 10, in the prior art injection molding machine, the tie rod fixing portions6to which the tie rods3are fixed are provided in four corner portions of the stationary platen2, and toggle link supporting points7of the toggle link mechanism71are provided at two upper and lower outer positions on the movable platen1. In the case where such a configuration is employed, the following problem may occur: the contact pressure at a junction surface14between the stationary-side mold half4and the movable-side mold half5increases with increasing distance from the center, and becomes low in a central region.

A number of techniques which have been developed to solve the above-described problem are disclosed in the patent documents below.

In a clamping mechanism for an injection molding machine disclosed in Japanese Patent Application Laid-Open No. H8-258103, square pyramid-shaped support mechanisms are used to support a stationary platen and a movable platen. Apex portions of the support mechanisms support the stationary platen and the movable platen so that clamping force may be generated in the central region.

In a mold clamping apparatus disclosed in Japanese Patent Application Laid-Open No. H11-170322, a groove for the prevention of distortion is provided between toggle link supporting points and a mold mounting surface to which a movable-side mold half is attached, so as to prevent distortion from occurring in the mold mounting surface.

Moreover, in a mold clamping apparatus for an injection molding machine disclosed in Japanese Patent Application Laid-Open No. 2007-253458, a detachable contact member is provided between each of a stationary platen, a movable platen and a peripheral portion of a corresponding clamping force transmission member. The contact member is attached or detached in accordance with the size of a mold to control the transmission of clamping force from the clamping force transmission members.

Further, in a mold clamping apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-111018, extended portions are provided on the periphery of a mold mounting surface as contact pressure adjusting portions for reducing pressure differences occurring across a junction surface between a stationary-side mold half and a movable-side mold half.

In the clamping mechanism of the injection molding machine disclosed in Japanese Patent Application Laid-Open No. H8-258103 and the mold clamping apparatus disclosed in Japanese Patent Application Laid-Open No. H11-170322, a decrease in contact pressure in the central region can be reduced by pressing only in the central region or by providing a groove to inhibit the transmission of the clamping force in a peripheral region. Such configurations are suitable for cases where a mold is located only in the central region. However, in the case where a mold is vertically or horizontally long and reaches the outside of connecting portions of divided platens in Japanese Patent Application Laid-Open No. H8-258103 or a portion corresponding to the groove in Japanese Patent Application Laid-Open No. H11-170322, the transmission of the clamping force is weak in the peripheral region. Accordingly, dimensional errors or burrs may occur in molded parts (seeFIG. 11).

In the mold clamping apparatus of the injection molding machine disclosed in Japanese Patent Application Laid-Open No. 2007-253458, the transmission of the clamping force to the peripheral region is controlled by attaching or detaching the contact members as clamping force transmission members. However, the contact members need to be provided as additional components. Accordingly, the complexity of the mechanism and the operation may increase as follows: mechanisms for attaching and detaching the contact members in accordance with mold size and the like need to be added; the contact members need to be attached or detached by hand operation; and the like.

In the mold clamping apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-111018, bearing surfaces for connection are provided on the periphery. Thus, the mold clamping apparatus is suitable for vertically or horizontally long molds. However, the effect of concentrating the clamping force at the center is small. Accordingly, in the case where a mold is located only in a central portion, problems such as a decrease in the clamping force may occur.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a mold mounting platen which is used in an injection molding machine to transmit optimal clamping force regardless of the size and shape of a mold.

The present invention provides a mold mounting platen for an injection molding machine. The mold mounting platen includes a mold mounting member and a clamping force transmission member. At least one of the mold mounting member and the clamping force transmission member includes a central bearing surface in a central portion thereof, a peripheral bearing surface provided outside the central bearing surface, and a recessed portion provided between the central bearing surface and the peripheral bearing surface. An amount of protrusion of the central bearing surface in a direction opposite to a direction of depth of the recessed portion and parallel to a mold opening/closing direction is larger than that of the peripheral bearing surface.

As described above, the central bearing surface is provided in the central portion of at least one of the mold mounting member and the clamping force transmission member; the peripheral bearing surface is provided outside the central bearing surface; the recessed portion is provided between the two bearing surfaces; and the amount of protrusion of the central bearing surface from the recessed portion is larger than that of the peripheral bearing surface. Accordingly, when the size of a mold is not so large and the mold is located only in a central region, the mold mounting member and the clamping force transmission member are connected to each other with the central bearing surface in contact. On the other hand, when a vertically or horizontally long mold is used, force applied to the mold causes the mold mounting member and the clamping force transmission member to be connected to each other with the peripheral bearing surface as well as the central bearing surface in contact, and therefore clamping force is transmitted even in a peripheral region. Thus, optimal clamping force can be provided regardless of the size and shape of a mold.

A difference between the amount of protrusion of the central bearing surface and that of the peripheral bearing surface may be larger than an amount by which the clamping force transmission member is deformed in the mold opening/closing direction at a surface facing the peripheral bearing surface at time of generation of rated clamping force.

In that case, since the difference between the amount of protrusion of the central bearing surface and that of the peripheral bearing surface is larger than the amount by which the clamping force transmission member is deformed in the mold opening/closing direction at the peripheral bearing surface at the time of generation of the rated clamping force, contact between the clamping force transmission member and the mold mounting member at the time of generation of rated clamping force is prevented from being made only by the deformation of the clamping force transmission member.

With the above-described configuration, the present invention can provide a mold mounting platen which is used in an injection molding machine to transmit optimal clamping force regardless of the size and shape of a mold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a view showing a toggle clamping mechanism for an injection molding machine of one embodiment of the present invention. Reference numeral1denotes a movable platen, and reference numeral2denotes a stationary platen. Moreover, reference numerals3denote tie rods. The movable platen1is configured to move along the tie rods3in the lateral direction inFIG. 1. The tie rods3are fixed to tie rod fixing portions6on a surface of the stationary platen2which is opposite from the movable platen1.

A movable-side mold half5and a stationary-side mold half4are respectively provided on the movable platen1and the stationary platen2to face each other. Moreover, a toggle link mechanism71is provided on a side of the movable platen1which is opposite from the stationary platen2. The toggle link mechanism71transmits the clamping force of the movable platen1side to the movable-side mold half5.

In the toggle clamping mechanism of the injection molding machine of this embodiment, each of the movable platen1and the stationary platen2is divided into a mold mounting member and a clamping force transmission member. Specifically, the movable platen1is divided into a movable-side mold half mounting member1aand a movable-side clamping force transmission member1b, and the stationary platen2is divided into a stationary-side mold half mounting member2aand a stationary-side clamping force transmission member2b.

FIGS. 2, 3A, 3Bare views showing the movable-side mold half mounting member1a.FIG. 2is a perspective view of the movable-side mold half mounting member1a,FIG. 3Ais a front view thereof, andFIG. 3Bis a cross-sectional view thereof taken along line A-A ofFIG. 3A. As shown inFIGS. 2, 3A, 3B, a central bearing surface8is provided in a central portion of a surface of the movable-side mold half mounting member1aopposite from a surface thereof to which the movable-side mold half5is attached, and a peripheral bearing surface9is provided in a peripheral portion thereof to surround the central bearing surface8. Moreover, a recessed portion10is provided between the central bearing surface8and the peripheral bearing surface9.

In this embodiment, the central bearing surface8and the peripheral bearing surface9are formed integrally with the movable-side mold half mounting member1aas one component. However, the central bearing surface8and the peripheral bearing surface9may be formed as separate components and attached to the movable-side mold half mounting member1a. Moreover, as shown in the cross-sectional view ofFIG. 3B, the cross-sectional shape of the recessed portion10is a rectangular shape in this embodiment, but not limited to this shape, and may be other shape, for example, a shape having a curved bottom portion such as a spherical bottom portion.

As shown in the cross-sectional view ofFIG. 3B, both of the central bearing surface8and the peripheral bearing surface9protrude in a direction opposite to the direction of depth of the recessed portion10, i.e., in a direction opposite from the surface of the movable-side mold half mounting member1ato which the movable-side mold half5is attached. The amount of protrusion of the central bearing surface8is larger than the amount of protrusion of the peripheral bearing surface9by δ. With a clearance having a height of δ, when the movable-side mold half mounting member1ais attached to the movable-side clamping force transmission member1b, the central bearing surface8of the movable-side mold half mounting member1acomes in contact with the movable-side clamping force transmission member1b. The size of δ may be appropriately set in accordance with the rigidity of the movable-side mold half mounting member1aand the movable-side clamping force transmission member1b, and is preferably approximately 0.2 to 2 mm.

FIG. 4is a cross-sectional view showing the movable-side mold half mounting member1aand the movable-side clamping force transmission member1battached to the foregoing. When clamping force is not generated, as shown inFIG. 4, a portion (connecting portion11) of the central bearing surface8of the movable-side mold half mounting member1ais in contact with the movable-side clamping force transmission member1b, and a portion (non-connecting portion12) of the peripheral bearing surface9of the movable-side mold half mounting member1ahas a clearance of δ to the movable-side clamping force transmission member1b. The size of δ is set so as to be larger than the amount of deformation caused in the movable-side clamping force transmission member1bwhen rated clamping force specified for the injection molding machine is generated.

Next, the operation of the injection molding machine of this embodiment will be described with reference toFIGS. 5 and 6.FIG. 5shows the case of a general mold in which molded parts are located in a central region, andFIG. 6shows the case where a vertically long mold is used.

In the case of a general mold in which molded parts are located in the central region as shown inFIG. 5, the mold is not located in a peripheral region. Accordingly, the clamping force13from the toggle link mechanism71is transmitted only through the central bearing surface8at the center, and is not transmitted through the peripheral bearing surface9on the periphery. Thus, the clamping force can be concentrated on the central region in the vicinity of the molded parts.

On the other hand, in the case where a vertically or horizontally long mold is used as shown inFIG. 6, the mold is partially located in the peripheral region. Accordingly, the clamping force13from the toggle link mechanism71can be transmitted even in the peripheral region. Specifically, as shown inFIG. 6, a peripheral portion of the mold mounting platen outside the connecting portion deforms to come in contact with the peripheral bearing surface9. Thus, the clamping force is also transmitted to regions around the molded parts located at outer positions. It should be noted that reference numeral15denotes the movable-side mold half.

As described above, the state of contact of the peripheral bearing surface9changes in accordance with the size and shape of a mold to be used, and a contact pressure distribution appropriate for the mold can be realized. Thus, defective molding such as the occurrence of burrs can be reduced in any type of mold.

In the above description, an explanation has been made using an example in which the central bearing surface8and the peripheral bearing surface9are provided on the movable-side mold half mounting member1aof the movable platen1. However, the central bearing surface8and the peripheral bearing surface9may be provided on the movable-side clamping force transmission member1bas shown inFIG. 7. Moreover, the central bearing surface8and the peripheral bearing surface9may also be provided on each of the movable-side mold half mounting member1aand the movable-side clamping force transmission member1b.FIG. 8is a cross-sectional view for the case where the central bearing surface8and the peripheral bearing surface9are provided on each of the movable-side mold half mounting member1aand the movable-side clamping force transmission member1b, showing a state in which the movable-side mold half mounting member1aand the movable-side clamping force transmission member1bare in contact with each other. In that case, also, as in the cases where the central bearing surface8and the peripheral bearing surface9are provided only on the movable-side mold half mounting member1aas shown inFIGS. 5 and 6, the state of contact of the peripheral bearing surface9changes in accordance with the size of a mold, and a contact pressure distribution appropriate for the mold can be realized. Thus, defective molding such as the occurrence of burrs can be reduced in any type of mold.

Moreover, in this embodiment, an explanation has been made using an example in which the central bearing surface8and the peripheral bearing surface9are provided on the movable-side mold half mounting member1aand the movable-side clamping force transmission member1bof the movable platen1. However, the central bearing surface8and the peripheral bearing surface9may also be provided on the stationary-side mold half mounting member2aand the stationary-side clamping force transmission member2bof the stationary platen2instead of the movable platen1, or the central bearing surface8and the peripheral bearing surface9may also be provided on the mold mounting member and the clamping force transmission member of each of the movable platen1and the stationary platen2.

In this embodiment, an explanation has been made using an example having a configuration in which the peripheral bearing surface9surrounds the perimeter of the central bearing surface8. However, the peripheral bearing surface9does not necessarily have to surround the entire perimeter of the central bearing surface8, and may be appropriately modified as needed. In one example, as shown inFIG. 9, peripheral bearing surfaces9may be provided which are located only at upper and lower positions.