JP2011218643A - Seal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal structure which can reduce or prevent the deterioration of durability of an elastic sealing member or the deterioration of sealing properties, even when a significant deformation of the elastic sealing member is required before and after the formation of a sealing part, for example, in case of foaming resin molding.SOLUTION: In this seal structure for a mold for foaming resin molding, an accommodating groove for the elastic sealing member is formed in the contact surface of at least one of a pair of mold members which form the sealing part by bringing the mold members into contact with each other through their respective contact surfaces, and further, an additional shallow accommodating groove is formed on the side edges of the accommodating groove, so that the sealing part can be formed even in the contact position of the paired mold members and also, even in the intermediate position retreating from the contact position.

Description

  The present invention relates to a sealing structure suitable for a resin molding die, particularly a foamed resin molding die that requires good sealing characteristics in a relatively wide range of mold positions.

  In foam molding of resin parts, in order to suppress appearance defects due to the occurrence of swirl marks (silver-white streaks caused by the bursting of bubbles), simultaneously with (or prior to) the injection of molten resin into the mold Inject high pressure gas into the mold (apply counter pressure). In order to maintain the pressure in the mold generated thereby, normally, as shown in FIG. 1, a pair of mold members constituting the mold 1, that is, a female mold member 1a including a resin molding cavity 2, and the same An accommodation groove 3 is provided at a position surrounding the cavity 2 of at least one of the male members 1b to be abutted (male member 1b in the example of FIG. 1), and an elastic seal member (usually having a circular cross section) A so-called O-ring is arranged. Further, in the foamed resin molding, as shown in FIG. 2 which is an enlarged view of a portion A in FIG. 1, more accurately than the housing groove 3 provided in the male member 1b, more accurately with the surrounding female member 1a. It is assumed that the O-ring 4 protrudes from the contact surface 1b1 by the dimension S, and this protruding dimension S is obtained by retracting (at least) one of the mold members 1a and 1b after resin injection into the cavity 2. The distance between the mold members 1a and 1b (the contact surfaces 1a1-1b1) (so-called core back distance, CB) at the time of completing the foam molding of the inside of the mold during foaming resin molding It is necessary to maintain the pressure. For this reason, in foamed resin molding, the compression margin of the O-ring becomes larger than that in normal resin molding, and when the mold is closed for resin injection, as shown in FIG. A part 4dp of the O-ring 4d generated by the compression is crushed and held between the contact surfaces 1a1-1b1 of the mold member, which is also combined with a large deformation in comparison with when the mold is opened. As a result, the durability of the O-ring is significantly reduced.

  On the other hand, as a sealing mechanism that can alleviate the above-described problem, an additional recessed groove 13a is provided at the bottom of the accommodating groove 13 of the elastic seal member provided in at least one of the pair of members 11a and 11b forming the seal portion, There is also a proposal of a seal mechanism that absorbs the deformation of the elastic seal member at the time and the expansion margin due to heating after sealing (Patent Document 1). However, depending on the recessed groove provided at the bottom of the housing groove formed in this way, the large deformation of the O-ring required for foamed resin molding cannot be dealt with and the sealing performance is deteriorated. There is also a fear.

JP 2009-97684 A

  The present invention can alleviate a decrease in durability or a decrease in sealability even when a large deformation of the elastic seal member is required before and after the formation of the seal portion, for example, in foamed resin molding. The main purpose is to provide a seal structure that can be prevented.

  The seal structure of the present invention has been developed to achieve the above-described object, and more specifically, a pair of molds that form a seal portion by being brought into contact with each other via respective contact surfaces. By forming an accommodation groove for the elastic seal member on at least one abutment surface of the member, and providing a shallow additional accommodation groove on the side edge of the accommodation groove, the contact position of the pair of mold members and the corresponding The seal portion is still formed even at an intermediate position that is retracted from the contact position. When the seal structure of the present invention is adopted, the large compression margin of an elastic seal member such as an O-ring is absorbed by an additional receiving groove provided in the vicinity of the abutting surface before and after the formation of the seal portion so as to face each other at the time of sealing. The area of the elastic seal member that comes into contact with the member (that is, the increase in the seal area) is increased to contribute to the improvement of the seal characteristics and the elasticity between the contact surfaces of the pair of seal contact members (for example, mold members). Application of an excessive compressive force due to a part of the seal member being crushed and sandwiched, and deterioration of durability of the elastic seal member accompanying this can be prevented.

The front cross-sectional schematic diagram containing the cavity and O-ring accommodation groove | channel of the conventional mold for foaming resin molding. The schematic cross section of the state which accommodated the O-ring in the male accommodation groove | channel in the A section of FIG. The enlarged view of the A section of FIG. 1 metal mold | die in a closed position. The schematic cross section which shows the cross-section of the O-ring accommodation groove | channel which has an additional depression groove in the bottom part in a prior art. The schematic cross section of the state which accommodated the O-ring in the male accommodation groove | channel in an example of the seal structure of this invention shown corresponding to FIG. FIG. 6 is a schematic cross-sectional view at a mold closing position of the seal structure of FIG. 5. (A) is explanatory drawing of the dimensional relationship of each part of FIG. 5, (b) and (c) are explanatory drawings of A cross section and B cross sectional shape in (a), respectively. The schematic cross section which shows another example of the seal structure of this invention corresponding to FIG.

  FIG. 5 is a schematic cross-sectional view showing the structure around the accommodation groove provided in the male mold 5b of the foamed resin molding die as an example of the seal structure of the present invention, corresponding to FIG. 2 (conventional example). With reference to FIG. 5, the cavity of the male mold 5b disposed facing the female mold 5a (shown by a dotted line together with the contact surface 5a1 at the core back position) provided with a cavity (not shown) is provided. In addition to the receiving groove 53 of the O-ring 54, the surrounding contact surface 5b1 is provided with additional receiving grooves 61 and 62 that are substantially symmetrical as a cross-sectional shape shallower than the receiving groove 53 on both side edges thereof. . 5 is shown as an enlarged view corresponding to the portion A of FIG. 1, more precisely, the additional accommodation groove 62 is arranged so as to surround the accommodation groove 53 and the additional accommodation groove 61. An O-ring 54 made of urethane rubber or the like that is generally excellent in strength and durability is disposed in the accommodation groove 53. For this arrangement, the mold 5 is closed (a pair of mold members) prior to injecting a foamable resin in foamed resin molding (for example, a polypropylene resin-based polymer or copolymer containing a baking soda-based foaming agent). 5a and 5b are brought into contact with the contact surfaces 5a1 and 5b1), and the portions that cannot be accommodated in the accommodation groove 53 of the O-ring 54d deformed by being crushed by the O-ring 54 are the additional accommodation grooves 61 and 62. The contact surface 5a1 of the female mold 5a is contacted with an enlarged area, and exhibits improved sealing performance, and is expanded to the space between the contact surfaces 5a1-5b1 of the mold members 5a-5b. There is nothing. Therefore, a part of the O-ring 54 is not deteriorated by excessive pressure between the contact surfaces.

  On the other hand, in order to promote foaming after the foamable resin is injected, the O-ring 54 is also moved when the contact surface 5a1 of the female mold 5a is retracted (core back) from the female mold 5b to the dotted line position in FIG. Since the abutment is made against the abutment surface 5a1 (indicated by the dotted line) of the female mold 5a over a certain area at the top, the foamed resin molding can be completed while maintaining the pressure inside the mold.

  In order for the seal structure of the present invention to exhibit good effects as described above with reference to FIGS. 5 and 6, it is desirable that a certain dimensional relationship be satisfied between the members. This point will be described with reference to FIG. 7A, which is a schematic sectional view substantially equivalent to FIG. That is, the protruding distance a from the contact surface 5b1 of the O-ring 54 is preferably equal to or longer than the core back distance CB, and more specifically, for example, in a range of a = 2.0 to 3.0 mm. . The depth b of the housing groove 53 is preferably equal to or greater than the radius of the O-ring 54 (more preferably 1.05 times or more and 1.10 times or less of the radius) in order to prevent the O-ring from falling off. The diameter c of the housing groove 53 is preferably equal to or smaller than the diameter of the O-ring 54 (more preferably 0.90 times or more and 0.95 times or less) in order to prevent the O-ring from falling off. The ratio e / b between the depth (maximum value) e of the additional accommodation groove and the depth b of the accommodation groove 53 is preferably about 20 to 30%. If the diameter of the receiving groove 53 is made smaller than the diameter of the O-ring 54 and the O-ring 54 is fitted, the deformed O-ring cross section becomes a slightly elongated ellipse, and the diameter of the O-ring 54 minus the receiving groove 53 Even when the protrusion distance a from the contact surface 5b1 of the O-ring 54 calculated as the depth b of the O-ring 54 is exactly the same as the core back distance CB, the substantial protrusion distance a is larger than the core back distance CB. At the core back position, a constant contact area between the top of the O-ring 54 and the contact surface 5a1 of the female mold 5a is ensured, so that the mold internal pressure can be maintained until the foamed resin molding is completed.

  The area of the cross section of the O-ring 54 that is not accommodated in the accommodation groove 53 (that is, the A cross section in FIGS. 7A and 7B) is (the distance e between the contact surface 5b1 and the opening surface of the accommodation groove 53). X (less than, preferably 0.5 to 0.9 times) the area of a cross section (B cross section in FIGS. 7A and 7C) determined by (distance between side walls d of additional accommodating grooves 61 and 62), It is preferable to effectively prevent the O-ring portion from being pinched between the mold contact surfaces 5a1-5b1 when the mold is closed.

In a specific embodiment, in the seal structure described with reference to FIGS. 5 to 7, a = 2 mm, b = 2.5 mm, c (= O-ring diameter) = 5 mm, d = 20 mm, e = 0.5 mm , A cross-sectional area = about 9.82 mm (= π × 2.5 ² ), B cross-sectional area = 10 mm ² (= 20 mm × 0.5 mm), core back distance CB = 1.6 mm By using a ring, it was confirmed that a foamed resin molding of about 1.5 to 1.8 times at about 180 to 230 ° C. of a polypropylene resin containing a baking soda-based foaming agent was smoothly performed, and 200 times or more. Even after molding of the foamed resin, no trace of deformation due to clamping (biting) of the O-ring between the mold contact surfaces was observed. On the other hand, in the conventional seal structure described with reference to FIGS. 2 to 3, the O-ring was damaged after foaming resin molding about 10 times and had to be replaced.

(Modification)
In the above, the preferable one aspect | mode of the seal structure of this invention was demonstrated, referring FIGS. However, it will be understood by those skilled in the art that the seal structure of the present invention can be implemented by variously modifying the above-described embodiments within the scope of the present invention. For example, in the above, an example in which the additional receiving grooves 61 and 62 have a substantially rectangular cross section formed stepwise between the receiving groove and the contact surface of the mold member is shown, but as shown in FIG. It is also possible to form a curved surface between the receiving groove and the abutting surface of the mold member and to form additional receiving grooves 81 and 82 having a curvature R, and generally a cross-sectional area of the elastic seal member protruding from the original receiving groove It is possible to form an additional accommodating groove having an arbitrary cross-sectional shape that gives a cross-sectional area (B cross-sectional area) larger than (A cross-sectional area).

  Further, in the above example, the example in which the housing groove having the additional housing groove is provided in the male mold is shown, but it is of course possible to provide the housing groove on the female mold side having the cavity. It is also possible to provide both the mold and the female mold.

  Moreover, in the above, the preferable application example which applies the accommodation groove | channel which has an additional accommodation groove | channel to resin shaping | molding, especially a foaming resin molding metal mold | die was shown, However, The sealing structure of this invention is not restricted to this, A big elastic seal member is large. Extremely effective for providing a general seal structure that can be deformed (for example, a deformation in which the contact width with the mating seal member exceeds the diameter of the elastic seal member, preferably 1.5 times or more). It is applicable to.

  As described above, according to the present invention, even when a large deformation of the elastic seal member is required before and after the configuration of the seal portion, for example, in foamed resin molding, the durability of the elastic seal member is reduced or Provided is a seal structure that can alleviate or prevent a decrease in sealing performance.

1 Mold (1a, 11a: Female mold (1a1: Contact surface), 1b: Male mold (1b1: Contact surface))
2 Cavity 3, 53 O-ring (elastic seal member) receiving groove 4, 54 O-ring (4d, 54d: deformation state, 4dp: biting portion)
5 Mold according to the present invention (5a: female mold (5a1: contact surface), 5b male mold (5b1: contact surface)
61, 62, 81, 82: Projection dimension CB from the housing groove of the additional housing groove SO ring CB Core back distance

Claims (4)

An accommodation groove for the elastic seal member is formed on at least one abutment surface of the pair of mold members that form a seal portion by being abutted with each other via the abutment surfaces, and side edges of the accommodation groove Further, by providing a shallower additional accommodation groove, the foamed resin is configured so that the seal portion is still formed at the contact position of the pair of mold members and the intermediate position retracted from the contact position. Seal structure for molding dies. The seal structure according to claim 1, wherein additional housing grooves that are substantially symmetrical are provided on both sides of the housing groove of the elastic seal member. The seal structure according to claim 1, wherein the additional accommodation groove is formed in a step shape between the accommodation groove and the contact surface of the at least one mold member. The seal structure according to claim 1 or 2, wherein the additional accommodation groove is formed with a curved surface between the accommodation groove and the contact surface of the at least one mold member.

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