JP4909858B2 - Mold structure for plastic pallets - Google Patents

Description

  The present invention relates to a mold structure used when molding a synthetic resin pallet by a counter pressure method.

  Conventionally, before the molten resin is injected into the cavity, a compressed gas is injected into the cavity so that the inside of the cavity is in a pressurized state, and then the molten resin is injected into the cavity while the inside of the cavity is maintained in a pressurized state. As an example, a so-called counter pressure method injection molding, in which a product is molded, is disclosed in Patent Document 1. By this counter pressure method, a product having a non-foamed surface layer (skin layer) and a uniform foamed state inside can be formed.

  Also, a synthetic resin pallet configured to reciprocate the ejector plate along the guide rod by inserting the guide rod into a through hole formed in the ejector plate disposed in the ejector box. A mold structure for use is disclosed in Patent Document 2 as an example.

Japanese Patent Laid-Open No. 1-22212 JP-A-9-109198

  In order to smoothly reciprocate the ejector plate along the guide rod, grease is configured between the guide rod and the ejector plate. In injection molding by the counter pressure method, the ejector is used. Since the compressed gas is injected into the box sealed space for each product molding process, the grease is pushed out from between the guide rod and the ejector plate by the injection of the compressed gas, thereby smoothly reciprocating the ejector plate. There was a problem that could not be done.

  In addition, in order to smoothly reciprocate the ejector plate, it is necessary to periodically supply grease between the guide rod and the ejector plate, but in the conventional synthetic resin pallet mold structure, In order to supply grease, it was necessary to disassemble the mold structure for the synthetic resin pallet, and it took considerable time and labor to supply the grease.

  An object of the present invention is to solve the problems of the above-described conventional synthetic resin pallet mold structure.

In order to achieve the above-mentioned object, the present invention provides a plastic resin pallet mold structure configured such that an ejector plate reciprocates along a guide rod disposed in an ejector box. In the ejector box located near the guide rod, a grease injection through hole communicating with the ejector box sealed space is drilled, and the grease injection through hole is closed by a removable sealing lid. Second, the guide rod is fitted into a bush disposed on the inner periphery of a through hole formed in the ejector plate, and a plurality of guide rods are provided on the inner peripheral surface of the bush. A grease groove is formed. Third, the spraying of the grease is performed in a state where the ejector plate is not located near the grease injection hole. It is obtained by the.

  Since the ejector box located near the guide rod has a grease injection through hole communicating with the ejector box sealed space, the grease injection through hole is closed by a removable sealing lid. Therefore, it is not necessary to disassemble the mold structure for the synthetic resin pallet. Therefore, the grease supply work time can be shortened and the grease supply work can be saved.

  The guide rod is fitted in a bush disposed on the inner periphery of a through hole formed in the ejector plate, and a plurality of grease grooves are formed on the inner peripheral surface of the bush. Compared to the case where the grease is simply applied, it is possible to lengthen the supply interval of the grease, and therefore it is possible to reduce the time for interrupting the production of the skid to supply the grease.

  Since the spraying of the grease is performed in a state where the ejector plate is not located near the grease injection hole, the sprayed grease can be effectively attached to the guide rod.

  When the compressed gas is injected into the ejector box sealed space, the grease groove is formed on the outer peripheral surface of the guide rod located in the through hole of the ejector plate, so that the grease groove formed on the outer peripheral surface of the guide rod is directly Therefore, it is possible to prevent the compressed gas from being blown, and therefore, it is possible to prevent the grease from being discharged from the grease groove, thereby reducing the number of times of the grease filling operation into the grease groove.

  Hereinafter, examples of the present invention will be described. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

  First, a synthetic resin pallet mold structure will be outlined with reference to FIGS. FIG. 1 shows an example in which a skid of a welding pallet is formed.

  First, the movable side portion of the synthetic resin pallet mold structure, such as the movable mold, will be outlined.

  1 is a movable side mounting plate, 2 is a movable mold receiving plate, and 3 is a cylindrical ejector attached between the movable side mounting plate 1 and the movable mold receiving plate 2. Is a box. Reference numeral 4 denotes a guide rod attached so as to bridge the movable side mounting plate 1 and the movable mold receiving plate 2. In addition, 2a is the angular core attached to the receiving plate 2 for movable molds.

  Reference numeral 5 denotes an ejector plate housed in a sealed space (hereinafter referred to as an ejector box sealed space) A1 surrounded by the movable side mounting plate 1, the movable mold receiving plate 2 and the ejector box 3. A guide rod 4 is inserted into a through hole 5 a formed in the plate 5 via a bush 6. Reference numeral 5b denotes an ejector rod attached to the surface of the ejector plate 5 located on the opposite side of the movable mold receiving plate 2. The ejector rod 5b is a through-hole formed in the movable-side mounting plate 1. It is inserted in 1a. Reference numeral 5 c denotes an ejector pin attached to the ejector plate 5. The ejector rod 5b is configured to reciprocate by a cylinder member or the like (not shown). In addition, 1b is a cylindrical guide cylinder attached to the surface of the movable side mounting plate 1 located in the ejector box sealed space A1 so as to surround the through hole 1a formed in the movable side mounting plate 1. The ejector rod 5b is fitted into the guide cylinder 1b in a sealed manner.

  Reference numeral 7 denotes a movable mold attached to the movable mold receiving plate 2. In this embodiment, the movable mold 7 is divided into a plurality of divided molds 7a. These are incorporated in the recess 2b formed in the movable mold receiving plate 2.

  The ejector box 3 located in the vicinity of the guide rod 4 is provided with a grease injection through hole 3a communicating with the ejector box sealed space A1. 8 is a sealing lid for closing the grease injection through hole 3a. Bolt insertion holes 8a are formed at four corners of the sealing lid 8, and an ejector located near the grease injection through hole 3a. The outer wall of the box 3 is formed with a screw hole 3b into which the tip end of the bolt B inserted into the bolt insertion hole 8a of the sealing lid 8 is screwed.

  As described above, the guide rod 4 is inserted into the through hole 5a formed in the ejector plate 5 via the bush 6 disposed on the inner periphery of the through hole 5a formed in the ejector plate 5. However, a plurality of grease grooves 6a are formed in the circumferential direction on the inner peripheral surface of the cylindrical bush 6, and the grease grooves 6a are filled with grease. Thus, the ejector plate 5 can be smoothly reciprocated with respect to the guide rod 4. In other words, the guide rod 4 is fitted into the bush 6 disposed on the inner periphery of the through hole 5 a formed in the ejector plate 5.

  As will be described later, compressed gas is injected into the ejector box sealed space A1 surrounded by the movable side mounting plate 1, the movable mold receiving plate 2 and the ejector box 3 at every product molding step. However, in this repeated compressed gas injection process, the grease is pushed out from the grease groove 6a formed on the inner peripheral surface of the cylindrical bush 6, and the ejector plate 5 cannot smoothly reciprocate. The problem will arise.

  In order to solve the above-described problems, it is necessary to periodically supply grease to the grease groove 6a formed on the inner peripheral surface of the cylindrical bush 6, but for a conventional synthetic resin pallet. In the mold structure, it was necessary to disassemble the synthetic resin pallet mold structure in order to supply grease, and it took considerable time and labor to supply the grease.

  In this embodiment, when replenishing grease to the grease groove 6 a formed on the inner peripheral surface of the cylindrical bush 6, the sealing lid 8 is removed by removing the bolt B attached to the outer wall of the ejector box 3. Accordingly, as shown in FIG. 4, the grease injection through hole 3 a formed in the ejector box 3 is opened, and the sprayed grease is passed through the grease injection through hole 3 a to the guide rod 4. By spraying, the grease to the grease groove 6a can be replenished easily and in a short time. If the ejector plate 5 is located near the grease injection hole 3a, the sprayed grease cannot be effectively attached to the guide rod 4, so that as shown in FIG. It is preferable to spray the grease in a state where the ejector plate 5 is not positioned in the vicinity of the grease injection through hole 3a.

  5 and 6 show an embodiment in which a grease groove 4a is formed on the outer peripheral surface of the guide rod 4 instead of forming the grease groove 6a on the inner peripheral surface of the cylindrical bush 6. FIG. . The grease groove 4a is formed on the outer peripheral surface of the guide rod 4 located in the through hole 5a of the ejector plate 5 when compressed gas is injected into the ejector box sealed space A1. By configuring in this way, it is possible to prevent the compressed gas from being directly blown into the grease groove 4a formed on the outer peripheral surface of the guide rod 4, and accordingly, the grease is discharged from the grease groove 4a. As a result, the number of grease filling operations into the grease groove 4a can be reduced.

  Next, with reference to FIG. 1 and FIG. 7, an outline of a fixed side portion such as a fixed mold of a synthetic resin pallet mold structure will be described.

  Reference numeral 10 denotes a fixed-side attachment plate, and 11 denotes a fixed mold receiving plate attached to the fixed-side attachment plate 10. Reference numeral 12 denotes a fixed mold. In the present embodiment, the fixed mold 12 is incorporated in a recess 11 a formed in the fixed mold receiving plate 11. Note that the fixed mold 12 can also be divided into a plurality of divided molds as necessary, similarly to the movable mold 7. Reference numeral 11a denotes an angular pin disposed on the stationary mold receiving plate 11, and the angular pin 11a contacts the movable mold 7 and the stationary mold 12 as shown in FIG. When it does, it is comprised so that it may insert in the through-hole 2a1 formed in the angular core 2a.

  Reference numeral 13 denotes a plurality of nozzles disposed on the fixed side portion of the synthetic resin pallet mold structure. Through the nozzles 13, a cavity C formed by the movable mold 7 and the solid mold 12 is provided. Molten resin will be poured.

  Next, a compressed gas injection structure for injecting compressed gas into the cavity C and the ejector box sealed space A1 will be described.

  3c is an ejector box side passage formed in the ejector box 3 for injecting compressed gas into the ejector box sealed space A1, and the ejector box side passage 3c is compressed via a switching valve (not shown). A pipe p1 connected to the gas supply source is attached. Reference numeral 2c denotes a movable mold side passage formed in the movable mold receiving plate 2 for injecting compressed gas into the cavity C from the movable mold 7 side. The movable mold side passage 2c includes A pipe p2 connected to the compressed gas supply source is attached via a switching valve (not shown). Reference numeral 11b denotes a fixed mold side passage formed in the fixed mold receiving plate 11 and the solid mold 12 for injecting compressed gas into the cavity C from the fixed mold 12 side. A pipe p3 connected to a compressed gas supply source is attached to the side passage 11b via a switching valve (not shown).

  The pipes p1 to p3 are connected to a switching valve (not shown), and the switching valve stops the compressed gas supply position for supplying the compressed gas to the pipes p1 to p3 and the supply of the compressed gas to the pipes p1 to p3. The compressed gas supply stop position to be switched and the natural exhaust position where the pipes p1 to p3 communicate with the atmosphere can be switched.

  Next, a skid molding process using the above-described synthetic resin pallet mold structure will be described.

  As shown in FIG. 7, in a state where the movable mold 7 and the fixed mold 12 are joined, first, from the ejector box side passage 3c to the ejector box sealed space A1 via the pipe p1. Supply compressed gas. When compressed air is supplied to the movable mold side passage 2c through the pipe p2, the compressed gas constitutes the contact gap G1 between the movable mold receiving plate 2 and the movable mold 7 and the movable mold 7. When the compressed air is supplied to the cavity C through the contact gap G2 between the split molds 7a and further supplied to the cavity C through the pipe p3, the compressed gas is exchanged with the movable mold 7a. It will be supplied to the cavity C through the parting surface with the fixed mold 12. In this way, the ejector box sealed space A1 and the cavity C are filled with the compressed gas.

  As described above, after the ejector box sealed space A1 and the cavity C are filled with the compressed gas, the switching valve is switched to the compressed gas supply stop position for stopping the supply of the compressed gas to the pipes p1 to p3. Molten resin is injected into the cavity C from the nozzle 13. When about 60 to 90% of the molten resin is injected into the cavity C, the switching valve is switched from the compressed gas supply stop position to the natural exhaust position where the pipes p1 to p3 communicate with the atmosphere. The compressed gas inside is discharged to the atmosphere.

  Thereafter, the movable side portion of the synthetic resin pallet mold structure including the movable side mounting plate 1, the movable mold receiving plate 2, the ejector box 3, the movable mold 7, etc. is replaced with the fixed side mounting plate 10 or the fixed mold. The movable mold 7 is released from the fixed mold 12 by separating from the fixed side portion of the synthetic resin pallet mold structure including the receiving plate 11 and the fixed mold 12. Next, as shown in FIG. 8, the ejector plate 5 at a substantially intermediate position between the movable side mounting plate 1 and the movable mold receiving plate 2 is moved to the movable mold as shown in FIG. The ejector pin 5 c is pushed out of the movable mold 7 by moving in the direction of the receiving plate 2, and the injection-molded skid is removed from the movable mold 7.

  As an example, in FIG. 9, six nozzles 13 are arranged substantially evenly on the fixed side portion of the synthetic resin pallet mold structure, and the molten resin passes through the common passage H and the branch passages h1 to h6. The six nozzles 13 are injected into the cavity C formed by the movable mold 7 and the solid mold 12.

Molten resin injected and injected molten resin from the branch passage h2 from the branch passages h1, in the confluence region J _1.2, it becomes confluent and the fact is injected injected molten resin from the branch passage h2 from the branch passage h3 The molten resin is merged in the merge region _J2.3 , and the molten resin injected from the branch passage h3 and the molten resin injected from the branch passage h4 are merged in the merge region _J3.4 . becomes, the molten resin injected and injected molten resin from the branch passage h5 from the branch passage h4 is the confluence region J _4.5, become confluent and the possible, the injected molten resin from the branch passage h5 from the branch passage h6 injected molten resin, in the joining region J _5.6, become confluent and the possible, the injected molten resin from the injected molten resin branch passage h6 from the branch passages h1 is In confluence region J _1.6, become confluent and the possible. Further, the molten resin injected from the branch passage h1, the molten resin injected from the branch passage h2, the molten resin injected from the branch passage h3, and the molten resin injected from the branch passage h6 are combined in the junction region J _1.2.3.6 . Furthermore, the molten resin injected from the branch passage h3, the molten resin injected from the branch passage h4, the molten resin injected from the branch passage h5, and the molten resin injected from the branch passage h6 are: In the merging area J _3.4.5.6 , merging will occur.

As described above, in the molten resin merging area J _1.2 , J _2.3 , J _3.4 , J _4.5 , J _5.6 , J _1.6 , J _1.2.3.6 , J _3.4.5.6 , as described above, the movable mold 7 The pressure at which the mold 12 and the fixed mold 12 are released is high, and the compressed gas injected into the cavity is a molten resin confluence region J _1.2 , J _2.3 , J _3.4 , J _4.5 , J _{5.6, J 1. 6} , J _1.2.3.6 and J _3.4.5.6 are compressed to a high temperature, and this high temperature compressed gas heats the molten resin to reduce the viscosity of the molten resin. The molten resin can easily enter the parting surface with the fixed mold 12, and burrs are easily generated. Further, the movable mold 7 and the fixed mold 12 are repeatedly brought into contact with and released from the movable mold. The parting surfaces of the mold 7 and the fixed mold 12 will be deformed. Frequency _{J 1.2, J 2.3, J 3.4} , J 4.5, J 5.6, J 1.6, J 1.2.3.6, so that the deformation of the movable die 7 and the stationary mold 12 located J _3.4.5.6 increases.

In order to solve the problem as described above, in this embodiment, as shown in FIG. 10, of the movable mold 7 and the fixed mold 12, the molten resin confluence region J _1.2 , J _2.3 , J _{3.4, J 4.5, J 5.6,} J 1.6, J 1.2.3.6, the hardness of the confluence region portion m1~m8 of the movable mold 7 and the stationary mold 12 positioned J _3.4.5.6, higher than the hardness of the other portions Preferably 30 or more.

In the injection molding in the counter pressure method, the hardness of the steel material used for the movable mold 7 and the fixed mold 12 (Rockwell hardness) is usually about 10, but in the present invention, as described above, of the movable mold 7 and the stationary mold 12, confluence area of the molten resin _{J 1.2, J 2.3, J 3.4} , J 4.5, J 5.6, J 1.6, J 1.2.3.6, the movable mold is located in J _3.4.5.6 7 and the joining region portions m1 to m8 of the fixed mold 12 are made harder than the hardness of other portions, and preferably 30 or more.

As described above, among the movable mold 7 and the stationary mold 12, the confluence region J _1.2 of the molten _{resin, J 2.3, J 3.4, J} 4.5, J 5.6, J 1.6, J 1.2.3.6, the J _3.4.5.6 The hardness of the merged area portions m1 to m8 of the movable mold 7 and the fixed mold 12 positioned is larger than that of the other parts, preferably 30 or more, so that the merged area of the movable mold 7 and the fixed mold 12 The deformation of the parts m1 to m8 can be prevented, and therefore the occurrence of flash can be prevented.

  In addition, as described above, by using a steel material having a hardness of 30 or more only in the merged area portions m1 to m8 of the movable mold 7 and the fixed mold 12, the increase in cost of the synthetic resin pallet mold structure is suppressed. be able to.

  FIG. 11 shows, as an example, an example in which a recess 12a is formed in a portion located in the joining region portion of the fixed mold 12, and a nest 12b made of a steel material having a hardness of 30 or more is attached to the recess 12a. Has been. In addition, the movable mold 7 also has an example in which a recess 7b is formed in a portion facing the insert 12b of the fixed mold 12, and the insert 7c made of a steel material having a hardness of 30 or more is attached to the recess 7b. Has been.

  By configuring as described above, the nesting 12b having a large hardness is attached to the fixed mold 12 in the merged area portions m1 to m8 to which a large pressure is applied due to the merged molten resin, and the movable mold 12 is movable to face the fixed mold 12. By attaching the nest 7c having a high hardness to the mold 7 as well, the deformation of the movable mold 7 and the fixed mold 12 in this portion can be reduced, and therefore the occurrence of flash can be suppressed.

  As an example, the skid S ′ formed as described above includes a deck s1, a corner beam portion s2 formed at four corners of the deck s1, and an intermediate beam portion s3 formed between the corner beam portions s2. And a central girder portion formed at the center of the deck s1, not shown. Then, as shown in FIG. 13, a hot plate U is disposed between a pair of skids S ′, and then a rib portion s2a constituting the corner beam portion s2 (FIG. 13 shows the corner beam portion s2). Only the rib s2a is shown, but the same applies to the intermediate spar portion and the central spar portion.) The tip portion s2a ′ of the rib is brought into contact with the hot plate U and melted, and then the pair of skids S After the hot plate U is discharged from between, the tip portions s2a 'of the melted rib portions s2a of the pair of skids S' are brought into contact with each other, so that the synthetic resin pallet S is formed from the pair of skids S ' Will be manufactured. Normally, the welding margin (the length of the tip portion s2a 'of the rib portion s2a melted by the hot plate U) of the rib portion s2a to be welded is approximately 2 mm.

  By the way, as described above, the surface layer (skin layer) of the rib part s2a is the non-foamed non-foamed surface layer s4 by the counter pressure method, and the rib part s2a has the foamed internal foamed part s5. In this case, the thickness of the tip portion s4a of the non-foamed surface layer s4, in other words, the distance from the tip surface s2a ″ of the rib portion s2a to the tip s5a of the internal foamed portion s5 is formed. When D1 is zero or thin, when the pair of skids S ′ are welded, as shown in FIG. 15, the inner foamed portions s5 are connected to each other on the welding surfaces of the rib portions s2a between the skids S ′. Therefore, there is a problem that the strength of the welded portion of the rib portion s2a between the skids S ′ is lowered.

  Therefore, in the present invention, the thickness D1 of the front end portion s4a of the non-foamed surface layer s4, in other words, the distance D1 from the front end surface s2a ″ of the rib portion s2a to the front end s5a of the internal foamed portion s5 is determined by the skid S ′. When the two are welded together, as shown in FIG. 16, the distance is such that the non-foamed surface layer s4 remains between the front end surfaces s2a ″ of the rib portions s2a of the pair of welded skids S ′. Is.

  As described above, the thickness D1 of the tip portion s4a of the non-foamed surface layer s4, in other words, the distance D1 from the tip surface s2a ″ of the rib portion s2a to the tip s5a of the inner foamed portion s5 is the rib of the skid S ′. It can be appropriately adjusted depending on the width W1 of the portion s2a, the pressure of the compressed gas injected into the ejector box sealed space A1, the resin used for injection molding in the counter pressure method, and the like.

  As described above, the distance D1 from the thickness of the tip portion s4a of the non-foamed surface layer s4, in other words, the tip surface s2a ″ of the rib portion s2a to the tip s5a of the internal foamed portion s5, is determined between the skids S ′. By setting the distance so that the non-foamed surface layer s4 remains between the tip surfaces s2a ″ of the rib portions s2a of the pair of skids S ′ that are welded, the rib portions s2a between the skids S ′ The strength of the welded portion is increased, and as a result, the strength and rigidity of the synthetic resin pallet S can be improved.

FIG. 1 is a vertical sectional view of a mold structure for a synthetic resin pallet according to the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is a perspective view of a sealing lid and the like constituting the mold structure for a synthetic resin pallet according to the present invention. FIG. 4 is an enlarged view of a main part similar to FIG. FIG. 5 is an enlarged view of a main part similar to FIG. FIG. 6 is an enlarged view of a main part similar to FIG. FIG. 7 is a vertical sectional view of the mold structure for a synthetic resin pallet according to the present invention. FIG. 8 is a vertical sectional view of a mold structure for a synthetic resin pallet according to the present invention. FIG. 9 is a schematic perspective view showing a state where a skid is molded using the synthetic resin pallet mold structure of the present invention. FIG. 10 is a plan view of the moving mold and the like of the synthetic resin pallet mold structure of the present invention. FIG. 11 is a partial vertical cross-sectional view of the synthetic resin pallet mold structure of the present invention. FIG. 12 is a perspective view of a synthetic resin pallet manufactured using a skid formed by the synthetic resin pallet mold structure of the present invention. FIG. 13 is a partial vertical sectional view of a process of manufacturing a synthetic resin pallet using a pair of skids. FIG. 14 is a partial vertical cross-sectional view of the rib tip portion of the skid. FIG. 15 is a partial vertical cross-sectional view of a welded portion of a synthetic resin pallet manufactured using a pair of skids. FIG. 16 is a partial vertical cross-sectional view of the welded portion of a synthetic resin pallet manufactured using a pair of skids.

Explanation of symbols

A1 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Ejector box sealed space J ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Melting area of molten resin S ・ ・ ・ ・ ・ ・·························································································· Piping 1 ············· Movable side mounting plate 2 ······················································································· ... Ejector box 5 ... Ejector plate 7 ... Moveable mold 7c ·················································· 8・ Fixed side mounting plate 11 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・Receiving a stationary mold plate 12 ............... fixed mold 12b .............. nest

Claims (3)

  In the plastic pallet mold structure that is configured so that the ejector plate reciprocates along the guide rod arranged in the ejector box, the ejector box is located in the vicinity of the guide rod, A mold structure for a synthetic resin pallet, wherein the grease injection through-hole is formed so as to be closed and the grease injection through-hole is closed by a removable sealing lid.   The guide rod is fitted into a bush disposed on the inner periphery of a through hole formed in the ejector plate, and a plurality of grease grooves are formed on the inner peripheral surface of the bush. The mold structure for a synthetic resin pallet according to claim 1.   The mold structure for a synthetic resin pallet according to claim 1 or 2, wherein the ejector plate is configured to spray grease in a state where the ejector plate is not positioned near the grease injection hole. .

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