JP2010047266A - Synthetic resin pallet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synthetic resin pallet capable of achieve strength, weight reduction and a core layer filling ratio of the pallet made of the synthetic resin with a good balance. <P>SOLUTION: The pallet made of the synthetic resin is formed by welding mutually a girder part of an upper deck board and a girder part of a lower deck board. For the upper deck board, a plurality of the girder parts are connected with a top board 5 forming a loading surface, and a reinforcing rib 6 is provided between the girder parts. For the reinforcing rib 6a connected orthogonally to the central girder part, a skin layer 14 of a virgin resin is provided on the surface, a core layer 15 of a regenerated resin is provided in its inside, and a hollow part 16 made by gas injection is provided in the innermost layer. The hollow part 16 projects so as not to project into the top board 5 beyond necessity. The top board 5 consists of a skin layer and a core layer. The thickness W of the top board 5 at a part where the reinforcing rib 6 is provided is 2-5 mm, and the maximum thickness T at the root on the top board 5 of the reinforcing rib 6 is 5-30 mm, and the height H of the reinforcing rib 6 including the top board 5 is set in a range of 10-50 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a synthetic resin pallet that is used to place various articles on a loading surface for transportation or storage.

Conventionally, a two-way pallet or a four-way pallet has been used as a synthetic resin pallet used when carrying or storing articles.
As such a synthetic resin pallet, there is a pallet generally constituted by an upper deck board and a lower deck board arranged in parallel to each other and a plurality of girders connecting the upper deck board and the lower deck board. Further, there are also an integrally formed type and a type formed by dividing the girder part into two at the substantially central part above and below the girder part and butting them together.
In addition, there is a so-called skid pallet composed only of a deck board and legs (girder).
And, for example, in the synthetic resin pallet described in Patent Document 1, in order to prevent heat from staying at the intersection of the deck board and the rib during molding and sinking after solidification, the intersection of the deck board and the rib In some cases, a hollow portion is formed by injecting gas into the thickest portion in the vicinity by a gas injection method to reduce the weight.

Recently, a synthetic resin pallet having a multilayer structure by a sandwich molding method has been proposed as a means for recycling the used plastic to save the environment and reduce the cost of the synthetic resin pallet. For example, the synthetic resin pallets described in Patent Documents 2 and 3 have thick reinforcing ribs between the spar corners connecting the spar corners and the spar corners, and the reinforcing ribs, the top plate, and the peripheral walls of the spar Are formed into two layers of a skin layer and a core layer.
Then, virgin resin is used as the skin layer, which is the surface layer, recycled resin is used as the core layer, which is the inner layer, and the resin that first forms the skin layer is injected into the mold from a single resin gate. It is said that a pallet having a two-layer structure can be obtained by injecting and molding a resin for forming the core layer into the mold after a delay.
Japanese Patent Laid-Open No. 11-100035 Japanese Patent No. 4079376 Japanese Patent No. 4079377

  However, in the synthetic resin pallet using such a sandwich molding method, for example, if the filling ratio of the core material such as recycled resin is increased in order to reduce the manufacturing cost, the core material that forms the inner layer when filling the mold When the molten resin is filled in a mold and allowed to flow, there is a problem that a phenomenon called a break that breaks through the previously filled skin layer and is exposed to the surface occurs. On the other hand, synthetic resin pallets are required to be lightweight while securing the overall strength, and simply by forming a two-layer structure using a plurality of synthetic resin materials as the material of the synthetic resin pallets. Although the strength of the synthetic resin pallet could be ensured, the weight reduction and the core layer filling rate could not be achieved in a well-balanced manner.

  In view of such circumstances, an object of the present invention is to provide a synthetic resin pallet that can achieve a good balance between strength, weight reduction, and core layer filling rate of the synthetic resin pallet.

  A synthetic resin pallet according to the present invention is a synthetic resin pallet having a deck board and a plurality of girders, and the deck board includes a top plate and a plurality of reinforcing ribs provided on the side of the top plate. A gas flow passage that is continuous with the gas gate portion and the gas gate portion in at least one of the plurality of girders. Among the reinforcing ribs, the reinforcing ribs outside the girders that are continuous to the gas flow path at the shortest distance are the skin layer provided on the most front side, the core layer provided on the inner side of the skin layer, It has a three-layer structure having a hollow portion by gas injection provided inside the core layer, and the thickness of the top plate of the portion where the reinforcing rib is provided is 2 to 5 mm, and the root of the reinforcing rib to the top plate The maximum thickness is 5-30mm, the height of the reinforcing rib including the top plate Characterized in that it is set in a range of 10 to 50 mm.

  The synthetic resin pallet according to the present invention has a thickness W of the top plate around the reinforcing rib outside the girder that is continuous to the gas flow path at the shortest distance, W = 2 to 5 mm, and the maximum root of the reinforcing rib to the top plate By setting the wall thickness T to T = 5 to 30 mm and the height H of the reinforcing rib including the top plate to the range of H = 10 to 50 mm, other reinforcing ribs that are outside the girder and are continuous with this reinforcing rib In addition, the skin layer, the core layer, and the hollow portion can be formed in a well-balanced manner on the top plate of the entire synthetic resin pallet. Therefore, the overall weight of the synthetic resin pallet can be reduced by forming the hollow portion, the strength of the synthetic resin pallet can be secured, and the core layer can be sufficiently filled in the top plate and the reinforcing ribs to increase the filling rate of the core layer. Can be improved. Moreover, by setting the range of the thickness W of the top plate, the maximum thickness T of the base of the reinforcing rib, and the height H of the reinforcing rib including the top plate, at the time of injection molding to the mold of the synthetic resin pallet It is possible to secure the balance of resin flow and suppress the resin flow at the reinforcing rib portion from partially increasing, thereby suppressing the break of the core layer.

  According to the synthetic resin pallet according to the present invention, since the reinforcing rib outside the girder portion that is continuous to the gas flow path at the shortest distance has a three-layer structure, weight reduction can be achieved by the hollow portion of the innermost layer, and the hollow The manufacturing cost can be reduced by the portion and the core layer, and the hollow portion by gas injection is formed in a balanced manner on the entire synthetic resin pallet. And the filling rate of the core layer to a top plate and a reinforcement rib can be improved.

In the synthetic resin pallet according to the embodiment of the present invention, the gas gate portion and the gas flow passage continuing to the gas gate portion are provided in the girder portion, and the reinforcement rib continues to the gas flow passage at the shortest distance. It is preferable that the reinforcing rib outside the girder part extends in a direction orthogonal to the extending direction of the girder part and is connected to the girder part.
Since the strongest part in the synthetic resin pallet is the girder part, a gas flow channel and a gas flow path continuous to the gas gate part are provided in at least one girder part of the plurality of girder parts. This gas flow path has a structure in which gas flows most easily, but when the gas flows outside the girder part, it passes between a plurality of reinforcing ribs and the top plate provided outside the girder part and is made of a synthetic resin pallet. Go around the whole. In this case, the gas flow outside the girder passes between the reinforcing ribs that easily flow out of the plurality of reinforcing ribs and the top plate.
Therefore, as a flow path for the gas to flow out from the inside of the spar to the outside of the spar, the reinforcing rib outside the spar that is continuous to the gas flow path at the shortest distance among the plurality of reinforcing ribs extends in the direction perpendicular to the spar. By connecting to, it is possible to form the ideal three-layered reinforcing rib with the gas flow resistance being minimized and forming the hollow part as the innermost layer, and the rib structure that allows the most resin and gas to flow. Can be formed. This makes it possible to improve the fluidity of the resin and gas to the other reinforcing ribs and the ribs on the front side in the flow direction of the resin and gas connected to the reinforcing ribs, and to form a synthetic resin pallet having a more uniform structure. .

The resin used for the skin layer and the core layer can be a resin having different properties. For example, a new resin (virgin resin) and a resin with an antistatic function are used for the skin layer, a new resin is used for the core layer, and a virgin resin is used for the skin layer. The core layer can be made of recycled resin. The surface of the synthetic resin pallet is formed with a clean skin layer made of virgin resin, and the core layer made of recycled resin is formed on the inner layer to reduce the manufacturing cost while maintaining the appearance of the surface. Can promote environmental protection through recycling.
In addition, when the synthetic resin is injected into the upper deck board and / or lower deck board mold provided with girders, the melt resin of the skin layer is MI (melt flow index), which is an index of resin fluidity, as the core layer. It is preferable that it is set to be larger than MI which is an index of resin fluidity. This can prevent the core layer from breaking through the skin layer during filling.

  A synthetic resin pallet according to an embodiment of the present invention will be described below with reference to FIGS. 1A and 1B are a top view and a back view of an upper pallet forming member of a synthetic resin pallet according to the embodiment, and FIG. 2 is a reinforcing rib and a resin gate in the upper pallet forming member shown in FIG. FIG. 3 is an enlarged cross-sectional view taken along line AA of the reinforcing rib outside the central girder that is continuous to the gas flow path at the shortest distance among the plurality of reinforcing ribs in FIG. 4 is a line AA of a reinforcing rib outside the central girder part that is continuous at the shortest distance to the gas flow path provided at a position adjacent to the central girder part, and a reinforcing rib outside the central girder part that is continuous to the gas flow path at the shortest distance FIG. 6 is a cross-sectional view of the reinforcing rib adjacent to the reinforcing rib adjacent to the reinforcing rib adjacent to the BB line and the reinforcing rib adjacent to the reinforcing rib outside the central beam portion that is continuous with the gas flow path at the shortest distance.

A synthetic resin pallet (hereinafter sometimes simply referred to as a pallet) 1 according to the embodiment shown in FIGS. 1 and 2 is a two-sided single-sided pallet having a substantially square shape, for example, a substantially square or rectangular box shape as a whole. is there. The plastic pallet 1 includes an upper pallet forming member 4A provided with an upper deck board 2 and a plurality of girders 3 connected to the back surface of the upper deck board 2, and a lower deck board (not shown) and a lower part provided with a plurality of girders. It consists of a deck board.
The upper deck board 2 of the synthetic resin pallet 1 has a central girder portion 3a formed at the center of the back surface of the plate-like top plate 5 forming a loading surface, and end girder portions 3b and 3b formed at both ends thereof. . The central girder part 3a and the end girder parts 3b, 3b extend linearly from one end to the other end of a pair of opposite sides of the top plate 5 and are parallel to each other. The lower deck board is also formed with a girder having the same structure. Then, the upper deck board 2 and the lower deck board are made to face each other and the end surfaces of the beam portions 3a, 3b,...

In FIG. 1 (b), the central beam portion 3 a and the end beam portion 3 b are connected by a reinforcing rib 6. The reinforcing rib 6 is formed in a lattice shape, and the height thereof is shorter than that of the central beam portion 3a and the end beam portion 3b. In the synthetic resin pallet 1 in which the upper pallet forming member 4A and the lower pallet forming member are welded together with the girders 3a, 3b,..., The region of the reinforcing rib 6 surrounded by the central girders 3a and the end girders 3b is fork inserted. A pair of communication holes 7 having a mouth are formed.
A grid-like rib 9 is formed on each of the central girder portion 3a and the end girder portion 3b, and a resin gate portion 10 communicating with the rib 9 is provided in the longitudinal central portion of the central girder portion 3a. The resin gate portion 10 is an opening portion of a resin valve provided in a mold (not shown) of the upper pallet forming member 4A at the time of injection molding. The resin gate portion 10 is connected to the top plate 5, the reinforcing rib 6 and the rib 9. The rib 9a orthogonal to the longitudinal direction of the central girder portion 3a forms a resin flow path connected to the resin gate portion 10.
The mold of the upper (lower) pallet forming member 4A is a one-point gate mold in which a resin gate portion 10 is provided at a central portion of the mold so that the resin flows uniformly throughout the pallet. Yes.

Since the gas for forming the hollow portion flows uniformly over the entire pallet, the gas gate portion 12a and the gas flow path 9b continuous to the gas gate portion are provided in the central girder portion 3a. The gas flow path 9b has a structure in which gas flows most easily. In the present embodiment, one resin gate portion 10 is provided in the central portion of the top plate 5, and a gas gate portion 12 a is provided in a substantially central portion at a position adjacent to the resin gate portion 10. And the resin flow path 9a is continuously formed in the wall part of the center girder part 3a. The gas flow path 9 b is connected from the gas gate part 12 a to the gas flow path provided in the wall part of the central beam part 3 a and the base part of the top plate 5. In the embodiment, only one gas gate portion 12a is disposed at the substantially central portion of the mold. For example, nitrogen gas, which is a kind of inert gas, is used as the gas injected from the gas gate portion 12a.
An appropriate number of gas gates 12 such as 2 to 4 may be arranged in the mold, but in order to allow the gas to flow in a balanced manner throughout the pallet, In addition, it is preferable that they are arranged so as to be substantially point-symmetric in plan view.

  For example, in the case of two points, gas gate portions 12a and 12b are disposed in the central girder portion 3a at positions that are substantially point-symmetric with respect to the resin gate portion 10 in the central portion (FIG. 2). reference). Further, in the case of four points, for example, gas gate portions 12a and 12b are disposed in the central girder portion 3a at a position that is substantially point-symmetric with respect to the resin gate portion 10 in the central portion, It is also possible to dispose gas gate portions 12c and 12d in the end beam portions 3b and 3b. In this case, gas passages that are continuous to the gas gate portions in the end beam portions 3b and 3b are provided, and the reinforcing ribs 6 outside the end beam portions 3b and 3b that are continuous to the gas flow channel at the shortest distance are reinforced as described above. The same dimensions as the ribs 6a are preferable from the viewpoint of the balance of gas flow.

  In addition, the four-way synthetic resin pallet has a configuration of one central girder, four intermediate girders, and four corner girders. In this case, as in the above-described embodiment, the central portion of the central girder is used for resin. A single-point gas gate may be provided in which a gate portion is provided, and a gas gate portion is provided adjacent to the resin gate portion and substantially at the center. One gas gate portion is provided for each intermediate beam. Alternatively, a 4-point gas gate may be used.

The resin gate portion 10 constitutes a valve gate opened in a cavity of a mold (not shown), and the resin raw material is supplied by two injection units (not shown) and filled in the mold. As the resin filled from the resin gate portion 10, a sandwich molding method is adopted in which two types of raw material resin consisting of a skin material and a core material are supplied to form two layers. Further, when the gas is supplied from the gas gate portion 12a, a gas assist method is employed in which a gas is injected into the upper (lower) pallet forming member 4A to form a hollow structure. Since the sandwich molding method and the gas assist method are disclosed in Japanese Patent Application Laid-Open No. 2007-8003 and the like, detailed description thereof is omitted.
By filling the mold of the synthetic resin pallet 1 with two types of resin and gas, the three-layered reinforcing ribs 6 and 9 are obtained, and the top plate 5 has a two-layer structure.

Next, the three-layered reinforcing rib 6a formed by filling the mold of the synthetic resin pallet 1 based on the sandwich molding method and the gas assist method will be described with reference to FIGS. Since the gas injected from the gas gate portion 12a has the highest injection pressure, and the gas flow path 9b has a structure in which the gas flows most easily, the hollow portion 16 is easily formed excessively and the strength is lowered. However, since the strongest part of the synthetic resin pallet is the girder part, there is no problem in reducing the strength of the central girder part 3a. The gas flow path 9b has a structure in which gas flows most easily. However, when the gas flows out of the central beam portion 3a, the plurality of reinforcing ribs 6 and the top plate 5 provided outside the central beam portion 3a. Spread through the entire plastic pallet. In this case, the gas flow outside the central beam portion 3 a passes between the reinforcing ribs 6 that easily flow and the top plate 5.
Therefore, the reinforcing rib 6a outside the central girder part 3a that is continuous to the gas flow path 9b among the plurality of reinforcing ribs 6 at the shortest distance as a flow path for gas to flow out from the central girder part 3a to the outside of the central girder part 3a will be described later. The gas flow resistance can be minimized and an ideal three-layer structure can be formed by connecting to the central beam portion 3a by extending in a direction orthogonal to the central beam portion 3a. it can.
Since the other reinforcing ribs 6 (6b, 6c,...) Adjacent to the reinforcing rib 6a branch off from the reinforcing rib 6a, it becomes difficult for gas to flow. Therefore, these reinforcing ribs 6 (6b, 6c,...) The hollow portion formed in the above also becomes smaller according to the difficulty of gas flow.

In the reinforcing rib 6 a shown in FIG. 3, the outermost surface layer is formed of a skin layer 14 made of a skin material, and a core layer 15 made of a core material is formed inside the skin layer 14. A hollow portion 16 formed by gas filling is formed and has an ideal three-layer structure.
FIG. 4 shows an enlarged cross-sectional view (a) of the reinforcing rib 6a outside the central beam portion 3a that is continuous to the gas flow path 9b among the plurality of reinforcing ribs 6a, and the reinforcing rib 6b adjacent to the reinforcing rib 6a. An enlarged sectional view (b) of FIG. 5 and an enlarged sectional view (c) of a reinforcing rib 6c adjacent to the reinforcing rib 6b are shown. The reinforcing ribs 6a, 6b, 6c,... Have the same shape (dimensions) in the present embodiment. However, the reinforcing rib 6b that is continuous with and adjacent to the reinforcing rib 6a has more than the reinforcing rib 6a. Since the gas hardly flows, the hollow portion 16 is formed slightly smaller than the hollow portion formed in the reinforcing rib 6a. The same applies to the hollow portion formed in the reinforcing rib 6c.
Moreover, since it becomes difficult for gas to flow as it goes to the outer peripheral part or the terminal part of the synthetic resin pallet, the size of the hollow part is also reduced accordingly. Therefore, by setting the reinforcing rib 6a outside the central girder portion 3a that is continuous to the gas flow path 9b at the shortest distance to a predetermined size as described later, the skin layer, the core layer, and the hollow portion as a whole pallet have a good balance. Will be formed.
In addition, the magnitude | size of the hollow part 16 formed in the reinforcing rib 6b and the reinforcing rib 6c may not necessarily follow the order of the adjacent position by the ease of gas flow.

  The skin layer 14 is composed of a virgin resin, and a polyolefin resin such as polypropylene or polyethylene is used as the virgin resin. When the skin layer 14 is a new resin, it is possible to form a clean surface layer with uniform quality, but it is expensive, and it is necessary to reduce the amount of use for cost reduction. Therefore, the skin layer 14 is thinly formed on the surface layers of the reinforcing rib 6, the rib 9 and the top plate 5.

The core layer 15 is made of a recycled resin such as a recycled plastic material, and the material is, for example, a polyolefin resin such as used polypropylene or polyethylene. Although the recycled resin of the core layer 15 is inexpensive, it may be mixed with PS (polystyrene) other than polyolefin resin, and may be mixed with resin materials of various colors, and is suitable for the surface layer. Absent.
Note that the MI, which is an index of the flow of the skin material and the core material during injection molding, is preferably set so that the MI of the skin material is larger than the MI of the core material. The MI of the skin material is, for example, 5 to 15 g / 10 min, and the MI of the core material is, for example, 2 to 10 g / 10 min.
The hollow portion 16 by gas injection is formed by, for example, pressure-injecting the inside of the core layer 15 before curing nitrogen gas or the like, and the hollow portion 16 is formed in the reinforcing rib 6 and the rib 9, and the top plate 5. It is important that the hollow portion 16 is advanced more than necessary so that the actual thickness w of the top plate 5 is reduced and the strength is not lowered. The actual thickness w is a thickness dimension from the top of the hollow portion 16 to the upper surface of the top plate 5.

Therefore, the dimensions of the top plate 5 and the plurality of reinforcing ribs 6 with respect to the reinforcing ribs 6a outside the central girder portion 3a that continues to the gas flow path 9b at the shortest distance are defined as follows. As shown in FIG. 3, the reinforcing rib 6a has a taper surface in which both side surfaces 61 have a slight inclination angle from the tip to the base of the top plate 5 to improve the formability, but the inclination angle is 0 °. May be.
The thickness W of the top plate 5 is set to 2 to 5 mm over at least the surrounding area where the reinforcing ribs 6 a are provided, preferably over the entire top plate 5 surface. If the thickness W is within this range, the reinforcing rib 6a and the top plate 5 are surely filled with the core material inside the skin layer 14, and the gas-filled hollow portion 16 is more than necessary from the reinforcing rib 6a to the top plate 5. It can be prevented from being spread out. Moreover, since the size of the hollow portion 16 in the reinforcing ribs 6b, 6c etc. that are continuously adjacent to the reinforcing rib 6a is smaller than the size of the hollow portion formed in the reinforcing rib 6a as described above, the entire pallet The strength of is secured.
On the other hand, if the thickness of the top plate 5 is less than 2 mm, a problem that the core material is difficult to be filled inside the skin layer 14 in the top plate 5 occurs. If the thickness of the top plate 5 exceeds 5 mm, the core material is reliably filled in the top plate 5, but the weight of the synthetic resin pallet 1 becomes excessive and the hollow portion 16 is in the top plate 5. Since it is formed larger than necessary, the actual thickness w of the top plate 5 becomes too thin, and a local strength reduction also occurs.

  Further, the crossing portion where the base including the concave curved portion that spreads the maximum thickness T at the base of the reinforcing rib 6a with the top plate 5 by the radius R (2 to 10 mm) of the reinforcing rib 6a intersects the surface of the top plate 5. The maximum wall thickness T is set to 5 to 30 mm as the length between them. This R portion is provided for the purpose of relaxing stress concentration and for making it easier for the synthetic resin pallet to be separated from the mold after molding. And the height H of the reinforcement rib 6a including the thickness W of the top plate 5 is set to 10-50 mm. If the maximum thickness T and height H of the reinforcing rib 6a are within this range, the core material and the gas can be easily filled inside the skin layer 14, and the corner portions 4b of the upper (lower) deck board 4A at the four corners (flow) There is an advantage that breakage of the core material and gas hardly occurs at the end). On the other hand, if the maximum thickness T and height H of the reinforcing rib 6a are less than this range, the core material and the gas are difficult to fill the inside of the skin layer 14, and if it exceeds this range, the fluidity of the synthetic resin and the gas Therefore, there is a problem that the core material or gas easily breaks through the skin layer and causes a break that is exposed to the surface at the corner portion 4b.

More specifically, when the thickness W of the top plate 5 in the reinforcing rib 6a is 2 mm and the maximum thickness T is 5 mm, the core layer 15 is reliably filled inside the skin layer 14 and the hollow portion is formed by gas filling. Since 16 is formed substantially in a triangular shape near the base portion of the reinforcing rib 6a, the actual thickness w of the top plate 5 is about 0.7 W to 0.9 W, that is, about 1.4 to 1.8 mm. There is almost no decrease in the strength of the portion, and the reinforcing ribs 6b, 6c, etc., which are continuous with the reinforcing rib 6a and adjacent to each other, are formed with a hollow portion 16 smaller than this. The skin layer 14, the core layer 15, and the hollow portion 16 are formed with good balance.
On the other hand, when the thickness W of the top plate 5 in the reinforcing rib 6a is smaller than 2 mm and the maximum thickness T is smaller than 5 mm, the core layer is formed on the reinforcing ribs 6b and 6c that are continuous with and adjacent to the reinforcing rib 6a. 15 is not filled or the hollow portion 16 is not formed, the strength can be ensured but the weight is not reduced satisfactorily. The skin layer 14, the core layer 15 and the hollow portion 16 in the entire synthetic resin pallet are not obtained. The balance becomes worse.

Further, when the thickness W of the top plate 5 in the reinforcing rib 6a is 5 mm and the maximum wall thickness T is 30 mm, the core layer 15 is reliably filled inside the skin layer 14, and the hollow portion 16 formed by gas filling has the reinforcing rib. In addition to being formed in the top plate 5, the actual thickness w of the top plate 5 is about 0.4 W to 0.8 W, that is, about 2.0 to 4.0 mm. In the continuous and adjacent reinforcing ribs 6b, 6c, etc., the hollow portion 16 is formed smaller than this, so that the strength of the synthetic resin pallet as a whole does not significantly decrease.
On the other hand, when the thickness W of the top plate 5 in the reinforcing rib 6a is larger than 5 mm and the maximum thickness T is larger than 30 mm, the core layer 15 is surely filled inside the skin layer 14, but the hollow is hollow. The portion 16 is formed to be larger than necessary, and the local strength is significantly reduced.
In addition, from the point of securing the strength, the thickness W of the top plate 5 is 2 to 5 mm, R is 2 to 8 mm, the maximum thickness T is preferably 6 to 26 mm, and the thickness W of the top plate 5 is 2 to 5 mm. It is particularly preferable that R is 2 to 4 mm and the maximum thickness T is 6 to 16 mm.

  In the above-described configuration, the reinforcing rib 6 (6a, 6b, 6c,...) Provided between the central beam portion 3a and the end beam portion 3b has been described. However, the ribs formed on the central beam portion 3a and the end beam portion 3b. 9 may have a similar configuration. When a part of the rib 9 is formed to be narrower than the lower limit value of the wall thickness T, a gas is not filled and a two-layer structure is formed.

The synthetic resin pallet 1 according to the present embodiment has the above-described configuration. Next, a method for manufacturing the synthetic resin pallet 1 will be described.
Although the manufacturing method of the upper pallet forming member 4A and the lower pallet forming member of the synthetic resin pallet 1 will be described, since the manufacturing method of the upper pallet forming member 4A and the lower pallet forming member is the same, the manufacturing method of the upper pallet forming member 4A is representative. To explain.
As shown in FIGS. 1 and 2, the resin gate portion 10 and the gas gate portion 12a are provided at the center position of the central girder portion 3a on the back surface of the upper pallet forming member 4A in the mold for injection molding the upper pallet forming member 4A. It is arranged. In order to injection-mold the upper pallet forming member 4A, a skin material and a core material, which are two kinds of resin raw materials, are sequentially injected from the resin gate portion 10 by a sandwich molding method.

When virgin resin is injected as a molten skin material from the resin gate portion 10 at once by the resin valve, the molten resin flows through the top plate 5 and wraps around the reinforcing rib 6 and rib 9. The molten resin of the skin material flows toward the respective corner portions 4b of the upper pallet forming member 4A while being in contact with the mold inner surfaces of the top plate 5, the reinforcing ribs 6 and the ribs 9 by the resin valve.
After a certain amount of skin material is injected, recycled resin is injected at once from the resin gate 10 as a molten core material. The core material flows inside the preceding skin material, flows through the top plate 5, the reinforcing ribs 6 and the ribs 9 as resin flow paths, and goes to each corner portion 4b. At this time, since the core material has a resin fluidity smaller than that of the skin material, the core material flows so as to form a two-layer structure in which the skin material is positioned on the surface layer and the core material is positioned on the inner layer without breaking.
Regarding the relationship between the injection timing and the injection amount of the skin material and the core material, if the injection timing of the core material is too early, the initial skin material injection amount becomes relatively small, and the corner portion 4b of the upper pallet forming member 4A that is the fluid end. The core material is easy to break. On the other hand, if the injection timing of the core material is late, the core material around the resin gate portion 10 is not replaced with the skin material, so that a problem that breaks easily occurs in this portion.
After the completion of the core material injection, the skin material is further injected and filled, so that the core material near the resin gate portion 10 is covered with the skin material.

After the molten resin of the skin material and the core material spreads uniformly in the mold of the upper pallet forming member 4A, gas is injected from the gas gate portion 12a in a few seconds. The gas injected from the gas gate 12 part a first flows into the reinforcing rib 6a outside the central girder part 3a adjacent to the central girder part 3a via the gas flow path 9b, and then continues to the reinforcing rib 6a. And it fills in the adjacent grid-like reinforcing ribs 6 (6b, 6c,...) And ribs 9. The gas injected into the mold is formed as a hollow portion 16 at the base portion having the largest thickness of the reinforcing rib 6 formed in two layers by the skin layer 14 and the core layer 15.
The top plate 5 is filled with the core material together with the skin material to form two layers, and the top plate 5 of the reinforcing rib 6a is formed so that the hollow portion 16 by gas filling does not protrude beyond the top plate 5 more than necessary. The thickness W is set in a range of 2 to 5 mm. When the thickness W of the top plate 5 in the reinforcing rib 6a is less than 2 mm, the core material is difficult to be filled. When the thickness W exceeds 5 mm, the core material filled in the top plate 5 increases, but the weight increases. At the same time, since the hollow portion 16 made of gas protrudes from the reinforcing rib 6 or rib 9 into the top plate 5, the actual thickness w of the top plate 5 at this portion becomes smaller than W, and the strength is lowered.
Further, the maximum thickness T of the base of the reinforcing rib 6a is in the range of 5 to 30 mm, and the height H of the reinforcing rib 6a is in the range of 10 to 50 mm, so that the core material and gas are filled in the reinforcing rib 6a. And the resin fluidity to each corner part 4b is securable. If the maximum thickness T and the height H do not satisfy the above lower limit values, the core material and the gas are not easily filled in the reinforcing ribs 6, and if the upper limit value is exceeded, the resin flow inside the reinforcing ribs 6 is partially accelerated. For example, the resin flow balance is deteriorated, and the core material breaks the skin layer at the corner 4b.

The thickness W of the top plate 5, the thickness T, and the height H of the reinforcing rib 6a in the reinforcing rib 6a described above are not only the reinforcing rib 6a but also the lattice-shaped reinforcing rib 6 (continuous to and adjacent to the reinforcing rib 6a). 6b, 6c,...) And the grid-like ribs 9 provided on the girders 3a and 3b are preferably applied.
In particular, the reinforcing rib 6a directly connected to the rib 9a of the central girder part 3a and the gas flow path 9b in the direction orthogonal to the central girder part 3a where the filled gas first strikes is the thickness of the top plate 5 described above. The thickness W, the thickness T of the reinforcing rib 6 and the configuration satisfying the numerical ranges of the height H are provided. The reinforcing rib 6a can form an ideal three-layer structure in which the hollow portion 16 is formed in the innermost layer by the resin and gas to be filled, and a rib structure in which the resin and gas can flow most easily can be formed in this portion. . This makes it possible to improve the fluidity of the resin and gas to the other reinforcing rib 6 and the ribs 9 of the girders 3a and 3b on the front side in the flow direction of the resin and gas connected to the reinforcing rib 6a. The synthetic resin pallet 1 can be formed.

In this way, the upper pallet forming member 4A is manufactured by injection molding, and similarly, the lower pallet forming member is also manufactured. And the synthetic resin pallet 1 can be manufactured by making the upper pallet forming member 4 </ b> A and the lower pallet forming member face each other and welding the beam portions 3 a and 3 b together.
When the thickness T or height H of the ribs 9 in the girders 3a and 3b is smaller than the lower limit value, the hollow portion 16 is not formed because the gas is difficult to fill, and the skin 9 A two-layer structure consisting of the layer 14 and the core layer 15 is formed.

  As described above, according to the synthetic resin pallet 1 according to the present embodiment, the reinforcing rib 6 has a three-layer structure including the skin layer 14 made of virgin resin, the core layer 15 made of recycled resin, and the hollow portion 16 made of gas. Since the hollow portion 16 does not protrude into the top plate 5 and the strength of the top plate 5 can be ensured, there is an effect that the weight of the synthetic resin pallet 1 and the filling rate of the core material can be improved. Can do.

Next, a modification of the present invention will be described with reference to FIGS.
FIG. 5 shows the main part of the synthetic resin pallet 1 according to the first modification. In the upper (lower) pallet forming member 4A constituting the synthetic resin pallet 1, the central girder portion 3a is directly connected to the joining portion of the rib 9a of the resin gate portion 10 and the gas flow path 9b of the gas gate portion 12a. The reinforcing rib 6 is not provided. In this case, the gas supplied from the gas gate portion 12a through the gas flow path 9b in the mold is supplied to the reinforcing ribs 6a and 6a (6) orthogonal to the central girder portion 3a provided at equal intervals on both sides of the merge portion. Is done. That is, these two reinforcing ribs 6a and 6a are the reinforcing ribs 6a outside the central beam portion 3a that are continuous to the gas flow path 9b at the shortest distance among the plurality of reinforcing ribs 6, and the AA cross section thereof. The structure constitutes an ideal three-layer structure shown in FIG.
Therefore, the reinforcing rib 6a may not be directly connected to the joining portion between the resin flow path of the rib 9a connected to the resin gate portion 10 and the gas flow path 9b connected to the gas gate portion 12a. .

FIG. 6 shows a main part of the synthetic resin pallet 1 according to the second modification. In the upper (lower) pallet forming member 4A constituting the synthetic resin pallet 1, the inclined gas flow path 9b is not provided in the gas gate portion 12a provided in the central girder portion 3a, and is substantially parallel to the rib 9a. The rib 9c constitutes a gas flow path. Outer rib reinforcing ribs 6a (6) orthogonal to the central beam portion 3a are provided on the extension line of the ribs 9c. In this case, the gas injected from the rib 9c serving as a gas flow path is centered on both sides. It is supplied to the reinforcing ribs 6a and 6a orthogonal to the portion 3a. That is, these two reinforcing ribs 6a, 6a are the reinforcing ribs 6a outside the central beam portion 3a that are continuous to the gas flow path 9c at the shortest distance among the plurality of reinforcing ribs 6, and the AA cross section thereof. The structure constitutes an ideal three-layer structure shown in FIG.
For this reason, the joining portion where the gas passage 9c joins may not be provided at the end of the resin passage of the rib 9a connected to the resin gate portion 10.
As described above, the gas flow path connected to the gas gate portion 12a may be provided as the rib 9c on the gas gate portion 12a. However, the rib 9c is not provided or the rib 9c is provided and the top plate is directly below. The gas flow path may be configured so that gas flows in five directions.

As shown in the above-described embodiments and modifications, the gas injected from the gas gate portion 12a provided in the central girder portion 3a of the upper (lower) pallet forming member 4A is moved from the central girder portion 3a to the outside of the central girder portion 3a. The reinforcing rib 6a that is initially filled after flowing has an ideal three-layer structure having the above-described width W of the top plate 5, the maximum thickness T of the reinforcing rib 6, and the height H. In this case, the arrangement position of the reinforcing rib 6 that is initially filled with gas is arbitrary, and is not limited to the above-described embodiment or modification, but is adjacent to the central beam portion 3a and orthogonal to the central beam portion 3a. It is preferable that it is disposed.
Further, the reinforcing rib 6 disposed at a position separated from the central beam portion 3a has a three-layer structure having the above-described width W of the top plate 5, the maximum thickness T of the reinforcing rib 6, and the height H. Of course, you may.
In addition, in the above-mentioned Example and modification, although the synthetic resin pallet 1 by a single-sided two-way insertion was demonstrated, a four-sided insertion may be sufficient, or a double-sided two-way insertion or a four-way insertion may be sufficient.
Further, the synthetic resin used as the skin material and the core material may be mixed with a foaming agent containing an organic or inorganic material and used as a foam.
Moreover, although virgin resin was used as the skin material constituting the skin layer 14, a recycled resin may be used instead. Even in this case, an additive such as a colorant may be added to the skin material.

The upper pallet formation member in the synthetic resin pallets by the Example of this invention is shown, (a) is a top view, (b) is a back view. It is a principal part enlarged view which shows the rib of the upper pallet formation member in FIG.1 (b), the gate part for resin, and the gate part for gas. FIG. 3 is an enlarged cross-sectional view taken along line AA of a reinforcing rib outside a central girder that is continuous with the gas flow path in FIG. 2 at the shortest distance. It is sectional drawing of the reinforcement rib in FIG.1 (b), (a) is an AA sectional view, (b) is a BB sectional drawing, (c) is a CC sectional drawing. It is the elements on larger scale of the upper pallet formation member similar to FIG. 2 which shows the 1st modification of an Example. It is the elements on larger scale of the upper pallet formation member similar to FIG. 2 which shows a 2nd modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Synthetic resin pallet 2 Upper deck board 3 Girder part 3a Center girder part 3b End girder part 5 Top plate 6, 6a, 6b, 6c Reinforcement rib 9 Rib 9b Gas flow path 10 Resin gate part 12a, 12b, 12c, 12d Gas gate part 14 Skin layer 15 Core layer 16 Hollow part

Claims (2)

A plastic pallet having a deck board and a plurality of girders,
The deck board includes a top plate and a plurality of reinforcing ribs provided on the side of the top plate.
One resin gate is provided in the center of the top plate,
A gas gate portion and a gas flow path continuing to the gas gate portion are provided in at least one of the plurality of beam portions,
Among the reinforcing ribs, the reinforcing rib outside the girder that is continuous to the gas flow path at the shortest distance is a skin layer provided on the outermost side, a core layer provided on the inner side of the skin layer, and the core layer The top plate of the portion where the reinforcing rib is provided has a thickness of 2 to 5 mm, and the root of the reinforcing rib to the top plate is provided. The synthetic resin pallet is characterized in that the maximum thickness is 5 to 30 mm, and the height of the reinforcing rib including the top plate is 10 to 50 mm.   2. The synthetic resin pallet according to claim 1, wherein the reinforcing ribs outside the spar that are continuous at the shortest distance extend in a direction orthogonal to the extending direction of the spar and are connected to the spar.

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