JPH07277338A - Plastic pallet and production thereof - Google Patents

Abstract

PURPOSE:To obtain a plastic pallet which is light and strong enough to withstand loads and further, supplied at a low cost and hardly stained and excellent in the cleaning property. CONSTITUTION:A pallet is closed at one side and opened at the other side. A three-dimensional structural molding 10 provided with ribs 11 toward the opened face is connected to another one to face each other at the closed faces to constitute a girder 1. A plastic flat plate 20 as a deck board 2 is connected with the rib 11 at the opened face of the molding 10 to form a laminated structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin pallet which is lightweight, has a load-bearing strength, can be supplied at a low cost, is resistant to stains, and has excellent cleaning properties, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Pallets used for carrying and storing articles such as a table for carrying articles by a forklift are
In terms of its function, it is desired that it is lightweight and has load-bearing strength. Conventionally, many pallets made of synthetic resin have been manufactured, but in order to have a lightweight structure, a large number of through holes are formed in the deck board to save the material (Japanese Patent Laid-open No. Sho 5).
No. 6-123248), or by embedding a metal reinforcing material to maintain the strength and to reduce the weight as a whole (Japanese Patent Laid-Open No. Sho 5).
No. 6-123249).

However, in the case of a pallet having a large number of through holes, there is a problem that dirt easily adheres to the inner walls of the through holes and the cleaning becomes difficult and time-consuming. On the other hand, in the case of a pallet in which a metal reinforcing material is buried to reduce the weight as a whole, equipment for burying the metal reinforcing material is expensive during manufacturing, and it is difficult to supply the pallet at low cost.

As a method for reducing the weight, there is also a method of manufacturing a pallet by thinning the wall thickness by a hollow molding method in which a parison of synthetic resin is blown by air so as to follow the inner surface of the mold. , It was difficult to form a pallet with a complicated shape. For this reason, it is difficult to manufacture a pallet that has load-bearing strength due to the formation of a large number of ribs, and in order to obtain sufficient strength, the pallet becomes a heavy-weight material, and in order to reduce the weight without reducing the strength, There was a limit.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional techniques, the present invention intends to provide a synthetic resin pallet and a method for producing the same which can meet the demands of the technical field and overcome the drawbacks of the conventional methods. It is a thing. That is, it is an object of the present invention to provide a synthetic resin pallet that is lightweight, has a load-bearing strength, can be supplied at a low cost, is resistant to stains, and has excellent washability, and a method for manufacturing the same.

[0006]

A pallet according to the present invention has a three-dimensional structure molded body having a closed surface on one side and ribs formed toward the opening surface on the other side, and an opening of the molded body. A structure is composed of a synthetic resin flat plate joined to the opening face by a rib facing the opening face as a constitutional unit, and in particular, a three-dimensional structural molded body is It is configured by a laminated body structure in which synthetic resin flat plates that are laminated and integrated by joining the convex portions and close the opening surface of the molded body are joined to both sides.

That is, the pallet according to the present invention can obtain a molded article having a complicated shape with a large number of ribs in a lattice shape or a honeycomb shape having a thin wall structure by the component constitution of the three-dimensional structure molded body and the synthetic resin flat plate. By combining these three-dimensional structural molded bodies with a synthetic resin flat plate, a structure having a high-strength panel structure in which the local section of the rib portion is I-shaped is formed.

The three-dimensional structure molded body may be molded by an injection molding method or the like, but is preferably molded by injection compression molding. This is because the strain is small and the thin-wall moldability is excellent. This injection compression molding is a method in which the cavity is filled with a molten resin in a state where the mold is opened, and the mold is compressed and shaped by closing the mold during or after the filling of the resin, Low-pressure molding is possible because the resin is filled in a thick state, and since the molded product is molded with no directionality in mechanical strength by being uniformly compressed in the mold, it is homogeneous in a large molded product. Suitable for manufacturing pallets that require high strength.

Further, preferable conditions for obtaining a three-dimensional structural molded body in which one end surface is a closed surface and ribs are formed toward the opening surface at the other end surface by injection compression molding are as follows. Is. First, as the resin of the material, it is possible to use a thermoplastic resin used in general injection molding, but it is preferable to use polypropylene or polyethylene (HDPE) which is inexpensive and has good moldability. Considering the plasticizing temperature of the resin and the fluidity of the resin in the cavity, it is appropriate that the molding temperature be in the range of 170 ° C to 330 ° C, but the cold flow mark is prevented from occurring due to the cooling and solidification of the resin during mold compression. It is preferable to set the temperature in the range of 200 ° C. to 280 ° C. from the standpoints of stable mold transferability and mass productivity. Press pressure is 50 kg / cm ^{2 to} 200 kg / c
80 kg / cm ^{2 to} 120 kg / cm ^{2 in} the range of m ²
Is preferable, and the pressing speed is 3 mm / sec to 50
5 mm / sec to 20 mm / s in the range of mm / sec
A range of ec is preferred. The opening of the mold is 0.1mm
˜20.0 mm, preferably 3.0 mm to 10.0 mm. By molding under such molding conditions, it is possible to mold a three-dimensional structural molded body having a uniform thin-walled structure with no sink marks or warpage on the ribs.

As the synthetic resin flat plate, a flat plate molded and processed by an injection molding method, an extrusion molding method, a calender roll method or the like can be used, and a method of obtaining a flat plate by an extrusion molding method of continuous molding is particularly preferable. This is preferable in terms of mass productivity and reduction of manufacturing cost. The resin used for molding may be polypropylene, polyethylene, ABS resin, polyurethane resin, or the like, but when the three-dimensional structure molded body is joined by heat welding, the same material as the three-dimensional structure molded body is used. Is preferably used. The three-dimensional molded body and the synthetic resin flat plate may be joined not only by heat welding but also by vibration welding, bonding with an adhesive, or the like.

The flat plates made of synthetic resin have a structure in which they are joined by ribs facing the opening surface of the three-dimensional structure molded body. The reason is that the local cross section in which the closed surface of the three-dimensional structure molded body, the rib, and the flat plate made of synthetic resin have a rib in the center and the flat plates are joined at both ends thereof has an I-shaped cross section structure. This I-shaped cross-section structure has a smaller amount of deflection than the T-shaped cross-section structure in which the local cross section of the rib portion in which a large number of ribs are provided on the lower surface of the deck board, which is often adopted in conventional synthetic resin pallets, A panel structure having a V-shaped cross section can provide a pallet structurally excellent in strength.

Further, in the present invention, the reason why the load bearing strength necessary for the pallet can be sufficiently obtained even if the three-dimensional structure molded body has a thin structure is as follows. That is, from the following relational expression, since the strength is greatly affected by the height of the rib, it is based on the finding that if thin-wall molding is possible, the weight can be reduced without impairing the strength. Is. Deflection amount under the same supporting load condition (υ) = a * 1 / I (a is a constant, I is a moment of inertia of area.) Second moment of area (I) = b * a * h ³ (b is a constant, a is the width of the rib and h is the height of the rib.)

In the pallet according to the present invention, one side has a closed surface and the other side has an open surface, and a three-dimensional structural molded body is formed which forms ribs toward the open surface, and the closed surfaces of the molded body are joined together. Then, the synthetic resin flat plate is joined to the ribs facing the opening surface of the molded body to close the opening surface and integrate them. In this case, a synthetic resin flat plate may be preliminarily bonded to the opening surface of the three-dimensional structure molded body, and then the closed surfaces of the molded body may be bonded to each other to form a laminated body,
Alternatively, the closed surfaces of the three-dimensional structure molded body may be bonded to each other to be laminated and integrated, and then the synthetic resin flat plate may be bonded to the opening surface of the molded body. The three-dimensional structure molded body and the synthetic resin flat plate can be joined to each other, or the three-dimensional structure molded bodies can be joined to each other by heat welding, vibration welding, bonding with an adhesive, or the like.

As described above, in the synthetic resin pallet and the method for manufacturing the same according to the present invention, the three-dimensional structure molded body and the synthetic resin flat plate have a thin-walled structure and a complex shape with a large number of ribs. It is easy to obtain a molded product, and it is possible to reduce the weight. Furthermore, a pallet excellent in load bearing strength can be constructed by combining it with a synthetic resin flat plate joined by ribs. Further, since the pallet has a closed structure in which the ribs are not exposed on the surface, it is hard to get dirty and can be easily washed. Then, by adopting the injection compression molding, it is possible to easily mold a three-dimensional structural molded body having a uniform thin wall structure, reduce the manufacturing cost, and supply at a low cost.

The pallet according to the present invention is not limited to a double-sided use type pallet in which three-dimensional structural molded bodies are joined together by their closed surfaces to be laminated and integrated, and synthetic resin flat plates are arranged on both sides. Alternatively, a pallet of a single-sided use type configured by a three-dimensional structural molded body and a synthetic resin flat plate joined to the opening surface thereof may be configured. In the present invention, for example, as shown in FIG. 1, in addition to a double-sided use type four-way pallet having fork insertion holes in the front, rear, left, right, four directions, as shown in FIG. Double-sided pallet with double-sided use, single-sided (skid type) double-sided, four-way pallet as shown in FIGS. 7 and 8, or for hand-held lift downward as shown in FIG. It is possible to manufacture a four-way pallet having an opening, and it can be applied to all pallets constituted by the girder portion 1 and the deck board 2.

[0016]

The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 shows an embodiment of a pallet according to the present invention, which has a deck board 2 on both sides.
And the girder portion 1 is configured as a double-sided four-way pallet having fork insertion openings in the front, rear, left, and right directions. As shown in FIG. 2, in the pallet, the three-dimensional structure molded body 10 having the ribs 11 of the honeycomb structure is arranged upside down, and the closed surfaces are joined to form the girder portion 1, and the molded body 10 is further formed. A flat plate 20 made of synthetic resin, which becomes the deck board 2, is joined to the opening surface of the with ribs 11.
Note that FIG. 2 shows the configuration of a quarter of the entire pallet.

To manufacture a pallet, first, as shown in FIG. 3, a three-dimensional structural molded body 10 in which one side is a closed surface and the other side is an open surface and ribs are formed toward the open surface is formed by injection compression molding. did. In this case, polypropylene is used as the molding material, the molding temperature is 240 ° C, and the pressing pressure is 1
Molding was carried out under the conditions of 00 kg / cm ² , pressing speed of 20 mm / sec, and opening of the mold of 6 mm.

Next, as shown in FIG. 4, the three-dimensional structural molded bodies 10 were arranged one above the other and bonded at a bonding temperature of 180 ° C. for a bonding time of 30 seconds to fabricate the girder portion 1. And FIG.
As shown in FIG. 2, a synthetic resin flat plate 20 to be the deck board 2 formed by extrusion molding is prepared, and the molded body 10 is prepared.
The opening surface was closed, and the rib 11 facing the opening surface was joined and integrated at a joining temperature of 180 ° C. for a joining time of 30 seconds to manufacture a synthetic resin pallet.

The finished pallet has a total weight of 1
The weight is 3 kg, and it is possible to reduce the weight to about half that of the conventional pallet having the same outer dimensions and the same strength. Table 1 shows the results of the strength test (according to JIS Z 0161) of the finished pallet.

[0020]

[0021]

As described above, the synthetic resin pallet and the method for manufacturing the same according to the present invention have a complicated structure having a large number of ribs with a thin structure due to the component structure of the three-dimensional structural molded body and the synthetic resin flat plate. It is easy to obtain a molded product having a shape, and it is possible to reduce the weight. Further, a pallet excellent in load bearing strength can be configured by combining it with a synthetic resin flat plate joined by ribs. Further, since the pallet has a closed structure in which the ribs are not exposed on the surface, it is hard to get dirty and can be easily washed. Further, by adopting the injection compression molding, it is possible to easily mold a three-dimensional structural molded body having a uniform thin wall structure, to reduce the manufacturing cost, and to supply at a low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a pallet according to the present invention.

FIG. 2 is an exploded perspective view of essential parts of the pallet shown in FIG.

FIG. 3 is a cross-sectional view showing a step of the method of manufacturing the pallet shown in FIG.

FIG. 4 is a sectional view showing a step of the method of manufacturing the pallet shown in FIG.

5 is a cross-sectional view showing a step of the method of manufacturing the pallet shown in FIG. 1.

FIG. 6 is a perspective view showing another embodiment of the pallet according to the present invention.

FIG. 7 is a perspective view showing another embodiment of the pallet according to the present invention.

FIG. 8 is a perspective view showing another embodiment of the pallet according to the present invention.

FIG. 9 is a perspective view showing another embodiment of the pallet according to the present invention.

[Explanation of symbols]

 1 girder part 2 deck board 10 three-dimensional structural molded body 11 rib 20 synthetic resin flat plate

Claims (5)

[Claims] 1. A three-dimensional structural molded article having a closed surface on one side and ribs formed toward the other open surface is joined together by the convex portions of the closed surface to be laminated and integrated to form a girder. And a flat plate made of synthetic resin for closing the opening surface of the molded body located on both sides of the girder portion is joined by ribs facing the opening surface to form a deck board. Synthetic resin pallet. 2. A three-dimensional structural molded body having a closed surface on one side and ribs formed toward the other open surface constitutes a girder portion, and the open surface of the molded body is closed, and the open surface is formed. A synthetic resin pallet, characterized in that a deck board is composed of synthetic resin flat plates joined by ribs facing each other. 3. The three-dimensional structure molded body is molded by injection compression molding.
The synthetic resin pallet described. 4. A three-dimensional structural molded body, in which one side is a closed surface and the other is an open surface, and ribs are formed toward the open surface, and the convex portions of the closed surface of the molded body are joined together. A method for manufacturing a synthetic resin pallet, characterized in that the synthetic resin pallets are integrated by laminating and integrally laminating the synthetic resin flat plate with a rib facing the opening surface of the molded body. 5. The method for producing a synthetic resin pallet according to claim 4, wherein the molding of the three-dimensional structural molded body is injection compression molding.