JP5426904B2 - Plastic pallet - Google Patents

Description

The present invention relates to a synthetic resin pallet that is used for carrying and storing various articles on a loading surface.

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. There are two types of synthetic resin pallets, one that is integrally formed and one that is formed by dividing the pallet into two substantially central portions at the upper and lower portions of the girders, but by joining the girders together. In addition, there is a so-called skid pallet composed only of a deck board and legs (girder). In these synthetic resin pallets, in order to achieve weight reduction and reduction in manufacturing cost, by filling the mold with molten resin and injecting an inert gas into the reinforcing rib after a predetermined delay time, There is one in which a hollow portion is formed in the reinforcing rib.

For example, in the synthetic resin pallet described in Patent Document 1, the pallet forming members obtained by dividing the pallet into upper and lower parts are opposed to each other, and the girder portions are melted and abutted to form a single piece. Such a pallet forming member forms a girder portion on the back surface opposite to the loading surface of the upper and lower deck boards, and reinforcing ribs are formed in a lattice shape on the back surface of each deck board including the girder portion. . A molten resin injection gate portion for injection-molding the pallet forming member is provided, for example, on the loading surface of the deck board that is removed from the reinforcing rib. When injection molding a synthetic resin pallet, the molten resin is injected into the mold from the molten resin injection gate portion on the loading surface, and the gas is blown in from the gas gate portion of the reinforcing rib after the resin injection, so that the inside of the reinforcing rib The gas channel is formed in the hollow portion. In this case, since the resin injection into the molten resin injection gate portion of the pallet forming member is performed last in the molten resin injection step, the resin in the gate portion remains at a high temperature even after the injection. On the other hand, when the gas blown into the reinforcing rib enters the molten resin injection gate portion through the gas flow path in the reinforcing rib, the resin in a high temperature state bursts and opens to the outside from the molten resin injection gate portion. There is a risk of malfunction. Therefore, in order to prevent this, the reinforcing rib is not provided on the back surface of the molten resin injection gate portion, and the thickness of the resin receiving portion which is a portion of the molten resin injection gate portion is made thinner than other portions of the deck board. By setting it as a part, the cooling and solidification of the resin in the resin receiving part is promoted to prevent the gas from entering the resin receiving part and the molten resin injection gate part.

Further, in the synthetic resin pallet manufacturing apparatus described in Patent Document 2 having a hollow portion by gas injection in the reinforcing rib, the mouth of the molten resin injection gate portion is enlarged in order to sufficiently supply the molten resin to the mold. doing. Then, after the supply of the molten resin is completed, the gas is injected into the mold from the reinforcing rib, and before the gas reaches the resin receiving portion region of the deck board formed in the molten resin injection gate portion, the cavity interval of the resin receiving portion is set. It is made smaller by the interval changing means to reduce the thickness of the resin receiving portion, and the resin pressure is increased to prevent gas from entering.

Japanese Patent No. 3443319 Japanese Patent Laid-Open No. 2007-8003

However, in the synthetic resin pallets described in Patent Documents 1 and 2, the resin receiving portion provided with the molten resin injection gate portion is thinner than the other area of the deck board, so that the manufactured synthetic resin pallet There is a problem that the strength of this part is reduced, and the product life is short because it is easily damaged by a load or an impact when the pallet is used.

In view of such circumstances, the present invention prevents a gas injected by gas injection from entering a resin gate for injecting molten resin and increases the strength of this portion to prevent breakage. The purpose is to provide a made pallet.

The synthetic resin pallet according to the present invention has a deck board and a girder, a resin gate bush is disposed on one side of the deck board, and a girder and a plurality of decks on the other side of the deck board. Hollow ribs are formed, and the hollow portions of the plurality of hollow ribs are formed by injecting gas from a gas gate, and the distance to the portion of the plurality of hollow ribs toward the center direction of the resin gate bush is L, and the resin When the thickness of the deck board where the gate bushing is disposed is t, the relationship between the distance L and the thickness t is t < L ≦ 3t, and the thickness of the deck board is substantially uniform throughout. A plurality of hollow ribs including four hollow ribs arranged in a cross shape around a portion corresponding to the outer periphery of the resin gate bush.
It is characterized in that the distance from the tip end portion of each rib to the deck board to the portion corresponding to the outer periphery of the resin gate bush is equal to each other .

According to the present invention, when the molten resin is filled into the mold of the deck board from the resin gate portion, and then gas is injected, the gas flows in the reinforcing rib, and the resin gate bush in the high temperature state in the resin gate portion. The distance L from the resin gate bush and the tip of the hollow reinforcing rib is t ≦ L with respect to the thickness t of the deck board where the resin gate bush is disposed. Therefore, even if the gas flows in the hollow reinforcing rib, it does not reach and break through the resin gate bush. Moreover, since the deck boat has a substantially uniform thickness t as a whole, there is no local reduction in strength near the resin gate bush, and the strength of the synthetic resin pallet can be ensured and the life can be maintained long. .

It is a top view of the two-way insertion synthetic resin pallet which is one embodiment of the present invention. It is a side view of the A arrow line in FIG. It is a side view of the B arrow line in FIG. It is a top view of the back surface of an upper surface deck board. It is a fragmentary sectional enlarged view of the central part vicinity of the back surface side of an upper surface deck board. It is a top view which shows arrangement | positioning of the hollow rib provided in the periphery of the resin gate bush. It is side surface fragmentary sectional view which shows arrangement | positioning of the hollow rib provided in the resin gate bush and its periphery.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of a two-way synthetic resin pallet (hereinafter sometimes simply referred to as a pallet) 1 according to an embodiment of the present invention. The pallet 1 is formed of an upper deck board 2, a lower deck board 3, and a girder 4, and has end girders 41 and 41 and an intermediate girder 42 as the girder 4. And the fork insertion hole 5 is formed between the end beam 41 and the intermediate beam 42 by welding the end surfaces of the end beam 41, 41 and the intermediate beam 42 (refer FIG. 2). Since the pallet 1 is two-way, fork insertion holes 5 are formed only on the pair of side surfaces, and no fork insertion holes are formed on the other pair of side surfaces (see FIG. 3). Further, a non-slip tape 6 is welded to the surface of the top deck board 2 of the pallet 1. A trace of the resin gate 7 and a trace of the resin gate bush 8 at the time of molding can be confirmed at the center of the surface of the upper deck board 2 (see FIG. 1). In this pallet 1, the resin gate 7 is injection-molded by one single-point gate at the center position, but it may be a multi-point gate using a plurality of resin gates.

As shown in FIG. 4, a plurality of ribs 9 are provided vertically and horizontally on the back surface of the top deck board 2. Most of the plurality of ribs 9 are hollow ribs 9a, and solid ribs 9b are provided around the fork insertion hole 5 side of the pallet 1 so that they are not easily damaged even if the forks collide. . A hollow rib 9b is also provided in the vicinity of the position corresponding to the outer peripheral portion of the resin gate bush 8 in the center so as to be substantially cross-shaped. The gas gate 10 is provided at a position that is point-symmetric from the central portion. The gas gate 10 may be provided on the front surface side of the top deck board 2 or on the back surface side.

FIG. 5 is an enlarged partial cross-sectional view in the vicinity of the center portion on the back surface side of the top deck board 2. The thickness of the upper surface deck board 2 is substantially uniform throughout the entire thickness t, and the thickness t is substantially uniform even in the vicinity of the resin gate bush 8 or other portions. Therefore, the upper deck board 2 itself is not locally lowered in strength in the vicinity of the resin gate bush 8. In the case of a synthetic resin pallet, if the thickness t is in the range of 2.0 to 5.0 mm, it has sufficient loading strength even when a load is loaded, and also secures bending strength. However, in consideration of the balance between strength and weight reduction, the thickness is preferably in the range of 2.8 to 4.5 mm, particularly preferably 3.0 to 4.0 mm.

The hollow ribs 9a (9aa, 9ab) arranged in a substantially cross shape provided in the vicinity of the position corresponding to the outer peripheral portion of the resin gate bush 8 in the center portion are formed in an R shape at the base portion with the upper surface deck board 2. The distance L (L ₁ , L ₂ ) is provided from the tip of the base to the portion corresponding to the outer periphery of the resin gate bush 8. In the case of forming hollow ribs 9a and solid ribs 9b as reinforcing ribs on a synthetic resin pallet, the width of these ribs is set to 4.8 to 10.0 mm. In consideration, it is preferably 5.0 to 6.0 mm. The height of the reinforcing rib is 20.0 to 40.0 mm. However, when considering the balance between strength and weight reduction, the height is preferably 34.0 to 36.0 mm, particularly 34. It is preferable to set it as 8-35.2 mm. These hollow ribs 9a and solid ribs 9b are provided so as to protrude from the top deck board 2, but their side surfaces have a slight inclination angle (1-2 °), The upper end surface has a slight r shape. Therefore, the above-described rib width is approximately the width of the uppermost surface of the rib. Further, the R shape of the base portion is set to R2.8 to 8.2 mm, but the R shape of the base portion of most ribs is set to 3.0 to 3.2 mm.

The distance L ₁ of the hollow rib 9aa provided in a position opposite to the resin gate bush 8, the distance L ₂ of the hollow ribs 9ab provided on the other of the opposing positions, different even with the same However, from the viewpoint of securing the strength of the portion corresponding to the resin gate bush 8, it is preferable that the distance (L = L ₁ = L ₂ ) is set to be the same. Inside the hollow rib 9a (9aa, 9ab), a hollow portion 11 is formed by the gas injected from the gas gate 10. For reference, the position of the resin nozzle 12 is shown.

FIG. 6 is a plan view showing the arrangement of the hollow ribs 9a (9aa, 9ab) provided around the resin gate bush 8. As shown in FIG. 6 (a) shows a case where the distance _{L 1} and the distance of the hollow ribs 9ab _{L 2} of the hollow ribs 9aa are the same, FIG. 6 (b), the distance of the distance _{L 1} and the hollow rib 9ab of the hollow rib 9aa It shows the case where L ₂ is different.

FIG. 7 is a side partial sectional view showing the arrangement of the resin gate bush 8 and the hollow ribs 9a (9aa, 9ab) provided in the periphery thereof. The hollow ribs 9a (9aa, 9ab) are arranged so as to be directed toward the center of the resin gate bush 8, and the tip end portion of the base with the top deck board 2 has an R shape. In order to improve the overall bending strength of the pallet 1, the upper end portion and the upper portion of the tip portion of the hollow rib 9a have an r shape, and the root portion, the upper end portion and the upper portion of the solid rib 9b are the same. It is said that the shape. When the distance from the tip of the R shape to the portion corresponding to the outer periphery of the resin gate bush 8 is L, the thickness of the top deck board 2 at the portion where the resin gate bush 8 is disposed is t. The relationship between t and t is t ≦ L.

If L <t, the distal end portion 11a of the hollow portion 11 may break through the vicinity of the distal end portion of the hollow rib 9a. In the vicinity of the resin gate bush 8, since the temperature has not yet decreased immediately after the completion of the resin injection, there is a portion in which the resin is in a molten state without being completely solidified. If the tip portion of the rib 9a is too close to the resin gate bush 8, the injected gas will break through the molten portion of the resin.

If the gas pressure to be injected is set low to prevent this, the hollow ribs 9a are not formed so as to spread over the entire pallet 1, and the weight cannot be reduced. Further, if gas is injected when the temperature of the resin gate bush 8 is lowered, the entire pallet 1 is cooled and solidified, and the hollow rib 9a cannot be formed on the entire pallet 1.

Thus, depending on various conditions such as injection conditions, gas pressure, the overall shape of the synthetic resin pallet, the number of ribs (9a, 9b) and how to arrange them, the strength and hollowness of the entire synthetic resin pallet are Although it is influenced, it should be surprising that under the conditions that take into account the balance between the flexural strength and impact strength of the synthetic resin pallet and the weight reduction and the productivity, t ≦ L. It turned out that the front-end | tip part 11a does not pierce the front-end | tip part of hollow rib 9a (9aa, 9ab). In consideration of safety of conditions, t <L is preferable, and 1.5t ≦ L is particularly preferable. However, it is meaningless to increase the distance L more than necessary. Since the strength in the vicinity of the bush 8 also decreases, the upper limit is preferably L ≦ 3t, and particularly preferably L ≦ 2t.

With such a simple relational expression, it is possible to mold a synthetic resin pallet that balances weight and strength, so that it can be used with one-point resin gates, multi-point resin gates, two-way or four-way inserts. It is possible to easily design a mold that takes into account the resin gate bush and the surrounding hollow ribs, both on one side and on both sides.

DESCRIPTION OF SYMBOLS 1 Synthetic resin pallet 2 Upper deck board 3 Lower deck board 4 Girder part 5 Fork insertion hole 6 Anti-slip tape 7 Resin gate 8 Resin gate bush 9 Rib 10 Gas gate 11 Hollow part 12 Resin nozzle

Claims (1)

In a plastic pallet with deck boards and girders,
A resin gate bush is disposed on one side of the deck board,
The girder and a plurality of hollow ribs are formed on the other surface side of the deck board,
The hollow portions of the plurality of hollow ribs are formed by injecting gas from a gas gate,
Of the plurality of hollow ribs, L is a distance from a tip portion of the base of the hollow rib toward the center of the resin gate bush to the deck board to a portion corresponding to the outer periphery of the resin gate bush. When the thickness of the deck board where the bush is disposed is t, the relationship between the distance L and the thickness t is t < L ≦ 3t ,
The thickness of the deck board is a substantially uniform thickness t throughout,
The plurality of hollow ribs include four hollow ribs arranged in a cross shape around a portion corresponding to the outer periphery of the resin gate bush,
A synthetic resin pallet characterized in that a distance from a tip portion of the base of each of the four hollow ribs to the deck board to a portion corresponding to the outer periphery of the resin gate bush is equal to each other .

Images