JPH11310236A - Synthetic resin pallet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic resin pallet comprising a pallet forming member including a solid plate-like part without forming a hollow part caused by blown gas coming around a gate and is vicinity at the time of injection-molding of the pallet forming member. SOLUTION: The synthetic resin pallet comprising two pallet forming members formed by injection-molding which are made to face each other and welded to unify, wherein a gate for injecting fused resin for molding each pallet forming member is provided on a plate-like part positioned out of a rein forcing rib and the vicinity of the gate is formed to be a thin part 19 which is thinner than other plate-like parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pallet made of synthetic resin, and more particularly to a pallet for a forklift used for carrying, moving and storing articles.

[0002]

2. Description of the Related Art Conventionally, synthetic resin pallets have been manufactured and used as forklift pallets.
Normally, this type of synthetic resin pallet is basically formed by injection molding a pallet forming member having a shape in which the pallet is vertically divided at an intermediate portion in the height direction of the leg portion.
The pallet forming members are integrally formed by heat welding.

[0003] There are various types of synthetic resin pallets, and here, a description will be given of a pallet made of two members having slightly different structures. When forming such a synthetic resin pallet, first, the upper and lower pallet forming members are formed by injection molding.

[0004] Each of the upper and lower pallet forming members includes a plate-like portion, a leg forming member provided at an appropriate position on the inner surface of the plate-like portion,
Further, reinforcing ribs are provided in a grid-like manner so as to intersect the inner surface of the plate-like portion vertically and horizontally. "Plate-like part" is a generic term that refers to a plate-like part that has a relatively large surface, and especially a plate-like part that is intended to carry a load on its surface. We call it "deck board".

Therefore, in the case of a double-sided synthetic resin pallet, both plate-like portions are deck boards, and in the case of a single-sided synthetic resin pallet, the plate-like portion on which a load is to be placed is particularly a deck board. The other surface is simply referred to as a plate-like portion. The upper and lower pallet forming members are opposed to each other, and the leg forming members are butted against each other, and the butted portions are welded and integrated by heat to form a synthetic resin pallet.

Further, reinforcing ribs are formed in a grid on the inner surface of the plate-like portion of each pallet forming member. Such reinforcing ribs increase the bending strength of the plate-like portion, and convey a load by a forklift. It is well known that it is extremely effective in preventing bending of a plate-shaped portion, particularly a deck board, when moving.

[0007] Such a reinforcing rib has the advantage of increasing the bending strength of the plate-like portion of each pallet forming member, and also destroys the synthetic resin pallet near the fork insertion opening which is fragile due to a collision of a fork of a forklift or the like. This has the advantage of increasing the strength against.
Therefore, such a reinforcing rib is formed on the entire plate-shaped portion of each pallet forming member constituting the synthetic resin pallet.

[0008]

However, since the conventional synthetic resin pallets have reinforcing ribs formed in a lattice shape on the inner surface of the plate-like portion of each pallet forming member in order to increase the bending strength, the weight of the pallets is large. However, there is a problem that as the weight increases, the amount of resin material used increases. for that reason,
Immediately after injection molding of the pallet forming member, it has been proposed to blow gas into the reinforcing ribs and flow into the reinforcing ribs, thereby forming a hollow portion, that is, a gas channel, in the reinforcing ribs. Forming a gas channel by blowing gas into the reinforcing ribs in this manner is called a gas injection method.

When the gas channels are formed in the reinforcing ribs by using the gas injection method, there is a great advantage that the weight of the entire synthetic resin pallet can be reduced while increasing the bending strength of the plate-like portion. However, when gas is blown into the reinforcing ribs, the gas tends to enter the reinforcing ribs and at the same time to flow into a portion where the resin temperature is high. The reason for this is that gas is apt to enter where the resin temperature is high because the resin is not solidified.

By the way, when injection molding a pallet forming member constituting this kind of synthetic resin pallet, molten resin is injected into a molding die from a plurality of locations on the deck board surface side. Therefore, the temperature of the molten resin injection part immediately after injection molding, that is, the gate part, is higher than that of the other parts. In other words, the injection resin is the softest in this part. Rather, the hollow portion may be formed around the gate portion.

As a result, gas channels are formed in the gate portion of the deck board, which is originally solid, and in the peripheral portion thereof. As a result, there is a problem that the thickness of the portion is reduced and the strength is reduced. .

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem. During injection molding of a pallet forming member that constitutes a synthetic resin pallet, a gas is blown into a reinforcing rib to enter the inside thereof. When forming the gas channel, the blown gas flows around the gate portion which is the resin injection portion on the surface of the plate-shaped portion of the pallet forming member and its peripheral portion to form a solid plate-shaped portion without forming a hollow portion. An object of the present invention is to provide a synthetic resin pallet including a pallet forming member provided.

[0013]

SUMMARY OF THE INVENTION The present invention is a synthetic resin pallet, and is configured as follows to achieve the above-mentioned technical object. That is, the present invention relates to a synthetic resin pallet in which a pallet forming member having a shape obtained by dividing a pallet into upper and lower parts is formed by injection molding by injecting a molten resin from the surface side thereof, and by welding and integrating these members to face each other. The two pallet forming members are formed on the inner surface of the plate portion to define a passage for inserting a fork when the plate portion and the pallet forming member are welded and integrated into a synthetic resin pallet. A plurality of leg forming members, reinforcing ribs formed in a lattice shape on the inner surface of the plate-like portion, and at least a gas channel formed by blowing gas into the reinforcing ribs during molding of the pallet forming member, the pallet forming member A gate portion for injecting the molten resin to be formed is provided on the plate portion at a position deviated from the reinforcing rib, and a peripheral portion of the gate portion is a thin portion thinner than other plate portions. And wherein the door.

<Specific Structure of the Present Invention> The synthetic resin pallet of the present invention is composed of the above-mentioned essential components, but the present invention can be established even when the specific components are as follows. The specific constituent element is characterized in that the synthetic resin pallet is a four-sided pallet. Further, the synthetic resin pallet of the present invention may be a two-way pallet.

According to the synthetic resin pallet of the present invention, as a whole, a pallet forming member having a shape obtained by dividing the pallet into upper and lower parts is formed by injection molding, and these are formed integrally by opposing each other by welding. When each pallet forming member is formed by injection molding, a gas is injected into the reinforcing ribs from, for example, a central portion of the pallet forming member before the inside of the reinforcing ribs provided vertically and horizontally on the inner surface of the deck board or the inner surface of the plate-like portion is solidified. Then, this is spread in each reinforcing rib, and a hollow portion, that is, a gas channel is formed therein by blowing gas.

At this time, the gas channel enters the reinforcing rib existing inside the pallet forming member. On the other hand,
The gate portion and its peripheral portion, which are resin injection portions, on the surface of the plate-shaped portion of the pallet forming member are thinner than other portions, so that cooling is faster, and as a result, the gate portion and its peripheral portion are injected. The solidification of the resin is promoted. Therefore, the gas blown into the reinforcing ribs does not flow around the gate portion on the surface of the plate-like portion and its periphery, whereby the plate-like portion or the deck board can be reliably formed solid.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a pallet made of synthetic resin according to the present invention. FIG. 1 is a side view showing a four-sided synthetic resin pallet 10 according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating the synthetic resin pallet 10 which is divided into upper and lower halves. FIG. 3 is a plan view showing the inside of the pallet forming member 10a, and FIG. 4 is a partial view showing a gate portion which is a resin injection portion of the deck board of the pallet forming member 10a and its peripheral portion. FIG.

As shown in FIGS. 2 and 3, the upper die pallet forming member 10a is composed of a deck board 11a and nine leg forming members 12a, 13a, 14a arranged inside the deck board 11a at predetermined intervals vertically and horizontally. It is comprised including. That is, these nine leg forming members 12a to 14a
, The reference numeral 12a indicates the upper die pallet forming member 1.
One central leg forming member having a substantially square cross section provided at the center of Oa is shown.

Reference numeral 13a denotes a corner leg forming member provided at the four inner corners of the deck board 11a, that is, at each corner, so as to surround the center leg forming member 12a, and reference numeral 14a denotes an inner periphery of the deck board 11a. 9 shows an intermediate leg forming member provided along an edge and at an intermediate portion between each corner portion.

The upper pallet forming member 10
Inside the deck board 11a, the reinforcing ribs 15
Are provided crossing each other vertically and horizontally. Such reinforcing ribs 15 are provided inside the leg forming members 12a to 14a in addition to improving the strength of the deck board 11a as well as the pallet 1 made of synthetic resin.
A large number are provided in order to resist an external impact such as zero.

Inside the center leg forming member 12a, gas distribution ribs 16 are formed at diagonal positions, and the ends of the gas distribution ribs 16 are reinforced by reinforcing ribs 15 through the wall of the center leg forming member 12a. It is connected to the. As shown in FIG. 5, the inside of the reinforcing rib 15 connected to the gas distribution rib 16 is blown by gas at the time of injection molding of the pallet forming member 10a.
0 is formed.

The method of forming the gas channel 20 will be described. The intersection 17 of the gas distribution ribs 16 arranged in the X shape in the central leg forming member 12a is the center point of the central leg forming member 12a. Pallet forming member 10
It is also the center point of a. The intersection of the X-shaped gas distribution ribs 16 is the gas blowing position.

That is, a pallet forming die (not shown) for forming the upper die pallet forming member 10a has one gas injection hole (not shown) at a portion corresponding to the inner center position of the pallet forming member 10 described above. ) Is provided. When the upper mold pallet forming member 10a is injection-molded by injecting the molten resin from a plurality of holes dedicated to the injection of the molten resin, the gas injection is performed before the insides of the reinforcing ribs 15 and the gas distribution ribs 16 are solidified. An appropriate gas such as air or nitrogen (hereinafter simply referred to as gas) is injected from the hole at a predetermined pressure.

The gas injected from the gas injection holes enters the reinforcing ribs 15 from the intersections 17 of the gas distribution ribs 16 via the ribs 16 and enters the gas channels 20 therein.
To form Therefore, the gas channel 20 is also a conduction path for the injected gas formed in the reinforcing rib 15, and all the conduction paths in the reinforcing rib 15 are in communication.

As a result, the average bulk density in the outer peripheral region (annular region having an outer peripheral edge width of 5 cm) of the synthetic resin pallet is larger than that in the central region inside the outer peripheral region. The “average bulk density” refers to the ratio of the weight to the volume of a certain area in the pallet forming member. That is,
If the average bulk density is ρ, then ρ = weight / volume.

Therefore, when comparing the average bulk density between the central area and the outer peripheral area of the pallet forming member, the weight / weight ratio of each of the central area and the outer peripheral area is calculated.
Calculate the volume. In this synthetic resin pallet, there are not many gas channels formed in the reinforcing ribs in the outer peripheral region of the pallet forming member, and many gas channels are formed in the reinforcing ribs in the central region. The density is higher in the peripheral region than in the central region.

Thus, in the synthetic resin pallet of the present invention, in the central region, the number of tubular structural parts is large, so that the bending strength against the plate-shaped portion is particularly high. It is possible to provide the property of being high, and to achieve weight reduction.
The average bulk density of the outer peripheral area / the average bulk density of the central area,
That is, the density ratio is about 1.05 to 1.8, preferably 1.1 to 1.5.

The reinforcing ribs 15 are provided via the gas distribution ribs 16.
Since the internal pressure of the gas blown into the inside uniformly acts on the inner wall of the mold portion, the thickness of the formed reinforcing rib 15 does not become extremely thin. By forming the hollow portion in the reinforcing rib 15 in this manner, effects such as a reduction in the weight of the synthetic resin pallet, a reduction in dimensional fluctuation during molding, and a reduction in molding time can be obtained.

After the gas is blown from the intersection 17 of the gas distribution rib 16, an opening serving as a gas inlet is formed at the intersection, and the gas channel 2 in the reinforcing rib 15 is formed.
0 is in a state of communicating with the atmosphere via this gas inlet. However, since this gas inlet is located in the central portion of the closed hollow cylinder, rainwater infiltrates the hollow portion in the reinforcing rib 15 through the gas inlet during use of the synthetic resin pallet. Never.

That is, the gas inlet is located inside the center leg forming member 12a, and a lower pallet forming member 10b described later is welded and integrated with the upper pallet forming member 10a to form the synthetic resin pallet 10. At this time, the central leg portion forming member 12a becomes a hermetically sealed hollow cylindrical central leg portion in cooperation with the other central leg portion forming member 12b, and is not exposed to the outside (atmosphere).

When the upper pallet forming member 10a is injection-molded, molten resin is injected into the pallet forming die from eight gate portions 18 on the deck board 11a surface side of the upper pallet forming member 10a. . In the upper die pallet forming member 10a thus formed,
A sprue S and a gate G are formed on the surface of the deck board 11a into which the molten resin has been injected, as shown in FIG.

This gate G is used for the upper pallet molding member 10.
a is cut after the molding of the
The surface of a becomes smooth. The portion of the deck board 11a after the gate G is cut, that is, the molten resin injection portion is referred to as a gate portion.

The gate portion (indicated by reference numeral 18 in FIG. 2) retains a considerable amount of heat even after molding since the injection of the molten resin is the last in the molding process of the upper die pallet molding member. The solidification of the surrounding resin is slower than in other parts. Therefore, as described above, when gas is blown into the reinforcing ribs 15 to form gas channels, the gas may enter the unsolidified gate portion 18 and its surroundings and form gas channels in the deck board 11a. is there.

Therefore, in the synthetic resin pallet 10 according to this embodiment, the gate portion 18 on the surface of the deck board 11a of the upper pallet forming member 10a is provided on a plate-like portion where the ribs 15 and the like do not exist. As shown in FIG. 4, the thickness is made thinner than other portions to form a thin portion 19. Thus, the upper die pallet forming member 10
Since the gate portion 18 and its peripheral portion in FIG. 1A are thinner than the other portions, the gate portion 1 immediately after the injection molding is used.
8 and its peripheral portion have a high cooling effect, and the solidification of the molten resin is promoted.

Thus, when gas is blown into the reinforcing ribs 15 almost simultaneously with the injection molding of the upper die pallet forming member 10a to form a gas channel, the gas is discharged even if the gate portion 18 and its peripheral portion are still at a high temperature. As a result, no gas channel is formed on the deck board 11a (plate portion).

On the other hand, the lower pallet forming member 10b shown in FIGS. 6 and 7 is similarly provided with the center leg forming member 12b and the corner leg forming member 13 inside the plate portion 11b.
b and the intermediate leg forming member 14b. These central leg forming members 12b and their surrounding leg forming members 13
The b, 14b are exactly the same as the corresponding leg forming members 12a, 13a, 14a in the above-mentioned upper die pallet forming member 10a, and have exactly the same formation position, cross-sectional shape and size.

In the lower pallet forming member 10b, four legs are virtually divided by a vertical center line and a horizontal center line passing through the center of the center leg forming member 12b. A reinforcing rib 21 is formed in a ring shape at a position substantially inscribed in the forming members 12b, 13b, and 14b. The gas flow ribs 22 are formed at diagonal positions inside the center leg forming member 12b.
Are connected to the annular reinforcing ribs 21 in the four sections described above via the wall of the center leg forming member 12b.

Further, inside the center leg forming member 12b, the intersection 23 of the gas distribution ribs 22 formed at diagonal positions thereof is finally used as a gas inlet similarly to the upper die pallet forming member 10a. . As a result, a hollow portion, that is, a gas channel is formed inside the reinforcing ribs 21 that are all connected to the gas distribution ribs 22, similarly to the upper die pallet forming member 10a. The method of forming the gas channel in the reinforcing rib 21 is based on the method of forming the upper die pallet forming member 10.
Since the gas channel 20 is formed in the reinforcing rib 15 in FIG.

The lower pallet forming member 10b
The opening 24 is formed in a portion surrounded by the reinforcing rib 21 formed at a position substantially inscribed in the four leg forming members 12b, 13b, 14b for each quarter section as described above. . The opening 24 is a portion serving as an entrance of a wheel when handling the synthetic resin pallet by a hand lift.

The synthetic resin pallet according to the present embodiment
The upper and lower pallet forming members 10a, 10b
Are opposed to each other, and each leg forming member 12a, 12b, 13
a, 13b and 14a, 14b are butted together, and the butted portions are welded and integrated. In this manner, the upper and lower pallet forming members 10a and 10b are opposed to each other, and the leg forming members 12a, 12b, 13a, 13b and 14a and 14b are abutted and welded and integrated to form a hollow cylindrical leg. 12, 13, 14 are formed, and the space (hole) between these legs is formed by the fork insertion hole 2.
It becomes 6.

Although the above-described embodiment is a four-sided synthetic resin pallet 10, it goes without saying that the present invention can be applied to a two-sided synthetic resin pallet. In the synthetic resin pallet 10, a groove may be formed on the surface of the deck board 11a directly above the reinforcing rib 15 and the slip stopper 27 (FIG. 2) may be arranged in this groove. At this time, since the gas channels 20 are formed inside the reinforcing ribs 15 as described above, it is possible to prevent the generation of a depression due to a sink in the bottom surface of the groove.

Next, the injection molding conditions for the pallet forming members 10a and 10b will be described. Injection molding conditions for the pallet forming member may be ordinary conditions. For example, when high-density polyethylene is used as a material, a melting temperature (cylinder temperature) of 200 to 250 ° C. and an injection rate of 2000 to 5000 c
A condition of about c / sec is preferable. Further, as a synthetic resin constituting the pallet, polyolefin such as polyethylene, polypropylene, ethylene-propylene copolymer or the like is generally used, but it goes without saying that other resins may be used in some cases.

Further, it goes without saying that additives such as a coloring agent and a filler may be appropriately used. Furthermore, a foaming material may be mixed with these synthetic resins by mixing a conventionally known blowing agent including a commonly used organic or inorganic one. The foaming ratio in this case is desirably about 1.01 to 1.4 times. In this case, the apparent density of the entire pallet is preferably about 0.65 to 0.95 times the density of the raw synthetic resin.

In FIG. 3, reference numeral 28 indicates that when the present synthetic resin pallet is used, a relative slip between the fork and the synthetic resin pallet does not occur when the fork is inserted into the fork insertion hole. 3 shows a non-slip rubber grommet press-fitted into a hole provided at an intersection of a reinforcing rib formed on an inner surface of a deck board.

In the synthetic resin pallet according to each embodiment of the present invention described above, the cross-sectional shape of the reinforcing rib is substantially trapezoidal as shown in FIG. 5, but the present invention is not limited to this shape. is not. For example, a reinforcing rib having a curved side surface or a reinforcing rib having a semicircular cross-sectional shape may be used.

[0046]

As described above, according to the synthetic resin pallet of the present invention, the thickness of the gate portion and the peripheral portion thereof on the surface of the deck board or plate-like portion of the upper or lower pallet forming member. Is thinner than the other parts, so that during injection molding of the pallet forming member, gas blown to form gas channels in the reinforcing ribs does not enter the gate portion, and a solid deck board or It is possible to provide a synthetic resin pallet including a pallet forming member having a plate-like portion.

[Brief description of the drawings]

FIG. 1 is a side view showing a four-sided synthetic resin pallet according to an embodiment of the present invention.

FIG. 2 is a plan view showing the deck board surface of the upper pallet forming member by vertically dividing the synthetic resin pallet shown in FIG. 1;

FIG. 3 is a plan view showing an inner surface of the upper die pallet forming member shown in FIG. 2;

FIG. 4 is a cross-sectional view schematically showing a gate portion on the deck board surface of the upper pallet forming member shown in FIG. 3 and its periphery.

5 is a cross-sectional view showing a cross section of a reinforcing rib formed on an inner surface of the upper die pallet forming member shown in FIG.

FIG. 6 is a plan view showing the bottom surface of the plate-shaped portion of the lower pallet forming member by vertically dividing the synthetic resin pallet shown in FIG. 1;

FIG. 7 is a plan view showing an inner surface of the lower die pallet forming member shown in FIG. 6;

[Explanation of symbols]

 Reference Signs List 10 Pallet made of synthetic resin 10a Upper pallet forming member 10b Lower pallet forming member 11a Deck board 11b Plate portion 12a Central leg forming member 12b Central leg forming member 13a Corner leg forming member 13b Corner leg forming member 14a Middle leg forming Member 14b Corner leg forming member 15 Reinforcement rib 16 Gas distribution rib 17 Intersection (gas injection section) 18 Gate section 19 Thin section 20 Gas channel (hollow section) 21 Reinforcement rib 22 Gas distribution rib 23 Intersection (gas injection section) 24 Opening 25 Reinforcing rib 26 Fork insertion hole 27 Non-slip tape 28 Grommet

Claims (3)

[Claims] 1. A synthetic resin pallet formed by forming a pallet forming member having a shape obtained by dividing a pallet into upper and lower parts by injection molding by injecting a molten resin from a surface side thereof, and welding and integrating these members so as to face each other. When the two pallet forming members are welded and integrated with the plate-shaped portion and the pallet forming member to form the synthetic resin pallet, the inner surface of the plate-shaped portion is formed so as to define a passage for inserting a fork. A plurality of formed leg forming members, reinforcing ribs formed in a grid on the inner surface of the plate-like portion, and at least a gas channel formed by blowing gas into the reinforcing ribs when molding the pallet forming member. A gate portion for injecting the molten resin for forming the pallet forming member is provided on the plate-shaped portion at a position separated from the reinforcing rib,
A pallet made of synthetic resin, wherein a peripheral portion of the gate portion is a thin portion having a smaller thickness than other plate portions. 2. The synthetic resin pallet according to claim 1, wherein the synthetic resin pallet is a four-sided pallet. 3. The synthetic resin pallet according to claim 1, wherein the synthetic resin pallet is a two-way pallet.