JPS61130031A - Manufacture of synthetic resin pallet - Google Patents

Abstract

PURPOSE:To make it possible to produce a lightweight pallet high in rigidity in a few steps using a few members, by blow molding a hollow deck board having projections and planar hollow legs having pillar sections juxtaposed, and thermally welding the projections and the pillar sections. CONSTITUTION:A deck board 1 and legs 2 are formed separately by a blow molding machine, the surfaces of projections 3 of the deck board 1 and pillar sections 4 of the legs 2 where joining will be effected are thermally welded by the hot plate welding, vibration friction welding, magnetic induction heating, or the like so that the legs 2 are joined to the deck board. Though it is required that the pillar sections 4 has a certain height to secure opening sections (b), the corners are liable to become thin. Therefore, the deck board 1 is also provided with projections 3 to secure the height and the opening sections of the pallet while the height of the pillar sections 4 is limited. Thus, the produced pallet is provided with the opening sections (a, b), and a fork lift can accessible in both directions (A, B) to handle a load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing synthetic resin pallets used in cargo handling machines such as forklifts and handlifts.

[Conventional technology and its problems]

For example, pallets made of synthetic resins such as high-density polyethylene and polypropylene are known to be lightweight, durable, and economically inexpensive. Pallets are divided into types that can be used on one side and types that can be used on both sides, but either type consists of a deck board on which the cargo is placed and legs that support it, with space around the legs to insert a fork. It is something.

[Synthesis 4i] In the case of fat pallets, the deck board and the legs may be molded integrally, or they may be molded separately and then joined together, but in the former case, if you want to obtain something with a certain level of strength, Since the shape is quite complex, it is often impossible to use blow molding, and injection molding also results in complicated molds and high costs. On the other hand, in the method of making the deck board and the legs separately and joining them with silk, bolts and Nandos are usually used to connect them, but it takes a lot of work to make one piece because it has to be done so that the head does not protrude. Furthermore, there is a risk that the bolts and pinholes may loosen during use, resulting in incomplete installation.

Another option is to attach the legs to the deck board with adhesive or by welding them, but it is difficult to ensure sufficient joint strength at the joint, and it requires attaching a large number of legs one by one. It takes time and effort.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a synthetic resin pallet, which eliminates the disadvantages of the conventional method and allows a highly rigid and lightweight pallet to be manufactured using fewer steps and members.

[Means for solving problems]

In order to achieve the above object, the present invention separately forms by blow molding a hollow deck board having a protrusion for coupling on the lower surface, and a hollow leg in the form of a flat plate that juxtaposes columnar parts and protrudes upward. The gist of this method is to attach the legs to the deck board by then heat-sealing the protrusion and the column body.

[Effect]

According to the present invention, since both the deck board and the legs are hollow, they are lightweight, and the deck board and the legs can be easily connected by heat fusion without using any other mounting members, and each leg has a columnar body. It is not an independent unit, but rather a flat plate-like unit with several units integrated, so it can be installed all at once and securely fixed.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Fig. 1 is a perspective view of a synthetic resin pallet manufactured by the method of the present invention, Fig. 2 is a view taken from the same arrow B, and Fig. 3 is a view taken from the -LA arrow shown above, where 1 is a deck board and 2 is a leg. , 3 is a protrusion integrally formed on the lower surface of the deck board 1, and 4 is a column protruding upward from the flat leg 2. A plurality of these are arranged in parallel at appropriate intervals.

First, to explain the materials forming the deck board 1 and the legs 2, they are both hollow bodies that are blow-molded separately, and are made of polyolefin resin that can be blow-molded into large sizes, such as high-density polyethylene, polypropylene, or
Mixtures of these are used.

For high density polyethylene, MI is Q, 5 (g/
A homopolymer of 10 n+in:l or less or a copolymer with an α-olefin such as butene-1 or hexene-1 is used.

For polypropylene, MFRI Cg/10m
1n) It is desirable to use the following ethylene/propylene block copolymers in terms of cold resistance strength. Alternatively, polypropylene (including homopolymers) and various elastomers (
For example, EPM, EPDM, EVA.

EEA, etc.) and low-density polyethylene are also used. Further, various fillers (for example, mica, talc, glass fiber, inorganic fillers such as Shirasu balloon charcoal, wood powder, waste paper, etc.) may be mixed as necessary.

As will be described later, it is preferable that the deck board 1 and the legs 2 are made of the same material because they are heat-sealed, but they may be made of different materials if they can be bonded well.

The deck board 1 is a flat plate with no unevenness on the upper surface, and on the lower surface, as shown in FIG. They are integrally formed at appropriate intervals such as in the middle.

Similarly, as shown in FIG. 12, the bottom surface of the deck board 1 is made up of a set of two walls C that are depressed from the back side during molding, and the bottom d is the wall C on the top side of the deck board 1. Continuous long ribs 5, 6.7 consisting of concave grooves fused to a lattice are installed in a lattice pattern, while ribs 8, 9 of a similar structure are arranged radially from the center of the de-tsuki board 1 between them. will be placed in “Another example is the 11th
As shown in the figure, vertical ribs 10 may be added instead of the radial ribs 8 and 9.

These ribs 5 to 10 are arranged to pass through the protrusion 3 for forming the joint surface 3a, or to hang over a part of the protrusion 3,
This maintains the continuity of the ribs and also ensures strong connections with other intersecting ribs.

In this way, many ribs are installed inside the pallet while maintaining continuity, and the ends of the ribs are connected at the joint surface 3a, so that the stationary load of the pallet and the load when it is being lifted are handled by a so-called continuous beam. It will be received as

This means that the fulcrum reaction force that occurs locally when the pallet is in use (for example, around the contact surface of the fork or around the joint between the legs and the deck board when the pallet is left still) can be absorbed by these continuous ribs. It helps in smoothly transmitting the stress to the entire deck board, dispersing and averaging the stress to various parts, and as a result, the deck board does not undergo local deformation, and therefore deformation can be kept to a small level overall.

On the other hand, as shown in FIGS. 4 to 9, the leg 2 consists of a flat plate-shaped girder 2a extending in the longitudinal direction, and a column body 4 is integrally formed upward from the girder 2a, and its upper surface is joined. This becomes surface 4a.

This column body 4 is a part that takes on the load due to cargo as a compressive load, and in this case, the compressive load e (arrow in Fig. 5)
is transmitted to the girder 2a or the ground plane via the side wall 4b. In particular, when the pallet is placed on the ground, the compressive buckling strength of the wall surface controls the load that can be mounted. Increasing wall thickness is effective in improving buckling strength, but it leads to increased weight.
I don't like it very much.

In addition, it is desirable for the side wall 4b to be parallel to the direction of the load e, that is, to stand upright, from the viewpoint of buckling resistance, but on the other hand, it is necessary to taper θ ( However, within 5°) is required. However, this angle θ generates a bending moment on the wall surface when the load e is applied, and greatly reduces the buckling limit load. Therefore, in order to eliminate such restrictions, an embossing rib 11 is installed inside the column body 4.
A double wall structure was installed to improve buckling strength.

In addition, a rib 1 continuous in the longitudinal direction is provided on the ground surface side of the girder 2a.
2, and if necessary, after installing this continuous rib 12, an auxiliary rib 13 may be added in the remaining space.

On the other hand, the girder 2a is chamfered in order to facilitate the entry of the fork and reduce damage to the girder 2a caused by the fork coming in and going out.
form 4.

Next, to explain the manufacturing method, such a de-tuki board 1 and the leg 2 are individually molded using a blow molding machine, and the respective joint surfaces 3 of the protruding part 3 of the de-tuki board 1 and the column body part 4 of the leg 2 are formed.
a, 4a are thermally fused by hot plate welding, vibration friction welding, electromagnetic induction heating, etc., and 1 lO12 is applied to the deck board 1. Here, "individual" means to be manufactured separately, and includes both cases where the same mold is used and molded in different cavities, and cases where completely different molds are used.

The "height" of the column body 4 needs to be constant in order to form the opening b (Fig. 1), but since the blow ratio is different from that of the girder 2a, it is necessary to have a certain height, especially at the corner part 4C. It is easy to make the wall thinner. For this reason, a protrusion 3 is also provided on the deck board 1 side to ensure the height and opening of the pallet, while the column body 4
I tried to keep the height down.

In this way, the protrusion 3 has the role of limiting and securing the welding area and at the same time adjusting the height of the column body 4 so that it does not become unduly high.

In this way, the manufactured pallet has openings a and b secured in the first drawing, allowing a forklift (including a hand lifter) to enter and handle the cargo from either direction of arrows A and B. (so-called four-way insertion type).

Further, as another embodiment, the legs 2 can be assembled in a grid pattern and attached in a cross-section.

Since the upper surface of the deck board 1 is flat, it is difficult for dust to accumulate and is easy to clean, making it sanitary.

In addition, since the side wall 4b of the column body 4 is made of a curved surface, the fork's contact with the curved surface is less than the lateral force.

Damage can be prevented.

If the back side of the deck board 1 is as shown in Figure 10, then if the fork enters from the entry direction, the rib 5°7.8.9
acts as a bridge and suppresses deflection during lift luck 1. Also, if the fork enters from direction B, rib 6
．． 8.9 plays a similar role.

When the back side of the deck board 1 is shown in Fig. 11, ribs are arranged mainly in the vertical direction, and the legs 2 are placed in the horizontal direction in the figure, so that these act as reinforcement materials. , there is no problem even if the number of ribs installed in the horizontal direction is reduced.

In addition, the J-button No. 12 provided on the girder 2a of the leg 2 contributes to improving the rigidity against bending of the noglet (the moment marked with l in Fig. 5), and the pallet no. 1- is supported on both sides of the noglet. This is effective in preventing deformation when lifted by a forklift. In particular, when the rib 13 is provided, it mainly serves to strengthen the pressure receiving surface of the forklift.

Regarding actual examples and test results, a mold based on the design was attached to a blow molding machine TPB-200 manufactured by Ishikawajima-Harima Heavy Industries, Ltd., and molded. The molding material was high-density polyethylene [homopolymer, density 0] made by the Phillips method.
．． 952 or higher, Ml (high load method 21.6 kg) 5] was used, and the deck board and legs (
After molding 3 pieces), both were fused. The deck board size was 1100 x 900 mm, height 1501 mm, deck board weight 10 kg, and leg weight 1.5 kg/piece.

When this pallet was subjected to a bending strength test based on JIS Z0602, the strength was 15 mm and 1.
The deformation was 25 mm under a load of 5 tons, and it was ranked as a Class B pallet for a 1-ton load.

When a compression test was conducted based on JIS Z 0602, the result was 3 mm at a 4/3 ton load/(per leg), which passed the A and B standards (within 4 mm) for pallets with a carrying capacity of 1 ton.

Same < , drop test based on y'rs z 0602 (
(Part of the corner fell from a height of 1m), but the parley
) The dimensional change rate of the diagonal length is 0%, and the standard for A and B types ±
1.5% or less).

In addition, 1 ton of resin (25 kg paper bags, 40 bags) was placed on the
A transportation test was conducted using a forklift, and the deformation during lifting and lowering of the fork was within 5 mm at the end of the pallet, and no practical problems were observed.

〔Effect of the invention〕

As described above, in the method for manufacturing a synthetic resin pallet of the present invention, the deck board and the legs can be easily joined by heat fusion without using base materials such as bolts, and a relatively wide joint surface is ensured. Therefore, stress concentration at the joint can be avoided.

Furthermore, since the deck board and the legs are not integrally molded, but are separated as separate molded products, uneven wall thickness distribution due to uneven blow ratios can be eliminated, and the thickness can be continuous with the back surface of the deck board and the legs. Advantageous measures can be taken in terms of strength, such as allowing the legs and deck board to be installed in any desired arrangement, and the wall thickness of the legs and deck board to be arbitrarily selected according to the required performance.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a synthetic resin pallet manufactured by the method of the present invention, Fig. 2 is a view taken from arrow B in Fig. 1, Fig. 3 is a view taken from arrow A in Fig. 1, and Fig. 4. is a perspective view of the leg, FIG. 5 is a front view of the same leg, FIG. 6 is a top view of the same, FIG. 7 is a bottom view of the same, FIG. FIG. 7 is a sectional view taken along the line Y-Y, FIG. 10 is a bottom view of the deck board, FIG. 11 is a bottom view of the deck board in another embodiment, and FIG. 12 is a bottom view of the deck board in another embodiment.
The figure is a sectional view of the main part showing the rib. 1...Deck board 2...Leg 2a...Girder 3...Protrusion part 3a...Joint surface 4...Column body part 4a...Joint surface
4b... Side wall 4C... Corner part 5.6, 7, 8, 9.10, 12.13... Rib 11
... Emboss rib 14 ... Chamfer' --- J) K --- Fig. 10 Fig. 11 Fig. 12

Claims (1)

[Claims] A hollow deck board having a protrusion for connection on the lower surface and a hollow leg in the shape of a flat plate that juxtaposes the column body and protrudes upward are separately formed by blow molding, and then the protrusion and the column body are formed separately. A method for manufacturing a synthetic resin pallet characterized by attaching legs to a deck board by heat-sealing the legs.