WO2021182291A1

WO2021182291A1 - Step board

Info

Publication number: WO2021182291A1
Application number: PCT/JP2021/008416
Authority: WO
Inventors: 後藤　敏晴; 遊佐　敦; 水谷　圭
Original assignee: マクセルホールディングス株式会社
Priority date: 2020-03-13
Filing date: 2021-03-04
Publication date: 2021-09-16
Also published as: JP2023057183A

Abstract

Provided is a lightweight step board that has excellent strength. A step board 1 that comprises a plurality of step board members 2 that are aligned in the width direction, making it so that the step board members 2 on either side support a worker even if some of the step board members 2 break. The step board members 2 each include a resin foamed layer 21 that comprises a polycarbonate resin or the like and a fiber-reinforced resin layer 22 that comprises carbon fibers or the like and is layered on a principal surface of the resin foamed layer 21, and, when Lc is the span of the step board members 2 in the longitudinal direction, the breaking weight (Wcb) of the step board members 2 is greater than 980Lc (N). As a result, the step board members 2 are lightweight but have increased strength and therefore make for a safer step board.

Description

Tread board

This disclosure relates to treads including scaffolding treads used at building construction sites and the like.

Scaffolding treads used at building construction sites are often made of metal such as iron and aluminum. Metal treads are relatively heavy. Therefore, the metal treads increase the cost burden for transportation, installation, removal, etc., and the physical burden on the workers. Hereinafter, a tread structure for the purpose of weight reduction is provided.

Japanese Unexamined Patent Publication No. 2012-140782 discloses a scaffolding structure that can be reduced in weight. The scaffold structure includes a skin member made of fiber reinforced plastic forming the tread surface and the bottom surface of the tread plate, and a core member made of foamed resin embedded in the skin member and continuously extending in the length direction. As a result, the scaffolding structure secures a predetermined strength while reducing the weight.

Japanese Unexamined Patent Publication No. 2012-140782

However, although the scaffolding structure can secure the strength by providing the skin member, since the core member is foamed rigid polyurethane, there may still be a problem in strength.

Therefore, it is an object of the present disclosure to provide a tread plate having excellent strength while reducing the weight.

In order to solve the above problems, this disclosure has taken the following solutions. That is, the treads according to the present disclosure may include a plurality of tread members arranged side by side in the width direction. Each tread member may include a resin foam layer and a fiber reinforced resin layer laminated on the main surface of the resin foam layer. The breaking load (Wcc) of each tread member may be Wcc> 980 Lc (N), where Lc is the distance between the fulcrums in the length direction of the tread member.

According to the tread plate according to the present disclosure, it is possible to improve the strength while reducing the weight.

FIG. 1 is an external perspective view showing the structure of the tread plate according to the embodiment. FIG. 2 is an external perspective view showing the structure of the tread plate member among the tread plates shown in FIG. 1.

The treads may include a plurality of tread members arranged side by side in the width direction. Each tread member may include a resin foam layer and a fiber reinforced resin layer laminated on the main surface of the resin foam layer. The breaking load (Wcc) of each tread member may be Wcc> 980 Lc (N), where Lc is the distance between the fulcrums in the length direction of the tread member.

Each tread member can secure the strength of Wcb> 980Lc (N), which is a relatively high breaking load. Further, the weight can be reduced by forming bubbles in the resin foam layer. In this way, the treads in which a plurality of tread members are arranged side by side in the width direction can improve the strength while reducing the weight.

Preferably, the resin foam layer may contain 50% by weight or more of the polycarbonate resin with respect to the resin foam layer. As a result, the tread plate member can obtain sufficient strength.

Preferably, the fiber reinforced resin layer may contain 50% by weight or more of the polycarbonate resin with respect to the resin contained in the fiber reinforced resin layer. The resin foam layer and the resin contained in the fiber reinforced resin layer may each have a sea-island structure containing a polycarbonate resin as a sea component. As a result, the resin contained together with the polycarbonate resin is formed inside the resin foam layer and the fiber reinforced resin layer as island components, and the surface of the main surface of the resin foam layer and the fiber reinforced resin layer is a sea component polycarbonate resin. Is exposed a lot. That is, when the fiber-reinforced resin layer is bonded to the main surface of the resin foam layer, the adhesiveness between the resin foam layer and the fiber-reinforced resin layer can be improved due to the compatibility between the polycarbonate resins. As a result, it is possible to suppress the peeling of the fiber reinforced resin layer from the resin foam layer, and it is possible to further improve the strength of the tread member.

Preferably, the fiber reinforced resin layer may be laminated on both sides of the main surface of the resin foam layer. Thereby, the bending strength can be improved against the stress applied from the vertical direction to the main surface of the tread member.

Preferably, the tread may further include a frame. The frame may include one selected from the group consisting of metals, carbon fibers, inert particles and fiber reinforced plastics. The plurality of tread members may be arranged inside the frame with both ends supported by the frame in the length direction orthogonal to the width direction. Thereby, a plurality of tread plate members can be reinforced.

Hereinafter, the embodiment of the tread plate 1 of the present disclosure will be specifically described with reference to FIGS. 1 and 2. As the tread plate 1, the tread plate 1 for scaffolding used at the construction site of a building can be mentioned as an example. Here, the scaffolding tread plate 1 will be described as the tread plate 1. However, the tread plate 1 can also be used as a ladder, a stepladder, a foldable scaffold, and a tread plate 1 such as a part of the floor of an automobile, a train, a bus, or the like. That is, in the present specification, the tread plate 1 means not only the tread plate 1 for scaffolding but also a plate material on which a person's foot is pressed from above when walking or the like. First, as shown in FIG. 1, the tread plate 1 includes a plurality of tread plate members 2, a frame 3, and a hook 4. Both ends of the plurality of tread members 2 in the length direction are supported by the frame 3. The plurality of tread plate members 2 are arranged side by side in the width direction inside the frame 3. The hook 4 is locked to a scaffolding support or the like to support the frame 3.

As shown in FIG. 2, each tread member 2 includes a resin foam layer 21 and a fiber reinforced resin layer 22.

The resin foam layer 21 contains 50% by weight or more of polycarbonate resin. The resin contained in the resin foam layer 21 may contain 100% by weight of the polycarbonate resin, may be a compound resin of the polycarbonate resin and at least one of the other resin and the inert particles, or may be a copolymerized polycarbonate resin. Other resins include ABS resin, AS resin, acrylic resin, polyester resin (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexanedimethylene terephthalate, polybutylene naphthalate, etc.), PPS resin, polyphenylene ether resin, polyether. Sulfone resin, polysulfone resin, polypropylene resin, polyethylene resin, polystyrene resin, fluororesin (for example, polytetrafluoroethylene), polyamide resin, polyimide resin, cycloolefin resin, ethylenetetrafluoroethylene resin, polyvinylidene fluoride resin, polylactide resin , Polybutylene succinate resin, polybutylene succinate adipate resin, polycabrolactone resin, hydroxybutyric acid-hydroxyhexanoic acid copolymer and the like. The other resins may be used alone or in combination of two or more. From the viewpoint of improving the strength of the resin foam layer 21, the polycarbonate resin is preferably 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more. The inert particles are talc, clay, silica, glass fiber, carbon fiber, cellulose, calcium carbonate, titanium oxide and the like. The inert particles may be used alone or in combination of two or more. From the viewpoint of weight reduction, the inert particles are preferably 40% by weight or less, preferably 30% by weight or less, and more preferably 20% by weight or less.

On the other hand, since the polycarbonate resin has a high melt viscosity and low fluidity, it is difficult for the physical foaming agent to be mixed and it is difficult to secure a high foaming ratio of the foamed molded product. Further, when the polycarbonate resin is physically foamed, it is plasticized only by adding a foaming agent, so that the melt viscosity tends to decrease, but the viscosity increases when the cooling step after the foaming treatment is started. Therefore, as will be described later, when the polycarbonate resin is extruded from the die of the extruder for molding, air bubbles near the surface of the resin foam layer 21 may be broken and the surface may be roughened. As described above, the polycarbonate resin may have a problem in moldability. To solve such problems, a polycarbonate resin having a low viscosity average molecular weight (including a resin obtained by blending a polycarbonate resin having a high viscosity average molecular weight with a polycarbonate resin having a low viscosity average molecular weight) is used, or a resin having good fluidity is used. Alternatively, it is conceivable to add an additive such as a filler to secure the fluidity. However, if a polycarbonate resin having an excessively low viscosity average molecular weight is used, the strength of the resin foam layer 21 may decrease. Therefore, in view of maintaining both the strength and moldability of the resin foam layer 21 in a well-balanced manner, it is preferable to alloy the polycarbonate resin and another resin having good fluidity. From such a viewpoint, the polycarbonate resin is preferably 90% by weight or less, more preferably 80% by weight or less. The other resin having good fluidity is at least one selected from the group consisting of polyester resin (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), ABS resin, AS resin, polypropylene resin, and acrylic resin. Two resins can be mentioned. From the viewpoint of improving the strength, the content of the polycarbonate resin contained in the resin foam layer 21 is preferably 100% by weight.

The polycarbonate resin is not particularly limited as long as it has a carbonate bond in the main chain, and examples thereof include aromatic polycarbonate, aliphatic polycarbonate, and aromatic-aliphatic polycarbonate. The polycarbonate resin can be obtained, for example, by a method of transesterifying a dihydroxy compound and a carbonic acid diester, or a method of intercondensing the dihydroxy compound and phosgene in the presence of an alkaline catalyst. The dihydroxy compound may be a compound having two hydroxy groups in the molecule, and may be bisphenol A, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane, or 2,2-bis (4-). Hydroxyphenyl-3-methylphenyl) propane, 2,2-bis (3-tert-butyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, bis ( Aromatic dihydroxy compounds such as 4-hydroxyphenyl) methane, 1,1-bis (p-hydroxyphenyl) ethane, 2,2-bis (p-hydroxyphenyl) butane; ethylene glycol, 1,2-propylene glycol, 3 Examples thereof include aliphatic dihydroxy compounds such as -methyl-1,5-pentanediol, 1,6-hexanediol, 1,3-propanediol, and 1,4-butanediol. These dihydroxy compounds may be used alone or in combination of two or more. In addition to the dihydroxy compound, the polycarbonate resin may contain a structural unit derived from a monohydroxy compound, a trihydroxy compound, or the like.

When the resin foam layer 21 is formed by including the polycarbonate resin and the polypropylene resin, the polypropylene resin can improve the foaming characteristics of the polycarbonate resin, that is, improve the fluidity and increase the foaming ratio, so that the tread plate can be formed. The weight of the member 2 can be reduced. Further, when the resin foam layer 21 is formed by including the polycarbonate resin and the ABS resin, the foaming ratio can be increased as in the case where the polypropylene resin is contained, so that the tread member 2 should be reduced in weight. Can be done. On the other hand, when the resin foam layer 21 is formed by including the polycarbonate resin and the polyester resin, the tread member 2 can maintain the strength because the polyester resin has the same strength as the polycarbonate resin. As described above, the tread plate member 2 can determine the resin to be combined with the polycarbonate resin depending on whether the weight reduction or the strength is emphasized. Even when the weight is reduced, the resin foam layer 21 contains 50% by weight or more of the polycarbonate resin, so that sufficient strength, which will be described later, is ensured.

Further, the resin foam layer 21 is foam-molded. The resin foam layer 21 has a foaming ratio of 1.2 to 4 times. When the foaming ratio is low, the strength of the tread plate member 2 is high, but the effects of heat resistance and weight reduction are lowered. On the other hand, when the foaming ratio is high, the strength of the resin foam layer 21 is reduced, but the heat resistance and lightness are improved. Therefore, in consideration of the balance between the strength, heat resistance and light weight of the tread plate member 2, the foaming ratio is preferably 1.2 times or more, preferably 1.5 times or more, more preferably 2 times or more. It is preferably fold or less, preferably 3.5 times or less, and more preferably 3 times or less.

The resin foam layer 21 is foam-molded with at least one of a chemical foaming agent and a physical foaming agent. Physical foaming agents include, for example, carbon dioxide, nitrogen, air, argon and helium. The chemical foaming agent is, for example, zinc carbonate, baking soda, azodicarbonamide and the like. Since the resin foam layer 21 is foam-molded using a chemical foaming agent, the foaming ratio tends to be high, so that the specific gravity of the resin foam layer 21 can be further reduced. However, when a chemical foaming agent is used, by-products such as water and ammonia are also generated, the viscosity average molecular weight is lowered, and the strength of the resin foam layer 21 is lowered. Therefore, in foam molding with a chemical foaming agent, the viscosity average molecular weight of the polycarbonate resin is preferably 30,000 or more. Further, the resin foam layer 21 is foam-molded using a physical foaming agent, so that not only a clean product can be obtained without polluting the environment, but also air, nitrogen, and carbon dioxide gas use air gas. Therefore, it is also advantageous in terms of cost. When the resin foam layer 21 is foam-molded by using a chemical foaming agent and a physical foaming agent in combination, the chemical foaming agent is 1% by weight based on the total weight (total weight) of the resin and the additive used for the foam molding. It should be less than. By foaming and molding with less chemical foaming agent than physical foaming agent in this way, the risk of a decrease in strength due to hydrolysis can be reduced, the environment is less likely to be polluted, and costs can be reduced. can. That is, it is possible to balance cost, strength and weight reduction.

The viscosity average molecular weight of the polycarbonate resin is 10,000 to 100,000. If the viscosity average molecular weight of the polycarbonate resin is too high, the viscosity increases and the torque required for the extruder described later increases, making extrusion processing difficult. As a result, if the molecular weight of the resin is increased, the strength of the molded product after processing can be improved, but the production itself is hindered. On the other hand, if the viscosity average molecular weight of the polycarbonate resin is too low, the bubbles tend to coalesce and the bubble diameter does not become uniform, so that the strength after curing decreases. In addition, the decrease in melt tension makes it difficult to foam. Therefore, the viscosity average molecular weight of the polycarbonate resin is preferably 10,000 or more, preferably 15,000 or more, and preferably 100,000 or less, preferably 50,000 or less. That is, by setting the viscosity average molecular weight of the polycarbonate resin to 10,000 to 100,000, it is possible to obtain the effects of improving the strength and reducing the weight of the tread plate member 2 while facilitating molding.

The viscosity average molecular weight of the polycarbonate resin may be obtained by mixing a resin having a viscosity average molecular weight of less than 15,000 or more than 50,000. For example, an aromatic polycarbonate resin having a viscosity average molecular weight of more than 50,000 improves the entropy elasticity of the resin, and thus exhibits good molding processability in foam molding of the resin foam layer 21. Such improvement in molding processability is even better than that of branched polycarbonate. In a more preferred embodiment, the polycarbonate resin comprises an aromatic polycarbonate resin having a viscosity average molecular weight of 70,000 to 300,000 and an aromatic polycarbonate resin having a viscosity average molecular weight of 10,000 to 30,000, and the polycarbonate resin blended with or without mixing these has a viscosity average molecular weight. An aromatic polycarbonate resin having a value of 16000 to 35000 can also be used. When the content of the other resin contained together with the polycarbonate resin is 30 to 50% by weight with respect to the resin foam layer 21, it is preferable to use a polycarbonate resin having a relatively high viscosity average molecular weight of 25,000 or more.

The viscosity average molecular weight in the present disclosure is calculated as follows. _{First, using an Ostwald viscometer, the specific viscosity (η SP} ) is calculated from a solution in which 0.7 g of aromatic polycarbonate (resin contained in the resin foam layer 21) is dissolved in 100 ml of methylene chloride at 20 ° C. The specific viscosity can be calculated by the formula {(t-t ₀ ) / t _0}. t ₀ is the number of seconds for the methylene chloride (solvent) to fall, and t is the falling speed of the sample solution. Using the calculated specific viscosity, the viscosity average molecular weight M is calculated by the formula _{{η SP} / c = [η] + 0.45 × [ ^{η] 2 c}.} [Η] in the formula is the ultimate viscosity {[η] = 1.23 × 10 ^-4 M ^0.83 }. Further, c in the formula is the concentration of aromatic polycarbonate (0.7%).

The fiber reinforced resin layer 22 is a fiber reinforced resin sheet containing fibers, and is laminated on both sides of the main surface of the resin foam layer 21. That is, the resin foam layer 21 is arranged between the two fiber reinforced resin layers 22. The fiber-reinforced resin layer 22 is formed in a shape substantially similar to the shape of the main surface of the resin foam layer 21. As a result, the tread plate member 2 can improve the bending strength against the stress applied from the vertical direction to the main surface of the tread plate member 2. That is, the fiber-reinforced resin layer 22 functions as a reinforcing material for the resin foam layer 21. In addition, one fiber reinforced resin layer 22 may be laminated on the main surface of one side of the resin foam layer 21.

The fiber reinforced resin layer 22 is a polyester resin, an epoxy resin, an acrylic resin, a polycarbonate resin, a polyether sulfone resin, a polyamide resin, a polyethylene resin, a polypropylene resin, a polylactic acid resin, a phenol resin, a polybutylene succinate resin, or the like. The resin contained in the fiber-reinforced resin layer 22 is not limited to these, and other resin materials may be used.

The fibers contained in the fiber reinforced resin layer 22 are carbon fibers, glass fibers, aramid fibers, polyester fibers, acrylic fibers, polyethylene fibers, polypropylene fibers, hollow metal fibers and the like. Hollow metal fibers are stainless steel, steel and the like. The fibers contained in the fiber-reinforced resin layer 22 are not limited to these, and other fiber materials may be used.

The basis weight of the fibers contained in the fiber reinforced resin layer 22 is 100 to 500 g / m ² . The fiber contained in the fiber reinforced resin layer 22 is at least one selected from the group of woven fabrics such as plain weave, twill weave and double weave, those which are aligned vertically, horizontally and diagonally and hardened, and non-woven fabrics, or these are superposed. It is a thing. The fiber contained in the fiber reinforced resin layer 22 is preferably a woven fabric that is sufficiently supplied in the market and easy to handle. If the basis weight of the fibers is too low, the tread plate member 2 is insufficiently reinforced by the fiber reinforced resin layer 22, and as a result, it becomes difficult to secure the strength. On the other hand, if the basis weight of the fibers is too high, the weight of the tread plate member 2 becomes relatively large, and it becomes difficult to reduce the weight. Further, in the case of a cloth heavier than 500 g / m ² , it becomes difficult to cut and the rigidity of the cloth becomes too high, which may reduce the workability when laminating. As described above, the texture of the fibers contained in the fiber reinforced resin layer 22 is more preferably 100 g / m ² or more, preferably 175 g / m ² or more, more preferably from the viewpoint of balancing the improvement of strength and the weight reduction. Is preferably 250 g / m ² or more, 500 g / m ² or less, preferably 425 g / m ² or less, and more preferably 350 g / m ² or less.

The breaking load (Wcb) of each tread member 2 configured in this way is 980 Lc (N), where Lc is the distance between the fixed ends where both ends of the tread member 2 in the length direction are fixed. (Wcb> 980Lc (N)), and even if the tread member 2 is destroyed near the center, it is considered that the worker can be supported. In detail, Wcb> 980Lc can be calculated as follows. In addition, 980Lc (N) is referred to as required yield strength.

In the tread plate 1, if the tread plate member 2 is to be destroyed, it is considered that the tread plate member 2 is destroyed in a portion where workers frequently come and go, that is, in the vicinity of the center in the length direction of the tread plate member 2. When the tread plate member 2 is broken near the center in the length direction, it becomes a cantilever beam supported by the frame 3 at one end of both ends. When the cantilever has a length L and a load W is applied to the tip of the cantilever, the bending moment M can be calculated by {M = L × W} (Equation 1).

On the other hand, the tread plate member 2 is in a state of both end support beams in which both end portions of the tread plate member 2 are supported by the frame 3 in a state where the tread plate member 2 is not destroyed. In the 3-point bending test, the length of the support beams at both ends (distance between fulcrums) is Lc, and when the load Wc is applied to the center of the length Lc direction of the support beams at both ends, the bending moment Mc is {Mc = Lc / 4 × It can be calculated by Wc} (Equation 2).

Further, the stress applied to the material can be calculated by dividing the bending moment M or the bending moment Mc by the section modulus Z, that is, {σ = M / Z} or {σ = Mc / Z} (Equation 3).

Here, it is considered that the stress at which the material breaks is the same regardless of whether the cantilever has a length L or a double-ended support beam having a length Lc. When the load leading to the fracture of the cantilever having the length L is Wb and the load leading to the fracture of the both end support beams (tread plate member 2) having the length Lc is Wcb, the above-mentioned (Equation 1) )-(Equation 3), the relationship {L × Wb / Z = Lc / 4 × Wcb / Z} (Equation 4) is established.

In this relation of (Equation 4), if the both-end support beam can secure the mechanical characteristics that can support the worker even if it is broken at the center in the length Lc direction and becomes a cantilever, the both-end support beam can be used. Even if it is destroyed near the center in the length direction, the safety of workers can be ensured more reliably. The tread plate member 2 is a composite of fibers that are not easily deformed and foamed resin. Therefore, it is expected that the tread plate member 2 will not be deformed when cracked at the center, a hole for completely fitting the foot cannot be formed, and a fine crack of several millimeters or less will be formed. Therefore, in the unlikely event that a person stands on the cracked portion, it is expected that a load will be applied to both sides of the cracked tread member 2. Therefore, it is considered that the load applied to the tip of the cantilever is at most 1/2 of the body weight of the worker. That is, assuming that the weight of the worker is 100 kg, which is relatively heavier than the average weight of a Japanese man, the load applied to the tip of the cantilever is 50 kg. Based on these conditions, the relational expression of {L × 50 (kg) × 9.8 <Wccb × Lc / 4} (Equation 5) is established from (Equation 4).

From this (Equation 5), the breaking load Wcc of the both ends support beam with the length Lc of both ends support beam being 1 m can be expressed by {Wcc> L × 50 × 9.8 × 4} (Equation 6). When this is calculated, it becomes {Wcc> 1960L (N)} (Equation 7). Further, since the length L of the cantilever beam is Lc / 2, the breaking load Wcc of the support beam at both ends can be expressed by {Wcc> 980Lc (N)} (Equation 8). That is, if the breaking load Wcb of the supporting beams at both ends is larger than the required yield strength of 980Lc, even if the supporting beams at both ends are broken near the center in the length direction and become a cantilever, the worker can be supported. It is thought that it can be done.

As described above, each tread member 2 can secure the strength capable of supporting the worker as described above by obtaining a relatively high breaking load of Wcb> 980 Lc (N), and the resin foam layer 21 Weight reduction can be achieved by forming bubbles. As described above, according to the tread plate member 2, it is possible to improve the strength while reducing the weight. The resin foam layer 21 has an apparent density of 0.3 to 0.8 when it contains 100% by weight of the polycarbonate resin. The polycarbonate resin has an apparent density of 1.2. Therefore, when the apparent density of the foamed polycarbonate resin is 0.3 to 0.8, the foaming ratio of the resin foamed layer 21 is 1.5 to 4 times.

Each tread member 2 has a width of 5 to 500 mm. The width of the tread member 2 is about the same as the average shoulder width of a worker (Japanese male), or smaller than the average shoulder width of a worker. As described above, the plurality of tread plate members 2 are arranged side by side in the width direction. That is, the tread plate 1 is destroyed even if one tread plate member 2 is destroyed by forming each tread plate member 2 with the above-mentioned width and further arranging the tread plate members 2 side by side in the width direction. Workers can be supported by the tread plate members 2 on both sides of the tread plate member 2. Further, as described above, each tread plate member 2 has excellent strength that can support the worker even in the state of a cantilever.

As shown in FIG. 1, the frame 3 has a substantially rectangular shape in a plan view. The frame 3 has a pair of facing frame members 31 and a pair of facing frame members 32. The frame member 31 has a substantially L-shaped cross section due to the flange portion 31a and the wall portion 31b. Each of the pair of frame members 31 is arranged so that the flange portion 31a is inside the wall portion 31b. The frame member 32 is formed in a flat plate shape. A plurality of partition plates 33 are provided on the upper surface of the flange portion 31a of one of the frame members 31. A partition plate 33 is provided on the upper surface of the flange portion 31a of the other frame member 31 at a position facing the partition plate 33 provided on the one flange portion 31a.

Frame 3 contains one selected from the group consisting of metals, carbon fibers, inert particles and fiber reinforced plastics. The frame 3 may contain one of these materials, or may contain two or more of them. With such a configuration, the frame 3 can obtain the strength to support the plurality of tread plate members 2.

The tread plate member 2 is fitted in a region surrounded by a wall portion 31b, a partition plate 33, and a flange portion 31a. As shown in FIG. 1, each of the tread plate members 2 is positioned by partition plates 33 provided at the four corners of the tread plate member 2, except for the tread plate member 2 adjacent to the frame member 32. That is, two partition plates 33 are provided on one frame member 31 side between the tread plate member 2 and the tread plate member 2 adjacent to the tread plate member 2. The tread plate member 2 adjacent to the frame member 32 is fitted in a region surrounded by the frame member 32, the partition plate 33, the flange portion 31a, and the wall portion 31b. The end portion of the tread plate member 2 facing the frame member 31 in the length direction is supported by the flange portion 31a. In this way, a plurality of tread plate members 2 are attached to the inside of one frame 3.

By providing the frame 3 on the side surface of the tread plate member 2 in this way, the tread plate member 2 can be reinforced and a plurality of tread plate members 2 can be arranged side by side in the width direction. As a result, for example, when the worker is supported by the upper surface of the tread plate 1, even if one tread plate member 2 is destroyed, the worker is supported by the tread plate members 2 on both sides of the destroyed tread plate member 2. can do. Further, a gap is formed by interposing a partition plate 33 between the tread plate member 2 and the tread plate member 2 adjacent to the tread plate member 2. As a result, the tread plate 1 can be reduced in weight. Further, depending on the place where the tread plate 1 is attached, the air permeability can be improved.

One tread plate member 2 may be arranged inside the frame 3, or a plurality of tread plate members 2 may be arranged. Further, the frame member 31 may also have a substantially L-shaped cross section. Further, the partition plate 33 may be provided with one partition plate 33 between adjacent tread plate members 2 on one frame member 31 side. The partition plate 33 is not limited to the above-described configuration as long as it can partition the adjacent tread plate members 2 and facilitate the positioning when the tread plate members 2 are fitted. Further, the partition plate 33 may be provided with one or a plurality of partition plates 33 on one of the frame members 31 depending on the number of tread plate members 2 attached to the inside of the frame 3. Further, the tread plate member 2 can be attached without providing the partition plate 33 inside the frame 3. The frame 3 is not particularly limited as long as it can support both ends of the plurality of tread members 2 in the length direction and the plurality of tread members 2 can be arranged in the width direction.

When a load is applied, the polycarbonate resin is plastically deformed by yielding and then fractured, but the amount of plastic deformation from yielding to fracture is large. Therefore, the polycarbonate resin does not break immediately after yielding and has a tenacious property. As a result, if the deformation of the tread plate member 2 is detected, the risk caused by the subsequent destruction of the tread plate member 2 can be dealt with with a margin.

Further, the resin foam layer 21 contains 50% by weight or more of the polycarbonate resin, so that the sea-island structure is formed by the polycarbonate resin and the resin contained together with the polycarbonate resin. That is, the resin foam layer 21 has a sea-island structure in which the polycarbonate resin is a sea component and the resin contained together with the polycarbonate resin is an island component.

At that time, the fiber-reinforced resin layer 22 includes a resin (a compound resin of a polycarbonate resin and at least one of another resin and inert particles, a copolymerized polycarbonate resin, or another resin) contained in the fiber-reinforced resin layer 22. 50% by weight or more of the polycarbonate resin may be contained with respect to the blended polycarbonate resin). In this case, the resin contained in the fiber-reinforced resin layer 22 is the same as the resin contained in the resin foam layer 21 described above, and thus the description thereof will be omitted. By including 50% by weight or more of the polycarbonate resin in the fiber-reinforced resin layer 22, a sea-island structure in which the polycarbonate resin is a sea component and the resin contained together with the polycarbonate resin is an island component is formed as in the resin foam layer 21. Will be done.

As described above, the resin foam layer 21 and the fiber-reinforced resin layer 22 each contain 50% by weight or more of the polycarbonate resin, so that the polycarbonate resin is a sea component and the resin contained together with the polycarbonate resin is an island component. Is formed. That is, the resin contained together with the polycarbonate resin is formed as an island component inside the resin foam layer 21 and the fiber reinforced resin layer 22, and the surface of the main surface of the resin foam layer 21 and the fiber reinforced resin layer 22 is a sea component. A lot of polycarbonate resin will be exposed. As a result, when the fiber-reinforced resin layer 22 is bonded to the main surface of the resin foam layer 21, as will be described later, the resin foam layer 21 and the fiber-reinforced resin layer 22 are adhered to each other due to the compatibility between the polycarbonate resins. The sex can be improved. As a result, the fiber-reinforced resin layer 22 can be prevented from peeling from the resin foam layer 21, and the strength of the tread member 2 can be further improved. The amount of the polycarbonate resin contained in each of the resin foam layer 21 and the fiber reinforced resin layer 22 is 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more, as described above. Is good.

Although the embodiments have been described above, the present disclosure is not limited to the above embodiments, and various changes can be made as long as the purpose is not deviated.

(Manufacturing method of tread plate 1)
Next, the manufacturing method of the tread plate 1 will be specifically described.

First, the manufacturing method of each tread member 2 will be described.

The resin foam layer 21 of the tread plate member 2 is molded by a deformed extrusion molding method. Specifically, first, in an extruder such as a screw, the pellets of polycarbonate resin and other resins, for example, pellets of polypropylene resin, inert particles, etc. are heated and melted, and the polycarbonate resin is 50% by weight or more. The molten resin material is produced by mixing so as to be. The blending ratio of 50% by weight or more of the polycarbonate resin (pellets) is a ratio to the weight including other resins (pellets) and inert particles charged into the extruder. Further, in the extruder, at least one of the chemical foaming agent and the physical foaming agent is injected into the produced molten resin material, and the molten resin material and the foaming agent are mixed.

Next, the molten resin material mixed with the foaming agent is poured into a die, and the resin foam layer 21 is formed while gradually lowering the temperature by passing the die. The die is open in the direction of extruding the molten resin material. At the same time, bubbles are generated in the molten resin material mixed with the foaming agent due to the pressure drop when passing through the die. As a result, the resin foam layer 21 is foam-molded.

At this time, the fiber reinforced resin layer 22 can be attached to the main surface of the resin foam layer 21. That is, the fiber reinforced resin layer 22 is attached to the main surface of the resin foam layer 21 before being cured by cooling without using an adhesive. As described above, the fiber reinforced resin layer 22 is formed by impregnating the resin with a fiber material woven by plain weave or the like. The method for producing the fiber reinforced resin layer 22 is not particularly limited. In the method of bonding the fiber reinforced resin layer 22 to the main surface of the resin foam layer 21, a solvent capable of dissolving the polycarbonate resin is applied to the surface of either the resin foam layer 21 or the fiber reinforced resin layer 22 or facing each other. An appropriate amount may be applied to both surfaces, and the two may be bonded together and then dried.

Next, the shape of the resin foam layer 21 and the fiber reinforced resin layer 22 is adjusted while being cooled in the cooling tank. In this state, the resin foam layer 21 and the fiber reinforced resin layer 22 are formed in a continuous plate shape. Therefore, these are cut to a predetermined size.

The method for molding the resin foam layer 21 is not limited to the deformed extrusion molding method, and may be another molding method such as injection molding. Further, the method for foam-molding the resin foam layer 21 may be appropriately changed according to the molding method for the resin foam layer 21. Further, in the above-mentioned manufacturing method, the resin foam layer 21 and the fiber reinforced resin layer 22 are cut together, but even if the continuous plate-shaped resin foam layer 21 is cut and then the fiber reinforced resin layer 22 is laminated. good.

Next, a plurality of tread plate members 2 are arranged side by side along the width direction inside the above-mentioned frame 3. In this way, the tread plate 1 can be created.

(Example)
As shown in Table 1 below, the tread members of Examples 1 to 4 and the tread members of Comparative Examples 1 to 4 were prepared, and the breaking load and weight of each tread member were measured.

The tread members of Examples 1 to 4 and the tread members of Comparative Examples 1 to 4 are each formed in a rectangular plate shape in a plan view, and the width, length, and thickness are as shown in Table 1. .. Further, in Table 1, PC means a polycarbonate resin, ABS means an ABS resin, PP means a polypropylene resin, CFRTP means a carbon fiber reinforced resin, and GFRTP means a glass fiber. Indicates reinforced resin. The PC resin ratio indicates the ratio of the polycarbonate resin contained in the resin foam layer.

In this example, the viscosity average molecular weight of the polypropylene resin is 100,000. The viscosity average molecular weight of the polycarbonate resin was adjusted to 25,000 by blending a polycarbonate resin having a viscosity average molecular weight of 10,000 and a polycarbonate resin having a viscosity average molecular weight of 300,000. Further, as CFRTP, a prepreg "TPWF E3163 (manufactured by Teijin Limited)" was used, in which a 200 g / m ² plain weave woven fabric was impregnated with a polycarbonate resin and the content of the woven fabric was 50% by weight. As GFRTP, a 360 g / m ² plain weave woven fabric (glass cloth WE181D100BS6B manufactured by Nitto Boseki Co., Ltd.) impregnated with an epoxy resin and having a woven fabric content of 30% by weight was used. The expanded polypropylene resin is polypropylene Sumitomo Noblen FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.

In Example 4, the alloy of the polycarbonate resin and the ABS resin contained in the resin foam layer is a PC / ABS alloy grade "T2754" manufactured by Teijin Limited. T2754 contains 50 parts of polycarbonate resin, 45 parts of ABS resin, and 5 parts of additives. That is, the resin foam layer of Example 4 contains 50% by weight of the polycarbonate resin.

In Comparative Example 4, the alloy of the polycarbonate resin and the polypropylene resin contained in the resin foam layer was 77 parts of "Panlite L-1250WQ" manufactured by Teijin Co., Ltd. as the polycarbonate resin and "SunAllomer" manufactured by SunAllomer Ltd. as the polypropylene resin. 23 parts of "PL400A", 7 parts of Septon 2104, which is a styrene-ethylene / propylene-styrene block copolymer manufactured by Kuraray Co., Ltd., and 130 parts of Tarku HST 0.8 manufactured by Hayashi Kasei Co., Ltd. as inert particles. ("Panlite", "SunAllomer" and "Septon" are registered trademarks). That is, the resin foam layer of Comparative Example 4 contains about 32.5% by weight of the polycarbonate resin.

Each of the tread plate members of Example 1, Example 3, Example 4, Comparative Example 1, Comparative Example 3, and Comparative Example 4 has a thickness in which fiber-reinforced resin layers are bonded to both sides of the main surface of the resin foam layer. Three tread plate members having a thickness of 5 mm are laminated to form a thickness of 15 mm. The tread member of Example 2 and Comparative Example 2 has a thickness of 5 mm by laminating fiber reinforced resin layers on both sides of the main surface of the resin foam layer.

The fracture load test was carried out by using a full-scale strength tester (AC-2000SIV manufactured by Tokyo Koki Co., Ltd.) and attaching a bending fulcrum manufactured for the tread member to the full-scale strength tester. As the bending fulcrum, a round bar having a diameter of 50 mm was divided in half to form a semi-cylindrical shape, and both ends of the tread member in the length direction were placed on the curved surface side to form a fulcrum. The test was carried out by a three-point load method in which the distance between the fulcrums at both ends of the tread member was 100 cm and the displacement was applied to the center at a crosshead speed of 2 cm / min. The breaking load (N) shown in Table 1 above was obtained from the measured value of the load and the measured value of the displacement amount.

The required proof stress in Table 1 is calculated based on the above (Equation 8). For example, since the tread member of the first embodiment has a length of 1800 mm, the required proof stress 1764 (N) can be calculated by calculating {980 × 1.8 (m)}.

As shown in Table 1, the tread members of Examples 1 to 4 had a fracture load larger than the required proof stress. Therefore, when a worker comes and goes on the upper surface of the tread member of Examples 1 to 4 and is destroyed at the center in the length direction, even one tread member whose length is halved can withstand the load of the worker. Can be done. Even if the tread member is destroyed near the center in the length direction, it is considered that the tread member is not completely damaged and is only destroyed to the extent that a crack in the width direction is formed in the center of the tread member in the length direction.

On the other hand, the tread members of Comparative Examples 1 to 4 had a smaller breaking load than the required proof stress. Therefore, the tread plate members of Comparative Examples 1 to 4 can be destroyed by the traffic of workers. Further, if the tread members of Comparative Examples 1 to 4 are broken near the center in the length direction, the safety of the worker cannot be surely maintained. As described in (Equation 8) above, the required proof stress (980 Lc) varies depending on the length of the tread member. Therefore, in order to improve the breaking load of the tread member, it is necessary to increase the thickness, and the weight increases accordingly. Therefore, the tread plate members of Comparative Examples 1 to 3 increase the cost burden for transportation, installation, removal, and the like.

Comparing the tread member of Example 1 and the tread member of Example 3, the width, length and thickness of each are the same, and the composition of the fiber reinforced resin layer is different. The weight was smaller and the breaking load was larger when the carbon fiber reinforced resin was used than when the glass fiber reinforced resin was used as the fiber reinforced resin layer. Therefore, it was confirmed that by using the carbon fiber reinforced resin, the weight can be further reduced and the strength can be further improved.

Comparing the tread member of Example 1 and the tread member of Comparative Example 3, the width, length and thickness of each are the same, and the resin contained in the resin foam layer is different. The tread member of Example 1 uses a polycarbonate resin for the resin foam layer, so that the breaking load satisfies the required proof stress. On the other hand, the tread member of Comparative Example 3 uses polypropylene resin for the resin foam layer, and the breaking load is significantly less than the required proof stress. As described above, it was found that the strength can be significantly improved by forming the resin foam layer with the polycarbonate resin.

Comparing the tread member of Example 4 and the tread member of Comparative Example 4, the width, length and thickness of each are the same, and the compounding ratio of the polycarbonate resin contained in the resin foam layer is different. The tread member of Example 4 containing 50% by weight of the polycarbonate resin has a breaking load satisfying the required proof stress, similarly to the tread member of Example 1 containing 100% of the polycarbonate resin. Therefore, it is considered that sufficient strength can be obtained by containing 50% by weight or more of the polycarbonate resin in the resin foam layer. On the other hand, although the tread member of Comparative Example 4 contains 32.5% by weight of polycarbonate, the breaking load is significantly lower than the required proof stress. That is, it is considered that the tread member of Comparative Example 4 cannot withstand the load of the worker when the length of the tread member is halved. It is considered that this is because the proportion of the polycarbonate resin contained in the tread member of Comparative Example 4 was less than 50% by weight, so that the strength was significantly reduced. Alternatively, the resin contained in each of the fiber reinforced resin layers (CFRTP) of Example 4 and Comparative Example 4 is a polycarbonate resin. As described above, when the polycarbonate resin contained in the resin foam layer is 50% by weight or more, a sea-island structure containing the polycarbonate resin as a sea component is formed. Therefore, it is considered that in Example 4, the adhesion between the resin foam layer and the fiber reinforced resin layer was improved and the strength was further improved, while in Comparative Example 4, the strength was significantly reduced.

Comparing the tread member of Example 1 and the tread member of Example 3 from the viewpoint of the adhesion between the resin foam layer and the fiber reinforced resin layer, the tread member of Example 1 has slightly stronger strength. It is considered that this is because the adhesiveness between the resin foam layer and the fiber reinforced resin layer was improved by using the same polycarbonate resin for the resin foam layer and the fiber reinforced resin layer in Example 1. In this way, it was confirmed that the strength can be further improved by allowing the same polycarbonate resin to appear on the surfaces of the resin foam layer and the fiber reinforced resin layer. It is presumed that the same can be said for the tread member of Comparative Example 3 in which the strength is significantly reduced due to the deterioration of the adhesiveness.

Further, the tread members of Examples 1 to 4 were lighter than the tread members of Comparative Examples 1 to 2 and 4. The tread member of Comparative Example 3 is relatively light in weight, but its strength is significantly lower than that of the tread members of Examples 1 to 4. As described above, the tread members of Comparative Examples 1 to 4 need to be increased in thickness in order to improve the breaking load. Therefore, it is considered that the weight of the tread members of Comparative Examples 1 to 4 becomes even heavier when they are actually used as scaffolding.

As described above, the tread members of Examples 1 to 4 can withstand the load of the worker even if the length of the tread members is halved due to the relatively high breaking load of Wcb> 980 Lc (N). I was able to obtain the strength that I could. Further, it was confirmed that by setting the content of the polycarbonate resin in the resin foam layer to 50% by weight or more, a high breaking load of Wcb> 980 Lc (N) can be appropriately obtained. Further, the weight of the tread plate member is 1 to 10 kg / m ^2, and the weight can be reduced as compared with Comparative Examples 1, 2 and 4.

The tread plate 1 is arranged by arranging a plurality of tread plate members configured in this way in the width direction. Therefore, since each tread member has the above-mentioned strength and a plurality of tread members are arranged side by side, even if one tread member is destroyed and falls, it is adjacent to each other. Tread plate members support workers. In this way, not only the strength of the tread plate members, but also by arranging a plurality of tread plate members, it is possible to take double safety measures, and it is possible to more reliably ensure the safety of workers.

1 tread plate, 2 tread plate member, 21 resin foam layer, 22 fiber reinforced resin layer, 3 frame, 31 frame material, 31a flange part, 31b wall part, 32 frame material, 33 partition plate, 4 hook

Claims

Equipped with multiple tread members arranged side by side in the width direction,
Each of the tread plate members includes a resin foam layer and a fiber reinforced resin layer laminated on the main surface of the resin foam layer.
The breaking load (Wcb) of each of the tread members is Wcc> 980 Lc (N), where Lc is the distance between the fulcrums in the length direction of the tread members.
The tread plate according to claim 1.
The resin foam layer is a tread plate containing 50% by weight or more of a polycarbonate resin with respect to the resin foam layer.
The tread plate according to claim 2.
The fiber-reinforced resin layer contains 50% by weight or more of a polycarbonate resin with respect to the resin contained in the fiber-reinforced resin layer.
A tread plate having a sea-island structure in which the resin foam layer and the resin contained in the fiber reinforced resin layer each contain a polycarbonate resin as a sea component.
The tread plate according to any one of claims 1 to 3.
The fiber-reinforced resin layer is a tread plate laminated on both main surfaces of the resin foam layer.
The tread plate according to any one of claims 1 to 4, and further
The tread has a frame and
The frame comprises one selected from the group consisting of metals, carbon fibers, inert particles and fiber reinforced plastics.
The plurality of tread plate members are arranged inside the frame so that both ends in a length direction orthogonal to the width direction are supported by the frame.