[0001] This invention relates to a toe-cap or boxtoe for use in safety foot wear such as
shoes and boots (hereinafter referred to collectively as "shoe") to reinforce structurally
the toe of a shoe and enhance the safety of the shoe.
[0002] Heretofore, the toe-caps of safety shoes made of steel have been exclusively accepted
for actual use because of appreciation of the extreme importance of the strength of
the uppers of safety shoes for protection of the wearer's toes against accidental
heavy impact.
[0003] The safety shoes which use toe-caps made of steel, however, entail the problem of
handicapping the wearer's mobility by an inevitable increase of weight of the safety
shoes owing to the use of steel as the material for the toe-caps. Recently, for the
sake of decreasing the weights of safety shoes, toe-caps having plastic layers superposed
one each on both sides of a steel core member thereof have been proposed in published
Japanese Utility Model Application, KOKAI (Early Publication) No. SHO 64-32609, for
example.
[0004] The toe-caps having plastic layers superposed on a steel core member thereof, however,
possibly fail to accomplish their object as a manufactured article because they are
liable to entail interfacial separation between the steel core member and the plastic
layers. Further, since these toe-caps are made of steel, their manufacture turns out
to be a troublesome work. Moreover, the toe-caps have a large weight because their
core members are made of steel.
[0005] In view of the problem encountered by the prior art as described above, the present
invention aims to provide a toe-cap for a safety shoe which is light and so strong
as to resist compression. More specifically, the present invention aims to provide
a novel light toe-cap for a safety shoe which passes the standard for toe-caps for
safety shoes [Japanese Industrial Standard (JIS) T 8101 "Safety Leather Shoes, Type
S"].
[0006] These objects are attained by the toe-cap or boxtoe according to the present invention.
According to the present invention, it is suggested that in a toe-cap for a safety
foot wear having a domed shape adapted to lie over the toes of the wearer and an open
end to receive the toes, the toe-cap is formed of a composite material comprising
a fiber-reinforced thermoplastic resin and at least one wire mesh or woven metallic
wire having a size of 7 to 200 meshes and embedded in the fiber-reinforced thermoplastic
resin.
[0007] In carrying out the present invention in one preferred embodiment, the wire mesh
is embedded in the central part of the fiber-reinforced thermoplastic resin in substantially
parallel with the surfaces thereof. In another preferred embodiment, the wire meshes
are embedded one each in opposite surface layers of the fiber-reinforced thermoplastic
resin in substantially parallel with the surfaces thereof. Preferably the fiber-reinforced
thermoplastic resin comprises a long-fiber reinforced thermoplastic layer having reinforcing
long fibers incorporated therein and a short-fiber reinforced thermoplastic layer
having reinforcing short fibers incorporated therein, and the wire mesh is embedded
in the short-fiber reinforced thermoplastic layer.
[0008] In a preferred mode of the toe-cap according to the present invention, the toe-cap
is formed of a composite material comprising (A) a short-fiber reinforced thermoplastic
layer having reinforcing short fibers incorporated therein, (B) long-fiber reinforced
thermoplastic layers lying one each in the opposite surface parts of the short-fiber
reinforced thermoplastic layer and having reinforcing long fibers incorporated therein,
and (C) a wire mesh having a size of 7 to 200 meshes and embedded in the aforementioned
short-fiber reinforced thermoplastic layer.
[0009] In another preferred mode of the toe-cap according to the present invention, the
toe-cap is formed of a composite material comprising (A) a long-fiber reinforced thermoplastic
layer having reinforcing long fibers incorporated therein, (B) short-fiber reinforced
thermoplastic layers lying one each in the opposite surface parts of the long-fiber
reinforced thermoplastic layer and having reinforcing short fibers incorporated therein,
and (C) wire meshes having a size of 7 to 200 meshes and embedded one each in the
aforementioned short-fiber reinforced thermoplastic layers. Preferably the composite
material further comprises skin layers made of a thermoplastic resin and lying one
each in the outside surface parts of the aforementioned short-fiber reinforced thermoplastic
layers.
[0010] Since the toe-cap according to the present invention is formed of a composite material
comprising a fiber-reinforced thermoplastic resin and at least one wire mesh having
a size of 7 to 200 meshes and embedded in the fiber-reinforced thermoplastic resin,
it is light and so strong as to resist such high compression as more than 1,100 kg.
Use of this toe-cap allows production of a safety shoe which gives the wearer comfortable
mobility and highly reliable safe use.
[0011] Examples of the thermoplastic resin which is advantageously used as a matrix resin
include, but are not limited to: nylon 6, polycarbonate (PC), polyethylene terephthalate
(PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and PBT/PC alloy.
[0012] The reinforcing fibers are glass fibers. The glass fibers fall under two types, short
fibers and long fibers. The long fibers include random mat type fibers, woven fabric
type fibers, and unidirectional mat type fibers. The short fibers have weak strength.
While the long fibers generally have sufficient strength, those of the woven fabric
type and the unidirectional mat type have poor flowability and entail a problem of
moldability and are at a disadvantage in necessitating a fabrication to be completed
as a manufactured article aimed at. The present invention contemplates constituting
a composite material comprising a glass-fiber reinforced thermoplastic resin and a
wire mesh embedded therein in such a manner that short glass fibers are arranged near
the wire mesh and long glass fibers are arranged in the other parts of the composite
material. Owing to this arrangement, the glass fibers are allowed infallibly to enter
the meshes of the wire mesh and consequently exalt the interlaminar strength.
[0013] The content of the glass fibers in the fiber-reinforced thermoplastic resin is desired
to be in the range of 30 to 65% and the diameter of the individual glass fibers in
the range of 9 to 13 µm. If the content of the glass fibers falls short of 30%, the
insufficient supply of glass fibers will naturally prevent the fiber-reinforced thermoplastic
resin and the toe-cap made predominantly thereof from acquiring sufficient strength.
If the content of glass fibers exceeds 65%, the fiber-reinforced thermoplastic resin
will be brittle. The excess supply of glass fibers, therefore, will put the composite
material at a disadvantage in entailing degradation of elasticity and restoring force
in spite of an increase in hardness and tending to break owing to concentration of
compressive force.
[0014] The fiber-reinforced thermoplastic resin manifests the strength thereof more conspicuously
when the diameter of the individual glass fibers is in the range of 9 to 13 µm. If
the diameter of the individual glass fibers is smaller than 9 µm, since the glass
fibers have a larger surface area for a fixed amount of glass fibers, the glass fibers
will not be sufficiently wetted with the thermoplastic resin and the fiber-reinforced
thermoplastic resin will fail to acquire high strength. Conversely, if the diameter
of the individual glass fibers exceeds 13 µm, the fiber-reinforced thermoplastic resin
will suffer from insufficient strength and brittleness.
[0015] The metallic materials which are effectively usable for the wire mesh include steel,
stainless steel, and nickel, for example. For the sake of enhancing the tight adhesiveness
of the fiber-reinforced thermoplastic resin with the wire mesh, it is recommendable
to give the wire mesh a physical or chemical surface treatment. Concrete examples
of the physical treatment include shot blasting and liquid honing which are intended
to coarsen a given surface. Concrete examples of the chemical treatment include bonderizing
treatment, chromic acid treatment, silane treatment, and zinc plating which are effective
for a wire mesh made of steel. The chromic acid treatment, oxide film-forming treatment,
etc. are available for a wire mesh made of stainless steel.
[0016] Now, the present invention will be described specifically below with reference to
the accompanying drawings, wherein:
Fig. 1 is a model diagram of the cross section of one example of the composite material
to be used for the manufacture of a toe-cap according to the present invention;
Fig. 2 is a model diagram of the cross section of another example of the composite
material to be used for the manufacture of the toe-cap;
Fig. 3 is an explanatory diagram of one example of a process of manufacture of the
composite material shown in Fig. 1;
Fig. 4 is an explanatory diagram of a process of manufacture of the toe-cap for a
safety shoe by the use of the composite material according to the present invention;
Fig. 5 is a perspective view of one example of the toe-cap according to the present
invention for use in a safety shoe;
Fig. 6 is a graph showing the relation between the mesh size of a wire mesh and the
diameter of individual metallic wires forming the wire mesh required for obtaining
prescribed strength; and
Fig. 7 is a graph showing the relation between the mesh size of a wire mesh used in
a toe-cap and the compressive strength exerted on the toe-cap for a safety shoe.
[0017] Referring to the drawings, Fig. 1 illustrates one example of the composite material
to be used for the toe-cap of the present invention. This composite material comprises
a short-fiber reinforced thermoplastic layer 2 having reinforcing short fibers 6 incorporated
in a thermoplastic resin 7, long-fiber reinforced thermoplastic layers 1 lying one
each in the opposite surface parts of the short-fiber reinforced thermoplastic layer
2 and having reinforcing long fibers 5 incorporated in the thermoplastic resin 7,
and a wire mesh 4 embedded in the short-fiber reinforced thermoplastic layer 2 disposed
in the central part of the composite material.
[0018] Fig. 2 illustrates another example of the composite material. The composite material
shown in Fig. 2 comprises a long-fiber reinforced thermoplastic layer 1 disposed in
the central part thereof, short-fiber reinforced thermoplastic layers 2 lying one
each in the opposite surface parts of the long-fiber reinforced thermoplastic layer
1, skin layers 3 made of the thermoplastic resin 7 and lying one each in the outside
surface parts of the short-fiber reinforced thermoplastic layers 2, and wire meshes
4 embedded one each in the short-fiber reinforced thermoplastic layers 2.
[0019] In the composite material illustrated in Fig. 1 and in the composite material illustrated
in Fig. 2 as well, short-fiber reinforced thermoplastic layers 2 are formed around
each wire mesh.
[0020] Fig. 3 illustrates a process for manufacture of the composite material shown in Fig.
1. Platelike fiber-reinforced thermoplastic materials 8 each having a short-fiber
reinforced thermoplastic layer 2 formed on the side confronting the wire mesh 4 and
a long-fiber reinforced thermoplastic layer 1 formed on the other side thereof are
opposed to each other across the wire mesh 4. When heat and pressure are simultaneously
applied to the outer surfaces of the opposed fiber-reinforced thermoplastic materials
8 with the wire mesh 4 interposed therebetween, the short-fiber reinforced thermoplastic
layers 2 are wrapped around the wires of the wire mesh 4 to give rise to a composite
material having the wire mesh 4 embedded in the short-fiber reinforced thermoplastic
layers 2 as illustrated in Fig. 1.
[0021] Production of a toe-cap for a safety shoe with the platelike composite material 9
is accomplished by cutting the platelike composite material 9 in the shape of a toe-cap
for a safety shoe, setting the toe-cap workpiece in place in a female mould 10, lowering
a male mould 11 to depress the workpiece against the female mould 10, and applying
heat and pressure to the workpiece interposed therebetween, as illustrated in Fig.
4. Consequently, the toe-cap 20 for a safety shoe illustrated in Fig. 5 is obtained.
[0022] The toe-cap 20 has a domed shape conforming to the toe part of a safety shoe or boot
so that, in use, it will cover the toes. The lower edge of the domed part 20a of the
toe-cap 20 is provided with an inwardly directed integrally moulded skirt part 20b.
[0023] The strength of the toe-cap for a safety shoe is affected to a great extent by the
properties of the wire mesh. If the wire mesh has a size of less than 7 meshes, for
example, the total surface area of the wire mesh is unduly small without reference
to the diameter of the individual wires of the wire mesh and the produced toe-cap
fails to acquire prescribed strength. If the diameter of the wires of the wire mesh
exceeds 620 µm, the adhesiveness of the wire mesh to the thermoplastic resin is insufficient
and the produced toe-cap tends to sustain cohesive failure even when the wire mesh
has a size of not less than 7 meshes. Conversely, if the wire mesh has a size of 200
meshes, the produced toe-cap fails to acquire the strength aimed at when the diameter
of wires of the wire mesh is less than 40 µm.
[0024] Fig. 6 graphically illustrates a hatched area representing the relation between the
mesh size of a wire mesh and the diameter of the individual wires of the wire mesh
which was found to pass the standard strength 1,100 kg of compressive resistance (JIS
T 8101, "Leather Safety Shoe, Type S") in an experiment performed on products using
wire meshes of varying mesh sizes and varying wire diameters. In these products, the
fiber-reinforced thermoplastic resin was nylon 6 resin containing 45% of glass fibers.
For the wire mesh in these products, steel wires which had undergone a liquid honing
treatment and then a chromic acid treatment were used.
[0025] Fig. 7 is a graph showing the relation between the compressive strength and the mesh
size of the wire mesh actually observed in products using wire mesh whose relevant
data fall within the hatched area of Fig. 6.
[0026] It is noted from the data of Fig. 7 that when the size of a wire mesh is less than
7 meshes, the total surface area of the wire mesh is unduly small and the strength
of the produced toe-cap tends to betray fluctuation. If the diameter of the wires
of the wire mesh exceeds 620 µm, the adhesiveness of the wire mesh to the resin is
unduly low and the produced toe-cap tends to sustain cohesive failure even when the
size of the wire mesh is not less than 7 meshes. Conversely, if the size of the wire
mesh exceeds 200 meshes, the reinforcing fibers are no longer wrapped around the wire
mesh and the produced toe-cap tends to induce ply separation. If the diameter of the
wires of the wire mesh is less than 40 µm, the produced toe-cap fails to acquire sufficient
strength even when the size of the wire mesh is 200 meshes.
[0027] From the foregoing detailed description, it will be evident that there are a number
of changes, adaptations, and modifications of the present invention which come within
the province of those skilled in the art. However, it is intended that all such variations
not departing from the spirit of the invention be considered as within the scope thereof
as limited solely by the claims appended hereto.
1. A toe-cap for a safety foot wear having a domed shape adapted to lie over the toes
of the wearer and an open end to receive the toes, characterized in that the toe-cap
(20) is formed of a composite material comprising a fiber-reinforced thermoplastic
resin (7) and at least one wire mesh (4) having a size of 7 to 200 meshes and embedded
in said fiber-reinforced thermoplastic resin.
2. A toe-cap according to claim 1, wherein said wire mesh (4) is embedded in the central
part of said fiber-reinforced thermoplastic resin (7) in substantially parallel with
the surfaces thereof.
3. A toe-cap according to claim 1 or 2, wherein wire meshes (4) are embedded one each
in opposite surface layers of said fiber-reinforced thermoplastic resin (7) in substantially
parallel with the surfaces thereof.
4. A toe-cap according to claim 1, wherein said fiber-reinforced thermoplastic resin
(7) comprises a long-fiber reinforced thermoplastic layer (1) having reinforcing long
fibers (5) incorporated therein and a short-fiber reinforced thermoplastic layer (2)
having reinforcing short fibers (6) incorporated therein, and said wire mesh (4) is
embedded in said short-fiber reinforced thermoplastic layer (2).
5. A toe-cap for a safety foot wear having a domed shape adapted to lie over the toes
of the wearer and an open end to receive the toes, characterized in that the toe-cap
(20) is formed of a composite material comprising (A) a short-fiber reinforced thermoplastic
layer (2) having reinforcing short fibers (6) incorporated therein, (B) long-fiber
reinforced thermoplastic layers (1) lying one each in the opposite surface parts of
said short-fiber reinforced thermoplastic layer (2) and having reinforcing long fibers
(5) incorporated therein, and (C) a wire mesh (4) having a size of 7 to 200 meshes
and embedded in said short-fiber reinforced thermoplastic layer (2).
6. A toe-cap for a safety foot wear having a domed shape adapted to lie over the toes
of the wearer and an open end to receive the toes, characterized in that the toe-cap
(20) is formed of a composite material comprising (A) a long-fiber reinforced thermoplastic
layer (1) having reinforcing long fibers (5) incorporated therein, (B) short-fiber
reinforced thermoplastic layers (2) lying one each in the opposite surface parts of
said long-fiber reinforced thermoplastic layer (1) and having reinforcing short fibers
(6) incorporated therein, and (C) wire meshes (4) having a size of 7 to 200 meshes
and embedded one each in said short-fiber reinforced thermoplastic layers (2).
7. A toe-cap according to claim 6, wherein said composite material further comprises
skin layers (3) made of a thermoplastic resin (7) and lying one each in the outside
surface parts of said short-fiber reinforced thermoplastic layers (2).
8. A toe-cap according to any one of the preceding claims, wherein the diameter of wires
of said wire mesh (4) is in the range of 40 to 620 µm.
9. A toe-cap according to any one of the preceding claims, wherein the content of said
reinforcing fibers (5, 6) in the fiber-reinforced thermoplastic resin (7) is in the
range of 30 to 65% and the diameter of said fibers is in the range of 9 to 13 µm.
10. A toe-cap according to any one of the preceding claims, wherein said reinforcing fiber
(5, 6) is a glass fiber and said wire mesh (4) is a woven metallic wire which has
undergone a surface treatment selected from the group consisting of shot blasting,
liquid honing, bonderizing treatment, chromic acid treatment, silane treatment, zinc
plating, and oxide film-forming treatment.