Note: Descriptions are shown in the official language in which they were submitted.
WO 95/06502 2 1,69 t 5 ~i PCT/AU94/00512
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SNOW SHOE
This invention relates to snow shoes.
The present invention provides a snow shoe device which increases the user's
footprint area, allowing increased support and aids in traction whilst
traversing upon soft
surfaces such as snow. 10
Many present devices are rather complex and relatively heavy assemblies
requiring
moving parts to function. These moving parts tend to wear and foul with ice
build-up.
Their weight makes them cumbersome. The older traditional tennis racket style
snow
shoes tend to fail after prolonged use on abrasive surfaces or particles such
as ice and
grit, which wear the cords that comprise the base. The size of these older
type snow
shoes tend to make them awkward to use. Also, known shoes are normally
relatively
long and rigid making them difficult to use on steep slopes.
According to the present invention there is provided a snow shoe comprising:
a platform; and
binding means for binding the heel and toe of a user's shoe or boot to the
platform
characterised in that the platform is substantially imperforate and that at
least peripheral
zones of the platform can be resiliently flexed.
The problems described above are substantially overcome by the present
invention.
The platform can be constructed of a wear-resistant and semi-flexible plastic
able to
tolerate sub-zero temperatures. The heel and toe of a sole of the user's
footwear is
bound by the binding means so that it is unable to separate away from or move
laterally
or longitudinally on the platforn.n whilst secured.
Preferably, the platform is able to flex along with the sole of the user's
shoe or
boot but preferably is least flexible across the ball of the foot area of the
platform.
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Preferably further, the platform is fastened to a person's footwear by
adjustable
and releasable straps, and adjustable locating blocks, without any part of the
fasteners
being included on the person's footwear.
Traction can be enhanced by indentations and/or cleats on the base of the
platform.
Preferably further, the front and rear of the platform are curved upwards and
can
flex to aid the user in motion.
In one form of the invention, the upward curved front of the platform enables
clearance with the surface of the snow during the motion of the user's step.
The curve
is directly at the front of the toe area of the platform. The platform then
flattens out to
a plane as it approaches the front edge of the platform. The curved upward
front of the
platform is flexible to enable a person's toe area on the platform to remain
on or about
the surface of the snow, when a downward force is acting on the toe area, and
the heel
is raised sufficiently so that the flat portion of the base on the curved
upward front of the
platform is on the surface of the snow. If the heel continues to be raised,
the front of the
platform is able to flex to enable the toe area to remain on or about the
surface of the
snow.
To assist in traction, the surface of the base of the platform may include
machined
or moulded shallow indentations across its entirety, except under and adjacent
to cleats
and at the perimeter of the base. The shallow indentations grip by allowing
snow to
intrude into and fill them, with a force exerted downward and perpendicular to
the
platform onto the top of the indentation.
The snow captured inside the indentation is then put into shear with the snow
directly under it, if any force sideways is applied by the side of the
indentation to the
captured snow. The indentations are shallow so as not to retain the snow when
the
platform is lifted off the surface of the snow. To increase traction on firmer
snow
surfaces a load-carrying platform may flex to approach the irregular shape of
the surface
WO 95/06502 216Q1~~ 5 PCT/AU94/00512
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it is upon. This inereases the surface area and amount of indentations on the
platform's
base which are in contact with and traction to the surface of the snow. On
softer snow
surfaces the platform is rigid enough to support the load of a person that the
platform was
intended for. The surface of the underside of the platform fittings has no
indentations
in regions where cleats are to be mounted. This enables better fixing and
tends to reduce
ice build-up adjacent to the cleats. The surface area of the periphery of the
base of the
platform has no indentations so as not to weaken it.
Preferably, the shallow indentations are circular grooves sunk into the base
of the
platfonm. The grooves are symmetrical to allow the platform to have traction
in any
direction along the surface of the snow. To aid in the flex of the platform,
the
indentations can be deeper across the ball of the foot area on the base of the
platform.
Preferably, metal cleats are fastened to the base of the platform at the toe
and heel
of the foot areas to increase traction and to protect the platform on harder
surfaces.
Altennatively, integrally moulded cleats may be provided. The locations of the
toe and
heel cleats on the lower surface of the platform, along with the footwear
locating blocks
on the upper surface of the platform, are adjustable for both the width of the
toe and
length of the footwear. Each of the toe cleats is screwed or bolted at both
ends through
the platform to a toe block. The cleat at the ball of the foot is secured by
rivets or
screws to a fixed position on the platform. The heel cleat is screwed or
bolted through
the platform to the heel block. The cleats may be fabricated from stainless
steel, sheet
aluminium or made from heat treated cast aluminium or other durable material.
Alternatively the cleats can be integrally moulded with the platform.
On the upper surface of the platform a moulded toe block is fastened on either
side of the toe of the footwear and is set at an angle to allow the toe of the
footwear to
move forward and be jammed between the blocks, preventing further forward or
sideways
movement of the toe of the footwear. The toe block is secured at both ends.
Straps are
secured between the platform and toe blocks. The straps are coupled to
fastening devices
for binding the platform to the shoes or boots of the user. The fastening
device may
comprise a buckle and/or velcro patches fixed to the straps.
WO 95/06502
PCT/AU94/00512
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The toe straps, when passed over the toe of the footwear, and are tensioned,
prevent the toe of the footwear from lifting off the platform and out of the
toe blocks.
To prevent the toe straps from sliding forward off the front of the footwear,
the location
of the toe blocks on the platform can be adjusted by appropriate selection of
mounting
holes through the platform.
To prevent the footwear from moving backwards out of the toe blocks, a moulded
plastic heel block is secured to the platform centrally behind and against the
heel of the
footwear. The heel block also has protrusions forward and to both sides of the
heel of
the footwear which stops sideways movement of the heel of the footwear. The
location
of the heel block on the platform is adjustable by a set of holes located
longitudinally
along the heel area of the platform so as to fit different length footwear. A
strap with
a tensioning device or velcro stitched to it is secured to the heel block by
passing through
a slot therein. When the strap is secured forward over the top of the foot and
tensioned,
it prevents the heel of the footwear from lifting off the platform and out of
the heel
block.
The toe and heel blocks could be integrally moulded with the platform.
The platform may be made larger or smaller depending on the weight, size and
footwear size of the user. The platform may be produced in a larger size for
softer snow
conditions. Preferably, the platform is not so wide as to unduly interfere
with the user's
normal stance or stride. There may be left and right foot platforms or they
may be the
same for both feet. To aid the user in descending a slope, the outside edge of
the rear
of the platform extends further back than the inside edge enabling a sharper
point on the
perimeter to be more easily dug into the snow. The inside edge of the front of
the
platfonn extends further forward than the outside edge. Similar to the big toe
of that
foot, this aids in the stability of the platform. Preferably, the perimeter of
the platform
is curved so as not to be easily snagged on obstacles.
The invention will now be further described with reference to the accompanying
drawings, in which:
,~ ~~~
WO 95/06502 2 55 PCT/AU94/00512
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Figure 1 is a schematic side view of a snow shoe device according to the
invention;
Figure 2 is a schematic view of the lower surface of the snow shoe;
Figure 3 is a perspective view of the upper surface of a snow shoe;
Figure 4 is a schematic view of the snow shoe device being flexed in
operation;
Figure 5 is a cross-sectional view along the line 5-5;
Figure 6 is a cross-sectional view along the line 6-6;
Figure 7 is across-sectional view along the line 7-7;
Figure 8 is a schematic view of the lower surface of the platform- showing the
preferred slope of indentations;
Figure 9 is a diagram showing one of the indentations in more detail;
Figure 10 is a cross-section along the line 10-10; and
Figure 11 is a schematic view of a shock absorbing element mounted in the heel
strap.
Refendng to Figure 1 shows a schematic side view of a snow shoe device 1
according to the invention. The drawing shows the snow shoe device for a
wearer's left
foot. The devices of the invention would normally be made in pairs of which
the right
hand shoe device (not shown) would comprise the mirror image of the device
shown in
the drawings.
The device 1 of the invention comprises a generally planar platform 6 which is
preferably moulded from plastics material so as to have a degree of
flexibility as will be
described hereinafter. The platform could be made by fabrication of sheet
material and/or
by pressing. -
The device includes a heel block 34 and a pair of toe blocks 41 and 42. The
device also includes a front strap 39 and rear strap 37. The straps 39 and 37
are
preferably formed from webbing. The rear strap may include a hollow
compressible body
35 (Figure 11) stitched between layers of the webbing to function as a shock
absorbing
element. As best seen in Figure 4, the shoe or boot 50 of the wearer is
supported on the
platform 6 with the heel of the shoe or boot 50 snugly engaged with the heel
block 34.
WO 95/06502 PCT/AU94/00512
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The rear strap 37 passes over the shoe or boot 50 (near or above the arch) so
as to
securely hold the heel of the boot or shoe on the platform 6. The toe of the
shoe or boot
50 is supported between the toe blocks 41 and 42 and the front strap 39 passes
over the
toe of the shoe or boot 50 and again securely holds the shoe or boot 50 in
engagement
with the upper surface of the platform 6. It is important to note that the
straps 37 and
39 and toe and heel blocks operate to hold the shoe or boot 50 in contact with
the
platform 6 at all times when the shoe is being used. This contrasts with known
forms
of snow shoes where there is usually considerable movement of the heel
relative to the
upper surface. In known arrangements this can facilitate use of the shoes but
it does have
the disadvantage that snow or ice tends to build up beneath the heel and
hamper their
operation.
As best seen in Figures 2 and 8, the underside surface 11 of the device is
preferably provided with indentations or projections 14 for increasing grip of
the
underside surface with the snow. The device also includes cleats which improve
the grip
of the device on snow or ice. It is preferred that the cleats are made of
durable material
such as metal and in particular pressed stainless steel so that they are
resistant to
abrasion. The location and number of cleats can be varied but the preferred
arrangement
is shown in Figure 2. In this drawing there is a heel cleat 17, ball cleats 18
(which are
integrally moulded with the platform 6) and a pair of toe cleats 21 and 22.
Figures 8 to 10 show the preferred shape and orientation of indentations in
the
underside surface of the platform. Figure 9 is a plan view of one of the
indentations.
It comprises a circular recess 100 with an oval island 102 the top surface of
which is at
the same level as the underside surface 11, as shown in Figure 10. For clarity
of
illustration, the major axes of the islands 102 are shown as straight lines in
Figure 8. The
preferred orientation of the islands 102 is shown schematically in this
drawing. It will
be seen that in a peripheral zone 104 the orientations of the major axes of
the islands 102
are generally parallel to the adjacent part of the rim 56, a broken line 106
generally
deliminating the inner periphery of the zone 104. Within the line 106, the
major axes of
the islands 102 are transverse to the longitudinal direction of the shoe, as
seen in Figure
8. It has been found that this orientation optimises the performance of the
shoes from
WO 95/06502 21U 9155 PCT/AU94/00512
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the point of view of minimising slipping. It is further preferred that the
diameter of the
recess 100 is in the range 15 to 25mm and preferably 19mm. It is further
preferred that
the depth of the recess 100 is in the range from 1 to 1.5mm and preferably
1.2mm. It
is further preferred that the sidewalls of the recess 100 and the island 102
taper inwardly
at an angle of say 3 and merge into the base of the island 102 at a radius of
about
0.5mm.
It is further preferred that the heel cleat 17 and toe cleats 21 and 22 arc
respectively located beneath the heel block 34 and toe blocks 41 and 42. In
this way the
mounting screws 51 can be used to interconnect the blocks and cleats. In the
illustrated
arrangement the platform 6 includes a number of forward screw holes 19 and
rearward
holes 33 through which the screws pass. A range of hole locations may be
provided so
as to permit adjustment of the location of the blocks and cleats according to
the size of
the shoe or boot 50 of the wearer. The screw holes for the screws 51 can be
made
elongate to provide further adjustment of the positions of the toe and heel
blocks on the
platform.
The heel and toe blocks are chosen so that when the shoes are used there is
little
or no movement applied to the foot of the user. Accordingly it is preferred
that the
centroid of the projected area of the foot of the user is aligned with the
centroid of the
area of the platform 11.
As best seen in Figure 6, the ends of the front strap 39 can be clamped
between
the platform 6 and the toe blocks 41 and 42. On the other hand the heel block
34 may
be provided with slots 5 (see Figure 1) through which the rear strap 37
passes.
The structure of the platform 6 is important to the performance of the snow
shoes
of the invention. The platform 6 is designed so that it has a degree of
flexibility which
enables it to flex with the normal flexure of the shoe or boot 50 of the user,
as illustrated
diagrammatically in Figure 4. It is also preferred that there be a greater
degree of
flexibility in the regions from the shoe or boot 50 towards the periphery of
the platform.
The platform is preferably provided with a peripheral rim or bead 56 which
provides
WO 95/06502 PCT/AU94/00512
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strength at the periphery and therefore resists excessive flexure or breakages
at the
periphery.
The platform is preferably moulded from plastics material such as
polyurethane.
However, other semi-flexible plastics materials may also be used such as
polyvinyl
chloride, polypropylene, polyethylene, nylon, ABS, polycarbonate, polyesters,
copolymers
and other engineering thermoplastics. It is preferred that the thickness of
the platform
at a central portion 58 has a thickness in the range from 5mm to 8mm and
preferably
7mm. The central portion 58 generally corresponds to the area which will be
contacted
by the shoe or boot 50 of the wearer. The platform then tapers somewhat
towards the
periphery and then thickens out to form the rim 56, as best seen in Figures 5,
6 and 7.
It is preferred that the minimum thickness of the platform is in the range
1.5mm to 4mm
and preferably 2mm. The thickness of the bead or rim 56 is preferably the same
as the
thickness of the central portion 58.
The platform 6 is also moulded so as to have an upwardly curved forward
portion
60 and an upwardly curved rear portion 62. These upwardly turned portions help
to
prevent the edges of the snow shoe being caught in the snow or on
obstructions. The
curved portions also assist to some extent in flexure of the end portions
about transverse
axes. This flexure makes the devices easier to use, particularly on steep
terrain, as seen
in Figure 4.
It is also prefeired that the platform 6 has a concave portion 70 (as seen in
side
view in Figure 1). This gives rigidity in the longitudinal direction. The
platform 6 may
be slightly concave across a central transverse cross-section but this is not
shown in
Figure 6.
It is further prefezted that the platform has concave profiles in the forward
and
rear portions 60 and 62 of the platform but these concave profiles are in
planes transverse
to the concave portion 70. This makes the front and rear portions more
resistant to
flexure about longitudinal axes because the concavity imparts a degree of
stiffness to the
end portions.
I I
CA 02169155 2004-11-16
WO 95/00502 PCT/AU94/00512
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It is further preferred that the upper surface of the platform 6 be smooth and
imperforate (except for the small screw holes 19 and 33) so that snow and ice
can fall
from the top surface without accumulating thereon.
It is preferred that the overall length of the platform 6 of an adult size
shoe is in the
range from 450mm to 600mm and preferably 490mm. It is further preferred that
the
width of the platform 6 is in the range 200mm to 400mm and preferably 260mm
near the toe region. It is further preferred that the heel region be narrower
by about
30% than the toe region and that the preferred width near the heel block 34 is
180mm. It is further preferred that there be more overhang at the toe of the
platform
than at the heel. The toe overhang is the distance between the centres of the
toe
blocks 41 and 42 and the front edge of the platform, the rear overhang is the
distance
between the centre of the heel block 34 and the rear edge of the platform. The
toe
overhang is in the range from 15% to 25% of the overall length and preferably
20%.
It is preferred that the heel overhang be about 50% of the toe overhang.
It is also desirable that the shoes of the invention be relatively light so
that they are
relatively easy to use and not tiring for the wearer. Prototypes have been
made and
tested and the weights were in the range 500-2000gm per pair.
The hardness of the platform is in the range from 50 to 90 shore D and
preferably 55
to 70 at about 18 C. The hardness will increase with decreasing temperature
and
thus the degree of flexibility will decrease with temperarture. Where the
platform is
to be produced by injection moulding it may comprise a RE-FLEXTM thermoplastic
polyurethane supplied by Townsend Chemicals Pty. Ltd., Victoria, Australia
such as
grades 223, 157 and 262 which have shore hardnesses of 95A, 65D and 75D
respectively, and tensile strengths at break of 366, 438 and 447kg/cm2
respectively.
A prototype has been tested for flexibility and the results are as follows.
The
underside surface 11 of the platform was supported near the toe and heel ends
and
a weight was applied at a point generally corresponding to the point where the
user's
weight would be concentrated at the ball of the foot, that is to say the
weight was
applied
WO 95/06502 1 PCT/AU94/00512
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at a point approximately 64mm from a line joining the toe blocks 41 and 42.
With a
weight of 13.5kg the downward deflection was approximately 80mm at -15 C and
150mm at +13 C.
A further prototype having a length of about 480mm and maximum width of
255mm was subjected to bending tests and the following results were obtained:
(i) at 5 C a vertical load of 4kg was required to produce a lateral deflection
of 100mm (measured at a point about 270mm from the heel end of the
platform);
(ii) at -20 C a vertical load of 8kg was required to produce the same
deflection as in (i).
Many modifications will be apparent to those skilled in the art without
departing
from the spirit and scope of the invention.
