Note: Descriptions are shown in the official language in which they were submitted.
CA 02535426 2006-01-09
Description
BACKGROUND OF THE INVENTION
Shoes for everyday wear provide poor traction on slippery surfaces, such as
ice and packed snow. Special
shoes for outdoor use (e.g., winter boots, hiking footwear) provide better
traction on packed snow but are
almost as useless on slippery ice, especially during the season when the
outdoor temperature is changing
around the freezing point, and during periods of freezing rain. When the
ground is covered with a glaze of
ice, it becomes a challenge to pursue routine outdoor tasks, such as getting
to the car on the driveway or
walking from the car to the mall, especially for the elderly and persons with
irregular gait. Moving across
slippery surface is an inconvenience and may result in injury. The fear of
possible injury during icy
conditions forces people to slow down or to stay indoors, which may not be an
option for certain
occupations. With the present invention, the possibility of slipping on ice is
significantly reduced. The
underlying traction enhancement method may be used in various antislip devices
and applications.
SUMMARY OF THE INVENTION
Antiskid and traction improvement devices that have been described in the art
provide this capability by a
variety of different means. In most cases, they are designed as overshoes and
are equipped with sharp
elements. Those qualities make many of the existing designs (a) too bulky, (b)
difficult to put on and take
off, and (c) unsafe to manipulate. In addition, the devices equipped with
sharp elements (cleats,
crampons) render the footwear extremely slippery when used on the smooth stone
floor (e.g., inside the
mall) and/or damage the flooring and therefore must be taken off before
entrance. Conversely, those
devices without sharp elements are not efficient on ice surfaces.
The antiskid attachment of the present invention is an improvement over the
existing and prior art devices
in that it is designed as a device easy to fasten and remove, small enough to
carry along, and cheap and
simple to produce. The design is flexible to work with almost any type of
footwear and provides an
improved degree of traction on both packed snow and ice without impeding
normal walking and running
movement. Having no cleats, crampons or other sharp or abrasive parts, the
device is not detrimental to
most flooring types. Using the inventive method of traction enhancement
described herein, the device
remains sufficiently stable on smooth stone floors, permitting transitory use
of the device indoors, thus
minimizing the inconvenience of changing or removing footwear every time one
enters indoors.
The inventive method of traction enhancement deploying the physical properties
of polyhedral shapes may
be used for different anti-slip devices, including but not limited to
footwear, tires and non-slip flooring.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 - overall view of the present invention in preferred embodiment;
FIG. 2 - detailed view of a polyhedral skid-resisting element in preferred
embodiment, illustrating
tetrahedral nature of the elements;
FIG. 3 - detailed view of the self-adjusting linkage;
FIG. 4 - detailed view of the swivel part of the self-adjusting linkage;
FIG. 5 - overall view of the present invention in preferred embodiment
attached to footwear;
FIG. 6 - diagram illustrating the performance of the polyhedral skid-resisting
element;
FIG. 7 - diagram illustrating the performance of the self-adjusting linkage;
FIG. 8 - diagram demonstrating contact pressure redistribution;
FIG. 9 (A, B) - other possible applications of the traction enhancement
method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
CA 02535426 2006-01-09
The present invention is directed to an improved anti-skid attachment for
footwear that integrates
performance, light weight, convenience of use and manufacturability.
Specifically, the invention comprises
a multitude of skid-resisting elements (1), preferably of, but not limited to,
tetrahedral shape, positioned
between the footwear (2) and the surface (3) (see FIG.5). The skid-resisting
elements may be built
specifically for the purpose, with the shape of the elements varying from a
pyramid with triangular faces
(tetrahedron) to a conical shape but not limited to the said shapes . For mass-
market applications, a
standard single jack chain or double loop (double jack) chain may be used
instead. FIG.2 explains the
tetrahedral nature of the single jack chain links used in preferred
embodiment. The device further
comprises front and back flexible linkage parts, each consisting of the
elastic loops (4, 5) and swivel
connectors (6) connecting the elastic loops to the skid-resisting elements.
The device is attached to the footwear by pulling the front elastic loop over
the toe of the shoe, stretching it
until the front skid-resisting elements are positioned without slack under the
front part of the shoe, with
swivel connectors positioned flush with the sides of the sole as shown on FIG.
3, then stretching the back
loop over the heel of the shoe (FIG. 5).
The swivel connectors (see FIG.4) consist of the swivel part (7) and an
additional link (8) inserted between
the swivel and the skid-resisting elements (links of jack chain in the
preferred embodiment). This
combination facilitates the process of putting the device on the shoe by
reducing susceptibility to tangles
and by eliminating the need to define the "top" and the "bottom" of the
attachment in order to achieve the
desired antiskid effect.
In addition, the connectors are designed as levers, and are shaped in such a
way that they are retained in
the correct position (described above, and as shown on FIG.3 and FIG.7) by a
relatively small tension
exerted by the soft elastic loop (4), as this force, applied to the longer
moment arm, creates sufficient
force to secure the vertical parts of the swivel against the sides of the
sole. In the previously known anti-
slip attachments, the elastic members must withstand the strain caused by the
anti-slip action, and
therefore they are made noticeably more rigid and hard to stretch.
The elastic loops are made of tubular or round-profile elastomeric material
which facilitates attaching of
the device to the shoes and self-adjustment of the antiskid elements on the
footwear.
Furthermore, this configuration of the connectors protects the elastic loops
from being damaged or cut
when stepping on sharp objects, as the elastic parts are located around the
vamp and heel of the shoe
and not under them.
The inventive method of the anti-slip enhancement is based on the following.
All known antiskid devices
are designed to increase sliding friction only. This provides adequate
traction on packed snow and rough
surfaces. However, traction on ice has a specific nature similar to friction
between lubricated surfaces,
with sliding friction being extremely low, and therefore cleats and crampons
are used to increase the
friction factor in the majority of antiskid devices that are currently
available. For reasons explained before,
cleats and crampons may be unacceptable in certain applications.
The present invention suggests transition from sliding to rolling friction as
a means of gaining control over
skidding. Rolling friction is minimal when spherical solids are placed between
the two surfaces. Being
polyhedrons with infinite number of summits, spheres offer no resistance to
rolling when the number of
summits approaches infinity. However, the rolling friction increases as the
number of summits decreases.
The least possible number of summits for a three-dimensional solid is equal to
four. Hence, the
tetrahedron will create maximum possible rolling friction and is the basic
shape for the preferred
embodiment.
Additionally, the suggested tetrahedral (or similar) antiskid elements will
provide traction improvement as
compared to regular ribbed or grooved antiskid surfaces and spikeless chains
in the following way.
Caused by lateral skidding force, the redistribution of pressure from 2 to 1
point per element (see chain
"footprints" on FIG.8) will double the pressure in contact points, negatively
impacting the ice surface
condition conducive to skidding, similarly to the effect delivered by spikes
and crampons, thereby
CA 02535426 2006-01-09
increasing the threshold of starting friction and preventing transiting to
sliding friction.
The use of non-slip elements having triangular (or mechanically equivalent to)
cross-section in other
applications, e.g.: winter tires (FIG.9A), non-slip floors (FIG.9B), will
bring equivalent benefits.
While many other attachments using chains may look similar, they do not have
the benefits of the
tetrahedral (in the preferred embodiment) shape of the antiskid elements and
therefore are less efficient
on ice. The existing attachments with carbonized steel crampons and cleats may
be more efficient on
plain hard ice, but are extremely uncomfortable on smooth hard surfaces, such
as tiled floors, and are
dangerous due to increased slipping, while being detrimental to most surfaces.
In addition, driving a
vehicle is not safe with those devices attached to the footwear, if possible
at all. The present invention
does not have the above disadvantages, and its suggested embodiment using
standard jack chain makes
it more appropriate for city use than the anti-skid devices presently
available.
