Note: Descriptions are shown in the official language in which they were submitted.
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Dr. Harry Gaus, 69151 Dilsberg
A roller sport device
This invention relates to a roller sport device, particularly a single-track
skateboard or a
single-track roller skate, having two roller axles disposed one behind the
other with single-
track rollers which run one behind the other which are disposed thereon, which
axles are
disposed on a board or on a supporting frame.
The invention relates in particular to a single-track at roller skate
consisting of a frame with
a shoe fixed thereto or and with rollers are situated one behind another.
Roller skates of this type are subject to minimum requirements which relate to
simple,
efficient propulsion, balance, to the possibility ofateering them and to their
resistance to
movement. The following properties are expected in addition: ease of running,
i.e. a high
speed for a low expenditure of energy, a use which is easy to learn, and good
controllability.
Factors which are particularly important are a dynamic, readily effected
progression of
movement and a definite perception of movement, which make travelling on
roller skates
interesting.
Two basic designs of roller skates as such are known:
as a twin-track device comprising four rollers on two axles, for which all
four rollers
are always in contact with the ground, and
as a single-track device comprising a plurality of disc-shaped rollers one
behind
another (in-line skater).
Most roller skates are propelled by a skating step, i.e. by alternately
travelling on one roller
skate on paths which are oriented obliquely away from the direction of travel
and with the
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aid of which a transverse momentum of the body can be converted in part into a
forwardly
oriented momentum. In the course of this procedure, an outward pressure is
exerted by the
legs alternately, approximately perpendicularly to the average direction of
travel. Propulsion
is more efficient the more strongly the legs can swing out to the side and to
the rear. With
twin-track roller skates this freedom is limited because the foot always has
to be
approximately parallel to the ground.
With in-line skaters, the freedom of movement is considerably restricted by
the ankle part of
the shoe, which is usually high. The purpose of the ankle part is to relieve
the ankle from the
enormous tilting moments which occur due to the narrow, disc-shaped rollers
which are used
on single-track roller skates of this type, even at a slight tilt (inclined
position) of the foot.
Single-track roller skates comprising a shallow shoe can also be obtained for
rapid travel,
but the ankles are very severely stressed.
The skating step necessitates the prevention of lateral slippage, in order to
make optimum
use of the lateral force. For roller skates, a high coefficient of friction in
relation to the
roadway conflicts with the requirement for steerability, which is made easier
by sliding in
relation to the roadway.
The possibility of steering some twin-track roller.skates is due to a
kinematic coupling
between the lateral tilting of the platform and the steering angle (tracking
angle) of the two
axles and thus of the four rollers. The angle of tilt is very limited, so that
the foot remains
almost horizontal. If the body is inclined into a turn, the ankle has to be
kinked. Executing
turns in a pronouncedly slanting position is thereby made difficult or
restricted. Regions of
unevenness in the roadway react on the steering on account of the
aforementioned coupling,
and result in instabilities of balance.
Skateboards are also equipped with two pairs of rollers which can be steered
kinematically
in this manner, and sometimes suffer from the same problems, even though the
coupling
between the board and the wearer is not fixed in this manner, as it is for a
roller skate.
Steering is based on rotating the roller skate and/or turning it about a
vertical axis against the
forces of friction. If the roadway is rough (uneven), a roller skate can be
turned more easily,
since the individual rollers temporarily lose contact with ground. A low
coefficient of
friction of the rollers in relation to the roadway makes this easier and
reduces the energy loss
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when executing turns. The rollers therefore generally consist of a relatively
hard plastics
material with low static friction. However, the execution of dynamic turns
involving
considerable centrifugal force is thereby restricted.
CH 185 999 and FR 569 896, for example, propose two-wheeled, single-track
roller skates
comprising a fixed front wheel and a trailing rear wheel, the vertical axis of
which is rotated
by movements of the heels in order to effect control. The trailing wheels are
fixed to a
vertical steering axle via a horizontal fork and are centred by strong
springs.
However, the steering effect of constructions of this type of is too slight to
be able to execute
tight turns. Moreover, if the pressure of the heel is inadvertently reduced
there is a risk of the
fork turning over and of the turn being executed on the wrong side of the
rollers, which is
accompanied by a considerable risk of accident or injury, particularly since
this effect is self
intensifying. Here also, the tilting moments which have to be exerted by the
ankle when
executing turns are enormous, due to the flat rollers, and make shoes with
high ankle parts
necessary. The freedom of movement is thereby considerably restricted,
however, just as it
is with in-line skaters.
The object of the present invention is to provide a roller sport device of the
type cited at the
outset which can be accurately steered kinematically without significant loss
of energy, with
which rapid, tight turns involving a pronouncedly inclined position can also
be executed, and
which comprises a high degree of lateral guidance. In the form of a roller
skate, the device
should also be capable of being used by average sporting persons wearing
shallow or half
height shoes, and should not result in excessively high stresses on the ankles
when executing
turns.
This object is achieved in that the rearmost of the two roller axles (rear
axle) can swivel
about an axle (steering axle) which points obliquely downwards and forwards
and which
forms a trailing angle, and is centred by means of elastic elements for
straight running, that
the running faces of the rollers are curved transversely to the direction of
travel and that the
running faces have a high coefficient of friction similar to that of rubber.
The steering of the device according to the invention is based on a course of
movement or
travelling technique which is known in skiing technology by the term heel
thrust or heel
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pressure. In the form of a roller skate, this heel thrust can be exerted in a
particularly simple
manner with slightly bent knees (spring-ready posture). The low swing
technique is
preferred: a brief inward swing of the knee is followed by an outward pressure
with
subsequent stretching of the legs in the turn.
In order to steer inwards, a force directed towards the outside of the turn is
exerted on the
rear roller for this purpose by the heel of the foot which is on the outside
of the turn (the left
foot for a right turn). Said rear roller is thereby rotated towards the
outside of the turn
against the spring force of the steering bearing, and which, due to the
steering axle which is
inclined by the trailing angle, thereby changes both the track (i.e. the
direction of rolling,
twisting of the roller axle about a vertical axis) and the tilt (lateral
inclination of the roller
axle). A turn is initiated due to the track angle.
The weight of the body is subsequently shifted on to the foot on the outside
of the turn, and
the body is inclined towards the inside of the turn depending on the radius of
the turn and the
speed. The left ankle can remain in a straight position or can be slightly
turned inwards. This
procedure is assisted by kinking the waist towards the outside of the turn and
rotating the
upper body towards the outside of the turn to compensate for spin (skiing
technique). The
roller skate then travels into the turn and generates a centrifugal force in
addition to the heel
thrust. The steering effect is thereby increased. The steering kinematics
according to the
invention therefore result in a pronounced oversteer and can be stabilised and
controlled by
removing the heel thrust.
After the weight has been completely shifted on to the foot on the outside of
the turn, the
other roller skate can be raised slightly. To stabilise the execution of the
turn, the knee can
be supported in the bend of the knee on the outside of the turn. The steering
deflection of the
rear roller axle results from the equilibrium of the turning moments about the
steering axle:
heel thrust force, centrifugal force and a component of the weight which acts
against he
elastic force of reaction of the resilient mounting. It is therefore possible
to make corrections
to the path travelled by changing the heel thrust force, or the inclination of
the roller skate,
or the distribution of weight between the front and rear roller axles.
Advantageous embodiments and developments of the invention are given in the
subsidiary
claims.
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Amongst other features, provision can be made for the trailing angle to range
between 30°
and 70°.
Provision can also be made for the running faces to be curved approximately
spherically,
with the roller radius as their radius of curvature, so that the distance from
the point of
contact of the respective roller to the centre thereof does not substantially
change over the
entire range of oblique positions which can be covered. The device is thus
very capable of
being steered dynamically.
In order to facilitate a better capacity for centring and a more stable
travelling position for
straight running, the running faces can also be shaped transversely to the
direction of
running so that the distance from the roller centre to the point of contact of
the roller is a
minimum when the roller axles are horizontal. This can also be achieved, for
example, by
making the running faces cylindrical over a narrow central region.
To prevent any overturning when the heel thrust is removed, the distance from
the rear roller
axle to the steering axle can be made less than the roller radius; the
distance from the
steering axle to the rear roller axle is preferably about 2/10 to 6/10 of the
roller radius.
When the rear axle and the steering are suitably designed, it is also possible
for the distance
between the rear roller axle and the steering axle to be zero or even negative
(roller axle in
front of the steering axle).
One embodiment of the invention makes it possible to achieve a particularly
simple
construction in that the two rollers are each divided transversely to the
roller axle into two
half rollers which are at a distance from each other so that the parts which
support the
mounting can be passed through.
In another form of construction, the rear roller axle is attached to a
steering body which can
swivel about the steering axle by overcoming elastic restoring forces. A
desired turn radius
can thereby be accurately controlled and it is possible to make a progressive
readjustment of
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the steering. Other advantages are: attenuation of travel noise, a variable
steering
characteristic and a flexible steering stop.
In this form of construction, the two half rollers of each roller can be
separately rotatably
mounted on the associated roller axle, wherein the front roller axle is fixed
and the rear roller
axle is fixedly attached to the steering body, or the two half rollers of each
roller can be
fixedly attached to each other by means of the associated roller axle, wherein
the front roller
axle is rotatably mounted in the frame and the rear roller axle is rotatably
mounted in the
swivelling steering body. A steering axle disposed at the rear results in the
following
advantages: executing turns without losses due to friction, steering by heel
thrust, skiing
techniques can be used, and a parallel swing technique can be used with a
considerably
inclined position.
In one advantageous embodiment of this form of construction, space for the
steering body
can be created by making the half rollers of at least the rear roller of shell-
like construction
so that they enclose a void. The internal steering which is thereby produced
provides
protection for the steering parts, and bearing forces and moments are
minimised. With this
attractive design, there is no risk of injury due to angular steering parts.
In another embodiment of the invention, the rollers consist of a supporting
shell made of
light metal or plastics and of an external covering made of a polymer with a
high coefficient
of friction (rubber, polyurethane, natural rubber) in relation to the road
surface. Considerably
inclined positions in turns and in dynamically changing turns are thereby made
possible. The
skating step which can thus be employed for propulsion is particularly
effective.
Furthermore, rolling noise is reduced and parallel swings can be employed for
propulsion.
In one advantageous embodiment, the rear roller is larger than the front
roller. The
advantages of this embodiment are: space for steering kinematics in the
rollers, the raised
position of the foot is the optimum for making swings, maximum use can be made
of the
space under the heel, dynamic appearance and visual dominance of the roller.
Depending on the particular circumstances, provision can be made on the roller
sport device
according to the invention for the spacing of each of the two half rollers of
a roller in
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relation to each other to be adjustable, and/or for the rollers to be provided
with a hard
covering further inwards and with a soft covering further outwards.
Other advantageous developments and improvements of the invention are possible
due to the
measures listed in other subsidiary claims.
Amongst other features, the frame can be provided with openings in order to
reduce weight.
Light metal or composite materials can also contribute to minimising the
weight.
Provision can be made for the steering stub to be integrally formed on the
frame or to be
anchored within the frame by a detachable friction cone joint. A detachable
steering axle
provides the facility of selecting the geometry and steering behaviour by
changing the
steering stub.
The rear roller axle can swivel about a steering axle which is at an angle (3
(trailing angle) to
the horizontal. If the double roller swivels about an angle a, this causes a
change in the
tracking angle y (direction of travel of the double roller) of 8y = a.sin(3
and a change in the
tilt angle s (lateral inclination of the double roller) of 8s = a.cos(3. At a
trailing angle of (3 =
45°, sin(3 and cos(3 are approximately 0.71. If the trailing angle is
greater, the steering effect
(tracking angle) becomes greater and the tilting effect becomes less, and vice
versa. At a
trailing angle ~i < 30° the steering effect is too slight to be able to
execute tight turns, and the
tilting effect (i.e. the alignment of the double roller opposite to the
inclination) can become
so large that turns are executed on the wrong (outer) roller half.
The point of intersection of the line of alignment of the steering axle with
the path travelled
and the point of contact of the double roller define a trailing effect which
has a stabilising
effect (like that of a weathervane) on motion. The trailing effect is also in
part determined by
other variables such as the roller diameter and the spacing between the axles,
i.e. the
distance between the steering axle and the roller axle.
Large trailing angles reduce the trailing effect and decrease the ratio
between the tracking
angle (i.e. the radius of the turn) and the tilt angle. A (negative) tilt is
desirable, however, so
as to be able to cover strongly inclined positions without travelling on the
outer edge of the
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considerably stressed (heel thrust plus centrifugal force) rear roller,
instead of on the curved
face.
Trailing angles (3 > 70° are therefore disadvantageous. The steering
radius defines the lever
on which lateral forces from the point of contact (heel thrust, etc.) act on
the steering
bearing. These forces (or moments) should be capable of counteracting an
elastic opposing
force on the steering bearing in order to make it possible to proportion the
steering reaction
(regulation of a desired turn radius). A large steering radius therefore
necessitates high
elastic opposing forces on the steering bearing and thus necessitates a heavy,
costly
construction. The same applies to the bending radius which defines the lever
at which the
weight due to the fixed introduction of force acts on the frame. The effective
steering radius
and the effective trailing effect depend on the inclination of the roller
skate, since the point
of contact shifts.
The eccentricity is the distance of the weight vector from the centre of the
rotationally elastic
bearing. It defines a lever which exerts a moment of weight on the bearing in
addition to the
force due to the weight. The bending radius and the eccentricity should be as
small as
possible, for weight- and cost-saving reasons.
When the rear roller swivels about the steering axle, it is not only the tilt
and tracking of said
roller which change, but also its vertical and horizontal position. If the
axle spacing is
comparable with the roller dimensions, the lateral displacement becomes
particularly
important. When executing a turn, this means that the roller as a whole is
displaced towards
the inside of the turn. This is all the more advantageous.
If the roller skate is at a slant (inclined), a component of the weight acts
at a steering radius
and allows the roller to swing out in relation to the inclined position. At
the same time, the
roller also swivels upwards and consequently the heel becomes lower. If
lateral pressure is
then applied by the heel so as to bring the roller on to its inclined face in
order to execute a
turn corresponding to the slanting position (inclination), the turning moment
exerted by the
weight has to be overcome.
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If the distance between the roller axle and the steering axle (hereinafter
also called the axle
spacing) is very large and the angle of swivel towards the wrong side is too
large, a
correction of the steering position is no longer possible , since the
requisite lateral force due
to heel thrust becomes greater than the static friction of the roller on the
roadway. Only a
complicated course of movement is capable of correcting this fixed position:
alignment of
the roller skate, followed by heel pressure and then further angling of the
roller skate for
executing the turn.
In order to prevent this, the usable axle spacing has to be selected so that
it is small enough
for the steering axle to be situated inside the rear roller. If the angle of
swivel a about the
steering axle is limited to small values (by limit stops), the usable axle
spacing can be
greater. The requisite angle of swivel results from the smallest desired turn
radius: turn
radius = wheelbase/tana.sin(3. The turn radius is equal to half the turning
circle diameter.
The axle spacing can also be selected to be zero. The effect of weight on the
steering can
then be practically eliminated, and it is only the horizontal transverse
forces which are
definitive for the steering behaviour. If the axle spacing is negative, the
weight produces a
steering deflection and consequently a turn in the direction of inclination,
and is therefore
correct with regard to the dynamics of movement. A trailing effect and a
steering radius
have to remain in every case, in order to make it possible to steer by means
of transverse
forces.
If the effect of weight on the steering is made to disappear (axle spacing
zero), the option of
correcting the steering by means of weight, i.e. by inclining the roller
skate, is also lost.
The contour of the rollers is selected so that as far as possible the ankle is
relieved from
tilting moments. The optimum contour would be one corresponding to a circle
about the
effective axis of rotation of the ankle (complete relief from stress).
The roller width, however, should not be greater than the width of the foot.
The tangent to
the roller edge should correspond to the maximum desired inclined position
(e.g. 45°).
Therefore, the rollers are in practice narrower and more curved than is
necessary for
complete compensation for tilt. Depending on the particular requirements, the
roller sport
CA 02403363 2002-09-16
1U
device according to the invention can also be provided with rollers which are
of
unsymmetrical construction.
In addition to the aforementioned kinematic relationships, what are purely
geometric
relationships play a part, such as the ground clearance of the frame and
steering parts, which
must be sufficiently large so that they do not get caught, or the distance of
the foot from the
ground, which should be as small as possible in order to exert only a slight
tilting moment
on the ankle. In addition, there are also purely relationships of form, in
order to create an
attractive, functional form.
Some advantageous features are given below in the form of a list, together
with their
advantageous effects:
Wide rollers:
- tilting moment on the ankle considerably reduced
- shallower shoe possible
- freely movable ankle possible
- soft, gripping rubber compound possible
- profiles which create an interesting form.
Large rollers:
- rolling resistance considerably reduced
- regions of unevenness can be travelled over easily
- travel shocks considerably reduced
- roller design visually emphasised.
Preadjustable, replaceable prestressed double springs:
- more stable straight running
- variable steering threshold.
Shallower shoe:
- ankle mobility
- wide, swinging ski step
- elegant and easy mode of travel (three effective joints).
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Examples of embodiments of the invention are illustrated in the drawings,
which comprise a
plurality of Figures, and are explained in detail below. The drawings are as
follows:
Figure 1 is a view, shown partly in section, of a completely equipped frame of
a roller
skate according to the invention;
Figure 2 is a plan view of the same frame, likewise shown partly in section;
Figure 3 is a side view of a complete roller skate according to the invention;
Figure 4 is a front view of the roller skate when executing a left turn;
Figures 5 to 7 are a side view, a rear view and a view from below of a
skateboard
according to the invention;
Figure 8 is a rear view of the same skateboard when executing a right turn;
Figures 9 to 11 are a side view, a plan view and a cross-section through a
frame of a
roller skate according to the invention;
Figures 12 to 15 are a side view and sectional views of a steering apparatus
comprising a
steering body which is swivel-mounted on a steering stub; '~
Figure 16 is a plan view of the steering stub and friction cone joint;
Figure 17 shows the appropriate steering body;
Figure 18 shows the possibility of fixing a brake block to the steering body;
Figures 19 and 20 are different views of another steering apparatus in its
installed state;
Figure 21 comprises different views of the steering sub which is used
therewith;
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Figure 22 is a side view of a steering apparatus which is fixed on both sides;
Figure 23 shows the steering axle which is used therefor;
Figure 24 is a detailed view of the fixing end thereof;
Figure 25 is a cross-section through the steering apparatus;
Figure 26 shows a roller skate provided with a parking brake and comprising an
integrally formed steering stub;
Figure 27 shows a roller skate comprising an integrally formed steering axle
which is
fixed on both sides;
Figure 28 is a cross-section through the steering apparatus thereof;
Figure 29 shows a roller skate comprising a steering stub fixed thereto at the
top and an
axle spacing equal to zero;
Figures 30 to 36 are different detailed views of a completely equipped roller
skate frame
with a built-on, straight steering stub;
Figures 37 to 40 comprise studies of the movement and of the planes of forces
of a roller
skate according to the invention when executing a turn;
Figures 41 to 50 show different embodiments of roller skates according to the
invention;
Figure 51 is a graph showing the approximate values of the elastic properties
of the
steering for different major applications;
Figure 52 shows another example of a roller skate according to the invention;
Figure 53 shows parts of the roller skate illustrated in Figure 52; and
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Figure 54 shows paths of the centre of gravity of a known roller skate and of
the roller
skate according to the invention in order to explain the improved propulsion
achieved by the roller skate according to the invention.
In the Figures, identical parts are denoted by identical reference numerals.
The frame 1 which is illustrated in Figure 1 is employed for mounting a shoe
which is not
shown in this Figure. It is equipped with lightening holes 1', front bearings
14 for the front
roller 12, two fixing plates 2 for a shoe, a non-positive friction cone joint
4, and the steering
stub 3 which forms the steering axle and which comprises a conical fitting and
a screw 5. A
steering body 6, which comprises the bearing 9 for the rear roller 7, is
joined to the steering
axle 3 by an elastomer 6', e.g. vulcanised rubber. The rear roller 7 can
thereby be swivelled
about the obliquely extending steering axle 3 against the elastic force of the
elastomer joint
6'.
The ends of a hairpin spring 1 l, which is held in the steering body 6, engage
on both sides of
a pin 10 which is fixedly attached to the steering axle 3. Prestressing said
hairpin spring 11
results in a minimum force (minimum turning moment about the steering axle)
for rotating
the steering body 6.
The axis of the friction cone joint 4 points towards the point of contact of
the rear roller 7, so
that although bending moments act on this joint there is no turning moment
about the axis
(no loosening of the screw due to twisting). An extended screw 5 suffices for
fixation, and
facilitates replacement by a steering device with a different characteristic.
The steering axle 3 is set at a trailing angle (3 and defines a trailing
effect (N) at the point of
contact of the rear roller 7.
When it rotates about the steering axle 3 the roller 7 is subjected both to a
change in its
tracking angle (direction of rolling) and in its lateral inclination (tilt).
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A shoe which is suitable for mounting on this frame has a stiff, solid sole
and is screwed to
the frame. The shoe should be made to fit the front of the foot and the heel
and should not
restrict the mobility of the ankle.
Some of the terms or definitions used for the geometry or kinematics are shown
in Figure 1:
E is the eccentricity, B is the bending radius of the steering stub, G is the
line of action of the
weight on the rear axle 8, L is the steering radius and A is the axle spacing.
Figure 2 is a plan view of the frame. The mounting for the front roller 12
consists of two ball
bearings 14, a distance sleeve 14', a front axle 13 and two nuts 13'.
The steering body 6 is shown partially in section. It consists of a light
metal extruded section
and is joined to the steering axle 3 by means of the elastomer 6'. The
steering body 6 bears
two grooves 6" for the hairpin spring 11 and a groove 6"' for fixing a brake
block (not
illustrated). In order to keep the gap between the halves of the rollers 7, 12
as small as
possible, the frame and the steering stub are drawn in at 15 and 16,
respectively. In order
nevertheless to provide the frame 1 with sufficient strength, it is vertically
reinforced in the
region of the constriction 15.
The rollers 7, 12 each consist of two individual, identical half rollers.
These in turn consist
of a supporting inner shell made of light metal and of a non-slip external
covering 7', 12',
e.g. of vulcanised rubber which is similar to that used in motorcycle tyres.
The external
shape is fashioned so that at an inclined position of about 45° (Figure
40) the outer edge of
the front roller 12 contacts the ground. The outer edge of the rubber covering
7', 12' is
reinforced by a rib 7", 12". The rollers 7, 12 are very wide so that in an
inclined position the
points of contact of the rollers are displaced as far as possible towards the
tilting side in
order to counteract the tilting moment. If tilting occurs accidentally, the
ankle is thus
relieved from stress, and a shoe with a shallow ankle part can be used.
The inner shells 7, 12 of the rollers are optimised for load-carrying capacity
at the minimum
weight. The shape of each half shell is approximately that of a hemisphere
comprising a
drawn-in spherical cap. In all inclined positions, the resulting vectors of
force are
substantially oriented towards the roller axles 8, 13, so that bending moments
on the axles
CA 02403363 2002-09-16
are minimised. The spherical shell has openings for lightening purposes (only
illustrated in
part; see Figures 41 et seq.). The half rollers can be produced by casting,
die-casting or
pressing methods, and can be internally ribbed.
In most of the embodiments illustrated, the rear roller 7 is of larger
diameter and greater
width than the front roller 12. This results in sufficient space for the
installation of the entire
steering apparatus 3, 6. The resulting ground clearance in front of the rear
roller is sufficient
for travelling on roads.
Figure 3 shows the entire roller skate including a shoe. It fulfils the
requirements of rollers
which are as large as possible for the lowest possible position of the foot
(balance, or
moments acting on the ankle).
The front of the shoe is positioned somewhat behind and below the top of the
front roller.
The heel is raised by about 15°. Since the weight is distributed over
both rollers, the
effective roller diameter, which is one of the factors which determines the
rolling friction, is
approximately the average diameter of the front and rear rollers. Values of 70
mm to 100
mm are advantageous for the front roller, and values of 100 to 130 mm are
advantageous for
the rear roller.
The rubber-covered rollers can be provided with a spiral channel tread
pattern. A profile
such as this can improve the adhesion when executing turns in the wet, in dust
or in sand, but
results in flexing losses. A covering of harder rubber is advantageous in the
middle of the
roller (for straight travel), and a covering of soft rubber and/or one with a
channelled profile
is advantageous at the edge of the roller (for executing turns).
Figure 4 is a front view of the roller skate when executing a left turn.
Figure 5 shows a skateboard 50 which is mounted on a roller frame 1 according
to the
invention. The height of the ankle is marked (S 1 ).
Figure 6 shows the skateboard from below, Figure 7 shows the skateboard from
behind, and
Figure 8 shows the skateboard from behind during a right turn. In order to
vary the steering
CA 02403363 2002-09-16
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behaviour and balancing capacity, provision can be made for the spacing of the
half rollers
from each other to be varied by distance pieces. Figures 9 to 18 show details.
Figure 9 shows the frame 1, which can be made of die-cast light metal, for
example, with the
front axle bearings 14, the receiver for the steering axle 4 and the screw 5.
Figure 10 is a plan view of the frame 1 and Figure 11 shows the frame in cross-
section. To
prevent buckling, the side under compression is made wider than the side under
tension.
Figures 12 and 13 are two views of the complete steering apparatus, which
comprises the
steering axle 3 (steel), the conical seating 4, and the countersunk region 16
at the roller
periphery for reducing the spacing between the half rollers, and which also
comprises the
pressed-in pin 10 for the transmission of force into the hairpin spring 11.
The steering body
6 consists of a machined light metal section.
Figure 14 is an identical view to that of Figure 13, and shows the position of
the steering
body 6 during straight running and when swivelling by ~15°. One limb of
the hairpin spring
11 is deformed in each direction of swivelling.
Figure 15 illustrates, on an enlarged scale, the geometry of the elastic
steering axle/steering
body joint. The steering body comprises a butterfly-shaped internal bore, lead-
in bores 3' of
which receive the flat steering axle 3. On rotation, the elastomer 6' is
deformed, whereupon
the spring moment progressively increases as far as a strongly progressive
stop. The steering
body 6 can be rotated, but can only be displaced radially by a slight extent,
since the bore is
constricted in the middle. An axial displacement is likewise impossible due to
the large
effective length. In addition, the elastomer 6' acts to a certain extent as a
shock absorber.
Figure 16 is a plan view of the steering stub 3. Figure 17 shows the steering
body 6, which is
preferably made of an extruded aluminium section.
Figure 18 shows the installation of a brake block 180 by insertion in the
groove 6"' (Figure
13) and the securing thereof by a split pin 181.
CA 02403363 2002-09-16
17
Figures 19 and 20 illustrate a considerably simplified design of the steering
axle and steering
apparatus, respectively. As shown in Figure 21, the steering axle 21 is an X-
shaped section,
which is made of steel, for example, which is bent and which is compressed
during bending
so that an approximately rhomboidal cross-section is formed. In order to fix
it to the frame,
the steering axle is cast in or die-cast in directly (insertion technique),
for which purpose the
axle can be roughened at the appropriate location.
Figure 20 is a cross-section on an enlarged scale. In this embodiment, the rod
22 for
receiving the force of the hairpin spring is designed as a die-cast part and
is pressed on to the
end of the steering axle 21. This design is lighter and less costly, but
prevents the steering
apparatus from being replaced.
Figure 22 shows another solution for the transmission of force into the
steering axle. The
frame 24 is forked around the rear roller so that both ends of a straight
steering axle 25 can
fit into the frame 24. The rectangular steering axle 25 is inserted in pockets
26 in the frame
24 from below and is fastened with screws 27. Since there are practically no
bending
moments, the steering apparatus can be of relatively simple design.
Figure 23 is an overall view of the parts of the steering apparatus. Figure 24
shows a milled
constriction 28 for reducing the roller spacing.
Figure 5 is a cross-section through the steering body 29 with the rolling
bearings 30 and the
roller axle 31. A particularly small axle spacing is provided here (see the
description of the
steering geometry). The ease of replacement and low weight of this design are
advantageous.
Figure 26 shows a design which comprises a steering axle 32 which is cast on
directly if the
frame 33 is made of light metal or of a particularly strong plastics material
(by a casting
method). The bending forces at the base of the steering axle are very high,
but can be
controlled particularly easily and inexpensively using known A1 casting
materials. In
addition, Figure 26 shows stone guards 138 and 139 which close the gaps
between the half
rollers in the region of the points of contact, and which are fixed to the
frame 1 and to the
steering body, optionally by being integrally formed thereon.
CA 02403363 2002-09-16
18
Figure 27 shows a support for the steering axle 34 at the top, so that the
bending moment
disappears at the lower lead-in thereof. The shoe 35 is somewhat higher for
this purpose,
however. This design is particularly light, inexpensive and stable.
The steering body 36 shown in Figure 28 has a bore 37 with a butterfly-shaped
cross-section,
by means of which it is slid over the steering stub. In this design, the
trailing angle can be
increased without losing much ground clearance, because the lower lead-in can
be of smaller
dimensions.
The design shown in Figure 29 allows other trailing angles to be employed. The
lower lead-
in is omitted. At the upper lead-in 140, the bending moment becomes less the
larger is the
trailing angle. The large extent of ground clearance despite the large
trailing angle is
advantageous.
The axle spacing is equal to zero here. If the cross-sectional profile of the
roller is
approximately circular, the line of action of the weight always passes through
the steering
axle. As a result of the shortened castor length and the short steering
radius, only small
turning moments act about the steering axle 141, so that the rotationally
elastic mounting
141 is shorter. A large part of the weight is absorbed by a step bearing at
the end of the
steering axle 141. The axle spacing can also be made negative by placing the
roller axle in
front.
Figure 29a comprises two views, on an enlarged scale, of the steering axle 141
with the
steering body 142 and the roller axle 143.
In the embodiments illustrated in Figures 26 to 29, however, the steering
apparatus cannot
be replaced, in order to alter the leading angle, for example.
Figures 26 and 27 also show a locking device 38 for the front roller. This
consists of a
plastics component which acts like a wedge, which can be fitted to an
extension 39 of the
frame 1 and which can fix the front roller. This device can easily be
identified from the
outside and can be used on locking faces for roller skates (escalators,
stairs). The device can
form an addition to the braking device shown in Figure 13.
CA 02403363 2002-09-16
19
In contrast to Figures 27 and 28, the embodiments illustrated in Figures 26
and 29 are shown
without prestressing springs. It is also possible to use a prestressed spring
there, however.
This can improve the steering capacity.
Figures 30 to 34 show an embodiment comprising separate functional units of
the steering
apparatus. Figure 30 is a side view, shown partially in section, of the roller
skate, whilst
Figures 31 to 34 are different views of the roller and of the steering
apparatus, some of
which are shown on an enlarged scale. The steering axle 41 is screwed to the
frame 1 by
means of a screw 42. The steering body 40 is mounted by means of two bearing
bushes 43,
44 on the shank of the steering axle 41 and can swivel about the latter.
A conical rubber buffer 47 is situated on a rod 46 which is screwed or pressed
into the
steering axle 41. Two extensions 49, 50 are integrally formed on the steering
body 40 and
constitute a fork ; they are provided with a hole for weight-saving. Depending
on the
steering angle, at least one of the extensions 49, 50 presses on the buffer 47
and thus
generates an elastic opposing force which opposes swivel. This force
progressively increases
with the extent of swivel.
The end of the rod 46 fits into a hairpin spring 48 which generates an
additional opposing
force. This spring is situated in a groove and is prestressed, and therefore
presses on a
support with a rest force. A minimum force is therefore necessary in order to
swivel the
steering body, i.e. a minimum turning moment is necessary for a steering
deflection. Thus
small accidental forces do not initiate a steering reaction. Longitudinal
forces from the
steering body 40 which act on the steering axle 41 are diverted into the
steering axle 41 by
the bearing bush 43 and a screw 46.
Figure 35 shows the roller skate of Figure 30 at a swivelling angle of
10° in a right turn
without tilting, whilst Figure 36 is a front view of the roller blade of
Figure 30 inclined at
3 5 ° in a right turn.
If the steering bearing is disposed outside the rear roller, which is not
illustrated as an
example of an embodiment, and is provided with a fork for receiving the
roller, the rollers
CA 02403363 2002-09-16
can be made in one piece. The steering geometry is less favourable, however,
but in certain
situations this can be less important than the advantages which can be
achieved thereby.
Figures 37 to 40 illustrate the steering operation by means of a heel thrust,
where the roller
skate, with the front roller 12 , the rear roller 7 and a shoe 51, is
illustrated from behind in
each case. The effective pivot 51' of the ankle and the effective pivot 51" of
the steering axis
are also illustrated. Figure 37 illustrates straight running. Figures 38 to 40
also show the
component of the weight Gh which acts on the rear axle, the resultant R from
the component
of weight Gh and the heel thrust F, together with the centrifugal force F1,
the tilting moment
K at the ankle and the turning moment D of the steering axle.
In the first phase of steering (Figure 38) a heel thrust F is generated, i.e.
a force directed
towards the outside of the turn by the heel of the foot on the outside of the
turn (the left foot
for a right turn). The rear double roller rotates towards the outside of the
turn against the
spring force of the steering bearing, and thus changes both the track (i.e.
the direction) and
the tilt. A trailing angle of 45° and a swivelling angle of the rear
double roller of 8.5° about
the steering axle result in the 6° which is shown for the tilt and
tracking angles. Due to the
tracking angle, a turn to the right is initiated (i.e. the rear double roller
is directed outwards
to the left).
In the second phase (Figure 39) the weight is shifted on to the foot on the
outside of the turn
(left foot), and the skater inclines his body towards the inside of the turn
according to the
turn radius and his speed. The left ankle can remain in a straight position or
can easily be
turned inwards. This process is assisted by kinking the waist towards the
outside of the turn
and rotating the upper body towards the outside of this turn (skiing
technique). The roller
skate then moves into the turn and generates a centrifugal force F 1 in
addition to the heel
thrust F. The steering effect is thereby intensified. The steering kinematics
therefore
basically constitute an oversteer effect and can be stabilised and controlled
by removing the
heel thrust. An inclination (inclined position) of about 20° and a
change in tracking and tilt
of about 6° are shown.
In the third phase (Figure 40) there is a complete shift of weight on to the
foot on the outside
of the turn (to the left as shown in Figure 48). The right roller skate
(Figure 40b) can easily
CA 02403363 2002-09-16
21
be raised. The right knee can be supported in the bend of the left knee.
Initiation of the
steering of the rear double roller 7 is effected by the equilibrium of turning
moments about
the steering axle: heel thrust force F, centrifugal force F 1 and a component
of weight Gh
against the elastic forces of reaction of the elastomeric mounting or of an
elastomeric or
metal spring. Tracking corrections can therefore be made without varying the
heel thrust
force or the inclination of the roller skates or the distribution of weight
between the front and
rear double rollers 7, 12.
An angle of swivel of 14° about the steering axle is illustrated; this
corresponds to a tracking
and tilt angle of 9.9°. In this example, the front double roller 12
travels at an inclination of
45° (as do the frame, shoe, etc),. However, the rear roller travels at
an inclination of only
35.1°, since the tilt of 9.9° is negative. More freedom as
regards an inclined position is
thereby imparted to the rear double roller 7.
Figures 41 to 50 show different embodiments of a roller skate according to the
invention for
different preferred applications.
The roller skate shown in Figure 41 has a relatively short wheelbase for tight
turns and
skilled movements. It is capable of being stressed. Since the steering axle
shown in Figures
12 to 19 is illustrated, the position of the foot is relatively high, which is
why a higher ankle
part of the shoe may be necessary.
On account of its longer wheelbase, the roller skate illustrated in Figure 42
is particularly
suitable for more rapid travel. The position of the foot is somewhat lower. A
shallower shoe
therefore provides sufficient balance. The steering axle is likewise designed
as shown in
Figures 12 to 19.
The roller skate shown in Figure 43 has a similar geometry and similar uses.
However, the
frame and the steering axle are of one-piece construction, as shown in Figure
29. The
considerable ground clearance in front of the rear roller makes it possible to
travel over
edges. However, the steering characteristic cannot be varied, since the
steering unit is not
replaceable.
CA 02403363 2002-09-16
22
In the roller skate shown in Figure 44, the steering axle is screwed' to the
frame and can
therefore be replaced.
Figure 45 shows a roller skate comprising a large front roller 52 (the front
and rear rollers
are identical), due to which travel shocks are reduced when travelling over
uneven surfaces,
and then is a definite travel sensation when travelling over edges.
The roller skate shown in Figure 46 comprises a particularly long wheelbase
with a very low
foot position for rapid travel and larger turn radii. The steering is designed
corresponding to
that shown in Figure 22, and the frame 53 is forked at the rear.
Figure 47 also shows a roller skate comprising a forked frame 54. In order to
support the
steering axle 56, only part of which is visible, the rear frame part 55
extends above the rear
roller 57. This design can therefore be made narrower than that shown in
Figure 46.
The roller skate illustrated in Figure 48 has a long wheelbase and a low foot
position, and
otherwise corresponds to that shown in Figure 44.
In the roller skate sheet illustrated in Figure 49, the shoe 51 is not raised
at the heel 58.
Figure SO shows a roller skate in which the steering axle 59 is mounted on
both sides.
Figure S 1 is a graph of approximate values of the elastic properties of the
steering for
various major applications. The restoring force F in Newtons at the point of
contact of the
rear roller is plotted against the angle of swivel a in degrees about the
steering axle. Curve
61 can be employed for shoes which are provided for slow travel with tight
turn radii and
accurate controllability of the line of travel.
Curve 62 can be selected if wide turns are to be executed rapidly with an
accurately
controllable line of travel. Curve 63 is employed for a roller skate which can
be employed
for rapid straight running or wide turns. The smallest turn radius is given by
the wheelbase
divided by the tangent of the tracking angle.
CA 02403363 2002-09-16
23
The embodiment shown in Figure 52 has a similar steering axle 71' to that of
the
embodiment shown in Figure 3. In addition to the wheel bearings, the steering
body 72,
which is mounted on the steering axle 71 by means two bearing bushes 73, 74
and which is
fixed axially by means of a screw 75, has an extension 6 which protrudes
outwards through
the gap between the two half rollers 7. In its rear region, the frame 70 is
widened into a box
shape in order to provide space for two elastic bodies 77, 78 (Figure 53). The
extension 76
fits between the two elastic bodies. The elastic bodies 77, 78 can be
prestressed, equally or
unequally, by means of two screws 79, 80 (minimum turning moment for a
steering effect).
Figure 53a) is an enlarged illustration of the rear region of the roller skate
shown in Figure
52, Figure 53b) is a section through the rear roller 7, the steering body 72
and the extension
76, and through the elastic bodies 77, 78 and the screws 79, 80. Figures 53c)
and 53d) are
views of the rear part of the frame 70 for straight running (c)) and when
executing a turn
(d))-
Figure 53e) illustrates the component parts of the centring device, and
comprises three views
of an elastic body 77 and two views of a screw 79, whilst Figure 53f)
comprises a view of
the steering axle 71 and of the steering body 72.
Figure 54 comprises graphs for explaining the propulsion during a skating
step: in detail,
Figure 54a) shows the movement of the centre of gravity of the body for
customary in-line
skaters, Figure 54b) is the same plot for a roller skate according to the
invention, and Figure
54c) is the same plot for a roller skate according to the invention during the
starting phase. v
denotes velocity, and the second letter in each case is a suffix, where q =
transverse, l =
longitudinal, r = resultant, a = additional and s = step.
The average propulsion momentum is m.(vl:%Zve). It decreases due to the
resistance to
motion and is increased by m.ve in each step. This increase is due to the
skating step, in
which by pushing back the foot which becomes free approximately transversely
to the
instantaneous direction of rolling a momentum m.vs is generated which is
directed obliquely
forwards. This momentum has a component m.ve which is added to the propulsion
momentum and a transverse component m.ve which is wasted. The centre of
gravity of the
body executes a movement which is composed of an approximately constant travel
in the
average direction of movement and of a superimposed lateral swing. The lateral
swing
CA 02403363 2002-09-16
24
constitutes "lost momentum" of magnitude 2m.vq, where vq = (vl+ve).tan(rw) and
rw is the
roll angle.
At a roll angle of 20°, for example, lost momentum of 2m.(vl+ve)Ø36
is generated during
each step. This means that 72% of the maximum propulsion momentum is wasted
due to the
unsatisfactory kinetics of the skating step. In this example it is assumed
that ve = 0.13 v1, i.e.
a loss in momentum of 13 % v1 is compensated for in each step.
In physical terms, an impulse, i.e. force x time, is not energy, but
physiologically the
generation of a force for a given time is equivalent to energy conversion in a
muscle.
With the roller skate according to the invention, the propulsion momentum is
likewise
increased by a skating step, but this is effected with an approximately
transversely oriented
momentum m.vs=m.vq. Due to this transverse momentum, the resultant momentum
m.vr is
increased by m.ve. At the end of momentum generation, the resultant is
deflected into the
direction of travel. The velocity is given by yr = v1 + ve = (v12 + vq2)~'. A
transverse
momentum of 52.6% v1 is required in order to add the same momentum of 13% of
v1. This
results in a somewhat larger initial roll angle of 28°, which is
insignificant, however.
Compared with conventional in-line skaters, however, there is a saving in the
force applied
of about 20% under otherwise identical conditions. The advantage of the roller
skate
according to the invention is at the start, which can be important,
particularly in
competitions, and is particularly pronounced on a gradient, because the roll
angle is then
very large. As a result of steering into the average direction of travel, a
path of travel which
is less wide is required compared with known in-line skaters under otherwise
identical
conditions.
The purely physical energy usage during a skating step must be the same in
both cases, since
the same resistance to motion, which has to be compensated for, is assumed.
Nevertheless, a
different amount of muscle work is necessary, since the methods of
compensating for losses
are different.
The velocity yr of the centre of gravity on the path has to be increased so
that the usable
component v1 is increased by ve each time. The transverse component vq has to
be reduced
CA 02403363 2002-09-16
to zero and built up again in the opposite direction. This results in twice
the amount of
physical muscle energy, since although a reduction in physical terms means
energy
recovery, it is actually a use of energy. The energy used (energy after the
step minus energy
before the step) in relation to the energy before the
step is then
(vl+ve)z + vl.tanz(rw) + (vl+ve)Z.tan2(rw)/vl2 + vl2.tan2(rw). Normalising v1
to 1 and at the
magnitudes indicated, this gives 1.4, i.e. 40% of the kinetic energy has to be
added per step
in order to effect constant travel on average.
With the roller skate according to the invention, the transverse component
disappears due to
the deflection shortly before each new step. The energy used per step is then
[(vl+ve)z - vlz]/vlz, which gives 1.283 and means that 28.3% of the kinetic
energy is added
per step in order to effect constant travel on average. This therefore results
in a saving of
physical energy of 11.7%.
