Note: Descriptions are shown in the official language in which they were submitted.
. WO90/01359 PCT/EP89/00896
}) ' ~ ¢, i
STEERABLE CHASSIS ARM NGEMENT FOR ROLLER SKIS.
The present invention relates to a chassis arrangement
having a steerable element, in particular a wheel, steerable
on tilting of said chassis relative to the ground, and to a
steerable element for use in a chassis.
A chassis arrangement having a steerable element which is
steerable on tilting of the chassis relative to the ground
is known from international application No. WO 88/04565.
In this known chassis arrangement t~e steerable element is
mounted on the chassis via first and second links. ~he first
link is pivotally supported at one end on said chassis and
supports a substantially horizontally disposed axle for said
steerable element, and the second link is pivotable about an
axis disposed parallel or oblique to the ground and
substantially intersecting the con~act area, where, in the
straight ahead position of the steerable element, the latter
contacts the ground. In addition means is provided between
said first and second linXs defining a substantially
WO90/01359 PCT/EP89/00896
ve-tical axis which substantially intersects the first said
axis at said contact area, and the steerable element is
swivellable about this vertical axis to effect steering on
pivotal movement of said second link about the ~irst said
axis under the moment created by the ground pressure and its
moment arm about the first said axis resulting from tilting
of the chassis.
The kncwn chassis (international application publication No.
wa 88/04565) is particularly envisaged for use with a roller
skate, a skateboard, a roller ski, a roller bob, a snow
scooter or the like, i.e. with devices where steering is
produced as a result of displacement of the user's weight
resulting in tilting of the chassis. Since the steering
element can have different forms, for example a wheel in a
roller skate or skateboard, a caterpillar type device in a
dry ski, or a ski, slid or mow device in a snow scooter,
this term will be understood whereever it is used in the
specification, to cover any of the relevant items, depending
on the particular construction of the device involved.
The aforementioned international application publication No.
Wo 88/04565 describes in detail the possible scope of
application of such a chassis and the fact that it is
applicable to one or two trac~ vehicles, for example to a
so-called in-line skate having two or more wheels arranged
in a line one behind the other, or to a roller skate of a
more conventional appearance with pairs of wheels arranged
on each axle~ The thoughts expressed in this respect in the
a~orementioned international application concerning the wide
applicability of the chassis des~gn are equally relevant
here.
The kinematics o~ a chassis of the above described kind are
such that frictional forces acting sideways on the steerable
- W090/01359 pcr/Ep~9/oo896
- 3 ~
element or wheel have substantially no effect on the
steering, since they have no moment arm about either of the
relevant axes, i.e. the first said axis or the vertical
axis. In straightahead running t~ reaction force at the
contact patcn also has substantially no moment arm about
either of the said axes, since it acts su~stantially
vertically through the vertical steexing axis. Thus the
reaction force also has no relevant moment arm which could
induce a steering moment. If, on the other hand, the user
displaces his weight so that the chassis is tilted relative
to the ground, the reac~ion force of the ground is moved
sideways so that it now has a moment arm about the first
said axis. This results in a small pivotal movement of the
specially cranked second link about the first said axis so
that the end of the second link adjacent the steering
element moves sideways. This in turn rotates the first linX
about its point of mounting on the chassis, resulting in
rotation of the steerable element or wheel about the
vertical axis and a steering movement to the right or left
depending on the direction of tilting of the chassis.
Tilting of the chassis to the left results in steering to
the left and vice versa. The amplitude of the steering
movement is related to the amplitude of the tilting
movement.
A problem arises with a chassis of the kind Xnown from
international application No. WO 88/04565 in as much as the
connection between the first and second links defining the
vertical axis is positioned above the steerable element or
wheel and re~uires a certain amount of space. It is however
known from experience of roller s~ates and the like that the
lower the chassis can be made the easier it is for the user
to skate thereon. Even a reduc~ion in height o~ as little as
1 cm has a substantial influence on the behaviour of the
skate.
WO90/013~9 PCT/EP89/00896
~ tl ~ 3 ',3 ,~
Tt is accordingly a first object of the present invention to
so further modify the chassis design of the abovementioned
kind that an extremely compact chassis is obtained, in
particular a chassis having an overall height which is
reduced to a minimum, with the task of manufacturing the
chassis being kept straightforward and with the cost of the
individual components and of the chassis being minimised.
Moreover, the chassis should be easy to assembly and
reliable in use.
It is a further object of the present invention to provide
an improved steerable element for use in a chassis, in
particular a steerable wheel which can be substituted for
existing non-steerable wheel assemblies in in-line s~ates
and the liXe to convert the same to more readily steerable
sXates, in particular skates capable of describing circular
arcs.
A yet further object of the present invention is to provide
a wheel and axle assembly which could be mounted on a
supermarket trolley to make the same more easily steerable.
In order to satisfy the first said object the present
invention is characterised in that said means provided
between said first and second links defining said
substantially vertical axis is disposed in the center region
of said steerable element, in the region of said
horizontally disposed axle.
In this way the means does not take up any space about the
steerable element and the chassis can be lowered until it is
only just clear of thè steerable element.
A particularly preferred embodiment is characterised in that
~ WO90/013~9 Pcr/Ep89/oo896
- _
said''means de~inins a subs~antiaily ver~'ca1 ax~'s c~m~ses
an 'axle t~be-sup~orted'by's'aid flrst linX with said . . ~ .
steerable element bein~ mounted on said axle tube: an axle
shaft supported by said second link and extending with
clea-ance through said axle tube, and pin means defining
said substantially vertical'axls and extending between said
axle tu~e and said-axle shaCt'.~'
.. .. . . . . ..
Here a particularly compact arrangement is o~tained since
the pin means de~ining the substantiaily vertical axis is
wholly disposed within the center of the wheel, or between a
pair of wheels if two wheels are mounted on said axle tube.
This is a protected position''where the pin means can readily
be protected against the ingress o~ abrasive elements or
water of the like, which would'otherwise result in
deterioration of the chassis.''~'
In practice the pin means preferably comprises two pointed
gimbal pins engaging in res~ective conical rëcesses in the
surface of said axle shaft; In such an arrangement t~e pins
are characterised in that'said gimbal pins are threaded at
the outside and engage in screw threads in said axle tube.
~his is a particularly si~ple embodiment and the ability to
screw th`e pins into the axle tube' enables thëm to be finely
adjusted during assembly.''They'can be held in thèir adjusted
p~sition either by the use of a metal bonding adhesive
(Loctite '~(re'gistered t-zdemarX))', or by a loc~ nut, or by
deforming the threads,~ or by some other similar means.
- , . : . .............. .. .. . . . .
,, ..... - . - : . ........... : .
This arrangement is not only simple to manufacture and to
adjust,'it also has the advantagë that the axle shaft can be
made thic~est at the portion where the pins engage, thus
e~suring that the axle shaft is strong at the position of
maximum bending mom~nt. In addition the axle shaft can be
~ YU/~ PCT/EP89/00896
~, S! ~
made more slender towards its ends, thus providing an ample
clearance between the axLe tu~e and the axle rod to permit
steering o~ the wheel.
- ... . . . . .
Moreover, the axle tube itself can be thickened in the
region where the pins engage to provide shoulders adjacent
the-thickened region against which the bearings for the
wheel can be mounted. Thus, the thlckened portion serves two
purposes, namely to support the bearings in the axial
direction of the axle tube and to provide a support for the (~
threaded pins.
Thus, a particularly preferred embodiment of the invention
is characterised in that said steerable element comprises a
single wheel mounted on said axle tube by two axially spaced
apart bearings, especially rolling element ~earings; and in
that said pins are disposed between said bearings.
With an arrangement of this kind the first and second links
can readily be formed as for~s as set forth in claim 6 and
can be secured to the chassis in preferred ~anner described
in clai~s 7 to 10.
In an alternative e~bodiment the first and second linXs taXe
the form of single arms which are preferabiy constructed and
arranged in the manner defined in ciaims 12, 13 and 14.
An alternative way of realising the vertical steerl;ng axls
is provided by an arrangement which is characterised in that
said first and second links are for~s each having a head end
mounted at said chassis and for~ ends positioned ad~acent
one another at said axle; in ~hat said steerable element
comprises a wheel;~in that said means de~ining a
substantially vertical axis comprises pzrtly spherical
surfaces at said for~ ends of said second link and mating
WO90/013~ YCI'/~ /00896
partly spherical surfaces provided either at the for~ ends
o~ sald ~irst link or.,.at.the:ends,'o~ said,axlP,'whërëby~ ''
relative sliding .movement can take'place~at said spherical'~
surf acPs about said vertical . axis . In this arrangëment the
axle prefera~ly extends through generally horizontâi slots
or recesses in the.forX ends o~-the' second link so that the
steering axis is kept vertical..-
~
. . _ ., . - ~
Although the pin means defining sa,d substantially ~ertical
axis is preferably located between an axle tube and an axle
sha~t as described a~ove it is also possible for the pin
means to comprise a pin disposed to one side o~ the
steerable element, which is preferably a wheel, with said
pin being inclined so that said,substantially vertical axis
intersects the contact area between.the steerable element
and the ground.
The pin and the vertical axis de~ined thereby will normally
be disposed in a vertical plane perpendicular'to the
straightahead direction of the steerable element but '
inclined in that plane towards the ground contact area or
patch, .. . . .....
The pin itself may be an integral part of an axle for the '
steerable element (wheel) or it may be a separate pin. In a
par,ticularly preferred arrangement the'pin is supported at '.
two spaced apart locations on said axle and at two spaced
apart locations on said second link. ~~'' ~
In a typical roller skate two,said chassis will be mounted
facing in opposite directions to the bottom of one shoe or
bo~t. The chassis arrangeme~t of ~he present invention has
the ad~antage that it is entirely reversible so that only
one chassis ar_angement needs to be ~anuCactu-ed ar.d czn be
used as desired for the ~ront or rear wheel.
~ c~
In order to satisfy both the first object of the present
invention and also the further object recited above a steer-
able wheel in accordance ~ith the present teaching (i.e.
comprising a hollow axle tube supporting the wheel, an axle
shaft disposed within said axle tube and means extending
from said axle tube to said axle shaft and defining an axis
permitting limited relative pivotal deflection or steering
movement between said axle and said axle tube, with said
axis being directed substantially towards the region of con-
tact between said steerable element and the ground) can also
be substituted for the steered wheels in the two-wheeled
roller skate of Swiss patent 603 198, for the steered wheels
in the chassis of the abovementioned international applicat-
ion Wo 88/04s65 and for the steered wheels in the chassis of
the further international application No. Wo 88/04564.
Such a substitution would lead to a higher degree of compact-
ness, lower constructional height and improved performance.
With such a steerable wheel resilient means is preferably
provided between the axle tube and the axle shaft to provide
a restoring moment to the normal straightahead steering
position. Such resilient means could for example co~prise an
elastomeric compound injected into the clearances between
the axle tube and the axle shaft or it could comprise
metallic spring elements disposed between the axle tube and
the axle shaft.
For effecting the substitution described above the axis
directed towards the region of contact between the steerable
element and the ground will normally be a vertical axis.
A most important, surprising and advantageous further
development of the present invention can however be achieved
if the axis is an inclined axis. This permits the
_ 9 _ ~ 7
construction of a chassis arrangement as defined in
independent claim 21, the prea~ble of this claim again being
based on the prior art arrangement of Wo 88/04565.
In general the inclined axis will be disposed in a vertical
plane containing the normal straightahead direction of said
steerable wheel but will be inclined so that it points
forwardly and downwardly through the contact region.
A steerable wheel of this kind has the particularly sur-
prising advantage that it can be substituted for the normal
wheels of an in-line skate to produce an improved skate
capable of permitting the user to skate in circular arcs. In
general the steerable wheel will be a wheel mounted via
bearings on the axle tube. It is possible for the axle shaft
to be mounted rigidly in the chassis, steering resulting
solely from the ~reedom of movement provided for the
steerable element by the disposition of the inclined axis.
Alternatively the axle shaft could for example be mounted in
a fork which is pivotally mounted on the chassis about a
horizontal axis ~in the normal straightahead position), e.g.
in the manner of a leading or trailing fork suspension for a
motor cycle. With an arrangement of this kind springing is
possible to improve ground contact and ride comfort. Such
s~prings will then act between the fixed part of the chassis
and the leading or trailing fork supporting the axle shaft
of the steerable element.
Whilst the use of a forked element to hold the axle shaft is
preferred it is also quite possible to support the axle
shaft at only one end by means of a suitably dimensioned
leading or trailing link. Indeed the steerable element may
also be fixed rigidly to the chassis via a single post
connecting one end of the axle shaft to the chassis.
-- l o ~ ~ 3 ~ ! ~ "7
In a further embodiment the notional point of intersection
of the inclined axis With said contact region is disposed in
front of the centre of said contact region, at least in the
non-worn state of said steerable element.
This arrangement improves the straight line stability of the
steerable element, and of a chassis on which it is mounted
and also compensates for wear of the steerable element. This
wear compensation aspect can be important if the steerable
element is a wheel provided with a solid tyre in the manner
o~ a roller skate, since such solid tyres are su~jected to
considerable wear in use resulting in a substantial change
in diameter of the steerable element. In some circumstances
advantages can be gained by displacing the notional point of
intersection of the inclined axis with said contact region
behind the centre of said contact region.
A further, particularly compact embodiment is characterised
in claim 39 in which the wheel is mounted on the axle tube
via at least one bearing, with the axle tube comprising an
inner race of said bearing. In this way a separate axle tube
can be saved as well as the complication of mounting the
inner race of the bearing, or inner races of the bearings,
on the axle tube. In this special embodiment the inner race
of the bearing would typically be provided with a nose,
containing the recesses for the gimbal pins defining the
inclined axis.
An alternative compact chassis arrangement is defined in
independent claim 53. The preamble of this claim is again
based on the prior art of W0 88/04565.
Further preferred embodiments of the present invention are
also set forth in the subordinate claims.
WO 90/01359 PCTtEP89/008g6
The invention will ~o~ be described in furt~er detail by way
0~ example only and wit~ reference to the drawings in which
are shown:
.
Fig. 1 a schematic sideview of a roller skate chassis
having fxont and rear wheels, with the mounting
points for the rear wheel being shown partly in
section to illustrate the arrangement,
Fig. 2 a section on the line II-II of Fig. 1 showing a
first embodiment of the means defining the vertical
axis,
Fig. 3 a cross-section similar to that of Fig. 2 but of a
modified embodiment showing the preferred means for
defining the vertical axis,
Fig. 4 a partly sectioned view of the axle shaft of the
embodiment of Fig. 3 as seen in a vertical section,
Fig. 5 a view of the axle shaft of the embodiment of Fig. 3
as seen from a~ove,
Fig. 6 a partly sectioned view of the axle tube of the
embodiment of Fig. 3,
Fig. 7 a view of the securing nut and washer arrangement
used in ~ig. 3 to secure the forX ends of the second
link to the axle rod,
Fig. 8 a view of one of the two identical gimbal pins used
with the embodiment of Fig. 3,
Fig. g a view of a sealing shield used with ~he wheel
bearings of the em~odi~ent of Fig. 3,
WO90/01359 PCT/EP89/00896
`" - 12 - 2~J~ 7
Fig. lo a view of a locking washer used with the nut of Fig.
7,
Fig. 11 a view similar to that of Fig. 5 but of a modified
embodiment of the axle shaft,
Fig. 12 a view in the direction of the arrow XII in Fig. 11
showing the axle shaft mounted within an axle tube,
Fig. 13 a perspective view of an alternative chassis
arrangement in accordance with the present
invention,
.
Fig. 14 a section through a steerable wheel when used in a
chassis arrangement similar to that of Fig. 13,
Fig. 15 a section through a steerable wheel in which the
axle shaft is supported on a single link,
Fig. 16 a view in the direction of the arrow XVI of Fig. 15
showing details of the suspension of the steerable
wheel.
Fig. 17 a schematic view of a chassis similar to that of
Fig. 1 but with a slightly modified link
arrangement,
Fig. 18 a view showing a chassis arrangement similar to that
o~ the Swiss patent 603 198 but incorporating a
steerable wheel in accordance with the present
invention, and
Fig. 19 a schematic view of a chassis similar to that of
international application No. WO 88/04564 but
WO90/013~9 PCT/EP89/00896
- 13 -
incorporating the steerable wheel in accordance with
the present invention.
Fis. 20 a perspective view of an al ternative axle tube
configuration,
Fig. 21 a partly sectioned end view of the axle tube of Fig.
20, with the sectioned portion being taken in the
plane XXI of Fig. 20,
Fig. 22 a partly sectioned side view o~ the axI e of Fig. 20
as seen in the direction XXII of Fig. 2l,
Fig. 23 a plan view of the axle shaft for the axle tube of
Fig. 20,
Fig. 24 a partly sectioned view of a yoke used with the ax~ e
shaft of Fig. 23,
Fig. 25 a partly sectioned view of the yoke of Fig. 24 as
seen in accordance with the arrow XXV of Fig. 24,
Fig. 26 a side view of a pin used with the axle s~aft and
tube of Figs. 20 to 25,
Fig. 27 a sectional illustration of a rubber spring grommet
used with the pin of Fig. 24,
Fig. 28 a sectional view of a threaded cap for retaining the
spring grommets of Fig. 27,
Fig. 29 a cross-sectional view of a further axle assembly
taken on the plane XXIX - XXIX of Fig. 30,
Fig. 30 a partly sectioned plan view of the axle of Fig. 29
W090/013~9 PCT/EP89/00896
- 14 - ~ 9~ r; ~ j
with the section being made on the plane XXX - XXX
of Fig. 29,
Fig. 3l a perspective view of yet another axle tube ln
accordance with the present invention, and
Fig. 32 an end view of a yet further axle assembly formed
within the inner race of a bearing,
Fig. 33 a perspective view of a modified axle tube similar --
to Fig. 20,
Fig. 34 a view of a cap which can be used with an axle tube
in accordance with Fig. 20 or in accordance with
Fig. 31 to achieve the same effect as is achieved
with the axle tube of Fig. 33,
Fig. 35 an end view of the cap of Fig. 34,
Fig. 36 a schematic view of an alternative axle shown partly
in cross-section and consisting of two parts,
Fig. 37 a plan view of one half of a two-part axle tube
similar to that of Fig. 36,
Fig. 38 an end view of an axle shaft suitable for use with
the embodiment of Fig. 36,
Fig. 39 a schematic view of an alternative chassis
arrangement, and
Fig. 40 a modified version of the arrangement of Fig. 39.
Referring now to Fig. 1 of the enclosed drawings there can
be seen a chassis lO for a roller skate having two single
W090/0]3~9 PCT/EP89/00896
-- ' S --
r a ~
wheels 11 and 12 at its front and rear ends respectivel~.
The chassis arrangement 13 for the wheel 11 is identical to
the chassis arrangement 14 for the wheel 12, the two chassis
arrangements are merely reversed in the way that they are
attached to the basic chassis 10. The basic chassis 10 in
the drawing is a single piece it could however also be two
pieces which are movable relative to one another in the
longitudinal direction of the roller skate to facilitate
adaptation to difference shoe sizes. Buffers 15 and 16 are
provided at the extreme front and rear ends of the roller
skate. The reason why the rear chassis arrangement 14 is
reversed relative to the front chassis arrangement 13 is
simply to ensure that when the sXater wishes to turn to the
left the front wheel ll steers to the left while the rear
wheel 12 turns to the right. This is necessary to ensure
that the axes of rotation of the two wheels 11 and 12
intersect in the desired manner at the center ~f the arc the
skater is turning around.
As can be seen each of the chassis arrangements 13, 14
comprises a first link 17 and a second link 18. The first
linX 17 has the shape of a fork with the fork ends 19, which
can readily be seen in Fig. 2, being connected to an axle
tube 21 on which the wheel 11 or 12 is mounted via rolling
element bearings 22, 23. Each first link 17 also has a head
end provided with a spherical bearing head 20 which engages
in a partly spherical recess 24 in the chassis. The recess
24 diverges towards the associated wheel so that there is
room for angular movement of the first link 17 about the
center of the spherical bearing head 20.
The second links 18 also have a generally forked shape with
their forked ends 25 being connected to opposite ends of an
axle shaft 26 disposed within the associated axle tube 21.
The head end of each of the second linXs 18 has a resDective
WO90/01359 PCr/~P89/00896
- 16 -
spigot 27 which engages in a generally cylindrical recess 28
in the chassis lO, the recesses 28 may be lined with a
~earing bush or the like as desired. Furthermore, the head
of each second link 18 has a flattened portion 29 with a
central aperture 31 through which a securing screw 32 passes
with clearance. Rubber bushes 33 and 34 are interposed on
each side of the flattened portion 29 so that the link is
resiliently mounted here.
It will be noted from Fig. 2 that a pin 3l extends in a
vertical direction through the axle tube and the axle shaft
and thus defines a vertical axis 35 about which the wheel
can rotate for steering movements. The spigot 27 defines an
axis 36 which, when projected, passes through the ground
contact patch 37 between the wheel 12 and the ground 38.
Since the spherical head 20 is rotatable in all directions
about its center the first link 17 is also rotatable about
an axis 39 which when projected also extends through the
contact patch 37 and intersects with the vertical axis 35
and the first said axis 36.
Various details are also apparent from the drawings of Fig.
2. For example it can be seen that the axle tube is
thickened between the two bearings 22, 23 to provide an
abutment shoulder for the inner races of these bearings. The
~ork ends l9 of the first link 17 engage on annular
shoulders of the axle tube, and these end shoulders are
turned over, i.e. permanently deformed at 41 to permanently
retain the ends of the first links on the axle tube. As an
alternative one could also use a circlip to retain the for~
ends l9 on the axle tube. The fork ends of the second links
are retained on the axle shaft by means of a nut and washer
assembly 42, 43, with the nut 42 being screwed onto a screw
thread 44 at the end of the axle tube. The washer 3 is
secured against rotation by means of a flat on the end of
W090/0l359 PCT/EP89/00896
the axle shaft and a correspondingly shaped recess in the
washer~
In operation, if the user wishes to turn to the left, he
leans to the left and the shift in the contact region 37
(out o~ the plane of the drawing of Fig. 1 for both wheels
in Fig. 1) results, so far as the front wheel 11 is
concerned, in a rotation of the second link 18 about its
spigot 27, i.e. about the axis 36 (not shown for the front
wheel of Fig. 1). This results in movement of the forX ends
25 of the frontmost second link 18 to the right as seen in
the longitudinal direction o~ the skate shown by arrow 45 in
Fig. l (since the ~ront ends lie above the axis 36). The
cooperation between the second link 18 and the first link 17
which is pivotally secured at its front end to the chassis
results in steering of the front wheel to the left. Because
the suspension of the rear wheel 12 is reversed relative to
that of Fig~ 1 this wheel steers to the right in the desired
manner. The rubber bushes 33, 34 provide a restoring force,
i.e. a restoring moment about the axis 36, which tends to
restore the wheels to the straight position.
An alternative embodiment is shown in Fig. 3 which is
basically very similar to the embodiment of Fig. 2 which is
why the same reference numeral have been used for
corresponding parts. The pin means is however replaced in
the embodiment of ~ig. 3 by two oppositely disposed gimbal
pins 51 (only the upper pin 51 is shown in Fig. 3) which
have hardened conical ends 52 which engage in
correspondingly formed conical recesses 53 in the center of
the axle shaft 26.
It will be noted that shields 57 are disposed between the
fork ends of the first links 17 and the associated inner
races of the bearings 22, 23 and serve to protect the
WO90/0l3~9 PCT/EP89/0~896
- 18 - 2 ~ 7
bearings against the ingress of contamination. Once again it
can be seen that the ends of the axle tube are turned over
the fork ends of the first link to secure them at 41. The
mounting of the fork ends of the second link 18 is effected
in the same manner in the embodiment of Fig. 3 as in Fig. 2.
The individual parts, namely the axle tube 21, the axle rod
26, the gimbal pins 51, the bearing shield 57, the securing
nut 42, and the loc~ing washer 43 whioh fits on a flat at
the end of the axle rod 26 can be seen in the scale 2 to 1
in Figs. 4 to 10 of the drawings.
Turning now to ~igs. 11 and 12 there are shown modified
versions of the axle shaft and axle tube previously
described, for example with reference to Figs. 5 and 6.
Parts in Figs. 11 and 12 and in the later figures having
counter-parts in the earlier figures will be designated with
the same reference numerals.
The axle shaft 26 of Fig. 11 is asymmetrically constructed
in that it has a nose 61 which projects to one side of the
axle shaft 26. The purpose of this nose is to provide space
for the recess 53 for the gimbal pin to be moved away from
the centreline of the axle shaft. In similar manner the axle
tu~e 21 (Fig. 12) is provided with asymmetically disposed
threaded bores 62 and 6~3 for receiving the threaded gimbal
pins 51. It will be noted from Fig. 12 that the inclined
axis 64 defined by the gimbal pins is disposed in a vertical
plane which contains the straightahead direction 65 of the
steerable element. Thus the inclined axis 64 subtends an
angle ~ with the true vertical 66. The brcken line 67
indicates that the axis can also ~e positioned so that it
does not pass through the cen~re 68 of the ground contact
patch, as does the axis 66, but instead intersects the
ground at a point 68' located at a distance d in front of
the centre of the ground contact patch 68. This arrangement
WO90/013~9 p~rlEp89/oo896
-- 19 ~
tends to improve the self-centering of the wheel and also
compensates for wear in the solid tyre which leads
conceDtually to vertically upward movement of the centre 68
o~ the ground contact patch. The broken llne 69 shows that
the axis can also be placed so that it intersects the ground
behind the centre 68 of the ground contact patch.
Although not shown in Fig. 12 the solid tyre, which may be
of rubber or polyurethane, for example, is mo~nted on the
axle via one or more bearings, in similar manner to that
shown in Fig. 2.
Fig. 15 shows an embodiment in which the axle shaft is
supported at one end only. Here the axle shaft 26 is formed
integrally with the second link 18 and the axle tube 21 is
~ormed integrally with the first link 17 as can be seen more
clearly from the plan view of Fig. 16. In this embodiment
the vertical axis 35 is realised in a slightly different
manner. The end of the axle shaft 26 remote from the second
link 18 is namely provided with a spigot 71 which engages in
a cylindrical bearing sleeve 72 mounted in the axle shaft
21, with the central longitudinal axis of the cylindrical
bearing sleeve 72 being coincident with the vertical axis
35. In addition to the spigot 71 there is provided a single
gimbal pin 51 which is again radially directed through the
tubular portion of the axle sleeve 21 into an appropriately
shaped recess 73 in the end of the axle shaft 26 remote from
the link 18. The recess 73 is in this embodiment a
cylindrical recess and contains a cup-shaped liner 74, the
cylindrical walls of which are disposed coaxial to the
vertical axis 35 and the bottom portion of which forms an
abutment for the gimbal pin 51. In practice the gimbal pin
51 is adjusted so that there is essentially no free play in
the vertical direction between the end of the axle shaft 26
and the wheel. Thrust loads are transmitted to the axle
W090/~1359 PCT/EP89/00896
- 20 ~
shaft 26 from the wheel via the horizontal flange 75 o~ the
cylindrical liner 72. A lock nut 76 is provided to secure
the gimbal pin 51 in position.
Figs. 17, 18 and 19 show how a steerable element in the form
of a wheel and having a vertical steering axis 35 (for
example in accordance with the embodiment of Figs. 2 to 10)
can be incorporated into various chassis designs. Fig. 17
shows an embodiment which is in fact closely similar to Fig.
1 o~ the present drawings but in which the rubber bushes 33,
34 are no longer used since these bushes are now
incorporated as a resilient elastomeric composition in the
hollow axle tube surrounding the axle shaft 26. Once again
it can be seen that the basic geametry o Fig~ 1 is retained
with the three intersecting axes 39, 35 and 37.
Fig. 18 shows that the application of the steerable wheel
with the internally defined vertical axis 35 to a chassis
which is otherwise constructed in similar manner to that
shown in Swiss patent 603 198. A comparison of that prior
art specification with the presently shown embodiment will
however reveal that the chassis of the Fig. 18 embodiment
can be made substantially lower since there is no need for
suspension structure to be provided above the wheel.
Fig. 19 shows an embodiment which resembles the chassis
shown in international application, publication No.
WO 88/04564 in which tilting of the chassis, as sensed by
laterally disposed wheels 80 (only one of which is shown in
Fig. 17), produces turning of a horizontally mounted axle 81
in the clockwise or anti-clockwise direction (X). This in
turn produces steering movement of a front wheel 82. In this
embodiment the axle tube is connected to a first link 83
which cooperates at its rear end with a ball-shaped member
85 at the end of a radial arm 84 of the shaft 81. The axle
WO90/01359 PCT/EP89/0089fi
- 21 -
,;", .......
shaft is fixedly connected via a pair of forks 86 to the
base member 87 of the chassis. It will be appreciated that
rotation of the shaft 81 about its horizontal fore and aft
axis 88 results in steering movement of the first link 83
such that the end which engages the ball member 85 moves in
a direction perpendicular to the plane of the drawing
depending on the direction of rotation of the shaft 81. This
movement produces steering movement of the wheel about the
vertical axis 35 as indicated by the double arrow y.
While the steerable element is preferably a wheel it could
also be used With other forms of steerable element.
Figs. 13 and 14 show two further possible em~odiments. since
the geometry of these emkodiments is basically similar to
that of Fig. 1 the same reference numerals have been used to
designate the individual parts and the description of parts
common to the e~'oodiment of Fig. 1 will not be given.
First of all it will be noted that the wheel 11 of the Fig.
13 embodiment is supported by links provided only at one
side of the chassis 10. The first link is integral with a
bar or tube 21 forming an axle for the wheel 11 and it will
be understood that the wheel ll is supported on the axle 21
via one or more bearings: On the axle 21 adjacent to the
first link 17 there is provided an integral pin go which
defines an inclined axis 92 which intersects the other two
axes 39 and 37 at the centre 8 o~ the ground contact region.
The pin 90 is slidingly rotatably received in a cylindrical
bearing 93 formed in the wheel end of the second linX 18. In
this case it can be said that the means provided between the
first and second links defining said substantially vertical
axis is disposed in the centre region of the steerable
element, in the region of the horizontally disposed axle 21.
WO90/0~359 PCT/~P89/~0896
- 22 -
Fig. 14 shows a slightly refined embodiment of the steerable
wheel of the embodiment of Fig. 13. In the Fig. 14
embodiment the pin 90 is a threaded pin which is screwed
into a lug 94 provided on the axle 21 adjacent the point 2t
which it merges into the first link 17A The pin also passes
through a further lug 95 of the axle tube and is thus
supported at two spaced apart locations in the axle tube 21.
The end of the first link 18 is also provided with two
spaced apart lugs 96 and 97 through which the pin 90 passes.
since the pin is doubly supported it can be made relatively
slender without being liable to breakage. Thus the
embodiment of Fig. 14 enables a particularly compact
arrangement to be realised. Once again the inclined axis 92
intersects the notional vertical axis 35 at the centre of
the ground contact patch at 68.
Turning now to Fig. 20 there is shown an alternative
embodiment of the axle tube 21 in accordance with the
present invention. This axle tube, or rather the complete
axle assembly is also suitable for mounting in a chassis by
an arrangement in which the ends of the axle shaft are
supported directly by the chassis or indirectly via a single
pivoted fork, e.g. in the form of a pair of trailing or
leading arms. Also the axle shaft could be mounted on a
chassis by a single link which is connected to one end of
the axle shaft only and which could be mounted about a
horizontal pivot axis at its other end, e.g. by a torsion
bar, e.g. as a front and/or rear wheel of a motorbike. In
this embodiment no further link means are used to connect
the ends of the axle tube to the chassis. This is also
fundamentally possible with the embodiments described
earlier, particularly if the vertical axis is tilted in the
vertical longitudinal plane of the chassis.
The axle tube 21 has a centrally disposed support portion
WO90/013~9 PCT/EP89/00896
- 23 -
~ ?~
100 which in this embodiment is integrally formed with the
material of the axle tube 21. The support portion lOO
comprises two arms 101, 102 which project in a generally
radi21 plane away from the axis of the axle tube 21. A space
103 is defined between the two arms 101, 102 and
communicates via an opening 104 with the interior 105 of the
axle tube. Formed in the arms lOl, 102 at the ends thereof
axe threaded bores 106, 107 which accommodate gimbal pins
for supporting the axle shaft in a manner which will later
be described. In addition the support portion 100 has two
radially directed cylindrical recesses 10~, lO9, that is to
say recesses which are aligned on an axis radial to the
central longitudinal axis of the axle tube 21 which ser~e to
ac~ommodate resilient spring elements in a manner which will
be described later. It suffices to state here, that the
recesses 108, 109 are threaded at their end portions, for
example as shown at lll in Fig. 20 to receive caps.
The precise shape of the axle tube of Fig. 20 can also be
seen with reference to the partly sectioned illustrations of
Figs. 21 and 22. Although Figs. 20, 21 and 22 show the axis
formed by the gim~al pins as being substantially vertically
directed, it will be understood that in the inbuilt position
of the axle this axis subtends the angle ~ described
previously in relation to Fig. 12.
Turning now to Fig. 23 there can be seen a side view of the
axle shaft used with the axle tube of Figs. 20 to 22. The
axle shaft 26 of Fig. 23 is in fact pressed into a bore 112
of a yoke member 113 and indeed until the collar 114 on the
shaft 26 abuts against the shoulder 115 of the yoke 113. The
bore 112 and the corresponding mating portion 116 of the
axle 26 are preferably tapered fractionally, so that the
conical surfaces ensure easy introduction of the axle shaft
into the yoke and a tight fit. As can also be seen from Fig.
W090/0l3~9 PCT/~P89/00896
- 24 -
.. .. .. ..
24 and from Fig. 2~, the yoke 113 has a nose portion 11~
which projects through th~ opening 104 of the axle tube 21
of Figs. 20 to 22 into the space between the two arms 101
and 102. As also seen in Fig. 25 the nose 116 has two
conical recesses 117, 118 which receive the points of the
gimbal pins inserted through the bores 106, 107 of the
embodiment of Fig. 20.
It will be appreciated from the foregoing disclosure that
the yoke 113 must be inserted into the axle tube and ~etween
the arms 101 and 102 before the shaft 26 is pressed through
the bore 112. The ends of the shaft 26 are formed in the
same way as the ends of the shaft of Figs. 4 and 5 and will
not be described here in further detail.
It will also be noted from Figs. 23 and 24 that the shaft is
provided with a transverse bore 119 with a corresponding
transverse bore 120 being formed in the yoke 113. The
purpose of these transverse bores 119 and 120 is to accept a
shouldered pin 121 as shown in Fig. 26. The shouldered pin
has a portion 122 which extends through the two bores 119
and 120, a shoulder or collar 123 which prevents the pin
falling through two bores 120 and 119, i.e. provides a
positive step limiting the movement of the shoulder pin, and
two spigots 124 and 125 which after insertion of the pin
project into the cylindrical recesses 108 and 109 of the
axle tube. The portion 122 can be tapered. As can be seen
these spigots 124, 125 are of substantially smaller diameter
than the cylindrical recesses 108, 109 and are surrounded in
operation by a cylindrical rubber grommet shown in
longitudinal section in Fig. 27. As can be seen from Fig. 27
the rubber grommets have a plane-cylindrical outer surface
126 which fits in one of the bores 108 or 109 respectively
and a plane cylindrical inner bore 127 which accommodates a
respective one of the spigots 125 and 124. Any deflection of
W090/0l359 PCr/EP89/00896
- 25 - 2
the axle shaft relative to the aligned position along the
axis of the axle tube causes compression of the rubber
grommets which thus generate a restoring force. The rubber
grommets are secured in position by screw caps introduced
into the threaded ends of the recesses, for example a
threaded cap such as is shown in section in Fig. 28.
It will be appreciated that the shouldered pin is also
inserted through the yoke 113 and the axle shaft 26 after
the latter two components have been united in the axle tube.
The shouldered pin has a double function in as much as it
not only transmits the resetting force to the axle shaft but
also secures the axle shaft within the yoke 113.
It will be appreciated that in use first and second
bearings, typically ball bearings are pushed over the
cylindrical shoulders of the axle tube on either side of the
support portion 100. I.e. until the inner races of the
bearings abut against the ring shoulders formed on and
directly adjacent the support portion lO0. Although not
shown in the drawings means may be provided at the ends of
the axle tube for securing the bearing inner races.
In a practical embodiment the axle tube and the yoke have
been made.of an aluminium alloy and the shaft of the steel
alloy. To ensure a firm seat for the gimbal pins, which in
the embodiment under discussion have conical points
(although they could also have other shaped ends, for
example hemispherical ends) the gimbal pins are not threaded
directly into the aluminium alloy but rather into
cylindrical steel inserts pressed into the alumlnium alloy.
In practice these inserts are shouldered cylindrical inserts
or conical inserts which are pressed into the arms 101 and
102 from within the space 103, so that their shape prevents
them from being pushed ou~wardly by the forces acting on the
W090/013~9 PCT/EP89/00896
- 26 -
gimbal pin.
An alternative embodiment is shown in the Figs. 29 and 30.
The general shape of the axle assembly of ~i~s. 29 and 30 is
similar to that of the axle assembly of Figs. 20 to 28
although the support portion lOO of this embodiment does not
include cylindrical recesses such as 108 and lO9 of the axle
tube 21 of Figs. 20 to 22.
In the embodiment of Figs. 29 to 30 is pre~erably formed as
an injection molding in a fibre reinforced plastic and has
the special feature that the arms lO1 and 102 are connected
together by a bridge piece 130 which merges via a web 131
into the yoke 113 surrounding the axle shaft Z6. The axle
shaft is formed in this case of steel and is em~edded in the
yoke 113 during the injection molding thereof. Of particular
interest in this embodiment is the fact that the web 131 has
a narrowed portion at 132 which defines the axis 64 which
permits limited relative pivotal deflection or steering
movement between the axle sha~t and the axle tube. In-the
embodiment shown this narrowed portion 132 extends over the
full vertical depth of the web 131. Although this embodiment
is preferred for a synthetic axle tube, it could also be
realised in metal. It need not necessarily be made in one
piece but could be assembled, for example the bridge piece
130 could be made in one piece with the yoke 131 and screwed
to the ends of the arms 101, 102.
Another possibility for forming the axle assembly would be
to make the axle tube of C-shaped section, i.e. with a
continuous slot along its length as shown in Fig. 31. In
Fig. 31 the C-section resembles the axle tube of the Figs.
20 to 23, however the C-shaped cross-section of the axle
tube is not restricted to this embodiment, it could also be
used for example with the embodiment of Figs. 29 to 30, and
WO90/01359 pcr/Ep89/oo896
- 27 - , ,,,,,~
indeed irrespective of whether the axle tube is made there
of one piece with a composite assembly. With such a C-shape
the tube could be resiliently dilated to allow gimbals to ~e
inserted between the yoke 113 and the arms 101, 102, e.g.
gimbals in the form of ball bearings, thus simplifying the
design. Indeed the gimbals could be an integral part of the
yoke, or at least previously assem~led therein.
Fig. 32 shows another particularly important embodiment.
Here the axle tube assembly is ~ormed by the inner race of
the bearing and this inner race is provided with noses 140,
141 which are spaced apart to receive the nose of a yoke 113
fashioned similarly to the yoke 113 of Fig. 24. As can be
seen from Fig. 32 the two gimbal pins are axially
displaceable in a bore 143 in the yoke 113 and indeed the
yoke 113 also has a transverse ~ore 145 which accommodates a
securing pin 146, for example a threaded pin. For assembly
of the axle the threaded pin 146 is removed and the gimbal
pins are pressed into the nose until they are flush with its
surface. The nose of the yoke 113 can then be inserted
between the two noses of the inner race of the bearing and
thereafter the pin 146 inserted in order to force the gimbal
pins outwards into their bearing seats in the noses of the
inner race. An arrangement of this kind is necessary since
the nose of the yoke 113 should be a fairly close fit within
the space between the noses of the inner race of the bearing
so as to ensure a sound fit and adequate bearing surface for
supporting the nose of the yoke for pivotal movements about
the axis 64 defined by the gimbal pins.
A thr,ust bearing, indeed even a roller thrust bearing could
also be inserted in the above described axle embodiments
between the yoke and the axle tube to ensure the thrust
loads arising in operation are adequately borne. The yoke
113 can also be formed integrally with the axle shaft 26.
WO90/01359 PCT/EP89/00896
- 28 -
~;, '~ '' '`; '' '' ''''
Turning now to Fig. 33 there can be seen an axle tube having
substantially the form of the axle tube of Fig. 20 however
the interior 105 of the axle tu~e is formed 50 that it has
the shape of an elongate slot in cross-section, at least at
the ends of the axle tubes. The axle tube could also be
C-shaped in cross-section which is indicated by the broken
lines 150, i.e. the portion 151 between the broken~lines 150
would be omitted. This modification would of course also be
made at the other end of the axle tube as is likewise
indicated by broken lines 152. It will be noted that the
axle tube of Fig. 33 does not include the cylindrical
portions 108, 109 of the Fig. 20 embodiment. However these
portions could also be provided if desired.
The purpose of the elongate slot-like cross-sectional shape
o~ the interior opening 105 of the axle tube of Fig. 33 is
to provide additional bearing surface for supporting the
axle shaft at its ends.
This arrangement can also be realised in an axle tube in
accordance with Fig. 20 or in an axle tube in accordance
with Fig. 31 by the use of caps 153 as shown in Figs. 34 and
35. That is to say the oaps ha~e an elongate slot-like
opening 154 corresponding to the shape o~ the elongate
cross-sectional opening 105 of Fig. 33 whereas the opening
of the axle tube is otherwise of generally cylindrical
shape. The caps can be press-fitted into or onto the ends of
the axle tube and can also be bonded thereto by means of
adhesive, or welded thereto. They can also carry resilient
elements, such as the rubber washer 155 shown in Fig. 34, in
order to generate the restoring or self-centering moment on
the axle shaft. The washer 155 could for example have a
circular opening corresponding to the diameter of the axle
shaft, rather than an elongate slot-like opening, so that
WO90/0l359 PCT/EP89/00896
- 29 -
deflection of the ends of the axle 26 about the axis defined
by the gimbals causes compression of the ru~ber washer.
Although in the present embodiment the axle shaft is
supported by the caps primarily at its ends it is also
possible for the axle shaft to be supported throuyhout its
length within the axle tube by corresponding bearing
surfaces. Moreover the axle shaft can have flats at its two
surfaces adjacent the bearing surfaces so that the bearinq
loads are reduced. With an arrangement of this kind the
gimbal pins merely define a pivot axis and the loads on the
axle are primarily borne by the bearing surfaces.
As shown in Fig. 36 the axle tube can also be formed in two
parts 160 and 161, with these two parts being shaped in
mirror-image fashion and being secured together by threaded
fasteners, for example the threaded fasteners 162 and 163.
The ~ormation of the axle tube in two at least substantially
identical halves reduces the manufacturing costs. Moreover,
cylindrical recesses such as 164 can also be provided to
accommodate rubber grommets 126 corresponding to the rubber
grommets used in the Fig. 20 em~odiment. If this is done
then the axle 26 of Fig. 38, which is provided with pins
such as 125 and 124 in Fig. 26, will be restored to its
straight head running position by the resilient action of
the grommets 126. An alternative to joining the two halves
of the axle housin~ together by threaded fasteners is shown
in Fig. 37. Here the axle tube ccmprises a tough plastic
material, it is again made in two halves (the lower half 160
being shown in Fig. 37) and the two halves are bonded
together by an adhesive, or by ultrasonic welding at the
mating faces such as 161, optionally after insertion of the
axle shaft 26. The ~ig. 37 embodiment shows the axle shaft
26 in plan view, the latter being provided wlth flats 165 at
its surfaces which rest on the bearing surfaces defined by
the two halves of the axle tube~
WO90/01359 PCT/EP89/00896
2 ~ 3 ~
With an arrangement as shown in Fig. 36 Of Fig. 37 the axle
shaft 26 can conveniently have the shape shown in end view
in Fig. 3~. That is to say the gimbal pins can be formed by
a throughgoing cylindrical pin 166 which may be a shouldered
pin. The two cylindrical ends o~ the pin 166 can be inserted
into corresponding cylindrical bearing bores o~ the two
parts of the axle tube prior to assembly of these two parts
o~ the axle tube~
The following comments can thus be made relating to the
embodiments of Figs. 33 to 38.
This embodiment ma~es it possible for the axle tu~e to be so
executed that the main load pick-up for the axle shaft does
not take place at the tips or spherical ends of the ~im~al
pins but rather at the sides of the axle shaft where it
emerges ~rom the axle housing, the axle shaft being made in
particular of steel. In the one embodiment a cap having a
guide and support cut-out (slot) is fixedly anchored in the
opening of the axle tube from both sides (for example by a
toothed, bonded, or welded fit or the like). The slot has
the width of the axle shaft diameter in the vertical
direction so that the axle can move slidingly. In the
horizontal direction the slot is so shaped that the axle can
make just the same steering movement as it would make
without the cap. It is however also possible to restrict the
freedom of movement of the axle horizontally by the cap,
which can, if desired, be done at one slde only.
In the event of a separate cap this can be execute~ as an
accessory or a replacement part for retrospective inser~ion
or for repair pUrpases by the user. The cap can be so
executed that it reinforces the axle tube, in particular
when the axle tube is of C-shape or consists of a tough
WO90/01359 PC~/EP89/nO896
plastic material. The caps likewise reinforce the axle
shaft, at least in the sense that they relieve the axle
shaft of substantial bending loads.
The caps can also be so executed that they have a spring
element of rubber, resilient plastic or of spring steel at
their rear side which returns the axle into the zero
position and acts in a shock-absorbing manner. Different
spring strengths can be provided to match different body
weights and performances. By displacing the springing into
the outer regions of the axle the spring element around the
central pin of the inner shaft can, if desired, be omitted,
whereby the special shaping of the housing in this region
ca~ also be omitted and simple tools can be used to
manufacture the housing or axle tube. In individual cases
optimisation will be effected relating to the loadability of
the axle and its manufacturing cost, depending on the
particular application. It is also conceivable that the axle
tube can be made in C-shape, the center of the C forming the
above described guide and support slot. Such a one piece
axle tube would have an opening for the insertion of the
axle which can be provided at the front or at the rear. It
makes it possible to insert the preassembled internal axle
or axle shaft. This axle shaft can for example be forged in
one piece if the springing is displaced to the ends of the
axle tube. Since the tools are somewhat more complicated and
expensive an embodiment of this kind may only be practicable
from a cost point of view when large numbers of axles are
being manufactured. When used as self-steering systems for
larger vehicles, as roller skates or roller skis, the guide
support for the axle ends can also be made using known ball,
roller or sliding bearings. Depending on the application the
central suspension of the axle shaft can then be relieved
and the cost of the tota1 construction can be optimised.
WO90/013~9 PCT/EP89/00896
- 32 -
It wlll be appreciated that the above described axle
assem~lies are particularly suited for use in in-line
skates, e.g. (without restriction) in three wheel in-line
skates in which the centre wheel is a plain wheel on a fixed
axle and the two outer end wheels have axle assemblies as
described herein with the axle assemblies being reversed
(e.g. as in Fig. 1) so that the steering axes of the wheels
are inclined at the same angle to the vertical direction but
are positioned on opposite sides of the Yertical direction.
Finally, a further compact version of a chassis arrangement
is shown in Fig. 39 with a further modification being shown
in Fig. 40. In the embodiment of Fig. 3g the chassis is
indicated generally by the reference numeral 200. The
chassis supports a wheel element 202 which is connected via
an axle 204 to a saddle~shaped yoke 206 which straddles the
wheel. That is to say the axle 204, which is a
straightforward axle directly supporting the wheel via one
or more bearings, is rigidly connected to the yoke 206. The
rear end of the yoke 206 is formed as a link 208 having a
spigot 210 which engages in a cylindrical bearins recess 212
in a generally cylindrical bearing mem~er 214. The
cylindrical bearing member 214 is mounted on a horizontal
transverse axle 216 within a bell-shaped recess 218 in the
chassis 200. The front end of the saddle 206 forms a second
link 220 which is connected to the cup 222 of a spherical
joint 224. The ball 226 of this spherical joint is connected
by a generally vertical link 228 to the chassis 200 with the
vertical link 228 passing through an opening 230 in the
chassis with clearance and having a head portion 232 which
traps a rubber bush 234 between itself and the chassis 200.
The role of the spherical cup 224 and the spherical ~all 224
can also be reversed, i.e. the second linX can connect with
the ball and the cap can be mounted on tAe vertical link
228.
WO90/013;9 PCT/EPX9/00896
~ 33 ~
An inverse arrangement is possible as shown in Fig. 40 in
which the vertical link 228 is disposed so that the
spherical joint 222 is disposed beneath the chassis 200 in
which case the resilient bush 234 is mounted above the head
232 of the link ~etween the head of the link and the chassis
200. The spigot porticn 236 o~ the vertical link 228 serves
for general location of the vertical link 228 within the
chassis. Additional resilience permitting springing of the
wheel in the vertical direction can be provided by a
resilient cushion 238, for example of foam rubber, inserted
between the yoke 206 and the chassis 200. Again two such
wheels can ~e mounted in opposition on a chassis in the
manner illustrated with respect to Fig. 1. It will be noted
that the spigot defines a first pivot axis 240 which passes
through the ground contact patch 242, that the axle and the
ground contact patch define a notional vertical axis 246 and
that the spherical joint in ground contact patch define a
further notional axis 248 with the wheel being constrained
by the seometrical arrangements to move around these axes
under the influence of the weight applied to the wheel and
the prevailing tilting forces which depend on the direction
in which the user wishes to steer.
In Figs. 39 and 40 only the rear wheels are shown, the front
wheels are o~ similar design but are reversed as in Fig. 1,
this is indicated by the illustration of the mountings for
the links 22~ for the front wheels.
It should be noted that the inclined axis of claim 21 is disposed
with a front wheel such that it points upwardly and forwardly
and with a rear wheel such that it points upwardly and rearwardly.
This orientation ensures, in accordance with the invention that
the chassis arrangement will steer to the left when the user leans
to the left and will steer to the right when the user leans to
the right.
