Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to wheels for
machines which normally require wide faced tyres
for the purpose of spreading the load carried over
grass covered ground or other soft surfaces, for
example, golf fairways. In particular, the
invention relates to wheels for use on golf carts,
grass mowing machines and other mobile apparatus.
According to the invention there is provided
a pneumatic tyre for mounting on a wheel hub, the
tyre having a plurality of ground engaging pads
disposed around the periphery of the tyre, each pad
being capable of at least a limited degree of
rotational displacement about a radial axis
relative to the tyre, whereby the tyre may turn
through the limited rotation relative to any pad
currently in ground contact, and means Por
returning each pad to its undisplaced positiorl when
the pad has moved out of contact with the ground.
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The tyre is preferably mounted on a
conventional wheel hub, and a conventional tube is
provided to inflate the tyre to the correct
pressure.
An embodiment of the invention will now be
described, by way of example, with reference to the
accompanying drawings, in which:
Figure 1 is a perspective view of a wheel
incorporating the tyre according to the invention;
Figure 2 is a cross-sectional view of the
wheel of Figure 1;
Figure 3 is a plan view of part of one o~
the pads shown in Figure 1; and
Figures 4 and 5 are diagrammatic views of
one of the pads of the wheel of Figure 1 in ground
contact.
Referring now to the drawings, wherein
similar numerals have been used to indicate like
parts, there is shown therein a wheel and tyre
generally indicated at 10 according to the
invention. The wheel 10 comprises a rigid hub 11
having mounted thereon a pneumatic tyre 12. The
tyre 12 incorporates a conventional inflatable tube
13, which when inflated pressurises the tyre to an
appropriate pressure. A plurality of ground
engaging pads 14 are disposed around and coupled
to a periphery 15 of the tyre 12. Each pad which
is of a resilient material, for example rubber, is
of a width of approximately 14 inches and of a
length in the direction of rotation of the tyre of
approximately 5 inches. As shown, the pads 14 are
slightly spaced apart and taper from their widest
central part 16 towards the ends 17.
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The pads 14 are coupled to the periphery of
the tyre 12 by a coupling means, as will now be
described, so as to permit each pad at least a
limited degree of rotational displacement about a
notional radial axis relative to the tyre 12. The
coupling means comprises a spindle 18 which passes
through an aperture 19 in the tyre 12. The spindle
18 has a plate member 20 fixed at its end 21, the
plate member 20 engaging an inner surface 22 of the
tyre to locate the spindle 18 in position.
A rubber washer 23 is fixed to the outer
surface 24 of the tyre in the region of the
aperture 19. A locking plate 25 is located on the
spindle 18 adjacent to the rubber washer 23, and a
locking nut 26 engages with suitable screw-threads
27 on the spindle 18, to securely lock the spindle
18 to the tyre 12.
A nylon bearing plate 28 is located over the
locking nut 26, the aperture 29 in the bearing
plate 28 into which the locking nut 26 is received
being of a greater diameter than the diameter of
the locking nut 26. Thus, the bearing plate 28 can
be rotated freely on the locking nut 26. The
ground engaging pad 14 comprises a base plate 30 on
which is fixed a rubber block 31 having a square
shaped aperture 32. The base plate 30 has a
circular aperture 33 through which a shoulder
portion 34 of the spindle 18 engages. The aperture
33 is very slightly greater in diameter than the
diameter of the shoulder portion 34 of the spindle
18, so that the pad 14 can turn freely relative to
the spindle 18.
The free end 35 of the spindle 18 is formed
as a square shape and the pad 14 is secured on the
spindle 18 by means of a square shaped retaining
block 36 which is held in place by a suitable
circlip 37 secured to the spindle 18 as shown.
AS shown the retaining block 36 is located
on the spindle 18 within the regi.on of the squared
shaped aperture 32 in the rubber block 31. The
retaining block 36 is of a diameter slightly less
than that of the aperture 32
It will therefore be appreciated that the
spindle 18 serves only the purpose of coupling the
pads 14 to the tyre 12. When the wheel 10 supports
any weight, the pads 14 carry the weight which is
transferred to the tyre 12, by the pad 14 pressing
against the nylon plate 28 which in turn presses
against the outer surface 24 of the tyre 12.
When the tyre 12 i5 turned relative to that
one of the pads 14 which is in contact with the
ground surface, the pad will remain stationary and
the tyre 12 and spindle 18 including the retainin~
block 36, will rotate a predetermined rotation
distance approximately 4 to 15. As the retaining
block 36 rotates, it will engage and compress the
walls of the rubber block 31 which define the
aperture 32. Thus, the rubber block 31 in the
region of the aperture 32 will be compressed and
the relative rotation movement of the tyre will be
determined, by the degree of resilience of the
rubber block 31 and by how long the pad 14 remains
in ground contact. Once the pad 14 moves out of
ground contact, the resilience of the rubber block
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31 causes the pad 14 to return to its normal
position. As described previously, the pads 14 are
tapered to facilitate relative turning of the pads.
Instead of using rubber block 31, expansion
springs ~not shown) may be used one fixed at one
side of each pad 14 with the other end of each
spring fixed to the hub 11 of the wheel. This will
enable the pads to be returned to their undisplaced
position.
As shown diagrammatically in Fi~ures 4 and 5
the invention provides a construction of wheel and
tyre which enables the substantial reduction of
ground compaction by spreading the weight carried
over a greater area being that of the pads 14 which
provide a very much larger area than that of the
typical tyre. The p.s.i. pressure exerted by the
pads on the ground surface is substantially less
than that exerted by convention wide faced tyres.
Also, this wheel can turn without damage to the
ground surface because the pads 14 remain
stationary on the ground surface while the wheel
itself turns. The damage to the ground surfaces
caused by wheels turning on sloping ground surPaces
is also mitigated because the pads 14 will always
remain flat on the ground surface as shown in
Figure 5.
The invention maintains the advantage of
pneumatic tyres being that of air cushioning.
In another embodiment of the invention the
entire circumPerence of the tyre is covered by a
one piece sleeve of flexible rubber which is
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attached by known means, Por example vulcanising to
each base plate 30. In order to gain the necessary
benefits of individual pads, the rubber ~leeve
would have a number of spaced apart slots, with the
space between each adjacent pair or slots defining
a recess for a pad. This arrangement would have a
continuous central rubber area with the necessary
flexibility to provide a smooth running revolution
of the wheel.
Rather than the coupling means shown in
Figure 2, another embodiment of the invention
provides a pneumatic tyre having flexible rubber
mountings integrally formed with and protruding
from its ground engaging surface. The ground
engaging pads are attached to the rubber mountings.
Such a flexible mountin~ would allow the hub of the
wheel to turn at ground contact and return the pad
to its undisplaced position as soon as it comes off
ground pressure. Also, rubber blocks, for example
car engine mounting blocks could be secured to the
tyre with the mounting block also fixed to the base
plate of the pads.
All the novelty and benefits of the
invention may be maintained by having the
combination of pneumatic tyre and pads manufactured
as a single unit rubber moulding. This would
eliminate the necessity for the mechanical linkage
between the pads and the tyre. The inherent
flexibility of the rubber would allow the pads to
twist to the necessary extent thereby eliminating
the need for the mechanical means of returning the
pad to its undisplaced position after each pad
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rolls off ground contact. The flexibility of the
relatively narrow region of pad in direct contact
with the tyre surface, would allow the hub of the
wheel to turn without causing the pad to slide at
ground contact when it takes the weight of the
machine. Fibre or other known reinforcing material
could be moulded (or inserted) with the tyre so as
to strengthen the wide cross section area of each
pad.
Other advantages of the wheel according to
the invention include: the tyre cannot wear out, or
be punctured; the pads are replaceable without
having to deflate the tyre; the size of the pads
can be selec-ted to suit the size of the wheel; the
tyre may or may not be tubeless.
