Note: Descriptions are shown in the official language in which they were submitted.
WO 93/15g23 21 2 9 8 51 PCI~/GB93/00269
VE}~ICLE WITH RETRACTABLE WHEEL
The present invention relates to vehicles with
retractable wheels, particularly, but not exclusively,
suitable for use in amphibious craft. In particular the
invention concerns the supporting of the wheel position
while the wheel is in use.
There are many different disclosures of amphibious
craft but in most cases the wheels are moveable between
a lower position in which they engage the ground and via
which the craft is driven on land, and a raised position
in which they are stored while they are not in use. In -
order to reach the required current levels of safety it
is necessary to support the wheels in at least the lower
position. In most disclosures the wheels are held in the
lower position by the retraction mechanism which raises
and lowers the wheels, for example a hydraulic ram. This
does not provide adequate safety as it does not cater
for ram failure. In the upper position the wheels are
also held and firmly supported by the retraction
mechanism.
It is the object of the invention primarily to
provide a safety stop ~or the wheel mechanism to support
the wheels, particularly in the lower position when
carrying the vehicle weight.
According to the present invention there is
provided a vehicle having a wheel which is moveable
between a lower position and a raised position by a
wheel retraction mechanism, characterised in that the
retraction mechanism comprises a support element
connected to the wheel via a coupling on the element and
mean~ for moving the said el~ment in a path encompassir.
a highest position of the coupling, a lowest position of
the coupling. and an-upward return beyond the said
lowest position; the means for moving the element
comprising a rotary member and the mechanism including
WO 93/lS923 212 9 8 5 1 PCI`/GB93/00~69
an abutment disposed in the path of the element to limit
the upward return of the element.
The support element may be an arm which is swung by
the rotary member 80 that the said highe~t and lowest
positions of the coupling are on a vertical plane taken
through the axis of the rotary member, The rotary member
may be directly driven from a motor, or may be turned
indirectly by a transmission such as a chain, band or
rope. Alternatively the support element may be a bar or
rod which is carried on an elliptical path by a
transmission such as a chain, band or rope. The
transmission may be continuous. Alternatively the
tranmission may have fixed ends and means is provided to
transmit the rotary movement by action on the
transmission between the ends. It is preferred that the
rotary member is driven by a transmission rather than
directly because it overcomes the problem of reliance on
particular sprocket or gear teeth and thus wear of those
teeth.
Where the transmission is continuous, the rotary
member may be a sprocket or truckle for example. In both
cases the support element is advantageously connected to
the wheel via a suspension device or shock absorber.
Advantageously the wheel is also stopped in the
raised position by an abutment disposed in the path of
the ~upport element to limit the down return of the
element past the hi~hest position of the coupling.
By overcentering the support element at upper and
lower positions the wheel is held in position by the
prevailing forces on the support element, thus removing
the necessity for other locking mechanisms, although a
lock or latch can al~o be used if desired, for example
actuated by the retraction mechanism motor.
A guide may be provided to determine the path of
the wheel during retraction in response to movement of
the support element.
W093/~5923 2 1 2 9 8 5 1 PCT/GB93/00269
Advantageously the element comprises at least one
crank arm which i8 rotatable about an axis between upper
and lower extreme pivotal positions defined by
respective abutments, the said coupling being spaced
from the said axis and the total angle of ~ovement of
the arm between the extreme positions being greater than
180 degrees.
Preferably a subsidiary locking arrangement i8
provided for the retractable wheel mechanism, the
loc~ing arrangement comprising a locking bar pivotally
connected at one end to the crank arm to pivot with
respect to the arm, and pivotally mounted via a support
at the other end, the arrangement including means
allowing for the change in distance between the said one
end of the locking bar and the said support as the crank.
arm pivots, and mean~ operable to lock the locking bar
when the crank arm is in an extreme pivotal position.
Advantageously the locking bar is pivotally mounted
via a support to pivot, and to slide on a first path, as
:~ 20 the arm pivots; wherein the means operable to prevent
` ` the said one end of the locking bar from moving includes
a locking member which is moveable in a second path
intersecting the first path; wherein the operation
includes the transfer of the locking member to block the
first path to prevent sliding movement of the locking
bar. Alternatively the locXing bar may be telescopic and
the means operable to lock the locking bar would lock
either the extension or the angle for example.
The present invention will now be described, by way
of example, with reference to the accompanying drawings,
in which:
Figure 1 shows the outline of the front part of an
amphibious craft cut away to illustrate in perspective a
heel support and retraction mechanism according to one
embodiment of the present invention,
WOg3/15923 ; PCT/GB93/~69
2129851 ~
Figure 2 shows the wheel mechanism of Figure 1 in
greater detail,
Figure 3 i8 a detailed view of part of the wheel
retraction mechaniQm of Figure 1,
S Figure 4 i9 an expanded view of the collar and
collar-carrier of the retraction mechanism of Figure 1,
Figure 5 illustrates a driven-wheel retraction
mechanism for an amphibious craft according to a second
embodiment and having an independent locking mechanism,
which may be u~ed for example for the rear wheels of the
craft of Figure l,
Figure 6 is a side view of part of the mechanism of
Figure 5,
Figure 7 is a part plan-view of an embodiment
lS similar to that of Figure 5,
Figure 8 is a side view of a further embodiment of the
wheel retraction locking mechanism, with one crank arm
shown in plan at Figure 8a, and
Figure 9 shows details of the independent,
subsidiary locking mechanism for the retraction
mechanism of Figure 5,
Figure 1 illustrates a steered forward wheel 10 of
a medium speed amphibious craft which wheel is
retractable into a compartment 1~ in the craft. The
wheel is supported by a wheel support mechanism 12 and
is rai~ed into the compartment for storage and lowered
for road use by means of a retraction mechanism 14.
As will be seen in Figure 1 and 2, the wheel
support mechanism includes a pillar 15 which is
pivotally mounted at the upper end to the craft. In this
case the pillar is mounted via a pivot 16 to a bracket
18 fixed to the inner wall 20 of the compartment. In
this particular craft the inner wall of the compartment
is part of the hull stress-bearing structure. The lower
end of the pillar 15 is also pivotally mounted via a
WOg3/15g23 21 2 9 S 5 1 PCT/GB93/~269
similar hinge pivot and bracket ~not shown). A collar 22
is fitted on the pillar 15 to be slidable up and down
the pillar and rotatable with the pillar. In this case
the section of the pillar and that of the collar are
both square. However the shape i8 not important so long
as the sections cooperate to prevent relative rotation
between the pillar and the collar.
The wheel 10 is fitted on a threaded stub-axle 24
which is coupled to the collar 22 via an arm 26 which
hold~ the stub-axle 24 out from the bottom of the
collar. The arm 26 is a double bracket construction with
a respective bracket 27 welded to each side of the
collar and the pin 24 is fitted into an infill piece 28.
Any suitable fabricated structure or casting designed to
lS support the stub axle would be adequate as the arm 26 to
replace the brackets 27, for example a box-section. The
collar 22 is moved up and down the pillar 15 by a collar
carrier 30.
The collar carrier 30 (see Figure 4) comprises
upper and lower ring brackets 32 and 39 joined at one
end by a connector bracket 36. A bar 38 is fitted at the
junction between the connector bracket 36 and the lower
ring bracket 34, the bar 38 incorporating a rod 39
protruding from each side. The lower end of a suspension
device 40 is pivotally fitted on each end of the rod 39.
Figure 4 illustrates the assembly of the collar 22
and collar carrier 30, which takes place before the
assembly is fitted to the pillar 15. The top of the
collar comprises a threaded ring 41. The collar carrier
30 is located with its ring brackets 32,34 one above and
one below the collar 22 and iQ held in position by a
first threaded cap 43 which passes through the upper
ring bracket 32 to screw into the threads of the ring 41
and a second threaded cap (not shown) which passes
through the lower ring bracket 34 upwardly to screw into
the bottom of the collar. The inner bore of the caps 43
;
WO93/15923 PCT/GB93~0jO~269
2129851
each have a square section to fit over the pillar 15.
The fitting of the collar and collar carrier
incorporates anti-friction surfaceQ or device~ between
the ring bracket 32 and the collar surface 41 and
between the lower ring bracket 3g and the threaded cap
(not shown). Suitable anti-friction devices include
anti-thrust races, or nylon bushes, or the ball race 95
shown. The wheel can be steered by means of a steer~ng
arm bracket 60 (Figure 2) carrying a ball 62 and fitted
to the pillar 15 by a plate 6g and four setQ of nuts 66,
bolts ~not seen) and spacer~ 68 which are welded to the
pillar. Movement of the steering arm bracket 60 by means
of the ball 62 causes rotation of the pillar about the
pivotal mountings. The collar 22 turns with the pillar
15 carrying the wheel with it. This action is described
in patent specification GB 2,218,0F2. The collar carrier
30 allows the pillar 15 to turn within it on thrust
races such as the ball race 45.
Each suspension device or shock absorber 40
comprises a compression ~pring 42 fitted around a piston
44 and damper 47 in the usual way. The upper end of the
two suspension devices 40 are both hinged to a support
element comprising a rod 48 mounted on and fixed to
travel with a double chain 50. The rod 48 is fitted to
the double chain 50 to be moveable with the chain.
The double chain 50 i8 a strong continuous chain
mounted about two pairs of rotary members in the form of
sprockets 52,54. The sprockets forming each of the
sprocket pairs 52,54 are locked together on a respective
3~ common shaft 55,53 to maintain parallel motion of the
chains to prevent tilting of the rod 98. The shafts
55,53, are supported for rotation on a frame 61. In this
case the shafts 53,55 forming the axes of the sprockets
are mounted vertically one above the other, but this is
not thought to be critical. In fact if a castor or
camber angle is required the axes may be deliberately
WO 93/15923 ~ 1 2 9 ~ 5 1 PCI~/GB93/00269
set not vertically one above the other to create, for
example, a 2 1/2 degree angle between the vertical and
the chains. The pillar 15 would have to be set at a
corresponding angle.
To raise or lower the wheels 10, one pair of the
sprockets 53,55 is driven either clockwise or
anticlockwise by an electrical motor (not shown) causing
the rod 48 to move up or down in a path determined by
the movement of the chains 50 and the position of the
sprockets 53,55. This in turn lifts or lowers the
suspension devices 40 and t~us the wheel 10 and in so
doing causes the collar carrier to move on the pillar
15. The locking of the wheels is achieved in two ways -
firstly the electric motor ~not shown) operates through
a gear box with final drive by worm and wheel which in
certain circumstances can prevent ~ovement of the chain
when the motor is not powered. Secondly, when the rod 48
passes either its highest or lowest point of its path
- and begins the return path it comes up against upper or
- 20 lower abutment block-~ 56,58 which are fitted to the
frame 61 in the path of the rod 48 and which arrest the
rod. The upper blocks 56 are fitted on the return for
the upward travel, far enough beyond the highest
position of the rod 48 so that when the rod is abutted
against the block the weight of the wheel is taken on
the block 56 rather than on the chains 50 or sprocket
teeth 53,55. The blocks 56,58 are shown schematically
in the drawings. In practice they need to be shaped so
that the rod is supported on each side of the suspension
unit mountin~s to permit the two suspension devices 40
to hang and swing freely therebetween. The lower blocks
58 are fitted on the return from the downward travel,
far enough beyond the lowest position of the rod g8 for
the upward reaction force from the road on the wheel to
be taken on the blocks 58 rather than on the chains 50
or sprocket teeth. In both locked overcentred positions
,
W093/15923 PCT/GB93J~69
2129851
the chains 50 will hold the rods 48 firmly against the
blocks, but they will not take the greater part of the
force.
The way that the rotary member i8 turned i8 of some
importance if both upper and lower locking i8 required
because the rotary member has to turn through more than
180. This cannot be achieved for example if the rotary
member is turned by the direct operation of a ram.
Although the primary advantage of this embodiment
0 iB the simple automatic locking system which requires no
mechanical or electrical operation by the driver, there
is subsidiary advantage in that significant variations
in the amount of lift that can be made are achieved by
simply lengthening or shortening the frame 61 (Figure 3)
and the distance between the sprockets 52 and S9.
Furt~ermore the load bearing capability of the mechanism
can be varied by increasing or decreasing the strength
of the components. No redesign is necessary. This means
that the same principle can be used for any hull,
whether it be a shallow hull, or a cathedral, dory of
deep-V section hull, even where the required wheel lift
is in excess of 2'6". The same principle can be used to
lift a pair of wheels and both forward and rear wheels.
Moreover the arrangement can be adapted to cater for
driven wheels as is described hereafter.
The above wheel retraction mechanism has been
illustrated and described in relation to front wheels
which are steered. The mechanism is equally suitable if
there is no steering or for use to raise and lower a
rear wheel.
In an amphibious craft having the wheel retraction
mechanism of Figure 5, for example for a rear wheel..the
wheel (not shown) is fitted on the bolts 71 and driven
by means of a chain drive or shaft (not shown~ in
casing 72. Details of the transmission can be found by
referring to our Patent specification GB 2,219,S55A. The
wo 93/l5g23 2 1 2 9 8 5 1 PCT/GB93/OO~g
~, .
chain casing 72 i8 pivoted at its upper end to a bracket
73 about a pivot 74 and the bracket 73 is fitted to the
inside of an enclosed wheel compartment (not shown)
being part of the hull stress bearing structure. The
wheel compartment is open only at the bottom, and is
disposed inside the mono-coque hull of the craft. The
bracket ~3 has two parallel sides 75 forming a channel
therebetween.
The wheel is raised and lowered by a retraction
mechanism 70 comprising a driven rigid crankshaft
pivoting on t~o bearings 85 supported by bracket sides
75, a pair of crank arms 89 driven by the crankshaft,
and a pintle 81 rigidly mounted between the crank arms
84 and firmly locked to them to form the crankshaft. The
retraction mechanism is connected to the casing via a
suspension system 76 ~ivotally mounted to the pintle 81
and comprising a spring 77 fitted outside a damper 78
and a secondary spring 79. At the upper end the spring
77 abuts a ~pring housing 80, which spring housing
incorporates an aperture allowing a secondary spring and
~; damper mounting 83 to protrude, enabling both the
hQusing 80 and the mounting 83 to pivot on the pintle
81. The spring housing 80 is pivoted to the pintle 81 by
means of two mounting brackets 82 attached to the upper
end of the ~pring housing 80. The crank arms 89 form
the "~upport element" of the claims.
The crankshaft is fixed to a rotary member in the
form of a sprocket 87 and driven from an electric motor
89 via sprocket 88 and a drive cbain 86 . The crank arms
84 are rotated through an arc defined by abutment stops
90,91 (described hereafter) by rotation of the shaft.
Movement of the~chain 76 turns one arm 84 via the
sprocket 77, and the second arm follows. The pivotal arc
of the crank arms 89, shown in Fiqure 6, is from a
lower, hatched position against a stop block 90, through
a lo~est position, through the bracket channel between
WO93/15923 ' ; ' ' PCT/GB93~00~69
2129851
the sides 75, through a highest position, and after a
downward return, to an upper stop block 91. As the
support element 84 rotate-~ between the limiting stop
blocks 90,91 (Figure 6), the chain casing 72 and wheel
are raised or lowered via the suspension system 76. When
the wheel is overcentred in its lowered position, ~the
support element shown hatched in Figure 6), the upward
force i3 shared by the stop block 90 and the pivot
bearings 85. When the support element is rotated to its
upper position, it is again overcentred against the stop
block 91. In this position any downward loads are shared
by the block 91 and the pivot bearings 85, rather than
loading the chain or motor. The angle of rotation of the
crank arm between stop blocks is more than 180 degrees.
A rectangular or square-section locking element or
bar 94 has a yoke 95 the-elements of which are pivoted
to the pintle 81 between the spring mounting brackets 82
and the webs of the crank arms 89. A roller 96 ~Figure
8) is fitt2d to the free end of the bar 94. Either
integral with the bracket 73, or separately adjacent the
bracket 73 there is a substantially vertical pa~sage 97
formed by a rectangular or square section tube 98 in
which slides a locking block 99, operable from the
cockpit via a link 101. The link 101 (Figure 9) may be
operated from the cock-pit via a lever syqtem including
rods, pivots and/or cables. The passage 97 has a through
opening 102 at a position substantially in a horizontal
line with the shaft bearings 85 and the single end of
the locking bar -is supported by a sleeve in the form of
a a pivoting sliding trunnion 103 hinged to pivot on
pins 104. As the crank arms rotate, the bar 94 slides
through the rectangular-section trunnion 103 and through
the opening 102 in the tube 98 to cross the passage 97.
The tube 98 is fitted to the bulkhead of the craft by
means of brackets 105 which support the trunnion 103 at
the pins 104. The locking block 99 (Figure 9) comprises
~WO93/15923 212 9 ~ PCT/GB93/~269
11
a wedge-~haped body 107 which can roll or ~lide in the
tube 98 via two pairs of small wheels or rollers 108
disposed in respective recesses 109. The body i9
essentially of the same section a~ the tube 98 but with
it~ leading and trailing edges curved. At the upper end
the locking block 99 is pivoted to the operating link
101 via a through bore 111.
When the crank arms 84 are in either extreme
position, i.e. against a block 90,91, then the locking
bar 94 is at its outermost position leaving the passage
97 free for the lock to pass to the bottom of the tube
98 behind the bar. In this position the locking bar 94
is prevented from passing through the passage 97 as the
roller 107 at the rear end of the bar engages the
locking block 99. The position of the locking bar is
then fixed until the locking block 99 is wi~hdrawn. Thus
the work of the stop block 90,91 is xeinforced by the
locking bar 94. To release the locking bar, when the
wheel is to be moved, the sliding lock 99 is raised by
an upward force on the link 101, which pulls the lock 99
out of the path of the locking bar 94 and thus leaves
the locking bar free to move throuclh the passage 97 and
thus enabling the crank arms 84 to turn. When the arms
8~ have reached their other extreme position the locking
bar is once again outside the opening and out of the
passage and the sliding block 99 may again be lowered to
lock the wheel position. The path of the roller 96 as
the cank arms turn is shown in Figure 8 at "B". The
location and positioning of the safety lock mechanism is
important. A line "A" is defined by the longitudinal
centre line of the bar 94 when the roller 96 is at its
furthest distance ~rom the tube 98. The locking tube 98
is mounted substantially at right angles to the line
"A". The geometry of the locking bar and crank arms is
such that the shortest line joining the axis of the
bearings 85 to the axis of the roller 96 is also line
W093/l5923 PCT/GB93/0~9-
21298~1 ` `
12
"A". This line not only ioins the central crank shaft
pivot 85 to the centre of the opening 102 but it also
equally divides the angle of movement e between the
- upper and lower positions of the locking bar
longitudinal axis.
Although the primary locks are described above as
blocks 90,91 which the arms engage, in a second
embodiment shown in Figure 8 the bracket sides are
shaped with two abutment surfaces 112 and the crank arms
have rear extensions 113 each of which carries a stop
block 114 which engages with the relevant abutment
surfaces 112.
The bracket sides can be boxed in to provide extra
strength where appropriate, and suggested areas are
lS illustrated at 116 and 117.
In one embodiment (not illustrated), the roller 96
has its axis guided at each end in a respective slot so
that the position of the roller axis changes (as the bar
9g moves between its extreme po~itions ) from one end of
the slot to the other. When the bar 89 is on line "A"
~; the roller axis is also on line "A".
`~ It will be appreciated that the additional security
of the independent locking facility will provide a
; further safety feature for the amphibious craft.
Tertiary locks may be additionally provided if required.
