Note: Descriptions are shown in the official language in which they were submitted.
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A Transmisslon System for a Transfer Device gripping'a Double
Wheel ;
The ob~ect of the invention is a transmission system ~or a
5 transfer device gripping a double wheel, wh$ch tran~fer device
is intended to move an aircraft or other device equipped with
double wheels over a base, and which transfer device includes at
least two friction rollers and motors to rotate them, that is,
ono for each wheel of the device to be moved, a friction roller
10 to be pressed against this, and compression devices to create
the pressure, and the system also includes a power device and
power transmission device~ to feed the driving force to the
motors Here the term double wheel also means the neighbouring
wheel~ of a bogie
lS
The construction o~ a trans~er device can be considerably ~ ~ ;
lightened lf the driving ~orce is transferred to the wheel of
the aircra~t ~rom a drive wheel or ~riction roller ~orming part
of the trans~er device A construction for a trans~er device - ;
20 that i~ universally applicable is ~hown in the Finnish Patent
Applloatlon FI 833275 (partly correopondlng to W085/01265) Thls
doe~ not requlre any contact with the undercarrlage o~ the
alrcraft in order to pres~ the drlve wheel against the ground
wh--l The oompr-~-ion i~ aohl-v-d by mean~ o~ th- mutual ~
25 mov-m-nt o~ compr-~lon roll-r~ oonnected by an lntermediate i ;
momber
In lt- most common form the intermediate member pulls the two
oompresslon rollers connected by it towards one another, when
30 they are pressed agalnst the ground wheel between them At least
one of the compressed wheels is now a friction roller or drive
wheel which transmits rotational force to the ground wheel o~
the alrcraft Other transfer devlces belonglng to the area o~
the lnvention~are ~hown in Finni~h Patent Applications FI861714, ;~
3S FI870313, and FI870710 In practice nearly all aircraft are
equipped with either double wheels or even larger bogie wheels
It is therefore natural to make the transfer device such that it
grips a double wheel, because then the force acting on the large
tyre can be reduced Trans~er devices equipped with a so-called
40 self-wedging friction roller are not advantageous in relation to
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202~8~
thi~, because they stress the ground wheel Or the aircraft
considerably more than a transfer device that qrips both wheels
with two or more friction rollers In any event this invention
can also be applied for example to a transfer device in
5 accordance with application FI870710, which shows a self-wedqing
trans~er device that grips a double wheel, and in which both
friction rollers are eguipped wlth their own motor and gearbox
A transrer device that grips double wheel~, e~pecially the nose
10 ground wheels, i~ shown in US patent publication 3,005,510 In
this neighbouring bogie wheels are driven by means of two
rriction tracXs, WhiCh are wedged between the two in-line bogie
wheel~ ~he hydraulic transmission includes both a direction
switch valve and a flow distribution valve, by means o~ which
15 the flow going to the rlght and lert side hydraulic motors can
be ad~u~ted The ad~u~tment take~ place by means o~ two
r-~trlotion polnt- that are connoet-d to one another, ~o that
wh-n th- ono deoreas-~ in ~iz- th- oth-r increa~e~ ~y mean~ o~
thi~ the no~e bogle wheels can be made to turn by restricting
20 th- flow going to th- hydraulic motors on one side at the same
tlme a- the re~trictlon on the other slde i8 lessened
Thi- invention i~ e~peoially related to such transrer devices in
whieh th- transfer tak ~ plae- only from one of the main
25 underearriage bogi-~ ~hi~ in it~-lf i- som thing new, becau~e
ln aeoordanoe with th- ~tate o~ th- art th- drive ha- alway~
b--n ymm-trlcal Asymmetrical driv- gives the aircrart a
turning fore-, whioh normally i~ of no consequenee as the
alreraft can be steered in the deslred direetion by means Or the
30 nose wheels Problems may appear in certain special
circumstances In terms of friction conditions an icy and snowy
airfield in winter is totally different from a dry asphalt
~urfaoe in summer In addition a ~trong ~ide wind may increase
the force turning the aircraft Practical experiments hav- shown
35 that moving an empty alrcrart on a very slu~hy alrfleld is
extxemely difficult One tyre of the double wheel may rise by
itself to carry in which case the other is able to rotate
freely Another phenomenon of the same kind appears on an icy
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air~ield when one o~ the wheels being driven begin~ to slip on
the ice All the hydraulic motors that are connected in the same
circuit lose their feed pressure, because the flow leaks through
the motors that are driving the slipping wheel Another seriou~
5 disturbance ari~es lf the nose wheels begin to slide laterally
Twisting then takes place around the undercarriage beside that
being pushed as lt remains in place
The intention of this invention i8 to achieve a transmission
10 eystem ~or a transfer device driving double wheels that will
creato a ~table push, even though the driving point used is the
main undercarriage that is located in a dif~icult position to
th- side o~ the centre line of the aircraft The characteristics
of the invention appear in the accompanying Patent Claim 1 The
15 main principle o~ the invention is to ~ynchronize the operation
o~ the variou~ motor~ and corr-~ponding ~riction rollers This
malnly mean~ that th- friction roller~ are locked to the ~ame
phas- and p--d o~ rotation I~ one o~ the wheels begin~ to
olip, th- ~riction roller o~ the wheel beside it continue~ to
20 drive Thi~ ~ame loo~ing also limit~ ~ide 81ip in the nose
whe-l-, because the neighbouring ground wheel~ have to turn at
di~-rent rotational speed~
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Th- ~orm ot application in aocordance with Patent Claim 2 i~ the
25 lmpl--t solution to th- problem o~ creating looking in a
hydraulio tran~mi~lon The di~tribution valve~ ~u~t absolutely
be pr-o~ure oomp-n~at-d 80 that the ~low i~ not able to esoape
through the motor o~ the wheel that i~ rotating ~reely A more
r-llable locking operation that the above is achieved by
30 implementing the system in accordance with Patent Claim 3, in
which case the synchronization o~ the motors as realized through
the op-rating components is considerably more pr-cise than the
~ormer The turning of the device to be moved while it i~ being
mov-d i8 made possible by lmplementing th- ~y~tem in accordance
3S with Patent Claim 4 Thls is especially important in connection
with a trans~er device equipped with two pumps and entirely
separate circuits, but it is also use~ul in connection with
hydraulic circuits created with flow distribution valves The
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invention can also be adapted to operation with electri¢
transmi~sion. The control of electric motors i~ most
advantageously based on frequency trans~ormer technology and the
entire system can be based on diesel-electrlc transmis~ion.
The ~orm o~ application in accordance with Patent Claim 7 makes
lt possible for the turning moment created by the one-sided push
Or the new method to be cancelled. In addition to the pushing
~orce a turning ~orce is al50 developed by the trans~er device,
10 which cancel~ either entirely or in part the turning ~orce given
to the aircraft by the pushing force. A braking device is most
easily created in a hydraulic system e,quipped with two pumps by
setting the pumps asynchronously, l.e. 80 that the output of the
one pump is set to be less than that o~ the other.
In what ~ollows the invention is illustrated with the aid of
example~ by re~erence to the accompanying ~igures, which show
variou~ ~orms o~ application of the invention.
20 Figur- 1 ~how~ the u~e of the tran~er device in moving an
airara~t
Figur- 2 shows the transfer device in the operating
position seen ~rom above
Flgur- 3 how~ the hydraulic transmission sy~tem o~ a
trans~er device in accordance with Figure 2 a~ a
whematlc diagram
Figure 4 shows a flow distribution valve in cross-section
Fiqur- S shows another hydraulic transmission oystem a~ a
6chematic diagram
In the situation shown in Figure 1 the transfer device 20 is
pushing aircraft 1 ~rom the right-hand main undercarriage 21, in
which there is a double wheel. The push causes a turning moment
around the le~t-hand undercarriage, which moment i~ cancelled by
3S the nos- wheel 22 o~ the aircra~t. Figure 1 includes an arrow
showing the pushing ~oroe o~ the tran~fer devic- and a broken
line showing the counter moment that arises in one form of
application, which cancels the force turning the aircraft. ;;
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During the transfer the aircraft 1 i8 steered by turning the
nose wheel 22 in the desired direction.
In Figure 2 only the undercarriage and ground wheels 6 of the
S airoraft 1 are shown. The transfer device moves on its own
wheels and in addition to them the principal components are
friation roller~ 3 and 4, the hydraulic motors 5 that drive them
together with gearboxes and power unit, which includes a
hydraulic pump unlt driven by a diesel motor.
~oth ground wheels 6 have their own friction rollers 3 and 4,
both o~ which are driven by hydraulic motor 5. The front
friction motor~ 4 are arranged, in a known manner, to be turned
to the sid-, so that the transfer device can mov- around the
15 ground wheels 6 of the aircraft 1. The ~upport o~ the front
roller 4 io arranged by mean~ o~ ~liding member 7, which is
moved by means o~ hydraulio oylinder 7 and which in ito extreme
posltion is also allowed to turn. Figure 2 shows the ~ame stage
in pu~hing as Figure 1.
The prlncipal components of the hydraulic transmission sy~tem in
Flgure 3 are the pump unit drlven by diesel motor 8, the
hydraullc motor- 5, and pre~sur- compen~at-d ~low di~tribution
valve~ 10. ~he pump unit includes a high pressure pump 9 and its
25 feed pump and lubricating oil oystem. Changes in direction and
g-aring ~ake place by altering the ~troke capacity of the high
pre~sure pump 8 and the direction of the flow. The motor~ 5 are
divid-d into two qroupo by means of the tlow distribution valves
10. One group drives the right-hand and the other the left-hand
30 ground wheel 6. The ~low distribution valves 10 really only
operate in one direction, in the reverse direction they permit
a free flow. On account of this two o~ them are requlred, one
for each direction.
35 Figure 4 shows the construction of a pressure-compensated ~low
distribution valve 10 in detail. The pipe coming from pump 9 is
oonneoted to connection 11 and the pipe~ coming ~rom the motor~
5 are connected to connections 12. The principal directions o~
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flow are marked with arrows in Figure 4. Pressure compen~ation
i9 arranged by the spindle 13, which i~ arranged to be moved.
Reverse flow takes place with practically no obstacle through
valves 14. In the sy~tem shown in Figure 3 one ot the steady
S ~low valves 10 divides the ~low precisely into two parts and the
other collects ~lows to pump 9.
Moro precise synchronization than the above i~ achieved by the
two pump system shown in Figure S. In this both of the
10 atorementioned motor groups use their own pump lS. The ~peed of
revolution of both is the same and the ad~ustment levers are
combined to be turned synchronously in normal conditions. In
good conditions valve 19 i~ kept open, 8e that thero i~ no
locklng between the right and lett-hand ground wheel~ the
15 alrtleld 1~ lcy or ln windy weathor valve 19 i- clo~ed, when the
ynchronous operation of the motors S tries to keep the aircraft
tralght. By etting the ad~ustment levers oS the atorementioned
pump- lS to ditterent position~ one begins to have a greater
output than the other. The motors S in the ¢ircuit with the
20 small-r tlow begin to have a braking etfect. It th- braking
olrcuit connects in the ~ituation in Pigure 1, i.e. in the
~ltuation ot the tran~er d-vice pushing trom the right-hand
~id-, to the right-hand ground wh--l 6, the turning moment
cr-ated by the pu-hlng torce created by the transter device 20
25 cancel- the moment. This ~ind o~ moment cancellation i~
nec-ssary tor example when moving relatively long types ot
airoratt on l¢y air~ield~ and in windy weather.
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