Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to suspension` systems ~or -t~ains
having a number of successive cars, and arranged to provide Eor a
suitable vehicle inclination matching -track curvature so as to
reduce -the centrifugal acceleration component reacting upon the
floor bearing level of the said cars of the train.
It is applicable -to railway vehicles, more particularly
the so-called articula-ted trains in which -the coupling between cars
prevents relative lakeral movements and the running gear and suspen-
sion components are located within the free space between cars. In
such articulated trains the sets of running gear and suspension are
situated in the space between vehicles, supporting the front ends
of the two adjacent cars. Consequently, the level adjustment valves
associated to each suspension system govern the height of the ends
of both car bodies. Further, in the articulated trains there are
two shafts, one at each end of the train, which only respectively
support the head and rear struc-tures for which the corresponding
level adjustment valves regulate, in this specific case, -the height
of only one car body.
It is well known that one of the factors limiting the
speed of trains on curves is the maximum permissible acceleration
in a lateral direction, to which passengers can be subjected with-
in the bounds of comfort.
Part of the centrifugal accelera-tion is compensated by
canting or sloping the plane of the track, so -that passengers are
only subjected to the centrifugal accelera-tion in the plane of the
canted floor of the cars.
Nevertheless, since the extent of cant has to be limited
to a ma~imum value to allow sharing of the tracks by fast and slow
trains and to allow or the possibility of stopping on a curve,
the angle of cant tends to be insufficient particularly in the case
of fast trains running on lines with limited radius curvesO This
is particularly important in areas or countries
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with an irregular topography.
In known constructiont in addition to the insufficient
cant there is the unfavourable effect of car inclination to~ards
the outside ofthe curve in the event of the suspension being dis-
torted, be~ause it is normally located on a plane considerably
below the centre of gravity of the suspended mass of the cars.
This slope is greater than might be assumed on first
impression, and is an inherent characteristic of each car. It
is defined as a coe~ficient representing the ratio ~hilst the
train is stationary on a canted track, between the angle formed
by the body in relation to the track, and the relevant angle of
cant. In the case of conventional trains the normal value of
the coefficient is 0.4 which means that 40% of the lavourable
effect of the cant is lost, when running with an insufficient
cant of the same magnitude as the said angle~
A procedure for achieving total compensation of the
centrifugal force for the purpose of the passengers,consists in
pendular oscillation of the cars, the longitudinal axis of rot~-
tion being located above the centre of gra~ityn Such perpe~di-
cularly running cars, which have not gone beyond the experi~entalstage, have a number of disadvantayes, of which the most impor-
tant is the lack of stability against rolling0 as the use o
shock-absorbers to correct this defect is translated into delays
on entering a curve.
Other ~nown apparatus employ artificial automatic con-
trol arrangements with centrifugal or other -~ypes of controls,
installed to detect the curve and transmit a signal to servo-
controls which ensure the tilting of thè cars. In spite o the
obvious advantages, they all suffer from delayed tilting on
entering curves~ due to the t;me required to ensure that the
train is in fa~t approaching a curYe and tha~ it is not simply
; an equivalent accidental moYement o the train, and also to the
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time required to product the actual tiltingu
As a solution to the problem, the installation of a
prosrammed computer in the train, following -the track character-
istics, has also been tried. However, this solution raises the
cost of the solution even further, owing t:o the particularly
hi~h inherent complexity.
According to the present invention, there is provided
a pendular suspension system for use in a train having a plur-
ality of cars, including sprin~s located independently from one
another symetrically on either side of central vertical longi- :
tudinal planes of respective adjacent cars and bearing upon a ::
running gear frame and carrying at least one adjacent car body,
the springs bearing upon a base located above the centre o~
gravity of the body and being able to yield vertically and hori-
zontally in response to unbalancing centrifusal force, the
arrangement being such that an inclination is induced over that
o~ the cant of the body while the train is travelling along a
canted curved path and relative movements tending to be produced
betl~een the body and the running gear are permitted to occur,
the springs being independent pneumatic springs of diaphragm
type having air inlet and exhaust means for level adjustment,
and means operatively associated with the air inlet and exhaust
means for cutting off flow of air therethrough and maintaining
. vertical deflect.ion of the springs and the body being tilted in
response to the centrifugal force arising during travel along
the canted curved path, said means being operative only when the
train reaches a speed above a predetermined minimum, and only
when the track has a sufficient predetermined degree of curva-
ture so as t~ reduce the passenger's awareness of unbalanced
centrifugal force.
Aocording ~o the d~ ~ ance bet~e~n 5p~i~ss th~r 1 i ht
above the centre of gravity, theix flexibility characterist:ics
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etcO, it is possible to achieve, within a wide ma~gin, the most
suitable ratio between required accelera-tion compensation by
tilting and the non-compensated acceleration to be tolerated in
comfort by the coach passenger.
For this application the pneumatic type of spring to
be used is able to be deflected either vertically or laterally
in such a way that the suspended body may tilt in order to par-
tially compensate centrifusal force.
These springs may belong to the suspension of an adja-
cent body or to a common suspension belonging to two adjacentbodies. These springs may also be applied to any type of running
gear either with two, four or rnore wheels.
On running through curved paths or tracks, relative
rotation between -the bodies and their corresponding running gears
are produced about respective vertical axes, so that the springs
already mentioned will have to deflect about said axes and longi-
tudinally thereof to allow for the corresponding movements.
This deflection longitudinally of said axes may also `~
be required even on a straight track while the brakes are applied
in order to resiliently balance the braking torque with the
additional advantage of damping the transmission of vibration.
In a preferred particular application of the system,
a diaphragm air spring on a known Talgo type running gear is used.
References will later be made to other possible ~ersions.
The pneumatic springs, besides the advantage of lack-
ing undesirable "natural vibration" of helical springs, have the
additional advantage of an easy adjustment in heigh~ of the cars
by means of level adjustment valves, also avoiding the tilting of
the vehicles due to unsymmetrical loads.
In the preferred caseJ and following the normal layout,
each spring has a level adjustment valve maintaining the spring
height. ~hen negotiating a curve, the valves close and the
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springs are distortcd vertically until the torque produced by
centrif~lgal force is balanced, thus resulti}lg in the tilting of
the car. In the event of large radius curves as well as lo~
speed running, having little effect on the t:ilt of the car,
the sa~e conditions as for straight-line travel are maintained.
Closure o the valves may he e~fected by electro-
magnetic means controlled by equipment detecting whether or not
the curve radius is smaller than the predetermined limit and
whether or not the speed is in excess of the limit which is
also prede~ermined, for the conditions to ke fulfilled so that
the val~es close.
A number of the advantages of the system can be des-
cribed as rollows:~
The inclination is achieved naturally by flexible dis-
tortion of the springs, not artificially or compulsorily by ~eans
~ of hydraulic cylinders or other actuating media. No additional
; force whatsoever is required to achieve this inclination. The
compressed air consumption is lower than that of a conventional
train with pneumatic suspension, the valves remaining closed wihen
negotiating curves when the highest consump-tion would otherwise
occur.
The inclination is gradual in accordance with the
variation in the curvature of the path being travelled, being
at any moment proportional to the effective centriugal force~
.
The centre of gravity moves outwards to load the wheel
sn that side, thus decreasing tlle risk o~ derailment.
Better ~auge space utilisation is achieved, the possi-
bility of interference on the inside of the curve being eliminated,
}n the event o the coach tilting inward~ If the coach does not
~ilt owing ~o low speed running or the ~rain being stationary,
the suspension spring level valves hold ~t parallel to the track
pl~ner ~his avoiding any interferenc~
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The invention will now be described by way of example
with reference to the accompanying drawings wherein:-
Figure l shows a diagrammatic transverse sectionthrough a rail car of a train fitted with air springs while
running on a straight track,
Figure 2 is also a diagra~matic tranverse section
through the car of Figure l, but on a curve, and
Figure 3 shows an electrical controls diagram for the
train.
A bogie frame or yoke 1 is shown in the form of an
inverted portal, housing wheels 2 supporting vertical arms 4
bearing suspension springs 3, as well as providing access fr~m
one car body of the train to another.
In order to facilitate the manufacture of the yoke,
the vertical arms 4 serving as suspension beariny poirts, may be
made independently. The said arms may be tubular and m~de o~
light alloy, and serve as receivers for the pneumatic suspension
springs 3.
A vehicle body 5 bears (in a manner not shown) on ~he
~20 suspension springs 3. On straight tracks, the body 5 is mai~-
tained at a constant level within a narrow marginl above the
plane of the track, by means of suspension-spring level-valve
controls. When negotiating a curve this occurs al50, provid7ng
the speed remains insufficient to achieve a minimum predetermir.~d
lateral acceleration. This condition applies in the case of
noxmal minimum radius tracks, as well as when the track radi~s
suficiently large to prevent passenger discomfort when travell-
ing at maximum speed on a straight track.
It is therefore necessary to detect the running speed
and the curve raaius, so as to trlgger electro-magnetic ~alves 9
for cu~ting off level~adjustment valves ll when specific values
ave been reached. These valves ll are interconnected as in~
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cated in Figure 3 in known man~er so as to be con-trolled and
compensated, one with another.
Speed can be determined by any known means, such as by
an elec~rical generator 6 located on a wheel shaft, to product
a signal (voltage~ proportional to the speed. On reaching a
given voltage level, a relay 7 closes a switch 13 in the control
circuit, which remains activated in the event that the train
~ reaches a curve having a suitable radius.
: The curve radius is detected ~y -the relative angle
between cars as they enter a curve for instance, using the rela-
tive displacement of adjacent car front ends. On reaching a
minimum stipulated movement corresponding to a particular level
of curve radius, one of a number of swi.tches 8 in respective
curve detectors 10, 10', closes and remains closed pxoviding the
relative longitudinal movemen-t does not drop below a given fixed
minimum value.
In consequence, in ordex that the control circuit be
energised thus actuating the electro-magnetic valves 9-cutting
~: off the le~el adjustment valves 11, the following two sets of
conditions must agree: speed above a given level and curve
radius below a given value. Eithex of these conditions indepen-
dently, is incapable of bringing the control-circui-t into active
co~dition, and thus actuation will only occur when the two sets
of conditions are existing together.
It is taken into account that the association of
energisation of electro-magnetic solenoid valves 9 with the
deactivation of level`control valves 11 as described, may be
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easily reversed in such a manner that when the electro-magnetic
solenoid valves 9 are de-energised, this occurs when the level
adjustment valves 11 are de~activated The difference.lies in
th~ fact that should a ~ailure occur in thP system, such as for
instance a power failure, in the irst case the train is main-
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tained in the curve and on a ~traight stretch so that it stays
parallel with the plane of the track, the level-adjustment
valves staying open, whereas in the second case, the train cants
over in the curves but the springs do not balance possible load
asymmetries on a straight stretch, the leve~ adjustment val~es
11 staying closed.
The curve detectors 10 and 10' may be located respec-
tively at the head and at the rear of the trainO This arrGnge-
ment ensures that the reaction occurs with a minimum delay in
both directions. In order to de~activate the circuit, the rear
detector is used in both cases.
It is important that the circuit activation means that
the level-adjustment valves 11 are cut-off, though this does not
presuppose that the car is tilting at the time nor that it will
only occur in the event of centrifugal force reacting proportion-
~ ally thereto.
; A pair of electro-magne,ic valves 9 for cut~ing off the
suspension springs 3 on a curve preventing any variation in the
air volume contained therein, are shown in Figure 3 interposed
bétween the said springs 3 and associated level-adjustment valves
11 .
The said level-adjustment valves 11 have a timer arrange-
ment (not shown) in accordance with known procedure, allowiny air
discharge after a given delay from the time when a variation in
the air volume contained within the spring begins to be called
for, following a change in load on the relevant spring. In this
~anner, it suffices that the said delay is greater than the
period between variation of the spring-loading to closure of the
~ valves 9, for the springs to perform from the start of the curve
a~ if they had been previously cut off.
The inta~e or diseharge o~ compressed air by t.he springs
~nly occurs if, for reasons o variation in lo~cling, the maximum
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or minimum heights established Eor the springs, are exceeded.
Any variation in loading within the range of the relevan-t limit-
ing heights or levels is not translated into a variation in the
compressed air volume contained within the springs. Each c~r
body will, on a strai~ht stretch, be in an essentially horizon-
tal position, since it can only vary from this position wi-t:~in
this range.
Another possible means of controlling -the start o~
oscillation comprises reduclng the said range to a mi~ute value
and eliminating the delay of the level-adjustment valves 11,
thus ensuring that the compressed air flow is substantially
restricted. In`this manner a slight variation in load woul~ be
detected by the level-adjustment valves 11.
Air would start entering the springs or would be cis-
charged from them at a very slow rate by means of restricto s
tending to delay for a little time the return of the suspencion
to its nominal level~ In the event of a considerable variation
in loading, the air flow allowed through the level-adjustme~t
valves 11 woula also be greater.
~0 On entering a curved portion of track, the suspension
progressively leaves the nominal horizontal plane and compressed
air starts to enter into one spring at a slow rate, also dis-
charging fxom the opposing spring at a slow rate, endeavouring
to restore the suspension to its nominal level though only until
the curve-detector equipment closes the electro-magnetic solenoid
valves~ As a result of a suitable compressed air flow, it is
possible ~o ensure that the compressed air volume contained wi~h-
in the springs only suffers a negligible variation, ~he spri~gs
having performed as if they had been de-activated (locked) ~efore
entering the curve.
The two variations may be considered functionally
e~uivalent, and for ~hat re~a~n-it is only pxoposed to describe
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the procedure for the variant desi~n with delayed operation of
the level-adjustment valves 11D
The complete cycle is as fo~ows:~-
It is assumed that the txain is travelling on a straightstretch at a speed requiring a pendular movement. The voltage
produced by the generator 6 will be greater than the minimum
predetermined value, and the relay 7 will close the switch 13.
The curve detector 10 at the head and the detector 10' a-t the
rear will be irl neutral position and the switches 8 and 8'
therein will open~ The car bodies 5 will have their floors
parallel with the track plane.
On entering ~ curve, the front ends, as well, of course,
as the rear ends, of adjacent car bodies will start approaching
each other on the inside of the curve whilst moving away from
each other on the outside. It is to be assumed that the curve
detectors are designed to operate by the approach of adjacent
detector heads towards each other, in which case the two switches
8 in the detector 10 are located at opposite sides of the train,
so as to be alternatively actuated, depending on whether the
curve is to the left or to the right.
As the train advances through the curve the ~ront ends
approach each other increasingly on the inside of the curve until
the minimum longitudinal displacement at the head of the train is
; reached, at which point one of the switches 8 is closed, thus
energising the circuit and closing the electromagnetic valves 9
pxeventing air rom reaching the pneumatic springs or from being
exhausted therefrom.
.
The level-adjustment valves 11 will be in an air intake
or exhaust position~ Erom the moment of entering the cuxve, and
a certain unbalance is achieved by the rising centrifugal force.
Nevertheless, the air intake or exhaust does not occur because
the delay established for the actuAtion o~ the valves has not
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expired, the electro-magnetic valves 9 being energis~d to pre~-ent
the air movement before the delay expires.
The sprinys will have been airtight from the moment
when the curve was first negotiated, the ~ody inclination being
proportional to the effective centrifugal force applied.
As the track radius is progresslvely reduced u~til a
constant radius is reached, the centrifugal force increases, and
consequently the inclination. C~ntrifugal acceleration differs
for each car negotiating the curve according to the rad~us of
~10 curvature of the particular stretch o-f track. Car body inclina-
tion also differs, with a given degree of relative rotation
between cars, due to the effect of and the increase in track
cant until the constant radius curvature is reached.
In the event of the need to brake on a curve, the
centrifugal force reduces according to speed and consequently
so does the car body incllnation. In the event of speed droppîng
below the minimum established level, the speed detector solenoid
7 is de-energised, the switch 13 opens and .he pneumatic suspe~-
sion functions norma1ly as if the train were on a straight length
of track. The same occurs in the event of a curve radius exceed-
ing the established value, so that switch 8 is unable to close,
and once the valve delay has expired, the train stays parallel to
the track plane, just as on a straight track.
Where, instead of braking, the speed is increased on
the curve~ the centrifugal force is increased correspondingly
with the car body inclination always maintaining the same rela-
tionship between compensated lateral acceleration for a car
incllnation~o '~' and the uncompensated lateral force to -
be withs~ood by the passengers and which distorts the suspension
to produce the inclination of the car bodyO
This relationship is an inherent property of the rail
car design. It may vary suitably by modifying the suspension
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heiyht above the centre of gravity, the distance between springs
etc.
On leaving the curve, the radius reduces progressively
until a point is reached when the head of the train comes within
the limit radius, thus opening the switch 8. The train car
bodies remain inclined since the control circuit stays energised
as one of the switches 8' at the end of the train stays closed,
until the complete train has passed that point.
In the event of the train running in the opposite dir-
ection, one of the switches 8' actives the circuit on enteringthe curve and the appropriate switch 8 is operated on leaving
the curve.
In the event of a curve in the other direction, the
process is exactly the same, with the sole dif~erence that
switches 8 and 8' of the respective detectors 10, 10' for ener-
gising the circuit are those located symmetrically on the oppos-
ing side of the train.
Equally, the curve can be detected by means of the
switch 8 or 8i located on the outside of the curve, instead of
those on the inside of the curve as described, in which case the
switches must close as the distance between front ends is
increased.
Each pair of single symmetrical detectors 10, 10' may
also be replaced by a single detector unit with two switches,
one of which activates the circuit as the distance between ront
ends is reduced (in the event of a curve, towards a particular
side), the other becoming operative as the distance between front
ends is increased ~in the event o a curve, towards the opposite
side).
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