Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to improvements in track
surfacing operations, and more particularly in the tamping
and leveling of a track consisting of rails mounted on
ties having two elongated edges extending transversely of
the rails and two ends extending in the direction of the
rails, the rails and ties intersecting at points spaced in
the direction of elongation of the track and the ties rest-
ing on ballast. The elongated edges of adjacent ones of
the ties define cribs therebetween, and the track is leveled
or graded in relation to a reference system.
In known t~ack leveling methods, the ballast is compact-
ed under the ties, and more particularly under the points
of intersection, by vibratory pressure exerted upon the
ballast under the ties inwardly from the two longitudinal
tie edges whereby the progressively more compacted ballast
raises the track, the track being independently lifted be-
fore and/or during the ballast tamping, if desired, until
it has reached the leveled position determined by a refer-
ence system including a pickup and transmitter of an error
signal for leveling the track in response to the error sig-
nal. While such track surfacing has been found quite use-
ful, the desired degree of ballast compaction under the ties
has not always been achieved.
It has also been proposed to provide mobile track
tamping machines with a tamping tool assembly vertically
movably mounted on a machine frame for tamping a respective
one of the ties, such an assembly comprising a pair of
opposed vibratory tamping tools arranged for immersion
in the cribs adjacent the tie and for reciprocation in the
direction of track elongation,with the tie positioned be-
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tween the opposed tools, and an additional vibratory tamp-
ing tool arranged for immersion in the ballast adjacent the
end of the tie and for reciprocation in a direction trans-
verse to the direction of track elongation. With such an
arrangement, the ballast is "boxed in" between the tamping
tools substantially from the point of intersection of the
rail and tie to the end of the tie, thus preventing the
outward displacement of ballast during the tamping operation.
However, no control over the leveling of the track or the
degree of ballast compaction is possible with such known
track tampers because they neither comprise a leveling re-
ference nor a tamping control.
It is also known to level track solely by tamping the
ballast under the ties. In such track leveling machines,
only opposed tamping tools reciprocated in the direction
of track elongation are used and a control terminates the
tamping operation in response to a reference signal indi-
cating the desired track level. If the track must be raised
to the desired level through a considerable lifting stroke,
2Q such machines also use independent track lifting mechanisms.
However, controlled uniform ballast compaction cannot be
achieved with such machines since the ballast may escape
laterally when the tamping pressure in the direction of track
elongation exceeds a given degree while, in other track
sections, the desired track level has been reached before
the ballast has been sufficiently compacted.
Furthermore, it has been proposed to assure the main-
tenance of a desired track level even under high tamping
pressures by holding the track in position d~ring tamping,
the track holding being so controlled that the track will
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not be raised beyond the desired level during tamping. This
prevents uncontrolled raising of the track but it does not
assure the termination of the tamping when a desired degree
of ballast compaction has been reached.
Thus, conventional track surfacing methods and apparatus
have not been able to assure a desired, preferably uniform
and optimal maximum, degree of ballast compaction under each
tie over a long track section. It is, therefore, ~he pri-
mary object of this invention to obtain such ballast com-
paction, which is particularlyimportant in track sections
designed for high-speed trains.
This and other objects are accomplished by the inven-
tion in a method of leveling a track in relation to a refer-
ence system by holding the track in the leveled position
under the control of the reference system in the region of
tamping, the ballast being pressed against the held track
until it has reached a controlled degree of compaction.
The track is jacked up towards the leveled position and
track jacking is terminated tenths of seconds up to several
seconds before track tamping has been completed, the bal-
last being compacted under the points of intersection of
the ties and rails by vibratory pressure exerted upon the
ballast under the ties inwardly from the two longitudinal
tie edges and preferably from the tie ends. This produces
not only a high degree of accuracy in the track level but
also on optimally and uniformly compacted ballast bed.
Since tamping proceeds always simultaneously with
jacking, track surfacing according to the present invention
does not disturb the position of those ballast pieces whose
sharp edges or corners bite into the underside of wooden
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ties when the track settles on the ballast bed, thus leav-
ing the ballast enmeshed with the ties. This is of parti-
cular advantage in high-speed traffic sections where the
passing trains have strongly settled the track, the method
of this invention providing for the track to be lifted during
leveling with the conventional track lifting mechanism with-
out destroying the intermeshing relationship of the ties
and ballast. Tamping while jacking according to the inven-
tion, the ballast piec~s remain undistur~ed in~heir re-
lationship to the undersides of the ties and are even press-
ed further into the undersides when the tamped ballast
presses upwardly against the held track after jacking has
ceased. This also assures a particularly sensitive approach
of the track to the leveled position since the track is not
torn out of its settled~osition but progressively p~essed
from the settled into the leveled position, which impr3ves
the accuracy of the leveling operation.
A mobile track tamping and leveling machine according
to the present invention combines a known type of a level-
ing reference system and of a tamping tool assembly which
comprises not only a pair of opposed vibratory tamping tools
-~ but preferably also an additional vibratory tamping tool
adjacent the tie end with a track holding device holding
the track at the leveled position controlled by the error
signal from the reference system. Furthermore, a control
regulates the track jacking and the drive means for the re-
ciprocation and for the vibration of the tamping tools so
that jacking and tamping initially proceed simultaneously
but jacking is terminated before ~mping has been completed.
With this combination of structures mounted on the
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mobile machine frame, the track will be leveled automatically
and the ballast tamping will be terminated automatically
when the optimal ballast compaction has been reached, the
machine being readily adaptable by the control to differing
ballast conditions while assuring long-lasting ballast com-
paction.
The above and other objects, advantages and features
of the present invention will become more apparent from the
following detailed description of a now preferred em-
bodiment thereof, taken in conjunction with the single figure
of accompanying drawing.
The drawing schematically shows an embodiment of a
ballast tamping and track leveling machine with a control
circuit 41 for the operation of crib and end tamping tools
8, 9,track lifting and leveling unit 12 and a track holding
mechanism 51. As shown in the drawing, the error signal from
reference signal pickup and transmitter 6 is transmitted to
sum-and-difference amplifier 43 which comprises an adjustable
resistance set to indicate the desired value, the error signal
being compared with the set value in the amplifier. The com-
parison signal is transmitted from amplifier 43 to stepping
switch 44 whose switching steps are adjustable. Depending on
the adjusbm~ of the switch, contact 45 is actuated in response
to the comparison signal received, which contact places the
drives for reciprocation of the tamping tools and for track
lifting and leveling unit 12 into a state of readiness. When
switch 44 moves contact 45 into its lower position, as shown in
FIG. 5, which produces a state of readiness for track lifting,
switch 42 is operated to transmit the comparison or error
signal directly to solenoid valve 47, which preferably is
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a servo valve. This valve is arranged in the hydraulic
supply conduit leading from tank 23 to lifting cylinder 22
and opening thereof permits hydraulic fluid flow to the cy-
linder for lifting unit 12 to raise the track in response
to the error signal. However, track lifting as well as
reciprocation of the tamping tools is effected only when
limit switch 48 affixed to the machine frame in the path of
the vertical movement of tamping tool assembly 7 is tripped
upon lowering of the tamping tools assembly, the limit switch
being connected to relay 49 which actuates control switch
46 in the electrical connection between switch 42 and
servo valve 47. The relay also actuates control switches
57 for operation of the tamping tools so that, depending on
the position of contact 45 controlled by switch 44, servo
valve 47 controlling the track lifting or servo valve 50
controlling the tamping tool reciprocation is actuated.
The machine operation is controlled in the following
manner:
When the comparison or error signal detected and trans-
mitted by amplifier 43 is below the tolerance, i.e. the
switching step, set at switch 44, contact 45 connected to
switch 44 is in the illustrated upper position, placing
the hydraulic supply to the tamping tool drives into a
state of readiness. When the error signal surpasses the set
tolerancej switch 44 moves contact 45 from its upper end
position to its lower end position to close switch 42 and
place the hydraulic supply to lifting unit 12 into a state
of readiness. Assuming control switches 46 and 57 to be
closed upon tripping of limit switch 48 caused by lowering
of the tamping tool assembly, servo valve 47 will be opened
a
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and the track will be raised by unit 12 as long as the
error signal value exceeds that of the set switching step
and until it is equal thereto, after which, i.e. in the
period between the set switching step value and the value of
the desired level, servo valve 47 is closed and servo valve
50 remains open for further compaction of the ballast by
the squeezing tamping tools after track jacking has been
terminated. Closing of valve 47 causes unit 12 to dis-
continue lifting the track, the illustrated dump position
of valve 47 permitting fluid to flow back from cylinder 22
into tank 23 to allow the track to be further raised by tamping.
Track holding mechanism 51 is mounted in the range of the tamping
tool assembly 90 as to prevent the tamped ballast from raising
the track above the desired level determined by the reference
system 5. In the illustrated embodiment, track holding mech-
anism 51 comprises two hydraulic cylinders for vertically mov-
ing the mechanism relative to the machine frame. The mechanism
further includes means engaging the track rails. A fluid
flow blocking device 52 is mounted in the hydraulic conduit
interconnecting the chambers of each of the cylinders of
track holding mechanism 51, this blocking device being actuated
electromagnetically and the solenoid for the actuation of block-
ing device 52 being connected to contact 45 for operation when
the contact has reached the illustrated middle position in-
dicating the desired level of the track, i.e. the track is held
by mechanism 51 at the desired level against further upward
movement by tamped ballast. This avoids excess lifting of the
track beyond the desired level during tamping. When the
tamping tool assembly i5 raised, limit switch 48 will open relay
49, thus opening control switches 57 and blocking device S2.
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As indicated by the chain-dotted lines in FIG. 5, the
amplifier and switches of the control circuit 41 are mounted
on a panel to simplify the operation and possible repairs,
the entire panel being replaceable in case of break-downs.
For an operation not contemplated by the invention, a
throw-over switch 55 is also mounted on the panel in the
connection between amplifier 43 and switch 44, operation of
switch 55 cutting out switch 44 and contact 45 from the control
circuit and transmitting the error signal from the amplifier
directly to servo valves 47 and 50, causing the track to be
lifted solely by unit 12 and not by tamping of the ballast.
A master pressure gage 53, which is preferably assoc-
iated with a pressure indicator, is mounted in the hydraulic
supply conduit for the tamping tool drives so as to make
it possible to obtain and control the desired degree of
ballast compaction by squeezing of the tools. Master switch
56 in the electrical control circuit is connected to press-
ure gage 53, a relay for the actuation of the master switch
being responsive to a set maximum pressure to open the master
switch and thus to interrupt,a direct circuit controlling
hydraulic fluid supply to the tamping tool drives. This
direct control circuit is in shunt with switch 44 and con-
tact 45 so that ballast tamping ~s continued until the set
maximum degree of ballast compaction against the counter
pressure of track holding device 51 has been reached after
the track has been lifted by jack 24. In its simplest,
illustrated form, the master switch is constituted by an
adjustable contact associated with the indicator of a con-
! tact manometer.
After tamping has been completed, the tamping tool
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,assembly is raised and opened limit switch 48 will actuate
relay 49 so as to interrupt hydraulic fluid flow to the
tamping tool drives. The mobile machine is then advanced by
a distance of two ties to start the next tamping and leveling
cycle.
Fully automatic operation of control 41 may be achieved
by connecting the control circuit, and also control l9, if
~ desired, to a suitable programmer 54 operating on an analog
- or digital computer basis, thus relieving the operator of
any control function and enabling him to concentrate on ad-
justing the operating results. Such a programmer will auto-
matically control the degree of tamping, the tamping tool
reciprocating times and pressures as well as the frequency
and/or amplitude of the tamping tool vibrations in response
to data transmitted to the programmer by the pressure adjust-
ment devices and corresponding to the condition of the
ballast. Such data may be stored, for instance, on perfor-
ated bands or cards, or magnetic tapes.
The operation of control 41 may be programmed in a
variety ways but when programmed according to this invention,
jack 22 ceases operation just before tamping has been completed,
the delay between terminating the track jacking, i.e. closing
valve 47, and tamping,i.e. closing valve 50, being of the order
~f some tenths of seconds to a few seconds, i.e. quite brief.
The control of FIG. 5 is preferably programmed to terminate track
jacking before the track has been raised to the desired level
and the final track raising stroke against the limit deter-
mined by holding mechanism 51 is effected solely by the con-
tinuing tamping. In this manner, track lifting unit 12
does not carry the track weight during those final tenths of
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seconds or seconds of surfacing but this weight presses
against the ballast during the final tamping. This downward
pressure aids in more rapidly and effectively increasing the
ballast compaction, and thus improves the quality of the
tamped track. This effect may be further increased, if
desired, by continuing tamping even after the track has been
pressed upwards against holding mechanism 51.
Depending on track conditions, tamping is continued
briefly after termination of jacking either until the track
level determined by holding mechanism 51 has been reached or
even for moments after it has been reached, the interval
between termination of jacking and tamping being varied
according to conditions. As is Xnown, it may be desired in
certain instances, for instance at rail joints, the set track
holdlng mechanism 51 slightly above the final desired level
for the track to give the track a chance to settle to this
level under train traffic immediately subsequent to the sur-
facing operation.
A track surfaced with a tamping and leveling machine
of the above described structure will be much more uni~ormly
tamped than has been possible with conventional machines
and will thus assure greater stability of the graded track.
This will make it possible to increase the length of the
time intervals between surfacing operation so as to obtain
considerable economy in the maintenance of tracks of a
high quality.
This application is related to copending Canadian app~ation
Serial No. 191,604, filed February 1, 1974.
