Note: Descriptions are shown in the official language in which they were submitted.
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RAILWAY BALLAST EXCAVATOR HAVING INCLINED PORTION
Field of the Invention
The invention relates to the excavation of ballast from beneath railway tracks
and the simultaneous elevation and piling of excavated ballast alongside the
railway
track. More particularly, the invention relates to an apparatus and method of
excavating railway ballast for the purpose of repairing small sections of
track using a
mobile endless-chain type excavator having a horizontal portion for excavating
the
ballast and an inclined portion for elevating the excavated ballast.
Background of the Invention
Railway lines generally comprise a set of spaced apart rails mounted on a
plurality of transversely placed railway ties that are located upon a bed of
compacted
ballast material. The rails, ties and ballast must be routinely replaced and
machines
for removing, cleaning and replacing ballast, such as described in US Patent
5,090,484, are known in the art. However, these machines are large and not
particularly well suited to removing ballast from relatively small sections of
track or for
repairing a portion of a track.
United States Patent 6,862,822, issued on March 8, 2005, discloses a mobile
railway track repair apparatus having an endless-chain excavator mounted on
the end
of an articulated arm of a conventional excavating vehicle. The endless chain
conveyor may be positioned at any desired angle or orientation beneath the
track and
may be readily replaced by a conventional excavating bucket. This apparatus is
limited in that ballast material can only be excavated from the immediate
vicinity of the
excavating vehicle and, since these vehicles are quite heavy, this can cause
track
instability resulting in misalignment and the need for extensive repair.
Moreover, when
the excavator is fully inserted beneath the tracks, excavated ballast material
accumulates immediately behind the excavator and must be dislodged in order to
remove the excavator. This spreads the material around in the vicinity of the
tracks,
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making it difficult to collect and remove at a later time. Although the
apparatus is
suited for small track repairs, the apparatus cannot be operated continuously
along a
small section of track, such as a siding.
United States Patent 3,967,395, issued on July 6, 1976, discloses an endless
chain excavator mounted to the front of a forklift vehicle. The excavator can
move
vertically along a vertical slide and can be rotated about a vertical axis.
The vehicle
must be driven toward the tracks from the side thereof in order to insert the
excavator
beneath the tracks and must be re-positioned when the ballast material has
been
removed. The excavated material accumulates behind the apparatus; the material
must therefore be dislodged as the apparatus is removed, with the
disadvantages
described above, and driven over by the forklift vehicle as the apparatus is
advanced
beneath the track. The apparatus is not suitable to continuous operation along
a small
section of track.
United States Patent 3,436,848, issued April 8, 1969, discloses an endless
chain excavator apparatus mounted on a railway vehicle for continuously
removing
ballast along a small section of track. The excavator may be moved
transversely to
the track using a horizontal screw mechanism and may be pivoted about a
vertical axis
to move from an orientation parallel to the tracks to an orientation
perpendicular to the
tracks. The apparatus is vertically moveable using a parallelogram linkage.
The chain
excavator extends under the full width of the tracks and can be used to
excavate
ballast from beneath an adjacent set of tracks, such as a siding. However, the
apparatus suffers in that accumulated material is deposited immediately
adjacent the
end of the chain excavator and hampers excavation of additional material. The
excavated material must therefore be manually dislodged or accumulated
simultaneously with excavation using a separate apparatus adapted for that
purpose.
This is operationally cumbersome and requires additional labour and equipment.
Moreover, the apparatus is vehicle mounted and neither the apparatus nor the
vehicle
can be readily removed from the railway tracks. This can pose a problem in the
event
of an oncoming train, even if the train is on an adjacent set of tracks.
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United States Patent 6,698,115, issued on March 2, 2004, discloses a mobile
track maintenance machine having a clearing chain for excavating bulk material
that
has a universal joint between each link of the chain. The chain has an
ejection end
positioned above a receiving end of a conveyor belt for transporting the
excavated
ballast and is guided to the ejection end in a curved guide track. The
ejection end is
oriented rearwardly of the excavating section of the chain and does not
discharge
material alongside the railway track in a direction parallel with the
excavating section.
The ballast material is not deposited in a pile but instead is simultaneously
transported
with the conveyor belt to a bulk material loading wagon coupled to the
machine. This
requires periodic emptying of the bulk material loading wagon and is
operationally
cumbersome as compared with simply depositing the material in a pile. Also,
the
excavating chain apparatus is mounted to a railway vehicle and neither the
apparatus
nor the vehicle can be readily removed from the track in the event of an
oncoming
train.
It would be desirable to provide an apparatus for excavating railway ballast
from
beneath a set of railway tracks that may be moved along a railway track for
continuous excavation of a small section of track and that is readily
disconnected from
the motive vehicle in order to permit both the apparatus and the vehicle to be
removed
from the set of tracks in the event of an oncoming train. It would be further
desirable
to provide a railway ballast excavating apparatus that also elevates the
excavated
material to facilitate pile formation alongside the track to alleviate the
need for
simultaneous removal of excavated ballast while permitting the ballast to be
readily
removed at a later time. However, no such apparatus is currently available and
the
need currently exists for an improved railway ballast excavating apparatus
having
some or all of the foregoing features.
Summary of the Invention
According to the present invention, there is provided an excavating apparatus
for excavating ballast material from beneath a railway track and for elevating
the
excavated ballast material, the apparatus comprising: a frame having a set of
railway
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wheels thereunder; and, an excavating unit laterally adjacent the frame, the
excavating
unit comprising an endless excavating chain mounted on a guide frame having a
first
portion and a second portion parallel to and inclined from the first portion,
the second
portion having an inclination angle relative to the first portion, the second
portion for
elevating and depositing excavated ballast in a pile adjacent the railway
track.
According to the present invention, there is further provided a system for
excavating ballast material from beneath a railway track comprising: a motive
vehicle
comprising a rubber-wheeled excavator having a set of selectively deployable
railway
wheels and an articulated arm; an excavating apparatus comprising a frame
having a
set of railway wheels thereunder and comprising a connection means for
releasable
connection with the articulated arm of the motive vehicle, the excavating
apparatus
further comprising an excavating unit laterally adjacent the frame, the
excavating unit
comprising an endless excavating chain mounted on a guide frame having a first
portion and a second portion parallel to and inclined from the first portion,
the second
portion having an inclination angle relative to the first portion, the second
portion for
elevating and depositing excavated ballast in a pile adjacent the railway
track; and,
wherein the motive vehicle is operable to move the excavating apparatus
longitudinally
along the track, to lift the excavating apparatus from the track and deposit
the
excavating apparatus adjacent the track, and to drive off of the track by
selectively
raising the railway wheels.
According to the present invention, there is yet further provided a method of
excavating ballast material from beneath a railway track comprising: providing
an
excavating apparatus comprising a laterally adjustable excavating unit
comprising an
endless excavating chain mounted on a guide frame having a first portion and a
second portion parallel to and inclined from the first portion, the second
portion having
an inclination angle relative to the first portion; transversely positioning
the first portion
of the excavating unit at a first operative position beneath the track; and,
operating the
excavating unit to remove ballast material from beneath the track using the
first
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portion, to elevate the ballast material using the second portion, and to
deposit the
ballast material in a first pile adjacent the railway track.
The frame may comprise a vertical slide for positioning the excavating unit at
a
desired height. The frame may comprise a knuckle having a vertical pivot axis
5 therethrough that may be operable using, for example, hydraulic cylinders to
open and
close, thereby pivoting the guide frame of the excavating unit about the
vertical pivot
axis. This allows the guide frame to be moved from a transport position
parallel to the
tracks to a working position transverse of the tracks. The frame may further
comprise
a horizontal slide oriented transversely to the railway track and the
excavating unit
may be mounted to the frame to permit the excavating unit to be placed at any
desired
transverse position relative to the railway track. The frame may further
comprise a tilt
mechanism that permits the guide frame to adopt any desired angular
orientation
relative to horizontal. This permits the guide frame to be inserted beneath
the tracks in
one orientation, then allows the orientation to be adjusted in response to
excavating
conditions, obstacles, etc. The frame may include any of the foregoing
features alone
or in combination and permits the excavating unit to be adjusted in height,
horizontal
position, parallel or transverse relationship with the tracks, and/or angular
orientation
relative to the tracks.
The apparatus lacks its own source of motive power and is moved along the
railway tracks using a motive vehicle. The motive vehicle is preferably a
rubber-
wheeled excavator having a set of selectively deployable railway wheels. The
motive
vehicle may be connected to the apparatus using one or more of a variety of
different
means, such as a tow bar, push bar, etc. Preferably, the motive vehicle is
releasably
connected to the apparatus using a connection means that is adapted for
receiving an
articulated arm of the motive vehicle. The connection means may comprise a
cradle
for receiving an excavating bucket attached to the end of the articulated arm.
The
cradle may comprise fore and aft transverse frame members that engage with the
excavating bucket when the motive vehicle is moved along the tracks to cause a
corresponding movement of the apparatus. The cradle may include clamping means
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for securing the bucket within the cradle or the bucket may be unsecured and
maintained within the cradle through downward pressure applied using hydraulic
cylinder mechanisms of the articulated arm.
The apparatus may be powered using a hydraulic motor or motors that may be
releasably connected to a source of fluid power on the motive vehicle using
suitable
fluid conduits. The releasable connection between the articulated arm and the
frame
and between the source of fluid power and the hydraulic motors) permits the
motive
vehicle to be readily de-coupled from the apparatus. In the event of an
oncoming
train, it is often desirable to remove the apparatus from the tracks to
prevent potential
damage to either the train, the apparatus, or the motive vehicle. In the prior
art, it has
been necessary to move the apparatus along the track until a siding has been
reached
that permits the apparatus and motive vehicle to be moved off-line. In the
present
invention, the releasable connections permit the apparatus to be readily
lifted from the
track using the articulated arm of the motive vehicle and set alongside the
tracks. The
railway wheels may then be raised, permitting the rubber-wheeled excavator to
be
moved off of the tracks alongside the apparatus. When the train has passed,
the
apparatus may be again positioned on the tracks using the excavator and work
may
be resumed. This saves a tremendous amount of wasted time as compared with
prior
art ballast excavating machines.
To facilitate removal of the apparatus from the track, the apparatus may be
equipped with a central lifting lug that provides a central connection point
for the
articulated arm. The apparatus may be equipped with ballast weights on the
opposite
side of the frame from the excavating unit to provide stability during cutting
operations.
These weights may be removed prior to lifting the apparatus from the tracks to
reduce
the overall weight being lifted. The allowable maximum weight of the apparatus
depends upon the lifting capabilities of the motive vehicle; however, it has
been found
that for most excavating vehicles of the size utilized in railway ballast
excavating
operations a maximum total weight of 11,000 Ibs is desirable. It is desirable
that the
apparatus be somewhat balanced while lifting and the frame may be devised in
such a
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manner as to balance the weight vis-a-vis the position of the central lifting
lug so that
the apparatus does not tip during lifting.
During ballast excavation, debris may have a tendency to accumulate within the
guide frame behind the excavating chain. The apparatus may desirably be
equipped
with debris clearing holes in the guide frame to permit the debris to
naturally fall out of
the guide frame and to permit debris to be readily cleared from the guide
frame using a
high-pressure water spray or jet of compressed air. The accumulation of debris
can
significantly affect the overall weight and balance of the apparatus and the
removal of
debris is desirable in facilitating the removal of the apparatus from the
railway tracks.
In operation, the excavating unit is first moved to a desired location with
the
guide frame of the excavating unit oriented parallel to the railway track. The
horizontal
slide is then operated to move the excavating unit transversely away from the
track.
The excavating unit can then be lowered to a desired height relative to the
track and
the excavating chain can begin to operate. The angular orientation of the
guide frame
may optionally be adjusted if desired. The knuckle is then used to pivot the
excavating
unit about a vertical pivot axis, bringing the guide frame from an orientation
parallel
with the tracks to an orientation transverse to the tracks. As the excavating
unit
engages the ballast during pivoting movement, ballast is removed using the
excavating chain and the guide frame is permitted to be inserted beneath the
tracks.
The motive vehicle is then operated in reverse to move the apparatus slowly
along the
railway tracks with the excavating chain continuously removing ballast
material as the
apparatus travels.
In the prior art, excavated material quickly accumulates in the vicinity of
the
outward end of the guide frame, which interferes with the rate of excavation,
increases
the likelihood for damage to the apparatus, and limits the amount of material
that can
be removed in each transit of the apparatus along the tracks. To overcome
these
disadvantages, the present invention is equipped with a first portion and a
second
portion that is parallel to the first portion but inclined thereto. This
second portion
serves to elevate the excavated material and deposits the excavated material
in a pile
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alongside the railway track. The angle of inclination in some part depends
upon the
amount of material desired to be removed in a single transit of the apparatus
along the
tracks. If the full width of the tracks is to be excavated in a single transit
(which
normally results in a first portion length in excess of 13 feet), then a
greater angle may
be required as compared with an excavating unit having a shorter first
portion.
However, larger inclination angles have the disadvantage of losing more of the
excavated material while elevating, causing the pile to be spread out
alongside the
tracks and generally reducing the efficacy of the second portion. It has
surprisingly
been found that only a small angle is required for proper pile formation, even
during
full-width cutting operations. The second portion may be inclined with respect
to the
first portion at an angle of from 10 to 45 degrees, preferably from 15 to 30
degrees,
more preferably from 20 to 23 degrees, yet more preferably about 22 degrees.
A further benefit of using the smallest allowable inclination angle is found
in the
excavating chain. Since the excavating chain is required to deflect upwardly
as it
travels from the first portion to the second portion, the excavating chain may
be
provided with one or more universal joints between each link. The universal
joints may
comprise a semi-spherical eye within a complementary bearing race that permits
the
normally vertical pivot axis between each link to deflect to an angular
orientation as the
joint passes from the first portion to the second portion. As the inclination
angle of the
second portion increases, so too does the required deflection of the universal
joint. In
order to keep the chain as robust as possible, it is therefore desirable to
utilize the
smallest allowable inclination angle in order to reduce the required
deflection of the
universal joint. The use of a joining link having two universal joints between
each
excavating link is desirable in that it allows the deflection angle of each
individual
universal joint to be further reduced.
Each excavating link of the excavating chain may comprise an outwardly
projecting excavating lug having a row of horizontally and vertically spaced
apart
excavating teeth. The individual teeth may be angled with respect to one
another.
The row of teeth may form an inclined row angle relative to the direction of
movement
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of the excavating chain. The row angle may correspond to the inclination angle
of the
second portion so that when the excavating link is on the second portion, the
row is
substantially horizontal. This facilitates elevation of excavated material
using the
second portion, thereby reducing the tendency toward pile spreading and
further
reducing the allowable inclination angle. The row angle may be from 10 to 45
degrees, preferably from 15 to 30 degrees, more preferably from 20 to 23
degrees, yet
more preferably about 22 degrees.
In the present invention, it is desirable that the second portion is
substantially
aligned with the first portion. This causes the second portion to eject
material
transversely of the railway track during operation of the excavating unit. If
the second
portion were not parallel with the first portion, the excavated material would
have a
tendency to be ejected from the first portion and not elevated using the
second portion.
Prior art devices have utilized a curved guide shield to prevent this ejection
of material;
however, a guide shield simply causes the excavated material to accumulate at
the
curve, reducing the throughput of the excavating apparatus and increasing the
likelihood for excavated material to become lodged, resulting in mechanical
failure. By
keeping the second portion substantially parallel with the first portion, the
need for any
guide shield is reduced and desirably eliminated.
Further features of the invention will be described or will become apparent in
the course of the following detailed description.
Brief Description of the Drawings
In order that the invention may be more clearly understood, embodiments
thereof will now be described in detail by way of example, with reference to
the
accompanying drawings, in which:
Fig. 1 is a side view of an embodiment of a system according to the present
invention in operation on a railway track;
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Fig. 2 is a top view of an embodiment of an apparatus according to the present
invention showing the excavating unit in the transport and operating
positions;
Fig. 3 is a side view of the apparatus showing the excavating unit in the
raised
and lowered positions;
5 Fig. 4 is a front view of the apparatus showing the excavating unit in the
transport position;
Fig. 5 is a front view of the apparatus showing the excavating unit in the
operating position while forming a pile of excavated material alongside the
railway
track;
10 Fig. 6 is a side cut-away view of an embodiment of an excavating chain for
use
with an apparatus according to the present invention;
Fig. 7a is a top view of the apparatus in operation at a first position
beneath the
railway track while forming a first pile of excavated material; and,
Fig. 7b is a top view of the apparatus in operation at a second position
beneath
the railway track while forming a second pile of excavated material.
Description of Preferred Embodiments
Throughout the drawings, like indicia will be used to refer to like features
of the
drawings. All indicia present on a given drawing need not necessarily be
described
with reference to that particular drawing.
Referring to Fig. 1, an apparatus according to the present invention comprises
a
frame 1 having a set of railway wheels 2 thereunder for engagement with rails
3
supported by railway ties 4. An excavator 5 has a set of rubber ground wheels
6, a set
of selectively deployable railway wheels 7 and an articulated arm 8 with an
excavating
bucket 9 at one end thereof that is releasably engaged within a cradle 10 of
the frame
1. The cradle 10 comprises fore and aft frame transverse frame members so that
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when the excavator 5 travels along the tracks, engagement of the bucket 9
against the
frame members causes corresponding movement of the apparatus. The excavator 5
is supplementaly connected to the frame by means of a tow bar 11. The
apparatus
lacks its own source of motive power and relies upon the excavator 5 for
movement
along the tracks.
The frame 1 further comprises a central lifting lug 12. In the event of an
oncoming train, the bucket 9 is disengaged from the cradle 10 and the
articulated arm
8 is connected to the lifting lug 12 using chains or other suitable means in
order to lift
and remove the apparatus from the tracks. The railway wheels 7 are then
selectively
raised and the rubber wheels 6 are used to maneuver the excavator 5 alongside
the
tracks. In order to reduce the overall weight of the apparatus, frame cutaways
13 are
provided and strategically positioned on the frame in order to balance the
weight of the
apparatus about the lifting lug 12. In the embodiment shown, the weight of the
apparatus is less than or equal to 11,000 Ibs.
Referring now to Fig. 2, the apparatus is shown in top view. An excavating
unit,
show generally at 14, comprises a guide frame 15 over which an endless
excavating
chain 16 passes. The excavating chain 16 is equipped with excavating lugs 17,
only
some of which are shown, that extend outwardly from the excavating chain. The
excavating unit 14 is mounted to the frame 1 by way of a knuckle 18 having a
vertical
pivot axis passing through pivot pin 19. The knuckle 18 is mounted to a
horizontal
slide 20 that moves within a slide sleeve 21. The combination of the knuckle
18 and
the slide 20 permit the excavating unit to adopt a transport position (denoted
as A)
close to the frame 1, an extended position (denoted as B) wherein the
excavating unit
14 is transversely spaced apart from the frame, and an operating position
(denoted as
C) wherein the excavating unit 14 is pivoted about the pivot pin 19 using the
knuckle
18 to move into a transverse orientation for excavating ballast material from
beneath
the railway tracks.
Iron ballast weights 22 are provided on the side of the frame 1 opposite the
excavating unit 14 to stabilize the unit during operation; the ballast weights
may
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increase the overall weight of the apparatus past 11,000 Ibs and are normally
removed
prior to lifting the apparatus from the tracks. A hydraulic motor 23 is
provided as part of
the excavating unit 14 for powering the excavating chain 16 in its passage
about the
guide frame 15. The hydraulic motor 23 is releasably connected to a source of
fluid
power (eg: hydraulic fluid pump) on the motive vehicle (not shown) and is
disconnected prior to lifting the apparatus from the tracks. The cradle 10 is
present on
both the front and rear of the apparatus; this permits the excavating unit to
be
positioned on either side of the railway track and permits the apparatus to be
towed in
either direction.
Referring to Fig. 3, the excavating unit 14 is shown mounted to a vertical
slide
24. This permits the excavating unit to be moved from a raised transport
position
(denoted as A) to a lowered position (denoted as D) that is either extended or
un-
extended. The horizontal slide 20 moves within sleeve 21 to cause extension or
retraction of the excavating unit 14. The knuckle 18 comprises a hydraulic
knuckle
cylinder 25 that is extended or retracted to cause pivoting movement of the
excavating
unit 14 about the vertical axis of the pivot pin 19. The guide frame 15
comprises a first
portion 26 and a second portion 27 that is upwardly inclined with respect to
the first
portion with an inclination angle of about 22 degrees. When the first portion
26 is
inserted transversely beneath the railway tracks and the hydraulic motor 23 is
used to
drive the endless excavating chain about the guide frame 15, ballast material
excavated using the first portion is elevated using the second portion and
ejected at
the exit end 28 of the second portion 27 to ultimately be deposited in a pile
adjacent
the railway track (not shown). The angular orientation of the excavating unit
14 is
adjusted by extension or retraction of angle cylinder 31. This causes the
excavating
unit 14 to pivot about a horizontal pivot axis passing through horizontal
pivot 32. The
angular orientation of the excavating unit can be adjusted by up to +/- 15
degrees from
horizontal in order to accommodate excavation around railway switches, upon
steep
embankments, or in other locations where it is difficult to obtain direct
horizontal
access.
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Referring to Figs. 4 and 5, the excavating unit 14 is shown in the transport
position (Fig. 4) parallel to the railway tracks 3 and is also shown in the
operating
position (Fig. 5) transverse to the railway tracks 3 and inserted beneath the
railway ties
4 in order to remove ballast material thereunder. The second portion 27 of the
guide
frame 15 is inclined with respect to the first portion 26 by an angle of about
22
degrees. This advantageously provides sufficient elevation of the excavated
material
to permit pile formation without undue loss of material from the excavating
chain that
could occur with overly steep inclination. The second portion 27 is parallel
to the first
portion 26 when seen in top view and inclined with respect to the first
portion 26 when
seen in front or side views. This co-alignment of the two portions reduces the
likelihood of excavated material being expelled at the inflection between the
two
portions and obviates the need for guides and shields for keeping material on
the
excavating chain during elevation. Of course, guides and shields may be
provided for
operator safety purposes, however these guides are not normally of the robust
nature
needed in maintaining excavated material on the chain during elevation.
Substantially
all of the excavated material leaves the excavating unit after being elevated
to the exit
end 28 of the second portion 27 and is deposited in a pile alongside the
railway track.
The formation of a pile is advantageous in that it allows for subsequent
retrieval and/or
replacement of the excavated material and spaces the excavated material apart
from
the track to permit repairs or other work to be more easily conducted. Bumpers
29 are
provided on the frame 1 above the railway wheels 2 to mitigate damage to the
frame
or motive vehicle upon inadvertent impact. The forward frame member 30 of the
cradle 10 engages with the bucket of the motive vehicle (not shown in Fig. 4)
to cause
movement of the apparatus along the tracks in response to travel of the motive
vehicle.
Referring to Fig. 6, an excavating chain comprises a plurality of excavating
links
33 interspersed with joining links 34. Each excavating link 33 comprises an
outwardly
extending excavating lug 41 to which a plurality of excavating teeth 42 are
mounted.
The excavating teeth 42 are horizontally and vertically spaced apart and form
an
inclined row having a row angle that is opposite in direction to the
inclination angle of
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the second portion 27 relative to the first portion 26. The row angle is
generally from
to 45 degrees. The excavating teeth 42 are splayed apart relative to one
another
as an aid both in excavating and elevating ballast material.
Each excavating link 33 further comprises a pair of vertically spaced apart
5 plates 35 having a pair of vertically aligned concentric holes 36. Each
joining link 34
has a universal joint (generally indicated at 40) at each end comprising a
semi-
spherical swivel bearing 38 received within a ball race 39 and having an
aperture
concentrically aligned with the holes 36 for receiving a link pin 37 inserted
therethrough. The link pin 37 permits the excavating link 33 to rotate
relative to the
10 joining link 34 about a vertical axis passing through the link pin as the
excavating chain
16 travels endlessly about the guide frame 15. As the universal joint 40
passes from
the first portion 26 to the second portion 27, the swivel bearing 38 moves
within the
ball race 39, permitting the joining link 34 to angularly deflect relative to
the excavating
link 33. The vertical spacing of the plates 35 corresponds to the inclination
angle of
the second portion 27 relative to the first portion 26 in order to permit
sufficient
deflection. The permissible deflection of each end of the joining link 34 is
normally
equally to at least half of the total inclination angle. As the excavating
link 33 moves
onto the second portion 27, the link pin 37 and the vertical pivot axis
passing
therethrough adopt the inclination angle of the second portion and the bearing
38
again moves within the ball race 39 to restore a substantially parallel
relationship
between the plates 35 and the joining link 34.
Referring to Figs. 7a and 7b, the excavating unit 14 is shown in a first
operating
position (Fig. 7a) and a second operating position (Fig. 7b). In the first
operating
position, the excavating unit 14 is inserted approximately half-way beneath
the railway
tracks 3 and deposits excavated material in a first pile 43 at a first spaced
apart
location from the railway tracks. After the excavating unit 14 is operated
along the
section of tracks to form the first pile, the apparatus is returned to the
beginning of the
section of tracks being worked on and re-inserted to a second operating
position
across the full-width of the railway tracks 3. As the apparatus is operated in
the
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second position, a second pile 44 is formed inwardly adjacent the first pile
43. This
method of operation of the apparatus is particularly advantageous in
situations where
a large quantity of material is being removed from beneath the tracks, as the
height of
the pile might exceed the height of the exit end 29. By creating two piles 43
and 44,
5 an excavating unit 14 having a relatively small inclination angle can still
be used to
remove a large quantity of material from beneath the tracks.
Other advantages which are inherent to the structure are obvious to one
skilled
in the art. The embodiments are described herein illustratively and are not
meant to
limit the scope of the invention as claimed. Variations of the foregoing
embodiments
10 will be evident to a person of ordinary skill and are intended by the
inventor to be
encompassed by the following claims.
