Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to rail fastenin~s and more
particularly to rail fastenings for use with concrete ties.
Use of rail fastenings to hold rails upon ties are known in the
art. Prior to the use of the new concrete or plastic type ties
wooden ties were used. A base plate was inserted between the
tie and the rail and spikes secured the base plate to the rail
to prohibit lateral or sideways movement. The head of the spike
itself rested upon the rail shoulder thereby prohibiting vertical
movement.
Concrete ties are generally employed for use on modern
railroads. In order to hold the rail and prohibit it from
lateral and vertical movement various types of base plates and
shoulder blocks have been employed. One method of meeting the
new requirements of concrete ties is to manufacture the preformed
concrete tie with a one piece shoulder block embedded within it.
The ties are set in place and the rail laid between two sets of
shoulder blocks. Thereafter, a resilient rail clip or ~androl*
clip is inserted through the bore hole in the shoulder block to
prevent the rail from vertically moving; while the shoulder
block prevents the rail from moving laterally.
Difficulties, however, arise when some concrete
ties, due to the imperfections in the casting, or overdue stress
begin to wear and crack. It is then necessary to change the
tie. Since the top part of the shoulder block protrudes
one and a half inches above the base of the rail, the rail
cannot be lifted over the shoulder block to allow the tie to
be removed ~hen changing the concrete tie on a spot removal.
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It is necessary instead to scarify the crib area immediately
adjacent the tie to the depth of at least one and a half inches
below the bottom of the tie. The tie is then levered over into
the removal slot and then withdrawn from under the track and
a replacement tie inserted in reverse order. The crib must
then be filled and tamped in order to secure the ballast. One
of the difficulties with the tamping process is that the newly
tamped road bed is never as solid as an established road bed
and track stability could be affected in hot weather. The
process is slow and inefficent and may require six to eight man
hours for the removal of each tie.
As an alternative to the embedded type of shoulder
block, precast ties with cavities adjacent the predetermined
rail position or precast ties with outside lips or raised
portions have also been used. The raised portion on the
extremities of the tie prevents lateral movement when a base
or shoulder block is placed between the lip and the rail. Such
a raised outside portion on a tie can be found illustrated in
Canadian Patent 1,145,729. The difficulty of tie removal,
however, still persists as the tie must be levered over into a
disturbed lower road bed in order that the lip on the upper
surface of the tie can clear the underside of the rail when the
tie is removed.
A third method of fastening rails to concrete ties
is accomplished by making preformed threaded bore holes in the
concrete tie. Bolts secure shoulder blocks and base blocks,
and are threaded into the bore holes. These clamp the shoulder
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block portivn and secure the base of the rail. With this type
of arrangement, the bolts and clamps can be removed and the
concrete tie pulled directly from under transversely to the
rails. The difficulty is that these devices are complex,
cumbersome and take a great amount of time to position. Rail
fastenings of this latter type are found in Canadian Patents
Nos. 891,373, 997,730 and 1,062,675.
It is an object of the present invention to provide a
simple two piece self-retaining shoulder block which can be
quickly and easily placed in the operating position, or removed,
permitting easy replacement of concrete ties.
It is a further object of the present invention to
provide a rail fastening which has a minimal number of components,
can be tapped into place by an applied force, and is self-retaining.
Therefore, this invention provides a two piece self-
retaining rail fastener for securing a rail to a concrete tie
comprising: a lower base plate adapted to be permanently embedded
in a tie with the upper most portion of said base plate in the
same plane or lower than the upper surface of the tie; an upper
shoulder block including an upper portion which abuts the rail
when in use, a lower portion the surface of which is adapted to
co-operate in an interlocking position with the upper surface
of said base plate, and a bore hole for use with a resilient rail
clip; said base plate being formed with a retaining means to
prevent lateral movement of the shoulder block; whereby when in
use, reactive forces exerted by the resilient rail clip against
the rail and shoulder block, fixedly engage said shoulder block
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to said base in the interlocking position.
In the present invention, precast concrete ties are
manufactured with the base plate of the shoulder block embedded in
the concrete tie. For a normal tie constructed for use with the
standard two rails, four such shoulder block base plates are
embedded. After the concrete ties are inserted, the rails are
laid in the appropriate position and the upper portion of the
two piece shoulder block is inserted with the use of a hammer or
other instrument.
In a first embodiment of the invention the upper shoulder
block is equipped with a projection on one side and a sloped
bottom on the other. The embedded base plate contains a groove
adapted to receive the projection and a retaining lip adjacent the
sloped bottom surface, opposite the groove. The upper shoulder
block is also equipped with a projection on its bottom surface to
serve as a retaining key. The upper surface of the base plate is
recessed to receive this key projection, such that when the two
parts are fitted together, longitudinal motion (i.e. motion in
the direction of the rails) of the shoulder block is restrained.
The key and recessed keyway are so configured as to provide a
force fit of the key within the keyway, thereby preventing movement
of the shoulder block during installation of a resilient rail clip,
such as that manufactured by the Pandrol Corporation and marketed
as a"Pandrol clip". The resilient rail clip used is preferably
in the form of an open ended "figure 8". The "figure 8'1 is con-
torted such that when in use, one end and the mid section are
lower than the end which is inserted through the bore hole. The
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Pandrol* clip is fitted in such a way that the mid section of the
clip rests upon the foot flange of the rail, providing a constant
downward exerted pressure. The other end of the clip rests on a
portion of the upper shoulder block opposite the side of the foot
flange. While the clip generates forces on both the shoulder
block and the rail base, there is a tendency for the shoulder block
to rotate about the inside portion of the bore hole in a counter-
clockwise direction towards the rail base thereby driving the
projection firmly into the groove in the base plate.
In a second embodiment of the invention the upper shoulder
block is provided with two projections or ribs and the lower base
plate is provided with two grooves adapted to receive the ribbed
shoulder block. The upper block is inserted longitudinally into
the lower base place, and since the grooves and ribs are tapered
slightly, the shoulder block wedges itself within the lower base
plate.
With constant operation upon the track bed a concrete
tie, due to defects or excessive wear, becomes damaged or cracked
and it is necessary to remove it on a spot basis. One simply
removes the resilient rail clip with the use of a hammer or the
like and taps out the upper shoulder blocks. This leaves the
concrete tie with the rails resting on it with base plates flush
with or slightly lower than the upper surface of the tie. By
levering or applying a force on the end of the tie,or by the use of
standard mechanized tie removal equipment, the tie may be removed
quickly and easily without any disturbance of the underlying ballast
bed. A new tie is then inserted and the reverse operation is
performed. The entire tie change operation can be completed in a
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fraction o the time required for the removal of ties with the
prior art rail fastenings.
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The overall result is more efficient tie handling, and minimum
rail bed disturbance, thereby resulting in better track stability.
In a further embodiment the upper shoulder block can be
constructed with varying heights. If it becomes necessary to shim
the track during seasonal weather fluctuations, the bore hole for
the pandrol clip will be located at the correct height to ensure
the prevention of sideways and vertical movement of the rail.
The invention is more fully described in conjunction
with the accompanying drawings wherein:
Figure 1 is a perspective view of a two piece single
flanged shoulder block;
Figure 2 is a perspective view of a two piece double
flanged shoulder block;
Figure 3 is a longitudinal cross section of a rail tie
with two two-piece single flanged shoulder blocks maintaining a
rail in position;
Figure 4 is a force diagram illustrating the forces on
the shoulder block and rail in the interlocking position.
In Figure 1 one sees an illustration of an upper shoulder
block 1 and a lower base plate 2 in the operative position. The
upper block 1 has a bore hole 3 and a shoulde~ 4 for receiving
a pandrol* cli~ (not shown). The upper shoulder block has a
sloped bottom 6 which is adapted to be received by the sloped
upper surface of the base plate 7. The lower base plate 7 is
equipped with a lip 5 and a groove 12. The latter groove 12 is
adapted to receive the longitudinal flange or rib 11 of the upper
shoulder block 1. To prevent longitudinal move~lent of the
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shoulder block during installation of the Pandrol* clip,
the key 9 projection of the shoulder block is retained by
the recess or key way 10 of the base plate 8. The upper
portion of the base plate 8 is flush with the surface of
the concrete tie (not shown). In Figure 1 in order to
place the shoulder block in the base plate the rib 11
enters the recessed portion of the base plate and is
forced into the groove 12. The sloped bottom of the
upper block 7 aids the operation.
In Figure 2 one views a second embodiment of
the invention, a double-flanged or ribbed shoulder block
and double-grooved base plate. One notes the top of the
base plate 2 is flush with the surface of the concrete
tie 13. In order to secure the double ribbed shoulder
block into the double grooved base plate it is necessary
to tap the shoulder block longitudinally from the side of
the base plate. A slight taper in one direction of the
grooves 12 and ribs 11 respectively allows the shoulder
block to be inserted in a wedge like manner.
In Figure 3 a rail 17 is placed on the surface
of a concrete tie 13 and a Pandrol* clip 15 is inserted
in the bore hole 3 of the upper shoulder block 1. While
one end of the Pandrol* clip is fitted into the bore hole
of the shoulder block 3, the mid-section rests upon the
foot of the rail 18 and the opposite end 16 rests on a
shoulder 4 of the shoulder block on the side opposite to
the rib 11.
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Figure 4 illustrates the self-locking concept
used in the single ribbed shoulder block. The Pandrol*
clip generates forces on the shoulder block and rail base
which tend to cause the shoulder block to rotate about
point B as shown in the direction of the arrow D thereby
driving the rib 11 into the groove 12 of the base plate
firmly. The forces of the Pandrol* clip thereby prevent
the lifting of the block from the base plate as the block
in the base plate is self-locking.
It is understood that this invention is not
limited to the illustration shown but can have many
various combinations or changes without departing from
the spirit of the invention.
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