Note: Descriptions are shown in the official language in which they were submitted.
CA 022440~4 1998-07-27
RAIL FA~ l~;N~SK
The present invention is concerned with rail
fasteners, particularly fasteners used where two rail
tracks cross.
Heavy haul railroads require, at various points,
two rail tracks to cross, and as a result a small gap
is created in each rail which the rolling stock must
jump. This creates a problem in that the heavy wheel
loads cause high impact and vibration, which result in
rapid deterioration of the crossing components and
produce considerable relative movement of the rail
structures.
Typically, such a rail crossing is constructed
from wooden ties sitting on top of crushed rock
ballast. The ties are affixed to heavy steel base
plates. Finally, the rail and rail junctions are held
down to the steel plates by elastic rail fasteners.
A significant problem is the premature failure of
the rail fasteners which are unable to cope with the
large amount of movement produced in the structure.
Many types of rail fasteners have been tried for this
application, but have not proved successful.
One solution is to build a bridge so that one
track passes completely over the other without a
crossing. However, this involves a very large cost and
may not be justified in all cases, and hence railroads
continue to utilise rail crossings.
Elastic rail fasteners in general use normally
have to cope with a vertical o~cillation of about lmm,
in some extreme cases extending to 1.5mm. However, on
a rail crossing a continuous upward movement of 4mm is
common, with occasional excursions to about 10mm. A
further difficulty with fastening rail crossings
relates to the available space for fitting the
fastenings. The rails and frogs (rail junctions) are
bolted together with clamping bars which take up
CA 022440~4 1998-07-27
considerable space and llmit the places where rail
fastenings can be applied. As a result, there are
limited places to attach the fasteners, and often as a
consequence there are insufficient fasteners on the
crossing to distribute the load adequately.
One solution to the deflection problem would be to
scale up the current fasteners so they could cope with
the occasional 10mm deflection. However, this would
make them extremely large and would only exacerbate the
problem of finding adequate room to apply them to the
crossing. A further problem with this approach is that
most currently available fasteners require relatively
complex manufacturing tooling. As specialised
fasteners for crossings are a relatively small run
product, this would cause a major cost problem.
Accordingly, it is desirable to provide a fastener
suitable for rail crossings which is able to cope with
the necessary deflection, but which is compact enough
to be fitted into a restricted space.
According to an embodiment of the present
invention there is provided elastic railway rail
fastening means for fastening a railway rail to an
underlying rail foundation, which fastening means
comprise a main clip having at a free end thereof a toe
for applying a downward force to a flange of an
adjacent rail when the fastening means are in use and a
mounting assembly adapted to be affixed to a base
member for retaining the main clip such that it extends
in a cantilever arrangement from the mounting assembly
towards an adjacent rail flange when the fastening
means are in use; characterised by one or more helper
clips ext~n~l ng when in use in a cantilever arrangement
from said mounting assembly in such a manner as to be
generally disposed above and in engagement with the
said main clip and to terminate, at a free end thereof,
between an adjacent edge of the rail flange and the
CA 022440~4 1998-07-27
mounting assembly, and further characterised in that
the said mounting assembly comprises a clamping bar for
clamping the said main clip and the or each said helper
clip to the said base member.
Preferably the clips have a generally flat, plate-
iike form, most preferably with a lateral taper at the
free ends of the main and helper clips.
It is desirable that the main clip and the or each
helper clip are ~;menqioned so as to operatively
produce a substantially constant stress in cantilever
parts of the main and helper clips.
It is also desirable that the mounting assembly is
such that there are no holes in the main and helper
clips below the said clamping bar.
lS Preferably, there i9 only one helper clip, the
free end of which terminates at a distance from the
adjacent rail flange edge which is not less than 15~ of
the span from the rail flange edge to a cantilever edge
of the clamping bar and not more than 80~ of this span.
Most preferably, the distance from the adjacent rail
flange edge is approximately 50~ of the span.
Preferably, when there is more than one helper
clip, the said helper clips are mounted one upon
another. Desirably, the cantilever length of each such
helper clip progressively decreases relative to the
underlying clip, 60 that they stagger back from the
toe.
In a preferred form, the size of the toe of the
main clip ("toe depth") is such that the toe can be
operatively affixed under a rail junction clamping bar,
which holds the rails and junction together.
The arrangement of the present invention provides
a multiple clip structure so as to reduce the length of
the fastener required to provide the necessary
deflection, whilst retaining a simple construction
suited to a short run product. As the fastener will
CA 022440~4 1998-07-27
occupy a relatively small space, more fasteners can be
applied so as to more successfully stabilise the rail
and maximise the life span of the crossing components.
A fastener embodying the present invention retains
the necessary strength to handle the associated
stresses, whilst retaining an overall compact
- configuration.
A further advantage of the preferred
implementation is that it provides a low profile flat
toe which can fit under the clamping bars holding the
rails and frogs together to further facilitate adequate
fasteners being fitted.
Whilst the primary focus of the inventive fastener
is for rail crossings, it will be appreciated that the
invention may be advantageously applied wherever
similar problems are encountered.
Reference will now be made, by way of example, to
the accompanying drawings, in which:-
Figure 1 is a side view, partly in section, of
fastening means embodying the present invention inplace retaining a raili
Figure 2 is a plan view of the fastening means
shown in Figure 1;
Figure 3 is an end view of the fastening means
shown in Figure l; and
Figure 4 is a plan view showing a possible
positioning of such fastening means around a frog.
It will be appreciated that the implementation
shown is only one of many possible, and that details
may be varied in accordance with the engineering
requirements of the particular railroad.
A fastener 20 comprises a substantially flat main
clip 1, a helper clip 2, and a mounting assembly 7.
Helper clip 2 is applied on top of main clip 1 so that
helper clip 2 does not extend to a toe 4 of the main
clip 1, which bears on a rail flange 3. The helper
CA 022440~4 1998-07-27
clip 2 terminates at a free end lying approximately
midway between the mounting assembly 7 and the rail
flange edge. In order to maximise the possible toe
load and available defiection for a given mass of
steel, and also allow the length of the main clip 1 to
be reduced, the size and shape of the main clip 1 and
helper clip 2 are chosen such that the stress in the
cantilever parts (extending from the mounting assembly
7 towards the rail flange 3) is substantially constant.
In particular, although the idealised
configuration would be for the tapered edges of the
main clip 1 to meet at a point which sits directly over
the rail flange edge and for the tapered edges of the
helper clip to meet at a point which sits midway
between the mounting assembly 7 and the rail flange
edge, since this would give the same uniform stress in
both clips (when the same thickness of material is
used), for practical reasons this configuration is
preferably modified.
Thus, the toe of the main clip 1 has been designed
so as to overlap the rail flange edge slightly, to
ensure that the clip 1 does not come off the rail if
there is any sidewards rail movement, and to have a
small, flat end, so that the bearing area is large
enough to give a bearing pressure which will not cause
undue wear on the main clip 1. The same shape has been
used on the free end of the helper clip 2 for
convenience in manufacture, since the same blanking
tool can be used for both the main and helper clips 1,
2.
Main clip 1 and helper clip 2 are held to the
mounting assembly 7 by a clamping bar 11 which is
tensioned by bolts 9 and respective nuts 10. If
necessary the bolts can be easily replaced by removing
the clamping bar 11 and sliding them sideways out of
slots 8. It will be appreciated that the clamping bar
CA 022440~4 1998-07-27
could be held down by other means such as a cam locking
device.
There are no holes in the main and helper clips 1,
2 beneath the clamping bar 11; thus the helper clip 2
S is able to contribute to the overall deflection of the
fastening without having to be used to compen~ate for
weaknesses which would otherwise be caused by holes in
a high stress area of the clips. Since there are no
significant stress concentrations in the clips, it is
possible to use a high working stress, thus providing
an efficient design with high deflection.
Since the flat toe 4 has a low profile, it can fit
underneath the rail junction clamping bars so that many
more fastenings can be applied if required than in the
prior art.
Mounting assembly 7 may be either a welded
fabrication or a steel casting. Operatively, mounting
assembly 7 would generally be held to the base plate 5
by field welds 6. Stops 12 and plate 13 locate the end
of the clip 1 and helper 2. Base plate 5 is attached
to the wooden ties (not shown) by screwspikes and
spring washers 15.
It will be appreciated that the general principle
of the present invention may be implemented in various
ways. For example, the main clip 1 and helper clip 2
may have different thicknesses if desired. A flat
profile is preferred for main clip 1 and helper clip 2
largely for reason~ of manufacturing economy, but
different profiles could be used if desired. Multiple
helper clips 2 could be provided, each overlapping
progressively less of the clip beneath.
In figure 4, an assembly incorporating fasteners
embodying the present invention is illustrated. A
plurality of fasteners 20 are attached around the frog,
so as to hold it firmly in position on base plate 5.
The gaps in the rails occur at point 16 on frog 3.
CA 02244054 1998-07-27
--7--
Ties 14 are shown in outline but are operatively
beneath the base plate 5, and affixed to the plate by
screwspikes and spring washers 15. It can be seen that
the compact structure of the fasteners 20 allows an
adequate number to be positioned so as to hold the rail
crossing firmly in place.
- In the attached claims use of the word "rail"
should be taken to encompass railway rail junctions
("frogs") as well as ordinary railway rails.
