Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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RAIN INSULATOR
The present invention relates to a rail insulator
comprising an electrically insulative body having a
S flank portion to be interposed between a shoulder
member and an edge of a rail flange and wherein at
least a laterally inner side of the flank portion has
applied thereto an abrasion resistant covering, for
example of metal. In a preferred form, the insulator
has a load reception portion integral with the flank
portion for extending on an upper side of the rail
flange for receiving a downward force of a clip portion
thereon, and an underside of the load reception portion
has an abrasive resistant covering.
The arrangement of the invention prevents
premature failure of the insulator as a result of a
combination of high compressive force and shear or
abrasion applied thereto.
Some examples off structures in accordance with
the invention will be illustrated with reference t othe
accompanying drawings.
Figure 1 is a partially perspective view showing a
rail fastening incorporating an insulator having an
abrasion resistant covering in accordance with the
invention.
Figure 2 is an isometric view of the rail
insulator employed in the rail fastening of Figure 1.
Figures 3a, 3b and 3c show components of the
insulator of Figure 2.
Figure 4 is an isometric view of a further form of
rail insulator having an abrasion resistant covering in
accordance with the invention.
Figure 4 a, 4b and 4c show components of the
insulator of Figure 4.
Figure 5 is a partially perspective view showing a
further form of rail fastening incorporating the
insulator of Figure 4.
Figures 6 and 7 are isometric views showing a side
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view and a rear view, respectively, of a further form
of rail insulator having an abrasion resistant covering
in accordance with the invention.
Figures 8 a, 8 b and 8c show components of the
S insulator of Figures 6 and 7.
Figures 9 and 10 are partial side views of a rail
fastener incorporating an insulator and illustrating
the compressive abrasion of the insulator resulting
from rail rocking.
In railway track, electrical currents or signals
are passed through the rails and are used to locate the
trains and to activate guarded road crossings. They
also serve to warn the track maintenance crew of rail
breaks such as a pullapart that occurs in cold regions.
In areas where concrete or steel ties or direct
fixation or similar installations are used, it is
necessary to isolate the rail to prevent a shorting out
of the current in both rails. Traditionally, pads and
insulators made from electrically insulative material
such as polymers are used between the rail and the tie
and between the rail and the shoulders to isolate the
rail from signal leakage. This invention relates to
insulators used between the rail and shoulders of
steel, concrete, direct fixation or other similar
installations.
Referring to the drawings, wherein like reference
numerals indicate like parts, Figure 1 shows a
fastening arrangement employing a steel tie 20,
electrically insulating cant pad 21 and a hook-in-field
and gauge shoulder members 22 and 23, together with
resilient clips 24, these element being generally as
and installed as described in, applicants International
application PCT/CA 99/00966 which should be referred to
for further details and the disclosure of which is
incorporated herein by reference.
The arrangement as shown retains a rail 26 having
a flange 27 providing outer edges 28. Before
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installation of the clips 24, insulator members 31 as
shown in more detail in Figure 2, are inserted between
each shoulder member 22 and 23 and the adjacent rail
flange edge 28. As best seen in Figures 3a, 3b and 3c,
each insulator member 31 comprises an electrically
insulative central or core member 32 formed of
conventional polymer material, and laterally outer and
inner abrasion resistant coverings 33 and 34 applied on
opposite sides of the core member 32. Preferably, the
coverings 33 and 34 are metal plates, preferably having
laterally extending side surfaces that engage with the
core member 32 so as to resist longitudinal rail
displacement. In the example shown, the core member 32
has longitudinally inclining laterally extending inner
and outer side surfaces 36 and 37 extending dove tail
fashion. The laterally inner covering 34 has a dove
tailed groove 38 with inclining surfaces 39 that
receive the edges 36 in the assembled condition and
likewise the outer covering 33 has inclining side
surfaces 41 that are received in the assembled
condition in an upper groove 42 in the core member 32
having the side surfaces 37.
The upper side of the outer covering 33 has a
channel section groove 43 in an upper side having
laterally extending sides 44. An inner portion 46 of
the clip 24 is received in the groove 43 and engagement
of the inner portion 46 with the channel sides 44
prevents lateral creep of the insulator 31 relative to
the shoulder 23 and clip 24.
In the example shown, a flank portion 47 of the
insulative core 32 that extends between the shoulder 23
and rail flange edge 28 in the installed condition has
inwardly extending cheek portions 48 at each end. The
end surfaces 49 of a plate like flank portion 51 of the
inner metal covering 34 are received between the cheek
portions 48 in the assembled condition, preventing a
longitudinal creep of the inner covering 34 relative to
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the insulative core 32.
Figure 9 is a side view, partially in section,
showing the rail fastening arrangement including an
insulator 31 in its normal, unstressed condition.
It has been found that, in service, the rail 26
rocks as a result of the lateral forces applied to the
side of the head of the rail 26 by the passing wheels.
This rocking is illustrated in Figure 10, wherein the
rail 26 has rotated about a fulcrum at the point of
engagement of the lower side of the rail flange edge 28
on the cant pad 21. The upper side of the rail flange
27 forces the insulator 31 upwardly relative to the
shoulder 23, as seen in Figure 10. The upper edge of
the rail flange edge 28 engages compressively on the
inner flank of the insulator 31. Since the contact
between the rail flange edge 28 and the insulator 31 is
essentially a line contact, a very high compressive
stress is applied to the insulator 31. At the same
time, there is a strong abrasion or shear forces
applied to the inner flank portion of the insulator 31
as a result of the rubbing contact with the rail flange
edge 28. In the present invention, the inner plate
like portion 51 of the abrasion resistant covering 34
absorbs and distributes the compressive and shear load
over substantially the entire area of contact between
the plate portion 51 and the flank portion 47 of the
insulative core member 32. Hence, the invention avoids
the application of high compressive forces and abrasion
or shear to the insulative core member 32 and avoids
premature failure of the structure of the insulating
member 32.
In the preferred form, the flank portion 51 of the
abrasion resistant covering is formed integrally with
an abrasion resistant covering portion 52 that in the
assembled condition extends on the underside of the
portion 42 of the insulative core member 32 that
receives the load of the inner portion 46 of the clip
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24, so as to absorb and distribute the compressive and
shear or abrasion forces applied to the underside of
the insulator 31 by the upper side of the rail flange
27.
Further, preferably an outer abrasion resistant
covering 33 is provided that has an upper portion 53
extending between the insulative core 32 and the inner
portion 46 of the clip in the installed condition and
that absorbs and distributes abrasion or shear and
compressive forces exerted by the clip 24 on the
insulator 31. Further, preferably a plate like outer
flank portion 54 is formed integrally with the upper
portion 53 and, in the installed condition, extends
between the insulator 31 and inner face of the shoulder
23 and absorbs and distributes compressive and shear
forces to which the insulator 31 may be subjected.
It may be noted that throughout the assembled
structure, the outer metal covering 33 is spaced from
the inner metal covering 34 by the thickness of the
insulative core 32, so that there is no conductive path
between the elements 33 and 34.
Figures 4, 4a, 4b and 4c show a further form of
insulator 61 for use with a known form of PANDROL
(trade mark) clip and fastening arrangement. Figure 5
shows the known form of clip 62 engaging a shoulder 63
and engaging the upper side of the insulator 61.
As seen in more detail in Figures 4a to 4c, the
insulator 61 comprises an electrically insulative core
member 64 and abrasion resistant outer and inner
coverings 66 and 67 preferably of plate form metal.
The core member 64 comprises a plate like flank
portion 68 and an upper load receiving portion 69.
The outer covering 66 comprises a generally planar
flank portion 71 that extends on the outer side of the
flank portion 68 of the core 64, and an upper portion
72 formed integrally with portion 71 that in the
assembled condition extends on the upper side of the
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portion 69.
An inner covering 67 similarly comprises a plate
like flank portion 73 that extends in the assembled
condition on the inner side of the flank portion 68 and
an upper load receiving portion 74 that extends on the
under side of the portion 69. The elements of the
insulator 61 are assembled together and function
broadly similarly to the insulator 31 described above
in detail in connection with Figures 1 to 3, 9 and 10.
It may be noted the outer abrasion resistant
portion 66 has longitudinally spaced laterally
outwardly extending ear portions 76 adjacent each end
of the flank portion 71. These ear portions 76 engage
opposite ends of the shoulder 63 in the installed
position, as seen in Figure 5, to locate the insulator
relative to the shoulder 63 and prevent longitudinal
creep.
Figure 6, 7 and 8a to 8c show an insulator member
76 comprising an insulative core 77 an outer metal
abrasion resistant covering 78 and an inner metal
abrasion resistant covering 79. The member 76 is
somewhat similar to the insulator 61 described above
with reference to Figures 4 and 5, except the outer
covering 78 terminates upwardly from the planar flank
portion 81 of the core member 77, so that the inner
side of the shoulder 63 engages directly on the
insulative core 81. The compressive and shear forces
exerted between the shoulder 63 and the insulator are
relatively small, and therefore the coverings 78 and 79
provide adequate resistance to failure of the
insulative core structure 81.
