Note: Descriptions are shown in the official language in which they were submitted.
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TAMPING BLADE FOR A RAILROAD TAMPING MACHINE
BackLrround of the Invention
The present invention relates to a tamping blade for a railroad-tamping
machine, and
more particularly to a tamping blade having an improved structure to resist
wear and a method
for producing the tamping blade.
During use of railroads, ballast supporting the railroads shifts away from the
railroad ties.
Railroad tamping machines maintain ballast to provide correct alignment and
elevation of rails.
These tamping machines employ tamping tools that push multiple vibrating
blades into the
ballast and then towards the rail to compact the ballast supporting the rail.
This provides a firm
foundation for the rail to support the load of the trains passing over it.
This procedure subjects
the tamping blade to extremely harsh conditions, as typical ballast includes
materials such as
rock, wooden cinders, concrete, slag and taconite. Because the ballast also
becomes compacted,
the tamping blade must break up the ballast in order to repair the ballast.
The abrasive nature of
the ballast causes tamping blades to wear quickly, necessitating repair or
replacement. Each
railroad-tamping machine can employ from sixteen to thirty-two tools. Thus,
wear and
replacement leads to significant expense both in time lost and the cost of
replacement blades.
Many attempts have been made to increase the life of tamping blades by
employing wear-
resistant materials such as tungsten carbide. For example, U.S. Patent
Application No.
2005/0109235 discloses a tamping tool that has a wear-resistant tip inserted
into a groove in the
end of its blade. Wear-resistant tiles are fixed on the portions of the blade
to further protect the
blade. Similarly, U.S. Patent No. 5,261,763 describes a tamping tool having a
paddle of carbon
steel construction with wear-resistant material brazed to the front, exposed
face of the paddle.
Current tamping blades employing wear-resistant materials are generally made
using a
soft metal pad. As long as the pad is not exposed to abrasion, and is
protected by wear-resistant
material, the pads will be fine. But when the wear-resistant material chips
off, or the metal pad is
otherwise exposed, the soft metal quickly wears away and the tamping blade
must be replaced.
There is therefore a need for a tamping blade that is less affected by
chipping.
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During use, the tamping blade must often break up the ballast. Current tamping
blades
employ a blunt leading face. The blunt leading face tends to incur impact
along the entire length
of the leading face and is inefficient for breaking up ballast. Concentrating
the impact in a
smaller area facilitates breaking up ballast. The stress at the point of
impact is greater for a non-
blunt blade. There is therefore a need for a tamping blade having a non-blunt
leading face
capable of withstanding the stress and wear occurring at the point of impact.
Hardening the metal pad also improves resistance to wear by abrasion. It is
therefore
desirable to combine wear-resistant material with a hardened metal pad.
However, application of
wear-resistant material by brazing or welding causes softening of hardened
metal, rendering a
heat treatment process useless. Using a heat treatment processes after
application of a wear-
resistant material, such as carbide, would cause the joining material, such as
a brazing silver
solder to melt off. There is therefore a need for a tamping blade that
combines a heat-treated pad
with a wear-resistant material and a process to manufacture a tamping blade
that combines a
heat-treated pad with a wear-resistant material.
Summary of the Invention
The present invention therefore discloses a tamping blade for a railroad-
tamping machine
to tamp ballast on a railway line. The tamping blade includes a pad that
attaches to a shank of a
railroad-tamping machine and is made of hardened steel. A wear-resistant
coating covers and
protects the surfaces used to tamp the ballast. Wear-resistant inserts are
fixed in a leading face of
the pad and absorb the greatest impact, as well as increase the efficiency of
the tamping process.
The wear-resistant inserts are positioned to reduce the formation of a wear
pattern during use.
The method for producing the tamping blade allows for use of a hardened steel
pad with a wear-
resistant coating and wear-resistant inserts.
These and further objects and advantages of the present invention will become
clearer in
light of the following detailed description of an illustrative embodiment of
this invention
described in connection with the drawings.
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Brief Description of the Drawings
The illustrative embodiment may best be described by reference to the
accompanying
drawings where:
Figure 1A shows a perspective view of one embodiment of the tamping blade of
the
invention.
Figure 1B shows a top view of one embodiment of the leading face of the
tamping blade
of the invention.
Figure 2A shows a side view of a wear-resistant insert of the invention.
Figure 2B shows a side view of a second embodiment of a wear-resistant insert
of the
invention.
Figure 2C shows a side view of a third embodiment of a wear-resistant insert
of the
invention.
Figure 3 shows a flow diagram of a method for producing the tamping blade of
the
invention.
All figures are drawn for ease of explanation of the basic teachings of the
present
invention only; the extensions of the figures with respect to number,
position, relationship, and
dimensions of the parts to form the preferred embodiment will be explained or
will be within the
skill of the art after the following description has been read and understood.
Further, the exact
dimensions and dimensional proportions to conform to specific measurements
will likewise be
within the skill of the art after the following description has been read and
understood. Values
provided are representative and are utilized to facilitate the description of
the preferred
embodiment.
Where used in the various figures of the drawings, the same numerals designate
the same
or similar parts. Furthermore, when the terms "upper," "lower," "side," "end,"
"bottom," "first,"
"second," "laterally," "longitudinally," "row," "column," "array," and similar
terms are used
herein, it should be understood that these terms have reference only to the
structure shown in the
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drawings as it would appear to a person viewing the drawings and are utilized
only to facilitate
describing the illustrative embodiment.
Detailed Description of the Preferred Embodiment
Refer now to Figure 1A, which shows a perspective view of one embodiment of
the
tamping blade 10 of the invention. The tamping blade 10 includes a pad 12. The
pad 12 includes
an attachment location 14 where the pad 12 can be attached to a shank of a
railroad-tamping
machine by welding or other known methods. The welding process should not
exceed 350
degrees F in order to avoid softening the pad 12. The welding process can be
done over a longer
period of time in order to avoid too much heat being applied to the pad 12.
The pad 12 further
includes a leading face 16 suitable for breaking up ballast and moving and
compacting ballast to
properly support a rail.
In order to withstand the harsh environment involved in tamping ballast, the
pad 12 is
preferably hardened. In the preferred embodiment, the pad 12 comprises a four
inch (4") by four
and one-half inch (4 %2") by three-fourths inch (3/a ') 4140 steel pad having
a hardness rating of
around fifty-five (55) on a Rockwell C scale. As those skilled in the art will
recognize, other
conformations of the pad 12 are possible and lie within the spirit and scope
of the invention.
To further protect the surfaces 36 coming into contact with the ballast, the
pad 12
includes a wear-resistant coating 18. In the preferred embodiment, the wear-
resistant coating 18
covers the portions of the bordering faces 20, 22, 24, 26 adjacent to the
leading face 16. In this
example embodiment, the wear-resistant coating 18 is a continuous coating made
of tungsten
carbide covering at least one inch (1") from the edge adjoining the leading
face 16 on each of the
bordering faces 20, 22, 24, 26. In this example embodiment, the coating 18 has
an average
thickness of at least one-eighth of an inch (1/8"). In an alternate
embodiment, the wear-resistant
coating 18 also covers the leading face 16.
The tamping blade 10 further includes a plurality of wear-resistant inserts
28. In the
preferred embodiment, the wear-resistant inserts may be made from tungsten
carbide or other
hardened material. Prior art tamping blades 10 commonly employ a blunt leading
edge. The
tamping blade 10 of the invention includes a plurality of hardened inserts 28
having a secured
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end 30 fixed within the leading face 16 and having a protruding end 32
extending from the
leading face 16.
As shown in Figure 1B, in the preferred embodiment the tamping blade 10
includes a
plurality of holes machined into the leading face 16. In one example
embodiment, the plurality of
holes 34 are machined to be three-quarters of an inch deep (3/4"). The
hardened inserts 28 are
one inch in length, cylindrical in shape and have a secured end 30 inserted
into the plurality of
holes 34, resulting in the protruding end 32 of the hardened insert 28
extending one-quarter of an
inch (1/4") from the surface 36 of the leading face 16. The plurality of holes
can be machined to
arrange the hardened inserts 28 in a "jogged" pattern. The "jogged" pattern
can be used to reduce
formation of wear patterns on the tamping blade 10 during use. In this
preferred embodiment, ten
holes are machined into the leading face 16, with each hole spaced one-eighth
of an inch (1/8")
from the subsequent hole and having an offset of three-sixteenths of an inch
(3/16") from a
centerline 38. Alternatively, the plurality of holes 34 can be machined to
arrange the hardened
inserts 28 in a straight line. Those skilled in the art will recognize that
other spacings and
patterns can be employed and lie within the spirit and scope of the invention.
In the preferred embodiment, the plurality of holes 34 have a dimension less
than the
wear-resistant inserts 28. This allows attachment of the wear resistant
inserts 28 without welding
or use of other material. A hammer or arbor press can be used to press fit the
wear-resistant
inserts 28 within the tamping blade 10. In this example embodiment, the
plurality of holes 34
have a diameter .002 inches less than the wear resistant inserts 28.
The protruding end 32 of the hardened inserts 28 allows for more efficient and
less-
wearing breaking up of ballast. The hardened inserts 28 concentrate the force
of the tamping
blade 10 into a smaller area, allowing for easier breaking up of ballast,
thereby requiring less
energy. During the horizontal vibration of the tamping blade 10 during the
tamping process, the
protruding end 32 of the hardened inserts 28 provides a raking effect to shift
the ballast into the
desired location 14. In the preferred embodiment, the hardened inserts 28
comprise tungsten
carbide or other wear-resistant material, such as hardened D2 steel. As those
skilled in the art
will recognize, other conformations and dimensions of the hardened inserts 28
on the tamping
blade 10 can be employed without departing from the spirit and scope of the
invention.
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The protruding end 32 of the hardened insert 28 may be shaped to best suit a
desired
application as shown in Figures 2A, 2B and 2C. In one preferred embodiment,
the protruding end
32 has an ovoid shape, as shown in Figure 2A. In a second preferred
embodiment, the protruding
end 32 has a conical shape, as shown in Figure 2B. In a third preferred
embodiment, the
protruding end 32 has a chisel shape, as shown in Figure 2C. In one example
embodiment, an
ovoid shape can be used to break up granite ballast. A conical shape may be
employed in hard
limestone. A chisel shape can be used in sands and soft limestones.
Figure 3 shows a flow diagram of a method for producing the tamping blade 10
of the
invention. Prior art tamping blades are hampered by the use of softer metal to
provide the base
pad 12. Because the process of soldering wear-resistant material to a base pad
12 would cause
softening of the metal used to form the base pad, there is little value to
hardening the base pad 12
prior to attachment of a wear-resistant material. After attachment of the wear-
resistant material,
the pad 12 cannot be subjected to the high heat required for heat treatment,
often as high as 1550
degrees Fahrenheit. This heat would result in melting the silver solder or
glue used to attach the
wear-resistant material.
In contrast, the method for producing a tamping blade 10 of the present
invention allows
for use of a wear-resistant material with a hardened pad 12. The method begins
with forming a
pad 12 in step 100. In the preferred embodiment, the pad 12 is formed as a
four-inch (4") by
four-and-one-half inch (4 Y2") by three-fourths inch (3/4") 4140 steel pad.
Next, the method applies a wear-resistant coating 18 on the portions of
bordering faces
20, 22, 24, 26 adjacent to the leading face 16 in step 110. In this example
embodiment, the wear-
resistant coating 18 is a continuous coating made of tungsten carbide covering
at least one inch
(1") from the edge adjoining the leading face 16 to the bordering faces 20,
22, 24, 26. In an
alternate embodiment, the wear-resistant coating may also cover a portion or
all of the leading
face 16 in addition to the bordering faces 20, 22, 24, 26.
After application of the wear-resistant coating 18, the method proceeds with
machining a
plurality of holes 34 in the leading face in step 120. The plurality of holes
34 can be machined in
various patterns to improve the wear resistance of the tamping blade 10. In
one example
embodiment, a "jogged" pattern as shown in Fig. 1 improves resistance against
formation of a
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wear pattern compared with a simple straight-line pattern. In the preferred
embodiment, the
plurality of holes 34 are machined to have a diameter smaller than the
diameter of wear-resistant
inserts 28 to be inserted into the leading face 16.
The pad is then heat-treated in step 130 to a hardness rating of at least
forty on a
Rockwell C scale, compared to the usual hardness rating of eighteen of typical
pads. In the
preferred embodiment, the pad has a hardness rating between forty and sixty.
In this example
embodiment, a hardness rating of fifty-five can be attained by a typical heat
treatment process of
heating the pad to a temperature approximately 1500 degrees F, controlled
cooling, and
tempering by reheating.
The method for producing a tamping blade 10 then provides for attachment of a
wear-
resistant insert 28 in each of the plurality of holes 34 in the leading face
16 in step 140. An arbor
press can be used to press fit the wear-resistant inserts 28 into the
plurality of holes 34.
Alternatively, a hammer can be used to press fit the wear-resistant 28 inserts
into the plurality of
holes 34. In the preferred embodiment, the wear-resistant insert 28 has a
protruding end 32 that is
shaped according to an intended use.
As the invention disclosed herein may be embodied in other specific forms
without
departing from the spirit or general characteristics thereof, some of which
forms have been
indicated, the embodiments described herein are to be considered in all
respects illustrative and
not restrictive. The scope of the invention is to be indicated by the appended
claims, rather than
by the foregoing description, and all changes which come within the meaning
and range of
equivalency of the claims are intended to be embraced therein.
I claim:
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