U.S. patent application number 10/379028 was filed with the patent office on 2004-09-09 for railcar draft gear housing.
Invention is credited to Anderson, David G., Wilt, Donald E., Withall, Andrew W..
Application Number | 20040173555 10/379028 |
Document ID | / |
Family ID | 32926592 |
Filed Date | 2004-09-09 |
United States Patent
Application |
20040173555 |
Kind Code |
A1 |
Wilt, Donald E. ; et
al. |
September 9, 2004 |
RAILCAR DRAFT GEAR HOUSING
Abstract
A railcar draft gear housing is disclosed. The railcar draft
gear housing is formed from an austempered ductile iron casting and
includes an open end, a closed end, and wall structure axially
extending between the housing's ends. The wall structure of the
housing defines an axial section between and spaced from the ends.
The axial section of the wall structure is configured to withstand
impact energy imparted to the housing in excess of 81,000 inch
pounds while retaining and exhibiting substantially linear
elasticity wherein the resultant ratio of stress to energy input
remains substantially constant thereby allowing for flexible
distortion of the housing in a manner promoting enhanced energy
damping characteristics.
Inventors: |
Wilt, Donald E.; (Batavia,
IL) ; Anderson, David G.; (Chesterton, IN) ;
Withall, Andrew W.; (St. Charles, IL) |
Correspondence
Address: |
John W. Harbst
1180 Litchfield Lane
Bartlett
IL
60103
US
|
Family ID: |
32926592 |
Appl. No.: |
10/379028 |
Filed: |
March 4, 2003 |
Current U.S.
Class: |
213/50 |
Current CPC
Class: |
B61G 9/24 20130101; B61G
7/10 20130101 |
Class at
Publication: |
213/050 |
International
Class: |
B61G 007/10 |
Claims
What is claimed is:
1. A railcar draft gear housing comprising: an austempered ductile
iron casting having an open end, a closed end, and wall structure
axially extending between said ends, with said wall structure
defining an axial section between and spaced from said ends, and
wherein said axial section of said wall structure is configured to
act as an elastic member capable of withstanding axial energy
imparted to said casting in excess of 81,000 inch pounds while
retaining and exhibiting substantially linear elasticity wherein
the resultant ratio of stress to energy remains substantially
constant.
2. The railcar draft gear according to claim 1 wherein said casting
is formed from a grade of ductile iron selected from the group
consisting of: ASTM Grade 1 ductile iron through ASTM Grade 5
ductile iron.
3. The railcar draft gear according to claim 1 wherein said casting
has an axial length measuring between about 14 inches and about 29
inches between said open and closed ends.
4. The railcar draft gear according to claim 1 wherein the axial
section of said sidewall structure has a cross-sectional area
measuring between about 9.5 inches and about 17.5 inches.
5. The railcar draft gear according to claim 1 wherein said casting
has a weight generally ranging between about 100 lbs. and about 150
lbs.
6. A railcar draft gear housing comprising: an as cast austempered
ductile iron casting having an open end, a closed end, and wall
structure axially extending between said ends, with said wall
structure defining an axial section spaced from and between said
ends for absorbing, dissipating and returning energy imparted to
said housing resulting from impact loads applied thereto, with the
axial section of said wall structure having a minimum yield
strength ranging between about 100 ksi. and about 150 ksi., with a
minimum compression in 2 inches ranging between generally about 3%
and about 15%, and with a BHN within a range of generally between
about 302 and about 500.
7. The railcar draft gear housing according to claim 6 wherein said
casting defines a series of openings arranged toward the closed end
for reducing the weight of said casting.
8. The railcar draft gear housing according to claim 6 wherein the
axial section of said housing is configured to withstand impact
energy in excess of 81,000 inch pounds while retaining and
exhibiting substantially linear elasticity wherein the resultant
ratio of stress to strain remains substantially constant whereby
allowing said housing to absorb, dissipate and return energy
imparted thereto.
9. The railcar draft gear according to claim 6 wherein said casting
is formed from a ASTM Grade 2 ductile iron.
10. The railcar draft gear according to claim 6 wherein said
casting has an axial length measuring between about 14 inches and
about 29 inches between said open and closed ends.
11. The railcar draft gear housing according to claim 6 wherein the
sidewall structure of said casting, including said axial section,
has a generally cylindrical cross-sectional configuration extending
between said open and closed ends.
12. The railcar draft gear housing according to claim 6 wherein
said axial section of said wall structure has a generally uniform
thickness over the length thereof.
13. The railcar draft gear housing according to claim 12 wherein
said axial section of said wall structure has a cross-sectional
area measuring between about 9.5 inches and about 17.5 inches.
14. A railcar draft gear assembly including a spring assembly for
dissipating energy forces imparted to said draft gear assembly and
a housing which surrounds said spring assembly, wherein said draft
gear housing is formed from an austempered composite metal material
having a density of generally about 0.25 lb./cu. in., and wherein
said housing includes an open end, a closed end, and wall structure
axially extending between said ends, with said wall structure
including a tubular axial section designed to offer over-solid
energy absorption protection for said draft gear assembly and is
configured to withstand impact energy in excess of 81,000 inch
pounds while retaining and exhibiting substantially linear
elasticity wherein the resultant ratio of energy input remains
substantially constant.
15. The railcar draft gear assembly according to claim 14 wherein
said housing has an axial length measuring between about 14 inches
and about 29 inches between said open and closed ends.
16. The railcar draft gear assembly according to claim 14 wherein
the tubular axial section of said sidewall structure on said
housing has a cross-sectional area measuring between about 9.5
inches and about 17.5 inches.
17. The railcar draft gear assembly according to claim 14 wherein
said housing defines openings arranged toward the closed end of
said housing so as to reduce an overall weight of said housing to
generally between about 75 lbs. and about 150 lbs.
18. A housing for an energy management system wherein said housing
is subjected to repeated axial impact loads, said housing
comprising: an austempered ductile iron casting having an open end,
a closed end, and wall structure axially extending between said
ends, with said wall structure defining an axial section between
and spaced from said ends, and wherein said axial section of said
wall structure is configured to withstand impact energy imparted to
said casting in excess of 81,000 inch pounds while retaining and
exhibiting substantially linear elasticity wherein the resultant
ratio of stress to energy input remains substantially constant.
19. An apparatus which, during operation, is subjected to repeated
axial loadings applied thereto, said apparatus comprising: an
as-cast elongated member formed from an austempered composite
material having a density of about 0.25 lb./cu. in., and wherein
said elongated member has first and second axially spaced ends with
wall structure axially extending between said ends, with said wall
structure including an axial section configured and designed to
offer over-solid energy absorption protection for said apparatus
and is configured to withstand impact energy in excess of 81,000
inch pounds while retaining and exhibiting substantially linear
elasticity wherein the resultant ratio of energy input remains
substantially constant.
20. The apparatus according to claim 19 wherein said as-cast
elongated member is formed from a grade of ductile iron selected
from the group consisting of: ASTM Grade 1 ductile iron through
ASTM Grade 5 ductile iron.
21. The apparatus according to claim 19 wherein the wall structure
of said as-cast elongated member, including said axial section, has
a generally cylindrical cross-sectional configuration extending
between said first and second ends.
22. The apparatus according to claim 19 wherein the axial section
of said as-cast elongated member is configured and designed to have
a generally uniform cross-sectional thickness over the axil length
thereof.
Description
FIELD OF THE INVENTION
[0001] This invention generally relates to an energy management
system subjected to extremely high impacts loads applied thereto,
and more particularly, to a railcar draft gear housing configured
to offer enhanced energy dampening capabilities to a railcar draft
gear assembly while advantageously being both stronger and weighing
significantly less than the same type prior art draft gear
housing.
BACKGROUND OF THE INVENTION
[0002] Energy management systems are used in a variety of
industrial applications wherein a vehicle is subjected to extremely
high impact loads and forces during operation. For example, in the
railroad industry, an energy management system in the form of draft
gear assemblies have been in widespread use on rolling stock for
many decades. A railcar draft gear assembly is used to cushion
shocks and dissipate energy encountered by railway rolling stock
during make-up and/or operation of a train consist on track
structure. The draft gear assembly typically nests in a pocket of a
railcar center sill. A typical draft gear assembly includes a
housing having a closed end, which abuts a rear wall of the pocket
within the car sill, and an open end.
[0003] It is recognized by persons skilled in the railcar draft
gear art, these draft gear assemblies must maintain certain minimum
shock absorbing capacity during in-track service. The railcar
industry furthermore continues to express interest in new, higher
capacity draft gear assemblies. Presently, minimum shock absorbing
capacity is specified by the Association of American Railroads
(AAR) Standards.
[0004] To accomplish and meet these standards, it is known to equip
such railcar draft gear assemblies with a suitable spring biased
mechanism arranged primarily within the confines of the draft gear
housing. A portion of the spring biased mechanism extends axially
beyond the housing to engage and operate in combination with a
follower plate. During in-track service, it is inevitable that
energy imparted to the railcar draft gear exceeds the reaction
capacity of the spring biased mechanism. As such, the draft gear
spring biased mechanism assumes an "over-solid" condition and all
remaining energy is imparted to the draft gear housing. As will be
appreciated by those skilled in the art, and while occurring on a
frequent basis, the energy required for the spring biased mechanism
to assume an "over-solid" condition is exceedingly substantial.,
i.e. in excess of 600,000 inch pounds. After the spring biased
mechanism reaches its "over-solid" condition, any excessive energy
is thereafter transferred through the draft gear housing into the
car sill and car body and, ultimately, to the lading carried
therewithin. Such energy imparted to the car frequently causes
significant damage to the lading carried within the railcar.
[0005] The railcar draft gear housing has been heretofore designed
from exceedingly massive ferrous metal, i.e., steel castings which
can withstand repetitive high energy impacts after the spring
biased mechanism has achieved an "over-solid" condition without
stress break or fracture. Such castings, however, typically require
further machining and/or other secondary operations prior to
incorporation of the spring biased mechanism therewithin. As will
be appreciated, such processes and/or operations require trained
manual efforts adding to the draft gear assembly costs without
contributing any appreciable benefit to its performance
characteristics.
[0006] With ever increasing fuel costs, there are continuing and
concerned efforts in the railroad industry to increase
productivity. Historically, increases have been achieved by
increasing the rolling stock comprising a train consist and
additionally the capacity of the railcars. Of course, increasing
the rolling stock comprising a train consist furthermore adds to
the dynamic energy transferred between adjacent cars comprising the
consist. AAR Standards regarding regulating the size of the
railcars along with the practical load limit of today's railroad
track system, however, has generally been reached. Accordingly,
attention is now being directed to other areas. For example,
lightening of the overall weight of the rolling stock without
sacrificing or unreasonably increasing costs is an on-going goal
and would improve railcars.
[0007] In the mid 1990's, the North American railroad industry
transported approximately 1.2 trillion ton-miles of lading in a
fleet consisting of about 1.5 million railroad cars with a revenue
of about $31 billion. Since the mid 1990's, such statistics have
only increased. Accordingly, and although minor improvements may
seem trivial when viewed with a narrow perspective, the overall
benefits to be achieved can be significant. Even when considering
individual train consists, it will be apparent, in a train consist
comprised of 100 cars, a mere five pound reduction in weight of
duplicated railcar components translates to one-half ton weight
reduction per train. As will, be appreciated, reducing the
cumulative empty weight of the 100 car train consist by one-half
ton allows that same train consist to transport an additional 1000
pounds of lading with no additional costs being added.
[0008] Thus, there is a need and continuing desire for a railcar
draft housing which is even stronger than known draft gear housing
of the same type and allow such draft gear housing to sustain
excessive energy applied thereto but is also significantly less
weight whereby contributing to fuel savings and increased train
lading capacity and which can be manufactured to such close
tolerances whereby substantially eliminating the need for
subsequent and expensive machining and/or other secondary
operations prior to actual use on the railcar.
SUMMARY OF THE INVENTION
[0009] In view of the above, and in accordance with the present
invention, there is provided a new and improved housing for an
apparatus or energy management system. In one form, there is
provided a railroad draft gear housing having improved operating
characteristics which can be manufactured at a lower cost than
heretofore known draft gear housing of a similar type. Although the
material of the railcar draft gear housing has been modified along
with its cross-sectional dimensions, it advantageously remains and
retains its interchangeability with draft gear housings serving the
same purpose while offering an improved strength to weight ratio.
The present railcar draft gear housing is especially advantageous
in that it is not only stronger than prior railcar draft gear
housings of the same type, it is also significantly lighter in
weight thereby contributing to fuel savings and/or increased lading
capacity for the associated railcar.
[0010] In accordance with a first aspect, there is provided a
railcar draft gear housing which combines the strength, ductility,
fracture toughness and wear resistence of steel with the
castability and product economies of ductile iron. The draft gear
housing of the present invention is produced from an austempered
ductile iron casting having an open end, a closed end, and wall
structure axially extending between the housing's ends. The wall
structure of the housing defines an axial section between and
spaced from the ends. In accordance with the present invention, the
axial section of the wall structure is designed and configured to
act as an elastic member which is capable of withstanding impact
energy imparted to the casting in excess of 81,000 inch pounds
while retaining and exhibiting substantially linear elasticity
wherein the resultant ratio of stress to energy input remains
substantially constant. That is, and unlike heretofore known steel
draft gear housings, the wall structure of the draft gear housing
is designed and configured to flexibly distort within a yield range
of austempered ductile iron whereby advantageously serving to
absorb, dissipate and return energy imparted thereto during
operation of the railcar and thereby enhancing overall operation of
a draft gear assembly, of which the housing forms an integral part,
without increasing the cost of such assembly.
[0011] Research has revealed superior results are obtainable when
the railcar draft gear housing is preferably formed from a grade of
ductile iron selected from the group consisting of: ASTM Grade 1
ductile iron through ASTM Grade 5 ductile iron. To accomplish the
preferred goal of interchangeability mentioned above, the railcar
draft gear casting preferably measures between about 14 inches and
about 29 inches in axial length between the open and closed ends.
Moreover, and to significantly lessen the overall weight of the
draft gear assembly, the axial section of the sidewall structure
for the railcar draft gear housing has a cross-sectional area
measuring between about 9.5 inches and about 17.5 inches.
Accordingly, the casting for the draft gear housing advantageously
weighs only generally between about 75 lbs. and about 150 lbs.
[0012] In accordance with another aspect, there is provided a
railcar draft gear housing produced from an as cast austempered
ductile iron casting having an open end, a closed end, and wall
structure axially extending between the ends. The wall structure
defines an axial section spaced from and between said ends for
absorbing, dissipating and returning energy imparted to said
housing resulting from impact loads applied thereto. Additionally,
the axial section of the wall structure has a minimum yield
strength ranging between about 100 ksi. and about 150 ksi., with a
minimum compression in 2 inches ranging between generally about 3%
and about 15%, and with a BHN within a range of generally between
about 300 and about 500. The ability of the axial section of the
housing's wall structure to absorb impacts without fracture or
breakage beyond a range permitted with steel castings of the prior
art coupled with the ability of the as-cast austempered ductile
iron casting to return to its original state or condition provides
the draft gear housing with a unique ability and structural
characteristic contributing significantly improved performance to
the draft gear assembly during railcar operation without requiring
costly and time-consuming machining and other secondary operations
to be performed on the draft gear housing.
[0013] The railcar draft gear housing casting is furthermore
preferably configured with a series of openings arranged toward the
housing's closed end to eliminate and minimize unnecessary mass and
reducing the overall weight thereof, thus, increasing the load
carrying capacity of the railcar. In a preferred embodiment, the
sidewall structure of the casting, including the axial section, has
a generally cylindrical cross-sectional configuration extending
between the housing's ends. The axial section of the wall structure
has a cross-sectional area measuring only between about 9.5 inches
and about 17.5 inches. Preferably, the generally cylindrical
cross-sectional configuration of the casting, at least through the
axial section, has a generally uniform thickness whereby allowing
the railcar draft gear housing to retain and exhibit substantially
linear elasticity wherein the resultant ratio of stress to energy
input remains substantially constant even after the energy imparted
solely to the housing exceeds 81,000 inch pounds.
[0014] Still another aspect relates to providing a railcar draft
gear assembly including a spring assembly for dissipating energy
forces imparted to said draft gear assembly and a housing which
surrounds the spring assembly. The draft gear housing is formed
from a high strength, low-alloy, austempered composite metal
material whose mechanical properties can be varied over a wide
range by a suitable choice of heat treatment and having a density
of generally about 0.25 lb./cu. in. The housing includes an open
end, a closed end, and wall structure axially extending between the
opposed ends. The housing wall structure includes a tubular axial
section designed to offer over-solid energy absorption protection
to the draft gear assembly. That is, and following the spring
assembly acting to effect energy absorption equal to or in excess
of 600,000 inch pounds and being compressed into an "over-solid"
condition, the draft gear housing is designed and configured to
provide the draft gear assembly with an at least an additional
81,000 inch pounds of energy absorption capability while retaining
and exhibiting substantially linear elasticity wherein the
resultant ratio of stress to energy remains substantially constant
whereby enhancing the overall life expectancy of the railroad
equipment.
[0015] According to still another aspect, there is provided an
apparatus which, during operation, is subjected to repeated axial
loadings applied thereto. The apparatus includes an as-cast
elongated member formed from an austempered composite material
having a density of about 0.25 lb./cu. in., and wherein said
elongated member has first and second axially spaced ends with wall
structure axially extending between said ends, with said wall
structure including an axial section configured and designed to
offer over-solid energy absorption protection for said apparatus
and is configured to withstand impact energy in excess of 81,000
inch pounds while retaining and exhibiting substantially linear
elasticity wherein the resultant ratio of energy input remains
substantially constant.
[0016] Accordingly, one object of the present invention is to
provide a new and improved housing for an apparatus or energy
management system which is not only interchangeable with but is
also stronger and lighter than a comparable energy management
system steel housing now in use whereby contributing to fuel
savings and/or increased lading capacity for the apparatus or
vehicle with which the energy management system is in operable
combination.
[0017] Another object of the present invention is to provide a
railcar draft gear housing having at least one axial section
capable of absorbing, dissipating and returning impact forces
imparted to the housing whereby adding enhanced dampening of
excessive energy imparted thereto and, thus, contributing to
improved performance of a draft gear assembly than heretofore
obtainable with known steel housings.
[0018] Yet another feature of the present invention relates to the
provision of a railcar draft gear housing which is made of a
stronger base material which permits openings to be designed into
the housing to enhance weight and material reduction essentially
without sacrificing strength.
[0019] An even further object of this invention relates to the
provision of a railcar draft gear housing which is made from a high
strength, low alloy, austempered composite material which is
lighter in weight and less costly than materials heretofore used
for railcar draft gear housings.
[0020] These and other objects aims and advantages of the present
invention will become readily apparent from the following detailed
description, drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a fragmentary side sectional view showing one form
of a draft gear assembly embodying features of the present
invention arranged in a pocket of a railcar centersill, with
component parts being shown in section;
[0022] FIG. 2 is a fragmentary top sectional view of the draft gear
assembly shown in FIG. 1 arranged in operable combination within
the pocket of the railcar centersill, with component parts being
shown in section;
[0023] FIG. 3 is an enlarged longitudinal cross-sectional view of
the draft gear assembly illustrated in FIGS. 1 and 2;
[0024] FIG. 4 is a plan view of the draft gear assembly illustrated
in FIG. 3;
[0025] FIG. 5 is a fragmentary sectional view taken along line 5-5
of FIG. 4;
[0026] FIG. 6 is a diagrammatic comparison showing proportional
limits of a housing according to the present invention and a
comparable steel draft gear housing; and
[0027] FIG. 7 is diagram showing characteristics of elasticity for
an axial section of the draft gear housing according to the present
invention.
DESCRIPTION OF THE INVENTION
[0028] While the present invention is susceptible of embodiment in
multiple forms, there is shown in the drawings and will hereinafter
be described a preferred embodiment of the invention, with the
understanding the disclosure is intended to set forth an
exemplification of the invention which is not intended to limit the
invention to the specific embodiment illustrated and described.
[0029] Referring now to the drawings wherein like reference
numerals indicate like parts throughout the several views, there is
shown in FIG. 1 an energy management system, generally identified
by reference numeral 10, and embodying features of the present
invention. In the exemplary embodiment, the energy management
system 10 is illustrated as a railcar draft gear assembly. As will
be appreciated by those skilled in the art, each railcar is
provided, toward opposed ends, with a railcar draft gear assembly
which functions to dissipate energy between adjacent railcars. It
will be appreciated, however, the teachings and advantages of the
present invention equally apply to other forms or types of energy
management systems without detracting or departing from the spirit
and scope of the present invention.
[0030] In the example illustrated, the railcar draft gear assembly
10 is arranged in operable association with a longitudinal
centersill 12 of a railcar, generally identified by reference
numeral 14. In the exemplary embodiment, the railcar centersill 12
has a top wall 16 with a pair of laterally spaced sidewalls 17 and
18 (FIG. 2) depending therefrom. It should be appreciated, however,
the draft gear assembly of the present invention can be used in
railcar sills not having a top wall. Advantageously, no
modifications or changes are necessary to conventional cast or
fabricated railcar centersills to enable use with the draft gear
assembly of the present invention.
[0031] In the embodiment shown in FIG. 2, the railcar centersill 12
includes a pair of laterally spaced front stops 20 and 22 and a
pair of laterally spaced rear stops 24 and 26. The stops 20, 22 are
axially spaced from stops 24, 26 to define a pocket 28 wherein the
draft gear assembly 10 is accommodated as either a new or
interchangeable repair/replacement assembly for the railcar. In
addition to those conventional features mentioned, the centersill
12 can have other standard features and can be manufactured of
standard materials using conventional, well known practices.
Suffice it to say, the centersill pocket 28 on railcar 14 has an
axial or longitudinal distance ranging between about 16 inches and
about 36 inches provided between the stops 20, 22 and 24, 26. In a
most preferred embodiment, the centersill pocket 28 has an axial or
longitudinal distance of about 24.625 inches between the stops 20,
22 and 24, 26.
[0032] Returning to FIG. 1, a conventional generally U-shaped yoke
30, having longitudinally extending and vertically spaced arms 32,
34 joined at one end to a wall 36, is arranged in operable
combination with the draft gear assembly 10. Preferably, the yoke
30 is a one-piece unit. As shown in FIGS. 1 and 2, a free end of a
standard coupler shank 40 extends between the spaced ends of arms
32 and 34 and is articulately joined to yoke 30 through a coupler
pin 42. A conventional follower plate 44, movably carried within
pocket 28, is operably associated with the end of the coupler shank
40 and effectively transfers energy between coupler shank 40 and
the railcar draft gear assembly 10.
[0033] Turning to FIG. 3, the railcar draft gear assembly 10
generally includes a housing 50 and a spring mechanism 60 for
dissipating energy axially imparted to the draft gear assembly
during operation of the railcar 14. As shown, draft gear housing 50
defines a longitudinal centerline 52 and has a base 54 defining a
closed end for housing 50, an open end 56, and a relatively thin,
fine featured wall structure 58 axially extending between the
axially spaced ends 54, 56. The draft gear housing 50 can measure
between about 14 inches and about 29 inches in length between the
ends 54, 56 depending upon the longitudinal opening defined by the
centersill pocket 28. With the longitudinal distance of the
centersill pocket 28 measuring about 24.625 inches, the draft gear
housing 50 will measure about 22.375 inches in length between ends
54, 56. In the one form, and with those exceptions noted below, the
draft gear housing wall structure 58 has a generally tubular or
hollow configuration defining a spring chamber 59 extending the
majority of its length.
[0034] Base 54 of housing 50 preferably has a generally rectangular
configuration for facilitating transfer of energy applied to the
draft gear assembly 10 to the stops 24, 26 on the centersill 12
(FIG. 2). In a preferred form, wall structure 58 has a generally
cylindrical cross-sectional configuration for a major portion of
its length. Notably, and as shown in FIG. 3, in the area where the
cylindrical-like configuration of the wall structure 58 is
integrally joined to the base 54, a round or curved transitional
area is provided whereby reducing the creation of a stress
concentration area in the housing 50.
[0035] As shown, the draft gear housing 50 is arranged in
surrounding relation relative to the spring mechanism or assembly
60. The spring assembly 60, accommodated in the spring chamber 59
of housing 50, can be of any of a myriad of different conventional
designs and types, i.e., one or more steel springs and/or a stack
of elastomeric spring pads, or a combination of both.
[0036] As shown in FIGS. 4 and 5, the housing 50 and spring
mechanism 60 are provided with cooperating instrumentalities 62 for
allowing a significant preload force to be imparted to the spring
mechanism 60 of the draft gear assembly 10. In the illustrated
embodiment, and toward the open end 56 of housing 50, an inner
surface 64 of the housing wall structure 58, is provided with a
series of equally and radially spaced lugs 66 which project toward
the longitudinal centerline 52 of the draft gear housing 50. These
draft gear housing lugs 66 are adapted and configured to cooperate
with suitably arranged openings 67 defined by a spring seat 68
arranged in spring chamber 59 (FIG. 5) of housing 50 in operable
combination with one end of the spring mechanism 60. The other end
of the spring mechanism 60 engages an interior surface at the
closed end 54 of housing 50. As will be appreciated, the
cooperating instrumentalities 62 between housing 50 and spring
mechanism 60 can take any of a myriad of other different designs
and shapes without detracting or departing from the spirit and
scope of the present invention.
[0037] Spring assembly 60 furthermore operably includes a plunger
70 arranged in operable combination with the spring seat 68. As
will be appreciated, plunger 70 axially moves with the spring seat
68 in response to energy being axially directed or imparted to the
draft gear assembly 10. As shown, and during operation of the draft
gear assembly 10 (FIGS. 1 and 2), a lengthwise portion of plunger
70 extends axially beyond the open end 56 of the draft gear housing
50 for operable engagement with the follower plate 44 carried
within the centersill pocket 28. In one form, the free end of
plunger 70 extends about 1.625 inches beyond the open end 56 of
housing 50. As will be appreciated, and with reduced or no energy
being imparted to the draft gear assembly 10, the preload of spring
mechanism 60 maintains the draft gear housing base 54 in abutting
relationship with the stops 24, 26 of the centersill pocket 28
while the free end of the plunger 70 urges the follower plate 44
into engagement with the stops 20, 22 at the opposite end of the
draft gear housing pocket 28.
[0038] The draft gear housing 50 of this invention is similar to
those of the prior art in order to maintain interchangeability,
with a first primary difference being the wall structure 58 of
draft gear housing 50 has an axial section, generally identified in
FIG. 3 by reference numeral 74, which is designed and configured to
advantageously absorb, dissipate and return energy imparted
thereto. That is, during operation of the draft gear assembly, and
after the spring mechanism 60 reaches or is moved to an
"over-solid" condition, the draft gear housing 50 remains operable
to further dampen excessive energy not absorbed by mechanism 60 and
applied directly to the housing 50 and which exceeds that level of
energy sustainable with prior art devices.
[0039] In addition, and as a second primary difference, the
inventive draft gear housing 50 has a superior strength to weight
ratio, i.e., housing 50 is stronger and more durable than prior art
steel draft gear designs As a result, the draft gear housing 50 can
offer significantly longer service life, thus, reducing downtime
required for servicing the draft gear assembly 10 and improving
operating expenses of the railcar using such railcar draft gear
housing
[0040] As another primary difference between the inventive draft
gear housing 50 and prior art draft gear housing designs, the
cross-sectional area of the wall structure 58 comprising the
majority of the housing 50 and axially extending between opposed
housing ends 54 and 56 has been significantly reduced. Moreover,
and with cut-outs or openings described below, the draft gear
housing 50 is of significantly lighter weight than comparable prior
art draft gear housing designs. As will be appreciated, reducing
the overall weight of the draft gear assembly 10 undoubtedly
contributes to both fuel savings, material costs, and furthermore
allows the lading capacity for the associated railcar to be
increased without adding significant costs to the railcar.
[0041] While internal dimensions of the draft gear housing spring
chamber or cavity 59 are comparable to prior art designs whereby
eliminating concerns over effective operation of tested spring
mechanisms 60, the outer dimensions of the draft gear housing 50
have been significantly altered to reduce the cross-sectional size
of the casting and, thus, reducing the weight thereof. Typical
prior art steel draft gear housings are designed with a
cross-sectional area having a minimum measurement of about 20.0
square inches and ranging as up to 24.5 square inches. Such
cross-sectional designs have been required to enable those prior
art draft gear steel housings to withstand the excessive levels of
energy axially applied thereto In contrast, the inventive draft
gear housing 50 has a cross-sectional area measuring between
generally about 9.5 square inches and about 17.5 square inches. As
such, even the maximum 17.5 square inch cross-sectional area design
of the inventive draft gear housing 50 is well outside the minimum
cross-sectional area of prior art draft gear housing designs.
[0042] The draft gear housing 50 of this invention is furthermore
different from steel draft gear housings of the prior art in that
the inventive draft gear housing 50 is fabricated from a high
strength, low alloy metal composite having a density of about 0.25
lbs./cu. inch, which is heat treated, and has a minimum yield
strength ranging between about 100 ksi. and about 150 ksi., with a
minimum compression in 2 inches ranging between generally about 3%
and about 15%, and with a BHN within a range of generally between
about 302 and about 500.
[0043] One of the more important considerations in making the high
strength housing 50 is to minimize the defects inside and on the
surface of the castings. Of course, near net shape casting
technology will reduce the costs of production. Accordingly, and to
better control the dimensional limits, the inventive housing 50 is
preferably cast using a lost-foam technique or process to achieve
an as-cast configuration. With such technique, polyaryrene or
polymethyl methacrylate is shaped into a foam replica of the
housing 50 and from which gating is attached. Loose sand is
vibrated therearound to form a mold with gating into which molten
metal is poured. As the molten metal is poured into the mold, the
foam replica is vaporized by the molten metal, and the hot cast
metal takes its place to form the casting within the sand mold. As
such, subsequent machining operations and related time consuming
secondary operations normally required with castings is
substantially eliminated. Alternatively, a green sand molding
process could also be used whereby producing an as-cast
configuration for the housing 50. The lost foam method and related
casting techniques are well known in the foundry art and, thus, no
further description need be provided therefor.
[0044] Because of the superior strength of housing 50, at least one
and preferably a pair of cut-outs or openings 76 can be provided
therein to effect further weight reduction by selectively
eliminating any unnecessary portions of the casting. As shown, and
without any adverse effect on the overall strength or life of the
housing 50, the openings 76 are preferably disposed toward the
closed end 54 of the housing and extend toward the open end 52 of
housing 50. Because loading on the housing 50 is primarily
compressive, and dissipation of the energy imparted to the housing
56 is primarily effected by the sidewall structure 58 axially
extending from the open end 56 of the housing 50, the arrangement
of the openings 76 toward the closed end 54 of the housing 50 have
a minimal adverse effect on the overall strength of the housing
50.
[0045] The inclusion of such openings or reliefs 76 in the casting
50 will not only reduce the weight thereof, but will furthermore
serve to reduce the amount of material necessary to cast such
housing 50. Of course, and as will be appreciated by those skilled
in the art, lesser materials used in the housing 50 will
furthermore facilitate the heat treating process described in
further detail below. Moreover, configuring the openings or
recesses 76, i.e., providing a triangular shape to the openings 76,
will furthermore advantageously facilitate transfer of energy along
the sidewall structure 58 to the closed end 54 and, ultimately, to
the stops 24, 26 on the centersill 12 of the railcar. While the two
above described openings 76 are included in the presently preferred
embodiment of housing 50, it will be appreciated other cut-outs or
reliefs having alternative configurations from that shown can also
be included if additional weight reduction is desired.
[0046] Toward the open end 56, housing 50 is preferably configured
with diametrically opposed guides 77 radially extending outwardly
from and formed integral with an outer surface of the housing wall
structure 58. As shown, each guide 77 is preferably configured as a
handle whereby facilitating handling of the housing 50. To
effectively serve their purpose, the overall distance measured
transversely between an outermost radial surface of the two guides
77 is slightly less than the distance measured between the two
laterally spaced sidewalls 17, 18 (FIG. 2) of the railcar
centersill 12. As such, the guides 77 promote unhindered axial
movements of the draft gear assembly housing 50 within the
centersill pocket 28 in response to both buff and draft loads being
imparted to the draft gear assembly 10 (FIG. 1) during operation of
the railcar 14.
[0047] Referring again to FIG. 3, and unlike prior art draft gear
housing having varying wall thicknesses along the axial length of
the draft gear housing, a salient feature of the innovative and new
housing 50 relates to configuring the wall structure 58, and
especially an axial section 74 of the wall structure 58, with a
generally uniform cross-section. Notably, the preferred uniform
cross-sectional configuration for the wall structure 58, and
especially the axial section 74 embodies a significant lengthwise
portion of the draft gear housing 50 with a resiliently deformable
characteristic when excessive energy is applied thereto and which
recovers to its original configuration when such excessive energy
is released therefrom.
[0048] It should be appreciated, however, and without detracting or
departing from the spirit and scope of the present invention, the
housing wall structure 58 can be comprised of more than one
similarly shaped or configured axial section 74. In such an
alternative design, the axial sections 74 would be axially
separated from each other along the length of wall structure 58
and, during operation of the draft gear assembly, cooperate with
each other to provide the housing 50 with a heretofore unachieved
energy absorbency thereby enhancing the dampening effect provided
by the housing 50. Regardless of whether one or more axial sections
74 are included as part of the housing wall structure 58, suffice
it to say configuring and designing one or more axial sections 74
of the draft gear housing wall structure 58 with a generally
uniform thickness yields a draft gear housing design which can
retain and exhibit substantially linear elasticity wherein the
resultant ratio of stress to energy input remains substantially
constant even after the energy imparted to the assembly housing 50
exceeds 81,000 inch pounds, while furthermore facilitating an
austempereing heat treatment process for the housing 50 described
in further detail below.
[0049] For commercial purposes, the inventive draft gear housing 50
is produced or formed from a grade of ductile iron selected from
the group consisting of: ASTM Grade 1 ductile iron through ASTM
Grade 5 ductile iron (ASTM 897/897M). These particular grades of
ductile iron are said to be heat treatable ductile irons to which
relatively small amounts of nickel, molybdenum, silicon, manganese
or copper have been added to improve the desired hardenability and
to derive the required strength and hardness properties required
for sustained operation of a railcar draft gear wherein enormous
impact loads are regularly and consistently imparted thereto. In a
most preferred embodiment, an ASTM Grade 2 ductile cast iron forms
the draft gear housing 50.
[0050] The alloy content or elemental composition of the ductile
iron is necessary for hardenability purposes or the
austemperability of the ductile iron. Without detracting or
departing from the spirit and scope of the present invention, the
chemical or elemental composition of the ductile iron can vary and
will, ultimately, be established between the foundry and the heat
treater. One presently preferred metallurgical or elemental
chemical composition of the ductile iron used to form the housing
50 is: carbon, in a range of between 3.6 and about 3.75 weight %;
silicon, in a range of about 2.4 and about 2.8 weight %; nickel,
having a maximum of about 2.0 weight %; manganese, in a range of
between about 0.18 and about 0.35 weight %; molybdenum, in a range
of between about 0.14 and about 0.19 weight %; copper, in a range
of about between about 0.40 and about 0.80 weight %; and, sulfur,
having a maximum of about 0.015 weight %; with the remaining
balance, of course, being iron. In a most preferred form, it is
desirable to maximize the alloy content of nickel and copper since
this is likely to lead to increase in retained austenite content.
Retained austenite enhances energy absorption of the housing 50 and
results in better toughness and fatigue strength.
[0051] It has been found the variables affecting as-cast ductile
iron also affect austempered ductile iron. That is, the
characteristics that result in good quality ductile iron also
promote good austempered ductile iron. In general, the critical
characteristics for the manufacture of austempered ductile iron can
be generalized as: 100 nodules/mm.sup.2 minimum; 90% minimum
nodularity; 0.5% maximum carbides & inclusions; 1% maximum
micro-shrinkage; minimum inclusion content; and, a controlled
pearlite/ferrite ratio.
[0052] After the draft gear housing 50 is formed, the housing 50 is
heat treated using an austempering process. Heat treatment of the
housing 50, through its influence on microstructure of the alloyed
casting, has a strong effect on energy absorption properties for
the housing 50. More specifically, the casting is heated to an
austensitized heat level sufficient to dissolve the carbon and
yields high strength along with improved wear resistence combined
with enhanced toughness. Unlike the relatively constant carbon
concentration inherent with steel, regardless of the heat treatment
applied thereto, and because of the presence of graphite particles,
the carbon content of an austempered ductile iron matrix can vary
depending upon on the thermal history to which the casting was
subjected. Here, the casting forming housing 50 is heated until the
entire casting is of a substantially uniform temperature above the
Ae.sub.3 temperature of the metal. As will be appreciated, the
relatively uniform cross-section of the housing wall structure 58,
and especially the axial section 74, advantageously facilitates
heating of the casting to a substantially uniform temperature above
the Ae.sub.3 temperature of the metal. The optimum austenitizing
temperature is dependent upon the elemental composition or
chemistry of the ductile iron forming housing 50 and the strength
grade desired. Moreover, the time the casting forming the housing
50 remains at the austenitizing temperature is equally as important
as the choice of Ae.sub.3 temperature and is a function of the
elemental composition of the ductile iron forming the casting, the
nodule count, and the section thickness of the casting. Suffice it
to say, the casting forming the housing 50 will preferably be held
at the Ae.sub.3 or austenitizing temperature for a time sufficient
to create an austenite matrix saturated with carbon. As will be
appreciated, this time is additionally affected by the elemental
composition or chemistry of the ductile iron forming housing
50.
[0053] After heating the casting to a substantially uniform
temperature above the Ae.sub.3 temperature, the casting is rapidly
quenched, enough to avoid formation of pearlite, to a temperature
in the lower bainite region just above the M.sub.s temperature, and
held at that temperature for a time which is at least sufficient to
cause transformation to form acicular ferrite precipitate within an
austentite matrix. As in all austempered grades, carbon is rejected
into the austentite matrix whereby the resulting microstructure of
housing 50 is acicular ferrite in a carbon stabilized austentite,
which is often designated ausferrite. This differs from bainite
(found in steels) which is acicular ferrite and carbon. Once the
ausferrite has been produced, the austempered housing 50 is cooled
to room temperature. This cooling rate will not affect the final
microstructure. As known, steel solidifies as a single phase solid.
In contrast, an austempered ductile iron solidifies through an
eutectic process. The solute distributors in steel are vastly
different from the solute distributors in austempered ductile iron
due to the different modes of solidification. Suffice it to say,
the solute distribution alters the carbon kinetics in cast
irons.
[0054] Turning now to FIG. 6, an example of the elasticity of the
axial section 74 of housing 50 as compared to a similar area on a
conventional steel draft gear housing is schematically illustrated.
As graphically illustrated, the ability of both the innovative
housing 50 and the prior conventional draft gear housing to absorb,
dissipate and return like amounts of energy axially imparted to the
respective housings remains substantially similar to a point.
[0055] After the axial application of about 81,000 inch pounds to
the tested housings, however, there is a remarkable difference in
their performance characteristics. More specifically, the energy
absorption capacity of the inventive housing 50 tested far greater
than conventional draft gear housings. Following an impact of about
81,000 inch pounds, the configuration and elemental composition of
the innovative draft gear housing 50, permits the axial section 74
of housing 50 to react with an elasticity illustrated by curve 80.
Notably, the elasticity of the housing section 74, illustrated by
curve 80, remains substantially linear wherein the resultant ratio
of stress to energy input is substantially constant. In contrast,
and as will be apparent from the graph illustrated in FIG. 6,
following the application of about 81,000 inch pounds to a
conventional prior art draft gear casting, the elasticity or
proportional limit of the prior art steel housing has been
exceeded, and, as graphically illustrated by curve 82, is lost
whereby indicating the prior art steel housing has fractured and
failed. Thus, and as illustrated in FIG. 6, designing and
configuring the wall structure 58 of the draft gear housing 50 with
an axial section 74 as described above and having an elemental
composition as described above, advantageously allows the draft
gear housing 50 to exhibit absorption, dissipation and return of
energy imparted thereto in a manner unachieved in the railcar draft
gear housing arts.
[0056] A draft gear housing embodying features of this invention
reacts to axial energy imparted thereto in the manner
diagrammatically illustrated in FIG. 7. In FIG. 7, the upper curve
90 illustrates compression of the draft gear housing 50, after the
spring mechanism 60 reaches an "over-solid" condition. The lower
curve 92 indicates expansion of the of the draft gear housing 50
following a reduction in axial energy applied thereto. The complete
cycle of compression and expansion in response to energy being
axially applied to the draft gear housing 50 comprises a hysteresis
loop, with energy being dissipated during the cycle. As will be
appreciated, with such energy dissipation, the draft gear housing
50 acts as a damper which reduces the transfer of energy to the
centersill 12 and, ultimately, to the loading within the railcar
14.
[0057] It will be understood, of course, the hysteresis loop
illustrated in FIG. 7 is set forth by way of example only. A
different austempered ductile iron composition for the draft gear
housing 50 can shift the curves somewhat and, thus, produce a
slightly different hysteresis loop without detracting or departing
from the true spirit and scope of the present invention. It should
be furthermore noted, the present invention is not limited to any
particular austempered ductile iron composition providing any
particular hysteresis loop and/or damping characteristic unless
expressly set forth in the appended claims.
[0058] The ductile iron material used to form the draft gear
housing 50 is less dense than other ferrous metals. Moreover, the
heat tempering process coupled with the properties of the materials
used to form the draft gear housing 50 allows the wall thickness
for the axial section 74 to be less thick than required for
heretofore used ferrous metals. Of course, reduced density of the
material used to form the draft gear housing 50 coupled with a
significantly lesser wall thickness cross-section readily
translates to less weight for the draft gear housing 50. In fact,
research has shown a draft gear housing embodying features of the
present invention can weight 30% to about 40% less than a
comparable draft gear housing formed from steel. Given the
extremely long haul distances some railcars travel, railcar weight
reductions are always sought after goals in the railcar industry.
In one form, the draft gear of the present invention weighed about
50 pounds lighter than a comparable prior art draft gear housing
formed from steel. Since, each railcar typically embodies two draft
gear assemblies, a 100 pound reduction in the empty weight of the
railcar, offered by the teachings of the present invention at
lesser cost than heretofore known draft gear assemblies, is another
significant advantage offered by the present invention over prior
art steel draft gear housings.
[0059] After the spring mechanism 60 of the draft gear assembly 10
achieves or assumes an "over-solid" condition", and the remaining
energy is applied to the draft gear housing of the present
invention, the axial section 74 of wall structure 58 will flex or
bulge radially outward whereby absorbing, dissipating, and,
ultimately, returning such energy imparted to the draft gear
housing 50 rather than merely passing or transferring such forces
to the railcar. As such, the railcar draft gear housing 50 is
specifically engineered and designed to offer and provide enhanced
force damping qualities beyond those of prior art draft gear
housing designs.
[0060] From the foregoing, it will be observed that numerous
modifications and variations can be made and effected without
departing or detracting from the true spirit and novel concept of
the present invention. Moreover, it will be appreciated, the
present disclosure is intended to set forth an exemplification of
the invention which is not intended to limit the invention to the
specific embodiment illustrated. Rather, this disclosure is
intended to cover by the appended claims all such modifications and
variations as fall within the spirit and scope of the claims.
* * * * *