Note: Descriptions are shown in the official language in which they were submitted.
CA 02561562 2012-04-17
TAPER UNDER TAPER PLATE TO INCREASE
SIDE FORCE ON THE MOVABLE PLATE
FIELD OF THE INVENTION
The present invention relates, in general, to draft gear assemblies for use in
cushioning both buff and draft shocks normally encountered by railway rolling
stock during =
make-up and operation of a train consist on a track structure and, more
particularly, the present
invention relates to a draft gear assembly having a tapered plate wherein a
portion of the bottom
surface which contacts the third lug of the housing is angled to increase the
side force on the
movable plate which increases the draft gear assembly's resistance to closure
and increases the
to capacity of the draft gear assembly.
BACKGROUND OF THE INVENTION
Draft gear assemblies which utilize friction-type clutch mechanisms to absorb
heat energy generated during service have been in widespread use in the
railroad industry for
many years to absorb both buff and draft shocks applied to the railway rolling
stock. Many of
such draft gear assemblies which were in use, prior to the present invention,
are taught in U.S.
Patent No.'s 2,916,163; 3,178,036; 3,447,693; and 4,645,187. Each of the above-
identified
patents is owned by the assignee of the present invention.
These draft gear assemblies are designed to receive coupler forces and
dissipate
them without damage to the car structure and lading. The assemblies are
disposed within an
elongated opening located in the center sill member of the railway car along
the longitudinal axis
thereof and behind the shank, or innermost end, of the railway car's coupling
mechanism. In this
position, these friction clutch type draft gear assemblies will absorb at
least a relatively large
portion of both the buff and draft forces generated during service. Such buff
and draft forces
encountered by such railway cars are usually being applied in an alternating
manner to the center
sill member during normal car operation on the track.
It is well recognized in the art that these draft gear assemblies must be
provided
with the capability of maintaining at least a certain minimum shock absorbing
capacity both
during making up a train consist and in-track service. Such minimum capacity
has been specified
by the Association of American Railroads (AAR) and is defined in the standards
issued by the
AAR. For example, friction clutch type draft gear assemblies have a specified
absolute minimum
capacity rating of at least 36,000 foot pounds. Any draft gear assembly with a
capacity rating
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which is determined to be below 36,000 pounds will not receive approval from
the AAR for
service on any railroad car which may be used in interchange.
It is, likewise, important to note that the heat energy absorbing action of
the
friction clutch mechanism must enable this minimum capacity rating to be
readily achieved
without exceeding a specified maximum 500,000-pound reaction force, or
pressure, being exerted
on the center sill member of the railway car during both such make-up and
operation of such train
consist. It has been found that such maximum reaction pressure is required to
enable these high
energy shocks to be readily absorbed without upsetting the end of the coupling
member shank
and/or damaging other critical car components and/or lading that is being
transported by such
railway car.
In order for the manufacturers of such friction clutch type draft gear
assemblies
to meet the requirements of the railroad industry, with the ever-increasing
load can-ying capacity
of their modern day railroad cars, it has become of extreme importance to
enhance the overall
rated capacity of the friction-type draft gear assemblies as much as possible.
This higher capacity
rating being found necessary in order to minimize any damage to such cars
and/or the lading due
to the increased forces being exerted on the center sill member of the cars by
the heavier loads
such cars are now carrying.
SUMMARY OF THE INVENTION
an increased capacity and resistance to closure.It is therefore an object of
the invention to produce a draft gear assembly having
It is a further object of the invention to provide a frictional cushioning
means for
a draft gear assembly wherein an additional side force is applied to the
movable plates from the
tapered plate.
It is yet a further object of the invention to provide a cushioning means for
a draft
gear assembly wherein an angle is provided on the portion of the bottom edge
of the tapered plate
which contacts the third rib of the housing and/or to the taper plates ear/lug
which sits on the
third rib so as to increase the side force on the movable plate, increasing
the capacity of the draft
gear and providing a greater resistance to closure.
It is an additional object of the invention to provide sufficient clearance
between
the angled edge surface of the tapered plate and the seat means of the draft
gear assembly while
accounting for wear of the compressible cushioning element.
Briefly, and in accordance with the forgoing objects, the invention comprises
a
draft gear assembly comprising a housing closed at one end and open at the
opposed end and
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having a rear portion adjacent the closed end and a front portion adjacent the
open end, a
compressible cushioning element centrally disposed within the rear portion
abutting the housing
end and extending longitudinally there from, a seat means abutting the
opposite end of the
compressible cushioning element during application and release of a force on
the draft gear
assembly, and a friction cushioning means positioned at least partially within
said front portion
of said housing for absorbing energy during a compression of said draft gear
assembly. The
friction cushioning means includes a pair of laterally spaced outer stationary
plates having an
outer surface for engaging the housing and an opposed inner friction surface,
a pair of laterally
spaced movable plates having an outer friction surface for movably engaging
the outer stationary
plates, an inner friction surface and at least one substantially flat edge
intermediate said outer
friction and inner friction surfaces for engaging the seat means, a pair of
laterally spaced tapered
plates having an outer friction and an inner friction surface wherein the
outer friction surface
movably and frictionally engages the inner friction surface of the movable
plate, a pair of laterally
spaced wedge shoes having an outer friction surface for movably and
frictionally engaging an
inner friction surface of the tapered plate, and a center wedge having a pair
of matching
predetermined tapered portions for engaging the tapered portion of the wedge
shoe to initiate
frictional engagement of said friction cushioning means and thereby absorb
energy. The housing
includes three horizontal ribs for positioning and/or holding the components
of the cushioning
means. A spring release means is provided which engages and longitudinally
extends between
the seat means and the center wedge for continuously urging the friction
cushioning means
outwardly from the compressible cushioning means to release the friction
cushioning element
when an applied force compressing the draft gear is removed.
The present invention increases the capacity and resistance to closure of the
draft
gear assembly by providing an angled bottom surface on the tapered plates
intermediate of the
inner and outer friction surface in the area where the tapered plate contacts
the third horizontal
lug of the housing. Providing an angle on the bottom edge surface of the
tapered plates in this
area increases the side force on the movable plates during the application of
a buffing shock to
the draft gear assembly.
Although a number of objects and advantages of the present invention have been
described in some detail above, various additional objects and advantages of
the draft gear
assembly of the present invention will become more readily apparent to those
persons who are
skilled in the art from the following more detailed description of the
invention, particularly, when
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such detailed description of the invention is taken in conjunction with both
the attached drawing
figures and with the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a longitudinal cross-sectional view of a draft gear assembly of
the
invention incorporating one form of a presently preferred embodiment of a
cushioning element
for the draft gear assembly.
Figure 2 is a longitudinal cross-sectional view of a draft gear assembly of
the
invention incorporating an alternative embodiment of a cushioning element for
the draft gear
assembly.
Figure 3 is a longitudinal cross-sectional view of a draft gear assembly of
the
invention incorporating an alternative embodiment of a hydraulic cushioning
element for the
draft gear assembly.
Figure 4 is a perspective view of the draft gear housing illustrating the
first,
second, and third horizontal lugs.
Figure 5 shows two different angles on the third rib.
DETAILED DESCRIPTION OF THE INVENTION
The draft gear assembly, according to the present invention, is installed in
alignment with a railroad car center sill between a front and a rear draft
gear lug. A vertical yoke
is connected to a coupler shank by a draft key with a coupler horn spaced from
a striking plate
and with a front follower member within the yoke which is positioned adjacent
to the front lugs,
all substantially in accordance with the prior art conventional practice as
illustrated in the
aforementioned U.S. Pat. No. 2,916,163.
Prior to proceeding to the more detailed description of the various
embodiments
of the instant invention, it should be pointed out that, for the sake of
clarity, identical components
which have identical functions have been identified with identical reference
numerals throughout
the several views that have been illustrated in the drawings.
Now reference is made, more particularly, to drawing Figs. 1-4. Illustrated
therein are the essential components a draft gear assembly, generally
designated 10, used in a
railway car (not shown). The assembly 10 includes a housing, generally
designated as 12. The
housing 12 is open at one end and has a rear portion 14 adjacent a bottom wall
16 which closes
the other end of housing 12. Rear portion 14 is provided for receiving therein
a compressible
cushioning means, generally designated as 26. Housing 12 includes a front
portion 18 adjacent
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the open end. Front portion 18 is in open communication with the rear portion.
Housing 12
additionally includes first, second, and third horizontal ribs 20,22, and 24
as shown in Figure 4.
The compressible cushioning element 26 is centrally disposed within the rear
portion 14 and has one end thereof abutting at least a portion of an inner
surface 28 of the bottom
wall 16 of housing 12. The compressible cushioning element 26 extends
longitudinally from
bottom wall 16 where the opposite end is placed into abutting relationship
with at least a portion
of one surface 30 of a seat means 32. Seat means 32 is positioned within the
housing 12 for
longitudinal movement therein for respectively compressing and releasing the
compressible
cushioning element 26 during application and release of a force on the draft
gear assembly 10.
As shown in Fig. 1, the compressible cushioning element 26, according to one
embodiment of the invention, comprises at least one and preferably at least
two springs 34, 35.
Fig. 2 shows an alternative embodiment for a compressible cushioning element
26 which
comprises an outer coil spring 36 and an inner rubber spring 37. Fig. 3 shows
another alternative
embodiment of the invention in which the compressible cushioning element 26 is
a hydraulic unit
38 such as taught in U.S. Pat. No. 3,447,693.
A friction cushioning means, generally designated as 40, is positioned at
least
partially within the front portion 18 of the housing 12. The friction
cushioning means 40 absorbs
energy during application of a force sufficient to cause a compression of the
draft gear assembly
10.
The friction cushioning means 40 includes a pair of laterally spaced outer
stationary plates 42 having an outer surface 44 and an opposed inner friction
surface 46. The
outer surface 44 engages the housing 12. A pair of laterally spaced movable
plates 48 of
substantially uniform thickness is also provided. Movable plates 48 have an
outer friction
surface 50 and an inner friction surface 52 and at least one substantially
flat edge 54 intermediate
the outer friction surface 50 and the inner friction surface 52 which edge 54
engages the seat
means 32. At least a portion of the outer friction surface 50 movably and
frictionally engages
the inner friction surface 46 of the outer stationary plate 42. A pair of
laterally spaced tapered
plates 56 is provided. The tapered plates 56 include an outer friction surface
58 and an inner
friction surface 60. The outer friction surface 58 movably and frictionally
engages at least a
portion of the inner friction surface 52 of the movable plate 48. The tapered
plates 56 include
an angled or tapered edge 62 intermediate the outer friction surface 58 and
the inner friction
surface 60. The angle of the tapered edge 62 may range from 10-40 degrees.
Figure 5 shows two
different angles for the tapered edge 62 of the tapered plate 56. The
laterally spaced outer
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stationary plates 42 and the tapered plates 56 sit on the third horizontal rib
24 of the housing 12.
This angled or tapered edge 62 is in the area where the tapered plates 56
contact the third
horizontal rib 24. Tapering the area of the tapered plate where the tapered
plate sits in the
housing requires the area under the third rib to be built up. This area is
also affected by the
corner coil spring seat. Friction cushioning means 40 further includes a pair
of laterally spaced
wedge shoes 64 which have at least a portion of an outer friction surface 66
movably and
frictionally engaging at least a portion of the inner friction surface 60 of
the tapered stationary
plate 56. Wedge shoes 64 have at least a portion of one edge 68 engaging seat
means 32 and a
predetermined tapered portion 70 on an opposed edge thereof. A center wedge 72
is provided
which has a pair of matching tapered portions 74 for engaging the tapered
portion 70 of the
wedge shoe 64 to initiate frictional engagement of the friction cushioning
means 40.
It has been discovered that providing an angle or taper 62 on the bottom
surface
of the tapered plates 56 in the area that contacts the third horizontal rib 24
of the housing 12,
results in a greater side force being applied to movable plates 56. Thus, the
capacity of the draft
gear and its resistance to closure is increased. A spring release means 76
engages and extends
longitudinally between the seat means 32 and the center wedge 72 for
continuously urging the
friction cushioning means 40 outwardly from the compressible cushioning means
26 to release
the friction cushioning means 40 when an applied force compressing the draft
gear assembly 10
is removed.
A draft gear typically has approximately 0.125" clearance between the bottom
edges of the taper plates 56 and the seat means 32. High loading from the
taper plate requires
that the housing's bearing area and the cross-sectional area on the taper
plate's ear remain equal
to the present design so shear failures do not occur. As the draft gear wears
out, the assembled
height of the spring type compressible cushioning elements 26 of Figs. 1 and 2
increases,
resulting in a reduced clearance between the bottom edges of the taper plates
56 and the seat
means 32. A draft gear nearly worn out has near zero clearance between the
bottom edges of the
taper plates 56 and the seat means 32. The present invention's new design
criteria and assembly
conditions are as follows:
For a 10 degree taper, approximately 0.176" of clearance is provided.
For a 20 degree taper, approximately 0.364" of clearance is provided.
For a 30 degree taper, approximately 0.557" of clearance is provided.
For a 40 degree taper, approximately 0.839" of clearance is provided.
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In operation, the buffing shock is transmitted from the coupler through the
front
follower to the central wedge 72, causing it to act through the wedge shoes 64
and thereby
compress all of the cushioning elements simultaneously. These parts will
furnish sufficient
cushioning for light buffing shocks. After suitable travel, however, the
follower will come
against the outer ends of the movable plates 48 introducing energy-absorbing
friction between
the movable plates 48 and the stationary plates 42 and 56 which have been
pressed together by
the action of the wedge shoes 64. As this action continues, the pressure
between the adjacent
surfaces of the plates has been enormously increased due to the fact that the
wedge shoes 64 are
loaded against the cushioning mechanism 40. The energy absorption and
dissipation through
friction and compression of the cushioning mechanism continues until the gear
is closed
including compression of cushioning element 26.
During release of the gear, the compressible cushioning element 26 is
maintained
in alignment by the seat means 32.
Thus, the present invention has been described in such full, clear, concise
and
exact terms as to enable any person skilled in the art to which it pertains to
make and use the
same. It will be understood that variations, modifications, equivalents, and
substitutions for
components of the specifically described embodiments of the invention may be
made by those
skilled in the art without departing from the scope of the invention as set
forth in the
appended claims.
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