Information
-
Patent Grant
-
6543955
-
Patent Number
6,543,955
-
Date Filed
Wednesday, January 24, 200123 years ago
-
Date Issued
Tuesday, April 8, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Rowold, Esq.; Carl
- Mora, Esq.; Enrique J.
- Beusse, Brownlee, Bowdoin & Wolter, PA
-
CPC
-
US Classifications
Field of Search
US
- 403 225
- 403 226
- 403 57
- 105 220
- 105 2211
- 105 22405
- 105 2241
- 465 87
- 465 903
- 465 92
- 465 112
- 465 113
-
International Classifications
-
Abstract
An elastomeric joint (100) that comprises a wing plate (102) including a base plate (104) generally extending along a first axis and generally perpendicular to a second axis is provided. The wing plate further includes a mutually opposite first and second bushing-receiving bores (120) co-axially aligned relative to a third axis perpendicular to said first and second axes. A plurality of elastomeric shear pads (106) is affixed on mutually opposite sides of the base plate. The plurality of shear pads is stacked generally perpendicular to the second axis. Top and bottom elastomeric bushings (122) are received by said respective bushing-receiving bores. Each elastomeric bushing comprises a plurality of torsion pads (124) and includes a respective pin-receiving bore(128). Each of the shear pads and torsion pads comprises a plurality of alternating layers of resilient and nonextensible materials, wherein the shear pads are compressed to provide stiff opposition to forces along said second axis, while accommodating differential displacement along the first axis and/or along the third axis, and wherein said elastomeric bushings are compressed to enable pivotal movement about the third axis while providing stiff opposition to radial forces on the bushings.
Description
BACKGROUND OF THE INVENTION
The present invention is generally related to mechanical coupling, and, more particularly, the present invention is related to elastomeric joints that may be configured to couple devices, such as steering linkages in railway vehicles.
In a railway vehicle, such as a locomotive, the vehicle body is mounted on a frame which in turn is mounted on a pair of longitudinally spaced apart multi-axle trucks having wheels which ride on the rails of a train track. The two trucks are typically identical, with each truck having typically two or three axles and a pair of wheels on opposite ends thereof. In an exemplary three axle diesel-electric locomotive, each axle further includes an integral electrical motor combination, or simply motor combo, for directly powering the wheels. The motor combos drive the wheels for propelling the locomotive either in forward or reverse directions utilizing inherent traction friction between the wheels and the rails. The locomotive, in turn, pulls or pushes a train of railway cars joined thereto. The trucks also include conventional brakes for stopping the locomotive again using the inherent traction friction between the wheels and the rails. Accordingly, traction loads must be carried between the axles and the frame during forward and reverse driving and braking operation. This is conventionally accomplished by suitably suspending the axles to the frame.
One important consideration in locomotive design is the ability of the axles to negotiate curves during operation. In a multi-axle truck, the leading axle negotiates a turn before the trailing axle which creates substantial lateral loading, e.g., steering loads, between the axles and the frame and affects efficient operation and longevity of the trucks. In order to accommodate typical problems associated with negotiating rail curves, self-steering trucks have been developed. Steering is accomplished by suitably interconnecting the leading and trailing axles so that the axles yaw in opposite directions to each other upon negotiating curves.
Axle suspension design is generally complex due to various mechanical considerations: the axles should be vertically suspended from the frame for accommodating vertical loads; the axles should be longitudinally constrained for carrying the forward and reverse traction loads to the frame; the axles should be also mounted for allowing self-steering yaw motion thereof in opposite angular directions between leading and trailing axles; and, the axles should be laterally constrained. Axle suspension in a three-axle truck may be further complicated since the leading and trailing end axles need to be angularly interconnected for self-steering, and the middle axle is independent from the leading and trailing end axles and is interposed longitudinally between such axles.
U.S. patent application No. 6,006,674, commonly assigned to the same assignee of the present invention, discloses an improved design over self-steering trucks that have undesirably included a large number of pivoting joints, which are typically made using conventional bearings or friction joints, and are thus susceptible to wear and fretting problems. It is desirable, however, to further improve the self-steering linkage by providing a multi-degree of freedom elastomeric joint that allows to further reduce the number of components subject to undesirable wear and still meet the complex mechanical constraints required by such self-steering linkage.
SUMMARY OF THE INVENTION
Generally speaking, the present invention fulfills the foregoing needs by providing in one aspect thereof, a multi-degree of freedom elastomeric joint that in fictionless engagement allows differential longitudinal and pivotal movement between adjoining ends of a pair of reaction arms used in a steering linkage of a railway truck.
In one exemplary embodiment, the joint comprises a wing plate that includes a base plate generally extending along a first axis and generally perpendicular to a second axis. The wing plate further includes a mutually opposite first and second bushing-receiving bores co-axially aligned relative to a third axis perpendicular to said first and second axes. A plurality of elastomeric shear pads is affixed on mutually opposite sides of the base plate. The plurality of shear pads is stacked generally perpendicular to the second axis. Top and bottom elastomeric bushings are received by said respective bushing-receiving bores. Each elastomeric bushing comprises a plurality of torsion pads and includes a respective pin-receiving bore. Each of the shear pads and torsion pads comprises a plurality of alternating layers of resilient and nonextensible materials, wherein the shear pads are compressed, e.g., compressively preloaded during installation, to provide stiff opposition to forces along said second axis, while accommodating differential displacement along the first axis and/or along the third axis by providing relatively low stiffness along such first and/or second axes, and wherein the torsion pads are compressed, e.g., compressively preloaded during installation, to enable pivotal movement about the third axis by providing relatively low torsional stiffness about that third axis while providing stiff opposition to radial forces on the torsion pads.
The present invention further fulfils the forgoing needs by providing in another aspect thereof, a method of assembling an elastomeric joint. The method allows for providing a wing plate that includes a base plate generally extending along a first axis and generally perpendicular to a second axis. The wing plate further provides mutually opposite first and second bushing-receiving bores co-axially aligned relative to a third axis perpendicular to the first and second axes. The method allows for affixing a plurality of elastomeric shear pads on mutually opposite sides of the base plate. The plurality of shear pads is stacked generally perpendicular to the second axis. A fitting step allows for interferingly fitting top and bottom elastomeric bushings in the respective bushing-receiving bores. Each elastomeric bushing comprises a plurality of torsion pads and includes a respective pin-receiving bore. Each of the shear pads and torsion pads comprises a plurality of alternating layers of resilient and nonextensible materials. Respective preloading steps respectively allow for compressively preloading the shear pads to provide stiff opposition to forces along the second axis, while accommodating differential displacement along the first axis and/or along the third axis, and for compressively preloading the torsion pads to enable pivotal movement about the third axis while providing stiff opposition to radial forces on the torsion pads.
DESCRIPTION OF THE DRAWINGS
FIG. 1
is an isometric view of an exemplary three-axle locomotive truck including a self-steering linkage that may benefit from an elastomeric joint in accordance with one aspect of the present invention;
FIG. 2
is an isometric view of first and second axles and the self-steering linkage of
FIG. 1
being removed from its mounting frame for clarity of illustration;
FIG. 3
is a schematic plan view of the truck frame illustrated in
FIG. 1
showing exemplary kinematic effects that may be experienced by the steering linkage when the truck is travelling in a straight line, shown in solid line, and when negotiating a curve, shown in dashed line;
FIG. 4
is a generally side isometric view of the elastomeric joint of the present invention connected to respective adjoining ends of an exemplary pair of reaction arms of the steering linkage;
FIG. 5
is a generally top isometric view of the elastomeric joint shown in
FIG. 4
;
FIG. 6
is a side view of the elastomeric joint of
FIG. 4
illustrating the coupling of top and bottom pins to respective top and bottom forked prongs in one of the reaction arms;
FIG. 7
is a top view of the elastomeric joint of
FIG. 4
illustrating an exemplary elastomeric bushing therein;
FIG. 8
is a view along line
8
—
8
in
FIG. 7
FIG. 9
illustrates further details regarding the elastomeric bushing of
FIG. 7
; and
FIG. 10
illustrates an isometric exploded view of the elastomeric bushings, and corresponding pins and prior to assembly into a wing plate of the elastomeric joint.
Before any embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DETAILED DESCRIPTION OF THE INVENTION
Illustrated schematically in
FIG. 1
is an exemplary railway truck
10
that may benefit from the teachings of the present invention. The truck
10
is one of two trucks which are configured for conventionally supporting a locomotive body (not shown) for powering a train of railway cars (also not shown). The truck
10
rides a pair of conventional rails
12
of a train track which includes various portions which are either straight or curved.
The trucks
10
are identical to each other and are typically mounted to the locomotive body in opposite orientations, with the following description of an exemplary truck
10
also applying to the other truck as well. The truck
10
includes a truck frame
14
having a longitudinal centerline axis CL. The frame
14
includes a pair of first and second laterally spaced apart and generally parallel side frames
14
a
and
14
b,
and three longitudinally spaced apart transoms
14
c,
14
d
and
14
e
extending laterally between and integrally joined to the side frames
14
a,
14
b.
The entire frame
14
is generally made as a single casting, with the first transom
14
c
being joined to longitudinal ends of the side frames for closing the truck frame
14
at one end, the second transom
14
d
being spaced longitudinally inwardly from the opposite ends of the side frame for leaving open the opposite ends of the frame
14
, and the third or middle transom
14
e
being spaced between the first and second transoms
14
c,
14
d
in a substantially conventional configuration. The truck frame
14
itself may include open C-sections or closed box sections.
As indicated above, the truck
10
is one of two identical trucks which support the locomotive body, with the locomotive being used for driving a train of railway cars attached thereto. The considerable loads for driving the railway cars is conventionally carried through the truck frame
14
at a suitable trunnion
14
f
disposed in the center of the second transom
14
d.
A plurality of identical journal boxes
16
are resiliently suspended from the side frames
14
a,
14
b
to in turn support a plurality of longitudinally spaced apart identical axles designated by the prefix
18
extending laterally between the side frames and having opposite ends rotatably mounted in respective ones of the journal boxes
16
. In the exemplary embodiment illustrated in
FIG. 1
, the truck
10
is a three-axle truck with the three axles being identical to each other except for placement in the frame
14
. The axles are therefore identified generally by the reference numeral
18
and specifically with a corresponding uppercase suffix, with first and second end axles
18
A and
18
B being disposed at longitudinally opposite ends of the frame
14
adjacent to the respective first and second transoms
14
c
and
14
d,
and the third or middle axle
18
C being disposed longitudinally therebetween and adjacent to the third or middle transom
14
e
in a conventional configuration. The axles
18
may each be removably joined to the respective journal boxes
16
.
The axles
18
themselves are conventional, with each axle including an axle bearing assembly, or simply bearing
18
a
at both opposite ends of the axle which are captured in respective ones of the journal boxes
16
. The axle bearing
18
a
is also conventional and typically includes a pair of tapered roller bearings for accommodating both radial and axial thrust loads, and which are mounted in a suitable annular bearing housing. Although modern trains typically use roller bearings instead of plain journal bearings, the bearing boxes which suspend the axles to the frame are typically still referred to as journal boxes.
Disposed immediately inboard of the end axle bearings
18
a
are respective wheels
18
b
which are also conventional for supporting the frame
14
on the rails
12
. In the exemplary embodiment illustrated in
FIG. 1
, the locomotive is a diesel-electric locomotive which conventionally provides power to conventional electrical motor
18
c
which are conventionally joined to respective ones of the axles
18
in a combination therewith typically called a motor combo. By suitably powering the motor combos
18
c,
the respective three axles
18
and wheels
18
b
thereon are powered for driving the truck
10
in either of two opposite longitudinal directions represented for example by a forward direction F and a reverse direction R relative to the centerline axis CL. The forward and reverse directions are relative and may be interchanged with each other if desired.
Self-Steering Truck Linkage
As
FIG. 1
indicates, the truck
10
includes various components arranged closely together in a compact arrangement to take relatively little space for self-steering linkage. The self-steering linkage includes various components which provide effective kinematic movements so that the end axles
18
A,
18
B yaw in opposite directions relative to each other when negotiating left or right curves on the rails
12
. As shown in
FIG. 1
, the three axles
18
are disposed coplanar in a horizontal plane with lateral motion being designated by the double headed straight arrow L which represents side-to-side motion perpendicular to the frame centerline axis CL and the rails
12
in the horizontal plane, with yaw rotation being designated by the double headed curved arrow Y also in the same horizontal plane. Further, the self-steering linkage should also be effective for carrying the substantial traction loads between the-wheels
18
b
and the truck frame
14
in an efficient manner without compromising the self-steering ability between the end axles
18
A,
18
B. The traction loads are created by powering the motors
18
c
to drive the axles
18
and wheels joined thereto in either the forward or reverse directions, with additional traction loads also being created in either direction upon application of conventional brakes found in the truck
10
.
The self-steering linkage is illustrated in various levels of assembly in
FIGS. 1-2
. By way of illustration, the middle axle
18
C illustrated in the exemplary embodiment of
FIG. 1
is not subject to self-steering. Further, although self-steering is being described with respect to a three-axle truck
10
, it may also be applied to a simpler two-axle truck since only the end axles would undergo self-steering and effect counter-yaw relative to each other when negotiating curves.
Referring to
FIG. 2
, the self-steering linkage includes a pair of longitudinally spaced apart bellcranks which are essentially identical to each other except for placement and orientation and are therefore generally referred with the reference prefix numeral
20
, followed by an uppercase suffix to identify individually located ones of the bellcranks
20
. A first pair of first and second bellcranks
20
A and
20
B are rotatably joined to the first side frame
14
a
(as shown in
FIG. 1
) longitudinally between the end axles
18
A,
18
B and described in more detail herein below. A second pair of third and fourth bellcranks
20
C and
20
D are rotatably joined to the second side frame
14
b
(as shown in
FIG. 1
) longitudinally between the end axles
18
A,
18
B and also described in more detail herein below. Since each of the bellcranks
20
are substantially identical the various components thereof are identified using the same lowercase reference numeral suffix.
Referring again to
FIG. 2
, respective pairs of traction links designated generally by the prefix
22
extend longitudinally along each of the side frames
14
a,
14
b
(see
FIG. 1
) for carrying the substantial tension and compression traction loads between the journal boxes
16
and the truck frame
14
. Individual end traction links
22
A-D are pivotally joined between respective ones of the end journal boxes,
16
and the crank arms
20
b
for carrying tension and compression loads therebetween through a connecting cross link
28
. As shown in
FIG. 2
, first, second, third, and fourth end traction links
22
A,
22
B,
22
C, and
22
D are respectively joined to the first, second, third, and fourth bellcranks
20
A,
20
B,
20
C,
20
D at the respective crank arms
20
b
thereof and to corresponding ones of the end journal boxes
16
. The four end links
22
A-D are preferably identical to each other.
Respective pairs of adjoining reaction arms designated generally by the prefix
24
extend longitudinally along each of the side frames
14
a,
14
b
(see FIG.
1
), with each reaction arm
24
being fixedly joined at one end to a respective one of the bellcranks
20
, and overlapping each other in pairs at opposite ends thereof. As shown in
FIG. 2
, first, second, third, and fourth reaction arm
24
A,
24
B,
24
C, and
24
D are suitably fixedly joined to respective ones of the first, second, third and fourth bellcranks
20
A-D at respective crankshafts
20
a
thereof.
As shown in
FIG. 2
, for example, each of the reaction arms
24
has longitudinally opposite proximal and distal ends
24
a
and
24
b,
with each proximal end
24
a
being suitably fixedly joined to a respective one of the crankshafts
20
a,
and the distal ends
24
b
adjoining each other in longitudinal overlap. The adjoining distal ends
24
b
of respective pairs of the reaction arms
24
are operatively joined together as described in more detail herein below for carrying lateral reaction loads independently between each of the reaction arms pairs
24
A,
24
B and
24
C,
24
D at each side frame
14
a,
14
b
upon rotation of the crankshafts
20
a
while permitting differential longitudinal and pivotal movement between the adjoining distal ends
24
b.
FIG. 3
illustrates schematically all four linkage subassemblies of corresponding bellcranks, traction links, and reaction arms mounted in the respective side frames
14
a,
14
b
relative to the three axles
18
A-C.
FIG. 3
schematically represents operation of the self-steering linkage under straight forward and reverse traction loads designated Tf and Tr during drive or braking as shown in solid line, and during negotiation of a left curve for example, in dashed line, showing exaggerated relative displacements of the components. The forward and reverse traction loads are carried in turn through the end axles
18
A,
18
B, journal boxes
16
(not shown), traction links
22
A-D, and the bellcranks
20
A-D to respective side frames
14
a,b.
The bellcranks
20
, traction links
22
, and reaction arms
24
are symmetrically laterally disposed relative to the frame centerline axis CL, and symmetrically longitudinally disposed relative to the middle axis
18
C.
The forward and reverse traction loads developed by the end axles
18
A,
18
B are carried directly into the side frames
14
a,b
through the respective bellcranks
20
joined thereto, with rotation of the bellcranks
20
being opposed or reacted by the cooperating adjoining reaction arms
24
A,
24
B and
24
C,
24
D. The forward traction force Tf at the first end axle
18
A effects corresponding inboard directed reaction force Rf at the corresponding first and third reaction arms
24
A,
24
C joined thereto. The forward traction force Tf at the second end axle
18
B effects outboard directed reaction force Rf on the corresponding second and fourth reaction arms
24
B,
24
D which opposes the inboard reaction forces from the adjoining first and third reaction arms
24
A,
24
C.
Under reverse traction loads Tr, corresponding oppositely directed reverse reaction loads Rr are effected at the adjoining pairs of reaction arms
24
A,B and
24
C,D. Accordingly, in one traction direction, e.g., forward traction Tf, the respective pairs of reaction arms are driven in opposite inboard and outboard directions toward each other, and in the opposite traction direction, e.g. the reverse traction force Tr, the adjoining reaction arms are similarly driven in opposite directions tending to separate apart the adjoining reaction arms. This symmetrical arrangement of the self-steering linkage ensures that the end axles
18
A,
18
B track straight relative to the frame centerline axis CL without yaw Y or lateral movement L. It also ensures that symmetric curving, i.e., same behavior in right-hand and left-hand curves, is obtained.
As will be appreciated by those skilled in the art, self-steering of the end axles
18
A,
18
B is efficiently effected as the truck negotiates either left or right curves, with the negotiating of a left curve being illustrated in dashed line in FIG.
3
. As the first end axle
18
A enters the left curve effected by the rails
12
shown in
FIG. 1
, the first axle
18
A is permitted to undergo limited self-steering in the yaw direction Y, which is counterclockwise (CCW) in the example illustrated in FIG.
3
. This yaw of the first axle
18
A causes the corresponding ones of the bellcranks
20
A,
20
C on opposite sides of the frame to corotate together, e.g. clockwise (CW), which in turn corotates together the corresponding first and third reaction arms
24
A,
24
C joined thereto which cantilever to counterrotate together the adjoining second and fourth reaction arms
24
B,D to counterrotate together the corresponding second and fourth bellcranks
20
B,
20
D joined thereto to counter-yaw the opposite second axle
18
B in the clockwise direction.
Whereas the traction links
22
primarily operate in simple tension and compression, the reaction arms
24
primarily operate in lateral bending without significant longitudinal net tension or compression loading therein. The reaction aims
24
provide cantilever or pivot motion to pivot the respective bellcranks
20
for obtaining counter-yaw between the first and second axles
18
A,
18
B. In the left curve operation illustrated in dashed line in
FIG. 3
, both pairs of reaction arms
24
move to the left, with the first and second reaction arms
24
A,
24
B moving outboard, and the third and fourth reaction arms
24
C,
24
D moving inboard. For a right curve not illustrated in
FIG. 3
, the opposite movement occurs for yawing the first axle
18
A in a clockwise direction, and counter-yawing the second axle
18
B in the counterclockwise direction.
The non-symmetrical rotational movement of the adjoining reaction arm pairs shown in dashed line in
FIG. 3
during self-steering illustrates the multi-functional joint required between the distal ends thereof. Since each reaction arm
24
must rotate during self-steering operation, both differential longitudinal and pivotal movement between the adjoining distal ends is required. And, the joint must also effectively carry the required lateral reaction forces Rf and Rr between the adjoining reaction arm distal ends which are laterally driven together or apart as described in more detail later hereinbelow.
In accordance with one aspect of the present invention, a multi-degree of freedom elastomeric joint
100
is provided for operatively joining together each respective adjoining pair of reaction arms
24
A,
24
B and
24
C,
24
D for accommodating differential movement therebetween during operation, for effectively carrying the lateral reaction forces Rf and Rr and for providing pivotal motion without having to use a pin that rotates about a metallic bushing. The reaction arms and their assembly to joint
100
are illustrated in more particularity in
FIGS. 4-6
wherein the first and second adjoining reaction arms
24
A, and
24
B are exemplarily illustrated, with the understanding that the third and fourth traction arms
24
C,
24
D are configured identically. As indicated above, and now referring to
FIG. 4
, the adjoining distal ends
24
b
of the reaction arms
24
must effectively carry the lateral reaction forces Rf and Rr therebetween which tend to bring together or separate the distal ends during operation. And, as the reaction arms
24
rotate inboard or outboard together during self-steering operation, the respective distal ends
24
b
thereof must accommodate differential longitudinal movement therebetween Dl and differential pivotal movement therebetween Dp. As shown in
FIG. 4
, in one exemplary embodiment, the distal end
24
b
of reaction arm
24
A is configured as a two-prong fork
96
and the distal end
24
b
of reaction arm
24
B is configured as a bracket
98
that is received by the two-prong fork.
Accordingly, a joint
100
as illustrated in
FIGS. 4-9
is provided for suitably joining the adjoining distal ends
24
b
of the reaction arms
24
for accomplishing these many objectives. The joint
100
in one exemplary embodiment comprises a multidegree of freedom elastomeric joint. A metal wing plate
102
, as illustrated in various levels of details
FIGS. 4-8
, includes a centrally disposed base plate
104
(
FIGS. 5 and 8
) generally perpendicular to the lateral axis L and generally parallel relative to the longitudinal axis F-R. A plurality of elastomeric shear pads
106
(
FIGS. 5 and 8
) are fixedly joined to the opposite surfaces of the base plate
104
. As shown in
FIG. 8
, the shear pads comprise a plurality of alternating layers of resilient material, e.g., natural or synthetic rubber, and nonextensible material, e.g., metal shims
108
. A cover plate
110
, as best shown in
FIG. 5
, is affixable to the bracket
98
by a plurality of fastener bolts
112
, for example, for clamping and compressing the shear pads
106
stacked on the base plate
104
against a back section
114
of the bracket
98
for allowing the wing plate
102
to translate relative to the bracket
98
upon shearing of the pads
106
in the longitudinal direction generally parallel with the frame centerline axis.
In another key feature of the invention and as best shown in cross-sectional view in
FIG. 8
, or in exploded view in
FIG. 10
, wing plate
102
includes top and bottom bushing-receiving bores
120
for receiving a respective elastomeric bushing
122
that, in one exemplary embodiment as shown in
FIG. 9
, is made up of a plurality of torsion pads
124
, e.g., generally cylindrical pads, that comprise a plurality of alternating layers of resilient material, e.g., natural or synthetic rubber, and nonexetensible material, e.g., metal shims
126
. The housing of bushing
122
has an outer diameter dimensioned to provide a relatively tight interference fit with the corresponding bushing-receiving bore. However, to better ensure the tightness of the fit, a suitable bonding polymer, such as Loctite, may be applied during assembly between the mating metal surfaces of the bushing and the bushing-receiving bore. Each bushing defines a pin-receiving bore
128
for receiving a pin
130
respectively received by respective openings
132
(
FIG. 5
) provided at the top and bottom fork prongs. The pin is dimensioned to have a diameter that provides a tight interference fit with the pin-receiving bore and the fork openings. As suggested above, the tightness of the fit between the pin and any mating metal surfaces may be enhanced through application of Loctite bonding polymer between such surfaces. It will be now appreciated by those skilled in the art that the elastomeric bushing of the present invention is configured to provide a relatively low rotational stiffness that enables large rotational or torsional displacement. Conversely, for avoiding radial displacements, the bushing is configured to provide relatively large radial stiffness. By way of example, at least one one radially extending slot, e.g., slot
140
(FIG.
9
), is provided in the torsion pads to enable compressively preloading the bushings against the surfaces that define the respective bushing-receiving bores. Further, it will be appreciated that providing relatively low longitudinal or axial stiffness in the torsion pads allows to maintain low reaction forces on the pins received by the bushings and this would result in longer life of the joint. In one exemplary embodiment, a pair of mutually opposite radially extending slots, e.g., slot pair
140
and
142
, aligned generally parallel relative to the longitudinal axis is provided to enable compressive pre-loading of the torsion pads against the surfaces that define the bushing-receiving bores. This pre-compression about the center of the bushing is believed to enhance load transfer ability along the radial direction of the bushing.
As shown in
FIG. 6
for example, since each pin
130
is fixedly mounted to a corresponding fork opening, e.g., opening
132
(FIG.
5
), its longitudinal movement is constrained therewith while the elastomeric bushing allows differential pivotal movement Dp without any metal-to-metal wear. As suggested above, the cover plate
110
(
FIG. 5
) clamps the shear pads affixed to wing plate
102
against the back plate
112
in a sandwich arrangement by compressing the shear pads
106
on opposite sides thereof. Differential longitudinal movement Dl between the adjoining ends
24
b
is provided within a suitable useful range by shearing of the elastomeric pads
106
upon relative longitudinal movement between the wing plate
102
and the bracket
98
. As the adjoining reaction arms
24
A,
24
B move inboard or outboard together, the corresponding differential pivotal movement Dp therebetween is accommodated by rotation of the wing plate
102
relative to the fork
96
due to the top and bottom elastomeric bushing without any metal-to-metal wear, and the differential longitudinal movement Dl is accommodated by shearing movement of the shear pads
106
. In this way, the required differential movement between the distal ends
24
b
of the adjoining reaction arms
24
A,
24
B and
24
C,
24
D is effected for allowing self-steering operation of the linkage. Since the shear pads
106
are resiliently distorted during differential longitudinal movement between the distal ends of the reaction arms
24
, an inherent resilient restoring force is created. Similarly, during differential pivotal movement of the distal ends of the reaction arms, resilient distortion of the torsion pads would create a resilient restoring force.
Since the joint
100
must suitably carry the lateral reaction loads Rf, Rr between the adjoining reaction arms, it is desirable that the shear pads
106
be substantially stiff in compression for minimizing differential lateral movement between the adjoining reaction arms for obtaining substantially equal but opposite yaw of the end axles
18
A,
18
B. As suggested above, in one exemplary embodiment, the construction of the joint shear pads comprises a plurality of alternating layers of metal shims and elastomeric material, such as natural or synthetic rubber, bonded together for increasing compressive stiffness thereof while permitting resilient shearing movements therebetween. The shear pads
106
may therefore be substantially stiff in compression for minimizing differential lateral movement between the fork
96
and bracket
98
for improving hunting speed, but are sufficiently resilient or flexible in shear for allowing the required differential longitudinal movement Dl, and, in cooperation with the top and bottom bushings, for allowing the required pivotal movement Dp. It will be appreciated that the foregoing embodiment is further configurable to provide an additional degree of freedom since the joint may be made substantially resilient or flexible in shear for allowing vertical movement. Although during operation of the truck, the coupling of the adjoining reaction arms does not demand any substantial loads along the vertical axis V (FIG.
8
), it will be appreciated that the joint of the present invention is configurable to provide such additional degree of freedom in applications where vertical displacement may be desirable. Moreover, even in the present application, having such additional degree of freedom may be helpful during assembly of the joint onto the truck. In one exemplary embodiment, the joint
100
may include one or more shim plates, e.g., shim plate
109
in
FIG. 5
, disposed in abutting contact with the shear pads and the cover plate, the back plate or both. Such shim plates may be used for aligning the respective pin-receiving bores of the top and bottom bushings with the corresponding pins
130
, and for adjusting, the spacing between the centrally disposed base plate, and the mutually opposite cover and back plates so as to adjust the level of pre-loading provided to the shear pads.
It will be understood that the specific embodiment of the invention shown and described herein is exemplary only. Numerous variations, changes, substitutions and equivalents will now occur to those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all subject matter described herein and shown in the accompanying drawings be regarded as illustrative only and not in a limiting sense and that the scope of the invention be solely determined by the appended claims.
Claims
- 1. An assembly for coupling adjoining ends of a pair of reaction arms in a steering linkage of a railway truck, said assembly comprising:a joint between the reaction arms comprising a rigid frame; an elastomeric bushing secured at one portion thereof to the frame and to one of the arms at another portion thereof; and a stack of elastomeric pads secured at one portion thereof to the frame and at another portion thereof to the other arm, with the frame being free of any direct connection or engagement with either arm, wherein pivotal movement between the adjoining ends of the arms is accommodated and resiliently resisted by the elastomeric bushing, and further wherein relative longitudinal movement between the adjoining ends of the arms is accommodated and resiliently resisted by the stack of elastomeric pads, with the frame being free of any direct connection or engagement with either arm, whereby relative longitudinal and pivotal movement between the adjoining ends of the arms is accommodated and resiliently resisted by deformation of the elastomeric bushing and stacks of pads, thus avoiding direct frictional engagement between the arms or between the arms and the frame, or both, subjecting these components to wear.
- 2. The assembly of claim 1 wherein said joint further allows, without direct frictional engagement, differential vertical movement between said adjoining ends.
- 3. The assembly of claim 1 wherein said joint comprises a wing plate including a base plate generally extending along a longitudinal axis and generally perpendicular to a lateral axis, said wing plate further including mutually opposite top and bottom bushing-receiving bores co-axially aligned relative to a vertical axis perpendicular to said lateral and longitudinal axes.
- 4. The assembly of claim 3 wherein said elastomeric pads are affixed on mutually opposite sides of said base plate, said plurality of pads stacked generally perpendicular to said lateral axis.
- 5. The assembly of claim 4 wherein said elastomeric bushing comprises top and bottom elastomeric bushings received by said respective bushing-receiving bores, each elastomeric bushing comprising a plurality of generally cylindrical pads including at least one radially extending slot configured to enable compression of said cylindrical pads against the surfaces defining said bushing-receiving bores.
- 6. The assembly of claim 5 wherein each elastomeric bushing includes a respective pin-receiving bore.
- 7. The assembly of claim 6 each of said elastomeric pads and generally cylindrical pads comprises a plurality of alternating layers of resilient and nonextensible materials.
- 8. The assembly of claim 7 further comprising a cover plate positioned to compress the plurality of elastomeric pads on each side of said base plate between said cover plate and a back section of a bracket.
- 9. The assembly of claim 8 further comprising top and bottom pins received by said pin-receiving bores.
- 10. The assembly of claim 8 further comprising at least a pair of shim plates respectively interposed between the cover plate, the back section of the bracket and corresponding elastomeric pads, the thickness of said shim plate pair being determinative of the level of compression applied to the elastomeric pads.
- 11. The assembly of claim 8 further comprising at least one shim plate interposed between the cover plate and the corresponding elastomeric pads, the thickness of said shim plate being determinative of the level of compression applied to the pads.
- 12. The assembly of claim 8 further comprising at least one shim plate interposed between the back section of the bracket and the corresponding elastomeric pads, the thickness of said shim plate being determinative of the level of compression applied to the elastomeric pads.
- 13. A method of assembling an elastomeric joint, said method comprising:providing a wing plate including a base plate generally extending along a first axis and generally perpendicular to a second axis, said wing plate further providing mutually opposite first and second bushing-receiving bores co-axially aligned relative to a third axis perpendicular to said first and second axes; affixing a plurality of elastomeric shear pads on mutually opposite sides of said base plate, said plurality of shear pads stacked generally perpendicular to said second axis; and interferingly fitting top and bottom elastomeric bushings in said respective bushing-receiving bores, each elastomeric bushing comprising a plurality of torsion pads and including a respective pin-receiving bore, each of said shear pads and torsion pads comprising a plurality of alternating layers of resilient and nonextensible materials; compressively preloading said shear pads to provide stiff opposition to forces along said second axis, while providing relatively low stiffness along said first axis and/or along said third axis; and compressively preloading said torsion pads to enable pivotal movement about said third axis while providing stiff opposition to radial forces on said torsion pads.
- 14. An elastomeric joint for coupling adjoining ends of a pair of reaction arms used in a steering linkage of a railway truck, said joint comprising:a wing plate including a base plate generally extending along a first axis and generally perpendicular to a second axis, said wing plate further including mutually opposite first and second bushing-receiving bores co-axially aligned relative to a third axis perpendicular to said first and second axes; a plurality of elastomeric shear pads affixed on mutually opposite sides of said base plate, said plurality of shear pads stacked generally perpendicular to said second axis; and top and bottom elastomeric bushings received by said respective bushing-receiving bores, each elastomeric bushing comprising a plurality of torsion pads and including a respective pin-receiving bore, each of said shear pads and torsion pads comprising a plurality of alternating layers of resilient and nonextensible materials, wherein said shear pads are compressed to provide stiff opposition to forces along said second axis, while accommodating differential displacement along said first axis and along said third axis, and wherein said torsion pads are compressed to enable pivotal movement about said third axis while providing stiff opposition to radial forces on said torsion pads.
- 15. The joint of claim 14 wherein said torsion pads comprise generally cylindrical pads and include at least one radially extending slot configured to enable compressive preloading of said torsion pads against the surfaces defining said bushing-receiving bores.
- 16. The joint of claim 14 wherein said torsion pads include a pair of mutually opposite radially extending slots configured to enable compressive preloading of said torsion pads against the surfaces defining said bushing-receiving bores.
- 17. The joint of claim 16 wherein said pair of radially extending slots are in alignment relative to said first axis.
- 18. An assembly for coupling adjoining ends of a pair of reaction arms used in a steering linkage of a railway truck, one of said reaction arms ends comprising a fork having a top prong and a bottom prong, the other one of said reaction arms ends comprising a bracket received by said fork, said assembly comprising:an elastomeric joint supported by said bracket, said joint comprising: a wing plate including a base plate generally extending along a longitudinal axis and generally perpendicular to a lateral axis, said wing plate further including mutually opposite top and bottom bushing-receiving bores co-axially aligned relative to a vertical axis perpendicular to said lateral and longitudinal axes; a plurality of elastomeric shear pads affixed on mutually opposite sides of said base plate, said plurality of shear pads stacked generally perpendicular to said lateral axis; top and bottom elastomeric bushings received by said respective bushing-receiving bores, each elastomeric bushing comprising a plurality of torsion pads including at least one radially extending slot configured to enable compression of said torsion pads against the surfaces defining said bushing-receiving bores, each elastomeric bushing including a respective pin-receiving bore, each of said shear pads and torsion pads comprising a plurality of alternating layers of resilient and nonextensible materials; a cover plate affixable to said bracket to compress the plurality of shear pads on each side of said base plate between said cover plate and a back section of the. bracket; and top and bottom pins received by said pin-receiving bores, said pins being fixedly connected to respective openings in the top and bottom prongs, wherein said shear pads provide stiff opposition to forces along said lateral axis, while accommodating differential displacement along said longitudinal axis, and wherein said elastomeric bushings enable relative pivotal movement of the reactions arms about said vertical axis while providing stiff opposition to radial forces on said torsion pads.
- 19. A method for coupling adjoining ends of a pair of reaction arms used in a steering linkage of a railway truck, one of said reaction arms ends comprising a fork having a top prong and a bottom prong, the other one of said reaction arms ends comprising a bracket received by said fork, said method comprising:providing an elastomeric joint in said bracket, said joint comprising a multi-degree of freedom elastomeric joint including respective pluralities of shear and torsion pads that in frictionless engagement allows differential longitudinal and pivotal movement between said adjoining ends; and affixing a cover plate to said bracket to compress the plurality of shear pads on each side of a base plate between said cover plate and a back section of the bracket, wherein said shear pads provide stiff opposition to forces along said lateral axis, while accommodating differential displacement along said longitudinal axis, and wherein said torsion pads enable relative pivotal movement of the reactions arms about said vertical axis while providing stiff opposition to radial forces on said torsion pads.
US Referenced Citations (11)