Information
-
Patent Grant
-
6439130
-
Patent Number
6,439,130
-
Date Filed
Thursday, April 5, 200123 years ago
-
Date Issued
Tuesday, August 27, 200222 years ago
-
Inventors
-
-
Examiners
- Morano; S. Joseph
- Olson; Lars A.
Agents
- Conley, Rose & Tayon, P.C.
-
CPC
-
US Classifications
Field of Search
US
- 105 1821
- 105 165
- 105 167
- 105 168
- 105 164
- 105 166
- 105 1991
- 105 210
- 105 2241
- 105 176
- 105 2181
-
International Classifications
-
Abstract
The invention concerns an inter-axle shear stiffening apparatus for a self-steering rail bogie and a self-steering rail bogie equipped with such apparatus. The apparatus has axle structures including axles (16, 16.1) which are journalled in axle box bearings (20, 20.1). Radial arms (30, 30.1) are connected rigidly to respective axle structures of the bogie an extend towards one another in a fore and aft direction. A lateral force transmitting device (60) acts between the arms to transmit lateral forces between them while accommodating relative lateral movement between them. The design of this device is such that, irrespective of the extent of relative movement between the arms, the device can only transmit between them lateral forces of limited, predetermined magnitude. This value is chosen such that the bogie is provided with sufficient inter-axle shear stiffness to enhance its hunting stability without excessive force couples being applied to the axle box bearings.
Description
BACKGROUND TO THE INVENTION
THIS invention relates to self-steering bogies for rail vehicles and in particular to the provision of inter-axle shear stiffness in self-steering bogies.
Inter-axle shear stiffness for self-steering bogies is commonly provided by means of cross-anchors which are fitted to the wheelset sub-frames, as proposed for instance in the known Scheffel cross-anchor design, or by means of A-frames which are connected to one another, at their apices, on the transverse centre line of the bogie, as proposed for instance in the known List Steering Arm design. However, on irregular track, and particularly at points and crossings, high shock loads are exerted on the wheelsets and transmitted to the sub-frames or A-frames. The frames must therefore be robust. Robustness is also necessary to ensure that the forces transmitted to the frames do not generate unduly high force couples on the journal roller bearings of the bogie wheelsets which could shorten the service life of those bearings. The required robustness results in heavy sub-frames or A-frames which considerably increase the unsprung wheelset mass and this can in turn reduce the hunting stability of the bogie at high speeds.
It is however understood that the inter-axle shear forces which are required to ensure effective wheelset guidance for hunting stability and curving performance are only a fraction, typically no more than 30%, of the shock forces encountered at points and crossings.
Against this background the present invention proposes to provide an apparatus which will limit the transmission of shear forces between the wheelsets to a level at which adequate hunting stability and curving performance can be attained but which will nevertheless be acceptable to the wheel journal roller bearings.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided an inter-axle shear stiffening apparatus for a self-steering rail bogie having axle structures including axles which are journalled in axle box bearings, the apparatus comprising arms which are rigidly connected or connectable to respective axle structures of the bogie to extend towards one another from the axle structures in generally fore and aft directions, and lateral force transmitting means for acting between the arms to transmit lateral forces between them while accommodating relative lateral movement between the arms, wherein, irrespective of the extent of relative movement between the arms, the lateral force transmitting means is only capable of transmitting between them lateral forces of limited, predetermined magnitude which provide the bogie with inter-axle shear stiffness to enhance hunting stability of the bogie but are insufficient to impose excessive force couples on the axle box bearings.
According to another aspect of the invention there is provided a self-steering rail bogie having axle structures including axles journalled in axle box bearings and including an inter-axle shear stiffening apparatus as summarised above, with the arms of the apparatus rigidly connected to the axle structures and the apparatus providing inter-axle shear stiffness to enhance the hunting stability of the bogie.
Other advantageous and preferred features of the invention are set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:
FIG. 1
shows a side view of a bogie retro-fitted with an apparatus according to the invention;
FIG. 2
shows a plan view of one side of the bogie;
FIG. 3
shows a detail of a bearing adaptor of the apparatus;
FIG. 4
illustrates a force transmitting device which can be used in the apparatus;
FIG. 5
shows a side view of a bogie manufactured with an apparatus according to the invention;
FIG. 6
shows a plan view of the embodiment of
FIG. 5
;
FIG. 7
illustrates another embodiment of force transmitting device which can be used in apparatus according to the invention;
FIG. 8
shows a side view of relevant parts of another embodiment of the invention;
FIG. 9
shows a plan view of the components seen in
FIG. 8
;
FIG. 10
shows a side view of a leaf spring used in the embodiment of
FIGS. 8 and 9
;
FIG. 11
shows a plan view of the leaf spring of
FIG. 10
;
FIG. 12
graphically illustrates the performance of the embodiment of
FIGS. 8 and 9
;
FIGS. 13 and 14
diagrammatically illustrate the application of the invention to motorised bogies;
FIG. 15
shows a side view of the motorised bogie of
FIG. 14
;
FIG. 16
illustrates a stop used in the embodiment of
FIGS. 8 and 9
;
FIGS. 17
to
21
illustrate different force transmitting devices with a degressive characteristic;
FIG. 22
shows a side view of an embodiment in which provision is made for axial shear stiffness and a yaw constraint;
FIG. 23
shows a plan view of the embodiment of
FIG. 22
;
FIG. 24
graphically illustrates the performance of a device such as that seen in
FIG. 17
;
FIG. 25
shows a side view of a three-piece bogie and illustrates an alternative axlebox suspension arrangement;
FIGS. 26
a
and
26
b
respectively show side and sectional views of another device which can be used to provide a degressive yaw constraint;
FIGS. 27
a
and
27
b
respectively show side and sectional views of a further device which can be used to provide a degressive yaw constraint; and
FIGS. 28
a
and
28
b
respectively show side and sectional views of yet another device which can be used to provide a degressive yaw constraint.
DESCRIPTION OF EMBODIMENTS
FIGS. 1
to
3
illustrate a three-piece self-steering rail bogie
10
to which an apparatus
12
according to the present invention has been retro-fitted to provide inter-axle shear stiffness between the axles
16
,
16
.
1
of the bogie. As is conventional, wheels
18
,
18
.
1
are fast with the axles
16
,
16
.
1
of the bogie
10
. The axles are supported in respective axle boxes
20
,
20
.
1
, located outboard of the wheels, by the usual journal roller bearings. Side frames
22
are suspended on the axle boxes
20
,
20
.
1
and support a transverse bolster
24
, on the transverse centre line
26
of the bogie, by means of springs
28
.
The apparatus
12
of the invention includes, on each side of the bogie, a pair of arms
30
,
30
.
1
. The arms are oriented generally in a fore and aft direction. First ends
32
,
32
.
1
of the arms are connected to the respective axle boxes
20
,
20
.
1
while the opposite, second ends
34
,
34
.
1
of the arms lie near to one another on the transverse centre line
26
. The arms
30
,
30
.
1
are appropriately shaped lengths of angle section steel with one leg
36
of the angle section vertical and the other leg
38
thereof horizontal.
The manner in which the first ends
32
,
32
.
1
of the arms are connected to the axle boxes
20
,
20
.
1
is now described with particular reference to
FIG. 3
of the drawings. The apparatus
12
includes, for each axle box, a bearing adaptor
40
which is mounted on the journal bearing
42
of the axle box and to which the vertical legs
36
of the arms are connected by bolts, welding, riveting, lock-bolting or other suitable means (not shown).
The apparatus
12
also includes, for each bearing adaptor, a shear pad assembly
46
which is located between the adaptor and side frame
22
, within the pedestal
48
of the side frame. In this embodiment, the shear pad assembly
46
comprises a number of individual, relatively thin rubber shear pads
50
. The upper surface of the bearing adaptor
40
is formed with steps
52
, this being allowed by the curvature of the lower surface of the bearing adaptor which bears on the journal roller bearing
42
of the axle box. Whereas the available space in the pedestal opening between the bearing
42
and the pedestal
48
may allow for only a single shear pad
50
to be placed on the vertical centre line of the bearing in the retro-fit application under discussion, the steps
52
provide space to accommodate stacks of shear pads at positions fore and aft of the centre line.
The multiple shear pad arrangement allows for appropriate levels of spring stiffness to be provided between the journal box and pedestal even in the limited space available in a conventional bogie. In particular the arrangement allows longitudinal spring stiffness to be reduced in order to improve the curving, i.e. self-steering, ability of the bogie. Although only a single step
52
is shown on each side of the roller bearing centre line in
FIG. 3
, it should be understood that there may be several such steps on each side, allowing for the placement of increasing numbers of individual shear pads with increasing distance from the vertical roller bearing centre line. This in turn can allow for variations to be made in the level of shear stiffness of the pedestal mounting.
It is however recognised that an inherent problem with a multi-step, multiple shear pad configuration as proposed above is the potential difficulty in ensuring that the pads in the various layers and stacks are equally loaded. In an alternative arrangement, shown in
FIG. 25
, pairs of inclined rubber pads
50
are provided in a configuration which will be less susceptible to unequal loading to give the appropriate levels of longitudinal spring stiffness.
Referring again to
FIGS. 1 and 2
, although the arms
30
,
30
.
1
are not strictly radial with respect to the journal bearing
42
, it will be understood that their orientation is generally radial. For convenience the arms are referred to herein as radial arms.
The second ends
34
,
34
.
1
of the arms
30
,
30
.
1
on each side of the bogie are connected to one another by a force transmitting device
60
on the transverse centre line
26
of the bogie. The device
60
transmits forces between the arms to provide inter-axle shear stiffness for the bogie
10
. It will however be understood that transverse forces transmitted between the ends
34
,
34
.
1
of the arms will generate force couples on the journal roller bearings
42
, particularly in shock load situations, which could result in premature failure thereof. For this reason, the design of the device
60
is such that, while it can transmit sufficient force between the arms for the bogie
10
to have adequate inter-axle shear stiffness for acceptable hunting stability and curving performance at design speeds, it does not transmit forces that could generate unacceptable couples on the journal roller bearings
42
.
One example of a suitable device
60
is illustrated in
FIG. 4
of the drawings. The device
60
seen in this Figure has a housing
62
accommodating sliding spring cups
64
and
66
, a pretensioned compression spring
68
acting between the cups and a shaft
70
which can slide on bearings
72
through the cups
64
and
66
. One end of the shaft carries an eye
74
which, in its application in the present invention, receives the end
34
.
1
of the arm
30
.
1
. An eye
76
at the other end of the device
60
is fixed to the housing
62
by arms
77
and receives the end
34
of the arm
30
. The relevant end of the shaft
70
is capable of longitudinal sliding movement relative to the eye
76
.
In situations where the relevant forces transmitted by the radial arms
30
,
30
.
1
tend to move the ends
34
,
34
.
1
towards one another, the shaft
70
moves to the left in
FIG. 4
, taking the spring cup
64
with it and thereby applying a further compressive force to the spring
68
. The spring cup
66
abuts a shoulder
78
at the end of the housing and does not move. At a limit position of movement of the shaft, a nut
80
on the shaft abuts the eye
76
. If, on the other hand, the relevant forces transmitted by the arms
30
,
30
.
1
tend to move the ends
34
,
34
.
1
apart from one another, the shaft
70
will move to the right in FIG.
4
. The nut
80
accordingly pulls the spring cup
66
to the right. The spring cup
64
abuts a shoulder
82
of the housing and cannot move so, once again, further compression is applied to the spring
68
in this situation.
The pretension applied to the spring
68
is such that the relative movement between the ends
34
,
34
.
1
is very small compared to the deflection which the spring has already undergone in pretensioning it from a relaxed state. Thus the maximum force which the spring can transmit from one radial arm to the other does not substantially exceed the pretension force in the spring. In practice, the pretension force in the spring is set in the factory to a value at which it can transmit forces between the arms which are sufficient to give the required level of inter-axle stiffness for acceptable hunting stability and curving performance of the bogie
10
, but which are insufficient to generate unacceptable couples on the journal bearings
42
.
The force transmitting device
60
described above is only one example of how limited force transmission may take place between the arms. Other embodiments are described below with reference to
FIGS. 7
to
12
and
17
to
21
.
Specific reference has been made to the apparatus
12
being of a retro-fit design. The ability to retrofit an apparatus of this nature is of course advantageous. It will however be understood that in the case of new bogies, corresponding apparatus can be installed at the time of manufacture. In this case, the radial arms
30
,
30
.
1
can be manufactured integrally as the wings of wing-type axle boxes. An example of such a construction is illustrated in
FIGS. 5 and 6
which show radial arms
30
,
30
.
1
formed integrally with wing-type axle boxes
20
,
20
.
1
.
The wing-type axle boxes of the new bogie depicted in
FIGS. 5 and 6
make use of two springs
84
per axle box, located respectively fore and aft of the vertical centre line, to achieve appropriate levels of longitudinal spring stiffness. However, bogies of original manufacture could also make use of a bearing adaptor and shear pad assembly located within the opening of the pedestal frame as described above for the retro-fit application. In these cases the radial arm could either be bolted on or made integral with the adaptor. Alternatively it would be possible in a new bogie to increase the size of the pedestal opening to accommodate a larger, single shear pad on the vertical centre line instead of an assembly of shear pads
50
as described above for the assembly
46
. With a larger and softer single shear pad it would also be possible to achieve a softer longitudinal spring effect in order to improve the curving characteristics of the bogie.
A major advantage of the invention as exemplified above is that, while adequate inter-axle shear stiffness is provided, the arms
30
,
30
.
1
can be of relatively lightweight construction, thereby adding relatively little to the unsprung mass of the bogie
10
compared to conventional designs. Although specific mention has been made of radial arms
30
,
30
.
1
which are of angle section, it will be understood that channels, I-sections or other cross-sections could also be used.
It will be understood that the force transmitting device
60
of
FIG. 4
has a very high level of initial stiffness to transmit lateral loads between the radial arms. After the initial spring pretension has been overcome there is little or no increase in the lateral loads which the device
60
can transmit between the radial arm, it being understood that the spring characteristic and the pretension applied thereto are set such that the lateral load which is transmitted after the pretension has been overcome is insufficient to cause damage to the journal bearings. While a high level of initial stiffness is appropriate to transmit the lateral load, it is however believed that a few millimeters of deflection should be allowed to take place.
FIG. 7
illustrates another force transmitting device
90
, similar to the device
60
, which allows for several millimeters of deflection prior to the pretension force in the coil spring
68
being overcome. In this case, the device
90
includes pairs of opposed Belleville or spring washers
92
at either end. The spring characteristic of the Belleville spring combinations is such they can accommodate a few millimeters of initial deflection in either direction.
FIG. 7
shows the pairs of Belleville washers with their concavities directed away from one another at one end and towards one another at the other end, but it will be understood that the arrangement could be the same at both ends.
As an alternative to Belleville washers, ring-shaped springs having an annular core of rubber or suitable polymer material, such as Vescoflex™, moulded between annular steel plates could be used.
FIGS. 8 and 9
illustrate another embodiment of the invention which uses a different type of force transmitting device in a radial arm configuration. This embodiment uses a pair of pretensioned leaf springs
100
as the force transmitting device. A typical one of these leaf springs is illustrated, in its manufactured state, in
FIGS. 10 and 11
. The spring
100
has straight ends
102
and
104
with a curved middle portion
106
. The straight ends
102
of the springs
100
are clamped by bolts
108
extending through holes
110
to the radial arm
30
.
1
with the springs parallel to one another. The radial arm
30
.
1
in this case has a box section which accommodates the springs spaced apart laterally from one another.
A pulling device (not shown) is then inserted through holes
112
at the opposite ends of the springs. Tension is applied to the pulling device to pull the springs into a straight condition or even past straight. A stop
114
is fitted to each spring at a point
116
corresponding to the end of the portion
106
which was curved prior to the pretensioning operation just described.
An example of a suitable stop
114
is shown in
FIG. 16
of the drawings. This stop
114
includes an upright plate
118
attached at its upper and lower ends to internally threaded members
120
. Spaced apart from the plate
118
is a pair of lugs
122
also attached to the members
120
. The leaf spring
100
can slide in the gap defined on one side by the plate
118
and on the other side by the lugs
122
.
A set-screw
124
extending through a tapped hole in the plate
118
is used to anchor the stop to the leaf spring at the chosen position
116
. Thus it will be understood that the stop is in fact slipped along the leaf springs
100
to the position
116
where they are anchored by means of the set-screws
124
.
Set screws
126
extend through the members
120
as illustrated. Once the stops
114
have been fixed to the leaf springs at the correct positions, the projecting ends
128
of the set screws
126
bear against the upright walls of the box section radial arm
30
.
1
. By adjusting the set screws
126
it is possible to bring the leaf springs into orientations in which they are straight and parallel to one another. The set screws are in turn locked in position by grub screws
130
. The inner end of the other radial arm
30
carries a transverse member
132
, termed a “crosshead”, which is positioned on the transverse centre line
26
of the bogie and which locates slidably between the free ends of the leaf springs
100
projecting from the other radial arm. In situations where shear forces between the axles tend to move the adjacent ends of the arms
30
,
30
.
1
towards or away from one another, the crosshead
132
will apply a force to one or other of the leaf springs in a manner tending to lift its stop
114
off the radial arm
30
.
1
.
Because of the pretension force stored in each leaf spring and the bearing of the stops
114
against the radial arm
30
.
1
, the free ends of the leaf springs act in the manner of pretensioned cantilevers having a length defined between the position
116
and the crosshead
132
. Thus lateral force can be transmitted between the radial arms with little initial lateral deflection as initial loading up to the value of the pretension force takes place.
However, if the lateral force is sufficient to overcome the prestress in the relevant leaf spring, the set screws
126
of the stop
114
on that leaf spring will be lifted off the radial arm
30
.
1
. Thereafter the full length of leaf spring acts in cantilever mode to take the applied lateral force. Clearly the shorter cantilever which acts initially is substantially stiffer than the longer cantilever which acts after the stop has been lifted. Accordingly the spring can flex more readily over its full length to take further applied loading without substantial transmission of the force between the radial arms
30
,
30
.
1
after the stop has lifted.
This is illustrated in
FIG. 12
which shows a theoretical plot of deflection on the horizontal axis against transmitted force on the vertical axis. In the initial stage A where the applied load is insufficient to overcome the prestress in the spring it will be seen that the spring can transmit a substantial load with very little deflection. In practice, as mentioned previously in connection with the device
60
of the first embodiment, it is desirable for there to be a few millimeters only of deflection during this stage.
The point B in the graph represents the point at which the applied load is equal to the prestress in the spring and the stop lifts off the radial arm. Thereafter in stage C the load which the spring can transmit increases only very slightly with increasing deflection.
As in the previous embodiments, the design is such that adequate lateral force can be transmitted during stage A to provide a suitable level of inter-axle shear stiffness. Thereafter the maximum transmitted force is insufficient to cause damage to the journal roller bearings.
Referring again to
FIG. 7
, the Belleville springs
92
provide the few millimeters deflection represented by stage A in FIG.
12
.
An important advantage which the embodiment of
FIGS. 8 and 9
has over that of
FIGS. 4 and 7
is the fact that the leaf spring device is more compact in a lateral sense than the transverse coil spring device. The leaf spring device may accordingly be preferred in situations where there are obstacles close to the rail track which could interfere with a bogie fitted with a transversely extending device such as the devices
60
.
Another advantage of the leaf spring device of
FIGS. 8 and 9
is that the initial force required to lift the stop
114
off the radial arm
30
.
1
can be varied merely by varying the length of the lever arm defined between the position
116
and the crosshead
132
, i.e. by varying the position of the stop on the leaf spring.
It will accordingly be understood that the use of leaf springs as described above lends itself to a particularly compact and versatile design able to provide both inter-axle shear stiffness and, as described below, a longitudinal yaw constraint.
The embodiments described above are applied to three-piece self-steering bogies. However the invention has wider application.
FIG. 13
illustrates the application of the invention to a motorised, self-steering bogie having axles
200
fitted with motors
202
. In this case, shear stiffness is provided by a transverse force transmitting device
204
, corresponding to the device
60
used in the previous embodiments and acting on the transverse centre line of the bogie between fore-and-aft extending radial arms
206
and
208
corresponding to the arms
30
,
30
.
1
.
FIG. 14
illustrates the application of the invention to a motorised bogie having axles
300
fitted with motors
302
. Shear stiffness in this case is provided by a leaf spring device
304
as described above in relation to
FIGS. 8 and 9
, the leaf springs being attached to an arm
306
extending rearwardly from one of the motor/axle assemblies and acting against a crosshead
308
carried on the transverse centre line of the bogie by an arm
310
extending forwardly from the other motor/axle assembly.
From
FIG. 15
, which shows a side view of the motorised bogie of
FIG. 14
, it will be seen that the arms
306
,
310
are radially orientated and corrrespond to the arms
30
,
30
.
1
.
It will also be noted that in
FIGS. 13 and 14
the force transmitting device is located inboard of the bogie wheels whereas in the previous embodiments, the devices are arranged outboard. Those skilled in the art will appreciate that inboard location is possible because of the inter-axle space which is available with motorised bogies.
Other embodiments of force transmitting device, with a degressive characteristic, are illustrated in
FIGS. 17
to
21
. Referring to
FIG. 17
, there is an annular cam member
418
composed of mating cam segments
418
.
1
and
418
.
2
and a series of circumferentially spaced balls
454
which seat, in the dead centre position, in a recess
422
formed by the mating cam segments. A biasing force to hold the balls
454
in this position is provided by a spring
456
acting on a cone
458
. The spring
456
surrounds a shaft
460
and is pretensioned by a sleeve
462
which acts against a shoulder
464
of the cone and screws onto the shaft at a thread
466
. The balls
454
are retained between the end surface
468
of the sleeve and a piston
470
which is locked to the shaft by a lock nut
472
and which bears against the end face of the cone
458
.
The dimensions are such that the ball-retaining gap between the opposing faces of the sleeve
462
and piston
470
is slightly greater than the ball diameter. Thus the balls are not tightly gripped between these faces and are able to move radially in the gap, as described below.
The cam segments
418
.
1
,
418
.
2
are pressed into a cylinder
474
and are held between an internal shoulder
476
of the cylinder and an internal guide nut
478
. Bushes
480
and
482
are provided in the cylinder
474
and in the sleeve
462
to allow for longitudinal sliding movement of the piston in the cylinder and of the sleeve in the guide nut respectively.
The shaft and cylinder carry respective couplings
484
and
486
by means of which they can be connected to members between which forces are to be transmitted, in the present case the inner ends
34
,
34
.
1
of the rail arms
30
,
30
.
1
.
In the rest or dead centre position seen in
FIG. 17
the balls
454
are retained in the recess
422
by the large diameter end of the conical surface of the cone
458
. When relative movement takes place between the ends
34
,
34
.
1
either towards or away from one another, the shaft
460
and cylinder
474
move relative to one another. Depending on the direction of relative movement, either the sleeve or the piston pushes on the balls. With application of a large enough force, the force of the spring
456
is overcome and the cone
458
slides on the shaft
460
to compress the spring further. The balls move out of the recess
422
and over the profiled cam surfaces
424
. Since the balls are acted upon by progressively smaller diameters of the conical surface of the cone, there is a progressively diminishing, i.e. degressive, restoring force.
FIGS. 18 and 19
show modified versions of the
FIG. 17
embodiment. Components corresponding to those in
FIG. 17
are designated by like numerals. In
FIG. 18
, conical disc springs, i.e. Belleville springs
488
, apply the necessary bias to the balls
454
in place of the cone and spring configuration of FIG.
17
. In
FIG. 19
rubber springs
490
are used in place of the disc springs
488
. Despite the different spring arrangements employed in
FIGS. 18 and 19
it will be appreciated that these embodiments operate in a fashion similar to
FIG. 17
, with the disc or rubber springs initially applying a large restraint to unseating of the balls from the recess
422
and thereafter the restoring force diminishes, i.e. degresses, with increasing deflection.
FIGS. 20 and 21
show another embodiment of force transmitting device which is an approximate reversal of the configuration in FIG.
17
. Here, coil springs
492
in spring housings
494
on the cylinder
474
act inwardly on individual balls
454
to retain them in recesses
422
in the shaft
460
which can slide in the cylinder in bushes
496
. As illustrated, there is a number of balls and corresponding springs which are circumferentially and longitudinally spaced apart from one another. In an alternative configuration there could be a plurality of balls spaced apart angularly in the same circumferential plane, i.e. without longitudinal spacing. This would decrease the overall length of the device.
It will be understood that the devices described above with reference to
FIGS. 17
to
21
can be used as the force transmitting device in the earlier embodiments of
FIGS. 1 and 2
,
FIGS. 5 and 6
or FIG.
13
. As is the case with the previously described devices for this purpose, the characteristics of the force-transmitting devices of
FIGS. 17
to
21
are such that a limited force can be transmitted between the radial arms
30
and
30
.
1
which is sufficient to achieve the required level of inter-axle stiffness but insufficient to place unacceptable couples on the journal roller bearings of the wheelsets, particularly in shock load conditions.
In addition to providing for transmission of a limited lateral force between the ends of the radial arms
30
,
30
.
1
, the devices of
FIGS. 17
to
21
can also be used to provide degressive yaw constraints for the wheelsets of a rail bogie to ensure that on straight track there is a relatively high resistance to yawing of the wheelsets while on curved track, where yawing movements must be accommodated if the wheelsets are to attain radial orientations for proper self-steering to take place, a reduced resistance to yawing is required.
The degressive force transmitting devices of
FIGS. 17
to
21
could, for instance, be arranged to act between the axle boxes of wheelsets on the same side of the bogie i.e. in the manner described with reference to FIG. 7 in the specification of South African patent 94/1641, to which reference should be made for the details. Alternatively such devices could be arranged to act between the bogie frame and the axleboxes of the wheelsets.
FIGS. 22 and 23
illustrate how degressive force transmitting devices such as those seen in
FIGS. 17
to
21
can be used both to constrain wheelset yawing in a degressive manner and to provide inter-axle stiffness according to this invention. As before these Figures show a three piece, self steering bogie
10
with wheelsets
18
,
18
.
1
journalled in axle boxes
20
,
20
.
1
on which side frames
22
are suspended. Radial arms
30
,
30
.
1
are connected to the axle boxes on each side of the bogie and extend towards one another with a force transmitting device
60
acting on the transverse centre line of the bogie between the adjacent ends
34
,
34
.
1
of the radial arms. The device
60
may be any one of the degressive force transmitting devices described above with reference to
FIGS. 17
to
21
. The characteristics of the device, determined inter alia by the spring pretension force and the profile of the cam member against which the balls act, is set such that the maximum force which can be transmitted between the radial arms is sufficient to provide adequate inter-axle shear stiffness for hunting stability at high bogie speeds but insufficient to place unacceptable couples on the wheelset journal bearings.
This is illustrated by
FIG. 24
which shows a graph similar to that of FIG.
12
. As shown here a large force can initially be transmitted with little deflection, i.e. movement of the ends
34
,
34
.
1
of the radial arms
30
,
30
.
1
towards or away from one another. Thereafter there is little or no increase in transmitted load with further deflection.
It will of course be understood that in each embodiment described above, the design of the force transmitting device is such that, irrespective of the amount of lateral movement between the adjacent ends of the radial arms, it is unable to transmit lateral forces which exceed a predetermined maximum force. The selected maximum force is great enough to generate a level of inter-axle shear stiffness consistent with acceptable hunting stability of the bogie but is insufficient to generate force couples on the axle box journal bearings which exceed what is considered to be an acceptable limit.
Referring again to
FIGS. 22 and 23
another force transmitting device
60
.
1
, similar to the device
60
and having a degressive characteristic as described above is used in the yaw constraint mode. It is seen acting between the radial arms
30
,
30
.
1
with the cylinder of the device mounted to a bracket
112
on the radial arm
30
and the shaft
113
of the device connected to a bracket
114
on the other radial arm
30
.
1
. The device
60
.
1
accordingly applies a double-acting degressive yaw constraint between the linked axleboxes.
FIGS. 26
a
and
26
B,
FIGS. 27
a
and
27
b
and
FIGS. 28
a
and
28
b
illustrate three further embodiments of devices which can be used to provide a degressive yaw constraint feature in a self-steering bogie.
Referring firstly to
FIGS. 26
a
and
26
b
, there is shown an embodiment
510
which includes a back plate
512
carrying spaced apart, projecting support pins
514
between which a leaf spring
516
is engaged. A cam member
518
is connected centrally to the leaf spring by studs
520
. The cam member has a central recess
522
and profiled cam surfaces
524
arranged symmetrically on either side of the central recess.
The device
510
also includes a roller
526
carried rotatably by a lever
528
consisting of spaced apart arms
530
between which the roller is located. Between the roller and its lower end, the lever
528
is supported pivotally on a pin
532
projecting from the back plate
512
. At the lower end of the lever a transverse pin
534
is attached via a spherical bearing
536
to the end of a link
538
.
The device
510
serves to transmit forces between the link
538
and the back plate
512
. In a practical application which the device is used to provide a longitudinal yaw constraint, the back plate may be fixed to or be part of the bogie frame with the link
538
being an axle box link extending from an axle box. The device
510
then serves to transmit longitudinal forces between the axle box and the bogie frame to provide a degressive yaw constraint for the relevant axle to improve hunting stability.
FIG. 26
a
shows the device at a central or dead centre position with the roller
526
seated in the recess
522
. The roller is held in this position by the action of the leaf spring
516
, which is pretensioned to provide a predetermined biasing force. Movement of the axle box link, for instance in the direction indicated by the arrow
40
, in response to yawing movement of the associated axle relative to the bogie frame, causes the lever
528
to rotate about the axis of the pin
532
. There is initially considerable resistance to this movement as a result of the seating of the roller in the recess
522
. However if the force applied by the link
538
is sufficient to unseat the roller from the recess, there will be a progressively decreasing restoring force, i.e. a degressive resistance, as the roller moves over the relevant cam surface as indicated by the arrow
542
. The device
510
accordingly transmits the force from the link to the back plate, i.e. from the axle box to the bogie frame, in a degressive manner with the magnitude of the transmitted force decreasing with increasing movement of the link.
It will be understood that if the link
538
moves in the opposite direction with sufficient force to unseat the roller from the recess, there will be a similar degressive restraint as the roller moves over the other cam surface
524
in the direction of the arrow
544
. Thus it can be seen that the device
510
is double-acting in the sense that the degressive restraint is applied irrespective of the direction of relative movement between the axle box link
538
and the back plate.
Components in
FIGS. 27
a
and
27
b
which correspond to those in
FIGS. 26
a
and
26
b
are designated by the same reference numerals. In this case the cam member
518
is clamped between two spring blades
546
supported by the back plate
512
. There is once again a roller
526
carried by a lever
528
.
In the practical example mentioned above, forces are again transmitted between an axle box to which the link
538
is connected and a bogie frame in a degressive manner, with an initially large resistance to unseating of the roller
526
and thereafter a progressively diminishing restoring force as the roller moves further and further along one or other of the cam surfaces
524
with increasing movement of the link
538
, i.e. with increased yawing movement of the axle.
In
FIGS. 28
a
and
28
b
, like components are again designated with like reference numerals. In this case, the leaf or blade springs of the embodiments of
FIGS. 26 and 27
are replaced by a pretensioned coil spring
548
which acts between the pivot pin
532
and a lug
550
on the cam mbmer
518
which is pivoted to the back plate
512
at a pivot
552
.
In
FIGS. 26
to
28
the spring force will in each case be kept as low as practically possible to reduce wear on the roller
526
while nevertheless catering for the transmission of appropriate yaw constraining forces in the required, degressive manner.
In the context of a longitudinal yaw constraint and referring again to the embodiment seen in
FIGS. 8 and 9
an added advantage is the ability to accommodate a longitudinal yaw constraint device between the leaf springs. The yaw constraint could, for instance, be similar to that illustrated in
FIGS. 22 and 23
. In the proposed arrangement one end of the degressive yaw constraint would be attached to a vertical pin
140
forming part of the crosshead
132
and the opposite end to another pin
142
extending vertically through the radial arm
30
.
1
between the springs
100
. It will be appreciated that in this way both inter-axle shear stiffness and a longitudinal yaw constraint can be provided very compactly.
Claims
- 1. An inter-axle shear stiffening apparatus for a self-steering rail bogie having axle structures including axles which are journalled in axle box bearings, the apparatus comprising arms which are rigidly connected or connectable to respective axle structures of the bogie to extend towards one another from the axle structures in generally fore and aft directions, and lateral force transmitting means for acting between the arms to transmit lateral forces between them while accommodating relative lateral movement between the arms, wherein, irrespective of the extent of relative movement between the arms, the lateral force transmitting means is only capable of transmitting between them lateral forces of limited, predetermined magnitude which provide the bogie with inter-axle shear stiffness to enhance hunting stability of the bogie but are insufficient to impose excessive force couples on the axle box bearings.
- 2. An apparatus according to claim 1 wherein the lateral force transmitting means is arranged to transmit lateral forces between adjacent ends of the arms substantially on a transverse centre line of the bogie between the axles.
- 3. An apparatus according to claim 2 wherein the lateral force transmitting means is arranged to transmit lateral forces between the arms substantially in the plane of the axle box bearings.
- 4. An apparatus according to claim 1 wherein the arms are arranged to be substantially radially oriented with respect to the axles.
- 5. An apparatus according to claim 1 wherein the lateral force transmitting means is arranged initially to transmit between the arms relatively large lateral forces, up to the predetermined magnitude, for relatively small relative movement between the arms and thereafter to transmit little or no further forces between the arms for relatively large relative movement between the arms.
- 6. An apparatus according to any one of the preceding claims wherein the lateral force transmitting means includes a spring to resist relative lateral movement between the arms, the spring being pretensioned to a value not substantially less than the predetermined magnitude.
- 7. An apparatus according to claim 6 wherein the spring is a coil spring.
- 8. An apparatus according to claim 6 wherein the spring comprises one or more leaf springs.
- 9. An apparatus according to any one of claims 1 to 5 wherein the lateral force transmitting means comprises a cam member presenting a cam surface in which a recess is formed, a detent and spring means biasing the detent to seat it in the recess, the detent when seated in the recess resisting relative movement between the arms while lateral forces are transmitted between them, with the arrangement being such that on transmission of lateral forces between the arms of the predetermined magnitude the detent is unseated from the recess and moves over the cam surface with little further transmission of lateral force between the arms.
- 10. A self-steering rail bogie, comprising:at least two axle structures including axles journalled in axle box bearings; and an inter-axle shear stiffening apparatus, said inter-axle shear stiffening apparatus comprising: an arm rigidly connected or connectable to each of said at least two axle structures of the bogie, said arms extending toward one another from said axle structures; a lateral force transmitting connector connected between and acting between the arms to transmit lateral forces between said arms such that, irrespective of the extent of relative movement between said arms, the lateral force transmitting connector transmits lateral forces of limited predetermined magnitude, said transmitted lateral forces being sufficient to provide inter-axle shear stiffness to enhance the hunting stability of the bogie but insufficient to impose excessive force couples on the axle box bearings.
- 11. A self-steering rail bogie according to claim 10 wherein the bogie is a three piece bogie.
- 12. A self-steering rail bogie according to claim 11 which comprises an inter-axle shear stiffening apparatus located outboard of wheels carried by the axles on each side of the bogie.
- 13. A self-steering rail bogie according to claim 10 wherein the bogie is a motorised bogie.
- 14. A self-steering motorized rail bogie, comprising:at least two axle structures including axles journalled in axle box bearings, wherein said axles carry wheels; and an inter-axle shear stiffening apparatus, wherein the inter-axle shear stiffening apparatus is located inboard of said wheels, said inter-axle shear stiffening apparatus comprising: an arm rigidly connected or connectable to each of said at least two axle structures of the bogie, said arms extending toward one another from said axle structures; a lateral force transmitting connector connected between and acting between the arms to transmit lateral forces between said arms such that, irrespective of the extent of relative movement between said arms, the lateral force transmitting connector transmits lateral forces of limited predetermined magnitude, said transmitted lateral forces being sufficient to provide inter-axle shear stiffness to enhance the hunting stability of the bogie but insufficient to impose excessive force couples on the axle box bearings.
- 15. A self-steering rail bogie according to any one of claims 10 to 14 and comprising degressive yaw constraint means acting between the axles to constrain yawing movements between the axles.
- 16. An inter-axle shear stiffening apparatus for a self-steering bogie having first and second axle structures including axles that are journalled in axle box bearings, comprising:a first arm rigidly connected or connectable to the first axle; a second arm rigidly connected or connectable to the second axle, said first and second arms extending toward each other when connected to the first and second axles, respectively; a lateral force transmitting connector connected between said first and second arms, said lateral force transmitting connector including a stiffening mechanism that transmits between said arms lateral forces having magnitudes less than a predetermined value for relatively small relative movement between the arms and transmits between said arms little or no lateral forces having magnitudes greater than said predetermined value, even for relatively large relative movement between said arms.
- 17. An inter-axle shear stiffening apparatus for a self-steering bogie having first and second axle structures including axles that are journalled in axle box bearings, comprising:a first arm rigidly connected or connectable to the first axle; a second arm rigidly connected or connectable to the second axle, said first and second arms extending toward each other when connected to the first and second axles, respectively; a lateral force transmitting connector connected between said first and second arms, said lateral force transmitting connector including a stiffening mechanism that transmits between said arms lateral forces having magnitudes less than a predetermined value for relatively small relative movement between the arms and transmits between said arms little or no lateral forces having magnitudes greater than said predetermined value, even for relatively large relative movement between said arms, wherein said lateral force transmitting connector comprises a spring, said spring being pretensioned with a force that is not substantially less than said predetermined value.
- 18. An inter-axle shear stiffening apparatus for a self-steering bogie having first and second axle structures including axles that are journalled in axle box bearings, comprising:a first arm rigidly connected or connectable to the first axle; a second arm rigidly connected or connectable to the second axle, said first and second arms extending toward each other when connected to the first and second axles, respectively; a lateral force transmitting connector connected between said first and second arms, said lateral force transmitting connector including a stiffening mechanism that transmits between said arms lateral forces having magnitudes less than a predetermined value for relatively small relative movement between the arms and transmits between said arms little or no lateral forces having magnitudes greater than said predetermined value, even for relatively large relative movement between said arms, wherein said lateral force transmitting connector comprises: a cam having a cam surface that includes a recess therein; a detent seated in said recess; and a spring urging said detent and said cam together such that said detent resists relative movement and transmits lateral forces between said arms when seated in said recess as long as the lateral forces are less than said predetermined value and unseats from said recess and transmits substantially no further lateral forces when the lateral forces exceed said predetermined value.
Priority Claims (3)
Number |
Date |
Country |
Kind |
98/7069 |
Aug 1998 |
ZA |
|
98/7070 |
Aug 1998 |
ZA |
|
99/2395 |
Mar 1999 |
ZA |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/IB99/01383 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO00/07864 |
2/17/2000 |
WO |
A |
US Referenced Citations (11)