The present invention relates to an axle assembly for rail vehicles such as railcars, subway cars trains, trolleys and the like. In particular, the present invention relates to such an axle assembly that includes a split axle assembly which allows the wheels to move axially inward and outwardly with reduced binding.
To ensure safe operation of trains, railcars, subway cars, trolleys and the like, devices have been used to measure gage restraint such as track stiffness and/or tie conditions. Examples of such devices are shown in U.S. Pat. No. 3,643,503 to Plasser et al., U.S. Pat. No. 3,816,927 to Theurer et al., and U.S. Pat. No. 3,869,907 to Plasser, deceased et al. In addition, devices have been designed to apply predetermined lateral force on the track, and to measure the lateral displacement to determine how much the track displaces under the predetermined and measured, lateral force. Such measure of displacement provides an indication of the track stiffness and the conditions of the ties so that necessary repair to the track can be made. An example of such a device is shown in U.S. Pat. No. 3,808,693 to Plasser et al. and U.S. Pat. No. 5,756,903 to Norby et al.
Two distinct approaches have been used in implementing a railroad gage restraint measurement system. These approaches include mounting the railroad gage restraint measurement system under a standard freight truck, and mounting such a measurement system on a railcar body. Regardless of where the measurement system is mounted, the railroad gage restraint measurement system generally includes a split axle assembly, also referred to as a telescoping axle assembly, that allows the wheels to be displaced axially relative to one another.
In the first approach, the conventional gage restraint measurement system is mounted to the truck and the modified freight truck self-steers through curves with minimal effect on the applied lateral forces while always keeping a consistent angle of attack relative to the rail. Because the stock suspension is used, the ride comfort is maintained while the number of specialized components is minimized. The system is designed so that active controls are not needed for force control. This results in a very simple measurement system with a minimal number of components with reduced cost and complexity. However, if the railroad gage restraint measurement system is mounted on the truck as part of the running gear, the measurement system is significantly damaged if the axle derails. In addition, such a measurement system can lead to a total derailment of the railcar to which the railroad gage restrain measurement system is attached. This risk may be minimized by manually locating and identifying the track hardware that poses a derailment risk, and retracting the lateral force application when such track hardware is encountered. This procedure can be automated, but not without increased complexity and cost.
In the second approach, the conventional railroad gage restraint measurement system is mounted to the railcar body, and the system requires custom designed components, and possibly, active controls to maintain lateral position of the railcar body relative to the center of the track. In addition, this approach requires fine adjustments to maintain a consistent angle of attack. Furthermore, if active controls are not used for lateral positioning, frictional forces and mass effects can seriously impact the applied forces. Predicting these effects is nearly impossible until the measurement system is operating under normal loading conditions on the track. This results in a significant decrease in data quality due to the poor axle tracking, i.e. following rails of the track, and large variations in lateral force. Another disadvantage in mounting the measurement system to the railcar body is the resulting effect of unloading the vehicle's suspension. If the measurement system is mounted to the mid-span of the railcar body, the addition of a supporting axle mid-span of the railcar body will substantially modify the railcar's designed response to the dynamic bounce, pitch, and roll of the railcar during testing, these responses being important to evaluate performance at higher testing speeds. Lastly, the railcar's ride quality may be degraded due to the lack of a suspension between the loaded axle and the car body.
Regardless of which approach is employed, railroad gage restraint measurement systems generally include a split axle assembly with a sliding barrel device that functions in a telescoping manner to allow the wheels to be axially displaced relative to one another. A major disadvantage of the conventional split axle designs is that the bending moment that is transferred across the sliding barrel device to the opposing wheel on the railroad track is generally very high. The sliding surfaces of the sliding barrel device which allows it to function in a telescoping manner has a tendency to bind, i.e. become temporarily stuck. This tendency for binding increases as the bending moment increases. Such binding results in random locking of the telescoping action of the split axle assembly so that the split axle does not accurately follow the actual rails of the track. Binding of the split axle results in excessive variation in the lateral forces which result in poor quality measurement data being obtained. Further, such binding can damage the track with excessive forces when the gage of the track narrows and the split axle assembly binds during axial movement.
To generate this rather large balancing moment, four hydraulic cylinders (not shown) are generally mounted at specific distances from the center of the axle 102 and apply lateral loads via the push-plates 108 (one shown). The net lateral load from these hydraulic cylinders is the applied force to the railroad track, i.e. lateral load (L) of 14,000 lbs. The sliding barrel (not shown) connecting the two axles of the split axle assembly 100 only has to transfer the variations in the moment. With enough lubrication, this can be done without causing the split axle 102 to bind within the sliding barrel, yielding good gage following performance, and good lateral force control. However, since the hydraulic cylinders are applying opposing forces, a large amount of stress is generated in the push-plates 108 and the sliding barrel thereby requiring a significant amount of material to resist deflection. The amount of material required to resist deflection adds significant cost and weight to the components of the split axle assembly making the axle weigh approximately 6,250 lbs.
U.S. Pat. No. 5,756,903 to Norby et al. discloses a track strength testing vehicle with a loaded gage axle. The loaded gage axle described in Norby et al. includes a split axle assembly where the shafts having a spindle are supported in a housing, and the wheels are supported by bearings inside the wheels which allow the wheels to rotate about the spindles. The reference further discloses that the wheels and the shafts are axially movable and are forced outward by hydraulic cylinders, the shafts being axially supported inside the housing by ultra-high molecular weight plastic slides. In use, however, the shafts of Norby et al. have also been found to bind within the housing thereby causing poor lateral tracking of the rails of the tracks, and also causing significant variations in the exerted lateral force which results in inaccurate gage measurements and measurement data.
Therefore, in view of the above, there exists an unfulfilled need for a split axle assembly for a gage restraint measurement system that avoids the disadvantages of the prior art. In particular, there still exists an unfulfilled need for a split axle assembly that significantly reduces the balancing moment required so that the associated load bearing components may be reduced in size, weight, and correspondingly, cost. In addition, there still exists an unfulfilled need for a split axle assembly that improves lateral tracking of the rails of the track and facilitates maintaining of consistent lateral force to provide accurate gage measurements and measurement data.
In view of the above, one advantage of the present invention is in providing a novel and improved gage restraint measurement system which allows evaluation of a railroad track to improve railroad safety and maintenance efficiency.
A further advantage of the present invention is in providing a novel and improved inner bearing split axle assembly that significantly reduces the balancing moment required so that the associated load bearing components may be reduced in size, weight, and cost.
Still another advantage of the present invention is in providing a split axle assembly that improves tracking of the rails and facilitates maintaining of consistent lateral force to provide accurate gage measurements and measurement data.
Yet another advantage of the present invention is in providing a split axle assembly that minimizes binding to facilitate axial movement of wheels.
These and other advantages are attained by a split axle assembly for obtaining gage measurements of a track in accordance with the present invention comprising a first wheel and a second wheel sized to roll along the track, the first wheel being laterally spaced from the second wheel, a first split axle secured to the first wheel so that the first split axle rotates with the first wheel, a second split axle secured to the second wheel so that the second split axle rotates with the second wheel, a first bearing for rotatably receiving the first split axle, and a second bearing for rotatably receiving the second split axle, where the first bearing and the second bearing are positioned inboard between the first wheel and the second wheel.
In accordance with one embodiment, the split axle assembly also includes brackets adapted to secure the split axle assembly to a truck or railcar body to allow lowering of the split axle assembly to an operative state, and to retract the split axle assembly to an inactive state. In this regard, one or more cylinders may be provided which is pivotally attached to the brackets that is operable to lower or retract the split axle assembly. The cylinders may be hydraulic cylinders and/or pneumatic cylinders.
In accordance with one implementation, the split axle assembly may be provided with a sliding barrel device adapted to allow the first wheel and the second wheel to axially move relative to one another. In this regard, the sliding barrel device includes an outer barrel, and at least one inner barrel axially movable in the outer barrel. Preferably, a first inner barrel and a second inner barrel is provided, the first inner barrel being connected to the first split axle and the second inner barrel being connected to the second split axle. In addition, the split axle assembly may further be provided with one or more cylinders for axially moving the first inner barrel and the second inner barrel relative to each other. In this regard, the cylinders may be hydraulic cylinders and/or pneumatic cylinders.
In accordance with another embodiment of the split axle assembly, the first bearing is received in a first bearing body and the second bearing is received in a second bearing body, the first bearing body and the second bearing body being axially movable relative to one another so that the first wheel and the second wheel are axially movable relative to one another. In this regard, a plurality of linear guides may be provided for allowing axial movement of the first bearing body and the second bearing body relative to one another. In one implementation, the plurality of linear guides include guide rails and guide rollers attached to the first bearing body and the second bearing body, the guide roller attached to the first bearing body movably engaging the guide rail attached to the second bearing body, and the guide roller attached to the second bearing body movably engaging the guide rail attached to the first bearing body.
In other embodiments, the guide rollers may include a wiper for removing debris from the guide rails as the guide rollers movably engage the guide rails. The guide rails may include a rail stop adapted to limit axial movement of the guide rollers. In addition, the guide rails may be offset from the first and second bearing bodies by spacer blocks.
In accordance with another embodiment of the present invention, one or more cylinders are provided which is adapted to axially move the first bearing body and the second bearing body relative to each other, the cylinders being attached to the first bearing body and the second bearing body. The cylinders may be implemented as hydraulic cylinders and/or pneumatic cylinders. In addition, a load cell may be provided which is adapted to measure lateral force exerted on the first wheel and/or the second wheel. In this regard, a thrust bearing may be disposed adjacent to the load cell and abutting the first split axle and/or the second split axle. Moreover, a stop may be provided to limit the amount of lateral force that is exerted on the load cell.
These and other advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when viewed in conjunction with the accompanying drawings.
The inner bearing split axle assembly 10 shown in
The split axle assembly 10 of the illustrated embodiment includes side frame extensions 16 connected to the truck 12 that allow mounting of vertical load applying hydraulic cylinders 18. The hydraulic cylinders 18 are connected at pivots 20 to the brackets 22 of the split axle assembly 10. Brackets 22 are pivotally mounted at pivotal mounts 24 to the truck 12 so that the hydraulic cylinders 18 can extend to cause the brackets 22 to pivot about the pivotal mount 24 thereby causing the wheels 26 of the inner bearing split axle assembly 10 to contact the track 11. Thus, the wheels 26 of the inner bearing split axle assembly 10 may be lowered into an operational state so that the wheels 26 assume the load of the front wheels 14 of the truck 12. Of course, whereas hydraulic cylinders 18 are illustrated in the embodiment of
The linearly aligned split axles 28 are secured to the wheels 26 and are enclosed in the two axle covering bearing bodies 30. The split axles 28 are axially movable relative to each other via the sliding barrel device 29 so that the wheels 26 are correspondingly axially movable as well. The bearing bodies 30 are connected together by push plates 33 and hydraulic cylinders 32 secured thereto that exert lateral force to the track 11 via the wheels 26 to allow obtaining of gage measurement data. In particular, the hydraulic cylinders 32 allow application of predetermined lateral force on the push plates 33 that is transferred to the rails of the track 11 so that lateral displacement of the track 11 may be measured. Based on the applied lateral force and the resulting lateral displacement of the track 11, the track stiffness and the conditions of the ties may be determined so that any necessary repair can be made. Moreover, as discussed below, the hydraulic cylinders 32 are also adapted to generate lateral forces against the bearing bodies 30 to substantially cancel the bending moments caused by downward pressure on the split axle assembly 10. Of course, in other embodiments, pneumatic cylinders may be used instead of, or in conjunction with, the hydraulic cylinders 32 shown in the illustrated implementation.
As previously noted, the significant difference in design provided by split axle assembly 10 in accordance with the present invention is that the bearing 31 is positioned inboard of the wheel 26. This placement of the bearing 31 results in a significant decrease in the requirements of the hydraulic cylinder, as well as the size and associated weight of the supporting push-plates 33. In addition, internal friction of the slide barrel 29 that resists axial movement of the wheels 26 and tend to cause binding of the split axles 28 is significantly reduced so that the dynamic response characteristics of the split axle assembly 10 is greatly improved as compared to conventional split axle assemblies which tend to bind and provide inaccurate gage measurement data.
By providing the bearings 31 of the split axle assembly 10 that are inboard of the wheels 26, the moment generated by the lateral force on the wheels 26 nearly cancels the moment caused by the vertical force on the bearings 31. In the illustrated embodiment of
In the illustrated embodiment of
As shown, the split axle assembly 40 includes wheels 42 that contact the track (not shown) when the split axle assembly 40 is lowered to an operative state. The split axle assembly 40 includes brackets 44 which allow mounting of the split axle assembly 40 to a truck or a railcar body. In addition, the brackets 44 also allow pivoting of the split axle assembly 40 between a lowered, operative position, and a retracted, inactive position. In this regard, hydraulic cylinders (not shown) that are pivotably attached to the brackets 44 may be provided to control the position of the split axle assembly 40 over the track. The mounting and general operation of the split axle assembly 40 is substantially similar to that described above relative to the previous embodiment of
The wheels 42 are secured to the split axles 46 so that the split axles 46 rotate with the wheels 42 when the split axle assembly 40 is in operation. The split axles 46 allow the wheels 42 to move axially relative to one another so that a lateral force may be exerted to the track, and gage measurements may be obtained to measure the lateral displacement of the track. As previously discussed, gage measurements obtained in such a manner provide an indication of the track stiffness and the conditions of the ties so that necessary repair can be readily determined. In this regard, the split axle assembly 40 includes linear guide assemblies 48, the details of which are discussed below, that minimize binding as the wheels 42 move axially relative to one another thereby allowing the wheels 42 to accurately follow the track.
In addition to the previously described wheels 42, split axles 46, and brackets 44, the split axle assembly 40 also includes various other axle components which are most clearly shown in
In a manner previously described relative to
Referring again to
The above alternated arrangement allows the guide rollers 66 to movably engage the guide rails 64 that are secured to the bearing body on the opposite side of the split axle assembly 40. This allows the first bearing body 60 and the second bearing body 60′ to move axially relative to one another. In particular, the guide roller 66 that is attached to the first bearing body 60 movably engages the guide rail 64 attached to the second bearing body 60′. In addition, the guide roller 66 that is attached to the second bearing body 60′ movably engages the guide rail 64 attached to the first bearing body 60. Thus, the above described arrangement of the linear guides 48 allows the first bearing body 60 and the second bearing body 60′ to axially move relative to one another so that the wheels 42 of the split axle assembly 40 are likewise movable relative to one another. Moreover, the axial movement is attained with minimal binding even when the vertical forces exerted on the first and second bearing bodies 60 and 60′ are high.
It should be noted that in the illustrated embodiment of
In operation, cylinders (not shown) such as hydraulic cylinders shown relative to the embodiment of
In addition, as the guide rollers 66 move within their respective guide rails 64, the wipers 67 ensure that the guide rails 64 are free of debris that may impede the movement of the guide rollers 66 along the guide rails 64. The rail stops 68 also prevent the guide rollers 66 from moving out of the guide rails 64 when the wheels 42 of the split axle assembly 40 are moved axially outward as far as possible.
It should now be evident how the present invention provides a unique split axle assembly for use in a gage measurement system which significantly reduces the balancing moment required by providing bearings which are positioned inboard of the wheels. This allows the associated load bearing components to be reduced in size, in weight, and in cost. In addition, it should also be evident how the present invention provides a split axle assembly that reduces the potential for binding, thus improving lateral tracking of the rails of the track and facilitating maintaining of consistent lateral force to provide accurate gage measurements and measurement data.
While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto. The present invention may be changed, modified and further applied by those skilled in the art. Therefore, this invention is not limited to the detail shown and described previously, but also includes all such changes and modifications.
This application claims priority to U.S. Provisional Application No. 60/364,604, filed Mar. 18, 2002.
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Number | Date | Country | |
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Number | Date | Country | |
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60364604 | Mar 2002 | US |