Claims
- 1. A lug for compression engagement with an inboard bolster edge region bordering a window opening in an inclined intermediate bottom wall portion of a bolster, said lug comprising an elongated main body with at least one passage having an axis extending therethrough, an outboard surface perpendicular to the axis of said passage at one end thereof for receiving compression forces and transmitting the same in distributed relation therethrough, and an inboard face contour providing a convexly contoured surface portion above the other end of said passage perpendicular to said axis to distribute said compression forces.
- 2. A lug as defined in claim 1 wherein said main body has wings projecting laterally from upper regions thereof, perpendicular to said axis of said passage.
- 3. A lug as defined in claim 1 wherein said main body has a pair of parallel side-by-side passages with substantially parallel axes.
RELATED APPLICATION
This application is filed as a division of pending application Ser. No. 472,428, filed May 22, 1974, now U.S. Pat. No. 3,924,542, issued Dec. 9, 1975 and entitled Railway Bolster Re-enforcement System.
This invention relates to re-enforcement of truck bolsters against bending stresses, particularly those bending stresses resulting from conventional center plate loading under actual operating conditions.
The invention has application to improvements in the arrangement and fabrication of new bolsters and also has application to numerous types of existing bolsters. Generally speaking, the older the bolster, the more need exists for re-enforcement of the center plate area against bending stresses associated with normal operating conditions. Excessive stresses cause cracking and ultimately lead to actual breaking of the bolster.
In the case of very old bolsters, for example 20 or 25 years or more, excessive bending stresses have resulted in cracking at the lower center plate region more than at any other region. In the case of more recent bolsters, excessive bending stresses have produced cracks at the top region of the center plate more than at the bottom region. Possibly design changes incorporated in the more recent bolsters were intended to correct the crack problem at the bottom but such design changes have not removed the source of the problem of cracking.
The bolster cracking and breaking problem has accelerated in recent years and is undoubtedly aggrevated by the fact that the operating speeds have been increased, the road beds have deteriorated, and the cars frequently carry greater loads than were anticipated when the bolsters were originally built.
The seriousness of the problem of bolster cracking cannot be overstated. There are times when a bolster upon developing a crack may be continued in service either because the existence of the crack is unknown or because no replacement is available. However, in nearly every case when a crack in a bolster breaks completely through, the broken bolster parts will hang down and catch against the ties and probably cause a derailment. The seriousness of a derailment depends upon the conditions at the time when the bolster breaks but the bolster is more likely to break under high-speed, heavy load conditions than at other times.
In summary, it now appears that the most important need for re-enforcement of bolsters exists in the case of the existing bolsters, not only because present operating conditions were not foreseen at the time such bolsters were designed, but also because of the difficulty and cost of replacing the entire group of existing bolsters.
There is, in addition, an important need for identifying the real cause of bolster failures so that new bolsters may be equipped with proper facilities for minimizing the cost for providing necessary re-enforcement against excessive bending stresses.
The present invention provides for pre-stressing the bolster center plate region in opposition to the stress pattern applied to the center region of the bolster by normal loading.
Upon application of the car load through the center plate, the bolster is flexed in the fashion of a simple beam supported at its ends and subjected to a central load so that the upper center plate region is subjected to compression and the lower center plate region is subjected to tension.
Thus, the pre-stressing provided in accordance with this invention subjects the bottom center plate region of the bolster to pre-compression stress in substantial opposition to the tension which this region is subjected to under normal loading.
In the presently preferred practice of the present invention, a re-enforcement system is applied to the bottom central section of the bolster in a configuration tending to bend or bow the bolster upwardly to oppose downward bending caused by normal loading, thereby relieving the central region of substantial stresses until the normal loading greatly exceeds the pre-stressing introduced by the re-enforcement system. The re-enforcement system of this invention comprises elongated, high-strength tension means extending crosswise of the bottom center section of the bolster and anchored in lug means engaging the inclined bottom wall sections in flanking relation to the center section and means for securing the tension means under predetermined tension between the lug means for pre-compressing the bottom center section of the bolster. Where upward bowing is achieved, a vertical force is applied through the internal bolster ribs to the top center plate section of the bolster to reduce the likelihood of cracking at the top.
In the preferred embodiment, the re-enforcement system utilizes a high-strength tension means having bent ends that are adaptable to a range of inclined bottom wall angles and that enable an upward bowing pre-stressed effect while requiring a minimum of underside clearance.
In the application of the invention to the various types of existing bolsters, a number of special purpose embodiments are provided including one embodiment for minimizing underside clearance such as is required in sprung trucks and numerous embodiments utilizing various numbers and shapes for the tension means to adapt to the larger bolster sizes and to correct for the special failure modes known to exist with certain bolster designs.
The invention is also concerned with an improved new bolster design wherein lugs are formed integrally with the bolster specifically to accommodate a re-enforcement system either as part of the original installation or after the bolster has been in use for a substantial time. In the case of new bolsters, in addition to the integral lugs, the invention is concerned with the arrangement of the internal center plate ribs of the bolster for more effectively developing the upward bowing action as part of the pre-stressing pattern produced by the re-enforcement system.
For any of the embodiments described above, the re-enforcement system has the important advantage that if a crack does exist, the growth of the crack will be retarded. In addition, even if the crack were to break completely through, the bolster parts can be retained by the re-enforcement system to prevent a serious derailment.
Other features and advantages of the invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which show structure embodying preferred features of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles.
US Referenced Citations (7)
Divisions (1)
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Number |
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472428 |
May 1974 |
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Patent Grant
4135833
