Patent Application
20180162421
The disclosure relates generally to a bolster for a railway car truck and more particularly to a bolster having increased strength in specified areas.
Railway cars typically consist of a rail car that rests upon a pair of truck assemblies. The truck assemblies include a pair of side frames and wheelsets connected together via a bolster and damping system. The car rests upon the bowl portion at the center of the bolster, which acts as a point of rotation for the truck system. The car body movements are reacted through the springs and friction wedge dampers, which connect the bolster and side frames. The side frames include pedestals that each define a jaw into which a wheel assembly of a wheel set is positioned using a roller bearing adapter.
The bolsters may be formed via various casting techniques. The most common technique for producing these components is through sand casting. High production manufacturing of bolsters in this casting process leaves the products susceptible to defects making the product vulnerable to high operating stresses and fatigue cycles.
The bolster may have life cycle requirements of fifty years. However, while in use, the bolster undergoes various loading situations particularly near the bowl portion and the ends where the bolster connects to the side frame. A means to reduce porosity defects will increase the strength of the bolster in these areas may extend the life cycle of the bolster,
Aspects of this disclosure relate to a bolster for a railway car truck, where the bolster may comprise a top wall, a bottom wall, a front wall, and a back wall; a first pair of shoe pockets at a first end of the bolster, where the first pair of shoe pockets are configured to be inserted into a bolster opening of a first side frame, and a second pair of shoe pockets at a second end of the bolster, where the second pair of shoe pockets are configured to be inserted into a bolster opening of a second side frame. A first center wall may be positioned toward the first end and engaged with the top wall and the bottom wall, and substantially centered between the front wall and the back wall, and a second center wall may be positioned toward the second end and engaged with the top wall and the bottom wall, and substantially centered between the front wall and the back wall. The bolster further comprises a pair of brake window openings defined in the front and back walls by brake window walls, a pair of lightener windows defined in the front and back walls by lightener window walls, and a bowl portion defined in the center of the bolster. Further, a thickness of a top portion of the first center wall may be greater than a thickness of a bottom portion of the first center wall proximate a first location between the bowl portion and the first end, and a thickness of a top portion of the second center wall may be greater than a thickness of a bottom portion of the second center wall proximate a second location between the bowl portion and the second end.
Additional aspects of this disclosure may relate to a bolster where the first location may be arranged between about 28.75 inches and 31.75 inches toward the first end from the center of the bolster; and the second location may be arranged between about 28.75 inches and 31.75 inches toward the second end from the center of the bolster. Alternatively, the center of the first riser may be arranged between about 28.25 inches and 31.25 inches toward the first end from the center of the bolster, and the center of the second riser may be arranged between about 28.25 inches and 31.25 inches toward the second end from the center of the bolster. Further, the thickness of a top portion of the first center wall proximate the first location may be between about 4.60 inches and 5.60 inches, the thickness of the bottom portion of the first center wall proximate the first location may be between about 3.51 inches and 4.51 inches, the thickness of a top portion of the second center wall proximate the second location may be between about 4.60 inches and 5.60 inches, and the thickness of the bottom portion of the second center wall proximate the second location may be between about 3.51 inches and 4.51 inches.
In addition, aspects of this disclosure may relate to a ratio of the thickness of a top portion of the first center wall proximate the first location to the thickness of the bottom portion of the first center wall proximate the first location may be between about 1.08:1 and 1.46:1, and the ratio of the thickness of a top portion of the second center wall proximate the second location to the thickness of the bottom portion of the second center wall proximate the second location may be between about 1.08:1 and 1.46:1. A thickness of a top portion of the first center wall proximate the first location may be between about 5.65 inches and 6.65 inches and the thickness of the bottom portion of the first center wall proximate the first location may be between about 3.40 inches and 4.40 inches, and a thickness of a top portion of the second center wall proximate the second location may be between about 5.65 inches and 6.65 inches and the thickness of the bottom portion of the second center wall proximate the second location may be between about 3.40 inches and 4.40 inches. The ratio of the thickness of a top portion of the first center wall proximate the first location to the thickness of the bottom portion of the first center wall proximate the first location may be between about 1.34:1 and 1.81:1. The ratio of the thickness of a top portion of the second center wall proximate the second location to the thickness of the bottom portion of the second center wall proximate the second location may be between about 1.34:1 and 1.81:1.
Still other aspects of this disclosure may relate to a bolster where a thickness of a top portion of the first center wall proximate the first location may be between about 4.45 inches and 5.45 inches and the thickness of the bottom portion of the first center wall proximate the first location may be between about 2.42 inches and 3.42 inches, and wherein a thickness of a top portion of the second center wall proximate the second location may be between about 4.45 inches and 5.45 inches and the thickness of the bottom portion of the second center wall proximate the second location may be between about 2.42 inches and 3.42 inches. The ratio of the thickness of a top portion of the first center wall proximate the first location to the thickness of the bottom portion of the first center wall proximate the first location may be between about 1.44:1 and 1.95:1. The ratio of the thickness of a top portion of the second center wall proximate the second location to the thickness of the bottom portion of the second center wall proximate the second location may be between about 1.44:1 and 1.95:1.
Yet other aspects of this disclosure may relate to a bolster where a thickness of an inner portion of the bottom wall proximate the first location may be greater than the thickness of an outer portion of the bottom wall proximate the first location, and wherein a thickness of an inner portion of the bottom wall proximate the second location may be greater than the thickness of an outer portion of the bottom wall proximate the second location. In addition, a thickness of an inner portion of the bottom wall proximate the first location may be between about 2.10 inches and 2.60 inches and the thickness of an outer portion of the bottom wall proximate the first location may be between about 0.85 inches and 1.35 inches, and a thickness of an inner portion of the bottom wall proximate the second location may be between about 2.10 inches and 2.60 inches and the thickness of an outer portion of the bottom wall proximate the first location may be between about 0.85 inches and 1.35 inches. The ratio of the thickness of an inner portion of the bottom wall proximate the first location to the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.82:1 and 2.46:1, and the ratio of the thickness of an inner portion of the bottom wall proximate the second location to the thickness of an outer portion of the bottom wall proximate the second location may be between about 1.82:1 and 2.46:1. A thickness of an inner portion of the bottom wall proximate the first location may be between about 1.44 inches and 1.94 inches and the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.18 inches and 1.68 inches; and a thickness of an inner portion of the bottom wall proximate the second location may be between about 1.44 inches and 1.94 inches and the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.18 inches and 1.68 inches. The ratio of the thickness of an inner portion of the bottom wall proximate the first location to the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.05:1 and 1.36:1, and the ratio of the thickness of an inner portion of the bottom wall proximate the second location to the thickness of an outer portion of the bottom wall proximate the second location may be between about 1.05:1 and 1.36:1.
Still further aspects of this disclosure may relate to a bolster where a thickness of an inner portion of the bottom wall proximate the first location may be between about 2.06 inches and 2.56 inches and the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.73 inches and 2.23 inches, and a thickness of an inner portion of the bottom wall proximate the second location may be between about 2.06 inches and 2.56 inches and the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.73 inches and 2.23 inches. Also, the ratio of the thickness of an inner portion of the bottom wall proximate the first location to the thickness of an outer portion of the bottom wall proximate the first location may be between about 1.05:1 and 1.35:1, and the ratio of the thickness of an inner portion of the bottom wall proximate the second location to the thickness of an outer portion of the bottom wall proximate the second location may be between about 1.05:1 and 1.35:1.
1111 Other aspects of this disclosure a bolster for a railway car truck may comprise a top wall, a bottom wall, a front wall, a back wall, a first pair of shoe pockets at a first end of the bolster, and a second pair of shoe pockets at a second end of the bolster. The bolster may also include a first center wall positioned toward the first end and engaged with the top wall and the bottom wall, and substantially centered between the front wall and the back wall, a second center wall positioned toward the second end and engaged with the top wall and the bottom wall, and substantially centered between the front wall and the back wall, a pair of brake window openings defined in the front and back walls by brake window walls, a pair of lightener windows defined in the front and back walls by lightener window walls, and a bowl portion defined in the center of the bolster. The thickness of a top portion of the first center wall may be greater than a thickness of a bottom portion of the first center wall, and a thickness of a top portion of the second center wall may be greater than a thickness of a bottom portion of the second center wall. Also, the thickness of the bottom wall adjacent the first center wall may be greater than the thickness of the bottom wall adjacent the front wall and the back wall; and a thickness of the bottom wall adjacent the second center wall may be greater than the thickness of the bottom wall adjacent the front wall and the back wall. The ratio of the thickness of the top portion of the first center wall to the thickness of the bottom portion of the first center wall may be between about 1.08:1 and 1.95:1, and the ratio of the thickness of the top portion of the second center wall to the thickness of the bottom portion of the second center wall is between about 1.08:1 and 1.95:1.
Other aspects of this disclosure may relate to a bolster where the ratio of the thickness of the bottom wall adjacent the first center wall to the thickness of the thickness of the bottom wall adjacent the front wall and the back wall may be between about 1.05:1 and 2.46:1, and the ratio of the thickness of the bottom wall adjacent the second center wall to the thickness of the thickness of the bottom wall adjacent the front wall and the back wall may be between about 1.05:1 and 2.46:1.
Lastly, aspects of this disclosure may relate to a bolster for a railway car truck may comprise a top wall, a bottom wall, a front wall, a back wall, a first pair of shoe pockets at a first end of the bolster, a second pair of shoe pockets at a second end of the bolster, a first center wall positioned toward the first end and engaged with the top wall and the bottom wall, and substantially centered between the front wall and the back wall; a second center wall positioned toward the second end and engaged with the top wall and the bottom wall, and substantially centered between the front wall and the back wall, and a bowl portion defined in the center of the bolster. The thickness of the bottom wall adjacent the first center wall may be greater than the thickness of the bottom wall adjacent the front wall and the back wall, and a thickness of the bottom wall adjacent the second center wall may be greater than the thickness of the bottom wall adjacent the front wall and the back wall.
The accompanying drawings are included to provide a further understanding of the claims, are incorporated in, and constitute a part of this specification. The detailed description and illustrated embodiments described serve to explain the principles defined by the claims.
In the following description of various example structures according to the invention, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various example devices, systems, and environments in which aspects of the invention may be practiced. It is to be understood that other specific arrangements of parts, example devices, systems, and environments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention.
Also, while the terms “top,” “bottom,” “front,” “back,” “side,” “rear,” and the like may be used in this specification to describe various example features and elements of the invention, these terms are used herein as a matter of convenience, e.g., based on the example orientations shown in the figures or the orientation during typical use. Nothing in this specification should be construed as requiring a specific three dimensional orientation of structures in order to fall within the scope of this invention. The reader is advised that the attached drawings are not necessarily drawn to scale.
The following terms are used in this specification, and unless otherwise noted or clear from the context, these terms have the meanings provided below.
“Plurality,” as used herein, indicates any number greater than one, either disjunctively or conjunctively, as necessary, up to an infinite number.
“Proximate” as used herein, means that a first feature is located within a range +/−1 inch of a second feature.
“Substantially constant” as used herein, when referring to a dimension means that a value is approximately the same and varies no more than +/−5%.
As described above, the main body section 115 of the bolster 100 may define a pair of brake window openings 125 configured to enable the use of brake rigging. These windows may also act as core prints to support the core in the mold when manufacturing the bolster 100.
At block 200, a mold for manufacturing the bolster 100 may be formed. The mold may include a first or drag portion and a second or cope portion. The first or drag portion of the mold may include a cavity formed in the shape of the first or drag side of the bolster 100. The second or cope portion may include a cavity formed in the shape of the second or cope side of the bolster 100.
The respective portions may be formed by first providing first and second patterns that define an outside perimeter of the first or drag side and second or cope side, respectively, of the bolster 100. The patterns may partially define one or more feed paths for distribution of molten material within the mold.
The mold may also include a plurality of risers that are integrally formed with the bolster 100 when the molten material fills the mold. The risers may be hollow cylindrical structures into which molten material fills during casting operations. The risers may be positioned at areas of the mold that correspond to thicker areas of the side frame that cool more slowly than other areas of the bolster. The risers function as reservoirs of molten material that compensate for contraction that occurs in the molten material as the molten material cools, and thus may prevent shrinkage, or hot tearing of the cast bolster in the thicker areas that might otherwise occur. The risers may be formed in the pattern or may be placed in the pattern before molding. Additionally, the risers may have any shape such as a tubular shape, elliptically shaped, side feeding, or conical shaped. Risers may be created from a material which insulates heat, or exothermic material which generates heat, or formed in the same material as the mold. As another option, the risers may be vented to the atmosphere or blind where they are not vented to the atmosphere. Exemplary risers 160, 162 are illustrated on bolster 100 in
At block 205, a bolster core 300 that defines the interior region of the bolster 100, as shown in
The bolster core 300 may be formed by any known method. In one example, the bolster core 300 may be formed by a corebox that includes a cope and drag portions that define the bolster core 300. Molding sand may be inserted into the core box and cured. The core box may then be removed to reveal the cured core. The bolster core 300 may be formed individually, integrally, or in some combination thereof. The bolster core 300 may be formed as two portions. For example, bolster core 300 may include a cope portion and a drag portion formed separately in separate core boxes (i.e., a cope mold and drag mold). After curing, the formed portions may be attached. For example, the cope and drag portions of a given core may be glued together to form the bolster core 300.
At block 210, the bolster core 300 may be inserted in the mold and the bolster 100 is cast. For example, the bolster core 300 may be inserted into the first or drag portion of the mold. The second or cope portion may be placed over the first portion and secured to the first portion via clamps, straps, and the like. In this regard, locating features may be formed in the first portion and the second portion to ensure precise alignment of the respective portions.
At block 215, after securing the respective portions, molten material, such as molten steel, may be poured into the mold. The molten material may flow through the gating and throughout the mold in the space between the mold and the bolster core 300. The bolster 100 may be formed from a carbon steel alloy that meets or exceeds the American Association of Railroads (AAR) Manual of Standards and Recommended Practices (MSRP), Specification M-201 (Dated Jan. 21, 2016), which is incorporated by reference, Grade B+ or alternatively meeting a Grade B, Grade C or similar steel alloy. Optionally, this same specification would apply if the bolster 100 is cast from a ductile iron.
The risers 160, 162 may be optimized in size to provide an optimal amount of feeding material during solidification of the molten material to prevent the formation of shrinkage voids and hot tears in critical areas of the bolster 100. Although, the risers may have any shape, the center wall risers 160 may be exothermic blind risers having a generally truncated conical shape, while the bowl risers 162 may have a generally cylindrical shape. The risers 160, 162 combined with the localized geometry of the bolster 100 around the risers 160, 162 may encourage directional solidification within the bolster 100 where the molten material begins to solidify in the regions of lowest temperature which may be furthest away from the feed and riser locations and then solidification of the molten material moves in a direction toward the regions of highest temperature which may be nearest the feed and riser locations. As the molten material solidifies in a dendritic manner toward the riser locations, the molten material that solidifies last may contain regions of increased shrinkage and porosity compared to the regions that solidified first. Thus, the risers 160, 162 combined with the localized geometry of the bolster 100 around the risers 160, 162 may create localized regions of increased solidity, reduced porosity, and improved strength within the regions of the casting where the molten material solidified first compared to the regions where the molten material solidified last nearest or within the risers 160, 162. Accordingly, the bolster 100 may comprise localized regions of greater solidity, reduced porosity, and increased strength shown as the darkened regions “S,” which are fed by the risers 160, 162 shown in
The bolster 100 may be x-rayed, ultrasonically tested, CT scanned, or examined using other non-destructive test methods to quantify the size of defects present in the casting. X-rays may be taken in accordance with ASTM E94-04(2010) “Standard Guide for Radiographic Examination,” which is incorporated by reference, or other methods of examination. The radiographic films may be graded and examined in accordance with ASTM E446-15 “Standard Reference Radiographs for Steel Castings Up to 2 in. (50.8 mm) in Thickness,” or ASTM E186-15 “Standard Reference Radiographs for Heavy-Walled (2 to 412 in. (50.8 to 114 mm)) Steel Castings,” which are both incorporated by reference. Using the dimensions contained herein in concert with the risers to feed the sections consistently results in maximum shrinkage defect sizes of in accordance with a Level 2. In most cases, shrinkage defects are less than Level 1 when compared to AAR MSRP M-210 (Dated 2013) criteria, which is incorporated by reference, the solidity standard may meet or exceed Class 1.
At block 220, the bolster 100 is removed from the mold, and the bolster 100 is finished. For example, any solidified material in the gating or risers may be removed. In some implementations, the mold may be configured so that a wedge or recess is formed in riser material just beyond an exterior surface of the bolster 100. The wedge or recess may enable hammering the riser material off, rather than more time consuming flame cutting utilized in known casting operations.
Further, the wall 170 of the bowl portion 107 may have a variable thickness. For example, the thickness of wall 170 of the bowl portion 107 proximate or adjacent the pair of bowl risers 162 and near the outer wall 172 of the bowl portion 107 may have a thickness, dimension “G,” while the thickness of wall 170 near the center of the bowl portion may have a thickness, dimension “H,” where the thickness, dimension “G,” is greater than the thickness, dimension “H.” These areas of variable thickness may be proximate or adjacent the locations of the bowl riser 162. Optionally, the bowl portion 107 may comprise two pair of bowl risers 162.
The prior art bolster 400 illustrated in
The top portion 136 of the center wall 130 may have a lateral thickness, dimension “A,” defined as the distance from the intersection of the front surface 152 of the top portion 136 of the center wall 130 with the interior surface of the upper wall 116 and the intersection of the back surface 154 of the top portion 136 of the center wall 130 with the interior surface of the upper wall 116. Similarly, the bottom portion 138 may have a lateral thickness, dimension “B,” defined as the distance from the intersection of the front surface 152 of the top portion 136 of the center wall 130 with the interior surface of the upper wall 116 and the intersection of the back surface 154 of the top portion 136 of the center wall 130 with the interior surface of the upper wall 116. The lateral thickness, dimension “A,” of the top portion 136 of the center wall 130 may be greater than the lateral thickness, dimension “B,” of the bottom portion 138 of the center wall 130. The tapered wall thickness provides additional strength along the top portion 136 of the center wall 130. Additionally, the lateral thickness may be expressed as a ratio of the top portion thickness, dimension “A,” to the bottom portion thickness, dimension “B.” The ratio of “A/B:1” may be within a range of 1.08:1 and 1.95:1 or alternatively, within the ranges disclosed below in Tables 1-3.
In addition, proximate or adjacent the location defined by the dimension “I,” the bottom wall 117 may have a wall thickness that is variable. The thickness, dimension “C,” may be defined as the thickness of the inner portion of the bottom wall 117, which is the distance from the interior surface of the bottom wall 117 near the intersection of the center wall 130 to the exterior surface of the bottom wall 117. The thickness, dimension “D,” may be defined as the thickness of the outer portion of the bottom wall 117, which is a distance from the interior surface of the bottom wall 117 near the intersection of the either the front wall 118 or the back wall 119 to the exterior surface of the bottom wall 117. The bottom wall thickness may taper such that the inner portion thickness, dimension “C,” near the intersection with the center wall 130 is greater than the outer portion thickness, dimension “D,” near the front wall 118 or the back wall 119. Additionally, bottom wall thickness may be expressed as a ratio of the inner portion thickness, dimension “C,” to the outer portion thickness, dimension “D.” The ratio of “C/D:1” may be within a range of 1.05:1 and 2.46:1 or within the ranges disclosed below in Tables 1-3.
When compared to a lateral cross-section of a prior art bolster 400 shown in
Since the railway car trucks may have different weight capacities, the bolster 100 may be designed with different dimensions to be specifically sized for a variety of the truck capacities, such as a 70 ton capacity truck, a 110 ton capacity truck, and a 125 ton capacity truck. Example ranges for the dimensions described above for the bolster 100 in accordance with this disclosure are set forth in Table 1 below:
Table 1 above describes some general ranges of dimensions that may be used and characteristics that may be exhibited by some specific examples of the bolster 100 and in accordance with this disclosure. A bolster 100 need not have dimensions and characteristics that fall within all of the ranges identified for each capacity type in Table 1 to fall within the scope of this disclosure.
Table 2 below provides additional, more particular ranges of dimensions, at least some of which may be exhibited by at least some example bolsters 100 in accordance with this disclosure:
The various ranges provided in Table 2 are simply examples. A bolster 100 need not have dimensions or characteristics that satisfy all of these identified ranges to fall within the scope of this disclosure.
Table 3 provides even more targeted dimensions and characteristics of a bolster 100 in accordance with a specific example of this disclosure. Of course, a bolster 100 need not have these specific dimensions and/or characteristics to fall within the scope of this disclosure.
While specific dimensions, characteristics, and/or ranges of dimensions and characteristics are set forth in the various tables above, those skilled in the art will recognize that these dimensions and ranges are examples that may be used in at least some examples of this disclosure. Many variations in the ranges and the specific dimensions and characteristics may be used without departing from this disclosure.
While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the claims. The various dimensions described above are merely exemplary and may be changed as necessary. Accordingly, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the claims. Therefore, the embodiments described are only provided to aid in understanding the claims and do not limit the scope of the claims.
