HK1185040A - Side frame and bolster for a railway truck and method for manufacturing same - Google Patents

Description

Side frame and bolster for a railway car truck and method of making same

Background

Railcars are typically comprised of railcars supported on a pair of truck assemblies. The truck assembly includes a pair of side frames and wheelsets connected together by a bolster and damping system. The car is supported on a central bowl of the bolster which serves as the point of rotation for the truck system. The bolster and side frames are connected by springs and friction wedge dampers that resist movement of the car body. The side frames include pedestal joists that each define a cutout into which a wheel assembly of the wheel set is placed using a roller bearing adapter.

The side frames and bolster may be formed by various casting techniques. The most common technique for producing these components is by sand casting. Sand casting provides a low cost, high throughput method for forming composite hollow shapes such as side frames and bolster. In a typical sand casting operation, (1) sand is poured around a pattern to form a mold, typically including a gating system; (2) moving the mold away from the mold; (3) placing the core in a closed mold; (4) filling the mould with hot liquid metal by pouring; (5) cooling the metal in the mold; (6) the solidified metal, known as the rough cast, is removed by stripping; and (7) grinding and cleaning the casting, which may include the use of a grinder, welder, heat treatment, and machining.

In sand casting operations, molds are made using sand as a base material, which is mixed with a binder to maintain shape. The mold is made in two halves-cope (top) and drag (bottom), which are separated along the parting line. Sand is poured around the mold and maintains the shape of the mold after it is removed from the mold. The mold is machined at a draft angle of 3 degrees or more to ensure release of the mold from the mold during withdrawal. In some sand casting operations, sand is supported during the molding process using a sand box during the fill process. The core is inserted into the mold and the cope is placed over the drag to close the mold.

When casting composite or hollow parts, the core is used to define a hollow interior, or to define a complex part that cannot otherwise be made by the form. These cores are typically made by casting sand and binder into a box shaped to create the features created by the core. These core boxes can be hand-packed or made using a core blower. The core is removed from the core box and placed in a mold. Core print indexing is used to place the core into the mold and prevent movement of the core as the metal is poured. Additionally, the chaplets may serve to support or inhibit movement of the core and fuse into the base metal during solidification.

The mold typically includes a gating system that provides access to the molten metal and controls the flow of metal into the mold cavity. This pouring includes a sprue, which controls the flow rate of the metal and is connected to the runner. The runner is the passage for metal flowing through the gate into the mold cavity. The gate controls the flow rate into the mold cavity and prevents liquid turbulence.

After the metal is poured into the mold, the casting cools and shrinks as the casting approaches a solid state. As the metal shrinks, it is necessary to continue to inject additional liquid metal into the shrinking region, otherwise voids will appear in the final part. In areas of high shrinkage, risers are placed in the mold to provide secondary reservoirs to be filled during the filling process. These risers are the last areas to solidify, so that the contents remain in the liquid state for a longer time than the cavity of the part being cast. As the contents of the mold cavity cool, the risers replenish the areas of shrinkage, ensuring the production of a solid final casting. The risers, which are open at the top of the cope mold, can also serve as outlets for gas escape during filling and cooling.

In various casting techniques, different sand mold binders are used to hold the sand in the shape of the mold. These binders have a large impact on the final product because they control dimensional stability, surface finish, and casting details that each particular process can accomplish. Two of the most typical sand casting methods include: (1) green sand, which consists of silica sand, organic binder and water; and (2) a chemical or resin binder material consisting of silica sand and a fast curing chemical binder such as phenolic urethane. Traditionally, sideframes and bolster have been manufactured using the green sand process due to the lower cost associated with molding materials. Although this method has been effective in producing these components for many years, the process has drawbacks.

There are problems associated with the sideframes and bolster produced by the green sand operation described above. First, the relatively large draft angle required for the die results in a corresponding draft angle for the cast product. In areas requiring flat sections, such as pedestal areas on the side frames and friction brake shoe pockets (friction brake shoe pockets) on the bolster, cores must be used to make these parts. These cores have a tendency to shift and float during casting. Such movement can lead to inconsistent final product dimensions, increased grinding times, or, if the specified dimensions are exceeded, component scrap. Other problems with these casting operations can be seen upon reading the description below.

Disclosure of Invention

It is an object of the present invention to provide a method of manufacturing a side frame mold for casting a side frame of a railway car truck. The sideframes include forward and rearward pedestal jaws for mounting wheel assemblies of the wheel sets. The method includes forming a drag and cope portion of a mold by casting material to define outer surfaces of the drag and cope portions of the side frame, respectively. The mold includes portions for casting a pedestal area of a side frame, the pedestal area including a pedestal roof, a contact surface, an outer vertical clamp, and an inner vertical clamp. The drag and cope portions are then cured.

It is another object of the present invention to provide a method of manufacturing a core for use with a mold for casting a side frame of a railway car truck, wherein the side frame includes forward and rearward pedestal jaws that mount wheel assemblies of wheel sets, and wherein each pedestal portion extends from a respective end of the side frame to a bolster opening of the side frame. The method includes forming separate drag and cope portions of at least one pedestal core. The drag and cope portions of the pedestal core define an interior region of at least one pedestal of the side frame. The method also includes connecting together the drag and cope portions of the pedestal core to form a pedestal core assembly that is inserted into the mold.

It is a further object of the present invention to provide a method of manufacturing a side frame of a railway car truck wherein the side frame includes forward and rearward pedestal jaws that mount wheel assemblies of wheel sets. The method includes providing a mold defining outer surfaces of a drag and a cope portion of the mold and at least one pedestal jaw, respectively. The molten steel is then poured into a mold and allowed to solidify. The cast sideframe is removed from the mold and consists of the final part, risers and gates. Excess material is ground off the cast sideframe to form the finished sideframe. The amount of excess material removed from the casting, in the form of core seams, parting line flash, risers, configuration dies, vents, is less than 10% of the total weight of the steel initially poured into the side frame mold.

It is a further object of the present invention to provide a side frame of a railway car truck, the side frame including a pair of side frame columns defining a bolster opening and a pair of pedestals extending from the respective side frame columns. Each pedestal jaw defines a cutout configured to mount a wheel assembly of a wheel set. The side frames include first rib plates disposed on inner sides of the side frame columns opposite to bolster sides of the side frame columns. Each side frame column defines an opening therein. The openings extend from the bolster side to the inner side of the corresponding side frame column. The opening extends through the first web and is sized to receive a bolt that secures the wear plate to the bolster side of the side frame column.

It is a further object of the present invention to provide a method of manufacturing a bolster of a railway car truck. The method includes providing a drag portion and a cope portion of a mold. In the body portion of the mold, the parting line separating the drag portion from the cope portion is substantially centered between the portions of the mold defining the brake window openings of the sides of the bolster. The method further comprises the following steps: inserting one or more cores in the mold, and casting the bolster.

It is a further object of the present invention to provide a core assembly for use in manufacturing a bolster of a railway car truck. The core assembly includes a body core that defines substantially the entire interior region of the bolster extending from its center to an inward gib at an outboard end portion of the bolster, and partially defines an interior end portion of the bolster extending from the inward gib to an outboard end of the bolster. The core assembly also includes an end core defining an interior region of an end portion of the bolster not defined by the body core.

It is a further object of the present invention to provide a method of manufacturing a bolster mold for casting a bolster of a railway car truck. The method includes forming a drag and a cope of a mold from a casting material to define outer surfaces of the drag and the cope of the bolster, respectively. The parting line separating the drag portion from the cope portion is substantially centered between portions of the mold defining the brake window openings of the sides of the bolster. The method also includes curing the drag portion and the cope portion.

It is a further object of the present invention to provide a core assembly for use in manufacturing a bolster of a railway car truck. The core assembly includes a body core that defines substantially the entire interior region of the bolster extending from the center of the bolster to an inward gib at an outboard end portion of the bolster, and partially defines an interior end portion of the bolster extending from the inward gib to a respective end of the bolster. The core assembly also includes an end core defining an interior region of the bolster end portion that is not defined by the body core.

It is a further object of the present invention to provide a method of manufacturing a bolster mold for casting a bolster of a railway car truck. The method includes forming a drag and a cope of a mold from a casting material to define outer surfaces of the drag and the cope of the bolster, respectively. The parting line separating the drag portion from the cope portion is substantially centered between the portions of the mold defining the brake window openings of the sides of the bolster. The method also includes curing the drag and cope portions.

Yet another object of the present invention is a method of manufacturing a bolster of a railway car truck. The method includes providing a mold including a drag portion and a cope portion. The parting line separating the drag portion from the cope portion is substantially centered between portions of the mold defining the brake window openings of the sides of the bolster. The method further comprises pouring the molten steel into a mould and allowing it to solidify. The cast bolster, which consists of the final bolster components, risers, and gating system, is then removed from the mold. Excess material is ground away from the cast bolster to form a finished bolster. The amount of excess material removed from the casting, in the form of core seams, risers, and gates, is less than 15% of the total weight of the steel initially poured into the bolster mold.

It is a further object of the present invention to provide a method for manufacturing a bolster of a railway car truck that includes providing a drag portion and a cope portion of a mold. In the body portion of the mold, a parting line separating the drag portion from the cope portion is substantially centered between portions of the mold defining the brake window openings of the sides of the bolster. The bolster is cast by inserting one or more cores into the mold and pouring molten material into the mold.

It is a further object of the present invention to provide a method of manufacturing a side frame of a rail car truck wherein the side frame defines an aperture for placement of a bolster. The bore is defined by a pair of opposing posts, a spring seat, and a compression member. Side frame molds for forming the mold drag and cope are provided along with one or more cores that define the interior region of the cast side frame. Here, the side frame pattern and one or more cores are configured to limit the spacing between facing columns to within a tolerance of about ±.038 inches.

It is a further object of the present invention to provide a method of manufacturing a side frame of a railway car, the method comprising: providing a side frame pattern for forming a lower pattern portion and an upper pattern portion of a mold; and providing one or more cores defining an interior region of the cast side frame, wherein at least some of the one or more cores define one or more core prints for placement of the one or more cores at the drag of the mold. The distance between the outside surface of the one or more core prints and the surface of the drag of the mold nearest the outside surface of the one or more core prints is less than or equal to about.030 inches.

It is a further object of the present invention to provide a method of manufacturing a bolster of a rail car that includes a pair of shoe pockets at each end configured to be inserted into a bolster opening of each side frame. The method comprises the following steps: providing a bolster pattern for forming a lower pattern portion and an upper pattern portion of a mold; and providing one or more cores defining an interior region of the cast bolster. The bolster pattern and the one or more cores are configured to limit an angle of a shoe pocket to within a tolerance of about ±.5 °.

It is a further object of the present invention to provide a method of manufacturing a bolster of a rail car that includes a pair of shoe pockets at each end configured to be inserted into bolster openings of side frames. The method comprises the following steps: providing a bolster pattern for forming a lower pattern portion and an upper pattern portion of a mold; and providing one or more cores defining an interior region of the cast bolster. The bolster pattern and the one or more cores are configured to limit a width between the pair of shoe pockets to within a tolerance of about ±.063 inches.

It is a further object of the present invention to provide a method of manufacturing a bolster of a rail car. The method comprises the following steps: providing a bolster pattern for forming a lower pattern portion and an upper pattern portion of a mold; and providing one or more cores defining an interior region of the cast bolster. At least some of the one or more cores define one or more core prints for placement of the one or more cores within a drag of the mold. The distance between the outside surface of the one or more core prints and the surface of the drag of the mold nearest the outside surface of the one or more core prints is less than or equal to about.030 inches.

It is a further object of the present invention to provide a mold for casting a side frame of a railway car truck. The sideframes include forward and rearward pedestal jaws for mounting wheel assemblies of the wheel sets. The mold comprises: cope and drag portions formed of molding material for defining outer surfaces of the drag and cope portions of the side frame, respectively. The mold includes a portion for casting at least one pedestal jaw of the side frame.

It is a further object of the present invention to provide a bolster of a railway car truck formed from a mold. The bolster includes a lower profile portion and an upper profile portion. The parting line defining the drag and cope portions is configured to: the parting line is substantially centered between the brake window openings in the sides of the bolster at the body portion of the bolster.

It is a further object of the present invention to provide a mold for manufacturing a bolster of a railway car truck. The mold includes a drag portion and a cope portion. The parting line separating the drag portion from the cope portion is configured such that it is substantially centered between portions of the mold that define the brake window openings of the sides of the bolster.

It is a further object of the present invention to provide a bolster of a railway car truck formed from a mold. The bolster includes a lower profile portion and an upper profile portion. The parting line defining the drag portion and the cope portion is configured to be substantially defined by the drag portion at an outer end portion.

It is a further object of the present invention to provide a mold for manufacturing a bolster of a railway car truck. The mold includes a drag portion and a cope portion. The respective mating surfaces of the drag and cope portions have non-planar complementary shapes.

Other features and advantages will be apparent to those skilled in the art upon review of the following drawings and detailed description. It is intended that all such additional features and advantages be included within this description, be within the scope of the claims, and be protected by the accompanying claims.

Drawings

The accompanying drawings are included to provide a further understanding of the claims and are incorporated in and constitute a part of this specification. The detailed description and the illustrated embodiments are described to explain the principles defined by the claims.

FIGS. 1A and 1B illustrate perspective and side views, respectively, of an example side frame of a railway car truck;

FIGS. 2A and 2B illustrate the interior surfaces of an exemplary side frame column including a pair of column reinforcement members;

FIG. 3 illustrates an example pedestal jaw of a cast side frame;

FIG. 4 illustrates an example operation for manufacturing a sideframe;

FIG. 5A illustrates an example drag and cope portion of a mold for forming a side frame;

FIG. 5B illustrates an exemplary riser and gating system for the side frame;

FIG. 6 illustrates an example mandrel that may be used with a mold;

FIG. 7 illustrates an example bolster that may be used in conjunction with the side frames described above;

FIG. 8 illustrates a riser and gating system for forming a bolster;

FIG. 9A illustrates an example mold for forming a bolster;

FIG. 9B illustrates an example bolster formed in the mold shown in FIG. 9A;

fig. 9C illustrates an example cross section of a bolster mold and a core within the bolster mold;

FIG. 10A illustrates a cross-section of the bolster in the area of the brake window;

FIG. 10B illustrates a cross-section of a friction shoe pocket of the bolster; and

FIG. 11 illustrates a core assembly that may be used with a mold for forming a bolster.

Detailed Description

FIG. 1A illustrates a perspective view of a side frame 100 of a railway car truck. The rail cars may correspond to trucks, such as those used in the united states to carry a total weight of over 220,000lbs (pounds) of cargo. Sideframe 100 includes a bolster opening 110 and a pair of pedestals 105.

The bolster opening 110 is defined by a pair of side frame columns 120, a compression member 125, and a spring seat 127. The bolster opening 110 is sized to receive an outboard end portion 705 (fig. 7) of the bolster 700 (fig. 7). A set of springs (not shown) are disposed between the outboard end portion 705 of the bolster 700 and the spring seat 127 and resiliently couple the bolster 700 to the side frame 100.

A pair of wear plates 135 are placed between brake shoe openings 710 of outboard end portions 705 of bolster 700 and side frame columns 120. For illustration purposes, a single example wear plate 135 is shown in fig. 1A in a separated mode. Wear plate 135 and friction wedges (not shown) act as shock absorbers to prevent continued vibration between side frame 100 and bolster 700. Each wear plate 135 may be made of metal. Wear plate 135 is configured to connect with the side of side frame column 120 facing bolster 700 (i.e., the bolster side of side frame column 120). The wear plate 135 may be attached by fasteners (e.g., bolts or bolt-and-nut assemblies) that allow the wear plate 135 to be removed.

In operation, movement of the bolster 700 within the bolster opening 110 creates pressure against the wear plate 135. In prior art sideframes, sideframe column 120 tends to elastically deform under these wedge pressures. As a result, the fasteners securing the wear plate 135 to the side frame column 120 become loose. To overcome these problems, one embodiment of the side frame 100 of the present application has a column reinforcement 205 (FIG. 2) in the form of a rib 205 disposed on the side frame column 120.

Fig. 2A and 2B illustrate the inner surface 130 of an exemplary side frame column 120 that includes a pair of column reinforcement members 205. Column reinforcement 205 is placed on the inner surface of side frame column 120 and extends between the sides of side frame 100. For example, column reinforcement 205 extends between drag section 102 and cope section 103 of side frame 100. The column reinforcement 205 may be centered about an opening 210 formed in the side frame column 120, the opening 210 being for the fastener described above. In contrast to the thickness of 625 ", which is used for conventional side frame columns without column reinforcement, the thickness T203 of side frame column 120 in the region of column reinforcement 205 may be about 1.125". Column reinforcement members 205 provide enhanced support to the side frame columns 120 to prevent deformation of the side frame columns 120 under such pressures. Furthermore, the column reinforcement 205 increases the length over which the fastener is tightened. In other words, the portion of the fastener that is tightened is longer than the existing side frame. This allows the fastener to have longer stretch during tightening, resulting in greater clamping force, and increased fatigue life of the bolted joint.

Returning to FIG. 1A, each pedestal 105 defines a pedestal jaw 140 into which the wheel assembly of the truck wheel set is mounted. Specifically, each pedestal jaw 140 includes a pedestal roof 116, an outboard vertical clamp 117, an inboard vertical clamp 18, and inboard and outboard contact surfaces 115 (referred to as thrust lugs) that are in direct contact with complementary surfaces of the adapter and wheel assembly. The contact surface 115 determines the alignment of the wheel assembly within the pedestal jaw 140. To provide accurate alignment, the contact surface 115 is cleaned in a grinding process to eliminate imperfections left in the casting process.

FIG. 3 illustrates an exemplary pedestal jaw 140 of side frame 100 after the side frame is removed from mold 500 (FIG. 5A) but before grinding. In this case, the contact surface 115 is not flat. Instead, contact surface 115 tapers to a draft angle D305 that corresponds to the draft angle of the mold used to fabricate side frame 100, as described below. The draft angle D305 may be about 1 ° or less, which is less than the draft angle of a prior cast side frame, which may be 3 ° or more. In one embodiment, the draft angle is about 3/4 °. Other portions may also have a smaller draft angle. For example, the pedestal roof 116 may have a draft angle of less than about 3/4 °. The die angle of the clamping plates 117 and 118 may be less than about 3/4. The smaller the draft angle, the less grinding is required to form a flat surface. Thus, the contact surface 115 of the side frame 100 requires less grinding time than prior cast side frames because there is no core seam in the pedestal area.

FIG. 4 illustrates an exemplary operation for manufacturing the sideframe 100 described above. The operation is better understood with reference to fig. 5 and 6.

At block 400, a mold 500 for fabricating the side frame 100 may be formed. Referring to fig. 5A, the mold 500 may include a drag 505 and a cope 510. The drag portion 505 of the mold 500 includes a cavity formed in the shape of the drag side 102 of the side frame 100. Cope portion 510 includes a cavity formed in the shape of cope side 103 of side frame 100.

Each section may be formed by first providing first and second dies that define the outer perimeters of lower and upper die sides 102 and 103, respectively, of side frame 100. The dies may partially define one or more feed passages 540 for distributing molten material within the mold 500. The one or more feed channels 540 are beneficially disposed in a central region of the mold 500, which allows for uniform distribution of the molten material throughout the mold 500. For example, feed passage 540 may be provided in an area of mold 500 that defines bolster opening 110 of side frame 100.

The pattern (not shown) also defines pedestal jaw portions 520 that define pedestal jaws 140 of side frame 100. In prior forming methods, the die did not define details of pedestal jaw 140. Instead, a core having the general shape of the interior region of pedestal jaw 140 is inserted into the mold prior to casting. The cores tend to move during casting and become imprecise in size, necessitating the elimination of large core seams.

The mold and set of risers 535 can then be inserted into respective sand boxes 525 and 526 to receive molding material 527. Risers 535 may be inserted into cope 510. The riser 535 corresponds to a hollow cylindrical structure, and molten material is filled into the riser 535 during casting. Risers 535 are provided in the areas of the mold corresponding to the thicker regions of the side frame that cool more slowly than the other areas of the side frame. The riser 535 acts as a reservoir of molten material to compensate for shrinkage of the molten material as it is cooled, thereby preventing shrinkage, or thermal tearing that might otherwise occur in the thicker areas of the cast side frame. FIG. 5B illustrates an exemplary riser 550 of the side frame 100.

The exact location of the required precision feed is generally unknown in existing casting operations. Thus, relatively large risers (e.g., 6 inches or more) are used to cover a large area. In contrast, in the disclosed embodiments of the present invention, the exact location where precise feeding is required is determined by various analytical techniques, as described below. Accordingly, relatively small diameter (e.g., about 4 inches or less) risers 435 can be used, which improves the production of the casting. The riser height may be between about 4 inches and 6 inches. In one embodiment, less than 10% of the total weight of the casting material poured into the mold ends up entering the riser. This makes the use of the casting material more efficient.

The size of flasks 525 and 527 will generally follow the shape of the pattern, unlike flasks used in prior casting operations. These flasks are typically sized to accommodate the largest cast product in a casting operation. For example, in existing casting operations, the flask may be sized to accommodate a bolster or even larger items. In contrast, as shown in FIG. 5A, sand boxes 525 and 527 according to the disclosed embodiment of the invention have a shape that follows the general shape of the casting. For example, the flasks 525 and 526 in FIG. 5A have the general shape of the side frame 100. The maximum distance L530 between the edge of the respective sand boxes 525 and 527 and the closest portion of the pattern to the edge of the sand box may be less than 2 inches. The flasks 525 and 527 minimize the amount of molding sand required to form the mold 500. For example, the ratio of sand to molten material poured into the mold in the next operation may be less than 5: 1. This is an important consideration given that the mold 500 may be used only once during casting.

Molding material 527 is then loaded into the flask 525 and spread over and around the mold until the flask 525 is filled. The molding material 527 is then scraped or leveled with the flask and then cured to harden the molding material 527. Once the molding material 527 solidifies, the mold is removed.

The molding material 527 may correspond to a chemical or resin binder material (e.g., phenolic urethane) rather than the greensand product used in existing casting operations. The chemical bond material product is capable of forming a mold with greater precision and finer detail.

To facilitate removal of the mold (not shown), the sides of the respective cavities of the lower and upper sections of the mold are formed with a draft angle D515 of 1 °, 3/4 °, or even less to prevent damage to the mold 500 when the mold is removed. The draft angle of the mold forms a corresponding draft angle D305 along the side of the side frame 100. The resulting draft angle on most surfaces of side frame 100 may have little consequence. However, in certain areas, such as the contact surface 115 of pedestal jaw 140, a draft angle greater than 1 ° is not tolerable. A chemical binder material such as phenolic urethane or a resin binder material is easy to form a side surface having a draft angle of 1 ° or less, as compared with a green sand product. In pedestal jaw 140, the greensand product requires additional cores to create these features to maintain flatness requirements. These cores create large seams and dimensional variations between the castings.

At block 405, a core assembly 545 is formed defining an interior region of the side frame 100. Referring to FIG. 6, the core assembly 545 may comprise one or more portions. For example, the core assembly 545 may include a pair of pedestal and window cores 605, a bolster core 610, a spring seat core 615, a lower tension member core 620, and a pair of internal clamp cores 625. Each pedestal core 605 defines a pedestal interior of the side frame from one end 101 (FIG. 1A) of the side frame to an inboard end of a side frame pillar 120 (FIG. 1A) of the side frame. Pedestal core 605 may define one or more core prints that form openings in the cast side frames. For example, the first set of pedestals 630 may form openings at the ends of the pedestal corresponding to the ends of the side frames. The second mandrel seat 632 may form an opening in the diagonal tension member 141 (fig. 1A) of the side frame. The third core print 634 may form a pillar window 142 (fig. 1A) in the side frame.

For example, a mold may be formed that includes a cope and a drag that define a given core. The sand may be inserted into the core box and cured. The core box is then removed to expose the cured cores. The respective cores may be formed separately, integrally, or in some combination of the above. The corresponding core may be formed in two parts. For example, each core (i.e., pedestal core, bolster core, etc.) may include cope and drag portions that are respectively formed in separate core boxes (i.e., cope and drag molds). After curing, the formed parts may be joined. For example, the cope and drag of a given core may be bonded together to form the core.

At block 410, the core assembly 545 is inserted into the mold and the side frame 100 is cast. For example, the core assembly 545 may be inserted into the lower mold section 505 of the mold 500. The cope portion 510 may be placed on the drag portion 505 and secured to the drag portion 505 by a clamp, a strap, or the like. In this regard, locating features may be formed on the drag portion 505 and the cope portion 510 to ensure precise alignment of the respective portions.

After the respective portions are fixed, a molten material such as molten steel is poured into the mold 500 through the opening of the upper mold portion 510. The molten material then flows through gate 540 and spreads throughout the space between mold 500 and core assembly 545 of mold 500.

At block 415, the mold 500 is removed from the side frame 100 and the side frame 100 is abraded. For example, the contact surface 115 is machined to eliminate the residual draft angle D305 portion resulting from the draft angle D515 of the mold. Other materials may be removed. For example, riser material formed at riser 535 is removed. In some embodiments, the mold 500 is configured to form a wedge or notch in the riser material outside the sides of the side frame 100. The wedge or notch enables the riser material to be hammered off, rather than the more time consuming flame cutting used in existing casting operations.

As shown by the various operations, the sideframe 100 can be produced with minimal scrap and minimal time. For example, the flask configuration minimizes the amount of casting material required to form the mold 500. The smaller risers result in less material (i.e., solidified steel) being removed during grinding. For example, the precision of the mold can produce a dimensionally accurate pedestal jaw. These improvements result in less than 10% of the material being removed during grinding.

In addition to these advantages, other advantages are realized. For example, as noted above, the flasks 525 and 526 are not necessary when casting the side frame 100. Accordingly, the flasks 525 and 526 can be used to form new molds when casting a given side frame 100.

As noted above, various analytical techniques can be employed to accurately determine the various dimensions. To achieve smaller tolerances than are typically achievable with greensand or chemical or resin binder materials such as phenolic urethane molding, an iterative process of casting and three-dimensional scanning is used to measure precise critical dimensions and variability. The method may be used throughout core box, mold making, core making, upper and lower mold portion making, and final part casting. By accurately measuring the various steps of the process, the exact shrinkage in three dimensions (i.e., vertical, longitudinal, transverse) and how the core and mold collapse during solidification are known.

In one embodiment, the scanning may use a 3D point cloud scanner, such as a Z scanner, a fabry laser scanner, or similar device. The 3D point cloud data may be as described inAndsuch as software, to measure and align the mold, core, and final part. These comparisons can be used to calculate actual casting shrinkage, where casting shrinkage is typically expressed in percent. For example, a typical molding shrinkage margin for carbon steel may be about 1.56%. This typical shrinkage margin is not precise and depends on the complexity of the shape being castBut may vary. In some cases, the shrinkage margin may be as high as 2%. For large castings, such as side frames or bolster, this range of shrinkage allowance can produce casting tolerances up to.5 "and out of tolerance. In the described embodiment, the method is used to determine the actual shrinkage in the vertical, longitudinal, and transverse directions, which is reflected in the mold dimensions.

In addition to calculating the shrinkage of the casting during cooling, it is also important to understand how the core and mold collapse during solidification. Controlling the collapsibility of the core and mold can control the tolerance range achieved. This can be achieved by combining the geometry of the molding material, the core and the mold. For side frame critical dimensions, such as column spacing A170 (FIG. 1B), pedestal spacing B175 (FIG. 1B), and column wear plate bolt spacing C270 (FIG. 2A), relief openings 550 (FIG. 1B) formed in the core and mold can be used to control the shrinkage of the casting. By forming the pedestal in the mold, rather than an external core, a +. 038 "tolerance is achieved between the centers of the pedestals, as shown. By adding a pair of symmetrical cushion openings 550 (fig. 6) in the bolster hole pattern core 610, centered about 10.6 "above the spring seat and about 2" from the upright posts, a ±.038 "pitch upright is achieved. That is, the dimensions A170 and B175 may be limited to ±.038 "such that the error magnitude for these dimensions is ±. 038". Additionally, bolt hole opening spacing C270 (FIG. 2A) may be uniform between all components and allow column bolt openings 210 of the produced components to be in the range of ±.020 "from one another. That is, dimension C270 may be limited to ±.020 ". The precise placement of the opening 210 facilitates the use of smaller mandrels to create the opening 210. 050 "for tighter assembly bolting than the fasteners.

In addition to determining the range of manufacturing errors for the mold and core to account for shrinkage and collapse, the core print size may be reduced. Reducing the clearance between the interface between the mold core print and the core protrusion reduces core movement during casting. Less core movement results in more precise wall thicknesses and more precise part tolerances. In addition to the accuracy of the mold and die tolerances, a controlled amount of sizing is achieved to minimize variations in the core print dimensions. The void used in the process is.030 ", where the mold is larger than the insert protrusion formed in the core.030", as shown by dimension F561, a cross-section taken along section 555 (FIG. 5A) is shown. That is, the distance F561 between the edge of the core print 630 and the nearest portion of the mold from the core print 630 is about.030 ". This means that the achievable wall thickness tolerance E560 (fig. 5A) on the final part is ±.020 ". That is, the wall thickness E560 may be limited to ±.020 ".

Another advantage of these operations is that the surface finish of the cast side frame is smoother than known casting operations. The smoother the surface, the greater the fatigue life of the part. The above-described operations facilitate fabricating a side frame having a surface finish of less than about 750 micro-inches RMS and a pedestal surface finish of less than about 500 micro-inches RMS.

FIG. 7 illustrates an exemplary bolster 700 that may be used in conjunction with a side frame 100 as part of a rail car truck. The bolster 700 includes a body portion 715 and first and second outboard end portions 705. The body portion 715 defines a bowl section 707 on which the rail car is supported. A pair of detent window openings 725 and a relief window 720 are defined on the longitudinal sides of the bolster 700. The brake window opening 725 and the buffer window 720 are configured to be substantially centered on a parting line that separates the drag portion and the cope portion of the die that forms the bolster, as described below. The first and second outboard end portions 705 are configured to be coupled to a pair of side frames 100. Specifically, each outboard end portion 705 is disposed in a bolster opening 110 of side frame 100 and defines a pair of side bolster plates 706 that are positioned below the bearing surface of the rail car. A set of springs is placed in the bolster opening 110 under the outboard end portion 705.

Each outboard end portion 705 includes a pair of friction shoe pockets 710. The surface of the respective shoe 710 is known from a grinding standpoint as a critical area of the bolster 700 because the shoe 705 is configured to abut the wear plate 135 and cooperate with the wear plate 135 to function as a shock absorber, as described above. A wedge is fitted into the shoe pocket and rubs against the bolster block wear plate.

As described above, the body portion 715 of the bolster 700 defines a pair of brake window openings 725 configured to enable use of the foundation brake. In the mold, these windows also act as core prints to support the main body core.

Bolster 700 may be formed in a manner similar to that of forming side frame 100. For example, the cope and drag portions of the mold may be constructed of a casting material, for example, a chemical binder material such as phenolic urethane or a resin binder material. The respective cavities in the mold cope and drag portions may be formed using a pattern that defines the exterior of the respective cope and drag portions of the bolster 700. The draft angle of the die side may be 1 ° or less. As in the side frames, the mold forming flasks may be sized to follow the shape of the pattern defining the bolster. The flask configured in this manner minimizes the amount of molding material required to cast the bolster. For example, in some embodiments, the ratio of molding sand to molten material poured into the mold in a subsequent operation may be less than 3: 1. This is an important consideration given that the mold can be used only once during casting.

Risers 805 (fig. 8) may be strategically located and sized to provide an optimal amount of feed material during solidification to prevent shrinkage cavities and hot tears from forming in critical areas of bolster 700. One or more feed channels 810 may be formed in the mold along the mold regions extending along the longitudinal sides of the bolster 700 for distributing molten material throughout the mold. For example, a uniform length of the feed passage 810 may be formed in the mold area used to form the detent window 720 and inside the inner gib 708 of the bolster 700, as shown. The feed passage 810 is advantageously placed in the center region of the mold, which allows for uniform distribution of molten material throughout the bolster 700 during casting. In contrast, in prior art bolster casting operations, molten material is poured into the bolster mold at the outboard end region 701. This results in uneven cooling of the material along the longitudinal plane of the bolster. For example, if molten material is poured into the bolster mold at the first end 701 of the bolster mold, the metal at the other end of the bolster mold will cool more rapidly than the metal at the first end 701 of the bolster mold. Once the portions are solidified, the flasks forming the drag and cope portions may be removed.

Fig. 9A illustrates an example closed cope 903 and drag 902 of a bolster mold 900. As shown, the parting line 905 separating the portions does not follow a straight line parallel to the edges of the cope portion 903 and drag portion 902 (as is the case in prior art bolster molds), as shown by the dashed line 901 in fig. 9A. Fig. 9B illustrates the relationship between parting lines 905 and bolster 700 cast in bolster mold 900. At the main body portion 715 of the mold, the parting line 905 is generally centered between the portions of the mold that define the brake window opening 720. The parting line 905 generally follows a path intermediate the top and bottom of the bolster 700. However, at brake shoe opening 710 at end 705, parting line 905 is configured such that brake shoe opening 710 is substantially defined in the drag portion of the mold. In other words, the parting line 905 does not pass through the shoe opening 710.

In prior casting operations, the entire parting line formed a plane that cut through the bolster. For example, the parting line may extend between the ends and may be centered within the ends such that the parting line bisects the brake shoe opening and passes through an upper portion of the brake window. In greensand, the brake shoe openings are made using a core, as this operation cannot form this shape.

Configuring a parting line according to embodiments disclosed herein has several advantages over existing parting line configurations. For example, the upper and lower portions of each braking window are known as high stress areas. The placement of the parting lines near such locations, as is typical with prior arrangements, renders the bolster more susceptible to high stresses. In contrast, in the embodiments disclosed herein, the parting line 905 is located in the middle of the brake window opening 720, where the stress is lower. The parting lines of the mold are also in the same position as the parting lines of the core. This provides a uniform wall thickness of the side walls, thereby promoting uniform cooling of the casting.

Grinding the shoe pocket 710 is not required because the parting line does not pass through the shoe pocket 710. In existing seam line configurations, the seam line may be a straight line bisecting the bolster and passing through the middle region of the shoe pocket. This may necessitate grinding the mandrel seam around the shoe opening. However, the parting line disclosed herein is configured to be over brake shoe aperture 710. That is, the brake shoe opening 710 is integrally formed in either the cope or drag of the die. As previously noted, the shoe opening 710 is a more critical area of the bolster 700. Therefore, it is advantageous to omit the grinding operation.

The cross-sectional thickness of the bolster is more symmetric about the parting line 905. As noted above, a pattern die is used to form the cavities of the lower and upper sections of the mold. The die is formed to have a draft angle that enables the die to be removed from the mold. The core box is used for manufacturing a core which defines the interior of the swing bolster. The two halves of the core box meet at a parting line from which the draft angle also extends to allow removal of the core. In the case where the parting line of the core and the parting line of the mold do not match, uneven wall thickness occurs. Placing the seam line toward the top of the bolster, as is typical in prior seam line configurations, can result in a bolster having a non-uniform thickness across its cross-section. The uneven thickness results in an excess of material being used in casting the bolster. The non-uniform thickness also prevents uniform cooling and shrinkage and voids can occur. To prevent shrinkage and voids, large risers must be used to replenish the critical sections. In contrast, arranging the parting line 905 as disclosed herein can form a bolster 700 having a uniform sidewall thickness around the parting line 905, such as thickness T in FIG. 10A₁1005 and T₂1010, respectively. In turn, this minimizes the amount of material required to cast the bolster 700 and allows the entire casting to cool evenly. In some embodiments, less than 15% of the cast material is removed from the cast bolster to form the finished bolster. The uniform cooling rate throughout the casting allows the use of relatively small risers.

Another advantage of the configuration of the parting line 905 disclosed herein is that it enables easy alignment of the cope and drag portions of the mold. In prior molding operations, locating features, such as pins and openings, were placed in the drag flask portion and the cope flask portion to align the two portions. Any number of misalignments in the locating features can result in misalignment between the bolster lower and upper profiles. However, the parting line 405 is keyed according to its geometry, and the drag and cope portions interlock substantially with each other in a two-part self-aligning manner. Thus, a pin and sleeve known in the art are not necessary to maintain the drag and cope portions in alignment.

After the drag and cope portions are formed, one or more cores 1100 defining the interior of the bolster 700 are formed. Referring to fig. 11, mandrel 1100 may be formed as described above with respect to block 405. Core 1100 may include a drag and a cope that together define substantially the entire interior of bolster 700. For example, the one or more body cores 1105 may include a drag 1105a and a cope 1105b that together define the entire interior region of the bolster 700. In other embodiments, each of the body cores 1105a and 1105b may define a respective half of the total interior area from the center of the bolster (i.e., the central transverse plane bisecting the bolster) to an inward tongue 709 (fig. 7) located at the outboard end portion 705 of the bolster 700. The body cores 1105a and 1105b may partially define an interior region between the inward bolsters 709 and the ends of the bolster 700. Each of the main body cores 1105a and 1105b may define a first core print 1120 and a second core print 1115. The separate end core 1110 may define an interior region at the outboard end portion 705 of the bolster 700 that is not defined by the body cores 1105a and 1105 b. The end core 1110 may be formed separately from the main body cores 1105a and 1105 b. The end core 1110 may be connected to the body cores 1105a and 1105b in a subsequent operation by, for example, an adhesive.

The techniques for limiting various dimensional tolerances described above with reference to the side frames may be applied to the bolster. Similar methods can be used to accurately measure the actual amount of core and mold breakup for critical dimensions of the bolster such as shoe pocket angle N1020 (FIG. 10B), shoe pocket width M1025 (FIG. 10B), and inner and outer cotter spacing G750 (FIG. 9B). By calculating the quantities in the mold, a tolerance of +. 5 ° for the shoe throat angle N1020 and a tolerance of +. 063 "for the shoe throat width M1025 are obtained on the final part. In addition, the inner gib 708 and outer gib 709 (FIG. 9B) may be fabricated in the bolster mold, thus limiting their separation G750 to a tolerance of ±.063 ".

A distance H950 (fig. 9C) between the respective core prints of the cores for manufacturing the bolster and the portions of the upper and lower dies closest to the core print surfaces may be set to about.030 ".

Another advantage of these operations is that the surface finish of the cast bolster is smoother than existing casting operations. The smoother the surface, the greater the fatigue life of the part. The above operations facilitate fabrication of a bolster having a surface finish of less than about 750 micro-inches RMS and a shoe pocket having a surface finish of less than about 500 micro-inches RMS.

While various embodiments of the embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and embodiments are possible within the scope of the claims. The various dimensions described above are merely exemplary and may be changed as necessary. Thus, it will be apparent to one of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the claims. Accordingly, the described embodiments are provided only to assist understanding of the claims and do not limit the scope of the claims.

Claims (9)

1. A method of manufacturing a bolster of a rail car, the bolster including a pair of shoe pockets at respective ends configured to be inserted into bolster openings of respective side frames, the method comprising:

providing a bolster pattern for forming a lower pattern portion and an upper pattern portion of a mold; and

one or more cores defining an interior region of a cast bolster are provided, wherein the bolster pattern and the one or more cores are configured such that a margin of error in an angle of a shoe pocket is within about +. 5 °.

2. The method of claim 1, wherein a surface finish of the cast bolster is less than 750 micro-inches RMS.

3. The method of claim 2, wherein a surface finish of the pair of shoe pockets is less than 500 micro-inches RMS.

4. The method of claim 1, wherein a draft angle of a shoe pocket sidewall of the cast bolster is not greater than about 3/4 degrees.

5. The method of claim 1, wherein the bolster pattern and the one or more cores are configured such that a margin of error in a spacing between respective inner and outer gibs of the cast bolster is within about +. 063 inches.

6. The method of claim 1, wherein the draft angle of each of the inner and outer spades is no greater than about 3/4 degrees.

7. A method of manufacturing a bolster of a rail car, the bolster including a pair of shoe pockets at each end configured to be inserted into a bolster opening of a side frame, the method comprising:

providing a bolster pattern for forming a lower pattern portion and an upper pattern portion of a mold; and

providing one or more cores defining an interior region of a cast bolster, wherein the bolster pattern and the one or more cores are configured such that a margin of error in a width between the pair of shoe pockets is within about +. 063 inches.

8. A method of manufacturing a bolster of a rail car, the method comprising:

providing a bolster pattern for forming a lower pattern portion and an upper pattern portion of a mold; and

providing one or more cores defining an interior region of a cast bolster, wherein at least some of the one or more cores define one or more core prints for placing the one or more cores within a drag of the mold, wherein a distance between an outside surface of the one or more core prints and a drag surface of the mold closest to the outside surface of the one or more core prints is less than or equal to about.030 inches.

9. The method of claim 8, wherein the bolster pattern and the one or more cores are configured such that a tolerance in wall thickness of the cast bolster is within ±.02 inches.