MX2008002205A - Yoke for a railway draft gear and method of making. - Google Patents

Abstract

Yokes utilized in railway coupling apparatus are designed according to the invention to have improved stress profiles and increased service life. Investment casting techniques used to make the yokes and other components of the coupling apparatus yield improved surface finishes and tighter dimensional tolerances of the parts without requiring hammering, coating or other post-casting treatment.

Description

RAILROAD TRACTION TRAIN OUTER AND MANUFACTURING METHOD This application claims the benefits of the U.S. Application. Application No. 11 / 676,165, filed on February 16, 2007. BACKGROUND OF THE INVENTION Environment of the invention The present invention is directed to railway carriage hooking devices and methods of manufacturing thereof. Particularly, the features described herein in connection with type E and type F forks are to provide improved stress profiles, which provide a longer life. The manufacturing methods of forks and other components of the hooking device are also described, using lost wax casting techniques.

DESCRIPTION OF THE RELATED ART There are relatively few known arrangements for the placement of railway traction trains between wagons. In the United States of America, the commonly used provisions are governed by the standards established by the American Association of Railroads ("American Association of Railways") ("AAR"). Generally speaking, two wagons in a train composition are joined by two heavy axles that extend from each wagon, and which are known as couplers, and each The coupler is attached to a fork that houses an impact absorbing element known as the traction train. Traditionally, the fork is an elongated structure with two lateral sections that extend from the tail section and are joined by it. The side sections (occasionally called "linings") are joined at the opposite end by a head section in which the fork is attached to the coupler with a key or pin. The traction train is located between the lateral sections of the fork, and between the tail section and the head section. The best known types of forklifts are Type E and Type F. The fork type E is governed by the AAR S-143, SY 40AE or YS93AE standards, for a gear cavity of 24 5/8 inches (62.58 cm) ), known here as "the S-143 standard", or simply "the Type E standard". The type F fork is governed by the S-149 standard. Forks differ fundamentally in the design and orientation of the pin or key used to attach the coupler to the fork, with respect to the rail car, although there are other important differences. The coupler is attached to the fork by means of openings in the head section of the fork, sometimes known as the slot of the key or the drilling of the pin, through which a key is passed through or a pin connecting both elements . When the train is in motion, the fork is under tension, and the compression forces are transferred to the load surfaces located at opposite ends of the fork, where the drive train is housed. There could be a plate between the fork and the drive train on the front side of the tail section, and it is also common that there is a plate located near the head section of the fork, exerting a force of the front of the traction train. In practice, the separation between railway wagons in a train composition allows a length of the specified fork. Depending on whether the fork is E-type or F-type, the length could be 41 1/8 inch (104,46 cm) or 37 1/2"(95,25 cm) respectively, as defined in the applicable AAR standard. The side sections of a fork are subject to tension and could stretch over time, making it difficult to remove the fork from the car due to deformations of the trimmings Consequently, two challenges faced by the present invention involve the sizing of the fork in a manner that (i) is more resistant to stretching during use and (ii) is easier to remove after being stretched with use.The sections of the fork that are subject to stress concentrations are also susceptible to cracks and faults with the These areas include the front of the key slot in the E type pitchforks., and the area where the side sections are attached to the tail section. So another of the challenges faced by the invention consists in the sizing of the fork, in such a way that it meets the requirements of the standard AAR specification, while, at the same time, the profile of effort in these zones is improved and in other areas of the fork. A further purpose of the invention is to develop manufacturing methods that allow the improvement of the dimensional tolerances of the fork, which in turn allows the sophisticated design elements described above to be incorporated. It has been found that these manufacturing techniques improve the surface finish of the components produced. Type E forks are described and claimed in U.S. Patents. Patent No. 5,096,076 and U.S. Patent No. 5,511,676, which are included herein as a reference. It is expected that the fork according to this invention will provide an improved stress profile in response to applied stress loads, compared to prior art forks.

SUMMARY OF THE INVENTION On the one hand, the invention concerns the design of the tail section of type F and type E forks. According to this aspect of the invention, the fork comprises: a tail section at one end of the fork and two opposite sections that extend from the tail section and end in a header section. The head section comprises an upper and a lower wall and opposing support walls substantially perpendicular to the upper and lower walls. Depending on whether the key or pin is oriented vertically (such as on a F-type fork), or horizontally (such as on an E-type fork), the upper and lower walls, or the opposing support walls, have opposite openings for receive the corresponding key or pin to hook the coupler of the rail car. On the opposite side the sections meet the tail section on the respective relief chamfers. Each relief chamfer has a radius of curvature composed substantially identical, such that an initial section of the composite radius is farther from a midline of the fork and has a radius of between 1/2 to 1 inch (1.27 to 2.54 cm), tapering to a second section of the composite radius, closer to the midline of the fork, and with a radius of between 1/2 to 2 inches (1.27 to 5.08 cm). It is possible to provide similar relief chamfers where the side sections meet the key slot walls in the header section of an E type fork. In most of the prior art E type forklifts, the side fittings are tapering towards in (to a horizontal plane in the midline of the fork) to form a narrower head section. In a preferred embodiment according to the present invention, the opposite side sections are kept parallel along their entire length. It has been found that the sharp radius of curvature in the front section of the nose of a type E fork causes unwanted stresses. This has been improved according to the present invention by providing a front surface of the key slot defined by an initial arc (which is standard in the industry), and wherein the peripheral front surface of each of the walls The support is defined by a second arc, which extends from the opposite sides of the front end of the groove of the respective key. An appropriate smooth curvature in the nose section is found when the center of curvature of the first arch and that of the second arch coincide. In a preferred incarnation, the tail section of the fork has been provided with a rear peripheral surface that forms at least one concave cutout. In a preferred incarnation, these cutouts are smoothed gutters, generally in a "U" shape. In preferred incarnations, the key slot walls have a flat, uniform appearance, free of concavities and do not include a reinforcing rib adjacent to the key slot. While the fittings of a conventional E-type fork have a standard width of 5 inches (12.7 cm), the inventors propose wider trimmings here, of 5 3/4 inches (14.6 cm) at their narrowest point, as in a type F fork. The invention also includes a rail car engaging component with superior dimensional tolerances and a better surface finish and a method for manufacturing such an improved component. It has been taken into consideration that the method could be applied to the manufacture of a fork or an articulated element, used to join the couplings. The lost wax casting technique of the invention initially comprises the creation of a destructible prototype of the component, and the coating of the prototype to form a temporary mold. The temporary mold is constructed of several layers. Then, the prototype is extracted from the temporary mold, the component is melted in metal (included with steel, but not limited to it) in the temporary mold and then the temporary mold is destroyed. To our knowledge, lost wax casting techniques have not previously been used for the melting of railway coupling components. The lost-wax casting technique results in tighter tolerances, so that Components produced with this process have dimensions within 3% of a design dimension, preferably within 1% of a design dimension, and a smooth surface finish, requiring little or no hammering or grinding. Such dimensional accuracy and surface finish can not be achieved using conventional green sand casting techniques.

BRIEF DESCRIPTION OF THE IMAGES Fig. 1 is a perspective view of a fork type E according to the invention. Fig. 2 is a side elevation view of the type E fork of Fig. 1. Fig. 3 is a top plan view of the type E fork of Fig. 1. Fig. 4 is a type E fork according to Fig. previous art. Fig. 5 is a perspective view of a fork type F according to the invention. Fig. 6a is a detail of a relief chamfer in the header section of the fork of Fig. 1. Fig. 6b is a detail of a relief chamfer in the tail section of the fork of Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED ENCARNATIONS As used herein, the addresses are relative to the normal orientation of a rail car. Therefore, "horizontal" generally means parallel to the earth and vertical is the perpendicular direction. "Above" and "superior" are in the direction of heaven. The words "forward" and "front or front" refer to the direction towards the header section of the fork, while "tail" and "back or rear" refer to the opposite direction. Take into account that the "fronts" of two forks in two adjacent rail cars look at each other. "Type E" and "Type F" are used to refer to types of forklifts in general, without reference to the details of a particular AAR standard. Someone with a skill common in the art will immediately understand that a "Type E" fork according to the invention could differ slightly from the AAR standard, and still be recognizable as an E-type fork, by virtue of the horizontal orientation of the coupler pin, while a fork type F is recognized by the vertical orientation of the pin. When reference is made here to a particular AAR standard, the reference is to the AAR standard in force at the time of submitting this request. When specific dimensions are given in this description, it should be understood that tolerances are allowed. Someone with ordinary skill in the art will understand that at a measurement less than 4 inches (10.16 cm) typically a tolerance of about 1/16 of an inch (0.16 cm) is allowed; to a measurement of 4 inches to 24 inches (10.61 to 60, 96 cm) typically a tolerance of about 3/32 of an inch (0.24 cm) is allowed; and to a measurement greater than 24 inches (60.96 cm) typically a tolerance of about 1/8 inch (0.32 cm) is allowed. As shown in Fig. 1, the fork 100 comprises sections 10 extending from the tail section 18 to the header section 20. Header section 20 comprises opposite support walls 24 and opposite top and bottom walls 26. In the case of type E fork of Fig. 1, support wall 24 could be referred to as a slot wall of the key. The side sections 10 meet the tail section 18 in the rear relief chamfers 23, and the side sections meet the walls of the key slot 24 in the front relief chamfers 22. The header section 20 is refers to the part of the fork in front of the front relief chamfers 22. A fork type F is illustrated in Fig. 5. In this type of fork, the openings 12 (sometimes referred to as pin holes), are vertically oriented during use, and are located in the upper and lower walls 26, and not in the support walls 24. In one aspect of the invention, an E-type fork with a reduced distance of less than 3 inches (7, 62 cm) (preferably 2 1/2 inches [6, 35 cm]) between the front of the slot of the key 12 and the front peripheral surface 14 of the fork. The reduced distance is obtained, without adding thickness around the slot of the key and retaining a satisfactory strength and rigidity, forming the front peripheral surface 14 as a continuous arc in the nose section, whose center of curvature coincides with the center of curvature of an arc defining the front of the key slot. This is shown in Fig. 2, wherein the front peripheral surface of each supporting wall (sometimes referred to herein as the "key slot wall" in afork type E) is defined by an arc whose center of curvature is coincident with the center of curvature that defines the front surface of the slot of the key. In the prior art, which is shown in Fig. 4 and which is described in U.S. Pat. PatentNo. No. 5,096,076, the side fittings 13 taper from the widest distance separating the linings, beginning to taper approximately where the header section 23 begins at the forward relief chamfers 32 toward the midline of the fork. The curved section of the nose 33 consequently comprises a narrower section, which results in a smaller radius for the nose section of the wall of the key slot. According to the preferred incarnations of the present invention, the linings are parallel along their entire length, which can be best seen in the raised view of Fig. 2 Traditionally, the E-type forklifts have had side fittings close to each other. 5 inches (12.7 cm) wide, while the F type fork covers have wider, 5 3/4 inches (14.61 cm). According to the present invention, the forks with key slot walls perpendicular to the side fittings (i.e., E-type forks) preferably have side sections 10 whose narrowest width Wi is about 5 3/4 inches (14, 61 cm) in the narrower section, tapering to a width of about 10 7/8 inches (27, 62 cm) at the widest point 2, where the sections 10 form the opposite walls 26 of the header section 20, even though those dimensions are not critical. The preferred length of an E-type fork in accordance with the invention is 40 5/8 inches (103.19 cm). The front peripheral surface 27 of the side sections 10 is preferably concave. Wider fittings increase the resistance and the life of the fork. In the prior art, the edges of the trimmings defining the width extend from the tail section equidistant from each other, and then up to a point, indicated with the numeral 39 in Fig. 4, the edges abruptly taper away from each other to form the header section. The radius of curvature at this point in the prior art is in the order of 2 to 3 inches (5.08 to 7.62 cm). This causes a concentration of stress where the edges begin to taper outward to find the header section. According to the present invention, it is preferable to create a gradual taper at the edges of the linings. As shown in Fig. 3, the edges of the sides 10 are described by a gradual taper with a radius of curvature greater than about 10 inches (25.4 cm), preferably greater than about 20 inches (50, 8 cm), and in its most preferred embodiment, in a range of 60 to about 70 inches (152.4 to about 177.8 cm) in the section of the steeper curve. Another aspect of the invention involves the design of the tail section of the fork to achieve a more even distribution of the efforts and a reduction in the weight of the fork in general. Although it is conventional to enable cuts in the tail section to reduce the weight of the fork, conventionally this has been done by creating recessed cavities in the side walls of the tail section, so that the rear surface has a wall substantially flat. Recently found that a rear peripheral surface comprising a large number of gutters, for example, two very flat "U" -shaped gutters 16 in the glue section 18, as shown in Fig. 3, improves the stress profile in the tail section. Another additional aspect of the invention includes modifications to the relief chamfers 22, 23, the areas where the side section 10 is attached to the head section 20 and the tail section 18. As shown in Fig. 1, the sections 10 are attached to the tail section in the relief chamfers 23, as shown in the detail of Fig. 6b and the side sections 10 are attached to the walls of the key slot in the front relief chamfers 22, as shown in the detail of Fig. 6a. In a conventional fork, the area where the fittings meet the tail section is subject to very high stresses. Conventionally, the problem has been faced with a relief chamfer, standardized according to the AAR S-139 standard. According to S-139, a relief chamfer is formed with a groove with a radius of 1/2 inch (1.27 cm), starting just in front of the tail section and extending into the tail section . It has now been found that the stress profile in this critical part of the fork can be improved by providing relief chamfers with compound radii. The first section of the radius composed of each chamfer, the part closest to the garrison, has a smaller radius Rl, and the second section of the composite radius, towards the midline of the fork (in an E type fork), has a radius greater R2 with respect to the radius of the first section. The largest section of the composite radio, which results in a more gradual taper of the rear chamfer 23 to the rear surface 44 of the traction gear cavity preferably has a radius twice greater than the radius of the chamfer section closest to section 10. It is preferable that the section with the longer curve The sharp radius of the compound radius in the relief bevel has a radius of curvature in the range of 1/2 inch (1.27 cm) to about 1 inch (2.54 cm), and the radius of the largest radius of the compound radius, in the range of 1/2 inch (1.27 cm) to about 2 inches (5.08 cm). As a non-limiting example, the first section of the composite radius should preferably be of the order of 1/2 inch (1.27 cm), while the second section should be of the order of 2 inches (5.08 cm). A very important aspect of the improved relief chamfer according to the invention is that the transition from the smaller radius to the front of the tail section is gradual rather than sudden. These same features can be incorporated with beneficial results to the front relief chamfer 23 where the linings meet the key slot wall 24 of the header section 20. The generally smooth contours described above with respect to the various features of improved design of the fork can be achieved in part because the forging method of the fork has been improved. Very large steel castings, such as the fork, have been conventionally manufactured using green sand casting, in which a mold is constructed of sand, and the parts are melted individually. According to the invention, a coupling component for a railway car is manufactured by forming a destructible prototype of the component using a destructible medium, for example, wax, expanded plastic foam, other destructible plastics or even ice. The prototype is coated with a semi-permanent coating, such as a porcelain grout, to form a temporary mold. The temporary mold is constructed of several layers. The prototype can be removed from the temporary mold and the component can be melted in the steel mold or some other suitable metal with high tensile strength. This procedure, known as lost wax casting, has not been previously used for the manufacture of railway coupling components. However, it has been found that castings using this technique result in components with better dimensional tolerances, such as within 3% of a design dimension, and requiring very little or no finishing by hammering or grinding. Many of the features described herein, including the tapering of the edges of the sections 10, the rounded front peripheral surface 14 of the wall of the key slot, the cutouts, generally smoothed in a "U" shape 16 , and the soft taper of the relief chamfers 22, 23, have been made possible by this new application of the lost wax casting process to the manufacture of railway coupling parts. In many cases, the lost-wax casting components have a smooth surface finish, and do not require additional grinding. Typically, the rail coupling components are made of steel, and steel for casting should be used. However, steel alloys, and others Suitable metals and metal alloys have been considered as well. The horquetas that weigh 190 Ib. (86.2 kg) or more can be manufactured according to the invention, which is surprising, since lost wax casting is normally used for less heavy parts. It has been considered that the articulated elements, which are used to join the wagon hooks, could also be manufactured using this technique. Typically, the articulated elements weigh about 70 Ib. (31.75 kg) or more. After the casting of the component, the temporary mold is destroyed.

EXAMPLE A stress analysis of the design of a fork according to the invention was carried out, and according to the prior art, modeled using Ansys® Workbench ™, version 10.0 finite element analysis design software, available from Ansys, Inc., Canonsburg, Pennsylvania. Using this software, a fork according to the invention, substantially as shown in Fig. 1, and a fork according to the prior art, substantially as shown in Fig. 4, were subjected to a load which is typical of that expected in the service. In the computed model, a tensile load of 300,000 Ib was applied. (136,077.71 kg) in longitudinal direction to the front walls 12 and 52 of the respective key slots, while the fork was constrained to the respective rear surfaces 44 and 54 between the respective relief chamfers. The equivalent efforts (von Mise) obtained have been tabulated in Table 1. The stresses were measured in the front relief chamfers, in the rear relief chamfers, in front of the key slot and in the back of the key slot. In addition, the stresses were measured at a point of the linings where the edges taper out to the head section, approximately in the position shown as 60 in Fig. 1 and as 39 in Fig. 4. The Efforts in the nose section were measured where the curved section of the nose begins in each case, in the concave area of the point identified as 34 in Fig. 4, and near the point identified as 64 in Fig. 1.

Table 1 The model showed that the fork according to the invention showed a significant reduction of stress in most of the critical areas in which the effort was measured, compared to the previous art (except for the back part of the key slot, where no significant reduction of effort was observed in the model.) The calculated stresses of the stress measurements carried out in real forklifts subjected to tensile forces, confirmed the accuracy of the computed model, at least in the terms of the relative stress reduction values, if not in measurements of absolute stresses. On the basis of computer modeling, it is believed that a rear relief chamfer with a composite radius will show a reduced stress profile in that area, responding to an elastic load of 300,000 Ib. (136,077.71 kg) applied to the fork as described in the previous example. A composite radius that has a first section close to the lining, with a radius in the range of about 1/2 inch (1.27 cm) to about 1 inch (2.54 cm), and a second section measuring at least twice as much as the first section of the radius, in such a way that the chamfer meets the rear wall of the traction train with a gradual taper, will exhibit an effort 15 percent less at least, preferably 30 percent less, than that obtained from a similar fork subjected to a similar load and having rear relief chamfers with a single (non-composite) radius of 1/2 inch (1.27 cm). These stress reductions are designed to be measured with finite element analysis software, as described in the previous example. Using the same criteria, a significant reduction of stress was observed in the lateral section at the point of the sharpest curve, where the edges of the linings are tapering to find the head section. If the tapering of the linings is done gradually, so that the edge of the lining is defined by a arch having a radius of curvature between 60 and 70 inches (152.4 and 177.8 cm), as shown in Fig. 1, contrary to the more sudden transition exhibited in the prior art of Fig. 4 , then the fittings present an effort that is at least 25% less under the same stress load; preferably the reduction of stresses is 50% or more compared to the prior art. The efforts of the nose section can be retained equal or even reduced, with respect to the prior art, even when the distance from the front peripheral surface to the front of the key slot is reduced (to 2 1/2 inches). (6,35 cm) in its most preferred embodiment), using the design criteria described in this document.

[0045] The following description is intended to be illustrative and not limiting of the invention, which is defined in the appended claims.

Claims (22)

WHAT IS REVINDED IS:

1. A fork for a railway wagon attachment device, comprising: a tail section at one end of the fork; two opposite sections, which extend from the tail section and end in a header section; the head section comprises an opposite upper and lower wall and supporting walls between the upper and lower walls and substantially perpendicular to the upper and lower walls; wherein the upper and lower walls, or the opposing support walls, have an opening for receiving a post or key for engaging a rail car coupler; where the sections meet the tail section in the respective relief chamfers, each relief chamfer has a substantially identical composite radius of curvature, such that an initial section of the composite radius is further from a midline of the fork and has a radius of between 1/2 to 1 inch (1.27 to 2.54 cm), tapering to a second section of the composite radius, closer to the midline of the fork, and with a radius of between 1 / 2 to 2 inches (1.27 to 5.08 cm).

2. The fork of claim 1, wherein the ends of the opposing sections extending from the tail section form the upper and lower walls of the head section, each of said top and bottom walls comprising a circular bore of the pin substantially identical.

3. The fork of claim 1, wherein the support walls are substantially perpendicular to the opposite sections extending from the tail section, and each of the support walls comprises a groove of the substantially identical elongated key.

4. The fork of claim 3, wherein the opposite sections are parallel to each other along their entire length.

5. The fork of claim 3, wherein the surface of the support wall is free of reinforcement sections with reliefs or depressions adjacent to the key slot.

6. The fork of claim 3, wherein the width of the opposite sections is 5 3/4 inches (14,605 cm) at its narrowest point.

7. The fork of claim 3, wherein the front surface of the key slot is defined by an initial arc, and where the front peripheral surface of each support wall is defined by a second arc, such an arc extending from opposite sides of the arc. front end of the key slot, and where the centers of curvature of the first arc and the second arc are coincident.

8. The fork of claim 3, wherein the distance from the forward end of the key slot to the forward end of the peripheral surface of the support wall is in a range of 2 1/2 to 3 inches (6.35 to 7). , 62 cm).

9. The fork of claim 3, wherein each of the opposite sections has a width of about 5 3/4 inches (14.605 cm) in its narrowest section, and gradually, continuously, widens to the head section, said taper having a greater wax radius of 10 inches (25.4 cm) in its tapered section.

10. The fork of claim 1, wherein the rear peripheral surface of the tail section comprises a large number of concave channels, generally in a "U" shape.

11. A fork for a railway wagon attachment device, comprising: a tail section at one end of the fork; two opposite sections, extending from the tail section and ending in a header section: the header section comprises an upper and a lower wall opposite and supporting walls opposite between the upper and lower walls and substantially perpendicular to the upper walls and lower; wherein the upper and lower walls, or the opposing support walls, have an opening for receiving a post or key for engaging a rail car coupler; and where the opposite sections are parallel to each other along their entire length.

12. A fork for a railway wagon attachment device, comprising: a tail section at one end of the fork; two opposite sections, which extend from the tail section and end in a header section; the header section comprising an opposing top and bottom walls and opposite support walls substantially perpendicular to the top and bottom walls; wherein the upper and lower walls, or the opposing support walls, have an opening for receiving a post or a key for engaging a rail car hooking device; wherein the tail section has a rear peripheral surface which forms at least one concave cut;

13. The fork of claim 12, wherein the upper and lower walls each comprise a substantially identical circular pin hole.

14. The fork of claim 12, wherein the support walls each comprise a groove of the elongated key substantially identical.

15. A method for manufacturing a rail car engaging component, comprising the steps of: forming a destructible prototype of the component in a destructible environment; coating the prototype to form a temporary mold; extraction of the temporary mold prototype, and casting of the metal component in the mold; where the component weighs more than about 70 Ib. (31.75 kg), and its dimensions are within 3% of a design dimension.

16. The method according to claim 15, wherein the component is a fork, with a weight greater than 190 Ib. (86.2 kg) approximately.

17. The method according to claim 15, wherein the prototype is made of wax.

18. The method according to claim 15, wherein the prototype is coated with a ceramic slurry to form the temporary mold.

19. A hooking device for a railway car manufactured with the method of claim 15.

20. An articulated element manufactured with the method of claim 15.

21. A method for manufacturing a fork for a railway wagon attachment device, comprising the steps of: forming a destructible prototype of the fork with a tail section at one end and two opposite sections parallel to each other throughout its length extending from the tail section and ending in a header section, the head section having been formed from the forward ends of the sections forming the opposite upper and lower walls of the head section and two walls of the head section. opposite key slot, disposed between the upper and lower walls, same walls of the key slot having a key slot elongaday and a front surface defined by a first arc; the walls of the key slot each having a front peripheral surface defined by a second arc with a center of curvature coincident with the center of curvature of the first arc, where the distance between the front of the slot of the key and the front of the second arch is less than 3 inches (7.62 is); coating the prototype to form a temporary mold; extracting the prototype: melting the metal component in the temporary mold; where the finished fork weighs more than 90 Ib. (86.2 kg) approximately, and their dimensions are within the V3% of a design dimension, without a final grinding.

22. A fork made with the method of claim 20.