Railcar coupler core with vertical parting line and method of manufacture

A method of casting a core includes the steps of preparing a first half of a corebox, preparing a second half of a corebox such that the parting line of a core formed from the first and second coreboxes runs along the vertical axis of the core.

FIELD OF INVENTION

The present invention relates generally to the field of railroad couplers, and more specifically to the cores used to produce the interior spaces of the knuckle of railroad couplers and the methods used to produce these cores, as well as the structure of the knuckle itself and its method of production.

BACKGROUND

Railcar couplers are disposed at each end of a railway car to enable joining one end of such railway car to an adjacently disposed end of another railway car. The engagable portions of each of these couplers are known in the railway art as knuckles. For example, railway freight car coupler knuckles are taught in U.S. Pat. Nos. 4,024,958; 4,206,849; 4,605,133; and 5,582,307.

Coupler knuckles are generally manufactured from a cast steel using a mold and three cores that produce the interior spaces of the knuckles. These three cores typically make up the rear core or “kidney” section, the middle core or “C-10” or “pivot pin” section, and the front core or “finger” section. During the casting process itself the interrelationship of the mold and three cores disposed within the mold is critical to producing a satisfactory railway freight car coupler knuckle.

The most common technique for producing these components is through sand casting. Sand casting offers a low cost, high production method for forming complex hollow shapes such as coupler bodies, knuckles, side frames and bolsters. In a typical sand casting operation, (1) a mold is formed by packing sand around a pattern, which generally includes the gating system; (2) The pattern is removed from the mold; (3) cores are placed into the mold, which is closed; (4) the mold is filled with hot liquid metal through the gating; (5) the metal is allowed to cool in the mold; (6) the solidified metal, referred to as raw casting is removed by breaking away the mold; (7) and the casting is finished and cleaned which may include the use of grinders, welders, heat treatment, and machining.

In a sand casting operation, the mold is created using sand as a base material, mixed with a binder to retain the shape. The mold is created in two halves—cope (top) and drag (bottom) which are separated along the parting line. The sand is packed around the pattern and retains the shape of the pattern after it is extracted from the mold. Draft angles are machined into the pattern to ensure the pattern releases from the mold during extraction. In some sand casting operations, a flask is used to support the sand during the molding process through the pouring process. Cores are inserted into the mold and the cope is placed on the drag to close the mold.

When casting a complex or hollow part, cores are used to define the hollow interior, or complex sections that cannot otherwise be created with the pattern. These cores are typically created by mixing sand and binder together and then filling a box shaped as the feature being created with the core. These core boxes are either manually packed or created using a core blower. The cores are removed from the box, and placed into the mold. The cores are located in the mold using core prints to guide the placement, and prevent the core from shifting while the metal is poured. Additionally, chaplets may be used to support or restrain the movement of cores, and fuse into the base metal during solidification.

The mold typically contains the gating system which provides a path for the molten metal, and controls the flow of metal into the cavity. This gating consists of a down sprue, which controls metal flow velocity, and connects to the runners. The runners are channels for metal to flow through the gates into the cavity. The gates can control flow rates into the cavity, and prevent turbulence of the liquid.

After the metal has been poured into the mold, the casting cools and shrinks as it approaches a solid state. As the metal shrinks, additional liquid metal must continue to feed the areas that contract, or voids will be present in the final part. In locations with heavy thick metal sections, risers are placed in the mold to provide a secondary reservoir of liquid metal. These risers are the last areas to solidify, and thereby allow the contents to remain in the liquid state longer than the cavity or the part being cast. As the contents of the cavity cool, the risers feed the areas of contraction, ensuring a solid final casting is produced. Risers that are open on the top of the cope mold can also act as vents for gases to escape during pouring and cooling.

In the various casting techniques, different sand binders are used to allow the sand to retain the pattern shape. These binders have a large effect on the final product, as they control the dimensional stability, surface finish, and casting detail achievable in each specific process. The two most typical sand casting methods include (1) green sand, consisting of silica sand, organic binders and water; and (2) no-bake or air set consisting of silica sand and fast curing chemical adhesives. Traditionally, coupler bodies and knuckles have been created using the green sand process, due to the lower cost associated with the molding materials. While this method has been effective at producing these components for many years, there are disadvantages to this process.

Many knuckles fail from internal and/or external inconsistencies in the metal through the knuckle. These inconsistencies can be caused when one or more cores move during the casting process, creating variances in the thickness of the knuckle walls. These variances can result in offset loading and increased failure risk during use of the knuckle.

Traditionally, each of the three cores needed to be set in a separate print in the mold which helps maintain each core's position. Furthermore, additional support mechanisms, such as manually inserted nails, are necessary to avoid shifting. These techniques are labor intensive and allow for human error.

Earlier designs may also allow turbulence in the flow of molten steel during the pour due to the sharp transitions in certain areas. When metal fills the molds under high velocity, it creates turbulence. Any sharp or abrupt transition in the molds or cores also creates turbulence, and/or pressure gradients that can also cause the cores to shift. Furthermore, the turbulence and pressure gradients can cause mold erosion, inclusions and reoxidation defects. These problems can cause solidification issues such as shrinkage and porosity, which in turn can lead to knuckle failure.

The issues above can all result in casting inconsistencies in the knuckle core surfaces. The ramifications of such inconsistencies and the low fatigue strength of the resulting parts can be extremely expensive, as The Association of American Railroads (AAR) has strict standards as to when a part must be scrapped and replaced. The 2011 Field Manual of the AAR notes at Rule 16, Section A, that “knuckles found broken or with cracks in any area . . . determined by visual inspection and/or by utilizing non-destructive testing as defined in AAR Specification M-220 shall be scrapped. (emphasis added). Due to these strict standards, and the expense of replacing these parts in the field, there is an ongoing need to improve the strength and/or fatigue life in coupler knuckles as well as a need to improve the design of the cores used to form the knuckles.

SUMMARY OF INVENTION

In a first embodiment a method of casting a core includes the steps of preparing a first half of a corebox, preparing a second half of a corebox such that the parting line of a core formed from the first and second coreboxes runs along the vertical axis of the core.

In a second embodiment a core for forming the interior spaces of a railcar part, said core includes a parting line along the vertical axis of the part.

In a third embodiment a railcar coupler knuckle has a top knuckle pulling lug with a wall thickness of between about 0.47″-0.53″ throughout the entire top knuckle pulling lug.

In a fourth embodiment a railcar coupler knuckle has a top knuckle pulling lug with a wall thickness that has a substantially constant thickness from the top of the front face of the top knuckle pulling lug to the bottom face of the top knuckle pulling lug.

A first goal of the present invention is to reduce core shifting during casting and therefore improve the strength and fatigue life of a coupler knuckle by utilizing two cores that include a unique interlock feature. A completed knuckle10is shown inFIGS. 1-3for reference. By way of background, the general parts of the completed knuckle will be recited here referring toFIGS. 1-3. A knuckle10has a buffing shoulder12, a C-10 pin hole14, a flag hole16, a front face18, a heel20, a hub22, a lock shelf24, a locking face26, a nose28, a pin protector30, a pulling face32, a pulling lug34, a spine36, a spine transition38, a tail40, a tail stop42, a thrower pad44and a throat46. Referring toFIG. 4, the first specialized core is a finger core48which forms the spaces in the front face18side of the knuckle10, and the second specialized core is a combination C-10/kidney core50, which forms the spaces in the C-10 pinhole14and tail40sections of the knuckle10.

With respect to the front portion of the knuckle10, the present invention utilizes a uniquely shaped first core referred to as a finger core48, shown inFIGS. 4-8.FIGS. 5,6and7show the finger core48connected to the kidney core50.

FIG. 4shows the finger core48about to be connected to the second, or C-10/kidney core, through the interaction of a lug52defined on a wall54of the finger core48and a slot56defined on a first wall58that forms a wall of the C-10 portion60of the C-10/kidney core50.FIG. 8shows the finger core48alone.

Referring again toFIGS. 5,7and14, the design of the lug52and slot56form an interlock feature, or first transition section62, between the cores48,50that forms a smooth transition from the kidney/C-10 core50to the finger core48in the transition section62. The advantage of this smooth transition section62is that it reduces the turbulence of the molten metal during the casting process which in turn reduces solidification issues such as inclusions, reoxidation defects and porosity in the metal, and reduces the possibility of mold erosion. This feature also reduces the occurrence of hot tears on the inside features of the knuckle10, which is a problem in existing castings. Furthermore, it results in much greater control of the dimensions between the C-10 pin hole14and the pulling lugs34and buffing shoulders12of the completed knuckle10.

The section62has been altered from the prior art transition section62shown inFIGS. 11,12and13by increasing the thickness of this area both horizontally and vertically. For example, in the prior art, as shown inFIGS. 11 and 12, sharp corners64are formed at a first end66of the transition section62adjacent to the end wall68of the C-10 core50at the point where the lug52of the finger core48enters the slot56of the C-10 core50. In the present invention, this sharp corner is eliminated and replaced with first radius70of about 0.10″ from the first vertical wall58of the C-10 portion60of the core50to the end wall68of the C-10 portion of the core, which will be referred to as the first positive stop surface74and will be further described below. The first radius70is shown as R1in the figures. A second radius80is formed on the finger core48and extends from the vertical wall of the second positive stop76on the finger core48and the outboard vertical portion78of the finger core48. The second radius80preferably measures about 0.10″ or greater and is labeled as R2in the Figures. The first radius70can also be described as measuring about 0.10″ between the first vertical wall58of the C-10 portion60of the core50to its tangent point with the second radius. The second radii can also be described as measuring about 0.10″ between the outboard vertical portion78of the finger core48and its tangent point with the C-10 portion of the core50.

The first transition section62between the C-10 portion60of the core and the finger core48has also been improved by increasing both the width W and the height H of the transition section62as shown inFIGS. 7 and 14over the prior art (shown inFIGS. 12 and 13). The transition section62has first82and second84sides forming the vertical axis86(FIG. 7) and third88and fourth90sides forming the horizontal axis92(FIG. 14). The height H is formed from the point where the radii R1and R2meet on the top side94of the transition section62and the point where R1and R2meet on the bottom side96of the transition section62. The width W of the transition section62is formed between the third88and fourth90sides of the transition section62as shown inFIG. 14. The third side88forms the inboard or throat side98of the knuckle10and the fourth side90forms the tail stop side100of the knuckle10. The corresponding height H1of about 2.40″ and width W1of about 0.922″ of the prior art are shown inFIGS. 12 and 13.

The height H of this transition section62is preferably greater than about 2.5″ and the width W is preferably greater than about 0.925″. Alternatively, the height H can be increased at least about 75% over the corresponding prior art height and the width W can be increased at least about 50% over the corresponding prior art width. In a preferred embodiment, the height H is about 3.98″ and the width W is about 1.33″.

These changes result in a smoother transition from the C-10/kidney core50to the finger core48than the prior art transition. The sharp angles64of the prior art are removed, and this smoother transition section62forms a more uniform wall102thickness in the corresponding area104of the finished knuckle10as shown inFIG. 15. The opening in the knuckle10in the area formed by the transition section62preferably about 3.0″ high and about 0.8″ wide.

An additional aspect of the design of the first transition section62of the present invention is the addition of a positive stop. The positive stop is formed from corresponding vertical walls74,76on the C-10 portion60of the C-10/kidney core50and the finger core48, respectively. As shown inFIGS. 5-7, the positive stop construction allows the finger core48and the C-10/kidney core50to seat completely against each other in an exact fit, further reducing shifting of cores. Moreover, the design of the positive stop surfaces74,76creates a 360° radius that extends around the entire connection joint108. This results in reduced stresses and enhanced solidification in the finished knuckle10and reduced likelihood of hot tears. This positive stop construction also helps form the large radii R1and R2as previously described. The larger radii help lower the stresses in the knuckle10as well, and provide a smoother, less turbulent flow of metal as the mold is filled. This in turn reduces the likelihood of hot tears.

A preferred construction of the first positive stop surface74of the C-10/kidney core50is shown inFIGS. 4,6and8-10. A slot56is defined in the first wall58of the C-10 portion60of the C-10/kidney core50and may preferably be between about 0.6-1.0″ wide and between about 2.00-3.5″ high. The slot is 56 is preferably slightly larger than 1.0″ deep to accommodate the lug52. However, it can be between 0.5-2.5″ deep depending on the size of the corresponding lug56. The first positive stop surface74is defined on the first wall58of the C-10/kidney core50a6nd extends 360° around the slot56, preferably measuring about 0.10-0.35″ outside of the slot56and being substantially parallel to the first wall58.

The corresponding second positive stop surface76having substantially equal measurements as the first positive stop surface74in order to maintain a substantially exact fit is defined extending 360° around the lug52extending from the wall54of the finger core48and being substantially parallel to the wall54of the finger core48. The second positive stop76preferably extends between about 0.10-0.35″ outside of the surface of the lug52. The lug52includes top110and bottom112walls that taper such that the height at the end114of the lug52that enters the slot56is less than the height of the opposite end116of the lug52. The lug52is preferably greater than about 1.0″ from the wall54of the finger core48to the end114of the lug52. The lug52is preferably between about 0.60-0.90″ wide and between about 2.75-3.25″ high. The taper angle A is preferably greater than about 1°.FIG. 4shows the finger core48being inserted into the C-10/kidney core50andFIG. 5shows the two cores48,50completely seated together with the first72and second74positive stops seated flush together and illustrates the smooth and substantially continuous transition section62between the two cores48,50. When the cores48,50are seated together, this interlock feature62effectively forms a transition section62having a height of greater than about 2.5″ and a width of greater than about 0.75″.

The larger size transition section forms a much more robust joint which reduces the chance of joint breakage during handling of the cores before assembly or while they are being placed as an assembly into the mold.

In an alternative embodiment (not shown), the kidney and C-10 cores are separate. The lug and the first positive stop surface are defined on the C-10 core on a second wall118. In this embodiment, the slot and the second positive stop surface are defined on the kidney core. The lug and slot and their respective stop surfaces are designed to fit together in the same way as the lug and slot from the previous embodiment.

In yet another alternative embodiment (not shown), a tab is defined on the slot and a corresponding hole is defined on the lug (or vice versa) to act as a failsafe so that the cores cannot be assembled backwards.

Another aspect of the present invention is the modification of a second transition120section (shown generally as the shaded portion inFIGS. 17 and 20) between the kidney59and C-10 60 portions of the C-10/kidney core50. As shown inFIGS. 11-13, prior art cores include an abrupt transition122at this point between these core sections59,60. This type of transition does not promote good metal flow throughout the knuckle during casting and can promote hot tears as the casting cools.

When feeding the casting from the front face18, the liquid metal tends to cool quicker in thinner sections. In prior designs, the wall thickness in this area varies quite a bit, especially in the abrupt transition section122shown inFIG. 16. Since the liquid metal has to pass through a thinner section first before coming to the thicker wall created by the abrupt transition122, it would cool more quickly which could cause defects in the final part.

In the present invention, as shown inFIGS. 4-7,14,15,17and20, material has been added to the second transition section120as compared to the same area in prior art cores such as the one shown inFIGS. 11-13,16,18and19. As shown inFIG. 17, the second transition section120is defined by the top wall124extending between the kidney side wall126of the upper C-10 core portion60and the knuckle tail side132. The bottom wall128extends between the lower wall of the C-10 core and the knuckle tail side132; the first side134and the second side136extend between the throat side138of the knuckle10and the tail side132of the knuckle10respectively. At least about 1.93″ of material has been added to the vertical height H2of this section making it at least about 3.50″ high and at least about 0.97″ of material has been added to the horizontal width W2of this section making it at least about 1″ wide. This smoother transition results in more uniform wall throat side wall140thickness as shown inFIG. 15.

This smoother transition and more uniform throat side wall140is located in the throat portion142of the knuckle10and has a first section A144closest to the knuckle tail40, a third section C148closest to the knuckle pulling face32, and a second section B146between the first144and third148sections (FIG. 16shows the same areas of typical prior art part using144a,146aand148arespectively). It is important to note that the length of each section has been generalized in the figures for reference purposes, and the claims are not meant to be limited by the exact dimensions of these sections as shown.

In one embodiment the throat side wall140thickness of the first section144is preferably greater than the throat side wall140thickness of the second section146and the throat side wall140thickness of the second section146is preferably greater than the throat side wall140thickness of the third section148. Furthermore, the difference in thickness of at least part of the throat side wall140in the first section144and at least part of the throat side wall140in the third section148is less than about 17%, the difference in thickness between at least part of the throat side wall140in the first section144and at least part of the throat side wall140in the second section146is less than about 11%, and the difference between the thickness of at least part of the throat side wall140in the second section146and at least part of the throat side wall140in the third section148is less than about 11%. In another embodiment, the difference in thickness between at least part of the throat side wall140in the first section144and at least part of the throat side wall140in the second section146is less than about 17%, and the difference between the thickness of at least part of the throat side wall140in the second section146and at least part of the throat side wall140in the third section148is less than about 30%. In yet another embodiment, the difference in thickness between at least part of the throat side wall140in the first section144and at least part of the throat side wall140in the second section146is less than about 4%, and the difference between the thickness of at least part of the throat side wall140in the second section146and at least part of the throat side wall140in the third section148is less than about 11%.

As an example, the thickness of at least part of the throat side wall140within section A144can be at least about 1.39″, the thickness of at least part of the throat side wall140within section B can be at least about 1.34″ and the thickness of at least part of the throat side wall140within section C can be at least about 1.19″. As a reference, in the prior art knuckle shown inFIG. 16, the thickness of at least part of the throat side wall140within section A144can be at least about 1.40″, the thickness of at least part of the throat side wall140within section B can be at least about 1.69″ and the thickness of at least part of the throat side wall140within section C can be at least about 1.19″.

In an additional embodiment the throat side wall140thickness of the first section144is preferably less than the throat side wall140thickness of the second section146and the throat side wall140thickness of the second section146is preferably less than the throat side wall140thickness of the third section148. In this embodiment, the thickness of the wall in the entire throat side wall142of the throat section comprising sections A, B and C varies by less than 10% throughout the throat section. In yet another embodiment, the entire throat side wall140comprising sections A, B and C varies by less than 17% throughout the tail stop side wall141. In yet another embodiment, the entire throat side wall140comprising sections A, B and C varies by less than 3.5% throughout the tail stop side wall141.

A similar change has been applied to the tail stop side133of the core. Material has been added to the vertical height H2and the horizontal width W2of this section. This smoother transition results in more uniform tail stop side wall141thickness as shown inFIG. 15. This smoother transition is located in the tail stop side wall141of the throat portion of the knuckle10and has a first section X145closest to the knuckle tail40, a third section Z149closest to the knuckle pulling face32, and a second section Y147between the first145and third149sections (FIG. 16shows the same areas of typical prior art part using145a,147aand149arespectively). It is important to note that the length of each section has been generalized in the figures for reference purposes, and the claims are not meant to be limited by the exact dimensions of these sections as shown.

In one embodiment, the tail stop side wall141thickness of at least part of the first section145is preferably greater than the tail stop side wall141thickness of the second section147and the tail stop side wall141thickness of the second section147is preferably greater than the tail stop side wall141thickness of the third section149. Furthermore, the difference in thickness between at least part of the tail stop side wall141in the first section145and at least part of the tail stop side wall141in the second section147is less than about 32%, and the difference between the thickness of at least part of the tail stop side wall141in the second section147and at least part of the tail stop side wall141in the third section149is less than about 68%. In another embodiment, the difference in thickness between at least part of the tail stop side wall141in the first section145and at least part of the tail stop side wall141in the second section147is less than about 4%, and the difference between the thickness of at least part of the tail stop side wall141in the second section147and at least part of the tail stop side wall141in the third section149is less than about 51%.

As an example, the thickness of at least part of the tail stop side wall141within section X144can be at least about 1.23″, the thickness of at least part of the tail stop side wall141within section Y can be at least about 1.19″ and the thickness of at least part of the tail stop side wall141within section Z can be at least about 0.58″. As a reference, in the prior art knuckle shown inFIG. 16, the thickness of at least part of the tail stop side wall141within section X144can be at least about 1.23″, the thickness of at least part of the tail stop side wall141within section Y can be at least about 1.81″ and the thickness of at least part of the tail stop side wall141within section Z can be at least about 0.58″.

In yet another embodiment, the entire tail stop side wall141comprising sections X, Y and Z varies by less than 32% throughout the tail stop side wall141. In yet another embodiment, the entire tail stop side wall141comprising sections X, Y and Z varies by less than 3.2% throughout the tail stop side wall141.

Furthermore, in another embodiment the tail stop side wall141thickness of the first section145is preferably less than the tail stop side wall141thickness of the second section147and the tail stop side wall141thickness of the second section147is preferably less than the tail stop side wall141thickness of the third section149. Again, in this alternative embodiment, it is preferred that the tail stop side wall141thickness throughout the entire throat section comprising sections, X, Y, and Z varies by less than 17%. In a further alternative embodiment, it is preferred that the tail stop side wall141thickness throughout the entire throat section comprising sections, X, Y, and Z varies by less than 3.5%. These changes result in a slightly thicker cross sectional area in one of the highest stress areas in the casting. The thicker area lowers the stress.

This newly designed second transition section120results in a knuckle10having walls150that are approximately 1.0″ thick or greater, as shown inFIG. 15. Additionally, an embodiment of the present invention has about 0.070″ of material less than a prior art core on the throat side138of the C-10 core60as shown inFIG. 21which shows a prior art core superimposed on an embodiment of the present core. This results in a core that measures about 2.370″ from the tail stop side wall152to the throat side wall154as shown inFIG. 21. This change results in a centrally located relief area155in the C-10 pinhole14of the resulting knuckle10that is greater than 108% of the pivot pinhole diameter, as shown inFIG. 39.

In an alternative embodiment of the invention, three cores are used as in the prior art, but with the structural changes to the transition sections as detailed above. Furthermore, with respect to utilizing separate C-10 and kidney cores, it is envisioned that a lug and slot connection mechanism with positive stops on the vertical walls of each core can be used in the same fashion as the lug and slot connection with positive stops between the C-10/kidney and finger cores, as previously described. This would form a transition section having positive stops, a lug and a slot in the area between the kidney and C-10 cores. The lug would preferably extend from the C-10 core into a corresponding slot on the kidney core.

In another aspect of the present invention, the rear core support156of the kidney section59of the C-10/kidney core50has been redesigned in order to improve core support and reduce shifting. During casting, the cores that form the interior spaces of the part are seated in the core prints of a mold160comprising cope and drag sections with the cores48,50positioned in the drag. The redesigned rear core support section156also eliminates a sharp corner162that is typically formed in prior art cores due to an acute angle164at the plane166where the rear core support156exits the cope and drag. An exemplary prior art design is shown inFIGS. 26 and 27.

The term “cavity” as used below refers to the portion of the cope and drag that forms the outside walls168of the knuckle10.FIG. 28shows the shape of the cavity in the drag with the combined cores48,50in position. The rear core support section156includes a straight section170and a flared section172and preferably extends at least 0.5″ outside the plane166of the cavity that forms the vertical outside wall168of the tail40of the knuckle10when the cores48,50are in place in the drag. Furthermore, the walls174of the rear core support156that extend outside this plane166flare outwards such that obtuse angles176are formed between the walls174and both the vertical and horizontal exit planes166,178of the rear core support156from the cavity as shown inFIGS. 22 and 24. These outwardly flared walls174increase the stability of the cores48,50, aid the solidification of the metal in these areas of the knuckle10, and reduce stress concentrations around the edge of the hole188in the knuckle tail40and reduce the likelihood of hot tears. Stress risers are also reduced in these areas due to the elimination of the acute angles in the prior art.

In a preferred embodiment the rear core support156comprises a flared section172and a straight section170. The top180and bottom182walls of the straight section170of the rear core support156are at least about 2.12″ wide. The side walls184,186of the straight section170of the rear core support156are at least about 1.76″ tall. The distance from the exit plane166to the end186of the core print is preferably at least about 0.25″. The radii of the corners196of the straight section170of the rear core support156are preferably about 0.3-0.6″. The width W3of the rear core support156is preferably about 2.12″ and the height is preferably about 1.76″. Furthermore, it is important to note that these measurements can change to accommodate different core print sizes. The area of the rear core support156is between about 1.5-4.0 square inches. In an alternative embodiment, the rear core support section156includes a smaller radius on the bottom of said rear core support section156than on the top of said rear core support section156.

The use of this core combination48,50results in a knuckle10as shown inFIG. 29that has an opening188in the knuckle tail40having a ratio of height to width of between about 1:0.4 and 1:1.3, a ratio of height to the maximum corner radius of between about 1:1.25 and 1:18, and a ratio of the width to the maximum corner radius of between about 1:1.75 and 1:22. The opening188in the knuckle tail40is between about 1.4-2.2″ wide and the height of the opening is between about 1.0-1.8″. In an alternative embodiment, the corner radii196,197are greater than about 0.25″. In a further alternative embodiment, the opening has a corner radius of between about 0.1-0.8″ In a further embodiment, the upper corner radii196are preferably at least 0.65″ and the lower corner radii197are preferably at least 0.4″.

In a further embodiment of the present invention, a method of forming a core for a coupler knuckle is provided. Traditionally, cores are formed in a mold that results in a part having a horizontal parting line199, as shown inFIG. 31. The cores are traditionally formed through a heated resin process or an Isocure process. The present invention utilizes a shell core process. As known in the art, a shell core process is a heat activated system that utilizes coated sand. The sand can be hot coated with a flaked phenolic novolak resin by mixing the resin with the sand and then heating it, melting the resin to coat the sand. The resin-coated sand is quenched with a water solution of hexamethylene tetramine and mulled until the sand mass breaks down. The sand is then aerated to particulate it. Alternatively, the sand can be warm coated. Calcium stearate, hexa-powder and water/alcohol solution of novolak resin is added to the sand and heated. This mixture is then cooled and aerated to particulate it. The coated sand from either of these processes is then placed in a heated corebox and allowed to dwell until the desired thickness of the shell of the fused sand in the heated core box is achieved. After curing, the shell is ejected from the box. Typically, in the more traditional processes which use an Isocure process, these coreboxes separate along the horizontal axis, forming a horizontal parting line and the walls are drafted accordingly.

The method of the present invention can incorporate a vertically oriented parting line190positioned along the approximate middle of the core running from the rear core extension198to the end of the C-10 portion of the core60. This parting line190is illustrated inFIG. 32on the completed core.FIG. 33shows the two halves of the corebox192in an open position. The first and second halves of the corebox192are prepared having the appropriate half of the features for the C-10/kidney core. The draft angles of the cores are also appropriately shifted to accommodate this change due to the reorientation of the parting line190. The resulting draft angle of the C-10 portion60of the vertically parted core is preferably less than 3°, which results in a C-10 portion of the final knuckle with a draft angle of less than 3° as cast. A further embodiment has no draft.

Although loading of the C-10 pin in the current design is avoided, should some loading occur after wear of knuckle10loading surfaces has occurred, a uniformly loaded C-10 pin will result because of the zero draft C-10 pin hole14. In comparison, the C-10 hole of a horizontally parted core typically has up to a 3° draft angle and results in point loading of the C-10 pin and knuckle C-10 pin hole14. Point loading of the C-10 pin is more likely to result in bending of the pin or pin failure, either of which can make the coupler knuckle10difficult or impossible to operate properly. Point loading can also occur in the drafted C-10 knuckle pin hole14, which can also lead to higher than expected loading conditions in the C-10 pin hole14. The 90° shift of the parting line allows for extremely accurate dimensioning of the C-10 pin hole as compared to point loading of a drafted C-10 pin hole.

The above method may be used to form cores through a shell core process, an air set process, or any other core production process known in the art.

Furthermore, if the cores48,50include an interlock feature such as that described above, a separate loose piece194can be used in the corebox192positioned in a recess on the outside of the C-10 portion of the corebox192on the side where the finger core48would include a corresponding lug52. The loose piece194includes an extension198on at least one side that extends into the opening that forms the C-10 portion of the core. The extension198of the loose piece preferably measures at least about 3.0″ high and at least about 0.8″ wide. Furthermore, the loose piece194includes a flat face200adjacent the extension198that forms the first positive stop74on the C-10 portion of the core. This flat face measures at least about 4.0″ high and at least about 1.3″ wide and extends 360° around the extension198.

The top knuckle pulling lug34was also redesigned to create a more unified wall thickness, as shown inFIG. 38as compared to the same area of a prior art core shown inFIG. 37. This change results in a knuckle10with a pulling lug vertical wall202that has a uniform wall thickness on the front face204of the pulling lug34. As shown inFIG. 37, the wall thickness of a traditional pulling lug face32varies from the top206of the pulling lug face32to the bottom208of the face32. In the example shown, the wall face32goes from 0.560″ at the top206of the pulling lug face to 0.49″ at the bottom208of the pulling lug face32. In the redesigned knuckle10of the present invention, the wall thickness remains substantially the same from the top206to the bottom208, as shown inFIG. 38. In an exemplary embodiment, the wall thickness remains at about 0.47-0.53″ from the top206of the pulling lug face32to the bottom208of the pulling lug face32. Alternatively, this uniform wall thickness of the front face32of the pulling lug34may be formed through the use of appropriately redesigned horizontally parted cores.

Because the pulling lugs34transmit the major portion of the longitudinal load applied to the coupler, the uniform wall thickness, particularly at the bottom radius210of the top pulling lug34, results in a stronger design. The uniform section wall thickness also permits more consistent metal filling and more consistent metal cooling, which should improve the solidity or soundness of the casting in this area and reduce the likelihood of hot tears. This is important because the AAR places a high standard on these areas of the knuckle. They are required to pass a static tension test of a minimum ultimate load of 650,000 lbs. This large load that must pass through these pulling lugs34can result in very high stress and deflections, not to mention the repeated loading of this feature creates extreme fatigue conditions requiring near perfect surface and subsurface material conditions.