Patent Application
20090301826
The present disclosure generally relates to railroad freight cars and, more particularly, to a a strut assembly for a railroad freight car brake beam assembly and a method of manufacturing such a railroad freight car strut assembly.
Railroad freight cars typically include an elongated car body supported toward opposite ends by a pair of wheeled trucks. Each wheeled truck includes a bolster laterally extending between two side frames with a wheel and axle assembly arranged to front and rear sides of the bolster. Each railcar also has a brake system operably associated therewith. A conventional brake system includes a brake beam assembly associated with each wheel and axle assembly and which is connected to brake rigging on the railcar. Each brake beam assembly is supported between the truck side frames to allow it to be operated into and out of braking positions in relation to the respective wheel and axle assembly.
One form of brake beam assembly commonly used in the railcar industry includes a compression member and a tension member arranged in a truss-like configuration with a strut assembly extending therebetween. A brake head, with a replaceable brake shoe, is arranged at each end of the brake beam assembly. It has been found beneficial for the brake beam assembly to maintain both a degree of camber in the compression member and a degree or level of tension in the tension member.
Brake beam assemblies on the railcar are typically operated in simultaneous relation by a power source from a brake cylinder or a hand brake and, through leverage, transmit and deliver braking forces to the brake shoes at the wheels of each wheel and axle assembly. On a typical railcar, brake rigging, including a brake push rod, transmits force, caused by the push of air entering the brake cylinder or by the pull of the hand brake, to the brake shoes.
The brake rigging on the railcar, used to transmit and deliver braking forces to the braking shoes of each wheel assembly, comprises a multitude of linkages including various levers, rods and pins. For example, brake levers are used throughout the brake rigging on each car to transmit as well as increase or decrease the braking force on each wheel and axle assembly
A conventional strut assembly on a railroad freight car brake beam assembly includes an elongated strut having a hollow center portion and two joined sides or walls, with one side being arranged on opposite sides of a longitudinal axis of the strut. When the brake beam assembly is assembled, the strut is operably connected to the tension and compression members proximate midlength of such members. A conventional strut has an axially elongated and generally centralized, close-ended slot between the two sides of thereof. Typically, a central portion of a brake lever extends through and is pivotally mounted in the slot between the opposed sides of the strut. Besides being pivotally supported by the strut, opposite ends of the brake lever are articulately connected through suitable connections to the railcar brake rigging. About midlength thereof, the strut defines two openings or bores aligned along an axis extending generally normal to the longitudinal axis of the strut. A lengthwise portion of a pivot pin passes endwise through the bores and through the central portion of the brake lever to define an axis about which the brake lever pivots during railcar operation.
To lower the upper end of the brake lever relative to the position it would occupy if the brake lever were vertical, such brake levers are inclined lengthwise of the brake beam a certain number of degrees, usually about 40°. The strut is designed to accommodate suitable inclination of the brake lever from vertical. To reduce strut wear and to facilitate operation of the brake beam assembly during operation of the railcar, a conventional strut assembly includes two brake pin bushings seated in the bores of the strut and which journal the pivot pin for the brake beam.
During use, a railcar can travel tens of thousands of miles between locations and over railbeds, some of which can be in significant disrepair. During railcar travel, the brake lever and related parts of the braking system are subject to vibration and wear. Accordingly, it is not unusual for one or more of the brake pin bushings to unseat from its respective strut bore and separate from the strut. The inclination of the bushings from vertical, coupled with gravity, also tends to cause at least one of the brake pin bushings to remove itself from the respective bore in the strut. Moreover, current research shows the brake pin bushings are exposed to forces and components of forces acting in a direction working to unseat or displace the brake pin bushings from their respective bore and be driven the out of position relative to the strut.
In some designs, the brake pin bushings are fabricated from a powder sintered metal. Unless powder sintered metal bushings are properly seated within their respective strut bore, such bushings can crack as they become displaced from their respective strut bore. Moreover, and even if such brake pin bushings remain partially seated in the strut bore, the powder sintered metal bushing is prone to chipping. Wear on the brake pin bushings can change the disposition about which the brake lever pivots, thus, changing the pressure exerted by the brake pads to the railcar wheels. Moreover, and under the rules of the American Association of Railroads (the “AAR”), bushing wear and cracking can result in condemnation of the brake beam assembly.
For a myriad of reasons, railroad freight cars are routinely inspected. Part of the inspection process involves an analysis of each railcar brake beam assembly on the railcar. When a particular railroad freight car is identified as having a brake beam assembly requiring repair or replacement, the freight car requiring such repair is usually separated from the remaining cars in the train consist and, then, moved to a facility where such repairs can be affected. Only after a suitable repair facility has been identified and becomes available, can replacement of a condemned brake beam assembly be affected.
Replacing a railcar brake beam assembly, for whatever reason, can be a time consuming process. Moreover, the valuable time lost in separating the railcar with the condemned brake beam from the remaining cars in the train consist, coupled with the time lost in scheduling a repair facility to accomplish replacement of the brake beam assembly, and the valuable time lost in affecting the repair or replacement of the condemned brake beam, along with the time lost in having to move the car with the condemned brake beam to the repair facility for replacement of the brake beam assembly are other considerations and unrealized costs involved with replacing a condemned brake beam. Of course, during this entire time period, the railcar is removed from service. Replacement of the condemned brake beam must also include the time lost in joining the repaired car to a train consist directed toward the original destination of the repaired car.
Thus, there is a continuing need and desire for a railroad freight car strut assembly and method of manufacturing a railroad freight car brake beam strut assembly wherein the brake pin bushings are inhibited from inadvertent displacement away from the axis of the strut assembly whereby extending the life of the strut assembly and thus reducing the time and expense the railcar can be out of service due to a faulty brake beam assembly.
In view of the above, and in accordance with one aspect, there is provided a method of manufacturing a railroad freight car brake beam strut assembly including the step of: providing a railroad freight car brake beam strut having a hollow center portion and an axially aligned slot defined between first and second joined sides or walls of the strut, with each side of the strut defining a bore opening to the hollow center portion and to an exterior of the strut, with the bores defined by the strut being aligned relative to each other along an axis extending generally normal to a longitudinal axis of the strut. The methodology of the present disclosure further includes the step of: pressing a bushing into each bore of the strut in a direction extending away from the longitudinal axis of the strut.
Preferably, the method of manufacturing a railroad freight car brake beam strut assembly can include the further step of: configuring at least one end of each bushing to facilitate and guide its entry into one of the bores defined by the strut. The method of manufacturing a railroad freight car brake beam strut assembly furthermore preferably includes the step of: providing a stop in operable combination with each brake pin bushing of the strut assembly. The stop for each brake pin bushing can be provided on either the strut or the brake pin bushing. In one form, an outer periphery of each brake pin bushing has a frusto-conical configuration, with one end of the brake pin bushing having a diameter smaller than an inner diameter defined by the strut bore, and a second end of the bushing having an outer diameter larger than the inner diameter defined by the strut bore.
According to another aspect, there is provided a method of manufacturing a railroad freight car brake beam strut assembly including the step of: providing a railroad freight car brake beam strut having a hollow center portion along with an axially aligned slot defined between first and second joined sides or walls of the strut, with the first side of the strut defining a first bore opening to the hollow center portion and to an exterior of the strut, and with the second side of the strut defining a second bore opening to the hollow center portion and to the exterior of the strut, and with the first and second bores defined by the strut being aligned relative to each other along an axis extending generally normal to a longitudinal axis of the strut and which is angled relative to vertical when the strut assembly is connected to a brake beam assembly. The method of manufacturing the railroad freight car brake beam strut assembly includes the further step of: pressing a first brake pin bushing into the first bore of the strut in a direction extending away from the longitudinal axis of the strut. The method of manufacturing the railroad freight car brake beam strut assembly further includes the step of: pressing a second brake pin bushing into the second bore of the strut in a direction opposed to the direction the first brake pin bushing is pressed into the first bore and extending away from the longitudinal axis of the strut.
Preferably, the method of manufacturing the railroad freight car brake beam strut assembly includes the further step of: configuring at least one end of each brake pin bushing to facilitate and guide their entry into one of the bores defined by the strut. In one form, each bushing defines an opening extending therethrough.
The method of manufacturing a railroad freight car brake beam strut assembly involves the further step of: repositioning the strut after the first brake pin bushing is pressed into the first bore and before the second brake pin bushing is pressed into the second bore in the strut. In one form, the method of manufacturing the railroad freight car brake beam strut assembly includes the further step of: extending a tool, operably coupled to a press, through the opening in the first brake pin bushing so as to press the second brake pin bushing into the second bore of the strut in a direction opposed to the direction the first brake pin bushing is pressed into the first bore and extending away from the longitudinal axis of the strut.
Preferably, the process for manufacturing a railroad freight car strut further involves the step of: arranging a stop in operable combination with each brake pin bushing of the strut assembly. In one form, an annular lip is provided on the strut in operable combination with each brake pin bushing. In another form, the outer periphery of each bushing has a tapered configuration, with one end of the bushing having a diameter smaller than an inner diameter of the bore in the strut, and a second end of the bushing having an outer diameter larger than the inner diameter of the bore in the strut. In another form, a brake pin bushing stop is provided on the strut. In yet another embodiment, the stop for each brake pin bushing is formed as part of the brake pin bushing.
According to another aspect, there is provided a method of manufacturing a railroad freight car brake beam strut assembly including the step of: providing a railroad freight car brake beam strut having a hollow center portion along with an axially aligned slot defined between first and second joined sides of the strut, with the first side of the strut defining a first bore opening to the slot and to an exterior of the strut, and with the second side of the strut defining a second bore opening to the slot and to the exterior of the strut, with the first and second bores defined by the strut being aligned relative to each other along an axis extending generally normal to a longitudinal axis of the strut. The method of manufacturing the railroad freight car brake beam strut assembly includes the further step of: pressing a first sintered powdered metal bushing into the first bore of the strut in a direction extending away from the longitudinal axis of the strut. Moreover, the method of manufacturing the railroad freight car brake beam strut assembly includes the further step of: pressing a second sintered powdered metal bushing into the second bore of the strut in a direction opposed to and paralleling the direction the first bushing is pressed into the first bore and extending away from the longitudinal axis of the strut.
Preferably, the method of manufacturing the railroad freight car brake beam strut assembly includes the further step of: configuring at least one end of each bushing to facilitate and guide its entry into one of the bores defined by the strut. In one form, the method of manufacturing a railroad freight car brake beam strut assembly includes the further step of: repositioning the strut after the first bushing is pressed in the first bore and before the second bushing is pressed into the second bore in the strut.
According to a preferred embodiment, the process for manufacturing a railroad freight car strut further involves the step of: arranging a stop in operable combination with each brake pin bushing to limit movement of each brake pin bushing in a direction extending away from the longitudinal axis of the strut. In one form, the stop arranged in operable combination with each brake pin bushing is pressed into the strut in a direction extending away from the longitudinal axis of the strut is formed as part of or in combination with the strut. Alternatively, the stop for each brake pin bushing is formed as part of or in combination with each brake pin bushing.
According to another aspect, there is provided a method of manufacturing a railroad freight car brake beam strut assembly includes the step of: providing a railroad freight car brake beam strut defining a longitudinal axis and having a hollow center portion along with an axially aligned slot defined between first and second joined sides of the strut, with each side of the strut defining a bore opening to the hollow center portion and to an exterior of the strut, with the bores defined by the strut being aligned relative to each other along an axis extending generally normal to a longitudinal axis of the strut. According to this aspect, the method of manufacturing a railroad freight car brake beam strut assembly includes the further step of: pressing a brake pin bushing into each bore of said strut in a direction extending away from the longitudinal axis of said strut. According to this aspect, the method of manufacturing a railroad freight car brake beam strut assembly furthermore includes the step of: providing a stop in operable combination with each brake pin bushing of the strut assembly.
Preferably, the method of manufacturing a railroad freight car brake beam strut assembly includes the further step of: configuring at least one end of each brake pin bushing to facilitate and guide its entry into one of the bores defined by the strut. In one form, the stop arranged in operable combination with each brake pin bushing is provided on the strut. In another form, a stop arranged in operable combination with each brake pin bushing is formed integral with the strut. In still another form, the stop arranged in operable combination with each brake pin bushing is formed as part of the brake pin bushing.
According to yet another aspect, there is provided a railroad freight car brake beam strut assembly including an elongated strut defining a longitudinal axis and having a hollow center portion with an axially elongated slot between first and second joined walls of the strut. The slot in the strut is inclined a predetermined number of degrees from vertical for accommodating an elongated brake lever extending through the strut. Each side wall of the strut defines a bore opening to the hollow center portion and to an exterior of the strut. The strut bores are aligned relative to each other to accommodate a lengthwise portion of a brake lever pivot pin extending through strut thereby connecting the brake lever to the strut and so as to define an axis about which the brake lever pivots. The strut assembly further includes a pair of brake pin bushings. One brake pin bushing is accommodated in each strut bore so as to journal the lengthwise portion of the brake lever pivot pin extending through the strut. Each brake pin bushing has first and second axially spaced ends. The strut assembly furthermore includes means for limiting the extent to which each brake pin bushing is inserted into each bore defined by the strut assembly in a direction extending away from the longitudinal axis of the strut.
Preferably, each brake pin bushing of the strut assembly is sized relative to the respective strut bore such that an interference fit is established between a periphery of the brake pin bushing and an inside diameter of the bore defined by the strut. In a preferred form, each brake pin bushing is formed from powdered sintered metal material.
While the present disclosure is susceptible of embodiment in multiple forms, there is shown in the drawings and will hereinafter be described preferred methods of manufacture, and the present disclosure is to be considered as setting forth exemplifications of various embodiments and methodologies which are not intended to limit the disclosure to the specific embodiments illustrated and methodologies described.
Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views,
As shown in
Each wheel and axle assembly 24 on railcar 10 has a brake beam assembly 30 arranged in operable combination therewith. In the illustrated embodiment, the side frames 18, 20 on each truck conventionally guide and support the brake beam assembly 30 for generally horizontal sliding movements. As shown in
Typically, each brake beam assembly 30 has brake heads 38 with friction brake shoes 39 disposed toward opposed ends thereof for engagement with the respective wheels 26, 28 of an associated wheel and axle assembly. The brake shoes 39 are moved into and out of braking relation with the wheels 26, 28 of a respective wheel and axle assembly through brake rigging, generally identified in
The strut assembly 36 of the brake beam assembly 30 shown in
A methodology for manufacturing the strut assembly 36 is disclosed. According to the present disclosure, the method for manufacturing a railroad freight car brake beam strut assembly includes the step of providing a railroad freight car brake beam strut, identified generally in
As shown in
As shown in
To reduce wear on the strut 36 resulting from continuous pivoting movements of the brake lever 42 about axis 55, strut assembly 36 further includes a pair of brake pin bushings 58 and 59. Bushings 58 and 59 are accommodated in the bores 51 and 53, respectively, of the strut 37 so as to journal a lengthwise portion of the brake lever pivot pin 54 extending endwise therethrough. In a preferred form, the brake pin bushings 58 and 59 are substantially identical relative to each other and are fabricated from a sintered powdered metal.
Brake pin bushing 58 has an outside diameter 58′ sized to establish a snug fit within the bore 51 in the side wall 50 of strut 37. In one form, the each brake pin bushing is such that a press fit is established between the outside diameter of the brake pin bushing 58 and the inner diameter of the respective strut bore into which the brake pin bushing is to be inserted. Each brake pin bushing also defines a throughbore 60 having an inner diameter 60′ which is sized relative to that portion of the brake lever pivot pin 54 passing theretrough. Moreover, brake pin bushing 58 has a first end 61 and an axially spaced second end 61′. Preferably, the axial spacing between the ends 61, 61′ of brake pin bushing 58 is generally equal to the cross sectional wall thickness of the strut 37 (the distance measurable between inner and outer strut surfaces in the area wherein the bore 60 passes therethrough). Similarly, brake pin bushing 59 has an outside diameter 59′ sized to establish a suitable press fit with the bore 53 in the side wall 52 of strut 37. Brake pin bushing 59 also defines a throughbore 60′ having an inner diameter 60′ which is sized relative to that portion of the brake lever pivot pin 54 passing therethrough. Moreover, brake pin bushing 59 has a first end 61 and an axially spaced second end 61′. Preferably, the axial spacing between the ends 61, 61′ of brake pin bushing 59 is generally equal to the cross sectional wall thickness of the strut 37 (the distance measurable between inner and outer strut surfaces in the area wherein the bore 60 passes therethrough). Each brake pin bushing 58, 59 is sized such that it can be passed into and through the slot 48 and can be positioned between the side walls 50, 52 of the strut 37 in the hollow center portion 41 of the strut 37.
According to the present disclosure, the method for manufacturing a railroad freight car brake beam strut assembly includes the further step of pressing bushings 58, 59 into bores 51, 53, respectively, of the strut 37. Notably, however, and according to the present disclosure, each brake pin bushing 58, 59 is pressed into the respective bore 51, 53 of the strut 37 in a direction extending away from the longitudinal axis 46 of the strut 37.
As shown by way of example in
In one form, a suitably configured plate or disc 63 is extended through the slot 48 between the side walls 50, 52 of strut 37 and is inserted between a distal end of the tool T and the brake pin bushing 58 to facilitate insertion of the brake pin bushing 58 into the bore 51 of the side wall 50 of the strut 37. In a most preferred form, the brake pin bushing 58 is pressed into the bore 51 defined by the side wall 50 until the brake pin bushing 58 reaches a predetermined position within bore 51 of strut 37. After the brake pin bushing 58 is positioned in bore 51 of strut 37, tool T is retracted and the plate or disc 62 is removed from the strut 37.
In the example shown in
After strut 37 is repositioned and operably supported in press P, as shown in
To facilitate insertion of the brake pin bushing 59 into the bore 53 of the strut side wall 51, the above-mentioned plate or disc 63 is extended through the slot 48 between the side walls 50, 52 of the strut and is inserted between a distal end of the tool T and the brake pin bushing 59. In a most preferred form, brake pin bushing 59 is pressed into the bore 53 defined by the strut side wall 52 until the brake pin bushing 59 reaches a predetermined position within bore 53 of strut 37. After the brake pin bushing 59 is positioned in bore 53 of strut 37, tool T is retracted and the plate or disc 62 is removed from the strut 37. Of course it will be appreciated the sequence of pressing the brake pin bushings 58, 59 into their respective bores 51, 53 can be reversed from that described above without detracting or departing from the spirit and scope of the present disclosure.
In a preferred embodiment, each brake pin bushing 58, 59 is suitably configured to facilitate insertion into their respective bores 51, 53 defined by strut 37. Although only one brake pin bushing is illustrated in
Although only one strut bore is shown by way of example in
In yet another embodiment, both the end of each brake pin bushing and the each strut bore can be configured to facilitate insertion of the brake pin bushing into the respective strut bore. That is, the end of each brake pin bushing adapted to be initially inserted into the respective strut bore can be chamferred or otherwise configured to facilitate insertion of the brake pin bushing 58, 59 into operable combination with the strut 37. Additionally, the annular marginal edge of each strut bore disposed closet to the longitudinal centerline or axis 46 of strut 37 can be chamferred or otherwise configured to facilitate insertion of the brake pin bushing 58, 59 into operable combination with the strut 37.
In a preferred embodiment, and as mentioned above, each brake pin bushing 58, 59 is pressed into operable association with strut 37 until each brake pin bushing reaches a predetermined position within the respective bore 51, 53 of strut 37. Preferably, a stop, generally indicated in
Since the stop 70 operably associated with brake pin bushing 58 is preferably the same as the stop 70 operably associated with the brake pin bushing 59, only the stop 70 arranged in operable combination with brake pin bushing 58 will be discussed in detail. In the embodiment illustrated in
In the example in
In the embodiment illustrated in
In the embodiment illustrated in
In the embodiment illustrated in
Another form of brake pin bushing, generally identified by reference numeral 458 in
As shown in
The head portion 472 of each brake pin bushing is sized radially larger than the outside diameter 458′ of the shank portion 474 of the brake pin bushing 458 such that a radial shoulder 475 is defined therebetween. Shoulder 475 on the brake pin bushing is designed to abut against the inner surface of the strut after the brake pin bushing is pressed into its predetermined position relative to the respective bore of the strut. Notably, the head portion 472 of the brake pin bushing is configured to extend radially past the outer diameter 458′ of the shank portion 474 of the brake pin bushing only to the extent required to limit axial displacement of the respective brake pin bushing into the respective strut bore into which the brake pin bushing is inserted and to limit inadvertent axial displacement of the brake pin bushing in a direction away from the axis 46 of strut assembly 36 during operation of the brake beam assembly 30 (
In the exemplary embodiment illustrated in
Still another form of brake pin bushing, generally identified by reference numeral 558 in
According to this embodiment, and as shown in
In this embodiment, each brake pin bushing further has a tapering outside surface 559′ whereby providing the brake pin bushing with a slight frusto-conical outer configuration. That is, the outer generally cylindrical surface of each brake pin bushing has a substantially constant taper extending axially between the first and second ends 561 and 561′, respectively, of the bearing. In the illustrated embodiment, the end of the brake pin bushing disposed proximate to the first end 561 has an outer diameter which is only slightly less than the inner diameter of the strut bore into which it is to be inserted. In one form, the end of the brake pin bushing disposed proximate to the first end 561 has an outer diameter which is about 0.005 inches smaller than the diameter of the strut bore into which the brake pin bushing is to be inserted. In the illustrated embodiment, that end of the brake pin bushing disposed proximate to the second end 561′ has an outer diameter which is slightly larger than the inner diameter of the strut bore into which it is to be inserted. In one form, the end of the brake pin bushing disposed proximate to the second end 561′ has an outer diameter which is about 0.030 inches larger than the diameter of the strut bore into which the brake pin bushing is to be inserted. Of course, rather than taper the outer surface of each brake pin bushing, it is within the spirit and scope of the present disclosure to either: taper the inner surface of the respective strut bores and maintain a substantially constant diameter for each brake pin bushing; or, to taper both the inner surface of the respective strut bores and the outer surface of each brake pin bushing to accomplish the desired end of inhibiting inadvertent axial shifting of the brake pin bushings in away from the axis 46 of the strut 37 after such brake pin bushings are arranged in operable combination with the strut 37.
In the illustrated embodiment, the outer surface 559′ of each brake pin bushing preferably has a generally constant taper between the opposed ends 561, 561′. As such, and when the brake pin bushing is pressed into the respective strut bore, in a direction extending generally normal to the axis 46 of the strut 37, a lengthwise portion of the tapering outer surface 559′ of the brake pin bushing will operably engage with the inner surface of the strut bore into which the bushing is being pressed in a manner inhibiting axial movement of the brake pin bushing in a direction extending away from the axis 46 of strut 37.
Regardless of which variety of stop or brake pin bushing design is utilized in combination with the strut assembly, and although the brake pin bushings are inclined a predetermined number of degrees from vertical during use of the brake beam assembly 30, one of the salient features of this disclosure involves the process of pressing the brake pin bushings into their respective strut bores in a direction away from the axis 47 of the strut 37. Moreover, the use of a limit stop in operable combination with each bushing, whether formed as part of the strut or part of the brake pin bushing, serves to positively position each brake pin bushing in predetermined relation relative to the respective strut bore into which the bushing is pressed. Furthermore, the provision of a limit stop in operable combination with each brake pin bushing and/or strut advantageously serves to limit inadvertent axial displacement of either brake pin bushing in the respective strut bore in a direction extending away from the longitudinal axis of the strut thus prolonging the usefulness of the brake pin bushings while maintaining a fixed axis about which brake lever rotates thereby enhancing performance of the brake beam assembly over an extended time period. The ability to maintain the brake pin bushings in operable combination with the strut while limiting axial displacement of the brake pin bushings away from the centerline of the strut during brake operation provides the brake lever, pivoting about the brake pin journalled by the bushings, with a relatively constant axis about which to pivot thereby offering consistent performance of the brake beam assembly during operation. These and other objects, aims and advantages of the present disclosure are all provided with minimal costs and simplistic design changes.
From the foregoing, it will be observed that numerous modifications and variations can be made and effected without departing or detracting from the true spirit and novel concept of the present disclosure. Moreover, it will be appreciated, the present disclosure is intended to set forth an exemplifications which are not intended to limit the disclosure to the specific embodiment illustrated. Rather, this disclosure is intended to cover by the appended claims all such modifications and variations as fall within the spirit and scope of the claims.
