BACKGROUND
The traditional three piece railway freight truck consists of one bolster and two side frames. The side frames are supported at the ends by the wheelsets. The bolster which carries the car body extends centrally through the side frames. The bolster is supported on suspension springs. Suspension damping is created by friction shoes located between the side frame column vertical wear surfaces and angled pocket surfaces in the bolster. The suspension contains load springs that support the bolster and control springs that support the friction shoes. The friction shoes angled surfaces bear against the bolster pocket having mating angled surfaces. The result of the control spring force acting on friction shoe against the angled support of the bolster is a wedge force acting on the side frame vertical wear surface. Damping is created by the wedge force of the friction shoe vertical surface and the side frame vertical wear surface creates sliding force resistance to movement. The friction shoe sliding force resistance increases as the control springs are compressed. The sliding force resistance reduces the vertical acceleration of the car mass, which allows the railway freight car to be stable for most track perturbations.
When the rail vehicle encounters vertical track perturbations that accelerate the traditional three piece railway freight truck suspension so there is limited compression of the control springs against the friction shoes, little sliding force resistance occurs and the rail vehicle vertical velocity increases. The force of friction is diminished when the friction shoe sliding velocity increases to the point that the friction shoe flat surface has low contact force to the side frames mating flat surface. This is due to a large difference in shoe flat surface material static to dynamic friction coefficient. The friction shoe is static till there is sufficient force to overcome the static friction. The large difference between static and dynamic friction allows the shoe to accelerate with such force there is little to no dynamic damping. The materials surface roughness, uneven force imparted on the shoe, and the structure vibration add to the low damping of the friction shoe. Once these conditions occur the control spring force upon the friction shoe is not sufficient and the vertical acceleration becomes excessive and the rail vehicle stability is reduced.
SUMMARY
The present friction damping arrangement stabilizes the friction shoe with a constant force device adjacent to and acting directly on the shoe vertical surface, such that it forces the friction shoe to remain in contact with the side frame mating surface creating resistance to sliding by constant damping. When variable damping is diminished, constant damping of the friction shoes is retained, which decreases vertical acceleration of the railway freight car, providing stability for most track conditions.
The present friction damping arrangement balances the constant force device with sufficient force acting directly on the friction shoe vertical surface material such that the low static to dynamic friction can be used. Since the dynamic friction is retained the railway freight car vertical velocity is reduced.
The present invention constant force device provides force through the bolster acting on the friction shoe vertical surface in turn acting on the side frame vertical wear surface. The force between the side frames and bolster is sufficient to prevent warping or parallelogram movement of the railway freight car truck wheel set and bolster in relationship to the side frames. The added force to prevent warping, increases the stability of the three piece railway freight car truck.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 is a perspective view of a railway freight car truck assembly in accordance with first embodiment of the present invention;
FIG. 2 is a partial cut away view of a railway freight car truck suspension in accordance with a first embodiment of the present invention;
FIG. 3 is a partial exploded view of a bolster and friction shoes of a railway freight car truck in accordance with a first embodiment of the present invention;
FIG. 4 is partial cut away view of the bolster end and friction shoes of a railway freight car truck in accordance with a first embodiment of the present invention;
FIG. 5 is a detailed partial cross sectional view of the bolster end and friction shoes with the cam per load device of a railway freight car truck in accordance with a first embodiment of the present invention.
DETAILED DESCRIPTION
Referring now to FIG. 1, is a perspective view of a three piece railway freight car truck assembly 1 is seen to be comprised of two laterally spaced side frames 7 between which bolster 8 extends. Bolster 8 is seen to include bolster ends 11, which extend through side frame 7 openings 14. Suspension springs 13 support bolster end 11 as well as friction shoes 12. Friction shoes 12 provide vertical damping in the form of sliding resistance between the side frames 7 and bolster 8. Bolster 8 is seen to include on its upper surface a bolster center bowl 10, and a pair of laterally spaced side bearings 9. Wheelset 5 consist of two wheels 2 pressed on an axle 3. Wheelset 5 has axle roller bearings 4 mounted at both ends of axle 3. The wheelset 5 bearings 4 support the side frames 7 on bearing connectors 6.
Referring now to FIG. 2, is a detailed cut away view of a traditional three piece railway freight truck suspension is shown with detailed partial views of bolster 8 and side frame 7 in partial section. Bolster ends 11 extend through side frame opening 14 which are supported by suspension springs 13. Suspension springs 13 consist of load springs 18 which support the bolster 8 and rail vehicle. Suspension springs 13 also include the control springs 17 that support friction shoes 12 that have a sloped surface bearing against a complementary sloped surface forming bolster angular pocket 20. The suspension springs 13 are compressed by the rail vehicle weight, lading, and track perturbations that occur when the rail vehicle is in transit. Damping is the result of the wedge force on the friction shoe 12 flat surface 22 resistance to sliding against and along the wear plate 16 of the side frame 7. The control spring 17 compression and force varies depending on the vehicle weight, lading and track perturbations that displace the rail vehicle vertically during transit. Variable damping is the result of the control spring 17 varying compression and force. The lateral springs 15 bear against the center rib 19 and place a constant force directly into shoes 12 that simultaneously direct the force to friction shoe 12 flat surface 22, which resists the sliding against and along vertical wear plate 16 of the side frame 7. The lateral springs 15 provide compression and force that are constant; therefore constant damping occurs.
Referring now to FIG. 3 a partial exploded view of bolster 8 and friction shoes 12 is shown. Friction shoe 12 is cast of steel or iron. The friction shoe 12 has a recessed surface 22 to hold the friction shoe insert 29. The friction shoe insert 29 is a composite or metallic material. The friction shoe 12 on its angled surface 21 has recesses 23 to retain lateral springs 15. The lateral springs 15 protrude through apertures 24 in the bolster angled pockets 20. The lateral springs 15 are preloaded and retained by cam 25 that are inserted through the bolster end 11 retaining holes 27 and the friction shoe 12 retaining holes 28. The cam 25 has a socket 26 on the end. Cam 25 with socket 26 are used to preload lateral springs 15.
Referring now to FIG. 4 is detailed cut away of the bolster end 11 and friction shoes 12 with the cam 25 per load device. The lateral springs 15 are preloaded and retained by cam 25 that is inserted through the bolster end 11 retaining holes 27 and the friction shoe 12 retaining holes 28. The cam 25 has a socket 26 on the end. Once the cam 25 is in place, it can be turned 90 degrees in retaining holes 27 and the friction shoe 12 retaining holes 28. The rotation of 90 degrees extend cam 25 against friction shoe 12 which in turn compress lateral springs 15. Once the bolster 8 is assembled into the side frames 7, the cam 25 with socket 26 can be turned 90 degrees and the lateral springs 15 will apply a constant force on friction shoe 12.
Referring now to FIG. 5 is a section of the bolster end 11 and friction shoes 12 with the cam 25 per load device. The lateral springs 15 are preloaded and retained by cam 25 that is inserted through the bolster end 11 retaining holes 27 and the friction shoe 12 retaining holes 28. The cam 25 has a socket 26 on the end. Once the cam 25 is in place, it can be turned 90 degrees in retaining holes 27 and the friction shoe 12 retaining holes 28. The rotation of 90 degrees extend cam 25 against friction shoe 12 which in turn compress lateral springs 15. Once the bolster 8 is assembled into the side frames 7, the cam 25 with socket 26 can be turned 90 degrees and the lateral springs 15 will apply a constant force on friction shoe 12.
Patent Application
20190092354
