Patent Application
20130055922
1. Field of the Invention
The invention relates to a wheel truck of a railroad freight car.
2. Description of the Related Art
As a critical part of a railroad freight car, a typical wheel truck includes two side frame assemblies and a bolster assembly. Journal-box guides disposed on two ends of the frame assembly are fixed on a front wheel pair and a rear wheel pair via roller bearing adapters, respectively. The bolster assembly has two ends, each of which is mounted in a central square box of the side frame assembly via a spring suspension device for supporting the load from the bolster assembly. The bolster assembly includes a lower center plate in the center and two lower side bearings on two ends. The lower center plate and the lower side bearings are matched with an upper center plate and two upper side bearings on the lower base of the freight car for supporting the weight of the freight car.
In early supporting structure of the freight car, the lower center plate of the bolster assembly supported all loads of the car body, whereas the lower side bearings assisted for positioning. Thereafter, in order to improve the critical speed of an empty freight car, the lower center plate was improved as a primary bearing structure, and the lower side bearing was improved to assist for supporting. The friction between the upper and lower side bearings can act as a resistance during the turnaround of the wheel truck to meet the requirement of speed-raising.
In above descriptions, the supporting achieved totally by the lower center plate and the supporting achieved by the combination of the lower center plate and the lower side bearings are commonly called center plate-type supporting. The wheel truck having the center plate-type supporting is advantageous in that when crossing curved tracks, the wheel truck is flexible in turning around, and the load is uniformly distributed on the wheels. However, it has defects that the vertical load of the body is directly applied on the center of the bolster assembly, and transmitted to the square boxes via the bolster assembly, which results in a large bending moment and sectional area of the bolster assembly. Correspondingly, the weight and the production cost of the assembly are increased, and the center plate has a low stability in rolling. Thus, it is very significant to eliminate the large bending moment produced by the bolster assembly and improve the performance and the running stability of the freight car when crossing curved tracks.
In view of the above-described problems, it is one objective of the invention to provide a wheel truck that has a light weight, reasonable stress state, good performance in crossing curved tracks, stable running, and meets the requirement of the speed-raising.
To achieve the above objective, in accordance with one embodiment of the invention, there is provided a wheel truck, comprising: a front wheel pair assembly and a rear wheel pair assembly; two side frame assemblies, each side frame assembly comprising a square box in a center and journal-box guides on two ends, and the journal-box guides being disposed on roller bearing adapters; two spring suspension devices, the two spring suspension devices being disposed in the square boxes of the two side frame assemblies, respectively; and a bolster assembly comprising two ends which are disposed on the two spring suspension devices, respectively. The bolster assembly comprises a pilot hole in a center and two mounting holes on the two ends, the pilot hole is rotationally matched with a cylindrical upper center plate of a car body for transmitting vertical and horizontal forces from the car body, and the two mounting holes are disposed above the two spring suspension devices, respectively. Each mounting hole receives a lower side bearing, and the lower side bearing is matched with a corresponding upper side bearing disposed on each side of the car body for transmitting the vertical load from the car body.
The vertical load of the car body is directly transmitted to the lower side bearings via the upper side bearings, then to the bolster assembly, and finally to the spring suspension device of the side frame assembly. The bolster assembly just bears pressures from the lower side bearings and the spring suspension device, and in the meanwhile, bending moment cannot be produced due to the vertical load of the car body. Thus, the weight of the bolster assembly can be largely decreased, and the stability of the bolster assembly can be greatly improved.
In a class of this embodiment, the lower side bearing comprises a first friction board, a second friction board, an inner pedestal, a bearing sleeve sleeving the inner pedestal, a pressure block, and an elastic component. The pressure block is disposed on an upper part of the inner pedestal, and the second friction board is disposed on a top of the pressure block. The first friction board is disposed on a top of the bearing sleeve. A friction coefficient of the first friction board μk and a friction coefficient of the second friction board μz meet the relation: μk>μz. The elastic component is disposed between the inner pedestal and the bearing sleeve for controlling a relative position of the inner pedestal and the bearing sleeve. A mechanical property of the elastic component meets following requirements: a) in an empty loaded state, a level position of the first friction board is higher than that of the second friction board so that the first friction board bears the load of the car body; and b) in a heavy loaded state, the level position of the first friction board is equal to that of the second friction board so that the first friction board and the second friction board bear the load of the car body.
The lower side bearing comprises the first friction board and the second friction board for supporting load in empty and heavy states; and the relative position of such friction boards are limited by the elastic component. When the car body is in the empty state, the weight of the car body is supported only by the first friction board, at this moment, the lower side bearing is in an elastic state, acting as a third elastic suspension system. Because the first friction board has a larger friction coefficient and a large static deflection, the critical speed and the safety in wheel load reduction can be improved during the empty state. When the car body is in the heavy loaded state, the first friction board is pressed down to the same level position as the second friction board. In such a state, both the first friction board and the second friction board support the load of the car body, the lower side bearing is in a rigid supporting state, and the stability of the freight car during the rolling of the wheel is improved. Because the second friction board has a smaller friction coefficient, the wheel truck has a good performance in crossing the curved racks in the heavy loaded state.
Advantages of the invention are summarized as follows:
The invention is described hereinbelow with reference to the accompanying drawings, in which:
To further illustrate the invention, experiments detailing a wheel truck are described. It should be noted that the following examples are intended to describe and not limited to the invention.
As shown in
As shown in
The height difference h controlled by the elastic component 5, the friction coefficient of the first friction board 3 μk and the friction coefficient of the second friction board 1 μz can be designed or adjusted according to the empty loaded state and the heavy loaded state, respectively. In actual manufacturing, the lower side bearing 13 employs the following two structures: One is that an outer wall of the inner pedestal 6 and an inner wall of the bearing sleeve 4 are in the form of conical structures. The elastic component 5 is a conical rubber layer disposed between the outer wall of the inner pedestal 6 and the inner wall of the bearing sleeve 4; and the elastic component 5, the outer wall of the inner pedestal 6, and the inner wall of the bearing sleeve 4 are integrated as a whole by sulfurization (as shown in
Working principle of the lower side bearing 13 is as follows: when the car body is in an empty loaded state, the first friction board 3 is higher than the second friction board 1, that is, a height difference h is formed. In such a state, the upper side bearing 17 presses on the first friction board 3 only. Because the deflection which is produced by the elastomer of the lower side bearing 13 due to the weight of the car body is smaller than the height difference h, the lower side bearing 13 is in an elastic state, and acts as a third elastic suspension system when the freight car is empty loaded. Further, because the first friction board 3 has a larger friction coefficient μk, it assures a high critical speed of the wheel truck in the empty loaded state. When the car body is in a heavy loaded state, the first friction board 3 is pressed down and in the same level with the second friction board 1, that is, the height difference between the first friction board 3 and the second friction board 1 is equal to zero. In such a state, the upper side bearing 17 presses on both the first friction board 3 and the second friction board 1. Because the deflection which is produced by the elastomer of the lower side bearing 13 due to the weight of the car body and the load is equal to or even larger than the height difference h, the lower side bearing 13 is in a rigid supporting state and most of the load of the car body is supported by the second friction board 1 when the freight car is heavy loaded. Further, because the second friction board 1 has a smaller friction coefficient μz, the wheel truck has a good performance in crossing curved racks in the heavy loaded state.
While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201010176894.1 | May 2010 | CN | national |
This application is a continuation-in-part of International Patent Application No. PCT/CN2010/079599 with an international filing date of Dec. 9, 2010, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 201010176894.1 filed May 14, 2010. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 14781 Memorial Drive, Suite 1319, Houston, Tex. 77079.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2010/079599 | Dec 2010 | US |
| Child | 13664405 | US |
