How the switch works
The basic rail is made of ordinary steel rails with a standard section of 12.5m or 25m. The main strand is a straight line, and the side strands are bent into a prescribed broken line or curved shape in advance in the factory according to the gauge of each part of the switch.
The important part of the point rail switch, relying on the pulling of the point rail, leads the train into the main line or the side line direction. The point rail can be divided into linear and curved types on the plane. The straight-line pointed rail is simple to manufacture and easy to replace, but the switch angle is large, and the impact force of the train on the pointed rail is large. China's newly designed turnouts No. 12 and No. 18 are straight-line rails and side rails are curvilinear. The impact angle of the curved tip rail is small, the radius of the guide curve is large, and the train entering and exiting the side line is relatively stable, but the manufacturing is more complicated, and the left and right openings cannot be used universally. Type in four forms.
There are two kinds of rail sections: ordinary section or special section. For the tip rail made of ordinary section rail, a reinforcing plate is generally added at the front end of the tip rail to increase its lateral rigidity. The tip rail made of special section steel rail has a thick section, strong integrity, high rigidity and good stability. The same height as the basic rail is called high special section, and the shorter one is called short special section. In order to facilitate the connection with the connecting part at the heel end, the rail with special section. The heel should be processed into an ordinary rail section. China has widely promoted the use of low-profile special-section rails.
Tine rail lengths vary by turnout number (see Frog) and the type of point rail. On China Railway, the length of the point rail of the No. 9 switch is 6.25m; the length of the straight point rail of the No. 12 switch is 7.7m, the length of the curved point rail is 11.3-11.5m; the length of the point rail of the No. 18 switch is 12.5m.
The structure of the tip rail is characterized by: thin, at the beginning, the section gradually widens, and its non-acting side is closely attached to the working side of the basic rail to ensure that the acting side of the linear tip rail is a straight line. The action edge of the lateral tip rail and the action edge of the guide curve are a circular curve. The abutting methods of the tip rail and the basic rail include the stick-point type and the hidden-point type. When using ordinary rails for slicing, place the sliced tip rail on the sliding bed 6mm higher than the basic rail to form a tip tip rail; when using a low-profile special section rail to process the tip rail, Make a 1:3 oblique cut below the gauge line of the lower forehead of the rail head, so that the tip rail is hidden under the gauge line of the basic rail, forming a hidden tip structure to protect the tip rail from being crushed by the wheels. In order to ensure that the tip rail has sufficient strength to withstand the pressure of the wheel, the part with the top width of the tip rail above 50mm can be fully stressed, the part with the top width of the tip rail below 20mm is stressed by the basic rail, and the part with the top width of the tip rail 20-50mm is the wheel. load transition. A necessary relative height difference of the top surface of the rail is maintained between the tip rail and the basic rail.
The heel end of the tip rail is the end where the tip rail is connected with the guide curve rail. The heel structure of the tip rail ensures that the tip rail can swing left and right on the plane according to different switch requirements, requiring firmness and stability, simple manufacture and convenient maintenance. The heel end of the tip rail mainly adopts the spacer iron fishplate type and the elastic bendable heel end structure. The spacer iron fishplate structure is mainly composed of spacer iron, heel splint and connecting bolts, etc., with fewer parts, and the tip rail can be moved flexibly, but the stability is poor. In the elastic bendable tip rail, a part of the rail bottom is cut off at 2 to 3 sleepers in front of the heel end to form a flexible part, so that the tip rail has sufficient elasticity to be moved from one position to another. The bottom of the tip rail and the end rail is not sliced in the speed-increasing turnout. Although the pulling power of the tip rail is increased, it is beneficial to maintain the strength of the tip rail at the heel end. In the cross-section seamless line, in order to limit the telescopic displacement of the tip rail, a stopper is installed on the base rail of the heel and the waist of the tip rail, which is beneficial to transfer the excessive temperature force to the outer base rail.
The spare parts on the switch device include sliding bed plate, rail support, top iron, various special forms of backing plate, switch pull rod and connecting rod, and switch machinery.