nels or tubes are provided with the spill plate for guide the cutting machine. For instance, a guide tube is provided for the shearer, a guide channel for the hook plow; and a face-side guide tube for haulage chain and a gob-side guide tube for the stabilizing bridge arm of the sliding plow.B. Ramp Plates
The ramp plates are mounted on the face side of the pans. They are used to scoop up the remnant coal on the floor when the conveyor is being advanced. This way, it ensures that the conveyor is always advanced to the predetermined position thereby allowing the shearer or plow to cut a full web. It must be noted however that the ramp plate cannot be used as a major coal-loading device. If there is too much coal left on the floor in front of the conveyor, the ramp plate may climb up during conveyor advance, allowing the coal to slip under the conveyor. As a result, the conveyor will lean toward the gob side, the shearer or the plow will climb up and leave the bottom coal, and in severe cases it may cut into the roof or the support canopy.
There are many types of ramp plates. The most commonly used ones are the linear, the bending, and the curved shape. The bending shape consists of two sections with different slopes. The lower section has a smaller slope for better scooping action. The curves ramp plates are used mostly for the sliding plow.
2-5 Chain Units
The chain unit consists of the link chains and flight bars. The link chain is usually denoted by its diameter and nominal pitch [25], such as ��228´6mm.
The chain unit must be very strong, rigid, and highly wear-resistant because it is subjected to heavy external loading, both dynamic and static [26], and needs to overcome frictional resistance.
3. Transfer Methods at Headentry T-junction
The modern longwall advances so rapidly that it is imposes two requirements on the entry transportation [27]: it must have 1 high carrying capacity and must be able to move along as the face advances.
The flexible belt conveyor is widely used as the entry transportation system to satisfy these requirements. Since the belt conveyor is much higher than the armored face conveyor and it is not convenient to adjust the length [28] constantly, a stage loader or a curved conveyor [29] is used to transfer the coal from AFC to the entry belt conveyor at the headentry T-junction.
The disadvantage of using stage loader to transfer coal from AFC to entry belt conveyor is that the return chain carries considerable coal fines [30] into bottom channel [31] of the conveyor pans. One of the remedial methods is to use the side discharge. In this method, a discharge pan with a deflector is inserted between the drive head and connecting pan of the AFC. The level section of the stage loader is installed exactly under the discharge pan. Thus the coal is discharge at the discharge pan instead of over the drive head.
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