Please select the most similar patent number from A, B, C and D. Which number is?
Disclosed is a roller mill, which comprises: a shell (10), the shell (10) being provided with a feed port (11) and a discharge port (12); a main shaft (20) which is provided in the shell (10) rotatably in a penetrating manner; a drive device (30) which is connected to the main shaft (20) in a driving manner; a bracket (40) which is installed on the main shaft (20); two or more than two grinding rollers (50), each of the grinding rollers (50) is rotatably installed on the bracket (40) around a shaft axis thereof; and a grinding disk (60) which is fixedly installed in the shell (10) and is opposite to the positions of the plurality of grinding rollers (50). The roller mill also comprises an axial position adjustment device (70) which is connected to the main shaft (20) and is used for driving the main shaft (20) to move in an axial direction so as to adjust the position of the main shaft (20). The roller mill has a simple structure and can adjust a rolling gap conveniently.
A: A motor drive apparatus, comprising a casing (10), a bottom housing (20) rotatably mounted within an open end of the casing (10), and a crank (30), a mounting cavity being formed between the casing (10) and the bottom housing (20), a first end of the crank (30) being rotatably mounted within the end of the casing (10) away from the bottom housing (20). The apparatus also comprises a central shaft (40) arranged along the axial direction of the bottom housing (20) and passing through the bottom housing (20), and an eccentric motor (50), a cycloid gear speed reduction mechanism (60), a first clutch mechanism (70) and a second clutch mechanism (80) arranged within the mounting cavity, a first end of the central shaft (40) extending into the mounting cavity and being mounted within the first end of the crank (30), two ends of the eccentric motor (50) being respectively rotatably mounted on the casing (10) and the bottom housing (20), the cycloid gear speed reduction mechanism (60) being sleeved on the outer periphery of the eccentric motor (50), the first clutch mechanism (70) being rotatably mounted on the casing (10) and being capable of driving the casing (10) to rotate, the second clutch mechanism (80) being sleeved on the outer periphery of the first end of the central shaft (40) and mounted on the casing (10). The apparatus may be mounted on a central shaft position of an existing bicycle frame.
B: A spindle structure. The spindle structure comprises a spindle core (10), a bearing structure (20), and a bearing base (30); the bearing base (30) is provided with a communication channel, the spindle core (10) is provided on the communication channel in a penetrating manner, the bearing structure (20) is provided in the communication channel, and the bearing structure (20) is sleeved on the spindle core (10); a spacer ring positioning structure (40) comprises a female spacer ring (41) and a sub-spacer ring (42), the sub-spacer ring (42) is sleeved on the spindle core (10), and an external thread is provided on the sub-spacer ring (42); the inner ring of the female spacer ring (41) is provided with an internal thread adapted to the external thread, and the female spacer ring (41) is rotatably provided on the sub-spacer ring (42) to drive the sub-spacer ring (42) to move. A driving member (50) comprises an operating section (51) and a driving section (52) connected to each other, the driving section (52) is provided with a first tooth-shaped portion (53), and the female spacer ring (41) is provided with a second tooth-shaped portion (43) adapted to the first tooth-shaped portion (53); the driving section (52) is movably provided in the communication channel of the bearing base (30) and matches the female spacer ring (41), and the operating section (51) penetrates out of the bearing base (30) and is located on the outer side of the bearing base (30). The structure can solve the technical problem in the related art that it is inconvenient to adjust the bearing pre-tightening force of the spindle structure. The present invention also relates to a machine tool comprising the spindle structure.
C: A power tool, comprising: a housing (10), a motor (14), a main shaft (40) powered by rotational power output by the motor (14), and a chuck (20) comprising a core body (21) connected with the main shaft (40), a plurality of jaws (22) movably arranged within the core body (21), and a chuck operation sleeve (23) arranged outside the core body (21) and capable of operably driving the jaws (22) relative to the core body (21) and thereby being able to lock or loosen tool bits held in the core body (21). The chuck (20) further comprises a locking assembly (24) located inside the chuck operation sleeve (23), said locking assembly (24) itself comprising a locking piece (242) movable relative to the core body (21); the chuck operation sleeve (23) operably drives the locking piece (242) along the axial direction of the core body (21) between a first position and a second position; when the locking piece (242) is in the first position, said locking assembly (24) allows the core body to rotate relative to the housing (10); when the locking piece (242) is in the second position, the locking assembly (24) prohibits rotation of the core body (21) relative to the housing (10). By integrating the tool-bit locking functions, the chuck (20) of the present power tool affords tools provided with said chuck (20) shorter overall length as there is no need to arrange an additional locking device on the housing (10).
D: Disclosed is an external circulation roller type vertical mill, wherein a partition plate (16) is arranged at the middle-upper part of a mill shell and divides the mill shell into a powder grinding barrel (29) and a powder selecting barrel (12); a powder selecting machine is arranged in the powder selecting barrel (12), an outlet of a powder selection coarse-powder ash hopper (14) of the powder selecting machine penetrates the partition plate (16) and extends into the powder grinding barrel (29), and an air inlet (15) is provided in the lower part of the powder selecting barrel (12); and a grinding disc (20) and a grinding roller (18) are arranged at the lower part of the powder grinding barrel (29), a nozzle ring (22) is arranged between the outer circumference of the grinding disc (20) and the mill shell, a discharge ring channel (23) is arranged at the lower part of the nozzle ring (22), a discharge port (25) is further provided in the bottom of the discharge ring channel (23), and a feeding pipe (6), used for feeding materials into the powder selecting barrel (12) by means of a material lifting mechanism, of the powder selecting machine is further arranged at the discharge port (25).
Answer: D