Novel crank device for oil pumping unit

The novel crank device comprises a crank body (1), a connecting screw rod (2), a sliding block (3) and an adjusting screw rod (4), an installation hole (11) is formed in the left end of the crank body (1), a long round hole (13) is formed in the right end of the crank body (1), an open groove (12) is formed in the installation hole (11), side nuts (21) are installed at the two ends of the connecting screw rod (2), and a middle nut (22) is installed in the middle of the connecting screw rod (2). The sliding block (3) is arranged at the right end of the crank body (1) in a sleeved mode through a sliding groove (31), the sliding block (3) is connected with the crank body (1) in a fastened mode through a fastening bolt (14), the front end of the adjusting screw rod (4) makes contact with the sliding block (3), the adjusting screw rod (4) is connected to the fixing block (5) in a screwed mode, and the fixing block (5) is fixedly connected with the crank body (1). The crank is easy to disassemble, assemble and adju