| 摘要 |
A well pumping unit including a derrick having first and second sheave sets attached near the top thereof, a drive mechanism, a counterweight, a polish rod assembly and cable members. The cable members form a closed loop extending from the polish rod assembly to the first sheave set, to the counterweight, to the second sheave set, to the drive mechanism, to the second sheave set, to the first sheave set and back to the polish rod assembly. The counterweight is suspended by the sheave sets and cable members between the sheave sets. When the drive mechanism operates in a first direction, the polish rod assembly is raised and the counterweight lowered. When the drive mechanism operates in a second direction, the counterweight is raised and the polish rod assembly lowered. The counterweight may be located within the derrick while the polish rod assembly and drive mechanism may be located outside of the derrick. The weight of the counterweight may be adjusted as desired. |
