Abstract: A spindle of an oil hydraulic cylinder includes a main body and a circular ring shaped copper coat. The main body defines a central axis and has a large diameter segment and a small diameter segment integrally extended from the large diameter segment. The copper coat is brazed on an outer surface of the large diameter segment. The center of the copper coat is arranged at the central axis, and the radius of the spindle is greatest at a portion of the spindle coated by the copper coat. The abrasion resistance of the copper coat is greater than the abrasion resistance of the main body. Thus, the spindle of the instant disclosure is a composite structure and is provided for reducing abrasion. Additionally, the instant disclosure also provides an oil hydraulic cylinder.

Abstract: A power converting device includes a power converting unit for converting an AC voltage input into a DC voltage output, a cooling fan for dissipating heat generated by the power converting unit, a detecting unit connected electrically to the power converting unit for detecting a current output of the power converting unit and for generating a control signal corresponding to the current output detected thereby, and a controller connected electrically to the cooling fan and the detecting unit for controlling rotational speed of the cooling fan in accordance with the control signal from the detecting unit.