Importance

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Abstract

A pipe layer having a swing speed adjustable system is provided, which can be used as a pipe layer or an excavator through replacement of attachments in accordance with work conditions, so that it serves as the pipe layer when it is required to pull up and carry a heavyweight oil pipe in order to lay the oil pipe under the ground, while it serves as the excavator when a quick swing work is required. The pipe layer having a swing speed adjustable system includes first and second variable displacement hydraulic pumps connected to an engine, control valves installed in a center bypass path of the first hydraulic pump, control valves installed in a center bypass path of the second hydraulic pump, a straight traveling valve installed on an upstream side of the center bypass passage of the first hydraulic pump to supply the hydraulic fluid from the first and second hydraulic pumps to a boom cylinder, a swing motor, a winch motor, and left and right traveling motors, respectively, and a variable load-hold check valve installed in an inlet-side flow path of the swing motor control valve to variably adjust a stroke of a poppet so that the amount of hydraulic fluid being supplied to the swing motor can be variably adjusted.

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First Claim