Variable priority device for swing motor in heavy construction equipment

Abstract

A variable priority device for a swing motor in heavy construction equipment including a variable orifice device installed in an arm cylinder-side parallel oil passage of an parallel oil passage for supplying oil pumped by a single pump to a swing motor and an arm cylinder, the variable orifice device serving to perform a switching operation between an orifice state and an orifice release state in response to a pilot pressure for moving the spool of a swing motor control switching valve. The variable orifice device includes a check valve disposed in the arm cylinder-side parallel oil passage and provided with a spring chamber and a spool resiliently supported in the spring chamber by a spring exerting a predetermined pressure such that the spool maintains an initial state for closing the arm cylinder-side parallel oil passage, the spool having an internal oil passage for performing an orifice function, and a cutoff valve connected to the spring chamber via an oil discharge passage and adapted to perform a switching operation for selectively opening and closing the oil discharge passage in response to the pilot pressure.

Dependencies are inferred from the claim text.