Abstract: Provided is a reusability determination method for a gear that makes it possible to determine reusability of a gear during or after use to increase the reuse ratio. The reusability determination method for a gear of the present invention includes a step of measuring a content of retained ? phases in the gear, a step of calculating a change rate of the content of the retained ? phases, a step of measuring residual stress applied to the gear, a residual stress ratio calculation step of calculating a residual stress ratio to residual stress in an initial state of the gear, and a reusability determination step of determining whether or not the gear is reusable on the basis of results of the calculation in the retained ? phase change rate calculation step and the residual stress ratio calculation step.

Abstract: Provided is a reusability determination method for a gear that makes it possible to determine reusability of a gear during or after use to increase the reuse ratio. The reusability determination method for a gear of the present invention includes a step of measuring a content of retained ? phases in the gear, a step of calculating a change rate of the content of the retained ? phases, a step of measuring residual stress applied to the gear, a residual stress ratio calculation step of calculating a residual stress ratio to residual stress in an initial state of the gear, and a reusability determination step of determining whether or not the gear is reusable on the basis of results of the calculation in the retained ? phase change rate calculation step and the residual stress ratio calculation step.

Abstract: A main spool (24) has a throttle passage (30) that, when the main spool (24) moves to an axial other side against a first return spring (27) in a main spool insertion hole (13), communicates a pilot pressure chamber (25) with a first tank port (15) and limits a flow amount of hydraulic oil to be discharged to the first tank port (15) from the pilot pressure chamber (25). When the main spool (24) moves to the axial other side along the main spool insertion hole (13), the throttle passage (30) communicates the pilot pressure chamber (25) with the first tank port (15) before a state where a first pump port (17) is communicated with an output port (16) and a state where the output port (16) is blocked from the first tank port (15).

Abstract: A main spool (24) has a throttle passage (30) that, when the main spool (24) moves to an axial other side against a first return spring (21) in a main spool insertion hole (13), communicates a pilot pressure chamber (25) with a first tank port (15) and limits a flow amount of hydraulic oil to be discharged to the first tank port (15) from the pilot pressure chamber (25). When the main spool (24) moves to the axial other side along the main spool insertion hole (13), the throttle passage (30) communicates the pilot pressure chamber (25) with the first tank port (15) before a state where a first pump port (17) is communicated with an output port (16) and a state where the output port (16) is blocked from the first tank port (15).

Abstract: A pilot valve assembly comprised of a pilot valve proper employing a spool to be displaced in a valve casing to bring a hydraulic pressure port and an output port into and out of communication with each other, an operation means having an operating lever with a cam member attached thereto, a pivoting shaft erected on an end plate of the pilot valve proper and connected with the manual operating lever through a universal joint, and a boot of a resilient material hermetically connected between the operation means and the end plate in such a way as to completely enshroud said universal joint, cam member and pusher, the end plate being detachably fixed to the mount member, and the boot having one end thereof connected to the operation means and having the other end hermetically gripped between the end plate and the mount member.

Abstract: A pilot valve assembly comprised of a pilot valve proper employing a spool to be displaced in a valve casing to bring a hydraulic pressure port and an output port into and out of communication with each other, an operation means having an operating lever with a cam member attached thereto, a pivoting shaft erected on an end plate of the pilot valve proper and connected with the manual operating lever through a universal joint, and a boot of a resilient material hermetically connected between the operation means and the end plate in such a way as to completely enshroud said universal joint, cam member and pusher, the end plate being detachably fixed to the mount member, and the boot having one end thereof connected to the operation means and having the other end hermetically gripped between the end plate and the mount member.

Abstract: A hydraulically driven industrial machine having a variable displacement type hydraulic pump adapted to take in and pressurized working oil from an working oil tank, a hydraulic actuator to be driven by pressurized working oil delivered from the hydraulic pump through a control valve to perform a predetermined job, a variable return oil cooling means capable of cooling return oil from the hydraulic actuator at a varying cooling rate, an operational load detection means adapted to detect an operational load factor of the hydraulic actuator, and a control means adapted to vary the return oil cooling rate on the basis of an operational load factor detected by the operational load detection means.

Abstract: A hydraulically driven industrial machine has a variable displacement hydraulic pump for pressurizing hydraulic oil from a hydraulic oil tank; a actuator driven and controlled by oil that is discharged from the hydraulic pump and is supplied through a controlled valve and performing predetermined work; cooling means with a variable cooling rate function, the cooling means cooling return oil from the actuator and varying the rate of cooling of the return oil; load detection means for detecting work load by the actuator; and control means for varying the rate of cooling of the return oil according to the work load detected by the load detection means.

Abstract: A hydraulic cylinder in which a recess (21) is formed in a piston rod (3) side end surface (20) of a piston (4) so that the recess (21) serves as an axial fitting portion, and an end of the piston rod (3) is fitted into the recess (21) of the piston (4) to ensure the coaxial relationship between the piston rod (3) and the piston (4). Axial threaded holes (24) are formed in an end surface (23) of the piston rod (3) and axial bolt through-holes (25) are formed in the piston (4). The end surface (20) of the piston (4) is disposed in face-to-face contact with the end surface (23) of the piston rod (3), and under the condition bolts (22) are inserted through the bolt through-holes (25) and screwed into the threaded holes (24) to fix the piston (4) to the piston rod (3). Accordingly, the strength of a piston connecting portion can be improved with a simple structure without use of any special high-strength material for the piston rod and without any special heat treatment.