Pressure maintaining apparatus, machine tool, and method of running pressure maintaining apparatus in machine tool

A machine tool, comprising:

• a plurality of hydraulic devices including a hydraulic device which needs to maintain pressure of hydraulic oil therein in a standby period;
• a main hydraulic apparatus including first supplying means for supplying the hydraulic oil to the hydraulic devices in an operation period;
• a pressure maintaining apparatus connected in parallel to an oil supply line of the main hydraulic apparatus and including second supplying means being smaller in output than the first supplying means;
• and
• a controller configured to control the main hydraulic apparatus and the pressure maintaining apparatus, wherein
• when any one or more of the plurality of hydraulic devices are operated, the controller stops the second supplying means and operates the first supplying means to thereby supply the hydraulic oil from the first supplying means to the hydraulic devices, and
• when all of the plurality of hydraulic devices are stopped, the controller operates the second supplying means instead of the first supplying means to thereby supply the hydraulic oil from the second supplying means to the hydraulic devices and maintain the pressure of the hydraulic oil in the hydraulic devices in the standby period.

A method of running a pressure maintaining apparatus in a machine tool including

• a plurality of hydraulic devices including a hydraulic device which needs to maintain pressure of hydraulic oil therein in a standby period,
• a main hydraulic apparatus including first supplying means for supplying the hydraulic oil to the hydraulic devices in an operation period, and
• a pressure maintaining apparatus connected in parallel to an oil supply line of the main hydraulic apparatus and including second supplying means being smaller in output than the first supplying means, the method comprising:
• when any one or more of the plurality of hydraulic devices are operated, stopping the second supplying means and operating the first supplying means to thereby supply the hydraulic oil from the first supplying means to the hydraulic devices;
• and
• when all of the plurality of hydraulic devices are stopped, operating the second supplying means instead of the first supplying means to thereby supply the hydraulic oil from the second supplying means to the hydraulic devices and maintain the pressure of the hydraulic oil in the hydraulic devices in the standby period.