Hydraulic driving device

A hydraulic driving device comprising:

• a cylinder,
• a piston which executes a stroke within said cylinder,
• a main control valve including a spool and a valve body which has a first oil chamber communicating with a high oil pressure source, a second oil chamber communicating with a low oil pressure source, and a third oil chamber communicating with either of said first and second oil chambers and a chamber in said cylinder, said chamber in said cylinder communicating with either of said first oil chamber and said second oil chamber through said third oil chamber in correspondence with a position of said spool driven by oil pressure changes within the respective oil chambers,
• characterized in that said main control valve further has a fourth oil chamber, a fifth oil chamber and a sixth oil chamber, and that said spool is provided with first surfaces upon which oil pressure in said fourth and fifth oil chambers act in the direction of communicating said first oil chamber and said chamber in said cylinder when said fourth and fifth oil chambers communicate with said high oil pressure source and second surfaces upon which oil pressure in said first and sixth oil chamber act in the direction of communicating said second oil chamber and said chamber in said cylinder when the oil pressure in said sixth oil chamber is a high pressure, and
• said hydraulic driving device further comprising:
• a first valve and first signal producing means for impressing a first signal to actuate said first valve, said first valve communicating said third oil chamber with said fourth oil chamber while said first signal is not impressed and communicating said fourth oil chamber with said low oil pressure source when said first signal is impressed,
• a valve arrangement, having at least a second valve, and second signal producing means for impressing a second signal to actuate said second valve, said valve arrangement communicating said fifth oil chamber with said high oil pressure source while said second signal is impressed and communicating said fifth oil chamber with said low oil pressure source when said second signal is released, and
• a third valve which communicates said sixth oil chamber with said high oil pressure source while said piston is operating in correspondence with said first signal and which communicates said sixth oil chamber with said low oil pressure source while said piston is operating in correspondence with said second signal, and
• means for acting upon said third valve in response to said piston nearing ends of its stroke for effecting reverse movement of the main valve, wherein said main control valve, first valve, valve arrangement, and third valve includes means for enabling said first signal to take precedence over said second signal whenever both of said signals are impressed simultaneously and whenever said signals are impressed in an overlapping manner prior to completion of an operation produced in accordance with one of said signals.

A hydraulic driving device comprising:

• a cylinder,
• a piston which executes a stroke within said cylinder,
• a main control valve including a spool and valve body which has a first oil chamber communicating with a high oil pressure source, a second oil chamber communicating with a low oil pressure source, and a third oil chamber communicating with either of said first and second oil chambers and a chamber in said cylinder, said chamber in said cylinder communicating with either of said first oil chamber and said second oil chamber through said third oil chamber in correspondence with a position of said spool driven by oil pressure changes within the respective oil chambers,
• characterized in that said main control valve further has a fourth oil chamber, a fifth oil chamber and a sixth oil chamber, and that said spool is provided with first surfaces upon which oil pressure in said fourth and fifth oil chambers act in the direction of communicating said first oil chamber and said chamber in said cylinder when said fourth and fifth oil chambers communicate with said high oil pressure source and second surfaces upon which oil pressure in said first and sixth oil chamber act in the direction of communicating said second oil chamber and said chamber in said cylinder when the oil pressure in said sixth oil chamber is a high pressure, and
• said hydraulic driving device further comprising:
• a first valve which communicates said third oil chamber with said fourth oil chamber while a first signal is not impressed and which communicates said fourth oil chamber with said low oil pressure source when said first signal is impressed,
• a valve arrangement, having at least a second valve, which communicates said fifth oil chamber with said high oil pressure source while a second signal is impressed and which communicates said fifth oil chamber with said low oil pressure source when said second signal is released, and
• a third valve which communicates said sixth oil chamber with said high oil pressure source while said piston is operating in correspondence with said first signal and which communicates said sixth oil chamber with said low oil pressure source while said piston is operating in correspondence with said second signal, and
• means for acting upon said third valve in response to said piston nearing ends of its stroke for effecting reverse movement of the main valve, further comprising a fourth valve which is disposed at an intermediate position of an oil passage communicating said second valve and said fifth oil chamber of said main control valve and which cuts off the communication between said second valve and said fifth oil chamber and connects said fifth oil chamber and said low oil pressure source, and means for operating said fourth valve after a delay of a fixed time with respect to the operation of said second valve.