Energy conservation type hydraulic elevator and speed control method of hydraulic elevator

An energy conservation type hydraulic elevator comprising:

• a main elevator having a main cylinder and a main ram mounted with a cage for carrying a load;
• a balance elevator having a subcylinder and a subram;
• a fluid path in communication with both of said main cylinder and said subcylinder;
• a first pump located along said fluid path, wherein said first pump can be driven by a motor and by fluid pressure in said fluid path, wherein when said first pump is driven by a motor, said first pump increases hydraulic pressure in at least a portion of said fluid path;
• wherein when said first pump is driven by fluid in said fluid path, said pump extracts power from said fluid;
• wherein a three-phase motor is connected to said first pump, said three-phase motor acting as driving means driving said first pump to increase hydraulic pressure in at least a portion of said fluid path, said three-phase motor also acting as power generating means for generating power such that when said first pump is driven by fluid in said fluid path, said first pump drives said three-phase motor as a generator;
• and
• the energy conservation elevator further including a second pump communicating with said fluid path, said second pump connected to said fluid path at a location between the first pump and the subcylinder.

An energy conservation type hydraulic elevator comprising:

• a main elevator having a main cylinder and a main ram;
• a balance elevator having a subcylinder and a subram;
• a fluid path communicating with both of said main cylinder and said subcylinder;
• pumping and generating means disposed along said fluid path for operating in a pumping mode and in a generating mode, wherein in a pumping mode, said pumping and generating means pumps hydraulic fluid located in said fluid path, and in a generating mode, said pumping and generating means extracts power from said fluid, said pumping and generating means including a first pump;
• and
• a second pump connected to said fluid path at a location between said pumping and generating means and said subcylinder.

A hydraulic elevator comprising:

• an elevator having a main cylinder and a main ram mounted with a cage for carrying a load;
• a fluid path for supplying fluid to said main cylinder and for removing fluid from said main cylinder;
• pumping means connected to said fluid path for pumping fluid through said fluid path to said main cylinder to cause said elevator to ascend and for being driven by said fluid when fluid is exiting said main cylinder for descending said main elevator;
• a valve disposed along said fluid path between said pumping means and said main cylinder;
• a motor connected to said pump, with an inverter control connected to said motor;
• and
• means for creating a negative pressure in a portion of said flow path on a pumping means side of said valve prior to an opening of said valve for carrying out a descending operation of said elevator.