Power unit for the supply of hydraulic actuators

• US 6,005,360 A
• Filed: 09/24/1997
• Issued: 12/21/1999
• Est. Priority Date: 11/02/1995
• Status: Expired due to Fees

• Current Assignee: SME Elettronica SPA
• Original Assignee: SME Elettronica SPA
• Inventors: Pace, Adolfo
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/936,682
• Time in Patent Office: 818 Days
• Field of Search: 318/376-378, 318/140, 60/477, 60/413-418, 60/476, 60/368, 60/389, 60/390, 91/358 R, 91/359, 91/361, 91/390
• US Class Current: 318/376
• CPC Class Codes: B66F 9/22 Hydraulic devices or systems
• CPC Class Codes: F15B 11/02 Systems essentially incorporating special features for controlling the speed or actuating force of an output member
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20515 Electric motor
• CPC Class Codes: F15B 2211/20569 capable of working as pump and motor
• CPC Class Codes: F15B 2211/40515 with variable throttles or orifices
• CPC Class Codes: F15B 2211/41554 being connected to a return line and a directional control valve
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/50518 using pressure relief valves
• CPC Class Codes: F15B 2211/5156 being connected to a return line and a directional control valve
• CPC Class Codes: F15B 2211/6333 representing a state of the pressure source, e.g. swash plate angle
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/7052 Single-acting output members
• CPC Class Codes: F15B 2211/88 Control measures for saving energy

Abstract

The invention discloses a power unit (1) which comprises: an accumulator battery (2); an electric converter (3) supplied by said accumulator battery (2); an electric motor (30) supplied by said converter (3); a hydraulic pump (4) mechanically connected to said electric motor (30), suited to put under pressure a liquid (50) which supplies one or more actuators (9) in order to lift a load (11) connected to them. Said pump (4) is of the reversible type and operates as a hydraulic motor suited to drive into rotation said electric motor (30) which operates as a generator supplying said battery (2) by means of said converter (3) whenever the descent by gravity of the load (11) supported by said one or more actuators (9) puts under pressure the oil held therein which passes through said pump (4) entering from the delivery opening (42) and coming out of the inlet opening (41).

Claims

1. A power unit for supplying liquid under pressure from a storage tank to at least one actuator operative between respective lifting and idle operations for lifting and maintaining a load comprising:

an accumulator battery;

a vectorial inverter supplied by said accumulator battery;

an electric motor supplied by said inverter including a torque control for controlling the motor with torque signals corresponding to the lifting and idle operations respectively;

a reversible hydraulic pump operative in first and second directions and at idle, mechanically connected to said electric motor, said pump having at least one suction opening hydraulically connected to the tank and at least one normally open delivery opening hydraulically connected to said at least one actuator for lifting the load when the pump is operated by the motor in the first direction to pressurize the liquid in response to the lifting torque signal, and said pump being operative in the second direction by pressurization of the liquid into the pump at the delivery opening, said pump being operative as a hydraulic motor for driving the electric motor to operate as a generator supplying said battery via the converter when the load is allowed to descend and said pump being operative to maintain the load when the motor is operated by the idle torque signal maintaining the shaft at idle against the lifted load via the normally open delivery opening.

2. A power unit according to claim 1 including a maneuvering device coupled to the inverter for selectively controlling revolutions of the motor.

3. A power unit according to claim 2 wherein the maneuvering device comprises a joy stick.

4. A power unit according to claim 2 comprising a channel for each actuator and wherein said delivery opening of the pump is hydraulically connected to each of said actuators and further including a distributor for each channel interposed between the delivery opening and each distributor for selectively enabling each actuator when a channel is selectively opened.

5. A power unit according to claim 1 wherein said reversible pump comprises a piston pump.