Mobile working machine

• US 6,584,769 B1
• Filed: 12/18/2000
• Issued: 07/01/2003
• Est. Priority Date: 06/27/1998
• Status: Expired due to Fees

• Current Assignee: Lars Bruun
• Original Assignee: Lars Bruun
• Inventors: Bruun, Lars
• Primary Examiner(s): LOPEZ, FRANK D
• Application Number:
  US09/719,860
• Time in Patent Office: 925 Days
• Field of Search: 604/14, 604/16, 604/19
• US Class Current: 60/414
• CPC Class Codes: B66F 9/22 Hydraulic devices or systems
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: F15B 1/024 used as a supplementary power source, e.g. to store energy in idle periods to balance pump load
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/212 the pressure sources being accumulators
• CPC Class Codes: F15B 2211/3057 having two valves, one for each port of a double-acting output member
• CPC Class Codes: F15B 2211/3116 the pump port being open in the centre position, e.g. so-called open centre
• CPC Class Codes: F15B 2211/50518 using pressure relief valves
• CPC Class Codes: F15B 2211/5159 being connected to an output member and a return line
• CPC Class Codes: F15B 2211/625 Accumulators
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups
• CPC Class Codes: F15B 2211/781 one or more output members having priority

Abstract

A hydraulic circuit for a mobile handling device includes a lifting cylinder suitable for handling a variable load and an accumulator for recovering or recycling lowering load energy. The hydraulic circuit also includes a variable hydraulic machine, driven by a drive unit, capable of developing full system pressure in two flow directions, to either of two ports. One of the two ports is connected to the accumulator, by a first connecting line, and the other is connected to the lifting cylinder, by a second connecting line. A second accumulator is connected to the first and second connecting lines by a check valve.

Claims

1. Mobile handling device with hydraulic circuit, which hydraulic circuit (L) comprises a lifting cylinder (1) arranged in a lifting device (100) suitable for handling a variable load and a first accumulator (6) for recovering or recycling lowering load energy, wherein the hydraulic circuit also comprises a variable hydraulic machine (3) with two ports (10, 11), which hydraulic machine is capable via a drive unit (D) of emitting full system pressure in two flow directions to said ports, one port (11) being connected to said first accumulator (6) and the other port being connected to said lifting cylinder (1), characterized

in that communicating with said hydraulic circuit (L) is a control value (13), said variable hydraulic machine (3) being connected to at least one of said first accumulator (6) and said lifting cylinder (1) without the connection going via the control valve (13),

in that the hydraulic circuit (L) comprises a second accumulator (20), which is connected via at least one nonreturn valve (31) to at least one of the lines between the first accumulator (6) and hydraulic machine (3) or hydraulic machine (3) and lifting cylinder (1), and

in that said second accumulator (20) is connected via said at least one nonreturn valve (31-32, 31-30) to both the connection between the first accumulator (6) and the machine (3) and the connection between the machine (3) and the lifting cylinder (1).

2. Mobile handling device according to claim 1, characterized in that neither said connection between said accumulator and said hydraulic machine nor said connection between said lifting cylinder and said hydraulic machine go through said control valve (13).

3. Mobile handling device with hydraulic circuit according to claim 2, characterized in that the hydraulic circuit (L) comprises a first stop valve (2) arranged in the line between one port (10) of the hydraulic motor and the lifting cylinder (1), and a second stop valve (5) arranged in the line between the hydraulic motor'"'"'s second port (11) and the first accumulator (6).

4. Mobile handling device with hydraulic circuit according to claim 3, characterized in that said first (2) and second (5) stop valves are controlled by a servo circuit (4, 9) which comprises a servo pump (4) and a valve unit (9) by means of which the stop valves (2, 5) are actuated to the open position when a control signal activates the changeover valve (9) to open the connection between the first accumulator (6) and lifting cylinder via the hydraulic machine (3).

5. Mobile handling device with hydraulic circuit according to claim 2, characterized in that said lifting cylinder (1) is of the double-acting type comprising a rod side (1A) and a cylinder side (1B), the side (1A) which is not directly connected to the hydraulic machine (3) being able to obtain oil from a hydraulic pump (12) via a control regulator (13).

6. Mobile handling device with hydraulic circuit according to claim 1, characterized in that disposed in direct connection to the lifting cylinder (1) is a pressure monitoring element (17).

7. Mobile handling device with hydraulic circuit according to claim 1, characterized in that the system pressure in said second accumulator (20) is considerably lower than in said first accumulator (6).

8. Mobile handling device with hydraulic circuit according to claim 1, characterized in that the hydraulic circuit (L) communicates with a second hydraulic circuit (S) for a slewing turning device (5), which second circuit (S) comprises valve elements (36, 37) which in connection with deceleration of said slewing part supplies hydraulic fluid to said first accumulator (6), this being filled and at the same time acting on the slewing part with a decelerating force.

9. Mobile handling device with hydraulic circuit according to claim 8, characterized in that said valve elements (36, 37) consist of sequential valves.

10. Mobile handling device with hydraulic circuit according to claim 8, characterized in that a nonreturn valve (38) is disposed in the line between said valve elements (36, 37) and said first accumulator (6).

11. Mobile handling device with hydraulic circuit according to claim 9, characterized in that said sequential valves (36, 37) are proportionally controlled so that the deceleration speed is determined by the pressure level of the sequential valves (36, 37).

12. Mobile handling device with hydraulic circuit according to claim 9, characterized in that said valve element'"'"'s drainage lines (43, 48) are connected to a control valve'"'"'s servo covers for the slewing movement so that the sequential valves (36, 37) receive a control pressure which is influenced by the pressure in the slewing circuit.