# US 2019/0169009 A1 · Power lift

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- Number: US 2019/0169009 A1
- Document ID: US20190169009A1
- Status: Published application
- Kind: A1
- Application number: 16/323,040
- Filed: 2017-08-29
- Published: 2019-06-06
- Earliest claimed: 2016-08-30
- Assignees: Clark Equipment Company
- Applicants: Clark Equipment Company
- Inventors: Nicolas Gales
- Web page: https://patentgrep.com/patent/US20190169009A1

## CPC

- B66F 9/22: Hydraulic devices or systems
- B66F 9/0655: {with a telescopic boom}
- E02F 3/433: {horizontal, e.g. self-levelling}
- E02F 3/436: {for keeping the dipper in the horizontal position, e.g. self-levelling}
- E02F 9/2029: {Controlling the position of implements in function of its load, e.g. modifying the attitude of implements in accordance to vehicle speed (control for hydraulic or pneumatic drives E02F9/2203, E02F9/2221 and E02F9/2253 take precedence)}
- E02F 9/2041: {Automatic repositioning of implements, i.e. memorising determined positions of the implement (for dipper-arms or bucket-arms E02F3/434, E02F3/437, E02F3/438, E02F3/439 take precedence)}
- E02F 3/432: {for keeping the bucket in a predetermined position or attitude}
- E02F 9/2225: {using pressure-compensating valves}
- F15B 2211/30515: Load holding valves
- F15B 2211/30585: having a single valve for multiple output members
- F15B 2211/30595: with additional valves between the groups of valves for multiple output members
- F15B 2211/3111: the pump port being closed in the centre position, e.g. so-called closed centre
- F15B 2211/50518: using pressure relief valves
- F15B 2211/50545: using braking valves to maintain a back pressure
- F15B 2211/50554: the pressure control means controlling a pressure downstream of the pressure control means, e.g. pressure reducing valve
- F15B 2211/50581: using counterbalance valves
- F15B 2211/5153: being connected to an output member and a directional control valve
- F15B 2211/5156: being connected to a return line and a directional control valve
- F15B 2211/7128: the chambers being connected in parallel
- F15B 2211/7142: the output members being arranged in multiple groups
- B66F: HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD ({invalid lifting devices A61G7/10; } mounting artificial islands on piles or like supports E02B17/00; scaffolding combined with lifting devices E04G1/22; lifting devices for sliding forms E04G11/24; lifting of buildings E04G23/06; shores or struts E04G25/00; lifts or other hoisting devices on ladders E06C7/12; props for mining E21D15/00)
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR

## Abstract

Power machines and control systems used thereon include a lift cylinder, a tilt cylinder, and a slave cylinder mechanically connected to assist the lift cylinder with raising a boom. With a lift control valve controlled to cause extension of the lift cylinder to raise the boom, pressure from a hydraulic source is provided to the slave cylinder to aid in raising the boom. Resulting increased pressure on a side of the slave cylinder opens load holding valves, allowing hydraulic pressure from the tilt cylinder to be communicated to the slave cylinder such that tilt cylinder pressure due to a heavy load on an implement aids in raising the boom.

## Claims

### Claim 1

A power machine having a frame, a boom pivotally coupled to the frame, a lift cylinder coupled between the frame and the boom to raise and lower the boom, a slave cylinder coupled between the frame and the boom to aid the lift cylinder in raising the boom, an implement interface to which an implement can be mounted, a tilt cylinder coupled between the boom and the implement interface to control rotation of the implement interface and implement relative to the boom, a power source configured to provide pressurized hydraulic fluid, and a control system configured to control provision of the pressurized hydraulic fluid from the power source to the lift cylinder, the slave cylinder and the tilt cylinder, the control system including a lift control valve coupling the power source to the lift cylinder and having a non-actuated position and first and second actuated positions for extending and retracting the lift cylinder, a tilt control valve having a non-actuated position and first and second actuated positions for extending and retracting the tilt cylinder;
characterized by the control system being further configured such that when the tilt control valve is in the neutral position and the lift control valve is in the first actuated position to extend the lift cylinder, pressurized hydraulic fluid is provided through the lift control valve to the slave cylinder to extend the slave cylinder and aid the lift cylinder in raising the boom, and such that extension of the slave cylinder causes increases in pressure in the tilt cylinder, resulting from a load carried by the implement, to be communicated to the slave cylinder to further aid the lift cylinder in raising the boom.

### Claim 2 (depends on 1)

The power machine of claim 1, wherein the control system further comprises:
a lift load holding valve coupled between the lift control valve and the lift cylinder;
a pressure reducing valve coupled between the lift load holding valve and the slave cylinder;
wherein the control system is configured such that when the tilt control valve is in the neutral position and the lift control valve is in the first actuated position to extend the lift cylinder, pressurized hydraulic fluid is provided through the lift control valve and through the pressure reducing valve to the slave cylinder to extend the slave cylinder and aid the lift cylinder in raising the boom.

### Claim 3 (depends on 2)

The power machine of claim 2, wherein the control system further comprises:
a tilt load holding valve coupled between the tilt control valve and the tilt cylinder;
a slave load holding valve coupled between the slave cylinder and the tilt cylinder; and
wherein the control system is configured such that when the tilt control valve is in the neutral position and the lift control valve is in the first actuated position to extend the lift cylinder, and pressurized hydraulic fluid is provided through the lift control valve and through the pressure reducing valve to the slave cylinder to extend the slave cylinder, extension of the slave cylinder causes the tilt load holding valve and the slave load holding valve to open and communicate increases in pressure in the tilt cylinder, resulting from the load carried by the implement, to the slave cylinder to further aid the lift cylinder in raising the boom.

### Claim 4 (depends on 3)

The power machine of claim 3, wherein the tilt load holding valve is coupled between the tilt control valve and one of a base side of the tilt cylinder and a rod side of the tilt cylinder, and wherein opening and closing of the tilt load holding valve is controlled by a pressure differential between the base side of the tilt cylinder and the rod side of the tilt cylinder such that the tilt load holding valve aids in self leveling of the tilt cylinder as the lift cylinder is extended or retracted.

### Claim 5 (depends on 4)

The power machine of claim 4, wherein the slave load holding valve is coupled between one of the base side of the tilt cylinder and the rod side of the tilt cylinder and one of a base side of the slave cylinder and a rod side of the slave cylinder, and wherein opening and closing of the slave load holding valve is controlled by pressure differential between the base side of the slave cylinder and the rod side of the slave cylinder.

### Claim 6 (depends on 5)

The power machine of claim 5, wherein the control system is configured such that extension of the slave cylinder causes increases in pressure differentials between the base side of the tilt cylinder and the rod side of the tilt cylinder, and between the base side of the slave cylinder and the rod side of the slave cylinder, thereby opening the tilt load holding valve and the slave load holding valve.

### Claim 7 (depends on 3)

The power machine of claim 3, and further comprising a check valve positioned between the pressure reducing valve and the slave cylinder and configured to allow pressurized hydraulic fluid to be provided through the lift control valve and through the pressure reducing valve to the slave cylinder, but to prevent pressurized hydraulic fluid from the slave cylinder from being provided to the lift cylinder.

### Claim 8

A method of controlling a power machine having a frame, a boom pivotally coupled to the frame, a lift cylinder coupled between the frame and the boom to raise and lower the boom, a slave cylinder coupled between the frame and the boom to aid the lift cylinder in raising the boom, an implement interface which an implement can be mounted, a tilt cylinder coupled between the boom and the implement interface to control rotation of the implement interface and implement relative to the boom, a power source configured to provide pressurized hydraulic fluid, and a control system configured to control provision of the pressurized hydraulic fluid from the power source to the lift cylinder, the slave cylinder and the tilt cylinder, the control system including a lift control valve coupling the power source to the lift cylinder and having a non-actuated position and first and second actuated positions for extending and retracting the lift cylinder, a tilt control valve having a non-actuated position and first and second actuated positions for extending and retracting the tilt cylinder, the method characterized by steps comprising:
actuating the lift control valve to the first actuated position to provide pressurized hydraulic fluid through the lift control valve to the lift cylinder to extend the lift cylinder and raise the boom;
identifying a condition of the tilt control valve being in the non-actuated position while the pressurized hydraulic fluid is provided to the lift cylinder and responsively providing pressurized hydraulic fluid through the lift control valve to the slave cylinder to extend the slave cylinder to aid the lift cylinder in raising the boom; and
identifying an increase in pressure in the slave cylinder and responsively causing increases in pressure in the tilt cylinder, resulting from a load carried by the implement, to be communicated to the slave cylinder to further aid the lift cylinder in raising the boom.

### Claim 9 (depends on 8)

The method of claim 8, wherein responsively providing pressurized hydraulic fluid through the lift control valve to the slave cylinder to extend the slave cylinder to aid the lift cylinder in raising the boom further comprises providing the pressurized hydraulic fluid through the lift control valve and through a pressure reducing valve to the slave cylinder to extend the slave cylinder and aid the lift cylinder in raising the boom.

### Claim 10 (depends on 9)

The method of claim 9, wherein responsively causing increases in pressure in the tilt cylinder, resulting from a load carried by the implement to be communicated to the slave cylinder to further aid the lift cylinder in raising the boom further comprises opening a tilt load holding valve and a slave load holding valve to allow the increases in pressure in the tilt cylinder to be communicated to the slave cylinder.