Loader

• US 7,717,664 B2
• Filed: 09/06/2007
• Issued: 05/18/2010
• Est. Priority Date: 09/08/2006
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Tudor, Richard, Bitter, Marcus
• Primary Examiner(s): UNDERWOOD, DONALD W
• Application Number:
  US11/851,034
• Publication Number:
  US 20080063501A1
• Time in Patent Office: 985 Days
• Field of Search: 414/699, 414/680, 414/718, 414/728, 604/59, 604/63, 280/754
• US Class Current: 414/699
• CPC Class Codes: B66F 17/003 for fork-lift trucks
• CPC Class Codes: B66F 9/22 Hydraulic devices or systems
• CPC Class Codes: E02F 9/226 Safety arrangements, e.g. hydraulic driven fans, preventing cavitation, leakage, overheating
• CPC Class Codes: F15B 11/003 Systems with load-holding valves
• CPC Class Codes: F15B 2211/50545 using braking valves to maintain a back pressure

Abstract

A loader includes a hydraulically operated extension arm, a load sensor for monitoring the load condition on the loader and a hydraulic arrangement for actuation of the extension arm and/or an implement attached to the extension arm. The hydraulic arrangement exhibits at least one hydraulic cylinder with one supply line on the piston rod side and one supply line on the piston side. At least one hydraulically switchable control device is coupled between a source of fluid pressure and a hydraulic tank, on the one hand, and the supply lines on the other hand. An actuating device is coupled for routing control pressure to the control device via first and second control pressure lines. An electronic control unit is connected for effecting operation of a control pressure control device, which is coupled to at least one of the control pressure lines, in response to a load signal received from the load sensor so as to actuate the control device for achieving a slowed-down actuation of the hydraulic cylinder in conjunction with the onset of a critical load condition. Thus, a restriction of a volumetric flow is achieved in at least one of the supply lines coupled to the hydraulic cylinder.

Claims

1. In a loader including a frame supported on front and rear axles carrying front and rear sets of wheels, a hydraulically operated extension arm mounted to the frame for swinging vertically between lowered and raised positions, an extensible and retractable hydraulic cylinder coupled between said frame and said extension arm for selectively moving said arm between said lowered and raised positions, a first supply line coupled to a piston rod side of said hydraulic cylinder, a second supply line coupled to a piston side of said hydraulic cylinder, a pressurized hydraulic fluid source, a hydraulic fluid tank, at least one hydraulically switchable control device coupled, on the one hand, to said first and second supply lines and coupled, on the other hand, to said fluid source and fluid tank, a hydro-mechanical actuating device being coupled to said fluid source and said fluid tank and being coupled and selectively operable for routing a control pressure to said control device via first and second control pressure lines, so as to effect actuation of said control device for controlling the flow of hydraulic fluid to and from said hydraulic cylinder, a load sensor located on said loader for monitoring a load condition on the loader and operable for creating an electrical load signal representing said load condition, and an electronic control unit coupled to said load sensor for receiving said electrical load signal and comparing it with a critical load stored in memory in said electronic control unit and for generating a control signal representing a difference between said load signal and said critical load, the improvement comprising:

said control device being a proportional valve mounted for movement in opposite directions from a centered hold position, wherein the flow of fluid to and from said fluid supply lines is blocked, respectively to a lift position wherein said fluid source is connected to said first supply line while said tank is connected to said second supply line, and to a lower position wherein said tank is connected to said first supply line while said fluid source is connected to said second supply line;

an electrically operable electro-hydraulic over pressure valve being coupled to one of said control pressure lines at a location downstream from said hydro-mechanical actuating device, and further being coupled to said electronic control unit for receiving said control signal whereby said electro-hydraulic over-pressure valve is operated in accordance with said control signal so as to effect changes in the pressure contained in said one of said control pressure lines so that said proportional valve acts to slow movement of said hydraulic cylinder in a direction causing an increase in said load signal.

2. The loader, as defined in claim 1, wherein said actuating device includes one of a joystick or actuating lever.

3. The loader, as defined in claim 1, wherein said loader is a telescopic loader.

4. The loader, as defined in claim 1, wherein said loader is a front loader.

5. The loader, as defined in claim 1, wherein said load sensor is arranged on one of said front and rear axles.