Caterpillar Inc.

Randall A Harlow

Steven P Seaney

David P Smith

Alan R Coutant

Stephen C Garnett

Jason Brinkman

Timothy L Hand

Richard J Skiba

John R Connolly

Chandrasekar Ramamoorthy

Robert A Lapke

Joseph F Duffy

James R Carlberg

Steven L Groth

Kevin Bacon

Richard A Arstein

Rita R Waller

Joseph T Phillips

This disclosure provides for pressure limiting a hydraulic system to a desired pressure value by a particular circuit by controlling and closing the compensator when the desired pressure setting is achieved. Closing the compensator will reduced the pressure head and flow in the circuit resulting in improved efficiency. One illustrated embodiment of the disclosure provides a relief valve in the pilot signal for a compensator. The method relates to limiting the pressure on an open side of the compensator, such that the pressure on the other side closes the compensator thereby limiting the pressure and also flow in the hydraulic circuit. In other words, the pressure on the open side is limited by the relief valve. Thus, the pressure on the other side increases thereby regulating the flow and pressure through the compensator. In another embodiment of the disclosure, instead of reducing the pressure on the open side, the pressure on the closed side is increased, thereby controlling the flow and pressure of the hydraulic circuit. The pressure can be increased by a pump or any other suitable mode.

Pressure limiting in hydraulic systems

A fan drive is disclosed which includes a planetary gear set having a first rotatable output member connected in driving relation to the fan, a second rotatable output member connected in driving communication with a hydraulic circuit, and a rotatable input member connected in driven communication with a power source, the first and second output members being connected in differentially rotatable communication with the input member. During operation, the hydraulic circuit is operable to vary the rotational speed of the second rotatable output member of the planetary gear set, to thereby vary the rotational speed of the first rotatable output member and the connected fan. According to one preferred aspect of the present invention, the input member of the hydraulic circuit is an input shaft of a hydraulic pump, the rotational speed of the pump being variable by throttling fluid flow therethrough. According to another preferred aspect of the present invention, the hydraulic circuit includes a hydraulic motor connected in driven communication with the second output member of the planetary gear set and in fluid communication with a hydraulic pump to enable power delivered to the hydraulic motor through the planetary gear set to be returned to the power source through the pump.

Hydro-mechanical fan drive

The present quick drop valve control provides both quick drop and float functions by moving a quick drop valve to a position interconnecting the drop and lift sides of a pair of lift cylinders when a directional control valve reaches a predefined position. The quick drop function valve is established by simultaneously energizing a first solenoid valve to communicate a shift end of the quick drop valve with a resolved pressure port of a resolver connected to the drop and lift sides and a first solenoid of a second solenoid valve to communicate a spring end of the quick drop valve with the drop sides so that the quick drop valve moves to the interconnecting position combining fluid expelled from the lift sides with fluid going to the drop side from a pump. The float function is established by simultaneously energizing the first solenoid valve to communicate the shift end of the quick drop valve with the resolved pressure port and a second solenoid of the second solenoid valve to communicate the spring end of the quick drop valve with the tank so that the quick drop valve moves to the interconnecting position effectively intercommunicating the pump, the tank and the lift sides and the drop sides of the lift cylinders.

Quick drop valve control

A check valve normally blocks fluid flow from a bore to a passage and includes a spring normally holding a ball in sealing engagement with a valve seat to form a primary metal-to-metal hard seal. Another spring normally holds a poppet in engagement with another valve seat causing an annular protuberance formed on the poppet to sealingly engage a resilient seal to provide a more positive secondary soft seat seal. The poppet is unseated from the valve seat by a stem of a piston prior to the ball being unseated from the valve seat by a guide stem of the poppet so that the soft seal is opened at essentially zero flow conditions.

Soft seal poppet type check valve

A blade control system includes a directional control valve, a fluid regeneration valve and a selector valve for selectively controlling fluid flow between a pump and first and second hydraulic cylinders and between the cylinders. With the valves positioned at preselected operative positions, pressurized fluid from the pump is directed to the head end chamber of the first cylinder, fluid expelled from the rod end chamber of the first cylinder is diverted to the head end chamber of the second cylinder, and fluid expelled from the rod end chamber of the second cylinder is combined with the fluid being directed to the head end chamber of the first cylinders to provide two stages of fluid regeneration for increasing the extension speed of the cylinder.

Blade control system for an earthmoving blade

Growing community of inventors

Brimfield, IL, United States of America

Randall A Harlow