System for one-hand control of two winches during hoisting of closed clamshell, with differentiation

A hydraulic system for controlling a clamshell bucket by two hoist lines of which a first can close and raise the clamshell and the second can dump the clamshell if raised relatively to the first, said system including a first hydraulic motor and winch for the first hoist line and a second hydraulic motor and winch for the second hoist line, and means operable at will, when the first winch motor is operated to draw in the first hoist line, for establishing connections placing the second motor hydraulically in series with the first motor, thereby tending to draw in the second hoist line at substantially the same speed as the first, and means effective throughout raising the clamshell for controlling the pressure of the hydraulic fluid thus supplied to the second motor to provide a pressure sufficient to draw in the second hoist line when slack;

• said system including means responsive to the back pressure of the fluid supplied to the second motor for limiting that pressure to a value too low to start dumping the clamshell.

A hydraulic system for controlling a clamshell bucket by two hoist lines of which a first can close and raise the clamshell and the second can dump the clamshell if raised relatively to the first, said system including a first hydraulic motor and winch for the first hoist line and a second hydraulic motor and winch for the second hoist line, and means operable at will, when the first winch motor is operated to draw in the first hoist line, for establishing connections placing the second motor hydraulically in series with the first motor, thereby tending to draw in the second hoist line at substantially the same speed as the first, and means effective throughout raising the clamshell for controlling the pressure of the hydraulic fluid thus supplied to the second motor to provide a pressure range sufficient to draw in the second hoist line when slack but limited to a pressure too low to start dumping the clamshell;

• said last named means including a bypass past the second motor, and means for closing said bypass when the back pressure in the fluid being supplied to the second motor is below the stated pressure range, while opening it if that range is exceeded.

A hydraulic system for controlling a clamshell bucket by two hoist lines of which a first can close and raise the clamshell and the second can dump the clamshell if raised relatively to the first, said system including a first hydraulic motor and winch for the first hoist line and a second hydraulic motor and winch for the second hoist line, and means operable at will, when the first winch motor is operated to draw in the first hoist line, for supplying to the second winch motor a sufficient supply of hydraulic fluid to operate said second winch motor enough to avoid the development of excessive slack in the second hoist line, and means effective throughout raising the clamshell for controlling the pressure of said supply to provide a pressure sufficient to draw in the second hoist line, when slack, but limited to a pressure too low to start dumping the clamshell;

• said system including solenoid valve means, and means on an operator's main control lever for him to selectively operate said solenoid valve means for either providing the system as defined or, at will, a system in which each of two operators' handles separately controls one of the motors.