Blade control device

A blade control device for use on a ground leveling machine and utilized with a laser projector turning at predetermined speed, said blade control device including a light receiving device mounted to a blade to receive the laser beam projected by said projector and providing a light receiving position deviation signal, a circuit for latching the light receiving position deviation signal output each time said light receiving device receives said laser beam, a lift cylinder control system for lifting said blade in a manner so as to make the value of the light receiving position deviation signal latched at said latch circuit zero, comprising:

• a sensor for detecting the working stroke of the lift cylinder for lifting said blade and providing an output signal;
• sampling means for sampling and holding the output signal of said sensor, said sampling being synchronized with the latching of said latch circuit;
• adding means to add the signal held by said sampling means and the light receiving position deviation signal latched at said latch circuit;
• and
• detecting means for detecting the difference between the added result of said adding means and the output signal of said stroke detecting sensor, said lift cylinder control system being operated in response to the difference detected by said first detecting means so as to make the value of the deviation signal zero.

A blade control device comprising:

• a blade;
• a light receiving device mounted to the blade and movable with respect to the blade in vertical directions;
• a light receiving device controlling system means for positioning, when in an automatic leveling mode where said blade is automatically controlled using a reference surface formed by a laser beam, said light receiving device to a height above the blade corresponding to a command value,
• a lift cylinder control system means, to which there is provided, when in the automatic leveling mode, a deviation signal representative of deviation of light receiving position of said light receiving device with respect to the laser beam projecting at a predetermined height, for lifting or lowering the blade so as to eliminate said deviation;
• first switching means for inputting said deviation signal, instead of said command value, to said light receiving device controlling system means during a topographic survey period;
• a manual control device for producing a manual control signal which lifts or lowers the blade by a manual operation;
• second switching means for inputting said manual control signal, instead of said deviation signal, to said lift cylinder control system means in the topographic survey period, said lift cylinder control system means being free from receiving signals from said light receiving device during said topographic survey period;
• and
• height measuring means for measuring the change in height of said light receiving device.

A blade control device comprising:

• a blade;
• a light receiving device mounted to the blade so as to be movable in vertical directions;
• a light receiving device controlling system means for positioning, when in an automatic leveling mode where said blade is automatically controlled using a reference surface formed by a laser beam, said light receiving device to a height corresponding to a command value;
• a lift cylinder control system means to which, when in the automatic leveling mode, a deviation signal representative of the deviation of the light receiving position of said light receiving device with respect to the laser beam projecting at a predetermined height is provided, for lifting or lowering the blade so as to eliminate said deviation;
• a manual control means for producing a manual control electronic signal output indicative of desired lifting or lowering of the blade in a manual operation;
• and
• switching means for inputting the signal output of said manual control means, instead of said command value, to said light receiving device controlling system means during manual operation, and for inputting said command value to said light receiving device controlling system means during the automatic leveling mode after the manual operation is finished, said lift cylinder control system means being free from receiving signals from said light receiving device during manual operation, and said light receiving device controlling system means being operable by said deviation value to move said light receiving device vertically relative to said blade during said manual operation.