Abstract: A video guidance system for visually displaying a row mark traced on the surface of a field during a previous traverse to the operator of a farm tractor pulling a planter has left and right row markers depending respectively from opposite outer sides of the planter for tracing row marks on the field; a video monitor on the tractor in the field of view of the operator; left and right video cameras mounted on the planter adjacent the outer edges thereof with the optical axis of each camera directed forwardly and inclined at a slight angle to the horizontal so that it images a substantial length of a row mark traced on a previous swath; and switch means for selectively connecting the video monitor to the left or to the right video cameras, whereby each scanning line of the video monitor raster creates a different spot on the image of the substantial length of the sensed row mark and such spots on successive scanning lines of the monitor raster are images of points spaced apart in said sensed row mark so the spot

Abstract: Apparatus for uniformly grinding the peripheral surface of a kiln ring of a rotating rotary kiln to axial flatness includes a grinder; an electrical motor for continually driving the grinder; a pneumatic cylinder for urging the grinder against the surface of the kiln ring; a current transformer for sensing the magnitude of current flow to the motor; and a controller which compares the magnitude of sensed motor current to a set point reference of desired current flow to the motor and supplies pressurized fluid to the pneumatic cylinder at a pressure which varies as an inverse function of the difference between sensed current and set point references and maintains the current flow to the motor equal to the set point reference.

Abstract: Apparatus for destroying weeds in and around crop rows has a high voltage source of electricity mounted on a vehicle; a coulter wheel for connecting the high voltage source to the ground; a plurality of weed contacting electrodes carried on the vehicle and insulated therefrom; and a plurality of isolating electrical reactance inductors each of which connects a weed contacting electrode to the high voltage source and limits the magnitude of current flowing through the high voltage source when the electrode contacts a weed to thereby minimize the voltage drop across the high voltage source and maintain substantially constant voltage on the remaining electrodes.

Abstract: A fork lift truck has a safety system for inhibiting further raising of the carriage or further forward tilting of the mast when an excessive tilting moment is acting on the truck and permits the truck operator to selectively simulate an overload on the truck and provides a visual indication that the safety system has responded properly to such simulated overload, thereby permitting the truck operator to test whether or not the truck is protected from picking up an overload.

Abstract: A fork lift truck has a safety system for inhibiting further raising of the carriage or further forward tilting of the mast when an excessive tilting moment is acting on the truck and permits override of the safety system so that the overload can be relieved by the operator under certain conditions without requiring the assistance of a second truck.

Abstract: A fork lift truck has an overload protective circuit which is responsive to an excessive tilting moment acting on the truck, as a result of a load on the raised carriage, to disable the mast tilting motor and carriage elevating motor from shifting the load supporting carriage in a direction which would increase the forward tilting moment and also has a crowbar circuit which, upon failure of the protective system to respond properly to such excessive tilting moment, opens an electrical circuit that also results in inhibiting the mast tilting and carriage elevating motors from further raising the carriage or further forward tilting of the mast on the overloaded truck, thereby providing enhanced protection against faulty operation resulting from component failure. One embodiment permits the truck operator to selectively simulate an overload and thereby initiate testing for component failure in the overload protective system.