27,249. Holme, E. M. Dec. 10. Motor control systems; switches. - A portable switchboard is provided by means of which electric reversible motors operating the control mechanism of a crane may be regulated. In an hydraulic crane, the valve operating lever 1, Fig. 1, of the hoisting- cylinder is connected to an endless chain 8 passing over a sheave 9 driven from an electromotor 12. Fig. 3 shows the arrangement of the circuits for controlling the motor 12 from the portable switchboard 20. Limit switches 15 are so arranged that when the lever 1 reaches the end of its stroke, current is cut off from the motor 12 and a brake operated by a coil 14 is applied thereto. This brake can also be applied to hold the lever 1 in any intermediate position, by moving the lever of the switch 20 into a position intermediate of the central and ' on' positions, the motor 12 being then cut out. A similar arrangement is provided for controlling the lever of the slueing cylinder. In the case of an electrically-actuated crane, the motors 112 operate the controllers 25, Fig. 4, of the hoisting and slueing motors. Each motor 112 drives, through worm gearing 11, a disk having projecting lugs 28 depending on each side of the controller lever 27 in such a manner that the disk can move a certain amount without actuating the controller lever 27, but, when the lever starts the barrel, contacts snap suddenly from one set of contacts to another. As the lever 27 moves from its central position, a switch 31 is set with a snap in the opposite direction by means of a lever 30. In connexion with the shafting 36 of the main hoisting and slueing motors, there are provided brakes operated by solenoids 114<x>, the cores 37 of which are connected by links 38 to levers 35 on the brake shafts. Fig. 6 shows the system of electrical connexions. When the lever 41 of the hoisting switch 20 is moved into either of the positions 3, circuit is made through the motors 112, resistance 44, and limit switch 115. At the same time, the main brake is removed by the coil 114<x>, and the brake of the motor 112 by the coil 114. When the lever 27 is fully thrown over, the switch 115 is opened and the circuit is broken. To restore the controller lever to the 'off' position, the lever 41 is moved to position 1, when the main brakes are applied by opening the circuit of the coil 114<x>, and the circuit is established through the motor 112 in the reverse direction through the switch 30. The resistance 44 being out of circuit, the lever 27 is quickly restored to the 'off' position, when the circuit is broken by the lever 27 at the switch 30. In order to throw the controller lever 27 only partly over, the switch 20 is moved first into position 3 and then into position 2, when the circuit of the motor 112 and brake coil 114 is broken and the lever 27 is stopped. The arrangement of the control circuits of the slueing-gear is similar, but the brake 114x is normally 'off,' and is applied, when desired, by pushes 42 on the slueing-switch 21.