The sense of falling once more made him clutch the cloak.
When the load to be weighed comes upon the platform, the end of the steelyard rises and unlocks the ratchet wheel through the pawl; the sprocket gearing is driven by the friction clutch, and drives the axle of the left-hand small pulley.
Together by clutch gearing the left-hand pulley and the adjacent sprocket wheel, and the pulley drives the sprocket wheel in the opposite direction to that which it had before.
The clutch mechanism is freed at the proper time by the action of the vertical rod at the end of the beam, and the brushes then he 4-lb weight is being lifted.
The drum-shaft is connected by a friction clutch with a shaft in the same line, on which are keyed a sprocket wheel and a ratchet wheel.
When the poise is at the zero end, and there is no load on the platform, the end of the steelyard is down, and has locked the ratchet wheel by means of the pawl; the shaft being thus locked, the sprocket wheels are stopped, the drum-shaft runs free by the friction clutch, and the two pulleys which are connected by the crossed band are running idle.
When the poise arrives at zero it frees the clutch which connects the pulley and the sprocket wheel, and the machine is then ready for the next load.
The engagement of the pulley and clutch is determined by a hand-controlled block F sliding on the shaft, the movement of which is communicated to the rightand left-handed screw shafts by links G connected to the levers H.
A fork or clutch rotates along with the shaft, and is capable of being moved longitudinally by a handle.