The engineer's sketch-book of mechanical movements, devices, appliances, contrivances and details employed in the design and construction of machinery for every purpose

by Thomas Walter Barber

Section 81.—SAFETY APPLIANCES FOR VARIOUS USES.

FOR HOIST CAGES, &c.

[1492]. Cam gear; operates by gripping the wood guides by a serrated eccentric cam surface on the breakage of the rope, the cam being pulled round by a spring which is kept out of action by the tension of the rope until it breaks.

[1493]. Strut or pawl gear; explains itself.

[1494]. Double wedge gear.

[1495]. Governor gear. The rope attached to the cage drives a governor acting on a brake or catch which is thrown into action if the cage gains excessive speed, used in Attwood Beaver’s Patent; American Elevator Co., &c.

[1496]. Rack and pawl gear.

[1497]. Cross grip lever gear.

[1498]. Safety hook to prevent accident from overwinding; the projecting horns A A strike the edges of the plate B, and throw the shackle C at top out of gear.

For hoist doors the best appliance is an ordinary spring lock opened only by a key, the doors being provided with springs to close them. Various automatic doors, revolving shutters, and other devices have also been tried. A simple and effectual protection is a continuous open-work screen wound upon a roller at top and bottom of lift, and attached to the top and bottom of cage and rising and falling with it, so that the doors into lift are all covered at all times except the one at which the cage happens to stand.

Safety valves (see [Section 89]). Various automatic alarm signals are applied to boilers to warn against low water or excessive pressure.

Automatic valves and other devices are applied to pumping and steam engines to prevent running away. See [note] to [Section 41].

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