[2486]. Adjustable spiral spring. A washer on top has four vanes below it drilled with holes to suit the diameter and pitch of the spring wire, which, being threaded through the vanes, is rendered inactive, so far as it is held by the vanes. This appliance, therefore, is used to shorten or lengthen the live or active part of a spiral spring.
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Section 81.—SAFETY APPLIANCES.
(See also [p. 182].)
[2487]. Guard for spur gearing.
[2488]. Guard for bevil gearing.
[2489]. Safety nut for a running screw. The nut takes no strain until the thread in the main nut gives way from wear.
Fire alarms (automatic) depend for their action on increase of temperature above a normal maximum.
Diaphragms are inserted in the pipe connections to hydraulic lift cylinders to admit or discharge the water at moderate speeds only, so that in case of a burst the lift should not descend too rapidly.