Lift machine

Pages:52-54
 
FREE EXCERPT
A8 Lift machine
A8.1. Methods of driving the car and the counterweight
A8. 1.1. The two following driving methods may be used:
by traction (use of sheaves and ropes);
by fixed attachment (use of a winding drum and ropes, or
chain drive wheels and chains).
A8.2. Use of belts to drive the machine
A8.2. 1. Belts may be used to couple the motor or motors to
the rotating part subjected to the mechanical brake action, pro-
vided that the belts are of the 'CV,' or toothed type; that there is at
least one more than the minimum number determined by calcula-
tion; and that in any case there are never less than three.
A8.3. Use of overhung sheaves or pulleys
A8.3.l. When overhung sheaves or pulleys are used, arrange-
ments should be made to prevent the ropes from leaving the sheave
or pulley grooves.
A8.4. Brake system
A8.4. 1. Thd lift should be fitted with a brake system which
must include a mechanical brake; additional means of deceleration
may be provided, for example dynamic braking.
A8.4.2. The brake system should act automatically in case of
failure of the electric supply to the machine or the controls.
A8.4.3. The brake system should be capable of stopping a
descending car travelling at contract speed with its contract load
increased by 25 per cent.
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