(a) Type of Driving Machine. All driving
machines shall be of the traction type.
EXCEPTION: Winding drum machines may be used for
freight elevators subject to the following:
1. They shall not be provided with
counter-weights.
2. The travel of
the elevator car shall not exceed 40 feet.
3. The rated speed of the elevator shall not
exceed 50 feet per minute. The installation of belt drive and chain drive
machines is prohibited.
(b) Material and Grooving for Sheaves and
Drums. Sheaves and drums used with suspension and compensating ropes shall:
(1) Be of metal finished grooves, provided
the grooves of sheaves not used to transmit power may be lined with rubber or
other sound isolating material.
(2)
Have a pitch diameter not less than:
(A)
40 times the diameter of the rope, where used with suspension
ropes.
EXCEPTION: Existing sheaves where 8x19 wire rope is
used and which have a diameter less than 40 diameters of the rope, but not less
than 32 diameters, and are provided with permanent marking "Use 8x19 Cables
Only."
(B) 32 times the
diameter of the rope, where used for compensating
sheaves.
(c)
Factor of Safety for Machines and Sheaves. See Design Section
3104.
(d) Bolts Transmitting Torque, and Set
Screws.
Bolts or other means used to transmit torque between the
driving sheave and the gearing, and their supports, shall be tightly fitted
without play.
Set screws or threaded portions of bolts or
screws shall not be used to transmit torque.
(e) Shaft Fillets and Keys. A fillet shall be
provided at any point or change in the diameter of driving-machine shafts and
sheave shafts to prevent excessive stress concentrations in the shafts.
Shafts which support drums, sheaves, gears,
couplings, and other members, and which transmit torque, shall be provided with
tight fitting keys.
(f) Cast Iron Worms and Worm Gears. Worms and
gears made of cast iron shall not be installed nor used as replacements in
elevator driving machines. Worms and worm gears shall be so arranged that in
the event of the worm shaft breaking the worm will still remain in mesh with
the worm gear.
(g) Friction Gearing
and Clutches. Friction gearing or a clutch mechanism shall not be used
in elevator driving machines for connecting the drums or sheaves to the source
of power.
(h) Driving
Machine Brakes.
(1)
The elevator
driving machine shall be equipped with a friction brake applied by a spring or
springs, or by gravity, and released electrically.
(2)
The brake shall be designed and
maintained to have a capacity sufficient to hold the car at rest with its rated
load.
(3)
Where
gravity is used to apply the brake, the weights shall be guarded to prevent any
obstruction being placed under the weights.