Quantcast Inspection of Interlocks and Cams

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As there is no positive mechanical connection between the electric contact and the door-locking
mechanism, this device insures only that the door will be closed, but not necessarily locked,
when the car leaves the landing. Should the lock mechanism fail to operate as intended when
released by a stationary or retiring car-cam device, the door can be opened from the landing side
even though the car is not at the landing. If operated by a stationary car-cam device, it does not
prevent opening the door from the landing side as the car passes the floor. Inspection of Interlocks and Cams. The inspection of the interlocks and their operating
cams or similar devices can be made more conveniently by moving the dumbwaiter car below the
opening. On doors or gates equipped with interlocks which are unlocked automatically by
retiring cams or similar devices, when the car is in a landing or leveling zone, place the car at
each landing at such a position above and below the landing that the automatic unlocking device
on the car cannot release the interlock. With the car door in the closed position and with the
hoistway door fully open, close the hoistway door slowly from the landing side until the
maximum clear opening is reached. Then the actuation of the operating device will cause the car
to start. Measure the distance from the nearest face of the door sill to the nearest edge of the door
or between the rigid meeting edges of biparting doors. Determine that from this position, the
door cannot be reopened from the landing side. The measured distance should not exceed 3/8
inch for vertically sliding counterweighted doors or 3/4 inch for vertically sliding biparting
counterbalanced doors. Inspect mechanical locks operated manually from the car, where used,
with hoistway door electric contacts. With the door in the fully closed position, pull on the door
which should be held closed by the lock. Determine that the locking member is in a position
to lock the door when or before the contact is closed by the door. Where the locking members of
such devices are operated by car cams, which are usually but not necessarily of the stationary
type, place the door in the fully closed position and move the car a sufficient distance away from
the floor to permit the locking member to lock the door. With the car in this position, pull or
push on the door, which should be held closed by the lock. Release the lock manually and open
the door. Then slowly close it to the position where the electric contact just closes and note
whether the locking member is in a position to lock the door. Examine any stationary or retiring
cams for operating interlocks, interlock contacts or door operators, to determine whether they are
in correct alignment with the roller arm of the interlock or door operating mechanism, whether
their travel is sufficient to insure proper operation of the interlocks or door operators, and
whether wear of chains, sprockets, etc., is not excessive. Figure 4-7 shows a typical cam


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