A novel device in connection with rope pulley blocks is illustrated in
the annexed engravings, the object of the appliance being to render it
possible to leave a weight suspended from a block without making the
tail of the rope fast to some neighboring object. By this arrangement
the danger of the rope slipping loose is avoided, and absolute security
is attained, without the necessity of lowering the weight to the ground.
The device itself is a friction brake, constructed in the form of a clip
with holes in it for the three ropes to pass through. It is made to span
the block, and is secured partly by the pin or bolt upon which the
sheaves run, and partly by the bottom bolt, which unites the cheeks of
the block. Thus the brake is readily attachable to existing blocks. The
inner half of the clip or brake is fixed solidly to the block, while the
outer half is carried by two screws, geared together by spur-wheels, and
so cut that although rotating in opposite directions, their movements
are equal and similar. One of the screws carries a light rope-wheel, by
which it can be rotated, the motion being communicated to the second
screw by the toothed wheels. When the wheel is rotated in the right
direction the loose half of the clip is forced toward the other half,
and grips the ropes passing between the two so powerfully that any
weight the blocks are capable of lifting is instantly made secure, and
is held until the brake is released.
A light spiral spring is placed on each of the screws, in order to free
the brake from the rope the moment the pressure is released. The hand
rope has a turn and a half round the pulley, and this obviates the need
of holding both ends of it, and thus leaves one hand free to guide the
descending weight, or to hold the rope of the pulley blocks.
_Engineering_ says these brakes are very useful in raising heavy
weights, as the lift can be secured at each pull, allowing the men to
move hands for another pull, and as they are made very light they do not
cause any inconvenience in moving or carrying the blocks about.
Manufactured by Andrew Bell & Co., Manchester.
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