A New English Patent Pulley Block.


The following description of a new pulley block, which we take from the
_Ironmonger_, does not give as clear an idea of the invention as could
be desired, but it shows that invention in this field has not yet
exhausted itself:

[Illustration]

"The block is made on the differential principle. The lifting chain is
passed over two sheaves, each of which is geared internally, the one
having one or more teeth in excess of the other. Revolving around these
internal teeth is a pinion, actuated by an eccentric, which is keyed on
to a shaft passing through the center of the block, with a bearing at
each end in the outside frame of the block. At one end of this shaft
is a wheel with an endless hand chain passing over it; this gives the
motion to the eccentric shaft. The teeth of the internal pinion are
broad enough to gear into the teeth of both the sheaves, but as there is
more teeth in one than in the other, they (the teeth) are not exactly
opposite each other, and therefore will not admit the teeth of the
revolving pinion without moving; but the tooth of the pinion, acting as
a wedge, and entering with great power, pushes the one tooth forward and
the other tooth back; and this continually occurring, a continual rotary
motion is given to the sheaves, in opposite directions, with a power
which is proportioned to the number of the teeth, the throw of
eccentric, and the leverage gained by the diameter of the hand wheel.
The lifting chain is passed over the one sheave, then down, and up over