IMPROVEMENTS IN DIFFERENTIAL PULLEY APPARATUS
Year: 1882

page_text: LETTERS PATENT to William Robert Lake of the firm of Haseltine, Lake,
"
& Co. Patent Agents, Southampton Buildings London for an invention of
IMPROVEMENTS IN DIFFERENTIAL PULLEY APPARATUS A communication
from abroad by François Roy, of St Etienne, France, Engineer.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at
the Office of the Commissioners of Patents on the 12th May 1882.
PULLEY
WILLIAM ROBERT LAKE of the firm of Haseltine, Lake, & Co Patent Agents,
Southampton Buildings, London " IMPROVEMENTS IN DIFFERENTIAL
APPARATUS "A communication [from abroad by François Roy, of St Etienne,
France, Engineer.]
This invention relates to differential pulleys worked by endless cords or ropes,
and designed to maintain a weight suspended, without the rope being held or made
fast and to ensure perfect security, at the same time preserving the force necessary
to lift the desired weight.
According to the said invention I provide a pair of pulley blocks with differential
pulleys, that is to say, with sheaves having two or more grooves of different
diameters, the larger groove being at one side of the sheave and the smaller at the
opposite side. For tackle which is only required to raise light weights I employ
sheaves with curved or semi-circular grooves as in the tackle ordinarily used. For
heavy weights I employ sheaves with angular and undulating grooves in order to
create more friction upon the rope and to give the weight, which tends to descend,
a greater resistance to overcome. An endless cord or rope is wound upon the said
sheaves so that when force is applied to that part of the rope which is wound upon
the larger groove of the top sheave the weight is thereby raised, and when force is
applied to the other part of the rope the weight is lowered. But if at any moment
the rope should be let go, the weight will still be suspended.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Paten filed
by the said William Robert Lake in the Great Seal Patent Office on the
11th November 1882.
WILLIAM ROBERT LAKE of the firm of Haseltine, Lake, & Co, Patent Agents,
Southampton Buildings, London " IMPROVEMENTS IN DIFFERENTIAL PULLEY
APPARATUS" A communication from abroad by François Roy, of St Etienne,
France, Engineer.
This invention relates to differential pulley apparatus worked by endless cords
or ropes and designed to sustain a weight without the rope being held or made
fast, and to ensure perfect security, at the same time preserving the power necessary
to lift the desired weight.
According to the said invention I provide a pair of pulley-blocks with differential
pulleys, that is to say with sheaves having two or more grooves of different
diameters, the larger groove being at one side of the sheave and the smaller at the
opposite side thereof. For tackle which is only required to raise light weights I
employ sheaves with curved or semi-circular grooves as in the tackle ordinarily used
and as represented in the accompanying drawing
For raising heavy weights I employ sheaves with angular and undulated grooves
in order to create more friction upon the rope and to give the weight, which tends
to descend, a greater resistance to overcome. An endless cord or rope is wound
upon the said sheaves in the manner illustrated in the drawing.
The operation of the said differential pulley apparatus is as follows, that is to
say if force is applied to the part B of the rope which passes around the largest
groove of the top sheave the weight will be raised because the amount of cord or
rope wound at the side is less than that unwound at B. If force is applied to the
other part of the rope the weight will be lowered. But if at any moment the rope
should be let go the weight will remain suspended.
The apparatus above described may be modified according to the purpose for
which it is required.
Having thus fully described the said invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it
understood that I claim-
The pulley-blocks provided with the differential pulleys having round or angular
grooves, undulated or not, as above described
In witness whereof I the said William Robert Lake have hereunto set my
hand and seal this Eleventh day of November in the year of our Lord One
thousand eight hundred and eighty two.
M PORT LAKE