Improvements in Worm Gearing for Hoisting Purposes.
Year: 1886

page_text: PROVISIONAL SPECIFICATION.
Improvements in Worm Gearing for Hoisting Purposes.
I, WILLIAM HORATIO HARFIELD, of Mansion House Buildings, in the City of
London, Mechanical Engineer, do hereby declare the nature of this invention to be as
follows:-
My improvements consist in the combination of a coarse threaded worm gearing
with a wheel, the pitch being such that the worm does not act as a pawl as in ordinary
worm gearing, but upon pressure being applied to the teeth of the worm by the
wheel, the worm freely revolves in its bearings and offers but slight resistance to the
rotation of the wheel.
In the case of capstans the wheel can be conveniently fixed to the top of the capstan
body, the whole freely revolving upon a spindle fixed to the ship's deck; the upper
part of the spindle carries a bracket with bearings which support the worm shaft
which can be actuated by crank handles or steam.
The worm shaft is provided with a brake to check to regulate its rotation and in
some cases with pawls to prevent its running back.
D
L
G. F. REDFERN,
4, South Street, Finsbury, London,
Agent for the Applicant.

page_text: Improvements in Worm Gearing for Hoisting Purposes.
I, WILLIAM HORATIO HARFIELD, of Mansion House Buildings, in the City of
London, Mechanical Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
My improvements consist in the combination of a coarse threaded worm gearing
with a wheel, the pitch being such that the worm does not act as a pawl as in
ordinary worm gearing, but upon pressure being applied to the teeth of the worm
by the wheel, the worm freely revolves in its bearings and offers but slight resistance
to the rotation of the wheel.
In the case of capstans the wheel can be conveniently fixed to the top of the
capstan body, the whole freely revolving upon a spindle fixed to the ship's deck; the
upper part of the spindle carries a bracket with bearings which support the worm
shaft which can be actuated by crank handles or steam.
The worm shaft is provided with a brake to check or regulate its rotation and in
some cases with pawls to prevent its running back.
In order to enable my invention to be fully understood I will proceed to describe
how the same can be carried into practice by reference to the accompanying drawings
in which figure 1 represents, by way of example, an elevation and figure 2, a plan of
a capstan with my improvements applied thereto. Figure 3 is a sectional side view
of the brake. Similar letters in all the figures represent similar parts.
a, shews the worm wheel, b, the coarse threaded worm gearing into it. This worm
is made in one piece with the spindle and is provided with crank handles b', 6, at the
ends. c, c', are bearings in which the spindle revolves. In the bearing c¹, I fix a
bush d, having an eccentric prolongation d', at one end; upon this eccentric portion
of the bush I place an arm e, having a knuckle f; this knuckle fits into a shoe 9, the
outer surface of the shoe bearing upon the inner surface of a flange h, fixed upon the
worm spindle.
The arm e, can be moved upon its axis freely through a certain angular distance
depending upon the eccentricity of the bush d, and the thickness of the shoe
When the arm e, is thrown over as far as it will go in one direction to a nearly
horizontal position the shoe g, is forced by the weight of the arm e, against the inner
surface of the flange h, and prevents further rotation of the worm shaft b, and
consequently of the capstan worn wheel a, but if the arm e, is pulled back to its
normal or vertical position the worm shaft b, can revolve in either direction should there
be
any strain
upon the capstan and will continue to revolve as long as the shoe 9, is
kept free from contact with the inner surface of the flange h. When the arm e, is
thrown over as far as it will go, to a nearly horizontal position in the opposite
direction then the weight of the arm acts upon the opposite side and the capstan is
pawled in the reverse direction.

page_text: For the purpose of illustration I have described and illustrated my invention as
applied to a capstan; its application to other hoisting mechanism will be obvious and
therefore needs no further description. It will also be understood that any other
suitable arrangement of brake and pawl may be employed although the arrangement
I have described and illustrated gives good results.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed I declare that what I claim is
1. A capstan driven by a coarse pitch worm and worm wheel substantially as
hereinbefore described and illustrated in the accompanying drawings.
2. The combination with a capstan (or other hoisting machine) of a coarse pitch
worm and worm wheel and a pawl or brake to prevent overhauling as herein before
described.
G. F. REDFERN,
4, South Street, Finsbury, London,
Agent for the Applicant.