IMPROVEMENTS IN REVOLVING SHUTTERS
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Jabez Henry Forshaw at the Office of
the Commissioners of Patents, with his Petition, on the 27th February
1866.
I, JABEZ HENRY FORSHAW, of Barrow-in-Furness, in the County of
Lancaster, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN REVOLVING SHUTTERS," to be as follows:-
This Invention relates to certain improvements in revolving shutters, and
in the mode of hanging the same, whether composed of wood or metal, whereby
they are more easily opened and closed; and the wear and tear produced
by the friction of the shutter in its guiding grooves or slots is greatly
reduced..
According to one mode of carrying out this Invention it is proposed to.
balance the shutter by the aid of a weight or weights, suspended by one or,
more chains or cords wound round a conical spiral grooved pulley fixed on to,
one or both ends of the roller upon which the shutter is coiled. This conical
spiral pulley acts in the same manner as the well-known "fusee" of a watch
or clock by compensating for the gradually diminishing or increasing diameter.
of the shutter roller, according as the shutter is being coiled or uncoiled; or
in lieu of the conical spiral grooved pulley above mentioned an ordinary grooved
pulley or pulleys may be used, the chain or cord by which the weight or
weights are suspended being of the same thickness as the shutter, and made

page_text: to coil upon itself, so that as the shutter is coiled or uncoiled on to or from
the roller, thereby increasing or diminishing the leverage or diameter of the
same, the diameter or leverage of the pulley or pulleys will vary in the same
proportion, and will adapt itself at all times to the greater or less weight of the
shutter.
By the arrangement above referred to it is obvious that the weight of the
shutter may be accurately balanced in any position, and facility is afforded
for readily opening or closing the same by the direct application of the hand
without the necessity for special pulleys, cords, and winch handles for that
purpose. Greater simplicity and economy of construction are consequently
ensured.
In order to avoid undue strain and friction in working revolving shutters
it is proposed to adopt a simple self-acting arrangement for ensuring that
the shutter shall always be perpendicular to its guiding grooves, whether
fully or partially coiled or uncoiled; this is accomplished by imparting to the
roller on which the shutter is coiled a horizontal parallel motion to and from
the guiding grooves, such motion being in exact proportion to the varying
diameter of the roller; for example, when the shutter is fully coiled the roller
will be at its maximum diameter, and the shutter ought to hang at a true
tangent from the coil, and be at the same time in a plane coinciding exactly
with that of the guiding grooves.
As the shutter is uncoiled or drawn down
the diameter of the roll diminishes, and in order to maintain the tangential
line of the shutter still in the plane of the grooves it follows that the roller
must approach towards the grooves in the same ratio as its diameter decreases,
or vice versa in the case of coiling up the shutter. This movement may be
obtained in various ways, but the following arrangement will be found to
answer well-Upon the axis of the roller which receives the shutter there
are formed at each end two eccentrics which respectively engage into two
correspondingly formed racks or notched supporting plates, the notches therein
being of a semicircular form. As these two eccentrics revolve round a common
centre corresponding to the axial centre line of the roller they engage into
or gear with the different notches in succession, the action being somewhat
similar to that of a fixed rack and a toothed pinion travelling over it,
a modification of which arrangement might also be employed, or a screw
motion or other equivalent mechanical contrivance used for the like purpose.