IMPROVEMENTS IN APPARATUS FOR REGULATING THE MOTION AND ACTION OF DOOR SPRINGS
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by Alexander Charles Moffatt at
the Office of the Commissioners of Patents, with his Petition, on the
19th December 1870.
I, ALEXANDER CHARLES MOFFATT, of Princes Street, Leicester Square,
in the County of Middlesex, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN APPARATUS FOR REGULATING THE MOTION AND
ACTION OF DOOR SPRINGS," to be as follows:-
This Invention relates to certain improvements in apparatus for
regulating the motion and action of door springs, the object being to
effect an uniform closing of a spring door in the central position of
movement, although the sole plate fixed in the floor may have changed
its original situation by the loosening of the screws or the stress of the
leverage.
In order to effect this result the axis on which the door swings is
provided (beneath the sole plate in the recess of the metal chamber)
with a crank set or keyed horizontally, such crank having a disc or
circular bearing plate thereon, the two opposite surfaces of the disc
bearing on two curved levers set on fulcra near the centre of the
spring.

page_text: Now in ordinary circumstances where the sole plate or chamber is in
its true position these curvilinear levers are at all points equidistant
from the centre of motion of the axis, and they are kept in such position
by means of an adjustable bar, with a projection thereon, so that each
extremity of the levers buts against the projection; but when the door
plate is out of its true line this adjustable bar is shifted in the requisite
direction, so as to compensate for the variation of the medial line, and
consequently the motion and action of the levers is regulated and con-
trolled by means of the central projection or stop for closing the door,
and by the extreme side stops for each opening. The mainspring is
connected at each extremity with the outer arm of each curved lever,
at about such point as may be necessary between the fulcra and the
curvilinear levers, or if the spring is required to be of a larger diameter
its points may be brought in contact or fixed to the curvilinear portion
of the lever; the action will be the same, for since the spring presses
constantly on each arm of the lever and forces both in contact with the
stop to close the door, it necessarily follows that the point of closing
must be regulated according to the position or angle of the central stop,
the internal curves of the levers at the closed position fixing the disc of
the crank in or out of line with the medial line of the door plate.
Above the sliding bar a fixed bar is set containing a slot at or near
each end, so that when the under bar is shifted two set screws may be
tightened on the slots, and passing into threads in the regulating bar
may hold the same in the required position. Or a horizontal lever may
be applied to the regulating bar, whereby it may be shifted, and the
lever can then be secured to the chamber by a set screw. This method
of securing the regulating bar would be preferable to the former. The
stems of the curvilinear crank levers may be serrated or notched with
saw teeth, in order that the spring may be adjusted to different powers
to suit the unequal pressure on each side of the door. The teeth hold
the extremities of the spring in position, notwithstanding the change in
the angles of the crank caused by the position of the determinable line
of the door centre.