CERTAIN IMPROVEMENTS IN STEAM ENGINES
Year: 1872

page_text: .
PROVISIONAL SPECIFICATION left by John Maddy at the Office of
the Commissioners of Patents, with his Petition, on the 1st July
1872.
.
I, JOHN MADDY, of Birmingham, in the County of Warwick,
Carpenter, do hereby declare the nature of my said Invention for
"CERTAIN IMPROVEMENTS IN STEAM ENGINES," to be as follows (that is
to say)-
My improvements particularly apply to the description of steami
engines known as horizontal engines, in which I prefer the piston rod
working through packing boxes both ends of the cylinder, and which
improvements may be divided into two parts :-
First. An equilibrium balance to compensate the weight of the
piston and rod, so that the piston rod shall work evenly through the
packing at the ends of the cylinder without bearing its weight on
the under side of such packing boxes, but shall bear evenly on all sides
through the packing.
Secondly. To increase the throw of the crank as a means of increasing
force without increasing the range of the stroke.
This I effect by applying to the outer end of the crank an axis
on which I place a friction roller, and to the end of the piston rod

page_text: I apply a rectangular frame the two sides of which are curved
about one-fourth each side described by the revolution of the crank
and friction roller, so that while the crank is traversing the dead points
of its revolution the piston will be stationary, during which time the
steam will be corrected by suitable valve gear and admitted at a time
when the crank is in position to receive the force of the steam, the
momentum of the fly wheel carrying it through the dead points as in
ordinary engines. This rectangular frame at the spring of the curves
will represent an opening equivalent to the diameter of the range of the
friction roller before referred to, and thus the reciprocating motion is
maintained by the roller working against the extreme or outer part of
the curved cross head or frame of the one side during one fourth of its
revolution, and then the piston will be stationary one fourth, when the
friction roller will again come into play performing the same operation
on the other corresponding side of the cross head or frame, thus making
up the revolution, the range of the piston being diminished just as much
each way lost in the throw of the crank by the crank and roller passing
over the curved sides of the cross head at the dead points of its throw,
as the piston during the time the crank is passing around the curved
surfaces does not move; thus, for instance, the crank may have a throw
of six inches, whilst the stroke of the piston will be contracted to nine
inches, thus yielding a force equal to one fourth gain on the mode
ordinarily in use. The rectangular frame stands vertical in a line
with the cylinder working between guide rolls, thus preserving a
strictly direct or parallel action to the cylinder; the weight of the
piston rod, to which the rectangular frame is attached, as also the
piston, being compensated for or counterpoised by allowing the piston
rod to work with and be fixed to the rectangular end of a bar of
Tiron; this bar rides on, by preference, two loose rollers, which
a lever set up identically like the levers of common
stilliards or weighing machines, with a compensating weight working
in a traversing groove, so as to set it exactly according to the weight
of the piston and rod, and as the piston reciprocates the T iron bar
works at the same time over the roller or rollers resting on the lever
below.
bear on