IMPROVEMENTS IN STEAM ENGINES
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by William McNaught, the elder,
John MºNaught, and William McNaught, the younger, at the
Office of the Commissioners of Patents, with their Petition, on the
22nd April 1874.
We, WILLIAM MCNAUGHT, the elder, JoHN MCNAUGHT, and WILLIAM
MCNAUGHT, the younger, all of Rochdale, in the County of Lancaster,
Engineers, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN STEAM ENGINES," to be as follows:-
The first part of our Invention relates to improvements in the present
methods of producing an instantaneous "cut off" by means of springs,
pistons, or weights suddenly released, and consists as herein-after
described, that is to say, in employing for this purpose two revolving
cams one for each end of the cylinder, the form of their peripheries
approximating to that of a geometric spiral of one revolution or of half-
a revolution having a sudden drop from its greatest radius to its least,

page_text: the difference of which radii being the amount of “lift.” As these
cams rotate they raise the ends of two levers in opposition to the force
of the aforesaid springs which suddenly depress their ends when the
drop in the cam arrives. These levers may be connected to any of the
class of valves herein-after described, so that raising them opens
the valve, and the sudden depression shuts it, producing the required
cut off which may be caused to occur carlier or later in the stroke within
a limited range by withdrawing or advancing those levers lengthwise,
either in the direction or contrary to the direction of the rotation of the
cams, this withdrawing or advancing being performed by the governor
by usual connections.
By employing two cams, one for each end of the cylinder, we can
adjust the amount of cut off at either end of the cylinder without
interfering with the other end. In order to inorease the range of the
said "cut off" we drive the shaft upon which the cams are mounted
by a pair of elliptical wheels which impart a varying angular velocity to
the said shaft and consequently to the said cams, and those wheels are
so geered to the fly wheel or crank shaft that the cams may have their
least angular velocity when the ends of the said levers are in the vicinity
of the drop on their periphery, by which means a greater range of
"cut off" is obtained than by the use of circular wheels.
In order to prevent concussion from the sudden drop, we employ an
arrangement of air cylinder having one or more holes in the periphery,
the piston of which after the lever is released passes over the said holes,
the air then becomes confined, and its resistance stops the piston and
consequently the valve to which it is connected. The said holes may be
opened or closed partially by shifting the position of a hoop fitted on
the said cylinder having holes through its periphery corresponding with
the holes in the cylinder.
The above described method of varying the cut off may be applied
either to Corliss valves or any description of slide valve, piston valve,.
girdiron valve, or rotating disc valve, whether on a stationary surface or
superimposed upon another valve, and either with oval or excentric or
circular wheels, and in connection with oval or excentric wheels, or the
air cylinder above described.

page_text: The second part of our Invention relates to an isochronous governor
which may be adapted either to an ordinary throttle valve or to the
varying of any cutting of mechanism. It consists in two or more
ordinary arms and balls hung from the top of a spindle in the ordinary
way, each arm having a roller mounted on a pin or stud attached thereto
cither above or below the ball. As the balls recede from the axis of the
spindle by virtuo of their centrifugal force, the said rollers act on the
under side of the curved arms or horns attached to a counterpoise
weight which slides on the said spindle and raises the said weight and
lowers it when the balls approach towards the axis of the said spindle, the
curvature of the said arms or horns being made proportionate to the
increased centrifugal force as the balls move outwards. The counterpoise
weight is connected to the valves in the usual manner.
The third part of our Invention relates to and consists in improve-
ments in valves. Superimposed upon any slide valve we employ
another valve similar to that known as the Corliss, the working surface
of which is a convex portion of a cylinder having a slit or slits similar
to those in a gridiron valve parallel with the axis with intervening solid
spaces which must be wider than the slits. The slide valve upon which
one or two of these are superimposed has a concave surface corresponding
to the convex surface of the superimposed valve with corresponding slits.
and spaces, which slits communicate with that end of the valve which
admits the steam into the cylinder. The cut off is effected by shunting
the spaces aforesaid on the aforesaid cylindrical valve over these slits,
thereby stopping any further supply of steam to the cylinder. For this
purpose we use a spindle adjusted to the axis of the cylinder of which
the valve faces a portion, which spindle passes through a stuffing box
and has a lever keyed upon it which is connected by a link to the lever
described in the first part of our Invention as being actuated in one
direction by the spiral cam, and in the other direction by the spring or
piston. This superimposed valve may be confined so as not to move
endwise, or it may partake of the endwise motion of the valve upon
which it rests.
The fourth part of our Invention relates to piston valves described in
the Specification of Letters Patent dated March Seventh, One thousand
cight hundred and fifty, and Number 12988, granted to William
McNaught, senior, and in the Specification of Letters Patent dated
"

page_text: December Twenty-seventh, One thousand eight hundred and fifty-six, and
Numbered 3079, granted to the said William M°Naught and another,
the said piston valve having four or more projections on the steam side
which would cover or uncover a like number of slits through the sides of
the cylindrical shell in which it worked by turning the said piston valve
round its axis, the steam being admitted to and exhausted from the
main cylinder by the usual reciprocating motion of the valve, as fully
described in the Specifications of the said Letters Patent.
Our present improvements consist in making the shell in which the
valve works in two separate pieces, one piece occupying the steam side of
the port and the other the exhaust side, free from any obstruction.
The piece on the steam side of the port has the slits through which the
steam passes in the thickness of metal instead of opening into a
chamber as heretofore, thereby diminishing waste space betwixt the
valve and the cylinder.
Our improvements in the valve itself consists in prolonging the
cylindrical part on the steam side and adopting slits through it
corresponding with the slits in the shell instead of projections as
heretofore, and thereby obtaining a proportion of wearing surface better
adapted to high pressures than heretofore, not being liable to wear
the shells taper; and, secondly, in making the valve more flexible by
employing a horse-shoe spring bearing equally on three equidistant
points of the periphery. The steam slits are opened and closed by an
intermittent rotatory motion in one direction; this is affected by con-
necting the levers mentioned under the first head of our Invention to a
lever and ratchet wheel mounted upon a hollow driving spindle which
passes through a stuffing box on the valve chest in such a manner that
when the last-mentioned lever rises by the action of the cam it seizes
hold of a fresh tooth of the ratchet wheel, and when the drop occurs
the piston valve is thereby turned on its axis so as to cut off the steam
by closing the slits.
The reciprocating motion of the piston valve is communicated by an
excentric in the usual manner. The rod from the piston is attached to a
swivel on the end of the valve spindle to admit of its being turned round.
This valve spindle passes through the hollow driving spindle and has
two, four, or six, or any number of projections which take into a like

page_text: number of grooves in the inside of the hollow spindle; by this means
the hollow spindle turns the valves round intermittently without
interfering with their reciprocating motion. The said hollow driving
spindle has a stuffing box at the outside end for the valve spindle to
5 pass through.