IMPROVEMENTS IN MOTIVE POWER ENGINES
Year: 1879

page_text: LETTERS PATENT to Norman Macbeth, of Bolton, in the County of Lancaster,
Engineer, for the Invention of "IMPROVEMENTS IN MOTIVE POWER ENGINES."
Sealed the 13th June 1879, and dated the 18th January 1879.
PROVISIONAL SPECIFICATION left by the said Norman Macbeth at the
Office of the Commissioners of Patents on the 18th January 1879.
NORMAN MACBETH, of Bolton, in the County of Lancaster, Engineer. "IMPROVE-
MENTS IN MOTIVE POWER ENGINES."
In engines in which steam, or other expansive vapour, or gas is admitted to the
cylinders, and exhausted therefrom by means of slide valves, I place the middle or
exhaust port with its length lying longitudinally in relation to the cylinder.
In engines in which the steam, or other expansive vapour, or gas is admitted to
the cylinders by means of reciprocating valves, such as slide valves, I place the cut
off valve or valves in or upon the main valve or valves, and actuate the same by
an arrangement of eccentric or cam gear in such a manner that the cut off valve or
valves shall receive two back and two forward motions for one back and ono
forward motion of the main valve or valves. A spring or weight may be used to
give the return motion of the cut off valve or valves, and automatic regulation of
the ratio of the cut off by the governor may or may not be used.
In balancing the pressure of the steam, or other expansive vapour, or gas upon
slide or other valves, I place a spring or weight in such a position in relation to the
balancing piston and its connections that any variation in the pressure of the steam,
or other vapour, or gas causes the spring to be compressed or expanded, or the
weight to change its position, and alters the position of the balancing piston in its
cylinder.
In lubricating the cylinders of steam or other engines I employ the pressure of
the steam, or other vapour, or gas to force the lubricant into the cylinder. I also
form a glazed partition or partitions so that the amount of lubricant entering the
cylinder may be seen.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Norman Macbeth in the Great Seal Patent Office on the 16th
July 1879.
NORMAN MACBETH, of Bolton, in the County of Lancaster, Engineer. "IMPROVE-
MENTS IN MOTIVE POWER ENGINES."
In engines in which steam, or other expansive vapour, or gas is admitted to the
cylinders, and exhausted therefrom by means of slide valves, I place the middle or
exhaust port with its length lying longitudinally in relation to the cylinder.
In engines in which the steam, or other expansive vapour, or gas is admitted to
the cylinders by means of reciprocating valves, such as slide valves, I place the cut
off valve or valves in or upon the main valve or valves, and actuate the same by an
arrangement of eccentric or cam gear in such a manner that the cut off valve or
valves shall receive two back and two forward motious for one back and one
forward motion of the main valve or valves. A spring or weight may be used to
give the return motion of the cut off valve or valves, and automatic regulation of
the ratio of the cut off by the governor may or may not be used.
And in order that my Invention may be fully understood and readily carried
into operation, I will proceed to describe the accompanying Sheet of Drawings,
reference being had to the figures and letters marked thereon.
Fig. 1 represents the valve face of an engine in which treble-ported slide valves
are used; in this engine the exhaust port is placed with its length lying longi-
tudinally with the cylinder face and the admission ports with their length lying
transversely across it. a, a, are the admission ports, and 6 the exhaust port. By
this means I obtain less clearance space in the admission ports.
In engines in which the steam, or other expansive vapour, or gas is admitted to
the cylinders by means of reciprocating valves, such as slide valves, as shewn in
Figs. 2, 3, 4, 5, 6, and 7, or in oscillating cylindrical valves, as shown in Fig. 8, I
place the cut off valves in or upon the main valve or valves and actuate the same
by means of an arrangement of eccentric or cam gear, in such a manner that the
cut off valve or valves receive two back and forward motions for one back and
forward motion of the main valve or valves.
Figs 3, 4, and 5 shew one modification of the main and cut off valves, and
the gear for working the same. a is the main valve; b, b, the cut off valve, shown
at the end of its stroke when the ports upon which it works are closed. The main
valve a receives a constant back and forward motion from the eccentric c, which I
prefer to place upon the crank shaft. The cut off valve is made in two sections,
one for each of the ports a¹, and it is fastened upon the spindle & which passes
through the hollow spindle & of the main valve; tho spindle d of the cut off valve
is attached to a buffer piston f contained in the sliding block which carries the end
of the double eccentric rod ; the buffer piston fand the cut off valve b are kept
constantly pressed towards the closed position by the spring g. To the buffer
piston fis hinged a driving bar or fork . Upon the eccentric c are cast or fixed
two projecting cam pieces i which act upon the tappet block k with its rod ? and
sliding block m. Upon the sliding block m and the driving bar or fork h aro
suitable catching edges n. The spring o or other equivalent keeps the tappet block
-pressed against the cam surface i. When the cams allow the tappet block k and
its connections to come into the position nearest to the centre of the eccentric, tho
catching edges n come into gear with one another, and on the tappet block k and
sliding block m being pushed away from the centre of the eccentric by the cam
picces i the cut off valve b is caused to slide upon the main valve a, thus opening
the two ports a', a¹. The cam pieces are placed in such a position in the circum-
ference of the eccentric c that the cut off valve opens slightly in advance of the
main valve. Although the two ports a¹ of the main valve are opened at the same
time, the steam can only enter that end of the cylinder at which the main valve

page_text: opens into it; the two sections of the cut off valve open in the same direction on
the main valve. Upon the cylinder piston reaching the point of the stroke where
it is desirable to cut off, a suitable arrangement of trippet gear causes the catching
edges n, n, to be detached from one another, upon which the spring g causes the
cut off valve to spring back to its closed position, thus shutting the two ports a', a'.
Any suitable form of trippet apparatus may be used for this purpose, or the trippet
arrangement may be dispensed with and the cam pieces i may be made to cause
the opening of the cut off valve, and the spring o, or its equivalent, or the spring g
may cause it to close, the tappet block being constantly in direct connection with
the spindle d of the cut off valve. If a trippet motion be used for disengaging the
catching edges n, it may either be regulated to vary the cut off by the governor or
by hand. In some cases it may be more convenient to transmit the motion from
the eccentric and its cam pieces through a rocking shaft and levers or their
equivalents.
Fig. 6 shews one modification of the arrangement of main and cut off valve, in
which the main valve is divided into two sections.
Fig. 7 shews an arrangement similar to Fig. 5, in which the spindle c of the
main valve is made solid, and the spindle d of the cut off valve is carried through
a hollow casing e' which is attached to and moves with the main valve spindle a
Figa 5 and 6 show cut off valves which will admit steain on each side of each of
the plates forming the sections of the same.
Figs. and 7 shew cut off valves which allow the steam to enter on one side
only of the plates forming the sections of the cut off valve.
Fig. 8 shews a modification of this arrangement as applied to oscillating cylin-
drical valves.
The two main valves a act together and receive back and forward motion from
one eccentric, upon which cam pieces, as before described, give two back and forward
motions for one back and forward notion of the main valves to the cut off valves b,
which both act in one direction and both open and close together. The action of
the main valves and cut off valves in this arrangement is similar in principle to the
arrangement shewn on Fig. 6.
The arrangements of valves above described may be modified in various ways,
and I do not tie myself to the particular form of gear for actuating the same, and
what I claim is,-
First. The particular arrangement and disposition of the cylinder ports, shewn in
Fig. 1, where only three ports are used.
Secondly. The particular arrangement of main and cut off valves, as shewn in
Figs. 2 to 8, with the method of actuating the cut off valve or valves by means of
cam pieces cast or fixed upon the eccentric for actuating the main valve or valves,
substantially as shewn and described.
In witness whereof, I, the said Norman Macbeth, havo hereunto set my
hand and seal, this Fifteenth day of July, One thousand eight hundred
and seventy nine.
NORMAN MACBETH. (L.S.)