IMPROVEMENTS IN VALVE GEAR FOR STEAM ENGINES
Year: 1879

page_text: LETTERS PATENT to John Robert Jefferies, of the Orwell Works, Ipswich, in
the County of Suffolk, for the Invention of "IMPROVEMENTS IN VALVE
GEAR FOR STEAM ENGINES."
Sealed the 17th October 1879, and dated the 7th August 1879.
PROVISIONAL SPECIFICATION left by the said John Robert Jefferies at the
Office of the Commissioners of Patents on the 7th August 1879.
JOHN ROBERT JEFFERIES, of the Orwell Works, Ipswich, in the County of
Suffolk. "IMPROVEMENTS IN VALVE GEAR FOR STEAM ENGINES."
This Invention has for its object improvements in valve gear for steam engines.
For this purpose I employ an ordinary slide valve for the primary admission of
steam to each end of the cylinder, and for controlling the exhaust therefrom, and
in addition I use in each of the steam passages leading from the ports in the valve
face to the two ends of the cylinder other valves, the opening and closing of which
is controlled by the governor in such a way as to be fully open during the exhaust,
but on the admission of steam to close earlier or later in the stroke, so as to cut off
the admission of steam to the cylinder earlier or later as the speed of the engine
increases or diminishes, so as to maintain the normal speed of the engine even
with a variable load thereon.
For the valves in the passages between the valve ports and the cylinder, I use
preferably rotary valves, and control the opening and closing of such valves,
preferably, by a suitably formed cam mounted on a spindle, which may be the
governor spindle driven at the same rate as the crank shaft.
In this case 1 mount the cam on the spindle, in such a manner as to revolve
with, but be capable of being moved end wise along it by the action of the governor
balls, and I cause two rods to be held by springs against opposite sides of the cam,
and connect one rod to an arm on the spindle of one rotary valve, and the other
rod to an arm on the spindle of the other valve.

page_text: When the governor balls are at their highest range the rods bear against a part
of the cam, which is so shaped that the rotary valves are caused to close anddenly
very near the beginning of the stroke so as to admit little or no steam to the
cylinder; and on the contrary when the governor balls are down and the position
of the cam shifted, the rods bear against a part of the cam, which is so shaped as
to keep the rotary valves open throughout the stroke, and the steam is then cut off
by the slide valve alone. The cam is also so formed that the rotary valves do not
begin to open for exhaust until the slide valve has covered the steam port.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Robert Jefferies in the Great Seal Patent Office on the 7th
February 1880.
JOHN ROBERT JEFFERIES, of the Orwell Works, Ipswich, in the County of
Suffolk. "IMPROVEMENTS IN VALVE GEAR FOR STEAM ENGINES."
This Invention has for its object improvements in valve gear for steam engines.
For this purpose I employ an ordinary slide valve for the primary admission of
steam to each end of the cylinder, and for controlling the exhaust therefrom, and
in addition I use in each of the steam passages leading from the ports in the valve
face to the two ends of the cylinder other valves, the opening and closing of which
is controlled by the governor in such a way as to be fully open during the exhaust,
but on the admission of steam to close earlier or later in the stroke, so as to cut off
the admission of steam to the cylinder earlier or later as the speed of the engine
increases or diminishes, so as to maintain the normal speed of the engine even with
a variable load thereon.
For the valves in the passages between the valvel ports and the cylinder, I use
preferably rotary valves and control the opening and closing of such valves,.
preferably, by a suitably formned cam mounted on a spindle, which may be the
governor spindle driven at the same rate as the crank shaft.
In this case I mount the cam on the spindle in such a manner as to revolve
with, but be capable of being moved endwise along it by the action of the governor
balls, and I cause two rods to be held by springs against opposite sides of the cam,
and connect one rod to an arm on the spindle of one rotary valve, and the other
rod to an arm on the spindle of the other valve.
When the governor balls are at their highest range the rods bear against a part
of the cam, which is so shaped that the rotary valves are caused to close suddenly
very near the beginning of the stroke, so as to admit little or no steam to the
cylinder, and on the contrary when the governor balls are down and the position
of the cam shifted the rods bear against a part of the cam, which is so shaped as to
keep the rotary valves open throughout the stroke, and the steam is then cut off
by the slide valve alone. The cam is also so formed that the rotary valves do not
begin to open for exhaust until the slide valve has covered the steam port.
In the Drawing hereunto annexed I have shewn valve gear arranged as above
described applied to a portable engine, but the system is applicable to all
descriptions of engines, and more particularly to stationary and slow speeded
engines.
Figure 1 is a cross section of the upper part of the boiler of a portable engine,
and of the valve gear; Figure 2 is a side elevation of the engine and upper part of
the boiler; Figure 3 is a plain view of the same partly in section.
In these Figures, A is an ordinary slide valve moved to and fro by an eccentric
on the crank shaft; B, B, are the steam passages leading from the steam ports of
the face against which the slide valve works to the two ends of the cylinder C;
D, D, are rotary valves one in each of the passages B, the way in which these
valves are formed is shown clearly in Figures 1 and 3. On the top of the spindle
of each valve D is an arm E; to each arm is jointed one end of a rod F; the
opposite end of one of theso rods is by means of a spring G caused to bear against
one side of a cam H, and the other rod by another spring G against the other side
of the cam. The way in which the rods are drawn in opposite directions by the
springs, so as to cause them to bear against opposite sides of the cam is shewn
clearly in Figure 3. The springs bear against collars on the rods and against an
abutment I, which stands up from the top of the jacket of the steam cylinder.
Other collars K, K, on the rods coming against the abutment serve as stops to
limit the endway movement, which can be given to the rods by the springs.

page_text: The cam H is carried on the governor spindle L, in such a manner that it turns
with the spindle, but can be moved endwise fo and fro along it. The cam is
coupled by rods M with a collar N, which is lifted or lowered on the governor
spindle by the action of the governor balls, as shewn at Figure 1. The cam is
made hollow, and is weighted with lead internally till it balances the governor,
say, at 140 revolutions per minute. The governor spindle is, as shewn, driven at
the same speed as the crank shaft.
The cam is so formed that whether it be in its highest or lowest position each
rotary valve is in turn held open during the time that the passage in which such
valve is situated is open to the exhaust, and it remains open until by the move-
ment of the slide valve, the passage has been shut off from the exhaust and opened
for the admission of steam. If the speed at which the engine is running is too
high and the governor balls are raised above their normal positions to such an
extent as to bring the lower part of the cam into position for the rods F to bear
against it, the rotary valve then at once closes by reason of a drop in the cam
coming opposite the end of the rod F which is connected to the valve, but if the
speed of the engine is below the normal rate and the upper end of the cam con-
sequently brought into position for the rods F to bear against it the rotary valve
is held open by the cam for a longer time, and by preference nearly to the end of
the stroke. When the rotary valve has been closed as above described by the
action of the spring on the rod in connection with it, the cam does not again act
on the rod to cause the valve to open until steain has been shut off by the action
of the slide valve from the passage in which the rotary valve is situated.
Having thus described the nature of my Invention, and the manner of per-
forming the same, I would have it understood that I do not confine myself to the
use of rotary valves for the cut off valves in the passages between the slide valve
and steam cylinder, as valves otherwise constructed might be employed in these
passages, but I claim as my improvements in valve gear for steam engines.
First. The employment of cut off valves controlled by the governor, and situated
in the steam passages between the slide valve and ends of the steam cylinder,
substantially as described.
Second. The combination of valve gear for steam engines, substantially as
described and shewn in the Drawing annexed.
In witness whereof, I, the said John Robert Jefferies, have hereunto set my
hand and seal, this Fifth day of February, in the year of our Lord One
thousand eight hundred and eighty.
JOHN ROBERT JEFFERIES. (L.S.)