Improvements in Valve Gear for Internal Combustion Motors.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Valve Gear for Internal Combustion Motors.
We, WILLIAM JOIN CROSSLEY, of Crossley Brothers, Limited, Openshaw, Man-
chester, and JAMES ATKINSON, of the Woodlands, Marple, Cheshire, Engineers, do
hereby declare the nature of this invention to be as follows:-
The object of this invention is to provide more suitable means for operating
the valves of internal combustion motors more particularly the exhaust valve. It
is specially applicable to the larger sizes of such motors.
The exhaust valve is commonly a mushroom seated lift valve, operated by a
lever provided with a roller which engages with a cam on a shaft driven by
gearing from the main shaft of the engine. As at the time of opening it is a
common occurrence to have a pressure in the cylinder of, say 40 lbs. per square
inch, a very considerable force is required to open the valve of a large engine,
the parts have to be made very strong to enable them to work efficiently and
without undue wear and tear. As this valve should open promptly and rapidly,
the strain is put on the gearing very suddenly, and our object is to distribute
this strain through a considerable portion of the cam's revolution whilst still
causing the valve to open very quickly.
To enable this invention to be clearly understood we append a sheet of draw-
ings in which Fig. 1 is an elevation showing the general arrangement of parts
and Fig. 2 shows the shape of a suitable cam to a larger scale.
A is the exhaust valve, B is the exhaust valve lever, C is a strong spring,
D is a bolt which keeps the spring C deflected to the proper extent when not in
contact with the exhaust valve, E is an adjustable set screw which, if necessary,
ensures the opening of the exhaust valve A, F is the cam which gives the desired
movement as it revolves in the direction shown by the arrow.
At the time of opening the exhaust valve of an internal combustion motor there
is commonly a considerable pressure in the cylinder, in a large engine working on
the "Otto" cycle this may be as much as 40 lbs. per square inch.
The spring C is initially deflected by the bolt I) to a considerable extent but
it can be still further deflected until it comes into contact with the adjustable
set screw E.
The cam G is formed so as to move the lever B very slowly until the valve A
is actually lifted when the motion may be continued more rapidly.
The operation is as follows:-
In the position shown in Figure 1 the cam roller is on the low concentric
portion of the cam and the spring C is clear of the end of the spindle of the exhaust
valve A. As the engine continues to revolve the cam moves round in the
direction shown by the arrow until the lever is moved a short distance and the
spring C comes into contact with the spindle of the valve A, at this time
the line G H on the cam F, see Figure 2, being opposite the roller. This may

page_text: a
be at the time when the piston is commencing a working stroke, there being
very high pressure in the cylinder and the pressure on the exhaust valve is so
high that the spring C is not strong enough to lift it. As the cam F moves
round from G H to GI the piston is making its working stroke and the spring C
is being very gradually deflected until it opens the exhaust valve A owing to its
increasing power and the reduced resistance due to the expansion of the gases in
the cylinder. Should the spring C be too weak to open the valve at the proper
time the set screw E comes into contact with its underside, and ensures the
opening. As soon as the exhaust valve A commences to open the resistance to its
continued movement rapidly decreases and it immediately opens to the extent by
which the spring C was previously deflected until the stop bolt D comes into
action. The cam I may be so formed as to give a subsequent rapid rise as there
is very little resistance at this time to the wide opening of the exhaust valve A.
In internal combustion motors as at present constructed the heavy initial open-
ing of the exhaust valve is performed during a very small movement of the cam
and a heavy momentary strain thrown upon the gear. In our improved arrange-
ment this work is distributed on the gearing which drives the cam shaft whilst
the cam moves from G H to I causing a very much lighter strain.
An initial rapid movement of the exhaust valve is very desirable with a view
to reduce the rush of very hot gases through the narrow opening of a slowly
lifting valve.
The drawings show a method of arranging the parts to an engine
as very commonly otherwise constructed; but we wish it to be understood that
there are very many ways in which a spring or its equivalent with a slowly
operating cam in combination can be arranged to give the gradually accumulating
power which will open an exhaust valve rapidly without throwing such a severe
strain on the gearing as would be otherwise necessary.
Dated this 98th dox of July 1898
We, WILLIAM JOHN CROSSLEY, of Crossley Brothers, Limited, Openshaw, Man-
chester, and JAMES ATKINSON, of the Woodlands, Marple, Cheshire, Engineers, do
hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the follow-
ing statement:
The object of this invention is to provide more suitable means for operating
the valves of internal combustion motors more particularly the exhaust valve. It
is specially applicable to the large sizes of such motors.
The exhaust valve is commonly a mushroom seated lift valve, operated by a
lever provided with a roller which engages on a cam on a shaft driven by
gearing from the main shaft of the engine. As at the time of opening it is a
common occurrence to have a pressure in the cylinder of, say 40 lbs. per square
inch a very considerable force is required to open the valve of a large engine,
and the parts have to be made very strong to enable them to work efficiently and
without undue wear and tear. As this valve should open promptly and rapidly
the strain is put on the gearing very suddenly and our object is to distribute
this strain through a considerable portion of the cam's revolution whilst still
causing the valve to open very quickly.

page_text: To enable this invention to be clearly understood we.appended to the Provisional
Specification a sheet of drawings to which we will now refer and in which Fig. 1
is an elevation showing the general arrangement of parts and Fig. 2 shows the
shape of a suitable cam to a larger scale.
A is the exhaust valve, B is the exhaust valve lever, C is a strong spring,
D is a bolt which keeps the spring C deflected to the proper extent when not in
contact with the exhaust valve, E is an adjustable set screw which if necessary
ensures the opening of the exhaust valve A, F is the cam which gives the desired
movement as it revolves in the direction shown by the arrow.
At the time of opening the exhaust valve of an internal combustion motor there
is commonly a considerable pressure in the cylinder, in a large engine working on
the "Otto" cycle this may be as much as 40 lbs. per square inch.
The spring C is initially deflected by the bolt 1) to a considerable extent but
it can be still further deflected until it comes into contact with the adjustable
set screw E.
The cam T is formed so as to move the lever B very slowly until the valve A
is actually lifted when the motion may be continued more rapidly.
The operation is as follows:-
In the position shown in Figure 1 the cam roller is on the low concentric
portion of the cam and the spring C is clear of the end of the spindle of the exhaust
valve A. As the engine continues to revolve the cam moves round in the
direction shown by the arrow until the lever is moved a short distance and the
spring C comes into contact with the spindle of the valve A, at this time
the line G H on the cam F, see Figure 2, being opposite the roller. This may
be at the time when the piston is commencing a working stroke, there being a
very high pressure in the cylinder and the pressure on the exhaust valve is so
high that the spring C is not strong enough to lift it. As the cum F moves
round from G H to GI the piston is making its working stroke and the spring C
is being very gradually deffected until it opens the exhaust valve A owing to its
increasing power and the reduced resistance due to the expansion of the gases in
the cylinder. Should the spring C be too weak to open the valve at the proper
time the set screw E comes into contact with its underside and ensures the
opening. As soon as the exhaust valve A commences to open the resistance to its
continued movement rapidly decreases and it immediately opens to the extent by
which the spring C was previously deflected until the stop bolt D comes into
action. The cam F may be so formed as to give a subsequent rapid rise as there
is very little resistance at this time to the wide opening of the exhaust valve A.
In internal combustion motors as at present constructed the heavy initial open-
ing of the exhaust valve is performed during a very small movement of the cam
and a heavy momentary strain thrown upon the gear. In our improved arrange-
ment this work is distributed on the gearing which drives the cam shaft whilst
the cam moves from G H to G I causing a very much lighter strain.
An initial rapid movement of the exhaust valve is desirable with a view
to reduce the rush of very hot gases through the narrow opening of a slowly
lifting valve.
The drawings above referred to show a method of arranging the parts to an engine
as very commonly otherwise constructed but we wish it to be understood that
there are very many ways in which a spring or its equivalent with a slowly
operating cam in combination can be arranged to give the gradually accumulating
power which will open an exhaust valve rapidly without throwing such a severe
strain on the gearing as would be otherwise necessary.
An arrangement in which a spiral spring is used is shown in a second
sheet of drawings which we now append. The operation is quite similar to
that described above in connection with the flat spring. K is a strong spiral
spring initially compressed to a definite desired pressure between the plates M
and P. The roller of the exhaust lever B causes the upper end of the bolt O to
come into contact with the end of the exhaust valve A when it is opposite the

page_text: line G H of the cam F. As the cam F revolves the spring K is compressed the
plate M being pressed downwards in the short cylinder N until it comes against
the stops at the bottom of this cylinder the roller being now opposite the line GI
of the cam F. At this time the spring K is compressed to such an extent that it
overcomes the pressure on the exhaust valve and forces it suddenly open to the
extent of the previous motion of the plate M in the short cylinder N the upper
part of which is enclosed by a cover L and thus forming an air dash pot to
prevent shock. If the spring K is not sufficiently compressed to open the exhaust
valve A at the proper time it is initially opened by the top end of the bolt O
and the wide sudden opening completed by the stored up energy in the spring K.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is:-
1. In an internal combustion motor the employment of a spring in conjunction
with a suitably shaped cam for the purpose of opening the exhaust valve promptly
by means of a gradually accumulated force, as described and illustrated.
2. In an internal combustion motor appliances for promptly opening the
exhaust valve by means of a gradually accumulated force, substantially as
described and illustrated.
A 1900