Improvements in or relating to Gearing for Actuating the Valves of Gas, Oil, and like Engines.
Year: 1899

page_text: PROVISIONAL SPECIFICATION,
Improvements in or relating to Gearing for Actuating the Valves of
Gas, Oil, and like Engines.
I, THOMAS RAE, of 15, Carlton Court, in the County of the City of Glasgow,
North Britain, Engineer, do hereby declare the nature of this invention to be
as follows, that is to say:-
My said invention relates to gearing for actuating the valves of gas, oil, and
like engines, and has for its object to improve the construction of such gearing,
so that it will be easier driven and run at a less speed than such gearing as
ordinarily constructed, thereby lessening the tear and wear and reducing the
possibility of noise and shake in the parts to a minimum.
In gas, oil, or like engines, working on what is called the "Otto cycle," the
necessary valves are ordinarily actuated by mean of levers worked by single
action or lift cams keyed on to a side shaft so as to come into action one after
the other.
The shaft is usually placed alongside the engine at right angles to the main,
or crank shaft of the engine, and driven by means of helical gear at a relative
speed of two revolutions of the crank shaft to one of the side shaft, this speed
being necessary, as the valve levers must be actuated in turn once for every two
revolutions of the crank shaft.
To obtain this relatively high speed of the side shaft, the angle or pitch of
the helix on what may be termed the worm and wormwheel, has to be acute,
with the result that such gear requires considerable power to drive it, and
though an accurate fit at first, it soon begins to wear and the parts to shake,
thus causing a noise every time the cams lift and drop the levers.
To overcome these objections and at the same time effect the desired object
of actuating the valve levers in turn once for every two relvolutions of the
cránk shaft I, according to my invention, instead of employing single action
cams, use a cam or cams on the side shaft having two, three, or other number
of acting surfaces or lifts, according to what may be found in practice best
adapted to any particular size and construction of engine.
As each acting surface of the cams only requires to come into operation once
for every two relvolutions of the crank shaft, I am thus enabled to connect the
side shaft with the crank shaft by gearing having considerably less angle or
pitch than usual, thus enabling the side shaft to be run at less speed than
usual. This lessens wear and tear and diminishes noise and shake in the parts.
For example if cams are employed having two acting surfaces, the side shaft
will require to be geared so as only to revolve once for every four revolutions
of the crank shaft, cams having three acting surfaces will enable the side
shaft to be run at one revolution for every six revolutions of the crank shaft,
and where cams having four acting surfaces are used, the ratio of revolutions
of the side shaft to the crank shaft need only be as one is to eight.
Where desired and the size of the cams will permit, antifriction rollers on

page_text: the ends of the valve levers may be employed as usual to encounter the cam
surfaces.
Dated this Twenty-ninth day of September Eighteen hundred and ninety
nine,
Improvements in or relating to Gearing for Actuating the Valves of
Gas, Oil, and like Engines.
I, THOMAS RAE, of 15, Carlton Court, in the County of the City of Glasgow,
North Britain, Engineer, do hereby declare the nature of this invention and
in what manner the same is to performed, to be particularly described and ascer-
tained in and by the following statement:-
My said invention relates to gearing for actuating the valves of gas, oil, and
like engines and has for its object to improve the construction of such gearing
so that it will be easier driven and run at a less speed than such gearing as
ordinarily constructed, thereby lessening the tear and wear and reducing the
possibility of noise and shake in the parts to a minimum.
In gas, oil or like engines working on what is called the "Otto cycle" the
necessary valves are ordinarily actuated by mean of levers worked by single
action or lift cams keyed on to a side shaft so as to come into action one after the
other. The shaft is usually placed alongside the engine at right angles to the main
or crank shaft of the engine and driven by means of helical gear at a relative
speed of two revolutions of the crank shaft to one of the side shaft this speed
being necessary as the valve levers must be actuated in turn once for every two
revolutions of the crank shaft.
To obtain this relatively high speed of the side shaft the angle or pitch of
the helix on what may be termed the worm and wormwheel has to be acute
with the result that such gear requires considerable power to drive it and
though an accurate fit at first it soon begins to wear and the parts to shake
thus causing a noise every time the cams lift and drop the levers.
To overcome these objections and at the same time effect the desired object
of actuating the valve levers in turn once for every two revolutions of the
crank shaft I, according to my invention, instead of employing single action
cams, use a cam or.cams on the side shaft having two, three, or other number
.of acting surfaces or lifts, according to what may be found in practice best
adapted to any particular size and construction of engine.
As each acting surface of the cams only requires to come into operation once
for every two revolutions of the crank shaft. I am thus enabled to connect the
side shaft with the crank shaft by gearing having considerably less angle or
pitch than usual, thus enabling the side shaft to be run at less speed than
usual. This lessens wear and tear and diminishes noise and shake in the parts.
For example if cams are employed having two acting surfaces the side shaft
will require to be geared so as only to revolve once for every four revolutions
of the crank shaft, cams having three acting surfaces will enable the side
shaft to be run at one revolution for every six revolutions of the crank shaft,
and where cams having four acting surfaces are used the ratio of revolutions
of the side shaft to the crank shaft need only be as one is to eight.
Where desired and the size of the cams will permit, antifriction rollers on
the ends of the valve levers may be employed as usual to encounter the cam
surfaces.

page_text: And in order that my said invention and the manner of performing the same
may be properly understood, I hereunto append a sheet of explanatory draw-
ings to be hereinafter referred to and showing by way of example in Figure 1,
a perspective view of part of an ordinary gas engine with the valve actuating
gearing is made according to one modification of my improvement, Figure 2,
being a side elevation of one of the cams used in this modification.
As shown in the drawings the side shaft, A, of the engine has keyed on it as
usual, two cams, one B, for actuating the ordinary exhaust valve lever C, and
the other D, for actuating the ordinary air and gas valve levers E. These
cams B, D, instead of having only a single acting surface as in such engines as
hitherto constructed are, according to my invention each made with three acting
surfaces or lifts, F, (Figure 2).
The side shaft, A, is driven as usual from the crank shaft, G, by worm and
wormwheel gear, H, and as each acting surface or lift, F, on the cams B, D,
only require to come into action to actuate the valve levers, C, E, in turn once for
every two revolutions of the crank shaft, G, I am thus enabled to employ
gearing, H, having considerably less angle or pitch than usual and such that the
side shaft A, will only be turned one revolution for every six revolutions of the
crank shaft instead of being turned one revolution for every two revolutions of
the crank shaft as in such engines as hitherto constructed.
This reduces the power necessary to drive the shaft A, lessening wear and
tear, and diminishing noise and shake in the parts.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
The employment of a cam or cams having two or more acting surfaces or lifts
for actuating the valves of gas, oil, and like engines substantially as and for the
purposes herein before described.
Dated this Wichtronth
1000