Improved Cam Mechanism.
Year: 1896

page_text: Date of Application, 2nd June, 1896-Accented, 18th July, 1896
COMPLETE SPECIFICATION.
Improved Cam Mechanism.
I, JOSEF POLKE, Machine Manufacturer of V Kohlgasse 26-28, Vienna,
Austria, do hereby declare the nature of my said invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
My invention relates to that class of mechanical movements which serve for
converting rotary motion into rectilinear motion and has for its object a construction
of this kind by means of which a uniform rotary motion may be converted into an
intermittent rectilinear motion producing several strokes of equal or unequal length.
This improvel mechanical movement may be employed for any purpose where
such intermittent motion is required but is particulary intended to be used for
operating, by one single connecting rod, the valves of gas- and similar engines..
In the annexed drawing my improved mechanical movement is shown as
constructed for operating the valves of a gas engine.
Figure 1 shows the mechanism in elevation; Figure 2 is a top view of the
same;
Figure 3 shows the eccentric roll detached ;
Figures 4 and 5 show the eccentric roll, on a somewhat larger scale, in elevation
and in section in line with the shaft, provided with a device for temporarily
altering the contour of the eccentric.
In all figures similar letters indicate like parts.
My improved mechanism essentially consists of the eccentric roll R which is
keyed, or otherwise rigidly attached, to a rotating shaft; in the present case this
is supposed to be the main shaft W of a gas engine. The mechanism further
consists of a lever H, which is pivoted at any suitable fixed point near the
eccentric R. Into the other free end of the lever H a fork G is rotably inserted,
within which fork a counterroll r turns freely upon a pin h, which also permits a
lateral movement of the roll r. By a spring F acting upon the lever H the roll
is continually kept pressed against the eccentric R, so that it must follow the
contours of the latter when this is rotated. The lever H is provided with the rod S
which transmits the movements of the former to the part or parts to be operated,
in this case, for example to the valve of the gas engine. For the present purpose
the roll R forms two eccentrics el and el of different contours, arranged beside
each other, which are connected by a groove n, crossing itself at one point. Thus,
when the roll R is rotated, the counter-roll will first follow the contour of one
eccentric until it is carried by the groove n across to the other eccentric, from
whence after it has completed its run around this latter, it is run back again unto
the first eccentric by the groove », whereupon it begins its run afresh.
The shape and number of the eccentric surfaces upon the roll R as well as the
corresponding number of grooves for carrying the counterroll from one eccentrie
to the other and back again depends upon the number and different lengths of
strokes which are to be imparted by the connecting rod S to another mechanism
for a certain purpose.
In the present case, which I have chosen as an example, four strokes of different
lengths with intermediate stops must be performed by the connecting rod S for
operating the valve of the gas engine.
The different phases to be produced by this movement in the present case are

page_text: the period of suction or admission, the period of compression, the period of
explosion and the period of exhaust. Corresponding to these four periods the
roll R is provided with the eccentric surfaces a-b-e, e-d-a, a-e- and f-g-a.
The movements produced by these surfaces are the following. The roll r, which
runs in the groove n, of the roll R, after leaving the exaust surface f-g-a of the
same arrives upon the surface a-b where it crosses the way for the explosion and
running upon the surface be causes the admission of gas into the cylinder. The
crossing of the groove n in that part of the roll R where the way for the perio!
of explesion and that for the first part of the period of suction or admission are
situated besides each other on the same level has been selected for the reason that
during this time, as well as during the period of compression the roll is running
against a concentric surface of the roll R, so that the rol S is at rest and all valves
closed. Arrived at the end of the suction period, the roll r, with its fork G has
again taken up its straight position as in the beginning, before it entered the
groove-crossing. When the roll passes over the surface b-c which presents a
shurt and steep ascent and descent, it produces that short, jerking movement of
the connecting rod S which causes the pushing open of the gas admission valve.
After the end of the gas admission the roll r, runs upon the concentric
surface e-d-a-e, of which e-d-a represents the period of compression
while a-e belongs to the period of explosion, as has already been stated. At the
end of the period of explosion the roll begins its ascent upon the surface --
for the exhaust, where it causes the opening of the exhaust valve. Now all the
movements described begin again.
In some cases it is desirable to produce, temporarily, a movement somewhat
different from the regular movements, as for instance in a gas-engine, when the
same is to be started. A gas engine is generally started by turning its fly wheel
either by hand or by means of a starting device. but in either case it becomes
necessary to reduce the resistance of the mixture in the cylinder by raising the
exhaust valve.
In order to produce this or similar temporary movements I provide my improved
mechanism with the following device. Into a hole bored through the roll Ra
pin Z is placed in such manner that its surface projects into the way of the
eccentric, as shown in Figures 4 and 5 of the drawing. In the present case the
pin Z projects into the middle part of the way for the compression. At one plice
the pin Z is provided with a recess w of such width and depth that no interruption
of the way of the roll R is formed. When the pin Z is in this position the
mechanism will operate in the usual manner as has been described. When,
however, the engine is to be started, the position of the pin Z is the roll R is
changed so that its full part wl projects into the way of the roll R. When the fly
wheel of the engine is now turned, the roll r will run over this obstruction and
therely cause the connecting rod S to open the exhaust valve. When the engine
is properly started the pin Z is pushed hack into its first position, where it causes
no interruption in the ordinary working of the mechanism.
The pin Z will, of course, have to be provided with means for arresting it in its
two positions. By way of example I have shown in the annexed drawing a device
for this purpose. The end of the pin Z projecting upon the outside surface of the
rull is provided with a forked piece g' rigidly attached thereto, and with its
forked part gripping a pin Z fitted into a central hole in the shaft W. This pin Z
is provided with a knob which permits it to be pulled out or pushed in, whereby
the pin is also shitted. The end of the pin z protruding at the other side of the
roll R is provided with two rests or notches 21, 2 into which a spring actuated
pin T may catch, so as to arrest the pin z in one or the other of its two positions
into which it has been brought by the shifting of the pin 2.
The described device for temporarily changing or interrupting the way or
contour of an eccentric may of course be employed for other purposes as well, and
the eccentric roll R, instead of producing the movements which have here been
described only by way of example, may be made to produce more or less

page_text: movements of different strokes and with different rests or interruptions. According
to the different movements to be produced the kind and number of eccentric and
concentric surfaces placed beside each other upon the roll R and the ways of the
groove connecting these surfaces will have to be determined.
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 :-
1. In combination with a single rod S, for imparting rectilinear movements of
different stroke and duration, a rotable roll R having upon its circumference two
or more eccentric or eccentric and concentric surfaces arranged beside each other
and a groove or grooves n connecting said surfaces, a lever H connected to the
rod S, a roll r adapted to move laterally and in the manner of a universal joint
upon said lever H and means for pressing said roll against the circumference of
said rotable roll R; substantially as set forth.
2. In mechanical movements of the kind herein described the combination with
the roll and the eccentric roll R of a pin z inserted into the latter, and provided
with a recess u, said pin z adjustable in the roll R and adapted to interrupt or
alter the way or contour upon the circumference of the roll R; substantially as
set forth.
3. In mechanical movements of the kind herein described, the combination with
the rod S adapted to operate the valves of a gas- or similar engine, of the lever H
carrying the movable roll r, of the roll R provided upon its circumference with
four ways a-b-c, c-d-a, a-e-f and f-g-a corresponding to and adapted
to produce the admission, compression, explosion and exhaust of a gas-engine and
provided also upon its circumference, with a crossed groove n, connecting the said
four ways, and of means for pressing the roll against the roll R, substantially as
set forth.