Note: Descriptions are shown in the official language in which they were submitted.
1018Z~)3
sackground of the Invention
The invention relates to the art of rotary en-
gines and more particularly to a rotary engine having an
exterior rotary output member driven by opposed pistons
housed within a stationary cylinder or stationary in-line
S cylinders.
The reciprocal internal combustion engine, as
those skilled in the art are well aware, is the result of
at least 75 years of technological progress. The method~ ~
of converting heat energy input to mechanical energy out- ~ -
put, while regardèd today as highly~developed, is less
efficient than is possible since conversion of the heat
energy to mechanical energy is done through the piston,
connecting rod and the crankshaft to the rotating output
member. This is true whether the internal combustion be
by spark ignition or by compression ignition. The losses
in the system are well recoqnized and have been extensively
examined over the years. The inefficiency of the connec-
ting rod-crankshaft piston engine is one of the reasons
why a good deal of effort has been turned since World War
II to the development of the rotary, turbine and other
types of compact power units.
The constraints imposed by connecting rod, crank-
shaft type engines are numerous. Connecting rod length
and crank radius with their fixed interrelatlonship to the
piston are the primary constraint factors and exert a pro-
found influence on the piston travel function and ultl-
mately on the engine performance. The rapid piston motion,
rise to and ~all from top dead center, at speed, present
the greatest problem to the engine designer since ignition
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must occur prior to the engine's achieving full compression
so as to provide time to reasonably complete burning which
continues while the piston moves away from top dead center.
Thus, the connecting rod and crankshaft cons-traint effec-
S tively prevents achievement of constant volume combusitonof the ideal cycle. A substantial amount of heat is lost
from the combusting fuel or working ~luid because o~ the
relatively slow expansion process which is determined by
the interrelationship of the connecting rod, piston and
crankshaft. Additionally, in conventional reciprocating
piston engines the exhaust valve will be opened beore the
piston has reached bottom dead center thereby causing ad-
ditional loss of energy.
In combusting the compressed fuel and thus pro-
viding energy to do work on the piston much energy is lost
through the cylinder head as waste heat. Ener~y is lost
because of the amount of surface area exposed to direct
flame during combustion process and combustion must be star-
ted before the piston reaches top dead center, causing the
piston to compress an already expanding gas. Energy
dumped into the coolant of a conventional engine, as waste
heat, may be up to as much as 60% of the total energy avail-
able from the burning fuel.
The linear piston movement in the power stro~e
is the initial conversion step from heat energy to mechani-
cal energy. The linear motion is in turn converted to the
angular motion of the connecting rod which in turn develops
the circular motion of the cran~shaft. Each of these com-
ponents subtracts from the final energy output and is a
design which is completely unbalanced. Balance is achieved
with the addition of compensating weights. Any excess
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~aJlB26(~3
weight which must be designed into the engine in the form
of counterweights, flywheels and other compensation fea-
tures and frictional losses associated with the motion of
such parts uses up energy to lessen engine efficiency.
As is well known, a four stroke cycle engine
turns its crankshaft 720 from combustion stroke to combus-
tion stroke on a given cylinder. A two stroke cycle en-
gine turns its output shaft 360 from combustion stroke
to combustion stroke. In either the four stroke cycle or
the two stroke cycle engine the distance in degrees rota-
tion, from the point of applied energy to the output, is
large since the design of the mechanical system, in the
case!of the four stroke cycle, is such that for each posi-
tive power stroke of the piston there are three (3) nega-
tive strokes the piston must go through. Further the length
of the connecting rod and the diameter of the crankshaft
are directly related to the stroke of the piston. In net
effect, there has been a great need in the automotive in-
dustry to develop a different engine, initially for higher
specific power output per pound of weight and more re-
cently to improve mileage and reduce pollution.
There are fundamental reasons why the industry
has not leaped into new engine production. Among those
are the fact that most engine cycles lead to larger and
more expensive units than conventional power plants and are
of such design that they radically depart from known tech-
nology. This is particularly true of external combustion ;
engines. Further, of the immediate reasonable alternatives,
such as for example, the Wankle rotary or the gas tuxbine,
each has difficulties. The Wankel which is a competitive
engine for small vehicles does not economically scale up-
101!~260:~
waxdly in power, and it is an example of radical departure
from known technology. The turbine which is competitive
for large vehicles does not scale down in power or size
economically However, the internal combustion engine does
not burn fuel completely, is very complex and its mechani-
cal and thermal efficiency leaves much to be desired to
say nothing of its ~uel consumption and horsepower loss.
Summary of the Invention
The Almar cycle rotary engine of this invention
is provided with a stationary support block of optional
shape which is supported at both ends. Mounted in and on
the block support are at least one but optionally a plura-
lity of aligned, parallel cylinders containing opposed pis-
tons.
The fixed support block is hollow solthat the
fuel line spark wires and intake and exhaust manifolds
are conveniently directed to each cylinder. The pistons
are provided with rigid piston rods at the outer end of
which is mounted a bearing for engaging with and exerting
linear pressure on an inclined inner cam surface of a
surrounding right circular-cylindrical rotary output mem-
ber. The rotary output member is rotatably supported on
block journals and is circular around the outside. The in-
side is provided with a continuous cam surface for each cy-
linder, which at certain positions of rotation is inclined
to the radial axis of the piston and which is engaged by fi ;
the bearings. While the continuous cam surface is not
necessarily an ellipse or a symmetrically continuous curve
it has several consistent and common characteristics. The
continuous cam track will provide for two top dead center
108;Z603
areas of constant volume and, in some cycles, two bottom
dead center areas of constant volume alternated so that
the cam track will be generally suggestive of an ellipse
in which the opposed radii will be symmetrical and which
will have a major and a minor axis at right angles to each
other. At top dead center only or at top dead center and
bottom dead center arcuate areas of constant volume radius
from the axis of rotation are provided. The expansion or
power stroke section of the invention, referred to as the
Almar engine, will occupy the initial area or general qua-
drant section of the cam which may actually be more or less
than 90 of rotation. The power stroke area may be fol-
lowed by a bottom dead center, constant volume radius area
which will be on or near the long or major axis of the cam
curve. In the case of the four-stroke-cycle, the bottom
dead center area of constant volume radius will be followed
by an exhaust section and after that another top dead cen-
ter area radially and symmetrically opposed from the first
top dead center area. The third general quadrant section
of the cam track is in an intake section and its profile
is the same as and is symmetrically radially opposed from
the power stroke or expansion section. In the last or
fourth general quadrant section the cam track will pro~ide
for compression back to top dead center and the profile of
~` 25 this fourth section will be the same as and symmetrically
radially opposed to the exhaust section.
Except in the case where the cam is of a mathe-
matically defined harmonic motion design, at no time does
any point on the profile of the cam surface extend be-
yond a straight line which is tangent to the last poi~
of constant volume radius. No reverse curve such as would
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~082603
be defined by inwardly extendi~g lobes are provided. Tran~
sition areas between arcuate constant volume sections are
defined to be smooth for placing the least amount of stress
on the bearings and to assure the bearings are in constant
contact with the cam surface. There will be a continuous
cam surface for each cylinder in a multi-cylinder engine.
The axes of each cam will be positioned or rotated with
respect to each other so that the mass of the rotary out-
put member remains balanced. It can be readily seen that `
in the case of the multi-cylinder engine in which the firing
order is in rotation, e.g., no two cylinders fire at the
same time, the positioning or angular rotational offset of
the cams to maintain balance is determined by the number
of cylinders. However, in the instance where the cylinders
~ire at the same time it is necessary to design all cams
to be in balance within themselves. The outside of the ro-
tary output member may be provided with gears to be engaged
by starter motor and for power takeoff.
Accordingly, it is among the many features, advan-
tages and objectives of the invention to provide a reci-
procating rotary engine in which the combustion chamber is
formed in conventional, opposed piston configuration which
utilizes all the refinements and advances of reciprocating
engine technology. The design of the engine allows for
the most rapid expansion process possible during the power
stroke to reduce heat loss through conduction while con-
verting heat energy to useful work. The engine completes
its power stroke in at least one half the time of the con~
ventional connecting rod engine and thus its expansion
time will be at least twice as fast. The Almar engine
; allows for maximum possible expansions to utilize as much
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of the heat energy as possible for useful work~ with the
lowest temperature exhaust gases consistent with the chosen
cycle being emitted. The engine can be designed to run
as a complete or extended cycle engine. The engine pro-
duces maximum possible pressure prior to expansion withoutcombustion starting before the piston reaches top dead
center. The increased speed of expansion from top dead
center to bottom dead center results in less heat loss to
the cylinder walls.
Because of constant volume combustion, the in- ,
gested fuel air misture can be igni~ed after the piston
has reached top dead center. This arcuate area of constant
volume radius can be designed to a specific burn time as
determined by the quality and type of fuel used. The
areas of constant volume at bottom dead center in a four ~-
stroke engine allow for maximum expansion of the gases be-
fore the exhaust valves open. This constant volume allows
a dwell time for the piston during which the exhaust valves
are opened thereby relieving pressures after employable
heat and pressure are utilized and before the exhaust
stroke is begun. The instant invention causes a more rapid
compression strokè than con-rod engines which results in
less heat exchange time between fuel/air misture and cy-
linder walls thus reducing heat loss. Valve timing be-
comes less critical due to the capability of the pistons
to dwell at top and bottom dead center. This is signifi
cant because it permits more design flexibility in valve
timing and minimizes valve overlap and slower valve rise
and fall. Minimizing valve overlap will give greater
volumetric efficiency with less intermixing o~ exhaust- -
intake gases.
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The engine is basically free from vibration and
is dynamically balanced. ~he thrust forces are e~ualized
b~ equal and opposite motion of the opposed pistons. Be~
cause of cam design and inherent engine characteristics
all acceleration and deceleration transitions are smooth.
Vibrations from the piston rod bearing-cam interface are
minimized and there is no intermittent loss of contact be-
tween cam surface and bearing. The sleeve, ~riction or
frictionless bearing which keeps the piston rod from mo~ing
in a direction perpendicular to the linear movement of the
piston, is placed as close to the load, i.e., the cam sur-
face, as possible which is at the extreme end of the cy-
linder wall or support housing.
The engine is basically free from objectionable
knock or pre-ignition arising from pressure peak singu-
larities which normally occur as a result of continuing
compression after combustion has started and as a result
of poor fuel-air mixture.
The period of constant volume at bottom dead
center, and the speed of the intake stroke more completely
mix the fuel-air mixture which is very help~ul in achieving
uniformity of the ingested charge prior to combustion and
causes the engine to be more tolerant of lean mixtures.
Burning of lean mixtures results in better emission manage-
ment and less tendency to misfire. Since the combustionchamber is formed between two pistons shaping such chamber
to minimize knock is much simpler than in the conventional
engine. Heat loss is minimized by the efficiency of the
cycle and the speed of expansion as well as the minimized
cylinder surface through which heat can be conducted. There
will be minimum restrictions on inflow during the intake
~ILO~ 3
process. The en~ine will make minimum contributions to
pollution because it is possible to burn very lean mix-
tures in constant volume areas as well as to more completely
burn the fuel.
S The engine has great design flexibility in that
a variety of cam designs can be chosen to fit the specific
characteristics of a given fuel. A wide variety of cycles
can be chosen with the same basic configuration and the
cam surface configuration can be varied to adapt the pis-
ton velocities to a specific end work use. Mass of the
rotating member can be altered within the same basic con-
figuration and the profile of the cam designed to pro-
vide a wide range of piston travel characteristics to op-
timize the time of constant volume and to tailor compres-
sion and expansion curves as befits various fuels and/or
cycles. This engine àlso enables the designer to fire a
multi-cylinder engine in rotation, that is firing cylin-
ders sequentially or to fire some or all of the cylinders
at the same time.
~0 The continuous cam track allows the instant
engine to conform more closely to an ideal thermodynamic
curve which of course varies with fuel type, compression
ratio, speed of the engine, type of cycle, etc. The con-
stant volume areas of the cam at top and ~ottom dead cen ;~
ter may be related to the operating speed of the englne
and/or the burning time o~ the fuel. The output curve
bacomes more closely matched to the curve of combustion
at any engine speed and permits constant volume burning
of the fuel charge for any type of fuel. The rotary out~
put member can be designed for high energy storage as a
; result of designing weight and speed into the rotary mem-
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2~
ber. The engine can be further designed to a particula~
intended engine and application, that is high speed low
torque or low speed high torque or constant speed type
engines without compensation features such as torque con~
verters. It is an important characteristic that any de~
sired velocity profile and any acceleration/deceleration
curve can be designed into the cam or cams. As a practical
matter and as a consequence of the invention's design ~;~
flexibility, it is possible to achieve variances in the
acceleration and deceleration profiles or characteristics.
The engine is designed to complete a ~wo stroke cycle with
180 of rotation of the output member, and complete a four
stroke cycle within 360 rotation of the output member.
Because of the opposed piston arrangement and the symmet-
rical distribution of the mass in the rotary output mem-
ber there is no need for counterweights or other compen-
sating features for maintaining balance since forces in
the engine are equal. The engine can use as many in-line
cylinders as desired and the cams can be rotated to desired
angles, to fire the cylinders simultaneously or to fire
them in series, thus making the engine extremely versatile
in its design capabilities and use applicatisns. The en-
gine is capable or being run with minor modifications from
an external energy supply or external combustion source.
Brief Description of Drawings
Figure 1 is a cross section view of a two cylinder
four piston embodiment showing details of construction and
~ arrangement of parts;
- Figure 2 is a cross section view along the line
2-2 of Figure 1 and further illustrating the details of
the cylinders, pistons, rotor and support manifold:
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BZ~03
Figure 3 is a partial cross section view showing
additional details of the structure of a cylinder and pis-
ton;
Figure 4 is a perspective view showing how the
rotor might look from the outside but without any protec-
tive housing around the rotor;
Figure 5 is an additional view showing four cy-
linders in line;
Figures 6 through 9 illustrate diagrammatically
the operation of a two stroke almar cycle, spark ignitioh
engine with opposed pistons as contemplated by this engine; .
Figure 10 is a horizontal cross sectional view :along the line 10-10 of ~igure 11 showing details of a
four stroke embodiment of the invention;
Figure 11 is a vertical cross sectional view
taken along the line 11-11 of Figure 10 showing additional
details of the four stroke Almar engine;
Figure 12 shows representative details of a non-
harmonically shaped valve cam;
Figure 13 shows representative details of a har-
monically shaped cam;
Figure 14 shows the operational sequence of the
four stroke embodiment;
Figure 15 shows general characteristics of a valve
cam; and
Figure 16 is a thermodynamic pressure-volume
curve showing both ideal and actual curves~
Description of Preferred Embodiment
As those skilled in the art are aware, it is neces-
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~L~826~3
sary to understand the constraints imposed on the design
of a connecting rod-crankshaft type reciprocating engine
in order to more clearly appreciate how the engine of this
invention removes such constraints. Essentially the con
straints are the connecting rod lengths from the wrist
pin axis of the piston to the crank axis, and the crank
radius from the crankshaft rotation axis to the crank-
shaft-con rod connection. The relationship between the
linear travel of the piston and the angle of crankshaft
rotation is determined by the ratio of connecting rod
length to crank radius. The ratio of connecting rod length
to crank radius has a profound influence on the piston
travel function and ultimately on engine performance. The
rapid rise and fall of the piston to and from top dead cen-
ter presents the greatest problem to the engine designer
. .
for it precludes burning at a constant volume at top dead
center and necessitates advance ignition to allow time for
, .. ... ..... .
the fuel to burn. For example, an engine operating at4800 rpm from the time of spark to the end of the fuel
burning period takes .002 seconds. This burn time occu-
pies 57 of time rotation. Thus, iring in the conven-
tional con rod crankshaft engine must begin well before top
dead center and obviously results in a direct loss in ef- `
ficiency, specific fuel consumption and horsepower.
Figure 16 represents a general comparison of
the actual and ideal thermodynamic curves for an Otto cy-
cle and illustrates where the losses occur between ideal
and actual. Such a curve is commonly seen in treatises
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which analyze and compare ideal performance with the
actual.* The compression stroke is represented by the line
1-2. An ideal combustion line would be represented by
2-3. The expansion cycle line is shown from 3 to 4 at
which time the exhaust ports would be opened and the pres-
sure would drop along the line 4-1. The exhaust stroke
would be represented by 1-0 and the intake stroke by 0-1
and thence back to the compression stroke 1-2. In per-
formance, however, the actual cycle is comparatively repre-
sented by the cross hatched portion showing a substantial
loss of efficiency in the engine. The work of the cycle
outside the cross hatched portion is not realized. It is
among other things the requirement to begin burning the
fuel prior to top dead center, the relatively slow expan-
sion process during and after combustion, and the opening
of the exhaust valves prior to the piston reaching bottom
dead center that account for the losses resulting in the
actual curve as opposed to the idealized curve.
The ad~antages of the instant engine accrue from
features inherent in its design. The essential mechanical
arrangements of parts and particularly cam design permit
the engine to have the smallest surface to volume ratio
during combustion; the most rapid possible expansion stroke;
the maximum possible pressure at the beginning of the ex-
pansion stroke without advanced ignition; and the maximum ~ ~
~ ... ':
*OBERT, "Internal Combustion Engines"~ p. 497f*~ 3rd Ed~ r
International Textbook Company, 1968~
LEWIS, "Gas Power Dynamics"r pp. 443~513, Van Nostrand
Company, New York~ 1962
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~)826~3
possible expansion. Finally, the simplicity of the design
lends itself to economical construction and low weight with
the consequent attainment of higher specific power and
overall cost savings because of fewer parts.
A two stroke embodiment of the invention is shown
in Figures 1 through 5 ~nd illustrates the construction
and general operating principles of two stroke engines. The
engine, generally designated by the number 10, consists of
a hollow manifold block support member generally designated
by the number 12. The member 12 is elongated as shown in
various drawings and is fixed at both ends so that it is
stationary. Internally it is provided in this case with a
partition 14 which as can be seen is slightly off-center
for reasons which will be explained hereinafter. Partition
14 divides the inside of member 12 into an exhaust manifold
section 16 and an intake manifold section 18. It will be
quite apparent that intake and exhaust manifolding could be
formed of pipin~ or tubing and directed to the cylinders
without partitioning the interior of the manifold block.
Supported by the manifold member 12 are cylinders generally
designated by the number 24. The cylinders have wall 26,
pistons 28, a piston rod 30, rod control bearing mount or
support 32 and threaded cap 34. Rod control bearing 36 is
supported in rod control ~earing support 32. It will be
noted that piston rod 30 is rigidly attached to the piston `
as by threads 38 and is supported by rod control bearings
36. At the outer end of piston rod 30 is secured a roller
bearinal mount 40 in the shape of a yoke supporting roller
bearing 42 on pin 44 which extends into both arms of yoke
40. It is to be noted, however, that other kinds of bearings
may be~ used such as friction, frictionless or slipper types.
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It Will be appreciated that the cylinders are provided with
fuel line 46, spark plug 48, exhaust gas ports 50 and air
intake ports 52.
The rotatable member or rotor generally designated
by the n~unber 60 is in effect a series of cam surfaces 62
or any other geometrical combination o~ curves which will
allow the piston to make a complete stroke within a prede-
termine number of degrees rotation in a single revolution.
The continuous cam surface may be epicycloidal or formed in
various symmetrical or asymmetrical configurations resem-
bling an elipse. The exact configuration of the cam will
vary depending, for instance on the degrees of rotation de-
sixed to complete a power stroke and the radii lengths in
a particular section of the cam as will be discussed in more
detail below. It will be noted that the outside of the
rotor is round and that for balance of weight, the long
axis of one cam surface 62 is in line with the short axis
of the adjoining cam surface 62O In this way, as explained
above, weight distribution in the rotor is balanced and
cylinders 24 can be arranged in line in the stationary
manifold support 12. Such angular offsetting of the cams
also contributes to strength in the rotor. The cams are pro-
vided with tracks 64 to engage in this instance, piston rol-
ler bearin~s 42. The number of cylinders, of course, will
depend upon the horsepower desired and such other factors
as the particular application or use of the engine. Rotor
60 has end walls 68 provided with a series of openings such
as is shown in Figure 4. In some designs it might be de-
sirable not to have these openings so that the cam and roller
chamb~r acts as a lubricant reservoir~ Bearing or bushing
;sections 70 are provided at each end of the engine and are
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journaled on bearings or bushings 72. Gear teeth 74 will
be provided for a power output. Figure 1 shows that a
starter motor 76 with p~nion gear 78 will engage ring gear
80 around the periphery of rotor 60.
~he cam for a two stroke engine will have an area
of constant volume (constant radius) at top dead center the
arcuate area of which may vary according to the type and
burning time of the fuel the particular engine is designed
to use. If the two stroke engine uses ports for manifolding
instead of valves there will be no constant volume area at
bottom dead center because of the Kadenacy effect,* that is
the negative pressure created in the cylinder by the opening
of the exhaust port. If the two stroke engine is mani~olded
with valves the area of constant volume at bottom dead cen-
ter is necessary for the same reasons as pertain to the four
stroke embodiment discussed hereinafter. :
As explained above, the Almar engine is versatile
in that it can be used in two stroke or four stroke mode
in spark or compression ignitionO For instance, in Figure
5 four cylinders 24 are used, but it will be understood
that one or three cylinders may be used or more than ~our,
again depending upon the intended application. It will
be appreciated that if an odd number other than one, of cy-
linders are used, such as three, the cam sur~aces would be
rotated 120 to each other, again to keep the rotor balanced.
In the instance where one cylinder is used or all cams are
aligned and where all cyIinders fire at the same time each
cam will be inherently balanced. ;
*IRVING~ "~wo-Stroke Power Units"-r pp~ 20 et seq, Hart Pub- ~
lishing Co., Inc., New York City, I968~ -
: .
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2~i~J3
Figures 6 through 9 illustrate an opposed piston
two stroke Almar cycle operation~ Cylinder 24 in Figure 6
is shown to be in position for a power stroke by ignition
of spark 48. In Figure 7 the pistons 28 h~ving completed
the power stroke open exhaust ports 50 before intake ports
52 are open and thus Figure 7 illustrates the position of
the piston at exhaust. Figure 8 shows pistons 28 as having
finished or completed their outward stroke at bottom dead
center, so that both exhaust ports 50 and intake ports 52
are open and thus Figure 8 represents the intake position
of the pistons. In Figure 9 the pistons have closed off
both intake and exhaust ports and thus it represents the`
compression stroke.
Figures 10 through 16 illustrate details of a four
stroke cycle spark ignition embodiment of the invention.
The engine generally designated by the number 100 includes
stationary manifold block member 102 in which is located a
cylinder generally designated by the number 104. Cylinder
104 includes water or coolant jackets 106 and cylinder walls
108. As can be seen cylinder walls 108 extend outwardly to
approximately the circumference or outer radial dimension
of block 102 so that the cylinder has opposed ends 110. Pis
tons 112 are provided within the cylinders and it will be
seen that each is formed with cavities 114 between which are
2S walls or raised sections 116. Spark plugs 118 are provided
for firing in the chambers defined by opposed recessed areas
114. Each piston is provided with rigid extensions or rods
120 extending outwardly to a piston rod end plate 122. An
intermediate partition 124 located radially relative to the
length of the stroke on each`side of the` cylindex provides
an inner engagement sur~ace 124. A compression spring 126
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~082603
is disposed between the intermediate walls 124 and piston
rod end plate 122 to resiliently bias and hold bearings
128 in engagement with the cam surface. Bearings 128
will rotate on shafts 130 and the piston rod or extension
120 will be guided by thrust control bearings 132 located
at the outer ends of the cylinder. It is to be noted that
while roller bearings 128 have been shown friction or slide
type bearings may also be used. Bearings 128 will bear on
the cam track generally designated by the number 140.
Figure 10 shows additional details of manifolding
and manifolding cams. The rotary output member surrounding
and rotatably mounted on block 102 is generally shown by the `
number 134. It includes drive cam member 136 having an in-
ner drive cam surface generally identified by the number
140. Rotary output member 134 has cam spacers 142 so that
on one side of drive cam 136 is an intake exhaust valve cam
146. Figure 15 shows that valve cams 144 and 146 are approxi-
mately identical in appearance except/ of course, that the
raised portions for compressing and opening the valves will
be located differently according to the timing required.
The cam surfaces 148 and 150 respectively of the two valve
cams engage valve stem pushers 152 and 154 which could also
be roller, friction or other types of bearings. If for in-
stance, cam member 146 is the intake valve cam it will en-
gage pusher 154 which in turn will depress valve stem 156
against spring pressure 158. Thus valve 160 would be dis-
engaged from its seat to enable combustion gases to enter
the cylinder through manifold channel 162. In like man-
ner on the exhaust side pusher 152 engages cam 144 to de~
; 30 press valve stem 164 to unseat valve 166 to enable exhaust
gases to be purged through the exhaust manifold channel 168
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~L~8~03
Rotary member side plates 170 are provided together with ap-
propriate bearing seals 172 for rotatably mounting the ro~
tary output member 134 on block 102~
~igures 14 and 15 are included to show that the
Almar cam curve configuration is an important feature of
this invention when considered with other design features.
The cam which is driven into rotation by action of the ex-
panding gases working on the pistons during the power stroke
of the cycle also controls piston motion during exhaust, in-
take and compression strokes. The cam curvature is designedto optimize particular features of engine performance for
which certain constraints in cam design are appropriate. A
preferred cam surface is that which permits constant volume
combustion in spark or compression ignited internal combus-
tion engines over a wide range of engine speeds, permits themost rapid expansion of burned gases after energy into
mechanical work, and then decelerates the piston to zero
velocity as rapidly and as efficiently and with as little
wear as possible. ~ny cam area which for instance wouId
cause bearing 12~ to lose contact with the cam surface or
which would result in intermittent bearing contact would be
obviously unacceptable. Also, any cam design which would
cause a large side thrust against the piston rod control
bearing, i.e., the beginning of the exhaust and compression
stroke would be unacceptable. Additionally, any portion of
the cam which would give rise to unnecessary problems of
stress and strain, lubrication or which were unnecessarily
complex would also be unacceptable. Preferred surfaces de-
pend for the most part upon the type of engine, fuel, materials,
size, specific power, speed, design for load, and other vari-
ables.
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:
The design constraints placed on the cam configura-
tion are set forth in the following general propositions.
The cam of Figure 12 illustrates a geometrical limitation
on the expansion or power stroke portion of the cam which
enables the most rapid possible expansion of the combustion
chamber or fastest possible expansion displacement of the
pistons in a cylinder. The maximum rate at which the pis-
ton moves away from top dead center during combustion is in
the acceleration area B of the expansion stroke and is es-
tablished by a tangent line T. The maximum value of Ri(index radius) in area B at any point during acceleration
of the piston cannot be greater than any point on line T
in area B which is tangent to the last radius value RKT
(constant radius top dead center) of the constant volume
area A. The length of the straight line T of section B ex-
tends for as long as acceleration is desired and of course
as its transition into area C is smooth. ~ must be a smooth `
curve which decelerates the piston until its linear velocity
is zero at the beginning of the bottom dead center area D.
Again, in following the tangent line T in Section B which
is tangent to circular arc ~ at the last constant volume
radius value RKT thereof, the piston accelerates as rapidly
as possible while maintaining a positive contact with the
cam surface while the pressure between the pistons is smoothly
2S decreasing.
The acceleration area B is shown to subtend 35
but could be larger or smaller and it is not necessar~ that
deceleration area C represent the same number of degrees of
rotation as area B. In order to establish cam deceleration
Section C it is necessary that it be plotted with the same
number of radii as the acceleration curve. Thus, for ex-
~ .
- 21 -
~0826C13
ample, seventy-one values of Ri during acceleration are es-
tablished at half degree intervals for the 35 o~ rotation
of section B. There will be the s.ame number of values for
Ri in the deceleration Section C if it is a lar~er angle
S but the index angle for extablishing values of Ri will be
greater than one half degree. If the deceleration Section
C is smaller than acceleration Section B in terms of num-
ber of degrees of rotation the values of Ri for Section C
will be at closer angular intervals than one half degree.
In any event and despite the angular intervals the same
values o~ the changes in Ri will be used in reverse order
to the point at which deceleration Section C joins or reaches
the only or first value of bottom dead center or the constant
volume Rkb. Thus, for example, if the last five values o~
changes in Ri or ~ Ri in the acceleration curve area B are:
Index Number Delta (~ ) Ri
.04~746
86 .048880
87 .Q48941
88 .049048
89 .049082
~hen the first five values of ~ Ri in the deceleration curve :
area C are:
.049082
91 .049048
92 .048941
93 .048880
94 .Q48746 ~
Accordingly, while the piston during deceleration in cam sec- :
tion C is still moving out toward bottom dead center and Ri ~:
is still increasing towards its maximum value at bottom dead
center the differences in Ri or ~ Ri are the reverse o~ the -- :
radius changes in the acceleration curve B. ~.;
The cam of Figure 13 represents a mathematical con- ..
straint on or expression of the acceLeration - deceleration .~ ~:
- 22 -
.~ :,.:,
. , ~ , . '.: : , .' .: : . :'
26(~3
profile of Sections B and C. Essentially, it is a harmonic
curve extending between the last constant volume radius of
top dead center and the first or only radius o~ bottom dead
center. In short, the harmonic curve extends through the
deceleration and acceleration sections of the expansion part
of the cam and is generally defined by the following ex-
pression: ,
R~ = S + [l-Cos(u)]
where u = ~ (~ - k)
0
k = beginning radius point for
the harmonic curve (last
constant radius at top dead
c,enter) in degrees
m = ending radius point for the
harmonic curve (first or
only radius at bottom dead
center) in degrees
L = 180 - (k + m)
S = 1/2 distance of travel of one
piston.
It is to be repeated that the expansion section
of the cam may b~ geometrical design or mathematical ex-
pression be greater or less than the first 90 or rotation.Again, any given radius on the cam has an opposite and equal
radius so that defining 180 of the cam also defines the
other 180 thus giving the cam equal and radially opposed '
symmetry. The cam does not require that there be an area
of constant volume (radius) at bottom dead center since the
need for constant volume at bottom dead center will be a
design variable.
The exhaust portion of the cam is designed to re- -
turn the piston f.tO top dead center with a minimum of thrust
loads against the piston rod control bearing. This is done
by the cam surface being designed so that the linear move-
- 23'-
.- . .: . . . - .
,, ,, ~.............. . . .
.. . . . . . . .
101~i32603
-
ment of the piston on the return movement is relati~ely
slow at the beginning of the exhaust stroke. When the pis~
ton has reached a point at which the distance from the face
of the piston to the control bearing is larger than the
distance from the control bearing to the point of contact
at the cam surface, then the cam profile from such point
to top dead center is designed so as to make the linear
movement of the piston very rapid. This type of cam de-
sign will allow for minimum wear on the piston, the piston
rods, the cylinder wall and the bearings. -The same cam pro-
file for expansion is used during that quadrant which con-
trols the intake stroke. A very rapid movement of the pis-
ton is accomplished during the initial part of the intake
stroke by which great turbulence of the fuel air mixture
is created. This gives the desired complete mixing of the
fuel-air ingested charge and again minimizing the wear on
the parts. The compression stroke area of the cam is the
opposite and radial equal of the exhaust section. It will
be appreciated that any two opposing sections or quadrants
of the cam will be the same so that the limitation of
equal and opposite radii is not violated.
Figures 14A through 14H depict timed views of a
one cylinder cam in a four stroke Almar cycle embodiment of -~
the engine. The intake manifold is shown on the left side ;~
of the cylinder and exhaust manifold on the right. View A
shows the engine at the beginning of the compression stroke.
At this time the intake valve has begun to close and will
be closed in a very fe.w more degrees of rotation. View B
shows the engine partially through its compression stroke
with both valves closed. By the ~ime the engine reaches top
dead center thé compression air fueI mixture has been ig~
~ 24 -
~, :
~ID8;260:3
nited, is burning, and is creating high pressure in the
clearance space between the pistons Note that by ~iew C
the cam has traveled only 90 of action rotation. For a
normal engine using a crankshaft, the piston travels from
bottom dead center to top dead center through a rotation
of 180.
On the power stroke View D, the pistons and rods
are seen to drive the rotating cami in a direction to allow
expansion of the hot gases. The cam is driven from opposite
sides in a balanced configuration so that there is no net
thrust on the cam in any direction and only radial, equal
and opposite force to make the rotor rotate. Note that
since the pistons are symmietrically oriented and are driven
in unison there is no unbalance of piston forces which
would operate to cause lateral vibration. View E shows the
pistons fully extended in the position of bottom dead cen-
tèr and the exhaust valve and now open to expel the spent
exhaust gases. Because of constant volume areas the piston
is exerting pressure on the cam throughout its total travel
and the exhaust valves do not have to open before the pis-
ton reaches bottom dead center. The cam's angular momen-
tumi in the case of a one cylinder engine, now carries the
.,i ...: .
rotor through this bottom dead center position and begins
to force the gases out of the cylinder during the exhaust
stroke. With two or more cylinders or multi-cylinders where
all cylinders are simultaneously fired angular momentum
carries the rotor through to the next ~iring stroke. The
angular momentumi carries the cam through the exhaust stroke
(View F~ continuing to expeI the gases until top dead center
~0 as shown in View G. It will be seen in the Views A through
G that there is always pressure in the cylinders forcing
- 25 -
1al82~03
the rod bearings to maintain contact with the rotating cam.
During the intake portion of the cycle it is necessary to
force the piston to extend and to this end the spring 126
as seen in other views is mounted between the cylinder and
bearing. The springs are always under compression so that
they act to maintain bearing contact with the cam.
~ 26 -