Mechanism for intermittent rotation of first and second shafts and continuous rotation of a third shaft

A rotary piston engine (20) is shown which includes a housing (22) having a cylindrical working chamber with inlet (56) and exhaust (54) ports. First and second piston assemblies (30 and 32) each of which includes at least one pair of diametrically opposed pistons (30A and 30B, and 32A and 32B) are located in the working chamber. Backstopping clutches (44 and 46) limit rotation of the piston assemblies (30 and 32) to one direction (42). Piston assemblies (30 and 32) are connected to the engine output shaft through a differential (78) and non-circular gear sets (74 and 76), each of which gear sets includes a tear-drop shaped gear (74A and 76A) and heart shaped gear (74B and 76B). When the cusp of the tear-drop shaped gear engages the recess in the heart shaped gear, the tear-drop shaped gear is prevented from rotating. The piston assemblies rotate intermittently whereby pistons of the stopped assembly are trailing pistons during portions of the power and intake phases of engine operation. In one embodiment, the tear-drop shaped gear include teeth in the form of rollers (132).

FIELD OF THE INVENTION 
This invention relates generally to a mechanism for interconnecting first, 
second and third shafts for intermittent rotation of said first and second 
shafts and continuous rotation of said third shaft. The mechanism is well 
adapted for use with rotary piston engines for providing the engine piston 
assemblies with intermittent rotation while the engine output shaft is 
continuously rotated. 
BACKGROUND OF THE INVENTION 
Mechanisms for providing piston assemblies of rotary piston engines with 
intermittent rotation are known as shown, for example, in U.S. Pat. No. 
1,224,642--R. B. Holmes; 2,657,676--G. E. Mallincrodt; and 
3,294,071--Turco. Such mechanisms are, however, generally relatively 
complicated in design and include braking systems, or the like, to 
intermittently stop rotation of the rotary piston assemblies. 
SUMMARY OF THE INVENTION 
An object of this invention is the provision of improved mechanism for 
interconnecting first, second and third shafts for intermittent rotation 
of said first and second shafts and continuous rotation of said third 
shaft. 
The present invention includes differential means having first and second 
input shafts and an output, together with first and second non-circular 
gear sets. Each of the first and second gear sets includes intermeshing 
generally tear-drop and heart shaped gears. The generally tear-drop shaped 
gears are formed with a cusp, and the generally heart shaped gears are 
formed with a recess engageable by the cusp of the associated tear-drop 
shaped gear during rotation of the gear sets. The differential output is 
connected through a third gear set, such as a circular gear set, to an 
output shaft. The heart shaped gears are affixed to the output shaft, the 
axis of rotation of which shaft extends through the recess formed in the 
heart shaped gears. Whenever the cusp of the tear-drop shaped gear engages 
the recess in the associated heart shaped gear, the tear-drop shaped gear 
is prevented from rotating. The tear-drop shaped gears of the first and 
second gear sets are connected to the first and second differential input 
shafts, respectively.

DETAILED DESCRIPTION 
Reference now is made to FIG. 1 of the drawings wherein an engine 20 is 
shown to include a stationary housing 22 having a cylindrical bore which 
is closed at opposite ends by end plates 24 and 26 attached thereto as by 
bolts or other suitable means, not shown, to form a cylindrical working 
chamber. In the engine shown in FIG. 1, the working chamber is divided 
into first and second pairs of diametrically opposite sub-chambers by 
pistons included in first and second piston assemblies 30 and 32. As also 
seen in FIG. 2, piston assembly 30 includes a pair of diametrically 
opposed pistons 30A and 30B, and piston assembly 32 includes a pair of 
diametrically opposed pistons 32A and 32B. The engine cylinder and pistons 
are also shown in FIGS. 3 and 4 of the drawings. 
Pistons 30A and 30B are affixed to hubs 34A and 34B at facing ends of 
tubular piston shaft sections 36A and 36B, respectively. Shaft sections 
36A and 36B together with associated hubs 34A and 34B, are supported for 
rotation about the axis of the cylindrical bore in housing 2 by end plates 
24 and 26, respectively, through suitable bearing means, not shown. Hubs 
34A and 34B are located in recesses formed at the inner walls of the end 
plates. An inner piston shaft 38 is rotatably mounted in the tubular shaft 
sections 36A and 36B and extends therebetween. Pistons 32A and 32B of 
second piston assembly 32 are attached to inner piston shaft 38 at 
diametrically opposite positions. Shaft 38 may be formed in 
interengageable sections, including section 38A to which pistons 32A and 
32B are attached, to facilitate assembly, which shaft sections rotate as a 
unit when in the illustrated engaged condition. Piston assemblies 30 and 
32 are rotatable about a common axis 40 and, in operation, rotate in the 
same direction as indicated by arrows 42. Backstopping, one-way, clutch 
means 44 and 46 on tubular shaft section 36B and inner piston shaft 38, 
respectively, prevent rotation of the piston assemblies in the direction 
opposite arrow 42. Any suitable one-way clutches, such as sprag-type 
clutches, may be employed to prevent such backward rotation. 
The working chamber is divided into two pairs of diametrically opposite 
sub-chambers by the four wedge-shaped pistons 30A, 30B, 32A and 32B. As 
will become apparent, each piston assembly alternately rotates and stops 
such that trailing pistons are stationary during at least a portion of the 
power and intake phases of engine operation, and periodically variable 
volume sub-chambers are provided between adjacent pistons. Sealing of 
sub-chambers to prevent the flow of gases therebetween is provided by any 
suitable means including for example, straight seal means 48 along the 
inner concave surfaces of pistons 30A and 30B which engage inner piston 
shaft section 38A. Generally U-shaped seal means 50 extend along the outer 
convex surfaces of pistons 30A and 30B, and along opposite ends thereof, 
for sealing engagement between the pistons and cylinder walls. Similarly, 
generally U-shaped seal means 52 extend along the outer convex surfaces of 
pistons 32A and 32B, and along opposite ends thereof, for sealing 
engagement between these pistons and cylinder walls. 
As seen in FIG. 1, engine housing 22 is provided with an exhaust port 54 
followed, in the direction of piston travel, by an intake port 56. Next, 
in the direction of piston travel, a fuel injection nozzle 58 is provided 
which is connected to a source of fuel, through which nozzle fuel is 
injected into the sub-chambers following intake of air through inlet port 
56. Finally, ignition device 60, such as a spark plug, is provided for 
ignition of the compressed air/fuel mixture contained in the sub-chamber. 
With the illustrated four-piston engine, the operating chamber is divided 
in four sub-chambers. Referring to FIG. 5, power and exhaust phases of 
engine operation occur during angular piston movement identified by 
double-headed arrow 62, and intake and compression phases occur during 
angular piston movement identified by double-headed arrow 64. It will be 
seen that all engine operating phases occur over angular piston movements 
of somewhat less than 180 degrees. That is, substantially one-half of the 
engine working chamber is used solely for intake and compression 
functions, and substantially the other one-half is used solely for power 
and exhaust functions. 
The engine as described thus far may be of substantially the same design as 
shown in U.S. Pat. No. 5,133,317 by the present inventor, the entire 
contents of which patent specifically are incorporated by reference 
herein. Novel connecting means, identified generally by reference numeral 
66, for operatively connecting the first and second piston assemblies 30 
and 32 to an engine output shaft 68 and providing the piston assemblies 
with intermittent rotation, now will be described with reference to FIGS. 
1 and 6 of the drawings. 
In the embodiment of the invention illustrated in FIGS. 1 and 6, connecting 
means 66 includes two pairs of circular gear sets 70 and 72, two pairs of 
non-circular gear sets 74 and 76, differential means 78, and gear set 80 
which, for purposes of illustration, comprises a circular gear set. As 
will become apparent, gear set 80 may comprise a pair of non-circular 
gears, such as elliptical gears, if desired. Suffixes A and B are used to 
identify separate gears of the gear pairs. Gear 70A of gear set 70 is 
connected to piston assembly 30 through outer piston shaft 36B, and gear 
72A of gear set 72 is connected to the other piston assembly 32 through 
inner piston shaft 38. For the illustrated 4-piston engine, circular gear 
pairs 70 and 72 are provided with a 1:2 gear ratio whereby gears 70B and 
72B undergo two complete revolutions for each complete revolution of 
piston shafts 36B and 38, respectively. 
Circular gears 70B and 72B are affixed to tubular shafts 82 and 84, 
respectively, which are rotatably mounted on spider shaft 86 of 
differential 78. Spider shaft 86, which for purposes of description also 
is defined as the differential output, is supported by suitable bearings, 
not shown, for rotation about axis 88 which extends parallel to piston 
shaft axis 40. Engine output shaft 68 also is supported by suitable 
bearings, not shown, for rotation about axis 90 which extends parallel to 
piston shaft axis 40 and spider shaft axis 88. Affixed to tubular shaft 82 
are teardrop shaped gear 74A of non-circular gear set 74 and end gear 78A 
of differential 78 for simultaneous rotation thereof with gear 70B. 
Similarly, tubular shaft 84 has affixed thereto teardrop shaped gear 76A 
of non-circular gear set 76 and end gear 78B of differential 78 for 
simultaneous rotation thereof with gear 72B. For purposes of description, 
shafts 82 and 84 to which differential end gears 78A and 78B are affixed, 
are defined as differential inputs. 
Differential 78 may be of any conventional type such as the illustrated 
bevel gear differential which, in addition to end, or sun, gears 78A and 
78B, includes spider, or planet, gears 78C and 78D rotatably mounted on 
spider cross shaft 78E. Spider gears 78C and 78D mesh with end gears 78A 
and 78B. The relationship between rotation of sun gears 78A and 78B, or 
differential inputs, and spider shaft 86, or differential output, of 
differential 78 is 
EQU z=(x+y)/2 (1) 
where: 
z is rotational rate of spider shaft 86, 
x is rotational rate of sun gear 78A, and 
y is rotational rate of sun gear 78B. 
During engine operation, sun gears 78A and 78B are intermittently prevented 
from rotation. From Equation (1), it will be seen that when one of the sun 
gears is stationary, spider shaft 86 rotates at twice the rate of the 
rotating sun gear. When both sun gears rotate at the same speed, spider 
shaft also rotates at that speed, with no relative motion between the sun 
gears and spider shaft. Backstopping one-way clutches 44 and 46 limit 
rotation of the sun gears 78A and 78B and teardrop shaped gears 74A and 
76A to one direction shown by arrows 42 seen in FIG. 1. 
Reference now is made to FIG. 7 wherein novel non-circular gear set 74 is 
shown in detail. Non-circular gear sets 74 and 76 are of the same design 
so that a detailed description of only one is required. In FIG. 7 gear set 
74 is shown in the position illustrated in FIGS. 1 and 6, which is 180 
degrees out of phase with gear set 76. As will become apparent 
hereinbelow, the degree to which gear sets 74 and 76 are rotationally out 
of phase varies continuously during engine operation. As viewed in FIG. 7 
gears 74A and 74B rotate in the direction of arrows 94 and 96, 
respectively. 
For purposes of illustration, the tear-drop shaped gear 74A is shown 
comprising a tear-drop shaped body formed with outwardly extending gear 
teeth about the periphery thereof. Heart shaped gear 74B is shown 
comprising a heart shaped body formed with outwardly extending gear teeth 
for engagement with gear teeth of the tear-drop shaped gear. Each gear is 
provided with the same number of teeth whereby the same teeth interengage 
during operation of the gears. 
Gears 74A and 74B are formed with circular arc sections identified by 
double headed arrows 100 and 102 having radii of r and 2r, respectively, 
to the gear pitch lines, portions of which pitch lines 100A and 102A are 
shown in broken lines in the drawing. With the 1 to 2 velocity, or gear, 
ratio of the circular arc sections, it will be apparent that circular arc 
section of gear 74A is twice that of the circular arc section of gear 74B. 
For example only, circular arc sections 100 and 102 may extend for 
200.degree. and 100.degree. respectively 
At opposite ends of the circular arc section 102, heart shaped gear 74B is 
formed with generally spiral-shaped mirror image sections that form a 
recess where the spiral-shaped sections intersect. The axis of rotation, 
90, of the heart shaped gear extends along said recess outside the body of 
the gear between a pair of adjacent gear teeth 104A and 104B. In the 
illustrated arrangement, shaft 68 is formed in sections, the ends of which 
sections are affixed to the heart shaped gears thereby providing access 
for engagement of teeth at the recess with teeth on the tear-drop shaped 
gear. The cusp, or pointed end, of tear-drop shaped gear 74A is provided 
with a tooth 106 which is adapted for engagement with the teeth 104A and 
104B on the heart shaped gear as seen in FIG. 7. When tooth 106 is 
positioned between adjacent teeth 104A and 104B, it will be seen that 
heart shaped gear 74B is rotatable about axis 90 while tear-drop shaped 
gear 74A is prevented from rotating about axis 88. It here will be noted 
that instead of forming shaft 68 in sections attached to the heart shaped 
gears, the shaft may be provided with off-set sections at the gears, or 
may be formed with notches, or depressions at the gears to accommodate the 
gear teeth thereat. 
Operation of the engine employing the novel gear mechanism of this 
invention will best be understood with reference also to FIGS. 8A-8D and 
9. Reference first is made to FIGS. 8A-8D wherein sequential operating 
positions of the engine pistons and non-circular gear sets 74 and 76 are 
schematically illustrated, and functions at the four engine sub-chambers 
are identified in chart form. Sub-chambers between adjacent pistons are 
identified by the letters A, B, C, and D. In the engine schematics the 
spark plug is located adjacent the top of the engine housing, and the 
spark plug, outlet and inlet ports, and fuel injection nozzle are located 
in the same relative positions as illustrated in FIG. 1. In the 
illustrated engine operation, fuel is injected during the compression 
phase. Alternatively, fuel may be injected at the end of the compression 
phase at the point labeled "ignition". Furthermore, a fuel/air mixture may 
be supplied to the engine through the inlet port, in which case no fuel 
injection means are required. Regardless of how and when fuel is 
introduced into the sub-chambers, or how it is ignited, FIGS. 8A through 
8D illustrate engine operation wherein the trailing pistons are prevented 
from rotating during at least a portion of the expansion and intake phases 
for improved engine operating efficiency. 
The piston assemblies and non-circular gear sets are shown at five 
different positions in each of drawings 8A through 8D, which positions are 
labeled 1 through 5. Together, drawing FIGS. 8A through 8D show angular 
positions of the piston assemblies and non-circular gear sets 74 and 76 
which occur during one complete revolution of the piston assemblies. Since 
the non-circular gear sets are connected to the piston assemblies through 
circular gear pairs 70 and 72 having a 1:2 gear ratio, the non-circular 
gears complete two revolutions for each revolution of the piston 
assemblies. Output shaft 68 also completes two revolutions for each 
revolution of the piston assemblies. 
At position 1 of FIG. 8A, ignition takes place in sub-chamber A between 
pistons 30A and 32A when sub-chamber A is substantially at its smallest 
volume, compression starts in sub-chamber B, air starts to be drawn into 
sub-chamber C through inlet port 56, and the exhaust of spent gases 
through exhaust port 54 begins at sub-chamber D. The power, compression, 
intake and exhaust phases occurring at the respective sub-chambers A, B, C 
and D continue from position 1 through position 5 of the piston assemblies 
shown in FIG. 8A. Fuel is injected into sub-chamber B at some point in 
piston travel during which fuel injection nozzle 58 communicates with 
sub-chamber B. As noted above, other means for supplying the engine with 
fuel are contemplated. 
At position 1 of FIG. 8A, the instantaneous velocity, or gear, ratio for 
both gear sets 74 and 76 is 1 and gears of both sets are rotating at the 
same rate. In FIG. 9, to which reference now is also made, a graph showing 
rotational speeds of gears 74A, 76A and interconnected gears 74B and 76B 
versus time is shown, for an engine operating at a constant output speed, 
S/2. In FIG. 9, the rotational rate of tear-drop shaped gears 74A and 76A 
is identified by reference characters 74A-S and 76A-S, respectively, and 
the rotational rate of heart shaped gears 74B and 76B affixed to engine 
output shaft 68 is identified by reference character 68-S. As seen in FIG. 
9, at time t.sub.0, the tear-drop and heart shaped gears are shown 
rotating at speed S/2. In FIGS. 8A-8D, times t.sub.0 -t.sub.16 are shown 
which correspond to times t.sub.0 -t.sub.16 in FIG. 9. 
During travel from position 1 to position 2 of FIG. 8A, the velocity ratio 
of gear set 74 increases from 1 to 2, while the velocity ratio of gear set 
76 decreases from 1 to 0. At time t.sub.1, gear set 74 is shown rotated to 
a position where circular arc sections of gears 74A and 74B are initially 
engaged to provide for the velocity ratio of 2. At the same time, gear set 
76 is shown rotated to a position where the cusp of tear-drop shaped gear 
76A initially engages the recess in heart shaped gear 76B thereby stopping 
rotation of tear-drop shaped gear 76A. Rotation of tear-drop shaped gears 
74A and 76A at speed S and at zero speed, respectively, at time t.sub.1 is 
shown in FIG. 9. These rotational speeds are maintained from time t.sub.1 
through time t.sub.3, during travel from position 2 to position 4 of FIG. 
8A. As seen in FIG. 8A, trailing piston 32A of expansion sub-chamber A, 
and trailing piston 32B of intake sub-chamber C are stationary during the 
time period between t.sub.1 and t.sub.3. By stopping trailing piston 32A 
during at least a portion of the expansion phase, engine efficiency is 
improved over prior art rotary piston engines wherein the trailing piston 
continues to move throughout the expansion phase. In addition, it will be 
noted that connection of leading piston 32B to the engine output shaft 68 
during a portion of the engine expansion phase from time t.sub.1 to time 
t.sub.3 is through gear set 74 during which time these gears have a 
velocity ratio of 2. As noted above, during other portions of the 
expansion phase, between times t.sub.0 and t.sub.1 and between times 
t.sub.3 and t.sub.4, the velocity ratio of gear set 74 is less than 2. As 
seen in FIG. 9, the rotational speed 74A-S of tear-drop shaped gear 74A 
decreases from S to S/2 between times t.sub.3 and t.sub.4. Simultaneously, 
the rotational speed 76A-S of tear-drop shaped gear 76A increases from 
zero to S/2 between times t.sub.3 and t.sub.4. 
In FIG. 8B, to which reference now is made, position 1 corresponds to 
position 5 of FIG. 8A at time t.sub.4. Operation continues in a similar 
manner to that described above with reference to FIG. 8A except now 
sub-chamber B comprises the expansion sub-chamber, and sub-chambers C, D 
and A comprise the compression, intake and exhaust subchambers, 
respectively. Between times t.sub.4 and t.sub.5 the velocity ratio of gear 
set 76 increases to 2 while that of gear set 74 decreases to 0. As seen in 
FIG. 9, between times t.sub.4 and t.sub.5 the rotational rate 76A-S of 
tear-drop shaped gear 76A increases from S/2 to S while the rotational 
rate 74A-S of tear-drop shaped gear 74A decreases from S/2 to zero. Then, 
between times t.sub.5 and t.sub.7, tear-drop shaped gear 74A, and 
associated piston assembly 30, are prevented from rotating by engagement 
of the cusp of tear-drop shaped gear 74A with the recess formed in 
associated heart shaped gear 74B. As a result, trailing piston 30B of 
expansion sub-chamber B and trailing piston 30A of intake sub-chamber are 
stationary during the time period between t.sub.5 and t.sub.7. Position 5 
of FIG. 8B corresponds to position 1 of FIG. 8C at time t.sub.8, and 
position 5 of FIG. 8C corresponds to position 1 of FIG. 8D at time 
t.sub.12. Between times t.sub.0 and t.sub.16, the piston assemblies 30 and 
32 complete one revolution during which time four engine operating cycles 
are completed. 
Where a circular gear set 80 is employed for connecting the differential 
output 86 to the engine output 68, the combined velocity ratio of gear 
sets 74 and 76 must equal 2 in order to satisfy the requirements of 
Equation (1), above, which defines the operation of differential 78. From 
an examination of the drawings and Equation (1), it will be seen that z is 
the rotational rate both of differential output shaft 86 and of heart 
shaped gears 74B and 76B through gear set 80, x is the rotational rate 
both of sun gear 78A and of tear-drop shaped gear 74A affixed thereto, and 
y is the rotational speed both of sun gear 78B and of tear-drop shaped 
gear 76A affixed thereto. Multiplying both sides of equation (1) by two 
results in: 
EQU x+y=2z (2) 
So long as the velocity ratio of gear sets 74 and 76 adds to 2, the 
differential and gear sets operate simultaneously without interference. It 
here will be noted that a gear set 80 of non-circular gears, such as 
ellipsoidal gears, may be used, in which case the shape of gear sets 74 
and 76 would have to be modified accordingly so that conditions specified 
by Equation (1) are satisfied at all times. 
Reference now is made to FIGS. 10 and 11 wherein a gear set 120 comprising 
a modified form of tear-drop shaped gear 122 and cooperating heart shaped 
gear 124 is shown, which gear set may be employed in place of gear sets 74 
and 76. Tear-drop shaped gear 122 is shown affixed to tubular shaft 82 
which, in turn, is rotatably supported on shaft 86 rotatable about shaft 
axis 88, in the manner of gear set 74 shown in FIG. 7. Similarly, heart 
shaped gear 124 is shown attached to shaft 68 rotatable about axis 90. In 
this embodiment, tear-drop shaped gear 122 comprises a body 126 sandwiched 
between a pair of end plates 128 and 130 that extend outwardly from the 
periphery of the body. Gear teeth in the form of rollers 132 are located 
about the periphery of the gear, which rollers are rotatably supported on 
axles 134 extending between the end plates 128 and 130. The rollers are 
adapted for engagement with teeth 136 formed about the periphery of the 
heart shaped gear. As with gear sets 74 and 76 described above, tear-drop 
shaped gear 122 is prevented from rotating when tooth 132A at the cusp 
thereof engages the heart shaped gear at the recess formed therein 
adjacent axis 90. With this arrangement, frictional engagement between 
interengaging teeth is reduced for reduced wear. It will be apparent that 
gear sets that include a combination of conventional gear teeth and 
roller-type teeth may be employed. For example, the circular arc sections 
of gears 122 and 124 may be provided with conventional gear teeth in place 
of the illustrated roller-type teeth 132 on gear 122 and associated teeth 
136 on gear 124. 
The invention having been described in detail in accordance with 
requirement of the U.S. Patent Statutes, various other changes and 
modification will suggest themselves to those skilled in this art. For 
example, the novel combination of differential 78, non-circular gear sets 
74 and 76, and gear set 80 for connecting the piston assemblies 30 and 32 
to output shaft 68 may be used in conjunction with other systems including 
different type engines. For example, it may be included in the connection 
of pistons of a reciprocating-piston engine to an engine output shaft 
without the use of the conventional crank mechanism. Also, it will be 
apparent that the circular arc sections 100 and 102 of gears 74A and 74B 
are not limited to the illustrated 200.degree. and 100.degree., 
respectively. In some applications for the tear-drop and heart shaped 
gears, it may be desired to either increase or decrease the circular arc 
sections, including a decrease thereof to zero degrees. It is intended 
that the above and other such changes and modifications shall fall within 
the spirit and scope of the invention defined in the appended claims.