Frictionless continuously variable transmission

An infinitely variable speed transmission is disclosed which transmits externally applied driving torque to an output shaft through a pinion arm which engages a gear mounted on the end of the output shaft. The pinion arm can freely pivot around the bevel gear throughout the full 360 degree rotation of the input and output shafts. A locking mechanism is provided which allows the user to lock the pinion arm to the bevel gear. This enables the applied torque to be transferred through the pinion arm to the output shaft. The distance separating the input and output shafts can be varied by the user. By selectively varying the shafts' separation the effective transmission ratio can be continuously varied.

FIELD OF THE INVENTION 
This invention relates generally to machine elements, mechanisms, and 
variable-ratio mechanical power transmissions and, more specifically, to 
infinitely and continuously variable transmissions. 
BACKGROUND OF THE INVENTION 
Mechanical transmissions containing either several discrete gear ratios or 
continuously variable mechanisms are necessary whenever it is desirable to 
operate a rotating power source at certain preferred angular velocities. 
Transmissions are utilized for a wide variety of applications, including 
use in machine shop equipment, construction equipment, other types of 
personal and public transportation, and product handling equipment such as 
conveyor lines. This need is especially common in the automotive industry 
because internal combustion engines produce very different levels of 
torque and power across their operating ranges. These should not, for 
purposes of this application, be viewed as the only uses for the 
hereinafter described invention. It can be applied in any situation where 
it is desirable to vary the angular velocity of a rotating shaft. 
Most mechanical transmissions contain a set of discrete gear ratios. This 
fixed number of ratios often results in an inability to continually 
operate the power source at its optimal setting. If a continuously 
variable transmission is used, however, the power source can be operated 
at its desired operational setting and the transmission's nominal ratio 
can be varied to change the angular velocity of the power output shaft as 
necessary. 
A transmission which performs in this manner is ideally suited for use with 
a power source which operates at preferred, fixed angular velocities. Such 
a power source, commonly referred to as a CVO (for "Constant Velocity 
Output"), often contains a massive flywheel which is spun and preferably 
maintained at a constant rate. The great angular momentum of these 
flywheels makes altering their speed a prohibitively slow process. When 
coupled to a continuously variable transmission the flywheel can be driven 
at a constant rate, while the transmission's nominal ratio can be changed 
to vary the vehicle's speed as desired. 
Current terminology in the art regards an infinitely variable transmission 
as one whose output ratio can be varied from 1:0 to some final ratio x:1, 
where x is some value greater than zero. Thus, at its lowest ratio, the 
power source of an infinitely variable transmission can rotate without 
driving the output shaft. Continuously variable transmissions, in 
contrast, can only be operated between two limiting ratios, an initial 
ratio y:1, where y is a value greater than zero and a final ratio z:1, 
where z is some value less than y. 
Both infinitely and continuously variable transmissions can be adjusted so 
that the nominal ratio varies smoothly and without discrete, quantifiable 
changes between the initial and final ratios. Since the present invention 
can be utilized to construct a transmission having an initial ratio of 
1:0, it is a true infinitely variable transmission. 
There are currently two principal types of infinitely/continuously variable 
transmissions. The first type depends solely on friction to transmit its 
power. This type of transmission can be further classified into two 
sub-categories. One sub-category, commonly termed "pulley transmissions", 
uses a flexible belt to transfer power between two pulleys whose effective 
diameters can be varied. As the pulleys' diameters are altered the 
effective transmission ratio varies. In the other sub-category, power is 
transferred through contact with a body of continuously varying shape. The 
typical shape is that of a cone or hyperboloid rotating about its center 
line. The nominal ratio will depend on where the continuously varying 
shape is contacted by the pickup shaft, since its effective diameter 
changes along its length. 
The second principal type of variable transmission transfers power using 
direct engaging mechanical contact, typically through gears. Such 
transmissions can be distinguished from the aforementioned "friction 
drives" because mechanical engagement transmissions do not transfer power 
solely by way of the shearing force developed as a result of the contact 
force exerted between two moving surfaces. (When two surfaces press 
against one another the resulting force vector can be resolved into two 
components. The normal component is that perpendicular to the contact 
plane of the two surfaces. The tangential, or shear component is the force 
exerted parallel to the contact plane of the surfaces.) In these 
mechanical drives, part, if not all, of the power is transferred via this 
shear force component. The present invention is of this second type of 
transmission. 
All existing designs for continuously and infinitely variable transmissions 
have a number of shortcomings. Each of the types previously mentioned has 
its own peculiar problems, caused, inter alia, by the manner in which the 
tranmission's ratio is altered. 
Both types of friction drives, i.e. pulley and variable diameter driving 
bodies, rely on friction to transfer power. The easiest way to decrease 
slippage, and thus power loss, is by increasing the contact forces between 
the parts transferring power. As this contact force increases, however, 
various problems may arise. Among these problems are structural fatigue 
and deformation. The touching parts may even begin to wear, necessitating 
replacement of the belt, pulley or rotating body. 
Variable transmissions using mechanisms other than pure friction, such as 
gears, to transfer power typically contain a substantial number of parts. 
See, for example, U.S. Pat. No. 4,184,388 (Sfredda). The Sfredda 
transmission, like the present one, is a mechanical transmission of the 
second type. Sfredda discloses an infinitely variable transmission 
utilizing a planetary gear system requiring a large number of parts to 
effect variability. The instant invention is readily distinguished from 
this and other transmission art because of its drastic simplification and 
reduction of parts. In fact, prior art teaches away from such simple 
mechanisms used in the present invention. This simplification is a primary 
advantage of the present invention. 
OBJECTS AND STATEMENT OF THE INVENTION 
It is therefore an object of the present invention to provide a simple 
apparatus for use in situations where it is desirable to interpose a 
mechanical transmission between a rotating power source and rotating 
output assembly. 
It is another object of the present invention to provide an apparatus, 
functioning as an infinitely variable transmission, which is substantially 
simpler than presently existing variable transmissions. 
It is another object of the present invention to provide an apparatus, 
functioning as an infinitely variable transmission, which obviates the 
need for the separate clutching mechanism normally required to allow the 
power input shaft to rotate without corresponding rotation of the output 
shaft. 
Still another object of the present invention is to provide an apparatus, 
functioning as an infinitely variable transmission, whereby the power 
input shaft to the transmission can be maintained at a fixed angular 
velocity while continuously varying the output shafts angular velocity 
over a range of speeds through variation of the transmission s nominal 
ratio. 
It is another object of the present invention to provide an apparatus, 
functioning as an infinitely variable transmission, which can be coupled 
to a rotating power source capable of operation at both fixed and varying 
angular velocities, and which, when so coupled, forms a system in which 
the settings of each component, power source and transmission, can be 
independently selected so as to allow the system to be operated for 
maximum power output, maximum efficiency, or any performance compromise 
between these two extremes. 
In one advantageous embodiment of an apparatus employing the present 
invention, the assembly for connecting the input shaft with the output 
shaft is as follows. The input and output shafts are aligned within a 
frame or housing in parallel such that their centerlines are not 
coincident. A drive means and input section, in the form of a plate 
containing a number of radial slots equiangularly spaced about its center 
and of uniform length, is rigidly mounted within the housing such that its 
center and the input shaft's center are coincident. A single head is 
slidably engaged within each slot and is connected, via a locking means 
(discussed in greater detail below), to an output section. This output 
section is composed of the output shaft concentrically fixed to a circular 
bevel gear. The output shaft has a number of freely rotatable pinion arms, 
mounted about an extension of the output shaft projecting through the 
bevel gear. The number of pinion arms can be varied but will coincide with 
the number of slots in the plate of the aforementioned input section. 
The distal end of each pinion arm contains a rotatably mounted pinion gear. 
The pinion gear engages the bevel gear and is freely rotatable thereabout. 
The input and output sections are linked by the aforementioned sliding 
head-plate assembly, wherein each head is fixed to a pinion arm. 
Driving of the said bevel gear is accomplished by providing a mechanism 
wherein the pinion gear of one or more pinion arms can be selectively 
locked and unlocked in a given sequence. When the pinion gear is locked, 
the pinion arm is no longer free to pivot about the bevel gear. Instead, 
the pinion arm, pinion gear and bevel gear cooperate as a single fixed 
unit. Force, applied to the sliding head through the input section, will 
be transferred through the pinion arm to the pinion gear, and, in turn, 
will be transferred through the pinion gear to the bevel gear rigidly 
fixed to said output shaft. 
In actual operation the invention performs as follows. The input shaft and 
drive means rotate as one body. The sliding heads engaged within the slots 
in the drive means can only slide radially, and so reciprocate in their 
respective slots as the drive means rotates. When the pinion assembly 
attached to a sliding head is locked, it will stay engaged at a fixed 
circumferential location on the bevel gear. Force is thus transmitted to 
the output shaft only through locked pinion assemblies. By selectively 
varying both the angle describing the sector of the bevel gear for which 
the pinion gear locks, and the excentricity of the parallel input and 
output shafts, it is possible to obtain wide variations in the nominal 
ratio of the transmission assembly. 
At least two futher advantages obtain to users who connect multiple units 
of the present invention to one another such that the output of the first 
unit drives the input of the second unit and so on, until reaching the 
assemblage's final output. The first advantage to this arrangement 
involves the multiplication of transmission ratios. By joining a number of 
similar individual units in the above mentioned fashion, the highest 
aggregate nominal ratio obtainable will be X.sup.n, where n is the total 
number of units attached to one another and X is the final `highest` 
individual nominal ratio of each unit. 
The other advantage to connecting multiple units in series is that it is 
possible to connect the individual transmission units in such a way that 
the primary input and output shafts can be kept parallel and their 
centerlines coincident at all times, while preserving both the ability to 
continuously vary the transmission ratio and the aforementioned 
exponential multiplication ratio. This is accomplished by rigidly 
attaching the output shaft of the first transmission unit to the input 
shaft of the second transmission unit and orienting the units in such a 
way as to enable them to cooperate as a single assembly. If only two 
transmission units are connected the output of the second becomes the 
primary output shaft. If additional units are connected, the output of the 
second unit is rigidly attached to the input of the third. The output of 
the third unit either becomes the primary output (if three units are used) 
or if additional units are used is attached to the input of another unit 
as described above. This linking process continues for as many units as 
are desired to effect a given final drive configuration. In operation, the 
transmission ratio of the total assembly is varied by displacing one or 
more of the subassemblies perpendicular to the input and output shafts. 
The foregoing objects, features and advantages of the present invention 
will become apparent from the following description of preferred 
embodiments in connection with the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings and, in particular, to FIGS. 1-6, there is 
depicted one embodiment for an apparatus in accordance with the present 
invention. 
FIG. 1 is a side view of the output means showing the output shaft 2 
connected to straight bevel gear 1. This shaft 2 is fixed into a frame or 
housing (not shown). Three pinions 3 continuously mesh with bevel gear 1 
and are held in engagement by radial pinion arms 4. Each radial pinion arm 
4 is independently rotatable about a common shaft 12 located at the center 
of bevel gear 1 in concentric alignment with output shaft 2. Pinions 3 are 
mounted on longitudinal shaft 14 and rotate freely thereon. In this 
embodiment, a sprocket 5 is fixed to the distal end of pinion 3 for 
coupled rotation about longitudinal shaft 14. The distal end of pinion arm 
4 is provided with a head 44 which contains sprocket engagement means 16. 
In accordance with this invention, means are provided for preventing 
rotation of the sprocket 5. As embodied, this means includes a plurality 
of balls 11 held in position in head 44 which balls engage sprocket 5 when 
the outermost ball is depressed. The sprocket engagement means shown 
represents only one method for preventing the rotation of sprocket 5 and 
pinion 3. Alternative methods including pins, shafts, levers, brake bands, 
etc., are contemplated and would not affect the overall operation of the 
present invention. 
Sprocket 5 is spring loaded 26 in a manner that allows it to undergo 
limited free rotation independent of the related pinion's movement. This 
lost rotational motion allows for the alignment of an indentation of 
sprocket 5 and the locking ball 11, when the ball engages the sprocket to 
prevent its rotational motion. 
Bevel gear 1 is rotatably driven by input means shown generally at 22 of 
FIG. 3. Input means 22 includes an equilateral triangular plate 6 having 
radial slots 7 formed therein at angles of 120.degree.. This angle 
.theta., corresponds to the number of pinions utilized in the output 
means. [.theta. is equal to 360.degree. divided by n, where n is the 
number of slots in the plate.]For example, if nine (9) pinions are to be 
used in engagement wit bevel gear 1, then an equilateral polygonal plate 
would be utilized having nine (9) radial slots formed therein at angles of 
40.degree.. With the teachings of the present invention, any number of 
pinions can be used to drive bevel gear 1 simply by designing a 
corresponding slotted plate. 
Radial slots 7 in plate 6 each receive a pinion arm head 44 which is driven 
radially within the slot 7 as plate 6 rotates. Input shaft 10 is 
adjustably mounted in the housing (not shown) and is fixed in the center 
of plate 6 where it serves to drive plate 6 in a rotational motion about 
its axis. 
In accordance with this invention means are provided for forcing the 
sprocket engaging means into engagement with the sprocket as embodied. 
Referring to FIG. 6 this means includes cam 8, which is rotatably mounted 
on input shaft 10 in a plane parallel to plate 6. The inner surface of cam 
8 is alternately brought into contact with sprocket engagement means 16 
and serves to move balls 11 into head 44 causing engagement of sprocket 5. 
In this engaged position, pinion 3 is blocked from rotating about bevel 
gear 1 and thus creates a rigid linkage through which bevel gear 1 is 
driven. 
In this embodiment, cam 8 is in the form of a sector of angle .theta. about 
the center of input shaft 10, wherein .theta.=120.degree.. This permits 
only one pinion 3 to drive bevel gear 1 at any given time, since the 
pinion arms 4 move, through radial slots 7 which slots are separated by 
angle, .theta., wherein .theta.=120.degree.. By forming cam 8 with an 
angle .theta. equal to the angle .theta. between the radial arms a drive 
system comprising a slot, a head, an engaged sprocket/pinion and bevel 
linkage is formed wherein only one sprocket is engaged at any given time, 
and thus only one pinion at a time will be driving. Where desired, these 
angles .theta. or .theta. can be varied to produce drive systems where 
more than one sprocket is engaged simultaneously or to produce a drive 
system wherein a spatial gap exists between the formation of rigid driving 
linkages, resulting in intermediate driving of bevel gear 1. 
Variations in the nominal gear ratio of the embodiment shown in FIGS. 4-6 
can be accomplished in a variety of ways. For example, as shown in FIGS. 
4-5, by incrementally rotating cam 8 through some arc of less than 
360.degree. about input shaft 10 and fixing it in the desired attitude, 
the Path followed by head 44 across cam 8 is lengthened or shortened, 
resulting in an increase or decrease, respectively, in the nominal gear 
ratio. In FIG. 4 the circle 111 represents the output circumference. In 
this manner, relatively minute variations in the gear ratio can be 
effected. 
In addition to incrementally rotating cam 8 as described above, the length 
of the input torque arm, defined as the radial distance between the center 
of a locked head 44 to the center of input shaft 10, can be varied by 
raising and/or lowering the input shaft 10 relative to output shaft 2. 
This vertical movement can provide even larger changes in the nominal gear 
ratio by creating a greater possible range of lengths for the input torque 
arms driving the head 44 across the zone defined by the edges of cam 8. 
Utilizing the methods outlined above, either together or separately, the 
nominal gear ratio can be varied smoothly over a wide range to achieve a 
desired ratio. This variation can be effected continuously to change the 
ratio in response to the needs or requirements of the operator or the 
equipment. 
Referring now to FIG. 7, there is depicted an alternate embodiment of the 
present invention. A primary input shaft 18 (corresponding to the input 
shaft 10 depicted in FIG. 3) is connected to an assemblage 26 which is 
described by and corresponds to the embodiment fully disclosed in FIGS. 
1-6. Assemblage 26 is rigidly coupled, via common shaft 30, to a second 
assemblage 28 which is also described by and corresponds to the embodiment 
fully disclosed in FIGS. 1-6. Common shaft 30 transmits power from shaft 
18 between assemblage 26 and assemblage 28. Shaft 30 also constrains the 
assemblages 26 and 28 to rotate as a single unit. The primary output shaft 
32 (corresponding to the shaft 2 depicted in FIG. 6) can then be connected 
as desired to equipment to be driven. The common shaft 30 is rotatably 
mounted in the push-pull rod 34 such that while the shaft is free to 
rotate it is constrained to follow the lateral movements of push-pull rod 
34. Push-pull rod 34 is slidably mounted in the transmission frame 36 such 
that it can be moved along a line perpendicular to the center line of 
shafts 18, 30, 32. 
Assemblages 26 and 28 are mounted in such an orientation that when viewed 
along centerline of shafts 18 and 32, assemblage 28 can be seen to have 
been rotated exactly 180.degree. from the orientation of assemblage 26. 
The purpose for maintaining the two assemblages 26, 28 in this particular 
orientation will become apparent when the operation of this embodiment is 
discussed below. 
In operation the nominal ratio of this embodiment is controlled by 
laterally shifting the push-pull rod 34. As push-pull rod 34 is displaced, 
the common shaft 30 and other parts attached to the bevel gear 24 and 
equilateral triangular plate 25 are also displaced. If, in FIG. 7, the 
push-pull rod 34 is shifted further to the right the nominal ratio of 
assemblage 26 will change from X:1 to X':1 where X' is some value less 
than X. At the same time, because assemblages 26 and 28 are mounted such 
that one is held at 180.degree. relative to the other, shifting push-pull 
rod 34 further to the right also changes the nominal ratio of assemblage 
28 from Y:1 to Y':1 where Y' is some value less than Y. X need not be 
equal to Y, but it is possible to construct an embodiment such that they 
are equal. Embodiments can be constructed where the nominal ratio R of the 
transmission is equal to X.sup.2 wherein X is the nominal ratio of each 
assemblage 26, 28. Likewise, moving the push-pull rod to the left will 
cause the nominal transmission ratio to decrease. 
FIG. 8 is a schematic block diagram describing the embodiment disclosed in 
FIGS. 1-6 and showing its functional component subassemblies. The input 
shaft 48 is connected to the input section 49. The input section 49 
contains parts corresponding to the input shaft 10 and equilateral 
triangular, plate 6 shown in FIG. 3. The input section 49 is connected to 
the output section 51 via the connecting means 50. The connecting means 50 
contains parts corresponding to the head 44, pinion arm 4, balls 11, 
sprocket 5, pinion 3 and cam 8 shown in FIG. 6. The output section 51 
contains parts corresponding to the bevel gear 1 and output shaft 2 shown 
in FIG. 6. 
FIG. 9 is a schematic diagram showing how the functional component 
subassemblies illustrated in FIG. 8 can be combined to produce alternate 
embodiments employing more than one unit described in this invention. In 
FIG. 9 the input and output sections, 49 and 51 respectively, are 
connected, as shown in FIG. 8, by connecting means 40. The output sections 
51 drive input sections 49 via common shafts 38. Because the common shafts 
38 force the output sections 51 to move with the input sections 49 which 
they drive, both in terms of angular and lateral movements, these 
output-input pairs 42 can be viewed as a single subassembly. If a single 
output-input pair 42 is used it must then be connected via connecting 
means 40 to a final output unit 51, which then drives the output shaft 52. 
If more than one output-input pair 42 is used, they are connected to 
additional output-input units 42. The final output-input unit 42 drives 
the output shaft 52 via a final output unit 51. 
In connecting the individual units which are disclosed in FIGS. 1-6 of this 
invention it is important to align the units so that lateral displacements 
of a single output-input pair 42 will not cause the nominal ratio of one 
of the two units it contains to increase and the other decrease. By 
orienting one unit 180.degree. relative to the other it is possible to 
simultaneously increase or decrease both units+ratios by shifting the 
output-input pair. 
It is also possible to move more than a single output-input pair 42 to 
effectuate a ratio variation. It is additionally possible to adjust a 
number of output-input pairs 42 separately or as a group. 
As has already been noted in the discussion concerning the preferred 
embodiment shown in FIG. 7, it is possible to construct the embodiment 
discussed in FIGS. 8-9 in such a way as to continuously preserve the 
concentricity of the input 48 and output 52 shafts, while also preserving 
the exponential multiplication ratio inherent in such multi-unit 
assemblies. 
Although particular illustrative embodiments of the present invention have 
been described herein, the present invention is not limited to these 
embodiments. Various changes, substitutions and modifications may be made 
thereto by those skilled in the art without departing from the spirit or 
scope of the invention defined by the appended claims.