This invention relates to apparatus for continuously variable rotary power transmission. More particularly, this invention relates to such apparatus which incorporate variously sized and shaped counter rotating friction wheels.
A known continuously variable power transmission comprises a conical wheel which is frictionally paired with a second wheel, the axes of rotation of the conical and second wheels typically being aligned so that they lie within a single flat reference plane. In such configuration, while the points of frictional contact between the conical and second wheels are near the conical wheel""s base, rotation of the conical wheel counter rotates the second wheel at a high speed. Conversely, frictional contact near the conical""s wheel""s point results in counter rotation of the second wheel at a relatively low speed. Such an assembly provides continuously variable rotary power transmission as a result of a potentially infinite number of positions of the second wheel between the conical wheel""s point and base.
In order for the above exemplary conical wheel transmission to effectively transmit rotary power, an acceptable level of friction must exist at the points of contact between the two wheels. A known means for enhancing wheel driving friction at such contact point forms one or both of the wheels from a material having a high coefficient friction, such as rubber. However, high friction materials, such as rubber, are often undesirably utilized because they lack durability. Another known means of enhancing wheel driving friction at the contact point is to widen the contact face of the second wheel, resulting in a lengthening of its zone of frictional contact with the conical wheel. However, in such configuration, opposing sliding friction force vectors invariably arise on opposite sides of a centrally located useful static friction zone. The resultant sliding friction undesirably causes heat build up, and undesirably reduces the mechanical efficiency of the rotary power transmission.
The instant inventive continuously variable transmission overcomes or ameliorates the problems discussed above by providing a dual conical friction wheel assembly which is capable of continuously variable power transmission through mechanical deformation of one of the friction wheels of the assembly, such friction wheel comprising an axially skewable scroll.
(Descriptions below use the spacial orienting terms xe2x80x9cforwardxe2x80x9d, xe2x80x9crearwardxe2x80x9d, xe2x80x9cupperxe2x80x9d, and xe2x80x9clowerxe2x80x9d solely for convenience of reference. The scope of the invention includes all spacial orientations.)
A primary structural component of the instant inventive continuously variable transmission comprises a rotatable scroll, preferably comprising an axially extending bar axle having a spindle mounted thereover in the manner of a quill assembly, the spindle being capable of rotating about the bar axle, the spindle preferably being further capable of sliding linearly along the bar axle.
A regular trapezoidally shaped ribbon or strap of sheet steel is preferably wrapped a multiplicity of times around the annular outer surface of the spindle, causing the angled edges of the trapezoidal sheet to form upper and lower conical friction wheel faces.
While the rotatable scroll is symmetrically configured, the pitches of its conical upper and lower faces are equal. Upon an upward skewing of the spiral wrappings of the rotatable scroll to enhance or increase the pitch of its conical lower face, the conical face of its upper face is correspondingly decreased. Conversely, downward skewing of the rotatable scroll increases the conical pitch of its upper face and correspondingly decreases the conical pitch of its lower face. Suitably, the skewable spirally wrapped component of the rotatable scroll may alternately comprise a multiplicity of nesting tubes having progressively narrower axial lengths, such nesting tubes being skewable as described above.
Second and third primary structures of the instant invention comprise upper and lower solid or non-skewable conical friction wheels. The conical friction wheels are necessarily held in frictional contact with the upper and lower conical faces of the rotatable scroll. The conical friction wheels are preferably mounted pivotally with respect to the rotatable scroll so that pivoting and counter pivoting motions of the conical friction wheels alternately skew the skewable (preferably spirally wrapped) component of the rotatable scroll upwardly and downwardly, altering the pitches of the scroll""s faces as described above. Upon clockwise pivoting of the upper and lower conical friction wheels with respect to the rotatable scroll, the faces of the scroll are skewed upwardly causing, upon counter rotation of the friction wheels against the scroll, the upper conical friction wheel to rotate faster than the lower conical friction wheel. Conversely, counter clockwise pivoting of the upper and lower conical friction wheels downwardly skews the faces of the scroll, causing the upper conical friction wheel to rotate more slowly than the lower conical friction wheel.
Mounting means in the nature of a support frame is preferably provided, the support frame enabling the upper and lower conical friction wheels to pivot in relation to the rotatable scroll for alternately upwardly and downwardly skewing the faces of the rotatable scroll, the support frame preferably further enabling the upper and lower conical friction wheels to counter rotate against the upper and lower conical faces of the scroll for continuously variable transmission of rotary power through the scroll.
Accordingly, an object of the instant invention is the transmission of rotary power through a skewable or deformable scroll for continuously variable power transmission.
Other and further objects, benefits, and advantages of the present invention will become known to those skilled in the art upon review of the Detailed Description which follows, and upon review of the appended drawings.