Abstract:
A constant power mechanical transmission with seamless, ripple free, infinitely variable torque multiplying outputs comprises an input shaft and an output shaft. The input shaft is coupled to a pair of oscillating levers whereby rotation of the input shaft causes oscillation of the oscillating levers in opposite directions. The oscillating levers are linked to the output shaft with one-way clutches in order to cause rotation of the shaft upon movement of the oscillating levers. The rotational speed of the output shaft can be infinitely varied by changing the throw of the oscillating levers.

Description:
[0001]     This patent application claims priority to U.S. Provisional Patent Application Ser. No. 60/238,888 filed on Oct. 10, 2000. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     This invention relates to mechanical apparatus for changing the speed and torque of the output shaft of a prime mover relative to its input shaft. More specifically, this invention is directed to an apparatus for providing up to an infinite number of seamless, ripple free changes of speed and torque from a power source such as a gas or diesel engine, an electric motor, a jet engine, a steam engine, the crank of a bicycle, or the like.  
         [0004]     2. Background Art  
         [0005]     Historically, significant efforts have been directed to the provision of transmission assemblies adapted for changing the speed and torque of a power source. Many of these assemblies have involved the use of ratchet drives, eccentrically-oriented cam assemblies, and variable length lever arms. Representative of past efforts in this regard are the structures disclosed in the following issued patents: U.S. Pat. Nos. 629,389; 3,803,931; 4,630,830; 4,487,085; 6,068,570; 4,936,155.  
         [0006]     For example, U.S. Pat. No. 629,389 discloses a bicycle in which it is stated, “The gear may be changed by substituting larger or smaller pulleys.” Thus, one would have to get off the bike, take out his tool kit, take-off the pulleys and attach new and different pulleys to change gear ratios. Furthermore, U.S. Pat. No. 629,389 is a one speed transmission.  
         [0007]     U.S. Pat. No. 4,936,155 discloses a transmission to provide constant power, speed changing and torque multiplication. The invention utilizes “a variable throw cam and cam follower system to provide ripple free output speeds and wide ranging torques.” The cam follower wheel makes point contact with said cam. With this configuration, the cam follower of the present transmission makes line contact with the cam, thus limiting torque and power capacity.  
         [0008]     U.S. Pat. No. 3,803,931 discloses “a variable speed transmission device comprises an output shaft rotated from a first eccentric member through unidirectional couplings”, thus rippled output speeds.  
         [0009]     In U.S. Pat. No. 4,487,085, “The cam is tapered from one end to the other to permit the gear ratio of the transmission to be varied in infinite increments by adjusting the position of the cam relative to the followers.” Power must pass the power through a tiny point of contact greatly limiting the power capacity of the transmission.  
         [0010]     In U.S. Pat. No. 4,630,839, “A bicycle having pivoted level pedal system (1, 2, 45) and lever arm length or gear ratio (speed) change devices (3, 4, 5, 6)” is disclosed.  
         [0011]     The device of U.S. Pat. No. 4,630,839 does not provide any means for removing ripple and, therefore, cannot provide seamless, ripple free outputs.  
         [0012]     U.S. Pat. No. 6,068,570 utilizes eccentrics 14 and 25 which it refers to as cams. The eccentrics 14 and 25 cannot provide ripple free outputs. Furthermore, the transmission of U.S. Pat. No. 6,068,570 does not provide means to produce an infinite number of output speeds.  
         [0013]     Thus, it would be advantageous to provide an infinitely variable torque multiplying, substantially constant power mechanical transmission that produces ripple free outputs, requires fewer components to assemble, is easier to manufacture, is adaptable to any prime mover providing ease of shifting, allows power shifting under load, can provide compression braking and can handle substantially more power and torque than prior art transmissions.  
       SUMMARY OF THE INVENTION  
       [0014]     The instant invention includes an input shaft journaled in a restraining support or housing, one or more oscillators, two or more output levers driven by one or more oscillators. The output levers are coupled to one-way clutches on the output shaft. The throw on the output levers is by selection and infinitely variable in order to change the rotational speed of the output shaft.  
         [0015]     In one embodiment the oscillators, levers and their respective fulcrum blocks may be rotatably coupled on a concentric shaft slidably splined on the input shaft for axial displacement relative to the fixed location of power take-offs.  
         [0016]     In another embodiment the output slides are moveable and the oscillators are not axially moveable.  
         [0017]     In all embodiments the movement of the power take-off members may be self powered and self locking.  
         [0018]     Various oscillator configurations are contemplated, related but not limited to a slidable member on slide guides, wherein oscillators are adapted for back and forth linear displacement of a member along the length of those guides.  
         [0019]     In other embodiments an oscillator may be a cam wherein a single cam will drive two levers.  
         [0020]     In yet further embodiments two drive cams, 180° apart, may drive the two power levers.  
         [0021]     In another configuration, each cam drives its power lever while another cam is configured to keep the drive cam follower wheel in contact with the drive cam at all times.  
         [0022]     In yet another configuration a spring is used to keep a cam or eccentric follower wheel in contact with the cam.  
         [0023]     In another configuration a pair of rollers journaled on the power take-off ride on the lever while a spring holds the lever in contact with these rollers.  
         [0024]     In another arrangement rack gears on the output slide drive a pinion gears integral with overrunning clutches journaled on the output shaft.  
         [0025]     In some embodiments a single cam drives two cam followers 180° apart kept in contact with the cam by spring forces.  
         [0026]     Likewise, the single cam may have an inner and an outer race, with one biasing cam follower wheel riding on the outer face and another cam follower wheel riding on the inner race with two cam follower wheels journaled on each independent axle.  
         [0027]     The instant invention may be adapted to include structures for selectively applying vector longitudinal force generated by transmission power levers directly on the cam/follower assemblies thereby power shifting the assemblies along the length of a shaft on which they are mechanically associated.  
         [0028]     In some embodiments the instant invention may include a control slide, constrained in a groove or along guide rails attached to the transmission housing, and integral with cam follower (oscillator) slide guides and fulcrum blocks connecting rods.  
         [0029]     In some embodiments the control slide is contoured with grooves having oppositively oriented inclined planes wherein rollers biased in cages against the oppositely angled inclined planes in the grooves function as opposed linear one-way clutches to lock the control slide to the housing or to selectively bias the rollers by moving the cage one way or the other wherein the lever forces generated within the transmission may move the control slide one way or the other, thus providing power shifting and automatic clamping.  
         [0030]     In another embodiment the one-way clutch cavities, rollers and cages may be in the power take-offs and automatically hold the power take-offs in selected positions or allow them to be moved by interior lever forces in one direction or the other on power levers.  
         [0031]     Screw or hydraulic positioners or the like may be used to move or to hold the control slide.  
         [0032]     One end of the cam driven lever provides zero output speed and maximum output torque. The other end of the lever, which may extend beyond the cam drive connection, provides the maximum output speed and a smaller output torque. Thus, the instant invention is an infinitely variable constant power transmission.  
         [0033]     In another embodiment, by not including a moveable control slide, the transmission may be used as a low cost, power dense, one or two fixed speed reducer.  
         [0034]     In yet another embodiment cam shaped links, sans cam followers, effectively remove ripple free selected output. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0035]     These and other advantages of the present invention are best understood through reference to the drawing, of which:  
         [0036]      FIG. 1  is a schematic block diagram representing the basic components and their function in accordance with the principles of the present invention.  
         [0037]      FIG. 2  is an exploded perspective of a first embodiment of a transmission with two spring biased cams in linear array in accordance with the present invention.  
         [0038]      FIG. 3  is a graphical representation of speeds delivered from first cam to an output shaft of a transmission in accordance with the principles of the present invention.  
         [0039]      FIG. 4  is a graphical representation of the speeds delivered from a second cam to an output shaft in accordance with the principles of the present invention.  
         [0040]      FIG. 5  is a graphical representation of how the speed from a first cam combines on the output shaft with the speed from a second cam to provide a wide selection of selected, totally ripple free, seamless output speeds of a transmission in accordance with the principles of the present transmission.  
         [0041]      FIGS. 6A, 6B  and  6 C are end, right side and left side views, respectively, of the transmission of  FIG. 2 .  
         [0042]      FIG. 7  is a perspective view of a second embodiment, a self biasing transmission in accordance with the principles of the present invention.  
         [0043]      FIGS. 8A and 8B  are sectional views of power shift assemblies A and B.  
         [0044]      FIG. 9  is a view of a power take-off that is equivalent to the roller type power take-off in accordance with the principles of the present invention.  
         [0045]      FIG. 10  is a side view of a bicycle of the present invention installed as a bicycle transmission.  
         [0046]      FIGS. 11A, 11B  and  11 C are left side, top and right side views of a third embodiment of a transmission in accordance with the present invention used as a bicycle transmission.  
         [0047]      FIG. 12  is a perspective drawing of the transmission of  FIG. 7  as a vehicle transmission.  
         [0048]      FIG. 13  is a cross-sectional side view of a planetary gear set providing selected forward, reverse, neutral and park when connected to the transmissions of this invention. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0049]      FIG. 1  is a schematic block diagram representing the basic components and their function of a transmission in accordance with the principles of the present invention comprising an input shaft  9  coupling a prime mover  10 , such as electric motor, the crank of a bicycle, a motor vehicle, an internal combustion or such as a jet engine, a steam engine, or a wind turbine propeller, to an oscillator, which may be a self biasing cam  11  or cam shaped link in line contact with its cam follower  12 . Line contact between cam and cam follower deliver well over 100 times the torque, or power, than by follower wheels with rounded rims used with variable throw cams. Biased oscillators  12  are coupled to levers  13  in line contact, or equivalent, with power take-offs  14  slidably and selectively clamped on the levers  13 : control means that power shift the position of the power take-off  14  and automatically lock it in a selected place on lever  13 . Power take-offs  14  are coupled to slides  15 , a rack gear  16  or equivalent pinned at one end to housing and in mesh with a pinion  17  integral with one-way clutches  20  on output shaft  19 . Cams, or cam shaped links, are designed to drive at ripple free, seamless speeds the output shaft which may turn the output at an infinite number of selected infinitesimally different speeds from zero rpm to a design maximum top speed. This is a torque multiplying constant power mechanical transmission. The lower the output speed, the greater the output torque.  
         [0050]     A second embodiment (see  FIG. 2 ) is comprised of an input shaft  20  rotatable in a housing  21 , a concentric cam shaft  22  slidably splined on input shaft  20 , and two or more cams  23  fixed to cam shaft  22  said cams are contoured to provide periods of constant linear speed to cam followers  24  biased against cams  23  by a spring  25 . A first cam 180° from a second cam. Two or more cam followers, comprised of follower wheels  26  rotatable on a stub shaft  6  extending from slide  27  that rides up and down just like an elevator in an elevator shaft. Guides  28  extending from blocks  29  held from rotating on rotating cam shafts  22  by guides  28  in grooves  33 . Control slide  30  fixed to guides  28  receives screw  31  the shank of which extends through housing  21  via bearing  32  that restricts back and forth motion of screw  31  while allowing screw  31  to rotate. The ends of guides  28  extend from control slide  30  into grooves  32  in housing  21 .  
         [0051]     Stub shafts  6  extending from followers  24  are held by bearings  34  in levers  35  connected to fulcrums  36  extending from and rotatable in blocks  37 . Cam shaft  22  is rotatable in blocks  37 . Guides  39  fixed to control slide  30 . Guides  39  extend from control slide  30  and ride in grooves  32  in housing  24 .  
         [0052]     Cam  23 , follower slides  24  and fulcrum blocks  37  remain in fixed axial locations because they are so restrained by control slide  30 .  
         [0053]     The shafts of rollers  40  riding on levers  35  are press fit into links  41 . Shaft  42  also press fits in link  41  extends from a bearings press fit into slide  46 . Slide  46  is slidable on guides  44  fixed to housing  21 .  
         [0054]     Tension members  45  are fixed at their upper ends to slides  46  and at their other ends to one-way clutches  47  journaled on output shaft  48 . Springs  49  fastened at their one end to tension members  45  are fixed at their other end to housing  21 . Said tension member arrangement could be replaced by rack and pinion gearing.  
         [0055]     In operation: Input shaft  20  rotates. It rotates cam shaft  22  and cams  23  causing cam followers  24  to reciprocate at a constant linear speed relative to the input speed during 180° of input shaft  20  rotation. First one follower  24 , see  FIG. 3 , moves at that constant speed, then the other follower  24 , see  FIG. 4 , moves at that same constant speed as the first follower pulled by spring  25  rewinds. Together, see  FIG. 5 , they provide a seamless, ripple free output from a cam and cam follower that are always in line, or equivalent, contact one with the other.  
         [0056]     Power levers  35  rotatable on and driven by followers  24  move up and down around fulcrum pivots  36 . Power take-off wheels  40  always in line contact or equivalent with levers  35  cause link  41  to rotate back and forth on slides  46 . Slides  46  move up and down on vertical guides  44  fixed in housing  21 , just like an elevator goes up and down in its shaft. First one is driven at a fixed speed, and then the other is driven at the same, ripple-free, seamless speed.  
         [0057]     Since the cam assembly, including fulcrums  36  is slidably splined on the input shaft, it can be slidably displaced relative to housing  21 . Thus, when fulcrums pivots  36  are in line with the centers of links  41 , those links will not move up and down. When cam assemblies are moved away from fulcrums  36 , links  27  begin to move at a constant speed up and down. The farther the cam assembly is moved, by control screw  31 , the faster slides  46  move.  
         [0058]     An infinite number of speeds are available.  
         [0059]     Slides  46 , fixed to one end of tension members  45  are, at their other end, fixed to over-running clutches  47  journaled on the output shaft  48 . The faster slides  17  move, the faster output shaft  48  turns. Another tension member fixed to said over-running clutches connects with a spring  49  fixed to housing  21 . That force also keeps power take-off wheels  40  on levers  35 .  
         [0060]     First one cam drives the output shaft, and then the other cam drives that output shaft at the same selected ripple-free, seamless output speeds.  
         [0061]      FIG. 7  shows the transmission of the invention in yet another embodiment where input shaft  301  rotatable in housing  302  is slidable in, but keyed to rotate with concentric shaft  303  rotatable in two guide blocks  310  as well as in two fulcrum blocks  346 . Two drive cams  304  fixed to concentric shaft  303  drive two cylindrical cam follower wheels  305  rotatable on shafts extending one each from two cam follower slides  307  riding on guide rods  308  extending from guide blocks  310 . Two cams  304 , fixed to concentric shaft  303 , in line contact with cam follower  307 , are contoured to drive cam followers at a seamless constant speed during the first 180° of each input shaft rotation. The second cam  304  keyed 180° away from the first described cam  304 , and in line contact with its cam follower wheel  305  drives its carrier  307  at the same seamless constant speed during the next 180° of input shaft rotation.  
         [0062]     Two biasing cams  311  keyed to concentric shaft  303  and in line contact with two cam follower wheels  312  journaled on cam follower  314  slidably or ball splined on the same guides  308  as driving cam followers  304 . Biasing cams  304  are contoured to always keep driving cam follower wheels  305  in contact with cams  304 . Biasing cam followers  314  are fixed to driving cam followers  307  by connector  347 . So that followers  314  are one with followers  307 .  
         [0063]     Stub shafts extending from followers  307  are rotatable in levers  315  pivotally pinned on fulcrum block  346 . The upper and lower surfaces of levers  315  are parallel. At least two rollers  344  roll on the upper surface, at least one roller  344  rides on the lower surface of each lever  315 . Roller shafts  343  are pinned to a connecting plate of power take-off  341 . Center lines of shafts  339  fixed to connecting plates of power take-off  344  intersect the center lines of levers  315 . Shafts  339  are rotatable in output slides  327  which ride on guides  338  fixed in and to housing  302 . Tension members  333  pinned to output slides  327  wrap around and are pinned to one-way clutches  334  and  335  journaled on the transmission output shaft  336 . Tension members  337  pinned to the opposite ends of output slides  327  wrap around output clutches  334 ,  335  and are pinned, at their other ends to those clutches. Said tension members could be replaced with rack gears in mesh with pinions on clutches  334 ,  335 .  
         [0064]     Control slide  309  is slidable in groove  348  in housing  302 . Cam follower slides  308  and fulcrum block rods  349  extending from fulcrum block are fixed to control slide  309 . Screw  3  threaded into control block  309  at its one end, its shank extending through housing  302  is rotatable, and restrained against axial motion, in housing  302 . Said shank extends outside of housing. A crank, or wheel, or other mode may be used to rotate screw  3  to move the control slide to change output speed. The axial location of cam, followers and fulcrum relative to each other are fixed by control block  309  and will not change as the array is moved by said controls.  
         [0065]     Screw  349  can be replaced by a self powered shift means comprised of linear opposed one-way clutches, as described in  FIG. 8 .  
         [0066]     In operation, the input shaft  301  turns the concentric shaft  303  and the cams  304  fixed thereon one 180° from the other. Rotating cams  304  take turn driving followers  314  at a constant speed. While the first follower rewinds the second follower is driven by the second cam at that same constant speed. Together they provide a seamless, ripple free output from a cam and cam follower that are always in line contact, one with the other. Biasing cams  311  keep drive cam follower wheels  305  in line contact with drive cam  304  at all times. No springs are needed. Line contacts or equivalent, see  FIG. 14 , deliver well over 100 times the torque force of point contact from rounded rim follower wheels.  
         [0067]     Power levers  315  rotatable on cam followers  307  oscillate up and down on fulcrum block  346 . Power rollers  344  rotatable on a power take-off  341 , two or more on the top surface of the lever and one or more on the bottom surface of the lever. Power take-offs  341  are journaled in output slides  327  riding on guide rods  308  fixed to housing  302 . Said slides are coupled to over running clutches  334  and  335  on the output shaft by rack and pinion gearing or by tension members drive described above.  
         [0068]     Move concentric shaft  303  assembly  350  relative to the power take-offs  340  to change transmission ratios. When the fulcrums  346  are in line with power take-offs the output speed is zero and the output torque is very large. The farther the lever is displaced from the power take-offs, the faster the output shaft turns.  
         [0069]     Simply turn screw  311  threaded in the control  309  slide to change speeds. Or the said screw  303  can be replaced by coupling said slide via opposing one-way clutches which share the same roller cage. This latter method, see  FIG. 8 , moves its opposing one-way clutches effortlessly and automatically locks it in selected locations on control slide  309 . When no control force is applied, the opposing one-way clutches are automatically locked in selected positions.  
         [0070]      FIG. 12  is a perspective drawing of the transmission for an automobile wherein the transmission of  FIG. 7  is shown feeding a planetary gear set  471  designed to provide a choice of forward or reverse drive as well as park or a free neutral. Compression drive means  472  are also shown.  
         [0071]     Variable speed output shaft  210  of  FIG. 7  driven by one-way clutches of the transmission of  FIG. 7  planetary gear set  411 , wherein gear  612  fixed to shaft  210  meshes with gear  614 , fixed to jack shaft  616 . Jack shaft  616  rotatable in carrier  618  fixed to output shaft  643 . Pinion  617  fixed to jack shaft  616  meshing with gear  619 , fixed to concentric shaft  629 . Brake drum  620  fixed to shaft  629  engages brake band  621 , controlled by the transmission operator. Pinion  624  fixed to jack shaft  616  and in mesh with idler gear  625 , rotatable on stub shaft  626 , extending from and integral with carrier  618 . Idler  625  in mesh with gear  630 , keyed to shaft  629 , fixed to brake drum  637 . Brake drum  637  is engageable with brake band  638 .  
         [0072]     In operation, brake bands  621  and  638  are free from drums  620  and  637 , and the transmission is in neutral. Tightening band  621  holds gear  619  still. Input gear  612  on shaft  210  is in mesh with gear  614 , which is fixed to jack shaft  616  and which rotates gear  617 , which then rolls around held gear  619  causing carrier  618  to rotate output shaft  643  in a reverse direction.  
         [0073]     Releasing break band  621  and tightening brake band  638  stopping brake drum  637  causes jack shaft  616  to rotate carrier  618 , fixed to output shaft  643  in a forward direction. When both brake bands  621  and  638  are tightened, the transmission is in park.  
         [0074]     Compression braking means are comprised of gear  473  coupled by a one-way clutch to output shaft  336 , of the transmission of  FIG. 8 . Gear  473  is in mesh with gear  474  fixed to the engine shaft, which is the transmission input shaft. When gear  474  is driven faster than engine speed by gear  472  we have compression braking.  
         [0075]     In yet another configuration, a bicycle type transmission that is self biasing, infinitely variable, torque multiplying and that never needs to move a chain from one sprocket to another to change speed rotors is disclosed.  FIG. 10  shows an illustration of the transmission in a bicycle.  FIG. 11A  is a top view of the transmission.  FIG. 11B  is a left hand view and  FIG. 11C  is a right hand view where a self biasing cam  501  driven by pedals  502  drives cam followers  505 A and  505 B pinned to bike frame  50 . Cam follower wheels  504  ride on the inner race of cam  501 . Cam  501  is designed to produce a ripple free, constant speed rotation of follower  505 A during the first 180° of pedal rotation and the same ripple free, constant rotation of follower  505 B in reverse during the next 180° of pedal rotation.  
         [0076]     Biasing cam follower wheel  514  in contact cams outer race  517  is designed to keep follower wheels  504  on cam  501 . Follower wheels  514  are independently journaled on shaft  516  fixed to and extending from followers  505 A and  505 B. Cam follower  505 A fixed to transfer shaft  509  journaled in tab welded to bicycle frame  50  is fixed at its other end to beam lever  518 . Bicycle frame extension  508  has walking beam extensions  510  connected by rods or cable  511  to a similar walking beam extensions  510  rotatably fixed to transfer shaft on one end rotatable in tabs  511  extending from bike frame  50  at its other send. Said walking beam is integral with beam  518 . Power take-offs  519  slidable splined on beam  518  has shafts  509  extending therefrom that journal cluster sprockets  521  comprised of a small sprocket fixed to a larger segment sprocket  521 .  
         [0077]     Power take-offs  519  with opposed linear over-running-clutches, see  FIG. 8 , comprised of rollers  523  in cage  524  biased against inclined planes of cavities  525  in power take-offs  519  slidable on beams  518 . Control cable  526  fixed to one end of cage  524  extends to twist grip, or control lever, on the handle bars of the bike. Another control cable  526  is fixed to the other end of cage  524  and at its other end to the same twist grip or lever. Move the twist grip or lever one way and the power take-off, impelled by interior transmission forces, moves that way. Move the twist grip, or lever, the other way and the power take-off moves the other way.  
         [0078]     Short segments of chain are pinned to bike frame  50 . Their other end is fixed to and wraps around small sprockets  520 , fixed to larger sprocket  521  segments. Roller chain  522  fixed to front sprocket segment  521  extends to rear sprocket  528  journaled on rear axle  529  fixed to bike frame  50  and then to lightly spring loaded idler  531  on rear fork of frame  50  and then back to and around sprocket  528  journaled on axle  529  and then back to the other larger sprocket segment  521  where it is pinned.  
         [0079]     The hub  532  of the bicycle&#39;s rear wheel is journaled on rear axle  529 . That hub is the outer race of roller clutches with wedge shaped cavities  533  and  534 . Rollers  30  in cages  31  are biased against the inclined plan of the wedge shaped cavity.  
         [0080]     In operation, when the pedal is pushed down the cam rotates. When the cam rotates cam follower  505 A oscillate. Cluster sprockets  521  journaled on power take-offs  519  are selectively positioned on beams  518 . Cluster sprockets  521  turned by chains fixed to bike frame  50  on their one end and to the smaller sprocket of cluster sprocket  521  on its other end turn larger sprocket segment  521  coupled by chain  22  to rotate rear wheel sprocket  528 . A walking beam cam follower  505 B pinned to bike frame  50  coupled to a walking beam lever  552  oscillates in reverse. Cluster sprockets  521  selectively positioned on beam  552  is coupled by chain  22  to the other rear wheel sprocket. Both rear wheel sprockets are fixed to inner races of one-way clutches in rear wheel hub. First one rear wheel sprocket drives the rear wheel, and then the other rear wheel sprocket drives the rear wheel. The speed of the rear wheel depends on the selected position of the power take-offs on oscillating beams  522 . Power shifting is effortless. When the twist grip is turned one way, roller  523  is held away from inclined plane of cavity  525  and internal transmission forces can push the power take-off in that direction. The other roller  523  remains biased to the inclined plane in its cavity  525  to keep power take-off from moving in the opposite direction. When the twist grip is turned the other way clutch roller  523  is held away from the opposite inclined plan in its cavity  525  allowing interior transmission forces to then move the power take-off in the opposite direction. When the twist grip is held still, rollers  523  are biased against both inclined planes and the power take-off is held fast to beam levers.  
         [0081]     The walking beams could be replaced with idler sprockets.