Abstract:
A crank including a mechanism capable of connecting the crank arm to a shaft to drive the shaft in rotation in either a unidirectional drive mode or a bidirectionally driving mode, the mechanism being quickly adjustable between modes. A coupler in the mechanism may be slidable between a first position engaging the crank arm with a hub portion fixedly mounted on the shaft and a second position in which a unidirectional clutch can operate to allow rotation of the crank arm freely about the shaft in one direction but cause rotation of the shaft in the opposition direction. The coupler may be arranged to be coupled only when the shaft is in a selected angular position.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to cranks for use in human-powered machines such as bicycles and crank-driven exercise machines and relates particularly to such a crank equipped with a unidirectional clutch and a coupler engageable to prevent the clutch from permitting the crank to rotate in either direction with respect to the shaft. 
   It is known to connect cranks drivingly to crankshafts through unidirectional clutches in exercise machines and bicycles, as taught in Day U.S. Pat. No. 5,860,329. Use of such clutches is known as a way to assist in training a person&#39;s muscles. While pedals equipped with such clutches are useful, use of the clutches is not always desired, as it may be preferred at times to use a crank to move a shaft optionally in either rotational direction, particularly in exercise machines. It may also be desirable to use a unidirectional clutch for specific training purposes during a portion of a bicycle ride, but it also may be desirable to use the same bicycle with its cranks fixed to extend conventionally in opposite directions during a portion of the same bicycle ride. It would also be desirable to use a stationary exercise machine equipped with a crank or a pair of cranks driving an input crankshaft through unidirectional clutches at some times, yet to be able to have cranks fixed in a conventional oppositely-directed arrangement to drive the shaft optionally in either direction at other times, or to permit one crank to move the other one of a pair at times. The cost of two bicycles or two exercise machines equipped with differently connected cranks would usually not be justified, and the time required to exchange cranks equipped with clutches for cranks fixed to a crankshaft so as to rotate the crankshaft positively in either direction is also unacceptable. 
   What is desired, then, is a crank assembly that can be used to drive a crankshaft in either of two modes. In a first mode, a unidirectional clutch should permit free rotation of the crank in one direction with respect to the crankshaft, but couple the crank to the crankshaft drivingly when the crank is moved in an opposite rotational direction. In a second mode, the crank should be coupled drivingly to the shaft so as to drive the shaft in either direction, and the mechanism should be able to be shifted between the two modes simply and quickly. 
   SUMMARY OF THE INVENTION 
   In response to the above-mentioned desire the present invention provides a crank including an associated mechanism through which an arm of the crank can be connected drivingly to a crankshaft and can be used in a first mode to drive the crankshaft in one rotational direction, but to rotate freely about the crankshaft in the opposite rotational direction. The mechanism can be adjusted quickly and easily to couple the crank arm drivingly to the crankshaft, and thus permit use of the crank in a second mode in which rotation of the crank arm in either direction causes the crankshaft to rotate. 
   In one embodiment a coupler is carried movably on an inner end of the crank arm and is movable between an engaged or coupled position and a disengaged or uncoupled condition. 
   In one embodiment engagement of the coupler results in the crank arm being held in a predetermined angular position with respect to the crankshaft or a hub portion of the crank attached to the crankshaft. 
   The foregoing and other features of the invention will be more readily understood upon consideration of the following detailed description, taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view showing a crank assembly including one embodiment of the present invention. 
       FIG. 2  is an isometric view of a crankset arrangement including pedals and crank arms mounted on a crankshaft. 
       FIG. 3  is an elevational view of the crank assembly shown in  FIG. 1 , taken in an axial direction with respect to a shaft on which the crank assembly might be mounted. 
       FIG. 4  is an exploded, partially cutaway view taken in the direction of line  4 - 4  in  FIG. 2 , showing the clutch and coupler mechanisms included in the crank assembly shown in  FIG. 1 , together with a portion of a shaft. 
       FIG. 5  is a sectional view of a portion of the crank assembly shown in  FIG. 3 , taken along line  5 - 5 , at an enlarged scale, with the coupler engaged to override the unidirectional clutch. 
       FIG. 6  is a view similar to  FIG. 5 , but with the coupler disengaged, to permit the unidirectional clutch to function. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   Referring now to the drawing figures which form a part of the disclosure herein, in  FIG. 1  a crank assembly  10  which is one embodiment of the invention includes a crank arm  12 , of a suitable material such as an aluminum alloy, that has a radially inner end  14  adapted to be attached to an end of a crankshaft as will be described in more detail presently, and an outer end  16 . The crank arm  12  as shown herein is equipped with an array  18  of parallel grooves and ridges and a set of threaded bores  20 , to accept adjustable attachment of a pedal at a selected location to provide a desired effective crank arm length, but it will be apparent that the crank could also be manufactured in a selected length with a conventional threaded bore (not shown) to accept a pedal or handle, depending upon the use to which the crank assembly  10  is intended to be put. 
   As shown in  FIG. 2 , a pair of crank assemblies  10 L and  10 R are equipped with respective pedals  22 , and each crank assembly  10 L,  10 R is attached to a respective one of a pair of opposite ends of a power input shaft, such as a crank shaft  30 , shown in simplified form, without the supporting bearings that would be necessary, such as the bearings in the bottom bracket of a bicycle or an exercise machine. 
   It will be understood that depending upon the intended application of the crank assembly  10  various rotary drive mechanisms such as chain sprockets or drive belt pulleys not shown herein may be associated with the shaft  30  or either of the crank assemblies  10 L and  10 R. 
   The inner end  14  of the crank arm  12  includes a portion which serves as a clutch housing  32 . A unidirectional clutch assembly  34  is fitted securely and tightly in the clutch housing portion  32 , as by being pressed into a place. A spindle  36  fits matingly within the clutch assembly  34  as a part of a hub  37  arranged to be driven by the clutch assembly  34 , and is made so that it can be fastened drivingly as an adaptor to mount the crank assembly  10  on an end of a shaft such as the crankshaft  30 . 
   With the hub  37  attached drivingly to the crankshaft  30 , the unidirectional clutch assembly  34  is engaged to drive the hub  37  and the crankshaft  30  when the crank arm  12  is moved in one rotational direction about the axis of rotation  38  of the crankshaft  30 , such as direction indicated by the arrow  40 . The clutch assembly  34  is disengaged when the crank arm  12  is moved about the axis  38  in the opposite direction, so that the crank arm  12  is moved about the axis  38  in the opposite direction so that the crank arm  12  is allowed by the clutch to rotate freely about the crankshaft  30 , as to the position shown in broken line at  39 , while the crankshaft  30  remains stationary. 
   It will be appreciated that the clutch assembly  34  in the crank assembly  10 L shown in  FIG. 2  is arranged so that it is engaged when the crank assembly  10 L is rotated as indicated by the associated arrow  40  in  FIG. 2 . 
   The clutch assembly  34  is not shown herein in complete detail, but in one embodiment the outer portion  42  is a roller clutch mechanism securely mounted in the clutch housing  32 , as by being pressed into place or by being inserted after heating the clutch housing  32 , while the spindle  36  fits snugly within the outer portion  42  and includes a hardened smooth cylindrical outer surface about which the outer portion  42  can rotate freely in the direction opposite the arrow  40 , but which is engaged drivingly by the outer portion  42  when it is rotated by the crank arm  12  moving in the direction indicated by the arrow  40 . For use of a pair of crank assemblies  10  on a bicycle a preferred clutch assembly  34  is a roller clutch such as a Torrington® drawn cup roller clutch available from The Timken Company, of Canton, Ohio, and which drivingly engages the spindle  36  at any angular position of the outer portion  42  with respect to the spindle  36 , in response to a very small angular movement, less than a degree of arc. Alternatively, for other applications of the crank assembly  10 , other types of unidirectional clutches, such as those using ratchet-and-pawl combinations that can be engaged only at a finite number of discrete relative positions, may be satisfactory. 
   In each crank assembly  10  a coupler  50  is associated with the inner end  14  of the crank arm  12  to override the operability of the unidirectional clutch assembly  34  by selectively coupling the crank arm  12  drivingly to the hub  37 . When the coupler  50  is coupled, rotation of the crank arm  12  about the axis  38 , either in the direction indicated by the arrow  40  or in the opposite direction, will correspondingly rotate the crankshaft  30  to which the hub  37  is attached. 
   Referring now also to  FIGS. 3 ,  4 ,  5 , and  6 , it will be seen that as part of the coupler  50  arrangement the inner end  14  of the crank arm  12  includes a pair of bosses  52  and  54  each defining a through-bore  56 . A third through-bore  58  is defined in the crank arm  12 , adjacent the clutch housing  32 . The coupler  50  includes a collar  60  that carries three connecting pins  62 , each of which is held fixedly in a respective hole in the collar  60  and extends slidably within respective one of the bores  56  and  58 . As indicated by the arrow  66  the collar  60  is moveable in an axial direction, parallel with the axis of rotation  38  defined by the clutch assembly  34 , between the coupled position shown in  FIGS. 1 ,  2 , and  5 , and an unlocked position shown in  FIG. 6 . The connecting pins  62  and the bores  56  and  58  are all parallel with the axis of rotation  38  and each other, and thus when the collar  60  is moved axially it performs as a pin carrier, and the connecting pins  62  slide within but remain engaged in the bores  56  and  58 , keeping the collar  60  from rotating with respect to the inner end  14  of the crank assembly  10 . 
   It may be seen that in the crank assembly  10  as shown the outer surface of the clutch housing  32  at the inner end  14  of the crank assembly is generally cylindrical, and without the mating slidable relationship of the connecting pins  62  with the bores  56  and  58  the collar  60  might be rotatable about the clutch housing  32 . 
   Instead of using the connecting pins  62  to prevent rotation of the collar  60  with respect to the clutch housing  32  the clutch housing  32  and collar  60  could be of other slidably mating non-circular shapes or might include mating slidable keys and key ways or be of a splined or fluted configuration permitting the collar  60  to be moved back and forth axially along the clutch housing  32  as indicated by the arrow  66  in  FIG. 1 . It will be appreciated, moreover, that the collar  60  could easily be removed from the crank assembly  10  if it is desired to use the unidirectioinal clutch without the option of overriding its function, thus reducing the weight of the crank assembly  10  slightly. 
   As may be seen in  FIG. 4 , each of the connecting pins  62  extends through the collar  60 , and an end of each of the connecting pins protrudes as a projecting portion  68 . The hub  37  includes a flange  70  securely and drivingly mounted to and extending radially outward about an inner end  72  of the spindle  36 , and the flange  70  defines receptacles in the form of through-bores  74  located to receive matingly the projecting portions  68  of the connecting pins  62  when the collar  60  is in the coupled position shown in  FIGS. 1 and 2 . 
   The hub  37  as shown is provided with radially inwardly directed splines  44  to mate with corresponding grooves  46  formed in an end of a shaft, such as the crankshaft  30 , to which the crank assembly  10  is to be attached, and the spindle  36  and flange  70  together thus constitute the hub  37  about which the crank arm  12  can rotate when the coupler  50  is uncoupled, and which acts to drive a shaft such as the shaft  30  to which it is attached. Internal threads  71  may be provided within the hub  37  for use in withdrawing the hub  37  from the end of a crankshaft  30 . 
   It will be understood that instead of the spline and milled groove arrangement shown in  FIG. 4  various other configurations of the end of a shaft might be used with corresponding internal shapes provided in the hub  37 , such as conventional tapered square bicycle crankshaft ends or any of several other currently available configurations for a bicycle bottom bracket crankshaft. Conceivably, the spindle  36  could be machined as an integral part of a shaft or a half-shaft. 
     FIG. 5  shows that when the coupler  50  is in the coupled position the projecting portions  68  of the connecting pins  62  are mated in the receptacles  74 , while the opposite end of each connecting pin  62  remains slidably engaged in a respective one of the bores  56  and  58 , preventing the collar  60  from being rotated with respect to either the crank arm  12  or the flange  70 . Since the flange  70  is fixedly mounted on the spindle  36  the coupler  50  thus couples the crank arm  12  to the hub  37 . 
   Preferably the spline and groove arrangement includes a slightly tapered snug fit in order for the hub  37  to be fitted tightly to the end of a shaft such as the crankshaft  30 . A special fastening bolt  75  includes a suitable drive socket and threads  76  that mate with an internal thread  78  in the end of the shaft  30 . A radially extending shoulder  80  engages the outer end of the  82  of the hub  37  to keep it tightly fastened to the end of the shaft  30  as shown in  FIGS. 5 and 6 , while a small gap  84  is provided between the radially outwardly extending outer shoulder  86  of the bolt and the clutch assembly  34  and a surrounding portion of the clutch housing  32 , to allow free rotation of the crank arm  12  with respect to the spindle  36  when the coupler  50  is uncoupled as shown in  FIG. 6 . 
   As may be seen best in  FIGS. 2 and 4 , the arrangement of the projecting parts  68  and the receptacles  74  may allow the coupler  50  to be coupled only in a unique position of rotation of the crank arm with respect to the flange  70 , so that when the coupler  50  is coupled the crank arm  12  will be in a predetermined position with respect to the flange  70  and thus the hub  37 . To assist in placing the crank arm  12  in the correct position for placement of the coupler  50  in the coupled condition, indicia such as a scored line  88  shown in  FIG. 1  may be provided on the flange  70  and the collar  60 . 
   Preferably a fastener or a detent such as a ball and spring detent  90  is provided in the collar  60  to hold the coupler  50  in the desired one of the coupled and uncoupled positions, to avoid inadvertent uncoupling. While the collar  60  is easily gripped to move it from alongside the crank arm  12  to the coupled position, a portion  92  of the collar  60  may be slightly larger in diameter than the flange  70 , may be knurled, or may have another easily grasped surface configuration to facilitate uncoupling the coupler  50  from the hub  37  to enable the clutch assembly  34  to control whether the crank arm  12  drives the hub  37 . 
   The collar  60  could alternatively be mounted non-rotatably on the flange  70  and could carry projections to be selectively mated with or removed from a mating relationship with the inner end of the crank arm  12  if desired, but such an arrangement might prove disadvantageous if it included connecting pins sliding within bores in the flange  70 , since the connecting pins might project beyond the inner side of the flange  70  and thus interfere with the frame of a bicycle or other machine on which such a crank assembly is used. 
   As an alternative to the collar  60  and sliding pins  62  another mechanism capable of being coupled and uncoupled easily without tools could also be used to couple the clutch housing  32  to the flange  70 . For example, a small pivoted lever arm (not shown) mounted on the crank arm  12  could selectively be engaged in a corresponding notch in the flange  70 , or a catch could be slidably mounted on the crank arm  12  to engage such a notch in the flange  70  and thus couple the crank arm to the hub  37  so as to overcome the unidirectionial clutch assembly  34 . 
   The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.