Abstract:
An improved eight speed chainless drive includes a gear case housed within the hub of the driving wheel of a utility tricycle with a drive shaft on the axis of the wheel. Three counter shafts rotatably mounted on ball bearings in the gear case are equally spaced around the drive shaft with six gears fixed on each counter shaft. The two gears on one end of each counter shaft are in constant mesh with two drive gears which can be selectively locked to the drive shaft, and the four gears on the other end are in constant mesh with four gears rotating freely on a driven gear carrier rotatably mounted on a ball bearing on the drive shaft, with provisions for selectively locking any one of the four to the driven gear carrier. Spring-loaded pawls mounted on steel pins in the end of the driven gear carrier engage a ratchet ring fixed in the wheel hub for driving the wheel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to multiple speed transmissions for bicycles and tricycles and more particularly to tricycle drives of the chainless type. 
         [0003]    2. Description of the Prior Art 
         [0004]    Typical gym equipment includes stationary bicycles, ellipticycles, and various steppers and stair climbers. An object of this invention is to provide the conditioning function of typical gym equipment in a durable, low maintenance tricycle that can be ridden with a conventional bicycle seat and pedals like a stationary bicycle, or with torque amplifying pedal beams like an ellipticycle, and is easily convertible between these two options. 
       SUMMARY OF THE INVENTION 
       [0005]    The eight speed transmission of this invention includes a gear case located inside the hub of the tricycle driving wheel with an integral cylindrical extension of the gear case extending outboard of the wheel hub on one side and fixed by the tricycle frame; a drive shaft on the axis of the wheel; three counter shafts mounted parallel to the drive shaft on ball bearings in the gear case with six gears fixed on each counter shaft; two drive gears rotating freely on the drive shaft and in constant mesh with the two end gears on each counter shaft with a means for selectively locking one or the other of the drive gears to the drive shaft; a driven gear carrier rotating freely in a fixed axial position on the drive shaft; four gears rotating freely on the driven gear carrier with each in constant mesh with a gear on each of the three counter shafts with a means for selectively locking any one of the four to the driven gear carrier; and a conventional one way clutch driving the wheel hub from the driven gear carrier. The transmission provides speeds one through four with the smaller drive gear locked to the drive shaft by sequentially locking the four gears rotating freely on the driven gear carrier to the driven gear carrier, and speeds five through eight with the larger drive gear locked to the drive shaft by sequentially locking the four gears on the driven gear carrier to the carrier. 
         [0006]    The means for locking one or the other of the drive gears to the drive shaft includes two orthogonally located slots through the drive shaft with the length of the slots equal to the travel required by the locking means; a hole through the center of the drive shaft with a guide bushing threaded into each end of the hole; multiple teeth cut in the bore of each drive gear with the length of the teeth equal to half the face width of the gear; a bar with a width equal to the length of the teeth in the drive gear bore and a tooth form on each end sliding in each of the orthogonal slots with the bars notched at their center so that they both are in the same plane; a compression spring in the hole through the center of the drive shaft between the orthogonal bars and the guide bushing; a drive gear selector rod with a reduced diameter end of the rod passing through the center of one orthogonal bar and threaded into the center of the other clamping the two orthogonal bars together; and a small pitch chain passing out through the guide bushing in the end of the drive shaft and connecting the drive gear selector rod with a shift rod located outside the transmission. 
         [0007]    A crank arm is mounted with a close slip fit on both ends of the drive shaft and clamped in place with bolts threaded into opposite sides of the crank arm with a reduced diameter end of each bolt an interference fit in both the end of the hole in the crank arm and the shallow flat bottomed matching hole in the drive shaft. The threaded portion of the bolt serves as both a pin driver and a pin puller for easy exchange of crank arms. 
         [0008]    A conventional bicycle pedal is threaded into one end of the crank arm with an integral extension of the crank arm on the other end with a slot and a notch for engaging one or the other of two roll pins in the shift rod. When a roll pin is positioned in the notch the orthogonal bars are in alignment with the teeth in the bore of one or the other of the two drive gears. 
         [0009]    The means for selectively locking any one of the four gears rotating freely on the driven gear carrier to the carrier includes two axial slots extending in from the clutch end of the carrier and a driven gear selector ring with a tooth form extending out through the slots for engaging internal teeth in the bore of a driven gear. The radial leg of a ring with the cross section of an angle is a located on one side of the selector ring with the longitudinal leg passing through the bore of the selector ring, and a ring with a rectangular cross section is located on the other side. A driven gear selector rod with an expanded diameter on the inboard end is located in the hole through the center of the drive shaft. A transverse pin extends across the diameter of the rectangular ring passing through the longitudinal leg of the angle ring, a longitudinal slot in the drive shaft, and a hole through the driven gear selector rod, and is locked in position by a set screw in the end of the selector rod. A compression spring is located between the expanded diameter end of the selector rod and the guide bushing in the end of the drive shaft. A small pitch chain passes out through the guide bushing and connects the selector rod with a shift rod with four roll pins through it. Identical crank arms are used on both sides of the transmission. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a plan view of a tricycle using the present invention. 
           [0011]      FIG. 2  is a side view of the same vehicle. 
           [0012]      FIG. 3  is a sectional view taken along the line  3 - 3  of  FIG. 2  with partial end views to show the crank arms and provisions for shifting gears. 
           [0013]      FIG. 4  is a section taken along the line  4 - 4  of  FIG. 2   
           [0014]      FIG. 5  is a section taken along the line  5 - 5  of  FIG. 2   
           [0015]      FIG. 6  is a section taken along the line  6 - 6   
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    Referring to  FIG. 3 , the transmission in accordance with the present invention includes a wheel hub  7 , a wheel hub closing plate  8 , a gear case  11 , a gear case closing plate  12 , and a drive shaft  14 . The wheel hub  7  is centered on the drive shaft  14  by the angular contact ball bearing  9 . The gear case is centered on the drive shaft  14  by the ball bearing  15 . The wheel hub closing plate  8  is centered by the angular contact ball bearing  10  which is seated on a cylindrical extension of the gear case  11 . The cylindrical extension of the gear case  11  is clamped in the tricycle frame preventing the gear case from rotating. The transmission is shown removed from the tricycle frame for clarity of depiction. 
         [0017]    Referring to  FIGS. 3 and 4 , three counter shafts  18  are mounted parallel to the drive shaft  14  on ball bearings  19  in the gear case  11  and in the gear case closing plate  12 . Six gears mounted adjacent to each other on the counter shaft  18  are forced to rotate at the speed of the counter shaft by the key  20  with a length equal to the distance between the bearings  19 . The end gear  24  on each counter shaft  18  is in constant mesh with the larger drive gear  23  on the drive shaft  14 , and the adjacent gear  22  on each counter shaft  18  is in constant mesh with the smaller drive gear  21  on the drive shaft  14 . A bar  25  and a bar  26 , each with a tooth form on both ends, slide in orthogonally located slots through the drive shaft  14 . The bars  25  and  26  are notched halfway through their width at the center so when nested together they lie in the same plane. As shown in  FIG. 4 , the ends of the bars  25  and  26  engage a tooth form machined in the bore of the drive gear  21 . 
         [0018]    Referring to  FIG. 3 , a hole is located in the center of the bar  25  with a threaded hole in the center of the bar  26 . A drive gear selector rod  30  is located in a hole bored through the center of the drive shaft  14 . The drive gear selector rod  30  has a reduced diameter threaded end which is screwed into the bar  26  clamping it to the bar  25 . A guide bushing  32  is threaded into both ends of the drive shaft  14 . A compression spring  31  is installed between the guide bushing  32  and the bars  25  and  26 . 
         [0019]    Referring to  FIG. 3 , a pedal crank arm  33  is located on both ends of the drive shaft  14  and locked in place with a pair of bolts  36  which transfer torque to the drive shaft. A small pitch chain  34  connects the drive gear selector rod  30  with the gear shift rod  35 . Two roll pins  51  are spaced so when the end roll pin is placed in a groove in the end of an integral extension of the crank arm  33 , the bars  25  and  26  are located in the position shown in  FIG. 3 , where the drive shaft drives the smaller drive gear  21 . If the gear shift rod  35  is moved so that the second roll pin is positioned in the groove in the end of the integral extension of the crank arm  33 , the bars  25  and  26  are positioned so the drive shaft  14  drives the larger gear  23 . The axial position of the drive gears  21  and  23  on the drive shaft  14  is maintained by a snap ring  28 , an integral shoulder  29 , and a spacer sleeve  27  with an inside diameter large enough to clear the ends of bars  25  and  26 . 
         [0020]    Referring  FIG. 3  and to  FIG. 5 , a driven gear carrier  40  is mounted on a ball bearing  58  on the drive shaft  14  so that the ball bearing  58  fixes the axial position of the carrier  40 . The largest gear  38  on the carrier  40  is in constant mesh with the smallest gear  37  on each of the three counter shafts  18 . Each of the four gears ( 38 ,  42 ,  44  and  46 ) on the driven gear carrier  40  has twelve equally spaced slots in its bore for engaging a driven gear selector ring  47 , which transfers torque from any selected driven gear to the driven gear carrier  40 . As shown in  FIG. 5 , the driven gear selector ring  47  has two teeth that extend out through diametrically opposed slots in the driven gear carrier  40  and engage slots in the driven gear  38 . Referring also to  FIG. 3 , the axial position of the driven gear selector ring  47  is controlled by a ring  48  with the cross section of an angle the radial leg of which is located on one side of the selector ring  47 , and the longitudinal leg of which is located in a small annular space between the drive shaft  14  and the inside diameter of the selector ring  47 . A ring  49 , with a rectangular cross section, is located on the other side of the selector ring  47 . A transverse pin  50  passes across the inside diameter of the driven gear carrier  40 , through diametrically opposed holes in the rectangular ring  49  and the longitudinal leg of the angle ring  48 , through a slot in the drive shaft  14 , and through a hole in an expanded diameter end of a driven gear selector rod  54 . The transverse pin  50  is held in position by a set screw in the end of the driven gear selector rod  54 . The axial position on the driven gear carrier  40  of the four driven gears  38 ,  42 ,  44 , and  46  is fixed by a snap ring  62  on the inboard end of the carrier  40 , a short cylinder  39  which maintains separation between adjacent gears while permitting unobstructed passage of the driven gear selector ring  47  between gears, and an integral shoulder  63  on the driven gear carrier  40 . 
         [0021]    A compression spring  52  is located in the hole through the drive shaft  14  between an expanded diameter end on the driven gear selector rod  54  and the guide bushing  32 . A small pitch chain  53  connects the driven gear selector rod  54  with a gear shift rod  61  with four spring pins  51  projecting out a short distance on both sides. When placed in a notch in the end of the crank arm  33  each of the spring pins  51  corresponds with the position required for the driven gear selector ring  47  to engage one of the four driven gears. 
         [0022]    Referring to  FIG. 6  as well as to  FIG. 3 , a pair of pawl pins  55  are press fit in the end of the driven gear carrier  40  and spring loaded pawls  56  mounted on them. A gear case closing plate  12  is attached to the gear case  11  with the screws  59  and the joint sealed with an “O” ring  60  with a sealing washer under the had of the screw  59 . A ratchet ring  57  press fit in the closing plate  12  engages the pawls  56  for transferring torque from the driven gear carrier  40  to the wheel hub  7 . A ball bearing type seal  13  installed in the gear case closing plate  12  prevents migration of oil from the gear case  11  to the wheel hub  7 . 
         [0023]    To illustrate an example design for a transmission according to the present invention, 16 pitch gears with a face width of ⅝ inch are used for the drive gears, 32 pitch gears with a ⅜ inch face width are used for the driven gears, and 1.875 inch is used for the distance between the drive shaft and the counter shafts. N1 is the number of teeth in the selected driver gear and N2 the number of teeth in its meshing counter shaft gear. N4 is the number of teeth in the selected driven gear and N3 is the number of teeth in its meshing counter shaft gear. The number of teeth in the selected gears and resultant transmission gear ratio, as well as the equivalent wheel diameter for a standard 26 inch diameter bicycle wheel, is presented for each transmission speed in the following table. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Speed 
                 N1 
                 N2 
                 N3 
                 N4 
                 Ratio 
                 Equiv Diameter 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 One 
                 42 
                 18 
                 54 
                 66 
                 1.908 
                 49 
               
               
                   
                 Two 
                 42 
                 18 
                 57 
                 63 
                 2.111 
                 54.9 
               
               
                   
                 Three 
                 42 
                 18 
                 60 
                 60 
                 2.333 
                 60.7 
               
               
                   
                 Four 
                 42 
                 18 
                 63 
                 57 
                 2.578 
                 67 
               
               
                   
                 Five 
                 48 
                 12 
                 54 
                 66 
                 3.272 
                 85 
               
               
                   
                 Six 
                 48 
                 12 
                 57 
                 63 
                 3.619 
                 94 
               
               
                   
                 Seven 
                 48 
                 12 
                 60 
                 60 
                 4.000 
                 104 
               
               
                   
                 Eight 
                 48 
                 12 
                 63 
                 57 
                 4.420 
                 115 
               
               
                   
                   
               
             
          
         
       
     
         [0024]    Referring to  FIG. 1  and  FIG. 2 , power is delivered to the transmission  7  with a conventional bicycle seat and conventional bicycle pedals. A molded fiberglass trunk  3  is mounted on the forward end of the tricycle to compensate for the weight of the rider on the rear end. The trunk  3  is bolted to a pair of pads  4  which are welded to the steering column  2 . The bolts are installed from inside an open trunk so that they are secure from tampering when the trunk is locked. The tricycle can be converted for delivery of power to the transmission with torque amplifying pedal beams by bolting the trunk  3  to the pads  5  welded on the rear end of the frame  1 , and replacing the pedal-mounting crank arms  33  with shorter crank arms with a spindle press fit in one end. A pedal beam is rotatably mounted near its center on the spindle and a stud type cam roller is bolted on the aft end of the pedal beam. The stud type cam roller engages a short length of steel track  6  fastened to the trunk  3  and provides a downward force to compensate for the weight of the rider on the cantilevered forward end of the pedal beam. The provisions for shifting gears are the same with both options for delivering power to the transmission. 
         [0025]    While this invention has been described in terms of a preferred embodiment, it is obvious that many variations are possible using the same basic configuration. For example, if three driver gears are used with three driven gears, a nine speed transmission results with the same total number of gears as with the preferred embodiment. If four countershafts are used, the gear tooth load is ¾ of the gear tooth load with three countershafts, but then the number of teeth in both the driver and driven gears must be divisible by four instead of three. It is therefore intended that the following appended claims be interpreted as including all such variations as fall within the true scope and spirit of the present invention.