Abstract:
A power assist module includes a battery powered motor mounted on a manually operated vehicle, such as a bicycle. The power assist module is fixedly mounted on the bicycle and can be easily removed without the need for tools, so that the bicycle can be manually operated in a conventional manner when so desired without carrying the extra weight of the power assist module. The power assist module includes a motor assembly which is operated through a gear reduction assembly to drive a crank drive gear mounted in conjunction with a crank arm of the bicycle.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electrically operated power assist apparatus for a manually operated vehicle, such as a bicycle, and, more particularly, to a new and novel construction of a power assist apparatus for a bicycle.  
         [0003]     2. Description of the Related Art  
         [0004]     By way of background,  FIG. 1  illustrates a standard bicycle which includes a front steering wheel  50  and a rear wheel  60 , which may be attached to a frame  20 . The frame has a head tube  32  which journals a front fork  52  for steering via handles bars  33  by a rider of the bicycle  100 . A seat tube  21  is carried by the frame  20  adjacent the rear wheel  60  and a seat post, upon which a saddle type seat  25  is positioned thereon to accommodate a rider, is slidably received in the seat tube  21  for adjusting the height of the seat  25 .  
         [0005]     In the standard bicycle  100 , a horizontally oriented crank journal  113  is positioned beneath the seat tube  21  for supporting a rider-propelled drive mechanism  120 . The drive mechanism  120  generally comprises a crank arm  123  having a first end journalled to each side of the crank journal  113  and an opposite second end rotatably supporting a pedal  25 . A chain sprocket  129  having a plurality of circumferential teeth is fixedly secured to the crank journal  113 . A chain  140  is wrapped around the chain sprocket  129  and a rear sprocket  150  mounted to the rear wheel  60 , whereby application of power by the rider on the pedals  25  rotates the sprockets  129 ,  150 , and hence the rear wheel  60 , to propel the bicycle  100 . A derailleur (not shown) is often substituted from the single rear sprocket  150 , and may have a plurality of sprockets to provide variable gearing for rider comfort and efficiency when encountering variable terrain.  
         [0006]     Bicycles have been utilized as a means of transportation for over one hundred years. From an environmental standpoint, bicycles are preferable to automobiles and motorcycles because they are non-polluting. However, some people are deterred from using a bicycle due to the effort required to pedal up one or more inclines, or hills. Therefore, if a power assist device was incorporated into a bicycle with a minimum degree of difficulty and expense, then people would be more inclined to use a bicycle as a means of travel, especially for short trips, since the overall physical effort to propel the bicycle would be minimal.  
         [0007]     Electric powered bicycles are known in the art, for example, as illustrated in U.S. Pat. Nos. 3,431,994 and 3,921,745. These types of electric powered bicycles incorporate an electric motor which is powered by one or more batteries. Typically, the motor operates through a drive wheel which frictionally engages with one of the wheels of the bicycle. Other methods include different configurations of direct drive systems, involving shafts, chains, and gears, but with the common feature of the driving motor being mounted on the bicycle frame in one position or another (e.g. near the pedaling sprocket, on one of the stays or on a rack above the rear wheel).  
         [0008]     However, the prior art direct drive power assist devices for a bicycle have generally required complex gearing arrangements. Upon removal of the wheel for maintenance, such as tire repair, precise reengagement of the direct drive device is difficult, leading to excessive wear and noise during operation. Also, complex gearing arrangements are difficult to maintain in precise alignment when the bicycle encounters road bumps and holes. Further, the prior art direct drive power assist devices for bicycles have not been designed to be readily removable from the bicycle to permit normal manual usage without the extra weight of the direct drive device.  
         [0009]     Accordingly, there is a need in the art for a modular power assist device for a bicycle that can be easily added to or removed from the bicycle, and which efficiently transmits torque to the crank journal without excessive noise or gear tooth wear due to misalignment.  
       SUMMARY OF THE INVENTION  
       [0010]     According to one aspect of the invention, there is provided a power assist module removably attachable to a bicycle for providing power to the bicycle. The bicycle has a frame supporting at least one driven wheel and a drive gear coupled to the driven wheel. The power assist module comprises: a housing; an electric motor supported by the housing; and an output drive gear supported by the housing and operatively coupled to the electric motor for selectively engaging and driving the drive gear of the bicycle. At least one frame mounting block extends from the housing and is adapted to engage the frame of the bicycle and automatically align the output drive gear for meshed engagement with the drive gear of the bicycle. An attaching hook extends from the housing and is engagable with the frame of the bicycle for selectively and removably attaching the power assist module to the bicycle.  
         [0011]     In another aspect, the present invention is a modular power assist device which can be readily added or removed from the bicycle without the need for tools, so that the bicycle can be manually operated in a normal manner when so desired without carrying the extra weight of the power assist apparatus.  
         [0012]     A further objective of the present invention is to construct a power assist apparatus for a bicycle that efficiently transmits torque to the crank journal without excessive noise or gear tooth wear due to misalignment.  
         [0013]     Another objective of the present invention is to construct a power assist apparatus which is composed of few parts, is of lightweight construction, is efficient, is durable and requires a minimum of maintenance.  
         [0014]     Another objective of the present invention is to construct a smoothly operating, vibration free, direct drive, power assist apparatus for a bicycle. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0016]      FIG. 1  is a side view of a prior art standard bicycle, which shares the same basic parts or components as the improved bicycle disclosed herein;  
         [0017]      FIG. 2  is a side view of a bicycle incorporating the preferred embodiment of the invention;  
         [0018]      FIG. 3  is a side view of the power assist module and its interaction with the crank drive gear according to one aspect of the invention;  
         [0019]      FIG. 4  is a side view of the upper hook arrangement of the power assist module;  
         [0020]      FIG. 5  is a perspective view of the mounting block that interfaces with the bottom bracket of the bicycle frame; and  
         [0021]      FIG. 6  is a fragmentary, perspective view of the bottom bracket and bicycle frame including the mounting positions for the hook and catch.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]     Referring to  FIGS. 2-6 , wherein like numerals indicate like or corresponding parts throughout the several views, the preferred embodiment of the invention includes a bicycle generally shown at  200  having a front steering wheel  50  and a rear wheel  60  attached to a frame  20 .  
         [0023]     The bicycle  200  has a crank arm  123  with a first end journalled to each side of a crank journal  113  and an opposite second end rotatably supporting a pedal  125 . The crank journal  113  includes a front chain sprocket  129  having a plurality of circumferential teeth and a toothed rear sprocket  150  mounted to the rear wheel  60 . A chain  140  is wrapped around each of the chain sprocket  129  and the rear sprocket  150  and in driving engagement with the teeth thereon whereby application of power by the rider on the pedals  125  rotates the crank journal  113  and propels the bicycle  200  as is commonly known in the art.  
         [0024]     The subject invention relates to a self-contained electric or power assist module  300 . The power assist module  300  is illustrated in detail in  FIG. 3 , and generally comprises a rechargeable bank of batteries  109  mounted within a stylized housing  104 , an electric motor  105 , a gear reduction assembly  106 , an output drive gear  112 , frame mounting blocks  107  and, an attaching hook  101  and clamp  102 . For reference, a phantom outline of a crank drive gear  108  is also shown in  FIG. 3 .  
         [0025]     An alternative location for the batteries  109  can be within the hollow interior of the frame  20 , either in the crossbar members, one of the down tubes, or in the interior of a moncoque type frame.  
         [0026]     Referring to  FIGS. 3, 5 , and  6 , in the preferred embodiment, the power assist module  300  interfaces with the frame  20  of the bicycle by way of the frame mounting blocks  107  engaging a machined bottom portion  20 B of the frame  20 . The machined surfaces of the bottom portion  20 B of the frame  20 , commonly referred to as the bottom bracket, are cylindrical and concentric to the center of the crank journal  113 .  
         [0027]     Referring specifically to  FIGS. 5 and 6 , the mounting blocks  107  include spaced apart and parallel mounting blocks  107   a  and  107   b  defining arcuate mating surfaces for mating flush against the frame mounting bottom portion  20 B and become concentric with the center of the crank journal  113 . The purpose of this arrangement is to ensure that the output gear  112  from the power assist module  300  and the crank drive gear  108  are correctly engaged, that is, the accuracy of their center-to-center distance  114  (shown in  FIG. 3 ), is maintained irrespective of the final positioning of the hooks  101  and clamps  102  that hold the module in place on the bicycle frame  20 .  
         [0028]     The installation and removal of the self-contained power assist module  300  is readily accomplished and without the aid of tools. The module  300  is installed onto the bicycle frame  20  by simultaneously engaging the upper hook  101  and the mounting blocks  107  onto their corresponding mating positions on the bicycle frame  20 , namely mating cavity  110  and cylindrical bottom frame  20 B. The mating cavity  110  includes a frame catch  110   a  for engaging with the hook  101  to releasably retain the hook in the cavity  110 . The mounting blocks  107  are the prime locators of the power assist module  300  onto the bottom frame  20 B and control the placement of the output drive gear  112  with respect to the frame  20 , and hence, the crank drive gear  108 . Once the module  300  is positioned relative to the bottom frame  20 B, the locking hooks  102 , located on the underside of the module  300 , are engaged with mating catches  121  on the frame  20 , and tightened in order to lock the module  300  securely to the frame  20 . An electrical connector  103  is located in the bicycle frame  20  and engages with a mating electrical connector  111  on the power assist module  300  when the module  300  interfaces with the frame  20 . No further assembly or rider intervention is required. Because the power assist module  300  can rotate, via the interface between the bottom frame  20 B and the mounting blocks  107 , an latitude between the upper hook  101  and the frame catch  110   a  is eliminated once the lower hook  102  is tightened into place within the mating catches  121 .  
         [0029]     Thus, being correctly engaged, the module output gear  112  can efficiently transmit torque to the crank drive gear  108  without excessive noise and gear tooth wear due to poor alignment. Because the cylindrical mounting surfaces of the bottom frame  20 B, pedal spindle axis of the crank journal  113 , and crank drive gear  108  are all concentric to each other, the accurate placement of the output drive gear  112  with respect to the driven crank drive gear  108  is ensured.  
         [0030]     In the preferred embodiment, the operation of the self-contained power assist module  300  is controlled by, for example, a handlebar mounted switch  99  that enables the rider to selectively turn the power assist module  300  on or off as desired. An electronic controller module  130 , located within the battery housing  104 , is utilized in order to regulate the amount of assist provided by the power assist module  300  depending upon the level of effort being expended by the rider. For example, the harder the rider pedals, the more assist is provided. When the rider begins moving the pedals and applying torque to the crank journal  113 , an electronic sensor  131  adjacent to or encircling the crank journal  113  sends electrical signals, in proportion to the load applied, to the controller  130  which processes the signals and determines the appropriate amount of current from the storage batteries  109  to be directed to the electric motor  105 .  
         [0031]     In the preferred embodiment, to effect the removal of the self-contained power assist module  300  from the bicycle frame  20 , the locking hooks  102  are disengaged from the mating catches  121 , the upper hook  101  is released from the frame catch  110   a , and the module  300  is removed. At this point, the electrical connection between the connector  103  and mating connector  111  also becomes disengaged.  
         [0032]     While the form of apparatus described herein constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus. For example, it is within the scope of the invention that the power assist module could also be used in conjunction with other manually operated vehicles such as tricycles, scooters, and the like.  
         [0033]     The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.