Abstract:
A bicycling shoe has a ferromagnetic backing plate positionably connected to its sole. A nonmagnetic support plate has a plurality of through holes, and is fixed to the backing plate. NdFeB magnets of alternating polarity are attached by epoxy to the sidewalls of the through holes and make magnetic contact with the backing plate. A similar backing plate, support plate and alternating polarity magnet assembly is fixed to a bicycle pedal. A post extends from the pedal to position the shoe laterally. When the shoe is in a pedaling position, the polarity of the pedal magnets is opposite to the polarity of the shoe magnets, and the shoe is gripped to the pedal to permit transmission of power on the up stroke. To disengage, the shoe is rotated about the post, until like magnets are brought into opposition and the shoe is ejected from its position on the pedal.

Description:
FIELD OF THE INVENTION 
     The present invention relates to bicycles and bicycling accessories in general, and to apparatus for releasably connecting a bicyclist&#39;s shoes to the bicycle pedals in particular. 
     BACKGROUND OF THE INVENTION 
     For over a century the bicycle has served as a low cost form of transportation, a children&#39;s toy, a recreational pursuit, and an object of sporting achievement. The conventional bicycle features two pedals mounted to a rotating drive sprocket, which engages a chain which drives the bicycle rear wheel. Since the early days of bicycles, specialized mechanisms have been employed to allow a rider to supply force to both pedals in both the down stroke and the up stroke of the rider&#39;s legs. 
     One approach to achieving this connection has been to connect a harness or clip to each pedal into which a conventional shoe may be inserted. These clips have the advantage that they do not require specialized bicycling shoes. On the other hand, unless the clips are strapped or fastened to the shoe, they may not be entirely effective in transmitting force on the up stroke. 
     To provide a better connection, mechanical systems requiring modifications to the bicycling shoe have been developed. These systems typically have a projection or recess in the shoe sole which achieves an interlocking fit with structure on the bicycle pedal. However, to achieve effective gripping connection, these systems may require a compound movement or a strong effort to release the shoe from the pedal, which may not necessarily be intuitive or rapidly executable. Furthermore, when exposed to dirt, mud, and road conditions, these mechanical connections can become contaminated, with a resultant deterioration in performance. In addition, a clip which protrudes from the sole will tend to inhibit walking in the shoe when the rider has dismounted the bicycle. 
     In bicycle touring, the ability to instantly release the foot from the pedal is imperative for safety reasons. For example, a change in road conditions or an obstruction may require the bicyclist to stop suddenly. A stopped cyclist must balance himself with one foot on the ground, or face upset of the bicycle. 
     In recent times the bicycle hobby has expanded to include bicycle touring and racing on poorly paved or unpaved venues. Ruggedly constructed bicycles, sometimes known as &#34;mountain bikes,&#34; are used on back roads or off road, and feature impact resistant frames and wider tires. Riding off smooth pavement calls for frequent release of the foot from the pedal, for shift balance on turns or around obstacles. 
     What is needed is a system for attaching the bicyclist&#39;s feet to the pedals in an effective manner for force transmission on the upward stroke which is at the same time easily and intuitively disconnectable. 
     SUMMARY OF THE INVENTION 
     The bicycle pedal, bicycling shoe arrangement of this invention has a bicycling shoe with a circular ferromagnetic backing plate positionably connected to its sole. A circular nonmagnetic support plate has a plurality of through holes, and is fixed to the backing plate. NdFeB magnets of alternating polarity are attached by epoxy to the sidewalls of the through holes and make magnetic contact with the backing plate. A similar backing plate, support plate and alternating polarity magnet assembly is fixed to a bicycle pedal. A post extends from the pedal backing plate and engages with an opening formed in the shoe backing plate and support plate to position the shoe laterally. When the shoe is in a pedaling position, the polarity of the pedal magnets is opposite to the polarity of the shoe magnets, and the shoe is gripped to the pedal to permit transmission of power on the up stroke. To disengage, the shoe is rotated about the post, until like magnets are brought into opposition and the shoe is ejected from its position on the pedal. The magnets may be circular or sector shaped, and various arrangements of magnets may be employed to achieve a gripping force of 60 pounds or greater. 
     It is an object of the present invention to provide a bicycle shoe and pedal assembly which allows the application of pedaling force on the upstroke. 
     It is also an object of the present invention to provide a bicycle shoe and pedal assembly which are non-mechanically linked for rapid connection and release. 
     It is an additional object of the present invention to provide a bicycle shoe and pedal assembly which has a strong vertical attachment force, but a minimal shear resistance force. 
     It is another object of the present invention to provide a bicycle shoe which makes secure engagement with a specialized bicycle pedal, but which permits walking in the shoe. 
     Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. IA is a perspective view of a bicyclist employing the bicycling shoes and pedals of this invention, wherein both shoes are magnetically engaged with the pedals for maximum application of pedaling force. 
     FIG. 2 is a fragmentary perspective view of the shoe of FIG. 1 being rotated for release from the pedal of FIG. 1. 
     FIG. 3 is a perspective view of the bicyclist of FIG. 1 with a shoe released from the pedal for assistance in bicycle maneuvering. 
     FIG. 4 is an exploded isometric view of the shoe and pedal assembly of FIG. 1. 
     FIG. 5 is a bottom plan view of the magnetic assembly module for a shoe of FIG. 1. 
     FIG. 6 is a front exploded schematic view of the shoe and pedal assembly of this invention. 
     FIG. 7 is a bottom plan view of an alternative embodiment magnetic assembly insert of this invention employing sector-shaped magnets. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring more particularly to FIGS. 1-7, wherein like numbers refer to similar parts, a conventional bicycle 20 is shown in FIGS. 1 and 3. The bicycle 20 has a frame 22 and a drive sprocket 24 rotatably mounted to the frame. Pedal arms 26 extend radially outwardly from the drive sprocket 24 and support two pedals 28, one on each side of the frame 22. 
     A bicyclist 30 mounts the frame and places his feet 32 on the pedals 28 and advances the pedals in an up and down pattern to rotate the drive sprocket 24 which is connected by a chain 34 to the gear assembly 36 on the rear wheel 38 of the bicycle 20. 
     The present invention provides a mechanism for attaching a wearer&#39;s shoes to a sporting device such as to the pedals of a bicycle. As shown in FIG. 4, the assembly 40 for connecting the bicyclist&#39;s shoe 42 to the bicycle pedal 28 has two modules, a shoe module 46 mounted to the sole 48 of the bicycling shoe 42, and a pedal module 50 mounted to the bicycle pedal 28. The modules 46, 50 are fabricated to selectably exert an attractive magnetic force between each other when opposite poles are positioned one over another, and to be rotatable to repel one another when like poles are positioned one over the other. Each module has a plurality or magnetic regions of opposite polarity, and the two modules face each other such that when the modules are positioned in pedaling position opposite magnetic regions face one another, and when the modules are rotated, like magnetic regions face one another. 
     The pedal module 50 has a backing plate 52 which is formed of a ferromagnetic material, preferably 1018 steel with electroless nickel plating. A corrosion-resistant material such as 400 series stainless steel may also be employed for the backing plate. The backing plate 52 has three countersunk fastener holes 54 through which extend fasteners 56, for example 5 mm ×8 mm FHP screws. The fasteners 56 fix the backing plate 52 to the pedal 28. A centering post 58 extends upwardly from the backing plate 52, and is positioned at the center of the circular backing plate 52. The centering post engages with a receptor cavity 60 in the shoe module 46, and serves to restrain lateral and tilt movement of the shoe with respect to the pedal. 
     A nonmagnetic support plate 62 is connected by fasteners 64, for example 3 mm ×6 mm FHP screws, which extend through countersunk fastener openings 66 into the backing plate 52. The support plate 62 may be formed of any nonmagnetic material including plastics, or carbon fiber composites, but is preferably formed of 6061-T6 Aluminum with electroless nickel plating. The support plate 62 has a central opening 68 which provides clearance for the backing plate post 58 to pass through. 
     Six cylindrical through holes 70 are formed in the support plate 62. The through holes are positioned equidistant from the central opening 68 and are positioned approximately 60 degrees from one another. A two pole cylindrical magnet 72 is fixed within each through hole 70, such that the bottom surface of each magnet 72 makes contact with the ferromagnetic backing plate 52. An epoxy resin adhesive, such as Loctite brand 680, 642, or 635 one part epoxy adhesive, is applied to the cylindrical side wall 74 of each through hole 70 and the cylindrical magnets 72 are thus held in place by adhesive connection to the support plate 62 only. The bottom surfaces of the magnets 72 are held in direct contact with the ferromagnetic material of the backing plate 52 without the interposition of adhesive therebetween. The magnets 72 are preferably formed of Neodymium Iron Boron (NdFeB). Alternatively, other high flux density magnets formed of materials such as Samarium Cobalt (SmCo) may be used. The six magnets are positioned with the two magnetic poles vertically aligned, and of alternating polarity. Thus a magnet 72 with its North pole extending upwardly is adjacent to a magnet with its South pole extending upwardly, and so on around the circle of the support plate. The magnets 72 preferably have electroless nickel plating. The plating prevents corrosion and also provides a hard wear-resistant surface. 
     The shoe module 46 is attached to a conventional bicycling shoe 42 such as a Shimano SPD brand bicycling shoe, from which the mechanical attachment member has been removed. Racing shoes may also be employed. The shoe module 46 has a ferromagnetic backing plate 76 which is connected to the sole 48 of the shoe 42. The backing plate 76 may be connected directly to the sole 48, or it may preferably be connected to a positionable plate 78, as shown in FIG. 4, which is slidable within the sole for positioning of the shoe module 46. The backing plate 76 has four centrally positioned countersunk attachment holes 80 through which fasteners 82 extend into the positionable plate 78. Tightening of the fasteners 82 grips portions of the shoe sole 48 therebetween and fixes the shoe module 46 in place. 
     A support plate 84 is formed of a nonmagnetic material, preferably aluminum, and has three countersunk fastener holes 86, through which fasteners 88, for example 3 mm ×6 mm FHP screws, extend to connect the support plate 84 to the backing plate 76. The support plate 84 has six cylindrical through holes 90 in which are mounted a plurality of cylindrical NdFeB magnets 92. The support plate 84 has a central hole 96, and the backing plate 76 has a central hole 98 aligned with the support plate central hole. The central holes 96, 98 receive the pedal module centering post 58. 
     As in the pedal module support plate, the magnets 92 of the shoe module support plate 84 are held in place by an epoxy adhesive applied between the magnet side walls and the side walls of the support plate through holes 90. The magnets 92 are also positioned with alternating polarity around the central hole 96. 
     As shown in FIG. 6, the shoe module 46 is positioned over the pedal module 50 such that the North polarity magnets 92 of the shoe module are superposed over the South polarity magnets of the pedal module, in a like way the South polarity magnets of the shoe module are superposed over the North polarity magnets of the pedal module. The effect of this superposition is to cause the shoe module 46 to be attracted to and gripped by the pedal module. The force of this gripping is sufficient to permit force to be imparted to the bicycle drive sprocket 24 on the upstroke. The force exerted between the two modules may be estimated as follows: ##EQU1## Where F=Force in pounds 
     B=Residual flux density 
     A=Pole area in square inches 
     L m  =Individual magnet thickness in inches 
     The magnets 72, 92 may be selected to achieve a desired magnetic attraction force between the modules. For example, selecting Type 35 NdFeB supplied by the Magnet Sales &amp; Mfg. Co. of Culver City, Calif., which have a residual flux density of 12.300 Gauss, with six magnets of about 0.20 square inch surface area, and 0.125 inch thickness, a force of about 60 pounds will be developed. Smaller magnets may be useful in applications requiring less force, for example a 25 pound force would be acceptable for children. Sixty pounds force is considered desirable for the expected exertion of an adult bicyclist. In the illustrated embodiment magnets of 0.50 inches diameter are employed. 
     The ferromagnetic backing plates serve as magnetic shunts between the magnets, increasing the effective attraction between the pedal module and the shoe module. 
     As shown in FIG. 1, when a bicyclist is pedaling, the shoe modules retain the bicyclist&#39;s shoes engaged to the pedal modules on the pedals. The centering post prevents lateral displacement of the shoe with respect to a pedal. The assembly&#39;s resistance to separation forces is great, hence it is difficult or impossible for the rider to pull his feet free of the pedals. However, release from the pedals is simply achieved by rotating the foot, as shown in FIG. 2. As shown in FIG. 5, there is a play of about 11 degrees in which a rider may rotate his foot with respect to the pedal, that is about degrees in each direction, designated α in FIG. 5. A rotation of greater than this amount will cause like magnets to come into superposition, thereby developing a repelling force which is on the order of the attractive force previously encountered. The effect of this repelling force is to instantly eject the rider&#39;s foot from the pedal. 
     Because the shoe modules 46 do not protrude below the level of the shoe sole 48, the modules do not encumber ordinary walking. For protection of the magnets of the shoe module while walking, a circular ferromagnetic plate of the same diameter as the support plate 84, may be magnetically attached to the shoe module. The protective plate (not shown) may have a thin rubber coating thereon to reduce the clicking noise of the plate on pavement. 
     The individual magnets may be shapes other than cylinders. An alternative embodiment module 100, shown in FIG. 7, employs generally sector-shaped magnets 102. The sector-shaped magnets offer the advantage of greater surface area than a circle for a given angular section of the module, and hence greater attractive force for a given diameter support plate 104. 
     In addition, although individual magnets of different polarity supported in the support plate will provide the maximum attractive force, it may be desirable to form the support plate and the magnets as a unitary part, with separate polarity regions imposed on the ferromagnetic element. Such a unitary part may be of lower cost in large quantities. 
     It should be noted that the invention may also be used on other types of bicycles, such as recumbent bicycles, as well as tricycles, or to connect a wearer&#39;s shoes to other sporting devices such as snow skis, water skis, snow boards, and skate boards. In addition, although six magnets have been illustrated on each module, a greater or lesser number may be employed. 
     It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.