Patent Grant
7011607
The present invention relates to exercise devices, and more specifically to a magnetic resistance unit adapted to be used in connection with an exercise device such as a bicycle trainer.
A number of resistance-type bicycle training devices have been developed that allow a person to stationarily train on a bicycle. Such bicycle training devices are commonly used indoors when it is not possible to ride the bicycle out of doors. Such bicycle training devices normally include a collapsible frame positionable on a floor and releasably attachable to the rear wheel of the bicycle. The frame supports a resistance unit which engages the rear wheel of the bicycle supported by the frame, to provide resistance to the rotation of the wheel. Therefore, as the person moves the pedals and, consequently, the rear wheel of the bicycle, the rotation of the wheel is opposed by the resistance provided by the resistance unit.
The resistance units utilized with devices of this type take many forms, including units utilizing fluid resistance mechanisms, electric resistance mechanisms and air resistance mechanisms, among others. While each of these types of resistance units provides adequate resistance to the rotation of the wheel in order to simulate outdoor riding, each type of mechanism also has certain drawbacks which limit the ability of the resistance unit to vary the simulated riding conditions.
As a result, many types of resistance devices now include magnetic resistance units which overcome many of the drawbacks associated with other types of resistance units. Certain types of magnetic resistance units normally apply resistance to the rotation of the bicycle wheel by application of eddy current forces to a conductive member which rotates along with a rotatable wheel or flywheel, which rotates along with the bicycle wheel. The eddy current forces result from rotation of the conductive member relative to a set of magnets positioned adjacent the conductive member. By moving the magnets relative to each other, an individual can adjust the flux density created by the magnets thereby the strength of the eddy current forces, to vary the resistance to the rotation of the flywheel. The resistance to the rotation of the flywheel is transmitted to the bicycle wheel, to vary the amount of effort on the part of the person to rotate the bicycle wheel in order to overcome the resistance provided by the magnets. A number of examples of bicycle trainers with magnetic resistance units which operate along these lines include Minoura U.S. Pat. Nos. Re 34,479; 5,468,201; 5,728,029; Lee U.S. Pat. No. 5,711,404; Hu U.S. Pat. No. 5,382,208; and Gunther et al U.S. Pat. No. 6,042,517. In each of these units, a number of magnets are disposed adjacent a conductive component interconnected with a flywheel a. As the flywheel rotates, the magnets establish eddy currents in the conductive member, to resist the rotation of the flywheel. The person can adjust the amount of resistance provided to the flywheel by utilizing a cable connected to an adjustment mechanism disposed within the resistance mechanism, that adjusts the position of the magnets with respect to each other or with respect to the conductive member, to increase or decrease the amount of resistance applied to the rotation of the flywheel.
While magnetic resistance units of this type are useful in providing a variable degree of resistance to a person utilizing a training device including the magnetic resistance unit, the structure of these units requires that the person must actively control the amount of resistance provided by the resistance unit at all times. Thus, if the person wishes to increase or decrease the amount of resistance supplied by the resistance unit while exercising, the person must manually adjust the position of the magnets in the resistance unit to achieve the desired amount of resistance. When exercising on the bicycle, it is highly inconvenient for a person to have to adjust the resistance provided by the resistance unit to achieve the desired level of resistance.
Therefore, it is desirable to develop a magnetic resistance unit for a bicycle trainer that has a simple construction and that automatically adjusts the resistance provided by the resistance unit. It is further desirable to have a magnetic resistance unit that provides progressive adjustment in the level of resistance according to the speed of rotation of the bicycle wheel.
It is an object of the present invention to provide a magnetic resistance unit for a bicycle training device that provides automatic adjustment of the resistance supplied by the unit to the bicycle.
It is a further object of the invention to provide a magnetic resistance unit that smoothly adjusts the resistance applied to the bicycle by the unit over an infinite number of resistance levels between a minimum resistance level and a maximum resistance level.
It is still another object of the invention to provide a magnetic resistance unit that has a simple and inexpensive construction, and that allows damaged or worn parts of the unit to be easily and inexpensively replaced.
The present invention is a magnetic resistance unit for use with an exercise device such as a bicycle training device, which is adapted to be secured to a frame forming a part of the bicycle training device. The frame is releasably attachable to a bicycle such that the resistance unit contacts the bicycle wheel to provide resistance to the rotation of the wheel. The resistance unit includes a mounting member in the form of a support arm pivotally attached to the frame, and a roller rotatably secured to the support arm at a location spaced from the frame. The roller is fixedly attached to one end of a shaft, and is adapted to be engaged by the bicycle wheel. The shaft extends axially outwardly from the roller and is fixedly attached opposite the roller to a flywheel that is rotatably disposed within a housing fixedly connected to the support arm around the shaft. The housing is formed of a conductive material, such as aluminum, and may include a magnetically attractive portion disposed adjacent the flywheel, that is magnetically attracted to a number of magnets disposed on the flywheel. The magnets are slidably disposed within supports located on the flywheel, and are biased inwardly. When the bicycle wheel rotates the roller, shaft and flywheel, the magnets cooperate with the housing to establish eddy currents on the conductive member, which act on the magnets to resist rotation of the flywheel, and to thereby impart resistance to rotation of the bicycle wheel. When the wheel is rotated at increasingly faster speeds, the magnets slide outwardly by centrifugal force along the supports on the flywheel against the bias, to increase the distance of the magnets from the axis of rotation. As the diameter of the path defined by the magnets increases, the distance of the eddy currents from the axis of rotation increases, which functions to increase resistance to the rotation of the flywheel, thereby increasing the difficulty of rotating the roller and bicycle wheel. As the bicycle wheel, roller and flywheel rotate at slower speeds, the inward bias of the magnets in the flywheel supports functions to move the magnets inwardly along the supports to decrease the diameter of the circular path defined by the magnets, thereby decreasing the resistance applied to the rotation of the bicycle wheel. The flywheel is preferably provided with a number of vanes that function to circulate air through the housing containing the magnets upon rotation of the flywheel, to cool the magnets and the housing. The magnets may be mounted to the flywheel or to a rotating member separate from the flywheel.
Various other features, objects and advantages of the invention will be made apparent from the following detailed description taken together with the drawings.
The drawings illustrate the best mode currently contemplated of practicing the present invention.
In the drawings:
With reference now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, a bicycle training device is indicated generally at 10 in
The frame 11 has a pair of generally forwardly extending legs 26 attached to opposite ends of a generally U-shaped support member 28. The legs 26 also preferably extend slightly outwardly with respect to the support member 28 to enhance the stability of the device 10. The legs 26 and support member 28 are formed of a generally rigid material, such as a metal tubing, preferably having a circular cross section. Each of the legs 26 is connected to the support member 28 by a brace 30 that is secured to support member 28. A bolt 32 extends through the leg 26 and brace 30, and a nut 34 is engaged with the threads of bolt 32 such that leg 26 is pivotable about bolt 32 between an extended position as shown and a folded position for storage. Opposite the brace 30, each leg 26 also includes a foot 36 formed of a resilient high friction material, such as rubber, that serves to prevent the leg 26 from slipping with respect to the surface 13 on which the frame 11 is positioned. The support member 28 also includes a pair of feet 36 attached to opposite ends of a horizontal cross member 38 secured to the support member 28 opposite the legs 26. The bar 38 serves to assist the legs 26 in holding the device 10 stable and stationary on the horizontal surface 13.
Training device 10 includes a releasable engagement mechanism 40 having a stationary first portion 42 located on one side of frame 11, and a movable second portion 44 having a manual release lever 46 located on the other side of frame 11. In a known manner, one end of the axle of hub 19 is engaged with stationary first portion 42, and lever 46 is operated to engage second portion 44 with the opposite end of the axle. In this manner, the rear of bicycle 12 is engaged with and supported by frame 11 such that rear wheel 18 is above the supporting surface 13, and can thus be rotated by operation of the pedals of bicycle 12.
Referring now to
The support arm 50 includes a first cylindrical end 74 and a second cylindrical end 76 joined by a generally rectangular section 77. The first cylindrical end 74 defines a channel 78 extending therethrough that is alignable with the opening 60 in each of the mounting members 52. When the channel 78 is aligned with the openings 60, a first shaft 80 can be inserted therethrough to pivotally secure the first end 74 and support arm 50 to the mounting members 52. The first end 74 also includes a protrusion 82 that extends outwardly from the first end 74 and functions to engage the support member 28 or plate 66 and limit the pivoting movement of the support arm 50 with respect to the support member 28.
The generally rectangular center section 77 joining the first end 74 and second end 76 increases in width as it extends from the first end 74 to the second end 76, but can also have a consistent width along its length. The center section 77 includes a central slot 84 extending through the center section 77 perpendicularly to the channel 78 in the first end 74. A threaded end (not shown) of the adjustment rod 72 opposite the sleeve 70 on plate 66 is inserted through the slot 84 and is threadedly engaged with a knob or handle 86. The handle 86 includes a generally cylindrical core 88 with which the adjustment rod 72 is threadedly engaged, and a finger grip portion 90 fixedly secured to the core 88 opposite the adjustment rod 72. The core 88 rests against a pair of curved surgaces 92 extending outwardly from the center section 77 on opposite sides of the slot 84 in order to limit the pivoting of the support arm 50 away from the support arm 28. By rotating handle 86 relative to adjustment rod 72, the position of core 88 on adjustment rod 72 can be adjusted to selectively adjust the angle of support arm 50 with respect to the support member 28. This allows the resistance unit 48 to be adjusted with respect to the support member 28 in order to accommodate wheels 18 having different diameters.
The second cylindrical end 76 is formed by a pair of generally circular flanges 94 extending outwardly from the center section 77 opposite the first end 74. Each of the circular flanges 94 is integrally formed with the center section 77 and includes a central opening 96 extending axially therethrough. A roller 98 is positioned between the flanges 94 and includes a passage 100 within which a shaft 102 is located. Roller 98 is shown as having generally the same diameter as flanges 94, although it is understood that roller 98 may have a diameter either greater or less than that of flanges 94. Shaft 102 is supported by bearings mounted to flanges 94, and extends through the central openings in order to rotatably support roller 98 between the flanges 94. The shaft 102 is fixed to the roller 98 such that the shaft 102 and roller 98 rotate together. The shaft 102 extends outwardly from one of the flanges 94. The shaft 102 can be fixed in position between the flanges 94 to retain the roller 98 rotatably between the flanges 94, by means of a snap ring 106 or other suitable engagement member secured to the shaft 102.
The present invention pertains to the construction and operation of resistance unit 48, which will be described hereafter. The support and mounting components of training device 10 described above are of conventional construction and assembly, and form no part of the present invention.
With reference to
Inner ring 108 is formed of a magnetically attractive material, such as iron or steel. In one embodiment, the material of inner ring 108 may be a steel alloy such as 1018 steel. Inner ring 108 includes an inner edge 112 spaced outwardly of the outer surface of the adjacent circular flange 94. Alternatively, inner ring may be formed so as to extend inwardly a greater amount than is shown, such that its inner edge is located closely adjacent the outer surfaces of flange 94 or simply defines an opening for shaft 102
Outer cup 110 includes a primary wall 111 and an outer peripheral flange 113. Inner ring 108 is connected to primary wall 111 in any satisfactory manner, such as by mechanical fasteners. Primary wall 111 includes a number of generally radially extending spaced apart spiral apertures 114 located inwardly of inner edge 112 of inner ring 108. In a manner to be explained, apertures 114 enable air to pass into or out of the flywheel housing 104.
Outer cup 110 is formed of a conductive material, which may be a metallic material such as aluminum or copper or a non-metallic conductive material such as graphite. In one embodiment, outer cup 110 is formed of an aluminum alloy such as an 1100 series aluminum alloy. Primary wall 111 and flange 113 are preferably integrally formed with one another, although it is understood that flange 113 may be formed separately from primary wall 111 and connected to primary wall 111 in any satisfactory manner. A series of angled openings 120 extend from the primary wall 111 to outer flange 113. The openings 120, along with the spiral apertures 114 allow air into and out of the interior of the housing 104 to cool the moving parts of the resistance unit 48.
Referring now to FIGS. 1 and 3–4, flange 113 of the outer cup 110 defines an open end 122 opposite primary wall 111 that receives a flywheel 124. The flywheel 124 is generally circular in shape and includes an outer rim 126, an inner hub 128 and a number of angled vanes 130 connecting the outer rim 126 with the hub 128. The flywheel 124 is formed of a rigid non-magnetic metallic material, such as zinc, although it is understood that other materials may be employed. Vanes 130 are preferably spaced equidistant from one another about the interior of the flywheel 124 and are angled with respect to the rim 126 and hub 128 to direct air inwardly toward the housing 104 upon rotation of flywheel 124. The hub 128 includes a central sleeve 132 that extends outwardly from one side of the hub 128 and defines a central opening 134 that passes axially through the center of the hub 128. The sleeve 132 and opening 134 receive the end of the shaft 102 which extends outwardly of flange 94. The flywheel 124 is fixedly mounted to the shaft 102 by a nut 135 or other suitable engagement member, such that the flywheel 124 rotates with the shaft 102. As best shown in
The flywheel 124 also includes a number of supports 140 extending between the outer rim 126 and the inner hub 128 between each pair of adjacent vanes 130. The supports 140 are spaced equidistant from one another and are recessed slightly inwardly from the side of the flywheel 124 positioned adjacent primary wall 111 of outer cup 108. Each support 140 includes a longitudinal groove 142 extending along and facing outwardly from the support 140 towards the inner surface of primary wall 111. Each groove 142 includes a shallow widened portion 144 adjacent the hub 128, and a deeper narrow portion 146 extending throughout widened portion 144 and outwardly toward the outer rim 126. The widened portion 144 receives and retains a disc-shaped magnet 148 that is capable of sliding along the widened portion 144 of the groove 142. Magnet 148 may be formed of any satisfactory magnetic material, such as a rare earth material, although it is understood that other magnetic materials may be employed. A biasing member such as a spring 150 is positioned within the narrow portion 146 of groove 142 outwardly of magnet 148. The outer end of spring 150 engages the end of the narrow portion 146 adjacent the outer rim 126. At its inner end, spring 150 bears against magnet 148. Spring 150 functions to bias magnet 148 inwardly towards the hub 128 to the position shown in
The springs 150 and magnets 148 are retained within the grooves 142 on each support 140 by a retaining plate 152 secured to the flywheel 124 over the grooves 142. The plate 152 includes a circular center portion 154 defining an opening 155 through which extends the central sleeve 132, and a number of arms 156 that extend radially outwardly along each of the supports 140. The center portion 154 can also be omitted such that the plate 152 is formed only of the arms 156 that conform in shape to the configuration of the supports 140. The plate 152 is secured to the hub 128 and supports 140 by appropriate fasteners (not shown) inserted through fastener openings 158 in the plate 152 into aligned bores 160 in the flywheel 124. When secured to the flywheel 124, the plate 152 is flush with the outer edge of the flywheel rim 126, so that the plate 152 does not interfere with the rotation of the flywheel 124 within the housing 104. Further, the plate 152 is formed of a non-magnetic metallic material, so as not to interfere with movement of magnets 148 within grooves 142.
In operation, resistance unit 48 of training device 10 functions as follows to impart resistance to rotation of bicycle wheel 18. With reference to
As the speed of rotation of flywheel 124 increases due to increasing speed of rotation of bicycle wheel 18, magnets 148 are subjected to centrifugal forces which act against the bias of the springs 150, such that magnets 148 slide radially outwardly along the widened portions 144 of grooves 142, to compress the springs 150. The magnets 148 continue to slide along the grooves 142 as the rotational speed of the flywheel 124 increases until the magnets 148 reach the position shown in
During operation, the presence of inner ring 108 functions to direct the magnetic flux of magnets 148, which increases the efficiency of operation of resistance unit 148, It is understood, however, that resistance unit 148 would function without inner ring 108 by interaction of the rotating magnets 148 with the conductive material of outer cup 110 to establish resistive eddy current forces.
As flywheel 124 rotates within housing 104, vanes 130 function to move air into and through housing 104, and through openings 114 and 120 toward roller 98. This functions to cool housing 104 and the bearings through which shaft 102 extends, to prolong bearing life and to prevent overheating of housing 104.
In operation, the flux density generated by magnets 148 remains constant (although there may be slight variations depending on the degree of overlap with inner ring 108), and resistive forces vary by adjusting the radial position of the magnets 148 relative to the axis of rotation. This is in contrast to most approaches in the prior art, which contemplate adjusting the flux density, e.g. by adjusting the degree of overlap between opposed magnets. Further, the approach contemplated by the present invention provides a progressive adjustment in the degree of resistance based upon speed of rotation. In many prior art designs, adjustment in resistive force is accomplished either manually or in a stepped fashion.
It is possible to vary the amount of resistance that can be generated by the resistance unit 48 by altering the material of inner ring 108 and/or outer cup 110, as well as the strength of the magnets 148 to provide an increase or decrease in the resistive eddy current forces established by rotation of flywheel 124. Also, the resistance generated can be altered by increasing or decreasing the number of supports 140 and magnets 148 disposed on the flywheel 124 to increase or decrease the amount of eddy current forces that must be overcome to rotate the wheel 18. The resistance can also be varied by changing the type of biasing member to an elastomeric member or the like, or changing the size, shape or strength of the spring 150 positioned on each support 140, or by changing the size of the inner disc 108, supports 140 and grooves 142 to provide a wider range between the minimum and maximum amounts of resistance generated by the unit 48. Resistance can also be varied by changing the distance between magnets 148 and the conductive material of outer cup 110.
In the embodiment of
While the invention has been shown and described with respect to specific embodiments, it is understood that variations are contemplated as being within the scope of the present invention. For example, and without limitation, it is considered that resistance unit 48 may be used on any type of exercise device such as a stair climber, swim stroke simulator, pedal-type trainer, elliptical trainer, roller-type bicycle trainer, treadmill, etc. As to specific features of resistance unit 48, numerous variations are possible. For example, any type of biasing arrangement may be used for biasing magnets 148 inwardly, and the invention is not limited to the use of springs as shown and described. For example, an elastomeric member or other type of resilient device may be employed. In addition, it is contemplated that use of springs may be replaced with another magnetic member, which is polarized so as to create opposing poles with each magnet 148 to provide a repelling force that biases each magnet 148 inwardly. Magnets 148 may be mounted for sliding movement to any part of flywheel 124, in place of supports 140 as shown and described. Further, while magnets 148 are illustrated as being mounted to flywheel 124, it is also contemplated that magnets 148 may be mounted to a separate rotating member, whether or not a flywheel or other rotating mass is employed. In an embodiment such as this, magnets 148 are mounted in a rotating member made of a material such as plastic, which includes grooves or passages within which magnets 148 are located and in which magnets 148 are inwardly biased and movable outwardly against the biasing force in response to increasing speed of rotation. Further, while housing 104 has been shown and described to include outer flange 113, it is contemplated that flange 113 may be eliminated and primary wall 111 employed on its own.
Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.
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