Magnetically variable air resistance wheel for exercise devices

A combination air load and magnetic load device applies load to a rotor of an exercise machine. The rotor includes a fan wheel and an eddy current disc. A non-rotating magnet plate faces the eddy current disc and is spaced from it by an air gap. The non-rotating magnet plate includes a circumferential array of permanent magnets, their polarity orientations alternated. The eddy current load is variable by manual or automated control of the air gap between the eddy current disc and the non-rotating magnet plate. The user can reduce the load by increasing the air gap, or increase the load by decreasing the air gap. The rotating fan wheel generates air movement for cooling of operator and equipment, and a corresponding fan load on the rotor. The rotating eddy current disc induces an eddy current load on the rotor.

FIELD OF THE INVENTION 
This invention relates to exercise equipment, specifically to an improved 
resistance or load device that can be used in a wide variety of exercise 
machines including, but not limited to, exercycles, rowers, step machines, 
ski machines, climbers, resistance machines, and their variations. The 
resistance device of this invention applies load to a rotating shaft by a 
combination of air resistance and magnetic resistance. 
BACKGROUND INFORMATION 
Conventional air load exercise devices presently offer several advantages 
over friction resistance devices which typically use pads or belts to 
apply a load. Air load devices offer a smoother resistance by eliminating 
the need for frictional contact between parts, thus also reducing the 
number of wearing parts. Air load devices are also simpler to calibrate 
for workload because of the known exponential relationship between 
revolutions per minute of the fan wheel and the corresponding load. Air 
load devices are distinct from all other load applying devices in that a 
by-product of the user's work is moving air which is effective for 
cooling. The cooling effect of this self-generated wind greatly enhances 
the potential work output of the user and also provides a more comfortable 
environment in which to exercise. By making exercise more comfortable, a 
user is more likely to workout longer and to continue with a given 
exercise program. 
Conventional air load exercise devices have several deficencies, however. 
Because load increases with increased rpm of the resistance wheel, the 
user is restricted to a narrow cadence or stroke speed range. For example, 
if one user of an air load exercycle wishes to pedal at his normal outdoor 
cycling cadence of 100 rpm, he would have to work significantly harder 
than another user of the same machine who chooses to pedal at his normal 
cadence of 55 rpm. In fact, these two users would not be able to use the 
same conventional air load exercycle at their respective cadences. Related 
to this problem is the fact that some air load resistance machines cannot 
accommodate users of a wide range of physical conditions because of the 
limited adjustability in load. Athletes who are interested in developing 
sport-specific muscles should be able to select a cadence or stroke that 
more accurately replicates the cadence or stroke they use in their sport. 
A football player using a step machine might want to develop power muscles 
by working at high load and low speed, while a cross country runner might 
want to develop endurance muscles by working at lower loads and higher 
speeds. A conventional air load machine does not accomodate the divergent 
needs to these two users. 
Finally, a conventional air load machine cannot be combined with an 
interactive microprocessor to vary the load level according to a 
preprogrammed course or time, or according to the heart rate of the user. 
An interactive exercise device is often more interesting to use; it pushes 
the user to higher workout levels; and, when heart rate is one of the 
input parameters, it provides a more effective and safer workout. 
There are several known magnetically variable load exercise devices. These, 
like the air load devices, are frictionless. Unlike the air load devices, 
the magnetic devices provide the advantage of a variable load. They 
however do not provide moving air with its highly desirable cooling 
effect. Users of the known magnetically loaded devices therefore suffer 
the output limiting effects of heat stress, and they perform at lower 
levels than they would be capable of in a cooling environment of moving 
air. 
Some of the magnetically variable load devices use an electromagnet to vary 
the load. This requires an electrical power source which may not always be 
convenient to the user. It also adds to complexity and cost of the 
equipment. Other magnetic variable load devices use small diameter eddy 
current discs which carry little momentum, and therefore have an uneven 
pulsating feel, especially at high load levels. Eddy current devices also 
generate a considerable amount of Joule heat as a by-product of the 
resistance the magnets provide. The elevated temperature levels of the 
eddy current discs and nearby magnets can reduce the amount of resistance 
being applied. The user may experience inconsistent load levels and, when 
used in ergometric machines, inaccurate readouts of workload levels. 
Variable magnetic loading devices are disclosed in U.S. Pat. Nos.: 
4,152,617 to Janson; 4,752,066 to Housayama; and 4,775,145 to Tsuyama. 
SUMMARY OF THE INVENTION 
The present invention is a combination air load and magnetic load device 
for applying load to a rotor. The rotor includes a fan wheel and an eddy 
current disc. A non-rotating magnet plate faces the eddy current disc and 
is spaced from it by an air gap. The non-rotating magnet plate includes a 
circumferential array of permanent magnets, their polarity orientations 
alternated. The eddy current load is variable by manual or automated 
control of the air gap between the eddy current disc and the non-rotating 
magnet plate. The user can reduce the load by increasing the air gap, or 
increase the load by decreasing the air gap. The rotating fan wheel 
generates air movement for cooling of operator and equipment, and a 
corresponding fan load on the rotor. The rotating eddy current disc 
induces an eddy current load on the rotor. 
It is an object of this invention to provide a magnetically variable air 
resistance device for applying a widely variable load to a rotating shaft. 
Another object is to provide, in such a device, means to preclude chain 
derailment or large tension slippage when load is varied. 
Another object is to provide a magnetically variable load device that will 
provide, as a by-product of the user's work, the cooling effect of moving 
air. 
Another object is to provide such a device that will apply a measurable, 
accurate and consistent load. 
Another object is to provide such a device without the requirement of an 
external power source. 
Another object is to provide such a device that will provide sufficient 
momentum for smooth resistance even at high load levels. 
Another object is to provide a magnetically variable air resistance device 
to reduce the need for additional stage gearing because of the combination 
of air and eddy current load. 
Another object is to provide a magnetically variable air resistance device 
which is quieter than air resistance alone because the base level 
resistance provided by the eddy current magnet resistance gives the device 
a higher total load at lower speeds than wind only designs, and therefore 
permits operation at slower rpm. 
Another object is to provide a magnetically variable air resistance device 
adapted for connection to an microprocessor for automatically load 
control. 
Another object is to provide such a device that can be made smaller than a 
conventional wind resistance wheel of comparable load level. 
Another object is to provide a magnetically variable air resistance device 
that will inherently dissipate the Joule heat generated by the eddy 
current resistance. 
Further objects, advantages, and features of this invention will become 
apparent from the following description, given in connection with the 
accompanying drawings.

DETAILED DESCRIPTION 
FIG. 1 is a side sectional view of a magnetically variable air resistance 
wheel according to this invention. FIG. 2 is an exploded view of FIG. 1 
which better illustrates the individual parts and their functions. A fan 
blade wheel 1 is fixed on a steel hub shell 2 which is rotatably supported 
on each side of the fan wheel by ball bearings 4 which in turn ride on a 
pair of cones 5 which are non-rotatably fixed to the axle 11. The device 
is fixed to the frame of an exercise machine by placing the axle 11 into a 
slotted frame mount (not shown) and securing it with nuts 10 and washers 9 
in a well known manner. The device is driven by a chain (not shown) 
operatively connected to a sprocket 3 which is fixed on the hub shell 2. A 
pulley may be substituted for the sprocket 3 if a V-belt drive is desired. 
A ferromagnetic disc 13 and eddy current disc 14 are fastened to the fan 
blade wheel 1 by suitable screw fasteners 15 threaded into the blades of 
the wheel 1. The ferromagnetic disc 13 is flat and uniformly spaced 
relative to the fan wheel 1. The eddy current disc 14 is made of a 
conductive nonmagnetic material, preferably copper or aluminum. 
A magnet plate assembly 18 and 18a is mounted on a magnet plate collar 18b 
which in turn is non-rotatably fixed on the axle 11. The collar 18b has 
sufficient axial length (e.g. at least one inch) to insure stable 
positioning of the magnet plate assembly 18 and 18a on the axle 11. Both 
the magnet plate 18, 18a and the eddy current disc 14 are thus positioned 
perpendicular relative to the axle 11. The magnet plate assembly includes 
a fixed magnet plate 18 and an adjustable magnet plate 18a. The interior 
surface of these plates 18 and 18a is an annular ferromagnetic backing 17 
which acts to concentrate the force of magnets 16 which are secured to its 
surface. 
The chain driven sprocket 3, fan blade wheel 1, ferromagnetic disc 13, and 
eddy current disc 14 rotate on the axle 11. The magnet plates 18 and 18a 
remain non-rotating. 
FIG. 3 is a partial view from the right end of FIG. 2, and shows more 
detail of the magnet plate assembly 18 and 18a. The adjustable magnet 
plate 18a pivots away from the vertical plane of the fixed magnet plate 18 
on hinges 22. The hinges 22 may be spring loaded where the additional 
spring force would help return the adjustable magnet plate 18a toward the 
eddy current disc 14 when cable tension is relaxed (see FIG. 5). The 
inside surface of the magnet plate assembly 18 and 18a is shown in FIG. 4. 
This surface faces the eddy current disc 14 and is spaced from it at a 
fixed distance approximately equal to the thickness of the eddy current 
disc 14. An annular ferromagnetic backing 17 is fixed to the magnet plates 
18 and 18a. The magnets 16 are secured to the backing 17 in an alternating 
north-south pattern as indicated in FIG. 4. Plate stops 27 are secured to 
the fixed magnet plate 18 with fasteners 27a to prevent the adjustable 
magnet plate 18a from moving beyond the plane of the fixed magnet plate 18 
in the direction of the eddy current disc 14. In this embodiment the fixed 
magnet plate 18 is sufficiently thick and rigid to prevent deflection or 
warpage when the adjustable magnet plate 18a is pivoted away from its 
vertical plane. Accurate positioning of the magnet plates is essential for 
assuring the accuracy of the workload. The magnet plate axle collar 18b 
connects the fixed magnet plate 18 to the axle. A user operated shift 
lever 26, shown in FIG. 5, is operatively connected to the adjustable 
magnet plate section 18a by means of a cable 23 at a cable anchor point 
19. 
FIG. 5 shows a manually variable resistance embodiment in which a shift 
lever 26 with an integral transducer sends positional information to a 
CPU. The shift lever 26 has detents to set the cable tension at a series 
of preset positions. The shift lever 26 is connected to the adjustable 
magnet plate 18a through a cable 23 extending through a cable housing 25 
on the frame of the exercise machine. The cable 23 attaches to the 
adjustable magnet plate 18a by a suitable connector at the cable anchor 
19. When the user pulls down on the shift lever 26, the cable 23 pulls the 
adjustable magnet plate 18a away from the eddy current disc 14. The 
increase in the size of the air gap reduces the magnetic force acting on 
the eddy current disc 14. As the shift lever 26 is pulled down the 
transducer sends a signal to the CPU indicating the position of adjustable 
magnet plate 18a. This information, along with the fan blade rpm 
information which is sent to the CPU by an rpm sensor, is used to 
calculate and display workload levels. When the shift lever 26 is pushed 
forward, the cable 23 tension is relaxed and the adjustable magnet plate 
18a moves toward the surface of the eddy current disc 14. Again the 
transducer sends a signal to the CPU indicating the new position of the 
adjustable magnet plate 18a. The adjustable magnet plate 18a will return 
to a position nearer the eddy current disc 14 because of the magnetic 
force between the magnets 16 and the ferromagnetic disc 13. 
If the magnetic force is insufficient to insure full return of the 
adjustable magnet plate 18a to the vertical plane of the fixed magnet 
plate 18, the force of gravity may be employed simply by arranging the 
device so that the hinges 22 are parallel with the ground with the fixed 
magnet plate 18 extending upward from the hinges. The weight of the 
adjustable magnet plate 18a will then assist the plate in its return to a 
position of greater resistance. This configuration of the device is 
preferred. If for some reason another configuration is desired, or the 
return of the adjustable magnet plate 18a is not reliable, then the hinges 
22 may be spring loaded in the direction that will assist in the return of 
the adjustable magnet plate 18a. These arrangements are preferred because 
of the economy of fewer parts and the reliability of simplicity of 
operation. It should also be noted that this variable tension arrangement 
permits the user to vary the load without dismounting the machine, and in 
fact the load can be varied while using the machine without the risk of 
chain or belt derailment, which is a possibility with devices that use 
discrete gears or a variable pulley to alter the load. 
FIG. 6 shows a second embodiment of this invention in which a ferromagnetic 
disc 13 and eddy current disc 14 are set in a recess of the fan blade wheel 
1. A magnet plate assembly 18 and 18a is similar to that in FIGS. 1-5, 
though smaller in relation to the fan blade wheel 1. 
FIG. 7 shows a third embodiment of this invention, in which a slide plate 
52 replaces the adjustable magnet plate assembly 18 and 18a of FIGS. 1-6. 
The slide plate 52 includes an annular ferromagnetic backing 51 with a 
circular array of magnets 53 arranged with poles alternating north and 
south. The slide plate 52 is fixed to a self-lubricating nylon slide plate 
collar 50 by fasteners 50a. An axle 45 includes a keyway 46 for an axle key 
49 to fix the slide plate collar to the axle 45. A pull rod 54 slides 
through the hollow end of the axle 45, threads into the center of the axle 
key 49, and is attached to the cable 23. Cable 23 is operated with the same 
type of shift lever 26 described in connection with FIG. 5. A cable pulley 
57 is secured to the frame to permit the necessary turn of the cable 23. 
Spring 60 urges the slide plate 52 back to a position near the eddy 
current disc 14 when cable tension is relaxed. A snap ring 61 acts as a 
stop for the spring 60, to secure the slide plate 52 on the axle 45. 
FIG. 8 is a detail of the slide plate embodiment showing the section of the 
axle 54 upon which the slide plate 51 and collar 50 slides. The splines 62 
act as a guide for the slide plate collar 50 and help limit free play in 
the slide plate 51. FIG. 9 shows the slide plate collar 50 in the position 
of maximum load when the cable is untensioned and the axle key 49 is all 
the way in. FIG. 10 shows the slide plate collar 50 in the position of 
minimum load when the cable is tensioned and the axle key 49 is slid all 
the way out, and pulling with it the slide plate collar 50 and the slide 
plate 51. 
FIGS. 11, 12, 13, and 14 show a fourth embodiment of this device where the 
magnet plate 77 remains stationary and load is changed by varying the 
position of a flux gate 76 which has gaps 76a equal in size to the gaps 
between magnets 78, shaped as shown. The shift lever 26 changes the 
position of the flux gate 76 by turning it a small amount on an axis 
parallel with the magnet plate 77. The cable 23 from the shift lever 26 
connects to the flux gate 76 at the flux gate arm 75. Spring 74 urges the 
gate 76 back when cable tension is relaxed. The flux gate works by "short 
circuiting" the magnetic field. FIG. 13 shows the position of the flux 
gate gap 76a that will provide maximum load. The magnets are unaffected by 
the flux gate, and the magnetic force is full. FIG. 14 shows the position 
of the flux gate gap 76a that will provide minimum load. Half of each 
magnet is "shorted", minimizing the magnetic field. Positions of the flux 
gate between these two extremes provide incremental variability in the 
resistance level. 
FIG. 15 shows this invention used in a recumbent exercycle ergometer. FIG. 
16 shows its use in a rowing machine. FIG. 17 shows its use in a step 
machine. FIG. 18 shows its use in a ski machine. 
FIG. 19 shows the summation of the load that is applied by the two 
different means of resistance, the air resistance (W) and the magnet 
resistance at different magnet positions (M1 to M5). The summation of 
these loads is represented in the relevant range by lines M1+W through 
M5+W. The detents in the shift lever 26 are spaced to provide equal 
percentage changes in the resistance level for each position selected. For 
example, if a five position shift lever is used, then moving the lever from 
position 5 to position 4 might reduce the amount of resistance being 
provided by the adjustable magnet plate segment of the device by 20%. 
Moving the lever to the next lower detent, position 3, would reduce the 
amount of resistance being provided by the adjustable magnet plate segment 
of the device by another 20%, for a total reduction in magnet plate 
resistance of 40%. It should be noted that these percentages do not 
represent nearly as large reductions in the total load because the load 
from the fan blade wheel 1 and the fixed magnet plate section 18 has 
remained constant. The load figure at different adjustable magnet postions 
is determined with the use of a dynamometer. 
FIG. 20 is a block diagram of a load measuring and microprocessing device 
combined with the manually adjusted load embodiment of this invention. 
User input is keyed into the CPU, the shift lever transducer sends a 
magnet postion signal to the CPU and a magnetic RPM sensor counts wheel 
RPM and sends this information to the CPU. From this information the CPU 
calculates and displays accurate work load levels. 
FIG. 21 is a block diagram of a load measuring and microprocessing device 
used in the interactive microprocessor adjusted load embodiment of this 
invention. In this embodiment the user has the option of entering a 
particular load level, or choosing a preprogrammed course, a target 
work-load level, or a target heart range, and the CPU will then vary the 
work-load by sending a signal to a stepper motor that will shift the 
position of the adjustable magnet plate. 
CONCLUSION 
Because the magnetically variable air resistance wheel avoids any 
frictional contact in the load applying method, users will find the 
resistance exceptionally smooth. Also, by avoiding frictional contact this 
device can operate under heavy use with minimal maintenance. Yet this 
device offers several advantages over conventional wind only resistance 
devices including, the ability to select pedal or step cadences, the 
ability to develop specific type of muscles (fast vs. slow twitch fibers), 
and greater load level range so users at various level of conditioning can 
use the same machine. This device also has several advantages over 
magnetic only resistance devices including the cooling effect of 
self-generated air turbulence, and a smoother resistance at high load 
levels because of the greater momentum of the fan wheel. Other advantages 
of this device will be apparent to those skilled in the art without 
departing from the spirit and scope of the claims. 
While the above description includes many specific details, these should 
not be construed as limitations on the scope of the invention, but only as 
examples of preferred embodiments thereof. Those skilled in the art will 
envision many other possibile variations that are within its scope. For 
example, there may be two or more segments of the magnet plate that are 
adjustable to provide even greater variabilty in the resistance level. The 
magnetic resistance portion of this device might be completely fixed, so as 
to apply a base load on a wind resistance wheel and thus avoid the need of 
a second stage drive. Such a fixed design could also be used to scale down 
the size of a wind resistance wheel to make a more compact exercise 
machine, or to make the wind resistance wheel quieter by operating at a 
lower speed. The position of the magnets and the eddy current resistance 
disc, and the means for varying the magnet position, might be varied any 
number of ways. For example, the fan wheel might be constructed so the 
blades are shorter and wider and the wheel itself looks like a horizontal 
tube. In this variation the eddy current resistance portion could be on a 
segment of the outer or inner portion of the wheel rim, and the magnets 
arranged in a tube that covers or fits inside this same segment of the 
wheel, with the variability coming from shifting the magnet tube over a 
larger area of the eddy current resistance portion of the wheel. 
Accordingly, the scope of the invention is limited only by the appended 
claims.