U.S. patent number 3,826,491 [Application Number 05/371,066] was granted by the patent office on 1974-07-30 for exercise treadmill.
This patent grant is currently assigned to Del Mar Engineering Laboratories. Invention is credited to Boyd B. Elder.
United States Patent |
3,826,491 |
Elder |
July 30, 1974 |
EXERCISE TREADMILL
Abstract
An exercise treadmill is provided for diagnostic and therapeutic
purposes, which includes, among other features, an eddy-current,
variable speed drive to obtain a belt speed range from zero to
maximum speed, and a differential drive through a slip clutch to
the two rollers imparting motion to the belt. Safety of the subject
is enhanced by an electrically non-conductive coating on the
handrails to eliminate any possibility of grounding electricity
through the patient's body. Incorporation of a chair as an integral
part of the assembly assures a rest place in appropriate proximity
to the walking surface. The treadmill walking surface is positioned
and maintained at the desired inclination with minimum apparatus
load by virtue of locating the fulcrum at approximately the
center-of-gravity. The inclination is displayed on a remote control
panel which also provides the capability of controlling all
functions of the unit.
Inventors: |
Elder; Boyd B. (Redondo Beach,
CA) |
Assignee: |
Del Mar Engineering
Laboratories (Los Angeles, CA)
|
Family
ID: |
23462328 |
Appl.
No.: |
05/371,066 |
Filed: |
June 18, 1973 |
Current U.S.
Class: |
482/7;
482/54 |
Current CPC
Class: |
A63B
22/025 (20151001); A63B 22/0023 (20130101); A63B
22/02 (20130101); A63B 22/0285 (20130101) |
Current International
Class: |
A63B
22/00 (20060101); A63B 22/02 (20060101); A63b
023/06 () |
Field of
Search: |
;272/69 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Oechsle; Anton O.
Assistant Examiner: Stouffer; R. T.
Attorney, Agent or Firm: Jessup & Beecher
Claims
What is claimed is:
1. A treadmill for diagnostic and therapeutic purposes, and the
like, including: a base, a frame pivotally mounted on said base
substantially at the center-of-gravity of said frame and of the
components carried thereby; a pair of rollers mounted on said frame
in spaced and parallel relationship; platform means interposed
between said rollers and mounted on said frame to define a walking
surface; an endless belt looped around said rollers and over said
platform means; a drive mechanism mechanically coupled to said
frame; and an inclination control mechanism coupled to said
frame.
2. The treadmill defined in claim 1, in which said drive mechanism
comprises an eddy-current unit mechanically coupled to a constant
speed electrical motor.
3. The treadmill defined in claim 1, wherein said drive mechanism
includes a slip clutch to introduce sufficient drag so as to
prevent coasting of said belt.
4. The treadmill defined in claim 1, in which said inclination
control mechanism includes an electrically operated reversible
linear actuator.
5. The treadmill defined in claim 1, and which includes electrical
meter means, and electrical circuitry connected to said meter means
and controlled by angular movements of said frame to cause said
meter means to provide an indication of the inclination of said
frame.
6. The treadmill defined in claim 1, and which includes a remote
control box electrically connected to said drive mechanism and to
said inclination control mechanism.
7. The treadmill defined in claim 5, in which said meter means is
mounted in a remote control box.
8. The treadmill defined in claim 7, in which said remote control
box is electrically connected to said drive mechanism and to said
inclination control mechanism.
Description
BACKGROUND OF THE INVENTION
The exercise treadmill has many applications as a diagnostic and as
a therapeutic aid in the overall evaluation of heart and lung
disease as well as for body health building. The treadmill has
proven to be the most effective instrument for subjecting a patient
to a continuous, but varied, exercise program; and treadmill stress
testing has become widespread as a basis for the medical evaluation
of various physiological responses to steady state exercise.
The prior art treadmill can be marginal in performance and
capabilities under certain circumstances. It is the purpose of the
present invention to provide an improved treadmill which will
exhibit the desired performance capabilities and safety features
while maintaining simplicity and trouble-free operation. One object
of the invention is to provide a simplified and positive heavy duty
drive system for controlling the speed of the treadmill belt over
the range from zero to the maximum speed. This is accomplished by
incorporation of an eddy-current variable-speed drive, with a
differential drive through a slip clutch to the two rollers
imparting motion to the belt.
Another object of the invention is to complete the insulation of
the patient thereby eliminating the possibility of the patient
being subjected to undesired electrical shocks. Electrical
isolation of the patient is assured by coating the handrail which
the patient holds while exercising, with a non-conductive material
such as, for example, polyvinylchloride (PVC).
Still another object of the invention is to provide a convenient
resting place for the patient to be utilized either during the
recovery phase of the stress test, when continued monitoring of the
various functions is desirable, or in case of an emergency wherein
termination of the stress testing is considered mandatory due to
the physician's concern over the patient's condition. This object
is satisfied by including an on-board chair, preferably capable of
being adjusted to permit the patient to assume a reclining
position. The chair is located at the level of, and in close
proximity to, the walking surface of the treadmill thereby being
available to the patient using the treadmill.
A further object of the invention is to provide an improved means
for positioning the walking surface of the treadmill at various
inclinations, as may be desired during the stress testing. With the
treadmill inclination pivot axis being located at approximately the
center-of-gravity of the unit, shorter actuator strokes and smaller
actuator forces are required to position the walking surface at a
desired inclination, and this allows the use of a smaller, lighter,
weight-positioning mechanism, as compared with that required for
positioning a unit of comparable weight which is pivoted at one
end, as is normal in prior art treadmills. An additional advantage
provided by a fulcrum at the approximate center-of-gravity of the
unit, is the ability to establish either a positive or a negative
slope to the walking surface, as desired.
Still a further objective of the invention is to provide a
convenient, accurate, and easily readable display of the angle of
inclination of the walking surface. This is accomplished by
incorporation of a calibrated meter reading in percent grade in the
remote control box adjacent to the controls utilized for regulating
the inclination of the walking surface.
These and other features and advantages and objects of the present
invention will become more readily apparent from the following
detailed description of one form of the invention, particularly
when taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of apparatus which may be constructed
to incorporate the concepts of the present invention, with
cut-aways to reveal certain elements of the apparatus;
FIG. 2 is a schematic diagram of the drive system of the apparatus
of FIG. 1;
FIG. 3 is a fragmentary perspective view of an actuator mechanism
which is utilized to position and maintain the walking surface of
the apparatus at a desired inclination;
FIG. 4 is a schematic representation of a remote control box front
panel in which the various controls and displays for the apparatus
of FIG. 1 are mounted; and
FIG. 5 is a fragmentary perspective view of a chair tilt
compensating linkage which may be incorporated into the
apparatus.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
The treadmill of the present invention as shown in FIG. 1 includes
a walking surface comprising an endless belt 10 extending over and
around a support plate 12. The belt 10 is looped around an end
roller 14 and an end roller 16, both of which are mounted on
conventional bearings attached to a frame 18 at each end of their
shafts. The belt 10 is driven by an eddy-current variable speed
electric drive motor which derives its power from the usual A.C.
mains.
The belt 10 is preferably an endless fabric belt composed, for
example, of nylon. The top side of the belt is treated with rubber
to provide a friction surface on which the patient walks, as well
as to assist in electrically isolating the patient. The underside
may be bare duck nylon ply, in a particular example, to minimize
friction between the belt 10 and the support plate 12 on which it
bears.
In prior art treadmills utilizing a similar walking surface, that
is, a belt moving over a flat plate, the friction developed by the
belt moving over the plate when a patient of heavy weight is
exercising, and particularly at low belt speeds, tends to cause
belt stoppage and/or drive motor overheating. To eliminate this
possibility, and to provide an adjustable speed control for the
belt over a range of from zero to a predetermined maximum speed, a
drive system including, inter alia, a constant high speed
electrical motor and an eddy-current variable speed drive, is
incorporated into the assembly in accordance with the
invention.
Additional advantages are realized with such a drive system, and
these include better motor cooling, as compared with the prior art
treadmills; as well as less noise, and a low level of radio
frequency transients which assures compatibility with the
biomedical instrumentation involved in stress test monitoring. To
provide sufficient friction in the drive system to preclude the
possibility of undesirable belt movement under a high angle of
inclination of the walking surface at zero belt speed conditions, a
low power loss slip clutch is incorporated into the drive system to
induce drag into one of the rollers 14 and 16.
The drive system is shown in some detail in FIG. 2, wherein an
eddy-current variable speed drive mechanism 20 is attached directly
to the output shaft of constant high speed motor 22. A pulley 24 is
keyed to the output shaft of the drive mechanism 20, and the pulley
24 is coupled to a pulley 26 by means of an endless positive drive
belt 30 routed around both pulleys. The pulley 26 is keyed to a
shaft 28 at an intermediate position on the shaft. One end of the
shaft 28 is rotatably supported by a conventional bearing 31
attached to frame 18. A pulley 32 is firmly affixed to the end of
the shaft 28 adjacent to the bearing 31. The other end of the shaft
28 is affixed to one rotating element of a slip clutch 34. The
other rotating element of the slip clutch 34 is attached to one end
of a shaft 36. The other end of shaft 36 is supported in a bearing
37 attached to frame 18. A pulley 38 is keyed to the end of the
shaft 36 adjacent to the bearing 37.
The pulley 32 is coupled to a pulley 40 by means of an endless
positive drive belt 44 which is routed around both pulleys.
Likewise, the pulley 38 is coupled to a pulley 46 by an endless
positive drive belt 50. The pulley 40 is keyed to a shaft 42, and
the pulley 46 is keyed to a shaft 48. A pair of rollers 14 and 16
are firmly attached to the shafts 42 and 48, respectively. The ends
of the shafts 42 and 48 are supported in bearings attached to frame
18, thereby assuring rotational freedom to the rollers 14 and 16
which are mounted on the respective shafts. With a speed reduction
ratio established between pulley 32 and pulley 40, which is greater
than the speed reduction ratio established between the pulleys 36
and 46, and with rollers 14 and 16 rotating at the same speed as
dictated by the belt 10 passing around both rollers without
slippage, it becomes readily apparent that the shaft 36, and its
attached element of clutch 34, will rotate at a speed slower than
that of shaft 28 and its attached element of clutch 34. The
slippage between the rotating elements of the clutch 34 thereby
induces sufficient drag in the roller 16 to prevent the undesired
coasting of the belt 10 at the higher inclinations of the walking
surface, and this is achieved with lower power loss. The overall
drive system, on the other hand, provides the desired performance
characteristics.
Referring again to FIG. 1, a handrail 52, which the patient
normally holds during the exercise program, will be observed. As
previously stated, the belt 10 has a non-conductive surface which
serves to assist in the electrical isolation of the patient.
Complete electrical isolation of the patient is achieved by coating
the handrail 52 with an electrically non-conductive material such
as, for example, polyvinylchloride (PVC) which can be applied by
conventional methods. With the patient holding the coated handrail,
and standing on the insulated belt 10, there is no possible path
for the flow of electrical current through his body to ground. This
total electrical isolation of the patient serves two worthwhile
purposes; namely it assures safety of patient from electrical
shock, and it also minimizes electronic noise interference, thereby
improving the quality of the electrocardiographic data taken by
adjacent electronic equipment during the exercise program.
During a standard treadmill stress test program, a requirement
exists for various belt speeds and inclinations of the walking
surface of the treadmill. As previously stated, in order to satisfy
the requirement for various belt speeds, a variable speed
differential drive system is included in the treadmill of the
present invention. In order to satisfy the requirement for various
inclinations of the walking surface, the frame 18 of the treadmill
of the invention, which supports the walking surface, is attached
to a base frame 56 (FIG. 1), with a limited freedom of angular
movement, and a linear actuator mechanism is included in the system
to control the angular position of the frame.
As shown in FIGS. 1 and 3, the frame 18 is attached to the base
frame 56 by a pair of axially aligned shafts 58. The shafts 58 are
placed in appropriately located holes machined in the frame 18 at
approximately the center-of-gravity of the rotatable assembly, and
these shafts being firmly attached to a corresponding pair of
supports 60 mounted on two parallel members of the base frame
56.
As also shown in FIG. 3, an actuator 62 is pivotally attached to
one traverse member of the base frame 56, and the actuator is
pivotally attached to a cross support 64 between parallel members
of the frame 18. The actuator 62 can be any conventional
electrically operated linear actuator, wherein a reversible
electric motor drives a lead screw through appropriate gearing to
provide a controllable actuator length. Selected angles of
inclination of the walking surface can thereby be obtained and
maintained by controlling the electric motor.
With the pivot point of the treadmill on its mounting frame located
at approximately the center-of-gravity of the rotatable assembly,
the length of the actuator stroke, as well as the magnitude of
actuator force required to rotate the assembly to a desired angle
of inclination, is considerably less than the stroke and force
which would be required if the assembly were rotated by a rear end
point, as is the case in the prior art units. An additional
advantage in having the pivot point at approximately the
center-of-gravity of the rotatable assembly, is that either a
positive slope or a negative slope to the walking surface can be
achieved if so desired.
Control of the actuator motor is afforded by conventional
electrical circuitry, including a switch 68 which is mounted in a
remote control box 54, as shown in FIGS. 1 and 4. The switch 68 is
a three-way switch electrically connected to the actuator 62 in
such a manner that a first switch position causes an electrical
current to flow through the actuator motor in one direction,
resulting in an extension of the actuator length; a second switch
position causes an electrical current to flow through the actuator
motor in the opposite direction, resulting in a contraction of the
actuator length; and a third switch position cuts off current to
the actuator motor and produces a braking effect. Depending upon
the position of the switch 68, therefore, the inclination of the
walking surface can be set to any desired angular position.
A conventional calibrated potentiometer 71 (FIG. 4) may be
mechanically coupled to the actuator 62 through a usual rack and
pinion assembly, so that the electrical resistance in the
potentiometer may be a function of the inclination of the walking
surface. A display meter 70 (FIGS. 3 and 4), calibrated to read
directly in percent grade of the walking surface, is electrically
connected to the potentiometer. As shown in FIGS. 1 and 4, display
meter 70 can be mounted adjacent to the switch 68 in the control
box 54, thereby providing a remote display of the walking surface
inclination disposed conveniently adjacent to the switch used to
control the inclination.
Another feature of the treadmill of the present invention is
concerned primarily with patient safety, and with the repeatability
of meaningful data. This feature involves the incorporation of a
chair 72 (FIG. 1) as an integral part of the treadmill. The chair
72 may be rigidly affixed to a non-rotatable element of the
treadmill, so that the plane of the seat of the chair will remain
unchanged regardless of the grade of the walking surface. The chair
may also be rigidly affixed to a rotatable element of the
treadmill, with the plane of its seat fixed at an angle relative to
the plane of the walking surface such that a safe and comfortable
seating surface exists over the entire grade range of the walking
surface. Also, the chair can be attached to a rotatable element of
the treadmill and rigged such that the plane of the seat remains in
approximately the same position relative to the plane of the floor
regardless of the angle of inclination of the walking surface.
In all of the above-mentioned methods of attachment, the chair is
positioned so that it does not hamper the normal use of the
treadmill, and yet be conveniently located with respect to the
walking surface in case of an emergency, or for use during the
recovery phase of the exercise program. The advantages of a chair
so positioned are twofold. Firstly, it provides a readily
accessible and convenient resting place for the patient in the
event some condition is observed during the exercise program which
prompts the physician's concern for the patient's condition and
necessitates termination of the exercise program. Secondly, it
provides a resting place, convenient to both the walking surface
and to the recording and display instrumentation, where monitoring
of the body functions can continue uninterrupted under ideal and
controlled conditions during the important recovery phase of the
exercise program. Preferably the chair is a conventional reclining
chair complete with leg and head rests wherein the patient can lie
in an approximately reclined position if so desired.
In the embodiment as shown in FIG. 1, chair 72 which is a
conventional reclining chair is made a part of the treadmill by
attachment to a support 74. The support 74 is rigidly attached to
the frame 18 by a bracket 76. In such an arrangement, the
established relationship between the plane of the chair seat and
the plane of the walking surface remains the same regardless of the
grade of the walking surface. However, the plane of the chair seat
relative to the plane of the floor does change as the different
grades of the walking surface are selected. A safe and comfortable
seat is assured over the limited grade range of the walking surface
by the proper selection of the fixed relationship between the seat
and walking surface. In the event it is considered desirable, the
seated patient can assume an approximately prone position by
manipulation of handle 78 thereby raising the leg rest 80 and
lowering the back rest 82.
In the embodiment as shown in FIG. 5, a tilt compensating linkage
for the chair is provided, thereby retaining the chair seat at the
selected angular relationship with the floor, regardless of the
grade of the walking surface. In the embodiment of FIG. 5, a chair
72 is attached to a bracket 84 which includes a bell crank 86 as an
integral part. The bracket 84 is pivotally attached to a cap 88 by
a bolt 90. The cap 88 is firmly affixed to the support 74 which, as
previously stated, is rigidly attached to the frame 18 by means of
the bracket 76. Also attached to the support 74 are two brackets 92
and 94. A bell crank 96 is pivotally attached to the bracket 92 and
to the bracket 94 by pins 98 and 100 respectively. An arm 102 of
the bell crank 96 is connected to the bell crank 86 by means of a
rod 104, using clevises 112, 116 and pins 114, 118, respectively,
to provide freedom of angular movement between the attached
members. A further arm 106 of the bell crank 96 is likewise
connected to an extension on a support 108 by means of a rod 110,
using clevises 120, 124 and pins 122, 126, respectively, to provide
freedom of angular movement between attached members. The support
108 is mounted on one of the shafts 58 providing pivotal support of
the rotatable walking surface.
With such an assembly, the plane of the seat of chair 72 will
remain fixed although the grade of the walking surface is varied
over the allowable range. For example, when the frame 18 is rotated
in a clockwise direction in FIG. 5, about the centerline of shaft
58 to achieve an increase in grade of the walking surface, the
distance between the centerlines of the pins 126 and 122 is
maintained constant by virtue of the presence of the rod 110. In
order to maintain this distance constant, the arm 106 of the bell
crank 96 is caused to rotate in a clockwise direction about the
centerline of the pin 98 thereby imparting a comparable clockwise
rotation to the arm 102 about the centerline of the pin 100. Since
the presence of rod 104 holds the distance between the centerline
of pin 114 in arm 102 and the centerline of pin 118 in bell crank
86 constant, a clockwise rotation of the arm 102 causes a
counterclockwise rotation of the bell crank 86 and the bracket 84
about the centerline of the bolt 90.
From the above description, it can be readily seen that, by
establishing the proper lengths for the arms of the bell cranks 86
and 96, as well as the extension of the support 108, the bracket 84
and, therefore, the seat of chair 72 are imparted to have an
angular movement about the bolt 90 equal but opposite to the
angular movement of the frame 18 about the pin 58. With such an
arrangement, the plane of the seat of chair 72 will thereby remain
at the same angular position relative to the plane of the floor
regardless of the selected grade of the walking surface. By having
a reclining chair such as chair 72 shown in FIG. 1 attached to
bracket 84, a safe and comfortable place convenient to the walking
surface and monitoring instruments is provided for the subject to
either sit or lie as desired.
While particular embodiments of the invention have been shown ane
described herein, modifications may be made. It is intended in the
following claims to cover all modifications which fall within the
spirit and scope of the invention.
* * * * *