US 3826491 A
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.
Description (OCR text may contain errors)
United States Patent Elder July 30, 1974 EXERCISE TREADMILL  Inventor: Boyd B. Elder, Redondo Beach,
 Assignee: Del Mar Engineering Laboratories,
Los Angeles, Calif.
 Filed: June 18, 1973  Appl. No.: 371,066
 US. Cl. 272/69, 272/58 [5|] Int. Cl A63b 23/06 '3 Field of Search 272/69  References Cited UNITED STATES PATENTS 3,l93,287 7/l965 Robinson 272/69 X 3,395,698 8/l968 Morchouse 272/73 UX 3,606,320 9/l97l Erwin, Jr. 272/69 3,643,943 2/1972 Erwin, Jr. ct al. i i 272/69 3,703,284 I H1972 Hesen i 272/69 3,737,163 6/l973 Sumrall 272/69 Primary ExaminerAnton O. Oechsle Assistant Examiner-R. T. Stouffer Attorney, Agent, or Firm-:Jessup & Beecher  ABSTRACT An exercise treadmill is provided for diagnostic and therapeutic purposes, which includes, among other features, an eddy-current, variable speed drive to ob tain 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 patients 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.
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SHEEI MIF 4 EXERCISE TREADMILL 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 physicians concern over the patients 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-ofgravity 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-ofgravity 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 aneddy-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 endlesspositive 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 meansof 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 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 l0'has a non-conductive surface which serves toassist 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 inclination. 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'rnachined 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 conven tional 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 physicians concern for the patients 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 ofa 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 1 10. 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 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.
What is claimed is:
l. A treadmill for diagnostic and therapeutic purposes, and the like, including: a base, a frame pivotally mounted on said base substantially at the center-ofgravity 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. 4K