Claims
- 1. An apparatus for use in the exercise of the human body, said apparatus comprising:
- filament matrix means of a selected length having a neutral axis defined therethrough, said filament matrix means having an oblong cross-section with a major axis of a selected width and a minor axis of a selected height defined therethrough, wherein the width of the cross-section is from 2-7 times the height, said filament matrix means having;
- two ends,
- filaments, a portion of said filaments being oriented at an angle of less than 3 degrees from said neutral axis, a portion of said filaments containing glass fibers, said filaments constituting from about 35 volume percent to about 70 volume percent of said filament matrix means and having an ultimate elongation design value from about 2 percent to about 6 percent, and
- a resin system constituting from about 30 volume percent to about 65 volume percent of said filament matrix means, and having an ultimate elongation design value from about 4 percent to about 12 percent, wherein the length and cross-section of said filament matrix means, and percentage of the volume of said filaments and said resin system included within said filament matrix means, and the ultimate elongation design value of said filaments and said resin system, are selected such that the maximum elongation in said filaments and said resin system, when the distance separating the ends of the filament matrix means is minimized by the application of force to said two ends, is less than the ultimate elongation design value of said filaments and said resin system,
- an outer protective sheath formed from an elastomeric material attached to said filament matrix means along the length thereof and having an outer circular cross-section and two ends terminating proximate said ends of said filament matrix means,
- two hand grips, one hand grip defined about each end of said outer protective sheath and positioned parallel to said neutral axis, and
- hand retention means operatively connected to one end of each of said hand grips, said hand retention means sized to allow the passage of a hand therethrough.
- 2. The apparatus of claim 1 wherein said two hand grips are formed separate from said outer protective sheath, each hand grip being press-fitted over one end of said outer protective sheath.
- 3. The apparatus of claim 1 wherein said two hand grips are formed common with said outer protective sheath about said filament matrix means by simultaneous injection molding of said hand grips and said outer protective sheath.
- 4. The apparatus of claim 1 wherein said hand retention means of each end of said hand grips further comprises;
- a washer having an opening defined therethrough, and
- a looped cord passed through said opening and knotted at both ends adjacent said opening, said washer and knotted ends encased within the material of said hand grip.
- 5. The apparatus of claim 1 wherein said hand retention means are formed common with each of said two hand grips by simultaneous injection molding of said hand grips and said hand retention means.
RELATED APPLICATION
This application is a continuation-in-part of application Ser. No. 172,927, Filed Mar. 25, 1988, entitled Apparatus for Use in the Exercise of the Human Body, Gordon L. Brown, Jr. inventor, issued Sept. 5, 1989 as U.S. Pat. No. 4,863,159.
Apparatus previously designed for the exercise of the human body will typically resist the force applied by the exerciser in a linear manner. Note for example bar bell weight sets, or exercise equipment which incorporates weights and pulleys wherein the exerciser pulls on a rope and thereby slides a weight system upwardly and downwardly on a vertical rail. In these systems the resistance applied to the exerciser is constant regardless of the position of the exercise equipment relative to the exerciser's body.
In the last several years optimum exercise results have been obtained by the use of variable resistance exercise equipment. Such equipment applies a variable non-linear resistance to the exerciser during the motion associated with an exercise movement. Note for example Nautilus equipment that incorporates a variable radius cam located between the exerciser and the weights. Rotation of such a cam requires the application of increasing force through portions of the cam's rotation.
Most variable resistance exercise equipment is not easily transportable, however, due to its weight and complexity, and therefore does not satisfy the need of the general population for an easily transportable exercise apparatus. It would be improbable for example, for a person leaving on a business trip to easily transport an entire Nautilus equipment assembly.
A lightweight, and therefore apparently portable variable resistance exercise apparatus therefore needs to be developed. The design and development of such an apparatus should incorporate any available new technology. Due to the close proximity of such an apparatus to the human body, such an apparatus should be safe to operate. Such an apparatus should also be easily manufacturable, lend itself to mass production, and have an acceptable longevity before failure.
In particular the longevity of the apparatus should allow enough cycles before failure to satisfy the purchaser's expectations for a piece of equipment that will last at least half a year or so. It can be easily calculated that such an exercise apparatus will be subjected to approximately 18,000 to 20,000 cycles during a six-month period of normal use. The cycles will vary in the strain imposed on the rod depending on the particular exercise being performed. The most severe strain is imposed when the rod is bent in a tear drop shape such that it's ends touch. Special consideration therefore need be directed to the selection of the material properties of such an exercise apparatus.
In related application Ser. No. 030,397, the exercise apparatus comprised a flexible fiberglass rod formed from a mixture of a tough, hardenable resin system and essentially longitudinal fiberglass filaments. Gripping the rod at both ends and thereafter attempting to bend the rod until both ends touched one another required the application of increasing force. The variable resistance feature of the rod is caused by the increase in the strain imposed on the fiberglass filaments located on the outer periphery of the rod, as the radius of curvature of the rod is decreased.
To evaluate the possibility of meeting the fatigue life requirement of 18,000 cycles, rods of 1/4" diameter and 3/8" diameter were tested. A goal was to achieve about 10,000 cycles without failure where each cycle would see the rod bent to a tear drop shape with the ends touching. If this could be done then the consumer would be able to expect about 18,000 to 20,000 cycles where the strain of each cycle would vary from very small to the maximum which results when the ends of the rod are touched together. Various types of resins and fibers were used to fabricate the rods. The test results are given as follows:
The maximum bending stress induced in the exercise rod bent into the shape of a teardrop, (FIG. 4), is given in Frisch-Fay, R., "Flexible Bars," London, Butterworths, 1962, pp. 1-11 as follows:
In general, the values of E and the ultimate tensile strength X will vary slightly with different resin systems. However, due to the lack of experimental data for the composite systems studied, they were assumed for the test to be the same for all resin systems.
Using Eqn. (1), the maximum flexural fatigue stresses induced in the 5-foot long 1/4-inch diameter E-glass and S2-glass rods are 105.4 ksi and 125.6 ksi, respectively. Although the values of the flexural fatigue stress for the E-glass and S2-glass rods are below the static tensile strength of the corresponding composites, they are too high to provide the required fatigue life of the exercise rods. To estimate the fatigue life of the rods at these fatigue stresses, it is necessary to have the fatigue curves of the various composites that were used in the exercise rods. In particular, it is more appropriate to have the fatigue curves of the composites made by the pultrusion process. It is obvious that such curves will not be readily available since it is expensive and time consuming to generate them. Hence, approximate relations between fatigue stresses and cycles to failure were used in this test for the E-glass and S2-composites, as set forth in Hahn, H. T., Hwang, D. G., and Chin, W. K., "Effects of Vacuum and Temperature on Mechanical Properties of S2-Glass/Epoxy," Recent Advances in Composites in the United States and Japan, edited by Vinson/Taya, ASTM STP 864, pp. 600-618. For the E-glass composites, we have
As can be seen, both the actual and predicted cycles to failure for both the 1/4-inch and 3/8-inch diameter rod are unacceptably low. An exercise apparatus therefore need be designed that has a maximum flexural fatigue stress so as to insure an acceptable longevity, in the neighborhood of 18,000 cycles, to insure consumer acceptance of the durability of the apparatus, yet is stiff enough to provide a good workout for the exerciser.
After extensive analysis and by use of Equations 1-3, it was finally determined that the appropriate cross-sectional geometry of the exercise apparatus that would satisfy both the stiffness and life requirements is that of an oblong, the oblong having a major axis of a predetermined selected width and a minor axis of a predetermined selected height wherein the width of the cross-section in a preferred embodiment is from 2 to 7 times the height of the cross-section, (FIG. 2).
More specifically, the desired cross section geometries, as shown in FIG. 2, are given in Table 1 for oblong shapes constructed of S-2 glass fibers and an epoxy resin as follows:
Depending on the placement of the men's or ladies' hands on the apparatus, the force required to bend the men's apparatus until the ends touch would be approximately 24 to 30 lbs., and for a ladies' apparatus would be approximately 16 to 22 lbs. The men's champion apparatus would require 35 lbs. to flex the apparatus into the tear drop shape until the ends touch.
In general, if the spacing between the hand grips is shortened below that of the designed spacing, a larger force is required to bend the exercise apparatus into the teardrop shape and the corresponding fatigue life of the apparatus is reduced. For this reason the apparatus is designed with hand grips at both ends that encourage the placement of the exerciser's hands in the desired position at the ends of the apparatus.
The flexural fatigue life prediction at about 18,000 cycles of the exercise apparatus shown in Table 1 is based on the assumption that no reverse bending will occur in the service life. It is therefore a feature of the present invention to incorporate marker means such as stenciling or other marking well known to the art on the exercise apparatus to entice bending of the apparatus only in one direction.
Furthermore, to manufacture an exercise apparatus that is both safe and durable, the properties of the materials that form the pultruded shape having the oblong cross-section must be carefully selected. As described below, the filaments in the resin system that form the variable resistance portion of the exercise apparatus must have an ultimate elongation design value higher than the anticipated or actual measured elongation of the outer filaments of the exercise apparatus at its point of maximum flection.
The resin system used to dimensionally stabilize the filaments should have an ultimate elongation design value of from 2 to 8 times the anticipated or actual measured elongation of the outer filaments of the exercise apparatus at its point of maximum flection and have enough toughness to give acceptable flexural fatigue life. The filaments should have an ultimate elongation design value of a minimum of 1% to 2% above the anticipated or actual measured elongation of the outer filaments of the apparatus.
In the final apparatus design, the resin system may comprise Shell EPON.RTM. 9310 resin and S2 glass or Shell EPON.RTM. 828 resin and S2 glass.
It is therefore a feature of the present invention for an exercise apparatus to be constructed from a hardenable mixture of resin and essentially longitudinally oriented filaments having an ultimate elongation design value greater than the anticipated or actual measured elongation of the outer filaments of the apparatus at its point of maximum flection.
It is an object of the present invention to manufacture an easily transportable exercise apparatus having a variable resistance to forces applied to the ends of the apparatus that is a direct result of the type and percentage volume of fiber reinforcement.
It is another object of the present invention to fabricate an exercise apparatus that is safe, durable and will maintain straightness with only a slight amount of bow through its useful life.
These and other features, objects and advantages of the present invention will become apparent from the following Detailed Description, wherein reference is made to figures in the accompanying drawings.
US Referenced Citations (16)
Continuation in Parts (1)
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Number |
Date |
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172927 |
Mar 1988 |
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Patent Grant
5004226
