Abstract:
An exercise device ( 10 ) includes a base ( 11 ) comprising a rigid piece of material which may be placed flat on a floor. An isokinetic resistance unit ( 12 ) is pivotally connected at a lower end to the base, with a harness ( 13 ) connected to an upper end of the resistance unit. A user uses the device by attaching the harness ( 13 ) preferably around the waist and, while standing on the base ( 11 ), bending to a squatting position and then returning to an upright position. The resistance unit ( 12 ) comprises a cylinder ( 30 ) and piston ( 31 ) arrangement which provides resistance as the user moves from the squatting position to the upright position. The resistance is provided through a negative pressure developed in a working chamber ( 38 ) defined between the piston ( 31 ) and a first end of the cylinder ( 30 ).

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to exercise devices and, more particularly, to an isokinetic exercise apparatus for exercising the legs and lower body. 
     BACKGROUND OF THE INVENTION 
     Numerous types of devices have been developed for exercising various muscles or muscle groups. Exercise devices generally provide some sort of resistance to the user&#39;s movement. For example, the resistance may be provided by weights, elastic elements such as springs, or pneumatic or hydraulic devices. Exercise machines which use weights to provide resistance are commonly bulky and not easily portable. Elastic elements generally provided resistance which varies as the elastic element is deformed. Also, elastic elements can wear out over extended use. Pneumatic and hydraulic resistance devices can provide a resistance which varies in proportion to the force applied by the user. Exercise in which the resistance is proportional to the force applied by the user is referred to as “isokinetic” exercise. Prior isokinetic exerciser devices for exercising the legs and lower body were free standing bulky devices which were not readily portable. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an easily portable and lightweight isokinetic exercise apparatus for exercising the legs and lower body. 
     The exercise apparatus according to invention includes a substantially rigid base and an isokinetic resistance unit mounted thereon. The isokinetic resistance unit is connected to the base by a pivot connection which allows the resistance unit to pivot about an axis parallel to a base axis. The base has two support areas spaced apart along the base axis, one support area on each side of the point at which the resistance unit is connected to the base. The apparatus further includes a harness or belt which is connected to an upper end of the resistance unit. 
     The isokinetic resistance unit relies upon a fluid, preferably air, for providing resistance. Also, the preferred resistance unit utilizes a negative pressure to provide resistance rather than a positive pressure. By utilizing negative pressure, the resistance unit according to the invention simplifies the required sealing arrangements. 
     The preferred resistance unit comprises a cylinder with a piston slidably received therein. A rod is connected to the piston and extends generally parallel and coaxially with the cylinder. The rod and piston are adapted to move with respect to the cylinder between a retracted position and an extended position. In the retracted position, the piston resides near a sealed lower end of the cylinder and the rod extends a relatively short distance beyond the opposite end of the cylinder. However, when the piston slides to the extended position in an upper end of the cylinder, the rod extends substantially beyond the upper end of the cylinder. The area of the cylinder defined between the piston and lower end of the cylinder forms a working chamber. The resistance unit also includes an air flow resistance opening and a one-way valve associated with the working chamber. A return spring may act between the piston and cylinder to bias the piston toward the lower end of the cylinder. 
     In operation, the user stands on the base and pulls the rod and piston to the extended position to allow the belt to be connected around the user&#39;s waist. With the belt fixed around the user&#39;s waist, the user bends their legs while keeping their back substantially perpendicular to the base and floor, and then completes the repetition by straightening their legs to return to the starting position. The rod and piston in the resistance unit move toward the retracted position as the user bends their legs, and then move toward the extended position as the user straightens their legs. However, the isokinetic resistance unit resists the movement toward the extended position, applying a resisting force through the rod and belt positioned around the user&#39;s waist. The resistance is generated by the negative pressure produced in the working chamber portion of the cylinder as the piston moves toward the extended position. The air flow resistance opening limits air flow into the working chamber, preventing the pressure in the working chamber from quickly equalizing with ambient pressure and maintaining the negative working chamber pressure as the user pulls the piston and rod toward the extended position. 
     The apparatus according to the invention provides good exercise for the lower body and particularly the legs. Yet the device is lightweight, easily portable, and may be stored easily. The use of negative pressure in the working chamber to provide resistance also simplifies the sealing arrangement required in the device. In particular, a sliding seal is required only between the piston and the cylinder. 
     These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric drawing of an exercise apparatus embodying the principles of the invention, with the resistance unit partially cut away to show the inner components. 
     FIG. 2 is an exploded side view of the base and resistance unit. 
     FIG. 3 is a side view showing the connection between the resistance unit and base. 
     FIG. 4 is a side view showing a lower portion of the resistance unit. 
     FIG. 5 is an isometric drawing illustrating the use of the exercise device shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, an exercise apparatus  10  according to the invention comprises a base  11 , isokinetic resistance unit  12 , and belt  13 . The resistance unit  12  is connected at a lower end to base  11  by a lower pivot connection shown generally at reference numeral  14 . Belt  13  is connected to the end of the resistance unit  12  opposite the end connected to base  11 . 
     Base  11  comprises a piece of substantially rigid material having a bottom surface which allows the base to be placed flat on a floor. The upper surface of base  11  includes a first support area  17  and a second support area  18  spaced apart along a base axis B. Resistance unit  12  is connected to base  11  at a location between the first and second support areas,  17  and  18 , respectively. 
     Referring now to FIG. 3 in addition to FIGS. 1 and 2, pivot connection  14  between resistance unit  12  and base  11  allows the resistance unit to pivot about an axis P which extends substantially parallel to base axis B. The illustrated pivot arrangement  14  includes a cylindrical pin  20  supported at both ends by projections  21  extending from base  11 . The cylindrical pin  20  extends through a pin receiving opening  23  through a lower end cap  22  positioned at a lower end of the resistance unit  12 . The illustrated base  11  may also include an indentation  24  which accommodates the lowermost end of resistance unit  12  and allows the resistance unit to pivot freely about axis P. Indentation  24  may be omitted by lengthening the projections  21  sufficiently to provide the required clearance between base  11  and the lowermost end of resistance unit  12 . 
     Resistance unit  12  includes a cylinder  30  and a piston  31 . A rod  32  is connected to piston  31  and extends substantially parallel to cylinder  30  through an opening  37  in an upper end cap  36 . The preferred form of the invention also includes a return spring  33 . O-rings  34  provide a seal between piston  31  and the inner wall of cylinder  30 . Although the O-ring sealing arrangement is preferred, those skilled in the art will appreciate that the apparatus  10  may use any sealing arrangement which provides a good sliding seal between piston  31  and cylinder  30 . It will be noted that no seal is needed between the opening  37  and rod  32  in the illustrated form of invention. End cap  36  and opening  37  serve to support rod  32  in the desired position generally parallel to cylinder  30 . 
     Piston  31  and rod  32  are adapted to slide with respect to cylinder  30  between a retracted position and an extended position. In the retracted position, piston  31  resides relatively near end cap  22  and rod  32  extends the length of the cylinder and out the upper end cap  36  for a relatively short distance. In the extended position, piston  31  is relatively nearer upper end cap  36  and rod  32  extends relatively further out of the upper end cap. In either the retracted or extended position, the area of cylinder  30  defined between piston  31  and lower end cap  22  comprises a working chamber, referred to generally in the drawings at reference numeral  38 . 
     As shown best in FIG. 4, an air flow resistance opening  40  and a one-way valve  41  are associated with the working chamber portion  38  of cylinder  30 . One-way valve  41  includes an opening  42  into the working chamber  38  with a flap of material  43  extending over the opening on the side of the opening external to the working chamber. Flap  43  may pivot outwardly in direction of arrow F. Air flow resistance opening  40  comprises a small opening into working chamber  38 . Although not shown in the drawings, a valve may be associated with air flow resistance opening  40  for adjusting the effective area of the opening. 
     The end of rod  32  opposite the end connected to piston  31  includes a suitable connector for connecting to belt  13 . The preferred connection allows the belt  13  to pivot at least somewhat with respect to rod  32  and may, for example, comprises an eye  45  at the end of the rod and a loop  46  extending from the belt. The illustrated belt  13  comprises a length of material which may be fastened around the user&#39;s waist with any suitable closure arrangement, including a Velcro closure or a suitable buckle (not shown). Although not shown in the drawings, shoulder straps which extend over the user&#39;s shoulders may be connected to belt  13  to help distribute the force provided by resistance unit  12  during use. Those skilled in the art will appreciate that any suitable harness arrangement may be substituted for the belt-type harness  13  illustrated in the drawings. Such alternative harnesses are to be considered equivalents to the belt  13  for purposes of the following claims. 
     The operation and use of exercise apparatus  10  may be described with reference primarily to FIG.  4 . With the base  11  placed on a floor or other relatively flat surface, the user pulls rod  32  toward the extended position, raising the belt  13  sufficiently to fasten it around their waist. With the belt  13  fastened and the user&#39;s feet positioned in the support areas  17  and  18  of base  11 , the user begins the exercise by bending their legs while keeping their back straight and substantially perpendicular to the floor. As user bends their legs, their waist moves relatively closer to base  11  and allows rod  32  and piston  31  to move toward the retracted position. Spring  33  may act between upper end cap  36  and piston  31  to help move the piston and rod  32  toward the retracted position. As piston  31  moves toward the retracted position, one-way valve  41  opens so that air may flow from working chamber  38  through opening  42 . With the one-way valve open, there is very little resistance to the flow of air out of working chamber  38 , and thus little if any resistance to the downward movement of piston  31  and rod  32  with respect to cylinder  30 . 
     After bending their legs to the desired extent, the user completes the repetition by straightening their legs while keeping their back straight and generally perpendicular to the floor. As user straightens their legs, piston  31  and rod  32  move toward the extended position. The upward movement of piston  31  creates a vacuum in working chamber  38  which pulls flap  43  tightly against opening  42  to close one-way valve  41 . The vacuum in working chamber  38  also draws in air through air flow resistance opening  40 . However, air flow resistance opening  40  is small enough to maintain the negative pressure in working chamber  38  for a period of time as piston  31  moves upwardly. The negative pressure in working chamber  38  resists the upward movement of piston  31 . This resistance to upward movement is transferred to the user through rod  32  and belt  13 . 
     Providing resistance through the negative pressure in working chamber  38  according to the invention simplifies the seals which must be used in resistance unit  12 . Although a positive pressure between piston  31  and upper end cap  36  could be used to resist the upward movement of the piston, such a resistance arrangement would require not only a sliding seal between the piston and cylinder but also a seal between the end cap opening  37  and rod  32 . 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit the scope of the invention. Various other embodiments and modifications to these preferred embodiments may be made by those skilled in the art without departing from the scope of the following claims. For example, resistance unit  12  may be connected oppositely to the connection shown in the figures, with rod  32  connected to base  11  and cylinder  30  connected to belt  13 . Also, although the end caps  22  and  36  are shown as separate elements, they may be formed integrally with cylinder  30 . Where separate end caps are used, they may be connected to the cylinder by any suitable means such as by an adhesive or welding, for example. Furthermore, although air flow resistance opening  40  and one-way valve  41  are associated with end cap  22 , these elements may be positioned elsewhere within the scope of the invention. For example, both the one-way valve  41  and air flow resistance opening  40  may be located on the piston  31 , with the one-way valve flap  43  on the upper surface of the piston. Also, although spring  33  is preferred for returning piston  31  to the retracted position, the spring may be omitted within the scope of the invention.