Abstract:
An exercise machine having infinite range limiting capability comprises: a frame; a pivotable exercise arm mounted to the frame configured to engage an exercising user and moveable along a stroke path having a fully extended position and a fully flexed position; a movement-resisting system for resisting movement of the exercise arm along the stroke path; an interconnecting unit for interconnecting the exercise arm and the movement-resisting unit so that movement of the exercise arm causes a portion of the movement-resisting unit to move in response thereto; and a range-limiting unit for limiting the distance the exercise arm moves along the stroke path during exercise. The range-limiting unit is connected to the interconnecting unit and is configured to enable a user of the exercise machine to select a first partially flexed position at any desired location along the stroke path such that the exercise arm moves between the first partially flexed position and the fully extended position serving during exercise. The range limiting unit is also configured so that movement of the exercise arm away from the fully extended position past the first partially flexed position by the user selects a second partially flexed position such that the exercise arm moves between the second partially flexed position and the fully extended position during exercise.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to exercise equipment, and relates more specifically to exercise equipment that enables the user to select an appropriate range of motion for the exercise. 
     BACKGROUND OF THE INVENTION 
     Many currently available exercise machines are designed to include an exercise arm or other member that moves in response to a force applied by the user of the machine. Typically, the exercise arm is connected to a resistance system, often a weight stack, that provides resistance to movement of the arm. Thus, as the user attempts to move the arm, the resistance system resists that movement, with the effect that the user exercises by repeatedly overcoming the resistance and moving the exercise arm. 
     Many exercise machines are configured so that a user can preselect certain exercise parameters. For example, if a weight stack is employed as the resistance system, the user typically can select any number of weights in the weight stack to provide resistance to movement. As a result, the user can customize an exercise routine that is best suited to the user&#39;s needs. 
     Some exercise machines have other features that enable a user to customize the exercise routine further. One example of such a feature is the so-called “range-limiter,” which is a device that enables the user to select the endpoints for the path the exercise arm will travel during exercise. A range limiter is particularly useful for exercise machines such as torso machines and hip-and-back machines, both of which condition and rehabilitate body regions which vary in flexibility and strength significantly between users and which are often injured, either acutely or chronically, and therefore can require limited range of motion exercise. 
     An exemplary and common range-limiting device, such as that illustrated in U.S. Pat. No. 5,356,360 to Johns, includes a range limiting cam that has a series of holes, any of which can receive a pin that is attached to a lever. The lever is attached to the frame of the exercise machine, and the cam is interconnected with the exercise arm. Movement of the pin to different holes determines the range of motion of the exercise device. A somewhat similar range limiter is shown in U.S. Pat. No. 5,263,914 to Simonson et al., in which range limiting capability is provided by a lever having holes that receive a limiting pin. 
     One shortcoming of each of these range limiters is their inability to provide “infinite” range limiting; i.e., the range of these devices is limited by the number and positions of the holes in the cam or lever. Such a machine may be unsuitable for exercisers having special exercise needs that may require the exercise machine to take a specific position that is not available with the holes offered by the lever or cam. 
     In addition, the range limiters of these machines are difficult, if not impossible, to adjust during exercise. As a result, a user that wishes to begin the exercise with a certain range of motion, then continue the exercise with a different range of motion, must actually cease the exercise, dismount the exercise machine, modify the range limits, remount the machine, and only then continue exercising. An exercise pattern of gradually increasing range of motion is not unusual, especially for rehabilitating exercisers who require that the portion of the body being exercised be stretched gradually to the point of full motion. 
     Another type of range limiter is disclosed in U.S. Pat. No. 5,104,121 to Webb, which illustrates a range limiter in conjunction with a torso exercise machine. The Webb range limiter includes a pair of sprockets mounted on a common shaft: one sprocket rotates with an eccentric cam attached to the exercise arm; and the other sprocket, which is larger than the first sprocket, rotates independently of the cam and is attached to the weight stack. A pawl having a latching tooth is attached to the larger sprocket. To establish an exercise starting position, the pawl is disengaged from the smaller sprocket via a handle, and the exercise arm is moved to a desirable starting position. The handle is then released, and the pawl is received between a pair of teeth of the smaller sprocket. The interaction between the pawl and the smaller sprocket fixes the sprockets relative to one another, which in turn connects the exercise arm and the weight stack. As a result, the relative positions of the small and large sprocket establish the starting position for the exercise arm. Although this system enables the user to select a range limit while seated in the exercise machine, it does not provide for infinite range limiting capability, as the range limits of the machine are restricted to discrete positions defined by the configuration of the sprockets and the pawl. 
     Another shortcoming of many exercise machines that employ cables or chains to connect the exercise arm and the weight stack is the inability of such machines to establish and maintain a constant belt tension, even when the machine is not in use. These machines should have slight tension (between 5 to 20 pounds) on the belts or chains in order to ensure that resistance is provided during the entire exercise stroke, and in particular at the beginning of the stroke. Most exercise machines of this type require periodic maintenance, during which time the belt or chain is disconnected from the weight stack. When the belts or chains are reconnected after maintenance, the tension must be re-adjusted. 
     Also, at times exercise machines malfunction by the lower end of the connecting rod that carries the weight becoming lodged against the top surface of the uppermost weight remaining in the weight stack. As a result, the weights connected with the connecting rod are suspended in a raised position. When this occurs, often the user will attempt to fix the problem by dislodging the lower end of the connecting rod. In response, the weights connected to the connecting rod immediately drop onto the remaining weights. As such, the user risks serious hand injury by attempting to fix the machine. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide a range-limiting device for an exercise machine that is not limited to a finite number of positions. 
     It is also an object of the present invention to provide such a range-limiting device that can be operated by the user when the user is in place to exercise and that can be adjusted between exercise strokes. 
     It is a further object of the present invention to provide a device that can provide constant tension to a belt or chain of an exercise machine. 
     These objects and others are satisfied by the present invention, which includes an exercise machine having infinite range limiting capability. The exercise machine of the present invention comprises: a frame; a pivotable exercise arm mounted to the frame configured to engage an exercising user and moveable along a stroke path having a fully extended position and a fully flexed position; movement-resisting means for resisting movement of the exercise arm along the stroke path; interconnecting means for interconnecting the exercise arm and the movement-resisting means so that movement of the exercise arm causes a portion of the movement-resisting means to move in response thereto; and range-limiting means for limiting the distance the exercise arm moves along the stroke path during exercise. The range-limiting means is connected to the interconnecting means and is configured to enable a user of the exercise machine to select a first partially flexed position at any desired location along the stroke path such that the exercise arm moves between the first partially flexed position and the fully extended position serving during exercise. The range limiting means is also configured so that movement of the exercise arm away from the fully extended position past the first partially flexed position by the user selects a second partially flexed position such that the exercise arm moves between the second partially flexed position and the fully extended position during exercise. With an exercise apparatus that is so configured, the user can set a new range limit (i.e., the second partially flexed position) merely by repositioning the exercise arm; he need not dismount the apparatus nor rely on a separate actuator. 
     Preferably, the exercise apparatus also includes a tensioning unit. Such an exercise apparatus includes the aforementioned frame, exercise arm, and movement resistance means, and interconnecting means, and also includes tensioning means. The interconnecting means includes a flexible member between the exercise arm and the movement-resisting means. The tensioning means, which is interconnected with the interconnecting means, maintains tension in the flexible member when the exercise arm is in the flexed position and when the exercise arm is in the extended position. This simplifies set-up and adjustment of the tension in the machine, and can also prevent accidents that occur when the connecting pin of an exercise machine becomes lodged above the weight stack. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a hip and back machine of the present invention. 
         FIG. 2  is a side section view of the hip and back machine of  FIG. 1  with a user illustrated in phantom line and with the weight exercise arm in its flexed position. 
         FIG. 3  is an enlarged view of the hip and back machine of  FIG. 1  illustrating the rotation of the exercise arm to a flexed position when the range limiting unit is disengaged to enable the weight belt to wrap onto the clutch pulley. 
         FIG. 4  is an enlarged perspective view of a range limiting unit included in the hip and back machine of  FIG. 1 . 
         FIG. 5  is a section view on the hip and back machine of  FIG. 1  showing the exercise arm in phantom line as it moves to its extended position during exercise. 
         FIG. 6  is a section view of the hip and back machine of  FIG. 1  illustratively how the exercise arm can be returned to the extended position after exercise to enable the user to dismount the machine. 
         FIG. 7  is an enlarged exploded perspective view of the components of the range limiting unit of the hip and back machine of  FIG. 1 . 
         FIG. 8  is an enlarged top section view of the range limiting unit of the hip and back machine of  FIG. 1  with the shoulder pin of the actuator system in its extended position. 
         FIG. 9  is an enlarged side view of the pinion and drive gear of the range limiting unit of the hip and back machine of  FIG. 1 . 
         FIG. 10  is a partial side view of the cable system of the hip and back machine of  FIG. 1 , with the helical spring included therein extended beyond its free length. 
         FIG. 11  is a partial side view of the cable system of the hip and back machine of  FIG. 1  with the helical spring included therein partially extended. 
         FIG. 12  is a partial side view of the cable system of the hip and back machine of  FIG. 1  showing the helical spring at its free length. 
         FIG. 13  is an enlarged section view of the drive gear and take-up pulley of the range limiter showing the relative position of the stop pin and the ridge of the drive gear as the stop pin rotates with the shaft. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more particularly hereinafter with reference to the accompanying drawings, in which an embodiment of the invention is shown. The invention can, however, be embodied in many different forms and should not be limited to the embodiment set forth herein; rather, this embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in this art. 
     Referring now to the Figures, a hip-and-back machine  20  is illustrated in  FIGS. 1 and 2 . As seen in  FIG. 1 , the leg extension machine  20  includes a skeletal frame  22 , a portion of which is covered by a plastic cover  23 . The frame  22  includes a base assembly  24  upon which rests a platform  28  configured to receive a reclining occupant for exercising. The platform  28  is supported by two vertical platform supports  26   a ,  26   b.    
     As best seen in  FIG. 2 , the frame  22  also includes three generally upright members  30   a ,  30   b ,  30   c  which are connected at their lower ends by a horizontal cross-member  31   a . The upright members  30   a  and  30   b  are connected at their medial portions by a horizontal cross-member  31   b . The upright member  30   b  terminates at its upper end at a range limiter support  33 , which extends horizontally between the upper end portions of upright members  30   a  and  30   c . The upright members  30   a  and  30   c , which are formed from a common tube, merge at their upper ends with a horizontal cross-member  31   d . Also, a cam support  32  extends between the upright members  30   a ,  30   b  slightly above the height of the platform  28 . Although the illustrated frame configuration is preferred, those skilled in this art will appreciate that other frame configurations can also be employed with the present invention. 
     Referring again to  FIGS. 1 and 2 , an exercise arm  44  is positioned above the front end (i.e., the end above a reclining occupant&#39;s torso) of the platform  28 . The exercise arm  44  includes a crank portion  45 , which is pivotally mounted to the cam-support  32  through a cam shaft  42 . The crank portion  45  follows a generally upwardly and rearwardly-extending arcuate path from the cam shaft  24  to a user-engaging portion  46 , which extends horizontally therefrom above and generally parallel with the front portion of the platform  28 . The user-engaging portion  46  is covered with a cylindrical cushion  47 , which is positioned to engage the user behind the knees during exercise, and includes a grasping handle  48 . 
     Still referring to  FIG. 2 , an eccentric cam  40  is mounted to the cam shaft  42  on the same side of the cam support  32  as the exercise arm  44 . The cam  40  includes an arcuate camming surface  41  about its periphery; the camming surface  41  is of sufficient width to engage an overlying cam belt  58  during operation. A slot  43  is positioned at one end of the camming surface  41 ; the slot  43  receives one end of the cam belt  58  and fixes it to the cam  40  via an attachment pin  39 . The cam  40  is configured so that, as the camming surface  41  wraps the cam belt  58 , the resistance provided to the user varies over the “stroke” of exercise to increase the benefit the user receives. The skilled artisan will recognize that other configurations, such as those in which cams of other eccentric or non-eccentric shapes are employed, can also be used with the present invention. 
     An idler pulley unit  50  is attached to the cam belt  58  at the end opposite the cam  40  ( FIG. 2 ). The idler pulley unit  50  includes the cam belt  58 , a carrier bracket  52  that is attached to the end of the cam belt  58  opposite the cam  40 , and an idler pulley  54  rotatably mounted on the carrier bracket  52 . Of course, the cam belt  58  can be replaced with a chain or other flexible member if the cam  40  is correspondingly configured. 
     Still referring to  FIG. 2 , the idler pulley unit  50  is suspended by a weight belt  66  that engages the idler pulley  54 . The weight belt  66  is secured at one end to a range limiting unit  90  that is mounted on a forward portion of the range-limiting support  33 . From its engagement with the idler pulley  54 , the weight belt  66  travels upwardly and rearwardly to engage a large positioning pulley  62  mounted on the rear portion of the range limiter support  33 . The weight belt  66  then travels downwardly to interconnect with a weight system  70 . As with the cam belt  58 , the weight belt  66  can be replaced with a chain or other flexible member with corresponding changes in the idler pulley  54  and the positioning pulley  62  (e.g., sprockets can be substituted for the pulleys if a chain replaces the weight belt  66 ). 
     Referring again to  FIG. 2 , the weight system  70  includes a plurality of vertically stacked weights  72 . Each of the weights  72  includes a horizontally-extending selection pin aperture (not shown) in one side wall and a vertically-extending connecting rod aperture  76  which intersects with the selection pin aperture  74  at the center of the weight  72 . Each weight  72  also includes a pair of guide rod apertures  78   a ,  78   b , which extend vertically through the weight  72  on opposite sides of the connecting rod aperture  76 . The guide rod apertures  78   a ,  78   b  and the connecting rod apertures  76  are positioned on each weight  72  so that, as the weights  72  are vertically stacked, the guide rod apertures  78   a ,  78   b  and the connecting rod apertures  76  are aligned to form passages in the weight stack. 
     Referring still again to  FIG. 2 , the weights  72  are maintained in their x-y positions (i.e., their positions along axes extending horizontally across  FIG. 2  (the x-axis) and extending normal to the page in  FIG. 2  (the y-axis) and their angular orientations relative to the frame  22  about a vertical axis by a pair of cylindrical guide rods  80   a ,  80   b . The guide rods  80   a ,  80   b  extend vertically between and are fixed to the cross-member  31   a  and the range limiter support  33 . Each guide rod  80   a ,  80   b  extends through a respective aligned set of guide rod apertures  78   a ,  78   b  in the weights  72  as they are vertically stacked. Two bushings (not shown) are slidably received on respective guide rods  80   a ,  80   b  and engage the uppermost of the weights  72 . 
     A connecting rod  82  ( FIG. 2 ) is connected to the end of the weight belt  66  that extends downwardly from the positioning pulley  62 ; this connection is achieved via a bracket  85  attached to the upper end of the connecting rod  82 . The connecting rod  82  extends downwardly through the connecting rod apertures  76  in the weights  72 . The connecting rod  82  includes apertures  84  which, when the connecting rod  82  is in a lowered position, align with corresponding selection pin apertures  74  of the weights  72 . Thus, by inserting a selection pin  88  into the selection pin aperture  74  of a desired weight  72  and the corresponding aperture  74  of the connecting rod  72 , a desired number of weights  72  can be interconnected with the exercise arm  44  to provide resistance to the movement thereof. 
     Although the illustrated weight system  70  is preferred., other systems in which weights are interconnected with the exercise arm  44  can also be employed with the present invention. For example, multiple weight stacks, such as those described and illustrated in co-assigned and co-pending U.S. patent application Ser. No. 08/691,693 can be employed. 
     As mentioned above, the range limiting unit  90  ( FIG. 4 ) is connected with the end of the weight belt  66  opposite the weight system  70  and is mounted on the range limiter support  33 . The range limiting unit  90  comprises a block housing  91 , a clutch pulley unit  100 , a drive gear unit  120 , and an actuation system  150 . These components are described in more detail hereinbelow. 
     The housing  91  ( FIGS. 4 ,  7  and  8 ) is a solid steel block comprising side walls  92   a ,  92   b  and a rear wall  93 . A hub aperture  98  and a drive pulley shaft aperture  99  each extend through the housing  91  between the side walls  92   a ,  92   b . The rear wall  93  includes an actuator aperture  95  that intersects with the hub aperture  98 . The side wall  92   a  also includes a circular coil spring recess  96  in its forward portion that has a tangentially-extending slot  97 . 
     Referring again to  FIGS. 4 ,  7  and  8 , the clutch pulley unit  100  comprises a clutch pulley  101  having an integral clutch pulley shaft  102 , a hub  103  and a pinion  108 . The clutch pulley  101  is attached to the end of the weight belt  66  opposite the weight system  70  and is rotatably mounted within the hub  103  via the clutch pulley shaft  102 . The clutch pulley  101  is configured to take up the weight belt  66  upon rotation thereof in the direction that is counterclockwise from the reference point illustrated in  FIG. 2 . 
     The hub  103  is mounted within the hub aperture  98  in the housing  91 , with the clutch pulley shaft  102  being mounted within the central apertures of the hub  103  and being retained on the shaft by an E-type retaining ring  107 . The hub  103  has an internal one-way clutch mechanism formed by clutch members  104 . Such one-way clutches are well-understood by those skilled in this art and need not be described in detail herein. The presence of these members  104  prevents the clutch pulley shaft  102  from rotating in the direction relative to the hub  103  that would enable the weight belt  66  to unwrap from the clutch pulley  101  (clockwise from the vantage point of  FIG. 2 ). The hub  103  also includes four recesses  106  spaced equally apart about its circumferential outer surface  105 . 
     Still referring to  FIGS. 4 ,  7  and  8 , on the side of the housing  90  opposite the clutch pulley  101 , the clutch pulley shaft  102  is connected to the pinion  108 . The pinion  108 , which is about 1 inch in diameter and has radially extending teeth  110 , is fixed to the clutch pulley shaft  102  so that the clutch pulley  101  and the pinion  108  always rotate as a unit. 
     Referring again to  FIGS. 3 ,  4 ,  7  and  8  and moving forward on the housing  91 , the drive gear unit  120  includes a drive gear  121 , a drive gear shaft  124 , a take-up pulley  140 , a power spring  128 , and a cam pulley  148 . The drive gear  121  is positioned adjacent to the pinion  108 . The drive gear  121  is mounted on the drive gear shaft  124 , which extends through the drive pulley shaft aperture  99  of the housing  90 . The drive gear  121  is free to rotate about the drive gear shaft  124  over an angular range of about 190 degrees; this angular range is defined by a stop pin  125  mounted on the shaft  124  and a ridge  127  on the lip of the drive gear  121  (see  FIGS. 7 ,  9  and  13 ). The drive gear  121  is about 5 inches in diameter and includes radially-extending teeth  122  that are sized to engage the teeth  110  of the pinion  108 . 
     Referring now to  FIGS. 7 and 8 , at its end opposite the drive gear  121 , the drive gear shaft  124  is attached to the rotating end  132  of the coiled power spring  128  via a slot  133 . The power spring  128  is coiled about the shaft  124  within the recess  96  in the housing side wall  92   a , with the end of the power spring  128  that is opposite the shaft  124  being fixed within the slot  97  in the housing side wall  92   a . The power spring  128  is sized and configured to bias the shaft  124  to rotate in the counterclockwise direction from the vantage point of  FIG. 2 . A retaining ring  129  retains the drive gear shaft  124  in place in the housing  91 . 
     Shown best in  FIGS. 9 through 12 , the take-up pulley  140  is mounted to the drive gear shaft  124  for coupled rotation therewith. The take-up pulley  140  is configured to take up a portion of a downwardly-extending upper cable  142 , which is attached at one end to the take-up pulley  140 . The upper cable  142  is attached at its opposite end to one end of a helical spring  144 , which is in turn attached at its opposite end to one end of a lower cable  146 . The lower cable  146  is attached at its opposite end to the cam pulley  148 , which is mounted on the cam shaft  42  for coupled rotation with the aforementioned cam  40 . The upper and lower cables  142 ,  146  and the helical spring  144  are sized so that, during most operation of the hip-and-back machine  20 , the helical spring  144  is stretched beyond its free length and therefore maintains the cables  142 ,  146  in tension. 
     Referring now to  FIGS. 2 ,  7  and  8 , the actuation system  150  comprises a handle  152  that is mounted on the platform  28  near the hip of a user. The handle  152  is connected through a sheath and cable unit  154  to a spring-loaded shoulder pin  158  that is mounted to the end wall  93  of the housing  90  within the actuator aperture  95  ( FIG. 8 ). The shoulder pin  158  is sized to fit within the recesses  106  of the clutch hub  103  and is biased by its spring to extend toward the hub  103  and into a recess  106 . 
     Exercise with the hip-and-back machine  20  commences with the exercise arm  44  in its inoperative fully extended position (this position is best illustrated in  FIG. 6 ). In this position, the exercise arm  44  is extended fully forward, the weights  72  of the weight stack  70  are lowered and stacked, and the weight belt  66  is fully unwrapped from the clutch pulley  101 . Tension is maintained in the system by the helical spring  144 , which is extended beyond its free length, and by the power spring  128 , which biases the take up pulley  140  in the clockwise direction from the vantage point of  FIG. 6 . The biasing of the power spring  128  also biases the drive gear  121  in the clockwise direction, which in turn biases the pinion  108  and, therefore, the clutch pulley  101 , in the counterclockwise direction as seen in  FIG. 6 . The biasing of the clutch pulley  101  causes the weight belt  66  to remain in tension. 
     Prior to exercising, the user inserts the selection pin  88  into the selection pin aperture  74  that corresponds to the desired number of weights  72  for exercise. The user then lies on his back on the platform  28  and is belted into place ( FIG. 2 ). 
     The user then pulls on the exercise arm  44  to move the exercise arm  44  to a desired flexed position. Because the clutch hub  103 , and in turn the clutch pulley  101 , are free to rotate relative to the housing  90 , the user can grasp the handle  48  and rotate the exercise arm  44  over his hips and toward his chest to the desired partially flexed position. 
     Simultaneously, and as illustrated in  FIG. 3 , the movement of the exercise arm  44  also causes the cam pulley  148  to rotate and take up the lower portion of the lower cable  146 . Wrapping of the lower cable  146  draws the helical spring  144  downwardly, which in turn unwraps the upper cable  142  from the take up pulley  140 . The take up pulley  140  rotates the drive shaft  124  and the drive gear  121 , as the drive gear  121  is oriented so that the stop pin  125  is in contact with the ridge  127 . 
     Rotation of the drive gear  121  drives the pinion  108 , the hub  103 , and the clutch pulley  101  counterclockwise from the vantage point of  FIG. 3 . This rotation of the clutch pulley  101  wraps up a portion of the weight belt  66 , with tension being maintained therein. 
     Once the user has selected the partially flexed position in which to commence exercising, initial slight extension of the user&#39;s legs from the partially flexed position toward the fully extended position causes the clutch pulley  101  and hub  103  to rotate within the housing  91  slightly (clockwise in  FIG. 5 ) until one of the recesses  106  in the hub  103  is positioned to engage the shoulder pin  158 , which extends to engage that recess (see  FIG. 8 ). With the shoulder pin  158  engaged in a recess  106 , the hub  103  is prevented from further rotation. In turn, the clutch pulley  101  is prevented from clockwise rotation within the hub  103  by the one-way clutch members  104 . As such, the clutch pulley  101  does not let out any of the weight belt  66 ; instead, the weight belt  66  is now set at a constant length. As a result, the exercise arm  44  is set in its initial partially flexed position. 
     After the exerciser has set the “flexed” position, he exercises by extending his legs until the exercise arm  44  reaches the extended position. Doing so causes the cam belt  58  to wrap around the camming surface  41  of the cam  40 , thereby drawing the idler pulley  50  lower and lifting the selected weights  72 . The clutch pulley  100  remains fixed and neither releases nor takes up more of the weight belt  66 . Similarly, neither the pinion  108  nor the drive gear  121  rotate during exercise. However, because the cam pulley  148  rotates with the cam  40 , the tension in the cables  142 ,  146  between the cam pulley  148  and the take-up pulley  140  tends to be reduced as the exercise arm  44  moves nearer the extended position. Because of this, the helical spring  144  interposed between the cables  142 ,  146  contracts. However, over the final stages of the stroke, as the exercise arm  44  approaches the extended position, the spring  144  contracts to its free length. At this point, the power spring  128  biases the take-up pulley  140  to maintain tension in the cables  142 ,  146 . 
     If, in the course of exercising, the user wishes to modify the partially flexed position to a location nearer his chest (as may be the case when the user becomes more flexible from the stretching of prior exercise repetitions), the partially flexed position can be adjusted by simply pulling the exercise arm  44  to a new partially (or fully) flexed position nearer the chest. The clutch pulley  101  is permitted to rotate relative to the hub  103  (counterclockwise in  FIG. 3 ) by the one-way clutch members  104  to take up more of the weight belt  66  without raising the weights  72 . Thus, the system enables the user to set any desired flexed position, even between exercise repetitions, without leaving the platform  28 . 
     After completing the exercise, the user can easily dismount the hip and back machine  20  by actuating the handle  152  (see  FIG. 6 ). This action retracts the shouldered pin  158  from its receiving recess  106 , which in turn enables the hub  103  to rotate within the clutch pulley aperture  98 . This action enables the clutch pulley  101  to rotate clockwise ( FIG. 6 ) to let out the weight belt  66  when the user pushes the handle  48  of the exercise arm  44  forwardly to the fully extended position. Rotation of the clutch pulley  101  drives the pinion  108  clockwise, which in turn drives the drive gear  121  counterclockwise. The cam  40  and cam pulley  148  rotate with the exercise arm  44 . Tension is maintained during the release of the exercise arm  44  by the spring  144 , then by the power spring  128 , as described above. 
     The cam belt  58 , the weight belt  66 , and the upper and lower cables  142 ,  146  are maintained in tension by both the helical spring  144  and the power spring  128  that biases the take-up pulley  140 . As described above, over most of the stroke of the exercise arm  44 , the helical spring  144  is extended beyond its free length, thus creating tension in both cables  142 ,  146 . By doing so, tension remains in the entire system (preferably about 6 pounds). When the stroke of the exercise arm  44  approaches the fully extended position, the helical spring  144  compresses to its free length prior to the exercise arm  44  reaching the extended position. In this instance, the power spring  128  draws the cables  142 ,  146  and the helical spring  144  upwardly to maintain tension in the system. 
     It is also noteworthy that the range limiter unit  90  is able to maintain tension in the system despite apparent mismatch of rotation between unit comprising the cam  40  and cam pulley  148 , which rotates at the most only about 190 degrees, and the clutch pulley  101 , which may rotate up to five times to wrap up the weight belt  66 . This difference in rotation is overcome in the sizing of the take-up pulley  140 , the drive gear  121  and the pinion  108 . Because the drive gear/pinion gear ratio is about 5 to 1, the clutch pulley  101  rotates five times for a single rotation of the drive gear  121 . Similarly, the take-up pulley  140  is sized to rotate approximately one time as the cam pulley  148  rotates through 180 degrees. As a result, movement of the exercise arm  44  such that the cam pulley  148  rotates through 180 degrees causes the clutch pulley  101  to rotate five times to wrap up the weight belt  66 . Of course, those skilled in this art will recognize that other configurations that convert the desired movement of the exercise arm  44  to the desired take-up of the clutch pulley  101  would also be suitable for use with the present invention. 
     In addition to the hip and back machine  20  illustrated herein, the range limiter unit  90  can also be employed with other exercise apparatus for which range limiting capability is desired. Examples of other suitable exercise machines include: machines for leg exercise, such as prone leg curl, leg press, seated leg curl, and seated calf machines; machines for hip exercise, such as hip abduction, adduction, and abduction/adduction machines, machines for neck exercise, such as 4-way neck, behind neck, and neck and shoulders machines; machines for the upper torso, such as 10-degree and 50-degree chest, chest and double chest, decline and incline press, bench press, reverse and super pullover, torso arm, seated dip, rowing back, and compound row machines; machines for the mid-torso, such as abdominal, lower abdominal, rotary torso, and low back machines; machines for the arms, such as multi-biceps, multi-triceps, and super forearm machines; and machines for the shoulders, such as lateral raise, overhead press, and rotary shoulder machines. 
     It should also be apparent to those skilled in this art that the range limiting unit  90  can be used with other apparatus in which the stroke of a particular component is desirably set to different lengths. Examples of alternative uses for the infinite range limiter include lawn mower height adjustment and chair backrest adjustment. Also, applications where a constant tension is desired, such as tie down straps for cargo transport or sailing equipment or string of musical instruments, are also contemplated for the automatic tensioning capability. 
     Those skilled in this art will appreciate that the tensioning capability of the hip-and-back machine  20  can be included in other exercise machines that lack a range limiting device. For example, the weight belt  66  can be connected to a clutch pulley mounted within a hub similar to that described hereinabove that is biased by a coiled power spring in the direction needed to take up the weight belt. The hub would be releasable for rotation relative to the frame by a shoulder pin or other releasing device, and its one-way clutch mechanism would permit rotation of the clutch pulley to take up the weight belt but would prevent rotation to let out the belt. Upon release of the shouldered pin, the hub would be free to rotate within its frame. Extension of the pin into a circumferential recess of the hub fixes the hub into place. The clutch pulley or other rotary member is then rotated within the hub by the power spring to take up the weight belt until a desired tension in the belt is reached. 
     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications of the exemplary embodiments are possible without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. In the claims, means-plus-function clause are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.