Abstract:
A loading device for an exercise machine includes a lever arm and a nitrogen gas compression spring in a force triangle that provides easy adjustment of the resistive load presented to a user. The nitrogen gas compression spring and the selected portion of the lever arm comprise two legs of the force triangle, with a slidable coupling selectively interconnecting the nitrogen gas compression spring with the lever arm at adjustment points on the lever arm. Both the nitrogen gas compression spring and the lever arm are pivotally mounted on a rigid member, with the distances between their pivots forming the third leg of the force triangle. The nitrogen gas compression spring exhibits a high resistance, a flat spring rate and is of rigid construction so that the lever arm and nitrogen gas compression spring are self-supported at all times. The nitrogen gas compression spring is coupled to the slidable coupling to produce a slight torque preload to maintain the contact orientation of the slidable coupling and the lever arm the same throughout the excursion of the lever arm for all force loadings.

Description:
BACKGROUND OF THE INVENTION AND PRIOR ART 
   The present invention relates generally to loading devices that connect to a handle or other user manipulated apparatus on an exercise machine. A wide variety of loading devices, including stacks of iron weights, bundles of bow springs, and various spring and lever systems have been used; yet most fail to provide convenient, finite adjustability of the load delivered. In exercise machines having bow springs, for example, the loading is changed by selecting among a few springs of differing resistance, which is somewhat inconvenient and lacks the advantage of the greater number of finite loads provided by spring and lever systems. 
   Lever and spring systems also present problems. Since they generally include a non-adjustable spring, the loading is changed by varying the leverage on the spring. It is difficult to conveniently vary the leverage because of the need to simultaneously change the lengths of two legs of the force triangle, without which the result is either (a) the starting position of the exercise is changed or (b) a change in compression or decompression of the spring is experienced. The latter is a particular problem because of the difficulty in making adjustments under spring loads. 
   One type of prior art device defines one leg of a force triangle as the selected one of a plurality of adjustment positions located along an arc that is equal to the radius of a second leg of the force triangle. With this solution, only a single leg of the force triangle need be changed for loading adjustments. Such an arrangement is shown in U.S. Pat. No. 3,638,941, issued Feb. 1, 1972 to Kulkens, where a coil tension spring is used to provide resistive load to the user. A coil tension spring is, however, generally undesirable because of its high spring rate that results in a rapid increase in loading through the exercise stroke. To reduce the effects of high spring rate, Kulkens preloads the spring in its rest (unactuated) position. But when in the rest position the tension of the preloaded spring forces the exercise arm against a stop and adjustment of the lever arm is still difficult and inconvenient. 
   U.S. Pat. No. 4,426,077, issued Jan. 17, 1984 to Becker discloses an exercise device that also includes a plurality of adjustment points located along an arc with a radius equal to the length of a preloaded spring leg of the force triangle. Becker addresses the preloaded spring adjustment problem by either (a) locking the spring in a partly extended state and moving the unloaded spring eye between adjustment points or (b) latching the rigid lever arm in a fixed position, and moving the loaded spring eye, via a roller, over the adjustment points. When the desired adjustment point is reached, Becker then either unlocks the spring or retracts the lever arm latch, as the case may be. The method is somewhat inconvenient in that the spring must be locked (or the lever arm latched) while the user is partially through an exercise stroke. Becker does describe a remote cable-actuated latching mechanism for reducing some of the inconvenience. 
   U.S. Pat. No. 4,684,125, issued Aug. 4, 1987 to Lantz shows a pair of parallelly aligned adjustment plates, each including an arcuately disposed pattern of mating adjustment holes, and a gas compression spring, the extended length of which comprises one leg of the force triangle. A removable pin couples the eye of the compression spring to the selected pair of adjustment holes. The lever arm, which would otherwise collapse when the pin is removed, must be supported by the user during load changes. The eye of the compression spring must also be visually aligned by the user with the desired pair of holes in the adjustment plates. When the pin is inserted through the selected hole pair, the lever arm is again supported by the compression spring. The task of simultaneously supporting the lever arm, aligning the compression spring eye, and inserting the pin is inconvenient, at best and difficult, at worst. 
   OBJECTS OF THE INVENTION 
   A principle object of the invention is to provide a novel loading device for an exercise machine. 
   Another object of the invention is to provide an improved loading device that is readily adjustable for providing different loading for the user. 
   A further object of the invention is to provide an exercise machine with an improved loading device. 
   A feature of the invention resides in the inclusion of a force triangle in which the variable lever arm and spring are self-supported at all times. 
   Another feature of the invention resides in a coupling mechanism for the variable lever arm and spring that is captivated, yet readily movable for changing the loading. 
   A further feature of the invention enhances smooth quiet operation of the exercise machine by slightly preloading the coupling mechanism in one direction on the lever arm. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the invention will be apparent upon reading the following description in conjunction with the drawings in which: 
       FIG. 1  illustrates the elements of the inventive loading device; 
       FIG. 2  is a front view of an exercise machine incorporating the inventive loading device; 
       FIG. 3  is a enlarged view of the left side coupling mechanism of  FIG. 2 ; 
       FIG. 4  is right elevation of the coupling mechanism of  FIG. 3 ; and 
       FIG. 5  is a sectional view taken along line  5 - 5  of  FIG. 4 ; 
   

   SUMMARY OF THE INVENTION 
   The present invention comprises a loading device, having a plurality of finite load adjustment points, that includes an adjustable arrangement of a compression spring and a lever arm. The compression spring and the selected portion of the lever arm comprise two legs of a force triangle, with a slidable coupling interconnecting the compression spring and lever arm at any of the plurality of adjustment points. The proximal ends of both the compression spring and lever arm are pivotally mounted on a rigid member, with the distance between the two pivots forming the third leg of the force triangle. The compression spring in the preferred embodiment of the invention is a nitrogen gas cylinder, chosen for its high resistance, flat spring rate and rigid construction. With the inventive arrangement, the lever arm and compression spring are self-supported and the slidable coupling is captivated at all times. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  of the drawings generally illustrates the basic elements of the invention. While it will be noted that  FIG. 1  resembles the right side loading device arrangement of the exercise machine shown in  FIG. 2 , it should be appreciated that the loading device of the invention is applicable to all types of exercise machines where a finite variable load is to be conveniently delivered to a user. The invention comprises a rigid Frame on which are mounted a Pivot A and a Pivot B. A Compression Spring is coupled at its proximal end to Pivot A and at its distal end to a Pivot C that is connected to a Slidable Coupling which is movable to different discrete positions along a lever arm. The proximal end of the lever arm is connected to Pivot A and its distal end carries a First Pulley. A Second Pulley is connected to the Frame and a Cable is attached to the Frame and passes over the First and Second Pulleys to Exercise Equipment (not shown). A first leg of a force triangle is defined by the fixed distance between Pivot A and Pivot B, a second leg of the force triangle is defined by the distance between the Pivot B and the adjustment point selected by the Slidable Coupling, and the third leg is defined by the length of the Compression Spring. The ratio of the distance between Pivot B and Pivot C and the fixed distance between Pivot B and the First Pulley determines the leverage or mechanical advantage of the system. As will be described in further detail below, the construction of the Slidable Coupling and its arrangement on the Lever Arm enables the application of extremely low loading forces to the Exercise Equipment and provides a self-supporting system that requires a minimum of dexterity for effecting changes in loading. 
   Referring to  FIG. 2 , implementation of the invention in a common cable type of exercise machine  10  is illustrated. Exercise machine  10  generally comprises a plurality of tubing sections that are securely affixed to each other, preferably by welding, and includes a pair of foot members  12  and  13 , and a pair of generally vertical upright members  14  and  15 . Foot member  12  is welded to outwardly flared lower sections of upright members  14  and  15 . A lower support member  16  is secured to upright members  14  and  15  and a pair of upper supports are defined by outwardly flared extensions  14   a  and  15   a  of upright members  14  and  15 . These extensions support upper pulleys  72  and  73  (and cables, not shown) for performing certain exercises. A short, spaced, horizontal support  19  is welded between upright members  14  and  15  and a vertical piece  18  is secured between support member  16  and another horizontally extending base member (hidden by foot member  13 ). A seat  20  is supported on horizontally extending portions  21  and  22  affixed to vertical piece  18  at their rearward ends and to a vertical post  24  at their forward ends. The bottom of vertical post  24  is welded to foot member  13 . It should be understood that the general configuration of the exercise machine is well known in the art and is used with various commercialized exercise machines that permit a user to perform different exercises with loads provided by weights, bow springs or other resistance systems. In the present invention, a pair of the loading devices described in  FIG. 1  is used to provide different loads to a user. 
   A left lever arm  30  and a right lever arm  31  are pivotally secured at their proximal ends to upright members  14  and  15  at pivots  32  and  33 , respectively. The lever arms  30  and  31  are also of rigid tubular construction and have pulleys  34  and  35 , respectively, mounted at their distal ends. It will be appreciated that considerable forces are experienced during use of the exercise apparatus and that construction of the members must be substantial. Preferably, the pivots  32  and  33  comprise steel bushings that are welded to the proximal ends of lever arms  30  and  31 , respectively. 
   Two compression gas springs  36  and  37  have their proximal ends secured to support member  16  at pivots  38  and  39 , respectively, and are coupled at their distal ends to lever arms  30  and  31  by slidable coupling mechanisms  50  and  51 , respectively. A left side cable  40  is secured to the left portion of support member  16 , trained over pulley  34 , passed through a lower pulley  70  that is also secured to the left portion of support member  16  and coupled, via a quick connect coupling  48 , to a user handle  44 . A right side cable  41  is similarly configured with respect to the right portion of support member  16 , pulleys  35  and  71 , quick connect coupling  49  and user handle  45 . The lever arms are formed in arcs that match the radii of the free lengths of the compression springs. A series of holes  42  and  43  is formed along each of the upper surfaces of lever arm  30  and lever arm  31  to establish pluralities of load adjustment points, respectively. 
   For certain types of exercises the upper pulleys  72  and  73  may be required. In that event a supplemental pair of cables (not shown) having quick connect couplings similar to quick connect couplings  48  and  49  would be passed through pulleys  72  and  73 . The user handles  44  and  45  would be removed from the ends of cables  40  and  41  and secured to the supplemental cables, the other ends of which would be attached to quick connect couplings  48  and  49 . A pair of stop elements  46  and  47  on cables  40  and  41  keep the cables under slight tension when the exercise machine is not being used, which facilitates the interchanges of cables and handles, as described. Lower pulleys  70  and  71  are preferably nearly tangent to the distal end of lever arms  30  and  31 , respectively, at the ends of the full excursions or strokes of the lever arms. 
   Referring to  FIGS. 3-5 , left side slidable coupling  50  comprises a generally triangular-shaped body  52  formed from mating portions  52   a  and  52   b  that are secured together by four bolts  60 - 63 . Matching semi-cylindrical openings  52   c  and  52   d  are formed in mating portions  52   a  and  52   b , respectively and are sized to permit body  52  to be readily movable along curved lever arm  30 . To facilitate such movement the ends of the openings that are formed in the mating portions are rounded, as indicated by reference character  53 , resulting in smooth bearing surfaces at points A and B. The slidable coupling body  52  is preferably molded of a durable plastic material. The bottom apices  52   e  and  52   f  of mating portions  52   a  and  52   b , respectively, have extensions that form a clevis for securing an eye  36   a  on the end of compression spring  36 , by means of an axle pin  64 . A ball-shaped handle  54  is provided for disengaging a spring-loaded plunger or pin  54   a , that passes through a pin aperture  52   g  formed in mating portions  52   a  and  52   b , and that is selectively engageable with the holes  42  that define the adjustment points along lever arm  30 . Pin  54   a  is biased toward engagement with lever arm  30  by a compression spring  54   b  that is captivated in a cylindrical recess  54   c  formed in mating portions  52   a  and  52   b . Pin  54   a  has an integral flange  54   d  that engages the bottom of compression spring  54   b . Pin  54   a  has a rounded end to facilitate engagement with the holes  42  in lever arm  30 . Weight markings or indicia  58  are provided on lever arm  30  to denote the loadings that correspond to the adjustment points. A viewing aperture  52   h  is formed in slidable coupling body  52  to indicate to the user the selected loading of the exercise machine. 
   Operation will be described in connection with the left side of exercise machine  10 , it being understood that a similar operation is applicable to the right side. A user selects the weight or desired loading of the exercise machine by pulling upwardly on ball handle  54 , thereby withdrawing pin  54   a  sufficiently from its associated one of holes  42  in lever arm  30  to enable slidable coupling body  52  to be moved along lever arm  30  to the desired adjustment point. When handle  54  is released, pin  54   a  engages the hole  42  corresponding to the selected adjustment point. Alignment of pin  54   a  with the holes  42  at the adjustment points along lever arm  30  is facilitated by visually aligning the viewing aperture  52   h  and weight markings  58 . Thus load changing is straightforward and readily accomplished since compression spring  36  is fully extended and acting only to support the weight of lever arm  30  (and the slight tension load of cable  40 ) and since slidable coupling body  52  is secured to compression spring  36  and captivated on lever arm  30 . It will be appreciated that the initial compression force of the compression spring in relation to the position of the adjustment point that is closest to upright member  14  and to the weight of the lever arm is chosen such that, under idle or conditions of no use, i.e., with no force being applied to cable  40  by the user, compression spring  36  supports the weight of the lever arm to maintain the integrity of the arrangement. Thus, in the preferred embodiment of the invention there is no need for the user to hold any of the parts to keep them from falling because none of the components of the force triangle are loose. 
   With particular reference to  FIG. 5 , it should be noted that a distance “D” is established between bearing surface B on slidable coupling body  52  and axle pin  64 , the attachment point of compression spring  36 . The arrangement effectively imparts a slight torque to slidable coupling body  52  which forces its surfaces A and B into engagement with lever arm  30 . It should also be appreciated that this relationship is maintained throughout the excursion of the lever arm, irrespective of the load setting. With it, the clearances necessary to enable the sliding coupling to be readily movable along the slightly curved lever arm do not result in any annoying clicks or similar noises resulting from the slidable coupling body rocking on the lever arm during excursions of the lever arm. 
   Another important aspect of the invention, specifically the described arrangement for imparting a slight torque to the slidable coupling body  52 , is that the position of axle pin  64  may be chosen to be at the extreme inboard end of the slidable coupling body  52  thus allowing the axle pin  64  of the compression spring to be brought very close to its corresponding upper pivot. The arrangement permits very small loadings (about five pounds) for the user, which is a significant benefit in that many users want or can only perform certain exercises with such small loadings. 
   What has been described is a novel loading device for an exercise machine that uses force triangles in which resistive load changes may be readily accomplished without requiring manual dexterity on the part of the user nor an interruption of an exercise routine. It should be appreciated by those skilled in the art that while use of the invention has been described in connection with a specific form of exercise machine, the invention is applicable to many types of exercise apparatus. For example, practice of the invention does not require the use of two lever arms and the invention is to be limited only as defined in the claims.