Abstract:
An adjustable dumbbell assembly of the type including two sets of weights, each including a radial opening extending from a central area to a peripheral area and at least one transversely extending opening in the central area communicating with said radial opening, and a weight supporting assembly operable to selectively connect and disconnect the two sets of weights thereto on opposite sides of a centrally located handle. The weight supporting assembly on each side includes a fixed weight supporting structure, movable weight selector structure, and manually turnable actuating structure. The structures are interrelated with respect to one another, so that when the fixed structure is in an operative position with respect to the weights, manually turning the actuating structure in one direction moves the selector structure in one direction and manually turning the actuating structure in an opposite direction moves the selector structure in the opposite direction.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application No. 11/350,169 filed Feb. 8, 2006, hereby incorporated by reference in its entirety, and for which priority is claimed, and this application further claims priority from Chinese Patent Application 200620157998.7, filed Nov. 17, 2006, also incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to exercise equipment, more particularly to an adjustable dumbbell.  
         [0004]     2. Description of the Related Art  
         [0005]     Referring to  FIGS. 1 and 2 , a conventional adjustable dumbbell  10 , as disclosed in U.S. Pat. No. 6,656,093 (see also U.S. Patent Application Publication No. 2004/0005969), includes a base  11  for supporting a plurality of weights  12 , a hollow handle  13 , two latches  14 , and two adjustable units  15 .  
         [0006]     Each of the weights  12  includes a lateral channel  121 , and a vertical groove  122  communicating with the lateral channel  121 . The lateral channel  121  has a width greater than that of the vertical groove  122 .  
         [0007]     The hollow handle  13  has two blocks  132  provided respectively on two opposite ends thereof for engaging the vertical grooves  122  of the weights  12 , and two conduits  133  laterally and respectively formed in the middle portions of the blocks  132 . Each of the blocks  132  includes a passage  135  communicating with the respective conduit  133 , and a plurality of spaced-apart apertures  134  communicating with the passage  135 . Each of the apertures  134  has a diameter greater than the width of the passage  135 .  
         [0008]     Each of the latches  14  is inserted slidably into one of the blocks  132  via the corresponding conduit  133 , and has a screw hole  141 .  
         [0009]     Each of the adjustable units  15  is provided at each end of the hollow handle  13 , and includes a barrel  151  having a catch  152  provided in a bottom portion thereof for insertion into one of the apertures  134  in the corresponding block  132 , a spring  153  disposed in the barrel  151  for biasing the catch  152  to engage one of the apertures  134  and for selectively or adjustably securing the latches  14  to the respective blocks  132 , and a bolt  154  passing through the barrel  151  to engage threadedly the screw hole  141  in the corresponding latch  14 . The bolt  154  is limited to slide and move along the passage  135  of the corresponding block  132  so that each latch  14  may also be limited to move and slide relative to the respective block  132 .  
         [0010]     In operation, when the catch  152  of the barrel  151  of each adjustable unit  15  is disengaged from the corresponding aperture  134  by pulling the barrel  151 . away from the corresponding block  132  against the spring  153 , each latch  14  may be moved and adjusted relative to the corresponding block  132 . When each latch  14  is moved to engage the lateral channels  121  of all of the weights  12  on one end of the hollow handle  13 , these weights  20  are secured to the corresponding block  132 . The number of the weights  12  at each end of the hollow handle  13  can be adjusted by simply moving the latches  14  relative to the blocks  132 , respectively.  
         [0011]     In the aforementioned conventional adjustable dumbbell  10 , the two adjustable units  15  are operated separately, and the catches  152  of the barrels  151  have to accurately spring back into the corresponding apertures  134  in the blocks  132  when the barrels  151  are released by the user.  
         [0012]     Referring to  FIGS. 3 and 4 , another conventional adjustable dumbbell  20  includes a plurality of weights  22  provided on each end of a hollow handle  21 , and two adjustable units  23 . The user operates the two adjustable units  23  to balance the number of the weights  22  at each end of the hollow handle  21 .  
       SUMMARY OF THE INVENTION  
       [0013]     One aspect of the present invention provides an adjustable dumbbell assembly including two sets of weights, each including a radial opening extending from a central area to a peripheral area and at least one transversely extending opening in the central area communicating with the radial opening, and a weight supporting assembly operable to selectively connect and disconnect the two sets of weights thereto on opposite sides of a centrally located handle.  
         [0014]     The weight supporting assembly on each side includes a fixed weight supporting structure, movable weight selector structure, and manually turnable actuating structure. The fixed weight supporting structure is configured and positioned to enter within the radial openings of the weights and into an operative position with respect thereto. The movable weight selector structure is configured and positioned to enter axially in one direction into the at least one transverse opening of the selected weights when the fixed structure is in the operative position thereof with respect to the weights and to withdraw axially in an opposite direction out of the at least one transverse opening of selected weights when the fixed structure is in an operative position with respect to the weights. The manually turnable structure is positioned and configured to be manually grasped at the end of the side and turned in opposite directions about an axially extending turning axis. The structures are interrelated with respect to one another so that when the fixed structure is in an operative position with respect to the weights manually turning the actuating structure in one direction moves the selector structure in one direction and manually turning the actuating structure in an opposite direction moves the selector structure in the opposite direction.  
         [0015]     According to another aspect of this invention, there is provided an adjustable dumbbell comprises a hollow handle having a connecting end and an adjustable weight supporting assembly including a screw rod extending into the hollow handle and operable to rotate relative to the hollow handle about a rotation axis, and a weight selector extending into the hollow handle and engaging threadedly the screw rod so as to be movable axially upon rotation of the screw rod about the rotation axis, the weight selector having a weight-supporting part extending outwardly through the connecting end of the hollow handle; and a plurality of weights, each of which is formed with an elongated radial opening having an enlarged central portion for extension of the weight-supporting part of the weight selector therethrough. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:  
         [0017]      FIG. 1  is a perspective view of a conventional adjustable dumbbell disclosed in U.S. Pat. No. 6,656,093;  
         [0018]      FIG. 2  is a partly exploded perspective view of the conventional adjustable dumbbell of  FIG. 1 ;  
         [0019]      FIG. 3  is a schematic front view of another conventional adjustable dumbbell;  
         [0020]      FIG. 4  is a schematic top view of the conventional adjustable dumbbell of  FIG. 3 ;  
         [0021]      FIG. 5  is a schematic partly sectional side view of the first embodiment of an adjustable dumbbell according to the present invention;  
         [0022]      FIG. 6  is a fragmentary exploded perspective view of the first embodiment;  
         [0023]      FIG. 7  is an exploded perspective view of an adjustment knob unit of the first embodiment;  
         [0024]      FIG. 8  is a fragmentary sectional view of the adjustment knob unit of the first embodiment in an assembled state;  
         [0025]      FIG. 9  is a partly exploded perspective view of the first embodiment, illustrating how a tube can engage engaging hole sections of a plurality of weights;  
         [0026]      FIG. 10  is a sectional view of the first embodiment in an assembled state;  
         [0027]      FIG. 11  is a view similar to  FIG. 10 , but with two tubes in another position;  
         [0028]      FIG. 12  is a sectional front view of the first embodiment, illustrating each tube supporting three weights;  
         [0029]      FIG. 13  is a view similar to  FIG. 10 , but with the tubes in still another position;  
         [0030]      FIG. 14  is a view similar to  FIG. 12 , but with each tube supporting two weights;  
         [0031]      FIG. 15  is a schematic partly sectional side view of a second embodiment of an adjustable dumbbell embodying the principles of the present invention;  
         [0032]      FIG. 16  is a top plan view of the second embodiment;  
         [0033]      FIG. 17  is an exploded perspective view of the second embodiment;  
         [0034]      FIG. 18  is an exploded perspective view to illustrate the configuration of a turn-indicating unit of the second embodiment;  
         [0035]      FIG. 19  is a fragmentary sectional view of the turn-indicating unit of the second embodiment;  
         [0036]      FIG. 20  is an exploded perspective view to illustrate the adjustable dumbbell of the second embodiment;  
         [0037]      FIG. 21  is a sectional view to illustrate the adjustable dumbbell of the second embodiment wherein the weight selector structure is moved to a position for supporting one of a plurality of weights of the second embodiment;  
         [0038]      FIG. 22  is a sectional view to illustrate another condition of the adjustable dumbbell wherein the weight selector structure is moved to another position for supporting three of the weights of the second embodiment;  
         [0039]      FIG. 23  is a sectional view to illustrate a condition of the adjustable dumbbell wherein the weight selector structure lifts three of the weights from a mounting seat base or of the second embodiment;  
         [0040]      FIG. 24  is a sectional view to illustrate yet another condition of the adjustable dumbbell wherein the weight selector structure is moved to yet another position for carrying two of the weights of the second embodiment; and  
         [0041]      FIG. 25  is a sectional view to illustrate another condition of the adjustable dumbbell wherein the weight selector structure lifts two of the weights from the mounting base or seat of the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0042]     Referring to FIGS.  5  to  10 , a first embodiment of an adjustable dumbbell according to the present invention is best shown in exploded view of  FIG. 6  to comprise a shaft or screw rod  30 , two selector tubes or weight carriers  41 ,  42 , a hollow handle in the form of a hollow grip bar or tube  50 , two first covers or inner fastening members  60 , two support units or limiting member seats  70 , two adjustment knob units or operating caps  90 , two sets of weights  100 , and a base or mounting seat  110  (see  FIG. 5 ).  
         [0043]     The hollow handle  50 , the fastening members  60  and the two support units  70  constitute fixed weight supporting structure for supporting the two sets of weights  100  on opposite sides of a central handle provided by the hollow handle  50 . The two selector tubes  41  and  42  constitute movable weight selector structure for selectively connecting and disconnecting a selected number of weights  100  to the fixed weight supporting structure  50 ,  60  and  70 . The shaft  30  and the two adjustment knob units  90  constitute manually turnable actuating structure for moving the weight selector structure  41 - 42 . The fixed weight supporting structure  50 ,  60  and  70 , the movable weight selector structure  41  and  42  and the manually turnable actuating structure  30  and  90  constitute together an adjustable weight supporting assembly which cooperates with the two sets of weights  100  to allow a user to selectively connect to the weight supporting assembly a selected number of weights  100  supported on the base  110  while leaving those not selected supported on the base  110 .  
         [0044]     The shaft  30  includes two opposite connecting ends  32 , an intermediate portion  31  between the connecting ends  32 , two shoulder portions  33  each defined between the intermediate portion  31  and the corresponding connecting end  32 , left- and right-handed threads  34 ,  35  that are formed on the intermediate portion  31  and that are axially spaced apart from each other, two screw holes  36  formed, respectively, in the connecting ends  32 , and two eccentric projections  37  projecting axially, outwardly, and respectively from end faces of the connecting ends  32 . The intermediate portion  31  has a diameter larger than those of the connecting ends  32 .  
         [0045]     The selector tubes  41 ,  42  are sleeved around and engage threadedly and respectively the left- and right-handed threads  34 ,  35  of the shaft  30 . The selector tube  41  includes inner and outer peripheral faces  411 ,  412 , and a threaded portion  413  (see  FIG. 9 ) formed in the inner face  411  and engageable with the left-handed thread  34  of the shaft  30 . The selector tube  42  includes inner and outer faces  421 ,  422 , and a threaded portion  423  formed in the inner face  421  and engageable with the right-handed thread  35  of the shaft  30 . Each of the selector tubes  41 ,  42  further includes two diametrically opposed guide pins  43 ,  44  projecting outwardly from the outer face  412 ,  422  of the corresponding tube  41 ,  42 .  
         [0046]     The handle  50  is sleeved on the outer faces  412 ,  422  of the tubes  41 ,  42 , and has two opposite engaging portions  51 , in the form of discs  51 , at two opposite ends thereof respectively.  
         [0047]     The fastening members  60  are sleeved slidably and respectively on the selector tubes  41 ,  42 , and are connected respectively to the engaging portions  51  of the grip rod  50 . Each of the first fastening members  60  includes inner and outer faces  61 ,  62 , a central hole  63  extending axially through the inner and outer faces  61 ,  62 , two diametrically opposed notches  64  extending axially through the inner and outer faces  61 ,  62  and in spatial communication with the central hole  63 , four angularly spaced-apart screw holes  65  extending axially through the inner and outer faces  61 ,  62  and disposed around the central hole  63 , and two diametrically opposed screw holes  66  extending axially through the inner and outer faces  61 ,  62  and aligning with the notches  64 .  
         [0048]     In assembly, each fastening member  60  is sleeved on the corresponding selector tube  41 ,  42  via the central hole  63  such that the inner face  61  abuts against the corresponding engaging portion  51  of the handle  50 . During this operation, the guide pins  43 ,  44  of each selector tube  41 ,  42  extend through the corresponding fastening member  60  via the notches  64 . Four bolts  67  are passed respectively through the screw holes  65  so as to engage threadedly the corresponding engaging portion  51  of the handle  50 , thereby securing each fastening member  60  to the corresponding engaging portion  51  of the handle  50 .  
         [0049]     Each of the support units  70  has upper and lower support seats  71  disposed above and below one of the selector tubes  41 ,  42 . The upper and lower support seats  71  of each support unit  70  include inner end faces  72  respectively connected to and facing the outer face  62  of the corresponding first cover  60 , outer end faces  73  opposite to the inner end faces  72 , intermediate sections  74  interconnecting the inner and outer end faces  72 ,  73  and provided with a plurality of spaced-apart spacers  76 , and guide grooves  75  extending axially from the inner end face  72  to the outer end face  73 .  
         [0050]     The guide pins  43 ,  44  of each tube  41 ,  42  are received slidably and respectively in the guide grooves  75  of the upper and lower support seats  71  of the corresponding support unit  70  so that axial movement of the tubes  41 ,  42  relative to the shaft  30  is limited, and rotation of the selector tubes  41 ,  42  relative to the shaft  30  is prevented. It should be noted that when the locations of the guide pins  43 ,  44  and the guide grooves  75  are interchanged, the same result is achieved.  
         [0051]     In this embodiment, five spaced-apart spacers  76  are provided on the intermediate sections  74  of the upper and lower support seats  71  of each support unit  70  for supporting four pieces of weights  100 . The distance between two adjacent ones of the spacers  76  is equal to one pitch of the left- and right-handed threads  34 ,  35  of the shaft  30 . Thus, when the shaft  30  is turned one revolution, i.e., 360°, the selector tubes  41 ,  42  move simultaneously in opposite directions one pitch towards or away the connecting ends  32  of the shaft  30 .  
         [0052]     During assembly, after the inner end faces  72  of the upper and lower support seats  71  of each support unit  70  are caused to abut against the outer face  62  of the corresponding fastening member  60 , two bolts  77  are passed respectively through the screw holes  66  so as to engage threadedly and respectively the inner end faces  72  of the upper and lower support seats  71 , thereby fastening each support unit  70  to the corresponding fastening member  60 .  
         [0053]     With reference to  FIGS. 6, 7 ,  8 , and  10 , the adjustment knob units  90  are respectively connected to the connecting ends  32  of the shaft  30  to allow the user to turn the shaft  30  relative to the handle  50  and to thereby move the selector tubes  41 ,  42  axially of the shaft  30  in opposite directions towards or away from the connecting ends  32  of the shaft  30 . Each of the adjustment knob units  90  includes a second cover or outer fastening member  80  and a cap  91 . The outer fastening member  80  is sleeved on one of the connecting ends  32  of the shaft  30 , and includes opposite inner and outer faces  81 ,  82 , an outer peripheral face  83  interconnecting the inner and outer faces  81 ,  82 , two diametrically opposed cutout portions  84  (see  FIG. 7 ) formed in the inner face  81  for receiving respectively the outer end faces  73  of the upper and lower support seats  71  of the corresponding support unit  70 , a through hole  85  extending axially through the inner and outer faces  81 ,  82  and disposed between the cutout portions  84  for insertion of the corresponding connecting end  32  of the shaft  30  therethrough, two diametrically opposed screw holes  86  extending axially through the inner and outer faces  81 ,  82  and communicating with the respective cutout portions  84 , and a positioning hole  87  formed in the outer face  82  and radially offset from the shaft  30 .  
         [0054]     After the outer fastening member  80  of each adjustment knob unit  90  is sleeved on the corresponding connecting end  32  of the shaft  30  via the through hole  85  until the inner face  81  abuts against the outer end faces  73  of the upper and lower support seats  71  of the corresponding support unit  70  and the corresponding shoulder portion  33  of the shaft  30 , two bolts  88  are passed respectively through the screw holes  86  so as to engage threadedly and respectively the outer end faces  73  of the upper and lower support seats  71  of the corresponding support unit  70 , thereby fastening the outer fastening member  80  to the upper and lower support seats  71  of the corresponding support unit  70 .  
         [0055]     The cap  91  is sleeved rotatably on the outer fastening member  80 , and includes a plate section  912 , an annular sleeve  913  that extends axially, inwardly, and integrally from an outer periphery of the plate section  912  and that is sleeved on the outer peripheral face  83  of the outer fastening member  80 , a tubular protrusion  914  projecting axially and inwardly from the center of the plate section  912 , an eccentric socket  915  projecting axially and inwardly from the plate section  912 , a central hole  916  formed in the plate section  912  and communicating with the tubular protrusion  914 , and a slot  917  formed in the tubular protrusion  914  adjacent to the through hole  916  for receiving the corresponding eccentric projection  37  of the shaft  30 .  
         [0056]     The cap  91  further includes a spring-loaded detent which has a compression spring  92  disposed in the socket  915 , and a roller  93  biased by the spring  92  to engage resiliently the positioning hole  87 . The roller  93  has a diameter larger than that of the positioning hole  87  so that the roller  93  can be easily removed from the positioning hole  87 .  
         [0057]     After the cap  91  is sleeved on the outer fastening member  80 , a bolt  94  is passed through the central hole  916  to engage the screw hole  36  in the corresponding connecting end  32  of the shaft  30 , so that the cap  91  and the outer fastening member  80  are secured to the shaft  30 .  
         [0058]     It should be noted that when one of the projections  37  of the shaft  30  is inserted into the slot  917  in the cap  91 , the roller  93  projects into the positioning hole  87  so as to enhance alignment and assembly.  
         [0059]     There are four of the weights  100  in each set thereof. Each of the weights  100  includes a straddling hole that has an engaging hole section  101  engageable with the corresponding selector tube  41 ,  42 , a long hole section  103  extending radially and outwardly from the engaging hole section  101  and through an outer peripheral face  102  of the weight  100 , and a short hole section  104  extending radially and outwardly from the engaging hole section  101  opposite to the long hole section  103 . Each of the long and short hole sections  103 ,  104  constitute a radial opening or hole which extends from a central area of each weight  100  to a peripheral area thereof and has a width smaller than a width of the engaging hole section  101 . The engaging hole section  101  constitutes at least one and preferably two opposed transversely extending openings or holes which communicate with the radial opening or hole defined by the hole sections  103 ,  104 . Through the presence of the long and short hole sections  103 ,  104 , each set of the weights  100  can be straddled on the upper and lower support seats  71  of one of the support units  70 . At this time, the weights  100  in each set are spaced apart from each other by the spacers  76 . Each of the weights  100  is prevented from moving axially by two adjacent ones of the spacers  76  of the upper and lower support seats  71 . Each of the selector tubes  41 ,  42  is movable between the upper and lower seats  71  of one of the support units  70  enabling the cylindrical exterior surface thereof to selectively engage the surfaces defining one or more of the engaging hole sections  101  of the weights  100 .  
         [0060]     The base  110  (see  FIG. 5 ) includes a plurality of spaced-apart retainers  112  projecting upwardly and integrally from a top face  111  thereof. The distance between two adjacent ones of the retainers  112  is equal to the distance between two adjacent ones of the spacers  76 . Each two adjacent ones of the retainers  112  cooperate with the top face  111  to define a receiving space  113  for receiving a corresponding one of the weights  100 .  
         [0061]     Each weight  100  is typically received in the corresponding receiving space  113  in the base  110  with the long hole section  103  facing upwardly, and the roller  93  is projected into the positioning hole  87  (see  FIG. 8 ). When the user desires to adjust the weight of the dumbbell of the present invention, he/she simply rotates the cap  91  of one of the adjustment knob units  90 .  
         [0062]     Referring to  FIG. 10 , if each selector tube  41 ,  42  is engaged to the engaging hole section  101  of only one of the weights  100  in each set, when the user grasps and lifts the handle  50  of the dumbbell, only one of the weights  100  in each set is carried away by the corresponding support unit  70 . The rest of the weights  100  remain on the base  110 .  
         [0063]     Referring to  FIGS. 11 and 12 , in combination with  FIG. 10 , to increase the number of the weights  100  on each side of the dumbbell of the present invention, the cap  91  of one of the adjustment knob units  90  is rotated in a clockwise direction. As an example, the cap  91  of one of the adjustment knob units  90  may be rotated clockwise two turns, so as to similarly rotate the shaft  30  two turns in the clockwise direction. This will result in each selector tube  41 ,  42  moving simultaneously two pitches toward the respective connecting ends  32  of the shaft  30  and thereby engaging the engaging hole sections  101  of three of the weights  100  in each set. Hence, when the user grasps and lifts the handle  50  of the dumbbell of the present invention, three of the weights  100  in each set are carried away by the corresponding support unit  70 , while the other weights  100  are left remaining on the base  110 .  
         [0064]     Referring to  FIGS. 13 and 14 , in combination with  FIG. 11 , to reduce the number of weights  100  on each side of the dumbbell of the present invention, the cap  91  of one of the adjustment knob units  90  is rotated in a counterclockwise direction. For example, if the cap  91  of one of the adjustment knob units  90  is rotated by one turn, the shaft  30  is similarly rotated one turn also in the counterclockwise direction. This will result in each selector tube  41 ,  42  moving simultaneously one pitch toward the handle  50  and away from the respective connecting ends  32  of the shaft  30 , thereby engaging the engaging hole sections  101  of two of the weights  100  in each set. Hence, when the user grasps and lifts the handle  50  of the dumbbell of the present invention, only two of the weights  100  in each set are carried away by the corresponding support unit  70 , while the other weights  100  are left remaining on the base  110 .  
         [0065]     It should be noted that during rotation of the cap  91 , the roller  93  is moved away from the positioning hole  87 , and abuts against the outer face  82  of the second cover  80 , thereby compressing the spring  92 . After the cap  91  has turned one revolution, the roller  93  is pushed by the restoring force of the spring  92  to extend back into the positioning hole  87 . This returning of the roller  93  back into the positioning hole  87  may be perceived by the user to thereby let the user know that the cap  91  has turned one revolution, and the number of the weights  100  on each side of the dumbbell of the present invention has been reduced or increased by one.  
         [0066]     From the aforementioned description, the advantages of the adjustable dumbbell of the present invention may be summarized as follows:  
         [0067]     1. Rotation of the cap  91  of one of the adjustment knob units  90  can permit each selector tube  41 ,  42  to move toward or away from the corresponding connecting end  32  of the shaft  30  so as to selectively engage one or more of the engaging hole sections  101  of the weights  100 . Hence, the weight on each side of the dumbbell of the present invention can be adjusted easily and quickly.  
         [0068]     2. Through coordination of the positioning hole  87  in the outer fastening member  80  and the spring-loaded detent of the cap  91 , the user is able to sensually perceive the number of turns the cap  91  has rotated and therefore the number of the weights  100  supported by each support unit  70 .  
         [0069]     Referring now more particularly to  FIGS. 15-24 , there is shown therein a second embodiment of an adjustable dumbbell having an adjustable weight supporting assembly similar to the weight supporting assembly previously described in which similar parts are designated by the same number with an added prime. As before, the weight supporting assembly operates with the two sets of weights  100 ′ to allow a user to selectively connect a selected number of weights  100 ′ supported on the base or mounting seat  110 ′ while leaving those not selected supported on the base  110 ′. The weights  100 ′ and base  110 ′ are constructed exactly in accordance with the weights  100  and base  110  previously described and hence no detailed description of the weights  100 ′ and base  110 ′ is believed necessary.  
         [0070]     The adjustable weight supporting assembly does differ but includes the basics as before: (1) a fixed weight supporting structure including a central handle  50 ′, two first covers or fastening members  60 ′ and two support units or limiting member seats  70 ′ for supporting the two sets of weights  100 ′ on opposite sides of the handle  50 ′, (2) a weight selector structure or weight carrier in the form of two selector tubes  41 ′ and  42 ′, and (3) a manually turnable actuating structure in the form of two adjustment knob units or operating caps  90 ′ and two shafts or screw rods  30 ′.  
         [0071]     The provision of two shafts  30 ′ rather than the single shaft  30  of the first embodiment constitutes a first of two differences between the two embodiments. The first difference translates into a difference in operation. In the first embodiment, either one of the two adjustment knobs  90  could be used to simultaneously move both movable selector tubes  41  and  42 , whereas in the second embodiment, one of the two adjustment knob units  90 ′ must be used to move the movable selector tubes  41 ′ or  42 ′ threadedly connected thereto, while the other one of the two adjustment knob units  90 ′ must be used to move the other of the movable selector tubes  41 ′ or  42 ′.  
         [0072]     The second difference is a selector viewing feature which is included in the second embodiment which is not present in the first embodiment, but could readily be embodied in the first embodiment. As best shown in  FIGS. 16 and 17 , each movable selector tubes  41 ′ and  42 ′ includes an upwardly facing planar surface  510  having weight scale marks or indicia  512  thereon corresponding to the numbers and values of the weights  100 ′. The hollow handle  50 ′ has an upwardly facing window opening  514  at each end thereof and the engaging portions  51 ′ fixed at each end of the handle  50 ′ have aligned window openings  516  therein. Preferably, a sight glass  518  is mounted in each window opening  516 .  
         [0073]     As best shown in  FIG. 16 , the sight glass  518  at each end of the handle  50 ′ is easily viewed by the user from above when the adjustable weight supporting assembly has been moved into cooperating relation with the two sets of weights  100 ′ supported in operative positions on the base  110 ′. The user can readily reach down and turn the adjustment knob unit  90 ′ on each side of the adjustable weight supporting assembly while viewing the associated sight glass  518 . to determine the number and combined value of the weights connected to each side. It will be understood that the structure of this viewing feature could be readily incorporated in the first embodiment.  
         [0074]     Except for the two differences included in the second embodiment discussed above, the second embodiment includes most of the structure included in the first embodiment and operates the same except for the operational difference noted.  
         [0075]     Each shaft or screw  30 ′ includes a connecting end  32 ′, having a shoulder portion  33 ′ and exterior right-handed threads  34 ′. A screw hole  36 ′ is formed in the connecting end  32 ′ and two aligned radial slots  37 ′ are formed in the extremity of the connecting end  32 ′.  
         [0076]     The selector tubes  41 ′,  42 ′ are sleeved around and engage threadedly with the right-handed threads  34 ′ of one of the screw rods  30 ′. The selector tube  41 ′ includes inner and outer peripheral surfaces  411 ′,  412 ′, and a threaded portion  413 ′ (see  FIG. 20 ) formed in the inner face  411 ′ and engageable with the right-handed thread  34 ′ of one of the screw rods  30 ′. As best shown in  FIGS. 21, 22  and  24 , the selector tube  42 ′ includes inner and outer faces  421 ′,  422 ′, and a threaded portion  423 ′ formed in the inner face  421 ′ and engageable with the right-handed thread  34 ′ of the other of the screw rods  30 ′. The selector tubes  41 ′,  42 ′ further include two diametrically opposed guide pins  43 ′,  44 ′ respectively projecting outwardly from the outer face thereof.  
         [0077]     The handle  50 ′ is sleeved on the outer faces  412 ′,  422 ′ of the selector tubes  41 ′,  42 ′, and has two opposite engaging portions in the form of sleeves  51 ′ at two opposite ends thereof, respectively. The engaging portions  51 ′ include tubular inner sections  323  fixed to the outer periphery of the handle  50 ′ inwardly of the ends thereof and outwardly flaring outer tubular sections  322  spaced radially from the outer periphery of the handle  50 ′ at the ends thereof.  
         [0078]     Each first cover or fastening member  60 ′ is in the form of a cylindrical ring which fits within the radial space between the inner periphery  301  of the outwardly flaring section  322  of the adjacent engaging portion  51 ′ and the outer periphery of the adjacent end of handle  50 ′. Each fastening ring  60 ′ is secured to the associated end of the handle  50 ′ by any means, such as, annularly spaced bolts  67 ′ (see  FIG. 17 ), extending through the engaging portion  51 ′ and threadedly engaged into the associated fastening ring  60 ′.  
         [0079]     As best shown in  FIG. 17 , each fastening ring  60 ′ is fixed to a pair of axially extending radially spaced support units  70 ′ by any suitable means, such as bolts  77 ′. It is within the contemplation of the present invention that the sleeve engaging portion  51 ′, the fastening member  60 ′, and pair of supporting units  70 ′, could be integrated into a single piece.  
         [0080]     Each of the support units  70 ′ has upper and lower support seats  71 ′ disposed above and below one of the selector tubes  41 ′,  42 ′. The upper and lower support seats  71 ′ of each support unit  70 ′ include inner end faces  72 ′, respectively, connected to and facing the outer face of the corresponding inner fastening member  60 ′, outer end faces  73 ′ opposite to the inner end faces  72 ′, intermediate sections  74 ′ interconnecting the inner and outer end faces  72 ′,  73 ′ and provided with a plurality of spaced-apart spacers  76 ′, and guide grooves  75 ′ extending axially from the inner end face  72 ′ to the outer end face  73 ′.  
         [0081]     The guide pins  43 ′,  44 ′ of each selector tube  41 ′,  42 ′ are received slidably and respectively in the guide grooves  75 ′ of the upper and lower support seats  71 ′ of the corresponding support unit  70 ′ so that axial movement of the selector tubes  41 ′,  42 ′ relative to the screw rod  30 ′ is limited, and rotation of the selector tubes  41 ′,  42 ′ relative to the screw rod  30 ′ is prevented. It should be noted that when the locations of the guide pins  43 ′,  44 ′ and the guide grooves  75 ′ are interchanged, the same result is achieved.  
         [0082]     In this embodiment, three spaced-apart spacers  76 ′ are provided on the intermediate sections  74 ′ of the upper and lower support seats  71 ′ of each support unit  70 ′ for supporting four pieces of weights  100 ′. The distance between two adjacent ones of the spacers  76 ′ is equal to one pitch of the right-handed threads  34 ′, of each shaft  30 ′. Thus, when either shaft  30 ′ is turned one revolution, i.e., 360°, the corresponding selector tube  41 ′ or  42 ′ moves in a corresponding direction one pitch towards or away from the connecting end  32 ′ of the shaft  30 ′.  
         [0083]     With reference to  FIGS. 20, 21 ,  22 , and  24 , an adjustment knob unit  90 ′ is respectively connected to the connecting end  32 ′ of each shaft  30 ′ to allow the user to turn the shaft  30 ′ relative to the handle  50 ′ and to thereby move the selector tube  41 ′ or  42 ′ axially of the shaft  30 ′ in opposite directions towards or away from the connecting end  32 ′ of the shaft  30 ′. Each of the adjustment knob units  90 ′ includes a second cover or outer fastening member  80 ′ and a cap  91 ′.  
         [0084]     Each outer fastening member  80 ′ is in the form of a disk having a central opening  85 ′ which allows the disk member  80 ′ to be sleeved on the connecting end  32 ′ of shaft  30 ′. The inner face of each disk member  80 ′ is disposed in abutting relation to the corresponding support unit  70 ′. Two diametrically opposed holes  86 ′ extend axially through each disk member  80 ′ and bolts  88 ′ extend through holes  86 ′ into threaded relation to the upper and lower seats  71 ′ of the associated support unit  70 ′.  
         [0085]     As best shown in  FIGS. 18 and 19 , each cap  91 ′ includes a relatively thick plate section  912 ′, an annular sleeve  913 ′ that extends axially, inwardly, and integrally from an outer periphery of the plate section  912 ′ and that is sleeved on the exterior periphery of the disk member  80 ′. An central hole  916 ′ is formed in the plate section  912 ′. Between an enlarged inner portion and an outer portion of the hole  916 ′, two lug like elements  917  are formed. The elements  917  are positioned and configured to engage within slots  37 ′ when the associated screw rod or shaft  30 ′ is engaged within the enlarged inner portion hole  916 ′.  
         [0086]     Each cap  91 ′ further includes a spring-loaded detent which has a compression spring  92 ′ disposed in an offset hole  915 ′ formed in the plate section  912 ′. A roller in the form of a ball  95 ′ biased by the spring  92 ′ to engage resiliently in a frusto conical positioning hole  87 ′ formed in the outer portion of the disk member  80 ′. The roller  95 ′ has a diameter larger than that of the positioning hole  87 ′ so that the roller  95 ′ can be easily removed from the positioning hole  87 ′.  
         [0087]     After the cap  91 ′ is sleeved on the disk member  80 ′, a bolt  94 ′ is passed through the central hole  916 ′ to engage the screw hole  36 ′ in the corresponding connecting end  32 ′ of the associated shaft  30 ′, so that the cap  91 ′ is secured to the shaft  30 ′.  
         [0088]     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment, but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.