referring to fig1 – 4 , a preferred embodiment of our exercise apparatus comprises a pair of outer rings 10 and 12 , preferably formed of tubular steel , aluminum or another rigid material . the rings 10 each have a number of tapped holes 14 , formed in regular intervals about their perimeter for securing inner rotatable rings in a manner which will be subsequently described . the two outer rings 10 and 12 are joined to one another by a pair of curved , tubular , connecting bars 16 and 18 . the ends of the bars are welded , or otherwise secured to spaced points on the perimeter of the outer rings 10 and 12 . a straight center bar 20 , which is preferably rectangular in cross - section , extends intermediate the two curved connecting bars 16 and 18 and also has its ends secured to the outer perimeter of the two rings 10 and 12 midway between the points of connection of the bars 16 and 18 . the connecting bar 20 may be solid or tubular . the bars 16 , 18 and 20 are connected to the rings 10 and 12 so that the rings , as well as their connecting bars , all lie in a common plane . the lengths of the bars 16 , 18 and 20 are preferably such that the centers of the two rings 10 and 12 are separated by approximately 10 – 15 inches , which represents a comfortable distance for gripping the exercise apparatus . a pair of inner rings 22 and 24 which have outer diameters slightly smaller than the inner diameters of the rings 10 and 12 , are secured within the outer rings by opposed pairs of retaining plates 28 , 30 , 32 and 34 . the retaining plates 28 , 30 , 32 and 34 have a number of screw holes 36 formed through their thickness . the retaining rings may be secured to the opposed faces of the outer rings 10 and 12 with screws 31 , to capture the inner rings 22 and 24 between them . inner rings 22 and 24 make a loose fit within the inner diameters of the outer rings 10 and 12 . each of the inner rings 22 and 24 has a cylindrical grip member 38 and 40 , preferably with a serrated surface , extending diametrically across the respective ring . a metal weight 42 is slidably supported on the straight connecting bar 20 . the fit is such that it may easily slide from one side to the other , as the bar is appropriately inclined . in fig1 , the weight 42 is shown at the end toward the right arm of the exerciser 50 and shown in phantom at a position adjacent to his left arm . in the embodiment of fig1 through 4 , weight supporting , rectangular cross - section extensions 52 and 54 , are fixed to the outer rings 10 and 12 respectively , at points diametrically opposed to the points where the center connecting bar 20 joins those rings . a plurality of weights may be supported on each extension 52 and 54 in the manner of a conventional barbell . fig1 and 3 illustrate crescent - shaped weights formed in accordance with the present invention . fig3 illustrates several conventional disc - shaped weights 60 secured on a bar end 52 and retained by a conventional spring clip 62 . another novel aspect of the present invention resides in the use of crescent - shaped weights 64 a , 64 b , and 64 c , rather than the conventional disc - shaped weights 60 . these crescent - shaped weights preferably have a thickness similar to the thickness of outer rings 10 and 12 and have central holes which allow them to be supported on the extensions 52 and 54 . they may be retained with conventional spring slips 62 . when equipped with the crescent - shaped weights , the exercise apparatus has a relatively flat profile and my be conveniently stored or packaged . the crescent - shaped weight 64 a has a concave surface with a diameter that approximates that of the outer ring so it slightly extends around the outer ring . the weights 64 b and 64 c have concave surfaces which allow them to closely nestle the convex surfaces of the larger weights . the crescent - shaped weights provide a number of advantages over conventional weightlifting bars which may be equipped with disc - shaped weights with central holes that fit over an extending bar such as the bar 52 in addition to the resulting compact configuration and ease of storage . disc - shaped weights tend to rotate during exercise resulting in forces that destabilize the conventional exercises that may be performed by the bar . the crescent - shaped weights lock into one another to prevent rotation . additionally , the crescent - shaped weights minimize the length of the exercise bar and thus lower force moments which tend to cause the bar to twist during use . finally , disc - shaped weights tend to make contact with the user &# 39 ; s elbows during many exercises , particularly trapezius pulls involving grabbing the center of the bar with both hands and lifting towards the chin . since the crescent - shaped bars do not extend out of the plane of the weightlifting apparatus , they do not create such interference . the embodiment of the invention illustrated in fig5 does not have the weight supporting extensions 52 and 54 which form part of the first embodiment of the invention . rather , the exercise apparatus simply consists of the rings and their rotatable handles and the associated connecting bars and the sliding weight . in alternative embodiments of the invention , an anti - friction bearing could be used to support the inner rings 22 and 24 within the outer rings 10 and 12 . this might be a ball bearing or a roller bearing . alternatively , the engaging surfaces of one of the elements could be coated with an anti - friction material . alternate physical arrangements also might be employed for securing the inner rings 22 and 24 within the outer rings 10 and 12 , as opposed to the retaining plates illustrated in the drawings . the use of connecting bars 16 , 18 and 20 which are preferably tubular , gives the weightlifting apparatus a rigidity without the weight of conventional barbells . in an alternative embodiment to the invention , the center bar 20 and its supporting sliding weight 42 could be omitted so as to only allow for symmetrical exercises . as illustrated in fig1 , by inclining the bar in one direction or another , asymmetrical forces would be imposed on the exerciser &# 39 ; s muscles while using the bar for otherwise conventional exercises .
an exercise barbell comprises a pair of rings connected by a pair of curved bars . the rings rotatably support handle members . extensions of the bar on the exterior of the two rings support crescent - shaped weights which conform to the outer diameter of the ring and to one another . the weights are relatively flat so the entire apparatus lies in a single plane . a straight bar connecting the opposed sides of the two rings supports a sliding weight which may be moved to one side of the bar or the other to allow asymmetrical exercises .