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 This application relates to Provisional U.S. patent application Serial No. 60/306,237, filed Jul. 19, 2001, the filing date of which is hereby claimed and which application is hereby adopted by reference as part of the present disclosure.
 This invention relates in general to exercise devices and deals more particularly with improvements in barbell assemblies.
 A barbell assembly of the type with which the present invention is concerned essentially comprises a plurality of weights or plates for selective positioning on opposite end portions of an elongated lifting bar. The removable plates are releasably retained on the opposite end portions of the bar by fixed inner and removable outer weight retention members or collars. The outer collars are slidably received on the bar and releasably secured in fixed position thereon by suitable locking devices, such as a set screws.
 It is essential that the removable weights be releasably secured in fixed position relative to the bar so that the opportunity for axial play between the weights and the bar is substantially eliminated. Any substantial tilting of the user manipulated bar from its normally horizontal exercising position causes the weight or weights at the lower end of the tilted bar to exert and axially outwardly directed force on an associated outer weight retaining collar and toward a free end of the bar. Such tilting motion in the presence of axial play between the weight or weights and the bar may cause the weights at the lower end of the bar to impact upon the associated outer retaining collar, thereby loosening, if not dislodging the outer weight retaining collar from the bar. A sudden loss of weight at one end of the bar can result in serious injury to the user. The present invention is concerned with this problem.
 Accordingly, it is the general aim of the present invention to provide and improved weight retention collar to reduce risk of occurrence of axial play in a barbell assembly.
 In accordance with the present invention, a barbell assembly includes at least one ferromagnetic weight slidably received on an outer end portion of an axially elongated lifting bar and positioned in an adjacent engagement with an inner weight positioning and retaining collar mounted on the bar axially inward of the weight. The barbell assembly further includes an outer weight retaining collar slidably received on the bar and magnetically coupled to the at least one weight, and a securing device carried by the outer weight retaining collar and grippingly engaged with the bar to releasably retain the outer weight retaining collar in fixed position adjacent an outer surface of the at least one weight.
 In the drawings and in the description which follows, the present invention is illustrated and described with reference to a typical barbell assembly embodying the present invention and indicated generally by the reference numeral
 Each group of one or more plates is positioned on the bar
 Each plate retaining member or outer collar
 In accordance with the present invention, at least the plates
 Further, and in accordance with the invention, the bar is, or may be made from a magnetic material, that is a material which is magnetized or is capable of being magnetized. However, alternatively the bar
 Preparatory to the performance of a body building exercise, one or more of the ferromagnetic plates are positioned on each end portion of the bar
 When the bar is made from a diamagnetic or paramagnetic material, as herein before discussed, no substantial resistance will be encountered when each retention collar
 It should be understood that the mechanical locking or clamping device associated with each outer collar comprises an absolutely essential part of the barbell assembly
 When the invention is practiced with a magnetic bar some resistance may be anticipated in positioning the outer collars on and removing them from the bar. However, once proper positioning is attained, the magnetic susceptibility of the bar may be utilized to contribute in maintaining the desired position of the collar and plates, so that the assembly may be locked in assembly without slack or play in the system.