fig1 is a front elevation view shoving the right end of a “ fixed weight ” type dumbbell 10 constructed in accordance with the invention herein . as is known , the left end ( not illustrated ) is preferably a mirror image of the right end . as stated hereinabove , the term “ dumbbell ” is used to denote both dumbbells and barbells . as is known in the art , the dumbbell 10 comprises a generally cylindrical bar 12 extending axially between two end regions , the right end region 11 being illustrated in fig1 . a tubular handle 13 typically extends co - axially about the bar for gripping by the user , and includes any of a number of surface features to enhance a secure grip by the user . a weight plate mass in the form of a single illustrated weight plate 14 is mounted about the bar 12 axially inward of the right end region 11 . the weight plate 14 is preferably formed from a non - magnetically - responsive material . common examples of such material are plastic and rubber compounds . those skilled in the art recognize that more than one weight plate may be mounted at each end region to yield the desired total weight plate mass of the dumbbell . it may also be recognized that the scope of the invention herein is not dependant on the weight plate 14 being non - magnetic although the invention is primarily directed to dumbbells with non - magnetically - responsive weight plates . a generally annular sleeve 16 having a flange portion 16 a and a hub portion 16 b is mounted on the bar axially outward of the weight plate 14 . preferably , the same is true at the unillustrated left end of the dumbbell . the annular sleeve has an inner diameter that fits over the bar 11 , and is slid axially inward over the bar until it reaches the weight plate 14 or other stop surface designed into the dumbbell . the outer diameter of the flange portion 16 a is preferably less than that of the weight plate 14 , but greater than that of the hub portion 16 b . the outer diameter is preferably less than that of the weigh plate 14 because , as will be shown , it is not necessary to have the same or greater diameter and , more importantly , it is highly undesirable to have it protrude radially from the dumbbell so as to potentially cause damage to surrounding items that it strikes or be damaged itself if the dumbbell is dropped onto the floor or other surface . the hub portion 16 b of the sleeve 16 has an outer diameter sized to fit through the generally central through - opening 17 of incremental weight plate 18 . incremental weight plate 18 is magnetically secured to the abutting surface of the flange portion 16 a by providing one or more appropriately oriented magnets in the flange and / or incremental weight plate . by way of example , reference is made to fig2 and 3 which respectively show front elevation and right side elevation views of the generally annular sleeve of fig1 . a pair of magnets 30 , 32 is shown affixed to the axially - outward surface of the flange portion 16 a . the magnets can be affixed to the surface , or embedded in the surface so as to be flush therewith or slightly below it . the face of the magnets can be exposed or be internally disposed within the flange . moreover , the magnets , and / or the magnetic region created within the flange , can be of any desirable shape within the radially - extending region between the id and od of the flange , and can be at as many regions around the flange as desirable . thus , although two magnetic regions are shown in fig3 , there may be one such region , four such regions , six such regions or any other desired number . fig4 is a left side elevation view of the preferred incremental weight plate 18 shown in fig1 . the incremental weight plate 18 is generally annular , having a generally central opening 40 and can be formed from either a magnetically - responsive material or a non - magnetically responsive material . examples of the latter include rubber - based mixtures and plastic materials . in the case where magnetically - responsive materials are used , the incremental weight plate will be attracted to the magnetic region ( s ) of the flange 16 ( a ) and thereby secured to the dumbbell . when the user desires to remove the incremental weight plate from the dumbbell , it is done in the conventional manner by applying an axially outwardly directed separating force against the incremental weight plate relative to the dumbbell . when the incremental weight plate is made from a non - magnetically responsive material , one or more magnetically - responsive regions 34 , 36 can be affixed to , or imbedded within , the incremental weight plate to interact with those of the flange and thereby magnetically secure the incremental weight plate on the dumbbell . for example , magnetic regions 30 , 32 of the flange ( fig3 ) can interact with magnets 34 , 36 of the incremental weight plate ( fig4 ) to secure the incremental weight plate to the dumbbell . the orientation of the magnets 34 , 36 of the incremental weight plate can be utilized to provide a feature by which the incremental weight plate can be easily detached from the dumbbell . specifically the face of magnets 34 , 36 abutting the flange 16 a are provided with opposite polarities , as are the magnetic regions 30 , 32 of the flange . for example , if magnets 34 , 36 respectively have the north and south pole facing the flange , and the magnetic regions 30 , 32 respectively have the south and north pole facing the incremental weight plate , the incremental weight plate will be securely mounted to the dumbbell when the flange &# 39 ; s magnetic region 30 abuts the incremental weight plate &# 39 ; s magnet 34 and the flange &# 39 ; s magnetic region 32 abuts the incremental weight plate &# 39 ; s magnet 36 . because of the magnetic attraction , removal of the incremental weight plate might be difficult , particularly since strong magnetically attractive forces are preferred in order to assure that the incremental weight plate does not slip from the dumbbell or move during the exercise movement . by rotating the secured incremental weight plate about the hub 16 b on which it is mounted , however , and generally aligning the incremental weight plate &# 39 ; s magnet 34 with the flange &# 39 ; s magnetic region 32 , the two will be caused to repel each other because of their now - abutting north poles . similarly , the flange &# 39 ; s magnetic region 30 will repel the incremental weight plate &# 39 ; s magnet 36 owing to their abutting south poles . consequently , the incremental weight plate will space itself from the flange , making its removal very easy . returning to fig1 , the weight plates 14 can be secured to the bar of the dumbbells by any of a number of means . for example , the weight plates may simply be captured between a flange 15 formed at the axially outward end of the handle 13 and the axially inward surface of the flange 16 a which can be used in lieu of the conventionally used dumbbell collar . accordingly , the annular sleeve 16 can be affixed to the barbell in a manner substantially identical to the manner by which conventional collars are affixed . for example , and as illustrated in fig1 , the sleeve 16 can be affixed to the dumbbell by means of a fastener such as an externally threaded bolt 22 that mates with an internally threaded region 24 at each end of the bar . the sleeve 16 accordingly includes a bolt - accommodating through - hole formed , preferably centrally , in its flange so that the bolt 22 can be tightened into the bar to secure the weight plate 14 between the collar 15 and the axially - inward surface the flange 16 a . alternatively , an axial sleeve having an externally threaded bolt - like protrusion can be utilized . as illustrated in fig5 , an annular sleeve 16 ′ having an internally - threaded shaft segment 16 b ′ protruding from its flange 16 a ′ can be screwed via that shaft into the internally - threaded end of the dumbbell &# 39 ; s bar . the shaft segment 16 c ′ can be affixed to the sleeve 16 by any known means . for example , it can be force - fit through an opening in the flange 16 a ′, or welded to the flange or secured by any one of numerously available chemical and / or mechanical fastening means . the sleeve 16 is also adaptable for use with adjustable dumbbells , both as an adapter to be used with pre - existing dumbbells , and as a component of an improved dumbbell . adjustable dumbbells are known , for example , that have bars with externally threaded end sections . dumbbells of this type utilize an internally threaded collar at each end of the dumbbell . each collar is threaded onto the bar after the weight plates at that end of the bar has been mounted , and rotated so that it advances progressively towards the handle of the dumbbell until it secures the mounted weight plate ( s ) against the respective flange ( or other plate - stopping surface ). as illustrated in fig6 , a sleeve 16 ″ can be utilized with an internally - threaded hub segment 16 b ″ to secure incremental weight plates to dumbbells of the type having externally threaded bars 12 ″. the internally threaded hub mates with the external threads of the bar so that the sleeve can be rotated onto the bar until the weight plates 14 ″ are captured between the axially inward face of the flange 16 a ″ and the handle &# 39 ; s flange 15 ″ ( or other plate - stopping surface ). the sleeve 16 ″ is screwed into the bar 12 ″ until the flange 16 a ″ contacts the weight plate 14 ″ and captures it against the handle 13 ″. a surface feature on the sleeve , such as axially - extending slots 42 , can be provided as a wrench - engaging surface to enhance the user &# 39 ; s ability to securely tighten the sleeve onto the dumbbell . moreover , the surface feature enhances the sleeve &# 39 ; s grippability so that a user can more securely tighten the sleeve by hand if a wrench is not used , but the use of a wrench is highly preferred for security . other surface features , such as axially - extending fiats or sleeves of polygonal cross - section , that can be readily gripped by a wrench or the human hand can be utilized as well . while it is recognize that the flange may be provided with wrench - accommodating surfaces as well , and it is intended that such surfaces be included within the scope of the invention . it is believed that the formation of such surfaces in the hub is more practical . as before , an incremental weight plate 18 ″ can then be mounted over the hub 16 b ″ of the sleeve , as desired , to be magnetically secured to the flange 16 a ″ whether or not the weight plate 14 ″ is magnetically responsive . returning to fig1 and 5 , those of ordinary skill in the art will recognize that the sleeves 16 , 16 ′ can be utilized as an adapter for conventional dumbbells wherein the weight plate 14 is secured to the bar by a collar and an internally threaded bolt . in this way , a dumbbell having nonmagnetic weight plates can be adapted to accommodate a magnetically - secured incremental weight plate . accordingly , the sleeve functions as an aftermarket adapter for use with conventional dumbbells , as well as being an original component of an improved dumbbell . likewise , the sleeve 16 ″ illustrated in fig6 and 7 can be used as aftermarket adaptors for conventional dumbbells having externally threaded bars . those of ordinary skill in the art will recognize that alternative means for releasably securing the incremental weight plate to the dumbbell can be used in place of the magnets described above . for example , the flange portion of the annular sleeve and the incremental weight plate can be fit with complimentary strips of adhesive - backed velcro ® to reliably but releasably secure the incremental weight plate against movement on the hub portion during the exercise movement . although the present invention and its advantages have been described in detail , it should accordingly be understood that various changes , substitutions and alterations can be made herein without departing from the spirit and scope of the invention as will be defined by the appended claims .
a dumbbell having weight plates onto which magnetically coupled incremental weight plates can be securely mounted comprises a bar , weights at the end regions of the bar , means for retaining the weight plates at the respective ends to define a handle region therebetween , and a sleeve of generally annular cross - section securely mounted about the bar at least one end region axially outward from the weight plate , said sleeve member having a hub portion for accommodating the through - opening of a weight plate , and a flange portion of greater exterior dimension than the hub portion and having at least one magnetically - responsive region for magnetically securing an incremental weight to the dumbbell when said incremental weight plate is mounted about said hub region . in accordance with the invention , an adaptor to convert conventional dumbbells to utilize magnetically - coupled incremental weight plates comprises elements and above .