Abstract:
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) a hub portion for accommodating the through-opening of a weight plate, and (b) 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 (a) and (b) above.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention pertains to barbells and dumbbells. Unless otherwise stated, the term “dumbbell” shall be used to mean “barbell” and “dumbbell”, individually and collectively 
         [0002]    There are two fundamental types of dumbbells: the “fixed weight” type, wherein the weight plates are permanently secured on the ends of an axially-extending bar, and the “adjustable” type, wherein weight plates are secured on an axially-extending bar by removable collars that permit the user to add or remove individual weight plates to the bar. 
         [0003]    The fixed weight type dumbbell is typically part of a set that provides a range of liftable weights, typically in 5 lb. increments. The weight plates of each such dumbbell are secured to the bar by one of a number of known means. For example, the weight plate(s) at each end of the bar may simply be captured between an axially inner flange and an annular collar mounted about the end region of the bar. Both end regions of the bar may be internally threaded in the axial direction to engage respective externally-threaded bolts that are accordingly tightened into the bar to secure a respective end cap against the weight plate(s) and thereby capture the weight plate(s) against the flange. A high-strength thread locker such as Loctite® is then preferably used to prevent the bolt from becoming loose, and uncommon bolt heads or other types of fasteners may be employed to prevent the user from intentionally loosening the plates. 
         [0004]    Similarly, adjustable dumbbells are known to use a variety of means for releasably securing the weight plates to the bar. One version utilizes a bar having externally-threaded end regions that engage an internally-threaded annular collar that is spun onto the bar and tightened against the weight plates to capture the weight plates against an axially inner flange. Such collars sometimes include wrench-engageable surface features to enhance the user&#39;s ability to securely tighten the collar onto the dumbbell. The collar can subsequently be removed in order to add or remove weight plates by unscrewing the collar from the bar. 
         [0005]    Other means for releasably securing the weight plates to dumbbells of both the fixed and adjustable types are well known, and it will be understood that the invention herein is usable and adaptable for use with all of them, and not limited to the configurations described herein by way of example. 
         [0006]    Whether a fixed weight type or an adjustable type dumbbell is used, it is frequently desirable to use an easily and quickly mountable and detachable weight plate that can add or subtract incremental weight to the existing weight plate combination on the dumbbell. For simplicity, this easily mountable and detachable weight plate will be referred to as an “incremental” weight plate because (as will become clear) it is used to incrementally vary the weight to be lifted. In some cases, the incremental weight is quite small; e.g., 0.25 to 2.5 lbs. (i.e., approx. 0.11 kg to 1.15 kg). In other cases, it can be greater or smaller. 
         [0007]    Generally, incremental weights are used to rehabilitate injured muscles and ligaments, wherein small increases/decreases in resistance are needed in the course of rehabilitation exercises. In other cases, small incremental weights are useful where the user is exercising smaller muscle groups or is older or physically weak or has reached a “plateau” that is preventing a major increase to the next full increment of lifted poundage. 
         [0008]    The use of magnetically mountable incremental weights is known as one means to quickly and conveniently add and subtract such weight. For example, U.S. Pat. No. 5,735,777 describes the use and application of magnetic “adaptive weights” that are removably attached to dumbbells and barbells. The content of that patent is hereby incorporated by reference. 
         [0009]    The advantages of magnetically coupled incremental weights have been offset by a number of deficiencies. First, they have not been usable with non-metallic weight plates, despite the fact that many dumbbells frequently utilize weight plates made from plastic, rubber and/or other non-magnetic materials. In addition to being less expensive to manufacture, for example, both plastic and rubber weight plates are less likely to cause chipping, marring and other surface damage to surrounding home furnishings and/or surrounding gym equipment such as racks and neighboring devices. Additionally, weight plates of such materials are less likely to damage inadvertently contacted woodwork, floors and walls. Moreover, weight plates made from such material can be more durable in that they are more likely to retain their aesthetic appearance because they are not susceptible, as with poorly plated metal weight plates, to chipping and rusting. Accordingly, the inability to use magnetically coupled incremental weight plates with increasingly popular non-magnetic dumbbell and barbell weight plates is a severe limitation. 
         [0010]    Secondly, there is a need for strong magnetic attraction between the incremental weight plate and the dumbbell to which it is attached, but that makes it difficult to remove the incremental weight plate. Strong magnetic attraction is desired owing to safety concerns that arise whenever a weight plate can fall from an exercise device or become loose and distracting. In addition, an incremental weight that shifts position during an exercise movement can cause a dynamic imbalance that detracts from the safety and efficacy of the exercise movement. 
       SUMMARY OF THE INVENTION 
       [0011]    The invention herein is directed to dumbbells having weight plates onto which magnetically coupled incremental weight plates can be securely mounted. The invention herein includes an adaptor and a method to convert conventional dumbbells into an improved configuration that can utilize magnetically-coupled incremental weight plates. 
         [0012]    Incremental weight plates are known in the art. They are typically annular, with the central aperture being sized to fit about the bar of the dumbbell. It should be recognized, however, that the incremental weight plate need not be round; it can be of any desired shape. As used throughout this specification, the term “annular” shall accordingly not be limited to denote a round shape, but will instead denote any and all shapes having a through-opening. Moreover, the term “annular” as used herein shall encompass shapes having a through-hole that is not necessarily centrally located. Lastly, and as previously stated, the term “dumbbell” includes dumbbells and barbells, individually and collectively. 
         [0013]    A dumbbell in accordance with the invention comprises a generally cylindrical bar extending generally axially between a pair of end regions respectively terminating at a respective end of the bar, at least one weight plate formed from a magnetically non-responsive material mounted about each end region, a generally annular member securely mounted about the bar at least one end region between the weight plate and the end of the bar, said generally annular member having (a) a hub portion for accommodating the through-opening of a generally annular incremental weight plate, and (b) a flange portion of greater exterior dimension than the hub portion and having at least one generally magnetically-responsive region for securing an incremental weight via magnetic force when said incremental weight plate is mounted about said hub region, and means securing said generally annular member to the bar. 
         [0014]    In accordance with the invention, an adaptor is provided for use with a dumbbell having non-magnetic weight plates. The adaptor comprises a generally annular member having (a) a hub portion having an inner dimension sized to fit around the dumbbell&#39;s bar and an outer dimension sized to fit through the through-hole of an incremental weight plate and (b) a generally annular flange portion of greater exterior dimension than the hub portion and having at least one magnetically-responsive region for securing an incremental weight via magnetic force when said incremental weight plate is mounted about said hub region, and means for permitting the adaptor to be secured to the bar. 
         [0015]    An adaptor constructed in accordance with the invention is slid onto the dumbbell, flange-end first so that the flange portion is closer to the dumbbell&#39;s weight plate than the hub region. The adaptor is secured to the bar. When needed, an incremental weight plate is slid over the hub portion, and is secured to the flange portion by magnetic attraction between the magnetically responsive regions of the flange portion and incremental weight plate. 
         [0016]    The magnetically-responsive region of the flange, in the aforedescribed dumbbell and in the aforedescribed adaptor, may be a magnet positioned to magnetically secure the incremental weight plate. Alternatively, the magnetically-responsive portion of the flange need not include a magnet if the secured portion of the incremental weight plate includes a magnet. 
         [0017]    Moreover, both the magnetically-responsive portion of the flange and the secured portion of the incremental weight can include a magnet in accordance with an optional feature of the invention, wherein an appropriate orientation of the magnets&#39; poles results in a magnetically-aided removal feature when the user wishes to remove the incremental weight plate from the dumbbell. Briefly, the adaptor and the incremental weight plate include magnetic regions whose poles are mutually oriented so that the incremental weight plate is magnetically attracted to the flange for secure mounting when the incremental weight plate is in a first position about the bar, and so that the flange and incremental weight plate repel each other when the incremental weight plate is rotated sufficiently about the bar from its first position. 
         [0018]    These and further details of the invention will be apparent to those of ordinary skill in the art from reading a description of the preferred embodiment of the invention described below, and of which the drawing forms a part. 
     
     
       DESCRIPTION OF THE DRAWING 
         [0019]    Of the preferred embodiments to be described hereinbelow, 
           [0020]      FIG. 1  is a front fragmentary elevation view in longitudinal section showing one end of a fixed weight dumbbell incorporating the invention herein; 
           [0021]      FIG. 2  is a front elevation view of the sleeve  16  of  FIG. 1  constructed in accordance with the invention; 
           [0022]      FIG. 3  is a right side elevation view of the sleeve shown in  FIG. 2 ; and 
           [0023]      FIG. 4  is a left side elevation view of an incremental weight plate in  FIG. 1  constructed in accordance with the invention 
           [0024]      FIG. 5  is a front elevation view of an alternative sleeve constructed in accordance with the invention; 
           [0025]      FIG. 6  is a front perspective view of a second embodiment of a dumbbell constructed in accordance with the invention; and 
           [0026]      FIG. 7  is a left side elevation view of the sleeve  16 ″ illustrated in  FIG. 6 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]      FIG. 1  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. 
         [0028]    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  FIG. 1 . 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. 
         [0029]    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. 
         [0030]    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  FIGS. 2 and 3  which respectively show front elevation and right side elevation views of the generally annular sleeve of  FIG. 1 . 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  FIG. 3 , there may be one such region, four such regions, six such regions or any other desired number. 
         [0031]      FIG. 4  is a left side elevation view of the preferred incremental weight plate  18  shown in  FIG. 1 . 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. 
         [0032]    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 ( FIG. 3 ) can interact with magnets  34 ,  36  of the incremental weight plate ( FIG. 4 ) to secure the incremental weight plate to the dumbbell. 
         [0033]    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. 
         [0034]    Returning to  FIG. 1 , 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  FIG. 1 , 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.    
         [0035]    Alternatively, an axial sleeve having an externally threaded bolt-like protrusion can be utilized. As illustrated in  FIG. 5 , 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. 
         [0036]    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). 
         [0037]    As illustrated in  FIG. 6 , 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). 
         [0038]    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. 
         [0039]    Returning to  FIGS. 1 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  FIGS. 6 and 7  can be used as aftermarket adaptors for conventional dumbbells having externally threaded bars. 
         [0040]    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 magents 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. 
         [0041]    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.