Abstract:
A dumbbell and incremental weight plate for same comprise a bar that extends generally axially between opposing end regions, a weight plate mass mounted about the bar at each end region, and at least one incremental weight plate mountable on the dumbbell. The weight plate mass and the incremental weight plate have respective magnetic regions that cause the incremental weight plate to be selectively magnetically secured to the weight plate mass or to be magnetically repelled from the weight plate mass to assist the user in removing the incremental weight plate from the dumbbell.

Description:
FIELD OF THE INVENTION 
     This invention pertains to exercise apparatus of the type employing movable weight plates. Examples of such devices are barbells, dumbbells, and cabled devices, such as the popular Universal machine, that utilize adjustable stacks of weight plates to resist the user&#39;s exercise movement. The foregoing equipment shall hereinafter be collectively referred to as “weight plate devices”, and the term “weight plate device” will be utilized to referred to one or more of them. 
     There are two fundamental types of dumbbells and barbells: the “fixed weight” type, wherein the weight plates are permanently secured on the ends of a bar, and the “adjustable” type, wherein weight plates are secured on the bar by removable collars that permit the user to add or remove individual weight plates to the bar. The fixed weight type is typically part of a set wherein a plurality of dumb bells (or barbells) provide a range of weights separated, typically, by 5 lb. increments. 
     Typically, it is desirable to have an easily and quickly mountable and detachable weight plate that can be used to selectively add or subtract incremental weight to a pre-existing weight plate combination or other pre-existing weight-training mass. 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. In other cases, it can be greater or smaller. 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. 
     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. 
     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, although many dumbbells and bar bells utilize plastic weight plates or plates made of other non-magnetic material. In addition to being less expensive to manufacture, plastic and rubber weight plates are less prone to cause chipping, marring and other surface damage to surrounding gym equipment such as racks and neighboring devices and are less prone to damage inadvertently contacted woodwork and walls. Accordingly, the inability to use magnetically coupled incremental weight plates with increasingly popular non-magnetic dumbbell and barbell weight plates is a severe limitation. 
     Secondly, there has been a need for strong magnetic attraction between the incremental weight plate and the dumbbell/barbell weight plate to which it is attached. In addition to safety concerns that arise whenever a weight plate can fall from an exercise device, it is undesirable for the incremental weight to shift position during an exercise movement because the resulting imbalance can detract from the safety and efficacy of the exercise movement. The strong magnetic attraction thus required not only makes it difficult to remove the incremental weight plate from the exercise device, but can also scratch or mar the weight plate surface to which the incremental weight attaches, adversely affecting the aesthetics of the device. Moreover, the magnetic micro weights are coupled to coated weight plates on some weight plate devices, and the decoupling effort can scratch or mar the coating, leading to the rusting of the underlying surface. 
     SUMMARY OF THE INVENTION 
     A dumbbell is disclosed herein comprising a bar that extends generally axially between opposing end regions, a weight plate mass mounted about the bar at each end region, means for retaining the mounted weight plate mass at the respective end regions to define a handle region axially inward of the end regions that can be gripped by a user during exercise movement of the dumbbell, and at least one incremental weight plate mountable on the dumbbell. The weight plate mass and the incremental weight plate have respective magnetic regions that cause the incremental weight plate to be selectively magnetically secured to the weight plate mass or magnetically repelled from the weight plate mass to assist the user in removing the incremental weight plate from the dumbbell. 
     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 DRAWINGS 
         FIG. 1  is a front elevation view showing one end of a dumbbell incorporating the invention herein; 
         FIG. 2  is a left side elevation view of the dumbbell of  FIG. 1 ; 
         FIG. 3  is a front elevation view of the dumbbell illustrated in  FIG. 1  with an added, magnetically responsive weight plate  20  being slid onto its outer shaft  14  in accordance with the invention; 
         FIG. 4  is a front elevation view of the dumbbell of  FIG. 1  with the magnetically-responsive weight plate fully mounted; 
         FIG. 5  is a right side elevation view of the magnetically-responsive weight plate shown in  FIG. 4 ; 
         FIG. 6  is a front elevation view of the dumbbell of  FIG. 1  with the magnetically-responsive weight plate fully mounted; 
         FIG. 7  is a left side elevation view of the dumbbell of  FIG. 6 ; 
         FIG. 8  is a front elevation view of a dumbbell incorporating a second embodiment of the invention; 
         FIG. 9  is a perspective elevation view of the dumbbell of  FIG. 8 , showing the magnetically-responsive weight plate positioned for mounting onto the dumbbell in accordance with the invention; 
         FIG. 10  is a right side elevation view of the sleeve  40  of  FIG. 8 ; 
         FIG. 11  is a left side elevation view of the right magnetically-responsive weight plate  34  illustrated in  FIG. 9 ; 
         FIG. 12  is a front elevation view of a dumbbell constructed in accordance with a third embodiment of the invention; 
         FIG. 13  is a side elevation view of the dumbbell of  FIG. 12 ; 
         FIG. 14  is a rear elevation view in schematic of a cabled exercise device constructed in accordance with a fourth embodiment of the invention; and 
         FIG. 15  is a perspective elevation view of another embodiment of a dumbbell constructed in accordance with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a front elevation view showing one end of a “fixed weight” type dumbbell  10  incorporating the invention herein. Although the invention is discussed in the context of a dumbbell, it should be recognized that bar bells are within the scope of the invention and the term “dumbbell” will be used to denote both devices. 
     The dumbbell  10  has two generally annular weight plates  12  respectively mounted at opposing ends of a longitudinally-extending shaft  14  in the convention manner. In practice, a plurality of weight plates may be mounted at each end to achieve the desired weight, or a single weight plate may be utilized. The end portion of the shaft  14  extends through and beyond the outermost weight plate. The weight plates  12  abut respective collars  11  which are located at longitudinally opposed positions on bar  14  to define a handle region  13  therebetween that is gripped by the user. 
       FIG. 2  is a left side elevation view of the dumbbell of  FIG. 1 . A pair of magnets  16 ,  18  are embedded in the outermost weight plate surface at both ends of the dumbbell. The magnets are preferably of the rare earth type, such as neodymium magnets. These are very strong magnets that can be relied upon to securely bind a magnetically-responsive incremental weight plate to the dumbbell. While two magnets  16 ,  18  are shown in diametrically opposite positions, any other number of magnets could be used, and other positions could be utilized without departing from the scope of the invention. 
     As illustrated in  FIG. 2 , one of the magnets  16  has its north pole facing outward, while the other magnet  18  has its south pole facing outward. The dumbbell illustrated in  FIGS. 1 and 2  has a “base weight” to which an incremental weight of desired poundage is to be added.  FIG. 3  is a front elevation view of the dumbbell of  FIG. 1 , but showing an outer weight plate  20  of incremental poundage mounted onto the outwardly extending portion of the shaft  14 . The weight plate  20  conveniently includes an integrally formed knurled portion  22  of relatively larger diameter that provides a graspable periphery preferably sized to be encompassed by the human hand so that the weight plate  20  can be rotated with one hand in the manner of a jar-top. 
       FIG. 4  is a front elevation view of the dumbbell of  FIG. 1  with the magnetically-responsive weight plate fully mounted. As illustrated in  FIGS. 3-5 , the plate  20  is annular, so as to fit concentrically about the shaft  14 . The incremental weight is thereby balanced with respect to the shaft, as is preferable for most lifting movements. Naturally, other shaped plates or non-concentric mountings can be provided if a unbalanced arrangement is desired. As further illustrated in  FIG. 7 , indicia can be stamped, molded or otherwise placed upon the incremental weight plate to display its added incrementally poundage. 
     The incremental weight plate  20  becomes magnetically coupled to the weight plate  12  when it is mounted onto the shaft  14  in the manner described below, thereby becoming securely mounted on the dumbbell without the need for a collar. For safety reasons, it is desirable to provide a firm degree of magnetic coupling so that the plate does not disengage during exercise movements. Accordingly, the increment plates can be difficult to remove when one wishes to do so. In accordance with the invention, a decoupling feature is therefore preferably included that aids the user in removing the incremental plate from the dumbbell. 
     Turning to  FIG. 5 , a right side elevation view of the incremental weight plate  20  is shown. This is the inwardly-facing surface of the incremental weight plate  20 : i.e., the surface that faces and engages the weight plate  12 . As shown in  FIG. 5 , a pair of magnets  24 ,  26  are embedded in the incremental weight plate and are positioned to overlie the magnets  16 ,  18  when the incremental weight plate is mounted onto the shaft  14 . The magnet  24  as its north pole facing the weight plate  12 , while the magnet  26  has its south pole facing the weight plate  12 . 
     The magnets  24 ,  26  that have been successfully use are 0.5 inches in diameter and 0.5 inches in length, with a tolerance of 0.005 inches. They are slip-fit into respective bore holes in the incremental weight plate, and the top of the bore walls are center punched radially inward around their peripheries to entrap the magnets within the bores. 
     When the incremental weight plate is mounted on to the shaft  14 , is positioned so that the south pole of magnet  26  over lies the north pole of magnet  16 , while the north pole of magnet  24  over lies the south pole of magnet  18 , thereby magnetically coupling of the incremental weight plate  20  and the weight plate  12  with a sufficient level of force that securely burns the two 
     When the user wishes to decouple the incremental weight plate from the dumbbell, the user merely grips the outer knurled periphery of the incremental weight plate with one hand, in the manner by which a jar top is gripped, while the dumbbell is held by the other hand. The incremental weight plate is then rotated about the shaft  14  by approximately 180° until the north poles of magnets  16  and  24 , as well as the south poles of magnets in  18  and  22 , respectively begin to repel each other, pushing the incremental weight plate  20  away from the weight plate  12 . Thus, the user need only apply a relatively easy twisting motion to the incremental weight placed  20  rather then pull the plates apart. The result is that the incremental weight plate seemingly “pops off” the dumbbell. 
     To prevent the rotating magnets from marring the surfaces of the weight plate  12  and the incremental weight plates  20 , the magnets are preferably recessed from the surfaces of the respective plates by 10 thousandths of an inch or so. Those skilled in the art will recognize that a greater number of magnets could be used, and that they can be positioned differently than those shown in the Figures. Regardless of the number of magnets or their respective positions, the respective poles of the magnets are utilized to attract or repel mating magnets to firmly hold the incremental weight plate on the dumbbell and to assist the user in removing the incremental weight plate, as the case may be. By properly selecting the number of magnets and their relative positions, decoupling with a rotation of less than 180° can be effected. 
     A second embodiment of the invention is shown in  FIGS. 8-11 .  FIG. 8  is a front elevation view of a dumbbell  30  of the “adjustable” type, wherein weight plates are secured on the bar by removable collars that permit the user to add or remove individual weight plates to the dumbbell.  FIG. 9  is a perspective elevation view of the dumbbell of  FIG. 8 , and  FIG. 10  is a side elevation view of the dumbbell of  FIG. 8 , showing the incremental weight plate  34  positioned for mounting onto the dumbbell in accordance with the invention. 
     In this embodiment, outer weight plates  32  and incremental weight plates  34  are mounted on opposite ends of a shaft  35  that extends through the dumbbell handle  37 . As will become clear, the outer weight plates  32  need not be magnetically responsive but can, instead, be made of polyurethane or other commonly utilized plastic material such as that found in less expensive dumbbell sets. 
       FIG. 11  is a left side elevation view of the right incremental weight plate  34  of  FIG. 8 , showing two magnets  38 . As before, one of the magnets has its south pole facing outward, while the other has its north pole facing outward. 
     The shaft  35  is of the known externally-threaded variety. Conventionally, weight plates are mounted onto the shaft and urged toward the dumbbell&#39;s handle until stopped by the collar  36  or a previously mounted weight plate. An internally threaded nut or other such fastening device is then rotated onto the shaft until securing contact is made with the weight plate. 
     In accordance with the invention, a sleeve  40  is mounted on to the shaft  35 . The sleeve preferably has a “T”-shaped cross-section, comprising an internally-threaded cylindrical portion  41  that is tightened onto the threaded shaft  35 , and a leading base portion  42  of relatively greater diameter that butts up against the outer plate  32 . The base portion  32  is formed from magnetically responsive material. Alternatively, as illustrated in  FIG. 15 , the base portion  32  can include two or more magnets  39  that respectively present a north and a south pole to the magnets of the incremental weight plate  34  for the coupling/decoupling affect previously described. In either case, the base portion  42  provides a magnetically responsive seat for the incremental weight plate  34  regardless of whether the outer plate  32  is made of magnetically-responsive material or not. Further, the base portion  42  provides a wear surface that prevents the outer plate  32  from being marred or damaged by the incremental plate  34 , particularly when the outer plate  32  is plated or coated with an aesthetically pleasing layer of material. 
     The sleeve  40  may be tightened onto the shaft  35  by mounting the sleeve and magnetically coupled incremental weight plate  34  together as a unit, and utilizing the incremental plate  34  as a handle in a jar-lid tightening manner. To enable the sleeve  40  to be more firmly tightened onto the shaft, however, a series of longitudinally-extending grooves  44  are preferably formed in the cylindrical portion  41  of the sleeve, as best shown in  FIG. 10 , for gripping by complimentary surfaces of a tightening tool.  FIG. 10  is a right side elevation view of the sleeve  40 . 
       FIG. 12  illustrates a third embodiment of the invention.  FIG. 12  is a front elevation view of a dumbbell  50  of the “fixed weight” type, wherein weight plates  52  are permanently secured on the ends of a shaft that extends through the dumbbell handle  58 .  FIG. 13  is a side elevation view of the dumbbell of  FIG. 12 . Again, the weight plates  52  may be magnetically responsive or not. An annular, longitudinally-extending cylindrical sleeve  54  having a relatively larger diameter base portion  60  is affixed to the dumbbell at each end of the dumbbell via a respective hex bolt  59  that is inserted into the end  57  of the sleeve  54 , extends through the sleeve and is threaded into an internally threaded end region of the shaft to secure the sleeve  54  and weight plate  52  against the collar  56  formed at each end of the handle  58 . Incremental weight plates can then be added and removed as described above, preferably but not necessarily utilizing magnets in the base portion  60  to repel the incremental weight plate when the incremental weight plate is rotated to bring its magnets into general alignment with the like-pole of opposing respective magnets in the base portion. 
     The invention herein is not limited to dumbbells or barbells. It can, for example, be applied to cable-type exercise equipment.  FIG. 14  is a rear elevation view in schematic of a cabled exercise device constructed in accordance with a fourth embodiment of the invention. An adjustable stack of weight plates  70  is lifted by a user who is pulling them upward by a cable  72  via a pulley  71  or other means known in the art. The stack of weight plates is guided by guide rods  73 , which guide the stack&#39;s movement vertically, and keep the plates evenly stacked as they move. “Sleeves” with magnetically-responsive base portions may be affixed, as at  74 , to the topmost weight plate to accommodate incremental weight plates, thereby offering a total poundage that falls between the increments of weight offered by the stack. The base portions of the “sleeves” may include magnets, as described above, to repel the incremental weight plate when the incremental weight plate is appropriately rotated, or the sleeve. The “sleeves” need not be annular in this application, and the term “sleeve” has been used only for consistency of terminology with respect to embodiments described above. 
     Alternatively, the “sleeves” of this embodiment can be positioned as at  76 , with the incremental weight plates being held magnetically above the stack until needed, and then being selectively decoupled from the “respective” sleeve and guided vertically about the respective guide rod  73  from the “sleeve” to the weight plate stack. Once again, the decoupling action can be purely manual, or the “sleeves” can include magnets in their base portions to repel the incremental weight plate when the incremental weight plate is suitable rotated, as described earlier. 
     Although the present invention and its advantages have been described in detail, it should 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 appended claims.