Abstract:
A magnetically dumbbell device and method are disclosed. The dumbbell device has a central base unit with at least one magnetic piece at each end of the base unit and one or more weights attachable to the ends of the base unit by means of magnetic force.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a National Phase Application of PCT International Application No. PCT/IL2007/000198, International Filing Date Feb. 13, 2007, entitled “Magnetically Adjustable Dumbbells” published on Aug. 30, 2007 as International Publication Number WO 2007/096864 claiming priority of U.S. Provisional Patent Application No., 60/774,661, filed Feb. 21, 2006, both of which are incorporated herein by reference in their entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to dumbbells for developing arm strength and more particularly to a method and device providing magnetically adjustable dumbbells. 
   BACKGROUND OF THE INVENTION 
   The present art provides dumbbells with adjustable weight. Usually the installing and removing of the additional weights is inconvenient and takes time. Making the removal of the weights easier may come at the sacrifice of the linkage strength between the additional weights to the dumbbell, and therefore may be unsafe, because of the danger that an additional weight will fall from the dumbbell while exercising. 
   A worm-based mechanism is a known method for installing and removing addable weights. 
   Using attraction force of magnets is a known method for attaching additional weights. 
   JP8332245 provides a dumbbell of a weight increasing and decreasing mechanism which can increase and decrease the weight of the dumbbell freely, making use of attraction force of a ferrite magnet, and trains a hand and an arm and promotes circulation of the blood. 
   None of the known art provides a method which enables installation of additional weights simply by attaching them with magnets and easy removal of the additional weights by rotation, without sacrificing the magnetic linkage force between the additional weights and the dumbbell. 
   It is therefore desired to have a device and method providing dumbbells with an easy-to-operate mechanism for installing and removing the additional weights, which enables strong and safe linkage between the additional weights to the dumbbell, while providing the comfort of using magnets for attaching the additional weights. 
   SUMMARY OF THE INVENTION 
   The method and device of the present invention provides magnetically adjustable dumbbells which enables installing additional weights magnetically and removing them easily using rotational motion. 
   The method and device of the present invention have the advantage of using rotational motion for detaching the additional weights from the dumbbells. In this method, the linkage between the additional weights and the dumbbell may be strong and safe while the releasing of the additional weights from the dumbbell may be easy and may not require usage of great force. 
   This invention provides a device comprising a base dumbbell. The base dumbbell may comprise at least one magnet chip within a surface to which an addable weight can be attached. The device may further comprise an addable weight which may be made of un-magnetizable material. The addable weight may comprise at least one magnetizable chip. When comprising more then one magnetizable chip, the magnetizable chips may be located over an imaginary circle in correspondence with a same amount of magnet chips within the attaching surface. The addable weight can be attached to the base dumbbell by coupling said magnetizable chip to said magnet chip. Rotation of said addable weight relatively to said surface may detach said magnetizable chip from said magnet chip using shearing force and may locate the magnet chip against the un-magnetizable material, and thus the addable weight may be released and removed easily from the base dumbbell. The rotation of said addable weight may be about a pivot located at the center of said surface. At least one addable weight may be arranged about said pivot, and preferably more then one. The perimeter of said addable weight may be jagged in order to facilitate easy gripping and rotating of said addable weight. 
   An additional addable weight may be attached to each addable weight. Each addable weight may comprise a central pivot that one or more additional addable weights may be adapted to rotate about. Each additional addable weight may require less releasing force then the addable weight it is added to. Smaller required releasing force may be provided by fewer magnets in the additional addable weight then in the addable weight it is added to, or by weaker magnets in the additional addable weight then in the addable weight it is added to. 
   This invention further provides a method for removing an addable weight from a base dumbbell. In order to release said addable weight from said base dumbbell it is possible to rotate said addable weight relatively to said base dumbbell. The rotation may detach a magnetizable chip comprised within said addable weight from a magnet chip comprised within said base dumbbell. Said rotation may be about a pivot located at the center of a surface of said base dumbbell to which said addable weight may be attached. Said addable weight may be made of un-magnetizable material. Said rotation may further locate said magnet chip against an un-magnetizable material, thus the addable weight may be released and removed easily from the base dumbbell. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the figures in which: 
       FIG. 1  is a schematic 3-D illustration of an embodiment of a device according to the invention; 
       FIG. 2  is a schematic 3-D illustration of a cross section of an embodiment of a device according to the invention; 
       FIG. 3  is a schematic illustration of an embodiment of a device according to the invention; and 
       FIG. 4  is a partial schematic illustration of another embodiment of a device according to the invention. 
   

   It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
   DETAILED DESCRIPTION OF THE INVENTION 
   This invention provides a device in which a rotational motion is used for detaching additional weights from a dumbbell. The linkage between the additional weights to the dumbbell may be strong and safe while the releasing of the additional weights from the dumbbell may be easy and may not require usage of great force. 
   Attention is made to  FIG. 1 , which is a schematic 3-D illustration of a device  10  according to some embodiments of the invention. Device  10  may comprise base dumbbell  20  and addable weights  12 . Base dumbbell  20  includes end parts  22 . Base dumbbell  20  may comprise at least one magnet chip  16  embedded within surface  21  to which an addable weight  12  can be attached. At least part of addable weight  12  may be made of un-magnetizable material. Addable weight  12  may comprise at least one magnetizable chip  14 . When comprising more then one magnetizable chip  14 , magnetizable chips  14  may be located over an imaginary circle centered substantially at the center of pivot  18  in correspondence with a same number of magnet chips  16  within the surface  21 . Addable weight  12  can be attached to base dumbbell  20  by coupling magnetizable chip  14  to magnet chip  16 . Rotation of addable weight  12  relatively to surface  21  may detach magnetizable chip  14  from magnet chip  16  using shearing force and may locate magnet chip  16  against the un-magnetizable material, and thus addable weight  12  may be released and removed easily from base dumbbell  20 . The rotation of addable weight  12  may be about pivot  18  located substantially at the center of surface  21 . The perimeter of addable weight  12  may be jagged with jags  13  in order to facilitate easy gripping and rotating of addable weight  12 . 
   The use of shearing force makes the detaching of magnetizable chip  14  from magnet chip  16  much easier then if pulling force is used. For example, in some embodiments of the invention the shearing force needed in order to detach magnetizable chip  14  from magnet chip  16  may be 0.45 kg, while the pulling force needed in order to detach same magnetizable chip  14  from same magnet chip  16  may be 2 kg. The ratio of the shearing force needed to the pulling force needed depends on parameters like diameter, thickness, and the kind of materials being used, but the sheering force needed is always much smaller then the pulling force needed in order to detach magnetizable chip  14  from magnet chip  16 . In some embodiments the ratio of the shearing force needed to the pulling force needed may be about 0.3. 
   When rotating addable weight  12  about pivot  18 , the effect of a lever with length r and a prop point at pivot  18  may decrease the shearing force needed for detaching magnetizable chip  14  from magnet chip  16 . The rotation of addable weight  12  may be facilitated by the effect of a lever with length R and a prop point at pivot  18 . 
   Attention is made to  FIG. 2 , which is a schematic 3-D illustration of a cross section of a device  10  according to some embodiments of the invention. Magnet chip  16  may be co-planar with surface  21  and may not protrude out of surface  21 . Addable weights  12  may be adapted to rotate about pivot  18 . 
   Attention is made to  FIG. 3 , which is a schematic illustration of a device  10  according to some embodiments of the invention. Rotation of Addable weight  12  about pivot  18  may release Addable weight  12  from base dumbbell  20 . The linkage between additional weights  12  to base dumbbell  20  may be strong and safe while the releasing of additional weights  12  from base dumbbell  20  may be easy and may not require usage of great force. 
   Attention is made to  FIG. 4 , which is a partial schematic illustration of a device  10  (not shown) according to some embodiments of the invention. Addable weight  12  may be attached to end part  22  of base dumbbell  20  (not shown). Addable weight  12  may rotate about pivot  18 . Additional addable weight  11  may be attached to addable weight  12 . Addable weight  12  may comprise a central pivot  19  that additional addable weight  11  may be adapted to rotate about. Additional addable weight  11  may require less releasing force then addable weight  12 . Further additional addable weights (not shown) may be connected to additional addable weight  11  in a similar way. Smaller required releasing force may be provided by fewer magnets in additional addable weight  11  then in addable weight  12 , or by weaker magnets in additional addable weight  13  then in addable weight  12 .