Patent Publication Number: US-8979719-B2

Title: Kettlebell and method of manufacturing a kettlebell

Description:
PRIORITY 
     The present application is a U.S. Nonprovisional Application and claims the priority benefit of pending UK Application No. GB 1110345.4, titled “KETTLEBELL AND METHOD OF MANUFACTURING A KETTLEBELL,” filed Jun. 20, 2011, the disclosure of which is incorporated herein by reference. 
     The present invention relates to an exercise device for weight lifting exercises and in particular to a kettlebell and a method manufacturing the same. 
     Kettlebells are a well known traditional weighted exercise device commonly used in gyms and have been largely unchanged over many years. Kettlebells comprise a weighted body with a single generally loop type handle which a user grips typically with one hand to lift and raise the kettlebell and carry out a number of exercises. Kettlebells are distinct to other types of exercise devices, for example dumbbells and barbells, in that they comprise a single weight and typical loop handle. The body is typically spherical and a range of kettlebells may be provided having differing weights. 
     Conventionally kettlebells are cast as an integral single one piece assembly from cast iron in varying sizes and weights. Kettlebells may be partially or fully covered in for example rubber or polyurethane to provide a more attractive appearance and provide protection when the kettlebells are dropped on the floor during use. Kettlebells are cast as a one piece structure in order to provide sufficient strength and robustness to withstand use. In particular kettlebells are subject to multiple impacts and jarring as they are dropped onto the floor and variously swung around by a user. Moreover due to the weight of the kettlebells and the swing movements carried out during exercise, it is highly undesirable for them to fail and for the body portion to become detached from the handle. 
     While such traditional kettlebells have been widely used, it has been identified that there are problems with such cast conventional kettlebells. In particular the finish of cast iron can be poor. This detracts from the appearance of the kettlebells and in relation to the handle is particularly undesirable as a rough cast surface is not ideal for gripping by a user. Furthermore, due to the loop shape of the handle machining of the cast loop handle to improve its surface further is not practical. Providing a covering over the outer surface of the cast kettlebells can improve the appearance and surface quality. 
     However providing a cover in the grip region is not ideal. Indeed it has been found important to provide a handle having both a suitable shape and surface for a user to grip and hold the kettlebells. One example of such an integral kettlebells is shown for example in US 20102055960. 
     More recently it has been proposed to cast the main body of the kettlebells and to then weld a metal loop handle to the cast body in a subsequent operation. This however has been found to also have its problems In particular welding of the handle to the cast body is not straightforward and requires accurate fabrication of both the handle and body. In addition welding for example a stainless steel looped handle (which is the preferred material for a handle due to its resistance and surface finish obtainable) to cast iron (which is the preferred material for the cast body) is in itself problematic. Furthermore such welded connections between a handle and body introduce a weakness especially if there are any defects in the welding due to for example the problems in such welding. It has been found that such kettlebells with welded handles may in use fail which is both undesirable and potentially dangerous. A welded connection between a handle and kettlebells body may also be unsightly and adds an additional manufacturing step and increases manufacturing costs. It is also difficult to accurately align the loop handle with the body to a sufficient accuracy and stability in order to achieve a satisfactory weld and weld quality. 
     It has also been proposed in U.S. Pat. No. 7,883,452 for example to couple a separate handle to a kettlebells by a pivotal screw connection. This arrangement is however more complex to manufacture and assembly comprising a number of components and such a pivotal connection may be prone to weakness and failure in use. 
     It is therefore desirable to provide an improved kettlebell which addresses the above described problems and/or which more generally offers improvements or an alternative to existing arrangements. In particular it is desirable to provide kettlebells with an improved handle arrangement which is suitably robust while also being relatively simple and cheap to manufacture. 
     According to the present invention there is therefore provided a kettlebell and a method of manufacturing a kettlebell as described in the accompanying claims. 
     In an embodiment of the invention there is provided a kettlebell comprising a handle and a main body portion. The main body weight portion is cast around a portion of the handle to thereby secure the handle to the cast main body portion. 
     By casting the body portion onto the end of the handle the body portion is both formed and attached to the handle in a single operation reducing manufacturing steps and adequately attaching the handle to the body portion. This means of fixing provides a secure connection between the main body and the handle which has been found to be far superior to previous fixing methods. As the body is formed about the handle there is no requirement for additional fixing means and as such no additional components to cause failure. The body may only become detatched from the handle through fracture of the handle or the body, the likelihood of which is extremely minimal. 
     The handle may comprise a loop handle having a grip portion and first and second arm portions extending from opposite ends of a centre portion attaching the grip portion of the handle to the cast body portion. The arm portions may have distal ends and the cast main body portion is cast around the distal ends of the handle arms. 
     The arms preferably extend at an angle in relation to each other and preferably to each other thereby preventing them from being pulled out of the cast body. 
     The handle may include interlocking features around the cast main body is cast to interlock the handle to the cast structure. 
     The interlocking features preferably comprise surface features formed on the handle. 
     The interlocking features may comprise grooves and/or projections formed in the outer surface of the portion about which the main body is cast. 
     A portion of the handle about which the cast main body is cast may be enlarged at least in one dimension. 
     A bore may be machined within a portion of the handle around which the main body is cast. The handle may comprise a stainless steel or chrome plated handle. A stainless steel handle and/or machined surface finish provides both an attractive appearance to the kettlebell and has a surface texture and finish which can be readily and comfortably gripped and grasped by a user. 
     The cast main body may be cast from cast iron. 
     The kettlebell may further comprise an outer cover around the outside of the at least the cast main body portion. 
     The coating may comprise a polyurethane or rubber material. 
     The portion of the handle around which the main body is cast preferably extends at an angle to the direction of load on the handle when in use. 
     A portion of the handle about which the main body is cast may be bent and preferably curved along at least a portion of its length. 
     In another embodiment of the invention there is provided a method of manufacturing a kettlebell comprising forming a handle; providing a mold having a first recess for receiving a portion of the handle and a second recess connected to the first recess for forming a main body portion of the kettlebell; locating the handle within the first recess of the mold with a portion of the handle extending and located in the second recess; casting the main body portion of the kettlebell within the second recess and around the portion of the handle located within the second recess; removing the handle and cast main body from the mold. 
     The mold preferably comprises a resin impregnated sand mold. 
     The method may further comprise covering the main body portion with a resilient cover. 
     The method may further comprise molding a resilient cover onto the main body portion. 
    
    
     
       The present invention will now be described by way of example only with reference to the following figures in which: 
         FIG. 1  is a schematic illustration of a kettlebell in accordance with the present invention; 
         FIG. 2  is a schematic vertical cross section of the kettlebell shown in  FIG. 1  showing the kettlebell in accordance with an embodiment of the invention; 
         FIG. 3  is a vertical cross section similar to  FIG. 2  through kettlebell in accordance with a second embodiment of the invention; 
         FIG. 4  is a vertical cross section through a kettlebell of a third embodiment of the invention; 
         FIGS. 5A and 5B  are schematic perspective and front views of the handle of the kettlebell shown in  FIG. 4 ; 
         FIG. 6  is a vertical cross section similar to that of  FIG. 2  through a kettlebell in accordance with an alternative embodiment of the invention; and 
         FIG. 7  is a vertical cross section similar to that of  FIG. 2  of a kettlebell in accordance with a yet further embodiment of the invention. 
     
    
    
     Referring to  FIG. 1  there is shown a kettlebell  10  in accordance with the invention. The kettlebell  10  comprises a generally spherical main body portion  12  connected (as discussed further below) to a loop handle  14 . The main body portion  12  is further covered with a polyurethane or rubber outer coating  16  to protect the main body  12  and also prevent the kettlebell  10  from damaging other objects. While the main body portion  12  is in this example generally spherical as is traditional for kettlebells it will be appreciated that the main body portion may have a different shape. 
     The loop handle  14  comprises a separate component and element of the kettlebell  10 , the handle  14  preferably comprises a stainless steel rod or chrome plated metal handle which is machined to provide and have a smooth outer surface and which is bent into a loop or formed shape. The handle  14  preferably includes a relatively straight centre section  13  which is sized such that it can be readily and easily grabbed by a user. A pair of curved arm sections  15  which are curved towards each other extend from either end of the straight section  13 . A stainless steel handle  14  and machined surface finish provides both an attractive appearance to the kettlebell  10  and has a surface texture and finish which can be readily and comfortably gripped and grasped by a user. Furthermore stainless steel is also generally resistant to corrosion and in particularly less affected by sweat from the users hand which could use deterioration if steel or some other materials could be used. The machined surface also provides a relatively smooth surface. 
     The main body portion  12  comprises a body of cast iron which, in accordance with the invention is cast around and onto the distal ends  18 ,  20  of the handle  14 . The main body portion is sized and shaped so as to produce a kettlebell  10  including the handle  14  of the appropriate desired weight. More specifically and to manufacture the kettlebell  10  the manufactured handle  14  is placed within a mold with the distal end  18 ,  20  of the handle  14  into a recess defined in the mold responding to the desired shape and size of the body portion  12 . Molten cast iron, or other material, is then poured into the mold and in particular recess and around the distal ends  18 ,  20  of the handle  14  to thereby both inform the body portion  12  around the distal ends  18 ,  20  of the handle portion and secure the handle  14  to the body portion  12 . The cast iron in particular both attaches to the distal ends  18 ,  20  of the handle  14  to secure the handle to the body structure. In addition the shape of the arm portions  15  of the handle  14  and in particular the inwardly curving arrangement and convergence of the distal ends  20  secure the handle  14  to the cast body  12  with the ends  18 ,  20  of the arm portions  15  of the handle  14  being prevented from being pulled out of the cast body portion  12  due to the inwardly curving nature of the arms  13 . As a result the handle  14  is securely attached to the body portion  12 . By casting the body portion  12  onto the end of the handle  14  the body portion  12  is both formed and attached to the handle in a single operation reducing manufacturing steps and adequately attaching the handle to the body portion  12 . 
     The ends  18 ,  20  of the handle  14  in particular extend at an angle with respect to each other and preferably at an angle to the direction of load which is generally vertical upon the handle  14  to thereby secure the handle  14  to the cast main body  12 . While the handle  14  is preferably a loop type handle, in other embodiments one may comprise only one main portion extending from the grip portion. 
     The mold for the cast iron main weight body portion  12  and kettlebell  10  preferably comprises a sand mold. The mold must however have sufficient strength when formed to support and locate the heavy stainless steel handle  14  in position during the casting of the body portion  12 . Accordingly it is preferred that a resin impregnated and reinforced sand mold and technique is used to form the mold. Such resin impregnated sand molds are relatively recent but well known and provide a relatively robust and sound cast mold for use in casting as compared to traditional sand molds. In particular simple sand cast molds would generally not have sufficient strength in order to securely and accurately locate the handle  14  in position. A more recent impregnated sand molds have sufficient strength to support the handle  14  during casting. Since such molding techniques are however known they will not be described further. 
     It will be appreciated that conventionally incorporating the handle  14  accurately into the mold during casting would not have been contemplated since, particularly due to its weight, it would have been anticipated that the handle  14  would move during assembly of the sand mold and casting. Furthermore conventionally kettlebells have been formed integrally as a one piece cast structure and this is the established general teaching. 
     The outer covering  16  in particular preferably covers the main weight body portion  12  and also interface between the handle and main weight body portion  12  to provide a more pleasing appearance to the dumbbell covering the rough cast surface of the body portion  12  and interface. In addition the covering also protects the cast body portion  12  from the element and accordingly corrosion as well as protecting both the kettlebell  10  from damage as well as due to the resilience of the outer covering protecting the other objects from damage by the kettlebell  10 . The covering  16  preferably does not however extend over the main part of the handle  14 . Such users prefer to grip a solid metal handle the coating  16  preferably comprises molded polyurethane or rubber or other suitable material which is molded around and onto the body portion  12  and kettlebell  10 . Molding and addition of such resilient coatings  16  onto a kettlebell is well known and will therefore not be described further. 
     Referring to  FIG. 3 , in an alternative embodiment generally similar to that described in relation to  FIGS. 1 and 2  and with like reference numerals for like features, at least one and preferably a plurality of grooves  22  are formed around the outer surface of the distal end portions  18 ,  20  of the handle  14 . The grooves  22  provide an improved key to interlock with the cast body portion  12  formed around the ends  18 ,  20  of the handle  14  with the cast material flowing into the grooves  22  further securing the handle  14  to the cast body portion  12 . The grooves may comprise circumferential grooves  22  around the distal ends  18 ,  20  of the handle  14  or may have any other configuration or shape. 
     Another alternative embodiment is shown in  FIGS. 4 and 5A  and  5 B. This is again generally similar to the previous embodiments and again like reference numerals are used for like features. In this embodiment the distal ends  18 ,  20  of the handle  14  are shaped and formed so as to further interlock with the cast body portion  12  formed around them. In particular as shown in  FIGS. 5A and 5B  showing the handle  14  on its own the distal ends  18 ,  20  of the handle  14  are formed such that they are widened and splayed in at least one direction such that when the body portion  12  is cast around the distal ends  18 ,  20 , these enlarged portions are retained in the structure. In particular in this case the distal ends  18 ,  20  are flattened for example by suitable forging such that the ends extend laterally wider than the width of the remaining portion of the handle  14 . 
     It will be appreciated that the distal end  18 ,  20  can be enlarged and formed in other ways to provide different shaped distal ends  18 ,  20  having dimensions in at least one direction to thereby interlock with the cast body portion  12 . 
       FIG. 6  shows a yet further variation and embodiment of the invention again similar to the previous embodiment with like reference numerals used for corresponding features. In this embodiment bolts  24  are fitted into bores  26  formed in the distal ends  18 ,  20  of the handle  14  prior to casting of the body portion  12  about the ends  18 ,  20  of the handle  14 . The bolts  24  project from the ends  18 ,  20  of the handle  14  thereby enlarging the ends  18 ,  20  of the handle  14  and further interlocking the handle  14  with the cast main body  12  which is cast around the ends  18 ,  20  of the handle  14  and bolts  24 . In an alternative variation the bolts  24  may be omitted and bores  26  simply provided in and extend through the ends of the handle  14  into which the cast material of the cast body portion  12  will flow during casting to interlock the handle  14  with the cast portion  12 . 
       FIG. 7  shows another alternative embodiment of the invention similar to the previous embodiments with again like reference numerals used for corresponding features. In this embodiment a tie bar  30  is fitted into bores  28  machined in the distal ends  18 ,  20  of the handle  14  which extends between and interconnects the distal ends  18 ,  20  of the handle  14 . The tie bar  13  is fitted to the handle  14  prior to casting of the main body portion  12  with the cast main body portion  12  extending around the tie bar and thereby interlocking and securing the tie bar and handle within the cast main body  12 . In a further variation on this embodiment the handle  14  itself may comprise a complete loop with the distal end  18 ,  20  being joined together and abutting each other. 
     In all these embodiments the handle  14  is secured to the cast main body  12  by virtue of the shape of the end  18 ,  20  and configuration of the handle  14  such that the handle  14  can not be removed and detached from the cast  12  and is mechanically secured thereto in addition to the cast material of the cast main body  12  adhering directly to the handle  14 . The mechanical interference of the handle with the cast main body  12  however provides a much stronger and secure attachment of the handle to the cast main body than for example is provided by simple adherence of the material to the metal of the handle  14  for welding. Furthermore by casting the main body  12  around the ends  20  of the handle  14  the connection between the handle  14  and main body  12  is hidden within the main body  12  providing a more aesthetically pleasing kettlebell  10 . 
     It will be appreciated that various further modification and variations to the kettlebell arrangement described and alternative embodiments may be provided. In particular while it is preferable to use a stainless steel handle  14  other materials may be used. Similarly whilst cast iron is the preferred material for the cast main body  12  in particular due to its density, weight and relative cheapness and ease of casting other materials may be used for the main body. In addition various alternative interlocking arrangements and formations in particular on the distal ends  18  and  20  of the handle  14  may be utilised to enhance the interlocking and interconnection between the handle and body  12 . In other embodiments the outer coating  16  may be omitted. 
     The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its scope as defined by the claims.