Patent Publication Number: US-2017373288-A1

Title: Battery pack

Description:
RELATED APPLICATIONS 
     This application also incorporates by reference in their entirety U.S. patent application Ser. No. 14/715,258, filed May 18, 2015, titled “Power Tool System.” 
    
    
     TECHNICAL FIELD 
     This application relates to cordless power tools and battery packs used in conjunction with cordless power tools. In one implementation, the invention is directed to a rechargeable battery pack for a cordless power tool having improved structural attributes and performance, particularly related to the mechanical interface between the battery pack and the power tool. 
     BACKGROUND 
     Various types of electric power tools are commonly used in construction, home improvement, outdoor, and do-it-yourself projects. Conventional power tools generally fall into two categories—corded power tools that are powered by an AC power source, e.g., an AC mains line, and cordless power tools that are powered by one or more DC power sources, e.g., a rechargeable battery pack. 
     The corded power tools generally are used for heavy duty applications that require high power and/or long runtimes, such as heavy duty sawing, heavy duty drilling and hammering, and heavy duty metal working. However, as their name implies, corded power tools require the use of a cord that can be connected to an AC power source. In many applications, such as on construction sites, it is not convenient or practical to find a continuously available AC power source and/or AC power must be generated by a portable power supply such as a generator, e.g. gas powered generator. 
     The cordless power tools generally are used for lighter duty applications that require low or medium power and/or short runtimes, such as light duty sawing, light duty drilling, and fastening. As cordless tools tend to be more limited in their power and/or runtime, they have not generally been accepted by the industry for all applications. They are also limited by weight since the higher capacity batteries tend to have greater weight, creating an ergonomic disadvantage. 
     As the desire for more powerful cordless power tools increases and as more powerful power tools are presented to the marketplace correspondingly more powerful battery packs to power the more powerful cordless tools must be developed. In order to provide more powerful battery packs, either additional cells are added to the battery pack or larger format cells are used in the battery pack. Under either circumstance the battery pack will increase in size and weight. The increased size and weight of the battery pack will place additional strain on the battery pack housing and mechanical interface system of the battery pack, particularly the rails of a rail and groove system common in slide-type battery packs. 
     SUMMARY 
     One aspect of the present invention is directed to a battery pack, comprising (1) a housing of a plastic material forming a mechanical interface for mechanically coupling the battery pack to a corresponding mechanical interface of a power tool, the housing mechanical interface including a rail, a groove and a sliding surface, the power tool mechanical interface including a rail, a groove and a sliding surface, wherein the housing mechanical interface is configured to receive the power tool rail in the housing groove between the housing rail and the housing sliding surface and the power tool mechanical interface is configured to receive the housing rail in the power tool groove between the power tool rail and the power tool sliding surface, and (2) a bracket encased within the housing plastic material, the bracket comprising a first portion positioned within the rail of the mechanical interface. 
     Another aspect of the present invention is directed to a battery pack, comprising (1) a housing of a plastic material forming a mechanical interface for mechanically coupling the battery pack to a corresponding mechanical interface of a power tool, the housing mechanical interface including a rail, a groove and a sliding surface, the power tool mechanical interface including a rail, a groove and a sliding surface, wherein the housing mechanical interface is configured to receive the power tool rail in the housing groove between the housing rail and the housing sliding surface and the power tool mechanical interface is configured to receive the housing rail in the power tool groove between the power tool rail and the power tool sliding surface, and (2) a U-shaped bracket encased within the housing plastic material wherein the bracket is positioned within the rail and the sliding surface and adjacent to the groove. 
     Another aspect of the present invention is directed to a battery pack, comprising (1) a housing comprising a plastic material and including a mechanical interface for mechanically coupling to a corresponding mechanical interface of a power tool, the mechanical interface comprising a rail, a groove and a sliding surface and (2) a U-shaped bracket encased within the housing plastic material wherein a first leg of the bracket is positioned within the rail and a second leg of the bracket is positioned adjacent to the sliding surface and a connecting member connecting the first leg and the second leg is positioned adjacent to the groove. 
     Another aspect of the present invention is directed to a method of manufacturing a battery pack, comprising the steps of (1) placing a metal U-shaped bracket in a mold; (2) placing a plastic material in the mold to surround the metal U-shaped bracket, such that the bracket is fixed in the plastic with (1) a first leg of the bracket positioned within a rail portion of a battery pack mechanical interface, (2) a second leg of the bracket positioned adjacent to a sliding surface of the battery pack mechanical interface and (3) a connecting member of the bracket connecting the first leg and the second and positioned adjacent to a groove of the battery pack mechanical interface. 
     Implementations of this aspect may include one or more of the following features. 
     Advantages may include one or more of the following: increased support for a removable battery pack when mated to a power tool, increased structural integrity for a removable battery pack mated to a power tool during operation of the power tool. 
     These and other advantages and features will be apparent from the description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary battery pack of the present invention. 
         FIG. 2  is a perspective detail view of the battery pack of  FIG. 1 . 
         FIG. 3  a section view of the battery pack of  FIG. 2  along lines  3 - 3 . 
         FIG. 4  is a perspective view of an exemplary insert of the present invention. 
         FIG. 5  is a section view of the battery pack of  FIG. 2  along lines  5 - 5 . 
         FIG. 6  is a perspective view of the battery pack of  FIG. 1 , including a partial cut-away of the battery pack housing to expose a portion of the insert of  FIG. 4 . 
         FIG. 7  is a side elevation view of the battery pack of  FIG. 1 . 
         FIG. 8  is a section view of the battery pack of  FIG. 7  along lines  8 - 8 . 
         FIG. 9  is a perspective transparent view of a top portion of a battery pack housing of a battery pack illustrating an alternate exemplary embodiment of an insert of the present invention. 
         FIG. 10  is a perspective view of an alternate exemplary embodiment of an insert of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , there is illustrated a removable, rechargeable battery pack  10 . The battery pack  10  may be used with a variety of cordless power tools, for example the cordless power tools illustrated and described in U.S. patent application Ser. No. 14/715,258, which is incorporated herein by reference. The battery pack  10  includes a housing  12 . The housing  12  may be made of a plastic material such as Polycarbonate-Acrylonitrile butadiene styrene sold under the brand name Cycology C3650 or Glass Filled Nylons (PA6). The housing  12  may be constructed using an injection molding process as is generally well known in the art. The housing may be formed by creating multiple housing parts, for example, a top housing part, a bottom housing part, and two side housing part. Various other housing forms are contemplated and included the present invention. 
     The battery pack  10  includes a plurality of battery cells  14 , illustrated in  FIG. 8 , for providing power to the attached power tool. The battery pack may include a variety of battery cells in a variety of configurations, as illustrated and described in U.S. patent application Ser. No. 14/715,258. 
     The battery pack housing  12  includes a power tool interface  16  for coupling to and mating with the cordless power tool. The power tool interface  16  includes a mechanical interface and interface elements for mechanically coupling the battery pack  10  to a corresponding mechanical interface and interface elements of the power tool to physically couple and mate the battery pack to the power tool and an electrical interface and interface elements for electrically coupling the battery pack  10  to a corresponding electrical interface and interface elements of the power tool to electrically couple and mate the battery pack to the power tool. 
     The illustrated exemplary battery pack  10  is what is commonly referred to as a slide or slide-type battery pack. In this type of battery pack the mechanical interface includes a pair of rails  18 , a pair of sliding surfaces  20  and a pair of grooves  22 , wherein in the grooves are positioned between the related rail  18  and sliding surface  20 . The mechanical interface of the power tool with which the battery pack  10  is designed to mate also includes a pair of rails, a pair of sliding surfaces and a pair of grooves. The battery pack  10  slides into mating engagement with the power tool. More particularly, the battery pack rails  18  slide along the sliding surfaces of the power tool and into the power tool grooves and the power tool rails slide along the battery pack sliding surface  20  and into the battery pack grooves  22 . The battery pack mechanical interface may also include a latch  24  which is received in a corresponding catch of the power tool mechanical interface. Alternatively, the battery packs may utilize a tower type mechanical interface. Both of these types of mechanical interfaces are well known by those of ordinary skill in the art. 
     As noted above, as battery packs become heavier, either due to the number of battery cells in the battery pack and/or the size of the battery cells in the battery pack the amount of stress and force placed on the mechanical interface increases. In addition, as the battery packs are placed on larger power tools, the amount of stress and force placed on the battery packs in general and the mechanical interface in particular increase when the power tool is dropped or otherwise abused. 
     To this end, the present invention adds a bracket  26 , also referred to as an insert, to the battery pack  10 . Referring to  FIG. 4 , an exemplary embodiment of the bracket  26  is illustrated. In the exemplary embodiment, the bracket is made of a metal material, such as AISI 1070 Carbon Steel (65MN STEEL). Alternatively, the bracket  26  may be made of a ceramic material. In the exemplary embodiment, the bracket  26  includes two U-shaped members  28   a,    28   b.  The U-shaped members  28   a,    28   b  are connected by a crossbeam member  30 . Each U-shaped member  28  includes a first portion or first leg  32 , a second portion or second leg  34  and a connecting member  36  that connects the first leg  32  and the second leg  34 . Each connecting member  36  may also include a plurality of through holes  38 —which will be explained in further detail below. The second leg  34  may also include a support member  40 —which will be explained in further detail below. The second leg may also include a through hole  42 —which will be explained in further detail below. The crossbeam member  30  may also include a plurality of through holes  44 . 
     During the manufacture of the battery pack, the bracket  26  is placed in a mold shaped to form the top portion of the housing. The support members  40  rest on a base of the mold. A top of the mold may include pins that are received in the crossbeam through holes  44 . The support members  40  and the pins/crossbeam through holes  44  serve to keep the bracket  26  in a fixed position relative to the mold such that as plastic material is injected into the mold the bracket  26  will remain in the desired position. As plastic material is injected into the mold, the plastic material surrounds and encases the bracket  26 . As illustrated in  FIG. 5 , during the molding process, the plastic material flows through the though holes  38  of the connecting member  36  to fasten and fix the bracket to the plastic of the battery pack housing. In a preferred embodiment, a ratio of the surface area of the through holes (and as such the plastic that flows through the through holes) to the surface area of the connecting member is approximately 1:5 and in a more preferred embodiment the ratio is 1:2. 
     As illustrated in  FIGS. 1-3 , the bracket  26  is positioned within and encased by the housing  12 . With regard to each U-shaped portion  28 , the first leg  32  is positioned within the rail  18 . The second leg  34  is positioned just below (in the orientation of the figures) and adjacent to the sliding surface  20 . The connecting member  36  is positioned just inside of (in the orientation of the figures) and adjacent to the groove  22 . The crossbeam  30  traverses a central portion of the housing and connects the two U-shaped portions  28   a,    28   b.    
     The bracket  28  provides additional support for the rail system. The bracket assists in holding the rails to the rest of the housing and prevents cracking of the housing near or about the rail/housing interface due to forces related to the weight of the battery pack or to dropping the power tool while the battery pack is coupled to the power tool. 
     Referring to  FIG. 6 , a set of battery pack terminals  46  are illustrated. The battery pack terminals  46  are part of the electrical interface of the battery pack  10 . During operation of the power tool, the battery pack terminals  46  increase in temperature due to the currents flowing through the terminals  46  and the resistance of the terminals. The U-shaped portion of the bracket  26  is positioned within the plastic housing so as to sink some of the heat generated by the terminals. 
     The shape of the bracket  26  is defined to maximize the surface area of the bracket. 
     The following conduction equation may be used to maximize surface area. 
         q=kA (T Hot −T Cold )/ L  
 
     The surface area (A) of the bracket  28  may be maximized by cutting slots and/or holes in the bracket  28  and/or creating bends in the material. The bracket  28  may be created by a single stamping and bent to create the final part or the bracket  28  may be created by several stampings to create several parts that when placed properly form the appropriate shape. The bracket may also be formed by casting. 
     As illustrated in  FIG. 9 , in an alternate embodiment, a bracket  28 ′ may be discrete U-shaped elements that are not connected by a crossbeam. Additionally, in another alternate embodiment, a bracket may be L-shaped elements with a first leg encased by the rail and the second leg encased by the housing adjacent to the groove. As illustrated in  FIG. 10 , in another alternate embodiment, a bracket  28 ″ may be may include a first portion or leg  48  that is encased by the rail and a second portion or leg  50 , offset from and perpendicular to the first leg  46  encased by the housing adjacent to the groove. The brackets  28 ″ may be connected by a crossbeam  30 ″. 
     In an alternate embodiment, all or part of the bracket may be formed as a wire mesh and bent to create a particular form. 
     In an alternate embodiment, the bracket  26  may be positioned in the injection mold such the crossbeam  30  abuts an upper portion of the mold to hold the bracket in place. As a result of this design, after the plastic material is injected into the mold and the housing is removed from the mold a portion of or all of the crossbeam  30  will be exposed. Thereafter, a label may be placed over the exposed metal to prevent electrostatic discharge. 
     In another alternate embodiment, the housing may be created in a two mold process. In other words, the bracket is encased in a first plastic (as described above) and the resultant plastic part is placed in a second mold and a second plastic (either of the same material as the first plastic part or of a different material) is injection molded around the first plastic part. 
     In another alternate embodiment, the second leg  34  of the bracket  28  serves as the sliding surface  20 . In other words, the second leg  34  is not fully encased by the plastic material of the housing but one surface of the second leg  34  is exposed and in the same plane as the sliding surface  20 . 
     Alternatively, a bracket or other metal insert may be encased in the plastic material in other parts and/or locations of the battery pack to provide additional strength for the parts. For example, an insert may be incorporated into the latch. Additionally, a metal insert can be placed in other parts of the battery pack housing to provide identifying information about the pack in the event of a catastrophic event. 
     Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of this application.