Abstract:
The invention relates to a rechargeable battery for handheld electromechanical tools, having a plurality of battery cells that are connected electrically to one another by means of flat electrical cell connectors, wherein in a region of the rechargeable battery in which two cell connectors overlap, an electrical insulator is fixed to a cell connector of an electrical cell bypass. The invention further relates to an electromechanical tool, in particular a cordless screwdriver, power drill, circular saw, jigsaw, power sander, or garden tool, having a rechargeable battery according to the invention.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on German Patent Application No. 10 2007 031 859.8 filed on Jul. 9, 2007, upon which priority is claimed. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a rechargeable battery for landheld electromechanical tools, which has a plurality of battery cells connected electrically to one another. The invention also relates to an electromechanical tool having a rechargeable battery of the invention. 
         [0004]    2. Description of the Prior Art 
         [0005]    Electromechanical tools is a term for all handheld portable electrically operated hand tools in which a motor is a usually inseparable component of the tool. It applies for instance to power drills, cordless screwdrivers, circular saws and jigsaws, right-angle sanders and similar power sanders, and, depending on the design, various garden tools, such as electrical hedge clippers. Rechargeable or nonrechargeable batteries for such tools should have the highest possible capacity, the least possible weight, and require the least possible amount of space and furthermore should be capable of being manufactured economically. 
         [0006]    Electrical connections among battery cells or battery pack cells inside a rechargeable battery are as a rule designed such that electrical cell connectors do not overlap. The avoidance of overlapping cell connectors sometimes makes additional cord connections inside the rechargeable battery necessary. As a result, more space inside the rechargeable battery is occupied, and this space could otherwise be used in other ways for instance for larger battery cells, or for a rechargeable battery that is smaller overall. Moreover, short cords that serve to circumvent or avoid overlaps of cell connectors are in particular hardly feasible technologically, or if feasible, then only at major effort and expense for assembly. 
         [0007]    German Patent DE 100 03 740 C1 discloses a battery within a heat dissipator, and in the battery, a plurality of battery cells are interconnected. These battery cells are connected parallel, and each three battery cells are electrically connected by means of one cell connector and form a battery cell packet. The battery cell packets of the battery are electrically connected by means of current bridges and connected in series. As a result of the series connection, there are no overlapping cell connectors or current bridges. For dissipation of heat generated in the battery, a flat cooling plate is provided on at least one face end of the battery; this plate is at least indirectly in thermal contact with the cell connectors and current bridges. 
         [0008]    Rechargeable batteries and battery pack cells are becoming increasingly compact, and under some circumstances overlapping of electrical cell connectors cannot always be avoided. Cord connections required for the purpose use up space inside the rechargeable battery and are cost-intensive to manufacture. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0009]    It is therefore an object of the invention to disclose an improved rechargeable battery. In particular, it is an object of the invention to realize a space-saving electrical cell connection inside the rechargeable battery, where overlapping of cell connectors can be allowed, and thus to disclose a cell connector and a rechargeable battery with such a cell connector. It is furthermore an object of the invention to realize all electromechanical tool with a rechargeable battery according to the invention. 
         [0010]    The objects of the invention may be attained by means of a rechargeable battery and an electromechanical tool. 
         [0011]    According to the invention, a preferably flat electrical cell connector for a rechargeable battery is made available, and by means of the cell connector, at least two battery cells of the rechargeable battery can be connected electrically to one another. An electrical insulator is secured to the cell connector of the invention in at least one region where the cell connector bypasses a further cell connector; together, the cell connector and the electrical insulator create the electrical cell bypass according to the invention. In other words, the cell connector of the cell bypass has an electrical insulator in the portion or portions where there is the risk of a short circuit to one or more other cell connectors. 
         [0012]    In a preferred embodiment of the invention, the electrical insulator is a plastic that is integrally molded or extrusion-coated or back-injected onto the cell connector by means of an injection molding process. Preferably, only that portion of the cell connector where the cell connector bypasses the other cell connector is provided with the electrical insulator. As a result, the cell connector and hence the rechargeable battery as well can be as small as possible. 
         [0013]    The rechargeable battery of the invention and the cell connector of the invention are inexpensive, economical, easy to assemble, and reliable, since direct cord connections between battery cells can be avoided. The cell connector is easy to design with respect to its geometry and its temperature and electrical insulation behavior. Moreover, by varying the geometry of the electrical insulator, the cell connector of the invention is safe and reliable, since it is adaptable to the requirements that exist inside the rechargeable battery. 
         [0014]    In a preferred embodiment of the invention, the cell connector of the cell bypass is constructed like a conventional cell connector at a contact portion and it can be welded to a battery cell. The contact portion is preferably bifurcated and is secured to the battery cell by means of two spot welds. 
         [0015]    A second contact portion of the cell connector is either constructed like the first contact portion or is embodied as a tab. It is furthermore possible, on a cell connector having conventional contact portions, to provide tabs on one end or in a middle region of the cell connector. By means of the current-carrying tab, it is possible to dispense with wiring of the battery cells, or by means of an electrical connection of a cord to a tab for a cord (cord tab) to simplify the wiring. Preferably, the tab is bent in the direction toward a battery cell, so that as little additional space as possible is used. 
         [0016]    In preferred embodiments of the cell bypass of the invention, the electrical insulator is embodied as a securing portion on a side remote from the cell connector. In other words, by means of a securing portion integrally shaped into the electrical insulator it is possible to position the cell bypass quickly and easily inside the rechargeable battery; after that, a portion of the cell connector, for instance embodied as a conventional contact portion, is welded to a battery cell. If a cable tab is present, then it is preferable to perform the electrical connection of the cord to the tab before mounting the cell bypass of the invention on the battery cell or cells. 
         [0017]    In preferred embodiments of the invention, the electrical insulator has two securing portions; the first securing portion is seated on one battery cell, and the second securing portion is seated on a battery cell directly adjacent to it. As a result, the cell bypass of the invention is seated securely on two battery cells, so that welding of a contact portion to a battery cell is simple to do. Each securing portion is preferably provided at least in part as an imprint or as a 3D negative of a face-end portion of a battery cell in the electrical insulator of the cell bypass. It is furthermore possible to lock or glue the applicable securing portion to a battery cell. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings, in which: 
           [0019]      FIG. 1  is a 3D view of four battery cells, with an electrical cell bypass according to the invention seated on them; 
           [0020]      FIG. 2  is a view similar to  FIG. 1 , with the cell bypass shown in an exploded view; 
           [0021]      FIG. 3  shows the cell bypass in perspective from below; 
           [0022]      FIG. 4  shows the cell bypass in perspective from above; 
           [0023]      FIG. 5  is a central cross section through the cell bypass disposed on a battery cell; 
           [0024]      FIG. 6  is a side view of an additional embodiment of the cell bypass; and 
           [0025]      FIG. 7  is a side view of a farther embodiment of the cell bypass. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    The invention will be described in detail below in terms of a rechargeable battery for handheld electromechanical tools. However, the invention should not be limited to such handheld tools but instead should pertain to rechargeable batteries in general. Hence the invention can be applied for instance to rechargeable batteries for motor vehicles with internal combustion engines or for drives of electric motor vehicles. It is moreover possible for instance to use the invention for rechargeable batteries for portable electronic devices, drives such as drives in model building, and for cell phones, cameras, and the like. 
         [0027]    When the term cell connector is used below, it is understood that it also includes the term cell terminal for a pole of the rechargeable battery; that is, the invention also relates to that portion of a rechargeable battery where the cell connector, in the form of a rechargeable battery pole, is visible on the outside of the rechargeable battery. 
         [0028]      FIG. 1  shows a rechargeable battery  1  or a rechargeable battery string  1  or a rechargeable battery packet  1  or a battery  1 ; a housing of the rechargeable battery  1  is not shown. The rechargeable battery  1  has four battery cells  10  connected in series with one another, and an electrical connection of the battery cells  10  is effected via three conventional electrical cell connectors  210 .  FIG. 1  moreover shows an electrical cell bypass  100  according to the invention, which is seated on the face end on two battery cells  10  located side by side. It is understood that it is also possible to provide the rechargeable battery  1  with more or fewer battery cells  10 , and to connect the battery cells electrically in series or parallel as needed. The cell bypass  100  according to the invention can furthermore be seated on only one battery cell or on more than two battery cells  11  and/or can have other configurations besides what is shown in the drawings, particularly in  FIGS. 3 ,  6  and  7 . 
         [0029]    The electrical cell bypass  100  of the invention essentially has an electrical cell connector  110  and an electrical insulator  130 ; the electrical insulator  130  insulates the cell connector  110  electrically, at least in some portions.  FIG. 2  shows the cell bypass  100  of the invention in an exploded view outside the battery cells  10 . In the exemplary embodiment shown, the cell connector  110  is a flat, strip like electrical conductor  1107  which has an angled or L-shaped configuration. The cell connector  110  has two contact portions  112 ,  116 , to which electrical contacts, such as poles  12  of a battery cell  10  or a conductor of a cord  300  (see  FIG. 6 ), can be connected electrically. The contact portion  112  serves preferably to provide electrical contact with one pole  12  of the battery cell  10 . The contact portion  112  here is preferably bifurcated or embodied in a forklike fashion; one spot weld is made at each of the two portions separated from one another by a gap, and the spot weld electrically connects the contact portion  112  to the applicable pole  12 . The other contact portion  116 , in the present exemplary embodiment, is embodied as a tab  116 , to which a further tab  116  or the cord  300  can be connected electrically. In a center portion  114 , the cell connector  110  has recesses  115 , preferably through recesses  115 , through which corresponding protrusions  135  of the electrical insulator  130  can pass inward or all the way through, thereby causing the cell connector  110  to be fixed to the electrical insulator  130 . 
         [0030]    In the present exemplary embodiment, the electrical insulator  130  has two securing portions  132 ,  142 . By means of the securing portion  132 , which is also called the insulation portion  132 , the cell connector  110  is secured to the electrical insulator  130  on the one hand, and on the other, the cell bypass  100  is thus seated on a face end of a battery cell  10 . The securing portion  142  is furthermore embodied such that on the one hand, electrical contacting of one pole  12  of a battery cell  10  is assured by the contact portion  112  of the cell connector  110 , and on the other, seating of the cell bypass  100  on a battery cell  10  is possible. 
         [0031]      FIGS. 3 and 4  show the cell bypass  100  of the invention in its state ready for use. The electrical insulator  130  here is preferably integrally molded or back-injected onto the cell connector  110  by means of an injection molding process. 
         [0032]    In  FIG. 3 , the two securing portions  132 ,  142  can readily be seen. The securing portion  132  has an at least partially circular pole recess  134 , by means of which the cell bypass  100  is seated on one pole  12  of a battery cell  10 . A recess  136  for a cell connector  210 , or for a contact portion  212  of a cell connector  210 , can be provided on the bottom of the pole recess  134 . This can be seen in cross section in  FIG. 5 . 
         [0033]    The securing portion  142  adjoining the securing portion  132  is essentially circular-annular in construction and has a central through recess  146 . The contact portion  112  of the cell connector  110  protrudes through this continuous recess  146 , and as a result the contact portion  112  can electrically contact the pole  12  of the battery cell  10 . The securing portion  142  has an at least partially circular pole recess  144 , by means of which the cell bypass  100  can be seated on a pole  12  of a battery cell  10 . 
         [0034]    Overall, the electrical insulator  130  is dumbbell-shaped, as can be seen readily in  FIG. 3 . The two securing portions  132 ,  142  touch and are preferably joined into one piece as they may be made of the same material as one piece. 
         [0035]    The tab  116  protrudes laterally from the securing portion  132 . Preferably, the tab  116  is bent out of a plane of the electrical insulator  130 , or a plane of the cell connector  110 , in such a way that in an installed state it is bent toward a battery cell  10 . This can be readily seen in  FIGS. 1 and 2 . Another embodiment, with a tab  116  bent away from a battery cell  10 , is shown in  FIG. 6 . 
         [0036]    By means of the two securing portions  132 ,  142 , which are preferably placed on directly adjacent battery cells  10 , a fixation of the cell bypass  100  in three rotational and two translational directions inside the rechargeable battery  1  is possible. That is, the cell bypass  100  can be pulled off two battery cells  10  in only one translational direction. A fixation in that direction can be effected on the one hand via a housing of the rechargeable battery  1  and on the other via the spot weld or other fastening of the contact portions  112 ,  116  to the battery cells  10 . It is furthermore possible to glue and/or lock the cell bypass  100  to the battery cell or cells  10 . 
         [0037]    In the embodiment of the invention shown in  FIGS. 1 through 5 , the cell connector  110 , in a peripheral region of its tab  116 , passes through the electrical insulator  130 . This can be readily seen in  FIGS. 4 and 5 , in which a locking bar  138  of the electrical insulator  130  fits over the cell connector  110  and clamps to a portion located below it of the electrical insulator  130 . Directly adjacent to this, the tab  116  emerges from the electrical insulator  130 . The cell connector  110  furthermore preferably has continuous recesses  115 , which liquid plastic can enter into as the electrical insulator  130  is being integrally molded on, and thus by means of hardened protrusions  135 , the cell connector  110  is additionally solidly connected to the electrical insulator  130 . In the present example, three continuous recesses are provided on a longer portion of the center portion  114 , and one continuous recess  115  is provided on a shorter portion, which is located in the vicinity of the tab  116 . 
         [0038]    The electrical insulator  130  can also have recesses  139 ,  149  on its edges, in order to make the space required by the rechargeable battery  1  as slight as possible. That is, the electrical insulator  130 , at those points where later space is required, for instance for a housing of the rechargeable battery  1 , has suitable recesses  139 ,  149 . Preferably, these recesses  139 ,  149  are provided in corner regions of the electrical insulator  130  or corner regions of the rechargeable battery  1 . Thus the recess  149  shown in  FIGS. 1 and 4 , for instance, of the securing portion  142  serves to allow the housing to be as close as possible to a battery cell  10  of the rechargeable battery  1 , and thus serves to make the rechargeable battery  1  as small in size as possible. 
         [0039]      FIG. 5  shows a battery cell  10  in section, with a cell bypass  100  according to the invention seated on it; the cell bypass  100  is shown in section in a region of its securing portion  132 . It can readily be seen how the cell connector  110 , with its center portion  114 , and the second cell connector  210 , in the region of its contact portion  212 , overlap and are separated electrically from one another by the electrical insulator  130 . In this overlapping region, the electrical insulator  130  is embodied as thin and strip like. Because at least in this region the cell connector  110  has the electrical insulator  130 , and the cell connectors  110 ,  210  are embodied as strip like and flat, the cell bypass  100  can be embodied in as flat a form as possible on one end of a battery cell  10 . In  FIG. 5 , the tab  116  bent in the direction of the battery cell  10  can also be readily seen. 
         [0040]      FIGS. 6 and 7  show two further embodiments of the cell bypass  100  of the invention. 
         [0041]      FIG. 6  shows an embodiment with a cord  300  connected electrically to the tab  116 ; the cable tab  116  is bent away from the battery cell  10 . The cell bypass  110  here can have either no securing portions or one securing portion or even two securing portions  132 ,  142 . In the present embodiment of  FIG. 6 , the cell bypass  100  has no pronounced securing portion  132 ,  142 ; instead, it is simply seated with the electrical insulator  130  at the top on the cell connector  210 , or its contact portion  212 . As a result, space can be saved at the edges of the battery cells  10 . 
         [0042]      FIG. 7  shows a mechanical connection of a cell connector  100  to a cell connector  210 ; this mechanical connection is made via the electrical insulator  130 . The fixation of the two cell connectors  110 ,  210  is effected via the integral molding or back-injection in a certain region and once again by means of corresponding recesses  115  and protrusions  135 . The cell connector  110  fits over the cell connector  210 , and the contact portion  116  is superimposed on the contact portion  212 . Between them is the electrical insulator  130 , so that no short circuit between the two cell connectors  110 ,  210  can develop. The contact portion  116  can be adjoined for instance by a tab, not shown in  FIG. 7 , to which in turn the cord  300 , a cell connector  110 ,  210 , or a battery cell  10  can be electrically connected. 
         [0043]    The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.