Patent Publication Number: US-2010124692-A1

Title: Battery pack and hand-held power tool

Description:
This claims the benefit of German Patent Application No. 10 2008 043 851.0, filed Nov. 19, 2008 and hereby incorporated by reference herein. 
     BACKGROUND 
     The present invention relates to a battery pack having a housing in which battery cells are arranged and having electric contact elements that are arranged on the housing. Such battery packs are used, among other things, in electrically operated hand-held power tools such as, for example, in electrically operated fastener driving devices. The invention also relates to a hand-held power tool of the type cited in the generic part of the subordinate claim. Such hand-held power tools draw the requisite operating power—at least at times—from a battery pack. 
     A battery pack of the generic type is known, for example, from German patent application DE 102 12 750 A1 that has several cells arranged in a housing. On one side of the housing, there are contact elements via which an electric connection can be established between the battery pack and the electric drive of a hand-held power tool. Latching elements arranged on the housing serve to attach the battery pack to the housing of a hand-held power tool. 
     German patent application DE 196 29 762 A1 discloses a hand-held power tool configured as an electrically operated fastener driving device that has an intermediate reservoir for kinetic energy in the form of a pneumatic spring. The energy stored in the pneumatic spring is used to rapidly accelerate a driving tappet of the fastener driving device. The pneumatic spring is charged by means of an electric drive that biases the pneumatic spring before a fastener driving procedure. A gas reservoir is arranged in the fastener driving device so that it is possible to repeatedly compensate for a loss of gas from the pneumatic spring caused by an unavoidable leakage that occurs. In order for the gas reservoir to contain sufficient gas for the entire service life of the fastener driving device, on the one hand, the gas cartridge has to be relatively large and, on the other hand, the gas in the reservoir has to be either liquefied or has to be in a supercritical state. Furthermore, there is also a cradle for a battery pack on the fastener driving device and this battery pack supplies the electric power for the electric drive. 
     SUMMARY OF THE INVENTION 
     A drawback of this fastener driving device is, first of all, that it is very large and secondly, that it is very laborious and expensive to replace the gas reservoir if it becomes empty before the end of the service life of the fastener driving device. 
     It is an objective of the present invention to develop a battery pack of the above-mentioned type that is optimally adapted for use with hand-held power tools whose operation requires electric power as well as gas that is under pressure. Another objective lies in putting forward a hand-held power tool that is adapted for operation with a battery pack according to the invention. 
     The present invention provides a battery pack having a housing in which battery cells are arranged and having electric contact elements that are arranged on the housing. Further, the battery pack has a gas reservoir and an output port for gas that is connected to the gas reservoir via a pressure line. 
     Thanks to this measure, the battery pack can supply not only electric power but also gas that is under pressure (such as, for example, compressed air). The gas that is under pressure and that is supplied by the battery pack can be used in a hand-held power tool such as an electrically operated fastener driving device with a pneumatic spring, for example, in order to compensate for a gas loss from the pneumatic spring due to leakage. The gas reservoir in the battery pack can be configured to be relatively small, since it can likewise be recharged during each battery charging procedure. Thus, a battery charger can be configured in such a way that, in addition to an electric contact point for charging the cells of the battery pack, it also has a connection point for the output port, in order to re-fill the gas reservoir in parallel to the electric charging procedure. 
     Advantageously, the gas reservoir is arranged inside the housing in such a way that the appearance of the battery pack does not differ from that of a conventional battery pack, and so that the gas reservoir is protected against penetration by dirt or moisture or against impact. 
     It is also advantageous for the contact elements and the output port to be arranged on a shared connection port so that, when the battery pack is attached to a device such as a hand-held power tool or charger, the contact elements and the output port are connected simultaneously to counter-contacts and to connection means located on the device. 
     It is also practical for an electronic unit to be provided that has a temperature sensor, so that, first of all, the temperature of the battery cells can be monitored and secondly, so that the gas reservoir can also be monitored indirectly (e.g. in case of severe cooling). Moreover, the electronic unit could also be connected to a pressure sensor to monitor the pressure in the pressure reservoir or to a pressure relief valve that functions as a safety valve. 
     When it comes to a hand-held power tool, the envisaged objective is achieved in that a connection means for an output port of a gas reservoir of the battery pack is arranged on the cradle for the battery pack, whereby said connection means is pneumatically connected to the device (such as, for example, a pneumatic spring). In this manner, an electric as well as a pneumatic connection can be established between the hand-held power tool and the battery pack. 
     Advantageously, the electric counter-contact elements and the connection means are arranged on a shared counter-connection port so that, when the battery pack is attached to the hand-held power tool, the contact elements and the output port are simultaneously connected to counter-contacts and connection means located on the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in the drawings below on the basis of an embodiment. The following is shown: 
         FIG. 1  a longitudinal section of a battery pack according to the invention, 
         FIG. 2  a longitudinal section of a fastener driving device with a battery pack according to the invention situated in a battery cradle. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a battery pack  10  according to the invention comprising a housing  11  and a plurality of battery cells  12  that are electrically connected to each other and that are arranged in the housing  11 . In this context, the battery pack can be configured, for instance, as a lithium-titanate, NiCd, NiMH, Li-ion, Li-polymer or Li—Fe battery. 
     The battery pack  10  also has an electronic unit  13  configured as an electronic control unit that is electrically connected to the battery cells  12  and monitors them, said electric unit being connected via an electric line  14  to electric contact elements  18  that are arranged on the housing  11 . The contact elements  18  are arranged at a connection port  17  that can be connected to a counter-connection port  37  of a hand-held power tool  30  (see  FIG. 2 ), of a charger or the like. The electronic unit  13  is also connected to a temperature sensor  21  such as, for instance, an NTC (negative temperature coefficient thermistor), as a result of which the temperature of the battery cells  12  can be monitored. 
     The housing  11  of the battery pack  10  also contains a gas reservoir  15  configured as a pressure vessel for a gaseous medium that is under pressure such as, for example, compressed air. Here, the gas reservoir  15  is connected via a pressure line  16  to an output port  19  that is arranged adjacent to the contact elements  18  at the connection port  17  on the outside of the housing  11 . Moreover, a valve  20  that, without being activated, prevents gas or gaseous medium from flowing out of the gas reservoir  15  is arranged in the pressure line  16  near the output port  19 . 
     In  FIG. 2 , the battery pack  10  is attached to a hand-held power tool  30  that is configured as an electric fastener driving device. The hand-held power tool  30  has electric consumers such as, for example, an electric drive motor  32  and an electronic control unit  33 . Moreover, the hand-held power tool also has a device  35  configured as a pneumatic spring. For this purpose, the drive motor  32  is configured so as to move a driving tappet  34  from its initial position shown in  FIG. 2  into a position in which it is biased against the pneumatic pressure spring or against the device  35 . 
     The pneumatic spring/device  35  is pneumatically connected to a connector or connection means  39  for the output port  19  of the battery pack  10  via a line  36  in which a valve means  40  is installed that can be regulated by the electronic control unit  33 . Here, the connection means  39  is arranged together with counter-contact elements  38  on a counter-connection port  37  for the connection port  17  of the battery pack  10  in the area of a cradle  31  of the hand-held power tool  30  for the battery pack  10 . When the battery pack  10  is attached to the cradle  31  of the hand-held power tool  30 , the connection port  17  is coupled to the counter-connection port  37  and an electric connection is established between the contact elements  18  and the counter-contact elements  38 , and, at the same time, a pneumatic connection is established between the output port  19  and the connection means  39 . A positioning element  41  that is configured as a mandrel and that is situated on the connection means  39  which—after the output port  19  and the connection means  39  have been coupled—extends into the output port, causes the valve  20  to open so that now the gas flow is only dependent on the controlled valve means  40 .