7  EP 3 800 012 A1 8  relatively large currents. Furthermore, the first electric socketofthe powersupplyunitshould comprise mechan- ical protection means in order to prevent a person from reaching the contacts of the socket with his/her fingers or an electric conductor and from getting an electri shock. Further, the plug-and-socket-connection should be water- and dustproof. Due to the fact that the power supply unit is located in a distance to the power tool and connected thereto by the flexible first cable, there is no risk that the plug-and-socket-connection will be uninten- tionallydisengaged even during intense use ofthe power tool. [0027] It would be possible that the power supply unit is an integral part of a vacuum cleaning device. In that case the power supply unit would be located inside the housing of the vacuum cleaning device. The socket of the power supply unit could be provided in the housing of the vacuum cleaning device. 5 c 10 15 20 [0028] Further, the power supply unit may comprise a second electric socket for releasably attaching the sec- ond cable to the power supply unit. The second cable is the power cable connecting the power supply unit to the mains powersupply.One end ofthe cable has a conven- tional plug for connecting the cable to a socket of the mains power supply. The opposite end of the second cable could be provided with another plug adapted for connection tothe secondsocketofthe powersupplyunit. The second socket may be embodied as a conventional 3-pole AC current inputmodule.In thatcase, the second cable could be a conventional power cable comprising a mains power supply plug on one end and a 3-pole AC currentplug forconnection to the 3-pole AC currentinput module on the other end. Respective power supply units and power cables are readily available off the shelf in large numbers and at reasonable prices. 25 30 35 [0030] The present invention refers to an electrically driven hand-guided powertool1.In the figuresthe power tool 1 is embodied as a polisher. However, it might just as well be embodied as a sander or any other hand- guided electric power tool. The power tool 1 comprises a tool housing 2 with a recess 7 for receiving at least a part 9 of a battery pack 6 (see Fig. 5). The design of the recess 7 essentially corresponds to the part 9 of the bat- tery pack 6 inserted therein, in order to allow insertion of the inserted part 9 of the battery pack 6 into the recess 7 and electric connection of the battery pack 4 with the power tool 1 and operation of the power tool 1 by means of electric energy originating from the battery pack 6. [0031] It is suggested that the power tool 1 comprises an adapter element 4 having an adapter housing 15 at leastpart8 ofwhich essentially corresponding to the form and design of the recess 7 and adapted to be inserted into the recess 7 after removal of the battery pack 6, in order to allow electric connection of the adapter element 4 with the power tool 1 (see Figs. 1 and 3). The adapter element 4 is connected to an external power supply unit 40 by means of a first electric cable 5 and the power supply unit 40 can be connected to an electronic mains power supply by means of a second electric cable 41 having amains powerplug5a atits distalend.The power supply unit 40 comprises an electric transformer 42 for transforming the electric energy from the mains power supply into electric energy corresponding to the electric energy supplied by the battery pack 6, in order to allow operation ofthe powertool1by means ofelectricenergy originating fromthe mains powersupplyand transformed by the power supply unit 40. The mains power supply voltage may be e.g.230 V or110V.Thevoltage provided by the battery pack 6 corresponds to the operation volt- age of the power tool 1, in particular of an electric motor and further electric and electronic components of the power tool 1 contained in the tool housing 2. The oper- ation voltage may be e.g. 12 V, 18 V, 24 V, 36 V or 48 V. [0029] Furtherfeaturesandadvantages ofthe present invention will be described in further detail hereinafter with reference to the accompanying drawings. Each of the features shown in the drawings and described herein, can be combined with any other feature even if such a combination is not shown in the drawings and/or not ex- plicitly described herein. The drawings show: 40 45 50 55 Figure 4 the battery pack of Fig. 2 in a more detailed, partially sectional view; Figure 3 the power tool of Fig. 1 in a more detailed, partially sectional view; Figure 2 a battery pack adapted for insertion into the recess of the housing of the power tool of Fig. 1 after removal of the adapter element; Figure 1 an electric power tool according to pr ferred embodiment of the present invention equipped with an adapter element inserted into a recess of the tool housing; Figure 9 the externalpowersupply unitforuse togeth- erwith the adapterelementin a second view. Figure 8 an externalpowersupply unitforuse togeth- erwith the adapterelementina firstview;and Figure 7 the adapterelementadapted forbeing insert- ed into the recess ofthe housingofthe power tool of Figs. 1, 3 and 6 in a more detailed, partially sectional view; Figure 6 the housing of the power tool of Figs. 3 and 5 without an adapter element or a battery pack inserted intothe recessofthe toolhous- ing; Figure 5 the power tool of Fig. 3 with a battery pack inserted into the recess of the tool housing instead of the adapter element; 5