9  EP 3 800 012 A1 10  [0032] According to the present invention, the power supply unit 40 is not inserted into the recess 7 of the tool housing 2 butratherlocatedexternally.Thepowersupply unit 40 is only connected to the power tool 1 by means of the adapter element 4 inserted into the recess 7 and the first cable 5. The adapter element 4 creates almost no heatduringoperation ofthe powertool1.Thisislarge- ly due to the fact that the adapter element 4 if at all com- prises only passive electric components which create al- most no heat during operation. The positioning of the power supply unit 40 in a distance to the power tool 1 eliminates any risk ofoverheating ofthe electricand elec- tronic components of the power tool 1 located inside the toolhousing2 due to heatfrom the powersupply unit40. An efficient heat dissipation is achieved by the fact that the power supply unit 40 can be freely located in t environment. Furthermore, the heat generated powersupply unit40 mayeasily dissipatetotheenviron- mentthrough respective cooling vents 43 provided in the power supply housing 44. The housing 44 may be made of metal or a plastic material. 15 10 5 electronic components of the power tool 1 on the one hand and the adapter element 4 or the battery pack 6, respectively, on the other hand. Of course, the electric terminals 14 and the contact pins 12 could be located at any other desiredposition,too,forexample in aside wall of the recess 7 and of the adapter housing 15 (or the battery housing 19), respectively. [0036] In principle the adapter element 4 is a special kind of plug element having an adapter housing 15 de- signed such that it can at least partly be inserted into the recess 7. The adapter housing 15 is provided with the contactterminals 14 in orderto establish the electriccon- nection to the contact pins 12 of the power tool 1. The adapterelement4 establishes an electricconnectionbe- tween the first electric cable 5 and the contact pins 12 of the power tool 1 located inside the recess 7. Preferably, no electricenergy istransformed bythe adapter element 4 because the electric energy is transformed externally by the power supply unit 40 and arrives at the adapter element 4 from the power supply unit 40 through the first electric cable 5. Hence, no bulky and heavy transformer has to be located in the adapter element 4. [0033] Furthermore,duetothe factthatthe powersup- ply unit 40 is provided outside of the recess 7 and does not form an integral part of the power tool 1, no re-ap- provalofthe powertool1 is necessary ifthebatterypack 6 is replaced by the adapter element 4 connected to the external power supply unit 40. The technical approval of the powertool1 obtained when operated with the battery pack 6 in most cases will also be valid for the power tool 1 when operated with the mains power supply through the adapter element 4 inserted into the recess 7 of the tool housing 2. 20 25 30 35 [0037] Ifatall,only smallerand lighterelectricand elec- tronic components which generate only a small amount of heat during operation are located in the adapter ele- ment 4 or the adapter housing 15, respectively. For ex- ample, the adapter element 4 may comprise a rectifier fortransforming an alternating voltage ofthemains pow- er supply into a direct voltage of the power tool 1 and/or an electronic filterelementforreducing interferencesand suppressing electronic disturbances. However, it is pre- ferred that these electric and/or electronic components are comprised by the power supply unit 40. To this end it is suggested that the power supply unit 40 comprises a rectifier 46 for transforming the alternating voltage of the mains power supply into a direct voltage (AD/DC- converter).Further,it issuggested thatthe power supply unit 40 comprises an electronic filter element 47 for re- ducing interferences and suppressing electronic distur- bances.The powersupply unit40 may comprise a printed circuit board (PCB) 48 to which some or all of the com- ponents 42, 46, 47, 48 of the power supply unit 40 are attached and/or electrically contacted. [0034] Finally, due to the fact that only the adapter el- ement4 isattached to the powertool1 and thattheadapt- er element 4 comprises not much more than the adapter housing 15, electric terminals 14 and electric cables 45 forconnecting the terminals 14 with the firstelectriccable 5 coming from the power supply unit 40 (see Fig. 3), the weight of the power tool 1 is evenly distributed along the longitudinalextension ofthe tool1.Preferably,the weight of the adapter element 4 (and part of the first electric cable 5 attached thereto and hanging down therefrom) is similar to the weight of the battery pack 6. Therefore, the power tool 1 according to the present invention can be easily used by a user over a longer period of time without signs of fatigue, no matter whether it is operated with energy from the battery pack 6 or from the mains powersupply(powersupply unit40 and adapterelement 4). 40 45 50 [0038] Alternatively, the power supply unit 40 may be embodied as a switched-mode power supply. Such a power supply unit 40 may be provided with a central processing unit for controlling the transformation of the electric energy. [0039] It is suggested that the tool housing 2 and the adapter element 4 are provided with corresponding at- tachmentmembers adapted to enterinto mutualengage- ment with each other upon complete insertion of the part 8 of the adapter element 4 to be inserted into the recess 7andto provide forareleasable attachmentofthe adapt- erelement4 to the toolhousing 2.The attachmentmem- bers provide for a safe and reliable attachment of the adapter element 4 to the tool housing 2. If desired, the attachment members can be manually actuated in order [0035] The adapter element 4 and the battery pack 6 are each provided with a socket element comprising the electric terminals 14 (schematically shown in Figs. 3, 4, 5 and 7), which is adapted for receiving respective con- tact pins 12 from the power tool 1, the pins 12 bei ng provided atthe farendoftherecess7.When the adapter element 4 or the battery pack 6 or their respective parts 8,9 are completelyinserted in tothe recess7,an electric connection is automatically established between t he 55 6