## Description 

[0001] The present invention refers to an electrically driven hand-guided powertool,in particulara polisheror a sander. The power tool comprises a tool housing with a recess for receiving at least a part of a battery pack, the design of the recess corresponding to the part of the battery pack inserted therein, in order to allow insertion ofthe part of the battery pack intotherecess and electric connection of the battery pack with the power tool and operation of the power tool by means of electric energy originating from the battery pack. 

[0002] Power tools of the above-mentioned kind are well known in the prior art. For example, EP 2 712 713 A1 describes a power tool with a battery pack which is inserted into a recess of the tool housing for operation of the power tool by means of electric energy originating from the battery pack. Battery operated power tools are particularly useful when a high degree of flexibility and moving around oftheuserwith the powertoolisrequired, for example when polishing or sanding small surfaces with a complex three-dimensional extension. Movement of the user and the power tool is not obstructed by an electric cable connecting the power tool to an electronic mains power supply. However, due to a limited capacity of battery packs, battery operated power tools run up against their limits where high power is required over a long period of time, for example when polishing or sand- ing large surfaces. 

[0003] Therefore, it is known from EP 2 712 713 A1 to replace the battery pack with a power supply unit which may be inserted into the recess at least in part instead of the battery pack. The power supply unit is attached to an electronic mains powersupply and comprises anelec- tric transformer for transforming the electric energy from the mains power supply into electric energy correspond- ing to the electric energy for operating the power tool. Hence, when replacing the battery pack with the power supplyunitthepowertoolisoperated foran almostinfinite amount of time by means of electric energy originating from the mains power supply and transformed by the power supply unit. 

[0004] The power supply unit known from EP 2 712 713 A1 is also called "mainsconnector". The term "main- sconnector" refers to a special switching power supply unit for cordless power tools. The power supply unit is in a battery-housing so it can be attached to the power tool just like a conventional battery pack. Hence, a "mains- connector" allows cordless power tools to be operated with electric energy originating from a mains power sup- ply. 

[0005] However, power tools with a power supply unit inserted into the recess ofthe toolhousing have a number of drawbacks. First of all, if a main power supply is de- veloped and sold for insertion into the recess of a tool housing insteadofthe battery pack,the entire powertool with the power supply unit inserted therein has to be ap- proved (testing and certification) in order to obtain the 

approvals (e.g. the VDE-approval) necessary for selling an electric power tool in the European Union. Even though the power tool with battery pack inserted therein may have already been approved, the replace- mentofthe batterypack bythe powersupply unitrequires a re-approval of the entire power tool together with the power supply unit inserted therein. 

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[0006] Further, during operation power supply units comprising electric transformers for transforming the electric energy from the mains power supply into electric energy corresponding to the electric energy supplied by the battery pack, a large amount of heat is generated. Thisisdue to the ratherlow efficiency ofknow transform- ers.If the powersupply unitis atleastpartly inserted into the recess of the tool housing heat issues may arise be- cause dissipating the generated heat through the tool housing is difficult and only possible to a limited extent. As a consequence, the power tool may often be auto- matically turned off as a safetymeasure in orderto avoid overheating of the electric and electronic components of the power tool located inside the tool housing. 

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[0007] Finally, power supply units comprising electric transformers for transforming the electric energy from the mains power supply into electric energy correspond- ing to the electric energy supplied by the battery pack are often rather heavy.This results in a shifting of weight of the power tool towards where the recess is provided, usually towards the rear end of the power tool, if the bat- terypackisreplaced by thepowersupplyunit.The power tool may no longer have an even distribution of weight, which may further obstructease ofuseofthepowertool. 

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[0008] Therefore,itisanobjectofthe presentinvention to provide for an electric power tool which may be oper- atedwith a batterypack orwithelectricenergy originating from a mains power supply and which overcomes the above drawbacks. In particular, the power tool should not have to be re-approved if operated with the mains powersupply instead ofthebattery pack,the overheating problemduring operationofthe powertoolwith the mains power supply should be overcome and the power tool should have an even distribution of weight no matter if it is operated by the battery pack or with the mains power supply. 

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[0009] Theseobjectsare solved by the electricallydriv- en power tool comprising the features of claim 1. In par- ticular, starting from the electric power tool of the above- mentioned kind, it is suggested that the power tool com- prises an adapter element having an adapter housing at least part of which corresponding to the form and design of the recess and adapted to be inserted into the recess afterremovalofthebatterypack,in ordertoallow electric connection of the adapter element with the power tool, the adapterelementbeing connected to an externalpow- er supply unit by means of a first electric cable and the power supply unit being connectable to an electronic mainspowersupplyby means ofa second electriccable, the power supply unit comprising an electric transformer fortransforming the electricenergyfromthe mains power 

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