Patent ID: 7866411

Claim:
Handheld power tool effecting a reciprocating movement, comprising: a reciprocating tool holder, a rotary shaft, a first eccenter assembly fixed to said rotary shaft and translating rotary movement of the shaft into reciprocating linear movement of said tool holder, a counterweight counteracting reactive forces generated by the tool holder, further comprising: a second eccenter assembly also fixed to said rotary shaft and translating rotary movement of the shaft into reciprocating linear movement of said counterweight diametrically opposite to and in phase with the reciprocating linear movement of the tool holder, each of said first and second eccenter assemblies comprising a first member securely mounted on said drive shaft and having a circular part eccentric to said drive shaft and a second member, which is rotatably adjustable and lockable relative to said circular part and which has an off-center crank pin imparting reciprocating linear movement as said drive shaft rotates, wherein said counterweight is mounted on a connecting rod driven by the crank pin of said second eccenter assembly and is interchangeable to counterbalance different tools.