主权项 |
1. A power tool comprising a stationary body, a shaft having at least one sensor and axially and rotationally movable relative to said body, and a transformer, said power tool further comprising:
a stator which is fixed relative to said body, and including at least one stator winding; and a rotor which is movable with said shaft, and including at least one rotor winding, wherein: a magnetic field is shared by said at least one stator winding and said at least one rotor winding and is used for creating a contactless signal connection between said body and said at least one sensor of said shaft, said stator has a substantially tubular form with a substantially uniform outer peripheral diameter and has a first part of a first length and a second part of a second length, said first part being shorter than said second part, and said first part having a smaller inner diameter than an inner diameter of said second part, said rotor has a substantially tubular form with a substantially uniform inner peripheral diameter and has a first part of a first length and a second part of a second length, the first part being longer than the second part, and the first part having a smaller outer diameter than an outer diameter of the second part of the rotor and smaller than the inner diameter of the second part of the stator, the rotor is arranged inside the stator such that a portion of the first part of the rotor reaches inside the first part of the stator, such that an air gap is formed between said second part of the stator and said second part of the rotor in which air gap a portion of the second part of the stator faces the first part of the rotor over a certain length (Lair), the at least one stator winding is arranged along the second part of the stator close to the first part of the stator and the at least one rotor winding is arranged along the first part of the rotor close to the second part of the rotor such that the at least one stator winding and the at least one rotor winding do not overlap, and at least one of said stator and said rotor is at least partly arranged with shielding means for reducing a flux leakage between said stator and said rotor, said shielding means being arranged on one of said stator and said rotor over a portion of said length (Lair) of said air gap, between the at least one stator winding and the at least one rotor winding. |