Patent ID: 8421570

Claim:
A rotary transformer for transmission of electrical power by electromagnetic induction between first ( 11 ) and second ( 12 , 12 ′, 12 ″) coils concentrically arranged on first ( 7 ) and second ( 8 ) tubular parts, respectively, made of a ferromagnetic material and coaxially mounted in such a way that the outer surface ( 13 a , 13 b , 13 c ) of the first part can rotate facing the inner surface ( 14 a , 14 b , 14 c ) of the second part, each part having opposing axial ends, each inner and outer surface comprising two straight cylindrical rotation surfaces ( 13 a , 13 c ) ( 14 a , 14 c ) having different diameters, each extending from a different one of the opposing axial ends to an intermediate radial shoulder surface ( 13 b , 14 b ) connecting the two straight cylindrical surfaces, said parts ( 7 , 8 ) being arranged head-to-foot one inside the other so as to delimit, between said shoulder surfaces ( 13 b , 14 b ), an annular space receiving said coils ( 11 , 12 , 12 ′, 12 ″) between two annular gaps each delimited by the facing cylindrical surfaces ( 13 a , 14 a ) ( 13 c , 14 c ) of said first ( 7 ) and second ( 8 ) parts, wherein each coil comprises only one layer of a plurality of windings, each winding having the form of a thin strip, and each coil is formed inside a metal ring by etching; wherein said layer of windings is fitted onto the part that carries it by means of a ring ( 9 , 10 ) made of an insulating material, said layer of windings being directly glued onto the insulating ring ( 9 , 10 ).