Drive device for rotatable operation of a drill bit of a down-the-hole hammer

The invention relates to a rotary device (101) for a down-the-hole hammer (1), which rotary device is accommodated in a rotation motor housing (3) and mounted behind a drill housing (2) for transferring a torque to a drill bit (8) and a pressurized drive fluid (22) to a striking mechanism (4) for the drill bit. The rotary device includes a cam curve with a plurality of drive lobes (28:1-28:3) and working chambers (30:1, 30:2, 30:3) along a circumference in the rotation motor housing (3), a rotor disc (38) carrying a plurality of radially movable vanes (40:1-40:12), which are accommodated in piston tracks (41:1-41:12) in the rotor disc. Characteristics of the rotary device are that it includes; an odd integer of a number of drive lobes (28:1-28:3), which is equal to or higher than three; an odd integer of a number of working chambers (30:1, 30:2, 30:3), which is equal to or higher than three; an odd integer of a number of vanes (40:1-40:12), which is equal to or higher than three, and wherein said number of vanes are simultaneously pressurized in each working chamber (30:1, 30:2, 30:3).