Abstract: A vehicle front seat of the kind capable of being selectively rotated into a forward position or rearward position has a turntable unit or rotation adjusting mechanism provided between the seat and a vehicle floor. The rotation adjusting mechanism includes a stationary circular guide and a rotating disk disposed inside the stationary guide. The rotating disk is provided with a latching arm having an engagement tooth. The stationary guide has a locking through hole for engagement with the engagement tooth of the latching arm. A cam is disposed inside the locking through hole and capable of contacting the engagement tooth inserted into the locking through hole. The cam is rotatable in response to movement of the engagement tooth. An amount of rotation of the cam is detected by a microswitch. The cam is provided with first and second circular arc cam surfaces and capable of absorbing possible errors in attached positions of the constituent parts of the rotation adjusting mechanism.

Abstract: A rotating device of a seat has a lower base member secured to a vehicle floor. The lower base member includes a radially inside annular raised part and a radially outside depressed annular part. An annular holder member includes a radially inner part and a radially outer part. The radially inside part is concentrically put on and secured to the radially inside annular raised part in a manner to define therebetween an annular space. An upper base member mounts thereon the seat. The upper base member includes a radially inner annular depressed part and a radially outer annular raised part. The raidally inner annular depressed part is spacedly inserted into the annular space. A first group of rolling balls are operatively arranged between the radially outer depressed annular part and the radially inner annular depressed part. A second group of rolling balls are operatively arranged between the radially inner annular depressed part and the radially outer part.