Thermodynamic properties of individual substances

An inertia locking seat belt retractor for winding a shoulder belt having one end mounted on the vehicle door to move the belt between stowed and restraining positions upon movement of the door. The retractor has a winding prevention mechanism including a pawl and ratchet for selectively blocking belt winding rotation of the belt reel to hold the belt extended at a set length to establish a slackened comfort condition relative the occupant. A manually actuatable control device has a normal condition blocking control of the pawl by a control disc frictionally clutched to the reel and is manually actuatable to release the pawl for control by the disc. The control disc actuates the pawl to provide the set length, defines a range of unwinding wherein the pawl is temporarily deactuated to permit subsequent rewinding to return the belt to the set length, and disengages the pawl upon still further unwinding rotation so that the pawl is deactuated upon belt unwinding during opening of the door. The manually actuatable control device may be operated to temporarily deactuate the pawl to allow belt unwinding. The pawl blocks return of the manually actuatable control device to the normal pawl blocking condition until belt unwinding causes the control disc to deactuate the pawl.