Strap retractor assembly

A strap retractor assembly for use in a vehicular seat belt arrangement including an elongated flexible retaining strap to be fitted to an occupant of a seat structure in a vehicle body, comprising:

• a reel shaft rotatable about an axis fixed with respect to the vehicle body and having said retaining strap anchored thereto at one end of the strap;
• biasing means urging the reel shaft to turn about said axis in a direction to have the retaining strap re-wound on the reel shaft;
• a ratchet wheel rotatable with the reel shaft about said axis;
• a pawl member movable into and out of a position engaging the ratchet wheel and prohibiting the ratchet wheel and the reel shaft from being turned in said direction about said axis;
• pulse generating means positioned in the vicinity of said ratchet wheel and operative to produce first pulses in response to rotation of the reel shaft in one direction about said axis and second pulses in response to rotation of the reel shaft in the opposite direction about said axis;
• resettable pulse counting means electrically connected to said pulse generating means and operative to count said first pulses forwardly and said second pulses backwardly;
• comparing means electrically connected to said pulse counting means and operative to compare the number of the pulses counted by said pulse counting means with a predetermined number of pulses and to produce a control signal when the number of the pulses counted by the counting means is in a predetermined relationship to the predetermined number of pulses;
• and
• electro-magnetically operated actuating means electrically connected to said comparing means and responsive to said control signal and operative to drive said pawl member into said position in response to the control signal.