Tensioning apparatuses for occupant restraint systems and associated systems and methods

1. An occupant restraint system for use in a vehicle, the occupant restraint system comprising:

a plurality of elongate webs configured to extend across at least a portion of an occupant seated in a seat carried by a vehicle;

a first electrically actuated web retractor operably coupled to a proximal end portion of one of the webs;

a second electrically actuated web retractor operably coupled to a proximal end portion of another one of the webs, wherein the first and second web retractors are configured to automatically wind and unwind the respective webs; and

a sensor assembly electrically coupled to the first and second electrically actuated web retractors, wherein the sensor assembly includes one or more acceleration sensors configured to sense vehicle accelerations and decelerations in one or more directions,

wherein the sensor assembly is configured to send electrical signals to the first and second web retractors in response to a dynamic event resulting in a vehicle acceleration above a predetermined threshold value, and wherein, in response to receiving the electrical signals from the sensor assembly, the first and second web retractors are configured to (a) automatically increase tension in the corresponding webs, and/or (b) prevent the corresponding webs from moving inwardly or outwardly.

2. The occupant restraint system of claim 1 wherein the plurality of elongate webs comprises a five-point restraint system including a first shoulder web, a second shoulder web, a first lap web, a second lap web, and a crotch web.

3. The occupant restraint system of claim 2 wherein:

the first electrically actuated web retractor is coupled to a proximal end portion of the first shoulder web;

the second electrically actuated web retractor is coupled to a proximal end portion of the second shoulder web; and

the first and second web retractors and the sensor assembly are configured to fixedly attach to a rear portion of the seat.

4. The occupant restraint system of claim 1 wherein the individual electrically actuated web retractors comprise:

a base;

a spool rotatably mounted to the base and fixedly attached to a rotating shaft, wherein the spool is configured to wind, unwind, and/or lock the corresponding webs during operation;

a gear assembly operably coupled to a first end of the shaft;

a locking wheel operably coupled to a second end of the shaft, wherein the second end is opposite to the first end;

a DC motor operably coupled to the spool and configured to rotatably move the spool; and

a solenoid operably coupled to the spool configured to lock and unlock the spool in response to signals from the sensor assembly.

5. The occupant restraint system of claim 1 wherein the one or more acceleration sensors of the sensor assembly comprises:

a first acceleration sensor configured to sense vehicle accelerations in a forward and/or aft direction along an X-axis;

a second acceleration sensor configured to sense vehicle accelerations in a lateral direction along a Y-axis;

a third acceleration sensor configured to sense vehicle accelerations in a vertical direction along a Z-axis; and

an activation circuit configured to (a) disable the web retractors during normal vehicle operation, and (b) transmit the electrical signals to the web retractors when the vehicle experiences a dynamic event resulting in one or more vehicle accelerations above the predetermined threshold value.

6. The occupant restraint system of claim 1 wherein:

the first and second web retractors are configured to automatically tension the corresponding webs with a first force during a first dynamic event resulting in a first vehicle acceleration above the predetermined threshold value; and

the first and second web retractors are configured to automatically tension the corresponding webs with a second force greater than the first force during a second dynamic event resulting in a second vehicle acceleration above the predetermined threshold value, and wherein the second vehicle acceleration is greater than the first vehicle acceleration.

7. The occupant restraint system of claim 6 wherein the first and second web retractors are configured to automatically return the corresponding webs to normal or pre-event tension levels after the first dynamic event and after the second dynamic event.