A belt roller for a safety belt having a belt coil for winding and unwinding the safety belt. The roller includes a lockable locking base which is connected to the belt coil and which is suitable for blocking the belt coil in the event of an abrupt rotation of the belt coil in the belt unwinding direction. The roller also includes a force transmission element which couples the belt coil and the locking base in a locking position and is inactive in an unlocking position. The force transmission element has a base member and a shearing portion which can be sheared off.
1. A belt roller for a safety belt having a rotatable belt coil for winding and unwinding the safety belt, a lockable locking base which is connected to the belt coil and which blocks rotation of the belt coil in the event of an abrupt rotation of the belt coil in the belt unwinding direction, and a force transmission element which couples the belt coil and the locking base in a locking position and is inactive in an unlocking position,
wherein the force transmission element includes a base member and a shearing portion configured to be sheared off from the force transmission element,
wherein the base member is retained in an axially displaceable manner in a recess of a first portion, wherein the first portion comprises either the belt coil or the locking base and a second portion comprises the other of the belt coil or the locking base, and
wherein the base member is configured to be axially displaced from a first position, in which the base member protrudes from the recess and engages the second portion, into a second position, in which the base member is separated from the second portion and is positioned more deeply within the recess than when the base member is in the first position, and
wherein, in the first position of the base member, the shearing portion blocks an axial displacement of the base member from the first position into the second position and wherein the base member is displaced from the first position into the second position only after the shearing portion is sheared off.
2. The belt roller as claimed in claim 1 , wherein the shearing portion has a stop face against which the second portion presses radially when the belt coil is rotated in the belt winding direction and wherein the shearing portion is sheared off by the second portion when the belt coil is rotated in the belt winding direction when the belt winding force acting on the stop face exceeds a predetermined force threshold.
3. The belt roller as claimed in claim 2 , wherein the shearing portion has a support face which is positioned in an axial direction at the outer side on the first portion and which, before the shearing portion is sheared off, blocks a displacement of the base member from the first position into the second position.
4. The belt roller as claimed in claim 3 , wherein the support face and the stop face are perpendicular.
5. The belt roller as claimed in claim 1 , wherein the belt roller is configured to be driven in the belt tightening direction and wherein the shearing portion is configured so that when the belt roller is driven in the belt tightening direction the shearing portion is sheared off and the base member is displaced from the first position into the second position.
6. The belt roller as claimed in claim 1 , wherein the belt roller includes a spring having a resilient force that urges the base member to move in the direction of the second position.
7. The belt roller as claimed in claim 1 , wherein the second portion has a recess having a first receiving portion and a second receiving portion and, in the first position of the base member, a portion of the base member engages in the first receiving portion of the second portion and the shearing portion engages in the second receiving portion of the second portion.
8. The belt roller as claimed in claim 7 , wherein the first receiving portion of the second portion is larger than the portion of the base member located therein so that the base member is moveable within the first receiving portion.
9. The belt roller as claimed in claim 1 , wherein the shearing portion has a support face which is positioned in an axial direction at the outer side on the first portion and which, before the shearing portion is sheared off, blocks a displacement of the base member from the first position into the second position.