Belt roller for a safety belt system of a passenger seat

In a belt roller for a safety belt system, a rod assembly has a torsion rod as well as at least one torsion sleeve which surrounds it coaxially. A stopping mechanism is provided with at least two axially offset stopping element sections, which can be adjusted either individually or jointly to the at least one torsion sleeve and to the torsion rod through the use of a control mechanism depending on the energy absorption capacity to be applied.

BACKGROUND AND SUMMARY OF THE INVENTION 
This application claims the priority of German Application No. 197 33 
787.2, filed Aug. 5, 1997, the disclosure of which is expressly 
incorporated by reference herein. 
The invention involves a belt roller for a safety belt system of a 
passenger seat, especially in a motor vehicle, with a pivoted hollow shaft 
used for rolling up a belt band and with a torsion rod structure placed 
coaxially inside the hollow shaft and connected with a twistlock thereto, 
to which devices to adjust its energy absorption capacity are allocated 
depending on the weight of the person sitting on the passenger seat, and 
with a blocking mechanism which can be brought to make an effective 
connection with the torsion rod structure to stop the hollow shaft in 
response to a defined jerk on the belt band. 
Such a belt roller is known from German Patent document DE 27 27 470 A1. 
The belt roller has a hollow shaft, on which the belt band to be pulled 
out is rolled up. The hollow shaft is penetrated coaxially by a torsion 
rod structure shaped like a single torsion rod, the clamping length of 
which is adjustable by a sliding sleeve. The relocation of the sliding 
sleeve and hence also the change in the energy absorption capacity of the 
torsion rod is accomplished through the use of a cable pull control which 
connects directly to a seat surface of the passenger seat. Depending on 
how deep the seat surface is depressed by the weight of the person sitting 
on this seat, an appropriate relocation of the sliding sleeve necessarily 
takes place and, accordingly, the limit desired in each case is imposed on 
the belt power. The torsion rod is connected to the hollow shaft with a 
twistlock on one side and can be activated on the opposite side by a 
stopping mechanism, which is activated in the well-known manner by a jerk 
on the belt band of the safety belt during its acceleration. 
From German Patent document DE 43 44 656 C1 an additional belt roller is 
known, the belt power limitation of which is adjustable in accordance with 
the weight of the person sitting on the passenger seat. For this purpose, 
a conically shaped torsion rod has been provided, which is also axially 
adjustable by a corresponding activation mechanism, thus creating the 
corresponding change in the energy absorption capacity of the torsion rod. 
It is the purpose of the present invention to create a belt roller of the 
above-mentioned type which provides a simple means of adjusting the belt 
power limitation to account for the different types of people having 
different weights who sit on the passenger seat. 
The present invention solves this task by the fact that the torsion rod 
assembly has a torsion rod and at least one torsion sleeve coaxially 
surrounding it, and that the stopping mechanism is equipped with at least 
two stopping element sections which can be adjusted either individually or 
jointly to the (at least one) torsion sleeve or to the torsion rod by 
means of a control mechanism depending on the energy absorption capacity 
to be applied. This permits a gradual change in the energy absorption 
capacity, with the number of steps to set the energy absorption capacity 
being defined by the number of torsion sleeves mounted radially and 
coaxially to enclose the torsion rod on the outside. 
According to the invention, the means to change the energy absorption 
capacity of the torsion rod assembly are provided directly in the area of 
the stopping mechanism and not--as in the current state of the art--on the 
opposite side of the belt roller. For this reason, there is a savings on 
construction components and a space-saving arrangement. The axial shift of 
the stopping sections makes it possible for all the stopping sections to 
act simultaneously, so that the torsion rod assembly can be blocked either 
partially or totally by the stopping blocking mechanism. 
In one preferred embodiment of the invention, the stopping element sections 
are located on a common stopping element, with the stopping element 
sections being placed at intervals in the direction of adjustment in such 
a way that the stopping element section activating the torsion rod is the 
first to achieve an effective connection with the torsion rod. This 
configuration ensures that the torsion rod itself is activated in the 
first stage of the belt power limitation. During the second stage, a joint 
activation of the torsion rod and the first torsion sleeve takes place, 
and, if possible, in a third stage the supplementary activation of the 
third torsion sleeve takes place, and so on. 
In another preferred embodiment of the invention, the stopping element 
sections are shaped as stopping gear elements that are adjustable radially 
to the torsion rod assembly, and, both on the torsion rod and on the (at 
least one) torsion sleeve, corresponding ring gears are provided. Due to 
the radial adjustability of the stopping gear elements, no additional 
construction space is required for the belt roller in the axial direction. 
Preferably, the ring gears are designed as toothed gears mounted on the 
adjacent front sides of the torsion rod and of the (at least one) torsion 
sleeve. The stopping gear elements are designed as pawls. 
In another preferred embodiment of the invention, at least one catch that 
can be adjusted by the control unit is assigned to the stopping element. 
The catch limits the stopping element in its adjustment path for a gradual 
effective connection with the torsion rod assembly. The catch can 
preferably be moved electromagnetically between its rest position and its 
operating position, which appropriately blocks the stopping element, with 
the shift of the catch by the control unit resulting from an electronic 
recognition of the weight in the area of the seat surface of the passenger 
seat. 
In yet another preferred embodiment of the invention, a gear notch of the 
ring gear on the torsion rod is configured in such a way that the 
respective stopping gear element meshes in both the first and the last 
step of the effective connection with the torsion rod assembly. This 
guarantees that, with extremely simple means, the torsion rod assembly is 
effective at all stages of the belt power limitation. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
A belt roller according to FIGS. 1 through 3 is part of a safety belt 
system for a vehicle passenger seat. The belt roller has a hollow shaft 1, 
which on its outer circumference is equipped with a winding area 2 to wind 
up a belt band of the safety belt. The hollow shaft 1, 2 has been mounted 
with freedom to rotate around a rotational axis D in a known manner. In 
addition, a retraction mechanism (not shown) is located in the hollow 
shaft 1, 2 which, in a known manner, effects the automatic rolling up of 
the belt band (not shown). 
Starting from a defined acceleration of the extraction of the belt band, 
further turning of the hollow shaft 1, 2 is stopped, so that the safety 
belt is locked (blocked) in the position it was originally fastened. This 
occurs in a known manner when the motor vehicle decelerates suddenly and 
the person sitting in the seat of the vehicle accelerates forward as a 
result. Through the locking of the safety belt, the actual restraining 
function of the safety belt is performed during this vehicular 
deceleration. In order to achieve the stopping of the hollow shaft 1, 2, 
this shaft has been placed in a stopping mechanism (not shown in detail), 
which, in a known manner, through the corresponding centrifugal force 
causes a catch pawl 10 to fall when the belt band is extracted with a 
jerk, this catch pawl being a stopping element of the stopping mechanism. 
The catch pawl 10 is mounted with freedom to swivel around an axis S 
parallel to the rotational axis D. The catch pawl 10 acts on a 
corresponding outer gear 7 (designed as a ring gear) of a toothed gear 6, 
which is mounted in a fixed position on the front end of a torsion rod 3 
that moves axially outward through the hollow shaft 1, 2. The torsion rod 
3 is part of a torsion rod assembly, which serves to limit the belt 
power--as described below in greater detail. The torsion rod 3 is placed 
within the hollow shaft 1, 2 coaxially to the rotational axis D and 
connected rigidly at its opposite end to the hollow shaft 1, 2. For this 
purpose, this end of the torsion rod 3 is fastened to a corresponding 
inner flange of the hollow shaft 1, 2, by means of a fastening device 5. 
Another part of the torsion rod assembly is a torsion sleeve 4, which 
surrounds the torsion rod 3 coaxially at a short distance and also 
projects with its end (on the right in FIGS. 1 to 3) beyond the 
corresponding end of the hollow shaft 1, 2. The torsion sleeve 4 can also 
be deformed when rotated during energy absorption. Both the torsion sleeve 
4 and the torsion rod 3 are clamped in the same form-fitting manner in the 
area of their respective opposite ends, so that a twistlock connection 
with the hollow shaft 1, 2 is achieved. In addition, on the face of the 
torsion sleeve 4 that projects from the hollow shaft 1, 2, there is 
mounted with a twistlock a toothed gear 8 provided with an external gear 9 
designed as a ring gear, with both the toothed gear 8 and the toothed gear 
6 preferably being welded to the torsion sleeve 4 and the torsion rod 3, 
respectively. The toothed gear 8 is displaced axially in a parallel radial 
plane with respect to the toothed gear 6 and is not as thick as the 
toothed gear 6. The diameter of the toothed gear 8 is larger that the 
diameter of the toothed gear 6. 
Further rotation of the hollow shaft 1, 2 is prevented by the dropping of 
the catch pawl 10 into the external gear 7 of the toothed gear 6, while 
the torsion of the torsion rod 3 causes a certain further relaxation of 
the belt band and, accordingly, imposes the desired limit on the belt 
power. The catch pawl 10 has two stop sections 11, 12 serving as stopping 
element sections in the form of stopping gear elements, with the stopping 
element 11 being assigned to the external gear 7 of the toothed gear 6 and 
the second stopping element 12 being assigned to the external gear 9 of 
the toothed gear 8. The catch pawl 10 falls radially into the two toothed 
gears 6, 8, with the stopping sections 11, 12 being displaced with respect 
to one another along the direction of adjustment R in such a manner that 
the stopping section 11 first falls into the external gear 7 of the 
toothed gear 6, without the stopping section 12 coming into contact with 
the external gear 9 of the toothed gear 8 (FIG. 2). If the catch pawl 10 
is radially swivelled still further inward, in the direction of adjustment 
R (FIG. 3), then the stopping section 12 will also fall into the external 
gear 9 of the toothed gear 8, as a backup. In this position, the catch 
pawl 10 thus activates both the toothed gears 6, 8 and thus the entire 
torsion assembly as well, in other words, both the torsion rod 3 and the 
torsion sleeve 4. The depth of the toothing of the external gear 7 is 
dimensioned in such a manner that even in the first position of the 
stopping section 11, as shown in FIG. 2, a sufficient blocking of the 
toothed gear 6 is achieved and that, however, in addition, a further, 
radial inward movement of the catch pawl 10 is still possible, due the 
corresponding depth of the toothing of the external gear 7, in order to 
ensure that the second stopping section 12 can also fall into the axially 
displaced external gear 9 of the toothed gear 8. 
As soon as both stopping sections 11, 12 have fallen into the respective 
external gears 7, 9, both the torsion rod 3 and the torsion sleeve 4 can 
be twisted at once, producing a belt power limitation at a higher level. 
The belt roller shown in FIGS. 1 to 3 thus permits a two-step belt power 
limitation. 
So that the two-step nature of the belt power limitation can be reliably 
controlled, a one-piece projection 13, projecting axially outward is 
provided on the stop pawl 10. The one-piece projection 13 can strike on a 
stop tappet 14. This stop tappet 14 is mounted so that it can move 
linearly and axially in the direction of arrow A between a rest position 
(FIG. 3) and an operating position (FIGS. 1 and 2). The stop tappet 14 is 
activated by a control unit, which, depending on the weight of the person 
who sits on the car seat, causes a shift of stop tappet 14 in its 
operating position or its rest position. The stop tappet 14 is supported 
by a housing part 15 of a belt roller housing (not shown in detail, 
because it is already known), so that it cannot be pushed aside by the 
force of the falling catch pawl 10. As soon as the stop tappet 14 has 
reached its operating position, the projection 13 is arranged in the 
direction of the arrow R in the stop tappet 14 when the catch pawl drops; 
this blocks any further movement of the catch pawl 10. In this operating 
position of the stop tappet 14 only the stop section 11 meshes with the 
outer gear 7 of toothed gear 6, so that the stopping mechanism has 
effective contact with the hollow rod 1, 2 only via the torsion rod 3. The 
former step is suitable for people with lesser weight. In the event the 
control unit--as described briefly below--has recognized that a heavier 
person is sitting on the car seat, the stop tappet 14 will be withdrawn to 
its rest position, thus causing the stopping mechanism to come into 
effective contact with the entire torsion rod assembly, i.e. both with the 
torsion rod 3 and with the torsion sleeve 4. The belt power limitation is 
hence increased proportionally. 
The stop tappet 14 is preferably activated by an electromagnet actuator, 
which is controlled by the control unit. In the area of a seat surface of 
the car seat, an electronic weight recognition system has been provided, 
which connects through the corresponding signal wires to the control unit. 
The control unit evaluates the corresponding weight recognition signals 
and sends the corresponding control commands to activate or deactivate the 
electromagnet, thus causing the corresponding linear shift of the stop 
tappet 14. Preferably, the stop tappet 14 is activated in one direction by 
a spring, so that the electromagnet's function is required only for the 
shift in the other direction. 
Similarly, the shift of the stop tappet 14 can also be carried out by means 
of cable tension according to the embodiments of the state of the art 
considered in the descriptive introduction. 
The foregoing disclosure has been set forth merely to illustrate the 
invention and is not intended to be limiting. Since modifications of the 
disclosed embodiments incorporating the spirit and substance of the 
invention may occur to persons skilled in the art, the invention should be 
construed to include everything within the scope of the appended claims 
and equivalents thereof.