Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
LOCKING DEVICE FOR A BELT RETRACTOR IN SAFETY BELTS
BACKGROUND OF THE INVENTION
The invention relates to a locking device for
a belt retractor for safety belts, in particular in
motor vehicles, having a winding shaft and a ratchet
wheel with locking teeth mounted thereon, with which,
upon response of a sensor system, a movable pawl which
is rotatable about a shaft secured on the housing and
is tensioned in position of rest, preferably by spring
action, can be brought into locking engagement, the
sensor system comprising a rotatable trip lever and
responding to accelerations of the belt webbing qxtrac-
tion and/or of the vehicle in excess of a limit value.
A locking device for a belt retractor must
lock in a narrow and precise acceleration range. At
many motor vehicle manufactures narrow locking toler-
ances are demanded. Frequently the meshing teeth of the
ratchet wheels and the pawl are not ideally pointed, and
it may happen that the tips of the teeth and of the
pawls impinge on one another, so that valuable time is
lost while the winding shaft continues to rotate and
the belt webbing can continue to be pulled out of the
belt retractor. Only after a delay can the skipping
tooth tips engage in the counter-serration and cause
the locking. The uncertainty range from the state
just before the engagement of the counter-serration to
the final complete engagement state is thereby increased.
From U.S. Pat. 3,918,658 a locking device
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with ratchet wheel, sensor system and trip lever is
known. Upon acceleration, deceleration or rollover
of the vehicle, i.e. when exceeding a threshold value,
the engaging tip of the trip lever comes in engagement
with the teeth oE an inertia wheel, thereby locking
the retractor.
At the moment of collision, as is known, the
pawl must absorb via teeth of the ratchet wheel the
entire occurring force, and for this reason the pawl
has in this known device been separated from the trip
lever. The trip lever need then only transmit the
accident signal given by the sensor system to trigger
an engagement function. However, the known belt
retractor has the disadvantage that it is constructed
with a rather complicated mechanism with inertia wheel,
gear train, lever transmissions, etc.
There has been proposed a locking device of
the above mentioned kind whereby it has been possible
to keep the sum of the tolerances of the individual
components of the locking device low and to achieve a
synchronization of the teeth coming into locking
engagement with one another. Since, as is known, a
plurality of interengaging parts constitutes a risk
for the intact functioning of the belt retractor, one
must keep the sum of the tolerances lower without using
high-precision and hence expensive components. The
older proposal has accomplished this in advantageous
manner, and this even in so-called automatics, i.e.
belt retractors where the user can in the normal case
pull out belt webbing slowly and return to the housing
as desired, that is, he can carry out slow movements
in the buckled state, while at the moment of accident
prompt locking is demanded and has been assured with
more or less certainty in such a way that after the
locking the belt can hardly be pulled out of the
retractor or not at all.
Similarly as in the older proposal, the
object of the invention is a well matched cooperation
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in time of the movement of the rotating ratchet wheel
and of the pawl, in other words, a synchronization,
to make the locking device safer.
The task of the invention therefore is the
improvement of the above explained locking device, so
that it can be built more completely and will not
respond overnervously, and synchronization between the
meshing teeth of the ratchet wheel and pawl is further
ensured.
SUMMARY OF THE INVENTION
In accordance with this invention, there is
provided a locking device for a belt retractor for safety
belts, in particular in motor vehicles, having a housing
including a winding shaft and a ratchet wheel with
lS locking teeth mounted thereon, with which, upon response
of a sensor system, a movable pawl, which is rotatable
about a shaft secured on the housing and is tensioned in
position of rest, can be brought into locking engagement,
the sensor system comprises a rotatable trip lever and
responding to accelerations of the belt webbing extrac-
tion and/or of the vehicle in excess of a limit val~e,
characterized in that the trip lever comprises a driver
means disposed thereon, the pawl is arranged as a sepa-
rate part next to the sensor system and comprises engage-
ment means for engagement with the driver means, and inthe unlocked state the driver means is spaced from the
engagement means.
This problem is solved according to the
invention in that on the trip lever a driver finger is
disposed, the pawl is arranged as a separate part next to
the sensor system and comprises a system for engagement
with the driver finger, and in the unlocked state a
distance of e.g. at least 1 mm is provided between the
driver finger and the engagement system. In contrast to
the older solution, the sensor system, which may comprise
e.g. a shell with a ball secured therein, is not attached
to the pawl or on a prolongation thereof, but is a sepa-
rate part next to the pawl. While the pawl is rotatably
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mounted on the retractor housing, the base with the shell
for the ball or respectively the base for the sensor
system is fixed to the housing. In some forms of realiz-
ation the sensor housing may be fairly bulky, especially
when relatively large sensors, e.g. balls, are used as
inertia masses. Now if this sensor housing or the base
is arranged, not on the pawl but separately offset to the
latter and next to the pawl, the entire housing of the
locking device can be built narrower. Obviously two
separate parts can be lodged in a housing requiring less
space than if both parts are combined in one.
By this narrower design, in particular by the
division between the pawl on the one hand and the sensor
system on the other, relatively larger sensor systems can
also be used. In the case of balls let it be mentioned
lS that formerly metal balls of a diarneter of 12 mm were
commonly used, while by the measures of the invention the
diameter can now be increased to 13, 14 or even 15 mm.
The advantage of the use of larger inertia masses resides
in that these cannot be influenced so readily from the
outside, owing to which the locking device as a whole
then appears less jumpy. In other words, the too
frequent locking sometimes observed is eliminated.
This too frequent locking, which rnakes the
belt retractor "nervous" so to speak, could occur in
the older proposal under certain conditions in part
also due to the fact that the spring, having pushed the
pawl into the inactive position and having held it
therein, could set up natural vibrations when traveling
over a bumpy road. The sensor system and in the spe-
cific case the inertia ball was then supported on thespring-loaded extension of the pawl by said spring.
By the natural oscillations and vibrations unintended
movements could be transmitted to the ball, so that the
older sensor system showed under certain circumstances
in extreme conditions nervous symptoms, i.e. locked
too often.
By the attachment of the sensor system on the
housing of the locking device these disadvantages are
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automatically eliminated.
While in the older proposal the rotatable pawl
is tilted after engagement of the trip lever with a trip
cogwheel mounted on the winding shaft and is thereby
brought into engagelnent with the teeth, the trip lever
according to the invention needs to expend still less
force. After engagement with the teeth of the trip
cogwheel it suffices that through the driver finger on
the trip lever a momentum is exerted on the rotatable
pawl, so that its teeth come into engagement with those
of the ratchet wheel. Also in the present case the pawl
is again held tensioned by a spring in the normal,
unlocked state. But the force thereof is small, and
the mass of the pawl is still smaller as compared with
the older proposal, so that the force to be transmitted
by the driver finger to the engagement system on the
pawl for triggering the tilting is small.
Due to the distance between the driver finger
and the engagement system in the unlocked state, pre-
ferably 1 mm, possibly also 2 mm, the driver finger comesinto abutment and engagement with the engagement system
only after the tip of the trip lever is already in
engagement with the teeth of the trip cogwheel made of
plastic. Otherwise the pawl would have to be actuated
directly through the trip lever. But according to the
invention, this is not the case. Instead, after engage-
ment of the trip lever with the teeth of the trip cog-
wheel, the belt upon rapid extraction at the moMent of
impact assumes the force for rotation of the trip lever
and then, after overcoming the above described distance,
for rotation of the pawl into locking engagement.
In other words, the pawl is not actuated
directly by the trip lever, but only (via the engagement
system) after the tip of the trip lever has penetrated
the circumference through the tooth tips of the trip
cogwheel and has come into engagement with a tooth.
Consequently the weight or the inertia of the pawl can-
not hinder the engagement of the trip lever into the
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teeth of the trip coywheel.
According to the invention, the engagement
system is expediently a pin and the driver finger is
a projection extending away from the trip lever, which
is arranged next to the pin on the side away from the
ratchet wheel. This design has proved especially
expedient, although the engagement system may also be
constructed conversely in such a way that on the driver
finger a pin is provided which approaches the pawl from
the side when the locking is to occur. In the case of
an elongated trip lever, its axis of rotation is pro-
vided approximately in the central region thereof, and
the driver finger extends in a direction next to the pin
in such a way that the above mentioned distance between
the driver finger and the engagement system lies on the
side away from the ratchet wheel.
According to the invention it is advantageous
also if the driver finger has an outwardly open recess
of greater width than the diameter of the pin and is
disposed, in the unlocked state, at or near the pin on
the side toward the ratchet wheel. Another similar form
of realization with very similar advantage is charac-
terized in that the driver finger has an outwardly closed
hole whose width is greater than the diameter of the pin
and is disposed, in the unlocked state, at or near the
pin on the side toward the ratchet wheel. On this side,
therefore, a guide or wall applies directly against the
pin, also in the unlocked inoperative state. ~s a
result, the pawl in its movement immediately forces the
trip lever to pivot and to engage, so that thereby
locking is initiated and the advantageous synchroniza-
tion effect according to the invention is seen espe-
cially clearly. Independently of the system which
triggers the pivoting of the pawl, there is synchroniza-
tion between the pawl and trip lever in any event.
In a specific embodiment, where only aninertia ball is provided as sensor system, it is quite
conceivable that the pawl will rotate in the direction
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of the teeth of the ratchet wheel even without the ball
moving, for instance because a suitable shock against
the vehicle acts faster and directly on the pawl.
Then the synchronization is still ensured by the prin-
ciples of the invention, i.e. the teeth of the pawl enterinto the correct counter-teeth of the ratchet wheel.
Thereby the skipping of teeth, as observed in some known
locking devices, is advantageously avoided.
By the construction according to the invention,
the trip lever is brought into engagement with the trip
cogwheel practically by the active force of the moving
pawl, so that provision for synchronized locking is
always made.
For further improvement of the device it is
provided according to the invention that the pawl has
at least two teeth matching the teeth of the ratchet
wheel. Thereby wear can be reduced considerably, with-
out increased manufacturing costs or space requirements.
According to the invention it is further
advantageous if the trip lever can be brought into
engagement with the teeth of a trip cogwheel mounted on
the ratchet wheel and if the ratchet wheel and trip
cogwhell have the same number of teeth. The
synchronization is thereby best ensured. Because of the
necessarily inevitable tolerances in manufacture, one can
further give the teeth of the pawl a slight lead with
respect to the locked state in the direction of rotation
of the ratchet wheel upon belt extraction, which means
that the teeth in the ratchet wheel still have a short
time for applying against the teeth of the pawl after the
pawl has been turned completely into locking engagement.
In further advantageous deveIopment of the
invention, the trip lever is so balanced or spring-
tensioned with respect to its axis of rotation that its
engagement tip is, in the unlocked state, spaced from
the trip wheel. For example, a leaf spring, extension
spring or compression spring or corresponding physical
configuration may be provided on the trip lever in such
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a way that it remains in the desired unlocked position
either by spring force or by weight. But the tensioning
force must be so slight that the sensor system is able
at all times to overcome it without impairing rapid
response of the belt retractor.
It is further advantageous if the pawl has
also a means for engagement with a further sensor member.
For example, on the side opposite the teeth with respect
to the axis of rotation of the pawl there may be con-
ceived a feeler arm or gripping finger, against whichthe driver finger of an acceleration sensor, e.g~ a
capsule fastened on the winding shaft, can strike in
order to rotate the pawl. Alternatively there may be
conceived an electromagnet or a corresponding counter-
piece on the pawl, with which an additional sensormember interacts. For example, at the moment of accident
an electric circuit may be closed and set the pawl into
rotation electromagnetically. This rotation may of
course be initiated also by pneumatic or hydraulic means.
In any case, the pawl, if it itself executes the rota-
tional movement first, then forces the trip lever into
synchronization.
BRIEF DESCRIPTION OF THE DRAWINGS
_
Further advantages, features and possibilities
of application of the present invention are evident from
the following description of preferred embodirnents in
connection with the drawings, in which:
Fig. 1 shows a schematic sectional view through a locking
device in the unlocked state;
Fig. 2 to 4, various forms of realization of the front
end of the trip lever shown broken off, with driver
finger;
Fig. 5, the same illustration as in Figure 1, but showing
the state of the device immediately before initi-
ating rotation of the pawl and after rotation of
the trip lever;
Fig. 6, still another state of the device of Figure 1,
namely in locking engagement; and
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FigO 7, another form of the locking device with accelera-
tion sensor.
DESCRIPTION OF THE P~EFERRED EMBODIMENTS
Safe and synchronized locking of a belt retrac-
tor, e.g. of a so-called automatic, is obtained with a
device as will be explained below with reference to the
forms of realization.
In the base 1 of a locking device is mounted,
according to Fig. 1, a winding shaft 2 for the belt
webbing shown schematically in dash-dot lines at the
bottom. On the shaft a ratchet wheel 3 is mounted, and
in addition there is mounted on shaft 2 a trip cogwheel
8, preferably of plastic, and in the form of Figure 7
additionally an acceleration sensor 10 in the form of
a capsule with fingers.
In the representation of the figures, to the
left of the ratchet wheel 3 a pawl with teeth 41 is
pivotable about an axis of rotation 42. When the pawl
passes from the state shown in Figure 1 to the state
shown in Figure 6, the teeth 41 of pawl 4 coMe into
engagement with the teeth of the ratchet wheel 3, and
the ratchet wheel 3 together with winding shaft 2 is
locked. Hence further belt extraction is irnpossible,
and the person seated in the vehicle is protectively
restrained at the moment of accident.
To the left of the axis of rotation 42 pawl
4 has a lug 43, under which the spring 12 fastened to a
mount or bracket 13 engages in such a way that pawl 4 is
normally tensioned into the unlocked position shown in
Figure 1. In addition pawl 4 carries a pin 9 below and
to the left of the axis of rotation 42.
In the forms of realization here shown, pawl
4 is in engagement under tensile stress, but alterna-
tively a differently constructed pawl may be conceived
rotatably mounted in such a way that it fulfills the
same function under compression or pressure.
In all forms of realization here shown, a
sensor system with inertia ball 6 is shown, mounted on
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a sensor housing 5 formed as a base with shell. The
dimensions of the shell are seen in broken lines, which
shell permits in the case of a momentum transmitted to
the sensor housing via the belt retractor a lateral
shifting of the inertia ball 6. At the upper end of the
sensor housing 5, a trip lever 7 is disposed pivotable
over an axis of rotation 75. In the region of the ball
this trip lever also has a recess, and on the opposite
side it has a kind of tip, but which need not necessarily
be pointed in the geometric sense. However, a faster
response is favored by a more pointed design. In the
central region of the trip lever 7 the driver finger 71
protrudes upward to the left of pin 9.
The trip lever 7 comes into engagement by its
tip 72 with the cogs of a trip cogwheel 8 made of plas-
tic, when by a transmitted momenturn the inertia ball 6
has been pushed to the left or right due to the inertia
of the mass in the shell of the sensor housing and
consequently the trip lever 7 turns clockwise according
to the represented figures.
The form of the trip lever 7 according to
Figures 1 and 5 to 7 is shown in Figure 2, while in
Figures 3 and 4 other designs of the driver finger 71
are shown. But in all embodiments one sees the dis-
tance - designated by a in Figure 1 - between driver
finger 71 and pin 9, namely on the side opposite the
ratchet wheel 3 with respect to pin 9. This distance
does not exist on the side toward the ratchet wheel 3,
i.e. to the right of pin 9, as is illustrated in the
drawing. In Figure 3 the driver finger 71 is formed
with a recess 73 open to the outside. The right side
of pin 9, therefore, applies against the guide or wall
located there likewise to the right of recess 73.
The same situation exists also in the form
of realization of Figure 4j where pin 9 is retained in
an externally closed hole 74. The latter may also be
formed as an oblong hole.
Essential for the function of locking is the
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fact that pawl 4 is actuated by trip lever 7, i.e.
rotated in the direction of locking engagement (counter-
clockwise) only after tip 72 of trip lever 7 is in
engagement with the cogs of the trip cogwheel 8, and is
continued to be rotated by the force of the traction on
the belt and hence the torque of the plastic cogwheel 8
from attainment of the state shown in Figure 5 clockwise
until the state shown in Figure 6 is reached. The shift-
ing of the pawl by the trip lever 7 thus occurs only in
the region between the states from Figure 5 to Figure 60
By the distance between finger 71 on the one
hand and pin 9 on pawl 4 on the other, which may pre-
ferably be 1 to 2 mm, it is ensured that as the inertia
ball 6 moves from the state of Figure 1 to that of Figure
5, trip lever 7 can be rotated without load, in
particular without load of the inertia mass of pawl 4,
from the state of Figure 1 into that of Figure 5.
So, when at the moment of accident, by dis-
placement of the inertia ball 6 into the state of Figure
5, trip lever 7 has reached the position shown in Figure
5 and hence finger 71 just applies against the outer
surface of pin 9 on pawl 4, and when then necessarily
belt webbing is extracted by forward movement of the
passenger, the winding shaft 2, ratchet wheel 3 and trip
cogwheel 8 rotate. Thereby, through engagement of the
teeth of the plastic wheel 8 with the tip 72 of trip
lever 7 the latter is rotated out of the state of Figure
5 into that of Figure 6. In so doing, the driver finger
71 pushes pin 9 and hence pawl 4 into the locking en-
gagement shown in Figure 6. This engagement is correctlysynchronized, because in proportion to the distance be-
tween the axis of rotation 75 and the tip 72 of trip
lever 7 the teeth on the trip cogwheel 8 are positioned
to those on ratchet wheel 3 under the angle previously
adjusted to the desired size.
The particular advantage of the form of finger
71 according to Figure 3 and 4 can be illustrated espe-
cially well with reference to Figure 7. In other words,
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it can be conceived that pawl 4 can be set in counter-
clockwise motion also by other factors without the
inertia ball 6 triggering the rotational processO For
example, an acceleration sensor 10, e.g. a rotary
acceleration sensor which is fastened on the winding
shaft 2 and carries a finger 101 on the left, may con-
tribute to the movement of pawl 4 through a wedge surface
on pawl 4 not shown here. Alternatively another finger
not shown instead of finger 101 may conceiveably be
disposed further up on the acceleration sensor 10 in
such a way that the latter acts via a lever at the top
of pawl 4, also not shown, to initiate the rotary move-
ment thereof. Also other forces acting froM the outside,
not shown here, can initiate the rotary movement of pawl
4, e.g. electromagnets, pneumatic or hydraulic cylinders,
etc.
In the form of realization of Figure 7, finger
101 on the acceleration sensor 10 presses on the trip
lever 7, so that the driver finger 71 abuts on pin 9
without the inertia ball 6 having become operative.
A further depression or turning of trip lever 7 clock-
wise by exertion of force Pl by finger 101 on the right
half of the trip lever causes the latter to rotate pawl
4 into locking engagement. P2 is the force of a spring
14 which strives to rotate the acceleration sensor 10
back into its normal position. In the state illustrated
in Figure 7, this force P2 is readily just overcome by
force Pl.
Conceivable also is a form of realization
wherein the inertia ball 6 can, by suitable design of
the shell in base S or by its weight or the like, trans-
mit to the trip lever 7 such a force or so great a
momentum that by its torque it can help to bring pawl 4
into locking engagement.
Although using the trip cogwheel 8 with the
relatively pointed teeth for the engagement with the
trip lever 7 is safer against rebound, alternatively
the teeth of the ratchet wheel 3 could be used to
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provide the engagement with the trip lever 7.
It is to be understood that variations and
modifications of the present invention may be made
without departing from the scope thereof. It is also
to be understood that the present invention is not to
be limited by the specific embodiments disclosed herein
but only in accordance with the appended claims when
read in light of the foregoing specification.
