The present invention relates. to a seat belt retractor
having both ELR and ALR functionality.
As known in the art, ELR means an emergency locking retractor,
which typically includes one or more inertial locking mechanisms, as more particularly
illustrated in EP 0 228 729 A1. A typical ELR seat belt retractor includes both
a vehicle sensitive locking mechanism and a web sensitive locking mechanism. The
vehicle sensitive locking mechanism and the web sensitive locking mechanism may
share common parts.
Often the vehicle sensitive locking mechanism includes
a housing member that is rotationally mounted relative to a side of the retractor
frame as well as to the retractor spool. This housing member is called a lock cup.
This housing member supports a movable inertial mass configured as a ball or standing
man. Acceleration in excess of a limit or severe rotation beyond a limit of the
vehicle value moves this inertial mass, which initiates lockup of the retractor.
The housing member typically includes a rotationally supported pawl, also referred
to as a sensor pawl since it cooperates with the inertial mass. Movement of the
inertial mass causes movement of the sensor pawl from a deactivated position to
an activated position.
In the activated position the inertial pawl engages one
or more teeth of a ratchet wheel. The ratchet wheel is loosely supported for rotation
about the rotational axis of the spool and rotationally movable with the retractor
spool. The engagement of the sensor pawl with the ratchet wheel links the ratchet
wheel to the spool, which causes the lock cup member to rotate with the rotating
spool. The rotation of the lock cup in concert with the rotation of the spool causes
a lock pawl to engage one or more teeth of another ratchet wheel, also referred
to as a lock wheel. The lock wheel and the ratchet wheel that cooperates with the
sensor pawl can be the same part. Engagement of the lock pawl with the teeth of
the lock wheel leads to the initial lockup of a typical seat belt retractor.
When the seat belt tongue is removed from a cooperating
seat belt buckle, the extended seat belt, also called seat belt webbing or webbing,
will be retracted onto the spool in response to a bias force typically provided
by a rewind spring. The rewind spring will rewind all of the available seat belt
webbing onto the spool, so that the seat belt retractor is ready for another use
cycle. This condition is typically called the stowed condition, as the seat belt
webbing is now stowed or rewound onto spool. In this mode of operation it is anticipated
and often required that the ELR locking mechanisms are in a deactivated condition
so that the seat belt webbing is free to be protracted or retracted without intervention
of the ELR locking mechanisms, that is the vehicle sensitive or web sensitive locking
mechanisms. Occasionally, as the seat belt webbing is moved to the stowed position,
the vehicle sensitive locking mechanism inadvertently will assume an undesirable
locked condition, which prevents the seat belt from being easily protracted from
the seat belt retractor. Fortunately this condition is usually temporary. This undesirable
condition is avoided in the present invention by biasing the sensor pawl, when the
seat belt is in a stowed condition, away from the ratchet wheel, preventing such
an inadvertent lock condition of the retractor. If the seat belt retractor is mounted
in a movable seat back, this feature will prevent the retractor from locking up
as the seat back is moved.
It is also known for an emergency locking seat belt retractor
to include ALR functionality. When in the ALR mode of operation, the vehicle sensitive
and web sensitive locking functions are bypassed. ALR functionality of a seat belt
retractor is typically activated as the seat belt webbing is secured about a child
seat. As known by those skilled in the art, the acronym ALR stands for automatically
locking retractor. In most situations, to activate the ALR mode of operation, most
if not all of the seat belt webbing is manually pulled out or protracted from the
spool prior to the seat belt being placed about a child seat. Then the seat belt
is released to envelop the child seat. As the last section of seat belt webbing
is protracted from the spool, the prior art retractor enters the automatic locking
mode (ALR) mode of operation.
ALR mechanisms often include one or more gears, which rotate
with the retractor spool and provide an effective measurement of the length of webbing
that has been removed from the spool. As the webbing is pulled from the spool, the
ALR mechanism typically presents a mechanical feature, which causes the retractor
to enter into the automatic locking mode of operation. One such ALR mechanism shown
in US 5 904 371 selectively biases an ALR pawl into engagement with a ratchet wheel
on extension of the last section of the seat belt. Biasing the ALR pawl into the
ratchet wheel initiates retractor lockup as provided by the vehicle sensitive locking
mechanism. The seat belt retractor will remain in the ALR mode of operation as the
length of protracted webbing is rewound on the spool and will return the seat belt
retractor to the ELR mode of operation upon full retraction of the belt.
The ALR mechanism in US 5 904 371 includes a spring-loaded
lever that is physically maintained out of engagement with the ALR pawl. The spring-loaded
member is biased onto an edge of a cam disk that rotates with the spool. After a
predetermined number of spool rotations corresponding to the removal of virtually
all of the webbing from the spool, the cam disk is rotated into a position to present
a notch to the spring-loaded lever. Thereafter the spring-loaded lever falls into
the notch, engages a surface of the ALR lever and moves the ALR pawl into engagement
with a tooth of the ratchet wheel to initiate lock-up of the seat belt retractor.
A seat belt retractor according to claim 1 overcomes the
described problems in known seat belt retractors. In the present invention a single
lever, in cooperation with other components, is used to control the locking mode
(ELR/ALR) of the seat belt retractor. When the seat belt is fully stowed on the
retractor spool, the lever is moved to a position that biases a sensor pawl upon
a vehicle inertia mass to effectively block out the ELR mode of operation. Upon
protraction of a small amount of webbing, the retractor enters an ELR mode of operation.
During the normal mode of use with some of the seat belt webbing protracted about
a vehicle occupant the retractor will remain in the ELR mode of operation, however,
the ALR mode of operation is not accessible until after all of the seat belt has
been pulled from the retractor.
This extension of the seat belt occurs when the seat belt
is being placed, for example, about a child seat. In the ELR mode of operation the
lever is displaced from the sensor pawl, and the sensor pawl and the vehicle inertia
mass are permitted to move in response to vehicle dynamic conditions. In the ALR
mode of operation the lever biases the sensor pawl into a cooperating ratchet wheel.
The change into the automatic locking mode (ALR) is effective not upon the protraction
of the last section of seat belt webbing but upon the initial angular rotation of
the spool, in the direction of retraction from the fully protracted condition. Entering
into the ALR mode of operation at the beginning of seat belt retraction causes less
strain on the sensor pawl than initiating the ALR mode on the full extension of
- Figure 1 shows a seat belt retractor incorporating the present invention.
- Figure 2 is an exploded perspective view of an ELR and ALR locking mechanism
incorporating the present invention.
- Figure 3 shows locking mechanisms used by a prior art seat belt retractor with
the seat belt webbing stowed on the spool.
- Figure 4 shows locking mechanisms used by a prior art retractor with the seat
belt webbing fully extended.
- Figure 5 is an isometric view of a lock cup.
- Figure 6 shows the locking components when the seat belt has been fully rewound
on the retractor spool to a stowed position.
- Figure 6A shows the locking components when enough of the seat belt has been
pulled out that the ELR mode of operation is active.
- Figure 7 shows the locking components with virtually all of the seat belt pulled
from the spool, just prior to activation of the ALR mode of operation.
- Figure 8 shows the position of various locking components at the beginning of
Figures 1 and 2 illustrate seat belt retractor 20 incorporating
the present invention. The seat belt retractor 20 includes a frame 22 that rotationally
supports a spool 24 in a known manner. Seat belt webbing 28 is wound about the spool
24 and can be protracted from and rewound onto the spool. The seat belt retractor
20 includes a primary locking system 30, which comprises lock wheel 32, also known
as a ratchet wheel, having a plurality of teeth 34. A lock pawl 36 has one or more
teeth 38. The lock pawl 36 may also include a sensor pawl pin 39 that functions
as a cam follower.
The seat belt retractor 20 is a dual mode retractor having
ELR and ALR modes of operation. As known in the art, and as used herein and in the
claims, ELR means an emergency locking retractor. An example of an ELR, which typically
includes one or more inertial locking mechanisms is disclosed in EP 0 228 729 A1.
As known in the art, and as used herein and in the claims, ALR means an automatically
locking retractor. An example of an ALR mechanism is disclosed in US 5 904 371,
which selectively biases an ALR pawl into engagement with a ratchet wheel on extension
of the last section of the seat belt.
When in the ELR mode of operation the seat belt retractor
20 utilizes inertial locking mechanisms to initiate the lockup of the retractor
that effects movement of the lock pawl 36 into engagement with the lock wheel 32.
These inertial locking mechanisms are generally referred to as a retractor locking
mechanism 40 comprising a movable inertial mass 42 and a sensor pawl 44, as shown
in Figure 2. The sensor pawl includes an extending pin or projection 45. The sensor
pawl is movable by a co-acting lever 130 into, and away from, the ratchet wheel
46, shown in Figure 1, having teeth 48. The wheel 46 rotates with and can be part
of the spool 24.
Movement of the inertial mass 42 in response to excessive
vehicle deceleration, or large displacement of the vehicle in roll or yaw, or rotation
of the surface upon which the seat belt retractor is mounted such as a seat back,
causes the inertial mass to move, roll or tip and engage an adjacent surface 44a
of the pawl 44, thereby placing the pawl 44 into engagement with the teeth of ratchet
wheel 46. Rotation of the ratchet wheel 46 with the sensor pawl engaged causes rotation
of an associated lock cup 60, as shown in Figure 2 and in phantom line in Figure
1, which initiates the locking up of the seat belt retractor. The lock cups 60 are
spring biased, typically against the frame 22 or another stationary retractor member,
such spring being shown by arrow 68, which react against a boss or projection 69
on the frame.
The seat belt retractor 20 utilizes a lock cup 60 to support
the inertial mass 42, which is supported by a basket 42a or other known support
structure. The basket is received within a well 61 of the lock cup 60. The basket
can be fixed or movable relative to the well 61. Engagement of the sensor pawl 44
to the ratchet wheel 46 couples the lock cup 60 to the ratchet wheel 46, or to the
spool 24, causing the lock cup to rotate with the spool for at least for some limited
number of degrees. The rotation of the lock cup moves the lock pawl 36 into engagement
with the teeth of the lock wheel 32 thereby completing the initial phases of the
locking of the seat belt retractor. The lock cup 60 may include a cam 66 that receives
the cam follower 39 of the lock pawl 36. The rotation of the lock ring 60 rotates
the lock pawl 36 about an axis 36a into engagement with the teeth of the lock wheel
If the seat belt retractor 20 includes an energy absorber
mechanism such as a torsion bar, after the seat belt retractor 20 is initially locked
up, the spool is permitted to rotate and the seat belt permitted to protract from
the spool 24 in a controlled manner as the torsion bar twists. The seat belt retractor
20 may also include a web sensor (not shown) that initiates a locking up of the
seat belt retractor in response to an excessive rate of extension of the web from
the retractor. This web sensor is housed in the lock cup as shown in US 5 904 371
and EP 2 287 29 A1. Activation of the web sensitive locking mechanism also couples
the lock cup to the spool, thereby also causing engagement of the lock pawl and
Seat belt retractor 20 will remain in the ELR mode of operation
during all times with the exception of when all of the seat belt webbing has been
retracted upon the spool, that is the stowed condition, or when in the ALR mode
of operation, which occurs in conjunction with the seat belt webbing being placed
about a child seat.
The ALR locking mechanism 80 of the present invention utilizes
a number of components known in the art. These known components include a ring gear
79, a center or eccentric gear 90, a movable or wobble gear 100 and a cam disk 110,
shown both in Figures 2 and 3. The ring gear 80 has a plurality of teeth 82 and
is, in the preferred embodiment of the invention, integrally formed on a surface
of the lock cup 60. The center, eccentric, gear 90 is secured to and rotatable with
spool 24. The spool 24 includes a stub axle or projection 27, shown in Figures 1
and 3, that extends through an opening 62 in the lock cup and is received within
a bore on a rear surface of the center gear, thereby permitting the center gear
90 to move with the spool. The center gear 90 includes an eccentric outer surface
92 received within an opening 102 of the movable, wobble, gear 100 and a raised
surface 94 that is concentric with the opening 62 and received within an opening
112 of a cam disk 110.
The movable, wobble, gear 100 has a centrally located opening
102 and a plurality of teeth 104 engageable with the teeth 82 of the ring gear 80.
As the center gear 90 rotates with the spool, the movable gear rotates and orbits
about the ring gear 80. The movable gear 100 further includes an upstanding pin
or projection 106.
The cam disk 110 has a concentric outer surface forming
a cam surface 114. The cam surface has at least one major indentation 116 and an
optional minor indentation 116a having a smaller depth. The cam disk 110 has an
arcuate slot 118 therein in which the projection 106 of the movable gear 100 is
received. The seat belt retractor will enter into the ALR mode of operation when
a lever is permitted to fully enter into the indentation 116.
Prior art ALR mechanisms are shown in Figures 3 and 4.
The prior art ALR mechanisms have a spring-loaded lever 230, like element 102 disclosed
in US 5 904 371, which functions as a cam follower 232 and also is used to activate
an ALR pawl 234, like the pawl 80 of US 5 904 371, to initiate the ALR mode of operation.
The present invention has a spring-loaded lever 130, which incorporates the above
functions and also incorporates new functionality, as compared to the prior art.
The lever 130 includes a known type of a projection 132, which functions as a cam
follower. The cam follower 132 is biased against the cam surface 114 by a bias spring
130a, which is sometimes indicated by an arrow.
The prior art ALR mechanism is activated upon the extension
of virtually all of the seat belt from the spool 24. Figures 3 and 4 are illustrative
of the operation of a prior art seat belt retractor and are used for the purpose
of illustrating some of the components of seat belt retractor 20. In the prior art
ALR mechanism with all of the seat belt webbing rewound about the spool, the various
components of the ALR mechanism achieve an orientation as shown in Figure 3. The
cam follower 232 will position itself in the minor indentation 116a, which prevents
premature movement of the cam disk 110. As the webbing is pulled from the spool,
the spool rotates causing the center gear 90 to rotate, which in turn moves movable
gear 100, which in turn causes the projection 106 to rotate and orbit about the
ring gear 80, as well as causing the projection 106 to move within slot 118 of the
cam disk 110. As more and more seat belt webbing 28 is protracted from the spool,
the projection 106 will be moved a sufficient distance to contact the end 120 (see
Figure 4) of the slot 118, thereby causing the cam disk 110 to rotate with the moving
The gear mechanism of the prior art is configured such
that when virtually all of the webbing has been removed from the spool the cam disk
110 will present the slot 116 to the cam follower 232, which causes the cam follower
to be pushed into the slot 116. This action does not happen in the present invention
because of the employment of a second cam disk 150. Thereafter the lever 230 lifts
the ALR pawl 234 into engagement with the teeth of the ratchet wheel 46 to initiate
the ALR mode of operation, which is initiated upon full or substantially full extraction
of the seat belt. The prior art seat belt retractor will remain in this mode of
operation until the webbing 24 is fully retracted. In the prior art ALR mechanism,
as the webbing 24 is retracted the center gear moves oppositely causing the movable
gear 90 and the projection 106 to move opposite to the prior motion. As the webbing
is retracted the projection 106 engages the opposite end 122 of the slot 118, pushing
the cam disk oppositely (counter-clockwise in Figure 3). This urges the cam follower
132 to move up a sloped surface 124 of slot 116 and become repositioned on the outer
surface of the cam surface 114. This motion disengages the lever from the ALR pawl
and ends the ALR mode of operation.
Returning to the present invention, reference is again
made to Figures 2 and 5. The lock cup 60 includes a plurality of resilient inwardly
directed flexible tabs 64 uniformly positioned about the ring gear 80 and concentric
with opening 62 of the lock cup 60. The cam surface 114 is received within these
tabs 64, which position the cam disk 110 concentric with the opening 62, as well
as the axis of rotation of the spool 24. Each tab 64 has an upraised wall portion
64a as well as an inwardly extending wall portion. The cam surface 114 rides against
an inner wall of the upraised wall portion 64a while the inwardly directed wall
portion 64b prevents the outer edge of the cam disk from moving away from the lock
cup and ring gear.
The ALR mechanism of the present invention further includes
a second cam disk 150 that assists in controlling the start of the ALR mode of operation
to begin upon rewinding of the spool after full extension of the webbing. The second
cam disk, in concert with the lever 130, also provides a controlled biasing of the
sensor pawl 44 to provide a stabilizing force upon the inertial mass 42 at or near
the complete retraction of the seat belt upon the spool to eliminate a source of
vibration and noise. The cam disk 150 also permits the lever to achieve a mid-position
to enable ELR mode of operation.
The second cam disk 150 includes a circular annular shaped
wall 152 having a thin internal rim 153. The rim 153 is rotationally supported by
the first cam disk 110. The first cam disk 110 includes a plurality of inwardly
directed tabs 156 similar in construction to the tabs 64. The tabs 156 include a
first wall portion 158a extending away from the surface of the cam disk 110 and
an outwardly directed portion 158b. An inner surface of portion 158a radially stabilizes
the annular wall 152 while a portion 158b holds the rim 153, and hence, the second
cam disk 150. The second cam disk 150 further includes an inwardly directed socket
160 having an opening 162 therein to loosely receive the projection 106 of the moving
gear 100. The second cam disk includes a first lobe or cam surface 164 positioned
generally opposite the socket 160 and a second lobe or cam surface 166.
As the seat belt webbing is extended from the spool, from
a fully stowed condition to a fully extended condition, the projection 106 of the
wobble gear 100 generally orbits in a circle centered on an axis collinear with
the axis of the spool while simultaneously rotating or oscillating, at a higher
frequency, about the circle, with such movement constrained to be within the slot
118. The slot 118 affords the locking mechanism a degree of lost motion, that is
when the projection 106 is not pushing on the ends of the slot 118, the first cam
disk 110 will not move. The projection 106 directly moves the first cam disk in
a clockwise manner in relation to Figure 6 during web extraction, and in a counter-clockwise
manner during web retraction. As the projection or pin 106 moves as described, it
also rotates within the opening 162 of the socket 160 of the second cam disk 150,
and carries the second cam disk 150 with the pin 106. The second cam disk 150 will
rotate clockwise and counterclockwise generally following the rotation of the wobble
Figure 6 shows the positions of the locking components
when the seat belt has been fully rewound on the retractor spool to a stowed position.
In this condition the ELR locking mechanism is blocked out from use. In this condition
the cam surface 166 urges the cam follower 132 away from the cam surface 114 of
the cam disk 110. The cam surface 166 moves the cam follower 132 a greater distance
away from the center of the spool.
As the seat belt webbing is extended from the seat belt
retractor, the spool will rotate in a clockwise direction (in relation to Figure
6); the various components of the gearing mechanisms will similarly rotate. As the
webbing is extracted, the wobble gear 100, via projection 106 and the socket 160,
moves the second cam disk 150 in a clockwise manner (see arrow on the second cam
disk). The first cam disk will generally remain in the initial position as the projection
or pin 106 is moved away from end 122 of slot 118 into a free zone. After the seat
belt has been slightly extended, the second cam disk will be moved by projection
or pin 106 sufficiently clockwise to permit the cam follower 132 to fall onto the
cam surface 114 of the first cam disk 110. In this mode of operation, the cam follower
132 moves inwardly to the cam surface 114, which moves the end 140 of lever 132
away from the pin 45 of the sensor pawl 44. This action permits the seat belt retractor
to enter into the ELR mode of operation and is shown in Figure 6A. Figure 6A shows
the position achieved by the locking components when the seat belt has been pulled
out a determinable amount in which the ELR mode of operation is active, however,
the ALR mode is not available.
In Figure 5, the lever 130 is rotationally mounted to the
lock cup 60. The lock cup is not shown in Figures 6, 6a, 7 and 8. Only a pin 60a,
which is part of the lock cup and which rotationally supports the lever 130 is shown.
Figure 7 shows the position achieved by the locking components
with virtually all of the seat belt pulled from the spool, just prior to activation
of the ALR mode of operation. The second cam disk 150 is configured to be located
above the slot 116 of cam disk 110 generally just before all of the webbing 28 has
been extracted as shown in Figure 7. The placement of the lobe or surface 164 above
the slot 116 prevents the cam follower 132 of the lever 130 from entering into the
slot 116. This prevents the seat belt retractor from entering into the ALR mode
of operation on full extraction of the webbing 28, as taught by the prior art. The
radial extent of the surface 164 is not critical, and it can be the same as the
radial extent of the surface 114, slightly smaller or greater as it acts as a blocking
surface. Upon release of the webbing 28 or the reduction of the force holding the
webbing in an extended condition, the webbing will begin to be rewound upon the
spool by operation of the rewind spring 29 (see Figure 1). The change of direction
of the spool 24 causes the center, eccentric, gear 90 to rotate oppositely causing
the moving, wobble, gear 100 to move oppositely as well (counterclockwise in Figure
7). This action causes movement of the projection or pin 106 away from end 120 of
slot 118, which moves the second cam disk 150 in a counterclockwise direction opposite
to the motion when the seat belt was being extended.
Figure 8 shows the position of various locking components
at the beginning of ALR operation. Upon a determinable amount of rotation of the
disk 150, the cam follower 132 is permitted to slide upon an edge 170 of the lobe
166, and enter into a groove 116, as this action permits the lever 130 to move inwardly.
Inward movement of the lever 130 raises the pin 45 of the sensor pawl 44 and moves
the sensor pawl 44 into engagement with the teeth of the ratchet gear 46 to now
begin the ALR mode of operation as the spool rotates in the direction of seat belt
As the spool rotates in a rewind direction the projection
106 continues to move the second cam disk 150 in synchronism with the movement of
the projection 106. After a determinable amount of webbing has been rewound onto
the spool, the projection 106 will eventually engage an end 122 of a slot 118, thereby
reengaging cam disk 110. Subsequently, the first cam disk 110 is returned to the
initial position corresponding to a fully rewound spool shown in Figure 6, completing
the cycle and positioning the lobe 166 under the cam follower 132, thereby biasing
the lever 130 downwardly or outwardly (in Figure 6) away from surface 114 or in
a counterclockwise manner (in Figure 2).
When the lever 130 is pushed outwardly upon engagement
with the lobe 166 of the second cam disk 150, the pin 45 of the sensor pawl 44 is
biased downwardly by a surface to hold the sensor pawl 44 upon the top of the inertial
mass 42. The lever 130 has a distal end 134 having a ring 136 defining an opening
138. The pin 45 of the sensor pawl 44 is received within the opening 138 of the
ring 136. One end 140 of the ring forms a first engagement surface and an opposite
end 142 of the ring forms a second engagement surface. When the lever 130 moves
into the groove 116 the second engagement surface 142 lifts the pin 45 and hence
the sensor pawl 44 into engagement with the ratchet wheel 46 initiating the ALR
mode of engagement, as shown in Figure 8. Upon return of the webbing to the spool,
as shown in Figure 6, the engagement surface 140 urges the pin 45, and hence the
sensor pawl 44, downwardly onto the inertial mass 44. This prevents the locking
mechanism from becoming activated in the stowed position, regardless of the physical
orientation of the seat belt retractor. The lever 130 assists in initiating the
ALR mode of operating by moving the sensor pawl and also blocks the ELR mode of
operation by preventing movement of the sensor pawl.