Note: Descriptions are shown in the official language in which they were submitted.
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- This invention relates to safe~y belt retractors.
In a safety belt retractor havin~ a coil spring which
is wound up when the belt is pulled out rom a storage reel,
a near maximum tension is exerted when t;he belt is worn by the
uæer. ~rhen the belt is disconnected from a fastening buckle
and released, the Epring retracts the belt onto the reel but
the tension decreases as the belt is rewound and this prevents
efficient stowage. Such known characterlstics of belt retrac-
tion are the reverse of what i.5 ideally required in practice
namely, a low tension when the be]t is worn and a high tension
to rewind the belt rapi.dly and Dositively when it is released
~or ~towage.
According to the present invention, a safety belt
retractor compr.ises a safety belt; a rotatable member for stor -
ing said belt; first and second bjassing means for biassing said
rotatable member to retract said belt, said first biassing means
being provided for applying a light retraction force to said
belt when worn; a lock-out device for disconnecting said
second bias~ing means ~rom said rotatable member a~ter said belt
has been e2tracted from said rotatable member whereby energy is
stored in said second biassing means and only said first biassing
means applies its retraction *orce to said belt; and threaded
mean~ for diaengaging said lock-out device to reconnect said
second biassing means to said rotatable member to enable said
~5 stored ener ~ to retract said belt; said threaded means being
driven by said rotatable member when said belt i~ retracted so
that said rotatable member rotates by a plurality of revolutions
before said lock-out device i~ di~engaged.
Preferably, the rotatable member rotates about a
longitudinal axis and the threaded ~eans is a~ially displaceable
.
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relative to said axis. The threaded means preferably comprises
a threaded bore in a shaft on which -the ~,afety belt is wound,
and an actuator which threadably engages said bore. The lock-
out device preferably comprises a ratchet wheel and a co-operating
pawl. The pawl engages the ratchet to prevent the energy stored
in the second biassing means from being relea~ed when the belt
is released after being secured about the user's body. ~he ~irst
biassin~ mean~ then applies a light tension for comfortably
maintaining the belt in contact with the user's body. The pawl
is disengaged when a predetermined length of the belt has been
retracted, which length i~ determined by said pluraiity of
re~olutions of the rotatable member. The predetermined length
allo~J~ maximum freedom of user mOVemQnt without di~engaging
the pawl from the ratchet. When the belt ia retracted beyond
said length the pawl is released from the ratchet and the second
biassing means supplements the drive of the first biassing means.
The increase in the retraction force then applied to the belt
en~ures that the belt is fully rewound. According to one
embodiment of the invention, the first and second biassing means
are respective 8pring8 and the ratchet is in the form of a wheel.
The pawl ls biassed towards the ratchet wheel to cause frictional
engagement therebetween. The pawl is thereby mored out o~
engagement with the ratchet wheel when the belt is withdrawn from
the shaft to a~oid ratchet noise. The frictional engage~ent
al~o return~ the pawl to a position ~or stopping the ratchet
wheel to prevent the second spring from unwinding when the
belt i8 released. Pre~erably, the first and second spring~
are connected in serie~ so that the first spring cushions
engagement between the actuator and the end of the threaded bore
in said shaft.
f~
:
~ccording to one arrangement of the latter embodiment,
the pawl is housed in a ratchet drum and the second spring
- is connected between the ratchet drum and a fixed housin~.
The first spring may then be housed in another drum whlch
is keyed to the ratchet drum. In an alternative arrangement
the first spring is located within the second spring 50 as
to reduce the overall width of the mechanism. In the latter
case, the first spring may be an extension o~ the second
spring with the ratchet wheel coupled to a point intermediate
the first and second springs. The ratchet wheel may be
attached securely to said intermediate point or it may be
coupled to a kink at said intermediate polnt where the
continuous spring pasæes through a slot in the ratchet wheel.
Pre~erred embodiments of the invention will now -be
described with reference to the accompanying drawings, in
which:
Figs. 1~a) and 1 (b) are graphs illustrating preferred
safety belt retraction characteristics,
- Fig. 2 is a sectional elevational view of a safety belt
~20 rewinding mechanism in a safety belt retractor according to
a ~iræt embodiment of the invention,
Fig. 3 is a section on line 3-~ of the mechanism of
Fig. 2,
Figs. 4 and 5 are end on end sectional elevational
views of a ratchet wheel used in the e~bodiment o~ Figs. 2
and ~,
Figs. 6 and 7 are plan and elevational views of a pawl
uæed in the embodiment o~ Figs. 2-5,
Fig. ~ is a sectional ele~ational view o~ a sa~ety belt
rewinding mechanism in a safety belt retractor according to
another embodiment o~ the invention,
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Fig. 9 is an end-on view of the operative part~ of the
mechanism shown in Fig. 8,
Fig. 10 schematically illustrates a special spring used in
another embodiment of the invention,
Fig. 11 is a sectional side elevation of another safety
belt rewinding mechanism in a safety belt retractor according
to another embodiment of the invention,
Fig. 12 is an end elevation, with an end cover removed, of
the mechanism of Fig~ 11,
Figs. 13, 14 and 15 are respectively sectiona~ inner side and
outer views of a ratchet member used in the mechanism of Fig.ll,
Figs. 16 and 17 are respectively side and elevational views
of a driving member of the mechanism of Fig. 11,
Figs. 18 and 19, which appear on the same sheet as Fig. 10,
are respectively end,on and side views of a pawl control member
of the mechanism of Fig. 11,
Figs. 20 and 21 are respectively side and elevational views
of an end cover of the mechanism of Fig. 11, and
Figs. 22 and 23 are respectively sectional and elevational
views of another safety belt rewinding mechanism,
Figs. l(a) and l(b) illustrate preferred belt retraction
characteriætics in which the load X or retraction force is plotted
~ against belt extension Y. Fig. l(a) shows the characteristics when
; a large person wears the belt. The belt is first withdrawn to
point A and the buckle is fastened. As the slack in the belt is
taken up by the reel the load or retraction drops to point B and
may decrease a little further partly along the line BC. When the
; belt is subsequently released for stowage, it is retracted along
line BC, but when the point C is reached, the retracting force
suddently increases to point D. Further retraction takes place
along the line DO.
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A
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Fig. l(b) shows similar characteristic9 when the belt is
worn by a small person. In this case, the sudden changes in
load or retraction force take place at a lower extension level
but the mode of operation i6 the same.
The area enclosed by A B C D represent stored work and the
energy is released back into the system at point C. Although not
shown in the graphs, in practical system~ that are envisaged, this
energy may be felt as a snatch su~ y pulling the ~elt ~ack bo~u~ the reel.
In a first embodiment of the invention, illustrated by Figs.
2-7 a shaft or reel spindle 1 is directly connected to a first coil
spring 2. Spring 2 is always drivably coupled to the spindle 1 and
the load/extension characteristic of spring 2 alone defines the
line BC of Figs. l(a) and l(b).
One end of spindle 1 has a tapped hole 3 which threadably
engages an actuating member 4, which member is rectangular in sec~
tion when viewed from the end of $pindle 1. An internally toothed
wheel 5, shown in Figs. 3, 4 and 5, has a rectangular hole 6 just
large enough to allow the actuating member 4 to be a sliding fit.
Thus, rotation of member 4 causes rotation of the toothed wheel 5
but axial movement of member 4 does not cause a corresponding axial
movement of wheel 5. Wheel 5 is dire ~ y connected to a second coil
spring 13.
An end cover 7 of the reel carries an internal projection 8
on which a pawl 9 is pivoted. Pawl 9 is biased to a central posi-
tion by means of a coil spring 10. As shown in Fig. 7~ the pawl
has a hole 9' which is enlarged at each end so that pawl 9 can
rock as well as rotate about the axis of projection 8~ In its
central position, the tip of the pawl 9 engages a space between the
teeth of wheel 5. The cover 7 also supports a pawl stop 11 which
is cantilevered so as to leave a space between it and the cover.
The pawl stop 11 normally stops anticlockwise rotation of the pawl
as viewed in Fig. 3.
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Actuating member 4 has, at its free end, a pip 12 aligned
with the pawl 9 in its central position.
In operation, assuming that member 4 is fully screwed home
in spindle 1 and that the belt is fully stowed on the spindle, as
the belt is withdrawn, spring 2 is wound. The direction of rota-
tion is such that any resistance to the rotation by member 4
causes member 4 to be more fully screwed into engagement with
spindle 1, for example, it has a left-hand thread. Because mem-
ber 4 is already fully home, it is forced to rotate with spindle 1
and the rectangular portion drives wheel 5 in the same direction.
To accommodate the motion, pawl 9 acts as a ratchet pawl and
clicks over the teeth by rotating first in a clockwise direction,
until it disengages from the toothed wheel 5, and then clicking
back towards the central position as each tooth moves past it.
Rotation of member 4 is resisted by spring 13 so that the total
resistance to belt withdrawal is the sum of resistances of spring
i 2 and spring 13. This is represented by lines O D A in Figs. l(a)
and l(b).
When a sufficient length of the belt is withdrawn, a small
amount is allowed to be rewound but, because of pawl stop 11,
pawl 9 does not act as a ratchet in the reverse direction, so
that wheel 5 and its associated spring 13 are drivably decoupled
from the belt. Thus, only spring 2 retracts the belt and the
force which is felt by the user is that shown by line BC in Fig. 1.
During the period that wheel 5 is stationary, actuating member
4 is also rotationally stationary and thus it is moved axially by
the screw thread, Eventually pip 12 engages the pawl 9 and causes
it to rock out of engagement with pawl stop 11. At this point,
pawl 9 is allowed to act as a ratchet in the reverse direction so
that the stored energy in spring 13 is released and wheel 5
rapidly catches up with spindle 1. When member 4 is screwed ~ully
home, both springs 2 and 13
h
lt~S~ t
drive spindle 1 to provide the operatin~ ch~racteristic~ of
line D0 in Figs. l(a) and l(b).
When the belt is next withdra~m, the pflwl 9 engages a tooth
of the wheel 5 and rotation of the wheel return~ the pawl to
the s~op 11 (as shown in ~ig, 3) ready for subsequen-t operation.
~igs. 8 and 9 shows an alternative embodiment in
which a plate 3~ frictionally engages a sp~ndle 31 and supports
a pawl control lever 32 which e~gage~ a recess ~3in a reel
casing 34. Pawl 35 is urged out o~ engagement wlth toothed
: 10 wheel 37 by compression spring 38
When the belt is wi.thdrawn, wheel 37 is driven because
it is fully bottomed on the threaded splndle 31. Plate 30
t rotates clockwise until lever 32 engageæ the wall of rece~s
~ 33 such that the lever 32 rotates anti-clockwise out of the ~ay
s 15 of the pawl 35. ~hus, pa~J]. 35 is moved by its spring 38 out
~i of engagement with-wheel 37. When the direction of spindle
31 is reversed, plate 30 move~ anti-clockwise, lever 32 moves
; clock~Jise and nudges pawl 35 into engagement with wheel 37.
Further movement causes lever 32 to move past pa~l 35 but,
~-20 because o~ the hooked shape of the teeth on the pawl and the
wheel, the pawl remains in engagement and pre~ents movement of
wheel 37. With wheel 37 held against rotation, continued
rotation of ~pindle 31 ca.uses axial movement of the wheel in
- its groove thread until it eventually slides ~ideways out of
engagement with pawl 35. Spring 3~ then moves pawl 35 out of
the way and the system restores itself to two spring operation.
In a further embodiment shown in Fig. 10 a single coil
spring 40 provides first ~nd second belt retraction mea~s . For
e~ample, section ~ acts as the first belt retraction means for
applying a continuous tensi.on to the belt (not shown) and
section F acts as the second belt retraction means which can be
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temporarily decoupled from the belt, for example, by a discon-
nectible ratchet, as in the previous embodiments. The spring
40 is anchored to a fixed part of the belt rewinding mechanism
at a point G which is intermediate the ends of sections A and B.
In the embodiment of Fig. 11 a shaft or reel spindle 41 is
mounted for rotation in a frame 42. The rewind mechanism is
mounted to the left of the frame as shown. No inertia locking
mechanism is shown, as this forms no part of the invention.
One end of spindle 41 has a threaded bore 43 and an exten-
sion 44 which has attached thereto the inner end of a spiral
spring 45. The spiral spring 45 is a fairly light spring and
is designed to allow only three to four turns between its unwound
` and its fully wound condition.
The outer end of spring 45 is attached to the inner wall
of a drum forming part of a driving member 46. This member is
shown in detail in Figures 16 and 17. The driving member 46
is keyed to ratchet member 47 shown in Figures 13, 14 and 15.
The central boss of the ratchet member has attached thereto the
inner end of a second spixal spring 49, which serves as a main
reel rewind spring. The outer end of spring 49 is attached to
a casing 50.
The central boss 48 of the ratchet member has an oval bore
51 into which slidably fits the head of a screw threaded pawl
control member 52 - best seen in Figures 18 and 19~ The screw
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threaded portion of the pawl control member is in threaded
engagement in the threaded bore 43 of the spindle 41.
The ratchet member also has a shallow circular recess 53
at the outer end of the oval bore, and a row of inwardly facing
ratchet teeth 54.
A mechanism end cover 55 carries a pivot pin 56 (see also
Fig. 20) for a pawl 57 which is spring loaded, by a spring 60,
against the face of the ratchet member 47. The pawl 57 is a
loose fit on pin 56 so that tilting of the pawl in directions
into and out of the plane of the paper, as viewed in Fig. 12,
is possible, as is normal pi~oted movement about pin 56. The
surface of the pawl which faces the ratchet member 47 has a small
protruding portion 57' which is received in the recess 53 in the
member 47. The protruding portion 57' is positioned on the pawl
57 such that it can engage the walls of recess 53 to limit the
angular travel of the pawl. In Fig. 12 the pawl is shown at its
extreme position in the anti-clockwise direction, but the pawl is
free to pivot in a clockwise direction about pin 56 until its tooth
disengages from the ratchet ring 54, further movement being prevented by the
engagement of the protruding portion 57' engaging the wall of recess 53.
When the protruding portion 57' is in the recess 53, the
rear surface of the pawl 57 is flat against the face S9 of the
ratchet member 47 and because of the spring bias of spring 60,
a certain amount of friction exists between the two surfaces.
Operation of the mechanism will now be described:
Assume first that the belt is fully wound on the reel and
that to unroll the belt the spindle 41 is to be rotated in the
direction indicated by the arrows of Figs. ll and 12.
On initial rotation to unreel the belt, spring 45 is wound
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up until it approaches the coil bound condition. Further wind-
ing causes driving member 46 to rotate which in turn starts to
wind up mainspring 49. As spring 49 is wound, the ratchet member
47 also rotates with driving member 46 and because of the fric-
tion between the ratchet member 46 and the pawl 57, the pawl
rotates from the position shown in Figure 12 in a clockwise
direction about its pivot to a new position such that its tooth
disengages from the ratchet teeth 54. Further pawl rotation is
prevented by the engagement of its protruding portion with the
wall of recess 53 in the ratchet member. Because the pawl tooth
is held out of engagement with the teeth 54 by friction there is
no clicking sound normally associated with ratchets, and the
ratchet member 47 rotates until the desired amount of webbing is
unreeled.
Assume now that the belt is buckled and that a small
amount of webbing is to be reeled in after the buckling opera-
tion. Upon initial rewind by the main spring, the pawl is
carried by friction to the position shown in Figure 12, at which
point further anti-clockwise direction of the movement of the
pawl is prevented by engagement of its protruding portion with
the wall of recess 53.
Because the pawl is now engaged with teeth 54, further
anti-clockwise motion of the ratchet member 47 is also prevented,
so that,spring 49 is effectively locked out of the rewind system,
Retraction of the webbing can now only take place by virtue of
the energy stored in light spring 45, and in this condition the
belt is very comfortable to wear.
When the belt is to be stowed, light spring 45 con-
-' tinues to wind webbing until its energy is almost exhausted
(after about 2 or 3 turns of spindle 41), but during this rota-
10581~4
tion the ratchet member 47 is fixed against rotation as is the
pawl control member 52. However, because the pawl control member
52 is in screw threaded engagement to spindle 41 the relative
rotation of the spindle and the pawl control member cause it to
move to the left (as seen in Figure 11). As the pawl control
52 moves to the left it engages the protruding portion of the
pawl 57 and pushes it out of recess 53.
When the pawl is freed from the restraint imposed by
the wall of recess 53, the main spring is able to rotate the
ratchet member 47 and the pawl anti-clockwise until the pawl
disengages from the teeth 54. The pawl is driven anti-clockwise
until it engages stop 21. The energy stored in spring 49 is now
released and the ratchet member 7 rotates rapidly until pawl
control member 52 is screwed fully home in spindle 41, at this
point the main spring acts to rewind the belt rapidly. Before
the pawl control member 52 is screwed fully home, some of the
energy of main spring 49 is used to rewind the small spring 45,
and this cushions the impact of the pawl control member homing
in the spindle 41.
The mechanism described above may be modified so that
the light spring 45 is of a smaller diameter than that of the
inner coil of the mainspring 49, whereby it can be located inside
the mainspring 49. In other respects the mechanism is essential-
ly the same. The advantage of this modification is that the
overall width of the reel is reduced, helping installation in
vehicles. When one spring is packed inside the other, it is
possible to make one of the springs merely an extension of the
other, but with some provision Eor taking the ratchet drive off
from an intermediate coil of the spring; the ratchet member could
be attached to the spring securely, or for example, by merely
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1~)5~34
putting a kink into the spring at a point where it passes through
the ratchet member.
It is also envisaged that a positive connection to the
intermediate coil may be completely unnecessary, and that the
friction forces operating between the spring and the ratchet
member will allow satisfactory operation; in such a design, the
spring would merely pass through a slot from the inner side to
the outer side of the ratchet member.
The disengageable ratchet used in the embodiments
10 described above is dispensed with in the arrangement shown in
Figures 22 and 23. In the latter arrangement, a spring assembly
70 is connected to a device for providing an over centre action
such that clockwise or anti-clockwise torques are applied to a
belt storage shaft 71. A spiral spring 72 is normally coupléd
between shaft 71. Thus, the resultant torque on shaft 71 is the
algebraic sum of the torques exerted by springs 70 and 72. As
the belt is initially withdrawn, the resultant torque is equal
to the torque exerted by spring 70 plus the torque exerted by
spring 72. This condition prevails until the over centre point
20 is reached and, beyond this point, the resultant torque is that
exerted by spring 72 minus that exerted by spring 70. The
additive torques ensure positive belt retraction when the belt
is released for stowage. The over centre point is selected with
regard to the type of belt used and the size of the user's body.
The differential torque is such as to ensure comfort with safe
operation.
Referring in greater detail to Figures 22 and 23, the
shaft 71 is rotatably supported between end plates 74 (only one
of which is shown), the end of the shaft shown in Figure 22
30 having two stepped sections 75, 76. The inner end of spiral
105~ 4
spring 72 is fixed to the stepped portion 75 and the outer end is
fixed to the casing 73.
The stepped section 76 supports a rotatable planet gear
ring or carrier 77 having an inwardly facing ring of teeth 77'.
The stepped section 76 is provided with a sun ring 78 which is
fast with shaft 71. The sun ring 78 drives the rotatable planet
ring 77 through each of three double planet gear wheels 79, the
planet wheels of smaller diameter meshing with the rotatable
planet ring 77 and the planet wheels of larger diameter meshing
with a fixed sun ring formed by teeth 73' in a circular recess in
casing 73. This arrangement forms an epicyclic gear box to step
down the drive of shaft 71 with respect to the planet ring 77.
For example, the gear ratio may be 30 turns on shaft 71 to 1
turn of ring 77, (in fact, the movement of ring 77 is limited to
an arc as described below).
An anchorage member 80 is fixed to and projects from the
planet ring 77. Member 80 has an abutment 81 and is caused to
move in an arc between the position shown in Figure 23 (where the
safety belt, not shown, is fully wound on shaft 71) and a stop 82
(which is contacted by abutment 81 if the safety belt is fully
withdrawn from shaft 71).
The spring assembly 70 is formed by three coaxial coil
springs 83, 84, 85. One end 83a, 84a, 85a of each spring is
anchored on member 80. The other end 83b, 84b, 85b of each
spring is anchored on a fixed pin 86 passing through a cover 87,
the casing 73 and the end plate 74. In operation, the shaft 71
rotates as the belt is withdrawn and this causes the anchorage
member 80 to travel slowly along an arc. This arc is generally
defined by a track indicated by dot and dash lines 91, 92
30 (Figure 23). The track, which bounds recess 93 (Figure 22), pre-
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i~)58~34
vents horizontal displacement of the planet ring 77 because a
rounded end 94 of member 80 abuts the face of the track 91, 92.
Referring to Figure 23, whilst member 80 moves between stop 81
and an over centre point 88 (lying on an axis passing through the
centre 89 of sun ring ?8 and the centre 90 of pin 86), the
spring assembly 70 expands and acts to supplement the rewinding
torque exerted by spring 72. The actual torque exerted by spring
assembly 70 is reduced, due to the geometry of the system, as
member 80 approaches the over centre point 88. When member 80
passes beyond the ovex centre point 88, the spring assembly 70
contracts so as to counteract the torque exerted by spring 72.
The counteractive torque exerted by spring assembly 70 increases
as member 80 moves away from the over centre point 88. This
compensates for the increasing torque exerted by spring 72 as
the belt is withdrawn from shaft 71. For example, when the belt
is secured across the user's chest, the compensating effect
allows the user to bend forwards without too much restriction
being imposed by the tension in the belt.
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