CA1058134A - Safety belt rewinding mechanism with improved belt retraction characteristics - Google Patents

Abstract

A B S T R A C T
Safety belt retractors are disclosed in the for of spring driven belt rewinding mechanisms. In some arrangements, a pair of spiral springs act in series or in parallel, one spring applying a constant rewinding torque to a belt storage shaft, the other storing energy when the belt is withdrawn. A ratchet maintains the stored energy and is disengaged by a screw threaded actuator, which moves coaxially to the storage shaft when the shaft rotates through a number of revolutions. The stored energy is released to supplement the rewinding torque of the first spring. In another arrangement, the ratchet is replaced by an over centre spring assembly. An epicyclic gear box drives a coil spring anchorage through a given arc to give an over centre action.

Description

`` lOS~ 4 - 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 .
. 2 .,, '.~, . , .. ..

1~)5~ 4 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, 1~581;~4 ~, .
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.

. 5--A

1l~5b~ 4 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.

~.

1~)5~ 4 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 . ' ~Q
' ``` 10S~ 4 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 ':

_g_ :11)5~134 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 ~.

1~)5~134 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 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-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.

Claims (24)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A safety belt retractor comprising a safety belt;

a rotatable member for storing said belt; first and second biassing means for biassing said rotatable member to retract said belt, said first biassing means being provided for apply-ing a light retraction force to said belt when worn; a lock-out device for disconnecting said second biassing means from said rotatable member after said belt has been extracted from said rotatable member whereby energy is stored in said second biassing means and only said first biassing means applies its retraction force to said belt; and threaded means for disengaging said lock-out device to reconnect said second biassing means to said rotatable member to enable said stored energy to retract said belt; said threaded means being driven by said rotatable member when said belt is retracted so that said rotatable member rotates by a plurality of revolutions before said lock-out device is disengaged.

2. A safety belt retractor according to claim 1 wherein said rotatable member rotates about a longitudinal axis, said threaded means being axially displaceable relative to said axis.

3. A safety belt retractor according to claim 2 wherein said rotatable member is a shaft on which said belt is stored, said threaded means comprising a threaded bore in one end of said shaft and an actuator which is threadably engaged with said bore.

4. A safety belt retractor according to claim 1 wherein said lock-out device comprises a ratchet wheel and a co-operating pawl.

5. A safety belt retractor according to claim 4 wherein said ratchet wheel houses said pawl.

6. A safety belt retractor according to claim 4 or 5 wherein said pawl is pivotally mounted and is also arranged for tilting movement for disengagement with said ratchet.

7. A safety belt retractor according to claim 3 wherein said lock-out device comprises a ratchet wheel and a co-oper-ating pawl, said pawl being pivotally mounted and also arranged for tilting movement for disengagement with said ratchet, a stop being provided for abutting said pawl when pivoted to enable normal ratchet and pawl action when said belt is extracted from said rotatable member, and said pawl being capable of being tilted by said actuator, after said plurality of revolutions of said rotatable member, to ride over said stop whereby said normal ratchet and pawl action is disabled.

8. A safety belt retractor according to claim 7 wherein said first and second biassing means are respective first and second spirally wound springs housed in a casing, said first spring having one end connected to said rotatable member and its other end fixed to said casing, said second spring having one end connected to said ratchet wheel and its other end connected to said casing, said ratchet wheel being in the form of a drum for housing said tilting pawl and said stop, said drum having a concentric hollow stub with an aperture therethrough, which aperture receives a portion of said actuator, said portion and said aperture being of a non-circular shape whereby said actuator is axially slidable relative to said stub but is fixed for rotation therewith.

9. A safety belt retractor according to claim 4 wherein said rotatable member is a shaft on which said belt is stored, said shaft having an axially threaded extension at one end thereof and said ratchet wheel being threadably mounted on said extension.

10. A safety belt retractor according to claim 9 wherein said pawl is pivotally mounted and has a hooked portion at one end for engaging any one of the plurality of teeth on said ratchet wheel.

11. A safety belt retractor according to claim 10 wherein a pawl control is frictionally coupled to said shaft and is operable for disengaging said pawl from said ratchet wheel when said belt is withdrawn from said shaft.

12. A safety belt retractor according to claim 11 wherein said pawl control includes a member frictionally mounted on said shaft and a lever pivotally mounted on said member, said lever being provided for interposition between the other end of said pawl and a fixed point on common rotation of said member and said shaft whereby said pawl is nudged into engagement with said ratchet wheel.

13. A safety belt retractor according to claim 12 wherein said first and second biassing means are respective first and second spirally wound springs housed in a casing, said first spring having one end connected to said shaft and its other end fixed to said casing, said second spring having one end connected to said ratchet wheel and its other end fixed to said casing, said pawl control being located between said first and second springs.

14. A safety belt retractor according to claim 4 wherein biassing means are provided for biassing said pawl towards a non-toothed portion of said ratchet wheel to cause frictional engagement between said pawl and said non-toothed portion of said ratchet wheel whereby said pawl is maintained out of engagement with said ratchet wheel, when the belt is withdrawn from said rotatable member, to avoid ratchet noise.

15. A safety belt retractor according to claim 14 wherein said frictional engagement also returns said pawl to a position for stopping said ratchet wheel to prevent said second biassing means from unwinding when said belt is released.

16. A safety belt retractor according to claim 15 wherein pivotal movement of said pawl is limited by a recessed portion of said ratchet wheel, said pawl being tilted out of engagement with said recessed portion by said actuator.

17. A safety belt retractor according to claim 16 wherein said first and second biassing means are respective spirally wound springs and said second spring is arranged to cushion engagement between said actuator and said rotatable member when said pawl is disengaged from said ratchet wheel.

18. A safety belt retractor according to claim 17 wherein said ratchet wheel is in the form of a drum and said pawl is held within said drum, said second spring being connected between said drum and a relatively fixed point.

19. A safety belt retractor according to claim 18 wherein a second drum is keyed to the ratchet drum, said first spring being housed in said second drum.

20. A safety belt retractor according to claim 14 wherein said first and second biassing means are respective springs, said first spring and second spring being connected in series.

21. A safety belt retractor according to claim 17 wherein the first spring is located within the second spring.

22. A safety belt retractor according to claim 21 wherein the first spring is an extension of the second spring and the ratchet wheel is coupled to a point intermediate the first and second springs.

23. A safety belt retractor according to claim 22 wherein the ratchet is securely attached to said intermediate point.

24. A safety belt retractor accprding to claim 22 wherein the ratchet wheel is coupled to a kink at said intermediate point.