GB2294384A - A safety belt retractor - Google Patents

Abstract

A retractor for a vehicle safety belt (4) comprises a housing within which a spindle is rotatably mounted. The spindle is spring-biased to retract the safety belt into the housing. The retractor is provided with an inertia mass which rotates with the spindle, about the axis of the spindle and a locking element for locking the spindle against rotation in a direction corresponding to the withdrawal of the safety belt from the housing, the locking element being activated in response to relative rotational movement between the inertia mass and the spindle. The retractor also comprises means for preventing activation of the locking element during retraction of the safety belt into the housing and for additionally preventing activation of the locking element during a predetermined angular rotation of the spindle corresponding to the withdrawal of safety belt from the housing following retraction of the safety belt. <IMAGE>

Description

DESCRIPTION OF INVENTION A SAFETY BELT RETRACTOR THE PRESENT INVENTION relates to a safety belt retractor such as a safety belt retractor intended for use within a motor vehicle.

A conventional safety belt retractor, for use in a motor vehicle comprises a housing which contains a spool.

One end of the safety belt is attached to the spool. The spool is spring biassed to "wind-in" the safety belt. A locking mechanism is provided which is actuated in response to either acceleration or deceleration of the vehicle in excess of a predetermined limit and/or in response to rapid withdrawal of safety belt from the housing, to lock the spool to prevent further safety belt being paid out. The mechanism responsive to rapid withdrawal of safety belt may be sensitive to angular acceleration of the spool in excess of a predetermined limit.

A conventional safety belt retractor is provided with an inertia wheel which is mounted for rotation with the spool, but which can turn relative to the spool within a limited angular range against a spring force. The movement of the inertia wheel relative to the spool moves locking elements to a locking position which prevent further rotation of the spool relative to the housing, thus preventing further safety belt being paid out from the housing.

The inertia wheel turns relative to the spool when the safety belt is paid out rapidly from the housing, thus giving the spool a swift rotational acceleration. Because of its inertia, the inertia wheel does not immediately rotate as rapidly as the spool, and thus moves angularly relative to the spool against the force of a spring which inter-connects the inertia wheel and the spool.

In many prior proposed retractors an acceleration sensitive device is provided which, when an acceleration in excess of a predetermined limit is detected, engages the outer periphery of the inertia wheel, thus effectively preventing any rotation of the inertia wheel. If the spool then rotates to "pay-out" safety belt, the locking elements are immediately moved to the locking position to prevent further rotation of the spool.

A problem can arise with a prior proposed retractor mechanism of this type. If the safety belt is being retracted into the mechanism, the spindle is rotating and the inertia wheel is rotating with the spindle. If the safety belt going into the retractor is stopped suddenly, the spool ceases rotating, and thus the spool is given a significant negative angular acceleration. The inertia wheel can continue to rotate, thus moving angularly relative to the spool and activating the locking elements.

Often, the locking elements are so designed that they are released from the locking position by releasing tension in the safety belt, thus permitting the retractor to draw some more safety belt in. However, if the safety belt being retracted into the retractor mechanism has been stopped simply because all of the safety belt has been drawn into the retractor and the safety belt is tight between the retractor and the anchorage point at the far end of the safety belt, it is not possible to pay any more safety belt into the retractor mechanism to release the locking elements. Thus, the retractor can be totally jammed.

Various solutions to this particular problem have been proposed. For example, it has been suggested that the movement of the inertia mass relative to the spool should be blocked by an element on the spool which is responsive to the direction of rotation of the spool, for example by being frictionally connected to the housing. Thus, the locking mechanism is effectively blocked whilst the safety belt is being retracted into the retractor mechanism. It has been proposed also that the spool may be provided with centrifugally operated braking shoes that limit the angular speed of the spool, at least whilst safety belt is being withdrawn into the retractor mechanism. This serves to limit the amount of deceleration when the spool has retracted all of the available safety belt.A further proposal involves the use of an arm which slides on the coil of safety belt on the spool and which thus senses when substantially all of the safety belt has been wound on to the spool. The arm actuates an arrangement which then blocks the locking mechanism.

Whilst the arrangements described above address the problem of preventing the retractor from becoming "jammed" during belt retraction, particularly at the end of the winding-in of the belt, a "jamming" problem may still arise in a situation where the safety belt passes over the tiltable back of a seat in order to reach the retractor.

It is known that when the tiltable back of a seat is moved from a tilted forward position to a raised or "in-use" position, it will move backwards to engage its fixing points and will then "bounce" or rebound to move forwards slightly before becoming engaged in the raised or "in-use" position. Where the webbing of the safety belt is passed over the back of the seat the sudden slight forwards movement of the seat back as it "rebounds" upon its fixing points will act rapidly to withdraw a short amount of safety belt from the retractor. This slight forwards movement of the seat back associated with paying out of a short length of safety belt can cause the activation of the locking elements thereby causing the retractor to again become jammed, with the belt stretched tight between the retractor and the anchorage point at the far end of the belt.The way in which this happens is illustrated schematically in Figures 1, 2 and 3 of the accompanying drawings. In Figure 1 the back of a seat is being raised from a titled forward position and the webbing of a safety belt which passes over the back of a seat is being withdrawn into the retractor. Figure 2 illustrates the situation as the back of the seat engages its fixing points and rebounds forwards very slightly pulling a short length of safety belt out of the retractor. Figure 3 illustrates the "neutral position" when the back of the seat is engaged in its fixing points in the raised or in-use position.

The present invention seeks to provide an improved safety belt retractor which addresses the problems outlined above.

According to the present invention there is provided a retractor for a vehicle safety belt, the retractor comprising a housing, a spindle rotatably mounted within the housing and to which one end of a safety belt is attached, the spindle being spring-biased for retracting the safety belt onto the spindle, an inertia mass mounted in the retractor to rotate with the spindle, about the axis of the spindle, and a locking element for locking the spindle against rotation in a direction corresponding to the unwinding of safety belt from the spindle, the locking element being activated in response to relative movement between the inertia mass and the spindle due to angular acceleration of the spindle, the retractor further comprising means for preventing activation of the locking element in response to said relative movement during retraction of the safety belt onto the spindle and for additionally preventing activation of the locking element during a predetermined angular rotation of the spindle corresponding to the withdrawal of safety belt from the housing following retraction of the safety belt.

Preferably the preventing means comprise a blocking element which inhibits said relative movement when in an operative position, the blocking element being movable between the operative position and an inoperative position, movement of the blocking element between the operative and inoperative positions being effected by means of a connection between the blocking element and a fixed part of the housing, the connection including a friction coupling connected in series with an arrangement adapted to move the blocking element between the operative and inoperative positions, said arrangement incorporating a predetermined degree of play such that following retraction of the safety belt the spindle must effect a predetermined angular rotation corresponding to the unwinding of safety belt from the spindle before the arrangement acts to move the blocking element from the operative position to the inoperative position.

Conveniently the predetermined degree of play incorporated into said arrangement is such that following withdrawal of safety belt from the spindle, the spindle must effect a predetermined angular rotation corresponding to the retraction of the safety belt before the arrangement acts to move the blocking element from the inoperative position to the operative position.

The friction coupling may be located between a part of the connection and the blocking element.

Advantageously the connection between the blocking element and a fixed part of the housing comprises a component rotatably movable between two predetermined positions in which the component engages two stops formed on, or connected to, a fixed part of the housing, the angle of rotation between said two stops corresponding substantially to said predetermined angular rotation of the spindle and providing said predetermined degree of play.

The component which is rotatably movable between the stops is frictionally coupled with a member forming part of the arrangement adapted to move the blocking element between the operative and inoperative positions, the component rotating with said member as it moves between said stops and transmitting a torque to the member adapted to move the blocking element when in engagement with either one of said stops, said torque causing the member to move the blocking element between the operative and inoperative positions.

Conveniently one of said stops is constituted by a part of a vehicle acceleration sensor which activates the locking element in response to vehicle acceleration in excess of a predetermined limit, the engagement of said component with the acceleration sensor preventing the acceleration sensor from activating the locking element, the arrangement being such that the component engages the part of the acceleration sensor during retraction of the safety belt into the housing and such that the element is disengaged from the acceleration sensor during withdrawal of safety belt from the housing.

Alternatively the friction coupling may be located between a part of the connection and the fixed part of the housing.

Preferably said predetermined angular rotation of the spindle is between 10 degrees and 20 degrees.

The preventing means may comprise a lever, the lever being pivotally mounted upon a component fixed to the spindle.

Conveniently the inertia mass defines a recess, part of the lever extending into said recess when the lever is in an operative position in which it prevents activation of the locking element, the engagement of said part of the lever in said recess serving to inhibit relative rotational movement between the inertia mass and the spindle.

In order that the present invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described, by way of example with reference to the accompanying drawings, in which: FIGURES 1 to 3 are schematic sectional illustrations of the movement of a back of a seat from a titled forward position to the raised position and the associated movement of safety belt webbing which passes over the back of the seat, as described above; FIGURE 4 is a diagrammatic illustration of a retractor having a housing and a spool upon which a safety belt is wound, with parts of the housing being cut away; FIGURE 5 is an elevational view of part of the retractor of Figure 1 illustrating the shaft of the spool, an inertia wheel and locking elements;; FIGURE 6 is a view corresponding to Figure 5 but showing the locking elements in the locking position; FIGURE 7 is an elevational view showing further components of the retractor including a vehicle acceleration sensor and components which act, under predetermined conditions, to prevent activation of the locking elements shown in Figures 5 and 6; FIGURE 8 is an exploded perspective view of the components of the retractor which act, under predetermined conditions, to prevent activation of the locking elements shown in Figures 5 and 6; FIGURE 9 is a view corresponding to Figure 7 but showing the components which act, in predetermined conditions, to prevent activation of the locking elements of Figures 5 and 6 in the position in which they prevent activation of those locking elements;; FIGURES 10 and 11 are schematic elevations of a slightly modified embodiment of the invention which is substantially equivalent to the embodiment shown in Figures 4 to 10; and FIGURES 12 and 13 are schematic elevations, equivalent to Figures 11 and 12 but showing a further embodiment.

Whilst in Figure 4 the housing is shown schematically as forming an enclosure completely covering the retractor, in practice the housing is more likely to take the form of a U-shaped metal frame with the spool being rotatably supported by the arms of the frame which is usually fixed to the chassis of the vehicle in which the retractor is installed. Thus, the term housing is to be understood to cover a frame of this type, which, in use, forms a fixed part of the vehicle Referring initially to Figure 4 of the drawings, a retractor mechanism 1 comprises a housing 2 containing a rotatably mounted spool 3 on to which a safety belt 4 is retracted. The spool is provided with a spring (not shown) tending to rotate the spool in the clockwise direction, as indicated by arrow 5, to draw safety belt 4 into the housing, with the safety belt being wound on the spool.

Referring now to Figure 5, mounted adjacent one end of the spool 3 is an inertia wheel 10. The inertia wheel is mounted to rotate about the same axis as the spool, but the inertia wheel can rotate relative to the spool through at least a limited angular extent. The inertia wheel may be of any appropriate material. The inertia wheel comprises an outer rim 11- and a central hub 12. The central hub is provided with two parallel slots 13, 14 which accommodate, respectively, two locking elements 15, 16. Each locking member is of elongate substantially rectangular form. The locking member 15 has, at one end, locking teeth 17. The locking member 16 has, at the opposed end, locking teeth 18. In the central region thereof each locking member is provided with a recess 19, 20 of a predetermined angular extent.Located within each recess is a lug 21, 22 formed integrally with the shaft 23 of the spool 3, the lugs extending radially outwardly from the shaft at diametrically opposed positions.

The locking members, as described, are located within a central aperture 24 defined by a metal locking ring 25 which is secured by appropriate securing means 26, to the housing so that the locking ring 25 is securely mounted in position. The aperture 24 is bounded by a plurality of teeth formed on the locking ring.

The inertia wheel 10 is biassed to the relative position with the shaft 23 as shown in Figure 5 by means of a spring.

It can be seen that when the illustrated components are in the condition illustrated in Figure 5, the teeth 17 and 18 provided at the ends of the locking members 15 and 16 are spaced from the other periphery of the aperture 24, meaning that the combination of the shaft 23 of the spool 3 and the inertia wheel is free to rotate in either direction. Thus, the safety belt can be withdrawn from, and retracted into, the retractor, provided that the inertia wheel does not move, relative to the shaft 23, in an angular sense, beyond a predetermined limit.

Referring now to Figure 6 it can be seen that if the shaft 23 is rotated rapidly in the anti-clockwise direction, (i.e. the direction of paying-out of safety belt) the inertia wheel 10, because of its inertia will tend to remain stationary. The shaft 23 will rotate, even though there is a spring inter-connecting the shaft 23 and the inertia wheel 10. The rotation of the shaft 23 causes the lug 21 to move effectively towards the right and the lug 22 to move effectively towards the left, thus driving the locking member 15 towards the right and the locking member 16 towards the left. The teeth 17 provided on the locking member 15 thus come into contact with the toothed periphery of the central aperture 24, and similarly the teeth 18 provided on the locking member 16 come into contact with the toothed periphery of the aperture 24.The teeth provided on the locking members thus move into a position in which they are in firm engagement with the teeth on the locking ring 25 forming the periphery of the aperture 24. Because the locking members 15 and 16 are locked in position, and because the lugs 21, 22 on the shaft 23 of the spool 3 are in the recesses 19, 20 of the locking members, the shaft 23 is locked against further rotation.

Referring now to Figure 7 of the accompanying drawings, a mounting plate 30 which provides support for one end of the central shaft 23 of the spool is illustrated, the mounting plate 30 having apertures 31 by means of which it is connected to the housing 2 and having a perpendicularly extending flange 32 provided at one side thereof which may be secured to the chassis of a motor vehicle. The locking ring 25 may be secured to the plate 30.

It can be see that the inertia wheel 10 is mounted adjacent the support plate 30. The inertia wheel 10 is provided with an axially protruding annular rib 33 on the side face of the wheel. The rib 33 is provided with securing means 34 which are secured to one end of the spring which interconnects the inertia wheel 10 and the shaft 23. The other end of the spring forms a coil which surrounds the shaft 23 of the spool 3. The end of the spring at the centre of the coil is connected to the shaft 23.

It will be observed that the inwardly directed surface of the annular rib 33 is formed with a recess 35 which serves as a stop or abutment for a further component of the retractor which is designed, in certain circumstances, to engage the inertia wheel and prevent movement of the inertia wheel in one direction, as will be explained hereinafter. One side of the recess 35 is of stepped form and this is simply to allow for tolerances in the relative positions of the inertia wheel and the further component which is designed to engage in the recess 35 in certain circumstances.

It is to be observed that the exterior of the inertia wheel 10 is provided with a plurality of projections 36 and a sensor mechanism 37 is provided which is responsive to vehicle acceleration in excess of a predetermined limit, the mechanism 37 being designed to cooperate with the projections 36 on the inertia wheel. The mechanism 37 comprises a housing 38 which is secured to the mounting plate 30. The housing 38 defines a recess which received a ball 39, such as a ball made of metal. A pivot 40 connects one end of an arm 41 to the housing 38. A central part of the arm 41 rests on top of the ball 39.

The arm 41 presents an upwardly turned terminal engagement portion 42 at its end remote from the pivot 40. The terminal engagement portion 42 is designed to engage and co-operate with the projections 36 formed on the periphery of the inertia wheel 10.

Should a vehicle incorporating the described arrangement be subjected to acceleration in excess of a predetermined limit the ball 39 will move within the recess defined by the housing 38, thereby causing the arm 41 to pivot upwardly about the pivot point 40 bringing the upwardly turned terminal engagement portion 42 into engagement with one of the projections 36 or into a space between two adjacent projections 36. It will be appreciated that when the arm 41 is in this position, should the inertia wheel tend to rotate in the anticlockwise direction (the direction necessary for safety belt to be paid out from the retractor) then the inertia wheel will be prevented from rotating by the terminal engagement portion 42 of the arm 41.If the shaft 23 continues to rotate, as would be the case when tension is being applied to the safety belt, there will be relative movement between the shaft and the inertia wheel (which is now locked against rotation) and the locking elements 15, 16 will move to the locking position, thereby preventing further rotation of the shaft 23. Thus the mechanism 37 forms a vehicle sensor which locks the safety belt retractor in order to prevent further belt from being paid out in the event of a vehicle acceleration in excess of a predetermined limit.

The retractor is provided with further components, which are illustrated within the central region of Figure 7 and in exploded, perspective view, in Figure 8, which act to prevent "locking" of the retractor during belt retraction, particularly at the end of the winding in process and which also act to prevent locking of the retractor when only a very short length of belt is paid out following retraction or partial retraction of the belt.

These further components comprise a spindle element 43, which is fixed on one end of the spindle 23; a lever 44 which is pivotally mounted upon a boss 45 which extends axially with respect to the spindle 23 and which forms part of the element 43; an annular controller 46 which controls movement of the lever 44 and which is mounted on the spindle element 43; and a part-circular ring 47 which is mounted upon the controller 46 and which carries a radially outwardly extending arm 48, the free, outer end of which carries a depending lug 49 designed to engage other parts of the retractor when in use.

All of the components 43, 44, 46, 47 and 48 are designed to rotate with the spindle 23. However, the connection between the ring 47 and the controller 46 is a friction coupling which permits relative movement between the components when a sufficient torque is applied to one of the components. It will, of course, be appreciated that the spindle element 43, the controller 46 and the ring 47 are all mounted co-axially with respect to the spindle 23 and at one end thereof.These components are arranged adjacent the inertia wheel 10 such that part of the lever 44 may be moved into and out of the recess 35 formed in the internal surface of the annular rib 33 of the inertia wheel, whilst the arm 48 extends radially beyond the periphery of the inertia wheel 10 so that the lug 49 at its free end may engage a stop 50 formed on the plate 30 when in a first position and may engage the lever arm 41 forming part of the car sensor mechanism 37 when in a second position (as shown in Figure 9).

Looking at these additional components in slightly more detail, the spindle element 43 is generally in the form of a wheel which is fixed upon one end of the spindle 23 and has a lower portion comprising a flange 51 with a radially outwardly projecting part 52 which carries the upstanding boss 45 upon which the lever 44 is mounted. The projecting part 52 of the flange 51 also carries, at a position radially inwardly of the boss 45 and slightly to one side thereof, a further upstanding boss 53 which forms a stop to limit movement of the lever 44. The spindle element has a central web-like portion 54 which extends into an upper portion comprising a pair of opposed, upper and lower flanges 55, 56 between which a channel 57 is defined.The upper flange 55 defines a pair of opposed, cut away portions 58 which each have an angular extent of approximately 90 degrees and which are designed to permit the mounting and retention of the controller 46 upon the upper portion of the spindle element 43.

The lever 44 comprises a main body 59 defining a bore 60 adapted to receive the upstanding boss 45 as a snug fit so that the lever is mounted thereon for pivotal movement about the central axis of the bore 60. The main body of the lever is formed, at one edge thereof, adjacent the bore 60, with an upstanding projection 61 by way of which the lever is connected with the controller 46. The main body of the lever 44 extends, at one end, into a narrow finger 62 which is directed generally radially outwardly with respect to the assembly of components in the retractor, as can be seen in Figure 7. The finger 62 forms that part of the lever 44 which is designed to be moved into and out of the recess 35 in the internal surface of the rib 33 of the inertia wheel 10.

The controller 46 has the general form of a ring or annulus comprising a pair of opposed upper and lower flanges 63, 64 interconnected by way of a web 65. The flanges and the web define an outwardly open channel 66 within which the ring 47 is designed to be received. The inwardly directed surface of the web 65 carries a pair of opposed projections 67 which are of like form and which each extend over approximately 90 degrees.The projections 67 are designed so as to permit mounting of the controller 46 on the upper portion of the spindle element 43 by lowering the controller 46 onto the upper portion such that the projections 67 pass through the cut away portions 58 of the upper flange 55 of the spindle element, following which the controller may be rotated through an angle of approximately 90 degrees so that the projections 67 are held captive within the channel 57 between the flanges 55, 56. The lower flange 64 of the controller 46 carries a radially outwardly extending forked projection 68 having arms 69, 70 between which the upstanding projection 61 on the upper surface of the lever 44 is received. Rotational movement of the controller 46 relative to the spindle element 43 causes pivotal rotation of the lever 44 about the boss 45.

The part-circular ring 47 which carries the arm 48 has a generally L-shaped cross-section, the base of the L being designed to be received within the channel 66 defined between the upper and lower flanges 63, 64 of the controller 46 as a tight snap-fit so that a friction coupling is established between the ring 47 and the controller 46. The upright part of the L-shaped ring extends up past the outer periphery of the upper flange 63, the inherent resilience of the material from which the ring 47 is formed ensuring that this part of its section is urged into engagement with the outer periphery of the upper flange 63. The arm 48 which extends outwardly radially from the ring 47 may take any convenient form but is illustrated as tapering towards its free end where it carries the depending lug 49.

In use the spindle element 43 is fixed to and rotates with the spindle 23, carrying the lever 44 with it.

The upstanding projection 61 on the lever 44 is received between the arms 69, 70 of the forked projection 68 on the controller 46 and therefore causes the controller to rotate with the spindle in the channel defined between the two flanges 55, 56 of the upper portion of the spindle element 43. The ring 47 which carries the arm 48 is frictionally coupled with the controller, being received within the channel 66 between the flanges 63, 64 and will therefore tend to rotate with the controller 46 unless prevented from so doing whereupon the friction coupling will slip, resulting in a torque being applied to the controller 46 in the direction opposite to the direction of rotation of the spindle 23.

When safety belt webbing 4 is being paid out from the retractor, the components described above are in the condition illustrated in Figure 7 with the spindle 23, spindle element 43 and controller 46 all rotating in an anti-clockwise direction about the axis of the spindle. It is to be observed that the depending lug 49 at the free end of the arm 48 has been moved into engagement with the stop 50 on the mounting plate 30 and although the ring 47 would normally follow the rotational movement of the controller 46, it is prevented from so doing by the engagement of the lug 49 with the stop 50. The friction coupling between the ring 47 and the controller 46 results in a braking torque acting upon the controller 46 in a direction opposite to its direction of rotation i.e. a torque acting in a clockwise direction, as indicated by the arrow 71 in Figure 7.

The braking torque 71 is transmitted to the lever 44 through the forked projection 68 and the upstanding projection 61 and causes the lever to be pivotally biassed in an anti-clockwise direction (as seen in Figure 7) about its pivotal mounting boss 45. This biassing torque ensures that the finger 62 of the lever 44 is held away from and out of the recess 35 in the internal surface of the rib 33 of the inertia reel 10 so that the inertia reel continues to operate in its usual manner during paying out of the safety belt webbing 4, the inertia reel acting to lock the spindle against rotation in the event of relative movement between the inertia reel and the spindle as a result of angular acceleration of the spindle in excess of a predetermined limit.

When the retractor subsequently retracts the safety belt webbing 4, such as when the safety belt has been removed from a passenger, the spindle 23 will rotate in a clockwise direction. Similarly the spindle element 43, the controller 46 and the ring 47 will also rotate in a clockwise direction. Rotation of the ring 47 in a clockwise direction will also cause the arm 48 carrying the lug 49 to rotate, thereby moving the lug 49 away from the stop 50 until it engages the lever arm 41 of the car sensor mechanism 37, as shown in Figure 9. When the lug 49 reaches the position illustrated in Figure 10 and engages the lever arm 41 of the car sensor, further rotation of the ring 47 and arm 48 in the clockwise direction is prevented and the friction coupling between the ring 47 and the controller 46 slips, resulting in a braking torque being applied to the controller in an anti-clockwise direction as illustrated by the arrow 72 in Figure 9. The engagement of the lug 49 with the lever arm 41 also serves to prevent movement of the lever arm 41 and therefore "blocks" the car sensor mechanism 37.In addition to preventing activation of the car sensor mechanism 37 when the safety belt webbing is being retracted into the retractor, the engagement of the lug 49 with the lever arm 41 forces the arm to hold the ball 39 firmly in the recess in the housing 38 which serves to inhibit the noise which would otherwise be generated by the rattling of the ball 39 within the housing 38 during belt retraction.

The anti-clockwise braking torque 72 which acts upon the controller 46 is transmitted to the lever 44 through the forked projection 68 and the upstanding projection 61 and causes the lever to be pivotally biassed in a clockwise direction (as seen in Figure 9) about its mounting boss 45. This biassing torque causes the finger 62 of the lever 44 to be moved into the recess 35 in the internal surface of the rib 33 of the inertia wheel 10.

It will be recalled that during belt retraction the spindle and the inertia wheel are rotating in a clockwise direction. If the spindle is now suddenly brought to rest, such as occurs when all of the safety belt webbing 4 has been withdrawn into the retractor, the inertia wheel 10 would tend to continue its clockwise rotation. However, the finger 62 of the lever 44 will engage the stepped edge of the recess 35 and prevent continued rotation of the inertia wheel, thereby preventing the relative movement between the inertia wheel 10 and the spindle 23 which is required in order to move the locking elements 15, 16 to the locked condition of Figure 6.

If the spindle 23 is now subjected to a sudden anti-clockwise rotation (corresponding to the paying out of belt webbing from the retractor), such as would occur when the tiltable back of a seat is moved to the raised position, as explained above, the spindle element 43, the controller 46 and the ring 47 carrying the arm 48 will move in an anti-clockwise direction also.It is to be noted however that the lever 44 will initially remain in the position shown in Figure 9 where the finger 62 is within the recess 35, until the ring 47 carrying the arm 48 has rotated through an angle alpha and the depending lug 49 on the end of the arm 48 engages the stop 50 on the mounting plate 30 whereupon a braking torque is applied to the controller 46 through the friction coupling between the controller and the ring 47, the braking torque then acting through the forked projection 68 and the upstanding projection 61 to move the lever 44 to the position illustrated in Figure 7 so that the finger 62 is removed from the recess 35.

It is to be appreciated that whenever the finger 62 of the lever 44 is within the recess 35, its engagement with one or other edge of the recess acts to prevent the required degree of relative movement between the inertia wheel 10 and the spindle 23 to activate the locking elements 15, 16. Thus, the locking elements 15, 16 are prevented from moving to the locking position when there is a short and sudden extraction of belt from the retractor unless the extraction of the belt is sufficient to cause the spindle and the associated elements, including the arm 48 carrying the lug 49 to rotate through an angle greater than the angle alpha whereupon the engagement of the lug 49 with the stop 50 causes the finger 62 of the lever 44 to move out of the recess 35, whereupon the inertia wheel can once again act in its usual manner to lock the retractor in the event of an angular acceleration of the spindle in excess of a predetermined limit.

The angle alpha will be within the range from 10 degrees to 20 degrees and the arrangement is designed such that when the finger 62 of the lever 44 is located within the recess 35 the inertia wheel 10 is constrained to move with the spindle 23 (i.e. cannot effect rotation relative thereto) to within a tolerance of 4 degrees. This very limited angular movement of the inertia wheel 10 relative to the spindle 23 is not sufficient to move the locking elements 15, 16 to the locking position. It will be appreciated from the description given above that the described arrangement permits a very short and sudden withdrawal of belt webbing from the retractor following retraction of the webbing without the locking elements 15, 16 acting to lock the retractor.This is achieved by providing the angle of play alpha in series with the friction coupling between the ring 47 and the controller 46 so that the lever 44 prevents the inertia wheel from operating in its usual manner over a short angular movement corresponding to the angle alpha when the retractor suddenly changes from retracting belt webbing to paying out belt webbing. The reference to items "in series" means that forces acting upon, and movement (or lack of movement) of one item is transmitted to, and cannot bypass, the other item.

The concept of providing a limited degree of play in series with a friction coupling in this way may be used in connection with alternative designs of retractor to that described and illustrated thus far and by way of example Figures 10 and 11 are schematic illustrations of the concept when applied to a slightly modified retractor design. In Figures 10 and 11 those components which correspond to components illustrated in the earlier drawings are marked with like reference numerals although they may be of differing design.

Figure 10 corresponds generally to the arrangement shown in Figure 7 whilst Figure 11 corresponds generally to the arrangement shown in Figure 9. Thus, Figure 10 illustrates an arrangement when belt webbing is paid out from the retractor whilst Figure 11 illustrates the same arrangement when belt webbing is being retracted. In Figures 10 and 11 the inertia wheel 10 is of part-circular form and is connected to the spindle 23 by way of a biasing spring 73. The spindle carries a pivotally mounted locking element 16 which is acted upon directly by the inertia wheel 10 in the event of movement of the inertia wheel 10 in the clockwise direction relative to the spindle 23.

As can be seen from Figure 10, when belt webbing is being withdrawn from the retractor the spindle 23 rotates in an anti-clockwise direction, carrying with it, by way of torque which is transmitted frictionally or otherwise, an element corresponding to the combination of the controller 46 and the lever 44. In turn there is a friction coupling between the controller 46 and a central element corresponding to the ring 47 carrying the arm 48. During this anti-clockwise rotation of the components the arm 48 is drawn into engagement with a fixed stop on part of the retractor housing whereupon a clockwise frictional torque is applied to the controller element 46 which carries an arm corresponding to the lever 44. The clockwise torque is greater than the torque applied to the controller by the anti-clockwise rotation of the spindle and this results in the arm corresponding to the lever 44 being off-set from the locking element 16 as can clearly be seen in Figure 10.

In Figure 11 the spindle 23 is rotating in a clockwise direction corresponding to belt webbing being retracted into the retractor. The spindle draws with it the element corresponding to the controller 46 and carrying the arm corresponding to the lever 44. The element corresponding to the arm 48 rotates in a clockwise direction until it engages a further stop on the fixed part of the housing, whereupon an anti-clockwise torque is produced which acts upon the element corresponding to the controller 46, which results in the arm corresponding to the lever 44 being moved in an anti-clockwise direction until it is located immediately adjacent part of the locking element 16 and serves to prevent movement of the locking element 16 to the locking condition. The angular extent between the two stops which are engaged by the arm 48 represents an "angle of play".Thus, should a short length of belt webbing now suddenly be pulled out of the retractor it will be necessary for the spindle and the elements mounted thereon, including the arm 48 to rotate through an angle alpha (corresponding to the angular extent between the two stops on the fixed part of the housing) before the arm corresponding to the lever 44 is once again moved to the position shown in Figure 10 in order to free the locking element 16 so that it may move to the locking condition.

In the arrangement illustrated in Figures 10 and 11 it will be appreciated that the friction coupling is located within the central region of the retractor close to the spindle 23 and the "play" which is represented by the angular extent between the stops on the fixed part of the housing is located radially outwardly of the spindle adjacent the housing of the retractor. It is not essential that the play and the friction coupling be arranged in this manner and Figures 12 and 13 illustrate a further embodiment in which the friction coupling is formed between the retractor housing and a component at a position radially outwardly of the spindle and an "angle of play" is provided at a more central position within the retractor.

Figure 12 shows the arrangement in the condition when belt webbing is being paid out from the retractor whilst Figure 13 shows the arrangement when belt webbing is being retracted into the retractor. The arrangement of the inertia wheel 10 and the locking element 16 mounted upon the spindle 23 is exactly the same as shown and described with reference to Figures 10 and 11. In this modified embodiment, however, the element corresponding to the controller 46 is formed, in addition to a part corresponding to the lever 44, with an arm 74 which is spaced from the arm corresponding to the lever 44 by an angular opening through which a further arm corresponding to the arm 48 extends, this further arm terminating with a friction pad or the like 75 which is permanently in engagement with part of the retractor housing.The angular spacing between the arm corresponding to the arm 48 and the arm corresponding to the lever 44 represents the "angle of play" alpha.

When safety belt webbing is being paid out from the retractor, the spindle 23 rotates in an anti-clockwise direction applying torque to the element corresponding to the controller 46 in order to rotate that element in an anti-clockwise direction. However, the frictional engagement of the pad 75 with the casing of the retractor results in a clockwise torque being applied to the element corresponding to the controller 46 which is greater than the torque applied to that element by the spindle, thereby biasing that element to the position shown in Figure 12 in which the arm corresponding to the lever 44 is off-set from the locking element 16 and does not inhibit movement of the locking element 16 to the locking position.

When safety belt webbing is being retracted into the retractor the spindle 23 rotates in a clockwise direction, tending to draw the element corresponding to the controller 46 with it. However, the frictional engagement of the friction pad 75 with the casing of the retractor results in the movement of the arm corresponding to the arm 48 to the position shown in Figure 13 in which the arm has moved through the angle of play alpha and engages the arm corresponding to the arm 44 urging that arm to a position in which it is immediately adjacent part of the locking element 16 and inhibits movement of the locking element 16 to the locking position. If a short length of safety belt webbing is now pulled out of the retractor it will be necessary for the arm corresponding to the arm 48 to move back through the angle alpha in order to engage the further arm 74 before the arm corresponding to the arm 44 is moved back to the position shown in Figure 12. Thus, the withdrawal of only a very short amount of safety belt will not cause the release of the locking element 16 so that it can move to the locking position.

It will be appreciated that various modifications may be made to the embodiments described above without department from the scope of the present invention, as defined by the appendant claims.

Claims (15)

CLAIMS:

1. A retractor for a vehicle safety belt, the retractor comprising a housing, a spindle rotatably mounted within the housing and to which one end of a safety belt is attached, the spindle being spring-biased for retracting the safety belt onto the spindle, an inertia mass mounted in the retractor to rotate with the spindle, about the axis of the spindle, and a locking element for locking the spindle against rotation in a direction corresponding to the unwinding of safety belt from the spindle, the locking element being activated in response to relative movement between the inertia mass and the spindle due to angular acceleration of the spindle, the retractor further comprising means for preventing activation of the locking element in response to said relative movement during retraction of the safety belt onto the spindle and for additionally preventing activation of the locking element during a predetermined angular rotation of the spindle corresponding to the withdrawal of safety belt from the housing following retraction of the safety belt.

2. A retractor according to Claim 1 wherein the preventing means comprise a blocking element which inhibits said relative movement when in an operative position, the blocking element being movable between the operative position and an inoperative position, movement of the blocking element between the operative and inoperative positions being effected by means of a connection between the blocking element and a fixed part of the housing, the connection including a friction coupling connected in series with an arrangement adapted to move the blocking element between the operative and inoperative positions, said arrangement incorporating a predetermined degree of play such that following retraction of the safety belt the spindle must effect a predetermined angular rotation corresponding to the unwinding of safety belt from the spindle before the arrangement acts to move the blocking element from the operative position to the inoperative position.

3. A retractor according to Claim 2 wherein the predetermined degree of play incorporated into said arrangement is such that following withdrawal of safety belt from the spindle, the spindle must effect a predetermined angular rotation corresponding to the retraction of the safety belt before the arrangement acts to move the blocking element from the inoperative position to the operative position.

4. A retractor according to Claim 2 or Claim 3 wherein the friction coupling is located between a part of the connection and the blocking element.

5. A retractor according to Claim 2, 3 or 4 wherein the connection between the blocking element and a fixed part of the housing comprises a component rotatably movable between two predetermined positions in which the component engages two stops formed on, or connected to, a fixed part of the housing, the angle of rotation between said two stops corresponding substantially to said predetermined angular rotation of the spindle and providing said predetermined degree of play.

6. A retractor according to Claim 5 wherein the component which is rotatably movable between the stops is frictionally coupled with a member forming part of the arrangement adapted to move the blocking element between the operative and inoperative positions, the component rotating with said member as it moves between said stops and transmitting a torque to the member adapted to move the blocking element when in engagement with either one of said stops, said torque causing the member to move the blocking element between the operative and inoperative positions.

7. A retractor according to Claim 5 or Claim 6 wherein one of said stops is constituted by a part of a vehicle acceleration sensor which activates the locking element in response to vehicle acceleration in excess of a predetermined limit, the engagement of said component with the acceleration sensor preventing the acceleration sensor from activating the locking element, the arrangement being such that the component engages the part of the acceleration sensor during retraction of the safety belt into the housing and such that the element is disengaged from the acceleration sensor during withdrawal of safety belt from the housing.

8. A retractor according to Claim 2 or Claim 3 wherein the friction coupling is located between a part of the connection and the fixed part of the housing.

9. A retractor according to any one of claims 1 to 8 wherein said predetermined angular rotation of the spindle is between 10 degrees and 20 degrees.

10. A retractor according to any one of Claims 1 to 8 wherein the preventing means comprise a lever, the lever being pivotally mounted upon a component fixed to the spindle.

11. A retractor according to Claim 10 wherein the inertia mass defines a recess, part of the lever extending into said recess when the lever is in an operative position in which it prevents activation of the locking element, the engagement of said part of the lever in said recess serving to inhibit relative rotational movement between the inertia mass and the spindle.

12. A retractor substantially as herein described with reference to and as shown in Figures 4 to 9 of the accompanying drawings.

13. A retractor substantially as herein described with reference to and as shown in Figures 10 and 11 of the accompanying drawings.

14. A retractor substantially as herein described with reference to and as shown in Figures 12 and 13 of the accompanying drawings.

15. Any novel feature or combination of features disclosed herein.