Abstract:
A safety device in a motor vehicle comprises a roller retractor ( 2 ) mounted at the top of the back ( 1 ) of a vehicle seat. The roller retractor ( 2 ) has wound on it a sheet-like element or net ( 3 ) which is extractable from the roller to engage anchoring means secured in or adjacent the roof of the vehicle. The length of net ( 3 ) to be extracted from the roller retractor ( 2 ) is different in different positions of the back of the seat. The roller retractor mechanism is associated with a locking mechanism ( 5 ) which is actuated in at least one of the alternative positions of the back of the seat to lock the extraction of more than a predetermined length of the sheet-like element from the roller retractor ( 2 ). The length is sufficient to enable the sheet to be secured to connecting means provided in the roof of the vehicle.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a safety device in a motor vehicle and more particularly relates to a safety device comprising a retaining element connected to the back-rest of the rear seat of a motor vehicle, the retaining element being adapted to extend between the back-rest of the rear seat of the vehicle and the roof of the vehicle in order to prevent luggage stored in the vehicle behind the back-rest of the rear seat moving forwardly should an accident arise in which the vehicle stops suddenly. 
     BACKGROUND OF THE INVENTION 
     It has been proposed to provide previously a retaining element in the form of a retractable net provided on a retractor roller mounted adjacent the top of the rear back-rest of a motor vehicle such as, for example, an estate car. In use, the net is pulled out over its full length and the free end of the net is engaged with anchorage points provided in the roof of the motor vehicle. It is to be appreciated that in this position, the net will prevent any objects present in the rear luggage compartment of the vehicle from moving forwardly into the part of the vehicle where the occupants of the vehicle are located, even if the vehicle does decelerate rapidly, for example in a crash. However, if the back-rest is tilted to a forward position, the net will be too short to reach the roof. If the net is made long enough to reach the roof when the back-rest is in a tilted forward position, then when the back-rest is in the elevated position, should an item of luggage impinge against the net during an accident situation, the net will have a sufficient length to permit the luggage to move forwardly into the compartment where the occupants of the vehicle are located. 
     The present invention seeks to provide an improved safety device. 
     SUMMARY OF THE INVENTION 
     According to this invention there is provided a safety device in a motor vehicle, the safety device comprising a roller retractor mounted adjacent the top of the back of a vehicle seat, the roller retractor having wound on it a sheet-like protective element, the seat back being moveable between alternate positions, the sheet-like element being extractable from the roller retractor to engage anchoring means secured in or adjacent the roof of the vehicle, the length of sheet-like material extracted from the roller retractor being different in the said different positions of the back of the seat, the roller retractor mechanism being associated with a locking mechanism, the locking mechanism being actuated in at least one of the said positions of the seat to lock the roller retractor to prevent the extraction of more than a predetermined length of said sheet from the retractor roller, the length being sufficient to enable the sheet to be secured to the connecting means provided in the roof of the vehicle. 
     Preferably said retractor comprises a retractor roller, the said sheet being wound on the roller. 
     Conveniently the roller is prevented from rotating by the locking mechanism. 
     Advantageously the locking mechanism comprises means adapted to engage an element co-rotating with the roller to prevent rotation of the roller, and actuating means, to actuate the engaging means, the actuating means incorporating a gear mechanism, there being selectively positionable means, which are positioned in dependence upon the position of the back-rest, adapted to engage part of said gear to prevent further rotation of the gear and to actuate the engagement mechanism. 
     In one embodiment the gear arrangement comprises a planetary gear. 
     Conveniently the planetary gear arrangement comprises a ring gear which is fixed in position relative to the back-rest, a planet holder which is rotatably mounted in position and which carries planet gears, and a sun gear engaged with the planet gears, the sun gear being connected to the said engagement means, a latch being provided which is movable to selected positions in dependence upon the position of the back-rest, the latch being adapted to engage engagement means provided on the planet holder. 
     Preferably the engagement means comprises one or more steps provided in the outer periphery of the planet holder. 
     In an alternative embodiment the gear comprises a ring-gear which is movably mounted in position, and adapted to be driven rotationally by a sun gear, and a sun gear engaging the ring-gear, the sun gear being connected to the engagement means. 
     Advantageously a latch is provided which is movable to selected positions in dependence upon the position of the back-rest, the latch being adapted to engage engagement means provided on the ring-gear. 
     Conveniently the engagement means comprises one or more steps provided in the outer periphery of the ring-gear. 
     Advantageously the engagement means comprise a clamping member having a periphery defining at least one cam surface and a movable element located between the cam surface and a clamping surface that surrounds the clamping member, the clamping member rotating with the roller extractor, the locking mechanism serving to retain said movable element substantially in position. 
     Conveniently a striker component is provided mounted in position and adapted to strike a locking member to cause the locking member to move when the seat back is moved to at least one predetermined position, the movement of the locking member changing the position of the latch. 
     Preferably the latch is carried by a catch that engages the locking member. 
    
    
     In order that the 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: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic side view illustrating a foldable back-rest for a rear seat of a motor vehicle, and an associated retractable luggable retaining element in the form of a net, 
     FIG. 2 is a diagrammatic side view illustrating the back-rest of FIG. 1 in three alternate positions, 
     FIG. 3 is an exploded view of an assembly mounted on the back-rest which incorporates the retractable net, and also an element that is fixed in position on the body of the motor vehicle, 
     FIG. 4 is a diagrammatic perspective view illustrating the component shown in FIG. 3 when in the assembled state, whilst also illustrating the component mounted on the body of the motor vehicle, 
     FIG. 5 is a side elevational view of the apparatus shown in FIG. 4, 
     FIG. 6 is a diagrammatic view illustrating the said component mounted on the body of the motor vehicle, and also illustrating a catch mechanism and a planet carrier for a planetary gear arrangement in a first condition, 
     FIG. 7 is a view corresponding to FIG. 6 illustrating the arrangement in a second condition, 
     FIG. 8 is a view corresponding to FIGS. 6 and 7 illustrating the arrangement in the third condition, 
     FIG. 9 is a diagrammatic view illustrating the catch, and also illustrating the planetary gear arrangement (with parts thereof cut away for the sake of clarity of illustration) in a first condition, 
     FIG. 10 is a view corresponding to FIG. 9 illustrating the arrangement in the second condition, 
     FIG. 11 is a view corresponding to FIGS. 9 and 10 illustrating the arrangement in a third condition, 
     FIG. 12 is an exploded view illustrating the catch, and the planet carrier, together with an associated manually operable lever, and also associated with one component of a clutch assembly, 
     FIG. 13 is an exploded view of the clutch assembly, 
     FIG. 14 is an elevational view of the clutch in a first condition, 
     FIG. 15 is a scrap view illustrating the position of a roller forming part of the clutch assembly when the clutch assembly is in the condition illustrated in FIG. 14, 
     FIG. 16 is a view corresponding to FIG. 14 illustrating the clutch assembly in an alternative condition, 
     FIG. 17 is a view corresponding to FIG. 15 illustrating the position of the roller when the clutch is in the alternative condition of FIG. 16, 
     FIG. 18 is a view, with parts thereof cut away illustrating the catch, a ring-gear and part of a clutch assembly of a modified embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to FIG. 1 of the accompanying drawings a back  1  of the rear seat of a vehicle is illustrated. The back  1  is provided, adjacent its upper edge, with a roller mechanism  2  extending the entire width of the back of the seat, which has retractably mounted upon it a luggage retaining element  3  in the form of a net. It is to be understood that alternatively the luggage retaining element could be in the form of a blind or an appropriate sheet of fabric. 
     The upper edge of the net  3  is provided with a rigid reinforcing element  4  adapted to be connected to anchoring means in the form of hooks or the like provided in the roof of the motor vehicle. 
     A locking mechanism  5  is provided which is associated with the roller mechanism  2 , and which will be described in greater details hereinafter. The locking mechanism  5  is provided to lock the retractor roller, to prevent further net being permitted to be withdrawn. Thus, when the net is in the operative position as illustrated in FIG. 1, should the vehicle in which the arrangement is provided be involved in an accident which involves substantial deceleration, which might cause luggage located behind the seat back  1  to move forwardly, the net  3  will prevent the luggage from moving forwardly. However, the locking arrangement is such that if the seat back is moved to an alternative position, a further length of net may be paid out, the retractor roller net mechanism then again being locked to retain the net in position. 
     Thus, as can be seen in FIG. 2, the seat back  1  may have an initial position  6  when the seat back reclines rearwardly. The net  3  is shown extending upwardly above the seat back, with the reinforcing rod  4  engaging a hook  7  which may be provided in the roof of the motor vehicle. 
     The seat back  1  may be tilted forwardly slightly, to a position as shown at  8  in FIG.  2 . The net  3  may still be connected to the same hook  7 , but the length of net extending between the back of the seat and the hook  7  is now less than the length of net extending between the back of the seat and the hook  7  when the back of the seat is in the position  6 . Consequently, some net has been drawn on to the roller retractor to achieve the condition illustrated by the numeral  8  in FIG.  2 . The mechanism will, however, again lock the roller retractor in this position to prevent further net being paid out. 
     The back of the seat  1  may be folded forwardly to be substantially horizontal, as shown at  9  in FIG. 2. A substantial length of net  3  may be withdrawn from the roller retractor  2 , the net extending substantially vertically to a second hook  10  provided in the roof of the motor vehicle. In this condition, the full extent of the net has been paid out from the roller retractor mechanism. 
     Referring now to FIG. 3 of the accompanying drawings, the catch arrangement  5  and the retractor roller  2  are illustrated in an exploded form. 
     A striker component  10  is provided adapted to be mounted securely to the body of the motor vehicle. The striker component  10  comprises two parallel spaced apart cylindrical striker elements  11 , 12  inter-connected by a bridging element  13 . 
     The striker component  10  is positioned so that, as the seat back  1  is moved pivotally from the position  9  illustrated in FIG. 2, towards the position  6  as illustrated in FIG. 2, the striker elements enter a guide slot  14  formed in an end plate  15  which is mounted on the side part of the back  1  of the vehicle seat. The upper edge of the guide slot is linear and the lower edge is curved, the edges diverging adjacent the mouth of the slot. The end plate  15  comprises a planar plate region  16  defining forwardly extending wings  17 , 18 , the slot  14  being formed in one of the wings  17  and in the planar portion  16 . 
     The planar portion  16  defines an aperture  19  which receives a pivoting support stud  20 , and further pivot support apertures  21 , 22  which will be referred to hereinafter. The planar portion  16  also defines two fixing apertures  23 , 24  adapted to receive fastening screws or the like to secure the end plate  15  in position. 
     The pivoting support stud  20  pivotally supports a locking element  25 , which defines a substantially centrally located aperture  26  which is mounted on the stud  20 , and which has a convoluted exterior which will be described hereinafter in greater detail. The locking element  25  is associated with a biassing spring  126  which imparts a predetermined rotational bias to the locking element  25 . 
     A catch  27  is provided which forms a further part of the locking mechanism, the catch  27  comprising an elongate element defining an aperture  28  which is mounted on a pivot stud  29 , the pivot stud being received in the aperture  21 . The catch  27  defines a forwardly extending nose  30 , on one side of the aperture  28  and on the other side of the aperture  28  defines a depending lug  31  and an axially extending projection  32  of cylindrical form. 
     The projection  32  is received within an aperture  33  formed in an elongate manually operable release arm  34 . The release arm  34  defines a further aperture  35  which is received on the pivot stud  29 . A spring  36  is provided to bias the manual release arm in a predetermined rotational direction. 
     A latch  36  is provided which is also mounted on the pivot support stud  29 . The latch  36  comprises two diverging arms  37 , 38 . An aperture  39  extending though the latch  36  is concentric with a tubular projection  40  which provides a bearing effect. The arm  38  carries an axially extending cylindrical projection  41 . A biassing spring  42  is provided associated with the latch adapted to bias the latch in an appropriate direction. 
     The pivot stud  29  is formed on the exterior a planetary gear housing  41 . The planetary gear housing is of substantially circular form having co-axially mounted on the end face directed towards the end plate  15 , a first substantially cylindrical projection  42  of a further diameter and a co-axially located second cylindrical projection  43  of a lesser diameter. Formed in the end face of the projection  43  is an aperture  44  adapted to receive a bearing element, as will be described hereinafter, which is received in the bearing aperture  22  formed in the end plate  15 . 
     A slot  45  is formed in the side wall of the projection  42  of greater diameter in the vicinity of the a pivot stud  29 . The slot is so located that when the latch  36  has been mounted on the pivot stud  29 , the arm  37  of the latch may be inserted through the slot  45  as the latch rotates about the pivot axis defined by the pivot stud  29 . 
     The planetary gear housing is fixed to the back-rest of the motor vehicle and contains, within the part of the housing of greatest diameter (i.e. not within the projections  42  or  43 ), a ring gear  46  which is fixed in position and which has inner toothing  47 . The ring gear  46  forms the outer gear of a planetary gear system. The planetary gear system incorporates a substantially circular gear carrier  48  which will be described hereinafter in greater detail, which defines three apertures  49 , 50 , 51  at equi-spaced regions on which are mounted three planet gears  52 , 53 , 54  and which also defines a central aperture  55 . The planet carrier  48  is located in the first cylindrical projection  42  of greatest diameter provided on the planetary gear housing  41 . The planet gears  52 , 53 , 54  are then located in a position where they are co-planar with the ring-gear  46  and have their outer-most teeth in engagement with the toothing  47  provided on the ring-gear  46 . A central sun gear  56  is provided which defines a central aperture  57 , the sun gear being located to be in engagement with the inner peripheries of the planetary gears  52 , 53 , 54 . 
     The sun gear  56  is associated with a spider element  57  having six projecting arms which form part of a clutch as will be described in greater detail hereinafter. Three of the arms of the spider element  57  are adapted to engage clamping rollers  58 , 59 , 60  which are held in position against a clamping element  61  which has convoluted exterior (which will be described in greater detail hereinafter), which define cam surfaces. The clamping element  61  is located within a clamping ring  62  which is connected to the open end of the planetary gear housing  41 . 
     The spider  57  and the associated components, including the rollers  58 , 59 , 60 , the clamping element  61  and the clamping ring  62  form a clutch that effectively secures the roller retractor mechanism  2  to the locking arrangement  5  in order to lock the roller to prevent the withdrawal of further net from the roller retractor mechanism  2 . 
     The roller retractor mechanism  2 , as can be seen more clearly in FIG. 3, comprises a roller drum  63  upon which the net  3  is wound. The roller drum has, at the illustrated end, a bearing  64  having a hexagonal outer periphery, and a substantially cylindrical inner bore  65 . The bore  65  is mounted on a support rod  66 , the support rod  66  also rotatably supporting the sun gear  56 , and the planet carrier  48  (by passing through the aperture  45 ), and also passing through the aperture  44  in the planetary gear housing  41  being received in the aperture  22  formed in the planar portion  16  of the end plate  15 . A helical spring  67  is provided located between the rod  66  and the drum  63  in order to provide a rotational bias to the drum tending to retract the net  3  on to the drum. 
     FIG. 4 illustrates the components of the locking mechanism  5  when in the assembled state. It can be seen that the projection  43  provided on the planetary gear housing  41  serves the function of spacing the main part of the planetary gear housing  41  from the end plate  15  by an appropriate distance to permit the locking element  25 , the catch  27  and the associated manual release lever  34  and also the latch  37  between the planetary gear housing  41  and the end plate  15 . It can be seen that the free end of the manual release arm  34  is accessible. 
     The striker component  10  is illustrated in position, and it can be seen that the striker elements  11 , 12  are aligned with the guide slot  14 . As shown in FIG. 5, the striker elements  11 , 12  of the striker component  10  are located in at a position spaced apart in a horizontal plane. It can be seen more clearly that the upper edge of the guide slot  14  is linear, whereas the lower edge is slightly curved. 
     Referring now to FIG. 6, the locking element  25  is illustrated, together with the catch  27 , the latch  36  and the planet carrier  48 . 
     The locking element  25  has a convoluted exterior. An initial curved region  70 , which is located at a position which is substantially tangential with reference to the axis defined by the aperture  26  is initially positioned, so that the depending lug  31 , provided on the catch  27 , is resting upon the curved surface  70 . The curved surface  70  terminates, at its left-hand end, as shown in FIG. 7, with a recess  71 . The configuration of the recess  71  corresponds with the configuration of the depending lug  31 . 
     Adjacent the recess  71  is a substantially “U”-shaped channel  72  having a width equal to the diameter of the striker element  12  of the striker component  10 . In an initial condition illustrated in FIG. 6, the channel  72  is inclined downwardly towards the right, but an extension of the upper-most edge of the channel is co-aligned with the striker elements  11 , 12 . 
     Moving further in a clockwise direction about the outer periphery of the locking element  25 , it can be seen that the outer periphery defines, adjacent the lower wall of the channel  72 , an outwardly directed abutment face  73  which is located adjacent a linear portion  74  which merges into a further inwardly directed U-shaped channel  75  which has a width equal to the width of the striker element  11 . 
     The planetary gear carrier  48  is of substantially circular form, but the outer periphery defining two radially inwardly directed discontinuities or steps. The step  80  represents a step between the outer-most periphery of the planetary gear carrier  48 , and the planetary gear carrier  48  then has an outer periphery portion  82  which is spaced from the aperture  55  by a distance less than the distance to the periphery of the planetary gear carrier located on the other side of the inwardly directed step  80 . Similarly the step  81  extends to a further arcuate portion  83  of the exterior of the planetary gear carrier  48 , this portion being located a lesser distance from the aperture  55  than the portion  82 . The portion  83  does merge, as one continues to move notionally around the planetary gear carrier in an anti-clockwise direction with a portion which extends back out to the full diameter of the planetary gear carrier as found as one re-encounters the inwardly directed step  80 . 
     It is to be observed that in the condition illustrated in FIG. 6, with the depending lug  31  of the catch  27  engaging the surface  70 , the arm  37  of the catch  36  is spaced from the outer periphery of the planetary gear carrier  48 , permitting the planetary gear carrier  48  to rotate freely. As will become clearer from the following description, the planetary gear carrier rotating any net is withdrawn from the roller retractor. Thus in this condition of the described embodiment the full length of the net  3  can be withdrawn from the roller retractor  2 . It is to be appreciated, therefore, that the catch will have the condition illustrated in FIG. 6 when the seat back is in the position  9  as illustrated in FIG.  2 . 
     It is also to be observed, with reference to FIG. 6, that the latch  36  is pivotally mounted for movement relative to the catch  27  and is spring-biassed, by spring  42  to a position in which the upper arm  37  extends upwardly above the catch  27 . The spring biassed arm enters the planetary gear housing  41  (not shown in this figure) through the slot  45 , so that the free end of the arm  37  is located adjacent the periphery of the planet carrier  48 . The projection  41  provided on the lower arm  38  of the latch engages the underpart of the forwardly projecting nose  30  provided on the catch  27 , to prevent the latch  37  rotating too far. 
     The arrangement will maintain this condition, as illustrated in FIG. 6, until the seat back has been moved up to the position  8  as illustrated in FIG.  2 . As the seat back approaches the position  8 , as illustrated in FIG. 2, the striker component  10  begins to enter the guide slot  14 , and the striker element  11  engages the upper part of the side wall of the slot  72 , causing the locking member  25  to rotate in a clockwise direction to such an extent that against the spring bias imparted to the combination of the latch  27  and the manual release lever  34  by the spring  36 , the latch  37  moves in a clockwise direction to bring the depending lug  31  into an engagement with the recess  71 . The components of the locking mechanism initially illustrated in FIG. 6 then have the condition illustrated in FIG.  7 . It can be seen that the U-shaped channel  72  is now substantially vertically oriented, and consequently retains firmly within it the striker element  12 . The depending lug  31  is received within the recess  70 , thus preventing further rotational movement of the locking element  25 . 
     It can be seen that the upper arm  37  of the latch  36  has been moved to an upper position, as compared with the position illustrated in FIG.  6 . The free end of the arm is biassed against the arcuate surface  83  forming part of the periphery of the planet gear holder  48 . Should the planet gear holder  48  attempt to rotate in the anti-clockwise direction, such rotation will be prevented by engagement of the step  81  with the end of the upper arm  37  of the catch  36 . However, should the planet carrier  48  rotate in a clockwise direction, as the planet carrier rotates, the outer periphery of the planet carrier will engage the upper surface of the upper arm  37  of the latch  36 , causing the latch  36  to pivot about the pivot axis defined by the support stud  29 , with the lower arm moving downwardly against the bias provided by the spring  42 . 
     It is to be appreciated that as the planetary gear moves in the anti-clockwise direction, net  3  is being paid out from the retractor roller  2 , whereas when the planet carrier  48  moves in a clockwise direction, the net  3  is being wound on to the retractor roller  2 . The step  81  is so positioned that the step  81  is brought into engagement with the free end of the arm  37  of the latch  36  when a sufficient length of net has been paid out to reach from the top of the back  1  of the seat to the hook  7  in the roof when the seat is in the position  8  as illustrated in FIG. 2 of the accompanying drawings. 
     If the seat back is moved from the position illustrated at  8  in FIG. 2 to the position illustrated at  6  in FIG. 2, the effect is that the striker component  10  is moved further into the slot  20 . However, this movement can only be achieved if the manual release arm  34  is initially moved so as to disengage the downwardly directed lug  31  from the recess  71 . When the lug  31  has been released from the recess  71 , the seat back may, of course, be moved forwardly to occupy the position illustrated at  9  in FIG. 2, in which case the spring  26  will return the locking element  25  to the position in FIG. 6, or instead, the seat back may be moved to have the position illustrated at  6  in FIG. 2, in which case the striker component  10  will be moved further into the slot  14 , causing the locking element  25  to rotate further in the clockwise direction as shown in FIGS. 6 to  8  against the bias provided by the spring  26 . It can be seen, therefore, that as the locking member  25  continues to rotate, the striker element  12  moves out of the channel  72 , whilst the striker element  11  moves into and is received by the channel  75 . If the manual release arm is then released, the depending lug  41  carried by the catch  27  engages the abutment  73  with the lower end of the depending lug resting on the planar surface  74 . The spring bias provided by the spring  26  biases the abutment  73  of the locking member  25  into firm engagement with the depending lug formed on the catch  27 . 
     It is to be noted that when the catch is in this condition, the upper arm  37  of the catch  36  is spaced slightly further out from the central aperture  55 , than when the components were in the condition illustrated in FIG.  7 . The free arm  37  of the catch  36  is now positioned to engage the step  80  and the associated arcuate surface  82 . Again, rotation of the planet carrier in the anti-clockwise position is prevented, whilst rotation in the clockwise direction is permitted. 
     FIG. 9 illustrates the catch and latch in position of FIG. 6, showing the planet carrier  48  and the associated planetary gear wheels. It can be seen quite clearly, in this condition, that the planet carrier  48  and the associated planetary gear wheels  52 , 53 , 54  may rotate freely. 
     FIG. 10 illustrates an alternative position, corresponding to the position of FIG. 6, and it can be seen that the latch  36  is in such a position that the free end of the upper arm  37  is substantially co-aligned with the step  81  of the planet carrier  48 . Should the planet carrier  48  rotate, from the position illustrated, in the anti-clockwise direction, which is the direction in which it will rotate should the net be drawn out from the roller retractor  2 , the net will be paid out until step  81  abuts the free end of the arm  37 . No further net may then be paid out. 
     FIG. 11 is a view corresponding to FIG. 10 illustrating a condition equivalent to that shown in FIG.  8 . Here, it is to be noted that the further length of net may be pulled out, as compared with the condition shown in FIG. 10, while the planet carrier  48  rotates by a few more degrees. However, in the condition of FIG. 11, the free end of the arm  37  is rotated substantially in alignment with the step  80  of the planet carrier, and when the planet carrier has rotated so that the step  80  is brought into abutment with the free end of the arm  37 , the planet carrier will again be locked in position. 
     When the planet carrier is locked in position, the plant wheels  52 , 53 , 54  are locked in position and consequently, the sun gear  56  will be locked in position. As a consequence the spider  57  is locked in position. 
     FIG. 13 illustrates the spider  57 , the rollers  58 , 59 , 60 , the clamping element  61  and clamping ring  62 . The spider  57  may be moulded of a plastics material. 
     It is to be observed that the spider  57  comprises six arms. Three arms  90 , 91 , 92  are equi-angularly spaced. Each arm is relatively wide and is thus rigid. Each arm terminates with two forwardly directed protrusions  93 , 94 . 
     Intermediate the arms  90 , 91 , 92  are three equi-angularly spaced arms  95 , 96 , 97 . Each of these arms terminates in a forwardly directed protrusion  98 . The arms  95 , 96 , 97  are made sufficiently thin to be resilient and flexible. 
     The clamping element  61  has a substantially hexagonal central aperture  100  formed therein which is adapted to receive the hexagonal outer surface of the bearing  64  provided at the end of the roller  63  so that the clamping element  61  moves in synchronism with the roller  63 . 
     The outer surface of the clamping element  61  defines three equi-angularly spaced recesses of U-configuration, such as the recess  101  each adapted to receive a projection such as the projection  98  on one of the resilient arms  95 , 96 , 97 . 
     Equi-angularly spaced between the recesses  101  are inclined cam faces  102 . As can be seen in FIG. 13, each cam face  102  is associated with a roller  58 , the roller  58  being located between the arms  93 , 94  of a substantially rigid arm such as the arm  90 . As can be seen in FIG. 13, the roller  58  is initially separated from the inner periphery  103  of the clamping ring  62 . 
     In the event that the sun gear  56  is prevented from rotating, should the roller  63  still rotate in a sense in which the net  3  is being paid out from the roller, the small rollers  58 , 59 , 60  will be entrained by the relative movement of the member  61  (which co-rotates with the roller  63 ) and will move up the cam faces  102  (see FIG. 17) to become clampingly engaged between the clamping member  61  and the inner face of the clamping ring  62 . As this occurs the resilient arms  95 , 96 , 97  become slightly deformed. The rollers, as seen in FIG. 17, become wedged firmly between the cam faces  102  and the inner periphery of the clamping ring  62 , and thus prevent further rotation of the roller  63  of the retractor roller mechanism  2 . The resilience in the arms  95 , 96 , 97  returns the rollers  58 , 59 , 60  to their initial position (i.e. the FIG. 13 position) when tension applied to the net tending to withdraw the net from the roller  63  is released. 
     Referring now to FIG. 18 of the accompanying drawings, a modified embodiment of the invention is illustrated in which the planetary gears, the planetary gear carrier and the fixed ring gear are replaced by a single moveable ring gear  104 , which has a toothed interior  105  which engages with the sun gear  56  mounted on the spider  57 . It can be seen that the axis of rotation of the spider is no longer concentric with the axis of the ring gear. 
     The exterior periphery of the ring gear defines a discontinuity or step  106  which corresponds to the step  80  or the step  81  described above. The upper arm  37  of the latch  36  is of a more upwardly directed configuration than in the previously described embodiment, but it can be seen that with the catch  27  in the position illustrated, the upper arm  37  of the latch  36  is located to engage the step  106  to prevent rotation of the ring gear  104  in the anti-clockwise direction. This will, of course, stop rotation of the sun gear  56  with the consequences described above with regard to the earlier embodiments. 
     It is to be appreciated that in the embodiment of FIG. 18 only one step  106  is provided, corresponding to a specific length of net being withdrawn from the retractor roller  2 . However, in this embodiment, two steps could be provided, as in the embodiment described above, corresponding to two slightly different lengths of net. Of course, the embodiment of FIG. 1 might be modified to have only a single step as in the embodiment of the FIG.  16 . 
     It is to be appreciated, therefore, that in use of the embodiments of the invention, the amount of net that can be withdrawn from the retractor roller depends upon the position of the back of the seat, and the length of net is sufficient to reach the associated hook or hooks provided in the ceiling so that he net is stretched relatively a tightly between the back of the seat and the hooks provided in the ceiling of the motor vehicle to prevent luggage from travelling forwardly.