Abstract:
This invention relates to a retraction and extension mechanism for extending or retracting a set of telescopic supports that connect a mirror head ( 10 ) to a mirror mounting bracket ( 11 ). It comprises a mirror mounting bracket ( 11 ) with a first tube ( 18 ) projecting from the mounting bracket ( 11 ). The mirror head ( 10 ) has a support ( 19 ) projecting from it that locates into and slides back and forth within the first tube ( 18 ). A roller ( 34 ) is mounting with respect to the support ( 19 ) and cable ( 29 ) is attached at one end with respect to the first tube ( 18 ) and a point between the roller ( 34 ) and the mirror head ( 10 ). It extends to and around the roller ( 34 ) and into the mirror head ( 10 ). The other end of the cable ( 29 ) extends into and is attached with respect to the first tube ( 18 ). A capstan ( 31 ) is located within the mirror head ( 10 ) and engages the cable ( 29 ). A motor ( 47 ) drives the capstan ( 31 ) in either direction to cause the mirror head ( 10 ) to extend or retract with respect to the mirror mounting bracket ( 11 ).

Description:
This invention relates to the extension or retraction of telescopic supports that are used to secure the mirror head of a rear vision mirror to a mounting bracket on a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     Although one application is with a rear vision mirror assembly, it should be realised that the invention should not be restricted to this particular application, as it will be suited to other applications. However, for ease of description, the invention will be described in relation to this application. 
     It is desirable to be able to move the mirror head, which holds the mirror, with respect to the mounting bracket on the motor vehicle in towards or away from the mounting bracket. 
     This enables the mirror head to be either positioned close to the side of the motor vehicle, or to be extended away from the motor vehicle to provide an increased field of view. A rear view may be obstructed by a vehicle body, a load on the vehicle, or a trailer that is being towed. In many of these instances, extending the mirror head outwardly will provide a increased field of view behind the vehicle. 
     Accordingly, it is an aim of the invention to provide a mechanism to extend or retract telescopic supports. 
     It is a further object of this invention to provide a means whereby a mirror head can be both manually or automatically moved towards or away from the mounting bracket of a motor vehicle mirror. 
     SUMMARY OF THE INVENTION 
     According to one aspect, the invention is a retraction and extension mechanism for extending or retracting a set of telescopic supports that connect a mirror head to a mirror mounting bracket comprising: 
     a mirror mounting bracket, 
     a mirror head, 
     a first tube projecting from said mounting bracket, 
     a support projecting from said mirror head that locates into and slides back and forth within said first tube, 
     a roller mounted with respect to said support, 
     a cable, attached at one end with respect to said first tube at a point between said roller and said mirror head, and extending to and around said roller and into said mirror head, the other end of said cable extending into and attached with respect to said first tube, 
     a capstan within said mirror head engaging said cable, and 
     a motor to drive said capstan in either direction to cause said mirror head to extend or retract with respect to said mirror mounting bracket. 
     The support may also comprise a tube and more than one set of telescopic first and second tubes may be used to mount the mirror head to the mirror bracket. 
     Preferably, a pair of first and second tubes are used, with one set of first and second tubes being located above the other set. A first cable extends from a connector in the upper tube set into the mirror head, around the capstan and into the lower set of first and tubular arms, around a roller in the end of the second tube in the lower set and back to a connector. A second cable extends from the other side of the lower connector into the mirror head, around at least one idler pulley and then into the upper set of first and second tubes. The end of this second cable is attached to the connector in the upper set via a roller that is mounted in the end of the second tube of the upper set. Movement of the first cable by the capstan will result in movement of the mirror head either towards or away from the mounting bracket. This will be described in more detail below in respect of a preferred embodiment. 
     Further, the invention may comprise a drive means for a cord comprising: a pair of contra rotating capstans that are rotatably mounted to a motor housing, said cable engaging with said capstans so that, with respect to each direction of movement of said cable through said drive means, the cable moves around the axis of one capstan in a direction opposite to that of the other capstan, 
     a pivot that allows said motor housing to rotate about an axis which is parallel to the axis of rotation of each of the capstans so that the extent of contact between the cable and the periphery of each capstan can be varied, and 
     torsion means acting with respect to said motor housing and pivot that acts to rotate said motor housing and to increase the extent of contact of said cable with respect to the periphery of each said capstan. 
     Preferably, the pivot is located equally distant between the axis of rotation of each capstan. This ensures that the extent of rotation of the axis of each capstan around the pivot is the same. 
     The torsion means may comprise either a torsion spring concentric with the pivot, or a coil spring fixed at one end with respect to the mirror head and attached to the motor housing at the other. The torsion means acts to rotate the motor housing in a direction which increases the extent of cable which is in contact with the periphery of each of the capstans. The torsion means is required to maintain at least a minimum degree of contact to ensure adequate drive connection between each of the capstans and the cable. If the extent of contact between the cable and the capstans becomes less than the minimum, then the cable will slip with respect to each of the capstans. 
     In one aspect of the invention, this is quite useful. If movement of the cable is prevented for whatever reason, then continued rotation of the capstans will tend to rotate the motor housing so that the extent of engagement between the cable and each of the capstans is reduced. This rotation, against the torsion means, will continue until the capstans start slipping with respect to the cable. At this point, the motor housing will cease rotating while maintaining sufficient force to act against the torsion means, and to thereby prevent any overload or stalling of the capstans. It will also be useful if the mirror head is moved manually. This will also cause rotation of the motor housing and result in slipping of the cable. 
     Preferably, one of the capstans is driven by an electric motor via reduction gearing, and the other capstan is driven via engaging ring gears that are on each of the capstans. This results in the contra rotation of the capstans. 
     The cable used on both the means for moving the mirror head and the drive means may comprise in a cord, belt or any other form of flexible cord. In addition, multiple cables may be used to produce a series of parallel cables that, together, act as a single cable. 
     As an alternative to contra rotating capstans, a single driven capstan may be used. The capstan may be spring loaded, or arranged in some other manner, so that it is pushed into the cable. The resultant angle of wrap must be sufficient to enable drive force to be applied to the cable. Any resistance to movement or any manual movement of the mirror head will result in deflection of the spring and slippage of the cable over the capstan. 
     A further alternative for the drive means may be a capstan in combination with a clutch. The clutch is designed to disengage upon manual movement or any resistance to movement being encountered. 
     In a second aspect, the invention is a retraction and extension mechanism for extending or retracting telescopic supports that connects a mirror head to a mirror mounting bracket comprising: 
     at least one first tube attached at one end to, and projecting from, said mirror mounting bracket, 
     at least one support attached to and projecting from said mirror head, that locate into and slide back and forth within a said first tube, 
     at least one wheel secured with respect to said support, the periphery of said wheel engaging against said first tube, and 
     drive means for rotating said wheel in either direction to move said first tube and support with respect to each other to cause said mirror head to extend or retract with respect to said mirror mounting bracket. 
     Preferably, the support comprises a tube and a pair of first and second tubes are used with one set of first and second tubes being located above the other set. The wheel and associated drive means may be located in one of the sets, or alternatively a wheel with associated drive means may be located in each of the sets of first and second tubes. 
     Preferably, the mounting of the wheel within one of the tubes includes a means of forcing the periphery of the wheel against one of the tubes. This may include a mounting which enables the wheel to move in a direction that is normal with respect to its axis of rotation and a spring means which pushes the wheel in the required direction. 
     Preferably, the wheel is mounted with respect to the tube which is located internally of the other tube. An aperture may be provided within the internal tube to enable the periphery of the wheel to locate against the outer tube. 
     In addition to the use of one wheel, two or more wheels may be used to provide the necessary drive force. 
     In addition to providing drive force, another function performed by the wheels will be to hold the mirror head in the required position while at the same time allowing manual movement of the mirror head without operation of the drive means. The friction force acting between the periphery of the wheel and one of the tubes must be sufficient to enable the wheel to move the mirror head. In addition, when the wheel is stationary, the applied force and resultant friction is high enough to prevent unwanted movement of the mirror head. The necessary force that will achieve these aims is not so large that it prevents manual movement of the mirror head. Manual movement will result in slippage of the wheel with respect to one of the tubes. Accordingly, with this invention, it is possible to manually move the mirror head to an extended or retracted position. 
     The wheel or wheels may be electrically driven, and the drive means preferably comprises an electric motor and drive pulley that is located within the mirror head and a cable which extends from the pulley into the telescopic tubes and that engages the wheel so as to cause it to rotate. 
     The cable within the telescopic tubes may either locate around the periphery of the wheel or some other element of the wheel which causes it to rotate. Alternatively, a pair of spaced wheels may have the cable located around them with an idler pulley, positioned between the pair of wheels, that pushes against the cable and in turn causes the cable to push against the pair of wheels. The pair of wheels may be slidably mounted with respect to their pivot to enable movement normal to the axis of the pivot to thereby cause the periphery of the wheels to bear against the inside surface of one of the tubes. 
     In order to fully understand the invention, a preferred embodiment will now be described, however it should be realised that the scope of this invention is not to be confined or restricted to the precise features of the embodiment. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The embodiment is illustrated in the accompanying illustrations in which: 
     FIG. 1 shows a schematic view of a mirror head, mounting bracket and location of drive means with associated cable according to a first embodiment, 
     FIG. 2 shows a top view of a drive means illustrated in FIG. 1, 
     FIG. 3 shows a side view of a drive means illustrated in FIG. 1, 
     FIG. 4 shows a schematic view of a mirror head, mounting bracket and drive means according to a second embodiment of this invention, 
     FIG. 5 shows a part schematic view of wheels and drive means in accordance with a second embodiment, 
     FIG. 6 shows a schematic view of a mirror head, mounting bracket and location of drive means according to a third embodiment, and 
     FIG. 7 shows a part schematic view of wheels and drive means used in the third embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a rear view mirror assembly according to a first embodiment comprises a mirror head  10 , a mounting bracket  11  and a upper and lower set of telescopic tubes  12  and  13  respectively. The mounting bracket  11  is attached to the side of the motor vehicle, and versions of the invention will be produced that are suited to both left and right side applications. 
     The mirror head  10  carries the rear view mirror. The tilt of the mirror is controllable about a vertical and horizontal axis by electric motors that are commonly known and used in this industry. The mirror head  10  comprises an assembly of a sub-frame  14  to which a moulded cover  15  is secured. 
     The telescopic tube sets  12  and  13  each comprise a first tube  18  that is secured at one end to the mounting bracket  11 . The other end of each first tube  18  locates through apertures within the moulded cover  15 . 
     Supports, which comprise second tubes  19 , are secured at one end to the sub-frame  14  and extend through the centre of each respective first tube  18 . The engagement of the first and second tubes  18  and  19  in this manner enable the telescopic movement of the tube sets  12  and  13 , thereby enabling the mirror head  10  to move toward or away from the mounting bracket  11 . 
     Friction pads  21  are generally drawn in FIG. 1, and comprise spring loaded pads that exert pressure between the first and second tubes  18  and  19  to prevent unwanted vibration of the mirror head  10  with respect to the mounting bracket  11 . The friction pads also prevent unwanted movement of the telescopic tube sets  12  and  13 . 
     FIG. 1 illustrates a series of cables (referred to in more detail below) and a drive means  25  which are used to cause movement of the mirror head  10  with respect to the mounting bracket  11 . 
     Firstly, connectors  27  are secured to each of the outer tubes  18 . Each of the connectors  27  project through elongate slots within the inner tube  19  to allow the necessary movement of the inner tube  19  with respect to the outer tube  18 . A first cable  29  is attached to the upper connector  27  and extends from the connector  27  into the moulded cover  15  of the mirror head  10 . The first cable  29  extends around an idler pulley  30  and then engages contra rotating capstans  31  and  32  of the drive means  25 . The first cable  29  extends around another idler pulley  33  that is mounted on the sub-frame  14  and a roller  34  that is mounted to the end of the lower second tube  19 . The first cable  29  is then connected to the lower connector  27 . 
     A second cable  35  is attached to the lower connector  27  and extends into moulded cover  15  of the mirror head  10  and around idler pulleys  36  and  37 . The second cable  35  then extends around roller  38  located at the end of the upper inner tube  19  and is then attached to the upper connector  27 . 
     The motor housing  40  of the drive means  25  has a pivot  41  which connects the drive means  25  to the sub-frame  14 . This enables rotation of the motor housing  40  about the pivot  41 . A spring  42  is secured at one end to the sub-frame  14 , and at the other end to the motor housing  40 . The spring  42  acts as a torsion means and tends to cause the motor housing  40  to rotate in an anti-clockwise direction as shown in FIG.  1 . This tends to increase the extent of contact between the periphery of each of the contra rotating capstans  31  and  32  and the first cable  29 . In addition, it acts to maintain the required tension within the first and second cables  29  and  35 . 
     Operation of the drive means  25  will cause the mirror head  10  to either move away from or towards the mirror mounting bracket  11 . 
     In order to make the mirror head  10  move towards the mounting bracket  11 , the drive means  25  is operated so that contra rotating capstan  31  is rotated in an anti-clockwise direction. This in turn reduces the length of the first cable  29  and shortens the distance between the idler pulley  30  and the upper connector  27 . As the upper connector  27  is fixed with respect to the mounting bracket  11 , which means the mirror head  10  will move towards the mounting bracket  11 . 
     As the length of the first cable  29  between the idler pulley  30  and connector  27  is being shortened, the length of the first cable  29  between idler pulley  33  and roller  34  is being lengthened. This enables the inner tube  19  carrying the roller  34  to move towards the mounting bracket  11 . 
     The movement of the inner tube  19  carrying roller  38  towards the mounting bracket  11  results in movement of the second cable  35 . As the roller  38  moves away from the upper connector  27 , a force results between pulley  36  and the lower connector  27 . The change in length of the second cable  35  between the upper connector  27  and roller  38  results in a shortening of the second cable  35  between the pulley  36  and lower connector  27 . This in turn acts in a similar manner to the shortening of the first cable  29  between the upper connector  27  and the pulley  30  and results in the inner tube  19  and therefore mirror head  10  moving closer to the mounting bracket  11 . 
     In order to move the mirror head in the opposite direction away from the mounting bracket  11  the direction of the contra rotating capstans  31  and  32  are reversed so that the contra rotating capstan  32  rotates in an anti-clockwise direction. This results in the length of the first cable  29  between roller  34  and pulley  33  being reduced which causes the mirror head  10  to move away from the mounting bracket  11 . Consistent with the description of the mirror head  11  moving inwardly, the length of the first cable  29  between the pulley  30  and the upper connector  27  increases with a resultant corresponding change in the various lengths of the second cable  35 . 
     The drive means of the first embodiment is illustrated in FIGS. 2 and 3. The drive means  25  comprises an upper and lower casing  44  and  45  which hold the contra rotating capstans  32  and  31  and electric motor  47  with its associated drive gears. 
     The contra rotating capstans  31  and  32  are moulded components that incorporate both the capstans  31  and  32  together with drive gears  48  and  49 . Respective capstans  31  and  32  and drive gears  48  and  49  rotate about a common axis and are journalled with respect to the upper and lower casings  44  and  45  so that the drive gears  48  and  49  mesh. Accordingly, rotation of the first capstan  31  will cause the second capstan  32  to rotate in the opposite direction. 
     The drive motor  47  drives a first worm drive  50  which drives a gear  51  of a second worm drive  52 . The second worm drive  52  drives the drive gear  49  of capstan  31 . 
     As seen in FIG. 1, the first cable  29  loops around capstan  31  in one direction and in the opposite direction around capstan  32 . The drive means  25  is pivotally mounted to the sub-frame  14  via a pivot  41  which comprises a pivot post  53 . A spring  42  is used to control the angle of wrap of the first cable  29  around each of the capstans  31  and  32 . By ensuring sufficient wrap of the first cable  29  around the capstans  31  and  32 , sufficient drive force can be imparted to the first cable  29  to cause movement of the mirror head  10 . 
     If the mirror head  10  becomes jammed, either when it is moving inwardly or outwardly, or if the mirror head  10  is moved manually either inwardly or outwardly, the drive means  25  will tend to rotate about pivot  41  so that the degree of wrap around the capstans  31  and  32  of the first cable  29  reduces sufficiently to enable it to slip with respect to the capstans  31  and  32 . 
     If the mirror head becomes jammed as it is being driven in either direction, the first cable  29  will become stationary, and the contra rotating capstans  31  and  32  will cause the drive means  25  to rotate about its pivot  53 . This will in turn act to reduce the angle of wrap of the first cable  29  around the capstans  31  and  32 . This results from the spacing of pulley  30  on a first side of the drive means  25  and with pulley  33  positioned on the other side of the drive means  25 . Once the angle of wrap reduces sufficiently, then the cable  29  will slip with respect to the drive means  25 . 
     If the mirror head  10  is being moved manually inwardly, the first cable  29  will be attempting to lengthen itself between capstans  32  and  34 . Because of the positioning of pulley  33  to the right of the pivot  53 , sufficient force will be applied to rotate the drive means  25  in a clockwise direction about pivot  53 . This in turn will reduce the angle of wrap around both capstans  31  and  32  and will enable slippage of the first cable  29 . 
     Alternatively, if the mirror head  10  is being pulled outwardly, the length of the first cable  29  between the upper connector  27  and capstan  31  will be increasing. Initially, the force applied by this section of the first cable  29  will cause the drive means  25  to rotate in a clockwise direction as a result of the pulley  30  being located to the left of the pivot  53 . Again, this rotation will continue until the angle of wrap around both capstans  31  and  32  reduce sufficiently to enable slippage of the first cable  29 . 
     Accordingly, the embodiments shown in FIG. 1 will enable the mirror head  10  to be moved electrically by the drive means  25  while at the same time providing an over-ride mechanism that will enable manual movement or effective disengagement of the drive means  25  should the mirror head become jammed. 
     A second embodiment of the invention is illustrated in FIGS. 4 and 5. FIG. 4 shows a schematic representation of the mirror head  10  and to first tubes  18 . A single cable  55  is wrapped at least once around a drive pulley  56  and extends into the combined first and second tubes  18  and  19  via pulleys  57 . The cable  55  engages wheels  58 ,  59  and  61 . The returned side of the cable  55  locates around pulleys  60 . 
     The features of the invention shown in FIG. 4 are largely the same as those shown in FIG.  1 . The embodiment includes a subframe  14  with attached second tubes  19 , outer tubes  18  which are also attached to a mounting bracket  11  (not drawn). Pulleys  56 ,  57  and  60  are secured to the sub-frame  14 . 
     The drive pulley  56  is preferably driven by a small DC motor in combination with a worm drive and gear to provide sufficient drive torque to pulley  56 . In addition, the drive pulley  56  is slidably mounted with respect to the sub-frame  14 , and a preloaded spring applies a force between the subframe  14  and the drive pulley  56 . This results in a pre-load or tension being applied to the cable  55 . Pulleys  57  and  60  are idler pulleys, and are used to route a cable  55  into and out of the second tubes  19 . 
     The wheels  58 ,  59  and  61  are illustrated in more detail in FIG.  5 . Each of the wheels  58  and  59  are rotatably mounted with respect to the inner tube  19  so that they are able to move normal to their axis of rotation. A pulley  61 , which is also fixed with respect to the inner tube  19  acts on the cable  55  between the wheels  58  and  59 . The tension in the cable  55  results in an outward force being applied by the cable to each of the wheels  58  and  59 . The cable  55  preferably locates in a groove in the periphery of each wheel  58 ,  59  and  61 , and one length of the cable  55  may pass between the inner and outer tubes  19  and  18 . 
     An aperture  62  is provided in the inner tube  19  through which the wheels  58  and  59  project so as to enable engagement against the inside surface of the outer tube  18 . An aperture  65  in the inner tube  19  is provided through which the wheel  61  projects to enable contact with the tube  18 . The tension in the cable  55  as a result of the positioning of pulley  61  results in the wheels  58  and  59  bearing firmly against the inside surface of the tube  18 . The force applied by wheels  58  and  59  cause the tube  18  to bear against wheel  61 . The resultant friction force will enable the wheels  58 ,  59  and  61  when rotated, to move the inner tube  19  with respect to the outer tube  18 , or when the mirror head  10  is manually moved, to slip with respect to the inner surface of the outer tube  18 . Accordingly, if the mirror head  10  is moved manually, the wheels will not cause the cable  55  to back drive the drive pulley  56  and will enable inward or outward movement of the mirror head  10  as a result of the wheels  58 ,  59  and  61  slipping with respect to the outer tube  18 . Movement of the cable  55  will rotate the wheel  61  in the opposite direction to the wheels  58  and  59 . This results in the required motive force being applied to the tube  18 . 
     The force applied by the wheels  58 ,  59  and  61  to the outer tube  18  will also act to hold the mirror head in position under normal operating loads. Accordingly, vibration within acceptable limits will not result in the mirror head  10  moving. 
     A third embodiment is illustrated in FIGS. 6 and 7. The arrangement shown in FIG. 6 is substantially the same as that shown in FIG. 4, the only difference being the arrangement of wheels  58  and  59 . This difference is illustrated in FIG.  7 . 
     In this embodiment, a third wheel  64  extends through a second aperture  65  so that it bears against the inside surface of the outer tube  18 . A pretension spring  66  applies a force between a mount  67  to which the wheels  58  and  59  are attached and a mount  68  to which the third wheel  64  is attached. The spring  66  is selected so that the wheels  58 ,  59  and  64  apply sufficient force to the inside surface of the outer tube  18 . As in the second embodiment, the wheels  58 , 59  and  64  are pivotally mounted with respect to the inner tube  19 , but are able to move normally with respect to their axis of rotation so that force provided by the spring  66  can be transferred to the inner surface of the outer tube  18 . 
     In both the second and third embodiments, the cable  55  engages the wheels  58  and  59  so that they are rotated as the cable  55  is moved by the drive pulleys  56 . Upon operation of the electric motor that rotates the drive pulley  56 , the wheels  58  and  59  rotate in the same direction and either move the inner tube  19  inwardly or outwardly with respect to the outer tube  18 . 
     As will be seen from the above descriptions, the three embodiments provide a simple and effective means of automatically moving telescopic tubes with respect to one another. The invention will have particular application in relation to rear view mirrors, however the invention will be equally suited to other applications involving the movement of telescopic tubes.