Abstract:
A telescopic assembly comprises a first portion and a second portion and a support bearing assembly that acts between the two portions; the two portions being able to move relatively along a common path during telescopic adjustment; the support bearing assembly being located between the two portions and locating the two portions relative to one another to remove free play between the two portions that would otherwise occur in at least one direction orthogonal to the telescopic movement; characterised in that the support bearing assembly is fixed in position between the two portions by a release mechanism that is arranged, in use, to cause the support bearing assembly to grip both the first and second portions when they are not moving telescopically, to automatically release that grip upon relative telescopic movement of the two portions that exceeds a predetermined distance, and to automatically re-engage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage of International Application No. PCT/GB2014/052265, filed Jul. 24, 2014, the disclosures of which are incorporated herein by reference in entirety, and which claimed priority to Great Britain Patent Application No. 1313221.2, filed Jul. 24, 2013, the disclosures of which are incorporated herein by reference in entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to an improved telescopic assembly, and in particular but not exclusively to a telescopic steering column shroud. 
         [0003]    There are many applications in which it is desirable for an apparatus to be telescopic so that the length of the apparatus can be adjusted. One common application of a telescopic arrangement is the steering shaft for a vehicle, and another related application is the shroud that surrounds the steering shaft. By allowing part of the shaft or shroud to move telescopically over another, the steering assembly can be adjusted for reach. In a crash, where a driver impacts the steering wheel, this can also allow the wheel to move and by controlling the rate at which the telescopic movement occurs, it is possible to absorb the energy in the crash in a controlled manner. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    According to a first aspect, the invention provides a telescopic assembly comprising a first portion and a second portion and a support bearing assembly that acts between the two portions, the two portions being able to move relatively along a common linear path during telescopic adjustment, the support bearing assembly being located between the two portions and locating the two portions relative to one another to remove free play between the two portions that would otherwise occur in at least one direction orthogonal to the telescopic movement, characterised in the support bearing assembly is fixed in position between the two portions by a release mechanism that is arranged, in use, to cause the support bearing assembly to grip both the first and second portions when they are not moving telescopically, to automatically release that grip upon relative telescopic movement of the two portions that exceeds a predetermined distance, and to automatically re-engage that grip when the relative telescopic movement has subsequently stopped. 
         [0005]    The first portion may comprise an inner tubular portion or an outer tubular portion, and the second portion may comprise the other of an inner portion and an outer portion, with an end of the inner portion fitting within an end of the outer portion, the support bearing assembly being located in the gap formed between the inner and outer portions. 
         [0006]    The inner and outer portions may comprise tubes which are arranged around a common axis along which the telescopic movement occurs, and the support bearing assembly may permit relative rotation between the two portions as well as permitting axial telescopic movement. 
         [0007]    The support bearing assembly may include an inner and outer annular bearing race, and a plurality of bearings located between the races. The bearings may comprise ball bearings or roller bearings, or a mixture of ball and roller bearings. The inner tubular portion may be fitted inside the inner annular race and the outer tubular portion may be fitted around the outer bearing race. 
         [0008]    One of the bearing races may be fixed in position on the first portion, and the release mechanism may be arranged to releasably grip the other bearing assembly to the second portion. For instance, where the first portion is an outer tube, the outer bearing may be secured to the outer tube whilst the inner bearing can releasably moved relative to the second (inner) portion. In that case a part of the release mechanism is located between the inner race and the inner tube. Where first portion is an inner tube the inner bearing race may be fixed in position and the outer race releasably gripped by the release mechanism. In that case the part of the release mechanism may be located between the outer race and the outer tube. 
         [0009]    The bearing race that is fixed to the first portion may engage the first portion through a resilient spacer. This ensures that a force is applied between the bearing race and the first portion, removing any free play. 
         [0010]    The bearing race, or resilient spacer if provided, may be secured to the first portion so that they cannot move during normal use. 
         [0011]    The release mechanism may include at least one gripper that contacts the second portion and at least one reaction member that acts between the bearing race and the gripper, the gripper in use securely gripping the second portion when the assembly is not moving telescopically, and automatically releasing its grip on the second portion when it is moving. 
         [0012]    The gripper or each gripper may comprise a roller, which may be a metal rod. The roller, when only subject to a low force from the wedge, can rotate freely along the second portion but when subject to a high force, as occurs when the telescopic movement has stopped, can no longer slide and so grips the second portion. To enhance this grip the roller and second portion may each have a high friction surfaces. 
         [0013]    Where the first and second portions are tubes, there may be at least two, and preferably at least three grippers located at spaced locations around the circumference of the second portion, each one associated with a respective reaction member. 
         [0014]    The grippers may be arranged in opposed pairs, spaced apart along the second portion along the direction in which the assembly can telescope, each pair being associated with a common reaction member. 
         [0015]    The release mechanism may include two or more reaction members, each reaction member being associated with two grippers. Each reaction member may comprise a first side that engages one gripper and a second side that engages the second gripper, the two sides extending away from each other on opposing sides of the bearing race and optionally being connected by a central region, each gripper in use being wedged between a respective side and the second portion. The sides may be tapered so that the gripper is wedged underneath the tapered side onto the second portion. 
         [0016]    The reaction member may comprise an integral part of the bearing race, or may be separate from the bearing race. Where it comprises two parts that are not connected, each part may form a half of the bearing race, the two half bearing races together providing the race for the bearings when the assembly is stationary. 
         [0017]    The release mechanism may also include a biasing means that is associated with each gripper, and which in use with no telescopic movement of the assembly, biases the gripper into a position where it is forced into engagement with the reaction member and the second portion, the biasing force being reacted in part by the reaction member and in part by the second portion. The biasing means may wedge the gripper between the reaction member and the second portion. 
         [0018]    Where each reaction member is associated with two grippers, there may be two biasing means, each applying a forced opposed to the other one in a direction towards a respective reaction member, pushing them together onto the reaction member. 
         [0019]    The release mechanism may be arranged so that when the assembly is moving telescopically, the two biasing means will apply a smaller force to the gripper than it does when it is not moving. 
         [0020]    The release mechanism may further comprise a slide element which is a sliding fit onto the second portion and passes between the bearing assembly and second portion, the slide element having opposed ends, one end on each side of the bearing races, each end defining a respective stopper, each of the biasing means acting between a stopper and a respective gripper. 
         [0021]    In an arrangement where the first and second portions are tubes, the slide element may comprise a hollow tubular collar that is a sliding fit onto the inner tube. 
         [0022]    The slide element may include at least one opening in which a respective reaction member and associated pair of grippers are accommodated so that the grippers can contact the second portion. 
         [0023]    The stoppers may comprise resilient lugs that extend out from the collar. A lock ring may be provided which is located around the collar between the lugs and forms a reaction surface against which the biasing means acts. Thus the biasing means may try to push the stopper away from the gripper. Because there is a stopper on each side of the bearing race, along with a respective biasing means on each side, the effect of the biasing means is to try to push the two stoppers away from each other, but because they are fixed relative to each other by being ends of a common collar, the result is that the biasing means reach an balanced position in which the grippers are pushed together onto the reaction member and in turn onto the second portion. 
         [0024]    The biasing means may each comprise at least one spring. Each spring may comprise a coil spring or a wavy spring. The spring may apply a force that is generally in line with the direction along which the assembly can move telescopically. 
         [0025]    Each spring may act upon the respective gripper through a release collar which forms part of the release mechanism. Where the first and second portions are tubular, the release collar may comprise a ring. An edge of the ring which contacts the gripper may be tapered so that the gripper is wedged between the edge and the second portion as a force is applied. The more it is wedged underneath the tighter it will be pressed onto the second portion. 
         [0026]    The assembly may be arranged so that upon telescopic movement the bearing assembly moves in the direction of telescoping to cause the bearing assembly to engage the release collar before the gripper and reaction member have moved, subsequent movement of the assembly pushing the release collar away from the associated gripper and proving an alternative path for the biasing force directly from the biasing means through the wedge to the bearing assembly away from the gripper, and thereby releasing the grip of the gripper on the first portion allowing the gripper to move. 
         [0027]    The release collar may include a protruding lip which the reaction member engages, the lip extending over the gripper. 
         [0028]    By providing an alternative force path that bypasses the gripper, the force on the gripper is reduced and so the grip of the gripper on the second portion is reduced. This allows the gripper to move relative to the second portion. For instance, where it is a roller it allows the roller to slide or roll along the second portion when the telescopic movement occurs. 
         [0029]    The amount of telescopic movement needed to release the grip of the grippers is set by the relative spacing between the release collars and bearing race when the assembly is at rest. This should be kept relatively small, say 2-5 mm or so. Only when the alternative path for the forces is established is the grip released. 
         [0030]    On reaching the desired telescopic position, the biasing means will work to restore a balanced position in which the reaction member and the sliding collar are centrally located and the full force is applied to the gripper. The grippers will then again grip securely onto the second portion. 
         [0031]    According to a second aspect, the invention provides a steering column assembly comprising a telescopic shroud having upper and lower portions that surround and support a telescopic steering shaft having upper and lower portions, one of the upper and lower portions of the shroud forming the first or second portion of a telescopic assembly of the first aspect of the invention and one of the upper and lower portions of the steering shaft forming the other of the first and second portions of the first aspect of the invention. 
         [0032]    The second aspect therefore provides an arrangement in which a sliding support assembly securely supports the shaft within the shroud. 
         [0033]    Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1( a )  provides a view of a part of an embodiment of a steering column assembly of the present invention prior to a collapse causing a telescopic movement; 
           [0035]      FIG. 1( b )  provides the same view of  FIG. 1( a )  but after a full collapse of the assembly during a crash; 
           [0036]      FIG. 2  is a schematic cross sectional view of one part of the support bearing assembly of  FIG. 1 ; 
           [0037]      FIG. 3  is a view corresponding to  FIG. 2  showing a practical implementation of the support assembly shown schematically in  FIG. 2 ; 
           [0038]      FIGS. 4( a ) to ( e )  show the assembly of the various parts of the support bearing assembly prior to fitting to the steering assembly; 
           [0039]      FIG. 5  shows the support bearing assembly being located between the shaft and shroud of the assembly of  FIG. 1 ; 
           [0040]      FIG. 6  shows an alternative embodiment of a support bearing assembly in an exploded view; and 
           [0041]      FIG. 7  is a cross sectional view of the support bearing assembly of  FIG. 6  when assembled. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]      FIG. 2( a ) and ( b )  provides a view of a steering column assembly which includes a telescopic arrangement within the scope of one aspect on the present invention. The steering column assembly comprises a shroud  1 ,  2  which comprises a tubular upper shroud portion  1  and a tubular lower shroud portion  2 , which are moveable relative to each other with the end of the upper shroud portion  1  being a sliding fit within an end of the lower shroud portion  2 . The shroud  1 ,  2  surrounds a telescopic steering column shaft  3 ,  4 . The shaft comprises an upper shaft portion  3  that at least partially surrounds a lower shaft portion  4 , the two portions being connected through complimentary axially extending splines  5 . 
         [0043]    The upper shaft portion  3  supports a steering wheel (not shown) and the lower portion  4  is connected to a steering rack which in turn connects to the road wheels of the vehicle. In this arrangement the upper shaft fits over the lower shaft and the upper shaft portion  3  moves whilst the lower shaft portion  4  does not move axially. Similarly, the upper, outer, shroud portion  1  is located towards the steering wheel and slides over the lower, inner, shroud portion  2 . The lower shroud portion  2  is axially fixed to a gearbox (not shown). The tubular upper shroud portion  1  may be secured to a fixed part of the vehicle using a clamp mechanism (not shown) that clamps onto a rail  6  on the upper shroud portion  1 . 
         [0044]    The space between the lower (outer) shroud portion  2  and the wall of the end of the upper shaft portion  3  of the steering shaft accommodates a support bearing assembly  10 . This snugly fills the space and ensures that the shaft  3 ,  4  is located securely within the shroud  1 ,  2 , providing support for the shaft  3 ,  4  close to the joint between the two shaft portions. In use the support bearing assembly  10  removes the free play that would other exist and this reduces the resonant frequency of the whole assembly compared with the same assembly without the support bearing assembly  10 . This can provide a welcome improvement in the levels of NVH (noise, vibration and harshness) perceived by a user when the vehicle is travelling along a rough surface. The outer shroud portion  2 , support bearing assembly  10  and shaft  3 ,  4  together form a telescopic assembly within the scope of the first aspect of the invention. 
         [0045]    The support bearing assembly  10  provides several functions. When the steering assembly is locked in its preferred position of use, after it has been adjusted for reach, the support bearing assembly  10  applies a radial force to the outer wall of the shaft  3 ,  4  portion and onto the inner wall of the shroud  1 ,  2 , and in doing so “grips” itself in position so that it cannot move axially along the shaft  3 ,  4  of its own accord. It must allow unimpeded rotation of the shaft  3 ,  4  within the shroud  1 ,  2 . However, it cannot be securely and permanently fixed to the walls of both the shaft  3 ,  4  and shroud  1 ,  2  as this would prevent the support bearing assembly  10  from being telescopically adjusted. 
         [0046]    To this end, the support bearing assembly  10  is fixed axially only to the shroud  1 ,  2  and is releasably gripping the shaft  3 ,  4  so it can move along the shaft  3 ,  4 . 
         [0047]    The support bearing assembly  10  is shown in more detail in  FIGS. 3 and 4 . It comprises a bearing assembly  11  having inner and outer races  12 ,  13  which extend around a common axis about which the shaft  3 ,  4  rotates, the inner peripheral surface of the inner race  12  facing the shaft and the outer peripheral surface of the outer race  13  facing the inside wall of the lower shroud portion  2 . A set of ball bearings (not shown) run in tracks formed in the two bearing races  12 ,  13  in a conventional manner. The outer bearing race  13  is fixed to the inner wall of the shroud portion  2  in this example by a resilient sleeve  14  (best seen in  FIG. 5 ) that hooks onto an end face of the inner shroud portion  2 . The inner bearing race  12  is releasably fixed to the outer wall of the shaft  3  through a release mechanism. 
         [0048]    The release mechanism holds the inner race in position and applies a force to the shaft  3 ,  4  to remove free play, yet automatically releases when the steering assembly is adjusted to release the force, ensuring that there is no excessive force resisting adjustment of the steering assembly. In this arrangement, the shroud  2  is a first portion within the meaning of the claims and the shaft  3  is in a second portion 
         [0049]    The reader will readily appreciate that this could be reversed, with the inner bearing race  12  fixed to the shaft and the outer bearing race  13  releasably fixed to the inner shroud portion  2  through the fixing mechanism. 
         [0050]      FIG. 2  provides an enlarged cross sectional view of a portion of the support bearing assembly  10  of the present invention viewed as a schematic, while  FIGS. 3 and 4  show a preferred implementation of the support bearing assembly  10 . As can be seen in  FIG. 2 , the bearing race  12 ,  13  of the support bearing assembly  10  is fitted onto a sliding collar  14  which is a sliding fit onto the outer wall of the end of the upper steering shaft portion  3 . This collar  14  forms a carrier for the various parts of the support bearing assembly  10 . A thin layer of grease may be provided between the sliding collar  14  and the shaft  3 ,  4 . 
         [0051]    Three openings  15  are provided in the collar  14 , spaced equi-distant around the collar  14 , and within each opening is a reaction member  16  and two grippers  17 ,  18 . Each gripper  17 ,  18  comprises a roller which contacts the shaft  3 ,  4 . 
         [0052]    Each reaction member  16  comprises two opposed side portions  16   a,    16   b  that extend on opposing sides of the inner bearing race  12  and contact a respective gripper  17 ,  18 . The underside of each side portion, which contacts the gripper  17 ,  18 , is tapered so that the spacing between the underside and the shaft  3 ,  4  is greater at the tip of the side portion  16   a,    16   b  and is smaller towards the centre region, defining a ramp or wedge. Each gripper  17 ,  18  is wedged under the tapered side portion in contact with the shaft  3  and is held in place by the walls of the opening  15  into which it is located. A force path therefore exists from the shaft  3 ,  4 , through the rollers  17 ,  18  to the reaction member  16 , and from the reaction member  16  through the bearing races  12 ,  13  and bearings to the shroud  2 . 
         [0053]    The side portions of the reaction member  16  are connected by a central region  16   c  which sits underneath the inner bearing race  12  and contacts the inner bearing race  12 . The portion that contacts the inner bearing race  12  is crowned and provides a low friction contact with the inner bearing race  12  so that they can slide easily relative to one another. 
         [0054]    Each roller  17 ,  18  is forced into a position underneath the tapered end portion of the reaction member  16  by a respective release collar  19 . Each release collar  19  comprises a ring that loosely surrounds a respective opposing end of the sliding collar  14 . An end face of the release collar  19  that engages the gripper is tapered, similar to the reaction member  16 , so that the gripper  17 ,  18  is wedged under the tapered end face of the release collar  19  onto the shaft  3 . 
         [0055]    The sliding collar  14  is provided with outwardly extending lugs or stoppers  20  at each end and between the lugs and each release collar is a locking ring  21  and a spring  22 . The spring  22  in this example comprises a wavy washer that is slid onto the sliding collar  14 . 
         [0056]    Each of the two release collars  19  is biased away from the stopper  20  at the end of the sliding collar  14  and towards the gripper  17 ,  18  by the spring  22  that forms a biasing means. This force is passed onto the gripper  17 ,  18 , causing the release collar  19  to apply a biasing force to the gripper  17 ,  18  pushing it under the reaction member  16 . The further it is pushed under the reaction member  16 , the more it grips the shaft  3 . The two springs  22  work against each other pushing the grippers  17 ,  18  towards one another and pushing the reaction member  16  into a central position under the bearing assembly  11 . 
         [0057]    When the steering is fixed axially in position, the gripper rollers  17 ,  18  are subject to equal forces from the two wavy springs  22  and are therefore thrust by equal amounts underneath the tapered ends of the reaction member  16  and the release collars  19 . This causes the force from the basing means to be passed through the roller  17 ,  18  onto the shaft  3 . 
         [0058]    When the steering assembly is adjusted telescopically the equilibrium of the forces in disturbed. For instance, consider movement that would cause the outer shroud  2  to move to the left relative to the inner shroud portion  1  in the schematic shown in  FIG. 2 . The shroud  2  pulls the outer bearing race  13  and hence the inner bearing race  12  with it towards the left. The rollers  17 ,  18  initially remain pressed into the shaft and so the rollers  17 ,  18  do not slide along the shaft  3 ,  4  initially. After a predetermined amount of travel, the inner bearing race  12  strikes a protruding lip on one of the release collars  19 , causing it to move away from the respective roller  17 ,  18 . This causes the force from the biasing means to pass directly to the bearing assembly  11  without flowing through the roller  17 ,  18  and so removes the grip of the roller  17 ,  18  onto the shaft  3 ,  4 . Further movement causes the other roller  18  to also release its grip. The bearing assembly  11 , rollers  17 ,  18  and sliding collar  16  are then free to move along the shaft  3 ,  4 . 
         [0059]    Upon the axial movement stopping, the springs  22  will continue to apply a force to the release collars  19  and the sliding collar  14 , causing the rollers  17 , 18  to be pushed back again under the reaction member  16  and to regain their grip on the shaft  3 ,  4  whilst moving the wedge back to its central position. The rollers  17 ,  18  then grip into the shaft  3 ,  4  to remove free play between the shaft  3 ,  4  and the inner shroud portion  2 . 
         [0060]      FIGS. 4( a ) to ( f )  to show one possible method by which the support bearing assembly  10  can be assembled. First the bearing assembly  11  is pressed onto the slide collar  14 , as shown in  FIG. 4( a ) . In this position it sits over the three openings in the collar slide  14 . In a next step, the three reaction members  16  are inserted into the openings  15  so that the central region contacts the inner bearing race  12 . The release collars  19  are then slid onto the ends of the slide collar  14 , followed by locating the rollers  17 ,  18  under the tapered ends of each reaction member  16 . Once this is complete, the wavy springs  22  and finally the lock rings  21  are slid into place, the lock rings  21  engaging the resilient stoppers  20  on the ends of the sliding collar  14 . In this position the wavy springs  22  are both compressed. 
         [0061]    The partial assembly is then fitted into the resilient sleeve  30  that is pressed into the end of the inner shroud portion  2 , and the steering shaft  3 ,  4  is threaded into the sliding collar  14  to complete the assembly as shown in  FIG. 5 . 
         [0062]    A second embodiment of a support assembly  100  is shown in  FIGS. 6 and 7  of the accompanying drawings. Many parts are similar in function to those of the first embodiment and have been numbered with the same reference numerals as the first embodiment incremented by 100, i.e. bearing  11  in the first embodiment are the bearings labelled  111  in the second embodiment. 
         [0063]    The key difference between this embodiment and the first embodiment is that instead of incorporating a standard deep groove bearing with a discrete resilient spacer, a manufactured bearing is used in which the inner race is in effect split in half so that the two halves can move apart during adjustment, giving the same effect as the use of a resilient spacer in that the pressure applied to the bearings  111  is released. To prevent the bearings from escaping they are retained in an annular cage that fits between the inner race and the outer race. Using a split inner race instead of a standard race and a resilient spacer can achieve a more compact arrangement, reducing the spacing required between the inner and outer tubes. 
         [0064]    The skilled person will appreciate that although the embodiments shown are a steering column assembly, the invention has far wider application. The described embodiments should therefore be seen as a guide rather than limiting the scope of the invention, which should be determined from the accompanying claims when read in conjunction with the whole description. 
         [0065]    In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.