Telescopic arrangement and steering column arrangement

Abstract

Telescopic arrangement comprising a first part (1) and a second part (2) and a support bearing assembly (10, 100) acting between the two parts (1, 2), wherein the two parts (1, 2) are able to move relatively along a common path during a telescopic adjustment, wherein the support bearing assembly (10, 100) is arranged between the two parts (1, 2) and localizes the two parts (1, 2) relative to each other in order to eliminate free play between the two parts (1, 2) which would otherwise occur in at least one direction orthogonal to the telescopic movement, wherein the support bearing assembly (10, 100) is fixed in place between the two parts (1, 2) by a release device which, in use, is arranged to cause the support bearing assembly (10, 100) to clamp both the first part (1) and the second part (2) when they are not move telescopically,to automatically release this clamping during a telescopic relative movement of the two parts (1, 2) exceeding a predetermined distance and subsequently to automatically resume this clamping when the telescopic relative movement has ceased, characterized in that the release device has at least one gripper (17, 18, 117, 118) that contacts the second part (2) and at least one feedback component (16, 116) that acts between the bearing ring (12, 13, 112, 113) and the gripper (17, 18, 117, 118), wherein the gripper (17, 18, 117, 118) securely clamps the second part (2) in use when the arrangement is not moving telescopically, and automatically releases its clamping on the second part (2) when it moves, and the gripper (17, 18, 117, 118) or Each gripper (17, 18, 117, 118) has a roller, wherein the at least three grippers (17, 18, 117, 118) are arranged at spaced locations around the circumference of the second part (2),where each is assigned to a corresponding feedback component (16, 116).

Description

[0001] The invention relates to a telescopic arrangement with the features of the preamble of claim 1 and a steering column assembly with the features of claim 33.

[0002] A generic telescope arrangement is known from US 2010 / 0 130 293 A1.

[0003] Furthermore, an arrangement with a release device and at least one gripper is known from FR 2 727 481 A1, wherein the gripper has a roller.

[0004] There are many applications where it is desirable for a device to be telescopic, allowing its length to be adjusted. A common application of a telescopic arrangement is the steering column of a vehicle, and another related application is the shroud that surrounds the steering column. By allowing a portion of the column or shroud to slide telescopically over itself, the steering column assembly can be adjusted longitudinally. In an accident where a driver strikes the steering wheel, this can further allow the steering wheel to shift, and by controlling the speed at which the telescopic movement occurs, it is possible to absorb the energy generated in the accident in a controlled manner.

[0005] According to a first aspect, the invention provides a telescopic arrangement comprising a first part and a second part and a support bearing assembly acting between the two parts, wherein the two parts are able to move relatively along a common linear path during a telescopic adjustment, wherein the support bearing assembly is arranged between the two parts and localizes the two parts relative to each other in order to eliminate free play between the two parts, which would otherwise occur in at least one direction orthogonal to the telescopic movement, characterized in that the support bearing assembly is fixed in place between the two parts by a release device which, in use, is arranged to cause the support bearing assembly to clamp both the first and the second part when they are not moving telescopically.to automatically release this clamping during a telescopic relative movement of the two parts that exceeds a predetermined distance, and then to automatically resume this clamping when the telescopic relative movement has ceased.

[0006] The first part can be an inner tubular part or an outer tubular part, and the second part can be the other of an inner part and an outer part, wherein one end of the inner part fits into one end of the outer part and the support bearing assembly is arranged in the gap formed between the inner and outer parts.

[0007] The inner and outer parts can include tubes arranged around a common axis along which the telescopic movement takes place, and the support bearing assembly can allow relative rotation between the two parts in addition to the axial telescopic movement.

[0008] The support bearing assembly can have an inner and an outer annular bearing raceway and a variety of bearing points arranged between the bearing raceways. The bearing points can include balls or rollers, or a mixture of both. The inner tubular part can be fixed inside the inner bearing ring, and the outer tubular part can be fixed around the outer bearing ring.

[0009] One of the bearing rings can be fixed in place on the first part, and the release mechanism can be arranged to detachably clamp the other bearing assembly to the second part. For example, if the first part is an outer tube, the outer bearing can be fixed to the outer tube, whereas the inner bearing can be detachably moved relative to the second (inner) part. In this case, part of the release mechanism is located between the inner bearing ring and the inner tube. If the first part is an inner tube, the inner bearing ring can be fixed in place, and the outer bearing ring can be detachably clamped by the release mechanism. In this case, part of the release mechanism can be located between the outer bearing ring and the outer tube.

[0010] The bearing ring, which is attached to the first part, can contact the first part via a spring-loaded spacer. This ensures that a force is applied between the bearing ring and the first part that eliminates any free play.

[0011] The bearing ring or, if present, the spring-loaded spacer can be attached to the first part in such a way that they cannot move during normal use.

[0012] The release device can have at least one gripper that touches the second part, and at least one feedback component that acts between the bearing ring and the gripper, wherein the gripper securely clamps the second part in use when the arrangement is not moving telescopically, and automatically releases its clamping on the second part when it moves.

[0013] The gripper, or any gripper, can include a roller, which may be a metal rod. When subjected to only a small force from the wedge, the roller can rotate freely along the second part. However, when subjected to a high force, which occurs when the telescopic movement has ceased, it can no longer slide and thus clamps the second part. To reinforce this clamping, both the roller and the second part can have surfaces with high friction.

[0014] Where the first and second parts are tubes, at least two and preferably at least three grippers can be arranged at spaced-apart locations around the circumference of the second part, each being assigned to a corresponding feedback component.

[0015] The grippers can be arranged in opposite pairs, spaced apart along the second part in the direction in which the arrangement can telescope, with each pair being assigned to a common feedback component.

[0016] The release device can have two or more feedback components, each feedback component being associated with two grippers. Each feedback component can have a first side that contacts one gripper and a second side that contacts the second gripper, the two sides extending away from each other on opposite sides of the bearing ring and optionally connected by a central area, with each gripper in use being wedged between its associated side and the second part. The sides can be chamfered so that the gripper is wedged onto the second part below the chamfered side.

[0017] The feedback component can be an integral part of the bearing ring or can be designed separately from the bearing ring. Where it comprises two parts that are not connected, each part can form one half of the bearing ring, with the two half-bearing rings together providing the raceway for the bearing positions when the assembly is at rest.

[0018] The release device may also include a pre-tensioning device assigned to each gripper, which, when in use and without telescopic movement of the arrangement, pre-tensions the gripper into a position in which it is forced into engagement with the return component and the second part, the pre-tensioning force being absorbed partly by the return component and partly by the second part. The pre-tensioning device can wedge the gripper between the return component and the second part.

[0019] Where each reaction component is assigned to two grippers, two pretensioning devices can exist, each applying a force opposite to the other in one direction towards a corresponding reaction component, thereby pressing them together on the reaction component.

[0020] The release device can be arranged such that when the arrangement moves telescopically, the two pre-tensioning devices exert a less force on the gripper than when it is not moving.

[0021] The release device may further include a sliding element which is located with a sliding fit on the second part and fits between the bearing assembly and the second part, wherein the sliding element has opposite ends, one end on each side of the bearing rings, each end defining an associated stop, each of the preload devices acting between a stop and an associated gripper.

[0022] In an arrangement where the first and second parts are tubes, the sliding element can be a hollow, tubular sleeve that slides onto the inner tube.

[0023] The sliding element can have at least one opening in which an associated feedback component and an associated pair of grippers are received in such a way that the grippers can touch the second part.

[0024] The stops can include resilient extensions that protrude from the sleeve. A retaining ring can be provided, arranged between the extensions around the sleeve, forming a reaction surface against which the preloading devices act. The preloading devices can thus attempt to push the stop away from the gripper. Because there is a stop on each side of the bearing ring, along with a corresponding preloading device on each side, the effect of the preloading devices is to attempt to push the two stops away from each other. However, since they are fixed relative to each other because they are the ends of a common sleeve, the preloading devices reach an equilibrium position in which the grippers on the feedback component are pressed towards each other and thus, in turn, towards the second component.

[0025] The preload devices can each include at least one spring. Each spring can be a coil spring or a wave spring. The spring can exert a force that generally coincides with the direction along which the arrangement can move telescopically.

[0026] Each spring can act on its associated gripper by means of a release sleeve, which forms part of the release mechanism. Where both the first and second parts are tubular, the release sleeve can be a ring. An edge of the ring that contacts the gripper can be chamfered so that, when force is applied, the gripper is wedged between the edge and the second part. The more it is wedged underneath, the more firmly it is pressed onto the second part.

[0027] The arrangement can be configured such that, during telescopic movement, the bearing assembly moves in the direction of telescoping to cause the bearing assembly to engage with the release sleeve before the gripper and the feedback component have moved, wherein a subsequent movement of the arrangement pushes the release sleeve away from the associated gripper and provides an alternative path for the preload force directly from the preloading device through the wedge to the bearing assembly away from the gripper, thereby releasing the clamping of the gripper on the first part, which allows the gripper to move.

[0028] The release sleeve may have a protruding lip which touches the feedback component, with the lip extending over the gripper.

[0029] By providing an alternative force path that bypasses the gripper, the force acting on the gripper is reduced, thus decreasing the gripper's clamping force on the second part. This allows the gripper to move relative to the second part. For example, where it is a roller, it allows the roller to roll or slide along the second part as the telescopic movement occurs.

[0030] The amount of telescopic movement required to release the gripper clamp is set by the relative distance between the release sleeves and the bearing ring when the assembly is at rest. This distance should be kept relatively small, approximately two to five millimeters or so. The clamp will only release when the alternative path for the forces is established.

[0031] Once the desired telescoping position is reached, the pre-tensioning devices work to restore an equilibrium position in which the feedback component and the sliding sleeve are centrally located and the full force is exerted on the gripper. The grippers will then securely clamp the second part again.

[0032] According to a second aspect, the invention provides a steering column assembly with a telescopic casing having upper and lower parts that surround and support a telescopic steering column with upper and lower parts, wherein one of the upper and lower parts of the casing forms the first or second part of a telescopic arrangement according to the first aspect of the invention, and one of the upper and lower parts of the steering column forms the other of the first and second part according to the first aspect of the invention.

[0033] The second aspect thus provides an arrangement in which a sliding support arrangement securely supports the column within the casing.

[0034] Only one embodiment of the present invention will now be described by way of example, with reference to and as illustrated in the accompanying figures, in which: Fig. 1(a) shows a view of part of an embodiment of a steering column assembly of the present invention before a collapse which causes a telescoping movement; Fig. 1(b) the same view from Fig. 1(a) shows, however, after a complete collapse of the assembly during an accident; Fig. 2 a schematic cross-sectional view of a part of the steering column assembly made of Fig. 1 is; Fig. 3 one of the Fig. 2. The corresponding view is which is a practical implementation of the schematic in Fig. The support bearing assembly shown in section 2 is shown; Fig. 4(a) to (e) show the assembly of the various parts of the support bearing assembly prior to installation in the steering column assembly; Fig. 5 the support bearing assembly between the column and the casing of the assembly made of Fig. 1 arranged shows; Fig. 6 shows an alternative embodiment of a support bearing assembly in an expanded view; and Fig. 7 a cross-sectional view of the support bearing assembly Fig. 6 in assembled state.

[0035] Fig. Figures 1(a) and (b) show a view of a steering column assembly that includes a telescopic arrangement within the scope of protection of an aspect of the present invention. The steering column assembly comprises a casing 1, 2, which has a tubular upper casing part 1 and a tubular lower casing part 2, which are movable relative to each other, the end of the upper casing part 1 being located in a sliding fit in one end of the lower casing part 2. The casing 1, 2 surrounds a telescoping steering column shaft 3, 4. The shaft has an upper shaft section 3 that at least partially surrounds a lower shaft section 4, the two sections being connected by complementary, axially extending splined connections 5.

[0036] The upper shaft section 3 carries a steering wheel (not shown), and the lower section 4 is connected to a rack, which in turn is connected to the vehicle's wheels. In this arrangement, the upper shaft fits over the lower shaft, and the upper shaft section 3 moves, while the lower shaft section 4 does not move axially. Similarly, the upper, outer casing section 1 is positioned in the direction of the steering wheel and slides over the lower, inner casing section 2. The lower casing section 2 is axially attached to a gearbox (not shown). The tubular upper casing section 1 can be attached to a stationary part of the vehicle by means of a clamping device (not shown) that clamps onto a rail 6 on the upper casing section 1.

[0037] The space between the lower (outer) casing section 2 and the wall of the end of the upper shaft section 3 of the steering shaft houses a support bearing assembly 10. This assembly snugly fills the space and ensures that the shaft 3, 4 is securely fixed within the casing 1, 2 by providing support for the shaft 3, 4 near the junction between the two shaft sections. In operation, the support bearing assembly 10 eliminates the free play that would otherwise exist, thereby reducing the resonant frequency of the entire assembly compared to the same assembly without the support bearing assembly 10. This can result in a welcome improvement in the NVH values ​​(noise, vibration, and harshness) perceived by a user when the vehicle travels over a rough surface.The outer casing part 2, the support bearing assembly 10 and the shaft 3, 4 together form a telescopic arrangement within the scope of the first aspect of the invention.

[0038] The support bearing assembly 10 performs several functions. When the steering column assembly is locked in its preferred operating position after being longitudinally adjusted, the support bearing assembly 10 exerts a radial force on the outer wall of the shaft section 3, 4 and on the inner wall of the casing 1, 2, thereby clamping itself in place so that it cannot move axially along the shaft 3, 4 on its own. It must allow unimpeded rotation of the shaft 3, 4 within the casing 1, 2. However, it cannot be rigidly and permanently fixed to the walls of both the shaft 3, 4 and the casing 1, 2, as this would prevent the support bearing assembly 10 from being telescopically adjusted.

[0039] For this purpose, the support bearing assembly 10 is axially fixed only to the casing 1, 2 and detachably clamps the shaft 3, 4 so that it can move along the shaft 3, 4.

[0040] The support bearing assembly 10 is in the Fig. 3 and Fig. 4 is shown in more detail. It comprises a bearing arrangement 11 with inner and outer bearing rings 12, 13 extending around a common axis about which the shaft 3, 4 rotates, the inner circumferential surface of the inner bearing ring 12 facing the shaft and the outer circumferential surface of the outer bearing ring 13 facing the inner wall of the lower casing part 2. A set of bearing balls (not shown) runs in a conventional manner in raceways formed in the two bearing rings 12, 13. In this example, the outer bearing ring 13 is attached to the inner wall of the casing part 2 by means of a resilient sleeve 14 (preferably in Fig. 5), which hooks onto an end face of the inner casing part. The inner bearing ring 12 is detachably attached to the outer wall of the shaft 3 by means of a release device.

[0041] The release mechanism holds the inner bearing ring in place and applies a force to the shaft 3, 4 to eliminate free play, yet releases automatically when the steering column assembly is adjusted to remove the force, thus ensuring that there is no excessive force resisting adjustment of the steering column assembly. In this arrangement, for the purposes of the claims, the casing 2 is a first part and the shaft 3 is a second part. The reader will readily understand that this could be reversed, with the inner bearing ring 12 fixed to the shaft and the outer bearing ring 13 detachably attached to the inner casing part 2 by means of the release mechanism.

[0042] Fig. Figure 2 shows a schematically enlarged cross-sectional view of a part of the support bearing assembly 10 of the present invention, while the Fig. 3 and Fig. Figure 4 shows a preferred implementation of the support bearing assembly 10. As shown from Fig. As can be seen in Figure 2, the bearing rings 12, 13 of the support bearing assembly 10 are mounted on a sliding sleeve 14, which sits with a sliding fit on the outer wall of the end of the upper steering shaft section 3. This sleeve 14 forms a support for the various parts of the support bearing assembly 10. A thin layer of grease may be present between the sliding sleeve 14 and the shaft 3, 4.

[0043] The sleeve 14 has three openings 15, equidistantly spaced around the sleeve 14, and each opening contains a feedback component 16 and two grippers 17, 18. Each gripper 17, 18 has a roller that contacts the shaft 3, 4.

[0044] Each feedback component 16 has two opposing side sections 16a, 16b, which extend on opposite sides of the inner bearing ring 12 and contact an associated gripper 17, 18. The underside of each side section contacting the gripper 17, 18 is chamfered such that the distance between the underside and the shaft 3, 4 is greater at the tip of the side section 16a, 16b and smaller towards the middle region, thereby defining a ramp or wedge.

[0045] Each gripper 17, 18 is wedged in contact with the shaft 3 under the chamfered side section and held in place by the walls of the opening 15 in which it is arranged. Thus, a force path exists from the shaft 3, 4 through the rollers 17, 18 to the feedback component 16 and from the feedback component 16 through the bearing rings 12, 13 and bearing points to the casing 2.

[0046] The side sections of the feedback component 16 are connected to each other by a central section 16c, which is located below the inner bearing ring 12 and contacts the inner bearing ring 12. The section that contacts the inner bearing ring 12 is convex and establishes low-friction contact with the inner bearing ring 12, so that they can slide easily relative to each other.

[0047] Each roller 17, 18 is forced into a position below the chamfered end section of the feedback component 16 by a corresponding release sleeve 19. Each release sleeve 19 has a ring that loosely surrounds a corresponding opposite end of the sliding sleeve 14. An end face of the release sleeve 19 contacting the gripper is chamfered similarly to the feedback component 16, so that the gripper 17, 18 is keyed onto the shaft 3 under the chamfered end face of the release sleeve 19.

[0048] The sliding sleeve 14 is provided with two outwardly extending projections or stops 20 at each end, and between the projections and each release sleeve are a retaining ring 21 and a spring 22. In this example, the spring 22 comprises a corrugated washer that is pushed onto the sliding sleeve 14.

[0049] Each of the two release sleeves 19 is forced away from the stop 20 at the end of the sliding sleeve 14 and towards the gripper 17, 18 by the spring 22, which forms a preloading device. This force is transmitted to the grippers 17, 18, causing the release sleeve 19 to exert a preload force on the gripper 17, 18, which presses it under the feedback element 16. The further it is pressed under the feedback element 16, the more it clamps the shaft 3. The two springs work against each other, pushing the grippers 17, 18 towards each other and forcing the feedback element 16 into a central position under the bearing assembly 11.

[0050] When the steering is axially locked in position, the gripper rollers 17, 18 are subjected to equal forces from the two wave springs 22 and are therefore pressed equally under the chamfered ends of the feedback component 16 and the release sleeves 19. This results in the force from the preload device being transmitted via the rollers 17, 18 to the shaft 3.

[0051] When the steering column assembly is adjusted telescopically, the balance of forces is disturbed. Consider, for example, a movement that would cause the outer casing 2 to move to the left relative to the inner casing part 1 in the Fig. The outer bearing ring 13, and consequently the inner bearing ring 12, is moved to the left as shown in the diagram 2. The outer casing 2 pulls the outer bearing ring 13, and thus the inner bearing ring 12, with it. The rollers 17, 18 initially remain pressed against the shaft, so that they do not initially slide along the shaft 3, 4. After a predetermined degree of displacement, the inner bearing ring 12 abuts a protruding lip on one of the release sleeves 19, causing it to move away from the corresponding roller 17, 18. This causes the force from the preloading device to be transmitted directly to the bearing assembly 11 without passing through the rollers 17, 18, thus releasing the clamping of the rollers 17, 18 on the shaft 3, 4. Further movement causes the other roller 18 to also release its clamping. The bearing arrangement 11, the rollers 17, 18 and the sliding sleeve 14 are then free to move along the shaft 3, 4.

[0052] After the axial movement stops, the springs 22 continue to exert a force on the release sleeves 19 and the sliding sleeve 14, causing the rollers 17, 18 to be pressed back under the feedback component 16 and regain their clamping on the shaft 3, 4, while at the same time the key is moved back to its central position. The rollers 17, 18 then lock onto the shaft 3, 4 to eliminate any free play between the shaft 3, 4 and the inner casing.

[0053] The Fig. Figures 4(a) to (f) show a possible procedure for assembling the support bearing assembly 10. First, the bearing arrangement 11 is pressed onto the sliding sleeve 14, as shown in Fig. 4(a) is shown. In this position, it sits over the three openings in the sliding sleeve 14. In a next step, the three feedback components 16 are inserted into the openings 15 so that the central portion contacts the inner bearing ring 12. Then, the release sleeves 19 are slid onto the ends of the sliding sleeve 14, followed by the positioning of the rollers 17, 18 under the chamfered ends of each feedback component 16. Once this is completed, the corrugated springs 22 and finally the retaining rings 21 are pushed into position, with the retaining rings 21 engaging the resilient stops 20 at the ends of the sliding sleeve 14. In this position, both corrugated springs 22 are compressed.

[0054] The sub-assembly is then inserted into the resilient sleeve 30, which is pressed into the end of the inner casing part 2, and the steering shaft 3, 4 is inserted into the sliding sleeve 14 to complete the assembly, as shown in Fig. 5 shown.

[0055] A second embodiment of a support assembly 100 is described in the Fig. 6 and Fig. Figure 7 of the attached figures shows that many parts are similar in function to those of the first embodiment and are designated with the same reference numerals as the first embodiment, increased by 100; i.e., bearing 11 of the first embodiment corresponds to bearing 111 in the second embodiment.

[0056] The main difference between this embodiment and the first embodiment is that, instead of providing a standard deep-slot bearing with a separate, spring-loaded spacer, a composite bearing is used in which the inner bearing ring is divided into two parts so that the two halves can move away from each other during adjustment. This produces the same effect as using a spring-loaded spacer, namely that the pressure exerted on the bearing points 111 is relieved. To prevent the bearing balls from falling out, they are held in an annular cage that fits between the inner and outer bearing rings. By using a split inner bearing ring instead of a normal bearing ring and a spring-loaded spacer, a more compact arrangement can be achieved, which reduces the required distance between the inner and outer tubes.

[0057] Those skilled in the art will recognize that the invention has a much broader range of applications, even though the embodiments shown are a steering column assembly. The described embodiments should therefore be understood as providing guidance rather than limiting the scope of the invention, which should be determined by studying the appended claims in conjunction with the entire description.

Claims

[1] A telescopic assembly comprising a first part (1) and a second part (2) and a support bearing assembly (10, 100) acting between the two parts (1, 2), the two parts (1, 2) being capable of moving relatively along a common path during telescopic adjustment, the support bearing assembly (10, 100) being arranged between the two parts (1, 2) and locating the two parts (1, 2) relative to each other to eliminate free play between the two parts (1, 2) which would otherwise occur in at least one direction orthogonal to the telescopic movement, the support bearing assembly (10, 100) being secured in place between the two parts (1, 2) by release means arranged, in use, to cause the support bearing assembly (10, 100) to release both the first part (1) and the second part (2) to clamp if they do not move telescopically,to automatically release said clamping upon a telescopic relative movement of the two parts (1, 2) which exceeds a predetermined distance and to then automatically resume said clamping when the telescopic relative movement has ceased, characterized bythat the release device comprises at least one gripper (17, 18, 117, 118) contacting the second part (2) and at least one reaction member (16, 116) acting between the bearing ring (12, 13, 112, 113) and the gripper (17, 18, 117, 118), wherein the gripper (17, 18, 117, 118) in use securely clamps the second part (2) when the assembly is not moving telescopically and automatically releases its clamping onto the second part (2) when it is moving, and the gripper (17, 18, 117, 118) or each gripper (17, 18, 117, 118) comprises a roller, wherein the at least three grippers (17, 18, 117, 118) are spaced locations around the circumference of the second part (2), each associated with a corresponding reaction component (16, 116). [2] A telescopic assembly according to claim 1, wherein the first part (1) comprises an inner tubular part or an outer tubular part and the second part (2) comprises the other of an inner part and an outer part, one end of the inner part fitting into one end of the outer part and the support bearing assembly (10, 100) being arranged in the gap formed between the inner and outer parts. [3] A telescopic assembly according to claim 1, wherein the inner and outer parts comprise cylindrical tubes arranged around a common axis along which the telescopic movement takes place, and the support bearing assembly (10, 100) allows, in addition to the axial telescopic movement, a relative rotation between the two parts (1, 2). [4] Telescopic arrangement according to claim 1, wherein the support bearing assembly (10, 100) has an inner and an outer annular bearing raceway and a plurality of bearing locations arranged between the bearing raceways. [5] Telescopic arrangement according to claim 4, wherein the bearing points comprise balls or rollers or a mixture of balls and rollers. [6] Telescopic assembly according to claims 1 and 2, wherein the inner tubular member is mounted within an inner bearing ring (12, 112) and the outer tubular member is mounted around an outer bearing ring (13, 113). [7] Telescopic arrangement according to claim 4, wherein one of the bearing rings (12, 13, 112, 113) is fixedly mounted in place on the first part (1) and the release device is arranged to releasably clamp the other bearing ring (12, 13, 112, 113) to the second part (2). [8] Telescopic assembly according to claim 4, wherein the first part (1) is an outer tube and the outer bearing is fixed to the outer tube, whereas the inner bearing can be releasably displaced relative to the second (inner) part (2). [9] Telescopic assembly according to claim 8, wherein a part of the release device is located between the inner bearing ring (12, 112) and the inner tube. [10] Telescopic assembly according to claim 4, wherein the first part (1) is an inner tube, the inner bearing ring (12, 112) is fixedly mounted in place and the outer bearing ring (13, 113) is releasably clamped by the release device. [11] Telescopic assembly according to claim 10, wherein a part of the release device is located between the outer bearing ring (13, 113) and the outer tube. [12] Telescopic assembly according to claim 4, wherein the bearing ring (12, 13, 112, 113) is fixed to the first part (1) and contacts the first part (1) via a resilient spacer, thereby ensuring that a force is applied between the bearing ring (12, 13, 112, 113) and the first part (1) which eliminates any free play. [13] Telescopic arrangement according to claim 4 or 12, wherein the bearing ring (12, 13, 112, 113) or the resilient spacer is fixed to the first part (1) in such a way that it cannot move during normal use. [14] A telescopic assembly according to claim 1, wherein the roller is a metal rod. [15] A telescopic assembly according to claim 1, wherein the roller can rotate freely along the second part (2) when subjected to only a small force from a wedge, but when subjected to a high force, which occurs when the telescopic movement has ceased, it can no longer slide and thus clamps the second part (2). [16] Telescopic arrangement according to claim 1, in which the roller and the second part (2) each have high friction surfaces to enhance the clamping. [17] A telescopic assembly according to claim 1, wherein the grippers (17, 18, 117, 118) are arranged in opposite pairs spaced along the second part (2) along the direction in which the assembly can telescope, each pair being associated with a common reaction member (16, 116). [18] Telescopic arrangement according to claim 1, wherein the release device comprises two or more reaction components (16, 116), each reaction component (16, 116) being associated with two grippers (17, 18, 117, 118). [19] A telescopic assembly according to claim 18, wherein each reaction member (16, 116) has a first side contacting a gripper (17, 18, 117, 118) and a second side contacting the second gripper (17, 18, 117, 118), the two sides on opposite sides of the bearing ring (12, 13, 112, 113) extending away from each other and optionally being connected by a central region, each gripper (17, 18, 117, 118) being keyed in use between an associated side and the second part (2). [20] Telescopic arrangement according to claim 19, wherein the sides are bevelled so that the gripper (17, 18, 117, 118) is wedged onto the second part (2) below the bevelled side. [21] A telescopic assembly according to claim 1, wherein the release means also comprises biasing means, such as a spring (22), associated with each gripper (17, 18, 117, 118) and which, in use when there is no telescopic movement of the assembly, biases the gripper (17, 18, 117, 118) into a position in which it is forced into engagement with the reaction member (16, 116) and the second part (2), the biasing force being absorbed partly by the reaction member (16, 116) and partly by the second part (2). [22] Telescopic arrangement according to claim 21, wherein the pretensioning device wedges the gripper (17, 18, 117, 118) between the reaction component (16, 116) and the second part (2). [23] A telescopic assembly according to claim 21, wherein each reaction member (16, 116) is associated with two grippers (17, 18, 117, 118) and wherein there are two biasing means each applying a force opposite to the other in a direction towards a respective reaction member (16, 116), whereby they are compressed on the reaction member (16, 116). [24] A telescopic assembly according to claim 23, wherein a release means is arranged such that when the assembly is moving telescopically, the two biasing means exert a smaller force on the gripper (17, 18, 117, 118) than they do when it is not moving. [25] A telescopic assembly according to claim 21, wherein the release means further comprises a sliding member slidingly fitted on the second part (2) and passing between the support bearing assembly (10, 100) and the second part (2), the sliding member having opposite ends, one end on either side of the bearing rings (12, 13, 112, 113), each end defining an associated stop, each of the biasing means acting between a stop and an associated gripper (17, 18, 117, 118). [26] A telescopic assembly according to claim 25, wherein the first part (1) and the second part (2) are tubes and the sliding element comprises a hollow tubular sleeve (19) which is a sliding fit on the inner tube. [27] Telescopic arrangement according to claim 26, wherein the sliding element has at least one opening in which an associated reaction component (16, 116) and an associated pair of grippers (17, 18, 117, 118) are received such that the grippers (17, 18, 117, 118) can contact the second part (2). [28] Telescopic assembly according to claim 27, wherein the sliding sleeve comprises stops (20) with resilient lugs extending from the sleeve (19), a locking ring (21) being provided which is arranged between the lugs around the sleeve (19) and forms a reaction surface against which the biasing means acts. [29] Telescopic arrangement according to claims 24 to 28, in which each spring (22) acts on the associated gripper (17, 18, 117, 118) via a release sleeve (19) which forms part of the release device. [30] A telescopic assembly according to claim 29, wherein the first part (1) and the second part (2) are tubular and the release collar (19) comprises a ring, and wherein an edge of the ring contacting the gripper (17, 18, 117, 118) may be chamfered so that the gripper (17, 18, 117, 118) is wedged between the edge and the second part (2) when a force is applied. [31] A telescopic assembly according to claim 30, wherein the assembly is arranged such that upon telescopic movement, the support bearing assembly (10, 100) moves in the direction of telescoping to cause the support bearing assembly (10, 100) to engage the release sleeve (19) before the gripper (17, 18, 117, 118) and the reaction member (16, 116) have moved, wherein subsequent movement of the assembly urges the release sleeve (19) away from the associated gripper (17, 18, 117, 118) and provides an alternative path for the biasing force directly from the biasing means through the wedge to the support bearing assembly (10, 100) away from the gripper (17, 18, 117, 118), thereby clamping the gripper (17, 18, 117, 118) on the first part (1) is released, allowing the gripper (17, 18, 117, 118) to move. [32] A telescopic assembly according to claim 31, wherein the release sleeve (19) has a projecting lip contacting the reaction member (16, 116), the lip extending over the gripper (17, 18, 117, 118). [33] A steering column assembly comprising a telescoping shroud having upper and lower portions surrounding and supporting a telescoping steering column having upper and lower portions, one of the upper and lower portions of the shroud forming the first portion (1) or second portion (2) of a telescopic assembly as claimed in any one of claims 1 to 32, and one of the upper and lower portions of the steering column forming the other of the first portion (1) and second portion (2) as claimed in any one of claims 1 to 32.

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