WO1993007404A1

WO1993007404A1 - Linear braking means

Info

Publication number: WO1993007404A1
Application number: PCT/AU1992/000529
Authority: WO
Inventors: John Russell Place
Original assignee: John Russell Place
Priority date: 1991-09-30
Filing date: 1992-09-30
Publication date: 1993-04-15
Also published as: EP0610253A4; EP0610253A1

Abstract

A brake is provided to resist linear movement of a rope, rod or similar elongate article. The brake consists of two abutments joined by a sleeve having two sets of helical threads wound in opposite directions so as to interweave. When the abutments are moved apart (e.g. by a lever pivoted on a supporting body) the sleeve both lengthens and contracts diametrically to grip an elongate article disposed therein. The article may only project into one end of the sleeve or may extend completely through the sleeve and abutments. The article is threaded through the brake or alternatively the brake may be openable along its length so that the elongate article may be placed therein. In a particular use, a pair of brakes (78) controls pivoting of knee hinge (72) of a leg brace. When a wearer's weight is placed on heel member (95), tape (94) is pulled and levers (87) are pivoted thus causing sleeves inside tubes (79) to elongate and contract about rigid pins (77).

Description

LINEAR BRAKING MEANS TECHNICAL FIELD

This invention relates generally to linear braking means for ropes, rods, wires and the like. Linear braking means of the type according to the present invention find particular application, by way of example, in orthopaedic braces. BACKGROUND ART

Many substantially linear articles require the controlled application of a braking force in their use. While a very large range of brakes suitable for use on circular devices such as wheels are in existence, the range of satisfactory linear brakes is comparatively limited. In particular brakes for use on ropes tend either to require the coiling of an intermediate portion of such rope about a drum, the drum then being acted on by a suitable rotary brake, or, the rope is led through a cam or wedging cleat which apply very high stress and local abrasion to the rope. Also, such cleats tend to be very abrupt in releasing their holding effect and must be backed-up to be released. Clearly advantages can be obtained if a feasible linear brake can be developed for use on ropes, rods, wires and other substantially linear articles. There are various handicaps which may affect the use of one's legs. To a degree some of these handicaps may be offset by use of an orthopaedic brace which is firmly attached to the respective upper and lower leg limbs and hinged proximate the knee. The hinge can be manually locked, such as in Australian Patent 480049 so as to provide the necessary rigidity in the legs for supporting the body weight, or unlocked to allow the leg to be bent, for example while seated. While it has long been acknowledged that an automatic one-way braked hinge, such as in US Patent 3826251, would be desirable, such attempts in the prior art have tended to function only to a limited degree. Also, rotary brakes have been incorporated in the hinge proximate the knee, but such brakes have generally- required very close tolerances and construction accuracy, and have been susceptible to adverse wear. Further, previous braked caliper devices have needed to be larger and heavier than ideal in order to provide good braking effect.

DISCLOSURE OF INVENTION According to one form of the invention there is provided a linear braking means comprising a first end abutment, a second end abutment spaced apart from the first end abutment, a diametrically contractable sleeve joining the first and second abutments, the abutments and the sleeve defining a path along which a linear article may pass into the sleeve, and extension means adapted to move the abutments relative to one another between a first position in which they are spaced apart a minimum distance and a second position in which they are spaced apart by greater than the minimum distance to lengthen the sleeve and thereby cause it to diametrically contract about the path along at least a part of the length of the sleeve.

The linear brake according to this invention may be used to brake a rope or wire hawser, a plurality of cords or threads or an elongate rod and has a wide range of possible useful applications. In one particular application the linear braking means is incorporated in an orthopaedic brace. In this embodiment the invention provides an orthopaedic brace having a first brace member adapted to be firmly secured to an upper part of a person's leg, a second brace member adapted to be firmly secured to a lower part of that leg, a hinge member connecting a lower end of the first brace member with an upper end of the second brace member and adapted to be positioned in axial alignment with the knee joint of that person's leg, the first and second brace member being interconnected by a linear brake, the linear brake comprising an elongate rod pivotally connected to one of the brace members and extending through the path of a linear braking means according to the first aspect of the invention, where the linear braking means is pivotally attached to the other brace member, the extension means of the linear braking means serving to move the abutments thereof into the second position and cause the sleeve to firmly grip the rod and thereby prevent relative rotation of the first and second brace members about the hinge when a user applies a downwardly directed load to the extension means.

Linear braking means according to the invention may be constructed which avoid many of the disadvantages of known linear braking means. It is possible, for instance, to greatly reduce rope abrasion of the type produced by clam cleats and the like. It is also, in preferred embodiments of the invention possible to construct the linear braking means so that the braking force can be gradually applied to or released from the braked linear article. When used in a brace the linear braking means has the advantage that there is infinite indexing capability between the relatively movable parts of the brace. It is also important that the linear braking means may be made as a one way brake enabling a wearer to rise up on the brace but not to collapse when weight is placed on it.

In some embodiments of the invention the sleeve is blind ended and the linear article (in this case usually a rod) projects into only one end of the sleeve. In other embodiments of the invention the linear article extends completely through the sleeve.

The diametrically contractable sleeve may be a rubber tube or a tube formed of a mesh, however, in preferred embodiments of the invention it comprises two helical arrays of threads, wires, ribbons or the like which are wound in opposite directions and are interwoven with one another. In each of these arrangements elongation of the sleeve causes it to diametrically contract and, conversely, a shortening of its length causes its diameter to expand. The wires or threads making up the helical arrays may be of any suitable material such as a plastics material or a metal. Suitable plastics materials include polypropylene and polyethylene terephthalate while suitable metals include stainless steel. If desired a wear resistant tube may be disposed radially inside the sleeve to prevent abrasive wear of the threads making up the sleeve. In one preferred embodiment of the invention the diametrically contractable sleeve is formed with a discontinuity along its length so that it may be opened when the abutments are in their first, or contracted, position to allow a rope or other linear article to be placed in the sleeve. The sleeve may be then closed around a part of the article and will contract about the article when the abutments are moved into their second, or extended positions.

One of the end abutments is preferably mounted on the linear braking means in such a way that as a force is applied to the linear article to urge it into, or withdraw it from, the sleeve so that one abutment is caused to be moved away from the other abutment in a manner which causes the sleeve to more tightly grip the linear article. This embodiment may also be utilised as a one-way brake resisting movement of the linear article in only one direction. A force applied to the linear article in a direction which will cause the abutments to move together will be permitted while movement of the linear article in the opposite direction will be resisted. If the linear article is flexible, such as a rope or wire, it may be led along a non-linear course from the linear braking means to the source of the load on the rope or wire. As the load increases it will endeavour to straighten the wire or rope and this straightening force may be used to move the one abutment away from the other. This may be achieved by passing the wire or rope around the end of a lever which carries the one abutment and is pivotally mounted on a body of the linear braking means. Straightening of the wire or rope will apply pressure to the lever causing it to move pivotally relative to the body and to move the one abutment away from the other abutment.

In another form of this embodiment a flexible linear article such as a rope may be connected at one end abutment and then looped back through the sleeve. The size of the loop may be enlarged or contracted by moving the rope through the sleeve. The loop of rope may be passed around another member such as a pulley to apply a force thereto. If a resulting force on that other member is increased the tension in the rope will increase and this tension will be transmitted to the one abutment to which the rope is attached. If the other abutment is fixed this increase in tension in the rope will cause the sleeve to be extended and to thus contract more tightly about the part of the rope which passes through the sleeve.

In another embodiment of the invention pressure of a rigid linear article into the sleeve may be used to urge the abutments apart and thereby increase the braking force applied to the linear article. In one form of this embodiment of the invention the one abutment is pivotally connected to one end of a lever which is pivotally connected at its other end to the body of the linear braking means or to some other support. The other abutment is movable relative to the body or other support and is pivotally connected to the lever intermediate its ends. Once the linear article has been initially gripped by the sleeve further inward force applied to the article will tend to move the other abutment in the direction of the force applied to the linear article. This force will be transmitted through the lever to the other abutment. Due to the different effective lever arm lengths for the respective abutments the one abutment will be moved a proportionately greater distance than the other abutment and the distance between them will be increased. This will in turn cause an elongation of the sleeve and a commensurate reduction in its diameter causing it to more tightly grip the linear article.

The linear braking means may include biasing means biasing the abutments into one or other of their respective positions. The biasing means may be a spring, a counter weight or any other suitable means. The biasing force may urge the abutment apart, in which case the biasing force must be overcome to release the linear article, or it may urge them together, in which case it must be overcome to apply a braking force. BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter given by way of example only is a preferred embodiment of the invention described with reference to the accompanying drawings in which:-

Figure 1 is a side elevational view of a linear braking means according to the present invention in which the abutments are in the first or contracted positions;

Figure 2 is a side elevational view of the linear braking means according to Figure 1 in which the abutments are in their second, or extended, positions;

Figure 3 is a plan view of the linear braking means of Figure 2;

Figure 4 is a sectional view along IV-IV of Figure 3 with the rope removed; Figure 5 is a side elevational view of another embodiment of a linear braking means according to the present invention in which the abutments are in their second, or extended, positions; Figure 6 is a plan view of the linear braking means of Fig. 5;

Figure 7 is a side elevational view of a third embodiment of a linear braking means according to the present invention with the abutments in their first, or contracted, positions;

Figure 8 is a side elevational view of the linear braking means of Fig. 7 with the abutments in their second, or extended, positions;

Figure 9 is an end elevational view of the linear braking means of Fig. 7 seen from its left hand end;

Figure 10 is an end elevational view of the linear braking means of Fig. 8 seen from its left hand end;

Figure 11 is a partly cut-away side elevational view of a leg brace incorporating a linear braking means according to the present invention with the abutments in their first, or contracted, positions;

Figure 12 is a partly cut-away side elevational view of a part of the leg brace of Fig. 12 on an enlarged scale with the abutments of the linear braking means in their second, or extended, positions;

Figure 13 is a partly cut-away rear elevational view of the part of the leg brace shown in Fig. 12.

The linear brake 10 seen in Figs. 1 to 4 is adapted to apply a braking force to a rope 11 and could be used as a cleat on a yacht although it may have many other useful applications. The linear brake 10 has a body 12, a pair of abutments in the form of tube 13 and ring 14, a helically woven sleeve 15 (see Fig 4) joined at its end to the respective abutments and a lever 16 pivotally connected to the body and adapted to move the abutments respectively between a first, contracted, position in which the sleeve 15 is relatively loose and of expanded diameter and a second, extended, position in which the sleeve 15 in stretched and consequently has a reduced diameter. The abutments 13 and 14 and the sleeve 15 define a path along which the rope 11 may pass through the sleeve 15. When the sleeve 15 is in the extended position its diameter is sufficiently reduced that it will tightly grip the rope 11 over a substantial part of the length of the sleeve 15.

The body 12 is U-shaped in section, having a base 17 and a pair of side walls 18, and is formed of stainless steel. At one end each side wall is formed with an upstanding tab 19, the tabs 19 being aligned transversely of the longitudinal axis of the body. A pin 21 extends through holes (not shown) in the tabs 19 at right angles to the longitudinal axis of the body 12. A pair of L-shaped plates 22 are connected to the free ends of the pin 21 outside the body and lying parallel to the side walls 18. The plates 22 extend downwardly from pin 21 to the level of base 17 of the body 12 and then each projects beyond the end of the body 12. The projecting ends of the plates 22 are connected by a pin 23 which lies parallel to pin 21. Each side wall 18 of the body 12 directly below the respective one of tabs 19 is formed with a horizontal slot 24. Each of the plates 22 is formed adjacent the apex of its two arms with a vertical slot 25 which overlaps with a corresponding one of the slots 24. The ring 14 forms one of the abutments and is swaged to one end of the sleeve 15. The ring 14 is formed with a tubular extension 20 surrounding one end of the sleeve 15 and slidably disposed within the tube 13. A spring 30 is disposed on the tubular extension 20 and serves to bias the two abutments apart. A pair of diametrically extending pins 26 project from each side of the ring 14, these pins 26 each extend through one of the slots 24 and into one of the slots 25.

The other end of the side walls 18 of the body 12 are chamfered off at an acute angle to the horizontal adjacent the base 17 and then rise vertically to form a step (not seen) at the point the ends meet the corresponding upper edges of the side walls 18. The lever 16 is pivotally connected by a pair of pivot pins 27 to the side walls 18 adjacent to the step. The lever is pivotally connected by a further pair of pivot pins 28 to the end of the tube 13 which forms the other of the abutments. The position of the pivot pins 27 and 28 is such that when the lever 16 is moved to lie parallel to the base 17 of the body 12 the pivot pins 28 are moved overcentre with respect to the pivot pins 27.

In use the rope 11 is threaded under the pin 23 and through the sleeve 15. The rope 11 may be pulled through the tube 15 whether the lever 16 is raised, which moves the abutments 13 and 14 into their contracted positions, or lowered to lie substantially parallel to the base 17 of the body 12 which moves the abutments into their second, or extended, positions. In the extended position spring 30 biases the abutments, tube 13 and ring 14, apart sufficiently for the sleeve 15 to frictionally engage with the rope 11. The rope 11, however, may only be pulled back through the sleeve 15 when the lever 16 is in the former position. Once the rope 11 has been drawn tightly into the sleeve 15 and the lever 16 lowered any force on the rope seeking to withdraw the rope 11 from the sleeve 15 will cause the rope to bear on pin 23 which will in turn cause the plates 22 to pivot about the pins 21. This in turn causes pins 26, and the ring 14 to which they are connected, to be forced in a direction away from the other abutment, tube 13. The tension in the sleeve 15, and hence its contraction about the rope 11, is thereby increased as the tension in the rope 11 is itself increased.

The linear braking means 10 shown in Figs. 5 and 6 is similar to the braking means 10 described with reference to Figs. 1 to 4 and only those features which differ from that embodiment will be described, similar parts of this embodiment bear the same numeric designation they had in the earlier described embodiment of the invention. The ring 14 is connected to the side walls 18 of the base 12 by a pair of linkage arms 29 and the rope 11 is passed under a pin 31 joining the upper ends of the side walls 18. The level of the pin 31 above the base 17 of the body 12 and the arrangement of the linkage arms 29 is such that when the lever 16 is in the lowered position to allow the abutments, tube 13 and ring 14, to move apart under the bias of the spring 30 thus pre-loading the sleeve 15 with sufficient tension to cause friction between rope 11 and sleeve 15. Any additional tension applied to the rope 11 in this position will cause the rope to bias the ring 14 downwardly and forwardly further tensioning the sleeve 15 and preventing the rope being drawn outwardly through the sleeve 15. The rope 11 may however be drawn inwardly through the sleeve 15 as pulling on the free end of the rope 11 will pull the ring 14 rearwardly against the spring 30 thereby contracting the length of the sleeve 15 and reducing its grip on the rope 11.

The linear braking means 50 shown in Figs. 7 to 10 differ from the earlier described embodiments as when the abutments are in their first, contracted, positions the sleeve is opened along its length to allow a rope 67 to be introduced into the sleeve 54. The linear braking means 50 includes a U-shaped body 51, a U-shaped plate 52 forming one abutment and two hemicylindrical shells 53 forming the other. Each of the hemicylindrical shells 53 is formed along one edge with a series of spaced apart portions rolled into aligned tubes. The portions of the two shells 53 interdigitate and the tubes receive an elongate rod 56 so that the two shells are hingedly connected together along one edge in the manner of a piano hinge. A woven mesh 54, made up of two diagonal arrays of threads which extend in opposite directions and are interwoven together, is connected at one end to the plate 52 and at the other end to the ends of the shells 53 distal to the plate 52. The side edges of the mesh 54, where the threads change direction, are slidably engaged with slots 55 along the free edges of each of the shells 53. The shells 53 are connected through rod 56 to a pair of transversely extending arcuate support members 57, one of which is disposed adjacent to the end of the rod 56 distal to the plate 52 and one of which is placed adjacent the mid point of the rod 56. Each of the support members 57 terminates at each end in a gudgeon 58 which project laterally on each side of the body 51. A pair of parallel arms 59 are pivotally mounted on the respective gudgeons 58 on each side of the body 51. The other end of each of the arms 59 is pivotally mounted on a pin 61 extending laterally from the upper edge of each of side walls 62 of the body 51. Each arm 59 has adjacent its connections with pin 61 a downwardly extending projection 63 which is pivotally connected to a linkage arm 64. Each linkage arm 64 thereby interconnects the pair of arms 59 on each side of the body 51 so that the arms 59 form a parallel motion linkage.

The plate 52 is adapted to slidably bear against one end of the side walls 62 of the body 51 which are upwardly extended adjacent that end. The side walls 62 are each formed with a downwardly extending cut-out 65 below the second of the support members 57. The arms 59 adjacent the end of the body distal to the plate 52 are formed with laterally outwardly extending tabs 66.

In use a rope 67 is laid in the brake 50 by moving it laterally in the direction of arrow A as seen in Fig. 7. If the tabs 66 are then pushed downwardly (as seen in the Figures), the shells 53 will be carried downwardly by the arms 59 and the support members 57. The shells 53 will, however, be forced inwardly by their engagement with the inside surfaces of the side walls 62 until the free edges of the shells 53 abut against one another forming the mesh into a tubular configuration. Simultaneously, the shells 53 are being moved away from the plate 52 which is caused to slide downwardly against the adjacent end of the side walls 62 of the body 51. This increased separation of the abutments elongates the mesh 54 which has the effect of decreasing its width and thus its diameter when it has assumed a tubular configuration. This reduction in diameter causes the rope 67 to be tightly gripped by the mesh 54. As is seen in Fig. 8, when the arms 59 are pivoted downwardly to their full extent, the gudgeon pins 58 assume an overcentre relationship with the pins 61 and the mesh 54 is stably held in its extended and diametrically reduced condition resisting movement of the rope 67. The rope 67 may be released by lifting the tabs 66 thereby returning the shells 53 and plate 52 to the condition shown in Fig. 7 and the mesh 54 to its contracted condition.

The leg brace 70 shown in Figs. 11, 12 and 13 includes a pair of upper brace members 71 connected respectively through a hinge 72 to one of a pair of lower brace members 73. At their upper ends the upper brace members 71 are joined by an arcuate transverse member 74 adapted to extend behind the wearer's thigh and to support a conventional thigh cuff 75. The lower brace member 73 are rivetted to a leg support 76 cast from a flexible plastics material and adapted to surround the wearer's calf, heel and foot. A conventional knee strap (not shown) is provided to extend from the lower brace member 73 around the user's patella.

Each of upper brace members 71 is connected to the corresponding lower brace member 73 by an elongate pin 77 and a linear braking member 78. Each pin 77 is pivotally connected to an arm 79a extending rearwardly from a corresponding one of the upper brace members 71 and its free end extends into a corresponding one of the linear braking members 78. Each braking member 78 comprises an elongate tube which is open at its upper end 81. A sleeve 97 (see Fig 12) is connected by a swaged ferrule (not shown) to the end 81 of the tube 79 and extends downwardly inside the tube 79 for substantially the full length of the tube 79. The sleeve 97 is formed of two interwoven sets of helical threads wound in opposite directions. The closed lower end of the sleeve 97 is crimped to a pin 82 which projects from the lower end of the tube 79. Each of the tubes 79 is biased upwardly by a respective tension spring 80 which extends between a radially extending tab on the tube 79 and a strut which extends transversely between the two lower brace members 73. The lower ends of lower brace members 73 are interconnected by a horizontally extending rod 83 (see Fig. 13). A bore 84 extends horizontally through each of the lower brace members 73 into the respective ends of the rod 83. The lower end of each of the tubes 79 is connected to a casting 85 which is tubular at its upper end and is connected to the lower end of the associated tube 79. A pair of spaced apart ears 86 extend downwardly from the rearward edge of the casting 85 parallel to the axis of the tube 79. A lever arm 87 extends between the ears 86 and is pivotally connected thereto mid-way along its length by a pin 90. At its inner end the lever arm 87 is pivotally connected to the pin 82 connected to the lower end of the sleeve and at its outer end it is pivotally connected to the rod 83 by a pin 88 which extends into one of the bores 84.

A U-shaped saddle 89 is connected at the ends of its arms to each of the pins 90 and hangs down below the ears 86. The two saddles 89 are interconnected by a transverse bar 91 and are each pivotally connected at their mid-points to one end of the bar 91. The mid-point of the bar 91 is pivotally connected to a downwardly extending tab 92. The tab 92 has a pair of downwardly extending flexible tapes 93 and 94 which are each connected to a heel member 95 connected to a heel portion of the leg support 76. The tape 93 extends from the tab 92 straight downwardly to the back of the heel member 95. The tape 94 extends downwardly to the rearmost part of the leg support 76 a little above the heel member 95 and passes through an aperture 96 therein and is connected from inside the man's leg support 76 to the front of the heel member 76. The tapes 93 and 94 are of such a length that when the linear braking member 78 is in its first, or contracted, position with the abutments, which comprise the tube 79 and pin 82, relatively close together and the sleeve diametrically expanded (see Fig. 12) the tapes 93 and 94 are drawn tight.

In use a wearer straps on the brace with his or her heel loosely in the heel portion of the leg support 76. Upon taking a step and placing weight on the heel member 95, the wearer's weight will bear down on the tape 94 which in turn will pull down the bar 91. The force applied to bar 91 is transmitted to each of the saddles 89 and these pull down the levers 87 which cause the sleeves of the two braking members 79 to be contracted about the pins 77. Once the initial engagement of the sleeves about the pins 77 has occurred, rotary motion of the upper brace members about their respective hinges will be transmitted through pins 77, the tube 79 and the ears 86 to lever arm 87. Any downward force from tubes 79 onto lever arms 87 serves to further increase the elongations of the sleeves and thus their contraction about the pins 77. There is thus a positive feedback mechanism operating to increase resistance to downward movement of the pins 77 relative to the respective tubes 79 in proportion to the downward force applied to the pins 77.

The leg support 76 is sufficiently flexible that a wearer can flex his or her ankle. If the wearer's ankle bends significantly, such as if he or she walks up stairs, the flexing of the ankle will cause tape 93 to draw down the bar 91 and consequently actuate the linear braking means 78 as has been described above.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS : -

1. A linear braking means comprising a first end abutment, a second end abutment spaced apart from the first end abutment, a diametrically contractable sleeve joining the first and second abutments, the abutments and the sleeve defining a path along which a linear article may pass into the sleeve, and extension means adapted to move the abutments relative to one another between a first position in which they are spaced apart a minimum distance and a second position in which they are spaced apart by greater than the minimum distance to lengthen the sleeve and thereby cause it to diametrically contract about the path along at least a part of the length of the sleeve.

2. A linear braking means as claimed in claim 1 in which the diametrically contractable sleeve comprises two helical arrays of threads, wires or the like which are wound in opposite directions and are interwoven with one another.

3. A linear braking means as claimed in Claim 1 the diametrically contractable sleeve is openable along its length when the abutments are in their first positions so that a linear article may be laid into the sleeve.

4. A linear braking means as claimed in Claim 3 in which the diametrically contractable sleeve comprises an array of diagonally oriented threads slidably joined to the free edges of a pair of hemicylindrical shells which are hingedly connected together along their other free edge, the hemicylindrical shells together forming one of the abutments, means being provided to force the free edges of the shells to which the threads are joined together as the abutments are moved into their second positions.

5. A linear braking means as claimed in claim 1 in which biasing means are provided in the linear braking means to bias the abutments into either their first or second positions.

6. A linear braking means as claimed in claim 5 in which the biasing means comprise a spring biasing the abutments into their first positions.

7. A linear braking means as claimed in claim 1 in which the abutments are mounted on the linear braking means in such a way that as a force is applied to a linear article in the linear braking means to urge it into, or withdraw it from, the sleeve so one abutment is caused to move away from the other abutment so as to cause the sleeve to more tightly grip the linear article.

8. A linear braking means as claimed in claim 7 in which the linear braking means is adapted to brake a rope, wire or other flexible linear article and in which the one abutment is mounted on a lever pivotally connected to a body of the linear braking member, the lever projecting into the direct path of the linear article from the braking means to the source of a load on the linear article such that as the load on the linear article increases straightening of the linear article will apply pressure to the lever causing it to move pivotally relative to the body and to move the one abutment away from the other abutment.

9. A linear braking means as claimed in claim 7 in which the linear braking means is adapted to brake a rod or other non-flexible linear article and in which the one abutment is pivotally connected to one end of a lever which is pivotally connected at its other end to the body of the linear braking means or to some other support, the other abutment being movable relative to the body or other support and pivotally connected to the lever intermediate its ends so that additional inward force applied to a linear article gripped by the sleeve will move the other abutment but will move the other abutment more thereby increasing the braking force on the linear article.

10. An orthopaedic brace having a first brace member adapted to be firmly secured to an upper part of a person's leg, a second brace member adapted to be firmly secured to a lower part of that leg, a hinge member connecting a lower end of the first brace member with an upper end of the second brace member and adapted to be positioned in axial alignment with the knee joint of that person's leg, the first and second brace member being interconnected by a linear brake, the linear brake comprising an elongate rod pivotally connected to one of the brace members and extending through the path of a linear braking means as claimed in any one of claims 1 to 9, which is pivotally attached to the other brace member, the extension means of the linear braking means serving to move the abutments thereof into the second position and cause the sleeve to firmly grip the rod and thereby prevent relative rotation of the first and second brace members about the hinge when a user applies a downwardly directed load to the extension means.