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This application was filed as PCT International application No. PCT/NZ97/00062 on May 22, 1997 and claims priority under 35 USC §119 based on New Zealand application No. 286637 filed on May 22, 1996. 
     This invention relates to devices which provide or allow for the adjustment and thereafter locking in the length of a member. 
     Lockable extending members are an integral part of many industries and used for the likes of propping, levelling, positioning or limiting of objects relative to a task. Known devices include sliding devices which are extendable and stepped by increments provided by teeth and dog or pin and hold type systems. A range of tensioning devices that lock two members together and rely on frictional resistance between them are also known. Flexible member materials are also known having papers on two separate members which conflict where a degree of pressure is applied to deform at least one of the members. Some wedging devices are also known where a wedge is inserted between two sliding members. 
     These prior art devices have drawbacks in that the pins are loose objects and prone to loss or damage. This can lead to sufficient were to make the device unsafe under load. Toothed racks also have similar problems and both forms are prone to shaking loose. 
     Tension based locking systems can be unreliable as they are prone to slippage and wear and also operator judgement as to the adequate tension for the environmental conditions. Special tools for tensioning the items may also be necessary and may be lost or damaged. 
     Those devices using flexible material tapers do provide some degree of random variation of the link yet are often set in increments who like narrowings in the diameter or a tubular member with a sprung external tube member chuck providing the constriction. These may be prone to material fatigue and weakening of the internal member. Further, operator judgement is required as to the adequacy of the locked position on the taper. 
     The use of a wedge on its own is also prone to loss and damage or shaking loose. 
     OBJECT OF THE INVENTION 
     It is an object of the present invention to provide apparatus allowing for the length of a member or assembly to be altered and selectively locked which at least in part overcomes one or more of the above mentioned disadvantages or which at least provides the public with a useful choice. 
     SUMMARY OF THE INVENTION 
     Accordingly in a first aspect the present invention may broadly be said to consist in an adjustment length member comprising: 
     a first member or assembly; 
     a second member or assembly having a sloped surface; 
     retaining means to retain said first and second members in sliding contact; 
     a constraint provided in or about said first and second members to limit the passage of the sloped surface on said second member through said constraint; and 
     an adjustment means to adjust at the constraint to vary the passage of the second member through said constraint in at least one direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention consists in the foregoing and also envisages constructions of which the following gives examples. 
     One preferred form of the present invention will now be described with reference to the accompanying drawings in which: 
     FIG. 1A depicts a constraining member  1  held in a sliding relationship with the tapered member  2  by tongue and grooves  5  along direction of slot  28  (now shown), the constrict is held by bolt  24 , washer  22  and nut  23 , that passes through member  1  via the fixed hole  25 , adjusting wedge  21  adjusts the constrict dimensions  27  between nut  23  and washer  22  and flared bolt nut  26 , either by turning the nut  23  or by sliding the wedge  21 , the dimensions of the constrict  27  are changed allowing more or less of the taper to fit in the constrained space and the change in length be arrested, the fixing of the bolt  26  through member  1  at hole  25  prevents the constrict assembly  26 ,  21 ,  22 ,  23  from sliding along member  1 , the high safety or fail safe nature of at least preferred forms of the present invention is enhanced by the constraining force applied by bolt  26  containing the expansion of the thrusting taper; 
     FIG. 1B depicts an alternative to the form of the invention which utilises nut  23  with or without adjusting taper  21 , nut  17  may be tensioned by winding lever  18   a  then swinging it over to position  16  to cam a constriction dimension  20 ; 
     FIG. 1C depicts a tongue and groove slide arrangement  5  with an I beam structure and member  1  with a taper member  2  fitting into the channel taper as depicted by  2   a;    
     FIGS. 2A &amp; 2B depicts a constriction device  3  and alternate position  15 , cam position  6 ,  7  vary constrict  12  of member  2  constrict is fixed at holes  4  and  4   a  alternative, pin  9  is a limiting mechanism; 
     FIG. 3 shows a preferred form of the present invention which provides an adjustable length member  100 , the adjustable length member  100  comprises a first member or assembly thereinafter “first member”)  1  and a second member or assembly (hereinafter “second member”)  2 , said second member  2  having a slope or sloping surface  101 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Present in preferred forms of the invention is a retaining means  3 . Said retaining means retaining said first and second members in contact preferably in sliding contact. 
     Also present in a preferred form of the present invention is a locking member or means  21 , said locking member or means  21 , capable of abutting said second member against said first member or vice versa thereby locking said first member and said second member in a position with respect to their length. 
     Preferred forms of the present invention may be used to provide for adjustable length or other dimension in a wide variety of other devices. For example, preferred forms of the present invention  100  may provide for adjustment in the length of a leg of a ladder thus enabling the ladder to be used safely on sloping or uneven ground. The operation of a preferred form of the present invention will now be described. The first member  1  and second member  2  can slide relative to each other thus enabling the overall length of said adjustable lockable device  100  to be adjusted. Once the correct length has achieved the locking member or means  21  is locked thus causing the adjustable length member  100  to be locked in place. Preferred forms of the present invention are produced from a metallic material such as aluminium, steel, preferably mild steel, or other suitable materials. Those skilled in the art to which the invention relates will realise that a variety of manufacturing techniques are possible, for example, machining or otherwise producing the devices  100 . 
     The constriction device means or locking member or means  3  may be one or more pin or bolt type devices, they may be arranged to lie through the first and second members by way of slots in the wedge to enable travel in the shear direction but will be fixed by holes in the second member. Alternatively they may be positioned to the sides of the first and second members and by way of end plates surround the two members, in this case either the pin, bolts or straps will be clear and free of the sides of first member but fixed to the second member. One side of the constricting device  3  and member must contain a means of applying pressure evenly to cause the constriction through the bolts. The wedge side may have a force distributing plate shaped in conjunction with the other components to evenly contact the slope surface of the wedge and the constricting apparatus. Another alternative is to utilise a sleeve or U with closing plate type constricting means shaped to perform the above mentioned roles along with the rest of the containment arrangement. The constriction means  3  will be fixed to the second member and contact the sloping surface of the wedge. 
     The constriction means  3  will have an adjustment means to adjust the members sliding extents by means of the size of the constriction. The preferred option is the use of an adjusting wedge arranged with the taper or slope opposed to that of the first member wedge and made operative through a U sleeve with the joining plate adapted to guide and support the adjusting wedge position. The contact surfaces of wedge slopes are, in preferred forms of the present invention, smooth. In preferred forms of the present invention the adjusting wedge has appendages or abutments that will prevent constriction release beyond that of the slope of the prime wedge and to prevent the dislodgement of the wedge through the narrower end. Alternatively a similar adjusting wedge may pass through slots or an end plate of the fore mentioned rod/bolts/strap, sleeve arrangements. Yet another alternative is to utilise nuts as the said constriction adjusters, those nuts may have swinging handles, those swinging handles may have a “flip past centre” cam actuator as a further pinch or tension release means to the plate below the nut. Yet another alternative is the use of the U sleeve with the deep end surrounding and fixed to the second member with a coaxial cam device pivoted through the sides of the U. The restrictive rotary direction of the cam must constrict with the thrust direction of the wedge. There may be a cam rotation limiting pin to limit the opening to the slope of the wedge to prevent total disengagement of the two members via a knob as shown in FIG.  3 . The removal of that pin  4  will enable relocation of the constricting mechanism  3  to another location on the second member as the added clearance will enable clearance of location dowels otherwise fixing the constriction device to the second member, the cam may have a lever and a spool to enable remote and/or manual control of the constriction. 
     Remote control linkages or cables may be fitted to the constriction adjusting means for ease of operation, spring loading to resist movements during shaking, vibrating or gravity may hold the wedges in contact with the constricting means  3 . Covers to prevent foreign objects, for example human appendages, entering the contraction space may also be fitted in preferred forms of the present invention. 
     Any combinations of alternative constricting or adjusting may be utilised. 
     It can be seen that the present invention provides an adjustable length member  100 . Such an adjustable length member may find a variety of uses in providing for the adjustment in length and then locking of a member, for example, legs of a ladder etc. The adjustment provided is preferably continuous between the maximum and minimum range in length of the member  100 . Preferred forms of the invention are robust in use in that they are relatively unaffected by contaminated by grease or other foreign bodies and/or parts of the device are bound together thus limiting the chance of smaller parts being lost due to operator error. 
     In use, it can be seen that at least the preferred form of the invention provides an apparatus in which the wedge or similar device can be used to change the dimension of the constriction to stop variation in the movement in at least a first direction between the two sliding members, one of which is tapered. In providing the apparatus in the manner shown, the wedge tends to lock into the constrict when the sliding members are under a compressive load. The compressive load tries to force the tapered member further into the constriction and can jam the wedge or similar adjuster in place. This reduces any risk of the items becoming free during use. To adjust the mechanism, the wedge must be withdrawn and this can realistically only be achieved in an unloaded condition. A cable and lever arrangement or any other arrangement connected to the wedge can facilitate removal of the wedge when desired. As previously mentioned, it may be desirable for a biasing means such as a spring or even rely on some gravity by arranging the wedge above the constriction to bias the wedge or other adjuster into the locked position. 
     Thus the present invention provides an adjustment length member which will at least provide the public with a useful choice. 
     Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if individually set forth. 
     Although this invention has been described by way of example and with reference to possible embodiments thereof it is to be understood that modifications or improvements may be made thereto without departing from the scope or spirit of the invention.

Summary:
This invention provides an adjustment length member ( 100 ) for fitment to a variety of apparatus including ladders. The preferred form provides two members ( 1,2 ) contained in sliding contact one of which ( 2 ) has a taper or sloped surface. The members pass through a constriction ( 3 ) and a member ( 21 ) adjacent, such as a wedge or camming device may be used to adjust the construction to limit the passage of the tapered member through the constriction.