Abstract:
An internal locking device ( 11 ) for a telescopic extendable pole ( 10 ) of the type comprising an inner and outer telescopic section ( 13,12 ) and a stop ( 22 ) on the outer section ( 13 ) which prevents detachment of the inner section ( 13 ) from the outer section ( 12 ). The locking device ( 11 ) has a mechanical locking means ( 18 ) which can be actuated to lock the two sections ( 12,13 ) together and a rotatable collar ( 24 ) is provided adjacent the locking means ( 28 ) to prevent contact between the stop ( 22 ) and the locking means ( 28 ).

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to an improved internal locking device for telescoping extendable poles. The present invention also relates to a telescopic pole including an improved internal locking device. 
       BACKGROUND ART 
       [0002]    Tubular telescopic poles comprising a plurality of telescoping sections which are slidably received one inside the other for permitting the length of the pole to be adjusted are known. In poles of this type, locking devices for selectively restricting the relative sliding movement between the respective telescoping sections are known, the locking devices usually being mounted on the internal pole section and being arranged to selectively restrict relative sliding movement between the respective telescoping sections of the pole when one pole section is rotated relative to the other pole section. 
         [0003]    The locking devices are generally a fragile mechanical apparatus that forces a surface area such as a cam or a nut into contact with the inner surface of the wall of the outer telescopic section of the extendable pole. This action causes the surface area to engage the slideable sections in a held selected position in the same manner as a brake until the cam or nut is disengaged and no longer contacts the inner wall surface of the outer telescopic section. The mechanical locking apparatus can include a cam operating mechanism or a screw and nut operating mechanism. 
         [0004]    To prevent the disengagement between the inner and outer tubular sections, the outer section is provided with a stop which is generally formed by punching, crimping or knurling an indent into the outside tube or by a sleeve positioned between the outside and inner sections 
         [0005]    During operation, impact of the fragile mechanical locking apparatus against the stop can cause irreversible damage. Further as the mechanical apparatus is located within the telescoping sections of the pole, access is not available for repair of the damaged parts. Impact of the mechanical locking apparatus against the stop can also cause jamming which results in the restriction of any further movement of the sliding sections of the pole. 
         [0006]    Failure of the locking device can also result from sand or grit entering the mechanical apparatus causing seizure. The seizure cannot be corrected because the mechanism is internal and cannot be accessed to remove the sand or grit 
         [0007]    Failure of the locking device can result in damage to property, serious injury and possible fatality, if the failure occurs when the telescopic pole is required during hazardous conditions such as boat mooring in adverse weather. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention aims to provide an improved locking device for telescopic extendable poles which overcomes or alleviates the above disadvantages or at least provides an alternative to the known telescopic pole locking devices. The present invention also aims to provide a telescopic extendable pole provided with an improved locking device. Other objects and advantages of the invention will become apparent from the following description. 
         [0009]    The present invention thus provides in one preferred aspect, an internal locking device for a telescopic extendable pole of the type comprising an inner and outer telescopic section and first stop means on said outer section adapted to prevent detachment of said inner section, said locking device being located on said inner section and including locking means adapted to cooperate with said outer section to lock said sections against movement and characterized by second stop means movable longitudinally with said inner section and located between said locking means and said first stop means and adapted to prevent contact between said first stop means and said locking means. 
         [0010]    The second stop means acts as a shock absorber shielding the locking means from striking the first stop means thus preventing damage to the locking means which is usually a fragile mechanical locking apparatus. 
         [0011]    Preferably the second stop means comprises an annular collar. Preferably the collar substantially occupies the annular space between the inner and outer tubular telescopic sections. 
         [0012]    Preferably the collar is mounted for free rotation relative to the inner section about an axis extending longitudinally of the inner section. 
         [0013]    Preferably the collar is located adjacent to the locking means. The locking means may typically comprise an inner member fixed to the inner tubular section and the collar may be mounted on a body of the inner member. The body of the inner member may be provided with an annular channel to rotatably receive the collar. The annular channel may be bounded by opposite shoulders whereby the collar may be captured therebetween. 
         [0014]    The collar in addition to acting as a shock absorber will also prevent unintentional jamming of the sliding telescopic sections. The collar also prevents sand and or grit from entering the locking device thus preventing seizure and failure of the locking means. The only point for entry of sand or grit into the interior of the telescoping pole is through the opening where the interior telescopic sliding section extends or retracts from the exterior section. The impact resistant collar is located between the opening and the locking means and because the outside diameter of the impact resistant collar is substantially the same as the inside diameter of the external section, any sand or grit will be prevented from bypassing the impact resistant collar and entering the mechanical components of the locking means. 
         [0015]    The present invention in a further preferred aspect provides a telescopic extendable pole of the type comprising an inner and outer telescopic sections and first stop means on said outer section adapted to prevent detachment of said inner section and a locking device located on said inner section and having locking means adapted to cooperate with said outer section to lock said sections against movement and characterized by second stop means mounted for movement longitudinally with said inner section and located between said locking means and said first stop means and adapted to prevent contact between said first stop means and said locking means. 
         [0016]    Preferably the second stop means comprises an annular collar which substantially occupies the space between said inner and outer sections. Suitably the collar is mounted for rotation about an axis extending substantially longitudinally of the pole and coaxially of the collar. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    In order that the invention may be more readily understood and put into practical effect, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein: 
           [0018]      FIG. 1  illustrates a common telescopic pole provided with an improved locking device according to an embodiment of the present invention; 
           [0019]      FIG. 2  is an isometric enlarged cut-away view of the region A of  FIG. 1  showing the improved internal locking device; 
           [0020]      FIG. 3  is an enlarged longitudinal sectional view of the telescopic pole showing the improved locking device and further showing the stop on the outer tubular section and the impact resistant rotating collar on the inner tubular section; 
           [0021]      FIG. 4  illustrates in side view the end of the inner tubular section projecting from the outer or external section and carrying the locking device; and 
           [0022]      FIG. 5  is a cross sectional view along line B-B of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    Referring to the drawings, there is illustrated a telescopic pole  10  incorporating an improved locking device  11  according to the present invention, the telescopic pole  10  as is conventional having slidable elongated telescopic sections comprising a larger diameter external telescopic section  12  and a smaller diameter internal telescopic section  13  which is telescopically slidable relative to the outer or external section  12 . The external section  12  is provided with a handle  15  at one end and a sleeve  16  at its other end surrounding the opening  17  in the end of the section  12  through which the inner sliding section  13  passes. 
         [0024]    The inner end of the telescopic section  13  within the outer section  12  is provided with a known mechanical locking apparatus  18  which when rotated with the section  13  relative to the section  12  locks the section  13  is a desired extended position relative to the section  12 . The mechanical locking apparatus  18  as shown in  FIG. 3  includes a tapering male threaded member  19  fixed to the inner end of the inner section  13  which is threaded into a corresponding tapering thread of a split collar  20 . Rotation of the threaded member  19  by rotation of the section  13  in one direction will cause radial expansion of the collar  20  and frictional engagement of the collar  20  with the inner wall  21  of the section  12 . This therefore locks the section  13  to the section  12 . The mechanical locking apparatus  18  described above is only one form of known locking apparatus which may be used with the present invention. Other forms of locking apparatus as known in the art may also be used. 
         [0025]    To prevent detachment of the inner section  13  from the outer section  12 , a stop  22  is located on the external section  12  between the sleeve  16  and the handle  15  in a preferred location that allows maximum travel of the internal sliding section  13 , the stop  22  being in the path of movement of the locking apparatus  18 . The stop  22  is of annular form and typically formed by crimping of the section  12 . 
         [0026]    To prevent direct contact between the mechanical locking apparatus  18  (which is relatively fragile) and the stop  22 , the present invention provides an impact preventing device  23  which is located adjacent to the mechanical locking apparatus  18  and positioned between the stop  22  and the mechanical apparatus  18 . 
         [0027]    The impact preventing device  23  comprises in this embodiment an annular collar  24  which is located in an annular channel  25  formed in the body  26  of the male threaded member  19 . The collar  24  is captured between opposing shoulders  27  and  28  defined by the channel  25  in the body  26  and by the end of the inner section  13  respectively with the body  26  extending into the end of the inner section  13  and being fixed thereto by rivets or crimping. Thus the collar  24  is positioned in the channel  25  prior to the connection of the body  26  to the inner pole section  13 . Further the collar  24  has a width slightly less than the width of the channel  25  and an inner diameter slightly greater than the diameter of the channel  25  at its radially inner face such that the collar  24  is freely rotatable about an axis extending longitudinally of the sections  12  and  13  and coaxially of the collar. 
         [0028]    As shown in  FIG. 5 , the collar  24  has an external diameter which is substantially the same as the internal diameter of the section  12 . The collar  24  being rotatable relative to the member  13  will thus allow free rotation of the tubular section  13  relative to the tubular section  12  so as not to interfere with the locking action of the mechanical locking apparatus  18 . The collar  24  however substantially occupies the annular space between the inner section  13  and the outer section  12  which will prevent sand, grit of any other materials bypassing to the mechanical apparatus  18  through the opening  17 . 
         [0029]    Where the inner section  13  is moved outwardly of the outer section  12 , the impact resistant collar  24  between the stop  22  and the mechanical apparatus  18  acts as a buffer for the protection of the mechanical apparatus  18 . Thus the collar  24  will absorb the impact of the stop  22  to thereby protect the fragile mechanical apparatus  18  from damage caused by impact with the stop  22   
         [0030]    In addition, as the collar  24  is rotatable it will prevent jamming of the of the slideable telescopic sections  12  and  13  of the telescopic pole  10  and further prevent sand or grit entering the mechanical apparatus  18 . 
         [0031]    The telescopic pole  10  with the locking device  11  of the invention may be used in many different applications. A typical application however is as a pole for boat hooks. The telescopic sections  12  and  13  of the pole  10  are typically formed as aluminium extrusions however they may be formed of other materials 
         [0032]    Whilst the rotatable collar  24  is described to be mounted on the male body of the mechanical locking apparatus  18 , it may alternatively be mounted on a purpose constructed mounting body fixed to the inner pole section  12  or mounted directly on the pole section  12 . The collar  24  typically if formed of plastics but may be formed of metal. The collar  24  may also be split longitudinally relative to the pole  10  to allow it to be passed longitudinally over the locking apparatus  18  for location in the channel  25 . The channel  25  may also be fully formed within the body  26 . Furthermore, the outer surface of the collar  24  may be provided with one or more grooves extending parallel to the central axis of the collar so as to allow air to pass from one side of the collar  24  to the other side of the collar  24  when the sections  12  and  13  are moved relative to each other. 
         [0033]    The term “comprising” or derivatives thereof as used throughout the specification and claims are taken to specify the presence of the stated features, integers and components referred to but not preclude the presence or addition of one or more other feature/s, integer/s, component/s or group thereof. 
         [0034]    Whilst the above has been given by way of illustrative embodiment of the invention, all such variations and modifications thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as defined in the appended claims.