Patent Publication Number: US-2007119656-A1

Title: Method of manufacture of ladder stabiliser

Description:
This invention relates to a method of manufacture of ladder stabilisers particularly a ladder stabiliser as disclosed in International Patent Publication WO 02/059446 which is incorporated by reference in its entirety.  
      International Patent Publication WO 02/059446 relates to a ladder stabiliser which supports a ladder, scaffolding or a trestle (herein generically referred to as “ladder”) on an uneven surface.  
      The stabiliser incorporates an inner member or telescopic leg having a plurality of holes which is telescopically engaged with a housing and thus movable within the housing and secured thereto at a desired location or hole by a securing means which involves a securing pin assembly having a knob or head, a casing, a spring and a pin as described in FIG. 5 of WO 02/059446. The pin is attached to the housing and extends through an adjacent aperture in the housing and through a selected hole in the telescopic leg to maintain the ladder at a desired height above the ground in use. Usually a pair of stabilisers support an adjacent upright of the ladder.  
      In use each housing of the pair of stabilisers is attached to an adjacent upright using a threaded attachment rod which extends through a hollow interior of an adjacent rung of the ladder and are retained in position by locking units engaging with the threaded rod at each end. In this regard there are provided hollow spacers which are integral with respective housings through which the threaded rod(s) may extend as shown in FIG. 3 of WO 02/059446.  
      It has now been discovered following manufacture of the ladder stabiliser as discussed above that the telescopic leg which preferably is of square cross section is a solid rod and difficulty has been experienced in relation to forming the plurality of apertures which extend through the rod transversely to a longitudinal axis thereof and provide satisfactory operation of the stabiliser in practice.  
      Also in relation to the formation of the abovementioned hollow spacers difficulty also has been experienced in establishing a suitable technique in attachment of the spacers to the housing so that the spacers are integral with the housing.  
      It is therefore an object of the invention to provide a method of manufacture of the stabiliser which may alleviate the difficulties or problems discussed above.  
      The invention therefore provides a ladder stabiliser which has a tubular housing and a telescopic leg which is movable within a hollow bore of the housing, said telescopic leg having a plurality of holes for co-operating with securing means to maintain the housing at a suitable height when in use for supporting a ladder, characterised in that said telescopic leg is formed with an integral locating groove wherein each of the plurality of holes is located so that they are in the exact centre width wise of the telescopic leg or coincide with a longitudinal axis of the hollow leg.  
      The invention also provides a method of manufacture of the abovementioned telescopic leg which includes the steps of:  
      (i) forming an initial groove in the telescopic leg which is made from solid rod; and  
      (ii) drilling a plurality of holes in the initial groove so that each of the holes have a centre which coincides with a longitudinal axis of the hollow leg.  
      In another aspect of the invention there is provided a method of forming a lug or spacer on a tubular housing of a ladder stabiliser for supporting a ladder, said lug or spacer being welded to an adjacent surface of the tubular housing only at a top location and bottom location respectively as a fillet weld which avoids deformation of the tubular housing and facilitates satisfactory operation of the stabiliser in use. 
    
    
      Reference may now be made to a preferred embodiment of the invention shown in the attached drawings wherein:  
       FIG. 1  is a perspective view of the ladder stabiliser of WO 02/059446 reproduced herein for convenience.  
       FIG. 2  is a perspective view of a single stabiliser shown in  FIG. 1  omitting the ladder and other stabiliser for convenience.  
       FIG. 3  is a perspective view of the housing of the stabiliser shown in  FIG. 1  or  FIG. 2  showing the position of the fillet welds applied to each of the spacers;  
       FIG. 4  is an exploded view of the components of the pin assembly shown in  FIG. 1 ;  
       FIG. 5  is a detailed view of attachment of the foot shown in  FIG. 1  to the telescopic leg;  
       FIG. 6  is a plan view of the telescopic leg showing formation of an elongate groove which bounds the spaced apertures formed in the telescopic leg;  
       FIG. 7  is another view showing application of the fillet welds to the spacers of the tubular housing;  
       FIG. 8  is another plan view of the telescopic leg showing a different embodiment to that shown in  FIG. 6 ;  
       FIG. 9  is a side view of the telescopic leg shown in  FIG. 8 ;  
       FIG. 10  is a bottom end view of the telescopic leg shown in  FIG. 8 ; and  
       FIG. 11  is a top end view of the telescopic leg shown in  FIG. 8 ;  
      FIGS.  12  to  14  are detailed views of the welds formed between the spacer and the tubular housing;  
      FIGS.  15  to  16  show detailed views of the plug stop located in the locating groove; and  
      FIGS.  17  to  18  show detailed views of the foot. 
    
    
      In the drawings reference is made in  FIG. 1  to a ladder stabiliser described in WO 02/059446 which describes a pair of stabilisers  10  and  10   a  which are supporting ladder  50 . There is also shown supporting feet  15  and  15   a  of each stabiliser  10  and  10   a . Two threaded rods  17  are inserted through a pair of aligned apertures  20  and  25  located on each tubular housing  16  and  16   a  respectively as shown. Each of apertures  20  and each of apertures  25  extend through spacers  11  and  12  respectively. The threaded rods  17  also are inserted through apertures  9  on each ladder upright  51  and  51   a  and thus extend through hollow ladder rungs  53  and  54  respectively. Movable locking nuts  18  are threaded onto each rod  17  at each end to securely fasten each of tubular housings  16  and  16   a  to respective outer sides of ladder uprights  51  and  51   a.    
       FIG. 1  also shows telescopic extension of inner members or telescopic legs  14  and  14   a  within respective housings  16  and  16 A.  
      Each of legs  14  and  14   a  are retained within an adjacent housing  16  and  16 A by pin assemblies  13  which extend through a plurality of spaced apertures  21  and  21   a  located on each telescopic leg  14  and  14   a . To adjust each leg  14  and  14   a  as required pin assembly is pulled outwardly and removed from each aperture  21  and  21   a  to facilitate movement of each leg  14  and  14   a  within tubular housings  16  and  16   a  as required. A more detailed view of pin assembly  13  is shown in  FIG. 4 .  
      Insofar as the method of manufacture of each stabiliser  10  or  10   a  as shown in  FIG. 1  as well as  FIG. 2 , it was necessary to weld each of spacers  11  and  12  to an adjacent outer surface of each housing  16  and  16   a.    
      However it will be noted that each housing  16  and  16   a  is of square tubular shape and is preferably formed from aluminium. It has now been found in practice that fillet welding is the desirable welding process of choice and was selected over other conventional methods of welding such as spot welding, butt welding, TIG welding, MIG welding or fusion welding.  
      However in relation to the tubular housings  16  and  16   a  having regard to the preferred grade of aluminium which is 6060 or 6061 which was chosen for the purpose of non corrosion and ease of machining and bearing in mind the choice of 32 mm×3 mm box section tube it was found that extreme care was required in fillet welding each of spacers  11  and  12  to tubular housing  16  and  16   a . It was found regardless of cross sectional shape of the spacer  11  and  12  (e.g.  FIG. 1  shows a square section while FIGS.  2  to  3  show a round cross section) that a fillet weld had to be applied to the top and bottom of each spacer  11  and  12  as shown in  FIGS. 3 and 7 .  
      Applying a fillet weld completely around the periphery or circumference of each spacer  11  and  12  only resulted in deformation of the square aluminium tube. A more detailed view of the location of each fillet weld is shown in  FIG. 7  and thus application of excess welds to each of spacers  11  and  12  about the periphery thereof has to be avoided at all costs.  
      In  FIG. 2  is shown stabiliser  10  having tubular housing  16 , spacers  11  and  12  and pin assembly  13  as well as foot attachment mechanism  7 .  
      In  FIG. 3  there is shown tubular housing  16  having spacers  11  and  12  extending outwardly therefrom having a cylindrical shank  7 , round flange  8  and hollow tubular lug  6  for receiving an outer end of a threaded rod  17 . Fillet welds  31  and  32  are applied at the top and bottom of each spacer as shown.  
       FIG. 4  shows a detail of pin assembly  13  showing pin head  33 , recess  34 , pin housing  35  having hollow bore  36  and attachment apertures  37 . There is also provided pin  38  having spring  39 , spring retainer  40  and screw threaded end  41  for insertion into hollow bore  36  and engagement with recess  34  of pin head  33 . It is important that spring  39  be located on pin  38  before insertion of pin  38  into hollow bore  36 .  
       FIG. 5  also shows further details of the foot  15  and attachment mechanism  5  wherein a bolt  43  is inserted through mating bore  44  in each leg  14  and locked in position by nut  45 . The foot  15  includes a base  46  and a swivel insert  47  which is retained within mating recess  48 .  
       FIGS. 2, 5  and  6  show another important feature of the method of the invention involving the formation of a groove  49  in telescopic leg  14  which facilitates formation of apertures  21  in telescopic leg  14 . There is also shown a plug stop  22  in tubular leg  14  in  FIG. 6 .  
      In  FIG. 7  there is also shown the position of fillet welds  31  and  32  on tubular housing  16  having regard to welding of spacers  11  and  12  to right hand tubular housing  16  and left hand tubular housing  16   a  described in  FIG. 1 . It is essential that fillet welds  31  and  32  be located top on bottom of spacers  11  and  12  as shown in  FIG. 7  because if for example the fillet welds were at the side of spacers  11  and  12  this would reset in deformation of tubular housing  16  and impair satisfactory functioning of movement of telescopic leg  14  in tubular housing  16 .  
      In FIGS.  8  to  11  there is described an alternative embodiment to the embodiment of FIGS.  5  to  6  wherein groove  49 A stops short of top end  56  of telescopic leg  14  as shown. The groove is suitably 10-20% of the height or thickness of telescopic leg  14  and preferably is 16% of the height of leg  14 . This is shown in  FIG. 10 .  
      It is extremely important that all holes  21  are formed or drilled in the exact centre of groove  49  or  49 A as shown by line  55  in phantom in  FIG. 8 .  
      In FIGS.  12  to  13  a detailed view of fillet welds  31  and  32  are provided in relation to a spacer  11  or  12  having an internal bore  60  together with aperture  61  for mounting of lug  6 . The sectional view in  FIG. 12  shows the shape of welds  31  and  32  and  FIG. 13  shows the length of welds  31  and  32 .  FIG. 14  shows the shape of a typical fillet weld.  
       FIG. 16  shows a perspective view of telescopic leg  14  showing groove  49 , holes  21  and plug stop  22 .  FIG. 15  shows a longitudinally sectional view of the top end  56  of telescopic leg  14  showing that plug  22  extends above holes  21  to function as an effective stop and thus prevent withdrawal of telescopic leg  14  from tubular housing  16 .  
      FIGS.  17  to  18  relate to the foot  15  and in particular the attachment of insert  47  to base  46 . Insert  47  has a pair of bottom holes or passages  62  which during the moulding process are filled with settable material to retain insert  47  totally within base  46 .  
      Base  46  is also provided with a bottom corrugated surface  63  to retain a secure hold on a support surface (not shown). There is also provided aperture  64  for insertion of bolt  43 .  
      Important features of the stabiliser  10  of the invention include:  
      (i) The telescopic inner adjustable leg  14  has unique features in that the shape of the leg and positioning of the holes  21  is very important. The depth, size, number of holes and the space between each hole are crucial for the exact smooth working of the leg  14  when in use. A full extension stopper and theft prevention has been allowed for in the positioning of a plug  22  at an exact location at the top of the leg  14 .  
      (ii) The design of the large polyurethane non slip foot  15  has a unique feature of an aluminium insert  47  which has three important holes drilled at relevant locations, i.e. hole  64  to allow perfect swivel movement once installed to the telescopic leg  14  and a pair of holes  62  is to enhance the bond between the polyurethane and the aluminium insert which prevents the foot from being ripped away from the insert.  
      (iii) The spacers  11  and  12  are machined into a unique shape and design to allow for a number of key elements, i.e. (1) to locate the threaded rod  17  and house the lock nut  18  at installation; (2) to allow movement of the ladders rope action and pulley system; (3) to facilitate an amount of weld  31  and  32  so that smooth operation and a world standard of retro fit is achieved; and (4) to facilitate extension of lug  6  which may have a diameter of 15 mm into a rung of, for example, 10 mm to provide shear strength on fibreglass chemically bonded rungs, and alignment with the styles or uprights  51  and  51   a  of the ladder. Also the threaded rod  17  used to fix the stabiliser  10  onto the ladder has the ability to be cut to a varied length to match the width of the ladder rung and has enough surface area to cover the existing holes  9  in the styles of the ladder after fitting.