Abstract:
A ladder cage comprises a plurality of spaced rings, having fasteners attached thereto. A plurality of vertical braces are each attached to respective ones of the fasteners, the vertical braces each having a mounting hole proximate each end, and extending between two of the plurality of rings. Each of the fasteners comprises a mounting pin having a slot therein, and a drop pin slidably mounted to that fastener for sliding in and out of its slot. An associated vertical brace is fastened to a ring by each fastener, as the fastener&#39;s mounting pin is received in the mounting hole of the associated vertical brace, and the drop pin of the fastener is received in the slot of said mounting pin, such that the drop-pin makes an angle of between about 30° and 60° to the vertical.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to building equipment, and more particularly to ladder cages for use with scaffolding and other structures. 
       BACKGROUND 
       [0002]    Tall structures such as communications towers, wind turbines, scaffolding, and the like are often equipped with a ladder that may be climbed to reach points of elevation on the structure, for service or the like. Often, such ladders provide the only easy access to these points of elevation. As well, the ladders typically extend completely vertically, to significant heights and present a risk to a climber. 
         [0003]    As such, these ladders are often surrounded by generally semi-circular rings, affixed at either side of the ladder typically along the extent of the ladder, Vertical bars extend between the rings. The rings and bars define a ladder cage, and provide security for the climber to inhibit a downward or outward fall away from the ladder. 
         [0004]    Typically, these rings are securely affixed to the ladder, and as such are not easy to install and cannot be easily moved or removed. For some structures, however, easy removal and installation are desirable. 
         [0005]    As such, there remains a need for a ladder cage assembly that may be easily installed and removed. 
       SUMMARY 
       [0006]    In accordance with an aspect of the present invention, there is provided a ladder cage comprising: a plurality of spaced rings, having fasteners attached thereto; a plurality of vertical braces, each having a mounting hole proximate each end, and extending between two of the plurality of rings, and attached at either end to respective ones of the fasteners; wherein each of the fasteners comprises a mounting pin having a slot therein, and a drop pin slidably mounted to that fastener for sliding in and out of its slot in its mounting pin; and wherein an associated vertical brace is fastened to a ring by that fastener, as its mounting pin is received in the mounting hole of the associated vertical brace, and the drop pin of the fastener is received in the slot of said mounting pin, wherein the drop-pin makes an angle of between about 30° and 60° to the vertical. 
         [0007]    In accordance with another aspect of the present invention, there is provided a ring for forming a ladder cage comprising: a ring shaped body having fasteners attached thereto; each of the fasteners comprising a mounting pin having a slot therein, and a drop pin slidably mounted to that fastener for sliding in and out of its slot in its mounting pin, wherein the drop pin is mounted so it may make an angle of between 30° and 60° to the vertical; and wherein an associated vertical brace may be fastened to the ring by that fastener, as its mounting pin is received in the mounting hole of the associated vertical brace, and the drop pin of the fastener is received in the slot of the mounting pin. 
         [0008]    In accordance with yet another aspect of the present invention, there is provided a method of assembling a ladder cage comprising: attaching two spaced rings having fasteners attached thereto to a ladder; each of the fasteners comprising a mounting pin having a slot therein, and a drop pin slidably mounted to that fastener for sliding in and out of its slot in its mounting pin, wherein the drop pin is mounted at an angle of between about 30° and 60° to a plane of its ring; attaching a vertical brace to the two spaced rings by inserting a mounting pin of corresponding ones of the fasteners on each of the two spaced rings into a hole of the vertical brace; and sliding a drop pin mounted to each of the corresponding one of the fasteners to rest at an angle of between 30° and 60° to the vertical into a slot in their mounting pins to fasten the vertical brace to the ring by the fastener on each of the two spaced rings. 
         [0009]    Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the figures which illustrate by way of example only, embodiments of the present invention, 
           [0011]      FIG. 1  is a perspective view of a ladder and ladder cage, exemplary of an embodiment of the present invention; 
           [0012]      FIG. 2  is a perspective view of a brace of the ladder cage of  FIG. 1 ; 
           [0013]      FIG. 3  is a perspective view of a ladder cage ring of the ladder brace of  FIG. 1 ; and 
           [0014]      FIG. 4  is a perspective view of a fastener of the ladder cage of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  is a perspective view of ladder cage  10 , exemplary of an embodiment of the present invention. Ladder cage  10  provides support/safety to a climber of ladder  12 . Ladder  12  may be part of a free standing structure (otherwise not shown), such as a building scaffold, a wind turbine tower, a communications tower, or the like. As illustrated, ladder cage  10 , when assembled forms a generally cylindrical cage that encircles a climber of ladder  12 . Ladder cage  10  is affixed around ladder  12 , to provide protection to a climber in case of a backward/outward fall. 
         [0016]    Cage  10  includes several rings  14 - 1 ,  14 - 2 ,  14 - 3 , . . .  14 - n  (individually and collectively rings  14 —only three are illustrated in  FIG. 1 ), and vertical braces  16  extending between rings  14  in the direction of extent of ladder  12 . Ladder cage  10  may be formed in several sections  18 - 1 ,  18 - 2 ,  18 - 3 , . . .  18 - n  (individually and collectively sections  18 )—with each section defined by two adjacent rings  14  and the vertical braces  16  between them. Sections  18  may extend continuously along the length of ladder  12 , or discontinuously, with sections separated by a space. Rings  14  are spaced along the extent of ladder  12 , typically, but not necessarily, at equal distances from one another. 
         [0017]    Vertical braces  16  are typically identical, having like dimensions. For convenience, vertical braces  16  in a section  18 —i.e. between the same two rings  14 —are identified with a common subscript in  FIG. 1 . Thus, in  FIG. 1 , vertical braces  16   1  all interconnect rings  14 - 1  and  14 - 2  in section  18 - 1 ; vertical braces  16   2  all interconnect rings  14 - 2  and  14 - 3  in section  18 - 2 ; vertical braces  16   3  all interconnect rings  14 - 3  and  14 - 4  in section  18 - 3 ; and so on. 
         [0018]    As illustrated in  FIG. 2 , each vertical brace  16  may take the form of a standard scaffold brace, formed of steel or aluminium, having a flattened ends  28 , extending from a generally cylindrical body portion  26 . Each flattened end  28  may further include a hole  24  for mounting brace  16  on a corresponding mounting pin. The mounting pin may take the form of a pin, a bolt, a post, a shaft, or any other suitable protrusion. 
         [0019]    As more particularly illustrated in  FIG. 3 , each ring  14  includes an arc shaped metal or alloy band  22 , having several fasteners  30  extending outwardly therefrom, and evenly spaced along band  22 . Band  22  may be formed of the same material as brace  16 —i.e. steel, aluminium, or the like. 
         [0020]    Each fastener  30  serves to secure one or two vertical braces  16  to a ring  14 . For a ring  14  shared by two sections  18  of cage  10 , a single fastener  30  receives an upwardly extending vertical brace  16 , and a downwardly extending brace  16 , as best illustrated by the enlarged portion of  FIG. 1 . The end of band  22  may be folded inwardly, and further include bolt and nut  60 ,  62  or similar fastener for bolting ring  14  to ladder  12 . The arc formed by band  22  is sized so that its inwardly folded ends of band  22  attach to vertically extending struts of ladder  12 , at equal vertical positions along ladder  12 , thus leveling the plane of ring  14  horizontally. Of course, as will be appreciated, ring  14  need not be formed of a flat band, but could instead be formed with a tubular cross-section tube, or having any other suitable cross-sectional geometry. Likewise, rings  14  need not be formed in circular arc shapes. For example, rings  14  may instead be rectangular, elliptical or formed in any other simple or complex shapes suitable for a given application. In the depicted embodiment, the distance between folded ends of band  22  is about 60 cm, the length of each brace  16  is about 1 m, and braces  16  are circumferentially spaced by about 20 cm around ring  14 . 
         [0021]    An example fastener  30  for fastening brace  16  to ring  14  is more particularly illustrated in  FIG. 4 . As illustrated, fastener  30  includes a mounting pin  32  mounted on a base  34 , and a U-shaped drop-pin  40 . Base  34  may be attached to ring  14 , and includes a slot  36 . Slot  36  is in a plane tangent to ring  14 . Mounting pin  32  includes a further slot  38 , in plane normal to that of slot  36 . U-shaped drop pin  40  has a curved top  42  and two flat arms  44  and  46  and is slidably received within slot  36 . Flat arms  44  and  46  are also oriented in planes normal to each other, so that arm  44  may be received in slot  36 , and slide freely therein, while arm  46  may be slid in, out of, and through slot  38 . A nib  48  on arm  44  stops arm  44  from being completely slid through slot  36 , thus preventing U-shaped drop pin  40  from being separated from base  34 . Alternatively, or additionally, arm  44  may include a hole for receiving a cotter pin or the like for preventing drop pin  40  from being separated from base  34 . Optionally, arm  46  may include a hole  50  on arm  46  for receiving a cotter-pin  52  or the like, to lock U-shaped drop pin  40  in place (as shown in  FIG. 1 ). Slots  36  and  38  and arms  44  and  46  are depicted as flat, but could take any suitable complementary shapes. For example, slots  36 ,  38  and arms  44  and  46  could be round in cross-section, semi-circular in cross-section, or any other suitable shape. 
         [0022]    As further illustrated in  FIG. 1 , U-shaped drop pin  40  is used to lock a flattened end  28  of brace  16  in place on mounting pin  32 . Conveniently, U-shaped drop pin  40  is pulled out of base  34  to open fastener  30 , and allow hole  24  of brace  16  to slide on and off of pin  32 , past slot  38 . U-shaped drop pin  40  may be sized and oriented so that, when drop pin  40  is pulled out of base  34  as far as nib  38  permits, sufficient horizontal space is provided between pin  32  and arm  46  so that arm  46  clears the vertical edges of end portion  28  of brace  16 , as hole  24  is slid onto pin  32 . After hole  24  is slid onto pin  32 , drop pin  40  may be slid into slot  38  to close fastener  30 , and optionally locked by pinning cotter-pin  52  into hole  50 . Drop pin  40  may also be sized and oriented to provide sufficient horizontal space between pin  32  and the inside of curved top  42  so that, once hole  24  is slid onto pin  32  drop pin  40  may be closed with arm  46  fully in slot  38  before the inside of curved top  32  contacts the vertical edges of end portion  28 . Of course, in order for fastener  30  to be able to accept both upwardly and downwardly-extending braces  16  with vertical end portions  28 , drop pin  40  should be at an angle to the vertical that will depend on the geometry of fastener  30  and end portions  28 . 
         [0023]    Fastener  30  is mounted to ring  14 , so that U-shaped drop pin  40  slides at an angle of about α=45° to the vertical (i.e. at an angle α to the plane of ring  14 ). In this way, U-shaped drop pin  40  is naturally pulled by gravity into slot  36 . Once drop pin  40  is slid into slot  38 , it locks one or more braces  16  into place on pin  32 , preventing brace  16  from sliding off pin  32 . Likewise, the size and angled orientation of U-shaped drop-pin  40 , provides clearance for both an upwardly and downwardly extending brace  16  to be received on pin  32 . As will now be appreciated, mount angles of less than or more than 45° may achieve the same effect. The mount angle may be any angle which provides sufficient clearance for braces  16 , given the geometry of drop pin  40 , and that result in a sufficient downward pull of drop pin  40  into slot  36  by gravity. For example, angles of between 30° and 60° may be appropriate. 
         [0024]    Conveniently, ring  14  with fasteners  30  allow for relatively quick assembly of ladder cage  10 . Two adjacent rings  14  may be attached to ladder  12 , and braces  16  may be attached to these rings  14 . U-shaped drop pins  40  may be quickly and readily slid between the open and closed position of fastener  30 , to allow for easy installation of braces  16 . At the same time, the effect of gravity biases U-shaped drop-pins  40  closed. With the aid of gravity, use of cotter-pins  52  is optional. 
         [0025]    Ladder cage  10  may similarly be disassembled, to allow easy removal, by sliding U-shaped drop pins  40  upward, providing clearance to allow the flattened ends  28  of braces  16  to be slid outward, off of pins  32 . Once braces  16  are removed from rings  14 , rings  14  may be removed from ladder  10 . 
         [0026]    As will be appreciated U-shaped drop pins  40  could be replaced with drop pins of another shape—for example linear drop pins could be used. 
         [0027]    pun In an alternate embodiment, fastener  30  (and hence drop pin  40 ) could be mounted to ring  14  so that it may be rotatable or pivotal about an axis of pin  32 . The drop pin  40  could be rotated to an arbitrary angular position as braces  16  are installed. For example, to suit a particular application or the preference of an installer, fastener  30  could be rotated so that drop pin  40  is in a substantially horizontal orientation, parallel to the plane of ring  14 , as the braces  16  are installed. Thereafter, the pin could be rotated to make a suitable angle with the vertical to lock drop pin  40  with the aid of gravity after brace(s)  16  is/are installed 
         [0028]    Of course, the above described embodiments, are intended to be illustrative only and in no way limiting. The described embodiments of carrying out the invention, are susceptible to many modifications of form, arrangement of parts, details and order of operation. The invention, rather, is intended to encompass all such modification within its scope, as defined by the claims.