Patent Publication Number: US-2005141970-A1

Title: Earth retaining safety framework and system

Description:
FIELD OF INVENTION  
      The invention relates to an earth retaining safety framework and safety system and relates particularly, though not exclusively, to such a safety framework and system for use in the protection of workers in excavations.  
     BACKGROUND OF THE INVENTION  
      In order to install or repair underground installations such as water and sewerage pipes or power lines, it is often necessary for workers to enter excavations in the area where the pipes or lines are located.  
      Due to the depths to which these excavations must be dug, there is a substantial risk of injury or death to workers entering these excavations in the event that the walls of an excavation collapse. In addition to the human risk, extensive property damage to the surrounding buildings, structures or infrastructures can occur.  
      As a result, safety devices have been developed to reinforce and support excavations, trenches, underground holes, bore-pits and manhole installations. For example, timber frameworks have been used to provide a means for retaining soil from collapsing in on an excavation. However, these timber frameworks have a number of disadvantages.  
      Timber frameworks are time-consuming to install, often taking up to half a day to position. This is largely due to the fact that the timber framework consists of a number of separate pieces that must be assembled and carefully aligned in the excavation before the framework can be used. Furthermore, it is difficult to obtain suitably long pieces of wood and there is the risk of breakage or splintering of the pieces of wood used in the framework. Timber often warps and can be subject to termite infestation requiring special treatment and storage to minimize possible damage.  
      The present invention was developed with a view to providing a safety framework and system that is easy to use and that can be quickly installed in an excavation.  
      References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.  
     BRIEF DESCRIPTION OF THE INVENTION  
      According to one aspect of the present invention there is provided a safety framework for positioning in an excavation, the framework comprising: a first substantially rectangular framework portion and a second substantially rectangular framework portion; and a plurality of elongate spacer members for retaining said second framework portion in a spaced apart relationship relative to the first framework portion, each said spacer member being mechanically coupled to said first and second framework portions by mounting means comprising a pin connection so as to facilitate a degree of lateral movement of the second framework portion relative to the first framework portion, and wherein said first and second framework portions together define a work space within which a worker can work in the excavation in relative safety.  
      Preferably said first framework portion comprises a pair of substantially parallel, opposed first elongate support members and a pair of substantially parallel, opposed second elongate support members substantially perpendicular to said first support members and secured to said first support members in an abutting arrangement.  
      Preferably said second framework portion comprises a pair of substantially parallel, opposed third elongate support members and a pair of substantially parallel, opposed fourth elongate support members substantially perpendicular to said third support members and secured to said third support members in an abutting arrangement. Preferably said first and second framework portions are of substantially the same size and shape.  
      Preferably said mounting means are provided on the first support members and comprise first mounting portions for positioning of the spacer members on the first support members. Preferably said mounting means are also provided on the third support members and comprise second mounting portions for positioning of the spacer members on the third support members. When the framework is assembled, the first mounting portions and the second mounting portions are preferably in substantially vertical alignment so that the spacer members are retained in a substantially vertical orientation. Preferably each of said first mounting portions is positioned respectively at a distance away from each end of the respective first support member. Preferably each of said second mounting portions is positioned respectively at a distance away from each end of the respective third support member. Preferably each of said mounting portions is positioned at an equal distance from the respective ends of the respective support members.  
      The support members and the spacer members are preferably generally square or rectangular in cross-section. The support members and the spacer members are preferably made of metal such as steel or aluminum. These components may be hollow to reduce the weight of the components.  
      The mounting portions may be in the form of mounting blocks projecting from the first and third support members. In this way, the upper and lower ends of the hollow spacer members may be positioned over the first and second mounting blocks respectively. Preferably each of the mounting blocks is provided with block apertures for alignment with spacer apertures in the ends of each spacer member. Thus, the spacer members may be secured to the mounting blocks by positioning a securing means such as a pin or a bolt through the aligned block apertures and spacer apertures to provide said pin connection. Preferably the securing means includes some form of safety locking means such as a ring clip or a sprung safety clip.  
      This way of retaining the first and second framework portions in a spaced apart relationship provides a relatively rigid framework whilst at the same time allowing some lateral movement of the second framework portion relative to the first framework portion. The rigidity of the framework allows for the assembly of the framework outside of the excavation, if required, so that the framework may simply be lowered into the excavation ready for use. The small amount of lateral movement of the framework portions means that the framework can be adjusted to level the framework on the floor of the excavation. The slight lateral movement also allows some stress relief for the support members.  
      Preferably, the safety framework comprises four spacer members to retain the second framework portion in a substantially horizontal orientation spaced at a desired distance from the first framework portion. The distance may be varied by changing the length of the spacer members to change the height of the work space as required for a particular excavation depth.  
      Preferably the spacer members are of equal length so that the first framework portion and the second framework portion are in substantially parallel alignment.  
      The lengths of the first and second support members and the third and fourth support members may also be varied according to the required dimensions of the excavation.  
      Preferably the second support members and the fourth support members comprise connecting members extending from the ends thereof to facilitate connection of the first and second support members to each other, and of the third and fourth support members to each other. Preferably the connecting members are in the form of flanges extending from two sides of each end of the second and fourth support members respectively. The connecting members are preferably secured by securing means such as screws, bolts or clips received through aligned apertures in the flanges and ends of the first and third support members respectively.  
      The first and third support members may be about 1800 mm in length and the second and fourth support members may be about 1000 mm in length. Typically the support members are made from 3 mm steel with a square cross section of about 100 mm by 100 mm. The spacer members may be about 1000 mm in length and made from 3 mm steel with a square cross section of about 50 mm by 50 mm.  
      The safety framework may further comprise third, fourth and further framework portions analogous to the first and second framework portions as are required for larger excavations. Further spacer members would of course be required in these cases to maintain the third, fourth and further framework portions in spaced apart relationship from the second and following framework portions.  
      The first support members may further comprise attachment means such as lugs or hooks. This would allow for attachment of the ends of chains or ropes to lower the framework into the excavation, for example by means of a crane of other lifting system. Conveniently there may be four hooks, with two on each first support member in a spaced apart relationship.  
      As already noted, forming the safety framework from steel, aluminum or strong plastic material allows the framework to be readily assembled either outside or inside the excavation. The small amount of lateral movement of the framework portions means that the framework can be easily adjusted to suit the level of the floor of the excavation.  
      According to a further aspect of the present invention there is provided a safety system for positioning in an excavation, the system comprising: a framework comprising: a first substantially rectangular framework portion and a second substantially rectangular framework portion; and a plurality of spacer members for retaining said second framework portion in a spaced apart relationship relative to the first framework portion, each said spacer member being mechanically coupled to said first and second framework portions by mounting means comprising a pin connection so as to facilitate a degree of lateral movement of the second framework portion relative to the first framework portion; and a plurality of panel members adapted to be supported by the framework on the respective sides of the first and second framework portions, wherein said first and second framework portions and the panel members together define a work space within which a worker can work in the excavation in relative safety.  
      Preferably said first framework portion comprises a pair of substantially parallel, opposed first elongate support members and a pair of substantially parallel, opposed second elongate support members substantially perpendicular to said first support members and secured to said first support members in an abutting arrangement. Preferably said second framework portion comprises a pair of substantially parallel, opposed third elongate support members and a pair of substantially parallel, opposed fourth elongate support members substantially perpendicular to said third support members and secured to said third support members in an abutting arrangement. Preferably said first and second framework portions are of substantially the same size and shape.  
      Preferably the panel members are positioned in a substantially vertical orientation supported by the framework. Preferably the panel members are positioned side by side abutting against the support members of the framework to form a wall around the framework. In this way soil or debris is prevented from entering the work space of the excavation.  
      Preferably each panel member has an outer face and an inner face. The inner face preferably abuts against the support members and the outer face contacts the soil of the excavation if the soil moves towards the framework to prevent the soil entering the work space.  
      The inner face may be provided with a raised pattern such as a “checkerplate” pattern to reduce the friction of the inner face against the support members when the panel members are placed in position in the safety system.  
      When the system is in use, a lower portion of each of the panel members is preferably positioned in the ground below the floor of the excavation. This allows the panel members to be anchored in the ground with the weight of the soil from the excavation walls pressing on the outer face of each panel member to retain the panel members in an upright configuration against the framework.  
      Preferably each panel member has first flanges extending from opposing vertical sides of the panel member. In use, the panel members are positioned in side by side arrangement with the first flanges extending away from the work space. In this way, the first flanges of a first panel member abut the first flanges of a second panel member positioned adjacent the first panel member. Thus the panel members cannot slide over each other and are held apart in a vertical alignment so as to prevent soil and debris from the excavation from entering the work space.  
      Each of the panel members may further be provided with a second flange extending from the upper edge of each panel member to assist in retaining soil and debris from entering the work space. The second flange also provides a hitting surface to allow the panel member to be hammered into the floor of the excavation. The first and second flanges assist in providing the panel members with rigidity and strength which is important in preventing soil or debris from entering the work space. The lower edge of each panel member preferably has no flange extending there from. Thus the lower edge of each panel member forms a cutting edge which can be readily driven into the soil of the floor of the excavation.  
      The panel members may each be provided with a panel aperture to allow for a crane hook or other means to lift the panel members for positioning in the system. Preferably the panel aperture is positioned at an upper end of each panel member.  
      Preferably the panel members are formed of 3 mm steel checkerplate and are dimensioned 600 mm by 2000 mm. With these dimensions, the safety system comprises 10 panel members with three being positioned on each of two sides of the framework and two being positioned on each of the other two sides.  
      Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The nature of the invention will be better understood from the following detailed description of a specific embodiment of the safety framework and safety system, given by way of example only, with reference to the accompanying drawings, in which:  
       FIG. 1  is a perspective view of a preferred embodiment of a safety framework according to the present invention;  
       FIG. 2  is an exploded view of the safety framework of  FIG. 1 ;  
       FIG. 3  is a perspective view of a preferred embodiment of a panel member of a safety system according to the invention showing the inner face of the panel member;  
       FIG. 4  is a perspective view of the panel member of  FIG. 3  showing the outer face of the panel member;  
       FIG. 5  is a perspective view of a preferred embodiment of a safety system according to the present invention positioned in an excavation;  
      FIGS.  6 ( a ), ( b ) and ( c ) are schematic top, side and end views respectively of a preferred embodiment of a safety pin and clip used in the safety framework of  FIGS. 1 and 2 ; and  
       FIG. 7  is a perspective view of the safety system of  FIG. 5  illustrating a worker at work in the work space.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A preferred embodiment of a safety framework generally indicated by the numeral  10  and a safety system generally indicated by the numeral  12  will now be described in detail with reference to the accompanying drawings. The safety framework  10  and the safety system  12  are typically positioned in an excavation  14  as shown in  FIGS. 5 and 7 , the safety framework defining a work space  16  within which a worker can work in the excavation in relative safety.  
      The safety framework  10  typically comprises a first substantially rectangular framework portion  18  having a pair of substantially parallel, opposed first elongate support members  20  in the form of square hollow steel sections and a pair of substantially parallel, opposed second elongate support members  22  in the form of square hollow steel sections secured to the first support members  20 . The safety framework  10  further comprises a second substantially rectangular framework portion  24  having a pair of substantially parallel, opposed third elongate support members  26  in the form of square hollow steel sections and a pair of substantially parallel, opposed fourth elongate support members  28  in the form of square hollow steel sections secured to the third support members  26 . In this embodiment the first and second framework portions  18  and  24  are of substantially the same size and shape.  
      The safety framework  10  further comprises spacer members  30  in the form of square hollow steel sections for retaining said second framework portion  24  in a spaced apart relationship relative to the first framework portion  18 . As can best be seen in  FIG. 2 , the spacer members  30  are supported on mounting portions in the form of eight mounting blocks  32  which project from the first support members  20  and third support members  26  respectively. In this way, the upper and lower ends of the hollow spacer members  30  may be positioned over the mounting blocks  32  respectively. When the framework  10  is assembled, the mounting blocks  32  are preferably in substantially vertical alignment so that the spacer members  30  are retained in a substantially vertical orientation. Preferably each of the mounting blocks  32  is positioned respectively at an equal distance away from each end of the respective first and third support members  20  and  26 .  
      Preferably each of the mounting blocks  32  is provided with block apertures for alignment with spacer apertures in the upper and lower ends of each spacer member  30 . Thus, the spacer members  30  may be secured to the mounting blocks by positioning a securing means such as a pin or a bolt through the aligned block apertures and spacer apertures to provide a pin connection. As can be seen most clearly in  FIG. 2 , the block apertures are aligned with the longitudinal direction of the respective support members  20  and  26 . The upper and lower ends of the spacer members  30  are secured to the mounting blocks  32  by inserting a safety pin  34  through the aligned block apertures and spacer apertures. The safety pin  34  thus effectively forms a pivot axis about which the spacer members  30  can pivot slightly. The pivoting movement of the spacer members  30  about this pin connection is constrained by the mounting blocks  32 , which are only slightly smaller in dimensions than the internal dimensions of the hollow ends of the spacer members  30 . A sprung safety clip  36  is provided to lock each safety pin  34  in its respective aperture. As can be seen most clearly in  FIG. 6 , the safety pin  34  has a handle portion  35  at one end, and an aperture  37  at the other end in which the safety clip  36  may be inserted to lock it in the aligned apertures.  
      Thus the spacer members  30  are securely attached to the first and second framework portions  18  and  24  so that the overall framework  10  is substantially rigid. However, due to the way in which the spacer members  30  are attached to the first and second framework portions  18  and  24  a degree of lateral movement of the second framework portion  24  relative to the first framework portion  18  is possible. The rigidity of the framework allows the framework  10  to be assembled outside of the excavation, if required, so that the framework may simply be lowered into the excavation ready for use. The small amount of lateral movement of the framework portions  18  and  24  means that the framework  10  can be easily adjusted to level the framework on the floor of the excavation. The slight lateral movement also allows some stress relief for the support members.  
      The second support members  22  and the fourth support members  28  have connecting means in the form of flanges  38  extending from the ends thereof. As can best be seen in  FIG. 2 , the flanges  38  have two sides, like a section of angle iron, and in this way provide a means of securely fixing the first and second support members  20  and  22  to each other, and the third and fourth members  26  and  28  to each other, due to the overlapping arrangement formed between the various components. As can be seen in  FIGS. 1 and 2 , the first and second support members  20  and  22  and the third and fourth support members  26  and  28  respectively are secured to each other using the pins  34  and clips  36  as previously described. The pins  34  are received through apertures in the flanges  38  that are aligned with corresponding apertures in the respective support members  20  and  26 .  
      Advantageously the first support members  20  are provided with four hooks  40  to allow for attachment of chains or ropes to lift the safety framework  10  and lower it into an excavation using a lifting device, such as a crane or excavator. The same hooks  40  can be used for lifting the framework  10  out of the excavation when the work is complete.  
      In the illustrated embodiment the first and third support members  20  and  26  are about 1800 mm in length and the second and fourth support members  22  and  28  are about 1000 mm in length. Typically the support members are made from 3 mm steel with a square cross section of about 100 mm by 100 mm. The spacer members  30  in this embodiment are about 1000 mm in length and made from 3 mm steel with a square cross section of about 50 mm by 50 mm.  
      The safety framework  10  of the invention may be configured for trenches of different sizes. For example, the spacer members  30  may be made of different lengths depending on the depth of the excavation. The safety framework  10  may of course have further framework portions positioned above the second framework portion to be suitable for a deeper excavation.  
      The preferred embodiment of the safety system  12  comprises a safety framework  10  and a plurality of panel members  44  that are placed in a vertical arrangement around the framework  10 , as can best be seen in  FIG. 5 . Preferably the panel members  44  are positioned side by side abutting against the support members of the framework  10  to form a wall around the framework. In this way soil or debris is prevented from entering the work space of the excavation.  
      As shown in  FIGS. 3 and 4 , the panel members  44  have an outer face  46  provided with a raised “checkerplate” pattern  48 , and an inner face  50 . The inner face  50  preferably abuts against the support members and the outer face  46  contacts the soil of the excavation, if the soil moves towards the framework  10 , to prevent the soil entering the work space. The panel members  44  are further provided with first flanges  52  extending from the opposing vertical edges of the panel members  44 . In use, the panel members  44  are positioned in side by side arrangement with the first flanges  52  extending away from the work space. In this way, the first flanges  52  of a first panel member abut the first flanges  52  of a second panel member positioned adjacent the first panel member. Thus the panel members  44  cannot slide over each other and are held side by side in vertical alignment so as to prevent soil and debris from the excavation from entering the work space as can be seen in  FIGS. 5 and 7 .  
      The panel members  44  also have second flanges  54  extending from their upper edges. The second flanges  54  present a surface for hammering of the panels into the ground so that the main body of the panel member is not damaged by the hammering action. The first and second flanges  52  and  54  assist in providing the panel members  44  with rigidity and strength which is important in preventing soil or debris from entering the work space. The lower edge  56  of each panel member preferably has no flange extending there from. Thus the lower edge  56  of the panel members  44  presents a cutting edge which can be readily driven into the soil of the floor of the excavation, to allow ease of positioning of the panels in the ground of the excavation  14 .  
      The panel members  44  are also provided with a panel aperture  58  at the upper end thereof for attachment of the panel member to a chain or rope used to lower the panel members into the excavation  14 . Preferably the panel members  44  are formed of 3 mm steel checkerplate and are dimensioned 600 mm by 2000 mm. With these dimensions, the safety system  12  comprises  10  panel members  44  with three being positioned on each of two sides of the framework  10  and two being positioned on each of the other two sides as shown in  FIGS. 5 and 7 .  
      As can be seen in  FIG. 5 , in use the panel members  44  extend at their upper edges beyond the second framework  24  and at their lower edges below the first framework  18  into the ground of the excavation  14  as shown by the dotted lines. This allows the panel members  44  to be anchored in the ground with the weight of the soil from the excavation walls pressing on the outer face of each panel member to retain the panel members in an upright configuration against the framework  10 .  
      As can be seen in  FIGS. 5 and 7 , the safety system  12  of this embodiment comprises ten panel members  44  arranged around the framework  10 . The complete installed safety system  12  is shown in  FIG. 7  where a worker  60  has commenced work in the work space  16  in the safety of the safety system  12 .  
      Now that a preferred embodiment of the safety framework and safety system have been described in detail, it will be apparent that it provides a number of advantages, including the following:  
      (i) It is of simple design, making it inexpensive to manufacture and easy to install.  
      (ii) It can be quickly assembled, either prior to lowering into an excavation, or in situ in the excavation.  
      (iii) It can be readily modified to suit any size excavation.  
      (iv) Due to the manner in which the spacer members are mechanically coupled to the framework portions via a pin connection, a degree of lateral movement of the framework portions is facilitated, which permits the framework to be easily adjusted to level the framework on the floor of the excavation.  
      It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. For example, it is not essential that the spacer members be square hollow sections; tubular sections would also function equally well. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described.