Patent Publication Number: US-2018030665-A1

Title: Composite Rig Mat Comprising Pultruded Composite Members

Description:
This application claims the benefit under 35 U.S.C. 119(e) to U.S. Provisional Application Ser. No. 62/367,332 filed Jul. 27, 2016. 
     The present invention relates to a composite mat which is suited particularly but not exclusively for use as a temporary road mat or work area mat, particularly of the type used in oil, logging, and mining industries where such mats are known to facilitate equipment transportation or vehicle traffic in areas where permanent roads are non-existent or too expensive and where the ground is not stable enough to regularly support heavy equipment. 
    
    
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention there is provided a rig mat comprising: 
     a first layer comprising a plurality of elongate first members extending parallel to one another in a longitudinal direction between first and second ends of the mat; 
     a second layer comprising a plurality of elongate second members spanning across the first members, parallel to one another and transversely to the first members such that each second member intersects a plurality of the first members at respective intersecting locations of the mat; 
     a plurality of fasteners mounted at selected intersecting locations, each fastener joining one of the first members of the first layer to one of the second members of the second layer; 
     wherein each of the first and second members is formed by pultrusion from composite material so as to define an elongated tubular body enclosing a longitudinal axis of the respective member; 
     the tubular body having on its outside first and second wide faces and first and second narrow faces, each face spanning from a first end to a second end of the respective member; 
     the first members being arranged in the first layer and the second members being arranged in the second layer such that the wide faces of the first members in the first layer are facing the wide faces of the second members in the second layer; 
     each of the first and second members having a thickness of the member measured between the first and second wide faces and a width of the member measured between the first and second narrow faces; 
     the tubular body having an interior peripheral surface which is spaced by a thickness of the pultruded composite material from an outer peripheral surface of the tubular body collectively defined by the first and second wide faces and the first and second narrow faces, the interior peripheral surface delimiting a cavity of the tubular body which spans from a first location at or adjacent the first end of the member to a second location at or adjacent the second end of the member; 
     each one of the first and second members including at least one reinforcing rib extending along a length of the cavity from the first location to the second location, said at least one reinforcing rib bridging the cavity in a direction of the thickness of the member and being spaced from the interior peripheral surface in a direction of the width of the member so as to resist compression of the tubular body in the direction of the thickness of the member. 
     That is, each layer having a face at an outer periphery of the mat that is collectively defined by one of the first and second wide faces of the members of that layer is arranged to define a exterior support surface of the mat which engages the ground or receives thereon for example a tire of a vehicle or feet of a user. As such, weight of the vehicle or the user on the mat acts as a compressive force on the mat which would otherwise displace one of the exterior support surfaces of the mat towards the opposite one of the exterior support surfaces. The reinforcing ribs of the members forming the mat layers rigidify the mat so as to withstand compression. 
     In one arrangement there are a plurality of reinforcing ribs each spaced from the next in the direction of the width of the member. 
     Typically the tubular body is rectangular in cross-section such that the first and second wide faces of each member are planar and parallel to one another, and the first and second narrow faces of each member are planar and parallel to one another. The faces may meet at right angles at their contiguous edges, or these contiguous edges may be rounded so that the outer peripheral surface is uninterrupted around its transverse circumference. 
     In some arrangements there is provided a third layer comprising a plurality of elongate third members spanning across the second members, parallel to one another and transversely to the second members such that one of the third members intersects one of the second members at each intersecting location between first and second members. Like the first and second members, these third members are formed from the pultruded composite material defining the elongated tubular body. In such arrangements with the third layer, one of the fasteners joins one of the first members to one of the third members with one of the second members sandwiched therebetween at each intersecting location. 
     In other arrangements there may be provided additional layers each comprising a plurality of elongated members spanning across the members of the adjacent layer, parallel to one another and transversely to the members of the adjacent layer, so that the number of layers is more than three. 
     In some arrangements the first and second ends of the respective member are open. In some arrangements the first end and the second end of the respective member are closed so that the cavity of the respective member is enclosed. 
     In one arrangement the first and second ends of the respective member are open and the cavity spans the full length of the respective member. 
     In such arrangements said at least one reinforcing rib typically spans the full length of the respective member. 
     Each fastener at the respective intersecting location may pass through one of the members of each layer at a spaced location from said at least one reinforcing rib thereof. 
     For example, the thickness of the respective member lies in a range between 1″ and 2.25″ and the width of the respective member lies in a range between 6″ and 10″. 
     The mat preferably includes a connecting arrangement so that it is connectable to another such mat and whereby a series of the mats may be connected together. In one arrangement of the mat having the connecting arrangement, selected members of an outer layer of the mat are arranged to project beyond one of the first and second ends of the mat so as to form fingers for interconnecting at corresponding gaps of another mat which are formed at locations of the selected members where an opposite end of the respective selected members is spaced longitudinally inwardly from the end of the mat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of mat according to the present invention. 
         FIG. 2  is a top plan view of the mat of  FIG. 1  where some reinforcing ribs are schematically illustrated. 
         FIG. 3  is a cross-sectional view of a portion of the mat of  FIG. 1  near one mat end, where some members of a middle layer are shown with a different number of reinforcing ribs. 
     
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION 
     There is illustrated in the accompanying figures a composite mat  10  which is particularly but not exclusively suited for use in oil, logging, and mining industries for forming a temporary work surface or road surface in areas where the ground is otherwise unstable or unsuitable for supporting thereon a permanent work or road surface. These types of mats may be considered to fall within the category of ‘rig mats’ which may be more broadly regarded as portable platforms. 
     In the illustrated embodiment the composite mat  10  comprises three layers respectively indicated at  13 ,  14 , and  15 . Each of the layers is formed by composite members  17  arranged in a common plane where the members  17  of the respective layer are oriented perpendicularly transverse to the members of the adjacent layer. The mat of the illustrated arrangement is generally rectangular in shape (in plan view) as is common of commercially available rig mats. 
     More specifically, there is provided a first bottom layer  13  comprising a plurality of composite members  17  which are arranged parallel to one another in a respective common plane with at least one of the exterior narrow faces  19 ,  20  which are on opposite sides of the respective member facing that of the adjacent composite member of the first layer  13 . As such, broad or wide exterior faces  21  and  22  of the respective member are positioned so as to face normally to the plane defined by the layer  17 . 
     The composite members  17  of the first layer  13  thus extend in a longitudinal direction of the mat  10  between a first mat end  25  and a second mat end  26 . Further, the members  17  of the first bottom layer  13  each are arranged in close proximity to the next of the first layer so that a gap between adjacent members  17  is considerably smaller than a width WM of the individual composite member which is measured from the first narrow face  19  to the second narrow face  20 . A thickness TM of the respective composite member  17  is measured between the first and second wide faces  21 ,  22 . 
     The composite mat  10  has a second middle layer  14  on top of the first bottom layer  13 . The second middle layer  14  comprises a plurality of the composite members  17  arranged in a respective common plane spanning across the composite members forming the first layer  13  such that each member  17  of the second layer  14  intersects a plurality of the first layer&#39;s members at respective intersecting locations IL of the mat. The composite members  17  of the second layer  14  are again oriented parallel to one another and lie in close proximity to one another to define a small gap between adjacent composite members. More specifically, the members forming the second layer  14  are oriented perpendicular to the members of the first layer  13  so as to be perpendicular to the longitudinal direction and to extend in a perpendicularly transverse direction between opposite sides  27 ,  28  of the mat. Further, the composite members of the second layer are arranged with their wide faces  21  facing the wide faces  22  of the first layer such that the members of adjacent layers are positioned with their wide faces in abutment with one another. 
     By the orientation of the composite members, the intersecting locations IL are arranged in transversely extending rows in which each transverse row of intersecting locations corresponds to the intersecting locations of one of the second layer members of the middle layer  14  extending in the perpendicularly transverse direction between the sides  27  and  28  of the mat. Plural transverse rows of intersecting locations IL are thus defined, each corresponding to one of the composite members  17  of the middle layer  14  so that the lateral rows are spaced in the longitudinal direction from one another between the first and second ends  25 ,  26  of the mat. 
     Furthermore, the composite mat  10  includes a third top layer  15  of the composite members  17  arranged on top of the second middle layer  14  so as to be opposite the first bottom layer  13 . The composite members of the third layer  15  again are arranged in a respective common plane spanning across the composite members  17  of the second layer  14  and each in close proximity to the next of the third layer  15  such that there is defined a small gap between adjacent composite members of the third layer. Further, the composite members  17  extend parallel to one another and transversely to the composite members of the second layer such that one of the composite members of the third layer intersects one of the second layer&#39;s members at each intersecting location IL formed between the members  17  of the first and second layer  13 ,  14 . The composite members forming the third layer  15  thus extend in the longitudinal direction and are aligned normally of the plane with corresponding ones of the members of the first bottom layer  13 . As such, each third layer member overlaps each intersection location IL formed between the first and second layers  13 ,  14 . 
     The three layer  13 ,  14 , and  15  are held together by fasteners  30 , for example rivet fasteners, in a conventional manner known in the art of rig mats. Each fastener  30  is positioned at one of the intersecting locations IL and passes through each one of the layers so as to compressively join together same. As such, the members of the second layer  14  are sandwiched between the composite members of the first bottom layer  13  and the third top layer  15  at each intersecting location. 
     Each composite member  17  forming the mat layers  13  through  15  is made by pultrusion from composite material so as to define a tubular body  32 . The tubular body  32  is elongated along a longitudinal axis of the composite member enclosed by the tubular body. The body may also be regarded as a tubular wall of the composite member. 
     The tubular body  32  of the illustrated embodiment has rectangular cross section such that the first and second wide faces  21 ,  22  of each member are planar and parallel to one another, and the first and second narrow faces  19 ,  20  of each member are planar and parallel to one another. As most clearly shown in  FIG. 3  but not in  FIG. 1  for convenience of illustration, contiguous edges of adjacent faces, for example each pair of one of the wide faces  21  or  22  and one of the narrow faces  19  and  20 , are rounded so that an outer peripheral surface of the respective member that is collectively defined by the narrow faces  19  and  20  and the wide faces  21  and  22  on the outside of the tubular body  32  is uninterrupted around its transverse circumference. 
     As mentioned earlier, each tubular body  32  is elongated in a longitudinal direction of the respective composite member from a first member end  33  to a second member end  34 . Each one of the narrow faces  19  and  20  and the wide faces  21  and  22  spans from the first to second member ends  33 ,  34 . 
     The tubular body of each composite member includes an interior peripheral surface  35  which is spaced by a thickness TB of the pultruded composite material from the outer peripheral surface and thus delimits a cavity  37  of the body. It will be appreciated that the material thickness of the body may vary at different locations about a periphery of the body such that the thickness of the composite material for example may be smaller between the interior peripheral surface  35  at one of the wide faces  21  or  22  than between the interior peripheral surface  35  at one of the narrow faces  19  or  20 . The cavity  37  spans from a first end location at or adjacent the first member end  33  to a second end location at or adjacent the second member end  34 . In the illustrated arrangement, the tubular body  32  is open at the first and second member ends  33 ,  34 , and the first and second end locations of the cavity are at the first and second member ends and thus correspond thereto, as shown schematically in  FIG. 1 . 
     It will be appreciated that each layer having a face at an outer periphery of the mat that is collectively defined by one of the first and second wide faces of the members of that layer is arranged to define a exterior support surface  38 ,  39  of the mat which engages the ground or receives thereon for example a tire of a vehicle, heavy equipment, or feet of a user. In the illustrated embodiment, the first bottom layer  13  defines one of the exterior surfaces  39  at its bottom and the third top layer  15  defines one of the exterior surfaces  38  at its top. 
     Further, persons skilled in the art of rig mats understand that these mats undergo substantial compressive forces which would otherwise act to displace one of the exterior support surfaces of the mat towards the opposite one of the exterior support surfaces. 
     Pultruded composite material inherently has good tensile strength because its constituent fibers are oriented longitudinally of the axis of the composite member; however the structure of pultruded composite material is not particularly suited to withstand the compressive forces which rig mats are typically subject to. 
     To reinforce the tubular body  32  in order to better withstand compression acting in a direction of the thickness TM of the member, each composite member  17  includes at least one reinforcing rib  40  extending along a full length of the cavity  37  from the first end location to the second end location, that is in the illustrated embodiment from the first to second member ends  33 ,  34 . The reinforcing rib  40  comprises an elongated sheet of pultruded composite material which bridges the cavity  37  in a direction of the thickness TM of the composite member  17  so as to resist compression of the tubular body in the direction of the thickness of the member as compressive forces acting on the respective member are typically substantially normal to the wide faces  21 ,  22  of the respective composite member. The rib  40  has a thickness of the order of that of the tubular body  32 . 
     Furthermore, the reinforcing rib  40  is spaced from the interior peripheral  35  surface in a direction of the width WM of the respective composite member. As such, the reinforcing rib forms a cell  42  within the cavity  37  to either side thereof in the width direction of the composite member. The respective cell  42  is defined by a face of each reinforcing rib bordering the cell and a portion of the interior peripheral surface  35 . As such, each cell  42  is an elongate sub-compartment of the respective cavity  37 . 
     Typically, the fasteners  30  are arranged at the intersecting locations IL to pass through each layer of composite members generally centrally through one of the cells  42  of each composite member so as to extend through to the respective member  17  to the side of the reinforcing rib(s) at a spaced location therefrom so as to clear of same. This is best shown in  FIG. 3  where a pair of fasteners  30  are shown passing through the layers  13  through  15  for illustrative purposes at only one of the intersecting locations IL. 
       FIG. 3  shows tubular composite members of the second layer  14  having different numbers of reinforcing ribs. In an arrangement having more than one reinforcing rib, each rib  40  is spaced from the next in the direction of the width WM of the composite member thus forming three or more cells  42 . 
     It will be appreciated that with the cavity  37  spanning the full length of the respective member  17 , edges of the respective reinforcing rib  40  are flush with a peripheral rim at each of the first and second member ends  33 ,  34 . Further, it will be appreciated the tubular body  32  and reinforcing rib(s)  40  are formed unitarily during manufacturing of the composite member  17 , that is during the pultrusion process. 
     Each composite member  17  of the composite mat  10  may have example dimensions as follows:
         Thickness TM of 1″ and width WM of 6″;   Thickness TM of 2.25″ and width WM of 10″.
 
Thus, the thickness TM of the respective member  17  may lie in a range between 1″ and 2.25″ and a width WM lying in a range between 6″ and 10″.
       

     Additionally, typically each mat  10  includes a connecting arrangement so that it is connectable to another such mat and whereby a series of the mats may be connected together by cooperating male and female components on each mat. In the illustrated embodiment as shown in  FIG. 2  and not in  FIG. 1  for convenience of illustration, the connecting arrangement comprises a series of fingers  44  located at evenly spaced transverse positions at the first end  25  of the mat. The fingers  44  are formed by arranging selected ones of the composite members  17  of the first bottom layer  13  to project beyond the first mat end  25 . As these selected members  17  are offset longitudinally in a longitudinal direction of the second mat end  26  from ends  34  of adjacent members  17  of the first layer  13 , gaps are defined at the second mat end as each end of the respective selected composite member is spaced longitudinally inwardly of the second mat end  26 . As such, finger-receptacles  46  are delimited by one narrow face of each of the adjacent members of the first layer and by the inwardly spaced member end of the respective selected composite member. In this manner cooperating male and female components are formed for connecting adjacent mats together. 
     Thus, two or more mats  10  are linkable together in a string of the mats by inserting the fingers  42  of a first mat into the receptacles  46  of a second adjacent mat. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.