Patent Publication Number: US-2016222598-A1

Title: Access mat

Description:
FIELD 
     There is described an access mat to allow access to environmentally sensitive areas, these access mats are also referred to by various other names such as: “rig mats”, “road mats”, “site mats” or “swamp mats”. 
     BACKGROUND 
     The standard that other access mats are measured against are lumber access mats that use 160 to 200 bolts to secure the lumber together. There have been numerous attempts to replace the bolted lumber access mats with other forms of mats. To date the alternative mats have not been successful in supplanting bolted lumber access mats. There will hereinafter be described an alternative form of access mat. 
     SUMMARY 
     There is provided an access mat has a rectangular body having a length dimension and a width dimension. The body includes three laminated layers of lumber laminated together by an adhesive and pressure, with each of the lumber having a longitudinal axis. A first layer of the at least three layers has a plurality of lumber, with the longitudinal axis of each lumber in a parallel orientation extending across the length dimension. A second layer of the three layers has a plurality of lumber with the longitudinal axis of each lumber in a parallel orientation extending across the width dimension. A third layer of the three layers has a plurality of lumber with the longitudinal axis of each lumber in an angular orientation relative to the longitudinal axis of the plurality of lumber of the second layer. Connectors are provided for connecting the body with other like bodies. 
     This cross-laminated lumber access mat was tested against bolted lumber access mat and, as will hereinafter be described, substantially out-performed the bolted lumber access mat. It is, of course, possible to fabricate a cross-laminated access mat having just two layers or more than three layers. A cross-laminated access mat having just two layers is not believed to have the requisite strength and stiffness. It would not be practical given the loads and abuse to which it would be subjected. A cross-laminated access mat having more than three layers would be viable, but each layer increase weight and at some point additional layers would tend to be redundant. 
     It is preferred that the longitudinal axis of each lumber of the plurality of lumber of the second layer is in an orientation that is perpendicular to the orientation of the lumber of the first layer. It is also preferred that the longitudinal axis of each lumber of the plurality of lumber of the third layer is in an orientation that is perpendicular to the orientation of the lumber of the second layer. It will be appreciated that another angular orientation, such as 45 degrees, would be viable. However, diagonal orientations would tend to reduce the strength of the body and result in a waste of materials during manufacture. 
     To facilitate lamination, it is preferred that the plurality of lumber of the first layer and the plurality of lumber of the second layer be closely spaced. However, it should be noted that it is preferred that the plurality of lumber of the third layer be are spaced farther apart. The reason for this is that it was discovered that removal of the access mats from wet and swampy areas could be problematic due to water adhesion. Having the lumber of the third layer spaced apart serves to relieve surface tension of the water. It also reduces the weight of the body, as fewer lumber are used. 
     There are various types of connectors that are well known for access mats. The form of connectors used is not critical to obtaining beneficial results from the access mat. The preferred form of connector, which will hereinafter be further described, is positioned at the ends of the body. The body has a first end and a second end. One of the connectors is a series of projecting tongues at one of the first end or the second end. Another of the connectors is a series of recessed tongue receivers at another of the first end or the second end. Each of the tongues of one access mat engage one of the tongue receivers of another access mat to connect the body with other like bodies. Some access mats connect at both the sides and the ends. These access mats are only intended to connect at their respective ends. The sides are allowed to “float” without connection. It will be appreciated that side connectors could be added, if desired or if the application required such side connectors. 
     One innovation in relation to the connectors is having each of the projecting tongues secured to the body by removable fasteners. This is very useful as it enables projecting tongues to be removable to facilitate replacement of damaged tongues. If the projecting tongues could not be replaced, damage to the projecting tongues could render the access mat useless as it could no longer connect with other access mats. 
     It is preferred that each of the projecting tongues and tongue receivers are positioned in the third layer. The third layer is the bottom layer. When the projecting tongues and tongue receivers are positioned in the bottom layer, the first layer (which is the top layer and the travel surface) is free from any obstruction which might catch during snow removal, serve to accumulate mud or otherwise interfere with movement along the travel surface. 
     At some sites, the access mats are positioned using a piece of equipment referred to as a “button top grapple”. The button top grapple is a tracked vehicle that uses pinchers having sharp teeth to grab the mats one each side. Each layer has a peripheral side edge. It is preferred that the peripheral side edge of the second layer extend outwardly past the peripheral side edge of the first layer and the third layer. The teeth of the pinchers on the button top grapple engage these peripheral side edge projections, and this protects the first layer and the third layer from sustaining damage to their respective peripheral side edges. 
     At other sites, the access mats are handled by fork lifts. Fork lift engagements, can sometimes cause corner damage. It is, therefore, preferred that metal elements be positioned at each corner of the body to protect the body from corner damage. The metal elements can be as simple as some bolts strategically positioned in the corners, where fork lift impact may occur. 
     Environmental disposal of access mats can be a problem. Especially bolt lumber access mats which may have welded metal frames and 160 to 200 bolts. Apart from the fasteners securing the projecting tongues and the metal elements protecting each corner of the body (optional features which may or may not be included in a customer&#39;s order), the body of the cross-laminated access mat has no metal components. Upon removal of the fasteners securing the projecting tongues and the metal elements protecting each corner of the body, the body can be disposed of on-site through chipping and spreading. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein: 
         FIG. 1  is a top perspective view of a cross-laminated access mat. 
         FIG. 2  is a bottom plan view of the access mat illustrated in  FIG. 1 . 
         FIG. 3  is a side elevation view of the access mat illustrated in  FIG. 1 . 
         FIG. 4  is a detailed section view of the access mat illustrated in  FIG. 2 . 
         FIG. 5  is a travel surface formed with a plurality of the access mat illustrated in  FIG. 1 . 
         FIG. 6  is a graph providing a maximum load comparison between the access mat of  FIG. 1  and a bolted lumber access mat. 
         FIG. 7  is a graph providing a deflection comparison between the access mat of  FIG. 1  and a bolted lumber access mat. 
         FIG. 8  is a graph providing a stiffness after prolonged use comparison between the access mat of  FIG. 1  and a bolted lumber access mat. 
     
    
    
     DETAILED DESCRIPTION 
     An access mat generally identified by reference numeral  10 , will now be described with reference to  FIG. 1  through  FIG. 8 . 
     Structure and Relationship of Parts: 
     Referring to  FIG. 1 , access mat  10  has a rectangular body  12  having a length dimension indicated by arrow  14  and a width dimension indicated by arrow  16 . Referring to  FIG. 3 , body  12  includes three laminated layers of lumber  18 , including: a first layer  20 , a second layer  22  and a third layer  24 . Referring to  FIG. 1 , each of lumber  18  has a longitudinal axis  26 . Referring to  FIG. 1 , first layer  20  has a plurality of lumber  18 , with longitudinal axis  26  of each lumber  18  in a parallel orientation extending across one of length dimension  14  or width dimension  16 . An orientation across length dimension  14  has been illustrated. Referring to  FIG. 3 , second layer  22  has a plurality of lumber  18  with a longitudinal axis  26  of each lumber  18  in a parallel orientation extending across another of length dimension  14  or width dimension  16 . An orientation across width dimension  16  has been illustrated, as first layer  20  was previously illustrated as being oriented across length dimension  14 . Referring to  FIG. 2 , third layer  24  has a plurality of lumber  18  with longitudinal axis  26  of each lumber  18  in an angular orientation relative to longitudinal axis  26  of the plurality of lumber  18  of second layer  22 , the layers being laminated together by application of an adhesive and pressure. It will be appreciated that a cross-laminated access mat having more than three layers would be viable, but each layer increases weight and at some point additional layers would tend to be redundant. Longitudinal axis  26  of each lumber  18  of the plurality of lumber  18  of second layer  22  is in an orientation that is perpendicular to the orientation of lumber  18  of first layer  20 . Similarly, longitudinal axis  26  of each lumber  18  of the plurality of lumber  18  of third layer  24  is in an orientation that is perpendicular to the orientation of lumber  18  of second layer  24 . It will be appreciated that another angular orientation, such as 45 degrees, would be viable. However, diagonal orientations would tend to reduce the strength of body  12  and result in a waste of materials during manufacture. Referring to  FIG. 3 , the plurality of lumber  18  of first layer  20  and the plurality of lumber  18  of second layer  22  are closely spaced. In contrast, the plurality of lumber  18  of third layer  24  are spaced farther apart leaving a clearly discernable gap  25 . The reason for this is that it was discovered that removal of access mats  10  from wet and swampy areas could be problematic due to water adhesion. Having lumber  18  of third layer  24  spaced apart with a gap  25  serves to relieve surface tension of the water. It also reduces the weight of the body, as fewer lumber are used. 
     Connectors are provided for connecting body  12  with other like bodies. There are various types of connectors that can be used, the form of connectors is not critical. Referring to  FIG. 2 , body  12  has a first end  30  and a second end  32 . One of the connectors is a series of projecting tongues  34 , which project past first end  30 . Another of the connectors is a series of recessed tongue receivers  36  at second end  32 . Referring to  FIG. 5 , each of projecting tongues  34  of access mat  10  engage one of tongue receivers  36  of another access mat to connect body  12  with other like bodies. Some access mats connect at both the sides and the ends. These access mats are only intended to connect at their respective ends  30  and  32 . The sides are allowed to “float” without connection. It will be appreciated that side connectors could be added, if desired or if the application required such side connectors. In  FIG. 5 , access mat  10  in the foreground has been flipped over, to show the comparative spacing of third layer  24 , as compared to the spacing of lumber  18  on first layer  20  for the remaining access mats  10 . Referring to  FIG. 2 , it should be noted that projecting tongues  34  and tongue receivers  36  are positioned in third layer  24  and that third layer  24  is the bottom layer. When the projecting tongues  34  and tongue receivers  36  are positioned in third layer  24 , first layer  20  (which is the top layer and the travel surface) is free from any obstruction which might catch during snow removal, serve to accumulate mud or otherwise interfere with movement along the travel surface. Referring to  FIG. 2 , it is preferred, but not essential, that each of projecting tongues  34  be secured to body  12  by removable fasteners. This is very useful as it enables projecting tongues  34  to be removable to facilitate replacement of damaged projecting tongues  34 . If projecting tongues  34  could not be replaced, damage to the projecting tongues  34  could render access mat  10  useless as it could no longer connect with other access mats. It is important to note that access mats  10  are made from cross-laminated lumber and do not require any fasteners. Referring to  FIG. 4 , fasteners used to secure projecting tongues are bolts  39  having a rounded head  41  and a nut  43  secured at a remote end  45 . Remote end  45  and nut  43  are positioned in a recess  47 , so that no portion of bolt  39  projects below third layer  24  which serves as the bottom layer. 
     There are some optional features which may be added to protect access mats from damage during handling. At some sites, access mats  10  are positioned using a piece of equipment referred to as a “button top grapple”. The button top grapple is a tracked vehicle that uses pinchers having sharp teeth to grab the mats one each side. Referring to  FIG. 4 , each layer of body  12  has edges  38 . It is preferred that edges  38  of second layer  22  extend outwardly past side edges  38  of first layer  20  and third layer  24  to form a side edge projection  42 . The teeth of the pinchers on the button top grapple engage side edge projection  42 , and this protects first layer  20  and third layer  24  from sustaining damage to their respective side edges  38 . 
     At other sites, access mats  10  are handled by fork lifts. Fork lift engagements, can sometimes cause corner damage. It is, therefore, preferred that metal elements be positioned at each corner  46  of body  12  to protect body  12  from corner damage. Referring to  FIG. 2 , the metal elements illustrated are bolts  48  positioned at corners  46 , to strengthen corners  46  where fork lift impact may occur. As discussed with reference to bolts  39 , bolts  48  are also recessed so that they do not project below third layer  24 , which serves as the bottom layer. 
     Environmental disposal of access mats can be a problem. Especially bolt lumber access mats which may have welded metal frames and 160 to 200 bolts. Apart from four fasteners  38  securing each projecting tongues  34  and four bolts  48  protecting each corner  46 , body  12  of access mat  10  has no metal components. Upon removal of bolts  39  securing the projecting tongues and the bolts  48  protecting each corner  46 , body  12  can be disposed of on site through chipping and spreading. 
     Comparative Testing Cross-Laminated Access Mats compared to Bolted Lumber Access Mats: 
     Referring to  FIG. 6 , access mats  10  are more than twice the strength of bolted mats. During testing, access mat  10  collapsed with a weight of 58,411 lbs, while a bolted lumber access mat of the same material crumbled at just 25,550 lbs. Referring to  FIG. 7 , at the point of collapse, the bolted lumber access mat flexed 8.88″, while access mat  10  only flexed a mere 1.60″. The tests clearly showed the stiffness and strength of access mat  10  far exceeded that of the bolted lumber access mat. 
     Referring to  FIG. 8 , a further test was conducted to simulate prolonged use. Each of the access mats were tested in third point bending with a span of 144″. Each of the access mats was cycled 100 times up to 10,000 lbs. After this abuse, another stiffness test was performed. Both of the access mats were loaded to failure. The maximum load and deflection at maximum load were recorded. The tests showed the comparative deterioration of the access mats over prolonged use, with access mat  10  again outperforming the bolted lumber access mat. 
     Access mats typically have a 14 foot length and an 8 foot width. As described above, it is preferred that cross-laminated access mats  10  be made from three layers. The lumber is, preferably, kiln dried and made from better quality lumber. The preferred type of lumber is SPF with the travel layer being of Douglas Fir. 
     When additional layers are added cross-laminated access mats can be used for a different purpose. For example, by adding more layers, access mat could be used to support the weight of a drilling rig or the weight of a crane. The number of layers, from 4 to 9, depend upon the size of the drilling rig or the size of the crane. 
     Advantages of Cross-Laminated Access Mats compared to Bolted Lumber Access Mats: 
     Access mats  10  provide the following damages, as compared to bolted lumber access mats: 
     1. Access mats  10  are more than twice as strong. 
     2. Access mats  10  have more than four times the stiffness. 
     3. Access mats  10  are better able to maintain stiffness after rigorous use. 
     4. Access mats  10  maintain shape and do not diamond or deform if mishandled. 
     5. Access mats  10  have no bolts protruding on the travel layer, so that tire damage due to bolts is eliminated. 
     6. Access mats  10  have an extended middle layer to minimize damage during installation and removal. 
     7. Access mats  10  have easy to replace tongues, so that they are not put out of service by tongue damage. 
     8. Access mats  10  are of cross-laminated lumber and are easily recycled through chipping. 
     9. Access mats  10  are of relatively light weight, so that freight costs are reduced. 
     In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
     The illustrated embodiments have been set forth only as examples and should not be taken as limiting a purposive interpretation of the claims.