Patent Publication Number: US-11661749-B2

Title: Vertical joint system for a surface covering panel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 16/699,297, filed on Nov. 29, 2019, which is a continuation of U.S. application Ser. No. 16/392,931, filed on Apr. 24, 2019, which is a continuation of U.S. application Ser. No. 15/507,602, filed on Feb. 28, 2017, now U.S. Pat. No. 10,316,526, which is a U.S. national stage of International Application No. PCT/AU2015/000531, filed on Aug. 31, 2015, which claims the benefit of Australian Application No. 2014903452, filed on Aug. 29, 2014. The entire contents of each of U.S. application Ser. No. 16/699,297, U.S. application Ser. No. 16/392,931, U.S. application Ser. No. 15/507,602, International Application No. PCT/AU2015/000531, and Australian Application No. 2014903452 are hereby incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a vertical joint system for a surface covering panel such as but not limited to a floor panel, wall panel or ceiling panel. 
     BACKGROUND ART 
     One form of vertical joint system for a surface covering panel may include male and female parts. The male and female parts are formed along the sides of the panel. The male and female parts engage each other to join corresponding panels when moved toward each other in a direction perpendicular to a plane of the panels. When the panels are flooring panels this direction is a vertical direction. The male and female parts have surfaces that contact each other to arrest vertical separation of engaged panels. 
     One potential problem with vertical joint systems is “lipping”. Lipping occurs when the upper edge of one panel lifts from the upper edge of the adjoining panel. This creates a lip or step at the upper edges of adjacent joined panels. To assist in reducing lipping one practice is to provide the contacting surfaces of the male and female parts at the front end of the joints. The front end of the joint is the end closest to an upper edge of an upper surface of the panels. An example of this is shown in U.S. Pat. No. 7,552,568 in which the front end of a male part has a surface formed with a locking heal that contacts a locking surface formed on the surface at the front end of a female part. An alternate practice is to uses separately manufactured plastic inserts or clips that are fitted into the panels. However this adds to manufacturing costs and the insert/clips at times fall out of the panels during transport and handling. 
     The above description of the background art does not constitute an admission that the art forms the common general knowledge of a person of ordinary skill in the art. Further, the above description is not intended to limit the application of the vertical joint system. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect there is disclosed a vertical joint system for a surface covering panel having an upper surface which is visible when the surface covering is laid and an opposed lower surface and a plurality of sides located between the upper and lower surfaces, the vertical joint system comprising:
         a male part along a first of the sides;   a female part along a second of the sides, the second side being opposite to the first side;   the female part having a protrusion that extends from the lower surface toward the upper surface and an outer most female surface on the protrusion,       

     the male part having a recess that opens onto the lower surface, a portion of the recess forming an inner most male surface; and
         wherein the outer most female surface and the inner most male surface arranged so that when the male part of one surface covering panel is engaged with a female part of a second surface covering panel the outer most female surface overlies the inner most male locking surface at a first location and a second location.       

     In one embodiment in at least one of the first and second locations the outer most female surface and the inner most male surface contact each other when the lower surfaces of two joined like panel lie in a common plane. 
     In one embodiment the outer most female surface and the inner most male surface contact each other at the first location and wherein the first location is closer to the lower surface than the second location. 
     In one embodiment the second location overhangs the first location. 
     In one embodiment the inner most male surface at the first location has a first surface portion with a first tangent plane at a first region of contact with the outer most female surface that is inclined at an angle θ m ° in the range of about 15° to 75° to a plane parallel to the upper surface. 
     In one embodiment the angle θ m ° is about 45° to a plane perpendicular to the upper surface. 
     In one embodiment the first surface portion is one of: a surface portion of a generally convex protuberance; and a planar surface portion. 
     In one embodiment the outer female surface adjacent the first region of contact and on a side nearest the bottom surface is generally inclined at an angle θ f °≤θ m °. 
     In one embodiment the angle θ f ° is about 15° to the plane parallel to the upper surface. 
     In one embodiment inner most male surface at the second location has a second surface portion with a second tangent plane at a second region of contact with the outer most female surface that is inclined at an angle β m ° in the range of about 15° to 75° to a plane parallel to the upper surface. 
     In one embodiment the second tangent plane is inclined at an angle β m ° of about 45° to a plane parallel to the upper surface. 
     In one embodiment at the second location the outer most female surface at the second region of contact with the inner most male surface has a surface portion lying in the second tangent plane. 
     In one embodiment the male part has a male protrusion adjacent to the male recess with an outer most male surface formed on the male protrusion distant the male recess; the female part has a female recess adjacent the female protrusion, wherein the female recess has an inner most female surface distant the female protrusion; and wherein inner most female surface overlies the outer most male surface. 
     In one embodiment the inner most female surface is provided with a series of contiguous recesses and the outer most male surface is provided with a nib; the inner most female surface and the outer most male surface configured so that when the male part is fully engaged with the female part the nib resides in a lowest one of the contiguous recesses; and in response to a relative rotation or uplift of the male part relative to the female part the nib can enter respective higher recesses sequentially to provide resistance to the withdrawal of the male protrusion from the female recess. 
     In one embodiment the female part has a datum surface on which the male part bears when the male and female parts of respective vertical joint systems, the datum surface providing a depth control for the male part when inserted into the female part. 
     In one embodiment the continuous gap extends between the male part and the female part from the datum surface to the second location. 
     In one embodiment the continuous gap extends between the male part and the female part from the datum surface to the first location. 
     In one embodiment the female part has a datum surface on which the male part bears when the male and female parts of respective vertical joint systems, the datum surface providing a depth control for the male part when inserted into the female part; and wherein the male and female parts are configured to contact each other when engaged at the one or both of the first and second locations in a manner to press the datum surfaces together. 
     In one embodiment the vertical joint system comprises a continuous gap from a location where the datum surfaces contact each other to a nearest one of the first location and the second location at which the male and female part contact each other. 
     In one embodiment the male part has a common male surface that lies on both the male protrusion and the male recess, the female part has a common female surface that lies on both the female protrusion and the female recess and wherein the vertical joint is configured so that when the male and female parts of respective vertical joint systems are coupled together with the respective lower surfaces in a common plane, a continuous gap is provided between the inner most female surface and the outer most male surface from the datum surfaces to at least the common male surface. 
     In a second aspect there is disclosed a vertical joint system for a surface covering panel having an upper surface which is visible when the surface covering is laid and an opposed lower surface and a plurality of sides located between the upper and lower surfaces, the vertical joint system comprising:
         vertically engageable locking parts on at least two opposed sides, the locking parts having proximal mutually receivable components near an edge of the upper surface of a panel in which the vertical joint system is provided, and distal mutually receivable components near an edge of the lower surface of the panel, and wherein the distal components are configured so that when the respective locking parts of two panels with the same vertical locking system are engaged, a surface on a side of one of the distal components nearest the lower surface overlies a surface on a side of the other distal component nearest the lower surface at a first location and a second location.       

     In one embodiment the proximal components have respective datum surfaces which contact each other providing a depth control mechanism for the vertical joint system when two panels with the same vertical joint system are engaged so that the upper surfaces of the two panels are substantially coplanar. 
     In one embodiment the distal parts of two like joint systems are configured to contact each other when engaged at the one or both of the first and second locations in a manner to press the datum surfaces together. 
     In one embodiment the surface on the side of the other distal component at the first location has a first surface portion with a first tangent plane that is inclined at an angle θ m ° in the range of about 15° to 75° to a plane parallel to the upper surface. 
     In one embodiment the angle θ m ° is about 45° to the plane parallel to the upper surface. 
     In one embodiment the vertical joint system comprises a continuous gap from a location where the datum surfaces contact each other to one of: the first location; the second location; and the lower surface. 
     In a third aspect there is provided vertical joint system for a surface covering panel having an upper surface which is visible when the surface covering is laid and an opposed under surface and a plurality of sides located between the upper and under surfaces, the vertical joint system comprising:
         a male part along a first of the sides;   a female part along a second of the sides, the second side being opposite to the first side;   the male and female parts being configured so that when the male part of one surface covering panel is engaged with a female part of a second surface covering panel to create an engaged joint having a proximal end near respective upper edges of upper surfaces of the panels and a distal end near respective lower edges of lower surfaces of the panels:   (a) at the proximal end of the engaged joint the male part rests on the female part in a datum plane controlling a depth of insertion of the male part in the female part so that the upper surfaces of the panels are co-planar;   (b) at the distal end of the engaged joint the male part at contacts on overlying portion of the female part to hold or press the male and female parts together at the datum plane.       

     In one embodiment the male and female parts are configured so that in the engaged joint a continuous gap is formed between the male and female part from the datum plane to where the male part at contacts on overlying portion of the female part. 
     In one embodiment the male and female parts are configured so that in the engaged joint a first continuous gap is formed between the male and female part from the datum plane to an intermediate location and a second continuous gap is formed from the intermediate location to the where the male part at contacts on overlying portion of the female part. 
     In one embodiment at the distal end the male part contacts an overlying portion of the female part at two locations which are spaced from each other. 
     In a fourth aspect there is disclosed a vertical joint system for a surface covering panel having an upper surface which is visible when the surface covering is laid and an opposed under surface and a plurality of sides located between the upper and under surfaces, the vertical joint system comprising:
         a male part along a first of the sides;   a female part along a second of the sides, the second side being opposite to the first side;   the male and female parts being configured so that when the male part of one surface covering panel is engaged with a female part of a second surface covering panel to create an engaged joint having a proximal end near respective upper edges of upper surfaces of the panels and a distal end near respective lower edges of lower surfaces of the panels:   (a) at the proximal end of the engaged joint the male part rests on the female part in a datum plane controlling a depth of insertion of the male part in the female part so that the upper surfaces of the panels are co-planar;   (b) at the distal end of the engaged joint the female part overlies the male part in at least one location; and   (c) a continuous gap is formed between the male and female part from the datum plane to one of: a nearest one of the at least one location; and, the lower surface of the panels.       

     In one embodiment the male part has a first surface portion with a first tangent plane at a first region of contact with a surface portion of the female surface at the distal end of the engaged joint that is inclined at an angle θ m ° in the range of about 15° to 75° to a plane parallel to the upper surface. 
     In one embodiment of each of the above aspects the vertical joint system comprises a laterally extending tongue and a groove, one of each on respective other opposed sides of the panel, the laterally extending tongue and the groove arranged to cooperate with each other to provide a laydown joint between two like panels when mutually engaged along the other opposed sides. 
     In a fifth aspect there is disclosed a vertical joint system for a surface covering panel having first and second opposed major surfaces and a plurality of sides located between the major surfaces, the vertical joint system comprising:
         a male part along a first of the sides;   a female part along a second of the sides, the second side being opposite to the first side;   the male and female parts being relatively configured so that during engagement of like first and second panels each provided with the vertical joint system by bringing the male part of a first panel toward the female part of the second panel in a direction perpendicular to a plane the male part while maintaining contact with the female part also moves laterally toward, then away from and subsequently toward the second panel.       

     In one embodiment the male part has a protrusion and an adjacent recess with a common surface forming a part of both the recess and the protrusion, the common surface being formed with a concavity. 
     In one embodiment the common surface includes a first portion that lies in a plane substantially perpendicular to a plane of a panel, the first portion being contiguous with the concavity. 
     In one embodiment the female part is formed with a female recess and an adjacent female protrusion, wherein the female recess has an inner most female surface and the male protrusion has an inner most male surface, the inner most male surface being on a side opposite the common surface; when the inner most female surface overlies the inner most male surface. 
     In one embodiment the inner most female surface is provided with a series of contiguous recesses and the male surface is provided with a nib; the inner most female surface and the inner most male surface configured so that when fully engaged the nib resides in a lowest one of the recesses; and in response to a relative rotation of the male part and female part the nib can enter respective higher recesses sequentially to provide resistance to the withdrawal of the male protrusion from the female recess. 
     In one embodiment the female protrusion and the male recess are relatively configured so that the female protrusion overlies the male recess in at least two locations which are spaced apart by a gap. 
     In a sixth aspect there is disclosed a vertical joint system for a surface covering panel having first and second opposed major surfaces and a plurality of sides located between the first and lower surfaces, the vertical joint system comprising:
         a male part along a first of the sides, the male part having an inner most male surface, an outer most male surface, and an intermediate common surface;   a female part along a second of the sides, the second side being opposite to the first side, the female part having an inner most female surface, an outer most female surface, an intermediate common female surface;   the inner most female surface being provided with a series of contiguous recesses and the inner most male surface being provided with a nib wherein; the inner most female surface and the inner most male surface are configured so that when fully engaged the nib resides in a lowest one of the recesses; and in response to a relative rotation of the male part and female part the nib can enter respective higher recesses sequentially to provide resistance to the withdrawal of the male protrusion from the female recess.       

     In one embodiment the outer most female surface and the outer most male surface are relatively configured so that the outer most female surface overlies the outer most male surface in at least two locations which are spaced apart by a gap when the male part is engaged in the female part. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
       Notwithstanding any other forms that may fall within the scope of the vertical joint system as set forth in the Summary, specific embodiments will now be described by way of example only with reference to the accompanying drawings in which: 
         FIG.  1   a    is a section view of a single panel showing male and female parts of a first embodiment of the disclosed vertical joint system on opposite sides of the panel; 
         FIG.  1   b    is a schematic representation of two mutually engaged surface covering panels each provided with the first embodiment of the disclosed vertical joint system; 
         FIG.  2    is a schematic representation of a surface covering panel provided with the vertical joint system as depicted in  FIGS.  1   a    and  1   b;    
         FIG.  3    is a schematic representation of two mutually engaged surface covering panels each having a second embodiment of the disclosed vertical joint system; 
         FIG.  4    is a schematic representation of two mutually engaged surface covering panels each having a third embodiment of the disclosed vertical joint system; 
         FIG.  5    is a schematic representation of two mutually engaged surface covering panels each having a fourth embodiment of the disclosed vertical joint system; 
         FIG.  6    is a schematic representation of two mutually engaged surface covering panels each having a fifth embodiment of the disclosed vertical joint system; 
         FIG.  7   a    depicts a surface covering made from engaged panels provide with embodiments of the disclosed vertical joint system; and 
         FIGS.  7   b - 7   k    illustrate a sequence of steps for replacing the damage panel of the surface covering shown in  FIG.  7   a    viewed along section AA. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
       FIG.  1   a - 1   b    and  2  depict a first embodiment of the disclosed vertical joint system  10   a .  FIG.  1   a    shows the joint system  10   a  as a male part  12  and a female part  14  on opposite sides of a panel P.  FIG.  1   b    shows the male joint  12  on one panel P 1  engaged with the female joint of panel P 2  where the panels P 1  and P 2  are identical to panel P. For ease of description the panels P, P 1  and P 2  will be hereinafter referred to in general as “panels P”. Each panel P has an upper surface  16  and an opposite lower surface  18 . The upper surface  16  may be considered as a top or wear surface of the panel P. The lower surface  18  may be considered as the undersurface which would ordinarily face a substrate or other support on which the panels P are laid or otherwise attached. 
       FIG.  2    depicts a rectangular form of the panel P. Here the panel P is formed with opposite longitudinal sides  20  and  22  and opposite transverse sides  24  and  26 . Each of the size  20 ,  22 ,  24  and  26  is located between the first and lower surfaces  16  and  18 . In one embodiment the male part  12  may be formed along a first longitudinal side  20  and the female part  14  may be formed along the opposite longitudinal side  22 . Additionally, a male part  12  can be formed along the transverse side  24  and a female part  14  can be formed along the opposite transverse side  26 . However as exemplified later the panel P can be formed with a male and female joint on only one side each. 
     The male part  12  has a protrusion  28  and an adjacent recess  30 . The protrusion  28  extends in a direction from the upper surface  16  toward the lower surface  18 . The recess  30  is formed or extends from the lower surface  18  toward the upper surface  16 . 
     Starting from the upper surface  16  the male part  12  has an upper edge U from which extends a generally vertical surface  32 . This is followed by a generally datum surface  34  and then an outer most (or proximal) male surface  36 . In this embodiment the datum surface  34  is a planar and horizontal surface. The outer most male surface  36  is generally inclined away from the recess  30  in a direction from the upper surface  16  toward the lower surface  18 . However the outer most/proximal surface  30  does not extend laterally beyond an upper edge U. A lower part of the outer most male surface  36  is formed with a nib  38 . The outer most male surface  36  is at a front or proximal end of the joint system  10   a  as is lies on a surface nearest the upper edge U of the panel Pin which the joint system is made. 
     A bottom surface  37  of the male protrusion is formed with a central concave recess  39  that projects toward the upper surface  16 . The recess provides a space for foreign material such as: wax or other lubricant which may be placed on surfaces of the joint system  10   a ; debris produced during manufacture which has not been fully removed; and debris that exists or is generated on site during installation. A portion of the male protrusion  28  to the left of the recess  39  which includes the outer most male surface  36  and nib  38  may be considered as forming a nose  41  of the protrusion  28 . The portions  37  and  47  provide the bottom end of the protrusion  28  with curved or rounded corners. 
     The male part  12  is also formed with an inner most (or distal) male surface  40 . The inner most/distal male surface  40  is at a back or distal end of the joint system  10   a  as it lies on a surface distant the upper edge U of the panel P in which the joint system  10   a  is made (or conversely closest to a bottom edge B of the panel P). The inner most male surface  40  is formed as a surface of the recess  30 . Located between the outer most male surface  36  and the inner most male surface  40  is a male common surface  42 . The male common surface  42  is a surface which is common to both the protrusion  28  and the recess  30 . 
     The male common surface  42  is formed with a concavity  44 . This is followed by a contiguous male planar portion  46 . The male planar portion  46  lies in a plane perpendicular to that of the surfaces  16  and  18 . Additionally the male planar portion  46  is located between the upper surface  16  and the concavity  44 . A convexly curved surface  47  extends between the concavity  44  and the recess  39 . 
     The outer most male surface  40  is formed with an undulating profile which forms a first generally convex protuberance  48 , a contiguous concave recess  50  and a contiguous second generally convex protuberance  52 . After the protuberance  52  the outer most male surface  40  extends to the major surface  18 . 
     The female part  14  is formed with a female protrusion  54  and a female recess  56  which is inboard of the protrusion  54 . When the male and female parts of like panels P 1  and P 2  are fully engaged the male protrusion  28  is located in the female recess  56  and the female protrusion  54  is located in the male recess  30 . 
     The female recess  56  has a surface  58  that depends generally perpendicular from an upper edge U of the upper surface  16  on a side opposite to that of the male part  12 . Contiguous with the surface  58  is a concavity  60 . The concavity  60  subsequently leads to a datum surface  62  in the recess  56 . The datum surface  62  lies parallel to the upper surface  16  and together with the datum surface  34  constitutes a datum plane for the joint system  10   a . Thus in an engaged joint system  10  both the datum surfaces  34  and  62  lie in the datum plane. The datum surface acts as a depth control for the insertion of the male part of panel P 1  into the female part of panel P 2 . When the datum surface  34  abuts the datum surface  62  insertion of the male part  12  and in particular the protrusion  28  into the female part  14 /recess  56  is halted. This ensures that the upper surfaces  16  of adjacent coupled panels P 1 , P 2  are essentially coplanar. 
     After the datum  62  the female part  14  is provided with an inner most female surface  64  that extends to a root of the recess  56 . The inner most (or proximal) female surface is at a front or proximal end of the joint system  10   a  as it lies on a surface near an upper edge U of the panel P in which the joint system is made. The inner most female surface  64  is formed with a plurality of recesses  66 ,  68  and  70 . The recess  70  is closest to the root of the recess  56 . 
     The female joint  14  is also formed with an outer most (or distal) female surface  72  on a side of the female protrusion  54  distant the recess  56 . The outer most female surface is at a back or distal end of the joint system  10   a  as it lies on a surface distant the upper edge U of the panel P in which the joint system is made (or conversely closest to a bottom edge Y of the panel P). A female common surface  74  forms part of the surface of both the female recess  56  and the female protrusion  54 . 
     The outer most female surface  72  is formed with a generally undulating profile and includes a first protuberance  76  followed by a concavity  78  followed by a contiguous second protuberance  80 . Contiguous with the second protuberance  80  is a further concavity  82 . The concavity  82  then leads to the lower surface  18  and edge Y on the female side. 
     The female common surface  74  includes a female generally planar portion  84  followed by a contiguous convex portion  86 . The female planar portion  84  is located between the convex portion  86  and the lower surface  18 . The female protrusion  54  has a very slightly curved, indeed almost planar, top surface  87  that is substantially parallel with the upper and lower surfaces  16 ,  18 . The portions  86  and  76  provide curved or rounded corners to the upper end of the protrusion  54 . 
     The inner most (i.e. distal) male surface  40  and the outer most (i.e. distal) female surface  72  can be considered to be a clasping surfaces because when male and female parts  12 ,  14  of the joint system  10   a  are engaged these surfaces are able to clasp each other to arrest vertical separation of engaged panels P. 
     In this embodiment the there is a minimum of about 30% of the thickness of the material of the panel P from the bottom of the recess  56  to the lower surface  18 . The location L 1  is at a horizontal level marginally below the bottom of the recess  56  and the second location L 2  is horizontal level above the bottom of the recess  56 . 
     When the male joint  14  of one panel P 1  is fully engaged with the female joint  16  of a second panel P 2  with the respective lower surfaces  18  coplanar, the following relationships between respective surfaces in parts of the joints exist: 
     (a) The surfaces  32  and  58  abut or are closely adjacent so as to form no gap or at least no easily discernable gap between joint panels P 1  and P 2  when viewed from a normal standing position. 
     (b) The datum surface  34  abuts the datum surface  62 . This forms a depth control mechanism so that the major surfaces  16  of the join panels P 1  and P 2  are substantially co-planar. Moreover the back end of the joint constituted by the male and female surfaces  40  and  72  when in contact at location L 1  generate tension or force in the protrusion  28  pulling the datum  34  onto the datum surface  62 , or otherwise pushing or pressing the datum surfaces  43 ,  62  together. In this way the contacting datum surfaces  34 ,  62  and the contacting surfaces at L 1  act to claps the joint together. 
     (c) The nib  38  resides in the lower most recess  70 . These provide a back-up or secondary vertical arrestment or grab resisting removal of the protrusion  28  from the recess  56 . However due to the existence of a gap between the proximal male surface  36  and proximal female surface  64  these surfaces do not provide a vertical locking function when the panels P are in a neutral plane, i.e. when the surfaces  18  of the joined panels P 1  and P 2  are co-planar. 
     (d) The male and female planar surfaces  46  and  84  face each other. The surfaces  46  and  84  may be in contact with each other or slightly spaced from each other. This can be dependent on environmental conditions such as temperature, manufacturing tolerances, and the condition of the underlying surface on which the panels are laid. However vertical joint  10   a  can be designed to ensure the existence of a gap in all expected environmental conditions or to ensure contact of the surfaces  46  and  84  in all expected environmental conditions. The gap when provided between the surfaces  46  and  84  can assist in allowing relative sliding between panels which can assist in the engagement of panels P together. Also the existence of such a gap can allow for the take up of wax or other lubricant. 
     (e) The outer most female surface  72  overlies the inner most male surface  40  in at least a first location L 1  and a second location L 2 . The first location L 1  is a lower of the locations, being closer to the lower surface  16 , and coincides with the location of protuberance  80 . The second of the locations L 2  is a higher of the locations and coincides with the location of the protuberance  76 . Thus in general terms the protuberance  76  overlies the protuberance  48  while the protuberance  80  overlies the protuberance  52 . The two locations L 1  and L 2  are spaced by a gap  88 . The gap  88  is formed between the concavities  50  and  78 . Also the second location L 2  overhangs the first location L 1 . The gap  88  and moreover the concavities/recess  50  and  78  provided relief during the engagement of the male and female parts enabling the parts to fit together without the need for heavy blows with a mallet and/or substantial deflection or distortion of the material in the joint. Such deflection or distortion can damage or break parts of the joint. Also when the panel is made of a plastics material, the material may maintain a degree of the deflection after engagement due to material memory. This results in lipping at the very time of, and due to, installation. 
     In the present embodiment the outer most (distal) female surface  72  contacts the inner most male surface  40  at least at the first location L 1 . This forms the primary vertical lock or arrestment for the joint system. The expression “vertical lock or arrestment” means locking or arresting vertical separation between the engaged panels. Also in this embodiment the surfaces  40  and  72  also contact each other at the second location L 2  simultaneously with contact at location L 1  so as to also form part of the primary vertical lock or arrestment. But in other embodiments this need not be the case. For example the protuberances  76  and  48  may be spaced apart when joined panels P are in the neutral plane but arranged to contact each other when the panels are either (i) under compression in a direction tending to push the surfaces  40  and  72  together, or (ii) relatively rotated as would occur during removal of say panel P 1  from panel P 2  where panel P 1  may be gripped (for example by a suction cup) and pulled upwardly and away from panel P 2 . 
     At the first location L 1  the inner most (i.e. distal) male surface has a first surface portion with a first tangent plane Tim that is inclined at an angle θ m  in the range of about 15° to 75° to a plane parallel to the upper surface. The first surface portion is constituted by a surface portion of the generally convex protuberance  52 . This surface portion could be either curved or planar. When it is planar (as shown in the embodiment of  FIGS.  1   a  and  1   b   ) then the plane of the surface portion is also parallel with the tangent plane T 1 . The angle θ m  may be any angle within the above range for example 15°, or 45° or 75°. Also the angle θ m  may be constituted by any sub range within the range of about 15° to 75°, for example 30° to 60°. In this embodiment the angle θ m  is 45°. 
     At the first location L 1  the outer most (distal) female surface  72  also has a first surface portion  81  with a first tangent plane T 1   f  that is inclined at the angle θ f . The first surface portion  81  of the outer most female surface is constituted by a surface portion of the generally convex protuberance  80 . This surface portion could be either curved or planar. In any event θ f °≤θ m °, and preferably θ f °&lt;θ m °. In one example θ m =45° and θ f =15°. 
     At the second location L 2  the inner most male surface has a first surface portion with a first tangent plane T 2   m  that is inclined at an angle β m  in the range of about 15° to 75° to a plane perpendicular to the upper surface. The first surface portion is constituted by a surface portion of the generally convex protuberance  48 . This surface portion could be either curved or planar. When it is planar (as shown in the embodiment of  FIGS.  1   a  and  1   b   ) then the plane of the surface portion is also parallel with the tangent plane T 2   m . The angle β m  may be any angle within the range for example 15°, or 45° or 75°. Also the angle β m  may be constituted by any sub range within the range of about 15° to 75°, for example 30° to 60°. 
     At the second location L 2  the outer most female surface also has a first surface portion with a first tangent plane T 2   f  that is inclined at the angle β f . The first surface portion of the outer most female surface is constituted by a surface portion of the generally convex protuberance  76 . This surface portion could be either curved or planar. When it is planar (as shown in the embodiment of  FIGS.  1   a  and  1   b   ) then the plane of the surface portion is also or at least is parallel with the tangent plane T 2   f . In the present embodiment β f =β m , but more generally β f ≤β m    
     The distal male and female surfaces  40  and  72  in effect provide a primary dual or two stage vertical lock at the back end of the joint when in contact with each other at both locations L 1  and L 2 . 
     (f) In this embodiment there is a continuous gap between the male and female parts  12 ,  14  from the location where the datum surface  34  contacts the datum  62  to the location L 2  where the protuberances  48  and  76  contact each other. However as will be exemplified in later, in other embodiments there may be contact between the planar surfaces  46  and  84  so as to divide the previously mention gap into two parts; one part from the contacting datum  62  and datum surface  34  to the contacting surfaces  46  and  84 , and a second part from the other side of the contacting surfaces  46  and  84  to the location L 2 . In yet another variation the second part can be extended to the location L 1  when the protuberances  76  and  48  are spaced apart. Further it is believed that in a further embodiment there may be a continuous gap from between where the datum surface  34  contacts the datum surface  62  all the way to the bottom surface  18 . 
     When the male and female parts are being engaged the male part  12  is first laid on top of a female part  14  so that the protrusion  28  is generally above the recess  56  and the recess  30  is generally above the protrusion  54 . The convexly curved surface  47  will rest initially on the convexly curved surface  86 . Also the planar surface  46  will be substantially parallel with but slightly aback of the planar surface  84 . When applying pressure in a vertical direction on the panel P 1  to engage with panel P 2  the surface  47  slides along the surface  86 . Thus while the protrusion  28  is moving in a generally vertical direction more deeply into the recess  56  it is also being translated in a lateral direction toward the panel P 2 . 
     As the downward motion of the male protrusion  28  continues eventually the convex portion  86  on the common female surface  74  enters the recess  44  on the male common surface  42 . It will be appreciated that this will result in a lateral translation of the male protrusion  28  away from the panel P 2  and the inner most female surface  64 . This translation provides a gap or space enabling easier entry of the protrusion  28  into the recess  56  and additionally easier entry of the protrusion  54  into the recess  30 . 
     As the motion of the panels P 1  and P 2  toward each other continues the recess  44  passes the convex portion  86  so that the male protrusion  28  now commences lateral motion toward the panel P 2  bringing the first male and female surfaces  36  and  64  closer together as well as the male and female engagement surfaces  40  and  72  closer together. Eventually the downward motion of the male part  12  into the female part  14  is arrested by the datum surface  34  contacting the datum surface  62 . This provides depth control resulting in the surfaces  16  of the panels P 1  and P 2  being co-planar when the panels P 1  and P 2  are finally fully joined. 
     Simultaneous with this at the back end of the joint initially the protuberance  76  sits in the recess  50 . Subsequently the protuberance  52  slides over the protuberance  76  and into the recess  78 . There after the protuberance  52  engages the protuberance  80  and the protuberance  48  slides under the protuberance  76 . This provides the primary vertical locking of the joint system  10   a . The male protrusion  28  sits in the female recess  56  but the proximal male surface  36  is spaced from the proximal female surface  64  at the front end of the joint system. Thus ordinarily the when the joined panels are in the neutral plane and generally unstressed the front end of the joint system  10   a  does not provide a vertical lock. 
     From the above description it will be appreciated that when the male and female joints  12  and  14  are being joined while the predominant motion is a vertical motion there is also slight lateral movement toward, away and then again toward each other. This greatly assists in the joining or insertion process. This is particularly beneficial when the panels provided with the male and female joints  12  and  14  are made from a plastic or composite material such as luxury vinyl tile (LVT), wood plastic composite material (WPC), or other plastics/PVC materials. However, it is to be understood that embodiments of the vertical joint system  10  are not limited to such materials. For example other materials from which the panels P may be made include natural timber, manufactured wood, wood laminates, and synthetic materials. The male and female parts  12 ,  14  can be cut, milled, extruded, or molded, or a combination thereof, into the panels P depending on the materials from which they are made and required manufacturing tolerance. 
     Once a surface covering for example a floor made from panels joined with a vertical joint system is laid it is subjected to contraction and expansion mainly due to temperature variations. Also forces are applied by the action of people walking on the floor and furniture placed or moving on the floor. A common problem with jointed flooring panels particularly made from plastics material is gapping at the joint and self-disengagement due to the a protrusion rotating out of a recess. 
     In the present embodiment of the vertical joint system  10  gapping and self-disengagement is attempted to be avoided by the interaction between:
         (i) the respective inner most male engagement surface  40  and outer most female engagement surface  72 ;   (ii) the common male surface  42  and female surface  74 ; and   (iii) the outer most male engagement surface  36  and inner most female engagement surface  64 .       

     The interaction between the inner most male surface  40  and outer most female surface  72  in resisting disengagement arises initially from the contact between the protuberances  52  and  78  at the location L 1 . This presents the primary vertical disengagement mechanism. Forces which act to vertically separate coupled male and female parts  12 ,  14  may be initially resisted by the engagement of the surfaces at location L 1 . 
     Substantially simultaneously (or shortly thereafter if they are initially spaced apart) the surfaces  40  and  72  increase their contact against each other at the second location L 2 . This is also believed to causes a re-direction of the separating force in a plane perpendicular to the tangent plane T 2  tending to close or at least resist the widening of the recess  56 . 
     Finally depending on the magnitude on the force acting to cause vertical separation the interaction between the outermost male engagement surface  36  and the inner most female engagement surface  64  commences. In particular the nib  38  will engage the lower most recess  70  in response to any upward motion or rotation. This in itself creates fiction to arrest any further displacement. However should this occur then the nib  38  can successively engage in the recess  68  and thereafter the recess  66 . Such engagements again add frictional force resisting separation of the engaged male and female parts  12  and  14 . 
     However the joint  10   a  is designed to be able to be disengaged (for example for the purposes of repair of a floor covering) by application of a force in a direction perpendicular to the upper surface  16  and away from the lower surface  18 . This is opposite to the direction of force required for the coupling of the joint system  10   a . This is explained later with reference to  FIGS.  7   a   - 7   k.    
       FIGS.  1   a  and  1   b    shows the adaptability of the present system  10   a  for surface covering panels P of various thicknesses. For example the system  10   a  could be used for panels of thickness in the range of, but not limited to say 5 mm-7 mm. In  FIG.  1    the distance AB may be 5 mm; AC 5.5 mm; AD 6 mm; DF 6.5 mm and EF 7 mm. However other thickness ranges are also possible such as 3 mm-7 mm. 
     The joint system  10   a  has been described above in terms of a male part  12  with a protrusion  28  and recess  30  and a female part  14  with a protrusion  54  and a recess  56 . However the vertical joint system  10   a  can also be descried in terms of vertically engageable locking parts on at least two opposed sides of a panel P, the locking parts having proximal mutually receivable components near an edge of the upper surface of the panel P in which the vertical joint system  10   a  is provided, and distal mutually receivable components near an edge of the lower surface of the panel P. The proximal mutually receivable components are exemplified by and may have all the features of the male protrusion  28  and the female recess  56  described in relations to all of the presently disclosed embodiments. Both of these components are near the edge of the upper surface  16  of the panel in which the joint system  10   a  is formed. The distal mutually receivable components are exemplified by and may have all the features of the male recess  30  and the female protrusion  54  described in relations to all of the presently disclosed embodiments. Both of these components are near the edge Y of the lower surface  18  of the panel in which the joint system  10   a  is formed. The proximal components being the protrusion  28  and the recess  56  are formed on opposite sides of the same panel P. Likewise the distal components being the protrusion  54  and the recess  30  are formed on opposite sides of the same panel P. 
     When the joint system  10   a  is viewed as such proximal and distal mutually receivable components then it is also apparent that the components are configured so that when the respective locking parts of two panels with the same vertical locking system are engaged, the surface  72  on a side of one of the distal components  54  nearest the lower surface  18  overlies a surface  40  on a side of the other distal component  30  nearest the lower surface  18  at a first location L 1  and a second location L 2 . All the full functionality and characteristic of the male and female parts  12 ,  14  apply to the system  10   a  when described in terms of the proximal and distal mutually receivable components; including for example the angular relationship between parts of the surfaces at the locations L 1  and L 2 . 
       FIG.  3    depicts a second embodiment of the vertical joint system  10   b . In describing and illustrating the joint system  10   b  the same reference number are used to denote the same feature as in the joint system  10   a . The joint system  10   b  only differs from the joint system  10   a  in the shape and configuration of the protuberance  80  on the outer most (distal) female surface  72  at the location L 1 . Specifically the protuberance  80  has a surface portion  81  that lies in a tangent plane T 1   f  that is parallel to the tangent plane T 1   m , i.e. θ f °=θ m °. Therefore when the protuberances  80  and  52  contact each other the tangent planes are coincident. 
       FIG.  4    depicts a third embodiment of the vertical joint system  10   c . In describing and illustrating the joint system  10   b  the same reference number are used to denote the same feature as in the joint system  10   a  and  10   b ; however for ease of distinction features which differ are provided with the suffix “c”. The joint system  10   c  only differs from the joint system  10   b  in:
         The shape and configuration of the inner most (proximal) female surface  64   c . The surface  64   c  omits the recess  66 ,  68 , and  70  and is formed with a greater concavity near the bottom of the recess  56 .   The shape and configuration the outer most (proximal) male surface  36   c  which is provided with a more pronounced convex curve but with a slight nib  38   c  just over about halfway down from the datum surface  34 . The nib  38   c  acts in a similar way to the nib  38  of the systems  10   a  and  10   b  which is omitted from the joint system  10   c . In particular in response to peaking of the panels P 1  and P 2  the nib  38   c  will eventually contact the surface  64   c  and provide additional resistance to vertical separation.   The replacement of the concavity  44  which is provided on the common male surface  42  of the joint systems  10   a  and  10   b  with a slightly curved and indeed almost planar portion  44   c.      The provision of a small taper  94  at the upper the edge U when the panel at the edge of the joints.   The inclusion of a small recess  96  at the bottom of surface  32 . This provides relief for engagement and minimizes the risk of a corner burr which may form during manufacture preventing full seating of the surfaces  32  and  34  on surfaces  58  and  62  respectively.   A more pronounced convex curvature on the top surface  87   c  of the female protrusion  54   c.          

       FIG.  5    depicts a fourth embodiment of the vertical joint system  10   d . In describing and illustrating the joint system  10   d  the same reference number are used to denote the same feature as in the joint system  10   a . The joint system  10   d  only differs from the joint system  10   a  in the relative dimensioning of the protrusion  54  and recess  30  so that at location L 2  the protuberances  48  and  76  are spaced apart when the joint is in the neutral plane. Thus there is a gap or space between the male and female joints  12 ,  14  all of the way from where the datum surface  34  contacts the datum surface  62  to the location L 1 . 
       FIG.  6    depicts a fifth embodiment of the vertical joint system  10   e . In describing and illustrating the joint system  10   e  the same reference number are used to denote the same feature as in the joint system  10   a . The joint system  10   e  only differs from the joint system  10   a  in the relative dimensioning of the protrusion  54  and recess  30  so that at locations L 1  and L 2  the protuberances  48  and  76 ; and  52  and  80 ; are spaced apart when the joint is in the neutral plane. Thus there is a gap or space between the male and female joints  12 ,  14  all of the way from where the datum surface  34  contacts the datum surface  62  to the lower surface  18 . In this embodiment gravity alone holds the datum surface  34  on the datum surface  62 . Thus the engaged joint has a small degree of lateral play. This may assist in engaging the male joint with the female joint and minimizing stress and tension in the joint when in the neutral plane and in the absence of other forces. However if for example a lateral compressive force is applied through the floor that may tend to give rise to peaking that force will also cause abutment of the distal male and female surfaces  40  and  72  which would then act to resist vertical separate and further peaking. 
     Broadly some embodiments of the disclosed vertical joint system may be described as follows:
         a vertical joint system  10   a ,  10   b ,  10   c ,  10   d  for a surface covering panel P having an upper surface  16  which is visible when the surface covering is laid and an opposed lower or under surface  18  with a plurality of sides  20 ,  22 ,  24 ,  26  (see  FIG.  2   ) located between the upper and under surfaces  16 ,  18 , the vertical joint system  10   a ,  10   b ,  10   c ,  10   d , comprising:
           a male part  12  along a first of the sides  20  or  24 ;   a female part  14  along a second of the sides  22  or  26 , the second side being opposite to the first side;   the male and female parts  12 ,  14  being configured so that when the male part of one surface covering panel P 1  is engaged with a female part of a second surface covering panel P 2  to create an engaged joint having a proximal end near respective upper edges U of upper surfaces  16  of the panels P 1 , P 2  and a distal end near respective lower edges Y of lower surfaces  18  of the panels P 1 , P 2 :
               (a) at the proximal end of the engaged joint the male part  12  rests on the female part  14  on a datum surface  62  defining a datum plane controlling a depth of insertion of the male part  12  in the female part  14  so that the upper surfaces  16  of the panels P 1 , P 2  are co-planar; and   (b) at the distal end of the engaged joint the male part  12  at contacts on overlying portion of the female part  14  to hold the male and female parts together at the datum plane  62 .   
               
               

     The embodiment for the joint system  10   e  differs from the above only in relation to the feature at paragraph (b) where instead for the joint system  10   e , at the distal end of the engaged joint the female part overlies the male part in at least one location L 1  and/or L 2 ; and there is a continuous gap is formed between the male and female part from the datum plane  62  to the lower surface  18  of the panels P 1 , P 2 . Thus there is no contact at L 1  or L 2  with the embodiment of vertical joint  10   e.    
     In the above embodiments of joint systems  10   a ,  10   b ,  10   c  and  10   d  the male and female parts  12 ,  14  may be configured so that in the engaged joint a continuous gap is formed between the male part  12  and female part  14  from the datum surfaces  34 ,  62  to where the male part  12  contacts on overlying portion of the female part  14  such as for example at location L 1  or L 2 . Although as previously described there can be two continuous gaps, one from the datum surfaces  34 ,  62  to an intermediate location where the common surface portions  42  and  74 , and a second from the intermediate location to location L 1  or L 2 . 
       FIG.  7   a    shows a plan view of a damaged panel P 1  in a floor and joined to panels P 2 , P 3 , P 4 , P 5 , P 6  and P 7 .  FIGS.  7   b - 7   k    illustrate a sequence of steps for replacing the damage panel P 1  when viewed along section AA of  FIG.  7   a    when the panel P 1  is made of a plastics or pliable material. The panels have the embodiment of the joint system  10   a , but irrespective of the specific embodiment of the joint system the sequence of steps remains the same. This sequence is as follows:
         A suction cup  100  is placed on panel P 1  near its transverse end  24 . ( FIGS.  7   a  and  7   b   )   The suction cup  100  is activated by lifting of a lever  102  so that the suction cup  100  grips the end of the panel P 1  ( FIG.  7   c   ).   With reference to  FIG.  7   d   , a person pulls upwardly on the suction cup  100  lifting the panel P 1  from an underlying substrate  104 . The end of the panel P 1  is lifted to be substantially parallel to the substrata  104  and the panels P 2  and P 3  are inclined downwardly from the sides of the panel P 1 . This is accommodated by a relative rotation of the male and female joints  12 ,  14  on each side. This rotation initially causes: (a) an increase in the contact pressure between the distal male and female surfaces  40 ,  72  with the protuberance  52  sliding further under protuberance  80 ; and (b) the protrusion  28  to rotate clockwise within recess  56  causing the proximal surfaces  36  and  64  to contact each other.
           More particularly the nib  38  starts to ride up the surface  64 , the datum surface  34  lifts off the datum surface  62  and the upper edge U of panel P 1  adjacent panel P 3  is now above the upper edge of the panel P 3 , while upper edge U of panel P 1  adjacent panel P 2  is now below the upper edge of the panel P 2 . With increased lift of the panel P 1  the angle ϕ of rotation between the lower surfaces  18  of P 1  and P 3  on one side and P 1  and P 2  on the other side the nib  38  rides up the surface  64  to reside in upper most recess  66  (for joint system  10   a ,  10   b ,  10   d  and  10   e ). For the system  10   b  an equivalent location is where the nib  38   c  reaches the part  93  of surface  64   c  where it commences to concavely curve. The angle ϕ may be in the range of about 175°-165°. The protrusion  28  is now primed for release from the recess  56 .   
           Referring to  FIG.  7   e   , while the panels are in the state shown in  FIG.  7   d   , the person holding the suction cup  100  pushes down on the panels P 2  and P 3  one at a time as depicted by arrows D. The one of these panels with having its female joint  14  engaged with panel P 1  will disengage. The person holding the suction cup  100  will not know beforehand that this is panel P 3 . This will only be found by pushing down on both P 2  and P 3  to see which one disengages in response to the push. This push on the panel P 3  will cause the nib  38 / 38   c  to ride further up the surface  64 / 64   c  releasing the protrusion  28  from the recess  56 . There is now either no or very minor resistance to relative lateral motion of the joints  12  and  14  which enables, with minimal force and effort, the distal surfaces  40  and  72  to separate and for the protrusion  54  to release from the recess  30 . Thus in summary pushing down on panel P 3  near its edge with panel P 1  snaps the protrusion  28  of panel P 1  from the recess  56  of panel P 3  and the protrusion  54  of panel P 3  from the recess  30  panel P 1 . This occurs in the vicinity of the application of the push and provides an opening  106  into which the person can insert one or more fingers.   From here the person can now in effect unzip the engaged joints  12 ,  14  for the entirety of the perimeter of the panel P 1 . With reference to  FIG.  7   k    the user can chase their finger(s) around the transverse side  24  of panel P 1  as shown by the path  108 . By either pulling up or pushing down on the panel P 4  (depending on whether the panel P 4  has its male or female joint adjacent the side  24 ) using the hand having the fingers previously inserted in the opening  106 , the joints along the side  24  now become disengaged.   Following the path  108  around to the panel P 2  the person can pull the male joint  12  of panel P 2  from the female joint on the adjacent side of the panel P 1 . ( FIG.  7   f   )   The person continues chasing their fingers and hand about the panel P 1  to fully disengage panel P 1  from panels P 2 , P 6 , P 5 , P 7  and P 3 ; pushing down or pulling up depending on whether the joint on those panels is the male joint  12  or the female joint  14 . The fully disengaged panel P 1  is now discarded. ( FIG.  7   g   ).   A new panel P 1   a  is inserted into the space left by the discarded panel P 1 . In doing so the panel P 1   a  is manipulated so that its female joints  14  along sides  22  and  26  are placed beneath the male joints  12  of the adjacent panels P 2 , P 6  and P 5 ; and its male joints  12  on sides  20  and  22  overlie the female joints  14  of panels P 3 , P 4  and P 7 . ( FIG.  7   h   )   A mallet  110  is now used to apply a vertical downward force along the mutually overlying male and female joints  12 ,  14  tapping about the perimeter of panel P 1   a . ( FIGS.  7   i  and  7   j   )   The surface covering of (e.g. floor on) substrate  104  is now reinstated as shown in  FIG.  7     k.          

     It should be noted that the above description of replacement of the panel P 1  is performed without the need to cut a corner of the panel P 1   a  which is the practice with plastics panels having prior art joints particularly with tongue and groove lay-down joints. This practice is dangerous due to the use of very sharp knives (e.g. a box cutter) and also regularly results in the unintentional cutting of an otherwise undamaged panel. In that event a further panel needs to be replaced. Also the removal process does not cut or damage the vertical joints system  10  on the other panels. This enables the replacement panel P 1   a  to be coupled to all of the surrounding panels P 2 -P 7  by coupling of the respective male and female joints, without the need for adhesives and enabling the full reinstatement of the surface covering. 
     Whilst specific embodiments of the vertical joint system have been described it should be appreciated that the vertical joint system may be embodied in many other forms. For example while the panels P are describes as being of rectangular shape, they may take other polygonal shapes. Also the panels are not limited in use as floor covering panels. They may be used to cover other surfaces such as walls or ceilings. In one example the panels can be arranged as a wall covering without needing to be adhered to a wall by first fixing a rail along the top of the wall, fixing a first panel or line of end to end joined panels to the rail then using embodiments of the disclosed joint system to coupled subsequent rows of panels to cover the wall. This produces a suspended wall covering. Avoiding the use of adhesives eliminates damage to the underlying wall in the event that the wall covering is to be subsequently removed or replaced. 
       FIG.  2    shows an embodiment where the joints system  10  provides male and female parts  12 ,  14  on each of two sides of the panel so as to form a fully vertically engageable and disengage able surface covering system. However the joint system  10  may be applied to only two sides and in particular to the short sides  24  and  26 , with laterally extending tongue and groove type joints on the other sides  20  and  22 . This results in a laydown surface covering system with the joint system  10  providing a “drop lock” on two (usually the short) sides only. 
     In other modifications or variations the panels may be provided with adhesive and preferably a re-stickable adhesive on the lower surface. The expression “re-stickable adhesive” throughout the specification and claims is intended to mean adhesive which is capable of being able to be removed and re-adhered, does not set or cure to a solid rigid mass and maintains long term (e.g. many years) characteristics of flexibility, elasticity and stickiness. The characteristic of being re-stickable is intended to mean that the adhesive when applied to a second surface can be subsequently removed by application of a pulling or shearing force and can subsequently be reapplied (for example up to ten times) without substantive reduction in the strength of the subsequent adhesive bond. Thus the adhesive provides a removable or non-permanent fixing. The characteristics of flexibility and elasticity require that the adhesive does not solidify, harden or cure but rather maintains a degree of flexibility, resilience and elasticity. Such adhesives are generally known as fugitive or “booger” glues and pressure sensitive hot melt glues. Examples of commercially available adhesives which may be incorporated in embodiments of the present invention includes, but are not limited to: SCOTCH-WELD™ Low Melt Gummy Glue; and GLUE DOTS™ from Glue Dots International of Wisconsin. 
     Also panels, particularly those made of plastics or polymer materials, provided with embodiments of the disclosed joint system  10   a ,  10   b  may be used as a substrate for another “face” panel such as but not limited to: ceramic tiles; natural stone tiles; metal panels; glass tiles and sheets; fiber cement tiles, boards or panels; and carpet tiles. Specifically such face panels can be permanently fixed to the underlying panels (substrates) to form a laminate product. This enables for example the installation of a floor that has the look and feel of a stone or ceramic tile floor but with the ability to easily replace a damaged tile in the same manner as described above in relation to the floor panels P. The face panels may also bear printed or sprayed on coating. For example a metal or fibre cement face panel may have a printed or sprayed on coating or surface decoration. In such embodiments a layer of reinforcing material such as a fiber reinforced composite material may be sandwiched between the substrate and the face panel to enhance rigidity. This may be beneficial for example where the face panel is made of a brittle material such as stone, ceramic or glass to assist in preventing cracking. 
     The surfaces  46  and  84  are described in this embodiment as being substantially perpendicular to the upper surface  16 . However in other embodiments they may be inclined up to about 20° in the same direction as the angles θ and β, i.e. so that when inclined the surface  46  overlies the surface  86 . 
     Further the ability of the male part  12  to move laterally toward, away from and then again toward an adjoining panel during the insertion process which facilitates ease of insertion may be achieved by in effect reversing the configuration of the male and female common surfaces  42  and  74  so that the convex portion  86  of the female protrusion  54  is replaced by a concave recess similar to the recess  42  while the recess  42  on the male protrusion  28  is in effect filled in so that the concave surface  47  extends continuously to the planar surface  46 . 
     In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in variations or embodiments of the joint system disclosed herein.