Abstract
A screening apparatus includes a plurality of spaced apart parallel beams and a plurality of screen panels mounted to the beams to form a planar screening surface. The panels are mounted to the beams by fixing members that extend in the longitudinal direction of the beams and that engage side edges of the panels. The fixing members have a pair of upstanding, longitudinal rails that are spaced apart to define a longitudinal gap between them and the panels are mounted to the beams by engagement between side edges of each panel with a rail of a fixing member. The side edges of each panel include an overhang that overlies an upper end of each rail and that extends into the gap between the rails. The rails and the overhang include locating gaps to receive a locking member to locate panels relative to the fixing members.
Claims
1. A screening apparatus, including: a plurality of spaced apart, substantially parallel elongate beams, a plurality of screen panels mounted to the beams to form a broad, generally planar screening surface, each panel being mounted to a pair of beams to bridge between two adjacent beams, each of the panels having a generally square or rectangular shape defining a first pair of substantially parallel edges and a second pair of substantially parallel edges, and the panels being mounted adjacent to each other so that facing side edges of adjacent panels are in close facing relationship, the panels being mounted to the beams by elongate fixing members that extend in the longitudinal direction of the beams and that engage the first pair of side edges of the panels, the fixing members having a pair of upstanding, generally longitudinal rails that are generally parallel and that are spaced apart to define a longitudinal gap between them, the panels being mounted to the beams by cooperation between the first pair of side edges of each panel with a rail of a fixing member, the first pair of side edges of each panel including a longitudinal overhang that overlies an upper end of a rail and that extends into the gap between the rails, each of the rails of each fixing member and the overhang of each panel being interrupted to form locating gaps that are aligned and within which a locking member is disposed to locate the panel relative to the fixing member against movement of the panel along the fixing member.
2. A screening apparatus according to claim 1, the overhang presenting an engagement surface for engagement with a facing engagement surface of the overhang of an adjacent screen panel within the gap between adjacent rails.
3. A screening apparatus according to claim 2, the engagement surface being a substantially flat surface that extends substantially perpendicular to the plane of the screening surface.
4. A screening apparatus according to claim 2, whereby engagement between the overhangs of adjacent screen panels prevents adjacent rails of a fixing member from flexing towards each other.
5. A screening apparatus according to claim 2, engagement between facing engagement surfaces of respective overhangs of adjacent screen panels extending above the gap between adjacent rails.
6. A screening apparatus according to claim 5, engagement between facing engagement surfaces of respective overhangs of adjacent screen panels extending to the screening surface.
7. A screening apparatus according to claim 1, the cooperation between the first pair of side edges of each panel and a rail of a fixing member including a projection extending from either one of the side edges of each panel and the rail of a fixing member, and a groove formed in the other of the side edges of each panel and the rail of a fixing member, the projection extending into the groove generally in a plane that is parallel to the plane of the screening surface and the projection and groove being located between the beam of the screening apparatus to which screen panels are mounted and the overhang of the screen panels.
8. A screening apparatus according to claim 7, the rails of the fixing members extending from a base and including an upright web section and a head at an upper end of the web section, the groove being formed in each rail between the base and the head, the overhang extending over the head and into the gap between adjacent rails, the portion of the overhang that extends into the gap having an inclined face so that the overhang portion can be pushed into engagement with the head of the rail and the overhang portion will ride along the inclined face as it enters the gap.
9. A screening apparatus according to claim 1, a single locking member substantially filling the space created by the locating gaps formed by a pair of adjacent screen panels and the rails of a fixing member.
10. A screening apparatus according to claim 1, the overhang of each of the first pair of edges of each screen panel including two locating gaps that are spaced apart and the rails of the fixing members including corresponding locating gaps for alignment with the locating gaps of the overhang, the screen panels being located relative to the fixing rail against movement of the panel along the fixing rail by a pair of locking members inserted into the aligned locating gaps.
11. A screening apparatus according to claim 1, each locking member including a pair of projections on opposite sides of the locking member for engaging under a projection formed in the facing edges of adjacent screen panels to locate the locking member within a locating gap formed between adjacent screen panels.
12. A screening apparatus according to claim 11, the projections of the adjacent screen panels being formed in a portion of the overhang of each of the screen panels within which the locating gap is formed.
13. A screening apparatus according to claim 11, the locking member projections being formed to extend generally perpendicular to the longitudinal extent of the fixing members.
14. A screening apparatus according to claim 11, the locking member projections being formed to extend generally parallel to the longitudinal extent of the fixing members.
15. A screening apparatus according to claim 1, the locking members being substantially square or rectangular and defining four walls, a projection extending from each wall for engaging under respective projections formed in facing edges of adjacent screen panels.
16. A screening apparatus according to claim 15, at least two of the projections formed in facing edges of adjacent screen panels being formed in a portion of the overhang of each of the screen panels within which the locating gap is formed.
17. A screening apparatus according to claim 15, all of the projections formed in facing edges of adjacent screen panels being formed in a portion of the overhang of each of the screen panels within which the locating gap is formed.
18. A screening apparatus according to claim 1, the locking members extending to a position above the screening surface to form deflectors.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:
(2) FIG. 1 is an isometric view of a portion of a screening deck according to one embodiment of the invention.
(3) FIG. 2 is a cross sectional view through II-II of FIG. 1 showing the connection between adjacent screening panels in the deck illustrated in FIG. 1.
(4) FIG. 3 is an exploded view of a single screening panel and its connection to the deck of FIG. 1.
(5) FIG. 4 is an assembled view of the arrangement of FIG. 3.
(6) FIG. 5 is an exploded view of a single screening panel and its connection to the deck of FIG. 1 but showing an elongate fixing member.
(7) FIG. 6 is an isometric view of a locking member according to one embodiment of the invention.
(8) FIG. 7 is a cross sectional view through VII-VII of FIG. 1 showing the locking member of FIG. 6 in place.
(9) FIGS. 8 and 9 show alternative forms of locking members according to the invention.
(10) FIG. 10 is an isometric view of a side clamp according to one embodiment of the invention.
(11) FIG. 11 is an end view taken in the direction A of FIG. 1.
(12) FIG. 12 is a cross sectional view through XII-XII of FIG. 1.
(13) FIG. 13 is a cross sectional view of a locking member according to a further embodiment of the invention.
(14) FIG. 14 is an isometric view of a side clamp according to one embodiment of the invention.
(15) FIG. 15 is a cross sectional view of a locking member according to a further embodiment of the invention.
DETAILED DESCRIPTION
(16) With reference to FIG. 1, a portion of a screening deck 10 is illustrated, comprising a plurality of elongate, longitudinal beams 11 each of which is formed from an angle of steel having a long portion 12 and short portion 13. The portions 12 and 13 are set at right angles to each other. While the beams 11 extend in the longitudinal direction of the screening deck 10, the beams 11 can equally extend perpendicular to the direction shown.
(17) The deck 10 illustrated in FIG. 1 is a portion of a deck only and illustrates a depth of four screening panels 15. The longitudinal length of the deck 10, in the direction of the beams 11 can be much greater.
(18) The beams 11 extend parallel to one another and support the panels 15 on the upper face of the short portion 13 of each beam 11. The panels 15 illustrated in FIG. 1 can be of any suitable size, but a common size is 305 mm by 610 mm. The screening deck 10 is one part of an overall screening apparatus. The screen deck 10 is supported on a sub frame which includes the beams 11 and which is part of a vibratory screen machine. The vibration that is generated is significant and requires the panels 15 to be securely fixed to the beams 11. The panels 15 are also subject to wear over time and even though the fixing of the panels 15 to the beam 11 are required to be secured, the preference is that the panels are also easily releasable to facilitate replacement.
(19) The panels 15 include a plurality of openings through the top surface thereof for screening product such as mining ore. The openings in the panel can vary from large to very small depending on the screened media required from the screening process.
(20) Typically, ore is fed onto one end of the deck 10 and the deck is vibrated so that the ore tends to shift from one end to the other with some of the ore passing through the openings of the panels 15 as it travels over the deck. Depending on the operation, the valuable ore could be the ore which passes through the openings, or the ore which remains on the deck. The panels 15 are attached to the screen deck 10 via elongate fixing members 20 which are mostly obscured in FIG. 1, but which are shown in other figures. The fixing members 20 are fixed to the upper surface of the short portion 13 of the beams 11 by any suitable arrangement, such as bolts. The fixing members can extend for a single length of a single panel 15, or, more preferably, for a greater number of panels, such as five panels.
(21) Most of the panels 15 will be in face to face engagement along side edges of each panel. For example, the panel marked P.sub.1 is engaged with facing edges of other panels 15 on all four edges. It is preferred that the panels have this face to face engagement, in order to prevent or minimise screening product from entering into the junction between adjacent panels 15 and through that junction to the beams 11 below or into the screened product that is collected below the screen deck. Any entry of such screening product between adjacent panels 15 can cause wear to the fixing members 20, or to the beams 11, thus compromising operation of the screening deck 10. With sufficient wear, worn components must be replaced and that results in down time of the screening apparatus. Wear of certain components, such as the beams 11, can require significant down time in order to replace the components. It is therefore important that the panels 15 be fixed to the deck 10 securely and with firm side edge engagement between adjacent panels.
(22) It is to be noted that the deck 10 includes side clamps 21 at each side of the deck 10, and in facing engagement with side walls 22. Side clamps 21 clamp via a bracket 23 and wedge 24 onto the upper edge surface of the panels 15 for the purpose of preventing lifting of the facing edge of the panels 15, preventing ingress of screening product between the side edges of the panels 15 and the walls 22, and also to protect the walls 22 (which are usually steel walls), from the impact of screening product which traverses the screen deck 10. The side clamps 21, like the panels 15, are usually made from a polyurethane material. The side clamps 21 can be used with a screening apparatus of the invention or with prior art screening apparatus.
(23) The manner in which the screen panels 15 interact with the fixing members 20 will be described hereinafter. For that discussion, it is important to note from FIG. 1, the existence of locking members 25 that assist to locate the panels 15 relative to the fixing rails 20 against movement of the panels 15 along the fixing rails. In this respect, while the deck 10 is shown as a flat, screening decks generally operate on an incline to promote travel of ore from one end of the deck (the feed end) to the other (the discharge end), and some decks incorporate inclined sections (these can be referred to as “multi-slope decks”), in order to increase the speed of ore from the feed end to the discharge end. The inclined sections can have a greater inclination at the start of the deck and reduce towards only a slight inclination so that screening product decelerates from a high speed at the entry or initial section of the screening deck, to a lower speed when the screening deck flattens out to a slight incline. These types of decks process the screening product more quickly than decks that have only a slight and constant incline over the length of the deck because the screening product travels over the deck more quickly due to the more greatly inclined sections.
(24) Particularly in the multi-slope types of decks, there is tendency for the screening panels to shift in the direction of screening product movement due to the loads placed on the panels by the moving screening product and that shift can cause gaps to open between adjacent panels and for screening product to fall through those gaps causing the problems mentioned above in relation to wear of deck components or contamination of screened product. For this reason, the present invention is intended to lock the panels 15 firmly in position on the fixing members 20 in order to prevent such panel shifting movement. That locking however is intended to be selective in that the invention can allow movement of the panels 15 relative to the fixing members 20 to allow proper and accurate location of the panels 15 on the fixing members 20, but once the panels 15 are correctly located, the panels can be locked against further movement relative to the fixing members 20. This differs from some prior art arrangements where the screening panels are locked as soon as they are fixed to the fixing members, so that initial pre-fixing movement along the fixing members is not provided or allowed.
(25) With reference to FIG. 2, a cross-sectional view of one full panel 15 (the central panel), and side edges of two adjacent panels 15 (to the left and right of the central panel) is illustrated. FIGS. 3 and 4 are exploded and assembled views of a single panel 15 relative to a single fixing member 20. FIGS. 2 to 4 show the configuration of the fixing members 20 and show that the fixing members 20 include a pair of rails 26 which extend from a base 27 and which are formed by webs 28 and heads 29. Recesses 30 are defined between the base 27 and the heads 29 and it can be seen that the side edges of the panels 15 each include a projection 31 that extends into the recesses 30 in order for the side edges of the panels 15 to cooperate with the rails 26 of the fixing members 20 to fix the panels 15 to the fixing members 20 and thus to the beams 11.
(26) The side edges of the panels 15 also include a longitudinal overhang 34 (FIG. 2) that overlies the upper end of the rails 26, or in other words overlies the heads 29 and includes a downwardly extending portion 35 that extends into the gap G (FIG. 2) between adjacent rails 26. It is intended that facing surfaces of facing portions 35 engage tightly to prevent ingress of screening product between the portions 35 and into the fixing members 20.
(27) The panels 15 are securely located on the beams 11 by cooperation between the projection 31 of the side edges of the panels 15 within the recess 30 of the fixing members 20. The panels 15 can be connected to the fixing members 20 by the projections 31 riding down the inclined surface 36 of the heads 29 and by the rails 26 bending inwardly towards each other as the projection 31 moves over the inclined surface 36 for insertion into the recess 30. With the projection 31 seated within the recess 30, the portion 35 is positioned within the gap G, and when a pair of panels have been assembled to the fixing member 20 as shown in FIG. 2, the respective portions 35 engage and prevent inward flexing or tipping of the rails 26 towards each other. By this arrangement, side edges of the panels 15 are securely held in place on the fixing members 20 by the secure engagement of the projections 31 within the recesses 30.
(28) However, as indicated above, it is a feature of the invention that the panels 15 are not only secured in the array formation shown in FIG. 1, but also against movement along the fixing members 20. In the illustrated form of the invention, prevention of that latter form of movement is by the use of locking members 40 that fit into locating gaps which are formed in the overhang 34 and in the rails 26. With reference to FIG. 3, gaps 41 are formed in the overhang 34, while gaps 42 are formed in the rails 26 of the fixing member 20. The gaps 41 and 42 form a locating gap into which the locking member can be inserted.
(29) With reference to FIG. 4, with the gaps 41 and 42 aligned, or overlaid, the locking members 40 can be inserted and it will be appreciated that once inserted, the locking members 40 lock the position of the panel 15 on the fixing member 20 through engagement with the edges of the gaps 41 and 42. While the locking members 40 remain in place, movement lengthwise of the panel 15 along the fixing member 20 is not possible.
(30) The figures mentioned above also show the manner by which the fixing members are fixed to the beam 11 and while this is a relatively standard arrangement, it will be briefly described as follows.
(31) Extending from the base 27 of the fixing member 20 are a pair of projections 45 (FIG. 3) that extend through openings 46 in the portion 13 of the beams 11 and while the projections 45 are not shown as being threaded, they include a thread over which the washers 47 pass and on which the nuts 48 thread. The nuts 48 tighten the fixing members 20 onto the beam 11, while a urethane cap 49 is also threaded onto the end of the 45 to protect the fixing arrangement (the projections 45, washers 47 and the nuts 48) against the corrosive effect of fines (very fine screening product).
(32) The fixing members 20 can be of any length suitable to secure one or more panels 15. FIG. 5 illustrates a fixing member 50 that is of a length suitable to fix four panels 15 thereto. It is envisaged that for commercial use, the fixing members 20 will have at least the length shown in FIG. 5 but potentially a greater length, although a smaller length is possible.
(33) The locking members 40 must firmly lock into the gaps 41 and 42 and must be constructed to maintain that locking engagement under operation of the deck 10 during a screening operation in which the deck is vibrated. Accordingly, the locking members 40 include a construction that is illustrated in FIGS. 6 and 7 and with reference to those figures, it can be seen that the locking member 40 has a generally rectangular shape and includes four projections or undercuts 52. Each undercut 52 projects from a side wall or edge of the locking member 40 and includes an upper surface 53. As shown in FIG. 7, two of the undercuts 52 on opposite sides of the locking members 40 engage a downwardly facing surface 54 of the inner edges or walls of the gaps 41 in adjacent panels 15 in order to lock the locking members 40 in place. The other two the undercuts 52 engage a downwardly facing surface of the other walls (the side walls) of the gaps 41 as will be below. The locking members 40 are intended to be a tight fit within the locating gaps formed by the overlying gaps 41 and 42.
(34) There is sufficient flexibility in the undercuts 52 in order to simply push the locking members 40 into the gaps 41 of an adjacent pair of panels 15 with the undercuts 52 compressing or deflecting to allow the locking members 40 to enter the gaps 41 and for the undercuts 52 to thereafter splay or flex outwardly once the upper surface 53 has penetrated to a position just below the downwardly facing surfaces 54. As shown in FIG. 7, the bottom face 55 of each locking member 40 rests on upwardly facing surfaces 56 (see FIGS. 3 and 4), of the rails 26 in the region of the gaps 42. By this arrangement, each of the panels 15 and the locking member 40 are firmly secured in place and because the locking member 40 is a tight fit within the gap 42, so that it bears against facing surfaces 57 (see FIG. 3) of the heads 29 of the rails 26, longitudinal movement of the locking members 40 is precluded and thus longitudinal movement of the panels 15 is also precluded.
(35) While the undercuts 52 engage the surfaces 54 of the inner walls of the panels 15 as shown in FIG. 7, the undercuts 52 also engage further downwardly facing surfaces 58 of the side walls that extend from the inner walls as shown in FIG. 3, so that the locking member 40 is secured against release out of the gaps 41 and 42 on each of its four sides. This forms a highly secure fitting.
(36) Locking members 25 and 40 are illustrated in FIG. 1, and from this, it can be seen that the locking members 25 have different shapes on the surface of the deck 10 to the locking members 40. The form of the locking members can vary and two other forms are illustrated in more detail in FIGS. 8 and 9. Each of the locking members 40, 60 and 65 have the same bottom or base end defining a rectangular shape with four undercuts 52. It is only the upper part of the locking members that differ and in FIG. 8, the locking member 60 is shown to have a diamond shaped upper end 61, while in FIG. 9, the locking member 65 has a pyramid shaped upper end 66. The upper ends 61 and 66 are shaped as deflectors, so that screening product travelling along the deck 10, that travels along the adjoining sections of adjacent panels 15 in which no screening openings exist, is deflected back onto portions of the screening panels that do have screening openings.
(37) Returning to FIG. 1, it will be evident that the arrangement which exists between adjacent side edges of adjacent panels 15 cannot be employed along the walls 22 of the deck 10 because there is no adjacent panel for the side edge panels to engage or abut. Nevertheless, is it important to secure the panels at the edges against longitudinal movement of the deck 10 at the side walls 22, so that the panels 15 that extend to the side walls 22 are also fully located against longitudinal movement. Also, it is important to secure the panels 15 at the edges against lateral movement toward and away from the side walls and against lifting movement away from the beams 11 of the screen deck.
(38) For this, the side clamps 21 have been configured so that they can support plugs or spacers (hereinafter “plugs”) for interaction with the panels 15. With reference to FIGS. 10 to 13, the side clamp 21 includes a rear face 70, a front face 71, an upper stepped edge 72 which is engaged by the wedge 24 for securing the side clamp 21 in place, and a lower or bottom edge 73. Extending from the lower edge 73 are projections 74 that each include an opening 75 for receipt of a plug 76, which is shown in side cross sectional view in FIG. 13.
(39) From FIG. 13, it can be seen that the plug 76 has a head 77, a neck 78 and a base 79. The dimensions of the openings 75 are such to snuggly or closely accept the neck 78, and the arrangement is that the base 79 is sufficiently flexible to allow it to be pushed through the smaller diameter opening 75 and to splay or recover once through the opening 75 to engage against the rear surface 80 of the projections 74, with the surface 80 being slightly inboard of the rear face 70 of the side clamp 21 so that the rear of the base 79 is coextensive with the rear face 70. The distance D.sub.1 between the bottom surface of the head 77 and the facing surface of the base 79 is also configured to be approximately the same as the distance D.sub.2 between front and rear surfaces of the projections 74.
(40) With reference to FIGS. 3 and 4, and assuming for the purposes of the description in relation to the plugs 76, that the side edge 82 of the panel 15 of FIGS. 3 and 4 is the side edge 82 shown in FIGS. 11 and 12, then it will be apparent that the side edge 82 includes openings or gaps 41 (see FIGS. 3 and 4) that are proximate the facing surface of the wall 22. The projections 74 of the side clamp 21 shown in FIG. 10 are therefore spaced apart for alignment with the gaps 41 in the side edge 82. The projections 74 of the side clamp 21 also have a width dimension W.sub.1 (see FIG. 10) that is the same, or just slightly smaller than the width dimension W.sub.2 of the gaps 41 (see FIG. 4). When the projections 74 are located within the gaps 41, side edges of the projections 74 bear against facing surfaces of the gaps 41 to locate the side edge 82 against longitudinal movement in the direction A (see FIG. 1) between the feed and discharge ends of the screen deck 10. By this arrangement, the side edge 82 is secured against that longitudinal movement to the same extent that that movement is secured at the opposite ends of the panels 15 by the earlier described locking members 25, 40, 60 or 65.
(41) The engagement should be enough to prevent longitudinal movement of the panels 15 in the direction A of FIG. 1. The fit of the projections 74 preferably should therefore be an interference type fit within the gaps 41. The bearing engagement can be firm engagement and the dimensions of the projections 74 and the gaps 41 can be made so that the panels must be forced into position on the projections 74, However, such a tight engagement is not considered to be absolutely necessary, so that a friction fit could be acceptable or even a slightly loose fit.
(42) For the panels 15 to be secured against lateral movement toward and away from the side walls 22 (movement in the direction B as shown in FIGS. 3 and 4), contact must be made with the inside or base surfaces 43 of the gaps 41, It is not intended that the projections 74 will engage the base surfaces 43, although in some arrangements this could occur, but rather, it is the intention that the plugs 76 engage the base surfaces 43, The plugs 76 can be made in different lengths or sizes as explained below, to accommodate variations in the spacing between the base surfaces 43 and the facing surface of the projections 74 of different screening decks or machines,
(43) The plugs 76 are proposed to be separate from the projections 74, so that different sized plugs can be used to accommodate different spacing between the base surfaces 43 and the facing surface of the projections 74 as necessary. Thus, in relation to FIG. 14, the side clamp 21 is again shown, having the same features and thus the same reference numerals as the side clamp 21 as shown in FIG. 10. However, in FIGS. 14 and 15, plugs 84 are illustrated and those plugs have a different and reduced depth D.sub.4 compared to the depth D.sub.3 of the plug 76 of FIG. 13. The plug 84 has a head 85, a neck 86 and a base 87. The dimensions of both the neck 86 and the base 87 can be the same as the neck 78 and the base 79 of the plug 76. Where the dimension differs in the respective plugs 76 and 84 is in the dimension or depth of respective heads 77 and 85. As can be seen in FIGS. 13 and 15, the head 77 is of greater dimension or depth compared to the head 85.
(44) The dimensions of the plug 84 is for snug or close receipt of the neck 86 within the openings 75, with the base 87 being sufficiently flexible to allow it to be pushed through the smaller diameter opening 75 and to splay or recover once through the opening 75 to engage against the rear surface 80 of the projections 74 in the same manner as the plugs 76 of FIGS. 10 and 13.
(45) The different sizes or depth of the plugs 76 and 84 illustrated in FIGS. 10 and 14 allows compensation for slight variations in the total width of the screening deck 10 between the opposite side walls 22 (see FIG. 1). This is important, because while the distance between the side walls 22 is specified for each screening deck, there can be slight variation along the length of the deck between the side walls (such as by slight bowing of the sides walls along their length), so that the size of the plug needed to engage the base surface 43 of the screen panels 15 can also vary. Moreover, different screen deck manufacturers manufacture their screen decks to different widths and where the variation between the width of the screen decks of different manufacturers varies only by a few millimeters (say up to 30 mm), the same side clamp can be used for each deck with the plugs being selected based on the distance that the plugs need to bridge,
(46) It is necessary for the plugs 76 and 84 to engage the base surface 43 of the gaps or openings 41. The engagement should be enough to prevent lateral movement of the panels 15 in the direction B of FIGS. 3 and 4. The fit of the plugs 76 and 84 should preferably be an interference type fit so that the faces 89 of the plugs 76 and 84 bear against the base surfaces 43 of the gaps 41. The bearing engagement can be firm engagement. The heads 77 and 85 can be made so that the panels must be forced into position against the plugs 76 and 84, although such a tight engagement is not considered to be absolutely necessary. What is necessary is that the heads 77 and 85 of the plugs 76 and 84 take up the gap between the projections 74 and the facing base surfaces 43 and bear against the base surfaces 43.
(47) The plugs 76 and 84 can have the same width dimension W.sub.1 (see FIG. 10) as the projections 74, so that the plugs 76 and 84 can also engage facing surfaces of the gaps 41 in the same way as the projections 74 engage facing surfaces of the gaps 41 to prevent longitudinal movement of the panels 15 in the direction A of FIG. 1. However, this is not a requirement. Also, where the plugs 76 and 84 have the same width dimension W.sub.1 as the projections 74, the plugs 76 and 84 might not contribute much to the resistance of longitudinal movement of the panels 15, particularly where the dimension of the head 77 or 85 of the plugs 76 and 84 is small. Where the head dimension is larger, then the plugs 76 and 84 can contribute to the resistance of longitudinal movement.
(48) The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the present disclosure.
