as shown if fig1 the mushroom tray of the present invention includes a tray portion , generally designated 11 , which includes opposing side walls 12 , 14 , opposing end walls 16 , 18 and a perforated bottom sheet 20 . the tray portion is made of a polyolefin , preferably a high - density polyethylene . in the alternative , the tray portion can be made of any plastic material which is relatively inexpensive and possesses the qualities of corrosion resistance , impact resistance , durability , and strength at elevated temperatures . as shown in fig2 the side wall 14 comprises inner and outer members 22 , 24 and a top wall 26 . side wall 12 is of similar construction . end wall 16 ( see also fig4 ) includes inner and outer members 28 , 30 , top wall 32 and web 34 . top wall 32 and web 34 extend between members 28 , 30 to define a longitudinal passage 36 . end wall 16 also includes a plurality of vertical webs 38 , extending between members 28 , 30 and web 34 . webs 34 and 38 act to stiffen the end wall 16 . end wall 18 is of similar construction . an end strut 40 is positioned within the longitudinal passage 36 and is retained therein by end caps 42 ( see also fig5 ). end strut 40 preferably is an i - beam made of a corrosion - resistant material such as aluminum . the bottom sheet 20 of the tray portion 11 is substantially flat and includes a plurality of channels 44 extending longitudinally of the tray between the end walls 16 , 18 ( see fig1 and 2 ). each channel opens downwardly and includes opposing side walls 46 , 48 and a top wall 50 ( see also fig5 ). the bottom sheet 20 also includes downwardly extending ribs 52 which criss cross to form a grid pattern . ribs 52 stiffen the floor 54 of the bottom sheet 20 to minimize flexing . as shown in fig3 and 5 , the channels include at least two pairs of opposing openings 56 , 58 in side walls 46 , 48 , respectively . preferably , each pair of holes 56 , 58 is adjacent to an end wall 16 , 18 for each channel 44 . pairs of clips 60 , one of which is shown in fig6 are inserted into the holes 56 , 58 and retain struts 62 within the channels 44 . struts 62 preferably comprise extruded aluminum i - beams , but can be made of other corrosion resistant material . the clips 60 each include a base portion 64 and a pair of protruding prongs 66 , 68 . the prongs 66 , 68 each terminate in a wedge - shaped portion 70 having an undercut segment 72 . as shown fig3 the base portion 64 of clips 60 is shaped to cover the holes 56 , 58 and the prongs 68 , 70 are shaped to support the upper flange 74 of the i - beam strut 62 , thereby retaining the i - beam within the channel 44 . the wedge - shaped portions 68 , 70 are shaped to retain the clips 60 within the holes 56 , 58 as shown in fig5 . in order to insert the prongs 68 , 70 of a clip 60 into one of the holes 56 , 58 , the prongs are deflected toward each other as the wedge - shaped portions 68 , 70 engage the walls 46 , 48 of the holes 6 , 58 then , as the undercut portions 72 engage the edges of the walls 46 , 48 surrounding the holes 56 , 58 , the prongs 66 , 68 spring away from each other to resume the position shown in fig6 . accordingly , the clips 60 are retained within the holes 56 , 8 by the engagement of the prongs 66 , 68 with the edges of the side walls 46 , 48 surrounding the holes . as shown in fig1 and 7 - 10 the tray portion 11 is supported by four legs 76 , positioned at each corner of the tray portion . the legs 76 are generally square in a horizontal cross - section and include bottom webs 78 forming recesses shaped to receive raised bosses 80 which are formed in the upper surface of the tray 11 ( see fig1 ). the recess 78 and boss 80 engagement enable the trays to be stacked in a vertical column . as shown in fig7 - 10 , each leg 76 includes a recess 82 which is defined by side walls 84 , 86 , 88 , 90 and a cruciform webbing 92 having an upper surface 94 which forms the bottom of the recess 82 . the cruciform webbing 92 also is connected to the bottom web 78 in the bottom of the leg 76 . the corners of the recesses 82 each include slots 96 which receive the flanges 98 of a cruciform insert 100 . as shown in fig7 the insert 100 is received within a corresponding recess 102 formed the corners of the tray portion 10 , and is shaped to rest upon the top surface 94 of the recess 82 . in order to strengthen the leg structure 76 , a length of tubing 104 is positioned within the leg and is shaped such that it contact the interior surface of wall 90 and flanges 98 of the insert . tubing 104 preferably is made of corrosion - resistant material such as aluminum . in addition , tubing 104 extends downwardly below the top surface 94 of the leg recess 82 and contacts the cruciform web 92 . the leg structure 76 is held in place by a suitable adhesive . the tubing 104 rests upon the upper surface of the recess 78 in the bottom of the leg assembly 76 . preferably , the leg assembly 76 is made of the same material as the tray portion 11 ; that is , a polyolefin or a high - density polyethylene . the assembly and use of the mushroom tray is as follows . the legs are first attached to the tray by applying adhesive to the cruciform inserts 100 , then inserting the inserts into the recesses 102 in the tray corners and then inserting the aluminum tubes 104 alongside the inserts . the legs 76 are then slid over the insert and tube combination 100 , 104 until the bottoms of the insert and tubes rest upon the upper surfaces 94 of the cruciform webs 92 of the legs 76 . the i - beam struts 62 are inserted into the underside of the channels 44 and retained therein by the clips 60 which are inserted through the holes 56 , 58 at the ends of the channels adjacent the end walls 16 , 18 . the clips 60 are retained permanently within the holes 56 , 58 by the prongs 66 , 68 , the undercut segments 72 of which engage the adjacent portions of the side walls 46 , 48 of the channels 44 . i - beam and struts 40 are inserted into the longitudinal passages 36 of the end walls 16 , 18 and are retained therein by end caps 42 . the mushroom tray is now ready to receive the mushroom growing medium , which is a combination of an appropriate compost mixed with mycelium . the trays can be stacked vertically , up to 7 trays high , by arranging the trays so that the bottom recesses 78 in the legs 76 receive the raised bosses 80 of the tray next below it . in addition , the top walls 26 , 32 of the tray portion 11 include treads which allow the stack to be climbed like a ladder for inspecting or picking the growth of mushrooms in the upper trays . after several flushes of mushrooms have been harvested , the trays emptied and disinfected in order to remove embryos of harmful molds or viruses . the disinfecting process typically includes elevating the temperature of the environment of the mushroom trays to approximately 152 ° f . throughout the growing process of the mushrooms , the trays may have to be moved by forklifts , and they are sufficiently rigid to be picked up by the forks of a forklift truck inserted under the side walls 12 , 14 of the tray . while the form of apparatus herein describe constitutes a preferred embodiment of this invention , it is to be understood that the invention is not limited to this precise form of apparatus , and that changes may be made therein without departing from the scope of the invention .
a mushroom tray comprising a tray portion having opposing sidewalls , opposing end walls and a substantially flat bottom sheet having a parallity of channels formed therein and extending therealong , corrosion - resistant i - beams positioned within the channels for strengthening and stiffening the bottom sheet , and a parallity of clips for securing the i - beams to the underside of the bottom sheet . in a preferred embodiment , the trays include downwardly projecting legs which are shaped enable the trays to be stacked vertically . also in the preferred embodiment , the trays are made of a polyolefin and the i - beams are made of aluminum . the end walls also preferably include i - beams for re - enforcement ; the i - beams are totally enclosed in the end wall structure to minimize exposure to a corrosive atmosphere .