in fig2 the spacer element 20 has a rectangular profile and two bores 28 are located near the ends thereof and extend through the web 21 each bore 28 adjoins an enlarged recess 29 coaxial therewith and extending into the head piece 22 the bores 28 serve to receive fixing bolts or screws 30 fig1 having heads received in the recesses 29 the bolts or screws 30 serve to secure the associated spacing element 20 and the plate 11 of the assembly to the spill plate attachment these spill plates are in turn secured to the conveyor pan side wall with the aid of mounting devices 32 fig4 welded into the v shaped grooves 31 in the pan side walls as shown in fig4 the devices 32 support and locate screws 33 permitting the attachment of the spill plates in side by side relationship with the pan side walls referring now to fig1 and 5 each cover plate 12 has recesses 36 having a similar rectangular profile to the spacing elements so as to receive the spacing elements 20 as shown particularly in fig1 where adjacent cover plates 12 are represented in their normal closed position and in their pivoted open position each plate 12 is shaped with the curved over lower region 12 34 providing an aperture a rear continuation of the region 12 34 provides a flange 12 39 extending parallel to the portion 14 of the plate 11 when the cover plate 12 is in the normal closed position the upper edge of the flange 12 39 is welded to the inner face of the cover plate 12 web plates 37 are welded between the flange 12 39 and the inner face of the cover.