10 each scraper wing 1 has below head web 2 an inside 11 which forms one of both lateral delimitations for insertion pockets 5 the other lateral delimitation of each insertion pocket 5 is formed by respective outsides 12 of central web 6 insides and outsides 11 12 diverge slightly as a result of which the width of insertion pockets 5 increases towards underside 7 or 8 for positive locking anchoring of horizontal chain links 52 having entrainment projections 58 in insertion pockets 5 grooves 13 and 14 are formed both in insides 11 of scraper wings 1 and in outsides 12 of central web 6 grooves 13 and 14 protruding upwards substantially from underside 8 of scraper 10 to underside 2 u2032 of head web 2 grooves 13 provided according to the invention in insides 11 and grooves 14 in the outsides of intermediate web 6 are particularly apparent from fig1 4 5 and 7 since grooves 13 and 14 run over the entire height of insertion pockets 5 they extend both across a region in which a scraper securing element 40 is received in each insertion pocket 5 as well as across the region directly below underside 2 u2032 of head web 2 in which limb beds 15 for limbs 56 of horizontal chain links 52 are formed fig3 and 4 show herein the status after and before mounting of horizontal chain link 52 and of scraper securing element 40 in insertion pockets 5 fig3 illustrates.