fig6 the plates 25 have openings 30 which widen conically towards the front convex faces 26 as indicated by reference numeral 31 the chain links 29 fit in the openings 30 and are secured with upstanding pins 32 to the plates 25 the pins 32 are located at the centres of a curvature of the curved faces 26 and each pin 32 engages through two adjacent chain links 29 which lie one over the other the links 29 are thence disposed in two parallel horizontal planes and to maintain the spacing between the links 29 cross pins 33 are provided to intersect the axes of the pins 32 thus the links 29 do not interengage as with a normal chain but instead are connected through the pins 32 as shown in fig1 and 3 the endmost link 29 of the chain 28 has a retaining piece 34 at one end which firmly engages on the bearing face 26 of the first plate 25 the chain 28 runs beneath the plates 25 and at the opposite end the end link 29 is coupled to an hydraulic piston and cylinder unit 35 which serves to tension the chain 28 the unit 35 is disposed beneath the conveyor pans 2 and has its cylinder connected with a pivot.