to fig2 in regard to the embodiment of fig1 and fig1 shows a perspective view similar to fig7 in relation to the embodiment of fig1 it will also be appreciated that the position of two opposed plates 50 gives adequate clearance for operation of the roller assembly 49 wherein plates 50 are spaced from plates 52 as shown in fig1 by gap 56 reference may now be made to another embodiment of the invention shown in fig1 15 and 16 showing roller assembly 49 a wherein there is shown roller support axle or shaft 1 b driven roller components 12 each having an inner metal roller sleeve 5 and outer rubber sleeve 7 and coupling assemblies 14 a each having disc 2 a welded to shaft 1 b disc 6 a welded to an internal surface of metal roller sleeve 5 and flexible coupling 8 a interconnecting discs 2 a and 6 a flexible coupling 8 a is located within disc 6 a and has projections 57 which engage with corresponding recesses 58 of disc 6 a as shown flexible coupling 8 a is also provided with recesses 59 which engage with corresponding projections 60 of disc 6 a thus in other words disc 6 a has a corrugated inner peripheral surface that engages with a corrugated outer peripheral surface of flexible coupling 8 a flexible coupling 8 a is also provided with a central aperture 61 having an inner corrugated surface having projections 63 and valleys or recesses 64 which engage with an inner corrugated disc 2 a welded to shaft 1 b as shown disc 2 a has an outer corrugated surface having projections 66 and valleys or recesses.