by screwing unscrewing it a user can tighten release the bar 115 to block the bar 115 in the desired position the eye bolt 215 cooperates with a flexion spring 220 in detail the flexion spring 220 is in the example shown and described constituted by a bent wire or by a foil of suitable material for instance silica steel or steel with high content of carbon or stainless steel particularly the spring 220 includes a hookup ring 220 a for hooking to the clamp body 205 adapted to be accommodated in the groove 213 provided in the clamp body 205 from the hookup ring 220 a a first wire segment 220 b departs which in the shown example is directed substantially orthogonally to a plane in which the hookup ring lies 220 a the first wire segment 220 b continues in a second wire segment 220 c directed so as to form an angle that when the spring is at rest is approximately 90 u00b0 the second wire segment 220 c preferably ends with a knob 220 d thus is disclosed a clamp 120 for clamping a support bar 115 of a conveyor 100 comprising a clamp body 205 for slidingly accommodating the support bar 115 and positioning means 220 for holding the support bar 115 in a predetermined position with respect to the clamp body 205 further comprising distinct tightening means 215 for blocking the support bar 115 in the predetermined position the tightening means 215 are separate from the positioning means 220 the positioning means 220 are elastic positioning means to elastically engage the support bar 115 in this embodiment the elastic positioning means are formed by a wire spring.