3 are separated from roller 2 which is fixed lever 52 rotates around a shaft 60 and bears against a camming surface 61 to move a rod 62 connected through the medium of a pin 63 to an inner core 64 carrying the shaft 15 of the roller 4 so as to be able to separate roller 4 from roller 3 rod 62 is housed in a body member 65 bolted as at 66 to the head 58 the above described separation mechanism also comprises recovery means consisting of a tension spring 65 mounted between heads 53 and 58 to counteract the action of levers 50 and 51 spring 65 is adjustable with a threaded pin 67 provided with lock nuts 68 while a further spring 69 opposes the action of lever 52 on rod 62 the basic operation of the apparatus is in the drive of rollers 1 2 3 and 4 to which effect the primary drive lever 5 so engages the profiles of the annular track 7 that each time the primary lever descends the secondary lever is caused to rise against the urging of springs 9 while the feed pawl 25 slides over the ratchet wheel 24 while each time the lever 5 rises springs 9 contract and cause the ratchet wheel 24 to rotate through the medium of feed pawl 25 and consequently shaft 6 and pinion 10 are caused to rotate this movement being transmitted to the remaining pinions 11 12 and 16 thereby the four rollers 1 2 3 and 4 rotate to.