| 摘要 |
A faller bar transfer mechanism is described for a screw type gillbox (10) which comprises at least one cam (34) located at the transfer end of each of the working and return screws (12, 14) to contact the faller bars (24) and move them between the working and return screws and vice versa. The cam has a backwardly directed profile with respect to its direction of rotation. The faller bars on transfer are fully displaced from the horizontal path of the next following faller bar by a vertical movement less than 85 % of the total transfer distance. The profile of the cam is chosen such that the faller bars are displaced 80 % or less of their total transfer distance by the time the cam has rotated through 100 % from the point of initial contact with the faller bar. The cam profile meets the end of the faller bar less than 30 % below the horizontal centre line between the screws. The faller bars are no more than 1 cm (three eights of an inch) longer than the distance between the driving screw spindles. The acceleration imparted to the faller bar by the cam is gradual and the knocking or "hammering" action of the bulk of previous gillboxes is avoided completely. The profile (44a) is preferably shaped so that the faller bar is brought up to a speed in the first portion of the cam revolution which will transfer between the two sets of screws. The profile is thereafter lowered so that, in normal use, the faller bar does not contact the cam at all. By this means it is possible to accelerate the faller bar to the minimum speed necessary for it to effect proper transfer and not continue acceleration beyond this point, thus minimizing the amount of retardation which must be applied to the faller bar when it reaches its destination, and allowing much faster machine operation. |
