The present invention relates to a knife feed system in a rotary drum cutter provided in a tobacco shredder or the like.
Generally, in a shredding machine for tobacco, tobacco leaves as raw material are conveyed under compression to a shredding port by means of two upper and lower press conveyors, the shredding port being formed in front of the press conveyors, and are shredded with a rotary drum cutter rotating in close proximity to the shredding port.
The rotary drum cutter is composed of a rotary drum and a plurality of knives disposed at predetermined intervals on the outer peripheral surface of the rotary drum. The cutting edge of each knife is ground continually during operation of the cutter by means of a grinder provided separately so as to be suited to a high speed processing over a long period of time. Further for maintaining constant the spacing between the knife edge and the shredding port, a knife feed system for feeding each knife continuously or intermittently little by little is provided in the interior of the rotary drum.
The abrasion loss of the knife differs depending on the raw materials to be shredded. If the feed of the knife is small despite of a large abrasion loss, it will be impossible to attain sharpness of the knife even after grinding and so consequently difficult to obtain shredded tobacco leaves of good quality, causing an increased loss of raw material. Furthermore if the knife is ejected to a larger extent than necessary despite a small abrasion loss, the knife which is expensive will be wasted. Therefore, it is necessary that the feed of the knife be changed according to the raw material to be shredded. In this connection, the knife feed system in conventional rotary drum cutters is constructed so that each knife is ejected in interlock with the rotation of the rotary drum. This construction was given rise to the problem that the replacement of parts must be done for adjusting the amount of ejection of the knife according to the kind of raw material used. An additional problem has existed in that when changing the knife the spacing between the knife and the shredding port must be adjusted under no-load rotation of the drum without feed of raw material, thus requiring much time for the adjustment.