GB690344A - Improvements in and relating to conveyors for sheet material - Google Patents

Abstract

690,344. Conveyers. AETNA-STANDARD ENGINEERING CO. June 22, 1950. [July 11, 1949] No. 15628/50. Class 78 (i). A method of straightening the position of a sheet of material lying askew relative to a conveyer, i.e. with one corner of its leading edge advanced relative to the other, consists in feeding the sheet on to the conveyer with the sheet travelling at a speed greater than the speed of the conveyer, and applying retarding forces to the sheet while travelling at said greater speed and thus being free from restricting forces other than dynamic friction with the conveyer, the resultant of which forces acts on the same side of the sheet as the advanced corner of its leading edge. In a classifier for metal sheets of the type wherein the sheets 11 are gauged and passed to a flipper 13 which is controlled by the gauge so as'to pass on-gauge sheets to a conveyer line 15, 16, 17 while deflecting off-gauge sheets to a conveyer line 19, 20, 21, the conveyers are provided with straightening devices in order that the sheets pass to stackers 18 and 22 in correct alignment with respect thereto. The conveyers, 15, 16 17 are separately driven by motors 27, 28, 29 at successively lower speeds and the conveyers 19, 20, 21 are driven at similar speeds to the conveyers 15, 16, 17 by motors 30, 31, 32. A conveyer 12 which feeds the sheets from the gauge to the flipper 13 is in turn driven at a greater speed then the conveyers 15 and 19 by means of a motor 25, which also drives a pair of edge flattening rollers 23. Each conveyer except the last in each line has a spring arm 41 which presses a roller against the discharge end of the belts so as to ensure that the sheets are shot horizontally onto the succeeding conveyer. Upon reaching the last conveyer in the ongauge line the sheets overlap, owing to the reduced speed so as to facilitate stacking. Each straightening device consists of one or more electromagnets placed near to the feeding end of a conveyer beneath the belts so as to act on the sheets while they are moving faster than the belt and before they slow by friction to the speed of the belts, the magnets also assisting such slowing by attracting the sheets towards the belts. The arrangement of the magnetic field to cause straightening of sheets lying askew with respect to the conveyer is indicated by the dotted rectangle in Fig. 3A. When the most forward corner 94 of the sheet 5 enters this field, eddy currents in the sheet in the shaded portion produce a retarding force acting along the arrow a, which is out of line with the line b passing through the centre of gravity of the sheet in its direction of movement. The resulting couple turns the sheet towards the aligned position. The magnets 58, 60, 62, 42, 66, 44, 74, 80, 81, 82, 46, 84 and 48 all act in this way and are controlled as required by the switchboards 93 and 98, so as to cut out some of the magnets if desired. There are further sets of magnets 72 and 85 which are controlled in such a manner as to create a field acting more or less on one side of the sheet as indicated in Fig. 4 for deliberately skewing the sheets after straightening, if required. This is carried out by having two rows of magnets e.g. one under each parallel belt 16a, 16b of the conveyer 16, the rows being separately controlled bv a switchboard 97. Further magnets 64, 68, 76, 78, 83, 86, 87 and 88 are provided to keep the sheets firmly pressed down towards the discharge ends of the various conveyers. All the magnets other than the sets 72 and 85 consist of pairs of magnets which are simultaneously energizable by the switches on boards 93 and 97, e.g. in the case of conveyer 15 one magnet of each pair is under belt 15a while the other is under belt 15b so producing the desired rectangular field. Specification 651,843 is referred to.