Apparatus For Conveying And Depositing Overlapped Sheets Of Paper And The Like

Abstract

Apparatus for conveying sheets emanating from transverse cutters or other sheet-ejecting machines in a flow line of successive end to end sheets in which the sheets are overlapped by upper and lower conveyor belt means with conveyor belt drive means being operative to move one conveyor belt means slower than the other conveyor belt means so that each successive sheet is overlapped with the immediately preceding sheet, the slower moving conveyor belt being stopped in response to the absence of at least one sheet in the flow line of successive sheets, the drive means for the slower conveyor belt means including a differential gear means including an input drive shaft and two driven shafts and means are operatively associated with said differential gear means for alternatively stopping and releasing both driven shafts.

Description

The removal of a defective sheet takes place prior to the time where the sheets become overlapped through reduction in their advance speed, so that there necessarily occurs a gap in the continuous flow of the overlapped sheets. Such a gap represents an interruption in the sheet-overlapping process, bringing about the danger that the frontal edge of the sheet following the removed or diverted sheet strikes or shoves upon the rear edge of the sheet preceding the removed sheet, thus resulting in disturbances during further conveying and depositing of the sheets.

In order to prevent this type of disturbances, it has been proposed that the slower-running conveyor belts be stopped for a short interval during removal of a defective sheet so as to avoid the development of a gap in the overlapped sheet succession. In this known embodiment, the conveyor belts were stopped by means of a brake acting upon the slower-running conveyor belts and a coupling device which was connected with the drive for the conveyor belts. It became apparent, however, that the responsive behavior of the brake and of the coupling were inadequate during high operating speeds and correspondingly quick or rapid movement of a succession of sheets, so that a timely stopping and restarting of the conveyor belts in dependency upon the activity of the divertor or gate was not ensured.

The object of the present invention is to provide for a control means for the slower running conveyor belts whose time for responding will be so short as to prevent the aforementioned drawbacks from appearing, and wherein said control means meets the expected requirements regarding functional safety by virtue of its simple construction at low expenditure.

Proceeding from an apparatus for conveying sheets emanating from transverse cutters or other sheet-ejecting machines which are being transferred by their becoming overlapped during such a phase, from faster running conveyor belts to slower-running conveyor belts which are stopped when one or several sheets are missing from the continuous flow of sheets in advance of the slower-running conveyor belts, it is now proposed to solve this object by connecting a differential gear with the drive for the slower running conveyor belts. This differential gear has associated with it a device for alternatingly stopping and releasing two driven shafts. In this arrangement, one of the two driven shafts of the differential gear drives the slower running conveyor belts while the other driven shaft is constructed as an idler shaft which can be stopped. The power train through the differential gear is transmitted while the idler shaft is stopped or held by the continuously running drive shaft via the released driven shaft for the conveyor belts, whereas the power train with the conveyor belt driven shaft being stopped or held, is transmitted by the drive shaft to the released idler shaft. The arrangement is furthermore constructed such that both of the driven shafts of the differential gear are each provided with a band brake so arranged that the pulling end portions of the brake bands can be actuated by a common cylinder piston unit.

Further and more specific objects of the invention will be apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a diagrammatic side view illustrating a transverse cutter and sheet moving system embodying the present invention;

FIG. 2 is a diagrammatic side view illustrating preferred embodiment of the conveyor belt drive,

FIG. 2a is a top plan view of the arrangement shown in FIG. 2, and

FIG. 3 is a diagrammatic view illustrating a further embodiment of the conveyor belt drive.

As can be seen particularly well in FIG. 1, the paper web 2 emanating from feed or supply roll 1 is fed through a flaw detection device 3 and then led through advancing or feed rollers 4 to a transverse cutter device comprising a pair of rotary knives 5 which divides the paper web 2 into individual sheets 6. The sheets 6 then reach the area of gate or diverter 8 via a feeder table 7. This gate or diverter 8 is in the position as shown in the drawing so that the moving sheets 6 pass between the fast running conveyor belts or tapes 9, 10, 11. A photoelectric cell 12 scanning the succession of sheets is mounted in the area of these conveyor belts. As sheets 6 move along, they reach the overlapping station which is formed by the lower and slower moving conveyor belts or tapes 13 cooperating with the upper conveyor belts or tapes 11. Thereafter, the sheets 6 are deposited on stack or layboy 14.

The drive for the slower moving conveyor belts 13 is effected through a differential gear means 15. As described above, this differential gear means 15 is constructed and mounted in such manner that, as a defective sheet is being removed resulting necessarily in the development of a gap in the flow line of sheets, an impulse is initiated by the photoelectric cell 12 to the drive for the slower moving conveyor belts 13 so that these conveyor belts 13 can be stopped for a brief interval.

As mentioned supra, the activation of gate 8 during the appearance of a defective spot takes place by means of an impulse emanating from the flaw detection device 3, said impulse being transmitted to a magnet 17 acting upon lever 16 of gate 8. The oscillating movement of gate 8 thereby causes the deflection of defective sheet onto defective stack 22 via conveyor belts 18, 19 and 20, 21.

FIG. 2 shows an enlarged embodiment and arrangement of differential gear means 15 which is connected with the drive of the slower moving conveyor belts 13. The drive or input shaft 23 of differential gear means 15 is connected with the continuously running main drive, not depicted herein, of the apparatus. Of the two driven shafts of the differential gear means, shaft 24 is constructed as an idler shaft, whereas shaft 25 drives roller 26 around which conveyor belts 13 are wound, FIG. 2a. Brake discs 27 and 28 are secured to the extensions of the driven shafts 24 and 25 and have brake bands 29 and 30 associated therewith.

One end of each of these brake bands 29 and 30 are each connected with a stationary point 21, whereas the other or pulling end portions of each brake band are connected to the opposite ends of the piston of a double-acting cylinder piston unit 32 which is fed from a compressed air source, not shown, under control of a magnetically actuate valve 33. The valve 33 is activated by means of an impulse initiated by photoelectric cell 12 scanning the succession of sheets.

In the operative embodiment as shown in the drawing, in which an uninterrupted sequence of sheets is conveyed to flawless stack 14, the slow-moving conveyor belts 13 run continuously. In this mode of operation the power train through gear means 15 is transmitted to conveyor belts 13 by drive shaft 23, while the driven idler shaft 24 is being braked or held and driven shaft 25 released. If as a result of detecting a defective sheet and the actuation of gate 8 released thereby, a gap develops in the succession of sheets being conveyed to flawless stack 14, photoelectric cell 12 senses this gap and sends an impulse to magnetic valve 33 with the effect that driven shaft 25 is stopped through the movement of the piston in cylinder 32 to the left, and driven shaft 24 is released. During this phase, the conveyor belts 13 are stopped, and the power train through the gear 15 is transmitted by the drive shaft 23 to the driven idler shaft 24 which has been released and is working as an idling shaft. As soon as the gap has passed the magnetically actuated valve is released and the piston in piston-cylinder unit 32 is moved to the right to release shaft 25 and hold shaft 24 whereupon conveyor belts 13 are again driven.

FIG. 3 shows a modification of the conveyor belt drive in such fashion that the driven shafts 24 and 25 which are provided with brake discs 27 and 28 are positioned opposite of each other. In this embodiment, brake discs 27 and 28 have associated with them brake shoes 34 and 35 which in conformity with the brake bands 29 and 30 of the above-described embodiment alternatingly stop and release the driven shafts 24 and 25 of differential gear 15. Otherwise, the method of operation and effects correspond to the drive of the conveyor belts as depicted in FIG. 2.

It is therefore clear that this invention provides a system for conveying and depositing sheets that emanate from a cross cutter which includes: 1. means for moving a paper web to a cross cutter so that the web is cut into individual sheets; 2. means in advance of the cross cutter for sensing or detecting a flaw in the web; 3. means for receiving and moving ejected cut sheets from the cross cutter in a flow line of successive sheets in end-to-end relation; 4. movable means interposed in said last-mentioned means and operative in response to said sensing means for diverting a sheet having a flaw therein from said flow line; 5. means for moving diverted sheets to a stack; 6. means for overlapping successive sheets including upper and lower conveyor belt means and means for driving the lower conveyor belt means at a slower speed to permit a successive sheet to overlap a preceeding sheet, and for delivering the sheets to another stack; 7. a differential drive gear including a continuously rotating input drive shaft and two driven shafts, one of said driven shafts driving said slower conveyor belt means and the other driven shaft constituting an idler shaft; 8. means for alternatively holding said idler shaft stationary and releasing said one driven shaft to allow the input shaft to drive said slower moving conveyor and for releasing said idler shaft and holding said one driven shaft to stop said slower moving conveyor belt means without stopping said input shaft; 9. sensing means operatively associated with the means for moving the sheets in a flow line of successive sheets in advance of said slower moving conveyor belt means for detecting a gap in said flow line occasioned by the absence of at least one diverted sheet for indicating a command impulse responsive to such a gap, 10. and means operative in response to such initiated command impulse for controlling the means for alternatively releasing and holding said driven shafts to actuate the same to release said idler shaft and hold said one shaft to stop said slower moving conveyor belt means while said gap exists and to hold said idler shaft and release said one driven shaft to allow said slower conveyor belt means to move when said gap is closed by another moving sheet.

Design and mode of operation of the flaw detector 3 and of magnet 17 for actuating the gate 8 are described and shown in the U.S. Pat. No. 3,070,365. The photoelectric cell 12 and the magnetic valve 33 for actuating the cylinder piston unit 32 are commercially available electro-optical or hydraulic units respectively. The differential gear 15 also represents, as can be recognized in FIG. 2a and 3, a known design which, in its basic form and in its mode of operation is for example used in motor vehicle construction.

Claims

I claim:

1. In apparatus for conveying sheets emanating from a transverse cutter or other sheet ejecting machines, means for receiving and moving ejected sheets in a flow line of successive end-to-end sheets, means for overlapping moving sheets including upper and lower conveyor belt means, drive means for said conveyor belt means including means operative to move one conveyor belt means slower than the other conveyor belt means so that each successive sheet is overlapped with the immediately preceding sheet, means for stopping said slower moving conveyor belt means in response to the absence of at least one sheet in the flow-line of successive sheets, and the drive means for said slower conveyor belt means including a differential gear means including an input drive shaft and two driven shafts and means operatively associated with said differential gear means for alternatively stopping and releasing both driven shafts.

2. Apparatus as claimed in claim 1 in which one of said two driven shafts of the differential gear means drives the slower moving conveyor belt means, while the other driver shaft is an idler shaft which can be stopped.

3. Apparatus as claimed in claim 2 in which said input shaft of the differential gear means is continuously rotating, the power train through said differential gear means being transmitted to the slower conveyor belt means from said input shaft by said one driven shaft when said idler shaft is stopped and said one driven shaft released, and the power train through said differential gear means being transmitted from said input shaft to said idler shaft when said one driven shaft is stopped to stop said slower moving conveyor belt and said idler shaft is released.

4. Apparatus as claimed in claim 3 in which the means operatively associated with said differential gear means for alternatively stopping and releasing both driven shafts includes a band brake means for each driven shaft, each bank band brake means having a pulling end, a cylinder, a piston means movable within said cylinder and having opposite end portions, said pulling ends of the band brake means being connected to the opposite end portions of said piston means, and means for controlling reciprocating movement of said piston means so that when one band means is applied to stop its associated driven shaft, the other band means releases its associated driven shaft when the piston means moves in one direction, and said other band means is applied to and stops its associated driven shaft and said one band means releases its associated driven shaft when the piston means moves in the opposite direction.