Suction device for feeding sheet material

Abstract: A suction device for feeding sheets (11) of material comprises a housing connectable by a pipe to a vacuum device (42) and having apertures over which the sheets pass and through which a suction effect can be created. An eccentrically mounted roller (46) imparts a distortion to the attracted sheets. A single endless perforated belt (30) passes over the apertured surface of the housing. The distortion-imparting roller (46) acts on the inside of the belt and is adjustable by knob (50) to vary the amount of distortion.

Description: This invention relates generally to suction feeder mechanisms for the feeding of sheet material and to methods of feeding sheet material. The suction feeders of the present invention are particularly adapted for use with collating machines, but the principles of the invention have much wider application to any circumstance where one wishes to feed sheets of material, whether paper or other materials. It is emphasised that the present invention is applicable not only to collating machines but also to photocopiers, printers, and indeed any other mechanism where sheets of material are to be moved around. In the feeding of sheet material it is desirable that there should be no misfeeds or double feeds. It is also desirable that the mechanism should be able reliably to feed sheets of different types of material. Although there are suction feeder mechanisms which function with reasonable reliability in terms of avoiding misfeeds and double feeds, or else incorporate sensors to detect if and when such faults occur, particular problems arise if one is designing one mechanism which is intended to be able to feed sheet material of different thicknesses and compositions. EP-B-0465062 describes a top sheet vacuum corrugation feeder with an air knife in the form of a single slot which supplies air at low pressure across the entire width of the sheet to create a thick boundary layer which causes separation of the sheets by aerodynamic drag during feeding of the top sheet. EP-A-0619259 describes a top sheet feeder mechanism which has a corrugator in the centre of a plurality of perforated belts which move around a plenum chamber. The corrugator is an endless band which extends around the full length of the plenum chamber, and hence is not adjustable. Air is supplied to the region between the underside of the belts and the surface of the top sheet, to assist in the separation of the sheets. The bottom run of the belts and the surface of the top sheet are parallel and their separation is maintained constant by the use of a movable tray on which the sheets are stacked. US-A-4336929 describes a sheet feeder for separating and feeding the bottom sheet of a stack, a spring-biased corrugating ramp being provided beneath a non-perforated feed belt operating over a suction housing. The corrugating ramp is depressed by heavy weight, stiff sheets to allow the sheets more closely to approach the suction housing. It is an object of the present invention to provide a suction feeder mechanism and a method which can reliably feed sheets of material with greatly reduced likelihood of misfeeds or double feeds. It is a further object of the invention to provide a mechanism and a method which enables one to feed sheet material which can vary from for example thin paper up to thick sheets of plastics material which are subject to a large electrostatic charge. Sheets of plastics material are particularly difficult to feed reliably, due to the build-up of electrostatic charges, and this has created particular problems in the past. The present invention solves or at least minimises these problems. The sheet feed of the present invention has many attributes: a) it is very economical; b) it does not require adjustments over a wide range of materials and sheet sizes; c) it is rugged and reliable; d) it operates without creasing or marking the sheets; e) it provides a very positive feeding mechanism; f) because of the very small amount of movement of paper and of the mechanism itself, it is possible for it to be not only very economical but also very fast. In accordance with the present invention there is provided a suction device for use in the feeding of sheets of material, comprising a vacuum device arranged to exert a suction effect on the sheets to attract them towards a position for onward movement, means to impart distortion to an attracted sheet, and a suction housing having an apertured surface through which a suction effect can be created to attract a sheet towards said surface, characterised by an endless perforated belt arranged to pass over said apertured surface, and corrugator means acting on the inside of the belt to impart distortion to the belt, the corrugator means being user-adjustable to vary the amount of distortion. Preferably, the corrugator means comprises a roller mounted for eccentric rotational movement. In a preferred embodiment the adjustment of the corrugator means is arranged to be effected by rotation of an adjusting knob mounted externally of the housing. The corrugator means may be a grooved roller. Preferably, the corrugator means is positioned centrally across the width of the housing. Desirably, the suction housing has apertures in the housing surface which display a chevron pattern overall. The apertures may comprise a plurality of parallel slots, with longer slots towards the outside edges of the housing and shorter slots towards the centre. In one embodiment there are four slots on each side of a central corrugator means, the two outer slots on each side being of equal length, the next inner slot being approximately half the length and the innermost slot being approximately half the length again. Preferably, the ratio of the transverse width of the housing to its length is approximately 3 to 1. Preferably, a portion of the housing surface to the rear of and to each side of the corrugator means is imperforate. Uniquely, the feed system requires no adjustment when changing paper sizes. One can cater for sheet sizes from 130 x 160mm to 364 x 520mm for example. One can use sheets from 40 to 240gms. In order that the invention may be more fully understood, an embodiment of sheet feeding mechanism in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of the feeder mechanism to illustrate the feed system; Fig. 2 is an underneath plan view of the suction box around which the feed belt travels; Fig. 3 is a view from below of the suction head comprising suction box and feed belt; Fig. 4 is a schematic side view of parts of the feeder mechanism to illustrate the air flows for separation of the sheets; and Fig. 5 is a diagrammatic plan view to illustrate how the air flows emanate from the air vents. In the various drawings the same parts are denoted by the respective same reference numerals. The sheet feeding mechanism shown in the drawings comprises a suction head, indicated generally at 10, which is designed and arranged to receive individual sheets 11 of paper, card, film or other like material from a stack 12 of sheets which are set on a supporting plate 14. In contrast to conventional suction feeders, the sheets in the stack 12 do not lie parallel to the underside of the suction head 10 but are set at a feed angle a with the leading edges of the sheets extending downwards away from the suction head. This feed angle a is preferably within the range of 5° to 15°, preferably about 10°. The suction head 10 will be described in detail hereinafter. Each sheet 11, as it is picked up and fed forward, is guided by guides 16, 18 to move forwards and then downwards between rollers 19, 20, 21. In front of the sheet stack 12 are a pair of fingers 22 which are pivotable and are positioned quite close to the centre of the stack width, as can be seen in Fig. 5. These serve as stops for sheets other than the topmost sheet and each has a serrated upper surface over which the sheet being fed will pass. The suction head 10 comprises a suction box 24 which is fitted with a front drive roller 26 and a rear idler roller 28. Around the rollers and box runs an endless belt 30, intermittently driven. The rear idler roller 28 is fitted with a cam 32 which is engaged by a cam 34 which is pivotable about a pivot pin 36. By pivotal movement of cam 34 the rear edge of the suction head 10 can be raised and lowered to alter the feed angle α. Fig. 2 shows the suction box 24 in greater detail. It consists of a rigid housing 38 which is provided with a connecting tube or pipe 40 which is connected to a vacuum device 42 (Fig. 3). The box is provided in its underside with slots, as will be described in more detail hereinafter. Around the box 24 runs the endless flexible belt 30 which has rows of perforations 44 running lengthwise of the box at regularly spaced intervals. The belt 30 is made of a material such as "Hyperlon" (R.T.M.) which is not too elastic, which has a good memory and does not generate static charges. Because the transverse width of the suction box 24 is approximately three times its length, the belt 30 is effectively a tube of material. By the operation of the vacuum device 42 the pressure within the suction box 24 can be reduced, and by virtue of the registration of the perforations 44 with the slots a reduced pressure is created at the perforations. This means that if the suction head is positioned above the stack 12 of sheets, application of the suction will cause the top sheet to be attracted to the belt. Positioned centrally across the width of the suction box 10 is a distortion wheel or roller 46 which is connected by a shaft 48 to an external adjusting knob 50. The wheel or roller 46 may be eccentrically mounted on the shaft 48 so that rotation of the adjusting knob 50 will cause an eccentric movement of the wheel or roller 46. The wheel 46 is preferably a grooved wheel, thus providing two circumferential ribs. The wheel or roller 46 projects from the bottom of the suction box and as it is rotated it increasingly distorts the central portion of the encompassing belt 30 adjacent to the leading edge of the box. It is to be noted that the corrugator 46 is within the belt 30. The amount of distortion of the belt is determined by the rotational position of the wheel or roller 46 and can be set in dependence upon the nature of the materials to be advanced from the stack. Sheets which are thin or difficult to separate will need a large hump, while stiff materials which are easier to separate need less distortion. This distortion of the central zone of the belt 30, coupled with the suction effect created at the perforated zones of the belt means that as the top sheet in the stack 12 is lifted to the belt it has an undulation imparted to it. The distortion of the belt also contributes to the repelling of the next, underlying sheet of material in the stack, thereby helping to avoid double feeding. In Fig. 2 the direction of movement of the sheets is indicated by arrows 52. The pattern of slots in the suction box, which work in conjunction with the corrugator 46, is important to the invention. As shown in Fig. 2, in each side of the box, i.e. on each side of the central corrugator, there are two outer slots 54a, 54b of equal length extending almost fully the length of the box, then a shorter slot 54c, and then a still shorter slot 54d. Slot 54c is about half the length of slots 54a, 54b, and slot 54d is about half the length of slot 54c. The slots all run from the leading edge of the box adjacent to the drive roller 26. This results in a chevron pattern of slots, with the area of the suction box behind and to the sides of the corrugator 46 being flat and imperforate. This prevents creasing of thin paper. The action of the chevron slot pattern is first to grip the sheet, via the aligned perforations 44, towards the outer edges of the suction box. Then, with actuation of the drive shaft 26, the belt and attracted sheet advance over the surface of the suction box. The shorter slots 54c, 54d provide added suction adjacent to the leading edge of the sheet to ensure that it is held to the belt at this edge in spite of the distortion introduced by the corrugator 46. In other words, this boost in suction is brought into effect at the time that the central portion of the sheet is distorted and might otherwise break away from the belt. The sheet is held more tightly at its leading edge when the central portion is distorted. The number, dimensions and position of the slots can be varied, provided that the leading edge boost is achieved. In Fig. 3 the belt 30 is shown with five rows of perforations 44 on each side of the corrugator 46. The four inner rows on each side are aligned with the slots 54a, 54b, 54c, 54d and in the passage of the belt over the suction box the perforations will pass along the length of the respective slots. The outer row 56 of perforations on each side of the belt 30 is aligned with a "dummy" slot 58 in the suction box. This dummy slot 58 can be converted into a true slot, for wider sheets of material, by breaking away a thin web of material which initially closes the slot. If one is feeding narrow sheets then the outer slot or slots in the suction box can be masked by tape to make the suction more efficient. Although not so shown in Fig. 3, the sheet 11 in practice would be over the belt 30. In order to achieve effective separation of the top sheet from the stack 12 it is important to use air flows. Figs. 4 and 5 show how this is applied. Fig. 5 shows the parts in an exploded arrangement for clarity. Three different air flows are utilised. Running along the bottom of the stack 12 from side to side is an air pipe 60 which is provided with for example four holes 62 facing upwards and creating a constant upward air flow as indicated by the arrows 64 towards the margins of the sheets. From the air pipe 60 air is ducted by pipe 66 to emerge at the centre of the width of the stack in front of the topmost sheet, as indicated by arrows 68. This second, constant air flow emerges as two flows, one each side of a deflector 70 (Fig. 5), and directed one each side of the corrugator. The third air flow consists of air blasts, i.e. pulses of air, produced from two nozzles 72 positioned laterally outside the fingers 22 and directed at the leading edge of the top sheet. These air blasts are indicated by arrows 74. The combination of the air blast with the constant air flows results in excellent and reliable separation of the top sheet. The pulsed air blasts from nozzles 72 are synchronised with the creation of the reduced pressure within the suction box. Also, the actuation of the drive for the drive shaft 26 is synchronised with the pump 42 which creates the reduced pressure, so that the advance movement of the belt, the suction effect and the pulsed air blasts are in the correct timed relationship.

Claims: A suction device for use in the feeding of sheets (11) of material, comprising a vacuum device (24, 42) arranged to exert a suction effect on the sheets to attract them towards a position for onward movement, means (46) to impart distortion to an attracted sheet, and a suction housing (24) having an apertured surface through which a suction effect can be created to attract a sheet (11) towards said surface, characterised by an endless perforated belt (30) arranged to pass over said apertured surface, and corrugator means (46) acting on the inside of the belt (30) to impart distortion to the belt, the corrugator means (46) being user-adjustable to vary the amount of distortion. A suction device according to claim 1, characterised in that the corrugator means comprises a roller (46) mounted for eccentric rotational movement. A suction device according to claim 1 or 2, characterised in that the adjustment of the corrugator means is arranged to be effected by rotation of an adjusting knob mounted externally of the housing. A suction device according to any of claims 1 to 3, characterised in that the corrugator means comprises a grooved roller. A suction device according to any of claims 1 to 4, characterised in that the corrugator means is positioned centrally across the width of the housing. A suction device according to any preceding claim, characterised in that the suction housing (24) has apertures (54a-d, 58) in the housing surface which display a chevron pattern overall. A suction device according to claim 6, characterised in that the apertures comprise a plurality of parallel slots, with longer slots (54a, 54b, 58) towards the outside edges of the housing (38) and shorter slots (54c, 54d) towards the centre. A suction device according to claim 7, characterised in that there are four slots on each side of a central corrugator means (46), the two outer slots (54a, 54b) on each side being of equal length, the next inner slot (54c) being approximately half the length and the innermost slot (54d) being approximately half the length again. A suction device according to any preceding claim, characterised in that the ratio of the transverse width of the housing (24) to its length is approximately 3 to 1. A suction device according to any preceding claim, characterised in that a portion of the housing surface to the rear of and to each side of the corrugator means (46) is imperforate.

Inventors: WATKISS CHRISTOPHER ROBIN, WATKISS, CHRISTOPHER ROBIN
Applicants: WATKISS AUTOMATION LTD, WATKISS AUTOMATION LIMITED
Application year: 1996
Main classification: B65H3
IPC codes: B65H3