EP0501213B1 - Device for transporting and piling flat objects - Google Patents

Abstract

A device for conveying and piling flat workpieces includes a conveyor comprising side-by-side endless belts with a vacuum chamber for each belt, which vacuum chambers are interconnected to a common source of vacuum and which chambers are separated by ducts which are in communication with either atmospheric air or pressurized air and contain ejector levers acting on an elongated flexible element to eject a sheet from the belts and to break the suction from the vacuum chambers on the sheet by uncovering openings in the ducts to supply air at atmospheric pressure or pressurized air to each of the vacuum chambers. The conveyor places the sheet in a piling store, which can then be removed as a batch of a certain number of sheets.

Description

The invention relates to a device for transporting and stacking flat objects, in particular cut sides, plates or cardboard boxes, of the type comprising a conveyor with sequentially driven endless belts acting jointly with a vacuum chamber and ejectors for moving flat objects away from the conveyor's endless belts for stacking in a store.

As a general rule, in the devices known to date, flat objects, for example sheets of corrugated cardboard, coming from a working machine are stacked in one or more stores from which they are then extracted for storage. or with a view to their routing to another destination, for example to another machine having to perform an additional operation on the corrugated sheets.

In practice, devices of the type described in the preamble to claim 1 are already known.

US Patent No. 3,820,779 relates to a device using, for transporting the corrugated sheets, a conveyor equipped with a plurality of parallel conveyor belts spaced laterally from each other. These conveyor belts are driven sequentially using a member in the form of a Maltese cross, making it possible to slow down and stop the conveyor belts at each advancement cycle of the plates. On the other hand, it was planned to install, above the conveyor belts, a vacuum device intended to suck the cardboard plates against the conveyor belts, the suction being effected through spaces left free between each of these belts. In addition, the lower part of the vacuum device consists of support members for the belts which are also spaced from one another so that the space left free between the belts is preserved.

The device described also comprises means for ejecting the plates, intended to move the latter away from the belts so as to drop them, by gravity, into one or more stores. These ejection means consist of two arms connected to each other, at their lower part, by a strip intended to come into contact with the upper face of the cardboard plate to be ejected.

These arms, arranged at each end of the conveyor, are controlled in synchronism with the sequential movement of the belts. In order to interrupt the suction effect created by the vacuum device, the two arms are provided with a valve arranged inside the vacuum device. When establishing the suction, the valve is moved away from the upper face of the support members of the belts by means of stops mounted on each of the arms of the ejection means. The suction is then cut off, during the ejection operation of a plate, by the return by gravity of the valve which will thus close the upper part of the spaces separating each support member from the belts.

One of the drawbacks of this kind of device lies in the fact that, when ejecting a cardboard plate, there is always a relative displacement between the ejector member and the upper face of the cardboard plate to be ejected. This slight relative displacement is acceptable when the work rates are relatively low. However, with current machines whose production rates are very fast, of the order of more than 10,000 cardboard plates per hour, a relative movement between the ejector member and the plate is not acceptable. In fact, at these rates, a relative movement between the ejector member and the plate results in very poor quality stacking, making any subsequent operation on the packet random.

To overcome this drawback, provision should be made, as is done in other devices, for providing a front stop against which the plates would come to stop, implying each time a shock of the front edge of the plate against the stop and by there a risk of deterioration of this edge of the plate, deterioration which, too, is not acceptable.

Another drawback presented by this kind of device is found in the control of the establishment of the suction. In fact, in the cited patent, at the start of the plate ejection operation, the suction effect will not be immediately cut off and the plate will remain "stuck" to the ejection members for a certain period, which will increase its fall time, by gravity, in the stacking magazine and may cause a possible collision with the next plate in the case of a high production rate. In any case, a high fall time will be detrimental to the performance of the device.

In the device described, the ejection members are controlled by means which are permanently coupled to the sequential control means of the conveyor belts. This feature is inconvenient when it is desired to use several successive stacking magazines, because, in this case, it is not possible without other to place two transport devices, as described, one following the 'other. In fact, since the action of the ejection members cannot be neutralized, it will be compulsory to provide for transport of the plates on two levels and to use a path deflector to direct the plates towards one or the other of the devices. transport and stacking as well as adding at least one additional transporter to this set. This will be costly and will further increase the risk of stack disturbance.

The object of the present invention is to remedy these drawbacks by solving the problem of transporting and stacking flat objects in machines for converting cardboard or corrugated cardboard.

To this end, according to one aspect of the invention, the device for transporting and stacking flat objects comprises a conveyor with endless belts driven sequentially, arranged side by side, the upper part of their lower strand respective is in contact with support members arranged so as to leave between them a space, communicating with a vacuum member, in which are placed ejection members equipped with means acting on the support members of the endless belts , so as to close the space left free between said support members, said ejection members being moved sequentially from top to bottom and from bottom to top, characterized in that the upper face of the lower strands of the endless belts bears against the lower face of a vacuum member composed of several separate vacuum chambers separated one from the other others by a channel, each of said vacuum chambers being provided with suction orifices located in the vicinity of the lateral edges of the endless belts, in that each of the vacuum chambers is connected to a common suction hood and in that that the ejection members, arranged in each channel separating two consecutive vacuum chambers, are constituted by elements pivoting sequentially to act on a linear member anchored, by one of its ends, to a fixed point and, by its other end, with compensating means and in that the linear member is arranged to close an opening in the lower part of said channel, disposed in the plane defined by the underside of the vacuum member.

According to a second aspect of the invention, the underside of the vacuum chambers has a convex surface whose curvature is defined by the arrow of the lower strand of the endless belts.

According to a third aspect of the invention, the latter provides a device for transporting and stacking flat objects comprising sequentially pivoting elements constituted by ejector levers acting on a linear member constituted by a strip of flexible material, anchored by one of its ends, to a first cross member placed at the upstream part of the conveyor, while its other end is held by compensating means, constituted by compression springs, fixed on a second cross member placed at the downstream part of the carrier.

According to another aspect of the invention, the latter provides a device for transporting and stacking flat objects, comprising channels, separating the vacuum chambers from one another, which are connected to the atmosphere or, according to a preferred embodiment, to a pressure source.

Advantageously, the device for transporting and stacking flat objects comprises ejection members which are constituted by pivoting levers whose sequential drive is disengageable with respect to the sequential drive of the endless belts of the conveyor.

The advantages obtained thanks to this invention consist essentially in that the transport and stacking of the flat objects can be carried out at high speed without there being any relative movement between the members for ejecting the flat objects and the upper face of these at the time of their distance from the conveyor belts and in that it is possible to achieve, using two identical devices, according to the invention, stacking flat objects in two consecutive stores by moving said objects in a single plane corresponding to the plane defined by the lower faces of the lower strand of the conveyor belts. Consequently, the device for transporting and stacking flat objects is distinguished by very high operating safety at high speed, by very high stacking precision and by the absence of deterioration of the flat objects transported and stacked.

• La figure 1 représente, en perspective, une station de réception d'une machine de transformation de carton ondulé,
• La figure 2 représente schématiquement, en vue de profil, un dispositif de transport et d'empilage,
• La figure 3 représente schématiquement, en vue de profil, une version simplifiée d'un dispositif de transport et d'empilage,
• La figure 4 représente, schématiquement, une vue en coupe partielle selon IV-IV de la figure 3, un transporteur en phase d'aspiration,
• La figure 5 représente schématiquement une vue en coupe partielle d'un transporteur en phase d'éjection d'un objet plat,
• La figure 6 représente schématiquement un dispositif de transport et d'empilage à deux stations,
• La figure 7 représente le mode de fixation d'une bande flexible servant à l'éjection des objets plats,
• La figure 8 représente un dispositif de transport et d'empilage comme celui de la figure 3 équipé d'une source de pression,
• La figure 9 représente une forme particulière de réalisation de la partie inférieure d'un transporteur, et
• La figure 10 représente un levier éjecteur.

An embodiment of a device for transporting and stacking flat objects is described below, by way of example, with the aid of the appended drawings in which:

• FIG. 1 represents, in perspective, a reception station for a machine for converting corrugated cardboard,
• FIG. 2 schematically represents, in profile view, a transport and stacking device,
• FIG. 3 schematically represents, in profile view, a simplified version of a transport and stacking device,
• FIG. 4 schematically represents a partial sectional view along IV-IV of FIG. 3, a conveyor in the suction phase,
• FIG. 5 schematically represents a partial section view of a conveyor in the phase of ejection of a flat object,
• FIG. 6 schematically represents a transport and stacking device at two stations,
• FIG. 7 represents the method of fixing a flexible strip used for the ejection of flat objects,
• FIG. 8 represents a transport and stacking device like that of FIG. 3 equipped with a pressure source,
• FIG. 9 represents a particular embodiment of the lower part of a conveyor, and
• Figure 10 shows an ejector lever.

The receiving station 1, of a corrugated cardboard processing machine, represented in FIG. 1 is formed by two lateral frames 2 and 3 connected to each other by crosspieces 4, 5, 6, 7, 8, 9, 10, 11 and 12. A conveyor 13 with endless belts 19, comprising a series of conveyor elements placed side by side, and of which only one element has been shown in this figure, is arranged between the side frames 2 and 3. The conveyor 13 is suspended at crosspieces 5 and 6. A stacking magazine 14 comprising a front wall 15 and a rear wall 16 is arranged below the conveyor 13. This stacking magazine 14 is, for its part, placed above a package evacuation device 17 resting on the crosspieces 8 and 11 and comprising two roller conveyors 18 and 19. The drive members of the endless belts 19 as well as the drive members of the ejector members, for example ejector levers 20, are arranged in a casing 21 fixed against the external face of the frame 3.

The transport and stacking device shown in FIG. 2 comprises a transport element composed of an endless belt 19 passing around a drive pulley 22 placed downstream of the transport element and around another pulley 23 placed upstream thereof. The drive pulley 22 is crossed by a control shaft 24 connected to sequential drive members (not shown) which can be in the form of a conventional cam and lever drive capable of transmitting an appropriate movement to the belts 19 This movement is advantageously chosen so that the belts 19 move at high speed during a first part of their advance and that their deceleration, to reach the stop, is as judicious as possible to preserve an optimum stop tempe. during which the corrugated cardboard 25 transported will be moved away from the endless belts 19 for stacking.

The upper face 26 of the lower strand 27 of each belt 19 (see FIG. 3) is in contact with the lower face 28 of each of the chambers depression 29 during the suction phase of a corrugated cardboard plate, that is to say when it is being moved in the device.

It should be observed that, in FIG. 2, the corrugated cardboard plate 25 is represented in its ejection phase, that is to say when it has been moved away from the endless belts 19. To carry out this removal operation of the corrugated cardboard plate 25 of the endless belts 19, ejector levers 20 mounted on the pivoting shafts 31 are used. The pivoting shafts 31 are connected, so that they can be temporarily disengaged, to drive members (not shown) whose movement, when transmitted, is synchronized with the movement or stopping of the endless belts 19. Thus, during the time of stopping the movement of the endless belts 19, the ejector levers 20 will be actuated by in such a way that their action on a linear member such as, for example, a flexible strip 32 or a section of belt causes the corrugated cardboard plate 25 to move away then to fall into the stacking magazine 14. This strip f the hose 32 is anchored at one of its ends to the cross-member 7 disposed upstream of the conveyor element while its other end is fixed, after passing around two idler rollers 33 and 34, to a compensating spring 35 mounted on the cross-member 4. The fixing of the flexible strip 32 will be explained in more detail during the description of FIG. 7.

Each of the vacuum chambers 29 is connected to a suction hood 36 by channels 37 and 38. The suction hood 36 is equipped with a turbine 39 mounted in the evacuation channel 40.

The stacking magazine 14, placed below the conveyor elements has a front wall 15 in the width of which is mounted a series of upper pneumatic cylinders 41 and a series of lower pneumatic cylinders 42. The stacking magazine 14 also has a rear wall 16 in which is mounted, a series of upper pneumatic cylinders 43 and a series of pneumatic lower cylinders 44. The series of cylinders 41 of the front wall 15 is mounted facing the series of cylinders 43 of the rear wall 16 while the series of cylinders 42 of the front wall 15 is mounted opposite the series cylinders 44 of the rear wall. The rods 45, respectively 46 of these jacks 41 to 44 are alternately advanced and withdrawn from the faces of the front 15 and rear 16 walls so as to temporarily form an upper grid and a lower grid for retaining the corrugated sheets 25.

Thus, when the desired height of the packet 47 of corrugated cardboard plates formed on the lower grid has been reached, the upper grid, formed by the rods 45 and 46 of the jacks 41 and 43 which will have been advanced, will retain the corrugated plates 25 from the conveyor elements, and the corresponding rods can be removed from the cylinders 42 and 44 so as to drop the packet 47 of plates located on the lower grid formed by the rods of the lower cylinders on the roller conveyor 18 which will evacuate the packet 47 to the exit of the receiving station. Then, the rods of the lower cylinders 42 and 44 will again be advanced so as to reform the lower grid and the rods 45 and 46 of the upper cylinders 41 and 43 will be removed so that the pack of corrugated sheets 25 accumulated on the upper grid falls again on the lower grid.

It should be noted that one could imagine another embodiment for the upper and lower grids, for example one could use a sort of comb retracting from each of the front and rear walls under the effect of a mechanism of the rod-crank type.

FIG. 3 represents a simplified version of a transport and stacking device in its suction phase, for example at the moment when, the endless belts 19 having stopped, the ejector levers 20 will start to push the flexible strip 32 downwards to move the corrugated cardboard plate away from the belts 19. In this version, the conveyor elements used are the same as those described with reference to FIG. 2. Consequently, the reference numbers will be identical. This version relates to a simpler embodiment of the stacking magazine 14, which always includes a front wall 15 and a rear wall 16. However, by a judicious choice of the height at which the jacks 41 and 43 are placed, it is it is possible to use only a series of these jacks to form a grid using rods 45 and 46. In this embodiment, the stacking of corrugated cardboard plates 25 is carried out directly on the rollers 48 of the conveyor rollers 18. The height of the pack of plates 47 having been reached, the rods 45 and 46 will be advanced and will retain the corrugated sheets 25 coming from the transporting elements until the packet 47 has been discharged by the roller conveyor 18 The rods 45 and 46 will then be removed and the pack of plates which will have formed on these rods 45 and 46 will again fall on the rollers 48 of the roller conveyor 18.

Figure 4 is a sectional view along IV-IV of Figure 3 showing the arrangement of the vacuum chambers 29 in the width of the conveyor 13 with endless belts 19. In this figure, only four vacuum chambers 29 have been shown but it is obvious that in practice the number of vacuum chambers 29 can be increased, this depending on the width of the conveyor 13.

The lower face 28 of each of the vacuum chambers 29 is located in a single plane 30 so that the upper face of the lower strand 27 of each endless belt 19 is in contact with its respective vacuum chamber during the suction of a corrugated cardboard plate 25. The vacuum chambers 29 are separated from each other by a channel 49 which either communicates with the atmosphere or is connected to a pressure source as will be described later in relation to FIG. 8. In each channel 49, provision has been made to mount an ejector lever 20 whose end 50 (see FIG. 3) is permanently in contact with the upper face 51 of the flexible strip 32. The lower part channels 49 has an opening 52 extending throughout each vacuum chamber 29. During the suction phase, the ejector levers 20 occupy a position such that the flexible strip 32 will close the opening 52 so that that a vacuum can be established, by the suction orifices 53 arranged in the lower faces 28 of the vacuum chambers 29, in the intervals 54 separating the lower strands 27 from the endless belts 19 and the flexible bands 32. Each ejector lever 20 is made integral with the shaft 31 by conventional fixing means, for example keys 55 and locking screws (not shown).

Figure 5 shows the conveyor 13 as it appears in the ejection phase of a corrugated cardboard plate 25. In this figure, the reference numbers are the same as those of Figure 4 due to the similarity of the two figures.

At the operating stage, represented by FIG. 5, the endless belts 19 are stopped and the flexible bands 32 have been pushed down under the action of the ejector levers 20 thus forcing the corrugated board plate 25 to fall on the rods 45 and 46 of the cylinders 41 and 43. As soon as the action of the ejector levers 20 causes the flexible strips 32 to come off from the lower faces 28 of the vacuum chambers 29, the suction established through the orifices 53 will be vented, on the one hand, by the zone 56 located between the conveyor 13 and the corrugated cardboard plate 25 and, on the other hand, by the openings 52 of the channels 49. Experience has shown that the only venting through zone 56 was not sufficient to allow the fall of the corrugated board plate 25 and that it was necessary, if one did not want the plate 25 to be again sucked against the conveyor 13 during the ascent of es flexible bands 32, to cause an additional atmosphere which is located as close as possible to the suction ports 53. Figure 8 will explain in more detail the additional assistance that can be provided to the ejection operation of the plate 25 using the channels 49 to bring supply air into the area 56. The arrows 57 and 58 represent the path followed by the suction flow when venting the vacuum chambers 29.

The transport and stacking device shown in FIG. 6 comprises two stacking magazines 60 and 61. These two stacking magazines 60 and 61 are constituted by two conveyors 62 and 63 in all points identical to the transporter 13 described above. These conveyors 62 and 63 arranged one after the other are arranged in such a way that the movement of the ejector levers 20 can be temporarily disengaged so that corrugated cardboard plates 64 are transported at 65 and at 66 in the stacking magazines 60 and 61 and then only ejected by the ejector levers 20 and the flexible bands 32 so as to form, according to a mode already explained, packages 67 and 68 which will then be evacuated by the roller conveyor 69. It is quite clear that one could imagine placing more than two consecutive stacking magazines to make a larger number of packages. One could also replace one of these stacking stores with a discharge station in which it would be possible to receive sheets of corrugated cardboard that did not conform or were damaged during their passage through the processing machine. One of the important features of this solution is that the passage from one stacking store to another takes place in a single transport plane. For practical reasons, the stacking magazines 60 and 61 should be arranged as close as possible to each other so as to ensure optimum transport of the corrugated sheets. To do this, one could for example nest the cylinders of the jacks 70 and 71 one inside the other so that the distance between the pulleys 72 and 73 is as small as possible.

FIG. 7 represents the method of attachment chosen for the flexible strip 32. As explained above, one of the ends 72 of the flexible strip 32 is anchored on the cross member 7. This cross member 7 is constituted by a metal tube 73 of rectangular section . A guide piece 74, machined in a metal tube of square section is attached by welding to the tube 73. A reinforcement 75 is welded to the face 76 of the tube 73. The end 72 of the flexible strip 32 is folded around a rod 77 of circular section. A stop shoe 78 has a housing 79 in which the end 72 of the flexible band 32 folded around the rod 77 engages. The end 72 is blocked by tightening, at least with screws. 80, the stop shoe 78 against the reinforcement 75. The flexible strip then passes over the guide piece 74 and its other end 81, also folded around a rod 82, is pinched between a plate 83, welded to the end 84 of a pull tab 85, and a counterplate 86 using screws 88 and nuts 89. The pull tab 85 has, at its end 91, a thread 90 on which a nut 92 engages and a lock nut 93 intended to ensure the tensioning, via the compression spring 94, of the flexible band 32. The compression spring 94 bears on the one hand against the ferrule 95, fixed against the cross-member 4 by screws 96, and on the other hand against a washer 97 retained by the nut 92 blocked by the lock nut 93. The compression spring 94 is mounted in a tube 98 fixed to the ferrule 95.

FIG. 8 represents the way in which it is planned to apply an overpressure in the channels 49 separating two vacuum chambers 29. For this purpose, the channels 49 will have been closed at their ends and connected, by a pipe 99, to the channel d 'evacuation 40 by a tu y to 100. Preferably, the pipe will be fitted with a pressure limiter 101 shown diagrammatically in this figure. It is understood that this way of producing the overpressure device is only an example and that a separate pressure source could also be used to supply the channels 49.

FIG. 9 shows a particular embodiment of the lower part of a conveyor 13. In fact, the lower strand 27 of the endless belts 19, even when these have been energized, always has an operating arrow 102 which has been deliberately exaggerated in this figure. This operating arrow 102 disturbs the suction when a vacuum chamber 29 is used, the lower face 28 of which is perfectly straight (see FIG. 3). To overcome this drawback, a vacuum chamber 103 is preferably used, the lower face 104 of which is machined as a function of the arrow 102 of the lower strand 27 of the endless belt 19, which has previously been measured or calculated. The lower surface 104 of the vacuum chamber 103 will therefore be a convex surface against which the endless belts 19 as well as the flexible bands 32 will bear.

FIG. 10 shows, by way of example, a method of constructing an ejector lever 20. The ejector lever 20 comprises a body 105 in which recesses 106 will have been provided in order to reduce its mass. Support means, such as a roller 107, are mounted at one end of the body 105. This roller 107 could be, for example a ball bearing. The other end of the body 105 is equipped with a shell 108 intended to hold the ejector lever laterally on its axis 31, using the screws 109 and 110. The key 55 ensures the transmission of the pivoting movement of the shaft 31 to the ejector lever 20.

Claims (8)

1. Device for conveying and piling flat workpieces, especially die-cut blanks, plates or open paperboard boxes, and comprising a conveyor (13) with endless belts (19) acting stepwise side by side and of which the upper part (26) of their lower drive side (27) is in contact with the supports (28) communicating with a vacuum device (39) and arranged in such a way as to leave between them an adequate space (49) containing the ejectors (20) equipped with a valve (32) itself acting on the supports (28) of the endless belts in such a way as to close the free space (52) left between the said supports, the said ejectors (20) being stepwise raised and lowered, characterized by the fact that the upper surface (26) of the lower drive sides (27) of the endless belts (19) presses against the lower surface (28) of a vacuum device composed of various distinguishable vacuum chambers (29) separated from one another by a duct (49), every one of the said vacuum chambers (29) being provided with aspiration holes (53) situated in the vicinity of the side edges of the endless belts (19), that every one of the vacuum chambers (29) is connected to a common aspiration hood (36) and that the ejectors arranged within each duct (49) separating two consecutive vacuum chambers (29) consist of elements pivoting stepwise and acting on a linear organ (32) fitted by one of its ends to a fixed point and, by its other end, to compensating means (35), and are arranged so as to close an aperture (52) of the lower part of the said duct (49), which aperture is arranged on a plane defined by the lower surface (28) of the vacuum device.
2. Device according to claim 1, characterized by a convex lower surface (28) of the vacuum chambers (29) with a convexity radius defined by the deflection (102) of the lower drive side (27) of the endless belts (19).
3. Device according to claim 1, characterized by the fact that the elements pivoting stepwise consist of ejecting levers (20) acting on a linear organ itself consisting of a flexible tape (32) fixed at one of its ends (72) on a first crossmember (7) located upstream of the conveyor (13), whereas its other end (81) is helf by compensating means (35) consisting of compression springs (94) fitted on a second crossmember (4) located downstream of the conveyor (13).
4. Device according to claim 1, characterized by the fact that the ducts (49) separating the vacuum chambers (29) from one another are connected to the atmosphere.
5. Device according to claim 1, characterized by the linear organ (32) consisting of a belt section.
6. Device according to claims 1 or 2, characterized by the fact that the ejectors consist of pivoting ejecting levers (20) the stepwise drive system of which is declutchable from the stepwise drive system of the endless belts (19) of the conveyor (13).
7. Device according to claims 1 or 3, characterized by the fact that the ducts (49) separating the vacuum chambers (29) are connected to a compressed air source.
8. Device according to claim 2, characterized by the fact that the ejecting levers (20) pivoting stepwise are equipped with supporting means (107) at their end which acts on the flexible tape (32).

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