EP0115237B1 - Device for stacking flat objects - Google Patents

Description

The invention relates to a device for stacking any flat object and more particularly a stacking device which stores in horizontal stacks flat objects conveyed in a unitary and vertical fashion by a belt conveyor for example.

Document FR-A-2 489 798 discloses a device for stacking thin and flexible objects driven by a conveyor, of the type stated in the preamble of claim 1. This device comprises a fixed body and a rotating drum pierced with openings mounted around the fixed body. The fixed body has a plurality of chambers open towards the drum, which are distributed so as to be between the reception zone on the drum of the objects driven by the conveyor and the substantially opposite zone on the stacking drum and holding the pile. These chambers are successively put under vacuum or pressure through individual valves on the connecting pipes to the suitable source.

In this device, the arrival of objects near the drum is detected and puts successive chambers under vacuum as the objects advance, for their guidance to the top of the stack in formation. As soon as the front edge of the objects at the end of the stack arrives, the chambers are successively pressurized to detach their rear part from the drum. The receptable is a tray receiving the battery, the position of which is controlled as the battery is built up.

In another stacking device, known from document BE-A-651 187, plies to be stacked on a stacking carriage are directed between the stack being formed and a stacking drum, through a slot, and the driving of the stacking carriage is controlled by a probe which reacts to the pressure of the stack.

In another device, known from document US-A-4 116 430, a rotary drum with sets of depressed openings causes successive folds which it receives towards those already stacked against a lateral bank.

The stack is formed on a bottom plate and is held by an adjustable rear edge. The folds are detached from the drum by sets of belts with separating elements which drive the front part of the folds to the lateral edge by applying it against the pile, their rear part is pressed against the pile by air jets.

Numerous devices performing the stacking function are fitted to the outlets of postal fold sorting machines currently in service. Such equipment has satisfactory performance in the usual way. Indeed, the manual recovery by an operator of the stack of flat objects formed allows some random storage faults of these objects. These faults are in particular: variation in the inclination of objects in the stack, variation in altitude, rear stapling or slight bending of the front edge of these objects.

By cons when considering in particular an automatic recovery of objects stored in a stacker it is essential to have a battery in which the previously mentioned defects are minor. The subject of the present invention is a device for stacking flat objects which remedies these faults by ensuring permanent maintenance of these objects throughout the stacking operation.

The invention relates to a device for stacking flat objects driven by a conveyor, comprising a fixed cylindrical body fitted internally with a suction circuit coupled to an orifice in the periphery of the cylindrical body, a drum pierced with a plurality openings regularly distributed on its periphery rotatably mounted around said cylindrical body and substantially orthogonal to the direction of arrival of the objects, ensuring the suction by suction of successive objects from the conveyor and their stacking in a receptacle, means for inserting successive objects between the stack and said drum, means for holding stacked objects mounted movable opposite said drum so that said drum remains in contact with the stack of objects, control means controlling said suction circuit and said means of insertion, said device being characterized in that said insertion means comprise the outlet of said conveyor oriented in a direction o bic relative to the faces of the objects stacked in the receptacle and a cam provided at the outlet of the conveyor actuated by the control means to cooperate in maintaining the stacked objects and push the rear edge of the objects during their stacking.

• - figure 1, une vue de dessus d'un dispositif d'empilage conforme à l'invention;
• - figure 2, une coupe dans un plan vertical des moyens de commande d'aspiration;
• - figure 3, une coupe dans un plan vertical d'un élément accessoire au dispositif de l'invention.

The invention will be better understood with the aid of the explanations which follow made with reference to the appended figures in which the same references designate the same elements. These figures represent:

• - Figure 1, a top view of a stacking device according to the invention;
• - Figure 2, a section in a vertical plane of the suction control means;
• - Figure 3, a section in a vertical plane of an element accessory to the device of the invention.

Figure 1 shows, top view, a horizontal section of the stacking device of the invention. On it flat objects 1 are approached on edge by a belt conveyor 2. A drum 3 rotating on itself in the direction of the arrow F1 is mounted coaxially on a cylindrical body 4 fixed and having a hollow recess 5. The axis of rotation of this drum is orthogonal to the direction of arrival of the objects 1 according to arrow F2 and is substantially parallel to the surface of these flat objects. The drum 3 has a plurality of openings 6 regularly distributed around its periphery. These openings 6 establish a communication for the passage of air between the outer 7 and inner 8 faces of the drum 3.

The recess 5 of the hollow body 4 includes a orifice 9 opening onto the surface of this body 4. In a preferred manner this orifice 9 has an elongated shape and is collinear with the generatrix of the cylindrical body 4 substantially closest to a receptacle 10. This receptacle 10 has a bank of jogging 11 and transport means comprising a set of belts 12 and 13 and a guide plate 14. The belts 12, 13 and the guide plate 14 move during the stacking operation in the direction of the arrows F3.

The recess 5 of the body 4 is permanently connected to a source of suction that is not shown. It has a section substantially in the form of a number 8. It is thus divided into two parts of circular section: the parts 15 and 16 connected together by a channel 17. The orifice 9 is located in the extension of these parts 15 and 16 emerging at the periphery of the body 4. The circular cylindrical part 16 serves as a housing for an elongated plug 18. This bushel acts as a valve. It is shown here in an open position. It allows the passage of air from the outside through the openings 6 in the direction of the suction source. The openings 6 pass in front of the orifice 9.

A pedal 20, articulated on an axis 21 parallel to the axis of the drum, comprises a pad 22 flush with the package 23 of flat objects 1 stacked in the receptacle 10. A handle 24 of the pedal 20, located on the same side of the pad 22 relative to the axis 21, comes to request a detector 25. This pedal 20 is held in the equilibrium position by a return spring 26. The detector 25 can be of an electromechanical type. A set of detectors 27 and 28, for example of a photoelectric type, determines the instants of passage of the objects 1 at the exit of the conveyor 2. The electrical signals produced by the detectors 25, 27 and 28 are directed on a control circuit 29, for example of an electronic type. Depending on the indications received, the control circuit 29 controls the commissioning of motors from a set of motors 30. These motors, not shown, in particular control the rotation of the plug 18 as well as the advancement of the means of transport of the receptacle 10.

The operation of the device of the invention is now described. The conveyor 2 is arranged on the side of the drum 3. Its outlet is oriented in an oblique direction relative to the surface of the objects already stacked in the receptacle. He directs the object 1 to be stacked to insert it between the package of objects 23 and the drum 3. On leaving the conveyor 2 the object 1 obscures the photoelectric cell of the detector 27 and this detector 27 sends a pulse to the circuit pilot 29. After a time delay corresponding to the time necessary for the go before the object 1 comes to be inserted between the package 23 and the drum 3, the pilot circuit 29 sends an order to the tilting motors of the plug 18 This plug 18 then turns in the direction of arrow F5, from a closed position to the open position shown in FIG. 1. Under these conditions, the suction source connected to the recess 5 sucks the rear face of the front front of the flat object to be stacked. This face is said to be posterior with respect to the direction of advance it will have in the receptacle 10.

As the drum is constantly rotating, it causes the object 1 to be stacked in the direction of the jogging edge 11. The orifice 9 has a development on the periphery of the body 4 limited on the order of two to three times the width of the step distribution of the openings 6 on the drum 3. As soon as the openings 6 of the drum 3 having participated in the aspiration of the object to be stacked have exceeded the limit of the orifice 9 they are no longer in connection with the source of aspiration. The front edge of the object 1 which was then pressed into a rolling contact on these active openings of the drum comes off naturally.

The drum continues its action until the front edge of the object to be stacked abuts on the jogging edge 11. The duration of this elementary action is limited by a time delay taking into account the speed of rotation of the drum 3 and of the distance separating the jogging edge 11 and the diameter of this drum parallel to this jogging edge. This time delay is a function of the time taken by the front edge of the object to be stacked to cross the distance separating the orifice 9 from the jogging edge 11.

At this time the control circuit sends an order, contrary to the previous one, to the motor actuating the plug 18 so as to interrupt the suction.

Here we see the peculiarities of the invention. On the one hand the adjustment of the duration of the suction action makes it possible to obtain a uniform jogging of all the objects to be stacked. On the other hand for this purpose, the stacking action exerted by the drum must be short. Also, so as not to be penalized by the rise times of the suction, the invention has provided, to have the plug 18 directly downstream of the inner face 8 of the drum 3. Under these conditions , the rise time of the suction is reduced to the duration of the evacuation of the interior volume of the plug 18. This volume being small this action is therefore rapid. Furthermore, when the valve is closed, the interruption of the suction is likewise very rapid. It follows from this feature that the setting of the suction time is precise.

During its advancement, the stacked fold 1 rubs under the pad 22 of the pedal 20. Under this action, this pedal 20 rotates about its axis 21 in the direction of the arrow F4. The end of the handle 24 of this pedal excites the detector 25. This detector 25 at this instant develops an order in the direction of the control circuit 29. This control circuit 29 then controls the action of the motors of the transport means 12, 13 and 14. The displacement of these means of transport causes the decompression of the package 23 until the friction exerted by the shoe 22 on the new stacked object is insufficient to counter the return force of the spring 26. In this case, the pedal 20 returns to its rest position and interrupts the action of the motors of the means of transport. The enslavement thus described may have a completely different appearance. In particular if the objects to be stacked are of homogeneous dimensions with one another, the pedal 20 and the detector 25 can be eliminated, this assembly being replaced by an additional sequential action produced by the control circuit 29 and initialized by the pulse of the detector 27 This sequential action then has the effect of advancing the means of transport one notch whose amplitude corresponds to the thickness of the objects to be stacked.

Another feature of the invention resides in the fact that the package of objects 23 is stacked in a receptacle 10 extending substantially horizontally. The vertical maintenance of these objects 1 in the horizontal stack on the side of the stacking members is essentially exerted by the generatrices of the drum in contact with this package. When no object is approached or between the approach of two objects, the suction source no longer being connected to the openings 6, the outer face 7 of this drum slides without friction on the stacked objects 1. It realizes their vertical maintenance. For this purpose, this face 7 is preferably smooth.

In Figure 2 there is a section of the drum 3 and the body 4 of the stacker in a plane perpendicular to the faces of the stacked objects. Note that the axis XX 'of rotation of the drum is parallel to the axis YY' of rotation of the plug 18 in its housing 16. The plug 18 thus rotates on itself alternately according to the commands of the piloting circuit 29 in the direction of the double arrow F5. In a variant, the openings 6 are slots made along generatrices of the drum around its entire periphery. In another variant of the invention the openings 6 made in the drum are holes. These holes can be distributed over the entire height of the drum in a plurality of alignments, parallel to a certain number of particular generatrices of the drum, these particular generatrices being regularly distributed at a given pitch all around the drum. In a preferred variant, the holes will be distributed over a plurality of helical alignments offset from one another at a given pitch over the entire periphery of this drum.

The reason for these particular distributions of the openings lies in the need to reduce the noise caused by the passage of air during the suction times. The arrangement of the holes according to offset helical alignments has the effect of breaking the rhythm of appearance of this noise linked to the pitch of distribution of the holes. Thus, opposite the longitudinal orifice 9, the vertical distribution of the holes is no longer uniform. Under these conditions it is possible to reduce the development of the orifice 9 to a width less than the offset step of the helical alignments. FIG. 2 finally shows the belt 13 of the means of transport of the receptacle 10. This belt 13 thus serves as a horizontal support for the stacked packages 23.

Figure 3 shows in section an accessory means for holding the invention. This accessory means is a cam 31, it is also visible in FIG. 1 at the outlet of the conveyor 2. This cam 31 comprises two fingers 32 in the form of a comma, secured to a shaft 33 which can rotate around an axis ZZ ' parallel to the axis of the drum. These two fingers are spaced vertically to press in two places on your rear side of the stacked objects. The rotation takes place in the direction of arrow F6 (Figure 1). The shaft 33 is driven by a motor, not shown, also controlled by the control circuit 29. The operation of this cam is as follows: when the front edge of an object obscures the photodetector 28, this photodetector 28 emits a pulse electric in the direction of circuit 29. This circuit actuates the motor of cam 31 so that it performs a revolution on itself. The speed and instant of passage of this cam 31 are calculated so that its end is erased in front of the front front of the stacking object which arrives, and so that in a continuous rotating movement it comes to press the rear front of the object just stacked on package 23.

This cam 31 thus has two functions. A first function: it allows the front edge of a newly approached object to come safely between the drum 3 and the pack 23 near the orifice 9. Indeed, depending on the nature of the objects and their conformation, the rear edges of stacked objects can spread out in a fan shape in the stack and thus hinder the insertion of a new object. The cam 31 is only necessary when the output of the conveyor 2 is slightly inclined relative to normal to the jogging edge 11. A second function consists in helping to maintain the pack of objects 23 in the receptacle 10. On the Figure 1 the cam 31 is shown in the working position, this position is not its rest position. The rest position is such that the orientation of the cam is substantially inclined relative to normal to the faces of the objects of the package 23.

In a preferred manner in the invention, the distance separating the end of the conveyor 2, being substantially at the height of the detector 27, from the orifice 9 is less than the length of the objects to be stacked. This length being measured perpendicular to the jogging edge 11. The difference between these two lengths is less than the distance separating the orifice 9 from the jogging edge 11. This allows the cam 31 to push back the rear edges of the objects to be stacked without them catching on the outlet of the conveyor 2 and they cannot thus cause jams.

The device for stacking flat objects according to the invention has been realized. After an adjustment phase concerning, in particular, the timing settings, it was found that the postal envelopes were stacked in which jamming incidents did not appear and in which the jogging tolerances of the objects stacked against the jogging edge 11 were lower than the tolerances allowable by automatic processing devices for stacked objects such as destackers for example.

Claims (6)

1. A device for stacking flat objects (1) conveyed by a conveyor (2), comprising a stationary cylindrical body (4) supplied on the inside with a suction circuit coupled to an inlet at the periphery of the cylindrical body, a drum (3) having a plurality of openings (6) which are regularly spaced out over its periphery, and being rotatably mounted about said cylindrical body, and essentially orthogonally with respect to the arrival direction of the objects, ensuring the taking up by suction of the successive objects coming from the conveyor and their stacking in a receptacle (10), means (2, 31) for inserting the successive objects between the stack and said drum, means (12, 13, 14) for maintaining the stacked objects which are mounted in a mobile fashion facing said drum, so that said drum remains in contact with the stack of objects, piloting means (29) controlling said suction circuit and said insertion means, said device being characterized in that said insertion means comprise the outlet of said conveyor (2) oriented in a direction which is oblique with respect to the faces of the objects stacked in the receptacle (10), and a cam (31) provided at the outlet of the conveyor and activated by the piloting means (29) for cooperating in the maintaining of the stacked objects and for pushing back the rear front of the objects during their stacking phase.

2. A device according to claim 1, characterized in that a valve (18) disposed in the cylindrical body (4) directly downstream of said opening (9) is inserted into said suction circuit.

3. A device according to claim 2, characterized in that said valve (18) is constituted by a cut-off member of elongated shape which is mounted pivotingly in a recess (16) made in said cylindrical body (4) for connecting the suction circuit to the openings (6) of the drum (3) which pass in front of said inlet (9), or for isolating them therefrom.

4. A device according to one of claims 1 to 3, characterized in that the openings (6) comprise a plurality of holes distributed over a plurality of helicoidal alignments regularly spaced out according to a given mutual pitch over the periphery of the drum in order to thus contribute to the reduction of the suction noise.

5. A device according to one of claims 1 to 3, characterized in that the openings (6) comprise a plurality of holes distributed over a plurality of generatrix lines regularly spaced out according to a given mutual pitch over the periphery of the drum (3).

6. A device according to one of claims 1 to 3, characterized in that the openings (6) are slots which extend along the generatrix lines of the drum (3).

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