EP1902989B1 - Apparatus for destacking postal deliveries with optimized management of the destacking conditions. - Google Patents

Abstract

The device has a feed hopper (1) to displace stacked postal items (3) e.g. letters, on a front edge at an extracting head (5). The head has a motorized drive actuated to separate a current item and stopped at each extraction of the current item and the items are straightened in the hopper in response to detection of signals (S) provided by sensors (20-22) e.g. reflective photocells, placed in the head. The signals indicate presentation of the current item with respect to the head, where driving of the head is actuated, if the signals indicate the current items`s presentation.

Description

The invention relates to a device for unstacking flat objects comprising a power supply magazine controlled to move flat objects in stack on edge facing an unstacking head with a motorized drive. The motorized drive comprising a perforated band and a vacuum chamber is operated to separate a first current object from the stack and drive it in a direction transverse to the moving direction of the stack of flat objects.

The invention more particularly relates to a device for unstacking postal items, such as letters and flat objects of large format, in a postal sorting machine for example.

From the patent document FR2797856 there is known a device for unstacking postal items which is provided with a main magazine 1 with a tape. As illustrated on the figure 1 , the main magazine 1 comprises in particular a belt conveyor 2 with a motorized drive on which an operator has the postal items 3 in stack on edge and a pallet 4 also with a motorized drive which extends in a substantially vertical plane and which is moved to push the back of the stack in the direction indicated by the arrow 6 facing the unstacking head 5.

The postal items of the stack are held laterally by a jogging edge 7 which extends in a substantially vertical plane along an edge of the belt conveyor 2. The substantially flat unstacking head 5 extends in a vertical plane transverse to the direction indicated by the arrow 6 for moving the stack of items 3 on the belt conveyor 2 and is capable of separating the first current item at the front of the stack in the transverse direction indicated by the perpendicular arrow 8 at the arrow 6.

The unstacking head 5 comprises two substantially rectangular openings in which a perforated strip 9 and one or more vacuum chambers or suction nozzles (not shown) are driven by a motor, cooperating to suck up the first shipment of the stack and to move it in the direction indicated by the arrow 8.

In operation, the stack of postal items 3 disposed in the main magazine 1 is moved by the motorized stepper type drives of the belt conveyor 2 and the pallet 4 which are actuated at the same speed. The first shipment to the front of the stack of mail is thus brought to bear against the unstacking head 5 so that this current mail piece of the stack is pressed against the unstacking head 5 and is separated from the stack by the combined effect of suction The mailpiece is then clamped between two deformable wheels 10 arranged in the extension of the head 5. These wheels 10 are motorized to convey the current shipment downstream of the unstacking device. They consist of an elastomer material elastically deformable so as to be able to adapt to different thicknesses of postal items.

For the rest of the sorting process, it is necessary for the postal items to be serialized at the output of the unstacking device with a constant pitch between consecutive items. The driving of the perforated band 9 and the suction nozzles is thus actuated and stopped at a constant rate.

This unstacking process is repeated as a new mailing at the front of the pile is presented in front of the unstacking head 5.

In the device of the document FR2797856 , the postal items of the stack are serialized continuously, that is to say with a constant unstacking rate.

Generally in a postal sorting machine, postal items leaving the unstacker are conveyed in series on edge to be brought in front of a read head. The read head acquires an image of each serialized send for an automatic decoding of the distribution or routing address of the sending by OCR processing ("Optical Character Recognition") . The postal items are then sent to sorting outlets corresponding to the automatically decoded addresses.

In this type of unstacking device, it has been found that a large proportion of postal items do not present themselves adequately in front of the unstacking head at the time of unstacking, which has the consequence that these items can be damaged or torn when supported by the wheels 10 for example. It may even happen that these shipments cause a jam in the unstacking device requiring the intervention of a maintenance operator and the stopping of the unstacking device. The intervention is expensive and slows the overall process of sorting. This situation may be particularly frequent with open mailings such as advertising brochures, magazines, etc.

The patent document EP0562954 presents a solution to this problem. In this document, the unstacker feeding device similar to that described above further comprises a motorized chute. The fall motorized is arranged between the belt conveyor and the unstacking head. The presence of this motorized fall has the effect of presenting in fan a number of first postal items (those arranged in the fall) which has the consequence that the first mailing to the front of the pile is loosened other shipments and therefore has more facility to present itself adequately against the unstacking head 5.

In the document EP0562954 , there are also provided presence sensors arranged to detect a certain fan tilt of postal items in the chute and also to detect the level of filling of the chute. In response to the signals provided by the sensors, the motorized chute and / or the belt conveyor are actuated to fill the chute and / or tilt the postal items adequately.

However, the provisions indicated above do not yet completely eliminate the situations of deterioration of postal items or stuffing situations in the unstacking device, for example when very flexible postal items tend to collapse in the fall.

The patent document WO2005 / 042386 discloses a device for unstacking postal items of the "tiler" type which is provided with a main magazine comprising a main belt conveyor and a pallet and a secondary conveyor disposed between the main conveyor and the unstacking head. The unstacking head comprises a band with a motorized drive actuated to separate a first current shipment from the stack and drive it in a direction transverse to the direction of travel of the mail stack. In a "tiler" unstacking device, the strip of the unstacking head does not cooperate with a vacuum chamber since the items are moved on one another so as to form a tiled pattern during the unstacking process.

In the document WO2005 / 042386 sensors arranged in the unstacking head make it possible to detect the inclination of the current mailpiece to be unstacked and in response to the signals supplied by its sensors the main belt conveyor, the pallet or the secondary conveyor are controlled to correct the tilt. In addition, the motorized drive of the unstacking head is actuated and stopped so as to obtain a constant pitch between postal items at the output of the unstacking device.

With the device of the document WO2005 / 042386 situations of deterioration of postal items or stuffing situations are still too important.

Document is also known US2002 / 153654 a device for unstacking flat objects with a control of the presentation of the objects in front of an unstacking head, comprising one or two sensors arranged in the unstacking head. Said command stops driving the unstacking head when the one or both sensors determine an inadequate presentation of an object. The unstacking of said object is activated when the presentation of the object becomes adequate, after correction of the presentation of the object. However, with this device an ineligible number of shipments are deteriorated and stuffing situations are frequent.

The object of the present invention is therefore to further improve a device for unstacking flat objects to prevent deterioration of these flat objects and the stuffing of the unstacking device

For this purpose, the subject of the invention is a device for unstacking flat objects comprising the features of claim 1.

With this arrangement, it is understood that the unstacking of the current mail in a stack of postal items can intervene only when it is adequately present with respect to the unstacking head, which avoids the situations of deterioration of postal items and / or stuffing.

• la pluralité de capteurs comprend un premier capteur disposé dans la tête de dépilage pour détecter la présence d'une partie inférieure de l'objet courant face à la tête de dépilage;
• la pluralité de capteurs comprend un second capteur disposé dans la tête de dépilage pour détecter la présence d'une première partie intermédiaire de l'objet courant face à la tête de dépilage, ladite première partie intermédiaire étant située au-dessus de ladite partie inférieure de l'objet courant ;
• la pluralité de capteurs comprend un troisième capteur disposé dans la tête de dépilage pour détecter la présence d'une seconde partie intermédiaire de l'objet courant face à la tête de dépilage, cette seconde partie intermédiaire étant située au-dessus de ladite première partie intermédiaire de l'objet courant;
• la pluralité de capteurs comprend en outre un quatrième capteur disposé pour détecter la présence d'un objet plat selon ladite direction transversale à la direction de déplacement de la pile d'objets plats.

The unstacking device according to the invention can include the following features:

• the plurality of sensors comprises a first sensor disposed in the unstacking head to detect the presence of a lower portion of the current object facing the unstacking head;
• the plurality of sensors comprises a second sensor disposed in the unstacking head for detecting the presence of a first intermediate portion of the current object facing the unstacking head, said first intermediate portion being located above said lower part of the current object;
• the plurality of sensors comprises a third sensor disposed in the unstacking head to detect the presence of a second intermediate portion of the current object facing the unstacking head, this second intermediate portion being located above said first intermediate portion the current object;
• the plurality of sensors further comprises a fourth sensor arranged to detect the presence of a flat object in said direction transverse to the direction of movement of the stack of flat objects.

According to a particular embodiment of the invention, the first sensor is a flag mechanical sensor, the second sensor is a reflection optical sensor, and the third sensor is a reflection optical sensor and the fourth sensor is an optical barrier sensor the first, second and third sensors are aligned vertically in the unstacking head.

In a particular embodiment of the invention, the feed magazine comprises a chute arranged between a main conveyor with a motorized drive and the unstacking head and a pallet with a motorized drive, said pallet being able to be moved along the main conveyor, the chute being provided with secondary conveyors with a motorized drive, the control unit acting on the motorized drives of the main conveyor, the pallet and the secondary conveyors to adequately present the current object in relation to the main conveyor at the unstacking head.

It should be understood that the main conveyor, the motorized pallet and the secondary conveyors in the chute are provided to be asynchronously controlled by the control unit which is further arranged to change the speed and direction of the motorized drives of the store. power supply to present the current object adequately.

According to another particular embodiment of the invention, the control unit is arranged to trigger an alarm at the end of a certain period during which the control unit 13 acts on the motorized drives of the main conveyor, of the the pallet and secondary conveyors without obtaining an adequate presentation of the current object with respect to the unstacking head.

The invention extends to a machine for processing postal items comprising such an unstacking device.

The feeding device according to the invention applies to flat objects, for example small and large format flat mailpieces, but can also find application in other areas of processing of flat objects such as books, books and magazines. checks or other.

The invention will be better understood on reading the description which follows in relation to the drawings. This description is given as an indicative and non-limiting example of the invention.

The figure 1 schematically illustrates a feeding device for a unstacker of flat mail items according to the state of the art.

The figure 2 schematically illustrates a feeding device for a unstacker flat mail items according to the invention.

The figure 3 is a flow chart illustrating the different steps of the signal control process provided by the sensors.

The figure 4 schematically illustrates the unstacking face with the sensors including the flag mechanical sensor.

The figure 5 illustrates a first situation of inadequate presentation of the current shipment relative to the unstacking head.

The figure 6 illustrates a second situation of inadequate presentation of the current shipment relative to the unstacking head.

The figure 7 illustrates a third situation of inadequate presentation of the current shipment relative to the unstacking head.

The figure 8 illustrates a fourth situation of inadequate presentation of the current mail with respect to the unstacking head.

The figure 9 illustrates a fifth situation of inadequate presentation of the current shipment relative to the unstacking head.

The figure 10 illustrates a sixth situation of inadequate presentation of the current shipment relative to the unstacking head.

The figure 11 illustrates a seventh situation of inadequate presentation of the current mail with respect to the unstacking head.

The figure 12 illustrates in the form of a table the signals of the sensors detecting an unsuitable presentation of the current item to be unstacked.

The figure 1 has already been presented in connection with the description of the prior art.

The figure 2 illustrates therefore a destacking device 1 of postal items according to the invention, such as letters and flat postal objects called large format, the elements common with that of the figure 1 carry identical numerical references.

This unstacking device is used to serialize shipments upstream of serial conveyors of postal items in which the items are separated in pairs with a normally constant pitch. The motorized drives of the deformable wheels 10 between which are clamped serialized shipments can be controlled at a variable speed to catch up if necessary gaps between consecutive shipments. This variable speed arrangement constitutes a synchronization system ensuring a constant pitch.

Advantageously, this synchronization system authorizes the performance of certain correction operations during a time window T compatible with the requirement of a constant pitch between consecutive items at the output of the unstacking device.

The unstacking device 1 comprises a main feed magazine 1 with a belt conveyor 2 with a motorized drive on which postal items 3 are arranged in stack on edge at the front of a pallet 4 with a motorized drive which s extends substantially in a vertical plane by being slightly inclined to support the rear of the mail stack.

The belt conveyor 2 and the pallet 4 move the stack of items 3 on edge in the direction of the unstacking head 5 in the direction 6.

There is also shown along the belt conveyor 2, a jogging edge 7 against which the lateral edges of the items are aligned.

On the figure 2 , there is shown a chute 11 in the form of a gutter, constituting a secondary feed store between the end of the main conveyor 2 and the unstacking head 5. The bottom of the chute 11 is located at a depth of about 100 mm below the upper surface of the conveyor 2 and has a width of about 98 mm in the direction 6.

The bottom of this chute 11 is provided with a set of secondary conveyors 12 with a motorized drive, for example here four belt conveyors, which move the shipments on edge in the chute in the direction 6 towards the unstacking head 5 .

The unstacking head 5 with a motorized drive extends vertically from the bottom of the chute 11 to a sufficient height corresponding at least to the maximum height of the postal items to be unstacked.

The unstacking head 5 in the form of a sheet is provided here with two rectangular openings arranged side by side in the direction 8. In each of these openings, an endless perforated strip 9 cooperates with vacuum chambers or nozzles suction (not shown) to enter and move in the direction 8 a current shipment of the stack facing the head.

According to the invention, the motorized drives of the belt conveyor 2, the pallet 4, the secondary conveyors 12 and the unstacking head (perforated strips 9 and suction nozzles) are provided to be controlled independently of each other. others but can of course be synchronized with each other by a control unit 13, for example a programmable data processing processor.

On the figure 2 for the sake of clarity, it is shown that a single control / control link between the control unit 13 and a conveyor 12 but it is obvious that the unit 13 is also connected by control / command links to the control unit. motorized drives of the conveyor 2, pallet 4, strips 9 (and suction nozzles).

According to the invention, the unstacking device comprises a set of sensors which each provide a detection signal to the control unit 13. On the figure 2 , it is also for the sake of clarity represented only a single control link between the control unit 13 and a sensor, but it is obvious that the unit 13 is also connected by control links to the other sensors operated according to the invention as described below.

More particularly on the figure 2 first sensors 20, 21 and 22 are shown which are arranged in vertical alignment in the unstacking head 5, here between the two openings in the head where the perforated strips 9 act.

The sensor 20 which is disposed at the bottom of the unstacking head 5 at the bottom of the chute 11 is here a mechanical flag sensor in the form of a retractable finger in the thickness of the head 5 to detect the presence of a shipment facing the lowest part (bottom) of the head 5.

The sensor 20 is illustrated in more detail on the figure 4 . It provides a signal indicative of the presence of a consignment when it is sufficiently retracted into the head under the effect of the push of the foot of the current consignment in the direction of the direction 6 itself pressed by the stack of shipments bearing against each other in the chute 11. This sensor 20 has more particularly, in the rest position, a free end protruding from the unstacking head which has a profile bevel widening in the direction of the direction 6 and whose flat portion is flush with the bottom of the chute 11. The sensor 20 moves in the direction 6 against a return spring R and the signal that it provides, when retracted inside the unstacking head 5, can also be indicative of the distance on which it retracted with respect to its rest position and therefore a pressure magnitude. We see on the figure 4 it is arranged below the lower line of perforated strips 9.

The sensor 20 is adapted to measure the pressure exerted by all the items in the drop at the foot of the items. A pressure of 0.3 Newton of the feet of the shipments against the unstacking head disposes the shipments of the fall fan open on the top. Fetching shipments facilitates their separation and reduces the multiple catch rate. A control of the pressure of the feet of the items can be provided and the pressure can be adjusted by feeding the chute 11 in postal items.

The sensor 21 is a reflection photoelectric cell disposed vertically above the sensor 20, for example 20 mm from the bottom of the chute, to detect the presence of a current shipment facing a first intermediate portion of the head above from the lower part of the head.

The sensor 22 is a reflection photocell arranged vertically above the sensor 21, for example at 90 mm from the bottom of the chute, to detect the presence of a current shipment facing a second intermediate portion of the head above. of the first intermediate part. As visible on the figure 4 these two intermediate parts are at the level of the perforated strips 9.

The sensors 20 and 21 are set to each provide a signal indicative of the presence of a shipment when this shipment is at a distance of less than about 4mm from the head 5 in the direction 6.

The sensor 22 is set to provide a signal indicative of the presence of a shipment when this shipment is at a distance of less than about 8mm from the head 5 in the direction 6.

It will thus be understood that the signals supplied by the sensors 20 to 22 are normally indicative of the presentation of the current item to be unstacked with respect to the unstacking head.

On the figure 2 three other sensors 23, 24 and 25 have also been shown.

The sensor 23 is a photoelectric barrier cell that operates along the unstacking head 5 and whose beam is oriented to cross the face of a shipment. This beam is drawn substantially in the direction 8 between a transmitter and a receiver of the sensor 23 at about 8 mm in front of the unstacking head 5 in the direction 6 and at a height of about 190 mm from the bottom of the chute 11.

On the figure 2 it is shown that a single element of the sensor 23 (transmitter or receiver) mounted on a lateral side of the unstacking head opposite the side where the deformable wheels 10 are arranged. It should be understood that the other complementary element of the sensor 23 is disposed on the other lateral side of the head, here on the inlet cone side upstream of the motorized deformable wheels 10. The sensor is arranged to detect the presence of a flat object in said direction indicated by the arrow 8.

The sensor 24 is also a photoelectric barrier cell identical to the sensor 23 but whose emitter and reflector are arranged at a height of approximately 112 mm with respect to the bottom of the chute and in the transition zone between the main conveyor 2 and the fall 11 on each side of the magazine 1. The signal provided by the sensor 24 is indicative of the presence of shipments in the chute.

The sensor 25 may be a mechanical contact sensor arranged to detect the presence of the pallet 4 at the transition zone between the main conveyor 2 and the chute 11.

Finally on the figure 2 two further sensors 26 and 27 (only one transmitter or receiver component of these sensors is shown) are shown which are photoelectric barrier cells arranged vertically one below the other and whose beams are oriented in the direction indicated by the arrow 6 to detect the presence of shipments in the entry cone near and upstream of the deformable wheels 10.

The use of these different sensors will be specified below for different situations of inadequate presentation of mail items facing the unstacking head.

On the figure 3 a simplified flowchart shows the operation of the unstacking device according to the invention with the sensors and more particularly the operation of the control unit 13.

In the preparation step 31, postal items are placed beforehand by the operator in stack on edge on the main conveyor 2 at the front of the machine. pallet 4. The control unit actuates all motorized drives for operation at a constant unstacking rate. The speeds of movement of the conveyor belt 2 and the pallet 4 are identical. The speed of movement of the belts of the conveyors 12 is slightly greater than that of the band 2 or the pallet. The speed of movement of the belts 9 is much greater than that of the belts of the conveyors 12. For example, in normal unstacking mode, the speed of the belt 2 is 0.096 m / s, that of the belts of the conveyors 12 is 0.152 m / s and that of the perforated strips 9 is 1.5 m / s.

The stack of shipments 3 singing then advances towards the unstacking head 5 and the first mailings to the front of the stack fall into the chute 11. In this example, the stack of shipments is split and the shipments on edge in the fall are placed in fan under the action of the faster movement of the conveyors 12 in the bottom of the fall and a first current to be unstacked is detected for example by the sensor 23.

At this point, the process continues at step 32 where the signals S provided by the sensors are controlled by the control unit 13 to determine whether the current mail item to be unstacked has a proper presentation with respect to the unstacking head to be stripped without risk of damage or jam.

If, in step 32, the signals S of the sensors are indicative of an adequate presentation of the current mail and that one is in the time window T compatible with a constant step, then in step 33 , the control unit 13 maintains in normal depilatory operation the belt conveyor 2, the pallet 4, the conveyors 12 and actuates the motorized drive perforated strips 9 and suction nozzles so as to depilate the shipment. The current sending is then serialized by passing between the deformable wheels 10, the motorized drive of the perforated strips 9 and the suction nozzles is stopped and the process loops on the step 32 for a new control of the S signals. loop process, shipments are unstacked at a constant rate of one mailing every 330 milliseconds.

If now, in step 32, the signals S provided by the sensors are indicative of an inadequate presentation of the current mail with respect to the unstacking head 5, the process continues in step 34 where the control unit 13 triggers a correction phase of the presentation of the current shipment relative to the unstacking head. We understand that, the training motorized perforated strips 9 and suction nozzles being stopped the current shipment is not depilated.

To carry out this correction, according to the invention the control unit 13 independently controls the motorized drives of the conveyor 2, the pallet 4 and the conveyors 12 of the chute so as to straighten the postal items which are in the chute 11 and thus correct the presentation of the current item to be unstacked.

The manner in which the adjustment is made is detailed below.

During the correction phase engaged in step 34, the unit 13 checks, in step 35, the signals S supplied by the sensors to the control unit 13 to determine whether the current mail is now adequate compared to the unstacking head. In practice, steps 34 and 35 can be performed almost simultaneously.

If in step 35, the signals S of the sensors are indicative of an adequate presentation of the current item to be unstacked and that one is in the time window T compatible with a constant pitch between consecutive items at the output of the unstacking device, then the control unit 13 continues the process in step 36 by operating the motorized drive of the unstacking head (perforated strips and suction nozzles).

The current to be despatched is then serialized between the deformable wheels 10 at the output of the unstacking device, the motorized drive of the perforated strips 9 and the suction nozzles is stopped and the normal unstacking operation is restored. The process then loops to step 32.

In step 35, if the signals S of the sensors are indicative of an inadequate presentation of the current mail item to be unstacked and / or that is outside the time window T, the process loops to the step 34 to continue the correction phase or adapt the correction according to the signals S.

Therefore, steps 34 and 35 are repeated as many times as necessary until a proper presentation of the current mail item to be popped up in the time window T is made, but it is preferable that beyond a certain period of time correction without obtaining an adequate presentation, an alarm is triggered to prevent the need for manual intervention.

According to the invention, an inadequate presentation of the current item to be unstacked with respect to the unstacking head 5 is detected on the basis of a control of the signals supplied by the four sensors 20, 21, 22 and 23. Conversely, a Proper presentation of the current mail item to be unstacked is detected on the basis of a control of the signals provided by the same sensors 20, 21, 22 and 23.

The criteria for judging whether or not the current item to be unstuffed with respect to the unstacking head can be codified in a truth table as illustrated on the figure 12 .

On the figure 12 this truth table has been illustrated with on the left a very schematic representation of the current mail item to be displayed in profile in correspondence with the value of the signal supplied by the sensors 20 to 24. A signal with the value of "1" indicates a detection of the presence of a shipment while a signal at the value of "0" indicates the absence of detection of the presence of a shipment. In the truth table, the drives of the motorized drives of the belt conveyor 2, the pallet 4 and the secondary conveyors 12 are also shown as a function of the signals supplied by the sensors 20 to 24.

According to some unsuitable presentation situations detected by the sensors, the control unit 13 can react by actuating the motorized drive of the unstacking head only if the current mail is not already engaged in the entry cone between the deformable wheels 10 (detected by the sensors 26 and 27). The control unit 13 can also, on detection of collapsed shipments in the chute, do not actuate the motorized drive of the unstacking head during the time window T, the time to straighten these shipments by pushing them with shipments on the main conveyor. If the control unit 13 detects by the sensors that only the foot of the current item is poorly presented, it may not operate the motorized drive of the unstacking head during the time window T so that the conveyors 12 in the fall have time to restore the presentation of this current shipment.

The process of recovery of shipments in step 34 of the figure 3 will be better understood in the light of the presentation of different example cases below.

On the figure 5 a situation has been illustrated in which the items 3 in the chute 11 collapse under their weight, so that the item to be unstacked is not completely pressed against the unstacking head 5.

This situation is detected by the control unit 13 because the sensor 22 produces a signal indicative of the absence of sending while the sensors 20, 21 and 23 each produce a signal indicative of the presence of a shipment. This situation corresponds to the third line of the truth table of the figure 12 .

Referring to the figure 3 for this example case in step 32, the control unit 13 detects an unsuitable presentation of the current item to be unstacked and orders at step 34 a correction phase of the presentation of the current item. relative to the unstacking head.

In step 34, the control unit 13 controls the motorized drives of the conveyor 2 and the pallet 4 by passing them at a low speed of displacement at 0.096 m / s. At the same time, the control unit 13 suspends the motorized drive of the belt conveyors 12, since as indicated by the sensors 20 and 21 the foot of the current mailpiece is correctly pressed against the head 5, which has the effect of to straighten shipments in the fall because new shipments arrive from the main conveyor 2 pushed by pallet 4.

During the correction phase, the unit 13 controls, in step 35, the signals of the sensors. In step 35, if the signals S of the sensors are indicative of an adequate presentation of the current item to be unstacked and which is in the time window T, the control unit 13 continues the process to step 36 by operating the motorized drive of the unstacking head (perforated strips and suction nozzles).

The current to be despatched is then serialized between the deformable wheels 10 at the output of the unstacking device, the motorized drive of the perforated strips 9 and the suction nozzles is stopped and the normal unstacking operation is restored. The process then loops to step 32.

On the other hand, in step 35, if the signals S of the sensors are indicative of an unsuitable presentation of the current item to be unstacked, the process loops in step 34 to continue the correction phase or to adapt the correction to function of the signals S.

In a non-illustrated situation where the sensors 21 and 23 provide a signal indicative of the presence of a shipment while the sensors 20 and 22 provide a signal indicative of the absence of a shipment, at step 34 the unit control 13 controls the belt conveyors 12 to pass in average speed to 0.152 m / s so as to straighten the shipments in the fall 11. This situation corresponds to the second line of the truth table of the figure 12 .

Another similar situation would occur with sensors 20, 21 and 22 which each provide a signal indicative of the absence of a sending while the sensors 23 and 24 each provide a signal indicative of the presence of a shipment. This situation corresponds to inclined consignments in the left-hand part of the fall on the figure 5 . In this case, the control unit 13 in step 34 controls the belt conveyors 12 to pass them at an average speed of 0.152 m / s and controls the motorized drives of the conveyor 2 and the pallet 4 by passing them in small movement speed at 0.096 m / s. This situation corresponds to the fourth line of the truth table of the figure 12 .

A particular situation would arise with sensors 21 and 22 which each provide a signal indicative of the absence of a sending while the sensors 20, 23 and 24 each provide a signal indicative of the presence of a shipment. In this case, the control unit 13 in step 34 controls the belt conveyors 12 to pass them in medium speed in reverse at 0.152 m / s and controls the motorized drives of the conveyor 2 and the pallet 4 in them. moving in low speed of displacement to 0.096 m / s. This situation corresponds to the fifth line of the truth table of the figure 12 .

On the figure 6 , there is illustrated another situation of inadequate presentation of the current mail to be unstacked with respect to the unstacking head. Here, the shipments in the chute 11 are collapsed from the top to the rear so that the sensors 20, 21 and 22 each provide a signal indicative of the presence of a shipment but the sensor 23 provides a signal indicative of the absence of a shipment. This situation corresponds to the seventh line of the truth table of the figure 12 .

In the example of the figure 6 , the sensor 24 detects the presence of a shipment. In step 32, the control unit 13 thus detects an inadequate presentation of the current mail with respect to the unstacking head 5. In step 34, the control unit 13 starts a correction phase consisting of simultaneously to interrupt the drive of the conveyor 2 for 25 milliseconds, change the speed of movement of the pallet in low speed to 0.096 m / s and interrupt the drive of the conveyors 12 of the chute. After the delay of 25 milliseconds, the unit 13 changes the speed of the belt conveyor 2 to 0.096 m / s.

This correction phase causes a shift between the pallet 2 and the conveyor 2 at the top of the shipments both on the main conveyor 2 and in the chute 11.

During the correction phase, the unit 13 checks, in step 35, whether the signals S of the sensors are indicative of an adequate presentation of the current item and that one is in the time window T. In this case, at step 36, the control unit 13 actuates the motorized drive of the unstacking head and continues the process as previously described.

On the other hand, in step 35, if the signals S of the sensors are indicative of an inadequate presentation of the current send, the process loops in step 34 to continue the correction phase or to adapt the correction as a function of the signals. S.

On the figure 7 another example of an inadequate presentation of the current item to be unstacked with respect to the unstacking head has been illustrated. In this example case, the top of the shipments in the chute collapses backwards and at the same time the foot of the shipments in the fall collapses towards the rear.

In this situation, the sensors 20 and 23 each provide a signal indicative of the absence of a sending while the sensors 21, 22 and 24 each provide a signal indicative of the presence of a shipment. This situation corresponds to the sixth line of the truth table of the figure 12 .

In step 34, the control unit 13 triggers a correction phase of suspending the drive of the belt conveyor 2 for 25 milliseconds and then changes the speed of the conveyor 2 to 0.096 m / s. At the same time the speed of movement of the pallet 4 has changed to a low speed mode at 0.096 m / s while the speed of the conveyors 12 has increased to an average speed of 0.152 m / s. This has the effect on the one hand to straighten the top of the shipments in the fall and at the same time to advance the foot of the shipments to the unstacking head.

During the correction phase, the unit 13 checks, in step 35, whether the signals S of the sensors are indicative of an adequate presentation of the current item and that one is in the time window T and the process continues as described previously.

On the figure 8 another example of an inadequate presentation of the current item to be unstacked with respect to the unstacking head has been illustrated. In this case of example, the feet of the items in the chute are set back relative to the unstacking head. The sensors 20 and 21 each provide a signal indicative of the absence of a sending while the sensors 22 and 23 each provide a signal indicative of the presence of a shipment. The sensor 24 also provides a signal indicative of the absence of sending in the chute. In this case the fall is insufficiently fed with shipments. This situation corresponds to the ninth line of the truth table of the figure 12 .

In step 34, the control unit 13 triggers a correction phase consisting of moving the conveyor 2 and the pallet 4 at a low speed of 0.096 m / s while the conveyors 12 are changed to an average speed of 0.152 m / s. s

This has the effect of feeding the fall 11 shipments by tamping these shipments in the fall. This results in a recovery of the current item to be unstacked.

On the figure 9 another example of an inadequate presentation of the current mail with respect to the unstacking head has been illustrated.

In this example, the sensors 21 and 24 each provide a signal indicative of the absence of a sending while the sensors 20, 22 and 23 each provide a signal indicative of the presence of a shipment. This situation corresponds to the tenth line of the truth table of the figure 12 .

In step 34, the control unit 13 passes the pallet 4 and the conveyor 2 of the main magazine in low speed at 0.096 m / s while it controls a reverse of the conveyors 12 at an average speed of 0.152 m / s.

This has the effect on the one hand to feed the fall 11 in shipments and to move back foot of the shipments already present in the fall, thus redressing all shipments in the fall 11.

On the figure 10 another example of an inadequate presentation of the current item to be unstacked with respect to the unstacking head has been illustrated.

In this exemplary case, the sensors 20, 21 provide a signal indicative of the absence of a sending while the sensors 22, 23 and 24 each provide a signal indicative of the presence of a shipment. This situation corresponds to the eleventh line of the truth table of the figure 12 .

In this example, the fall is too much fed with mail that collapses in their lower part.

In step 34, the control unit 13 passes the conveyor 2 and the pallet 4 in low speed at 0.096 m / s for 25 milliseconds and then interrupts their operation. At the same time, it passes conveyors 12 at an average speed of 0.152 m / s to straighten shipments in the fall without fueling the drop in shipments.

On the figure 11 , the presentation of the items is similar to the situation of the figure 10 but the foot of the shipments collapses on the front. The sensor 21 provides a signal indicative of the absence of a sending while the sensors 20, 22, 23 and 24 each provide a signal indicative of the presence of a shipment. This situation corresponds to the twelfth line of the truth table of the figure 12 .

In this situation, the control unit 13 passes the conveyor 2 and the pallet 4 at low speed for 25 milliseconds and then interrupts their operation. At the same time, it passes the conveyors 12 in reverse at a speed of 0.152 m / s to straighten the shipments in the fall.

It is understood that the invention is not limited to the sole embodiment of the unstacking device described above. In particular, one would not depart from the scope of the invention by modifying the detail of the sensors, by modifying the number of sensors, by applying different corrections in response to the signals provided by the sensors.

Claims (10)

1. An unstacker device for unstacking flat objects, which device comprises a motor-driven feed magazine controlled so as to move flat objects in a stack and on edge facing an unstacking head (5) provided with a motor-driven drive having a perforated belt and a suction chamber, which motor driven drive is actuated so as to separate a current first object from the stack and so as to eject it in a direction that is transverse to the direction in which the stack of flat objects is moved, in which device the motor-driven drive is actuated and stopped each time a current object is unstacked, and the stack of flat objects is straightened up in the magazine in response to detection of signals delivered by a plurality of sensors disposed in the unstacking head, a first sensor (20) being disposed to detect presence of a bottom portion of the current object facing the unstacking head (5), a second sensor (21) being disposed to detect presence of a first intermediate portion of the current object facing the unstacking head (5), said first intermediate portion being situated above said bottom portion of the current object, characterized in that a third sensor (22) is disposed to detect presence of a second intermediate portion of the current object facing the unstacking head, said second intermediate portion being situated above said first intermediate portion of the current object, said sensors (20,21,22) being disposed in the unstacking head in a manner such as to deliver signals indicating that said current object is presented appropriately relative to the unstacking head (5), and in that the drive of the unstacking head is actuated if the signals indicate that the current object is presented appropriately.
2. An unstacker device according to claim 1, in which the unstacking head (5) comprises a metal sheet provided with two openings side-by-side.
3. An unstacker device according to anyone of claims 1 or 2, in which the first sensor (20) is a flag mechanical sensor, the second sensor (21) is a reflection optical sensor, and the third sensor (22) is a reflection optical sensor.
4. An unstacker device according to anyone of claims 2 or 3, in which the first, second, and third sensors (20,21,22) are aligned vertically in the unstacking head between said two openings.
5. An unstacker device according to anyone of the preceding claims, in which said plurality of sensors further includes a fourth sensor (23) disposed to detect presence of a flat object in said direction that is transverse to the direction in which the stack of flat objects moves.
6. An unstacker device according to claim 5, in which said fourth sensor (23) is an optical barrier sensor.
7. An unstacker device according to anyone of the preceding claims, in which the feed magazine comprises a drop-forming feed (11) disposed between a main conveyor belt (2) with a motor-driven drive and the unstacking head (5), and a paddle (4) with a motor-driven drive, said paddle being suitable for being moved along the main conveyor belt, the drop-forming feed being provided with secondary conveyor belts with a motor-driven drive (12), the control unit acting on the motor-driven drives of the main conveyor belt, of the paddle, and of the secondary conveyor belts so as to present the current object appropriately relative to the unstacking head.
8. An unstacker device according to claim 7, in which the control unit (13) is arranged to change the speeds and the directions of the motor-driven drives of the feed magazine in order to present the current object appropriately relative to the unstacking head (5).
9. An unstacker device according to claim 8, in which the control unit (13) is arranged to trigger an alarm at the end of a certain time for which the control unit (13) has been acting on the motor-driven drives of the main conveyor belt, of the paddle, and of the secondary conveyor belts without obtaining appropriate presentation of the current object relative to the unstacking head.
10. A machine for handling postal items, said machine including an unstacker device according to claim 1.

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