AU615915B2

AU615915B2 - A device for unstacking flat objects

Info

Publication number: AU615915B2
Application number: AU18141/88A
Authority: AU
Inventors: Roland Allio; Raymond Chifflet; Gilbert Del Fabro; Emmanuel Delbe; Guy Forella; Francois Gillet; Philippe Jeantin; Etienne Serot
Original assignee: Cga Hbs
Current assignee: Solystic SAS
Priority date: 1987-06-18
Filing date: 1988-06-20
Publication date: 1991-10-17
Anticipated expiration: 2008-06-20
Also published as: FR2616762B1; EP0295686B1; EP0295686A1; AU1814188A; DE3868989D1; FR2616762A1; CA1320226C

Description

r i

AUSTRALIA

Patents Act 615915 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: 4 0#e 0-* APPLICANT'S REFERENCE: F 16019/JP *0 S,*Namefs) of Applicant(s): o 0 Societe Anonyme Dite:

CGA-HBS,

Compagnie Generale D'Automatisme Address(es) of Applicant(s): 0 4.

0 "44 12, rue le la Baume, .a Paris 76008,

FRANCE.

S*".Address for Service is: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA ".:Complete Specification for the invention entitled: A DEVICE FOR UNSTACKING FLAT OBJECTS Our Ref 97001 POF Code: 1501/47915 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6003q/1 1 C 1 -i I :i i i 1A A DEVICE FOR UNSTACKING FLAT OBJECTS The present invention relates to a device for unstacking flat objects, i.e. a device for taking flat oljects one-by-one from a stack in order to present them one-by-one in an exit position to be taken up by a destination machine.

These flat objects may, in particular, be postage ithems and the unstacking device may be used for feeding an indexing and/or sorting machine.

~x~r~couu orT-E Nr.E~r~ .0 Conventionally, devices for unstacking flat objects essentially comprise a magazine for storing a stack of postage items and an unstacking head at the end of the magazine. The magazine includes drive means for presenting the first item in the stack in a well-defined position and standing on edge. The o000 15 uistacking head may be constituted by a suction cup which performs a plunging movement to come into contact with the first item in the stack and to grasp it by suction, and which *coo*: is moved in translation in order tL take the item away from its stopped position to an exit position where it is taken up by the destination machine. During this time, the stack advances in the magazine and the next item takes the place of the a SR preceding item.

British patent specification GB-A-2 125 367 illustrates 0 °this type of equipment. Although it includes a bellows, the e000 suction cup is relatively rigid and only its lip adapts to the shape of the surface of the object to be grasped.

8 0 Suction cup systems are known in other fields where the problem of separating flat objects one-by-one does not occur in the same way (cf. the following patent documents: US-A-3 724 687, DE-A-Si 552, US-A-3 193 281, EP-A-O 212 865, DE-C-I 112 538).

Postage items can be very varied in nature, and the surfaces they present to the unstacking head may be stiff or floppy, smooth or porous, and the item as a whole may be thin or thick, light or heavy. The unstacking head must be capable of grasping and moving thick and heavy items having stiff and smooth surfaces as well as open items; its suction force must therefore be sufficiently high. However, in a given batch of postage, there may also be light single sheets which are thin and porous and which have a natural tendency to adhere to one another so that the high suction force of the unstacking head tends, from time to time, to pick them up together and move them together to the exit position.

Unstacking, i.e. taking the items from the stack one-by-one thus remains a problem which is not fully solved.

The object of the present invention is thus to provide an improved unstacking head which is considerably S better at separating thin objects, in particular, without degrading its performance when unstacking other objects.

t The present invention thus provides a device for unstacking flat objects in a stack of such objects, said device comprising an unstacking head including a first suction cup for grasping the first flat object in said stack and moving it towards an exit position where the grasped object is released, said suction cup comprising a bellows made of a flexible material and adapted upon t. suction heing applied thereto to grasp said first object and to retract under effect of said suction, entraining therewith at least a surface of the grasped object.

a The present invention also provides a metho of unstacking flat objects in a stack of such bjects comprising the steps of: providing an unstacking head having a suct'o cup adapted upon suction being applied thereto to g sp the first flat object in said stack, said sucti cup comprising a 30 bellows made of flexible material- and advancing said suction cup to rds a surface of said first Sobject until it grasps aid object and retracts under t effect of said suction entrailing therewith at least said surface of the gras ed object.

The grase object may be jerked by the retraction of the sucto n cup, and it thus tends to be separated from another ject to which it may be adhering.

The invention may also provide means for accurately S3- splacing the suction cup towards the first object in the SU L -2- -o -v

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IiinI therewith at least a surface of the grasped object, said unstacking head being provided with a shoe disposed to one side of the suction cup, and fixed relative to te mount carrying,, the suction cup, with the surface of the shoe being close to the grasping plane of the suction cup, said shoe providing an obstacle to the surface of the grasped flat object when the suction cup retracts, thereby warping said surface.

The present invention also provides a method of unstacking flat objects in a stack of such objects comprising the steps of: providing an unstacking head having a suction cup adapted upon suction being applied thereto to grasp the first flat object in said stack and to move it towards an °oew 15 exit position where the grasped object may be released, said suction cup comprising a bellows made of flexible material; advancing said suction cup towards a surface of said first object until it grasps said object and retracts eoo under effect of said suction, entraining therewith at least said surface of the grasped object; and providing said unstacking head with a shoe disposed to one side of the suction cup, said shoe being fixed relative to the mount carrying 44 suction cup such that :0 -25 the surface of the shoe is close to the grasping plane of Sthe suction cup, said shoe providing an obstacle to the surface of the grasped flat object when the suction cup retracts, thereby warping said surface.

SThe grasped object may be jerked by the retraction of the suction cup, and it thus tends to be separated from another object to which it may be adhering.

The invention may also provide means for accurately displacing the suction cup towards the first object in the stack, said means may comprise a mount provided with plunging guide means and with drive means. The guide means are preferably two parallel slides and the drive means are prefezably an electric motor with rack-and-pinion transmission.

The invention may also provide carriage means for -2A-

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1 i i I moving the suction cup from its grasping position to an exit position where the grasped object is released.

Preferably, said carriage is guided by two parallel slides and is driven by an electric motor, via a belt transmission.

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-2B- 3 In addition, the invention provide for a which isfixed to the mount adjacent to the suct-ioi cup and which has a surface close to the suction-oupgrasping plane. The shoe thus constitutes an obstacl6 when the suction cup retracts, thereby warping Eurface of the object to be grasped and making it eser to separate the first object from the stack.

Finally, the invention/provide a method of controlling the movements of the head, in which the plunging movement of the suction cup is essentially constituted by a rapid advance over a determined distance (which may be interrupted on detecting the presence of an item), followed by a slow advance until the item has been grasped.

BIEF DE3SORIPTI0JOF-1 Ti DRAWIN6K i t An embodiment of the invention is described by way of S 15 example with reference to the accompanying drawings, in which: Figure 1 is an overall view of an unstacking device in r accordance with the present invention; Figure 2 is a side view in partial section of the conventional magazine of the Figure 1 unstacking device; Figure 3 is an elevation view in partial section of the .Figure 1 unstacking head; t, Figure 4 is a fragmentary plan view of the mount carrying the suction cup and of the shoe in the Figure 1 unstacking K head; Figure 5 is a cross-section view on the axis of the carriage showing the mount and its drive means; Figure 6 is a plan view of the retracted suction cup r~ C C S showing the action of the shoe which causes the surface 100 of c a grasped postage item to be warped by the suction cup; and Figure 7 is a flow chart showing an example of how the movements of the unstacking device of the preceding figures may be controlled.

The unstacking device shown in Figure 1 comprises a magazine 1 and an unstacking head 2 mounted end on, i.e. in front of the magazine 1. The magazine 1 is conventional. It is shown in Figure 2 in side vie,?, with a side plate removed in order to show how poi4,tage items are presented to the unstacking head.

The magazine 1 is intended to be manually loaded with a stac of postage. Its top is open and the stack of postage is placed on a bottom 9 which slopes relative to the horizontal wiLth a slope that rises from the back going towards the front.

The stack of postage is placed in front of a backplate against which it rests. An internal side piece 11 optionally retains the stack while it is being loaded. Postage drive means drive -the stack as loaded towards the unstacking head 1.

The drive means comprise an endless chain 17 and belts 12 passing over pulleys 13 and 15, one of which is a driving pulley. The backplate 10 slides along a side guide 25 by means o of a non-referenced slider and includes a lug (not shown) which is engaged between the links of the chain 17. The stack of postage is thus driven in the direction of arrow fl by the *0 edges of the items standing on the belts 12 and by the back- 0.00.:plate 10 supporting the back of the last item. When a new stack is loaded, the backplate is disengaged from the chain 17 and is moved backwards by hand.

.9 The side piece 11 is extended by a jogging edge 31 and a 0:.::terminal jogging surface 30 at the end of the magazine against which the items are urged by wheels 36, 38, 37, and 35 whose 00. axes are parallel to tha belts and whose surfaces are flush 00 0 with the belts and whichr are rotated with a motion towards the jogging edges 30, 31 which is communicated by friction to the 000.

6 items in the stack as they move towards the unstacking head.

Continuity of the bottom 9 is ensured between the wheels by a crenelated extension 39.

In addition, the surfaces of the wheels are helically formed, thereby preparing the items for unstacking by accelerating and then decellerating the motions of the bases of the items as they slide against the jogging edge.

A single electric motor with an appropriate transmission can be used for driving the belts, the chain, and the jogging wheels.

Finally, there is an abutment 5 on the extension 39. It stops the first item in the stack in a position suitable for the items to be grasped by the unstacking head. A detector, e.g. constituted by one or more photoelectric cells, serves in conventional manner to determine that an item has reached the abutment 5. The drive means are then stopped or declutched.

When the item is removed, the drive means are put back into operation.

The unstacking head referenced 2 in Figure 1 is shown in greater detail in the elevation, plan, and end views of Figures 3, 4, and 5. It is essentially constituted by a mount 50 which is movable along arrow f 2, and carried by a carriage 60 which is itself movable along arrow f 3. The mount 50 carries a suction cup 88 and a shoe Cosa, 15 Displacement along arrow f2 serves to move the suction cup *GOOD*88 and the shoe 90 towards the first item in the stack which is o stopped in the magazine against the abutment 5 and whose presence is indicated by the detection means, as mentioned above. Movement continues until the surface of said item is taken up by the suction cup under the effect of the suction which is maintained therein. Displacement along arrow f3 then serves to move the item grasped by the suction cup 88 to the exit position 40 where it is released by the suction cup by turning off the s~.ction, after which it is taken up by destination means (not shown) such as an indexing machine or a postal sorting machine.

The carriage 60 slides relative to two parallel slides and 51 carried by pillars 99 fixed to the frame of the machine.

To this end, it is driven by a notched belt 54 kept taut between wheels 57 carried on respective shafts 56 carried by tabs 55 and 59, said belt being driven by an electric motor 58.

More precisely, the carriage 60 comnprises two parallel sliders 61 and 62 provided with bores 63 containing bearings through which the slides 51 and 52 pass. The sliders are interconnected by a bridge 64 for receiving and supporting the plunging motion drive motor 95 and provided with a central bore 96 for passing the shaft of said motor, which shaft is coupled to a drive pinion 76.

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The carriage 60 is coupled to the notched belt 54 by two clamping pieces 65 and 66 which are pressed against each other and which are fixed to the slider 62. Each of the sliders 61 and 62 carr.,as two pillars 67 and 68 on which the parallel slides 69 of the, mount 70 are themselves mounted.

Although not shown, simple detection means may be fixed on the pillars 99 for detecting when the carriage 60 is to the left (as seen in Figure 1) in a given starting position from which the unstacking head grasps the item provided by the magazine 1, or else to the right in a given exit position which is where the unstackcing head releases the items it has previously grasped.

The mount 70 slides on the slides 69 by rmans of two parallel sliders 71 and 72 provided with bores 73 containing bearings having respective ones of the slides 69 passing therethrough. The sliders are interconnected by a bridge 74 which carries the suction cup support 80. A rack 75 is fixed beneath the bridge 74 against slider 72. The drive pinion 76 meshes with the rack so that the motor 95 can drive the Mount 70 from a starting position (to the right in Figure 3) towards a grasping position (to the left in Figure 3) under conditions which are explained below.

Also not shown, are sensors which -may be fixed to the piliars 67 and 68 for detecting, in conventional manner, that the mount is either in its starting position or else in its position of maximum advance. The mount may also carry a proximity sensor for detecting the presence of an item in -he stack at a certain distance in front of the suction cup.

The suction cup support 80 essentially comprises a support bracket 81 having an axial bore 82, 83 which is tapped at each end. The bore 83 is connected to a flexible suction pipe via an end piece 84. It opens out into the bore 82 which serves to fix a suction cup mounting tube 86 via an end piece 87, optionally together with a gasket. The suction cup 88 is a part having one or more bellows (in this case it has two); it is made of flexible material such as rubber, and is capable of retracting when its orifice 89 is pressed against the closure surface, thereby pulling said surface towards the mount 7 A pressure minimum detector, or "vacuostat", may be connected to the pipe 85 in order to indicate that the suction cup 88 has grasped an item, whenever the pressure in the pipe falls below a given threshold.

The shoe 90 is fixed on the suction cup mounting tube by means of an angled arm 91 including a clamp which is tightened by a screw 92. The end of the shoe 90 lies in the same plane as the orifice 89 of the suction cup 88. When an item 100 is presented in front of the orifice 89, the suction cup snatches it and retracts, thereby warping the surface of the item as shown in outline in Figure 6 since the item is pulled by the orifice 89 as it retracts relative to the shoe 90 while being simultaneously retained by the shoe 90 which prevents it from accompanying the orifice of the suction cup 88 as it moves.

ego0 15 The next item in the stack which is not subjected to the same effects does not warp in the same manner. It therefore 99 separates fran the item which has just been grasped. The more 0 suddenly the s'iction cup 88 snaps back, the greater the o separation effect, since a sudden snatch takes advantage of the inezL--.a of the second item resisting the motion which is 99 imparted to the first item. It may be observed that the 00 retraction movement of the suction cup is more sudden for lightweight items, thereby particularly improving the o unstacking of thin objects which are generally the most difficult to separate from one another.

A sequence of operations for the unstacking head described ,****above is now described with reference to the flow chart of Figure 7.

This sequence of operations is preferably implemented by means of a microprocessor whose input signals are constituted by signals from the sensors whose existence is mentioned above.

These sensors are accompanied by a sensor (not shown in the figures) for sensing displacement of the mount 50 and constituted, for example, by a conventional pulse strip. The pulses frant this sensor are supplied to the microprocessor which permanently keeps track thereof in a mremory register.

The input signals available to the microprocessor are summarized below: DET signal from a detector carried by the mount and indicating the presence of an item to be unstacked at a determined distance in front of the suction cup; E 1.4 mount 50 in its starting position; E 1.1 carriage 60 in its starting position; E 1.3 a cycle control signal which may come from a button pressed by an operator for requesting the machine to extract an item from the stack, or which may be automatically supplied by the destination machine; MO pulse count relating to the pulse strip and continuously defining the position of the mount a first constant; PLI the vacuostat signal indicating the presence of a grasped itemv; MW1 a recorded intermediate value; jK2 a second constant; K6 a third constant; and E 1.2 carriage 60 in its arrival position.

In general, the processor returns periodically to the process illustrated by Figure 7 at the point where it left it during a preceding period (a step marked by a rectangle) and it interrogates an input in order to determine whether it should move on to the next step.

When the machine is switched on, the processor always begins from a beginning of cycle situation DC. The processor then performs the following sequence of steps: 4 RR so long as the signal E 1.4 is absent, the processor causes the mo.unt 50 to reverse rapidly by applying an output control signal to the power supply circuit of the motor instructing it to reverse the mount RC if the signal E 1.4 is present, then the mount 50 has reeched its starting position, or if the commnand RR has been 9 given to return the mount 50 to said position, and so long as the signal E 1.1 is absent, the processor applies a command signal RC to the control circuit for the motor 58 in order to cause it to drive the carriage 60 by means of the belt 54 towards its starting position; AR when the signals E 1.4 and E 1.1 are both present, then both the mount and the carriage have reached their respective starting positions, and if the signal E 1.3 is absent, then nothing further occurs; however, if the signal E 1.3 is present, the microprocessor applies a command signal to the power supply circuit of the motor 95 instructing it to cause the mount 50 to advance rapidly, i.e. as fast as possible with the hardware being used, and another command signal causes suction to be applied to the suction cup 88, e.g. by opening a 15 valve; AL when a detector carried by the mount 50 indicates that an item is present by supplying a signal DET, or when the mount 50 has advanced over a predetermined maximum distance, the count MWO which indicates its position becomes equal to a constant K5 (which may be applied to inputs of the microprocessor or which may be entered into a register by the manufacturer), the microprocessor instructs the power supply circuits of the motor 95 to cause the mount 50 to advance S'slowly instead of quickly without losing excessive time and while maintaining suction; MWO MW1 advance the mount 50 slowly and the suction cup 80 carried thereby ends up by grasping the first item from the stack, thereby giving rise to the signal PLI, after which the processor transfers the count value provided by the register MWO into the register MW1 while the commands described 1i in step AL continue to be applied, thereby making it possible to confirm that the item has been grasped while suction cup retraction takes place; RL when, after the preceding step, the mount 50 has further advanced through a distance corresponding to a count value K2, the microprocessor performs the operation MW1 K2 MWO, and when it obtains a positive response it applies a new command to the power supply circuit of the motor causing the mount 50 to reverse slcv;wly with the suction cup 88 carrying the grasped item, and with suction being maintained; RCR =slow reverse continues until MWO is again equal to MW1, after which the microprocessor replaces the slow reverse comimand by a fast reverse comnmand which differs from the command RR solely in that suction is maintained; TR the purpose of rapid reverse is to bring -the grasped item into a posi czlon which suits the destinatiion machine by travelling over a distanuce determined by a constant K6, that is why when the count MWO becomes less then MWl K6, the microprocessor stops the motor 95 in the position it has reached and appl.4es a command signal to the power supply circuit of the motor 58 to cause the carriage to move towards the exit position; and AD when the carriage 60 arrives in -the exit position, the signal E 1.2 is present and the microprocessor stops the carriage, and then turns off the suction so that the suction cup 88 releases the item it has grasped; after an appropriate time delay, the microprocessor returns3 to the cycle beginning

DC.

Naturally, in the above summnary of operations, when the microprocessor performs a step and provides the commands specified, all other commands are cancelled. Depending on the circuits used, this may require special commands for stopping It: I z'toperations which are taking place.

The unstacking device duscribei3 above and for which a sequence of operations has been given includes only one suction cup 88. In some applications it can happen that jogging is not always good enough and that items escape fromn the suctio~n cup 88 b ecause they are too far from the jogging edge 30. A solution to this problem, which is an extension of the present invention, consists in providing a second carriage such as together with a second suction cap. The second carriage and its suction cup may be controlled in the same way as the first carrialge (but naturally with different starting and arrival 11 positions), and the effect of said second carriage is to grasp such items and bring them to the first suction cup 88.

Naturally the above description is given purely by way of non-limiting example, and numerous variants may be imagined without thereby going beyond the scope of the invention.

CI

Claims

2. A device according to claim 1, including a carriage for moving said first object to said exit position, wherein said unstacking head includes plunging means for moving the suction cup towards said first object, and SSq;d M6')Ar' a lice lnc)L /Z wherein said plunging meal. compriseae mount guide means enabling it to move linearly relative to said carriage in a direction towards said first object, the suction cup being fixed to said mount, said plunging means further including drive means for moving the suction cup towards said first object.
3. A device according to claim 2, wherein said drive means comprise an electric motor, a drive pinion driven by the motor, and a rack in which the pinion meshes, the rack being fixed to said mount while the motor and the pinion are fixed to the carriage.
4. A device according to claim 2 or 3, wherein said guide means comprise two slides fixed to the carriage and two sliders fixed to the mount and associated with respective ones of the slides. A device according to any one of claims 2 to 4, 39 wherein translation means are associated with said -12- I I a a 1. I carriage adapted to move said carriage from a position in which the suction cup is capable of grasping said first flat object to said exit position in which said suction cup is to release said grasped object, together with translation drive means for driving said carriage to said exit position.
6. A device according to claim 5, wherein said translation means comprise two fixed slides and two sliders fixed to the carriage and associated with respective ones of the slides.
7. A device according to claim 5 or 6, wherein said translation drive means comprise an ele Lric motor fitted with a pinion driving a belt, together with pulley wheels on either side of the carriage and means keeping the belt 15 taut, with the carriage being coupled to the belt between the two pulley wheels.
8. A device according to any one of the preceding claims, wherein a second suction culp is provided to one side of the first suction cup, on the side opposite said 20 exit position, and at a distance such as to be capable of .grasping objects in the stack which are so far offset as to escape from the first suction cup, with the movement of said second suction cup being generally parallel to that of the first. 25 9. A device for unstacking flat objects substantially as herein described with reference to the accompanying drawings. A method of unstacking flat objects in a stack of such objects comprising the steps of: providing an unstacking head having a suction cup adapted upon suction being applied thereto to grasp the first flat object in said stack and to move it towards an exit position where the grasped object may be released, said suction cup comprising a bellows made of flexible material; advancing said suction cup towards a surface of said first object until it grasps said object and retracts under effect of said suction, entraining therewith at A-O least said surface of the grasped object; and SO J -13- providing said unstacking head with a shoe disposed to one side of the suction cup, said shoe being fixed relative toA.-he mount carrying the suction cup such that the surface of the shoe is close to the grasping plane of the suction cup, said shoe providing an obstacle to the surface of the grasped flat object when the suction cup retracts, thereby warping said surface.
11. A method according to claim 10, further comprising the steps of: advancing the suction cup rapidly over a first distance; and advancing the suction cup slowly over a second distance until it grasps said object.
12. A method according to claim 11 wherein said first 15 distance is determined oy detecting said object in front of said suction cup. I
13. A method according to claim 11 or 12 further comprising the steps of: detecting that said object has been grasped by the suction cup; advancing the suction cup slowly over a short I distance after detecting that said object has been grasped; and reversing the suction cup slowly over a predetermined distance. 25 14. A method according to claim 11, 12 or 13 further comprising the step of: moving the suction cup to an exit position; and releasing said grasped object. 1 15. A method of unstacking flat objects substantially as herein described with reference to the accompanying drawings. Dated: 26 July 1991 PHILLIPS ORMONDE FITZPATRICK Attorneys for: SOCIETE ANONYME DITE: COMPAGNIE GENERALE D'AUOMATISMA CGA-HBS ii 2 8 22'- L -14-