SE1051192A1 - Removal device - Google Patents

Abstract

18 ABSTRACT Transition device that is adapted to receive objects from a first horizontalconveyor having a first speed and to feed the objects to a second horizontalconveyor having a second speed and to position the objects at predefinedpositions on the second conveyor, where the incoming objects of the firstconveyor have a variab|e spacing, and where the transition device is adaptedto acceierate the objects individually from the first speed to the second speeddepending on the position of the object on the fist conveyor. The advantageof the invention is that objects having a variab|e spacing from a first conveyorcan be positioned on a second conveyor at predefined positions. (Figure 1)

Description

TRANSITION DEVICETECHNICAL FIELD The present invention relates to a transition device adapted for moving anobject from a first conveyor having a first speed to a second conveyorhaving a second speed. The spacing between the incoming objects variesand the objects are positioned on the second conveyor at predefinedpositions. The transition device is adapted to be used in a conveyorsystem.

BACKGROUND ART Conveying devices, such as those which are used for moving objectsbetween different stations in a factory, usually comprise a conveying trackin the form of a belt or a chain. The conveying tracks can be recessed in atrench with vertical side surfaces. Alternatively, they can be located on thehorizontal upper surfaces of the trench or arranged in some other way.The objects to be conveyed may be arranged on the conveying trackseither directly or via supporting means. Larger objects are often conveyedon supporting means also known as pallets, and smaller objects may beconveyed using a small carrier often referred to as a carrier puck. Someproducts, such as boxes, packages or bottles are often conveyed directlyby the conveyor tracks.

For objects that are conveyed directly by a conveyor track, it is importantthat the object is conveyed without any sliding or slipping between theobject and the conveyor track. lt is a further advantage to be able toprovide a well defined spacing between the products, especially at somepositions on the conveyor track. lf the products are travelling at higherspeeds, a gap between two products may be required in order for thesystem to be able to separate the products. Regardless of the spacing of the incoming objects, a predefined spacing of the outgoing objects isdesirable.

Different ways of obtaining a predefined gap between objects are known.One common solution is to let a second conveyor run at a higher speedthan the first, previous conveyor. With both conveyors running at constantspeeds and with the objects of the first conveyor being positioned in apredefined manner, e.g. packed against each other, a predefined gap canbe obtained between the objects on the second conveyor. ln this solution,the objects are pulled from the first conveyor by the second conveyor.There will thus be a relative movement, i.e. slippage, between the productand the first and/or the second conveyor during the transition of the object.The object will experience a sudden difference in speed at the moment itreaches the second conveyor, which can cause instability of the object.Further, the acceleration/motion of the objects is depending on the frictioncoefficient and is not completely predictable, which will give somedeviations in the gap spacing. ln this solution, the objects cannot beaccurately positioned on the second conveyor which means that thissolution cannot be used for feeding a cleated conveyor or for mergingobjects from different conveyors to one conveyor.

By adding a sensor, such as a photo-electric sensor that detects productedges, and a control system that actively modifies the conveyor speeds asthe objects are transferred to the system described above, a system thatcan position objects can be provided. By modifying the first and/or thesecond conveyor speed, the gap spacing between objects can be variedsuch as a positioning offset can be created. The sensor can give objectposition feedback to the control system, which can use this information tocontrol the conveyor speeds such that the products are positioned asdesired on the second conveyor belt. ln this solution, the objects are also pulled from the first conveyor by thesecond conveyor. There will thus be a relative movement, i.e. slippage,between the product and the first and/or the second conveyor during thetransition of the object. The object will experience a sudden difference inspeed at the moment it reaches the second conveyor, which can causeinstability of the object. Further, the acceleration/motion of the objects isdepending on the friction coefficient and is not completely predictable,which will give some deviations in the gap spacing. The friction coefficientfurther sets an upper limit for the maximum acceleration that is possible.All products that are positioned on each of the conveyors are affected bythe speed alterations, which will further affect the stability of the objects. ln such a system, there is a strong relation between the production rateand the maximal possible positioning offset, i.e. the gap spacing betweenobjects. ln practice, at high production rates, this makes it necessary tohave several conveyors, e.g. three to five conveyors in sequence, in orderto create a sufficient positioning offset, which must be at least the same asan object length, for feeding a cleated conveyor or for merging objectsfrom different conveyors to one conveyor. ln order to reduce the dependency of the friction coefficient between thefirst conveyor and the objects in the examples given above, the firstconveyor can be provided with an object holding means, e.g. a so calledchoke belt, such that the objects are held between the first conveyor andthe choke belt or between two choke belts. The objects are thus forced toaccelerate with the first conveyor. This makes it possible to use higheracceleration in the speed alterations of the first conveyor without riskingslippage or instability of the objects. A photo-sensor will give objectposition feedback to the controls system. The second conveyor usuallytravels with a constant speed. ln this solution, all products that are placed on each of the conveyors areaffected by the speed alterations. The gaps between the products in thechoke belt section are determined by the momentary speed of the objectsas the objects enter the choke belt section. lf the choke belts areaccelerated rapidly, an undesired gap may be pulled between the objectsjust entering the section, due to the fact that products upstream of thechoke belt section are only accelerated by the friction force from theunderlying conveyor. This effect has a big negative impact on possibleproduction rate, since the spacing between the objects varies. When thechoke belts are started and stopped, pulsations are created in the backlogof accumulated products upstream of the conveyor. These pulsations can damage the objects and may also increase wear.

US 5,762,175 discloses a solution that ensures packs which arrive atirregular intervals from one another to be transported further atpredetermined spacing from one another. The incoming packs areaccumulated in an accumulated group in the region of an accumulatingconveyor, which transfers the individual packs one after the other, inaccordance with the timing of the machine, onto an intermediate conveyorwhich in turn feeds the packs to the removal conveyor. The separatepacks are gripped in the region of the intermediate conveyor by means oftwo mutually opposite arranged belts and are thereby conveyed at highspeed in a precise manner. By letting the packs group in an accumulatedgroup, thereby bearing on each other, a well-defined position for the incoming packs is created.

US 3,827,545 discloses a method and apparatus for changing the spacingbetween discrete flexible web products. The discrete web products moveon an inlet conveyor with a constant inlet pitch and a constant inlet speedand are transferred to an outlet conveyor moving at a second constant speed where the products are spaced apart with a second constant outlet pitch. A speed regulator transfers the web from the inlet conveyor to thesecond conveyor with a fixed speed transfer function.

US 3,812,948 discloses a device that separates and conveys articles,such as chocolate bars, which are moved in engagement with each otherby an input conveyor and are transferred by a periodically operatingtransfer member onto an output conveyor which operates in synchronismwith said transfer member which engages the articles during theirconveying movement and moves the same with a speed which is greaterthan the speed of the output conveyor. The transfer member comprises apusher which transfers the articles from the path of the input conveyor tothe path of the output conveyor in such manner that the articles will be inspaced relation to each other on said output conveyor. The outputconveyor consists of an endless chain, which is fitted with actuatorsperpendicularly attached to the chain pushing the articles.

US 4,934,510 discloses a bottle inspecting assembly wherein a supplyconveyor supplies a sequence of upright glass bottles at a first speedthereon to an intermediate conveyor comprising several sets of beltswhich grips the opposite sides of the bottles, accelerates them from thefirst speed to a much greater speed across a gap and deposits them on adelivery conveyor means which is driven at a second speed so that thebottles are in spaced, upright positions on the delivery conveyor to permitinspections to be made.

US 4,682,684 discloses a method and an arrangement for the transfer ofobjects from a first to a second conveyor, the latter being driven at ahigher constant speed than the first conveyor. ln such a transfer of objectsbetween conveyors equipped with driving or load contacting elements(plate or a bar positioned at intervals of the total width of the conveyor),damage to the objects is avoided if these are given a temporary increasein speed at the moment of transfer. The increase in speed occurs because the driving element of the first conveyor is tipped forward directly beforethe transfer in the direction of movement of the conveyor, so that the totalspeed of the object at the moment of transfer substantially corresponds to the speed of the second conveyor.

US 2003/014153 A1 discloses a production line for small parts orconductor ends that are transported by means of workpiece carriers fromwork station to work station in a production direction. An interchangedevice is connected between the two transfer devices, the first transferdevice handing over the work piece carriers to the interchange device andthe interchange device feeding the workpiece carriers to the secondtransfer device. The interchange device serves as an adapter for differentworkpiece carrier spacing (pitch dimensions) of the first and second groups.

US 4,987,991 discloses a system for changing the speed of conveyedsheets. The system includes a speed changing belt operating at aconstant linear speed, flexible holding means and an acceleration lobe onsaid belt. The acceleration lobe is positioned to engage the trailing portionof the sheet and to provide a continuously increasing radius at the tangentcontact portion as the belt travels around a pulley whereby the outersurface velocity of the lobe and the sheet in contact therewith continuously increase from the incoming speed to a desired second speed.

All these systems may work fine for some types of objects, but arenevertheless depending on a given object spacing for the incoming objectsof the feeding conveyor. There is thus still room for improvements.

DISCLOSURE OF INVENTION An object of the invention is therefore to provide a transition device that isadapted to create a product flow with objects positioned at predefined positions from an infeed flow where the spacing between the objectsvaries. The object is achieved in that the transition device is provided withan adaptive and variable acceleration. A further object of the invention isto provide a dynamic positioning device comprising a transition device. Afurther object of the invention is to provide a dynamic merging device thatcan merge two infeed product flows. Another object of the invention is toprovide a method that can create a product flow with objects at predefinedpositions from an infeed flow where the spacing between the objects varies.

The solution to the problem according to the invention is described in thecharacterizing part of claim 1 with regards to the transition device and inclaim 10 regarding the method. The other claims contain advantageous embodiments and further developments of the transition device. ln a transition device that is adapted to receive objects from a firsthorizontal conveyor having a first speed and to feed the objects to asecond horizontal conveyor having a second speed and to position theobjects at predefined positions on the second conveyor, where theincoming objects of the first conveyor have a variable spacing, the objectof the invention is achieved in that the transition device is adapted toaccelerate the objects individually from the first speed to the second speed depending on the position of the object on the fist conveyor.

By this first embodiment of the transition device according to the invention,it is possible to obtain a product flow with objects positioned at predefinedpositions from an infeed product flow where the spacing varies betweenthe objects.

The transition device may comprise one or more transition rollers ortransition belts that will transfer the object from the first conveyor to thesecond conveyor. The transition roller or transition belt is controlled such that the object is individually accelerated. ln an advantageous development of the invention, the transition device iscomprised in a dynamic positioning device that will position objects on aconveyor at predefined positions. The conveyor may comprise fixedposition devices, such as cleats. The incoming objects are positioned atthe predefined positions or in the pockets between the cleats with apredefined gap regardless of the distance between the incoming objects. ln another advantageous development of the invention, at least twotransition devices are comprised in a dynamic merging device that willmerge two incoming product flows into one product flow with the objectspositioned at predefined positions.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which Fig.1 shows a schematic side view of a first embodiment of adynamic positioning device comprising a transition deviceaccording to the invention, Fig. 2 shows a schematic side view of a development of the firstembodiment of a dynamic positioning device comprising atransition device according to the invention, Fig. 3 shows a top view of a second embodiment of a dynamic merging device comprising two transition devices according to the invention.MODES FOR CARRYING OUT THE INVENTION The embodiments of the invention with further developments described inthe following are to be regarded only as examples and are in no way tolimit the scope of the protection provided by the patent claims.

Figs. 1 and 2 show a first embodiment of a dynamic positioning device fora conveyor system comprising a transition device according to theinvention. The dynamic positioning device 1 comprises a first conveyor 2,a second conveyor 3 and a transition device 4 positioned between the firstconveyor and the second conveyor. The speed of the first and secondconveyor may be constant or may vary depending on the requirements onthe dynamic positioning device and the number of objects that is to behandled during a specific time period. The speed of the conveyors ishowever constant during the transfer of an object from the first to thesecond conveyor. The first conveyor transports objects 7 with a first speedv1 from a production line or the like. The invention is especially suitable forhigh-speed production lines, with a product rate of up to several 100products per minute. The products may be e.g. cardboard boxes, poly-wrapped packs or bottles. The products travelling on the first conveyor aresupplied with a first flow rate, i.e. a specific number of products perminute, and with a varying spacing between them. ln the first embodimentof the invention, the dynamic positioning device will enable a flow ofobjects on the second conveyor where the objects are positioned atpredefined positions and where the deviation of the spacing between thepredefined positions of the objects is very small. The absolute deviationwill depend on e.g. the speed of the second conveyor, the size and weightof the object and the resolution of the measurement system and thesensor used, but is preferably in the order of less than 5%.

A predefined position for the object is defined as a region on the secondconveyor in which the object can be placed without interfering with anotherobject. This region may have approximately the same length as the objectbut is preferably somewhat longer than the object in order to increase thetolerances of the system. When an object is to be positioned on thesecond conveyor, it must be positioned within such a region. Dependingon the product flow, this may lead to that some regions will be empty onthe second conveyor. lf the object is too late for a specific region, it will instead be placed in the next region, i.e. the next predefined position.There may also be a predefined spacing between the regions, such thatthe objects will never bear on each other, even when they are placed asclose to each other within two adjacent regions. The size of a region andthe spacing between the regions are preferably predefined depending e.g.on the type and size of the objects and the speed of the conveyors.

The transition device will receive objects trave||ing with a first speed fromthe first conveyor and will deliver the objects to the second conveyortrave||ing with a second speed that may be constant. The first and secondconveyors are arranged in a horizontal way, i.e. the carrying plane of theconveyors is horizontal such that the objects can lay or stand on theconveyors without falling off. The transition device comprises one orseveral driven rollers or belts. Depending on the orientation of thetransition device and the type of object, it may suffice with a single drivenroller and a passive support roller or support surface, but two or moredriven rollers may provide, depending on the objects, a better support forthe transferred objects. ln the shown examples, two driven transitionrollers 5, 6 are used. These transition rollers are ramping up and down inspeed for each object that travels on the first conveyor. When an objectreaches the end of the first conveyor and thus enters the transition device,the rollers rotate with a speed that is the same as for the incoming productflow, i.e. the same as the speed v1 of the first conveyor. When the object isno longer in contact with the first conveyor, the object is only held by thetransition rollers. For longer objects, the rear part of the object may still bein contact with the first conveyor when the front part of the object is heldby and accelerated by the transition rollers. ln this case, the rear part ofthe object may slide some on the first conveyor. The transition rollers willnow accelerate the object to the same speed as the discharged productflow, i.e. to the speed v2 of the second conveyor. The object can now enterthe second conveyor with the same speed as the second conveyor. 11 Thus, there is no or a minimized relative movement, i.e. slippage, betweenthe object and the first conveyor and no relative movement, i.e. slippage,between the object and the second conveyor during the transition of theobject from the first to the second conveyor. When the object has enteredthe second conveyor and is no longer in contact with the transition rollers,the ro||ers slows down to the speed v1 of the first conveyor and are readyto receive a new object. A first sensor 8 is used to detect when an objectreaches the transition device from the first conveyor. A second sensor 9may be used to give object position feedback to the control system fromthe second conveyor. ln this way, the objects are received to the transitiondevice with a variation in time, and are delivered to the second conveyorat predefined positions. During the transition, the object is accelerated in asmooth, controlled way with no slippage between the ro||ers and the objectand the acceleration of the objects is predictable and is not depending onthe friction coefficient between the object and the conveyors. Theacceleration of an object is depending on the time when it arrives at thetransition device and on the instantaneous position of the predefinedposition on the second conveyor, i.e. when the object must be fed to thesecond conveyor. The acceleration rate and the time for the completeacceleration are also dependent on the speed of the first and the second conveyor.

The transition device can also be used to feed objects to the downstreamsecond conveyor having fixed position devices 10, e.g. in the form ofcleats, that define the positions for the objects. The transition ro||ers arecontrolled so that products are securely fed into the pockets between thecleats in a continuous motion without stopping or restricting the upstreamproduct flow. This is done by either shifting the acceleration step in time orto control the acceleration parameters such that the object will be placedat one of the fixed positions. ln this way, the position of the object on thesecond conveyor can be controlled within the limits set by the object rateand the speeds of the first and second conveyor. lf the object arrives at 12 the transition device too late to reach a specific fixed position, thetransition device will adapt the acceleration such that the object will beplaced at the next position.

One advantage of the dynamic positioning device is that the objects on thefirst conveyor can be transported at a constant speed, thereby eliminatingupstream pulsations. Further, the objects are securely held during theacceleration phase, thus ensuring product stability. The positioning on thesecond conveyor is done by a single driven roller or a pair of rollers in onestep, which allows for a very compact machine design. The totalaccelerated inertia is minimized since only one object and the transitionrollers must be accelerated, which reduces the requirements on the drivesystem. Further, the function is not depending on the length of the objects,which allows for a very flexible system that can handle different productvariants. The distance between the first and the second conveyor can beadapted to the length of the objects in order to avoid slippage.

Depending on the object characteristics, such as size, weight, shape,friction, etc, and the required production rate, the design of the transitiondevice may be altered in different ways. The transition rollers can bepositioned horizontally such that they grip the object from above and frombeneath or vertically such that they grip the object from the sides. Forsome objects, it is possible to use only one horizontal roller that drives theobject at the bottom of the object and where the top is guided by a guiderail. lt is also possible to use one vertical roller that drives the object at oneside and use a fixed guide rail as a support surface to support the otherside of the object. For longer objects, short conveyors or belts may beused instead of transition rollers to accelerate the object and to givesufficient support to the object. lt is also possible to use several transitionrollers in order to support a longer object. Depending on the object, it isalso possible to use other means to accelerate the object in a controlledway. A metallic object may e.g. be accelerated by a magnetic field. 13 ln a second embodiment, shown in Fig. 3, a dynamic merging device isused to merge two separate product flows. The dynamic merging devicecomprises two transition devices, a first transition device 23 and a secondtransition device 24, which are positioned at two separate product flows. lnthe shown example, each product flow comprises the same objects whichare transported with a relatively high first speed by two infeed conveyors,a first infeed conveyor 20 and a second infeed conveyor 21. The speed ofthe first infeed conveyor 20 is v20 and the speed of the second infeedconveyor 21 is v21. The speed of the first and the second conveyor may bethe same or may differ. The objects 7 may e.g. come from two productionstations that each produce objects at a given production rate. A typicalinfeed rate of the first and the second conveyor is 0 - 1000 objects perminute. The infeed rate of the first and the second conveyor may be thesame, or the infeed rate may differ between the two conveyors, dependinge.g. on the production capacity of the upstream production or feedingstations. The two infeed flows are merged in the dynamic merging deviceto a third conveyor 22 that will transport all objects with a speed v22. Thespeed v22 is at least twice the speed of the infeed conveyor having thehighest speed, depending e.g. on the required spacing of the objects onthe second conveyor.

The objects that are transported on the infeed conveyors may have aconstant spacing between them or may bear against each other, or thespacing may vary somewhat. lnfeed sensors will detect when the objectsenters the transition devices and the control system can thus control thetransition devices such that the objects will be released at the right moment in order to merge the objects.

Each transition device 23, 24 comprises in the shown example ahorizontal driven transition roller and a horizontal passive transition rollerthat will transfer the object from the two infeed conveyors to the thirdconveyor without slippage. The first transition device 23 receives objects 14 from a first infeed conveyor 20 and the second transition device 24receives objects from a second infeed conveyor 21, and feeds the objectsto the third conveyor 22 in a consecutive manner. Each object is fed to aspecific position such that the objects will not co||ide with each other. Thespecific positions will be held even if an object from one of the infeed conveyors is missing.

The transition rollers will accelerate the object from the first speed to thesecond speed and will release them to the second conveyor. Since twoproduct flows will be merged into one product flow, the transition ro||ersare controlled such that the objects from one infeed conveyor areseparated by relatively large gaps, approximately 2 times the productlength or more, depending on the required spacing for the objects on thesecond conveyor. Such a gap represents a predefined position of anobject. The transition devices of the first and the second infeed conveyorsare synchronized such that the objects are merged. A first infeed sensor26 and a second infeed sensor 27 are used to detect the incoming objects.lt is also possible to use sensors after the transition devices in order togive feedback to the control system. The second conveyor comprises amerging section 28 that is wide enough to receive the product flows fromboth infeed conveyors. The product flow is then merged by simpleconverging guiderails 29. lt is also possible to use a separate mergingconveyor belt corresponding to the merging section. The merging processis done in continuous motion, without stopping or restricting the upstreamproduct flow, and can reach very high production rates.

The invention is not to be regarded as being limited to the embodimentsdescribed above, a number of additional variants and modifications beingpossible within the scope of the subsequent patent claims.

REFERENCE SIGNS ¿.CP ¿F? m.CP mmmm:FFPNf m9? mE' m9? mF? Dynamic positioning deviceFirst conveyor Second conveyorTransition deviceTransition rollerTransition roller Object First sensor Second sensor Position device Dynamic merging deviceFirst infeed conveyorSecond infeed conveyorThird conveyor First transition deviceSecond transition deviceFirst infeed sensorSecond infeed sensorMerging section Guide rail

Claims (1)

1. _ Transition device (4, 22, 23) that is adapted to receive objects (7) from a first horizontal conveyor (2) having a first speed and to feedthe objects to a second horizontal conveyor (3) having a secondspeed and to position the objects at predefined positions on thesecond conveyor (3), where the incoming objects of the firstconveyor have a variable spacing, c h a r a c t e r i z e d in thatthe transition device (4, 22, 23) is adapted to accelerate the objectsindividually from the first speed to the second speed depending onthe position of the object on the fist conveyor. .Transition device (4, 22, 23) according to claim 1, c h a r a c t e r i z e d in that the transition device (4, 22, 23)comprises a circular roller (5, 6). .Transition device (4, 22, 23) according to claim 2, characterized in that the transition device (4, 22,23) comprises two circular ro||ers (5, 6). .Transition device (4, 22, 23) according to claim 1, c h a r a c t e r i z e d in that the transition device (4, 22, 23)comprises a belt. _ Transition device (4, 22, 23) according to any of claims 1 to 4, c h a r a c t e r i z e d in that the transition device (4, 22, 23) ispositioned along a horizontal plane which is parallel to the plane ofthe first and the second conveyor (2, 3). .Transition device (1) according to any of claims 1 to 4, c h a r a c t e r i z e d in that the transition device (4, 22, 23) ispositioned along a vertical plane which is perpendicular to the planeof the first and the second conveyor (2, 3). 17 Dynamic positioning device (1) for a conveyer system, comprising afirst horizontal conveyor (2) running with a first speed and a secondhorizontal conveyor (3) running with a second speed, where thesecond speed is higher than the first speed and where the incomingobjects of the first conveyor have a variable spacing,c h a r a c t e r i z e d in that the dynamic positioning device (1)further comprises a transition device (4, 22, 23) according to any of c|aims 1 to 6. Dynamic positioning device (1) according to c|aim 7,c h a r a c t e r i z e d i n that the second conveyor (3) comprises fixed position devices (10). Dynamic merging device (1), adapted to merge objects (7) from afirst infeed conveyor (20) and a second infeed conveyor (21) to athird conveyor (22), c h a r a c t e r i z e d in that the devicecomprises a first transition device (23) and a second transition device (24) according to any of c|aims 1 to 6. 10.Method for positioning objects on a second conveyor at predefined 11 positions, where the incoming objects of a first conveyor have avariable spacing, where the speed of the second conveyor is higherthan the speed of the first conveyor, comprising the steps ofdetecting when an object arrives at a transition device, acce|eratingthe object with the transition device and re|easing the object to the second conveyor at a predefined position. .Method according to c|aim 10, where an object is acceierated depending on the time when it arrives at the transition device andon the instantaneous position of the predefined position on the second conveyor.