EP0656865A1

EP0656865A1 - A method and a system for controlled loading of articles onto a sorting conveyor

Info

Publication number: EP0656865A1
Application number: EP93919040A
Authority: EP
Inventors: Viggo Jensen
Original assignee: Kosan Crisplant AS
Current assignee: Kosan Crisplant AS
Priority date: 1992-09-04
Filing date: 1993-09-03
Publication date: 1995-06-14
Also published as: AU4945193A; DK109792D0; JPH08500808A; WO1994005572A1

Abstract

By an oblique feeding of articles (8) onto vacant areas or trays (4) of a sorting conveyor (2) it is known to use a feeding conveyor (6, 14), on which the articles are successively accelerated up to the required loading speed. This feeding shall be initiated from standstill, when the vacant area (4A, B, C) is located at a certain distance from the place of infeed, and the associated time lapse makes it difficult to arrange for a correct feeding into trays immediately succeeding each other, particularly if the supply of the articles to the feeding conveyor is not fully synchronous. The invention provides for an improvement into different manners, viz. for one thing by a length separation of the feeding conveyor in individually controllable sections (14a-d), whereby one article (8) may be under rapid final loading whilst other articles may be under acceleration at lower speed on the same conveyor, and for another thing by the use of requirement controlled accelerations, which may lead to intermediate velocities higher than the feeding speed. Hereby lately supplied article may catch-up with a vacant tray (4), which could not otherwise be reached with the use of a standard acceleration to the feeding speed.

Description

A METHOD AND A SYSTEM FOR CONTROLLED LOADING OF ARTICLES ONTO A SORTING CONVEYOR.

The present invention relates to a method for feed¬ ing transportation objects onto a conveyor of such a type that advances objects positioned in well-controll¬ ed, mutually separated positions, in particular a con¬ veyor sorter of the type comprising a movable row of carrier platforms or trays for single objects to be selectively discharged at different receiving stations alongside the conveyor. With these conveyor type sor¬ ters, certain.problems are encountered when an optimal utilization of the actual sorting capacity is desired, since the feeding of objects, e.g. parcel post packages, should take place in an optimized synchronous manner, which only occurs in exceptional cases.

The sorter conveyor is moved at quite great veloci¬ ty to achieve ample capacity, and therefore it constitu¬ tes a special problem to deposit the objects at exact positions on the conveyor as the objects are apt to skid uncontrollably on the conveyor if they are merely inser¬ ted sideways onto the conveyor with enough speed to be deposited on a vacant space thereon. For the same reason, special "inclined feeders" have been developed enabling the objects to be fed sideways concurrent with being advanced so fast on the obliquely debouching feeder conveyor that their velocity component in the longitudinal direction of the sorter conveyor is commen¬ surate with the velocity of the sorter. Hereby, it is possible to feed objects for pin-point positioning on a rapidly moving conveyor, e.g. on a vacant tray between two already filled trays thereon.

However, substantial requirements are demanded of the applied control equipment to utilize this form of feeding operation in practice. An object or a package, e.g. to be delivered at a given positon on the conveyor, must be accelerated from a standstill point of reference up to the relatively high rate of delivery, which is bound to take some time. It is crucial to have full control of the position of the package on the feeding conveyor to ensure that the loading is going to take place exactly in the desired space and, as a case in point, the feeding operation will fail if the feeding belt is started up so fast that the package will slip on this belt. Thus, the feeding of the package must be initiated reasonably well ahead of the actual discharge onto the conveyor.

Various techniques have already been suggested by which to improve these conditions, e.g. by building up the feeding conveyor in sections in such a way that the objects may be advanced to a stand-by position as close as possible to the conveyor belt, guided by position detectors to offset possible skidding of the objects on one or more feeding conveyors. It has furthermore been suggested to control the start-up of the last feeding belt with just enough "delicacy" to prevent a slippage between the web and the object during the final spurt of the object, whereby the timing of the delivery of the object onto the conveyor will be very accurately de¬ termined.

It still applies, though, that the feeding belt start command must be executed well in advance before the actual loading onto the conveyor takes place, and the feeding belt will then be occupied up until the point when the loading has been made, and the feeding belt is subsequently has again been stopped. This means a restriction of the effective feeding belt throughput, and the purpose of this invention is to increase this capacity.

To a great extent, the invention seen in relation to the prior art may be likened to the entry of cars on a motorway. If the cars are to merge into the traffic flow, from a standstill position to find an opening there, it is essential to contemplate well in advance where this opening*will appear so that the start of the merge operation, at a given acceleration, may be ini¬ tiated in time. If, on the other hand, a flowing inter¬ weaving is chosen, where the accessing is performed with varied or variable speed, then there is a much better chance of merging successfully into the opening in the car line, even though the opening may not be spotted or made available till rather late in the operation. The essential part is for the entering party to have picked up sufficient speed to avoid spending extra time on acceleration from immobility. It is also essential that, along the way, the entering party may drive faster, temporarily exeeding the motorway traffic speed, hence reaching the opening. These reflections have proved to be of great relevance for many sorters systems.

According to the invention, a controlled variable velocity of the feeding conveyor is used, in that the packages may thusly be accelerated in advance to a medium velocity from which they may relatively fast be decelerated or accelerated further, depending on a de¬ tected requirement. In this way, packages may in many instances be deposited in vacant spaces so far advanced that they could not have been reached using the usual feeding control, and precisely herein the sorter capaci¬ ty can be increased quite considerably.

For the invention, however it is a further signifi¬ cant feature that the feeding conveyor may be composed by a number of series-connected, individually control¬ lable conveyors, in that it will hereby be possible to guide and advance more packages simultaneously, each of which may be accelerated or decelerated as required, with a view to being deposited on successive vacant trays on the sorter conveyor. Thus, a given package could be accelerated on a specific belt section while another package could be decelerated on a different belt section. The feeding conveyor may thus advance several packages simultaneously, and by doing so a noticeable increase of the feeding capacity is achievable.

The invention is explained in more detail in the following with reference to the drawing, in which:

Fig. 1 is a schematic top view of a system accord¬ ing to the invention, and

Fig. 2 is a diagram of various velocity modes.

In Fig. 1, a sorter conveyor 2 comprises an endless row of laterally tiltable transportation trays 4 passing one or more feeding stations 6 of the oblique feeder belt type. The conveyor 2 extends further along a deli¬ very area where the transportation objects, in the fol¬ lowing named packages, which are loaded into the respec¬ tive trays 4, are discharged selectively at relevant receiving stations by tipping the trays sideways.

A primary oblique feeder 6 may be of an elementary controlled kind on which packages 8 are advanced from a point of receipt and encoding area 10 for sideways deli¬ very into the passing, pre-emptied trays 4. The feeding is performed at such velocity and timed such that the packages are deposited in respective single trays with a velocity component in the direction of advancement of the conveyor 2 corresponding to the the velocity of advancement of this conveyor, such that the packages are deposited in well-defined positions on trays whose iden¬ tity is controlled by an associated control computer.

In this station 6, objects are delivered on some of the passing trays 4, but not necessarily in any fixed pattern, i.e. often one or more vacant trays will appear inbetween the loaded trays. In the following feeding station, generally designated 12, packages are advanced successively to a starting position on an acceleration belt 14 which is started depending upon the package being in place and a tray appearing on conveyor 2, e.g. tray 4A, which is vacant and able to arrive at the feeder 8 just when the latter delivers the started pack¬ age. In his example, a preceding vacant tray 4B cannot be used because the belt 14, as it is, starts up with the greatest possible acceleration for safety position¬ ing of the package on the belt.

The package, however, enters the belt 14 from a preceding belt 16 at a certain speed, and according to the invention this is exploited such that the package on the belt 14 is not slowed down if a vacant tray appears immediately following tray 4A, which the package may still reach when a 'flying start⁷ like this is used. In certain particularly fortunate cases where it is possi¬ ble to utilize the maximum acceleration on belt 14 the package may even be on time to be deposited even closer, on tray 4C, but otherwise the acceleration need only be controlled such as to let the package arrive at the exact moment when the following tray, 4B, passes the station.

The drawn positioning line X in Fig. 1 may repre¬ sent the last reachable tray position for a moved vacant tray if the tray in station 12 is to receive a package deposited in the standard way; halted in the stand¬ by/start position on the belt 14. In this case, the position x is shown, placed in front of the feeder 6, but here the computer will already be informed whether the tray will be filled in this station.

Fig. 2 shows the velocity V of the belt 14 cor¬ related to the longitudinal position L of the package on this belt. The package is delivered on the belt with a velocity VI, and if no vacant tray is available the belt is slowed to a stop along the depicted curve portion a. When a vacant tray in position X appears the belt 14 is started at maximum acceleration, curve b, whereby the package will manage, at velocity V2, to be transferred to the tray just when the latter passes the station.

In station 12, if an incoming package is headed for the belt 14 just when the empty tray passes position X, according to the invention, the belt 14 may be started or kept from stopping, such that the package is received at the velocity VI and is then forwarded without halt¬ ing, but with a controlled acceleration depending on how far the empty tray is from the station. If, at this point, the tray is in the shown position Y on the con¬ veyor, a correct delivery is achievable provided the package is slowed down a little, cf. curve c in Fig. 2, and subsequently accelerated to the correct feeding velocity V2. The closer the empty tray is to the station when the package is deposited on the belt 14, the more the belt needs to be accelerated for the package to reach the tray in time, cf. e.g. curve d. Position Z on the conveyor 2 corresponds to the last attainable tray position if the package is to arrive using maximum ac¬ celeration, cf. curve e. It is true that towards the final stage of this operation, a steady slowing of the belt must be performed to ensure a reduction of the velocity of the package to the feeding velocity V2, without slipping, but it may be noted that the level of velocity can be considerably higher than at the ordinary and conventional feeding, cf. curve b.

If the package arrives on the belt 14 after the empty tray has passed position Z, this tray cannot be reached from station 12, but it may then be used in the next feeding station. The belt 14, in return, could be stopped, curve a, unless a new empty tray is already on its way after position X on the conveyor 2.

The system may also be used in installations where the length of the delivered packages is measured in the feeding stations, such that a single tray 4 or a couple of these trays are allocated for the packages as requir¬ ed.

Here the invention is described in connection with the use of a single, relatively long feeding belt 14, but as shown in Fig. 1 at the extreme right, this belt may be sectioned into successive individually controlled belt lengths, for example four lengths 14a)-14d). Each of these conveyors are of relatively short length in consequence of which they will have correspondingly little intertia, i.e. they can rapidly be speeded up or down. Hereby it will be possible to guide and advance a multitude of packages 8 simultaneously on the entire conveyor 14 in such a differentiated way that each of the packages are controlled dynamically for correct delivery on the respective trays 4. This option, in particular, determines the said increase of the feeding capacity. The packages 8 may be delivered irregularly from the conveyor 16 and may yet in many instances suc¬ ceed in being deposited regularly onto the trays 4 rather than being temporarily stopped.

The said longitudinal sectioning of the feeder generally conditions an increase of capacity, even if the individual sections are arranged, in a standardised way, so as to accelerate the objects to an initial ve¬ locity for the ensuing section. If the objects are de¬ livered in a regular or synchronized manner on the feeder 14, several objects under acceleration, on the same feeding section, can thusly be handled at mutually varying rates of velocity, i.e. the objects may follow one another at relatively short interspacings.

Claims

C L A I M S :

1. Method for controlled loading of objects to well-defined mutually separated positions on a main conveyor, in particular a sorter conveyor with carrier trays for the objects, by which method the objects are transported successively to an area of receipt on a dirigible feeder conveyor on which the objects are acce¬ lerated for sideways delivery onto a desired carrier place of the main conveyor with a velocity component in the longitudinal direction of the latter, the feeder conveyor being controlled depending upon the actual carrier place passing a release area at a certain spac¬ ing prior to the place where the sideways delivery is effectuated, characterized in that a feeder conveyor is used which is divided, in its longitudinal direction, into a number of sectionalized conveyors being individu¬ ally controllable; and in that these conveyors in con¬ nection with an irregular supply of objects to the feeder conveyor are controlled, with variable accelera¬ tion, such that the rate of advancement of the objects is currently adjusted to the given options for the deli¬ very of the objects onto the regularly occurring carrier places on the main conveyor, whereas at least some of the sectionalized conveyors are sometimes geared up to speeds, at which the said velocity component is greater than the rate of advancement of the main conveyor.

2. Method according to claim 1, characterized in that the sectionalized conveyors are controlled in con¬ sideration of the available carrier places being more or less advanced in the said release area, which is of a certain length.

3. A system for execution of the method according to claim 1 comprising a main conveyor and at least one feeder conveyor, the path of which is forwardly and inwardly inclined towards the main conveyor and is di- rigible for controlled loading of objects to passing vacant carrier places on the main conveyor, characte¬ rized in that, in its longitudinal direction, the feeder conveyor is divided into several individually controlled sub conveyors of which at least one is arranged with a control system enabling current requirement-detected velocity changes for dynamically adjusting the feeding conveyance for a correct loading in of the individual objects.

4. A system according to claim 3, characterized in that the sub conveyors or one or more of these are a- dapted for acceleration regulation to a velocity exeed- ing that at which the objects are fed onto the main conveyor.