GB2266086A

GB2266086A - A method and a system for controlling the advance of products in a conveyor system, for example, in an automatic packaging system

Info

Publication number: GB2266086A
Application number: GB9303496A
Authority: GB
Inventors: Renzo Francioni
Original assignee: Cavanna SpA
Current assignee: Cavanna SpA
Priority date: 1992-04-15
Filing date: 1993-02-22
Publication date: 1993-10-20
Anticipated expiration: 2013-02-22
Also published as: ITTO920343A0; ITTO920343A1; NL9300635A; FR2690132A1; ES2070727A2; IT1259543B; ES2070727R; GB2266086B; ES2070727B1; FR2690132B1; GB9303496D0; DE4311927A1

Abstract

The invention is applied to a conveyor system including a main line (1), on which a flow of products arranged in rows advances with the longer sides of the products (A) oriented along the direction of advance, and at least one branch line onto which respective fractions of the flow of products (A) are directed. Initially, the products (A) advance on the branch line with their longer sides oriented transverse the direction of advance and they are then turned round (5) so as to advance once more with their longer sides arranged along the direction of advance. Before they are turned round, the products (A) are subjected to an accumulation step. The flow of products output from the accumulation step (4), measured in terms of the number of products (A) per unit of time, is governed by the flow of products taken in by a handling station (W) situated further downstream, also measured in terms of the number of products per unit of time. <IMAGE>

Description

2266086 A METHOD AND A SYSTEM FOR CONTROLLING THE ADVANCE OF PRODUCTS IN A

CONVEYOR SYSTEM, FOR EXAMPLE, IN AN AUTOMATIC PACKAGING SYSTEM The present invention relates in general to the transportation of products and has been developed with particular attention to its possible use in automatic packaging systems for, for example, food products.

In particular, the present invention may be applied to a conveyor system including a main conveyor or line on which a flow of products advances with the products arranged in rows, and one or more branch conveyors or lines for withdrawing and taking in the rows of products.

A system of this type is described, for example, in the present Applicant's patent application GB-A-2 246 996.

In such a system the articles advance on the main conveyor line arranged "lengthwise", that is, with their longer sides oriented along the direction of advance. Individual rows are withdrawn onto the branch lines by being moved transverse the main conveyor line. Thus, the articles advance on the branch lines arranged "crosswise", that is, with their longer sides or iented transverse the direction of advance. The branch lines are usually intended to supply further processing stations such as, for example, wrapping or boxing machines, for example, a wrapping machine of the type described in the United States patent US-A-4 955 184, also assigned to the present Applicant.

These stations or machines usually operate on a continuous flow of equally-spaced products positioned so as to have a precise space-time relationship (a so-called phase relationship) with the operating cycle of the station.

2 it should also be noted that, in the majority of cases, operating sCations, such as wrapping machines, process products "lengthwise"; in other words, the products they receive must advance with their longer sides oriented along their direction of movement. For example, these might be wrapping machines which form wrappers of the type currently knows as "flow-packs", in which the products.(for example, biscuits or piles of biscuits) are inserted in a tubular wrapper which is closed by a longitudinal seal and is subsequently subdivided by transverse seals.

For this reason, in solutions of the prior art, the products withdrawn from the main conveyor line underwent a series of manimulations on the branch lines or conveyors, and these generally included:

- an operation to bring successive rows closer together in order to eliminate discontinuities between the rows withdrawn from IC-he main line in succession, so as to give rise to a substantially continuous flow of products, a turning operation in which the products which are initially arranged "crosswise" are rotated (usually through 90 0) relative to the direction of advance, so as to advance "lengtliwise"; naturally, this rotation may even be achieved by taking advantage of the fact that, rather than extending in only one direction, the branch line has an elbow, or 90 0 bend; in this latter case, the products may be turned round at the same time as the direction of advance of the branch line is changed; - an alignment operation for ensuring that the products to be processed are arranged precisely lengthwise, and 3 - an operation for acc=ulating the products or gathering them together in order to eliminate local spaces between successive products in the flow; starting from this accumulated condition, a conveyor, which is governed by the speed of operation of the processing station situated downstream, can draw off the individual products with a precise flow density (metering), precise spacing, and a precise space-time relationship (phase relationship) with the operating cycle of the processing station situated downstream (for example, a wrapping or a boxing machine).

Although this type of solution has been found very i.L. to satisfactory, L. is difficult t- carry out, particularly in large-capacity ys-IL-ems, in which the linear speed of advance of the products is very fast.

This is due to the fact that it may even be necessary to have several stages in cascade in order to carry out some of the operations described above correctly (particularly when a very precise operation has to be performed on a flow of articles which are moving at a high speed), thus increasing the overall length of the branch line. Therefore, this results in an increase in the space taken up by the line, which nay create difficulties during the arrangement of the layout of the systems (the so-called layout stage); in fact the layouts must take account of the size and configuration of the premises in which the systems are installed.

The object of the preent invention is to provide a solution to these problems.

According to the present invention, this object is achieved by virtue of a method and a system for controlling the advance of products in a conveyor 4 system including a main conveyor line on which a f low of the products advances with the longer sides of the products oriented along the direction of advance, and at least one branch line, onto which at least a respective fraction of the flow of products is directed with the products initially advancing on the branch line with their longer sides oriented transverse the direction of advance, and on which the products are subjected to a turning operation so as to advance with their longer sides oriented along the direction of advance,, and to at least one accumulation operation, characterised in that the accumulation operation is carried out bef ore the turning operation.

One of the most impor-IL---ant aspects of the present invention is based on the recognition of the fact that the accumulation of the articles on the branch lines can be carried out uT)s-IL----ea-Tn of all the other operations (the turning of the products, their alignment, etc.) with the consequent advantage that it can be carried out on products which are still advancing crosswise as they are withdrawn from the main conveyor line, and not on products which have already been arranged lengthwise. Clearly, the accumulation or products which are arranged crosswise requires less space for a given number of products processed per unit of time, which results in a smaller overall size of the branch line, and hence of the system as a whole, particularly if it includes several branch lines.

In this connection, it should be noted that the solution described in the application GB-A-2 246 996 already mentioned above, provides for the products which are on the branch lines to be accumulated under certain operating conditions.

This accumulation condition occurs, however, as a result of a purely accidental phenomenon which may arise when the processing station associated with one or more of the branch lines stops operating moment-arily so that the flow of products advancing on the main line has to be distributed to a smaller number of branch lines. Moreover, it should also be noted that t_his previous ly- known solution relates to a situation in which the processing stations operate on articles which are advancing crosswise, since no turning and/or alignment operation is specifically provided for.

The present invention thus addresses the specific problem which results from the fact that, although the accumulation operation is carried out on products which are arranged crosswise, in conditions in which the density to which the products are accumulated is determined by their transverse dimensions, the handling stations further downstream take in the products according to their longitudinal dimensions.

The invention will now be described, purely by way of non-limiting example, with reference to the appended drawings, which comprise a single drawing showing, in plan, the general structure of part of a system formed according to the invention for packaging products such as food products.

Essentially, the appended drawing is a schematic plan view of part of an automatic packaging system, for example, for food products.

A main conveyor or line, indicated 1 (constituted, in widely known manner, by several conveyors, typically belt conveyors, in cascade), receives from a supply station (not shown but located generally at the bottom of the plan view of the drawing) a flow of products A arranged in rows, that is, in successive lines arranged generally transverse the direction of advance (vertically from the bottom to the top with reference 6 to the drawing). Each row thus includes a certain number o-f- products which are assumed to be generally elongate (for example, biscuits or similar food products) and which advance on the conveyor line 1 arranged lengthwise, that is, with their longer sides arranged along their direction of movement.

A branch conveyor or line, indicated 2, however, extends from a withdrawal station 3 - usually known in the sector as an RFS, that is, a row f eeding station.

The function of the RFS 3 is to withdraw individual rows of products A from the flow advancing on the main line 1 in order to send them towards a corresponding user station W. This may be constituted, for example, by a wrapping machine for packaging the products A individually or in groups; for example, this may be a wrapping machine of the type described in United States-Patent 4 955 184.

The criteria for the formation of the RFS stations 3 in various configurations are widely known in the art and do not need to be recited herein. In general, the stations 3 can be f ormed so as to be able to withdraw products A presented on the main line 1 both upstream and, possibly, downstream of the individual station 3, with reference to the direction in which the products A advance on the conveyor 1.

In this connection, it should also be noted that, although the drawing refers to the presence of a single branch line 2, a packaging system such as, for example, a system for the automatic packaging of food products, usually includes several branch lines 2 which branch out from the main line 1 in succession. This is all in accordance with the general configuration described, 7 for example, in the British patent application GB-A-2 246 996 already cited several times above. In the specific embodiment, the appended drawing refers to a branch line 2 situated in the position furthest upstream with reference to the general direction in which the products A advance on the main line 1. Thus, it can be seen that the flow of products A is compact with complete rows upstream of the branch line 2, but has empty positions, downstream of the branch line 2, which correspond to the rows which have been withdrawn by the branch line 2. In any case, methods of operation almost identical to those described below, with reference to the line 2, are also encountered in all the other branch lines present in the system.

As a result of the withdrawal effected by the station 3, which operates transverse the direction in which the products A advance on the main line 1, the products A initially advance on the line 2 "crosswise", that is, with their longer sides arranged transverse their direction of advance on the line 2.

It is assumed, however, that the handling station W (for example, a flowpack wrapping machine) is intended to operate on products A arranged "lengthwise", that is, with their longer sides arranged along the direction of advance.

For this reason, after they have passed through an accumulation station 4, which will be mentioned further below, the products A are sent to a turning station 5, the function of which is essentially to rotate the products A through 90 0 so as to move them from their "crosswise" positions to positions in which they are oriented "lengthwise".

8 The turning station 5 is of generally known type and may be formed, for example, according to the teachings of British patent application GB-A-2 143 793.

Immediately downstream of the turning station 5, in the direction in which the products advance on the branch line 2 (from left to right with reference to the drawing), is an alignment station 6 for precisely aligning the products A which are advancing lengthwise. This station may also be formed according to known criteria, for example, as described in the present Applicant's patent application TO92A000032 in which the products A are aligned laterally against an abutment surface.

The products A thus aligned are then distributed in a metered manner and in exact spacetime coordination (in phase) with the operating cycle of the station W in a metering-timing unit 7.

This station is also formed according to widely known principles, for example, according to the basic teachings of British patent 1 412 679 and subsequent developments thereof established by the present Applicant.

With reference again to the station 4, it has been stated that this station is intended to perform a general accumulation of the products A whilst preventing the occurrence of conditions in which the products processed are gathered too closely together (with the consequent risk of damage). The station 4 is formed according to the criteria described in detail in United States patent 4 962 844 assigned - to the present Applicant.

9 An important characteristic of the present invention is that the station 4 is located upstream of the stations 5, 6 and 7 in the branch line 2, and not downstream of the stations 5 and 6 as in a conventional arrangement.

in other words, the station 4 is not intended to perform its accumulation function on products A which are already advancing lengthwise, after the rotation effected by the station 5, but on products which are still arranged crosswise.

This solution has been found particularly advantageous because the transverse dimensions of the products A processed are generally shorter than their longitudinal dimensions (for example, half as long, or even much less in the case of very elongate products such as bars of food products, etc.).

This results in two advantages:

- in the first place, the overall size of the station 4 (and hence of the branch line 2) for a given number of products A accumulated is correspondingly reduced in comparison with a situation in which the accumulation is carried on products advancing lengthwise, - in the second place, it is possible to effect greatly improved accumulation and regulation of the flow of products A for a given overall size of the station 4.

As regards this latter aspect, it should be remembered that the station 4 (in this connection, see the United States patent 4 962 844 cited above) is constituted by a certain number of conveyors 4a (typically motordriven belts) in cascade.

in general, in order to be able to perform its function correctly, each conveyor 4a must be able to accommodate at - least two products A simultaneously (even if not throughout their lengths or widths).

Clearly,' therefore, if one had to operate on products arranged lengthwise, each belt 4a would have to be about twice as long as an individual product A.

If, on the other hand, one operates - according to the present invention on products arranged crosswise, the length of each conveyor 4a need only be about twice the width of each product A.

This means that the number of conveyors 4a included in the station 4 may be increased, for example, to ten or more, so that a greatly improved and very delicate accumulation operation can be achieved, particularly when very sensitive products are involved (for example, very crumbly baked products to which the application of appreciable stresses is to be avoided).

In the solution according to the invention, however, it is necessary to take account of an important factor.

On the one hand, it is true that the products A are subjected to the accumulation operation whilst they are still arranged crosswise. It is also true, however, that, when the products A are taken in by the handling station W, they are arranged lengthwise.

Now, the operation of the stations (the upstream stations 4, 5, 6, 7) which supply the products A to the station W is generally governed (tachometrically regulated) by the speed of operation of the station W.

11 Stated simply, the station W indicates to the stations sit-uatedupstream the number of product-s A it can take in per unit of time.

In general, therefore, and according to a widely known solution (see, for example, the British patent 1 412 679 already cited above) the main motor 8 of the handling station W pilots the metering-timing station 7 (and the stations upstream thereof) by means of a general arrangement, schematically indicated 9, for governing its drive. means. In particular, the governing arrangement may be formed either by an electronic coupling arrangement (for example, of the type currently known as an "electric shaft") or by a mechanical governing arrangement.

In the solution according to the invention, upstream of the station W, typically in correspondence with the metering-timing station 7, are sensor means, for example, an optical sensor 10, which detects precisely the speed at which the products A are taken in (the number of products per unit of time) by the station 7, and hence by the station W. In the specific embodiment, the detector 10 may be the detector, or one of the detectors, already present in the station 7 for effecting the metering-timing operation. For example, this may be a photoelectric sensor produced by the German company Erwin Sick.

The output signal of the sensor 10 is sent to the main processing unit (typically a PLC) 11 which supervises the operation of the line 2 and of the system as a whole. The PLC 11 therefore acts on the main motor 12 of the accumulation station 4 (in known manner) so that it outputs a flow of products (products per unit of 12 time) corresponding to the flow taken in by the station W.

The governing of the accumulation station 4, in relation to the stations downstream, is thus not achieved in terms of the absolute speed (the linear speed of advance of the respective conveyors) but in terms of the number of products per unit of time, so that the fact that the products A, which are supplied crosswise by the station 4, are taken in lengthwise by the station W can be left out. of consideration. This also enables account to be taken of the f act that the products A, which are packed close together in the accumulation station 4, may vary to a greater or lesser extent in width.

A further sensor 13 (which may also be an optical sensor and, if appropriate, one of the sensors already present, in any case, within the accumulation station 4) supplies the PLC 11 with a signal indicative of th e extent to which the products A are gathered together in the station 4 (in particular, in its output portion) so that any situations in which the f low of products A withdrawn from the main line 1 is insuf f icient for the requirements of the station W at the time in question can be identified. When there is a signal indicative of excessive thinning of the flow arriving at the station 4, the PLC 11 can act on the motor 8 of the station W to reduce its operating speed according to the flow of products A available at the time in question.

In other words, the solution according to the invention has a dual mechanism for governing (or tachometrically controlling) the operating speeds of the various 13 stations arranged in cascade. More precisely, there is:

- a downstream to upstream governing mechanism (feedback) for causing the accumulation station 4 to supply the stations (5, 6, 7) situated downstream, and hence the machine W, with a flow of products - measured in terms of the number of products per unit of time and not in terms of the speed of advance of the products A - which corresponds to the speed at which the products A are taken in by the user station W, and - an upstream to downstream governing mechanism, the purpose of which is essentially to regulate the speed of operation of the user station W so as to take account of any excessive thinning of the flow of products A arriving at the accumulation station 4.

Naturally, the two tachometric control arrangements described above cooperate in a concomitant manner so that the speeds of operation of the various conveyors 4a are controlled selectively:

i) according to the general mechanism described in United States patent 4 962 844 in Which, each conveyor "copies" the movement of the conveyor situated immediately downstream, ii) in dependence on the general speed (products/unit time) at which the products A are supplied by the accumulation station 4, which is determined by the speed at which the products A are taken in by the user station W, and also iii) in dependence on any variations in this speed at 14 which the products are taken in, which may take place as a result of the detection of an excessive thinning of the flow of products A arriving at the accum.Lilat--ton station 4.

Naturally, the principle of the invention remaining the same, the details of construction and forms of embodiment may be varied widely without departing from the scope of the present invention.

Claims

1. A method of controlling the advance of products (A) in a conveyor system including:

- a main conveyor line (1) an which a f low of the products (A) advances with the longer sides of the products oriented along the direction of advance, and - at least one branch line (2), onto which at least a respective fraction of the flow of products (A) is directed with the products (A) initially advancing on the branch line (2) with their longer sides oriented transverse the direction of advance, and on which the products (A) are subjected to a turning operation (5, 6) so as to advance with their longer sides oriented along the direction of advance, and to at least one accumulation operation (4), characterised in that the acc=ulation operation (4) is carried out before the turning operation (5).

2. A method according to Claim 1, applied to a conveyor system in which the products (A) are supplied to a subsequent processing station (W) in a metered manner (7) at a given frequency, on the at least one branch line (2), after the turning operation (5), characterised in that the frequency of the metered supply relates to the number of products (A) supplied per unit of time, and in that the accumulation operation is carried out so as to achieve a output flow-rate of a corresponding number of products (A) per unit of time.

3. A method according to Claim 2, characterised in that 16 lt includes the step of detecting (B) any excessive thinning of the flow of products (A) subjected to the accumulation operation and the step of correspondingly reducing (9) the speed of operation of the subsequent processing station (W) until the excessive thinning is eliminated.

4. A system for controlling the advance of products (A) in a conveyor system, including:

- a main conveyor line (1) on which a f low of the products (A) advances with the longer sides of the products oriented along the direction of advance, and - at least one branch line (2), onto which at least a respective fraction of the f low of products (A) is directed with the products (A) initially advancing on the branch line (2) with their longer sides oriented transverse the direction of advance, and which includes a station (5, 6) for turning the products (A) so that they advance with their longer sides oriented along the direction of advance, and at least one station (4) for accumulating the products, characterised in that the accumulation station (4) is disposed upstream of the turning station (5).

5. A system according to Claim 4, characterised in that:

- downstream. of the station (5) for turning the products (A), the at least one branch line (2) includes a station (7) for supplying the products to a subsequent processing station (W) in a metered manner and at a given frequency, 17 - the metering station (7) is operated at a frequency which relates to the number of products (A) supplied per unit of time, and - the acc=ulation station (4) is operated so as to output a f low of products (A) per unit of time which corresponds to the frequency of operation of the metering station (7).

6. A system according to Claim 5, characterised in that it includes means (13) for detecting any excessive thinning of the flow of products (A) in the accumulation station (4) and tachometric means (11, 8) for correspondingly reducing the speed of operation of the subsequent processing station (W) until the excessive thinning is eliminated.

7. A method of controlling the advance of products (A) in a conveyor system substantially as hereinbefore described with reference to the accompanying drawing.

8. A system for controlling the advance of products (A) in a conveyor system substantially as hereinbefore described with reference to and as shown in the accompanying drawing.