GB2146795A

GB2146795A - Monitoring the operation of processing plant

Info

Publication number: GB2146795A
Application number: GB08411131A
Authority: GB
Inventors: David Lindqvist
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-09-19
Filing date: 1984-05-01
Publication date: 1985-04-24
Also published as: KR850002796A; IT8422709A0; IT8422709A1; JPS6067055A; FR2552243A1; ES8507713A1; SE8305006L; IT1176712B; SE8305006D0; DE3434233A1; ES536000A0; GB8411131D0

Abstract

In a processing plant in which workpieces are conveyed to selected work stations according to a programme, the computer programme chosen for the plant operation and representing a simulated operating schedule is run through during the actual operation of the plant in synchrony with the latter. The plant comprises a number of sensors by means of which data on actual events taking place in the plant, such as the passage of the workpieces through certain sections of the plant, are recorded. These sensors allow the computer to compare the actual operation with the simulated operating schedule. In response to any discrepancy between the actual and the simulated operating data, an output signal initiates manual or automatic corrective measures.

Description

SPECIFICATION A method in line-production systems and a device for performing the method The subject invention concerns a method in line-production systems, wherein is used a processing plant, comprising a conveying device for advancing the intended workpieces and a number of work stations adapted to perfom a number of operations on the workpieces, said conveying device arranged to be addressed to carry workpieces to selected work stations in accordance with a predetemined programme to perfom the operations specific to the individual workpieces.The method comprises planning the purposeful constraction of the plant as regards the work stations and the operation with a view to transport the workpieces by means of the conveying device through the various work stations by simulating operating schedules in a computer while utilizing established data received in the computer concerning operations required for processing said workpieces, data on the operations, adequate construction and equipment of the work stations to perform said operations.

The invention likewise concerns a device for performing the method in line-production systems, said device comprising a processing plant including a conveying device for transporting the workpieces involved in the production and a number of work stations designed to perform operations on said workpieces. The conveying device is adapted to be addressed by means of addressing equipment to carry the workpieces up to selected work stations in accordance with a predetermined programme for performing the operations specific to the individual workpieces.

In the production of articles on an industrial scale the use of production-line systems has been well known for a long time. Such production-iines comprise several work stations in which a blank is machined or processed to produce the desired article. In some cases such production-lines are designed to produce the finished article from the raw-material stage but in others only some of the processing operations are perfomed, such as production of the finished artile from a semi-finished product, production of a semi-finished product from unprocessed or only partly processed blanks or part treatment involving e. g. surface finishing, control operations or packing.

It is characteristic in such line-production that the work-piece is advanced along a route of transport on which it passes a number of work stations in which it is successively subjected to the processing operations necessary to give the workpiece the intended finished condition. The processing plant required to achieve this consequently must consist both of conveyor means to move the workpiece along the route of transport, and a number of work stations. Some operations may take longer than others, with the result that some work stations may be multiplied, allowing the flow or workpieces to be directed along several parallel routes to perfom the operation involved. As a rule queue-foming devices are likewise required, where the workpieces may collect between stations to even out the differences in operational duration.When the work stations are operated manually attempts are made to plan the individual operations in such a way that optimum time equalization of the various operations is obtained in order to avoid as far as possible waiting times and insufficient capacity utilzation in some stations.

In order to be able to process mutually different articles it is sometimes desirable to be able to vary the operations along the production line. It may for instance be desirable to produce different or various articles simultaneously and mix them with each other to satisfy varied demands. In other cases it may be desirable to produce short series of different or various articles in succession or to alternative long and short series.

This may be achieved by designing some stations to perform alternating operations or by designing alternative work stations for alternative operations, in which case the routes of the workpiece through the stations are controlled accordingly. Obviously, both methods may be used in one and the samc plant. Also in plants not directly constructed for such variety of production a need may arise from time to time for minor or major modifications of the processing method, such as may be occasioned by model changes of the article produced.

Processing plants of the kind referred to above form a complicated system. The aim is to design such plants in a manner ensuring satisfactory and preferably optimum results as regards volume or production in relation to the resources used. Another aim is to ensure minimum risks for disturbances in the course of the processing operation. The degree of complication increases with increased number of work stations and becomes particularly large when in addition thereto varied processing operations are to be perfomed. In order to obtain satisfactory results it is above all necessary that the plant is planned in a purposeful manner as regards the choice of work stations and other equipment and the planning of the flow of transport. Secondly, monitoring is required to check that the planned results are actually achieved and that the plant operates without disturbances.Should such disturbances arise they must be eliminated soonest possible, in the case of temporary faults by using corrective measures, in the case of faults in the system by making changes in the plant itself or in the operation.

In an attempt to achieve optimum results through plant planning it is known to make use of simulated operation of a plant model to systematicaliy test various alternatives of plant construction. By using computers to effect such simulated operation an excellent means is provided to establish the conditions which will give the optimum results in the plant under certain predetermined data conditions.

The actual plant is then constructed on the basis of the results obtained during the simulated operation. In the cases when it has become possible to establish these conditions in such a manner that they correspond to a very high degree to the future and actual conditions of operation, planning based on such simulation with the aid of computers have proved to give excellent results. The disturbances that nevertheless do occur during the practical opcration of the plant are overcome by elimination of the sources of the disturbances as they arise. There is no need to question the established and adopted system as such. In other words, a plant constructed on the basis of well-performed computer simulation usually gives the expected result after a certain running-in period.

In the type of manufacture where several short series alternate rapidly or where the articles are to be fomed with certain individual modifications, perhaps in a very large number of varieties, it is obviously particularly valuable to be able to use computer simulation to plan the plant and to detemine the flow of operations required to produce the articles in its various modifications. Despite the excellent conditions mentioned in the aforegoing computer simulation has not had the expected success in practical tests to make plants designed for varied production function with optimum results. This is due to the difficulty in computer simulation to consider all the irrational factors arising during the actual operation, causing operational disturbances and necessitating some running-in adjustments.

Difficulties of this nature arise every time a new production programme is adopted which becomes all the more annoying the more frequent such programme changes are.

The purpose of the subject invention is to provide a method in production-line systems, whereby it becomes possible to use the advantages of computer simulation also in the production involving varied working operations and short, successive series.

The purpose of the invention could also be expressed as a method with the aid of which it becomes possible immediately or after a short period to make a plant function in the exact manner established during the computer simulation and to maintain this function for the entire period that the adopted working process is being used.

Another purpose of the subject invention is to provide a device by means of which the advantages outlined above may be achieved.

The purposes of the invention are achicved by perfoming the method in such a manner that the computcr programme chosen for the operation of the plant represents an established operating schedule and that this schedule is run through during the actual operation of the plant and in synchrony therewith, the plant being provided with a number of control means to record the data of the events actually taking place in the plant, such as passage of the workpieces and their dwelling in certain sections of the plant, said control means being connected to the computer and used to supply the computer with data for comparison of the actual operation and the results theref rom with those of the simulated operating schedule and the results established during such simulated operation, said device being provided with indicating means which are maintained connected to the computer and arranged, in response to a signal received from said computer as a result of lack of agreement between the actual and the simulated operational data, to indicate irregularity of operation so as to initiate manual and/or automatic corrective measures to bring the operation into agreement with the intended programme of the simulated operation.

The device in accordance with the invention comprises in a manner known per se a computer which is adapted to receive data relating to the workpieces to be processed in the plant with regard to the required working operations, data relating to the respective working operations regarding factors such as operation interval and required machinery and tool equipment and, when relevant, the competence of the operator, data relating to the conveying device with regard to factors such as transport interval relating to transportation between and within the respective work stations provided to perform the working operations and the computer is also adapted to simulate operating schedules controlling the plant performance in the working operations and in the transport to effect the adopted processing of the respective workpieces in order to establish a purposeful working sche dule regulating the operation of the plant with the aid of such simulation. The plant is provided with control means, preferably in the form of sensors. The sensors are designed to transfer infomation to the computer regarding the advancement of the transport means by the conveying device and regarding the pas sage of the workpieces past certain check points in the plant and to identify the work pieces supplied to the plant, said computer arranged, in response to the infomation re ceived from these control means, to run the adopted operating schedule in synchrony with the actual events in the plant while comparing the operating schedule with the actual opera tion, said device additionally comprising indi cating means designed to display infomation regarding lack of agreement between the operating schedule run in the computer and the simultaneous actual operation of the plant.

The invention will be described in the following with reference to one embodiment thereof given by way of example and showing its application within the clothing industry. In the following description reference will be made to the accompanying drawings, wherein, Fig. 1 illustrates a work station in a processing plant; Fig. 2 shows a diagram of the plant as a whole; Figs. 3 and 4 show two operation alternatives in accordance with the diagram of Fig.

2; and Fig. 5 is a diagram showing the device as a whole including said plant.

Fig. 1 shows one example of a work station that may be included in a plant in which the invention may be applied. The plant comprises a main conveyor 1, the main part of which consists of a preferably endless loopshaped rail 2 (only a part of the rail of the main conveyor is shown in Fig. 1). The rail encloses a drive member in the form of a wire, a chain or equivalent means which travels continuously inside and along the rail 2, thus moving a number of projecting crabs 3 along the rail. The crabs 3 are intended to support product carriers 4 which slide along the rail 2 by means of wheels. The product carriers are designed to support the workpieces 15 to be processed in the plant. Fig. 1 shows the workpieces 15 as textile pieces which will form a shirt when sewn together.

From the main conveyor 1 branches off one branch conveyor 5 for each work station in the plant. Each such branch conveyor comprises an entrance switch point comprising a stretch of rail 6 which may be folded downwards towards the main conveyor, and an actuating device 7. The switch 6, 7 is followed by a downwardly sloping entrance portion 8 of the rail 9 which extends past the work station. The portion 8 continues up to a stop position represented by a stop member 10. Shortly after the stop member 10 the rail 9 continues in an upwardly extending portion 11. The branch conveyor 5 teminates in a downwardly sloping delivery portion 12 ending above the rail 2 of the main conveyor 1.

The switch point 6 may be folded between two positions, one in which it is raised above the rail 2 of the main conveyor, as illustrated in Fig. 1 and a second position in which its free end abuts against the rail 2. In the first position the switch point 6 allows the product carriers to pass past and continue along the main conveyor. In the second position the product carriers will be guided onto the switch point 6 and when they reach the downwardlysloping part of the branch conveyor rail 9 they will slide down into abutment against the stop member 10. The folding downwards of the switch point 6 will occur when the actuating device 7 has indicated that the product carrier approaching the branch conveyor is to be sided into the associated work station.This could be effected in a variety of ways but in Fig. 1 is indicated a mechanical system comprising projectable and retractable guide cam members on the product carrier, provided to be moved between ah Outer and an inner position thereby, affecting the actuating device 7. The latter is arranged in response to abutment against the device of a predetemined combination of project cam members being in their outer positions in a series of cam members, to effect the folding movement downwards of the switch point 6. When no such combination exists the switch point 6 will remain in its upwardly directed position.

In this manner correctly coded product carriers with the products suspended therefrom may be sided into the desired branch conveyor to reach the desired work station. In the following this predetermined siding into selected branch conveyors will be referred to a "addressing".

The stop member 10 forms a waiting point for the product carriers. When the person serving the work station wishes to treat the product which is suspended from the product carrier closest to thc stop member 10, several product carriers may form a queue ahead of the stop member, the product may be moved to a suitable position for being treated. The work piece 15 may now be treated. The drawing figure shows a sewing operation to be performed by means of a sewing machine 16 which constitutes the machine equipment of the work station. The sewing machine is served by an operator. When the work to be performed in this work station is completed the product may be advanced by manoeuvering a pedal 55. It will then be released and will slide down to the lowest level of the rail 9.

In order to allow the product carrier to reach the next work station in the intended processing cycle it must be re-addressed when the mechanical addressing system mentioned above is used, and this is effected when the product carrier passes an addressing unit 17.

In the addressing unit 17 a number of cam members may be projected or retracted by means of keys to shift the cam members on the product carriers as the latter passes past the addressing unit 17. The cam members of the product carrier, when thus shifted, consequently form a new combination adapted to convey the product carrier to the next appropriate work station.

When the work piece is to be advanced further, the product carrier 4 is conveyed from the lowemost part of the rail 9 along the rising part 11 thereof. The advancement is effected by means of driving cogs 18 which perform a to and fro movement along the rail portion 11. The stroke of the movement is sufficient to allow the product carrier to be caught by the lowemost cog which may be folded forwards and to be conveyed up to a lock member 19 to be thereafter caught again by an upper cog and conveyed to the delivery portion 12. From the latter it slides down onto the rail 2 of the main conveyor 1 and continues along the latter to the next work station of its address. The arrangement just described appears in closer detail from Swedish Patent No. 352 052.

One possible composition of a processing plant as a whole appears from Fig. 2. This drawing figure illustrates the loop-shaped main conveyor 1 and a number of branch conveyors 5. The branch-conveyors 5 lead up to or past a number of work stations, in Fig. 2 identified by numeral references 21-27. Some of the stations may be manned (indicated by a circle 28) whereas the operation of other stations, such as stations 23 and 24 may be fully automatic. Fig. 2 also illustrates the work positions of the products, represented by stop member 10, and the re-addressing unit 17. At the entrance portion 8 and at the exit portion 11 of the branch conveyors 5 are positioned sensing means 20, see also Fig. 1. The drawing figures likewise show a feed-in unit 30 and a discharge unit 31. These units have separate sensing means 32 and 33, respectively.Also the main conveyor 1 is equipped with a sensor 37. The sensors 20, 32, 33 and 37 will be described in closer detail in the following.

The feed-in unit 30 is intended to allow new product carriers to be fed into the main conveyor 1 as new work pieces are to be supplied to the plant. A unit of this kind may be mechanical but need not necessarily be so, since the main conveyor may be supplied with new workpieces manually from a nearby storage of blanks or semiproducts. The discharge unit 32 is arranged to receive workpieces which have been processed through the entire operational programme and therefore are ready to be transferred either to a storage or to be dispatched. Preferably, the discharge unit 32 comprises a branch line 34 on which the product carriers may be stored and to which they are addressed in the same manner as described in connection with the work stations.Also in this case manual operation of the finished products is possible, in which case the finished products are lifted off the main conveyor for further transport.

During the operation of the plant the workpieces thus will be fed successively into the main conveyor 1 and will then be carried to the selected work stations in which the intended processing will take place. The work operations need not be effected in the sequence fomed by the respective work stations.

The product carriers may travel several times around the main conveyor, thus returning to 'stations they have previously passed by.

When all operating processes have been performed on the workpieces it is addressed to its final address, the discharge unit 31.

In the foregoing has been described the possible disposition of a conveyor to carry products along a main conveyor and to selected work stations to which they are addressed. The intention is to provide a possibility to construct a processing plant including on the one hand transport means for conveyance of the workpieces and on the other work stations in which the predetermined work operations are performed in sequence. The plant is of the kind wherein the workpieces according to their need for processing may be conveyed to all or only selected ones of the work stations in a predetermined sequence.By designing stations for alternative work operations respectively by excluding some operations by allowing certain workpieces to pass by the associated work stations on the main conveyor it becomes possible without any changes having to be made in the plant and only by addressing the workpieces selectively to perform different kinds of processing operations in varying number of operations on the workpieces which are fed into the plant in succession. Major alterations of the operations or of the nature of the processing could be effected by modifying the work stations as such, for instance changes in the specifications of the work in and operation of the manual stations, exchange of tools, larger or smaller degree of utilization of the available processing capacity or exchange of the machines or apparatuses used.

The transport mechanism could also be adapted to carry the workpieces through doubled but identical work stations which may be chosen according to the available capacity. By designing the plant in this manner it becomes possible to shift manufacturing of workpieces of different types and requiring different degrees of processing by making adjustment in the transport mechanism, sometimes supplemented with changes in the work station as regards the working operations performed therein. It is likewise possible to process mixed workpieces, each one of which is addressed to the work stations relevant to the particular workpiece.

It has been mentioned in the aforegoing that processing of different workpieces may be performed in the plant. The expression processing" is used herein in the widest sense of the word. As mentioned initially the processing could be of a variety of different kinds and types ranging from the manufacture including mounting, assembly, checking and controlling of a complete product from the basic raw material to more limited operations such as mounting or packing. The type of processing, machining or treatment to be performed on the workpieces determines the layout and construction of the work stations whereas the principle of the conveyor with its possibility of addressing the workpieces remains the same.

One example of the design of a conveyor has been described in the aforegoing. The example used in the description is from the clothing industry. Other types of products require that the conveyor be altered accordingly. A common type of transport mechanism used to advance various types of workpieces is the conveyor belt as opposed to the overhead conveyor shown. The conveyorbelt type of transport mechanism must be equipped with switches, branch conveyors, push members and similar devices to distribute the workpieces to the various work stations. In the reading of the following description of the method of plant operation in accordance with the invention should be considered that the nature, lay-out and construction of the plant used and its process of operation may vary within very broad limits.

In a plant of the nature defined it must be possible to perform mutually different work cycles, often in rapid sequence. In some manuffacturing processes several short series of articles may be produced daily. In other cases, a series of continuously differring workpieces may be processed in the plant. The former is often the case within the clothes industry where garments of various designs, different materials and different sizes are manufactured in comparatively short series. The latter case often occurs for instance in the assemby & apparatuses, where a basic model is varied according to the orders on hand.

The purpose of the method in accordance with the subject invention and the device for performing the method is to establish in a rapid and rational manner the optimum operation process for each type of workpiece as well as the data to govern the disposition of the plant with regard to transport routes and the construction and disposition of the work stations. In addition, it should be possible to use the programme obtained for the operation of the plant to control the plant.

The following main principles apply to the method: A. Laying down the necessary operntional steps for each type of workpieces to be processed. This means establishing data regarding type of operational steps, duration of the various operational steps and, when the operation steps are interdependent, the sequence in which they must be performed.

B. When several types of workpieces, e.g.

variations and modifications of a basic design or model, are to be manufactured simultaneously the sorting to be used is established and consequently the operational steps to be varied within the assortment.

C. The data required to produce the workpieces within the assortment as regards the routes of transport are established. Thus are established the types of product carriers that are required for the products involved.

D. On the basis of the operational steps to be performed and, if relevant, the modifications thereof, are established what types of work stations are required in the plant. At the same time the equipment, such as the tools, etc. is established for these work stations.

E. Likewise on the basis of the laid-down operational steps and the established choice of work station it is established what work force is required. In this connection the particular competence required in some stations is determined and what work force possessing the required competence is available. Also the capacity of the work force may be investigated, allowing the length of the operational steps to be adapted to the capacity and skill of the available work force.

F. Laying-down the data required for the conveyor. In particular should be established what kind or product carriers is needed to suit the assortment of workpieces to be produced (cf. point C).

Information, such as the length of time required to move the workpieces through the various part-stretches within the plan, should be available.

G. The present status of the plant is establisted, that is, its construction and disposition for treatment of earlier series of products.

H. To the extent possible, the irregular situations that may arise should be established or at least the most frequent situations of this kind. As examples of these may be mentioned deficiencies in a workpiece when it is fed into the plant or the supply into the plant of the wrong workpiece, faults in the work stations, requiring replacement of tools, not planned but necessary breaks for the workforce, fault in the conveyor. To remedy these possible faults there should be established what corrective measures are necessary. It may be advantageous to distinguish between faults of a temporary nature and faults relating to the nature of the system. The former require indivisual and occasional corrective measures whereas the latter may make it necessary to change the operation in order to prevent fu ure faults of the same nature.

On On the basis of the laid-down data according to A-H above is established the rational planning of the processing of the workpiece and its movements within the plant. In this connection must be considered both the disposition of the plant, thus the selection of work stations and their equipment, whereby in addition to the consideration of the immediate need as regards operational steps preferably plans should also be contemplated to avoid unnecessary changes in the plant, i.e., the present status of the plant should be consi dered (G). The manning of the work stations should be laid down on the bais of the required skill and competence, the aimed4or capacity and the availability of work force.

Likewise, the required nature and design of the conveyor should be established, such as e.g. what type of product carriers is required.

By considering the laid-down factors it becomes possible initially to establish the necessary and most adequate construction and disposition of the plant with regard to the product or the products/product varities that are to be manufactured within the period planned.

Subsequently, the routes of the products through the plant are laid down while considering the work stations through which each workpiece should pass. Due regard must then be taken to the necessary sequence of the work stations. The route of transport should be planned to avoid unnecessary movement and to ensure minimum transport work and time.

J. Laying down a check schedule. One of the purposes of the method is precisely that the planning mentioned in the aforegoing should result in an optimum operating schedule and also to check that this operating schedule is in fact followed. This requires checking the advancement of the products within the plant. In addition, it may be necessary to check the products at various points within the plant to ensure that when the various work operations have been performed the workpieces have been processed as intended.

K. The operation of the plant is started in accordance with the planned schedule.

L. Checks that the processing is performed in accordance with the planned schedule are made continuously during the plant operation.

When the checks show operational irregularities, this is displayed to allow corrective measures. These could be effected manually or in some cases by automatic means, such as by reversal of a route or transport, as will be described in the following.

Planning the constrution and dispostion of a plant to adapt it to perform specified work operations on the basis of the workpieces to be processed as defined in A-l above is already known. Computers have proved an excellent aid in such planhing operations. The available basic data may be supplied to the computer which will then compute alternative plans while evaluating the results to allow the optimum operation schedule for the plant to be laid down as also its most useful construction and disposition.

This method of establishing the mode of operation is usually reffered to as computer simulation. Computer simulation is in itself an excellent aid but the operating schedule thus obtained requires extensive manual work before it can be put to practical use and need checks to be performed during operation as well as running-in of the plant on the basis of experience gained from the operation. The purpose of the invention is to make rationalization possible also on these points. The means therefor essentially are the following a. The operating schedule is laid down, including the foreseeable. possible irregularities, viz. faults that may occur during operation.

Alarm facilities related to these faults are established and, to the required extent, the directions for corrective measures or the data controlling corrective impulses. In the planning is likewise laid down the operation schedule with regard to the functions of the various control and checking means and their positions within the plant to allow faults to be picked up at the stage of the processing and at the point on the route of transport that is suitable for correction of the respective fault.

b. The plant is equipped with control and checking means relating to the functions mentioned. The control and checking means may be of several principal types, such as means registering the passage of a certain product past a definite point along the route of transport and means registering the condition of the respective products at a certain point along the transport route. The first type of check means thus merely indicate the movements of the various products or of their product carriers within the plant. In this way, errors in the routes of transport may be indicated as also unplanned-for queues in the work stations and loss of products along the route of transport. which may be the case, should the product for instance fall off its carrier.The second type of check means provide an opportunity to check the function of the work stations and whether the latter are set correctly, occurrences of tool failures and the like. In other words, this type of check means consist of some type of inspection means. They could be e.g. autumatic measure and control means or manned inspection stations. Preferably the plant, particularly the conveyor mechanism, is provided with means devised to emit synchronizing impulses to the computer to allow the operating programme to be advanced at the rate of plant operation.

In the check and control means category may also be included the communication systems provided at the work points when the latter are manned. With the aid of such communication systems, generally comprising a keyboard, the operator may feed in information on the working situation. In this manner information on faults, errors, interruptions in the processing and other data of interest for the correct functioning of the plant and its results may be supplied and be made part of the continous follow-up of the operation of the plant effected by the computer. Preferably, the inspection stations, when manned, should likewise be equipped with similar communi- cation systems.

c. Display equipment which is connected to the computer by means of which the plant operating schedule is laid down and to which are coupled also the check means devised to trigger off an alarm at the occurrence of faults by indicating the nature of the faults and preferably also how the faults may be corrected.

Display equipment of this kind preferably includes one or several screens on which the information on the plant operation may be displayed after processing by the computer of the reports supplied to it by the check and control means (b) while comparing the simulated planning programme with the actual operation. Screens of this kind may be located centrally as well as in at least the manned work stations. In addition, some kind of alarm system, such as sonor signals or intermittent flashing lights may be installed to draw attention to faults requiring immediate action in order to prevent serious interruptions of the plant operation.

d. Plants with a high degree of automatized operation may be equipped with means which are connected to the computer in the way described under (c) in the aforegoing and which are devised to effect automatic corrective measures at the occurence of faults, thus making manual measures unnecessary, at least for the moment. Examples of such measures are re-routing of the paths of transport in the device, whereby the workpieces will be advanced through an operational alternative work station while passing over the station which is no longer operational. Another type of corrective measure could be automatic exchange of tools.

e. Functions of the computer which allow display of data received in the process of plant operation. Data of this kind may be reports onthe production, such as number and type of products produced during a defined period, the planned production including the time of its completion and reports on the occurrences of operational disturbances affectiong the production. Equipment of this kind may also be used to produce personnel reports and data on salaries and wages. In this case the computer must be connected to a printer which is devised to supply the information in document form. Working list relating to future operational periods may be produced in this way.

One embodiment of the check and control means according to (b) above appears in the drawings. For instance, there are shown the means registering the passage of a certain product past a definite point along the route of transport, such as the above-mentioned sensors 20. As appears both from Figs. 1 and 2 these sensors are positioned at the inlet as well as at the outlet end of the branch conveyor 5. This allows the passage of the products to be registered both when the latter are moved into the work station and when they leave it to be again routed onto the main conveyor. The sensors 20 may be adapted to function in any one of two different ways.

Either is registered only the passage of one product carrier without indivicual identification or the conveyed product. In order to enable the computer to perform the required tasks, i.e. control the plant operation and supply information on the production results, it is necessary that the information in the computer regarding the positions of the individual workpieces is always up-to-date. However, this cannot be effected without direct identification in that the computer always is able to calculate the probable position and point of passage of a definite product carrier. For if the computer is synchronized with the main conveyor and the identity of the product is supplied to the computer when the product is supplied into the main conveyor (at 30 in Fig.

2) this allows the computer, on the basis of the synchronizing impulses, to continuously calculate the advancement of the product along the main conveyor and in response to the information supplied regarding the addresses of the product carrier the computer may establish the moment when the product carrier is sided into a branch conveyor and on the basis of its knowledge of the required dwelling time in the work station the computer may calculate the period within which said product carrier will be returned to the main conveyor and thus pass past the associated sensor. To arrange a sensor also at the inlet of the branch conveyor, as suggested herein, provides a further check that a workpiece has actually entered a certain work station. Alternatively, if only one sensor is used, the latter may be positioned at the inlet of the branch conveyor.

However, when a direct and individual check of the product carriers is desirable, as may be the case for instance because the dwelling time in the various work stations cannot be established in advance with the required accuracy, the sensors may instead be adapted to identify the product carriers individually. For this purpose the latter are provided with identification means 38 (Fig. 1), such as a bar-code which may be read by the sensor 20 upon the passage of the product carrier.

Also in this system the computer may be used to perform probability calculations regarding the moment of passage of a certain product carrier. To effect this, the computer need not be adapted to identify the signal emitted by the sensor with the aid of the question "what product carrier passes" but instead with the aid of the question "has a certain product carrier passed". This is advantageous, since the reading of passing identification means, whether they are in the form of bar-codes or of other types, is somewhat unreliable at the present stage of the technical know-how.

However, in the latter case the computer may be adapted to interpret a vague signal as correct, within predetermined limits. The work of the computer is also facilitatcd, resulting in shorter, processing times, when the computer signal need not induce the computer to search its entire register of relevant product carriers, but instead the processing may be restricted to checking one or a limited number of probable product carriers.

It has also been mentioned previously that sensors 32 and 33 are provided at the inlet unit 30 and the outlet unit 31. The sensor 33 at the outlet unit may be of the same kind as the sensors 20. On the other hand, the sensor 32 at the inlet unit must be adapted to identify directly the workpieces fed into it.

Particularly in the case of mixed production or short-series production it is necessary that the nature of each workpiece is determined so as to allow it to be correctly addressed to the work stations and its advancement within the plant to be controlled properly by the computer. In series involving several workpieces which are to be processed in an identical manner such identification could of course be effected collectively for all workpieces within the series.

This identification of the workpieces fed into the plant may be effected in a variety of different ways. One suitable way is by means of a separate terminal which is used to produce information of the type of workpiece, either a single one or a series, that will be the next one to be fed into the plant. The terminal may be provided with a manual by means of which may be fed in with the aid of keys the information regarding the identification of the workpiece, or it may be provided with some kind of reader in which case each type of workpiece carries a means of identification, such as a magnetic card. When sensors of the first-mentioned, more simple type is used in the plant the probability calculation concerning the positions of the product carriers in the plants starts on the basis of the passage registered by the sensor 32.When the directidentiffying type of sensors are used, the computer must be supplied with information on the identity of the product carrier and at the same time on its connection with the type of product associated therewith, as the product carriers are fed into the plant.

Atlernatively, when the identification of the product carriers is effected by means of a code the latter may be related to a certain type of product. In this case it is necessary to use, for each type of workpiece, product carriers carrying exactly the code related to this specific type of workpiece. The relationship of the code to the type of workpiece preferably is recorded in the computer memory, allowing the computer to establish immediately the type of product carriers that is being fed into the plant past the sensor 32.

Fig. 2 shows a further check means 37 as mentioned under (b). The check means 37 is intended to be used for the synchronizing function.

Preferably, it is a photoelectric cell emitting a signal each time a crab 3 (Fig. 1) passes the cell, thus registering the advancement of the main conveyor.

Fig. 5 illustrates schematically an overall view of the device (of the processing plant, however, is shown only the lowermost part according to Fig. 2). As illustrated, the plant is connected to the computer, designated by 40, by means of its control means, viz. the sensors 20, 32, 33 and 37. The computer has a memory unit 41 to which may be supplied data regarding the work stations, the operations and so on, such as standard times and required processing equipment. The computer simulation may be performed on the basis of these data. To communicate with the computer there is a manual keyboard 42 and the results of its activities may be displayed on a screen 43 and/or a printer 44.As described in the aforegoing a communication unit 46 may be coupled to the computer, said unit preferably consisting of keyboards located at the manned stations and in these stations certain information supplied by the computer may also be shown on a display 47, such as a screen.

It has also been mentioned previously that the device is to include indicating or display means which in the course of the operation are able to indicate operational irregularities as well as called-for corrective measures. As indicating means of this kind may be used the screen 43 and in the manned stations the devices 47. As an example has been shown that the plant may also be provided with an alarm system, for instance a bell 45, by means of which an alarm may be sounded as soon as immediate actions are required.

Figs. 3 and 4 show two operational applications of the plant illustrated in Fig. 2. In Fig.

3 the heavy dotted line indicates the route of the relevant products through the plant. It is also apparent that compared with Fig. 2 the work station 22 is altered from a manual station to an automatic one in conformity with stations 23 and 24. The manned station 25 has only one operator in Fig. 3.

During the operation the workpieces to be processed are fed in at 30. They travel along the main conveyor 1 the operation of which provides synchronizing impulses to the computer by means of the sensor 37. In the computer is run the programme forming the basis of the planning of the plant and its flow of transport. According to this flow of transport the product carriers with the products suspended therefrom are carried along the branch conveyors 5 and into the relevant work stations. In the latter the processing takes place, whereupon the product carriers travel further out onto the main conveyor 1 and in doing so they pass the associated sensors 20.The product is then identified with the aid of its associated product carrier by one of the methods described and the computer may register whether the products have reached the work stations according to the operating schedule, whether they have been processed as planned and again been moved from the work station.

Should the latter not be the case within the period laid down in the operating schedule produced through the computer simulation, this indicates the existence of some fault or error. Owing to the lack of agreement between the actual events and the operating schedule an impulse is produced from the computer to alert the personnel who may correct the fault. As mentioned before, alternatively some automatic corrective measures may be used.

For example, if for some reason processing in station 22 is to be performed before processing in station 21, the addressing may be designed to ensure that the workpieces are first sided into station 22 while passing over station 21. Thereafter they may travel on the main conveyor in a loop and back to station 21 to receive the ensuring of transport unnecessarily. On the other hand, exchange of the stations 21 and 22 for one another may involve more inconveniences than does the longer route of transport.

As mentioned before there are other possibilities except by means of sensors to affect the computer to ensure that unexpected events may result in corrective measures. For instance, the plant may be provided with means for inspection and quality control. In the manned stations there should be facilities allowing the personnel to give information on the occurrence of faults, lack of material or the like and need for intervals. As mentioned in the aforegoing the most rational manner to effect this is by direct communication with the computer with the aid of a manual. In this manner attention may be drawn to the situation to allow appropriate measures to be taken.

For certain events the computer may also be adapted to direct the flow to a storing area or to form queues of product carriers until a normal flow may be resumed.

Fig. 4 represents processing in a fewer number of stations than the total of those shown in Fig. 2. For instance, in the throughflow stations 21, 24 and 27 are skipped. In other words, these stations are idle. Alternatively, the stations 21, 22 and 23, 24, re, spectively may form parallel lines. Should the processing time in any one of these stations be considerably longer than in stations 25 and 26 these stations, shown as being manned, will therefore be idle for a certain period of time. This may be avoided, provided supplementary tasks are given to these stations, but alternatively by doubling the stations in which the processing time is longer.

The computer is then directed to choose the one of the pair of doubled stations that is free when a new product comes up.

The described example which refers to the clothes industry, uses mechanical addressing equipment to distribute the workpieces to the various work stations. Thus, the computer is not used for the direct control of the workpieces: Nor is control of the processing work performed in the work stations contemplated, except via messages from the computer to the manned stations or to the supervising personnel. The function of the computer thus is to indicate whether the intended process and course of actions is actually effected, once the planning thereof has been made with the aid of the simulation.

By thus separating the mechanical control means from the computerized planning and control means, considerable advantages are obtained. The mechanical control system is very sturdy and reliable and is based on thoroughly tested technology. It does not require complicated wiring and electric power means, such as solenoids and motors, can largely be dispensed with. The control device does not become dependent on any central part and the risk of a total collapse or break down therefore is practically out of the question. Even if the computer system should become inoperative the plant operation may continue, however without the control function exerted by the computer.

However, it is entirely within the scope of the invention to computerize the plant operation jointly with the computer control thereof.

To do so requires that the computer is adapted to emit control impulses and that the addressing equipment of the conveying device is adapted to respond to such impulses. It is likewise possible to integrate the control of automatic functions within the work stations with the computer control. Equipment is available to effect this control by means of a computer.

Claims

1. A method in line-production systems, wherein is used a processing plant, comprising a conveying device for advancing the intended workpieccs, and a number of work stations which are adapted to perform a number of operations on the workpieces, said conveying device arranged to be addressed to carry workpieces to selected work stations in accordance with a predetermined programme to perform the operations specific to the individual workpieces, said method comprising planning the purposeful construction of the plant as regards the work stations and the operation with a view to transport the work pieces by means of the conveying device through the various work stations by simulating operating schedules in a computer while utilizing established data received in the computer concerning operations required for said workpieces, data on the operations. adequate construction and equipment of the work stations to perform said operations, wherein the computer programme chosen for the operation of the plant respresents an established operating schedule and that this schedule is run through during the actual operation of the plant and in synchrony therewith, the plant being provided with a number of control means to record the data of the events actually taking place in the plant, such as passage of the workpieces and their dwelling in certain sections of the plant, said control means being connected to the computer and used to supply the computer with data for comparison of the actual operation and the results thereof with those of the simulated operating schedule and the results established thereinsaid device being provided with indicating means which are maintained connected to the computer and arranged, in response to a signal received from said computer as a result of lack of agreement between the actual and the simulated operational data, to indicate irregularity of operation to initiate manual and/or automatic corrective measures to bring the operation into agreement with the intended programme of the simulated operation.

2 The method claimed in claim 1, wherein signals are emitted by means of said conveying device in response to the movements of its conveying members, and in that said signals are used to synchronize the operating schedule running in the computer with the operation of the plant.

3. The method claimed in claim 2, wherein synchronizing signals are emitted at intervals suitable for advancing the computer programme in predetermined time sections.

4. The method claimed in any one of the preceeding claims, wherein the momentary positions of the workpieces within the plant are established in the computer by registration of the identity of the workpieces in the computer at the feed-in of the respective workpiece into the plant, whereupon said computer is adapted to perform a probability calculation as regards the positions of the respective workpieces within the plant, based on the information in the computer on the conditions of movements of the conveying device and the information supplied to the computer regarding the intended dwelling time of the workpieces in the selected work stations, said latter information preferably supplied to said computer by means of said control mcans in the form of sensors adapted to sense the passage of a workpiece or its carrier in the conveying device, when the workpiece or its carrier enters and/or leaves the respective work stations.

5. The method as claimed in any one of the claims 1-3, wherein the momentary positions of the workpieces in the plant are established in the computer by providing each workpiece or its carrier in the conveying device with an identification code which may be registered by said control means in the form of sensors, said code being supplied to the computer in the form of a corresponding identifying signal produced by said control means.

6. The method as claimed in any one of the preceeding claims, wherein said method is a combination of the following measures: establishing data on the workpieces to be processed in the plant with regard to the operations required to be performed thereon; establishing data on said operations with regard to factors such as operation time and the required machinery and tool equipment and, when relevant, the competence of the operator; establishing data relating to the conveying device as regards factors such as time of transport between and within the respective work station provided to perform the work operations; supplying said data in the memory of said computer; simulating in said computer the operating schedules of the performance of said plant of the operations and the transports with a view to perform the established processing on the workpieces; establishing a purposeful operating programme by means of said simulation; constructing the plant with particular consideration of the arrangement of the work stations to perform the established work operations with regard to the flow of workpieces in the conveying device; initiating operation of the plant in accordance with the laid-down operating schedule concerning the processing of the respective workpieces; running said operating schedule in said computer in synchrony with the operation of the plant; supplying said computer with control information on the progress of the processing in the plant, such as information on the momentary positions of the workpieces in the plant and the progress of the work operations in the work stations; comparing by means of said computer the operating schedule run in said computer and the actual events in the plant during the operation of the latter as registered by said control means; registering in said computer any lack of agreement bctween said operating schedule in the computer and the actual operation of the plant; and informing, on the basis of verified lack of agreement, the supervising personnel, for instance by means of information displayed on a screen, for the purpose of initiating corrective measures and/or actuation of means adapted to effect automatic mechanical correction.

7. A device for performing the method in line production according to any one of the claims 1-6, said device comprising a processing plant including a conveying device for transporting the workpieces involved in the production, and a number of work stations designed to perform operations on said workpieces, said conveying device being adapted to be addressed by means of an addressing unit to carry the workpieces up to selected work stations in accordance with a predetermined programme for perfoming the operations specific to the individual workpieces, wherein said device comprises in a manner known per se a computer which is adapted to receive data information on the workpieces to be processed in the plant with regard to the required work operations, data relating to the respective work operations regarding factors such as operation lengths and the required machinery and tool equipment and, when relevant, the competence of the operator, data relating to the conveying device with regard to factors such as duration and length of transport between and within the respective work stations provided to perform the work opcrations, and which is also adapted to simulate operating schedules controlling the plant performance of the work operations and of the transports to effect the adopted processing on the respective workpieces in order to establish a purposeful working schedule regulating the operation of the plant with the aid of such simulation, said plant provided with control means, preferably in the form of sensors which are adapted to transfer to the computer information regarding the advancement of the transport means by their conveying device and regarding the passage of the workpieces past certain check points in the plant and to identify the workpieces supplied to the plant, said computer arranged, in response to the information received from these control means, to run the adopted operating schedule in synchrony with the actual events in the plant while comparing the operating schedule with the actual operation, said device additionally comprising indicating means adapted to display information regarding lack of agreement between the operating schedule run in the computer and the simultaneous actual operation of the plant.

8. A device as claimed in claim 7, wherein any manned work stations are equipped with communication means to the computer, whereby said data regarding the control of the actual operation can be supplied to the computer by means of said communication means, and in that said indication from the dator of the existence of lack of agreement between the operating schedule and the actual operation may be displayed by means of said communication means.

9. A device as claimed in any one of the claims 7 or 8, wherein the workpieces or their carriers in the conveying device are provided with identification means which may be read by the control means, prefferably the sensors, to allow the momentary positions of the workpieces to be registered in said computer, as said workpieces pass said sensors.

10. A device as claimed in any one of the claims 7, 8 or 9, wherein the conveying device and its addressing equipment is of a mechanical nature and that the workpieces are supported in said conveying device by product carriers, each one of which is adapted to be addressed with the aid of coding to mechanical conveyor switches to direct the product carriers to or past said work stations, so that the connection of said computer with the plant is essentially limited to the communication with said control means.