The manufacturing process of a three-dimensional piece-like product depends on whether the piece is machined from solid raw material or whether the shape of the piece is produced by letting a fluid or viscous raw material set into a desired form. In machine cutting, a blank is separated from a three-dimensional piece of raw material and formed into the desired shape by removing excess material in various manners. In compression-based methods the raw material usually is a piece cut from a sheet-like material, formed when two compressor parts, matching in shape, are pressed against the piece from different sides. In casting, injection-moulding and similar methods the basic structure of the piece is produced when a fluid or viscous raw material sets or a powdery or granular raw material is compressed into form. Semifinished objects produced by all the basic methods are usually further processed in various surface treatment and finishing stages.

A problem in the automation of production often is the transfer of semifinished pieces between the various manufacturing stages. Early industrial production was mainly based on the assembly line and its more advanced versions in which a con¬ veyor transports separate semifinished pieces from one part of the production facil¬ ity to another. Naturally, this arrangement only works in a very limited area. In batch production, a certain number of products are manufactured at a time and placed in a jig in which they can be transferred through the various manufacturing stages and/or from a manufacturing stage to another. The placing of pieces in the jig and their removal from it as well as the moving of the jigs are in this case non¬ productive stages. Furthermore, in batch production, one and the same manu¬ facturing step, such as coating, is carried out identically for all pieces in a jig and individual handling of products is not possible except by removing the desired individual pieces from the jig.

In the packaging industry, the handling of semifinished products differs from the above because the packagings manufactured can be surface treated in the press while they are still in the form of a continuous sheet or roll of material (packaging board, for example) after which a cutting machine separates the individual end

products and a folding machine provides them with a three-dimensional shape. However, this process, too, is characterised in that when a product becomes three- dimensional, it is an individual piece and its handling requires a separate conveyor.

United States Patent document US 4 907 326 discloses a method for manipulation of small-diameter pipes in a manufacturing process. The pipes are moved on the line in a direction perpendicular to their longitudinal axes and adjacent pipes are temporarily connected by necks that allow the strip of pipes to be rolled up.

Finnish patent document FI 88597 deals with bushing studs comprising a plastic bushing which contains a metal stud. The plastic bushings are manufactured in a five-chamber mould as a short, five-unit-long strip where adjacent bushings are connected by a neck made of the same material.

European patent application document EP 0 718 087 Al describes the manufacture of small plastic dishes or plates. Extrusion-moulded thermoforming plastic is used to produce two planar layers between which "absorbing material", apparently glue of some kind, is directed. The plates are formed in hollows made on the surface of the shaping drum and they are detached from the strip of material by means of perforation. At the end of the manufacturing line the plates are cut separate and the edges of the strip of material and other superfluous parts are returned to the cycle.

European patent application EP 0 402 694 A2 has principally the same idea as the French document except that the strip of material is not manufactured by means of lamination.

United States Patent document US 3 687 104 shows that a strip of material can be fed from a difficult processing phase to another. Between successive immersion reservoirs there are pressurised air locks into which pressurised air is supplied and the same pressurised air is used to raise the immersing liquids from the bottom of the reservoirs to the operating level. The pressurised air locks prevent the immersion liquids from escaping from the reservoirs.

It is an object of this invention to provide a method whereby the handling of three- dimensional products in a manufacturing process is easy to automate. It is another object of the invention to provide a method suitable for individual further processing of uniform pieces during a manufacturing process without sacrificing the degree of automation.

The objects of the invention are achieved by chaining the three-dimensional pieces for the duration of the manufacturing process so that the strip comprised of the pieces can be rolled up or folded into a stack. The chaining is carried out by manufacturing the pieces in a mould which has parts at its ends that create necks connecting consecutive pieces.

The method according to the invention is characterised in that the pieces handled in the manufacturing process constitute a strip containing a plurality of consecutive pieces such that the consecutive pieces are joined by flexible necks, which are created in the injection-moulding stage at the beginning of the manufacturing process when the material used for the injection moulding of a certain piece is attached to a protruding tongue on the previous piece.

The invention is based on a perception according to which the three-dimensionality of a piece does not prevent a series of consecutive pieces from being processed as a long, flexible strip that can be rolled up or folded into a stack. In a strip arranged into a roll or stack a great number of pieces can be easily transferred over long dist¬ ances between machines carrying out different manufacturing steps. The stages of a process may be located in different places, being of the roll-to-roll type, or they may be made consecutive so that the strip comprised of the pieces runs from a stage to another. In a preferred embodiment consecutive pieces are interconnected by the same material of which they are made, so that no separate taping or support material is needed to attach the pieces to the strip. A strip may contain either consecutive pieces only, so that the width of the strip equals the width of an individual product, or both parallel and consecutive pieces. The manufacturing steps may be repeated identically for all pieces or individual processing can be specified even for a single piece. For process control and product identification the strip comprised of the pieces may contain identification information formed on the products or inter¬ connecting necks.

It is known to package small individual pieces, such as screws, earplugs, electronic components and machine gun cartridges, in strips for handling. That, however, is specifically packaging, i.e. the finished products are tied to each other using a certain binding material. The present invention relates to the manufacture of products, not to the use of them. From manufacturing it is not known such chaining of single three-dimensional pieces.

The invention will now be described in more detail with reference to the preferred embodiments presented by way of example and to the accompanying drawing wherein

Fig. 1 illustrates basic forming according to the invention, Fig. 2 illustrates the vacuum evaporation step according to the invention,

Fig. 3 illustrates the surface treatment step according to the invention.

Fig. 4 illustrates an advantageous way of forming the neck between pieces,

Fig. 5 shows a strip according to the invention containing pieces,

Fig. 6 shows a second strip according to the invention containing pieces, Fig. 7 illustrates the manufacturing of a large piece using the method according to the invention, and

Fig. 8 shows the large piece according to Fig. 7 finished.

Like elements in the Figures are denoted by like reference designators.

Fig. 1 schematically illustrates the principle according to the invention in which three-dimensional pieces 1 produced by a certain manufacturing step form a long continuous strip. A press 3 as such is a known tool the jaws 3a and 3b of which are at regular intervals pressed against each other, giving the material injected or other¬ wise produced between said jaws a certain three-dimensional shape. In this example it can be contemplated that the raw material used is injection-moulded plastic and the products 1 manufactured are mobile phone shells. For consecutive pieces not to be separate, the jaws of the press 3 are formed such that a small plastic tongue is left at the "trailing end" (on the right in the Figure) of each piece, said tongue being superfluous with regard to the intended shape of the piece. When injection- moulding the next piece, a small plastic tongue is similarly formed at the "leading end" (on the left in the Figure) of the piece, said tongue being superfluous with regard to the intended shape of the piece and fusing into the tongue at the trailing end of the previous piece. A neck 2, of the same material as the pieces themselves, is thus formed between the consecutive pieces.

Instead of injection moulding, the three-dimensional shape of the pieces can be produced in many other ways as well. If, for example, the raw material is a strip-like plastic film, the shape of the piece can be created by blowing, pressing or deep- drawing. Then the neck between pieces comprises that part of the plastic film which is left out of the blowing, pressing, or deep-drawing mould, or the mould may have an especially shaped portion for the neck part. The shape of the piece may also be produced by rolling.

The strip comprised of pieces is at this stage wound into a roll 4, because in the embodiment according to this example no work stage immediately follows the manufacturing. When the roll is not too tight, the pieces will not be subjected to compressive or twisting strain and, therefore, their three-dimensional form will not suffer. To protect the surfaces of the pieces, a cushioning and shielding extra strip made of a soft plastic sheet, for example, may be added onto the upper or lower side or onto both sides of the strip comprised of pieces. Instead of being rolled up, the strip comprised of pieces could be folded into a stack.

Fig. 2 illustrates the next step in the same manufacturing process utilising a roll 4 of pieces. Reference designator 1 represents one particular piece and reference designator 2 represents the neck between two consecutive pieces. Reference designator 5 represents a vacuum chamber where a metal plating is vaporised on the surfaces of the pieces e.g. to shield against electromagnetic interferences. In order to secure the tightness needed to produce a vacuum, the strip comprised of the pieces enters the vacuum chamber and leaves it through a certain gate arrangement (not shown) in which the edges of the gate are pressed against the strip at a certain neck or necks during each vacuum evaporation step. When a vacuum evaporation step is completed, the gates are opened and the strip moves forward for as many pieces as there is room for in the vacuum chamber. No processing stage follows immediately after this stage, so the strip containing the vaporised pieces is again wound into a roll 6 or folded into a stack. Protective intermediate layers can be used in the roll in the same manner as was described above, referring to Fig. I . If a protective inter¬ mediate film was earlier used in the roll 4, it naturally has to be removed from the respective surfaces before evaporation. Alternatively, the protective film on one side can be taken through the evaporation as part of the strip so that it prevents the evaporation material from sticking onto the protected surface.

Fig. 2 further illustrates how the method according to the invention facilitates the treatment of chained pieces from all sides especially when the interconnecting neck is of the same material as the pieces themselves. The portion left untreated is no bigger than the cross section of the connecting point of the neck and the piece. To illustrate the simultaneous treatment from all sides Fig. 2 shows vacuum evaporation both under and over the piece.

Fig. 3 illustrates surface treatment belonging to the same manufacturing process.

The strip comprised of evaporated pieces is brought to the surface treatment in a roll 6. The pieces are taken in the form of strip to a dip varnishing tank 7 and thence to surface paint spraying 8 and to a drying machine 9. Other exemplary surface

treatment steps illustrated by Fig. 3 include printing 10, attachment of sticker or label 11, and making of identification pattern by laser 12.

Two alternatives are provided for the last step in Fig. 3. In the first alternative, a laser cutter 13 separates the pieces from the strip, after which they have to be treated as single pieces in general. In the second alternative, the finished pieces are wound into a roll 14 or folded into a stack so that they can be easily transported and placed into an assembly phase of a more complex product. If the strip of pieces has multiple pieces parallely or the strip is otherwise adapted such that it is possible to cut off a certain number of pieces without cutting the whole strip, the laser cutter 13 may detach from the strip individual pieces while the rest of the pieces are wound into a roll 14. Pieces cut off may be rejects detected by quality control or pieces detached for special examination for process control or other purposes.

In a preferred embodiment, the shape of the neck between pieces can contribute to the successfulness of the varnishing or corresponding manufacturing step. By this it is meant that in accordance with Fig. 4 a neck has a trough 2a or angle 2b which, with respect to the position of the strip emerging from the dip varnish, is lower than the other parts of the neck. Gravity makes the extra varnish drain into said trough or angle and not to form a thick stripe of varnish on the edge of the piece proper.

Fig. 5 shows a strip of pieces according to the invention, seen from a direction perpendicular to the plane of the strip. Pieces 1 are linked by necks 2 comprising two parts. The invention as such does not limit the shape or size of the neck, but it has to be so flexible that the strip of pieces can be rolled up or folded into a stack. Flexing of the neck here also includes flexing along the boundary between a rigid neck and a rigid piece. A fold, or so-called zero-length neck, connecting two consecutive pieces is considered a neck, too. Not all consecutive pieces need have flexible necks between them, these only have to appear at sufficient intervals. Above it was described how in a preferred embodiment the necks are made of the same material as the pieces themselves. However, application of the invention does not necessitate that, but the necks may also be made of tape, film or other additional material. Fig. 6 shows a second strip of pieces according to the invention, seen from a direction perpendicular to the plane of the strip. The pieces 1 are connected to each other both consecutively and parallely. At the edge of the strip, two pieces connected consecutively are linked together by a similar neck portion 2 as in Fig. 5. At the middle of the strip, a certain neck portion 15 links four adjacent pieces together. Here, arrow 16 shows the strip's direction of movement and arrow 17

shows the direction perpendicular to the direction of movement. The Figure shows only part of the pieces in the strip.

Above it was described mainly the manufacture of smallish three-dimensional pieces using the method according to the invention wherein a piece gets its complete form prior to all other manufacturing steps and wherein the strip comprised of three- dimensional pieces is rolled up or folded into a stack. However, certain pieces in their three-dimensional form are so big that when they are rolled up, the resulting roll is unreasonably big even with a small number of pieces. If in the manufacture of such pieces it is possible to utilise a certain two-dimensional manufacturing stage, the invention can be applied in such a manner that all forms required by the three- dimensional shape of a piece are produced in the two-dimensional piece and the substantially two-dimensional pieces preformed in this manner are handled in the following stages as a strip in accordance with the invention.

Figs. 7 and 8 illustrate an exemplary embodiment for manufacturing a large three- dimensional piece. The end product is a box-shaped lamp reflector and its manu¬ facturing material is sheet metal or plastic sheet. In Fig. 7, a part 1 has been cut or die-cut from an elongated strip of material, said part comprising a rectangular central plate 18, a hole 19 in the middle of said central plate, diagonal ridges 20 stiffening and shaping the central plate, rectangular side walls 21 connecting with the long sides of the central plate, T-shaped locking branches 22 at the ends of the side walls, rectangular end walls 23 joined to the short sides of the central plate and on both of them two curved locking gaps 24. Said part is connected with the next and previous similar part (not shown) by means of a two-part neck 2 so that the consecutive pieces form a strip. The pieces travel through the various manufacturing steps in the form of strip, said steps including, depending on the properties required of the reflector, metallisation, painting, varnishing, attachment of adhesive labels, identification marking and/or other known steps. The forming of the pieces into the final three-dimensional shape is preferably carried out as the last step to take full advantage of the strip-likeness according to the invention. Fig. 8 shows a finished reflector viewed from the direction of an end wall, the side walls and end walls having been bent 90 degrees from their original position around the fold connecting the walls and central plate, and the locking branches on the side walls having been pushed into the locking gaps in the end walls.

Above it was described mainly the manufacture of identical products, where the same manufacturing steps are repeated identically for all pieces in the strip.

However, in a computer-controlled production process it is possible to identify a

product in a certain strip. Immediately after the first forming step (press 3 in Fig. 1) of the product or anywhere else in the process there may be a laser printer or other controllable marking device which produces an individual serial number or a corresponding marking at regular intervals or, if random sampling is required, randomly either onto a piece or onto the neck between pieces. After the marking device, at any stage of the process, there may be a reading device which reads the marking and controls the operation of the process in a desired manner. Manu¬ facturing of individual products as such does not require identification markings; for example, in computer-controlled spray painting, each piece in the strip can be painted with a different colour. However, identification markings make it possible to direct individual treatment specifically to a certain piece. Information about the quantities of successive pieces conveyed within the process is a sort of identifi¬ cation, too. A quality control element may e.g. inform a later marking element about a fault it has detected and since the marking element knows it is located X pieces later in the line than the quality control element, it waits for a time corresponding to the transfer of X pieces before making a rejection mark on the piece passing it.

It is obvious to a person skilled in the art that the products discussed above are exemplary only. The invention is not limited to the manufacture of any particular product. The manufacturing steps described above are exemplary only, and the invention does not limit the number or nature of the steps in the manufacturing or refining process. Manufacturing steps can be arranged such that they are physically successive so that the strip need not be rolled up or folded into a stack between the steps but it can be run flat from a machine to another. Strip handling according to the invention can be used throughout a process or in part of a process. The greatest advantage is gained when the strip handling according to the invention replaces as many handling steps of individual pieces as possible. In an application of the invention all manufacturing steps are in succession so that the strip of pieces can run flat all the time. In that case, the necks between the pieces need not be very flexible (in the extreme case, they need not be flexible at all). However, because of the inflexibility this application is not considered very advantageous.

The strip-handling of pieces according to the invention reduces non-productive work carried out for fransporting individual pieces in the various phases of the manufacturing or refining process. As the transportation often has been performed manually, the invention increases the level of automation of the process. Identification of pieces transported in a strip can be easily carried out either by

using identification markings or by counting the pieces. Thus it can be said that the invention achieves its objects.