FR2708509A1 - Method of mass production of small boxes having faces which are printed using screen printing - Google Patents

Abstract

The field of the invention is that of packages of the little-box type, these little boxes being open and having no lid, generally called small boxes, small cases or "trays". The objective is to provide a method which makes it possible to improve substantially the quality of graphical printing on the small wooden boards which serve as the head and side small boards for manufacturing the small boxes. The method consists in preparing (31, 32) a set of boards having a size such that they each correspond to a plurality of identical small boards; in simultaneously printing (33) a plurality of patterns on those places on the said board which correspond to the small boards; in separating (34) each small board by cutting the said printed board; and in assembling (35) the small boxes by means of the said separated printed small boards.

Description

Method for mass production of crates with screen printed faces
The field of the invention is that of packages of the type of boxes, open and without cover, generally called crates, crates or "trays".

 Crates are usually intended for storing and transporting goods, typically vegetable foodstuffs such as certain fruits or vegetables (apples, apricots, melons, tomatoes, etc.). These are frequently placed on a single layer, or sometimes on several superimposed layers, loose or aligned, being if necessary held in place in a honeycomb support attached to the crate.

 The crates are mainly marketed to producers, agricultural cooperatives or central purchasing centers, to be used for the transport of goods from producer to distributor and retailer, or even directly for the presentation of products to customers.

 There are essentially two categories of crates which compete intensely in these markets: cardboard crates and wooden crates.

 Wooden crates are the first to appear historically. They appear in the form of crates, and were notably celebrated by the poet Francis Ponge in "Le pris pris des chose", Gallimard, 1942. Their advantage is that they are fully recyclable. The natural material also allows good humidity exchange for the benefit of the foodstuffs stored there.

 Cardboard crates have appeared more recently than wooden crates, and have achieved strong market penetration. They are commonly made of treated cardboard (waxed or plasticized), and appear more sellable and better destructible.

Their success is real, but they saturate the current recycling capacities.

 Recent market developments have been marked by the development of information and advertising marking practices on the sides of crates. These markings are intended to make the container and content more attractive to the purchaser (distributor or end customer), while strengthening customer loyalty through the techniques of creating brand images.

 One of the reasons for the success of cardboard boxes, despite their unfavorable eco-balance sheet - due in particular to the techniques of manufacturing paper pulp, and the content of waxed or plasticized material -, is that they have allowed up to now to obtain a quality of marking unequaled by the wooden crates. The efficient printing techniques of the paper and cardboard industries have been used with undeniable efficiency to obtain contrast, polychromy, gradient effects, etc., which enhance the verbal and figurative signs desired by the crate buyers.

The manufacturers of wooden crates have tried to compete by also adapting printing techniques available to the specific constraints of the wood. In
In this case, the wooden crates consist of plywood boards - most often poplar, but not exclusive - which have a certain thickness and therefore a capacity limited to bending. The process which has been implemented up to now, taking into account these constraints, is printing by flexography. This process consists of making bronze shots from the patterns to be printed, which cooperate with a rotary drum system / ink rollers. The plywoods are brought individually into contact with the rollers, and receive the colored pattern there, before being assembled to form the final crate.

 Flexography however has the disadvantage of making it difficult to perfectly overlay successive color layers. Frequently, a discrepancy is thus observed, which results in obtaining a poorly colored, imperfect, blurred, and low quality pattern. The nature of the printing process does not effectively overcome this problem.

 This difficulty has thus far constituted an insurmountable handicap for the traditional wooden crates, vis-à-vis the cardboard crates.

 The objective of the invention is to solve this handicap.

 More specifically, a first objective of the invention is to provide a method of manufacturing wooden crates which makes it possible to obtain a graphic printing quality of the wooden boards comparable to that obtained on cardboard packaging.

 Another objective of the invention is to provide such a method, the implementation of which is compatible with the industrial requirements of manufacturing yield, and of cost price.

 An additional objective of the invention is to provide such a process which is easily insertable upstream of a conventional production line for wooden crates.

 The invention also aims to provide such a method which allows different implementation variants depending on the manufacturing conditions required.

These objectives, as well as others which will appear subsequently, are achieved according to the invention using a process for the mass production of crates with printed faces, each crate being of the type comprising in particular two head boards and two side boards joined by cleats, bars and slats, in which at least one of said boards is intended to receive a printing pattern, the method being characterized in that it comprises the following steps:
- A set of plates of a size is prepared such that they each correspond to a plurality of identical boards;
- Simultaneously printing a plurality of patterns at the corresponding locations of the boards on said plate;
- Each board is individualized by cutting out said printed plate;
- The crates are assembled by means of said individualized printed boards.

 Performing the printing operation on a large plate relative to the size of the boards of a crate has advantages in synergy with each other.

 First of all, the simultaneous printing of several boards on the same plate allows a substantial saving in time and cost, unlike traditional flexography where the board is printed by sheet.

 On the other hand, and quite essential, the large plates have a much better capacity for bending than the short and narrow panels serving as head and side boards for the crates. This is essential to allow adequate planning of the wood surface at the time of printing. Failing this, clearly, the print quality is impaired at the level of the relative recessed portions, especially when making flat areas, that is to say colored background areas on a relatively large surface.

 This concern of obtaining a good flatness of the support to be printed is one of the basic specificities of the invention. It is found in two other characteristics of the process: the preliminary surfacing of the plates, and the planarization of the plates by suction on the printing machine.

 In a preferred embodiment of the invention, the boards constituting the crates are made of wood, and more particularly of poplar plywood. Other materials may however be considered.

 In this case, it is advantageous to carry out the preliminary surfacing in the form of a sanding of the plate to be printed, on the face intended to receive the printing.

This sanding operation is all the more efficient and economical, because it is implemented on a plate corresponding to a plurality of boards.

 To improve the flatness, finally, the plate to be printed is preferably "pressed" against the printing table by an air suction system (for example by perforations made in the printing table and forming suction cups by means of vacuum cleaner or vacuum pump) for the duration of the printing operation.

 According to another advantageous characteristic of the invention, the printing method used is screen printing.

 The choice of screen printing is quite unexpected, since this process is usually reserved for printing posters or other paper supports.

Those skilled in the art have hitherto been dissuaded from using screen printing to print a rigid, thick, absorbent and living support - therefore deformable - like wood. In addition, the design of screen printing machines is at the very least unsuitable for this type of support, in particular as regards the methods of gripping and driving the support to be printed.

 After numerous attempts to adjust the machine and select the inks, we managed, against all odds, to obtain a result not only satisfactory, but even remarkable from the point of view of the quality obtained and the effect rendered, all the more spectacular since it was unexpected on this type of support.

 Thus, the process of the invention makes it possible to preserve the use of an ecological material - wood -, while nevertheless sacrificing to the marketing requirements of modernity i.e. the aesthetic expectations of distributors and consumers.

 The invention also relates to a printing machine implementing the above printing method.

Preferably, the printing machine of the invention comprises means for suctioning the plate to be printed on a printing table by means of suction cups, as well as a mechanism for gripping and driving the plates in machine input consisting of:
- On the one hand of a tilting element intended to lift the leading edge of the plate at the time of its introduction into the machine;
- on the other hand, a clamp whose jaws extend transversely along the leading edge of the printing plate, said clamp being mounted on drive means in longitudinal translation relative to a printing table so to bring the gripped plate to the printing location of the printing table.

 In order to be able to print polychrome patterns, each plate can be passed through the machine several times, each pass corresponding to a single-color application.

 In an embodiment suitable for mass production, the printing machine consists of several printing tables arranged in series, each printing table ensuring the printing of a single-color pattern element of said patterns to be printed. In this way, the production rate can be substantially accelerated.

 Finally, the invention also relates to printed crates assembled with printed boards manufactured according to the above method.

Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention given by way of illustration and not limitation, and the attached drawings, in which:
- Figure 1 is a partial we of a typical crate;
- Figure 2 shows a plate usable to form printed boards according to the method of the invention;
- Figure 3 shows schematically the succession of different stages of a printing process according to the invention;
- Figure 4 shows schematically the main components of a printing machine implementing the method of the invention.

 As shown in FIG. 1, a crate 10 is made up of head boards 11,12, and side boards 13,14, assembled together using angle brackets 15-17 surmounted by support bars 18 The bottom of the crate is formed from spaced slats 19 forming the covering surface, crossed with bars 20 ensuring the solidity of the assembly.

 The different elements are generally made of raw wood (poplar, pine), or preferably plywood (mainly poplar). The thickness of the boards is usually on the order of 2 to 5 mm, typically 3 to 4 mm.

The whole is secured by metal staples or equivalent.

 The dimensions of the crates are generally defined to be compatible with their palletization. The pallets used typically have the dimensions 1.00 m x 1.20 m, which led to the selection of the dimensions 600 x 400, 500 x 300, 600 x 330, 400 x 300, 300 x 200.

 The height of the crates is not standardized, and depends on the uses. Consequently, the head or side boards can optionally be split into two half-panels 14a, 14b which are juxtaposed one above the other in a joined or spaced manner. Vertical uprights 21 come if necessary to stiffen the assembly between the corner cleats.

 The invention is more particularly developed for printing the head and side boards 11,12,13,14. However, it can also be used to obtain the impression of other elements constituting the crate.

 According to the invention, and as shown in FIG. 2,1, printing is carried out on plates 25 of a certain dimension corresponding to a plurality of boards 26a, 26b, ..., 26i, ....

When the plate 25 is fully printed, that is to say when all the colors of the different single-color elementary patterns 27a, 27b, ... have been
affixed, the boards 26i can be individualized. The separation can be carried out by any means. Advantageously, one uses a rotary cutter formed by two rotary blades in slight peripheral overlap, and the movement of which in opposite directions ensures cutting in the manner of a pair of scissors.

 After individualization, the boards 26i can be used as head boards 11, 12, or as side boards 13, 14, depending on the dimension given to them.

 FIG. 3 shows diagrammatically the succession of steps of an advantageous embodiment of the method of the invention.

 After bringing a plate 25 to dimensions 31, it first undergoes a sanding operation 32 making it possible to improve the surface condition.

 The plate is then introduced into the screen printing machine, to be subjected to the printing 33 of the different patterns by one or more successive single-color passes 33a, 33i.

 After individualization 34 by cutting, the printed boards obtained are used in the assembly phase 35 of the crates.

 FIG. 4 schematically represents a screen printing machine implementing the method of the invention.

 Screen printing is a printing process which uses a screen of silk previously treated to allow the ink to pass through only in the places where it is required to constitute the pattern.

The ink is deposited from an inking carriage 41 mounted on a gantry 42a, 42b, and which can be lowered 43 towards the printing table 44 to affix
Ink by "wiping". The total surface of the printing table is covered by the longitudinal displacement 45 of the gantry.

 The introduction of a printing plate 25 is carried out by means of a clamp 46 mounted on a carriage 47 movable longitudinally 48. In order to facilitate the gripping operation, the machine comprises a tilting element 53 intended to lift the edge 54 of the plate 25 at the time of its introduction into the machine.

 Parallel to the gripping operation of the board 25 at the input of the machine, the printing table 44 retracts downwards 49. This makes it possible to bring the plate 25 to the printing position 50 (symbolized in dotted lines) by displacement of the clamp 46 on its carriage 47. The centering of the plate 25 in the printing position 50 is ensured by means of frustoconical centering pins 51, 52 which, when the printing table returns to the high position , are plugged into corresponding bores made previously in the plate 25.

 The movement of the clamp 46 takes place below the silk screen (not shown), so that the ascent of the printing table 44 brings the plate 50 into contact with the screen during the passage of the carriage - ink pad 41.

 To keep the plate 25 in place, by planing it as best as possible, suction means 55 are provided in the printing table 44. Advantageously, these printing means consist of perforations 55 distributed in all the useful zones of table 44, and forming suction cups by means of a vacuum cleaner or a vacuum pump.

 After printing, the plate is extracted from the machine, and can be driven to a second printing table intended to affix another element of single-color pattern, or stored while waiting for a new passage in the same machine after changing the screen of silk and the working color of the inking carriage, or brought to cutting if the printing operations are completed.

 Of course, the invention applies without difficulty for the manufacture of any crate or any wooden box, whatever the dimensions, the essence, and the subsequent use of the packaging obtained.

Claims (13)

 1) A method of mass production of crates with printed faces, each crate being of the type comprising in particular two head boards and two side boards joined by cleats, bars and slats, in which at least one of said boards is intended to receive a pattern printing,  characterized in that it comprises the following stages:  - A set of plates (25) of a size is prepared such that they each correspond to a plurality of identical boards (26a, 26b, ..26i ..),.  - The crates (10) are assembled by means of said individualized printed boards.  - Each board (26i) is individualized by cutting out said printed plate (25);  - simultaneously printing a plurality of patterns (27a, 27b) at the corresponding locations of the boards on said plate (25);  2) A method according to claim 1 characterized in that the plates (25) are made of wood.  3) Method according to any one of claims 1 and 2 characterized in that the wood used is a poplar plywood.  4) Method according to any one of claims 1 to 3 characterized in that it comprises a prior step (32) of surfacing the plates to be printed by sanding.  5) Method according to any one of claims 1 to 4 characterized in that the printing process used is screen printing.  6) Method according to any one of claims 1 to 5 characterized in that the printing patterns are composed of at least two colors (27a, 27b), and in that the printing is carried out in several passes (33a , 33i) each single color.  7) Method according to any one of claims 1 to 6 characterized in that the plurality of patterns affixed on a plate consists of all identical patterns arranged at the corresponding locations of the boards on said plate.  8) Printing machine for implementing a method according to any of claims 1 to 7.  9) Printing machine according to claim 8 characterized in that it comprises suction means (55) of the plate to be printed on a printing table (44).  10) Printing machine according to any one of claims 8 and 9 characterized in that it comprises a mechanism for gripping and driving the plates at the input of the machine consisting of:  - On the one hand a tilting element (53) intended to lift the leading edge (54) of the plate (25) at the time of its introduction into the machine;  - On the other hand, a clamp (26) whose jaws extend transversely along the leading edge of the printing plate (25), said clamp (46) being mounted on means (47) for driving longitudinal translation relative to a printing table (44) so as to bring the gripped plate (25) to the printing location (50) of the printing table (44).  11) Printing machine according to any one of claims 8 to 10 characterized in that it consists of several printing tables arranged in series, each printing table ensuring the printing of a single-colored pattern element (27a, 27b) of said patterns to be printed.  12) Printed board according to the method of any one of claims 1 to 7.  13) Printed crate or box made with printed boards according to the method of any one of claims 1 to 7.