EP0305793B1 - Pencil-manufacturing process and apparatus - Google Patents

Abstract

The process for the continuous manufacture of pencils comprises the stages of arranging pencil leads between two half-boards slotted longitudinally and fixed together by adhesive bonding and pressing in order to form sandwich boards (1), of trimming the transverse ends of these boards and then of cutting the latter between the leads housed in the longitudinal slots. After having trimmed the ends of the boards in order to free them, a protective layer (19), onto which an identifying marking (20) is printed, is deposited on the faces thus formed, the depositing of the protective layer and the printing of the marking being effected by means of a device for spraying under pressure drops of a protective and printing liquid respectively, comprising spraying heads (15a, 15b; 16a, 16b). <IMAGE>

Description

The present invention relates to the field of chain production of pencils, and more particularly a method of this manufacture and the installation for the implementation thereof.

• pose des mines dans des rainures préencollées appropriées pratiquées longitudinalement dans une première demi-planchette en bois ;
• après application de colle, pose d'une seconde demi-planchette de forme identique et pourvue de rainures, la face rainurée étant également préencollée, puis mise sous presse des planchettes ou "sandwichs" contenant les mines ;
• rognage pur affranchir les extrémités de ces planchettes, et découpage dans le sens longitudinal, entre les mines, pour former les crayons.

As will be recalled below, with reference to the appended drawing, the process for the continuous manufacture of pencils, as it is currently implemented in a manner known per se, comprises the following main steps:

• laying mines in suitable pre-glued grooves made longitudinally in a first wooden half-board;
• after applying glue, laying a second half-board of identical shape and provided with grooves, the grooved face also being pre-glued, then press-pressing boards or "sandwiches" containing the leads;
• pure trimming free the ends of these boards, and cutting in the longitudinal direction, between the mines, to form the pencils.

Thus, in this process, once the second half-board has been laid, the mines are visible from the outside only by their ends, on the transverse edges of said board. However, there are currently nearly twenty different shades of black lead pencils, and a hundred different colored leads. It is therefore imperative to be able to mark the boards before the final cutting, so as to distinguish these different shades. On the other hand, it is also necessary, after the trimming step, to coat the franked slices of the boards, in order to avoid in the final step and the subsequent manipulations that graphite dust, coming from the ends of the mines , do not dirty or damage the installations.

Currently the aforementioned problem is solved, in an unsatisfactory and not very rational way, by interrupting the production line to arrange the boards on suitable supports in order to apply a thin layer of a colored varnish on the transverse ends of the boards, by example using a spray gun type device.

In addition to the significant disadvantage of interrupting the continuous process, this technique also has the disadvantage of not being able to be implemented automatically and of achieving an insufficient result as regards marking, since it is practically impossible to distinguish with certainty the small boards marked only by a specific color, when these can be about 80 to 120 in number.

DE-C-681364 proposes to spray a protective layer on the two end edges of an already formed pencil.

The object of this invention is to provide a method which makes it possible to remedy the aforementioned drawbacks, and which can be implemented entirely automatically and with a marking which is easy to carry out and then to decipher.

The process for the continuous production of pencils which is the subject of this invention and which aims to achieve the above-mentioned object has the characteristics set out in claim 1.

On the other hand, a second object of the invention consists of a device for implementing the above method, which is defined in claim 5.

The appended drawing to which the following description refers, illustrates schematically and by way of example the invention.

FIG. 1 is a diagram illustrating a known production line in which the improvement according to the invention is incorporated.

Figure 2 is a schematic perspective view showing the arrangement of the marking devices with respect to the movement of the boards.

Referring first to Figure 1, the diagram presented illustrates the different stages of the manufacturing process with regard to each of these stages the progress of manufacturing.

The half-boards 1 are first subjected to a longitudinal grooving operation in a grooving machine 2. Then, in a device 3, after depositing a thread of glue in each groove 5, the leads 4 are arranged in these grooves. A second half-board 1, the grooved face of which is coated with a layer of adhesive, is then placed on the first so as to form in 6 a board or sandwich 1 ′ containing the leads 4. This board 1 ′ is subjected to the action of a drum-press 7 so as to securely fix the two half-boards 1 (pressure according to the arrows I).

The boards 1 ′ are then trimmed at their transverse ends, so as to free them and thus provide boards with sharp edges, by means of a trimmer 8 (not shown).

It is at this stage of the manufacturing process that the coating and marking device 9 is arranged, which is more particularly the subject of the invention. Indeed, after the trimming operation, the boards 1 ′, continuing to advance continuously, are provided on their edges with a layer of protective paint or varnish on the one hand, and on the other hand with a marking identification may include numbers and / or coding letters.

Finally, the boards 1 ′ thus protected and marked are brought into a cutter 10, in which they are cut longitudinally between the leads 4 to form the rods 11, for example of hexagonal section.

One of the main aspects of this invention consists in the particular application of a newly known technology for marking by jet of liquid, for example ink, allowing printing at high speed and with high precision. This technique involves the combined action of a vibrating device of the piezoelectric type and a system for pressurizing an appropriate liquid, forcing it through a nozzle of small diameter, and which leads to the '' obtaining a standardized drop train (emission frequency, diameter of the drops, jet break position). When the jet is broken, the drops are individually charged at variable levels, passing between electrodes brought to an adequate electrical potential. The drops then pass between plates brought to a high potential where they undergo a deflection proportional to their charge and in accordance with the desired impact position.

A device of the aforementioned type (by example "Willet Printos" from the company Willett Sarl in Paris, or "Jaime 2000" from the company Image in Valence, France), is therefore incorporated into the installation for making pencils, after adaptation for this particular new application.

As shown in the diagram in FIG. 1, and in more detail in that of FIG. 2, the coating and marking device 9 comprises two generators 12, 13 of jets of pressurized liquid, arranged one after the other. in the direction of travel of the boards 1 ′. The two generators 12, 13 are controlled by a common programmable control unit 14 and are each connected to two print heads 15a, 15b; 16a, 16b, arranged in pairs on either side of the path of travel of the boards 1 ′.

As illustrated in FIG. 2, the boards 1 ′ travel in the direction of arrow II between the print heads 15a, 15b; 16a, 16b, arranged transversely with respect to this movement on a drive device, generally of the endless type, and which can be constituted by two parallel chains or bands 17, by a single wide band, etc. The boards 1 ′ are positioned on this advance device by means of stop members 18. The sandwich board 1 ′ (A) after having been trimmed at its ends passes first between the heads 15a, 15b which are designed to squirt on the edges of said board 1 ′ (B) a protective base layer 19, for example a varnish. Then, the board 1 ′ (C) is provided on its edges thus coated with a marking or coding 20 (letters, numbers or combination of the two) passing between the heads 16a, 16b, which are designed to print with precision of such signs, corresponding to the hardness of the mines or to their color. These heads 16a, 16b therefore preferably project a printing ink.

Of course, the whole of the protection and marking device 9 operates automatically, the control unit common to the two generators 12, 13 being programmable as a function in particular of the running speed of the boards 1 ′, the dimensions of the slices of these to be treated, the nature and characteristics (viscosity, etc.) of the respective liquids to be sprayed, etc. On the other hand, measurement and / or detection members (not shown) are provided to automatically supply the control unit with the information necessary for its operation, such as the instantaneous position of each board, the dimensions thereof. ci, etc. All these means can be incorporated into the print heads.

Thanks to this original application of a new technique, the pencil manufacturing process can be streamlined. The use of jets under pressure of an appropriate liquid makes it possible to obtain a thin protective coating very quickly dry and the printing without interruption of the scrolling of the boards of marking or coding indications thereon.

On the other hand, the same liquid jet technique in the form of droplets can be used, in the continuous manufacturing process of pencils, for the prior gluing either of the grooves, or of the entire grooved surface of the two half -planks forming the "sandwich". In this case, it is therefore necessary to incorporate into the installation for the implementation of the method, a jet device under liquid pressure, for example of the type described with reference to the attached drawing, more particularly at the groover and before the drum press. It will thus be possible to have a generator with a head for ejecting liquid glue in the form of calibrated droplets in order to deposit in each groove half-boards, before the placement of the mines, a thread of glue; if necessary, a second generator with ejection head will be arranged so as to coat with a layer of glue the grooved surface of the other half-boards before the sandwiches are formed by pressing. This additional variant makes it possible to further rationalize the manufacturing process and above all to ensure better quality of the pencils thus manufactured, in particular thanks to the possibility of guaranteeing the deposition of glue in each groove intended to receive a lead, which is not not the case with the techniques currently used.

Claims (9)

1. Process for the continuous manufacture of pencils, comprising the steps of laying the pencils leads between two half small boards which are longitudinally grooved and which are fixed together by gluing and pressing to form sandwiches small boards, of trimming the transversal ends of these small boards, and then to cut them between the leads disposed within the longitudinal grooves, characterized by the fact that after clipping said ends to trim them, a protecting layer is applied onto the edges thus formed, on which an identification mark is printed, the deposition of the protecting layer and the printing of the mark being carried out by jet under pressure of drops of a protecting liquid respectively a printing liquid.
2. Process according to claim 1, characterized by the fact that between the steps of trimming and of cutting the small boards are passed, with their longitudinal axis perpendicular to the direction of advance thereof, between two pairs of projection heads disposed the one after the other in the direction of advance, the first pair being adapted for the projection of drops of a protecting liquid and the second form the projection of drops of a printing ink, each pair being connected to a piezoelectric generator for putting the projecting liquid respectively the printing liquid under pressure, and both generators being controlled by a programmable control unit.
3. Process according to claim 1 or to claim 2, characterized by the fact that, prior to the laying of the leads in the grooves of the half small boards, a streak of glue is applied into these grooves by jet under pressure of liquid glue drops.
4. Process according to one of claims 1 to 3, characterized by the fact that a layer of glue is applied onto the grooved surface of the half small boards before the formation of small boards sandwiches by pressing, by jet under pressure of liquid glue drops.
5. Plant for the working of the process according to claim 1, which comprises, disposed the ones following the others, a grooving machine, a device for laying the leads and a pre-gluing device, a press-drum, a trimming device and a cutting device, a coating device and a marking device by jet under pressure of drops of a protecting liquid, respectively a printing liquid being placed between both last elements of the plant.
6. Plant according to claim 5, characterized by the fact that the coating and marking device comprises a programmable control unit which is connected to two piezoelectric generators for putting under pressure a protecting respectively a printing liquid, each generator being connected to a pair of projecting heads, these projecting heads being disposed on both sides of the passage way of the small boards.
7. Plant according to claim 6, characterized by the fact that it comprises measuring and/or detecting means for providing the control unit with the information necessary for its working.
8. Plant according to one of claims 5 to 7 for the working of the process according to claim 3, characterized by the fact that it comprises a projecting device under pressure of drops of liquid glue disposed between the grooving machine and the device for laying the leads, in such a manner to apply a spreak of glue in each of the grooves of the half small boards.
9. Plant according to one of claims 5 to 7 for the working of the process according to claim 4, characterized by the fact that it comprises a projecting device under pressure of liquid glue drops disposed before the drum-press, in such a manner to apply a layer of glue onto the grooved surface of the half small boards.

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