METHOD AND PLANT FOR THE CONTINUOUS PRODUCTION OF OBJECTS FROM PULP MATERIAL

Abstract: The invention relates to the production of objects by suction-moulding pulp mass so as to form blanks or preforms (46) of at least approximately the same shape as the finished objects, after which the blanks or preforms are dried completely or partly and then subjected to finishing treatment so as to produce the final object. The new feature consists in that a number of blanks or preforms are moulded together in the form of an integral body with the blanks or preforms being mutually connected by bridge elements having such a mechanical strength that the integral body can be conveyed without being deformed to a number of work stations adapted each to perform its own finishing operation on each of the blanks or preforms (46) constituting part of the integral body, after which the finished objects are liberated by disrupting the securing connection to the bridge system.

Description: METHOD AND PLANT FOR THE CONTINUOUS PRODUCTION OF OBJECTS FROM PULP MATERIAL. TECHNICAL FIELD The present invention relates to a method for the continuous production of objects from pulp material, said method being of the kind set forth in the preamble of claim 1. In the present connection, the term "pulp material" is to be understood as applying to a fiber-containing pulp mass, that may also contain or consist of waste paper. BACKGROUND ART In the continuous mass production of objects from pulp material it is known to use a moulding machine with a rotating mould carrier, on the periphery of which suction moulds are placed side by side, said moulds being periodi¬ cally immersed in a pulp mass during the rotation of the mould carrier, so that a layer of pulp mass can be deposited on the suction moulds by applying suction to them during their passage through the pulp mass. When the moulds subse¬ quently again are lifted free of the pulp mass, the moist blanks or preforms thus produced are removed from the suction mould, partly by blowing air through the latter, partly by aspirating the blanks or preforms onto corresponding counter- -moulds placed on the periphery of a pressing rotor, the axis of which is parallel to the axis of the mould carrier, and facing the latter. From this latter rotor, the blanks or preforms are transferred to supporting and conveying means adapted to convey the blanks or preforms having been transferred through a drying apparatus. It is not possible with suction-moulding wet material to produce objects immediately having their precise final shape. Hence, with this in itself rational method of production, it is normally necessary to carry out a subsequent finishing treatment of each individual dried blank or preform, e.g. by a post-pressing operation, an edge-cutting operation, imprinting and the like. In automatically operating plants, in the present connection being the rule rather than the exception, if an economically justifiable production is to be achieved, the conveying of the blanks or preforms towards and between the individual work stations and the processing of the blanks or preforms in the latter must be performed individually at the production rate. This has especially shown itself to be a disadvantage, when the suction-moulding method is to be utilized in a rational manner, not only for the mass pro¬ duction of objects with relatively large surfaces, such as the well-known egg trays, but also for the production of small objects, e.g. planting pots of the kind used by gar- deners for planting-out operations, as conveying and proces¬ sing the blanks or preforms individually in this case can make it difficult to maintain economically justifiable pro¬ duction rates. DISCLOSURE OF THE INVENTION On the above background, it is the object of the present invention to provide a method of the kind referred to initially, with which it is possible in an economically justifiable manner to produce even relatively small objects from pulp material, and further make the requisite plant more flexible with regard to rational production of both large and relatively small quantities of objects on one and the same plant. This object is achieved by according to the present invention to proceed as set forth in the characte- rizing clause of claim 1. By proceeding in this manner, a large number of blanks or preforms are formed ready for further processing while still constituting parts of a considerably larger integral body, that can be conveyed towards and between the individual work stations and processed in all of these or in some se¬ lected ones. By giving this larger, integral body a mould- -surface size equal to the size necessary for producing the largest object desired, it is achieved that one and the same plant, merely by exchanging the moulds, can be used in an economical justifiable manner for mass-producing both large and small quantities of both large and small finished ob¬ jects. Proceeding in the manner set forth in claim 2 makes it possible to take into consideration that the dried blanks or preforms, whether constituting a single object or each comprising a plurality of objects, will not be deformed while being conveyed, at the same time making it possible to let the various objects have different heights. Proceeding as set forth in claim 3 results in the advantage that the blanks or preforms, while being conveyed towards and between the work stations, are held in positions ensuring a uniform finishing treatment of each individual blank or preform. In that case, the integral body may be given the shape indicated in claim 4, with the result that the means requii d for the positive mechanically controlled conveying are placed outside of the blanks or preforms pro¬ per. The conveying movement may be in the nature of pushing, pulling or carrying. Claim 5 indicates an advantageous con¬ struction of a unitary grate structure formed from bridges interconnecting the individual blanks or preforms, said grate structure e.g. forming a frame with which the integral body can rest on the above-mentioned plane, continuous con¬ veying surface during the conveying. Not until the integral body has passed through all the work stations desired to be used for the finishing treat- ment, will the blanks or preforms, now processed into the finished objects, be liberated from the bridge connection, after which they can be packaged with a view to being dis¬ patched. The present invention also relates to a plant for carrying out the method according to the invention. This plant is of the kind set forth in the preamble of claim 6, and it is according to the invention characterized by the features set forth in the characterizing clause of claim 6. The mode of operation of this plant, as well as the effects and the mode of operation of the embodiments of the method and the plant being set forth claims 2-5 and 7-8, respectively, will be evident from the following detailed portion of the present description. BRIEF DESCRIPTION OF THE DRAWINGS In the following detailed portion of the present description, the invention will be explained in more detail with reference to the drawings, in which Fig. 1 diagrammatically shows an embodiment of a complete plant according to the invention, and Fig. 1A is a diagrammatic overall view of the work stations of the plant, whereas Figs. 2-14 are illustrations showing exemplary embodiments of work stations sequentially constituting parts of the plant for stepwise finishing treatment and packaging of the objects being produced in the plant. DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 shows diagrammatically a plant consisting of a suction-moulding station 10 for moulding blanks or preforms from pulp material. The station 10 comprises a rotatable mould carrier 12, on the outside of which are placed several liquid-permeable suction moulds 14 adapted to be connected with a source of sub-atmospheric and super-atmospheric pres¬ sure. The mould carrier 12 is with a part of its circumfe¬ rential surface immersed in a vessel 16 containing a fiber pulp. This pulp may be made from a fiber-containing raw material, including waste paper or cardboard. During the immersion in the pulp mass, a layer of fiber material is deposited by suction on the mould surfaces of the suction mould 14. Subsequently, when the moulds 14 are lifted free out of the pulp vessel 16, the fiber layer having been deposited by suction is blown off from the suc¬ tion mould 14 by supplying air under pressure to the latter. At the same time, the moist blank or preform is being aspi- rated onto a corresponding counter-mould (not shown) placed on the circumference of a pressing rotor (not shown) being placed with its axis parallel to the axis of the mould car¬ rier 12 and facing the latter's periphery. From the pressing rotor, the moist blank or preform is blown off and laid on to a conveying track (not shown) , on which the blank or preform is conveyed through a drying oven 18. From the drying oven 18, the substantially or com¬ pletely dried blank or preform is placed on a conveying surface 20, from which it is conveyed up to and passes a number of work stations for completing its processing. The conveying surface 20 is formed as a plane con¬ tinuous supporting surface, on which the blanks or preforms may be conveyed by being pushed or pulled or carried. In the embodiment shown, the finishing line of the plant is divided into three mutually parallel part-lines, the total capacity of which is matched to the production capacity of the moulding station 10,12 and the drying station 18. In the example shown, the finishing line comprises va¬ rious work stations, shown diagrammatically in the following Figures: Fig. 2 shows a sprinkling station for moistening the surface of blanks or preforms with a view to making a subsequent post-pressing operation more effective, Fig. 3 shows a station for final sprinkling of the blanks or preforms with colouring matter, as well as an immediately adjacent drying section for quick drying of the colouring matter having been applied, Fig. 4 shows a station for post-pressing of the blanks or preforms, e.g. in order to give the latter a well-defined final shape and/or to give them smooth outside surfaces, this possibly being an advantage, if later the blanks or preforms are to be provided with an imprint, a laminate or a label, Fig. 5 shows a station for providing the blanks or preforms with a laminate 22, Fig. 6 shows a station providing the blanks or preforms with an imprint 24, Fig. 7 shows a station providing blanks or preforms with a label 26, Fig. 8 shows a station with tools 28 for punching holes in the blanks or preforms, Fig. 9 shows a station with an embossing tool for forming fold lines 32, Fig. 10 shows a station for separating the individual blanks or preforms by using a parting tool 34 and an abutment platen 36 or some other resilient base. The separation may be com¬ plete, e.g. all the way around the blanks or preforms, or partial, e.g. by making incisions solely along a part of the sides of the blanks or preforms. Fig. 11 shows the separation of the blanks or preforms 46 from a body 48, the latter until this point having held the blanks or preforms together as a bridge body. The libe¬ rated blanks or preforms are placed on a base 40. Fig. 12 shows a number of blanks or preforms having been stacked successively on the base 40. Fig. 13 shows the blanks or preforms having been stacked on the base 40 while being conveyed into a collecting bag 42. Fig. 14 shows a number of bags 42 collected on a pallet 44. As will be evident from this explanation with as¬ sociated drawings, in the plant according to the invention a number of blanks or preforms 46, in the present example planting pots, have been moulded in the suction-moulding station 10 in the form of a common continuous body with bridges interconnecting the blanks or preforms 46, said bridges for the sake of simplicity being shown in the form of a common bridge sheet 48 in the drawing. Instead of a common plate, the bridge connection may also be formed from ribs, and the bridge connection may also comprise a directly abutting connection between the mutually facing sides of two adjacent blanks or preforms 46. The mechanical strength of the bridge system is such that the integral body 46,48 can be conveyed continuously to a number of work stations, each adapted to perform its own finishing operation as explained above. From this ex- planation it is also evident that each blank or preform 46 is or may be subjected to individual processing in each work station. When the processing of the blanks or preforms 46 in an integral body is complete, the blanks or preforms are liberated from the bridge system through a separating pro¬ cess. Likewise, the above explanation provides an example of the integral body 46,48 preferably being shaped in such a manner, that it - with a view to conveying it - can rest on a substantially plane and continuous conveying surface 20 without deformation being caused to the integral body as such or any of the individual blanks or preforms 46. In the example, this is achieved by giving the bridge sheet 48 the shape of a grid-like frame, with which the integral body 46,48 rests on the conveying surface 20 and is moved along the latter. In order to ensure an effective control of the con¬ veying of the integral body towards and through the various work stations, it is according to the invention advantageous to give the integral body 46,48 such a shape that it can be conveyed in a positively controlled manner between the work stations by means of suitable conveying means. For this purpose, the integral body 46,48 can be provided with late¬ rally protruding tabs 50, vide e.g. Fig. 2, adapted to be engaged and moved by suitable conveying means, e.g. in the shape of gripping members, or else the integral body may be carried forward by suitable supporting and carrying members using the tabs 50. In the manner described above, it is possible in a plant according to the invention to work e.g. with suction moulds having a base area of 400 x 600 mm. With this base size, the plant can be used for producing objects with large areas, such as egg trays. The same base size does, however, make it possible to produce objects each having a substan¬ tially smaller area size, but which in the manner indicated above can be produced as parts of integral bodies likewise having a base area corresponding to the above, for which reason it is sufficient to exchange suction moulds with the above-mentioned standard base area, if the production is to be changed from one type of object to another. Thus, the integral bodies can, in the same manner as products having a large area, be produced in an economically justifiable manner by suction moulding of a pulp material. LIST OF PARTS 10 15 20

Claims: C L A I M S: 1. Method for the continuous production of objects from a pulp material, said method comprising the steps of a) moulding blanks or preforms of at least approximately the same shape as the finished objects by aspirating pulp mass against a liquid-permeable mould surface, b) complete or partial drying of the blanks or preforms thus produced, and c) final finishing processing of the completely or partially dried blanks or preforms so as to produce the final objects, characterized in d) that a plurality of blanks or preforms are moulded to¬ gether as an intergral body with the blanks or preforms mutually connected by bridges having a mechanical strength sufficient to allow the integral body to be conveyed con¬ tinually to a number of work stations, each adapted to per¬ form its own finishing operation on the blanks or preforms constituting parts of each integral body, and e) that the finished objects then are liberated by disrupting their securing connections to the bridge system. 2. Method according to claim 1, characterized in that the integral body is given such a shape that it with a view to being conveyed can rest on a substantially plane and continuous conveying surface or carried "floating" by suitable support means without deformation being caused to itself or the individual blanks or preforms. 3. Method according to claim 1 or 2, characterized in that integral body is given such a shape that it can be conveyed under positive mechanical control and engagement between the work stations by means of suitably adapted con¬ veying means. 4. Method according to claims 2 and 3, characterized in that the integral body is shaped with laterally protruding tabs able to be gripped or engaged by conveying means in the form of gripping means. 5. Method according to any one or any of the claims 1-4, characterized in that at least some of the bridges interconnecting the blanks or preforms are given the shape of a continuous, grid-like object. 6. Plant for the continuous production of objects from pulp material while carrying out the method according any one or any of the claims 1-5 and of the kind comprising a) at least one suction-moulding station (10,12) for moulding blanks or preforms (46) of at least approximately the same shape as the finished objects by aspirating pulp mass against a liquid-permeable moulding surface, b) a drying station (18) for complete or partial drying of the blank or preform thus produced, c) at least one work station for finishing processing of the final object, and d) a conveying path (20) for conveying the blank or preform to the work station or stations, characterized in e) that the suction-moulding station (10,12) is adapted to produce integral bodies (46,48) each consisting of a plu¬ rality of blanks or preforms (46) mutually connected through bridges (48) , said integral bodies being adapted to be con¬ veyed along said conveying path (20) , f) that the work station or stations is/are adapted to fi- nish-process all the blanks or preforms in each integral body simultaneously, the station or stations for this purpose comprising a number of working means corresponding to the number of blanks or preforms, said working means being placed in substantially the same configuration as the configuration of the blanks or preforms in the integral body and adapted to process the blanks or preforms substantially simultane¬ ously, and g) that the plant comprises at least one station (Fig. 10) adapted to disrupt the bridges with a view to liberating the . individual finished-processed objects (46) from each other. 7. Plant according to claim 6, characterized in that the conveying path (20) is provided with conveying means adapted to hold the integral body and move the latter under positive mechanical control along the conveying path with the intergral body resting on this path or on conveying support means. 8. Plant according to claim 6 or 7, characterized in that the disrupting station comprises means for stacking the individual objects produced by the liberating step.

Inventors: JENSEN JORGEN DYRLUND, JENSEN, JOERGEN, DYRLUND
Applicants: HARTMANN AS BRDR, JENSEN JORGEN DYRLUND, BRDR. HARTMANN A/S
Application year: 1993
Main classification: D21J7
IPC codes: D21J7