Title:
APPARATUS FOR THE PRODUCTION OF PRESSED BOARD
Document Type and Number:
United States Patent 3824058
Abstract:
An apparatus or plant for making pressed board from particulate or fibrous material, comprises a dispensing station for depositing such material on a movable surface, e.g. a conveyor and/or tray, a prepress for compacting the mat of this material and a multiplaten press for the final pressing stage. The prepress has at least two stages and is operated to compact the mat in these stages alternately, i.e., one mat is compacted in one stage of the prepress while a previously compacted mat is removed from the other stage and a new layer of the material introduced therein by alternatingly operable service mechanisms for charging and discharging the prepress.
Inventors:
Axer, Heinrich (Nettetal-Lobberich, DT)
Heckmanns, Ernst (Straelen, DT)
Heckmanns, Ernst (Straelen, DT)
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Sponsored by: Flash of Genius |
Application Number:
05/321796
Publication Date:
07/16/1974
Filing Date:
01/08/1973
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Referenced by:
Export Citation:
Assignee:
G. Siempelkamp & Co. (Krefeld, DT)
Primary Class:
Other Classes:
425/339, 100/209, 425/317, 425/327, 425/DIG.200, 425/130
International Classes:
B27N3/20; B27N3/08; B29J5/08
Field of Search:
425/130,317,80,338,339,455,DIG.200,327,406 100/195,196,199,137,207,140,209
US Patent References:
| 1883887 | Drier for fiber board | October 1932 | Farley | |
| 2878728 | Press feeding apparatus | March 1959 | Clark | |
| 2883705 | Method of and apparatus for molding rubber and rubber-like articles | April 1959 | Hartley | |
| 2923030 | Methods and apparatus for producing pressed wood-particle panels | February 1960 | Himmelheber et al. | |
| 3173976 | Method and device for the formation and transport of blanks, formed of particles such as wood shavings, fibres and the like destined to be compressed to boards | March 1965 | Paerels et al. | |
| 3428505 | METHOD OF AND APPARATUS FOR THE PRODUCTION OF PRESSED BOARD | February 1969 | Siempelkamp | |
| 3611482 | October 1971 | Hutz |
Primary Examiner:
Spicer Jr., Robert L.
Attorney, Agent or Firm:
Ross, Karl Dubno Herbert F.
Claims:
We claim
1. An apparatus for the production of compressed board, comprising:
2. The apparatus defined in claim 1 wherein said prepress comprises a stationary intermediate bed, an upper press platen overlying said bed and defining a stage between itself and said bed, a lower press platen disposed below said bed and defining a lower stage between itself and said bed, and independently operable but alternating drive means connected to said platens.
3. The apparatus defined in claim 2 wherein at least one of said devices comprises at least one conveyor, said bed being disposed at the level of said conveyor.
4. The apparatus defined in claim 2 wherein each of said devices comprises a pair of stacked conveyors, at least one conveyor of each stack being shiftable vertically.
5. The apparatus defined in claim 2 wherein at least one of said devices comprises a swingable platform for changing the level of a layer displaced therealong.
6. The apparatus defined in claim 2 wherein at least one of said devices comprises a pair of belt conveyors interconnected by a parallelogrammatic linkage.
7. The apparatus defined in claim 2 wherein at least one of said devices is formed with a conveyor having a discharge blade adapted to be withdrawn over another conveyor to deposit a layer upon the latter without distortion.
8. The apparatus defined in claim 2 wherein said dispensing station is provided with a first conveyor belt adapted to advance said layers, said charging device comprising a pair of stacked conveyors, one of said conveyors lying at the level of said low platen in an open condition of the lower stage of said multilevel prepress, said upper platen being shiftable vertically to the level of the upper surface of said bed.
9. The apparatus defined in claim 8 wherein each stage of said press is provided with a respective endless conveyor for advancing said layers through said press.
10. The apparatus defined in claim 9 wherein said discharge device comprises a pair of stacked conveyors at least one of which is vertically movable.
1. An apparatus for the production of compressed board, comprising:
2. The apparatus defined in claim 1 wherein said prepress comprises a stationary intermediate bed, an upper press platen overlying said bed and defining a stage between itself and said bed, a lower press platen disposed below said bed and defining a lower stage between itself and said bed, and independently operable but alternating drive means connected to said platens.
3. The apparatus defined in claim 2 wherein at least one of said devices comprises at least one conveyor, said bed being disposed at the level of said conveyor.
4. The apparatus defined in claim 2 wherein each of said devices comprises a pair of stacked conveyors, at least one conveyor of each stack being shiftable vertically.
5. The apparatus defined in claim 2 wherein at least one of said devices comprises a swingable platform for changing the level of a layer displaced therealong.
6. The apparatus defined in claim 2 wherein at least one of said devices comprises a pair of belt conveyors interconnected by a parallelogrammatic linkage.
7. The apparatus defined in claim 2 wherein at least one of said devices is formed with a conveyor having a discharge blade adapted to be withdrawn over another conveyor to deposit a layer upon the latter without distortion.
8. The apparatus defined in claim 2 wherein said dispensing station is provided with a first conveyor belt adapted to advance said layers, said charging device comprising a pair of stacked conveyors, one of said conveyors lying at the level of said low platen in an open condition of the lower stage of said multilevel prepress, said upper platen being shiftable vertically to the level of the upper surface of said bed.
9. The apparatus defined in claim 8 wherein each stage of said press is provided with a respective endless conveyor for advancing said layers through said press.
10. The apparatus defined in claim 9 wherein said discharge device comprises a pair of stacked conveyors at least one of which is vertically movable.
Description:
FIELD OF THE INVENTION
The present invention relates to the production of pressed board and, more particularly, to an apparatus, plant or installation for the manufacture of pressed board from fibrous or particulate materials.
BACKGROUND OF THE INVENTION
Numerous systems have been provided heretofore for the production of pressed board of various properties or characteristics. The term "pressed board" is intended to be generic to the boards or sheets made from fibers or particulate materials of various types, with or without externally supplied binder, and having a wide variety of properties. For example, fibrous materials consisting predominantly of cellulose can be compacted to provide a low-density board with high porosity for use as a thermal or acoustical insulation, using a minimum of binder. By contrast, highly compacted wood-fiber, sawdust or chipboard can be made with a high density for use as structural materials. The board may have still higher density when, in place of or in addition to the naturally occurring abietic resins, thermally activated resins or thermally hardening resins of the phenol-formaldehyde, resorcinol or urea-type are supplied. The product may have a smooth or rough finish, may be water-permeable or impervious to gases and moisture, may be provided with an aesthetically pleasing surface or with natural wood-grain appearance. The properties of the product may be modified by using facing layers of relatively fine comminuted materials and a core layer of a relatively coarse material etc. All such products can be denoted, for the purposes of the present invention, as pressed board.
In general, pressed board may be produced by depositing a layer or mat of noncoherent or loosely coherent material, with or without such binders as have been mentioned above, upon a surface, subdividing the layer and/or trimming it into rectangular configuration, and pressing the layer with or without heating (preferably with heating) between the platens of a platen press. It is a common practice to provide, for this purpose, a multiplaten press consisting of a plurality of vertically spaced heated platens, a press-closure device for simultaneously moving the platens together and a fluid-responsive system, e.g. a hydraulic cylinder, to compact the platens betwen a head plate and a bed plate.
On the charging side of the press there may be provided a multilevel rack capable of depositing the layers or mats upon the respective platens while, at the exit side of the press, another rack is provided to receive the pressed board and advance it to further processing, e.g. to a curing or tempering kiln.
Between the charging rack and the mechanism for dispensing the comminuted material, e.g. wood fibers, sawdust or wood chips, there is customarily provided a prepress which operates in the cadence of advance of the mats to compact each mat or layer and impart a greater coherency to the latter while leveling the layer so to improve the effectiveness of the final press operation and the ability to handle the mat.
A typical installation for the manufacture of pressed board, especially chipboard, fiberboard and the like, comprises a dispensing station at which the mat or layer is initially formed, a multiplaten main press, a press-charging device (e.g. the aforementioned rack), a press-emptying device, and associated conveyors adapted to advance the mat or layer of limitedly coherent material from the dispensing device to the charging rack, a prepress for precompression of the layers being provided along this path.
A prepress of the latter type, of course, may operate in the cadence of advance of the layers or mats as already indicated and it is even known to provide multiplaten prepresses upon which the mats are deposited for simultaneous compaction. A key problem with such systems is that all of the press stages must open and close simultaneously and thus the press stroke must await deposition of a layer or upon each of the prepress stages. Thus if the time required for formation of a mat or layer of a certain length is represented as Δ t and there are x stages of the prepress, the press must remain open for a period at least equal to x Δ t before precompression can commence. The press cycle is thus greater than x Δ t. To eliminate this lag in the operation of the production line, it is possible to provide a charging rack ahead of the prepress so that the mats can accumulate while the press is closed and then charge all of the platens when the press reopens. Apart from the fact that a charging rack of this type adds significantly to the cost of the system, it will be apparent that the press stroke cannot be less than x Δ t.
Furthermore, most conventional dispensing systems are able to adjust the thickness of the layer deposited (e.g. to vary the thickness of the final pressed board) only by varying the rate at which the receiving surface is moved past the dispensing device. Thus the receiving surface must be slowed to increase the thickness of the deposited layer, thereby increasing the duration Δ t. For the thick pressed board, therefore, the prepress cycle is increased in duration. It will be noted also that, when all of the platens of the prepress are to be closed simultaneously, the hydraulic device used for this purpose will have a stroke equal to the product of x and the displacement of each platen so that additional time is required for a greater number of platens of the prepress. The mechanical and hydralic dead time of the press and its recycling time are comparatively large. This is the case whether or not the layers or mats are moved on carrying trays through the system or are displaced by conveyors (e.g. conveyor tablets) therethrough.
To avoid some of these disadvantages, it has been proposed to increase the number of platens and thereby reduce the dead time per mat or layer. This has been found to be unsatisfactory as well and increases the capital cost of the installation.
OBJECTS OF THE INVENTION
It is the principal object of the present invention to provide an improved apparatus, plant or installation for the production of pressed board whereby the aforementioned disadvantages can be obviated.
It is another object of the invention to provide an apparatus for producing particle board, fiberboard or the like with a prepressing stage having a short stroke time and recycle period.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter, are attained, in accordance with the present invention, in a plant or apparatus for the production of pressed board having a prepress of the multiplaten type with at least two alternately actuatable platens individually shiftable to compact respective mats or layers during alternate half cycles of the prepress operation.
According to a more specific feature of the invention, the apparatus for the production of pressed board comprises a dispensing station for forming a succession of mats or layers of noncoherent or limitedly coherent material, a multiplaten main press downstream of the dispensing station, a charging rack immediately upstream of the main press and a discharge rack or device immediately downstream of the main press, and associated conveyors for advancing the layers from the dispensing station to and through the main press. Along the path between the dispensing station and the main press, there is provided according to the present invention a multiplaten prepress which, advantageously, has fewer press stages than the main press and is provided at its upstream and downstream sides with respective service devices for inserting the layers into thr prepress and removing it therefrom.
The invention principally resides in that the multiplaten prepress is an alternate-stroke press in which the plates move in opposite directions during respective half cycles of the press operation, the service devices likewise being operated to alternately dispose a layer upon at least one press platen during one half of the prepress cycle and upon the other platen during the second half of the press cycle, the discharge device being operated inversely to the feed device so that the press layers may be removed.
The invention makes use of the fact that a single-stage press can operate, for mechanical and hydraulic reasons, with a very short stroke or recycle period, so that the multiplaten press thus becomes an assembly of single-stage presses.
According to another feature of the invention, the multiplaten prepress is a two-stage press having a fixed central platen or bed against which a movable upper platen and a movable lower platen can be urged in opposite directions by mechanical or hydraulic platen-displacement means, the latter means being alternately operable for shifting the respective platens. The fixed central bed or platen preferably lies in line with the conveyor paths mentioned earlier.
With a two-stage prepress, according to the invention, the plant is greatly simplified, especially when the charging and discharging service devices each include two service stages respectively alignable with the platens of the prepress at least in the open position of the respective platen, at least one service stage being vertically shiftable for this purpose. The service stages may be conveyor tablets, swingable platforms or the like, or swingable platforms may be provided ahead of or behind each service rack in the direction of travel of the layers for positioning the latter on the respective layers. The service devices can be provided with belt conveyors which are shiftable by means of parallelogrammatic lankages and can be inserted into the different levels of the two-stage prepress.
According to the principles of this invention, the transport means in and adjacent the prepress are constituted by conveyor belts and, where support or carrying trays are not provided for the layers, the conveyor may have an inclined discharge end adapted to deposit the layer upon a subsequent conveyor without free fall or without the formation of gaps therebetween.
The system described above has significant advantages over the prior art, particularly with respect to the extremely short period or stroke and can be used for the production of very thin particle board or fiberboard as well as for the production of relatively thick pressed board.
DESCRIPTION OF THE DRAWING
The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompany drawing in which:
FIG. 1 is a somewhat diagrammatic elevational view illustrating a plant for the production of pressed board according to the present invention;
FIG. 2 is a detail view, greatly enlarged, of the region illustrated at II of FIG. 1;
FIG. 3 is a cross-sectional view taken along the line III -- III of FIG. 2;
FIG. 4 is a detail view of the region IV of FIG. 2 but illustrating another embodiment of the invention;
FIG. 5 is a view similar to FIG. 1 of the charging side of the prepress according to another embodiment of the invention;
FIG. 6 is a view similar to FIG. 5 illustrating still another embodiment; and
FIG. 7 is a detail view of another press charging device ahead of the prepress according to the present invention.
SPECIFIC DESCRIPTION
In FIGS. 1 - 3, we have shown an apparatus for the production of pressed board which comprises a dispensing station 2 having a plurality of hoppers 3 offset one behind the other in the direction of travel (arrow A) of the material adapted to form the pressed board 1. The hoppers 3 are provided with the usual dispensing heads 3a, 3b and 3c for respectively depositing a layer of fine particles, a layer of coarse particles and another layer of fine particles upon a conveyor 3d to form a layer 14 which may be subdivided transversely to the direction of movement to form respective mats or layers.
At the other end of the production line, there is provided a multiplaten press 4, represented diagrammatically in the drawing and preferably of the type described in commonly assigned U.S. Pat. No. 3,050,777 and 3,209,405. The dispensing devices 3, 3a, 3b and 3c as described in commonly owned U.S. Pat. No. 3,282,767, the layers being trimmed and shaped as described in U.S. Pat. No. 3,051,219, 3,096,227 and 3,428,505. The conveyor 3d may be of the type described in commonly owned U.S. Pat. No. 3,224,758.
Flanking the press 4, there are provided a charging rack 5 and a discharging rack 6 which may be formed with conveyor tablets or conveyor-band tablets for advance of the pressed board or the layers (see U.S. Pat. No. 3,565,725).
Between the multiplaten-press charging station 5, which operates as described in U.S. Pat. No. 3,565,725, and the layer-forming station 2, there is provided a conveyor arrangement which includes a two-level platen press 8 (i.e., the prepress) and means for charging and discharging this prepress (i.e., the service devices for the prepress) together forming part of the transport path.
At the upstream of the prepress 8, i.e., between the conveyor 3d and the prepress, there is provided a charging device 9 while a discharging device 9' is provided between the prepress and the charging rack 5.
The two-level prepress 8 is an alternate-cycle press which is shown in an open condition in FIGS. 1 and 2. More particularly, the press 8 comprises a fixed central bed 10, preferably in line with the conveyor 3d and the general transport path, which is mounted in a frame 10a and carries an upwardly facing heated or unheated bed plate 10b and a downwardly facing heated or unheated bed plate 10c. Juxtaposed with these platens are an upper platen 11 carried by the pistons 11a of a hydraulic cylinder arrangement 11b schematically shown in FIG. 3, while a lower platen 12 is carried by pistons 12a of cylinders 12b for movement toward and away from the plate 10c.
The press platens 11 and 12 are thus shiftable independently of one another and in alternate half cycles, the charging device 9 and the discharging device 9' likewise operating in alternation to feed and discharge the two-stage prepress 8.
The charging device 9 comprises a pair of conveyor-band tablets (see U.S. Pat. No. 3,565,725), of which at least the upper one is vertically movable while the discharge device comprises conveyor-band tablets 7', the upper member of which is vertically displaceable. The stages of the press can be provided with conveyor belts 20 for advancing the layers into and out of the press.
The system of FIGS. 2 and 3, shown to use press-charging trays, operates as follows:
A prepressed slab 13 of the comminuted material lies upon the lower press platen 12 and, when its conveyor 20 is driven, carries the slab 13 onto the lower conveyor 7' of the discharge device 9'. The conveyors 20 may be driven or undriven and, in the latter case, the prepressed body may be shifted from the prepress by the introduction of a new layer 14 upon its charging tray 19. During this period, the upper press platen 11 closes to compact the layer 14 therein, the previously discharged body 13 being carried by the upper conveyor 7' of the discharge device 9' in the direction of arrow B, the conveyor carrying member 13 having lowered from the dot-dash position previously. The upper stage 15 of charging device 9 is, during this period, provided with a new layer 14 as the layer 14 of the lower stage 17 is advanced into the press.
When the upper stage 16 of the press opens, the alternate half-cycle commences, i.e., the platen 12 closes to compact the new layer 14 deposited thereon. The lower conveyor 7' of the discharge device 9' rises into alignment with the upper conveyor 20 and the prepressed layer of the upper stage 16 is deposited upon this conveyor of the discharge device. Meanwhile, the conveyor 15, in its upper position, deposits a layer 14 of uncompacted comminuted material in the upper stage 16.
In the embodiment illustrated in FIGS. 1 - 3 the service devices 9 and 9' are provided with conveyor-belt stages, the belts 18 of which are driven alternately in the previously described pattern with automatic or programming means of conventional construction.
When a charging plate 19 is not used, the conveyors may have the configuration shown for the conveyor 21 of FIG. 4, i.e., the conveyor may have a transfer blade 22 which can be shifted from the right to the left to overlie the conveyor 20 and deposit the mat 14 thereon smoothly and uniformly (see U.S. Pat. No. 3,565,725).
In FIG. 5, we show a modification in which the dispensers 103 of the dispensing station 102 deposit the layer 114 of comminuted material upon a conveyor 103d for subdivision into mats, as previously described but not here illustrated. Ahead of the charging device 109, provided with conveyors 107, as previously described, there is provided a swinging platform or tipple 109a which can deposit the mats selectively upon the conveyor belt 107. The charging device 109, of course, is operated in the manner previously described to feed the mats alternately to the lower press platen 112 or the upper press stage 116 of the prepress 108.
In the modification of FIG. 6, the swinging platform 209a is provided between a conveyor 9a and the press, the system otherwise being similar to that of FIG. 1. FIG. 7 shows that the conveyor tablets 307 can be provided with a parallelogrammatic linkage 307a for movement into and out of the prepress to deposit the mats therein.
The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.
The present invention relates to the production of pressed board and, more particularly, to an apparatus, plant or installation for the manufacture of pressed board from fibrous or particulate materials.
BACKGROUND OF THE INVENTION
Numerous systems have been provided heretofore for the production of pressed board of various properties or characteristics. The term "pressed board" is intended to be generic to the boards or sheets made from fibers or particulate materials of various types, with or without externally supplied binder, and having a wide variety of properties. For example, fibrous materials consisting predominantly of cellulose can be compacted to provide a low-density board with high porosity for use as a thermal or acoustical insulation, using a minimum of binder. By contrast, highly compacted wood-fiber, sawdust or chipboard can be made with a high density for use as structural materials. The board may have still higher density when, in place of or in addition to the naturally occurring abietic resins, thermally activated resins or thermally hardening resins of the phenol-formaldehyde, resorcinol or urea-type are supplied. The product may have a smooth or rough finish, may be water-permeable or impervious to gases and moisture, may be provided with an aesthetically pleasing surface or with natural wood-grain appearance. The properties of the product may be modified by using facing layers of relatively fine comminuted materials and a core layer of a relatively coarse material etc. All such products can be denoted, for the purposes of the present invention, as pressed board.
In general, pressed board may be produced by depositing a layer or mat of noncoherent or loosely coherent material, with or without such binders as have been mentioned above, upon a surface, subdividing the layer and/or trimming it into rectangular configuration, and pressing the layer with or without heating (preferably with heating) between the platens of a platen press. It is a common practice to provide, for this purpose, a multiplaten press consisting of a plurality of vertically spaced heated platens, a press-closure device for simultaneously moving the platens together and a fluid-responsive system, e.g. a hydraulic cylinder, to compact the platens betwen a head plate and a bed plate.
On the charging side of the press there may be provided a multilevel rack capable of depositing the layers or mats upon the respective platens while, at the exit side of the press, another rack is provided to receive the pressed board and advance it to further processing, e.g. to a curing or tempering kiln.
Between the charging rack and the mechanism for dispensing the comminuted material, e.g. wood fibers, sawdust or wood chips, there is customarily provided a prepress which operates in the cadence of advance of the mats to compact each mat or layer and impart a greater coherency to the latter while leveling the layer so to improve the effectiveness of the final press operation and the ability to handle the mat.
A typical installation for the manufacture of pressed board, especially chipboard, fiberboard and the like, comprises a dispensing station at which the mat or layer is initially formed, a multiplaten main press, a press-charging device (e.g. the aforementioned rack), a press-emptying device, and associated conveyors adapted to advance the mat or layer of limitedly coherent material from the dispensing device to the charging rack, a prepress for precompression of the layers being provided along this path.
A prepress of the latter type, of course, may operate in the cadence of advance of the layers or mats as already indicated and it is even known to provide multiplaten prepresses upon which the mats are deposited for simultaneous compaction. A key problem with such systems is that all of the press stages must open and close simultaneously and thus the press stroke must await deposition of a layer or upon each of the prepress stages. Thus if the time required for formation of a mat or layer of a certain length is represented as Δ t and there are x stages of the prepress, the press must remain open for a period at least equal to x Δ t before precompression can commence. The press cycle is thus greater than x Δ t. To eliminate this lag in the operation of the production line, it is possible to provide a charging rack ahead of the prepress so that the mats can accumulate while the press is closed and then charge all of the platens when the press reopens. Apart from the fact that a charging rack of this type adds significantly to the cost of the system, it will be apparent that the press stroke cannot be less than x Δ t.
Furthermore, most conventional dispensing systems are able to adjust the thickness of the layer deposited (e.g. to vary the thickness of the final pressed board) only by varying the rate at which the receiving surface is moved past the dispensing device. Thus the receiving surface must be slowed to increase the thickness of the deposited layer, thereby increasing the duration Δ t. For the thick pressed board, therefore, the prepress cycle is increased in duration. It will be noted also that, when all of the platens of the prepress are to be closed simultaneously, the hydraulic device used for this purpose will have a stroke equal to the product of x and the displacement of each platen so that additional time is required for a greater number of platens of the prepress. The mechanical and hydralic dead time of the press and its recycling time are comparatively large. This is the case whether or not the layers or mats are moved on carrying trays through the system or are displaced by conveyors (e.g. conveyor tablets) therethrough.
To avoid some of these disadvantages, it has been proposed to increase the number of platens and thereby reduce the dead time per mat or layer. This has been found to be unsatisfactory as well and increases the capital cost of the installation.
OBJECTS OF THE INVENTION
It is the principal object of the present invention to provide an improved apparatus, plant or installation for the production of pressed board whereby the aforementioned disadvantages can be obviated.
It is another object of the invention to provide an apparatus for producing particle board, fiberboard or the like with a prepressing stage having a short stroke time and recycle period.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter, are attained, in accordance with the present invention, in a plant or apparatus for the production of pressed board having a prepress of the multiplaten type with at least two alternately actuatable platens individually shiftable to compact respective mats or layers during alternate half cycles of the prepress operation.
According to a more specific feature of the invention, the apparatus for the production of pressed board comprises a dispensing station for forming a succession of mats or layers of noncoherent or limitedly coherent material, a multiplaten main press downstream of the dispensing station, a charging rack immediately upstream of the main press and a discharge rack or device immediately downstream of the main press, and associated conveyors for advancing the layers from the dispensing station to and through the main press. Along the path between the dispensing station and the main press, there is provided according to the present invention a multiplaten prepress which, advantageously, has fewer press stages than the main press and is provided at its upstream and downstream sides with respective service devices for inserting the layers into thr prepress and removing it therefrom.
The invention principally resides in that the multiplaten prepress is an alternate-stroke press in which the plates move in opposite directions during respective half cycles of the press operation, the service devices likewise being operated to alternately dispose a layer upon at least one press platen during one half of the prepress cycle and upon the other platen during the second half of the press cycle, the discharge device being operated inversely to the feed device so that the press layers may be removed.
The invention makes use of the fact that a single-stage press can operate, for mechanical and hydraulic reasons, with a very short stroke or recycle period, so that the multiplaten press thus becomes an assembly of single-stage presses.
According to another feature of the invention, the multiplaten prepress is a two-stage press having a fixed central platen or bed against which a movable upper platen and a movable lower platen can be urged in opposite directions by mechanical or hydraulic platen-displacement means, the latter means being alternately operable for shifting the respective platens. The fixed central bed or platen preferably lies in line with the conveyor paths mentioned earlier.
With a two-stage prepress, according to the invention, the plant is greatly simplified, especially when the charging and discharging service devices each include two service stages respectively alignable with the platens of the prepress at least in the open position of the respective platen, at least one service stage being vertically shiftable for this purpose. The service stages may be conveyor tablets, swingable platforms or the like, or swingable platforms may be provided ahead of or behind each service rack in the direction of travel of the layers for positioning the latter on the respective layers. The service devices can be provided with belt conveyors which are shiftable by means of parallelogrammatic lankages and can be inserted into the different levels of the two-stage prepress.
According to the principles of this invention, the transport means in and adjacent the prepress are constituted by conveyor belts and, where support or carrying trays are not provided for the layers, the conveyor may have an inclined discharge end adapted to deposit the layer upon a subsequent conveyor without free fall or without the formation of gaps therebetween.
The system described above has significant advantages over the prior art, particularly with respect to the extremely short period or stroke and can be used for the production of very thin particle board or fiberboard as well as for the production of relatively thick pressed board.
DESCRIPTION OF THE DRAWING
The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompany drawing in which:
FIG. 1 is a somewhat diagrammatic elevational view illustrating a plant for the production of pressed board according to the present invention;
FIG. 2 is a detail view, greatly enlarged, of the region illustrated at II of FIG. 1;
FIG. 3 is a cross-sectional view taken along the line III -- III of FIG. 2;
FIG. 4 is a detail view of the region IV of FIG. 2 but illustrating another embodiment of the invention;
FIG. 5 is a view similar to FIG. 1 of the charging side of the prepress according to another embodiment of the invention;
FIG. 6 is a view similar to FIG. 5 illustrating still another embodiment; and
FIG. 7 is a detail view of another press charging device ahead of the prepress according to the present invention.
SPECIFIC DESCRIPTION
In FIGS. 1 - 3, we have shown an apparatus for the production of pressed board which comprises a dispensing station 2 having a plurality of hoppers 3 offset one behind the other in the direction of travel (arrow A) of the material adapted to form the pressed board 1. The hoppers 3 are provided with the usual dispensing heads 3a, 3b and 3c for respectively depositing a layer of fine particles, a layer of coarse particles and another layer of fine particles upon a conveyor 3d to form a layer 14 which may be subdivided transversely to the direction of movement to form respective mats or layers.
At the other end of the production line, there is provided a multiplaten press 4, represented diagrammatically in the drawing and preferably of the type described in commonly assigned U.S. Pat. No. 3,050,777 and 3,209,405. The dispensing devices 3, 3a, 3b and 3c as described in commonly owned U.S. Pat. No. 3,282,767, the layers being trimmed and shaped as described in U.S. Pat. No. 3,051,219, 3,096,227 and 3,428,505. The conveyor 3d may be of the type described in commonly owned U.S. Pat. No. 3,224,758.
Flanking the press 4, there are provided a charging rack 5 and a discharging rack 6 which may be formed with conveyor tablets or conveyor-band tablets for advance of the pressed board or the layers (see U.S. Pat. No. 3,565,725).
Between the multiplaten-press charging station 5, which operates as described in U.S. Pat. No. 3,565,725, and the layer-forming station 2, there is provided a conveyor arrangement which includes a two-level platen press 8 (i.e., the prepress) and means for charging and discharging this prepress (i.e., the service devices for the prepress) together forming part of the transport path.
At the upstream of the prepress 8, i.e., between the conveyor 3d and the prepress, there is provided a charging device 9 while a discharging device 9' is provided between the prepress and the charging rack 5.
The two-level prepress 8 is an alternate-cycle press which is shown in an open condition in FIGS. 1 and 2. More particularly, the press 8 comprises a fixed central bed 10, preferably in line with the conveyor 3d and the general transport path, which is mounted in a frame 10a and carries an upwardly facing heated or unheated bed plate 10b and a downwardly facing heated or unheated bed plate 10c. Juxtaposed with these platens are an upper platen 11 carried by the pistons 11a of a hydraulic cylinder arrangement 11b schematically shown in FIG. 3, while a lower platen 12 is carried by pistons 12a of cylinders 12b for movement toward and away from the plate 10c.
The press platens 11 and 12 are thus shiftable independently of one another and in alternate half cycles, the charging device 9 and the discharging device 9' likewise operating in alternation to feed and discharge the two-stage prepress 8.
The charging device 9 comprises a pair of conveyor-band tablets (see U.S. Pat. No. 3,565,725), of which at least the upper one is vertically movable while the discharge device comprises conveyor-band tablets 7', the upper member of which is vertically displaceable. The stages of the press can be provided with conveyor belts 20 for advancing the layers into and out of the press.
The system of FIGS. 2 and 3, shown to use press-charging trays, operates as follows:
A prepressed slab 13 of the comminuted material lies upon the lower press platen 12 and, when its conveyor 20 is driven, carries the slab 13 onto the lower conveyor 7' of the discharge device 9'. The conveyors 20 may be driven or undriven and, in the latter case, the prepressed body may be shifted from the prepress by the introduction of a new layer 14 upon its charging tray 19. During this period, the upper press platen 11 closes to compact the layer 14 therein, the previously discharged body 13 being carried by the upper conveyor 7' of the discharge device 9' in the direction of arrow B, the conveyor carrying member 13 having lowered from the dot-dash position previously. The upper stage 15 of charging device 9 is, during this period, provided with a new layer 14 as the layer 14 of the lower stage 17 is advanced into the press.
When the upper stage 16 of the press opens, the alternate half-cycle commences, i.e., the platen 12 closes to compact the new layer 14 deposited thereon. The lower conveyor 7' of the discharge device 9' rises into alignment with the upper conveyor 20 and the prepressed layer of the upper stage 16 is deposited upon this conveyor of the discharge device. Meanwhile, the conveyor 15, in its upper position, deposits a layer 14 of uncompacted comminuted material in the upper stage 16.
In the embodiment illustrated in FIGS. 1 - 3 the service devices 9 and 9' are provided with conveyor-belt stages, the belts 18 of which are driven alternately in the previously described pattern with automatic or programming means of conventional construction.
When a charging plate 19 is not used, the conveyors may have the configuration shown for the conveyor 21 of FIG. 4, i.e., the conveyor may have a transfer blade 22 which can be shifted from the right to the left to overlie the conveyor 20 and deposit the mat 14 thereon smoothly and uniformly (see U.S. Pat. No. 3,565,725).
In FIG. 5, we show a modification in which the dispensers 103 of the dispensing station 102 deposit the layer 114 of comminuted material upon a conveyor 103d for subdivision into mats, as previously described but not here illustrated. Ahead of the charging device 109, provided with conveyors 107, as previously described, there is provided a swinging platform or tipple 109a which can deposit the mats selectively upon the conveyor belt 107. The charging device 109, of course, is operated in the manner previously described to feed the mats alternately to the lower press platen 112 or the upper press stage 116 of the prepress 108.
In the modification of FIG. 6, the swinging platform 209a is provided between a conveyor 9a and the press, the system otherwise being similar to that of FIG. 1. FIG. 7 shows that the conveyor tablets 307 can be provided with a parallelogrammatic linkage 307a for movement into and out of the prepress to deposit the mats therein.
The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.