US3611482A - Installation for the production of pressed board - Google Patents

Abstract

A CONTINUOUS LAYER OF COMMINUTED MATERIAL IS STREWN ONTO A CONTINUOUSLY MOVING FIRST CONVEYOR AND IS DIVIDED INTO SEPARATE MATS AND IS PRECOMPRESSED UNDER A DRUM. THE FIRST CONVEYOR FEEDS THE MATS TO A SECOND CONVEYOR OVER A JUNCTION BETWEEN THE CONVEYORS WHICH CAN BE RECIPROCATED LONGITUDINALLY. THE DOWNSTREAM END OF THE SECOND CONVEYOR CAN BE ALSO BE LONGITUDINALLY RECIPROCATED TO DEPOSIT THE INDIVIDUAL MATS ON ONE OF A GROUP OF SUPERPOSED TIER CONVEYORS WHICH ARE INDIVIDUALLY OPERABLE TO PICK UP THE MATS AND JOINTLY OPERABLE, E.G. BY A RACKAND-PINION ARRANGEMENT TO DEPOSIT THE MATS ON THE PLATENS OF A MULTILEVEL PRSS. THE SECOND OR ACCELERATING CONVEYOR IS OPERABLE AT TWO SPEEDS: A RELATIVELY LOW SPEED CORRESPONDING TO THAT OF THE FIRST CONVEYOR AND A RELATIVELY HIGH SPEED CORRESPONDING TO THAT OF THE TIER CONVEYORS. IN THIS MANNER, WITH SEQUENCED SPEED CHANGE OF THE SECOND CONVEYOR AND RECIPROCATION OF THE JUNCTION, THE MATS ARE SEPARETED FROM ONE ANOTHER. A CHUTE BELOW THE DOWNSTREAM END OF THE SECOND CONVEYOR CAN RECEIVE DEFECTIVE MATS OR MATS WHICH CONTINUE TO BE FED WHILE THE CHARGING RACK EMPTIES INTO THE PRESS.

Description

Oct. 12, 1971 s. HUTZ 3,611,482

INSTALLATION FOR THE PRODUCTION OF PRESSED BOARD Filed Oct. 1, 1969 5 Sheets-Sheet 1 g 3 l S INVliN'l (m; Gerhard Hut:

0 Y m g m 43 53 [MA m. R t t w k n R @w k @m i. l .m mmm m 5 F WHHH M Ov W 0 V Mb v M Q H mm m t qw w A Oct. 12, 1971 G. HuT'z 3,611,482

INSTALLATION FOR THE PRODUCTION OF PRESSED BOARD Filed Oct. 1, 1963 I 5 Sheets-Sheet 8 Fl 2 I Ger hafd HUfZ INVIiN'IUR.

A {Ross Attorney Oct. 12,1971 G. HUTZ 3,611,482

INSTALLATION- FOR THE PRODUCTION OF PRESSED' BOARD Filed Oct. 1. 1969 5 Sheets-Sheet 3 Attorney G.Hu1"z INSTALLATION FOR THE PRODUCTION OF PRES SED BOARD Filed Oct. 1. 1969 Oct. 12, 1911 5 Sheets-Sheet 4 a 9mm Gerhard HUfz IN VIiN OR SS r TD Attorney 0a. 12 1971 G. HUTZ 3,611,482

INSTALLATION FOR THE PRODUCTIONVOF PRESSED BOARD Filed Oct. 1, 1969 5 Sheets-Sheet 6 fa 5c Gerhard HU'fz v; INVIiN'l ()R. Q

Attorney United. States Patent Olfice Patented Oct. 12, 1971 3,611,482 INSTALLATION FOR THE PRODUCTION OF PRESSED BOARD Gerhard Hutz, Suchteln, Germany, assignor to Firma G. Siempelkamp & (30., Krefeld, Germany Continuation-impart of application Ser. No. 712,202, Mar. 13, 1968. This application Oct. 1, 1969, Ser. No. 862,881 Claims priority, application Germany, Nov. 22, 1868, P 18 240.4 Int. Cl. B29j 5/08 US. Cl. 184 R Claims ABSTRACT OF THE DISCLOSURE A continuous layer of comminuted material is strewn onto a continuously moving first conveyor and is divided into separate mats and is precompressed under a drum. The first conveyor feeds the mats to a second conveyor over a junction between the conveyors which can be reciprocated longitudinally. The downstream end of the second conveyor can also be longitudinally reciprocated to deposit the individual mats on one of a group of superposed tier conveyors which are individually operable to pick up the mats and jointly operable, e.g. by a rackand-pinion arrangement to deposit the mats on the platens of a multilevel press. The second or accelerating conveyor is operable at two speeds: a relatively low speed corresponding to that of the first conveyor 'and a relatively high speed corresponding to that of the tier conveyors. In this manner, with sequenced speed change of the second conveyor and reciprocation of the junction, the mats are separated from one another. A chute below the downstream end of the'second conveyor can receive defective mats or mats which continue to be fed while the charging rack empties into the press.

This is a continuation-in-part of my copending application Ser. No. 712,202, now Pat. No. 3,518,728, filed on Mar. 13, 1968 and entitled, Apparatus for the Manufacture of Pressed Board.

The present invention relates to an installation for producing pressed board.

In the commonly owned copending application Ser. No.

702,026 (Pat. No. 3,565,725), filed Jan. 31, 1968, there is described and claimed a method of producing pressed board from comminuted and loosely coherent material as well as an apparatus for carrying out this method in serriatum. The serial production of pressed boards and sheets from comminuted and generally fibrous material (usually cellulose) which may be admixed with or inherently contains a thermally activatable binder, has been proposed heretofore. For the most part these earlier methods have involved the dispensing of the comminuted material onto a surface to form a generally flat and hopefully uniform layer thereon, the surface being conveyed into a press. The system of this prior application represents a marked improvement over earlier arrangements in which charging plates are employed and must be recirculated to the mat-forming dispensing station after the press has been discharged. The improved system provides a conveyer means at a stationary dispensing station whose upper surface receives a layer of comminuted material and carries this layer into a stationary intermittently operable press spaced from its dispensing station. The conveyor has a first portion driven past the dispensing station at a substantially constant speed for continuous deposition of the comminuted material to form the layer, a further portion of the conveyor means being intermittently driven to carry the layer into the press. This system is arranged to transfer sections of the layer of comminuted material, in the form of mats, onto the intermittently operable conveyer without changing the speed or interrupting the continuous drive of the first conveyer portion.

The system of the prior application also makes use of so-called conveyor pallets or tablets which constitute a substitute for the charging plates of earlier systems and consist of relatively thin assemblies formed by an endless con'veyer band which may be held stationary or driven to retain or displace the mats and pressed sheets. The two-part conveyer system previously described may be used to advance a successionof sheets to a charging station at which a stack of such conveyer pallets is provided, the stack being elevated in step with the supply of the mats to dispose each of the mats upon a respective conveyer pallet or level of the stack. Thereafter, the conveyer pallets may be concurrently advanced onto the respective levels of the press and/or an intermediate charging rack adjacent the press to deposit, by rotation of the respective bands, each of the mats onto a respective press platen for compression. The conveyer pallets or tablets may thus be deemed to be charging stages or levels of a multilevel charging rack with conveyer bands forming the receiving surface of each level; they are synchronously shiftable into the press and, during their return movement (in the rearward direction) can have their receiving surfaces synchronously displaced in the forward direction so that relative movement of the mat and the platen is zero and the mat is deposited upon the press platen without material distortion. The charging of the individual conveyer tablets is carried out by positioning the successive conveyer tablets at a charging level, via the discharge end of a conveyer (e.g. of the type described in my copending application Ser. No. 712,687 (Pat. No. 3,482,675), entitled, Twin Conveyer System for the Transport of Loosely Coherent Mats, filed Mar. 13, 1968). The discharge tongue of this conveyer is disposed at the trailing edge of the conveyer tablet which is driven at the speed of the conveyer band to shift the mat onto the tablet with minimum distortion. The charging rack is then raised to position the next conveyer tablet to receive the mat, and the procedure is repeated until the rack is fully charged. At this time, assuming completion of the previous cycle, the conveyer tablets are advanced synchronously into the press to deposit their mats upon the respective plates in the manner previously described.

A problem arising in this system, however, is that the mats are not always positioned centrally upon the platens by the charging conveyer tablets. As a result, nonuniform stresses develop in the press with detriment to the press structure and with formation of nonuniform pressedboard sheets.

The parent application thus provides an improved system for the charging of presses with loosely coherent mats of the character described which is designed to overcome the disadvantages arising from noncentral placement of the mats.

This object is attained, in accordance with the parent application, by providing means for adjusting the position of the mats, independently of variation in length, substantially centrally upon the conveyer tablet and/ or the press platen, such means including at least at one level of a charging stage or press stage a sensing beam of radiation which is interruptible by the leading edge of the latter associated with this stage to then immobilize the charging con-veyer tablet to precisely position this leading edge in its desired position so that it will lie centrally in the press; the control means includes a servomotor driving the conveyer band thereof or a servomotor positioning the conveyer tablet within the press as will be apparent hereinafter.

According to a more specific feature of that system, the leading-edge detector is a light beam projected across the path of the mat at the charging level of the conveyer talblet rack and is connected via the usual amplifier and servosystems with the drive motor for the conveyer band of each of the conveyer tablets as it is positioned at the mat-receiving level so as to terminate advance of the conveyer band when the leading edge is properly positioned on the rack to result in central positioning of the mat when the latter is disposed in the press by the conveyer tablets.

In general terms, therefore, it can be said that a priorart installation for the production of fiber board, this term being used generically to include pressed board made with sawdust wood chips, pulverized wood, cellulose particles derived from wood and other sources, and structural or decorative sheets of composite material which are rendered coherent by pressing a layer of the comminuted material, basically comprises a strewing station in which one or more layers of the comminuted material are deposited upon a flat surface, a charging station or rack with a plurality of levels disposed one above an other and along with the platen of a multiplaten press, the multiplaten press, a press-discharge station adapted to receive the compacted sheets from the press, and transport means between these various stations to ensure delivery of the mats of comminuted material to the press and the withdrawal of the individual compact sheets therefrom.

In systems prior to the developments described in the aforementioned applications, it has been necessary, for the most part, to make use of charging plates or trays upon which the individual mats were disposed and which served to carry the loosely coherent comminuted layers into the press.

Only after the layers were compacted, was it possible to remove the compacted material (sheets) from the plates, i.e. to separate the charging plates from the sheets, and return the plates to the dispensing or strewing station for reuse. Upon such separation, the compacted sheets may be handled without the danger of damage to the finished product.

It is self-evident that the use of charging plates of this type has the significant disadvantage that considerable space is required to accommodate the return and storage of the charging plates from one end of the production line to the other, that the dimensions of the various stations must be increased to accommodate the added load and dimensions of the charging plates, and that the need to return and store the charging plates involves possible delay in the production sequence and considerable handling expense.

To avoid these disadvantages, the use of so-called conveyer tablets and various conveyer-belt arrangements has been proposed, the principle of these systems being that the loosely coherent mats may be handled by conveyor belts in which there is no substantial relative movement of the upper reach of the conveyor belt and the material deposited thereon. These systems have \been described in the copending applications mentioned earlier.

It is, therefore, the general object of the instant invention to extend the principles set forth in the parent application to make an improved installation for the production of pressed board.

Another object of the invention is to provide a plant of the character described whereby the dispensing station is continuously operable.

A more specific object is to provide such an installation which allows a mat of very low coherence to be conveyed from the dispensing station to the press without distorting them.

Yet another object is to provide such an installation which can operate at high speed and which can selectively discard any imperfect mat prior to pressing without greatly interrupting the Work cycle of the installation.

In recent years, there has been an increasing tendency to make use of natural or synthetic-resin binders, preferably of the thermally activatable type, in conjunction with it comminuted material mentioned earlier, such binders increasing the structural strength, rigidity, impermeability to fluid and the aesthetic appearance of the pressed board emerging from a hot-platen, multilevel press. I have now found that the use of such binders, e.g. phenol-formaldehyde, resorcinol-aldehyde, urea and melamine-type resins, as additives to the comminuted materials, and the use of residual quantities of the abietic resins naturally present in wood fibers, imparts to the layers of comminuted material to be converted into pressed board, especially structural board, sufiicient cohesion in the mat stage as to permit the process to be carried out continuously without distortion or damage to the comminuted materials, using conveyor belts and the like, at economical speeds and substantially no incorporation of the press cycle or of the strewing station opera tion. For example, it has become a common practice, as also noted in the aforementioned applications and the prior application to which they refer, to provide a plurality of strewing or dispensing devices at the strewing station to deposit successive layers of comminuted materials, thereby forming a composite mat in the sense that it is composed of a plurality of distinct superimposed layers which, upon compression, are united into an integral body. It has been found, in connection with such systems, especially where, for example, a layer of relatively fine particles is initially to be deposited upon the receiving surface to be followed by one or more layers of relatively coarse particles and a final layer of relatively fine particles in the formation of a sheet having surface zones of fine appearance, that intermittent operation of the strewing station and the dispensing devices at the latter give rise to irregularities in the layer formation and result in a high proportion of defective boards. Accordingly, the art has long sought a system whereby the continuous operation of the dispensing station can be ensured.

The aforementioned objects are attained and the desired results achieved, in accordance with the present invention, which is based upon my discovery that a layer of comminuted material containing binder of the aforedescribed type permits handling in a manner not heretofore possible, because of the increased coherence of the unpressed layers, which may be of the single layer or multilayer type as described above, prior to precompression or subsequent thereto. The invention resides in the provision of a conveyor means which continuously operates at the dispensing station and transfers the continuously formed uniform material, after initial subdivision 1nto mats, to an accelerating conveyor with a minimum of relative movement of the latter conveyor surface and the mats during transfer, the accelerating conveyor, in turn, feeding the mats onto superimposed band or conveyor tablets of a charging rack, also with a minimum of relative movement of the transferred mats and the receiving surface of these band tablets. The charging rack receives the mats in succession and thereafter transfers all of the mats of its bank of conveyor tablets onto the respective levels of a multiplaten press substantially simultaneously.

According to an important feature of this invention, prior to subdivision of the mats at a sawing station, in which individual mats sections are severed from the continuous layer body emerging from a dispensing station by a transversely moving saw blade provided with a suction hood for removal of the detritus of the severing operation, a prepressing system is provided in the form of a large-diameter drum against which the continuous layer is urged from beneath a continuously moving conveyor surface. The conveyor cooperating with the precompressing drum passes over an anvil member which, in accordance with a more specific feature of the invention, is formed along its upper surface with a multiplicity of nozzles through which a gaseous or liquid pressurized fluid is forced to maintain a fluid cushion between the conveyor band and the anvil surface. This cushion has the dual function of providing the pressure necessary to hold the continuous layer against the drum with the desired precompression pressure and providing a lubricating film between the conveyor band and the anvil surface to facilitate continuous movement of the conveyor band therepast.

At the inlet side of the multiplaten press, I provide means cooperating with the charging rack or operable in synchronism therewith for engaging the previously formed sheets in the press and pushing them at least partly out of the latter so that they may be engaged, at the discharge side of the press, between respective bars of mangle-type rollers, the latter withdrawing the finished sheets from the press and supplying them to a destacking station from which the plates may be fed in succession to a tempering kiln or the like.

An installation for the production of pressed board in accordance with the invention allows a continuous layer of comminuted material to be formed on a moving transport surface at a dispensing station, a succession of longitudinally spaced loosely coherent mats to be formed from the layer at a separating station, and finally the compaction of the mats pressed in a multilevel or multiplaten press.

This installation has a first conveyor which receives the succession of spaced-apart mats and operates at a substantially constant speed to form the transport surface. A second conveyor downstream of the first conveyor forms therewith a longitudinally reciprocable mat-transferring junction which aids in the transfer of the mats from the first to the second conveyor without distortion. Finally, a charging rack is provided between the press and the downstream end of the second conveyor, which rack has a number of superposed tiers each corresponding to a respective level of the press and formed by a respective endless tier conveyor. These tier conveyors are mounted on a common frame which is vertically and horizontally reciprocable and are individually operable to receive a mat from the second conveyor while being jointly or simultaneously operable to deposit the mats on the respective levels of the press, the entire rack being shifted horizontally in between the press platens for this latter operation.

The second conveyor is operated at a relatively low speed corresponding to the speed of the first conveyor to accept the mats therefrom and is operated at a relatively high speed corresponding to the operational speed of the tier conveyors to transfer the mats to the tiers of the rack.

According to a further feature of the present invention, the mat-transferring junction between the first and second conveyors is reciprocable by making the downstream end of the first conveyor closely overlie the upper surface of the second conveyor and by reciprocating merely this first conveyor end. To do this the first conveyor consists of a pair of endless bands one inside the other, the inner one of which is driven while only the outer one extends over the second conveyor. This outer band or belt is spanned over a relatively pointed discharge nose or tongue which allows transfer of the mat from one belt to the other without distortion.

In accordance with yet another feature of the inven tion the extreme downstream end of the second conveyor can also be reciprocable back and forth over a discard chute. This reciprocation allows the charging rack to be raised or lowered as the tiers are filled, while permitting easy discarding of any imperfect mat.

In an alternative embodiment of the installation, the outer belt of the first conveyor is spanned over a tongue or table as is the extreme upstream end of the second conveyor band. This forms the mat-transferring junction between the ends of the two belts that is virtually gapless so that the mats can pass over it without being distorted. The two tables, bars or tongues which define this gap are then reciprocated back and forth with a rhythm which will be described more fully below.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description, reference being made to the accompanying drawing, in which:

FIG. 1A is a partially schematic side elevational view of a portion of an installation according to the present invention;

FIG. 1B is a view similar to FIG. 1A of the remainder of the installation shown therein;

FIG. 2 is a detail of FIG. 1B in enlarged scale;

FIG. 3 is another detail of FIG. 1B, in enlarged scale;

FIG. 4 is a view similar to that of FIG. 3 showing an alternative embodiment of the invention;

FIG. 5 is yet another detail of FIG. 1B, in enlarged scale;

FIG. 5A is a detail view constituting a variant of FIG. 5;

FIGS. 6 and 7 are largely schematic views showing the operation of the installation according to the present invention;

FIG. 8 is a top view of a detail of FIG. 1A;

FIG. 9 is a side-sectional view showing part of the installation according to another embodiment of the invention; and

FIG. 10 is a plan view of a part of the plant.

As shown generally in FIGS. 1A and 1B, the installation for making pressed board consists of a dispensing station 1, a charging rack 2, a platen press 3 and an unloading rack 4, with a first conveyor 5 and second, gapincreasing accelerating conveyor 6 connecting the dispensing station 1, which consists of five hoppers 1ae, to the loading rack 2. The conveyor belt 5 has an extreme downstream end 7 which can reciprocate horizontally and the belt 6 has a similar downstream end 8.

Between the dispensing station 1 and the second conveyor 6 is a subdividing device 9 which can move back and forth across the band 5 while being able to move with the band 5 for a short distance. The commonly assigned US. Pat. No. 3,428,505 issued on Feb. 18, 1969 to E. Siempelkamp and entitled, Method of and Apparatus for the Production of Pressed Board, describes such a device which is equipped with a vacuum arrangement 23 to pick up the waste fibers made as the device 9 forms a gap 14a between two mat sections 14 on the conveyor 5.

Between the subdividing device 9 and the dispensing station is a precompression station 30. The conveyor 5 consists of a very stiff inner belt 22 spanned between rollers 22a and 22b and extending just under the area of the precompression station 30 and the subdividing device 9. Outside this belt 22 is another belt 20 which extends the full distance between the dispensing station 1 and the subdividing device 9. Finally, a third belt 21 of lighter and more flexible properties than belts 20 and 22 extends the full way between the dispensing station 1 and the edge 7. The belts 22 and 20 serve to reinforce the belt 21 at the points where it is stressed most greatly.

The precompression device 30 consists basically of a roller 19 having a diameter D at least ten times greater than the thickness 1 of the continuous layer 47 formed by the hoppers la-e. As shown in greater detail in FIG. 8, below the roller 19 is a counterpressure block 31 formed on its upper fiat side with a plurality of nozzle openings 31a which communicate with the hollow interior of the block 31 which is in turn pressurized through a conduit 31b connected to an air compressor 310. In this manner, an ideal pressure of 2 to 3 kg./crn. can be exerted between the roller 19 and the block 31 to precompress the layer 47 without wearing the belts 20-22 to any great extent as is done in most prior-art devices. Although such precompression is not a necessity, it facilitates later handling of the mats 14 and generally improves the overall quality of the finished pressed board.

In FIG. 9 I show an arrangement wherein a continuous operable conveyor delivering the layer to the subdividing arrangement 9 is, in turn, formed of three successive conveyor bands. A conveyor band receiving a multilayer stack of comminuted material from the dispensers 1a-1e, is provided with a discharge end formed with a transfer tongue 105a, the upper surface of which is represented at 1051; and is horizontal and overlies the rising path of a conveyor band 205 adapted to carry the continuous layer beneath the precompression drum 30.

The band 105 is turned around the rounded acute anglevertex 1050 and then passes along the downwardly and rearwardly inclined face of the tongue 105a to minimize distortion of the layer as the transfer from band 105 to band 205 occurs. To this extent, the transfer or junction of the band is similar to that represented in FIG. 3. and discussed in greater detail below.

The band 205, in turn, passes around a conveyor roller 205a whose left hand outline 205b lies beneath the vertex 1050 of the tongue 105a so that the upper left-hand quadrant of the rotation of the roller 205a carries the band 205 upwardly to pick up the layer displaced along the conveyor 105 in the direction of arrow 1052 and continue the movement of this layer in the original horizontal plane as represented by arrow 205C.

The band 205, which is individual to the precompressing station in this embodiment, passes beneath the fixedly positioned drum 30 such that the distance 205d between the lowermost portion of drum 30 and the upper face of band 205 defines the thickness of the precompressed layer advanced toward the mat-forming station.

At this region of precompression, the band 205 passes over an anvil 131 which lies in a horizontal plane at a spacing from the drum 30 approximately equal to the sum of the thickness of the band 205 and the gap 205d. The anvil 131 has a box-like lower portion 131a whose interior defines a chamber 13111 communicating with the nozzle perforations or apertures 1310 of a cover 131d for the lower portion, the upper surface 131e of this cover confronting the underside 2052 of the belt 205. Compressed air or, as shown in FIG. 9, a hydraulic fluid is supplied under pressure to the chamber 131b via a pump 131 to form a lubricating and pressurizing cushion between the surfaces 1312 and 205e, reducing the drag on the band 205 and producing a pressure in the direction of arrows 131g of 2 to 3 kg./cm. this pressure being the pressure with which the layers are precompressed. A pan 131h, underlying the band 205, collects the hydraulic fluid and feeds it to a reservoir 131 from which it is withdrawn by the pump 131 The precompressed layer emerging from beneath the drum 30 passes over a table 205 at the discharge end of the conveyor 205, this table having a horizontal surface 205g which adjoins a downwardly and rearwardly inclined flank 20511 in an acute-angle vertex 205 as shown at the right-hand side of FIG. 9. Flank 205k insures that the return stretch of the band 205, after passing about the edge 205 closely parallels the upwardly moving stretch 305a of the succeeding conveyor band 305 which carries the precompressed layer continuously to the mat-forming station.

At its upper reach 30512, the band 305 passes from an upwardly and forwardly inclined flank 305C of a table 305d onto the horizontal surface 305e which is coplanar with the surface 305g. Surfaces 305:: and 3052 adjoin one another in an obtuse angle at 305 corresponding to the supplementary angle of the vertex 205i. Moreover, the rising stretch 305a of the band 305 is held beneath the discharge edge 2051' of the preceding belt 205 by a roller 305g. Thus the transfer of the layer between belts 205 and 305 is effected in a manner similar to that illustrated in, and discussed with reference to, FIG. 4.

FIGS. 1B and 2 show more specifically how a mattransferring junction 35 is formed between the ends of the two conveyors 5 and 6. The belt 251 is spanned over a beam or table 7 and over a roller 38 and is driven by a motor 42. The belt 6 is spanned over a similar board or table 36 and a drive roll 34 connected to a motor 41. The two beams 7 and 36 are jointly coupled (since they are fixed relative to each other) to a cylinder 49 which can reciprocate them horizontally according to an operation sequence which will be described below.

The junction 35 is very narrow since the edge 37 of the board 36 comes very close to the board 7 so that the mats 14 can pass across it with no distortion. If the speeds of the two conveyors 5 and 6 are identical, reciprocation of the gap 35 caused by the cylinder 49 will have no effect on the mats 14. Also, the angle of the gap formed at the junction 35 is advantageously inclined into the direction of travel of the mats 14. The roller 38 is preferably spring biased toward the left in FIG. 1A so that as the gap 35 is moved back and forth it can take up the changes in length of the belt 21. Here, too, the discharge edge 7a of the continuous conveyor (5, 305) overlies the rising stretch of the accelerating conveyor 6 and extends beyond the rearmost outline 34a of the roller 34.

The conveyor 6, as shown in FIGS. 1B and 3 has a downstream end 8 which can be reciprocated back and forth like the junction 35, with a spring-biased roller 39 taking up the changes in effective length of the belt 6.

Directly downstream of the end 8 as shown in FIG. 1B is a chute 11 which is covered by a flap 10 that can open to receive a mat 14. Some means of flaw detection, as a lamp and a line of photoelectric cells, is preferably coupled to this flap 10 to open it and to prevent the end 8 from moving to the right should an imperfect mat 14 arrive on the belt 6. The trough orchute :11, which extends horizontally transversely of the transport path, forms a downwardly convergent hopper terminating in a duct 11a leading to a suction blower 1112 which returns the comminuted material to the dispensing station 1a'1e.

The charging rack 2, as shown in FIGS. 1B and 5, consists of a plurality of tier conveyors 12 carried by a frame 15 which can be moved up and down by a cylinder 48 and back and forth by a cylinder 51. A motor 24 mounted fixedly on a leg 52 supporting the frame 15 is provided with teeth 25 forming with recesses 27 in a shaft 26 which serves to drive a belt 13 through a roller 54. Also mounted on this shaft 26 is a pinion 28- which is connected thereto by a freerunning or unidirectional clutch (not shown) which grabs on rotation of the shaft in direction A but idles in direction B. Such a freerunning clutch is described on p. 8-51 of Mechanical Engineers Handbook (McGraw-Hill; 1964). This pinion 28 meshes with a rack 29 fixed to the uprights 52. FIG. 5A shows a modification wherein the rack 29 is replaced by a chain .129 engaging the sprocket 128, the system otherwise being equivalent.

In this manner, the motor 24 can be coupled to each conveyor 12 as it is placed in line with its clutch teeth 25 and can drive this conveyor in direction A to take on a mat 1-4. When the whole rack 2 is full, the cylinder 51 is actuated to move the frame 13 to the left, thereby causing the pinion 28 to roll along the rack 29 while the shaft 26 does not turn. As the conveyors 12 are withdrawn, however, from the press 3 the clutch locks and causes the roller 54 to turn in direction A at a speed exactly equal to the withdrawal speed, since the diameter of pinion 28 is the same as that of the downstream roller of the conveyor 12.

The press 3 consists of a plurality of platens 16 between which the loosely coherent mats 14 are pressed, under the effects of heat, to form hard pressed boards 17. A cylinder 50 closes the press 3. The commonly assigned US. Pat. No. 3,050,777 issued on Aug. 28, 1962 to E. Siempelkamp and entitled, Multiplaten Press, describes such a press.

FIG. 4 shows how, if there is enough room between the tiers of the rack 2, a table 40 can be used to guide the downstream edge of the belt 13 so that the edge '8' need not be as pointed as that of FIG. 3. With a blunter edge 8 the belt 6 tends to last longer.

Between the press 3 and the rack 2 is an upright arm 32a mounting a plurality of pushers 32 which bear against the finished boards 17 as the rack 2 is shifted to the right to push them out of the press 3.

As shown in somewhat more detail in FIG. 10, a previously formed plate 17 may rest upon each plate of the multiplaten press 3, the charging side of which is shown diagrammatically in FIG. 10. Each plate 16 is associated with a respective tier conveyor 13 of the charging station 2, the tier conveyors or band tablets 13 being jointly shiftable toward the press 3 on support frame 15 within the charging rack 52. To this end, horizontal guide rails 2a and 2b, shown flanking the frame 15, may be provided, the piston 51, shown diagrammatically in FIG. 1B, being employed for this purpose. The upright arm 32a is here shown as a frame carried by bars 32b and supporting the pushers 32 which lie just below the transfer nose 13a of the respective band tablet 13 when the latter are prepared to deposit their mats upon the platens 16 of the press. The pushers 32 are, however, aligned with the rearmost edge 17a of each respective finished plate 17 so that a movement of the frame 32a to the right (arrow 320) will force each plate 17 into engagement between a respective pair of the rollers 33, the latter drawing sheets out of the press while the conveyors 13 enter the latter to deposit these sheets. The transfer between conveyor tablet 13 and the press platen 16 is effected with the aid of the transfer nose 13a which performs in the manner of the transfer nose 7 shown in FIGS. 6 and 7. The bar 32b may be slideably received in the frame members 15 and may be urged by tension springs 32d to the right so that, after the pushers 32 have shifted the board 17 to the rollers 33, the frame 32a can engage the press while continued displacement of the frame 15 and conveyors 13 to the right is possible. Upon retraction of the frame 15, the frame 32a and the pushers 32 are restored to their original positions.

Immediately to the right of the press 3 is a plurality of the driven mangle-type rollers 33 which grip the boards 17 as they come out of the press 3 and pull them into the rack 4 from which they are unloaded one-by-one from the bottom by a conveyor 18. The rack 4 of the discharge station can be vertically stepped (downwardly) to permit the individual plates to be shifted to the right from below (destacked) by the conveyor 18.

A typical operational sequence is described below:

As the conveyor 5 moves at a constant speed the hoppers 1ae dispense fibrous comminuted material, with the end hoppers 1a and 1e distributing the finest grade, to form an even layer 47 on the upper belt 21. This layer 47 is compressed at a pressure of 2 to 3 kg./cm. by the roller drum in the precompression station 30. The sub- .dividing device 9 travels with the layer 47 for a short length as it transversely cuts it into mats 14 separated by spaces 14 (see US. Pat. No. 3,428,505).

As a mat 14 arrives at the end 7 of the band 21, as shown in FIGS. 1B and 6, either the edge 7 moves to the right over the band 6 as shown in FIG. 6 or the junction 35 moves correspondingly to the right until it arrives at about the middle of band 6. At this moment the tip 7 is immediately and rapidly withdrawn such that the entire mat 14 is left resting on the band 6. All this time the speed of bands 5 and 6 has been synchronized by the control 43 through the motors 41 and 42.

Once this mat 14 rests fully on the band 6 the speed of motor 41 is immediately increased and, if the mat is a good one, the edge 8 is brought up adjacent to an empty conveyor 12 (FIG. 3) which is driven also at a high speed equal to the increased speed of the belt 6. Thus, as shown in FIG. 7, the mat is quickly and accurately passed onto the conveyor 12 which stopsthrough the aid of a photoelectric device as shown in the parent applicationand holds it once it is centered.

As one mat 14 is being quickly discharged, the nose 7 moves slowly to the right, at a speed equal to the normal transit speed of the belt 21 until it is in the middle of the band 6 again. The band 6 is again slowed down to a speed equal to that of belt 21 and the edge 7 is retracted as before to transfer the next mat 14. At the same time, the edge 8 is retracted and the frame 15 is raised to bring another conveyor 12 into line with the band 6. Thence, the operation is repeated, with any bad mats 14 being discarded into the chute 11 whence they are ground up and put in the hopper 1c. When a mat is discarded, the rack 2 is not indexed.

Once the rack 2 is full, the entire frame 15 with all conveyors 12 is moved to the right by the cylinder 51 so that each conveyor 12 is moved all the way into the press 3, with the arms 32a pushing the previously pressed boards out far enough to be gripped between the rollers 33 and pulled out. When the cylinder is actuated to retract the frame 15, the clutches lock and the mats 14 are rolled off onto the press platens 16 as is described above. Then the press 3 is closed.

The gap 14a between the mats 14 is advantageously wide enough to permit the various functionings of the machine. However, it might be necessary when the belt 21 is operated at high speed to discard a mat 14 during the press-loading operation to maintain continuity at the dispensing station.

I claim:

1. In an installation for the production of pressed board in which a continuous layer of comminuted material is formed on a moving transport surface and a succession of longitudinally spaced apart mats is subdivided from the layer and then the mats are compressed in a multilevel platen press, in combination:

first conveyor means receiving said succession of spaced apart mats and operable at a substantially constant speed;

a second conveyor adjacent to the downstream of said first conveyor means and forming therewith a direct mat-transferring junction longitudinally reciprocable to deposit said mats on said second conveyor without distortion;

a charging rack between said press and said second conveyor and having a number of superposed tiers each corresponding to a respective level of said press and formed by a respective endless tier conveyor, said tier conveyors being individually operable to receive a mat from said second conveyor and jointly operable to deposit the mats on the respective levels of said press, said second conveyor being operable at a relatively low speed corresponding to the speed of said first conveyor means for accepting mats therefrom and a relatively high speed corresponding to the speed of said tier conveyors to transfer said mats to the tiers of said rack upon alignment of said second conveyor and said tier conveyors, said second conveyor having a downstream end longitudinally displaceable toward and away from said charging rack and a position wherein said second conveyor is forwardly of the rearmost portion of the tier conveyors, said rack being vertically displaceable to align each one of said tier conveyors consecutively with said second conveyor and horizontally reciprocable into and out from said press between the platens thereof; and

unloading rack means downstream of said press for collection of the finished pressed boards therefrom.

2. The combination defined in claim 1, further comprising precompressing means for compacting said layer 53f said comminuted material prior to subdivision of said ayer.

3. The combination defined in claim 2, further comprising subdividing means downstream of said precompression means for longitudinally subdividing said layer into said succession of mats.

4. The combination defined in claim 3 wherein said subdividing means includes a saw arranged above said first conveyor means and is longitudinally displaceable therewith to subdivide said layer during transport thereof, and suction means for carrying ofl" material removed from said layer by said saw.

5. The combination defined in claim 1 wherein said precompressing means is located along said first conveyor means and includes a drum above said first conveyor and engageable with said layer and a counterpressure member below and having a surface juxtaposed with the underside of said first conveyor means.

6. The combination defined in claim 5 wherein said precompressing means further includes a source of fluid under pressure and said member is formed along its said surface with openings communicating with said source to form a fluid cushion between said first conveyor means and said surface of said member.

7. The combination defined in claim 1 wherein said first conveyor means includes at least two endless bands, one of said bands being inside the other, and the other only extending to said junction.

8. The combination defined in claim 7, further comprising precompressing means for compacting said comminuted material prior to longitudinal subdivision thereof, said first conveyor means further including a third endless band within said one of said bands and arranged below said precompressing means.

9. The combination defined in claim 7 wherein said second conveyor includes an endless belt, one of said bands of said first conveyor having a downstream end portion extending over and adjacent said belt, said portion terminating in a downstream edge longitudinally reciprocable relative to said belt.

10. The combination defined in claim 7 wherein said second conveyor includes an endless belt having an upstream end, one of said bands of said first conveyor means having a downstream end immediately adjacent said upstream end of said belt and forming therewith said junction, said ends being spanned over respective elements jointly longitudinally reciprocable.

11. The combination defined in claim 1, further comprising a disposal chute between said second conveyor and 12 said rack, said second conveyor being operable to shunt a mat into said chute.

12. The combination defined in claim 1 wherein each of said tier conveyors comprises a drivable shaft, a roller mounted on said shaft, an endless belt spanned over said roller, a unidirectional clutch mounted on said shaft, a pinion mounted on said clutch, and a member fixed relative to said conveyor and engaging with said pinion, said conveyors being jointly displaceable between the platens of said press such that said clutch allows relative movement between said pinion and said shaft on displacement into said press but locks said pinion and shaft together on withdrawal therefrom to deposit a mat on a respective platen.

13. The combination defined in claim 12, further comprising a motor operatively connectable to each of said shafts in succession for driving same.

14. The combination defined in claim 12, wherein each of said tier conveyors further includes an element extending transversely to the direction of transport thereof, said belt being spanned over said element, said element being at the extreme upstream end of said belt.

15. The combination defined in claim 14 wherein said element is rounded at its extreme downstream edge.

References Cited UNITED STATES PATENTS 2/1961 Thurnher 214--16.4 7/1967 Siempelkamp l9876 US. Cl. X.R. 189; 21416.4

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