US3232827A - Pulp molding apparatus utilizing multiple vat chambers - Google Patents

Description

Feb. 1, 1966 J. E. FOOTE ETAL 3,232,827

PULP MOLDLNG APPARATUS UTILIZING MULTIPLE VAT CHAMBERS Filed Nov. 4, 1964 INVENTORS JAMES E. FOOTE ROGER WELLS ATTORNEY United States Patent 3,232,827 PULP MOLDENG APPARATUS UTEIZING MULTIPLE VAT HAMBERS James E. Foote, Westport, and Roger Wells, Stamford,

Comm, assignors to Diamond International Corporation, a corporation of Delaware Filed Nov. 4, 1964, Ser. No. 408,899 14 Claims. (Cl. 162-228) The present application is a continuation-impart of application Serial No. 191,985 of James E. Foote, filed May 2, 1962, now patent No. 3,165,437.

The present invention relates to an improved pulp molding apparatus, and more particularly to an apparatus for forming molded pulp articles utilizing multiple vat chambers.

The use of molded pulp articles, such as meat trays, egg cartons, flower pots, etc, has become quite universal, generally because of the throw away character of the articles, ease in manufacture, relatively low cost, and the rapid rate and simplicity by which similar articles can be uniformly produced.

There is a constant endeavor in the industry to maintain the quality of the articles at a maximum, this generally being afforded by the consistency of the molding material used and the degree to which molding conditions can be controlled during article production. Many molded pulp articles, when mass produced, must be rejccted as imperfect due to excessive warpage, excessively thinned out sections, variation in weight along the length of the products, etc. Many of these problems, parti ularly a lack of uniformity iri weight of the articles along their length, are generally due to a lack of homogeneity of the article producing fibers in the pulp slurry; this lack of homogeneity is due to eddy currents in the pulp stock slurry. Other causes of lack of uniformity are due to the washing away of the pulp preform on the suction molds after deposition, the running of lightly held gelatinous pulp toward the trailing end of the dies as the dies leave the pulp slurry, etc.

Many attempts have been made in the prior art to overcome the problems of excessive warpage and lack of uniformity, but these have not always been entirely successful from the standpoint of either accomplishing of desired result or being sufliciently inexpensive, partly because some of the causes of warpage and lack of thickness regularity have not been known. The above mentioned application of James E. Foote has provided a first practical success in accomplishing the above ends.

It is, therefore, an object of the present invention to provide an improvement of the invention of James E. Foote, mentioned above, and described in application Serial No. 191,985 and filed May 2, 1962.

It is another object of the present invention to overcome the problems of the prior art, such as indicated above.

It is another object of the present invention to provide a new and improved apparatus for producing uniform pulp molded articles.

It is another object of the present invention to provide a uniform and consistent pulp slurry where the pulp fibers therein are uniformly consistent and properly oriented in a substantially undisturbed condition so that articles may be produced in controlled conditions without loss of time, excessive rejects, and without substantial modification of presently available equipment.

It is another object of the present invention to provide an apparatus which will prevent lightly held gelatinous pulp from running down toward the trailing end of a pulp molded article.

It is another object of the present invention to provide a pulp stock slurry in constant movement within a slurry tank to obviate flocculation and channelling so that a suction die in contact with the pulp stock slurry contacts a relatively homogeneous mass without material fiber disorientation or washing of the pulp preforms forming on the suction dies.

It is another object of the present invention to provide a relatively simple, inexpensive and highly effective apps.- ratus for accomplishing the above objects.

Other objects and the nature and advantages of the instant invention will be apparent from the following description of an exemplary embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectional side elevation, partly schematic, of one embodiment of an apparatus in accordance with the present invention;

FIG. 2 is a view, similar to FIG. 1, showing a preferred embodiment of the present invention;

FIGS. 3 and 4 are sectional views, partly schematic, showing a detail of the general apparatus of FIG. 2 as other embodiments; and

FIG. 5 is a partly schematic, broken away, sectional view taken in a plane perpendicular to the planes of FIGS. 14 through a typical suction die and showing two embodiments of requisite attaching means.

Referring to the drawings in detail, wherein like reference characters are used to designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a suitable suction die carrier generally at ll), which preferably takes the form of a revolving molding drum 12 which may rotate continuously or intermittently about its axis 13. The drum 12 has a plurality of suction molding dies 14 spaced peripherally thereabout and connected via hollow spokes to a source of vacuum as is well known in the art. A curved molding vat shown generally at 16 is provided in essentially complenemtary facing relationship to the drum 12. The vat 16 is provided with suitable bottom and side Walls, described below, and is adapted to contain a fibrous pulp stock slurry. A stock entrance 18, a vat discharge exit 2t) and an overflow exit 22 are provided for the vat 16. A circulating pump 24 (note FIG. 2) is provided to recirculate pulp stock between the exits 2t) and 22 and the entrance 18.

At the discharge or exit end 20 of the vat 16 is provided a stock reservoir 26 into which a suit-able supply of pulp stock slurry is introduced; the reservoir 26 communicates with an inlet conduit 28 connected to the circulating pump 24. The pump 24 communicates with an outlet conduit -39 having a valve 32 therein and the conduit 30 is connected to the stock inlet 18. The overfiow exit 22 is, in turn, connected via a suitable conduit 34 to the recirculating system at a point upstream from the circulating pump 24, such as by connecting the pipe 34 to the reservoir 26, as shown in FIG. 2. Stock as needed may be admitted to the reservoir 26 via a pipe 3d; similarly, white Water may be added to the system via a pipe 38.

The reservoir 26 may be more or less frusto conical as shown in FIG. 1, or it may have a more complex shape, as shown in FIG. 2. In FIG. 2, the reservoir 26 comprises a more or less conical chamber 261 with a bafile 262 extending radially thereacross. Directly below t-he baffie .262 is an outlet 263 for the conduit 28. Inaddition, a conical sub-chamber 264 may be provided adjacent and connected to the chamber 261 for admission of white water via the pipe 38.

A primary chamber $2 is provided in the vat 16 above the inlet 18 and within the primary chamber 42 directly above the inlet 18 is provided a suitable baflle 40 for breaking the direction of flow of the stock slurry arriving from the conduit 30. The level of the pump stock J! slurry within the vat 16 is maintained at least as high as the top of a separator 44 dividing the overflow outlet 22 from the vat 16.

The rate of circulation of the pulp stock slurry will be suflicient to prevent the channelling and flocculation of the stock which is essential in order to produce pulp articles of a uniform quality. Part of the stock will circulate through the vat 16 into the overflow exit 22 and part will circulate from the primary chamber 42 of the vat into a secondary chamber 46 of the vat and then to the discharge exit 20.

The vat 16 of the present invention is relatively complex in structure compared to anything known in the prior art and is formed from a plurality of walls which separate the vat 16 into the primary chamber 42 and the secondary chamber 46.

In the embodiment of FIG. 1, the primary chamber 42 is defined by an outer wall 48 and requisite side walls (not shown). Separating the primary chamber 42 from the secondary chamber 46 is a false bottom wall 50 which extends laterally across the entire width of the vat 16. The length of the false bottom 50 is preferably equal in length to two process steps during the rotation of the drum 12, i.e., the wall 50 should be of such a length so that two suction dies 14 are disposed over it during rotation of the drum 12 (as shown in FIG. 1). Either a slot or a lateral row of holes 52 is provided across the width of the false bottom 50 to provide communication between the secondary chamber 46 and the primary chamber 42.

In the embodiment of FIG. 2, a wall 54 delineates the bottom surface of the primary chamber 42. Two false bottom walls 56 and 58 separate the primary chamber 42 from the secondary chamber 46. The wall 56 is highly perforated to permit flow of pulp therethrough while the wall 58 is imperforate.

wall 60 of the secondary chamber at about /2 way along its length thereof.

A critical aspect of the present invention is the relationship between the location of the discharge exit and the force of pulp slurry infeed to the secondary chamber 46. The apparatus should operate so that the difference between the force of infeed and the static head of slurry downstream from the lowermost point of travel (step 3) of each die 14 due to any elevation of the discharge exit 20 above the infeed point is sutficient to maintain a net flow of slurry past the dies 14 in a direction the same as their direction of travel. In most instances, as shown in FIGS. 1-4, the discharge exit 20 will therefore be located approximately at a point adjacent and only slightly downstream from the extreme downward position of the dies 14. Noting the numbered steps in FIGS. 1 and 2, the dies 14 leave the surface of the stock in the secondary chamber 46 after step 3. In normal molding procedures, the mold leaves the surface of the stock in the vat after steps 4 or 5; as the molds leave the stock in the upward direction, the last formed and lightly held gelatinous pulp has a tendency to run down toward the trailing edge of the pulp deposit and this causes the trailing edge of the item produced to be thicker than the leading edge and also causes the pulp to cling to the lip of the trailing edge which provides feathery edges of pulp fibers on the article which must be washed off with deckle showers. With the discharge exit 20 located immediately after step 3, at a point adjacent the extreme downward position of travel of each die 14, the stock falls away from the mold in a horizontal plane as the mold advances from step 3 toward step 4, and this reduces the deposition of extra stock on the trailing edge of the article produced and also reduces the formation of feathery edges of pulp fibers sufficiently to eliminate the need for deckle showers,

In the vat embodiments 16 of both FIGS. 1 and 2, the provision of baflles 41), holes (such as those in wall 56 or holes 52), and the by-pass section 62, all combine to reduce the rate of movement of velocity of stock in the secondary chamber 46 to a level significantly lower than the velocity of pulp in the primary chamber 42; eddy currents and washing of a deposited pulp preform is thereby maintained at a minimum.

Any desired form of die 14 or die carrier 12 can be utilized, and in this exemplary embodiment, there is disclosed the rotary type which includes a transverse supporting shaft 13 defining the axis of generation of the curvature of the walls or 60. The shaft 13 extends through a suction manifold communicating through a plurality of radially extending suction lines to the circumferentially spaced suction mold dies 14 mounted on the outer rim of the die carrier 12, in a manner well known in the art.

As is conventional in the art, a negative pressure vacuum will be intermittently communicated through suitable valve mechanisms (not shown) to the suction mold dies 14 when they are introduced into the pulp stock slurry vat 16. Accordingly, when suction is applied at the exposed effective surface of the suction mold dies 14, a pulp preform will be deposited on the outer surface of the suction mold dies 14. The dies 14 will be continuously or intermittently (stepwise) moved through the vat 16 and especially the secondary chamber 46 thereof in the manner indicated by the direction arrow in FIGS. 1 and 2; stock deposition on the effective surface of the suction dies 14 will be, for the most part, in the secondary chamber 46 in which the stock slurry moves at a low velocity.

Extending transversely between each pair of dies 14 and extending radially from the die carrier 12 are wiper blade elements 64, preferably of the type described in copending application Serial No. 301,371, filed August 12, 1963, in the name of Roger Wells. If desired, wiper blades of the type described in parent application Serial No. 191,985 and called scraper or pusher bars may also be used. The wiper blades 64 includes a free lower edge 66 which contacts and rubs against the secondary chamber forming Walls 50 (FIG. 1) and (FIG. 2). The free end 66 of the Wiper blade 64 effect a sealing or contacting relation with the secondary chamber forming walls 50 and 60. The wiper blades 64 each form forwardly thereof accumulator chambers when the free ends contact the wiper blade contacting walls 50 or 60, which accumulator chambers maintain a relatively quiescent zone of pulp stock slurry therein which slurry is relatively homogenous, well mixed and moving at a relatively low rate.

Thus the combined effect of baflies, holes between chambers, and bypass sections, together with the wiper blades 64, give a quieting effect to the stock as it is molded during critical periods. In addition, the creation of eddy currents and washing of the deposited pulp preform is minimized. The wiper blades between each molding die serve to trap the stock and dampen out eddy currents, which eddy currents can cause variation in weights and the various items mounted on the individual molding dies. In addition, as the molding wheel steps, the wiper blades force the trapped stock to move in unison with the molds. This substantially reduces irregular washing of the molded articles and produces an article with a much more uniform distribution over its entire area.

The purpose of the transverse holes 52 in the false bottom 50 of the embodiment of FIG. 1 is to introduce stock to the accumulator chamber at step 3. Further holes are not provided because when stock slurry is provided for a particular step (e.g. steps 2 or 3) it is desirable to maintain the slurry in a quiescent state and further holes would have a contrary effect.

The embodiment of FIG. 2 is preferred because the use of a bypass section 62, causing the pulp in step 3 to be received solely from that not used during step 2, reduces washing of the pulp deposit, i.e. the bypass causes less washing of the article than stock entering through holes in the false bottom. In an intermittently operating machine, the wiper blades 64 are in position shown in FIG. 2 about 56% of the time.

It may be desirable in certain situations to utilize dilution water jetting means such as a row of transversely located spray pipes 68 or 68. In the embodiment of FIG. 2 the spray pipes are shown in two alternate positions, either one of which may be used; thus spray pipes 68 may be positioned in the primary chamber 42 between the baflie 40 and the perforated false bottom 56, or the spray pipes 68 may be positioned in the secondary chamber 46 between the false bottom 56 and the wiper blade contacting wall portion 60. The purpose of such pipes 6t}v or 68' is to provide diluting water to reduce the consistency of the stock, to reduce the weight of the articles directly downstream from the dilution outlets. With the improved control due to the provision of the wiper blades and the secondary chamber, the improved controlled stock flow may be further effectively controlled by such dilution means.

Another item which may be used in the present invention, particularly the embodiment shown in FIG. 2, is the. utilization of a shielding means comprising a laterally extending plate 70. The shielding plate 70 prevents pulp deposit formation during step 1. This makes it possible to. increase the static head and depth of the stock in the vat. Although increasing the static head improves forrnation to some extent, the use of such a shielding plate 70 may not always be desired when extra molding time is more desirable, i.e. extra molding time is offered by having step 1 under vacuum.

FIG. 4 shows another device which may be utilized in the present invention, and more particularly in the embodiment of FIG. 2. In this case the secondary chamber forming wall 60' is periodically made shorter than twice the distance between wiper blades 64-. In this embodiment a hinge 72 is provided between the wall 66 and an extension thereof 74. A cam 76 and suitable linkage 78 is associated with the bottom extension 74 and the rotation of the cam 76 periodically moves the extension 74 about the hinge 72 to dump the stock from between the blades 64 at step 3. The purpose of this is to permit a flow of stock across the stationary mold during intermittent operation to wash the bottom of the pulp deposit thin without reducing the wall thickness. For a given weight article the wall strength can be increased at the expense of the bottom.

This hinge need not be operated intermittently. Thus in FIG. 3 the wall 60 may be so formed with a dip 89 so as to give a continuous flow in step 3 to achieve the desired washing characteristics. Similarly the extension 74 in FIG. 4 may be adjusted about the hinge 72 to be opened a fixed amount without rotation of the cam 76 to provide the same results.

As described in copending application Serial No. 301,371, it is desirable in the present apparatus to provide some sealing arrangement at the sides of the drum and, thus, side skirts may be utilized as shown in copending application Serial No. 391,371. Otherwise, side sealing arrangements such as shown in FIG. 5 may be utilized. Side skirts $2 may be attached directly to the drum 12 at its peripheral edges 84 via a bolt 86. A filler piece 88 may be provided between the edge 84 and the skirt 82. The purpose of the side skirts is to prevent slurry from flowing behind the dies 14 in the area adjacent spokes 90 of the drum 12. If desired, side sealing means 92 may also be provided extending into the vat 16 in the opposite direction from the side skirts 82. The

6 side sealing ring 92 may extend peripherally about the entire drum 12, and may be formed of rubber, neoprene coated canvas inch thick or any suitable material. It is preferably held in place by the bolt 36 between the side skirts 82 and the filler piece 88.

Another means of holding the side skirt 82 and the side seal 92 is also shown in FIG. 5. Here an angle iron 94 is provided between the die 14 and the drum 12. The side skirts 32' and the side seal 92 are anchored to the angle iron via bolt $6.

The combined effect of the different elements of the apparatus disclosed herein provides optimum conditions for pulp deposition by providing a quiescent zone during th most important phases of molding and by reducing the tendency of lightly held gelatinous pulp to run down towards the trailing edge of pulp molded objects. The invention thus provides an improvement over [the invention of parent application Serial No. 191,985 which is itself highly successful.

Although the invention shown is embodied in a preferred form, it is intended that the disclosure be ill-usrative trather than definitive. It will be obvious to those skilled in the ant that various changes may be made without departing from the scope and spirit of the invention and therefore the invention is not to be limited to what is shown in the drawings and described in the specification, but only as indicated in the appended claims.

What is claimed is:

1. In an apparatus for forming molded pulp articles comprising a slurry vat, an entrance into said vat, means communicating with said vat to feed a pulp stock there.- to through said entrance to maintain the pulp slurry in substantial agitation and homogeneity, wall means forming a primary chamber in said vat into which the pulp stock slurry is initially introduced and a secondary chamher in proximity to and communication with said primary chamber, a suction die carrier mounted above said vat and including at least one molding die thereon movable in one direction through said secondary chamber first downwardly and then upwardly for receiving a pulp preform thereon, the improvement comprising transversely extending wiper blade means disposed in trailing relation to said molding die and contacting a portion of said wall means as one molding die passes through said slurry in said vat, and vat discharge means for passing said slurry out of said secondary chamber at a point slightly downstream and approximately adjacent the extreme downward position of said die.

2. A device in accordance with claim 1 wherein a portion of said wall means comprises a perforated false bottom separating said primary and secondary chambers, and wherein a plurality of dies are mounted on said die carrier with said dies having leading and trailing wiper blades.

3. A device in accordance with claim 2 wherein said portion of said wall means which said wiper blades contact is the same portion comprising said perforated false bottom, said false bottom having at least one solid portion extending longitudinally a distance about equal to the distance between wiper blades, said perforated false bottom being approximately equal in length to twice the distance between wiper blades, and said perforations consisting of a single transverse row of apertures at about the longitudinal center of said false bottom.

4. A device in accordance with claim 3 further comprising a battle means in said primary chamber adjacent said entrance means and wherein said bafiie means and said entrance means lie below said transverse row of apertures.

5. A device in accordance with claim 2 wherein said portion of said wall means which said wiper blade contacts is different from said portion comprising said perforated false bottom, said perforated false bottom being highly perforated and acting to break the force of slurry flowing from said primary chamber to said secondary chamber, and wherein said wiper blade contacting wall portion is not substantially greater in length than twice the distance between wiper blades, said wiper blade contacting wall portion comprising a by-pass section extending beyond said wiper blades, said by-pass section extending transversely across said wiper blades contacting portion and being spaced a distance about equal to the distance between the wiper blades from the leading edge of said wiper blade contacting wall portion.

6. A device in accordance with claim wherein the length of said wiper blade contacting wall portion is about equal to twice the distance between wiper blades and wherein said by-pass is located at about the longitudinal center thereof.

7. A device in accordance with claim 5 further comprising bafile means in said primary chamber adjacent said entrance means and wherein said bafile means and said entrance means lie below said highly perforated false bottom and said highly perforated false bottom is spaced horizontally adjacent said wiper blade contacting wall portion.

8. A device in accordance with claim 5 wherein the length of said wiper blade contacting wall portions is less than twice the distance between wiper blades.

9. A device in accordance with claim 5 further comprising means to periodically lengthen and shorten the length of said wiper blade contacting wall portion to provide one period when said length is less than twice the distance between two wiper blades and another period when said length is substantially equal in length to twice the distance between two wiper blades.

10. A device in accordance with claim '7 further comprising laterally extending dilution water jetting means in said vat wherein said laterally extending dilution water jetting means is positioned in said primary chamber between said balfle and said highly perforated false bottom.

11. A device in accordance with claim 7 further comprising laterally extending dilution water jetting means in said vat wherein said laterally extending dilution water jetting means is positioned in said secondary chamber between said highly perforated false bottom and the leading edge of said wiper blade contacting wall portion.

12. A device in accordance with claim 5 further comprising means to shield said dies from pulp during a portion of travel through said vat, said shielding means comprising a laterally extending plate positioned in said secondary chamber above said highly perforated false bottom and in contacting relation with the free ends of said wiper blades, said plate being about equal in length to the distance between wiper blades, the leading edge of said shield plate being positioned above the stock slurry level in said vat and the trailing edge thereof being spaced a distance from the leading edge of said wiper blade contacting wall portion.

13. A device in accordance with claim 1 comprising side skirts extending from said suction die carrier adjacent said die to prevent slurry from flowing behind said die and also comprising side sealing means extending parallel but in the opposite direction from said side skirts, and means to attach said side skirts and said sealing means to said die carrier.

14. In an apparatus for forming molded pulp articles comprising a slurry vat, an entrance means into said vat, means communicating with said vat to feed a pulp stock thereto through said entrance to maintain the pulp slurry in substantial agitation and homogeneity, wall means forming a primary chamber in said vat into which the pulp stock slurry is initially introduced and a sec ondary chamber in proximity to and communicating with said primary chamber, a suction die calrier mounted above said vat and including at least one molding die thereon movable in one direction through said secondary chamber first downwardly and then upwardly for receiving a pulp preform thereon, the improvement comprising transversely extending wiper blade means disposed in trailing relation to said molding die and contacting a portion of said wall means as said one molding die passes through said slurry in said vat, and vat discharge means for passing said slurry out of said secondary chamber at a point downstream from the lowermost point of travel of said die where the weight of said slurry in said secondary chamber at said discharge means does not exceed the force of infeed of said slurry into said secondary chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,730,450 10/1929 Chaplin 162-391 1,979,794 11/1934 Chaplin 162-183 2,000,085 5/1935 Maginnis 162-392 2,925,863 2/1960 Chaplin 162-391 2,961,368 11/1960 Lyons 162-390 2,995,187 8/1961 Wells 162-390 3,011,546 12/1961 Peppler et a1 162-390 3,043,742 7/1962 Chaplin 162-390 3,165,437 1/1965 Foote 162-390 DONALL H. SYLVESTER, Primary Examiner.

Claims (1)

14. IN AN APPARATUS FOR FORMING MOLDED PULP ARTICLES COMPRISING A SLURRY VAT, AN ENTRANCE MEANS INTO SAID VAT, MEANS COMMUNICATING WITH SAID VAT TO FEED A PULP STOCK THERETO THROUGH SAID ENTRANCE TO MAINTAIN THE PULP SLURRY IN SUBSTANTIAL AGITATION AND HOMOGENEITY, WALL MEANS FORMING A PRIMARY CHAMBER IN SAID VAT INTO WHICH THE PULP STOCK SLURRY IS INITIALLY INTRODUCED AND A SECONDARY CHAMBER IN PROXIMITY TO AND COMMUNICATING WITH SAID PRIMARY CHAMBER, A SUCTION DIE CARRIER MOUNTED ABOVE SAID VAT AND INCLUDING AT LEAST ONE MOLDING DIE THEREON MOVABLE IN ONE DIRECTION THROUGH SAID SECONDARY CHAMBER FIRST DOWNWARDLY AND THEN UPWARDLY FOR RECEIVING A PULP PREFORM THEREON, THE IMPROVEMENT COMPRISING

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