US2995187A - Flexible partition for stock vats - Google Patents

Description

Aug. 8, 1961 Filed April 20, 1960 R. WELLS 2,995,187

FLEXIBLE PARTITION FOR STOCK VATS 3 Sheets-Sheet 1 INVENTOR Roger Wells BY $21. CD. +z oc: s

ATTORNEY 1961 R. WELLS 2,995,187

FLEXIBLE PARTITION FOR STOCK VATS Filed April 20, 1960 3 Sheets-Sheet 2 mm v M v i I IIB J; I I W I I INVENTOR Roger Wells los BY *fi b.1120 F I G a 7' ATTORNEY Aug. 8, 1961 w Ls FLEXIBLE PARTITION FOR STOCK VATS 3 Sheets-Sheet 5 Filed April 20, 1960 FIG INVENTOR Roger Wells FIG.|2.

ATTORNEY FIG.I3.

United States Patent 2,995,187 FLEXIBLE PARTITION FOR STOCK VATS Roger Wells, Stamford, Conn., assignor to Diamond National Corporation, New York, N.Y., a corporation of Delaware Filed Apr. 20, 196i), Ser. No. 23,432 21 Claims. (Cl. 162--390) This invention relates to partitions for stock vats of rotary pulp molding machines. More particularly, the invention relates to flexible partitions for dividing a pulp stock vat of a rotary pulp molding machine into a plurality of separate compartments adapted to contain different kinds or grades of pulp stock, for use in the production of multi-ply molded pulp articles composed of a plurality of successively deposited superposed different layers.

In the manufacture of many molded pulp articles, particularly food trays, pie plates and other types of containers, it is often desirable to provide such articles with a multi-ply structure wherein different kinds or grades of pulp are successively deposited in well defined separate layers inter-felted into a composite multi-ply article. For example, in a two-ply molded pulp pie plate, the bottom layer may be composed of a coarse grade of ground wood pulp stock, and the top layer may be composed of a fine grade of sulfite pulp stock possessing high whiteness and containing a sizing agent which imparts a smooth surface finish thereto. It may also be desirable in some instances to incorporate differently colored dyes into the top and the bottom layers to impart a distinctive appearance to the multi-ply articles.

A specific type of molded pulp container in which a multi-ply structure is desirable, has become increasingly important commercially, namely, the molded pulp food trays utilized for the packaging and sale of meat, poultry and the like, in retail food markets. These food trays usually take the form of a relatively shallow, generally rectangular container, and a transparent covering sheet of cellophane or polyethylene may be wrapped around the tray and heat sealed to the bottom thereof. Such food packages present an attractive display while providing adequate protection during the sale and temporary storage of the food, particularly for naturally wet or juicy fresh poultry, such as chicken sections. It is important for these trays to be capable of absorbing any exuded blood, natural juices or other free fluids, and to prevent such fluids from being free to run around the inside of the sealed food package during normal handling by prospective purchasers. For this purpose, the multiply tray may be composed of an outer layer of nonabsorbent molded pulp, and an inner layer of absorbent pulp may be provided to soak up the above mentioned free fluids. Preferably this inner layer is provided with a plurality of small cup-shaped depressions adapted to serve as fluid traps. These depressions may be formed simultaneously with the molding of the main body of the tray by attaching to the usual drainage screen on the forming face of the pulp mold a plurality of uniformly spaced solid projecting nubbins made of metal, rubber or a suitable plastic. Details of certain features of such molded pulp containers, and molds and methods for making them, are disclosed and claimed in co-pending application Serial No. 793,819, filed February 17, 1959, titled Molding Pulp Articles Having Depressions, also naming Roger Wells as inventor.

Multi-ply molded pulp articles have customarily been manufactured by successive dipping a formaninous mold into a series of tanks or vats, each containing different grades or kinds of pulp stock, to accrete by suction deposition the successive different layers of pulp on the mold. Usually, these vats of pulp slurry have been separately spaced units, and the mold or a series of molds have been advanced into and out of the tanks in a plurality of separate successive operations. Efforts have been made in the past to produce multi-ply molded pulp articles on a rotary molding machine within a single pulp stock vat, by providing partitions intended to subdivide the vat into a plurality of separate compartments adapted to containv different pulp stocks, through which a series of molds are advanced successively during rotation of the machine. However, in these prior art machines considerable difliculty was generally encountered in attempting to provide partitions capable of effectively preventing intermixing of the different pulp stocks from the separate compartments as the series of molds were advanced therethrough.

An object of the present invention is to provide new and improved apparatus for molding mul-ti-ply pulp.

articles.

Another object of the invention is to provide new andimproved partitions for stock vats used in the production of multi-ply pulp articles on rotary pulp molding machines.

Still another object of the invention is to provide new and improved partitions for maintaining sealing contact with a series of molds being advanced successively through a compartment containing pulp stock, in the operation of a rotary pulp molding machine.

Yet another object of the invention is to provide flexible partitions for dividing a stock vat of a rotary pulp molding machine into separate compartments, and for maintaining sealing contact with a series of molds being advanced successively through the separate compartments, to prevent interrnixing of the ditferent pulp stocks in the production of multi-ply molded pulp articles.

Other objects and the nature and advantages of the instant invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view, partially in section, of

a rotary pulp molding machine including a stock vat divided into separate compartments by a partition embodying the present invention;

FIG. 2 is a vertical sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a side elevation view of a partition representing a second embodiment of the invention;

FIG. 4 is a side elevation view of a partition representing another embodiment of the invention;

FIG. 5 is a fragmentary vertical sectional view of a foraminous suction mold provided with a plurality of projecting nubbins for producing multi-ply molded pulp trays having cup-shaped depressions formed therein,

which mold is shown in sealing contact with a partition embodying the invention;

FIG. 6 is a fragmentary top plan view of a portion of a molded pulp tray produced by the pulp mold shown in FIG. 5;

FIG. 7 is a vertical sectional view taken along the FIG. 12 is a plan view of a portion of the partition.

shown in FIGS. 10 and 11; and

FIG. 13 is a plan view of another portion of the partion of FIGS. and 11.

In accordance with certain features of the invention, in a rotary pulp molding machine for producing multiply molded pulp articles, said machine including a rotatable drum having a plurality of foraminous molds mounted on its periphery, and a pulp stock slurry vat in which the drum is partially immersed for advancement of the molds therethrough, a flexible vertical partition is mounted in the vat for dividing the vat into a plurality of separate compartments adapted to contain different pulp stocks through which the molds are advanced successively during rotation of the drum, said flexible partition being in liquid sealing tangential wiping contact with the portions of the drum and molds being advanced therepast, thereby effectively preventing intermixing of the different pulp stocks in the compartments separated by the partition. In one embodiment of the invention the flexible partition is in lightly wiping liquid sealing contact with the drum and the molds, while in another embodiment of the invention wherein the molds are provided with projecting nubbins for producing cupshaped depressions in the pulp articles molded thereon, the flexible partition is adapted to scrape the advancing nubbins as well as form wiping sealing contact therewith.

Referring to FIGS. 1 and 2, a plurality of conventional foraminous suction molds 20 are mounted at equal intervals circumferentially spaced around the periphery of a cylindrical drum 22 mounted above and partially submerged within a pulp stock slurry tank 24 for rotation about a horizontal axis therein. Each of the molds 20 communicates through one of a plurality of radial channels 26 with a central hollow shaft 28 extending axially through the drum 22 and communicating with an exterior source of suction (not shown). Suitable driving means (not shown) operatively connected to the shaft 28 is provided for rotating the drum 22 either continuously or intermittently. During the rotation of the drum 22 the molds 20 are advanced successively through liquid pulp stock slurry contained within the vat 24, while suction applied to the molds 20 through the channels 26 during immersion of the molds 20, causes pulp fibers to be extracted from the slurry and deposited onto the forming surfaces of the molds 20, thereby forming initially molded pulp articles known as preforms. In the usual manner, the suction is continued while the molds 20 are advanced upwardly above the slurry to extract excess moisture from the preforms until the molds reach a transfer mechanism indicated generally at 30, where the suction on the successive molds 20 is shut off momentarily while the transfer mechanism 30 removes the preforms therefrom.

The transfer mechanism 30 is shown only schematically, and it is intended to be conventional in construction. This mechanism includes a plurality of dies 32 contoured to fit snugly against the successive molds 20 to remove the pulp preforms therefrom when suction is applied to the dies 32. A rotatable die carrier 34 on which the dies 32 are mounted radially is positioned adjacent to the drum 22 and mounted directly over one end of a conveyor belt 36, adapted to transport the successive pulp preforms to a drying oven (not shown).

Although the molds 20 are shown located at twelve equal intervals on the periphery of the drum 22, it is evident that the number of intervals may be varied from fewer to many more than twelve, depending upon the size of the drum and the size and spacing of the molds. At each of these intervals four of the molds 20 may be mounted in a row as shown in FIG. 2, or any convenient number from only one to many more than two of the molds may be mounted at each interval on the periphery of the drum 22. Instead of employing the drum 22, a wheel or any other suitable type of conveyor may be employed to advance the molds successively through the vat 24.

Multi-ply molded pulp articles are formed on the molds 20 by successively depositing at least two different layers of pulp fibers on these molds as they are advanced through the vat 24. For a two-ply molded pulp article this result is achieved by subdividing the tank 24 into two separate sections or compartments 38 and 39, each of which is adapted to contain a slurry of a different pulp stock. During clockwise rotation of the drum 22, as viewed in FIG. I, the molds 20 are advanced in succession through the vat 24 in an arcuate path, first passing through the compartment 38 wherein a slurry of one kind or grade of pulp stock is maintained, and then advancing through the compartment 39 where a slurry of a difierent pulp stock is present. The slurries in the two compartments 38 and 39 may be composed of dilute fibrous dispersions in water of distinctly different grades of pulp stock in suitable concentrations, or they may be of the same grade of pulp stock in different concentrations, or differently colored, or one slurry may contain a sizing agent while the other may not. Although only two compartments or sections of the vat 24 are present in the apparatus shown in FIG. 1 to illustrate the principles of the invention, it is apparent that three or more compartments could be provided in different portions of the vat 24, if desired, to produce multi-ply molded pulp articles having the corresponding number of plies.

In accordance with the present invention, a flexible vertical partition 40 is mounted within the pulp slurry vat 24 and extends transversely thereacross, as shown in FIG. 2, thereby subdividing the vat 24 to form the separate compartments 38 and 39 thereof, for the purpose of maintaining separation between the compartments 38 and 39 and preventing any intermixing of the different pulp stocks contained therein. The lower end of the vertical partition 40 is secured to a base bar 42 extending transversely across the inside of the bottom of the vat 24, and the partition 40 may be removably attached to the base bar 42 by means of a plurality of spaced bolts 44, or other suitable fasteners. The upper end of the vertical partition 40 is bent over into a substantially horizontal position, wherein the end portion thereof is in tangential contact with the surfaces of the molds 20 being advanced therepast, and this end of the partition 40 is in lightly wiping liquid sealing contact therewith. At least the upper portions of the partition 40 should be sufficiently flexible to conform generally to the irregular surface defined by the molds 20 and by the intervening and surrounding portions of the surface of the mold carrier drum 22, as is best shown in FIG. 2. Preferably, the flexible partition 40 is composed of relatively thin, impervious, rubber sheet material. For example, the partition 40 may be made of a flexible rubber sheet having a thickness of about /4 inch and a length of about 3 inches, of which the last inch of the upper end thereof is in tangential sealing contact with the advancing molds 20.

It is evident that one of the principal difficulties encountered in attempting to prevent intermixing of the pulp stocks contained in the compartments 38 and 39 is the possibility of having small quantities of the stock in the compartment 38 being swept into the compartment 39 by the molds 20 projecting from the periphery of the drum 22. Similar difficulties may be expected at opposite ends of the drum 22, where some clearance is usually provided between the ends of the drum 22 and the side walls of the slurry bath 24. In order to overcome these difficulties, the peripheral surface of the drum 22 is provided with filler bars 46 mounted between each adjacent row of the molds 20 thereon. The filler bars 46 may project radially outwardly from the surface of the drum 22 the same distance as that of the molds 20 thereon or a trifle less. Thus, as the flexible upper end of the partition 40 contacts the successive molds 20 being advanced therepast during rotation of the drum 22, the filler bars 46 mounted intermediate adjacent successive 'molds 20 allows the upper end of the partition 40 to conform more closely to the surfaces of the molds 20 and'the drum 22'. Likewise, opposite ends of the-drum 22 may be provided with a pair of annular radially mounted skirts 48, which are wiped in sealing contact by a pair of flexible vertical blades 50 mounted on the sides of the vat 24 directly above the vertical partition 40 and forming an upwardly extending continuation thereof.

The force of the tangential sealing contact between the upper end of the flexible partition 40 and the contoured surfaces of the advancing molds. 20 and the. adjacent portions of the periphery of the drum 22 should be sufficiently light to wipe in liquid sealing contact therewith, without actually scraping the said surfaces of the molds and drum. At this stage of the molding operation, the freshly deposited layer of pulp fibers being formed on the molds 20 is quite soft and pliable, being almost gelatinous in consistency and having comparatively little resistance to abrasion. Hence, any scraping or strong rubbing action by the flexible. partition 40 against this pulp deposit is likely to rub off some of the deposit, possibly form it into balls and blobs, and form score marks in the deposit. It is also likely that the scraping effect would produce non-uniform thicknesses in the resultant molded pulp articles. Therefore, when the flexible partition 40 is in direct wiping contact with the freshly deposited layer of molded pulp, as it is in the embodiment of the invention illustrated in FIGS. 1 and 2, the force of contact should be merely a lightly wiping contact. It is evident that the surfaces of the flexible partition 4%) itself should be smooth and polished to prevent scoring and scraping effects.

Due to the fact that suction is constantly applied to the molds 20 during the entire time they are being advanced through the compartments 38 and 39, and While they are in wiping contact with the upper end of the flexible partition 40, the suction being applied internally to the molds 20 has the effect of pulling the contacting upper end portion of the flexible partition 40 towards the mold surfaces. One result of pulling of the free, flexible upper end of the partition 40 towards the advancing molds 20 in this manner, is the bending of this end of the partition 40 into conformity with the contour of the surfaces of the advancing molds 20 and the maintenance of a liquid-tight seal therewith, and since the partition is impervious, thereby preventing intermixing of the pulp stock from the separate compartments 38 and 39. Another important result of having this end of the flexible partition 40 pulled towards the advancing molds 20, is the fact that the pressing of the contacting end of the partition 40 against the freshly deposited layer of pulp fibers squeezes some of the excess water. out of the deposited pulp and smoothens the surface thereof. In addition to its desirable smoothening effect on the deposited pulp fibers, this squeezing action causes the deposited pulp fibers to become denser and firmer, thereby improving the appearance and strength of the molded pulp product. Any reduction in excess moisture at this stage of the molding operations has the effect of speeding up final drying operations, which are eventually necessary to remove all excess moisture, thereby effecting important economies in production costs.

Referring again to FIG. 1, a fresh supply of pulp slurry may be admitted, when needed, to the compartment 38 through a supply pipe 52, and similarly a supply pipe 54 is provided to supply pulp slurry as needed to the compartment 39. These supply pipes 52 and 54 may be provided with float control valves (not shown) to maintain the slurries in the compartments 38 and 39 at the desired constant level automatically. The upper level of the slurries in the two compartments 38 and 39 may be maintained at approximately equal heights above the bottom of the vat 24, but it is preferred to have the slurry in the compartment 39 maintained at a higher level than that of-the' compartment 38, asiis illustrated in FIG. 1,

in order to create a differential in hydrostatic pressure. This diflerence in hydrostatic pressure assists in pressing the free upper end of the partition 40:

therebetween.

towards the advancing molds 20, and it also helps to further. minimize possible intermixing of the two different pulp stocks, since there would be less pressure in the compartment 38 from which the slurry would normally have a tendency to flow into the compartment 39 during clockwise rotation of the drum 22.

When only light wiping contact is desired between theflexible partition 40 and the surfaces of the advancing molds 20 and drum 22, without scraping or strong rubbing contact therebetween, the entire partition 40 may be made from a relatively thin flexible sheet composed of rubber or other suitable plastic materials, which construction is suitable for the embodiment of the invention illustrated in FIGS. 1 and 2. Of course, only the upper end portion of the partition 40 need be very flexible for this purpose, and the lower end portion of the partition 40 where it is secured to the base bar 42, may be relatively inflexible and thick.

In FIGS. 3 and 4, there are shown specific alternative embodiments of the invention wherein greater flexibility is imparted to the upper end of the partition than tothe lower end thereof. In FIG; 3 there is shown a flexible partition 60 of gradually tapered construction, which is adapted to be incorporated into a rotary pulp molding machine in the same manner as the previously described partition 40. The partition 60 is secured at its lower end to a base bar 62, corresponding to the previously described base bar 42., by means of a plurality of bolts, of which only one bolt 64 is shown. The partition 60 is made of flexible sheet material which diminishes gradually in thickness as it tapers from its lower end to its upper end. One possible Way of attaining the desired taper in the construction of the partition 60 is by molding rubber, polyethylene, polystyrene, or other suitable plastics, to form a tapered solid, flexible sheet thereof. However, it is preferred to construct the tapered partition 60 by consolidating a plurality of flexible, resinimpregnated. sheets of graduated length to form a composite tapered laminate, such as a laminate of resin-impregnated glass cloth.

In the embodiment of the invention illustrated in FIG. 4, a flexible partition 70 is secured to a base bar 72 by means of a plurality of bolts, of which only one bolt 74 is shown, in the same manner as the partition 60. The partition '70 includes a relatively stiff lower portion 76, which may be made of rubber sheeting about Mr inch thick, and an upper portion '78 of the partition 70. is formed by a relatively flexible thin sheet of rubber, polyethylene, or the like, which is attached to the thicker rubber bottom portion 76 by means of a plurality of spaced fasteners, of which only one fastener 79 is shown. The relatively thin, flexible upper portion 78 of the partition 70 may have a thickness ranging from about .008 inch up to about .020 inch, and the surfaces thereof should be relatively smooth and polished.

FIG. 5 shows a relatively stiff, flexible partition 80 having its lower end secured to a base bar 82 by means of a plurality of spaced bolts, of which a bolt 84 is shown, which partition 80 is adapted to be mounted within a slurry vat 85 in the previously described partitions 40, 60 and 70. The upper end of the partition 80 is bent over into a substantially horizontal position in tangential contact with the forming face of a foraminous suction mold 86 being advanced therepast. The mold 86 comprises a standard perforated forming plate 88 contoured to form a molded pulp tray thereon. A foraminous wire mesh straining screen 90 covers the forming face of the perforated plate 88 and the screen 90 is secured around the periphery of the plate 88 by means of a retaining ring '92, which is attached thereto by a plurality of bolts, of which one bolt 94 is shown. The mold 86 corresponds 7 generally in structure and in function to one of the molds shown in FIGS. 1 and 2, but the mold 86 is provided with a plurality of solid projecting nubbins 96 secured at intervals to the screen for forming depressions in pulp trays being molded on the mold 86.

In FIGS. 6 and 7, there is shown a molded pulp tray 100 having a plurality of spaced cup-shaped depressions 102 therein, which is representative of the type of molded pulp articles having depressions formed therein which are producible by foraminous suction molds having projecing nubbins, such as the mold 86 and its projecting nubbins 96. The tray 100 is two-ply in construction, and it includes an upper ply or layer of absorbent molded pulp 104 and a lower ply or layer of non-absorbent molded pulp 106. The cup-shaped depressions 102 are formed in and extend entirely transversely through the absorbent pulp layer 104 in that portion of the tray 100 constituting the inside bottom thereof.

In the particular tray 100 illustrated in FIGS. 6 and 7, the cupshaped depressions 102 formed by the projecting nubbins 96 of the mold 86 may have certain critical dimensions so that these depressions 102 are capable of functioning as mechanical fluid traps in the completed tray 100. However, the formation of the cup-shaped depressions 102 is described merely to illustrate the principles of the present invention, and it should be understood that molded depressions in the form of apertures or perforations having any desired size or shape may be produced in a similar manner by suitably arranged projecting nubbins.

In the molding of the tray 100, the mold 86 is advanced from right to left, as viewed in FIG. 5, past the flexible, vertical partition 80, and the layer 104 is formed first by suction deposition onto the screen 90 and the projecting nubbins 96. The flexible partition 80 forms a liquid-tight seal with the mold 86 during the advancement thereof, and the partition 80 is also in scraping or strongly rubbing contact with the projecting nubbins 96 on the mold 86. Due to this arrangement, any portion of the first deposited pulp layer 104 which happens to project beyond the nubbins 96 is evenly scraped off by the partition 80 as the nubbins 96 advance therepast. During continued movement of the mold 86 beyond the flexible partition 80, the pulp layer 106 is gradually deposited on top of the previously deposited layer 104. Due to the clean scraping action of the partition 80 in removing any excess portion of the layer 104 projecting beyond the nubbins 96, and the fact that the partition 80 forms a liquid-tight seal effectively preventing intermixing of the different pulp stocks on opposite sides thereof, the boundary line between the layers 104 and 106 in the completed composite molded pulp tray 100 is quite sharp and well defined. It is evident that the projecting nubbins 96 hold the flexible partition 80 away from the perforated forming plate 88 and the straining screen 90 at a fixed distance therefrom, thereby preventing complete removal of the initially deposited pulp layer 104. Furthermore, such scraping or strong rubbing action could not be tolerated in the case of the molds 20 which lack any projecting nubbins, and only light wiping action, such as is obtainable from the partitions 40, 60 or 70, is acceptable when no projecting nubbins are present on the molds.

Similar scraping or strong rubbing action is obtainable from a flexible partition 110 shown in FIGS. 8 and 9, in the form of an expansible, flexible diaphragm of sheet material. Opposite side edges of the partition 110 are secured to a plurality of spaced base bars 112 by means of a plurality of fasteners 114, thus forming the sheet material into a generally vertically disposed curved loop. The partition 110 extends entirely transversely across a stock vat 115, which is provided with inlet pipes 116 adapted to admit compressed air, or other fluid under 8 admission of fluid pressure in this manner causes the central portion of the partition 110 to rise upwardly and press into close conformity with the surface of a mold 118 being advanced therepast. The mold 118 corresponds generally to the mold 86, and it includes a perforated forming plate 120 having a straining screen 122 mounted thereon, and a plurality of projecting nubbins 124 are secured to the screen 122 at intervals thereon. When the diaphragm type partition 110 is expanded, it forms a liquid tight seal with the mold 118, and it presses in scraping or strongly rubbing engagement with the projecting nubbins 124. In view of the great amount of wear likely to result from the rubbing and scraping contact of the partition 110 with the projecting nubbins 124, it is desirable to construct these members from relatively tough, wear-resistant, smooth-surfaced plastic material, such as neoprene. In addition, a thin film 126 of an extra tough, flexible, wear-resistant, smooth-surfaced sheet material may be interposed between the upper portion of the partition 110 and the projecting nubbins 124. One edge of the film 126 may be anchored to the bottom of the slurry vat 115 by a fastener 128, while the opposite edge of the film 126 extends in the direction of movement of the mold 118, and this edge of the film 126 is free to flex to conform to the contour of the mold 118.

An important advantage accruing from the expansible characteristic of the flexible diaphragm 110 is the fact that a liquid-tight seal may be maintained against the mold 118, thereby positively preventing intermixing of the different pulp stocks maintained on opposite sides of the partition 110, regardless of the presence or absence of internal suction applied to the mold 118 during molding operations thereon. The liquid-tight seal is maintained by the expansible partition 110 independently of any difference in hydrostatic pressure of the slurries of the two different pulp stocks. Moreover, the inflatable, flexible nature of the partition 110 enables it to fit into close conformity with the contour of a row of the molds 118 over the entire contacting area therebetween.

The expansible partition 110, either by itself or combination with the protective, wear-resistant film 126, exerts a definite scraping or strong rubbing action against the projecting nubbins 124 of the mold 118 being advanced therepast, when the partition 110 is in an expanded condition during molding operations. Thus, the embodiment of the invention represented by the expansible partition 110 is designed for the construction of molded pulp articles having depressions formed therein, such as the tray 100 illustrated in FIGS. 6 and 7.

Still another embodiment of the invention is illustrated in FIGS. 10, 11, 12 and 13, wherein a flexible, vertical partition, indicated generally at 140, is adapted to exert light wiping contact with a succession of advancing molds which lack projecting nubbins as do the molds 20. The lower end of the partition is secured to a base bar 142 by means of a plurality of fasteners 144, in a manner similar to that in which the partitions 40, 60, 70 and 80 are mounted. The partition 140 is made up of three separate superimposed thin sheets 146, 147, and 148, which are joined together at their lower ends by the fasteners 144. These sheets are quite flexible and thin, and they are preferably composed of a smooth surfaced, tough, wear-resistant plastic material, such as Mylar film. The three separate sheets constituting the partition 140, are mounted in light wiping contact with different portions of a plurality of suction molds mounted on the periphery of a rotatable drum 152, of which only a fragment is shown, corresponding to the molds 20 and the drum 22 of FIGS. 1 and 2. The molds 150 are each provided with peripheral retaining rings 154, which are secured to the drum 152 by means of spaced bolts 144. During rotation of the drum 152 to advance the molds 150 from right to left, as viewed in FIG. 11, the sheets 146, 147 and 148 are contacted successively by the mold 150 in the order in which the sheets are enumerated.

First, the sheet 146 is wiped by each of the successive molds 150, and the upper end of this sheet is provided with a perfectly straight horizontal edge 158 arranged to engage only the projecting forming faces of the molds 150, without touching the retaining rings. 154 or the surface of the drum 152. Next, the intermediate sheet 147 is reached by the successive molds 150 immediately after they have advanced beyond the sheet 146. This intermediate sheet 147 is provided with a plurality of upwardly projecting tabs 16%) formed on an otherwise straight upper edge 161, which tabs are arranged to wipe that portion of the molds 150 intervening between the projecting forming faces thereof and the retaining rings 154. Pinally, the sheet 148 is provided with a plurality of upwardly projecting tabs 162 adapted to wipe the surface of the drum 152 in between the retaining rings 154 of adjacent molds 150 just after the sheets 146 and 147 have been passed by the molds 1519. Thus, by providing the freely flexible upper ends of each of the three sheets 146, 147 and 148 with a different special configuration, these sheets cooperate to conform closely to the contoured surfaces of the molds 150 and the drum 152 advancing therepast, and to engage said surfaces in lightly wiping tangential sealing contact.

In order to impart some stiffness to the lower end of the flexible partition 14%, for the same reason this is done in the construction of the partitions 60 and 70, a relatively stiff loop 166, formed by folding a strip of canvas or rubber sheeting upon itself, is secured by the fasteners 144 to the base bar 142 behind the lower ends of the sheets 146, 147 and 148. The relatively stiff loop 166 provides a resilient backing for the very flexible thin sheets 146, 147 and 148, which assists in holding these sheets vertically disposed in wiping contact with the molds 150 and the drum 152,.

Apparatus embodying the invention enables multi-ply pulp articles to be molded in a single slurry vat, by effectively subdividing the vat into separate compartments adapted to contain slurries of different pulp stocks, through which a series of molds may be advanced successively without causing intermixing of the different pulp stocks. The pulp articles produced are characterized by improved density and smoothness, and the boundaries between the plies of the articles are clearly defined.

Although the invention has been illustrated and described with particular reference to rotary pulp molding machines of the type represented by a rotatable drum having a plurality of foraminous suction molds projecting from its periphery, it is contemplated that flexible partitions embodying the invention may be incorporated into stock vats of other types of rotary pulp molding machines, such as the well known cylinder machines, pressure formers and rotary filters. In such other pulp molding machines, flexible partitions embodying the present invention may serve, not only as dividers between two adjacent compartments of a stock vat, but also as a terminal partition for one end of an uncompartmented stock vat.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and, therefore, the invention is not intended to be limited to what is shown in the drawings and described in the specification but only as defined in the appended claims.

What is claimed is:

1. In apparatus for molding multi-ply pulp articles, including a rotatable drum means having a plurality of foraminous suction molds mounted on its periphery for rotation through a pulp slurry vat mounted below the drum means, and a plurality of separate compartments provided in the vat adapted to contain slurries of different pulp stocks through which the molds are advanced successively during rotation of the drum means, the improvement comprising a flexible vertical partition mounted in the bottom of the vat and extending extirely transversely thereacross between said compartments, and the upper" portion of said vertical partition being mounted in liquid sealing tangential wiping contact with the surfaces of the drum means and the molds advancing therepast duringrotation of the drum means, thereby effectively preventing intermixing of the different pulp stock slurries contained in the separate compartments,

2; The structure of claim 1; said drum means including filler bar means interposed between adjacent sue tion molds and projecting outwardly from said drum means substantially the same distance as said molds whereby said flexible partition will sealingly engage said filler bar means and suction molds with a minimum of distortion thereof to aid in preventing intermixing of said different pulp stock slurries in the separate compartments.

3. The structure of claim 1; said vat including flexible sealing blades at opposite sides thereof and sealingly engaging adjacent sides of said drum means for aiding to prevent intermixing of said different pulp stock slurries in the separate compartments.

4. The apparatus defined by claim 1, wherein the vertical partition is constructed from a relatively thin,

flexible, smooth-surface sheet material, having its lower end secured to the inside bottom of the slurry vat, and having its upper end freely flexible in lightly wiping liquid sealing contact with the surfaces of the drum means and the molds advancing therepast.

5. The apparatus defined by claim 4, wherein the vertical partition of sheet material is tapered lengthwise so that it diminishes gradually in thickness from its secured lower end to its freely flexible upper end.

6. The apparatus defined by claim 5, wherein the tapered vertical partition of sheet material is a composite laminate constructed from a plurality of consolidated resin-impregnated sheets graduated in length.

7. The apparatus defined by claim 4, wherein the vertical partition is provided with a relatively stiff lower portion constructed from a relatively thick sheet material having its lower end secured to the inside bottom of the slurry vat, and the upper portion of the partition is constructed from a relatively thin, flexible, smoothsurfaced sheet material.

8. The apparatus defined by clm'm 4, wherein the vertical partition is constructed from a plurality of separate superimposed thin sheets joined together at their lower ends, said sheets having differently contoured upper edges adapted to engage different portions of the surfaces of the drum and the molds advancing therepast.

9. The apparatus defined by claim 8, wherein the vertical partition is constructed from three separate superimposed thin sheets, the upper edge of one of said sheets being substantially entirely straight transversely across the vat and adapted to contact only the outermost projecting surfaces of the molds, and the upper edges of the other two sheets being generally straight but having projecting tab portions adapted to contact the periphery of the drum means and the other surfaces intervening between adjacent molds on the drum means.

10. In apparatus for molding multi-ply pulp articles, including a rotatable drum having a plurality of foraminous suction molds mounted on its periphery for rotation through a pulp slurry vat mounted below the drum, said molds having a plurality of nubbins projecting from the forming face thereof for forming depressions in pulp articles molded thereon, and a plurality of separate compartments provided in the vat adapted to contain slurries of different pulp stocks through which the molds are advanced successively during rotation of the drum, the improvement comprising a flexible vertical partition mounted in the bottom of the vat and extending transversely thereacross between said compartments, the upper portion of said vertical partition being mounted in tangential scraping contact with the projecting nubbins on the molds advancing therepast during rotation of the drum, and said partition being in liquid sealing wiping contact with the surfaces of the drum and the molds thereby effectively preventing intermixing of the different pulp stock slurries contained in the separate compartments.

11. The apparatus defined by claim 10, wherein the vertical partition is constructed from a relatively thick, flexible, smooth-surfaced sheet material, having its lower end secured to the inside bottom of the slurry vat, and having its upper end free to flex in liquid sealing scraping contact with the mold and nubbin surfaces advancing therepast.

12. The apparatus defined by claim 10, wherein the vertical partition is an expansible flexible diaphragm having its opposite edges secured to the inside bottom of the slurry vat, and means for admitting fluid under pressure into the interior of the diaphragm to cause expansion thereof, thereby urging the upper portion of the expanded diaphragm into liquid sealing scraping contact with the mold and nubbin surfaces advancing therepast.

13. A partition for stock vats of rotary pump molding machines including a series of foraminous suction molds mounted on the periphery of a rotatable drum means for movement in succession through pulp stock slurry contained in a vat thereof, comprising a flexible sheet of smooth-surfaced impervious material disposed generally vertically and extending entirely transversely across the stock vat, and means for removably securing the lower end of the sheet to bottom of the stock vat, the upper end of said sheet being unsecured, freely flexible, and being bent over into a generally horizontal position in liquid sealing tangential wiping contact with the surfaces of the drum means and the molds advancing therepast.

14. The partition defined by claim 13, wherein the sheet of impervious material is a plastic material and is tapered lengthwise so that it diminishes gradually in thickness from its secured lower end to its freely flexible upper end.

15. The partition defined by claim 14, wherein the tapered sheet of plastic material is a composite laminate constructed from a plurality of consolidated sheets graduated in length.

16. A partition for stock vats of rotary pulp molding machines including a series of foraminous suction molds mounted on the periphery of a rotatable drum for movement in succession through pulp stock slurry contained in a vat thereof, each of said molds being secured to the periphery of the drum by a retaining ring, said partition comprising a plurality of separate superimposed flexible thin sheets of smooth-surfaced impervious material disposed generally vertically and extending entirely transversely across the stock vat, and means for removably securing the lower ends of said sheets together and to the bottom of the stock vat, the upper ends of said sheets being unsecured, freely flexible, and being bent over into a generally horizontal position in liquid sealing tangential wiping contact with the surfaces of the drum and the molds advancing therepast, said sheets having differently contoured upper edges adapted to engage different portions of the surfaces of the drum and the molds advancing therepast.

17. The partition defined by claim 16, wherein the plurality of separate sheets comprising the partition are three sheets of plastic film, the upper edge of one of said sheets being substantially entirely straight transversely across the vat and adapted to engage only the outermost projecting surfaces of the advancing molds, the upper edge of another of said sheets being generally straight, but having tab portions adapted to project into wiping engagement with the surfaces between the molds and their retaining rings, and the other of said sheets being generally straight but having tab portions adapted to project into wiping engagement with the periphery of the drum intervening between adjacent molds thereon.

18. A partition for stock vats of rotary pulp molding machines including a series of foraminous suction molds mounted on the periphery of a rotatable drum means for movement in succession through pulp stock slurry contained in a vat thereof, comprising an expansible flexible diaphragm constructed from a sheet of smoothsurfaced wear resistant impervious material disposed generally vertically and extending entirely transversely across the stock vat, means for removably securing opposite edges of the sheet to the bottom of the slurry vat, and means for admitting fluid under pressure into the interior of the diaphragm to cause expansion thereof, the upper portion of said diaphragm being disposed generally horizontally and being in liquid sealing wiping contact with the surfaces of the molds advancing therepast when the diaphragm is expanded.

19. The partition defined by claim 18, wherein a flexible thin film of tough smooth-surfaced wear resistant plastic material is interposed between the expansible dia phragm and the advancing molds and in contact therewith for preventing wear resulting from the normal wiping contact thereof, and means for securing one end of said film to the bottom of the stock vat, the opposite end of said film being unsecured and freely flexible to conform to the contours of the upper portion of the diaphragm and the surfaces of the advancing molds.

20. In apparatus for molding multi-ply pulp articles, including a rotatable drum means having a foraminous suction forming surface on its periphery for rotation through a pulp slurry vat mounted below the drum means, and a plurality of separate compartments provided in the vat adapted to contain slurries of different pulp stocks through which the forming surface of the drum means is advanced successively during rotation of the drum means, the improvement comprising a flexible vertical partition mounted in the bottom of the vat and extending entirely transversely thereacross between said compartments, the upper portion of said vertical partition being mounted in liquid sealing tangential wiping contact with the surface of the drum means advancing therepast during rotation of the drum means, and means for maintaining a difference in hydrostatic pressure of the slurries in the separate compartments, thereby effectively preventing intermixing of the slurries and causing the upper end of the flexible partition to be pressed against the surface of the rotating drum means.

21. The apparatus defined by claim 20, wherein the drum means is rotatable in one direction through a pulp slurry vat divided into two separate compartments, the forming surface of the drum means being advanced in succession through first one and then the other of said two compartments, and the difference in hydrostatic pressure maintained in the two compartments results from having the upper level of the slurry in said first compartment at a lower level than of the other compartment, whereby higher hydrostatic pressure is maintained in the second compartment reached by the successively advanced drurn forming surface during rotation thereof.

References Cited in the file of this patent UNITED STATES PATENTS Chaplin Oct. 8, 1929

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