US2920700A

US2920700A - Pulp molding

Info

Publication number: US2920700A
Application number: US612786A
Authority: US
Inventors: Wells Roger
Original assignee: Diamond National Corp
Current assignee: Diamond National Corp
Priority date: 1956-09-28
Filing date: 1956-09-28
Publication date: 1960-01-12
Anticipated expiration: 1977-01-12

Description

R. WELLS PULP MOLDING Jan. 12, 1960 2 Sheets-Sheet 1 Filed Sept. 28, 1956 INVENTOR Roger Wlls BY MRL A L0K A ATTORNEY Jan. 12, 1960.

R. WELLS PULP MOLDING 2 SheetsSheet 2 Filed Sept. 28, 1956 ATTORNEY United States Patent 2,920,100 PULP MOLDING it Wells, Plattsburg, N.Y., assignor to Diamond aflonal Corporation, a corporation of Delaware This invention relates to pulp molds, and more particularly to a drainage trap for pulp molds.

This application is a continuation-in-part of my copending application Serial No. 612,855 filed September 2!, 1956.- Q In the manufacture of molded pulp articles, such as pie 'or household plates, for example, it is customary to initially form a partially molded article, known as a preform, by dipping a foraminous mold into a liquid pulp slurry, and simultaneously applying suction to the mold to cause a layer of wet pulp fibers to be deposited thereon; subsequently the resultant pulp preform is com- 'pletely dried and finished to produce the molded article desired. Suction is continued while the mold is advanced from the initial forming position in the pulp slurry to an article discharge position, which may be located adjacent to a conveyor belt moving toward a final drying chamber. The suction extracts most of the excess liquid from the wet preform by the time the mold reaches article discharge position, but a small quantity of residual liquid usually remains inside the mold.

The molded pulp preform is ejected from the mold at the discharge station by stopping the suction, and then blowing or sucking the preform from the mold. In the systems employed heretofore, any small quantity of residual liquid which remained in the mold was likewise blown or sucked out, and frequently this liquid was blown upon the preform being ejected. Usually the liquid was blown upon one edge of the preform, making this edge limp and soggy. Since at this stage of its formation the molded pulp article was still damp and only lightly compacted, it was readily susceptible to damage from splashing liquid. The limp soggy edge tended to collapse slightly, resulting in a deformed product. Often the soggy edge was so wet that it failed to dry completely during the subsequent drying operation, and when a plurality of such articles were stacked following this operation, the damp edges would become crushed. Consequently, many of the articles produced were defective due to blemishes, collapsed edges, or warping caused by lack of uniformity in drying characteristics.

An object of this invention is to provide pulp molds with means for preventing any excess liquid from being blown upon a molded pulp article at the time it is being discharged from a molding machine.

Another object of the invention is to provide a new and improved drainage trap for pulp molds.

Still another object of the invention is to provide a drainage trap for pulp molds which are employed in nonrotary molding machines.

' Other objects and the nature and advantages of the instant invention, will be apparent from the following description taken in conjunction with the accompanying Fig. 5 is a fragmentary side elevational view of a pulp molding machine having a plurality of individual molds embodying the invention, corresponding to the mold illustrated in Fig. 4.

In conventional pulp molding machines of the rotary type, such as is shown, for example, in Fig. l, a'plurality of foraminous molds M may be mounted on the outer ends of a plurality of tubular arms A connected to a source of suction (not shown) and extending radially outward from a hollow, horizontally mounted, rotatable shaft S. Upon rotation of the shaft S, the molds M are advanced in a circular path in which they become successively immersed momentarily in liquid pulp slurry and then continue their movement through an arc of about 270 to a discharge station. Suction is applied to the molds while they are immersed in the pulpslurry to cause layers of Wet pulp fibers to be deposited thereon, which layers are known as preforms. The suction is continued while the molds are being advanced to the discharge station, where the suction is stopped and the wet preforms are blown or sucked from the molds. The suction applied during the movement of the molds toward the discharge station extracts most of the excess liquid from the wet preforms carried thereon, but a small pool of residual liquid usually collects inside the bottom of each mold. At the discharge station the tubular arm carrying each mold is disposed generally horizontally, and the mold has been turned to bring its forming face into a generally vertical plane. Hence, the pool of residual liquid collects at the bottom of each mold on one edge of the forming face thereof.

In order to prevent the residual liquid from being blown out of the mold and blown onto the edge of the pulp preform being discharged, each mold may be provided with a drainage trap of the type described in detail in the copending application previously referred to. In general, this trap includes a plurality of small standpipes mounted in the perforations in the forming face of the mold, which standpipes project into the chambered interior of the mold a distance suflicient to prevent residual liquid from escaping through the perforations. For the rotary type of molding machine, it may only be necessary to provide standpipes in the portion of the mold which is near the bottom thereof when the mold is disposed horizontally at the discharge station, but it is also advantageous to provide standpipes in all of the perforations over the entire area of the forming face of the mold.

The present invention relates particularly to drainage traps for pulp molds employed in non-rotary molding machines, such as vertically reciprocating machines or other types having up and down movement. In such machines, it is important to be able to drain the molds without tilting or turning them, and at the same time prevent residual liquid from being blown out'onto a pulp preform being discharged. The advantages of this arrangement are especially evident in the manufacture of very large molded pulp articles on individual molds.

Referring to Fig. 2, a foraminous mold indicated generally by the numeral 10 is mounted on the lower end of a vertically reciprocable tubular arm 12 connected to a source (not shown) of both suction and of compressed air. The mold 10 includes a conical chambered body 14 having a circular flange 15 formed on the lower and larger open end thereof. The chambered body 14 may be an integral part of the arm 12 as shown, or it maybe 'removably joined thereto in any suitable manner. A circular forming plate 16 having a bevelled rim 18 secured to the flange 15 covers the open lower end of the chambered body 14. The plate 16 is provided with a plurality of transverse perforations 20-20 located at uniform intervals over the entire area of the plate 16 and its 18 Usually, the plate 16 is made of cast bronze, but it may also be molded from a plastic compound, such as a thermosetting resin. The outer or forming face of the plate 16 is covered. by a coextensive, circular, copper finestraiuing screen 22. A ring 23 secured to the rim 18 of, the plate 16 by a plurality ofbolts 24-44 holds the screen 22 snugly against the plate 16.

In producing a pie plate, for example, a preform representedby alayer26 of wet pulp is deposited on the screen 22 by applying suction to the tubular arm 12 while the mold is lowered and immersed in liquid pulp slurry contained in an open tank (not shown). Then the mold 10. is elevated, and the preform 26 is ejected by stopping the suction and then admitting compressed airto the arm 12. to blow the preform '26 off the mold 10.

In order to prevent residual liquid which is in the interior'of the chambered body 14 from being blown out through the perforations 20-20, a plurality of standpipes. 28-28. are. provided one for each of the perforations 20-20 in the plate 16 and its rim 18. The stand pipes 28-28 project inwardly from the plate 16 into the chambered body 14 for a sufficient distance to trap a relatively large pool of liquid therein. In one type of pulp mold extensively employed commercially, the perforations are about inch in diameter, and in this mold standpipes having a length of about twoinches performed satisfactorily. The standpipes. 28-28 may be threaded or otherwise seated or fitted into the perforations; 20-20, as desired.

A tubular extension 30 extends from the arm 12 through the; chambered body 14 and down betweenthe standpipes 28-28 to a point spaced a short distance above the forming plate 16. It may be necessary to bendthe upper portions of a few of the standpipes 28-28 sideways in order to accommodate the extension 30. During the continued application of suction to the arm 12. after the. mold 10.,has been lifted out and elevated above the liquid pulp slurry, the residual liquid in the chambered body 14. is sucked out through the extension 30 until the upper level of the remaining pool of liquid, indicated at 32, coincides with the point at which the open lower endof the extension 30v is located. This point is spaced a short distance above the formingplate 16, and yet it is well below the upper ends. of the standpipes 28-28. When the suction applied to the arm 12 is stopped, and compressed air is admitted thereto to blow the preform 26 off the mold 10, there is no. danger that the residual liquid in the body 14 will be blown out through the perforations 20-20 in the plate 16, because the upper level 32 of the residual liquid is so far below the upper ends of the standpipes 28-28. Thus, the vertically reciprocable mold 10 may be. drained of most of the excess liquid, and the preform 26- may be blown off, without tilting or turning the mold 110, and without blowing any residual liquid on the preform 26 being ejected.

Inthe second embodiment of theinvention, illustrated in Fig, 3, a mold, indicated generally by the. numeral 50 is mounted. on the, lower end of av vertically reciprocable arm. 52, which in this case may be a. solid arm or post. The mold 50 includes a conical chambered body 54 having a circular flange 55 formed on the lower-and larger open end thereof. The chambered body 54' is secured tothe arm 52 by a threaded joint 56. A circular forming plate 57 having a bevelled rim. 58 secured to the flange 55 covers the open lower end of the chambered body 54. The plate 57 is provided with a plurality of transverse perforations 60-60, located at uniform intervals over the entire area of the plate 57 and its rim 58., The outer or forming face of the plate 57 is covered by a coextensive,'circular, fine-straining screen 62. A ring 63 secured to the rim 58 of the plate 57 near its periphery by a plurality of bolts 64-454 holds the screen 62 snugly against the plate 51. A preform represented by: a layer 66 of wet pulp isdcposited on the screen; 62 by applying. suction to.

the interior of the body 54 while the mold 50 is immersed in liquid pulp slurry.

The suction is created in the interior of the chambered body 54 by connecting a source of suction (not shown) to a pair of pipes 68-68 which pass through the conical side walls of the body 54 and extend into its interior on opposite sides of the arm 52. A plurality of standpipes 70-70 are fitted one for each in the perforations 60-450 in the plate 57 and its rim 58, in the same way as the standpipes 28-28 described for the first embodiment of invention shown in Fig. 2. The pipes 68-68 extend downwardly between the standpipes 70-70 to a point spaced a short distance above the forming plate 57 but well below the upper ends of the standpipes'70-70. The upper ends of a few of the standpipes 70-70 may be bent sideways, as shown in Fig. 3, in' order to accommodate the pipes 68-68. If necessary, the pipes 68-68 may be bent to provide angular elbows 72-72 in order to have these pipes project perpendicularly toward the forming plate 57. The point at which the lower ends. of the pipes 68-68 terminate above the plate 57 determines the maximum upper level 74 of the pool of residual liquid which may remain when the mold is drained by the application of suction to the pipes 68-68.

In order to supply the mold 50 with compressed air to blow off the pulp preform 66, the pipes 68-68 may be connected through suitable valves (not shown) to a source. of compressed air, in addition to their connection to the source of suction. In such case, the pipes 68.--68 would serve the dual purpose of connecting thev mold 50 to a source of: compressed air and a source of suction alternately.. However, the compressed air may alien natively be supplied separately through apipe 76 which passes through the side walls of the chambered body' 54 above the level at which the pipes 68-68 enter the body 54.. I

Although the mold 50 is designed primarily for usein non-rotary molding machines, such as vertically reciprocating machines or other types having up and down movement, this mold may be modified to adapt it for use. in rotary machines. By extending the standpipes 70-70 upwardly, as shown in broken lines in Fig. 3, the upper ends of. these standpipes may be elevated above the form! ing plate 57 a distance suflicient to substantially eliminate the danger of having any residual liquid blown through the plate 57 during the ejection of the preform 66, even when the mold 50 is turned upside down during the. normal movement of a rotary molding machine.

Fig. 4 shows an embodiment. of the invention designed for employment in another type of non-rotary molding machine, in which, the molds are subjected to a basic up and down: movement not limited to vertical reciprocation. By subjecting the molds to both horizontal and vertical movements, the molds. may be advanced in a sinuous path successively through a series of horizontally disposed tanks containing pulp slurry ofv different grades'or colors. In this. manner, it is possible to rapidly produce molded pulp articles which are laminated from a plurality of different grades of pulp stock.

A mold indicated. generally by the number comprises a chambered body 102 having a circular flange 103 formed on the open. lower end thereof. A circular forming plate 104 having a bevelled rim 105 covers the open end of the chambered body 102. The plate 104 is provided with a plurality of transverse perforations 106- 106 located at uniform intervals over the. entire area of the plate 104 and its rim 105. The outer or forming'iacc of the-plate1'04 is: covered by a coextensive, circular, finestraining screen 108. A ring 110 secured to the 105 near its periphery by a plurality of bolts 112 holdsthe screen 108 snugly against the plate 104 and secures the plate 104 to the flange 10.3.

A pipe 114 projecting; downwardly into the of the chambered. body. 102 from the. central upper portion thereof may be connected-alternately team suction and a source of compressed air. extends downwardly between a plurality of elongated standpipes 116-116 which are fitted one for each in the perforations 106-106 formed in the plate 104 and its rim 105. The lower end of the pipe 114 is positioned a short distance above the forming plate 104 but well below the upper ends of the standpipes 116116. A few of the standpipes 116116 may be bent sideways in order so accommodate the pipe 114 between them, as is clearly shown in Fig. 4.

Frorri opposite sides of the flange 103 on the chambered Body 102 a pair of arms 118-118 extend angularly upward to a pair of pulleys 120-120 which travel on a suitable conveyor mechanism (not shown). In this manner, the entire mold 100 may be suspended and carried by the conveyor mechanism. A series of such molds may be linked together end-to-end with adjacent molds of the series being joined to the same pulley.

In Fig. 5, there is schematically illustrated a series of linked molds 125125, each of which corresponds in structure to the mold 100 illustrated in Fig. 3. The molds 125125 are linked together end-to-end by oppositely projecting arms 126126 joined to pulleys 128-128 which are supported on a conveyor mechanism (not shown). By means of this conveyor mechanism the molds.125--125 are advanced in a generally horizontal sinuous path in which they become successively dipped into a tank 130 containing liquid pulp slurry. During the momentary period of immersion of each mold 125, suction is applied thereto through a pipe 132, which corresponds to the pipe 114 of the mold 100, thereby causing a layer of wet pulp to be deposited on the forming face of the mold.

The series of molds 125-125 may be successively dipped into a series of tanks similar to the tank 130 containing pulp slurry, thereby successively depositing a plurality of layers of pulp on each mold. Different grades of pulp stock may be deposited in successive layers. For example, in forming a molded pulp pie plate, a fine grade of pulp may be deposited in the first layer, next a coarse grade of pulp may be deposited thereon, and finally another layer of fine pulp may be deposited. The resultant pie plate will have smooth, fine-grained exterior surfaces, and a coarse interior which imparts resiliency to the completed plate. Tanks of pulp slurry having different colors may be employed to form molded pulp plates having one color on one side thereof and a different color on the opposite side. 1

The embodiment of the invention illustrated in Figs. 4 and 5 is not limited to use with a series of sequentially arranged tanks of slurry, or to any particular type of suspension or conveyor system. In some instances, the series of molds may be dipped into only one tank of slurry, and for this only a simple system for carrying the molds is required. After each mold emerges from the single tank or the last tank of a series thereof, the suction applied to the mold is stopped and compressed air is applied to discharge the wet pulp preform therefrom. The preform may be discharged downwardly directly onto a traveling conveyor belt (not shown) without tilting or turning the mold, or employing an auxiliary transfer device.

The primary feature of this embodiment of the invention is the fact that pulp preforms formed on the molds may be discharged therefrom without the necessity of turning the molds over to drain them, and yet residual liquid in the molds is prevented from splashing onto the preforms being discharged. The suction applied to the interior of each mold, through the pipe 114 in the case of the mold 100 and through the pipe 132 for each mold 125, draws the level of the residual water down below the upper ends of the standpipes. Hence, when compressed air is subsequently applied to theinterior of each mold to discharge the wet pulp preform therefrom, there is no danger of blowing the residual water through the standpipes onto the preform being discharged.

The pipe 114 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 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. A pulp molding machine including a series of foraminous molds movable in a sinuous path successively through a tank containing liquid pulp slurry, each of said molds comprising a chambered body having an open lower end, a perforated forming plate covering the open end of the body, said plate having a plurality of transverse perforations at uniform intervals over its entire area, a plurality of standpipes mounted one for each in the perforations in the plate, said standpipes projecting upwardly into the chambered body a distance suflicient to prevent residual liquid from escaping through the perforations and to trap a pool of residual liquid within the chambered body, a tube extending through the upper end of the chambered body, said tube being alternately communicating with a source of suction and a source of compressed air to form pulp articles on the mold while immersed in the slurry and subsequently discharge them therefrom, and a tubular extension extending from said tube downwardly through the chambered body and between the standpipes to a point spaced above the forming plate but well below the upper ends of the standpipes, whereby liquid may be drained from the pool through the tube without tilting or turning the mold.

2. The invention defined by claim 1, in which the series of molds are linked together end-to-end and move in a sinuous path successively through a series of tanks containing liquid pulp slurry.

3. In a pulp molding machine having a series of foraminous molds movable from an initial forming position immersed in liquid pulp slurry to a discharge position elevated above the slurry, said molds being subjected to suction in the forming position to deposit pulp thereon from the slurry and being subjected to a blast of compressed air in the discharge position to discharge initially formed pump articles therefrom, the improved mold comprising a chambered body having an open end and being connected selectively to a source of suction and a source of compressed air, a perforated forming plate covering the open end of said body, said plate having an exterior forming face contoured to mold pulp articles thereon and having a plurality of transverse perforations spaced generally uniformly over its entire forming face, a plurality of standpipes mounted in the perforations on the interior of the forming plate and projecting inwardly toward the chambered body, one of said standpipes being mounted in each of the perforations, said standpipes projecting inwardly a distance sufficient to prevent residual liquid from escaping through the perforations and to trap any residual liquid at the discharge position, and a tube connected to the source of suction and extending through the chambered body to a point below the upper ends of the standpipes for draining liquid therefrom without tilting or turning the mold.

4. In a pulp molding machine having a series of foraminous molds mounted rotatably for movement in a circular path from an initial forming position to a discharge position, said molds being successively immersed in liquid pulp slurry in the initial forming position while being subjected to internal suction to deposit pulp thereon from the slurry and being elevated above the slurry in the discharge position and subjected to an internal blast of compressed air to discharge initially formed pulp articles therefrom, the improved mold comprising a chambered body having an open lower end and being connected internally to both a source of suction and a source of compressed air, a perforated forming plate covering the open end of said body, said plate having an exterior forming face contoured to mold pulp articles thereon and having a plurality of transverse perforations spaced generally uniformly over its entire forming face, a fine-straining screen covering the perforated plate, a plurality of standpipes mounted onefor each in the perforations, said standpipes projecting upwardly into the chambered body a distance sufficient to prevent any residual liquid from escaping through the perforations and to trap such liquid when the mold is at the discharge position, a pair of tubes connecting opposite sides of the upper portion of the chambered body to the source of suction, a separate pipe mounted in said upper portion of the body for providing the connection to the source of compressed air, and a pair of tubular extensions extending from said suction tubes downwardly through the body and between the standpipes to a point spaced above the forming plate but well below the upper ends of the standpipes.

References Cited in the file of this patent UNITED STATES PATENTS 1,537,195 Salisburg May\12, 1925 2,118,491 Chuse May 24, 1938 2,163,585 Chaplin June 27, 1939 2,415,244 Hillbom Feb. 4, 1947 2,772,608 Emery -e Dec. 4', 1956