US2920701A - Pulp molding - Google Patents

Description

R. WELLS PULP MOLDING Jan. 12, 1960 Filed Sept. 28, 1956 IiVVE N TOR Beyer Wells MR4 g; F; c K 5 ATTORNEY United States Patent PULP MOLDING er Wells, Plattsbnrg, N.Y., asign'or to Diamond ational Corporation, a corporation of Delaware I Application September 28, 1956, Serial No. 612,855

4 Claims. (Cl. 162-392) This invention relates to pulp molds, and more particularly to a drainage trap for pulp molds.

In the manufacture of molded pulp articles, such as pie plates, it is customary to initially form partially molded articles, known as preforms, by successively dipping a series of foraminous molds into a liquid pulp slurry, and simultaneously applying suction to the molds to cause layers of wet pulp fibers to be deposited thereon; subsequently, the resultant pulp preforms are completely dried and finished to produce the molded articles desired.

- The suction referred to is continued while the series of molds is advanced from the initial forming position in the pulp slurry to an article discharge position located adjacent to a conveyor belt. By the time each of the molds reaches the discharge position, the suction has removed most of the excess liquid from the wet preforms carried thereon, but a small quantity of residual liquid usually remains inside each mold.

Molded pulp preforms are discharged and transferred to the conveyor belt by blowing or sucking them from the molds one at a time in succession. In the systems employed heretofore, any small quantity of residual liquid which remained in the molds was likewise blown or sucked out from the molds, and frequently this liquid was blown upon the preforms being transferred to the conveyor belt. Usually the liquid was blown upon one edge of the preforms, making this edge limp and soggy. Since at this stage of their formation the molded pulp articles were still damp and only lightly compacted, they were readily suspeptible to damage from splashing liquid. The limp soggy edges tended to collapse slightly, resulting in a deformed product. Often the soggy edges were so wet that they .failed to dry completely during the subsequent drying operation, and when the 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 a new and improved drainage trap for pulp molds.

Another object of the invention is to provide pulp molds with means for preventing any excess liquid from 'being'blown upon molded pulp articles at the time they are-being discharged from a molding machine.

Other objects and the nature and advantages of the instant invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein: Fig. l is a side elevational view, partially in section, of a pulp molding machine provided with a plurality of individual molds embodying the present invention; Fig. 2 is an enlarged vertical section of one of the individual molds shown in Fig. l; and

Fig. 3 is a vertical section of a mold forming another .embodiment of the invention.

, Referring to Fig. 1, the pulp molding machine shown "ispnovided with a plurality of foraminous molds 10, Whichare designed by way of example to form pie plates.

Patented Jan. 12, 1960 One of the molds 1010 is mounted on the outer ends of each of a plurality of tubular arms 1212, which are secured to and extend radially outward from a horizontally mounted, rotatable, hollow shaft 14. Rotation of the shaft 14 advances the molds 1010 in a circular path in which they are successively immersed momentarily in a liquid pulp slurry 16 containedin a tank 18. In some types of molding machines the molds are advanced continuously at a uniform speed through the slurry, while in other types of machines the molds are advanced intermittently.. While the molds are being advanced in this manner, suction is appliedsimultaneously to each of the arms 12-12 by a pumping means (notshown) associated with the hollow shaft 14. The suction causes the pulp slurry to flow. through the foraminous forming faces of the molds which are immersed in the slurry, thereby causing layers of wet pulp fibers to be deposited thereon.

During the movement of the series of molds 1010 in their circular path passing through the liquid pulp slurry 16, the tubular arms 1212 are likewise advanced in a circular path. Each of the arms 1 212 extends substantially vertically downward at the time the mold carried thereby is immersed in the pulp slurry 16. From this initial forming position each of the molds 1010 is advanced, in a clockwise direction as viewed in Fig. 1, through a circular arc of approximately 270 to an article discharge position located adjacent to a conveyor .belt 20. In the discharge position of the molds 1010, the arms 1212 carrying them are disposed substantially horizontally.

Suction is applied continuously toall of the molds 1010 while they are being advanced from the initial forming position in the pulp slurry 16 to the article discharge position adjacent to the conveyor belt 20. This action causes most of the excess liquid to be drawn from the wet preforms carried by the molds 1010. The excess liquid is sucked radially inward through the tubular arms 12-12, and thence through the hollow shaft 14 to a drainage tank (not shown) from which the liquid may be returned to the tank 18, if desired.

During the removal of the excess liquid from the pulp preforms on the forming faces of the molds 10-10, practically all of the liquid is likewise removed from the inside of the molds. However, a small quantity of residual liquid usually remains which collects by the action of gravity at the bottom of each mold when it is located at the discharge position. When the still somewhat damp and incompletely compacted pulp preforms are discharged and transferred to the conveyor belt 20 by blowing or sucking them from the molds 1010 at the discharge position, the danger exists that this residual liquid may also be blown or sucked out from the molds and blown onto the preforms being discharged.

In accordance with the invention, the possibility of having residual liquid blown or sucked out of molds at the discharge position is prevented by providing a drainage trap in each mold. Referring to Fig. 2, a mold 22 corresponding to one of the molds 1010 of Fig. 1 is shown mounted on the outer end of a tubular arm 24. The mold 22 includes a conical chambered body 25 having a flange 26 formed at the outer end thereof. .The chambered body 25 resembles an expanded hollow head, which may be an integral part of the arm 24 as shown, or it may be removably joined thereto in any suitable manner. The chambered body 25 iscovered by a circular forming plate 27 having a beveled rim 28. The plate 27 and the rim 28 are provided with a plurality of transverse perforations 2929 positioned at uniform intervals from one side to the other and from the top to the bottom thereof. The forming plate 27 is usually made of cast bronze, but it may also be molded from a thermosetting resin. The outer or forming face of the plate 27 is covered by a coextensive circular fine-straining screen 30, which may be made of copper. The screen 30 is held against the plate 27 near its periphery by means of a ring 32 secured to the flange 26 by a plurality of bolts 34-34. The interior ofthe chambered body functions as a vacuum chamber for the mold 22 when suction is applied to the tubular arm 24. In producing a pie plate, for example, a layer 36 of wet pulp is deposited on the screen by applying suction to the tubular arm 24 while the mold 22 is immersed in liquid pulp slurry during the operation of a molding machine similar to the machine previously described.

In Fig. 2 the mold'22 is shown at the article discharge position with the tubular arm 24 disposed substantially horizontally. In this position a smallpool '38 of residual liquid has collected at the bottom of the mold by the action of gravity. The pool 38 of residual liquid is trapped in the bottom of the chambered body25, and itis prevented from being blown out through the perforations 29-29 in the plate 27 which are located in this portion of the mold, by means of a plurality of standpipes -40. One of the standpipes 40-40 is mounted in each of the perforations 29-29 in the portion of the bevelled rim 28 which is located at the bottom of the mold 22 when it is in the discharge position shownin Fig. 2. The standpipes 40-40 extend inwardlyfrom the rim 28 at a distance suflicient to trap the maximum quantity of residual liquid normally expected to collect in the bottom of the mold 22. In order to fulfill this purpose, the standpipes 40-40 must be sufiiciently long to project above the highest expected upper level :of'the' pool'38 of residual liquid. 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 inch performed satisfactorily. The standpipes 40-40 may be threaded or otherwise fitted into the perforations 29-29, as desired.

In the application of either external suction or internal vthe pulp molding machine continues, the mold 22 is advanced from the discharge position down to the initial forming position in the liquid pulp slurry, and the previously described sequence of operations is then repeated.

Fig. 3 shows an embodiment of the invention designed particularly for usein other types of molding machines, such as machines employing a vertically reciprocable motion or any other non-rotary type of motion, but which may also be employed in rotary machines. In the embodiment of the invention shown in Fig. 3, a mold 42, corresponding to the mold 22 shown in Fig. 2, is mounted on the outer end of a tubular arm 44. The mold 42 includes a conical chambered body 45 having a flange 46 at the outer end thereof. The body 45 is covered by a circular forming plate 47 having a bevelled rim 48. Both the plate 47 and the rim 48 are provided with a plurality of transverse perforations 49-49 located at equal intervals over their entire surface area. A coextensive circular fine-straining screen 50 covers the plate 47 and is held near its periphery by a ring 52 secured to the flange 46 by a plurality of bolts 54-54. A layer 56 of wet pulp formed on the screen 50 represents a preform deposited by' the application of suction in a manner similar to that described in the description of the first embodiment of the invention, except that the movement of the mold is not necessarily a rotary type of motion.

A small pool 58 of residual liquid, which has collected at the bottom of the mold 42 by the action of gravity istrapped therein and prevented from being blown out 4 through the perforations 49-49 by means of a plurality of standpipes 60-60. One of the standpipes 60-60 is mounted in each of the perforations 49-49 over the entire area of the plate 47 and the rim 48. The standpipes 60-60 extend inwardly from the plate 47 and the rim 48 a distance sufficient to project about the highest expected upper level of the pool 58 of residual liquid. The standpipes which are located at the bottom of the mold when it is in the position shown in Fig. 3 prevent the pool 58 of liquid from escaping through the perforations 49-49 in-this area, while the rest of the standpipes trap any liquid which may be adhering or flowing down the upperinside surfaces of the plate 47 and the rim 48. Furthermore, afterlong periods of service by ordinary molds, i.e., molds not equipped with standpipes embodying the invention, fibers and slimy bacterial growths tend to deposit around the inner ends of each of the perforations. The resultant conical mounds resemble the mouths of small volcanoes, and they create miniature liquid traps from which liquid may be blown through the perforations over the entire area of the plate 47 and the rim 48. Such difiiculties are effectively over come by molds embodying the invention, since the provision of standpipes in each of the perforations prevents the formation of the volcanic mounds entirely and traps any residual liquid adhering or flowing down the inside surfaces of the forming plate and its rim. Itwill 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 inthe appended claims; What is claimed is:

1. In a pulp molding'machine having a series of fo= raminous molds rotatable from an initial forming position immersed in liquid pulp slurry through a circular path to a discharge position 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 pulp 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, and a plurality of standpipes associated with the perforations on the interior of the forming plate and projecting inwardlytoward the chambered body, one of said standpipes being associated with each of the perforations, said standpipes projecting inwardly a distance sufiicient to prevent residual liquid from escaping through the perforations and to trap a pool of residual liquid at the discharge position. p

2. The invention claimed by claim 1, in which the molds are disposed horizontally at the discharge position, and the standpipes are associated only in the perforations which are located near the bottom of the mold when the mold is disposed in this position.

3. In a pulp molding machine having a series of foraminous molds mounted rot-atably for movement through 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 chamberedbody having an open end and being connected internally .to both a source of suction and a source of compressed air, aperforated forming plate covering said open end o'fthe chambered'body', said pla'tehaving 81113- terior forming face contoured to mold pulp articles thereon and having a plurality of transverse perforations spaced generally uniformly over its entire forming face, a finestraining screen covering the forming face of the plate, and a plurality of standpipes mounted in the perforations, one of said standpipes being mounted in each of the perforations, said standpipes projecting inwardly into the chambered body a distance sufiicient to prevent any residual liquid from escaping through the perforations and to trap such liquid therein when the mold is at the discharge position.

4. In a pulp molding machine having a series of foraminous molds mounted rotatably for movement through a circular path from an initial forming position to a discharge position, said molds being disposed vertically and 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 disposed horizontally and elevated above the slurry in the discharge position while being 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 end and being connected internally to both a source of suction and a source of compressed air, a circular forming plate having a beveled rim covering said open end of the chambered body, said plate and rim having a plurality of transverse perforations spaced generally uniformly over their entire area, a coextensive circular fine-straining screen covering the perforated plate and rim, and a plurality of standpipes mounted in the perforations which are in the lowermost segment of the plate and the rim when the mold is disposed horizontally in the discharge position, one of said standpipes being mounted References Cited in the file of this patent UNITED STATES PATENTS 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 Dec. 4. 1956

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