US2333433A - Apparatus and process for making capsules - Google Patents

Description

Nov. 2, 1943. v c. E. MABBS 2,333,433 I APPARATUS AND 'PROCESS FOR MAKING CAPSULES Filed Feb. 28, 1940 2 Sheets-Sheet 1 imam;- Car/.5 07/06/26 67 I e lfi'ci ays Nov. 2, 1943. c. E. MABBS APPARATUS AND PROCESS FOR MAKiNG CAPSULES Filed Feb. 28,' 1940 2 Sheets-Sheet 2 Car/ ,5: 0770666 the preferred embodiment and manner of car- Patented Nov. 2, 1943 UNITED STATES PATENT OFFICE APPARATUS AND PROCESS FOR. MAKING CAPSULES Scherer Application February 28, 1940, Serial No. 321,266

11 Claims.

This invention relates to the capsulation of core materials in the liquid or plastic state in a shell of gelatin or other soluble material and the general object is to provide a capsule having a plurality of separated cells of various core materials walled off, each from the other, in a single globule of the shell material.

Another objectis to provide a polyceliular capsule in which the several cells of core material are embedded in a single generally spheroidal globule of the solidified shell material.

A further object is to form capsules of the above character by natural drop formation.

The invention also resides in the novel character of the apparatus employed in carrying out the improved process.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a schematic view of an apparatus for carrying out the invention.

Fig. 2 is a diametrical section of the nozzle taken along the line 2-2 of Fig. 1.

Fig. 3 is an enlarged view of the lower end of the nozzle. I

Fig. 4 is a fragmentary longitudinal sectional view taken along the line 44 of Fig. 3.

Figs. 5 and 6 are views similar to Fig. 4 illusgating successive stages in the capsule forma- Fig. 7 is a cross-sectional view of a double cell capsule.

' l.il ig. 8 is a similar view of a capsule with three ce 3.

While the invention is susceptible of various modifications and alternative constructions and maylbe practiced in" various ways, I have illustrated in the drawings and will herein describe rying out the invention. It is to be understood that I do not thereby intend to limit the invention by such disclosure but aim to cover all modifications, alternative constructions, and methods falling within the spirit and scope of the invention as expressed in the appended claims. 4

In the form selected for illustration, the im'-' proved capsule indicated generally at 9 includes a plurality of cores Ill and H, two as shown in Fig. 7 and three in Fig. 8, composed of or containing the materials to be capsulated which materials are usually liquid or plastic at ordinary temperatures and ordinarily comprise an oil or an oil vehicle having the active ingredient dispersed or dissolved therein. The cells are generally spherical in shape, somewhat flattened on their adjacent sides, and embedded in a solidified shell l2 preferably comprising a single globule of material, usually gelatin, which is immiscible with the core materials and which congeals from liquid state on cooling to ordinary room temperatures. The shell is seamless, relatively thin walled, and of generally spheroidal shape and the cells are separated within the shell by a thin partition H which is usually somewhat thinner than the outer shell wall.

The capsule may be produced by natural drop formation by subjecting quantities of the nonmiscible shell and core materials to the natural forces of gravity, capillarity, and surface tension. In forming a two celled capsule, the invention contemplates discharging measured quantities of the core materials l3 and I 4 from separated orifices i 5 and I6 surrounded by an orifice I! from which'the shell material iii in the liquid state is discharged, timing the discharge of materials so that each will be emitted from its respective orifice at the proper time and in the proper positional relation to form a single compound drop, thereby permitting the free functioning of the natural forces which cause drops to form, and maintaining the proper shape of the latter and separation of the core globules during solidification of the shell material. Preferably, the three orifices face downwardly and are arranged to discharge the materials into a column' ll! of cooled receiving liquid immiscible with the shell material and having a density correlated with that of the compound drop so that gravitation of the drop is prolonged suifl-. ciently to permit of solidification of the capsule shell. I

In the apparatus illustrated, the orifices l5 and I6 are of circular shape-and constitute the lower ends of vertical passages 20 and 2| in a rod 22 preferably composed of insulating material so as to minimize heat transfer between the cold core materials and the gelatin solution. The rod is supported in an insulating body 23 through which extend passages 24 and 25 that connect the pass ges 20 and 2| with short conduits 26 and 21 leading from the dischargeoutlets oi plunger type pumps 28 and 29. The latter are capable of close volumetric displacement adjustment-and draw the respective core materials I3 and 14 from supply tanks 30 and 3|. By immersing these tanks in coolant baths 32 and circulatin thel'coolant through the jackets 33 and it surrounding the pump cylinders, the core materials 2 assess:

are maintained at temperatures well below the gel point of the shell material.

A supply of gelatin solution l8 of the proper concentration is containedin a tank 35 immersed in a water-bath and maintained at the proper temperature by an immersion heater 31. An exchangeheater 38 Within the bath 36 is connected by pipes 39 with a jacket 40 around a pump 4| forming a thermo-siphoning system for maintaining the pump cylinder at the desired temperature.

The pump II is of the metering plunger type and operates to draw the solution through a tube 42 and discharge through a conduit 43 that leads through a passage 44 in the body 23 to an annular passage 45 surrounding the rod 22. A nozzle head 46 secured to the body 23 has an internal bore 41 defining the lower end of the passage 45 which extends well below the orifices l and I6 and terminates in'the orifice i'l, the diameter of which determines the size of the capsule. Be-

point of the shell material. It should have some dehydrating properties and its interfacial surface energy relation to that of the gelatin solution should act to accelerate the action of capillarity on the gelatin and cause the drop to take a generally spherical shape after it becomes freed wherethe compound drops first contact the liqtween the orifice I1 and the orifices l5 and l5,

the gelatin passage 45 communicates through an annular orifice 48 with a vertical chamber 49. Holes 50 open outwardly from this chamber to constitute the latter a capillary ring the' purpose of which will be explained later.

The pumps 28, 29, and 4| may be of any well known type, each adapted to eject an accurately metered quantity of fluid during each down stroke of its piston rod 5|. The latter is raised by a spring 52 and projected downwardly with an accelerated motion by a cam surface 53 actingon a follower 54 that bears against the upper end of the piston rod. By adjusting nuts 55, the pump stroke may-be varied in length and the amount of core and shell materials discharged intermittentLv through the orifices maybe adjusted as desired. Proper timing of the discharges is effected :sby driving the cams 53 from a common shaft Drop formation in the manner contemplated may best be effected by shaping of the cams to provide for gradual acceleration of the pump plungers to a high rate near the end of the discharge stroke and for a rapid return stroke. Thus, the rate of fiow of the ejected materials increases as the volume of the dropincreases, and preferably the rate of this increase is such as to maintain a constant rate of increase in the drop diameter and to time the completion of the drop with its separation from the nozzle. The spring return of the plungers functions to give a sharper uid. This may be accomplished by providing two columns of the liquid, one within the other,

and circulating the liquid through the two col-- umns by admitting the cooled liquid at the bottom of the outer column. In the present instance, the inner column is defined by a vertical glass tube 6| placed within a larger glass tube 62 with its upper end disposed -some-.

what below the maintained level in the outer tube. The lower end' of the tube 62 is fitted in a tubular projection 54 on the closed top of y a tank 65 having an upwardly opening extension 56 which rises above the liquid level to be maintained. The tank and tube 63 are filled with the receiving liquid which is cooled by circulation of refrigerant or a chilled liquid through an exchanger 61 within the tank. Circulation of the cooled receiving liquid upwardly through the tube 62 anddownwardly through the tube Si is efiected by a motor driven gearpump 58 arranged to withdraw liquid. from the uppermost part of the tank and deliver such liquid through a cooling coil 59 within the exchanger to the lower end of the tube 52. The cooled fluid thus circulates as indicated bythe arrows in Fig. l.

The nozzle is positioned in alinement with the tube 5i so that the falling drops 10 descend therethrough at a rate determined by the relative densities of the compound drop and receiving liquid. With the present arrangement, the

' density ofthe receiving liquid/should be slightly pump valveaction and assists thereby in prevent- 1 ing dribble at the nozzle.

The lower end .of the rod 22 is specially shaped to enable the shell material to flow in between the two or more orifices l5 and i6 and result in some capillary action that will assist in drawing the shell material in between the globules Ill and I I to insure the formation of a definite wall l2 of shell material separating the two globules in the final capsule. To this end, the rod may be formed with an end recess 51 extendingtransversely between the passages" and 2| withits opposite ends diverging upwardly and converging substantially to a point as indicated at 58 at the outer surfaces of the rod. The passages 20 and 2| thus extend through two projections BI and 80 less than that-of the compound drop so that each falling drop will descend slowly and yet not interfere with the formation of the succeeding drop. The descent is prolonged sumciently to enable the shell material to cool below the gel point and thereby congeal to a rubbery consistency. The capsules thus formed descend through the open lower end of thetube GI and are delivered to suitable mechanism for retrieving the capsules. As herein shown, this mechanism comprises a simple endless conveyor- H having buckets-12 receiving'the capsules and elevating them out of the liquid is after which the excessive liquid is removed in any suitable way.

The progressive formation of the capsule will now be traced. As a preliminary, it will be observed that the nozzle orifices, arranged as above described, provide for the discharge of globules of core and shell materials in the relationwhich they occupy in the finished capsules, which general relation ismaintained during the action of the natural forces on the globules from the time they emerge from the orifices until final congealing of the shell material to form a completed capsule. a

After the falling of one drop and during the return strokes of the pump'plungers, the materials will be positioned in the nozzle as shown in Fig. 4. Through the action of the capillary ring 49, the surplus materials which are necessarily present for drop-formation are retracted into the nozzle bynatural capillary forces. ,as the'pump plungers descend-simultaneously, globules Band 14 of the core materials form and hang from the orifices i and I 6 and a similarly shaped globule I5 becomes suspended from the nozzle tip with its lower portion projecting into the receiving liquid (Fig. 5) by which it is partially supported. As the globules increase in size progressively during the active pump stroke, the action of capillarity and surfacetension reacts in accordance with the liquid column stability law to reduce the diameters of the different liquid columns immediately below the orifices l5, l6, and I! until finally these columns are pinched off when the weights of the individual globules i3 and 14 or the composite drop exceed the natural forces tending to hold the drops suspended from the orifices. By proper timing of the pump strokes, this action may be made to occur substantially simultaneously with the difierent globules as shown in Fig. 6 which illustrates the condition existing near the endof the active pump strokes which the core materials are about to break from their orifices. Finally, at the end of the pump strokes, the weight of the three liquids ejected less the buoyant force exerted on the erally spheroidal shape as shown-practically instantaneously by the action of the surface energy of the gelatin solution shell while at the same time maintaining the core globules separated from each other. The natural forces thus acting cause a slight flattening of the cells at their adjacent sides and slight depressions [2 in the shell at points between cells.

During the descent of the compound drop thus formed, heat from the gelatine is absorbed bythe cores and by the receiving liquid until, before the drop reaches the lower end of the column, all

of the shell material will be congealed sufficiently to be handled by the retrieving mechanism, the 7 core globules being then supported in a substantially solid mass of gelatin.

- The size of the finished capsule is determined by the quantities of core materials to be elected during each stroke of the pumps 28 and 29 and these in turn determine the amount of shell material required to be supplied by the pump 4 I. The

- combined-weight of the core and shell materials which form the drop determines the size of the orifice I! under the established drop weight and liquid column stability laws. i

In the formation of capsules having three or more cells, various arrangements of thecore material orifices may be employed. In order. however, that th resulting capsule will be as nearly spherical aspossible, it is preferred to arrange the orifices in an annular series. This will result in a capsule shaped approximately as shown in Fig. 8. V

The process'above described provides for the formation of polycellular capsules in continuous succession and at a rate determined bv arious controllable factors. Obviously, the core materials may be different in kind and relative quantitles and any desired number may be included. I claim as my invention: 1 1. Capsulatin apparatuscomprising, in combination, laterally spaced projections each having a downwardly facing end orifice, means for discharging measured quantities of liquid core materials from the respective orifices to form separated drops, an annular chamber surrounding said projections and terminating in an orifice surrounding and disposed below said first orifices,

mechanism for discharging liquid solidifiable shell material through said chamber to enclose said drops and cause a compound drop to fall from said last mentioned orifice, and a column of liquid receiving the composite drop during formation thereof and having a density less than the drop, said liquid being maintained at a temperature substantially below that at which said shell material will congeal.

2. Capsulating apparatus comprising, in combination, means providing a plurality of laterally spaced downwardly facing orifices with a recess disposed between and extending above the adjacent orifices,means for discharging measured quantities of liquid corematerials from the respective orifices to form separated drops thereon,

an annular chamber surrounding said orifices and I communicating with said recess above the orifices,

said chamber terminating in and disposed below said first orifices, mechanism for discharging liquid solidifiable shell material through said chamber to enclose said drops and cause acompound drop to fall from .said last mentioned orifice.=- H

3. Capsulating apparatus comprising, in com-' bination, laterally spaced projections each having a downwardly facing orifice, means for discharging, measured quantities of liquid core materials from the respective orifices to form separated drops, an annular chamber surrounding said projections and terminating in an orifice surrounding and disposed below said first orifices,'and mechanism for discharging liquid solidifiable shell material through said chamber to enclose saiddrops and cause a compound drop to fall from said last mentioned orifice.

,4. Capsulating apparatus comprising, in combination, a plurality of laterally spaced'orifices, means for discharging measured quantities of liquid core materials from the respective orifices to form separated globules thereon, an annular chamber surrounding said orificesand terminating in an orifice spaced'therefrom, mechanism for discharging liquid solidifiable shell material through said chamber to enclose said globules and cause a compound globule to separate from said last mentioned orifice, and. a body of liquid receiving the composite globule during formation thereof.

5. Capsulating apparatus comprising, in coma bination, a plurality of laterally spaced orifices,

surrounding said orifices and terminating in anmeans for discharging measured quantities of liquid core materials from the respective orifices to form separated globules. an annular chamber other orifice, and mechanism for discharging liquid solidifiable .shell material through said chamber to enclose said globules and cause a compoundglobule to separate from said other orifice.

6. The method of forming a polycellular compound drop which includes the steps of intermittently discharging spaced globules of at leasttwo liquids from spaced orifices, and simultaneously discharging a quantity of a third liquid from a surrounding orifice to form a shell around and between said globules and cause the compound drop to separate from the latter orifice, said intermittent discharge being. carried out at such a rate that saidtwo first liquids form as 4- aaas,4ss

separate drops and the third liquid completely surrounds said separate drops maintaining their separation and said compound drop separates as a compound drop under the natural forces of gravity and surface tension fromthe discharge 5 'I. The method of forming polycellular capsules having at least two cells ofcore liquids embedded in a body of a shell material-which is congealable from a liquid stateand immiscible in said from said orifice and carrying out 'such intermitfirst liquids, said method comprising intermittently discharging a quantity of said shell liquid from an orifice to form a globule, simultaneously discharging separated globules of said core liquids within said first globule before separation thereof from said orifice, carrying out said, intermittent discharge at such a rate that the shell liquid completely surrounds said separated globules of core liquids maintaining their separation and said compound globule of shell and core liqthe composite globule is subjected to the natural forces of gravity and surface tension.

8. The method of forming polycellular capsules having separated cells of at least two liquids embedded in a body of a third liquid which is con gealahle and immiscible in said first l quids, said .method comprising intermittently discharging a quantity of said third liquid from an orifice to form a drop, and during formation of said drop,

simultaneously discharging drops of said first liq-- uids from separated orifices disposed within and above said first orifice, said intermittent discharge being carried out at such a rate of speed'that a compoimd drop is formed upon the thirdlliquid orifice and separates therefrom under the natural forces of gravity and surface tension, and 40 said third liquid during the formation-of .such compound drop flows completely about and enclosw individual drops of the first two liquids maintaining their individualseparation within the compound drop.

9 The method of forming polycellular capsules having a plurality of liquid cells embedded in a body of another material which is congealable' and immiscible in said first liquids, said method comprising intermittently discharging a quantity of said congealable liquid from a downwardly facing orifice to form a drop, and simultaneously discharging separated drops of said .first liquids .from spaced apart downwardly facing orifices within said first drop before separation thereof tent discharge at such a rate of speed that a compound drop of said two first liquids within said congealable liquid is formed upon the orifice and separates therefrom as a compound drop under the natural forces of gravity and surface tension and the congealable liquid during the formation of such drop fiows about the individual drops of-the first two liquids maintaining their supporting the drop during its formation in a liquid having a density less than that of the com.- pound drop and carrying out such discharge at such a rate that the compound drop separates as acompound drop from said orifices under the natural forces of gravity and surface tension.

11. The process of capsulation which comprises discharging separatedrops of immiscible core material and shell material from surrounding orifices to form acompound drop of core and shell material pendent upon said orifices, discharging said core materials from separate orifices form-, j ing separate globules of corematerial within and separately surrounded by said shell material, and carrying out said discharge in such a manner that the compound drop separates from the orifices under the natural forces of gravity and Surface tension. v

' CARL E. MAZBBS.

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