US2331572A - Fabrication of capsule shells and filled capsules - Google Patents

Description

9 R. P. SCHER-ER 2,331,572

FABRICATION OF CAPSULE SHELLS AND FILLED CAPSULES Filed 001;. 16, 1939 /0 INVENTOR.

Hm BY F0555? f EChEFE? ATTORNEYS.

' content. substance in molds.

Patented Oct. 12, 1943 FABRICATION or CAPSULE SHELLS AND FILLED CAPSULES Robert P. Scherer, Detroit, Mich.

Application October 16, 1939, Serial No. 299,627

12 Claims.

This invention relates to the fabrication of uniform, seamless, hermetically sealed capsule shells about capsule content material, which content material may be either in a fluid or in a solid state.

An object is to provide a capsule shell which is seamless, which is of uniform thickness and structure throughout and whichforms a her metlcally sealed envelope about the content substance. The capsule shell formed according ,to

this improved process is free from leak holes or thin areas which are liable to rupture.

Another object is to fabricate capsule shells of this character rapidly and economically and to provide complete filled capsules wherein the shell is of uniform thickness and homogeneity.

This improved process may be employed to reform the shells of filled capsules which capsules exhibit thin areas liable to rupture, incipient leak holes, or undesirable shapes regardless of how such capsules may have been originallyv formed. In capsules carrying a liquid content this reforming is carried out without leakage of the liquid content material. Through this treatment such capsule shells may be reformed while in situ about the content substance into shells of uniform thickness and homogeneity of structure. This improved process may be employed to reform or rearrange the capsule shell or envelope about its contained core to obtain uniformity of thickness and structure even though such core may be a solid pellet or itself a capsule and even though the enveloping shell may have been established thereon by spraying, dipping,

molding, or in any other fashion.

Furthermore, the process may be employed not I only to reshape or reform the capsule shell but to reshape a conformable interior or core into 'spherical shape.

Heretofore hermetically sealed capsule shells have generally been formed about the capsule It has been cus- I ment-about the content substance as to produce tomary to provide complementary shell portions this character wasinthe capsulating in liquid form of expensive vitamin products. Leakage of such content materials representedsubstantial loss. Furthermore, accurate measurement of capsulecontents and hermetic seal of the con tent material were essential requirements.'

Other objects, advantages and important features of my invention will further appear from the following specification, and claims. The drawing illustrates diagrammatically one form of simple apparatus suitable for carrying out the invention and wherein:

Figure 1 ,is a. diagrammatic sectionalview through one form of simple apparatus operable to carry out the process of this invention, and

Figure 2- is a diagrammatic. elevational-view of simple apparatus operable to carryout this invention in conjunction with the apparatus of Fig. 1. v

I propose to advance filled capsules by freely passing them ,through a liquid medium heated to the molten temperature of the capsule shell. Such advance is so carried out that surface tension acting upon the molecules of the capsule shell, which shell. becomes molten in the medium, causes them to fall into such a rearrangea shell of uniform thickness and homogeneity of structure. The temperature of the liquid medium and its specific gravity are points of importance and bear a definite relationshipto the melting point of the capsule shell material and the specific gravityof the ,filled capsule. The temperature of the liquid medium must besuch as to render the shell molten or at least sufficiently plastic to respond to surface tension'tc produce the desired result. The specific gravity of the suspending medium must be such that the filled capsule is suspended within and by theliquid medium for such a time as to permit the accomplishment of the desired result. The fluid medium should be of such a nature that the interfacial tension between it and the molten shell substance beat a maximum. This can .be accomplished through choice of fiuid medium and/or addition of substances soluble in fiuid medium which will accomplish this result. Ad-

dition of similarsubstances to the shell are also The specificgravity of the liquid medium may be slightly less than that of thefilled capsules and such capsules will then be entered therein movement therethrough but adapted to act upon the shell material or shell coating material which is in a fiuid state when the capsule is introduced in the liquid medium, chemically rather than thermally to gradually render the shell structure sufliciently solid after response to surface tension has produced the desired uniformity that it may be handled without deformation.

Gelatin is a well known material used in the fabrication of capsule shells but other plastic or thermoplastic material might be employed satisfactorily with this process.

Suitable oils, solutions, electrolytes or mixtures thereof having the desiredspecific gravity may be employed as the medium through which the capsules are advanced. Relatively light liquids such as petroleum fractions may be used if thecapsules are to be permitted to fall by gravity therethrough. Relativelyheavy liquid such as halogenated derivatives of methane, ethane, ethylene, et cetera, may be used if the capsules are allowed to float upwardly therethrough. Carbon bisulfide and carbon tetrachloride may be used. The liquid medium through which the capsules are passed should be of such a character as not to interact with the shell or to be miscible with the material thereof. Preferably there should be a close approach in the relative speclfic gravity of the liquid medium and the capsules being advanced therethrough, whereby the capsules will be suspended therein for such a time as to permit theshells to respond to surface tension to assume a uniform thickness and structure throughout.

A liquid column acting thermally upon the capsule shell offers a simple method of accomplishing the result desired. ,Preferably I propose to provide a column of liquid consisting of aplurality of strata of different temperatures and if desired of different densities. The' stratum in which the capsules first enter should be heated to a temperature-sufficiently high to act upon the capsule shell rendering it molten or plastic and responsive to surface tension activity to produce uniformity during movement of the capsule through the liquid. The second stratum in which the capsules thereafter enter should be a cooling stratum adapted to solidify and harden the capsule shells sufficiently to permit handling without deformation.

The heated stratum may be maintained at the desired high temperature by suitable heating mechanism associated with that portion of the container wherein such heated stratum is located. The cooling stratum may be maintained at the desired low temperature by suitable cooling apparatus associated with that portion of the container wherein such solidifying stratum is cated. Such structural apparatus is within the knowledge of the art and readily adaptable to its use. The two strata may be ofthe same liquid or different liquids. They may have the same specific gravity or the specific gravity may vary.

If the high temperature stratum of liquid is supported upon the cooling stratum of liquid the capsules should enter at the top of the column and pass by gravity downwardly and out from the bottom. If the two strata were of such relative density as to permit the heated stratum being maintained at the bottom of the column capsules should be entered at the bottom of the column to float upwardly into the cooling strata to emerge at the top.

This process may be employed to reform capsules molded according to known molding processes thereby producing a uniformity of thickness and character of the capsule shells. The capsules may be formed in any desired manner. The capsule content substance may be enveloped within capsule shell material in any suitable manner. Content pellets or core substance may be enveloped within shell material by molding, dipping, sypraying, or in any manner desired. The process may constitute part of a complete process of fabricating filled capsules which includes first forming filled capsules in a shape that may be other than the final shape and with a shell exhibiting substantial variation in thickness and density and thereafter reshaping the capsule content substance simultaneously with the reshaping of the shell to final shape and uniformity of thickness and density.

In Fig. l of the drawing there is a schematic showing of one form of simple apparatus which might be employed to reform capsule shells as hereinabove set forth or to cooperate to produce filled capsules according to thedisclosure herein. In this drawing numeral i0 indicates a U- tube having one leg surrounded at I! by heat applying apparatus. A fluid heating medium may circulate through the jacket I2 heating the liquid within that portion of the tube surrounded thereby. This heating medium would flow from a suitable source not shown and be subject to control as desired. Cooling apparatus i4 surrounds the same leg of the tube below the heating means. Fluid cooling medium may circulate through such cooling jacket from a suitable source not shown and subject to provided controls to cool the liquid within that portion of the tube surrounded thereby. Two strata of liquid of varying temperatures are thereby produced. There is an upper heated stratum and a lower cooled stratum. Filled capsules may be deposited into the upper'end of this tube in any desired manner.

The capsules are introduced into this liquid column to gravitate down through the liquid. The temperature of the upper strata will be maintained at the melting or plasticizing temperature range of the capsule shell material acted upon. The temperature of the lower strata will be maintained at a temperature to produce solidification of such shell material. The specific gravity of the liquid and the height. of the liquid column will be so adjusted with respect to the specific gravity of the filled capsules as to cause the capsules to move through the liquid at such a speed as to permit the desired surface tension activity of the capsule shell structures during the time of suspension of the capsules within the heated stratum of liquid. Movement of the capsules through the cooling fluid is similarly adjusted to produce solidification of the capsule shell sufilcient to permit handling of the capsules Without deformation. The liquid column into which the capsules are introduced extends straight down so that the capsules will fall therethrough without striking the side wall of the tube.

A pump l6 of any suitable type is provided to circulate liquid through an outlet 20..to enter the.

across the bottom and up theother liquid column. The capsules will be picked up by this current of liquid before striking the bottom of the U-tube but the current flow is not sufficiently strong to distort the capsule shells. They-will move upwardly through the opposite leg and to overflow from the upper end l8 thereof. This overflow is into a hopper or the like 22. This hopper has a screened outlet into the. pump intake 24 so that the lqiuid fiows back into the pump for recirculation.

In Fig. 2 of the drawing thereis illustrated a simple apparatus adapted to cooperate with the apparatus shown in Fig. 1 to produce completely formed filled capsules from the beginning and wherein the process described in connection with Fig. 1 constitutes. a part of a complete novel process of capsule fabrication. assuming the capsule content substance to be conformableto surface tension activity of itself and of the capsule shell, as would be the case if the content substance were a liquid, the completely filled capsule would take on a spherical shape during its suspension within the layer acting upon the shell material to render it responsive to surface tension.

In Fig. 2 there is shown a delivery tube 30 which leads from a suitable source not shown of capsule content or similar substance. ,This content substance delivery tube extends in spaced concentric relationship through an outer deliva viscous molten plastic tube 38 beyond the extremities of delivery tubes 30 and 32. Through tube 30 the content substance is discharged as a core into the discharging tube 38 of plastic terial substantially filling said plastic tube and discharging thereinto before the plastic tube had appreciably constricted. Suitable means would be provided to pinch, twist, or break off filled sections or short lengths of the filled tube 38. Simple severing means such as scissor like mechanism illustrated diagrammatically at 40 might be employed to cut off these short filled lengths. Thisscissor like mechanism would pinch the wall of the tube together at the ends across said sections sealing the content material therein. These sealed filled sections would then fall into the upper end of the U-tube I gravitating therethrough as hereinabove described.

The capsule content material might be delivered either in solid or liquid form and at whatever temperature was desired. Delivery of the content material would occur simultaneously with the delivery of the shell material forming the plastic tube. The breaking off of the plastic tube sections might occur within or above the liquid medium in the U-tube.

If the capsule content material were of a character which would be responsive to surface tension as, for example, if it were a liquid it would respond with the shell to assume a. spherical Normally, and

shape under the influence. of surface tension while sustained within the liquid medium. At the same time local areas of the shell varying .in thickness and density would rearrange their -molecules to form a shell of uniform thickness andhomogeneity throughout. The specific gravity and height of the column of liquid acting upon the capsule shell to induce its response to surface tension would be such that for the particular. capsules being treated when this response had been completed the capsule would pass directly from this liquid layer into another layer adapted to solidify and harden the shell structure. This second layer might be a layer of cooling liquid ifacting upon a thermoplastic shell in which the shell would be solidified as it passed therethrough sufiicient to permit handling of the filled capsules without deformation as hereinabove described.

It is understood that the capsule content material might be ln the form of solid or preformed pellets. Such pellets might be solid at ordinary temperatures or might be formed of material liquid at atmospheric temperature but solidified by low temperature. Such pellets might even be in the form of separate capsules upon which it was desired to add an external shell possessing certain desired characteristics different from those of the shell directly used in-capsulatlng the content material. The outer capsule shell could be superimposed as hereinabove set forth. Such outer capsule shell might not be suitable as a container for the particular capsule content. For example the capsule might be coated with a lacquer having an amyl acetate vehicle and introduced in wet form into an ethanol bath. The ethanol medium solidifies coating by removal of amyl acetate from lacquer. Ethanol and glycerine mixture might also be used.

What I claim is:

1. That method of shaping the plastic shell of a capsule while the same is in situ enveloping capsule content substance comprising freely passing the filled capsule through and in direct con- .tact with a fluid medium acting upon the shell to render the shell responsive to surfacetension' and continuing such passing for a length of time sufficient to cause the shell to assume a surface tension induced shape and thereafter solidifying the shell in such form.

2. That method of shaping the plastic shell of a capsule while the same-is in situ enveloping capsule content material comprising freely passing the filled capsule through and in direct contact with a fiuid medium acting upon the shell rendering it responsive to surface tension, said shell assuming in response thereto a surface tension directed form and thereafter passing the shell from said fiuid medium into and through a fluidmedium adapted to solidify the shell in such surface tension directed form.

3. That method of shaping the thermoplastic shell of a capsule while the same is in situ enveloping capsule content material comprising freely passing the filled capsule through and in direct contact with an inert liquid medium having a specific gravity closely approaching that of the filled capsule and heated to a temperature sufficient to render the shell responsive to surliquid medium at a temperature sufficiently low to solidify said shell by cooling.

4. That method of shaping the thermoplastic shell of a capsule while the same is in situ enveloping content material comprising freely passing the filled capsule through and in direct contact with a liquid medium inert with respect to the shell and heated to a temperature sufficient to render the shell material responsive to surface tension and for a sufficient time to permit the shell to assume a surface tension induced form and thereafter cooling said capsule shell without substantially altering said form.

5. That method of shaping a filled capsule having a thermoplastic shell enveloping content material responsive with the shell to surface tension activity comprising freely passing said filled capsule through and in direct contact with a liquid medium inert with respect to the shell and heated to a temperature approximating the melting point of the capsule shell material and for a length of time sufficient to render the capsule shell responsive to surface tension to assume a spherical shape and substantially uniform thickness throughout and thereaftersolidifying the shell at such shape and thickness.

6. That method of shaping a filled capsule having a thermoplastic shell enveloping fiuid content material responsive with the shell to surface tension activity comprising freely passing said filled capsule through a liquid medium inert with respect to the shell and having a specific gravity closely approaching that of the filled capsule and heated to a temperature approximating the melting point of the capsule shell material and for a time sufilcient to render the capsule shell responsive to surface tension causing the shell to assume a spherical shape and substantially uniform thickness throughout and thereafter passing the filled capsule directly from such liquid medium into and through a second liquid medium having a temperature sufficiently low to solidify the shell by cooling at such surface tension induced shape and thickness.

'7. That method of shaping the plastic shell of a capsule while the same is in situ enveloping a solid core comprising freely passing the filled capsule through a liquid medium having a specific gravity approaching that of the filled capsule and adapted to act upon the capsule shell to render it responsive to surface tension and for a length of time sufficient to cause the shell to assume about the solid core a surface tension induced form and thereafter solidifying the shell in such form.

8. That method of shaping the thermoplastic shell of a capsule while the same is in situ enveloping capsule content material liquid at atmospheric temperature but solidified for application of the capsule shell comprising freely passing the filled capsule through a liquid medium having a specific gravity approaching that of the filled capsule and being inert chemically with respect thereto and having a temperature sufficient to render the shell of the capsule responsive to surface tension and continuing the passing of shell without substantial alteration of such surface tension induced form.

9. That method of fabricating filled seamless capsules comprising forming a tubular section of thermoplastic shell material, filling said tubular section with capsule content material, sealing the ends of said tubular section about said content material, freely passing said filled section through and in direct contact with a liquid medium inert with respect to the tubular shell and having a specific gravity approaching that of the filled section and heated to a temperature sufilcient to render the tube material responsive to surface tension and for a time sufficient to cause the tubular hell to assume a spherical capsule shape and thereafter passing said capsule through a liquid medium having a temperature sufficiently low to cool and solidify the capsule shell.

10. That process of capsulation which comprises delivering liquid capsule shell material and capsule content substance to a discharge orifice, extruding the combined shell material and content substance through said orifice with shell material in the form of a tube surrounding the content substance, closing the end of the tube beyond the orifice, compressing the wall of the tube together at a point spaced from its closed end and sealing and severing the same at such point forming a filled tubular capsule, freely passing said capsule through a liquid column inert with respect to the shell and with the capsule shell in a suificiently fluid state to respond to surface tension and for a time sumcient to cause the capsule shell during such passage to undergo surface tension reshaping forming a seamless capsule wall about the content substance.

11. That process of capsulation which comprises enveloping capsule content substance within a wall of plastic capsule shell material, which envelopment includes the step of compressing portions of the wall together and sealing the same together along said line of compression about the content substance, freely passing said capsule through a liquid column inert with respect to the capsule shell and with the capsule shell material in a sufficiently fluid state to respond to surface tension and for a time sufficient to cause the shell material to fiow and form throughout a seamless capsule shell enveloping the content substance.

12. That method of fabricating filled capsules comprising discharging a capsule of non-spherical shape and consisting of core material surrounded by thermoplastic shell material into a liquid medium inert with respect to the shell and having a specific gravity which approaches that of the filled capsule and having a temperature as high as the melting point of the shell material and freely passing the filled capsule through and in direct contact with said medium for a time sufficient to render the shell responsive to surface tension and to induce spherical capsule shape and form and thereafter directly passing said capsule into and through a liquid medium having a temperature sufficiently low to cool and solidify the capsule shell material.

ROBERT P. SCHERER.

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