US2299039A - Method of fabricating capsules - Google Patents

Description

fiat. E3, 1942. R. P. SCHERER 7 METHOD OF FABRICATING CAPSULES Fil d March 5, 1940 INVENTOR. F755;? F. 527mm? MS C?WZZW ATTORNEYS.

I Patented Oct. 13, 1942 i UNITED STATES PATENT ()FFICE METHOD or FABRICATING CAPSULE Robert P. Scherer, Detroit, Mich.

Application March 5, 1940, Serial No. 322,376

8 Claims. (c1. 18-58) This invention relates to improvements in the fabrication upon a mold of self-supportingshells or capsule sections.

One object of the invention is to provide such a shell economically and rapidly and to provide a shell having the desired uniformity of thickness throughout and to provide an improved process and apparatus for fabricating such a shell.

One type of shell for. which this invention is suitable is the conventional telescoping gelatin capsule shell commonly used for the capsulation of quinine or other powdery substances and the invention is here illustrated in connection. with the formation of such shell though obviously shell structures widely varying in size and shape might be produced by the improved process here set forth.

Telescoping capsules formed in two halves and having such a difference in diameter as to permit telescoping engagement have heretofore been formed upon molds. In their manufacture the mold is dipped into a bath of molten gelatin and then withdrawn with a gelatin coating thereupon. When such a mold is lifted from the bath the liquid gelatin tends to flow down upon the mold and this tendency must be rapidly counteracted or the coating will collect unevenly upon the mold. According to the present commercial practice, while the gelatin is in the molten state the mold is revolved ormoved through the air in such marineras to prevent the coating from flowing down or collecting at one place thereupon in greater thickness than at another. This motion is continued until the coating solidifies or hardens.

I have discovered that this tendency can be counteracted and even reversed after it has commenced by immersing the coated mold in a suspending liquid having substantially the same specific gravity as'the specific gravity of the molten coating .and retaining the coated mold with the coating in a molten state within: the suspending liquid for sufficient time to permit the coating to res ond to interfacial tension to rearrange itself uniformly upon the mold and to solidify thereupon .to the point of self-support before removing the mold from the liquid and thereafter removing the coated mold from the liquid and removing the shell from the mold.

Various objects, advantages, and'meritorious features of this invention will more fully appear from the following description, appended claims,

' and accompanying drawing, wherein:

Figure 1 illustrates a telescop ng capsule shell of conventional construction each half of which is formed upon a .mold,

Fig. 2 illustrates schematically that step in molding one half of such a shell following removal of the coated mold from the bath of molten gelatin showing the mold carrying a molten coatl coated mold surface within a bath of suspending,

liquid, which liquid has a specific gravity that is gravity counteractive with respect to the plastic coating on the mold and wherein the coating has rearranged itself upon the mold to a substantially uniform thickness over the coated surface of the mold,

Fig. 4 illustrates the mold following removal from the suspending liquid with the plastic coating solidified and distributed evenly thereupon,

Fig. 5 illustrates in partly broken away section the shell removed from the mold and cut off evenly at the open end and solidified into selfsupporting form,

Fig. 6 illustrates a globular form of capsule. which might be fabricated upon a mold according to, my process,

Fig: 7 illustrates a modified form of mold element provided with threads adapted to form internal threads within'the shell, a

Fig. 8 illustrates schematically a tank for suspending liquid within which coated molds may be immersed to carry out the process. herein described, and

Fig.9 illustrates a mold frame provided with Fig'. 10 illustrates a' female mold and coating therein.

The showing here made is generally schematic and intended only for purposes of illustrating the process. A mold frame 20 is provided with a plurality of depending individual mold elements or fingers 22 which may be dipped into a bath of molten plastic material such as an aqueous molten solution of gelatin-with the mold fingers submerged within the molten gelatin to such a depth as to collect the desired coating 23 of gelatin thereupon. The mold frame maythen be re- I moved and mounted upon the conveyor belt 24 above the suspending liquidtank 26 and advanced through the liquid in'the tank. Two conveyor beltsmay be provided one upon each side of the tank. These belts may carry pegs 25 upon which the mold frames may be removably received as at shown. The conveyor may be advancedslcwly and at such'a rate of speed that the coating will be properly formed and-solidified upon the molds.

Suitable driving mechanism, not shown in detail, will be provided for this purpose. The tank may be heated at one end through the use of heating coils 28 and cooled at the opposite end through the use of cooling coils 30.

The tank will contain suspending liquid which has a specific gravity substantially equal to that of the molten plastic material such as liquid gelatin. However, absolute equality of specific gravity is not essential but merely equality throughout a predetermined range which will insure production of desired results as hereinafter set forth.

counteractive with respect to the gelatin or when the specific gravity of the suspending liquid is described as matching the specific. gravity of the gelatin. In the operation of the process. the gelatin does not tend to rise onto the uncoated surface of the mold but remains on the coated portion for the reason that when the mold carrying the gelatin coating is immersed in the sus- The s ecific gravity of the suspending liquidwithin the tank is such that it will counteract the effect of gravity upon the gelatin when such gelatin is in a state sufliciently molten to permit it to respond, when immersed within the suspending liquid, to interfacial tension to rearrange itself over the coated surface of the mold into a substantially uniform thickness. Wherever within the claims the specific gravity of the suspending liquid is described as gravity counteractive with respect to the plastic material, such as gelatin, or as matching the specific gravity of the gelatin what is meant is that the specific gravity of the suspending liquid matches thatof the gelatin so closely that the gelatin will not sink therein and neither will it rise unduly.

The mold of It is obvious that a suspending liquid could to a limited degree partially counteract the effect of gravity upon the gelatin but yet fail to counteract it suificiently to prevent the gelatin from settling down upon the mold and even dropping off the mold into the tank. It is also obvious that the suspending liquid could possess a specific gravity so high as to so counteract the effect of gravity upon the gelatin that such material would float upwardly within the suspending liquid and pending liquid the suspending liquid wets the uncoated upper part of the mold and prevents adhesion of gelatin thereto.'

It will be observed that when the mold is first withdrawn from the molten gelatin bath that the a variation in thickness. The mold coating'is relatively heavy at the lower end of the mold and thins out to a relatively thin film at the top of the coated surface. Within the suspending medium this coating re-arranges itself under interfacial tension into substantial uniformity of thickness. I 1

Fig. 7 is provided with threads which form threads in the shell and along the line of the thread there is a different shell thickness from elsewhere but the words substantial uniformity of thickness are used to describe this obtained with a female mold.

thin out unduly upon the lower end of the mold.

Each of these results would be unsatisfactory.

Various oils, solutions, mixtures, or electrolytes may be used as the, suspending liquid medium. Carbon tetrachloride, carbon bisulphide, mineral oil, fractions of petroleum and mixtures thereof may be used to produce a suspending liquid having the desired specific gravity as to gelatin, for,

example, and depending upon the specific gravity of the plastic compound. Gelatin has a specific gravity of 1.27 and when in aqueoussolution may be employed at a specific gravity of, for example, 1.100.

Wnen a mold coated with molten gelatin at a specific gravity of 1.100 is immersed in a suspending liquid having a specific gravity of 0.950 it has been found that the mobile gelatin flows down upon the mold and tends to drop off the lower end into the tank. If the specific gravity of the suspending liquid is 1.050 a slight bulge of liquid is relatively high.

Throughout the claims the formation of a shell or coating upon a mold or other object is described. This coating will, in the formation of hollow capsule shells, be removed from themold.

While the suspending liquid tank shown in Fig. l 8 is illustrated as heated at one end and 'cooled at the opposite end whereby the coating could be retained in the molten state for such time as was necessary to effect the desired re-arrangecoating will form at the bottom of the mold but as the specific gravity of the-suspending liquid approaches more closely to that of the molten" ment and thereafter could be rapidly solidified, such a construction is not essential. It has been found that satisfactory results can be obtained merely by immersing a mold coated with molten gelatin in a suspending liquid at atmospheric temperature. The desired re-arrangement and solidification will occur therein.

What I claim is: i

1. That method of forming a shell of plastic material comprising coating a mold surface with said material in the molten state, thereafter immersing the coated mold surface in a liquid having a specific gravity which is gravity counteractive with respect to the molten plastic material and retaining the coated mold with the plastic material inthe molten state within the liquid for sumcient time to-permit theplastic coating to re-arrange itself upon the mold into a coating of substantially uniform thickness and causing elatin rises upon the coated surface of the mold and thins out at the lower end of the mold and the result is not satisfactory; The range which a shell upon the mold and thereafter,

the coating to solidify at suchthickness forming removing the shellfrom the mold.

facial tension to rearrange itself upon the surface of the mold and which has high interfacial suspending liquid heated to a temperature sufflcient to maintain the gelatin in a molten state for sufficient time to cause re-arrangement of the gelatin coating under interfacial tension in ,a

coating of uniform thickness and is thereafter maintained within a suspending liduid having a temperature adapted to solidify the shell material by cooling for suflicient time to solidify the coating into a self-supporting shell, and-thereafter removing the shell from the mold.

4. That method of forming a gelatin shell comprising dipping a mold into an .aqueous gelatin solution, removing the mold witha coating of gelatin thereon, immersing the coated mold into suspending liquid having a specific gravity matching that of the gelatin and retaining the coated mold within said liquid for suflicient time to cause the gelatin coating to re-arrange itself upon the mold under interfacial tension and to solidify into a self-supporting uniform thickness shell, removing the mold from said liquidand removing the shell from the mold.

5. That method of forming a self-supporting gelatin shell which comprises coating the surface of a mold with said gelatin solution, immersing the coated mold surface in a suspending liquid which is inert with respect to the gelatin material and which has a specific gravity greater than 1.0 but not greater than 1.27 and which has a temperature sufficiently high to maintain the gelatin in the molten state to respond to intertension with respect to the gelatin, moving the coated mold following such rearrangement of the coating into a suspending liyuid which in inert and gravity counteractive with respect to the coating and which has a temperature sufllciently low to cool the gelatin to form a self-supporting shell upon the mold, removing the mold from the liquid and removing the shell from the mold.

6. That method of forming a shell of plastic material comprising immersing a shell mold coated with said plastic material in a liquid bath having a specific gravity which is gravity counteractive with respect to the plastic shell material and with the shell material in a fluid state and retaining the same in said bath until the shell material has become self-supporting upon the mold and thereafter removing the shell from the mold.

'7. That method of forming a shell of plastic material comprising immersing a shell mold in a bath of fluid plastic material producing a coating thereon and thereafter transporting the coated mold into a suspending liquid bath having a specific gravity substantially approximating that of said fiuid plastic shell material and retaining the same therein until said shell material has solidified upon the mold and thereafter removing the same from the mold.

8. The method defined in claim 6 wherein the face of the mold covered with plastic material is in part threaded and the plastic material fills said threads wherein the plastic material is suflie ciently flexible when removed from the mold to permit such removal.

ROBERT P. SCHERER. I

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