US2513852A

US2513852A - Method for encapsulating

Info

Publication number: US2513852A
Application number: US718527A
Authority: US
Inventors: Alfonso M Donofrio
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-12-26
Filing date: 1946-12-26
Publication date: 1950-07-04
Anticipated expiration: 1967-07-04

Description

ly 4, 1950 A. M. DONOFRIO 2,513,852

METHOD FOR ENCAPSULATING Filed Dec. 26, 1945 s Sheets-Sheet 2 FlgIX INVENTOR.

ALFONSO M. DONOFRIO July 4, 1950 A. M. DONOFRIO 2,513,852

' METHOD FOR ENCAFSULATING Filed Dec. 26, 1946 3 Sheets-Sheet 5 INVENTOR. ALFONSO M. DONOFR IO Patented July 4, 1950 UNITED STATES PATENT OFFICE;

METHOD FQR ENCAPSULATING- Alfonso M. Donofrio, Toledo, Ohio ApplicationDeeember 26, 1946;, SQrialNo. 718,527

8 Claims.

only onecapsule need. be taken to adminster two different. medicinal substances. The instant application is a further development of the method illustrated, in my above-mentioned co-pending application and may. make use of a portion of the mechanism disclosed therein.

While the earlier filed application disclosed a method of producing multi compartnient capsules, the instant application is directed towards a method of producing a single compartment symmetrical; capsule employing-only a portion of the mechanism disclosed in the earlier application.

The machines employed in the art of" encapsuliating prior to thisinvention produce spherical and ellipsoidal capsules through the use of coacting substantially hemispherical and semi-ellipsoidal dies. Insome prior art machines each die is cut in the periphery of a drumor rotating wheel and two such wheels are rotated toward each other with their peripheries contacting and the capsules are formed between the wheels. Forming a capsulein this manner requires that the two wheels be maintained in perfect register so that the sealing action around. the rims of the two, die pockets functions properly and operates to efiectivelyseal the-capsules as they are formed. In other, machinerythepockets are formed in 00- actin-g flat die plates and, again, the two pockets forming each capsule must carefully bemaintained in registration. This same requirement also is true of athird form of prior art device in which individual capsules are formed from the end of a filled tube of capsulating material by being pinched on the end of the tube. In order to maintain the two pockets of'all of these prior art machines in proper registration complex. gearing and timing mechanismsorguides and. slides must be employed.

It is an object of this invention to provide a method of encapsulating in which: symmetrical spherical and ellipsoidal capsulescan be produced from two sheetsof elastic material, only one of which needs be pocketed;

It is. another object of this. invention topmvide a method. of, producing asymmetrical spherical or ellipsoidalcapsulev using only one. pocket formed in a single die member, for example, a in ta in i wheele a single die p ate.

I: accomp sh the. ab ve objects. by th pratt ce of the method, which will b disclosed either on pecial. app ratus illu trated. n. the drawings... or on. other. apparatus. which is well kn w n. the prior art and, illustrated here merely in COJQIIQCP tion with he xplanation t method f." th invention- In the dra gs:

Figure I is, a schematic illustration ofa form of apparatus constituting a. part of the instant invention and on which the encapsulatingmethod of the instant invention can be carried out;

Figure II is a fragmentary vertical sectional view in greater detail and on a larger-scale of a portion of apparatus similar-to that illustrated-in Figure, I but embodying a modified die wheel.

Figure 111- is a fragmentaryview in elevation on an enlarged scale of several hemispherical die pockets such as might be employed inthe mechanism illustrated in Figure I.

Figure IV is a fragmentary verticai sectional view of a hemispherical capsule immediatelyaft er sealing but prior to severance from the-mate;- rial" which forms its walls.

Figure V is a vertical sectional view of onetype of ellipsoidal capsule manufactured in accordance with the method of this invention.

Figure VI is a plan View of the capsule illustrated' in Figure V.

Figure VII- is a vertical sectional viewof an;- other type of ellipsoidal capsulemanufactured in accordance with the method of the=invention.

Figure VIII is a plan view of the capsule illustrated in Figure VII;

Figure IX is a schematic illustration: of the apparatus disclosed in my earlier co-pending application and illustrates how this apparatus also may be employed in practicing the method offthe instantinvention.

Figure X is a simplified vertical sectionaliview of'a flat die plate such asthat known-in the prior art as employed; in manufacturing capsules in ac,-. corclance with the method" of: the; instant invention.

Figure XI is a fragmentaryvertical sectional view-0n anenlargedscaleof the capsulating plate shown in Figure X and illustrating one step. in the, method of the instant inventionas practiced on this type of, apparatus.

Figure XIII is a view similar to Figures X and XI but illustrating a still later step in the method embodying the instant invention.

Figure XIV is a view similar to Figure III but of semi-ellipsoidal pockets which may be employed in accordance with the method of the instant invention for the production of spherical capsules.

Figure 'XV is a fragmentary vertical sectional view on an enlarged scale of a semi-ellipsoidal capsule such as would be formed in the semiellipsoidal pockets illustrated in Figure XIV and shown before it is severed from the main'strips of capsulating material which form its walls.

Figure XVI is a verticalsectional view of a spherical capsule which is the product resulting from the formation of the semi-ellipsoidal cap sule shown in Figure XV.

The apparatus schematically illustrated I in Figure I is designed for practicing the method of the invention in the production of symmetrical ellipsoidal capsules such as that shown in FigureV.

As explained above, in order to produce a symmetrical ellipsoidal capsule it has been neces- [sary in the past to employ two co-acting die members. In accordance with the instant invention I am able to eliminate one of these two co-acting die members and, therefore to elimihate the necessity for maintaining any of the parts of the machinery on which the method constituting the invention is carried out in perfect alignment or registration with other parts of the machinery. Furthermore, the elimination of one of the die members simplifies the mametering means a charge of the substance to be encapsulated is 'deposited in the pocket beneath the filling shoe 8.

The die wheel continues to rotate moving the filled pocket in the gelatinous material beneath a rotating smooth surface sealing drum II around which is fed a second sheet I2 of gelatinous material. The sealing drum II is power driven and mounted onf an adjustable bracket i3 so that the spacing between its periphery and the periphery of the die wheel I can be the practice of the method of the invention can I) I be carried out there is shown in Figure I a single die wheel I which is providedwith a plurality of hemispherical die pockets 2 formed in its periphery. The die wheel 11 rotates at a substantially fixed rate of speed on a central hub 3.

stance which is soluble in the stomach or intestinal fluids. The sheet passes over one or more feedin rolls 5 and thence up and over the peripheral surface of the die wheel I. It will be observed that each of the hemispherical pockets 2 has a central port 6 leading inwardly to the inner surface of the die wheel 2 adjacent the outer surface of the hub 3. The hub 3 is ported and has a circumferentially extending slot 7 which is connected with a vacuum line. The circumferentiall extending slot l is in line with the inner ends of the ports 6 and extends around the periphery of the hub 3 a sufiicient distance so that suction is maintained on each of the die pockets 2 for a period during the rotation of the die wheel I. The sheet '4 of elastic material contacts the surface of the die wheel i and as each of the pockets 2 over which it extends approaches the location of a filling shoe 8 its port 6 registers with the slot and vacuum is applied to the die pocket 2. This depresses the material overlying the die pocket forming a hemispherical pocket in this material itself. As the die wheel continues to rotate the depressed hemispherical pocket passes beneath the filling shoe 8 which is formed on thelow'er' end of a tube 9 connected to a source of filling substance l0. By a--pump-=or--other adjusted to provide sufiicient space between the wheel and drum to permit the two sheets l and 52 of gelatinous material to pass between the two surfaces but to seal them firmly around the edge of each of the die pockets 2. Each of the die pockets 2 has a lip i l to provide a raised surface against which the two sheets of gelatinous material can be sealed.

As the die wheel I continues to rotate the ports 6 of each of the die ockets 2 pass beyond the limits of the slot l and suction no longer is applied to the pockets 2. Shortly thereafter each of the formed hemispherical capsules is severed from the sheet of material by passing beneath the smooth surface of. a severing drum 15 which is mounted onan adjustable bracket It so thatit can be properly spaced with respect to the die wheel l to pinch off the two

sheets

4 and 12 of gelatinous material against the lip I l of each of the die pockets 2.

At this point in the proces the capsules are hemispherical in shape, as shown in Figure IV, and are really severed from the gelatinous material, being maintained in a web formed from the two sheets 4 and i2 ofgelatinous material simply by the tackine'ss of the gelatin. As the die wheel I rotates further each of the ports B-of the die pockets comes in line with a pressure; port I! in the hub 3 which ejects each hemispherical capsule from its die pocket.

The operation of the mechanism shown, in FigureI which has been described illustrates the method of the invention for the production of ellipsoidal capsules from two sheets of gelatin or other elastic material which are identical insofar as their elastic and internal physical characteristics are concerned. If the two sheets 4 and I2 are fed into the die wheel I as explained and the only stress created in either of the sheets -When the suction on the pocket in the die wheel is released the substance in the formed capsule transmits the hydrostatic pressure created by the stretched sheet 4 to the unstretched sheet l2 and,

if the sheets are substantially identical, the resulting deformation of the sheet I2 will be substantially symmetrical with the deformation of the sheet 4. Figure V shows a transverse sectional view of the resulting capsule and Figure VI shows a plan view of this same capsule.

The final form of the capsules produced in accordance with the methods of the invention can be modified at will by changing the physical condition or characteristics of the two sheets of gelatin or other plastic material which form, respectively, the pocket and..the.. c.losure-iorthfi pocket; If, for example, the sheet of. plastic material which isto be pocketed is stretched in acircumferential direction with respect tothe die wheel, the resulting capsules will be oval, i. e. shaped like an ellipsoid of revolution which is rotated about its longer axis. Such a capsule is illustrated in Figures VII and VIII. In order to produce this capsule by longitudinally stretching one sheet of material, it is necessary only to revolve the two feeding rolls at a constant but slower speed than the die wheel I. This results in stretching the web of material between the feedingrolls 5' and the die wheel I so that when it is pocketed greater stress exists in a circumferential direction than exists in an axial direction (both with respect to the die wheel i). Thus, when the capsule is ejected from the die pocket and severed from the connecting web of material it contracts. to a greater degree in one direction than it does in the other, thus forming an oval capsule. The preliminary stretching plus the stretching that occurs during pocketing conditions the pocketed section for greater total contraction and the resulting greater hydrostatic pressure transmitted by the contents bulges the unstressed sheet I2 to a greater degree transversely to the plane of sealing of the two sheets than if neither of the sheets of gelatin has been preliminarily stretched.

Other ways of providing a higher degree of stress in the sheet of material to be pocketed may be employed. For example, the sheet of gelatin or other capsulating mate-rial which is to be pocketed may be thicker than the sheet which is to close the pockets. If this is true, then when the capsules are released by the die wheel the thicker sheet forming the pocket, which has a, tendency to contract, is stronger than the resisting sheet which close-s the pocket. Under these conditions it is possible to produce a capsule the shape of which is somewhere intermediate the two shapes shown in Figures V and VII. Theoretically, under these conditions it would be possible to ro. duce a spherical capsule from the hemispherical capsule shown in Figure IV but, as later will be explained, the method of the invention can be used to produce spherical capsules very simply and without requiring the great differential in stress in the two sheets of gelatin.

If the two sheets of gelatin or other capsulating.

material have different percentages of drying agent, or of solvent, or of moisture, one sheet will tend to dry and shrink more rapidly than the other sheet. This sheet with the greater tendency to shrink and dry is pocketed, and when the capsule is sealed and released the shrinking of the pocketed sheet distends the closing sheet until equilibrium is reached between the forces exerted on the substance in the capsule.

By controlling the relative tendency to contract of the two sheets of capsulating material the resulting shape of the finished capsules can be predetermined and the position of the parting line between the two halves of the capsules can be accurately and positively controlled to fall directly on the center plane of the capsule. However, even if this careful and positive control is not fully maintained almost symmetrical capsules still result inasmuch as the sheets of gelatin tend to approach a spherical shape because a spherical shape is the smallest which will contain a given volume of a substance capable of transmitting hydrostatic pressure. Such variations from spherical shape as are desired are accomplished; by controlling the extent to and the directions in which the capsule walls are conditioned to contract. I v

The instant invention contemplates the formation of symmetrical ellipsoidal capsules-from. two. sheets ofgelatin only one of which need bepocke eted or dimpled in contrast. to prior art methods and machines which, in order to form sym-.- metrical ellipsoidal capsules, pocketed or dimpled both sheets of capsulating material. The. terms ellipsoidal and generally ellipsoidal are usedto describe all shapes falling generally within their broadest meanings and includenotonly ellipsoids of revolution on either their shorter or their longer axesbut also oblate spheroids, ovals and spheres. which are but modifications. of. the same general form.

The-subsequent action of the apparatus shown in Figure I is very simple consisting only of passing the web of severed but still retained capsules around apair of stripping rolls. [8. which cause the now ellipsoidal capsules to. be pushed, out of the web and; carry the pierced. web. away to be returned to,v the gelatin forming machine. The capsules drop-into a pan. 19. for cooling and hardening, and arethen washed. to remove any. objectionable film.

In Figure II a more detailed view is. shown of a modified form. of die wheel. which is. designed to permit thevolumetrical content of thecapsules to be varied at will. In this structure a, die wheel 20 is provided with aplurality of cylindrical openings 2| extending radially through its outer surface. Each of theopenings 2| is surrounded by. an annular raised lip 22 identical with the lip M- formed around the hemispherical pockets in the structure shown in FigureI. Each of the openings 21 is connected through a port 23 to the interior of the die wheel 20 adjacent the periphery: of its hub 24.

A plug 25 is variably positionable in each of the openings 2L Each of the plugs 251s a short longitudinallybored cylinder which: hasa longitudinally extending rack 26 cut in one side. The rack 26 meshes with an elongated axially extending pinion 21 which is rotatable withinan axially extending: bore 28' in the die wheel 26. The pinion 21 can, therefore, extend throughout the length of the diewheel 20 meshing with racks cut-on plugs in alternate circumferential rows of openings 2i. The pinion 21' and all other pinions like it may extend out one end of the die wheel 20 where they can be individually adjusted or all can be driven in unison by a single gear rotatable with respect to the die wheel 28- or by other suitable means (not shown). By. thus controlling the radial position of the plugs 25 the depth towhich a sheet 29 of gelatin isdrawn into the openings 2| and the internal volume of the. capsules to be formedv can be controlled.

The operation of. the apparatus shown in Figure II is identical with the operation of the apparatus shown in Figure I with the exception already mentioned that the volume of the capsules produced thereby can be varied at will. Figure II also clearly illustrates the construction of a filling shoe 30 formed on the end of a tube 3! in communication with a supply of substance to be encapsulated. The bottom of the filling shoe 3!] is provided with a beveled flange 32 which has a vertical edge considerably thicker at its forward end than at its rear end and which thus maintains a scraping action over the surface of the sheet of gelatin on which it bears and also maintains a seal around each of the pockets formed in this sheet of gelatin while each pocket is being filled. This is particularly advantageous when the substance to be. encapsulated is granular or pasty which, if permitted to remain on the portions of the sheet 29 of geltain overlying the circular lips 22, might prevent the effective sealing of the sheet 29 of geltain to a second sheet 33 of gelatin which converges with the sheet 29-beneath a sealing drum 34. This illustrates another advantage accruing from the elimination of the second die wheel of the prior art because only one sheet of gelatin need be so carefully cleaned to prevent failures in sealingwhile two cleaning controls are required when both sheets of gelatin are pocketed and filled.

= Also it can be more clearly seen in Figure II how theraised lips 22 around each of the openings 2l-provide a relieved space 35 beneath the two sheets of gelatin 29 and 33 between adjacent openings 2|. When the capsules are out or severed from the sheet of gelatin the remaining web portion of the sheets of gelatin is squeezed into these relieved spaces 35 to permit the severing action to take place against the lips 22.

Figure III is a fragmentary view in elevation of a portion of the die wheel, showing how each lip l4 surrounds its pocket 2. The wheel moves in the direction of the arrow in this figure.

Figure IX illustrates apparatus which was disclosed in my earlier application for the practice of a method of producing multi-compartment spherical capsules. This apparatus is shown operating under the method of the present invention to produce symmetrical ellipsoidal capsules from two sheets of gelatin only one of which is pocketed. In this machine two coacting die rolls 36 and 31 are driven in synchronism and under the process of my earlier application would produce two-compartment spherical capsules formed of three sheets of

capsulating material

38, 39 and 40 (sheet 40 being shown in broken lines) with the two sheets 39 and 40 forming opposite hemispheres of the sphere and the sheet 38 forming the partition. Through the use of this same machine and employing only two sheets of capsulating material, for example, No. 38 and 39 the method of the instant invention can be carried out. As in the employment of the machine shown in Figure I, the final shape of the capsule depends upon the relative stresses in the

sheets

38 and 39. If they are not preliminarily stressed at all, capsules of oblate spheroid shape result or if they are of different thicknesses, are stretched to a different degree, or if the two sheets incorporate a different amount of a Volatile substance, capsules of symmetrical ellipsoidal shapes may be produced. By making only these few changes this machine adapts itself as well to the carrying out of the method embodying the instant invention as do the mechanisms shown in Figures I and II. In the mechanism illustrated in Figure IX, in addition to the co-acting die wheels 36 and 31, there also are provided a pair of dimpling rollers 4| and 42 which force the pocket forming sheets of gelatinous material into the pockets in the die wheels. This may be advantageous when very thin gelatin is employed since thethin gelatin might not withstand the suction without rupturing.

' Thus, by the use of the one apparatus shown in Figure IX both the method of the prior application and the method of the present application can be performed to produce either multi.

8v compartment spherical capsules or single compartment, symmetrical substantially ellipsoidal capsules.

Figures X, XI, XII and XIII illustrate a Way of carrying out the method of the instant invention employing a single die plate. In Figure X there is shown a simplified cross section of a die plate 43 in the upper surface of which are formed a plurality of die pockets 44. Each of the pockets 44 is connected through a duct 45 to an exhaust line 46. Each of the pockets 44 has a raised edge 41. To produce symmetrical ellipsoidal capsules in accordance with the practice of the instant invention a sheet of gelatinous material 48 may be stretched across the top of the plate 43 (as shown in Figure VIII) and held in place by a clamping frame 49.

Depending upon the shape of the finished capsules that is desired, the first sheet of gelatin, or other material, may be given a different internal stress or tendency to contract either in one direction (by stretching, for example) or in all directions in the ways explained. After the sheet 43 of gelatin is clamped suction is applied to the line 46 which depresses the lower sheet 43 into the pockets, as shown in Figure XI. The pockets are then filled with material to be encapsulated and the second sheet of gelatin 5!) is laid across the frame 43 (as shown in Figure XI) and clamped in place (as shown in Figure XII) by a clamping frame 5|.

The capsules are then sealed and severed from the web formed by the two

sheets

48 and 50 either by rolling a roller over the surface of the upper sheet 50 or by squeezing a flat p1ate down on the upper sheet 50 which seals the two sheets together over the raised edges 41 and severs the hemispherical capsules thus formed from the remaining web of the two sheets 48 and '50 of the plastic capsulating material. During this operation suction is still maintained on the line 46 and the ducts 45. After the capsules have thus been formed they may be ejected from the pockets by admitting pressure to the pockets or otherw1se.

Upon ejection the differential stresses existing in the two sheets of

capsulating material

48 and 50 equalize and deform the fiat sides of the hemispherical capsules to produce symmetrical substantially ellipsoidal capsules, of a shape depending upon the relative tendency to contract of the two sheets.

Figure XIV illustrates the shape of the pockets in either a die wheel or a die plate which may be employed to produce spherical capsules very easily in accordance with the instant invention. Figure XIV shows a fragment of a die wheel (in which case it rotates in the direction of the arrow) or plate 52 in which are formed a plurality of semi-ellipsoidal pockets 53. A raised edge 54 surrounds each of the pockets 53. In Figure XV there is shown in cross section a semi-ellipsoidal capsule formed from a pocketed sheet 55 of capsulating material and a fiat sheet '56 of capsulating material. In accordance with the invention the pocketed sheet 55 is so treated that there is produced in it greater internal stress than that existing in the sheet 56 and thus, when the semiellipsoidal capsule shown in Figure XV is severed from the web of the sheets of capsulating material, the resulting equalization of the stresses produces the spherical capsule shown in Figure XVI.

Elongated ellipsoidal capsules also may be produced in the die pockets shown in Figure XIV by "using "two sheets of "capsulating material neither of which has been preliminarily stressed fo'r treated. In this case, the two sheets have the same tendency to contract before the pocket forming sheet is pocketed and the resulting'capsule has a cross section similar to that shown in Figure V and an elevation similar to that shown in Figure VIII. Again, the shape of the finished capsule may be modified by treating the two sheets of capsulating material in different ways as explained above.

The method of the invention is directed generally toward encapsulating substances in symmetricalcapsules using only one die member; As

"has been explained the shape of the resulting symmetrical capsules can be modified from that of 'a thin oblate spheroid to an almost perfect sphere by the manner in which the sheet of material to be pocketed is treated. Fundamentally, the only necessity to produce a symmetrical capsule from a single pocketed sheet of gelatin or other capsulating material and a flat sheet of a similar material is to fill the pocket or dimple with the substance to be encapsulated, to seal the two sheets of material together tightly around the edges of the pocket and to release the semi or half capsule thus formed from all restraint. The subsequent equalization of the stresses in the two sheets of plastic material produces the symmetrical ellipsoidal form. The relative lengths of the major and minor axes of the ellipsoids and the relative proportions of the finished capsules can be controlled as explained by properly apportioning and directing the stresses which are created in the pocketed sheet of material so that in being equalized against the unstressed sheet of material they will modify and control the resulting shape of the capsule as desired.

By the practice of this invention highly attractive commercially acceptable capsules can be manufactured with considerably more rapidity and facility and considerably less expense than by the processes and apparatus disclosed in the prior art.

The method of the instant invention can be practiced not only on the several forms of apparatus illustrated in the drawings but also on many other forms of apparatus which are known in the art or which might be devised and old apparatus as well as the new apparatus herein disclosed may be modified in various ways to produce resulting modifications in the appearance and content of the capsules produced in accordance with this invention.

Having described the invention, I claim:

1. A method of forming capsules of generally ellipsoidal form that comprises forming a pocket in a longitudinally stretched sheet of resilient capsulating material, filling the pocket thus formed with the substance to be encapsulated, laying a sheet of unstretched resilient capsulating material over the substance, sealing the two sheets of capsulating material around the edge of the pocket and cutting the capsule thus formed from the two sheets of capsulating material, whereby as the difierence in internal stress in the two sheets of capsulating material is equalized the capsule changes in shape to a symmetrical shape formed from matching and equal pockets in the two sheets of capsulating material.

2. A method of forming ellipsoidal capsules that comprises forming hemispherical pockets in a sheet of elastic material that is under a certain internal stress, filling the pockets with the substance to be encapsulated, laying a sheet of elastic pockets and cutting the capsules thus formed from the sheets of elastic material whereby the equalization of the different stresses existing in the two sheets of elastic material pulls the two sheets of elastic material sealed around the substanceinto a symmetrical shape aroundthe substance.

=3. A-method of forming spherical capsules that comprises forming semi-ellipsoidal pockets in a sheet of elastic material that is under a certain internal stress, filling the pockets with the substance to be encapsulated, laying a sheet of elastic material that is under much less internal stress over the substance, sealing the two sheets of elastic material together around the edges of the pockets and cutting the capsules thus formed from the sheets of elastic material whereby the equalization of the different stresses existing in the two sheets of elastic material pulls the two sheets of elastic material sealed around the substance into a symmetrical. shape around the substance.

4. A method of forming ellipsoidal capsules that comprises forming hemispherical pockets in a sheet of elastic material that is under tension in a direction transverse to the longer axis of the desired ellipsoidal capsules, filling the pockets with the substance to be encapsulated, laying a sheet of elastic material that is under much less tension over the substance, sealing the two sheets of elastic material together areund the edges of the pockets and cutting the capsules thus formed from the sheets of elastic material whereby the equalization of the difierent stresses existing in the two sheets of elastic material pulls the two sheets of elastic material sealed around the substance into a symmetrical shape around the substance.

5. A method of forming spherical capsules that comprises forming semi-ellipsoidal pockets in a sheet of elastic material that is under tension in a direction parallel to the longer axis of the semiellipsoidal pockets formed therein, filling the pockets with the substance to be encapsulated, laying a sheet of elastic material that is under much less internal stress over the substance, sealing the two sheets of elastic material together around the edges of the pockets and cutting the capsules thus formed from the sheets of elastic material whereby the equalization of the different stresses existing in the two sheets of elastic ma 7* terial pulls the two sheets of elastic material sealed around the substance into a symmetrical shape around the substance.

6. A method of forming symmetrical capsules that comprises forming a pocket in a sheet of elastic material that has been preliminarily stretched in one direction, filling the pocket with the substance to be encapsulated in a form that is capable of transmitting hydrostatic force, covering the substance with a sheet of elastic material that is under considerably less stress than the pocketed sheet of material, and sealing the two sheets of material together around the substance along the edge of the pocket, whereby the greater stressed pocketed material upon contracting bulges the less stressed covering material as the stresses in the two sheets of material tend to equalize.

7. A method of forming capsules of generally ellipsoidal form that comprises forming a pocket in a sheet of resilient capsulating material having a certain amount of longitudinal internal stress, filling the pocket with the substance to be encapsulated, covering the filled pocket with another sheet of resilient capsulating material having substantially less longitudinal stress than said first sheet of resilient capsulating material after being pocketed, sealing the edges of the two sheets of capsulating material around the substance and cutting the capsule thus formed from the sheets of capsulating material, the two sheets of capsulating material reacting physically one upon the other whereby the resulting capsule is substantially symmetrical in shape.

'8. A method of forming capsules of generally ellipsoidal form that comprises stretching a sheet of resilient capsulating material in a longitudinal direction, forming a pocket in said longitudinally stretched sheet of capsulating material, filling the pocket with the substance to be encapsulated,

covering the filled pocket with an unstretched REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 564,340 Reed July 21, 1896 1,151,063 Sweet Aug. 24, 1915 1,531,504 Roberts Mar. 31, 1925 1,610,974 Sarna Dec. 14,1926 2,152,101 Scherer Mar. 28, 1939 2,219,578 Pittenger Oct. 29, 1940 2,296,294 Scherer Sept. 22, 1942 2,323,581 Weckesser July 6, 1943