US2135790A - Package of material - Google Patents

Description

Nam @3, E93. H. F. BOEGER PACKAGE 0F MATERIAL Filed July l5, 1956 17g/ IN VEN TOR.

@WJ ATTORNEYS.

Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE PACKAGE F MATERIAL tion of Delaware Application July 13, 1936, Serial No. 90,327

6 Claims.

This invention relates to an advantageous package of material containing a volatile constituent, and pertains particularly to a package Which is suciently hermetic as to` preserve the contained material at its desired content of volatile constituents, for a sufficiently long period to insure that there will be no appreciable loss during storage, so that the material Will reach the ultimate user from the distributor in good condition.

One of the important objects of the invention is to provide a package which may be easily and inexpensively prepared and which Will preserve a moisture-containing hydrocolloid composition or the like against loss of volatiles during storage periods.

The package of the present invention is primarily adapted for enclosing thermoplastic dental molding compositions. These compositions are semi-rigid When cool and must be heated to render 2Q the same fluent for use. Hydrocolloid compositions of this general type are described in U. S. Patent No. 1,672,776 and in the two U. S. patents of Harrison, Nos. 2,021,258 and 2,020,311. These materials have been conventionally marketed in the form of sticks or cylinders about one inch in diameter and four inches long, Wrapped in tinfoil envelopes or the like, or as described in U. S. Patent No. 1,977,580, enclosed in a cellulosic envelope Which is in turn enclosed in a moisture-imll pervious envelope such as a glass bottle or a Wax coating. Foil wrappers are objectionable in that they are not suiiciently moisture-retentive, and such Wrappers also cause discoloration of the contained composition due to the metallic contact. This discoloration prejudiced the user. In View of the fact that the package described in Patent No. 1,977,580 relies upon an external coating to provide the necessary moisture-imperviousness to the package, and the internal coating is relied upon only as a container for the material during the boiling operation which is employed to render the material fluent, a package which has the external coating removed ready for use will be rendered worthless in the event that it is not used at that time, inasmuch as it cannot be again stored without undue moisture loss, except in the case of the glass bottle type of external container, which is relatively expensive to manufacture.

A particular object of the present invention is to provide a package which comprises a stick of thermoplastic material, containing volatile constituents, an impervious envelope enclosing one end and substantially the full length of the stick and having an open end, and a solid closure member disposed at the open end of the envelope, in which (Cl. G-46) the envelope is in close compressive engagement with said closure member.

A further object of the invention is to provide a package which comprises a stick of thermoplastic material containing volatile constituents, an impervious envelope enclosing one end and substantially the full lengthv of the stick and which projects beyond the other end of said stick, and a solid closure member disposed Within the projecting portion of said envelope, in which the closure member is provided with shoulder means, and in which the envelope is in close compressive engagement with said closure member at the position of said shoulder means.

A further object of the present invention is to provide a package comprising an impervious envelope or container having a solid closure member at one end thereof, together With means providing positive compressive engagement of said envelope with said closure means.

A further important object is to provide a package of the character described, which comprises a moisture-impervious envelope structure capable of elastic deformation at temperatures adjacent or in the neighborhood of the boiling point of Water.

According to the present invention a moistureimpervious envelope coating is provided for a body of such impression composition which adequately protects the same from contamination and preserves the moisture content thereof, such envelope coating being of a material which is of high mechanical strength at ordinary temperatures but readily capable of elastic deformation at elevated temperatures whereby the packages may be immersed in Water and heated to render the contained composition fluent after which the package may be kneaded to homogenize the composition and render the same suitable for use, Without danger of rupture of the envelope during the kneading operation.

rlhe coating material should be one which, even at the elevated temperatures at which the contained impression composition is handled to render the same uent, retains a high degree of mechanical strength, and preferably also remains substantially moisture-impervious. The coating material is preferably one having a melting point somewhat in excess of 100 C. and relatively resilient and capable of elastic deformation at temperatures in the neighborhood of 100 C. The ability of the material to elastically deform at the high temperatures should persist to an important degree during cooling from adjacent 100 C. to in the neighborhood of to 40 C., as it is common practice in dental technique to continue the kneading of the heated composition until the tem.- perature thereof has dropped to a point such that it may be inserted within the mouth of a patient without undue discomfort. The coating material is preferably also one which will exhibit a marked shrinkage upon cooling or drying, or one which may be shrunken in a convenient manner.

rThe envelope may be pre-formed of a material such as a suitably moisture-prooied cellulosic composition (such as a material formed from an inter-solution of a cellulosic compound andr a moisture-proofing material such as rubber, resins, resinous gums, and high melting-point waxes) or from a resinous material such as the commercially available Koroseal (a polymerized vinyl halide). Alternatively, the envelope may be formed in position about the stick of hydrocolloid and the closure member, in which case I prefer to employ a suitable solution of such a resin or other moisture-impervious composition, such as the commercially available material known as Korolac which comprises a solution of the above-mentioned Vinyl resin in a suitable solvent. Of the above-set-forth materials, the resin Koroseal (and the coating material resulting from the use of xorolac) is particularly advantageous in view of its property of shrinking upon imersion in hot water. The coating formed from Koroiac exhibits this feature of shrinking in hot water to a greater degree than the envelope formed directly from the Koroseal material and for this reason greater latitude is had in the formation of the packages of the present invention when the envelope coating is formed from Korolac solution.

The package of the present invention may comprise; essentially, an elongated stick or cylinder of thermoplastic material disposed within an envelope which extends substantially the full length thereof and closedat one end, the other end of the package being closed by means of a solid and preferably lsubstantially rigid closure member which is in tight compressional engagement within said envelope. According to the preferred embodiment of the invention, a suitable compression member is provided exteriorly of said envelope in position to engage the aforesaid envelope and force the same into positive compressive engagement with said closuremember, whereby said closure member is maintained in position with respect to said envelope during the above-mentioned boiling and kneading operations.

Other features and advantages of the present invention will be brought out in the following specific description of certain embodiments thereof, or will be apparent therefrom. The accompanying drawing illustrates such embodiments of the invention and referring thereto:

Fig. 1 is a broken away longitudinal View of a package according to the present invention, in an intermediate step in the process of forming the same;

Fig. 2 is a longitudinal section of one end of the package shown in Fig. 1, at a later stage in the process of manufacture;

Fig. 3 is a view corresponding to Fig. 2, showing the finished package;

Fig. 4 is a perspective view of a package formed according to the steps shown in Figs. 1 through 8;

Fig. 5 is a sectional view corresponding to the upper end of the showing in Fig. 1, illustrating a further modification of the invention;

Fig. 6 is a view corresponding to Fig. 5 showing a still further modified form of the invention;

Fig. 7 is a Vview corresponding to Fig. 5, showing a further modification of the package;

Fig. 8 is a view corresponding to Fig. 2, showing the form of package illustrated in Fig. 7 in a further step in the process of completion;

Fig. 9 is a view corresponding to Fig. 3 showing the form of invention shown in Fig. '7 in completed condition;

Fig. 10 is a view corresponding to Fig. l showing one end of a package in partly completed condition, in a further modication of the invention;

Fig. 11 is a view of one end of a finished package, with the envelope broken away, showing a further modification of the invention; and

Figs. 12 and 13 are views corresponding to Fig. 11, showing further modifications of the invention.

Referring to the drawing, and in particular to Figs. 1, 2 and 3, a stick of thermoplastic composition is shown at I. A solid closure member 2, formed of any suitable relatively rigid material upon which the contained composition will have no chemical or physical action, such as a medium hard vulcanized rubber, or one of the numerous synthetic resins or other molded plastic materials, such as Bakelite, is provided at one end of the stick I and is secured thereto in such manner as to support the vweight of said stick when lifted by the closure member. This support may be provided by employing a closure member having a recess 3 of sufficient size to receive one end of the stick I, and a plurality of prongs or the like 4 are preferably provided adjacent the outer end of this recess in position to enter the body of material. The stick I may be mounted on the member 2 by forcing the said member over the end of the stick, making the prongs 4 pass through the material, and then twisting said member to provide a fresh surface against which said prongs may bear. The form of invention shown in Figs. 1 to 3 is preferably produced by a dipping operation, as by immersing the stick and the attached closure member in a uid body or bath of coating material, and for this purpose I provide a suitable dipping member 5 which is preferably provided with a conical lower end B adapted to fit within a coactingly shaped hole 'I in the member 2. In the envelope-forming operation, the stick I and its thereto-secured closure member 2 may be supported vertically through the agency of the member 5 and dipped into a suitable fluid bath of coating material such as the above-mentioned solution of Koroseal, namely, Korolac, or the like, preferably to a level somewhat above the upper end of said member 2, so that a portion of the lower end of said member 5 is coated,V

as shown at 8 in Fig. 1, a substantially continuous envelope coating being provided for said stick, which envelope projects beyond the end of the said stick to cover the major portion of the closure member 2 as shown at 9. After the coating 9 has dried or solidified to a sufficient extent, the member 5 may be removed from the member 2 and the portion 8 of the envelope 9 is preferably forced down into the opening T as shown in Fig. 2. The member 2 is preferably provided with shoulder means such as a projecting peripheral rim portion Il at the upper end thereof, over which the envelope 9 extends. To complete the closure of the package, I may then place a small compression member I2 in position over the opening 1, as shown in Fig. 3, after which a deformable metal covering member I3 may be spun or crimped into place over the projecting rim portion II as shown at I4 in said Fig. 3. According to this embodiment, the envelope 9 is forced into secure compressive engagement with the rim portion 1a of the opening 1 in the closure member 2, through the agency of the member I2, and is further secured in compressive engagement between the projection II and the portion I4 of the covering member.

In this form of the invention two separate sets of interengaging compression means are provided to force the envelope into compressive engagement with the solid closure member, namely, the member I2 which is in engagement with the envelope portion at the portion 1a of the closure member 2, and the portion I 4y of the cover I3 which is in engagement with the envelope portion at the position ofthe rim II. In each of the forms of the invention herein disclosed, the solid closure member is provided with shoulder means, and a compression member cooperating with the closure member in position to engage such shoulder means upon axial movement thereof with respect to the solid closure member in either direction, with a portion of the moisture-impervious envelope secured in positive compressive engagement between such shoulder means and the compression member.

If desired, in the above form of the invention the covering member I3 may be provided with a partially cut-away portion I5 of less width than the compression member I2, which may be pulled away from the main body of said covering member to enable the same to be removed by tearing the metal adjacent the end of the cut-away portion, as at I6 in Fig. 4, after the manner of the deformable seal customarily employed for catsup bottles and the like.

The material contained in the package is made ready for use by the dental technician by immersing the entire package in a body of water, which is brought to a boil and maintained at that temperature for a period of five to eight minutes. The package is then removed from the boiling water and kneaded to a smooth consistency and allowed to cool to a temperature in the neighborhood of 40 C. One end of the package is then opened as by means of a sharp knife or pair of scissors if the lower end I 1 of the package is to be opened, or by tearing away the deformable portion of the covering member I3 as above described, and removing the closure member 2, if the upper end of the package is to be opened. The soft plastic material is then squeezed into an impression tray or the like and used by the dental practitioner in the customary manner. In the event that a package of material has been brought to a soft or sol condition by the above boiling operation and it was then decided that the material was not to be used, the unopened package may be allowed to cool and placed back in storage without damage by the boiling operation, the package not having been subjected to any permanent physical change and therefore still possessing its hermetic properties.

In Fig. 5 I have illustrated one end of a stick at 2l such as a stick of hydrocolloid or other thermoplastic composition, secured to a cap or closure member 22 through the agency of a spiral attachment member 23 embedded in said member 22. The closure member is attached to the stick 2l by rotating the same with respect to said stick to cause the spiral member 23 to enter the stick after the manner of a corkscrew. The closure member 22 is shown as provided with a peripheral groove 24 which may extend in spiral fashion about the circumference thereof, preferably for somewhat more than a complete revolution. After the member 22 and stick 2I have been dipped into the coating material through the agency of the member 5 as above described in connection with the first form of the invention, to form a coating 25, a suitable compression member such as a coil spring 26 is then preferably wrapped around the member 22 in position to engage the coating and force the same downwardly into the groove 24 after the manner shown. The member 5 may be withdrawn either before or after this last operation, and the portion of the coating material which surrounds the opening from which the member 5 is withdrawn may be cut away, for example, at a position such as is indicated by the arrows a.

The form of package illustrated in Fig. 6 may comprise a stick of thermoplastic 26, an abutting solid closure member 21 provided with rather coarsely threaded side Walls 21a and an enclosing envelope 28 which preferably extends over the end of the member 21 as at 28a. The member 21 may be secured to the stick 26 through the agency of a spiral attaching member 23 in accordance with the showing in Fig. 5, if desired, and the envelope 28 may be formed by the abovedescribed dipping procedure through the agency of a suitable dipping member 5. The envelope 28 may be maintained in positive compressive engagement with the closure member 21 through the agency of a metal cap or the like 29 which is threadedly disposed over the end of the closure member to engage the portion of the coating 28 which overlies the threaded side walls 21a of said cap member, and force said coating portion into engagement with said member.

The form of invention illustrated in Figs. 7, 8, and 9 may comprise a closure member 3| provided with a thereto-secured spiral or corkscrew member 32 adapted to engage a stick 33 of material after the manner described in connection with Fig. 5, and an opening 34 in the upper end adapted to receive the tapered end 6 of a dipping member 5. The lower or inner end of the hole 34 is preferably recessed as at 35, the function of which will be subsequently brought out. The member 3i is attached to the stick 33 as above described, and the assembly is dipped into a bath of coating material to form a layer or envelope 36, being dipped to such a depth as to extend the coating material up about the lower end of the member 5 after the manner shown at 31. After the coating 35 has solidified or dried to the proper extent, the member 5 is removed and the portion 31 of the coating 36 is forced downwardly within the opening 34 after the manner shown in 8. A resiliently deformable compression member such as a cork or stopper 38 is then forced into the opening 34 as shown in Fig. 9, forcing the portion 31 of the coating 36 outwardly into compressive engagement with the side walls of the opening 34. The member 38 is pushed into the opening 34 a suicient distance so that the lower end thereof will enter the recessed space 35, where it will expand beneath the shoulders 39 of said recess and firmly position itself within the closure member 3|, to position said closure member with respect to the envelope.

In Fig. 10 I have illustrated a Inodied form of dipping member 40, the upper end or handle portion of which is shown broken away and the lower end 4I of which is preferably enlarged and may be of substantially the same proportions as one or the other of the closure members 22 or 3l above described. The dipping member is pro- III vided with an axial bore 42 threaded to receive a corkscrew member 43, which member 43 extends the full length of the member 40 and terminates in a ring or the like 44 adapted to be grasped between the thumb and forenger to turn the corkscrew member and move it longitudinally of the member 40. According to this form of device, the portion 4l of the dipping member is brought into abutment with an end of a stick 45 of impression material such as a hydrocolloid or other thermoplastic, the portion 44 turned to force the lower end 46 of the member 43 into the stick 45,'and the assembly is then dipped in the coating material to some such level as indicated at 41 to form a coating 48. After the coating 48 is properly solidified or dried, the portion 44 is rotated in the reverse direction, withdrawing the portion 46 from the stick 45, and the dipping member may then be forcibly removed from the stick. Where a material such as Korolac is employed in the formation of the coating, the dipping member is more readily removed before the Korolac has thoroughly dried, as the material is somewhat more resilient in an undried condition. After the dipping member is withdrawn from the envelope 48, a solid closure member 49 is inserted in its place, the upper end of the coating 48 being preferably cut away as shown at 5I in Fig. 1l. The closure member 49 is shown as provided with a peripheral recess 52 and after the member 49 is brought into position closely abutting the stick 45, a compression member such as a split spring ring 53 may be placed about the envelope in position to force the envelope inwardly into said groove 52 into compressive engagement with the closure member 49, after the manner shown in Fig. 1l. It will be apparent that the means shown in Figs. 5 and 11 for obtaining compressive engagement of the envelope coating with the rigid closure member may be used interchangeably. It may be noted that the split spring ring 53 is not required to closely abut at its end portions particularly if the envelope material is formed of Korolac or a like material, in view of the pronounced shrinkage of that material, which will cause the envelope to shrink close around the closure member into close engagement with the recess 52 in sufficiently tight compressive engagement therewith to prevent loss of volatiles from the package. Any space which may occur between the ends of the ring will permit the envelope to stretch under the force of kneading when the material is brought to sol condition, and if the package is held in an upright position, with the closure member at the top, air contained in the package may be forced out through such space, due to the stretching of the envelope at that point, although the plastic hydrocolloid material will not escape through such a small space.

The package may be rendered adequately hermetic without utilizing the split ring 55, if desired, by immersing the closure end of thepackage in hot water to a level beyond the position of the recess 52, to cause the envelope to shrink downwardly into the recess into secure engagement therewith.

The form of package illustrated in Fig. 12 may comprise a stick 6i provided with an envelope coating B2 which may be formed after the manner described in connection with Figs. l0 and 11, if desired, and a rigid closure member 63 placed at the end of the stick 5I. The ends of the envelope B2 are brought over the edge of the member 63 as shown at 64,4 which member is preferably of somewhat larger diameter Ythan the stick 5l and is preferably also provided with a rounded rim 5 after the manner shown. The compression member preferably comprises a lid of metal or the like 65 which may be crimped or spun over the rim portion 66 of the member 63, forcing the portion 54 of the envelope 62 into firm compressive engagement with said member.

The form of package shown in Fig. 13 may comprise a solid closure member 1| attached to a hydrocolloid stick T2 in any suitable manner as through the agency of a corkscrew member "E3 corresponding to the member 23 shown in Fig. 5, and said closure member 'H is preferably provided with a peripheral recess 'I4 in a manner comparable to that shown at 52 in Fig. 11. Before the envelope 'i6 is formed on the package, I dispose a suitable positioning means such as a split ring i5 within the recess i4. This positioning means is not required to tightly engage this recess, but should be of such proportion as to maintain its position with respect thereto. The envelope 'i5 is then formed by dipping the package into a suitable solution such as the abovementioned Korolac, and the envelope material will flow inwardly about the member 'l5 and also coat the outside thereof so that said member 'i5 becomes embedded in the envelope coating as shown at il. The subsequent drying of the envelope material will cause the envelope to tightly engage the closure member 'il whereby moisture loss from the package is prevented and in any subsequent boiling and/or kneading operation, the member if serves to position the closure member ii with respect to. the envelope so that endwise dislocation thereof under pressure will be prevented.

in each of the above-described forms of the invention, a suitable compression member is provided to positively force the envelope into compressive engagement with the solid closure means. When the coating is formed from Korolac or similar material, there will be sufficient compressive engagement of the envelope' with the solid closure member upon drying, even in the absence of the compression or positioning member above described, that escape of moisture from the contained material is substantially prevented. For example, specimens have been subjected to an extended storage period without significant loss in moisture content, in the absence of any compression or positioning means. The compressive engagement of the envelope with the closure means is also in general adequate to maintain the closure member in position during the above-mentioned boiling operation, but in view of the fact that the envelope material will soften to such an extent in boiling water that the principal proportion of the compressive engagement is lost, the heated package will not stand any degree of handling such as is produced during a kne-ading manipulation of the package, and for this reason I prefer to employ the abovementioned compression or positioning member to maintain the desired engagement of the envelope with the closure member during the boiling and kneading operation. In view of the fact, however, that these impression compounds are frequently brought into the desired iiuent or sol state in a special fo'rm of apparatus, such as a mixing syringe, I contemplate the possibility of forming the complete package in the absence of this compression or positioning member, inasmuch as the package in this form is adequate to prevent significant loss of moisture from the cont-ained hydrocolloid, and is thus a commercially operative package.

Each of the above-described forms of package may alternatively be prepared by the use of a preformed capsule or the like instead of the aboveset-forth dipping procedure. The forms shown in Figs. 1 to 4 may thus be prepared by employing a capsule of somewhat greater length than the stick l plus the closure member 2, folding the projecting end over the head of the member 2, immersing that end of the package into boiling water for a few seconds, and then applying the compression member I2 and the covering i3 as above described. The forms shown in Figs. 5, 6, 10, and 11 may be comparably prepared, and particularly, in the case of the forms shown in Fig. 6, the Korolac material will shrink about the threaded portion 27a into very secure engagement with the closure member 21. When a preformed capsule is employed in the formation of the type of package shown in Figs. 7, 8, and 9, I preferably use a capsule of sufcient length that the projecting end thereof may be tucked downwardly into the opening 34, the envelope then being thoroughly heated by immersion in hot water at that end of the device to soften the envelope, and the stopper member 38 forced into the opening 3d when the material is still in heated condition.

In the formation of the envelope coating by a dipping procedure, I may employ a mixture of cellulose and rubber in a suitable solvent, such as may be formed from an intermixture of two equal volumes of cyclohexanol or cyclohexanol acetate in which from 10% to 30% by weight of celluloid and raw rubber has been respectively dissolved, the mixture being preferably evaporated to a thin honey-like consistency.

Where the Celluloid-rubber mixture is employed, it will be necessary to allow the envelope coating to dry to some extent before the compression member is placed in engagement therewith. In general, I prefer to employ a composition which will solidify or gel at a more rapid rate than the above-mentioned Celluloid-rubber mixture, such as the above-mentioned Korolac. In the above-mentioned Korolac the Koroseal is in solution at a relatively high temperature, but solidies to a gel form at a relatively lower temperature. When the stick of hydrocolloid material and the associated closure member is dipped into a heated bath of Korolac, the material will gel out on contact with the hydrocolloid composition and form a continuous envelope over the dipped area, which may be handled almost immediately.

As a specific example of the formation of envelope coatings by a dipping procedure where the envelope coating is formed of the resin Korolac, I heat a body of Korolac containing approximately 10% Koroseal to a temperature in the neighborhood of 130 C. The coating thus formed will be in the neighborhood of one-eighth of an inch thick on gelling, which coating will dry down to a layer approximately ve-thousandths of an inch thick in a period of 48 hours, during which the above-described shrinkage takes place. Where heavier coatings are desired, multiple dipping may be practiced in such manner as to form a plurality of superimposed thicknesses of coating material in the production of membranes in excess of 0.01 inch in thickness. Alternatively, the thickness of the coating can be varied by a control of the temperature of the dipping bath and the temperature of the stick of hydrocolloid when dipped. For example, if a temperature lower than 130 C. is employed for the dipping bath, a thicker coat will be formed and similarly, if the stick of hydrocolloid is chilled before dipping, a heavier coat will result.

Other methods of attaching the rigid closure member to the stick or cylinder of hydrocolloid material will occur to those skilled in the art and I do not choose to be limited to the specific arrangements herein delineated, but rather to the scope of the appended claims. Furthermore, the dipping member 5 may be left in engagement with the finished package, if desired, either by permanently ataching the same to the rigid closure member or by forming the same integrally therewith, so that a handle member will be provided for use by the dental practitioner or his technician in the boiling operation, as will be apparent to one skilled in the art.

I claim:

l. A package of reversible moisture-containing thermoplastic impression material which is semi-rigid when cool and requires heating to render the same fluent for use, comprising: a stick of such impression material; a flexible moisture-impervious envelope enclosing one end and substantially the full length of said stick and projecting beyond the other end thereof; a solid closure member disposed within the projecting portion of said envelope and provided with shoulder means; compression means cooperating with said closure means in position to engage said shoulder means upon axial movement with respect thereto, and said envelope having a portion secured in positive compressive engagement between said compression means and said shoulder means.

2. A package as set forth in claim 1, said envelope being formed of a material having high mechanical strength at temperatures between atmospheric temperature and 100 C. and capable of resilient deformation at temperatures between 35 and 100 C.

3. The package set forth in claimll 1, said shoulder means on said closure means comprising a peripheral recess, and said compression means having a portion extending within said recess.

4. The package set forth in claim 1, said shoulder means comprising an inwardly directed recess in the outer end of said closure means, and said compression means comprising a plug member disposed within said recess.

5. A package of reversible moisture-containing thermoplastic impression material which is senil-rigid when cool and requires heating to render the same fluent for use, comprising: a stick of such impression material; a flexible moisture-impervious envelope enclosing one end and substantially the full length of said stick and projecting beyond the other end thereof; a solid closure member disposed within the projecting portion of said envelope and provided with coarsely threaded side Walls; a threaded cap member engaging said envelope at said projecting portion and forcing the same into compressive engagement with the coarsely threaded side walls of said closure member.

6. A package of reversible moisture-containing thermoplastic impression material which is semi-rigid when cool and requires heating to render the-same fluent for use, comprising: a 'stick of hydrocolloid material; a flexible moisture-impervious envelope enclosing one end and substantially the full length of said stick and ing said envelope at said projecting portion and projecting beyond the other end thereof; a solid forcing the same into compressive engagement closure member disposed within the projecting with said closure member at the position of said portion of said envelope and provided with a rim portion.

5 projecting peripheral rim portion at the outer HENRY F. BOEGER. 5

end thereof, and a compression member engag- CERTIFICATE 0E CORRECTION. Patent No.. 2,155,790. November 8, 1958.

HENRY E. BCEGER.

It :Lev hereby certified that the State of Incorporation of the assignee in the above numbered patentwas erroneously given as "Delaware" whereas said State should have been given as "California", as shown by the rec- 0rd of assignments in this office; and that the said Letters Patent should be read with this correction therein, that the same may conform to the record of the case in the Patent Ofice Signed and sealed this 18th day of March, A. D. 19M..

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

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