US3704677A

US3704677A - Method for making and applying a bottle cap

Info

Publication number: US3704677A
Application number: US888116A
Authority: US
Inventors: Jens L Moller
Original assignee: Continental Can Co Inc
Current assignee: Continental Can Co Inc
Priority date: 1968-11-26
Filing date: 1969-12-18
Publication date: 1972-12-05
Anticipated expiration: 1989-12-05

Abstract

The subject is a bottle cap of the type which is first pushed on, but thereafter may be twisted off and on. A shell is made from a cupped blank having a substantially straight skirt. The skirt is then knurled or fluted, the inside root diameter of the flutes being a close sliding fit on the crests of the bottle finish threads to which the cap is to be applied. When knurling, the rim of the skirt is curled inward slightly to an inside diameter about the same as the inner root diameter of the flutes. After inserting a suitable seal ring or disc, the shell is pushed down over the threaded finish of the bottle into sealing engagement with the lip. While so holding the cap, portions of the skirt are conformed to the thread formations on the bottle finish, thus providing a releasable threaded engagement. As the threads are formed in the skirt, the inwardly turned edge is closely conformed to the finish, in which position the edge is shielded against accidental contact by the fingers, when unscrewing the cap to open the bottle.

Description

United States Patent 1 Moller [451 Dec. 5, 1972 I 1 METHOD FOR MAKING AND 3,123,241 3/1964 Nofer et a1 ..215/39 APPLYING A BOTTLE CAP 2,010,228 8/1935 Gibbs ..113/121 A 7 t l lnvem or Jens! Moller westmom Przmary Examiner-Charles W. Lanham [73] Asslgneez Continental Can Company, Inc., Assistant Examiner-Michael J. Kennan New York, NY. Attorney-George E. Szekely, Joseph E. Kerwin and 221 Filed: Dec. '18, 1969 w'lham [21] Appl. N0.: 888,116 [57] ABSTRACT Related US. Application Data The subject is a bottle cap of the type which is first pushed on, but thereafter may be twisted off and on. [62] E i 1968 A shell is made from a cupped blank having a substantially straight skirt. The skirt is then knurled or fluted, 7 the inside root diameter of the flutes being a close Sliding fit on the crests of the bottle finish threads to [58] i C A which the cap is to be applied. When knurling, the rim le 0 can "'i' ii 4 of the skirt is curled inward slightly to an inside 3 44 diameter about the same as the inner root diameter of the flutes. After inserting a suitable seal ring or disc, 56 R f Ct d the shell is pushed down over the threaded finish of 1 e erences l e the bottle into sealing engagement with the lip. While UNITED STATES PATENTS so holding the cap, portions of the skirt are conformed to the thread formations on the bottle finish, thus 3,135,408 6/1964 St. Jacques ..215/39 providing a releasable threaded engagemem AS the 876,361 1/1908 Kraft et a1 "113/121 A threads are formed in the skirt, the inwardly turned 3,517,848 6/1970 Kesler et a1 ..215/43 edge is closely conformed to the finish in which posh 3,219,004 11/1965 W11t011 ..113/121 A tion the edge is Shielded against accidental Contact by 3,523,624 8/1970 Curry ..215/39 the fingers, when unscrewing the p to p the 3,503,534 3/1970 Moller ..2l5/39 2,302,542 11/1942 Gibbs ..113/121 AA 1,658,603 2/1928 Kowal .l 13/121 A 4 Claims, 11 Drawing Figures 1,659,703 2/1928 Ramsey ..113/121 A Q: 7 I I 33 l l H 1111 21. ii 1 i@1 18 b 1|| /WI "1 \I I7 (Q R K K V I11 m1 111111 20 1'21 PKTENTEDIJEB 5 I972 SHEET 3 0F 4 METHOD FOR MAKING AND APPLYING A BOTTLE CAP BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to caps of the type primarily intended for sealing bottles of carbonated beverages, more particularly the type which can be applied and sealed in a manner similar to the conventional crowning procedures, but which may thereafter be unscrewed and used as a reclosure-in the manner of screw or lug caps.

2. The Prior Art In recent years, there has been an increasing demand for beer and soft drinks large bottles, such as half quarts and quarts. This demand has been stimulated in large part by price and convenience factors. However, a major deterrent to wider acceptance of larger bottles for home consumption is possible wastage by virtue of unused contents losing carbonation and going flat.

Conventional crown caps cannot ordinarily be used as reclosures, since they are almost invariably spoiled in removing them. Various types of reclosure stoppers, plugs, and caps have been brought on the market, but have not met with substantial acceptance. Convenience is best served by providing a reusable cap on each bottle, for example, a thread or lug cap. Such a cap is also desirable for'small bottles, not usually requiring reclosure, to enable the user to remove the cap without a bottle opener.

Tooling and equipment problems, particularly in the soft drink bottling field, generally require that press-on cap application be retained, to be generally adaptable to crowning presses, or comparable equipment, which has been found most satisfactory and economical in the bottling conditions involved. It has heretofore been proposed that caps be made of substantially conventional crown form, in sizes to fit over a finish with suitable thread formations and threaded in situ. However, the conventional crown cap entails a configuration in which the skirt is flared out, or at least substantially spaced from the bottle finish, with a sharp edge for engagement by prying bottle opener. A cap of this basic configuration does not lend itself to turning with the fingers, particularly because of the hazard in cutting fingers on the exposed edge. Also, threaded closure quality and the characteristics obtained with conventional crown forming and crimping techniques have not been found entirely satisfactory. Various modifications and alternatives have been proposed to overcome the configuration with a suitable pry edge. Except for costlier varieties available only at premium prices, the combination caps in general use are dangerous, in that the sharp pry edge is exposed to contact with the fingers of a user twisting the cap.

SUMMARY OF THE INVENTION It is an object of this invention to provide a bottle cap for push-on application, with dependable twist-off removal and reclosure, which is simple and economical to manufacture and apply.

It is a further object of this invention to provide a cap of the general type designated which is producible with minimum material of ordinary commercial quality, reliably conformable to simple thread-form finishes, and which can be applied thereto on substantially standard capping machines at high production rates.

It is a still further object of this invention to provide a cap of the general class indicated, in which a shielded edge may be formed without extra material or extra operations as compared with conventional crown caps of similar size and sealing requirements.

The foregoing and other objects and advantages derive from a novel formation and application of the cap, utilizing a cupped blank having a straight skirt so formed as to produce a shell with fluted or knurled skirt, the skirt retaining its generally straight character. In the same die forming operation,- the skirt rim is coaxed inward to an edge diameter substantially congruent with the diameter at the knurl valleys which diameter is slightly larger than the bottle thread or lug crest diameter. The finished cap, having a seal ring, disc, or gasket in the shell, is pushed down with force to compress the seal on the bottle lip. While the cap is several problems, but prior to this invention, no fully thus held, coacting die members form portions of the skirt upon the thread formations, seating the rim with its edge in shielded position at a diameter less than that of the knurl crests.

By virtue of the structure and procedure described, not only are the cap threads well formed and even, but a lead thread of substantial extent is formed through the rim, so that the cap can be unscrewed without distorting the inturned rim. The cap can be easily retightened, with minimum cross-threading hazard, and without pounding or snap action. Thus, the cap operates after its initial application as a twist cap, assuring the advantages thereof in ease of removal and reclosure, with the mechanical advantage of the thread or lug formations to effect a tight seal upon reclosure. The knurling affords an excellent finger grip, the crests acting to keep the fingers safely away from the sharp rim edge.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a section similar to the section of FIG. 2, showing the configuration of the shell after withdrawal from the tooling and upon insertion of the seal element;

FIG. 5 is a section through a portion of a bottle neck having a threaded finish, showing the application of the cap of FIG. 4 with the cap held in sealing position, just prior to actuation of the thread-forming die part;

FIG. 6 is a section similar to that of FIG. 5 showing the fully formedcap held in the crimping die,just prior to die retraction;

FIG. 7 is an elevation of a bottle top with a cap according to this invention applied thereto, a portion of the cap being broken away to show the bottle thread formation;

FIG. 8 is a section similar to FIG. 1, taken through a modified cup, showing a skirt variation;

FIG. 9 is a section similar to FIG. 2, illustrating a different knurling method, as applied to the cup shown in FIG. 8;

FIG. 10 is a horizontal section of Line 1010 of DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 shows the first stage in the preparation of the cap. At this stage, the shell blank 8 is a simple cup having a slightly crowned top panel 10 and a straight cylindrical skirt 1 I, joined by radius 12. Such caps are readily mass-produced by blanking and forming in wellknown manner from metal strip of suitable analysis and temper, generally comparable to that used for conventional crowns.

FIG. 2 shows the configuration of the fully formed shell, seen as resting against the tool 13 at the completion of the knurl. Tool 13 is a roll, rail or segment, according to the type of equipment selected for the operation. That is, the part may be clamped and tool 13 rolled about skirt II; the tool 13 may be held stationary and the part rolled against the working face; or tool 13 may oscillate as the part revolves on a mandrel. In any case, the action being generally that of rolling, tool 13 is hereafter referred to as a roll. The view is fragmentary, it being understood that the part is symmetrical about the vertical axis. The rim of roll 13 is circumferentially undulated or ribbed, with the traverse peaks I4 tangent to a cylinder whose diameter is less than the outside diameter of the shell blank skirt 1 1, whose maximum diameter is controlled by the undulation root diameter, at roots 15. When roll 13 is pressed and rolled against cylindrical shell shirt 11, the undulated or ribbed surface forms corresponding undulations, flutes or knurling by deformation of skirt 1 1, the resulting configuration being in effect a straight knurl. As best seen in FIG. 3, the resulting skirt contour is generally sinusoidal in cross-section, with peaks and valleys on the outer surface thereof constituting elements of cylinders, as determined by the

corresponding roll elements

14 and 15.

In a representative size, the desirable flute pitch angle is about 12, that is, there are about 30 flutes. Ample stiffening is effected with flute depth on the order of twice the thickness of a representative suitable material, it being understood that the number of flutes may vary according to the cap diameter, as well as thickness and temper of the material selected. In general, the cap made and applied according to this invention has characteristics conducive to use of somewhat thinner material than heretofore feasible in crown caps of comparable size.

Referring again to FIG. 2, the forming roll is provided with a bottom radius 16, blending outward from the undulation valleys 15, toward the peaks 14. As skirt 11 is being knurled, the radius 16 coaxes edge 17 inward, correspondingly forming the radiused, inturned .rim 18, which is virtually wavele'ss at edge 17. The roll v13 is so contoured that the finished diameter of edge 17 is substantially the same as diameter D, FIG. 3, resulting in a smooth blending of fluted skirt 11 into the rim 18, free of raggedness or irregular formation, the skirt remaining generally straight.

A liner, gasket, or a sealing ring of substantially any type ordinarily used with crown caps, may be readily adapted as a seal for use in the cap of this invention. FIG. 4 shows the cap of FIGS. 2 and 3 with a preferred liner 19, which has been found most suitable to the application and service conditions here involved. The design and performance characteristics of the liner here shown, as they obtain in associating with crown caps, are described in US. Pat. No. 3,127,920, issued to Henry .I. Dorn, June 8, I965.

FIGS. 5 and 6 show a preferred mode of applying the cap of FIG. 4 to the finish of a typical bottle 20. The tooling shown fragmentarily is that which is suitable for use in the crowning presses generally employed in operations of the character involved. The bottle finish is provided with exterior thread formations 21. Form ations 21 are not necessarily complete turns, but may be merely elements of threads, or thread-form lugs. However, best results are obtained if formations 21 constitute the equivalentof about two-thread length. The threading may be single or compound.

The cap 9 is pushed over the top of bottle 20, which is centered in die ring 22, in turn centering cap 9 on bottle 20. Edge 17 and flute valleys 32 closely telescope the thread formation 21. Punch 23 is brought down on cover panel 10 with sufficient pressure to seal liner 19 on lip 24, which pressure may, be established by spring-loading punch 23 in a well-known manner. Punch 23 is compounded with a follower ring 25, guided by punch 23 at the interface 26. In the stage of FIG. 5, follower 25 is in partially retracted position.

Referring now to FIG. 6, the view is rotated one-half the fluting pitch from the view of FIG. 5, as indicated by section lines in FIG. 3. While punch 23 holds cap 9 in sealing position, follower 25 advances toward die 22 and cap 9. The die 22 is of the resiliently collapsible type, made of rubber, for example. The depth of die 22 is somewhat greater than the depth of cap 9, the tooling and part being so positioned that the top face 28 of die 22 is initially in or slightly above the plane of cap cover panel 10, with cap 9 in its sealed position. Follower 25 has a shallow conical lead face 27, while collapsible die 22 is an annulus of normally rectangular cross-section. As ring 25 advances toward die 22, the leading face 27 first contacts die face 28, compressing ring 22, thereby setting up fluid pressure conditions characteristic or rubber of other polymeric materials, with an intensified radially inward bias in consequence of the component in that direction established by the conical face 27, which tends to crowd the die material inward and distribute the deformation pressure uniformly around the circumference of die 22 as follower 25 advances. The pressure of die 22 against skirt 11 and consequent flow of die material into flute valleys 32 causes the valley walls 29 to press against the creasts of thread elements 21, with an accompanying collapsive effect, due to pressure above and below the thread creasts, forming interrupted female thread elements 30 in skirt 11. The flute peaks 33, not being subject to the concentrated bent stresses, are substantially undistorted by the die pressure, assuring resistance to destructive collapse, and retaining the generally stiff characteristics of the fluted skirt 11. Also, the general stiffness of skirt 11 is suff cient to minimize ovality or other irregular formation due to imperfect distribution of constrictive pressure.

At the same time that die 22 forms the thread elements 30 in skirt- 11 the pressure on inturned rim l8 collapses portions thereof inward along the lowermost bottle thread formation 21 against collar 31, the diameter whereof is the same as, or slightly greater than, the root diameter of threads 21. Thus, the lowermost skirt thread formations extend into the rim l8; constituting thread leads, while the edge 17 hugs the finish without general bending relative to the line of skirt 1 1, minimizing residual stresses in skirt 11, and aiding retention of thread conformation in subsequent removal and reclosure.

The working stroke of follower 25 is so regulated as to assure the displacement of die 22 in the amount required for conforming the knurl roots of skirt 11 to threads 21. Overloading of the tool is prevented in the usual manner, by suitable spring loading. Follower 25 is desirably relieved at 125 so that at maximum stroke relative to punch 23, follower 25 will not strike panel 10, thus precluding bottoming and possible marring of cap 9. On completion of the follow stroke, cap skirt 11 is fully formed, locking cap 9 in sealed position on hot tle 20. Punch 23 and follower 25 thereupon retract to positions of readiness for operation upon the next bottle and cap presented. It will be understood that the tooling described may be incorporated in the usual multi-station capping press for automatic, high-volume production.

The general configuration of the completed closure is best seen in FIG. 7. As here shown, the finish has a triple thread formation 21, each element of which is somewhat more than one-third turn along the helix,

establishing an overlap whereby to provide two-thread engagement of substantial arcuate extent in three sectors around the circumference of the finish. The arrangement assures ample grip with the cap in sealing position, minimizes cocked engagement of the threads, and keeps thread friction minimum when turning the cap free or tightening. Edge 17, being inturned well inside the diameter of flute peaks 33, is fully guarded against finger contact when the user removesor replaces cap 9. The knurled skirt surface provides an excellent non-slip finger grip.

The finish thread length is selected such that rim 18 of cap 9, when tight, lies with edge 17 in a horizontal plane through the thread termini 121 of the lowermost thread formations 21, whereby thread leads are formed through rim 18 when the cap 9 is applied as previously described. This provision assures easy starting for reclosure. In the case of the usual beverage bottle top, a finish length of about l/4 inch, a thread pitch of about 3/32 of an inch, and a helix angle of about 10 constitute a suitable thread formation, which in the threeelement configuration shown provides a desirable quick-acting removal and reclosure, with correspondingly short turn of the cap 9. With this thread dimensioning, the uppermost formation 21 starts somewhat below the lip 24, minimizingthe chipping, galling, and splintering hazards which otherwise may obtain in a threaded glass finish. The uppermost finish band 34 is held to a diameter about the same as the thread root diameter, thus acting as a pilot for replacing the cap. 7

The closure structure and proportions above described can be executed in usual bottle top sizes with a cap blank and total material requirement less than that involved with conventional crown caps, effectuating excellent economy in material costs, particularly as compared to designs heretofore proposed for push-on, twist-off caps of the class involved.

MODIFICATION The above described embodiment involves formation of the flutes and coaxed rim in a cylindrical skirt by means of a one-piece roll. Knurling and coaxing of a slightly flared or coniform skirt is illustrated in FIGS. 8, 9 and 10, in which parts corresponding to those of FIGS. 1 through 5 are given like reference numerals with the addition of 100.

The blank 108 of FIG. 8 is similar to blank 8 of FIG.

- 1, having a top panel 110 and a skirt 1 11, connected by radius 112. However, in this case, the skirt 111 is slightly flared or coniform, downwardly and outwardly, being substantially a portion of a right circular cone, except that the narrow rim 118 is substantially cylindrical. Thus, the rim 118 is bent slightly inwardly of a downward extension of the main skirt portion 111.

As seen in FIGS. 9 and 10, the final forming tool assembly consists of three principal tools, a cap mandrel 150, a coaxing tool 151, and a knurling tool 152. Referring particularly to FIG. 10, the mandrel is provided with equally spaced ribs 153, alternating with valleys 154 of substantially the same circumferential extent in each case as the corresponding rib 153. The valleys 154 are outwardly convex, on a circle centered on the center of mandrel 150. That is, the roots 154 constitute arcs of a common circle concentric with mandrel 150. Knurling tool 152 is a rail segment provided with ribs 155 and valleys 156 which are complementary to the formations of mandrel 150, so that the mandrel 150 and roll'l52 can be loosely meshed as shown, with clearance for material to be formed between them.

Skirt 111 is a loose fit over the mandrel 150. The crest diameter of ribs 153 at the base of the mandrel cone is smaller than the inside, or root, diameter of the coaxed rim 118, at edge 117, so that the completed shell can be stripped from mandrel 150 without interference or distortion of rim 118. A seen in FIG. 10, skirt 111 is knurled progressively, being held to mandrel 150 by segment 152 along that element which is instantaneously in the working plane 161. The relief of the forming roots at 162 and 163 affords clearance to minimize jamming or seizing as the material is rolled and bent over the meshing

ribs

153 and 155.

FIG. 11 schematically illustrates a suitable tool setup in a rotary machine arrangement. A number of vertical spindles 158 are mounted around the periphery of a table 159, which is rotatably mounted on a column 160. Mandrels 150 are revolvably supported on spindles 158. The knurling segment 152 and coaxing die 151 are concentric with table 159 and are fixed in position for rolling mesh traverse of mandrels 150 as table 159 rotates, the relationship being as shown in FIG. 10. The arcuate extents of the knurling and coaxing segments l52, 151 are such that each mandrel 150 makes at least one full revolution in traverse of full ribs 155, which drive the mandrel on spindle 158 as the skirt 11 1 is knurled. The usual blend section is preferably incorporated in

tools

151, 152 to minimize chatter or jar at the beginning of the pass. Otherwise, sudden or irregular capture of the part may cause malformation and seizing. A shown in FIG. 9, ribs 155 may be relived at their upper ends, along lines 164, to avoid fluting through the cap radius 112, This results in a blend radius 165 between root 132 and radius 112, which latter is maintained around the cap.

The shell formed as shown in FIGS. 9 and may be completed in a manner similar to cap 9 of FIG. 4 and then applied to the bottle substantially as in FIGS. 5 and 6, in the manner previously described. It will also be apparent that the blank and tool combination of FIG. 2 may be implemented as in FIG. 11 to produce shells 88 economically in quantity.

With either cap form, 9 or 109, the same salient advantages are realized. The generally straight skirt, 11 or 111, can be readily constricted by essentially direct radial forces uniformly applied against substantially the entire length and circumference at the skirt, as by the arrangement of FIGS. 5 and 6. A pressure sufficient to conform the knurlroots to the finish threads will not, and need not, alter the general configuration of the skirt, the flutes affording the stiffness necessary to prevent general distortion or localized malformation, while providing the controlled leverage and backing of sufficient magnitude to cause good thread formation in the knur] roots upon constriction. Because there is no sharp, general bending of skirt, such as required for crimping the sharply flared skirt of conventional crown caps, the cap according to this invention is not subject to the strain failures characteristic in sharp bending of sheet metal. Hence, lighter weight, ductile material of less costly analysis and temper may be used, further facilitating good thread formation and maintenance of shape for reclosure. Also, the skirt length for caps hereindescribed is generally less than that required for conventional crimp closure, permitting a smaller cutedge diameter for the cap blank.

The slight skirt taper of the blank and shell in the form of FIGS. 8 and 9 assists in preventing the skirt material from riding up the tool faces and holds the rim down on the coaxing die. The modified form has the same advantageous characteristics as the cap of FIG. 4. The slight bending of the skirt relative to the top panel when constricting the skirt does not involve significant strain, being readily accommodated in the top radius.

Where particular operations or tools are separately shown or described herein, for example, formation of cups from strip, description in such manner is given only for the sake 'of clarity.

It will be understood that the various forming operations for either of the embodiments described are not necessarily performed in single stages of independent machines, or stations, but are preferably integrated by use of compound tools and automatic transfer devices in the manner well known in the tool and die art related to crowns, caps and similar small parts generally.

It will also be understood that such terms as punch", die", roll and mandrel are used herein as seems most apt in describing a particular tool or part thereof, and not to infer that one or the other is necessarily the moving part where relative motion of the several tool parts is indicated. Wherever the terms threads or thread formations are used herein, such terms are used as descriptive of the preferred embodiment, and not by way of limitation to particular such formations shown, the invention being readily adaptable to camming lug finishes and other equivalent twist engagement means.

The foregoing descriptions of particular embodiments are given by way of example. Other forms, variations, and modifications may be devised by those skilled in the art, following the teachings herein, without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. A method of forming a cap having a top panel and a skirt adapted for conformation to external thread formations on the finish of a bottle or the like, which method comprises:

a. blanking and forming sheetmaterial to form a cup having a generally straight skirt;

b. knurling a principal lengthwise portion of said skirt by circumferential bending deformation of said material for establishing a circumferential series of straight flutes in said skirt, while maintaining said skirt generally straight; and

c. coaxing the rim of said skirt radially inwardly of the major diameter of said flutes for constituting said cap with the edge of said skirt inwardly of the major diameter of said flutes in a generally straight skirt depending from said top panel.

2. A method of forming a cap according to claim 1, wherein said cup skirt is generally coniform, a narrow rim portion of said cup skirt being slightly inturned relative to the general line of said cup skirt, whereby to predispose said rim for said coaxing.

3. A method of closing a container mouth having ex- I ternal thread formations, the closure including a cap having a top panel and a generally straight shirt, said skirt having a circumferential series of axial flutes along a substantial portion of the length of said skirt, said flutes being constituted by circumferential bending deformation of said skirt, and said skirt having a rim terminating in an inturned edge, said method comprising the steps of:

a. holding said cap on said month with said skirt telescoped over said thread formations; and applying substantially direct radial pressure along and about substantially the entire length and circumference of said skirt, of an intensity to effect constriction of said skirt, thereby conforming root elements of said flutes to said thread formations and collapsing said rim;

thereover, the intensity of said pressure being sufficient to conform portions of said rim to said thread formation portions for establishing lead thread formations in said rim.

Claims

1. A method of forming a cap having a top panel and a skirt adapted for conformation to external thread formations on the finish of a bottle or the like, which method comprises: a. blanking and forming sheetmaterial to form a cup having a generally straight skirt; b. knurling a principal lengthwise portion of said skirt by circumferential bending deformation of said material for establishing a circumferential series of straight flutes in said skirt, while maintaining said skirt generally straight; and c. coaxing the rim of said skirt radially inwardly of the major diameter of said flutes for constituting said cap with the edge of said skirt inwardly of the major diameter of said flutes in a generally straight skirt depending from said top panel.

3. A method of closing a container mouth having external thread formations, the closure including a cap having A top panel and a generally straight shirt, said skirt having a circumferential series of axial flutes along a substantial portion of the length of said skirt, said flutes being constituted by circumferential bending deformation of said skirt, and said skirt having a rim terminating in an inturned edge, said method comprising the steps of: a. holding said cap on said month with said skirt telescoped over said thread formations; and b. applying substantially direct radial pressure along and about substantially the entire length and circumference of said skirt, of an intensity to effect constriction of said skirt, thereby conforming root elements of said flutes to said thread formations and collapsing said rim; whereby to constitute a twistably removable cap on said container, with said edge in protected position relative to fingers grasping said skirt to twist said cap.

4. A method of closing a container mouth according to claim 3, wherein said rim overlies portions of said thread formations when said cap is telescoped thereover, the intensity of said pressure being sufficient to conform portions of said rim to said thread formation portions for establishing lead thread formations in said rim.