US3543559A

US3543559A - Cup blanking and forming method and tooling therefor

Info

Publication number: US3543559A
Application number: US785899A
Authority: US
Inventors: Jerry D Hawkins; Bill G Reid
Original assignee: Continental Can Co Inc
Current assignee: Continental Can Co Inc
Priority date: 1968-12-23
Filing date: 1968-12-23
Publication date: 1970-12-01
Anticipated expiration: 1987-12-01
Also published as: GB1245547A; BE743516A; DE1936523A1; NL6918649A; SE372183B

Description

.1970 J. D. HAWKINS ETAL 3,543,55

CUP BLANKING AND FORMING METHOD AND TOOLING THEREFOR FiledDed. 25, 1968 3 Sheets-Sheet 1 INVENTORS JERRY D. HAW S BILL G.R

Dec. 1, 1970 HAWKlNs E TAL. 3,543,559

CUP BLANKING AND FORMING METHOD AND TOOLING THEREFOR Filed Dec. 25, 1968 3 Sheets-Sheet 2 2 INVENTORB v JERRY D. HAWKINS BILL e. REID Dec. 1, 1970 D, w ms ETAL 3,543,559

CUP BLANKING AND FORMING METHOD AND TOOLING THEREFOR Filed Dec. 23, 1968 VENTORS JER D. HAWKINS BILL 3 Sheets-Sheet 8 I G. REID United States Patent 3,543,559 Patented Dec. 1, 1970 3,543,559 CUP BLANKING AND FORMING METHOD AND TOOLING THEREFOR Jerry D. Hawkins, Country Club Hills, and Bill G. Reid, Bolton, 11]., assignors to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Dec. 23, 1968, Ser. No. 785,899 Int. Cl. B21d 51/48 US. Cl. 72-335 Claims ABSTRACT OF THE DISCLOSURE A method of forming a corrugated crown cap having an uncorrugated lip at an angle to the flange, and compound tooling for forming the cap in a double-acting press. The method comprises gripping the margin of the blank with predetermined pressure, draw forming and corrugating the skirt and flange while constricting the marginal portion of the blank, under restraint of the grip, then restraining the flange, leaving the lip free, and bending the lip. The tooling includes blanking and forming punches in a first assembly, and a nested die set in a second assembly. The blanking punch and an anvil grip the margin of the blank, while the forming punch, telescoped in the blanking punch, coacts with the forming die, telescoped in the anvil, to draw and corrugate the skirt and flange, constricting the marginal portion of the blank under restraint of the grip. The grip pressure is predetermined by a spring biasing the anvil toward the blanking punch. At the completion of the draw, a shoulder on the forming punch restrains the flange against the upper face of the forming die. Continued downward motion of the forming punch bends the lip between the anvil bore and a collar on the forming punch.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to mass production of crown caps in presses of the multi-action type, with compound tool and die sets. The invention relates more particularly to a method and tooling for blanking and forming such caps having a smooth, uncorrugated lip extending at an angle to the corrugated flange or web.

The prior art There is a large demand for small crown caps, of which the cap for a beverage bottle is a representative example. The basic contour of the standard crown cap is a cup with a generally horizontal flange, the flange being adapted for crimping to hold the crown tightly on the bottle top. Usually, such crowns are corrugated along the skirt and flange for stiffening effect. Crowns have heretofore been successfully mass-produced at low cost in gang punch presses by means of compound tool and die sets which punch blank discs from the strip material and then form and corrugate the caps by drawing the discs dropping down from the blanking operation.

It is a usual characteristic of crowns formed by the most economical methods of the prior art that when the flange thereof is crimped on the bottle finish the sharp edge of the rim stands away from the bottle. Consequently, a person grasping the cap may cut his fingers on the projecting edge. This condition is particularly dangerous with twist crowns. It has been proposed so solve this problem by curling the rim of the flange or skirt in order to protect or tuck the edge, so that persons handling the finished product will not suffer cut fingers. Alternatively, it has been proposed to coin, tumble, roll or similarly break or round the edge, which is inherently sharp by virtue of shearing from thin sheet metal, The various such proposals heretofore made for solving the edge problem have involved additional material for the part, special materials, extra operations and set-ups, or all of these, with a resultant substantial increase in the cost of the article. In the case of crown caps, competitive conditions have precluded adoption of the substantially more costly cap forms on any large scale. There is wide demand for a cap of the protected edge, or no-cut type, but at little or no premium over the less satisfactory caps now in general use.

It has been proposed to form a twist-type crown cap with a smooth lip at such angle to the cap flange that the lip assumes a position with the edge inward of the smooth lip and is protected thereby, when the cap is crimped. However, heretofore there has been no satisfactory method of tooling for economically producing such smoothlip caps in quantity.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method of forming crown caps having a narrow, uncorrugated lip portion bent at a substantial angle to the plane of the flange, which method can be practiced economically in mass production.

It is a further object of this invention to provide tool ing for blanking and forming crown caps or similar articles from sheet metal according to the method of this invention, where in the operations of blanking, flanging, drawing and lip bending can be performed in a single, rapid stroke, without transferring the part, yet minimizing machine and tool cost, tool breakage and wear.

It is a still further object of this invention to provide a method and tooling for making crown caps of a type requiring forming and bending a narrow, uncorrugated lip portion relative to the flange, which method and tooling can be readily incorporated and practiced in high speed presses of the type in general use for making such crowns, which is economical of material, and which retains the basic configuration and proportions of the cap for closure in accordance with usual practices.

The foregoing and other objects and advantages of the novel method are achieved by gripping the marginal portion of the blank to restrain constriction of the marginal portion, while draw forming the cap panel and skirt, and forming corrugations inwardly of the gripped portion, then restraining the flange, inwardly of the lip portion, against bending relative to the skirt, leaving the lip portion free, and then bending the lip portion relative to the flange. The cut edge diameter of the blank exceeds that of a conventional crown at most by the small amount required to form the narrow lip. A crown formed according to the method and with the tooling of this invention has the general configuration and crimping characteristics of crowns as heretofore made, but has a lip bent to an angle which assures a protected position for the edge when the crown is crimped on a bottle.

The tool assembly according to this invention need be little or no larger than assemblies for making conventional crowns. The tooling can be incorporated into press equipment in normal use for conventional crown forming, without major modification in mounting, set-up, or the general mode of press operation. The additional compounding for the sequence required to blank and form according to this invention is provided in the tooling itself by a novel design and arrangement of the punch and die parts, whose operation requires little or no greater stroke or pressure than required to form crowns as heretofore made.

The prior practice in mass-production tooling for crown caps generally involves duplexing the blanking punch and the forming punch for double-action. The blanking punch knocks the blank down to the forming die. The forming punch and die then form and corrugate the skirt and flange, which latter is constituted by the constricted marginal portion of the blank. In this prior practice, the corrugations inherently extend to the edge of the cap.

In tooling according to this invention, the marginal portion of the blank is gripped between the blanking punch and an anvil surrounding the forming die, while the skirt is drawn and corrugations are formed, the marginal portion constricting under restraint of the grip. The grip is maintained on the lip portion substantially until the corrugations are formed inwardly of the lip portion. The flange is then restrained between a shoulder on the forming punch and the upper face of the forming die, leaving the lip portion free, whereupon continued motion of the forming punch carries the cap and forming die downward relative to the outer anvil, bending the lip portion between the anvil bore and a collar on the forming punch.

The foregoing and other features, objects and advantages of the invention will be best understood from the following description and the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary vertical section through an article representative of those which may be produced according to the method and tooling of this invention;

FIG. 2 is a vertical section through a tool assembly constructed and arranged according to this invention, shown in position at initiation of the blanking stage, also fragmentarily showing associated press parts, die block and strip guide, the view being divided as FIGS. 2A and 2B, to permit use of a satisfactory scale;

FIG. 3 is a fragmentary vertical section similar to FIG. 2, showing the position of the tools after a blank has been severed and gripped, preparatory to draw form- 8;

FIG. 4 is a fragmentary section, similar to FIG. 3, showing the position of the tools and condition of the part at the completion of the draw forming operation;

FIG. 5 is an enlarged fragmentary plan view of a portion of the die assembly shown in FIGS. 24 inclusive, showing details of the provisions for corrugation form- FIG. 6 is a fragmentary top plan view of the cap in its condition at the stage of FIG. 4;

FIG. 7 is an enlarged fragmentary section through a portion of the tool assembly as in the position of FIG. 4; and

FIG. 8 is a fragmentary section similar to FIG. 4, showing the position of the tools and condition of the part at the completion of the lip bending operation;

DESCRIPTION OF THE PREFERRED EMBODIMENT The method of forming articles according to this invention will be best understood by describing the method in association with preferred tooling for practicing the method in mass production, that being the principal application of the method. However, it will be understood that the method of operation to produce articles of the desired characteristics is not limited to the particular tooling shown and described.

FIG. 1 shows the general configuration of an article of the form for which the method and tooling according to this invention are particularly adapted. The article here shown is a crown cap having the form of a shallow cup, with a slightly crowned or dished panel 10, a cylindrical wall or skirt 11, a flange 12, extending outwardly from skirt 11, and a narrow. lip 13, which extends nearly at right angles to flange 12 in a direction away from panel 10. A plurality of corrugation ribs 9 extend between skirt 11 and flange 12, terminating inwardly of lip 13. The cap is here shown inverted from the position in which it is normally seen in use, the position shown being that in 4 which the article appears in subsequent drawings illustrating the production method and tooling.

FIG. 2 shows a tooling assembly, or die set, constructed and arranged according to this invention for high-speed production of caps as shown in FIG. 1. FIG. 2b is a downward continuation of FIG. 2a. Those skilled in the art of blanking and forming small articles from sheet metal will readily understand that the tooling assembly as shown in FIG. 2 may be ganged in line, or in a ring, whereby to produce a number of like articles in simultaneous operation of the several sets in one machine assembly. It is a significant feature of the method and tooling according to this invention that same may be implemented in such gang-press arrangement for economical, high-production operation.

In FIG. 2 only so much of the press is shown as assists in understanding the operation sequence as shown here and in the subsequent views. The press parts shown include a bed 15 and a ram 16. Ram 16 is associated with suitable toggle mechanism or the like (not shown), constituting with bed 15 a press of the double-acting type, as well known for performing combined blanking and forming operations in a set of complementary tool assemblies. Die block 17, resting on bed 15, supports a suitable strip guide, generally indicated by the reference numeral The first, or punch, assembly consists of the blanking punch, sleeve 19, and the forming punch 20, which carries an ejector pin 21. Sleeve 19 is actuated by ram 16 pressing on shoulder 22 of the clamping sleeve 23, in which sleeve 19 is held by means of clamping nut 24.

In FIG. 2 the position of the parts is that prevailing on the downward stroke of ram 16, just as sleeve 19 severs a blank 8 from the strip 7, in the first stage of double action. Forming punch 20 and the seating rod 21 are in retracted position, ready for downward stroke under effect of second-stage punch actuation.

The second, or die, assembly, held in die block 17, consists principally of the blanking die 25, a gripping anvil 26 and the forming die 27, which carries an ejector anvil 28. Blanking die 25 is fitted to die block 17 by means of clamping screws or bolts 29. The other die members are nested in blanking die 25, with clearance for assembly, adjustment and for relative axial motion as hereafter more particularly described.

In the position of FIG. 2, no downward pressure has been brought to bear on the movable die parts, which are thus at their uppermost position. Ejector anvil 28 is biased to its upward position by spring 32, the limit of upper position being determined by the adjustment of the stop and

jam nuts

33, 34 at the lower end of rod 35, projecting downward from the head of anvil 28. Forming die 27 and anvil 26 are supported on and biased upward by the heavy pressure spring 36, which rests on bushing 37 in the bolster 38. At its upper end, spring 36 bears on pad 39, forming the lower end of the yoke 40, which is an extension of the body of the forming die 27. Shoulder 61 of pad 39 bears on bed insert 71, and shoulder 31 of forming die 27 bears on and suports anvil 26. Yoke 40 also houses the ejector anvil spring 32. Shoulder 41 serves as a limit to the downward motion of ejector anvil 28.

Referring now to FIG. 3, sleeve 19 has completed its blanking stroke and severed blank 8, which is here supported around its marginal portion by anvil 26. The stroke of sleeve 19 and upper position of anvil 26- are so related that the clearance between sleeve 19, at full downward stroke, and anvil 26 is less than the minimum thickness of any blank 8. As sleeve 19 approaches the limit of its stroke, blank 8 is gripped between sleeve 19 and anvil 26, 'whereafter, on the final increment of stroke, sleeve 19 pushes anvil 26 downward, against the bias of pressure spring 36. Clearance accommodates this downward movement of anvil 26 and also provides allowance for a possible double blank, which may occur in high speed operation, due to failure of part ejection after the previous stroke. Otherwise, bottoming of anvil 26 on insert 49 may result in crushing or breaking sleeve :19, or other tool parts.

By virtue of anvil 26 bearing on shoulder 31 of die 27, the latter moves downward with anvil 26. As best seen in FIG. 2, the downward thrust on anvil 26 and die 27 is yieldably opposed by spring 36, acting through pad 39 and yoke 40, supporting die 27. By selected setting of bushing 37, the spring 36 may be preloaded to a desired value corresponding to the optimum gripping pressure along marginal portion 79 of blank 8, between sleeve .19 and anvil 26, for a purpose hereafter shown.

Referring again to FIG. 3, the forming punch 20 is at its first operational position, clamping the center of blank 8 on ejector anvil 28, preparatory to draw forming. Ejector pin 21, advanced under biasing action of spring 42 (FIG. 2A), provides pre-seating pressure and a predisposing bias of blank 8 toward level position upon concave anvil face 44, opposing the correspondingly crowned nose 43 of punch 20. At this stage the top faces 56, 57 and 58 of anvil 26, die 27 and anvil 28 respectively present a continuous level support for blank 8, the members being so disposed by virtue of the stop shoulder 31 of die 27 and the limiting stop nut 33 (FIG. 2B) on rod 35, extending from anvil 28. Spring 32, supporting crowning anvil 28, being lighter than spring 36 (FIG. 2B), biasing die 27 and anvil 26, permits anvil 28 to move downward relative to die 27 and anvil 26, as punch 20 and anvil 28 draw the center of blank 8 into die 27. The cupping draw tends to cause wrinkling or buckling of the cap material in formation of the skirt portion. In the formation of crown caps, the buckling action is accommodated by al lowing material to flow into suitable die pockets 52, 54, establishing the corrugation ribs typical of such caps. However, the restraint effected upon the marginal portion 79 of blank 8 by gripping between punch 19 and anvil 26, under pressure corresponding to bias of spring 36, obviates the development of corrugations in the gripped blank portion. The gripping pressure or restraint is established by means of spring 36, as before described, so that the marginal annulus constricts at substantially the same rate as the draw rate of skirt 11, that is, the gripping pressure exerted on blank 8 between sleeve 19 and anvil 26 is less in amount than that to tension the material to its yield point in drawing skirt 11. Thus, the material is not substantially stretched in the draw, and skirt 11 will not be subject to substantial necking. In making the representative bottle cap here shown, a total gripping pressure on the order of 1,000 lbs. has been found suitable.

From comparison of FIGS. 3 and 4 it will be seen that as draw forming proceeds and marginal portion 79 (FIG. 3) constricts, the area of the gripped annulus decreases at the rate of draw. By virtue of the constant total grip pressure being etfective on decreasing area, the unit pressure on the lip portion 80 increases, as the material therein is drawn toward the upper face 55 of forming die 27. In the stage of FIG. 4, the forming punch 20 is at its second operational position, draw forming being complete. Further travel of forming punch 20 relative to forming die 27, is precluded by virtue of shoulder 45 of crowning anvil 28 bottoming in yoke 40*, supporting die 27 The provisions for corrugating are best seen in FIG. 5. Spaced grooves 52 are cut lengthwise of cavity wall 53 of die 27. In draw forming, between the stage of FIG. 3 and the stage of FIG. 4, the material constituting the flange 14, and the portion of skirt 11 adjoining flange 14, for a substantial length toward panel 10, are constricted from the outer annulus of blank 8. The constriction involves a gathering effect, accompanied by tendency to buckle and corrugate in a fairly regular pattern. The die grooves '52, 54 accommodate the buckled material in the form of corrugation ribs 9 (FIG. 1), which extend between skirt 11 and flange 12. The gathering effect being minimal in the portion of skirt 11 toward panel 10, and further inhibited by panel 10, no corrugations develop in that skirt portion.

In the course of the draw forming, the lip portion 80, is under an increasingly intense gripping pressure, as above described. The pressure not only prevents buckling or corrugation during the draw and constriction, but so inhibits the transmission of the corrugation stresses and strains that substantially no stresses and strains subsist in lip portion 80. Therefore, even after lip portion is freed of restraint, substantially no blemish develops, the surfaces retaining at least the smoothness of the original material, in fact enhanced by wiping under the pressure of the grip restraint during constriction of the margin. The restraint is maintained substantially until the completion of forming and corrugating, resulting in the cap configuration at the stage of FIG. 4, as shown in FIG. 6, with ribs 9 extending between skirt 11 and flange 12, and lip portion 80 free of corrugations.

The relative positions of the lip portion, flange and skirt to the several tool elements, at the stage of FIG. 4, is best seen in FIG. 7. Flange 12 is capture and restrained between shoulder 47 of punch 20 and upper face 55 of forming die 27. Lip portion 80 is resting substantially free on upper face 52 of anvil 26, below counterbore 65 in sleeve 19. That is, lip portion 80' is free of the restraint upon flange 12 and virtually free of the grip between sleeve 19 and anvil 26. Desirably, the diameter of counterbore 65 is such as nearly corresponds to, or is slightly smaller than, the average diameter of edge 14 at the stage here shown, the edge diameter being necessarily subject to a small variation with variation in the cut edge diameter from piece to piece, with tool wear, and with other variations in the material and tool operation. As previously observed, the grip on lip portion 80 is maintained substantially until completion of corrugation. After the draw corrugation has progressed to substantial extent, in the manner previously described, the buckling stresses are so relieved by formation of the ribs in skirt and flange that no substantial deleterious effect results, should lip portion 80 be relieved from its grip just before the final small increment of draw, as may occur with a minimum cut ed-ge diameter.

The continuing downward stroke of punch 20 from its position in FIGS. 4 and 7 carries with it forming die 27 and the captured workpiece, against the bias of spring 36 (FIG. 2B). The weight of anvil 26 and pressure of lip portion 80 moves anvil 26 the distance permitted by remaining clearance 60, whereupon anvil 26 bottoms on shoulder 64 of insert 49, and fully frees the grip on lip portion 80. Further downward movement of the workpiece under impetus of punch 20 bends the lip portion 80 between the collar 50* of the punch 20 and the bore 51 of anvil 26. FIG. 8 shows the condition at completion of the stroke. Clearance to accommodate the edge 14 is provided by counterbore 65 in sleeve 19, the counterbore diameter being such that, with anvil 26 downward, edge 14 will clear the corner 86; as lip por-' tion 80 bends up.

Since the lip portion of the material has been maintained free of wrinkling or corrugation stress, as described in connection with FIGS. 3, 4 and 5, blemishing is substantially obviated in formation of the lip 13. The cap is thus completed to the configuration of FIG. 1, with a smooth, unblemished lip 13. Also, there is substantially no scufiing along corrugation ribs 9. This scuif-free condition in the corrugation areas derives principally from the arrangement and operation wherein the draw forming of the skirt and the corrugations is complete and the cap is captured between forming punch and forming die, before bending of the lip begins, as above described. Thus, there is no relative motion under pressure, between the cap, the forming die and the forming punch, after the corrugations are formed, and substantially no working,

Wiping, cocking or the like of the flange or skirt, under pressure exerted in bending the lip.

After lip 13 is formed, the several movable punches and die parts retract or return to their ready positions and the strip material 7 is advanced for the next blanking and forming stroke. As forming punch 20 retracts, ejector pin 21, under bias of spring 42 (FIG. 2A), frees the cap from punch nose 43. Ejector anvil 28, under bias of sping 32, forces the cap from die 27.

The foregoing description of a preferred embodiment is given by way of example. Those skilled in the art will be enabled thereby to devise variations and modifications within the spirit and scope of the invention as defined by the claims.

We claim:

1. In a method of forming a crown cap from a disc blank of sheet material, said cap including a cover panel, a skirt extending from said panel, a flange extending laterally outward from said skirt, corrugations extending between said skirt and said flange, and an uncorrugated, inclined lip extending from said flange outwardly of said corrugations, the steps of:

(a) gripping said blank along a marginal portion thereof to restrain said marginal portion substantially uniformly against constriction, and to hold said blank in a plane;

(b) applying draw forming means, with pressure normal to said plane, against a portion of said blank inwardly of said marginal portion, to form said panel, said skirt and said corrugations, while constricting said marginal portion against said gripping restraint, to form said flange and a lip portion outwardly of said flange portion from the outer portion of said marginal portion, and maintaining said gripping restraint along said lip portion outwardly of said corrugations until said corrugations are substantially fully formed;

(c) restraining said flange inwardly of said lip portion against bending relative to said skirt, leaving said lip portion substantially free of restraint; and

(d) applying bending means against said lip portion to bend said lip portion relative to said flange, whereby to form said uncorrugated, inclined lip.

2. In a method of forming a crown cap, the steps according to claim 1, including applying said draw forming pressure to said blank in one direction normal to said plane, and applying said lip portion bending means against said lip portion with pressure on said lip portion in a direction opposite to said one direction, whereby to form said lip inclined from said flange in a direction away from said skirt and said panel.

3. In a method of forming a crown cap, the steps acccording to claim 1, including controlling said gripping restraint for exerting pressure upon said marginal portion in an amount to inhibit transmission of corrugation stresses and strains into said lip portion, said amount being less than that to tension said material in said drawforming beyond the yield point of said material, whereby to constitute said lip substantially free of blemish and said skirt substantially free of necking.

4. In a method of forming a crown cap, the steps according to claim 2, including applying the total said gripping pressure initially along an annulus of said marginal portion, near the edge thereof, said marginal portion including said lip portion, said marginal annulus having a radial extent not less than the radial extent of said lip portion, and applying said total pressure by means of rigid gripping members with radially fixed grip surfaces opposed along an annulus having an inner diameter substantially equal to the diameter of said edge at completion of said constriction, whereby to increase the amount of said gripping pressure upon unit area of said lip portion along said edge during said drawing and said corrugating, relative to unit pressure upon said lip por- 8 tion subsisting upon initial application of said total pressure.

5. Apparatus for forming a crown cap from a disc blank of sheet material, said cap including a cover panel, a skirt extending from said panel, a flange extending laterally outward from said skirt, corrugations extending between said skirt and said flange, and an uncorrugated, inclined lip extending from said flange outwardly of said corrugations, said apparatus comprising: first and second tool assemblies containing relatively reciprocable means for performing work upon said blank, including complementary gripping means for gripping said blank substantially continuously along an annular marginal ortion thereof; complementary draw forming means in said assemblies, coaxial with said gripping means, including first forming means in said first assembly movable between a retracted position and first, second and third operational positions, and second forming means in said second assembly cooperable with said first forming means, as said first forming means moves between said first and second operational positions, for forming said panel, said skirt and said corrugations, while constricting said marginal portion under restraint of said gripping means to establish said flange and an uncorrugated lip portion outwardly of said flange, said lip portion being substantially freed from said gripping means, with said first forming means at said second operational position; and complementary lip bending means in said assemblies, including first bending means in said first assembly and second bending means in said second assembly, arranged for coaction, to bend said lip portion relative to said flange, upon movement of said first forming means between said second and third operational positions, whereby to constitute said crown cap with said uncorrugated lip.

6. Apparauts according to claim 5, wherein said assemblies include complementary blanking means, coaxial with said gripping means and said forming means, for severing said blank from said material.

7. Apparatus according to claim 6, wherein said blanking means includes a blanking die in said second assembly, said gripping means including a sleeve in said first assembly movable between a retracted position and a gripping position, for coaction with said blanking die to sever said blank, and for following said blank, while said sleeve moves between said retracted and gripping positions.

8. Apparatus according to claim 7, said gripping means including an anvil in said second assembly having an annular upper face for opposing said sleeve and said marginal portion of said blank, said anvil being movable between a first position and a second position, said first anvil position being that for said anvil to intercept said blank and said sleeve at a sleeve position between said retracted position and said gripping position less distant from said gripping position than an amount equal to the thickness of said blank; and said second assembly including yieldable means for biasing said anvil to said first anvil posittion with a predetermined bias value, whereby to adapt said gripping means for gripping said marginal portion with a pressure corresponding to said bias value.

9. Apparatus according to claim 8, said first forming means having a nose and a collar defining with said nose a shoulder set back from the end of said nose; said sccond forming means having a cavity for coaction with said nose to form said panel, said skirt and said corrugations, as said first forming means moves between said first and second operational positions, and an annular upper face for coaction with said shoulder to restrain said flange in a generally planar attitude substantially as said first forming means attains said second operational position.

10. Apparatus according to claim 9, including stop means for limiting movement of said anvil toward said second anvil position, and for establishing said second anvil position at a distance from said first anvil position at least equal to the maximum thickness of said blank, whereby to obviate incidence of said gripping pressure in an amount greater than the amount corresponding to said bias value.

11. Apparatus according to claim 10, including means for releasably engaging said second forming means with said anvil, with said upper faces of said anvil and said second forming means coplanar, and for accommodating movement of said anvil and said second forming means together between said first and second anvil positions, under pressure of said first forming means upon said second forming means overcoming said bias, said second forming means being telescoped in said anvil in position for said upper face of said second forming means to back said blank when said anvil is at said first position and while said first and second forming means coact to draw said skirt and to form said corrugations.

12. Apparatus according to claim 11, wherein said yieldable means is arranged for action against said second forming means and for coaction with said engaging means to bias said second forming means and said anvil together toward said first anvil position, unidirectional limit means being arranged for engaging said anvil in opposition to said bias, to establish said first anvil position, the value of said bias being greater than the value of force exerted upon said second forming means opposite to said bias, as said first forming means moves between said first and second operational positions, said bending means including a bore in said anvil arranged for coaction with said collar to bend said lip portion, in a direction away from said panel, with said anvil at said second position, upon movement of said first forming means between said second and third operational positions, and while said shoulder and said upper face of said second forming means restrain said flange in said attitude.

13. Apparatus according to claim 12, including a counterbore in said sleeve for freely accommodating the peripheral portion of said lip portion, while said bending means bend said free lip portion relative to said flange in a direction away from said panel and said skirt and toward said sleeve at its said gripping position.

14. Apparatus according to claim 12, wherein said bias value corresponds to a grip pressure upon said marginal portion of an amount to inhibit transmission of corrugation stresses and strains into said lip portion, said amount being less than that to tension said material to its yield point in draw forming said skirt, as said first forming means moves between said first and second operative positions, whereby said apparatus is adapted to constiute said crown cap with said lip substantially free of blemish and said skirt substantially free of necking.

15. Apparatus for forming a crown cap from a disc blank of sheet material, said cap including a cover panel, a flange extending laterally outward from said skirt, corrugations extending between said skirt and said flange, and an inclined lip extending from said flange outwardly of said corrugations, said apparatus comprising: first and second t'ool assemblies containing relatively reciprocable means for performing work upon said blank; complementary draw forming means in said assemblies, said draw forming means including first forming means in said first assembly sequentially movable, between first, second and third positions, and second forming means in said second assembly adapted for cooperation with said first forming means to form said panel, said skirt, said flange and said corrugations, as said first forming means moves between said first and second positions, and to restrain said formed blank between said first and second forming means in relative positions thereof substantially to preclude bending of said flange relative to said skirt and bodily movement of said formed blank and said first and second forming means relative to each other, leaving a lip portion of said blank outwardly of said flange free of said restraint, upon completion of said forming and during movement of said first forming means between said second and third positions; and complementary lip bending means in said assemblies, including first bending means in said first assembly and second bending means in said second assembly, said first and second bending means being arranged for coaction to bend said lip portion relative to said flange, upon movement of said first forming means between said second and third p0- sitions, whereby to mitigate scuffing along said corruga tions while bending said lip.

References Cited UNITED STATES PATENTS 2,251,433 8/1941 Wareham 113-121 2,605,730 8/ 1952 Dennis 72-348 3,258,954 7/1966 Dennis 72-335 RICHARD J. HERBST, Primary Examiner