Necking-in Die Pilot

Abstract

An inner die pilot for use with an outer die of a die set for necking-in, i.e. reducing the diameter of or forming a neck in the end of a can body. The pilot is comprised of a ringed central body portion and an integral, substantially S-shaped collet having a plurality of substantially S-shaped segments defined by slots running substantially radially outward from the periphery of the central body. Each segment includes substantially vertical support members and substantially horizontally arched bridge members adjoining the central body and the support members. The slots in and the areas between the support and bridge members can be filled with a hard but resilient material such as polyurethane.

Description

BACKGROUND OF THE INVENTION

This invention relates to the manufacture of cans, and more particularly to the manufacture of necked-in cans, i.e. can bodies whose ends are of a reduced diameter. Still more particularly, the invention relates to a novel inner die pilot for a die set that is used to neck-in can bodies.

The conventional beer or beverage can is not uniform in its outer diameter. It has a bead or double seam of metal surrounding one or both of its ends and the double seam protrudes out beyond the vertical plane of the wall of the can body. This seam is formed by the interfolding of metal during can manufacture when a can end is secured to a can body. Conventional three-piece beer and beverage cans formed from a blank and two separate ends, have a double seam at both ends, while more recent two-piece cans such as impact extruded or deep drawn cans, formed from a one-piece body and bottom end and a separate top end, have only one double seam. In either case, the protruding double seam has caused handling, stacking and packaging problems because it prevents cans from being placed flushly alongside each other. When such cans are so placed, the double seam of one over or underrides adjacent double seams of the other and the cans become askewed or staggered.

In order to overcome this protruding double seam problem, ends of can bodies have fairly recently been manufactured to have necks or reduced diameters so that when can ends are attached to either end of can bodies, the resulting double seams do not protrude beyond but fall substantially flush with the vertical plane of the wall of the can body. Necking-in cans not only is advantageous because it solves these handling and stacking problems but also because it requires a little less material to make each can. Considering the billions of cans manufactured each year such a saving can be significant and substantial.

Methods of necking-in or reducing the diameter of a can body generally involve compressing a straight-walled can body between two necessarily quite rigid surfaces of a die set, one surface being interior and the other exterior of the can body. One or both of the surfaces or the can itself may have a rotational motion. As a can is being necked-in and its circumference is being reduced, folds or wrinkles of compressed metal form in the can wall. Other defects such as cracks and flat spots also appear. One of the problems encountered in necking-in operations has been to prevent these defects from occurring or to eliminate the wrinkles and flat spots once they occur. For conventional cans, i.e. those formed from a flat blank and rolled into a cylindrical form and having edges of the blank attached to each other by a soldered, interlocked hook seam or by a soldered or adhered juxtaposed lap seam, the problem has been especially acute since the presence of the protruding double metal thickness of the can hooked or lapped side seam on one portion of the wall as opposed to the single thickness of the rest of the can wall, has made it difficult to manufacture dies, necessarily substantially rigid and often having rotational motion, that are flexible enough to compensate for the side seam yet rigid enough to present enough resistance against the rest of the can wall to prevent defects and/or to iron or press out wrinkles and flat spots.

One method of overcoming this side seam non-uniform thickness problem has been to provide one surface of the die set with a groove for receiving the side seam. This method is not satisfactory because machinery required to orient the side seam of each can to the groove is unduly complex and costly. Also, such a method is not fast enough for highly automated can manufacturing systems.

Another problem with using such rigid die sets is that they are not adaptable for use with cans of different diameters and cans made of metals of different thicknesses. For example, dies having an orienting groove are not satisfactory for recently developed impact extruded or deep drawn cans, e.g. aluminum cans, which do not have lap seams and which are less thick and may have smaller diameters than conventional cans of steel or tin free steel.

The inner pilot of this invention is advantageous because it eliminates the need for complex and costly orienting and rotating machinery by being flexible enough to compensate for side seams no matter where they strike the pilot, yet rigid enough to prevent or eliminate the aforementioned defects from occuring in the rest of the can wall. The pilot is also advantageous because it is of simple construction, is adaptable for necking-in cans of various sizes and metal thicknesses, and is readily utilizable in fast, highly automated can manufacturing systems.

SUMMARY OF THE INVENTION

This invention is an inner pilot for use with an outer die of a die set for forming a neck of reduced diameter in the ends of can bodies. The pilot has a ringed central body portion and an integral, peripheral, substantially S-shaped collet having a plurality of substantially S-shaped segments defined by slots running substantially radially outward from the periphery of the central body. The S-shaped segments are comprised of substantially vertical support members and substantially horizontally arched bridge members adjoining the central body and the support members. A resilient material such as for example polyurethane can be used to fill the slots between the segments and the areas between the bridges and support members. Although in the preferred embodiment of the pilot of this invention, a bridge member adjoining the central body is located adjacent the trailing horizontal surface of the pilot, and a bridge member adjoining the support members is adjacent a horizontal leading surface of the pilot, it is also within the scope of this invention to provide a bridge member adjoining the central body adjacent a leading horizontal surface, and a bridge member adjoining the support members adjacent a trailing horizontal surface of the pilot.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the inner pilot of this invention showing a broken away view of a few of its S-shaped segments and part of its central body.

FIG. 2 is a cross sectional view of a straight-walled can body about to contact the mouth of an outer die encompassing an inner pilot, the view of the pilot being taken substantially along lines 2--2 of FIG. 1.

FIG. 3, another cross sectional view, shows a can body necked-in between the outer die and inner pilot of FIG. 2.

FIG. 4 is an enlarged top sectional, fragmentary view of a portion of the inner pilot taken along lines 4--4 of FIG. 3.

FIG. 5 is an enlarged, cross sectional, fragmentary view taken along lines 5--5 of FIG. 4 and shows the side seam portion of a can wall necked-in between an outer die and inner pilot.

FIG. 6 is a cross sectional view showing an inner pilot whose S-shaped segments have channels that are not filled with a resilient material.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing in detail, FIG. 1, shows an inner pilot 10, also commonly referred to as a punch, having a central body portion 12 in turn having a shank 14 with a bore 16 for accommodating means such as an Allen head cap screw (not shown) for fastening the pilot to an inner spindle (46 in FIGS. 2 and 3). Integral with and peripheral to central body 12 is a substantially S-shaped collet, generally designated 18, having a plurality of substantially S-shaped segments 20 defined by slots 22 running substantially radially outward from the peripheral wall 24 of central body 12. A broken away portion of inner die pilot 10 shows the S-shape of segments 20 and shows that each segment has substantially horizontally arched bridge members 26 and 28 and substantially vertical support members 30 and 32. Horizontally arched bridge member 26 integrally adjoins central body 12 with inner vertical support 30. Horizontally arched bridge member 28 integrally adjoins inner support 30 to outer vertical support 32. The bridges and support members of each segment also form oppositely facing annular U-shaped channels 36 and 38, which can be filled with a hard but resilient material 34 which can be a suitable material such as rubber or polyurethane. Annular channels 36 and 38 and slots 22 of collet 18 are shown filled with material 34 from the broken away section located at about 9 o'clock on the pilot clockwise around to a position at about 6 o'clock on the pilot. From about 6 to about 8 o'clock, channel 38, channel 36 (not shown), and slots 22 are not filled with material 34.

FIG. 2 shows a die set generally designated 40, for forming a neck of reduced diameter in the end of a straight-walled can body. More particularly, FIG. 2 shows a cross section of an outer die generally designated 42 and a cross section of the inner pilot 10 taken substantially along lines 2--2 of FIG. 1. Pilot 10 is fastened to inner spindle 46 of a die set assembly (not shown) and to outer die 42 by bolt 44 which can be any bolt or suitable fastening means such as an Allen head cap screw. FIG. 2 shows a fragmentary cross section of the end of an unflanged, straight-walled can body 48 aligned with the mouth 50 of chamber 52. Can body 48 is shown having an inner vertical side seam 54 of double metal thickness along the wall of its body. The substantially vertical walls of chamber 52 are a combination of substantially smooth surfaces of decreasing diameter and are comprised of an inwardly-angled orienting surface 56, a substantially vertical support surface 58, an inwardly-angled shoulder-forming surface 60, and a substantially vertical neck-forming surface 62. The cross sectional view of pilot 10 in FIG. 2 shows central body portion 12 having shank 14 with tines T for engaging bolt 44 and fastening pilot 10 to inner spindle 46. The cross sectional view also shows peripheral wall 24 of central body 12 which coincides with the inner terminal surfaces of slots 22, and forms one of the walls of U-shaped channel 36. Peripheral wall 24 can be visualized as continuous if an imaginary line is drawn joining the inner terminal surfaces of slots 22 all the way around pilot 10. FIG. 2 also shows a small neck-receiving clearance 64 between outer surface 66 of collet segment support member 32 and neck-forming surface 62 of outer die chamber 52. Clearance 64 usually is about the width of a can body wall of single thickness and is the interstitial area in which the can end is abuttingly given its necked-in contour.

The right side of FIG. 2, being a cross section through central body 12 and through the middle of a segment of S-shaped collet 18, shows the integral nature of pilot 10, while the left side of the Figure, being a cross section through a slot 22, shows a portion of the outer peripheral wall 24 of central body 12.

FIG. 3 is another cross section of the die set 40 of FIG. 2. FIG. 3 shows the straight-walled end of can body 48 after it has been necked-in or given its reduced diameter by having been forced to take the increasingly reduced diameter contour of outer die chamber wall surfaces 58, 60 and 62. The upper portion of can body 48 is shown having been given shoulder 60', and neck 62', in clearance 64 (FIG. 2), by tightly abutting and opposing surfaces 66 of S-shaped segment support member 32 and neck-forming surface 62 of outer die 42.

FIG. 4 is an enlarged sectional view taken along lines 4--4 of FIG. 3. FIG. 4 shows side seam 54 of FIG. 3 turned counterclockwise about 90.degree. and shows how a series of S-shaped segments 20 collapse as they engage the side seam. More particularly, FIG. 4 shows necked-in can wall 62' and its side seam 54 in clearance 64 between wall surface 62 of outer die 42 and surfaces 66 of support members 32 of segments 20 which are part of collet 18 of central body 12. Support members 32 are shown compensating for the heretofore problematical double metal thickness of side seam 54 by collapsing radially inward against and into rigid but resilient supporting material 34 in channel 38 and slots 22. Each individual S-shaped segment compensates by collapsing inwardly according to the thickness of the can body wall abutting it and this compensation of each individual segment is independent of, does not affect, and is not affected by the compensatory or non-compensatory action of any other segment. This individual and independent action of segment support members 32 can be seen by observing that segment support member A is least collapsed and is flush against a wall portion of single thickness. Members B and C are most inwardly collapsed by the double thickness of the side seam, while D and E are gradually less collapsed. F, like A, is least collapsed and is flush up against a wall portion of single thickness. Thus, through this individual compensatory response, each member, regardless of the thickness of the wall portion that it abuts, remains substantially flush against and thereby provides pressure against all portions of the can wall. This compensatory action and pressure prevents problematical folds, wrinkles, cracks and other defects from resulting in or near in the necked-in area of the can.

FIG. 5 is an enlarged, fragmentary view taken along lines 5--5 of FIG. 4 and shows the double thickness of side seam 54 in clearance 64' between outer die 42 and surface 66 of S-shaped segment 20. FIG. 5 shows that clearance 64 is enlarged to clearance 64' by the double metal thickness. Support members 30 and 32 and adjoining bridge members 26 and 28, forming the S of S-shaped segment 20, compensate in some manner for the double metal thickness of side seam 54 for example by collapsing or bending in the manner shown. The rigid but resilient material 34 in channels 36 and 38 and in slots 22 provides enough resilience to allow collapsing compensatory action of the various members 26, 28, 30 and 32 of segment 20 yet also provides enough pressure and resistance against side seam 54 so that it can be necked-in without problematical wrinkles, etc.

The material used to fill slots 22 and grooves 36 and 38 can be any suitable substantially rigid but resilient material which allows satisfactory compensatory action by S-shaped segments 20, yet sufficiently and fairly uniformly resists this compensatory action so that wrinkles, folds and other necking-in defects do not occur adjacent the necked-in area of a can. Suitable materials for filling the slots and channels can for example be polyurethane or rubbery materials.

FIG. 6 is a cross-sectional view showing another embodiment of inner die pilot 10 of this invention. It shows S-shaped collet 18 having S-shaped segments whose slots 22 (not shown) and whose channels 36 and 38 are not filled with a rigid but resilient material. Although this embodiment is wholly adequate for satisfactorily necking-in can bodies, pilots having filled slots and channels may be more advantageously used for certain types of necking-in operations. For example, non-filled pilots are suitable for mechanically stripping or removing necked-in cans from an inner pilot, but for an air stripping operation it is more advantageous to use a filled pilot since the filling material prevents air from escaping through the slots and channels and thereby provides a substantially air-tight operation.

FIG. 6 shows substantially horizontal leading and trailing surfaces LS and TS respectively designated in relation to the horizontal surface that leads the pilot into or first enters the perimeter of a can body. FIG. 6 also shows that horizontally arched bridge member 26 which integrally adjoins central body 12 with inner vertical support 30 need not be adjacent the trailing surface TS of the pilot but can be adjacent the leading surface LS, and similarly, horizontally arched bridge member 28 need not be adjacent trailing surface TS but can be adjacent leading surface LS.

Methods of necking-in a can basically involve relative movement between the can and the outer die such that the movement causes the can wall and the neck-in contoured surfaces of the outer die to snugly abut and pass or wipe over each other so that the contour of the outer die surface is imparted to the can wall. Methods vary according to what moves, i.e. the can, the inner pilot, the outer die, or any combination thereof, during the necking-in operation.

For the sake of convenience, the imparting of a necked contour to a can will be described by an operation in which the can is moved into a stationary die set. The end of a straight-walled can 48 is aligned with mouth 50 of outer die 42. As the can end is brought up along orienting surface 56 and along substantially vertical surface 58, the uppermost part of its rim strikes and passes diagonally inward along shoulder-forming surface 60 until it glances off outer surface 66 of an S-shaped pilot segment 20 by which action the can end is moved upward into clearance 64 where it is given its neck by snugly and opposingly abutting inner pilot segment surface 66 and outer die surface 62.

Other methods of effecting relative movement are to move both the die set and the can, or to move the die set down over and onto a stationary can. A well known method is to move a can end up into the outer die mouth until it is adjacent orienting surface 56, bring the inner pilot down into and fully inside of the end of the can and then either hold the pilot and can stationary and move the outer die down over them, or hold the outer die stationary and move the pilot and can up into it.

The die pilot of this invention can be employed in methods which neck-in one or both ends of a can body.

The inner pilot of this invention can be made of any suitable material which could be used for making dies such as conventional tool steel or carbide or a combination thereof. For example, segment surfaces 66 on support members 32 adjacent outer die inwardly-angled shoulder-forming surface 60 can be made of or sprayed with a more durable material such as carbide.

Dimensions of the pilot, its members, slots and channels can vary depending on such factors as the diameter of the can, the thickness of its walls and the thickness and width of its side seams. Support and bridge members can be of varying thicknesses, but especially desirable results are obtained when they are of uniform thickness. This appears to effect uniformity of segmentary resistant and compensatory action and means that when for example the lowermost surface of channel 36 is arcuate, outer surface 32' (FIG. 5) is also. Surface 32' (in FIG. 5) is an orienting surface and is important in high speed operations, for example when spindle 46 moves to load a can onto pilot 10.

Often, without being changed, the same pilot can be used equally well for cans with or without side seams, and similarly a pilot can be used to neck-in different cans having different diameters and wall thicknesses.

While the presently preferred embodiments of this invention have been hereby illustrated and described, it will be understood that the invention may be still otherwise variously embodied within the scope of the claims which follow:

Claims

I claim:

1. An inner pilot for use with an outer die of a necking-in die set for forming a neck of reduced diameter in the ends of can bodies, wherein said outer die has a chamber for receiving said pilot, said chamber having a combination of substantially smooth-surfaced walls of increasingly reduced diameter for forming said neck in said can bodies when the ends of said bodies are abuttingly brought into the interstices between said inner pilot and said walls, said pilot being comprised of a central body portion and an integral, peripheral, substantially S-shaped collet having a plurality of substantially S-shaped segments defined by slots running substantially radially outward from the periphery of said central body, said S-shaped segments being rigid but resilient and including substantially vertical support members and substantially horizontally arched bridge members adjoining said central body and said support members.

2. The pilot of claim 1 wherein a rigid but resilient material fills said slots and the areas between said bridge and said support members.

3. The pilot of claim 2 wherein said resilient material is polyurethane.

4. The pilot of claim 2 wherein said pilot has a generally horizontal leading surface and a generally horizontal trailing surface, and a said bridge member adjoining said central body is adjacent said trailing surface and a said bridge member adjoining said support members is adjacent said leading surface.