GB2092492A - Improvements relating to can manufacture - Google Patents

Abstract

A spin flanger, for flanging a necked-in can body (A) has an axially and rotationally movable head (20) provided with a freely-movable pilot for entering a pre-formed neck to align can body (A) with the spin head (20). Spin- forming rollers, mounted on the periphery of the head, are rotatable on axes normal to the head rotation axis and each has a rim and body portion with meeting surfaces making an included angle of e.g. 120 DEG , the rim in use initially flares the end edge of the can body and the body portion (which ex- tends substantially normally to the head rotation axis) completes the spin- formed flange. The head is cammed towards the can body and spin forming is accomplished while the head is moved by the cam at constant velocity. <IMAGE>

Description

SPECIFICATION Improvements relating to can manufacture The present invention relates to improvements relating to can manufacture.

More particularly, the invention is concerned with a method of applying flanges to a drawn and iron (D & I) container, i.e. the so-called 2 piece beverage can, and with the tool used for putting a flange on the partially-formed container. D & I refers to the process used to manufacture the container. A shallow metal cup is drawn from a thin metal sheet and then punched through a plurality of ironing rings which thin the wall without substantially reducing the diameter. During this process the wall of the container is reduced to about one third of its original thickness, thus leaving a cylindrical container shell open at one end with a thinner side wall than bottom. At its open end the shell is trimmed to the right length and square with respect to the axis of the container.It is at this stage that the container is first necked and then flanged such that the container may be thereafter double seamed with a can end, during a closure process after filling.

D & I containers are generally made out of aluminium or tin-plated steel and during the ironing process the metal is substantially worked, particularly in the side wall and thus the hardness of the material increases and ductility decreases. Consequently, there is a potential for the metal to be overworked to the point of failure. One mode of failure is cracking of the outer periphery of the flange. More particularly, a radial crack occurs in areas of the flange where the metal has an inclusion or a weak point.

For many years containers have been drawn and ironed from Iowtemper(T1 and T2) box annealed tin plate steel. This metal has operated successfully in providing the required combination of strength, hardness and ductility, such that flange cracked cans could easily be kept below a predetermined number per thousand. It has been found to be more desirable to use higher temper metals to manufacture D & I containers. These higher temper materials can be used in thinner gauges to permit a greater number of containers to be made per pound of steel and yet the performance and strength of the container so produced is equivalent to or better than thicker gauge cans.

In experimenting with higher temper materials of thinner gauge, it has been found that the D & I process can be applied without much difficulty except for flange cracking. Techniques for overcoming the flange cracking problem include, inter alia, re-annealing before flanging and flanging to a shorter flange length or angle. All of these approaches have their disadvantages and limitations.

The usual method of flanging uses a commerical flanging head having cones carried to rotate about their axes parallel to the axis of rotation of the total head. The tool is carried on a necker-flanger machine and is brought into the open end of the trimmed D & BR< I container shell. The cones are rolled and moved against the upper inside edge of the container shell in such a way that the open end is flared outwardly to give the necessary flange configuration for an effective double seam. Use of this type of commercially available flanging head has produced about three times as many cracked flanges per thousand containers with higher temper materials than with the low temper steels or the softer aluminium materials.

We have been seeking to develop method and apparatus suitable for flanging, on high speed commerical equipment, higher temper metals of thinner guage than hitherto and to minimize the amount of flange cracking incurred. In the course of our work, we have refined the parameters of a new flanging head such that the number of cracked flanges per thousand cans spin flanged are reduced to a minimum.

We have, accordingly, adopted a new approach to a commerical flanging head for D & I containers; the new head is disclosed and its operation is explained herein.

In a periodical called Tooling and Production dated October 1978, two researchers from the U.S.

Steel Corporation disclose their experimental, inclined-axes flanging head. The improvements of the present disclosure are adapted to that device and, more specifically, are inclined to make that device operate in a commercial environment. That is to say, that the improvements herein were necessary in order to make that experimental device suitable for high speed commerical operation on a necking and flanging machine. The U.S. Steel device includes a head having six rollers disposed radially about the head, each being mounted for rotation about an axis normal to that of the head. The spin flanging device as proposed by U.S. Steel Corporation caused the end of the container to crush when used in a commerical necker-flanger, producing a rippled or fluted flange totally unacceptable for use in a double seam with a can end closure.

Three specific improvements were responsible in practice for producing an acceptable flange and for minimizing the number of cracked flanges per thousand. A piloting device was added to the drive axis of the inclined axes spin flanging head. The piloting device guides the can as it approaches the rollers, each of which is supported on an inclined axis. Without the piloting device the axial orientation of the container shell in a commercial necker-flanger was not certain, and container shells could be caught between the roller and the body of the flanging head.

In addition, the pilot aids in forming a more uniform flange because it holds the can in a central position relative to the spin flanging rollers.

The roller configuration disclosed in connection with the experimental U.S. Steel Corporation head included a large diameter rim section with a smaller central hub. The rim section splayed away from the hub at an angle of 110 such that the surface of the rim section intersected the axis of the hub at an angle of about 70% It has been found that angles of greater than 1000 up to 1500, and preferably 1200 for the inclination between the hub and rim, are required in order to keep the rollers from interfering with the neck of the can. The radius between the hub and rim should be from about 0.070 to 0.090" (1.78 to 2.28 mm).

Our third modification to adapt and use an inclined axes spin flange head with a commercial neckerflanger relates to the way in which the flanging head is used. Commerical necker-flangers include a camming device which moves the flanging head or the container shell axially for contact with the flanging rollers. The camming device is designed to assure that the flanging rollers contact the can during a constant velocity portion of the cam profile. We have found that any acceleration during the critical contact portion of the spin flanging operation will cause the flange, to crush developing a rippled or fluted surface.

It is found that the inclined-axes spin flanging head disclosed herein minimizes residual stress in flanges by providing gentler, smoother and more constant fiange-forming operation well suited to the harder temper materials which can be used in thinner gauges for fabricating D & I cans.

According to one aspect of the invention, there is provided an inclined-axis spin flanging head apparatus for outwardly flaring the upper edge of the sidewall of a hollow thin wall cylinder into a flange the head apparatus comprising a rotatable and axially translate carrier means carrying a plurality of operative elements for engaging a cylinder to produce a flange extending radially to said sidewall, the operative elements being freely rotatable and of two types; the elements of the first type being supported to rotate on a plurality of axes each inclined to the carrier rotation axis, each of said plurality of axes being radially positioned on the head for mounting rotary members having surafaces angularly dis posed relative to the carrier rotation rotary axis, a first surface of each rotary member being inclined inwardly toward the axis of a cylinder to be flanged at an angle greater than 1200 and up to 1500 to the carrier rotation axis, and a second surface of the rotary member being more steeply inclined to the carrier rotation axis and extending radially outward from the said first surface, said first and second surfaces merging together with a radius of curvature in the range of 0.070 to .090" (1.78 to 2.28 mm); an element of the second type being supported to rotate on an axis coaxial to the carrier rotation axis and adapted to guide the inside of a cylinder into a position of alignment relative to the said surfaces of the rotary members so that the axis of the said cylinder is substantially in alignment with the carrier rotation axis; and axial translating means for dis placing the carrier means with constant velocity in use to change the relative axial relationship between the carrier means and the edge of the cylinder sidewall to cause the inside of the edge to engage the said first and second surfaces during a spin flange forming operation.

According to another aspect of the invention, there is provided a roller system in a spin flanging head, wherein a plurality of rollers are mounted to rotate about axes located in a plane perpendicular to the rotation axis of the spin flanging head, each roller of the system having a pair of surfaces wherein the first surface is provided on a rim portion on the roller and is inclined inwardly so that the first surface makes an angle in the range of 1200 to 1500 to the head rotation axis, and the second surface is formed by a main body portion of the roller which is substantially perpendicular to the head rotation axis, the second surface outwardly extending from said rim along the roller axis, and the surfaces merging into one another with a radius of curvature in the range of 0.070 to 0.090" (1.78 to 2.28 mm), the rollers in use engaging an open end of a thin hollow wall cylinder with the area of said rim adjacent the said radius of curvature and to guide said edge, upon axial relative movement between the said edge and the roller, by means of the radiussed portion onto the second surface to produce an outward radially extending flange on the cylinder.

The invention further provides a method for spin flanging a hollow thin walled cylinder, including the steps: (i) arranging an inclined-axes spin flanging head for rotary and axial movement in alingnment with the axis of the hollow thin wall cylinder, (ii) supporting said cylinder in axial alignment with said rotary axis of the spin flanging head, (iii) moving the spin flanging head axially into engagement with an open end of said hollow thin wall cylinder with a constant velocity, and then spin-forming the end edge of the cylinder by (iv) engaging rollers mounted to rotate on said inclined axes with the said edge of said cylinder, the rollers including surfaces which, in the course of the said constant velocity movement, first flare and then radially form a flange on the said flange.

The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which: Figure 1 is a side cross-sectional view of a prior art commercial spin flanging head, Figure 2 is a side cross-sectional view of the inclined axis spin flanging head according to the present invention, Figure 3 is a schematic illustration of the camming which takes place in moving the container into the spin flanging tool, and Figure 4 is a fragmentary cross-sectional view of a roller shown in the flanging head illustrated in Figure 2.

As background for the complete understanding of the invention a brief description of a necker-flanging machine in which it is used will be included. We, American Can Company, manufacture and sell a Model 201 -862necker4langer machine. The purpose of the machine is to accept a pretrimmed 2-piece D & BR< I container shell and first neck its upper end inwardly and then bend outwardly a flange for doubleseaming. Necking is necessary for several reasons, one of which is to keep the outside diameter of the doubleseamed container uniform so that the container can easily roll through processing plant equipment. By necking the container, the overall diameter of the subsequently doubleseamed end can be made identical to or less than that of the body.In certain instances it is even useful to double-neck the open end of the container such that an end of smaller diameter can be applied. This helps in lowering the cost in that the amount of material necessary for the end is reduced. Another aspect of necking in a container, which relates somewhat to flange cracking, is the ability to limit the radial extent of the distal portion of the flange so that the circumferential stresses in the metal about the periphery of the flange are kept to a minimum.

The machine for necking and flanging carries container shells on their sides by a series of turrets which are mounted on a horizontal axis. Each turret carries the container shell in position such that relative axial movement is permitted between it and the tools which operate to perform necking or flanging functions. For aluminium cans, the steps of the operation are necking and then flanging. For the harder steel cans, the machine pre-necks them on a first turret, further necks on a second turret and finally flanges on the last turret.

As is evident by the foregoing, the harder the metal the more susceptible the container flange is to cracking. In the preferred embodiment, material such as T-4 temper continuously annealed tinplated steel is used. This material is much harder and stronger than that heretofore used. For an example, the T-1 containers were made from a 103# plate.

This terminology is standard in the can making industry and refers to the amount of steel in a base box of tinplate. A base box is a package of 112 sheets of steel 14" by 20" (35.5 by 50.8 cm) or a total of 31,360 square inches of area on one side (20.2 sq.

metres). Since steel is sold by the pound weight the base box convention is a shorthand means by which the weight of the material used is designated. By going to the harder T-4 temper material, tinplate of 95&num; per base box weight (95 Ibs or 43 kg) can be used to make containers of equal or greater strength than those fashioned from T-1 103# plate (103 Ib or 46.7 kg). The impact of this gauge reduction with the same size blank is best appreciated with respect to an understanding that the T-4 95&num; tinplate steel allows the manufacture of one extra container per pound of steel or roughly 95 additional containers per base box. This of course, implies that the extra hardness and reduction in ductility does not add additional cracked flanges which would cause the additional containers to have to be scrapped.

The improved flanging head of the present disclosure has been found to produce, in a commercial environment, the lighter gauge higher temper containers with no more than the standard number of cracked flanges per thousand containers, i.e. no more than the number obtained with the standard T-1, 103&num; plate.

Turning now to Figure 1 a cross-sectional view is given of the prior art flanging head 10, carried on a necking/flanging machine (not shown) by a holder 11 which rotates and moves axially in and out in accordance with a cam (also not shown). However, profile for cam movement is shown in Figure 3 and will be discussed in detail later. The holder 11 carries a plate-like support or cone holder 12 designed to support a plurality of ball bearings 13 for each of the cones 14 such that they may rotate about axes parallel to that of the holder 11 on the ball bearings 13. Each cone 14 has a chamferred lead area 14a and a necked-in support shoulder 14b whereby the container A is flanged when the cone 14 meets with the necked-in container A due to the axial movement of the flange head 10, the spinning motion of the cone holder 12 and the rotating motion of the individual cones 14.There are four or five os such cones 14, depending on the inside diameter of the can, arranged (in Figure 1 only three are shown) so that the container A is formed during the operation which moves the spin flanging head 10 axially into the open end of the necked container A. The parallelism between the axes of the 14 and the holder 11 is apparent fron the description and Figure 1.

In Figure 2 the inclined axes spin flanging head 20 of this invention is shown. The head 20 includes a holder 21 including hub portion 21 a designed for mounting a yoke 22 by means of bolts 23 which extend through the light portion 22a of the yoke 22 and into the hub 21a of the holder 21. The yoke 22 has a pair of inner and outer legs 24a and 24b respectively which are spaced apart and carry a stud 25 which is mounted to be radially disposed with respect to the hub 21a and is inclined to the axis of holder 21, preferably at 900 thereto. Stud 25 supports a pair of axially spaced apart roller bearings 26 carried inside a roller 27 for rotatably supporting the roller 27 relative to the stud 25 between the legs 24a and 24b of yoke 22, see Figure 4 as well.There is a plurality of such rollers 27 radially disposed about hub 21a such that they function to engage a container brought axially to bear against them. Each roller 27 of the six rollers 27 on the preferred embodiment has a rim portion 28 and a hub portion 29. The angle B between the surfaces of the rim 28 and the hub 29 is critical to the performance of the roller 27. This angle should be greater than 1100 and no more than 1500, preferably about 1200. The radius between the intersection of the surfaces of the hub 29 and the rim 28 should be between 0.070 and 0.090" (1.78 to 2.28 mm).

In the center of hub 21a is a hollow recessed portion 21 b designed to receive a pilot 30 axially disposed to rotate freely with respect to the inclined axis spin flanging head 20. The pilot 30 is secured axially by a shouldered mounting bolt 31 which carries a pair of spaced apart ball bearings 32 that support a flanged pilot 33. Pilot 33 includes a central outwardly extending mounting portion 34 adapted to cooperate with the bearings 32 and fit within and be received by recess 21 b such that portion 34 is capable of rotating about the same axis as that which the inclined-axes spin flanging head 20 rotates about. The outer radial periphery 33a of the flange portion of pilot 33 is shaped to receive the inside diameter of a container shell across the necked-in portion with a clearance of 0.010" per side for supporting and guiding the end of container shell A into cooperative engagement with rollers 27 during the flanging operation.

From the foregoing, it will be seen that the rollers 27 rotate about axes inclined with respect to the rotation axis of holder 21 (e.g. at 900 thereto), in contrast to the prior art where the cones 14 rotate about axes parallel to the holder rotation axis.

Figure 3 is a schematic representation of the cam path used in connection with the movement of the inclined axis spin flanging head 20 of Figure 2 into the container A. At each end of the schematic diagram the cam follower C is shown phantom in its retracted position. The cam is a groove cut into the edge of a circular disc (not shown) which groove has varying axial positions such that it can activate the follower to move the inclined spin flanging head 20 of Figure 2 to and from the container shell A. Going from the right in Figure 3 to the left, we traverse the groove of the cam as the disc rotates through 3600 whil the follower moves in accordance with the path shown.More specifically, the movement of the rollers 27 to and from the container A is represented by the vertical movement of the follower C shown in phantom, and the rotation of the cam is linearly set out from right to left on the camming time diagram, Figure 3. At the top of the schematic drawing the individual segments of the cam action are specified in degrees for each segment; at the bottom the total degrees of rotation travelled from zero to 3600 are specified. From zero to 450 of rotation starting from the right and going to the left, we have a period of dwell wherein the inclined axes spin flanging head 20 is retracted and held apart from the container A.

From 450 to 850 there is a harmonic rise on the cam such that spin flanging head 20 is brought quickly into position for contact with container A. From 850 to 950 there is a modified cycloidal motion which is substantially constant in velocity but is designed to bring the head 20, i.e., rollers 27 into contact or engagement with the container A, to begin the flanging operation. For the following 1000 there is continual constant velocity increase in movement such that the rollers 27 are throughout the entire 1100 of rotation (from 850 to 1950) moved about 0.0078" (0.02 mm) per degree of cam rotation toward the container A; the last 100 from 1850 to 1950 is in modified cycloidal in nature.For the next 20 , i.e.

from 1950 to 2150the lifted position ofthefollowerC is in a dwell state such that the rollers 27 are held against the now outwardly formed flange of container A. This 200 of dwell is necessary in order to set the flange and overcome any tendency to spring back. It takes 500 more, from 2150 to 2650 of rotation for the cam follower C to retract the head 20 or cause the same to fall away from the container A and this motion is harmonic in order to speed the retraction.

The rest of the rotation of the cam or 950 is for dwell and extends to the initial 450 of dwell. Without constant velocity during the flange spinning operation a fluted or rippled flange will be generated.

While a specific high temper material of a given plate weight and material has been described in connection with the preferred embodiment and while a particular American Can Company necker flanger has been explained in connection with the inclined axes spin flanging head 20, the invention in its broadest context is to the specific areas of improvement added to inclined axes spin flanging heads. It is desired that the claims which follow cover any design or use for such a head which includes the novel and unique improvements herein disclosed.

The three advances which we have devised, namely (i) the specific angular relationship between the rim and body portions of the roller (greater than 1100 up to 1500) responsible for flaring and flanging, preferably coupled with the rounded transition (radius 0.070 to 0.090"); (ii) the concept of driving the head in contact with the cylindrical shell at constant velocity while spin forming; and (iii) the provision of a freely-rotatable pilot adjacent the path swept by the rollers during rotation of the spin-flanging head; can be used independently of one another and this invention embraces the use of any one of them alone or in conjunction with another.

Claims (11)

1. An inclined-axis spin flanging head apparatus for outwardly flaring the upper edge of the sidewall of a hollow thin wall cylinder into a flange, the head apparatus comprising a rotatable and axially translatable carrier means carrying a plurality of operative elements for engaging a cylinder to produce a flange extending radially to said sidewall the operative elements being freely rotatable and of two types; the elements of the first type being supported to rotate on a plurality of axes each inclined to the carrier rotation axis, each of said plurality of axes being radially positioned on the head for mounting rotary members having surfaces angularly disposed relative to the carrier rotation rotary axis, a first surface of each rotary member being inclined inwardly toward the axis of a cylinder to be flanged at an angle greater than 1200 and up to 1500 to the carrier rotation axis, and a second surface of the rotary member being more steeply inclined to the carrier rotation axis and extending radially outward from the said first surface, said first and second surfaces merging together with a radius of curvature in the range of 0.070 to 0.090" (1.78 to 2.28 mm); an element of the second type being supported to rotate on an axis coaxial to the carrier rotation axis and adapted to guide the inside of a cylinder into a position of alignment relative to the said surfaces of the rotary members so that the axis of the said cylinder is substantially in alignment with the carrier rotation axis; and axial translating means for displacing the carrier means with constant velocity in use to change the relative axial relationship between the carrier means and the edge of the cylinder sidewall to cause the inside of the edge to engage the said first and second surfaces during a spin flange forming operation.

2. A flanging head according to claim 1, wherein the rotary members are rollers mounted at intervals around the periphery of the carrier means and all rotatable about axes perpendicular to the carrier rotation axis.

3. A flanging head according to claim 1 or claim 2, wherein each rotary member is a roller having a skirt or rim defining the first surface and a smallerdiameter main body portion defining the second surface, the latter surface making an angle to the former of 1200.

4. A roller system in a spin flanging head, wherein a plurality of rollers are mounted to rotate about axes located in a plane perpendicular to the rotation axis of the spin flanging head, each roller of the system having a pair of surfaces wherein the first surface is provided on a rim portion on the roller and is inclined inwardly so that the first surface makes an angle in the range of 1200 to 1500 to the head rotation axis, and the second surface is formed by a main body portion of the roller which is substantially perpendicular to the head rotation axis, the second surface outwardly extending from said rim along the roller axis, and the surfaces merging into one another with a radius of curvature in the range of 0.070 to 0.090" (1.78 to 2.28 mm), the rollers in use engaging an open end of a thin hollow wall cylinder with the area of said rim adjacent the said radius of curvature and to guide said edge, upon axial relative movement between the said edge and the roller, by means of the radiussed portion onto the second surface to produce an outward radially extending flange on the cylinder.

5. The roller system according to claim 4, wherein the head includes a piloting member mounted for free rotary motion about an axis coaxial to that of the head, the piloting member being adapted to fit within the open end of the cylinder and to guide same into engagement with said rollers.

6. The roller system according to claim 4 or 5, including means for producing relative axial movement between the head and a cylinder during said flanging operation, said means being controlled by a cam having a constant velocity profile.

7. A method for spin flanging a hollow thin walled cylinder, including the steps: (i) arranging an inclined-axes spin flanging head for rotary and axial movement in alignment with the axis of the hollow thin wall cylinder, (ii) supporting said cylinder in axial alignment with said rotary axis of the spin flanging head, (iii) moving the spin flanging head axially into engagement with an open end of said hollow thin wall cylinder with a constant velocity, and then spin-forming the end edge of the cylinder by (iv) engaging rollers mounted to rotate on said inclined axes with the said edge of said cylinder, the rollers including surfaces which, in the course of the said constant velocity movement, first flare and then radially form a flange on the said edge.

8. The method of claim 7, wherein the flaring is performed by a rim portion of each roller and the flanging is performed by a main body portion of each roller, there being a transition curvature between the rim body portions of each roller of about 0.070 to 0.090" (1.78 to 2.28 mm).

9. An inclined spin flanging head apparatus substantially as herein described with reference to and as shown in Figures 2 to 4 of the accompanying drawings.

10. A roller system of a spin flanging apparatus substantially as herein described with reference to and as shown in Figures 2 to 4 of the accompanying drawings.

11. A method of spin flanging according to claim 1 and substantially as herein described with reference to and as shown in Figures 2 to 4 of the accompanying drawings.