FR2499882A1 - TOOL FOR FORMING STAMPED CONTAINERS - Google Patents

Abstract

THE OBJECT OF THE INVENTION IS TO PROVIDE A TOOL ALLOWING THE STAMPING AND THINNING OF THE WALLS OF THE SIMULTANEOUS CONTAINER, WITHOUT DAMAGE TO ANY PRE-COATING, AND FINALLY PROVIDING A CONTAINER WHOSE WALLS HAVE A UNIFORM THINNING. FIRST ELEMENTS, SUCH AS THE INITIAL PARTS OF A PUNCH 21 AND DIE 22 ASSEMBLY COOPERATE TO DEFORM BLANK 20, AND SECOND ELEMENTS WHICH MAY BE CONSTITUTED BY THE LATERAL INTERVAL BETWEEN PUNCH AND DIE, COOPERATE TO THIN THE WALL.

Description

The present invention relates to a forming tool for transforming

  a thin sheet of pre-coated metal

into a hollow container.

  More particularly, the invention relates to a tool for manufacturing, by stamping and thinning of metal, bodies of stamped boxes, intended to constitute, with a cover, what are called boots in two bodies. For twenty years, beverage boots have been manufactured by processes comprising such operations in which the material is first stamped to establish the internal diameter, then is pushed through a series of thinning rings which simply have the function of thinning the side wall without significantly affecting the diameter. The operations are

  performed at high speed under a flow of refrigerant

  rant / lubricant in order to facilitate the operation, in particular by heat dissipation. Containers should be washed and, in some cases, chemically treated, to remove lubricant residue and to improve the corrosion resistance of organic coatings and decorations that are subsequently deposited on the container. In the past 25 years, progress has been made in the production of stamped boots for food products. These containers were made from materials such as aluminum and low-income steels to facilitate the stamping operation. In addition, the containers were given a height approximately equal to or less than the diameter of the container and the containers were made in one or at most two stamping operations.

  The advantage of a deep-drawn container results from the elimination

  nation of side seal and double seal bottom that exist

  in a traditional three-piece container. More precise-

  ment, to make a three-piece box, a flat blank of material is rolled into a cylinder shape and is sealed along one side by welding, gluing or brazing. This hollow cylindrical body is associated with a closure bottom fixed by a double seal. The cylindrical body can be pre-coated

  and the side seal area can be masked with a strip.

  The side seal and double bottom seal operations are such that the quality of the container depends

  strongly from these joints. It is evident that the cylindrical body

  drique must be provided with flanges so as to receive the bottom, which is set up in the factory, and the cover which

  is put in place after filling the container. The opera-

  flange and seal formation require some care and can cause problems, including

in the area of the side seal.

  It is only recently that it has been possible to manufacture, by multiple stamping, two-piece containers for food products made from tin-free steel and provided with an organic pre-coating so that it is no need to perform post-coating or post-treatment operations. More particularly, a double stamping operation was used to manufacture a

  "24 oz. 404 x 307" type tin-free steel container.

  Box manufacturers conventionally indicate the diameter of the completed double joint, expressed in inches and sixteenths of an inch and then the height expressed in inches and sixteenths of an inch. Consequently, the aforementioned container has a diameter of 4 4/16 inches or 07.95 mm and a height of 3 7/16 inches or 87.3125 mm. Its interior capacity is around 71 centilitres. For a long time, it has been desired to manufacture a container whose height is notably greater than the diameter, using a pre-coated raw material in a multiple stamping process. It is particularly desirable to manufacture such a container in the dimensions corresponding to the common types: "16 oz. 303 x 406" (47.3 cl - 80.9625 x 111.125 mm,) "15 oz. 300 x 407" (44, 4 cl - 76.2 x 112.7125 mm) or "11 oz. 211 x 400" (32.5 cl

- 60.2625 x 101.6 mm).

  The Applicant has recently manufactured and sold

  stamped containers of the types "16 oz. 303 x 406" and "15 oz.

  300 x 407 "and has experimentally manufactured" 11 oz. 211 x 400 "using a raw material

  pre-coated. It was necessary to perform a triple operation

  stamping ration for making the aforementioned containers and this process tends to increase the thickness of the

  side wall area of the container which is close to the end

open moth.

  The degree of thickening increases from the bottom to the top of the container and also to the edge of the collar. This thickening results from the stamping of the material from a flat disc-shaped blank and from the variable circumferential compression of the material as a function of its distance from the bottom of the box finally formed. The additional thickness of material recorded at the top of the container does not serve any useful function and corresponds to a loss of material, increasing

the weight and cost of the container.

  In the technology previously adopted for stamping containers, a combination of a punch and a die is used and there is sufficient annular clearance between the outer surface of the punch and the inner surface of the die so that the metal is not crushed or thinned during forming. These clearances are between about one and a quarter and twice the thickness of the stamped material (for the types of steel and aluminum used for the manufacture of boxes). Also the rounding (or the surface

  on which the metal is stamped) of the stamping die

  sage has a radius of curvature less than 3.2 mm in order to

  facilitate the movement of metal through the matrix.

  The use of such a tool causes a backflow of the metal and a thickening of the top of the side wall

  of the hollow container finally formed, as indicated above.

  On the contrary, the stamping and thinning process

  The so-called "D & 1" metal sement used for the manufacture of beverage containers involves play that is less than the initial thickness of the metal between the thinning ring and the punch. More specifically, the difference between this

  clearance and the thickness of the metal corresponds to the degree of thinning

  ment of the side wall of the container. Usually, a metal having no organic coating passes through three different thinning rings in a D&I operation during which the sheet with electrolytic tinning called "ETP" 'and with treatment "T-1" undergoes a reduction of about 15% in the first pass, a reduction of about 25% of its new thickness in the second pass, and a reduction of about 40% of its new thickness in the last pass, while the metal and

  the tools are sprayed with a lubricating coolant.

  This operation increases the side wall length Up to several times that of the can which was formed in an ordinary operation with one or two stamping phases. The cross-sectional configuration of the slimming ring includes a chamfer, a flange and finally a clearance angle. The thinning process begins on the chamfer and is terminated by the collar, so that no stamping takes place at this time. The D&I process has

  has so far been a process in which a stamping-

  wise and thinning takes place in a lubricant / coolant flow. Coatings are normally deposited after the container has been deburred and then cleaned of the lubricant by washing. To improve such a process, it is desirable to be able to concurrently draw and thin an organic pre-coated metal without having to remove the lubricant / coolant and find a way to make a container before a

uniform wall thickness.

  The invention therefore aims to provide a container which has a relatively uniform side wall and a minimum thickness necessary to prevent

  formation of flats and crushing of the packed container.

  The invention also aims to provide a method using which a container can be made from a pre-coated raw material and has a uniform side wall, by simultaneously reducing the diameter and

  of the wall thickness in each of the multiple operations.

  The invention also aims to provide a tool which can be used to reduce both the diameter and the wall thickness in a single operation without using

  lubricants to be removed later.

  The invention further aims to allow economical and safe manufacture of the container, this manufacture being new as regards profiling techniques

and implementation.

  The preferred container is made from a double reduction sheet, and more specifically from a "DR8" or "OR9" type treatment sheet weighing 65 "pounds per base box", or about 1.46 kg / m '. In the preferred embodiment, the container is made from "TFS" free steel, tinned sheet metal, nickel plated steel, or a steel-based material. The designations "DR8" or "DR9" correspond to a specification for tinned rolled products and they relate to the process by which the metal undergoes a thickness reduction by cold rolling in two stages with a preforming phase

  by annealing between the two cold rolling operations.

  The steel undergoes a thickness reduction of approximately S9% in the first rolling stage, then it is annealed, then it undergoes a thickness reduction of approximately 25 to 40% in the second final stage of cold rolling . The terminology "pounds per base box" used for base weight is

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  standardized in the box manufacturing industry; it initially related to a humanity of steel intervening in a basic box (or: 'baae box ") in c-tinned consisting of 112 sheets of steel of 356 x 50 mnm, (14 x 20 inches) that is to say 20.23 m 'of rtle. At present, the "basic bolte" corresponds to a quantity

  steel of 20.23 m 'of cut sheet or coil.

  This material can be coated, on what will be final-

  the outer surface, of a resin type coating-

  epoxy or organosol coating. The inner surface can be coated with a layer consisting of a combination of resins which has been found to withstand the severe multiple forming operation. The interior and exterior coatings are capable of withstanding the stresses generated during stamping and thinning operations during the manufacture of the boxes. As a result, the container may be made from a material that has undergone a relatively heavy conditioning treatment, and it may not

require post-coating.

  The preferred method used to make a container

  pient desired consists in using a minimum quantity of steel with strong conditioning treatment OR8 or DRS and 11 involves one to three simultaneous stamping operations which can be carried out in a press such as that described in French patent 8,004,256 issued to the plaintiff. In the case of a box having undergone a triple stamping and thinning, the diameter of the box and its wall thickness are simultaneously reduced in each forming operation. More specifically, the first operation ensures roughing and forming of the sheet of pre-coated material by giving it a shallow bowl shape where the diameter is greater than the height. during

  this operation, the wall thickness is reduced by thinning

  sizing during stamping so that the wall is finally brought to a thickness approximately 0.025 mm less than the thickness of the bottom (initial thickness of the pre-coated material). The second operation produces a re-drawing of the container and decreases the diameter, again shrinking

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  simultaneously the wall, in order to maintain a reduced thickness from top to bottom. In this second operation, the diameter is reduced and the height increased so

  that these values are roughly equal. The final operation.

  further reduces the diameter and again simultaneously produces a thinning of the side wall by establishing the desired thinness and uniformity for the container in its final configuration. During this operation, the bottom of the container can also be profiled as described by

  example in French patent 81.02608.

  In operations where the diameter is reduced and the side wall is thinned, the thinning is stopped before it reaches the flange in any of the multiple operations. As a result, the flange and the side wall area adjacent to it can be

  left thicker. In all cases, stopping the operation

  ration defines until the side walls are thinned

  the collar may or may not be maintained.

  In a fourth operation, the container flange is sectioned and the container is transferred to a crimping machine. Note that a container

  complete can be manufactured without having to perform operations-

  washing, recovery, post-coating or

  other energy consuming operations.

  The incorporation of a thinning phase in the multiple stamping process makes it possible to give the original circular blank a smaller diameter than that necessary to make a container of similar size not subjected to thinning. Consequently, the quantity of steel used for this container is less than that which is necessary for stamped containers of the same

  cut. This reduction in the quantity of steel allows

  nominate material and reduce the final weight of the

pient.

  The tool or matrix used to perform simultaneous-

  stamping and thinning is a new combination of stamping tool technology

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  and slimming. This means that the elements involved in the respective tooling, and in particular the profile of

  matrix considered in section, are adapted to produce simul-

  both a deep drawing and a thinning of the side wall of the container body. The increase in thickness

  of the material that occurs during circumferential compression

  of the metal to form a hollow cylindrical container is reduced during stamping, so that the thickness of the side wall may be less than

  the initial thickness of the material.

  The present invention relates to a stamping die

  wise with a rounded shape which is curved inwards towards the punch. The dimensions of the punch and of the die are chosen so that the metal must become thinner to pass in the annular interval existing between these elements. Another modification made to the stamping die concerns a collar which is placed below of the rounding of the matrix to ensure that it

  produces a thinning of metal at the same time as the opera-

  stamping. The metal being stamped is first bent over the die round as the punch pulls the metal inside the die. The metal is then pulled on the flare and it has to straighten out to become part of the right side wall. It is entirely desirable that the turnaround at the end of the rounding

  before the thinning begins.

  It is preferable that a transition chamfer or bevel connects the rounding of the die to the thinning collar. This transition zone can be axially short or long depending on the operation to be performed; it also contributes

  to make the process less susceptible to alignment defects

  is lying. The thinning collar is long enough to thin the side wall without tearing off the precoat

  and to obtain an acceptable service life for the tool.

  A draft angle is provided in the matrix which constitutes a longitudinal support for the collar. The part

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  The matrix clearance angle is also necessary to absorb the circumferential stress generated by the thinned container during its passage. We have found that, by correctly choosing the radius of the matrix fillet, the angle and the length of the transition zone, the dimensions of the collar and the clearance angle, it was possible to use a pre-material. -coated by stamping and thinning to form boxes whose coating integrity was sufficiently preserved to meet commercial requirements. Depending on the final configuration (height / diameter ratio) of the container, it is passed through several tools such as those described above to give it the preferred configuration and make it undergo the necessary thinning. This operating flexibility allows the process to be adapted to a wide range

boots sizes.

  Other advantages and characteristics of the invention

  will be highlighted, in the following description,

  given by way of nonlimiting example, with reference to the appended drawings in which: - FIG. 1 is a partial side sectional view showing the blank being transformed into a shallow bowl in the first phase of the process, making

  intervene a tool exerting a combined action of stamping

wise and slimming.

  - Fig. lA is a partial section view on an enlarged scale of the tool zone of FIG. 1; - Fig. 2 is a partial side sectional view showing the bowl which continues to be transformed into a

  container with an approximate height / diameter ratio

  vement equal to one using another tool exerting a combined drawing and thinning action in the second phase of the process - fig. 2A is an enlarged partial cut-off nozzle of the Ficg tool area. 2 - Fig. 3 is a partial 13terIa.e sectional view showing the container continuing to be transformed; -. an elongated box in which the thickness of the side wall is slightly less than the thickness of the initial blank, using a tool exerting a ca.i .. drawing and thinning action in the triesiè; phase of the process - fig. 3A is a partial sectional view on an enlarged scale of the tool zone of FIG. 3, - Fig. 4 is a side sectional view of a container after completion of its forming by the tools and according to the

  method of the invention, the side walls being relative-

  uniform and slightly thinner than the parts

  non-profiled from the bottom of the container.

  In the figures, there is shown a tool used in the different phases of a manufacturing process

  of a container. To simplify the description of the figures and

  of the invention, identical parts of the tool have been designated by identical references. In Figs. 1 and 1A, the pre-coated metal to be transformed into a container has been designated by 20, while it has been designated by 30 in FIGS. 2 and 2A and by 40 in Figs. 3 and 3A. Likewise, the tooling has been designated as a whole by 25 in FIG. 1, par 35 in FIG. 2 and par 45 in FIG. 3. The finished container has been designated by 50 in FIG. 4. The numerical references of the series "20" are used in Figs. I and IA, that the numerical references of the series "30" are used in Figs. 2 and 2A, and that the numerical references of the series "40" are used in FIGS. 3 and 3A. Similar reference numbers have been used

  in Figs. 1 and 1A, 2 and 2A and 3 and 3A.

  Now considering FIG. 1, we see that there is shown a punch 21 used for stamping a metal blank 20 in pre-coated sheet in the form of a bowl by means of a stamping die 22, and in

  particular on a rounding of matrix 22a (cf. Fig. IA).

  The rounding of matrix 22a has a radius of curvature ccnpris between 0.75 and 3.2 r ;. Fig. 1l shows the angle E of the reinforcement cane which extends inwards from the end of the rounding of the die _23 to a straight part 2499882 or forming collar 22 b constituting the thinning part of the die 22. The collar 22b is generally oriented vertically or parallel to the axis of the punch 21. Consequently, the angle E, which defines the junction zone between the rounding 22a and the collar 22b, corresponds to an inclination of about half a degree to 3. The collar 22b has a vertical length of between 0.25 and 2.5 mm and it extends from its junction point with the cone starting from the round 22a until the start of a stripped part 22c of the matrix 22 , the draft angle being designated by F. This stripped part 22c is inclined outward from the vertical by an angle of between approximately a half and 150 and it is designed to absorb circumferential and longitudinal stresses s' exert in the matrix 22 under the effect of the forces generated during thinning. More specifically, and as shown in Figs. 1 and 1A, the initial blank has its original thickness where it is held under the clamp 23 of the tool, before it is drawn in the interval existing between the punch 21 and the die 22. This thickness of material increases as one approaches the rounding of matrix 22a and it decreases slightly just after the material

  has crossed the point of contact of the die round 22a.

  There is still a slight thinning when the material is straightened when it leaves the round 22a and when it becomes a part of the side wall. The material is greatly thinned when it is flattened in the interval

  existing between the die 22 and the punch 21.

  The side wall of the container or bowl has a slight wedge shape in section. Indeed, the thickness increases with the height above the bottom. This is explained by the fact that the thickness of the material entering the thinning zone is constantly increasing under the effect of the circumferential compression. This greater thickness of the material entering the thinning zone 22b exerts a greater load on the tool 25, which is elastic and deforms. Furthermore, since the elasticity of the metal is a proportional phenomenon, an increase in thickness of the incoming material produces an increase

thickness of the outgoing wall.

  There is shown in FIG. 2 a punch 31 which is used for stamping the bowl formed by the tool 25 of FIG. 1 in order to transform it into a more slender container with a smaller diameter. The tool 35 of FIG. 2 is similar to that of FIG. 1. The rounding 32a of the stamping die visible in FIG. 2A, has a radius of curvature between 0.75 and 3.2 mm. Fig. 2A also shows the angle G of the one which starts internally from the end of the rounding of the die 32A and which extends to a straight part or collar 32b which constitutes the

  thinning part of the matrix 32. The thinning collar

  cissement 32b is oriented vertically or parallel to the axis of the punch 31. The angle G, which corresponds to the junction zone between the rounding of die 32a and the collar 32b, corresponds to an inclination of about 0 to 30. The collar has a vertical length of approximately 0.25 to 2.5 mm and it extends from its junction point with the cone starting from the rounding of the die 32a to the start of a stripped part 32c of the matrix 32, which has an angle H visible on the

  Fig. 2. This stripped part 32c is inclined outwards

  laughing from the vertical from an angle H of between about a half and 10 and it is designed to absorb circumferential and longitudinal stresses exerted in the matrix 32 under the effect of the forces generated during the phase of thinning. More specifically, and as shown in Figs. 2 and 2A, the cup material has its original thickness when it is held below the drawing sleeve 33 of the tool 35 and before being drawn in the interval existing between the punch 31 and the die 32 This thickness of material increases as one approaches the rounding of matrix 32a and it is slightly decreased just after the material has crossed the point of contact of the rounding of matrix 32a. There is still a slight thinning when the

13 2499882

  matter is straightened when it leaves the rounding 32a and when it becomes part of the side wall. Matter

  is greatly thinned when it is flattened in the inter-

  valley existing between the die 32 and the punch 31.

  The side wall of the container or bowl has a slight wedge shape in section. In fact, the thickness increases with the height above the bottom. This is explained by the fact that the thickness of the material penetrating into the thinning part 32b of the matrix 32 constantly increases under the effect of circumferential compression. This greater thickness of the material entering the thinning part 32b of the matrix 32 exerts a greater

  load on the tool 35, which is elastic and deforms.

  In addition, since the elasticity of the metal is a proportional phenomenon, an increase in thickness of the incoming material produces an increase in thickness of the outgoing wall. In Fig. 3, there is shown a punch 41 which is

  stamping the container 30 of FIG. 2 through

  median of a stamping die 42, and in particular

  by means of a rounding of matrix 42a (cf. Fig. 3A).

  The die round 42a has a radius of curvature of between 0.75 and 3.2 mm. Fig. 3A also shows the angle J of the cone which starts internally from the end of the rounding

  42a up to a collar 42b which corresponds to the part of amin-

  cisse of the matrix 42. The collar 42b is oriented vertically

  setting or parallel to the axis of the punch 41. The angle J defining the junction zone between the die round 42a and the collar 42b corresponds to an inclination of between approximately 0 and 30. The thinning collar 42b-a a vertical length approximately between 0.25 and 2.5 mm and it extends from the junction with the cone starting from the rounding of the matrix 42a to the start of a stripped part 42c of the matrix 42 which has a clearance angle K. This knot part 42c is inclined outward from the vertical at an angle of about a half to 150 and is designed to absorb stresses

14 2499882 circumferential and longitudinal circumferential occurring in the matrix 42 under

  the effect of forces generated during thinning of the UR material More specifically. and as shown in Figs. 3 and 3A, the rerouted eúeciplen has its initial thickness when it is kept below the sleeve

  drawing 43 of the tool 45 before being drawn in the inter-

  valle existing between the punch 41 and the matrix 42. This thickness of material increases as one approaches the rounding of matrix 42a and it decreases slightly just after the material has crossed the point of tangency of

  rounding of matrix 42a. It still undergoes a slight thinning

  when it leaves the rounding of the matrix 42a and when it becomes part of the side wall of the container. The material is substantially thinned when it is crushed in the gap between the die 42

and the punch 41.

  The side wall of the final container has a cross section

  wedge shape which is not measurable because the opera-

  multiple slimming options have reduced defects

  uniformity due to stamping. Although the thick-

  As the material entering the thinning part of the matrix increases constantly due to the circumferential compression, the effect is reduced because the

  percentage reduction in diameter is less. Therefore

  quence, the final container has a side wall thickness

practically uniform.

  As the figures show, the material of the container is a metal which is provided beforehand with thin and uniform layers of coating on what will ultimately constitute the interior and exterior surfaces. These coating layers are arranged so as to be stamped with the metal and not to be torn or damaged so that the protective covering of the metal is pierced although there is a thinning during the process.

  of material in and on the matrix {of.

U. $ patent. NI standard.

  Figure 4i shows the finished manufacturing container,

2499882

  this container comprising a flange 51, a side wall 52 and a bottom, designated as a whole by 53 and provided with a circumferential planar part 54 facing downwards and with a central lady-shaped part 55. The thickness of the material in the side wall 52 of the final container 50 is relatively uniform. The thickest part of the

  container is constituted by the flat part 54 which has the thickness

  initial sor of the blank from which the container was made. In the other wall zones, the material has been thinned to a thickness approximately 0.025 mm less than the initial thickness of the pre-coated side. The reduction in thickness of the side wall 52 has been explained above

  when describing multiple stamping operations

  and simultaneous thinning highlighted in the figures. The thinning of the lady-shaped part 55 of the container bottom is carried out near the lower end of the punch 41 in FIG. 3. The punch 41 has a recessed area 41a which is arranged to receive a profiled part of the tool (not shown) which comes into contact with the central area of the bottom of the container to form the dome in the bottom wall 53. During of lady 55 forming, the bottom material of the container is

  lengthened so that a slight decrease occurs

wall thickness.

  The punch may have a peripheral taper or taper in order to increase the thickness of the thinned side wall. If the punch has a conical profile, the side wall part near the bottom is thicker, so that the final container can better resist deformations

in this critical corner area.

  The radius of the stamping die has a critical influence on the stresses generated in the material when it is pulled by the punch from below the blank holder. More specifically, the rounding of the stamping die and the conical part leading to the throat collar must be adjusted to minimize wrinkling which occurs naturally as the

16 2499882

  diameter of the unstretched material is reduced. As the material is pulled inward toward the rounding of the stamping die, radiating lines of residual stress are generated even if the material is held by a blank holder and even if it occurs a

  thickening. Non-circumferential constraints

  uniforms produce a non-homogeneous deformation in the material, as evidenced by a variation

  hardening in the side wall of the final container.

  This deformation increases the risk of cracks forming in the flange parallel to the axis of the box. As explained above, the material at the top of the container may not be subject to thinning and

  therefore remain thicker. This additional thickness

  mental increases resistance to cracking. However,

  in some processes it is intended to submit the whole

  ble from the container to a thinning and subsequent form-

  a collar. Consequently, the importance of the rounding of the matrix and of its conical part is greater since

  the need to minimize the strain strain

tion is greater.

  The conical part existing between the die round and the thinning collar has a critical influence from another point of view, namely to minimize the stress generated in the material being stamped. This means that the conical part is used to pilot or guide the. punch when it pushes the material towards the thinning part of the matrix. More specificly,

  the tolerances concerning the position of the collar, the concentration

  tricity of the punch and the die and the different angles and radii involved in the cross-sectional configuration of the die profile all cooperate to generate a certain

  degree of transverse movement between the punch and the die.

  A wide angle conical part acts to center the movement of the punch relative to the die and causes a more uniform flow of the material in the annular gap between the punch and the die. It is to highlight that,

17 2499882

  with multiple operations, the uniformity of the container wall from one side to the other varies to a certain degree depending on the clearances and tolerances involved in the implementation operation. This non-uniformity poses a problem with respect to the tooling involved in the next operation, and it has been found that a conical portion of steep inclination contributes to solving this problem and minimizing the influence of the initial condition. from the container

  so that it is properly implemented in the ope-

  next ration. Thus, we have found that it is possible to perform, under certain conditions, the second and the

  third simulating stamping and thinning operation

  tanned with a cane angle of 00.

  In a preferred embodiment of a container of the "303 x 406" type, an elongated and shallow bowl is first formed using the punch 21 and the matrix 22 from a circular blank having a approximate diameter of 201.854 mm, the resulting bowl having a diameter

  interior of 127.178 mm and a height of approximately 50.8 mm.

  The thickness of the material in the non-thinned bottom of the bowl is 0.193 mm and the average thickness of the side wall of the bowl is approximately 0.178 mm. In Fig. 2, the bowl 20 of FIG. 1 is re-drawn in the form of a more slender container and of smaller diameter, the height of which is approximately 85.1 mm and the internal diameter of which is approximately 96.65 mm. Again, the thickness of material in the bottom remains at a value of about 0.193 mm, while the thickness of the side wall takes a value

0.170 mm average.

  Finally, the container 30 of FIG. 2 is re-stamped to the dimensions of the final article, the height being approximately 112.40 mm and the internal diameter approximately 77.72 mm. The material thickness of the bottom remains the same but

  the wall thickness has a relatively uniform average value

0.162 mm shape.

  Of course, the present invention is not limited to the embodiments described above, which can make

18 2499882

  the subject of many variations. More specifically,

  claims are intended to cover modifications and

  variants which make it possible to adapt the tooling to containers of different sizes, to different materials, to different processes or else to any combination of the aforementioned means in order to produce a container having an overall thickness relatively uniform to the using a tool which performs simultaneously stamping and a

  thinning enough to not only counter

  balance the thickening of the wall but slightly reduce

  the wall thickness of the container.

Claims (10)

  1. Tool for forming a thin sheet of pre-   coated in the form of a hollow container, characterized in that it comprises a plurality of means for defining the shape of the container body, this body having a cross section of predetermined configuration with a side wall and a closed bottom wall, each of said means comprising first elements which cooperate to establish said cross-sectional configuration and second elements which   cooperate to thin said side wall.   2. Tool according to claim 1, characterized in that said first elements are the initial parts of a punch assembly (21,31,41) and matrix (22,32,42) aligned axially, said parts cooperating beforehand for forming said cross section configuration by stamping. 3. Tool according to claim 2, characterized in that said second elements are constituted by the lateral interval defined by the profile of said die and by its position relative to said punch so as to define a variable annular space through which said wall side is pulled when the punch moves the material through said matrix.   4. Tool according to claim 3, characterized in that said container is cylindrical and has a straight section   generally circular in configuration.   5. Tool according to claim 3 or 4, characterized in that said radial lateral gap is less than   the thickness of the material from which said reci- pient is formed.   6. Tool according to claim 5, characterized in that the section of the matrix zone corresponding to said first elements comprises a rounded (22a, 32a, 42a) on which said material is previously stamped and a   non-curved part which is formed by the immediate surface-   adjacent to said rounding and intervening when the   punch drives the material through said matrix.   7. Tool according to claim 6, characterized in that said die profile corresponding to said second elements comprises a thinning collar (22b, 32b, 42b) which is constituted by a die section parallel to the axis and which is plact replay radially inward   towards said poi.ncn in order to thin said side wall   stripe when the punch pulls transversely audit collar.   8. Tool according to the araetris e ration that said matrix profile loireend a part having a conical profile directed v.ers lante.rzieur and extending from   the end of the said rounding: î ice.usqueaudit collet.   9. Where does it stand in accordance with the claim 8, characterized in that said conical part has a steep slope, forming an angle   (E, C, 3) less than 3 relative to the axis of the punch.   10. Tool according to claim 8 or 9, characterized in that said conical part has a steep slope and facilitates   the axial alignment of the punch relative to the collar.