GB2350575A - Forming mandrel - Google Patents

Abstract

An assembly and method for forming a sheet metal blank, optionally provided with interlocking formations on a pair of opposing edges, around a mandrel 4 disposed within a known bodymaker 2. The blank is brought into correct register with the mandrel and held in contact with an upper surface of said mandrel 4 whereupon a pair of forming wings 34,36 disposed immediately above and proximately of the mandrel are caused to come into contact with the mandrel thus deforming the blank around said mandrel. After the initial forming operation is complete, that is when the forming wings have completely surrounded the mandrel and the blank is compressed between the wings and the mandrel and thus adopts the cross-sectional shape thereof, the forming wings are fractionally retracted to allow slight elastic recovery of the blank which in turn permits any interlocking formations to engage fully in the lower region of said mandrel. In accordance with the invention, the mandrel, which may be comprised of a number of components is static throughout the forming operation, and the contact surfaces 44,46 of the forming wings are resiliently deformable to allow the blank to elastically recover against such surfaces during and after the initial forming operation. A static mandrel is an essentially simple article to engineer whereas an expanding mandrel used in the prior art machines is intrinsically complex.

Description

2350575 Forming Mandrel

This invention relates to a forming mandrel, and more specifically to the combination of a mandrel and the automated forming tools which are specifically adapted for the forming of sheet materials around the said mandrel. A particular application for this invention is in the field of tin box manufacture, although it is to be mentioned that the invention is not exclusively limited to this particular field of technology and may have wider application.

Automated tin box manufacture is accomplished by)uxtaposing several different pieces of machinery and providing transfer means therebetween. Tin boxes can be manufactured in a vast number of different shapes and sizes and accordingly a single piece of machinery is required to be sufficiently versatile to enable manufacture of tin boxes in a large number of said shapes and sizes. It will be understood by those skilled in the art that the machinery used has a number of different components which can be exchanged to facilitate the manufacture of different boxes and currently the length of time taken to exchange all these various components to enable a particular set of machines to manufacture a different box shape can be up to an entire day. The invention hereinafter set forth, and also set forth in our co-pending applications have as their object the reduction of this time. Any reduction achievable in the "changeover" time is especially desirable when it is considered that tin box production rates using the machinery described hereinafter may reach 40 per minute.

Tin boxes can contain a wide variety of different goods, such as bottles, chocolates, biscuits, tea, coffee and the like. Manufacturers of such products commonly consider the containment of their product in tins because of the rigidity and durability which the sheet steel, from which such tins are commonly made, provides.

2 Additionally, the containment of a product in a tin box may also suggest that the product therein is of a certain quality, especially as ornate and detailed print effects can be obtained on the surface of the metal plates from which the tin boxes are manufactured. Such effects cannot be achieved, or are achieved only to a much lesser degree by the containment of products in cardboard cartons or receptacles of plastics materials. A tin box in which such a product is contained has the further advantage of being reusable to contain other household items such as screws, nuts bolts, pencils and pens, etc. after the product originally contained therein has been consumed or otherwise utilised.

The various separate machines required in the manufacture of tin boxes are an "Automatic Curling Notching and Beading" machine, a "bodymaker", a "round and irregular scamer", and an "end feeder", each of which has a specific task to perform during the process of tin box manufacture. Each of these is now described.

The first stage in the process of automated tin box manufacture is the profiling of a simple sheet steel, and generally rectangular, blank from which the walls of the tin box are ultimately constituted. The blank is fed through an "Automatic Notching, Curling and Beading" machine, referred to hereinafter as an ANCB machine. This machine consists of a plurality of consecutively driven rollers disposed both above and below the blank as it passes therebetween, each of said rollers performing a forming step on the blank. The particular profile of each blank as it exits the ANCB machine depends on the ultimate shape of the tin, but in general the blank is substantially flat with the exception of a hem provided parallel with one of the longer edges of the blank and proximate thereto, a bead is provided on one of said longer edges, a partial curl is provided around the alternate longer edge, and a pair of hooks oppositely disposed with respect to one another are provided on the shorter edges.

3 Additionally, the ANCB machine has cutting means which notch the corners of the blank to preclude any interference effects which may be caused by said corners either when the blank is profiled and provided with the hooks along its shorter edges, when it is formed into the cross-sectional shape of the tin box, or when wrapped around and attached to the base of said tin box.

The hem provides a surface behind which the beaded lip of a tin lid can engage to inhibit the removal of a lid separately formed and applied around the uppermost edge of the tin box, the bead is provided to hide the sharp longer edge of the blank which ultimately forms said uppermost edge of the tin box, the partial curl on the alternate longer edge of the blank is provided to facilitate the attachment of the blank, after same has been formed into the desired cross-sectional shape, to the base of the tin box, and the hooks provided along the shorter edges of the blank facilitate the connection of said edges to one another after the forming operation.

The profiled blank is then fed from the ANCB machine into a bodymaker by a feed mechanism which generally comprises a pair of reciprocating feed bars whose motion is best described as being that of a "walking beam" in conjunction with "disappearing guides" which simultaneously urge the profiled blank towards and over a forming mandrel and precisely align said blank thereon. The disappearing guides are rotated away from the blank when it is held in contact with the uppermost portion of the mandrel, which is generally of similar shape to the desired cross- sectional shape of the tin box to be manufactured, by a mandrel clamping arrangement. The removal of the disappearing guides (so-called because they are retracted and seem to "disappear" within the machine during the forming of the blank around the mandrel) allows a pair of forming wings pivotally connected together and disposed above the mandrel 4 to rotate about their pivot and form said blank, which is at this stage still substantially planar, around the said mandrel. The forming operation performed by the wings also constrains the oppositely disposed hooks on the shorter edges of the blank to interlock on the underside of the mandrel whereupon a second forming tool, commonly known as a hammer, is caused to impact sharply against the lowermost surface of the mandrel and compress the interlocked hooks against one another between the contact surface of the hammer and the mandrel surface. The compressed metal of the blank in the interlocked region forms the vertical seam within the wall of the tin box. During all forming operations the blank is clamped against the upper surface of said mandrel by said mandrel clamping arrangement.

The bodymaker thus forms the walls of the tin box into the desired crosssectional shape whereafter the hollow wall section is fed into the round and irregular seamer which seamingly attaches a base provided with a peripheral flange by simultaneously compressing and deforming said peripheral flange and the partial curl provided on one of the edges of the blank together to form a seam. 1n practice, the bodymaker is responsible for the formation of the hooks on the shorter edges of the blank to facilitate connection of said edges to one another.

The seamer is conventionally Juxtaposed with the bodymaker and an end feeder, these two pieces of machinery providing the body of the tin box and its base respectively which are connected together by the seamer. The seamer is also provided with a turret table which intermittently rotates, the intermittency dependent on the rate of production of tin boxes, the duration of the various forming steps throughout the production process, and the rate of infeed of blanks.

This invention is specifically concerned with the provision of a novel mandrel combined with suitably modified forming wings.

There are many disadvantages associated with the current type of mandrels used in bodymaking machinery. Firstly, the mandrels must be capable of withstanding the significant pressures exerted thereon by the forming wings which are repeatedly brought to bear against the mandrel during the forming operation on the profiled blank. Accordingly, the mandrels are generally constructed of solid steel sections and as a unit, a mandrel can be weighty.

Secondly, the various solid steel sections of which a mandrel is comprised must be accurately machined to the exact dimensions of the inside of the particular tin box which it is desired to manufacture. It is to be noted that for each particular shape of tin box which it is desired to manufacture a specifically designed mandrel must be provided.

Thirdly, the general construction techniques involved in the manufacture of mandrels is complicated by the requirement for expansion and contraction thereof. Such characteristics are necessitated by the particular configuration of the forming wings which act on the preformed substantially planar blank disposed atop the mandrel, and the provision of the interlocking hooks provided along the typically shorter edges of the blank. In particular, as the forming wings are rotated downwardly and make contact with the substantially planar blank, the forming wings deform respective sides of the blank on either side of the mandrel until the shorter edges of the blank which are provided with the oppositely disposed hooks overlap to a predetermined degree. Depending on the configuration of the forming wings, the overlapping of said edges may automatically result in the interlocking engagement of said hooks, but in any event the mandrel is expanded in with the forming 6 wings substantially surrounding the deformed blank on the mandrel to ensure the side walls of the blank are urged outwardly and thus the hook provided on the edge of the blank in contact with the mandrel is urged outwardly and behind the hook provided on the alternate overlapping edge. This expansion also temporarily enlarges the cross-sectional shape of the blank, and therefore the adjacent edges are brought closer together. Interlocking of the hooks is thus ensured.

It will be appreciated by those skilled in the art that the provision of a mandrel which can be either hydraulically or mechanically actuated to expand or contract while retaining its overall crosssectional shape is a particularly complex mechanical engineering problem.

It is thus the primary object of this invention to overcome the abovementioned disadvantages associated with mandrels used in bodymaking machinery.

According to the present invention there is provided a mandrel for use in a bodymaker, said mandrel being disposed proximate forming means adapted to substantially surround said mandrel during a forming operation and which can be retracted to allow for release of the article formed on said mandrel, characterised in that said mandrel is non-expanding and in that the contact surface of at least one of the forming means is resiliently deformable to allow the formed article on the mandrel to recover slightly after the forming operation.

Preferably the forming means comprise a pair of forming wings which can be rotated around the mandrel the form an article thereon, and further preferably both the contact surfaces of said wings are resiliently deformable such that the two sections of the 7 article being formed on either side of said mandrel by said wings can recover slightly.

Most preferably, the disposition of the forming wings around the mandrel is such that a blank disposed on the mandrel and provided with oppositely disposed hooks along edges thereof axially parallel with the axis of the mandrel is deformed around the mandrel until said edges overlap and the oppositely disposed hooks along said edges interlock with one another.

Preferably, the forming wings are marginally retracted to allow the formed article to elastically recover against the resiliently deformable contact surfaces of the forming wings.

Preferably the resiliently deformable contact surfaces of the forming wings are provided by resiliently deformable pads applied to the solid surfaces of said forming wings.

The use of a non-expanding mandrel has heretofore been considered impossible because of the requirement to ensure that the oppositely disposed hooks are interlocked before the hammer impacts same to form a seam in the formed article. The provision of resiliently deformable pads and the configuration of the tips of the forming wings which cause the edges provided with the oppositely disposed hooks to overlap and said hooks to interlock precludes the requirement for an expanding and contracting mandrel. This allows for the overall cost of bodymaking machinery to be significantly reduced.

A specific embodiment of the invention is now described with reference to the accompanying diagrams provided by way of example, wherein:

8 Figure 1 shows a schematic end elevation of a mandrel and associated forming wings according to the prior art,

Figure 2 shows a schematic end elevation of a mandrel and associated forming wings according to the invention, Figure 3 shows a schematic end elevation of the mandrel of Figure 2 with associated forming wings disposed therearound in the process of forming a blank around the mandrel, and Figure 4 shows a schematic end elevation of the mandrel with the associated forming wings retracted slightly from the position shown in Figure 3.

Referring firstly to Figure 1, there is shown bodymaking apparatus 2 for use in the manufacture of the hollow body sections of tin boxes. The apparatus consists of a mandrel 4, which in this embodiment is generally square in cross-section but it is to be appreciated that any particular shape of mandrel may be required dependent on the particular crosssection of the body of the tin box which it is desired to manufacture. As mentioned above, the mandrel 4 is constituted of a plurality of movable sections 6, 8, 10, 12 which are mechanically connected to a cam mechanism 14 provided in the centre of the mandrel 4. Said cam mechanism 14 may be rotated to urge each of the movable sections 6, 8, 10, 12 outwardly from the central axis of the mandrel 4 along which the cam mechanism 14 is disposed, and thus a sheet of metal 16 formed around the outer surfaces of the movable portions 6, 8, 10, 12 can be expanded by virtue of the outward movement of said portions. This is particularly useful for ensuring interlocking engagement of a pair of oppositely disposed hooks 18, 20 provided along the edges of the sheet 16 when said sheet is formed completely around said mandrel 9 4 by a pair of rotatable forming wings 22, 24 which rotate in the directions shown by arrows 26, 28.

The expansion of the various mandrel portions 6, 8, 10, 12 is further of advantage during the seaming step wherein a hammer (not shown) impacts the oppositely disposed interlocking hook portions 18, 20 against the mandrel to form a seam. In particular, when the mandrel portions are expanded outwardly, the formed sheet 16 is stretched against the outer surfaces of the movable portion and thus the frictional contact between the said sheet and the movable portions ensures that the said sheet cannot slip of slide thereover.

Referring now to Figure 2, there is shown a solid mandrel 30 on which is disposed a substantially planar sheet 32 on the uppermost arcuate corner of the mandrel 30 against which it is retained by a mandrel clamping arrangement (not shown). A pair of rotatable forming wings 34, 36 are provided proximately above the mandrel and are capable of rotating about a common axis 38 to deform the sheet 32 over the surface of the mandrel 30. It will be appreciated that the Figures appended hereto are to a certain extent schematic and the distance between common axis 38 and the mandrel 30 may be varied to suit particular sizes of forming wing, but in any event the ultimate orientation of the forming wings should be as shown in Figure 3.

In similar manner to the prior art configuration, the sheet 32 is provided with a pair of oppositely disposed hooks 40, 42 which are caused to interlock by virtue of the deformation of the said sheet as the forming wings 34, 36 come into contact therewith. In particular, it should be mentioned that the forming wings 34, 36 are of dissimilar shape and orientation with respect to the mandrel surface over which the sheet is deformed to ensure that the side of the sheet 32 provided with the hook 42 is deformed around the mandrel surface before the alternate side of the sheet 32 provided with the hook 40 to ensure the interlocking engagement of said hooks as shown in Figure 3.

In accordance with the invention, the forming wings 34, 36 are provided with resiliently deformable pads 44, 46 which are capable of elastically deforming during the forming operation.

More specifically, during the forming operation, the deformable pads 44, 46 are compressed against the outer surfaces of the mandrel 30 when the forming wings 34, 36 are disposed in the position shown in Figure 3. In this condition, the forming wings 34, 36 have reached the extremity of their downward rotation, and are hydraulically or mechanically urged against the outer surfaces of the mandrel 30 to effectively deform the sheet 32 interposed between the pads 44, 46 and the outer surface of said mandrel.

Immediately after the condition in Figure 3 has been reached, and the hooks 40, 42 have interlocked as shown in Figure 3, the forming wings 34, 36 are rotationally retracted slightly to allow the sheet 32 to elastically recover after its deformation against the surfaces of the pads 44, 46. In this manner the interlocking engagement of the hooks 40, 42 is completed and the sheet 32 continues to be retained in frictional engagement with the contact surface of the pads 44, 46. It is this frictional contact between the sheet 32 and the pads 44, 46 which ensures precise positioning of the said sheet on the mandrel during the subsequent seaming operation in which a hammer (not shown) impacts the interlocking hooks 40, 42 against the lowermost arcuate corner of the mandrel 30, thus forming a seam thereat.

Thus the invention provides a far simpler and far less extensive mandrel assembly than as currently used in the prior art machinery, and furthermore the ability of the apparatus to precisely position

11 and retain the deformed sheet 32 in place around the mandrel during a subsequent seaming operation is not compromised.

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Claims (8)

1 - A forming assembly for use in a bodymaker, said assembly including a mandrel having one or more component parts and forming means disposed proximate thereto and adapted to substantially surround said mandrel during a forming operation, said forming means being capable of retraction to allow for release of the article formed on said mandrel, wherein said mandrel or the component parts thereof are static in that there is no expansion thereof while the forming means are disposed therearound, the contact surface of at least one of the forming means being resiliently deformable to allow the formed article between said surface and said mandrel to recover slightly after the forming operation.

2. An assembly according to claim 1 wherein the forming means comprise a pair of forming wings which can be rotated around the mandrel the form an article thereon.

3. An assembly according to claim 2 wherein the contact surfaces of both said forming wings are resiliently deformable such that the two sections of the article being formed on either side of said mandrel by said wings can recover slightly.

4. An assembly according to claim 3 wherein the disposition and configuration of the forming wings around the mandrel is such that a blank disposed on the mandrel and provided with oppositely disposed hooks along edges thereof axially parallel with the axis of the mandrel is deformed around the mandrel until said edges overlap and the oppositely disposed hooks along said edges interlock with one another.

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5. An assembly according to any preceding claim wherein the forming means are fractionally retracted after having been disposed substantially around the mandrel to allow the formed article to elastically recover against the resiliently deformable contact surfaces of said forming means and to allow for any formations provided on adjacent edges of the formed blank to interlock fully.

6. An assembly according to any of claims 2-4 and on claim 5 as it depends on claims 2-4 wherein the resiliently deformable contact surfaces of the forming wings are provided by resiliently deformable pads applied to the solid surfaces of said forming wings.

7. A method of forming a blank around a mandrel mounted within a bodymaker, said method comprising the steps of bringing a blank of material into register with a mandrel comprised of one or more components defining an exterior surface around which said blank is to be formed, causing actuation of forming means disposed proximate said mandrel whereby said forming means contact said blank and form same around the mandrel by forcing the blank to assume the cross-sectional shape of the mandrel, wherein the mandrel remains static while the forming means are disposed therearound, said forming means having at lease one contact surface or a portion thereof which is resiliently deformable to allow for some elastic recovery of the blank after initial forming thereof around said mandrel.

8. A method according to claim 7 wherein the forming means are fractionally retracted after the initial forming step performed on the blank to allow for elastic recovery of said formed blank against the resiliently deformable contact surfaces of said forming means.