GB2235641A

GB2235641A - An apparatus for producing lids or similar articles of metal sheet

Info

Publication number: GB2235641A
Application number: GB9010953A
Authority: GB
Inventors: Helmuth Neben
Original assignee: Alfons Haar Maschinenbau GmbH and Co KG
Current assignee: Alfons Haar Maschinenbau GmbH and Co KG
Priority date: 1989-05-23
Filing date: 1990-05-16
Publication date: 1991-03-13
Also published as: GB9010953D0; DE3916665A1; DE3916665C2; FR2647374A1

Abstract

The lower tool of a deep drawing press is constructed of two coaxial drawing dies 20, 24. The outer drawing die 24 is moved downwards by the drive mechanism of the upper tool when an outer, upper tool part 16 engages the die 24 via a holder 26. The bell-section upper tool part 16 bends the lid edge downwards and inwards in the space provided by the downward movement of the die 24. Upon the return stroke, before inner upper tool parts 10a, 10b disengage the die 20, the die 24 is allowed to rise and engages the partly curled lid edge with a forming clearance 24b and completes the curling process in cooperation with inner upper tool part 10b. <IMAGE>

Description

AN APPARATUS FOR PROCUDING-LIDS OR SIMILAR ARTICLES OF METAL SHEET The

invention relates to an apparatus f or producing lids or similar articles of metal sheet.

Lids f or cans or other containers are produced f rom sheet plates by punching or simultaneous press shaping. With this shaping, the lids get a curled edge or rim which is formed at a container rim by bordering after being placed onto the container such, that a tight connection is provided. For that, the lid edge is shaped such by a rolling deformation that the lid edge grips under the container bead from below. It is desirable to produce the lid edge .. /2 arch-like in cross section to have a favourable basic form for its curling at the container bead.

From DE-OS 35 34 362, an apparatus is known where the upper and lower tool form the lid into the intended shape by pressure. The upper tool is concentrically encircled by a tool section relatively movable thereto and having the aim to co-act with a punching tool and to cut out the lid blank. The lower tool consists of an inner drawing die and an outer annular drawing die surrounding the inner drawing die, relatively movably supported with respect to the inner drawing die and driven by a drive mechanism. Around the outer drawing die, an annular holder is supported. Upon a movement of the upper and lower tool against each other, the lid blank is first cut off between tool section and punching tool. Afterwards, the free edge section of the lid blank is bent around the outer drawing die about a right angle with the assistance'of the tool section. Upon this movement of the tools, the tool section displaces the annular holder relative to the outer drawing die. This one consists of two annular drawing die sections, among these, the outer one is moved upwards by the annular holder to .. /3 provide a f ree space into which the angled section of the lid edge can be formed. This shaping takes place by assistance of a conical section of the tool section acting on the lid edge with a further downward movement of the tool section.

with the known apparatus, it is indeed possible to carry out a specific shaping of the lid edge at a single stroke. However, the shaping only takes place during the working stroke, i.e. by a single shaping step. It is, however, relatively difficult to reproducibly produce a sufficiently curled lid edge in this way.

The object of the invention is to provide an apparatus for the production of lids and similar articles of metal sheet wherein reproducibly, a sufficient curling of the lid edge is achieved.

This object is attained by the invention.

In the apparatus according to the invention, the bellshaped tool section has a forming clearance which upon an .. /4 upward movement bends the lid edge section f urther inwardly which has been angularly curled between tool section and outer drawing die. The outer drawing die has a second forming clearance facing the inner drawing die, and the driving mechanism of the drawing die presses it upwards prior to upper and lower tool being separated so that the pre-curled lid edge gets into contact with the second f orming clearance and is to a suf f icient extent curled into the forming space provided between the forming clearance, the inner drawing die and upper tool. Only af ter that, the f orming tools are brought back into their initial position.

The apparatus according to the invention renders therefore possible the punching and complete shaping of a lid inclusive of its curled edge by a single stroke, with the shaping of the lid edge taking place in three subsequent steps without enhancing the expenses for the forming tools. Particularly, the apparatus of the invention renders also possible a uniformly curled lid edge with a reduced thickness of the sheet material and greater hardness of the material. The apparatus also permits to produce a uniform .. /5 1 and immaculately curled shape with relatively small dimensions of the curled lid edge, i.e. with relatively short length thereof. For reasons of saving material, it is intended to use material for the rim as less as possible.

According to an embodiment of the invention, the outer drawing die is formed as one piece. This is a simplification compared with the previously described, known apparatus which has an outer, two-piece drawing die.

Another embodiment of the invention provides that the pressure ram acts on the upper tool by a spring mechanism and the bell section is fixedly attached to the pressure ram and the outer drawing die is pressed by a spring mechanism towards a stop of the drawing die. Whereas in the known apparatus the individual tool sections are hydraulically actuated and therefore have to be adequately controlled, the invention only necessitates a normal ram actuation of the upper tool to carry out the described forming processes. By suitable spring mechanisms between the ram and the upper tool, between the outer drawing die ---. 36 - 6 and a f ixed support and the annular holder and the fixed support, an automatic control of the relative movements takes place. Such a designed apparatus can be produced with very low expense and is also less subject to wear.

Advantageous developments of the invention are specified in further claims.

An example embodiment of the invention is explained in detail in the following along accompanied drawings.

Fig. 1 diagrammatically shows a cross section through an apparatus according to the invention.

Figs. 2 to 5 show a part of the apparatus of Fig. 1 in different operational states.

An upper tool 10 is supported by a spring mechanism 11 and 12, respectively, on a plate 13 f ixedly attached to a pressure ram 14 driven upwardly and downwardly by a notshown press drive along double arrow 15. The upper tool 10 is surrounded by a bell-shaped tool section 16 f ixedly attached to plate 13 as indicated by a threaded bolt 17. A section 18 of the upper tool 10 having a larger diameter .. /7 i 1k - rests on a ring-shaped shoulder of the tool section 16 as shown in Fig. 1.

An inner drawing die 20 is fixedly attached to a stationary plate 21 as indicated by a threaded bolt 22 and an intermediate ring 23. The inner drawing die 20 is surrounded by a ring-shaped outer drawing die 24. The outer drawing die 24 rests on a ram 25 which, in turn, is supported by a spring. The outer drawing die 24 is surrounded by an annular holder 26 resting on a bolt 27 which is pressed upwardly by a spring 28 to press the annular holder 26 upwardly. A Cutting tool 29 is fixedly attached to plate 21 as indicated by bolt 30. The cutting tool 29 limits the upward movement of annular holder 26.

The working process of the apparatus shown in Fig. 1 is demonstrated by Figs. 2 to 5. In the Figures 2 to 5, the tool arrangement is shown in an enlarged.scale and with some details. In particular, it is to be seen that the upper tool 10 consists of an inner tool section 10a and an outer tool section 10b encircling the inner tool section. Both are connected with the pressure ram 14 by spring .. /8 mechanisms. The lower forming surface of section 10b is upwardly displaced relative to the lower forming surface of section 10a. The forming surfaces could also be placed in a common plane. It is further to be seen that the bellshaped section 16 has a section 16a of larger thickness and a section 16b of smaller thickness by which a ringshaped circular forming clearance 16c is provided facing the upper tool 10. The inner diameter of section 16a corresponds to the outer diameter of tool section 10b. The inner diameter of section 16b is insignificantly larger than the inner diameter of annular holder 26.

It is further to be seen that the outer drawing die 24 has at the lower end a broadening 24a which on the one hand co-acts with a shoulder 20a of the inner drawing die limiting relatively the upward movement of the outer drawing die 24 to the inner drawing die 20. On the other hand, the enlarged section 24a co-acts with the annular holder 26 if it is moved downwardly towards the spring mechanism 28.

The outer drawing die 24 has at its upper end a f orming clearance 24b facing the inner drawing die 20, the largest .. /q i 1_ 1 inner diameter thereof nearly corresponding with the outer diameter of tool section 10b.

The initial position before the forming process is started is demonstrated in Fig. 2. A sheet plate 40 is pushed between the tools and the pressure ram 14 has already traveled a part of its working stroke. However, the individual tool sections are., in the same position as indicated in Fig. 1. In the position shown in Fig. 3, the upper tools 10a, 10b have completely drawn the lid 41 together with inner drawing die 20 and outer drawing die 24. The. bell section 16 fixedly attached to the pressure ram, co-acts with the punching tool 29 and punches out the lid blank at the beginning of the forming process, with the annular holder 26 being displaced back against an associated spring mechanism 28. The spring mechanism for the outer drawing die 24 is designed such that the outer drawing die 24 keeps its position shown in Fig. 3 with the press forming of lid 41 described.

The actual shaping of the lid is not further described.

Fig. 3 shows further that on a correspondingly upward movement of the bell-shaped section 16, it places the .. /10 -4 - 10 annular holder 26 in contact with enlarged section 24a of outer drawing die 24. Since the upper tools 10a, 10b are connected with the pressure ram by spring mechanisms, the pressure ram can be moved downwards further. Therefore, the bell-shaped section 16 also moves further downwards and carries along the outer drawing die 24 downwards. By that, the internal side of section 16a of bell section 16 gets into contact with right- angled, downwardly curled edge of lid 41. The right-angled curling of the edge takes place by the co-action of section 16b of bell section 16 and of the outer side of the outer drawing die 24 as can be seen in Fig. 3. By the lateral contact of section 16a of bell section 16 with the lid edge only on one side, it is f lexed inwardly as can be clearly seen in Fig. 4. The pressure ram has now reached its lower dead center.

Upon the upward movement of the pressure ram 14, f irst of all, only bell section 16 is moved upwards whereas tool sections 10a and 10b still contact the lid and the inner drawing die 20, respectively, due to the spring mechanisms. Due to the upward movement of the bell section 16, annular holder 26 and the outer drawing die 24 can also move upwards. By that, the forming clearance 24b of outer drawing die 24 co-acts with the partly curled lid edge as is de- .. / 11 -1 k - 11 monstrated in Fig. 4. With the assistance of the forming clearance 24b, the curling is finished. The lid edge is provided with semi-circular shape and this is sufficiently prepared to be attached to a container by a correspondingly rolling process.

When pressure ram 14 moves further upwards, the tool sections are turning back into the initial position as shown in Fig. 1 and Fig. 2, respectively. A second forming step can start.

It is clear that the control of the outer drawing die 24 can also occur in a different manner, for example with an adequate cam-controlled drive.

.. /12 f k!

Claims

C 1 a i m s

1. An apparatus f or producing lids or similar articles of metal sheet having a curled edge comprising an upper tool operated by a pressure ram, a lower tool which gives the lid the intended form together wth the upper tool by pressure, a tool section concentrically encircling the upper tool and relatively movable thereto,.an annular holder encircling the lower tool and being relatively movable thereto which is pressed towards the upper tool by a drive mechanism, a punching tool encircling the annular holder and having a ring-shaped cutting edge which co-acts with the tool section when the upper tool approaches the lower tool, with the lower tool including an inner drawing die, an outer drawing die surrounding the inner drawing die, relatively movably supported with respect to the inner drawing die and driven by a drive mechanism such, that the outer drawing die can be moved relative to the inner drawing die after the co-operation of upper and lower tool, with the tool section having an upper portion having a smaller internal diameter and a lower portion having a larger internal diameter which is slightly larger than the outer diameter of the outer .. /13 j C drawing die such, that upon a further downward movement of the tool section,, the lid edge is bent downwardly and inwardly into a free space provided by the downward movement of the outer drawing die, characterized in that the bell-shaped tool section (16) has a forming clearance (16c) at its end facing the Upper tool (20) and the outer drawing die (24), has a second forming clearance (24b) at its upper end which faces the inner drawing die (20) and after exceeding the lower dead center of the pressure ram (14), the drive mechanism urges back the outer drawing die upwardly prior to the upper and lower tool (10, 20) being separated for further shaping the curled lid edge in the second forming clearance (24b).

2. The apparatus of claim 1, characterized in that the outer drawing die (24) is formed in one piece.

3. The apparatus of claim 1 or 2,characterized in that the pressure ram (14) acts on the upper tool (10) by a spring mechanism (11, 12) and the bell section (16) is fixedly attached to the pressure ram and the outer drawing die (24) is pressed by a spring mechanism towards the upper tool (10) against a stop of the drawing die (20).

.. 114 (.1

4. The apparatus of claim 3,characterized by a dimensioning of the spring mechanism (25) of the outer drawing die (24) such that the outer drawing die (24) keeps its position when the lower portion (16b) of the bell section (16) bends the lid edge around the upper side of the drawing die (24).

5. The apparatus of one of the claims 1 to 4,characterized in that the largest diameter of the second f orming clearance (-24b) in the outer drawing die (24) is nearly equal to the smaller internal diameter of the bell section (16).

.. /15 Published 1991 atIbe Patent Office. State House. 66/71 HghHolbom. TondonWCIR47P.Furthereopiesniay be obtained from Sales Branch, Unit

6. Nine Mile Pbint Cwmlelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.

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