Metal deforming – By relatively movable offset tool-faces – Embodying three or more coacting relatively movable tools
Patent
1987-08-04
1989-04-11
Larson, Lowell A.
Metal deforming
By relatively movable offset tool-faces
Embodying three or more coacting relatively movable tools
72397, 72404, B21D 504
Patent
active
048194735
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of and apparatus for press forming sheet metal. The invention has particular application to progressive press forming of sheet metal articles which have intersecting form lines and which would require the application of very high press forces if they were to be shaped by conventional stretch-forming or drawing techniques.
BACKGROUND ART
In a typical progressive press forming operation a sheet or strip of metal is advanced through successive stages of a die and a desired final product shape is imparted to the metal in progressive stages. The metal is advanced between the stages whilst the die components are open and press forming of the metal is effected in each stage during each closing stroke. U.S. Pat. No. 4,309,889 discloses a typical progressive press forming operation.
A problem that exists in conventional progressive press forming is that, during a pressing operation, metal can be pulled from one direction only. This arises from the fact that in a two-stage progressive forming operation for example, metal cannot be pulled back to the first stage whilst it is being worked-on in the second stage and/or it cannot be pulled into the second stage whilst it is subjected to a press forming operation in the first stage. Thus, all metal which is to be pulled into the first stage must be provided from the input side of the tool and all metal which is required to be pulled into the second stage must be provided from the output side of the tool. This restricts the shaping which ca be applied to the metal and/or requires that the shaping be created by stretch-forming the metal. The latter approach requires expensive tooling and high powered presses.
U.S. Pat. Nos. 2,510,024 and 2,954,068 and British patent specification No. 1,398,027 disclose press tools which operate in a manner such that metal is pulled into the tools from two directions during formation of longitudinally extending corrugations. However, the tools which are disclosed in the referenced patent specifications cannot be used to form articles which have intersecting form lines.
DISCLOSURE OF THE INVENTION
The present invention distinguishes over prior art press forming arrangements in that it is directed to a press forming method which is suitable for shaping sheet metal articles which have intersecting fold lines. A strip of the sheet metal is advanced through a multi-stage die and a forming operation is effected in each stage of the die during each closing stroke of the die. During a first time interval of each closing stroke. Press forming is effected in one stage of the die whilst metal in the or each other stage is movably clamped. whereby metal can be pulled into said one stage from the or each other stage of the die. Then, during a second time interval of each closing stroke, the metal is immovably clamped in all stages of the die.
Because the metal in the further stages of the die is not clamped during the initial time interval of each closing stroke and because the metal may then be pulled into the stage in which press forming is being effected. complex press forming operations may be effected in the die without the need for very high die closing forces.
The invention may also be defined as providing an apparatus in the form of a metal press forming die. The die includes multiple stages through which a strip of metal is advanced and in which forming operations are effected during each closing stroke of components of the die. The die components are arranged such that, during a first time interval of each closing stroke, press forming is effected in one stage of the die whilst metal in the or each other stage is movably clamped, whereby the metal can be pulled into said one stage from the or each other stage of the die. Additionally, the die components are arranged such that, during a second time interval of each closing stroke, the metal is immovably clamped between the die components of all stages of the die.
The invention will be more fully understood from the following description
REFERENCES:
patent: 1341721 (1920-06-01), Opitz
patent: 2079553 (1937-05-01), Fraser
patent: 2712340 (1955-07-01), Sandberg
patent: 2847053 (1958-08-01), Hardman
Australian Design Marketing PTY., Ltd.
Larson Lowell A.
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