Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1996-10-25
2001-03-27
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C029S509000, C029S521000, C029S243500, C029S283500
Reexamination Certificate
active
06205640
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method for joining together two or several overlaying sheet formed members, an apparatus for carrying out said method and a joint resulting from said method. Such joining procedures could e.g. be carried out by first drawing and then laterally extruding the material of the two sheet formed members to be joined into an enlarged shape which will interlock the members. A joint produced by means of this method will typically be of the leakproof type. The members could also be joined by lancing and forming a part of one member through an unblanked part of the other member and thereafter staking the lanced and formed part of the one member to an adjacent surface of the other member to secure the members together in overlaying relation. A joint produced by means of this method will typically be of the non-leakproof type.
BACKGROUND ART
Methods and apparatuses for joining sheet formed members together, thereby producing leakproof or non-leakproof joints, are previously known. Of particular interest in some applications is a type of leakproof joint which is made by means of drawing said sheet formed members into a cup-shaped or protruding portion having a cylindrical or slightly conical side wall and a bottom wall and subsequently compressing said bottom wall creating a lateral extrusion of the same thereby forming a laterally enlarged shape which mechanically interlocks the sheet formed members. The present invention, however, is also concerning other types of joints.
U.S. Pat. No. 4,459,735 discloses an apparatus, a method and a joint of this type. The method is of the single stroke type which means that the whole procedure takes place during one single relative movement between a punch and a coacting die. For the compression of the bottom wall of the cup-shaped portion an anvil is arranged fixed at the bottom of the die cavity which cavity is laterally expandable.
Double-stroke methods are also known from e.g. WO 89/07020 according to which the compression takes place during a second stroke outside the die cavity. This cavity is generally laterally non-expandable.
One problem with the leakproof joints of the above type is the relatively low resistance against so called shear and peeling forces.
It turns out that the drawing depth into the die cavity and the gap between the punch and the die cavity are critical parameters.
If the drawing depth is too big and/or the gap between the punch and the die cavity is too small the side wall of the cup-formed or protruding portion, especially on the sheet formed member touching the punch, will be too thin and there is a risk that this side wall will break when exposed to forces tending to separate the members. The problem is emphasized when the joint is made between more than two sheets.
On the other hand, if the drawing depth is too small and/or the gap between the punch and the die cavity is too big, the lateral extrusion of the bottom wall during the compression will not be sufficient to create the interlocking between the sheet formed members and there is a risk that the members separate for that reason, when exposed to forces.
DISCLOSURE OF THE INVENTION
One object of the present invention is to provide a method for joining sheet metal and/or other sheet material producing a joint of the leakproof or non-leakproof type having considerably improved strength in relation to known joints.
The claimed apparatus utilizes a new punch construction which considerably will contribute to the strength of the joint.
Another object of the invention is to provide an apparatus which is less sensitive to variations in the total thickness of the sheet members.
An advantage of the invention is the simplicity of the solution.
The present invention, which provides a solution to the said technical problems, is characterised according to the appended claims.
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Attexor Equipements S.A.
Hughes S. Thomas
Omgba Essama
Young & Thompson
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