EP0995514A1

EP0995514A1 - Panel assembly of hemmed panels and its method of manufacture

Info

Publication number: EP0995514A1
Application number: EP99307792A
Authority: EP
Inventors: Robert Hindley 8 Renoir Close May
Original assignee: MG Rover Group Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 1998-10-17
Filing date: 1999-10-04
Publication date: 2000-04-26
Anticipated expiration: 2019-10-04
Also published as: GB9822625D0; GB2342607B; DE69908732T2; GB9923274D0; DE69908732D1; EP0995514B1; GB2342607A

Abstract

Production of a satisfactory outer profile for a hemmed joint is often difficult due the bending of a hem being conducted without anything to provide back resistance to the bending motion. A first inner panel 4 and a method for joining the first inner panel to a second outer panel 8 are disclosed. A hem 22 of the second panel 8 is wrapped around an edge 2 of the first panel provided along at least a part of its length with a die cast bead 14 to secure the edge of the first panel within a channel 34 formed thereby in the second panel. The die cast bead 14 provides a back resistance during this bending of the hem portion about the lip of the bead.

Description

The present invention relates to an improved method of assembling a panel assembly, in particular by hemming and to a panel for use in the method. The invention has particular, but not exclusive utility in the automotive industry.
It is known to join panels together by hemming. In this method, an outer panel is provided beneath an inner panel. The inner panel is provided with a flat edge where it is desired to join the panels together. The outer panel extends beyond each edge that it is desired to hem. The extending portion or hem of the outer panel is bent around the flat edge of the inner panel and flattened to the inner panel to form a "U" shaped groove around the edge of the outer panel in which the inner panel is located.
Production of a satisfactory outer profile for the joint is often difficult due the bending of the hem being conducted without anything to provide back resistance to the bending motion.
In addition such a joint is not particularly secure. When the joint is twisted, for example, the inner panel may be withdrawn from the groove. Further process are often employed in order to ensure that the joint will be durable. However, such operations clearly add to the cost and time involved in the production of the joint. Further, obtaining a consistently reproducible joint of satisfactory quality is difficult.
One known method of solving these problems is to provide a raised portion along the edge of the inner panel. However, in this method it is necessary to have a special tool, provided with a slot corresponding to the raised portion. If the slot is not present, the raised portion will be flattened and the advantaged gained by providing an inner panel with a raised portion is lost.
It is an advantage of the present invention that it provides for a reproducible secure hemmed joint without the need for specially adapted tooling or further processing of the joint.
According to a first aspect of the invention, a method for joining together a first panel and a second panel by hemming comprises the steps of providing the first inner panel, providing the second outer panel, the second panel having a hem, placing the second panel beneath the first such that the hem extends beyond an edge of the first panel and bending the hem around the edge of the first panel to secure the edge of the first panel within the second panel characterised in that the edge of the first panel is provided along at least a part of its length with a bead.
According to a second aspect of the invention a panel for use in a hemming process characterised in that it comprises a bead extending along at least a part of its length.
Since the channel formed by the hem wrapping around the bead has a mouth narrower than a thickness of the bead, it will not be possible to pull the first panel from the second without damaging the channel.
Preferably, the bead extends along the entire length of the edge of the first panel.
Preferably, the bead is an integral part of the edge of the first panel.
Preferably, the first panel is a die cast member. This has the advantage that the panel and bead can be produced to a high tolerance with regard to dimensional accuracy. When the hem is bent around the bead, the profile formed will be accurate, consistent and more tightly formed than has previously been possible.
Preferably, the bead takes the form of a ridge extending out from a surface of the first panel.
According to a third aspect of the present invention, a motor vehicle door panel comprises a first inner panel and a second outer panel characterised in that the first and second panels are joined together by the method of the first aspect of the invention.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which
Figure 1 shows a side view of an edge of a first panel and an edge of a second panel for joining together by the method of the present invention;
Figure 2 shows a side view of the edge of the first panel and the edge of the second panel joined together by the method of the present invention; and
Figure 3 shows a detail of Figure 2.
Referring to the Figures, there can be seen an edge portion 2 of a first inner panel 4 and an edge portion 6 of a second outer panel 8.
The edge portion 2 of the first inner panel 4 has an upper surface 10 and a lower surface 12. A bulbous profile or bead 14 is provided extending along at least a part of the edge portion of the first inner panel. The bead 14 extends from the lower surface 12 of the first inner panel above the upper surface 10 of the first inner panel to form a ridge or lip 16 along that part of the edge of the first inner panel.
The first inner panel 4 is conveniently manufactured by die casting, though any other suitable method may be used. The first inner panel is conveniently manufactured from cast steel, though any other suitable material, for example aluminium, may be used.
The edge portion 6 of the second outer panel 8 has a main portion 20 and a hem portion 22. The main portion of the edge portion has an upper surface 24 and a lower surface 26. The hem portion 22 is provided at an angle to the main edge portion and forms an acute angle therewith by way of a curved intermediate portion 28. The angle may be formed during the manufacture of the second outer panel or subsequent thereto. The hem portion 22 is provided with an inner surface 30 and an outer surface 32.
The second outer panel 8 is conveniently manufactured from sheet steel, though any other suitable material, for example aluminium, may be used.
The method of joining the first inner panel 4 and the second outer panel 8 will now be described. The second outer panel 8 is placed with the lower surface 26 of the main edge portion on a locating die (not shown). The first inner panel is then placed with the lower surface 12 on the upper surface 24 of the main edge portion of the second panel such that the bead 14 is located adjacent the intermediate portion 28 of the edge of the second panel. In this position the hem portion 22 of the second panel extends over the lip 16 of the bead 14 of the first panel (Figure 1).
A hemming punch (not shown) is then used to stamp the hem portion 22 of the second outer panel to the edge portion of the first inner panel. The punch impacts the outer surface 32 of the hem portion 22 causing the hem portion to bend around the lip 16 of the bead 14 of the first panel such that the inner surface 30 of the hem portion comes into contact with the upper surface 10 of the first panel.
The bead 14 provides a back resistance during this bending of the hem portion about the lip of the bead. This allows the hem portion 22 to be tightly wrapped around the bead 16 to form a channel 34 at the edge of the second outer panel 8 having a narrow mouth 36 extending along the hemmed edge of the second outer panel. The edge 2 of the first inner panel 4 in this way becomes trapped inside the channel 34 formed by the second outer panel 8 since the bead 14 of the first inner panel 4 cannot pass through the mouth 36 of the channel 34 without distorting the channel.

Claims

A method for joining together a first inner panel (4) and a second outer panel (8) by hemming comprises the steps of providing the first inner panel (4), providing the second outer panel (8), the second panel (8) having a hem (22), placing the second panel beneath the first such that the hem (22) extends beyond an edge (2) of the first panel and bending the hem (22) around the edge (2) of the first panel to secure the edge of the first panel within the second panel characterised in that the edge (2) of the first panel is provided along at least a part of its length with a die cast bead (14).
A method according to claim 1, characterised in that the bead (14) extends along the entire length of the edge (2) of the first panel (4).
A method according to claim 1 or claim 2, characterised in that the bead (14) is an integral part of the edge (2) of the first panel (4).
A method according to any previous claim characterised in that the first panel (4) is a die cast member.
A method according to any previous claim characterised in that the bead (14) takes the form of a ridge (16) extending out from a surface of the first panel (4).
A panel for use in a hemming process characterised in that it comprises a die cast bead (14) extending along at least a part of its length.
A panel according to claim 6, characterised in that the bead (14) extends along the entire length of the edge of the panel.
A panel according to claim 6 or claim 7, characterised in that the bead (14) is an integral part of the edge of the panel.
A panel according to any of claims 6 to 8, characterised in that the panel is a die cast member.
A panel according to any of claims 6 to 9, characterised in that the bead (14) takes the form of a ridge (16) extending out from a surface of the panel.
A motor vehicle door panel comprising a first inner panel (4) and a second outer panel (8) characterised in that the first and second panels are joined together by a method according to any of claims 1 to 5.