Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-01-06
2001-09-25
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S292000
Reexamination Certificate
active
06294043
ABSTRACT:
The present invention relates to a method of manufacture of a structure and to a structural member for use in the method. The invention particularly relates to the manufacture of a space frame structure for an automobile, but should not be considered limited to such an application.
Recently there has been interest in reducing the weight of automobiles in order to improve fuel economy and performance. There has consequently been a move to use aluminium in place of steel in the manufacture of automobiles. Whilst aluminium has many advantages over steel, in particular in terms of weight saving, it is difficult to form a space frame for a vehicle from aluminium since welding of aluminium is difficult.
U.S. Pat. No. 5,209,541 discloses a method of manufacture of a space frame for an automobile from aluminium structural members. The method involves the bonding of the aluminium structural members together with a suitable bonding material such as an acrylic adhesive. The method requires that two structural members to be joined together are each provided with a shaped channel and that an interconnecting member is provided to be inserted into both the channels of the two aluminium members, with the interconnecting member being secured there by adhesive. The method involves complications since the structural members must be machined to give a specific cross section in the areas of joints and also since interconnectors must be used.
DE-A-3525830 shows how a bootlid for an automobile can be made by the bonding together of two metal sheets which are shaped with grooves which provide a gap for adhesive.
DE-A-3811427 shows how two tubular members of an automobile space frame can be joined together end to end by providing the tubular members with specifically manufactured end portions which cooperate together to define a series of channels for receiving adhesive and also two apertures through which adhesive can be injected in order to adhere the two components together.
EP-A-0523831 shows how a motor car structure can be built up from flat panels joined together, each panel comprising two mutually parallel spaced apart structural skins braced with respect to each other by a core of expanded material united to both skins. Each joint between the two panels comprises a series of integral projections formed on a first panel formed by cutting the first panel to a required shape and also recesses in the second panel which correspond to the projections, the projections being inserted into and bonded in the recesses by means of an adhesive.
DE-A-4202391 shows how two automobile panels can be connected together by a joint with an L-shaped cross section, which acts as an interconnecting member. The L-shaped joint has two channels, one for each of the panels to which it is joined. Each channel is formed with a cross section which defines a groove for receiving adhesive in order that a panel inserted into the channel can be adhered to the channel by adhesive in the groove.
DE-A-4124627 shows how a body panel for a vehicle can be provided with a corrugated edge section so that the panel can be joined to another panel by inserting the corrugated edge into a channel provided at the edge of the second panel. The corrugated edge serves to locate the first panel in the channel at the edge of the second panel whilst the adhesive is setting and also serves to define a gap for the adhesive.
The present invention in a first aspect provides a method of manufacture of a structure which comprises a plurality of structural members bonded together, the method comprising the steps of extruding a structural member with a chosen cross-section, and joining extruded structural member to another structural member by bonding with an adhesive, wherein when the extruded structural member is bonded to the structural member the depth of the adhesive between the two structural members varies with variations in the cross-section of the extruded structural member, characterised in that the cross-section of the extruded structural member is chosen so as to enhance the performance of the adhesive bond between the structural members.
In a second aspect the present invention provides a structural member for use in the method of manufacture described above which is a hollow, elongate extrusion of aluminium or an alloy of aluminium and which has a plurality of longitudinally extending spaced apart ribs for defining a gap between the structural member and a further structural member bonded thereto.
In a third aspect the present invention provides a method of manufacture of a structure wherein first and second structural members are bonded together with adhesive, characterised in that the first structural member is provided on a first surface with a plurality of spaced apart exterior ribs which abut an adjacent surface of the second structural member when the structural members are bonded together and which define between the first surface of the first structural member and the adjacent surface of the second structural member a gap for receiving adhesive, whereby the ribs define a chosen depth of adhesive between the first and second structural members in order to optimise the bond between the first and second structural members.
In a fourth aspect the present invention provides a structural member for use in the above described method which is an extrusion and which has a plurality of longitudinally extending exterior ribs provided on a first surface to define between the first surface and an adjacent surface of a second structural member bonded to the structural member a gap for receiving adhesive, whereby the ribs can define a chosen depth of adhesive.
In a further aspect of the present invention there is provided a method of manufacture of a structure which comprises a tubular elongate structural member, the method comprising the steps of forming the tubular elongate structural member with a chosen cross-section, and joining the tubular elongate structural member to a second structural member by bonding with an adhesive, wherein when the tubular elongate structural member is bonded to the second structural member the depth of the adhesive between facing surfaces of the tubular elongate structural member and the second structural member varies with variations in the cross-section of the tubular elongate structural member, characterised in that the cross-section of the tubular elongate structural member is chosen to enhance the performance of the adhesive bond between the tubular elongate structural member and the second structural member.
Bonding of structural members with adhesive and optionally with mechanical fasteners in addition to adhesive, is advantageous over welding and over the use of mechanical fasteners alone. The resulting bond does not suffer from heat distortion and does not suffer from reduction in material properties occasioned by the heat of welding. The resulting joint is also stiffer that a joint which would result from purely mechanical fastening (e.g. with nuts and bolts). Furthermore, the bonding process enables the use of hollow tubular members of a wall thickness thinner than that which would be necessary if welding is used as a joining method (welding causes some depletion of metal and consequent weakening of the structural members). However, the strength, efficiency and durability of a bonded joint depends on the thickness of adhesive between the two structural elements joined. Therefore it is very important to control the thickness of the adhesive layer between the two structural members. The present invention solves this problem in all of its aspects by shaping the members to be joined in a fashion that the depth of adhesive is a planned and controlled depth. The extrusion of material to form a structural member with a chosen cross-section is a very efficient way of forming the structural member, particularly if the member is made of aluminium or an alloy of aluminium. The required cross-section is obtained in one operation and the formed member requires little or no further machining.
REFERENCES:
patent: 3
Greig Daryl John
Sears Kenneth John
Ball Michael W.
Fulwider Patton Lee & Utecht LLP
Lotus Car Limited
Musser Barbara J.
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