Method of assembly of first and second component

Abstract: A method of assembly of a first (10, 110) and second component (12, 112) comprising the steps of providing the first component with a projection (14), 114), providing a second component with a plastics engagement surface (22, 122), assembling the first and second components such that the projection is held substantially rigid relative to the first component and the plastics engagement surface is plastically deformed around the projection then allowing the plastics engagement surface to further creep around the projection such that the force required to disassemble the first and second components increases

Description: The present invention relates to methods of assembling a door latch mounting plate (a first component) and a latch housing (a second component), and in particular the method of assembling a latch housing onto a door latch mounting plate of a vehicle. Various known methods of attaching two components together are by the use of separate fixings such as screws, nuts and bolts, separate clips and the like. Alternatively gluing can be used. However, all these methods require components or material (glue) in additional to the first and second components to be connected together. FR2773580 shows a vehicle door latch which utilises hooks and resilient clips as a securing method. An object of the present invention is to provide a cheap method of connecting a door latch mounting plate and a latch housing together. Thus according to the present invention there is provided a method of assembly of a first and second component as defined in the accompanying independent claim. The invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a isometric view of a first and second component to be connected together according to the present invention: Figure 2 is a isometric view of a second embodiment of a first and second component to be connected together according to the present invention: Figure 3 is a view taken in the direction of arrow A of the first and second component of figure 2 in an assembled condition. With reference to figure 1 there is a shown a first component 10 and a second component 12. First component 10 is made of a rigid material, in this case steel, and includes a projection 14 in the form of a barb having a ramp surface 16 and a retention surface 18. First component 10 further includes an abutment surface 20. It should be noted that the barb 14 and abutment surface 20 face in opposite directions. Second component 12 is made of a plastics material and includes a plastics engagement surface 22 having a ramp portion 24. The second component 12 further includes a further abutment surface 26. It should be noted that further abutment surfaces 26 faces plastics engagement surface 22 and ramp portion 24 and defines a recess 25. The components are assembled together by moving the first and second components in the direction of arrows F relative to each other. It should be noted that the distance E between the upper edge 20A of abutment surface 20 and the upper edge 16A of ramp surface 16 is less than the distance D between the lower edge 26A of further abutment surface 26 and the lower edge 24A of ramp portion 24. Thus initial entry of the first component 10 into the recess 25 is not restricted and furthermore is guided by ramp surface 16 in engagement with ramp portion 24. It should be noted that the distance B between the plastics engagement surface 22 and the further abutment surface 26, is less than the distance C between the abutment surface 20 and barb edge 14A. Thus progressive engagement between the first and second components causes the plastics engagement surface to plastically deform around the relatively rigid barb 14 since the distances B and C provide for an interference fit between the first and second components. Once the first and second components are fully engaged, in this case wherein top surface 28 of the first component lies flush with surface 30 of the second component, the assembly is left to stand for a predetermined time, typically 24 hours. During this predetermined time period the plastics material of the plastics engagement surface in the vicinity of the barb edge 14A is under a stressed condition and tends to relax and creep away from barb edge 14A. Some material will creep along the ramp surface 16 and other material will creep behind the retention surface 18. In particular that material that creeps behind the retention surface 18 tends to increase the force required to disengage components in the direction of arrows G. With reference to figures 2 and 3 there is shown further first and second components 110 and 112, having features labelled 100 greater than those features which perform the same function on first and second components 10 and 12. In this case the abutment surface 120 is in the form of a barb 140 which faces barb 114. Barbs 140 and 114 define a recess 142. Furthermore the second component includes a boss 144 which includes a plastics engagement surface 122 which faces away from the further abutment surface 126 also included on the boss 144. In this case the first component 110 is a steel mounting plate of a door latch and the second component 112 is a plastics housing of a door latch. First component 110 is made from sheet metal having a first surface 146 and a second surface 148. In this case tabs 150 and 152 are bent upwardly and the edges of tabs 150 and 152 provide for barbs 114 and 140. In particular it can be seen that barb 114 lies in the plane defined by tab 150 and barb 140 lies in the plane defined by tab 152. Furthermore the planes defined by tabs and 150 and 152 are coincident. During assembly of the first and second components, the boss 144 applies a separating force to the tabs 150 and 152. However, the tabs remain substantially fixed relative to the main body portion 110A of component 110 by virtue of the thickness T of the sheet metal material and by virtue of the width W of the tabs. Thus tabs 150 and 152 are substantially rigid and substantially do not act in a resilient manner. In particular by providing the barbs in the plane of the tabs this provides for a particular rigid arrangement. Consideration of figure 3 shows the first component 110 and the second component 112 in a fully assembled condition and progressively, over time, plastics material proximal barbs 114 and 140 creeps in the direction of arrows H along the ramp surfaces of barbs 114 and 140, and also creeps in the direction of arrows J behind the retention surfaces of barbs 114 and 140. It can be seen that it is that material that creeps in the direction of arrows J that effectively increases the interference fit between the first and second components and therefore increases the force required to separate the components in the direction of arrows G. The applicant is the first to realise that this progressive creeping with time of the plastics material can be utilised to increase a retention force of a door latch mounting plate and a latch housing. Thus by providing a suitable time period wherein this creep can take place, when the the door latch mounting plate and the latch housing are subsequently used and subjected to pull away forces, they will remain attached when subject to higher pull away forces.

Claims: A method of assembly of a first and second component (10, 12; 110, 112) including the steps of providing the first component in the form of a door latch mounting plate, providing the second component in the form of a latch housing characterised in that the method includes the steps of providing the first component with a projection (14; 114), providing the second component with a plastics engagement surface (22; 122), assembling the first and second components such that the projection is held substantially rigid relative to the first component and the plastics engagement surface is plastically deformed around the projection then allowing the plastics engagement surface to further creep around the projection such that the force required to disassemble the first and second components increases. A method as defined in Claim 1 in which the projection is held substantially rigid relative to the first component by virtue of the strength of the first component and projection. A method as defined in Claim 1 in which the projection is held substantially rigid relative to the first component by virtue of an abutment surface (20; 120) associated with the projection co-operating with a further abutment surface (26; 126) associated with the plastics engagement surface. A method as defined in Claim 3 in which the abutment surface (20; 120) and further abutment surfaces (26; 126) acts during assembly to provide an engagement force between the projection and the plastics engagement surface. A method as defined in claim 3 or 4 in which the abutment surface (120) faces towards the projection (114). A method as defined in any Claim 3 or 4 or 5 in which the further abutment surface (126) faces away from the plastics engagement surface (122). A method as defined in Claim 3 or 4 in which the abutment surface (20) faces away from the projection (14). A method as defined in Claim 3 or 4 or 7 in which the further abutment surfaces (26) faces towards the plastics engagement surface (22). A method as defined in any one of Claims 3 to 8 in which the abutment surface includes a further projection (140). A method as defined in Claim 9 in which the further projection is a barb (140) having a ramp surface and a retention surface. A method as defined in any preceding claim including the steps of providing the first component with a planar portion having first and second faces defining a plane and an edge, profiling the edge to provide the projection (14; 114) in the plane. A method as defined in Claim 3 and 11 further including the step of profiling an edge of the planar portion to provide the further abutment. A method as defined in any preceding claim in which the projection is a barb having ramp surface (16; 116) and a retention surface (18; 118). A method as defined in Claim 13 in which the barb is relatively sharp. A method as defined in any preceding claim further including the step of using the assembled components, in use there being a disengagement force applied. A method as defined in any preceding claim in which the door latch mounting plate is made from sheet metal. A method as defined in Claim 16 when dependent on claim 9 or 10 in which the projection is formed on a tab which is bent from the sheet metal and the further projection is formed on a further tab which is bent from the sheet metal. A method as defined in Claim 17 in which the tab and further tab define a tab plane and the projection is in the tab plane.

Inventors: SPURR NIGEL, SPURR, NIGEL
Applicants: ARVINMERITOR LIGHT VEHICLE SYS, ARVINMERITOR LIGHT VEHICLE SYSTEMS (UK) LTD
Application year: 2001
Main classification: F16B4
IPC codes: F16B4