Abstract:
A method of assembly of a first and second component comprising the steps of providing the first component with a projection providing a second component with a plastics engagement surface 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:
[0001]    This application claims priority to United Kingdom (GB) patent publication number 0011460.3 filed on May 13, 2000.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to methods of assembling a first component and a second component, and in particular the method of assembling a latch housing onto a door latch mounting plate of a vehicle.  
           [0003]    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.  
           [0004]    However, all these methods require components or material (glue) in addition to the first and second components to be connected together.  
         SUMMARY OF THE INVENTION  
         [0005]    An object of the present invention is to provide a cheap method of connecting two components together.  
           [0006]    Thus according to the present invention there is provided a method of assembly of a first and second component comprising the steps of providing the first component with a projection, providing the second component with a plastics engagement surface, 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.  
           [0007]    According to a further aspect of the present invention there is provided a method of assembling a first and second component, the method comprising the steps of providing the first component with a projection and an associated abutment surface, providing the second component with a plastics engagement surface and an associated further abutment surface, assembling the first and second component such that the plastics engagement surface is plastically deformed around the projection, then maintaining the engagement between the plastics engagement surface and the projection by virtue of co-operation between the abutment surface and further abutment surface such that the plastics engagement surface can further creep around the projection such that the force required to disassemble the first and second components increases.  
           [0008]    According to a further aspect of the present invention there is provided a method of assembling a first and second component comprising 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 a projection in the plane, providing the second component with a plastics engagement surface, assembling the first and second components such that 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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The invention will now be described, by way of example only, with reference to the accompanying drawings in which;  
         [0010]    [0010]FIG. 1 is an isometric view of a first and second component to be connected together according to the present invention:  
         [0011]    [0011]FIG. 2 is an isometric view of a second embodiment of a first and second component to be connected together according to the present invention:  
         [0012]    [0012]FIG. 3 is a view taken in the direction of arrow A of the first and second component of FIG. 2 in an assembled condition. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    With reference to FIG. 1 there is 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 .  
         [0014]    It should be noted that the barb  14  and abutment surface  20  face in opposite directions.  
         [0015]    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 .  
         [0016]    It should be noted that further abutment surfaces  26  faces plastics engagement surface  22  and ramp portion  24  and defines a recess  25 .  
         [0017]    The components are assembled together by moving the first and second components in the direction of arrows F relative to each other.  
         [0018]    It should be noted that the distance E between the upper edge  20 A of abutment surface  20  and the upper edge  16 A of ramp surface  16  is less than the distance D between the lower edge  26 A of further abutment surface  26  and the lower edge  24 A 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 .  
         [0019]    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  14 A. 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.  
         [0020]    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  14 A is under a stressed condition and tends to relax and creep away from barb edge  14 A. 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.  
         [0021]    With reference to FIGS. 2 and 3 there is shown further first and second components  110  and  112 , having features labeled  100  greater than those features which perform the same function on first and second components  10  and  12 .  
         [0022]    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 .  
         [0023]    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 .  
         [0024]    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.  
         [0025]    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.  
         [0026]    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  110 A 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.  
         [0027]    Consideration of FIG. 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 .  
         [0028]    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.  
         [0029]    The applicant is the first to realize that this progressive creeping with time of the plastics material can be utilized to increase a retention force of two components. Thus by providing a suitable time period wherein this creep can take place, when the two components are subsequently used and subjected to pull away forces, the components will remain attached when subject to higher pull away forces.  
         [0030]    The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner, and should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications are within the scope of this invention. It is understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.