Abstract:
A clip for attaching a component to a mounting surface of a container has a generally tubular body with outwardly extending projections and a component retaining aperture. The clip and the container are formed from similar plastic materials with the container material having the same or lower melt index value. The component is assembled with the clip by insertion through a gap in the clip wall widened under a deflecting force. The clip is placed in contact with the mounting surface while the container has latent heat to melt at least one of the contacting projections and form a bond area attaching the component/clip assembly to the mounting surface of the container.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to fasteners for plastic containers and, in particular, to a clip for attaching a component to a mounting surface of a plastic material container. 
     Plastic containers, such as automobile fuel tanks, are well known. Fuel tanks are part of the fuel system for the automobile and used for storing the liquid fuel, such as gasoline or diesel fuel, for the automobile&#39;s internal combustion engine. Fuel tanks typically include components disposed therein including fuel delivery modules, fuel pumps, fuel filters, and various other components of the fuel system. 
     Most prior art plastic fuel tanks are constructed of plastic materials such as high density polyethylene (HDPE) and low density polyethylene (LDPE), among others, utilizing a blow-molding process. In the blow-molding process, the plastic material is extruded into a mold and then pressurized against the sides of the mold, forming the tank as a single, unitary body. These prior art plastic fuel tanks typically include a plurality of components such as wiring harnesses, vapor lines, and the like, attached to the exterior surface thereof. Traditionally, these components are attached to the blow-molded fuel tanks with clips using a costly and time-consuming process known in the art as a “hot plate welding” process. The hot plate welding process involves heating a surface of the clip, heating a portion of the exterior surface of the tank, and then placing the respective heated areas of the clip and tank in contact with one another to form a bond. After the clips are hot plate welded to the exterior surface of the tank, the components are then placed in the clips. Other alternatives to the hot plate welding process include the use of a spin welding process, an ultrasonic welding processes, or by creating a die lock in the molded tank. Creating a die lock, however, is generally difficult and occasionally impossible due to geometry constraints. In addition, the clips of the prior art are orientation specific in that the clips have a specific mounting surface that must be oriented towards the exterior surface of the container to which it is to be attached in order to be attached correctly. Any deviation in the mounting orientation of the clips can result in an inadequate bond. 
     Moreover, regulatory changes affecting evaporative emissions have driven fuel tank designs to internalize the components that traditionally have been welded to the outside surface of plastic fuel tanks, such as valves and vapor lines because these each of these external component connections are a potential evaporative emissions source. Hot weld points that penetrate the tank permeation barrier, in particular, are noted sources of evaporative loss. Attaching components to the interior surface of blow-molded tanks is difficult without first creating a large opening in the tank and then placing the components in the interior of the tank. The large opening is an additional evaporative emissions source, which defeats the purpose of minimizing evaporative emissions from the tank. Components are also placed inside tanks on rods, which results in a hole in the side of the tank that must be sealed. More recently, fuel tanks have been manufactured with a process known as thermoforming, which provides for additional configurations for fuel tanks because the tank is formed in two halves having opposing planar attachment faces that are then joined together. Because the tank is formed in halves, this presents an opportunity to locate components inside the fuel tank that previously have been located on the exterior of the tank. 
     It is desirable to attach components to a surface of a plastic container without the use of hot plate welding in order to reduce the overall cost of the containers. It is also desirable to attach components to the interior surface of plastic containers without regard to the orientation of the clips. It is desirable to reduce the amount of evaporative emissions emanating from fuel tanks. 
     SUMMARY OF THE INVENTION 
     The present invention concerns a clip for attaching a component to a mounting surface constructed of a plastic material. The clip includes a preferably tubular clip body of any suitable shape having a central aperture defined by an interior surface and an exterior surface. A plurality of projections are formed on and extend radially outwardly from the exterior surface. The projections can be in the shape of barbs, ridges, teeth, dimples, small hemispheres, or the like. A gap extends through a wall of the clip body between the interior and exterior surfaces and has a width insufficient to pass the component. In one embodiment, the gap extends between opposite ends of the clip body generally parallel to a longitudinal axis. Alternatively, the gap is helical in shape extending around the clip body between the opposite ends. Regardless of its shape, the clip body wall can be deflected outwardly to widen the gap for receiving the component in the central aperture. When the deflecting force is removed, the clip returns to the original shape and the component is securely retained. 
     The clip body is preferably constructed of high density polyethylene (HDPE), low density polyethylene (LDPE), or the like. The clip body is adapted to receive a component, such as a fuel vapor line or wiring harness, in the central aperture and to adhere to a mounting surface, such as the interior or the exterior surface of a thermoformed fuel tank, without the aid of unique assembly fixtures or pre-heating of the clip. 
     The clip body adheres to the mounting surface because when placed against the mounting surface, such as during the thermoforming process of a plastic fuel tank, the contacting projections are melted by the latent heat of the recently formed mounting surface. The mounting surface is preferably constructed of HDPE or LDPE material having a melt index slightly lower than the melt index of HDPE or LDPE material of the clip body. If the melt index is lower, the polymer is more viscous. More importantly, the mounting surface has a much greater thermal mass in comparison to the clip body. Because of the large difference in the respective thermal masses of the mounting surface and the clip body and because of the difference in the melt indexes of the mounting surface and the clip body, the latent thermal mass of the plastic material of the mounting surface transfers enough heat into the clip fins to melt the clip fins to create a bond between the mounting surface and the clip body. Thus, the clip welds immediately to the mounting surface when the projections contact the mounting surface. The wall thickness of the clip body acts advantageously as an insulating barrier, stopping the weld process when the projections have melted to the weld area. 
     The present invention is adaptable to be installed on the component during the component manufacturing process, minimizing the burden when the component is later assembled with the mounting surface. The clip is advantageously not orientation-specific in that the clip may be welded in 360-degree orientation around the longitudinal axis of the clip body with no change in function, minimizing the need for any additional processing of the clip once it is placed on the component. 
     The clip is preferably manufactured by an injection molding process. Alternatively, this clip may be formed in a simple multi-cavity open-close mold having minimal dimensional requirements. The clip also may be manufactured using a continuous extrusion process, where the axial shape of the clip is extruded, then cut to length and slit along a helical angle, the helical slit being such as to increase the likelihood of a weld bond across the clip opening. 
     The present invention recognizes that thermoforming and processes that support internalization of components allow the opportunity to create a new type of clip that advantageously does not require specialized tools or processes for installation. The clip according to the present invention is simply pressed against a mounting surface having a latent heat and it automatically welds to the mounting surface. The present invention recognizes that by utilizing the latent heat at a mounting surface of a thermoformed plastic material, a clip formed of a similar plastic material can be welded to the mounting surface by utilizing different thermal masses. 
     The clip of the present invention may be used advantageously with HDPE and LDPE fuel tanks. In addition, those skilled in the art will appreciate that this type of clip may be used for attaching many types and shapes of components to various mounting surfaces constructed of plastic or similar materials. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
     FIG. 1 is a plan view of a clip in accordance with the present invention; 
     FIG. 2 is a plan view of the clip in FIG. 1 shown with a component disposed therein; 
     FIG. 3 a  is an elevation view of the clip shown in FIG. 1; 
     FIG. 3 b  is an elevation view of an alternative embodiment of the clip according to the present invention; 
     FIG. 4 is an exploded elevation view of an assembly including a plastic container and the clip of FIG. 1 attached to a component; and 
     FIG. 5 is a cross-sectional view of the clip and component of FIG. 2 shown welded to a mounting surface. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, a clip for attaching a component to a plastic material mounting surface is indicated generally at  10 . The clip  10  includes a generally tubular clip body  12  having a wall with an interior surface  14  and an exterior surface  16 . The clip body  12  is preferably constructed of a plastic material such as high density polyethylene (HDPE), low density polyethylene (LDPE), or a similar material having a first predetermined melt index value. Although shown as being circular in cross section, the tubular clip body  12  can be of any suitable cross-sectional shape adaptable to receive a component and be attached to a mounting surface, outlined in more detail below. 
     A plurality of generally tooth-shaped projections  18  extend radially outwardly from the exterior surface  16 . The projections  18  preferably extend axially along the entire length of the exterior surface  16 , and are spaced about the entire circumference of the exterior surface  16 . A gap  20  extends through the wall of the clip body  12  and is bounded by a pair of edges  22  and  24  of the wall. The gap  20  allows the clip body  12  to resiliently deform in an opening direction indicated by arrows  26  when the clip  10  is being attached to a component, outlined in more detail below. The interior surface  14  defines a generally circular central aperture  28  therein for receiving a component, discussed in more detail below. 
     Referring now to FIG. 2, the clip  10  is shown with a component  30  disposed in the aperture  28 . An exterior surface  32  of the component  30  is in close contact with the interior surface  14  of the clip body  12 . The component  30  is preferably a wiring harness, a vapor line, a conduit, or a similar device having a cross-sectional shape that corresponds to the aperture  28 . 
     During assembly of the clip  10  to the component  30 , force is exerted at the edges  22  and  24  to force them in the opening direction indicated by the arrows  26 , deforming the clip body  12  as seen in FIG.  1 . After the component  30  is disposed within the aperture  28 , the force is released and the clip body  12  returns to its original profile, best seen in FIG. 2, the edges  22  and  24  moving in a closing direction indicated by arrows  34 , best seen in FIG.  1 . 
     Referring now to FIG. 3 a , the clip  10  is shown in side elevation view to demonstrate that the projections  18  on the exterior surface  16  of the clip body  12  extend along the entire axial length of the exterior surface  16 . The gap  20  extends in a straight line along the longitudinal axis of the exterior surface  16 . 
     Referring now to FIG. 3 b , an alternative embodiment of the clip according to the present invention is indicated at  10 ′. In this alternative embodiment, a gap  20 ′ extends in a helical shape along the exterior surface  16 ′. The helical gap  20 ′ advantageously allows the clip  10 ′ to retain a component, such as the component  30  of FIG. 2, increasing the likelihood of a weld bond across the gap  20 ′ and reducing the possibility of the component  30  falling out of the gap  20 ′ when the clip assembly is mounted to a mounting surface, discussed in more detail below. 
     Referring now to FIG. 4, two clips  10  are shown disposed on the elongated component  30 , such as a vapor line for an automotive fuel system, forming a component/clip assembly  36 . However, depending upon the size and shape of the component  30 , the component/clip assembly  36  may have only one clip  10  or more than two of the clips. A plastic container, such as an automotive fuel tank, is indicated generally at  38 . The tank  38  is preferably constructed of HDPE, LDPE, or a similar material having a predetermined second melt index that is lower than the first melt index of the HDPE or LDPE material of the clip body  12 . The tank  38  includes an upper tank portion  40  and a lower tank portion  42 . A wall of the upper portion  40  has an exterior surface  44  with a downwardly facing attachment surface  46  defining a wall edge. A wall of the lower portion  42  has an exterior surface  48  with an upwardly facing attachment surface  50  defining a wall edge. 
     Each tank portion  40  and  42  is formed separately, preferably by a thermoforming process. After the tank portions  40  and  42  are formed by the thermoforming process but prior to joining the tank portions  40  and  42 , the component  30  is placed in the aperture  28  of at least one of the clips  10 , forming the component/clip assembly  36 . After being formed by the thermoforming process, the tank portions  40  and  42  are formed to the shape of the tank, but remain at a relatively high temperature having a thermal mass greater than the thermal mass of the projections  18  on the clip body  12 . Preferably, the material of the tank  38  and the material of the clip body  12  are similar, such as the same grade of HDPE or LDPE, but the material of the tank  38  has a lower melt index than the material of the clip body  12 . The component/clip assembly  36  is placed in contact with a high temperature interior surface  52  of the upper tank portion  40  as shown in FIG. 5, or a high temperature interior surface of the lower tank portion  42  (not shown). 
     The ones of the projections  18  on the exterior surface  16  of the clip body  12  that make contact with the high temperature interior surface  52  of the upper tank portion  40  melt, forming a bond area  54  between the clip body  12  and the interior surface  52 . The interior surface  52  is preferably in a solid state, but at a relatively high temperature at or above the melting point of the material of the clip body  12 . Alternatively, the high temperature interior surface  52  is in a still molten state after the thermoforming process, advantageously aiding in forming the bond area  54  between the clip body  12  and the interior surface  52 . 
     Alternatively, the clip  12  is placed in contact with one of the exterior surfaces  44  and  48 , forming a bond area between the clip body  12  and the exterior surface of the tank  38 . The clip  10  is now securely welded to the wall of the tank  38 . The thermoforming process leaves the walls of the tank portions  40  and  42  in a solid state, but at a relatively high temperature at or above the melting point of the material of the clip body  12 . The projections  18  contacting the tank wall surface melt to form the bond or weld area  54 , securely affixing the component/clip assembly  36  to the tank  38 . The thickness of the clip wall between the surfaces  14  and  16  acts advantageously as an insulating barrier and creates a dramatic increase in surface contact, reducing the temperature and stopping the weld process, when the projections  18  have melted into the weld area  54 . 
     Because the projections  18  extend from the entire circumference of the exterior surface  16 , the orientation of the exterior surface  16  of the clip body  10  with respect to the interior surface  52  is immaterial and any of the projections  18  may be melted to form the weld area  54 . However, if the gap  20  happens to face the surface  52 , the gap will be welded closed. With the alternate embodiment clip  10 ′, some portion of the helical gap  20 ′ will always face the surface  52  and will be welded closed. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope. For example, the projections  18  are shown as generally tooth-shaped but those skilled in the art will realize that the projections could be barbs, ridges, teeth, dimples, small hemispheres, or the like.