The present invention relates to plugs for holes and in particular to plugs that may be used to block holes in the components of vehicles, ships, boats and aircraft during and after assembly and treatment.

During the manufacture of vehicles, ships, boats and aircraft components are used which may contain holes. Holes may also be provided in components, particularly structural components to enable assembly, to allow for drainage of fluids or allow for passage of cabling and the like. In many instances it is necessary to seal and/or close the holes after assembly to reduce the likelihood of subsequent corrosion. This is because in some instances the holes are not used in assembly, thus providing a location for potential corrosion. In other instances although material, such as cabling or tubing, passes through the holes, the hole is not filled and the rim of the hole remains a location for potential corrosion, this may be the case when tubing is used to contain electrical wiring or when other tubes such as drainage tubes are present.

Currently the holes are either left open or are closed by forcing mastic into the holes, generally by hand. In the production of automobiles the mastic is generally applied after the automobile has been subject to the e-coat anticorrosion process. In the e- coat anticorrosion process the metal frame of the vehicle is passed through a bath of anticorrosion fluid and the anticorrosion material is deposited on the metal parts of the vehicle by an electrolysis process in which the metal frame of the vehicle is used as one of the electrodes. After the e-coat process the vehicle is baked to dry and consolidate the anticorrosion coating. Subsequently the vehicle after assembly will be painted. It is important that the holes be filled prior to painting to minimise contamination due to the paint.

The use of manually applied mastic to fill the holes has the disadvantage that in order to ensure that the holes are sealed one generally uses an excess of the mastic. This is expensive and can also result in some mastic passing through the holes leading to contamination and extra weight in the vehicle, ship, boat or aircraft. There is also the possibility that overtime the mastic will degrade and/or fall away from the hole providing a site for potential corrosion.

Furthermore, during the e-coat process, the flowing anticorrosion fluid must go in the cavities created by the metal parts of the vehicle for coating the internal surfaces of these cavities with the anticorrosion material. Furthermore, in a second step, the anticorrosion fluid must leave the cavity, when the vehicle is removed from the bath of anticorrosion material. In addition, the position of holes on the metal parts is important for the electrification of the vehicle during the electrolysis process. The closed metal parts can create an electric barrier and therefore the intensity of the electrolysis process can be reduced. As a result, less anticorrosion material is deposited on the metal parts of the vehicle causing sites for potential corrosion.

In one current technique the holes are filled at the trim shop or the paint shop during the vehicle manufacture after the e-coat process. In this process the plugs are manually placed and the plugs comprise a carrier made of a polymeric material or a metal surrounded with a hotmelt material. The hotmelt material flows and adheres to the metal parts around the holes during a low temperature heating process. When cooled, the hotmelt material seals the holes. Such plugs are described in the United States Patent 5,505,324.

The plugs placed at the trim shop or the paint shop, have the disadvantage that it is difficult and sometimes impossible to reach certain holes and thus they cannot be plugged in this way. Furthermore, they cannot be placed during the assembly of the metal parts of the vehicle before the e-coat process because they would not allow the anticorrosion fluid to pass through the holes leaving uncoated areas as a potential source of corrosion. Another disadvantage is the requirement for additional operators at the trim shop or the paint shop for placing the plugs in the holes which increases the cost of the vehicle manufacture. Accordingly, the plugs can be placed only in holes accessible to the operator. This means that the holes not accessible are not filled, for instance the holes present on the internal metal parts cannot be closed. In some cases, in order to avoid this situation, the design of metal parts and the position of the holes are changed so that the holes are accessible to the operator. Consequently, the position of such holes in metal parts is not optimized for the flow of anticorrosion material when the vehicle will go in and go out of the bath and the electrolysis process can be disturbed causing some sites for potential corrosion. WO 2003 / 098080 describes conical plugs which are foamable and may be placed in incompletely filled holes in structures to prevent corrosion over time; preferably the plugs are made of a foamable material which can be foamed in the e-coat oven used in automobile manufacture. This kind of plug can fill or incompletely fill holes in the vehicle subframe, especially holes not accessible at the trim shop or the paint shop. However these plugs completely encase the circumference of the hole before the e- coat process disturbing the electrolysis process and the flow of anticorrosion material.

United States Patent 5,829,482 describes plugs formed of a foamable material which can be foamed during the baking of the anticorrosion coating. This plug is retained in the hole by a plurality of expanding slots. The plug has also a central aperture through the foamable material which allows the passage of an anticorrosion material for instance and which is closable by the application of heat to foam the foamable material. The design and the production of such plugs are costly. In addition, these plugs can reduce significantly the opening of the hole due to the large volume of plug needed at the circumference of the central aperture and for providing and securing the expanding slots.

United States Patent Application 2008/0073923 describes another technique for filling holes in automobile structures. This solution is to provide foam fillers which make it possible to use the holes after provision of the foam fillers and which prevents the foam from swelling out from the holes when they are filled. The plug comprises a laminar shape containing a hole the overlays the hole to be closed which is closed by the foaming of the foamable material which may be accomplished in the e-coat bake oven. However, this solution results in complete closure of the cavity in the vehicle frame at a position near the hole due to the expansion as is shown in Figure 5b of the application. This possibility can be a disadvantage for the vehicle manufacturer if the cavity to be used for installing cables for example. The plug is also difficult to make.

The present invention provides a plug that overcomes these problems.

The present invention therefore provides a plug having a cruciform cross section and made from an expandable material.

By a cruciform cross section is meant that the plug is provided with a plurality of extensions (or arms) extending from a central portion. The extensions being such that they will touch the internal circumference of the hole to hold the plug in place. In this way the area of the circumference of the hole touching the plug prior to foaming is minimised to the area of the ends of the extensions. The area of the circumference of the hole that is coated can therefore be increased in certain circumstances so that the potential for corrosion is decreased. Furthermore, the spaces between the extensions allow for ready flow of the anticorrosion fluid without displacement of the plug. The expandable material is usually a foamable material.

In a preferred embodiment the plug is made from a flexible and expandable material. The plugs are simple to make and can be integrally moulded from the expandable material. Alternatively the plugs may be made by extrusion and cutting of the extrudate.

In a further embodiment the plug is laminar and comprises a core as a carrier for the expandable material. The core can be co-extruded with expandable material, alternatively it can be extruded and then overmoulded with the expandable material, or injected in a two shot moulding process. Alternatively, the plug can be produced with the patented process named Exjection ©. The core can provide strength to the plug and can also reduce the amount of foamable material that is required which can have economic benefits as typically the foamable material is more expensive that the core material.

In another embodiment, the plug can be conical having a base of greater cross section than the end.

The size of the plug may be chosen according to the size of the hole to be filled. However in the manufacture of automobiles the holes produced in the vehicle frame may be any shape, if they are circular they are typically 5 to 50 millimetres more typically 10 to 30 millimetres in diameter and accordingly when a conical plug is used at least part of the conical section will pass through a hole of this size. In this embodiment the base of the plug is preferably of a size that it will not pass through the hole. In this way the plug is prevented from passing through the hole. In some instances the plug may pass entirely into the hole. The plug may also be provided with an extension protruding from the base at the side opposite from the conical section to aid location in the hole and enable verification that a plug has been placed in the hole. This is particularly useful if the entire plug passes into the hole.

The plugs can have various shapes. The cruciform cross-section can form a 3 legged star, a cross, or a five or more legs star. The preferred embodiment is a crossed shape having 4 extensions and a central body portion. For rectangular and oblong holes, the central body can be elongated along the longer direction of section of the oblong hole. The plug can include small cuts on the extensions for creating and/or retaining mechanical devices. The cuts create a shape where the hem of the hole can be placed. The cuts can have various shapes. The path designed by the cuts around the plugs can be an ellipsoidal, as a screw for instance. This allows the plug to be mechanically fixed when the extensions are made of flexible material, the plugs can be adapted to various dimensions of the hems, i.e. the thickness of a panel.

The use of the plug will now be described in relation to automobile manufacture wherein the automobile is subjected to the e-coat anticorrosion process. The vehicle sub frame is assembled in the normal manner and then plugs according to the present invention are inserted into any unused or incompletely filled holes in the vehicle sub frame. The vehicle sub frame is then subjected to the e-coat process. Following the e-coat the sub frame is baked in a curing oven. The expandable material from which the plug is made is preferably selected so that it expands under the conditions employed in the curing oven. The expandable material therefore foams in the curing oven and fills the hole to effect a seal, the expansion is preferably such that the foamed material encapsulates the rim of the hole. Where the hole has little depth the expandable material may foam so that it encapsulates both sides of the hole so that the entire surface of the hole is provided with a protective layer. Where the hole is at the end of an elongated tube the expanded material may encapsulate only one rim. Subsequently, if desired, a sealant, such as mastic, may be applied to the surface of the expanded plug, which serves to retain the sealant and prevent it passing through the hole to ensure effective use of the sealant. The plug is made of an expandable material so that it will expand to fill the hole. The material may also be such that, on expansion, it will bond to the interior wall of the structure. Accordingly, the plug may be made from an expandable adhesive material, which can be activated to expand (typically foam) and optionally to act as an adhesive. Accordingly the expandable adhesive must expand at the desired temperature and in a preferred embodiment be sufficiently adhesive to firmly bond to the component in which the hole is formed.

Prior to activation, the material or materials from which the plug is made is preferably dry and not tacky to the touch, since this facilitates shipping and handling and prevents contamination. The plug is preferably made of a flexible material and thermoplastic materials such as ethylene polymers and copolymers used as raw materials for acoustic baffles are preferred, preferred materials are copolymers of ethylene and vinyl acetate or copolymers of ethylene and acrylate and/or methacrylate esters..

The foamable material may also be chosen to provide some rigidity and reinforcement to the overall structure. In this instance examples of other preferred foamable materials include foamable epoxy-base resins and examples of such materials are the products L4300, L7102, L2806, L2810, L2820, L4161 , L7220, L5234, L5235 and L5236, which are commercially available from L & L Products of Rome Michigan USA or L & L Products Europe SAS and other products such as Sikabaffle©300 from SIKA. The material should be chosen according to the rate of expansion and foam densities required. It is further preferred that the material expand at the temperatures experienced in the e-coat baking oven, typically 120°C to 205°C more typically 150°C to 170°C.

The plug may be made extrusion, stamping and die cutting or by injection moulding providing that the temperatures used in fabrication are below the temperatures at which the expandable material will foam. Where the plug comprises a foamable material provided on a carrier the carrier may be of any suitable material. For example, it may be of metal, plastic, woven or non woven fabric. In a preferred embodiment the carrier is a film or foil and the foamable material may be extruded onto the moving film or foil at a temperature below that at which it foams. The extrudate can then be cut to produce plugs of the desired size.

The plugs can be positioned manually in the holes or with the help of a tool or robot.

Examples of uses of the plugs include the filling of holes formed in the A, B and/or C pillars or the rails in the frames or the floor or the chassis and engine supports of vehicles, the holes being formed for passage of cabling or tubing or for various attachments, or for the draining a fluid during the car manufacturing. Alternatively the plugs may be used to fill the ends of tubing such as the tubing used to reinforce vehicle doors against side or front impact.

The invention is illustrated by the accompanying drawings in which: Figure 1 shows cross sections through several different plugs according to the invention.

Figure 2 shows a rectangular cruciform structure provided with a carrier material.

Figure 3 shows a cross section through one extension of a conical plug according to the invention.

Figure 4 shows how locators can be formed in the extensions of plugs according to the invention.

Figure 5 shows how a plug can be inserted manually into a hole in a panel.

Figure 6 is a schematic illustration of the manufacture of plugs according to the invention.

Figures 1a to 1h show different cross sections of plugs according to the invention. In each instance the plug comprises extensions (1) projecting from a central portion (2). The embodiments illustrated in Figures 1a to 1d and 1 h are useful for filling circular holes and the embodiment shown in Figures 1e to 1g are useful for filling rectangular or oblong holes.

Figures 2a to 2d illustrate a cross shaped plug, Figure 2a including a carrier (3) and a foamable material (4). The carrier may be a plastic or metal foil. Figure 2b shows a carrier containing a fibrous core which again may be of metal or plastic although it could be of glass. In Figure 2c the plug is strengthened by the provision of glass fibre (5) within the foamable material (4). The plug in Figure 2d is just of the foamable material. The carriers may be used in any of the plug shapes illustrated in Figure 1.

Figure 3 is a cross section through one of the extensions (1) having a conical end (2).

Figure 4 shows various cross sections through the extension (1) and how attachment means can be provided in the extensions. In Figure 4a the attachment means are cuts (6); in Figure 4b it is a hook (7); in Figure 4c it is a single cut (8); in Figure 4d it is a series of ellipsoidal cuts (9) and in Figure 4e it is a circumferential arrow cut (10). Figure 5 shows a hand tool (11) which can be used to inject a plug (12) into a hole (13) in a panel (14).

Figure 6 shows an extrusion process for the production of plugs according to this invention and which are formed of a foamable material on a carrier. In this process a carrier material (15) is fed from an extruder having an extrusion die of the shape required for the plug. A foamable material (16) is extruded onto and around the carrier, the extrudate cools so it is not tacky and is compressed by the rotating wheel (17). It then passes to a die cutting device (18) where the extrudate is cut into the individual plugs (19).

The plugs of the present invention are more easily applied than the traditional application of plugs in the automobile trim shop. The plugs can readily be applied in any location so providing greater design flexibility for a panel designer who can provide as many holes as required and they can be provided in the optimum locations. The use of the plugs of the invention enables them to be applied in a body shop of an assembly system as opposed to the trim shop. In addition the plugs of the invention are economic in that they can cover more whole area for a given amount of product.