Hot and Cool Air Bonding Apparatus

1. Technical Field

This invention relates to bonding apparatuses and techniques and, more particularly, to an apparatus and method for bonding automotive fiber reinforced plastic (FRP) members together.

2. Discussion of the Related Art

Various techniques are currently employed for bonding fiber reinforced plastic (FRP) members together for use in automotive body applications such as, but not limited to, hoods, doors, bumpers, and the like. There has been an outgrowth in the number of apparatuses and methods available for producing bonded FRP assemblies due to the growing trend in the automotive industry to replace heavier metal components with plastic assemblies. These assemblies are typically bonded by heating an adhesive placed between the mating surfaces of two FRP members to a temperature exceeding its curing temperature.

FIGS. 1-3 illustrate in simplified manners, examples of well known bonding techniques that use heat to bond an FRP assembly consisting of FRP members 10 and 12 with adhesive 14 placed therebetween. FIG. 1 illustrates dielectric heating apparatus 16 that produces radio frequency electrostatic fields between electrode 18 and block member 20. The electrostatic fields quickly heat adhesive 14 to a temperature above its curing temperature to thereby bond FRP members 10 and 12. Commonly assigned U.S. Pat. No. 4,941,936 to Wilkinson et al. and U.S. Pat. No. 4,941,937 to Iseler et al. disclose examples of dielectric heating techniques which are hereby incorporated herein by reference. Dielectric heating techniques have the advantage of reducing cycle times along with the accompanying disadvantage of heating an FRP assembly in a manner that is difficult to control and maintain.

FIG. 2 illustrates bonding apparatus 22 that utilizes cartridge heaters 28 for heating metal block members 24 and 26. Block members 24 and 26 in turn heat the air flowing through air circuits 30, a portion of which, flows through openings 32 for heating adhesive 14 between FRP members 10 and 12. One disadvantage with this type of bonding technique is that it requires a large supply of compressed air to operate efficiently.

FIG. 3 illustrates bonding apparatus 34 that utilizes heated steam and/or hot water flowing through passages 40 for heating metal block members 36 and 38. Block members 36 and 38 in turn heat adhesive 14 between FRP members 10 and 12. This bonding technique has the disadvantage of requiring a high cycle time when compared to the bonding techniques illustrated in FIGS. 1 and 2.

When bonded FRP assemblies are used in exterior automotive body applications, it is of the utmost importance that the bonding technique employed does not adversely effect the surface qualities of the exterior FRP members and that the technique provides even bonding not withstanding the size of the FRP members.

Thus, it would be desirable to produce a bonding apparatus that improves the surface qualities of a resulting FRP assembly and that provides uniform bonding strength throughout the assembly. Further, it would be desirable to provide a bonding technique that expeditiously adheres a first FRP member to a reinforcement FRP member without affecting surface qualities or bonding strength characteristics.

Pursuant to the present invention, a bonding apparatus and method for expeditiously bonding automotive fiber reinforced plastic (FRP) members is disclosed. The apparatus provides the resulting bonded assembly with uniform bonding characteristics and improved surface qualities. While the present invention will be described in connection with the bonding of FRP members, it will be understood that other plastic materials or even metal may be used.

In accordance with the teachings of one embodiment of this invention, an apparatus is provided for bonding a first member, typically an automotive outer skin member, to a reinforcement member. An uncured adhesive is located on the mating surface of the first member. First and second nest members are provided for receiving and supporting the first member and the reinforcement member in a spaced relationship. Relative movement of the nest members is controlled such that the mating surface of the first member engages a corresponding mating surface of the reinforcement member with the adhesive therebetween. Switchable heating and cooling assemblies first provide pressurized heated air to the nest members that in turn channel the heated air about portions of the outer surfaces of the first member and the reinforcement member. Thereafter, the switchable heating and cooling assemblies provide cool air to the nest members which in turn channel the cool air about the same portions of the outer surfaces of the first member and the reinforcement member. The pressurized heated air heats the adhesive to a temperature exceeding its curing temperature, and the pressurized cool air facilitates the cooling process for the resulting assembly.

In the preferred embodiment, after the pressurized heated air has been provided to the nest members, a bypass chilling system provides pressurized chilled air to the nest members which in turn channel the chilled air about portions of the outer surfaces of the first member and the reinforcement member, thereby decreasing the time required for the resulting assembly to cool.

The various advantages of the present invention will become apparent to those skilled in the art after reading the following specifications and by reference to the drawings in which:

FIG. 1 is a simplified illustration of a prior art bonding apparatus;

FIG. 2 is a simplified illustration of a second prior art bonding apparatus;

FIG. 3 is a simplified illustration of a third prior art bonding apparatus;

FIG. 4 is an exploded perspective view of an assembly comprising an exterior automotive body member and a reinforcement member therefor;

FIG. 5 is a simplified illustration of a quartz heating apparatus;

FIG. 6 is a plan view of the second nest member of the bonding apparatus with the exterior automotive body member removed, in accordance with the present invention;

FIG. 7 is a cross-sectional view of the bonding apparatus of FIG. 8 in the open position, in accordance with the present invention;

FIG. 8 is a partial cutaway perspective view of the bonding apparatus, in accordance with the present invention;

FIG. 8A is an enlargement view of a partial cutaway of the bonding apparatus of FIG. 8, in accordance with the present invention;

FIG. 9 is an enlarged view of a partial cross-sectional view of the bonding apparatus of FIG. 8, in accordance with the present invention; and

FIG. 10 is a simplified air flow diagram of the bonding apparatus of FIG. 8, in accordance with the preferred embodiment of the present invention.

The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention or its application or uses.

The present invention is particularly concerned with bonding reinforced exterior automotive body assemblies such as, but not limited to, hoods, doors, and bumper assemblies. The invention provides an apparatus and expeditious method for bonding a first, typically exterior, fiber reinforced plastic (FRP) member to a second reinforcement member, which is also preferably manufactured of a FRP material although other plastic materials or even metal may be used.

The invention is described in detail below with reference to the manufacture of an automotive hood assembly, however, it will be appreciated by those skilled in the art that the present invention, as defined by the appended claims, is clearly not limited to this particular application. Furthermore, the invention is described with reference to the hood assembly members being formed from FRP materials, however, it will be appreciated by those skilled in the art that the use of other plastic materials or metals is within the scope of the present invention. Hood assembly 42 is illustrated in the drawings and consists of a relatively thin (about 0.080 to 0.120 inch thick) outer skin member 44 and reinforcement member 46. Outer skin member 44 and reinforcement member 46 are constructed of FRP material and are preferably made from thermosetting sheet molding compound (SMC) material which has been compression molded under vacuum. U.S. Pat. Nos. 4,488,862; 4,551,085; and 4,612,149 owned by the Budd Company of Troy, Mich., relate to such techniques and are hereby incorporated herein by reference. Outer skin member 44 includes outer surface 48 and inner mating surface 50. Similarly, reinforcement member 46 includes outer surface 52 and inner mating surface 54.

In order to bond outer skin member 44 to reinforcement member 46, a bead of adhesive 56 is laid on a mating portion of inner mating surface 50. The adhesive 56 is a thermosetting resin that exhibits a change in dielectric properties when cured. The adhesive 56 preferably contains a resin consisting of uncrossedlinked polymers and monomers, with a second part consisting of a hardener or catalyst. Epoxy resin adhesives are presently preferred, although polyurethanes should prove to be acceptable. These adhesives are to be distinguished from glues such as animal glues which do not rely upon a chemical change to effect their adhesive qualities. As will appear clear from the following discussion, the present invention utilizes this characteristic of certain adhesives to great advantage. By way of a specific, but nonlimiting example, adhesive 56 is a Lord 380.backslash.382 epoxy adhesive available from Lord Corporation.

As shown in a simplified manner in FIG. 5, reinforcement member 46 is preferably preheated in quartz heating apparatus 58 or any other suitable type of heating unit prior to being bonded with outer skin member 44.

In FIG. 8, hot and cool air bonding apparatus 60 is shown in a partial cutaway perspective view and is in a closed position with the outer skin/adhesive/reinforcement member assembly 42 located therein.

FIG. 7 is a cross-sectional view of hot and cool air bonding apparatus 60 in an initial open position. With apparatus 60 in the open position, outer skin member 44 and reinforcement member 46 are carried into bonding apparatus 60 with reinforcement member 46 positioned within first nest member 62 and outer skin member 44 positioned within second nest member 70. As will be apparent to those skilled in the art, this can be accomplished in a variety of manners. Reinforcement member 46 is secured by vacuum assemblies 64 that include vacuum cups 66. Locators 68 ensure that reinforcement member 46 is in a proper position prior to being bonding with outer skin member 44. In a similar fashion, outer skin member 44 is secured by vacuum assemblies 72 that include vacuum cups 74. Vacuum assemblies 64 and 72 are connected to a standard vacuum source, not shown. Support members 76 support and position skin member 44 in a proper position prior to being bonding with reinforcement member 46. First nest member 62, locators 68, and vacuum assemblies 64 are all rigidly attached to base member 78 which in turn is coupled to hydraulic cylinders 80 as shown in FIG. 8. Similarly, second nest member 70, vacuum assemblies 72, and support members 76 are all rigidly secured to base member 82. Hydraulic cylinders 80 and guide posts 150, provided at the four corners of apparatus 60, control the movement of apparatus 60 between the open and closed positions. Cylinders 80 cause base member 78 to move in the direction of base member 82 until inner mating surface 54 of reinforcement member 46 contacts adhesive 56 located on inner mating surface 50 of outer skin member 44.

As best shown in FIG. 6, which is a plan view of second nest member 70 with outer skin member 44 removed, second nest member 70 has a modular design and is formed from a series of individual block members 84. Each of block members 84 is individually secured to base member 82 by bolts 86. Block members 84 are preferably made from aluminum but can be made from any other metal or suitable material. As is apparent, the series of block members 84 form a closed loop that substantially corresponds to the shape of the outer periphery of outer skin member 44. Block members 84 include top surfaces 88 that have contours respectively corresponding to the contours of outer surface 48 of outer skin member 44.

As is best shown in FIG. 9 which is a partial cross-sectional view illustrating apparatus 60 in the closed position, slots 90 are formed within each of top surfaces 88 of block members 84. Returning to FIG. 6, when the series of block members 84 are secured to base member 82, slots 90 are aligned and form a single slot extending around the closed loop formed by block members 84. Bonding manifold 92 is positioned within slots 90 and includes apertures 94 that are formed in the direction towards outer skin member 44. Bonding manifold 92 is preferably made out of stainless steel tubing. Connector tubes 96, also preferably made out of stainless steel tubing couple bonding manifold 92 to main manifold 98 that is located on the outer periphery of second nest member 70. Main manifold 98 is also preferably formed from stainless steel tubing.

Returning to FIG. 7, first nest member 62 is also modular in design and is formed from a series of block members 100 that are individually secured to base member 78 by bolts 102. Block members 100 are also preferably made from aluminum but can be made from any other metal or suitable material. As with second nest member 70, block members 100 are positioned in series and form a closed loop that is a mirror image of the closed loop formed by second nest member 70. It should be noted that the modular designs of first and second nest members 62 and 70 allows block members 84 and 100 to be individually interchanged and/or replaced to reflect changes in the configuration of the members being bonded. As most clearly shown in FIG. 9, block members 100 include top surfaces 104 that have contours respectively corresponding to the contours of the outer surface 52 of reinforcement member 46. As with block members 84, slots 106 are formed within each of surfaces 104. When the series of block members 100 are secured to base member 78, slots 106 are aligned and form a single slot extending around the closed loop formed by block members 100. Bonding manifold 108, preferably made out of stainless steel tubing, is positioned within slots 106 and includes apertures 110 that are formed in a direction towards reinforcement member 46. Connector tubes 112, also preferably made out of stainless steel tubing, couple bonding manifold 108 to main manifold 114 that is located on the outer periphery of first nest member 62. Main manifold 114 is also preferably formed from stainless steel tubing. It should be noted that the shape and diameters of bonding manifolds 92 and 108, connector tubes 96 and 112, and main manifolds 98 and 114 are used by way of example and other shapes and diameters are within the scope of the invention. Additionally, stainless steel is used by way of example and other suitable materials are within the scope of the present invention.

As is shown in FIG. 8, bonding apparatus 60 includes two switchable heating and cooling assemblies 116 and 118. Assembly 116 provides pressurized air to main manifold 98 that in turn directs the air through connector tubes 96 to bonding manifold 92. The air is then forced through apertures 94 in the direction of outer surface 48 of outer skin member 44. In a similar fashion, assembly 118 provides pressurized air to main manifold 114 that in turn directs the air through connector tubes 112 to bonding manifold 108. The air is then forced through apertures 110 in the direction of outer surfaces 52 of reinforcement member 46. 100 and 84 of nest members 62 and 70 cooperate in a manner such that slots 106 and 90 respectively form channels above reinforcement member 46 and below outer skin member 44. The forced air that is expelled through apertures 94 and 110 enters these channels and exerts substantially equal pressure on outer surfaces 48 and 52, thereby improving bonding characteristics of the resulting assembly 42. In order to facilitate the flow of the forced air through slots 106 and 90, apertures 134 and 136, extending from within slots 106 and 90 through block members 100 and 84 to the surrounding atmosphere, allow a portion of the forced air to exit slots 106 and 90.

FIG. 10 is an illustration of the air flow through switchable heating and cooling assembly 118. It will be apparent that the air flow through assembly 116 is accomplished in a similar fashion. It should be noted that assemblies 116 and 118 have the same features and are described below with reference to assembly 118. In accordance with the preferred embodiment, blower unit 120, which is driven by electric motor 122, draws air from the environment surrounding apparatus 60 through air filter 124, cooling unit 126, and muffler 128. During the heating phase of the bonding process, cooling unit 126 is disabled and valve 152 is set such that the blower unit 120 forces the air through heater 130. The air is quickly heated to a specified temperature and forced through main manifold 114 and connector tubes 112 to bonding manifold 108. The heated air then exits through apertures 110 into slots 106 in the direction of outer surface 52.

Insulation 132 and 144 is respectively located between bonding manifolds 108 and 92 and block members 100 and 84. Insulation 132 and 144 minimizes the transfer of heat between bonding manifold 108 and block members 100 and between bonding manifold 92 and block members 84. This reduction in the transfer of heat in turn reduces temperature changeover times for bonding manifolds 108 and 92.

After assembly 118 has provided heated pressurized air for a predetermined time period, heater 130 is disabled, cooling unit 126 is activated, and valve 152 is reversed such that an air passage to bypass duct 142 is open. Blower unit 120 draws air through activated cooling unit 126 such that the air is chilled and forces the chilled air through bypass duct 142 to main manifold 114. The chilled air is then forced through connector tubes 112 to bonding manifold 108. The chilled air then exits through apertures 110 into slots 106 in the direction of outer surface 52. The application of the chilled air to assembly 42 reduces the time required for assembly 42 to cool down. It will be apparent to one skilled in the art that assemblies 116 and 118 may be constructed without cooling unit 126, valve 15, and bypass duct 142. In such an embodiment, during the cooling phase of the bonding process, heater 130 is disabled and blower unit 120 continues to draw air through air filter 124 and muffler 128. The air is forced through heater 130 in such a manner that heater 130 is quickly cooled down. This air is then directed to main manifold 114 and eventually to bonding manifold 108. This air exiting bonding manifold 108 through apertures 110 is at a sharply reduced temperature when compared to the air that was flowing prior to heater 130 being disabled.

In order to precisely control the amount of forced air entering bonding manifolds 92 and 108, connecting tubes 96 and 112 are provided with valves 138. In addition, as shown in FIG. 8A, in order to monitor the approximate temperature of the forced air exiting bonding manifolds 92 and 108, thermocouples 140 are provided in close proximity to apertures 134 and 136 within block members 100 and 84.

In accordance with the method of bonding in accordance with the present invention, bonding apparatus 60 is initially in an open position as shown in FIG. 7. Reinforcement member 46 and outer skin member 44, with adhesive 56 on mating surface 50, are positioned within nest members 62 and 70 in a spaced relationship. Next, hydraulic cylinders 80 cause base member 78 to move in a direction towards base member 82 until mating surfaces 50 and 54 are engaged with adhesive 56 therebetween. Next, during the heating phase of the bonding process, switchable heating and cooling assembles 116 and 118 supply heated air to bonding manifolds 92 and 108 and ultimately hood assembly 42 as previously described above. This heated air is supplied at a pressure within the range of 0.5 to 8 pounds per square inch at a temperature of approximately 550.degree. F. This heated air is supplied for approximately 15 seconds. Thereafter, assemblies 116 and 118 provide cooler temperature air, as previously described above, to bonding manifolds 92 and 108 and hood assembly 42 for approximately 45 seconds at a pressure within the range of 0.5 to 8 pounds per square inch. It will be apparent to one skilled in the art, that when the pressurized heated air is provided within slots 90 and 106, the adhesive between outer skin member 44 and 46 is heated to a temperature above its curing temperature such that outer skin member 44 and reinforcement member 46 are evenly bonded. As will be apparent to one skilled in the art, the pressure, temperature, and time period at which the hot and cool air is provided to slots 90 and 106 is used by way of example, and other operating parameters are within the scope of the present invention.

From the foregoing it can be seen that use of the hot and cool air bonding apparatus improves the surface qualities of a resulting FRP assembly and provides uniform bonding strength throughout the assembly. Further, compared to the prior art bonding techniques, the hot and cool air bonding apparatus expeditiously bonds the FRP assembly without adversely affecting surface qualities or bonding strength characteristics.

The foregoing discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications, and variations can be made therein without the departing from the spirit and scope of the present invention as defined by the following claims.