Patent Publication Number: US-2006012070-A1

Title: Gasket assembly

Description:
FIELD OF THE INVENTION  
      The present invention pertains generally to gaskets for sealing, and more particularly to a foam-in-place gasket having reduced friction characteristics.  
     BACKGROUND OF THE INVENTION  
      Foam-in-place gaskets find many applications in sealing between abutting components. In certain applications, foam-in-place gaskets are used in dynamic environments to seal between relatively movable abutting components. For example, foam-in-place gaskets are often used to seal between adjacent panel sections of overhead garage doors. As the garage doors are raised and lowered, the gasket is exposed to compressive forces and shear forces as the individual panel sections pivot about hinges which connect their adjacent upper and lower laterally extending edges.  
      Foam-in-place gaskets function best in compression. Their performance is degraded when exposed to lateral shearing forces. Exasperating this problem is the fact that foam-in-place gasket materials typically exhibit high coefficients of friction, and therefore, shear forces are increased due to the materials&#39; tendency to resist sliding movement between the surfaces they seal against. Accordingly, the gaskets used in garage doors, and in other applications where they are exposed to lateral or shearing forces, can fail after a relatively short service life, requiring time and expense to replace the gaskets. A need therefore exists for an improved foam-in-place gasket which can be used to seal between abutting components in dynamic environments.  
     SUMMARY OF THE INVENTION  
      The present invention provides a gasket assembly formed from foam material and is suited for use in dynamic environments where the gasket assembly will be exposed to lateral shearing forces. The gasket assembly comprises a layer of foam material disposed in a desired arrangement on a substrate, such as the edge of a garage door panel. The foam material may be applied as an elongate bead, or in any desired pattern. In one embodiment, the upper surface of the foam gasket material is covered with a layer of thermoplastic material such that areas of the surface remain exposed. The thermoplastic material may be applied to the foam material in a fiberized pattern, i.e., in a manner that is controlled and non-random. Suitable illustrative patterns are oscillating, looped or swirl patterns.  
      The fiberized form of the layer of thermoplastic material is such that the foam material is not completely encapsulated by the thermoplastic material. Accordingly, foam material applied to the substrate in a foam-in-place process may continue to cure after the layer of thermoplastic material has been applied. In one embodiment, the thermoplastic material is selected to have a coefficient of friction that is less than that of the foam gasket material, so that the gasket assembly is less susceptible to being torn, or otherwise damaged, as a result of shearing forces exerted on the gasket assembly by sealed components.  
      In another embodiment, thermoplastic material is applied as spaced, parallel beads that extend either parallel or transverse to a longitudinal extent of the foam material. In yet another embodiment, the thermoplastic material is applied on top of the foam material in a repeating omega-shaped pattern, or as spaced-apart dots or drops.  
      In another embodiment, the gasket assembly further includes a second layer of thermoplastic material disposed between the substrate and the foam gasket material. The second layer of thermoplastic material helps to bond the foam material to the substrate and may be applied as a uniform web, or in a fiberized arrangement as discussed above with respect to the first layer of thermoplastic material. The thermoplastic material for the first and second layers is preferably the same material.  
      In another aspect of the invention, a method for making a gasket includes dispensing a first layer of thermoplastic material to a substrate, forming a layer of foam material on the first layer of thermoplastic material, and dispensing an second layer of thermoplastic material on the foam material. The first layer may be applied as a uniform coating, or in fiberized form. The second layer is applied on top the foam material such that areas of the surface of the foam material remain exposed.  
      In another aspect of the invention, a system for making gaskets includes a first liquid material dispensing gun, a foam dispenser downstream of the first liquid material dispensing gun, and a second liquid dispensing gun downstream of the foam dispenser. In one embodiment, the system further includes a conveyor for moving a substrate past the first liquid material dispensing gun, the foam dispenser, and the second liquid material dispensing gun, respectively, whereby a gasket assembly according to the invention, as described above, may be formed.  
      In yet another embodiment, a plurality of longitudinally extending beads of thermoplastic material are formed simultaneously with the foam material in a coextrusion process.  
      The features and objectives of the present invention will become more readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.  
       FIG. 1  is a perspective view of a foam-in-place gasket assembly according to the present invention;  
       FIG. 2  is a cross-section of the foam-in-place gasket assembly of  FIG. 1 ;  
       FIG. 2A  is a cross-sectional view of another embodiment of a foam-in-place gasket assembly according to the present invention;  
       FIGS. 3A-3D  are a perspective views of other embodiments of foam-in-place gasket assemblies according to the present invention;  
       FIG. 4  is a perspective view of still another embodiment of a foam-in-place gasket assembly according to the present invention;  
       FIG. 5  is a schematic illustration of a system for making foam-in-place gasket assemblies according to the present invention; and  
       FIG. 6  is a cross-sectional view of another embodiment of a foam-in-place gasket assembly according to the present invention. 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIGS. 1 and 2 , a gasket assembly  10 , illustrative of the invention, includes a layer of foam gasket material  12  disposed on a substrate  14 , such as the top edge surface of a panel used in a sectional overhead garage door. Advantageously, the gasket  12  may be applied as a bead of foam-in-place material along the substrate  14 . After application to the substrate  14 , the material expands to create the foam gasket  12 , as known in the art. The gasket assembly  10  further includes a layer  16  of protective material disposed on top of the foam material  12 . The layer  16  comprises a filament of thermoplastic material disposed atop the foam material in a fiberized pattern. The fiberized pattern may be a repeating pattern, such as for example, a looped or swirling pattern ( FIG. 1 ) or an oscillating pattern (layer  16   a  of  FIG. 3 ).  
      The fiberized pattern of layer  16  does not completely encapsulate the exposed surfaces of the foam material  12 . Because foam-in-place materials typically cure by absorbing moisture from the environment, the unencapsulated configuration of layer  16  permits the foam-in-place bead to fully cure even after application of layer  16  of thermoplastic material. Advantageously, the material of layer  16  is selected to have a friction coefficient which is less than the friction coefficient of the foam-in-place gasket material  12 . Accordingly, when the gasket assembly  10  is used in applications where the gasket assembly  10  is exposed to shear forces, the reduced friction coefficient facilitates sliding movement between the adjacent components that are sealed by the foam material  12 . Moreover, the repeating pattern of layer  16  provides a relatively uniform dispersion of thermoplastic material on the bead of foam material  12 , without creating areas having excessive build-up or agglomeration, as would otherwise tend to occur if layer  16  were applied in a random fashion.  
      The gasket assembly  10  may further include layer  18  of thermoplastic material disposed between the substrate  14  and the foam material  12 . Layer  18  of thermoplastic material securely bonds the foam material  12  to the substrate  14  so that the gasket assembly  10  will not readily tear away from the substrate  14  when exposed to lateral shearing forces, such as those experienced by adjacent garage door panels when the door is opened and closed. Layer  18  may be disposed on the substrate  14  in any pattern or arrangement which provides a secure bond between the foam material and the substrate. For example, layer  18  may be applied in a repeating pattern such as an oscillating, looped, or swirl pattern ( FIG. 1 ) or it may be applied in a random fiberized manner, or as a continuous uniform coating of material  18   a  ( FIG. 3 ).  
      Alternatively, when the foam material  12  and the substrate material are selected such that the foam-in-place gasket will readily form a bond with the material of the substrate  14 , the foam-in-place gasket material  12  may be applied directly to the surface of the substrate  14  ( FIGS. 2A and 4 ) without the need for layer  18  of thermoplastic material.  
      Advantageously, the layer  18  of thermoplastic material may be selected to be the same material used for the layer  16 . The thermoplastic material for the layers  16 ,  18  may be a reactive polyurethane, ethylene vinyl acetate (EVA), polyolefin, polyamides, or other materials suitable for adhering to foam material and providing a reduced friction coefficient.  
       FIGS. 3A-3D  depict additional embodiments of gasket assemblies  10   c,    10   d,    10   e,    10   f  according to the present invention. In  FIGS. 3A and 3B , a layer of thermoplastic material is applied to the top of the foam material  12  in the form of spaced parallel beads  15 . The beads  15  may extend in a direction substantially parallel to a longitudinal extent of the foam material  12 ,  FIG. 3A , or may extend in directions substantially transverse to the longitudinal extent of the foam material  12 ,  FIG. 3B . In yet another embodiment of a gasket assembly  10   e  according to the present invention, thermoplastic material may be applied to the top of the foam material  12  as a plurality of spaced drops or dots  17 ,  FIG. 3C . In  FIG. 3D , a gasket assembly  10   f  according to the present includes a layer of thermoplastic material  16   b  applied to the top of the foam material  12  in a pattern resembling a series of repeating omega shapes.  
      While  FIGS. 1 and 3  depict a gasket assembly  10  according to the present invention in the form of an elongate bead of foam material, it will be recognized that the gasket assembly may have other configurations as well. For example, and with reference to  FIG. 4 , there is shown another embodiment of a foam gasket assembly  10   b,  according to the present invention, in the form of a “closed” gasket, i.e., the gasket forms a closed loop. In the embodiment shown, the gasket assembly  10   b  has a generally rectangular configuration, but it will be recognized that the gasket may be formed in other configurations as well. In this embodiment, the substrate  14  comprises material formed in the desired gasket shape. The foam-in-place gasket  12  may be applied directly to the substrate  14 , or a layer of thermoplastic material (not shown) may first be applied to the substrate  14  to bond the foam-in-place material  12  to the substrate, as described above. After the foam-in-place material has expanded to the desired gasket profile, and has cured sufficiently to support the weight of the upper layer, layer  16  of thermoplastic material is applied on top of the foam material  12 , as described above.  
      Referring now to  FIG. 5 , there is shown a system  20  for manufacturing a gasket assembly  10 , as described above. The system  20  includes first and second liquid material dispensing guns  22 ,  24  and a foam dispensing head  26  arranged proximate a conveyor  50  such that the first liquid dispensing gun  22  is positioned upstream of the foam dispensing head  26 , and the foam dispensing head  26  is upstream of the second liquid dispensing gun  24 . Exemplary liquid dispensing guns which could be used with the invention are the CF Series Controlled Fiberation™ guns available from Nordson Corporation of Westlake, Ohio. An exemplary foam dispensing head is the pro-meter VDK metering system, with an A6900 gun module, also available from Nordson Corporation. Each of the liquid material dispensing guns  22 ,  24  is provided with liquid material, such as hot melt adhesive, from a bulk melter  28  which receives thermoplastic material in solid form and melts it to a temperature suitable for dispensing from the guns  22 ,  24 .  
      Gasket material in solid form is provided to a second bulk melter  30  where it is heated and melted prior to being supplied to a foam material processor  32  which aerates the liquid gasket material. An exemplary bulkmeter is the BM200 series bulkmeter, and an exemplary foam material processor is the FoamMix® dispensing system, both available from Nordson Corporation. The aerated gasket material is then provided to the foam dispensing head  26  which includes a gear pump  34 , a nozzle  36  configured to dispense the gasket material  12  as an elongate bead, and a solenoid  38  for operating the nozzle  36  between open and closed positions to thereby dispense the foam-in-place material to a substrate  14 .  
      The first and second liquid dispensing guns  22 ,  24  are operated by respective solenoid valves  40 ,  42  for actuation between open and closed positions and are coupled to a source of compressed air  44  for attenuating and controlling the pattern of liquid material dispensed therefrom, as known in the art. The solenoids  40 ,  42  of the first and second liquid dispensing guns  22 ,  24  may be controlled by a first, liquid pattern controller  46 . A second dispense head controller  48  may control the operation of the gear pump  34  and solenoid  38  of the foam dispensing head  26 .  
      A substrate  14 , such as a garage door panel section, is supported on the conveyer  50  for movement along a machine direction  52  beneath the first liquid material dispensing gun  22 , the foam material dispense head  26 , and the second liquid material dispensing gun  24 , respectively. A sensor  54  positioned adjacent the conveyor detects the presence of the substrate  14  moving along the conveyer  50  and sends a signal to the pattern control  46  and dispense head control  48  to initiate dispensing layers  16 ,  18  of thermoplastic material and the foam material layer  12  to create the gasket assembly  10  as described above. Specifically, as the substrate  14  is moved in the machine direction  52  along the conveyer  50 , the first liquid material dispensing gun  22  applies a layer  18  of thermoplastic material to the substrate  14 . Layer  18  may be in the form of a continuous web, a random fiberized arrangement, a repeating pattern, or in other suitable forms.  
      As the substrate  14  continues along the conveyer  50 , the foam material dispense head  26  applies an elongate bead of foam material  12  to the substrate  14 , atop layer  18  of thermoplastic material. The substrate  14  continues along the conveyer  50  while the bead of foam material  12  expands to the desired gasket shape. After the foam material  12  has fully expanded and has sufficiently cured to support upper layer  16 , the second liquid material gun  24  dispenses layer  16  of thermoplastic material atop the foam material  12 .  
      Advantageously, the spacing A between the first liquid material dispensing gun  22  and the foam material dispense head  26 , is selected such that the foam material  12  is applied atop layer  18  of thermoplastic material during a time when the lower layer  18  may bond the foam material  12  to the substrate  14 . The spacing B between the foam material dispense head  26  and the second liquid material dispensing gun  24  is selected to correspond to the speed of the substrate  14  along the conveyor  50  such that the foam material  12  has sufficient time to fully expand to the desired gasket profile and to cure sufficiently to support the weight of layer  16  of thermoplastic material on top of the foam material  12 . Advantageously, selective adjustment of the spacing A and spacing B may be automatically controlled by the system  20  to accommodate changes in the speed of the conveyor  50 . This may be accomplished by, for example, mounting guns  22 ,  24  to movable supports or to robot arms that are cooperatively controlled to move to the correct positions to accommodate changes in the speed of the conveyor  50 .  
      Referring now to  FIG. 6 , there is shown yet another embodiment of a gasket assembly  10   f  according to the present invention. In this embodiment, a plurality of longitudinally extending beads  60  of thermoplastic material are formed concurrently with the foam material  12  in a coextrusion process. The beads  60  of thermoplastic material are spaced around the entire periphery of the foam material  12 . When the coextruded foam material and thermoplastic beads are deposited on a substrate  14 , the beads  60   a  that are sandwiched between the substrate  14  and the foam material  12  help bond the foam material  12  to the substrate  14 .  
      While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant&#39;s general inventive concept.