Abstract:
An intermediate sealing element and method for unsealing a vacuum membrane from one tool surface and transferring it to another tool surface without damaging the vacuum membrane. The intermediate sealing element forms a continuous path around the periphery of a vacuum membrane and is sealed directly to one or more vacuum membranes and a tool surface using any means known in the art to create an airtight seal between two surfaces. The intermediate sealing element is able to withstand high temperatures and high pressure without altering its structural characteristics. Because of its durability, the intermediate sealing element can be removed from the tool surface without tearing or elongating, subsequently allowing the vacuum membranes to be detached from the tool surface without tearing or elongating.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention relates to sealing a vacuum membrane to a tool surface, such as in the manufacturing of composite structures. More particularly, the present invention relates to unsealing and transferring a vacuum membrane from a tool surface without damaging the vacuum membrane. 
         [0003]    2. Related Art 
         [0004]    Vacuum compression is used in manufacturing processes to compress various types of material in preparation for hardening or curing. For example, to form a composite part of an aircraft, composite part laminate material may be laid onto a tool surface, such as a lay-up tool, and covered with a vacuum membrane. The vacuum membrane is sealed to the tool surface around the entire periphery of the vacuum membrane and air between the vacuum membrane and the tool surface is removed, thereby inducing a pressure differential on the laminate and compressing the vacuum membrane toward the surface. The compressed material is then cured to become a strong, light-weight part. 
         [0005]    Some manufacturing processes require moving the compressed material from one tool surface to another tool surface prior to curing. In this situation, two vacuum membranes may be used, wherein one vacuum membrane is placed under the composite part laminate and another is laid over the composite part laminate. Both vacuum membranes are sealed to each other and to the tool surface around the entire periphery of the vacuum membranes. Once the air is removed from between the two vacuum membranes, the vacuum membranes are removed from a first tool surface and transferred to a second tool surface prior to cure. However, because the vacuum membrane is typically very thin, for example, only two to three thousandths of an inch thick, unsealing and removing the vacuum membrane from the tool surface may damage or wrinkle the vacuum membrane. Damaging either of the vacuum membranes can allow air to seep in between the vacuum membranes. 
         [0006]    Accordingly, there is a need for an improved method of sealing a vacuum membrane to a tool surface that does not suffer from the problems and limitations of the prior art. 
       SUMMARY 
       [0007]    The present technology provides an intermediate sealing element and method for unsealing a vacuum membrane from one tool surface and transferring it to another tool surface without damaging the vacuum membrane. The intermediate sealing element forms a continuous path around the periphery of a vacuum membrane and is sealed directly to one or more vacuum membranes and a tool surface using any means known in the art to create an airtight seal between two surfaces. 
         [0008]    In various embodiments of the invention, the intermediate sealing element is operable to withstand a temperature of 800° F. and a pressure of 250 psi without compromising its structural integrity. In other various embodiments of the invention, the intermediate sealing element is operable to withstand a temperature of 350° F. and a pressure of 100 psi without compromising its structural integrity. Because of its durability, the intermediate sealing element can be removed from the tool surface without tearing or elongating, thereby facilitating the detachment of one or more vacuum membranes from the tool surface without tearing or elongating. 
         [0009]    A method of using the intermediate sealing element comprises sealing a first side of the intermediate sealing element to a first tool surface; sealing the first side or a second side of the intermediate sealing element to a first vacuum membrane, thereby creating an airtight seal between the first tool surface and the first vacuum membrane; and unsealing the first side of the intermediate sealing element from the first tool surface to relocate the first vacuum membrane. The method may further comprise sealing a second vacuum membrane to the second side of the intermediate sealing element. 
         [0010]    In various embodiments of the invention, the method may comprise disposing a material between the first vacuum membrane and the second vacuum membrane, then urging the first vacuum membrane toward the first tool surface by a differential pressure. The vacuum force may also urge the second vacuum membrane toward the first tool surface, thereby compressing the material disposed therebetween. 
         [0011]    In other various embodiments of the invention, the method may comprise sealing the second side of the intermediate sealing element to a second tool surface. 
         [0012]    These and other important aspects of the present invention are described more fully in the detailed description below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    An embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0014]      FIG. 1  is an isometric view of an intermediate sealing element disposed on a first tool surface and constructed in accordance with a first embodiment of the present invention; 
           [0015]      FIG. 2  is a cross-sectional view of the intermediate sealing element of  FIG. 1 , wherein a first face of the intermediate sealing element is sealed to the first tool surface and a first vacuum membrane; 
           [0016]      FIG. 3  is a cross-sectional view of the intermediate sealing element of  FIG. 2 , wherein a second face of the intermediate sealing element is sealed to a second vacuum membrane; 
           [0017]      FIG. 4  is a cross-sectional view of the intermediate sealing element of  FIG. 3 , wherein the intermediate sealing element is unsealed from the first tool surface in preparation for sealing to a second tool surface; 
           [0018]      FIG. 5  is a cross-sectional view of the intermediate sealing element of  FIG. 4 , wherein the second face of the intermediate sealing element is sealed to the second tool surface; 
           [0019]      FIG. 6  is a cross-sectional view of the intermediate sealing element constructed in accordance with a second embodiment of the present invention, wherein the first vacuum membrane is sealed to the second face of the intermediate sealing element; and 
           [0020]      FIG. 7  is a cross-sectional view of the intermediate sealing element of  FIG. 6 , wherein the second vacuum membrane is sealed to the second face of the intermediate sealing element. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  illustrates an intermediate sealing element  10  constructed in accordance with an embodiment of the present invention. The intermediate sealing element  10  may be used as an intermediary between two or more of a first vacuum membrane  12 , a second vacuum membrane  14 , a first tool surface  16 , and a second tool surface  18  (see  FIG. 4 ). The intermediate sealing element  10  is particularly suited to facilitate transferring a composite part laminate  20 , compressed between the vacuum membranes  12 , 14 , from the first tool surface  16  to the second tool surface  18  in the manufacture of composite parts for aircraft or other applications. 
         [0022]    The vacuum membranes  12 , 14  may be any substantially malleable, air-tight material. The first tool surface  16  and the second tool surface  18  may be the surface of any mold, table, lay-up tool, mandrel, or cure tool known in the art or used in manufacturing processes involving sealing vacuum membranes to a surface. 
         [0023]    The intermediate sealing element  10  may be composed of any substantially durable material. For example, the intermediate sealing element  10  may be composed of metal, plastic, or an elastomer, such as rubber or fluoroelastomer. In various embodiments of the invention, the intermediate sealing element  10  may retain its structural integrity and usefulness when exposed to temperatures as high as about 800° F. and when exposed to pressures as high as 250 psi. In various other embodiment of the invention, temperatures less than or equal to about 350° F. and pressure less than or equal to about 100 psi will not alter the structural characteristics of the intermediate sealing element  10  or otherwise diminish the capacity of the element  10  to form an airtight seal with a surface or vacuum membrane and to be transferred from a first surface or location to a second surface or location. Specifically, for example, a temperature equal to or less than about 350° F. will not cause the intermediate sealing element  10  to melt. However, the intermediate seal may be composed of materials with other structural temperature and pressure thresholds according to the particular requirements of its particular application. 
         [0024]    In various embodiments, the intermediate sealing element  10  is more durable than the vacuum membranes  12 , 14  and is more resistant to structural damage and structural alteration caused by high temperatures and high pressure. Specifically, the intermediate sealing element  10  may be thicker and/or more rigid than the vacuum membranes  12 , 14 . For example, the intermediate sealing element  10  may be between 0.0075 inches and 0.25 inches thick, or more specifically between 0.009 inches and 0.02 inches thick. The vacuum membranes  12 , 14  may each be between 0.0005 inches and 0.005 inches thick, or more specifically between 0.001 inches and 0.004 inches thick. However, the intermediate sealing element  10  may be any size or thickness required by a given application and may be used with vacuum membranes of any size and thickness. 
         [0025]    Referring also to  FIG. 2 , the intermediate sealing element  10  may have a first face  22 , a second face  24 , an outer edge  26 , an inner edge  28 , and may form a continuous path along the periphery of the first vacuum membrane  12 . The inner edge  28  of the intermediate sealing element  10  may at least partially overlap the vacuum membranes  12 , 14  so that the vacuum membranes  12 , 14  can be sealed to the intermediate sealing element  10 . The continuous path may be any shape required by a given application. For instance, the intermediate sealing element  10  may form a continuous square, as illustrated in  FIG. 1 . However, the intermediate sealing element  10  may form a continuous path of any shape or size required to make contact with the entire periphery of the first vacuum membrane  12 . Vacuum membranes may also vary in size and shape depending on the application. 
         [0026]    The intermediate sealing element  10  may be sealed to the tool surfaces  16 , 18  and the vacuum membranes  12 , 14  by any sealing compound, lip seal, rubber vacuum seal, or mechanical seal known in the art for creating an airtight seal between two surfaces. For example, as illustrated in  FIG. 2 , rubber vacuum seals  30 , 32  may be attached to each side of the intermediate sealing element  10 , thereby allowing a seal to form between one of the rubber vacuum seals  30 , 32  and either the first tool surface  16  or the second tool surface  18  by means of vacuum force or positive pressure. Alternatively, various types of sealant tape  34  may be used to form a seal between the intermediate sealing element  10  and at least one of the first tool surface  16 , the second tool surface  18 , the first vacuum membrane  12 , and the second vacuum membrane  14 , as illustrated in  FIGS. 2-7 . 
         [0027]    As illustrated in  FIGS. 2-5 , a method of using the intermediate sealing element  10  comprises sealing the first face  22  of the intermediate sealing element  10  to the first tool surface  16  and sealing the first face  22  or the second face  24  of the intermediate sealing element  10  to the first vacuum membrane  12 , thereby creating an airtight seal between the first tool surface  16  and the first vacuum membrane  12 . The method may further comprise the step of unsealing the first face  22  of the intermediate sealing element  10  from the first tool surface  16  to relocate the first vacuum membrane  16 , as illustrated in  FIG. 4 . 
         [0028]    In various embodiments of the invention, the method may further comprise sealing the second vacuum membrane  14  to the second face  24  of the intermediate sealing element  10 , as illustrated in  FIG. 5 . The method may also comprise sealing the second face  24  of the intermediate sealing element  10  to the second tool surface  18 . The second face  24  of the intermediate sealing element  10  may be sealed to the second tool surface  18  either before or after unsealing the first face  22  of the intermediate sealing element  10  from the first tool surface  16 . 
         [0029]    As illustrated in  FIG. 3 , the method may comprise disposing a material, such as composite part laminate  20 , between the first vacuum membrane  12  and the second vacuum membrane  14 , then urging the first vacuum membrane  12  toward the first tool surface  16  by a differential pressure. The differential pressure may also urge the second vacuum membrane  14  toward the first tool surface  16 , thereby compressing the composite part laminate  20  disposed therebetween. Alternatively, in various embodiments of the invention, any material of sufficient size and weight such that it would not be removed from between the two vacuum membranes  12 , 14  by a pressure differential when air is removed from between the vacuum membranes  12 , 14  may be substituted for the composite part laminate  20 . 
         [0030]    More specifically, in one embodiment of the invention, the first tool surface  16  is sealed to the first face  22  of the intermediate sealing element  10  near the outer edge  26  of the intermediate sealing element  10 , and the first vacuum membrane is sealed to the first face  22  of the intermediate sealing element near the inner edge  28  of the intermediate sealing element  10 , as illustrated in  FIG. 2 . Then a composite part laminate  20  or a suitable alternative, as described above, is laid on top of the first vacuum membrane  12 , and the second vacuum membrane  14  is sealed to the second face  24  of the intermediate sealing element  10  near the inner edge  28  of the intermediate sealing element  10 , as illustrated in  FIG. 3 . Air is then removed from between the first and second vacuum membranes  12 , 14  using vacuum means known in the art, thereby urging the first and second vacuum membranes  12 , 14  toward each other and toward the first tool surface  16 . 
         [0031]    In one embodiment of the invention, a thin vacuum distribution media (not shown) may be disposed between the first vacuum membrane  12  and the first tool surface  16  to prevent the first vacuum membrane  12  from sealing off against the first tool surface  16 , as the first vacuum membrane  12  is pulled down against the first tool surface  16  by a pressure differential. A pressure differential may be created, for example, by removing air from between the first vacuum membrane  12  and the first tool surface  16 . The vacuum distribution media may be, for example, fiberglass, and keeps the vacuum membranes  12 , 14  tight and smooth against the first tool surface  16 . The vacuum distribution media also allows the first vacuum membrane  12  to be more easily peeled away from the first tool surface  16  for transfer to another location. 
         [0032]    Once the air has been removed from between the vacuum membranes  12 , 14 , the outer edge  26  of the intermediate sealing element  10  may be unsealed from the first tool surface  16 , as illustrated in  FIG. 4 , while remaining sealed to the vacuum membranes  12 , 14 . This allows the vacuum membranes  12 , 14  and the composite laminate part  20  to remain sealed and compressed during transfer to the second tool surface  18 . 
         [0033]    In one embodiment of the invention, the second tool surface  18  may be moved toward the first tool surface  16 , such that the intermediate sealing element  10 , vacuum membranes  12 , 14 , and composite laminate part  20  require little or no lifting to be transferred from one surface to the other. As illustrated in  FIG. 5 , once the intermediate sealing element  10  is unsealed from the first tool surface  16 , the second face  24  of the intermediate sealing element  10  may be sealed to the second tool surface  18  near the outer edge  26  of the intermediate sealing element. Then heat may then be applied to cure the compressed composite laminate part  20 . 
         [0034]    In an alternative embodiment of the invention, illustrated in  FIGS. 6-7 , the first vacuum membrane  12  may be sealed to the second face  24  of the intermediate sealing element  10  near the inner edge  28  of the intermediate sealing element  10 , and the second vacuum membrane  14  may be sealed to the second face  24  of the intermediate sealing element  10  near the outer edge  28  of the intermediate sealing element  10 . 
         [0035]    Although the invention has been described with reference to the preferred embodiments illustrated in the attached drawings, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. It will be appreciated, for example, that the transferring of vacuum sealed membranes from one location to another may apply to other manufacturing processes other than the manufacturing of composite parts for aircraft and the like.