Abstract:
An inflatable sealing device includes a bushing and a plunger which is movably guided in the bushing through application of air pressure from an air supply to execute a predefined limited stroke. A sealing tube is connected to the plunger and has an interior space which is connected to the air supply to radially expand the sealing tube when air pressure is applied.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of prior filed copending PCT International application no. PCT/EP2007/051498, filed Feb. 16, 2007, which designated the United States and has been published but not in English as International Publication No. WO 2007/113042 and on which priority is claimed under 35 U.S.C. §120, and which claims the priority of German Patent Application, Serial No. 10 2006 015 184.4, filed Apr. 1, 2006, pursuant to 35 U.S.C. 119(a)-(d), the contents of which are incorporated herein by reference in its entirety as if fully set forth herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates, in general, to an inflatable sealing device for a molding tool. 
         [0003]    Nothing in the following discussion of the state of the art is to be construed as an admission of prior art. 
         [0004]    The production of coated plastic products, in particular of foamed sandwich plastic products with a polyurethane material core, involves a production process in which insert material (insert), which forms the outer skin for example, is placed in a cavity as well as a skin, which possibly forms the inner surface. Placed into the cavity between the insert, which may involve, e.g., a deep-drawn film or a metal part such as an aluminum element etc., and the skin is plastic material, for example a foam material, such as polyurethane material which cures as thermosetting or thermoplastic material. In this way, a sandwich product is formed after curing which is composed of several layers; According to the above-stated example, this means an insert layer forming the outer skin, a polyurethane layer forming the core, and a skin layer forming the inner side. 
         [0005]    As the interstices between the insert and the skin is filled, no foam material should escape between insert and skin to the surroundings, especially in the marginal area of the product being made, when a certain pressure builds up in the foam material. An inflatable sealing tube can hereby be used which is placed in a half-mold on the parting surface side, causing a desired sealing between skin and insert, as the sealing tube presses against the skin and in turn the skin against the insert. The degree of sealing is defined by the applied air pressure. Preferably, a sealing device should, of course, extend over the entire circumference of the cavity in order to ensure the sealing action throughout. 
         [0006]    It would be desirable and advantageous to provide an improved inflatable sealing device to obviate prior art shortcomings and to ensure a sealing up to precisely predefined ends so that even narrow transitions can be sealed, while allowing simple installation into the molding tool so as to eliminate the need for producing separate molding parts. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one aspect of the present invention, an inflatable sealing device includes a bushing, a plunger movably guided in the bushing through application of air pressure from an air supply to execute a predefined limited stroke, and a sealing tube connected to the plunger and having an interior space connected to the air supply to expand the sealing tube when air pressure is applied. 
         [0008]    The arrangement of the combination of sealing tube and plunger with limited stroke ensures a simple sealing up to a precisely defined end of the sealing device because the sealing in the form of the tube and the extendible plunger is “inflatable’ up to the defined end. As a result, also tight transitions can be reliably sealed. Moreover, a standardized round tube may be used as element for the sealing so that no excessive costs incur. The limited stroke of the extendible plunger prevents damage to skin and insert, on one hand, and ensures that the integrity of the inflatable sealing device cannot fall apart, when the molding tool is open. 
         [0009]    The stroke limitation may be realized by arranging on the outer circumference of the plunger a groove or a recess in which an engagement part of the bushing projects, with the groove or the recess as well as the engagement part dimensioned to constructively establish the limited stroke. Of course, the construction may also be realized with exchanged elements, i.e. the bushing has an inner circumference provided with a groove into which an engagement part of the plunger projects or engages. It is only essential that the interaction of recess/groove and engagement part result sin a stop for the movement of the plunger. 
         [0010]    A simple construction for producing the engagement part, arranged on the bushing, may involve a retaining or Seger ring which is firmly received in an inner groove of the bushing. 
         [0011]    To ensure the tightness, a separate seal may be arranged between the plunger and the bushing. An O-ring may be provided for example which is inserted in a groove either of the plunger or the bushing. 
         [0012]    To avoid damage to the skin, the head area of the plunger may be provided with a plastic covering or a plastic cap, alternatively also with rubber or respectively soft material. 
         [0013]    To prevent the sealing tube from collapsing, a filler cord may be arranged in its interior space and may have a cross section configured in the shape of a star. 
         [0014]    For flow dynamics, a channel may be provided in the plunger to establish a flow connection with a blind bore in which the sealing tube is inserted. The other end of the channel may be configured with an inlet which narrows in flow direction. As a result of such a narrowing, for example conically shaped inlet, the force is determined in dependence on the applied air pressure for pushing the plunger upwardly and for pressing the skin against the insert. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0015]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0016]      FIG. 1  is a greatly schematized sectional illustration of a closed molding tool with insert, skin and foam material, with the end between insert and skin being sealed by means of a sealing device according to the invention; 
           [0017]      FIG. 2  is a schematic side view of a first embodiment of a sealing device according to the invention which is removed from the molding tool; 
           [0018]      FIG. 3  is an exploded drawing of the inflatable sealing device according to  FIG. 2 ; 
           [0019]      FIG. 4  is a cross section through the sealing tube with filler cord; 
           [0020]      FIG. 5  is a perspective illustration of a bushing for the sealing device of  FIG. 2  in accordance with the invention; 
           [0021]      FIG. 6  is a perspective illustration of a plunger for the sealing device of  FIG. 2  in accordance with the invention; 
           [0022]      FIG. 7  is a schematic illustration of the air channels in the plunger of the sealing device according to with the invention; 
           [0023]      FIG. 8  is two sealingly interacting inventive sealing devices according to  FIG. 2  in side-by-side relationship; 
           [0024]      FIG. 9   a  is an exploded drawing of a second embodiment of an inflatable sealing device according to the invention; 
           [0025]      FIG. 9   b  is a schematic illustration of a sealing device according to  FIG. 9   a  in assembled state; 
           [0026]      FIG. 10  is a detailed illustration of a milling contour for a seal of a sealing device according to  FIG. 9   a ; and 
           [0027]      FIG. 11  is a schematic sectional illustration of a sealing device according to  FIG. 9   a  in assembled state. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0029]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown a greatly schematized sectional illustration of a closed molding tool  10  to show the operation of a sealing device according to the invention, generally designated by reference numeral  22 . The molding tool  10  includes a bottom half-mold  12  and a top half-mold  14 , which are depicted in closed state and define a mold cavity between them. Placed in this mold cavity is, on one hand, an insert  16  which bears upon the top half-mold  14 , and a skin  18  which bears upon the cavity surface of the bottom half-mold  12 . Introduced between the insert  16  and the skin  18  is a polyurethane material which cures so as to produce overall after curing a sandwich product comprised of insert, polyurethane core and skin. 
         [0030]    To prevent escape of plastic or liquid polyurethane material before curing, the sealing device  22  is arranged in the marginal area of the foaming mold, shown in  FIG. 1  only by the section through a sealing tube. The sealing device  22  is received in a groove or recess of the bottom half-mold  12  and embraces the cavity essentially entirely in the parting plane between the half-molds  12 ,  14 . 
         [0031]    The details of the inflatable sealing device  22  can be seen in  FIGS. 2 to 7 . All Figures show a shortened round sealing tube  34 . The round sealing tube  34  may be designed much longer in the actual embodiment. 
         [0032]    The sealing device  22  includes a bushing  24  or sleeve which receives a plunger  26 , e.g. made of brass, which has a limited stroke to move back and forth. The round sealing tube  34  is connected to the head zone of the plunger  26  and is inflatable, as will be described hereinafter. As shown in detail in  FIGS. 3 ,  5 , and  6 , the bushing  24  has an inner groove in which a Seger ring  32  is firmly seated. The plunger  26  includes on the other side in midsection a stepped ring-shaped groove  40  or recess. The head zone of the plunger extends above the stepped groove  40 . Arranged below the stepped groove  40  is an essentially cylindrical part of the plunger which includes essentially in midsection a further more shallow annular groove  38 . An O-ring is inserted in this annular groove  38 . 
         [0033]    When the plunger  26  and the bushing  24  are assembled together, the Seger ring  32  extends into the region of the stepped groove  40 , with a stop being formed by the cylindrical lower part of the plunger  26  in combination with the Seger ring  32  for preventing an excessive upward displacement of the plunger  26  out of the bushing  24  and thus limiting the stroke. The stroke limitation is indicated i.a. in  FIG. 8  by the characters A and B and may be selected for example in the range of 5 mm. 
         [0034]    The plunger  26  has in this way a mobility of about 5 mm. Formed in the head zone of the plunger is a blind bore  48 , as can be seen in  FIG. 7 . Received in this blind bore  48  is an open end of the round sealing tube  34 . 
         [0035]    The bore  48  is fluidly connected with a further bore which defines an air channel  44  and is provided in the plunger  26  in a manner shown in  FIG. 7 . At the end opposite to the blind bore  48 , the air channel  44  respectively ports into a conical expansion  46  or constriction, as viewed in flow direction. This conical expansion  46  is thus formed in the present case on the lower end of the plunger. 
         [0036]    When assembled, a plastic covering  28  is arranged around the head of the plunger  26 . Moreover, the interior of the round sealing tube  34  accommodates a filler cord  36  which—as can be seen in FIG.  4 —has a substantially star-shaped cross section. 
         [0037]    The mode of operation of the present inflatable sealing device  22  can be seen from  FIG. 2 . When air under a predefined pressure is supplied from below to the plunger  26 , the conically designed constriction  46  fluidly acts in such a manner that the plunger  26  is pushed upwards in dependence on the air pressure and presses the skin  18  with its plastic cover  28  against the insert  16 . The plastic cap or a respective coating of the head part of the plunger  26  prevents damage to the skin  18 . Air flows via the channel  44  and the blind bore  48  into the interior of the round sealing tube  34  which radially expands in accordance with the air pressure and thereby also presses the skin  18  against the insert  16 . Overall, a linear sealing can be established up to a very sharp limitation, with the limitation being defined on the one side by the limited contact area of the end of the plunger  26  and on the other side by the tube end. 
         [0038]    By placing—as shown in FIG.  8 —two respective sealing devices  22  and  22 ′ next to one another, a sealing transition between two sealing devices can be established almost seamlessly because both plungers  28  and  28 ′ press the skin  18  upon the insert  16  when aligned immediately next to one another. In the further course of action, the skin  18  is pressed upon the insert  16  by the two round sealing tubes  34 ,  34 ′. The bushing may hereby be configured also as part of the tool. It thus does not necessarily have to be provided as separate structure. 
         [0039]      FIGS. 9   a  to  11  show a further embodiment of a sealing device according to the invention. In the following description, parts corresponding with those in  FIGS. 2-8  will be identified by corresponding reference numerals, followed by a “ ”. 
         [0040]    A sealing device  22 ′ according to the invention includes again a bushing  24 ′ or sleeve which receives a plunger  26 ′ with limited stroke for back-and-forth movement. The round sealing tube  34 ′ is connected in the head zone with the plunger  26 ′ which is inflatable, as will be described hereinafter. 
         [0041]    The plunger  26 ′ includes a lower stop flange which impacts against the bushing  24 ′ in the upper end position, when assembled. Arranged above the stop flange is an essentially cylindrical part of the plunger  26 ′ in which a further more shallow annular groove  38 ′ is arranged essentially in midsection. An O-ring  30 ′ is seated in its annular groove  38 . 
         [0042]    Further arranged in the lower area of the bushing  24 ′ is a sealing recess  54  for receiving an O ring seal  50  which has a contour as shown in  FIG. 10  which shows only a bushing portion  52 . The O ring seal  50  seals the bushing  24 ′ against the molding tool, when installed. 
         [0043]    After assembly of plunger  26 ′ and bushing  24 ′, the sealing device  22 ′ is placed into the respective recess of the tool (cf.  FIG. 11 ). The tool has a bore  62  with internal thread in the area of the bushing receptacle for threaded engagement of a stud screw  60 . After insertion of the sealing device  22 ′, the bushing  24 ′ can be secured by means of the stud screw, thereby enabling a wanted positioning of the bushing  24 ′ in its axial direction. 
         [0044]    The plunger  26 ′ cam only move in a defined region in the bushing  24 ′, with a stop for the plunger being established by the tool and a stop being established by the lower end of the bushing  24 ′. The stop flange of the plunger  26 ′ bears respectively against these stops. The plunger  26 ′ of the sealing device  22 ′ may move more or less upwardly depending on the adjustment of the bushing  24 ′. 
         [0045]    As a consequence of the construction of the screw fastening of the bushing  24 ′, the entire sealing device  22 ′ mat be exchanged rapidly and easily; There is no need for a special tool and moreover the safety construction does not require much space. 
         [0046]    The stroke limitation may again be selected in the range of 5 mm. The plunger  26 ′ has in this way again a mobility of about 5 mm. Like in the first embodiment, the head zone of the plunger is formed with a blind bore. Received in this blind bore  48  is an open end of the round sealing tube  34 ′. 
         [0047]    The blind bore is fluidly connected with a further bore which defines an air channel  44 ′ and is provided in the plunger  26 ′. At the end opposite to the blind bore  48 , the air channel  44 ′ respectively ports into a conical expansion or a constriction, as viewed in flow direction. This conical expansion is thus formed in the present case on the lower end of the plunger  26 ′. 
         [0048]    When assembled, a plastic covering  28 ′ is arranged around the head of the plunger  26 ′. Moreover, the interior of the round sealing tube  34 ′ accommodates a filler cord  36 ′ which again has a substantially star-shaped cross section. 
         [0049]    The mode of operation of the inflatable sealing device  22 ′ can be seen  FIG. 11 . When air under a predefined pressure is supplied from below to the plunger  26 ′, the conically designed constriction fluidly acts in such a manner that the plunger  26 ′ is pushed upwards in dependence on the air pressure and presses the skin  18  with its plastic covering  28 ′ against the insert. As a consequence of the plastic cap or a respective coating of the head part of the plunger  26 ′, damage to the skin is prevented. Air flows via the channel  44 ′ and the blind bore into the interior of the round sealing tube  34 ′ which radially expands in accordance with the air pressure and thereby also presses the skin against the insert. Overall, a linear sealing can be established up to a very sharp limitation, with the limitation being defined on the one side by the limited contact area of the end of the plunger  26 ′ and on the other side by the tube end. 
         [0050]    In summary, the sealing device according to the invention ensures a reliable sealing up to the defined ends of the sealing device in an inflatable manner, whereby even tight transitions can be sealed. The use of a standardized round tube as seal in the sealing device has a cost-saving effect. Moreover, the plunger cannot disintegrate as a result of the stroke limitation and cannot move upwards in an unwanted manner. 
         [0051]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.