Abstract:
A sealing lip assembly for surfboards or sailboats, which closes the underwater side of the opening of the centerboard case or fin case in a virtually flow-tight and non-vortical manner in every position of the centerboard, and including two sealing lips, with each lip defined by a sealing area capable of flexing along the longitudinal axis of the assembly, a resilient area perpendicular to the longitudinal axis, and a mounting portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sealing lip assembly for sealing the underwater or bottom side of centerboard or variable keel fin systems on surfboards and sailboats. 
     2. Description of the Prior Art 
     Various seals are used today for sealing the underwater or bottom side of centerboard systems on surfboards and sailboats, but they do not completely fulfil their function of closing the opening in the centerboard case in a flow-tight and non-vortical manner in every position of the centerboard. 
     These seals are made, for example, of rubber, plasticized PVC or sailcloth which is screwed or glued to the surfboard or sailboat by the aid of thin ledges. The advantage of these materials is that the centerboard can be pressed out of the centerboard case without great expenditure of energy because the resistance against being bent up is small. However, during sailing or surfing the small resistance allows for the sealing lips to be pressed in undesirably or, when the oncoming flow is lateral, to be raised up in the slack area, giving rise to vortices on the bottom of the boat or board. When the centerboard is pivoted into the centerboard case, the sealing lips are increasingly drawn into the centerboard case at the rear and cannot form a continuous transition from the bottom of the boat or board to the centerboard. 
     Soft rubber or synthetic seals are glued to the surfboard but are often detached and tear during surfing. Furthermore, the known seals cannot be adapted without any transition to the shape of the sliding bottom in mass production. 
     For these reasons, sealing lips are dispensed with today in many surfboards having fully lowerable centerboard systems, the centerboard case being profiled so as to be as favorable to flow as possible. 
     SUMMARY OF THE INVENTION 
     The invention is based on the problem of closing the bottom side of the centerboard case or fin case in a virtually flow-tight and non-vortical manner in every position of the centerboard of fin. 
     This problem is solved according to the invention by having the sealing lip assembly comprise two sealing lips, said sealing lips consisting of a sealing area flexible on the longitudinal axis, a resilient area perpendicular to the longitudinal axis, and a mounting portion. 
     When the centerboard is introduced into the centerboard case (from above) the sealing lips are pressed apart downwardly when the centerboard passes through the bottom opening in the centerboard case. When the centerboard is then pivoted rearwardly into the centerboard case, the sealing lips rise up against the pivoting direction, due to the bias in the pressed apart area, thereby closing off the opening in the centerboard case in a virtually flow-tight and non-vortical manner in every position of the centerboard. 
     Some embodiments of the invention are shown in the drawings and shall be described in more detail as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a transverse cross-section of the centerboard case as disposed perpendicular to the longitudinal axis of the case (on the left: unsupported sealing lip; on the right: supporting sealing lip); 
     FIG. 2 is a transverse cross-section of the centerboard case and the centerboard, and disposed perpendicular to the longitudinal axis of the case (on the left: retracted centerboard position; on the right: extended centerboard position); 
     FIG. 3 is a transverse cross-section of the centerboard case, and disposed perpendicular to the longitudinal axis of the case (on the left: unsupported sealing lip; on the right: supported sealing lip); 
     FIG. 4 is a transverse cross-section of the centerboard case, and disposed perpendicular to the longitudinal axis of the case (on the left: unbiassed state; on the right: biassed state); 
     FIG. 5 is an enlargement of a detail in FIG. 4 in the sealing area; and 
     FIG. 6 is a perforated spring band steel insert. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To support the optimum sealing lip function it is advantageous for the sealing lip to be slightly biassed in the installed state. Furthermore, the centerboard should be designed in the pivoted-in state in such a way as to produce a further slight bias of the sealing lip along the entire length. 
     The recess in the centerboard case should be adapted as exactly as possible to the shape of the centerboard in the longitudinal direction so that the centerboard may pivot about a horizontal axis, as shown in all embodiments depicted herein, and does not overtax the spring force of the seal in the rear portion when the oncoming flow is lateral. As shown in FIG. 1 wherein the centerboard case is depicted with the bottom thereof being directed upwardly, as is the case for all embodiments depicted herein, a support (d) of the seal, which extends as far as the bottom opening in the centerboard case and at the same produces a slight bias of the seal, prevents the seal from being pressed into the centerboard case since the spring area of the profile decreases toward the rear in the pivoting-in direction due to the support. In the pivoting-out direction the spring area remains constant along the entire length, allowing for the centerboard to be pivoted out easily. As is apparent from FIGS. 1 and 3, the left-hand portions of these figures depict embodiments of the invention wherein no support (d) is provided for imparting a slight upward bias to the sealing lip in each case, thereby causing the sealing area (a) of each lip to dip downwardly into the case opening when the centerboard or keel fin is pivoted into the case. By contrast, the embodiments of the invention shown in the right-hand portions of FIGS. 1 and 3 are each provided with a support (d) for imparting a slight upward bias to their respective sealing lips, thereby preventing the sealing area of each lip from dipping downwardly into the case opening. As previously indicated herein, each support (d) extends along the entire length of the case opening. 
     The support is interrupted as often as possible by transverse grooves so that any contamination, e.g. sand, which might enter can be washed out by the water, so that the spring-back of the seal into the closed position is not obstructed. 
     The mounting area (c) of the sealing lip profile is not decisive for its function and is therefore not described in any detail. It should be designed in such a way as to allow for a firm hold on the surfboard and a mass-produced fit into the bottom of the board without any transition. 
     Good restoring power of the spring area (b) is the condition for the perfect functioning of the sealing lip assembly. This restoring power is ensured even in the case of lasting stress (e.g. pivoted out centerboard position) by the selection of certain materials or combinations of materials. The cross-section of the profile is designed in such a way that the spring force of the spring area, while the stability is sufficient, is as small as possible so that the centerboard can be easily moved. 
     The sealing area (a) of the sealing lip profile is designed in such a way that the frictional resistance between the centerboard and the seal is as small as possible (small contact surface, low coefficient of friction of the material). Furthermore, the sealing area (thick area of the profile) ensures a sufficient bias of the sealing lip on the longitudinal axis when the centerboard is pivoted out, so that the sealing lips rise up against the pivoting direction when the centerboard is pivoted in. 
     The material used for the sealing lips may be a glass-, carbon- or other fiber-reinforced synthetic material. A spring steel/synthetic material combination may also be used for this profile, whereby the perforated spring steel (FIG. 6) ensures the necessary restoring power and the synthetic material (e.g. polyethylene) is responsible for the sliding and stability properties, the possibility of mounting the spring steel and encasing it. 
     The assembly in FIG. 3 is made of hard, brittle synthetic materials and biassed on the inside with an elastic synthetic material or rubber (e). 
     FIG. 4 shows a variant of a spring steel/synthetic material profile which to a very great extent prevents the sealing lips from being pressed into the centerboard case. 
     The upper profile part (f) ensures a continuous transition from the sealing area to the mounting portion of the profile and is designed in such a way as to offer little resistance in the pivoting-out direction. 
     In the pivoting-in direction the upper profile part is subjected to tension beyond the closed position of the sealing lips, thereby preventing the sealing lips from being pressed into the centerboard case. 
     The sealing lip has in the sealing area a thickness of 0.2-5 mm, preferably 0.5-2 mm, and a length perpendicular to the longitudinal direction of 0.2-15 mm, preferably 3-8 mm. 
     The sealing lip has in the spring or resilient area a thickness of 0.05-3 mm, preferably 0.1-1.0 mm, at the transition to the sealing area, and a thickness of 0.05-10 mm, preferably 0.1-1.0  mm, at the transition to the mounting portion. 
     The length of the spring or resilient area is 10-60 mm, preferably 15-30 mm. 
     The transition from the resilient area to the sealing area and to the mounting portion is continuous. 
     The sealing side of the sealing area has a radius of 0.1-2.5 mm, preferably 0.3-1.0 mm. 
     The resilient area of the sealing lip is biassed opposite to the pivoting out direction, preferably with a radius of 10-100 mm. 
     The inside portion of the resilient area of the sealing lip is provided with an elastic synthetic material or rubber with a thickness of 0.1-3 mm. 
     The sealing lip has a spring band steel insert with a thickness of 0.05-0.5 mm, preferably 0.1-0.2 mm, and a width of 10-60 mm, preferably 30-50 mm. 
     The spring band steel insert is provided with slots perpendicular to the longitudinal axis spaced at 5-30 mm. 
     The slots have a length of 10-50 mm and a width of 1-25 mm, preferably 5-15 mm, in the sealing area and a width of 1-15 mm, preferably 4-8 mm, in the mounting area.