Abstract:
The instant invention incorporates an asymmetrical purge valve tilted to fit within the confines of a chamber having a substantially elliptical cross-section. The elliptical cross-section is oriented to minimize the frontal area presented in the direction of swimming movement. The reduced cross-section results in a corresponding reduction of drag when the diver is swimming underwater.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention is generally related to snorkels used by skin divers and swimmers. More particularly, this invention is related to devices that help purge water from a snorkel.  
         [0003]     2. Description of the Prior Art  
         [0004]     Skin divers and swimmers use the snorkel as a means to breathe while swimming face down on the water surface. The snorkel functions as a conduit between the diver&#39;s mouth and the overhead air (hereinafter “skin diver”, “swimmer” and “diver” will be used interchangeably). Typically, the open end of the snorkel conduit extends a short distance above the water surface. Occasionally, due to swimming movements or wave action, small amounts of water flow or splash into the open end of the snorkel and partially floods the conduit. An experienced skin diver can sense when water enters the snorkel and responds by immediately stopping inhalation. Respiration is resumed after the snorkel has been purged of water. Inexperienced skin divers find occasional flooding especially troublesome because, undetected, water can be inhaled resulting in coughing and extreme discomfort.  
         [0005]     Water will also flood the snorkel when the swimmer deliberately dives below the water surface. The snorkel conduit will be completely flooded with water when the swimmer returns to the surface. When the open end of the snorkel is again above the water surface, the flooded conduit is purged for respiration by exhaling an explosive blast of air into the mouthpiece.  
         [0006]     Surface tension forms the purging blast of air into a bubble that spans the cross section of the snorkel conduit. Pressure within the bubble expands the bubble toward the open end of the conduit. As the leading surface of the bubble moves away from the mouthpiece, the bulk of the water within the conduit is pushed ahead of the bubble and out the open end.  
         [0007]     The purging bubble of air will slip past water that adheres to the inside surface of the conduit. After the purging air bubble is spent, residual water will flow down the inside surface toward the mouthpiece. Also, water which splashes into the open end of the snorkel conduit due to swimming movements or wave action will typically strike and adhere to the inside surface of the conduit and thereafter flow toward the mouthpiece. Water accumulates at the lowermost portion of the snorkel conduit, typically adjacent the mouthpiece, and can soon obstruct the conduit. Unless the conduit is completely blocked, a slow and cautious inhalation is possible after which another purging exhalation can be made.  
         [0008]     The respiratory effort needed to purge a snorkel is significant. Some skin divers and swimmers lack the respiratory strength needed to completely purge a flooded snorkel with a single exhalation, and must repeat the purging procedure several times. Also, water will sometimes enter the snorkel just as the swimmer has completed an exhalation, leaving very little air in the lungs to satisfactorily complete a purge.  
         [0009]     A popular solution places an externally directed purge valve in the snorkel conduit at a location near the snorkel mouthpiece. Water in a flooded conduit that extends above the ambient water surface will drain through a purge valve. A purge valve will drain the snorkel conduit until the water level within the conduit matches the ambient water level. Theoretically, because the total volume of water in the flooded snorkel is reduced by the initial flow through the purge valve, the respiratory effort required to purge the remaining water is also reduced.  
         [0010]     Unfortunately, a purge valve also provides an alternate path for forcefully exhaled air. A purge valve will quickly and wastefully dissipate the explosive blast of purging air when the purge valve is located close to the mouthpiece. One solution to this problem places a purge valve in the snorkel conduit at a location approximately midway between the mouthpiece and the open end of the snorkel conduit.  
         [0011]     At mid-length of the snorkel conduit, the purge valve will be close to the ambient water surface when the skin diver is swimming face down on the water surface. At such a location, the purge valve will drain that portion of the snorkel conduit that extends above the purge valve and the water surface, but will not initially interfere with the purging blast of air. Even at this location, the purge valve will dissipate the forcefully exhaled air and the amount of residual water adhering to the inside surface of the conduit between the purge valve and the open end will be substantial. Residual water subsequently accumulates at the lowermost portion of the snorkel conduit and obstructs the conduit. Consequently, a single purge valve, even when located mid-length of the snorkel conduit, is of limited benefit.  
         [0012]     The applicant addressed the problems of the prior art by the teachings of U.S. Pat. No. 4,879,995 titled Snorkel for Skin Divers, filed Oct. 13, 1987 and issued Nov. 14, 1989; and continuation U.S. Pat. No. 5,092,324 titled Snorkel for Skin Divers, filed Oct. 12, 1989 and issued Mar. 3, 1992. The applicant&#39;s patents teach a conduit divided approximately mid-length by a bell-shaped chamber having a symmetrical purge valve. The purge valve is located adjacent and above the water surface when the snorkel is in use by a skin diver swimming face down on the water surface. The purge valve opens under slight hydrostatic pressure and quickly drains water from the upper portion of the conduit when the skin diver returns to the surface after swimming or diving underwater. After a purging exhalation, or after splashing into the open end of the upper conduit due to swimming movements or wave action or-the-like, the forces of molecular cohesion and adhesion cause water to flow down the inside surface of the upper conduit and chamber to the purge valve. The purge valve opens under slight hydrostatic pressure and drains the water to ambient at a rate sufficient to prevent overflow into the lower conduit. Drainage of the lower conduit is facilitated by an optional second purge valve located at the bottom of a second chamber below the mouthpiece. The lower portion of the conduit is purged for respiration by exhaling a forceful blast of air into the mouthpiece that pushes the water upward. The effort required to purge the snorkel is reduced because the bulk of the ascending water flows out the first purge valve, without the need to overflow the snorkel top. The chamber located below the mouthpiece captures residual water in the snorkel after a purging exhalation and any water that overflows the first purge valve. The second chamber also captures fluids that may drain from the swimmers mouth through the mouthpiece.  
         [0013]     Snorkels based on the teachings of U.S. Pat. No. 4,879,995 and U.S. Pat. No. 5,092,324 have been successfully marketed to the diving and swimming community under the trade name “Impulse Snorkel”. However, swimmers have complained that the size and bulk of the Impulse Snorkel&#39;s mid-length bell-shaped chamber causes excessive drag when moving through the water, this problem is solved by the instant invention.  
       SUMMARY OF THE INVENTION  
       [0014]     The instant invention incorporates an asymmetrical purge valve tilted to fit within the confines of a chamber having a substantially elliptical cross-section. The elliptical cross-section is oriented to minimize the frontal area presented in the direction of swimming movement. The reduced frontal area results in a corresponding reduction of drag when the diver is swimming underwater.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0015]     A detailed description of the invention is made with reference to the accompanying drawings wherein like numerals designate corresponding parts in the several FIGS.  
         [0016]      FIG. 1  is a side sectional view of a snorkel having an upper purge valve that has been constructed in accordance with the principles of the instant invention.  
         [0017]      FIG. 2  is a cross-sectional view taken in the direction  2 - 2  of  FIG. 1 .  
         [0018]      FIG. 3  is a cross-sectional view taken in the direction  3 - 3  of  FIG. 1 .  
         [0019]      FIG. 4  is an exploded partial view of the several components incorporated into the snorkel of  FIG. 1 .  
         [0020]      FIG. 5  is an oblique view showing only the purge valve and the snorkel component that carries it.  
         [0021]      FIG. 6  is a close-up side view of the snorkel of  FIG. 1  showing the purge valve open.  
         [0022]      FIG. 7  is a close-up side view of an alternate configuration showing the purge valve closed. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for purposes of illustrating the general principles of the invention.  
         [0024]     Referring to  FIG. 1 , the inventive snorkel is pictured in the approximate position of use by a diver swimming face down on water surface  12 . (For clarity, the diver is not shown in the FIGS.) The words “upper” and “lower” or “above the water surface” and “below the water surface,” or the like, are made with reference to the orientation of the snorkel as shown in  FIG. 1 .  
         [0025]     The inventive snorkel includes conduit  14  whose length is divided into upper conduit  14   a  and lower conduit  14   b  by a bulge located at approximately mid-length. The bulge forms a chamber that houses purge valve  22 . Purge valve  22  opens to ambient through side opening  26 . Side opening  26  is advantageously located above water surface  12  when a swimmer is breathing through the inventive snorkel.  
         [0026]     Upper conduit  14   a  extends into the air above water surface  12  and has an end with ambient opening  18 . Opening  18  is advantageously unobstructed and located in-line with the conduit&#39;s longitudinal axis, thereby providing a substantially unrestricted respiratory flow path to ambient.  
         [0027]     Lower conduit  14   b  extends underwater and has an end closed by purge valve  30 . Purge valve  30  is arranged to allow fluid, for example water or saliva, to flow freely from conduit  14   b  to ambient.  
         [0028]     Purge valves  22  and  30  are, typically, a thin flexible diaphragm of a resilient material, for example silicon elastomer or the like, which is mounted in such a way that it can selectively flex under slight pressure to allow flow in one direction only. Reverse pressure forces the diaphragm to seal closed. Consequently, purge valves  22  and  30  prevent the reverse flow of water from ambient into conduit  14 .  
         [0029]     Mouthpiece  40 , above purge valve  30 , branches from the side of conduit  20 . Mouthpiece  40  is adapted to be held by the mouth of the diver and provides a flow path from conduit  14  to the interior of the mouth. (In the FIGS., the opening of mouthpiece  40  should be considered covered by the diver&#39;s mouth.) Although the preferred configuration includes purge valve  30 , the instant invention can be incorporated on snorkels that do not include purge valve  30  by terminating the underwater end of conduit  14   b  at mouthpiece  40 .  
         [0030]     Conduit  14  is constructed of a rigid or semi-rigid material, for example, acrylic or vinyl plastic or the like. Conduit  14  is best configured to approximately follow the curvature of the diver&#39;s head. The upper portion of conduit  14  smoothly curves to place upper opening  18  approximately over the center of the head.  
         [0031]     Providing a substantially smooth flow path that is free of abrupt changes in path direction facilitates respiration and purging. While not so limited, the curvature of conduit  14  may, for example, follow an elliptical path adjacent the side of the swimmer&#39;s head. Alternately, the upper portion of conduit  14  can be straight.  
         [0032]     When a diver swims or dives below the water surface, water will pour into the snorkel through opening  18 , flooding the snorkel. As the diver surfaces and assumes the face down, surface swimming stance, water in the snorkel above ambient water surface  12  will drain through purge valves  22  and  30 .  
         [0033]     Water and saliva remaining in lower conduit  14   b  are purged by forcefully exhaling air into mouthpiece  40 . Surface tension forms the exhaled air into a bubble that expands upward in conduit  14   b . As the leading surface of the bubble moves away from mouthpiece  40 , the bulk of the water within conduit  14  is pushed ahead of the bubble toward and out opening  18 . Furthermore, as water in the snorkel is lifted above ambient water surface  12  by the purging bubble of air, the water will also flow to ambient through opening  26 . This purging action is facilitated by the instant invention because conduit  14  provides a substantially smooth and unimpeded flow path.  
         [0034]     When optional purge valve  30  is provided, a forceful exhalation will also expand downward, forcing fluid below mouthpiece  40  to flow to ambient through purge valve  30 . The outflow of water will flex purge valve  30  outward. Consequently, a purging exhalation forces water within conduit  14  to be cleared both above and below mouthpiece  40 .  
         [0035]     Conceivably, conduit  14  can be fabricated as a single piece in which purge valve  22  and related components are inserted through one of the conduit ends, However, fabrication is facilitated by dividing conduit  14  into several parts. For example, conduit  14  can be advantageously divided into three parts: upper conduit  14   a , lower conduit  14   b , and coupler  14   c.    
         [0036]     Upper conduit  14   a  extends above the water surface. Lower conduit  14   b  extends below the water surface. Coupler  14   c  holds purge valve  22 , provides side-opening  26 , and joins upper conduit  14   a  to lower conduit  14   b . Opening  16   b  of coupler  14   c  is configured to smoothly join with the interior of lower conduit  14   b.    
         [0037]     A two-part arrangement can be also be used in which the top of lower conduit  14   b  holds purge valve  22 , provides side-opening  26  and joins directly the bottom of the upper conduit.  
         [0038]     Opening  16   a  (see  FIG. 1  ) resides within the lower portion of upper conduit  14   a . The cross-section of the lower portion of upper conduit  14   a  gradually expands to form a bulge or chamber so that space is provided around opening  16   a  to enable water in upper conduit  14  to easily reach and flow to ambient through purge valve  22  and side opening  26 . When assembled, the lower edge of upper conduit  14   a  forms a watertight seal with ledge  25  (see  FIG. 4 ).  
         [0039]     Although not so limited, conduits  14   a  and  14   b  have substantially the same cross-section, for example circular or elliptical. Reducing the frontal area presented in the direction of swimming movement minimizes snorkel drag. Consequently, the chamber surrounding purge valve  22  is configured to have a substantially elliptical cross-section, and the chamber is orienting so that the ellipse minor axis faces the direction of travel, Furthermore, a substantially elliptical cross-section adjacent purge valve  22  enables the inventive snorkel to be routed relatively close to the head, also resulting in lower swimming drag.  
         [0040]     The transition from the inside cross-section of upper conduit  14   a  to the larger substantially elliptical inside cross-section adjacent side opening  26  is gradual, smooth and without break. Therefore, the inside surface contour is uniform and without abrupt changes in the direction of fluid flow.  
         [0041]     Purge valve  22  is located adjacent and above side opening  26 . Purge valve  22  is oriented and mounted in such a way that the lower unrestrained edge can selectively flex under slight pressure to allow flow in one direction only. Reverse pressure forces purge valve  22  to seal closed against shelf  20 . Consequently, purge valve  22  will allow flow to ambient, but prevents the flow of water from ambient into conduit  14 .  
         [0042]     As best seen in  FIG. 2 , the outer edge of purge valve  22  is circular. A portion of purge valve  22  is cutout by circular opening  23 . Circular opening  23  is offset from the center of purge valve  22  thereby giving purge valve  22  an asymmetrical shape having a narrow portion  22   a  and a wide portion  22   b.    
         [0043]     Circular opening  23  is mounted in circular groove  24  (see  FIG. 4 ) so that wide portion  22   b  is adjacent and above opening  26 . The mounting is configured with sufficient clearance to enable diaphragm  22  to flex as needed to make a watertight seal against shelf  20 .  
         [0044]     As best seen in  FIG. 3 , tilting groove  24 , and thereby purge valve  22 , with respect to the longitudinal axis of conduit  14  accommodates the elliptical cross-section of conduit  14  adjacent opening  26 . As described supra, having a substantially elliptical cross-section adjacent diaphragm  22  and opening  26  provides a smaller frontal area in the direction of swimming movement, and close mounting to the swimmer&#39;s head, both of which reduces swimming drag. Furthermore, tilting groove  24  so that portion  22   b  of purge valve  22  is lower than portion  22   a  facilitates the guidance of water toward opening  26 .  
         [0045]     The purging bubble of air will clip past water which adheres to the inside surfaces of conduits  14   a  and  14   b . In general, very little water will remain on the inside surface of lower conduit  14   b  because the initial driving pressure within the bubble close to mouthpiece  40  is significantly higher than ambient.  
         [0046]     Referring to  FIG. 6 , after the purging air bubble is spent, the forces of molecular cohesion and adhesion cause residual water to flow (depicted as arrows in  FIG. 6 ) down the inside surface of conduit  14   a , around opening  16   a  to the unrestrained portion  22   b  of purge valve  22 . Similarly, water which splashes into opening  18  due to swimming movements or wave action will strike and adhere to the inside surface of upper conduit  14   a  and thereafter flow directly to the unrestrained portion  22   b  of purge valve  22 .  
         [0047]     The gradual transition from the inside cross section of upper conduit  14   a  to the larger substantially elliptical inside cross section adjacent purge valve  22  is smooth and uninterrupted so that the forces of cohesion and adhesion maintain a substantially sheet like flow of water which will not break away from the inside surface. Similarly, the forces of molecular cohesion and adhesion cause water to follow the inside surface of the curve of upper conduit  14   a.    
         [0048]     Water will flow down the inside wall of conduit  14   a  directly to the unrestrained outside edge of purge valve  22 . Slight hydrostatic pressure will flex unrestrained portion  22   b  of purge valve  22  away from shelf  20  and drain water to ambient at a rate sufficient to prevent overflow into lower conduit  14   b . Providing portion  22   b  of purge valve  22  with a sufficient area facilitates rapid drainage of water.  
         [0049]     Water cannot flow through portion  22   a  of purge valve  22  because portion  22   a  is restrained between groove  24  and shelf  20  (see  FIG. 6 ). Portion  22   a  of purge valve  22  serves to properly locate and maintain the position of portion  22   b  with respect to opening  26 . The asymmetrical aspect of purge valve  22  allows fluid flow only past the widest portion  22   b.    
         [0050]     Fabricating purge valve  22  with an elliptical circumference and a centrally located cutout for mounting does not provide sufficient diaphragm flexibility to reliably function as a purge valve. The asymmetrical design of the instant invention provides the necessary flexibility.  
         [0051]     Upper conduit  14   a  is drained by purge valve  22  when water develops hydrostatic head by being above ambient water surface  12 . Purge valve  22  is advantageously located approximately mid-distance between mouthpiece  40  and opening  18 . At approximately mid-distance between mouthpiece  40  and opening  18 , purge valve  22  will normally be above ambient water surface  12  when the user is swimming face down on the water surface and, consequently, purge valve  22  will continuously drain any water that flows or splashes into conduit  14   a.    
         [0052]      FIG. 7  illustrates an addition to the instant invention in which hood-like projection  14   a  of conduit  14  covers and protects the ambient opening for purge valve  22 . Opening  26   a  has the same function as opening  26 .  
         [0053]     It is understood that those skilled in the art may conceive of modifications and/or changes to the invention described above. Any such modifications or changes that fall within the purview of the description are intended to be included therein as well. This description is intended to be illustrative and is not intended to be limiting. The scope of the invention is limited only by the scope of the claims appended hereto.