Second pressure-reducing stage for underwater use equipped with a bypass duct and method for making same

Abstract

A second pressure-reducing stage for underwater use includes a supply duct of a breathable gas, in which a valve of a pressure reducing device to reduce the pressure of the breathable gas is provided, the valve being interposed between an inlet of the supply duct and a suction/exhalation mouth to suction/exhale the breathable gas; a casing containing a pressure-sensitive device to control the opening/closing of the valve, the supply duct and the suction/exhalation mouth leading into the casing; and a bypass duct for supplying at least part of the flow of the breathable gas from the supply duct, downstream of the valve, directly into the suction/exhalation mouth, the by-pass duct joining the suction/exhalation mouth through an opening having an axis oriented in a direction which converges towards the axis of the suction/exhalation mouth.

The invention claimed is: 
     
         1 . A second pressure-reducing stage for underwater use, comprising:
 a supply duct ( 107 ) of a breathable gas in which a valve of a pressure reducing device to reduce the pressure of the breathable gas is provided, the valve being interposed between an inlet of said supply duct ( 107 ) and a suction/exhalation mouth ( 102 ) to suction/exhale said breathable gas;   a casing ( 106 ) containing pressure-sensitive means to control an opening/closing of said valve, the supply duct ( 107 ) and the suction/exhalation mouth ( 102 ) leading into said casing and being in communication therewith; and   a bypass duct ( 101 ) for supplying at least part of a flow of said breathable gas from the supply duct ( 107 ) downstream of said valve, directly into the suction/exhalation mouth ( 102 ),   wherein the by-pass duct ( 101 ) joins the suction/exhalation mouth through an opening having an axis oriented in a direction which converges towards a longitudinal axis of said suction/exhalation mouth.   
     
     
         2 . The second pressure-reducing stage according to  claim 1 , wherein an angle enclosed between an axis (A2) of an outlet of the by-pass duct ( 101 ) leading into the suction/exhalation mouth and the longitudinal axis (A1) of the suction/exhalation mouth is less than 90°. 
     
     
         3 . The second pressure-reducing stage according to  claim 1 , wherein the by-pass duct ( 101 ) joins the supply duct through an outlet having a longitudinal axis (A4) oriented at an angle with respect to a longitudinal axis of the supply duct ( 107 ) between 75 and 105°. 
     
     
         4 . The second pressure-reducing stage, according to  claim 1 ,
 wherein the supply duct ( 107 ) has the longitudinal axis (A3) oriented according to a first direction and the suction/exhalation mouth ( 102 ) has a longitudinal axis (A1) oriented according to a second direction, said first and said second directions being different from each other and crossed to one another,   wherein the by-pass duct ( 101 ) has a first connecting section ( 201 ) to connect to the supply duct ( 107 ) with a longitudinal axis (A4) of an outlet leading into the supply duct ( 107 ) oriented transversely to a longitudinal axis (A3) of said supply duct ( 107 ) with a predetermined incidence angle, the by-pass duct ( 101 ) having a second connecting end-section ( 401 ) to connect to the suction/exhalation mouth ( 102 ), a longitudinal axis (A2) of the an opening leading into said suction/exhalation mouth ( 102 ) being oriented transversely to the longitudinal axis (A1) of said suction/exhalation mouth ( 102 ) with a second incidence angle, and   wherein said first connecting section ( 201 ) and said second connecting section ( 401 ) of the by-pass duct ( 101 ) are connected together through one or more intermediate sections ( 301 ,  601 ,  501 ,  701 ) having at least two curvatures with two different radii of curvature and/or according to different directions of curvature.   
     
     
         5 . The second pressure-reducing stage according to  claim 1 , wherein said casing ( 1 ), said supply duct ( 107 ), said suction/exhalation mouth ( 102 ), and said by-pass duct ( 101 ) are made of plastic. 
     
     
         6 . The second pressure-reducing stage according to  claim 4 , wherein the one or more intermediate sections ( 301 ,  501 ,  601 ,  701 ) of the by-pass duct ( 101 ) are made to adhere against at least part of an outer wall, at least of the supply duct ( 107 ) and/or the suction/exhalation mouth ( 102 ) and/or part of an outer wall of the casing ( 1 ) provided between the suction duct ( 107 ) and the suction/exhalation mouth ( 102 ). 
     
     
         7 . The second pressure-reducing stage according to  claim 1 , wherein walls delimiting the by-pass duct ( 101 ), and the supply duct ( 107 ) and/or the suction/exhalation mouth ( 102 ) and/or the casing, are made of a same material and in one piece. 
     
     
         8 . The second pressure-reducing stage according to  claim 4 ,
 wherein the first connecting section ( 201 ) of the by-pass duct leads into the supply duct ( 107 ) with the outlet having the longitudinal axis (A4) perpendicular to the longitudinal axis (A3) of the supply duct ( 107 ), and extends with a first straight intermediate section ( 301 ) of the one or more intermediate section whose longitudinal axis is parallel to the longitudinal axis of said supply duct ( 107 ) and said outlet is connected to said first straight intermediate section ( 301 ) with a 90° curvature toward the casing ( 1 ),   wherein the second connecting section ( 401 ) of the by-pass duct ( 1 ) leads into the suction/exhalation mouth ( 102 ) through the opening, the opening having the opening having the longitudinal axis (A2) oriented at an acute angle with respect to the longitudinal axis (A1) of the suction/exhalation mouth ( 102 ) and from which the second connecting section ( 401 ) of the by-pass duct ( 1 ) branches off, the second connecting section having a longitudinal axis parallel to the longitudinal axis of the opening, and   wherein between said second connecting section ( 401 ) of the by-pass duct ( 101 ) and said first straight intermediate section ( 301 ) there is a second intermediate linking section ( 601 ) linked to said second section ( 401 ) for connection to the suction/exhalation mouth and to the first straight intermediate section ( 301 ) with a respective curved length ( 501 ,  701 ), said curved lengths having identical or different directions and/or angles and/or radii of curvature.   
     
     
         9 . The second pressure-reducing stage according to  claim 8 , wherein the longitudinal axis (A3) of the supply duct ( 107 ) extends in a different plane with respect to the longitudinal axis (A1) of the suction/exhalation mouth ( 102 ), wherein the longitudinal axis (A21) of the second connecting section ( 401 ) for the connection to the suction/exhalation mouth ( 102 ) is in a plane coincident with a plane containing the longitudinal axis of said suction/exhalation mouth ( 102 ) or whose distance from the plane containing the longitudinal axis of said suction/exhalation mouth ( 102 ) is different from a distance of a plane containing the longitudinal axis (A3) of the supply duct ( 107 ) and said second intermediate section ( 601 ), the longitudinal axis of the second intermediate section ( 601 ) having an inclination with respect to said planes, and the curved lengths ( 501 ,  701 ) being made with angular extensions corresponding to said inclination. 
     
     
         10 . A process of manufacturing a second pressure-reducing stage for underwater use equipped with a bypass duct, the process comprising the steps of:
 providing a sacrificial insert whose shape matches at least an inner compartment of the by-pass duct,   placing said sacrificial insert in a mold provided with at least one or more injection nozzles;   providing sacrificial positioning supports for said sacrificial insert; and   closing the mold and injecting a forming plastic to form a casing, a supply duct, and suction/exhalation mouth portions of the second pressure-reducing stage.   
     
     
         11 . The process according to  claim 10 , wherein the sacrificial insert ( 50 ,  70 ) is made to match the a shape both of an inner compartment of the by-pass duct ( 101 ) and at least part of an inner compartment of the supply duct ( 107 ) and/or of a suction/exhalation mouth ( 102 ), said sacrificial insert ( 250 ,  350 ;  270 ,  370 ) being provided at least over an angular amplitude in a circumferential direction and along an axial length at respective openings leading the by-pass duct ( 101 ) into said supply duct ( 107 ) and/or into said suction/exhalation mouth ( 102 ). 
     
     
         12 . The process according to  claim 10 , wherein said sacrificial insert ( 50 ,  70 ) comprises a part ( 150 ,  170 ) shaped to match an inner compartment of the by-pass duct ( 101 ) and a part ( 250 ,  270 ) of the sacrificial insert matching the entire supply duct ( 107 ) and a part ( 350 ,  370 ) of the sacrificial insert matching the inner compartment of the suction/exhalation mouth ( 102 ), respectively at ends of said part matching the inner compartment of the by-pass duct ( 101 ). 
     
     
         13 . The process according to  claim 12 , wherein the part ( 250 ,  270 ) of the sacrificial insert matching the supply duct ( 107 ) in its entirety and/or the part ( 350 ,  370 ) of the sacrificial insert matching the inner compartment of the suction/exhalation mouth ( 102 ), are made tubular. 
     
     
         14 . The process according to  claim 10 , wherein the sacrificial insert is positioned in a forming mold by using inserts, shaped as protrusions of a mold part inserted either inside a part of the sacrificial insert matching the supply duct ( 107 ) in its entirety and/a the part of the sacrificial insert matching an inner compartment of the suction/exhalation mouth in order to obtain a tubular shape of said supply duct and/or said suction/exhalation mouth. 
     
     
         15 . The process according to  claim 10 , wherein said sacrificial insert is made in one piece by injection molding with a plastic material that is removable by solution. 
     
     
         16 . The process according to  claim 10 , further comprising a step of providing and arranging a plurality of injection nozzles of a plastic material for forming the casing, the supply duct, the suction/exhalation mouth and the by-pass duct, which are arranged along a length of said by-pass duct. 
     
     
         17 . The process according to  claim 16 , further comprising the step of supplying a plastic material through the plurality of injection nozzles at different times according to a predetermined time sequence.