Abstract:
An inflatable penile prosthesis includes an implantable pump having a bypass valve. The bypass valve includes a cavity having a valve seat at a port, a poppet and a spring. The poppet includes a valve member and a stem extending from the valve member. In operation, the poppet includes a sealing position, where the valve member seals the port through contact with the valve seat, and a deflating position, where the valve member is displaced from the valve seat. The spring is configured to bias the valve member toward the valve seat, wherein the spring engages a portion of the stem while the poppet is in the deflating position.

Description:
CLAIM TO PRIORITY 
     The present application claims priority to U.S. application No. 60/865,325, filed Nov. 10, 2006 and entitled “Inflatable Penile Prosthesis Bypass Valve Noise Reduction.” The identified provisional patent application is hereby incorporated herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     One common treatment for male erectile dysfunction is the implantation of a penile prosthesis. An exemplary inflatable penile prosthesis  10  is shown in  FIG. 1 . Penile prostheses typically include a pair of inflatable cylinders  12 , which are fluidly connected to a reservoir  14  via a pump and valve assembly  16  through tubing  18 . The two cylinders  12  are normally implanted into the corpus cavernosae of the patient and the reservoir  14  is typically implanted into the patient&#39;s abdomen. The pump assembly  16  is implanted in the scrotum. A detailed description of the exemplary penile prosthesis  10  is provided in U.S. Publication No. 2006/0135845, which is hereby incorporated by reference herein. 
     During use, the patient actuates the pump  16  and fluid is transferred from the reservoir  14  to the pump  16  through tubing  20 . The fluid travels through the pump  16  and into the cylinders  12  through tubing  18 . This results in the inflation of the cylinders  12  and thereby produces the desired penis rigidity for a normal erection. Then, when the patient desires to deflate the cylinders  12 , a valve assembly within the pump  16  is actuated in a manner such that the fluid in the cylinders  12  is released back into the reservoir  14 . This deflation then returns the penis to a flaccid state. 
     The pump and valve assembly  16  includes fluid pathways allowing the flow of fluid to and from the reservoir  14 , as well as to and from the cylinders  12 . In some designs this fluid flow is controlled by one or more poppet valves positioned in the fluid pathways within the housing of the pump and valve assembly  16 . 
     A compressible pump bulb  22  is typically attached to the housing  24  of the pump assembly  16  and is in fluid communication with the various fluid pathways. In order to inflate the cylinders  12 , the compressible pump bulb  22  is actuated by the patient, thereby urging fluid in the bulb  22  past the poppet valves into the cylinders  12 . In order to deflate the cylinders  12 , the valve housing  24  is grasped and squeezed, such as at button  26 , through the patient&#39;s tissue, causing the various poppet valves to unseat and allow fluid to flow back to the reservoir  14  through a ball check valve (i.e., bypass valve) contained in the housing  24 . 
       FIG. 2  is simplified illustration of an exemplary bypass valve  30  during cylinder inflation or a steady state condition. The bypass valve  30  includes a poppet  31  in the form of a spherical valve member  32  within a bypass cavity  34 . The valve member  32  is biased against a valve seat  36  of an input port  38  of the cavity  34  by a spring  40 . The coils of the spring  40  are not shown in the figures in order to simplify the illustrations. 
       FIG. 3  is a simplified illustration of the bypass valve  30  during cylinder deflation. During deflation of the cylinders  12 , the operator releases the seal formed by various poppet valves within the housing  24  to direct a flow of fluid, represented by arrows  42 , from the cylinders  12  through the input port  38  of the bypass cavity  34 . The pressure of the flow of fluid overcomes the bias force supplied by the spring  40  and displaces the valve member  32  from the valve seat  36 . The flow of fluid  42  travels through the bypass cavity  34 , through an output port  44  and back to the reservoir  14 , as mentioned above. 
     As the flow of fluid is continuously modulated by the throttling of the valve  30 , the ball  32  moves rapidly (vibrates) toward and away from the valve seat  36 , as indicated by arrow  46 . This vibration induces an audible sound outside of the pump  16 . As the velocity of the flow decreases in response to decreasing pressure within the cylinders  12 , the frequency of the sound increases, eventually sounding like a high pitched scream (approximately 3000 Hz) toward the end of the deflation operation. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to solutions to the bypass valve noise problem during deflation operations of the inflatable penile prosthesis. 
     One embodiment of the invention is directed to a bypass valve of an implantable pump of an inflatable penile prosthesis that utilizes frictional resistance to movement of the poppet to reduce noise during deflation operations. 
     In accordance with another embodiment of the invention, audible noise during deflation operations is decreased by decreasing the frequency at which the spring and poppet system naturally vibrate through an increase in the mass of the poppet and/or a decrease in the spring constant of the spring as compared to bypass valves of the prior art. 
     These and other features will become apparent with a careful review of the drawings and the corresponding detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exemplary inflatable penile prosthesis. 
         FIG. 2  is a simplified cross-sectional view of a bypass valve during cylinder inflation or a steady state condition. 
         FIG. 3  is a simplified cross-sectional view of a bypass valve during cylinder deflation. 
         FIG. 4  is a chart containing Robinson-Davidson equal loudness curves adopted by the International Standards Organization as the basis for ISO 266:1987. 
         FIG. 5  is a simplified cross-sectional view of a bypass valve of an inflatable penile prosthesis during cylinder inflation or a steady state condition, in accordance with embodiments of the invention. 
         FIG. 6-9  are simplified cross-sectional views of embodiments of a bypass valve during cylinder deflation operations. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The frequency of a vibrating spring mass system is proportional to √{square root over (K/M)}, where K=the spring constant and M=the system mass. The bypass valve  30  of  FIGS. 2 and 3  form such a spring mass system and the frequency of vibration of the sound generated during cylinder deflation is affected by the spring constant of the spring  40  and the mass of the valve member  32 . 
     Conventional bypass valves, such as that depicted in  FIGS. 2 and 3 , utilize a spherical valve member  32  (i.e., a ball) that is formed of synthetic sapphire having a diameter of 3/32 of an inch and a mass of 28 mg. The typical spring  40  of the conventional bypass valve has a spring constant on the order of 80 gm/cm. The resultant frequency of the sound generated during cylinder deflation is in the range of 3000 Hz. 
     While decreasing the spring constant and/or increasing the mass of the ball will decrease the system vibrating frequency, such a change would not affect the actual sound level (i.e., amplitude). However, the human ear perceives the loudness of sound differently at different frequencies. This effect is seen in the Robinson-Davidson equal loudness curves adopted by the International Standards Organization as the basis for ISO 266:1987, shown in  FIG. 4 . For instance, a sound with a loudness of 10 dB at 3,000 Hz will sound 33% as loud at 1,000 Hz and 10% as loud at 100 Hz, and a 20 dB sound at 3,000 Hz will sound 65% as loud at 1,000 Hz and 36% as loud at 100 Hz. 
     Since the sound levels generated by conventional bypass valves during deflation of the penile prosthesis cylinders are low and the primary frequencies of the generated sounds are in the range of 3,000 Hz, modifying the spring constant and poppet mass can have a significant affect on the sound frequency and therefore the perceived loudness. Embodiments of the invention are directed to decreasing the system vibrating frequency such that the sound generated during cylinder deflation is perceived as having a lower amplitude than that generated by the conventional bypass valve. This is accomplished by increasing the mass of the poppet  31  and/or decreasing the spring constant of the spring  40 . 
     In accordance with one embodiment, the mass of the poppet  31  is increased relative to the conventional design discussed above through an increase in the size of the valve member  32  (e.g., greater than 3/32 of an inch) of the poppet  31 . In one exemplary embodiment the poppet  31  includes a spherical valve member  32  having a diameter of ⅛ of an inch or more. The poppet  31  can take on other non-spherical shapes, such as that described below, that have a larger volume than conventional valve members. Thus, even if the material forming the valve member  32  and the spring  40  are conventional, the larger volume valve member  32  will have greater mass than the conventional design resulting in a reduction to the frequency of vibration of the system and a perceived reduction in the noise level. 
     In another embodiment, the poppet  31  is formed of a material that is more dense than the synthetic sapphire of conventional poppets  32 . For example, the valve member  32  can be formed of stainless steel or other relatively dense material (e.g., titanium carbide) that is not subject to corrosion and is appropriate for human implantation. The increase in the mass of the otherwise conventional poppet  31  and spring  40  system, will result in a decrease in the frequency of vibration of the system and a perceived reduction in the noise level. 
     In accordance with another embodiment, the spring constant of the spring  40  is decreased to provide a reduction to the frequency of vibration of the poppet  31  and spring  40  system. 
     Embodiments of the invention include setting the frequency of vibration of the spring  40  and poppet  31  system to less than 2500 Hz through an increase in the density of the poppet  31 , an increase in the volume of the poppet  31 , and/or a decrease in the spring constant of spring  40 . In another embodiment, the frequency of vibration of the spring  40  and poppet  31  system is set to below 1500 Hz using the same techniques. 
     In accordance with one exemplary embodiment, the frequency of vibration of the spring  40  and poppet  31  system is decreased significantly below the 3000 Hz frequency of the conventional valve member and spring systems by increasing the mass of the poppet  31  to approximately 5 times that of the conventional valve member and by reducing the spring constant of the spring  40  by one-third of that of the conventional spring. In one embodiment, the mass of poppet  31  is increased by forming the valve member  32  out of stainless steel and increasing the diameter of the spherical valve member  32  to ⅛ of an inch. These changes in the mass of the valve member and the spring constant relative to the conventional bypass valve result in a decrease in the frequency of the sound generated during cylinder deflation by approximately 63%. Thus, a conventional bypass valve sound of 10 Db and at a frequency of 3000 Hz that is generated during cylinder deflation can be reduced to 1100 Hz. This reduction in the frequency is perceived by the human ear as a further reduction in loudness by approximately 67%. 
     In accordance with another embodiment of the invention, vibratory movement of the poppet within the bypass cavity is resisted to thereby reduce noise that is generated during cylinder deflation operations. In general, frictional resistance is applied to the poppet to impede vibratory movement of the poppet relative to the valve seat. 
       FIGS. 5-9  are a simplified cross-sectional views of a bypass valve  50  of an inflatable penile prosthesis in accordance with embodiments of the invention. The bypass valve  50  includes a spring  51  and a poppet  52  comprising a valve member  54  and a stem  56  that extends from the valve member  54 . The bypass valve  50  also includes some of the conventional elements described above, which are numbered accordingly. The valve member  54  operates as described above to engage the valve seat  36  to seal the input port  38  during inflation and steady state operating conditions, as shown in  FIG. 5 . 
     In accordance with one embodiment, the poppet  52  includes a sealing position, shown in  FIG. 5 , in which a side  58  of the valve member  54  that is opposite the stem  56  engages the valve seat  36  to seal the input port  38 . In one embodiment, the side  58  of the valve member  54  has a spherical shape or convex shape, which facilitates the sealing of the circular valve seat  36 . The side  58  of the valve member  54  can take on other shapes that conform well to the perimeter of the valve seat  36 . 
     The poppet  52  also includes a deflating position, shown in  FIGS. 6-9 , in which the valve member  54  is displaced from the valve seat  36  thereby opening the input port  38  to a flow of fluid  42  from the cylinders  12  ( FIG. 1 ). During cylinder deflation operations, forces will be applied to the poppet  52  that encourage its vibration toward and away from the valve seat  36 , as indicated by arrow  60 . 
     The stem  56  extends from a side  62  of the valve member  54  that is opposite the side  58  designed to seal the valve seat  36 . The stem  56  is configured to engage a portion of the spring  51  during cylinder deflation operations. This contact with the spring  51  occurs at a location of the spring  51  where there is relative movement between the spring  51  and the stem  56 . As a result, a frictional force is generated at the contact point that resists movement of the poppet  52  relative to the spring  51 . This frictional resistance to movement of the poppet  52  dampens the vibratory movement of the poppet  52  during cylinder deflation operations and reduces noise. 
     The amount of frictional resistance between the poppet  52  and the spring  51  depends on the surfaces of the spring  51  and the stem  56 , the contact area, and the pressure applied between the stem  56  and the spring  51 . The amount of frictional resistance to movement of the poppet  52  can be set based on empirical testing to provide the desired damping of the vibratory movement of the poppet  52  and noise reduction based on the flow of fluid that is generated during cylinder deflation operations. 
     In the embodiment illustrated in  FIG. 5 , the stem  56  of the poppet  52  is received within the cylindrically shaped spring  51 . In one embodiment, the stem  56  is sized to allow the poppet  52  to pivot slightly relative to a longitudinal axis  63  ( FIG. 5 ) of the cavity  34  during cylinder deflation operations, such that an end  64  of the stem  56  contacts the spring  51 , as shown in  FIG. 6 . This contact dampens vibratory movement of the poppet  52 , as discussed above. 
     In the embodiment of the bypass valve  50  provided in  FIG. 7 , the spring  51  has a diameter D that varies along its length. In one embodiment, the spring  51  includes one or more conically shaped sections  66 . In another embodiment, the spring  51  has an hourglass shape, as shown in  FIG. 7 . The variable diameter D of the spring  51  results in at least one constricted portion  68  that contacts the stem  56  and provides the desired frictional resistance to the vibratory motion of the poppet  52 . 
     In one embodiment, the spring  51  has a generally cylindrical shape when the poppet  52  is in the sealing position ( FIG. 5 ). However, when the spring  51  is forced to contract during cylinder deflation, the spring  51  buckles into an arced shape resulting in contact with the stem  56 , as illustrated in  FIG. 8 . The contact provides the desired dampening of vibratory motion of the poppet  52 . 
     In the embodiment of the bypass valve  50  shown in  FIG. 9 , the stem  56  has a diameter D that varies along its length. In one embodiment, the stem  56  includes one or more conical sections  70 . The variable diameter of the stem  56  results in an expanded section that contacts the spring  51  and provides the desired frictional resistance to the vibratory motion of the poppet  52 . 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.