Abstract:
A valve system regulates the air pressure in the space(s) between a residual limb, or liner-covered limb, and a hard socket of an external prosthesis, and may include a manually-controlled air outlet and inlet valve on a distal region of a hard socket, and/or an automatic one-way outlet valve. The manually-controlled valve is opened and closed by partial rotation/twisting of a handle portion, which creates slight separation of the handle and base portions through which may pass air. The handle and base are prevented from becoming entirely separated during normal use by a snap-fit of the base onto the handle that retains the ability of the handle and base to rotate relative to each other by means of a ramp system, and a stop(s) that limit(s) the amount of relative rotation of the handle and base portions of the valve.

Description:
This application claims benefit of provisional application Ser. No. 61/024,913, filed Jan. 31, 2008, and is a continuation-in-part of non-provisional application Ser. No. 11/527,752, filed Sep. 25, 2006, which claims benefit of provisional application Ser. No. 60/719,785, filed Sep. 24, 2005, the entire disclosures of all of these applications being incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to prosthetics, and more specifically to a valve system for air release from an external prosthetic such as may be used on a residual limb. 
     2. Related Art 
     Gravitational and other forces tend to cause separation between a prosthetic limb and a residual limb. This happens, for example, during the swing phase of the gait, when a prosthetic leg is additionally subjected to centrifugal forces. The manner in which an artificial limb is suspended and/or attached to the residual limb determines the amount of control an amputee has over the prosthesis. Patients have routinely worn a variety of belts, straps, cuffs and harnesses to prevent the prosthetic limb from separating from the residual limb, but such devices are inconvenient and tend to cause chafing against the patient&#39;s body, giving rise to sores and abrasions. 
     It has long been appreciated that differential air pressure, often referred by those of skill in the art as “suction,” may be utilized to retain or suspend, or assist in retaining or suspending, a prosthetic limb on a patient&#39;s residual limb. “Suction suspension” typically involves a hard socket and a cooperating liner positioned between the residual limb and the prosthetic socket. The liner is rolled onto the residual limb for a suction, slight compression, and/or gripping connection of the inner gel layer (or otherwise tacky layer) of the liner to the skin of the residual limb. The liner-covered limb is then inserted into the prosthetic socket, and the outer surface/layer of the liner preferably forms a suction, grip, or other interference fit to the socket to interfere with the socket falling off the limb. 
     Said “suction” fit between the liner and the socket, due to the material and texture of today&#39;s preferred liner as further discussed below, may more accurately be referred to as a “partial-suction” fit. In such a “partial-suction” fit, the outer surface of the liner and its close fit with the interior surface of the socket will provide significant resistance to air entering the socket from outside the socket (via the top opening of the socket). Still, because today&#39;s preferred liners do not form a true air-tight seal with the socket, some air will slowly enter the socket, especially during the swing portion of the wearer&#39;s gait and during periods of relative inactivity. 
     Socket liners frequently have been called “suction liners,” “gel liners,” “roll-on liners” or “suspension liners” and include the “first generation” of gel-layer-only liners, and also the modern “second generation” liners currently preferred by most wearers of prosthetics. These modern liners “second generation” liners typically comprise a thin textile/fabric outer layer that is fixed to the gel-like inside layer. Thus, the second generation of liners is similar to the first generation in its connection to the residual limb, but its connection to, or cooperation with, the socket is modified by the presence of the textile/fabric layer. The term “suction liner” began with the first generation liners, which featured the gel layer contacting both the residual limb (liner&#39;s inner surface) and the socket (liner&#39;s outer surface), and which, therefore, could be used to create a fairly high amount of pressure differential between the inside of the socket (in the “well” of the socket) and the surrounding ambient air. The terms “suction liner” and “suction socket” are still used by many manufacturers, prosthetic technicians, insurance and medicare/medicaid entities, and wearers of prosthetics, even though the modern liners, with their textile/fabric outer layers, typically do not form what would be called “true” or “pure” suction with the socket, as further discussed below. See the discussion of suction liners in Janusson, et al. (U.S. Pat. No. 6,706,364) and Janusson, et al. (U.S. Pat. No. 6,626,952). 
     Preferred socket liners are usually fabricated from silicone, urethane, or other gel-like material that grips the limb to such an extent that they need to be rolled-onto the limb from a rolled-up “doughnut” form, rather than pulled on like a sock. When rolled-on, there is little, if any, air remaining between the inner surface of the roll-on liner and the limb, and the roll-on liner is snug against the limb all the way around the circumference of the limb. Also, the inner surface of the roll-on liner is of such material and tacky texture that air will not be able to, or be very unlikely to, enter between the roll-on liner and limb. Thus, the roll-on liner may be said to form a suction fit and/or a slight compression fit with the limb. A distal force on the liner, such as caused by the swing of a gait with a prosthetic leg, may tug on the roll-on liner but typically does not loosen, lower, or remove the liner from the limb. 
     The hard socket is usually laminated or otherwise fabricated from polyethylene, polypropylene, or other copolymers, for example, and is donned over the liner and the residual limb. A suction-fit, including a partial-suction fit, as discussed above, may form between the liner-sheathed limb and the interior of the socket. A “true” suction fit (allowing high suction, greater amount of vacuum) will be more likely to form if the liner exterior surface is smooth and flexible enough to conform to the contours of the residual limb, for example, non-air-permeable material such as the silicone, urethane, or other rubbery or gel-like material such as described above for the liner-to-limb connection; if the interior surface of the socket is also smooth and non-air-permeable; and, of course, if the socket has no un-sealed holes or apertures. 
     A “partial” suction fit (allowing lower suction, low amount of vacuum) is more likely to form if one of these conditions is not met, for example, if the outside of the liner is the thin fabric or other woven material bonded to a rubbery/gel-like interior layer of the liner, for example, as described above for “second generation” liners. In such a case, some air will tend to leak through or past the fabric layer of the modern liners into the well of the socket, that is, between the liner and the socket interior surface, so that there is typically not a true air-tight seal between the two. However, the air leaks fairly slowly because of the preferred close fit between the contour of the liner-cover limb and the contour of the internal surface of the socket. This slow air leakage and close fit typically allow their to be a “partial” suction fit between the socket and the liner outer surface, and this “partial” suction fit tends to be more comfortable for many wearers that a “true” or “full” suction fit. In other words, a textile/fabric-covered liner and the resulting “partial” suction tends to be more comfortable than the stronger “tugging” on the residual limb created by the “full” suction of first generation, gel-layer-only liner. The air that slowly leaks into space(s) in between the socket and the liner tends to be expelled with each step due to the force of the residual limb pushing into the socket. This way, modern, fabric-covered roll-on liners still tend to create some pressure differential between the well of the socket and the ambient air. 
     Therefore, many of skill in the field of prosthetics still apply the term “suction” to a fit or suspension of the prosthetic to the limb ranging from excellent suction (with a “true” seal, large resistance to equalization of pressure between the inside and the outside of the socket) to slight suction (with a “partial” seal, small resistance to said equalization such as in many popular liners). Therefore, the terms “suction,” “suction-fit,” and “suction suspension” herein are therefore not limiting to a particular amount of pressure differential, but to the general process known well in this field of providing a “roll-on” liner or other “interference” liner that helps keep a socket on a residual limb while creating at least a small amount of blockage/hindrance to air freely moving in and out of the socket well past the residual limb. 
     Therefore, it may be said that any region or amount of negative pressure in the space(s) between the liner-sheathed stump and the interior of the socket, relative to ambient (outside of the socket), may help to hold the prosthesis upon the limb during use. Certainly, more suction is more secure than slight suction, but there may be comfort sacrifices that result from more suction, for example, chaffing or pulling on the limb. A high-suction prosthesis suspension system may cause the user a discomforting disturbance of circulation in the limb on which the prosthesis is worn, due to the build up of a high degree of partial vacuum during walking, particularly in warm humid weather. Therefore, a very popular conventional roll-on liner is one such as the Ohio Willow Wood Alpha™ liner, which has multiple layers, that is, a rubbery/gel-like inner layer and a thin fabric outer layer bonded to the inner layer, so as to moderate the suction to a reasonably effective amount without allowing the great forces on the limb that can result from a high amount of suction. A “suction liner” or “roll-on liner” suspension, even in moderate range of suction provided by the preferred liners, gives the patient the ability to better control the prosthesis and provides for useful sensory or proprioceptive feedback. This is because there is a more intimate connection between the limb and the prosthetic, over much of the surface area of the limb, compared to old-fashioned waist belts, distal locks, or other methods. Suction or roll-on liner suspension also make a prosthesis feel lighter as compared to other forms of suspension. 
     A valve system may be used in combination with a suction/roll-on suspension system in order to regulate the air pressure in the socket, so that undesirable pressure differentials do not prevent or complicate the donning and doffing of the socket. Conventional valves aim at relieving buildup of pressure when the lined limb is inserted into the socket, which is typically a snug fit by design, to prevent a positive pressure inside the socket relative to outside of the socket (ambient air) and therefore to allow donning. 
     Because the typical valve system is a one-way valve, or “check valve” that only allows air to be expelled from the socket, it is intended to maintain a slight negative pressure (slight, partial suction) relative to ambient once the socket has been fitted on the residual limb and used. The process of walking and other weight-bearing will tend to push the limb further into the socket, but the swing portion of the gait will tend to pull the socket off the limb. The pushing of the limb further into the socket may cause the valve to allow air to be expelled, and the pulling of the socket during the swing portion of the gait will tend to create suction in the socket because the valve will not allow air to enter the socket through the valve. 
     In applications wherein the multi-layer roll-on liner allows air to slowly leak into the socket well, as discussed above, or wherein a seam, connection, lock or other aperture in the socket allows air to leak into the socket, weight-bearing steps will tend to expel air from inside the socket through the valve and then said leaking will tend to replace at least some of it (especially on the swing of the gait). Therefore, there may be frequent opening and closing of the valve, perhaps for each, or for many, of the user&#39;s steps. Many conventional valves for these applications are known to either not work very well, to plug easily, or to make embarrassing noise with each step as the air is expelled. 
     There are many valve systems in use in the market. Typical valve systems use an inner base that passes from the inside of the socket to the outside of the socket. The outer housing and the valve are then threaded onto the inner base or threaded to the socket wall in an attempt to create an air-tight seal between the valve and the socket wall. Such systems require a generally flat socket wall surface for installing the valve and outer housing to prevent air from leaking out of the socket around the outer housing instead of being expelled through the valve at the desired air pressure determined by the one-way valve structure. 
     Issued patents and patent publications relating to valve systems are listed as follows: Underwood (U.S. Pat. No. 1,586,015), Catranis (U.S. Pat. No. 2,530,285), Sharp et al. (U.S. Pat. No. 2,533,404), Hauser (U.S. Pat. No. 2,790,180), Edwards (U.S. Pat. No. 4,010,052), Carrow (U.S. Pat. No. 4,106,745), Greene (U.S. Pat. No. 5,201,774), Hill (U.S. Pat. No. 5,490,537), Hill (U.S. Pat. No. 5,709,017), Slemker et al. (U.S. Pat. No. 6,287,345), Perkins (U.S. Pat. No. 6,334,876), Hoerner (U.S. Pat. No. 6,361,568), Caspers (U.S. Pat. No. 6,508,842), Laghi (U.S. Pat. No. 6,544,292), Caspers (U.S. Pat. No. 6,761,742), Abrogast et al. (U.S. Pat. No. 6,797,008), Caspers (U.S. Publication No. 2004/0181290), and Patterson et al. (U.S. Publication No. 2004/0260403). 
     SUMMARY OF THE INVENTION 
     The present invention is a valve system for helping to regulate the air pressure in the space(s) between a residual limb, or liner-covered limb, and a hard socket of an external prosthesis. The valve system may be used to regulate said air pressure for improved donning and doffing the prosthesis, and/or during walking and other normal use of the prosthesis. 
     The preferred valve system comprises a manually-controlled air outlet and inlet valve that may be installed on a distal region of a hard socket, and/or an automatic one-way outlet valve. The manually-controlled valve may be used to open the socket well to the outside air by providing an air passage from a distal region of the socket well, so that, when the wearer inserts his/her residual limb into the socket, air is pushed out through the manual valve rather than building up pressure inside the socket. Also, when a user wishes to doff the prosthetic, he/she may manually open the valve to allow air to flow through the valve into the socket, equalizing the air pressure inside and outside the socket, for easier removal of the limb. 
     The manually-controlled air outlet and inlet valve is preferably opened and closed by twisting of a handle portion of the valve system, wherein partial rotation of the handle portion relative to the base portion of the valve system creates slight separation of the handle and base portions to form a gap through which may pass air from the well of the socket. This simple twisting, or partial rotation, allows sure and repeatable control of the valve wherein the valve stays in either the open or closed position without the user&#39;s hand holding the valve in that position. Thus, after opening the manual valve, the valve stays in hands-free open status, while the wearer may use his/her hands to don or doff the prosthesis. The manual valve preferably comprises a system for preventing the handle and base from becoming entirely separated during normal use, so that the handle portion does not fall off of the prosthesis. Also, the manual valve preferably comprises a stop (s) that limit(s) the amount of relative rotation of the handle and base portions of the valve, so that the user need only rotate the handle a small amount, for example, less than 90 degrees, to affect opening or closing the valve. The stop(s) may be part of the system for preventing the handle and base from entirely separating, or may be provided in addition to said system for preventing. 
     In one embodiment, the valve system comprises only said manual valve, while in another embodiment, the valve system comprises both a manual valve and also an automatic one-way air outlet valve. In yet another, less-preferred embodiment, the valve system may comprise only the automatic one-way air outlet valve. 
     In embodiments comprising the automatic air outlet valve, said automatic valve is a “one-way” or “check” valve, with a valve stem that “pops” or otherwise opens consistently and quietly at a small differential pressure, for example, a pressure inside the socket (in the distal space(s) between said socket and the limb or liner-covered limb) that is ≦3 psi pressure above ambient pressure (outside the socket). 
     The valve system, whether it includes only a manual valve, both manual and automatic valves, or only an automatic valve, are preferably adhesively mounted on the outside of the socket. Thus, the valve system is easier to mount than conventional valves due to this preferred adhesive mounting and due to preferably no part of the valve being installed from the inside of the socket. The preferred valve system has no threaded attachment to the socket, and no portion that extends into the hard socket. The preferred valve system comprises a base portion that is installed on or near the outside surface of the hard socket, preferably without threaded connection between the base and the hard socket. A hole is drilled in the hard socket from the outside surface of the socket to the inside surface of the socket, to align the hole in the socket with the bores/passages in the valve system. The other portions of the valve system, for example, the handle and the optional one-way valve structure, are then connected to the base portion, without said other portions requiring any contact with, or direct attachment to, the hard socket. Said other portions may be removable for cleaning, replacement of o-rings or other seals, and/or for other maintenance without removing the base from the hard socket. 
     The inventors envision, however, that features of the invented valve system may also be incorporated into a valve that is attached to a hard socket by other means than are discussed herein as being preferred. For example, conventional mounting systems for air expulsion valve in the industry, as discussed in the Related Art section above, may allow a valve with some of the invented features of the present invention to be used in a format wherein the valve is connected to a base that protrudes or resides inside the hard socket. 
     In embodiments comprising a one-way air outlet valve, the one-way valve stem may have a polygonal side wall, or have other recesses or grooves in its side wall(s) to create passages through which air may flow quietly. Alternatively, the valve stem may be cylindrical and the channel in which the valve stem slides (the valve housing bore) may be polygonal or have recesses or grooves in its wall(s), to create passage through which air may flow quietly. Or, both valve stem and the housing bore may be non-cylindrical. The preferred low-profile, external-mounting of the valve, and the quieter action of, and quieter air flow from, the one-way valve as it “pops” and expels air frequently during walking, may result in a less intrusive and less noticeable apparatus than is more acceptable and less embarrassing to wearers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a hard socket and liner combination, wherein one embodiment of the invented valve is shown attached to the outside of the hard socket. In this view, the liner is shown as spaced from the socket, but it will be understood from the foregoing discussion, that the liner and socket will tend to be in close contact for at least part of the length along the socket and preferably all around the circumference of the liner and socket at or near the top (proximal region) of the socket. Some space between the liner-covered limb distal end and the socket interior surface distal end is normally present, so that the limb does not reach all the way to the distal end of the well of the socket. 
         FIG. 1B  is a schematic view of a hard socket holding a residual limb with second generation roll-on liner, with one embodiment of the invented valve system installed on the hard socket distal portion. This view illustrates more accurately the preferred relationship of residual limb, roll-on liner, socket and valve. 
         FIG. 1C  is a schematic cross-section detail view of a two-layer liner on a residual limb RL, such as in  FIG. 1B , wherein the liner has an inner gel-layer G that contacts the residual limb RL and an outer fabric layer F that adhered to the gel-layer G. 
         FIG. 2  is a front perspective view of the valve embodiment of  FIG. 1 , which valve embodiment comprises a one-way air outlet valve but not a manual air inlet and outlet valve. 
         FIG. 3  is a front view of the valve embodiment shown in  FIGS. 1 and 2 , with a front cover, o-ring/gasket, and spring removed to better show internals of the valve. 
         FIG. 4  is a side view of the valve embodiment shown in  FIGS. 1-3 . 
         FIG. 5  is a cross-sectional side view of the embodiment shown in  FIGS. 1-4 , and the valve is shown in the closed position. 
         FIG. 6  is a cross-sectional side view of the embodiment shown in  FIGS. 1-5 , wherein the valve is shown in the open position allowing air to be expelled. 
         FIG. 7  is an exploded perspective view of the valve embodiment shown in  FIGS. 1-6 . 
         FIG. 8  is an alternative embodiment of a valve stem that may be used in the embodiment of  FIGS. 1-7  and that has an o-ring in its end surface. 
         FIG. 9  is a cross-sectional view of an alternative embodiment of valve system, installed on a hard socket exterior surface over a hole, wherein the valve system comprises a one-way outlet valve similar to the embodiment of  FIGS. 1-7  and also comprises one embodiment of the invented manual air inlet and outlet valve. In  FIG. 9 , the one-way outlet valve is shown in the closed position, which means that the pressure inside the socket well has not reached a level above the ambient pressure that caused the valve stem to move outward and open the one-way valve passage. In  FIG. 9 , the manual valve is in the closed position. 
         FIG. 10  is a cross-sectional view of the embodiment of  FIG. 9 , wherein the manual valve is still in the closed position, but the one-way outlet valve has opened to allow expulsion of air from the socket well. 
         FIG. 11  is a cross-sectional view of the embodiment of  FIGS. 9 and 10 , wherein the one-way valve is in the closed position, but the manual valve has been opened, by turning/rotating the handle portion relative to the base portion, so that air may enter or exit the hard socket well from a passageway between said handle portion and said base portion. 
         FIG. 12  is a side view of the embodiment of  FIGS. 9-11 , removed from the hard socket, wherein the base portion is shown in cross-section and the manual valve is shown closed and the one-way valve is hidden inside the handle portion. 
         FIG. 13  is a side view of the embodiment of  FIGS. 9-12 , removed from the hard socket, wherein the base portion is shown in cross-section and the manual valve is opened, and the one-way valve is hidden inside the handle portion. 
         FIG. 14  is a cross-sectional view of an alternative embodiment of the invented valve system installed on a hard socket wall over a hole, which valve system comprises a manual valve in the closed position and which does not comprise a one-way inlet and outlet valve. 
         FIG. 15  is a cross-sectional view of the embodiment of  FIG. 14 , wherein the handle portion has been turned/rotated to open the manual valve, so that air may enter or exit the hard socket well from a passageway between said handle portion and said base portion. 
         FIG. 16  is a cross-sectional view of the embodiment of  FIG. 12 , viewed along the line  16 - 16  in  FIG. 12 , this cross-section portraying positions of tabs and ramps in a position wherein the manual valve is closed. 
         FIG. 17  is a cross-sectional view of the embodiment of  FIGS. 12 and 13 , viewed along the line  17 - 17  in  FIG. 13 , this cross-section portraying positions of tabs and ramps in a position wherein the manual valve is closed. 
         FIG. 18  is a side view of the embodiment of  FIGS. 14 and 15 , with the handle portion separated from the base portion. In  FIG. 18 , the external ramps of the handle portion are shown (the one near the viewer in solid lines and the one hidden from view in dashed lines) and the cooperating bore and internal ramps of the base portion are shown in dashed lines. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the Figures, there are shown several, but not the only, embodiments of the preferred valve system for prosthetics.  FIGS. 1-8  illustrate an embodiment having only a one-way air outlet valve.  FIGS. 9-11  illustrate an embodiment having both a one-way air outlet valve and an embodiment of a manual valve.  FIGS. 12-18  illustrate an embodiment that having only an embodiment of a manual valve. 
     Referring to embodiments that include a one-way air outlet valve, it will be understood by one of skill in the art after reading this application and viewing the drawings, that, once the air pressure inside the hard socket (relative to the ambient pressure outside the socket) exceeds the crack pressure of the one-way valve, the invented one-way or “check” valve opens and air is expelled out through the valve. This is useful during donning of the socket, as the insertion of the limb, or liner-covered limb, increases pressure in the socket well; the one-way valve system opens to generally equalize the ambient pressure and the pressure inside the socket in order to allow the donning. 
     After donning, when the wearer takes each step, pressure is exerted downward on the limb, that is, toward the bottom of the socket well, and this also increases the pressure inside the socket well. Again, the preferred one-way valve will “crack” or “pop” to relieve this pressure, and then close when the pressure is generally equalized by cessation of the downward pressure of the step, and/or when the swing phase of the gait suspends the prosthetic from the residual limb/liner and a slight suction/vacuum (relative to the ambient pressure) tends to be created in the socket. The preferred valve is designed with a “crack pressure” in the range of ≦3 psi differential, and more preferably 1-3 psi, or most preferably 1-2 psi, differential, so that, with this slight suction/vacuum, and preferably with any pressure differential below the “set-point” (selected from the range of 1-3, or 1-2, psi positive pressure inside the socket well, that is, 1-3 or 1-2 psi above the ambient pressure outside the socket well), the valve will close to not allow air into the socket through the one-way valve. 
     Valve system  10  is adapted to cooperate with a suspension system  100  for external prosthetic devices, which, as discussed in the Related Art section, preferably include a liner that provides at least some blockage/hindrance to air passing between the socket and the liner. As shown in  FIG. 1 , the preferred suspension system  100  comprises a liner  103  received on a residual limb, and a hard socket  105  adapted to fit over the liner  103  and residual limb. The hard socket  105  comprises a sidewall  110  defining an interior space I, wherein the sidewall  110  comprises an outer surface  115  and an inner surface  120 . 
     The liner  103  is preferably a roll-on liner, and may be of various types, as discussed in the Related Art section, which provide varying amounts of “suction.” Modern liners comprising both an inner gel layer and a textile/fabric outer layer are preferred, and the preferred valve system of the invention cooperates well with these liners. The valve system embodiments comprising a one-way air outlet valve are specially adapted to allow air to be expelled quietly and consistently, even as often as every step, as may be desired with the amounts of air “leakage” experienced with fabric-covered liners. 
     As shown in  FIGS. 2-7 , valve system  10  comprises a base  20  having an internally threaded circular bore  22  extending through the base  20 . The base  20  is generally cylindrical in shape and is preferably fabricated from a durable polymeric material or “plastic.” Alternatively, the base  20  may not comprise threads, but may instead have other adaptation for joining to the one-way valve assembly that is inserted and secured to the base. For example, a bayonet or other latching mechanism that anchors or secures the valve assembly into the base may be used. 
     The base  20  has a generally flat bottom portion  24  and a slightly curved or rounded top portion  26  (see  FIG. 4 ). The bottom  24  of the base  20  may be slightly concave to mimic the contour of the outer surface  115  of the socket in the preferred distal installation area on the socket. See  FIGS. 1 and 1B , wherein the region labeled as “Distal Area” (or D) is indicative of the preferred, but not the only, region for attachment of the invented valve system. Distal attachment is preferred, wherein “distal” broadly refers to attachment of the valve system to the socket in a region below where the lower-most end of the residual limb will reach in the socket during use. Distal attachment of the valve system, however, preferably does not include attachment of the valve system at the bottom-most point of the socket, as this location is occupied by the post leading to the prosthetic foot and/or a distal lock that connects to the lower-most end of the residual limb. 
     With the valve system  10  placed on a distal area of the hard socket  105 , it may expel air as needed even when the residual limb is nearly fully, or fully, inserted into the socket. Also, in this area, the valve system  10  is discreet when covered by clothing and does not protrude (as it would from a more proximal side of the socket) to catch on clothing or other items. 
     After the base  20  is attached to the hard socket  105 , preferably by adhesive, a hole  125  is drilled through the sidewall  110  of the hard socket  105  via the bore  22  in the base  20 , so that the hole  125  generally aligns with the interior bore  22 , and bore  32  and opening  62  discussed below, for fluid communication between the socket well, hole  125 , bores  22 ,  32  and opening  62  to vent air out of the socket interior I. 
     One may see from the drawings that the preferred valve  10  has base  20 , o-ring  40 , valve housing  30 , stem  50  and ring/cover  60  all being coaxial, creating a passageway or “exit path” for air to pass through when the one-way valve opens. Note that, when fully assembled, the ring/cover  60  may snap into housing  30  (so that it can be easily removed for cleaning of the system) or may be attached to housing  30  by other methods such as adhesive. 
     In use, when the air pressure inside the hard socket  105  (between the liner-covered residual limb and the socket interior surface) exceeds the desired air pressure, as further discussed below, the air will force the valve stem  50  to move away from the opening  125  in the hard socket  105 , compressing the spring  55  against the ring  60 . This movement of the stem  50  unseats the end  54  of the stem from the sealing surface  38 , allowing air to flow around the end  54  and along the sides of the stem to the opening  62  of the ring, and out to the ambient air. 
     In other words, the valve system  10  comprises the valve assembly  11  that is inserted into the base  20 , which valve assembly  11  comprises a valve housing  30  having an internal circular bore  32  with a conical sealing surface  38  and an external threaded portion  34 . The threaded portion  34  on the valve housing  30  has a slightly smaller diameter than the threaded bore  22  in the base  20 , so that it may cooperate with the threaded bore  22  in the base  20 . As explained above for the base  20 , the valve housing  30  may be otherwise adapted for connecting/securing to the base. For example, the valve housing may not have any threads and may instead have bayonets that are received in slots in the base when the valve housing is inserted into and rotated in the base. 
     The exterior of the valve housing  30  is shown as “hex-shaped,” but other shapes may be used, such as other polygonal shapes or a cylindrical shape. The hex-shape is preferable as it may allow the technician to easily install and tighten the valve housing or the entire assembly in the base. Also, because the hex-shape provides a good surface to grip, it may allow the user to manually open the valve, in effect by disassembling the valve (removing the valve assembly from the base), if necessary, prior to the user removing his/her residual limb from the hard socket  105 . 
     An o-ring  40  or other seal is placed in a recess in the base  20  between the base  20  and the valve housing  30 . Once the valve housing  30  is threadably or otherwise received and secured in the base  20 , an air tight seal is created between the base  20  and the housing  30 . 
     The valve assembly  11  further comprises a valve stem  50  received in the bore  32  of the housing  30 . The valve stem  50  slides axially inside the bore  32  to seat against the sealing surface  38  of the housing, when the valve is closed, and to move away from and unseat from the sealing surface  38  when the valve is open. A spring  55  biases the valve stem  50  into the closed, seated position to close the valve except when a differential air pressure overcomes the spring  55  bias and pushes the valve stem  50  away from the sealing surface. Spring  55  is preferably a cylindrical coil compression spring, the design of which is the main determining factor in the crack pressure of the valve and which one of average skill can design after reading this disclosure. 
     The valve assembly, including the bias spring  55 , are adapted so that a differential pressure selected from a certain amount will “crack” or “pop” open the valve. In other words, the valve assembly and particularly the spring  55  are preferably designed so that, when the pressure on the “inner side” of the valve (to the left in  FIGS. 5 and 6 , and typically on the inside of the socket between the liner-covered limb and the interior surface of the socket at the lower end of the socket) is a certain amount above the pressure on the “outer side” of the valve (to the right in  FIGS. 5 and 6 , and typically outside the socket), then the valve will open. This “certain amount” is preferably in the range of 1-3 psi, and more preferably in the range of 1-2 psi. As soon as the differential pressure drops (that is, as soon as the inner pressure is less than the predetermined amount, preferably 1-3 psi or 1-2 psi, higher than the outer pressure) the spring  55  will again bias the valve stem  50  to the closed, seated position. Thus, as discussed above, the valve will open, if necessary, with each step of the wearer&#39;s gait, to allow air to vent from the socket well, and then quickly close after the air has been vented and/or when the swing portion of the gait lowers the pressure inside the socket well. 
     The valve stem  50  preferably has an internal bore  52  (or other hollow or recessed end or cavity that opens to the housing bore preferably at the spring-end of the valve) that may receive air that is flowing out of the valve in the “exit path” comprising passing around the stem, through or around the spring, and out through the outer end of the valve (at ring  60 ). Internal bore  52  may provide extra space for this flowing air, as it passes around or through the spring to exit the valve, thus helping prevent unpleasant noise or venting sounds that might occur with too-narrow portions of the exit path. Further, various embodiments of the bore  52  may be advantageous during the molding or machining process, for weight reduction, and/or for cooperating with or connecting to a spring or other bias member. The preferred location of the spring  55  places the spring between the flat face  53  of the valve stem  50  and the inner face  63  of the ring  60 , and held there securely enough that it may be repeatedly compressed between those surfaces and then released, when the valve opens and closes, respectively, without significantly shifting from its preferred radially-centered position. 
     Further, as shown in  FIG. 8 , there may be an o-ring  58  or other material on the generally conical end  54  of the stem  50 , which o-ring  58  or other material is preferably a softer or more flexible material, compared to the preferred brass or hard plastic valve stem  50 , for enhancing the seal between the stem  50  and the sealing surface  38 . Alternatively, the entire stem  50 , the conical end  54  of the stem, or another portion of the stem may be made of a softer plastic or other material with enhanced sealing performance. 
     Retaining ring  60  is a generally thin disc that is friction-fit, snapped, or otherwise secured and anchored into the bore  32  of the housing  30  to retain the spring  55  and the stem  50  in their proper positions inside the housing. The ring  60  is preferably secured to the housing, on ledge  39 , in such a way that it will not normally come out of the housing, but that an external prosthesis technician could pry or otherwise remove it to clean the valve assembly  11  and/or replace parts of the valve assembly  11 . Ring  60  has an opening  62  through which the air is expelled. Alternative ways of retaining the valve stem, spring, and/or other parts as may be desired, in the housings of the valve may be used. 
     The preferred stem  50  is a hexagonal, or other polygonal shape, so that it has multiple flat or generally flat sides  56 . Therefore, the air may flow along the end  54  of the stem and through the bore  32  of the housing in between the housing inner surface and one or more of the flat sides  56 . This provides multiple passages for the air, with each preferably being a relatively wide passage (that is, radially wider than if the stem where cylindrical inside a cylindrical housing bore), which is believed to be important for reducing air-venting noise. These passages may be said to be “spaced gaps” between the stem and the housing, in that they are spaced apart (separated) by the edges  57  of the stem, which contact, or come very close to, contacting the bore  32  surface. These gaps, therefore, may also be called non-annular gaps or non-annular spaces, as the gap/space between the stem and the bore of the housing is preferably not simply a continuous, annular space around the entire stem, but rather multiple axial passageways that are separated/spaced apart by the edges  57  that are close to, or that contact, the bore  32 . It may also be said that, because the stem and the housing bore are not the same shape (and particularly not the same circumferential shape), there are multiple gaps between the stem and the housing bore created by this difference in shape. This also places the stem  50  in the housing in a slidable arrangement, where it slides axially in the housing bore  32 , with contact being between the edges  57  of the sides  56  and the bore  32  surface, but not all the way around the circumference of the stem. This may be important for keeping the stem freely slidable in the bore  32  and less prone to plugging, seizing and/or becoming fouled to an extend that the valve would make more noise. 
     The preferred combination of an axially-sliding stem, and a polygonal or other stem shape, that provides multiple air passages along the sides of the stem (which are relatively wide by being flat, recessed, or otherwise spaced from the preferably cylindrical housing bore wall) are believed to be at least part of the reason for the quiet, consistent, and effective operation of the valve. Also, the preferred low crack pressure that is achievable with the preferred valve with repeated, consistent operation, is believed to be important and beneficial for quiet operation and effective prosthetic suspension without large swings in socket pressure. 
     Preferably, the base  20 , valve housing  30 , and retaining ring  60  are fabricated from a light-weight durable material, for example, Delrin™ plastic; however, other materials may be used such as aluminum, titanium, nylon or other plastics. Additionally, the stem  50  may be hard plastic or brass, but also may be manufactured from other materials, for example, including other metals, plastics, or combinations thereof. 
     The preferred valve system  10  is adapted to be fitted on the outside surface  115  of the hard socket  105 , and most preferably only to the outside surface  115 . The valve system  10  is preferably attached with adhesive, by applying adhesive of types known in the field of prosthetic sockets to the bottom  24  of the base and/or to the outer surface  115 . Other securement means may be used, but adhesive is preferred as it has been found to be reliable, easy to use, and not requiring any other fasteners or complex or protruding parts. Preferably, no portion of the valve system  10  extends through the socket wall, or into the interior space I of the hard socket  105 , or contacts the inside surface  120  of the hard socket  105 . The opening/hole  125  in the socket wall is made by drilling or otherwise cutting through the socket wall, and this step preferably does not include any threading or other shaping or preparing of the socket or the hole therein. Thus, the preferred valve and attachment of the valve may be used effectively with modern thin-walled, light-weight sockets. The valve system  10 , in the preferred but not all embodiments, consists essentially only of, and may consist only of, a base, a valve housing, an o-ring or other seal, a stem with or without supplemental sealing member or portion, a spring and a retainer ring or other closure or cover. This simple design is effective in terms of manufacture, installation, and operation, and has many benefits over prior art valves, including over the prior art valves that are more complicated, prone to plug-up, prone to make venting noise, that include ball-and-spring systems, and/or that screws/threads into the socket wall and/or that resides on both sides of the socket wall. In the preferred embodiment of the invented valve system, only the base, and more preferably only its bottom surface ( 24 ) or portions of the bottom surface ( 24 ), is in contact with the hard socket. 
     Preferred embodiments may be described as a one-way pressure-control system for a prosthetic hard socket, wherein the prosthetic socket comprises a wall having an outer surface and an interior surface defining a well for receiving a residual limb, and said wall has a hole extending from said outer surface to said interior surface; and wherein the valve system comprises: a base connected to said outer surface and having a base bore positioned over said hole in the wall; and the valve housing being connected to said base and extending into said base bore and having a housing bore generally coaxially aligned with said base bore and in fluid communication with said hole in the socket wall, said valve housing having a sealing surface; a valve stem received in said housing bore and slidable into a first, sealed position wherein a portion of said valve stem (preferably a sealing end) seals against said sealing surface and into a second, unsealed position away from the sealing surface; and a spring biasing the valve stem into the first, sealed position until said air pressure inside the prosthetic socket well is at a differential pressure in the range of 1-3 psi greater than ambient pressure outside the socket, at which time the valve stem is pushed by said differential pressure into said second, unsealed position so that air leaves the socket well by flowing through the hole and through the valve system. Alternatively, or in addition, the valve stem circumference may be not the same shape as the housing bore circumference (preferably one of the two being non-circular) so that, when the valve stem is in the second, unsealed position, air flows around the valve stem through axial gaps between the valve stem and the housing. Preferably, this difference in circumference/shape occurs along the stem side portion, which is the side portion of the stem not adapted to contact the sealing surface. The axial gaps are preferably different from simply an annular space all the way around the stem, and, instead, are axial passages separated by edges that come close to, or touch the housing bore. These edges&#39; proximity to the housing bore wall keeps the valve stem generally centered in the housing bore, while air flows freely past the valve stem through said axial gaps. Thus, the valve stem may be described as being shaped so that multiple axial gaps between the stem and a stem housing extend along the length of the valve stem to receive air flow when the valve stem is in the second, open position, and so that said multiple axial gaps are separated by axial edges of the valve stem that contact or come close to said stem housing and keep said valve stem generally centered in said housing. In many embodiments, said valve stem further has a hollow end with an opening near said spring, wherein said opening is in communication with the air passageway(s) through the valve, providing additional space for air to flow or reside, further reducing air venting noise. The venting of air sooner (at lower differential) and with less-restricted flow, compared to prior art vents is believed to be instrumental in reducing or eliminating the sudden, louder pop, squeak, or sputtering sounds of prior art devices. 
     The invention may also comprise the methods of installing and using such a valve system. For example, some embodiments of the invention may comprise a method of installing a pressure-relief valve in a prosthetic socket, wherein the method comprises: providing a hard socket; providing a one-way air valve comprising a base with a base bore, a removable valve stem housing with a housing bore, valve stem, and a spring; adhesively attaching said base to the outside of the socket; drilling a hole through the socket by inserting a drill bit through said base bore and drilling through the socket to make a hole in the wall generally coaxially aligned with said bore in the base; inserting and securing said housing into the base so that the housing bore is generally coaxially aligned with said base bore and said hole in the wall; inserting the valve stem and spring into the housing bore so that said valve stem slides in the housing bore to a closed position and an open position to allow venting of air out of the socket well when pressure builds in the socket to a differential pressure that is greater than ambient pressure. Preferably, the method comprises no insertion of any part of the air valve into the socket well, and no part of the air valve extends through the socket wall to reach the well. Preferably, the only attachment of the air valve to the socket is adhesive connection of the base to the outer surface of the socket, and, preferably, there is no threaded attachment of the air valve to the socket. 
     Referred now to  FIGS. 9-11 , an alternative embodiment comprises a valve unit  110  that includes a manual valve as well as a one-way valve. From the cross-sectional view of  FIGS. 9 and 10 , one may see that the one-way valve assembly  111  is threadably connected to a handle  120  that generally serves the same purpose relative to the valve assembly  111  as base  20  serves to valve assembly  11 , however, handle  120  is not directly attached to the socket. Instead, handle  120  is preferably expanded in diameter and/or provided with a flared outer circumference portion, or grip portion  121 , of hexagonal or other polygonal shape, to provide the user a larger, and preferably easily-rotatable grip surface when operating the manual valve. Further, instead of having a flat bottom (or rear surface) that attaches directly to the hard socket, handle  120  has a rear protrusion  123  that is received in and operatively connected to base  170 . It is base  170  that is directly connected to the socket, preferably in the same way as discussed above for the base  20 , that is, by adhesive. As discussed in detail for base  20 , base  170  preferably does not connect to, or include, any structure that reaches through the socket wall or into the socket well, but rather firmly is glued/adhesively attached to a distal region of the socket exterior wall surface. As discussed with base  20 , a hole (H in  FIGS. 9-11 ,  14 ,  15 ) may be drilled through the socket wall after attachment of the base  170  to the socket, or by other means or steps. As may be understood from discussion of such an attachment, it will be understood that such an attachment will be effective for a thin-walled socket and will be convenient and simple compared to more complex mechanisms that require fasteners or clamps or other structure both on the inside and the outside of the wall. 
     The operative connection of handle  120  (preferably with its valve assembly  111  including valve casing  111 ′) and the base  170  allow said handle and base to form a manual valve system that is substantially or entirely independent of the operation of the one-way valve. Handle  120  is preferably rotatable relative to base  170 , and is preferably coaxial with the base  170 . Upon rotation, in one direction, the handle  120  move close to the base  170  to seal against the base, and, upon rotation in an opposite direction, the handle  120  moves out away from the base  170  to create a space between the handle and base that allows air flow between the handle and base. In the manual valve closed position, shown in  FIGS. 9 and 10 , the rear surface  124  of the handle grip portion  121  seals to the front flange  172  of the base  170 , most preferably by means of an o-ring or gasket  174  provided in a groove on the flange  172  or otherwise retained on the flange. One may see in  FIGS. 9 and 10  that the one-way valve assembly  111  may operate as described above for valve assembly  11  (closed in  FIG. 9  and “popped” open in  FIG. 10 ) when the manual valve system is closed, that is, when the handle  120  and base  170  are in closed, sealed condition. When the manual valve is closed, the only passageway possible for air exit through the valve  110  is to pop the one-way valve. It is noteworthy that, whether the manual valve is closed, air may pass through the base  170  (through bore  176 ) and through the rear aperture  125  in the rear protrusion  123  to reach the one-way valve stem  150 , and, upon opening the stem  150  (as discussed above for stem  50 ), the air may flow around the stem and out of the one-way valve assembly via opening  162 . When the manual valve is opened, as discussed below, air will flow out via the space/gap between the base  170  and the handle  120 , rather than popping the one-way valve, or will flow in via said space/gap, depending upon the relative pressures inside the socket and outside the socket. 
     The preferred method of operating the manual valve is by rotation of the handle  120  relative to the base  170 , wherein cooperating structure of the handle and base serves to distance the handle  120  from the base  170  upon at least a portion of said rotation. Said cooperating structure preferably comprises at least one ramp on either of said handle  120  or said base  170  and at least one riding member on the other of said handle or base, wherein relative rotation of the handle and base allow the riding member to “ride” or slide along the ramp to change the relative axial location of the handle and the base. Said at least one ramp is slanted so that rotation preferably in the range of 30-270 degrees (more preferably 30-90 degrees and most preferably 30-70 degrees) distances the handle from the base enough to unseal the two from each other for air flow there-between. The riding member may be a protrusion or ramp. When the riding member is itself a ramp, one may consider the ramps to cooperate as do threads, but only threads that allow less than a full rotation. In other words, the handle may be unscrewed from the base less than a full rotation, so that the handle movement has an axial component to move the handle slightly out from the base. The rotational operation of the valve, in each of the opening direction and the closing direction, preferably is only a partial rotation (30-270 degrees, more preferably, a partial rotation in the range of 30-90 and, most preferably 30-60, degrees). Opening by rotation in the range of about 30-60 degrees, and closing in the opposite direction by rotation the same amount (also in the range of 30-60 degrees) is particularly comfortable and easy to perform, as the user simple “twists” the handle a short distance one way and then the other. The especially-preferred operation, therefore, is more like a quick twist than an screwing/unscrewing a threaded system. 
     In the especially-preferred embodiment, two ramps  127 ,  129  are provided 180 degrees apart on the outer, cylindrical surface  134  of the rear protrusion  123 . Two tabs  177 ,  179  are provided on the interior cylindrical surface of the bore through base  170 , and extending between the tabs  177   179  on said interior surface are ramps  181 ,  182 . When the preferred handle  120  is rotated clockwise relative to the preferred base  170 , ramps  181 ,  182  ride along ramps  127 ,  129  to pull the handle closer to the base, as if the handle were being screwed into the base, to an extent that seals the handle to the base at o-ring/gasket  174 . When the preferred handle  120  is rotated counterclockwise relative to the preferred base  170 , ramps  181 ,  182  ride in the opposite direction along ramps  127 ,  129  to allow the handle to be slightly distanced from the base, as if the handle were being unscrewed part-way from the base, to an extent that unseals the handle from the base at o-ring/gasket  174 . In this open condition, as shown in  FIG. 11 , air may flow out from the socket or into the socket through the space S (space S shown in  FIG. 15 ) between the handle and the base. 
     Tabs  177 ,  179  move, during said rotation, preferably between limiting structure (L,  FIGS. 16 and 17 ) that is preferably at the ends of ramps  127 ,  129 . The tabs  177 ,  179  may move between said limits L in areas of the outer surface  134  that is recessed relative to the areas upon which the ramps  127 ,  129  are located. 
     The handle  120  and base  170  are preferably connected and disconnectable by means of a snap system, wherein the handle snaps into the base and then is rotatable relative to the base. In the preferred embodiments, the handle and base snap together by the handle being positionable relative to the base in a position wherein portions of the ramps  181 ,  182  and/or tabs  177 ,  179  snap over slightly-protruding structure on the outer, cylindrical surface  134  to a point wherein the handle is base is held on the handle. Preferably, spaces (significantly wider than the tabs  177 ,  179 ) exist between the two ramps  127 ,  129  on the surface  134  (said relatively recessed areas mentioned above) and, as the two tabs  177 ,  179  into those recessed spaces, slide, portions of ramps  181 ,  182  also slide into said spaces and portions of ramps  181 ,  182  snap over the cooperating ramps  127 ,  129  on the handle rear protrusion outer surface  134 . There may be an optional slight protrusion at the entry of the recessed spaces over which the tabs may snap. When the tabs slide into the recessed spaces and the ramps  181 ,  182  snap over ramps  127 ,  129 , the base ends up in a position relative to the handle wherein the base is close to, and generally tight against the handle, and the manual valve is therefore closed. In this position, the handle and base have snapped together, and are in position for the ramps to slide along each other to open the manual valve when the handle is twisted counterclockwise relative to the base. If substantial pulling on the handle were conducted, the handle might snap off of the base, this is unlikely to happen unintentionally, as only twisting is necessary, and not pulling or pushing, to open and close the manual valve. 
     In  FIGS. 12-15 , and  18 , there is shown yet another embodiment  210 , wherein the valve system  210  comprises only a manual valve and not a one-way air outlet valve. The valve system  210  may be the same as that described above for  FIGS. 9-10 , but, instead of the handle having a bore there-through that receives and cooperates with a one-way valve assembly, the handle  120 ′ is closed at its front (toward the right in  FIGS. 12-15 , and  18 . The handle may still have a front, central indent, as portrayed in  FIGS. 14 and 15 , but this is preferably simply an optional indent or depression. As in the embodiment of  FIGS. 9-11 , the embodiments of  FIGS. 12-15  and  18  allows air to flow out of, and into, the socket, by flowing axially through a portion of the passageway (the portion in the base) and radially (through the space between the flange of the base and the rear side of the rear protrusion  123  of the handle. 
     The hard socket is preferably chosen from many conventional rigid prosthetic sockets currently available on the market. The suspension and/or connection systems for connection the hard socket may include locks, straps, and other mechanisms that are available on the market. 
     Although this invention has been described above with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to these disclosed particulars, but extends instead to all equivalents within the broad scope of the following claims.