1. Field of the Invention
This invention relates to the design of reed valves.
2. Background of the Invention
A reed valve consists of a reed 1a (FIG. 1), generally designed to be a long slender cantilever made from metal or plastic, flat and rectangular in shape. The fixed end 1b of the flat face is attached to a stationary surface 1c, whereas the opposite free end 1d is free to deflect, primarily about the thinner cross-sectional axis 1h of the reed. The free end of the reed covers a port 1e also located also on a stationary surface, hereby referred to as a ported surface 1f. The deflection is caused by fluid flowing perpendicular to the flat face of the reed's free end. Where fluid flows through the port upward and away from the ported surface, the flow encountering the reed deflects the reed away from the ported surface, providing an opening 1g for continued free flow of fluid, and is referred to the permitted flow condition. Whereas, for fluid flowing reversely downwards towards the ported surface, and through the port, the reed is deflected towards the ported surface, causing contact with the ported surface, thereby covering the port, and blocking further flow of fluid. The reverse flow direction is referred to as the unpermitted flow direction. Therefore, fluid flow is permitted in one direction, and prevented in the opposite direction.
Reed valves function similarly to check valves, but are much lighter, and much more flexible. The lighter, more flexible reed requires less fluid force to deflect, and therefore provide distinct advantages over check valves. Because of these lower forces, reed valves actuate with lower differential pressures, flow rates, and for fluids with lower mass densities. Reed valves also provide advantages over check valves related to maintaining alignment of the reed free end relative to the port. While the reed is relatively free to bend about its minor axis 1h, flexure is prevented laterally due to bending rigidity about its major axis 1i. Additional alignment features such as sliding guides 2a (FIG. 2) required for check valves are not required, thereby eliminating additional friction or binding forces that can inhibit the motion of the check valve plunger 2b. Less inhibited motion of the reed valve allows the reed valve to operate more consistently at lower pressures, flow rates, and fluid densities than check valves.
The major disadvantages of reed valves are, because of the lightness and flexibility, the reed must be long and slender. As such, the overall envelope of the reed valve is generally much larger than that of a check valve. For applications inline with piping systems, reeds require relatively large and complicated housings, and may be more susceptible to leakage, and may impractical in application due to the relatively large size. Additionally, reed valves do not contain higher pressures, due to the thin, slender section required for flexibility.
The proposed art is a compact reed 3a (FIG. 3) that is thin and flexible as the existing art, but is more compact in overall envelope, and therefore able to fit within the cross sectional envelope of adjoining piping. The compactness of the proposed art allows for larger porting and sealing surfaces within smaller housings, and therefore offers more opportunities for practical application. The proposed art achieves these advantages by utilizing maximum length arms 3b which maximize the flexural length 3c within the limitation of the port and respective piping diameter envelope. In addition to maximizing flexibility by maximizing length, the arm length extension creates an offset 3m between the end of the arms and the center of the reed sealing surface 3g. The offset 3m permits further flexure of the arms and the reed sealing surface, thereby increasing the overall reed flexibility. The thickness 3d of the thinner minor flexural axis further maximizes flexibility. The thickness may be the same as the remainder of the reed to simplify manufacturing of the reed by machining, cutting, or etching processes, or may be different to achieve other design goals.
The high flexibility of the arms also reduces stresses resulting from deflection of the reed arms. Such stresses, particularly at junctions 3e from the arm to the fixed base 3i and from the arm to the reed sealing surface 3g, otherwise could be high. In applications where a high number of deflection cycles are anticipated, higher stresses could result in fatigue fracture of the reed arm. The stresses may be further reduced at the said junctions by utilizing compound radius transitions, also considered part of junctions 3e. A large radius 5a (FIG. 5) widens the arm 3b, distributing stresses over a wider surface. A smaller radius 5b further transitions the arm geometry in the larger area of adjoining structure, controlling any stress concentrations. Both the flexible arms and the compound radii transitions minimize stresses, allowing for longer life in high cycle environments.
The arm thickness 3d, width 3f, and location near the reed sealing surface edge 3h offers less restriction to flow than would other designs where the arms were thicker, wider, or placed farther away from the sealing surface edge 3h. Smaller overall dimensions of the reed arms provide less drag area and more remaining area in the compact space for fluid to flow. Furthermore, the arms are placed close to the sealing edge to take advantage of direction of the flow streamlines exiting the plane of the sealing surface. Close to the reed sealing surface edge 3h, the streamlines 4a (FIG. 4) run parallel to the reed sealing surface 3g. As such, alignment of the width 3f of arm 3b with the flow streamlines 4a is least restrictive to flow. Aligned with the flow streamline 4a, the projected area of the arm on the flow is minimized, maintaining a larger remaining passageway for flow. Furthermore, the orientation of the arm width provides structural rigidity and strength of the valve to resist any inadvertent drag forces. Conversely, flow streamlines near port 4d or close to the housing wall 4e are oriented perpendicularly to the arm 3b width. As such, less area would be available for free flow, drag forces on the arms would be higher due to the higher frontal area, and drag related bending about the arm 3b weaker minor axis would produce higher stresses, and lower fatigue life.
To allow for a thin reed to resist high pressures under reverse flow conditions, a grated seat 3j (FIG. 3) is used in lieu of a single hole port. The grated seat supports the reed sealing surface span against pressure forces in the unpermitted flow direction. The grating contains a plurality of holes 3k (FIG. 3), which maximizes flow area in the permitted flow direction, while providing structural support via material remaining between holes 3k, referred to as grating 3l, to resist pressure forces in the unpermitted flow direction. Furthermore, the holes 3k need not be equal in diameter or spacing. The size and spacing may be different in order to adjust the velocity and direction of the streamlines 4a encountering the arms. For instance, the flow streamlines incident on the arms may be adjusted to be more parallel to the sealing surface 3g by reducing the hole 3k diameters on the outer perimeter of the hole pattern, and enlarging the hole 3k at the center of the pattern. Enlarging the center hole would promote higher fluid velocity in the center of the port 4d opening, whereas reducing the hole size at the outer perimeter would inhibit flow velocities at the port 4d periphery. The velocity gradient would therefore bend the streamline 4a more into alignment with the arm width 3f. 
A reed 3a assembled with a grated reed seat 3j defines a reed valve assembly.
The novelty of the proposed art is advantageous for liquid fluids as well as gas fluids. Operation in liquid applications provides for more sensitive actuation of the valve. The grated design allows exposure to higher pressure forces that typically are associated with liquid applications. The proposed art has fewer parts, as the spring, alignment mechanism, and sealing surface may be integrated into one part. As such, the more complicated multiple part check valve construction typically associated with fluidic service is replaced with a simpler, more reliable, and more cost effective integrated part.
3. Objects and Advantages
The objects and advantages of the proposed invention are:                a) A reed valve that is thin and flexible as the prior art, but is able to fit within the envelope of adjoining piping, allowing for smaller housings,        b) Through the design of the flexural element junctions, able to minimize stresses related to deflection, thereby improving fatigue life,        c) A simple design manufacturable by machining, cutting, or etching processes,        d) The ability to consolidate multiple parts found in similarly compact check valves, such as springs, alignment features, and sealing surfaces, into one part,        e) Small flexural element cross-sectional dimensions that offer low restriction to flow, and also by orientation of the flexural element cross-sectional minor and major dimensions within the flow streamline, maximizes remaining area available for fluid flow        f) Orientation of the said minor and major dimensions to provide strength needed to structurally support the element from any inadvertent fluidic drag forces,        g) Support of the sealing surface by a grated seat against the pressure forces in the unpermitted flow direction, and        h) The size and location of specific passages in the grated seat to promote or inhibit fluid flow in specific locations in the port area, which affect the direction and velocity of resulting streamlines, particularly in the area of the flexible arms.        
Further objects and advantages of the design will become apparent from a consideration of the drawings and ensuing description.
USPTO Backgrounds
USPTO Backgrounds