Abstract:
A check valve is provided to maintain fluid flow in a single desired direction through a conduit. The check valve requires a greater fluid pressure to open the check valve to allow fluid to pass in a desired direction than an amount of pressure required to keep the check valve in its open position. This variable opening force performance is provided by providing a closure arm exerting a closure force on a flapper urging the flapper toward its closed position. Contact between the closure arm and the flapper occurs between a follower on the closure arm and a cam surface on the flapper. A contour of the cam surface on the flapper, and especially a hump on the cam surface causes the closure arm to exert a variable amount of force on the flapper depending on the position of the flapper. When the flapper is closed a relatively large amount of force is exerted on the flapper. When the flapper is open a relatively smaller amount of force is exerted on the flapper by the closure arm. The dimensions and contours of the follower and the cam surface can be customized to provide desired closure arm force exerting characteristics for the check valve of this invention.

Description:
FIELD OF THE INVENTION 
     This present invention relates generally to check valves for keeping fluid from traveling in a reverse direction and more specifically, to a check valve having a variable opening-force threshold. 
     BACKGROUND OF THE INVENTION 
     Backflow check valves are typically utilized in fluid-carrying pipelines to prevent the backflow or return of downstream fluids, such as from service lines or main supply lines. Such backflow check valves are commonly situated between the main supply line and a facility&#39;s (school, home, etc.) service line. Examples of such check valves may be found by reference to U.S. Pat. No. 6,050,293 to Lin et al., U.S. Pat. No. 3,789,874 to Hills, U.S. Pat. No. 4,887,792 to Kuo, U.S. Pat. No. 3,482,603 to Outcalt and U.S. Pat. No. 3,334,858 to Hay. 
     Though Hills, Kuo, Outcalt, and Hay all disclose a check valve assembly for backflow prevention in pipelines, their designs are disadvantageous in light of the present invention. All of the aforementioned devices require a specific predetermined threshold fluid pressure to initially open the check valve, and thereafter, require the fluid pressure to remain relatively constant, if not greater, to maintain the check valve in an open position. A decrease in fluid pressure often results in check valve “flutter” and the associated signature noise, wherein the flutter noise is caused by the valve plate flapping back and forth due to the lack of requisite pressure to maintain the check valve in a consistently open position. Furthermore, none of the aforementioned devices incorporate into their design the ability to allow opening of the check valve upon variance of fluid flow threshold. 
     Therefore, it is readily apparent that there is a need for a check valve having a variable opening force threshold, wherein the check valve requires a relatively larger initial forward flow pressure to open the check valve but thereafter requires a relatively smaller forward-flow pressure to keep the check valve in an open position, thereby reducing check valve “flutter” and allowing closure of the check valve upon the ceasing of forward flow and/or the initiation of backflow. 
     SUMMARY OF THE INVENTION 
     Briefly described, in a preferred embodiment, the present invention overcomes the above-mentioned disadvantages and meets the recognized need for such a device by providing a check valve with variable opening force threshold, wherein the check valve requires a relatively large initial forward-flow pressure to open the check valve but thereafter, only requires a relatively small forward-flow pressure to maintain the check valve in an open position. As such, the present invention reduces check-valve flutter and allows closure of the valve upon backflow or if forward flow is reduced below a predetermined minimum threshold. 
     According to its major aspects and broadly stated, the present invention in its preferred form is a check valve generally comprising a check-valve assembly having a mounting member, a buttress, a valve seat, a valve plate, a pivotable cam arm, a pivotable closure arm and a follower wheel. 
     More specifically, the present invention is a check valve having a mounting member to secure the check-valve assembly into a body such as a pipeline. The mounting member preferably includes a mounting section, a valve seat section and a buttress, wherein the buttress carries a flapper assembly, a pivotable cam arm and a pivotable closure arm. The flapper assembly generally has a valve plate and a plate cap. The valve plate is attached to the pivotable cam arm. The pivotable cam arm includes a hump forming a cam surface opposite the valve plate. A follower wheel attached to the pivotable closure arm rests on the cam surface of the hump. When a forward flow of fluid pushes against the plate cap, the follower wheel of the pivotable closure arm must first overcome the hump of the pivotable cam arm to open the valve. Upon reaching a predetermined opening threshold pressure, the pivotable closure arm is sufficiently loaded that the attached follower wheel overcomes the cam hump thus allowing the valve to fully open. Thereafter, only minimal force is required to maintain the valve in an open position due to the contour of the remainder of the cam surface. 
     OBJECTS OF THE INVENTION 
     A feature and advantage of the present invention is the novel and unique initial opening-force threshold of the device. 
     A feature and advantage of the present invention is the ability of the check valve, after reaching the initial opening-force threshold, to remain open with relatively slow fluid flow or minimum pressure. 
     A feature and advantage of the present invention is the ability of the check valve to remain open with relatively slow fluid flow yet still avoid check valve flutter commonly associated with such conditions. 
     A feature and advantage of the present invention is that the hump on the pivotable cam arm can be varied in size, shape and slope to adjust the overall performance of the check valve relative to the initial forward flow force and thus create a suitable check valve for any fluid flow conditions. 
     A feature and advantage of the present invention is its ability to be incorporated into any environment where prevention of fluid backflow is desired. 
    
    
     These and other objects, features and advantages of the invention will become more apparent to one skilled in the art from the following descriptions and claims when read in light of the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood by reading the detailed description of the preferred and alternate embodiments with reference to the accompanying drawing figures, in which like reference numerals denote similar structure and refer to like elements throughout, and in which: 
     FIG. 1 is a top perspective anterior view of a check-valve assembly according to a preferred embodiment of the present invention. 
     FIG. 2 is a top perspective posterior view of a check-valve assembly according to a preferred embodiment of the present invention. 
     FIG. 3 is a partial cutaway perspective view a check-valve assembly according to a preferred embodiment of the present invention showing the check-valve assembly mounted in a pipe. 
     FIG. 4 is a top plan view of a check-valve assembly according to a preferred embodiment of the present invention. 
     FIG. 5 is a posterior elevation view of a check-valve assembly according to a preferred embodiment of the present invention. 
     FIG. 6 is an anterior elevation view of a check-valve assembly according to a preferred embodiment of the present invention. 
     FIG. 7 is a side elevation view of a check-valve assembly according to a preferred embodiment of the present invention. 
     FIG. 8 is a section view along line  8 — 8  of FIG. 4 of a check-valve assembly according to a preferred embodiment of the present invention showing the check-valve assembly in a closed position. 
     FIG. 8A is a detailed section view of a portion of FIG. 8, taken along line  8 A— 8 A of FIG.  8  and showing the follower wheel of the pivotable closure arm resting on the hump of the cam surface when the check-valve assembly is in the closed position. 
     FIG. 9 is a section view similar to that of FIG. 8, but showing the check-valve assembly in an initially partially opened position. 
     FIG. 9A is a detailed section view of a portion of FIG. 9, taken along line  9 A— 9 A of FIG.  9  and showing the follower wheel of the pivotable closure arm resting just past the hump of the cam surface when the check-valve assembly is in the initially partially opened position. 
     FIG. 10 is a section view similar to that of FIG. 8, but showing the check-valve assembly in a fully opened position. 
     FIG. 10A is a detailed section view of a portion of FIG. 10, taken along line  10 A— 10 A of FIG.  10  and showing the follower wheel of the pivotable closure arm resting on the upper ramp portion of the cam surface when the check-valve assembly is fully opened. 
     FIG. 11 is an exploded perspective view of a check valve assembly according to a preferred embodiment of the present invention. 
     FIG. 12 is a graphical representation depicting the check-valve assembly position relative to fluid flow pressure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In describing the preferred and alternate embodiments of the present invention, as illustrated in FIGS. 1-12, specific terminology is employed for the sake of clarity. The invention, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish similar functions. 
     Referring now to FIGS. 1-2, the present invention in its preferred embodiment is a check-valve assembly  10 , wherein check-valve assembly  10  generally is formed of three assemblies which can move relative to each other including a mounting member  20 , a flapper assembly  120  and a pivotable closure arm assembly  340 . 
     More specifically, mounting member  20  is preferably approximately circular and ring-like in shape having a mounting section  22 , a valve seat section  50  and a valve buttress  70 . Valve seat section  50  preferably has a reduced diameter as compared to mounting section  22 , thereby forming lip  24  on mounting section  22  and lip  52  on valve seat section  50 . Mounting section  22  preferably has mounting throughholes  32 ,  34 ,  36  and  38  formed through and on the outer edge of lip  24  of mounting section  22  and mounting throughholes  40  and  42  formed through lip  24  of mounting section  22  for securing check-valve assembly  10  to body A (FIG.  3 ). Body A is any housing unit commonly known and used in the art of fluid flow such as, for exemplary purposes only, pipes for carrying and transporting fluids. Surface  54  of valve seat section  50  defines valve seat  56 , wherein valve seat  56  serves as a sealing surface when flapper assembly  120  is in the closed position. To allow for the movement of fluid through mounting member  20 , mounting section  22  and valve seat section  50  of mounting member  20  further define a preferably centrally positioned passage  30  therethrough. 
     Now referring more particularly to FIGS. 2 and 11, buttress  70  extends preferably generally perpendicular from the lower portion of surface  54  of valve seat section  50 . Buttress  70  is preferably semi-circular or trough-like in shape and comprises a top wall  72  and a bottom wall  74  joined with a first sidewall  78 , a second sidewall  80 , a third sidewall  82 , a fourth sidewall  84 , a fifth sidewall  86 , a sixth sidewall  88 , a seventh sidewall  90 , an eighth sidewall  92 , a ninth sidewall  94 , a tenth sidewall  96 , an eleventh sidewall  98 , a twelfth sidewall  100  and a thirteenth sidewall  102 . 
     Specifically, first sidewall  78  extends approximately perpendicular from surface  54  toward the posterior of check-valve assembly  10  to second sidewall  80 . Second sidewall  80  extends from first sidewall  78  in a preferably downwardly sloping manner toward the posterior of check-valve assembly  10  to third sidewall  82 . Third sidewall  82  extends preferably downwardly from second sidewall  80  to fourth sidewall  84 . Fourth sidewall  84  extends approximately perpendicular from third sidewall  82  toward the anterior of check-valve assembly  10  to fifth sidewall  86 , wherein first closure arm pin throughhole  104  is formed generally centered on forth sidewall  84 . 
     Fifth sidewall  86  extends approximately perpendicular from fourth sidewall  84  to sixth sidewall  88 . Sixth sidewall  88  extends approximately perpendicular from fifth sidewall  86  toward the anterior of check-valve assembly  10  to seventh sidewall  90 , wherein first cam arm pin throughhole  108  is formed in sixth sidewall  88  proximal to seventh sidewall  90 . 
     Seventh sidewall  90  extends approximately perpendicular from sixth sidewall  88  and approximately parallel with surface  54  to eighth sidewall  92 . Eighth sidewall  92  extends approximately perpendicular from seventh sidewall  90  toward the posterior of check-valve assembly  10  to ninth sidewall  94 , wherein eighth sidewall  92  has a second cam arm pin throughhole  110  formed therein proximal to seventh sidewall  90  and wherein first cam arm pin throughhole  108  aligns with second cam arm pin throughhole  110 . 
     Ninth sidewall  94  extends approximately perpendicular from eighth sidewall  92  to tenth sidewall  96 . Tenth sidewall  96  extends approximately perpendicular from ninth sidewall  94  toward the posterior of check-valve assembly  10  to eleventh sidewall  98 , wherein second closure arm pin throughhole  106  is formed generally centered on tenth sidewall  96 . Eleventh sidewall  98  extends preferably upward and approximately perpendicular from tenth sidewall  96  to twelfth sidewall  100 . Twelfth sidewall  100  extends from eleventh sidewall  98  to thirteenth sidewall  102  in a preferably upwardly sloping manner. Thirteenth sidewall  102  extends from twelfth sidewall  100  to surface  54  of valve seat section  50 , wherein thirteenth sidewall  102  is approximately perpendicular to surface  54 . 
     Mounting section  22 , valve seat section  50  and buttress  70  can all be formed as a single molded or machined unit from any material and/or method known within the art to form mounting member  20 . Alternatively, mounting section  22 , valve seat section  50 , and buttress  70  can all be separately molded or machined from any material and/or method known within the art and thereafter attached together by any method known within the art. 
     More specifically, referring now to FIGS. 2,  8  and  11 , flapper assembly  120  generally comprises a pivotable cam arm  122 , a valve plate assembly  140 , a plate seal  200  and a closure plate  220 . Preferably, cam arm  122  is preferably generally an elongated rectangular-shaped member, wherein the first elongated sidewall  128  of cam arm  122  is bent slightly inward proximal to the mid-region of first elongated sidewall  128  thereby producing an angled leg portion. A nose portion  124  extends from second elongated sidewall  130  proximal to the mid-region thereof. The upper surface of nose portion  124  is generally ramped and serves as caming surface  126  for follower wheel  360 . Nose portion  124  preferably has a distal end that serves as a hump  125  for the follower wheel  360  to overcome during use, as more fully described below. A throughhole  132  is positioned preferably equa-distant from the mid-region and the first end  136  of cam arm  122  for mounting cam arm  122  to flapper assembly  120 . A throughhole  134  is positioned proximal to the second end  138  of cam arm  122  for pivotably mounting cam arm  122  to buttress  70 . Second end  138  of cam arm  122  is preferably rounded or tapered to facilitate pivotation of cam arm  122  while mounted to buttress  70 . While only one cam arm  122  is shown, multiple arms could pivotably support the flapper assembly relative to the buttress  70  of the mounting member  20 . 
     Valve plate assembly  140  is preferably circularly shaped and comprises a front wall  142  and a rear wall  146  joined by an outer peripheral wall  144 . Along periphery  148  of rear wall  146  are formed a series of pockets  150 ,  152 ,  154  and  156  for capturing fluid backflow, thereby facilitating the ultimate closure of flapper assembly  120 . 
     Rear wall  146  preferably has a first upper cam arm alignment plate  158  and an opposing parallel second upper cam arm alignment plate  160  formed on the upper vertical center of rear wall  146 . Rear wall  146  further has a first lower cam arm alignment plate  162  and an opposing parallel second lower cam arm alignment plate  164  preferably positioned on the lower vertical center of rear wall  146 . First upper cam arm alignment plate  158  and second upper cam arm alignment plate  160  are separated a sufficient distance to snugly receive first end  136  of cam arm  122 . First lower cam arm alignment plate  162  and a second lower cam arm alignment plate  164  are separated a sufficient distance to snugly receive the mid-region of cam arm  122 . 
     Flanking first and second upper and lower cam arm alignment plates,  158 ,  160 ,  162  and  164 , respectively, are first cam arm mounting bracket  166  and second cam arm mounting bracket  168 . First cam arm mounting bracket  166  and second cam arm mounting bracket  168  are preferably somewhat crescent shaped and comprise preferably centrally positioned first mounting bracket throughhole  170  and second mounting bracket throughhole  172 , respectively, wherein first mounting bracket throughhole  170  and second mounting bracket throughhole  172  are horizontally aligned. 
     Pivotable cam arm  122  is seated and positioned between first, second, third and fourth cam arm alignment plates,  158 ,  160 ,  162  and  164 , respectively, and first and second cam arm mounting brackets,  166  and  168 , respectively, wherein cam arm mounting pin throughhole  132  is aligned with first and second mounting bracket throughholes  170  and  172 , respectively, and wherein first elongated sidewall  128  of cam arm  122  approximately abuts rear wall  146  of valve plate assembly  140 . Once positioned, cam arm  122  is secured to valve plate assembly  140  by inserting cam arm mounting pin  184  through first mounting bracket throughhole  170 , cam arm mounting pin throughhole  132  and second mounting bracket throughhole  172 . First and second ends of cam arm mounting pin  184  are preferably fitted with lock rings  186  and  188  to secure cam arm mounting pin  184  in position, wherein lock rings  186  and  188  snugly rest within a peripheral recessed area formed on each end of cam arm mounting pin  184 . Once attached, the valve plate assembly  140  preferably does not pivot relative to the cam arm  122 . As an alternative, some relative movement can be accommodated. 
     As best shown in FIGS. 5,  8  and  11 , flanking first cam arm mounting bracket  166  are throughholes  174  and  180 , and flanking second cam arm mounting bracket  168  are throughholes  176  and  178 . Throughholes  174 ,  176 ,  178  and  180  extend through valve plate assembly  140  and are dimensioned to receive bolts  302 ,  300 ,  304  and  306 , respectively, to secure closure plate  220 , plate seal  200  and valve plate assembly  140  together. A peripheral lip  201  extends from front wall  142  of valve plate assembly  140  thereby defining a recessed area  182  dimensioned for receiving on the inner diameter thereof plate seal  200 . Plate seal  200  is preferably washer-like in shape, and comprises a front wall  202 , an outer peripheral wall  204 , a rear wall  206  and an inner peripheral wall  208 . Plate seal  200  further preferably has a centrally positioned passage  210  therethrough defined by inner peripheral wall  208 . Plate seal  200  is dimensioned to be received within recessed area  182  of valve plate assembly  140  such that rear wall  206  of plate seal  200  and outer peripheral wall  204  preferably abut front wall  142  and lip  201 , respectively, of valve plate assembly  140 . 
     With continued referenced to FIGS. 8 and 11, closure cap  220  is preferably a circular disk having a first section  222  and a second section  224 , wherein second section  224  has a reduced diameter thereby forming lip  230  and area  226  opposite a front wall  228  of first section  222 . Lip  230  on the periphery of second section  224  is dimensioned to be snugly received within passage  210  of plate seal  200 , wherein lip  230  of second section  224  abuts inner peripheral wall  208  of plate seal  200 , and wherein area  226  of plate cap  220  abuts front wall  202  of plate seal  200 . Extending through closure cap  220  are throughholes  240 ,  242 ,  244  and  246 , positioned to align with throughholes  174 ,  176 ,  178  and  180 , respectively, of valve plate assembly  140  for receiving bolts  302 ,  300 ,  304  and  306 , respectively. 
     Flapper assembly  120  is pivotably secured to check valve buttress  70  via cam arm pivoting pin  320  and cam arm lock rings  322  and  326 . Cam arm pivoting pin  320  extends through first cam arm pin throughhole  108 , through lock ring  322 , through cam arm pivoting pin throughhole  134 , through lock ring  326  and then through second cam arm pin throughhole  110 . Both ends of cam arm pivoting pin  320  have a recessed area formed thereon for receiving and securing lock rings  330  and  332  therein. 
     Pivotable closure arm  340  is preferably forked in shape and comprises a first tong member  342 , a second tong member  344  and a tong leg  346 . First tong member  342  and second tong member  344  are separated by a width similar to the width of a follower wheel  360 . First tong member  342  possesses a first follower wheel pin throughhole  348  and second tong member  344  possesses a second follower wheel pin throughhole  350 . Tong leg  346  possesses a closure arm pin throughhole  352 . Follower wheel  360  is preferably spool-like in shape with alignment lips on either edge and possessing a centrally positioned follower wheel pin throughhole  362 . Follower wheel  360  is rotatably secured between first and second tong members  342  and  344 , respectively, via follower wheel pin  364 . Follower wheel pin  364  is located on a flapper contact end of the arm  340  and extends through first follower wheel pin throughhole  348  of first tong member  342 , through follower wheel pin throughhole  362  of follower wheel  360  and finally through second follower wheel pin throughhole  350  of second tong member  344 . 
     Pivotable closure arm  340  with secured follower wheel  360  is secured to check valve buttress  70  at a pivot end opposite the flapper contact end via closure arm pivoting pin  370  and springs  372  and  374 . Closure arm pivoting pin  370  extends through first closure arm pin throughhole  104 , through spring  372 , through closure arm pin throughhole  352 , through spring  374  and through second closure arm pin throughhole  106 . Both ends of closure arm pivoting pin  370  are then fitted with closure arm pivoting pin nuts  376  and  378  to secure closure arm pivoting pin  370  in place. 
     Referring now to FIGS. 1-12, in use, check valve assembly  10  is secured to body A. When flapper  120  is in the closed position, plate seal  200  of valve plate assembly  140  abuts sealing surface  56  of valve seat  50 , and cam surface  126  of the apex of hump  124  rests on follower wheel  360  as illustrated in FIGS. 8-8A. When the initial fluid supply pressure and force through conduit C (FIG. 3) are relatively large in the forward fluid flow direction F and pushes against front wall  228  of closure cap  220 , flapper  120  is pushed off of sealing surface  56  of valve seat  50  toward a more open position as illustrated in FIGS. 9-9A. As a result, cam surface  126  of the apex of hump  124  pushes and rolls against follower wheel  360 . A continued large forward flow results in follower wheel  360  of pivotable closure arm  340  to completely overcome hump  124 , thus pushing flapper  120  to its fully opened position as illustrated in FIGS. 10-10A. When flapper  120  is in this fully opened position, follower wheel  360  is positioned at the base of hump  124  as illustrated in FIGS. 10-10A. As illustrated in FIG. 12, after flapper  120  has been opened fully, a low pressure and overall slower forward fluid flow is sufficient to maintain flapper  120  in its fully opened position. 
     Flapper  120  will fully close upon the occurrence of one of two events, a complete halt of forward fluid flow in direction F or backflow of fluid in direction B. When forward fluid flow stops, the pressure and force needed to hold flapper  120  in an opened position is absent. The tension generated in springs  372  and  374  during the initial opening of flapper  120 , and the downward pivotation of pivotable cam arm  122 , is released. In turn, this release in tension forces pivotable cam arm  122  to spring forward, forcing follower wheel  360  to rotate back over cam surface  126  of hump  124  so that the apex of hump  124  once again rests on follower wheel  360 , resulting in closure of flapper  120  as illustrated in FIGS. 8-8A. When flapper  120  is in its closed position, plate seal  200  of valve plate assembly  140  once again abuts sealing surface  56  of valve seat  50 . 
     In the event of backflow in direction B, fluid force will push against second section  224  and pocket  232  of closure cap  220  as well as accumulate in pockets  150 ,  152 ,  154  and  156  of valve plate assembly  140 , forcing flapper  140  to fully close, via upward pivoting of pivotable cam arm  122  and rotation of follower wheel  360  back over cam surface  126  of hump  124 . Once fully closed, plate seal  200  of valve plate assembly  140  abuts sealing surface  56  of valve seat section  50  thereby preventing backflow contamination of untainted fluid in the main supply pipeline. 
     Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only, and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. For instance, while the flapper assembly  120  and closure arm assembly  340  are shown pivotably attached, they could be configured to move linearly or pivot about different axes than those shown and still maintain the contacting follower and cam surface to perform as desired. Also, the follower wheel  360  could be lobed or merely be configured as a non-rolling skid to slide upon the cam surface. The lengths and pivot points of the assemblies  120 ,  340  could also be adjusted to alter performance characteristics to match desired design parameters. The check-valve assembly  10  could be removably inserted into a conduit body A as shown or build into the conduit body in an integral fashion. Accordingly, the present invention is not limited to the specific embodiments illustrated herein, but is limited only by the following claims.