Abstract:
A vacuum relief unit and method for venting air into a pool pumping system when a pressure level within the system drops below a first pressure level limit. The unit includes a closed air chamber, a device for venting chamber air from the air chamber into the pool pumping system when the pressure level in the pool pumping system drops below the first pressure level limit, a device for venting atmospheric air into the air chamber when the pressure level within the air chamber drops below a second pressure level limit that is lower than the first pressure level limit, and a device for delaying operation of the atmospheric air venting device when the pressure within the air chamber is no longer below the second pressure level limit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/821,466, filed Aug. 4, 2006, the contents of which are incorporated herein by reference. In addition, this application is related to U.S. Pat. Nos. 5,682,624 and 6,251,285, both to Ciochetti and both incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to pool safety equipment. More particularly, this invention relates to a method and unit for preventing an obstruction from being trapped by suction to an inlet of a pool filter pump system. The unit can be mounted directly to a skimmer lid of the pool filter pump system, and operates to vent air into the system when a vacuum level within the system exceeds a specified vacuum limit, as is the case if the drain or another inlet connected to the system is partially or completely obstructed, such as by a child or foreign object. 
     To maximize enjoyment and maintain proper sanitary conditions, swimming pools must be constantly cleaned of debris, dirt and other contaminants. Such a requirement is particularly demanding in the case of commercial pools and hot tubs that are likely to be used by a large number of people. For most pools and tubs (hereinafter simply referred to as pools for convenience), the primary task of cleaning is performed by a filter pump system that continuously draws water through a drain located at the bottom of the pool, typically at or near its deepest point, and through a number of suction lines located elsewhere, typically along the perimeter of the pool. As with all pools, but particularly commercial pools, a high rate of water flow must be achieved through a suitable filtering medium in order to maintain an acceptable level of cleanliness. Consequently, a high capacity pump must be employed to draw the water from the pool, with a relatively larger pump generally being required as the size of the pool increases. 
     A significant hazard with the use of such large filter pumps is the potential for individuals and particularly children to become drawn and trapped against the drain or a suction line as a result of the vacuum created by the pump when the drain or suction line inlet is obstructed. Occurrences of this type of accident have caused the pool industry to look for solutions. One approach has been to modify the drain construction, examples of which include U.S. Pat. No. 4,658,449 to Martin, directed to a protective adapter for covering a pool drain, and U.S. Pat. No. 3,940,807 to Baker et al., directed to modifying the drain opening itself in order to more uniformly distribute the flow of water toward the center of the drain. While such approaches may be acceptable for many pool applications, a solution that is capable of being retrofitted to an existing pool without altering the appearance, size or construction of the drain is often more desirable and practical. Furthermore, these solutions only reduce the suction level at the drain, and safer operation of a pool can be achieved if the dangerous suction condition at the pool drain is completely eliminated if the drain is obstructed by a child. 
     As a solution, vacuum relief valves and units for preventing a child or an object from being trapped by suction to a drain or any other suction line are taught in U.S. Pat. Nos. 5,682,624 and 6,251,285 to Ciochetti. The valve taught by U.S. Pat. No. 5,682,624 is configured for mounting directly to a suction line between a drain or suction line and the filter pump, while the valve taught by U.S. Pat. No. 6,251,285 is configured for installation as a lint trap cover on an otherwise conventional lint trap unit located upstream of a pool filter pump. Both valves generally operate by causing the filter pump to quickly lose its prime when a child or object obstructs or becomes trapped against the drain or suction line inlet, so that the vacuum created by the filter pump is completely eliminated. In particular, the valves permit air to rapidly flow into the drain and suction lines if a predetermined vacuum level is exceeded within these lines, as is the case if the drain or one of the pool&#39;s suction line inlets becomes partially or completely obstructed. The rapid influx or venting of air eliminates the vacuum within the lines and, therefore, the resulting unsafe condition. The response of the valve is preferably damped such that the valve will remain open sufficiently long to cause the filter pump to completely lose its prime. 
     Operational aspects of certain vacuum relief valves currently on the market include the ability to be locked in the open (venting) position to allow for the release of an obstruction without time constraints. Such valves do not reset themselves, but must be manually reset in order for the pump to return to normal operation. However, a valve can be unnecessarily actuated by a transient vacuum spike (pressure drop), for example, during pump startup, and certain valves may have a tendency to rapidly open and close during pump startup. Furthermore, pump damage can occur if the pump continues to run when the valve is locked open and continues to vent air into the pump. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a vacuum relief unit and method for venting air into a pool pumping system when a pressure level within the system drops below a pressure level limit. 
     According to a first aspect of the invention, the unit includes a closed air chamber containing chamber air, a device for venting the chamber air from the air chamber into the pool pumping system when the pressure level in the pool pumping system drops below the first pressure level limit, a device for venting atmospheric air into the air chamber when the pressure level within the air chamber drops below a second pressure level limit that is lower than the first pressure level limit, and a device for delaying operation of the atmospheric air venting device when the pressure within the air chamber is no longer below the second pressure level limit so that atmospheric air continues to be vented into the air chamber by the atmospheric air venting device after the pressure in the air chamber is no longer below the second pressure level limit. 
     According to a second aspect of the invention, the method involves venting chamber air from an otherwise closed air chamber into the pool pumping system when the pressure level in the pool pumping system drops below the first pressure level limit, venting atmospheric air into the air chamber when the pressure level within the air chamber drops below a second pressure level limit that is lower than the first pressure level limit, and delaying operation of the atmospheric air venting device when the pressure within the air chamber is no longer below the second pressure level limit so that atmospheric air continues to be vented into the air chamber by the atmospheric air venting device after the pressure in the air chamber is no longer below the second pressure level limit. 
     According to preferred aspects of the invention, the vacuum relief unit addresses a number of operational issues of vacuum relief valves. First, the vacuum relief unit is operable to vent air into a pumping system for a sufficient time to clear an obstruction, but without necessarily being locked in the open (venting) position. Second, the unit is able to absorb transient vacuum spikes (pressure drops), and as a result does not unnecessarily vent sufficient air into the pumping system to lose prime during pump startup and other normal transient conditions. Third, the unit is able to reset itself in the closed position after an obstruction has been cleared or otherwise after the unit has vented air into the pumping system. Another preferred aspect of the unit is that it can be readily installed as a separate unit in a skimmer, and therefore is simple to install and more financially accessible to individuals who own private pools. 
     Other objects and advantages of this invention will be better appreciated from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary cross-sectional view of a vacuum relief unit in accordance with an embodiment of this invention. 
         FIGS. 2 and 3  represent cross-sectional and plan views of a pump priming delay mechanism of the vacuum relief unit of  FIG. 1 . 
         FIGS. 4 and 5  are cross-sectional and plan views of a flutter valve of the pump priming delay mechanism of  FIGS. 2 and 3 . 
         FIG. 6  is a fragmentary cross-sectional view of the pump priming delay mechanism shown in  FIGS. 2 and 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A vacuum relief unit  10  is represented in the Figures as comprising an air chamber  12  defined by a dome-shaped housing  20 , two diaphragms  14  and  16  that operate in series within the housing  20 , and a piston  18  also within the housing  20 . The housing  20  is configured to be installed in the cover of a pool lint trap (not shown) connected to a pumping system of a pool, hot tub, etc., and is provided with threads  22  at a lower end thereof to permit the housing  20  to be threaded into an opening formed in a conventional lint trap cover. However, it should be understood that the unit  10  is not limited to this type of installation. 
     From  FIG. 1 , it is evident that the first and second diaphragms  14  and  16  are not mechanically coupled to each other. The first diaphragm  14  operates to seal the chamber  12  from a suction line of a pool (not shown) to which the lint trap is connected, and only opens to permit venting of air within the chamber  12  to the suction line if a sufficiently low subatmospheric pressure level is reached in the suction line. (For purposes of clarity, relative levels of vacuum will be discussed in terms of pressure (relative to absolute zero pressure), so as not to confuse what is meant by a “low” or “high” vacuum level.) The pressure level at which venting occurs is determined by a spring  24  mounted to a post  28  on which the diaphragm  14  and spring  24  are mounted. The diaphragm  14  is normally closed against a web  34  under the force of the spring  24 , whose force holding the diaphragm  14  closed can be made adjustable with a fastener  26  secured to the end of the post  28 . The diaphragm  14  and its support assembly (post  28 , spring  24 , and fastener  26 ) are housed within a cavity  32  formed by a boss  30  that extends into the air chamber  12 . The post  28  can be seen as disposed within a passage in the web  34 , which serves as a seat for the diaphragm  14 . Vent holes  36  and  38  are provided in the web  34  and in the walls of the boss  30  to allow air to flow from the air chamber  12  and past the diaphragm  14  when the diaphragm  14  is not seated against the web  34  (as shown in  FIG. 1 ). 
     The second diaphragm  16  seals the air chamber  12  from atmospheric air outside the housing  20 , and only opens to permit air from the atmosphere to vent into the chamber  12  if a sufficiently low pressure level is reached in the chamber  12 . According to a preferred embodiment of the invention, the pressure level in the air chamber  12  required to actuate the diaphragm  16  is lower than the pressure level in the suction line required to actuate the diaphragm  14 . Furthermore, the chamber  12  is preferably of sufficient size to act as a buffer for absorbing brief pressure drops during pump startup. As a result, the second diaphragm  16  is able to remain closed while the first diaphragm  14  is open for a brief period of time. 
     Similar to the first diaphragm  14 , the pressure level at which venting is allowed to occur through the second diaphragm  16  is determined by a compression spring  44  mounted on the piston  18 , on which the diaphragm  16  and spring  44  are also mounted. The diaphragm  16  is normally closed against the web  48  under the force of the spring  44 , whose force holding the diaphragm  16  closed can be made adjustable, for example, with one or more spacers  68  between the lower end of the spring  44  and the boss  30 . As will become evident below, the opening and closing of the diaphragm  16  determines when air is vented to a pumping system. For this reason, it will typically be useful to adjust the spring load provided by the spring  44  with a vacuum gauge to optimize the operation of the unit  10  for the capacity of a given pumping system. 
     The piston  18  on which the diaphragm  16  is mounted is received and free to reciprocate within a bore  42  at the upper end of the boss  30 . The upper end of the piston  18  is received and reciprocates within a cylinder  46 , represented as being defined by an upper protuberance on the housing  20 . The diaphragm  16  can be seen as being operable to close against a seat defined by a web  48 , which delineates a second cavity  50  between the air chamber  12  and the cylinder  46 . Vent holes  52  connect the second cavity  50  to atmospheric air, so that the second cavity  50  remains at atmospheric conditions at all times.  FIG. 1  represents the condition in which a sufficiently low pressure within the air chamber has unseated the diaphragm  16  from the web  48 , allowing air to flow from the surrounding atmosphere through the vent holes  52 , into the second cavity  50 , past the diaphragm  16 , and into the air chamber  12 . 
     Together, the diaphragm  16 , piston  18 , cylinder  46 , and web  48  are components of what is termed herein a pump priming delay mechanism  40 , shown in greater detail in  FIGS. 2 through 6 . The piston  18  prevents the second diaphragm  16  from reclosing too quickly, ensuring that atmospheric air continues to be supplied to the air chamber  12  and the suction line in the event that a sufficiently low pressure is sustained in the pumping system for a sufficiently long duration (for example, a sustained obstruction) to unseat the diaphragm  14  and then unseat the diaphragm  16 . In effect, though the diaphragm  16  is adapted to open and close at lower pressure levels than the diaphragm  14 , the diaphragm  16  will not prematurely close as the pressure level rises above the pressure level required to close the diaphragm  16 , but instead gradually closes as the pressure level approaches (or exceeds) the pressure level required to close the diaphragm  14 . 
     To achieve the above functionality,  FIGS. 2 and 6  shown the travel of the piston  18  into the cylinder  46  as being resisted by a flutter valve  54  at the upper end of the cylinder  46 . The flutter valve  54  is retained at the upper end of the cylinder  46  by a retaining lip  56 , and is biased by a spring  62  to normally close a pair of intake vents  58  at the top of the cylinder  46 . A pair of intake holes  64  are formed in the flutter valve  54  so as not to be aligned with the intake vents  58  of the cylinder  46 . The nonalignment of the intake vents  58  and holes  64  can be maintained by preventing the flutter valve  54  from rotating within the cylinder  46 , such as with complementary axially-oriented features (not shown) on the cylinder  46  and valve  54 . A bleed vent  60  formed at the upper end of the cylinder  46  remains open when the intake holes  58  are closed by the flutter valve  54  as a result of a bleed hole  66  formed in the valve  54  to be aligned with the bleed vent  60  in the cylinder  46 . 
     When a vacuum within the pumping system causes the first diaphragm  14  to travel downward and vent air from the air chamber  12  into the pumping system, the diaphragm  16  initially remains closed as a result of requiring a lower pressure level for actuation. Accordingly, if the vacuum drop (pressure decrease) in the pumping system is not sufficiently low or of sufficient duration, air is only drawn from the air chamber  12 . Once the diaphragm  14  recloses, inherent air leakage through the diaphragm  16  gradually allows the air chamber  12  to return to atmospheric conditions. 
     If the pressure level within the pumping system is sufficiently low and of sufficient duration, the pressure level within the air chamber  12  will eventually cause the second diaphragm  16  to travel downward, unseating the diaphragm  16  from the web  48  and allowing atmospheric air to be vented into the chamber  12 . The corresponding downward travel of the piston  18  draws atmospheric air into the cylinder  46  through the intake vents  58  in the cylinder and the intake holes  64  in the flutter valve  54 . In the event that the low pressure level is sustained, sufficient air is vented through the diaphragm  16 , air chamber  12 , and diaphragm  14  to cause the pumping system to lose its prime, allowing any obstruction that might have caused the pressure drop to be freed from the drain/suction line of the pool. In the event that the obstruction can be freed before the pumping system loses its prime, the pressure level is likely to rapidly rise within the air chamber  12 , prompting the second diaphragm  16  to rapidly travel upward under the force of the spring  44  to engage the web  48  and block the flow of atmospheric air into the chamber  12 . The correspondingly rapid upward stroke of the piston  18  compresses the air within the cylinder  46 , forcing the flutter valve  54  upward to close the intake holes  58  so that further travel of the piston  18  (and therefore the second diaphragm  16 ) is delayed as the remaining air within the cylinder  46  is vented to atmosphere through the bleed hole  64  in the valve  54  and the bleed vent  60  in the cylinder  46 . 
     While the invention has been described in terms of a specific embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, it is well within the capability of those skilled in the art to alter the physical configuration of the vacuum relief unit  10  from that shown, and employ various materials and processes to make and assemble the individual components of the unit  10 . Therefore, the scope of the invention is to be limited only by the following claims.