Patent Publication Number: US-8534572-B2

Title: Sprinkler to top riser and housing seal cartridge for gear drive sprinkler

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 11/438,621 filed on May 22, 2006 which is based on and claims priority to U.S. Provisional Application 60/682,994, filed May 20, 2005, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Gear drive sprinklers have a larger riser diameter than spray heads and the pressure load on the riser against the sprinkler housing top is much greater so that having the riser come up and seat against the rubber is undesirable. In my U.S. Pat. No. RE 35,037 I disclosed a gear driven sprinkler where the riser bottoms against the retraction spring when it is loaded up by the irrigation system pressure in the body can of the sprinkler. Also shown is a long cylindrical riser seal portion that extends down to seal to the riser at its bottom circumference when the sprinkler is in the up extended position. 
     U.S. Pat. No. 4,316,579 is a good summary of riser seal prior art. 
     One problem with known devices is that the soft rubber seal portion tends to lose dimensional stability over time, and then effectiveness of the seal deteriorates. Also known seals have not been completely effective as a low pressure seal to prevent blow-by while the sprinkler is being pressurized. 
     Thus, a need exists for an improved seal construction for sprinkler risers. 
     SUMMARY 
     The present invention seeks to satisfy the above described need by providing an improved seal construction in which an internally hard plastic core is molded into the rubber seal. This permits the less dimensionally stable rubber portion of the seal to retain the proper tolerances over time. 
     Also, with its hard core, the seal is configurable to provide a small downwardly angled low pressure seal to limit water blow-by during the sprinkler pressurizing phase and yet is soft and flexible enough to ensure minimum resistance during sprinkler riser retraction by the retraction spring when the water pressure is turned off. 
     The stack-up height of the retraction spring coils is such as to carry the high mechanical housing pressure load on the riser up against the sprinkler housing can top. A seal extension cylindrical portion extends downwardly and touches the riser on an upward flange portion of a spring carrier ring around the riser to provide a positive clamping seal to prevent leakage around the riser at high pressure. This clamp seal for high pressure allows the thin flexible lip portion of the riser seal to be thin and flexible since it does not have to seal against high pressure. The rubber portion of the seal cartridge are connected by channels so that a seal ring around the outside of the seal cartridge can provide the seal between the seal cartridge and the body can. 
     There is a step on the outside circumference of the seal cartridge to transmit the pressure load on the spring cartridge by the riser against the retraction spring and the seal seat position to the sprinkler housing can top. 
     Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a cross-section of a sprinkler riser housing seal cartridge according to the invention with the riser in the retracted position. 
         FIG. 2  shows a cross-section of the same sprinkler with the riser pressurized fully up with the riser seat on the spring and a portion of the riser seal also touching and sealing against the riser spring carrier ring. 
         FIG. 3  is an enlarged partial cross section similar to  FIG. 2  showing details of the seal cartridge. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows a cross section of a sprinkler  1  having an outer housing or body  4 , a rotary drive mechanism  5 , a riser  2 , and a nozzle assembly  6  mounted at the top of riser  2 . Here, riser  2  in the retracted position.  FIG. 2  shows the same sprinkler with the riser  2  in its fully extended position resulting from compression of riser return spring  8  by the pressure of the water entering the sprinkler at its lower end  7 . 
     Sprinkler  1  as illustrated is conventional, and its construction and operation are well known to those skilled in the art. The seal cartridge according to the invention, generally denoted at  3 , is shown as used in sprinkler  1 , and will be described in that context in detail in connection with  FIG. 3 . It is to be understood, however that this is exemplary, and only for purposes of illustration. The invention is directly applicable to any other sprinkler system which employs a riser. 
     Referring now to  FIG. 3 , only the portion of sprinkler  1  including seal cartridge  3 , the associated portions of riser  2  and sprinkler housing  4  are shown. Seal cartridge  3  is comprised of a hard plastic outer shell  10  formed of ABS or any other material having similar properties, and a resilient circumferential ring  12  formed of a polyurethane material such as Pellthane® or an equivalent, around the outside of shell  10  which provide a resilient rubber seal to the sprinkler body housing inside surface  15 . This ring  12  of resilient polyurethane material is bondable during molding to cartridge shell  10  and the ring  12  is fed during the co- or insert molding process by circumferentially spaced ribs  13  down from a resilient material ring  14  around the top of the seal cartridge to form an unitary structure with ring  12 . 
     An inner surface seal, i.e., the portion which defines the inside diameter of the seal, can be formed by a tubular body  16  of resilient polyurethane material extending down from resilient ring  14  spaced radially inward from ribs  13 , and bonded to the inner surface of shell  10 . Shell  16  terminates at its lower end in a reduced diameter lip seal  20  which functions to prevent low-pressure blow-by during upward movement of riser  2 . 
     Alternatively, the inner surface seal may be in the form of circumferentially spaced axial ribs positioned in grooves formed in the inner surface of shell  10 . This can provide guidance and centering of riser  2  during the riser upward movement, and helps ensure the smaller lip seal  20  functions properly during the riser upward movement. 
     Extending downward from inner seal portion  16  radially outward from lip seal  20 , is a cylindrical extension  22  of cartridge shell  10  in which is formed a support groove  31  for riser return spring  8 . This is covered by resilient radial collar portion  32  connected to cylindrical inner seal portion  16  by a thin downwardly extending neck portion  33 . Collar  32  is seated on the riser spring carrier ring  40  upper cylindrical portion  41  which is tight fitted to the riser around its bottom. 
     This resilient material  32  is fed during molding as a continuous thin cylinder of material or with multiple ribs from above down the inside of the seal cartridge hard shell  10  around the inside circumference. 
     The main feature of the seal cartridge is its thin lip seal cartridge to riser  20  which is flexible and allows easy riser retraction but adequate seal for the pressure (such as 7 to 10 p.s.i.) necessary to push the riser  2  full bottoming on the retraction spring  10  spring groove  30  and seal cartridge step  60  to the sprinkler body top  70 . 
     This construction is very strong due to the hard nature of the shell plastic material and well able to carry hard forces during sprinkler system water hammer occurring where empty lines fill with water. 
     Good high pressure sealing is provided by slight compression of resilient collar  32  after assembly. The result of the illustrated construction is a durable and leak-free seal which provides long term reliability and smooth operation for the riser. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.