Abstract:
A duplex strainer for straining material includes a housing, housing inlet port through which material enters the housing under pressure for straining and an outlet port through which strained material exits the housing. The housing includes a first strainer chamber having the first and second ports in separate fluid communication with the housing. A second strainer chamber includes third and fourth ports in separate fluid communication with the housing. The first port opposes the third port and the second port opposes the fourth port. A valve control structure includes a first three-way ball valve disposed within the housing for controlling fluid flow between the first port, third port and the housing. A second three-way ball valve is disposed within the housing to control fluid flow between the housing, second port and fourth port.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a duplex strainer and, in particular, to a duplex strainer having an improved flow diverter mechanism. 
     Duplex strainers have been developed in order to permit continuous straining and cleaning of a flow. Duplex strainers generally include two strainer chambers and some type of mechanism for diverting the flow from one chamber to the other to permit cleaning, servicing or repairing of one chamber while the other one is in use. This permits the flow through the duplex strainer to remain continuous. 
     One such duplex strainer is known in the art described in U.S. Pat. No. 4,496,463 which includes a unitary housing with an inlet port and an outlet port. A first and second strainer chamber, each having first and second ports, are in separate fluid communication with the housing. A scotch yoke design converts rotation of a first shaft into reciprocal lateral displacement of first and second disc assemblies to permit either the first or second strainer chamber to be closed off to flow while the other of the first or second strainer chambers remain open to flow. 
     Another design of the duplex strainer consists of two cylindrical plugs or one tapper plug as transfer valve and having one piece body casting. Such a duplex strainer has been satisfactory for its intended application, however, it suffers from the disadvantages that the casting of a unitary piece body is difficult. Furthermore, it is difficult to effect a tight seal with the sleeve and it was impossible to perform in-line repairs upon the strainer. Accordingly, it is desired to provide an improved duplex strainer which overcomes the disadvantages of the prior art design. 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with the present invention, a duplex strainer for straining a material such as a liquid, steam or gas flowing through the strainer, is provided. The strainer includes a housing having an inlet port through which the material enters the housing under pressure for straining and an outlet port through which the strained material exits the housing. The housing includes a first strainer chamber having first and second ports in separate fluid communication with the housing. A second strainer chamber mounted to said housing including third and fourth ports in separate fluid communication with the housing. The first port opposes the third port, and the second port opposes the fourth port. 
     A first three-way ball valve is disposed within the housing for controlling communication between the housing first port and third port. A second three-way ball valve is disposed within the housing to control fluid communications between the housing, second port and fourth port. A shaft couples the first three-way ball valve to the second three-way ball valve so that the two move in unison, rotation of the three-way ball valve controls flow of the material into the first chamber and the second chamber. 
     Accordingly, it is the object of the present invention to provide an improved duplex strainer. 
     Another object of the present invention is to provide a duplex strainer having an improved mechanism for effecting flow diversion. 
     Yet another object of the invention is to provide a duplex strainer which includes a field replaceable seat design so that the strainer body stays in line and does not need to be removed. 
     A further object of the invention is to provide a duplex strainer which eliminates the need of a shut-off valve upstream of the strainer. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification. 
     The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: 
       FIG. 1 is a partial sectional perspective view of a duplex strainer constructed in accordance with the invention; 
       FIG. 2 is an exploded view of part of the duplex strainer constructed in accordance with the invention; 
       FIG. 3 is a sectional view of the Duplex strainer constructed in accordance with the invention, showing the liquid flow path therethrough; and 
       FIG. 4 is a sectional view taken along line  4 — 4  of FIG. 3. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference is first made to FIGS. 1 and 2 which depict a duplex strainer, generally indicated at  10 , constructed in accordance with the invention. Duplex strainer  10  includes a housing  20 , a first straining chamber assembly  30  formed in housing  20 , and a second straining chamber assembly  40  coupled to housing  20 . The valve assembly, generally indicated at  80 , is disposed within housing  20  and controls fluid flow between housing  20  and each of straining chamber assemblies  30 ,  40 . 
     As can be seen more clearly in FIG. 2, housing  20  is divided by a divider  22  into an upper chamber  24  and a lower chamber  26 . A channel  29  extends through divider  22 . A system entrance port  23  communicates with upper chamber  24  to provide an input for fluids into housing  20 . Similarly, a system exit port  25  communicates with lower chamber  26  to allow fluids to exit from housing  20 . A straining chamber assembly entrance port  19  provides fluid communication between straining chamber assembly  30  and upper chamber  24 . A straining chamber assembly exit port  27  provides fluid communication between straining chamber assembly  30  and lower chamber  26 , so that a fluid, unless prevented by valve assembly  80 , flows into housing  20  through system entrance port  23 , then into straining chamber assembly  30 , through straining chamber  30  and into lower chamber  26  through straining chamber assembly exit port  27 . The overall flow of fluid through straining chamber assembly  30  is in a substantially C-shaped pattern. 
     Reference is now made to strainer basket assembly  40  which will be described in detail, strainer basket assembly  30  not shown in detail being substantially a mirror image of strainer basket assembly  40 , the primary difference being that strainer basket assembly  30  forms a unitary member with housing  20 , while strainer basket assembly  40  is attached to housing  20  and will be discussed in detail below. Strainer basket assembly  40  includes a straining chamber  32  therein. A flange  34  extends entirely about the inner diameter of straining chamber  32 , extending towards the center of straining chamber  32  to form a lip therein, dividing straining chamber  32  into an upper portion and a lower portion. An entry port  36  is provided at the upper portion of straining chamber  32  providing fluid communication between upper chamber  24  of housing  20  and straining chamber  32 . Similarly, exit port  38  provides fluid communication between the lower portion of straining chamber  32  and lower chamber  26  of housing  20 . A releasable cover  42  is mounted to straining chamber  32  by a stud and knob  44  to maintain straining chamber  40  in a sealed condition during operation. An O-ring  57  is disposed between cover  42  and straining chamber  32  to prevent fluid leakage during straining. 
     A basket, generally indicated at  46 , is dimensioned to be received within straining chamber  32 . Basket  46  includes a strainer  48 . A flange  54  extends from the top of strainer  48 . Flange  54  is dimensioned to rest on flange  34  within straining chamber  32 . Basket  46  also includes the handle  52  for removal of basket  46  to allow the removal of strained material trapped within strainer  48  as will be discussed in detail below. An O-ring  56  is disposed between flanges  34  and  54  to prevent the leakage of unstrained fluid into the lower portion of straining chamber  32 . In an exemplary embodiment, straining chamber  32  is provided with a drain  68 , having a threaded inner surface  70 . A threaded plug  58  releasable seals drain  68  to allow drainage of straining chamber  32  as needed. 
     A plurality of bolt holes  62  are formed in a face  71  of housing  20 . Strainer basket assembly  40  is mounted to housing  20  by a plurality of bolts  60  releasable secured in bolt holes  62  and corresponding bolt holes (not shown) formed adjacent exit and entrance ports  38 ,  36  of strainer basket assembly  40 . When attached, entrance port  36  provides a fluid pathway between straining chamber  32  and upper chamber  24  of housing  20 . Similarly, exit port  38  provides a liquid path between straining chamber  32  and lower chamber  26  of housing  20 . The liquid flow path is substantially C-shaped, exiting housing  20  through entrance port  36 , down through straining chamber  32 , and basket  46 , and returning to housing  20  through exit port  38 . An O-ring  64  is disposed between housing  20  and entrance port  36 , and a second O-ring  66  is disposed between housing  20  and exit port  38  to provide a tight seal between the housing  20  and straining basket assembly  40  to prevent leakage. 
     The flow of fluid between housing  20  and strainer basket assemblies  30 ,  40  is controlled by valve assembly  80 . Valve assembly  80  includes a first three-way ball valve  72  rotatably disposed within lower chamber  26 . Three-way ball valve  72  has three openings,  74 ,  76 ,  78 , all of which communicate with each other so that a fluid may pass from any one opening to any one of the other openings through three-way ball valve  72 . A notch  82  is formed in a surface of three-way ball valve  72 . Three-way ball valve  72  rotatably sits within lower chamber  26  so that any one of openings  74 ,  76  and  78  may be aligned with straining chamber exit port  27  or strainer chamber exit port  38 . Notch  82  is positioned substantially coaxially with channel  29 . 
     A second three-way ball valve  84  rotatably sits in upper chamber  24 . Like three-way ball valve  72 , three-way ball valve  84  has three openings,  86 ,  88  and  90  in fluid communication with each other. A notch  92  is formed on one side of ball valve  84  and a second notch  110  (FIG. 4) is formed on the opposed side of three-way ball valve  84 . Openings  86 ,  88  and  90  are disposed so that any one of them may be placed in fluid communication with straining chamber entrance port  19  and straining chamber entrance port  36 . 
     A shaft  94  is rotatably disposed within channel  29 . O-rings  98 ,  99  are disposed about shaft  94  to prevent fluid flow within channel  29 . Shaft  94  includes a first flange  95  received by a notch  110  in three-way ball valve  84 . A second flange  93  formed on the opposed end of shaft  94  and is received within shaft  82  so that rotation of shaft  94  causes three-way ball valve  72  and  84  to rotate in unison. A second shaft  96  is rotatably mounted within a second channel  100  formed within housing  20 . O-rings  101 ,  102 ,  103  are mounted about shaft  96  to prevent fluid flow through channel  100 . A flange  97  is formed on shaft  96  and is received by notch  92  in three-way ball valve  84 , so that rotation of shaft  96  causes rotation of three-way ball valve  84  and, in turn, three-way ball valve  72 . As a result any opening in each respective three-way valve may be brought in alignment with either exit port (valve  72 ) or entrance port (valve  84 ). 
     Shaft  96  extends through housing  20 . A handle  104  is mounted on shaft  96  to facilitate rotating shaft  96  and in turn three-way ball valves  72 ,  84  in a desired indexed position. Pegs  106 ,  108  extend from housing adjacent handle  104  and to stop rotation of handle  104  when valves  72 ,  84  are in a desired orientation relative to the various exit and entrance ports preventing overrotation of valves  72  and  84 . 
     Reference is made to FIG. 4 wherein three-way ball valve  84  is seated between a left  seat  28  and a right  seat  114 . The second three-way ball valve  72  is seated between an left  a seat  116  and a right  seat  112    113 . Removal of chamber assembly  40  allows on-site access to any one of seats  28 ,  112 ,  114  and  116 . 
     Reference is made to FIGS. 1, 3 and 4 wherein a fluid flow pattern is illustrated. A fluid enters body  20  at entrance port  23  in the direction of arrows A (FIG. 3), and continues to flow in the direction of arrow A through an opening  88  of three-way ball valve  84 . Fluid floods upper chamber  24  until it follows the path of least resistance through three-way ball valve  84  and out opening  86  in the direction of arrows B (FIG. 4). The fluid flows in the direction of arrows B through entrance port  36  of basket straining chamber  40 . It flows in the direction of arrow C into basket  46  and through strainer  48  in the direction of arrows D. The fluid is strained by strainer  48  prior to exiting through exit port  38  into opening  76  of three-way ball valve  72 . The fluid then exits three-way ball valve  72 . The fluid exits three-way ball valve  72  through opening  78  in direction of arrow E (FIG. 3) and continues through lower chamber  26  in the direction of arrow F. The fluid flows in the direction of arrow G through exit  25 , completing the flow path. 
     It should be noted, in the above example, three-way ball valves  72 ,  84  were positioned so that no opening of either of the three-way ball valves cooperated with entrance or exit ports of strainer basket assembly  30  (FIG. 4). Accordingly, the entire straining operation was performed by strainer basket assembly  40 , allowing the removal of basket  48  from strainer basket assembly  30  without interfering with operation of the strainer. By isolating strainer basket assembly  30  access can be gained to basket  46 , to empty basket  46  of strained materials, perform maintenance on chamber  32 , or other tasks involving basket assembly  30  without interfering with operation of the entire system of duplex strainer  10 . 
     It should be understood that by rotating handle  104  substantially 90° and thereby rotating three-way ball valves  72 ,  84 , opening  88  will be brought in fluid communication with entrance port  19  simultaneously with opening  90  being brought in fluid communication with entrance port  36 , so that the fluid will flow into both strainer basket assemblies  30 ,  40  simultaneously to provide a dual straining function. At the same time, opening  74  will communicate with exit port  27  while opening  78  will communicate with exit port  38 , providing a continuous flow path for both strainer basket assemblies  30 ,  40 . Similarly, by rotating handle  104  substantially 180° from the position shown FIGS. 3 and 4, three-way ball valves  72 ,  84  will also be rotated 180° bringing opening  86  in fluid communication with entrance port  19  and opening  76  in fluid communication with exit port  27 , isolating strainer basket assembly  40 , preventing fluid from flowing therethrough to allow service access of strainer basket assembly  40  without interruption of a straining process. 
     By providing a duplex strainer in which at least one strainer basket assembly is bolted to the housing and not formed integrally therewith, the manufacture of duplex strainers is simplified. Furthermore, by providing a three-way ball valve as a flow transfer valve, leakage at low pressure is reduced, allowing the inlet of the strainer to be shut off, isolating the pump as well as other equipment, limiting the need of a shut-off valve upstream of the strainer. Furthermore, the use of a three-way ball valve allows field maintenance of the duplex strainer without interfering with a continuous straining function. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the spirit and scope of the invention, it is intended that all matter contained in the above construction as shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.