Abstract:
An exhaust system comprising: an exhaust chamber having a longitudinal axis and an outer wall defining alternating longitudinally-extending ribs and grooves; and an insert within the exhaust chamber, the insert including a plurality of fins extending generally perpendicular to the longitudinal axis, each fin including a distal edge extending substantially close to the plurality of ribs, the insert defining expansion chambers between adjacent fins. Pressurized gas flowing through the exhaust chamber flows along the grooves and expands within the expansion chambers to reduce the pressure of the pressurized gas prior to the gas exiting the exhaust chamber. The fins may in some embodiments be sufficiently stiff to resist substantial deflection under the influence of the gas.

Description:
BACKGROUND 
     The present invention relates to an exhaust system for a pressurized fluid. 
     SUMMARY 
     In one embodiment, the invention provides an exhaust system comprising: an exhaust chamber having a longitudinal axis and an outer wall defining alternating longitudinally-extending ribs and grooves; and an insert within the exhaust chamber, the insert including a plurality of fins extending generally perpendicular to the longitudinal axis, each fin including a distal edge extending substantially close to the plurality of ribs, the insert defining expansion chambers between adjacent fins. Pressurized gas flows through the exhaust chamber along the grooves and expands within the expansion chambers to reduce the pressure of the pressurized gas prior to the gas exiting the exhaust chamber. The fins may in some embodiments be sufficiently stiff to resist substantial deflection under the influence of the gas. 
     In another embodiment the invention provides an exhaust system comprising: an exhaust chamber adapted to reduce the pressure of a pressurized gas flowing through the exhaust chamber; an exhaust fluid inlet adapted to admit the pressurized gas into the exhaust chamber; an exhaust fluid outlet adapted to vent the pressurized gas out of the exhaust chamber; and a resonator stem within the exhaust fluid outlet and adapted to facilitate a change in direction of the pressurized gas as the gas flows through the exhaust fluid outlet. 
     In another embodiment, the invention provides a method for constructing an exhaust system, the method comprising the steps of: (a) providing an exhaust chamber that defines a longitudinal axis and that includes a wall defining a plurality of alternating ribs and grooves; (b) providing a unitary insert that includes a flange, an outlet, a resonator stem within the outlet and having a longitudinal extent, and a plurality of substantially rigid fins having distal ends and defining expansion chambers between the fins; (c) inserting the unitary insert into the exhaust chamber with the longitudinal extent of the resonator stem being substantially parallel to the longitudinal axis, and with the fins extending substantially perpendicular to the longitudinal axis of the exhaust chamber with the distal ends substantially close to the ribs and grooves of the exhaust chamber wall; and (d) fastening the flange of the insert to the exhaust chamber wall. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a double diaphragm pump embodying the present invention. 
         FIG. 2  is a cross-section view of the pump taken along line  2 - 2  in  FIG. 1 . 
         FIG. 3  is an exploded view of an exhaust assembly for the pump. 
         FIG. 4  is a perspective view of an insert of the exhaust assembly. 
         FIG. 5  is a cross-section view of the exhaust assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIGS. 1 and 2  illustrate a double diaphragm pump  10  having a housing defining first and second working chambers  15 . The first and second working chambers  15  are divided with respective first and second flexible diaphragms  20  into respective first and second pumping chambers  25  and first and second motive fluid chambers  30 . The diaphragms  20  are interconnected through a shaft  35  such that when one diaphragm  20  is moved to increase the volume of the associated pump chamber  25 , the other diaphragm is simultaneously moved to decrease the volume of the associated pump chamber  25 . The pump  10  includes an inlet  40  for the supply of a motive fluid (e.g., compressed air or another pressurized gas) and a valve  45  for alternatingly supplying the motive fluid to the first and second motive fluid chambers  30  to drive reciprocation of the first and second diaphragms  20  and the shaft  35 . Simultaneously with supplying the motive fluid to one of the motive fluid chambers  30 , the valve  45  places an exhaust assembly  50  in communication with the other motive fluid chamber  30  to permit motive fluid to be expelled therefrom. 
     In operation, as the diaphragms  20  and shaft  35  reciprocate, the first and second pump chambers  25  alternatingly expand and contract to create respective low and high pressure within the respective first and second pump chambers  25 . The pump chambers  25  communicate with an inlet manifold  55  that is connected to a source fluid to be pumped, and also communicate with an outlet manifold  60  that is connected to a receptacle for the fluid being pumped. Check valves ensure that the fluid being pumped moves only from the inlet manifold  55  toward the outlet manifold  60 . When one of the pump chambers  25  expands, the resulting negative pressure draws fluid from the inlet manifold  55  into the pump chamber  25 . Simultaneously, the other pump chamber  25  contracts, which creates positive pressure to force the fluid into the outlet manifold  60 . 
     With reference to  FIG. 3 , the exhaust assembly  50  includes an exhaust chamber  70  and an insert  75 . The exhaust chamber  70  includes an outer wall  80 , which in the illustrated embodiment is cylindrical and defines a longitudinal axis  85  running down the center of the chamber  70  from an exhaust fluid inlet  90  to an exhaust fluid outlet  95  ( FIG. 5 ). The exhaust chamber  70  may be integrally cast with a portion of the pump housing in some embodiments, or may be separately fabricated and mounted to the pump housing. It may also exist in various other geometries, and the illustrated cylindrical geometry should not be regarded as limiting. The inner surface of the wall  80  includes alternating longitudinal (i.e., extending generally parallel to the longitudinal axis  85 ) ribs  100  and grooves  105 , and also includes a longitudinal key slot  110 . Although the ribs and grooves  100 ,  105  of the illustrated embodiment are integrally formed into the chamber wall  80 , they may be provided on a separate template and mounted to an inner surface of the chamber wall  80  in other embodiments. 
     With reference to  FIGS. 3 and 4 , the insert  75  includes a plurality of perpendicular (i.e., substantially perpendicular to the longitudinal axis  85  of the exhaust chamber  70  when assembled) fins  115 , a longitudinal key  120  extending across the distal ends of the fins  115 , a flange  125 , a collar  130 , and a resonator stem  135 . The illustrated insert  75  is integrally formed as one part by a process such as casting, and is constructed of a substantially rigid material such as aluminum, steel, cast iron, or rigid plastic. The illustrated fins  115  are rigid (i.e., do not deflect under the influence of the motive fluid), but in other embodiments the fins  115  maybe compliant and deflectable. In other embodiments, the fins  115  may be sized to contact the ribs  100  in the exhaust chamber wall  80 . In such embodiments, the fins  115  may have some flexibility, such that they deflect during insertion, but are substantially rigid once inserted. 
     The flange  125  includes a plurality of fastener holes  140 . When the key  120  of the insert  75  is received within the key slot  110  of the exhaust chamber wall  80 , the fastener holes  140  of the flange  125  align with fastener holes  145  in the wall  80  of the exhaust chamber  70  to facilitate mounting the insert  75  to the exhaust chamber  70 . In the illustrated embodiment, a gasket  150  is interposed between the flange  125  and the edge of the exhaust chamber wall  80  to create a substantially airtight seal therebetween. The flange  125  is spaced from the last fin  115  with spacers  155  and the key  120 , and the flange  125  includes a central hole  160 . 
     The collar  130  surrounds the central hole  160  in the flange  125 . The illustrated collar  130  is generally cylindrical and defines a collar longitudinal axis which is generally collinear with the exhaust chamber longitudinal axis  85  when the exhaust assembly  50  is assembled. Together, the central hole  160  and collar  130  define the exhaust fluid outlet  95  through which motive fluid escapes from the exhaust chamber  70 . The illustrated collar  130  includes recesses  170  for receiving a coupler  175  ( FIG. 2 ) to facilitate connecting a conduit to the exhaust fluid outlet  95  so that the flow of exhausted motive fluid can be steered in a desired direction. 
     The resonator stem  135  extends from the last fin  115  through the central hole  160  of the flange  125  and into the space within the collar  130 . The longitudinal extent of the resonator stem  135  is substantially collinear with the collar longitudinal axis, and thus with the longitudinal axis  85  of the exhaust chamber  70  when the exhaust assembly  50  is assembled. 
     Turning now to  FIG. 5 , the distal ends of the fins  115  are in close proximity with the ribs  100 , and expansion chambers  180  are defined between the fins  115 . As used herein, the terms “in close proximity” and “substantially close” are used in reference to the spacing between the fins  115  and ribs  100  means that the distal ends of the fins  115  are sufficiently close to the ribs  100  (whether in contact with the ribs or not) to create back pressure that causes the motive fluid to expand into the expansion chambers  180 . In other words, the distal ends of the fins  115  must be close enough to the ribs  100  to prevent the motive fluid from blowing past the insert  75  without expanding into the expansion chambers  180 . 
     As high pressure motive fluid flows into the exhaust chamber  70  through the exhaust fluid inlet  90 , it flows around the outside of the insert  75 , as indicated with the arrows in  FIG. 5 . More specifically, the motive fluid flows through the grooves  105  along the wall  80  of the exhaust chamber  70  and expands into the expansion chambers  180  between the fins  115 . As the motive fluid moves from expansion chamber to expansion chamber on its way through the exhaust chamber  70 , it incrementally cools and loses pressure. In this regard, the expansion chambers  180  may be termed “cascading expansion chambers” because the motive fluid “spills” from one to the next. 
     Once the motive fluid flows around the last fin  115 , it is flowing in a direction generally perpendicular to the longitudinal axis  85  of the exhaust chamber  70 . As indicated with the arrows in  FIG. 5 , the resonator stem  135  facilitates a smooth change in direction of the motive fluid from flowing generally toward the longitudinal axis  85  of the exhaust chamber  70  to flowing generally parallel to the longitudinal axis  85  (i.e., a 90° turn in the illustrated embodiment). The resonator stem  135  thus reduces noise by transitioning the movement of exhaust fluid into a substantially laminar flow prior to exiting the exhaust fluid outlet  95 . 
     Various features and advantages of the invention are set forth in the following claims.