Abstract:
A valve for a gas-driven motor and a valve assembly and reciprocating pump incorporating the valve are provided. The valve includes a shiftable valve for alternatively supplying a motive gas through first and second supply ports to opposed first and second power pistons in opposed motive gas chambers, respectively, and for effecting alternating exhaust of said chambers. The shiftable valve has a front face with a valve projection located thereon and a rear face with a valve projection located thereon.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to air valves and more particularly to air valves designed to minimize icing and improve efficiency for a reciprocating pump or the like. More specifically, this invention relates to an improved fluid operated, double diaphragm pump, and, more particularly, to the valve construction for such a pump. 
   The use of a double diaphragm pump to transfer materials is known. Typically such a pump comprises a pair of pumping chambers with a pressure chamber arranged in parallel with each pumping chamber in a housing. Each pressure chamber is separated from its associated pumping chamber by a flexible diaphragm. As one pressure chamber is pressurized, it forces the diaphragm to compress fluid in the associate pumping chamber. The fluid is thus forced from the pumping chamber. Simultaneously, the diaphragm associated with the second pumping chamber is flexed so as to draw fluid material into the second pumping chamber. The diaphragms are reciprocated in unison in order to alternately fill and evacuate the pumping chambers. In practice, the chambers are all aligned so that the diaphragms can reciprocate axially in unison. In this manner the diaphragms may also be mechanically interconnected to ensure uniform operation and performance by the double acting diaphragm pump. Exemplary pumps in this regard are shown and described in U.S. Pat. Nos. 4,854,832 and 5,584,666 (hereafter, “the &#39;832 and &#39;666 patents”), the specifications of which are incorporated herein by reference. 
   In designing air motor valving used to control the feed air to and exhaust air from the diaphragm chambers of such pumps, however, it is desirable to exhaust the diaphragm chambers as quickly as possible in order to obtain a fast switch over and high average output pressures. Large temperature drops are generated with such rapid exhausting of the diaphragm chambers, however, which cause the valve to become extremely cold and can cause ice formation from moisture in the exhaust air. 
   The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter. 
   SUMMARY OF THE INVENTION 
   According to the present invention, a valve for a gas-driven motor and a valve assembly and a reciprocating pump incorporating the valve are provided. The valve includes a shiftable valve for alternatively supplying a motive gas through first and second supply ports to opposed first and second power pistons in opposed motive gas chambers, respectively, and for effecting alternating exhaust of said chambers. The shiftable valve has a front face with a valve projection located thereon and a rear face with a valve projection located thereon. 
   The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is an elevational view of a diaphragm pump showing an air motor major valve according to the present invention and showing a left housing chamber in partial section; 
       FIG. 2  is a cross sectional view taken along the section line “ 2 - 2 ” in  FIG. 1 , showing a reduced icing air valve according to the present invention; and 
       FIG. 3  is the cross-sectional view of  FIG. 2  showing the reduced icing air valve according to the present invention sequentially moved to the position as shown. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning to the drawing figures, a double diaphragm pump is shown illustrated incorporating the valve construction of the present invention in which like numbers refer to like parts in each of the figures. According to common practice, the various dimensions of the component parts as shown in the drawings are not to scale and have been enlarged for clarity. 
   Shown in  FIG. 1  is a partial sectional view of a double diaphragm pump incorporating a main housing  100  that defines first and second opposed and axially spaced housing chambers. Each housing chamber includes a pressure chamber  26  and a fluid chamber  31  that are separated by a flexible diaphragm  29  as depicted by the partial sectional view of the left housing chamber as shown in  FIG. 1 . The pressure chamber, fluid chamber, and diaphragm in the right housing chamber are similarly arranged and form a mirror image of those components in the left housing chamber. 
   Each of the diaphragms  29  is fashioned from an elastomeric material as is known to those skilled in the art. The diaphragms  29  are connected mechanically by means of a shaft  30  that extends axially through the midpoint of each of the diaphragms. The shaft  30  is attached to the diaphragm  29  by means of opposed plates  33  on opposite sides thereof. Thus, the diaphragms  29  will move axially in unison as the pump operates by the alternate supply and exhaust of air to the pressure chambers of the pump as discussed in greater detail in the &#39;832 and &#39;666 patents. In brief, upon reciprocating the diaphragms of the pump, fluid that passes into each fluid chamber from associated inlet check valves is alternately compressed within and forced outwardly through associated outlet check valves. Operation of the fluid check valves controls movement of fluid in and out of the pump chambers causing them to function as a single acting pump. By connecting the two chambers through external manifolds, output flow from the pump becomes relatively constant. 
   The specific structure of the present invention relates to the construction of the reduced icing air valve and, more specifically, its major valve construction that provides and exhausts motive gas, respectively, to and from an air motor. Referring to  FIG. 1 , shown located between the left and right housing chambers is a center body housing  6  to which is attached to a valve block or body  2  having an air inlet  121 . As shown in  FIGS. 2 and 3 , valve block  2  is generally a two piece construction that facilitates the assembly of a major valve, that is comprised of the valve block  2 , a spool  1 , a valve insert  70 , and a valve plate  3 , to center body housing  6 . 
   Spool  1  is a differential piston having a large diameter end  170  and a small diameter end  160  as shown in  FIGS. 2 and 3 . Small diameter end  160  includes a rear face  161  having a valve projection  162 . Large diameter end  170  includes a front face  180  having a valve projection  182 . Valve projections  162  and  182  may be cylindrical shapes that are chamfered as shown to facilitate sealing respectively against valve seats in the form of constricted regions  166  and  156  described in detail below. Small diameter end  160  and large diameter end  170  also include annular grooves having seals  164  and  174  respectively which engage against the walls of a chamber  84  located in valve body  2 . Spool  1  also includes an annular groove  68  which receives a valve insert  70  that extends through the wall of valve body  2  and slides against valve plate  3 . Preferably, valve plate  3  and valve insert  70  are constructed of materials that are chemically inert and/or are internally lubricated to minimize chemical compatibility problems and reduce frictional loads, respectively, while also permitting the use of motive gas sources that are dirty. 
   The motion of valve insert  70  is limited by the wall of valve body  2  to correspond with the range of motion of the travel of the spool  1  in chamber  84 . The spacing and position of valve insert  70  and the relative positions of first aperture  34  and second aperture  36  are such as to be consistent with the operation of the device as will be described below. As shown by the sequential movement of spool  1  in  FIGS. 2 and 3 , valve insert  70  is reciprocally moved to alternately cover first aperture  34  and second aperture  36  defined through the valve plate  3 . Supply port  25  is located in center body housing  6  and is in fluid connection with pressure chamber  26  of the left housing chamber, which is located in the paper as shown. Supply port  27  is located in center body housing  6  and is in fluid connection with pressure chamber  26  of the right housing chamber, which is located out of the paper and not shown. By this construction, an air supply provided to air inlet  121  is alternately provided to supply ports  27  and  25  via second aperture  36  and first aperture  34  to fill pressure chambers  26  of the right and left housing chambers, respectively. 
   Shown in  FIG. 2  is an end view of a pilot valve consisting of a pilot piston  7  and an actuator pin  9  that extends into pressure chamber  26  of the right housing chamber. A second actuator pin  9  that is located in line with and on the opposite side of pilot piston  7 , extends into the pressure chamber  26  of the left housing chamber as shown in  FIG. 1 . During operation of the pump, as the diaphragms reciprocate, the diaphragm plates alternately contact the actuating pins causing the pilot piston  7  to shift position. This shift in position of pilot piston  7  causes pneumatic pilot signals to be sent to the front face  180  of spool  1  via a passage  190  and a port  90  and, alternately, to exhaust chamber  23  via an exhaust port in center body housing (not shown). When a pilot signal is provided to port  90  via pilot piston  7 , spool  1  shifts downward to the position shown in  FIG. 3 . When a signal is not provided to port  90 , spool  1  shifts upward to the position shown in  FIG. 1  due to supply air in chamber  84  acting on the back side of large diameter end  170 . In this manner, pilot piston  7  causes spool  1  to shift within valve body  2  at the end of each pump stroke thereby alternating the exhausting and filling of the pressure chambers and their corresponding fluid chambers. 
   As shown in  FIGS. 1 and 2 , pressure chamber  26  of left chamber housing (in the paper) is in fluid communication with air supply provided to air inlet  121  via supply port  25  and vented sequentially through exhaust port  159 , outer exhaust passageway  165 , and inner exhaust passageway  167  to an exhaust chamber  23  that exhausts to atmosphere via an exhaust port  123 . Pressure chamber  26  of right chamber housing (out of the paper) is similarly in fluid communication with air supply provided to air inlet  121  via port  27  and vented sequentially through an exhaust port (out of the paper and not shown), to outer exhaust passageway  155 , and inner exhaust passageway  157  to exhaust chamber  23 . By this construction, the pressure chambers  26  of the left and right housings are alternately exhausted upon reciprocating movement of spool  1  as described in greater detail below. 
   A constricted region  166  located within valve block  2  defines a valve seat area into which valve projection  162  mates, thereby permitting the opening and closing of the exhaust passageway defined by outer exhaust passageway  165  and inner exhaust passageway  167 . Similarly, a constricted region  156  located within valve block  2  defines a valve seat area into which valve projection  182  mates, thereby permitting the opening and closing of the exhaust passageway defined by outer exhaust passageway  155  and inner exhaust passageway  157 . 
   During operation of the pump, air passing from pilot piston  7  through passage  190  to port  90  impinges on front face  180  to cause spool  1  to move to and remain in its extreme bottom position as shown in  FIG. 3 . An O-ring  183  disposed in valve block  2  to fit circumferentially around valve projection  182 , seals and separates chamber  84  from inner exhaust passageway  157 . Simultaneously, because of the position of the valve insert  70 , supply air from inlet  121  flows through chamber  84  through the first aperture  34  in valve plate  3  and into pressure chamber  26  of the left housing via supply port  25 . In this position, valve projection  162  is forced to seat in constricted region  166  thereby sealing off outer exhaust passageway  165  and permitting air pressure chamber  26  of the left housing chamber to fill. By this motion into its seated position, valve projection  162  breaks up any ice that may have formed in the constricted region  166  during the previous exhaust cycle of the pressure chamber of the left housing. Conversely, valve projection  182  is moved out of constricted region  156 , thereby opening the pressure chamber  26  of the right housing chamber to exhaust sequentially via outer exhaust passageway  155  and inner exhaust passageway  157 . As supply air fills pressure chamber  26  of the left housing chamber, a portion of this air enters outer exhaust passageway  165  via exhaust port  159 , thereby warming the outer exhaust passageway  165  prior to its next exhaust cycle while also applying pressure to valve projection  162 , which assists the spool to shift and helps alleviate sticking of the spool. 
   Thus, air pressure acting on the diaphragm  29  in the left housing chamber forces it to the left expelling fluid from the fluid chamber  31  through an outlet check valve. The shaft  30  likewise moves to the left as does the right diaphragm (not shown) which causes air to exhaust from the right pressure chamber. Pumped fluid is drawn into the right fluid chamber while fluid is pumped from the left fluid chamber  31 . 
   As the diaphragms move to the left, movement of the actuator pin located in the right chamber is effected due to engagement of diaphragm plate located therein, thereby forcing the pilot piston to shift and removing the pilot signal to passage  190  and port  90 . In the absence of the pilot signal to port  90 , the supply air pressure within chamber  84  exerted on the backside of large diameter end  170  causes spool  1 , and valve insert  70  with it, to move to its extreme topmost position shown in  FIG. 2 . Simultaneously, because of the position of the valve insert  70 , supply air from inlet  121  flows through chamber  84  through the second aperture  36  in valve plate  3  and into pressure chamber  26  of the right housing chamber via supply port  27 . In this position, valve projection  182  is forced to seat in constricted region  156  thereby sealing off outer exhaust passageway  155  and permitting air pressure chamber  26  of the right housing chamber to fill. By this motion into its seated position, valve projection  182  breaks up any ice that may have formed in the constricted region  156  during the previous exhaust cycle of the pressure chamber  26  of the right housing chamber. Conversely, valve projection  162  is moved out of constricted region  166 , thereby opening the pressure chamber  26  of the left housing chamber to exhaust sequentially via exhaust port  159 , outer exhaust passageway  165 , and inner exhaust passageway  167 . As supply air fills pressure chamber  26  of the right housing chamber, a portion of this air enters outer exhaust passageway  155 , thereby warming the outer exhaust passageway  155  prior to its next exhaust cycle, while also applying pressure to valve projection  182 , which assists the spool to shift and helps alleviate sticking of the spool. 
   Pressurized air then flowing from air inlet  121  into the pressure chamber of the right housing chamber causes the diaphragm located therein to move to the right. This in turn causes the connecting shaft  30  to move the left diaphragm  29  to the right, thereby exhausting the pressure chamber of the left housing chamber and causing the left fluid chamber to fill. 
   The movement of plate  33  to the right in  FIG. 1  will ultimately engage that plate with the actuator pin  9 , thereby causing the pilot piston  7  and, in turn, spool  1  back again effecting movement to the left of the diaphragms and shaft  30 . In this manner, the reversal of operation of the pump is effected, which will continue to oscillate or cycle as long as air is supplied through the inlet  121 . 
   There has been set forth a preferred embodiment of the invention. However, the invention may be altered or changed without departing from the spirit or scope thereof. The invention, therefore, is to be limited only by the following claims and their equivalents.