Abstract:
A valve apparatus and pneumatically driven diaphragm pump incorporating same having a valve body having a longitudinal axis and an actuator having an axis with a first end and a second end. The first and second ends have first and second diaphragms, respectively, disposed thereon and located transversely to the axis of the actuator. Upon inserting the actuator into the valve body, the first and second diaphragms define wall portions of first and second chambers at the first and second ends of the axis of the actuator, respectively, and a chamber defined between the diaphragms.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to valves and more particularly to directional control valves for pneumatic applications. 
   Spool valves are used and known in the art as directional control valves for changing the direction of a motive fluid to and from pistons or diaphragms located within cylinders or other chambers, respectively. A conventional spool valve comprises a valve body and a sliding spool actuator which, upon shifting therein, alternately defines flow passages within the valve body to a supply pressure or an exhaust port causing a cylinder&#39;s piston rod or chamber&#39;s diaphragm to be moved and work performed. 
   Typically, such directional control valves have been used as the major distribution valve for providing a pressurized motive fluid, e.g., pressurized air, to chambers associated with a double acting diaphragm pump. Examples are shown in commonly assigned U.S. Pat. Nos. 4,854,832, 5,391,060, and 6,722,256, the disclosures of which are incorporated herein by reference. In U.S. Pat. No. 5,391,060, a spool valve is disposed in a valve body and connects air supply and exhaust ports to appropriate diaphragm air chambers via O-rings located on the spool valve. U.S. Pat. Nos. 4,854,832 and 6,722,256, include a spool valve having a spool actuator that has “U”-cup seals and receives a sliding “D” valve that establishes fluid interconnections upon shifting of the spool valve. As shown in the aforementioned patents, preferably, the spool actuators are differential actuators having at least two diameters to respond to a differential pressure in order to prevent stalling of the valve. 
   The seals used on such spool actuators such as the “O”-ring and “U”-cup seals described above, however, require excellent inner surface finishes on the valve body bores. To prolong seal life, a lubricant is also generally used either in the bore or in the seal itself to help reduce friction in moving the piston. However, many pumping applications require a lubrication-free environment to avoid contamination of the media being handled. 
   The foregoing illustrates limitations known to exist in present valving devices. 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 an alternative valving apparatus is provided including the features more fully disclosed hereinafter. 
   SUMMARY OF THE INVENTION 
   According to the present invention, a valve apparatus and pneumatically driven diaphragm pump incorporating same are provided having a valve body having a longitudinal axis and an actuator having an axis with a first end and a second end. The first and second ends have first and second diaphragms, respectively, disposed thereon and located transversely to the axis of the actuator. Upon inserting the actuator into the valve body, the first and second diaphragms define wall portions of first and second chambers at the first and second ends of the axis of the actuator, respectively, and a chamber defined between the diaphragms. 
   The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with accompanying drawing figures. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is a sectional view of a valve apparatus according to the present invention; 
       FIG. 2  is partial perspective and partial exploded view of a center body section of a conventional double diaphragm pump attached to a valve apparatus according to the present invention; 
       FIG. 3  is a side view of the center body section and assembled valve apparatus shown in  FIG. 2 ; 
       FIG. 4  is a partial sectional view of the double diaphragm pump shown in  FIG. 2  showing the sequential operation of the valve apparatus according to the present invention; 
       FIG. 5  is an enlarged sectional view showing the region shown bounded by dashed lines in  FIG. 4 ; 
       FIG. 6  is a partial sectional view of the double diaphragm pump shown in  FIG. 2  showing the sequential operation of the valve apparatus according to the present invention; and 
       FIG. 7  is an enlarged sectional view showing the region shown bounded by dashed lines in  FIG. 6 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As used herein, the term “diaphragm” means a flexible barrier that divides two fluid containing chambers or compartments. 
   The invention is best understood by reference to the accompanying drawings in which like reference numbers refer to like parts. It is emphasized that, according to common practice, the various dimensions of the diaphragms and the associated pump parts as shown in the drawings are not to scale and have been enlarged for clarity. 
   Referring now to the drawings, shown in  FIG. 1  is a valve apparatus according to the present invention comprising an actuator  42  disposed within a chamber  59  located in a valve block or body  2 . Actuator  42  is a generally cylindrical spool member having a first end surface  55  and a second end surface  80  positioned within chamber  59  which is connected to a motive fluid such as compressed air via fluid pressure inlet  86 . Actuator  42  has a substantially constant diameter with annular rings  69  having outer diameters that are substantially the same as the inner diameter of chamber  59 . An annular groove  68  is defined between annular rings  69  which receives a sliding valve insert  70  that extends through the wall of valve body  2  and slides against a valve plate  3  as shown. 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. 
   Chamber  59  is disposed between and coaxially aligned with a first chamber  58  and a second chamber  60 . A first diaphragm  15  is attached to first end surface  55  of actuator  42  and disposed between first chamber  58  and chamber  59 . A second diaphragm  16  is attached to second end surface  80  of actuator  42  and disposed between second chamber  60  and chamber  59 . First and second chambers  58 ,  60  are alternately connected via first and second passages  56 ,  62  to a pneumatic pilot signal or to atmosphere to effect shifting of actuator  42  as described in detail below and may be accomplished via a separate mechanical or electrical shifting device. Exemplary shifting devices in this regard being conventional pilot valves that can be solenoid or mechanically activated trip rods to control pneumatic shifting logic, which are known in the art and therefore not described in detail. 
   Preferably, first diaphragm  15  and second diaphragm  16  are mechanically fastened to their respective ends of actuator  42  and clamped between chamber  59  and first and second chambers  58 ,  60 , respectively. Clamping of the diaphragms in place may be accomplished by a first end cap  57  and a second end cap  61  which threadingly engage inner threads of valve body  2  preferably with sealing members  17  that engage the diaphragms as shown. Sealing members may be discrete elements as shown or may be integrally provided with the diaphragm members as described in detail further below. The diaphragms are manufactured from a flexible material, preferably, from an elastomeric material as is known to those skilled in the art. 
   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 actuator  42  in chamber  59 . Valve plate  3  includes an exhaust aperture  35 , a first aperture  34 , and a second aperture  36  defined through its thickness. The relative spacing and positions between exhaust aperture  35 , first aperture  34 , and second aperture  36  are configured such that during operation of the device, first aperture  34  and second aperture  36  are alternately connected to exhaust aperture  35 . As described above, supply fluid pressure inlet  86  is connected to chamber  59  and provides fluid pressure to first aperture  34  and second aperture  36  when these apertures are not in fluid connection with exhaust aperture  35 . In this manner, actuator  42  slides valve insert  70  between a first position in which first aperture  34  is connected to supply air when second aperture  36  is connected to exhaust and a second position in which second aperture  36  is connected to supply air when first aperture  34  is connected to exhaust. 
   To provide for actuation in response to pressure differential, the diaphragms are preferably of different diameters relative to one another with first diaphragm  15  having a smaller diameter than second diaphragm  16  as shown. Thus, when pilot fluid pressure is applied to chamber  59 , the actuator  42  will be biased toward the larger, first diaphragm  16  due to the larger exposed surface area. When pilot fluid pressure is supplied to chamber  60 , the actuator  42  will shift toward the smaller, second diaphragm  15 . If pilot fluid pressure is discontinued, the supply pressure from supply fluid inlet  86  again returns the spool to be biased toward the larger, first diaphragm  16 . It is to be understood that diaphragms of equal diameter may be alternatively incorporated into the valve apparatus according to the present invention to provide a non-differential design. 
   Although useful in a variety of applications, the valving apparatus described above may be incorporated as the major valve construction that provides and exhausts motive gas, respectively, to and from an air motor such as those used in diaphragm pumps as described in detail below. 
   Shown in  FIGS. 2–7  is a center body section  125  of a conventional double diaphragm pump attached to a valve body  120  incorporating the valve construction of the present invention. The center body section  125  is shown in the partial perspective view of  FIG. 2  attached to air caps  126  which define first and second opposed axially spaced pressure chambers  127  over which flexible pumping diaphragms (not shown) are mounted as is known in the art. Shown in  FIG. 3  is a side view of one of the air caps  126  having a pilot valve comprising a pilot piston  7  and an actuator pin  9  as is known in the art. During operation of the pump, as the pilot piston shifts position with the reciprocation of the diaphragms, pneumatic pilot signals accordingly shift an actuator  142  to shift within valve body  120  at the end of each pump stroke thereby alternating the exhausting and filling of the pressure chambers  127  via ports  128 . 
   Shown in the partial sectional views of  FIGS. 4 and 6  is the sequential operation of a valve apparatus according to the present invention as configured for and used in conjunction with a pneumatic double diaphragm pump. The valve apparatus comprises an actuator  142  disposed within a chamber  159  located in a valve block or body  120  and connected to a motive fluid such as compressed air via fluid pressure inlet  186 . A first diaphragm  115  and a second diaphragm  116  are integrally attached to actuator  142  and define a first chamber  158  and a second chamber  160 , respectively, with the inner surfaces of first and second end caps  157 ,  161  inserted into valve body  120 . O-ring seals  171  are provided as shown between the end caps  157 ,  161  and the inner surface of valve body  120  to effect sealing therebetween. 
   First and second chambers  158 ,  160  are alternately connected via first and second passages  156 ,  162  to a pneumatic pilot signal or to atmosphere by pilot piston  7  to effect shifting of actuator  142 . Chamber  159  is disposed between and coaxially aligned with first chamber  158  and second chamber  160 . 
   Actuator  142  is a generally cylindrical spool member having annular rings with projections  169  on both sides of a valve insert  170 . Valve insert  170  slides against a valve plate  130  as shown and, preferably, is also engaged by an annular ring  168  provided on actuator  142 . As shown in  FIGS. 4–7 , first diaphragm  115  and second diaphragm  116  are mechanically clamped between first and second end caps  157 ,  161  and valve body  120 , respectively, by an integral bead portion  117  provided around the periphery of the diaphragms. In this manner, the circumferential bead portions seal chambers  159  from chambers  158  and  160 . 
   The motion of valve insert  170  is limited by the wall of valve body  120  to correspond with the range of motion of the travel of the actuator  142  in chamber  159 . Valve plate  130  includes an exhaust aperture  135 , a first aperture  134 , and a second aperture  136  defined through its thickness. The relative spacing and positions between exhaust aperture  135 , first aperture  134 , and second aperture  136  are configured such that during operation of the device, first aperture  134  and second aperture  136  are alternately connected to exhaust aperture  135 . When connected to exhaust aperture  135 , first aperture  134  and second aperture  136  permit pressure chambers  127  to be exhausted via their respective ports  128 . As described above, supply fluid pressure inlet  186  is connected to chamber  159  and provides fluid pressure to first aperture  134  and second aperture  136  when these apertures are not in fluid connection with exhaust aperture  135 , thereby filling pressure chambers  127  via their respective ports  128 . In this manner, actuator  142  slides valve insert  170  between a first position in which first aperture  134  is connected to supply air when second aperture  136  is connected to exhaust and a second position in which second aperture  136  is connected to supply air when first aperture  134  is connected to exhaust. 
   To provide for actuation in response to pressure differential, the diaphragms are preferably of different diameters relative to one another with first diaphragm  115  having a smaller diameter than second diaphragm  116  as shown. Thus, when pilot fluid pressure is applied to chamber  159 , the actuator  142  will be biased toward the larger, second diaphragm  116  due to the larger exposed surface area. When pilot fluid pressure is supplied to chamber  160 , the actuator  142  will shift toward the smaller, first diaphragm  115 . If pilot fluid pressure is discontinued, the supply pressure from supply fluid inlet  186  again returns the spool to be biased toward the larger, second diaphragm  116 . It is to be understood that diaphragms of equal diameter may be alternatively incorporated into the valve apparatus according to the present invention to provide a non-differential design. 
   With respect to materials selections, actuator  142  may be manufactured from a flexible material, preferably, from a thermoplastic elastomer (TPE) or a thermoplastic urethane (TPU) material that is injection molded. As shown by the partial perspective and partial exploded view of  FIG. 2  and the sectional views of  FIGS. 4 and 6 , “core-outs” may be located longitudinally along the length of these components to facilitate injection molding of these parts. An exemplary material that can be used to injection mold actuator  142  is a 4300 Series polyurethane material available from Parker Hannifin Corporation, Engineered Polymer Systems Division, Salt Lake City, Utah. Although shown integrally provided on actuator  142 , diaphragms  115 ,  116  may alternatively be provided as discrete components attached thereto to facilitate manufacture and/or use of different materials. It is also contemplated that co-molding may be used to integrally provide diaphragms on the actuator using different materials. The selection of different diaphragm materials may be for various reasons including, for example, variation of the flexure properties of the diaphragms. 
   End caps  157 ,  161  and valve body  120  can be similarly be injected molded preferably using a thermoset plastic material or otherwise fabricated using a composite or metal material. As shown by the perspective exploded view on  FIG. 2  and the sectional views of  FIGS. 4 and 6 , “core-outs” may be located longitudinally along the length of these components to facilitate injection molding of these parts. 
   Preferably, valve plate  130  and valve insert  170  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. 
   While embodiments and applications of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein described. For example, although described above with respect to use with pneumatically operated double diaphragm pumps, it is contemplated that the valve apparatus according to the present invention may be incorporated into other pneumatic or hydraulic devices. It is understood, therefore, that the invention is capable of modification and therefore is not to be limited to the precise details set forth. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the spirit of the invention.