Abstract:
A pump having a diaphragm positioned within a diaphragm housing comprised of an air cap and a fluid cap. The air cap and fluid cap include inner surfaces that cooperate to define a diaphragm chamber in which the diaphragm moves between a withdrawn deformed position and an extended deformed position. The inner surfaces of the air cap and fluid cap are designed to fully accommodate the movement of the diaphragm between its withdrawn deformed position and an extended deformed position. Finite element analysis is used to estimate the diaphragm&#39;s withdrawn deformed position and an extended deformed position.

Description:
BACKGROUND 
   The present invention relates to pumps and more particularly to air-operated diaphragm pumps. Conventional air-operated diaphragm pumps typically include a diaphragm positioned within a diaphragm chamber surrounded by a diaphragm housing. The diaphragm housing is comprised of an air cap and a fluid cap that cooperate to form the diaphragm housing. The diaphragm chamber is comprised of two separate chambers: an air chamber and a fluid chamber. On one side of the diaphragm, between the air cap and the diaphragm, the air chamber is formed. Air is alternatingly supplied and evacuated from the air chamber to drive the diaphragm back and forth. On the other side of the diaphragm, between the diaphragm and the fluid cap, the fluid chamber is formed, through which a fluid to be pumped flows as the diaphragm moves back and forth. In conventional pumps, the air cap and fluid cap are typically formed with inner surfaces of a constant radius or other simple shape. The diaphragm is often coupled to one end of a piston, which may be coupled on its other end to a second diaphragm in a double-diaphragm arrangement. 
   SUMMARY OF THE INVENTION 
   In conventional air-operated diaphragm pumps, the shape of the inner surfaces of the air cap and the fluid cap are designed such that the diaphragm may unintentionally contact either of the inner surfaces at the extent of its stroke or leave unwanted space between one of the inner surfaces and the diaphragm at the extent of its stroke. Contact between the diaphragm and one of the surfaces of the diaphragm housing can cause wear and fatigue of the diaphragm. Unwanted space between the inner surface of the air cap or fluid cap and the diaphragm can reduce efficiency of the pump. A diaphragm housing that is designed with a shape to reduce contact between the diaphragm and the inner surfaces of the air cap and fluid cap and reduce the space between the inner surfaces of the air cap and fluid cap and the diaphragm at the extent of its stroke would be welcomed by users of air-operated diaphragm pumps. 
   According to the present invention, a method of producing a pump comprises selecting a diaphragm, determining the extent to which the diaphragm will deform when pressurized in a diaphragm chamber of a pump, and designing the diaphragm chamber to house the diaphragm based on determining the extent to which the diaphragm will deform. 
   Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description exemplifying the best mode of carrying out the invention as presently perceived. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The detailed description particularly prefers to accompanying figures in which: 
       FIG. 1  illustrates a diaphragm chamber of a conventional air-operated diaphragm pump with a diaphragm in an extended position; 
       FIG. 2  illustrates the diaphragm chamber of  FIG. 1  with the diaphragm in a withdrawn position; and 
       FIG. 3  illustrates a pump according to the present invention having two diaphragm chambers with a right diaphragm in an extended position, a left diaphragm in a withdrawn position, and a piston connecting the two diaphragms. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1 and 2 , a conventional air-operated diaphragm pump  500 , as discussed in the background section above, is shown. The conventional pump  500  includes a piston  502  coupled to a diaphragm  504  using two diaphragm washers  506 . The diaphragm  504  is housed in a diaphragm chamber  508  defined within a diaphragm housing  509  formed by the cooperation of an air cap  510  and fluid cap  512 . A rim  514  of the diaphragm  504  is pinched between the air cap  510  and the fluid cap  512  when they are joined to form the diaphragm housing  509 .  FIG. 1  shows the piston  502  of the pump  500  in an extended position with the diaphragm  504  therefore pushed to an extended position within the diaphragm chamber  508 .  FIG. 2  shows the piston  502  of the pump  500  in a withdrawn position with the diaphragm  504  thereby pulled to a withdrawn position in the diaphragm chamber  508 . While  FIGS. 1 and 2  represent the diaphragm  504  in two different positions within the same diaphragm chamber  508 , it will be readily understood by those of ordinary skill in the art that  FIGS. 1 and 2  could also represent two different diaphragms coupled to opposite ends of the piston in a double-diaphragm pump arrangement. In this way,  FIGS. 1 and 2  would represent a single state of the double-diaphragm arrangement. In other words, when one diaphragm is in the extended position as shown in  FIG. 1 , the diaphragm on the other end of the piston of the double-diaphragm pump arrangement would be in the position as shown in  FIG. 2 , as would be readily apparent to those of ordinary skill in the art. 
   Referring again to  FIGS. 1 and 2 , the diaphragm  504  divides the diaphragm chamber  508  into a fluid chamber  516  between the diaphragm  504  and the fluid cap  512 , and an air chamber  518  between the diaphragm  504  and the air cap  510 . As will be readily apparent to those of ordinary skill in the art, the insertion and evacuation of pressurized air into and out of the air chamber  518  causes the diaphragm  504  to move back and forth, thereby pumping fluid into and out of the fluid chamber  516 . As shown in  FIG. 1 , with pressurized air pumped into the air chamber  518 , the diaphragm  504  and piston  502  are moved to an extended position. Movement to this position forces fluid in the fluid chamber  516  to be pumped out of the fluid chamber  516 . With the piston  502  and the diaphragm  504  moved to the withdrawn position as shown in  FIG. 2 , additional fluid is drawn into the fluid chamber  516  to be pumped out of the fluid chamber  516  when the piston  502  and the diaphragm  504  move back to their extended position as shown in FIG.  1 . 
   As shown in both  FIGS. 1 and 2 , the air cap  510  is formed with an inner surface  520  and the fluid cap  512  is formed with an inner surface  522 , which together define the diaphragm chamber  508 . Inner surfaces  520  and  522  are formed to accommodate the range of motion of the piston  502  and the diaphragm  504  within the diaphragm chamber  508 . When designing and manufacturing the conventional diaphragm pump  500 , the range of motion of the diaphragm  504  is typically accommodated by forming the inner surfaces  520  and  522  by simple methods that it is hoped will permit the unrestricted motion of the diaphragm  504  when the pump  500  is actually manufactured and put to use. For example, as shown in  FIGS. 1 and 2 , the inner surface  522  is formed with a relatively consistent radius  524 . Forming the inner surface  522  with the relatively consistent radius  524  provides for relatively easy manufacture of the fluid cap  512  and provides a shape to the inner surface  522  that it is hoped will fully accommodate the range of motion of the diaphragm  504 . However, until the pump  500  is actually manufactured and used, it is not known whether the fluid cap  512  has been formed to truly accommodate the full range of motion of the diaphragm  504 . 
   For example, an exterior surface  526  of the diaphragm  504  may actually contact the inner surface  522  of the fluid cap  512  when the piston  502  and the diaphragm  504  are in the extended position at the extent of the their stoke, as shown in FIG.  1 . Additionally, when the piston  502  and the diaphragm  504  are at the extent of their stoke as shown in  FIG. 1 , it is desirable to have pumped as much of the fluid in the fluid chamber  516  out of the fluid chamber  516  as is possible. A large volume of unpumped fluid stagnating in the fluid chamber  516  can decrease the efficiency of the pump  500 . 
   Similarly, the inner surface  520  of the air cap  510 , while not formed with a relatively consistent radius like the inner surface  522  of the fluid cap  512 , is nevertheless formed with a relatively simple shape that it is hoped will accommodate the range of motion of the diaphragm  504 . However, using conventional methods of designing the typical air cap  510 , the relationship between an interior surface  528  of the diaphragm  504  and inner surface  520  of the air cap  510  is not known. When the piston  502  and the diaphragm  504  are in their withdrawn position as shown in  FIG. 2 , the air chamber  518  may be needlessly large, which requires additional pressurized air to be pumped into the air chamber  518  to drive the piston  502  and the diaphragm  504 . Again, as with the fluid chamber  516 , to maximize the efficiency of the pump  500 , it is desirable to evacuate as much of the air chamber  518  as possible when the diaphragm  504  is in its withdrawn position, as shown in FIG.  2 . 
   Referring now to  FIG. 3 , an air-operated double-diaphragm pump  100  according to the present invention includes a piston  102  coupled on either end to a first and second diaphragm  104 ,  106 , respectively, using diaphragm washers  108 . The diaphragms  104  and  106  are each contained in a diaphragm chamber  110  defined within a diaphragm housing  112  comprising an air cap  114  and fluid cap  116 . Each diaphragm chamber  110  is divided into fluid chamber  124  between the fluid cap  116  and the diaphragm  104  or  106  and an air chamber  130  between the air cap  114  and the diaphragm  104  or  106 . As mentioned above with regard to conventional double-diaphragm pumps, the diaphragms  104  and  106  of the double-diaphragm pump  100  operate in a reciprocating manner such that the diaphragm  104  is in a withdrawn state of its stoke when the diaphragm  106  is in an extended state of its stoke. Thus, when the diaphragm  104  is in an extended state, it will be positioned within its diaphragm chamber  110  much like the diaphragm  106  is shown positioned in its diaphragm chamber  110  in FIG.  3 . Similarly, in its withdrawn state, the diaphragm  106  will be positioned much like the diaphragm  104  is shown positioned in FIG.  3 . 
   As can be seen in  FIG. 3 , with the diaphragm  106  in its extended position, an exterior surface  118  of the diaphragm  106  closely follows an inner surface  120  of the fluid cap  116 . The exterior surface  118  of the diaphragm  106  particularly follows the inner surface  120  of the fluid cap  116  between a rim  122  of the diaphragm  106  where the diaphragm  106  is secured between the air cap  114  and the fluid cap  116  and that portion of the diaphragm  106  that is sandwiched between the diaphragm washers  108 . The remainder of the inner surface  120  of the fluid cap  116  is formed with a relatively smooth curve for ease of manufacture, but to minimize space between the inner surface  120  of the fluid cap  116  and the diaphragm  106  and diaphragm washers  108  when the diaphragm  106  is in its extended position. 
   To minimize the remaining volume of the fluid chamber  124  when the diaphragm  106  is in its extended position, the pump  100  and its diaphragm housings  112  have been designed and manufactured with the deformed shape of the diaphragm  106  in mind. To do this, a computer model of the diaphragm  106  is first built. The type of material to be used for the diaphragm  106  and other known parameters for the manufacture of the pump  100  are used in constructing the computer model of the diaphragm  106 . Once the computer model of the diaphragm  106  is constructed, a pressure is applied to the diaphragm model to simulate the environment the diaphragm  106  will experience in the actual pump. Using a nonlinear finite element analysis (FEA) methodology, the diaphragm  106  is then analyzed to estimate the shape of the diaphragm  106  in its deformed state. For example, the shape of the diaphragm  106  in  FIG. 3  is the result of performing finite element analysis on the diaphragm to estimate that its deformed shape in its extended position will be as shown in FIG.  3 . The fluid cap  116  can then be designed to maximize the efficiency of the pump  112  by minimizing the volume of the fluid chamber  124  when the diaphragm  126  is in its extended position as shown in FIG.  3 . Of course, manufacturing constraints may also be considered. 
   Alternatively, instead of using finite element analysis to estimate the deformed shape of the diaphragm  106 , the diaphragm  106  could actually be placed in a test chamber and measurements could be taken to estimate the deformed shape of the diaphragm  106  when it is actually in the finished pump  100 . In either case, some estimation of the deformed shape of the diaphragm  106  is used to design the diaphragm housing  112 . Additionally, it will be readily apparent to those of ordinary skill in the art that the nonlinear finite analysis discussed above could alternatively have been performed without the use of a computer. 
   Similarly, as shown in  FIG. 3 , in its withdrawn state, an interior surface  126  of the diaphragm  104  closely follows an inner surface  128  of the air cap  114 . This reduces the volume of the air chamber  130  created between the interior surface  126  of the diaphragm  104  and the inner surface  128  of the air cap  114 . This is accomplished in the pump  100  according to the present invention by analyzing the diaphragm  104  to predict its withdrawn deformed shape and accordingly designing the diaphragm housing  112  and, particularly, the air cap  114 . As with the design of the fluid cap  116 , the air cap  114  is designed to fully accommodate the predicted shape of the deformed diaphragm  104 . The computer model of the diaphragm  104  is constructed and placed in a nonlinear FEA package with a pressure differential on one side to simulate the diaphragm shape at its most withdrawn position of the stoke. As with the design of the fluid cap  116 , the path of the diaphragm  104  is documented and graphed to design and construct the air cap  114  to accommodate the full range of motion of the diaphragm  104  once placed in an actual pump. In this way, any undesirable dead space in the air chamber  130  can be eliminated to maximize efficiency, while avoiding abrasive rubbing contact between the diaphragm  104  and the inner surface  128  of the air cap  114 . 
   As mentioned above, the diaphragm  104  could be analyzed using non-computerized means. For example, a test diaphragm could be constructed and placed in a test chamber with a pressure differential applied to it to actually measure the deformed shape of the diaphragm. Also, nonlinear finite element analysis could be performed on the diaphragm  104  to predict its deformed shape, with or without the use of a computer. In all cases, the diaphragm  104  or  106  is analyzed to predict its deformed shape in actual use to better design the diaphragm housing  112  and particularly the inner surfaces  120  and  128  of the fluid cap  116  and the air cap  114 , respectively. 
   Although the invention has been described in detail with reference to certain described constructions, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.