Abstract:
A method of lubricating and cooling a de-ionized water positive displacement pump having a reciprocating piston using tap water instead of de-ionized water to cool and lubricate the plunger and seals, resulting in longer service life of the pump.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention is directed to a fluid reciprocating positive displacement pump for de-ionized water and in particular to a method of lubricating and cooling such a pump with tap water.  
         [0002]     More practically, a three-piston/plunger pump is a positive displacement, reciprocating pump. With each revolution of the crankshaft there is a direct motion of the plunger rods (piston) resulting in a positive output of flow from the pump. The pistons are offset 120° in relation to each other. The output of the pump (flow) is in direct relation with the RPM of the pump. The bore and stroke determine the amount of liquid handled with each revolution.  
         [0003]     Pumps of this type have a particular application in high pressure pumping de-ionized water for many uses including electronic part processing. The pumps typically have a high-pressure Teflon® seal distal from the motor rotating shaft within the pump housing and low-pressure seals made, for example, from butylnitrile located proximal to the motor shaft within the pump housing.  
         [0004]     This style of pump requires lubrication and cooling to insure its longevity. Typically, the pump is cooled and lubricated between the seals by the fluid being pumped. De-ionized water from the inlet source is directed to the pump head and is circulated between the high pressure seal and the low pressure seal.  
         [0005]     De-ionized water is usually stored and used at ambient temperatures of 90°-100° F. Hence, this cooling technique is not optimal.  
         [0006]     It is well known that de-ionized water is not very conductive (15-16 megaohms) versus tap water which is more conductive (0-2 megaohms). This means that de-ionized water is highly abrasive of the seals in that it provides no lubrication while tap water with its ions performs lubrication.  
         [0007]     Because the plunger is not well cooled and the seals are not lubricated, pump failure occurs. If a high pressure seal fails, low pressure seal failure soon follows signified by a leaky pump housing spraying pumped de-ionized water. The crankshaft side of the low pressure seal is exposed to atmosphere. Thus, cooling and lubricating of this seal is also very important. If the low pressure seal fails, the cooling/lubricating water leaks through the pump housing.  
         [0008]     There is a need for a new lubrication method for pump seals which uses tap water rather than de-ionized water for lubrication.  
       SUMMARY OF THE INVENTION  
       [0009]     A method of lubricating and cooling a de-ionized water positive displacement pump having reciprocating pistons/plungers using tap water instead of de-ionized water to cool and lubricate the plunger and seals, resulting in longer service life of the pump.  
         [0010]     A principle object and advantage of the present invention is that the use of tap water instead of de-ionized water to cool and lubricate the pump&#39;s high-pressure seal, plunger and low pressure seal results in longer service life and less maintenance of the reciprocating positive displacement pump for de-ionized water. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]      FIG. 1  is a schematic cross-section of a pump with lubrication provided by tap water as opposed to de-ionized water. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]     A reciprocating positive displacement three-piston pump for use with the present invention is shown in  FIG. 1  as reference numeral  10 .  
         [0013]     The pump  10  includes a pump housing  11  and a crankshaft housing  12  encompassing a crankshaft  14  externally driven (not shown) connecting rod  16 . The crankshaft  14  is connected to a piston or plunger  18  in a manner well-known through rod  16  to produce reciprocating motion of the plunger or piston  18  as the crankshaft  14  rotates.  
         [0014]     The plunger  18  reciprocates within a pump chamber  20  and cooling and lubricating chamber  21 . The pump chamber  20  has a low-pressure seal  22  which seals the pump chamber  20  within the pump housing  11 . Backup seal  23  protects the crankshaft housing  12 , crankshaft  14 , rod  16  and their typical petroleum lubricants. The pump chamber  20  has a high-pressure seal  24  which seals the compression chamber  26  from the cooling and lubricating chamber  21  and low-pressure seal  22 .  
         [0015]     The pump  10  has an inlet chamber  28  which receives de-ionized water A from a source (not shown). The inlet chamber is normally closed by an inlet valve  30 .  
         [0016]     The pump  10  has an outlet chamber  32  for pumping pressurized de-ionized water B to a destination (not shown). The outlet chamber  32  is normally closed by an outlet valve  34 .  
         [0017]     The plunger  18  is lubricated by tap water C flowing from a source (not shown) through an inlet  36  to contact the plunger  18 , the high-pressure seal  24  and the low-pressure seal  22  and, thus, lubricate and cool the plunger  18  and seals  22  and  24 . Tap water D is then discharged through an outlet  38 . In the context of this application, “tap water” shall be defined as any non-de-ionized water such as city water. City water typically is 30-40 PSI. In this application, the city water is suitably valved down to 2-3 PSI.  
         [0018]     By this arrangement and method of cooling and lubricating, pump  10  and its constitutent parts have significantly greater longevity in between service and maintenance down times. This is because tap water C at 40°-50° has greater cooling capacity than de-ionized water A at 90°-100° F. Also, tap water C is a better lubricant with its metal ions than abrasive de-ionized water A.  
         [0019]     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar to or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety to the extent allowed by applicable law and regulations. In case of conflict, the present specification, including definitions, will control.  
         [0020]     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.