Abstract:
A control valve for a reverse osmosis water purifying system provides a feed water port, a squeeze water port, a drain port, and a product water connection, each of which open into a bore. A first, second, and third O-rings are located in the bore successively between the feed water port, the squeeze water port, the drain port, and the product water connection. A control piston is moveably located in the bore of the housing. The control piston includes a vent/drain well in which a side is chamfered. The vent/drain well provides a fluid passage between the squeeze water port and the drain port when the vent/drain well passes over the second O-ring. The fluid passage includes an opening formed between the second O-ring and the chamfered side of the vent/drain well, where the size of the opening is responsive to the position of the control piston.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit pursuant to 35 U.S.C. 119(e) of U.S. Provisional Application No. 62/351,188, filed Jun. 16, 2016, and U.S. Provisional Application No. 62/351,494, filed Jun. 17, 2016, each of which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
     Field 
       [0002]    The present invention relates to the field of reverse osmosis water filters; and more specifically, to control valves for reverse osmosis water filters. 
       Background 
       [0003]    The present invention represents improvements in the reverse osmosis control valve disclosed in U.S. Pat. No. 6,110,360. That valve was a considerable advance in the art at the time of its development. However it still had some problems, which problems have been accentuated as reverse osmosis filter system performance in terms of rate of production of product water has greatly increased over the years, as more fully described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the invention by way of example and not limitation. In the drawings, in which like reference numerals indicate similar elements: 
           [0005]      FIG. 1  illustrates a control valve in accordance with the present invention in a system shutoff position. 
           [0006]      FIG. 2  illustrates the control valve of  FIG. 1  in a product water dispensing position. 
           [0007]      FIG. 3  illustrates the control valve of  FIG. 1  in a product water production position. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. 
         [0009]    In the following description, reference is made to the accompanying drawings, which illustrate several embodiments of the present invention. It is understood that other embodiments may be utilized, and mechanical compositional, structural, electrical, and operational changes may be made without departing from the spirit and scope of the present disclosure. The following detailed description is not to be taken in a limiting sense, and the scope of the embodiments of the present invention is defined only by the claims of the issued patent. 
         [0010]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like may be used herein for ease of description to describe one element&#39;s or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0011]    As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising” specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. 
         [0012]    The terms “or” and “and/or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and/or C” mean “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive. 
         [0013]    Control valves in accordance with U.S. Pat. No. 6,110,360 were first introduced in Florida, typically a warm water market. The valve used a Teflon piston as stated in the patent, selected to avoid wear on the O-rings from piston motion, and proved to be a success as long as there was never a severe shift in water temperatures. However, when cutting the Teflon material at one temperature to fabricate the piston, then operating the control valve at a lower temperature, the piston will shrink beyond operational dimensions, with the result that the water system will drain on its own. While Teflon has the desired lubricity, it is too unstable a material to properly function over a substantial temperature range, as can be expected in probably most regions of the U.S. and many other countries. To overcome this problem, the present invention utilizes a much more stable family of plastics for the material of the control valve piston, namely, acetal types of plastic, such as by way of example, Delrin as manufactured by DuPont and Celcon as manufactured by Celanese. The acetal plastics are much more stable than Teflon and maintain the required dimensional tolerances over the required temperature range to provide highly satisfactory operation over any reasonable temperature range. 
         [0014]    Also, the control valve of U.S. Pat. No. 6,110,360 was developed at a time when the daily output of a typical reverse osmosis membrane was on the order of 15 gallons per day. In that regard, it is important to note that in the design of the control valve of U.S. Pat. No. 6,110,360, all of the functional operations are related to timing—when to vent, when to turn off, when to turn on, etc. In that regard, the control valve is intended to operate in conjunction with reverse osmosis filter systems having a bladder in the product water storage tank, whereby product water may be added to the internal volume of the bladder while the outer surface of the bladder is vented to atmospheric pressure during product water generation, and to provide squeeze water, that is reverse osmosis filter membrane waste water at tap water pressure, to the outer surface of the bladder to pressurize the product water during product water dispensing. 
         [0015]      FIGS. 1, 2 and 3  illustrate a control valve in accordance with the present invention wherein the major components of the control valve may be seen. The control valve includes a housing  20  with a control piston  22  therein, sealed at the left end by cap  24  and O-ring  26 . The housing  20  includes four ports, namely a feed water port  28  (reverse osmosis filter membrane waste water at tap water pressure), a squeeze water port  30  and a drain port  32 , together with product water connection  34 . In these Figures, the cross section shown is a form of composite cross sections to place the ports  28 ,  30 , and  32  and product water connection  34  in the same plane, which has distorted the control piston  22 , though except for the flow path  40 , the control piston  22  has a surface of revolution. 
         [0016]    At the right end of housing  20  is a feed water metering screw  36  which has an extension  38  extending into an axial opening in the control piston  22 , which together with flow path  40 , allows a slow but positive rate of feed water through feed water port  28  when not blocked by O-rings between the housing  20  and the control piston  22 , namely, O-ring  42 . 
         [0017]    In this embodiment, the reverse osmosis filter membrane is always exposed to the full feed water pressure in feed water port  28  and the left end, the larger end of control piston  22 , is always exposed to a product water pressure through product water connection  34 , which as shall be subsequently described, is isolated from reverse flow back to the product water storage tank by a check valve there between. Accordingly, as may be seen in  FIG. 1 , when the product water storage tank is full of product water, the product water pressure in the storage tank will increase by continued, though slower, production of product water to increase the pressure in the product water connection  34 , ultimately forcing the control piston  22  to the far right position, as shown in  FIG. 1 , because of the difference in the areas of the two ends of the control piston  22 . In this far right position, O-ring  42  blocks any feed water flow past the O-ring, stopping all water flow in the system. In that regard, as mentioned before, the reverse osmosis membrane in this embodiment is coupled to the raw water source (tap water) at all times, with feed water port  28  being coupled to the waste water outlet of the reverse osmosis filter unit. Accordingly, shutting off the flow through feed water port  28  shuts off all water flow through the system. 
         [0018]    When a product water dispensing valve is opened to dispense the reverse osmosis filtered water, the product water pressure in product water connection  34  will immediately drop, allowing the feed water pressure in feed water port  28  to force the control piston  22  to the far left position, as shown in  FIG. 2 , moving the control piston past O-ring  42 , but not past O-ring  44 , so that now the feed water port  28  is coupled to the squeeze water port  30  to pressurize the outer surface of the bladder in the product water storage tank, which in turn forces product water within the bladder through the dispenser. 
         [0019]    When the dispensing stops, the squeeze water port  30  is still coupled to the feed water port  28  so that the product water coupled to product water connection  34  is still at the squeeze water pressure, which is equal to the feed water pressure. Accordingly, control piston  22  will start to move to the right until the squeeze water port  30  is coupled to the drain port  32 , as may be seen in  FIG. 3 . In this position, O-ring  42  blocks flow from feed water port  28  around the right end of control piston  22 . Also, with the control piston  22  in the position shown in  FIG. 3 , the restricted feed water flow in flow path  40  is also coupled to the drain port  32  through vent/drain well  48  in the control piston  22 . This causes the squeeze water pressure on squeeze water port  30  and on the outside of the product water storage tank to fall to atmospheric pressure. However, the check valve previously mentioned prevents product water from flowing back out of product water connection  34 , and of course because the dispensing valve is now closed, product water cannot flow out of the product water connection  34  through the dispensing valve, so the control piston  22  will stop at the position shown in  FIG. 3 . Under this condition, the pressure on the outside of the bladder in the product water storage tank is essentially atmospheric, and the feed water flow past the reverse osmosis membrane and through feed water port  28  is restricted. During this time, product water is being produced, thereby filling the storage tank with product water, after which product water pressure will increase as previously described, moving the control piston  22  to the far right position shown in  FIG. 1 , shutting the system off. 
         [0020]    However in the prior art systems, the low speed of movement of the control piston proved to be of vital importance for proper operation of the control valve. The vent/drain well of the piston in the prior art systems was cut at 90 degree angles. This has been found to cause at least two problems in the best present-day systems. 
         [0021]    The first problem is that the width of the channel of the vent/drain well  48  from one wall to the other wall represents the time between squeeze venting and system shut down. Using the latest reverse osmosis membrane technology for current high product water production rates of 60 to 100 gallons per day achievable in the newest reverse osmosis filtering systems, such as those of U.S. Pat. No. 7,601,256, the faster water causes the control piston  22  to move from the full squeeze position (dispensing) ( FIG. 2 ) through squeeze water exhaust position ( FIG. 3 ) to shutdown ( FIG. 1 ) and never make water. This would only occur during the initial startup phase of the reverse osmosis filter system. Still, the system would not work right out of the box. 
         [0022]    This problem is solved in the present invention by chamfering at least one side of the vent/drain well  48  in the control piston  22  as shown in the Figs. For the purposes of this specification, “chamfering” the side of the vent/drain well  48  means providing an angled wall on the vent/drain well as shown in the Figs. The “chamfering” extends into the vent/drain well  48  sufficiently further than the O-ring  44  such that the “chamfering” provides a path past the O-ring  44  that opens slowly as the control piston  22  moves to the right. The “chamfering” may extend to the full depth of the vent/drain well  48  as shown in the Figs. so that the “chamfering” connects the outer cylindrical surface of the control piston  22  to the parallel cylindrical surface at the bottom of the vent/drain well. 
         [0023]    The chamfering of the side of the vent/drain well  48  achieves two things. First it starts venting the squeeze water past O-ring  44  early and slowly. This allows the system to stabilize and avoids or minimizes any momentary maintenance of product water pressure after venting of squeeze water occurs, slowing the movement of control piston  22  to the right and allowing it to stop when the squeeze water is vented past O-ring  44 , stopping the flow of product water to the left side of the control piston  22 , but holding its volume of water by the check valve previously described. Then when the system fills to product water storage tank bladder capacity, the product water pressure increases to supply more product water through product water connection  34 , whereby the control piston  22  now continues the movement toward the right to finish the cycle to the full shut down as shown in  FIG. 1 . 
         [0024]    Finally, the chamfering of the vent/drain well  48  also prevents the otherwise square corner of the vent/drain well  48  from catching the O-ring  44 , and provides a self-centering action to avoid that problem. 
         [0025]    While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. The description is thus to be regarded as illustrative instead of limiting.