Abstract:
A blending pump assembly for accurately maintaining the proper ratio of two fluid components. Flow of a first fluid is utilized to drive a fluid motor, which in turn drives a pumping mechanism to inject a proportional amount of a second fluid into the flow of the first fluid. The fluid motor and pump are sized so that a predetermined ratio between the two fluids is maintained regardless of changes in pressure and flow rate of such first fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 11/593,826 entitled “Blending Pump Assembly,” now U.S. Pat. No. 7,404,705, filed with the U.S. Patent and Trademark Office on Nov. 7, 2006 by the inventor herein, which application is a continuation of U.S. patent application Ser. No. 10/719,605 entitled “Blending Pump Assembly,” now U.S. Pat. No. 7,131,826, filed with the U.S. Patent and Trademark Office on Nov. 21, 2003 by the inventor herein, which application is based upon and claims benefit of copending and co-owned U.S. Provisional Patent Application Ser. No. 60/428,115 entitled “Blending Pump Assembly”, filed with the U.S. Patent and Trademark Office on Nov. 21, 2002, by the inventor herein, the specifications of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention disclosed herein relates generally to a proportioning pump assembly, and more particularly to a pumping apparatus that maintains the ratio of two pumped fluids, which ratio is unaffected by alterations in the pressure and velocity of the flowing fluids. 
     2. Background of the Prior Art 
     Several devices have been developed for injecting predetermined quantities of liquid additives into a liquid flow stream. For example, beverage dispensing valves that provide for the mixing of carbonated water and syrup to produce a dispensed beverage are well known in the art. Other applications such as adding medication to drinking water with such additives as chlorine or iodine and adding fertilizer concentrate to irrigation water are similarly well known. 
     A number of fluid pumps have been designed that inject an additive into the primary fluid stream where the primary fluid provides the motive fluid for activating the additive injection pump. For example, U.S. Pat. No. Re. 35, 780 to Hassell et al. discloses a beverage dispensing valve having two sets of oval gears in which the ratio of two liquid beverage constituents is maintained by the interaction of the oval gear pairs, which are sized so that the desired ratio is maintained. Flow is regulated through use of solenoid operated pallet valves for each liquid component. 
     U.S. Pat. No. 3,821,963 to Olsen et al. discloses a liquid proportioning apparatus for injecting a liquid into the flow of a driving liquid. The apparatus uses an eccentric paddle wheel as the fluid motor to drive a separate pump for a second liquid to be injected into the driving flow. 
     U.S. Pat. No. 6,357,466 to Walton et al. discloses an apparatus for generating a mixture of a first fluid and a measured quantity of a second fluid in a fluid stream. The gears of a flow meter rotate when a first fluid is passed through the flow meter. A shaft connected coaxially with a gear of the flow meter is connected with a gear of a cavity pump for a second fluid so that the second fluid is pumped through the cavity pump when the first fluid is directed through the flow meter. 
     While the above-mentioned compound motor/pump assemblies have been generally satisfactory to enable a driving fluid to be used as the motive force to drive a fluid motor which in turn drives a proportional pump, these devices have not enjoyed significant commercial success. While positive displacement pumps, such as gear pumps, may at times have the capacity to be used as a fluid motor, their design typically enables leakage past the gears between the gear teeth and the housing, and between the gear sidewalls and the housing. For mixing applications requiring precise mixing ratios, this leakage (and the variable mixing ratios that result) can render such assemblies useless. Unfortunately, manufacturing the gear pump components with ultra-tight tolerances to minimize such clearance often increases the cost of such assemblies to render them uneconomical. Moreover, very small clearances may result in high friction and difficulty in getting the motor started at low fluid pressures. Still further, prior art fluid motor and pump assemblies have typically been provided in configurations that limit their adaptability to varied mixing ratios due to a fixed relationship between the rate of rotation of a driving gear in the fluid motor and a driven gear in the fluid pump, and thus fail to provide a practical pump assembly enabling customized mixing proportions to be obtained. It would be advantageous to provide a means to adjust the flow proportion in a fast, easy manner. Accordingly, there remains a need for an apparatus that enables consistent, direct proportioning of flow of two liquids independent of the pressure and velocity of the driving liquid while enabling both fine and gross adjustment of the flow ratio in a simple manner, but of a sufficiently simplistic construction so as to maintain ease of manufacturing and low cost. 
     SUMMARY OF THE INVENTION 
     The blending pump assembly of the instant invention comprises a fluid motor, the motor having an inlet fluidly connected to a source of a first fluid and an outlet, a pump having an inlet fluidly connected to a source of a second fluid and an outlet, such fluid motor being operatively engaged with such pump through a drive which transfers torque from the fluid motor to the fluid pump, the fluid motor and pump being interconnected in such a way that a predetermined ratio between such first fluid and such second fluid is consistently maintained, irrespective of the pressure and velocity of the driving liquid. In a first exemplary embodiment, the blending pump assembly may be provided an internal recirculation channel controlled by a valve to enable adjustment of the fluid proportions. In a second exemplary embodiment, the blending pump assembly may be provided with modular quick-connect fluid pump blocks that provide varying flow rates for a given angular velocity of the driving gear of the fluid motor. Likewise, the blending pump assembly may simultaneously provide both a recirculation channel and a modular quick-connect fluid pump block to enable both fine and gross adjustment of the ratio between dispensed diluent and concentrate. 
     The blending pump assembly described thus provides proportioning of two fluids in a tightly controlled manner, and may provide adjustment of such proportion for fine and gross control of the ratio of such two fluids. 
     The compound motor/pump structure allows torque produced from the shaft of a fluid motor assembly to be used to drive a pump assembly connected thereto in such a way that the output from the pump maintains a desired proportion to the output of the fluid motor, irrespective of the flows therethrough. The first fluid motor assembly is preferably driven by fluid pressure from a first fluid directed through an inlet port, which flow in turn drives the shaft of the fluid motor assembly. The torque generated by the fluid motor is translated from the shaft to an impeller in the connected pump. A fluid motor body includes an inlet for a first fluid and a corresponding outlet, while the pump body includes an inlet for a second fluid and a corresponding outlet. 
     In one embodiment, the first fluid inlet and outlet on the fluid motor body are in fluid communication with one pair of circular gears positioned within a fluid chamber in the motor, and the second fluid inlet and outlet on the pump body are in fluid communication with a second pair of circular gears positioned within a fluid chamber in the pump. The first pair of circular gears comprises a gear motor, while the second pair of circular gears comprises a gear pump. Alternately, the gear pairs may be replaced with a single gear element in either or both of the pump and motor assemblies, such as an eccentrically mounted impeller. Each gear or gear pair, as the case may be, preferably rotates in its own housing, fluidly separate from the other gear pair. 
     In another embodiment, the fluid inlet and outlet on the fluid motor body are in fluid communication with a plurality of reciprocating pistons connected to a crankshaft for providing rotary movement of a drive shaft. The drive shaft, in turn, is operatively connected to the fluid pump. 
     In one aspect of a preferred embodiment of the invention, a recirculation channel is provided in the pump assembly that enables fine adjustment of the compound motor/pump output. More particularly, a “tee” connector may be positioned in the flow line of the pump, downstream of the pump outlet, which allows fluid communication between the pump flow line downstream of the pump and the pump flow line upstream of the pump. A needle valve or similarly constructed flow control device may be positioned in the flow branch interconnecting the downstream line with the upstream line. In this way, minute adjustment of such flow control device may bleed off a portion of the fluid output from the pump assembly, directing such fluid back to the pump input, and in turn enable fine adjustment of the amount of fluid dispensed from the pump flow line for a given amount of first fluid passing through the fluid motor. 
     In an aspect of another embodiment of the invention, gross adjustment of the proportional flow of a first fluid to a second fluid may be provided in a simple adjustment step. More particularly, the pump housing may be pivotally attached to the motor housing, and an intermediate drive mechanism, such as a gear train, may be provided between the two such that torque from the fluid motor drive shaft is transferred to the drive shaft of the driven member of the pump through such gear train. The gears between the two housings may be selected to provide the desired proportional speeds of the motor and pump. Moreover, because the pump housing is pivotally mounted to the motor housing, the pump housing may be pivoted to allow access to and replacement of the gears of the gear train, and thereafter pivoted and locked back into a position in which the gears of the gear train engage one another, thus enabling gross changes in proportioned flow rates to be achieved in a quick and easy manner. Alternately, the gear train may remain fixed, and the driven gear or gears within the pump may vary from pump housing to pump housing, such that switching out one pump housing for another may provide changes in proportioned flow rates. 
     In operation of a first embodiment, a pressurized first fluid is provided to the fluid motor fluid channel inlet and is delivered to the operative motor member(s) therein for providing rotation thereof. The first fluid then flows out of the fluid channel outlet. It can be understood that, as one of the rotational members of both the fluid motor and the fluid pump is on a common rotating shaft (or operatively engaged with one another through a connecting mechanical drive such as a gear train), the pressurized first fluid provides for the driving force for the gear pump for the second fluid. The operative members are dimensioned such that, for each revolution of the common shaft, a predetermined ratio of such first and second fluid is delivered. Moreover, such ratio is maintained regardless of the rotation rate of the members. The pump output may be finely adjusted by permitting a portion of the output to recirculate back to the pump inlet thereby reducing the quantity of such second fluid injected into the first driving fluid stream, and may be grossly adjusted by replacing drive gears between the fluid motor and fluid pump or by replacing the entire pump housing with a different capacity pump. In addition, as the member(s) of the fluid pump serve as a pump, it is not necessary to pressurize the second fluid source for the delivery thereof to the blending pump assembly. 
     Notably, with respect to the above-described embodiments, the connection between the fluid motor and pump is one of a direct drive engagement, such that a desired proportional flow may be maintained at all times, irrespective of the pressure or velocity at which the driving fluid flows through the fluid motor. Moreover, the mechanisms provided herein for both fine and gross adjustment require few parts, such that the compound motor/pump assembly of the instant invention requires less maintenance, and may likewise be provided at lower cost, than prior known blending apparatuses. Still further, the features of fine and gross adjustment of proportional flow rates set forth herein enables much finer proportioning control than previously known blending apparatuses, and thus may be used in applications requiring very large proportioning ratios. 
     The various features of novelty that characterize the invention will be pointed out with particularity in the claims of this application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features, aspects, and advantages of the present invention are considered in more detail, in relation to the following description of embodiments thereof shown in the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a blending pump assembly according to one embodiment of the instant invention. 
         FIGS. 2 and 3  are cross section views of the blending pump assembly of  FIG. 1 . 
         FIG. 4  is a cross section view of the pump portion of the blending pump assembly of  FIG. 1 . 
         FIG. 5  is a cross section view of a vane pump or motor assembly according to an alternate embodiment of the instant invention. 
         FIGS. 6   a  and  6   b  are exploded and sectional views of a screw pump assembly according to another embodiment of the instant invention. 
         FIGS. 7   a  and  7   b  are exploded and sectional views of a piston pump assembly according to another embodiment of the instant invention. 
         FIGS. 8 and 9  are exploded and sectional views of a blending pump assembly according to another embodiment of the instant invention. 
         FIG. 10  is an exploded view of the blending pump assembly of  FIG. 8 , showing another feature of the instant invention. 
         FIG. 11  is a sectional view of an alternate embodiment of the fluid motor assembly. 
         FIG. 12  is a schematic drawing of a first and second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention summarized above and defined by the enumerated claims may be better understood by referring to the following description, which should be read in conjunction with the accompanying drawings in which like reference numbers are used for like parts. This description of an embodiment, set out below to enable one to build and use an implementation of the invention, is not intended to limit the enumerated claims, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and exemplary embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
     A first preferred embodiment of the compound motor/pump assembly of the instant invention is shown in  FIG. 1 . A blending pump assembly, generally designated as  10 , includes a lower gear motor assembly  12  and an upper gear pump assembly  15 . Lower gear motor assembly  12  comprises gear motor body  17  and cover  18 , the motor body  17  having an inlet fluid channel  21  and an outlet fluid channel  24  (best seen in  FIG. 2 ). Inlet fluid channel  21  may be in fluid communication with a pressurized source of a first fluid as shown in  FIG. 7 . Motor body  17  further includes a cavity  27  wherein a first pair of gears  30 ,  31  is nested. Gears  30 ,  31  may be circular gears having a plurality of teeth about their periphery, such that the teeth of gear  30  intermesh with the teeth of gear  31 . In the particular embodiment depicted in  FIG. 1 , shaft  34  is rotatively secured to motor body  17  and fixedly secured to gear  30 , and extends from gear  30  upward through aperture  36  in cover  18  to provide a drive axle  39  for upper gear pump assembly  15 . Gear  31  freely rotates on shaft  35 , rotatively secured between motor body  17  and cover  18 . 
     Notably, alternate fluid motor constructions may likewise be used without departing from the spirit and scope of the invention. For example, instead of gears  30 ,  31 , a vane pump, a flexible rotor pump, or similarly configured pump assemblies capable of being driven by a motive fluid and transferring torque to a drive shaft  39  may be used for motor assembly  12 . 
     Referring to  FIGS. 3 and 4 , gear pump assembly  15  comprises a gear pump body  42 , to which a cover  43  is attached ( FIG. 1 ). A second pair of gears  46 ,  47  is nested in pump body  42 . Gears  46 ,  47  may be circular gears having a plurality of teeth about their periphery, such that the teeth of gear  46  intermesh with the teeth of gear  47 . Gear  46  is securely attached to drive axle  39  such that rotation of gear  30  causes simultaneous rotation of gear  46 . A seal  48  in aperture  36  may be provided for preventing fluid communication along shaft  34  between cavity  27  and gear pump body  42 . Gear  47  freely rotates on shaft  49 , rotatively secured between pump body  42  and cover  43 . Pump body  42  has an inlet port  51  and an outlet port  52  creating a flow channel  55  through gear pump assembly  15 . Inlet port  51  is in fluid communication with a source of a second fluid as shown in  FIG. 12 . Such second fluid source need not be pressurized. 
     In one embodiment of the invention, a recirculation channel  58  is provided in pump body  42  having an adjustable flow control device, such as valve  60 , to adjust flow through recirculation channel  58 . Valve  60  may, for example, comprise a valve stem  62  extending through gear pump cover  43  (best seen in  FIG. 1 ) and a valve handle  65  to permit adjustment of flow through valve  60 . Valve  60  may be any appropriate type of flow control device having throttling characteristics and is preferably a needle valve enabling fine control of flow through recirculation channel  58 . Flow through recirculation channel  58  is in the direction indicated by arrow  69  in  FIG. 3 . 
     In an alternate embodiment, the fluid motor, the pump, or both may be other than gear assemblies, in which the fluid motor and pump have a common rotating shaft. For example, a vane pump assembly, as illustrated in  FIG. 5 , can be used as the fluid motor, the pump, or both. Such a vane pump assembly  70  may comprise body  71  having an inlet fluid channel  72  and an outlet fluid channel  74 . A slotted impeller  76  having a plurality of vanes  78  is eccentrically supported on shaft  80 . Shaft  80  is rotatively secured to body  71 . A seal  81  may be provided to prevent fluid leakage along shaft  80 . The impeller  76  is located close to body  71  so a crescent-shaped cavity  83  is formed. Vanes  78  fit within slots of the impeller  76  and are configured to extend into such cavity  83  to form a slideable seal against body  71 . 
     When vane pump assembly  70  is utilized as a fluid motor, inlet fluid channel  72  may be placed in fluid communication with a pressurized source of a first fluid (see  FIG. 12 ). The pressurized fluid enters the inlet fluid channel  72  and impinges on a first of such plurality of vanes  78  causing impeller  76  to rotate in the direction shown by arrow  85 . Such motion of impeller  76  also causes shaft  80  to rotate. Shaft  80  extends outward from body  71  to provide a drive shaft for a connected pump. The pressurized fluid passes through cavity  83  to outlet fluid channel  74 . 
     When vane pump assembly  70  is utilized as a pump, shaft  80  causes impeller  76  to rotate. As the impeller  76  rotates and a second, unpressurized fluid enters the pump, the vanes  78  are pushed to the wall of body  71  forming a tight seal. As impeller  76  rotates, the vanes force such second fluid into the crescent-shaped cavity, and sweep the fluid toward the fluid outlet channel  74 . 
     Other combinations of fluid motors and pumps having a common rotating shaft shared between the motor and pump can be used, such as a gear motor, as described with reference to  FIGS. 1 and 2 , and a vane pump, as described above. In such a case, the shaft of one of the gears in the gear motor drives the impeller of the vane pump. In another embodiment, a vane pump assembly can be used as a fluid motor with its shaft connected to drive one of the gears of a gear pump. Other motor assemblies and/or pump assemblies of generally similar construction may likewise be utilized, such as a flexible vane pump, a screw pump, as shown in  FIGS. 6   a  and  6   b , etc. 
     Referring to  FIGS. 7   a  and  7   b , a reciprocating-type fluid motor, indicated generally as  125 , is shown. Reciprocating motor  125  comprises a plurality of at least three drive units  127 ,  128 ,  129  each including a piston movable within a cylinder; and a valve assembly  132  for controlling the introduction of pressurized fluid into the cylinder of the respective drive unit and the discharge of spent fluid therefrom for driving the piston of the respective drive unit; each of the pistons being coupled to the drive shaft  135  such that the pistons initiate their respective forward strokes at different angular positions of the drive shaft. 
     According to one preferred embodiment, the drive units  127 ,  128 ,  129  and valve assembly  132  are arranged in a linear array with the valve assembly  132  at one end of the respective drive unit and in abutting relation to the valve assembly of the adjacent drive unit, and with the drive shaft  135  coupled to the pistons at the opposite ends of the drive units. In the described embodiment, the pistons of the drive units are coupled to the drive shaft  135  via a crankshaft  138  that includes a crank arm for each piston. Such a construction thus permits any desired number of drive units to be coupled to the drive shaft  135  in a modular manner according to the force requirements for any particular application. Preferably, the drive shaft  135  includes a single crank arm to which the pistons of all the drive units are pivotally coupled. Such a construction is particularly advantageous in that it permits the drive units to be coupled, in a convenient and compact manner, to a common drive shaft of a rotary device. 
     In  FIG. 7   a , crankshaft  138  comprises three cranks  141 ,  142  and  143 . Corresponding to each of cranks  141 ,  142  and  143 , the motor  125  comprises three connecting-rod assemblies, which comprise pistons  147 ,  148  and  149 , and cylinders  151 ,  152  and  153 . Valve assembly  132  comprises valves  156 ,  157  and  158  having fluid inlet port  161  and fluid outlet port  162 . Valves  156 ,  157  and  158  serve as pivots of the connecting-rod assemblies, being inserted respectively into sleeves  166 ,  167  and  168 . Valves  156 ,  157  and  158  can be designed as one unit.  FIG. 7   b  shows the pivotal connections between the pistons  147 ,  148  and  149  and the crankshaft  138 . In some embodiments, motor  125  may include a housing, such as shown at  173 . 
     In yet another embodiment, as shown in  FIG. 8 , gear pump body  42  is pivotally mounted to cover  18  of fluid motor assembly  12  via a pivot screw  90 . When tightened, screw  90  locks the position of gear pump body  42 , but when loose, screw  90  allows gear pump body  42  to pivot freely about screw  90 . Once again, shaft  34  extends upward from first gear  30  in fluid motor assembly  12 , and a motor drive axel  39  extends through cover  18 . Mounted on the exposed end of motor drive axel  39  is a first drive train gear  91 . As described above, application of a pressurized driving fluid through fluid motor assembly  12  will cause rotation of gear  30 , in turn causing rotation of drive shaft  39  and first gear  91  mounted thereon. While in the particular embodiment shown in  FIG. 8 , fluid motor assembly  12  comprises gears  30 ,  31 , as explained above, alternate fluid motor configurations could likewise be utilized without departing from the spirit and scope of the invention, including a vane pump, flexible rotor pump, gear pumps having gears of other geometries, piston pump, and any other pump assembly which may be driven via application of a pressurized fluid to the flow channel passing therethrough. 
     In the particular embodiment depicted in  FIG. 8 , gear pump body  42  may be constructed to provide an opening between the bottom of gear pump body  42  and cover  18  of fluid motor assembly  12 , such opening being of sufficient size to accommodate first gear  91  and a second gear  92 . In the embodiment of  FIG. 8 , gear pump body  42  is depicted as optionally utilizing a flexible vane pump assembly  70  having a flexible rotor  76  mounted within gear pump body  42 , with a fluid inlet  95  and fluid outlet  96  directing fluid through gear pump body  42  and the open chamber  94  thereon holding flexible rotor  76  ( FIG. 9 ). In such case, flexible rotor  76  would preferably be mounted on pump drive axel  93 , which in turn is mounted to second gear  92 , such that rotation of second gear  92  causes rotation of flexible rotor  76  to in turn pump fluid through the pump assembly. Of course, as explained above, alternate gear elements (such as one or more parallel tooth gears) may be used for the pump assembly without departing from the spirit and scope of the invention. 
     Because gear pump body  42  is pivotally mounted to cover  18 , access may be had to both first gear  91  and second gear  92  by pivoting gear pump body  42 . Preferably, first gear  91  is removably attached to drive axel  39 , such that first gear  91  may be removed and replaced with a gear having a different gear geometry, thus enabling gross modification of the rotational speeds of gears  30 ,  31  and of flexible rotor  76 , which in turn modifies the proportional flow rates between the fluid motor assembly  12  and the gear pump assembly  15 . 
     Alternately, or in addition to the above, second gear  92  may likewise be removably attached to flexible rotor  76 , such that second gear  92  may be replaced instead of or in addition to first gear  91  to enable gross modification of the proportional flows between fluid motor assembly  12  and gear pump assembly  15 . Still further, first and second gears  91  and  92  may be maintained, and gear pump body  42  may be interchangeable with a second pump body  44 , as shown in  FIG. 10 , having fluid inlet  98  and fluid outlet  99  directing fluid through pump body  44  and the open chamber  97  thereon holding a different rotor  79  or other gear members of varying construction in different gear pump bodies. The single screw connection provided by pivot screw  90  enables quick interchange of such alternate pump body configurations. 
     Likewise, while not particularly shown in  FIG. 8  or  9 , gear pump assembly  15  may be provided with recirculation channel  58  and valve  60 , as discussed above, to also enable fine adjustment of the proportional flows between fluid motor assembly  12  and gear pump assembly  15 . 
     In yet another aspect of the invention, and as particularly shown in  FIG. 11 , instead of providing the fluid motor with cylindrical gears, in order to account for variable clearances that may result from tolerances in the manufacturing process without exorbitantly increasing manufacturing costs, the gear members  30  and  31  may be provided as round, parallel tooth gears having a tapered perimeter  101 . In this case, the benefits of using a positive displacement pump as the fluid motor may be maintained without the associated disadvantages of leakage past the motor gears. More particularly, the positive displacement pump, and more particularly a gear pump, allows the fluid that drives the motor to likewise provide the lubrication for the gears and rotating shafts. Gears are quite common and easily manufactured whether by machining or, for low cost, molding from plastics or sintered from metal powders. However, for mixing or metering applications, it is desirable that there be little or no leakage past the gears by the driving fluid in order to obtain maximum output torque of the motor, and in mixing applications, that a repeatable and constant amount of driving fluid passes through the pump for each revolution of the gear set. To minimize leakage past the motor gears, it is advisable to have very close clearance fits between the perimeter of the gear teeth and the circular gear housing, and to have very little side clearance between the sides of the gears and the housing. In order to provide minimal clearance without exorbitantly increasing the manufacturing costs and risking high friction conditions (which in turn could render it difficult to start the fluid motor at low fluid pressure), the gear members in fluid motor assembly  12  are formed as parallel tooth gears having a tapered or cone-shaped perimeter  101 . The chambers in which tapered gears  30  and  31  sit is likewise preferably tapered so that the gears  30  and  31  can be individually placed in the tapered housing to a depth that would ensure a close fit regardless of manufacturing tolerances. Notably, such manufacturing tolerances may cause a clearance to be produced between the top and bottom walls of the gears and the top and bottom walls of the chamber, respectively. Such clearances are preferably filled with upper and lower flat shims  102  to the required thickness, thus resulting in close clearances between both the outside diameters of the gears as well as between the gear faces and the motor housing. 
     Operation of the blending pump assembly of the present invention will now be described with reference, for exemplary purposes, to the particular embodiment shown in  FIG. 1  and the schematic drawings in  FIG. 12 . The fluid motor assembly  12  is driven by fluid pressure from a first fluid  105  directed through inlet fluid channel  21 . Thus, in the particular embodiment depicted in  FIG. 1 , it is the flow of fluid that drives the first pair of gears  30 ,  31  in gear motor assembly  12 , as opposed to driving the gears to cause fluid to flow. Gears  30 ,  31  are meshed together and counter-rotate relative to each other when the first fluid  105  is directed through the inlet fluid channel to the outlet fluid channel  24 . Shaft  34  from one of the fluid pressure driven gears, gear  30 , extends upward through the housing to drive one of the gears, gear  46  of the gear pump assembly  15 , which in turn will cause the gears  46 ,  47  in gear pump assembly  15  to counter rotate relative to each other in order to draw a second fluid  107  through inlet port  51  and pump such second fluid  107  out through outlet port  52 . 
     It can be seen, therefore, that flow of such first fluid  105  enables the pumping of such second fluid  107  since one gear of each pair is secured to a common rotating shaft. The first pair of gears and second pair of gears are sized to provide a predetermined proportion of such second fluid  107  based on the flow of such first fluid  105 . The proportional flow of the second fluid in relation to the first fluid may be finely adjusted by adjusting the amount of flow through recirculation channel  58  by use of valve  60 . Since pump assembly  15  provides a positive displacement gear pump, increased flow through recirculation channel  58  results in decreased flow through outlet port  52 . Additionally, the proportional flow may be grossly adjusted by changing the gears in the gear train between fluid motor drive axel  39  and fluid pump drive axel  93  (or by replacing gear pump body  42  with an alternate gear pump body having a distinct gear or rotor configuration) to enable a single pump assembly to be used in a wide variety of mixing applications. 
     As shown in the schematic view of  FIG. 12 , the combined fluid motor/pump apparatus  10  thus enables the proportional mixing of two distinct fluids, wherein the fluid pressure from the first fluid  105  serves as a driving force for a pump to pump a second fluid  107 . Blending pump assemblies may be combined in series, such that the mixture from a first assembly  111  may be continuously diluted by directing the mixture through a second assembly  114 , while directing the driving fluid through a second non-driven (or fluid pressure driven) motor with a common rotating shaft. 
     The invention has been described with references to a preferred embodiment. While specific values, relationships, materials and steps have been set forth for purposes of describing concepts of the invention, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the basic concepts and operating principles of the invention as broadly described. It should be recognized that, in the light of the above teachings, those skilled in the art could modify those specifics without departing from the invention taught herein. Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is intended to include all such modifications, alternatives and other embodiments insofar as they come within the scope of the appended claims or equivalents thereof. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein. Consequently, the present embodiments are to be considered in all respects as illustrative and not restrictive.