Abstract:
A master/slave pump assembly employs a dual diaphragm pump as the master pump. An abrasive fluid, such as a resin containing abrasive particles, can be pumped by the dual diaphragm pump without the damage that would result from exposure of seals to the abrasive fluid. The slave pump, which can pump a catalyst or other secondary fluid, is driven in response to movement of the diaphragms and the shaft connecting the two diaphragms. A force or a signal dependent upon the actual mass flow rate of the primary fluid, can be communicated hydraulically or electrically to the slave pump, regardless of viscosity or environmental factors. An adjustable linkage is employed to alter the ratio of the mass flow rates of the two fluids.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a master/slave pump assembly for use in precision metering, multiple component pumping systems in which an auxiliary or slave pump operates in unison with a main or master pump. This invention is also related to dual diaphragm pumps in which a flexible diaphragms pump fluid through a pumping chamber as the diaphragms and a shaft or rod on which they mounted are reciprocated in response to an actuating force, such as a pneumatic force. 
     2. Description of the Prior Art 
     U.S. Pat. No. 4,830,586 discloses a double acting diaphragm or dual diaphragm pump that includes two flexible pumping diaphragms connected by a shaft. The diaphragms and the shaft reciprocate in response to alternative pressurization of chambers between the two pumping diaphragms Supplemental pressure chambers in combination with an additional supplemental diaphragm act with the primary pressure chambers and the pumping diaphragms to effectively increase the pressure acting on the fluid within the pumping chambers. This pump also includes an inlet manifold and an outlet manifold communicating with pumping chambers on the outer side of each diaphragm. Ball check valves are provided at the entrance and exit of each pumping chamber. 
     The ARO 1″ High Pressure 3:1 Ratio (Metallic) Diaphragm Pump is one version of a dual diaphragm pump commercially available from Ingersoll-Rand Company This commercial dual diaphragm pump possesses some of the characteristics of the dual diaphragm pump disclosed in U.S. Pat. No. 4,830,586. This commercially available pump does not appear to include the supplemental diaphragm, but it does include pistons connected to the two pumping diaphragms. 
     U.S. Pat. No. 6,280,149 discloses an air drive dual diaphragm pump including a linear displacement sensor generating an output voltage proportional to the relative position of a shaft or connecting rod extending between the two diaphragms. Various factors, including the dynamics of the fluid being pumped affect the rate of reciprocation of the diaphragms and the shaft connecting them. For more viscous fluids, the reciprocating rod and diaphragm will reciprocate more slowly for a given air pressure, and the output mass flow rate of viscous fluid will be reduced. One embodiment of an active feedback apparatus includes an inductance coil surrounding ferromagnetic material in the rod. The position of the rod is then dependent upon the inductance of the coil In another embodiment, a linear displacement sensor is disposed next to a diametrically tapered portion and the output voltage potential depends upon the relative position between the linear displacement sensor and the tapered portion. The instantaneous position, velocity and acceleration of the connecting rod can thus be determined. Volumetric displacement of the diaphragm pump and thus be monitored and actual dispensing/metering control, stall prevention, noise control and over travel control are intended benefits of the active feedback An electronic feedback system of this type does not appear to have been previously employed as part of a master/slave pump assembly. 
     It does not appear that dual diaphragm pumps have been previously employed in a precision metering, multiple component pumping systems in which an auxiliary or slave pump operates in unison with a main or master pump. Such pumps are used to deliver multiple fluids in a metered amount for precise mixing One use of such master/slave pump assemblies is to deliver a resin and a metered amount of catalyst to a mixing zone or mixing element. A precise ratio between the mass flow rate of resin and of catalyst is required for proper operation of such systems. In the fiberglass reinforced product industry, it is essential that the proper ration of catalyst to resin be maintained for proper curing of the finished product. This ratio is not fixed for all applications. Temperature, humidity and product variations can require a different ratio of catalyst to resin. Thus some adjustment of the relative mass flow rates is necessary for any practical assembly. One prior approach that is discussed in U.S. Pat. No. 6,015,268 employs an adjustable linkage between master pump and the smaller volume slave pump. Adjustments can be made by changing the connection between a linking arm and a slave pump drive arm to shorten or lengthen the pumping link arm. U.S. Pat. No. 6,015,268 discloses an adjustable assembly in which an auxiliary or slave pump is coupled to the drive shaft of a master pump by an adjustable rack and pinion gear system. The slave pump is linked to the master pump by a ball joint attached to a yoke of an oscillating quadrant arm coupled to the pinion gear shaft. The amount of secondary or auxiliary fluid, such as a catalyst, is adjusted by adjusting the working length of the oscillating arm. In that patent, an air driven actuator or motor drives coaxial pistons in opposed displacement pumps. It is necessary to seal the pistons relative to their respective cylinders. When the primary fluid, such as a resin used in a fiberglass reinforced product, includes a significant number of abrasive particles or fillers, the life of these seals can be relatively short. The trend is to include more and more additives in resins for a number of reasons, including flammability and other safety related requirements. Therefore, it becomes more and more difficult to operate those pumps for an extended period without replacing damaged seals. 
     Other prior art master/slave pump assemblies have exposed and separate air motors and fluid or pumping sections that are connected by tie rods at a junction point between the two components. These other prior art assemblies are similar to that shown in U.S. Pat. No. 6,280,149 in that the air motor and the fluid section have an exposed junction point between them where a linkage to a slave pump can be attached. Diaphragm pumps do not have a similar exposed and available attachment point for connecting a linkage between the diaphragm master pump and a slave pump. Attempts have been made to extend the connecting shaft or rod in a diaphragm pump through the fluid pumping section and through the end caps on the diaphragm pump forming one side of the pumping chambers to the exterior of the pump, where a connection can be made to a slave pump However, this approach requires introduction of seals where the extended shaft or rod enters and exits the fluid pumping chamber. These seals, which would normally comprise O-rings would be exposed to the pumped fluid. When an abrasive fluid or a fluid including abrasive particles, fillers or fibers is pumped, such seals are damaged or will rapidly deteriorate resulting in excessive maintenance and down time for such pumps. With the invention described herein no additional seals will be exposed to an abrasive fluid. 
     SUMMARY OF THE INVENTION 
     This invention comprises an apparatus for pumping plural component fluids at proportional mass flow rates. The apparatus or assembly includes a master pump including a diaphragm for pumping a primary fluid, such as a resin, at a first mass flow rate dependent upon reciprocation of the diaphragm. An intermediate actuator, responsive to movement of the diaphragm, generates an output force dependent upon movement of the diaphragm. This intermediate actuator can be hydraulically or electrically connected, directly or indirectly connected to the diaphragm, or the response can be generated in other ways. The output force from the intermediate actuator drives a slave pump. The slave pump pumps a secondary fluid, such as a catalyst, at a mass flow rate dependent upon reciprocation of the diaphragm. In this manner the primary and secondary fluids can be pumped separately at proportional mass flow rates dependent upon reciprocation of the diaphragm in the master pump. This invention is especially suited for pumping a primary fluid containing abrasive particles, because unlike conventional pumps with elastomeric seals in the flow path of the primary fluid, the diaphragms would not be subject to significant damage or deterioration as a result of exposure to the abrasive particles. The ratio of the primary fluid mass flow rate to the secondary fluid mass flow rate can be altered by an adjustable linkage connecting the intermediate actuator to the slave pump. 
     This invention also comprises a metering pump assembly for pumping two fluids at flow rates in a ratio independent of the viscosity of the two fluids. This metering pump assembly includes a diaphragm master pump for pumping a first fluid and a slave pump for pumping the second fluid The diaphragm pump includes pump actuation means, such as a pneumatic actuator, and a pumping chamber on at least one side of a diaphragm. A fluid tight chamber is located between the diaphragm and the pump actuation means. In the preferred embodiment, a dual diaphragm pump is employed A hydraulic fluid is disposed in the fluid tight chamber. A hydraulic line communicating between the fluid tight chamber and one side of a slave pump actuating piston so that movement of the diaphragm is communicated to the slave pump actuating piston by the hydraulic fluid. The second pump is driven by movement of the actuating piston. The flow rate of second fluid is therefore dependent upon movement of the diaphragm, which pumps the first fluid, and is independent of the viscosity of the first fluid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of a master/slave pumping system using a dual diaphragm pump to pump a primary fluid and a slave pump dependent upon the dual diaphragm pump. 
     FIG. 2 is a view of a dual diaphragm pump of the type that can be used in the system of FIG.  1 . 
     FIGS. 3A and 3B are exploded views showing the components of the dual diaphragm pump of FIG.  2 . FIG. 3B is a continuation of FIG.  3 A. 
     FIG. 4 is a view of an alternate embodiment in which an electrical sensor monitoring operation of the master pump is used to control the slave pump. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A master/slave pump assembly comprising the preferred and representative embodiment of this invention is especially useful in delivering the following examples of fluid systems in a fixed ratio or proportion: 
     Unsaturated polyester resins 
     Vinylester resins 
     Epoxy resins 
     Catalyzed contact cements 
     Water based catalyzed contact cements, among others 
     This list of components with which this master/slave pump assembly can be used is not intended to be all inclusive, but this assembly is especially suited for use with a primary fluid or resin that may contain fillers or particles, which may be abrasive and which might tend to damage elastomeric or other seals that are used in conventional pumps that have heretofore been used in multiple component pumping and metering assemblies. 
     A master/slave pump assembly according to this invention includes a master pump  2  and a slave pump  60 . A primary fluid, such as a resin containing abrasive fillers or fibers would be pumped through the master pump  2  The slave pump  60 , which functions in unison with the master pump  2 , would pump a secondary fluid, such as a catalyst, to a mixing zone, such as a spray head for dispensing a fiberglass mixture prior to curing or solidification. 
     Of course the fluid components, such as the resin and the catalyst, should be pumped in the proper proportions to the mixing zone to insure formation of a satisfactory end product. Therefore, the mass flow rate of fluid through the slave pump  60 , which is typically the smaller of the two pumps, should always be dependent upon the mass flow rate through the master pump  2 . For a specific application, the ratio of the mass flow rate of the secondary fluid relative to the mass flow rate of the primary fluid should be constant, even if the mass flow rate of the primary fluid should fluctuate during operation of the master/slave pumping or metering assembly. Fluctuations could be due to changes in temperature or pressure or other environmental conditions; to variations in the force driving the master pump, such as changes in air pressure for a pneumatically actuated pump; or to variations in the mass flow rate of material entering the master or primary pump  2 . Although this ratio of secondary fluid to primary fluid should remain constant for a specific application, any master/slave pump assembly used in such applications should be suitable for use with different constituent material, which will require different proportions of primary and secondary fluids. Therefore the master/slave pump assembly must be adjustable, but must also be capable of stable operation when adjusted for a specific mixture or application. An adjustable or variable mechanical proportional linkage  70  located between the master pump  2  and the slave pump  60  permits such adjustment. 
     Two alternative means for insuring that the slave pump  60  will be dependent upon the master pump  2  will be discussed with reference to this invention. The first approach is illustrated in FIGS. 1-3 A &amp; B. This first embodiment employs a hydraulic fluid  50  and an intermediate fluid actuator  80  connected between the master pump  2  and the slave pump  60 . The hydraulic fluid  50  transmits a force to the intermediate fluid actuator  80 , which in turn transmits a force through the adjustable linkage  70  to the slave pump  60 . The force transmitted by this hydraulic means is dependent upon the mass flow rate through the master pump  2 , and therefore the mass flow rate through the second or slave pump  60  will be dependent upon the mass flow rate of the primary fluid. The second approach employs an electrical sensor  90  to monitor the movement of the actuating pistons  20 A and  20 B or the rods or shafts  30 A &amp;  30 B, whose reciprocation cause the primary fluid to be pumped through the master pump  2 . The electrical signal sensed by sensor  90  will in turn be input to a servomechanism  94 , which will then transmit a force to the secondary or slave pump  60 . Since this force will be proportional to the mass flow rate of the primary fluid, caused by reciprocation of pistons  20 A and  20 B, and shafts  30 A &amp;  30 B, the mass flow rate of the secondary fluid will be proportional to the mass flow rate of the primary fluid. 
     For both the hydraulic and the electrical means of controlling operation of the slave pump in response to the operation of the master pump, or for that matter other means, the master pump  2  comprises a diaphragm pump In the preferred embodiment a dual diaphragm pump having two reciprocating fluid pumping diaphragms  10 A and  10 B located on opposite sides of a pump actuator  4  is employed. In the preferred embodiments, a modified ARO 1″ High Pressure Diaphragm Pump—3.1 Fluid to Air Ratio (Metallic) Pump, manufactured and sold by Ingersoll-Rand Company as PH10 style pumps, is used as the master dual diaphragm pump  2 . This dual diaphragm pump  2  is pneumatically actuated by an air motor  4  of conventional construction, which includes spool valves that cause reciprocation of the diaphragms  10 A &amp;  10 B to alternatively pump fluid through pumping fluid chambers  6 A and  6 B located at either end of the dual diaphragm pump  2 . The air motor  4  operates in the same manner as for conventional applications of the basic diaphragm pump, which is used in a modified form in this invention. Furthermore, it is not necessary that the master pump  2  be pneumatically actuated. For these reasons, additional description of the air motor  4  is not necessary for a full understanding of this invention. Although the pump actuation means described in U.S. Pat. No. 4,830,586 is not the same as that employed in the dual diaphragm pump used in the preferred embodiment, a pump of the type shown in that patent could be employed and therefore the disclosure of U.S. Pat. No. 4,830,586 is incorporated herein by reference. The two diaphragms  10 A and  10 B adjacent opposite ends of pump  2  are respectively connected to pistons  20 A and  20 B by a rods or shafts  30 A and  30 B so that the diaphragms  10 A and  10 B reciprocate with the pistons  20 A and  20 B. The rods or shafts  30 A and  30 B is connected to the center of the circular diaphragms  10 A and  10 B. As seen in FIGS. 3A and 3B, the outer periphery of each diaphragm  10 A and  10 B is bolted to the outwardly facing edges of the adjacent cylindrical pump outer body section  40 A and  40 B. Each diaphragm  10 A and  10 B is flexible so that, as best seen in FIG. 1, the diaphragms flex inwardly and outwardly as the pistons  20 A,  20 B and shafts  30 A,  30 B reciprocate in opposite directions relative to the stationary body sections  40 A and  40 B. 
     The air motor  4 , which is connected through the rod assemblies  30 A and  30 B to the pistons  20 A and  20 B, first applies a force tending to move piston  20 A outwardly bringing the other piston  20 B with it. When the pistons  20 A and  20 B have shifted to one extent of their travel, a valve means in the air motor  4  shifts and the pressure differential between opposite sides of the pistons  20 A and  20 B also shifts to drive the piston assembly in the opposite direction. As the pistons  20 A and  20 B shift first in one direction and then in another, the diaphragms  10 A and  10 B flex to first open a pumping chamber  6  on one end of the pump and close the pumping chamber  6  adjacent the other end of the diaphragm pump  2 . As either diaphragm  10 A and  10 B closes the adjacent pumping chamber  6 , the ball check valve  48  connecting the inlet manifold  44  with the closing pumping chamber  6  and opens the ball check valve  48  communicating with the outlet manifold  46 . Thus fluid is force out of the closing pumping chamber. As one pumping chamber  6  is closing, the pumping chamber  6  at the opposite end of the pump  2  is opening. The ball check valve  48  between the inlet manifold and the opening pumping chamber  6  is opening, drawing fluid from the inlet manifold  44  into the opening pumping chamber. At the same time the outlet ball check valve in the opening pumping chamber  6  is closing, allowing that pumping chamber to fill as the primary pumped fluid is being expelled from the opposite pumping chamber. 
     Only the ball check valves  48  and the diaphragms  10 A and  10 B move as fluid is pumped through the pumping chambers.  6 . The end caps  42 A and  42 B, forming the outer wall of each pumping chamber  6  are bolted to the respective stationary body sections  40 A and  40 B. Pumping chamber volume changes are due entirely to the flexing diaphragms  10 A and  10 B. Since the diaphragms  10 A and  10 B are one piece members and since they are bolted between adjacent body sections  40 A and  40 B and end caps  42 A and  42 B, no seals, which may be subject to damage by abrasive particles are required for the reciprocating diaphragms  10 A and  10 B. The ball and ball seats in the ball check valves  48  are exposed to any abrasive fibers in the pumped fluid, but these components do not slide relative to each other and do not require the use of an elastomeric o-ring seal of the type used in a conventional pump in which a piston acts directly on the pumped fluid. 
     The actuating pistons  20 A and  20 B do slide relative to the cylinders  26 A and  26 B and O-rings  28 A and  28 B do seal this interface These actuating pistons  20 A and  28 B, as well as the O-rings  28 A and  18 B are not exposed to the pumped fluid or to any abrasive particles contained within that primary fluid or resin. The actuating pistons  20 A and  20 B are located on opposite sides of a bulkhead  41  is each body section  40 A and  40 B from the diaphragms  10 A and  10 B. The rods or shafts  30 A and  30 B do extend through holes in the center of the bulkhead  41 , but O-rings seals  32  on opposite sides of the bulkhead seal the space on one side of the bulkhead  41  from the other side. These O-ring seals  32  are also located on the side of the diaphragms  10 A and  10 B that is not exposed to the primary pumped fluid, which may contain abrasive particles. 
     Closed cavities  8 A and  8 B are formed between the bulkhead  41  of each body section  40 A and  40 B and the adjacent diaphragms  10 A and  10 B in a conventional dual diaphragm pump on which the master pump  2  is based. In the first embodiment of this invention, these cavities  8 A and  8 B are filled with a hydraulic fluid, such as 10 weight hydraulic oil. In the preferred embodiment two ports are provided in each of the closed cavities  8 A and  8 B. First ports  54 A and  54 B are connected to a linear fluid actuator  80  through hydraulic lines  52 A and  52 B. Fill ports  86 A and  86 B are located adjacent to the fluid actuator  80  with isolation valves  88 A and  88 B located between the actuator  80  and the fill ports  86 A and  86 B. To fill the hydraulic fluid chambers  8 A and  8 B, the isolation valves  88 A and  88 B are closed and the fill ports  86 A and  86   b  are opened. The vent ports  56 A and  56 B are also open. Hydraulic fluid is added through the fill ports  86 A and  86 B and air in the chambers  8 A and  8 B is vented through open ports  56 A and  56 B. When the hydraulic chambers  8 A and  8 B are full, the vent ports  56 A and  56 B are capped and the fill ports  86 A and  86 B are also capped. Isolation valves  88 A and  88 B are then opened so fluid communication is established between the hydraulic chambers  8 A and  8 B and the fluid actuator  80 . 
     In the preferred embodiment, the other ends of these hydraulic lines  52 A and  52 B are connected to an intermediate hydraulic actuator  80  including an actuator piston  82  in a cylinder  84 . Hydraulic line connections for lines  52 A and  52 B are located on opposite sides of the actuator piston  82 . One hydraulic line  52 A is connected to master pump hydraulic chamber  8 A and the other hydraulic line  52 B connects the opposite side of the actuator piston  82  with the other master pump hydraulic chamber  8 B. Thus as the diaphragms  10 A and  10 B are shifted, hydraulic fluid will be pumped first to one side of the actuator piston  82  and then to the other side, causing actuator piston  82  to cycle at the same frequency as the diaphragms  10 A and  10 B. Thus the movement of the actuator piston  82  will depend directly upon the mass flow rate of primary fluid pumped through the master pump  2 . The output of the actuator piston  82  can then be connected through linkage  70  to drive the slave pump  60 . Linkage  70  pivots about axis  72 . Adjustment of the linkage connection of the slave pump  60  relative to the pivot point  72  will alter the amount of secondary fluid pumped by the slave pump  60  during each cycle of the master dual diaphragm pump  2 . 
     Linkage  70  is adjustable so that the stroke of the slave pump piston is dependent upon the relative adjustment of the linkage  70 . When the linkage  70  is adjusted the ratio of the mass flow rate of the catalyst or second fluid pumped by the slave pump  60  relative to the mass flow rate of the resin or primary fluid pumped by dual diaphragm pump  2  is also changed. Adjustable linkages of this type are commonly used to adjust the proportion of primary to secondary fluids, and adjustable linkage  70  is substantially the same as those used in prior art master slave pumps. Typical ratios of primary to secondary fluids with which this master/slave pump assembly can be used range from 2:1 to 100:1. 
     Although the embodiment of FIGS. 1-3A and  3 B uses a hydraulic fluid to link the slave pump  60  to the master pump  2 , other means can be employed. FIG. 4 shows that electrical sensing means, such as an inductance coil  90  can be used to sense the motion of the rods or shafts  30 A and  30 B connecting the diaphragms  10 A and  10 B to the air motor  4 . U.S. Pat. No. 6,280,149, which is incorporated herein by reference, discloses the use of an inductance coil in this manner. That patent also discloses other electrical sensing means for detecting the movement of a shaft attached to diaphragms in a diaphragm pump. Since the motion of the either shaft  30 A or shaft  30 B is dependent upon the mass flow rate of the primary fluid actually pumped through a dual diaphragm pump, this signal can be used to control the slave pump  60  so that it will pump the corresponding proportional amount of secondary fluid. In the embodiment of FIG. 4, the signal derived from inductive coil  90  is input into a conventional servomechanism  92 , which causes a linear actuator  94  to move in a manner dependent upon this input signal. The linear actuator  94  can then be attached to adjustable linkage  70  in the same manner as shown and discussed with respect to the hydraulic embodiment of FIG.  1 . 
     The embodiments of FIGS. 1-4 are representative in nature and the instant invention could be implemented in other ways by those skilled in the art. The two basic embodiments depicted herein do however comprise cost effective means of implementing this invention. Although primarily intended for pumping relative viscous primary fluids containing abrasive fillers or particles, such as fiberglass resins, this invention could also be employed in transporting other multiple component systems. This invention is also not limited to use with the basic dual diaphragm pump described herein, and additional enhancements could also be made to this assembly. Therefore this invention is defined by the following claims and is not limited to the representative embodiments depicted herein.