Mixing apparatus
BACKGROUND OF THE INVENTION 
     This invention relates to mixing apparatus, and more particularly mixing apparatus of a type employed to mix fluids together in a desired ratio. 
     Mixing apparatus are frequently employed in offset printing press operations where it is desirable to apply a mixture of etch concentrate dissolved in water to the nonprinting portions of a printing plate mounted on a plate cylinder. Damping rollers, which roll through a fountain pan filled with the mixture, apply it to the printing plate. The quality of printed material produced will depend upon the accuracy with which the mixture may be regulated to correspond to different ink or paper types. 
     In the past, some mixing apparatus have utilized a bypass conduit arrangement in combination with a main conduit wherein a number of eductors, a series of conduit restrictions, and/or a system of valves were required to effectuate accurate proportional mixing of two fluids. The first fluid was forced into the bypass conduit in such prior structures, due to valve or restriction arrangements, and would flow through an eductor disposed within the bypass conduit thereby causing a second fluid to be drawn into the first fluid and become premixed prior to being further mixed with the first fluid flowing into the main conduit. With such prior structures, when it was desired to increase the proportionate amount of second fluid to be mixed with the first fluid, flow of the first fluid through the main conduit had to be restricted (i.e., by a valve) so that a larger head pressure would be built up in the bypass conduit, thereby increasing the lifting suction generated by the eductor located therein, while at the same time restricting the amount of first fluid flowing through the main conduit. Thus, such prior apparatus depended upon critical relationships of fluid pressures, in order to attain the desired mixing ratio of the fluids which necessitated additional components such as an eductor in the bypass conduit. 
     Other mixing apparatus either relied upon a gravity feed system thereby restricting the location of the apparatus; mix the fluids together in a fixed predetermined ratio and then accumulate same in a storage reservoir or the like; or introduce a second fluid in an undiluted state directly into the main fluid conduit, with or without employing an eductor. Thus, the prior mixing apparatus were complicated in design often requiring a multiplicity of parts, both electrical and mechanical, and were costly and difficult to manufacture and service. 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to provide an improved mixing apparatus which avoids the shortcomings associated with prior structures of this general type. 
     It is a further object of the present invention to provide an improved, low cost, and simplified mixing apparatus for readily mixing two fluids together in a desired ratio regardless of the variations in the flow rate of one fluid through a main conduit of the apparatus. 
     It is still another object of this invention to provide a mixing apparatus which is versatile, and may be employed in a variety of arrangements where a mixture of fluids is necessary. 
     SUMMARY OF THE INVENTION 
     The objects of this invention are achieved by a mixing apparatus according to a preferred embodiment which assures accurate mixing of two fluids in a predetermined ratio. Fluid from a first source, under pressure, flows through a primary conduit and an eductor integral with the primary conduit before exiting the apparatus. Fluid from a second source is drawn through a secondary conduit and into the primary conduit at the eductor, to which the secondary conduit is connected. A diversion conduit extends between and is connected at one end to the primary conduit upstream of the eductor and at the opposite end of the secondary conduit upstream of the connection between the secondary conduit and the eductor. By reason of the arrangement of the conduits, a predetermined amount of fluid from the first source is drawn into the diversion conduit and then intermixed with fluid drawn from the second source through the secondary conduit. The intermixed fluids then flow into the eductor and entrain with the first fluid flowing through eductor from the primary conduit. A valve means mounted in the diversion conduit regulates the amount of fluid from the first source that is allowed to be diverted into the diversion conduit. The flow of fluids drawn through the diversion conduit and the secondary conduit is dependent on the first fluid flow in the primary conduit through the eductor. 
     For a more complete understanding of this invention, reference should now be had to the embodiment illustrated in greater detail in the accompanying drawings and described below by way of an example of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the preferred embodiment of a mixing apparatus employing principles of this invention with a cover therefor shown in place; 
     FIG. 2 is an enlarged fragmentary sectional view taken along line 2--2 of FIG. 1, with the cover removed, and with portions of various components thereof shown cut away; 
     FIG. 3 is an enlarged sectional view taken along lines 3--3 of FIG. 1. 
    
    
     While the invention will be described in connection with a preferred embodiment, it is to be understood that the invention is not intended to be limited thereto. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and principally FIG. 1, a preferred embodiment of the improved mixing apparatus 10 is shown. The apparatus includes a protective housing 9 provided with a cover 11. Disposed within the housing are various components of the apparatus to be hereinafter described. 
     A status light 12 is mounted on the upper portion 11a of the cover and indicates when the apparatus is operating. On a front portion 11b of the cover 11 is mounted a fluid monitoring indicator 13 and a fluid mix control 14. The fluid monitoring indicator 13 reflects the level of fluid (e.g., etch solution) accumulated within a compartment 15 of a storage tank 16, disposed within the housing 9, through a float assembly 13a (FIG. 2). A small pointer or the like 13b connected to an upright rod 13c forming a part of the assembly 13a, moves up or down along an elongated slot 13d provided in cover portion 11b in response to a change in fluid level within compartment 15. A hinged door 17 is provided in the lower portion 11c of the cover to allow access to compartment 15. When the pointer 13b reaches a predetermined position relative to slot 13d, fluid may either be manually added to compartment 15 through door 17 or automatically fed into the compartment 15 by way of a known valve/float assembly, with the fluid being provided from an outside source (not shown). 
     A second compartment 18 is provided in the storage tank 16 and is disposed adjacent compartment 15. A valve/float assembly 19 (see FIG. 3) is located within compartment 18 and is adapted to maintain therein a predetermined level of fluid (e.g., water). As the fluid level falls, a float 19a, forming a part of the assembly 19, will move downwardly with the fluid level and cause a lever 19b to pivot, thereby opening a valve 19c mounted on a wall of the compartment. The valve 19c is connected to an outside source of the desired fluid at a fitting 19d. When the water level again rises, the float moves in an opposite direction, closing valve 19c and stopping further flow of fluid into the compartment. 
     The apparatus 10 is connected to a source of electricity through suitable wiring 20. An outlet port 21 is provided on an upper side wall portion 11d of cover 11 to which suitable piping or hose 21a may be connected. With the fluid mix control 14 manually adjusted to a desired setting and the apparatus in an operational mode, as indicated by light 12, a desired mixture of the two fluids (e.g., etch and water) will flow through the piping 21a, as will be described more fully hereinafter. 
     Referring now to FIG. 2, it will be noted that compartments 15 and 18 of storage tank 16 are approximately equal in volume, each, for example, being adapted to hold 21/2 gallons of fluid. A portion 11c of the cover 11, which overlies the storage tank 16, has mounted thereon a pump 31. The pump motor 32 has depending therefrom a pump column 33 which extends into compartment 18. A pump body 34 is connected to the lower end of the column and is provided with an intake 35 on the underside thereof and a discharge port 36 on an upper surface thereof. The discharge port 36 is connected to a suitable fitting 37 mounted on a cover portion 11c, by means of a tube section 39. Fitting 37 forms the inlet end of a primary conduit 38. 
     Primary conduit 38 extends upwardly from fitting 37 and includes a vacuum breaker 40. Extending laterally from the vacuum breaker is a conduit section 38a to which is connected a first inlet side 41a of an eductor 41. The discharge side 41b of the eductor is connected to the outlet port 21. 
     As seen in FIG. 2, a secondary conduit 42 is provided which extends upwardly from compartment 15 through an opening 43 formed in cover portion 11c. Attached to the lower end 44 of conduit 42 is a conventional one-way valve 45 which allows fluid (etch) to enter conduit 42, but will now allow the fluid in conduit 42 to return to compartment 15 and mix with the fluid remaining in the compartment 15. A cylindrical screen 46, extending from the underside of cover 11c to the base 47 of the compartment 15, encompasses the conduit 42 and valve 45 thereby preventing impurities in the etch, drawn from compartment 15, from clogging the conduit 42. The secondary conduit 42 extends upwardly from compartment 15 to a T-connector 42a and from there to a second inlet 41c of the eductor 41. 
     Interconnecting the primary and secondary conduits 38 and 42 respectively, is a diversion conduit 48. The diversion conduit is disposed substantially perpendicular to conduits 38 and 42, and is connected to the primary conduit 38 at junction fitting 38b and is connected to the secondary conduit 42 at the T connector 42a. Fitting 38b is located upstream from vacuum breaker 40, as seen in FIG. 2. 
     The fluid mix control 14, previously mentioned, is adapted to adjust the setting of a valve 49 (FIG. 3) which is located within the diversion conduit 48. Valve 49 controls the amount of fluid (water) which can be diverted from primary conduit 38 at the junction fitting 38b. 
     The relative interior cross-sections of the secondary and diversion conduits 42 and 48 are of smaller dimension when compared to that of the primary conduit 38. Thus, even though valve 49 is in a fully open position only a relatively small amount of fluid in the primary conduit 38 will be diverted through conduit 48, thereby assuring that there is a continuous flow of fluid from conduit section 38a through the eductor 41 when pump 31 is operating. 
     In operation, water from compartment 18 is drawn into pump body 34 through intake 35 and discharged under a predetermined pressure through outlet 36 and tube 39 into the primary conduit 38. When the water reaches junction fitting 38b, a portion thereof will be diverted into conduit 48 depending uppn the setting of valve 49. Notwithstanding the diversion conduit 48, most fluid will flow through the primary conduit 38 past vacuum breaker 40 and into the first inlet 41a of the eductor. The vacuum breaker relieves any vacuum build-up that might occur when the apparatus is shut down. When the apparatus is operational, however, the vacuum breaker 40 does not interfere with fluid flow through the primary conduit. 
     The flow of water, under pressure, through the restricted venturi-like passageway V of the eductor 41 generates a suction force in the secondary conduit 42, the latter being connected to the second inlet 41c of the eductor. At a predetermined flow of water through the passageway V, enough suction will be generated to draw fluid (etch) from compartment 15 to T-connector 42a whereupon it will intermix with the fluid flowing through diversion conduit 48. The mixture then passes through inlet 41c into passageway V. Depending on the setting of valve 49 the extent to which the etch will be diluted prior to reaching passageway V can be accurately controlled. Therefore, although the suction force generated by the flow of water from the primary conduit through the eductor 41 will remain nearly constant, the proportion of etch to be mixed therewith may be varied depending on the amount of water that is allowed to flow through the diversion conduit 48. The more water allowed to enter conduit 42 at the T-connector 42a, the greater the quantity of etch that will be displaced in secondary conduit 42 upstream of T-connector 42a, resulting in a more dilute etch and water mixture flowing to the eductor 41. Water entering the conduit 42 at connector 42a is prevented from flowing down conduit 42 into compartment 15 by the one-way valve 45. In the preferred embodiment, the amount of etch entrained with the water is variable between one and six ounces per gallon of water. 
     The outlet tube 21a which is connected to port 21 may be curved downwardly so as to allow gravity to assist in the movement of the mixture flowing from the apparatus. While the mixture has been illustrated and described as being discharged from the apparatus through suitable piping, it should be understood that the fluid mixture may be directly discharged from tube 21a into a portable batch collector. 
     Thus, it will be noted that an improved mixing apparatus is provided that is of simple and uncomplicated construction, is inexpensive to manufacture, yet accurate, reliable and versatile in operation. 
     For example, it is apparent that a mixing apparatus according to this invention may employ conduits of varying sizes, and/or a multitude of eductor configurations. Furthermore, the apparatus may be readily adapted to accurately control the mixing of three or more fluids. Neither is it anticipated that the invention is to be employed solely in conjunction with printing presses, as the teachings of this invention may be applied to a variety of situations wherein it is desirable to mix fluids. It is, therefore, contemplated by the appended claims to cover any such modifications or other embodiments and incorporate those features which constitute the essential features of this invention within the true spirit and scope of the following claims.