APPARATUS FOR TREATING LIQUID

Abstract: Disclosed is an apparatus for treating liquid and especi­ ally a dispensing head for such a liquid which is to be subse­ quently heated to a relatively high temperature. The dispens­ ing head can be used for sterilization of UHT temperature, in which the fluid, such as a liquid, is heated by direct contact with steam while it in the form of a very thin, free-falling film or a continuous falling stream so that heating of the fluid is accomplished without the fluid coming into contact with any surface and particularly metal surfaces which are hotter than the fluid product being heated and with minimum agitation and turbulence of the fluid product. The use of the film dis­ pensing head enables maximum and uniform heat penetra­ tion in a minimum time interval with the film or stream being maintained as this as possible and unbroken by introducing steam at a relatively low velocity in a large volume vessel. Preferably a flow control is incorporated into the apparatus to maintain a constant flow rate of fluid and to maintain a con­ stand and critical fluid level in the bottom portion of the large volume vessel with the flow characteristics of the apparatus and the internal forces produced by the apparatus serving to counterbalance each other to provide a relatively simple but jet accurate flow rate, and liquid level controls for the fluid being heated.

Description: The present invention relates to an apparatus for treating liquid, especially milk according to the preamble of claim 1, for example as disclosed in US-A-3 032 423. A falling "film" of milk is ideally suited to a high temperature/short interval heating process required to produce sterilized milk of good flavor quality. Examples of falling films are disclosed in the Davies et al Patent No. 2,899,320 (see FIGURE 1) and the Evans Patent No. 3,032,423 (see FIGURES 2, 3 and 4). While each of these patents discloses a falling film of milk in a heating vessel, the falling film is not isolated in space, but is held by surface tension to vertically disposed plates (designated 5 in Davies et al and 35 in Evans ) for guiding the milk through a heating chamber. It was originally thought that the use of such plates would lead to uniformity in heating the milk since the plates would be maintained at a relatively high and constant temperature by steam or some other heated medium circulating within the heating vessel. However, it has been discovered that the exposure to such guide plates at high temperature causes product burn-on and adversely effects the taste of the resulting milk product. In particular, the taste of the milk is adversely effected by exposure to a metal surface during heating and also by exposure to a surface which is hotter than the milk itself. In the case of the vertical guide plates mentioned, it was not realized (see Davies et al , Col. 6, lines 40-45) that these surfaces become hotter than the milk being fed into the apparatus. Specifically, it has been experimentally discovered that guide plates of the type used in Davies et al and Evans (see FIGURE 3) overheat at certain spots even when covered with the flowing product. Resultant "hot spots" cause the flowing product to burn onto the plate or screen. Once "burn-on" starts it rapidly gets worse and causes undesirable buildups of burned product to grow quickly, causing flavor distortion and disruption of the product flow which soon destroys uniformity of the falling film of product. "Hot spots" commonly occur at edges, weld spots, etc., and it is virtually impossible to completely eliminate them. The same effect is illustrated in FIGURE 4. In this case a screen 39 is used to form the film, but "hot spots" and burn-on continue to occur. A similar arrangement using a screen is illustrated in Davies Patent No. 3,771,434, previously mentioned, and a similar effect occurs there. In addition, the problem of maintaining the screen sanitary is a significant one. As the screen has many small openings in its mesh, fine particles of material invariably collect on the screen surface. These materials are extremely difficult to dislodge during any cleaning period, and accordingly it is difficult to maintain the equipment in a sterile and fully sanitary condition after a short period of operation. Furthermore, clogging of the screen destroys the falling film and causes the device to stop operating effectively after a short time. Accordingly the presence of a screen in such an apparatus can cause three separate problems, taste distortion, accumulation of particles leading to the lack of a sterile environment, and breaking and distortions of the falling film. Accordingly, one object of this invention is to provide an improved apparatus for treating liquid food products, especially milk, without taste distortion during (milk-) sterilization. For achieving such desirable result, an apparatus for treating liquid is characterised by the features specified in the characterising portion of claim 1. Briefly, these and other objects of the invention are attained by the provision of a novel dispensing head by which the liquid to be treated is formed into a continuous isolated film which is kept free from contact with any surface hotter than itself for a selected interval of time. The dispensing head is designed so that the film remains intact as a continuous film for the entire period during which it is subjected to heat treatment. This dispensing head is especially useful for preparing the liquid for a subsequent heat treatment by subjecting the film to a high temperature gas, such as steam, which is supplied so as to prevent any turbulence which would disturb the fluid film. The film formed by the dispensing head can be rapidly cooled subsequent to heat treatment. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: FIGURE 1 is a schematic illustration on one form of prior art sterilizing system, from Davies et al Patent No. 2,899,320; FIGURE 2 is a cut-away illustration of another form of prior art sterilizing system from Evans Patent No. 3,032,423; FIGURE 3 is a cut-away illustration showing further details of the prior art apparatus shown in FIGURE 2; FIGURE 4 is a cut-away illustration showing an alternative embodiment of the prior art system shown in FIGURE 3; FIGURE 5 is a perspective illustration of a dispensing head and isolated film in accordance with the present invention; FIGURE 6 is a cut-away side view of the dispensing head shown in FIGURE 5; FIGURE 7 is a plan view of a distribution plate; FIGURE 8 is a side view of an end cap structure for a dispensing head; FIGURE 9 is an illustration of an end feed dispensing head; FIGURE 10 is a perspective illustration of a flow distribution tube for use in the structure of FIGURE 11; FIGURE 11A is a side view of a dispensing head; FIGURE 11B is a cut-away end view of the structure shown in FIGURE 11A; FIGURE 12 is a perspective illustration of a two-film branching network in which the dispensing head can be used; FIGURE 13 is a perspective illustration of a four-film branching network; FIGURE 14 is a cut-away side view of a sterilization chamber or ultra high temperature (UHT) heat in which the dispensing head according to the present invention is arranged; FIGURE 15 is a schematic illustration in perspective of a liquid processing system employing the sterilization chamber with the dispensing head of the invention. Although the present invention is applicable to an unlimited variety of fluent or liquid products, including such products as beer, orange juice, soup containing particulate matter such as meat and vegetables and other non-food products, many of the detailed aspects of the preferred embodiments are described as utilized with milk, since of all foods milk is perhaps the most complex and requires the most delicate and precise handling in its sterilization if flavor distortion is to be prevented. Accordingly emphasis is placed in this specification on the treatment of milk with the understanding that numerous other foods can be treated in substantially the same manner but with much less complexity. Accordingly, a problem thought by many to be insurmountable was presented to the present inventors: how to heat milk to a temperature of approximately 149°C (300°F) for a period of only one second and then rapidly reduce the temperature below 74°C (165°F) while preventing the milk from experiencing any substantial turbulence, agitation or physical stress and preventing the milk from engaging a surface having a higher temperature than the milk itself. Furthermore, the solution, to have any commercial merit, required a system which was relatively simple to construct, inexpensive to produce, and self-cleaning to the maximum extent possible so that it could easily be maintained in sterile condition for long production runs. A successful device capable of commercial exploitation, must solve all of these problems and maintain a fully uniform or consistent output product. Although the previously mentioned patent to Davies (3,771,434) provided the closest approach to the solution of this problem known at the time that application was filed (1972), extensive research conducted by the Applicants has now revealed a series of important improvements which yield the desired result, that is, a truly sterilized milk which cannot be distinguished by the consumer from conventional fresh milk. As pointed out previously, it should be noted that the present application is couched in terms of processing milk because of the unique sensitivity of milk to heat treatment. Substantially all other known liquid products, including foods and other types of liquid products, can also be processed according to the same technique, since most other products do not have the extreme sensitivity exhibited by milk to physical stress during heating. In contrast to the prior art apparatuses described above, the present apparatus, illustrated in FIGURE 5, includes a supply pipe 52 feeding a dispensing head 54 comprised of a cylindrical length of pipe with a slit 56 along a lower surface thereof. The purpose of the dispensing head is to form a thin, continuous isolated film, designated 58 in the drawings. Since the formation of the film is of considerable importance to the operation of the present invention, further details of the nature and formation of the film will be presented. It is first pointed out that the isolated film of the present invention is a continuous film. By continuous is meant that the film is never broken into droplets, nor is any portion ever disconnected from the central body of the film in the course of its fall and heating in the sterilizing apparatus of the present invention. This is in direct contrast to certain devices disclosed in the prior art which have been used particularly for the purpose of drying or evaporating liquids. For example, attention is directed to the Monsanto patent (441,106 issued November 18, 1890) and the Okada patent (3,621,902 issued November 23, 1971). In these patents the liquid material to be processed is sprayed or dropped from an appropriate distribution manifold into a heated atmosphere. However, the purpose of the spraying or dropping is to create finely divided particles or droplets of the material which provide a large surface area to permit rapid evaporation of water within the material being processed to speed evaporation. Evaporation of this sort would, of course, totally destroy the natural quality of milk sought for in accordance with the teachings of the present invention. In contrast, the present invention deals exclusively with a falling continuous film of milk from which every particle is connected to every other and no isolated droplets are formed. The film 58 is also isolated because, once it leaves the slit 56, it never engages anything until it reaches the bottom of the sterilizing chamber (to be described subsequently). Because it is thus isolated from all components within the sterilizing chamber, the film is not contaminated by engaging any surface hotter than itself in contrast to typical prior art devices shown in FIGURES 1-4. Because of the important function that the thin continuous isolated film has in the context of the present invention, a considerable amount of attention has been directed by the Inventors to the proper forming of this film and to forming the film in such a way that the film continues to be formed without interruption during lengthy processing runs in the apparatus of the invention. It has been observed experimentally that the configuration and appearance of a free-falling film or column of liquid changes considerably depending upon the initial velocity of the liquid prior to free fall. If the velocity is too high, droplets of liquid form, some spraying or spashing occurs and the surface of the falling body of liquid is not smooth. If the velocity or flow rate of the liquid is within a specified range, however, the falling body of liquid forms a continuous unbroken surface in free fall with a mirror-like surface and no splashing or spraying of particles results, even when the falling body of liquid impinges on a rigid surface. If the velocity or flow rate is too low, then the continuous body of falling liquid breaks into droplets since the amount of liquid in free fall is not sufficient to maintain the continuous surface of the film or column. Again spraying and splashing of liquid particles occurs. Experimental measurements on free-falling liquid bodies passing through a slit indicate that liquids must have an average initial flow velocity falling within a prescribed range to form a continuous free falling body. In the case of water, for example, the following measurements apply: For an initial velocity of less than approximately 0.46 m/s (1.5 feet per second), the falling film or column breaks up and the flow is not sufficient to maintain the falling liquid in a continuous state. For initial velocities between 0.46 and 1.07 m/s, (1.5 and 3.5 ft. per second), the falling body maintains a smooth and perfectly continuous surface. For initial velocities above 1.07 m/s, (3.5 ft. per second), some splashing occurs and the surface of the falling body of liquid is no longer smooth and continuous. This experimental data indicates that the existence of a relationship between the surface tension forces acting on the particles of falling liquid, the forces of motion created by the initial velocity of the liquid prior to its entering a state of free fall, and the gravitational forces acting on the liquid during free fall. For water with an initial velocity between 0.46 and 1.07 m/s, (1.5 and 3.5 ft. per second), an equilibrium condition is reached among these various forces resulting in the formation of a continuous laminar film or column of free falling liquid. This equilibrium may be destroyed if one or more of the variable forces is significantly changed. For example, a liquid with a viscosity different from that of water has a different range of initial velocities if a continuous free falling body of liquid is to be formed. However, all liquids, no matter what their viscosity, can be made to form a continuous body in free fall simply by measuring the appropriate parameters of the liquid and appropriately controlling the forces acting on the liquid. In the case of the present invention, where the liquid falls into a steam heated pressure vessel, the effect of steam flow on the falling liquid must also be considered. If the velocity of the steam acting on the liquid is sufficiently high, the falling body of water will be broken up and the formation of a continuous falling body will become impossible. Similarly, if the falling body of liquid is exceptionally thin and fragile, then even small steam currents will cause it to break up resulting in spraying and splashing of the falling liquid. Based on these considerations, the following method for designing a free falling film of liquid passing through a slit has been developed in accordance with the concepts of the present invention: 1. The liquid is first studied to determine the optimum initial velocity at which a continuous body of the liquid will be formed and maintained when the liquid is in free fall. 2. The desired flow rate of the falling film is determined. 3. The length of the slit through which the film must fall is determined from the dimensions of the vessel in which it is placed, or other similar physical constraints. 4. The width of the slit is calculated so as to provide an initial velocity which is the optimum velocity of the liquid for forming a continuous body while in free fall at the determined flow rate of the liquid. Either the length or width of the slit, or both, can be varied to arrive at the desired cross sectional area which produces the desired average initial velocity. 5. The liquid flow must be evenly distributed throughout the slit so that approximately the same volume of liquid falls through each linear segment of the slit. The last of these factors, evenly distributing the liquid flow throughout the slit, has created a serious technical problem. If, for example, an arrangement of the type illustrated in FIGURE 5 is used without any internal flow distribution structure, a continuous film cannot be formed. This is because fluid supplied through the supply pipe 52 will not inherently distribute itself uniformly throughout the length of the dispensing head 54. In fact, a distinct pressure minimum will be positioned at the center of the flow distribution head while pressure maxima will exist at opposite ends thereof. Accordingly a flow distributing structure of the type illustrated in FIGURE 6 is required. As shown in FIGURE 6, the supply pipe 52 feeds the dispensing head 54. The dispensing head itself is constructed of an inner pipe 60 which is divided into an upper chamber 64 by a distribution plate 66. The upper chamber 62 is in direct communication with the supply pipe 52 and is always completely filled with liquid. Flow rates and other parameters are determined so that the liquid surface indicated by the line 68 entirely covers the distribution plate 66 at all times. The distribution plate contains a pluralty of distribution apertures 70, as illustrated in FIGURE 7. The distribution apertures may be sized progressively with the largest at the center and the smallest near the extremities of the distribution plate. Thus in this arrangement the smallest distribution apertures 70 are found near the ends of the dispensing head 54 where the fluid pressure is normally highest, while the largest distribution apertures are near the center of the dispensing head where the pressure is normally lowest. The purpose and function of this arrangement is to provide a substantially uniform flow through the distribution plate 66 throughout its length. The actual sizing of the holes can be calculated easily using conventional mathematical analysis. Furthermore, as an alternative to varying the size of the holes along the length of the distribution plate, small holes of equal size can be used with the distribution of holes arranged to provide uniformity of flow through the distribution plate along its entire length. The distribution plate is thus used to solve the problem of producing uniform output flow along the entire length of the dispensing head 54. However, the individual streams of liquid falling through the apertures 70 in the distribution plate must be integrated to form a continuous film. For this reason, a trough 72 is supported within the lowest chamber 64 of the inner pipe 60 to collect the liquid falling through the distribution apertures 70. The trough 72 is supported within the lower chamber 64 by means of suitable mounting members 74 which are arranged so as not to impede the flow of liquid out of the trough over the top of its side walls 76 and out through the slit 56. This combined structure thus serves several purposes. First, flow is evenly distributed throughout the length of the dispensing head by the distribution plate 66. Second, the liquid dropping through the distribution plate is integrated into a continuous body by the trough 72. Third, the trough is permitted to overflow so that the liquid flows along the walls of the lower chamber 64 of the inner pipe 60 and out slit 56 in the form of a continuous, isolated free-falling film 58. The apparatus of FIGURE 6 is normally constructed of stainless steel with external insulation 75 being formed of a suitable material resistant to degradation at high temperatures. With this structure, both sides of the slit 56 are formed of stainless steel since the inner pipe 60 is formed of that material. The open ends of the dispensing head 54 are preferably closed by a removable end cap 86 as shown in Figure 8. The end cap includes a stainless steel cap 88 having an extended rim 90 having an inner diameter somewhat greater than the outer diameter of the inner pipe 50 so that the rim fits around the pipe 60. Within the cap 88 is a sealing gasket 92 formed of Teflon, suitable rubber or another appropriate material of similar properties. The gasket presses against the open end surface, designated 94, of the inner pipe 60 providing a fluid tight seal. The end cap 86 is held in place by a suitable overcenter or snap-action mechanism 96. This mechanism includes a pair of bearing members 98 (only one shown) secured to opposite sides of the outer surface of pipe 60. These bearing surfaces have a central recess 100 into which each of the two legs 102 of the actuator arm 104 are pivotally inserted. The actuator arm includes a pair of circular coupling points 106, one of which is located on either side of the pipe 60. A coupling member 108 of general U-shaped configuration is connected to each of the circular coupling points 106 on opposite sides of the pipe 60 and extends across a groove 110 in the end surface of cap 88. By appropriate motion of the actuator arm 104, the end cap is either pressed in position to seal the open end of the inner pipe 60 or is released from the pipe 60 to permit easy access to the interior thereof. A similar cap is positioned at the opposite end of the pipe 60. The dispensing head shown in Figures 6-8 is characterized as a "center feed" head because the fluid supplied to the head is delivered through the supply pipe 52 which is positioned at the center of the dispensing head 54. An alternative to this surface is the "end feed head" illustrated in Figure 9. In this arrangement, the supply pipe 52 is coupled to a flow dividing manifold 112 which is coupled to both ends of a modified dispensing head 114, whereby an equal flow of liquid is supplied to opposite ends of the head 114. This design has several important advantages over the center feed design previously described. First, no "dead flow" spots are created in the end feed design, thus providing a potentially more sanitary arrangement. The flow distributor can also be more easily cleaned and serviced in place. Furthermore, the flow is more evenly distributed and splitting or other deformation of the falling film 58 is less likely to occur. In addition the need for the end cap structure illustrated in Figure 8 is eliminated. The modified dispensing head 114 retains the slit 56 for forming the film 58 and the entire assembly is fully insulated, although the insulation is not shown in Figure 9. However, the film distribution plate 66 is eliminated and replaced by a flow distribution tube 116. The flow distribution tube is inserted into a length of stainless steel pipe 118 having the slit 56 in a lower surface thereof, and appropriate mounting flanges 120 and 122 to permit a fluid tight coupling with the flow dividing manifold 112. The flow distribution tube 116 is illustrated in more detail in Figure 10 as including a central body (passing member) 124 having a conical end flange 126 at either end thereof. The end flange 126 may be either formed integrally with the central body 124 or may be coupled to the central body by conventional means. The outer diameter of the central body 124 is less than the inner diameter of the pipe 118 to provide a flow space 128 between these two structures. The end flanges 126 at either end of the flow distribution tube is expanded to the same diameter as the inner diameter of the pipe 118, thereby providing a fluid seal for directing all fluid from the flow dividing manifold 112 into the interior opening of the flow distribution apertures 130 drilled through the central body 124 fo the distribution tube. These apertures are varied in size or density in the same manner as previously described with respect to the distribution aperture 70 of the distribution plate 66. However, the distribution pattern is different in the case of the appartus illustrated in Figure 12 because the pressure distribution in the end feed system is different from that in the center feed system, as will be apparent to those skilled in the art. Specifically, the size or density of the holes should be decreased toward the center of the flow distribution tube 116 and increased toward the ends thereof. The flow distribution apertures 130 are oriented toward the top surface of the distribution tube when the distribution tube is in place in the distribution head. When assembled in this manner, fluid flowing through the interior of the distribution tube 116 passes out through the distribution apertures 130 and flows around the outer surface of the distribution tube into the flow space 128 and out through the slot 56 to form the continuous isolated film 58. In many instances it is desirable to have more than one dispensing head in use at the same time. For instance, it maybe desirable to have a plurality of heads operating within a sterilization device in order to increase the flow handling capability of the device and efficiently utilize the interior space of the device. In the past, a manual valve has been utilized for controlling the flow to each dispensing head. However, when several films are in use it becomes difficult to properly adjust the valves to provide appropriate flow distribution to all film forming heads. As a result, unequal flow distribution sometimes occurs causing one or more film to be imperfectly formed so that splashing can occur causing droplets to burn onto hot surfaces of the sterilization device causing some contamination of the treated product. Furthermore, unless a flowmeter is used in each of the feed pipes, it becomes difficult for an operator to adjust the valves and visually determine the appropriate film formation for each falling film. To eliminate the expense of multiple flowmeters and other disadvantages, a unique approach to solving this fluid flow distribution problem has been developed and will now be described mathematically. The flow equation for an incompressible fluid flowing through an orifice in a pipe is (see Mechanics of Fluids ; Shames, Irving H., McGraw Hill, 1962, p. 168): Where: Cd is the coefficient of friction Q is the flow rate A₁ is the cross sectional area of the pipe A₂ is the cross sentional areas of the orifice (slit) P₁ is the pressure before the orifice (slit) P₂ is the pressure after the orifice (slit) ρ is the density fo the liquid For A₁>>A₂ the flow can be approximated as: Equation 2 reveals that the flow in a pipe and through a slit orifice is directly proportional to the cross sectional area of the slit and directly proportional to the square root of the pressure. Figure 11A and 11B depict a dispensing head with an inner pipe 60 having a slit 56. According to equation 2, the flow through the slit will depend on the square root of P1-P2 and cross sectional area of the slit which is the length of the pipe times the slit width (Lt). If the difference between P1 and P2 remains constant or P1 remains constant, (since P2 is constant for all tubes), then the flow Q will be proportional to the area of the slit opening. If the slit width (t) is also the same for the tubes, then the flow Q will be proportional to the length of the tube. For more than one dispensing head in a sterilizer, if the pressure in the vertical pipe is the same for all heads, then the flow Q would be distributed proportional to the length of the film, thus providing optimum film formation for all films at a specified flow rate. The design for distributing the flow coming into the sterilizer should be such that the pressure in the dispensing heads is equal for all films. If the slit widths are the same for all dispensing heads, then the flow will be directly proportional to the slit length. A very simple design incorporating these concepts is shown in Figure 12 for two films and in Figure 13 for four films. The two film design illustrated in Figure 12 includes the flow supply pipe 52 feeding a branch pipe 134 having two arms, each coupled to a dispensing head 140, 142. These dispensing heads may be equivalent in design to either the center feed or end feed units previously described. The diameter of the branch pipe 134 is constant and is the same in both arms 136 and 138. If one of the dispensing heads is shorter than the other, then according to the equations set forth above the flow will be unequally distributed in the arms 136 and 138, the arm leading to the dispensing head with the longer slit receiving the greater quantity of fluid. Similarly, in Figure 13 a distribution unit for forming four separate films is illustrated. In this unit a supply pipe 52 is coupled to branch pipe 134 again having arms 136 and 138. However, the arm 136 is coupled to a second branch 144 having arms 146 and 148 which are coupled to a second branch pipe 154 which in turn has two arms 156 and 158 coupled respectively to dispensing heads 160 and 162. Thus the arrangement in Figure 13 is similar to that in Figure 12, but with an additional stage of distribution added. The same system can be scaled up to handle essentially any number of dispensing heads. Although shown only for an even number of heads, the system works equally well for an odd number of heads. However, some orificing of the flow may be necessary. Using this design, equal pressure would be provided for all dispensing heads. This distributing system does not need any valves or any operator interaction. It is flexible in that unneeded film supply pipes may be capped off, and it provides optimum film formation for a given flow. Although the dispensing heads have been illustrated as being formed of straight or linear lengths of pipe, or of linear pipes arranged in parallel, they need not be limited to these types of configurations. Other configurations for the film forming heads work equally well. Referring now to Figure 14, the film 58 of the present invention is shown positioned within a sterilizaiton chamber or UHT unit 176. The sterilizaiton chamber 176 is based on that disclosed in Davis Patent No. 3,771,434 in terms of its general structural configuration including its insulated outer wall structure 177 and conical lower portion 180. The dispensing head 54 including slit 56 is an improvement in accordance with the present invention, however, it should be noted in this regard that a plurality of dispensing heads of any of the previously disclosed types and configurations can be used in the structure illustrated in Figure 14 as can the flow distribution devices of Figs. 12 and 13. In the apparatus shown in Figure 14, saturated steam at the temperatures and pressures previously described is applied through steam supply pipe 196 to a vertical baffle 198 which surrounds the perimeter of the sterilization chamber 176. The baffle 198 is coupled to the interior surface of the sterilization chamber 176 at its lower end 200, and is so shaped as to provide an upwardly directed channel 202 for all steam entering through the steam supply pipe 196. Thus the velocity of the incoming steam causes it to impinge upon the adjacent surface of the vertical baffle 198 and to be subsequently directed straight upwardly through channel 202 along the outer wall of the sterilization chamber.

Claims: An apparatus for treating liquid by exposure to a heated gas wherein there is a dispensing head (54; 114; 140, 142; 150, 152, 160, 162) for said liquid having a liquid supply means (52) and a horizontally extending discharge slit (56) for emitting said liquid as a thin continuous free-falling film (58), characterized in that there is within said dispensing head (54; 114; 140, 142; 150, 152, 160, 162) a liquid distributor (66; 116) which is arranged to initially receive said liquid and having outlets (70; 130) arranged as a plurality of apertures for distributing said liquid uniform to said slit (56). An apparatus as in claim 1, characterized in that within said dispensing head (54; 114; 140, 142; 150, 152, 160, 162) there is a trough (72, 76) receiving liquid from said distributor (66; 116) to form a continuous body of liquid flowing to said slit (56). An apparatus as in claim 1 or 2, characterized in that said liquid distributor (66) comprises a generally flat plate. An apparatus as in claim 1, characterized in that said liquid distributor (116) comprises a tubular member. An apparatus as in one of claims 1 to 4, characterized in that said liquid distributor (66; 116) comprises a non-uniform distribution of apertures (70; 130). An apparatus as in claim 5, characterized in that said distribution of apertures (70; 130) includes a series of openings of progressively smaller size in accordance with an increasing liquid pressure. An apparatus as in claim 5, characterized in that said distribution of apertures (70; 130) includes a plurality of openings of similar size spaced to provide a progressively smaller density of openings in accordance with an increasing liquid pressure. An apparatus as in one of claims 1 to 7, characterized in that said liquid distributor (66; 116) divides said dispensing head (54; 114; 140, 142; 150, 152, 160, 162) into two chambers (62, 64; 128). An apparatus as in claim 1 or 2, characterized in that said supply means (52) is coupled to said dispensing head (54; 140, 142; 150, 152, 160, 162) at only one point for forming a center feed supply apparatus. An apparatus as in claim 1 or 2, characterized in that said supply means (52) is coupled to both ends (126) of said dispensing head (114) for forming an end feed supply apparatus. An apparatus as in claim 1, characterized by removable end cap means (86) for enclosing opposite ends of said dispensing head (54;140, 142; 150, 152, 160, 162).

Inventors: NAHRA, JOHN E., WOODS, WALTER C.
Applicants: DASI INDUSTRIES, INCORPORATED
Application year: 1980
Main classification: A23L3
IPC codes: A23L3, A23C3, B01J19