Liquid level control separator for foam formation

Abstract

A process and system for forming a foam web are disclosed. A foaming suspension of a material, such as fibers and other particles, is supplied to one or more forming zones sequentially located along an inclined forming surface. A plurality of corresponding drain devices are located below the forming surface to drain excess fluid from the newly formed web. The flow rate of the fluid drained from the web is controlled in relation to the flow rate or pressure of the foaming suspension of fibers supplied to the forming zones.

Description

Technology Field

[0001] The present invention relates to a liquid level control separator for foam formation. Background Technology

[0002] Many tissue products, such as facial tissues, bathroom tissues, paper towels, and industrial wipes, are produced by the wet-laid process. A wet-laid web is manufactured by depositing an aqueous suspension of pulp fibers onto a molded fabric and then removing water from the newly formed web.

[0003] To improve various properties of the tissue web, the web was also formed according to a foaming process. During the foaming process, a foamed suspension of fibers is formed and diffused onto a moving porous conveyor to manufacture the initial web. The foamed web can demonstrate improvements in bulk, elasticity, caliper, and / or absorbency. In addition to tissue webs, foaming can be used to manufacture all different types of webs and products. For example, relatively long fibers and synthetic fibers can be incorporated into the web using the foaming process. Therefore, the foaming process can be more useful than many wet laid processes.

[0004] In a given conventional foam forming system, one or more fan pumps flow the foam from the separation silo to the backwater tank through a short race. This arrangement can have disadvantages. For example, a large fan pump and / or vacuum assistance may be required to provide sufficient suction pressure for the low-density form in the separation silo. As another example, the compressibility of the foam in the separation silo may limit the vacuum applicable in the separation silo.

[0005] A system for improved foam handling between separation silos for backwater tanks would be useful.

[0006] Generally, the present disclosure relates to an improved process and system for flowing foam between a separator and a tank. A pump can be operated to flow foam from the separator to the tank. The pump can be controlled to maintain the liquid level of the foam within the separator based on a signal from a sensor that detects the liquid level of the foam within the separator. The process and system of the present disclosure can advantageously help reduce or prevent over-draining or under-draining of the foam from the separator. Additionally, over-draining of the foam from the separator can entrain large bubbles into the flow of foam from the separator, which can reduce foam density and impede the foam flow. In contrast, under-draining of the foam from the separator can lead to vacuum loss within the separator, foam formation within the separator, and introduction of the foam into the vacuum source. These negative effects of over-discharge and under-discharge can be limited or prevented by operating a pump to maintain the liquid level of the foam in the separator. The process and system of the present invention can also advantageously help provide a consistent residence time for the foam in the separator, which can improve foam stability.

[0007] In one exemplary embodiment, the foam forming system comprises a headbox and a tank. A separator is positioned between the headbox and the tank along a flow path for the foam between the headbox and the tank. The separator comprises an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam. The foam forming system also comprises a pump. A sensor is operable to determine the liquid level of the foam within the separator. A controller receives a signal from the sensor corresponding to the liquid level of the foam within the separator and is configured to operate the pump, at least partially based on the liquid level of the foam within the separator, to maintain the liquid level of the foam within a determined range within the separator.

[0008] In another exemplary embodiment, the foam forming system comprises a tank. The vacuum separator comprises an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam. The vacuum separator is coupled to the tank through the first outlet so that the foam can flow from the vacuum separator to the tank. A pump is operable to flow the foam from the vacuum separator to the tank. A sensor is operable to determine the liquid level of the foam within the vacuum separator. A controller is configured to determine the liquid level of the foam within the vacuum separator based at least partially on a signal from the sensor, and to operate the pump to maintain the liquid level of the foam within a determined range within the vacuum separator based at least partially on the determined liquid level of the foam within the vacuum separator.

[0009] In another exemplary embodiment, a method for forming a foam comprises the steps of: flowing the foam from a head box to a vacuum separator; flowing free air from the foam out of the vacuum separator through a vacuum outlet of the vacuum separator; and operating a pump to flow the foam out of the vacuum separator through a foam outlet of the vacuum separator. The step of operating the pump comprises the steps of determining the liquid level of the foam in the vacuum separator using a sensor and adjusting the flow rate of the pump to maintain the liquid level of the foam within a determined range in the vacuum separator based at least partially on the determined liquid level of the foam in the vacuum separator.

[0010] Other features and aspects of the present invention will be described in more detail below. Brief explanation of the drawing

[0011] The present invention will be described more specifically and completely in the remainder of the specification with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a system and process for forming a web from a foamed suspension of a material according to an exemplary embodiment of the present disclosure; FIG. 2 is a schematic diagram of a system and process according to an exemplary embodiment of the present disclosure for depositing a foamed suspension of a material on a forming surface according to the present disclosure; FIG. 3 is a schematic diagram of a system and process according to an exemplary embodiment of the present disclosure for separating free air from the flow of foam during the foam formation of a nonwoven web. FIG. 4 is a flowchart of a process according to an exemplary embodiment of the present disclosure for separating free air from the flow of foam during the foam formation of a nonwoven web. The repeated use of reference characters in this specification and drawings is intended to indicate identical or similar features or elements of the present invention. Specific details for implementing the invention

[0012] definition

[0013] When introducing elements of the content of the invention or preferred embodiment(s) of the content of the invention, the phrases “one,” “one,” “the,” and “the” mean that one or more of those elements are present. As used herein, the terms “comprising” and “comprising” are intended to be inclusive in a manner similar to the term “consisting of.” Similarly, the term “or” is intended to be inclusive in general (i.e., “A or B” is intended to mean “A or B or both).” As used herein throughout the specification and claims, approximation language is applied to modify any quantitative expression that may be permissibly modified without causing a change in the underlying function involved. Accordingly, values ​​modified by the terms, e.g., “about,” “approximately,” and “substantially,” are not limited to specific exact values. In at least some cases, approximation language may correspond to the precision of the instrument used to measure the value. For example, approximation language may indicate being within a 10% margin.

[0014] As used herein, the term "foam-formed product" refers to a product formed from a suspension comprising a mixture of solids, liquids, and dispersed bubbles.

[0015] As used herein, the term "foam-forming process" refers to a process for manufacturing a product comprising a suspension comprising a mixture of solids, liquids, and dispersed bubbles.

[0016] As used herein, the term "foaming fluid" means any one or more known fluids compatible with other components in a foam-forming process. Suitable foaming fluids include, but are not limited to, water.

[0017] As used herein, the term "foam half-life" refers to the time elapsed until half of the initial foam mass returns to liquid water.

[0018] As used herein, the term "layer" refers to a structure that provides an area of ​​the substrate in the height direction of the substrate composed of similar components and structures.

[0019] As used herein, the term “nonwoven web” means a web having a structure of individual fibers or threads interconnected, though not in an identifiable manner as in a knitted web.

[0020] As used herein, unless explicitly stated otherwise, when used in relation to material composition, the terms “percent,” “%,” “weight percentage,” and “weight-based percentage” each refer to the weight-based amount of a component as a percentage of the total weight, except where explicitly stated otherwise.

[0021] In this specification, the term “personal hygiene absorbent articles” refers to articles intended and / or fitted to be positioned attached to or in close proximity (i.e., adjacent to the body) to absorb and contain various liquid, solid, or semi-solid exudates discharged from the body. Examples include, but are not limited to, diapers, diaper pants, training pants, youth pants, swim pants, and women’s hygiene products including, but not limited to, menstrual pads or pants, incontinence products, medical clothing, surgical pads and bandages, etc.

[0022] As used herein, the term “superabsorbent material” refers to a water-swellable, water-insoluble organic or inorganic material comprising a superabsorbent polymer and a superabsorbent polymer composition capable of absorbing at least about 10 times its own weight, or at least about 15 times its own weight, or at least about 25 times its own weight in an aqueous solution containing 0.9 wt% sodium chloride under the most favorable conditions.

[0023] As used herein, the term "machine direction" refers to the direction of movement of the molding surface to which fibers are attached during the formation of a nonwoven web.

[0024] As used herein, the term "intersecting machine direction" refers to a direction perpendicular to the machine direction defined above.

[0025] As used herein, the term “pulp” refers to fibers from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse. Pulp fibers may include hardwood fibers, softwood fibers, and mixtures thereof.

[0026] As used herein, the term “average fiber length” refers to the average length of a fiber, fiber bundle, and / or fiber-like material determined by measurements using microscopic techniques. A sample of at least 20 randomly selected fibers is separated from a liquid suspension of fibers. The fibers are placed on a microscope slide prepared to suspend the fibers in water. A tinting dye is added to the suspended fibers to color the cellulose-containing fibers so that they can be distinguished or separated from synthetic fibers. The slide is placed under a Fisher Stereomaster II Microscope—S19642 / S19643 series. Measurements of 20 fibers from the sample are taken at 20X linear magnification using a scale of 0 to 20 mil, and the average length, minimum and maximum lengths, and deviations or coefficients of variation are calculated. In some cases, the average fiber length will be calculated as the weighted average length of fibers (e.g., fibers, fiber bundles, fiber-like materials) determined by equipment such as the Kajaani fiber analyzer model number FS-200, available from Kajaani Oy Electronics in Kajaani, Finland, for example. According to standard test procedures, samples are treated with a cold immersion solution to ensure that no fiber bundles or shives are present. Each sample is disintegrated in hot water and diluted in an approximately 0.001% suspension. When testing using the standard Kajaani fiber analysis test procedure, individual test samples are drawn from the diluted suspension in portions of approximately 50 to 100 ml. The weighted average fiber length may be an arithmetic mean, a length-weighted mean, or a weight-weighted mean, and can be expressed by the following formula:

[0027]

[0028] Here

[0029] k = maximum fiber length

[0030] x i = fiber length

[0031] n i = Number of fibers with length xi

[0032] n = total number of measured fibers.

[0033] One characteristic of the average fiber length data measured by the Kajaani fiber analyzer is that it does not distinguish between different types of fibers. Therefore, the average length represents the average based on the lengths of all different types of fibers (if present) within the sample.

[0034] As used herein, the term "staple fiber" refers to discontinuous fibers made of synthetic polymers such as polypropylene, polyester, post-consumer recycled (PCR) fibers, polyester, nylon, etc., and those that are not hydrophilic may be treated to become hydrophilic. Staple fibers may be cut fibers, etc. Staple fibers may have a cross-section that is circular, bicomponent, multicomponent, shaped, hollow, etc.

[0035] details

[0036] A person skilled in the art will understand that this discussion is merely illustrative of exemplary embodiments and is not intended to limit the broader aspects of the invention.

[0037] Generally, the present disclosure relates to a system and method for forming a foam from a nonwoven web. In the system, a separator silo is separated from a backwater tank, and a pump may be configured to flow the foam from the separator silo to the backwater tank. The pump may be controlled to maintain a consistent liquid level range for the foam within the separator silo. Additionally, the liquid level of the foam within the separator silo may be measured by a sensor, such as a capacitive load, and the pump may be controlled based on the sensor measurement. The separator silo may be configured to operate under vacuum, and the backwater tank may be configured at ambient pressure.

[0038] The system and process of the present disclosure may provide various advantages and benefits. For example, the system may include a fan pump configured to be separate from the pump and to pressurize the foam from the backwater tank to the headbox. The fan pump can operate with increased efficiency and robustness by utilizing the pump to maintain a consistent liquid level range for the foam within the separator silo. Thus, the suction head for the fan pump may be improved and / or a centrifugal pump may be used in the fan pump rather than a vacuum-assisted centrifugal pump. As another example, the vacuum liquid level within the entire system may be increased, and the desired vacuum liquid level may be separated from the machine height. Thus, the height difference between the free surface of the foam within the separator silo and the free surface of the foam within the backwater tank may be substantially reduced by utilizing the pump to maintain a consistent liquid level range for the foam within the separator silo. As another example, using a pump to maintain a consistent liquid level range for the foam in the separator silo can help reduce or prevent over- or under-ejection of the foam from the separator silo. Thus, the entrainment of large bubbles into the foam flow from the separator silo can be avoided and / or the introduction of foam into the vacuum source for the separator silo can be avoided. As another example, using a pump to maintain a consistent liquid level range for the foam in the separator silo can help provide a consistent residence time for the foam in the separator, which can improve foam stability.

[0039] Referring to FIGS. 1 and 2, exemplary embodiments of a system and process according to aspects of the present invention are shown. Generally, during the process, a solid material such as fibers and / or superabsorbent particles, water, and a foaming agent are added to a tank and mixed until a desired air content, bubble size / foam stability, and a solid dispersion such as a fiber dispersion are achieved. Then, the fiber-containing foam may be optionally diluted during the process, particularly when a recycling stream is present. In one exemplary aspect, the air content of the foaming suspension is about 30% to about 65%. As described below, exemplary aspects of the process and system of the present invention relate to separating the foam from free air and managing the foam, for example, during the foaming of a nonwoven web.

[0040] FIG. 1 illustrates a system and process for preparing a foamed suspension of fibers and forming a web from the foamed suspension of fibers. The exemplary system illustrated in FIG. 1 is provided as an example, and it will be understood that any suitable web forming system may be used according to the present invention. As illustrated in FIG. 1, the system may include a mixing tank (12) configured to form a foamed suspension of fibers. Then, the foamed suspension of fibers may be supplied to a headbox or web forming system (10), which deposits the foamed suspension of fibers onto a porous forming surface (26) to form a web (14). The mixing tank (12) may be in communication with a water supply unit (22) for supplying water to the tank and a foaming agent or surfactant supply unit (24) for supplying a surfactant to the tank (12). Fiber material may also be supplied to the tank (12) and combined with water and surfactant. An aqueous solution formed by combining a surfactant and water can be stirred and formed into a foam to form a foamed suspension of fibers. As described above, in addition to fibers, various other materials can be combined in the tank (12). These other materials may include, for example, superabsorbent particles.

[0041] The surfactant or blowing agent may include, for example, any suitable surfactant. In one exemplary embodiment, for example, the blowing agent may include sodium lauryl sulfate, also known as sodium laureth sulfate or sodium lauryl ether sulfate. Other blowing agents include sodium dodecyl sulfate or ammonium lauryl sulfate. In other exemplary embodiments, the blowing agent may include any suitable cationic and / or amphoteric surfactant. For example, other blowing agents include fatty acid amines, amides, amine oxides, fatty acid quaternary compounds, etc. In one exemplary embodiment, a nonionic surfactant is used. The nonionic surfactant may include, for example, an alkyl polyglycoside. In one aspect, for example, the surfactant may be a C8 alkyl polyglycoside, a C10 alkyl polyglycoside, or a mixture of C8 and C10 alkyl polyglycosides.

[0042] A blowing agent can generally be combined with water in an amount greater than about 0.1% by weight, for example, in an amount greater than about 0.5% by weight, for example, in an amount greater than about 0.7% by weight. One or more blowing agents can generally be present in an amount of about 0.01% by weight to about 5% by weight, for example, up to about 2% by weight.

[0043] When a foaming agent and water are combined, the mixture may be subjected to forces that allow it to either blend or otherwise form foam. Foam generally refers to an aggregate of hollow cells or bubbles.

[0044] Foam density may vary depending on the specific application and may vary depending on various factors including the fiber material used. In one exemplary embodiment, for example, the foam density of the foam may be greater than about 200 g / L, e.g., greater than about 250 g / L, e.g., greater than about 300 g / L. The foam density is generally less than about 600 g / L, e.g., less than about 500 g / L, e.g., less than about 400 g / L, e.g., less than about 350 g / L. In one exemplary embodiment, for example, a low-density foam having a foam density generally less than about 350 g / L, e.g., less than about 340 g / L, e.g., less than about 330 g / L may be used. The foam may generally have an air content greater than about 40%, e.g., greater than about 50% (50%), e.g., greater than about 60%, at standard temperature and pressure (STP). The air content is generally less than about 75 volume%, for example less than about 70 volume%, for example less than about 65 volume%.

[0045] The foam can be formed in the presence of a fiber material, or alternatively, the foam can be formed first and then combined with the fiber material. Generally, any fiber capable of making a base sheet, such as a tissue web or other similar type of nonwoven fabric, can be used.

[0046] Fibers suitable for manufacturing the web include, but are not limited to, any natural or synthetic cellulose fibers, including wood or pulp fibers obtained from deciduous and coniferous trees, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute, hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and softwood fibers such as northern and southern softwood kraft fibers; and hardwood fibers such as eucalyptus, maple, birch, and poplar. Pulp fibers may be prepared in high yield or low yield forms and may be pulped by any known method, including the kraft method, the sulfite method, high-yield pulping methods, and other known pulping methods. Fibers produced from the organosolve pulping method may also be used.

[0047] Some of the fibers, such as up to 100% by dry weight or about 5% to about 30% by dry weight, may be synthetic fibers, such as rayon, polyolefin fibers, polyester fibers, bicomponent syscore fibers, or multicomponent binder fibers. The fibers may be virgin fibers or recycled fibers. The fibers may be staple fibers and may have an average length of about 3 mm to about 150 mm. An exemplary polyethylene fiber is Fybrel®, available from Minifibers, Inc. (Jackson City, Tennessee). When containing synthetic polymer fibers, the web may be thermally bonded at the points where the fibers intersect.

[0048] Synthetic cellulose fiber types include rayon and viscose of all variations, or other fibers derived from chemically modified cellulose. Chemically treated natural cellulose fibers, such as mercerized pulp, chemically hardened or cross-linked fibers, or sulfonate fibers may be used. For good mechanical properties when using paper fibers, it may be desirable for the fibers to be relatively undamaged and in a generally unrefined or slightly refined state. Recycled fibers may be used, but virgin fibers are generally free of contaminants and are useful for mechanical properties. Polished fibers, regenerated cellulose fibers, microbial cellulose, rayon, and other cellulose materials or cellulose derivatives may be used. Suitable paper fibers may also include recycled fibers, virgin fibers, or mixtures thereof. In some embodiments where good compressibility is possible, the fibers may have a Canadian Standard Freeness of at least 200, more specifically at least 300, even more specifically at least 400, most specifically at least 500.

[0049] Other paper fibers that may be used include paper broke or recycled fibers and high-yield fibers. High-yield pulp fibers are paper fibers produced by a pulping process that provides a yield of about 65% or more, more specifically about 75% or more, and even more specifically about 75% to about 95%. Yield is the amount of treated fibers expressed as a percentage of the initial wood mass. Such pulping processes include bleached chemithermomechanical pulp (BCTMP), chemical thermomechanical pulp (CTMP), pressure / pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high-yield sulfite pulp, and high-yield kraft pulp, all of which result in high levels of lignin in the fibers formed. High-yield fibers are widely known to be harder in both dry and wet states compared to conventional chemically pulped fibers.

[0050] The web can also be formed without a significant amount of internal inter-fiber bonding strength. In this regard, the fiber furnish used to form the base web can be treated with a chemical debonding agent. The debonding agent may be added to the foam fiber slurry during the pulping process or added directly to the headbox. Suitable debonding agents that may be used include cationic debonding agents such as fatty dialkyl quaternary amine salts, monofatty alkyl tertiary amine salts, primary amine salts, imidazoline quaternary salts, silicone quaternary salts, and unsaturated fatty alkyl amine salts. Other suitable debonding agents are disclosed in Kaun’s U.S. Patent No. 5,529,665, which is incorporated herein by reference in its entirety. Specifically, Kaun discloses the use of a cationic silicone composition as a debonding agent.

[0051] In one exemplary embodiment, the debonding agent used in the process of the present invention is an organic quaternary ammonium chloride, specifically, a silicon-based amine salt of a quaternary ammonium chloride. For example, the debonding agent may be PROSOFT.RTM. TQ1003 commercially available by Hercules Corporation. The debonding agent may be added to the fiber slurry in an amount of about 1 kg (1 kg / ton) to about 10 kg (10 kg / ton) per metric ton of fibers present in the slurry.

[0052] In an alternative exemplary embodiment, the deconjugator may be an imidazoline-based formulation. Imidazolin-based deconjugators can be obtained, for example, from Witco Corporation. The imidazoline-based deconjugator may be added in an amount of 2 kilograms (2.0 kg / ton) to about 15 kilograms (15 kg / ton) per metric ton.

[0053] Additionally, other optional chemical additives may be added to the aqueous paper pulp or to the formed initial web to provide additional benefits to the product and process. The following materials are included as examples of additional chemicals that may be applied to the web. The chemicals are included as examples and are not intended to limit the scope of the invention. These chemicals may be added at any point in the papermaking process.

[0054] The types of chemicals that may be added to the paper web generally include, but are not limited to, absorbent aids in the form of cationic, anionic, or nonionic surfactants, humectants, and plasticizers, such as low molecular weight polyethylene glycol and polyhydroxy compounds, such as glycerin and propylene glycol. Materials that provide skin health benefits, such as mineral oil, aloe extract, vitamin E, silicone, and lotion, may also be incorporated into the final product.

[0055] Other examples of such materials include, but are not limited to, odor control agents such as deodorizers, activated carbon fibers and particles, baby powder, baking soda, chelating agents, zeolites, perfumes, or other odor blockers, cyclodextrin compounds, oxidizing agents, etc. Superabsorbent particles may also be used. Additional options include cationic dyes, gloss agents, wetting agents, softeners, etc.

[0056] Returning to FIG. 2, once a foam suspension of fibers is formed in the tank (12) (Fig. 1), the foam suspension of fibers can be supplied to a web forming system (10). As illustrated in FIG. 2, the web forming system (10) may include one or more forming zones. In an exemplary embodiment of FIG. 2, three forming zones are illustrated, including a first forming zone (50), a second forming zone (52), and a third forming zone (54). The forming zones (50, 52, and 54) are located along a porous forming surface (26). In one exemplary embodiment, as illustrated in FIG. 2, the porous forming surface (26) may be inclined with respect to a horizontal line. For example, the porous forming surface (26) may be oriented at an angle greater than about 10 degrees (10°) with respect to the horizontal line, e.g., greater than about 20 degrees (20°), e.g., greater than about 30 degrees (30°), and generally less than about 60 degrees (60°), e.g., less than about 50 degrees (50°). Each forming zone (50, 52 and 54) may be configured to accommodate a separate, independent flow of the foam suspension of the fibers to deposit the foam suspension of the fibers onto the forming surface (26). For example, the first forming zone (50) may deposit the foam suspension of the fibers directly onto the forming surface (26). However, the second forming zone (52) may be configured to deposit a second flow of the foam suspension of the fibers on top of the fibers deposited by the first forming zone (50). Similarly, the third forming zone (54) can deposit a flow of an aqueous suspension of fibers on top of the fibers deposited by the first forming zone (50) and the second forming zone (52). In this way, a multilayer web can be formed. However, it should be understood that the system and process of the present invention may include only a single forming zone for forming a single layer web.

[0057] As illustrated in FIG. 2, each forming zone (50, 52, and 54) may be fluidly connected to a separate, independent foam fiber supply line. For example, the first forming zone (50) may be fluidly connected to the first foam fiber supply line (56), the second forming zone (52) may be fluidly connected to the second foam fiber supply line (58), and the third forming zone (54) may be fluidly connected to the third foam fiber supply line (60). The first, second, and third supply lines (56, 58, and 60) may be configured to supply a foam suspension of fibers to each of the respective forming zones (50, 52, and 54) at determined and selected flow characteristics, such as volumetric flow rate, pressure, air content, and / or density. In this regard, each of the supply lines (56, 58, and 60) may be fluidly connected to the mixing tank (12) as illustrated in FIG. 1. For example, the first supply line (56) may include a first injection line (62) connected to the mixing tank (12). Similarly, the second supply line (58) may include a second injection line (64), while the third supply line (60) may communicate with the third injection line (66). The injection lines (62, 64 and 66) may all communicate with the mixing tank (12) to supply a foamed suspension of fibers to each of the forming zones (50, 52 and 54). Alternatively, the system (10) may include a separate mixing tank, and each of the first, second, and third injection lines (62, 64 and 66) may be connected to a different respective mixing tank to supply a foamed suspension of fibers to the web forming system (10).

[0058] As described, each of the foamed fiber supply lines (56, 58, and 60) may include a pumping device, a flow meter such as a volumetric flow meter, a pressure monitoring device, and / or a temperature monitoring device. Each of the foamed fiber supply lines (56, 58, and 60) may also be in communication with a density monitoring device. The density monitoring device may be part of one of the other devices, for example, a part of a flow meter. Alternatively, the density of the foamed fiber suspension may be calculated using information received from another device.

[0059] For example, the first foamed fiber supply line may include a first pumping device (68), a first flow meter (74), a first pressure monitoring device (80), and a first temperature monitoring device (81); the second foamed fiber supply line (58) may include a second pumping device (70), a second flow meter (76), a second pressure monitoring device (82), and a second temperature monitoring device (83); and the third foamed fiber supply line (60) may include a third pumping device (72), a third flow meter (78), a third pressure monitoring device (84), and a third temperature monitoring device (85). The pumping devices (68, 70, and 72) may be adjustable so that the foaming suspension of the fiber can be supplied independently to each forming zone (50, 52, and 54) at a desired, selected flow rate and / or pressure. Flow meters (74, 76, and 78), pressure monitoring devices (80, 82, and 84) (e.g., volumetric flow rate), and temperature monitoring devices (81, 83, and 85) can monitor flow rate, pressure, and temperature upstream from the forming surface to calculate at least one feature of the flow of the foamed suspension of fibers at the forming surface.

[0060] In one exemplary embodiment, the flow meters (74, 76, and 78), pressure monitoring devices (80, 82, and 84), and temperature monitoring devices (81, 83, and 85) may be configured to communicate with one or more controllers. The controller may include a microprocessor or any suitable programmable device. The pumping devices (68, 70, and 72) may also be configured to communicate with one or more controllers. The controller may be configured to adjust the pumping devices (68, 70, and 72) based on information received from the flow meters (74, 76, and 78), from the pressure monitoring devices (80, 82, and 84), and / or from the temperature monitoring devices (81, 83, and 85). In this way, the foamed suspension of fibers can be supplied to each molding zone (50, 52 and 54) at a flow rate within a desired set point and / or a pressure within a desired set point to optimize the formation of a web on the forming surface (26).

[0061] Information received from flow meters (74, 76, and 78), from pressure monitoring devices (80, 82, and 84), and / or from temperature monitoring devices (81, 83, and 85) can be used to determine the characteristics of the foamed suspension of the fiber at the measurement location. Additionally, the density of the foamed suspension of the fiber can be measured or calculated from information received from various devices. In one embodiment, this information can be transmitted to a controller to calculate at least one characteristic of the foamed suspension of the fiber at the forming surface. In particular, the controller can be programmed to correct the volumetric flow rate determined at the forming surface based on changes in density, pressure, and temperature. For example, the foamed suspension may experience a pressure drop when discharged from a supply line onto the forming surface, which changes the density of the foamed suspension. One method for calculating downstream values ​​of the foamed suspension is disclosed, for example, in U.S. Patent No. 4,764,253, which is incorporated herein by reference.

[0062] As illustrated in FIG. 2, facing the first forming zone (50) along the forming surface (26) may be a first drain device (86) in fluid communication with the first drain line (92). Facing the second forming zone (52) may be a second drain device (88) in fluid communication with the second drain line (94). Similarly, facing the third forming zone (54) may be a third drain device (90) in communication with the third drain line (96). The first, second, and third forming zones (50, 52, and 54) may be adjacent to each other along the forming surface (26) and may be located on one side of the forming surface (26). The drain devices (86, 88, and 90) may also be adjacent to each other and may be located on the opposite side of the forming surface (26) in alignment with the forming zones (50, 52, and 54). As the foam suspension of the fibers is deposited on the forming surface from each forming zone (50, 52 and 54), a web (14) may be formed, and an excess of fluid may enter the corresponding drain device (86, 88 and 90). The drain device may be any suitable static or dynamic drain device capable of draining fluid from the web or from the forming surface. The drain device may be a static suction or vacuum box. Alternatively, the drain device may be a drum, such as a rotating drum, that applies suction.

[0063] As illustrated in FIG. 2, each drain line (92, 94, and 96) may include a corresponding flow control device, a flow meter, a temperature monitoring device, and a pressure monitoring device. For example, the first drain line (92) may include a first flow control device (98), a first flow meter (104), a first temperature monitoring device (105), and a first pressure monitoring device (110); the second drain line (94) may include a second flow control device (100), a second flow meter (106), a second temperature monitoring device (107), and a second pressure monitoring device (112); and the third drain line (96) may include a third flow control device (102), a third flow meter (108), a third temperature monitoring device (109), and a third pressure monitoring device (114). The flow control devices (98, 100, and 102) may be any suitable device for controlling flow through the line and may be adjustable valves or pumps. For example, a pump may be used to apply suction to the forming surface. Alternatively, drainage may occur via gravity. In another exemplary embodiment, each flow control device (98, 100, and 102) may be a combination of a pump and an adjustable valve.

[0064] In one exemplary embodiment, the system (10) may further include one or more controllers (116). The controller (116) may include a microprocessor or any suitable programmable device. As illustrated in FIG. 2, each flow control device (98, 100, and 102), each flow meter (104, 106, and 108), each temperature monitoring device (105, 107, and 109), each density monitoring device, and / or each pressure monitoring device (110, 112, and 114) may communicate with the controller (116). The controller (116) may receive information from flow meters (104, 106 and 108), temperature monitoring devices (105, 107 and 109), optional density monitoring devices and / or pressure monitoring devices (110, 112 and 114) to adjust flow control devices (98, 100 and 102) for controlling the flow rate of fluid drained from each of the drain devices (86, 88 and 90). A combination of receiving information from flow control devices (98, 100 and 102), pressure monitoring devices (110, 112 and 114), temperature monitoring devices (105, 107 and 109), and / or optional density monitoring devices, which may be volumetric flow meters, may be used to quantify fluid discharge flows containing both gas and liquid. In one exemplary embodiment, the controller (116) can use the information to calculate a flow rate, such as a volumetric flow rate at the forming surface, and control the volumetric flow rate based on at least one feature of the foamed suspension supplied to the forming surface. Then, the controller (116) can control the flow control devices (98, 100 and 102) to achieve the calculated discharge flow rate through each drain device and drain line.

[0065] In an exemplary embodiment, the process and system of the present invention may further include a sealing zone (120) located along the molded fabric (26) and fluidly communicating with a sealing fluid supply line (122). As illustrated in FIG. 2, the sealing fluid supply line (122) may include a pumping device (124), a flow meter (126), a pressure monitoring device (128), and a temperature monitoring device (129). The sealing fluid supply line (122) is intended to supply a fluid, in particular a liquid, to the sealing zone (120). The sealing fluid may be any suitable liquid. For example, the sealing fluid may be water, a water and surfactant solution, etc. In one exemplary embodiment, the sealing fluid may be non-fibrous. The sealing fluid may be supplied to the sealing fluid zone (120) at a flow rate and / or pressure so that the sealing fluid deposited on the forming surface (26) forms a fluid seal that prevents airflow in the upstream longitudinal direction. Information received from a flow meter (126), a pressure monitoring device (128), a temperature monitoring device (129), and optionally a density monitoring device can be used to calculate the volumetric flow rate of the foam at the forming surface.

[0066] As illustrated in FIG. 2, the sealing zone (120) may be located upstream adjacent to a plurality of forming zones. The sealing zone (120) may also be positioned opposite a sealing drain device (130) connected to a sealing drain line (132). The sealing drain line (132) may include a flow control device (134), a flow meter (136), a temperature monitoring device (137), and a pressure sensing device (138) that are all in communication with the controller (116). In this way, the drainage flow rate of the sealing fluid may be controlled based on the flow rate or pressure of the sealing fluid entering or exiting the sealing zone (120). By including the sealing zone (120), better formation of the web (14) occurs opposite to the first forming zone (50).

[0067] A web forming system (10) as illustrated in FIG. 2 may also include a suction zone (140) located adjacent to a plurality of forming zones and downstream from the forming zones. The suction zone (140) may be fluidly connected to a drain line (142) that may include a pressure monitoring device (144). The suction zone (140) is intended to draw fluid through the initial web (14) after the web has been formed. The suction zone (140) is intended to remove excess fluid, particularly liquid, from the web (14). In one aspect, the discharge flow rate of the foamed suspension of fibers drained through one or more drain devices may be controlled so that excess fluid from one or more forming zones enters the suction zone (140). Ideally, the suction zone (140) facilitates the draining of fluid from the web (14) without causing any harmful effects.

[0068] As illustrated in FIG. 2, all drain lines (92, 94, 96, 132, and 142) can be supplied to a separation tank (150). The separation tank (150) can be configured to separate free gas from the foam. As shown, the separation tank (150) may include a liquid outlet (154) and a gas outlet (152) that can be connected to a vacuum source. The liquid collected in the separation tank (150) may include a mixture of water and surfactant. As illustrated in FIG. 2, a pumping device (156) can be used to pump liquid from the separation tank (150) to a liquid tank (158), which can also be positioned in communication with a water supply source (160). The liquid tank (158) can be used to recirculate the mixture of water and surfactant back into the process through the supply lines (56, 58, 60 and 122).

[0069] Referring again to FIG. 1, after the initial web (14) is formed from the web forming system or headbox (10), the web (14) can be supplied to various different downstream processes. FIG. 1 merely illustrates an exemplary embodiment of a process for drying the web (14) after formation. As illustrated, the web (14) is formed on a forming surface (26) and transported downstream. For example, the endlessly running formed fabric (26) can be supported and driven by a roll (28).

[0070] Once formed on the formed fabric (26), the formed web (14) may have a viscosity of less than about 50%, e.g., less than about 20%, e.g., less than about 10%, e.g., less than about 5%. In practice, the formed viscosity may be less than about 2%, e.g., less than about 1.8%, e.g., less than about 1.5%. The formed viscosity is generally greater than about 0.5%, e.g., greater than about 0.8%.

[0071] Once the wet web (14) is formed on the molded fabric (26), the web (14) is transported downstream and optionally further dehydrated. For example, the process may optionally include a plurality of vacuum devices (16), such as a vacuum and a vacuum roll. The vacuum box helps to remove moisture from the newly formed web (14).

[0072] As illustrated in FIG. 1, the formed fabric (26) may also be placed in communication with a steam box (18) positioned over a pair of vacuum rolls (20). For example, the steam box (18) can increase dryness and reduce moisture fluctuations in the cross direction. Steam applied from the steam box (18) heats the moisture in the wet web (14), causing the water in the web to be discharged more easily, particularly with the vacuum rolls (20). From the formed fabric (26), the newly formed web (14) is transported downstream and dried. The web (14) can be dried using any suitable drying device. For example, the web (14) may be air-dried, placed on a heated drying drum, creped, or left uncreped. In FIG. 1, for example, the formed web (14) is placed in contact with two heated drying drums (38 and 40). In one exemplary embodiment, from the drying drums (38 and 40), the web (14) may be supplied to an aeration dryer before being wound into a roll.

[0073] The embodiment of FIG. 2 is for forming a multilayer web. In another aspect, the process of the present invention can be used to produce a single-layer web from a foamed material suspension.

[0074] Now, returning to FIG. 3, according to an exemplary embodiment of the present invention, a system (200) for separating the foam from free air and managing the foam is illustrated, for example, during the foaming of a nonwoven web. It will be understood that the system (200) may be used in or together with any foaming system or process for forming a web from a foamed suspension of fibers. For example, the system (200) may be used in or together with the exemplary systems and processes illustrated in FIG. 1 and 2 and described above. Accordingly, the system (200) is described below in more detail in the context of the exemplary systems and processes illustrated in FIG. 1 and 2. However, it will be understood that the system (200) may be used in or together with other systems and processes for forming a web from a foamed suspension of fibers in alternative exemplary embodiments.

[0075] As illustrated in FIG. 3, the system (200) includes a separator (210) and a tank (230). The separator (210) may be positioned between a headbox, e.g., a web forming system (10) (Fig. 1), and the tank (230). Additionally, the separator (210) may be positioned along a flow path for foam between the headbox and the tank (230). Thus, the separator (210) may receive foam flowing from the headbox to the tank (230). The separator (210) may be configured to separate free gas from the foam within the separator (210). The headbox and the separator (210) may be connected via pipes, piping, conduits, etc.

[0076] The separator (210) may include an inlet (220), a first outlet (222), and a second outlet (224). The inlet (220) may be in fluid communication with a head box, and a flow of foam (FF) may enter the separator (210) through the inlet (220). As shown, the separator (210) may include a plurality of inlets (220) in an exemplary embodiment. Each inlet (220) may be in fluid communication with and connected to each of the drain lines (92, 94, 96, 132, and 142) (Fig. 2). Thus, foam from various parts of the web forming system (10) may enter the separator (210) through each of the inlets (220). In another exemplary embodiment, two or more foam streams from the web forming system (10) are combined upstream of the separator (210) and can enter the separator (210) through a single inlet.

[0077] The first outlet (222) can be fluidly connected to the tank (230), and the foam flow (FF) can exit the separator (210) through the first outlet (222). Thus, the foam flow (FF) can pass through the first outlet (222) on the flow path for the foam between the headbox and the tank (230). The second outlet (224) can be fluidly connected to the vacuum source (270), and the free air flow (FA) can exit the separator (210) through the second outlet (224). Additionally, the vacuum source (270) can be operated to create a vacuum within the internal volume (216) of the separator (210). The vacuum within the internal volume (216) of the separator (210) can remove large bubbles from the foam within the separator (210) by suction. Then, free air from the large bubble can exit the separator (210) through the second outlet (224). In contrast, air entrained within the foam as dispersed bubbles is retained within the foam flow (FF) and can exit the separator (210) through the first outlet (222).

[0078] As described above, the separator (210) may be configured to remove free air from the foam flow (FF) passing through the separator (210) between the headbox and the tank (230). Gravity may facilitate the separation of free air from the foam within the separator (210). Additionally, relatively dense foam may settle toward the bottom portion (212) of the separator (210), and relatively less dense free air may rise toward the top portion (214) of the separator (210), which is assisted by a vacuum within the internal volume (216) of the separator (210). To help separate free air from the foam flow (FF), the first and second outlets (222, 224) may be spaced apart on the separator (210). For example, the separator (210) may extend along the vertical direction (V), for example, between the bottom portion (212) and the top portion (214). The first outlet (222) may be located at the bottom portion (212) of the separator (210), and the second outlet (224) may be located at the top portion (214) of the separator (210). Thus, for example, the first and second outlets (222, 224) may be spaced apart along the vertical direction (V) on the separator (210) and / or may be located opposite each other along the vertical direction (V) on the separator (210). Additionally, the first outlet (222) may be positioned to accommodate a relatively dense foam that sinks toward the bottom (212) of the separator (210), and the second outlet (224) may be positioned to accommodate a relatively less dense free air that rises toward the top (214) of the separator (210). The inlet(s) (220) may be positioned, for example, along the vertical direction (V) between the first and second outlets (222, 224). Thus, the flow (FF) of foam may enter the internal volume (216) of the separator (210) between the first and second outlets (222, 224) and / or in the middle portion of the separator (210).

[0079] The tank (230) can be fluidly connected to the separator (210). Additionally, the foam flow (FF) can exit the separator (210) through the first outlet (222) and flow into the tank (230). The separator (210) and the tank (230) can be connected via pipes, piping, conduits, etc. Within the tank (230), water, surfactant(s), or other fluids may be added to the foam within the tank (230). The tank (230) can also be fluidly connected to a headbox, for example, a web forming system (10) (Fig. 2), so that the foam within the tank (230) can be reintroduced into the headbox for foam formation of a nonwoven web. Thus, the tank (230) can be configured to recirculate the foam flow (FF) into the foam forming process. The tank (230) and the headbox may be connected via pipes, piping, conduits, etc. In a given exemplary embodiment, the internal volume (232) of the tank (230) may be adjacent to the ambient atmosphere. Thus, for example, the pressure within the internal volume (232) of the tank (230) may be greater than the vacuum within the internal volume (216) of the separator (210) during the operation of the system (200). In an exemplary embodiment, the internal volume (232) of the tank (230) may be adjacent to the ambient atmosphere through a valve (234). In another exemplary embodiment, the top portion of the tank (230) may include an opening or other connection to the ambient atmosphere. The internal volume (232) of the tank (230) may be larger than the internal volume (216) of the separator (210). For example, the internal volume (232) of the tank (230) may be more than 2 times (2X), more than 5 times (5X), or more than 10 times (10X) the internal volume (216) of the separator (210).

[0080] The system (200) also includes a feature for maintaining the liquid level of the foam (LF) in the separator (210). As illustrated in FIG. 3, the system (200) includes a pump (240) and a sensor (250). The pump (240) may be positioned along a flow path for the foam between the headbox and the tank (230). For example, the pump (240) may be positioned downstream of the first outlet (222), for example, between the separator (210) and the tank (230). The pump (240) may be operable to cause the foam to flow out of the internal volume (216) of the separator (210) through the first outlet (222). Additionally, the flow (FF) of the foam may exit the separator (210) at the first outlet (222) during the operation of the pump (240). In a given exemplary embodiment, the pump (240) may be a positive displacement pump, such as a rotary, reciprocating, or linear positive displacement pump. Using a positive displacement pump may, for example, be advantageously aided in pumping foam from the separator (210) through the first outlet (222) during the operation of the pump (240) due to the positive displacement pump's ability to handle viscous fluids more efficiently than a centrifugal pump. Since the foam in the foam flow (FF) may be non-Newtonian, the density and viscosity of the foam in the foam flow (FF) may vary based on location and process. Therefore, when the pump (240) is a positive displacement pump, the pump (240) may be particularly suitable for pumping foam. However, it will be understood that the pump (240) may be a centrifugal pump in an alternative exemplary embodiment.

[0081] The sensor (250) may be operable to determine the foam liquid level (LF) in the separator (210). For example, the sensor (250) may detect and / or measure the height of the foam liquid level (LF) along, for example, the vertical direction (V) within the internal volume (216) of the separator (210). The foam liquid level (LF) may correspond to the boundary between the foam and free air within the internal volume (216) of the separator (210). For example, as previously described, the separator (210) may separate free air from the foam within the separator (210). The free surface of the foam facing the upper portion (214) of the separator (210) may correspond to the foam liquid level (LF) in the separator (210). The sensor (250) may be configured to detect the foam liquid level (LF). For example, the sensor (250) may be a capacitive rod mounted on the separator (210) and extending into the internal volume (216) of the separator (210). For example, the capacitive rod may be mounted on the separator (210) at the top portion (214) of the separator (210) and may extend downward along the vertical direction (V) toward the bottom portion (212) of the separator (210). The capacitive rod may detect a change in capacity that varies as a function of the foam liquid level (LF) within the separator (210) and may output a signal corresponding to the foam liquid level (LF) within the separator (210). Other sensors may be used to detect the foam liquid level (LF) in the separator (210). For example, the sensor (250) may include an optical sensor, a camera, an ultrasonic sensor, a radar sensor, etc., configured to detect the liquid level (LF) of the foam in the separator (210) and output a signal corresponding to the liquid level (LF) of the foam in the separator (210).

[0082] The system (200) may also include a processing unit or controller (260) that may be generally configured to facilitate the operation of at least a part of the system (200), or may communicate operably with it. In this regard, the pump (240), the sensor (250), and other components of the system (200) may communicate with the controller (260). Thus, for example, the controller (260) may receive input from the sensor (250) and may adjust the operation of the pump (260) based at least partially on the input from the sensor (250). The pump (240), the sensor (250), and other components of the system (200) may communicate with the controller (260), for example, via one or more signal lines or a shared communication bus. In this way, input / output ("I / O") signals may be routed between the controller (260) and various operating components of the system (200).

[0083] As used herein, the terms “processing unit,” “computing unit,” “controller,” etc. may generally refer to any suitable processing unit, such as a general-purpose or special-purpose microprocessor, microcontroller, integrated circuit, application-specific integrated circuit (ASIC), digital signal processor (DSP), field programmable gate array (FPGA), logic device, one or more central processing units (CPU), graphics processing units (GPU), other processing units performing special calculations, semiconductor devices, etc. Additionally, these “controllers” are not necessarily limited to a single element and may include any suitable number, type, and configuration of processing units integrated in any suitable manner to facilitate device operation. Alternatively, the controller (260) may be configured using a combination of discrete analog and / or digital logic circuits (e.g., switches, amplifiers, integrators, comparators, flip-flops, AND / OR gates, etc.) to perform control functions instead of using a microprocessor and, for example, relying on software.

[0084] The controller (260) may include or be associated with one or more memory elements or non-transient computer-readable storage media, such as RAM, ROM, EEPROM, EPROM, flash memory devices, magnetic disks, or other suitable memory devices (including combinations thereof). These memory devices may be components separate from the processor or may be embedded within the processor. Additionally, these memory devices may store information and / or data accessible by one or more processors, including instructions that can be executed by one or more processors. It should be understood that instructions may be software written in any suitable programming language or may be implemented in hardware. Additionally or alternatively, instructions may be executed logically and / or virtually using separate threads on one or more processors.

[0085] For example, the controller (260) may be operable to execute programming instructions or microcontrol code associated with the operating cycle of the system (200). In this regard, the instructions may be software or any set of instructions that, when executed by the processing unit, cause the processing unit to perform operations such as executing one or more software applications and adjusting the operating parameters of the pump (240). Additionally, it should be noted that the controller (260) as disclosed herein may be operable to perform any method, method step, or part of the method as disclosed herein. For example, in some exemplary embodiments, the method disclosed herein may be implemented in programming instructions stored in memory and executed by the controller (260).

[0086] The memory device may also store data that can be retrieved, manipulated, generated, or stored by one or more processors or parts of the controller (260). The data may include, for example, data to facilitate the execution of the method described herein. The data may be stored locally (e.g., on the controller (260)) in one or more databases and / or distributed so that the data is stored in multiple locations. Additionally or alternatively, one or more database(s) may be connected to the controller (260) through any suitable network(s), for example, a high-bandwidth local area network (LAN) or a wide area network (WAN). In this regard, for example, the controller (260) may further include a communication module or interface that can be used to communicate with one or more other components(s) of the system (200), the controller (260), or any other suitable device, for example, through any suitable communication line or network(s) and using any suitable communication protocol. A communication interface may include any suitable component for interfacing with one or more networks, such as a transmitter, a receiver, a port, a controller, an antenna, or other suitable components.

[0087] The controller (260) may be configured to control the operation of the pump (240) to maintain the liquid level (LF) of the foam within the separator (210). For example, the controller (260) may receive a signal from the sensor (250) corresponding to the liquid level (LF) of the foam within the separator (210). Based at least partially on the liquid level (LF) of the foam within the separator (210), the controller (260) may operate the pump (240) to maintain the liquid level (LF) of the foam within a determined range within the separator (210). For example, the controller (260) may adjust the operation of the pump (240) to increase the flow rate of the foam flow (FF) from the separator (210) in response to the detected liquid level (LF) of the foam from the sensor (250) being greater than the determined range (R). Conversely, the controller (260) may adjust the operation of the pump (240) to reduce the flow rate of the foam flow (FF) from the separator (210) in response to the detected foam liquid level (LF) from the sensor (250) being below a determined range (R). The determined range (R) may be selected to limit or prevent over-discharge and / or under-discharge of the foam from the separator (210). For example, the lower limit of the determined range (R) may be located above the first outlet (222) along the vertical direction (V), and the upper limit of the determined range (R) may be located below the second outlet (224) along the vertical direction (V). As a specific example, the lower limit of the determined range (R) may be located at least 25 cm above the first outlet (222) along the vertical direction (V), and the upper limit of the determined range (R) may be located at least 25 cm below the second outlet (224) along the vertical direction (V). Such spacing may advantageously help to limit or prevent over-discharge and / or under-discharge of foam from the separator (210). In an exemplary embodiment, the determined range (R) may be less than 50 cm, less than 25 cm, less than 10 cm, etc. along the vertical direction (V).This size of the determined range (R) can help provide a consistent residence time for the foam in the separator (210) during the operation of the system (200).

[0088] As illustrated in FIG. 3, the system (200) may also include an additional pump (280). The additional pump (280) may be positioned downstream of the tank (230). The additional pump (280) may be operable to flow foam from the tank (230) to a headbox, e.g., a web forming system (10) (Fig. 2). In an exemplary embodiment, the additional pump (280) may include a fan pump. By maintaining the liquid level (LF) of the foam within a determined range (R), the additional pump (280) may operate with increased efficiency and rigidity. Additionally, in an exemplary embodiment, the additional pump (280) may not use vacuum assistance due to the pump (240) maintaining the liquid level (LF) of the foam within the determined range (R).

[0089] FIG. 4 illustrates a method (400) for forming a foam according to an exemplary embodiment of the subject matter. For example, the method (400) may be used in or with the system (200) (Fig. 3) to help maintain the liquid level of the foam within a vacuum separator. The controller (260) of the system (200) may be programmed or configured to implement the method (400). Although the method (400) is described in more detail below in the context of the system (200), it will be understood that the method (400) may be used in or within any suitable system or process in alternative exemplary embodiments.

[0090] In 410, the foam can flow from a headbox, such as a web forming system (10) (Fig. 2), to a vacuum separator, such as a separator (210) (see Fig. 3). Thus, the flow (FF) of the foam can enter the separator (210) in 410. In 420, free air from the foam can flow out of the vacuum separator, for example, through a second outlet (224).

[0091] In 430, the liquid level of the foam within the vacuum separator can be determined. For example, a sensor (250) can detect and / or measure the liquid level (LF) of the foam within the internal volume (216) of the separator (210) in 430, and the sensor (250) can output a signal corresponding to the liquid level (LF) of the foam. In 440, the liquid level (LF) of the foam can be compared with a determined range. For example, a controller (260) can compare the determined liquid level (LF) of the foam from the sensor (250) with a determined range.

[0092] The method (400) may also include the operation of a pump controller based on comparing the liquid level of the foam with a determined range. For example, in 450, the operating parameters of the pump may be adjusted to change the flow rate of the foam from the vacuum separator when the detected liquid level of the foam is outside the determined range. In a given exemplary embodiment, in 450, the controller (260) may increase the operating speed of the pump (240) to increase the flow rate of the foam flow (FF) from the separator (210) when the detected liquid level (LF) of the foam from the sensor (250) is greater than the determined range (R). Conversely, in this exemplary embodiment, the controller (260) may decrease the operating speed of the pump (240) in 450 to decrease the flow rate of the foam flow (FF) from the separator (210) when the detected liquid level (LF) of the foam from the sensor (250) is less than the determined range (R). In 460, the operating parameters of the pump may be maintained or supported to maintain a constant flow rate of the foam from the vacuum separator when the detected liquid level of the foam is within a determined range. In a given exemplary embodiment, in 460, the controller (260) may maintain the operating speed of the pump (240) to maintain a constant flow rate of the foam (FF) from the separator (210) when the detected liquid level (LF) of the foam from the sensor (250) is within a determined range (R).

[0093] In an exemplary embodiment, the average residence time of the foam in the vacuum separator may be substantially constant during the method (400). Thus, for example, the average residence time of the foam in the separator (210) may vary during the method (400), such as less than 1 minute, less than 30 seconds, less than 10 seconds, etc. Such a consistent residence time may advantageously improve the stability of the foam during the method (400).

[0094] During method (400), the interior of the vacuum separator may be under vacuum. Thus, for example, a vacuum source (270) may operate during method (400) to create a vacuum within the internal volume (216) of the separator (210) to suck and remove large bubbles from the foam within the separator (210). During method (400), the internal volume of the backwater tank receiving the flow of foam from the vacuum separator may be adjacent to the surrounding atmosphere. Thus, for example, because the flow (FF) of foam exits the separator (210) and flows into the tank (230), the internal volume (232) of the tank (230) may be adjacent to the surrounding atmosphere during method (400).

[0095] FIG. 4 illustrates steps performed in a specific order for the purpose of illustration and discussion. Those skilled in the art will understand that, by using the disclosures provided herein, steps of any of the methods described herein may be adapted, rearranged, extended, omitted, or modified in various ways without departing from the scope of the invention.

[0096] A person skilled in the art can practice these examples and other modifications and variations of the present invention without departing from the spirit and scope of the invention as more specifically described in the claims. Furthermore, it should be understood that aspects of the various embodiments may be interchangeable in whole or in part. In addition, a person skilled in the art will recognize that the foregoing description is merely illustrative and is not intended to limit the invention as further described in these claims.

[0097] Exemplary Examples

[0098] First exemplary embodiment: A foam forming system, wherein the system comprises: a head box; a tank; a separator disposed between the head box and the tank along a flow path for foam between the head box and the tank, wherein the separator comprises an inlet for foam, a first outlet for foam, and a second outlet for free air from foam; a pump; a sensor operable to determine a liquid level of foam within the separator; and a controller configured to receive a signal from the sensor corresponding to a liquid level of foam within the separator and, based at least partially on a liquid level of foam within the separator, to operate the pump to maintain a liquid level of foam within a determined range within the separator.

[0099] Second exemplary embodiment: A foam forming system in the first exemplary embodiment, further comprising an additional pump positioned downstream of the tank in a flow path for foam between the tank and the head box, wherein the additional pump is operable to flow the foam along the flow path between the head box and the tank.

[0100] Third exemplary embodiment: In the second exemplary embodiment, the additional pump comprises a fan pump, forming a foam system.

[0101] Fourth exemplary embodiment: A foam forming system in any one of the first to third exemplary embodiments, wherein the inlet is positioned between the first and second outlets along a vertical direction.

[0102] Fifth exemplary embodiment: A foam forming system in any one of the first to fourth exemplary embodiments, wherein the first outlet is located at the bottom portion of the separator and the second outlet is located at the top portion of the separator.

[0103] Sixth exemplary embodiment: A foam forming system in any one of the first to fifth exemplary embodiments, further comprising a vacuum source coupled to the separator through a second outlet of the separator, wherein the vacuum source is operable to create a vacuum within the internal volume of the separator.

[0104] 7th exemplary embodiment: In the 6th exemplary embodiment, the internal volume of the tank is adjacent to the surrounding atmosphere, a foam forming system.

[0105] Eighth exemplary embodiment: A foam forming system in any one of the first to seventh exemplary embodiments, wherein the pump comprises a positive displacement pump.

[0106] Ninth exemplary embodiment: In any one of the first to eighth exemplary embodiments, the sensor comprises a capacitive load, a foam forming system.

[0107] 10th exemplary embodiment: A foam forming system in any one of the 1st to 9th exemplary embodiments, wherein the volume of the tank is greater than the volume of the separator.

[0108] 11th Exemplary Embodiment: A foam forming system, wherein the system comprises: a tank; a vacuum separator coupled to the tank through the first outlet so as to allow the foam to flow from the vacuum separator to the tank, the vacuum separator comprising an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam; a pump operable to flow the foam from the vacuum separator to the tank; a sensor operable to determine the liquid level of the foam in the vacuum separator; and a controller configured to determine the liquid level of the foam in the vacuum separator based at least partially on a signal from the sensor, and to operate the pump to maintain the liquid level of the foam within a determined range in the vacuum separator based at least partially on the determined liquid level of the foam in the vacuum separator.

[0109] 12th Exemplary Embodiment: In the 11th Exemplary Embodiment, a foam forming system further comprising an additional pump disposed downstream of the tank, wherein the additional pump is operable to cause the foam to flow from the tank.

[0110] 13th Exemplary Embodiment: A foam forming system in which, in either the 11th or 12th Exemplary Embodiment, the inlet is positioned between the first and second outlets along a vertical direction.

[0111] 14th exemplary embodiment: A foam forming system in any one of the 11th to 13th exemplary embodiments, wherein the first outlet is located at the bottom portion of the vacuum separator and the second outlet is located at the top portion of the vacuum separator.

[0112] 15th Exemplary Example: A foam forming system in any one of the 11th to 14th exemplary examples, further comprising a vacuum source coupled to the vacuum separator through a second outlet of the vacuum separator, wherein the vacuum source is operable to create a vacuum within the internal volume of the vacuum separator.

[0113] 16th Exemplary Example: In the 15th Exemplary Example, the internal volume of the tank is adjacent to the surrounding atmosphere, a foam forming system.

[0114] 17. Exemplary Embodiment: A method for forming a foam, the method comprising: a step of flowing a foam from a head box to a vacuum separator; a step of flowing free air from the foam out of the vacuum separator through a vacuum outlet of the vacuum separator; and a step of operating a pump to flow the foam out of the vacuum separator through a foam outlet of the vacuum separator, wherein the step of operating the pump comprises a step of determining the liquid level of the foam in the vacuum separator by a sensor and a step of adjusting the flow rate of the pump to maintain the liquid level of the foam within a determined range in the vacuum separator based at least partially on the determined liquid level of the foam in the vacuum separator.

[0115] 18th Exemplary Example: In the 17th Exemplary Example, the interior of the vacuum separator is under vacuum.

[0116] 19th exemplary embodiment: A method in which the residence time of the foam in the vacuum separator is substantially constant in either the 17th exemplary embodiment or the 18th exemplary embodiment.

Claims

Claim 1 A foam forming system for forming a web, comprising: a head box; a tank; a separator disposed between the head box and the tank along a flow path for the foam between the head box and the tank, and comprising an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam; a pump disposed along a flow path between the head box and the tank; a sensor operable to determine the liquid level of the foam within the separator; and a controller, wherein the controller is configured to receive a signal from the sensor corresponding to the liquid level of the foam within the separator and, at least partially based on the liquid level of the foam within the separator, operate the pump to maintain the liquid level of the foam within a determined range within the separator. Claim 2 A foam forming system according to claim 1, further comprising an additional pump positioned downstream of the tank in a flow path for foam between the tank and the head box, wherein the additional pump is operable to flow the foam along the flow path between the head box and the tank. Claim 3 In paragraph 2, the foam forming system, wherein the additional pump includes a fan pump. Claim 4 A foam forming system according to any one of claims 1 to 3, wherein the inlet is disposed between the first and second outlets along the vertical direction. Claim 5 A foam forming system according to any one of claims 1 to 3, wherein the first outlet is located at the bottom of the separator and the second outlet is located at the top of the separator. Claim 6 A foam forming system according to any one of claims 1 to 3, further comprising a vacuum source coupled to the separator through a second outlet of the separator, wherein the vacuum source is operable to generate a vacuum within the internal volume of the separator. Claim 7 In paragraph 6, the internal volume of the tank is a foam forming system adjacent to the surrounding atmosphere. Claim 8 A foam forming system according to any one of claims 1 to 3, wherein the pump comprises a positive displacement pump. Claim 9 A foam forming system according to any one of claims 1 to 3, wherein the sensor comprises a capacitive load. Claim 10 A foam forming system according to any one of claims 1 to 3, wherein the volume of the tank is larger than the volume of the separator. Claim 11 A foam forming system for forming a web, comprising: a tank; a vacuum separator comprising an inlet for a foam, a first outlet for a foam, and a second outlet for free air from the foam, wherein the vacuum separator is coupled to the tank through the first outlet so as to allow the foam to flow from the vacuum separator to the tank; a pump operable to cause the foam to flow from the vacuum separator to the tank; a sensor operable to determine the liquid level of the foam within the vacuum separator; and a controller, wherein the controller is configured to determine the liquid level of the foam within the vacuum separator based at least partially on a signal from the sensor, and to operate the pump to maintain the liquid level of the foam within a determined range within the vacuum separator based at least partially on the determined liquid level of the foam within the vacuum separator. Claim 12 A foam forming system according to claim 11, further comprising an additional pump disposed downstream of the tank, wherein the additional pump is operable to cause the foam to flow from the tank. Claim 13 A foam forming system according to claim 11 or 12, wherein the inlet is positioned between the first and second outlets along the vertical direction. Claim 14 A foam forming system according to claim 11 or 12, wherein the first outlet is located at the bottom of the vacuum separator and the second outlet is located at the top of the vacuum separator. Claim 15 A foam forming system according to claim 11 or 12, further comprising a vacuum source coupled to the vacuum separator through a second outlet of the vacuum separator, wherein the vacuum source is operable to generate a vacuum within the internal volume of the vacuum separator. Claim 16 In paragraph 15, the internal volume of the above tank is a foam forming system adjacent to the surrounding atmosphere. Claim 17 A method for forming a foam web, comprising: a step of flowing a foam from a head box to a vacuum separator; a step of flowing free air from the foam out of the vacuum separator through a vacuum outlet of the vacuum separator; and a step of operating a pump to flow the foam out of the vacuum separator through a foam outlet of the vacuum separator, wherein the step of operating the pump comprises a step of determining the liquid level of the foam in the vacuum separator by a sensor and a step of adjusting the flow rate of the pump to maintain the liquid level of the foam within a determined range in the vacuum separator based at least partially on the determined liquid level of the foam in the vacuum separator. Claim 18 In paragraph 17, the method wherein the interior of the vacuum separator is under vacuum. Claim 19 A method according to claim 17 or 18, wherein the residence time of the foam in the vacuum separator is substantially constant.

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