Patent Application
20180243943
The present invention relates to a mixer and mixing method, and more specifically, a scraper-type mixer and mixing method for preparation of gypsum slurry in which a rotary driving device is located above or below a housing and a rotary disc is rotated by a rotary shaft of the rotary driving device extending through an upper or bottom plate of the housing.
A gypsum board is known as a board having a gypsum core covered with sheets of paper for gypsum board liner. The gypsum boards are widely used in various kinds of buildings as architectural interior finish materials because of their advantageous fire-resisting or fire-protecting ability, sound insulation performance, workability, cost performance and so on. In general, the gypsum boards are produced by a continuous pouring and casting process. This process comprises a mixing and stirring step of admixing calcined gypsum, adhesive auxiliary agent, set accelerator, foam (or foaming agent), and so forth with a quantity of mixing water in a mixer; a forming step of pouring calcined gypsum slurry prepared in the mixer (referred to as “slurry” hereinafter) into a space between sheets of paper for gypsum board liner and forming them into a continuous plate-like belt form; and a drying and cutting step of roughly cutting the solidified continuous belt-like layered formation, drying it forcibly and thereafter, trimming it to be a product size.
Usually, a thin and circular pin-type mixer (also called as a “centrifugal pin-type mixer”) is used as the mixer for preparing the slurry in the gypsum board production process and so forth. This type of mixer comprises a flattened circular housing and a rotary disc rotatably positioned in the housing, as disclosed in, for example, PCT Pamphlet of PCT International Application No. WO 00/56435 (Patent Literature 1). A rotary driving device is located above the housing. A rotary shaft of the rotary driving device extends through a center part of the upper cover or upper plate of the housing. The shaft is fixed to a center part of the rotary disc. The upper plate of the housing is equipped with a plurality of upper pins (stationary pins). The upper pins depend from the upper plate down to the vicinity of the rotary disc. The rotary disc is equipped with lower pins (movable pins). The lower pins are vertically fixed on the disc and extend up to the vicinity of the upper plate. The upper and lower pins are arranged in radially alternate positions. A plurality of ingredient feeding ports for feeding the aforementioned materials into the mixer are disposed in a center region of the top cover or upper plate of the housing. The materials to be mixed and kneaded are supplied onto the disc through the respective feeding ports. The materials are mixed and kneaded while being moved radially outward on the disc under an action of centrifugal force. A slurry discharge port for delivering the mixture (slurry) out of the mixer is provided on a periphery of the housing or a lower plate (bottom plate) thereof. The slurry is delivered out of the mixer through the slurry discharge port.
As another type of mixer, a scraper-type mixer is known in the art. This type of mixer stirs the ingredients to be mixed with the use of a rotary disc and a scraper. For example, the mixer as disclosed in Japanese Patent Laid-Open Publication No. 7-1437 (Patent Literature 2) comprises a flattened circular housing and a rotary disc rotatably positioned in the housing, similarly to the pin-type mixer as set forth above. A rotary driving device is located below the housing. A rotary shaft of the rotary driving device extends through a center part of the lower plate (bottom plate) of the housing. The shaft is fixed to a center part of the rotary disc. A scraper is attached to a lower surface of the disc. Furthermore, another scraper is positioned under an upper cover or upper plate, in the vicinity of its underside surface. The upper and lower scrapers rotate together with the rotating disc. The materials to be mixed and kneaded and the mixing water are supplied onto the disc through respective feeding ports of the upper cover or plate. The materials and water are stirred and mixed while being moved radially outward on the disc under an action of centrifugal force, and then, are delivered out of the mixer through a slurry discharge port.
[Patent Literature 1] PCT Pamphlet No. WO 00/56435
As described above, the pin-type mixer and the scraper-type mixer are known in the art, as mixers for preparation of the gypsum slurry. The pin-type mixer can mix and knead the gypsum slurry necessarily and sufficiently in a short period of time. Therefore, the strength of set gypsum can be improved. Thus, the pin-type mixer is considered advantageous for ensuring the strength of the set gypsum. For such reasons, the pin-type mixers are used in many production processes for production of gypsum boards, at present.
However, in the pin-type mixer, many pins are attached to the disc. Therefore, the mixer has a large number of mechanical parts. In addition, relatively frequent maintenance and care of the pins, replacement of the pins, and so forth are required because of abrasion or wear of the pins. Thus, costs for maintenance and care are increased and a great deal of manpower is required for replacement of the pins and so forth. This is one of the problems of the pin-type mixer. Furthermore, the many pins are located in the mixing area of the pin-type mixer. Therefore, a relatively large number of narrow regions or dead water regions exist in the mixing area. The slurry tends to stay in such regions. This is another problem of the pin-type mixer, which has been already recognized. Furthermore, the pin-type mixer is considered advantageous for improvement of the strength of the set gypsum. However, a so-called “re-tempering” phenomenon owing to excessive mixing and kneading is apt to occur. This may result in a problem of reduction in the strength of the set gypsum.
On the other hand, the mixing area of the scraper-type mixer has a relatively simple configuration. Therefore, this type of mixer is advantageous for simplification of maintenance and care. In addition, the narrow regions or dead water regions in which the gypsum slurry is apt to stay are hardly generated in the mixing area of the scraper-type mixer. This is advantageous for preventing the stay and adhesion of the slurry in or to the interior of the mixer, and so forth.
As regards the scraper-type mixer, a position of an internal end of the scraper, the number of the scrapers, the orientation and position of the scraper, and so forth have to be designed. Therefore, when designing these matters, it is necessary to take into consideration: a positional interference of the internal end of the scraper, with respect to the rotary shaft, powder inlet port, liquid inlet port; prevention of the stay of the gypsum slurry in a center region of the rotary disc; and so on. Thus, it is very difficult to optimize the number of scrapers, the configuration, orientation and position of the scraper, and so forth in such a manner that a delivery pressure of the slurry is sufficiently obtained by means of centrifugal forces or rotational powers of the rotary disc and the scraper. For instance, the scraper-type mixer as disclosed in Patent Literature 2 has a slurry discharge port positioned on a lower plate. This is because the slurry is discharged from the mixing area, relatively greatly depending on gravity. However, in the arrangement that the slurry is gravitationally discharged, the position of the slurry discharge port is limited to the lower plate (or a lower part of an annular wall in vicinity of the lower plate). Therefore, the positional relationship between the mixer and a production line is limited. This results in loss of design flexibility of a gypsum board manufacturing apparatus.
In the scraper-type mixer, as the position of the slurry discharge port depends on the gravity, retention time of the slurry is relatively short. Therefore, it is difficult to mix and knead the slurry uniformly and sufficiently in the mixing area. Thus, a set slurry mass, which is obtained from the slurry produced by the scraper-type mixer, is considered to hardly exert its sufficient strength. However, according to the studies and findings of the present inventors in recent years, it is possible to uniformly and sufficiently mix and knead the slurry and ensure the desirable strength of the set slurry mass, if the number of the scrapers, the orientation and position of the scraper, and so forth, are appropriately predetermined, and the location of the slurry discharge port is preset in a position mainly depending on the centrifugal forces or rotational powers of the rotary disc and the scraper.
It is an object of the present invention to provide a scraper-type mixer and mixing method that can increase the retention time of the gypsum slurry in the mixing area, whereby the slurry can be sufficiently mixed and kneaded in the mixing area.
Furthermore, it is an object of the present invention to provide a scraper-type mixer and mixing method that can uniformize the density distribution and the velocity distribution of the slurry in the mixing area, whereby the slurry can be uniformly mixed and kneaded in the mixing area.
Furthermore, it is an object of the present invention to provide a scraper-type mixer and mixing method wherein a scraper can be suitably positioned in a housing of the mixer and wherein the slurry discharge port can be positioned in a vertically center region of an annular wall, or at a higher location on the wall.
The present invention provides a mixer for preparation of gypsum slurry, which has a circular housing defining a mixing area for mixing and kneading of the gypsum slurry, a rotary disc positioned in the housing and rotated in a predetermined rotational direction, a rotary driving shaft integrally connected with the rotary disc, a scraper positioned in the mixing area, and a slurry discharge port provided on the housing for feeding the gypsum slurry of the mixing area onto a production line;
wherein said rotary driving shaft extends through an upper or lower plate of said housing to be connected with said rotary disc;
wherein an inner end portion of said scraper is positioned in a center region of said rotary disc, an outer end portion of the scraper is positioned in a peripheral zone of the disc, and said slurry discharge port is positioned on an annular wall of said housing; and
wherein said slurry discharge port is provided with a fluid passage dividing member which divides an opening of the port into a plurality of narrow openings so as to increase fluid resistance on the gypsum slurry flowing out of said mixing area through said opening of the port.
From another aspect of the invention, the present invention provides a mixing method for gypsum slurry with use of a mixer for preparation of the gypsum slurry, the mixer having a circular housing defining a mixing area for mixing and kneading of the gypsum slurry, a rotary disc positioned in the housing and rotated in a predetermined rotational direction, a rotary driving shaft integrally connected with the rotary disc, a scraper positioned in the mixing area, and a slurry discharge port provided on the housing for feeding the gypsum slurry of the mixing area onto a production line;
wherein an inner end portion of said scraper is positioned in a center region of said rotary disc, an outer end portion of the scraper is positioned in a peripheral zone of the disc, said slurry discharge port is positioned on an annular wall of said housing, and an opening of said slurry discharge port is divided into a plurality of narrow openings so as to increase fluid resistance on the gypsum slurry flowing out of said mixing area through said opening of the port; and
wherein said rotary driving shaft extends through an upper or lower plate of said housing, and the shaft rotates said rotary disc and said scraper about a rotational axis of the shaft so that said slurry is mixed and kneaded in said mixing area and the slurry is moved toward the periphery of the mixing area by centrifugal force acting on the slurry, whereby the slurry flows out of said mixing area through said slurry discharge port.
According to the above arrangement of the present invention, the fluid resistance at the slurry discharge port is increased, so that the retention time of the slurry in the mixing area is so extended as to enable sufficient mixing and kneading of the gypsum slurry in the mixing area. Preferably, the opening of the slurry discharge port is divided into a plurality of slits or narrow fluid passages by horizontal, vertical, or lattice guide member. A total area of the slurry discharge port, which includes a fractionation port (or ports), is set to be in a range, preferably, from 2% to 10%, more preferably, from 3% to 8% of a total area of an inner circumferential surface of the annular wall. Furthermore, an open area ratio of the slurry discharge port (including the fractionation port(s)) is set to be in a range, preferably, from 50% to 80%, more preferably, from 55% to 75%.
The present invention also provides a mixer for preparation of gypsum slurry, which has a circular housing defining a mixing area for mixing and kneading of the gypsum slurry, a rotary disc positioned in the housing and rotated in a predetermined rotational direction, a rotary driving shaft integrally connected with the rotary disc, a scraper positioned in the mixing area, and a slurry discharge port provided on the housing for feeding the gypsum slurry of the mixing area onto a production line;
wherein said rotary driving shaft extends through an upper or lower plate of said housing to be connected with said rotary disc; and
wherein an inner end portion of said scraper is positioned in a center region of said rotary disc, an outer end portion of the scraper is positioned in a peripheral zone of the disc, and the scraper is bent or curved backward in a rotational direction of the disc between said inner and outer end portions.
From another aspect of the invention, the present invention provides a mixing method for gypsum slurry with use of a mixer for preparation of the gypsum slurry, the mixer having a circular housing defining a mixing area for mixing and kneading of the gypsum slurry, a rotary disc positioned in the housing and rotated in a predetermined rotational direction, a rotary driving shaft integrally connected with the rotary disc, a scraper positioned in the mixing area, and a slurry discharge port provided on the housing for feeding the gypsum slurry of the mixing area onto a production line;
wherein an inner end portion of said scraper is positioned in a center region of said rotary disc, an outer end portion of the scraper is positioned in a peripheral zone of the disc, and the scraper is bent or curved backward in a rotational direction of the disc, between said inner and outer end portions; and
wherein said rotary driving shaft extends through an upper or lower plate of said housing, and the shaft rotates said rotary disc and said scraper about a rotational axis of the shaft so that said slurry is mixed and kneaded in said mixing area.
According to the above arrangement of the present invention, the scraper, which is bent or curved backward in the rotational direction, uniformizes the density distribution of the slurry and the fluid velocity distribution of the slurry, respectively, in the mixing area. Therefore, the slurry can be uniformly mixed in the mixing area. For instance, in a case where the scraper is bent in only one position, an angle of a bending part is set to be, preferably, an angle in a range of 45±15 degrees, more preferably, an angle in a range of 45±10 degrees. Preferably, the scraper has a plurality of the bending parts, or the scraper is generally curved, whereby the scraper extends outward from a center area of the mixer, substantially along an involute curve. Preferably, a distal end portion of the scraper is oriented at an angle in a range of 75±15 degrees with respect to a radial direction of the mixing area.
Preferably, an annular basal part is positioned in the mixing area in concentricity with a rotational center of the rotary disc, wherein the annular basal part is rotated integrally with the rotary disc in the housing, and wherein the inner end portion of the scraper is fixed to the annular basal part, so that the scraper is supported horizontally. With such an arrangement, a device, which supports the inner end portion of the scraper, can be ensured in a center part of the rotary disc, so that the inner end portion of the scraper can be firmly supported. Furthermore, the annular basal part prevents a slurry staying region or a dead water region from being formed in the center region of the rotary disc. Therefore, the inner end portion of the scraper can be positioned in the center region of the rotary disc. In addition, the annular basal part improves flexibility in design of the number of the scrapers, orientation and position of each of the scrapers, and so forth. Thus, according to the present invention, a delivery pressure of the slurry can be improved by optimizing the number of scrapers, orientation and position of each of the scrapers, and so forth, and thus, the slurry discharge port can be positioned in a vertically center region of the annular wall or at a higher location on the wall.
More preferably, a center axis of the scraper is oriented in a direction at an angle ranging from 60 degrees to 120 degrees with respect to a line segment passing through a supporting center of the scraper and a center of rotation of the rotary disc. Desirably, a diameter of the annular basal part is set to be three or more times as large as a diameter of the rotary driving shaft, and the inner end portion of the scraper is fixed onto an upper surface of the annular basal part. More desirably, the center axis of the scraper is oriented in a direction perpendicular to the above line segment. According to such an arrangement, the slurry in the mixing area can be energized radially outward of the rotary disc by the scraper; therefore, the slurry discharge port can be provided in an optimized position of the annular wall of the housing.
Preferably, a pin is provided to stand on the periphery of the rotary disc, for augmenting the fluid flow of the slurry flowing out of the mixing area through the slurry discharge port. According to such an arrangement, the delivery pressure of the gypsum slurry can be further increased by the pin, which energizes or pushes the slurry moving to the periphery of the mixing area, in a tangential or radially outward direction of the rotary disc. Furthermore, a distal end portion of the scraper can be positionally matched with the pin and supported by the pin, whereby further stable support of the scraper can be ensured.
In the mixer with the scraper bent or curved backward in the rotational direction, the rotary disc is, preferably, formed with a gear tooth portion on the periphery of the rotary disc, instead of the above pin, for augmenting the fluid flow of the slurry flowing out of the mixing area through the slurry discharge port. According to such an arrangement, the slurry moving to the periphery of the mixing area is energized or pushed in the tangential direction or radially outward direction of the rotary disc by the gear tooth portion and the bent or curved scraper, so that the delivery pressure of the slurry is additionally increased.
According to the scraper-type mixer and mixing method in which the slurry discharge port is positioned on the annular wall and the opening of the port is divided into the narrow openings for increasing the fluid resistance on the slurry effluent from the mixing area, the retention time of the gypsum slurry in the mixing area can be increased, whereby the slurry can be sufficiently mixed in the mixing area.
Furthermore, according to the scraper-type mixer and mixing method in which the scraper is bent or curved backward in the rotational direction of the rotary disc, the density distribution of the slurry and the velocity distribution of the slurry in the mixing area can be uniformized, whereby the slurry can be uniformly mixed in the mixing area.
Furthermore, according to the scraper-type mixer and mixing method in which the annular basal part is positioned in the mixing area in concentricity with the center of rotation of the rotary disc and the inner end portion of the scraper is fixed to the annular basal part, the scraper can be suitably positioned in the housing of the mixer and the slurry discharge port can be positioned in a vertically center region of the annular wall, or at a higher location on the wall.
With reference to the attached drawings, preferred embodiments of the present invention are described hereinafter.
As shown in
The sheet 1 is conveyed together with the slurry 3 to reach a pair of forming rollers 18 (18a, 18b). An upper sheet of paper 2 travels partially around a periphery of the upper roller 18a to convert its direction toward a conveyance direction. The diverted sheet 2 is brought into contact with the slurry 3 on the lower sheet 1 and transferred in the conveyance direction substantially in parallel with the lower sheet 1. A continuous belt-like three-layered formation 5 constituted from the sheets 1,2, and the slurry 3 is formed on a downstream side of the rollers 18. This formation 5 runs continuously at a conveyance velocity V while a setting reaction of the slurry proceeds, and it reaches roughly cutting rollers 19 (19a, 19b). If desired, a variety of forming devices, such as the forming device depending on a passing-through action of an extruder or a gate with a rectangular opening, may be employed instead of the forming rollers 18.
The cutting rollers 19 sever the continuous belt-like layered formation into boards of a predetermined length so as to make boards, each having a gypsum core covered with the sheets of paper, in other words, green boards. The green boards are conveyed through a dryer (not shown) that is located toward a direction shown by an arrow J (on a downstream side in the conveyance direction), whereby the green boards are subjected to forced drying in the dryer. Thereafter, they are trimmed to be boards, each having a predetermined product length, and thus, gypsum board products are produced.
As shown in
A circular opening 25 is formed at a center part of the upper plate 21. An enlarged lower end portion 31 of a vertical rotary shaft 30 extends through the opening 25. The shaft 30 is connected with a rotary driving device (not shown), such as an electric drive motor, and driven in rotation in a predetermined rotational direction (clockwise direction R as seen from its upper side in this embodiment). If desired, a variable speed device, such as a variable speed gear mechanism or a variable speed belt assembly, may be interposed between the shaft 30 and an output shaft of the rotary driving device.
A powder supply conduit 15 is connected to the upper plate 21, for feeding the mixing area 10a with the powder ingredients P to be mixed. A water supply conduit 16 is also connected to the upper plate 21, for supplying a quantity of mixing water L to the area 10a. If desired, an internal pressure regulator and so forth (not shown) may be further connected to the upper plate 21, for limiting excessive increase in the internal pressure of the mixer 10.
Fractionation ports 8e, 8f, each of which may be regarded as a kind of slurry discharge port, are provided on the annular wall 23, on the opposite side of the section 4. The fractionation conduits 8a, 8b are connected to the ports 8e, 8f, respectively. In this embodiment, the ports 8e, 8f are positioned, angularly spaced at a predetermined angle α from each other.
A slurry discharge port 40, which constitutes the slurry delivery section 4, is formed on the annular wall 23, angularly spaced at a predetermined angle β from the fractionation port 8f in the rotational direction R (on the downstream side). The port 40 opens on an inner circumferential surface of the wall 23.
As shown in
A foam-feeding conduit 45 for feeding the foam or foaming agent M to the slurry is connected to a hollow connector section 41. A foam feeding port 46 opens on an internal wall surface of the section 41. The foam or foaming agent M for adjusting the volume of the slurry is fed to the slurry in the section 41 by the conduit 45.
The slurry and foam are introduced through the hollow connector section 41 into a vertical in-chute area (intratubular area) in the slurry delivery tube 42. The slurry and foam turn around the center axis of the tube 42, so that the slurry swirls in the in-chute area of the tube 42. The slurry and foam are subjected to a shearing force so as to be mixed with each other, whereby the foam is uniformly dispersed in the slurry. The slurry in the tube 42 gravitationally flows down in the in-chute area. Then, the slurry is delivered to the widthwise center area of the lower sheet 1 through the slurry outlet tube 7 (
In the housing 20, a rotary disc 32 is rotatably positioned. A lower face of the end portion 31 of the shaft 30 is fixedly secured to a center part of the disc 32. An axis of rotation or a center axis of the disc 32 coincides with the center axis 10b of the shaft 30. The disc 32 is rotated with rotation of the shaft 30 in a direction as indicated by the arrow R (clockwise direction).
As shown in
As shown in
As shown in
The fixing or anchoring tools 71 for supporting the inner end portion of the scraper 50 are positioned in a pair. As shown in
As shown in
The scraper 50 has a structure comprising a member 51 formed from a metal and an abrasion-resistant ceramic plate 52 embedded in an upper surface of the member 51. The scraper 50 has a cross-section of an isosceles trapezoid shape, which comprises horizontal upper and lower faces 53, 58, a vertical front and rear faces 54, 55, inclined front and rear faces 56, 57, and the distal end face 59. Inclination angles θ2, θ3 of the inclined faces 56, 57 with respect to the lower face 58 are substantially the same. The upper face 53 is spaced apart at a very small distance S from the lower surface of the upper plate 21. The distance S is set to be a value in a range from 1 to 5 mm. As shown in
As shown in
As shown in
As shown in
An open area ratio of the slurry discharge port 40 is set to be, preferably in a range from 50% to 80%, more preferably, in a range from 55% to 75%, wherein the open area ratio of the port 40 is defined by “A2/A1”, wherein “A1” is the total area of the port 40 along the inner circumferential surface of the annular wall, in other words, “W×T”, and wherein “A2” is an effective open area of the slit 48, in other words, “W×t×the number of slits”. In the example as illustrated in the figure, “the number of slits” is five. Similarly, the open area ratio of the fractionation port 8e, 8f is set to be, preferably in a range from 50% to 80%, more preferably, in a range from 55% to 75%, wherein the open area ratio of the port 8e, 8f is defined by “A4/A3”, wherein “A3” is the total area of the port 8e, 8f along the inner circumferential surface of the annular wall, and wherein “A4” is an effective open area of the port 8e, 8f.
Furthermore, the total area “A1+A3” of the slurry discharge port 40 and the fractionation ports 8e, 8f is set to be in a range from 2% to 10%, preferably in a range from 3% to 8%, with respect to the total area of the whole circumferential surface of the annular wall 23 (the diameter of the circumferential wall surface×3.14×the height of the circumferential wall surface).
Alternatively, the horizontal guide member 47 and the horizontal slit 48 may be modified to be a vertical guide member and a vertical slit, or the guide member may be inclined with respect to the fluid direction of the slurry. Furthermore, as shown in
In the mixer 10 as shown in
As shown in each of the figures included in
The annular basal part 70 is not necessarily integral with the rotary shaft 30 and the enlarged lower end portion 31, but the part 70 may be formed with an inner circumferential surface 76 spaced apart from an outer circumferential surface of the portion 31. In
The operation of the mixer 10 is described hereinafter.
In operation of the rotary driving device, the rotary disc 32 and the scrapers 50 are rotated in the direction R, and the powder ingredients P and the mixing water L to be mixed in the mixer 10 are fed into the mixer 10 through the powder supply conduit 15 and the water supply conduit 16. The powder ingredients P and the mixing water L, which flow into the mixing area 10a, are agitated and mixed, and are moved radially outward on the rotary disc 32 under the action of the centrifugal force, until reaching the peripheral zone of the disc 32. The scrapers 50, 60 scrape off or remove the slurry adhered to the lower surface of the upper plate 21 and the upper surface of the lower plate 22. The pins 36 scrape off or remove the slurry adhered to the inner circumferential surface of the annular wall 23.
The slurry reaching the peripheral zone of the mixing area 10a is pushed outward and frontward in the rotational direction by the pins 36 and flows through the slurry discharge port 40 to the hollow connector section 41. The foam feeding port 46 of the foam-feeding conduit 45 feeds the slurry with a required quantity of foam or foaming agent M. The slurry including the foam or foaming agent M flows into the slurry delivery tube 42 through the section 41 and is subjected to the rotational power and the shearing force in the tube 42, whereby mixing of the slurry is further progresses. Thereafter, the slurry is delivered onto the widthwise center part of the lower sheet 1 through the slurry outlet tube 7.
The slurry reaching the peripheral zone of the mixing area 10a also flows into the fractionation tubes 8a, 8b through the fractionation ports 8e, 8f. Such slurry is delivered to the edge zones of the lower sheet 1. For instance, the slurry in vicinity to the ports 8e, 8f is delivered to the tubes 8a, 8b without the foam or foaming agent fed to the slurry. Therefore, the slurry fed to the edge zones of the lower sheet 1 has a relatively high specific gravity.
In such an operation of the mixer 10, the scrapers 50 energize the slurry of the mixing area 10a radially outward of the rotary disc 32, so as to cause the slurry to be discharged out of the mixing area through the ports 40, 8e, 8f, in cooperation with the aforementioned action of the pins 36. Since the fluid resistance on each of the ports 40, 8e, 8f is increased by provision of the aforementioned slits-configuration (or, the lattice configuration or the like), the retention time of the slurry in the mixing area 10a is extended. Therefore, the slurry is sufficiently mixed in the mixing area 10a.
The scraper 50 as shown in
The powder supply port of the powder supply conduit 15, which is located on the upper plate 21, is shown as an opening 17 by a dotted line in
The mixer 10 as shown in
The mixer 10 as shown in
Furthermore, in the mixer 10 as shown in
According to the experiments of the present inventors with respect to the mixer 10 having the aforementioned arrangement, the density distribution and the fluid velocity distribution of the slurry in the mixing area 10a are uniformized in a case where the scrapers 50 bent or curved backward in the rotational direction are used, whereby the slurry can be sufficiently mixed and kneaded in a relatively short period of time. The main reasons for this are considered to be as follows:
(1) In a case of the scraper-type mixer, the dead water region or the slurry staying region is hardly generated in the mixing area 10a, in comparison with the pin-type mixer;
(2) In a case of the bent or curved scraper 50, the dead water region or the slurry staying region is hardly generated behind the scraper 50 (on the side backward in the rotational direction); and
(3) A relatively strong force or pressure directed radially outward of the mixing area 10a is given to the slurry by the scraper 50.
Although the present invention has been described as to the preferred embodiments, the present invention is not limited thereto, but may be carried out in any of various modifications or variations without departing from the scope of the invention as defined in the accompanying claims.
For instance, the annular basal part different from the rotary shaft is formed around its enlarged lower end portion in the aforementioned embodiments, but the annular basal part may be formed by additionally enlarging the diameter of the lower end portion of the rotary shaft.
Furthermore, although the pins are arranged in a single-row along the periphery of the rotary disc in the aforementioned embodiments, the pins may be arranged, for example, in double-rows along the periphery of the rotary disc, wherein the pins are provided to stand in pairs, on the periphery of the rotary disc.
Furthermore, the mixer of the present invention may be used for not only production of gypsum boards, but also production of gypsum based boards, such as glass mat boards, or gypsum based boards with glass fiber nonwoven fabric.
The present invention is applicable to a scraper-type mixer and mixing method in which a plurality of scrapers are arranged in a mixing area. According to the mixer and mixing method of the present invention, the retention time of the gypsum slurry in the mixing area can be increased, whereby the slurry can be sufficiently mixed in the mixing area; or the density distribution and the velocity distribution of the slurry in the mixing area can be uniformized, whereby the slurry can be uniformly mixed and kneaded in the mixing area. Thus, the practically remarkable effects can be obtained from the present invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/073972 | 8/26/2015 | WO | 00 |
