Pulverization device

Abstract

Provided is a pulverization device which pulverizes a pulp sheet to produce pulp fibers, which is capable of suppressing defects such as burning of the pulp fibers and failure to pulverize the pulp sheet, and which is compact and has high processing performance. A pulverization device (100) is provided with a plurality of rotating blades (122) that are attached to a rotation shaft (124) and that rotate along with the rotation shaft to pulverize a pulp sheet. A pulverization space index I [m3 / kg] is defined by the formula (V×N×60 [min])÷Amax, where V [m3] is the volume of a void space in an imaginary cylinder, N [rpm] is the rotational speed of the rotation shaft, and Amax [kg / h] is the maximum pulverization amount. The radius of the imaginary cylinder is the distance from the center of the rotation shaft to an end part of the rotating blade which is disposed furthest from the center of the rotation shaft in the radial direction of the rotation shaft. The height of the imaginary cylinder is the length of the section in which the plurality of rotating blades are disposed in the axial direction of the rotation shaft. V, N, and Amax are set such that the pulverization space index I is not less than 12.0.

Description

Crushing equipment

[0001] The present invention relates to a pulverizer that pulverizes a pulp sheet, which is a raw material for an absorbent body, to produce pulp fibers.

[0002] As disclosed in Patent Document 1 (JP 2015-62463 A), a crushing device is known that rotates a rotary blade and crushes a pulp sheet with the rotary blade to produce pulp fibers for manufacturing an absorbent body.

[0003] JP 2015-62463 A

[0004] A common problem with such a crushing device is that it is required to achieve a high processing capacity in a compact device.

[0005] However, when trying to achieve this, depending on the conditions, problems such as scorching of pulp fibers or insufficient crushing of the pulp sheet may occur. To avoid such problems, crushing devices are actually designed with a considerable margin of error. Therefore, there is room for improvement in the performance of crushing devices.

[0006] The object of the present invention is to provide a crushing device that crushes a pulp sheet, which is the raw material for an absorbent body, to produce pulp fibers, and that is compact and has high processing capacity, and that can prevent problems such as scorching of the pulp fibers and insufficient crushing of the pulp sheet.

[0007] The crushing device of the present invention crushes a pulp sheet to produce pulp fibers. The crushing device includes a rotating shaft, multiple rotary blades, a motor, and a casing. The multiple rotary blades are attached to the rotating shaft and rotate together with the rotating shaft to crush the pulp sheet. The motor rotates the rotating shaft. The casing has a supply port through which the pulp sheet is supplied and a discharge port through which the pulp fibers are discharged. The casing houses the rotary blades attached to the rotating shaft. Here, the volume of the void space within the imaginary cylinder is defined as V [m ３ ], the rotation speed of the rotary shaft is N [rpm], and the maximum crushing amount of the crushing device is Amax [kg / h]. ３ / kg] to (V [m ３] × N [rpm] × 60 [min] ÷ Amax [kg / h]. The virtual cylinder has a radius that is the distance from the center of the rotary shaft to the end of the rotary blade that is located farthest from the center of the rotary shaft in the radial direction of the rotary shaft, and a height that is the distance in the axial direction of the rotary shaft where multiple rotary blades are located. In the above definition, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is set to be 12.0 or more.

[0008] The inventors of the present invention set the grinding space index I to 12.0 m ３ / kg or more, it has been found that problems such as scorching of pulp fibers during pulverization and extremely insufficient pulverization of the pulp sheet can be suppressed. ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are set, so that problems such as pulp fiber burning and extremely insufficient grinding of the pulp sheet can be suppressed without having to allow for an excessive safety margin.

[0009] 1 is a schematic diagram of an absorbent body manufacturing apparatus having a pulverizer according to an embodiment of the present invention. It is a schematic diagram of a pulverizer according to an embodiment of the present invention, viewed along the axial direction of the rotation shaft of the pulverizer. It is a schematic top view of the rotor and bearing device of the pulverizer of FIG. 2, with the casing and bearing box drawn by two-dot chain lines. It is a schematic diagram of a rotary blade (rotary blade plate) attached to the rotation shaft of the pulverizer of FIG. 2, viewed along the axial direction of the rotation shaft. It is a planar drawing of the arcuate surface on which the cutting edges of the rotary blades of the rotor of the pulverizer of FIG. 2 are arranged, and is a diagram for explaining the arrangement of the cutting edges of the rotary blades. It is a partially enlarged view of the rectangular area designated by the symbol VI in FIG. 3, and is a diagram for explaining void spaces. It is a graph plotting the maximum pulverization volume and the pulverization space index (data from Table 1) when a pulp sheet is pulverized using a pulverizer tester, with the horizontal axis representing the maximum pulverization volume and the vertical axis representing the pulverization space index, and the symbols of each plot indicate the quality of the obtained pulp fiber. 8 is a schematic view of the rotary blade (rotary blade plate) used in the test to obtain the graph of FIG. 7 (data in Table 1), as viewed along the axial direction of the rotary shaft. FIG. 9 is a schematic view of the crushing device according to Modification A, as viewed along the axial direction of the rotary shaft of the crushing device.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the crushing device according to the present invention will be described with reference to the drawings.

[0011] It should be noted that the embodiments described below are merely examples of the present invention and do not limit the scope of the present invention. Those skilled in the art will understand that various modifications can be made to the following embodiments without departing from the spirit and scope of the present invention as defined in the claims.

[0012] (1) Absorbent Body Manufacturing Apparatus An absorbent body manufacturing apparatus 1 having a pulverizer 100 according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of the absorbent body manufacturing apparatus 1.

[0013] The absorbent body P manufactured by the absorbent body manufacturing apparatus 1 is an article formed by molding pulp fibers into a predetermined shape. The absorbent body P is used, for example, in disposable diapers, sanitary napkins, etc., and is an article that absorbs bodily fluids such as urine and menstrual blood.

[0014] The absorbent body manufacturing apparatus 1 includes a pulverizer 100, a fiber-stacking device 10, a duct 20, and a suction conveyor 30 (see FIG. 1 ). The pulverizer 100 pulverizes a pulp sheet S formed into a sheet by agglutinating pulp fibers to generate pulp fibers. In other words, the pulverizer 100 is a device that loosens (defibrates) the sheet-shaped pulp fibers into a flocculated state. The duct 20 functions as a pulp fiber passage that guides the pulp fibers generated by the pulverizer 100 from the pulverizer 100 to the fiber-stacking device 10. The fiber-stacking device 10 forms the pulp fibers pulverized by the pulverizer 100 into an absorbent body P of a predetermined shape. The absorbent body P manufactured by the fiber-stacking device 10 is transported by the suction conveyor 30 to a subsequent process of the absorbent body manufacturing apparatus 1.

[0015] The crushing device 100 will be described in detail later.

[0016] The duct 20 has a first opening 22 disposed at the most upstream position in the pulp fiber conveying path and a second opening 24 disposed at the most downstream position in the pulp fiber conveying path (see FIG. 1 ). The first opening 22 is connected to a pulp fiber discharge outlet 114 formed in a casing 110 (described later) of the crushing device 100. The second opening 24 is disposed so as to face a portion of the outer circumferential surface of a fiber stacking drum 12 (described later) of the fiber stacking device 10. The pulp fibers flowing into the duct 20 from the first opening 22 are supplied from the second opening 24 to a recess 12a (described later) provided on the outer circumferential surface of the fiber stacking drum 12.

[0017] The fiber stacking device 10 mainly includes a fiber stacking drum 12 (see FIG. 1).

[0018] The fiber stacking drum 12 is a hollow, cylindrical rotating drum. The outer periphery of the fiber stacking drum 12 rotates in the direction of arrow K1 around a rotation axis extending along the center of the cylindrical fiber stacking drum 12 (see FIG. 1). Recesses 12a are formed on the outer periphery of the fiber stacking drum 12 to collect pulp fibers and form the pulp fibers into an absorbent body P of a predetermined shape. The recesses 12a have a shape corresponding to the absorbent body P so that the shape of the pulp fibers extracted from the recesses 12a corresponds to the shape of the absorbent body P. The exterior and interior of the fiber stacking drum 12 are connected via holes 12b formed in the bottom (radially inside) of the recesses 12a (see FIG. 1). The holes 12b are designed to have dimensions that allow the passage of air containing pulp fibers that flows into the recesses 12a from the duct 20 but do not allow the pulp fibers to pass through.

[0019] The interior of the fiber stacking drum 12 is divided by partition walls 14 arranged inside the fiber stacking drum 12, and multiple spaces are formed along the circumferential direction of the fiber stacking drum 12 (see FIG. 1). One of the multiple spaces, the suction space Si (see FIG. 1), is a space into which air is sucked out from an opening (not shown), and is a space with a lower pressure (negative pressure) than the pressure outside the fiber stacking drum 12. The suction space Si takes in air from the space outside the fiber stacking drum 12 through holes 12b formed in the bottom of the recess 12a. Another of the multiple spaces, the blow-out space So (see FIG. 1), is a space arranged adjacent to the suction space Si in the circumferential direction of the fiber stacking drum 12, and is arranged downstream of the suction space Si in the rotation direction of the fiber stacking drum 12 (see arrow K1 in FIG. 1). The blow-out space So is a space into which air is blown in from an opening (not shown), and is a space with a higher pressure (positive pressure) than the pressure outside the fiber stacking drum 12. The blowing space So blows air out to the space outside the fiber stacking drum 12 through holes 12b formed at the bottom of the recess 12a. When the fiber stacking drum 12 rotates, the positions of the suction space Si and the blowing space So inside the fiber stacking drum 12 do not change.

[0020] The second opening 24 of the duct 20 faces a part of the outer peripheral surface of the fiber stacking drum 12, where a suction space Si is formed across the outer peripheral surface. Because the fiber stacking drum 12 rotates, the part of the outer peripheral surface of the fiber stacking drum 12 that faces the second opening 24 changes as the fiber stacking drum 12 rotates. As the fiber stacking drum 12 rotates and the recesses 12a formed on the outer peripheral surface of the fiber stacking drum 12 move while facing the second openings 24 of the duct 20, air containing pulp fibers supplied from the duct 20 flows into the recesses 12a, and the air passes through holes 12b in the bottom surface of the recesses 12a and flows into the suction space Si, which has a lower pressure than the supply space Sa. However, because the holes 12b are designed to have dimensions that do not allow the pulp fibers to pass through, the pulp fibers that flow into the recesses 12a do not flow into the suction space Si, but are instead stacked in the recesses 12a.

[0021] The suction conveyor 30 is disposed adjacent to the blowing space So inside the stacking drum 12 via the stacking drum 12 (see FIG. 1). The suction conveyor 30 is disposed downstream of the suction space Si in the rotation direction of the stacking drum 12 (see arrow K1) (see FIG. 1). The suction conveyor 30 is a conveyor that sucks air from the conveyor surface (transport surface) as shown by the arrow in FIG. 1. The suction conveyor 30 sucks pulp fibers (absorbent P) stacked in the recesses 12a on the outer surface of the stacking drum 12, releases the absorbent P from the recesses 12a, and transports the released absorbent P. The absorbent P transported by the suction conveyor 30 is transported to a subsequent process and used in disposable diapers, sanitary napkins, and the like.

[0022] (2) Crusher The specific configuration of the crusher 100 will be described below with reference to FIGS. 2 to 8. FIG. 2 is a schematic diagram of the crusher 100 as viewed along the axial direction of a rotary shaft 124 (described later) of the crusher 100. FIG. 3 is a schematic top view of the rotor 120 and bearing device 130 of the crusher 100, with the casing 110 and bearing box 134 (described later) depicted by dashed double-dashed lines. In other words, FIG. 3 is a view perpendicular to the axial extension of the rotary shaft 124. FIG. 4 is a schematic diagram of the rotary blade 122 (rotary blade plate 123) attached to the rotary shaft 124 as viewed along the axial direction of the rotary shaft 124. FIG. 5 is a planar drawing of the arcuate surface on which the cutting edge 122a of the rotary blade 122 (described later) of the rotor 120 is arranged, and is a diagram for explaining the arrangement of the cutting edge 122a of the rotary blade 122. Figure 6 is a partially enlarged view of the area indicated by the rectangle VI in Figure 3, illustrating the void space. Figure 7 is a graph plotting the maximum crushing amount Amax and the crushing space index I (data from Table 1) when crushing the pulp sheet S using a crushing device tester, with the maximum crushing amount Amax on the horizontal axis and the crushing space index I on the vertical axis, and the symbols on each plot indicate the quality of the resulting pulp fiber. Figure 8 is a schematic view of the rotary blade 122 (rotary blade plate 123) used in the test to obtain the graph of Figure 7 (data from Table 1), viewed along the axial direction of the rotary shaft 124.

[0023] The crushing device 100 mainly includes a casing 110, a rotor 120, and a bearing device 130 (see FIG. 2).

[0024] (2-1) Rotating Body As shown in FIG. 3, the rotating body 120 includes a rotating shaft 124, a plurality of rotary blades 122, and a motor 126.

[0025] The rotary shaft 124 is driven by a motor 126 to rotate (see arrow K2 indicating the direction of rotation) around a rotary axis O (see FIG. 3) that extends through a center O1 (see FIG. 2) of the rotary shaft 124.

[0026] The plurality of rotary blades 122 are attached to a rotary shaft 124. Although the shape is not limited thereto, when the rotor 120 is viewed along the axial direction of the rotary shaft 124, each rotary blade 122 has a cutting edge 122a (a radially outer end portion of the rotor 120) formed in a claw shape.

[0027] The manner in which the rotary blades 122 are attached to the rotary shaft 124 is not limited, but for example, the plurality of rotary blades 122 are attached to the rotary shaft 124 in the following manner.

[0028] As shown in FIG. 4 , the rotating body 120 has a plurality of rotary blades 122 arranged along the circumferential direction and a plurality of rotary blade plates 123 each having a mounting hole 123a formed in the center. Note that the number of rotary blades 122 provided on each rotary blade plate 123 depicted in FIG. 4 is merely an example, and the number of rotary blades 122 provided on each rotary blade plate 123 may be determined as appropriate. A plurality of rotary blade plates 123 are attached to a rotary shaft 124 along the axial direction of the rotary shaft 124, spaced a predetermined distance from each other. A spacer (not shown) may be used to position the rotary blade plates 123 in the axial direction of the rotary shaft 124. Specifically, each rotary blade plate 123 is attached to the rotary shaft 124 so that the rotary shaft 124 passes through the mounting hole 123a and is fixed to the rotary shaft 124 in a predetermined manner. Each rotary blade plate 123 is attached to the rotary shaft 124 at an angle offset from the adjacent rotary blade plate 123 so that the cutting edges 122a of the rotary blades 122 are offset in the circumferential direction of the rotary shaft 124 as shown in Fig. 5. However, in Fig. 2, to avoid cluttering the drawing, only the rotary blade plate 123 that is located at the forefront is shown.

[0029] When the rotating body 120 (the rotating shaft 124 to which the rotating blades 122 are attached) is driven to rotate by the motor 126, the multiple rotating blades 122 attached to the rotating shaft 124 also rotate together with the rotating shaft 124, come into contact with the pulp sheet S supplied to the crushing device 100, and crush (defibrate) the pulp sheet S.

[0030] (2-2) Bearing Device The bearing device 130 rotatably supports the rotating body 120. More specifically, the bearing device 130 rotatably supports the rotating shaft 124 of the rotating body 120. The crushing device 100 has a pair of bearing devices 130, and the rotary blade 122 (rotary blade plate 123) of the rotating body 120 is disposed between the pair of bearing devices 130.

[0031] As shown in FIGS. 2 and 3, each bearing device 130 mainly includes a ball bearing 132, a bearing box 134, and a base 136.

[0032] The ball bearings 132 are bearings that rotatably support the rotary shaft 124. The ball bearings 132 are preferably deep groove ball bearings. When a deep groove ball bearing is used, axial misalignment between the pair of ball bearings 132 is more easily tolerated than when other types of ball bearings are used.

[0033] The ball bearing 132 may use steel balls as rolling elements. However, when the rotation speed of the rotating shaft 124, set by a method described below, is high (for example, when the rotating shaft 124 is operated at a rotation speed exceeding 3,500 rpm (e.g., 4,000 rpm)), the rolling elements of the ball bearing 132 are preferably ceramic balls 132a. Furthermore, when the rotation speed of the rotating shaft 124 is increased and the diameter of the rotating shaft 124 is accordingly increased, the DN value (the product of the inner diameter [mm] of the ball bearing 132 and the rotation speed [rpm] of the rotating shaft 124) also increases. When the DN value exceeds 300,000 (for example, 450,000), the rolling elements of the ball bearing 132 are preferably ceramic balls 132a. By using ball bearings 132 with ceramic balls 132a as rolling elements, the bearing's life is likely to be extended, even when the rotation speed and DN value of the rotating shaft 124 are increased.

[0034] The inventors of the present application have also discovered that when ceramic balls 132a are used as rolling elements, the decrease in efficiency due to slippage in the ball bearing 132 is more easily suppressed than when steel balls are used as rolling elements, and power loss is relatively small even when the rotating shaft is rotated at high speed.

[0035] Furthermore, it is preferable that the ball bearings 132 are of the grease-filled type. By using grease-filled ball bearings 132, the structure around the ball bearings 132 can be simplified compared to when oil-lubricated (oil-supply) bearings are used. Furthermore, when oil-lubricated bearings are used, there is a risk of fire or other accidents if oil somehow flows into the casing 110 (described below). In contrast, the crushing device 100, which uses grease-filled ball bearings 132 without an oil supply structure, does not have this risk.

[0036] The bearings do not necessarily have to be grease-filled ball bearings, and may be, for example, oil-lubricated high-speed angular contact ball bearings, etc. However, using grease-filled ball bearings has the advantages described above.

[0037] Furthermore, the sealing structure of the ball bearing 132 may be either a contact type or a non-contact type, but a non-contact type is preferable. By using a non-contact type sealing structure, it is possible to reduce the generation of frictional heat during high-speed rotation.

[0038] The bearing box 134 is a housing that houses the ball bearing 132. The bearing box 134 is not attached to the casing 110 that houses the rotary blade 122, but is supported from below by the base 136. The bearing box 134 is disposed apart in the axial direction of the rotary shaft 124 so that a space is formed between the bearing box 134 and the casing 110. In other words, the ball bearings 132 are disposed apart in the axial direction of the rotary shaft 124 so that a space is formed between the ball bearings 132 and the casing 110. For example, the ball bearings 132 (more specifically, the bearing box 134) and the casing 110 are preferably disposed apart by a distance of at least 1 / 6 and at most 2 times the radius r (the distance to the end 122b of the rotary blade 122 that is disposed farthest from the center O1 of the rotary shaft 124 in the radial direction of the rotary shaft 124), as described below. With this configuration, it is possible to prevent the crushing device 100 from becoming excessively large, while also suppressing the adverse effects of heat inside the casing 110 on the performance of the ball bearings 132.

[0039] When viewed along the axial direction of the rotating shaft 124, the bearing box 134 preferably has a main body 134a that houses the ball bearing 132, and legs 134b that extend from the main body 134a in a direction perpendicular to the axial direction of the rotating shaft 124 (the left-right direction in FIG. 2). The legs 134b of the bearing box 134 are fixed to the base 136 and support the ball bearing 132 not only in the up-down direction but also in the direction perpendicular to the axial direction of the rotating shaft 124 (the left-right direction in FIG. 2).

[0040] (2-3) Casing As shown in Fig. 2, the casing 110 is a housing that houses the rotary blade 122 (rotary blade plate 123) attached to the rotary shaft 124. As shown in Fig. 1, the casing 110 has a supply port 112 through which the pulp sheet S is supplied by a sheet conveying device (not shown), and a discharge port 114 through which pulp fibers generated when the rotary blade 122 crushes the pulp sheet S are discharged.

[0041] (2-4) Setting Parameters of the Crushing Device A common objective of the crushing device 100 is to achieve high processing capacity in a compact device.

[0042] On the other hand, the pulp fibers generated by the crushing device 100 are also required to meet a quality standard. Specifically, the pulp fibers generated are required to be, for example, non-burning. Furthermore, the pulp fibers generated are required to contain a certain amount of undefibrated pulp fibers or less. Furthermore, it is preferable that the pulp fibers generated have a constant fiber length (i.e., the fibers are not crushed too finely). Conventionally, priority has been given to ensuring that the pulp fibers generated meet a quality standard, and crushing devices have actually been designed with a considerable margin in terms of device size and processing capacity.

[0043] In response to this, the inventors of the present application discovered that by quantifying the conditions for satisfying the objectives of achieving high processing capacity in a compact device and the objective of producing pulp fibers that meet quality standards, it is possible to provide a compact, high-processing capacity crushing device that can suppress defects such as pulp fiber burning and insufficient crushing of pulp sheets.

[0044] More specifically, the inventors of the present invention define the milling space index I [m ３ / kg], and the structure of the pulverizing device 100 (specifically, the volume V [m ３ ]), maximum grinding amount Amax [kg / h], and rotation speed [rpm] of the rotating shaft 124, it was found that it was possible to satisfy the quality standards of pulp fiber.

[0045] First, the milling space index I [m ３ / kg], the volume V of the void space in the virtual cylinder C [m ３ The definitions of the maximum grinding amount Amax [kg / h] and the maximum grinding amount Amax [kg / h] are explained below.

[0046] Grinding space index I [m ３ / kg] is (V [m ３ ]×N[rpm]×60[min])÷Amax[kg / h].

[0047] The virtual cylinder C that appears in the definition of the void space is a virtual cylinder (see the part indicated by the thick dotted line in Figure 3) whose radius is r (see Figure 4) and whose height is h (see Figure 3) and whose distance from the center O1 of the rotation shaft 124 to the end 122b of the rotary blade 122 that is located farthest from the center O1 of the rotation shaft 124 in the radial direction of the rotation shaft 124 is the distance between the rotary blades 122 and the center O1 of the rotation shaft 124 in the axial direction of the rotation shaft 124.

[0048] The volume of the void space in the virtual cylinder C is V [m ３ ] means the volume of the part of the imaginary cylinder C where no components exist. In other words, the volume V [m ３] means the volume of the hollow portion within the imaginary cylinder C. For example, as shown in Figure 4, when the rotary blade plate 123 is viewed along the axial direction of the rotation shaft 124, the hatched portion where no rotary blades 122 are present is included in the void space. Also included in the void space is the gap between adjacent rotary blades 122 in the axial direction of the rotation shaft 124 (in other words, the gap between the rotary blade plates 123), which is shown hatched in Figure 6. Note that if a spacer is placed between adjacent rotary blade plates 123, the space where the spacer is placed is excluded from the void space.

[0049] The maximum crushing amount Amax [kg / h] is the maximum design value of the crushing amount (the amount of pulp sheet S that can be processed per hour) that is allowable for the crushing device 100 .

[0050] The inventors of the present application used a test machine for the crushing device 100 to determine the shape of the rotary blade plate 123, the diameter of the rotary blade plate 123 (twice the radius r of the imaginary cylinder C), the rotation speed of the rotary shaft 124, the maximum crushing amount Amax [kg / h], and the volume V [m ３ ] is changed as shown in Table 1, and the milling space index I [m ３ / kg] and the quality of the pulp fiber were determined (see Table 1). The shape in Table 1 refers to the shape of the rotary blade plate 123, and the numbers in Table 1 indicate which rotary blade plate 123 was used among the rotary blade plates 123 in FIG. 8. The grinding space in Table 1 is V [m ３ ] × N [rpm] × 60 [min].

[0051] Based on the test results in Table 1, the maximum crushing amount Amax and the crushing space index I are plotted on a graph in Figure 7, with the maximum crushing amount Amax on the horizontal axis and the crushing space index I on the vertical axis. The symbols in the plots in Figure 7 correspond to the pulp fiber quality column in Table 1 and indicate the quality of the obtained pulp fiber.

[0052] As a result, the inventors of the present invention set the milling space index I at 12.0 m ３ / kg or more, it has been found that problems such as scorching of pulp fibers during pulverization and extremely insufficient pulverization of the pulp sheet S can be suppressed (see Table 1 and FIG. 7).

[0053] The inventors of the present invention also set the milling space index I to 14.0 m ３ / kg or more, it has been found that the possibility of pulp fibers in the form of relatively large lumps that have not been sufficiently pulverized being mixed into the pulp fibers produced can be reduced (see Table 1 and Figure 7).

[0054] Furthermore, the inventors of the present invention set the grinding space index I to 21.5 m ３ / kg or more, more preferably the grinding space index I is 20.0 m ３ / kg or more, it was found that the possibility of excessively pulverized pulp fibers being mixed into the produced pulp fibers can be reduced (see Table 1 and FIG. 7).

[0055] Based on these results, the inventors of the present application have determined that the volume V [m ３ It has been found that it is preferable to set the rotation speed N [rpm] and the maximum crushing amount [kg / h] as follows:

[0056] First, the inventors of the present application have determined that, from the viewpoint of avoiding major defects in terms of the quality of pulp fibers, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is desirably set to 12.0 or more.

[0057] Furthermore, the inventors of the present application have found that in order to reduce the possibility of insufficiently pulverized pulp fibers in the form of relatively large lumps being mixed into the pulp fibers to be produced, it is important to consider the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is preferably set to 14.0 or more.

[0058] In addition, the inventors of the present application have determined that, from the viewpoint of reducing the possibility that excessively pulverized pulp fibers are mixed into the pulp fibers to be produced, the volume V [m ３], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is preferably set to 21.5 or less. More preferably, the inventors of the present application have found that, from the viewpoint of reducing the possibility of excessively pulverized pulp fibers being mixed into the pulp fibers to be produced, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is preferably set to 20.0 or less. ３ / kg] becomes too large, the amount of excessively crushed pulp fiber increases, and the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is preferably set so as not to exceed 23.0.

[0059] By using the milling space index I in this way, the volume V [m ３ ], rotation speed N [rpm] and maximum crushing amount Amax [kg / h] can be numerically determined, so the crushing device 100 of this embodiment can prevent problems such as pulp fiber burning and insufficient crushing of the pulp sheet, and can also realize a crushing device that is compact and has high processing capacity.

[0060] (3) Features (3-1) The crushing device 100 of the above embodiment crushes a pulp sheet S to produce pulp fibers. The crushing device 100 includes a rotary shaft 124, a plurality of rotary blades 122, a motor 126, and a casing 110. The plurality of rotary blades 122 are attached to the rotary shaft 124 and rotate together with the rotary shaft 124 to crush the pulp sheet S. The motor 126 rotates the rotary shaft 124. The casing 110 has a supply port 112 through which the pulp sheet S is supplied and a discharge port 114 through which the pulp fibers are discharged. The casing 110 houses the rotary blades 122 attached to the rotary shaft 124. Here, the volume of the void space within the imaginary cylinder C is defined as V [m ３], the rotation speed of the rotary shaft 124 is N [rpm], and the maximum crushing amount of the crushing device 100 is Amax [kg / h]. ３ / kg] to (V [m ３ ] × N [rpm] × 60 [min]) ÷ Amax [kg / h]. The imaginary cylinder C is an imaginary cylinder whose radius is r, which is the distance from the center O1 of the rotary shaft 124 to the end 122b of the rotary blade 122 that is arranged farthest from the center O1 of the rotary shaft 124 in the radial direction of the rotary shaft 124, and whose height is h, which is the distance of the section in which the multiple rotary blades 122 are arranged in the axial direction of the rotary shaft 124. In the above definition, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is set to be 12.0 or more.

[0061] The inventors of the present invention set the grinding space index I to 12.0 m ３ / kg or more, it was found that problems such as scorching of pulp fibers during pulverization and extremely insufficient pulverization of the pulp sheet S can be suppressed (see Table 1 and FIG. 7). In this pulverizer 100, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are set, so that problems such as pulp fibers burning and the pulp sheet S being significantly insufficiently ground can be suppressed without requiring an excessive safety margin.

[0062] More preferably, in the crushing device 100, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 14.0 or more.

[0063] The inventors of the present invention set the grinding space index I to 14.0 m ３ / kg or more, it was found that the possibility of insufficiently pulverized pulp fibers in the form of relatively large clumps being mixed into the pulp fibers to be produced can be reduced (see Table 1 and FIG. 7). ３], rotation speed N [rpm] and maximum crushing amount Amax [kg / h] are set, so that pulp fibers in the form of relatively large lumps that have not been sufficiently crushed are less likely to be mixed into the pulp fibers being produced, even without an excessive safety margin.

[0064] (3-2) Preferably, in the crushing device 100, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 23.0 or less.

[0065] By satisfying the above conditions, the crushing device 100 can prevent the pulp sheet S from being crushed excessively, thereby producing high-quality pulp fibers.

[0066] More preferably, in the crushing device 100, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 21.5 or less.

[0067] The inventors of the present invention set the grinding space index I to 21.5 m ３ / kg or more, it was found that the possibility of excessively crushed pulp fibers being mixed into the produced pulp fibers can be reduced (see Table 1 and FIG. 7). ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are set, so that excessively ground pulp fibers are less likely to be mixed into the pulp fibers being produced, even without an excessive safety margin, and higher quality pulp fibers can be produced.

[0068] (3-3) The crushing device 100 of the above embodiment crushes a pulp sheet S to produce pulp fibers. The crushing device 100 includes a rotating shaft 124, a plurality of rotating blades 122, a motor 126, a casing 110, and a ball bearing 132. The plurality of rotating blades 122 are attached to the rotating shaft 124 and rotate together with the rotating shaft 124 to crush the pulp sheet S. The motor 126 rotates the rotating shaft 124. The casing 110 has a supply port 112 through which the pulp sheet S is supplied and a discharge port 114 through which the pulp fibers are discharged. The casing 110 houses the rotating blades 122 attached to the rotating shaft 124. The rolling elements of the ball bearing 132 are ceramic balls 132a.

[0069] Conventionally, crushers use steel balls as rolling elements in the bearings that support the rotating shaft. However, if the rotation speed of such crushers is increased too much, problems such as damage to the bearings due to frictional heat and reduced efficiency can occur.

[0070] In contrast, if ceramic balls 132a are used as the rolling elements of ball bearing 132, ceramic is heat resistant, so even when rotating shaft 124 at a higher rotation speed than in conventional crushing devices and operating the crushing device under high load, damage to ball bearing 132 due to frictional heat is likely to be suppressed. The inventors of the present application have also discovered that by using ceramic balls 132a as the rolling elements of ball bearing 132, a decrease in efficiency due to slippage in ball bearing 132 can also be suppressed.

[0071] If ceramic balls 132a are used as the rolling elements of the ball bearing 132, the crushing space index I [m ３ Even if the rotating shaft 124 is operated at high speed so that the load (load) [kg / kg] satisfies the above-mentioned numerical value and the DN value (a dimensionless quantity, which is the product of the bearing inner diameter [mm] and the rotational speed [rpm] of the rotating shaft 124) becomes a large value, the life of the bearing is unlikely to be shortened.

[0072] (3-4) In the crushing device 100 of the above embodiment, the ball bearings 132 are of the grease-filled type.

[0073] In the crushing device 100, since an oil-lubricated ball bearing is not used, the structure around the ball bearing 132 can be simplified.

[0074] Furthermore, when oil-lubricated bearings are used, if oil for some reason flows into the casing 110, it may lead to a fire or other accident. In contrast, the crushing device 100, which uses grease-filled ball bearings 132 without an oil supply structure, does not have this risk.

[0075] (3-5) In the crushing device 100 of the above embodiment, it is preferable that the ball bearing 132 has a non-contact sealing structure.

[0076] By adopting a non-contact sealing structure, it is possible to reduce the generation of frictional heat during high-speed rotation that would otherwise be caused by the presence of the sealing structure.

[0077] (3-6) In the crushing device 100 of the above embodiment, the ball bearings 132 are arranged at a distance from each other so that a space is formed between the ball bearings 132 and the casing 110. More specifically, the bearing boxes 134 that house the ball bearings 132 are arranged at a distance from each other so that a space is formed between the ball bearings 132 and the casing 110.

[0078] In the crushing device 100, the inside of the casing 110 is prone to become hot. Therefore, if the ball bearings 132 (bearing box 134 that houses the ball bearings 132) are in contact with the casing 110, the heat inside the casing 110 may adversely affect the performance of the ball bearings 132. In contrast, by locating the ball bearings 132 away from the casing 110, the ball bearings 132 are less susceptible to the effects of the heat inside the casing 110.

[0079] (4) Modifications (4-1) Modification A The shapes of the leg portion 134b of the bearing box 134 and the base 136 are not limited to the shapes illustrated in FIG.

[0080] For example, it is preferable that the width in the left-right direction of the legs 134b of the bearing box 134 and the base 136 when viewed along the axial direction of the rotation shaft 124 is relatively large as shown in FIG.

[0081] For example, the maximum width W1 of the leg portion 134b of the bearing box 134 is preferably at least three times but less than six times the diameter D1 (see FIG. 3) of the portion of the rotating shaft 124 that is supported by the ball bearing 132.

[0082] Furthermore, for example, it is preferable that the average width W2 of the base 136 of the bearing box 134 is at least three times but less than six times the diameter D1 of the portion of the rotating shaft 124 that is supported by the ball bearing 132.

[0083] With this configuration, vibrations are easily suppressed even when the rotating shaft 124 rotates at high speed, and damage to the ball bearings 132 and a decrease in the efficiency of the crushing device 100 can be suppressed.

[0084] (4-2) Modification B In the drawing of Fig. 3, the diameter D2 of the portion of the rotating shaft 124 housed in the casing 110 and where the rotary blade 122 is attached is set larger than the diameter D1 of the portion of the rotating shaft 124 supported by the ball bearing 132 (diameter D1 < diameter D2), but the shape is not limited to that drawn in Fig. 3 and may be a shape where the relationship of diameter D1 ≥ diameter D2 is also acceptable. However, a shape where diameter D1 < diameter D2 is preferable because it can reduce deflection and prevent the occurrence of resonance.

[0085] <Additional Notes> Finally, the technical ideas that can be understood from the above embodiment will be added below.

[0086] A crushing device according to a first aspect of the present invention crushes a pulp sheet to produce pulp fibers. The crushing device includes a rotating shaft, a plurality of rotary blades, a motor, and a casing. The plurality of rotary blades are attached to the rotating shaft and rotate together with the rotating shaft to crush the pulp sheet. The motor rotates the rotating shaft. The casing has a supply port through which the pulp sheet is supplied and a discharge port through which the pulp fibers are discharged. The casing houses the rotary blades attached to the rotating shaft. Here, the volume of the void space within the imaginary cylinder is defined as V [m ３ ], the rotation speed of the rotary shaft is N [rpm], and the maximum crushing amount of the crushing device is Amax [kg / h]. ３ / kg] to (V [m ３] × N [rpm] × 60 [min] ÷ Amax [kg / h]. The virtual cylinder has a radius that is the distance from the center of the rotary shaft to the end of the rotary blade that is located farthest from the center of the rotary shaft in the radial direction of the rotary shaft, and a height that is the distance in the axial direction of the rotary shaft where multiple rotary blades are located. In the above definition, the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is set to be 12.0 or more.

[0087] The inventors of the present invention set the grinding space index I to 12.0 m ３ / kg or more, it has been found that problems such as scorching of pulp fibers during pulverization and extremely insufficient pulverization of the pulp sheet can be suppressed. ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are set, so that problems such as pulp fiber burning and extremely insufficient grinding of the pulp sheet can be suppressed without having to allow for an excessive safety margin.

[0088] A pulverizer according to a second aspect of the present invention is the pulverizer according to the first aspect, wherein the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 14.0 or more.

[0089] The inventors of the present invention set the grinding space index I to 14.0 m ３ / kg or more, it was found that the possibility of pulp fibers in the form of relatively large lumps that have not been sufficiently pulverized being mixed into the pulp fibers to be produced can be reduced. In the pulverization device according to the second aspect, the volume V [m ３ ], the rotation speed N [rpm] and the maximum crushing amount Amax [kg / h] are set, so that pulp fibers in the form of relatively large lumps that have not been sufficiently crushed are less likely to be mixed into the pulp fibers being produced, even without an excessive safety margin.

[0090] A pulverizing device according to a third aspect of the present invention is the pulverizing device according to the first or second aspect, wherein the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 23.0 or less.

[0091] The crushing device according to the third aspect can prevent the pulp sheet from being crushed excessively, thereby producing high-quality pulp fibers.

[0092] A pulverizer according to a fourth aspect of the present invention is the pulverizer according to the third aspect, wherein the volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 21.5 or less.

[0093] The inventors of the present invention set the grinding space index I to 21.5 m ３ / kg or more, it has been found that the possibility of excessively crushed pulp fibers being mixed into the produced pulp fibers can be reduced. ３ ], the rotation speed N [rpm] and the maximum crushing amount Amax [kg / h] are set, so that even without an excessive safety margin, excessively crushed pulp fibers are less likely to be mixed into the pulp fibers being produced, and higher quality pulp fibers can be produced.

[0094] A crushing device according to a fifth aspect of the present invention is the crushing device according to any one of the first to fourth aspects, further comprising a ball bearing for rotatably supporting the rotating shaft. The rolling elements of the ball bearing are ceramic balls.

[0095] In the crushing device according to the fifth aspect, even when the rotating shaft is rotated at high speed and the crushing device is operated under high load, the life of the bearings is not likely to decrease, and highly efficient operation is likely to be achieved.

[0096] A crushing device according to a sixth aspect of the present invention is the crushing device of the fifth aspect, wherein the ball bearings are of a grease-filled type.

[0097] In the crushing device according to the sixth aspect, since no oil-lubricated ball bearings are used, the structure around the ball bearings can be simplified.

[0098] Furthermore, when oil-lubricated bearings are used, if oil gets into the casing for some reason, it could lead to fires, etc. In contrast, crushing equipment that uses grease-filled ball bearings without an oil supply structure does not have this risk.

[0099] A crushing device according to a seventh aspect of the present invention is the crushing device according to the fifth or sixth aspect, wherein the ball bearings are arranged apart from each other so that a space is formed between the ball bearings and the casing.

[0100] In a crusher, the inside of the casing is prone to become hot. Therefore, if the ball bearings are in contact with the casing, the heat inside the casing may adversely affect the performance of the bearings. In contrast, in the crusher according to the seventh aspect, the ball bearings are disposed away from the casing, so that the ball bearings are less susceptible to the heat inside the casing.

[0101] A crushing device according to an eighth aspect of the present invention is the crushing device according to any one of the fifth to seventh aspects, wherein the ball bearing preferably has a non-contact sealing structure.

[0102] In the crushing device according to the eighth aspect, the non-contact type sealing structure is adopted, so that the generation of frictional heat during high speed rotation can be reduced.

[0103] 100 Crushing device 110 Casing 112 Supply port 114 Discharge port 124 Rotating shaft 122 Rotating blade 122b End 126 Motor 132 Ball bearing 132a Ceramic ball 134 Bearing box Amax Maximum crushing amount C Virtual cylinder h Height I Crushing space index N Rotation speed r Radius S Pulp sheet V Void space volume

Claims

1. A grinding device for grinding a pulp sheet to produce pulp fibers, comprising: A rotation axis; A plurality of rotary blades are attached to the rotary shaft and rotate together with the rotary shaft to crush the pulp sheet; A motor that rotates the rotary shaft; a casing having a supply port through which the pulp sheet is supplied and a discharge port through which the pulp fibers are discharged, the casing housing the rotary blade attached to the rotary shaft; Equipped with When a virtual cylinder is imagined, the radius of the virtual cylinder is the distance from the center of the rotating shaft to the end of the rotating blade that is disposed farthest from the center of the rotating shaft in the radial direction of the rotating shaft, and the height of the virtual cylinder is the distance of the section in the axial direction of the rotating shaft in which the multiple rotating blades are disposed. The volume of the void space in the virtual cylinder is defined as V [m ３ ]year, The rotation speed of the rotating shaft is N [rpm], When the maximum crushing amount of the crushing device is Amax [kg / h], Grinding space index I [m ３ / kg] is (V [m ３ ]×N[rpm]×60[min])÷Amax[kg / h], The volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount Amax [kg / h] are the grinding space index I [m ３ / kg] is set to be 12.0 or more; Crushing equipment.

2. The volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 14.0 or more; 2. The comminuting device according to claim 1.

3. The volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 23.0 or less; 3. A crushing device according to claim 1 or 2.

4. The volume V [m ３ ], the rotation speed N [rpm] and the maximum grinding amount [kg / h] are the grinding space index I [m ３ / kg] is set to be 21.5 or less; 4. The crushing device according to claim 3.

5. The rotary shaft is further supported by a ball bearing. The rolling elements of the ball bearing are ceramic balls.

2. The comminuting device according to claim 1.

6. The ball bearing is of a grease-filled type.

6. A comminuting device according to claim 5.

7. The ball bearings are spaced apart so that a space is formed between the ball bearings and the casing.

7. A crushing device according to claim 5 or 6.

8. The ball bearing has a non-contact sealing structure.

7. A crushing device according to claim 5 or 6.