Centrifugal separator

Abstract

To provide a centrifugal separator which achieves overload protection of a gear box with a simple structure.SOLUTION: A centrifugal separator of the invention includes a bowl, a screw conveyor, a gear box, and a torque control device. The torque control device includes: a torque arm fixedly connected to a shaft of the gear box; and a torque lever which holds the torque arm to prevent rotation of the shaft of the gear box when centrifugal separation is performed and which releases holding of the shaft to allow the rotation and stop occurrence of a differential velocity when an overload, caused by torque becoming a predetermined torque or larger, occurs in the gear box. In a connection part between the torque arm and the shaft of the gear box, a bushing is fitted in a space between an outer peripheral surface of the shaft and a bearing enclosing the outer peripheral surface to connect the torque arm to the shaft with the bushing and allow the torque arm and the shaft to rotate integrally.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a centrifugal separator for separating a solid-liquid mixture from a solid-liquid mixture, and more particularly to torque control of a gearbox that generates a differential speed between a bowl and a screw conveyor. [Background technology]

[0002] A centrifugal separator known as a decanter is known as a device for separating solids from a treatment liquid containing solids. Figure 8 shows a schematic diagram of the basic structure of a decanter. A horizontal decanter 1 includes a bowl 11 that rotates around a horizontal axis and a screw conveyor 12. Although not shown, a vertical decanter is also known in which the bowl 11 and screw conveyor 12 rotate around a vertical axis.

[0003] Bowl 11, which rotates to separate the processing liquid therein into solid and liquid, is a cylindrical body with one or both ends formed into a conical shape. Screw conveyor 12 is a rotary conveying means equipped with screw blades 12a that convey the solid material resulting from solid-liquid separation in bowl 11. Screw conveyor 12 is hollow along the central axis of rotation, and processing liquid supply nozzle 13 is inserted with a slight clearance so as not to come into contact with screw conveyor 12. Processing liquid discharged from the tip of supply nozzle 13 is supplied to a processing liquid chamber in screw conveyor 12, and is then discharged from supply hole 14 by the action of centrifugal force and supplied into bowl 11.

[0004] In this configuration, when the treatment liquid containing solids is continuously supplied into bowl 11 and bowl 11 is rotated at a predetermined rotation speed, the treatment liquid is separated into a solid phase and a liquid phase in bowl 11 by the action of centrifugal force. The solids are transported toward one end of bowl 11 by screw conveyor 12, separate from the liquid phase in the conical portion, and discharged through solids outlet 15. Meanwhile, the liquid phase (separated liquid) overflows and is discharged from separated liquid outlet 16 on the opposite side.

[0005] If the bowl 11 and the screw conveyor 12 rotate at the same speed, the solids in the bowl 11 cannot be transported. Therefore, the bowl 11 and the screw conveyor 12 are connected by a gearbox to generate a differential speed. Typically, the bowl 11 is rotated by a motor, and the screw conveyor 12 is rotated via a gearbox. The screw conveyor 12 rotates at a speed (differential speed) corresponding to a gear ratio setting, etc. In this configuration, if the conveying torque of the screw conveyor 12 increases depending on the condition of the solids in the bowl 11, an overload may occur in the gearbox, potentially causing damage to the internal gears. One known solution to this problem is to install an overload prevention device. However, it has been pointed out that existing overload prevention devices have a complex connection structure with the gearbox and a large number of parts (see, in particular, Patent Document 1). Furthermore, there is a risk of oil filling the gearbox leaking from the connection. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4808219 [Patent Document 2] China Utility Model Registration No. CN217940513 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a centrifugal separator that prevents overload of the gearbox with a simple configuration. [Means for solving the problem]

[0008] The gist of the present invention is as follows. (1) The present invention provides a centrifugal separator including a bowl that rotates to separate a treatment liquid therein into solid and liquid, a screw conveyor that rotates at a differential speed relative to the bowl and conveys solid matter in the bowl toward a discharge outlet, a gearbox that generates the differential speed between the bowl and the screw conveyor, and a torque control device for the gearbox, The torque control device comprises a torque arm fixedly connected to the shaft of the gear box, and a torque lever that holds the torque arm to prevent the shaft of the gear box from rotating when centrifugal separation is performed, and releases the holding of the shaft to allow it to rotate when a predetermined torque overload occurs in the gear box, thereby stopping the generation of the differential speed, At a connection portion between the torque arm and the shaft of the gearbox, A bushing is fitted between the outer circumferential surface of the shaft and a bearing surrounding the outer circumferential surface, and the torque arm and the shaft are connected by the bushing to be rotatable together. (2) The bushing has a tapered portion that expands in diameter from the tip to the base end along the axial direction, and is fitted axially from the tip between the outer surface of the shaft and a bearing surrounding the outer surface, bringing the tapered portion into close contact with the bearing. [Effects of the Invention]

[0009] According to the present invention, a torque control device is provided which includes a torque arm fixedly connected to the gearbox shaft, and a torque lever which holds the torque arm to prevent the gearbox shaft from rotating when centrifugation is being performed, and which releases the hold on the shaft to allow it to rotate when a predetermined torque overload occurs on the gearbox, thereby stopping the generation of differential speed.At the connection between the torque arm and the gearbox shaft, a bushing is fitted between the outer surface of the shaft and the bearing surrounding the outer surface, and the torque arm and shaft are connected by the bushing so that they can rotate together, thereby making it possible to prevent overload on the gearbox with a simple configuration.

[0010] Furthermore, by fitting a bushing between the outer periphery of the shaft and the bearing surrounding it, the rotation axis of the shaft can be maintained in the correct position. As a result, oil leakage from the gearbox can be prevented. This effect can be further enhanced by providing a tapered section to the bushing. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a vertical cross-sectional view of a centrifugal separator according to a preferred embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view of a torque arm of the centrifugal separator. [Figure 3] FIG. 2 is an enlarged view of a torque arm of the centrifugal separator. [Figure 4] FIG. 2 is a development view of the torque arm. [Figure 5] FIG. 2 is an enlarged view of a torque lever of the centrifugal separator. [Figure 6] FIG. 2 is an enlarged view of a torque lever of the centrifugal separator. [Figure 7] FIG. 10 is an explanatory diagram showing another configuration of the torque control device. [Figure 8] FIG. 1 is a diagram showing the configuration of a conventional centrifugal separator. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a centrifugal separator according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the technical scope of the present invention is not to be construed as being limited by the following embodiments.

[0013] FIG. 1 shows a decanter 2 as a preferred example of a centrifugal separator. The decanter 2 includes a casing 22 having a solids outlet 20 and a separated liquid outlet 21 disposed on the bottom side thereof, a bowl 3 disposed within the casing 22, a screw conveyor 4 for transporting the solids separated by centrifugal separation within the bowl 3, and a feed tube 5 for supplying the solids-containing treatment liquid into the bowl 3. The bowl 3 has both shafts rotatably supported by a bearing mechanism 23, such as a bearing disposed outside the casing 22. The screw conveyor 4 has both shafts rotatably supported by a bearing mechanism 24, such as a conveyor bearing. Reference numeral 25 denotes a partition wall that divides the space within the casing 22, reference numeral 26 denotes a support frame for the decanter 2, and reference numeral 27 denotes a support member for supporting the feed tube 5.

[0014] When the power of motor 28, which is a drive mechanism, is transmitted to pulley 28b on the bowl 3 side via rotating belt 28a, bowl 3 rotates, and the rotational power is further transmitted to screw conveyor 4 via gearbox 6 and spline shaft 61, which are differential speed generating devices, causing bowl 3 and screw conveyor 4 to rotate at a relative differential speed. As an example of normal operation, bowl 3 is rotated at a predetermined rotation speed selected from a range of 500 to 8000 rpm, and screw conveyor 4 is rotated at a differential speed of 0.5 to 50 rpm relative to bowl 3, and centrifugal separation is performed.

[0015] Bowl 3 has a conical portion 31 formed at one end of its cylindrical body, and a disk-shaped member called a front hub 32 at the other end. The body of bowl 3 forms a pool (liquid reservoir) for the treatment liquid supplied into bowl 3. Meanwhile, conical portion 31 forms a beach portion where solids transported by screw conveyor 4 separate from the liquid phase, and a solids discharge outlet 33 is provided at its end. Furthermore, front hub 32 is provided with a separated liquid discharge outlet 34 through which the separated liquid overflows and is discharged. Separated liquid discharge outlet 34 is a circular opening that penetrates front hub 32.

[0016] The screw conveyor 4 has spirally formed screw blades 41 on its outer circumferential surface for transporting the solid material in the bowl 3. Furthermore, the screw conveyor 4 has a supply hole 42 on its outer circumferential surface. The supply hole 42 communicates with a liquid supply chamber 43 formed inside the screw conveyor 4 on the tip side.

[0017] The feed tube 5 is close to or inserted into the liquid supply chamber 43 without coming into contact with the rotating bowl 3 and screw conveyor 4. A pipe from a liquid supply means such as a pump is connected to the base end of the feed tube 5. The treatment liquid supplied by the liquid supply means is discharged from the tip of the feed tube 5 into the liquid supply chamber 43, and the treatment liquid supplied into the liquid supply chamber 43 is discharged from the supply hole 42 by the action of the centrifugal force of the rotating screw conveyor 4 and supplied into the bowl 3, where it is separated into solids and separated liquid by the above-mentioned action and discharged. The control unit 7 is a computer, control panel, etc. that controls the operation of the decanter 2.

[0018] The torque control device 8, which controls the torque of the gearbox 6 and enables overload prevention, includes a torque arm 81 and a torque lever 82. The torque arm 81 is disposed on the gearbox 6 side, and the torque lever 82 is disposed on the support frame 26 side, for example.

[0019] As shown in FIGS. 2 to 4, the torque arm 81 is fixedly connected to the shaft 62 of the gearbox 6 using a bushing 83. In other words, the torque arm 81 is directly connected to the shaft 62 of the gearbox 6 without the use of a power transmission mechanism such as a coupling. Because it is directly connected, no bearing for the torque arm 81 is provided separately from the gearbox 6. In other words, a simple connection structure is achieved with a small number of parts.

[0020] The shaft 62 is the shaft of the sun gear (not shown) of the gearbox 6. The gearbox 6 shown in FIGS. 2 to 4 is an example of a two-speed gearbox. Of course, this is not limited to a two-speed gearbox. When the motor 28 rotates the bowl 3, the gearbox 6 transmits power to a shell 63 having a ring gear on its inner circumferential surface. The rotation of the shell 63 causes the first-stage and second-stage planetary gears (not shown) disposed therein to rotate and revolve, thereby rotating the spline shaft 61 (see FIG. 1) of the screw conveyor 4 at a speed corresponding to the gear ratio. The shell 63, the first-stage planetary gear, and the shaft 62 are rotatable relative to one another via bearings 64, 65, and 66. When the gearbox 6 prevents the sun gear shaft 62 from rotating, a differential speed is generated. When the shaft 62 is allowed to rotate, the differential speed is not generated, and the bowl 3 and the screw conveyor 4 rotate at the same speed.

[0021] The torque arm 81 has an arm 81b extending in the diameter direction around the outer periphery of the annular portion 81a. Furthermore, a pad 81c is provided at the tip of the arm 81b. A fan-shaped weight 81d, for example, is provided at a position opposite the arm 81b across the rotation axis of the torque arm 81 to prevent eccentricity due to mass imbalance when the torque arm 81 rotates. The torque arm 81 is made of metal, for example, iron or stainless steel.

[0022] A pedestal 81e is provided on the annular portion 81a of the torque arm 81. A flange portion 83a of the bushing 83 is in surface contact with this pedestal 81e directly or via a bracket or the like, and the torque arm 81 and the bushing 83 are fixed to each other with a bolt 83b, which is an example of a fixing means. Meanwhile, the shaft 62 and the bushing 83 are adapted to rotate integrally by fitting a key 62a into key grooves formed in the shaft 62 and the bushing 83, respectively. However, the structure and fixing means relating to the connection between the torque arm 81 and the bushing 83, and the structure and fixing means relating to the connection between the bushing 83 and the shaft 62 may be modified as appropriate.

[0023] On the other hand, the bearing 64 is provided on the gearbox 6 side, allowing the torque arm 81, bushing 83, and shaft 62 to rotate as a unit. Furthermore, the oil seal 67 is supported on both sides by the bearings 64 and 65, preventing oil leakage from the gearbox 6. In other words, if the bearing 64 were not provided and the oil seal 67 were supported on one side by the bearing 65, as in the conventional configuration, an unbalanced radial load (a load acting perpendicular to the axis) would be applied to one side of the oil seal 67, causing the rotation axis of the shaft 62 to shift slightly, creating a gap in the oil seal 67 and resulting in oil leakage. In this embodiment, the bearing 64, which supports the torque arm 81, bushing 83, and shaft 62 so that they can rotate as a unit, is used to prevent oil leakage. The portion of the bushing 83 between the bearing 64 and the shaft 62 is tapered in the axial direction. This tapered portion 83d increases in diameter from the tip toward the base end where the flange 83a is located. Therefore, when assembling the torque control device 8, first the annular portion 81a of the torque arm 81 is passed over the shaft 62, and then the bushing 83 is fitted in the axial direction. By providing the tapered portion 83d, when the bushing 83 is fitted, a force acts in a direction that pushes the bearing 64 apart, thereby making it possible to closely contact the bearing 64 and the bushing 83 and to maintain the rotation axis of the shaft 62 in the correct position. As a result, the application of an unbalanced load to the oil seal 67 is suppressed, and the effectiveness of preventing oil leakage from inside the gearbox 6 is improved.

[0024] With the above configuration, the torque control device 8 of this embodiment can directly and fixedly connect the torque arm 81 to the shaft 62, and further, the shaft 62, torque arm 81, and bushing 83 can rotate integrally via the bearing 64.

[0025] Next, the configuration of the torque lever 82 will be described with reference to FIGS. 5 and 6. FIG. 5 shows the state during normal operation when centrifugal separation is being performed, and FIG. 6 shows the state when overload of the gearbox 6 is being avoided. As shown in FIGS. 5 and 6, the torque lever 82 is disposed on a base plate 84 fixed to, for example, the support frame 26 (FIG. 1) of the decanter 2. Note that FIG. 5 uses color to make the range of the torque lever 82 easier to understand. The torque lever 82 is rotatable by a shaft 82a, which serves as a rotation axis, provided on the base plate 84. One end of the torque lever 82 is provided with a torque lever pad 82b that receives a pad 81c provided at the arm tip of the torque arm 81. The other end of the torque lever 82 is connected to one end of a spring-type cylinder 85 via a shaft 82c, which serves as a rotation axis. The other end of the cylinder 85 is rotatable by a shaft 85a, which serves as a rotation axis.

[0026] The base plate 84 is provided with a stopper 86 for normal operation and a stopper 87 for overload prevention. During normal operation, the locking member 82d of the torque lever 82 abuts against the stopper 86, preventing the torque lever 82 from rotating further downward. Similarly, during overload prevention, the locking member 82e of the torque lever 82 abuts against the stopper 87, preventing the torque lever 82 from rotating further upward.

[0027] A limit switch 9 is provided on the upper side of the cylinder 85. The limit switch 9 is arranged so that a bar 91, which is the switch detection end, comes into contact with the outer circumferential surface of the cylinder 85. Fig. 5 shows the limit switch 9 in the OFF state, and Fig. 6 shows the limit switch 9 in the ON state.

[0028] The operation of the torque control device 8 configured as described above will be further described with reference to FIGS. 5 and 6. During normal operation as shown in FIG. 5, the torque lever pad 82b of the torque lever 82 holds the torque arm 81, preventing it from rotating. That is, even if the torque arm 81 attempts to rotate due to the force transmitted from the shaft 62, the torque arm 81 is prevented from rotating by the elastic force generated by the spring in the cylinder 85. If the force of the cylinder 85 is too strong, it will not be possible to prevent overloading of the gearbox 6. Therefore, the spring constant of the spring in the cylinder 85, for example, is set so that the state shown in FIG. 6 will be transitioned to when a predetermined torque is applied to the shaft 62. The cylinder 85 may be an air cylinder, and the setting may be pneumatic. The predetermined torque for transitioning to the state shown in FIG. 6 is set, for example, to a torque that prevents damage to planetary gears, etc. Of course, the torque may be set for other reasons. For example, a load cell 82f may be provided in the torque lever pad 82b to detect torque or load (see FIG. 5).

[0029] Even during normal operation, the gearbox 6 is loaded by the resistance of the screw conveyor 4 when transporting solids. However, the force of the cylinder 85 is greater, and the torque lever 82 holds the torque arm 81, preventing the shaft 62 from rotating. However, depending on the conditions in the bowl 3, for example, the solids may be dehydrated excessively, increasing the transport torque of the screw conveyor 4. In some cases, the solids may become compacted in the beach area of the bowl 3, making transport difficult. In such cases, the torque applied to the gearbox 6 exceeds a predetermined torque (i.e., the gearbox 6 is overloaded). When the overload occurs, the force of the cylinder 85 weakens, the spring inside the cylinder 85 compresses, and the torque arm 81 pushes the torque lever 82, causing it to rotate. In other words, the state transitions from Figure 5 to Figure 6.

[0030] 6, the torque lever pad 82b separates from the torque arm 81, causing the torque arm 81 to rotate. That is, the shaft 62 rotates in the gearbox 6, the differential speed stops being created, and the bowl 3 and screw conveyor 4 rotate at the same speed. When the bowl 3 and screw conveyor 4 start rotating at the same speed, the screw conveyor 4 stops transporting solids, and as a result, the load on the gearbox 6 is eliminated or becomes very small.

[0031] 6, the cylinder 85 pushes up the bar 91 of the limit switch 9, turning it ON. The ON signal from the limit switch 9 is sent to the control unit 7, which then starts to stop the operation of the decanter 2 by slowing down the rotation of the bowl 3 and stopping the supply of the treatment liquid.

[0032] According to this embodiment, by including the torque control device 8 described above, it is possible to provide a decanter 1 that prevents overload of the gearbox 6 with a simple configuration. Furthermore, it is possible to prevent oil leakage from the gearbox 6. That is, compared to the decanter 2 shown in FIG. 7, when the shaft 62 of the gearbox 6 and the shaft of the torque arm 81 are connected by a coupling 9, an additional bearing mechanism 91 for the torque arm 81 is required to prevent oil leakage, but according to this embodiment, this can be omitted and a simple configuration can be achieved.

[0033] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various substitutions, modifications, changes, etc. in form and detail can be made therein without departing from the spirit and scope of the invention as defined by the appended claims. [Explanation of symbols]

[0034] 2 decanters 3 bowls 4. Screw conveyor 5 Feed Tube 6 Gearbox 7 Control Unit 8 Torque control device 81 Torque arm 82 Torque lever 83 Bushing

Claims

1. A centrifugal separator comprising: a bowl that rotates to separate a treatment liquid therein into solid and liquid; a screw conveyor that rotates at a differential speed relative to the bowl and conveys solid matter in the bowl toward a discharge outlet; a gearbox that generates the differential speed between the bowl and the screw conveyor; and a torque control device for the gearbox, The torque control device comprises a torque arm fixedly connected to the shaft of the gear box, and a torque lever that holds the torque arm to prevent the shaft of the gear box from rotating when centrifugal separation is performed, and releases the holding of the shaft to allow it to rotate when a predetermined torque overload occurs in the gear box, thereby stopping the generation of the differential speed, At a connection portion between the torque arm and the shaft of the gearbox, a bushing fitted between an outer peripheral surface of the shaft and a bearing surrounding the outer peripheral surface, and the torque arm and the shaft connected by the bushing so as to be rotatable together as a unit;

2. The bushing has a tapered portion whose diameter increases from a tip end to a base end along an axial direction, 2. The centrifugal separator according to claim 1, wherein the shaft is fitted from the tip in the axial direction between the outer circumferential surface of the shaft and a bearing surrounding the outer circumferential surface, with the tapered portion being in intimate contact with the bearing.

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