Screw conveyor intermediate bearing

Abstract

To provide intermediate bearings to support a screw shaft at appropriate intervals to minimize the deflection of the screw shaft, because of the adverse effects such as contact between a screw blade and an inner diameter of a conveyance tube due to the deflection of the screw shaft and crushing of a conveyed article due to the bite of the conveyed article, in a screw conveyor with a built-in screw having the same central axis as a cylindrical conveyance tube, when constructing a long-distance conveyance tube for powder and granules.SOLUTION: A screw conveyor with a unit length that does not cause adverse effects due to deflection of a screw in a conveying pipe described above is manufactured, and an intermediate bearing unit, as shown in Figure 1, is connected to enable smooth rotation of the screw shaft, dustproof and waterproof measures for the screw shaft rotating parts, and easy assembly and disassembly to construct a long-distance conveying pipe line using the screw conveyor.SELECTED DRAWING: Figure 1

Description

Technology field

[0001] The present invention relates to a screw conveyor for conveying powdery or granular materials, and more particularly to an intermediate bearing for enabling long-distance conveyance by the screw conveyor.

[0002] A spiral structure in which a thin strip-shaped plate with a large aspect ratio is wound around an axis at a specific interval and fixed is called a screw, the axis alone is called a screw axis, and the wrapped plate-like material is called a screw blade. The housing that houses the screw is a cylindrical tube with the same central axis as the screw, called a conveying tube. A structure with a rotation drive device for a screw set in a conveying pipe is called a screw conveyor.

[0003] When a screw rotates inside a conveying pipe and is transporting grains or other materials, if the radial gap between the outer diameter of the screw blade and the inner diameter of the conveying pipe becomes less than 1.5 times the long diameter of the material, the material will become jammed and the screw will stop rotating.If the screw is 4m or less in length, the reduction in the gap is due to the bending of the screw shaft, but this is not a problem.However, if the screw is over 6m in length, the reduction in the gap due to the bending of the screw shaft cannot be ignored.On the other hand, the maximum length of stainless steel pipes commercially available for use as conveying pipes is 6m.It is therefore more economical and convenient for transport purposes to manufacture not only the conveying pipes but also the screws in 6m increments. For the above reasons, in order to make long-distance transport over 6m possible, the screw shaft must be extended in several stages, but in order to minimize the deflection of the screw shaft, an intermediate bearing is required for the screw shaft. [Background technology]

[0004] At present, pneumatic transport is the mainstream method for long-distance transport of powder and granular materials. Advantages include the ability to freely select the pipeline route, the ability to construct long pipelines, and the ability to prevent the transported material from scattering or being mixed with foreign matter from the outside due to the sealed pipeline structure. Disadvantages include the extremely high power consumption compared to other transport devices, which significantly increases running costs. The air flow velocity for transport is at least 15m / sec, which is fast enough to cause fragmentation of the transported material and significant wear at the bends in the pipeline. It is not uncommon for the capacity of the blower, which generates the air for transport, and the capacity of the accompanying electric motor to exceed 250 kW, and in many cases, all of these are custom-made. A rotary pump is required to send the powder into the transport pipe, and additional equipment such as a cyclone is required at the discharge section to separate solids and gases.The design requires many complex calculations and is not easy.

[0005] There are few practical examples of screw conveyors (conveying devices with a screw built into a cylindrical conveying pipe) that form the basis of this invention for long-distance transport, and most practical examples of screw conveyors are those with a screw built into a U-shaped trough. This type of conveyor has a wide range of uses, including in the civil engineering, food, and agricultural industries, and most conveyors are less than 5m long. The advantages of the proposed screw conveyor are that, as with pneumatic conveying, the material being conveyed does not scatter and there is no mixing of foreign matter from outside due to the sealed pipes, and as the material is conveyed filling the pipes, the conveying speed is extremely slow compared to the minimum 15m / sec of pneumatic conveying, therefore there is no wear on the pipes or crushing of the material being conveyed, and the greatest advantage is that the power required for conveying is extremely small; according to data from the graduation research project by the Powder and Particle Engineering Research Group of the Department of Mechanical Systems Engineering at Kinki University College of Technology in 2005, when comparing the power consumption for conveying superabsorbent polymers over the same distance and with the same conveyance amount, screw conveying required only 1 / 20 of that of pneumatic conveying. Unlike pneumatic conveyance, screw conveyors do not require special equipment such as a rotary pump on the supply side or a cyclone on the discharge side. When designing a pipeline, the transport volume can be calculated simply by the following formula: Conveyance volume = effective cross-sectional area of pipe x screw pitch x bulk density x rotation speed x efficiency Effective cross-sectional area = Inner cross-sectional area of conveying pipe - Cross-sectional area of screw shaft [Prior art documents]

[0006] [Patent Document 1] JP 6-201517 A Screw conveyor bearing device This proposal aims to prevent powder material from getting caught in the sliding part of a sliding bearing by constantly sending high-pressure air to the sliding part, and its design concept is different from that of the air purge method. Summary of the Invention [Problem to be solved by the invention]

[0007] In order to transport powder and granular materials over long distances by utilizing the advantages of screw conveyors, the required length can be achieved by adding multiple individual screw conveyors, each about 6 m long. However, as mentioned above, simply adding screw shafts is not enough to deal with the bending of the screw shafts, so an intermediate bearing is required to support the screw shaft for each screw conveyor of unit length. The functions required of an intermediate bearing include allowing the screw shaft to rotate smoothly, preventing dust and moisture from entering the rotating part of the bearing, being able to be washed with water while assembled to the conveying pipeline, having compensation to reduce any increase in resistance to the movement of the conveyed goods that occurs due to the structure of the intermediate bearing, and being easy to assemble and disassemble. [Means for solving the problem]

[0008] 5 ball bearings are used in the bearing section to ensure smooth rotation of the screw shaft.

[0009] To prevent dust and moisture from getting into the rotating parts of the bearing, The bearing house 7, which holds the outer ring of the ball bearing 5, is spindle-shaped, and conical covers 12, which are fixed to the screw shaft at both ends and can rotate together with the screw shaft, are attached with a gap of 0.5 to 1 mm between the conical part of the bearing house 7 and the inside of the conical cover 12 so that they do not come into contact with each other. An O-ring 18 is placed in the opening 12-a of the cone cover 12 to prevent leakage when the outer periphery of the bearing house 7 and the cone are filled with air for air purging inside the bar 12. The air for air purging is supplied through the air holes 23 of the four stems 10 connecting the bearing house to the outer ring, and is taken in from the air supply port 22 for air purging of the outer ring 11, and sent between the conical part of the bearing house 7 and the inside of the conical cover 12. The air pressure for the air purge is set to 200 KPa or more, which is higher than the outside air pressure, and the pressure difference at the opening 12-a of the conical cover 12 prevents the intrusion of dust and moisture.

[0010] When washing the intermediate bearing with water while it is installed in the conveying pipe line, in order to improve the washing ability, especially between the conical cover opening 12-a and the stem 10 where dust tends to accumulate, the air pressure for air purging is 200 to 250 kPa during normal operation, but during washing, high-pressure air of 0.5 MPa or more is supplied through the same air path as the air path for air purging and sprayed over the O-ring 18 at the conical cover opening 12-a. The general purpose of O-rings is to maintain airtightness, so they are used in a compressed state with pressure applied between the inner and outer circumferences. The required degree of compression of the O-ring 18 is such that it maintains airtightness at a pressure of 200 to 250 KP, but leaks at a pressure of 0.5 MPa or more.

[0011] Countermeasures against increased resistance to movement of the transported goods by installing the bearing house 7 of the intermediate bearing inside the transport pipe; In order to compensate for the reduction in the internal cross-sectional area of the conveying pipe due to the installation of the bearing house 7, the diameter of the outer ring 11 supporting the bearing house 7 is increased so that the cross-sectional area between the bearing house 7 and the outer ring 11 is equal to or greater than the cross-sectional area of the conveying pipe portion. The bearing house 7 has a spindle-like shape with conical ends, and one end of the conical cover 12 attached to fit this shape is also conical to reduce the resistance to the movement of the powder. The structure of the intermediate bearing makes it impossible to construct continuous screw blades, resulting in missing sections of the screw blades. These missing sections do not provide axial thrust for the transported material, so to compensate for this, auxiliary blades 20 are attached to the outer periphery of the parallel section of the conical cover 12 to ensure axial thrust.

[0012] The entire conveying pipeline, including the intermediate bearing, can be easily installed and removed. For example, when connecting and assembling 6m conveying pipes, if the screw is to be attached after the conveying pipes are connected, it will be inserted from the end of the conveying pipe, so a clearance of at least 6.5m is required. To avoid this method of work, the connection work is performed with the screw inserted in the conveying pipe. To enable the above work, the intermediate bearing unit is composed of three blocks: an upstream conveying pipe adapter, an intermediate bearing part, and a downstream conveying pipe adapter. Each block is fastened with easily detachable ferrules 13 and 14. When assembling for the first time, first, without attaching the cap 8 of the bearing house 7, the bearing 5 and oil seals 4, 6 are fitted into the holes machined to the H tolerance of the mounting part from the mounting side of the cap 8 using a special tool, then the distance collar 21 is inserted and the cap 8 is attached, and then the O-ring 18 is attached. With the downstream conveying pipe adapter attached to the downstream conveying pipe, the fastening screw 3 side of the downstream screw 2 is pulled out from the downstream conveying pipe adapter to a distance where the conical cover 12 can be attached, and the conical cover 12 is attached. Next, the screw direction of the downstream screw shaft is inserted into the bearing house until it is stopped by the side of the bearing. The fixing part of the bearing inner ring of the downstream screw shaft is processed into a clearance fit of f7 to make it easy to insert and remove. The fixing of the bearing inner ring and downstream screw shaft is done by clamping the side of the bearing inner ring when fastening the upstream screw shaft 1. As with the downstream screw shaft, the threaded portion of the upstream screw shaft is extended to a distance where a conical cover 12 can be attached, and after attaching the conical cover 12, it is fastened to the downstream screw shaft. When fastening the screw shafts, a so-called spigot structure 1-a is used to ensure that the axial centers are aligned. The upstream and downstream conveying pipes are fastened using the intermediate bearing ferrule fastening clamp. Disassembly is performed in the reverse order of assembly.

[0013] The intermediate bearing of the screw conveyor has been unitized (Figure 1) to make it versatile, and the upstream conveying pipe adapter 16 + intermediate bearing part + downstream conveying pipe adapter 17 have been unitized as a set, standardizing conveying pipe specifications from 40A to 400A. [Effects of the Invention]

[0014] The present invention has made it possible to construct long-distance pipelines using screw conveyors for transporting powder and granular materials, with little power loss, no crushing of the transported objects, and little wear on the pipelines. [Brief explanation of the drawings]

[0015] [Figure 1] Cross-sectional view of the intermediate bearing of the screw conveyor of the present invention [Figure 2] Air hole for purging air from intermediate bearing of screw conveyor of the present invention DETAILED DESCRIPTION OF THE INVENTION

[0016] (The entire proposed intermediate bearing) As shown in Figure 1, the entire proposed intermediate bearing is made up of three blocks: upstream conveying pipe adapter + intermediate bearing section + downstream conveying pipe adapter. Each block is fastened together not with bolts and nuts, which are cumbersome to work with, but with ferrules, which are easy to attach and detach, and the whole is unitized.

[0017] (Dustproof and waterproof) As shown in Figures 1 and 2, an air purge system is used in which air at higher pressure than atmospheric pressure is sent in to prevent dust and moisture from entering the rotating parts of the ball bearing 5 and oil seals 4, 6. In more detail, the bearing house 7 that holds the outer ring of the bearing is spindle-shaped with conical ends, and conical covers 12 that rotate in the same direction as the screw shaft and are fixed to both ends are positioned so that the inside of the conical covers does not come into contact with the outer periphery of the bearing house. Compressed air used for air purging or cleaning is supplied from the air supply port 22 for air purging shown in FIG. 2, and is sent to the inside of the conical cover 12 from the conical parts at both ends of the bearing house 7 via the air purging air holes 23 of the stem 10. An O-ring 18 is placed between the outer periphery of the bearing house and the inside of the conical cover at the opening 12-a of the conical cover to prevent air leakage during air purging. Regarding the degree of compression of the O-ring 18, the degree of compression of the O-ring 18 was set to satisfy two conditions: no leakage during the air purging operation, and high-pressure air is sent into the air path for air purging during water washing, and is sprayed out from the opening 12-a of the conical cover 12 toward the stem 10, so that high-pressure air will cause leakage.

[0018] (Screw shaft fastening and ball bearing fitting) The screw shaft is fastened with a screw joint at the ball bearing installation location, and a joint method with a spigot structure 1-a as shown in Figure 1 is used to align the shaft center. The fitting part 2-a between the ball bearing inner ring and the screw shaft is a clearance fit, making it easy to attach and detach during assembly and disassembly. The ball bearing inner ring and screw shaft are fixed together by clamping the ball bearing inner ring by tightening the shaft fastening screw 3. [Explanation of symbols]

[0019] 1 Upstream screw 1-a Spigot concave 2 downstream screw 2-a Ball bearing inner ring fitting 3 Screw shaft fastening screw 4 stickers 1 5 ball bearings 5-a Ball bearing outer ring fitting 6 Seal 2 7. Bearing House 8 Cap 9 Cap mounting screws 10 Stem 11 Outer ring 12 Cone Cover 12-a Conical cover opening 13 Ferrule for intermediate bearing 14 Ferrule for conveying pipe 15 Upstream conveying pipe 16 Upstream conveying pipe adapter 17 Downstream conveying pipe adapter 18 O-ring 19 Flat head screw 20 Auxiliary blade 21 Distance Color 22 Air supply port for air purge 23 Air purging hole 24 Cap tightening female screw 2

Claims

1. In an intermediate bearing for a screw conveyor that transports powder and granular materials, the bearing house, which is installed in line with the central axis of the transport pipe, is spindle-shaped, and funnel-shaped conical covers, which are fixed to the screw shaft at both ends and can rotate with the screw, are placed close enough to the conical parts at both ends of the bearing house so as not to come into contact with each other.The space between the conical covers and the bearing house is filled with air at a pressure higher than atmospheric pressure from outside the transport pipe through an air hole in the stem that supports the bearing house, a so-called air purging method is used to prevent the intrusion of foreign matter such as dust or moisture into the rotating part.

2. In the intermediate bearing described in paragraph 1 above, with regard to the adapter connecting the intermediate bearing portion and the conveying pipe, the outer diameter of one side of the adapter is the same as the outer diameter of the intermediate bearing outer ring, and the other side is the same as the outer diameter of the conveying pipe.As a result, the conveying pipe adapter has a sloping portion shaped like a cut-out cone due to the difference in outer diameter at both ends.The sloping angle of this sloping portion is the same as the sloping angle of both ends of the bearing house and the cone cover, making this an intermediate bearing with a structure that allows the conveyed material to be transported smoothly.

3. In the intermediate bearing described in paragraph 1 or 2, the stem supporting the bearing house is provided with an air hole for supplying air for air purging or high-pressure air for cleaning, and the cross-sectional shape of the stem is a deformed rhombus, which reduces the flow resistance of the transported goods.

4. In the intermediate bearings of items 1 to 3 above, an O-ring is attached to the opening of the conical cover to prevent air leakage from the air purge between the bearing house and the conical cover, and an air pressure of 200 KPa is maintained for the air purge, but when cleaning with water, an air pressure of about 0.5 MPa is applied and the air is sprayed out past the O-ring to the outside, enhancing the cleaning effect. A typical O-ring achieves this purpose by compressing the inner and outer diameters to maintain airtightness at high pressure, but this intermediate bearing has a structure with an O-ring compression ratio that causes no leakage at 200 KPa but causes leakage at 0.5 MPa.

5. In the intermediate bearings of items 1 to 3 above, the stem that fixes the bearing house inside the conveying pipe makes it impossible to construct a continuous screw, which reduces the thrust in the screw axial direction.To compensate for this, an intermediate bearing is constructed in which an auxiliary vane with the same twist angle as the twist angle of the upstream or downstream screw is attached for one pitch to the outer periphery of the parallel part of the upstream or downstream conical cover.

6. In the intermediate bearings of items 1 to 3 above, the screw shaft is extended to ensure the required length to enable long-distance transport of transported goods, the extension is made by a threaded joint at the inner ring of the ball bearing inside the bearing house, the fit between the inner ring of the ball bearing and the screw shaft is made by providing the screw shaft with an f tolerance, or so-called clearance fit, making it easy to attach and detach the ball bearing and the screw shaft, and the fixing of the inner ring of the ball bearing to the screw shaft is achieved by clamping the inner ring of the ball bearing with the fastening force of the threaded joint, thereby fixing the inner ring of the ball bearing to the screw shaft.

7. In the intermediate bearings of paragraphs 1 to 3 above, the fit between the outer ring of the ball bearing in the bearing house and the bearing house has an H tolerance, and the housing that holds the outer ring of the bearing is about 5 mm wider than the total width of the multiple ball bearings, so that the intermediate bearing has a structure that can accommodate the expansion and contraction of the screw shaft.

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