JP2012000551A - Screw conveyor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw conveyor which structurally prevents a tip from falling off from a pedestal without using brazing or bonding.SOLUTION: An engaging recess 21 of the pedestal 11 is engaged to an engaging projection 15 of the tip 10. In this engagement state, a groove 19 serving as a cotter receiving part and a groove 13 serving as a cotter locking part are locked through a cotter 12. A plurality of pairs of the pedestal 11 and the tip 10 are adjacently mounted along the leading end of a spiral blade 53.

Description

  The present invention relates to a screw conveyor of a centrifuge for solid-liquid separation of a stock solution containing a solid substance, and in particular, a screw conveyor in which a chip made of an abrasion-resistant material is attached to a base fixed to the tip of a spiral blade. About.

  Conventionally, screw decanter type centrifuges are used for solid-liquid separation of a stock solution containing a solid substance such as a slurry. As shown in FIG. 6, the centrifuge 50 includes an outer cylinder 51 that rotates in one direction, and is coaxially disposed in the outer cylinder 51 and has a rotational speed difference from the outer cylinder 51 in the same direction. And a rotating screw 52. The screw 52 includes an inner cylinder 54 and a spiral blade 53. In the centrifugal separator 50, the stock solution is supplied from the stock solution supply port 55 via the discharge port 58 between the outer tube 51 and the inner tube 54. And the undiluted | stock solution receives the centrifugal force of the rotating outer cylinder 51, and is isolate | separated into solid liquid by the difference in specific gravity of a structural component. Further, the screw 52 that rotates relative to the outer cylinder 51 by the amount corresponding to the rotational speed difference moves the solid object to the right in the drawing along the axial direction of the outer cylinder 51. As a result, the stock solution is separated into a solid liquid, the liquid is discharged from the discharge port 57, and the solid material is discharged from the discharge port 56.

  Further, the screw 52 having a rotational speed difference from the outer cylinder 51 is easily worn by the tip of the spiral blade 53 due to the action of the solid material contained in the stock solution, and requires early repair and replacement. Become. In order to reduce this amount of wear, for example, a ceramic chip 60 is attached to the tip of the spiral blade 53 as shown in FIG. As shown in FIG. 8, the tip 60 is brazed to a stainless steel base 61 welded to the tip of the spiral blade 53 using a silver solder.

  Since the chip 60 called a so-called carbide chip is weak against heat and easily cracks, a brazing operation or a welding operation requires skill to prevent the chip 60 from being overheated. Moreover, even with skilled technology, the yield of these operations is poor and is said to be 90%. In addition, since the heating conditions are severe, it is extremely difficult to use a cemented carbide tip having a hardness equivalent to V10 of JIS classification. Furthermore, there is a report that industrial waste is contained in what is handled as the stock solution, and the brazed portion is corroded, and the chip 60 is detached from the pedestal 61. Various proposals have been made to solve the problems related to brazing and welding.

  As shown in FIG. 9, the screw conveyor of Patent Document 1 has a chip 66 attached to a recess provided in a pedestal 65. One end of the tip 66 is a bent portion 67, and the bent portion 67 is inserted into the pocket 68 of the pedestal 65 while the tip 66 is rotated counterclockwise, and a gap between the inner wall of the pocket 68 and the bent portion 67 is inserted. Is filled with an adhesive 69.

  As shown in FIG. 10, in the screw conveyor of Patent Document 2, the pedestal 70 and the chip 72 are bonded and fixed in a state in which the protruding strip portion 73 of the chip 72 is fitted in the lateral groove 71 of the pedestal 70. Further, a vertical groove 74 is formed in the pedestal 70, and a concave portion 75 is formed on the side of the chip 72 opposite to the convex strip portion 73. A mounting piece 76 is inserted into the vertical groove 74 and the concave portion 75 and fixedly adhered thereto.

  As shown in FIG. 11, the screw conveyor of Patent Document 3 stores a chip 82 in a storage recess 81 of a pedestal 80, and the chip 82 and the pedestal 80 are fixed by screws 83.

JP 7-171439 A Japanese Patent Laid-Open No. 7-289942 Japanese Patent Laid-Open No. 10-128156

  In the screw conveyor of Patent Document 1, if the pedestal 65 is first welded to the tip of the spiral blade and then the tip 66 is fixed to the pedestal 65, the problem of damage to the cemented carbide tip due to heating can be solved. However, since the fixing of the chip 66 to the pedestal 65 depends on the adhesive strength of the adhesive, another problem arises that the adhesive strength is reduced due to a change in the adhesive over time or due to a chemical reaction caused by the stock solution. Yes.

  In the screw conveyor of Patent Literature 2, the adoption of the mounting piece 76 prevents the chip 72 from shifting in the width direction with respect to the base 70. Further, the left and right side walls of the vertical groove 74 are inclined surfaces, and the vertical groove 74 is shaped like a dovetail so that the mounting piece 76 does not float from the vertical groove 74. Therefore, the chip 72 does not float from the pedestal 70. However, since the pedestal 70, the chip 72, and the mounting piece 76 are fixed to each other by bonding, this screw conveyor has the same problem as that of the screw conveyor of Patent Document 1.

  The chip 82 in the screw conveyor of Patent Document 3 is fixed to the base 80 with screws 83. For this reason, there is no problem related to the adhesive, but there is a problem that the screw 83 falls off.

  The present invention has been made paying attention to such a problem, and an object of the present invention is to provide a screw conveyor that structurally prevents chips from falling off a pedestal without brazing or bonding. There is.

  In order to solve the above problem, the invention of the screw conveyor according to claim 1 is a screw conveyor of a centrifuge in which a chip made of an abrasion-resistant material is attached to a base fixed to the tip of a spiral blade. Is provided with an engagement concave portion and a cotter receiving portion, and the chip is provided with an engagement convex portion and a cotter locking portion, and the engagement convex portion is engaged with the engagement concave portion. In the state in which the chip is prevented from shifting inward in the radial direction of the screw conveyor, the chip is moved to the screw conveyor by locking the cotter receiving portion and the cotter locking portion via a cotter. This is characterized in that it is prevented from shifting outward in the radial direction.

  According to the said structure, the shift | offset | difference of the chip | tip to the radial inside of a screw conveyor was prevented by engagement of the engagement convex part of the chip | tip with the engagement recessed part of a base. Further, this engagement state prevents the chip from separating from the pedestal in the direction perpendicular to the contact surface between the chip and the pedestal. Further, the engagement between the cotter receiving part and the cotter locking part via the cotter prevents the chip from being displaced radially outward of the screw conveyor. For this reason, the chip is fixed to the pedestal in a state where it is prevented from shifting in the radial direction of the screw conveyor and is prevented from moving away from the pedestal.

  A plurality of pedestals and chips are attached along the tip of the spiral blade. For this reason, since the chips are adjacent to each other, there is no room for the chips to be displaced along the width direction. Further, the cotter is prevented from dropping from the inserted base by the adjacent base or chip. Therefore, the tip and the base are fixed.

  According to a second aspect of the present invention, in the screw conveyor of the first aspect, the tip is formed in a block-like body having a rectangular cross section, and the engaging convex portion is formed on the base in the tip. It is characterized by having a slope formed on the surface opposite to the abutting surface.

  According to a third aspect of the present invention, in the screw conveyor according to the first or second aspect, the cotter receiving portion and the cotter locking portion may be configured so that the pedestal and the tip are in contact with each other on the spiral surface. It is either a curved groove portion formed in a direction along the tip of the blade or a linear groove portion formed along each width direction.

  According to a fourth aspect of the present invention, in the screw conveyor according to the first or second aspect, the cotter receiving portion is formed in a direction along the tip of the spiral blade on the surface of the pedestal that contacts the tip. Or a linear groove formed along the width direction of the pedestal, and the cotter locking portion is a width of the chip on the surface of the chip that contacts the pedestal. It is a protrusion formed along the direction.

  According to a fifth aspect of the present invention, in the screw conveyor according to any one of the first to fourth aspects, the pedestal has a long spiral shape so that a plurality of the chips can be engaged. It is formed and fixed along the tip of the spiral blade.

  According to the present invention, the engagement state between the base and the chip can be maintained by the engagement between the cotter receiving portion and the cotter engagement portion via the cotter. In addition, the cotter is prevented from dropping from the inserted base by the adjacent base or chip. Therefore, it is possible to provide a screw conveyor in which the pedestal and the chip are engaged without being affected by the stock solution and without being changed with time.

The perspective view which shows the base and chip | tip attached to the spiral blade of 1st Embodiment. The assembly state of the base and chip | tip attached to the spiral blade of 1st Embodiment is shown, (a) is a front view, (b) is AA arrow sectional drawing of (a). The assembly state of the base and chip | tip attached to the spiral blade of 2nd Embodiment is shown, (a) is a front view, (b) is BB arrow sectional drawing of (a). The assembly state of the base and chip | tip attached to the spiral blade of 3rd Embodiment is shown, (a) is a front view, (b) is CC sectional view taken on the line of (a). The perspective view which shows the base of 4th Embodiment. The partial cross section figure which shows the centrifuge of a prior art. The perspective view which shows the screw conveyor of a prior art. The front-end | tip part of the spiral blade of a prior art is shown, (a) is a front view, (b) is DD sectional view taken on the line of (a). The assembly state of the base and chip | tip of a prior art is shown, (a) is a front view, (b) is EE arrow sectional drawing of (a). The perspective view which shows the base and chip | tip of another prior art. The assembly state of the base of another prior art and a chip | tip is shown, (a) is a front view, (b) is FF arrow sectional drawing of (a).

(First embodiment)
Hereinafter, embodiments embodying the present invention will be described with reference to FIGS. 1 and 2. In addition, about the same structure as a prior art, the same code | symbol used in the description shall be used.

  As shown in FIGS. 1 and 2, the stainless steel pedestal 11 is welded to the tip of a stainless steel spiral blade 53 at a welded portion 24. The pedestal 11 includes a first protrusion 25 and a second protrusion 26 that protrude outward in the radial direction of the screw conveyor. An engaging recess 21 is formed between the first protrusion 25 and the second protrusion 26. The surface of the second protrusion 26 on the side of the engagement recess 21 is a flat contact surface 20 with which the chip 10 is contacted. A linear groove portion 19 as a cotter receiving portion is formed on the contact surface 20 along the width direction of the base 11 (left and right direction in FIG. 2A). In the engagement recess 21, the inner surface of the first protrusion 25 connected to the bottom 23 is a slope 22 that is inclined with respect to the contact surface 20.

  The chip 10 is formed into a substantially trapezoidal block-shaped body by a cemented carbide chip of wear-resistant material. The contact surface 14 corresponding to the substantially trapezoidal bottom surface is formed in a flat shape so as to contact the contact surface 20 of the base 11. The contact surface 14 is formed with a linear groove 13 as a cotter locking portion at a position corresponding to the groove 19. Further, one end surface 17 side of the chip 10 is an engaging convex portion 15 having a slope 16. The other end surface 18 of the chip 10 is disposed opposite to the inner surface of the outer cylinder 51 in the centrifuge 50.

  In FIG. 2A, the pedestal 11 and the chip 10 are drawn as squares having the same width in the width direction. However, in practice, no gap is generated between the adjacent pedestals 11 and between the chips 10. Moreover, the base 11 and the chip 10 are formed in a fan shape in which the respective widths increase outward in the radial direction of the screw conveyor. However, as shown in FIG. 2A, the pedestal 11 and the chip 10 may be quadrangles having the same dimension in the width direction.

As shown in FIG. 2, the state in which the tip 10 is assembled to the pedestal 11 welded to the spiral blade 53 is obtained as follows.
As shown in FIG. 1, by engaging the engagement convex portion 15 of the chip 10 with the engagement concave portion 21 of the base 11, the contact surface 20 of the base 11 and the contact surface 14 of the chip 10 come into contact. In this engaged state, the slope 22 of the base 11 and the slope 16 of the chip 10 are in close contact. For this reason, the chip 10 cannot move inward in the radial direction of the screw conveyor. Further, as long as the contact between the contact surface 20 and the contact surface 14 and the contact between the inclined surface 22 and the inclined surface 16 are maintained, the pedestal 11 and the chip 10 cannot move in the separation direction on each contact surface. It has become.

  Furthermore, if the cotter 12 is inserted into the space formed by the groove 19 and the groove 13, the groove 19 and the groove 13 are locked via the cotter 12. Then, the chip 10 cannot move in the radial direction of the screw conveyor. Accordingly, since the engagement between the base 11 and the chip 10 is maintained in a close contact state, the chip 10 is fixed to the base 11 in a state in which no displacement occurs in any direction except the width direction.

  However, as shown in FIG. 2A, a plurality of pairs of the base 11 and the chip 10 are arranged adjacent to each other at the tip of the spiral blade 53. For this reason, dropping of the cotter 12 from the space formed by the groove portion 19 and the groove portion 13 does not occur even when the cotter 12 is not press-fitted. Further, the chip 10 cannot be moved in the width direction by the adjacent chip 10 or the base 11. Therefore, the chip 10 is fixed to the pedestal 11 in a state where no displacement occurs in any direction. Prevention of the cotter 12 from falling off at the base 11 located at the end will be described later.

  In addition, although the cotter 12 of this embodiment is a square bar-shaped body with which the side surfaces which oppose are parallel, it is good also as a square bar-shaped body where at least one side is a slope. Further, the projected area in the axial direction can be increased by making the cotter 12 a curved rectangular bar. If the cotter 12 having such a shape is press-fitted into the space formed by the groove portion 19 and the groove portion 13, the cotter 12 is prevented from falling off, and the engagement concave portion 21 and the engagement convex portion 15 are more reliably secured. It is kept in close contact.

  Furthermore, when arranging the plurality of bases 11 at the tip of the spiral blade 53, instead of the bases 11 located at both ends, an end base (not shown) in which the engaging recess 21 and the groove part 19 are not formed is provided. It may be arranged. In this way, the chip 10 and the cotter 12 of the pedestal 11 adjacent to the end pedestal are immovable in the width direction. Further, caulking may be applied to the boundary between the pedestal 11 and the cotter 12 disposed at both ends without disposing the end pedestal. Further, this caulking may be applied to the pedestal 11 and the cotter 12 of all combinations.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) In the above embodiment, the base 11 and the tip 10 welded to the spiral blade 53 are fixed using the cotter 12. For this reason, in assembling the chip 10 to the pedestal 11, since the chip 10 is not heated, a cemented carbide chip having a hardness equivalent to V10 of JIS classification can be used as the chip 10. In addition, since the brazing operation between the base 11 and the chip 10 can be omitted, the number of man-hours can be reduced.

  (2) In the above embodiment, after engaging the engaging recess 21 and the engaging protrusion 15, the groove portion 19 as the cotter receiving portion and the groove portion 13 as the cotter locking portion are interposed via the cotter 12. It was made to lock. For this reason, the cotter 12 does not come off unless the engaged state is released, and the engaged state is maintained unless the cotter 12 comes off. Therefore, unless the cotter 12 is forcibly removed, the fixed state between the base 11 and the chip 10 is maintained.

  (3) In the above embodiment, the groove portion 19 and the groove portion 13 are formed along the respective width directions of the base 11 and the chip 10. For this reason, in order for the cotter 12 to remove | deviate from the space formed by the groove part 19 and the groove part 13, the cotter 12 must move to the width direction. However, a plurality of pedestals 11 are welded adjacent to the tip of the spiral blade 53. Therefore, the cotter 12 cannot move left and right because of the adjacent pedestal 11, chip 10, or cotter 12. Furthermore, if the cotter 12 is press-fitted and used, the cotter 12 cannot be moved to the left and right in the respective pedestals 11 and chips 10. The immovable cotter 12 can maintain the locked state between the base 11 and the chip 10.

  (4) In the above embodiment, like the linear groove portion 19 and the linear groove portion 13, the shapes of the respective portions of the base 11 and the chip 10 are the same in the respective width directions. For this reason, each processing of the base 11 and the chip | tip 10 can be easily performed by a wire cut etc., for example.

(Second Embodiment)
Next, a second embodiment that embodies the present invention will be described with reference to FIG. 3 with a focus on differences from the first embodiment.

  In the pedestal 31 of the present embodiment, the groove portion 32 as the cotter receiving portion is a concave portion formed wide between the end portion of the contact surface 20 and the bottom portion 23 of the engaging concave portion 21. Further, a groove portion 35 serving as a cotter locking portion is interposed on the surface of the chip 30 facing the pedestal 31 so that the first contact surface 33 on the end surface 18 side and the first contact surface 33 are more outward. A protruding second contact surface 34 is formed. Therefore, since the engaging convex part 15 of the chip 30 of this embodiment has the protruding second contact surface 34, it is thicker than the engaging convex part 15 of the first embodiment. When the chip 30 is assembled to the pedestal 31 and the second contact surface 34 is disposed so as to contact the bottom of the groove 32, the space left in the groove 32 becomes the space for inserting the cotter 12. .

  As shown in FIG. 3B, the chip 30 is assembled to the base 31 by moving the chip 30 along the first direction S1 in a non-contact state between the contact surface 20 and the first contact surface 33. Start with. When the second abutment surface 34 slides with respect to the abutment surface 20 and a part of the engagement projection 15 abuts against the engagement recess 21, the second abutment surface 34 can enter the groove 32. Next, if the tip 30 is moved along the second direction S2, the engagement recess 21 and the engagement protrusion 15 are brought into close engagement with each other. Furthermore, if the cotter 12 is inserted into a space formed by the groove 32 and the groove 35, the chip 30 is fixed to the pedestal 31.

And in this 2nd Embodiment, in addition to the effect in 1st Embodiment, the following effects can be acquired.
(5) In the above-described embodiment, the engaging convex portion 15 is formed to have a thick shape by causing the second contact surface 34 to protrude outward from the first contact surface 33. For this reason, since the posture of the chip 30 is maintained with the thick engaging protrusion 15 as a base, the contact state is more reliable without the contact surface 20 and the first contact surface 33 being separated. Maintained.

(Third embodiment)
Next, a third embodiment that embodies the present invention will be described with reference to FIG. 4 with a focus on differences from the first embodiment.

  As shown in FIG. 4, the pedestal 41 of the present embodiment is formed with a groove portion 43 as a cotter receiving portion that is wider than the groove portion 19 and narrower than the groove portion 32. Further, a protrusion 42 as a cotter locking portion is formed on the contact surface 14 of the chip 40 along the width direction. When the chip 40 is assembled to the pedestal 41 and the protrusion 42 is disposed in the groove 43, the space left in the groove 43 becomes the space for inserting the cotter 12.

  As shown in FIG. 4B, the assembly of the chip 40 to the pedestal 41 is started by moving the chip 40 along the first direction S1 in a non-contact state between the contact surface 20 and the contact surface 14. Is done. When the protrusion 42 slides with respect to the abutment surface 20 and a part of the engagement protrusion 15 abuts against the engagement recess 21, the protrusion 42 enters the groove 43. You can enter. Next, if the chip 40 is moved along the second direction S2, the engagement concave portion 21 and the engagement convex portion 15 are brought into close contact with each other to be in an engaged state. Further, if the cotter 12 is inserted into a space formed by the groove 43 and the protrusion 42, the chip 40 is fixed to the pedestal 41.

And in this 3rd Embodiment, unlike the effect in 1st and 2nd embodiment, the following effects can be acquired.
(6) In the above embodiment, the protrusion 42 as the cotter locking portion along the width direction is formed on the contact surface 14 of the chip 40. For this reason, the chip 40 forms a block-like body having a uniform thickness. Therefore, the chip 40 is excellent in strength because no recess is formed.

(Fourth embodiment)
Next, a fourth embodiment embodying the present invention will be described with reference to FIG. 5 with a focus on differences from the first to third embodiments.

  As shown in FIG. 5, the pedestal 45 of the present embodiment has the same cross-sectional shape as the pedestal 11 of the first embodiment, and is formed in a long shape so that a plurality of chips 10 can be attached. A plurality of chips 10 can be assembled and fixed to the pedestal 45 in an adjacent state. And in order to make it easy to weld the base 45 along the front-end | tip of the spiral blade 53, the lower end part 46 of the base 45 is curving along the front-end | tip shape of the spiral blade 53. FIG. The engaging recess 21 and the groove 19 are also curved so as to follow the tip of the spiral blade 53. In order to obtain the curved pedestal 45, the linear pedestal 45 may be formed and then curved by pressing or the like, or the curved member may be subjected to cutting or the like.

  When the plurality of chips 10 are attached to the pedestal 45, the plurality of chips 10 are arranged without unevenness in a direction orthogonal to the direction along the tip shape of the spiral blade 53. Thus, since the several chip | tip 10 forms the uniform continuous surface along the front-end | tip shape of the spiral blade 53, the undiluted | stock solution containing a solid substance receives the smooth conveyor effect | action along the said continuous surface. it can.

  In addition, the groove part 13 of the chip 10 (not shown) may be linear or curved. Moreover, the cotter 12 inserted in the space formed by the groove portion 19 and the groove portion 13 is not particularly limited and can have a known shape.

And in this 4th Embodiment, in addition to the effect in 1st-3rd embodiment, the following effects can be acquired.
(7) In the above embodiment, the pedestal 45 is formed in a long shape so that the plurality of chips 10 can be assembled, and is curved so that it can be welded along the tip of the spiral blade 53. Formed. For this reason, unlike the case of welding a plurality of pedestals 11, the work of adjusting the arrangement position and posture for each pedestal 11 is not required, and therefore the number of man-hours for welding the pedestal 45 to the spiral blade 53 can be reduced.

  (8) In the above-described embodiment, since the plurality of chips 10 are attached to the long pedestal 45, the plurality of chips 10 are arranged without being uneven in the direction perpendicular to the direction along the tip shape of the spiral blade 53. It was possible to arrange so as to form various continuous surfaces. For this reason, like the prior art, it can prevent that the chip | tip 10 which protruded wears earlier than the other chip | tip 10, and can shorten the usable period of a screw conveyor. That is, since the wear of the plurality of chips 10 is averaged, the usable period of the screw conveyor can be extended.

  (9) In the above embodiment, the plurality of chips 10 can be arranged so as to form a uniform continuous surface. For this reason, since the continuous surface can exert a smooth conveyor action on the stock solution, it is possible to effectively perform solid-liquid separation of the stock solution by centrifugal force.

(Example of change)
In addition, the said embodiment can also be changed and actualized as follows.
An engaging protrusion in the direction perpendicular to the width direction is provided on one surface of the surfaces on which the bases 11, 31, 41 and the chips 10, 30, 40 face each other, and the engaging groove in the same direction is provided on the other surface. To provide. Due to the engagement between the engagement ridge and the engagement groove, it is possible to prevent the chips 10, 30, and 40 from shifting in the width direction with respect to the bases 11, 31, and 41.
In the second and third embodiments, in order to engage the chips 30 and 40 with the pedestals 31 and 41, the chips 30 and 40 are first moved along the first direction S1, but are moved along the second direction S2. Then, rotate in the direction along the first direction S1.
In the fourth embodiment, the cross-sectional shape of the pedestal 45 is the same as the cross-sectional shape of the pedestal 11, but the cross-sectional shape of the pedestal 31 or the pedestal 41 is the same.

  10, 30, 40 ... chip, 11, 31, 41, 45 ... pedestal, 12 ... cotter, 13, 19, 32, 35, 43 ... groove, 15 ... engaging convex, 16, 22 ... slope, 21 ... engagement Joint recess, 42 ... ridge, 50 ... centrifuge, 53 ... spiral blade.

Claims (5)

  In a screw conveyor of a centrifuge in which a tip made of wear-resistant material is attached to a pedestal fixed to the tip of a spiral blade, the pedestal is provided with an engagement recess and a cotter receiving portion. Providing a mating convex portion and a cotter locking portion, the engaging convex portion is engaged with the engaging concave portion to prevent the tip from shifting radially inward of the screw conveyor. A screw conveyor characterized in that the tip is prevented from shifting radially outward of the screw conveyor by locking the cotter receiving portion and the cotter locking portion via a cotter in a state.   The chip is formed in a block-like body having a rectangular cross section, and the engaging convex portion includes a slope formed on a surface opposite to the surface in contact with the pedestal in the chip. The screw conveyor according to claim 1.   The cotter receiving portion and the cotter locking portion are formed along curved grooves formed in the direction along the tip of the spiral blade or in the width direction on the respective surfaces where the pedestal and the chip contact each other. The screw conveyor according to claim 1, wherein the screw conveyor is any one of a straight groove portion.   The cotter receiving portion is a curved groove portion formed in a direction along the tip of the spiral blade or a linear groove portion formed along the width direction of the pedestal on the surface of the pedestal contacting the tip. 3. The cotter locking portion is a ridge formed along the width direction of the chip on the surface of the chip that contacts the pedestal. 4. Screw conveyor.   5. The pedestal is formed in a long spiral shape so that a plurality of the chips can be engaged, and is fixed along the tip of the spiral blade. The screw conveyor according to one item.

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