CN112720892A

CN112720892A - 3D prints quick even agitated vessel of injection molding material

Info

Publication number: CN112720892A
Application number: CN202011472525.7A
Authority: CN
Inventors: 陈红庆; 王涵宇; 郝殷俊
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-12-15
Filing date: 2020-12-15
Publication date: 2021-04-30

Abstract

The invention discloses a rapid and uniform stirring device for 3D printing injection molding materials, which comprises a base, wherein one end of the base is provided with a first sliding groove, a stirring box is arranged in the first sliding groove, a supporting plate is arranged at one end of the stirring box far away from the first sliding groove, one side of the supporting plate is provided with a supporting frame which is fixedly connected with the base, one end of the supporting plate is provided with a second sliding groove, the stirring box is positioned between the first sliding groove and the second sliding groove, a limit groove is arranged in the stirring box, a nut is arranged in the limiting groove, the nut is sleeved on the screw rod and is in threaded connection with the screw rod, one end of the nut is fixedly provided with an air cylinder, one side of the air cylinder is provided with a baffle plate, a second motor is arranged above the baffle plate, the output end of the motor II is connected with a stirring shaft, and the stirring shaft penetrates through the baffle and extends to the outside of the baffle, and connecting plates are symmetrically arranged. Has the advantages that: the stirring is more rapid and uniform, and the stirring speed is improved.

Description

3D prints quick even agitated vessel of injection molding material

Technical Field

The invention relates to the technical field of 3D printing equipment, in particular to equipment for quickly and uniformly stirring 3D printing injection molding materials.

Background

3D printing is one of the rapid prototyping technologies, which is a technology for constructing an object by using an adhesive material such as powdered metal or plastic and the like in a layer-by-layer printing manner on the basis of a digital model file. 3D printing is typically achieved using digital technology material printers. The method is often used for manufacturing models in the fields of mold manufacturing, industrial design and the like, and is gradually used for directly manufacturing some products, and parts printed by the technology are already available. The technology has applications in jewelry, footwear, industrial design, construction, engineering and construction (AEC), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, firearms, and other fields.

Injection molding is a method for producing and molding industrial products. The products are generally produced by rubber injection molding and plastic injection molding. The injection molding can be classified into injection molding and die casting. An injection molding machine (an injection machine or an injection molding machine for short) is a main molding device for making thermoplastic plastics or thermosetting materials into plastic products with various shapes by using a plastic molding die, and the injection molding is realized by the injection molding machine and the die. However, the existing injection molding raw material stirring device for 3D printing has the defects of poor stirring effect, low stirring speed, non-uniform stirring and complex operation.

An effective solution to the problems in the related art has not been proposed yet.

Disclosure of Invention

The invention aims to provide a device for quickly and uniformly stirring a 3D printing injection molding material, which aims to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: a rapid and uniform stirring device for 3D printing injection molding materials comprises a base, wherein one end of the base is provided with a first chute, a stirring box is arranged in the first chute, one end of the stirring box, which is far away from the first chute, is provided with a supporting plate, one side of the supporting plate is provided with a supporting frame, the supporting frame is fixedly connected with the base, one end of the supporting plate is provided with a second chute, the stirring box is positioned between the first chute and the second chute, the stirring box is internally provided with a limiting groove, a nut is arranged in the limiting groove, the nut is sleeved on a screw rod, the nut is in threaded connection with the screw rod, one end of the nut is fixedly provided with a cylinder, one side of the cylinder is provided with a baffle plate, a second motor is arranged above the baffle plate, the output end of the second motor is connected with a, a scraper is arranged on one side, away from the stirring shaft, of the connecting plate, a spiral blade is arranged on the stirring shaft and below the connecting plate, a feed inlet and a discharge outlet are arranged on one side of the stirring box, a support column is arranged on the base, a moving mechanism is arranged on the support column and comprises a T-shaped support, the T-shaped support is fixedly connected with the support column, a third motor is arranged inside the T-shaped support, the output end of the third motor is connected with a rotating shaft, a disc is sleeved on the rotating shaft, a fixed column is arranged on the disc, a connecting rod is sleeved on the fixed column, a third chute is arranged on the connecting rod, the fixed column is positioned in the third chute, a fan-shaped plate is fixedly arranged at one end of the connecting rod, a first tooth is arranged at one end, away from the connecting rod, a second movable, the first tooth is meshed with the second tooth, and one end of the second movable rod is fixedly connected with the stirring box.

Furthermore, a bearing seat is fixedly arranged on the inner wall of the stirring box, and one end of the screw rod penetrates through the bearing seat and extends into the bearing seat.

Furthermore, one end, far away from the bearing seat, of the screw rod is connected with the output end of a first motor, and the first motor is fixed on the inner wall of the stirring box.

Furthermore, a through hole is formed in the middle of the sector plate, a movable shaft is arranged in the through hole, and the sector plate is connected with the T-shaped support through the movable shaft.

Furthermore, clamping plates are symmetrically arranged on the T-shaped support, sleeves are arranged on the clamping plates, and the second movable rods penetrate through the sleeves.

Further, support frame one side symmetry is equipped with buffer board one, buffer board one is kept away from support frame one end is equipped with the sleeve, run through in the sleeve and be equipped with the slide bar, the slide bar run through in the sleeve extends to be equipped with the stopper in the sleeve, the slide bar is kept away from stopper one end is equipped with buffer board two, sleeve outside cover is equipped with buffer spring, the buffer spring both ends are fixed respectively buffer board one with on the buffer board two.

Furthermore, the connecting plate is fixedly connected with the scraper through a plurality of movable rods I.

Furthermore, a wheel frame is arranged at the bottom of the base, a roller is arranged at one end, far away from the base, of the wheel frame, and the roller is connected with the wheel frame through a wheel shaft.

Furthermore, a reinforcing rib is arranged between the support frame and the support plate.

Furthermore, cover plates are arranged on the feeding hole and the discharging hole.

The invention provides a rapid and uniform stirring device for a 3D printing injection molding material, which has the following beneficial effects:

(1) when the 3D printing injection molding material is stirred, firstly, the injection molding material can be placed into a stirring box from a feeding hole, then the baffle is controlled to ascend and descend through an air cylinder, when the baffle moves to a proper position, the air cylinder stops working, a motor II works to drive a stirring shaft to rotate, a spiral blade works to stir the injection molding material, the injection molding material can be driven to move upwards through the spiral blade, and the stirring effect of the injection molding material is improved; by arranging the scraper, the adhesion amount of the injection molding material on the inner wall of the stirring box can be reduced to the maximum extent, the waste of the injection molding material is reduced, and the cleaning of the inner wall of the stirring box can be reduced; through the threaded connection of the screw rod and the nut, when the motor works, the screw rod rotates, so that the nut can move on the screw rod along the limiting groove, the air cylinder can move, and the helical blades can stir the injection molding materials at the corners, so that the stirring is more thorough; through being equipped with moving mechanism, when three during operation of motor for axis of rotation work to let the disc rotate, under the cooperation of fixed column, connecting rod, sector plate, tooth one and tooth two, will make the incessant round trip movement of movable rod two, thereby rock about realizing the agitator tank, make the stirring more even fast, improved the speed of stirring.

(2) Through being equipped with the bearing frame to play spacing fixed stay's effect to the screw rod, when motor one during operation, the screw rod can rotate. Through being equipped with the loose axle to play the effect of limit support to the sector plate, let the sector plate rotate round the loose axle, through being equipped with the sleeve, thereby play the effect of limit support to movable rod two, movable rod two can be in sleeve round trip movement.

(3) Through being equipped with buffer board one, buffer board two, when the agitator tank rocks and strikes on buffer board two, through buffer board one, buffer board two, slide bar, stopper and buffer spring's cooperation to can play fine buffering effect, avoided the agitator tank directly to strike the support frame on, cause the damage to the support frame.

(4) The first movable rod is arranged, so that the connection between the scraper and the connecting plate is realized. The roller wheels are arranged at the bottom of the base, so that the roller wheels can be moved conveniently, and the equipment is convenient to use. Through being equipped with the apron to can prevent that the dust from entering into the agitator tank, cause the pollution to the material of moulding plastics. Through being equipped with the strengthening rib to strengthen fixing between support frame and the backup pad, make equipment during operation more stable.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a 3D printing injection molding material rapid and uniform stirring device according to an embodiment of the invention;

FIG. 2 is a schematic structural diagram of a moving mechanism in a 3D printing injection molding material rapid and uniform stirring device according to an embodiment of the invention;

fig. 3 is an enlarged view at a in fig. 1.

Reference numerals:

1. a base; 2. a first sliding chute; 3. a stirring box; 4. a support plate; 5. a support frame; 6. a second chute; 7. A limiting groove; 8. a nut; 9. a screw; 10. a cylinder; 11. a baffle plate; 12. a second motor; 13. a stirring shaft; 14. a connecting plate; 15. a squeegee; 16. a helical blade; 17. a feed inlet; 18. a support pillar; 19. A discharge port; 20. a moving mechanism; 21. a T-shaped bracket; 22. a third motor; 23. a rotating shaft; 24. a disc; 25. fixing a column; 26. a connecting rod; 27. a third chute; 28. a sector plate; 29. a first tooth; 30. A second movable rod; 31. a second tooth; 32. a bearing seat; 33. a first motor; 34. a through hole; 35. a movable shaft; 36. a sleeve; 37. a first buffer plate; 38. a slide bar; 39. a limiting block; 40. a buffer spring; 41. A second buffer plate; 42. a first movable rod; 43. a cover plate; 44. reinforcing ribs; 45. and (4) fixing the cylinder.

Detailed Description

The invention is further described with reference to the following drawings and detailed description:

the first embodiment is as follows:

referring to fig. 1-3, the rapid and uniform stirring device for 3D printing injection molding materials according to the embodiment of the invention comprises a base 1, a first chute 2 is arranged at one end of the base 1, a stirring box 3 is arranged in the first chute 2, a supporting plate 4 is arranged at one end of the stirring box 3 away from the first chute 2, a supporting frame 5 is arranged at one side of the supporting plate 4, the supporting frame 5 is fixedly connected with the base 1, a second chute 6 is arranged at one end of the supporting plate 4, the stirring box 3 is positioned between the first chute 2 and the second chute 6, a limiting groove 7 is arranged in the stirring box 3, a nut 8 is arranged in the limiting groove 7, the nut 8 is sleeved on a screw rod 9, the nut 8 is in threaded connection with the screw rod 9, an air cylinder 10 is fixedly arranged at one end of the nut 8, a baffle 11 is arranged at one side of the air cylinder 10, and, the output end of the second motor 12 is connected with a stirring shaft 13, the stirring shaft 13 penetrates through the baffle 11 and extends to the outside of the baffle 11, a connecting plate 14 is symmetrically arranged on the outside of the baffle 11, a scraper 15 is arranged on one side, away from the stirring shaft 13, of the connecting plate 14, a spiral blade 16 is arranged on the stirring shaft 13 and below the connecting plate 14, a feed inlet 17 and a discharge outlet 19 are arranged on one side of the stirring box 3, a supporting column 18 is arranged on the base 1, a moving mechanism 20 is arranged on the supporting column 18, the moving mechanism 20 comprises a T-shaped support 21, the T-shaped support 21 is fixedly connected with the supporting column 18, a third motor 22 is arranged inside the T-shaped support 21, the output end of the third motor 22 is connected with a rotating shaft 23, a disc 24 is sleeved on the rotating shaft 23, a, the improved stirrer is characterized in that a third sliding groove 27 is formed in the connecting rod 26, the fixing column 25 is located in the third sliding groove 27, a sector plate 28 is fixedly arranged at one end of the connecting rod 26, the sector plate 28 is far away from one end of the connecting rod 26 and is provided with a first tooth 29, a second movable rod 30 is arranged below the first tooth 29, one side of the second movable rod 30 is provided with a second tooth 31, the first tooth 29 and the second tooth 31 are meshed with each other, and one end of the second movable rod 30 is fixedly connected with the stirring box 3.

Through the scheme of the invention, the beneficial effects are as follows: when 3D printing injection molding materials are stirred, firstly, the injection molding materials can be placed into the stirring box 3 from the feeding hole 17, then the air cylinder 10 controls the baffle 11 to ascend and descend, when the baffle moves to a proper position, the air cylinder 10 stops working, the second motor 12 works to drive the stirring shaft 13 to rotate, the helical blade 16 works to stir the injection molding materials, and the helical blade 16 is arranged to drive the injection molding materials to move upwards so as to improve the stirring effect of the injection molding materials; by arranging the scraper 15, the adhesion amount of the injection molding material on the inner wall of the stirring box 3 can be reduced to the maximum extent, the waste of the injection molding material is reduced, and the cleaning of the inner wall of the stirring box 3 can also be reduced; through the threaded connection of the screw 9 and the nut 8, when the motor I33 works, the screw 9 rotates, so that the nut 8 can move on the screw 9 along the limiting groove 7, the air cylinder 10 can move, and the helical blades 16 can stir the injection molding materials at the corners, so that the stirring is more thorough; through being equipped with moving mechanism 20, when the third 22 during operation of motor for axis of rotation 23 work to let disc 24 rotate, under the cooperation of fixed column 25, connecting rod 26, sector plate 28, tooth one 29 and tooth two 31, will make the incessant round trip movement of movable rod two 30, thereby realize rocking about agitator tank 3, make the stirring more even fast, improved the speed of stirring.

Example two:

referring to fig. 1 and 2, for the stirring box 3, a bearing seat 32 is fixedly disposed on an inner wall of the stirring box 3, and one end of the screw 9 penetrates through the bearing seat 32 and extends into the bearing seat 32. For the sake of description, the end of the screw 9 far from the bearing seat 32 is connected with the output end of a motor one 33, and the motor one 33 is fixed on the inner wall of the stirring box 3. For the sector plate 28, a through hole 34 is formed in the middle of the sector plate 28, a movable shaft 35 is arranged in the through hole 34, and the sector plate 28 is connected with the T-shaped support 21 through the movable shaft 35. For the T-shaped support 21, the T-shaped support 21 is symmetrically provided with clamping plates, the clamping plates are provided with sleeves 36, and the second movable rods 30 penetrate through the sleeves 36.

Through the scheme of the invention, the beneficial effects are as follows: by arranging the bearing seat 32, the screw 9 is limited, fixed and supported, and when the first motor 33 works, the screw 9 can rotate. Through being equipped with movable shaft 35 to play the effect of limit support to sector plate 28, let sector plate 28 rotate around movable shaft 35, through being equipped with sleeve 36, thereby play the effect of limit support to second movable rod 30, second movable rod 30 can be in sleeve 36 round trip movement.

Example three:

referring to fig. 3, for the supporting frame 5, a first buffer plate 37 is symmetrically arranged on one side of the supporting frame 5, a fixed cylinder 45 is arranged at one end of the first buffer plate 37, which is far away from the supporting frame 5, a sliding rod 38 penetrates through the fixed cylinder 45, the sliding rod 38 penetrates through the fixed cylinder 45 and extends into the fixed cylinder 45, a limiting block 39 is arranged in the fixed cylinder 45, a second buffer plate 41 is arranged at one end of the sliding rod 38, which is far away from the limiting block 39, a buffer spring 40 is sleeved on the outer side of the fixed cylinder 45, and two ends of the buffer spring 40 are respectively fixed on the first buffer plate 37 and the second buffer plate 41.

Through the scheme of the invention, the beneficial effects are as follows: through being equipped with buffer board one 37, buffer board two 41, when agitator tank 3 rocks and strikes on buffer board two 41, through buffer board one 37, buffer board two 41, slide bar 38, stopper 39 and buffer spring 40's cooperation to can play fine buffering effect, avoided agitator tank 3 directly to strike support frame 5 on, cause the damage to support frame 5.

Example four:

referring to fig. 1, for the connection plate 14, the connection plate 14 is fixedly connected to the scraper 15 through a plurality of movable rods 42. For the base 1, a wheel frame is arranged at the bottom of the base 1, a roller is arranged at one end, away from the base 1, of the wheel frame, and the roller is connected with the wheel frame through a wheel shaft. For the support frame 5, a reinforcing rib 44 is arranged between the support frame 5 and the support plate 4. For the inlet 17, a cover plate 43 is provided on both the inlet 17 and the outlet 19.

Through the scheme of the invention, the beneficial effects are as follows: the connection between the scraper 15 and the connecting plate 14 is realized by providing a movable rod 42. The roller wheels are arranged at the bottom of the base 1, so that the movement facilitating effect is achieved, and the use of equipment is facilitated. By providing the cover plate 43, it is possible to prevent dust from entering the stirring tank 3 and contaminating the injection material. By arranging the reinforcing ribs 44, the fixation between the support frame 5 and the support plate 4 is enhanced, and the equipment is more stable in operation.

In summary, with the above technical solution of the present invention, the working principle and all the beneficial effects are as follows: when 3D printing injection molding materials are stirred, firstly, the injection molding materials can be placed into the stirring box 3 from the feeding hole 17, then the air cylinder 10 controls the baffle 11 to ascend and descend, when the baffle moves to a proper position, the air cylinder 10 stops working, the second motor 12 works to drive the stirring shaft 13 to rotate, the helical blade 16 works to stir the injection molding materials, and the helical blade 16 is arranged to drive the injection molding materials to move upwards so as to improve the stirring effect of the injection molding materials; by arranging the scraper 15, the adhesion amount of the injection molding material on the inner wall of the stirring box 3 can be reduced to the maximum extent, the waste of the injection molding material is reduced, and the cleaning of the inner wall of the stirring box 3 can also be reduced; through the threaded connection of the screw 9 and the nut 8, when the motor I33 works, the screw 9 rotates, so that the nut 8 can move on the screw 9 along the limiting groove 7, the air cylinder 10 can move, and the helical blades 16 can stir the injection molding materials at the corners, so that the stirring is more thorough; through being equipped with moving mechanism 20, when the third 22 during operation of motor for axis of rotation 23 work to let disc 24 rotate, under the cooperation of fixed column 25, connecting rod 26, sector plate 28, tooth one 29 and tooth two 31, will make the incessant round trip movement of movable rod two 30, thereby realize rocking about agitator tank 3, make the stirring more even fast, improved the speed of stirring. By arranging the bearing seat 32, the screw 9 is limited, fixed and supported, and when the first motor 33 works, the screw 9 can rotate. Through being equipped with movable shaft 35 to play the effect of limit support to sector plate 28, let sector plate 28 rotate around movable shaft 35, through being equipped with sleeve 36, thereby play the effect of limit support to second movable rod 30, second movable rod 30 can be in sleeve 36 round trip movement. Through being equipped with buffer board one 37, buffer board two 41, when agitator tank 3 rocks and strikes on buffer board two 41, through buffer board one 37, buffer board two 41, slide bar 38, stopper 39 and buffer spring 40's cooperation to can play fine buffering effect, avoided agitator tank 3 directly to strike support frame 5 on, cause the damage to support frame 5. The connection between the scraper 15 and the connecting plate 14 is realized by providing a movable rod 42. The roller wheels are arranged at the bottom of the base 1, so that the movement facilitating effect is achieved, and the use of equipment is facilitated. By providing the cover plate 43, it is possible to prevent dust from entering the stirring tank 3 and contaminating the injection material. By arranging the reinforcing ribs 44, the fixation between the support frame 5 and the support plate 4 is enhanced, and the equipment is more stable in operation.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The quick and uniform stirring equipment for the 3D printing injection molding material is characterized by comprising a base (1), wherein one end of the base (1) is provided with a first sliding groove (2), a stirring box (3) is arranged in the first sliding groove (2), one end, far away from the first sliding groove (2), of the stirring box (3) is provided with a supporting plate (4), one side of the supporting plate (4) is provided with a supporting frame (5), the supporting frame (5) is fixedly connected with the base (1), one end of the supporting plate (4) is provided with a second sliding groove (6), the stirring box (3) is positioned between the first sliding groove (2) and the second sliding groove (6), a limiting groove (7) is arranged in the stirring box (3), a nut (8) is arranged in the limiting groove (7), the nut (8) is sleeved on a screw rod (9), and the nut (8) is in threaded connection with the screw rod (9), the improved stirring device is characterized in that an air cylinder (10) is fixedly arranged at one end of the nut (8), a baffle (11) is arranged on one side of the air cylinder (10), a motor II (12) is arranged above the baffle (11), the output end of the motor II (12) is connected with a stirring shaft (13), the stirring shaft (13) penetrates through the baffle (11) and extends to a connecting plate (14) which is symmetrically arranged outside the baffle (11), a scraper (15) is arranged on one side, far away from the stirring shaft (13), of the connecting plate (14), a spiral blade (16) is arranged on the stirring shaft (13) and below the connecting plate (14), a feeding port (17) and a discharging port (19) are arranged on one side of the stirring box (3), a supporting column (18) is arranged on the base (1), a moving mechanism (20) is arranged on the supporting column (18), and the moving, the T-shaped support (21) is fixedly connected with the supporting column (18), a motor III (22) is arranged inside the T-shaped support (21), the output end of the motor III (22) is connected with the rotating shaft (23), a disc (24) is sleeved on the rotating shaft (23), a fixing column (25) is arranged on the disc (24), a connecting rod (26) is sleeved on the fixing column (25), a sliding groove III (27) is formed in the connecting rod (26), the fixing column (25) is located in the sliding groove III (27), a sector plate (28) is fixedly arranged at one end of the connecting rod (26), a tooth I (29) is arranged at one end, far away from the connecting rod (26), of the sector plate (28), a movable rod II (30) is arranged below the tooth I (29), a tooth II (31) is arranged on one side of the movable rod II (30), and the tooth I (29) and the tooth II (31) are mutually meshed, one end of the second movable rod (30) is fixedly connected with the stirring box (3).

2. The 3D printing injection molding material rapid and uniform stirring device according to claim 1, wherein a bearing seat (32) is fixedly arranged on the inner wall of the stirring box (3), and one end of the screw (9) penetrates through the bearing seat (32) and extends into the bearing seat (32).

3. 3D printing injection molding material rapid and uniform stirring equipment according to claim 2, characterized in that one end of the screw (9) far away from the bearing seat (32) is connected with the output end of a first motor (33), and the first motor (33) is fixed on the inner wall of the stirring box (3).

4. The 3D printing injection molding material rapid and uniform stirring device according to claim 3, wherein a through hole (34) is formed in the middle of the sector plate (28), a movable shaft (35) is arranged in the through hole (34), and the sector plate (28) is connected with the T-shaped support (21) through the movable shaft (35).

5. The 3D printing injection molding material rapid and uniform stirring device according to claim 4, wherein clamping plates are symmetrically arranged on the T-shaped support (21), sleeves (36) are arranged on the clamping plates, and the second movable rods (30) penetrate through the sleeves (36).

6. The 3D printing injection molding material rapid and uniform stirring device according to claim 5, wherein a first buffer plate (37) is symmetrically arranged on one side of the support frame (5), a fixed cylinder (45) is arranged at one end, far away from the support frame (5), of the first buffer plate (37), a sliding rod (38) penetrates through the fixed cylinder (45), the sliding rod (38) penetrates through the fixed cylinder (45) and extends to a limiting block (39) arranged in the fixed cylinder (45), a second buffer plate (41) is arranged at one end, far away from the limiting block (39), of the sliding rod (38), a buffer spring (40) is sleeved on the outer side of the fixed cylinder (45), and two ends of the buffer spring (40) are respectively fixed on the first buffer plate (37) and the second buffer plate (41).

7. The 3D printing injection molding material rapid and uniform stirring device according to claim 6, characterized in that the connecting plate (14) is fixedly connected with the scraper (15) through a plurality of movable rods I (42).

8. The 3D printing injection molding material rapid and uniform stirring device according to claim 7, wherein a wheel frame is arranged at the bottom of the base (1), and a roller is arranged at one end of the wheel frame away from the base (1), and is connected with the wheel frame through a wheel shaft.

9. The 3D printing injection molding material rapid and uniform stirring device according to claim 8, characterized in that a reinforcing rib (44) is arranged between the supporting frame (5) and the supporting plate (4).

10. The 3D printing injection molding material rapid and uniform stirring device according to claim 9, wherein the feed inlet (17) and the discharge outlet (19) are provided with cover plates (43).