CN112156965A

CN112156965A - Screening sand device is used in road and bridge construction

Info

Publication number: CN112156965A
Application number: CN202011028450.3A
Authority: CN
Inventors: 李万明
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-09-26
Filing date: 2020-09-26
Publication date: 2021-01-01

Abstract

The invention discloses a sand screening device for road and bridge construction, and belongs to the technical field of sand screening devices. A sand screening device for road and bridge construction comprises a cylindrical screen mesh which is obliquely arranged, wherein a lower port of the cylindrical screen mesh is rotatably connected with an end cover, an upper port of the cylindrical screen mesh is fixedly connected with a ring, an upper port of the ring is rotatably connected with a feed opening, a cylindrical housing fixedly connected with the end cover is sleeved on the outer wall of the cylindrical screen mesh, a driving motor is fixedly installed on the side wall of the feed opening, the output end of the driving motor is fixedly connected with a first gear, the outer wall of the ring is fixedly connected with a ring gear meshed with the first gear, an anti-blocking device connected with the ring gear is arranged at the upper end of the cylindrical screen mesh, and a scattering device is arranged inside the cylindrical screen mesh; the cylindrical screen is higher in sand screening efficiency, the problem of blockage of the screen holes can be effectively solved in the sand screening process, and the sand screening efficiency is further improved.

Description

Screening sand device is used in road and bridge construction

Technical Field

The invention relates to the technical field of sand screening devices, in particular to a sand screening device for road and bridge construction.

Background

In the construction of roads and bridges, a large amount of sand grains are often needed, in order to make the strength and stability of the roads and bridges reach the best, the sand grains with uneven thickness need to be screened, along with the development of science, the screening work of the sand grains is mostly screened by sand screening equipment such as a sand screening machine, the efficiency is greatly improved compared with the traditional manual screening, and the sand screening method is widely used.

However, the problem that the screen is blocked often occurs in the use of the existing sand screening equipment, so that the sand screening efficiency of the sand screening equipment is greatly reduced, and although some equipment has certain anti-blocking capacity, the anti-blocking effect is relatively general.

Disclosure of Invention

The invention aims to solve the problem that a screen mesh in sand screening equipment in the prior art is easy to block, and provides a sand screening device for road and bridge construction.

In order to achieve the purpose, the invention adopts the following technical scheme:

a sand screening device for road and bridge construction comprises a cylindrical screen mesh which is obliquely arranged, wherein a lower port of the cylindrical screen mesh is rotatably connected with an end cover, an upper port of the cylindrical screen mesh is fixedly connected with a ring, an upper port of the ring is rotatably connected with a feed opening, the end cover and the lower end of the feed opening are both fixedly provided with supporting legs, the outer wall of the cylindrical screen mesh is sleeved with a cylindrical housing which is fixedly connected with the end cover, the side wall of the feed opening is fixedly provided with a driving motor, the output end of the driving motor is fixedly connected with a first gear, the outer wall of the ring is fixedly connected with a ring gear which is meshed with the first gear, the lower end of the cylindrical housing is fixedly connected with a material receiving cover which is communicated with the cylindrical housing, the lower end of the material receiving cover is provided with a first feed opening, the lower end of the end cover is provided with a second feed opening, and, the inside of drum screen cloth is equipped with breaks up the device.

Preferably, the anti-blocking device comprises a rectangular box fixedly connected to the upper end of the cylindrical housing, a bottom plate is fixedly connected to the inner bottom of the rectangular box, a plurality of through holes corresponding to meshes of the cylindrical screen are formed in the upper end of the bottom plate, an insertion rod is connected to the through holes in a sliding mode, the insertion rod is connected to the through holes in a sliding mode, a pressing plate is connected to the upper end of the insertion rod in a sliding mode, the pressing plate is connected to the bottom plate through a reset spring in an elastic mode, a rotating rod parallel to the pressing plate is connected between the two ends of the rectangular box in a rotating mode, a first cam matched with the pressing plate is fixedly connected to the outer wall of the rotating rod, and a second gear meshed with the ring gear is.

Preferably, the scattering device comprises a rotating shaft connected to the inner wall of the end cover in a rotating mode, the right end of the rotating shaft extends into the cylindrical sieve, the rotating shaft is located in the cylindrical sieve and is fixedly connected with a plurality of uniformly distributed stirring rods, the left end of the rotating shaft extends to the outer wall of the end cover and is fixedly connected with a large turntable, the left end of the rotating rod extends to the left side of the end cover and is fixedly connected with a small turntable, a connecting rod is rotatably connected to the outer edge of the side wall of the large turntable, and the tail end of the connecting rod is rotatably connected to the outer edge of the side wall of.

Preferably, connect the interior bottom of material cover to first discharge gate slope setting, the upper end of connecing the material cover interior bottom surface rotates the swash plate that is connected with rather than the laminating, the lower extreme lateral wall fixedly connected with slide of swash plate, the lower extreme lateral wall that connects the material cover be equipped with slide complex fluting, the lower extreme fixedly connected with of slide is dull and stereotyped, the lower extreme that connects the material cover rotates through two supports and is connected with the transmission shaft, the left end fixedly connected with of transmission shaft and the dull and stereotyped second cam that corresponds, the right-hand member fixedly connected with and the third gear of ring gear meshing of tightening art transmission shaft.

Preferably, the inner wall of the upper end of the cylindrical housing is rotatably connected with a scraper which is obliquely arranged, and the side wall of the scraper is elastically connected with the inner wall of the cylindrical housing through a torsion spring.

Preferably, the outer walls of the transmission shaft, the third gear, the ring gear, the first gear, the small turntable and the large turntable are all sleeved with protective covers.

Preferably, the lower end of the inserted rod is hemispherical.

Preferably, an anti-blocking rod fixedly connected with the lower end of the inclined plate is arranged in the first discharging port.

Preferably, the inlet of the feed opening is curved upwards in an arc shape.

Preferably, the flat plate is elastically connected with the lower end face of the material receiving cover through a jacking spring.

Compared with the prior art, the invention provides a sand screening device for road and bridge construction, which has the following beneficial effects:

1. this screening sand device is used in road and bridge construction, driving motor can drive ring gear through first gear and rotate, ring gear can drive the drum screen cloth through the ring and rotate, the grains of sand are filtered through pivoted drum screen cloth, the fine sand of screening can drop in the material cover that connects of lower extreme, then discharge from first discharge gate, and the coarse sand can slide down in the drum screen cloth effect of slope and fall the end cover, discharge from the second discharge gate at last, pivoted drum screen cloth can carry out automatic turn-ups to the grains of sand, the screening efficiency is high.

2. This road and bridge construction is with screening sand device, when the drum screen cloth rotated the screening, ring gear can drive the bull stick through the second gear and rotate, the bull stick then can drive first cam and rotate at the rectangle box, first cam then can be with discontinuous press down the roof pressure board, the roof pressure board is automatic re-setting under reset spring's effect, and realize the reciprocal slip from top to bottom of roof pressure board, so the roof pressure board then can drive the inserted bar reciprocal slip from top to bottom of lower extreme, thereby will be located the downthehole sand grain top of drum screen cloth and advance in the drum screen cloth, with this circulation, the inserted bar then can effectively solve the problem of screen hole jam, thereby promote the screening efficiency of drum screen cloth.

3. This road and bridge construction is with screening sand device, when the bull stick rotated, the bull stick can drive the small turntable and rotate, and the small turntable passes through the connecting rod with crank rocker mechanism's principle and drives the big carousel horizontal hunting, and the big carousel then can drive the puddler through the pivot and carry out horizontal hunting at the interior bottom of drum screen cloth to stir the grains of sand, further promote screening efficiency.

4. This screening sand device is used in road and bridge construction, get into in the fine sand and connect the material cover after, the upper end that the fine sand can drop the swash plate, ring gear passes through third gear revolve, the third gear passes through the transmission shaft and drives the second cam rotation, the second cam then can be intermittent with dull and stereotyped jack-up that makes progress, the dull and stereotyped jack-up that then can make progress through the left end discontinuity of slide with the swash plate, thereby the left end that makes the swash plate carries out the luffing motion, thereby it changes the landing in first row of material to lead to the fine sand on the swash plate.

Drawings

FIG. 1 is a schematic structural view of a sand screening device for road and bridge construction according to the present invention;

FIG. 2 is a schematic structural view of the site A in FIG. 1 of a sand sieving device for road and bridge construction according to the present invention;

FIG. 3 is a schematic structural view of a sand sieving device for road and bridge construction shown in FIG. 1 at B;

FIG. 4 is a left-side sectional structural diagram of a sand screening device for road and bridge construction according to the present invention;

FIG. 5 is a schematic structural view of a sand sieving device for road and bridge construction shown at the position C in FIG. 1;

FIG. 6 is a schematic structural view of a sand sieving device for road and bridge construction shown at D in FIG. 4; .

In the figure: 1. a cylindrical screen; 2. an end cap; 3. a torsion spring; 4. a circular ring; 5. a feeding port; 6. supporting legs; 7. a cylindrical housing; 8. a material receiving cover; 9. a rectangular box; 10. a first discharge port; 11. a second discharge opening; 12. a drive motor; 13. a first gear; 14. a ring gear; 15. a base plate; 16. a through hole; 17. inserting a rod; 18. a top pressing plate; 19. a return spring; 20. a rotating rod; 21. a first cam; 22. a second gear; 23. a small turntable; 24. a rotating shaft; 25. a stirring rod; 26. a large turntable; 27. a connecting rod; 28. a sloping plate; 29. a drive shaft; 30. a third gear; 31. grooving; 32. a flat plate; 33. the spring is tightly propped; 34. a second cam; 35. an anti-blocking rod; 36. a slide plate; 37. a scraper.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Example 1

Referring to fig. 1-6, a sand sieving device for road and bridge construction comprises a cylinder screen 1 which is obliquely arranged, the lower port of the cylinder screen 1 is rotatably connected with an end cover 2, the upper port of the cylinder screen 1 is fixedly connected with a ring 4, the upper port of the ring 4 is rotatably connected with a feed opening 5, the lower ends of the end cover 2 and the feed opening 5 are both fixedly provided with supporting legs 6, the outer wall of the cylinder screen 1 is sleeved with a cylinder housing 7 which is fixedly connected with the end cover 2, the side wall of the feed opening 5 is fixedly provided with a driving motor 12, the output end of the driving motor 12 is fixedly connected with a first gear 13, the outer wall of the ring 4 is fixedly connected with a ring gear 14 which is meshed with the first gear 13, the lower end of the cylinder housing 7 is fixedly connected with a material receiving housing 8 which is communicated with the cylinder housing 7, the lower end of the material receiving housing 8 is provided with a, the upper end of the cylindrical screen 1 is provided with an anti-blocking device connected with a ring gear 14, the interior of the cylindrical screen 1 is provided with a scattering device, sand grains are input from a feed opening 5 after a driving motor 12 is moved, the sand grains can slide into the cylindrical screen 1 under the action of gravity, the driving motor 12 can drive the ring gear 14 to rotate through a first gear 13, the ring gear 14 can drive the cylindrical screen 1 to rotate through a ring 4, the sand grains are screened through the rotating cylindrical screen 1, screened fine sand can fall into a material receiving cover 8 at the lower end, then discharge from first discharge gate 10, and the coarse sand can be discharged from second discharge gate 11 in the cylinder screen cloth 1 effect gliding of slope falls end cover 2 at last, and pivoted cylinder screen cloth 1 can carry out automatic turn-ups to the grit, and the screening efficiency is high, prevents that stifled device can prevent that cylinder screen cloth 1 from appearing blockking up in the use, breaks up the device and can carry out the turn-ups to the grit in the cylinder screen cloth 1.

Furthermore, the inlet of the feed opening 5 is curved upwards in an arc shape, so that the sand particles are not easy to accumulate during feeding.

Example 2

Referring to fig. 1, 2, 4 and 6, basically the same as embodiment 1, further: the anti-blocking device comprises a rectangular box 9 fixedly connected to the upper end of a cylindrical housing 7, a bottom plate 15 is fixedly connected to the inner bottom of the rectangular box 9, a plurality of through holes 16 corresponding to the meshes of the cylindrical screen 1 are formed in the upper end of the bottom plate 15, inserting rods 17 are slidably connected in the through holes 16, top pressure plates 18 are fixedly connected to the upper ends of the inserting rods 17, the top pressure plates 18 are elastically connected with the bottom plate 15 through reset springs 19, rotating rods 20 parallel to the top pressure plates 18 are rotatably connected between the two ends of the rectangular box 9, first cams 21 matched with the top pressure plates 18 are fixedly connected to the outer walls of the rotating rods 20, second gears 22 meshed with the ring gears 14 are fixedly connected to the right ends of the rotating rods 20, when the cylindrical screen 1 is rotated and screened, the ring gears 14 drive the rotating rods 20 to rotate the rotating rods 20 to drive the first cams 21 to rotate in the rectangular box 9, and the first cams 21 press the top pressure plates 18 downwards discontinuously, the top pressure plate 18 automatically resets under the action of the reset spring 19, the top pressure plate 18 can slide up and down in a reciprocating mode, the top pressure plate 18 can drive the inserting rod 17 at the lower end to slide up and down in a reciprocating mode, sand grains in the screen holes in the top of the cylindrical screen 1 are pushed into the cylindrical screen 1, and the inserting rod 17 can effectively solve the problem that the screen holes are blocked due to circulation, so that the screening efficiency of the cylindrical screen 1 is improved.

Furthermore, the inner wall of the upper end of the cylindrical housing 7 is rotatably connected with a scraper 37 which is obliquely arranged, the side wall of the scraper 37 is elastically connected with the inner wall of the cylindrical housing 7 through a torsion spring 3, and the scraper 37 is tightly pressed against the outer wall of the cylindrical screen 1 under the action of the torsion spring 3, so that protruded sand grains clamped in the mesh holes of the cylindrical screen 1 can be pushed into the cylindrical screen 1.

Furthermore, the lower end of the inserted rod 17 is hemispherical, so that the inserted rod 17 can be pushed into the screen hole more easily.

Example 3

Referring to fig. 1 and 3, basically the same as in embodiment 1, further: the scattering device comprises a rotating shaft 24 which is rotatably connected to the inner wall of an end cover 2, the right end of the rotating shaft 24 extends into a cylindrical screen mesh 1, the lower end of the rotating shaft 24, which is positioned in the cylindrical screen mesh 1, is fixedly connected with a plurality of uniformly distributed stirring rods 25, the left end of the rotating shaft 24 extends to the outer wall of the end cover 2 and is fixedly connected with a large turntable 26, the left end of a rotating rod 20 extends to the left side of the end cover 2 and is fixedly connected with a small turntable 23, the outer edge of the side wall of the large turntable 26 is rotatably connected with a connecting rod 27, the tail end of the connecting rod, when the rotating rod 20 rotates, the rotating rod 20 can drive the small rotating disc 23 to rotate, the small rotating disc 23 drives the large rotating disc 26 to swing left and right through the connecting rod 27 according to the principle of a crank rocker mechanism, and the large rotating disc 26 can drive the stirring rod 25 to swing left and right at the inner bottom of the cylindrical screen 1 through the rotating shaft 24, so that sand grains are turned, and the screening efficiency is further improved.

Example 4

Referring to fig. 1 and 5, basically the same as in embodiment 1, further: the inner bottom of the material receiving cover 8 is obliquely arranged towards the first discharge port 10, the upper end of the inner bottom surface of the material receiving cover 8 is rotatably connected with an inclined plate 28 attached to the inner bottom surface of the material receiving cover 8, the side wall of the lower end of the inclined plate 28 is fixedly connected with a sliding plate 36, the side wall of the lower end of the material receiving cover 8 is provided with a slot 31 matched with the sliding plate 36, the lower end of the sliding plate 36 is fixedly connected with a flat plate 32, the lower end of the material receiving cover 8 is rotatably connected with a transmission shaft 29 through two supports, the left end of the transmission shaft 29 is fixedly connected with a second cam 34 corresponding to the flat plate 32, the right end of the contraction transmission shaft 29 is fixedly connected with a third gear 30 meshed with a ring gear 14, after fine sand enters the material receiving cover 8, the fine sand falls onto the upper end of the inclined plate 28, the ring gear 14 rotates through the third gear 30, the third gear 30 drives the second cam 34 to rotate through the transmission shaft 29, the second cam 34 intermittently, so that the left end of the sloping plate 28 swings up and down, thereby causing fine sand on the sloping plate 28 to slide down into the first discharge port 10 more easily.

Furthermore, the outer walls of the transmission shaft 29, the third gear 30, the ring gear 14, the first gear 13, the small turntable 23 and the large turntable 26 are all sleeved with protective covers to play a protective role.

Furthermore, an anti-blocking rod 35 fixedly connected with the lower end of the inclined plate 28 is arranged in the first discharging port 10, and the anti-blocking rod 35 in the first discharging port 10 slides up and down under the action of the inclined plate 28, so that the first discharging port 10 is prevented from being blocked.

Furthermore, the flat plate 32 is elastically connected with the lower end surface of the material receiving cover 8 through a jacking spring 33, and when the inclined plate 28 swings intermittently up and down, the jacking spring 33 can enable the inclined plate 28 to swing quickly and downwards to reset.

The working principle is as follows: in the invention, when sand screening operation is required to be carried out on sand grains, the driving motor 12 is started to input the sand grains from the feed opening 5, the sand grains slide into the cylindrical screen mesh 1 under the action of gravity, the driving motor 12 drives the ring gear 14 to rotate through the first gear 13, the ring gear 14 drives the cylindrical screen mesh 1 to rotate through the ring 4, the sand grains are screened through the rotating cylindrical screen mesh 1, screened fine sand falls into the receiving cover 8 at the lower end and is then discharged from the first discharge opening 10, coarse sand slides down into the end cover 2 under the action of the inclined cylindrical screen mesh 1 and is finally discharged from the second discharge opening 11, the rotating cylindrical screen mesh 1 can automatically turn over the sand grains, the screening efficiency is high, when the cylindrical screen mesh 1 rotates and is screened, the ring gear 14 drives the rotating rod 20 to rotate through the second gear 22, the rotating rod 20 drives the first cam 21 to rotate in the rectangular box 9, the first cam 21 presses the top pressing plate 18 downwards discontinuously, the top pressing plate 18 automatically resets under the action of the reset spring 19, so that the top pressing plate 18 slides up and down in a reciprocating manner, the top pressing plate 18 drives the lower insertion rod 17 to slide up and down in a reciprocating manner, sand grains in the screen holes in the top of the cylindrical screen 1 are pushed into the cylindrical screen 1, and accordingly, the insertion rod 17 can effectively solve the problem of screen hole blockage, the screening efficiency of the cylindrical screen 1 is improved, the rotating rod 20 drives the small rotating disc 23 to rotate while the rotating rod 20 rotates, the small rotating disc 23 drives the large rotating disc 26 to swing left and right through the connecting rod 27 according to the principle of a crank rocker mechanism, the large rotating disc 26 drives the stirring rod 25 to swing left and right at the inner bottom of the cylindrical screen 1 through the rotating shaft 24, sand grains are turned over, the screening efficiency is further improved, after fine sand enters the material receiving cover 8, fine sand can drop the upper end of swash plate 28, ring gear 14 rotates through third gear 30, third gear 30 passes through transmission shaft 29 and drives second cam 34 and rotate, second cam 34 then can be intermittent with dull and stereotyped 32 jack-up that makes progress, dull and stereotyped 32 then can be through slide 36 with the left end intermittent type jack-up that makes progress of swash plate 28, thereby make the left end of swash plate 28 carry out the luffing motion, thereby lead to fine sand on the swash plate 28 to change the landing to in the first discharge gate 10, and anti-blocking rod 35 in the first discharge gate 10 slides from top to bottom under the effect of swash plate 28, thereby prevent that the condition of jam from appearing in first discharge gate 10.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. The utility model provides a road and bridge construction is with screening sand device, drum screen cloth (1) including the slope setting, its characterized in that, the lower port of drum screen cloth (1) rotates and is connected with end cover (2), last port fixedly connected with ring (4) of drum screen cloth (1), the last port of ring (4) rotates and is connected with feed opening (5), the equal fixed mounting of lower extreme of end cover (2) and feed opening (5) has supporting leg (6), the outer wall cover of drum screen cloth (1) is equipped with drum housing (7) with end cover (2) fixed connection, the lateral wall fixed mounting of feed opening (5) has driving motor (12), the first gear (13) of output fixedly connected with of driving motor (12), the outer wall fixedly connected with of ring (4) and the ring gear (14) of first gear (13) meshing, the lower extreme fixedly connected with of drum housing (7) connects material cover (8) that feed through with drum housing (7) of drum housing (7), the lower extreme fixedly ) The material receiving cover is characterized in that a first discharge port (10) is arranged at the lower end of the material receiving cover (8), a second discharge port (11) is arranged at the lower end of the end cover (2), an anti-blocking device connected with a ring gear (14) is arranged at the upper end of the cylinder screen (1), and a scattering device is arranged inside the cylinder screen (1).

2. The road and bridge construction sand screening device according to claim 1, wherein the anti-blocking device comprises a rectangular box (9) fixedly connected to the upper end of a cylindrical housing (7), a bottom plate (15) is fixedly connected to the inner bottom of the rectangular box (9), a plurality of through holes (16) corresponding to the screen holes of the cylindrical screen (1) are formed in the upper end of the bottom plate (15), insertion rods (17) are slidably connected in the through holes (16), a top pressure plate (18) is fixedly connected to the upper ends of the insertion rods (17), the top pressure plate (18) is elastically connected with the bottom plate (15) through a return spring (19), a rotating rod (20) parallel to the top pressure plate (18) is rotatably connected between the two ends of the rectangular box (9), a first cam (21) matched with the top pressure plate (18) is fixedly connected to the outer wall of the rotating rod (20), the right end of the rotating rod (20) is fixedly connected with a second gear (22) meshed with the ring gear (14).

3. The road and bridge construction sand screening device according to claim 2, wherein the scattering device comprises a rotating shaft (24) rotatably connected to the inner wall of the end cover (2), the right end of the rotating shaft (24) extends into the cylindrical screen (1), the rotating shaft (24) is located in the cylindrical screen (1), the lower end of the rotating shaft (24) is fixedly connected with a plurality of uniformly distributed stirring rods (25), the left end of the rotating shaft (24) extends to the outer wall of the end cover (2) and is fixedly connected with a large rotating disc (26), the left end of the rotating rod (20) extends to the left side of the end cover (2) and is fixedly connected with a small rotating disc (23), the outer edge of the side wall of the large rotating disc (26) is rotatably connected with a connecting rod (27), and the tail end of the connecting rod (27) is rotatably connected to the outer edge of the side wall of the.

4. The sand screening device for road and bridge construction according to claim 2, the inner bottom of the material receiving cover (8) is obliquely arranged towards the first discharge port (10), the upper end of the inner bottom surface of the material receiving cover (8) is rotatably connected with an inclined plate (28) attached with the material receiving cover, a sliding plate (36) is fixedly connected with the side wall of the lower end of the sloping plate (28), a slot (31) matched with the sliding plate (36) is arranged on the side wall of the lower end of the material receiving cover (8), the lower end of the sliding plate (36) is fixedly connected with a flat plate (32), the lower end of the material receiving cover (8) is rotatably connected with a transmission shaft (29) through two supports, the left end of the transmission shaft (29) is fixedly connected with a second cam (34) corresponding to the flat plate (32), and the right end of the tightening transmission shaft (29) is fixedly connected with a third gear (30) meshed with the ring gear (14).

5. The road and bridge construction sand screening device as claimed in claim 1, wherein the inner wall of the upper end of the cylindrical housing (7) is rotatably connected with a scraper (37) which is obliquely arranged, and the side wall of the scraper (37) is elastically connected with the inner wall of the cylindrical housing (7) through a torsion spring (3).

6. The road and bridge construction sand screening device as claimed in claim 4, wherein the transmission shaft (29), the third gear (30), the ring gear (14), the first gear (13), the small turntable (23) and the large turntable (26) are all sleeved with protective covers.

7. The sand screening device for road and bridge construction as claimed in claim 2, wherein the lower end of the insert rod (17) is formed in a hemispherical shape.

8. The sand screening device for road and bridge construction according to claim 4, wherein an anti-blocking rod (35) fixedly connected with the lower end of the inclined plate (28) is arranged in the first discharge port (10).

9. The road and bridge construction sand screening device as claimed in claim 1, wherein the inlet of the feed opening (5) is curved upwards in an arc shape.

10. The road and bridge construction sand screening device as claimed in claim 4, wherein the flat plate (32) is elastically connected with the lower end surface of the material receiving cover (8) through a jacking spring (33).