CN212127583U

CN212127583U - Full-automatic blue algae collecting and dewatering ship

Info

Publication number: CN212127583U
Application number: CN201921417571.XU
Authority: CN
Inventors: 韩水成; 韩吉
Original assignee: Hangzhou Shengji Metal Plastic Co ltd
Current assignee: Hangzhou Shengji Metal Plastic Co ltd
Priority date: 2019-08-29
Filing date: 2019-08-29
Publication date: 2020-12-11
Anticipated expiration: 2029-08-29

Abstract

The utility model discloses a dewatering boat is collected to full-automatic blue alga, including collecting ship, traction vessel, rail, it is provided with airtight flotation tank to collect ship bilateral symmetry, the bow bottom plate forward position of collecting the ship is equipped with the overflow door, and the effect is the thick blue alga of water purification and the upper overflow aspect before the separation ship, the rear of overflow door is equipped with the introducing port, the introducing port below is provided with nanometer air supporting cabin, and the effect adopts nanometer air supporting technique to further make the suspension algae come-up that is located the aquatic top, introducing port rear end below is equipped with the drainage well, and the effect is to pass through the drainage pump bottom water purification and discharge hull outside again to reduce the moisture content of lower flow aspect blue alga.

Description

Full-automatic blue algae collecting and dewatering ship

Technical Field

The utility model relates to a special environmental protection machinery that the surface of water used, concretely relates to full-automatic blue alga is collected and is dewatered ship.

Background

Along with the development of society, more and more blue algae are arranged on the water surface of inland lakes of inland rivers, and once the climate is warmed and erupted, the blue algae will smell and harm aquatic animals, and if the deteriorated water quality is not timely salvaged, the normal life of people can be seriously influenced. Although there are several special ships for salvaging blue algae before the market, the effect and the benefit are not very satisfactory, the common point of the principle is that the 'pump for sucking the algae to the sky' is used for directly sucking the algae, so that scattered and thin blue algae are difficult to collect into the ship, even after the thick blue algae naturally accumulated at the edge of the pump opening is broken into algae-water mixed liquid by the pump, the water content of the 'algae' sucked into the ship is still high, the subsequent transportation and dehydration treatment are all caused to be very difficult, and the cost is increased. And the collection range is limited by the width of the ship body, and the collection ship also adopts an oil engine as power, so that the energy consumption is high, the noise is high, and oil drops enter a water system to cause secondary pollution.

SUMMERY OF THE UTILITY MODEL

The utility model discloses a purpose lies in to a great deal of not enough of several current blue alga salvage ships, has designed the blue alga of the various natural forms of the full-automatic collection surface of water (scattered, thin, suspension, gather) of a large tracts of land, and can also collect into a full-automatic blue alga collection dehydration ship of algae thick liquid, algae mud with the automatic dehydration of the blue alga of collecting into ship.

In order to achieve the purpose, the utility model relates to a full-automatic blue algae collecting and dewatering ship, which comprises a collecting ship, a traction ship and a fence, wherein the collecting ship is symmetrically provided with closed floating boxes at two sides, the front edge of a bow bottom plate of the collecting ship is provided with an overflow door which is used for separating pure water in front of the ship and thick blue algae at an overflow layer, the rear part of the overflow door is provided with an inlet port, a nanometer air floating cabin is arranged below the inlet port and used for further promoting floating of suspended algae above water by adopting a nanometer air floating technology, a drainage well is arranged below the rear end of the inlet port and used for discharging bottom pure water outside the ship body again through a drainage pump, thereby reducing the water content of the blue algae at the overflow layer, a primary mixed flow adjusting plate, a middle-level drainage plate and a final-level overflow adjusting plate are arranged behind the drainage well in sequence and used for turning and mixing the blue algae, so that the surface layer blue algae and the carried coagulant are completely flocculated. The last stage overflow adjusting plate is provided with an algae slurry dewatering cabin behind, and is used for further dewatering the algae slurry flowing in from the front into algae mud, and gradually sinking and stacking the algae mud so as to prevent the forward-layer-surface blue algae from continuously flowing in due to accumulation of the layer-surface blue algae. The algae slurry dewatering cabin is sequentially provided with a dewatering pump cabin, a water diversion pump cabin and an operation cabin.

The overflow door is inclined backwards by a certain angle when closed and is sealed, the inclination aims to automatically fall down by self gravity when the flow layer is opened or adjusted, and the sealing aims to prevent external water from flowing in when algae is discharged. The overflow door is parallel to the water surface and is lower than the designed water surface for a certain distance when opened, and the aim is to enable external algae water to smoothly flow into the ship in a natural normal state. The upper edge of the overflow door is not provided with a sprayer, the inlet end of the sprayer is connected with a coagulant storage box, and the wine spraying amount can be adjusted at will through a built-in valve, so that the coagulant sprayed from the wine sprayer can be effectively mixed with the layer blue algae and the suspended blue algae overflowing from the upper edge of the overflow door to the maximum extent.

In a further scheme, the top surface of the nano air-floating cabin is lower than the water surface outside the ship body, a nano air-floating generator is arranged in or connected outside the nano air-floating cabin, and an upper cover plate of the nano air-floating cabin is provided with dense air exhaust holes, so that floating of suspended algae on the upper introduction port layer and buoyancy of blue algae on the upper introduction port layer are further promoted.

The further proposal is that the upper opening of the drainage well is rectangular, the periphery of the lower part is closed, and the bottom is provided with an opening and communicated with the water diversion pump cabin through a water diversion pipe arranged at the bottom of the ship.

The upper edges of the primary mixed flow adjusting plate and the non-stage overflow adjusting plate are flush with the bottom surface of the introducing port, overflow plate doors which can be turned backwards at will and can control the thickness of layer blue algae are arranged on the upper edges of the primary mixed flow adjusting plate and the non-stage overflow adjusting plate, the upper edges of the overflow plate doors are slightly lower than the outer water surface after being turned up, the overflow plate doors are rectangular, the side edges and the bottom edges of the primary mixed flow adjusting plate and the non-stage overflow adjusting plate are hermetically connected with the inner wall of the ship body, the upper edge of the middle-stage drainage plate is higher than the outer water surface by a certain distance, the side edge of the middle-stage drainage plate is hermetically connected with the inner wall of the ship body, and a gap is formed between the bottom edge of the middle-stage drainage plate. The function is to enable the blue algae mixed with the coagulant to be further coagulated and flocculated through the mixed flow of up and down turning over.

The algae slurry dewatering cabin is integrally a filter frame, an interlayer gap is arranged between the periphery of the outer surface of the filter frame and the inner wall of the ship body, the filter frame is fixed on the inner side wall of the ship body in a point-shaped connection mode, the interlayer gap is completely communicated with the dewatering pump cabin, and a layer of plate-shaped filter screen or a layer of dense filter cloth superposed on the plate-shaped filter screen can be installed on the filter screen on the filter frame according to actual needs. The purpose is for preventing the interior algae thick liquid of filter frame can not leak the net when further dehydration, can not block up simultaneously, still be equipped with the ditch in the preceding, the rear direction of filter frame bottom center, and the filter frame bottom net's centre all has certain slope to both sides. The purpose of the arrangement is to facilitate discharging and discharging of the blue algae slurry or the algae mud, and a proper net bag of the dried stalk can be laid to facilitate discharging and discharging of the crane.

The upper edge of the front side of the dehydration pump cabin is higher than the outer water surface, the two side edges of the dehydration pump cabin are hermetically connected with the inner wall of the ship body, and a rectangular gap is arranged between the lower edge of the dehydration pump cabin and the bottom plate of the ship body, namely the rectangular gap penetrates through the outer gap of the preposed filter screen frame. An algae slurry dewatering pump is arranged in the dewatering pump cabin, an outlet of the algae slurry dewatering pump is communicated with a slag water return pipe, the tail end of the slag water return pipe is a flat pipe which is similar to a cuboid, the flat pipe is communicated to the upper part of the introducing port, and the bottom surface of the flat pipe is provided with no dense small holes, so that the residual coagulant left in the filtered water is fully utilized, and the cost is saved. And a water filling valve and a filter screen frame backflushing pump which are communicated with outside water are also arranged at the bottom in the dehydration pump cabin.

The water diversion pump cabin is an independent sealed cabin with an upper opening, the bottom of the water diversion pump cabin is communicated with a water diversion pipe, a water diversion pump is arranged in the water diversion pump cabin, the water diversion pump is connected with two water outlets which lead to the outside of the ship, the two water outlets are symmetrically arranged on the ship body and are higher than the outer water surface, the operation cabin is arranged on the stern, a rear buoyancy tank is arranged below the operation cabin, and a propeller is arranged in the central position behind a control box arranged above the operation cabin.

In a further aspect, the sprayer is drilled with closely spaced, uniform holes.

The further proposal is that a storage battery storage box is arranged in the closed buoyancy tank, and the front edges of the two sides of the bow of the collecting ship are symmetrically provided with connecting hanging rings of the fence. The front ends of the left and right side fences are respectively connected with the upper towing boat, so that the left and right side towing boats respectively pull one fence to form a splayed blocking load during specific operation, guide the blue algae on the water surface in front to collect to the front edge of the collecting boat and drag the collecting boat to move ahead. The blue algae on the surface of the layer enters the ship in a natural state along with water flow.

The utility model has the advantages and characteristics: through multistage, circulation to the blue alga dehydrate, condense, flocculate, the efficient is cleared up blue alga pollution waters on a large scale, and guarantees that most blue alga of collection is in the natural floating state to the degree of difficulty of the follow-up blue alga separation of further reduction improves greatly the dehydration rate that contains blue alga sewage and dewaters, overall structure design benefit, simple structure, convenient operation, intensity of labour is little, and the noise is little, with low costs, environmental protection.

Drawings

Fig. 1 is a front view of the specific structure of the present invention.

Fig. 2 is a top view of the specific structure of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

example 1

As shown in fig. 1 to 2, a full-automatic blue algae collecting and dewatering ship comprises a collecting ship 1, a towing ship 2 and a fence 3, and is characterized in that two sides of the collecting ship 1 are symmetrically provided with closed buoyancy tanks 4, the front edge of a bow bottom plate of the collecting ship 1 is provided with an overflow gate 5 for separating clean water in front of the ship and thick blue algae on an overflow layer, the rear part of the overflow gate 5 is provided with an inlet 6, a nano air flotation cabin 7 is arranged below the inlet 6 for further promoting floating of suspended algae above water by using a nano air flotation technology, a drainage well 8 is arranged below the rear end of the inlet 6 for discharging bottom clean water outside a blue algae hull again through a drainage pump 25 so as to reduce the water content of a downstream layer, a primary mixed flow adjusting plate 9, a middle-stage drainage plate 10 and a final overflow adjusting plate 11 are sequentially arranged behind the drainage well 8, the effect is that the surface layer blue algae and the flocculation agent carried by the surface layer blue algae are completely flocculated by turning the mixed flow downwards and upwards. The last stage overflow adjusting plate 11 is provided with an algae slurry dewatering cabin 12 at the back, which is used for further dewatering the algae slurry flowing from the front into algae mud, and gradually sinking and stacking the algae mud so as to prevent the algae flowing towards the front layer from ceaselessly flowing due to the accumulation of the blue algae on the layer. The algae slurry dehydration cabin 12 is followed by a dehydration pump cabin 13, a diversion pump cabin 14 and an operation cabin 15 in sequence.

The overflow door 5 is inclined backwards by a certain angle when being closed and is closed, the inclination aims at automatically falling by self gravity when opening or adjusting a flow layer, and the closing aims at preventing external water from flowing in when algae is discharged. The overflow door 5 is parallel to the water surface and is lower than the designed water surface for a certain distance when opened, so that external algae water can smoothly flow into the ship in a natural normal state. The upper edge of the overflow door 5 is provided with a sprayer 17, the inlet end of the sprayer 17 is connected with a coagulant storage box, and the wine spraying amount can be adjusted at will through a built-in valve, so that the coagulant sprayed from the wine sprayer 17 can be mixed with the layer blue algae and the suspended blue algae overflowing from the upper edge of the overflow door 5 to the maximum extent.

The top surface of the nano air-floating cabin 7 is lower than the water surface outside the ship body, a nano air-floating generator is arranged in or outside the nano air-floating cabin 7, and the upper cover plate of the nano air-floating cabin 7 is provided with dense air exhaust holes, so that floating of suspended algae on the upper introduction port 6 layer and buoyancy of blue algae on the layer are further promoted.

The upper opening of the drainage well 8 is rectangular, the periphery of the lower part of the drainage well is closed, the bottom of the drainage well is provided with an opening and is communicated with the water diversion pump cabin 14 through a water diversion pipe 18 arranged at the bottom of the ship.

The upper edges of the primary mixed flow adjusting plate 9 and the non-stage overflow adjusting plate 11 are flush with the bottom surface of the introducing port 6, overflow plate doors which can be turned backwards at will and can control the thickness of blue algae on the layer surface are arranged on the upper edges of the primary mixed flow adjusting plate and the non-stage overflow adjusting plate, the upper edges of the overflow plate doors are slightly lower than the outer water surface after being turned up, the overflow plate doors are rectangular, the side edges and the bottom edges of the primary mixed flow adjusting plate 9 and the non-stage overflow adjusting plate 11 are hermetically connected with the inner wall of the ship body, the upper edge of the middle-stage drainage plate 10 is higher than the outer water surface by a certain distance, the side edge of the middle-stage drainage plate 10 is hermetically connected with the inner wall of the ship body, and a gap is formed between the bottom. The function is to enable the blue algae mixed with the coagulant to be further coagulated and flocculated through the mixed flow of up and down turning over.

The algae slurry dewatering cabin 12 is integrally a filter frame 19, an interlayer gap is arranged between the periphery of the outside of the filter frame 19 and the inner wall of the ship body, the filter frame 19 is fixed on the inner side wall of the ship body in a point-shaped connection mode, the interlayer gap is completely communicated with the dewatering pump cabin 13, and a layer of plate-shaped filter screen or a layer of dense filter cloth superposed on the plate-shaped filter screen can be installed on the filter screen on the filter frame 19 according to actual needs. The purpose is for preventing the interior algae thick liquid of filter frame can not leak the net when further dehydration, can not block up simultaneously, filter frame 19 bottom center front and back still is equipped with the ditch on to, and filter frame 19 bottom net's centre all has certain slope to both sides. The purpose of the arrangement is to facilitate discharging and discharging of the blue algae slurry or the algae mud, and a proper net bag of the dried stalk can be laid to facilitate discharging and discharging of the crane. The sprayer 17 is drilled with small holes in a dense and uniform manner.

The sealed buoyancy tank 4 is internally provided with a storage battery storage box, and the front edges of the two sides of the bow of the collecting ship 1 are symmetrically provided with connecting hanging rings of the fence 3. The front ends of the left and right side fences 3 are respectively connected with the upper towing boat 2, and the towing boats 2 on the left and right sides respectively pull one fence 3 to be in a splayed blocking load, guide the blue algae on the front water surface to collect to the front edge of the collecting boat 1 and drag the collecting boat 1 to move forwards during specific operation. The blue algae on the surface of the layer enters the ship in a natural state along with water flow. The upper edge of the front side of the dehydration pump cabin 13 is higher than the outer water surface, the two side edges are hermetically connected with the inner wall of the ship body, and a rectangular gap is arranged between the lower edge of the dehydration pump cabin 13 and the bottom plate of the ship body, namely the gap penetrates through the outer part of the preposed filter screen frame 19. An algae slurry dewatering pump 21 is arranged in the dewatering pump cabin 13, an outlet of the algae slurry dewatering pump 21 is communicated with a slag water return pipe 22, the tail end of the slag water return pipe 22 is a flat pipe which is similar to a cuboid, the flat pipe is communicated to the upper part of the introducing port 6, and the bottom surface of the flat pipe is provided with no dense small holes, so that the residual coagulant left in the filtered water is fully utilized, and the cost is saved. And a water filling valve 23 and a filter screen frame back flushing pump 24 which are communicated with outside water are also arranged at the bottom in the dewatering pump cabin 13.

The diversion pump cabin 14 is an independent sealed cabin with an opening on the upper surface, the bottom of the diversion pump cabin 14 is communicated with a diversion pipe 18, a diversion pump 25 is arranged in the diversion pump cabin 14, the diversion pump 25 is connected with two water outlets leading to the outside of the ship, the two water outlets are symmetrically arranged on the ship body at positions higher than the outer water surface, the operation cabin 15 is arranged at the tail of the ship, a rear buoyancy tank 26 is arranged below the operation cabin, and a propeller 28 is arranged at the central position behind a control box 27 arranged above the operation cabin.

Description of the operation flow:

the operation steps corresponding to the utility model are that after the preparation work before the operation is done according to the live condition, two towing ships respectively tow a fence which is unfolded in a splayed shape. Meanwhile, the irrigation valve 23 is opened on the collection ship, the algae slurry dewatering cabin 12 enters water, and finally the collection ship 1 is integrally sunk to the designed water level. I.e. the distance of the bottom surface of the intake opening 6 below the outer water surface is equal to the distance of the submerged part of the pen 2. Closing the irrigation valve 23, opening the overflow door 5, starting the drainage pump (25), starting the algae slurry dewatering pump 21, starting the nano air flotation generator, and opening the coagulant adjustment valve. The surface layer blue algae carried in the fence 2 in front continuously crosses the overflow door 5 in a natural state along with the water flow and passes through the inlet 6 along with the forward movement of the towing ship 2, and most of the purified water is separated outside the ship by the overflow door 5. Meanwhile, the layer blue algae overflowed through the overflow gate 5 is flocculated by the flocculation agent primarily, and then the suspended algae is promoted to float upwards and attach to the layer algae through the nano air flotation arranged below, so that the layer algae is further increased in buoyancy and thickened. Further separating the algae water. Under the drainage action of the algae slurry dewatering pump 21, the thick blue algae on the layer surface is further flocculated after being stirred by the up-down mixed flow of the primary mixed flow adjusting plate 9, the middle-stage drainage plate 10 and the final overflow adjusting plate 11. And flows into the algae slurry dewatering chamber 12 to stay, the algae water is naturally layered with time, and the bottom slag water is returned to the inlet 6 through the filter frame 19 to be sprayed on the layered algae. And can be recycled. The blue algae left in the algae slurry dewatering cabin 12 is continuously thickened and deposited, and finally is converted into algae mud until being discharged. At the same time, under the action of the diversion pump 25, the diversion water separated into pure water below the introducing port 6 falls into the diversion well 8 and is discharged out of the ship. It is worth noting that the overflow gate 5, the control valve of the sprinkler 17, the primary mixed flow adjusting plate 9, the unsmooth overflow adjusting plate 11, the algae slurry dewatering pump 21 and the drainage pump 25 are adjusted in time according to the actual situation of the algae amount on the water surface during operation, so that the efficiency and the effect are maximized.

After the operation is finished, the traction ship 2 is closed, the overflow door 5 is closed, the nano air flotation generator is closed, the control valve of the sprinkler 17 is closed, all residual water in the ship is discharged, and the algae mud is discharged and unloaded. The screen frame backflushing pump 24 is opened to flush the screen clean. The traction boat 2 and the fence 3 are put in the lead-in opening 6, and the propeller 28 is started to return.

The above-mentioned embodiments further explain the objects, technical solutions and advantages of the present invention in detail. It should be understood that the above description is only exemplary of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A full-automatic blue algae collecting and dewatering ship comprises a collecting ship (1), a traction ship (2) and a fence (3), it is characterized in that the two sides of the collecting ship (1) are symmetrically provided with closed floating boxes (4), an overflow door (5) is arranged at the front edge of a bow bottom plate of the collection boat (1), an introduction port (6) is arranged behind the overflow door (5), a nanometer air floating cabin (7) is arranged below the leading-in opening (6), a drainage well (8) is arranged below the rear end of the leading-in opening (6), a primary mixed flow adjusting plate (9), a middle-stage drainage plate (10) and a final-stage overflow adjusting plate (11) are sequentially arranged behind the drainage well (8), be equipped with algae thick liquid dehydration cabin (12) behind last stage overflow regulating plate (11), set gradually dehydration pump cabin (13), diversion pump cabin (14), operation cabin (15) behind algae thick liquid dehydration cabin (12).

2. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the overflow door (5) is inclined backwards at a certain angle when closed and is closed, the overflow door (5) is parallel to the water surface and is lower than the designed water surface for a certain distance when opened, a sprayer (17) is arranged on the upper edge of the overflow door (5), the inlet end of the sprayer (17) is connected with a coagulant storage box, and the wine spraying amount can be adjusted freely through a built-in valve.

3. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the top surface of the nano air floating cabin (7) is lower than the water surface outside the ship body, a nano air floating generator is arranged in or connected with the nano air floating cabin (7) externally, and dense exhaust holes are formed in an upper cover plate of the nano air floating cabin (7).

4. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the upper opening of the drainage well (8) is rectangular, the periphery of the lower part of the drainage well is closed, the bottom of the drainage well is provided with an opening and communicated with the water diversion pump cabin (14) through a water diversion pipe (18) arranged at the bottom of the ship.

5. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the upper edges of the primary mixed flow adjusting plate (9) and the non-stage overflow adjusting plate (11) are flush with the bottom surface of the introducing port (6), overflow plate doors which can be turned backwards randomly and can control the thickness of layer blue algae are arranged on the upper edges of the primary mixed flow adjusting plate and the non-stage overflow adjusting plate, the upper edges of the overflow plate doors are slightly lower than the outer water surface after being turned up, the overflow plate doors are rectangular, the side edges and the bottom edges of the primary mixed flow adjusting plate (9) and the non-stage overflow adjusting plate (11) are hermetically connected with the inner wall of the ship body, the upper edge of the middle-stage drainage plate (10) is higher than the outer water surface by a certain distance, the side edge of the middle-stage drainage plate (10) is hermetically connected with the inner wall of the ship body, and a gap is formed between the bottom edge of the middle-stage drainage.

6. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the algae slurry dewatering cabin (12) is integrally a filter frame (19), an interlayer gap is arranged between the periphery of the outside of the filter frame (19) and the inner wall of a ship body, the filter frame (19) is fixed on the inner side wall of the ship body in a point-shaped connection mode, the interlayer gap is completely communicated with the dewatering pump cabin (13), filter cloth is arranged on the filter frame (19), grooves are further formed in the front and rear directions of the center of the bottom of the filter frame (19), and the middle of a bottom net of the filter frame (19) has certain gradients to both sides.

7. The full-automatic blue algae collecting and dewatering ship according to claim 6, characterized in that: the upper edge of the front side of the dehydration pump cabin (13) is higher than the outer water surface, the two side edges are hermetically connected with the inner wall of the ship body, a gap is arranged between the lower edge of the dehydration pump cabin (13) and the bottom plate of the ship body, an algae slurry dehydration pump (21) is arranged in the dehydration pump cabin (13), the outlet of the algae slurry dehydration pump (21) is communicated with a slag water return pipe (22), the tail end of the slag water return pipe (22) is a rectangular flat pipe, the flat pipe is communicated to the upper part of the introducing port (6), the bottom surface of the flat pipe is provided with no dense small holes, and the bottom in the dehydration pump cabin (13) is also provided with an irrigation valve (23) communicated with the outer water and a screen frame backflushing pump (24).

8. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the diversion pump cabin (14) is an independent sealed cabin with an upper opening, the bottom of the diversion pump cabin (14) is communicated with a diversion pipe (18), a diversion pump (25) is arranged in the diversion pump cabin (14), the diversion pump (25) is connected with two water outlets leading to the outside of the ship, the two water outlets are symmetrically arranged on the ship body and are higher than the outer water surface, the operation cabin (15) is arranged at the stern, a rear buoyancy tank (26) is arranged below the operation cabin, and a propeller (28) is arranged in the central position behind a control box (27) arranged above the operation cabin.

9. The full-automatic blue algae collecting and dewatering ship according to claim 2, characterized in that: the sprayer (17) is drilled with small holes which are dense and uniform.

10. The full-automatic blue algae collecting and dewatering ship according to claim 1, characterized in that: the sealed floating box (4) is internally provided with a storage battery storage box, and the front edges of two sides of the bow of the collecting ship (1) are symmetrically provided with connecting hanging rings of the fence (3).