GB2252575A - Separating device for fishing dredge - Google Patents

Abstract

A separating device for separating debris and foreign objects from a sandy substrate is mountable on the rear of a tractor and comprises excavating means (17) for digging a substrate and conveying means (24) e.g. a conveyer belt, for conveying the substrate and any foreign bodies contained within the substrate to a sieving assembly (22). The sieving assembly vibrates so that foreign bodies and debris may be separated from the substrate which falls through the sieving assembly to the ground. The separating device has particular application in the harvesting of clams and other shell-fish from a sandy substrate. The device also has application in the removal of litter and other debris from sandy substrates such as beaches and deserts. <IMAGE>

Description

"SEPARATING DEVICE" The invention concerns a separating device for separating debris and foreign objects from a sandy substrate.

The removal of objects from a sandy substrate is a difficult operation. For example, the cleaning of beaches frequently requires the removal of bottles, cans, plastics containers, cigarette ends etc.

by hand. Clearly, this is a time-consuming, tedious and costly operation. Furthermore, deserts are frequently the location for discharging rounds of ammunition such as bullets or shells. Following discharge of such ammunition shell casings are discarded and must subsequently be removed by hand.

Shellfish are bred in a sandy substrate and are a popular sea-food and due to their popularity a number of fishfarms today specialise in their cultivation. However, the cultivation and harvesting of shellfish from a sandy substrate can be a labour intensive operation.

For example, clams such as Tapes Semidecussata, are grown from seed produced under controlled conditions in a hatchery, "fattened" in mesh-covered frames for a year and are then sown on a sandy substrate in enclosed areas referred to as "parcs". Parc locations are ideally selected so as to be accessible at low Spring Tides only. The clams grow in parcs at typical densities of 500 per square metre. However, the location of parcs and the growth density combine to make the harvesting of shellfish such as clams difficuit as a large number of shellfish must be harvested in the relatively short time period offered by low Spring Tides. The most common method of harvesting the clams from sand is by digging followed by separation of the substrate and the clams and cleaning with water.

It is an object of the invention to provide an automated device capable of removing and separating foreign objects or debris from a sandy substrate.

It is also an object of the invention to provide an automated harvesting device capable of firstly harvesting, secondly separating and thirdly cleaning shellfish, such as clams.

According to the invention there is provided a device mountable on the rear of a tractor for separating foreign bodies from a substrate comprising excavating means and conveying means for conveying substrate and foreign bodies excavated to a vibratable sieving assembly such that the substrate and foreign bodies are sieved and the foreign bodies separated from the substrate.

Preferably, the conveying means comprises an inclined chute having a conveyor belt floor on which the substrate and foreign bodies can be conveyed to the sieving assembly. Suitably, the conveyor belt comprises a mesh-like material through which the substrate can fall and foreign bodies can be retained on the belt.

Preferably, the excavating means comprises a blade mounted across the lower end of the chute and a deflector mounted either side of the blade so that the substrate and foreign bodies excavated by the blade are directed into the chute. Suitably, the deflector comprises a triangular box.

Preferably, the sieving assembly comprises an upper sieving platform overlapping a lower sieving platform, the upper sieving platform being positioned adjacent the upper end of the conveyor belt so that the substrate and foreign bodies are deposited on the upper sieving platform. Suitably, the upper sieving platform comprises a series of transverse bars on which large foreign bodies are retained and through which small foreign bodies can pass to the lower sieving platform.

Suitably, lower sieving platform comprises a mesh on which the small foreign bodies and substrate can be riddled so that small particles pass through the mesh. Preferably, cleansing means are mounted at the overlap so that substrate can be removed from foreign bodies on the lower sieving platform. Suitably, the cleansing means comprises brushes, revolving wheels or water jets.

Preferably, at least one container is mountable on a support means beneath the lower platform so that the foreign bodies retained on the lower platform can move to the edge of the platform due to the vibration of the sieving assembly and can fall into the container.

Suitably, the support means comprises a series of parallel bars between which one or more containers can be supported.

Preferably, the conveyor belt is rotatable about an upper transverse shaft and a lower transverse shaft mounted at the upper and lower ends of the chute respectively, the upper shaft being connected to the sieving assembly by cam means so that rotation of the upper shaft causes simultaneous reciprocation and vibration of the sieving assembly.

Suitably, the upper-shaft is rotatable by means of a drive means connected to the upper shaft. Preferably, the drive means comprises a hydraulic motor mounted on the upper shaft.

One embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of the front and one side of a harvesting device according to the invention; Figure 2 is a perspective view of the end and other side of the device; Figure 3 is a view of the drive mechanism for a shaker assembly of the device and; Figure 4 is a perspective view of a part of the device of Figure 1.

Referring to the drawings there is described one embodiment of a harvesting device 1 which is adapted for use in the harvesting of shellfish, such as clams, from a sandy substrate such as parcs. The harvesting device comprises a mainframe 2 which carries at the front thereof a mounting frame 3 for attaching the device to the three-point linkage to the rear of a tractor. The tractor mounting frame 3 includes an upright post 6 mounted on a front transverse member 7 of the mainframe 2. The post 6 is supported by brace members 4,5 which are welded at one end of the top of the post 6 and at their other ends to respective longitudinal side members 10 of the mainframe 2.

Brackets 8 and 8a, adapted for connection to the three-point linkage of the tractor are mounted, respectively, on the post 6 and member 7.

The mainframe 2 supports a chute 15 comprising a floor 16 having sidewalls 20,21 and a blade 17 having inner and outer triangular deflector boxes 18,19.

The floor 16 of the chute 15 is adapted to function as a conveyor 24 which, when in motion, bears matter upwards towards a shaker assembly 22, the floor 16 being a series of linked steel bars 23 which support a mesh-like conveyor belt 24.

The shaker assembly 22 (see Figs. 2 and 3) comprises an upper platform 43 and a lower platform 45 located beneath a shaker overhead tray 65.

The shaker assembly 22 removes extraneous matter such as sand from harvested clams using a shaking motion which is more fully described below.

Movement of the conveyor belt 24 and shaker assembly 22 is effected by means of rotation of an upper shaft 25 which extends transversely across the mainframe 2 and is journalled in suitable bearings. The conveyor belt 24 rests on sprocket wheels 27 on shaft 25 and rotates about a second shaft 26 at its lower end.

The conveyor belt 24 may travel between shafts 25,26 in an upwards or downwards motion. Upon rotation of the upper shaft 25 the toothed sprocket wheels 27 rotate and engage the conveyor belt 24 between links of the steel bars 23 and translational motion of the conveyor belt 24 takes place.

Rotation of the upper shaft 25, and other moving parts of the device, is effected by means of a hydraulic motor 29, illustrated in Figure 2.

The hydraulic motor 29 may be controlled from a gearbox located within a tractor by means of flexible hydraulic pipes 30 which may be disconnected when not in use. Alternatively, the moving parts of the machine are driven either by the power take off shaft through a 2:1 right angle drive reduction gearbox and then a chain and sprocket, or by means of a hydraulic motor coupled to the hydraulic system of the tractor.

Figure 1 also shows a main sprocket 31 which projects from the upper shaft 25. The main sprocket wheel 31 engages a drive chain 32 which in turn engages a smaller sprocket 33, the smaller sprocket 33 being mounted on a shaker shaft 34.

The sprocket 31, the chain 32 and sprocket 33 comprise the means by which activation of the shaker assembly 22 is effected. Shaking is automatically effected by transferral of the rotational motion of the hydraulically controlled shaft 26 to translational motion of the drive chain 32 by means of the main sprocket 31.

The engagement by the sprocket 31 of the drive chain 32 is more clearly illustrated in Figure 3. Teeth 35 of the support wheel 27 grip the belt 24 at the outer links 36 of the linked steel bars 23. The chain 32 engages the smaller sprocket 33 which is mounted on the shaker shaft 34, the shaker shaft 34 extending transversely beneath the shaker assembly 22.

The shaker shaft 34 terminates at crank pins 37,38, crank pin 37 being mounted adjacent sprocket 33. Crank-arms 39,40 extend from the crank pins 37,38 to engage the shaker assembly 22 at a transverse beam 60.

Activation of the hydraulic motor 29 results in rotation of the upper shaft 25, the rotation of the shaft 25 being transferred to the conveyor belt 24, as described hereinabove, and to the drive chain 32 by means of the sprocket 31 whereby the smaller sprocket 33 is also rotated. As the smaller sprocket 33 is fixedly mounted on the shaker shaft 34 said shaft 34 rotates and causes the crank-pins 37,38 mounted at its ends also to rotate. Rotation of the crank-pins 37,38 in turn imparts a reciprocating motion to the crank arms 39,40.

The crank-arms 39,40 are connected by the transverse beam 60 which abuts uprights 53,54, the uprights 53,54 being fixed between platform 45 and shaker members 55,56, whereby the reciprocating motion of the crank arms 39,40 causes the beam 60 to displace the lower platform 45 and an upper platform 43.

Figure 2 shows the separation and cleaning devices of the shaker assembly 22 in detail. The shaker assembly 22 comprises firstly an upper platform 43 having transverse steel bars 44, each bar being substantially enclosed within a plastic sheath, and secondly, a lower platform 45 parallel to the upper platform 43 but extending beyond the upper platform 43 to the rear of the device. The lower platform 45 comprises a sheet of steel mesh 46 having steel sidewalls 47,48.

The upper platform 43 is supported by the lower platform 45 by means of uprights 49,50,51,52, (51,52 not shown in Figure 2), the lower platform 45 being in turn mounted by means of uprights 53,54 on shaker members 55,56.

The harvesting 1 device is mounted on an axle 57, the axle 57 being held by wheels 58,59 on fixed forks.

The shaker assembly 22 further comprises means for disintegrating friable matter present on the lower platform 45, said means being a series of brushes or bristles 61 which are mounted over the mesh 46 in an overlap region of platforms 43 and 45. The brushes or bristles 61 project from a member 62 which extends transversely across the shaker assembly 22, the member 62 being supported by two upright bars 63,64.

The upright bars 63,64 are secured between the shaker members 55,56 and a stationary overhead tray 65. The height of the member 62 and consequently of the brushes or bristles 61 above the lower platform 45 may be adjusted by varying the position of the member 62 on the upright bars 63,64.

The overhead tray 65 over the upper platform 43 is fixedly mounted on the shaker members 55,56, by-passing the shaking mechanisms of the invention, and may be used for the storage of empty clam boxes etc.

The overall operation of the present embodiment of the shellfish harvesting device of the invention will now be described.

Referring to Figure 4, the clam harvesting device of the invention is mounted on the three point linkage of a tractor. The device may be raised or lowered as required by means of the three point linkage. In use, the device is lowered to a depth of approximately 12 cm in a sandy substrate.

Suitably, the blade 17 is a steel plate approximately 148 cms. long, about 36 cms. wide and about 95 mm thick.

The depth to which the blade 17 excavates the substrate may be adjusted, in particular, by means of the tractor's lift arms and top-link.

Forward motion of the tractor results in a digging or shaving action by the metal blade 17 to dig up and dislodge the clams from the substrate and to direct the clams up the chute 15. Triangular deflector boxes 18,19 are provided at each lateral side of the metal blade 17. The purpose of these deflectors is to deflect to each side of the machine clams which might otherwise be damaged by coming into contact with the frame of the machine or be broken by the wheels. The clams so deflected are left in ridges on either side of the machine and may be collected on the next traverse of the parc by the machine.

Rotation of the upper shaft 25 is initiated and controlled by an operator located within the tractor. As described hereinabove, rotation of the upper shaft 25 is translated to the conveyor belt 24 by means of the upper sprocket wheel 27.

Continuous upward movement of the conveyor belt 24 transports substrate excavated (i.e. shellfish, sand1 debris etc.) in an upwards direction towards the shaker assembly 22. The mesh-like nature of the conveyor belt 24 has a sieve-like effect and allows extraneous matter such as sand to fall through the conveyor belt to the ground.

Upon reaching the upper shaft 25 region the substrate remaining on the conveyor belt 24, which includes the shellfish being harvested, drops through upper platform 43 to the lower platform 45. The transverse steel bars 44 of upper platform 43 serve to break up any large clumps of substrate or alternatively to prevent any large solid pieces of matter such as rocks or wood from impinging on the mesh 46 of the lower platform 45.

The rotation of the upper shaft having imparted a reciprocating motion to the crank arms 39,40 the lower platform 45 is undergoing a shaking motion when struck by the substrate descending from the upper platform 43. The rapid backwards-forwards motion of the lower platform 45 causes the mesh 46 to sieve or riddle the substrate and to remove the bulk of any remaining extraneous matter from the shellfish harvested.

Sieving is further enhanced by the brushes 61 which also help remove any substrate which may cling to the harvested shellfish. The height of the member 62 is adjusted in order to optimise the cleaning and sieving action of the brushes 61. The harvested clams or shellfish move backwards due to the uprights 53,54 being inclined at an angle to the vertical, the angle decreasing as the lower platform 45 moves to the rear during the backward stroke of the crank arms 39,40.

The collection region 66 comprises a series of parallel transverse rollers 67 supported by a frame 68, the rollers 67 being constructed of plastic piping over steel bars and being spaced apart such that boxes may be supported between the rollers 67. The shaking motion of the shaker assembly 22, described above, causes clams to undergo displacement toward the collection region 66 along the lower platform 45. The lower platform overlaps the collection region 66 whereby the separated and cleaned clams fall from the platform 45 into boxes supported in the collection region 66. The outer rollers of the frame 68 lie in a plane which is higher than the plane formed by the parallel transverse rollers 67 within the frame 68.The 'lip' formed by the rollers in a higher plane prevent collection boxes from undergoing lateral movement, caused by vibration of the shaker, and falling off the frame 68. The roller bars 68 also facilitate easy removal of collection boxes by hand using a simultaneous lifting and pulling force.

In an alternative embodiment of the harvesting device of the invention the shaker assembly is provided with a "sparging tube" or lateral spray which rinses the harvested shellfish during the separation process and removes any particularly sticky or viscous substrate from the shellfish. Any excess substrate on the shellfish is undesirable as it merely adds weight to the collection boxes.

In yet a further embodiment of the invention the wheels may be mounted in revolving self-aligning forks to facilitate easy manoeuverability in confined spaces.

Various modifications may also be effected to the harvesting device of the invention in order to adapt the device to particular environmental conditions. For example, a nylon mesh net may be placed over the plastic conveyor or belt in order to minimise damage to the plastic belt caused by large quantities of stones. Similarly, the upper shaker platform may be modified to facilitate the automatic ejection of stones through a side chute. In addition, the height of the main frame could be adjustable to facilitate raising and lowering of the platform as dictated by the substrate to be excavated e.g. for soft sand where the device may sink.

The harvesting device of the invention also has application in the harvesting of wild clams, cockles or bottom grown oysters.

Claims (16)

1. A device mountable on the rear of a tractor for separating foreign bodies from a substrate comprising excavating means and conveying means for conveying substrate and foreign bodies excavated to a vibratable sieving assembly such that the substrate and foreign bodies, are sieved and the foreign bodies separated from the substrate.

2. A separating device according to Claim 1 wherein the conveying means comprises an inclined chute having a conveyor belt floor on which the substrate and foreign bodies can be conveyed to the sieving assembly.

3. A separating device according to Claim 2 wherein the conveyor belt comprises a mesh-like material through which the substrate can fall and foreign bodies can be retained on the belt.

4. A separating device according to Claim 2 or Claim 3 wherein the excavating means comprises a blade mounted across the lower end of the chute and a deflector mounted either side of the blade so that the substrate and foreign bodies excavated by the blade are directed into the chute.

5. A separating device according to Claim 5 wherein the deflector comprises a triangular box.

6. A separating device according to any of the preceding Claims wherein the sieving assembly comprises an upper sieving platform overlapping a lower sieving platform, the upper sieving platform being positioned adjacent the upper end of the conveyor belt so that the substrate and foreign bodies are deposited on the upper sieving platform.

7. A separating device according to Claim 7 wherein the upper sieving platform comprises a series of transverse bars on which large bodies are retained and through which small foreign bodies together with substrate can pass to the lower sieving platform.

8. A separating device according to Claim 6 or Claim 7 wherein the lower sieving platform comprises a mesh on which the small foreign bodies and substrate can be riddled so that substrate passes through the mesh.

9. A separating device according to any of Claims 6, 7 or 8 wherein cleansing means are mounted at the overlap so that substrate can be removed from small foreign bodies on the lower sieving platform.

10. A separating device according to Claim 9 wherein the cleansing means comprises brushes, revolving wheels or water jets.

11. A separating device according to any of claims 6 to 10 wherein at least one container is mountable on a support means beneath the lower platform so that the foreign bodies retained on the lower platform can move to the edge of the platform due to the vibration of the sieving assembly and can fall into the container.

12. A separating device as claimed in claim 11 wherein the support means comprises a series of parallel bars between which one or more containers can be supported.

13. A separating device according to any of the preceding Claims wherein the conveyor belt is rotatable about an upper transverse shaft and a lower transverse shaft mounted at the upper and lower ends of the chute, the upper shaft being connected to the sieving assembly by cam means so that rotation of the upper shaft causes simultaneous reciprocation and vibration of the sieving assembly.

14. A separating device according to Claim 11 wherein the upper-shaft is rotatable by means of a drive means connected to the upper shaft.

15. A separating device according to Claim 12 wherein the drive means comprises a hydraulic motor mounted on the upper shaft.

16. A separating device substantially as hereinbefore described with reference to the accompanying drawings.