GB2274640A - Sampling device - Google Patents

Abstract

A sampling device 10 (Figure 1) for obtaining a sample from the bed of a lake or other aquatic environment comprising an open-ended container 12 for the sample and a flexible blade-like closure member 15 which is movable in the plane of the member to close the lower end of the container once the sample has been gathered. The blade follows an arcuate path in the closed position and can be of rolled stainless steel sheet. A drive includes a remotely released catch or trigger operated after a delay. <IMAGE>

Description

SAPLING DEVICE The present invention relates to sampling devices and in particular, but not exclusively, to sampling devices such as box corers for sampling sediments from the beds of lakes and other aquatic environments e.g. reservoirs and oceans.

Sampling sediments in lakes etc., is a well-established technique commonly performed by using various types of box-corers. Known corers essentially consist of an open-ended suspended metal or plexiglass box which can be lowered from a surface craft until it contacts and then partially sinks into the bed to be sampled. The bottom of the box is then closed by a pair of mechanically operated jaws mounted at its lower end and the loaded box is hauled back into the surface craft for further processing of the sample.

One -drawback of these known corers, is that the jaws frequently leak causing sample disturbance on retrieval.

Another drawback is that because the open jaws offer a relatively large cross-sectional area to the sediment surface, penetration of the corer into the sediment is restricted unless weights of many tens of kilograms are added. These weights have the disadvantage of making effective manual handling of the corer virtually impossible and a mechanical winch is invariably provided in the surface craft to assist in the introduction of the device into the water and its removal therefrom following sampling.

According to the present invention, a sampling device for obtaining a sample from the bed of a lake or other aquatic environments with soft sediments comprises an open-ended container for the sample and a blade-like closure member which is movable in the plane of the member to close the lower end of the container once the sample has been gathered.

Conveniently, when in its closed position, the blade-like closure member extends in a downwardly convex arcuate plane across the lower end of the container.

Conveniently, the blade-like closure member comprises a flexible rolled stainless steel sheet e.g. of some 300 iim or so thickness.

Conveniently, the sampling device also includes drive means for driving the closure member to its closed position.

Conveniently, the drive means comprises one or more tensator springs and the device includes a remotely releasable catch operative, until released, to hold the closure member in the open position against the closing action of the tensator springs.

Conveniently, the container is provided with a lid member to close the upper end of-the box once the sample has been gathered.

Conveniently, the sampling device includes control means operative to promote closure of the lid member.

Conveniently, the sampling device includes a first form of trigger assembly which is responsive to the continued paying out of the container-suspending cable or like support means following grounding of the container to initiate closure of the closure member and then, if present, the lid member.

Conveniently, the trigger assembly includes a delay mechanism so as to delay closure of the closure member and, if present, the lid member until some time after the container has come to rest e.g. typically, 2 to 5 seconds.

Alternatively, the device may include a second form of trigger assembly which is responsive to the pulling in of the suspending cable or like support means following grounding of the container to initiate closure of the closure member and, if present, the lid member.

Conveniently, the space beneath the closed closure member is vented by a tube or like duct means extending from said space to or adjacent the level of the closed lid member.

Conveniently, the container comprises a box of parallelapiped shape and square cross-section when viewed in plan, the internal width and breadth of the box (viewed in plan) each being about 20 cm or less and preferably 12 cm or less and the height of the box typically being 50 cm or less giving an internal sampling volume of some 720 cubic centimetres, say.

Conveniently, the sampling device has a weight of 15 kilograms or less, e.g. 13.5 kilograms or less.

Conveniently, the device is adapted to receive one or more weights e.g. totalling (device plus weights) some 30 kilograms, say (depending on the consistency of the particulate sediment to be sampled).

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a perspective scrap view of a box-corer sampling device according to the present invention with its top and bottom closure members in the closed position; Figures 2 and 3 show somewhat diagrammatic side and top views, partly in section, of the same box-corer when partially closed, Figure 3 being taken along line III-III in Figure 2; and Figures 4 and 5 show somewhat diagrammatic scrap views of alternative forms of trigger assembly to that disclosed in Figure 2.

Referring first to Figure 1 to 3, it will be seen that the device (10) comprises a container 12 of parallelapiped form with top and bottom steel closure members 14,15 shown closed in Figure 1 and partially open in Figure 2.

The walls of container 12, which are respectively of brass (walls 17,18) and perspex (20,21), have their lower ends tapered to facilitate entry into the sediment to be sampled. The top edges of perspex walls 20,21 carry magnetic strips 23,24 (Figure 3) to hold the top closure member or 'lid' 14 in place in the lid-closed position of Figure 1. As an alternative, the walls 17,18 may be made out of stainless steel instead of brass.

The bottom closure member or 'blade 15 is constructed of a flexible sheet of rolled stainless steel of slightly greater width than the brass walls 17,18 (see Figure 3) and the perspex walls 20,21 are internally grooved at their lower ends to provide arcuate guide channels 26,27 for the blade where it extends into the inside of the container as hereinafter described.

At its upper end, the blade 15 is secured with the top ends of three tensator springs 29 between two channel members 33,34, one on either side of a side wall extension 36. This latter acts as a guide for the channel members as they travel between an uppermost blade-open or 'blade primed' position (indicated by reference numeral 38 in Figure 2) and the lower 'blade closed' position illustrated in Figure 1. Figure 2 shows the device 10 at an intermediate stage of its operation.

As shown in Figures 1 and 2, the brass wall 17 is interrupted to provide a slot 40 which allows the blade 15 to extend from outside the container into the interior volume of the container.

Brass L-section guides 42,43 secured to the edges of perspex walls 20,21 hold the upper section of the blade close to brass wall 17.

As shown, the tensator springs 29 are rotatably supported on a common axle mounted in lug portions 45,46 of the side walls 20,21 above the level of brass guides 42,43.

Reference numerals 48,49 indicate two saddle weights which can be attached to the brass walls 17,18 by screws (not shown) to increase the effective weight of the device 10, if so desired, prior to sampling.

As shown most clearly in Figure 1, the side wall extension 36 is apertured at 51,52 to allow latching of the lid 14 and blade 15 in their fully open and primed positions. In this respect, reference numeral 54 in Figure 1 indicates a spring-loaded latch which will engage in aperture notch 56 to hold the lid 14 open until displaced by channel members 33,34 as will be hereinafter described.

Similarly, in their blade-open uppermost position 38, the channel members will be secured in place by a pivoted crank 56 (Figure 2) having a hooked lower end 57 adapted to engage under channel member 34 in the blade-open position. At the top of the device, the upper end of crank 56 is engaged by the downwardlytapering face of a vertically displaceable control cam 58.

The cam 58 is in turn supported on a rod 60 slidably mounted in a cylinder 62. This latter is secured by strap members 64,65 to the upper ends of side wall extension 36 and side wall 18.

At its upper end, the rod 60 carries a shackle member 67 by which the device 10 can be suspended by a cable or the like from a surface craft (not shown).

The device 10 is completed by an open-ended tube 69 venting the space beneath the closed blade 15 to a level above that of the closed lid member 14.

In use, the device 10 is first cleaned and appropriate saddle weights 48,49 are fitted if necessary to increase the effective weight of the device from typically 13.5 kg, say, without the weights, and up to 30 kg, say, with the weights. Next the lid 14 is latched open and the channel members 33,34 are forced upwardly against the restraining pull of the tension springs 29 until crank end 57 is engaged under channel member 34. Clearly, the shackle member 67 must at all times be held in its uppermost position to prevent premature firing of the device before it is lowered over the side of the surface craft into the water. In a modification (not shown), a safety catch is provided for this purpose rather than just rely on the positioning of shackle member 67.

With the lid 14 and blade 15 latched in their open positions as above described, the device is now lowered from the surface craft down through the water of the lake etc. whose bed is to be sampled until it contacts and then sinks into the soft sediment lying at the bottom. During this time, the weight of the container 12 acting on the cylinder 62 will result in the cam 58 being held in its uppermost position relative to the container.

When the device 10 has come to rest, however, after having sunk to the maximum extent possible in the sediment, the weight of the cam and the supporting cable etc. will result in the cam 58 moving downwardly relative to the remainder of the device 10 thereby causing the upper end of lever 56 to ride up the inclined surface of the cam as shown in Figure 2. This in turn will result in an inward movement of lower arm of lever 56 to disengage the hooked end 57 from the channel member 34 whereupon the tensator springs 29 will operate to drive the blade downwardly, around the guide grooves 26,27 and into a transverse stop groove 71 formed in the opposite brass wall 18.

As they are dragged downwardly, the channel members 33,34 will knock the latch 54 out of the retaining notch 56 so that the lid 14 will fall under gravity to the lid-closed position shown in Figure 1. There it is held firmly shut by the action of the magnetic strips 23,24.

The device 10 is now hauled into the surface craft and the lid 14 is opened to allow removal of material from the container for laboratory testing e.g. using a conventional core tube technique.

It should be noted that because the tensator springs 29 are still under tension at the moment when the blade 15 engages in stop groove 71, a good seal is established between the blade and the end wall 18. Similarly, it will be appreciated that because the weight of the retained sample in container 12 forces the blade 15 into intimate contact with the lower surfaces of slot 40 and side grooves 26,27, a very efficient seal is also established between the blade and the other three walls of the container. As a result, virtually all of the original water content can be retained in the gathered sample and this compares very favourably with conventional corers which frequently leak around the jaws.

Turning now to Figure 4, this shows a variation of the first device in which closure of the blade 15 and lid 14 is delayed (typically by 2 or 3 seconds) through use of a hydraulic damper 73 to slow the downward movement of the cam 58. This ensures that the device 10 has properly settled before the sample is taken.

Figure 5 illustrates a second embodiment of the invention in which blade and lid closure is only triggered when the supporting cable is raised following the coming to rest of the device in the sediment bed. Accordingly, in the embodiment of Figure 5, the top end of crank 56 is located above the upwardly tapering surface of the cam 58 rather than below it and the rod 60 is locked to the cylinder 62 by a gravity catch 75 which is pivotally mounted on the cylinder 62. This catch engages with a collar member 77 on the rod 60 while the device 10 is being lowered through the water as shown in Figure 5 in broken outline.

Once the container 12 has grounded, however, the contact pressure between catch 75 and collar member 77 will be reduced thereby allowing the catch 75 to pivot to its full-line position.

Separation of the collar member 77 and cylinder 62 is prevented by two or more compression springs 79 until, as above indicated, the upward pull on the suspending cable is sufficient to overcome the restraining action of the springs and allow the cam 58 to move upwards and displace the crank 56 to trigger blade and lid closure.

It will be noted that Figures 4 and 5 show different shapes of cam 58 to that illustrated in the embodiment of Figures 1 and 2 and in practice one of any of a wide variety of shapes may be chosen provided only that the crank-engaging surfaces of the cam are properly disposed for it to function as desired.

Although, clearly, a wide variety of dimensions may be chosen, typically, the box corer need only be some 24 cms square (and bevelled) when viewed in plan and because of this and the fact that it does not employ a jaw mechanism for lower end closure, the device presents a relatively small cross sectional area and can enter soft sediments to a depth of over 30 cm when weighted adequately.

Although the actual penetration value in any particular case will depend on sediment consistency and box weighting, the low-resistance design of the corer generally allows the device to be relatively lightweight without any sacrifice in performance.

Indeed, for most sediments, only saddle weights of 4 kg. or less are required to be fitted. This results in a corer which can readily be operated by hand from a small boat.

Having two opposed side walls of the box of a perspex material, e.g. plexiglass, ensures that any sediment stratigraphy can be viewed and the quality of recovery checked.

In an additional procedure, the collected sediment can be sub-sampled by routine piston coring on deck.

The main purpose of the corer is to collect undisturbed samples of surficial sediment from any reasonable depth of water and the prototype device has been operated successfully at depths from 7 m to over 1400 m.

Claims (15)

1. A sampling device for obtaining a sample from the bed of a lake or other aquatic environment comprising an open-ended container for the sample and a blade-like closure member which is movable in the plane of the member to close the lower end of the container once the sample has been gathered.

2. A sampling device as claimed in Claim 1 in which. when in its closed position, the blade-like closure member extends in a downwardly convex arcuate plane across the lower end of the container.

3. A sampling device as claimed in Claim 1 or Claim 2 in which the blade-like closure member comprises a flexible rolled stainless steel sheet e.g. of some 300 pm or so thickness.

4. A sampling device as claimed in any preceding claim including drive means for driving the closure member to its closed position.

5. A sampling device as claimed in Claim 4 in which the drive means comprises one or more tensator springs and including a remotely releasable catch operative, until released, to hold the closure member in the open position against the closing action of the tensator springs.

6. A sampling device as claimed in any preceding claim in which the container is provided with a lid member to close the upper end of the box once the sample has been gathered.

7. A sampling device as claimed in any preceding claim in which the sampling device includes control means operative to promote closure of the lid member.

8. A sampling device as claimed in any preceding claim in which the sampling device includes a trigger assembly which is responsive to the continued paying out of the container-suspending cable or like support means following grounding of the container to initiate closure of the closure member and, if present, the lid member.

9. A sampling device as claimed in Claim 8 in which the trigger assembly includes a delay mechanism so as to delay closure of the closure member and, if present, the lid member until some time after the container has come to rest.

10. A sampling device as claimed in any of claims 1 to 7 including a trigger assembly which is responsive to the pulling in of the suspending cable or like support means following grounding of the container to initiate closure of the closure member and, if present, the lid member.

11. A sampling device as claimed in any preceding claim in which the space beneath the closed closure member is vented by a tube or like duct means extending from said space to or adjacent the level of the closed lid member.

11. A sampling device as claimed in any preceding claim in which the container comprises a box of parallelapiped shape and square cross-section when viewed in plan, the internal width and breadth of the box (viewed in plan) each being 20 cm or less and preferably

12 cm or less and the height of the box typically being 50 cm or less giving an internal sampling volume of some 720 cubic centimetres, say.

13 A sampling device as claimed in any preceding claim having a weight of 15 kilograms or less, e.g. 13.5 kilograms or less.

14. A sampling device as claimed in any preceding claim adapted to receive one or more weights.

15. A sampling device substantially as herelnbefore described with reference to, and/or as illustrated in,- Figures 1 to 3 or Figure 4 or Figure 5 of the accompanying drawings.