METHOD AND DEVICE FOR DEMINING

Abstract: The present invention relates to a method and a device for increasing the clearance effectiveness of such mechanical mine clearing tools (7) that operate on the rotary cultivator principle and which thus incorporate a number of mutually parallel demining discs (9) each one of which should have a number of teeth angled in opposite directions around its periphery. The present invention is based on the fact that impact devices (16) are located between each pair of demining discs (9) and that each said impact device is so designed that when the demining tool (7) cuts through the upper ground layer that is to be demined the ground layer between each two adjacent demining discs (9) is impacted by successive impact devices.

Description: METHOD AND DEVICE FOR DEMINING The present invention relates to a method and a device for rapid clearance of landmines lying freely on the surface or buried in the upper ground layer, both small anti-personnel (AP) mines and larger anti-vehicle and anti-tank mines. For rapid clearance of routes through minefields the military have previously used primarily chain flails and mine ploughs. Theses are most appropriate for military purposes and have achieved far from the 100% clearance result that is desirable in civil mine clearance operations after a conflict is over. Civil mine clearing operations have thus been achieved by the time consuming and labour intensive method of using probes or, perhaps, mainly by the use of electromagnetic mine detectors. The latter are, in fact, very sensitive but there are AP mines that do not contain any metal at all and are thus not detected. Moreover, the number of false indications that have to be checked is always high, especially in areas where battles have occurred as there is always a multitude of fragments in the ground in such areas. In latter years, however, increasing interest has been focused on mechanical mine clearance vehicles that operate in a similar way to the mechanical rotary cultivator principle. They have been shown to have good capacity, and although they cannot operate in all types of terrain they clearly constitute a positive addition to the field of mine clearing. Many of these rotary cultivator type demining tools are designed with horizontal rotation shafts fitted with multi-disc cultivators, each disc usually being fitted with individual teeth around its periphery. SUBSTITUT SHEET (RULE 26) ISA/SE The basic concept for the rotary cultivator disc type of mine clearing device is described in WO 95/24604, while DE 4.442.135 describes a variant of the same basic concept in which the various discs incorporate very large teeth machined direct in the actual disc and with apertures to reduce the risk of damage in the event of mine detonations in or under the demining tool. The objective with demining tools that function on the rotary cultivator principle is that they shall 'chew' the mines in their path into small fragments or cause the mines to detonate. In practice it has been shown that usually mines are made to detonate in or under the demining tool which is usually no problem in the case of AP mines, but anti-vehicle and anti-tank mines easily cause damage to the demining tool. Consequently, it should be easy to repair or replace. In practice, however, the main problem with demining tools of the above rotary cultivator type has not been damage to the demining tool by mine detonations initiated, but that individual mines— especially small AP mines — can pass undamaged through the demining tool. Quite simply, it has been difficult to achieve the virtual 100% mine clearance effect necessary in civil mine clearing. The cultivator discs cannot be located too densely as the closer they are to each other the higher the machine power that is needed. The objective of the present invention is to raise the clearance percentage of demining tools of the above mentioned basic type. As a demining tool of the above rotary disc roller type works the upper ground layer down to a pre-determined depth the soil worked collects between the cultivator discs and this accumulated soil sometimes includes undamaged individual mines. We have now— significantly — found that mines embedded in this accumulated soil between the cultivator discs can be made to detonate if we mount a number of impact devices in the form of impact segments between the cultivator discs. These impact segments co-rotate with the shaft of the rotary cultivator discs and are arranged in a plane parallel with the cultivator discs with several impact segments in one and the same plane with a space between each impact segment so that as impact segments in the same plane follow each other (in rotation) they work the accumulated soil between the cultivator discs. The number of such impact devices in each plane may be 2-10, but preferably 5-10. In the preferred design they also have a leading edge relative to their direction of rotation that is bevelled rearwards in the direction of rotation of the roller such that the section of the impact segment closest to the axis of rotation first meets the accumulated soil between the cultivator discs and the leading edge of each impact segment has a sawtooth form. The design of the leading edge of each impact segment and the space between each impact segment in the same rotational plane results in working of the accumulated soil between each two adjacent cultivator discs while the intermittent agitation of the accumulated soil by the impact devices acts to trigger all types of pressure sensitive AP mines. Practical tests with live mines in completely realistic conditions have shown that by supplementing an otherwise equivalent demining tool with the impact devices claimed in the present invention, the mine clearance capability is increased from approximately 95% to 99%. The present invention is defined in the Patent Claims below, and shall now be described in more detail with reference to the appended figures: Figure 1 shows a diagonal projection of a demining vehicle, while Figure 2 shows the design principle of the demining tool, and Figure 3 shows a detailed illustration of one of the impact devices as claimed in the present invention, and Figures 4 & 5 show different mechanical attachments for the impact devices. The main parts of the demining vehicle 1 illustrated in Figure 1 are the chassis 2, the engine unit 3, control cab 4, drive tracks 5 and 6, and the actual demining tool 7. The latter comprises a roller-shaped shaft 8 fitted with a number of parallel demining discs 9, each of which is fitted with peripheral teeth 10 made of a hard material to minimise wear round the periphery of the demining discs 9. The demining tool 7 is journalled to enable rotation in an inverted cradle 11 which in turn can be raised or lowered to enable different operating depths in the upper ground layer. The engine 3 is used to drive both the demining vehicle 1 and to rotate the demining tool 7. The demining tool 7 illustrated in Figure 1 is of a more general nature and is not designed in accordance with the present invention. The demining tool 12 in Figure 2 is shown in more detail to illustrate the design as claimed in the present invention. It consists of a central tubular roller shaft 13, a number of demining discs 14, although only a few are illustrated in the figure, each one incorporating a number of fingers around its periphery and generally designated 15, each fmger free on three faces (around the axis of rotation) and each of which can be fitted with a tooth holder of the type vaguely indicated on Figure 1 that can in turn be fitted with a tooth made of hard material. To provide these demining discs 14 with the optimal operating characteristics the fingers at the periphery are angled outwards in opposite directions and at varying angles from the main plane of the demining discs so that they form a zigzag pattern around the demining discs. The actual angles cannot be specified generally but must be tested and tried. The impact devices 16 as claimed in the present invention, the design of which is shown in more detail in Figure 3, are mounted between each two adjacent demining discs 14. The impact devices 16 are mounted between the demining discs 14 with a certain distance between them. The number of impact devices at each station on the roller, i.e. within each space between two adjacent demining discs, is 2-10 and preferably 5-10. They can be mutually aligned or be slightly displaced laterally in relation to each other. Between each two impact devices there is always a large or small space. The impact devices 16 incorporate an oblique — relative to the main direction of operation of the demining tool 12 — leading edge which one-after-one strike the accumulated soil that they are designed to demine further and further outwards from the rotational axis of the demining tool 12. The main direction of operation is designated A on Figures 3 and 5. To enhance their effectiveness each impact device also has a sawtooth shaped leading edge as illustrated in the figures. Each sawtooth comprises a longitudinal edge 17, which only slightly deviates from the main direction of the leading edge of the impact device 16, and a short lateral edge 18 that cuts mainly right through the main direction of the leading edge of the impact device 16. In the general type of demining tool 12 illustrated in Figure 2 with a central roller it is desirable to restrict the number of welded joints to a minimum. However, it is difficult to avoid welding the demining discs to the roller. On the other hand, it is possible to attach the impact devices mechanically. Figure 4 illustrates part of a longitudinal projection of a demining tool of the type as claimed in the present invention in which 17 denotes the roller shaft, 18, 19 and 20 denote the demining discs, and 21 and 22 signify two impact devices. The latter are welded onto holders 23 and 24 which are in turn attached to each side of the demining discs by bolts 25-27. Another variant of mechanical attachment of the impact devices is shown in Figure 5 in the form of a cross-section through a demining tool illustrating the central roller shaft 28, a demining disc 29, and two semi-circular attachment devices 30 and 31 with lugs 32-35 assembled and held together by bolts 36 and 37, and showing some of the impact devices 38 welded to each of the attachment devices 30, 31.

Claims: PATENT CLAIMS We hereby claim and desire to secure by Letters Patent the following. 1. A method for increasing the effectiveness of mine clearance when clearing landmines by working the upper ground layer where mines can be expected to be deployed by means of a vehicle-mounted, mechanically driven, rotary cultivator type demimng tool (12) whose basic configuration comprises a demining unit rotating around a horizontal shaft, the active parts of the said demining unit consisting of a number of parallel, demining discs (14) located at a certain distance from each other and rotating around the said shaft and preferably with circular toothed (10) outer peripheries which when the demining tool (12) is in operation cut down into the upper ground layer to a pre-determined depth with the objective of there causing any mines in their path to detonate or to fragment such mines into harmless fragments wh erein the said upper ground layer is worked not only by the demining discs (14) but whereby the zones between the said discs is also worked by impact devices (16) located in these zones such that the said impact devices (16) impact with the ground layer between each pair of demining discs (14) several times per rotation of the demimng tool (12). 2. A device for the method claimed in Claim 1 for clearing landmines by working the upper ground layer in or on which mines may be deployed by using a vehicle-mounted demining tool (12) operating similar to a rotary cultivator with a basic form comprising a demining body, rotating around a horizontal roller shaft, whose main parts consist of a number of parallel demining discs (14) located at a certain distance from each other and rotating around the said roller shaft (13) and preferably with circular toothed outer peripheries which as the demining tool (12) operates cut down into the upper ground layer to a pre-determined depth with the objective of causing any mines in their path to detonate or to be fragmented into harmless fragments where i n the demining tool (12) incorporates some radially projecting, preferably fixed impact devices (16) located in the space between each two adjacent demining discs (14) which impact devices (16) follow each other and impact with the ground layer between the demining discs (14) as the demining tool(12) rotates. 3. A device as claimed in Claim 2 wh er e i n each impact device ( 16) has an oblique leading edge in the direction of impact relative to the ground layer with which it impacts such that the section of the said impact device (16) closest to the axis of rotation of the demining tool (12) impacts with the ground layer first. 4. A device as claimed in Claim 3 wh e re i n the said oblique edge relative to the ground plane incorporates sawtoothed notches (17, 18). 5. A device as claimed in Claim 4 wh ere in each of the said sawtoothed notches (17, 18) has a long longitudinal edge (17) in the main direction of the oblique edge and a short lateral edge (18) that is in the main at right angles to the former. 6. A device as claimed in any of the Claims 2-5 wh er e i n the number of impact devices (16) between each pair of demining discs (14) is 2-10 and preferably 5-10 and whereby there is a free space between each two said impact devices in the same radial plane. 7. A device as claimed in any of the Claims 2-6 w h e re i n each impact device (21, 22) is attached to the demining discs (18, 19) located on either side of it via a dedicated holder (23, 24). 8. A device as claimed in any of the Claims 2-6 wh ere i n the demining tool (12) has a central roller shaft (28) on which its demining discs (29) are mounted, preferably by welding, and whereby each impact device (38) is attached between the said demining discs (29) by dedicated holders (30, 31) attached in or around the roller shaft (28). 9. A device as claimed in any of the Claims 2-8 wh ere i n the p eriphery o f each demining disc (14) incorporates a number of fingers (15) cut out such that each said fmger has three free faces and each finger (15) carries at least one tooth holder incorporating a tooth (10) made of hard material. 10. A device as claimed in a Claim 9 w h er e i n each successive finger (15) is angled out at different angles relative to the main plane of the demining disc (14) and whereby each said fmger (15) is angled out at an opposite angle from adjacent fingers and is also fitted with a tooth constructed of a hard material.

Inventors: KARLEN ANDERS, KARLEN, ANDERS
Applicants: BOFORS AB, KARLEN ANDERS, KARLEN, ANDERS
Application year: 1998
Main classification: F41H11
IPC codes: F41H11