TITLE: PRECISION SEED DRILLS

This invention relates to precision seed drills and to furrow opening coulters therefor.

Examples of precision seed drills, being agricultural or horticultural seed drills of the kind to which the present invention relates, are drills for sowing vegetable seeds comprising ceil wheel or belt or pneumatic-type. seed selection mechanisms, such as the well known "Webb" and "Stanhay" seed drills. The trade mark "Stanhay" is a registered trade mark of Hestair Stanhay Limited. More specifically, the expression "precision seed drill" as used in this specification is intended to mean an agricultural or horticultural seed drill comprising a seed reservoir, and a seed selection mechanism, the seed selection mechanism comprising a drivable seed selection member having individual seed receptors adapted to select seeds from the seed reservoir and to handle them one at a time and optionally including means to singulate seeds ih or on said receptors, the seed selection mechanism being* arranged to deliver seeds to a furrow opened by a coulter having a coulter body portion extending lengthwise of the furrow, the coulter being optionally followed by furrow closing means such- as a press wheel, finger tines or the like.

As regards the seed selection mechanism, in addition to the cell wheel and belt type already mentioned_.there are. pneumatic mechanisms employing positive or negative pressure differentials in relation to apertured disc or drum type seed pick-up members. In the case of one well known example of the drum-type mechanism, the drill is provided with a single centralised seed dispensing mechanism with delivery tubes extending to multiple row units. In the case of the plate type pneumatic selection mechanisms these are usually provided on the basis of one selection mechanism per row unit of the seed drill. Moreover, in addition to such pneumatic selection mechanisms there are the well known and somewhat old-fashioned plate type mechanisms used for many years in maize planters and the like, and the more recent so-called "plateless" mechanisms employing finger or spoon-type individual seed pick-up elements. In the case of substantially all such precision type seed drills, each row unit has its own furrow opening coulter in which the coulter body extends lengthwise of the furrow opened and is subjected to very arduous operating conditions leading to rapid wear of the coulter body.

The wear of the coulter body has two results .

Firstly , the initial V-section of the coulter loses ^v its angular profile and eventually changes to approximately a round section . This causes the drill or furrow in the soil to be correspondingly. profiled. It will be appreciated that when seeds are dropped into a furrow of this profile they will be likely to come to rest at various locations in the lower portion of the furrow , and not necessarily at bottom dead centre. This contrasts with the situation where the coulter is in its unworn state and has a V-section , since the corresponding V-section furrow produced strongly promotes seed deposition precisely at the apex of the V.

Secondly , the wear of the coulter body causes a reduction in drilling depth whereby the operator needs to make a depth adjustment in the coulter control mechanism , and this is time-consuming and reduces the cost-effectiveness of the drilling operation.

All in all , the rapid wear of existing coulter bodies leads to variability in drilling depth with corresponding variation in crop yield , and reductions in drilling efficiency.

This problem of coulter wear is to be clearly distinguished from that of non-precision type drills such as the conventional cereal crop drill in which the seed dispensing mechanism usually comprises a resilient or fluted roll which handles the seed as a flow or else in discrete seed bundles. Such drills usually have upright coulters such as tine coulters which are not subject to the same wear problem as the longitμdinally . extending precision drill type coulters discussed above. Previous proposals for meeting this problem in relation to the coulters of precision seed drills include ^' the provision of coulters having specially hardened zones and coulters which are readily detached and exchanged for • a new coulter. However, these approaches to the problem by no means meet the farmer's needs since interchange of coulters is time-consuming and expensive, and the production of suitably hardened coulters by special metallurgical techniques is not really cost-effective having regard to the increase in coulter life obtained.

Thus, despite the fact that this wear problem for coulters of this type has existed for a great meany years, it still remains to be solved and it is an object of the present invention to provide a precision seed drill and a coulter therefor offering improvements in one or more of the respects identified above.

According to the invention there is provided a precision seed drill, as defined herein, wherein said coulter body is a metallic structure provided with a relieved zone in the wearing region of the coulter, and provided with an insert in said relieved zone, the insert comprising a ceramic material and being formed to provide a soil-engaging surface of the coulter in said wearing region.

The invention also provides a coulter for a precision seed drill as defined herein, the coulter comprising a metallic structure provided with a relieved zone in the wearing region of the coulter, the coulter being provided with an insert in said relieved zone, the insert comprising a ceramic material and being formed to provide a soil- engaging surface of the coulter in said wearing region^*.

Preferably, said insert is bonded by a suitable adhesive to said metallic structure of the coulter. Alternatively, the insert may be mechanically joined to the body portion of the coulter, such as by riveting or otherwise.

The profile of the insert may be such as to correspond and/or complement and/or merge or blend with the contours of the external surface of the coulter body. The insert may also be provided with a soil engaging surface which initially at least, stands somewhat proud with respect to the contours of the remainder of the coulter body so as to provide for a degree of wearing-down of the insert surface during use.

The profile of the coulter is preferably such as to include a narrow leading end or nose portion (at the forward end of the coulter with respect to the operative direction of forward movement of the drill during use) , and a wider mid-portion, followed by an open-bottomed rear portion or boot portion for seed deposition. It is in this latter portion that seeds from the seed selection mechanism are _deposited either direct from the seed selection mechanism or via delivery tubes.

The invention also provides any novel feature or concept or novel combination of features or concepts disclosed herein.

Two embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

Fig 1 shows a side elevation view of a coulter for a cell-wheel type precision seed drill; and

Fig 2 shows a side elevation view of a coulter for a belt-type precision seed drill;

^■ Figs 3 to 9 show, in more detail, two further embodi¬ ments of the invention corresponding quite closely with those described above. In Figs 3 to 9:

Fig 3 shows a side elevation view of a coulter having certain features in common with the coulter of Fig 1 ; Fig 4 shows a section on the line A-A in Fig 3; Fig 5 shows, on a larger scale a portion of Fig 4;

Fig 6 shows a side elevation view of a coulter having many features in common with the embodiment of Fig 2; Fig 7 shows a section on the line VII-VII in Fig 6_? Fig 8 shows, on a larger scale, a section on the line VIII-VIII in Fig 6; and Fig 9 shows a front elevation view in the direction IX in Fig 6. Figs. 10 and 11 show side elevation and plan views of a modified insert assembly for the embodiment of Fig. 6 , incorporatin a quick-attach/detach arrangement , the direction of viewing in Fig. 11 bein indicated by arrow XI in Fig. 10.

The coulter 10 of"Fig. 1 forms part of a row unit of a multi-row precision seed-drill ( not shown ) .

The precision seed drill comprises a toolbar mounted on the hitch links of an agricultural tractor by means of the usual A-frame and extending transversely with respect to the direction of operative forward motion of the drill. Mounted on the toolbar at laterally spaced intervals along its length are 4 , 6 or more individual row units each of which is supported on and pulled by the toolbar and each of which is operative to select seeds one at a time in sequenc from a seed reservoir and to deliver the seeds one at a time to a furrow opened in the soil by the coulter 25 , whereupon the furrow is closed by a press wheel , and this completes the drilling operation. Thus , each row unit comprises a seed reservoir or hopper which feeds seeds to a cell-wheel type seed selection mechanism from which seeds are dropped into the furrow opened by coulter 10, after which a press wheel (not shown) closes the furrow. Coulter 10 comprises a nose portion 12 mounted on the body of the row unit by means of a forward pivot aperture 14. The coulter further comprises a body portion 16 extending longitudinally with respect to the direction F of forward travel of the drill. Coulter 10 further comprises a rear portion 18 which is open-bottomed whereby seeds 20 from the seed selection mechanism can be deposited in the bottom 22 of a furrow 24, the seeds being released in the direction indicated by arrow 26 and lying on bottom 22 at equally spaced intervals, Coulter 10 and its body portion 16 are formed as a metallic structure, specifically an iron forging, having a relieved zone 28 in the wearing region 30 at the bottom of the coulter.

An insert 32 comprising ceramic material is mounted in relieved zone 28 and is formed to provide a soil-engaging surface 34 of the coulter in the wearing region 30. The profile of insert 32 comprises a curved portion 36 of relatively large radius of curvature and forming the leading edge of the furrow-opening portion of the coulter, and a portion 38 of relatively small radius of curvature at the trailing end of the furrow-opening portion of the coulter. Insert 32 is formed as a solid moulded member having the side-elevation profile shown in Fig 1. The profile of the insert along its leading edge 40, as viewed in the direction V1 i.is substantially V-shaped for furrow-opening purposes. In other words, edge 40 is comparatively narrow in width (measured laterally with respect to direction F) and widens in the rearward direction. Along the rear or trailing edge 42 of insert 32, the insert has a flat or slightly rounded surface for furrow-bottom formation purposes.

Along its two straight edges 44, 46, insert 32 is substantially flat for co-operation with the corresponding flat metallic surfaces•of coulter body portion 16, to which

_* it is bonded. For normal usage, the bonding technique employed comprises using an epoxy resin such as the resin sold by Ciba-Geigy under reference number 2007 (which cures at 150° Centigrade in one hour).. or under reference number 2005 (which cures at 20° Centigrade to 100° Centigrade). Alternatively, the bonding agent known as AV138 which cures at ambient temperature and also has gap-filling properties to provide a good blend between the ceramic and the coulter, may be employed.

Alternatively, for maximising the adhesion between the insert and the coulter body portion, the machined surface of the body portion is first shot-blasted to produce a gap of 0.006 inches (0.01524 centimetres) between it and the insert 32. Then the insert is bonded to the coulter body with the epoxy resin followed by heat treatment.

In use, coulter 10 performs substantially as a con¬ ventional metal-only coulter with the difference that the performance of the coulter remains the same as that of a new coulter for a period at least five times longer than usual.

The life of a conventional coulter is limited to a certain number of hundreds of acres due to the rapid wear discussed in detail above. Initial indications for coulter 10 suggest that its life expectancy is increased by from five to fifteen times as compared with a conventional coulter.

In the embodiment of Fig 2, the precision seed drill is otherwise similar to that of Fig 1 but comprises a belt-type seed selection mechanism such as that of the well known Stanhay S870 precision seed drill.

Each row unit comprises a coulter 50 which is otherwise arranged with respect to the drill and its row unit as described above in relation to Fig 1.

Coulter 50 has a different profile from coulter 10, being a metallic structure provided with a relieved zone 52 in the forward wearing region of the coulter, and provided with an insert 54 in the form of a tapered nose in the relieved zone, the insert comprising a ceramic

material and being formed to provide the soil engaging surface of the coulter in the wearing region.

Coulter 50 has a linear leading edge 56 formed, in part, by insert 54 and the profile of the leading edge, as viewed from the front is substantially V-shaped. The lower surface 58 of the coulter is substantially flat or slightly rounded.

Insert 54 is bonded to the coulter body portion 60 substantially as described above in relation to the Fig 1 embodiment and in-use the coulter operates in substantially the same way as that embodiment.

Among the modifications which could be made in the above-described embodiments while remaining within the scope of the invention are changes to the shape and form both of the coulter body portion and the corresponding insert. Considerable variation in the details of the ceramic material may be employed while retaining the hard wearing characteristics thereof. Likewise, many alternative bonding agents may be employed or alternative mechanical fastening techniques to secure the insert to the coulter. In the embodiment of Figs 3 to 5 coulter 70 is generally similar in structure to coulter 10 of Fig 1 but comprises a solid body portion 72 in the form of an iron forging having spaced coulter side plates 74, 76 secured thereto. Body portion 72 is formed with a relieved zone 78 in its wearing region 80.

An insert 82 of ceramic material is mounted in relieved zone 78.

As shown in Fig 5 insert 82 is secured by a layer 84 of bonding agentto the coulter body portion 72 and side plates 74, 76.

Insert 82 comprises a ceramic material in the form of aluminium oxide. The insert is produced by a process of controlled ball milling and spray drying followed by forming by means of die pressing, firing in a kiln and subsequent grinding. An example of a ceramic material suitable for the purpose is that available under the trade mark Deranox 975 which is available from Anderman and Ryder Limited of East Molesey, Surrey. Equivalent alternative ceramic materials may equally be used. In the embodiment of Figs 6 to 9 coulter 90 has a relieved zone 92 and is provided with an insert 94 in the form of a tapered nose of ceramic material shaped and formed to provide the soil engaging surface of the coulter in its wearing region.

As shown in Figs 7 and 8, insert 94 is secured by a layer 96 of bonding agent to the side and base plates 98, 100 and 102 of the coulter.

In the embodiment of Figs. 10 and 11 there is shown a modification of the embodiment of Fi s. 6 to 9 in which the ceramic coulter insert 110 ( corresponding to insert 94 in Fig. 6 ) is arranged to be readilv and quickly detachable and attachable* for replacement purposes.

Thus , it is to be understood that the remainder of the coulter of this embodiment corresponds to that of Fig. 6.

The ceramic insert 110 is otherwise constructed as shown in Fig. 6 but is provided with a screw.threaded fastener member 112 havinq a shank 114 bonded within a bore 115 in the ceramic insert 110 , an annular flange 116 likewise bonded to the insert , and a stud 118 formed with a screw

thread 120 to be received in a clearance opening ( not shown ) formed in the coulter, body and. secured by means of a nut ( also not shown ) inserted through the hollow coulter body structure and tightened by conventional means such as a socket spanner.

In this way , the coulter insert can be readily attached and detached. It will be appreciated that considerable variation of the structure and arrangement of the screw threaded fastener member and the co-pperating structure on the coulter could be provided , and indeed the detailed form of the fastener member itself can be varied according to particular requirements.