GB2137061A - Soil Cultivating Implements - Google Patents

Abstract

A soil cultivating implement of the kind which comprises a row of rotary soil working members 3 that extends substantially horizontally perpendicular to the direction A is at least partly sustained from the ground surface by a roller 14 located rearwardly of the members 3. To enable the seated tractor driver to effect a vertical adjustment of the heavy roller, a pivotably mounted (7) carrying structure 8, 9 of the roller 14 is connected to a lifting device or hitch 27 by a tie member 23 of telescopic formation comprising a ribbed inner part 30 and an outer part 31 having a housing 32 containing a spring-loaded locking bolt that will co-operate with the ribs of the part 30. The locking bolt can be withdrawn against its springloading by turning a lever 33 remotely controllable from the driving seat of the tractor 28 by pulling upon a control rope or cable 34 whereafter the driver can use the lifting device or hitch of the tractor 28 to raise or lower the frame whilst gravity maintains the roller 14 against the ground surface and the tie member 23 extends or contracts. Indicating means 36, 37 show the chosen bodily level of the ground roller 14. Alternative constructions of the remotely- controllable position-setting means, the locking means and the indicating means are described and illustrated including a hydraulically operable tie member and co-operating locking means. <IMAGE>

Description

SPECIFICATION Soil Cultivating Implements This invention relatives to soil cultivating implements or machines of the kind which comprise a frame provided with a coupling member or trestle constructed and arranged for connection to a lifting device or hitch carried by a tractor or other vehicle, said frame supporting a plurality of soil working members that are drivable to rotate about substantially vertical, or at least upwardly extending, axes, and said frame being at least partly sustained from the ground surface, when the implement or machine is in use, by a roller whose bodily level is adjustable relative to that of said frame. The expression "implement(s) or machine(s)" will be shortened to "implement(s)" alone throughout the remainder of this document for the sake of brevity.

It is necessary that the rollers of such implements should be sufficiently strong to resist the forces which are exerted upon them, during operation, without becoming bent or otherwise deformed but this strength involves a roller of heavy weight and it is consequently often a difficult and strenuous job to change the bodily level of the roller relative to that of the frame to vary the maximum depth of penetration into the ground which is possible by the soil working members that are rotatably carried by that frame, or at least by a portion thereof. In particular, if the tractor or other operating vehicle driver is to effect this adjustment, he/she has to leave his/her driving seat to do so and it is an object of the invention to render this unnecessary and to make the adjustment generally simpler and less tedious to achieve than heretofore.

According to one aspect of the invention, there is provided a soil cultivating implement of the kind set forth, wherein remotely controllable positionsetting means and locking means are furnished whose construction and arrangement are such that the bodily level of said roller relative to that of said frame can be changed and can be retained in a fresh setting, both from a location remote from the roller itself.

Preferably, indicating means is also provided to show the bodily level of the ground roller, said indicating means being visible from the driving seat of the tractor or other vehicle, particularly when that seat is inside a driving cabin.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a plan view of a soil cultivating implement in accordance with the invention shown connected to the rear of an agricultural tractor, Figure 2 is a side view as seen in the direction indicated by an arrow II in Figure 1, Figure 3 is a scrap sectional elevation, to an enlarged scale, illustrating indicating means of the implement of Figures 1 and 2 in greater detail, Figure 4 is a plan view, to an enlarged scale as compared with Figures 1 and 2, of an alternative form of locking mechanism usable in an implement in accordance with the invention, Figure 5 is a section on the line V-V in Figure 4, Figure 6 is a plan view illustrating one of the mechanisms of the embodiment of Figures 4 and 5 of the drawings to an enlarged scale and in greater detail, Figure 7 is a section on the line VIl-VIl in Figure 6, Figure 8 is a side view corresponding to Figure 2 but illustrating a third embodiment in accordance with the invention, Figure 9 is a diagram illustrating the way in which a fluid-pressure operated mechanism of the embodiment of Figure 8 is constructed and functions, and Figure 10 is a side elevation similar to Figures 2 and 8 but showing a further alternative embodiment which, however, incorporates the locking and setting mechanisms of Figures 8 and 9.

The soil cultivating implements which will be described, and that are illustrated in the accompanying drawings, are intended primarily, but not exclusively, for use in preparing seedbeds from previously worked soil in which seedbeds seeds can germinate and, after appropriate thinning of the seedlings, if required, can grow on to maturity. Referring now to Figures 1 to 3 of the accompanying drawings, the soil cultivating implement that is illustrated therein is in the form of a rotary harrow and comprises a hollow boxsection frame portion 1 of elongate configuration whose longitudinal axis extends substantially horizontally transverse and usually, as illustrated, substantially horizontally perpendicular, to the intended direction of operative travel of the implement that is indicated throughout the drawings by an arrow A.A plurality, of which there are twelve in the example that is being described, of substantially vertical, or at least upwardly extending, shafts 2 are rotatably journalled in bearings carried by upper and lower walls of the frame portion 1 so as to lie in a single row that is parallel to the transverse length of the hollow frame portion 1, the longitudinal axes/axes of rotation of the twelve shafts 2 being parallel to one another and being spaced apart at regular intervals which advantageously, but not essentially, each have a magnitude of substantially 25 cms. Each shaft 2 projects downwardly from beneath the bottom of the hollow frame portion 1 and is there provided with a corresponding soil working member that is generally indicated by the reference 3 (Figure 2).

Each soil working member 3 comprises a substantially horizontally disposed support or carrier 4 defining arms that project in diametrically opposite directions from the shaft 2 concerned and whose outer ends terminate in corresponding sleeve-like holders. Fastening portions of rigid soil working tools in the form of tines 5 are firmly but releasably received in the holders that have just been mentioned and soil working portions of the tines 5 project downwardly into the ground, when the implement is in use, to an extent that is adjustable in a manner which will be described below.

The top and front of the frame portion 1, with respect to the direction A, is provided with two pairs of angular supports 6, each pair being arranged mid-way between the axes of rotation of the second and third soil working members 3 as counted from the neighbouring end of the single row of twelve such rotary soil working members and as seen in front of rear view. The two symetrically similar supports 6 of each pair are spaced apart from one another by a short distance and a strong pivot 7 is mounted between them so as to define a substantially horizontal axis that is substantially parallel to the row of soil working members 3, the axes defined by the two pivots 7 being co-incident with one another.

An arm or carrier 8 extends rearwardly from each pivot 7 with respect to the direction A and has its leading end arranged so as to be upwardly and downwardly turnable about that pivot 7 between limbs of the corresponding supports 6.

Each carrier 8 is in the form of a hollow beam of quadrilateral, and preferably square, cross-section and it will be seen from Figures 1 and 2 of the drawings that each carrier 8 projects rearwardly from the corresponding pivot 7 over the top of the hollow frame portion 1 and rearwardly behind that frame portion 1 by a distance which is substantially half the fore-and-aft width of the frame portion 1. The rearmost ends of the two carriers 8 are rigidly interconnected by a transverse beam to the top of which beam 9 both carriers are welded or otherwise secured. The beam 9 extends substantially horizontally parallel to the row of soil working members 3 throughout substantially the whole of the combined working width of those members 3 and, like each carrier 8, is of hollow formation and quadrilateral crosssection.The preferred cross-section is, as illustrated, a square one.

The opposite ends of the transverse beam 9 carry downwardly and rearwardly inclined brackets 10 to which corresponding downwardly and rearwardly inclined support plates 11 of substantially, but not essentially, oblong shape are releasably secured by bolts. Lowermost regions of the two support plates 11 have corresponding bearing housings 13 releasably secured to them and these two bearing housings 13 support substantially horizontally aligned bearings in which stub shafts 12 at the opposite ends of a freely rotatable ground roller 14 are received. In the embodiment which is being described, the ground roller 14 is a so-called packer roller but this is not, of course, essential.

The ground roller or packer roller 14 comprises a support 1 5 of circular cylindrical configuration to the outer surface of which is secured, at regularly spaced apart intervals, a plurality of groups or crowns of tine-like teeth 1 6 and, in order to keep both the teeth 1 6 and the convex surface of the cylindrical support 1 5 as free as possible from stubbonly adhering mud, clods of earth, weed remnants and the like, the edge of a scraper 1 7 bears against, or is located very close to, the convex surface of the support 1 5 between the neighbouring groups or crowns of teeth 1 6.

The scrapers 1 7 make engagement with, or are located very close to, said surface of the roller support 1 5 at locations which are at the back of the roller 14 with respect to the direction A and close to the surface of the ground. Each scraper 1 7 is carried at the lower end of a corresponding arm 18 and the upper ends of the arms 18 are secured to the rear of a horizontal beam 1 9 so as to project downwardly therefrom, the beam 19 extending parallel to the transverse beam 9 and being rigidly connected to the rear of that beam 9 by a plurality, such as four, of relatively spaced supports 20.

The two carriers 8 and the transverse beam 9 together constitute a carrying structure for the ground roller 14. The top of the transverse beam 9 is provided, close to the mid-point of that beam, with a pair of upwardly projecting lugs 21 that are spaced apart from one another by a short distance along said beam 9. A horizontal pivot pin 22 defining an axis that is parallel to the length of the beam 9 interconnects the spaced lugs 21 and has one end of a tie member, that is generally indicated by the reference 23, turnably mounted thereon. The tie member 23 extends obliquely upwardly and forwardly, with respect to the direction A, from the pivot pin 22 and has its leading upper end connected by a further relatively parallel pivot pin 24 to a forked bracket 25 whose base is secured to the lower edges of a pair of upright and relatively spaced plates 26.It can be seen from Figure 1 of the drawings that the upper end of the tie member 23 is pivotally connected, by the pin 24, to the bracket 25 alongside the outer surface of one of the downwardly projecting limbs of that bracket 25.

The relatively parallel upright plates 26 are bolted to rear portions of further relatively spaced and relatively parallel plates which are located at the top of a coupling member or trestle 27 of the implement so as both to be substantially parallel to the direction A. The coupling member or trestle 27 is of substantially isosceles triangular configuration as seen in front or rear elevation and is mounted principally at the top and front of the hollow frame portion 1 mid-way across the working width of the implement. Downwardly and rearwardly divergent tie beams 29 strengtheningly connect locations close to the apex of the coupling member or trestle 27 to widely spaced apart locations at the top and rear of the hollow frame portion, with respect to the direction A.

The coupling member or trestle 27 comprises a pair of horizontally spaced apart lower coupling points and, near its apex, a single upper coupling point and is intended for use in connecting the implement pivotally to the free ends of lower lifting links 25 of a three-point lifting device or hitch at the rear of an agricultural tractor 28 or other operating and propelling vehicle and also pivotally to the free end of the single, adjustablelength, upper lifting link of the same lifting device or hitch.

The tie member 23 comprises a lower part 30 and an upper part 31 which are telescopically slidable relative to one another. The lower part 30 has a ribbed surface which is afforded by a plurality of neighbouring rings that are arranged to co-operate with a locking bolt located internally of a housing 32 that is provided at the lowermost and rearmost end of the upper part 31 of the tie member 23. The profiled lower part 30 and the co-operating locking bolt inside the housing 32 together constitute a locking mechanism. The locking bolt is operable by turning a spring-loaded lever 33 attached to a pivot which penetrates into the interior of the housing 32, said lever 33 being capable of actuation from the driving seat of the tractor 28 or other vehicle by pulling upon a flexible but inextensible control member 34 that may be in the form of a length of strong twine, rope or cable.

When, as will usually be the case, the tractor 28 or other vehicle has a driving cab, the end of the control member 34 that is accessible to the driver will be located inside that cab at a position close to the driving seat. The tie member 23 which is pivotally connected to the carrying structure 8, 9 of the packer roller 14 is operable to retain that roller 14 at any chosen bodily level relative to the soil working members 3 and frame portion 1 and it will be appreciated that, since the implement bears upon the ground surface principally by way of the roller 14, it is this relative bodily level which determines, to a large extent, the maximum depth of penetration of the tines 5 into the soil which is possible when the implement is in use.The locking bolt which forms part of the tie member 23 can, of course, be employed to retain any chosen bodily level of the roller 14 relative to that of the soil working members 3 and frame portion 1 for as long as may be required.

When a change in the bodily level of the roller 14 is required, the control member 34 is pulled forwardly by the driver who occupies his/her driving seat on the tractor 28 to turn the lever 33 and its pivot in an anti-clockwise direction as seen in Figure 2 of the drawings which movement releases the lock between the parts 30 and 31 of the tie member 23. The three-point lifting device or hitch of the tractor 28 is then raised or lowered, as may be required. When the lower lifting links 35 of that lifting device or hitch are moved downwardly with the implement bearing against the ground surface, the lower part 30 of the tie member 23 will be pushed further telescopically into the upper part 31 thereof as the bodily level of the roller 1 4 rises relative to that of the soil working members 3 and hollow frame portion 1.As soon as the desired bodily level has been attained, movement of the threepoint lifting device or hitch is stopped and the control member 34 is released to allow the spring-loading of the lever 33 to re-engage the locking bolt inside the housing 32. This action increases the maximum depth of penetration of the tines 5 into the soil which is possible. If, on the other hand, the lower lifting links 35 of the three-point lifting device or hitch are raised with the locking bolt inside the housing 32 released, the frame portion 1 and soil working members 3 will also be caused to move upwardly whilst gravity will maintain the roller 14 in contact with the ground surface as the lower part 30 of the tie beam 23 moves telescopically further outwardly from the interior of the upper part 31.As soon as the desired new setting has been reached, the control member 34 is released to allow the spring-loading to re-engage the locking bolt to maintain this new setting as long as may be required. This adjustment, it will be understood, reduces the depth of penetration of the tines 5 into the soil which is possible whilst the implement is in use.

The particular bodily level of the roller 14 relative to the hollow frame portion and soil working members 3 that has been adopted can be seen from the driving seat of the tractor 28 (through the rear window of the driving cab if one is provided) since each carrier 8 has a corresponding pointer 37 welded or otherwise rigidly secured to it alongside a corresponding strip 36 that is secured to the top and rear of the hollow frame portion 1 so as to project generally upwards therefrom. Each strip 36 has a surface which faces forwardly with respect to the direction A and upon which a corresponding scale marked from "0" to "10" is marked (see particularly Figure 3 of the drawings).The pointers 37 move over the scales carried by the strips 36 and it is therefore easy for the driver of the tractor 28 to establish any required maximum depth of penetration of the tines 5 of the soil working members 3 into the ground.

Shield plates 39 whose shapes can be seen best in Figure 2 of the drawings are located immediately beyond the opposite ends of the single row of rotary soil working members 3, the two shield plates 39 having rims around their edges of which lower portions bear slidably against the ground surface. The two substantially vertically disposed shield plates 39 are substantially parallel to one another and to the direction A when the implement is in operation and each of them is carried by a corresponding arm 38 of which a portion extends substantially horizontally parallel to the direction A in pivot brackets carried by the top of the hollow frame portion 1 at a short distance from the corresponding end of that frame portion.Each shield plate 39 is thus upwardly and downwardly turnable about the axis afforded by the pivotably mounted portion of the corresponding arm 38 so that said shield plates can match undulations in the surface of the soil that may be met with by the implement during operative progress in the direction A. The shield plates 39 co-operate with the neighbouring soil working members 3 at the opposite ends of the single row thereof in cultivating the soil to substantially the same thorough extent as is produced by co-operation between immediately neighbouring soil working members 3 at locations closer to the centre of the implement.In addition, the shield plates 39 also serve substantially to prevent the rapidly moving tines 5 from projecting stones and other hard objects laterally of the path of travel of the implement so that the danger of damage or injury from this cause is very much reduced, if not completely eliminated. When the implement is undergoing inoperative transport whilst still connected to the raised three-point lifting device or hitch of the tractor 28, both shield plates 39 are advantageously turned upwardly and inwardly through substantially 1 800 about the axes of the corresponding pivotally mounted portions of the arms 38 to lie in substantially inverted positions on top of the hollow frame portion 1.

Each of the shafts 2 is provided, inside the hollow frame portion 1, with a corresponding straight- or spur-toothed pinion 40, the sizes of the pinions 40 being such that the teeth of each of them mesh with those of the or each immediately neighbouring pinion 40 in the single row of twelve (in this embodiment) such pinions.

One of the centre pair of shafts 2 in the row of twelve such shafts has an upward extension through the top of the hollow frame portion 1 into a gear box 41 which is secured in position immediately above the frame portion 1. Shafts and bevel pinions (not visible) inside the gear box 41 place the upward extension of the shaft 2 that has just been mentioned in driven connection with a rotary input shaft 43 of the gear box 41 whose leading splined or otherwise keyed end projects substantially horizontally forwards from the front of the gear box 41 in substantially the direction A where it can be connected to the rear power take-off shaft of the agricultural tractor 28 or other operating vehicle by way of a telescopic transmission shaft 44, which is of a construction that is known per se, having universal joints at its opposite ends.The back of the gear box 41, with respect to the direction A, is provided with a change-speed gear 42 whose construction is not the subject of the present invention. It suffices to say that the splined ends of two shafts project into the casing of the change-speed gear 42 and can co-operate with the internally splined hubs of co-operating pairs of toothed pinions of different sizes. The two pinions of each pair can be interchanged, or can be exchanged for other pairs, to give different transmission ratios and thus allow the speed of rotation of the soil working members 3 to be increased or decreased in response to substantially the same speed of driving rotation that is applied-to the rotary input shaft 43 of the gear box 41.

In the use of the soil cultivating implement that has been described with reference to Figures 1 to 3 of the drawings, the coupling member or trestle 27 is connected to the single upper lifting link and two lower lifting links 35 of the three-point lifting device or hitch at the rear of the agricultural tractor 28 or other vehicle which both moves and operates the implement and the rotary input shaft 43 of the gear box 41 is placed in driven connection with the rear power take-off shaft of the same tractor 28 or other vehicle by way of the known telescopic transmission shaft 44 which has universal joints at its opposite ends.As the implement moves forwardly over the ground in the direction A, each soil working member 3 works an individual strip of soil, extending in that direction, whose width is the same as, or a little greater than, the distance between the axes of rotation of immediately neighbouring shafts 2 so that, as a consequence, the individual strips of soil overlap, or at least adjoin, one another to produce a single broad strip of worked ground that will have a width of substantially, but not necessarily exactly, 3 metres in the case of the example that is being described.Due to the successively intermeshing engagement between the twelve pinions 40, each shaft 2, soil working member 3 and pinion 40 will revolve, during the use of the implement, in the opposite direction to the or each immediately neighbouring similar assembly as indicated by small arrows for some such assemblies in Figure 1 of the drawings. As mentioned above, the two soil working members 3 which are at the opposite ends of the single row of twelve such members 3 co-operate with the shield plates 39 in thoroughly working the soil at the margins of the broad strip of ground that is worked by the implement.

When an increase or decrease of the maximum depth of penetration of the tines 5 into the soil which is possible is required, this can be brought about by the driver of the tractor 28 or other operating vehicle without having to leave the driving seat merely by bodily displacing the packer roller 14 either upwardly or downwardly in level relatively to that of the frame portion 1 and soil working members 3 using the lifting device or hitch to which the implement is connected and the control member 34 in the manner that has already been described. As soon as the locking bolt contained in the housing 32 is re-engaged, the new depth setting of the implement will be maintained until a further adjustment is made. It will be remembered that any particular depth setting can readily be obtained merely by visually checking the positions of the pointers 37 relative to the scales carried by the strips 36. The scrapers 1 7 co-operate with the convex surface of the cylindrical support 1 5 of the ground roller 14 in shedding lumps of soil, mud and the like from between the groups or crowns of teeth 1 6 with the result that large accumulations of soil tend to be prevented from forming on the roller 14 and from being left on the surface of the ground that is being cultivated. Such large accumulations, it will immediately be realised, are a distinct disadvantage when a seedbed is being prepared.

It is not, of course, essential that the ground roller 14 should be in the form of a packer roller and the use of the present invention is equally advantageous when the ground roller 14 is of a different construction. The three-point lifting device or hitch of the tractor 28 and the tie member 23 of the implement together constitute remotely controllable setting means whilst the tie member 23 itself affords remotely actuable locking means by virtue of the spring-loaded locking bolt contained within the housing 32 which bolt is normally engaged but is releasable, against the action of the loading spring, merely by pulling on the control member 34 to turn the lever 33.

Figures 4 to 7 of the drawings illustrate in embodiment in which the bodily level of the roller 14 relative to that of the hollow frame portion 1 and soil working members 3 can be changed from the driving seat (whether or not enclosed in a cabin) of the tractor 28 without having to use the tie member 23, reliance being placed upon the lifting device or hitch of the tractor 28 alone for this purpose. In this embodiment, a locking mechanism that is generally indicated by the reference 45 is-employed, said locking mechanism 45 co-operating with at least one of the arms or carriers 8 and being remotely controllable.A plate 46 whose shape can be seen best in Figure 5 of the drawings has its lower edge welded or otherwise ridigly secured to the flat top of the hollow frame portion 1 and extends substantially vertically upwards therefrom immediately alongside one of the carriers 8 (see Figure 4). The plate 46 and the immediately neighbouring carrier 8 are pivotable relative to one another about a substantially horizontal axis defined by a strong pivot pin 47 that is located above the top of the hollow frame portion 1 but close to the front thereof with respect to the direction A. The plate 46 includes an upper portion 48 that is located well above the top of the hollow frame portion 1 and a major part of which is disposed rearwardly of that frame portion 1 with respect to the intended direction of operative travel A.The upper portion 48 has a leading edge which extends substantially vertically downwards at a position just rearwardly of the fore-and-aft centre of the hollow frame portion 1 and the lower end of this edge is joined to the leading extremity of the plate 46 by a downwardly and forwardly inclined edge, said leading extremity being located immediately behind the front of the hollow frame portion 1 considered in relation to the direction A. The plate 46 is located at that side of the immediately neighbouring carrier 8 which is remote from the centre of the implement and forms part of the locking mechanism 45, the upper portion 48 of the plate 46 being formed with a curved row of slots 49 that are located successively one above the other at substantially regularly spaced apart intervals.

It can be seen from Figure 5 of the drawings that all of the slots 49, except the second one counting from the lowermost end of the two, are inclined to the horizontal whereas said second one is horizontally disposed in substantially parallel relationship with the top of the closely neighbouring carrier 8. Moving upwardly through the row of slots 49, they are successively displaced a little further forwardly in the portion 48 of the plate 46, with respect to the direction A, and, except for said second slot, the slots thereabove are successively more steeply inclined to the horizontal whereas the lowermost or first slot is also inclined gently to the horizontal but in the opposite direction to the higher slots.The arrangement is, in fact, such that, by turning the carrier 8 and plate 46 relative to one another about the axis defined by the strong pivot pin 47, any chosen one of the slots 49 can be in a position in which its length is parallel to the upper surface of said carrier 8. The enlarged flat and substantially oblong head 50 of a locking bolt 51 can be engaged in any chosen one of the slots 49 to maintain the carrier 8 and plate 46 in a corresponding relative angular setting about the axis defined by the pivot pin 47.However, in addition, the complete locking bolt 51 is turnable about a substantially vertical, or at least upwardly extending, axis defined by a pivot pin 52 that lies just in front of the bolt head 50 in the direction A, said bolt head carrying a forwardly projecting lug 54 which is turnably connected to a pair of vertically spaced lugs 55 by the substantially vertical pivot pin 52. The lugs 55 are rigidly secured to one side of a horizontally extending, but vertically disposed, strip 56 whose lower edge, at the rear thereof, is welded to the top of the transverse beam 9. The head 50 of the locking bolt 51 is rigidly secured to one end of an arm 53 that extends substantially horizontally transverse to the direction A, said arm 53 being a part of the bolt 51 which bolt is turnably displaceable about the axis defined by the upright pivot pin 52.In addition to being secured to the transverse beam 9, the upper edge of the strip 56 is secured to the upper surface of the associated carrier 8 at the edge of the upper surface which adjoins the plate 46. The side of the strip 56 which is remote from the arm 46 carries a guide plate 57 in register with the bolt head 50 and said guide plate 57 is formed with a slot which registers with a slot in the strip 56 itself and, when appropriateiy positioned, with any chosen one of the slots 49 in the portion 48 of the plate 46. When in the locking position which is shown in full lines in Figure 4 of the drawings, the bolt head 50 is entered through the aligned slots in the guide plate 57 and the strip 56 and through the chosen slot 49.

The front and rear ends of the strip 56 are provided with supports 58 and 58A, respectively, said supports 58 and 58A projecting perpendicularly from the strip 56 in a direction away from the arm 46 and the leading support 58 serving as a stop. An upright pin 59 is secured to the arm 53 so as to project both upwardly above that arm and downwardly therebeneath (see Figure 7), the pin or projection 59 being spaced along the arm 53 from the bolt head 50 by a distance which is not less than one quarter of the total length of the arm 53, said pin 59 projecting upwardly and downwardly from the arm 53 by substantially equal distances. The upper end of the pin 59 has a flat head which prevents the end of a tension spring 60 that is wound around said pin 59 from becoming upwardly detached from that pin.The opposite end of the tension spring 60 is secured to an anchorage at the leading end (with respect to the direction A) of a screwthreaded pin 61 (Figures 4 and 5) whose shank passes immediately above the upper edge of the rear support 58A and through an opening in a lug 63 which projects perpendicularly from the side of the strip 56 just in front of said rear support 58A. Nuts 62 are arranged on the screw-threaded shank of the pin 61 at opposite sides of the lug 63 and it will readily be apparent that the anchorage at the leading end of the pin 61 can be moved either forwardly or rearwardly with respect to the direction A, any desired position of that anchorage being arrived at, and maintained, by adjusting the nuts 62 lengthwise of the shank of the pin 61 and tightening them against opposite sides of the lug 62 as may be required.

A support 64 in the form of a large lug projecting horizontally from the same side of the strip 56 as does the much smaller vertically disposed lug 63 is located immediately in advance ofthat smaller lug 63 with respect to the direction A and carries, at the end thereof remote from the strip 56, an upwardly projecting bolt 65 which serves as a stub shaft. It will be noted from Figure 5 of the drawings that the support 64 is secured to the strip 56 at a horizontal level just beneath the middle of that strip 56 considered in a vertical direction.An arm 66 is turnably mounted about the stub shaft 65 beneath the head of the bolt which affords that stub shaft but above the support 64, the bolt which affords the stub shaft 65 having a compression spring or spring washer located around its shank between the support 64 and a nut which co-operates with that shank (see Figure 5) so that, whilst the arm 66 can turn about the stub shaft 65, it does not do so entirely freely, there being some frictional opposition. The stub shaft can also be tilted to some extent.

An end region of the arm 66 that is remote from the stub shaft 65 has the edge thereof which faces the centre of the implement bevelled in such a way that the free extremity of the arm 66 is nearly, but not quite, pointed (see Figures 4 and 6 of the drawings). A plate 67 is welded or otherwise rigidly secured to the lower surface of this bevelled region of the arm 66 and it will be seen from the drawings that said plate 67 is substantially horizontally disposed and shaped to define two opposed noses 68 and 69 which are spaced apart from one another by a short distance lengthwise of the arm 66 and which, as seen plan view (Figure 6), are both disposed alongside the edge of the arm 66 which faces the strip 56.The nose 68 which is nearest to the end of the arm 66 defines a stop surface a of straight configuration whose length is inclined at an angle of substantially 450 to the longitudinal axis of the arm 66. The other nose 69 defines a second stop surface b which surface b is straight and in parallel relationship with the stop surface a. Both stop surfaces a and b are inclined inwardly from their outer ends towards the end of the arm 66 that is turnably mounted on the stub shaft 65 and the gap between them give access to a substantially oblong recess whose longer edges are parallel or substantially parallel to the longitudinal axis of the arm 66. The edge of the nose 69 which is remote from the recess 70 is straight and in substantially parallel relationship with the stop surfaces a and b.The plate 67 has a downwardly offset portion 71 (see particularly Figure 7) and this portion 71 lies principally beneath the recess 70 between the noses 68 and 69 (see Figure 6). As can be seen in Figure 7, approximately half of the portion 71 is inclined downwardly from the remainder of the plate 67 at an angle of substantially 300 to the horizontal whilst approximately the other half thereof is in substantially horizontally parallel relationship with said remainder of the plate 67. The plate 67 and the arm 66 together constitute an arresting mechanism for maintaining the locking bolt 51 in the inoperative position thereof that is shown in broken lines in Figure 4 and in full lines in Figure 6 of the drawings. The arm 66 carries, substantially mid-way along its length, an upwardly projecting pin 72 (Figure 4) around which one end of a helical tension spring 73B is engaged.The opposite end of the tension spring 73B is engaged with the anchorage carried by the screw-threaded pin 61 together with one end of the aforementioned tension spring 60. The tension spring 73B tends constantly to turn the arm 66 angularly about the stub shaft 65 and thus keeps the edge of that arm 66 which faces the strip 56 continuously in engagement with the portion of the upright pin 59 that projects downwardly beneath the arm 53 of the locking bolt 51.

The end of the arm 53 which is remove from the head 50 of the locking bolt 51 carries a supporting bracket 74A (Figure 4) comprising two substantially horizontally disposed but vertically spaced apart lugs between which lugs a pulley 76A is rotatable about an upright axle pin 75A whose opposite upper and lower ends are supported by the two lugs of the bracket 74A. A flexible but inextensible control member 77A in the form of a length of strong twine, cord, rope, cable or the like has one end tied or otherwise firmly secured to an eye 78A that is fastened to one side of the coupling member trestle 27 at a location substantially vertically above the leading edge, with respect to the direction A, of the hollow frame portion 1. The control member 77A passes rearwardly from the eye 78A, around the pulley 76A and forwardly therefrom, through the eye 78A, to a location where it can be pulled forwardly by the driver of the tractor 28 or other vehicle without that driver having to leave his/her driving seat. If, as will usually be the case, the seat is inside a driving cab, when the leading end of the control member 77A is, of course, located inside that cab.

When the bodily level of the ground roller 14 has to be raised or lowered relative to that of the hollow frame portion 1 and soil working members 3 to change the maximum depth of penetration of the tines 5 into the soil which is possible during the use of the implement, the locking mechanism 45 is first actuated by pulling forwardly on the control member 77A which action turns the locking bolt 51 anguiarly about the substantially vertical axis defined by the pivot pin 52 from the locking position shown in full lines in Figure 4 of the drawings to substantially the unlocked position that is shown in broken lines in the same Figure, the displacement of the locking bolt 51 about this axis being against the resilient opposition of the spring 60.As soon as the head 50 of the bolt 51 is withdrawn from one of the slots 49 in the portion 48 of the plate 46, the carriers 8 can turn upwardly or downwardly about the axis defined by the strong pivot pin 47 and an aligned strong pivot pin (not shown) that corresponds to the other carrier 8. During the forward turning movement of the locking bolt 51 about the pivot pin 52, the downwardly projecting portion of the upright pin 59 which it carries meets the edge of the nose 69 that is nearest to the stub shaft 65 and slides along that edge until it moves around the tip of the nose 69, between the stop surfaces a and b and along the latter into the recess 70. The tension spring 60 can then be relied upon to maintain the lower part of the pin 59 in that part of the recess 70 which lies at the root end of the stop surface b.The locking bolt 51 is thus maintained in the position shown in broken lines in Figure 4 and in full lines in Figure 6 of the drawings whilst the tractor driver either raises or lowers the three-point lifting device or hitch of the tractor 28 or other vehicle to change the bodily level of the roller 14 relative to that of the frame portion 1 and soil working members 3.

As soon as the required fresh bodily level of the roller 14 has been attained, this being checked by the positions of the pointers 37 against the scales carried by the strips 36 (Figure 3), the control member 77A is again pulled forwardly which causes the lower portion of the pin 59 to move obliquely forwardly (with respect to the direction A) along the recess 70 until it is in engagement with the nose 68 and alongside the downwardly offset end of the portion 71 of the plate 67. The arm 66 and the parts which it carries will be in the position shown in broken lines in Figure 4 of the drawings at this time and, upon then relaxing the pull on the control member 77A, the spring 73B will tend to turn said arm 66 back in a clockwise direction as seen in Figure 4 through a few degrees and into substantially the position thereof that is shown in full lines in the same Figure.

Thus, the lower end of the pin 59 is moved into vertical register with the downwardly offset part of the plate portion 71 and, upon still further relaxing the pull on the member 77A, the stretched spring 60 will start to turn the locking bolt 51 back towards its locking position and the lower end of the pin 59 will ride up the incline of said plate portion 71 and onto the upper surface of the nose 69 alongside the edge of the arm 66 which faces the strip 56. It will be apparent that the arm 66 itself has to turn downwardly to some extent to allow this to take place and it will be remembered that the stub shaft 65 about which the arm 66 is turnable incorporates resilient means (visible in Figure 5) which permits this marginal downward tilting of the arm 66.

Continued relaxation of the pull on the control member 77A allows the pin 59 to move further towards the stub shaft 65 to a position where its lower end no longer contacts the upper surface of the plate 67 but where the side of its lower portion again contacts the edge of the arm 66 which is closest to the strip 56. Provided that the flat head 50 of the locking bolt 51 is correctly in register with the chosen one of the slots 49, the spring 60 will return the locking bolt 51 to the position shown in full lines in Figure 4 in which said bolt head 50, whose free end may be bevelled to assist it in engaging the chosen slot 49, occupies substantially the position shown in Figures 4 and 5 of the drawings or an equivalent position in which, as seen in Figure 5, a different slot 49 has been selected.Although the illustrated control member 77A is intended to be pulled manually forwards by the tractor driver against the action of the spring 60, this is by no means essential and power-operated means such as a pneumatically or hydraulically operated piston and cylinder assembly could be employed as an alternative. The arresting mechanism of this embodiment could be employed in an agricultural implement other than a soil cultivating implement of the kind set forth at the beginning of this description.

Figures 8 and 9 of the drawings illustrate an embodiment in which, as in the case of the embodiment of Figures 4 to 7 of the drawings, those parts of the implement which are similar or identical to parts that have already been described with reference to the embodiment of Figures 1 to 3 of the drawings are indicated by the same references as are employed in Figures 1 to 3 and will not be described again in detail.In the embodiment of Figures 8 and 9 of the drawings, the locking mechanism that is afforded by the tie member 23 of the first embodiment is replaced by an alternative tie member that is generally indicated by the reference 72A which tie member 72A, however, again extends obliquely upwardly and forwardly with respect to the direction A having its opposites ends pivotally connected to the transverse beam 9 and to the forked bracket 25 in the manner described with reference to Figures 1 to 3 of the drawings. The tie member 72A comprises a double-acting fluidpressure operated piston and cylinder assembly 73A, which assembly 73A has the lower end of its piston rod pivotally connected to the transverse beam 9 and the upper end of its cylinder pivotally connected to the bracket 25 by the horizontal pin 24.The piston and cylinder assembly 73A is hydraulically coupled by ducts which are shown diagrammatically in Figure 9 to a controlled double-acting non-return valve 73 which valve 73 constitutes a locking mechanism to ensure that, when arranged in a predetermined setting of length, the piston and cylinder assembly 73A cannot slowly change its length due to, for example, seepage of oil or other hydraulic fluid.

As can be seen in Figure 8 of the drawings, the non-return valve 73 comprises a cylindrical housing 74 mounted on top of the assembly 73A in substantially parallel relationship therewith. A lower duct 75 and an upper duct 75' both support the housing 74 and couple the fluid-pressure equipment of the valve 73 to the opposite ends of the cylinder of the assembly 73A. The duct 75 communicates with one side of a single-acting one-way unit 76 and, similarly, the duct 75' communicates with one side of a single-acting one-way unit 76' as illustrated diagrammatically in Figure 9.

The opposite sides of the two one-way units 76 and 76' communicate respectively with flexible ducts 77 and 77' that, in the use of the implement, are coupled to the hydraulic system of the tractor 28 or other vehicle by way of known quickly-releasable and leak-proof hydraulic connections that are not shown in the drawings.

In addition, the duct 77' is connected to the oneway unit 76 by a duct 78 and, similarly, the duct 77 is connected to the one-way unit 76' by a duct 78'.

In the use of the embodiment that has been described with reference to Figures 8 and 9 of the drawings, connecting the flexible duct 77' to hydraulic pressure and relieving the duct 77 of hydraulic pressure causes the one-way unit 76' to tend to open but the piston 79 of the assembly 73A cannot yet move to the right as seen in Figure 9 of the drawings and obliquely downwardly to the left as seen in Figure 8 because the one-way unit 76 is still closed. Such movement can only commence when the oneway unit 76 is opened which takes place as a result of the pressure in the duct 77' reaching said unit 76 by way of the control duct 78.The piston 79 is thus caused to move to the right as seen in Figure 9 of the drawings towards the opposite end of the cylinder of the assembly 73A thus bodily displacing the ground roller 14 downwardly about the substantially horizontal axis defined by the aligned pivots 7 and such movement is allowed to continue until the required bodily position of the roller 14 has been reached. Pressure is then withdrawn from the duct 77' and the two one-way units 76 and 76' immediately both close so that the oil or other hydraulic fluid in the cylinder of the assembly 73A is trapped at both sides of the piston 79 of that assembly which prevents the piston 79 from moving in either direction in its cylinder.The units 76 and 76' are parts of the generally indicated non-return valve 73 and, in this embodiment, constitute a locking mechanism which is hydraulically operable from the driving seat of the tractor 28 and from inside the driving cabin of that tractor 28 when, as will usually be the case, such a driving cabin is provided.

When it is desired that the piston 79 should be moved in the opposite direction in the cylinder of the assembly 73A, hydraulic pressure is applied to the flexible duct 77 and is withdrawn from the flexible duct 77', this pressure acting upon the one-way unit 76 and, by way of the duct 78', upon the one-way unit 76'. The opened units 76 and 76' allow the piston 79 to move back to the left as seen in Figure 9 of the drawings and such movement continues until the required bodily position of the ground roller 14 has been reached at which time pressure is withdrawn from the duct 77 as well as the duct 77' causing the closure of both one-way units 76 and 76' and the trapping of the oil or other hydraulic pressure medium at both sides of the piston 79.

One of the two carriers 8 forming part of the carrying structure of the ground roller 14 has a supporting bracket 80 fastened to it and one end of the sheath of a Bowden cable 81 is adjustably secured to this bracket 80. The core of the Bowden cable 81 is fastened to an anchorage at the top and rear of the hollow frame portion 1 which anchorage is located substantially vertically beneath the bracket 80. The opposite end of the flexible Bowden cable 81 has its sheath connected to a support 84 and its core connected to a simple known mechanism (not shown), such as a rack and pinion, which will move a pointer 82 over a sector-shaped plate 83 carrying a dial marked with numerals from "1" to "10" for indication by the pointer 82.The plate 83 is rigid with the support 84 and that support is constructed so as to be capable of being readily mounted within the view of the driver of the tractor 28 or other vehicle when occupying the driving seat of that tractor or other vehicle. When a driving cabin is provided, as will usually be the case, the parts 82, 83 and 84 will be mounted at any convenient point in that cabin.

When employing the embodiment of Figures 8 and 9 of the drawings, the hydraulic system of the tractor 28 or other vehicle is employed to release the locking means that is afforded by the valve 73 and subsequently to increase or decrease the length of the tie member 72A by moving the piston 79 in an appropriate direction in the cylinder of the assembly 73A. The pointer 82 is moved by the core of the Bowden cable 81 and, when the driver sees that the desired bodily level of the roller 14 has been attained, the hydraulic system of the tractor 28 or other vehicle is again employed to stop the change in the length of the tie member 72A, the valve 73 acting in the manner described above effectively to lock the piston 79 in a corresponding position lengthwise of the cylinder of the assembly 73A. These actions are all remotely controlled from the driving cabin, or at least from the driving seat, of the tractor 28 or other vehicle.

Figure 10 of the drawings illustrates an embodiment in which the hollow frame portion 1 that rotatably supports the rotary soil working members 3 is upwardly and downwardly displaceable relative to a frame 86 by way of two parallelogram linkages 85 which are spaced apart from one another along the length of the hollow frame portion 1. The frame 86 comprises, as seen in plan view, a leading frame beam 87 that extends substantially horizontally perpendicular to the direction A at a location in advance of the hollow frame portion 1 with respect to that direction A and a trailing frame beam 87 that is parallel to the leading beam 87 but that is disposed behind the hollow frame portion 1 considered in the direction A. Supports 88 that extend substantially, although not exactly, parallel to the direction A rigidly interconnect the leading and rear beams 87 of the frame 86.A substantially central region of the leading frame beam 87 carries a coupling member or trestle 89 that is of substantially isosceles triangular configuration as seen in front or rear elevation which coupling member or trestle 89 is constructed and arranged for connection to the three-point lifing device or hitch at the rear of the agricultural tractor 28 or other propelling and operating vehicle. Tie beams 90 strengtheningly connect an upper portion of the coupling member or trestle 89 to lugs projecting upwardly from the supports 88 at locations adjacent to the rear frame beam 87. In this embodiment, the packer ground roller 14 is replaced by a ground roller 1 4A of open-work, cage-like formation.The roller 1 4A comprises a central axially extending shaft to which a plurality of circular support plates 91 are secured at regularly spaced apart intervals. A plurality, such as twelve, of elongate elements 92, in the form of lengths of rod, are entered through regularly spaced apart holes around the periphery of each support plate 91 skeletally to define the ground-engaging surface of the roller 14A. The elongate elements 92 are preferably, but not essentially, wound helically to some extent around the longitudinal axis/axis of rotation of the roller 14A.Downwardly and rearwardly, with respect to the direction A, inclined arms 93 carry substantially horizontally aligned bearings which support the opposite ends of the ground roller 1 4A in a freely rotatable manner, the upper leading ends of the two arms 93 being bolted or otherwise rigidly secured to corresponding substantially horizontally disposed arms 94 whose leading ends are pivotally connected to corresponding lugs that project downwardly and rearwardly from the leading beam 87 of the frame 86, the pivotal connections of the arms 94 to these lugs being substantially horizontally aligned in a direction that is parallel to the transverse length of the hollow frame portion 1. A carrier beam 95 rigidly interconnects the arms 94 and is secured to those arms 94 at locations close to the leading upper ends of the inclined arms 93.The carrier beam 95 is substantially horizontally parallel to the longitudinal axis of the hollow frame portion 1 and, adjacent its mid-point, lugs 21A that are carried by its upper surface are pivotally connected to the lower, rear, end of the piston rod of the piston and cylinder assemblies 73A by the previously mentioned strong and substantially horizontally disposed pivot pin 22.

The ground roller 1 4A of the embodiment df Figure 10 of the drawings can be bodily displaced upwardly or downwardly in substantially exactly the way that has already been described with reference to Figures 8 and 9 of the drawings except that, in this case, the frame portion and soil working members 3 are independently movable relative to the frame 86 so that it is the bodily level of the ground roller 1 4A relative to that of the main frame 86, rather than to that of the frame portion 1 and soil working members 3, which determines the maximum depth of penetration of the tines 5 into the soil which is possible.Unless exceptionally hard soil is being dealt with, gravity will normally cause the hollow frame portion 1 and rotary soil working members 3 to occupy a position in which the links of the parallelogram linkages 85 are tilted downwardly as far as is permitted by stops which are not visible in Figure 10 but, should at least one of the rapidly rotating soil working members 3 encounter, for example, a large buried rock, the parallelogram linkages 85 allow the frame portion 1 and soil working member 3 to move upwardly to avoid damage, or at least serious damage. As soon as the members 3 have moved over the buried rock or other obstacle, gravity will rapidly cause the tines 5 of those members 3 to resume their normal depth of penetration into the soil.

Although certain features of the implement embodiments that have been described and/or that are illustrated in the accompanying drawings will be set forth in the following claims as inventive features, it is emphasized that the invention is not necessarily limited to those features and that it includes within its scope each of the parts of each implement embodiment that has been described, and/or that is illustrated in the accompanying drawings, both individually and in various combinations.

Claims (27)

1. A soil cultivating implement of the kind set forth, wherein remotely controllable positionsetting means and locking means are furnished whose construction and arrangement are such that the bodily level of said roller relative to that of said frame can be changed and can be retained in a fresh setting, both from a location remote from the roller itself.

2. An implement as claimed in claim 1, wherein the position-setting means comprises a tie member interconnecting the frame and carrying structure of the roller, said tie member being variable in length.

3. An implement as claimed in claim 2, wherein the tie member is constructed and arranged in such a way that its length can be varied by raising or lowering the lifting device or hitch of the tractor or other vehicle to which the implement is connected in the use thereof.

4. An implement as claimed in claim 2, wherein the construction and arrangement of the tie member are such that its length can be varied by changing the degree of extension of the piston rod from the cylinder of a hydraulic piston and cylinder assembly principally affording said tie member.

5. An implement as claimed in claim 3, wherein said tie member comprises two telescopically slidable parts whose relative positions can be fixed by a locking mechanism that is remotely actuable by said locking means.

6. An implement as claimed in claim 5, wherein the locking mechanism comprises a shaped profile on one of said parts and a remotely actuable locking bolt supported by the other of said parts and arranged to co-operate with the profile of said one part.

7. An implement as claimed in claim 4, wherein the construction and arrangement are such that the piston of said piston and cylinder assembly can be locked at any chosen position lengthwise of the cylinder of said assembly by actuation of a remotely-controlled double-acting non-return valve.

8. An implement as claimed in claim 7, wherein said valve is disposed in a housing forming part of the tie member.

9. An implement as claimed in claim 8, wherein, when the implement is in use, said valve is in communication with the hydraulic system of the operating tractor or other vehicle.

10. An implement as claimed in any one of claims 2 to 9, wherein said coupling member or trestle is of substantially triangular configuration as seen in front or rear view and is constructed for connection to the three-point lifting device or hitch of an operating tractor or other vehicle, said tie member interconnecting the carrying structure of the roller and a location at substantially the apex of said coupling member or trestle.

11. An implement as claimed in claim 10, wherein the connection of the tie member to the carrying structure of the roller substantially coincides with a plane containing the mid-point of the axial length of the roller.

12. An implement as claimed in any one of claims 2 to 11, wherein the carrying structure of the roller includes two relatively spaced arms each of which is turnable upwardly and downwardly with respect to said frame about a horizontal or substantially horizontal axis that extends perpendicular, or at least transverse, to the intended direction of operative travel of the implement.

13. An implement as claimed in claim 12, wherein said locking mechanism comprises a locking bolt which is angularly displacable about an upwardly extending axis and by which locking bolt at least one of the two relatively spaced arms of the carrying structure of the roller can be retained in a chosen position relative to said frame.

14. An implement as claimed in claim 13, wherein the locking bolt has a head which is of substantially oblong configuration.

1 5. An implement as claimed in claim 14, wherein the head of the locking bolt is shaped for entry in any chosen one of a plurality of slots that are formed one above the other in a supporting plate that occupies a fixed position relative to said frame.

16. An implement as- claimed in claim 15, wherein the locking bolt is supported by one arm or carrier of the roller carrying structure and said slotted supporting plate is fastened to the frame, said slots being so disposed as to be respectively in substantially parallel relationship with the top of said arm or carrier when any such slot is in register with the locking bolt.

1 7. An implement as claimed in claim 16, wherein said slots are disposed one above the other with the leading end of each slot further advanced, with respect to the intended direction of operative travel of the implement, than is the leading end of the or each slot located therebeneath.

18. An implement as claimed in any one of claims 13 to 17, wherein an arresting mechanism is provided to retain the locking bolt in a withdrawn inoperative position.

1 9. An implement as claimed in any preceding claim, wherein indicating means is provided to show the bodily level of the ground roller, said indicating means being visible from the driving seat of the tractor or other vehicle which moves and operates the implement during the use of the platter.

20. An implement as claimed in claim 19 when read as directly or indirectly appendant to claim 2, wherein said indicating means comprises a dial carried by said frame and a co-operating pointer mounted on the carrying structure of the roller.

21. An implement as claimed in claim 19 when read as directly or indirectly appendant to claim 2, wherein the indicating means comprises a Bowden cable whose sheath is supported on said frame and whose core is connected to the carrying structure of the roller, the opposite end of said core being operatively coupled to a pointer which is movable over a co-operating dial, and wherein the pointer and dial assembly is constructed so as to be capable of being mounted in a position in which it is readily visible from the driving seat of a tractor or other vehicle which moves and operates the implement, whether or not said driving seat is contained inside a driving cabin.

22. An implement as claimed in any preceding claim, wherein said soil working members are arranged in a row that extends substantially horizontally perpendicular, or at least transverse, to the intended direction of operative travel of the implement, each soil working member being drivable about a corresponding substantially vertical, or at least upwardly extending, axis from the power take-off shaft of the tractor or other vehicle which moves and operates the implement in the use of the latter.

23. A soil cultivating implement of the kind set forth, substantially as hereinbefore described with reference to any of the embodiments illustrated in the accompanying drawings.

24. An arresting mechanism for retaining the locking bolt of a locking mechanism in an inoperative position in a soil cultivating or other agricultural implement as claimed in any one of claims 13 to 18, wherein the arresting mechanism comprises a pivotable arm provided, adjacent one end thereof, with two relatively spaced guide surfaces between which surfaces a projection rigid with said locking bolt is movable into a recess, and wherein one side of said recess is so designed that, when the locking bolt is moved for a second time in the direction which brought said projection into the recess, the projection will ride out of the recess to a position in which it is no longer retained by the arresting mechanism and can return to its operative locking position.

25. An arresting mechanism as claimed in claim 24, wherein the guide surfaces and the opening are formed in a shaped plate which is secured to the lower surface of said arm.

26. An arresting mechanism as claimed in claim 24 or 25, wherein said arm is resiliently urged into engagement with the projection of the locking bolt in such a way that, when the locking bolt is displaced towards said one end of the arm, the projection moves along the edge of that arm and then between the guide surfaces.

27. An arresting mechanism as claimed in any one of claims 24 to 26, wherein a part of the mechanism that is located between said recess and the edge of said arm which is located alongside that recess is so shaped that, upon a second movement of the locking bolt in the direction which engaged its projection in the recess, said projection moves out of that recess, the latter forming a guide by which the projection may be disengaged from the recess to allow the locking bolt to return to its operative locking position.