This invention relates to a grubber implement for deep loosening of the soil and of the type specified in . the introductory clause of claim 1. Such implements, whether mounted behind a tractor or rigidly on a large size traction machine, are used for cutting grooves in the soil to a depth of ca. 80 cm in order to effect drain¬ age and some aeration of the soil. Even though the tooth is normally sharpened along its front edge it neverthe¬ less requires extreme traction forces to cut its way through the ground and soil. For counteracting a natural raising tendency the almost vertical tooth is normally provided with a lowermost portion projecting forwardly with some downward inclination. Though still used to some extent, this type of grubber implement and the resulting soil treatment is generally acknowledged as being of questionable value, because of the high traction power requirements and because the soil treatment is limited to the groove areas.

Another known type of grubber implement, the so- called pivot-share grubber, is much more efficient for generally treating the soil, because its tooth is pro¬ vided with power operated shares which are pivoted up and down during the operation, whereby the soil is local-

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ly subjected to a loosening treatment which clearly seems to take place not only immediately adjacent the groove, but even way out laterally of the groove. This is highly advantageous, but connected with serious drawbacks ¹ in other respects, e.g. the formation of extra wide grooves or groove portions which stand almost high polished and cause both an undesirably high drainage effect and a long lasting risk of local ground sinking.

It is the purpose of this invention to provide an im- plement which is of simple design and shows outstanding properties as to both relatively low traction force re¬ quirements and very high soil improvement effects sub¬ stantially without any kind of serious associated negative effects. The grubber implement according to the invention is primarily characterized in the features stated in the characterizing clause of claim 1, i.e. by having a simple grubber tooth which, in use, assumes a pronounced forward- ly inclined position. Experiments have s-hown that the tooth is relatively very easy to pull through the soil when it is well inclined and that by changing its inclina¬ tion towards the vertical it will come to a critical angular position determined by the character of the soil, from which a further increase of the tooth inclination will almost immediately result in a really drastically increased moving resistance, viz. the same much higher resistance as normally created by the teeth of the known grubber im¬ plements. It has been found that it is impossible to pre¬ dict the said critical inclination for a given area and that it may even vary considerably along one single work¬ ing track, so it is an important feature, therefore, that the tooth inclination is adjustable while the tooth is in actual operation. The tooth is still easy to drive when it assumes an undercritical inclination, but it is of course important to adjust it to a position as steep as possible in order to make it operate to a depth as large as possible.

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In addition to this very important result of the in¬ vention there is obtained another result which is probably even still more important, viz. a surprisingly high soil improving effect without associated negative consequences. A complete description of the effect of the invention in this respect tends to be very voluminous and scientific, and in this connection- it is deemed sufficient to explain that the generally inclined grubber tooth exerts a raising action on the engaged soil portions, -and when it meets a compacted soil layer it will thus tend to locally lift the layer, whereby the layer is subjected to a breaking effect producing capillary cracks even way out from the sides of the tooth. The tooth groove itself is not caused to show any wide portions or any pronounced wall compaction, because - as stated in claim 1 - the tooth front edge is not sharp, but pronounced blunt so as to promote a local soil lifting more than a lateral displacement of the soil engaged by the tooth front edge. Thus, the said considerable reduction of the necessary traction forde is obtainable even when the front edge of the tooth is pronounced blunt, because the tooth is pronounced inclined.

As explained below the implement according to the in¬ vention furthermore shows a plurality of further advantages due to the angular adjustability or powered angular ova- bility of the grubber tooth.

A preferred embodiment of a grubber implement accord¬ ing to the invention is illustrated in the accompanying drawing, in which:-

Fig. 1 is a perspective view of the implement, ^' Fig. 2 is a perspective view of a detail thereof, and Figs. 3-6 are side wiews illustrating different appli¬ cations of the implement.

The implement shown in Fig. 1 comprises a horizontal chassis 2 made of two opposed iron beams 4 being frontwise provided with a mounting structure 6 enabling the implement to be connected with a standard three-point lift system of

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an agricultural tractor, comprising opposed lift arms 8 and a top rod 10. The mounting structure 6 is connected with the main chassis 2 by means of braces 12 and 14. At the rear end of the chassis 2 is mounted a grubber tooth 16 which is pivotally held by a pivot pin 18 between the two beams 4. The tooth 16 projects downwardly, but has an upper extension 20, the top of which is pivotally con¬ nected with the piston rod 22 of a hydraulic cylinder 24 having its opposite end pivoted to brackets 26 secured to the beams 4 to hereby make the angular position of the tooth 16 adjustable. The chassis 2 is provided with wheels 28, e.g. ordinary automobile wheels.

The downwardly projecting portion of the tooth 16 is substantially straight, though bottomwise the tooth is provided with an interchangeable, forwardly protruding tooth point member 30 as well known per se. As shown in Fig. 2 the lower front edge portion of the tooth 16, as designated 30, is prepared for receiving a separate front edge member 32 being of a wear resistant material and having a generally rounded front edge configuration. Above this member 32 the tooth front edge may be constituted by a piece of round iron 34 welded to the front edge of the body of the tooth 16.

As illustrated in Fig. 3 the tooth 16 may be adjusted to assume a forwardly inclined position designated A, in which it is relatively easy to pull through the soil, e.g. with an inclination somewhere between 30 and 45 with the vertical direction. The cylinder 24 is double acting and is connected with an operation handle adjacent the driver's position in the tractor, whereby the tooth in¬ clination is easily adjusted even during the grubbing work. The tooth should stand as steep as possible, and the ope¬ rator will easily notice when it reaches its optimal posi¬ tion during the work, because further tilting of the tooth towards the vertical will almost abruptly show the conse¬ quence that the moving resistance of the tractor is

enormously increased.

When the height position of the tractor lift is properly adjusted the inclined tooth will provide a down¬ ward pressure on the rear end of the tractor or even on the entire tractor, and the tractor, therefore, may operate even on a very slippery ground with a remarkable speed.

In operation the inclined tooth will exert a certain lift action on the soil layers, sufficiently to cause an important crack formation therein over an area substantially broader than the tooth track itself. This lift action is highly important, and it is promoted by the tooth having a blunt front edge, this of course being a remarkable feature. It is not desired to generally cause a resulting lifting off of earth, and such action is counteracted by the wheels 28. Apart from its described main function the implement shows a row of further possibilities:

A) In operation in very hard soil the tooth may be reciprocated by means of the cylinder 24 to promote the penetration. A vibrator unit (not shown) associated with the tooth may serve the same purpose.

B) The tooth is usable for digging up, by its general movement or by actuation of the cylinder 24, various types of bodies such as big stones and root pieces from the earth. It is even usable for cutting roots and thus for stump clearing purposes.

C) As illustrated in Fig. 4 the tooth is usable to pick up stones or the like and clamp them against the under¬ side of the chassis 2, whereafter the entire implement may be raised by the tractor lift and used for transportation of the clamped body. As shown in Figs. 1 and 6 the chassis may be provided with a front end claw 36 usable - especially with the wheels 28 removed - for enabling large items or e.g. bundles of trunks or the like to be picked up and transported: The wheels 28 may be hight adjustably mounted, also for this purpose. The claw 36 may be freely rearwardly pivotal.

D) As shown in Fig. 5 the tooth is pivotal into a laid down transport position, in which the implement is towable, supported by the wheels 28.

E) In the same position of the tooth the implement can be moved by hand, the wheels 28 being located near its center of gravity.

F) The tooth is lowerable into its operative position even at a location closely against a rear hindrance such as a building wall, because it is lowerable from a rearwardly projection (see Fig. 6) combined with reverse driving of the tractor and forward pivoting of the tooth.

G) Should the tractor get stuck the tooth 16 is usable for pushing or pulling it by actuation of the cylinder 24.

H) The grubber tooth, of course may be used for laying cables or pipes, when fitted with the necessary equipment as well known in the art. A special possibility is to supply water to the tooth groove through suitable channel or tubing means on the tooth. Due to its effect in the soil the grubbe is particularly advantageous for the laying of evaporator pipes for heat pump systems.

The implement may be largely modified within the scope of the invention, e.g. by having a hand driven oil pump for actuation of the cylinder 24 if the implement is moved by means other than a tractor, e.g. pulled by a cable, whereby the implement is usable even in otherwise difficult areas. The cylinder 24 may be replaced by other suitable means for positively adjusting the angular position of the tooth.

The invention also comprises the described method of during the operation with the tooth in its pronounced in- clined position effecting a working adjustment of the tooth inclination forwardly or rearwardly towards the said optimal position.

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