GB2117614A - Soil working machines - Google Patents

Abstract

A rotor unit 10a for soil-working machines comprises hub with a hub plate 15 and a projecting boss, and a plurality of blades 18a having shanks 19a mounted at 30,31 on a face of the plate, with each shank having an edge portion at 22a tangentially abutting the boss. The blades may be placed on one side or both sides of the plate 15 and the removable points 23 have cutting edges 28 at both ends. <IMAGE>

Description

SPECIFICATION Soil-working machines The present invention relates to soil working machines and more especially to a rotor adapted to be rotated by means of a motor for working the soil.

The rotor of the present invention is particularly adapted for working upon the sub-soil as part of a "double-digger" machine e.g. as described in British Patent 1 512480 which is designed for working top soil and sub-soil simultaneously but in separate layers, a plough removing the top soil so as to expose the sub-soil which is then cultivated by means of the rotor.

Existing rotor designs for double digger machines have been adapted for use in sub-soil from rotors originally designed for loosening top soil. In consequence, the rotors do not operated very successfully on compacted soil which is found at depth.

Existing blade arrangements and hub sizes make it difficult for loosened soil to flow through the rotor.

Additionally, the known rotor cannot operate to a depth greater than 15 cm because the length and curvature of the shanks permits only small bite lengths which give excessive pulverisation, high rates of wear and a high power requirement. A need has been found for a rotor capable of operating at greater bite lengths thereby reducing the degree of pulverisation, the amount of blade wear and the power required for sub-soil loosening.

There has resulted a new rotor with longer blades, in relation to hub size with a more carefully controlled angle of approach and with a blade distribution all of which make demands upon the mounting of the blades to the hub. Indeed rotors specially designed for high performance upon compacted sub-soils tend to place great demand upon the strength of the mounting and the invention is more particularly concerned with this problem.

According to the invention there is provided a rotor for soil-working machines comprising at least one hub with a hub plate and a projecting boss, and a plurality of blades having shanks mounted on a face of the plate with each shank having an edge portion tangentialiy abutting the boss.

In a non-preferred design in which all the blades are mounted to one face of the hub plate, it is convenient to have an edge portion of one shank abutting an edge portion of an adjacent shank.

However it is preferred to utilise a hub plate which is intermediate between two oppositely projecting bosses. In a device of this kind an edge portion of each shank on one face of the hub plate may be arranged to abut a mounting element serving a blade on the opposite face.

Preferably a side edge portion of each shank abuts the hub and an end edge portion of each shank abuts a said mounting element, which might be a bolt head or nut or rivet element.

There are preferably provided two hubs separated by a chain case. The inner blades (adjacent to the gear) may have tip portions offset inwardly below the level ofthe chain case. The outer blades may have tip portions offset outwardly symmetrically with the inner blades. In this way the digging paths of the blades can be evenly distributed across the width of the furrow, not withstanding the presence of the chain case.

In the preferred case each blade is formed with a shank and a replaceable digging point in the form of a pick tine. Each point is preferably curved in the direction of rotation. Preferably also each point is symmetrical about the longitudinal centre and is symmetrically mounted to the shaft so that either end can serve for digging.

An embodiment of the invention is hereafter described with reference to the accompanying drawings in which Figure 1 is an elevational view along the axis of a rotor unit in accordance with the invention; Figure 2 is an elevational view at right angles to Figure 1 showing the main components of a complete rotor; and Figure 3 is a diagram indicating operating parameters of the rotor.

In Figure 2 the axial distribution of components of the rotor is indicated, there being rotor units 1 0a, 10b adaptedto be mounted on a shaft 11 on opposite sides of a chain case 12 adjacent to bearing housings 13. Only the left hand rotor unit 10a is shown in detail, the right hand unit being normally in mirror image relationship. In general the rotor of the invention can consist of one or a number of units of the type illustrated e.g. at 1 Oa, depending upon the application and especially whether it is to be used on top soil or sub-soil. The preferred rotor to be describes is particularly useful in connection with a double digger as described in British Patent No. 1 512480.

Each rotor unit comprises a hub 14 having a hub plate 15 situated intermediate between an interior projecting boss 16 and an exterior projecting boss 17, the interior boss 16 in the case of each unit being of greater axial length so as to project beyond the attached blade shanks and their mounting elements.

Six rotor blades 18a, 18b are mounted to the hub 14 of rotor unit 10a, the blades 18a being mounted on the outward side of the plate 15 and the blades 18b on the inward side. The blades are uniformly distributed so that on each side the blades are 120 apart with a blade 18b situated midway between each two blades 18a. The blades 18a, 18b have differently formed shanks 19a, 19b,the shanks 19a containing an outward oblique portion 20a serving to offset a tip portion 21a of the shank from a hub portion 22a of the shank. Likewise the shanks 19b of the blades 18b have oblique portions 20bwhich offset inwardly tip portions 21 b from hub portions 22b.

A replaceable point 23, which is the same in the case of each blade, is mounted to the tip portion 21 a, 21 b of each shank by means of two bolts 24,25. The bolts are countersunk on the concave cutting face of The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

bit 23 and extend through step surfaces in the backs of the shanks where they are secured by respective nuts 26, 27. The stepped surfaces form a taper in the plana of Figure 1 at the ends of the shanks to provide clearance between the backs of the blades and the uncut soil.

Each point 23 is shaped as a pick tine, with a cutting edge 28 at each end. Since they are symmetrically bored to receive the bolts 24, 25, each point, after a certain period of wear, can be removed, rotated through 1800 and replaced, or else replaced altogether. In this way it is possible to ensure that undamaged and sharp blades are always present and can be easily replaced during a service operation.

The hub plate 15 is bored with two circular arrays of bore holes for receiving mounting elements in the form of bolts for the blades. As shown in Figure 1 there is an outer ring 30 near the periphery of the hub plate 15, and an inner ring of bore holes, all being situated at the same radius, for receiving a second series of bolts 31. The bolts 31 are so arrangedthattwo bolts projectthrough each shank hub portion 22a, 22b, a first bolt 31 a being situated adjacent the end edge 32 of a shank, which is cut at an angle of substantially 60 to the inner side edge 33 of the shank, and a second bolt 31 b positioned intermediate between the bolt 31a and the bolt 30 and adjacent the edge 33.

The bolt heads and nuts are so spaced and arranged that each end edge 32 of a shank abuts against a bolt head or nut in respect of the mounting element for the next adjacent blade on the other side of the hub plate. At the same time the inner side edge 33 of each shank abuts the outer peripheral surface of one of the bosses 16, 17. In this way the blades are extremely securely mounted. Upon en gaging the soil there will be a tendency firstly for the blade to pivot about the end bolt 30 so that the tangential thrust is taken against the bosses 16, 17 of the hub. In the course of the passage of the blade through the soil, the reaction force tends to be taken more closely along the direction of the length of the shank in the hub region and the thrust is therefore taken against the appropriate bolt or other mounting element of the next adjacent blade.In this way the shear forces acting on the mounting bolts and on the bores in the shanks are distributed and compensated in an optimum manner.

It will be appreciated from an inspection of Figure 1 that it would be possible, if it were so desired, to arrange all of the blades upon one face of the hub plate, in which case each shank would have a side edge which abutted against not only the peripheral surface of the stub but also an end surface of an adjacent shank. It would be possible in this way to construct the rotor of Figure 2 e.g. with all of the points projecting towards the chain case as at 18b, in order possible to form a narrow trench. The opposite arrangement with the blades all as at 18a is of course possible also e.g. for forming parallel, even narrower trenches.

Other variations are possible within the scope of the appended claims.

It is naturally possible to arrange each hub with different numbers of blades. For example, instead of three blades on each side the rotor could have two blades on each side. Forthis purpose the additional bore holes 40 are provided on the same radius as the bores for bolts 30. It will be seen that these are on a diameter which is at right angles to the diameter containing the bolts 30 for the uppermost and lowermost of the blades in Figure 1. Obviously one diametrical pair of blades would normally be positioned on one side of the blade and the other diametrical pair on the other side of the plate 15.

In the preferred case using two rotor units each of six-bladed construction for operating on the subsoil, it is preferred to have a rotor diameter of 61 to 76cm which will give a working depth of 30 to 36 cm. The operating parameters are best viewed in Figure 3 in which h = Ridge Height R = Rotor Radius BL = Bite Length D = Rotor Depth M = Blade Mounting Angle I = Impact Angle It can be seen from Figure 3 that the bite length will in general be much less than the depth of the work, which is in general, up to 20cm with two shanks or 18cm with three shanks per rotor circumference at a forward speed of 4 km per hour.

Also the ridge height h is reduced to a minimum. The reversible points give the same cutting action as a pick tine, i.e. their cutting resistance is small com pared with the conventional L-shaped blade. The blades derive great rigidity and strength from the interlocking and abutment of the adjacent shanks on the hub. With a relatively narrow chain case there is sufficient proximity of each rotor to enable the inner blades to disrupt the soil beneath the chain case by tensile failure rather than by direct shear. In general the rotor operates by tensile failure of the sub-soil due to the optimal spacing and easy penetration of the blades. This results in lower pulveration of the sub-soil and a lower power requirement. There is less blade wear and therefore longer life.The chisel points are in general self sharpening and the device is simple to manufacture and especially to maintain.

In Figure 3 the blade mounting angle M and impact angle I are indicated for a straight pointed blade. The equivalent angles are indicated for the preferred rotor in Figure 1 and it will be seen that in the case of a curved point the line of entry 100 can be considered to be the chord line of the arcuate point 23. The angle of impact is subtended between the line 100 and a line 101 which defines the ground level at maximum depth. In Figure 1 this is deter mined by the edge of the hub plate 15. In the preferred case the angle I is 45" at maximum depth and it is preferably within the range 40 to 500.

The clearance angle can be defined as lying between the tangent to the line of sweep at the end of the point and the line through the point and passing through the position on the shank outer surface of maximum approach to the soil. In Figure 1 this is shown by the line 102. When forward speed is taken into account, the clearance angle will vary. In order to avoid heeling problems the soil clearance angle should always have a positive value and this is determined interalia by the blade mounting angle M, subtended between the line 102 and the radius to the end of the point.The blade mounting angle M should preferably be from 50 to 70 , and in Figure 1 it is about 60% Also shown in Figure 1 is the wedge angle W which is subtended between the lines 100 and 102.

In the embodiment of Figure 1 this is 35". Preferably is should fall within the range 25" to 500.

A further parameter of significance is the ratio of the rotor sweep diameter to the hub plate diameter, which in the embodiment of Figure 1 is 3:1. It is preferably not less than 2.5:1.

The above parameters are of importance in obtaining maximum performance. Thus important performance characteristics given by the rotor of Figure 1 can be summarised as follows.

1. Its ability to withstand use in heavy soils and to withstand shock loads produced by contact with rocks keyed into compacted soil. This is achieved in general by the mounting arrangement of the blades in accordance with the invention preferably with interlocking shanks.

2. The provision of easily replaceable wearing parts.

3. Good soil flow clearance and ability to accommodate a wide range of soil types and conditions. In general this is achieved by the distribution of the blades and the ability to use a 4 or 6 blade distribution with the same hub plate. Thus in heavy cohesive soils a rotor can be used with two blades on each side of the hub plate, together with increased rotor speed. This produces good soil flow clearance and the advantage of increased centrifugal speed to the soil aggregate. However to accommodate lighter soils in addition, the ratio of sweep diameter to hub plate diameter is of importance, since the hub plate diameter effectively determines the maximum depth. It is preferred that this ratio should be not less than 2.5:1. In the embodiment of Figure 1 it is 3:1.

4. The use of an impact angle (I) designed to create a path through the soil profile such as to produce a low ratio of upward thrust to forward thrust, high initial impact, good penetration and "suck-in" qualities. This is determined in part at least by the impact angle (I). Ideally this should be 45" to achieve the best combination of impact force, mechanical strength and durability. The blade will then pass at 90" to the radius at its lowest point. The angle of wedge (W) is also of significance as regards providing the necessary force and mechanical strength and durability.

5. A blade mounting angle (M) ensuring that the bite length is greaterthan the depth in soft soils without leading to heeling at greater depth.

Claims (16)

1. A rotorforsoil-working machines comprising at least one hub with a hub plate and a projecting boss, and a plurality of blades having shanks mounted on a face of the plate, with each shank having an edge portion tangentially abutting the boss.

2. A rotor according to claim 1 wherein an edge portion of one shank abuts an edge portion of an adjacent shank.

3. A rotor according to claim 1 wherein an edge portion of a shank on one face of the hub plate abuts a mounting element serving a blade on the opposite face.

4. A rotor according to claim 3 wherein a side edge portion of each shank abuts the hub and an end edge portion of each shank abuts a said mounting element.

5. A rotor according to claim 3 or 4 including two hubs separated by a chain case and wherein the inner blades, adjacent to the gear, have tip portions offset inwardly below the level of the gear.

6. A rotor according to claim 5 wherein the outer rotor blades have tip portions off-set outwardly generally symmetrically with the inner blades.

7. A rotor according to claim 6 wherein the digging paths of the blades are evenly distributed across the width of the furrow.

8. A rotor according to any preceding claim wherein each blade is formed with a shank and a replaceable point in the form of a pick tine.

9. A rotor according to claim 8 wherein each point is curved in the direction of rotation.

10. A rotor according to claim 8 or claim 9 wherein each bit is symmetrical about the longitudinal centre and is symmetrically mounted to the shank so that either end can be mounted for cutting.

11. A rotor according to any of claims 7 to 10 wherein there are 2 or 3 blades on each face of the hub plate.

12. A rotor according to any preceding claim wherein the ratio of the rotor sweep diameter to the hub plate diameter is not less than 2.5:1.

13. A rotor according to any preceding claim wherein the impact angle at maximum depth is from 40" two 50".

14. A rotor according to any preceding claim wherein the wedge angle is from 25 to 50".

15. A rotor according to any preceding claim wherein the blade mounting angle is from 50 -70 .

16. A rotor substantially as described herein with reference to the accompanying drawings.