Earth moving equipment

A cutting tool for an excavating machine is described which comprises a support arm having an inner end adapted to be movably mounted on the machine and an outer end, a shovel member having a substantially flat working face and carried by the support arm at its outer end, and a plurality of cutting teeth arranged to contact the material to be excavated in advance of the said shovel member and fixed rigidly thereto, the arrangement being such that the said working face is substantially perpendicular to its direction of motion as it contacts the material to be excavated. Assemblies of such cutting tools are also described, which are particularly smooth and efficient in operation.

This invention relates to earth moving machinery, and in particular to 
cutting tools and assemblies of cutting tools for earth moving machinery. 
In known forms of earth moving machinery, the tractive effort required is 
frequently very great, and may absorb a major part of the power output of 
the machine. Furthermore, in order to ensure that frictional forces 
developed between the machine and the ground are sufficient to transmit 
the tractive efforts required, the weight of the machine must often be 
considerably greater than would otherwise be necessary. This in turn leads 
to a requirement for still greater tractive effort. However, these 
problems may be alleviated by the employment of a cutting tool assembly 
forming a separate part of the earth moving machine, which is caused to 
move relative to the machine. This movement may be, for example, of a 
rotary or oscillatory nature. The action of such a cutting tool assembly 
is to break up the soil, so as to enable it to be more easily shovelled or 
otherwise moved. The soil may then, for example, be collected in a bucket 
arrangement attached to or associated with the cutting tool. A machine 
which employs a cutting tool of this type will require a relatively small 
tractive effort, and will therefore be capable of operation under adverse 
conditions where other machines might become ineffective. 
In order to reduce the required power output to the minimum, it is 
desirable that the cutting tool should operate with maximum efficiency. 
This is particularly so when the machine is self-propelling, as power 
absorbed by the cutting tool reduces the power available for traction. 
Desirably also, the cutting tool should operate as smoothly as possible in 
order to ensure even progression and a steady power output, so that the 
maximum instantaneous power output required of the machine may be kept as 
low as possible. 
Accordingly the present invention is directed to providing a cutting tool 
for an earth moving machine which is effective in cutting, breaking and 
excavating a wide variety of soils, minerals, and other materials under 
various environmental conditions. In further aspects, the invention seeks 
to provide an assembly of such cutting tools which is particularly smooth 
in operation. These and other aspects of the invention will be apparent 
from the following description. 
According to the present invention a cutting tool for an excavating machine 
comprises a support arm having an inner end adapted to be movably mounted 
on the machine and an outer end, a shovel member having a substantially 
flat working face carried by the support arm at its outer end, and a 
plurality of cutting teeth arranged to contact the material to be 
excavated in advance of the shovel member and fixed rigidly thereto, the 
arrangement being such that the flat face of the shovel member is 
substantially perpendicular to its direction of movement as it contacts 
the material to be excavated. 
Preferably the cutting teeth are all fixed to the substantially flat 
surface of the shovel member and extend in directions both perpendicular 
thereto and parallel thereto. 
Preferably also the cutting teeth are fixed to the shovel member in spaced 
relationship so that some of the material to be excavated may pass between 
them. 
Very conveniently the cutting teeth are welded to the shovel member. 
According to a further feature of the invention, a cutting tool assembly 
comprises a plurality of cutting tools each in accordance with the 
invention. 
Conveniently such an assembly includes an axially rotatable member to which 
the inner end of the support arms are fixed so that the support arms 
extend generally radially outwards from the rotatable member. 
The disposition of the cutting tools on the axially rotatable member is of 
particular importance to the smooth and efficient operation of the cutting 
tool assembly. 
Most advantageously, the cutting tools are staggered around the 
circumference of the rotatable member. 
Preferably the teeth of successive cutting tools around the circumference 
are offset from one another in the axial direction of the rotatable 
member, so that successive teeth cut material which has passed between 
preceding teeth. 
For optimum results, the distribution of cutting tools around the 
circumference of the rotatable member should be substantially even. 
Preferably, the cutting tools should also be staggered along the length of 
the rotatable member in the axial direction thereof. 
Advantageously smooth operation is further ensured by arranging that the 
cutting tools are disposed symmetrically about the plane passing through 
the mid-point of the axially rotatable member and perpendicular to the 
axis thereof. With such an arrangement it is found that end thrusts on the 
axially rotatable member, and turning moments in the axial plane are 
reduced to a minimum, thus enabling smoother operation and more precise 
control.

The cutting tool shown in FIG. 1 and indicated generally as 1 comprises a 
shovel plate 2 carried at the outer end of a support arm 3 in a recess 4 
thereon which is shaped to receive it. The arm 3 and the shovel plate 2 
are both made from flat plate material, and are fixed at right angles to 
each other. 
Three cutting teeth 5 are disposed along the outer end of the shovel plate 
so as to extend both forwardly (perpendicular) to the plate and outwardly 
(parallel) thereto. The dimension of the teeth perpendicular to the plane 
of the arm is kept relatively small. The teeth 5 are provided with a 
recess 6 whereby they are located against the outer end of the shovel 
plate, to which they are fixed by welding along the outer edge 7 and the 
flat working face 8 of the shovel plate 2. 
The support arm 3 is provided with a hole 9 where the design permits, 
purely for the purpose of saving weight and material. 
As shown in FIGS. 2 to 4 a cutting tool assembly for an earth moving 
machine comprises a plurality of cutting tools fixed rigidly to a central 
drum 10 rotatable about its axis. The inner end of each support arm has an 
arcuate section 11 to facilitate this fixing, and is provided with 
shoulders 12 which abut against the shoulders of adjacent arms. The 
cutting tools 1 are staggered both around the circumference of the drum 
and axially of the drum in a manner and for reasons explained hereinafter. 
The drum 10 is mounted for rotation about its longitudinal axis on an earth 
moving machine (not shown). The drum 10 may be conveniently driven by a 
remote power source through any convenient transmission system (not shown) 
comprising for example, a sprocket and chain arrangement, or a hydraulic 
motor which could most advantageously be mounted inside the drum 10. In 
any event, the remote power source is conveniently, in the case of a 
self-propelled earth moving machine, a suitable power take-off point of 
the main traction engine. 
The operation of the cutting tool assembly in use is as follows. The earth 
moving machine moves in the direction of the arrow A (FIG. 4) whilst the 
drum 10 is rotated in the direction of arrow B (FIG. 4). The cutting tool 
assembly is thus moved forward against the working face 13 of the material 
to be excavated. By virtue of the rotation of drum 10, successive cutting 
tools 1 are brought into contact with the soil. In each cutting tool 1, 
the teeth 5 first contact the soil to loosen and break it up. This results 
in a small build-up of soil which is carried forwardly and upwardly along 
the working face 13 to be lifted clear thereof by the working face 8 of 
the shovel plate 2. The speed of rotation of the assembly is such that the 
soil carried by the shovel plate 2 tends to be thrown radially outwards by 
centrifugal forces. This will be to some extent counteracted by the 
frictional forces between the soil and the shovel plate, but nevertheless, 
at some point during the revolution of the cutting tool 1 soil material 
picked up from the working face 13 will be flung off. The cutting tool 
assembly thus has a centrifugal self-cleaning action, and the need to 
provide a separate means for removing excavated material from the cutting 
tool is eliminated. This is particularly important when excavating sticky 
materials, such as wet clay. 
It is desirable in many applications that some means be provided for 
guiding the excavated material towards a particular required location. 
This may be, for example, either the ground to one side of the excavated 
area, or alternatively some suitable collection means. As shown in FIG. 4 
only, a deflector casing 14 is provided which partially surrounds the 
cutting tool assembly over its entire length. The casing extends from just 
beyond the level of the un-excavated material at the forward side of the 
cutting tool assembly, to well beyond the top centre position. The height 
of the casing above the ground on the forward side should preferably be 
adjustable so as to accommodate varying depths of cut. In some instances 
the depth of cut may be greater than the diameter of the cutting tool 
assembly, so that an overhang is formed in the material to be excavated, 
so the range of adjustment of the casing 14 should be fairly wide. The 
casing is so shaped that the gap between the tips of the teeth 5 and the 
inner surface of the casing gradually increases in the direction of 
rotation of the drum 10 in order to provide passage for increasing 
quantities of excavated material flung from the shovel plates. The exit 
angle of the casing is so chosen as to guide the excavated material in the 
desired direction, and may also be adjustable. 
Conveniently an elevator 15 may be provided to the rear of the cutting tool 
assembly, the elevator being so positioned in relation to the casing 14 
that excavated material drops onto the elevator. The elevator surface 
moves upwardly in the direction of arrow C (FIG. 4). It may then be 
arranged that the excavated material is disposed of in any desired manner. 
For example a second elevator (not shown) may be provided which carries 
the excavated material and deposits it to one side of the machine. 
Alternatively, the elevator 15 may be arranged to fill a hopper 16 which 
is periodically discharged. 
For efficient operation of the cutting tool and assembly, it is 
particularly important to ensure that there is no excessive tendency for 
any permanent accumulation of soil to take place on the cutting tool. The 
design of the assembly must therefore be such that virtually all the 
excavated material picked up by a cutting tool 1 at one pass is removed by 
the centrifugal self-cleaning action described above before a subsequent 
pass commences. Thus, the design of the cutting tools is such as to 
eliminate all unnecessary projections and obstacles around which soil 
might tend to build up. 
Thus, the shovel plates 2 have flat working faces 8, which are arranged to 
be perpendicular to their direction of movement as they engage the soil. 
In this way the tendency for excavated material to adhere permanently to 
the shovel plate is kept to a minimum consistent with the requirement that 
the material should be removed from the working face 13. 
For similar reasons, the cutting teeth 5 are kept narrow in directions 
perpendicular to their plane of motion, and are fixed to the shovel plate 
2 by welding in preference to using a bulkier fixing method such as a bolt 
which might have simplified their replacement. In practice when teeth need 
replacement owing to wear or damage, they are simply cut off and fresh 
teeth welded in their place or a replacement shovel plate and tooth 
assembly may be fitted. Long tooth life may be achieved without undue 
expense by using a high grade steel for the teeth only, and a less 
expensive grade for the shovel plates which are subject to less wear. 
The tendency for excavated material to build up on the cutting tools is 
further reduced by the employment of support arms 3 for the shovel plate 
2. This open type of construction permits excavated material to pass over 
the tops of the plates freely rather than becoming compacted towards the 
centre of the drum. 
The relative disposition of the cutting teeth on successive cutting tools, 
and the relative disposition of the cutting tools themselves is of great 
importance to the efficient and smooth operation of the cutting tool 
assembly. As best seen in FIGS. 2 and 3, the cutting tools 1 are arranged 
in twelve groups of four in each group. For convenience of description, 
the cutting tools are identified by the positions occupied on the drum 10 
by the arcuate sections 11 of their respective support arms 2, which are 
designated as shown in FIG. 3 by the references A1, A2, A3, A4 (first 
group); B1, B2, B3, B4 (second group); . . . N1, N2, N3, N4 (twelfth 
group). 
Taking the group A1, A2, A3, A4 as an example, all four cutting tools are 
identical in construction, and in particular each cutting tool is provided 
with three teeth 5 disposed in the same relative position along the 
radially outer edge of the shovel plate 2. The four cutting tools are 
disposed around the surface of the drum at 90.degree. intervals, with the 
arms extending radially outwards. Each of the four arms is staggered 
slightly in the axial direction from the other three, so that during a 
complete revolution each tooth cuts on a line which is not cut by any 
other tooth. By this method the whole of the area swept by the cutting 
tools A1, A2, A3, A4 is evenly cut by the teeth thereof during a complete 
revolution. It is found in practice that this staggering of the teeth 
provides a particularly effective cutting tool assembly, and furthermore 
that the excavated surface has a particularly smooth finish. Successive 
groups of cutting tools B1-B4, C1-C4, etc., along the length of the drum 
are similarly arranged so that the teeth in each group are similarly 
staggered, and the area swept by successive groups adjoin one another. 
Thus an even, smooth and effective cutting action is achieved across the 
entire width of the drum. As will be readily apparent a similar staggering 
of teeth might alternatively be achieved by changing the numbers and/or 
the relative positions of the teeth on successive cutting tools in each 
group, instead of staggering successive cutting tools axially within each 
group. 
In addition to the axial staggering of the cutting tools, it is also found 
beneficial to stagger the arms 3 of successive groups of cutting tools in 
the circumferential direction. Thus, whilst each group consists of four 
cutting tools disposed around the circumference at 90.degree. intervals, 
the groups themselves are displaced circumferentially with respect to 
adjacent groups. Thus, the group B1, B2, B3, B4 is displaced 
circumferentially with respect to group A1, A2, A3, A4 by 45.degree., 
group C1, C2, C3, C4 is displaced circumferentially with respect to group 
B1, B2, B3, B4 by 30.degree., etc. The circumferential staggering is so 
arranged that the cutting tools are distributed evenly around the drum at 
15.degree. intervals. For reasons explained below, the cutting tools are 
disposed symmetrically in pairs on the drum. The number of pairs of 
cutting tools engaging the soil at any instant is thus substantially 
constant, this contributes considerably to the smooth operation of the 
cutting tool assembly, the power required remaining substantially constant 
throughout the complete revolution of the drum. 
The arms are disposed symmetrically about the plane passing through the 
mid-point of the drum axis and perpendicular thereto. Thus for example, 
the position of tool M2 corresponds exactly to that of tool A2, B3 
corresponds to L3, E3 corresponds to H3, etc. It is found that this 
arrangement eliminates end thrusts and twisting moments to which the 
assembly would otherwise be subjected during use, owing to the asymmetric 
cutting action which would otherwise occur. This gives rise to a machine 
in which the loads on the bearings supporting the drum are reduced, and 
operation is both smoother and more easily controlled with accuracy. In 
the case of the two cutting tools F4, G4 their relative disposition in the 
assembly is such that they would overlap. In the case of this pair only, 
therefore, a section including one tooth is cut from the side of the 
shovel plate of cutting tool F4, so that the two shovel plates abut. They 
are then welded together along their abutting edges. Similarly the shovel 
plates of cutting tools F3 and G3 abut (without cutting) and are welded 
together. 
Whilst the material with which the cutting tool and assembly is to operate 
has been referred to in the specification variously as soil, minerals and 
other materials, it will be readily understood by those skilled in the art 
that the invention is capable of excavating a wide variety of material 
both on the earth's surface and in mining operations beneath the surface, 
and the invention should in no way be considered as limited to use with 
any particular material. It should be understood that the invention is 
also eminently suited to agricultural use for ploughing, especially deep 
ploughing. Other uses for the invention include land stabilisation, 
wherein excavated material is mixed with a binder, e.g., lime or cement, 
before being re-deposited. 
By use of a cutting tool assembly in accordance with the invention, an 
exceptionally smooth excavated surface may be obtained. The wheels or 
tracks of the excavating machine may therefore run upon the smooth 
excavated surface produced by the cutting tool assembly, thus permitting 
exceptionally precise control of the excavating operation. 
Such precise control would, for example, enable a machine incorporating 
cutting tools in accordance with the invention to be constructed, which 
would further incorporate control means programmed to cut a particular 
profile. Thus, for instance, a carriageway having a controlled gradient 
could be formed by a series of such machines passing over previously 
uneven ground. Alternatively, the machine could be arranged to control the 
height and attitude of the cutting tool assembly in response to a signal 
in the form of, for example, a laser beam, received from a remote point. 
The cutting tool is readily adapted for attachment to motivating means 
having other than purely rotary movement. A series of tools could, for 
example, be attached to a chain which could be arranged to move around 
sprockets disposed either vertically or horizontally relative to one 
another. Such a construction would be particularly suitable for cutting 
ditches and trenches.