TECHNICAL FIELD

THIS INVENTION relates to an apparatus for digging narrow ditches, trenches or holes in soil which can subsequently be excavated. In particular, this invention is directed to a power driven apparatus which can dig into soil containing rocks, roots and other obstructing materials.

BACKGROUND ART Known types of powered digging apparatus include rotary hoes which normally comprise a number of digging elements coupled to a motor. The rotating hoe is movable across ground by wheels which are either driven or are free wheeling. Rotary hoes are suitable only for "clean" soils by which is meant soils which are relatively free from rocks and roots. Known rotary hoes are particularly hazardous when used in soils contaminated with roots, as the rotary hoes can lurch forward if a digging element engages a root. Furthermore, known rotary hoes are not designed for digging narrow trenches. A second type of known powered digging apparatus known under the trade name "ditch-witch" comprises a chain excavating assembly which is usually mounted to the back of a tractor. The assembly comprises a rigid arm around which a ^• chain rotates and the chain is provided with a number of digging buckets which usually have a sharpened leading edge. Again, this apparatus is unsuitable for use in soils heavily infested with roots as the digging buckets are not suited to

dig through roots. The arm is biased and when an obstruction is encountered the arm simply rides over the obstruction. The obstruction must then be removed manually.

DISCLOSURE OF THE INVENTION The present invention has been devised with the general object of at least partially overcoming the above disadvantages of the prior art.

In one form the invention resides in an earthworking apparatus comprising:- an elongate support means; at least two rotatable, spaced-apart digging members mounted at one end of said support means; drive attachment means adjacent the other end of said elongate support means for engaging a drive to rotate said digging members; a ground engageable post member pivotally connected to the elongate support means whereby said support means can be pivoted about its connection to the post member to move the digging members between a ground engaging position and an elevated position.

The digging members preferably define spaced parallel cutting planes. The outermost cutting planes define the width of the narrowest trench that can be dug using the apparatus. The support means and post member are preferably so dimensioned and constructed that they lie between imaginary planes co-planar with the outermost cutting planes so that during an earthworking operation the digging members

provide clearance for the support means and the post member.

The elongate support means can be of any convenient size and length to support the digging members. For example, the elongate support means can be in the form of one or more plate members or a tubular section member, which can be perforated if desired to reduce its overall weight.

The elongate support means is provided with means to support for rotation the plurality of digging members at said one end. For example, the digging members can be mounted on a common shaft journalled in a bearing at said one end of the support member. Preferably, the shaft extends from each side of the elongate support means and a respective digging member is removably mounted on each end of the shaft.

The shaft is preferably protected from damage by a cover secured to the support means and extending partway between the cutting members. The cover is preferably rigid of uniform transverse cross-section. Advantageously, the cover is arcuate in transverse cross-section and evenly spaced from the shaft. In this embodiment, the cover can serve a dual function, its secondary function being to provide a ground engaging stop between the cutting members to limit the cutting members depth of travel. With this arrangement, a trench of uniform depth can be achieved.

The digging members are preferably digging wheels each having a hub portion, the hub portion having a bore for receiving a respective end of the shaft, and a plurality of digging elements thereon. The digging elements can be

integral with the digging wheels, or separate elements fixed to the peripheral edge or faces of the wheels by welding, soldering or by screw threads or other types of mountings, to allow replacement of worn or damaged digging elements. The digging elements are preferably in the form of raised metal lugs which are of a generally tapered cone configuration. Alternatively, the digging elements can be in the form of tungsten carbide teeth, sharpened steel teeth, hardened headless bolts or hardened steel rods. The size and number of the digging elements are selected to suit the hardness of the ground to be worked and the power output of the drive means.

The drive attachment means can be of any desired form depending on the nature of the drive. In the preferred embodiment, a chain saw motor is employed and the drive attachment means comprises nuts, bolts, and spacers which rigidly secure the chain saw motor adjacent the end of the support means.

The drive can be of a variety of types depending on the power required, e.g. an internal combustion engine such as a lawn mower engine or a chain saw engine, an electric motor or the power take off of a tractor. Alternatively, the drive means can be an air motor or hydraulic engine. Preferably however, the drive means comprises a chain saw engine, and the support means is connected to the chain saw housing (the chain saw blade removed beforehand) .

Where a chain saw engine is employed it is preferable

that the chain saw engine be equipped with anti-vibration handles and that the chain saw motor be mounted to the elongate support means via a drive attachment means which comprises a vibration damping mounting such as a rubber engine mounting. Advantageously, bracket and clamp means are employed which are rigidly secured to the elongate support means and are coupled to the anti-vibration handles. In this embodiment, vibration along the elongate support means between the motor and the digging members is reduced in order to prevent resonance effects which may cause fractures or cracks in the support means to occur over a long period of use.

Power can be transmitted from the drive means to the digging members through any suitable type of transmission such as a drive shaft, compressed air tubing, endless belts or chains, toothed belts, and the like. Where the support means is hollow such as a hollow box section at least part of the transmission is conveniently located inside the support means. In a preferred embodiment, the transmission means comprises at least one endless drive belt driven by the chain saw drive pulley.

The transmission means can be provided with a clutch means or an overload cut out means. However, if a chain saw drive is used, the chain saw engine is usually provided with such means.

The post member can be provided with a series of spaced slots which engage with a pivot pin on the support means to

allow quick and simple adjustment of the height of the support means relative to the post member. The support means may also be provided with a plurality of locations at which the post member can be pivotally coupled to it, allowing adjustment of the centre of gravity of the apparatus to suit the operator and the operating conditions. The post member is preferably located on the engine side of the centre of gravity of the apparatus to minimise the tendency of the digging members to kick up during use. The height and size of the post member can be varied to suit the size and weight of the support means. The post member can be provided with a ground engaging plate, spike or wheel depending on the required manoeuvrability. It is preferable that the ground engaging plate be located in use at a position which provides balanced operation of the earthworking apparatus. Advantageously, the ground engaging plate or spike is mounted so that it can be moved transversely and in this regard, it is preferable that the post member include a transversely extending portion from which an extension member downwardly depends between the transversely extending portion and the ground engaging plate, spike. In this' way, the extension portion can be moved and secured at transversely spaced locations in order to balance the earthworking apparatus. The apparatus can be tilted about its connection to the post member to move the digging wheels between a ground engaging position and an elevated position. The post member

serves to support the weight of the support means, digging members and the drive while still rendering a high degree of manoevrability due to the pivot connection between the post member and the support means. As a consequence of the clearance afforded to the elongate support means and post member by the digging members, the post member can be located in a partially completed trench and an operator can complete the trench to the desired depth using the apparatus with a high degree of stability and safety. A guard or screen is preferably provided adjacent the digging members to protect an operator against any debris thrown out by the digging members. The guard or screen is typically in the form of a flexible cowling. Advantageously, the guard or screen is equipped with foldable arms which can be used to increase the width of the flexible portion of the cowling for different applications.

It is preferable that the flexible cowling be mounted rearwardly of the cutting members and that a digging wheel cover be employed above the digging wheels in order to deflect any additional material being thrown by the digging wheels. This is particularly pertinent where soil and debris has accumulated beneath the cowling and the accumulated debris can engage with the cutting wheels and be thrown upwardly toward the operator. Advantageously, the digging wheel cover is of rigid construction and includes a plate with opposed downwardly extending flanges, the flanges being located just outside the outermost cutting plane defined by

the digging members.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by reference to the following description of a preferred embodiment thereof in which:-

Figure 1 is a perspective view of the earthworking apparatus of the preferred embodiment of the invention;

Figure 2 is a top view of the attachment of the drive means to the elongate support means; Figure 3 is an end view of the digging members of the embodiment; and

Figure 4 is a perspective view of an alternative digging member having removable digging elements.

The illustrated embodiment is designed for digging narrow trenches in rocky and/or root containing ground, and comprises an elongate support means 10, a drive attachment means 11, for in this case a detachable chain saw motor and accompanying housing 36 (shown in phantom), a pair of digging members 12 and a post member 13 pivotally connected to the support means 10. The drive attachment means 11 (as seen in

Figure 2) comprises spaced holes 37 in support means 10 through which bolts 38 and spacers 39 enable the chain saw motor and housing 36 to be mounted in operative position on the support means 10. The mounting can be rigid but in the illustrated embodiment, rubber mountings 40 are employed to damp motor vibration being transferred to the support means

10. In order to stabilise the motor, a bracket 41 including

clamps 42 and 43 is employed. The chain saw motor is of the type employing anti-vibration handles 44 and 45 so while the bracket 41 is rigidly fixed to the support means 10 at 46, the "three point" connection afforded by attachment 11 and claims 42 and 43 tends to stabilise the apparatus while reducing vibration between the motor and the support means 10. The bracket portion 47 extends beneath the motor 36.

The digging members 12 are mounted on opposed ends of a shaft 15 journalled in bearings 14 located at the bottom end of the elongate support means 10, which is of box section construction. A nut 17 is threaded onto each end of shaft 15 to secure the respective digging member 12 against a collar 16 on the shaft.

Each digging member 12 is in the form of a wheel and having a hub portion 18 and rim portion 19. Apertures 20 can be provided in the wheel to reduce its weight. A plurality of digging elements 21 are spaced around the rim portion 19 of the wheel. These digging elements, which are integral with the rim portion, have a substantially conical configuration and are formed from hardened material.

The other (upper) end of the elongate support means is provided with a first and second spaced parallel plate members 22, 23 fastened to opposite sides of the box section support means. A pulley 27 is mounted on shaft 26 journalled in bearings 24, 25 mounted on plate members 22, 23. The pulley 27 is driven from the chain saw drive pulley 35 by drive belt

28. (It may be necessary to provide a suitable pulley on the power output shaft of the chain saw) . The diameter of pulley 27 is about twice that of the chain saw drive pulley.

A second pulley 29 is provided on shaft 26 between the first and second bearing assemblies as shown, and is connected by a drive belt 30 extending through the box section to a pulley 30 (not shown) which is mounted on shaft 15 between the digging wheels 12. In this manner, the wheels 12 are driven by the chain saw engine. Additional idler pulleys (not shown) may be provided within the support means to maintain belt tension. Preferably, two intermediate idler pulleys are positioned to bias the drive belt inwardly to form an intermediate narrowing of the drive belt. The drive belt is preferably of the reinforced rubber type although toothed belts and drive chains can alternatively be used. If drive chains are used, the abovementioned pulleys can be substituted by toothed sprockets.

Referring specifically to Figure 3, the apparatus is provided with a removable cover 16A of part circular cross- section in order to protect the bearings 14 and shaft 15 against damage. As can be seen, the cover is also effective as a stop limiting the depth of travel of the wheels 12. The cover is curved in transverse cross-section.

A guard or screen 31 is attached to the elongate support member behind the digging members 12 and protects the operator against stones and roots thrown out by the digging members. The guard is typically in the form of a flexible

cowling to provide maximum protection and also to enable the cowling to pass into a partially dug trench. Where wider trenches are being dug, the flexible cowling can be broadened by moving foldable arms 48 from the retracted position (as shown in Figure 3) to a partially extended position (as shown in Figure 1). An optional digging member cover 49 (shown in phantom) can be employed.

The post member 13 which is pivotally connected to the elongate support means at a position between the chain saw engine and the digging members. If a guard 31 is fitted, the pivot means is preferably provided behind the guard. The post member can be provided with a series of spaced apertures 32 for receiving a pivot pin which is held in a bearing assembly 33 provided on the lower face of the support member. The use of a bearing assembly 33 provides a smooth pivotal coupling between the apparatus and post member 13.

The post member is provided with a ground engaging foot 36 and can additionally contain a ground engaging spike (not shown) on the base of the foot to firmly secure the post into the ground. In the illustrated embodiment, the foot position can be adjusted to optimise balance of the apparatus.

Referring ¹ to Figure 4, there is illustrated an alternative cutting member 12 having a hub 18, a rim 19 and cutting element 21 (only some of which are shown) . The cutting elements a simple threaded rods which are each secured in place using two bolts 21A and 21B. The outer bolts 21A are partially housed in respective hexagonal

recesses 21C in the rim 19. Tool openings 20 enable spanner access to bolts 21B thereby facilitating replacement of any damaged cutting elements.

In use, the box section support member is pivotally attached to post member 13 and the chain saw motor is started to rotate digging members 12. The operator then tilts the apparatus about the post connection by using hand grips provided on the chain saw housing so that the digging members engage the ground. After a section of trench is dug to the limited depth allowed by cover 16A. The section of trench is excavated and the process is repeated until the desired depth is achieved. By virtue of cover 16A providing a depth limit the capacity of the apparatus is not usually exceeded while digging and a consequence there is minimal wear and tear and less chance of overloading the motor. The apparatus enables the digging of narrow trenches typically 12 inches in width and is thus especially useful for digging trenches for the laying of conduits such as water pipes or electric cables.

Further variation can be achieved by adjusting the height of attachment of the support means to the post member.

The digging members can also be manoeuvred in a sideways motion by turning the support means around post member 13 thereby enabling wider trenches to be dug and the walls of trenches to be shaped. The apparatus is also useful for digging holes into earth banks and the like. This is achieved by pivoting the support means to a substantially horizontal position and

positioning the digging members against the vertical wall of the earth bank. The post member can be levered forward to provide a forward motion to the apparatus.

Whilst the above has been given by way of illustrative example of the present invention, many variations and modifications may be made thereto by persons skilled in the art without departing from the broad ambit and scope of the invention as defined in the appended claims.