GB2092104A - Mechanical digger - Google Patents

Abstract

A small, light-weight mechanical digger comprises an I-shaped chassis (1, 2, 3), wheels (4) carried by the rear transverse chassis member (3), forwardly and downwardly inclined laterally adjustable feet (9) carried by the front transverse chassis member (2), a jib (11) mounted at the front of the chassis for rotation about a vertical slew axis (A-A) under the action of a fluid cylinder connected between an arm (12) and a point (13) fixed relative to the chassis, and a power unit (5), operator's seat and control means (6) mounted on the chassis. As shown the jib (11) has a bucket arm (14) pivoted about a horizontal axis C by a cylinder (not shown) and carrying a bucket (15). The jib (11) is of obtuse-angled V form and is pivoted to luff about horizontal axis B by a cylinder (not shown). The weight of an operator seated astride the power unit (5) acts as the main counterweight of the machine. The digger may be shifted backwards or forwards by bringing the bucket (15) into engagement with the ground so as to lift the feet 9 off the ground and then using the controls to drive the main body of the machine forwards or backwards. The wheels (4) may be replaced by wheels which may be locked against rotation and which have radial projections. <IMAGE>

Description

SPECIFICATION Mechanical diggers This invention is concerned with mechanical diggers, and in particular with a digging machine of compact and very efficient design.

Powered mechanical diggers currently available on the market are of very considerable size and are driven by relatively high power motors. If access to a digging site is restricted it is often very difficult, if not impossible, to manoeuvre the machine into a digging position. Another disadvantage of the known diggers arising due to their size and high power engines is their cost.

The present invention aims to provide a mechanical digger which is inexpensive, efficient, and compact so that it can be driven into locations which cannot be reached by the known diggers.

According to the invention there is provided a mechanical digger comprising a chassis, ground wheels mounted on oposite sides of the chassis adjacent the rear end thereof, ground engaging feet mounted on opposite sides of the chassis adjacent the front end thereof, a jib structure attached by journal means to the chassis at the front end thereof for rotation of the jib structure about a substantially vertical slew axis relative to the chassis, a digging implement carried by the jib structure, a fluid cylinder coupled between the journal means and a point fixed with respect to the chassis and positioned rearwardly of said slew axis, said cylinder being actuable to rotate the jib structure about said slew axis, power means mounted on the chassis for supplying pressurised fluid to the cylinder, and control means mounted on the chassis for controlling the supply of fluid from the power means to the cylinder.

A full understanding of the invention will be had from the following detailed description which is given with reference to the accompanying schematic drawings, in which: Figure 1 shows a machine embodying the invention in side view; Figure 2 is a plan view of the machine; and Figure 3 is a side view illustrating a modification to the machine.

The mechanical digger illustrated in the drawings has a chassis of I-shaped configuration including a longitudinal member 1 and front and rear transverse members 2, 3, all the chassis members being of box-beam form. Rotatably mounted at the opposite ends of the rear transverse member.3 are a pair of ground wheels 4. An engine 5 together with an operator's seat and controls 6 are also carried by the chassis towards the rear.

At each end of the forward transverse chassis member 2 is connected a support device consisting of a beam 7 which telescopes into the member 3, a downwardly and forwardly inclined leg 8 fixed to the beam outer end, and a ground engaging foot in the form of a metal plate 9. The support devices are adjustable laterally of the chassis and can even be removed if desired when driving the machine between digging operations.

A jib support member 10 is articulated to the front end of the chassis for pivotal movement about a vertical axis A-A. The member }0 has a pair of spaced side plates between which the lower end of a V-shaped jib 11 is received and pivoted for movement about a horizontal axis B-B. Fixed to one of the side plates of member 10 is a rearwardly inclined arm 12, and a double acting hydraulic ram is connected between the free end of the arm 12 and a point 1 3 fixed with respect to the chassis, e.g. on the base of the control structure 6 or a bracket fixed to the chassis member 1. This ram, for convenience called the slew cylinder, can be actuated to rotate the member 10 hence the jib 11 about the axis A-A.

A bucket arm 14 having a digging bucket or scoop 1 5 attached to one end is pivoted intermediate its ends to the upper end of the jib 1 , for rotation relative thereto about a horizontal axis C-C parallel to axis B-B. An hydraulic ram, the bucket cylinder (not shown), is connected between the free end of the bucket arm 14 and an anchorage point 1 6 provided by a pair of plates 1 7 fixed to the opposite sides of the jib 11 adjacent the angle or bent in the jib.A further hydraulic ram, the jib cylinder (not shown), is connected between a second anchorage point 1 8 provided by plates 1 7 and an anchorage point 1 9 on the jib support member 10. As will be easily understood by those readers skilled in the art, the bucket cylinder controls rotation of arm 1 4 about axis C-C and the jib cylinder controls rotation of the jib about axis B-B, whereby the two cylinders may be operated in co-ordinated manner in order to cause a digging action or motion of the bucket 1 5, as indicated by the curved bucket trajectory lines shown in Figure 1.The slew cylinder is actuable to move the bucket to either side of the trench being dug for emptying the bucket, the permitted angle of rotation about axis A-A being for example about 60 to each side of the centre position.

From the foregoing description it will be appreciated that the digger of the invention is of very simple construction and may be very compact, for example the length of the chassis between the axis A-A and the rear wheel axis may be only 36 inches (91 cms) and the jib height only 33 inches (84 cms). As the power unit of the digger is required to drive only the three hydraulic rams, i.e. the bucket, jib and slew cylinders, an engine of lower power, such as 2-3 horse power, it all that is needed. In this connection it is worth noting that the engine and controls remain stationary and do not slew with the jib, which assists in minimising the power requirement.The simplicity of the design, small dimensions and low power engine combine to make the machine comparatively inexpensive to manufacture, yet in spite of these characteristic features it has been found that when digging a trench 1 ft. (30 cms) wide the machine of the invention is just as efficient as other larger and more powerful machines in present use.

The machine can also be of light weight, which in combination with the small size makes it very easy to manoeuvre into position, thereby enabling the machine to be moved into locations which are inaccessible to larger conventional diggers. In use the major counterweight to stop the machine tipping about the front feet 9 under the weight of the bucket is provided by the weight of the operator himself who sits on the machine, e.g.

astride a casing or body enclosing the power unit 5, so that this centre of gravity is situated generally over or near the wheel axle. Taking advantage of the body weight in this way not only helps to minimise the machine weight, but also allows the length of the chassis to be relatively short.

It is possible to shift the digger backwards or forwards, e.g. as the digging of a trench progresses, by bringing the bucket 1 5 into engagement with the ground to lift the feet 9 off the ground and then operating the controls to drive the main body of the digger backwards or forwards relative to the bucket which rests firmly on the ground.

In Figure3 there is illustrated a modification to the digger, the parts of the digger not shown being as described above in relation to Figures 1 and 2.

In place of the conventional wheels 4 the machine is equipped with wheels 20 having radial projections 21 on their periphery. The projections preferably take the form of lugs or blades uniformly spaced apart around the wheel and inclined forwardly to the wheel radius at the point of contact with the ground. A device is also provided to lock the wheels 20 securely against rotation. As shown this device comprises a bolt 22 which is spring loaded to engage in any one of a series of holes provided around the wheel, it being possible to withdraw the bolt and fix it in the retracted position when the wheels are to be unlocked for rotation. Other forms of locking device are of course possible.

The wheel lugs 21 are adapted to penetrate into the ground, and when the wheels are locked against rotation they provide a strong resistance against the digger being moved by the reaction forces exerted on the bucket during digging operations.

Other modifications are possible without departing from the invention and will occur to skilled readers.

In the lower part of Figure 2 there is illustrated an alternative method of attachment for the front feet to the chassis. In this case the upper end of the leg 8' carrying the foot 9' is provided with a plate 7' which is pivoted to the chassis member 2 by a fixed pin 7a and is locked in the adjusted position by a removable pin 7b. The pin 7b can be passed through selected holes in the plate 7' to adjust the lateral position of the foot plate 9'.

Claims (14)

1. A mechanical digger comprising a chassis, ground wheels mounted on opposite sides of the chassis adjacent the rear end thereof, ground engaging feet mounted on opposite sides of the chassis adjacent the front end thereof, a jib structure attached by journal means to the chassis at the front end thereof for rotation of the jib structure about a substantially vertical slew axis relative to the chassis, a working implement carried by the jib structure, a fluid cylinder coupled between the journal means and a point fixed with respect to the chassis and positioned rearwardly of said slew axis, said cylinder being actuable to rotate the jib structure about said slew axis, power means mounted on the chassis for supplying pressurised fluid to the cylinder, and control means mounted on the chassis for controlling the supply of fluid from the power means to the cylinder.

2. A digger according to claim 1, wherein the cylinder is coupled to an arm extending laterally from the journal means and is operable to turn the jib structure through an angle of about 600 to either side of the longitudinal axis of the digger.

3. A digger according to claim 1 or 2, wherein the cylinder extends generally longitudinally of the digger.

4. A digger according to claim 1, 2 or 3, wherein the length of the chassis between the slew axis and the wheel axis is of the order of 36 inches (91 cms).

5. A digger according to any preceding claim, wherein the chassis is I-shape in configuration with a longitudinal member and front and rear transverse members.

6. A digger according to claim 5, wherein the rear transverse member supports the ground wheels.

7. A digger according to claim 5 or 6, wherein the front transverse member supports the ground engaging feet.

8. A digger according to claim 7, wherein the feet comprise members carried at the lower ends of respective legs which are inclined downwardly and forwardly with respect to the chassis member.

9. A digger according to any one of the preceding claims, wherein the ground engaging feet are adjustable in position laterally of the chassis.

10. A digger according to any one of the preceding claims, wherein the jib structure comprises a V-shaped jib including a obtuse angle between the two limbs thereof, one end of the jib being pivoted to the journal means for movement about a first substantially horizontal axis, an arm carrying the working implement being pivoted to the other end of the jib for movement about a second substantially horizontal axis, and respectively fluid cylinders coupled to the jib and arm to control the rotation thereof about said first and second axes, said cylinders being connected to the power means via the control means.

11. A digger according to any one of thepreceding claims, wherein the control means inciudes manual controls so arranged that the body weight of a correctly positioned operator is located substantially rearwardly of the slew axis and acts as a major part of the counterweight to prevent the digger tipping about the ground engaging feet under the weight of the working implement.

12. A digger according to any one of the preceding claims, wherein the wheels have peripheral projections arranged to penetrate the ground, and releasable means are provided to fix the wheels against rotation.

13. A digger according to claim 12, wherein the projections comprise lugs spaced apart around each wheel.

14. A digger according to claim 13, wherein the lugs are inclined downwardly and forwardly from the roots to the tips thereof at the position where the wheel contacts the ground.

1 5. A mechanical digger substantially as herein described with reference to the accompanying drawings.