GB2031843A - Face loading shovel excavator - Google Patents

Abstract

The invention relates to a face loading shovel excavator in which the shovel bucket (5) is pivotted at the forward end of a bucket arm (4) which is pivotted to the forward end of a boom (3) pivotally connected at its other end to the excavator vehicle (1,2). The functions of moving the boom (3), arm (4) and bucket (5) are performed hydraulically by a hoist ram (7), a crowd ram (9) and a bucket ram (10). To enable the bucket to be moved in a substantially straight-line horizontal path by actuation of the crowd ram (9) alone, the hoist ram (7) for the boom is pivotally connected to one lever arm (D-F) of a bell-crank lever (6) which is pivotted on the boom (3) and of which the other lever arm (E-F) is pivotally connected to one end of a rigid link (8) of which the other end is pivotted (I) to the bucket arm (4). <IMAGE>

Description

SPECIFICATION Face loading shovel excavator The invention relates to a face loading shovel excavator. In such excavators, a bucket for digging out soil is supported at one end of a bucket arm which, in turn, is supported from a boom connected to the excavator vehicle so that the bucket can be pushed out horizontally forwardly by hydraulic rams acting on the boom and the bucket arm to dig out soil.

It has hitherto been customary to pivotally connect the bucket arm to the forward end of the boom, and to support the bucket at the forward end of the arm for pivotal movement. The inner end of the boom is pivotally connected to a part of the excavator vehicle, which may conveniently be of the endless track type, and which is rotatable about a vertical axis. The functions of moving the boom, arm and bucket are controlled by three hydraulic rams or pairs of rams, which conventionally have had to be operated at the same time to control the horizontal path and inclination of the bucket as it is pushed forwards. Thus conventional excavators not only require that their operators be highly skilled in the operation of their excavators but also capable of sustaining a heavy work load.

Naturally, designers have attempted to reduce the number of function controls. In one such excavator, as described in U.S. Patent 3,927,781, the horizontal movement of the bucket is achieved by a single control function by incorporating an additional levelling hydraulic ram connected in a hydraulic system with the hoist ram, which controls the movement of the boom, to cause the boom to lower as the bucket ram is moved forwards by the crowd ram and to rise as the arm moves back. Therefore the bucket height is held constant as the arm is moved forward or backward. A mechanical parallelogram type link system formed by the bucket arm and bucket ram with four pivot points and a wrist linkage is so constructed as to maintain the bucket at a preset angle which remains substantially constant regardless of arm movement.

Again, U.S. Patent No. 3,792,786 describes an excavator in which the bucket is carried from a parallelogram system (which includes the arm) from the end of the boom, the hoist ram being connected to the boom through a hinge on the arm which is set in such a manner that, due to automatic coordination between the positions of the arm and the boom, the bucket lip is constantly at the level of the excavator supporting surface during operation of the ram which moves the arm. The angle of the bucket is controlled by a bucket ram during forward rectilinear motion of the bucket. Thus two function controls have to be simultaneously operated to maintain a preset angle of the bucket during arm movement.

The present invention has for an object to provide a face loading shovel excavator having a simple and improved mechanical linkage which permits nearperfect horizontal translational movement of the bucket by the operation of only one of the three primary function controls, which provides extra power assistance to the crowding operation as the shovel fills with soil, and which does not require any additional hydraulic ram for achieving the result. The invention also enables, if desired, the known arrangement for maintaining a preset angle of the bucket, regardless of bucket arm movement, to be embodied in the excavator.

The invention consists in a face loading shovel excavator comprising an excavator vehicle, a boom pivotally connected to said vehicle and angularly adjustable with respect thereto by a hoist ram extending between the vehicle and the boom, a bucket arm pivotally connected to the forward end of the boom and angularly adjustable with respect thereto by a crowd ram extending between the boom and the bucket arm, and a shovel bucket pivotally connected to the forward end of the bucket arm for pivotal movement of a bucket ram, characterised in that the hoist ram is pivotally connected to one lever arm of a bell-crank lever which is pivotted on the boom and of which the other lever arm is pivotally connected to one end of a rigid link of which the other end is pivotted to the bucket arm, movement of the bucket arm by the crowd ram causing the link to pivot the bell-crank on the boom and thereby, without actuating the hoist ram, change the angular position of the boom during bucket arm movement so that the pivotal connection of the shovel bucket to the bucket arm moves in a substantially horizontal path.

By appropriate dimensioning and location of the parts, the action of the bell-crank lever as it is turned, with the hoist ram locked, by the movement of the arm by the crowd ram, will cause the boom to rise or fall to keep the bucket movement substantially horizontal. Preferably the arrangement is such that said one lever arm of the bell-crank lever is moved, during bucket arm movement by the crowd ram, to both sides of a dead-centre position in which the axis to which it is pivotally connected, and that in said dead-centre position the bucket arm is substantially vertical. The boom will then rise as the bucket arm moves from its inward position to its vertical position, whereafter the boom will be lowered, to maintain the substantially level movement of the bucket through its full range of displacement.

The rigid link between the bell-crank lever and the bucket arm is under tension while the mechanism is being moved by the crowd ram to said dead-centre position, and thereafter is under compression, the potential energy of the lowering boom then being used to augment the tooth force of the shovel, giving extra power assistance as the shovel fills and reducing the work required from the crowd ram.

In order that the invention may be more clearly understood, reference will now be made to the accompanying-drawings, in which Figure 1 is a schematic view of an excavator according to one embodiment of the invention with the bucket in its inward position, Figure 2 is a similar view showing the mechanism in the dead-centre position with the arm vertical, and Figure 3 is a similar view with the bucket in its forward position.

Referring to the drawings, the excavator comprises a crawler vehicle 1 on which is mounted a turret 2 rotatable on the vehicle through 360 about the vertical axis X-X by a power drive. Pivotted to the turret at point C is a boom 3 at the forward end of which a bucket arm 4 is pivotted at H. At the lower or forward end of the arm 4 a bucket or shovel 5 is pivotted at M.

A bell-crank lever 6 is pivotted at F on the boom 2.

In the embodiment shown, this lever 6 is in the form of a triangular plate and comprises two further pivots D and E, the two lever arms of the bell-crank lever being defined by the link portions of the plate 6 between the pivots D-F and E-F respectively.

A hoist ram 7 is pivotted at one of its ends to the turret at A, its piston rod being connected to the pivot Don the plate 6. A rigid link 8 connects the pivot E on the plate 6 to a pivot I on the arm 4.

Movement of the arm 4 is effected by a crowd ram 9 pivotted at one end to the pivot B on the boom 3 and having its piston rod connected at pivot J to the arm 4.

The bucket 5 is actuated by a bucket ram 10, one end of which is pivotted at G to the boom 3, its piston rod being pivotted at Lto a wrist linkage comprising two links 11, 12 both connected at one end to the pivot Land having their other ends connected to a pivot K on the arm 4 and to a pivot N on the bucket 5 respectively. The position of the pivot G is selected such that a quadrilateral is formed by the pivots G, H, K, L so that the tooth portion 5a of the bucket 5 can be maintained at a predetermined angle with respect to the horizontal when the arm 4 is moved and the boom 3 is moved between its raised and lowered positions.

The rams 7,9 and 10 are independently operable by control devices provided in the operator's cab and are capable of controlled infinite variations of length between fixed maxima and minima.

The mechanism thus comprises a collection of mechanical linkages and its mode of operation will now be described. In the position of the mechanism shown in Figure 1, the crowd ram (link B-J) is at its minimum length. For the pivot M to move horizontally by extension of the crowd ram, pivot H must rise in an arc about pivot C until the position shown in Figure 2 is reached and the arm 4 is vertical. If the pivot M continues its horizontal path to the position shown in Figure 3, it will be necessary for pivot H to fall in an arc about pivot C.

The increase and decrease in the distance between pivots A-F as the pivot H rises or falls is controlled, in accordance with the invention, by the bell-crank lever 6 and the link 8. In the position shown in Figure 1, the lever arm D-F and the hoist ram A-D constitute two articulated links such that the sum of the lengths D-F and D-A will equal the length A-F when the links A-D, D-F are aligned in the dead-centre position illustrated in Figure 2. Thus, as the arm 4 is moved forward by the crowd ram, the link 8 causes the bell-crank lever to turn relative to the boom 3, firstly to cause the pivot H to rise until the angle A-D-F reaches 180 , i.e. the dead-centre position shown in Figure 2. Thereafter, further turning of the bell-crank lever 6 decreases the length A-F and the pivot H is lowered as shown in Figure 3.

Suitable proportions for the bell-crank lever 6 and the rigid link 8, and the position of the pivots I, must be selected so that the length of the link A-D need not be altered (i.e. the hoist ram can be locked) while pivot M is moved horizontally from the position shown in Figure 1, through the position of Figure 2, to the position shown in Figure 3 by the crowd ram 9 alone.

Since, as mentioned above, the linkages provided by the bucket ram 10 (G-L), by the links 11 (L-K) and 12 (L-N), and by the bucket 5 (M-N) make it possible in known manner to maintain the bucket at a preset angle, the embodiment described with reference to the drawings not only enables the bucket to move forwards along a substantially horizontal path by the operation of the crowd ram 9 alone, but also maintains the preset angle during the arm movement.

During the first part of the movement of the arm from the position shown in Figure 1 to that shown in Figure 2, the rigid link 8 will be under tension as it moves the bell-crank lever 6 to raise the boom 3.

After the dead-centre position 4the potential energy of the boom places the rigid link 8 under compression thereby reducing the work load on the crowd ram and augmenting the tooth force, which is of particular advantage during the latter part of the movement of the bucket when the bucket is becoming filled with soil.

Claims (3)

1. Aface loading shovel excavator comprising an excavator vehicle, a boom pivotaHy connected to said vehicle and angularly adjustable with respect thereto by a hoist ram extending between the vehicle and the boom, a bucket arm pivotally connected to the forward end of the boom and angularly adjustable with respect thereto by a crowd ram extending between the boom and the bucket arm, and a shovel bucket pivotally connected to the forward end of the bucket arm for pivotal movement by a bucket ram, characterised in that the hoist ram is pivotally connected to one lever arm of a bellcrank lever which is pivotted on the boom and of which the other lever arm is pivotally conncted to one end of a rigid link of which the other end is pivotted to the bucket arm, movement of the bucket arm by the crowd ram causing the link to pivot the- bell-crank on the boom and thereby, without actuating the hoist ram, changing the angular position of the boom during bucket arm movement so that the pivotal connection of the shovel bucket to the bucket arm moves in a substantially horizontal path.

2. An excavator according to claim 1, characterised in that said one lever arm is moved, during bucket arm movement by the crowd ram, to both sides of a dead-centre position in which the axis of the hoist ram is aligned with said one lever arm to which it is pivotally connected, and that in said dead-centre position the bucket arm is substantially vertical.

3. A face loading shovel excavator constructed substantially as hereinbefore described with reference to the accompanying drawings.