GB2075952A - Improvements in or relating to forward acting power shovels - Google Patents

Abstract

A forward acting power shovel is provided with deflecting sheaves 24, 26 to deflect the two sections 19, 22 of the hoist rope rearwardly of the boom 3 and thus provide a resultant forward force on the boom to resist jackknifing. As shown the first hoist rope section 19 extends from hoist drum 18, passes over the sheave 24, over a sheave 20 and a sheave 21 and back to a further sheave 20. The second hoist rope section 22, which is a continuation of the first hoist rope section 19, passes from the further sheave 20 over the sheave 26 to a crowd drum 12. When the drum 18 is reeled in while the drum 12 is driven in crowd action, or idling, the second hoist rope section 22 urges the drum 12 to provide an additional crowd force or a crowd force. <IMAGE>

Description

SPECIFICATION Improvements in or relating to forward acting power shovels Conventional forward acting power shovels generally have a forwardly angled boom with the dipper handle shiftably supported by a saddle block intermediate the ends of the boom and the dipper itself located forward of the boom. There is a crowd mechanism to move the handle and dipper forwardly, a retract mechanism to move the handle and dipper rearwardly, and one or more hoist ropes that pass around the tip of the boom to the dipper to raise and lower it. The boom is footed on a frame and held in a forwardly angled position by stay ropes between the boom tip and frame. The stay ropes prevent the boom from pivoting further forwardly, but there is generally no positive stop to prevent the boom from tipping rearwardly.When a substantial crowd force is applied, there is a reaction force that tends to tip the boom rearwardly, which is called jackknifing and is highly undesirable. Heretofore, it has often been possible for jackknifing to occur at or below maximum crowd force, and it has been the responsibility of the operator to reduce the crowd force when necessary to prevent it.

This invention contemplates the provision of at least one deflecting sheave on the boom that deflects the hoist rope substantially rearwardly from its normal line, thus creating a resultant forward force on the boom that resists jackknifing, preferably even at maximum crowd force. The preferred embodiment utilizes a hoist-assist reeving comprising a first hoist rope section that passes up and around the tip of the boom to the dipper and a second section that returns overthetip of the boom to a crowd drum so that hoist pull develops a crowd force, and there are deflecting sheaves for both sections to provide cumulative resultant forces.

The invention is extremely simple and inexpensive, yet highly effective.

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Fig. 1 is a somewhat schematic side view, partially broken away, showing a forward acting power shovel incorporating a prferred embodiment of the invention, Fig. 2 is a somewhat schematic fragmentary top view, partially broken away, showing the front end of the shovel of Fig. 1, Figs. 3 and 4 are fragmentary schematic views in perspective illustrating the reeving of the shovel of Fig. 1, Fig. 3 showing only the crowd and retract ropes and Fig. 4 showing only the hoist ropes, and Fig. 5 is a schematic force diagram illustrating the effect of the deflecting sheaves.

The power shovel shown in Fig. 1 includes a frame 1 mounted on crawlers 2, a boom 3 footed on the frame at 4 and in a forwardly angled orientation (to the right as seen in Fig. 1), and a dipper means comprising a dipper handle 5 and a dipper 6. The dipper handle 5 extends through and is extensively and retractably supported by a saddle block 7 that is pivotally mounted on the boom 3 by a shipper shaft 8, the shaft 8 in the embodiment shown being approximately at the effective center of gravity of the boom 3. As seen most clearly in Fig. 2, the handle 5 extends through an opening 9 in the boom 3.

The boom 3 is freely pivotable in the plane of the paper as seen in Fig. 1. It is held from pivoting further forwardly orto the right by stay ropes 10 extending between the boom point and an A-frame 11 on the frame 1. There is no normal tendency for the boom 3 to pivot rearwardly or to the left, because its center of gravity is forward of the foot 4. Extension of the dipper handle 5 forwardly or to the right in a crowding action will, however, result in a rearward reaction force at the shipper shaft 8 which will urge the boom 3 to pivot rearwardly, and it is this jackknifing that the invention is intended to prevent.

The crowd and retract means is seen most clearly in Fig. 3. A crowd drum 12 is mounted on the frame 1 and, as shown, comprises two parts that operate in unison. Suitable drive and brake means (not shown but well known to those skilled in the art) are provided to power the drum 12 in either direction, hold it stationary, or allow it to idle. A shipper guide drum 13 is rotatable on the shipper shaft 8 and is provided with a plurality of grooves to separately accommodate the several ropes referred to hereafter. A crowding or extension action is provided by a pair of crowd ropes 14 connected to opposite parts of the crowd drum 12 and passing around the guide drum 13 to be connected to the rear or inner end of the dipper handle 5 at 15.Retraction is effected by a retract rope 16 connected to one of the parts of the drum 12, in a manner opposite to the connections of the crowd ropes 14, and extending around the guide drum 13 to be connected to the dipper handle 5 at a point 17 near its outer or forward end. The connections to the crowd drum 12 are such that rotation of the drum in a clockwise direction as seen in Fig. 3 will cause the crowd ropes 14 to be reeled in and the retract rope 16to be payed out, resulting in a crowd action in which the dipper handle 5 and the dipper 6 are extended forwardly. Counterclockwise rotation results in reeling in of the retract rope 16 and paying out of the crowd ropes 14 to provide a retracting action in which the dipper handle 5 and dipper 6 move to the rear.

The hoist means is seen most clearly in Fig. 4. An appropriately powered hoist drum 18 is mounted on the frame 1. A first hoist rope section 19 extends from the drum 18 upwardly and forwardly along the rear of the boom 3 and then around one of a pair of coaxial boom point sheaves 20 to a padlock sheave 21 connected to a dipper 6 nearthe outer end ofthe handle 5. A second hoist rope section 22, that is actually a continuation of the section 19, extends back around the other boom point sheave 20 and then downwardly and along the rear of the boom 3 to be connected to one of the sections of the crowd drum 12 in a manner opposite to the connections of the crowd ropes 14.When the hoist drum 18 is reeled in orpayed out with the crowd drum 12 held stationary, the dipper 6 will, respectively, be raised or lowered. When the drum 18 is reeled in while the drum 12 is being driven in a crowd action, or idling, however, the hoist rope section 22 will urge the drum 12 to rotate in a clockwise direction as seen in Figs. 3 and 4 to provide a crowd force or additional crowd force. This hoist-assist type of reeving is known, but the invention is particularly useful in combination with it.

A first deflector bracket 23 fixed to the rear of the boom 3 rotatably mounts a first deflector sheave 24 over which the first hoist rope 19 passes, the hoist rope section 19 thus being deflected substantially rearwardly of the normal, straight line it would take between the drum 18 and associated boom point sheave 20. A second deflector bracket 25 is mounted on the opposite side of the rear of the boom 3 somewhat below and rearward of the bracket23, and rotatably mounts a second deflector sheave 26.

The second hoist rope section 22 passes over the deflector sheave 26, and is thus deflected substantially rearwardly from the normal, straight line it would otherwise take between the associated boom point sheave 20 and the crowd drum 12.

The effect of the deflector sheaves 24,26 is shown schematically, with reference to sheave 26 and hoist rope section 22, in Fig. 5. When the hoist rope is being reeled in or pulled, there is a pull force 27 at the sheave and an opposite reaction force 28 resulting from weight and loading. A resultant force 29 perpendicular to the centerline of the boom 3 effectively acts forwardly on the boom 3, and thus resists jackknifing.

The locations and sizes of the deflector sheaves will be determined buy a number of factors, such as contemplated loading and structural limitations like the need to clear other parts, but a suitable specific design can easily be developed by one skilled in the art. By way of example, in the preferred design shown the boom 3 is 8.5m (28 feet) in length and its centerline (a line between the foot 4 and the center of rotation of the sheaves 20) is at a 55" angle to a horizontal line through the foot 4. Its weight, expressed as a vertically downward force at the center of gravity (approximately the location of the shipper shaft 8) is approximately 13,270 kgs (29,300 Ibs).The overall length of the handle 5 and the dipper 6 is approximately 9.8m (32 feet 3 inches) and their overall total weight is approximately 12,360 kgs (27,280 Ibs). The maximum crowd force, expressed as a horizontally rearward force at the shipper shaft 8, is approximately 75,200 kgs (166,000 Ibs). The first deflector sheave 24 deflects the first hoist rope section 19 approximately 38 cms (15 inches) rearwardly, in a direction perpendicular to the boom centerline, from its normal line, and the second deflector sheave 26 deflects the second hoist rope section 22 approximately 56 cms (22 inches) rearwardly in a direction perpendicular to the boom centerline.At a hoist line pull of approximately 52,770 kgs (116,500 Ibs), this develops resultant forces, perpendicular to the boom centerline, of approximately 10,650 kgs (23,5001 bs) at the sheave 24 and 15,400 kgs (34,000 Ibis) at the sheave 26. The effective forces at the sheaves 24,26 are substantially the same because the sheave 24 is located farther up the boom, and this prevents twisting of the boom 3 about its center line. The resultant forces are cumulative, and the net effect is that jackknifing is substantially prevented even at maximum crowd force It should be noted that the forward resultant force will increase as pull force increases.

The foregoing disregards otherfornesthat come into play in actual operation, but that are well known to those skilled in the art and do not change the basic operation ofthe invention. There is, for example, a forward force on the boom 3 where the hoist rope sections 19,22 pass over the point sheaves 20, and a forward force is also exerted by the weight of the handle 5 and dipper 6. All of these forces will vary depending ore pull force, dipper position and loading, but under all circumstances the resultant forces at the deflector sheaves 24, 26 will act to resist jackknifing.

While a preferred embodiment ofthe invention has been shown and described, it will be obvious that various modifications are possible without departure from the scope of the invention. The invention may obviously be used on machines of various types and specific configurations. It is particularly useful in combination with the hoist-assist reeving shown, since the two hoist rope sections can be deflected lesser distances to provide a relatively large cumulative force, but it can obviously be used with other reeving arrangements including a single hoist line with a single deflecting sheave. While the anti-jackknifing force should ideally be enough to prevent jackknifing even at maximum crowd force, any substantial deflection causing a substantial resultant force will be helpful. In view of the possible modifications, the invention is not intended to be limited by the showing or description herein, or in any other manner except insofar as may be required.

Claims (4)

1. A power shovel comprising a frame, a forwardly angled boom footed on the frame, dipper means comprising a dipper handle extensibly and retractably supported on and intermediate the ends of the boom and a dipper disposed forward of the boom, crowd and retract means for the dipper means, hoist means comprising a hoist drum and at least one hoist rope leading from the hoist drum along the back ofthe boom and aroundthe boom tip to the dipper means, and an anti-jackknifing arrangement comprising at least one deflecting sheave mounted on and extending rearwardly of the boom, the hoist rope passing over the deflecting sheaves and thus being deflected substantially rearwardly of a normal line, such deflection resulting in a forward force on the deflecting sheave(s) and boom in response to pull on the hoist rope.

2. A power shovel as claimed in claim 1,wherein the crowd means comprises at least one crowd rope connected to the dipper means and a crowd drum to which the other end of the crowd rope is attached, actuation ofthe crowd drum in one direction causing the dipper means to be extended in a crowding action, the hoist means comprises a first hoist rope section leading from the hoist drum around the tip of the boom to the dipper means and a second, continuing hoist rope section leading back from the dipper means around the tip of the boom to the crowd drum, said second section being connected to the crowd drum in a manner to cause rotation of the crowd drum in said one direction upon application of a hoist pull and two deflecting sheaves are associated, respectively, with the hoist rope sections.

3. A power shovel as claimed in claim 2, wherein the two hoist rope sections and their respective deflecting sheaves are spaced laterally on the boom, and the deflecting sheaves are arranged so that the forward forces generated at each are substantially equal.

4. A power shovel constructed and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.