Mobile Load-lifting Machines

Abstract

In a mobile load-lifting machine such as a wheeled crane in which the front and rear pairs of wheels are arranged for relative extension and retraction in accordance with the load-handling position of the machine or crane and in which at least one pair of wheels such as the front pair are inturnable for load-slewing movement of the machine, the provision of means for ensuring appropriate inturning of said pair of wheels according to the extended or retracted position of the front and rear wheels and which consists of a movable member linked to the pivotal mounting of the inturnable wheels and cooperating with a stop member which latter is adjustable in accordance with the wheel extension and retraction for permitting corresponding variation in the extent of movement of the movable member and hence of inturning movement of the inturnable pair of wheels.

Description

This invention relates to mobile load-lifting machines such as a wheeled crane wherein provision is included for relative front and rear wheel extension or retraction in accordance with the load-handled or load-handling position or attitude of the crane or machine together with provision for inturning at least one pair of wheels of the crane or machine for load-slewing movement.

The object of this invention is to provide means for ensuring appropriate wheel inturning of the crane or machine according to the extended or retracted position of the wheels.

In a practical embodiment of the invention as applied to a mobile or wheeled crane the construction and arrangement is as follows reference being had to the accompanying drawings in which:

FIG. 1 is a side elevation of the crane,

FIG. 2 is a plan view (without jib) and

FIG. 3 is a detail side elevation of the compensating linkage.

The front wheel axle beam 2 is interconnected by a pair of struts 10 and a hydraulic ram 11 (or a pair thereof) with the crane jib 1 for forward extension or rearward retraction in accordance with luffing movement of the jib 1 while the front wheels 3 are also arranged to be inturned and driven such as by independent hydraulic motors 13 thereto for obtaining slewing movement of the crane about the rear wheels or about turntable support on the latter or as shown about a retractable turntable 5.

Luffing of the jib 1 is effected by means of the hydraulic ram 11 and which due to its interconnection between the jib 1 and struts 10 from the latter to the front axle beam 2 forward extension of the beam 2 and front wheels 3 is obtained with forward luffing of the jib (by contraction of the ram 11) and vice versa. For this purpose front chassis structure 6 carrying the front axle beam 2 is slidable in a fore and aft direction relative to a rear chassis structure 7 carrying the transverse pivotal mounting 8 of the jib 1 and the rear wheels 4.

When the front wheels 3 are extended away from the rear wheels 5 on forward luffing of the jib 1 it will be appreciated that they are required to travel along a larger turning circle L when inturned for slewing movement as against a smaller turning circle S when they are retracted towards the rear wheels 5 and axis of slewing movement. Accordingly the front wheels 4 require to be inturned to a greater extent for following the larger turning circle L than for following the smaller circle S and in accordance with this invention the extent of inturning of the front wheels 3 is varied according to their extension or retraction for obtaining a satisfactory slewing action. Mechanism for this purpose is as follows:

The pivotal mounting of each front wheel stub axle or driving motor assembly 13 thereof about its corresponding kingpin or like pivotal mounting 12 is connected by an arm 15 fast with the assembly to a link 16 which is in turn pivotally connected to a corresponding arm 17a, 17b of an angularly movable double-armed lever 17 pivotally mounted about a central vertical axis at 19 on the front axle beam 2.

The double-armed armed lever 17 is arranged for hydraulic ram operation e.g., by a pair of double acting rams 20 having a push/pull action on the lever 17 by pivotal connection of the piston rods of the rams 20 to an arm 18 rotationally fast with the lever 17 the cylinders of the rams being pivotally mounted at 21 on the front axle beam 2.

The connection of the links 16 from the front wheel assembly arms 15 is such that on the lever 17 being turned in a clockwise direction (FIG. 2) the front wheels 3 are inturned as indicated in dotted lines and vice versa. In the example shown the front wheels 3 are straight ahead when the arms 17a, 18 are at about the "two o'clock" position and are fully inturned at about the "four o'clock" position of the arms 17a, 18. However such positioning may be varied according to practical requirements.

When the front wheels 3 are fully inturned in this way, the arm 18 abuts a locating stop 22 in order to limit inturning of the wheels 3 beyond a required extent for a particular turning circle. The stop 22 is carried by an angularly adjustable plate 23 pivoted about the vertical axis 19 of pivotal movement of the lever 17 and arm 18. As the stop 22 is angularly advanced in the clockwise direction by corresponding turning movement of the plate is permits a greater extent of pivotal movement of the arm 18 and hence of the lever 17 for a greater extent of inturning of the front wheels 3 and vice versa.

In order to obtain corresponding angular adjustment of the stop plate 23 with forward extension or rearward retraction of the front axle beam 2, the plate 23 is provided with a rearwardly extending arm 24, the rear end of which cooperates by a runner 25 with a horizontal slot or guideway 26 inclined to the fore and aft axis of the crane and provided in a plate 27 carried by the rear chassis structure 7.

For travelling movement of the crane (i.e., with the front wheels 3 in the straight-ahead position) the rear wheels 4, also shown provided with independent motor drives 14 are steerable by hydraulic ram operation at 29 controlled by the steering wheel 30 at the driver's position 31, the rear wheel assemblies being interconnected by a track rod 32 for steering pivotal movement about kingpin pivots 34 from the rear axle beam 33.

For travelling purposes the front axle beam 2 may be fully extended by appropriate retraction of the ram 11 in order to lower the jib 1 to a substantially horizontal position so as to reduce the head room of the crane as much as possible.

An internal combustion engine 35 is shown carried as a counterweight by a stepped-down rear part 7a of the rear chassis structure 7 for driving hydraulic pumps for operation of the various rams 11, 20 and 29 of the crane including a hydraulic motor of the winch 36 and also jacks of the retractable turntable 5. Control of the several hydraulic circuits is effected by suitable control means (not shown) at the drivers position 31 which control preferably includes hydraulic interlocking arrangements to provide foolproof operation of the crane as far as possible.

Thus, as the front wheel axle beam 2 is extended the coaction of the runner 25 with its guideway 26 is such that the stop plate 23 is turned for moving the stop 22 in the clockwise direction to permit a greater extent of turning movement of the lever 17 and hence inturning movement of the front wheels 3 to properly follow a greater turning circle. Conversely on retraction of the axle beam 2 the stop plate 23 is angularly adjusted so as to reduce the extent of angular movement of the lever 17 and hence inturning of the wheels 3 to suit a smaller turning circle.

If desired the rear wheels 4 may be also arranged to be inturned for slewing movement in which case similar compensating mechanism to that already described is desirably applied to the inturning of the rear wheels 4 so that they follow substantially the same turning circle as that of the front wheels 3 and in accordance with the relative extension or retraction of the front and rear wheels 3,4 as determined by the luffed position of the jib 1. However the stop plate to the lever linked to the rear wheel axle assemblies is connected to a slide or runner cooperating with an inclined guideway on the forward chassis structure 6 carrying the front wheel axle beam 2.

Claims

I claim:

1. A mobile load-lifting machine of the character described comprising a rear chassis structure; a front chassis structure slidably engaging said rear chassis structure longitudinally for fore and aft chassis extension and retraction of the machine; ram means acting between the chassis structures for operating them for such relative sliding movement according to load-handling requirements of the machine; a rear pair of wheels carried by said rear chassis structure; a front pair of wheels carried by the front chassis structure, one of said pair of wheels being carried by pivotal mountings from the corresponding chassis structure and inturnable about said pivotal mountings for slewing movement of the machine; further ram means acting between the corresponding chassis structure and the pivotal mountings for operating the inturnable wheels for inturning movement; angularly movable lever means carried from the corresponding chassis structure between the inturnable wheels and linked to the pivotal mounting of the latter for angular movement with inturning movement of said wheels; and angularly movable stop member carried from the corresponding chassis structure and cooperating with the angularly movable lever means for limiting angular movement of the latter and likewise inturning movement of the inturnable wheels, and guide means carried by the other chassis structure with which the corresponding chassis structure is slidably engaged and slidably cooperating with the stop member for effecting angular adjustment thereof on relative sliding movement of the chassis structures so that the extent of inturning movement of the inturnable wheels is appropriately varied in accordance with chassis extension and retraction of the machine.

2. A mobile load-lifting machine according to claim 1 wherein the guide means includes a longitudinal guideway inclined to the fore and aft axis of the machine and slidably cooperating with an arm extending from the stop member for imparting angular adjustment to the latter on relative sliding movement of the chassis structures.

3. A mobile load-lifting machine according to claim 1 wherein the angularly movable lever means and the angularly adjustable stop member are mounted for their angular movements about a common vertical axis from the corresponding chassis structure.

4. A mobile load-lifting machine according to claim 1 wherein the angularly movable lever means includes a double-armed lever to corresponding arms of which are linked the pivotal mountings of the inturnable pair of wheels.

5. A mobile load-lifting machine according to claim 4 wherein the arms of the doubled-armed lever are each connected to a corresponding ram of a pair of rams carried by the corresponding chassis structure for angular operation of the lever means in imparting turning movement to the pivotal mountings of the inturnable wheels.

6. A mobile load-lifting machine according to claim 1 wherein the further ram means acting between the corresponding chassis structure and pivotal mountings of the inturnable pair of wheels is arranged to operate the latter by being connected to the angularly movable lever means linked to said pivotal mountings.