GB2151580A

GB2151580A - A self-propelled lifting device

Info

Publication number: GB2151580A
Application number: GB08418186A
Authority: GB
Inventors: Vizia Carmine De
Original assignee: CDF SS
Current assignee: CDF SS
Priority date: 1983-12-27
Filing date: 1984-07-17
Publication date: 1985-07-24
Also published as: GB8418186D0; DE8422345U1; GB2151580B; FR2557085A1; IT1160249B; IT8368358A0; DE3427689A1

Abstract

A self-propelled lifting device comprises two tracked motor vehicles (10) and (12) having respective turntables (14) and (16) rotatable around vertical axes and interconnected by an extendible horizontal structure (34). An arm (18) and a coacting arm (20) interconnected at their tops by an adjustable pull rod (22) are pivoted at the bottom to the turntable (14) of the first vehicle by respective pivots (13), (15) disposed in a position such that the resultant of the axial forces transmitted from the arm (18) and coacting arm (20) to the turntable (14) passes through the rotary bearing surface of the turntable (14) to the vehicle (10). <IMAGE>

Description

SPECIFICATION A self-propelled lifting device The invention relates to a self-propelled lifting device of the kind comprising a first tracked motor vehicle having a turntable rotatable around a substantially vertical axis, an arm and a coacting arm extending upwards and joined at the bottom to the turntable of the first vehicle around respective- substantially horizontal pivots, a moving means for coupling a load borne by the arm, an adjustablelength pull rod connecting the top of the arm and the coacting arm, a second motor vehicle at a distance from the first vehicle and having a turntable rotatable around a substantially vertical axis and bearing a counter-weight, a bearing column connecting the top of the coacting arm to the turntable of the second vehicle, a connecting element comprising a substantially horizontal extendible structure having its ends pivoted around parallel substantially horizontal axes to the turntable of the first and the second vehicle respectively, and means for angularly moving the arm and coacting arm respectively relative to the turntable of the first vehicle, lowering and raising the movable coupling means relative to the arm, and rotating the arm and the coacting arm relative to a substantially vertical axis.

In known self-propelled lifting devices of the above kind, the pivots connecting the arm and coacting arm to the turntable of the first vehicle are conventionally disposed in a position such that the resultant of the axial forces transmitted by the arm and coacting arm to the turntable runs outside the region where the turntable rotatably bears on the vehicle structure.

In such cases the first vehicle is subjected during operation to considerable tilting moments which must be opposed by using a large counterweight on the second vehicle.

The counterweight, however, is often inadequate to cope with the loads to be raised and the resulting tilting moments, and therefore an additional counterweight usually has to be placed directly on the turntable of the first vehicle on the side opposite the pivots of the arm and coacting arm relative to the axis of rotation of the turntable or the extendible connecting structure.

This has the obvious disadvantage of excessively increasing the weight of the apparatus, making it difficult and sometimes dangerous to handle.

Owing to the large tilting moments, the bearings for connecting the turntable to the vehicle need to be sophisticated and expensive and have a short working life, and additional motor units are also needed for rotating the turntable.

The object of the invention is to avoid these disadvantages by constructing a self-propelled lifting device in which the tilting moments applied in operation to the first vehicle are substantially reduced, thus permitting a drastic reduction in the counterweights, To this end, according to the invention, the pivots of the arm and coacting arm to the turntable of the first vehicle are disposed in a position such that the resultant of the axial forces transmitted by the arm and the coacting arm to the turntable of the first vehicle passes through the rotary bearing surface of the turntable to the vehicle.

As a result of this feature, the tilting moments applied in operation to the first vehicle are substantially reduced, thus advantageously reducing the counterweight applied to the second vehicle and avoiding the need for additional counterweights on the turntable of the first vehicle or on the extendible connecting structure.

This solution also considerably simplifies the rotary connection between the turntable of the first vehicle and the bearing structure thereof. The connection can be in the form of a simple sliding bearing, which is relatively cheap and has a long working life.

Finally, there is the advantage of eliminating the need for auxiliary motor units for rotating the turntable of the first vehicle, since it can easily be driven by operating the second vehicle.

The result is a substantial reduction in costs per tonne limited by the lifting device according to the invention, compared with conventional devices.

Preferably, the pivots of the arm and coacting arm to the turntable of the first vehicle are disposed near and on opposite sides of the axis of rotation of the turntable.

The apparatus according to the invention is simplified in that the first vehicle can be the body of an existing commercial tracked crane, modified simply by combining its turntable with two bearing plates facing opposite directions relative to the axis of rotation of the turntable for bearing the pivots for the arm and coacting arm, and a coupling part for connection to the corresponding end of a connecting element on the turntable of the second vehicle.

Other features and advantages of the invention will be clear from the following detailed description with reference to the accompanying drawings, given by way of non-limitative example only, in which: Figure 1 is a diagrammatic view in elevation of a self-propelled lifting device according to the invention and Figure 2 is a larger-scale view of part of the device.

Referring first to Figure 1, the lifting device according to the invention mainly comprises a first tracked motor vehicle 10 and a second tracked motor vehicle 12, each having a turntable or turret 14, 1 6 rotatable around a vertical axis. The axis of rotation of turntable 14 of vehicle 10 is indicated by A in the drawings.

The bottom end of a crane arm 1 8 and the bottom end of a coacting arm 20 are pivoted to turntable 1 4 around respective parallel horizontal pivots 13 and 15. Arms 18 and 20 are interconnected at their tops by an adjustable length pull rod 22. Arm 1 8 bears a lifting cable 24, the free end of which bears a coupling means 26 for securing to a load. An additional arm and coacting arm (not shown in the drawings) can be pivoted to the top end of arm 1 8 and bear an additional lifting cable.

The bottom end of a bearing column 32 is connected by a transverse pivot 30 to the turntable 1 6 of the second vehicle 12, which carries a counterweight 28. The top end of column 32 is connected to the top of the coacting arm 20.

Reference 34 denotes an extendible connecting element, the ends of which are connected by horizontal pivots 36, 38 respectively to turntable 14 and turntable 1 6.

Element 34 is preferably teiescopic and is connected to the bottom part of arm 1 8 by a jointed pull rod 40.

Figure 2 is a detailed view of vehicle 10. It advantageously comprises the body of an existing commercial tracked crane modified by combining turntable 14 with two bearing plates 42 (only one of which is shown in the drawing) facing opposite directions relative to the axis of rotation A, and a part 44 for attaching the pivot 36 to the connecting element 34.

Vehicle 10 has motor-driven tracks 46 borne by a bearing structure (general reference 48) on which turntable 1 4 rests with interposition of an ordinary sliding bearing 50. Bearing 50 can be made up e.g. of one or more annular elements comprising sectors of anti-friction material, e.g. nylon.

Turntable 1 4 also has a guide cab 52 and a group of motor-driven lifting means 54 (Figure 1) for lifting and lowering the coupling means 26 and varying the inclination of arms 18 and 20.

Turntable 1 4 does not have any motordriven device for rotating it since. as will be explained hereinafter, rotation is obtained from the rear vehicle 1 2.

As clearly shown in Figure 2, pivots 1 3 and 1 5 for securing arms 1 8 and 20 to turntable 1 4 are disposed in a position such that the resultant R of the axial forces transmitted to platform 1 4 by arms 1 8 and 20 passes through the bearing surface of turntable 1 4 to the structure 48 of vehicle 10, i.e. via bearing 50. Pivots 1 3 and 1 5 are normally situated near and on opposite sides relative to the axis of rotation A of turntable 14.

Owing to this arrangement, there is a considerable reduction in the tilting moments applied to vehicle 10 during use of the device according to the invention, so that counterweight 28 can be considerably reduced and there is no need for additional counterweights placed directly on turntable 1 4 or the cornecting element 34.

As has been said, turntable 1 4 is rotated relative to structure 48 by vehicle 1 2, which moves along a circular path having its centre at the axis of rotation A of turntable 1 4.

The previously-described arrangement of vehicles 10 and 1 2 and the connecting structure 34 ensures that the entire device is very easy to manoeuvre during operation and that the load applied to the lifting means 26 has wide flexibility of movement. This is also due to the reduced weight of vehicles 10 and 12, made possible by reducing the tilting moments applied during operation to vehicle 10, owing to the position of pivots 1 3 and 1 5. In addition to the previously mentioned advantages, this greatly increases the carrying capacity of the device, with a consequent appreciable reduction in the operating cost per torne lifted.

Of course, without altering the principle of the invention, details of construction and embodiments of the invention can be widely varied from that described and illustrated without thereby departing from the scope of the invention.

Claims

1. A self-propelled lifting device comprising a first tracked motor vehicle having a turntable rotatable around a substantially vertical axis, an arm and a coacting arm extending upwards and joined at the bottom to the turntable of the first vehicle around respective substantially horizontal pivots, a moving means for coupling a load borne by the arm, an adjustable-length pull rod cornecting the top of the arm and the coacting arm, a second motor vehicle at a distance from the first vehicle and having a turntable rotatable around a substantially vertical axis and bearing a counterweight, a bearing column connecting the top of the coacting arm to the turntable of the second vehicle, a connecting element comprising a substantially horizontal extendible structure having its ends pivoted around parallel substantially horizontal axes to the turntable of the first and the second vehicle respectively, and means for angularly moving the arm and coacting arm respectively relative to the turntable of the first vehicle, lowering and raising the movabie coupling means relative to the arm, and rotating the arm and the coacting arm relative to a substantially vertical axis, characterised in that the pivots of the arm and coacting arm to the turntable of the first vehicle are disposed in a position such that the resultant of the axial forces transmitted by the arm and the coacting arm to the turntable of the first vehicle passes through the rotary bearing surface of the turntable to the vehicle.

2. A device according to Claim 1, characterised in that the pivots of the arm and coacting arm to the turntable of the first vehicle are disposed near and on opposite sides of the axis of rotation of the turntable.

3. A device according to Claim 1 or Claim 2, characterised in that the turntable of the first vehicle is rotatably borne by a structure via a simple axial sliding bearing.

4. A device according to one or more of the preceding claims, characterised in that the first vehicle is the body of a commercial tracked crane modified by combining its turntable with two bearing plates facing opposite directions relative to the axis of rotation of the turntable for bearing the pivots for the arm and coacting arm and a coupling part attached to one end of the turntable for cornection to the corresponding end of a connecting element on the turntable of the second vehicle.

5. A device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.