The invention relates to a -dumper of a relatively light construction.

Known dumpers have various disadvantages known to persons skilled in the art, one of them being that they depend on external means for loading.

The aim of the present invention is to avoid, or at least mitigate, some of the disadvantage of known dumpers and to make the dumper according to the invention self-loading and off-loading at selected heights.

This is achieved, according to the invention, by a dumper comprising a chassis carried by front wheels and rear wheels, an extendable and retractable upright support carried by the chassis, arm structure fixed to and extending forwardly from the support, means for extending and retracting the support and thereby lifting and lowering the arm structure _t a carrier pivotally attached by a first pivot to the arm structure, a bucket attached to the carrier, and means for tilting the carrier with the bucket about the first pivot with respect to the arm structure, the dumper being so designed that when it stands on a horizontal ground and the arm is at its maximum lifted position, the first pivot is situated over a plane passing through the horizontal diameters of the front wheels and delimited by their frσntmost and rearmost portions. The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Pig. 1 is a side elevation showing the dumper with a lowered bucket, Pig. 2 is a side elevation showing the

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dumper with a raised bucket,

Pig. 3 is a detail showing the bucket tilting mechanism in side elevation from the left hand side, and, Pig. 4 is a front elevation of the bucket and its tilting mechanism.

The dumper comprises a chassis 1 carried by front wheels 2 and rear wheels 3 , driven by hydraulic motors (not shown). The illustrated dumper is an articulated dumper the chassis of which comprises a front part carried by the front wheels 2 and a rear part carried by the rear wheels 3, the two parts being interconnected by an articulated joint controlled by a ram (not shown) which enables turning of the two parts with respect to each other. The ram is controlled by a hydraulic distributor (not shown), which in turn is controlled by a steering wheel 5 in front of the operator's seat 6. Next to the operator's seat 6 is a control bank 7, (indicated diagrammatically by two control levers) and below the seat is a power unit 8 comprising a diesel engine and pumps for hydraulic liquid which are driven by the engine.. All the parts mentioned so far are known per se. In the illustrated preferred embodiment the front part of the chassis has in plan two spaced- apart substantially parallel arms having free forward ends carrying outwardly the front wheels and delimiting a free space for receiving the arm structure in its lowermost position.

The dumper according to invention has an extendable and retractable upright support in the form of a central lift column 9 which comprises a stationary inner column 1OA firmly attached to the chassis 1, an inner intermediate column 10B and an

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outer column 1OC. The columns 1OB and 1OC are ^■ vertically displaceable by a ram (not shown) situated inside the column 1OA and a ram 11 connected at one end to a lug attached to the outer column 1 OC and the other end to a lug attached to the intermediate column 10B. In the illustrated preferred embodiment all the three columns are formed by square sections between which may be provided means (known per se) for reducing friction between the two columns. To the outer column 1OC is firmly fixed a bucket support arm 12 extending forwards substantially at right angles thereto. Between the outer column 10C and the bucket support arm 12 are provided two spaced apart strengthening gussets 13 to which is pivotally connected a cylinder of a ram 14- The bucket support arm 12 has, at its end remote from the outer column 10C, a downwardly extending vertical element 15 (Pig.3), so that the arm 12 is substantially It- shaped. Instead of the central lift column 9 as described, another lifting device may be used, such as a telescopic cylinder, a scissor-lift device, parallel-linked lifting arms or fork-truck-type mast. Two spaced-apart bucket support members 16 are at one end pivotally connected by a first pivot P1 to the vertical element 15. The dumper is so designed that when it stands on a horizontal ground and the arm is at its maximum lifted position, the ^' first pivot is situated over a plane passing through the horizontal diameters of the front wheels and delimited by their frontmost and rearmost portions. It is advantageous if the pivot P1 is situated substantially vertically above the axis of rotation of the front wheels 2 as is best apparent from Pig.

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2. The other ends of the members 16 are connected to a cross member (not shown) of a bucket cradle 17. The relevant parts of the dumper are so designed that, when the arms structure is in its lowermost position, the axis of the front wheels substantially coincides with the axis of the first pivot. Each of the bucket support members 16 is provided with a gusset 20, to which is pivotally connected the piston rod of the ram 1 . The bucket cradle 17 is formed by a substantially U-shaped support element 18 provided at the open ends with spaced-apart substantially parallel oblique arms 19« The bucket cradle 17 carries a bucket 21, a front portion of which is pivotally connected by a second pivot P2 to the free ends of the oblique arms 19- The second pivot P2 is positioned rearwardly from the front edge of the bucket.

The provision of the vertical element 15 which enables the pivot P1 to be situated below the arm 12 is not essential; it is only advantageous because it lowers the low position of the bucket 21 and its centre of gravity. The vertical element 15 together with the pivot P1 may be left out and a pivot P3, taking over the function of the pivot P1 , situated on the arm 12, while the tilting of the cradle 17 is still performed by the ram 14- The last mentioned embodiment may be modified by extending the bucket support members 16 beyond the pivot P3 and attach to these extended portions one end of a ram (not shown) the other end of which is attached, directly or indirectly, to the arm 12. In that case the ram 14 is no longer required.

While the provision of a single ram 14 (or its substitute, just mentioned non-illustrated ram)

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-substantially in a plane containing the axis of symmetry of the dumper is advantageous and sufficient, it will be understood that instead of this single ram two rams (not shown) situated substantially sideways of the bucket 21 may be provided.

On each side of the bucket 21 is situated a ram 22, the cylinder of which is pivotally connected to the support element 18 and the piston rod of which is pivotally connected to a rear portion of the bucket 21.

As is apparent from the description, the illustrated dumper according to the invention has six rams, namely a first ram (not shown) which controls the articulated joint and thereby steers the dumper, a second ram (not shown) and a third ram 11 which lift and lower, respectively, the columns 10B and 10C and thereby the bucket 21, a fourth ram 14 which tilts the bucket cradle 17 and thereby the bucket 21 about the pivot P1 and finally fifth and sixth rams 22 which tilt the bucket 21 about the pivot P2.

For loading material situated on the ground the bucket is tilted about the pivot P1 to the position shown in Figure 1 in chain-dotted lines in which, by driving the dumper forwards, the bucket acts as a bucket of a front loader so that it loads itself with the material on the ground. Then the bucket may be titled by the ram 14 about the pivot -P1 to the position for transport shown in solid lines and emptied e.g. by being brought to the position shown in dashed lines by being tilted about the pivot P2 by the operation of the rams 22. This is suitable for emptying the bucket 21 on the ground or a region only slightly above the ground. If the bucket is intended to be emntied to

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a region relatively high above the ground, e.g. into a skip, it is first lifted to the position shown in dashed lines in Pig. 2 and then tilted about the pivot P2 to the position shown in solid lines in Pig. 2.

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