Traversing hoists – Adjustable to transport or nonuse position – Collapsible or foldable boom
Reexamination Certificate
2000-06-23
2001-09-18
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Adjustable to transport or nonuse position
Collapsible or foldable boom
Reexamination Certificate
active
06290078
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for the independently controlled motorized unfolding/folding of a crane jib made up of elements joined together by articulation, with two consecutive jib elements which can nest one inside the other when the jib is in the folded position.
DESCRIPTION OF THE PRIOR ART
German patent application No. 3 441 573 already discloses a tower crane, the jib of which is made up of two elements, known respectively as the jib root and the jib tip, which are articulated together about a horizontal axle located approximately mid-way up the jib. The jib root has a cross section of triangular shape, and the jib tip has a cross section of U-shape so that folding the jib tip onto the jib root about the aforementioned horizontal axle may be continued until the two jib elements are nested one inside the other.
This known folding device also comprises a link rod linking the upper members of the two jib elements, said link rod being articulated to the front end of the upper member of the jib root, and sliding in lateral guides in the shape of arcs of a circle provided at the rear of the jib tip.
In the aforementioned German patent application No. 3 441 573, the unfolding/folding of the jib is motorized by means of a sheathed cable, controlled by the articulation between the jib root and the top of the mast of the crane. What this means is that the dynamics of the unfolding/folding of the jib elements are dictated by the movement of the jib root.
In consequence, the bulk of the jib while it is being assembled is always great, and does not allow the avoidance of any obstacle that might be present. In addition, it is impossible to unfold/fold the jib tip when the crane is working, in an attempt to avoid an obstacle or in order to distribute a load using a short-jib configuration.
French patent application No. 2 546 496 describes another tower crane with a jib made up of two elements articulated together and which can be nested when in the folded position. The two jib elements are articulated together about a horizontal axle located mid-way up the jib, the jib root in this instance having a U-shaped cross section, while the jib tip has a cross section of triangular shape. The unfolding/folding of the jib is motorized by means of a cable associated with a circular-arc-shaped lever arm, which is itself motorized by the articulation of the jib root to the top of the mast of the crane.
This motorization device makes it possible to place the jib in a “swan-neck” position when continuing to raise this job. However, it retains the same disadvantages as those present in the previous document, because the dynamics of unfolding/folding the jib elements are still dictated by the movement of the jib root.
SUMMARY OF THE INVENTION
The present invention sets out to overcome these drawbacks by providing a folding/unfolding device that makes it possible, while assembling the crane or while the crane is working, to avoid obstacles such as existing buildings, trees, power lines, etc., while at the same time making it possible to increase the load-carrying capacity by folding the jib tip.
To this end, the subject of the invention is essentially a device for the motorized unfolding/folding of a crane jib made up of elements joined together by articulation, with two consecutive jib elements which can nest one inside the other when the jib is in the folded position, these two elements having respective cross sections which allow them to nest, and being articulated together about a horizontal axle located approximately mid-way up the jib, the front jib element having, in its rear part, lateral guides in the shape of arcs of a circle housing a transverse horizontal axle connected to the rear jib element, the unfolding/folding device comprising, to motorize it, on the one hand, a double-acting ram located in the vertical mid-plane of the jib and articulated by a first end, about a horizontal axle, to the rear jib element in the region of the upper member or members of this element and, on the other hand, a set of link rods made up of a straight link rod articulated, on the one hand, to the second end of the ram and, on the other hand, to the rear part of the front jib element in the lower part of this element and of a cranked link rod articulated, on the one hand, to the second end of the ream and, on the other hand, to the front part of the rear jib element in the lower part of this element, the cranked link rod leaving space, at its cranked region, for the passage of the horizontal axle housed in the circular-arc-shaped lateral guides.
respective ends of these links rods, opposite those articulated to the ram, are preferably articulated to respective clevis mounts, one fixed to the lower part of the front jib element and the other fixed to the lower part of the rear jib element.
This then yields a device for unfolding/folding two nesting consecutive jib elements, such as a jib root and a jib tip, in the case of a jib made of two articulated elements, which is a motorized device controlled independently by a special-purpose ram. Deploying the ram rod allows the jib elements to be unfolded into an aligned relative position, and retracting the ram rod allows the jib elements to be folded until they are completely nested, it also being possible to attain any intermediate relative position. Thus, the position of the jib tip is no longer dictated by that of the jib root, and the jib tip may, at any moment, be brought into a desired position in order to avoid an obstacle. What is more, the jib tip may occasionally be folded to allow the crane to operate with a short jib and thus increase the load-carrying capacity of the crane. The link rod system is designed to allow the front jib element to rotate through 180° with respect to the rear jib element.
According to one embodiment of the device, the rear part of the front jib element comprises two vertical lateral plates, in each of which a guide and buffer slot in the form of an arc of a circle is formed, each slot having, passing through it, one end of the transverse horizontal axle connected to the rear jib element, and each lateral plate having, passing through it, the axle that articulates the front jib element with respect to the rear jib element and which is located approximately mid-way up the jib.
The articulation slots thus provided on the lateral faces of the front jib element, such as jib tip, fulfill the following functions:
they act as upper stops which, in collaboration with the horizontal axle passing through these slots, provide a connection between the upper members of the two jib elements, such as the jib root and the jib tip when the jib is aligned;
they act as lower stops for the same axle, when the jib is fully folded, the two jib elements then being nested one inside the other;
they provide this axle with safe guidance during the operations of unfolding and folding the jib elements.
Advantageously, the axle that articulates the front jib element with respect to the rear jib element and which is located approximately mid-way up the jib, has functional play, so as to free this axle of any load, to make the system connecting the two jib elements an isostatic system when this jib is aligned.
According to one embodiment of the device of the invention, the front ends of the members of the rear jib element are connected by a transverse stiffening sleeve through which the aforementioned transverse horizontal axle passes.
To provide the connection at the lower members of the jib elements, it is contrived that, according to an additional feature, the lower members of the rear jib element comprise, at their front end, support and guiding means for the rear ends of the lower members of the front jib element; these means preferably comprise, at the front end of each lower member of the rear jib element, a horizontal support and a lower guide afforded by a support plate, and a lateral guide afforded by a ramped support plate, a combination such as this making it possible to take up all the loads and accuratel
Brahan Thomas J.
Oliff & Berridg,e PLC
Potain
LandOfFree
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