Traversing hoists – Adjustable to transport or nonuse position – Collapsible or foldable boom
Reexamination Certificate
2000-02-11
2001-08-21
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Adjustable to transport or nonuse position
Collapsible or foldable boom
C212S225000
Reexamination Certificate
active
06276541
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to tower cranes in which the jib, made as several successive elements articulated together, can be folded so that the crane can be transported, particularly by road. More specifically, the invention is aimed at crane jibs which, toward their tip, have two relatively short elements. The invention relates still more specifically to a device for simultaneously unfolding or folding such crane jib tip elements.
DESCRIPTION OF THE PRIOR ART
Cranes are already known in which the jib includes a relatively short tip element. By way of example, reference may here be made to a certain crane HD 32A marketed since 1993 by POTAIN, the erection and dismantling instructions for which crane describe the method of folding and unfolding the jib tip element. The folding of this jib element, which is motorized by two lateral gas springs, takes place in the vertical plane of the crane runway, and the jib tip element is immobilized in the work position by two connecting rods working in tension. The gas springs are used for unfolding the jib tip element, whereas this element is folded manually. The jib tip element is immobilized in the folded position using straps.
This known system allows just one jib tip element, of a length not exceeding two meters, to be folded. Moreover, this known system requires special motorizing.
Elsewhere, there exist systems for unfolding/folding a jib tip in a horizontal plane. A system of this kind requires, for unfolding and folding the jib tip, a ground space which is often incompatible with the space available on the site where the crane is being used. This is particularly true when the crane is being dismantled, or when the crane is installed a short distance from a building which it has constructed. This system, also, requires special motorizing.
The present invention sets out to avoid the drawbacks of the existing systems, mentioned hereinabove, by supplying a technical solution which is suited to crane jibs of the kind concerned here, and which allows:
the crane and particularly its jib to be transported in a minimum amount of space that complies with the road-going gage width stipulated in official regulations, while at the same time maximizing the useful length of the jib in the work position;
the crane to be erected and dismantled in a minimum lateral amount of space;
simple and economical implementation, in particular avoiding any special motorizing.
SUMMARY OF THE INVENTION
The subject of the invention is a device for folding or unfolding tower crane jib tip elements, the jib comprising a succession of elements articulated one to the next about horizontal axes, these elements comprising at least two relatively long main elements, and at least two relatively short tip elements, the device being essentially one wherein connecting members are provided connecting the front part of the last main jib element, the intermediate jib tip element and the end jib tip element in such a way that the two tip elements can be unfolded or folded simultaneously, in a vertical plane, relative to the remaining part of the jib, at least one tip element being foldable in a direction approximately perpendicular to the main elements, this device being motorized by the crane's lifting cable and for this purpose comprising an unfolding arm borne by the front part of the last main jib element, and fitted with a pulley over which the lifting cable can pass during the operations of unfolding or of folding the jib tip elements, the lifting cable then being attached to one of said tip elements.
In order to perform these operations of unfolding or folding the jib tip elements, the lifting cable is, for example, attached to a shackle at the front end of the end jib tip element.
Advantageously, the aforementioned connecting members comprise at least one link-rod system located in a vertical plane and connected by articulations about horizontal axes to, respectively, the two tip elements and the front part of the last main jib element. The device may comprise two symmetric link-rod systems, arranged one on each side of the jib in parallel vertical planes.
Each link-rod system for simultaneously unfolding or folding the two jib tip elements, comprises, in one embodiment, a three-point lever articulated by its intermediate point to a top of the intermediate jib tip element, a front connecting rod articulated by one end to the front point of the lever and, by its other end, to the end of the jib tip element, and a rear connecting rod articulated by one end to the rear point of the lever and, by its other end, to the front part of the last main jib element.
Advantageously, the lever and one of the connecting rods of each link-rod system comprise respective holes which come into alignment when the jib tip is in the unfolded position, and which are designed for locking using a pin which immobilizes the lever with respect to this connecting rod and which consequently immobilizes the entire link-rod system in the aligned position. Thus stiffened, the link-rod system acts as a tie rod, when the crane is in the work position, with respect to the two jib tip elements. This link-rod system can also act as triangulation for the jib unfolded on the ground, which is also one possible position for transport on site.
As a preference, the unfolding arm is articulated about a horizontal axis to the front part of the last main jib element and includes stop and/or locking means for stopping it in the deployed position of use and in the position in which it is folded up against this main jib element.
In one embodiment, the device that is the subject of the invention also comprises a sling fixed to the front part of the end jib tip element and is designed to be attached to the rear end of the first main jib element when this jib is entirely folded. This arrangement applies more specifically to instances in which, if the crane is in the folded transport position, the intermediate jib tip element is approximately vertical and points downward, whereas the end jib tip element is oriented obliquely, pointing upward, in which case it lies near the rear end of the first main jib element also known as the “jib root”.
In the latter instance, in particular, the device is also motorized by a ram used for the overall unfolding/folding of the jib, particularly a ram associated with an intermediate folding element inserted between two main elements of the jib. By virtue of this ram, the last main jib element can be inclined slightly and raised so as to bring the jib tip elements clear of the rear end of the jib root. This allowing the sling to be disconnected and the tip elements unfolded without these elements encountering any obstacle.
Overall, the folding or unfolding device that is the subject of the present invention offers the following advantages:
This device allows the two jib tip elements, which elements may have a combined length of the order of 3300 mm, to be folded in an available height of the order of 2100 mm, while at the same time respecting the standardized overall gage width for road transport, particularly by semitrailer.
Two jib tip elements are unfolded or folded simultaneously, which allows the number and duration of operations to be reduced.
Unfolding or folding is performed using motorizing systems which already exist for other functions (lifting cable, ram for the overall unfolding/folding of the jib), and thus without calling for special motorizing.
The operations of unfolding and of folding the jib tip elements do not require manual interventions that involve a significant amount of effort.
Finally, these unfolding and folding operations become achievable in a minimum lateral amount of space which is brought down to the width of the points via which the crane rests on the ground.
REFERENCES:
patent: 2573528 (1951-10-01), Woodslayer et al.
patent: 3433117 (1986-03-01), None
patent: 331856 (1989-09-01), None
patent: 414646 (1991-02-01), None
patent: 473518 (1992-03-01), None
patent: 536060 (1993-04-01), None
patent: 0 733 584 A1 (1996-09-01)
Brahan Thomas J.
Oliff & Berridg,e PLC
Potain
LandOfFree
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