Traversing hoists – Methods
Reexamination Certificate
2000-01-21
2002-07-23
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Methods
C212S178000, C212S177000
Reexamination Certificate
active
06422408
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and a device for mounting the constituent elements of the revolving part of a tower crane, this invention being more particularly intended at the construction and mounting of the masthead of tower cranes.
Heavy-duty cranes used on building and civil engineering work sites are generally “top turning”, that is to say have a stationary mast, the height of which can be adjusted by means of additional mast elements, and a revolving top part which can be oriented about a vertical axis and which comprises a delivery jib and a counterjib which constitutes a support for the counterweights.
More specifically, the revolving part of such a crane usually includes a revolving pivot, surmounted by a masthead also known as the “jib bearers”, the jib and the counterjib being situated one on each side of the masthead. The jib is articulated by its rear end to the front face of the jib bearer and is held in a roughly horizontal position by means of one or more lines of jib tie rods each obliquely connecting the top of the jib bearer to a point on the jib. Similarly, the counterjib is articulated by its anterior end to the rear face of the jib bearer and is kept in a roughly horizontal position by means of one or more lines of counterjib tie rods each obliquely connecting the top of the jib bearer to a point on the counterjib.
European Patent Application EP 0 635 450 A1, in the name of the Applicant, describes a method for mounting the delivery jib and the counterjib of such a tower crane. According to this method, the jib elements are aligned and assembled on the ground with their tie rods, then the jib tie rods, and possibly those of the counterjib, are raised and aligned using auxiliary lifting gear such as a mobile crane. Next, using the same equipment, the entire jib or counterjib is lifted up with the tie rods, and the jib or counterjib is offered up to the previously mounted masthead so that the free ends of the lines of tie rods are offered up correctly to the top of the masthead, thus allowing the tie rods to be pinned directly to the top of the masthead.
European Patent Application EP 0 846 650 A1 in the name of the Applicant also discloses a method for mounting the tie rods of the jibs of tower cranes, of the kind at issue here, whereby:
In a first step, the counterjib is joined to the base of the already mounted masthead, the end of the tie rod of the counterjib is joined to a mounting strap attached temporarily to the masthead, the strap is raised using a mounting cable which forms lifting tackle between this strap and the top of the previously mounted masthead until the tie rod is aligned, and the counterjib tie rod is pinned to the top of the masthead.
In a second step, the same is done with the jib tie rod or rods, that is to say the jib is joined to the base of the masthead, on the opposite side to the counterjib, by pinning, the free end of the jib tie rod or tie rods is or are connected to a mounting strap attached temporarily to the masthead, this strap is lifted up using the aforementioned mounting cable which forms more lifting tackle between said strap and the top of the previously mounted masthead until the tie rod or tie rods, joined together, are aligned, and the jib tie rod or tie rods is or are pinned to the top of the masthead.
This method too is implemented by initially aligning and assembling the jib elements on the ground, and by using auxiliary lifting gear to offer up the counterjib, and then the jib, against the previously mounted masthead.
This solution proves to be more attractive than the one in European Patent Application EP 0 635 450, particularly in the case of heavy-duty tower cranes, the jibs of which have many tie rods. However, it still has certain drawbacks.
In particular, the method according to document EP 0 846 650 A1 requires special motorization, with an auxiliary winch and tackle or with a handwinch and tackle, to align and pin the jib and counterjib tie rods, hence resulting in a certain amount of constructional complication in the device for implementing the method.
Setting up the tackle needed for aligning and pinning the jib and counterjib tie rods also takes time. This method also ties up the auxiliary lifting gear for a relatively lengthy period of time, which lifting gear has to be used not only for the main handling operations but also during the intermediate operations which are lifting up the counterjib tie rods and the jib tie rods using the aforementioned tackle. Finally, the method under consideration requires several manual pinning assembly operations to be carried out “up in the air”, at a certain risk to those involved who have to move along those parts of the crane which are being temporarily held by the auxiliary lifting gear.
What is more, this kind of method entails producing the revolving part of the crane as three “packages”, namely the “jib” assembly, the “counterjib” assembly and the “jib bearer with tackle” assembly. This requires a significant amount of space for storing and transporting the constituent parts of the revolving part, and also means that the auxiliary lifting gear has to raise the three “packages” in succession.
SUMMARY OF THE INVENTION
The present invention sets out to avoid these drawbacks, and its object is therefore to provide a method and a device for mounting the constituent elements of the revolving part of a tower crane, of the kind in question, which simultaneously allow:
a reduction in the volume needed for storing and transporting the constituent parts of the revolving part, looking to nest the elements where possible;
a reduction in the number of components and auxiliary parts specific to the crane mounting operations, particularly by eliminating the tackle and its motorization, which previously were dedicated to these operations;
a simplification and limitation on the number of operations of assembling the constituent elements of the revolving part done “up in the air”, and making these operations more safe for those involved by reducing the number of handling and assembly operations performed “up in the air”, particularly by reducing the number of main packages;
a reduction in the time for which the auxiliary mounting gear, such as the mobile crane, is used.
To that end, the method according to the invention essentially consists, in the case of a tower crane, the revolving part of which comprises a masthead or jib bearer, a delivery jib which is articulated by its posterior end to the front face of the jib bearer and connected to the top of the jib bearer by one or more tie rods, and a counterjib which is articulated by its anterior end to the rear face of the jib bearer and connected to the top of the jib bearer by one or more tie rods:
in assembling, on the ground, an assembly formed by the counterjib, its tie rod or rods and a rear part of the jib bearer which is made in two separable parts, namely a front part and the rear part, and in also assembling on the ground another assembly formed by the jib, its tie rod or rods and the front part of the jib bearer:
using handling or lifting gear, in lifting up the pre-built assembly formed by the counterjib, its tie rod or rods and the rear part, the jib bearer, and in assembling this assembly, by pinning along a horizontal axis, on the revolving pivot or on a mast or mast-cab element connected to this revolving pivot;
using the handling or lifting gear, in lifting up the pre-built assembly formed by the jib, its tie rod or rods and the front part of the jib bearer, and in assembling this assembly, by pinning along a horizontal axis, on the revolving pivot or the mast-cab;
in using at least one pin to join the respective tops of the front part and the rear part of the jib bearer together.
Thus, the invention is based essentially on initially dividing the jib bearer into two parts, a front part and a rear part respectively, which allows two distinct assemblies to be pre-built on the ground, one of these assemblies comprising the counterjib and the rear part of the jib bearer, a
Lissandre Michel
Millet Yves
Brahan Thomas J.
Oliff & Berridg,e PLC
Potain
LandOfFree
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