Telescopic Jibs

Abstract

This invention relates to a locking device for a telescopic jib constituted by at least three sections and by a motive member connected between the first and second sections, and comprising at least one bolt capable of integrating the second and third sections in their relative end positions, wherein this bolt is arranged on the rear end of the third section and may be selectively inserted into at least three catches, said catches being respectively unitary with the rear end of the second section, with an element unitary with the first section and with the front end of the second section, whilst the second catch is arranged near the front end of the first section.

Description

The present invention relates to telescopic jibs, with which certain cranes are provided, and more particularly to a locking device for a telescopic jib having at least three sections.

It is known to expand the different sections of jibs that have at least three sections.

As is known, a first ram is arranged between the first and second sections and a second ram between the second and third sections. This arrangement, which requires the use of two rams, generally leads to heavy and cumbersome equipment.

In order to obviate these disadvantages, the applicants have conceived a device for locking the different sections together, which, when operating in successive phases, enables the different sections of a telescopic jib comprising at least three sections to be extended out, with one ram connected between two of the sections.

The invention therefore has for its subject a locking device for a telescopic jib constituted by at least three sections and by a motive member, preferably a ram, connected between the first and second sections.

This device comprises at least one bolt arranged at the rear end of the third section and capable of being selectively inserted into at least three catches. These catches are unitary, respectively, with the rear end of the second section, with an element unitary with the first section and with the front end of the second section, the second catch moreover being arranged near the front end of the first section.

According to a preferred embodiment, the bolt is constituted by fingers mounted to slide in a slideway unitary with the third section, capable of being actuated by a ram.

Moreover, the catches are advantageously constituted by apertures made in the elements with which they are unitary.

Finally, the element with which the second catch is unitary may be constituted by a rod fixed to the inner face of the bottom of the first section.

The invention will be described in greater detail with reference to the accompanying drawings, in which:

FIG. 1 is a schematic section through a telescopic jib provided with the locking device according to the invention;

FIG. 2 and 3 are partial views in section of a telescopic jib provided with the device according to the invention.

Referring now to the drawings, FIG. 1 shows a telescopic jib comprising three sections. In the present case, section 1 constitutes the bottom section articulated to the turret or the platform of a crane, section 2 is an intermediate section and section 3 is usually designated as boom section. The jib is in the "non-telescoped out" position, so that section 3 is arranged inside section 2, which is itself arranged inside section 1. A motive member, such as a hydraulic ram 4, is connected between sections 1 and 2.

A device with bolt 5 is arranged at the end of the section 3 and comprises at least one bolt such as fingers 6 or 7 mounted to pivot on the element 3 in the schematic representation shown. Finger 6 may cooperate with catches 8 and 9 unitary with section 2 and respectively arranged at the level of the rear and front ends of said section 2. As for the finger 7, it may penetrate into the catch 10 unitary with a rod 11 fixed to the bottom 12 of the section 1 and substantially parallel to the axis of said section 1.

FIGS. 2 and 3 show the locking device according to the invention in an embodiment given by way of example.

According to this embodiment, a support 13 is made unitary with the section 3. It comprises slideways 14 for guiding the fingers 6 and 7. A connecting rod 15 is articulated to the support 13 about an axis 16, whilst a ram 17 is connected between support 13 and connecting rod 15. Return tippers 18 are articulated about axes 19 on the support 13. The tippers 18 are provided with grooves 20 which cooperate with lugs 21 unitary with the fingers 6 and 7 for controlling the displacement of said fingers 6 and 7. Finally, a threaded rod 22 is connected between a shouldered shaft 23 about which the return tippers 18 and the connecting rod 15 are articulated.

It will be noted that the catches 8, 9 and 10 are constituted by apertures made in the actual walls of the sections 1, 2 and 3. Moreover, switches 24 for controlling the supply and/or delivery of the rams 4 and 17 are arranged to be unitary with the section 3. The switches 24 are actuated by cams 25, some of which are unitary with an extension of the threaded rod 22 and another with an end of the rod 11. These switches 24 belong to the assembly for servo-controlling the different movements of the rams which makes possible the sequence operation as explained hereinafter.

The completely closed jib may operate as follows:

The finger 6 is inserted into the catch 8 of section 2 (FIG. 2). By extending the ram 4, the momentarily integral group of sections 2 and 3 emerges from the section 1. It will moreover be noted that, inas much as the jib is not oriented towards the ground, this movement may be effected without locking the finger 6 in the catch 8. The finger 6 is then automatically removed from the catch 8 in order to insert the finger 7 into the catch 10 of the rod 11 and thus provisionally integrate sections 1 and 3. The section 2 is then returned into the section 1. Finger 7 is then removed from catch 10 in order to lock finger 6 into catch 9. Sections 2 and 3 are therefore integrated. It is then sufficient to remove the section 2 from section 1, by extending the ram 4, in order to terminate the telescoping of the jib.

It will be noted that the two movable sections of the jib have been telescoped automatically and with a single ram 4, whatever the orientation of said jib. Operation may in particular be carried out with the jib in any inclined position. This automatic maneuver which is completely mechanised, and this possibility of telescoping, which is independent of the orientation, are new advantages which the machines known prior to the present invention did not have. In fact, the practical use of the new machines according to the invention contributes a simplification of the equipment and a simplicity of maneuver which were previously unknown.

It will furthermore be noted that the simplification of the equipment is essentially due to the judicious arrangement of the bolt 5 which enables it to cooperate with the different catches 8, 9 and 10. The prior arrangements did not enable the different sections 1, 2 and 3 to be selectively integrated with a single bolt, and, consequently, as several rams 4 and/or several rams 17 were required, were more complex and expensive than the arrangement according to the invention.

Claims

What is claimed is:

1. Locking structure for a telescopic jib constituted by at least a first outer section, a second section and a third inner section, an element connected to the first section and by a single motive member connected between the first and second sections and comprising at least one bolt disposed on the rear end of the third section and capable of integrating the second and third sections in telescoped positions and in extended positions, the bolt being adapted for selective insertion in at least three locking catches the first of which is unitary with the rear end of the second section, thus to integrate the second and third sections to move them together relatively to the first section, the second catch being unitary with the element connected to the first section near the front end of the first section to maintain the third section in extended position relatively to the first section after extension of the assembled second and third sections relatively to the first section whereby the second section may be free to move rearwardly relatively to the first and third sections, the third catch being unitary with the front end of the second section to integrate the second and third sections whereby the assembled second and third sections may be extended together relatively to the first section, all said rearward and extended movements being effected by the single motive member.

2. A device as claimed in claim 1, wherein the bolt is constituted by fingers mounted to slide in a slideway unitary with the third section and capable of being actuated by a ram.

3. A device as claimed in claim 1, wherein the catches are constituted by apertures made in the elements with which they are unitary.

4. A device as claimed in claim 1, wherein the element with which the second catch is unitary is constituted by a rod fixed on the inner face of the bottom of the first section.