GB2184092A

GB2184092A - Luffing jib cranes

Info

Publication number: GB2184092A
Application number: GB08629425A
Authority: GB
Inventors: Harry Hellwig; Klaus-Dietrich Sturm; Horst Schreiber
Original assignee: MAN Takraf Fordertechnik GmbH
Current assignee: Takraf GmbH
Priority date: 1985-12-11
Filing date: 1986-12-09
Publication date: 1987-06-17
Also published as: DE3640064A1; GB2184092B; DD243262A1; GB8629425D0

Abstract

A luffing jib crane provided with a carrier 5 which is arranged beneath the jib 6 and whose pivot 8 coincides with the pivot point 9 of the jib 6 and with first luffing cylinders 1 disposed between the carrier 5 and the crane structure 3, and further luffing cylinders 11 are arranged in the vicinity of the jib mounting 9, between the jib 6 and the carrier 5 or the upper portion 3 of the crane structure. The advantage is that large load moments are achieved both in the shallow and in the steep position of the jib 6. <IMAGE>

Description

SPECIFICATION Luffing jib cranes This invention relates to jib cranes, and in particular to such cranes having a telescopic jib having a large range of luffing movement.

Disclosed in patent specification GB 598 408 is a luffing apparatus which makes it possible to achieve a high support moment and thereby large load moments, by means of a carrier mounted rotatably on the upper portion of the crane and movably on the jib, with the jib in the horizontal or slightly luffed working position. However, the large spacing of the mounting locations of the jib and the luffing cylinders which are arranged between the upper portion of the crane and the carrier means that it is not possible to achieve large lift heights, as a result of the limitation of the luffing cylinder length.

In the case of known automobile cranes, the spacing of the mounting locations of the jib and the luffing cylinders is kept small thereby making it possible to achieve large luffing angles and thereby great lift heights. A disadvantage is that, by virtue of the low support moment in the horizontal jib position, only the inherent mass of the jib can be luffed up.

Furthermore, patent specification DD 224 012 discloses a luffing mechanism for jib cranes, in which the mounting points of the luffing cylinders are arranged longitudinally displaceable both on the jib and also on the upper portion of the crane.

Luffing apparatuses with displaceable luffing cylinder mountings may admittedly have a greater luffing range, but they require a higher level of expenditure as the point of engagement of the luffing cylinder mounting on the jib and the upper carriage arrangement of the crane varies, and therefore the entire range must be dimensioned for the relatively high mounting forces. Added to that is that additional energy is also required for actual displacement purposes. Another disadvantage is that, as a result of the limited load carrying capacity of the luffing cylinders and in order to ensure longitudinal mobility of the pivot mounting points of the luffing cylinders, that construction can only be used in relation to jib cranes with low load moment.

The invention is based on the problem of providing a luffing mechanism which can transmit a load moment both in the horizontal and in the steep operating position of the jib and in which the mounting locations of the luffing cylinders are arranged at a precisely defined location on the jib and the upper portion of the crane respectively.

According to the present invention there is provided a luffing jib crane having first luffing cylinders pivotally mounted in fixed mountings between an upper portion of the crane structure and a carrier pivotally mounted on said structure, the telescopic extension movement of the first luffing cylinders producing a first range of luffing movement of said carrier and the jib which is pivotably mounted on said structure and which is carried by the carrier during such luffing movement, the mounting location of the carrier coinciding with the pivot point of the jib, and further luffing cylinders being arranged between the jib (6) and the carrier or the crane structure for producing a second range of luffing movement of the jib.

The mounting locations of the first luffing cylinders for effecting the first shallow luffing range are not fixedly connected to the jib but to the carrier on which the jib is supported.

The force components in the longitudinal direction of the jib are transmitted to the jib mountings by way of the carrier. Disposed in the vicinity of the jib mountings are the further luffing cylinders for producing the steep range of luffing movement, of which upper mountings are fixedly and rotatably connected to the jib and lower mountings are arranged either on the carrier or on the upper portion of the crane. In the shallow range of luffing movement, luffing up is effected only with the front luffing cylinders, until they move into their limit position. In that connection the rear luffing cylinders are mounted on the carrier.

When the rear luffing cylinders are mounted on the upper portion of the crane, they are telescopically extended jointly with the front luffing cylinders. When, in that alternative embodiment, the crane is luffed further beyond the shallow or flat range of luffing movement, the jib moves away from the support location on the carrier and the system of the front luffing cylinders with carrier remains in that position. The rear luffing cylinders continue the luffing movement of the jib until the limit position of the rear luffing cylinders if reached.

Two embodiments of the invention wiil now be described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a crane according to the present invention showing the shallow or flat range of luffing movement achieved with the rear luffing cylinder arranged between the jib and the carrier, Figure 2 shows the steep range of luffing movement of the embodiment shown in Fig.

1, Figure 3 is a side elevation of another embodiment of a crane according to the present invention showing the shallow range of luffing movement achieved with the rear luffing cylinder arranged between the jib and the upper portion of the crane, and Figure 4 shows the steep range of luffing movement of the embodiment shown in Fig.

3.

In the embodiment illustrated in Fig. 1, the front luffing cylinders 1 are mounted with their base pivot points 2 in the upper swivel por tion 3 of the crane. The upper mountings 4 of the front luffing cylinders 1 are arranged on a carrier 5. In this arrangement the jib 6 lies loosely on a front support location 7 of the carrier 5. The location of the rear pivot mounting 8 of the carrier 5 coincides with the pivot point 9 of the jib 6. The base pivot points 10 of the rear luffing cylinders 11 are disposed on the carrier 5. The upper pivot mountings 12 of the rear luffing cylinders 11 are arranged on the jib 6.When the front luffing cylinders 1 have reached their fully extended length and the luffing movement is continued with the rear luffing cylinders 11, the jib 6 comes away from the support location 7 on the carrier 5 and the jib 6 moves into the steep range of luffing movement.

Fig. 2 shows the steep range of luffing movement in the embodiment in which the front luffing cyliners 1 together with the carrier 5 remain in the upper limit position of the shallow range of luffing movement. The rear luffing cylinders 11 are extended to reach the upper limit position of the steep range of luffing movement.

In the second embodiment shown in Figs. 3 and 4, the shallow range of luffing movement is shown in Fig. 3. The front luffing cylinders 13 are mounted with their base pivot points 14 on the upper portion 15 of the crane. The upper mountings 16 of the luffing cylinders 13 are disposed on a carrier 17. The location of the rear mounting 18 of the carrier 1 7 coincides with the pivot point 19 of the jib 20.

The jib 20 rests loosely on a front support location 21 of the carrier 17. The rear luffing cylinders 22 have their lower pivot mounting 23 located in the upper portion 15 of the crane. The upper pivot mounting 24 of the rear luffing cylinders 22 are disposed on the jib 20. In the shallow range of luffing movement, the front luffing cylinders 13 and the rear luffing cylinders 22 are telescopically extended jointly. That increases the support movement.

Fig. 4 shows the steep range of luffing movement of the embodment in which the front luffing cylinders 13, together with the carrier 17, remain in the upper limit position in respect of the shallow range of luffing movement. The rear luffing cylinders 22 which have not yet reached their fully extended position are now extended into fully extended position which achieves the upper limit position of the steep range of luffing movement.

Claims

1. A luffing jib crane having first luffing cylinders pivotally mounted in fixed mountings between an upper portion of the crane structure and a carrier pivotally mounted on said structure, the telescopic extension movement of the first luffing cylinders producing a first range of luffing movement of said carrier and the jib which is pivotably mounted on said structure and which is carried by the carrier during such luffing movement, the mounting location of the carrier coinciding with the pivot point of the jib, and further luffing cylinders being arranged between the jib (6) and the carrier or the crane structure for producing a second range of luffing movement of the jib.

2. A luffing jib crane as claimed in claim 1, in which said further luffing cylinders are arranged closer to the pivot point of the jib than the first luffing cylinders.

3. A luffing jib crane as claimed in claim 1 or claim 2, in that other lifting elements are provided instead of the hydraulic luffing cylinders.

4. A luffing jib crane substantially as hereinbefore desribed with reference to and as illustrated in Figs. 1 and 2 or Figs. 3 and 4 of the accompanying drawings.