GB2176455A

GB2176455A - A cable pulley block

Info

Publication number: GB2176455A
Application number: GB08610325A
Authority: GB
Inventors: Werner Bantle
Original assignee: MAN WOLFFKRAN
Current assignee: MAN WOLFFKRAN
Priority date: 1985-04-26
Filing date: 1986-04-28
Publication date: 1986-12-31
Also published as: GB2176455B; DE3515155A1; DE3515155C2; CH669376A5; GB8610325D0

Abstract

A cable pulley block (4) has a support divided into two relatively rotatable portions (5), a first cable pulley (8, 9) being mounted on each portion (5). A further cable pulley (11) is movable between a position below the first cable pulleys (8, 9) for two-stranded operation and a position above the first cable pulleys (8, 9) for four-stranded operation. The first cable pulleys (8, 9) are separable by means of relative rotation of the portions (5) to allow the further cable pulley to pass on change-over between the first cable pulleys (8, 9) such that the width of the cable pulley block (4) may be reduced. <IMAGE>

Description

SPECIFICATION A cable pulley block The invention relates to a cable pulley block for changing the operation of a lifting cable between two- and four-stranded operation in a lifting apparatus.

In known apparatus, a block and tackle arrangement having lifting apparatus is provided comprising two first cable pulleys or cable pulley sets, preferably equal in diameter and located at the same height, a support being preferably deltashaped in elevation and supporting the first cable pulleys, and a cable pulley deflection block having a further cable pulley or cable pulley set, preferably of the same diameter as the first cable pulleys and being attached to the lower end of a vertically displaceable connecting member, which may be raised for four-stranded operation or lowered for two-stranded operation.

In a cable pulley block of the known type, the distance between the first cable pulleys must be greater than the greatest diameter of the further cable pulley since the further cable pulley moves between the first cable pulleys in order to effect the change-over between two- and four-stranded operation. The known cable pulley block support must therefore have a relatively large structural width.

An object of the invention is to provide a cable pulley block having a relatively small structural width without impairing or rendering impossible the relative movement between the first cable pulleys and the further cable pulley.

This object is achieved according to the invention by the provision of a cable pulley block for changing the operation of a lifting cable between two- and four-stranded operation in a lifting apparatus, wherein the cable pulley block comprises a support having two pivotably-connected portions, a first cable pulley mounted on each of the said portions and separable by relative rotation thereof, and a further cable pulley movable relative to the first cable pulleys between a position therebelow and a position thereabove on separation thereof.

In this way, the structural width of the support is reduced when the portions are in a closed position.

A narrow structural width is advantageous since a smaller cable pulley block is cheaper to manufacture. When a narrow cable pulley block is used in a tower crane, the trolley as well as the jib length can be shorter in design so that the inherent weight of these components is reduced, thus enabling the load moment of the crane to be increased.

To allow a change-over between two- and fourstranded operation to be carried out rapidly and without depositing the cable pulley block onto a separate frame, according to a further feature of the invention the cable pulley block has part-cylindrical guide means and wedge-shaped faces for initiating and guiding the separation of the first cable pulleys.

The cable pulley block has a particularly small structural width, if, according to an advantageous development of the invention, the distance between the first cable pulleys corresponds approximately to the sum of the widths of the connecting member and the part-cylindrical guide means on the support.

An embodiment of the invention is now described with reference to the accompanying drawings, wherein: Figure 1 shows a side view of the cable pulley block in a position for two-stranded operation; and Figure 2 shows a side view of the cable pulley block of Figure 1 during the change-over to fourstranded operation.

A trolley having a frame 1 is capable of travelling in known manner along the horizontal jib of a tower crane. The trolley carries two deflection pulleys 2 for guiding a lifting cable 3 such that the cable 3 passes around two first cable pulleys 8, 9 of the cable pulley block 4.

The cable pulley block 4 comprises a support which is delta-shaped in elevation and is divided lengthwise along a vertical plane into two symmetrical portions 5. The two portions 5 are pivotably joined together at their lower corners by means of a hinge. The hinge pin may be formed by a horizontal bolt 6 which extends parallel to the shafts 7 of the first cable pulleys 8, 9.

The two first cable pulleys 8, 9 are preferably equal in diameter and at equal heights, and are mounted symmetrically about the vertical plane on the portions 5. In the case of two-stranded operation, the lifting cable 3 is guided by the first cable pulleys 8, 9 only. The first cable pulleys 8, 9 are arranged at a relatively small distance from one another. Part-cylindrical guiding faces 10 are symmetrically arranged concentrically to the first cable pulley shafts 7 for guiding the separation of the first cable pulleys 8, 9.

A further pulley 11 which is adjustable in height and is vertically movable relative to the first cable pulleys 8, 9, is provided for allowing the changeover between two- and four-stranded operation.

The further cable pulley 11 is preferably equal in diameter to and has its axis parallel with that of the first cable pulleys 8, 9, and has a holder 12 and a connecting member 13 extending vertically upwards therefrom. The connecting member 13 is releasably connected to the trolley frame 1 by means of a horizontal pin supported in passages in two lateral portions 16 on the trolley frame 1 and penetrating a passage 14 in the connecting member 13.

The longitudinal axis of the shaft of the further cable pulley 11 and the longitudinal axis of the connecting member 13 are arranged so as to lie in the same vertical plane dividing the support into the portions 5 when the portions 5 are in a closed position. The holder 12 of the further cable pulley 11 has wedge-shaped faces 17 located above the pulley 11 in the lower region between the part-cylindrical guiding faces 10, which allow initiation of the relative rotation of the portions 5 during relative vertical movement of the first cable pulleys 8, 9 and the further cable pulley 11. The holder 12 of the further cable pulley 11 also has wedge-shaped faces 18 located below the pulley 11 as well as corresponding part-cylindrical supporting faces 19, by which the holder 12 rests during two-stranded operation on the corresponding cylindrical faces of the hinge means.The guiding faces on the holder 12 are composed of wedge-shaped faces 17, partcylindrical guiding faces 20 adjacent thereto and further wedge-shaped faces 18, the further wedgeshaped faces 18 adjoining the part-cylindricsal guiding faces tangentially at an angle of about 120 from the longitudinal axis of the connecting member.

To change over from two- to four-stranded operation, the entire pulley block 4 is initially raised by means of the crane lifting gear until the passage 14 in the connecting member 13 is aligned with the passages in the lateral portions 16, and the pin 15 is then introduced there into (see Figure 1). The support 5, 8, 9 is subsequently lowered by suitable actuation of the lifting gear. During the lowering operation, the two portions 5 are pivoted outwards into an open position due to the part-cylindrical guiding faces 10 engaging with and sliding on the wedge-shaped faces 17 and then on the part-cylindrical guiding faces 20 of the holder 12, the position of the angle of maximum opening being shown in Figure 2. The part-cylindrical guiding faces 10 are guided on the guiding faces 20, 18 of the holder 12 by further lowering of the support 5, 8, 9 such that the two portions 5 close completely when the support 5, 8, 9 is located immediately beneath the further cable pulley 11.

To change-over from four- to two-stranded operation, the support 5, 8, 9 is raised while the connecting member 13 is still coupled to the trolley frame 1, the portions 5 being opened and then closed again by guidance of the part-cylindrical guiding faces 10 on the wedge-shaped faces 18 of the holder 12 and part-cylindrical guiding faces 20 and the wedge-shaped faces 17 until the twostranded operation position shown in Figure 1 is regained. The pin 15 may then be removed.

Claims

1. A cable pulley block for changing the operation of a lifting cable between two- and fourstranded operation in a lifting apparatus, wherein the cable pulley block comprises a support having two pivotably-connected portions, a first cable pulley mounted on each of the said portions and separable by relative pivoting of the said portions, and a further cable pulley mounted to allow relative movement between the further cable pulley and the first cable pulleys between a position in which the further cable pulley is below the first cable pulleys and a position in which the further cable pulley is above the cable pulleys on separation of the first cable pulleys.

2. A cable pulley block as claimed in Claim 1, wherein the support is substantially delta-shaped and is divided into the two portions along a substantially vertical plane, the two portions being substantially symmetrical about the plane.

3. A cable pulley block as claimed in Claim 1 or 2, wherein the two portions are pivotable about hinge means located below the further cable pulley.

4. A cable pulley block as claimed in any one of the preceding claims, wherein guide means are provided such that relative pivoting of the portions is effected by vertical displacement of the further cable pulley relative to the first cable pulleys.

5. A cable pulley block as claimed in Claim 4, wherein the guide means comprise part-cylindrical faces concentric with the first and further cable pulleys.

6. A cable pulley block as claimed in Claim 5, wherein the guide means further comprise wedgeshaped faces adjacent the further cable pulley for initiating separation of the first cable pulleys.

7. A cable pulley block as claimed in any one of the preceding claims, wherein the first cable pulleys and the further cable pulley are of equal diameter.

8. A cable pulley as claimed in any one of the preceding claims, wherein the further cable pulley is attached to the lower end of a substantially vertical, vertically-displaceabie connecting member whereby the further cable pulley is vertically displaced.

9. A cable pulley block as claimed in any one of the preceding claims, wherein the cable pulley block is attached to the trolley of a bridge or jib crane.

10. A cable pulley block as claimed in Claim 8 and 9, wherein the connecting member is releasably attachable to the trolley for retaining the connecting member in a raised position.

11. A cable pulley block substantially as herein described with reference to the accompanying drawings.