GB2176456A

GB2176456A - Apparatus for changing over the operation of the lifting cable in a crane

Info

Publication number: GB2176456A
Application number: GB08610326A
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: GB2176456B; DE3515156C2; GB8610326D0; CH670622A5; DE3515156A1

Abstract

The changeover between two- and four-stranded operation of the lifting cable of a bridge or tower crane is carried out automatically without the need for the block and tackle to be lowered to ground level. The crane has a trolley (1) movable on a raised track and comprising a change-over pulley block (9) having a vertically displaceable coupling member (12), portions (14) for receiving the coupling member (12), and openings in the coupling member (12) and receiving portions (14) for receiving a horizontally displaceable pin (13). The pin (13) is axially loaded by a compression spring (22) such that on alignment of the openings (15) in the coupling member (12) and receiving portions (14), the pin (13) moves automatically thereinto, thus retaining the coupling member (12) in a raised position for four-stranded operation. The pin (13) may be automatically retracted by the abutment of a transverse member against fixed stops at a particular point on the raised track, whereupon the coupling member (12) drops into a lowered position for two-stranded operation and is retained by a stop. <IMAGE>

Description

SPECIFICATION Apparatus for changing over the operation of the lifting cable in a crane The invention relates to an apparatus for changing over the lifting cable from two-stranded to fourstranded operation and vice-versa in a bridge or tower crane having a trolley capable of travelling on a raised track or jib.

In known apparatus, a lifting block and tackle arrangement is provided comprising a change-over cable pulley block having a vertically displaceable coupling member, a horzontally displaceable pin and openings in lateral portions on the trolley and a passage in the coupling member for receiving the pin. The pulley block is lowered to ground level and the pin is displaced manually.

Alternatively, the coupling member of the pulley block is provided with a horizontal bolt the ends of which spread clamping arms apart against the action of a compression spring as the pulley block is raised. At a desired position, the bolt engages with openings in the clamping arms and the clamping arms close under the action of the spring, thus fixing the position of the bolt. For releasing the bolt, unlatching means are provided on the pulley block which is lowered to ground level for changing over from four- to two-stranded operation, the unlatching means preferably being brought into operation by hand. The pulley block is then raised to the trolley, whereby the clamping arms are pivoted apart by means of the unlatching means until the bolt is released.The pulley block is then lowered to ground level and the unlatching means preferably returned to their inoperative position by hand.

An object of the invention is to provide an apparatus with a minimum number of simple components wherein the pin is displaced automatically and therefore as quickly as possible.

The invention provides apparatus for changing the operation of a lifting cable between two- and four-stranded operation in a crane having a trolley movable on a raised track, the trolley comprising a block and tackle arrangement for lifting a load, a change-over pulley block having a vertically displaceable coupling member, portions for receiving the coupling member, and openings in the cou pling member and receiving portions for receiving a horizontally displaceable pin, wherein the pin is axially loaded by a compression spring such that on alignment of the openings in the coupling member and receiving portions, the pin moves automatically thereinto, thus retaining the coupling member in a raised position for four-stranded operation, and the coupling member is retained by a stop in a lowered position for two-stranded operation when the pin is retracted from the openings.

Automatic release of the pin may also be achieved when the pin comprises a transverse member which rests on a stop on the trolley when in the position for four-stranded operation. Stop means are then provided in the vicinity of the end of the jib of a tower crane such that the pin is automatically retracted as the trolley reaches a predetermined point on the track.

An embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a side view of the apparatus according to the invention; Figure 2 is an enlarged side view of part of Figure 1 showing the pin positioned for four-stranded operation; Figure 3 is a plan view of the part shown in Figure 2 with the pin positioned for two-stranded operation; and Figure 4 is a section along the line IV-IV shown in Figure 2, in which the position for four-stranded operation is shown in the left-hand half and that for two-stranded operation in the right-hand half.

A trolley 1 is axially movable by means of running wheels 2 on the track of a tower crane jib.

The trolley 1 has, in addition to the running wheels 2, a frame 3 and cable pulleys 4a, 4b. During twostranded operation, the lifting cable 5 runs over one cable pulley 4a on the frame 3, then over cable pulleys 6, 7 on a tackle block 8 and finally over the second cable pulley 4b on the frame 3. A vertically displaceable change-over cable pulley block 9 with a cable pulley 10 is arranged in a recess of the tackle block 8. The pulley block 9 has a narrow coupling member 12 which is provided at its upper end with a horizontal passage or opening 11 which is able to receive a pin 13 and whose longitudinal axis runs transversely to the axes of the cable pulleys 6, 7, 10 and parallel to the direction of travel of the trolley 1.

Two upwardly directed portions 14a, 14b are arranged sufficiently far apart on the frame 3 to allow the coupling member to be received therebetween. The portions 14 are each provided with an opening for receiving the pin 13. A pin retaining member 16 is attached to the coupling member 12, preferably at the upper end thereof.

The retaining member 16 is fork-shaped in transverse vertical section and is vertically displaceable to a limited extent between the portions 14 and two] or [-shaped members 17. The retaining member 16 has an annular shoulder 18 which rests on the upper edges of the members 17 during twostranded operation, the upper portion of the retaining member 16 acting as a stop for the pin 13 and preventing horizontal movement thereof.

On the portion 14b closest to the free end of the crane jib, there is detachably fixed a housing 19 having a passage 20 wherein a compression spring 22 is arranged surrounding the shaft 21 of the pin 13. One end of the compression spring 22 rests on the inner end face of the housing 19 and the other end on an annular face of the pin having a diameter larger than that of the shaft 21. The shaft 21 passes through the base of the housing 19 and carries at its outwardly projecting end a horizontal transverse member 23 which abuts against the housing 19 in two-stranded operation and has two arms directed radially outward from the pin 13.

The configuration and dimensions of the housing 19, the pin 13 and the compression spring 22 are such that the head of the pin is retracted almost completely into the housing 19 during twostranded operation when the compression spring 22 is fully compressed and the retaining member 16 rests on the shoulder 18. On change-over to four-stranded operation, the coupling member 12 is raised and the pin passes automatically through the opening in portion 14b, through the opening 11 in the coupling member 12 now aligned therewith and through the opening in portion 14a such that movement of the coupling member relative to the portions 14 is prevented.

Two stops 24 are rigidly arranged on the jib in the vicinity of the crane mast such that at a predetermined position the transverse member 23 abuts agains the stops 24 and the pin 13 is retracted into the housing 19 and two-stranded operation is reintroduced.

During two-stranded operation, the cable pulley 10 of the pulley block 9 is located beneath the cable pulleys 6, 7 and the retaining member 16 is located in its lower position (shown in the right-hand portion of Figure 4), the upper portion of the retaining member 16 preventing the spring-loaded pin 13 from passing through the opening 11 in the coupling member 12 into the opening in the portion 14a. On changing over to four-stranded operation, the pulley block 9 is moved upwards and is received between the two portions 14, the retaining member 16 being raised simultaneously with the coupling member 12. The openings in the portions 14 and the coupling member 12 become aligned and the pin 13 is automatically displaced by the compression spring 22 through the aligned openings.A secure lock is thereby achieved, since the compression spring 22 acts continuously on the pin to prevent retraction thereof.

If a change-over from four-stranded operation back to two-stranded operation is required, the pin 13 has to be retracted into the housing 19. For this purpose, the trolley 1 is driven to its end position closest to the jib pivot, such that the transverse member 23 abuts against the stops 24 and the pin 13 is retracted into the housing 19 during further movement of the trolley 1. The coupling member 12 is thus automatically released and the coupling member 12 and cable pulley block 9 drops under gravitational forces. The retaining member 16 attached to the coupling member 12 falls therewith until the shoulder 18 rests on the upper edge of the members 17, the pin 13 being thereby prevented from returning to its previous position.

In this way, the need to lower the pulley block to ground level is obviated.

Claims

1. Apparatus for changing the operation of a lifting cable between two- and four-stranded operation in a crane having a trolley movable on a raised track, the trolley comprising a block and tackle arrangement for lifting a load, a change-over pulley block having a vertically displaceable coupling member, portions for receiving the coupling member, and openings in the coupling member and receiving portions for receiving a horizontally displaceable pin, wherein the pin is axially loaded by a compression spring such that on alignment df the openings in the coupling member and receiving portions, the pin moves automatically thereinto, thus retaining the coupling member in a raised position for four-stranded operation, and the coupling member is retained by a stop in a lowered position for two-stranded operation when the pin is retracted from the openings.

2. Apparatus as claimed in Claim 1, wherein the raised track is provided on the jib of a tower crane and the longitudinal axis of the pin is parallel thereto, the pin comprising a transverse member engageable with stop means located in the vicinity of the pivoted end of the jib such that the pin is automatically retracted from the openings at a predetermined point on the track.

3. Apparatus substantially as herein described with reference to the accompanying drawings.