A LOW-PROFILE CRANE WITHOUT TOPPING TOWER

Abstract: A hoisting line (9) extends from a winch (8), over a second pulley (12) at the head end (3) of the jib (1) of a crane, around a movable pulley (14) and over a third pulley (13) at the head end (3) of the jib (1) to a depending load hook (18). The movable pulley (14) is supported by a topping line (7) which extends over a first pulley (11) at the tail end (2) of the jib (1), around a fifth pulley (15) fixedly mounted on the base (4) of the crane and is attached to the first pulley (11). Loading in the hoisting line (9) is therefore transferred to the topping line (7) extending between the first and fifth pulleys (11 and 15) and topping of the jib (1) about an axis (5) between the tail and head ends (2 and 3) is effected by a light-weight piston-cylinder assembly (6).

Description: A Low-Profile Crane without Topping Tower TECHNICAL FIELD OF THE INVENTION The invention relates to a crane in which topping is eff¬ ected " by coupling the topping rigging to the hoisting rig- ging in such a way that no topping tower or mast is requi¬ red, to provide a compact, low-profile crane. BACKGROUND ART In conventional deck crane construction, the topping rig¬ ging extends from a topping tower or mast to the head end of the jib and is controlled independently of the hoisting rigging " by means of a topping winch. However, in some applications, for example on hoard ships,- the necessary weight and overall height of a crane provided with a top¬ ping tower or mast has disadvantages and so alternative means, such as a fluid-operated piston-cylinder assembly must he provided to effect topping of the jih. However, this necessitates the use of a very heavy-duty piston- cylinder assembly and the jib and its mounting must be constructed with corresponding robustness. This not only increases the cost of the crane, but substantially reduces any saving in weight achieved by the omission of the top¬ ping tower or mast. » DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a crane which does not require a topping tower or mast for the topping rigging but which is substantially lighter and more economical to construct than known cranes pro¬ vided with fluid-operated, piston-cylinder assemblies for topping the jib. According to the invention, there is provided a crane comprising a jib having a tail end and a head end; first pulley means mounted on the tail end of the jib, second OMPI and third pulley means mounted on the head end of the jib, and fourth pulley means reciprocable between the first pulley means at the tail end of the jib and the second and third pulley means at the head end of the jib; mounting means for supporting the jib for pivotal move¬ ment about a horizontal axis extending transversely of the jib; a double-acting, piston-cylinder assembly ext¬ ending between the jib and the mounting means for pivot¬ ing the jib about the horizontal axis; fifth pulley means fixedly mounted on the mounting means below the first pulley means at the tail end of the jib; at least one topping line extending around the first and fifth pulley means and having opposite ends respectively connected to the fourth pulley means and to one of the first and fifth pulley means; a hoisting winch; and a hoisting line ext¬ ending from the hoisting winch to the second pulley means, around the second and fourth pulley means, from the fourth pulley means to the third pulley means and around the third pulley means to depend from the head end of the jib. Preferably, the first, second, third and fourth pulley means are supported so that the or each topping line acts on the fourth pulley along an axis which is disposed above the horizontal pivotal axis of the jib. In a crane such as this, where the hoisting rigging is coupled to the topping rigging by means of the fourth pulley means, the turning moment exerted on the jib by a load suspended from the depending end of the hoisting line is counteracted by the moment exerted by the topp¬ ing rigging extending between the first and fifth pulley means. It is therefore possible to effect topping by means of a relatively light-duty piston-cylinder assembly. Thus, when it is required to lift a load, the hoisting winch subjects the hoisting line to tension and this ten¬ sion is transferred into the topping rigging by means of the fourth pulley means coupling the hoisting and topping riggings. The fourth pulley means therefore tend to move towards the head end of the jib so that the topping rigg¬ ing tends to pull the first pulley means down to the fixed fifth pulley means, thus tending to raise the jib. In this case, it is often necessary to use the piston-cylin¬ der assembly to prevent the jib from topping until the hoisting line has been sufficiently shortened. Thereafter, topping of the jib can be effected merely by releasing the piston-cylinder assembly or by applying a very small lift- ing force by means of the piston-cylinder assembly. Similar considerations apply when lowering a load and so has been found that effective topping control can be effected with a relatively light-duty piston-cylinder assembly. Moreover, as a result of the coupling bf the hoisting and topping riggings, substantially level luff¬ ing may also be achieved. Clearly, to maintain static equiblibrium when a load is supported from the head end of the jib, the mounting means must be prevented from tilting and, for this purpose, it is convenient to use a counter-weight which is supported on the mounting means on the opposite side of the hori¬ zontal pivotal axis of the jib to the load. However, the components of the crane may be constructed so that this counter-weight is not excessive and the total weight of the crane is less than an equivalent crane provided with a topping tower or mast. To increase the loading transmitted from the hoisting line to the topping rigging, the second and fourth pulley means may each be provided with a plurality of pulleys so that there is a two or more part purchase between these two pulley means. However, even where the second and fourth pulley means are each only provided with one pulley, the loading transmitted from the hoisting line to the topping rigging is twice the weight of the load. OMPI - - Where a plurality of topping lines are used, it is possible to ensure that the loading on each such topping line does not exceed the loading on the hoisting line by ensuring that the number of topping lines equals the number of lengths of the hoisting line extending from the fourth pulley means to the second and third pulley means. In this case, the third and fifth pulley means must also each contain the pulleys for each of the topping lines. To. ensure that the crane operates in a predictable manner, particularly where more than one topping line is employed, the fourth pulley means may be mounted for movement along guide means which extend along a rectilinear axis between the first pulley means at the tail end of the jib and the second and third pulley means at the head end of the jib. To avoid jack-knifing, or uncontrolled lifting of the jib, as a result of tensile loading on the hoisting line, the first pulley means and the fifth pulley means may be dis¬ posed at different distances from the horizontal pivotal axis so that the axis of the first pulley means is movable into an end position alongside the fifth pulley means on a radial plane containing the horizontal pivotal axis and the axis of the fifth pulley means. In this situation the topping line extending between corresponding pulleys in the first and fifth pulley means are substantially aligned with the radial plane and so, as the first pulley means move into this position, the turning moment imposed on the jib by each said topping line progressively decreases to zero. In fact, elevation of the jib beyond this inclina¬ tion results in the imposition of a restoring force in each said topping line which urges the jib to pivot in the opposite direction. BRIEF DESCRIPTION OF THE DRAWINGS Two embodiments of the invention are hereinafter described, O P /,, IP by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a schematic view of a preferred embodiment of the invention, showing a jib and its mounting means in phantom outline; Figure 2 is a view of the hoisting and topping riggings of the crane shown in Figure 1; Figure 3 is a schematic view of the hoisting and topping riggings of an alternative form of crane; and Figure h is a schematic view of the riggings shown in Figure 3, when the crane is topped. BEST MODES FOR CARRYING OUT THE INVENTION The crane shown in Figure i has a jib i formed of two triangular frames 16 which are held together by cross braces 17 so as to converge towards the head end 3 of the jib 1. First pulley means in the form of two pulleys 11 are mounted at the tail end 2 of the jib 1, adjacent one of the apices of each of the triangular frames 16. Second and third pulleys 12 and 13 are mounted at the head end 3 of the jib i, adjacent another of the apices of each of the triangular frames 16. A hoisting line 9 extends from a hoisting winch 8 supported on a mounting platform k and is trained around the second pulley 12, around a fourth pulley Ik , between the tail and head ends 2 and 3 of the jib 1, and over the third pulley 13 to a depending load hook 18. The mounting platform k also supports a shaft 5 which in turn supports the jib 1 for pivotal movement about a horizontal axis extending transversely of the jib 1 and coinciding with the third of the apices of each of the triangular frames 16. The mounting platform 4 also supports fifth pulley means, in the form of two O PI Λ,,. WIPO , pulleys 15 which are arranged below the pulleys 11 of the first pulley means at the tail end 2 of the jib i. Opp¬ osite ends of the two topping lines 7 are respectively attached to one of the pulleys 11 and to one arm of a yoke 19 supporting the fourth pulley Ik and the two topp¬ ing lines are trained around the first and fifth pulleys 11 and 15. The mounting platform is mounted above a fixed ring gear 20 and provided with a pinion 21 meshing with the ring gear 20. A motor 22 carried by the mounting plat¬ form k is operable to drive the pinion 21 to thereby cause a rotation of the mounting platform 4 about a ver¬ tically extending axis 23 through the centre of the ring gear 20. Part 24 of the mounting platform 4 serves as a counter-weight ' for at least partly balancing loads ' carr¬ ied by the load hook 8. The upper members 10 of the two triangular frames 16 serve as rectilinear guides for the yoke19 connecting the two topping lines 7 to the fourth pulley 14 so as to allow the fourth pulley 14 to move backwards and forwards along a rectilinear path between the two pulleys 11 of the first pulley means at the tail end 2 of the jib 1 and the second and third pulleys 12 and 13 at the head end 3 of the jib 1. A light-weight hydraulic piston-cylinder 6 extends from the jib 1 to the mounting platform 4. As shown in Figure 2, when the hoisting line 9 supports a load L there is an anti-clockwise turning moment of L.x, where x is the horizontal distance between the load hook 18 and the axis of the shaft 5. However, as shown, a loading of L is transmitted from the hoisting line 9 to each of the topping lines 7 through the fourth pulley 14 and, as the horizontal distance between the axis of the shaft 5 and the line of action of the topping lines 7 OM - 7 - extending between the first and fifth pulleys 11 and 15 is approximately y, the clockwise turning moment resist¬ ing the load L is approximately 4L.y. The force there¬ fore required to be exerted by the hydraulic piston- cylinder assembly 6 is thus the difference between value of these clockwise and anti-clockwise turning moments and so topping can be effected with very little effort. In the alternative arrangement of the crane, shown in Figure 3, there is only one topping line 7 and a load L suppor- ted by the load hook 18 induces a tension of 2L in this single topping line 7. In this case, the topping line 7 must be capable of withstanding twice the loading in the hoisting line 9. Clearly, from reference to both illustrated embodiments, it is advantageous if the .hoisting line 9 extending from the hoisting winch 8 to the second pulley 12 passes through or close to the axis of the shaft 5 so as to en¬ sure that the clockwise turning moment exerted by the topping line of lines 7 is not substantially counteracted by the tension in the hoisting cable 9 extending between the jib 1 and the hoist 8. As shown in Figure 3, the centre distance 24 between the shaft 5 and the first pulley 11 is greater than the cen¬ tre distance 25 between the shaft 5 and the fifth pulley 15. Thus, when the jib 1 is elevated, as shown in Figure 4, the first pulley 11 moves to an end position.along¬ side the fifth pulley 15 such that the axes of the first and fifth pulleys (Hand 15) lie on a radial plane 26 containing the axis of the shaft 5. On further upward tilting movement of the jib 1, the tensile loading in the topping -line 5 urges the jib to return to the posi¬ tion it occupies for the arrangement shown in Figure 4.

Claims: CLAIMS A crane, comprisin :- a jib (i) having a tail end (2) and a head end (3); first pulley means (ll) mounted on the tail end (2) of the jib (i), second and third pulley means (12 and 13) mounted on the head end (3) of the jib (i),,and fourth pulley means (14) reciprocable between the first pulley means (ll) at the tail end (2) of the jib (l) and the second and third pulley means (12 and 13) at the head end (3) of the jib (1); mounting means (4) for supporting the jib (l) for pivotal movement about a horizontal axis (5) ext¬ ending transversely of the jib (i); a double-acting, piston-cylinder assembly (6) ext¬ ending between the jib (i) and the mounting means (4) for pivoting the jib (l) about the horizontal axis (5); fifth pulley means (15) fixedly mounted op the mounting means (4) beϊow the first pulley means (ll) at the tail end (2) of the jib (l); at least one topping line (7) extending around the first and fifth pulley means (ll and 15) and having ~ opposite ends respectively connected to the fourth pulley means (14) and to one of the first and fifth pulley means (ll and 15); a hoisting winch (8); and a hoisting line (9) extending from the hoisting O Λ,„ winch (8) to the second pulley means (12), around the second and fourth pulley means (12 and 14), from the fourth pulley means (14) and around the third pulley means (13) to depend from the head end (3) of the jib (i). 2. A crane, according to Claim 1, characterised in that the first, second, third and fourth pulley means (ii, 12, 13 and 14) are supported so that the or each topping line (10) acts on the fourth pulley means (14) along an axis which is disposed above the horizontal pivotal axis (5) of the jib (i). 3. A crane, according to Claim 1 or Claim 2, charac¬ terised in that:- the number of topping lines (7) equals the number of lengths of the hoisting line (9) extending from the fourth pulley means (14) to the second and third pulley means (12 and 13); and the first and fifth pulley means (ll and 15) con¬ tain pulleys for each of the topping lines (7) so that the topping lines (7) are each subjected to the same loading as the hoisting line (9). 4. A crane, according to any preceding claim, charac¬ terised in that guide means (iO) for the fourth pulley means (14) extend along a rectilinear axis between the first pulley means (ll) at the tail end (2) of the jib (l) and the second and third pulley means (12 and 13) at the head end (3) of the jib (l). 5. A crane, according to any preceeding claim, charac¬ terised in that the first pulley means (ii) and the fifth pulley means (15) are disposed at different distances (24 and 25) from the horizontal pivotal axis (15) so that the first pulley means (ll) are movable into an end position alongside the fifth pulley means (15) so that the hori¬ zontal pivotal axis and the axes of the first and fifth pulley means (ll and 15) lie in the same plane (26).

Inventors: MORRISON R
Applicants: MORRISON R, SPEEDCRANES LTD
Application year: 1979
Main classification: B66C23
IPC codes: B66C23