US3349925A - Jib crane - Google Patents

Description

Oct. 31, 1967 J. N. M. WAERUM ETAL 3,349,925

JIB CRANE Filed March 24, 1966 2 Sheets-Sheet 1 INVENTORS 9w.) Mme/M M (421,, m um) ATTORNEYS 7 Filed March 24, 1966 Oct. 31', 1967 J. N. M. WAERUM ETAL 3,349,925

JIB CRANE 2 Sheets-Sheet 2 INVENTORS wax), wfiwdw+ k ATTORNEY 5 United States Patent 3,349,925 JIB CRANE Julius N. M. Waerum, Hellerup, and Helge E. Krex, Charlotteulund, Denmark, assignors to Byggeriets Maskinstationer Aktieselskab, Copenhagen, Denmark Filed Mar. 24, 1966, Ser. No. 537,168 Claims priority, application Denmark, Mar. 26, 1965, 1,579/ 65 9 Claims. (Cl. 212-48) ABSTRACT OF THE DISCLOSURE This invention relates to apparatus for vertically stabilizing a crane jib by means of a jib holding rope extending from a yoke which is pivotally supported upon the upper end of the crane jib. Pulleys for receiving a hoisting rope are mounted on the yoke on one side of the yoke pivot axis and guide rollers for the hoisting rope are mounted on the other side of the yoke pivot ,axis. The jib holding rope is attached to the yoke means at a point extending beyond the location of the guide rollers and attached to a derrick at a point horizontally spaced from the pivoting axis of the jib. The jib holding rope is of a fixed length and the jib is elevated by a pivoting motion of the derrick. The placement of the jib holding rope connection to the yoke means in conjunction with the location of the pulleys and guide rollers with respect to the yoke pivot axis provides an improvement in the stabilization of the jib means especially at steep positions or elevations of the jib. Jib stabilization may alsoqbe obtained by attaching the jib holding rope to an angled extension of the yoke.

This invention relates to a crane having a jib which is pivotally mounted at its lower end and which at its upper end carries a shaft pivotably supporting a yoke which on one side of the shaft carries at least one pulley for a hoisting rope and on the other side of the shaft-carries a guide roller for the hoisting rope and is connected with a balancing rope or balancing rope set, the jib being held in raised position by means of a holding rope or holding rope set extending from the yoke to a point horizontally spaced from the pivoting axis of the jib. Such a yoke is used for keeping the pulley or pulleys of the hoisting rope at a horizontal distance from the upper end of the jib so that the load keeps clear of the jib even when the latter is in a steep position.

In a known crane of this type, the holding rope or holding rope set of the jib is attached to the shaft of the yoke and the length of this holding rope or holding rope set determines the pivoting position ofthe jib. The length of the balancing rope or balancing rope set is so selected that the yoke will assume a substantially horizontal position, ie a position such that the pulley and the, guide roller are located at approximately the. same level.

The invention is based on balancing rope or balancing rope set of the yoke may, without difficulty, take over the function of the holding rope or holding rope set of the jib and that, in addition to the apparent simplification of the crane, even an improved stabilization of the latter is obtained. Accordingly, the characteristic feature of the invention is that the holding rope or holding rope set of the jib is constituted by the balancing rope or balancing rope set of the yoke.

If the balancing rope or balancing rope set is attached the recognition that the to an extension of the yoke located in: an imaginary plane 3,349,925 Patented Oct. 31, 1967 through the axis of the shaft of the yoke and the axis of the pulley or pulleys, it has been found that in very steep positions, the jib may have a tendency to tilt backwards. If, however, according to a further feature of the invention, the balancing rope or balancing rope set is attached to an extension of the yoke forming an angle with the said imaginary plane through the axis of the yoke shaft and the axis of the pulley or pulleys, it has been found that even if the jib assumes very steep positions the crane may operate satisfactorily without the occurrence of the said tendency towards backward tilting of the jib.

The invention will now be described in further detail with reference to the accompany drawings in which FIG. 1 shows one form of a crane according to the invention in non-loaded condition,

FIG, 2 part of the crane illustrated in FIG. 1 in loaded condition,

FIG. 3 part of another form of the to the invention,

FIG. 4 a diagrammatic illustration of parts of a known crane, as a background for explaining the principles of the invention, and

FIG. 5 a diagram for explaining the invention.

In the drawings, 1 is a crane jib which, at its lower end, is pivotably mounted on a base 3 by means of a shaft 2. The base is provided on its bottom face with a turntable 4 cooperating with a corresponding turntable 5 on a foundation 6. In the embodiment illustrated in FIG. 1 the turntable 5 is directly mounted on the foundation 6, but it will be understood that a crane tower may be interposed between these two parts.

The base 3 is provided with a counterweight 7 and moreover carries ,a winch 8 for a hoisting rope 9 and another winch 10 for a hauling rope 11. At its upper end the jib 1 carries a shaft 12 on which a yoke 13 is pivotably mounted. On one side of the shaft 12 the. yoke 13 carries a set of pulleys 14 and on the other side of the shaft 12 a guiding roller 15. In the embodiment of FIGURES 1 and 2. the yoke 13 is extended beyond the guiding roller 15, and to the end of this extension 16 there is attached a set of ropes 17, the guiding ropes, which are located in a plane perpendicular to that of the drawing so thatv the set is illustrated as a single rope. The two ropes of the rope. set 17 are spaced from one another in the lateral direction for the purpose of stabilizing the crane towards lateral forces. The lower end of the rope set 17 is attached to a derrick 18 which is pivotably connected to the base 13 adjacent the foot point of the jib 1. The outer end of the derrick carries a set of pulleys 19 for the hauling rope 11 and also extends around the set of pulleys 20 carried by the base 3.

The hoisting rope 9 extends from the winch 8 across the guiding roller 15 to the set of pulleys 14 and around a block 21 carrying ahook 22.

In the embodiment illustrated in FIGURE 3, the. extentension 16 to which the set of ropes 17 is attached, forms an angle with the imaginary plane through the shaft 12 and the axis of the set of pulleys 14, the extension 16 being perpendicular to the said plane.

The crane diagrammatically illustrated in FIGURE 4 comprises, in addition to the parts already mentioned, a further set of ropes 23 which is connected with the shaft 12 of the yoke 13.

The invention is based on the recognition that this additional set of ropes 23 may be omitted, and its functi'on may be taken over by the set of ropes 1-7 whichwill.

crane according then constitute both the holding rope set of the jib and the balancing rope set of the yoke. At this point attention should be drawn to the fact that the known construction illustrated in FIGURE 4 is statically overdefined, which is apparent from the fact that if the set of ropes 23 is removed the crane will assume the position illustrated in FIGURE 1. On the other hand, the crane according to the invention is statically defined, which is apparent from the fact that if one of the structural elements 17 or 18 is removed the crane will collapse.

The crucial point of the present invention is the recognition that the crane can be used without any trouble without provision of the additional set of ropes 23. At first sight one would believe that when a load is suspended in the hook 22, the yoke would tilt to vertical position instead of tilting to the position shown in FIGURE 2. It can be demonstrated, however, that the position illustrated in FIGURE 2 is a position of equilibrium which, surprisingly, is at a very good approximation independent of the size of the load. This will be explained in further detail with reference to FIGURE 5. In the diagram shown in that figure, the jib 1 is represented by a rod 1', the set of ropes 17 by another rod 17' and the yoke 13, 16 by a rod 13', 16'. Assuming that the rods are weightless and all connections between the rods are frictionless, the rod system may be moved to the position shown in FIG- URE 5, where the rods are denoted by 1', which position corresponds to the position of the crane in non-loaded condition as illustrated in FIGURE 1. It will be realized that the crane will assume the position illustrated in FIG- URE 1 in non-loaded condition because the pull of the jib, resulting from the force of gravity, will give rise to a moment in the anti-clockwise direction about the shaft 2, which moment will maintain the set of ropes 17 in the position illustrated.

The position which the outer end of the rod 13', 16 assumes in this position of the rod system, is denoted by 14'. If it is now assumed that the rod 1 is tilted about its foot print, its upper end will move along a circle denoted by the reference character a in the figure. Moreover, the rod 17' may rotate about its lower point and its upper end will move along a circular are denoted by the reference character b. Since the length of the rod 13', 16' is conStant, the position of this rod may, by virtue of these geometrical conditions, be depicted in each angular position of the rod 1. This has been done in FIGURE for three different positions of the rod, namely the position 1, the position 1" and the position 1" and to these correspond three different positions of the outer end of the yoke, 14', 14" and 14". It will be seen that the intermediate point 14" is located at a lower level than the two other points 14' and 14". This means that if the rod system is tilted about the foot point of the rod 1 and 17, the tip of the yoke will move along a curve having a minimum point which is not very far removed from the starting point. In other words, if the tip of the yoke is loaded the system will on its own account move to this minimum point or point of equilibrium.

The illustration in FIGURE 5 is based on a certain inclination of the rod 1', namely corresponding to the inclination of the derrick 18 illustrated in FIGURE 5. If the inclination of the derrick 18 is changed by means of the hauling winch 10, it can be shown by repeated tracing of the diagram in FIGURE 5 that also in such a changed position the curve along which the tip of the yoke moves by tilting of the system will have a minimum point. Only when the position of the jib 1 comes very close to vertical position will it be found that the said point of equilibrium no longer exists, but by suitably selecting the length of the jib 1, the yoke 13, 16, the set of ropes 17 and the derrick 18, viz, as illustrated in FIGURE 1, the crane can be used without difiiculty up to very steep positions of the jib, and even steeper positions in the case of the embodiment illustrated in FIGURE 3. Besides the geometrical conditions explained above, the conditions of forces, viz, the weight of the jib 1, the pull in the set of ropes 17, the pull in the hoisting rope part 9 and the gravity of the load, will of course also have to be considered. These conditions may be treated mathematically but it has been found that very complicated trigonometric equations will result which cannot be manually solved. However, these have been mechanically solved by means of mathematical computers and it has been found that when the conditions of forces are combined with the geometrical conditions, a point of equilibrium does in fact exist. It has been mentioned above that the position of equilibrium is very nearly independent of the weight of the load. This is true when the weight of the load is above a value which is great relative to the weight of the jib 1' itself. It has been mentioned previously that the pull of the force of gravity on the jib 1 gives rise to a moment in the anti-clockwise direction about the shaft 2 so that in non-loaded condition the crane 2 will assume the position shown in FIGURE 1. In the case of a small load only a small tilting of the yoke will take place. In the case of a great load the yoke tilts in the anti-clockwise direction but only until the previously mentioned point of equilibrium has approximately been reached.

It will be understood that instead of the said set of ropes 17 a single rope may be used, viz, if the jib is not .subjected to any lateral forces, or if other measures are taken to counteract such forces.

We claim:

1. A crane comprising:

a supporting structure,

jib means having a lower end and an upper end and pivotally mounted at said lower end about a horizontal pivot axis on said supporting structure,

yoke means having a yoke pivot axis intermediate a first end portion and a second end portion, said yoke means being pivotally supported at said yoke pivot axis at said upper end,

said yoke means including pulley means for receiving a hoisting rope, said pulley means being located at said first end portion,

said yoke means further including guide roller means for receiving said hoisting rope, said guide roller means being located at a point intermediate said pivot axis and said second end portion,

jib holding and balancing means connected to said yoke means at said second end portion outwardly of said guide roller location and to a point horizontally spaced from the horizontal pivot axis of said jib, and said ji'b holding and balancing means forming the only means for stabilizing said jib means.

2. A crane according to claim 1 wherein said connection with said yoke means is at a position furthest removed from said yoke pivot axis.

3. A crane according to claim 1 wherein said second end portion forms an angle with a plane formed through said yoke pivot axis and the location of said pulley means and said guide roller means.

4. A crane according to claim 3 wherein said angle is approximately 5. A crane according to claim 1 further comprising derrick means pivotally mounted on said supporting structure and wherein said jib holding and balancing means is of a fixed length, said derrick means including said point horizontally spaced from the pivot axis of said jib, and said jib means being pivoted on said supporting structure in accordance with the pivotal movement of said derrick means.

6. A crane according to claim 5 further comprising hauling means mounted on said supporting structure and connected to said derrick means for pivoting said derrick means in a vertical plane.

7. A crane according to claim 6 wherein the connection of said yoke means is at a position within said sec- 5 6 and end portion furthest removed from said yoke pivot References Cited aXlS- UNITED STATES PATENTS 8. A crane according to claim 6 wherein said second end portion forms an angle with a plane formed through 7 3/1955 Brown 212 48 said yoke pivot axisand the location of said pulley means 5 FOREIGN PATENTS and said guide roller means. 1,142,016 3/1957 France.

9. A crane according to claim 8 wherein said angle 686,384 1/1940 Germany.

appmxlmately ANDRES H. NIELSEN, Primary Examiner.

Claims (1)

1. A CRANE COMPRISING: A SUPPORTING STRUCTURE, JIB MEANS HAVING A LOWER END AND AN UPPER END AND PIVOTALLY MOUNTED AT SAID LOWER END ABOUT A HORIZONTAL PIVOT AXIS ON SAID SUPPORTING STRUCTURE, YOKE MEANS HAVING A YOKE PIVOT AXIS INTERMEDIATE A FIRST END PORTION AND A SECOND END PORTION, SAID YOKE MEANS BEING PIVOTALLY SUPPORTED AT SAID YOKE PIVOT AXIS AT SAID UPPER END, SAID YOKE MEANS INCLUDING PULLEY MEANS FOR RECEIVING SAID YOKE MEANS INCLUDING PULLEY MEANS FOR RECEIVING SAID FIRST END PORTION, SAID YOKE MEANS FURTHER INCLUDING GUIDE ROLLER MEANS FOR RECEIVING SAID HOISTING ROPE, SAID GUIDE ROLLER MEANS BEING LOCATED AT A POINT INTERMEDIATE SAID PIVOT AXIS AND SAID SECOND END PORTION, JIB HOLDING AND BALANCING MEANS CONNECTED TO SAID YOKE MEANS AT SAID SECOND END PORTION OUTWARDLY OF SAID GUIDE ROLLER LOCATION AND TO A POINT HORIZONTALLY SPACED FROM THE HORIZONTAL PIVOT AXIS OF SAID JIB, AND SAID JIB HOLDING AND BALANCING MEANS FORMING THE ONLY MEANS FOR STABILIZING SAID JIB MEANS.

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