EP0379448A1 - Crane with a lifting jib and with a jib push-back device - Google Patents

Abstract

This crane is of the type comprising a rotating pivot (5), a jib- holder (6) which is integral with the pivot (5), a mechanism platform (7) connected to the rear of the pivot with a mobile counterweight (8), a lifting jib (9) articulated on the pivot, and means (20, 24) for lifting the jib and for raising weights. According to the invention, there is provided a jib push-back device (16), associated with the platform (7) which is suspended on the jib-holder (6), at the rear, by means of tie rods (14), and, at the front, by means of rodding (15) which also comprises pushers (37), the front of the platform (7) being linked to the pivot (5) by shafts (13) which are mobile in vertical slots (12). When the jib (9) arrives in the lifted position, means of support (54) supported by its foot (17) interact with the pushers (37) and the assembly resists continued movement. Applications: tower cranes, mobile cranes. <IMAGE>

Description

The present invention relates to a luffing jib crane of the type comprising a fixed or mobile support structure, such as a vertical tower, mounted on a rotating part about a vertical axis, consisting of a rotating pivot, an arrow carrier bearing on the rotating pivot, a platform of mechanisms located behind the rotating pivot and supporting a counterweight that can be moved from front to back and vice versa, and a lifting arrow directed towards the front and articulated at its base around a horizontal axis on the rotating pivot. The invention relates more particularly to an arrow return device, the operation of which is associated with the platform of the mechanisms, the object of this device being to avoid that in the raised position, the arrow does not come back to the rear of the lifting device, in particular under the action of external stresses, which can be, for example, inertia effects, the action of the wind or a breaking of slings.

There are already known different types of lifting jib cranes equipped with a jib return device.

According to a first known type, the platform of the mechanisms forms with the rotating pivot a monobloc assembly provided with an inclined ramp descending towards the rear on which a mobile counterweight moves retained by one or more control cables passing over one or more pulleys of return arranged on the front part of the monobloc assembly and fixed under the boom at a predetermined distance from its articulation to allow optimum movement of the counterweight when the boom is raised. In this case, the boom in the raised position comes to rest on elastic means, the fixed members of which are secured to the boom holder or of the platform of the mechanisms and the movable members of which cooperate with stops arranged on the boom and exert together a progressive effort on the arrow to keep it in stable equilibrium. These elastic means can be mechanical, such as springs, hydraulic or pneumatic, such as jacks, or even electro-mechanical, a particular embodiment of these means being indicated by document US-A-4 270 663; generally they generate dynamic effects in the structure of the arrow by causing uncontrolled oscillations which harm the behavior of the device.

According to a second known type, illustrated for example by document DE-A-3 438 937, the platform of the mechanisms is provided with a support on which are articulated two bent arms which are arranged on either side of the platform and the rear ends of which carry the counterweight and the front ends are connected to the base of the boom by articulated connecting bars; the assembly formed by the front part of the arms, the connecting bars, the base of the arrow and the platform of the mechanisms forms a deformable quadrilateral. In this case, the raising of the boom causes the rotation of the two bent arms around their common articulation on the support of the platform and consequently the displacement of the counterweight forwards. During lifting, the counterweight exerts a degressive tilting moment around the articulation on the support; at the end of lifting, the counterweight passes vertically to this articulation then exerts a progressive moment of retention in the opposite direction to the previous one which opposes the continuation of the lifting movement of the boom and keeps the boom at a standstill stable balance. As it appears through the description of the operation, the boom return device combines here, unlike the previous one, the two functions of balancing the boom during lifting and returning the boom at the end of lifting, and consequently this device does not optimize the two functions. We can also cite here the document GB-A-930021, which describes a fairly equivalent embodiment, illustrated in particular by its figure 2.

The present invention remedies these drawbacks by providing a lifting jib crane whose jib return device is dissociated from the counterweight displacement device and does not cause uncontrolled oscillations.

To this end, the luffing jib crane according to the invention comprises in a known manner a rotating pivot surmounting a support structure such as a vertical tower, a jib holder integral with the rotating pivot and inclined towards the rear, a platform of the mechanisms connected to the rear of the rotating pivot on which is mounted rolling a counterweight movable from front to back and vice versa, a lifting boom articulated at its base on the rotating pivot, means for lifting the boom and lifting the loads and a device driving the displacement of the counterweight along the platform of the mechanisms, inclined slightly forward, by means of one or more cables connecting said counterweight to the base of the jib, and this crane with lifting jib is characterized in that the mechanism platform is suspended from the boom holder, in its rear part, by means of tie rods connection, and in its front part, by means of a connecting rod belonging to an arrow return device further comprising pushers bearing on the connecting rod and kept at rest in position on the arrow carrier by means of consoles 'support, and is provided in its front part with means forming substantially vertical slides for horizontal axes of connection with the rotating pivot or vice versa, and in that the jib foot carries support means cooperating with the free end pushers when the boom is in the raised position.

According to a preferred embodiment of the invention, the crankshaft of the arrow return device consists of a rigid assembly of two connecting rods forming a triangulated isosceles trapezium whose small base is articulated under the arrow carrier at intermediate height and of two other connecting rods articulated at their first end to the large base of the rigid trapezoid assembly and at their other end to two supports symmetrically fixed on either side on the front part of the platform of the mechanisms, and is assembled from such that in normal working position, the assembly of said connecting rod is flat.

According to an additional characteristic, the pushers of the arrow return device are articulated at their first end on the articulation axes connecting the two parts of the connecting rods previously defined.

Thus, at the end of lifting, the boom comes into contact with the free ends of the pushers which leave their support console on the boom holder and exert a resistant force tending to oppose the continuation of the movement; this effort is increasingly important as the boom is raised because the pushers move the hinge pins on the rear connecting the two parts of the crankshaft which are tensioned under the effect of the masses of the platform of the suspended mechanisms and counterweight.

Advantageously, at least one of the two pushers is adjustable in length and the support means of the boom foot cooperating with the free ends of the pushers form a guide funnel, so that the contact of the arrow on the two pushers takes place simultaneously and safely.

According to another characteristic, the means forming substantially vertical slides, for the axes of connection of the platform of the mechanisms with the rotary pivot, are constituted by lights vertical. In a particular construction, the connection of the front part of the platform of the mechanisms with the rotating pivot consists of two sets of clevis and tenon arranged symmetrically on either side of the rotating part of the crane; the ends of the platform side members form the tenons while the recovery elements on the rotating pivot form the yokes. Each yoke and tenon assembly is connected by an axis with two diameters, with a part of larger diameter constituting the central part which moreover comprises two large flats with parallel faces over its entire length and is arranged in the lumen formed in the tenon , while the second diameter smaller than the spacing of the flats is that of the two end parts of the axis which are mounted in the two branches of the yoke with the interposition of rings of diameter at least equal to that of the central part.

According to an additional characteristic, the lumens of the tenons are double and of rectangular shape and are each provided with two sliding pads, of greater thickness in their central part, which are arranged vertically inside and on either side. said lights so that they provide between them a space of constant width equal to the spacing of the flats of the connecting axes with two diameters.

This arrangement allows the front part of the platform of the mechanisms to move freely in the vertical direction with respect to the articulation on the rotary pivot, when the boom return device comes into action.

• Figure 1 est une vue d'ensemble latérale d'une grue conforme à l'invention, avec indication de deux positions de la flèche relevable ;
• Figure 2 est une vue latérale simplifiée de la partie haute de la grue, la flèche étant abaissée ;
• Figure 3 est une vue de dessus simplifiée de cette même partie haute ;
• Figure 4 est une vue similaire à figure 2, montrant la flèche en position relevée à l'instant où elle entre en contact avec les poussoirs du dispositif de renvoi de flèche ;
• Figure 5 est une vue similaire à la précédente, montrant la flèche en position relevée maximum et l'action du dispositif de renvoi de flèche sur la plateforme des mécanismes ;
• Figure 6 est une vue schématique en perspective du dispositif de commande de déplacement du contrepoids et du dispositif de renvoi de flèche ;
• Figure 7 est une vue en perspective éclatée de la liaison entre la plateforme des mécanismes et le pivot tournant ;
• Figure 8 est une vue en coupe suivant VIII-VIII de la liaison réalisée par les éléments visibles à la figure 7 ;
• Figure 9 est une vue en coupe partielle de l'extrémité des poussoirs coopérant avec les moyens d'appui prévus sur la flèche.

Anyway, the invention will be better understood with the aid of the description which follows, with reference to the appended schematic drawing representing, by way of nonlimiting example, an embodiment of this crane with lifting jib with deflection device arrow:

• Figure 1 is an overall side view of a crane according to the invention, with indication of two positions of the lifting boom;
• Figure 2 is a simplified side view of the upper part of the crane, the boom being lowered;
• Figure 3 is a simplified top view of the same upper part;
• Figure 4 is a view similar to Figure 2, showing the boom in the raised position at the time it comes into contact with the pushers of the boom return device;
• Figure 5 is a view similar to the previous one, showing the boom in the maximum raised position and the action of the boom return device on the platform of the mechanisms;
• Figure 6 is a schematic perspective view of the movement control device of the counterweight and the arrow return device;
• Figure 7 is an exploded perspective view of the connection between the platform of the mechanisms and the rotating pivot;
• Figure 8 is a sectional view along VIII-VIII of the connection made by the elements visible in Figure 7;
• Figure 9 is a partial sectional view of the end of the pushers cooperating with the support means provided on the arrow.

With particular reference to Figures 1 and 2, the crane shown schematically in the drawing comprises in a known manner a vertical tower 1 anchored to the ground, or rolling thereon, surmounted by a fixed pivot 2 supporting, via of an orientation device 3, a rotating part 4 mainly consisting of a rotating pivot 5, a jib holder 6, a platform of the mechanisms 7 on which is mounted rolling a movable counterweight 8, and a lifting boom 9.

The arrowhead 6 of triangular horizontal section, with point facing forward as shown in Figure 3, is integral with the rotating pivot 5 and is inclined to the rear.

The platform of the mechanisms 7, the framework of which consists of two longitudinal members 10 connected to the rotary pivot 5 by means of tenons 11 having openings 12 crossed by horizontal connecting axes 13, is suspended from the jib holder 6, in its rear part, by means of tie rods 14, and in its front part, by means of the connecting rod assembly 15 of an arrow return device 16, described in detail below.

The lifting jib 9 of rectangular or square section ends at its base with two legs 17 forming a gantry, articulated at 19 on the rear part of the rotary pivot 5, which allows it to step over the base of the jib holder 6 during lifting -see figure 3.

Mechanization of the upper part of the crane is ensured by:
- a boom lifting winch 20, mounted at the rear of the platform of the mechanisms 7, which controls the winding of a lifting cable 21 connecting the tip of the lifting boom 9 to the drum 22 of this winch passing over pulleys 23 disposed at the top of the arrow holder 6;
- a load lifting winch 24, also mounted on the platform of the mechanisms 7, which controls the winding of a lifting cable 25 on a drum 26, the lifting cable 25 passing over an angle corrector 27 and on a pulley 28 placed at the top of the arrow holder 6, and forming a haul between a hook 29 to which the load is suspended and the arrow holder 6 passing through the tip of the lifting arrow 9.

The dead weight of the lifting jib 9 is balanced by the counterweight 8 mounted rolling inside the side members 10 of the platform of the mechanisms 7 which has a slope α directed towards the front, the front end of this platform 7 being located lower than its rear end.

As shown in Figure 6, the counterweight 8 consists of several elements 18 attached suspended under the platform of the mechanisms 7 by means of rollers 30 rolling on the side members 10. In the stabilized position, the counterweight 8 is retained by a set of two cables 31 arranged symmetrically on either side of the platform of the mechanisms 7, fixed at 32 on the counterweight element 18 located closest to the tower 1 and at 33 on the upper members 34 of the foot of the lifting jib 9 in passing successively on pulleys 35 disposed at the rear of the platform of the mechanisms 7 and on pulleys 36 disposed at intermediate height on the rear link rods 14.

The deflection device 16 shown in FIG. 6 consists of the linkage 15 already mentioned and two pushers 37.

The connecting rod 15 is produced by a rigid assembly 38 of two connecting rods 39 forming a triangulated isosceles trapezium whose small base is articulated at 40 under the arrow-carrier 6 substantially at mid-height, and by two other connecting rods 41 linked by axes articulation 42 at the large base of the rigid assembly 38 forming a trapezoid and by suspension axes 43 to two supports 44 symmetrically fixed on the side members 10 towards the front end of the platform of the mechanisms 7. The two pushers 37 are articulated at their first end on the axes 42 connecting the two parts 38 and 41 of the connecting rod assembly 15. In the normal working position, the entire connecting rod assembly 15 forms a plane and the two pushers 37 rest freely on a console 45 fixed in a predetermined position on the front face of the jib holder 6 - see Figure 2.

As shown in FIGS. 7 and 8, the connection between the platform of the mechanisms 7 and the rotary pivot 5 is carried out by assembling the tenons 11 in yokes 46 by means of the connecting pins 13 which are at two diameters: the part of larger diameter 47 constitutes the central part of each axis 13, which moreover comprises two large flats 48 with parallel faces over its entire length and is arranged in the slots 12 of the stud 11, and the second diameter, smaller than the spacing of the flats 48, is that of the two end parts 49 of the axis 13 which are mounted in the two branches 50, 51 of the yoke 46 with the interposition of rings 52 of diameter at least equal to that of the central part 47. The openings 12 of the studs 11 are double and of rectangular shape and are each provided with two sliding shoes 53, of greater thickness in their central part, which are arranged vertically inside and on the right and left 'other of these lights 12 and in such a way that they provide between them a space of constant width "d" equal to the spacing of the flats 48 of the axes 13. The yoke 46 is integral with the rotary pivot 5.

The operation of the previously described crane is as follows:

In the position shown in Figure 2, the lifting boom 9 is in the low position and exerts a maximum moment of overturning on the front of the crane; to balance this moment, the counterweight 8 is then in the maximum retracted position on the platform of the mechanisms 7 and retained in this position by means of the cables 31. In this position, the linkage 15 forms a plane and the connecting axes 13 are located in the high position in the slots 12 formed in the studs 11 of the platform of the mechanisms 7, the slope α of which is then at its maximum value.

During the lifting of the boom 9, the overturning moment on the front of the crane exerted by the boom 9 gradually decreases and this decrease is compensated by the forward movement of the counterweight 8 along the platform of the mechanisms 7 under the action of its self-weight whose tangential component due to the slope, that is to say the component parallel to the platform 7, keeps the cables 31 in tension; as the arrow 9 straightens, the distance separating the fixing points 33 from the pulleys 36 decreases and the counterweight 8 approaches as much the vertical tower 1.

At the end of lifting, as shown in FIG. 4, the arrow 9 comes into contact with the pushers 37 by means of support means 54 fixed on the boom foot 17. Advantageously, at least one of the two pushers 37 is adjustable in length by means for example of a screwed head 55 and the support means 54 cooperating with the free ends 56, 57 of the pushers 37 form a guide funnel 58 in such a way that the contact of the arrow 9 on the two pushers 37 takes place simultaneously and in complete safety - see FIG. 9.

While the arrow 9 continues to straighten, the force exerted on the pushers 37 increases and causes the rearward displacement of the hinge pins 42 of the linkage 15; simultaneously the counterweight 8 continues to approach the vertical tower 1 and exerts an increasing force on the suspension axes 43 of the platform, that is to say ultimately on the linkage 15, this which has the effect of further increasing the resistance offered by the pushers 37.

By moving rearward, the articulation axes 42 of the pushers 37 cause, via the linkage 15, the lifting of the front part of the platform of the mechanisms 7 through the slides 12, with guidance by the axes 13.

In the final position, as shown in FIG. 5, the linkage 15 no longer forms a single plane and the connecting axes 13 are located in the low position in the slots 12 formed in the studs 11 of the platform of the mechanisms 7, the slope of which α is then at its minimum value. In the extreme positions, the axes 13 do not abut on the ends of the slots 12; the platform of the mechanisms 7 therefore remains permanently suspended from the jib holder 6.

By the combined and simultaneous action of the movement of the counterweight 8 and the deformation of the connecting rod assembly 15, the pushers 37 return the arrow 9 forward when one continues to want to straighten it beyond a position of security. An equivalent result is obtained when, under the action of the front wind, the boom 9 is pushed towards the rear of the crane.

A lifting jib crane is thus produced with a jib return device 16 dissociated from the movement device of the counterweight 8 but whose operation is associated with the platform of the mechanisms 7 and with the position of the counterweight 8 so that in position raised, the arrow 9 remains firmly maintained in equilibrium without causing uncontrolled oscillations whether in normal service or with wind.

Of course, the invention is not limited to the only embodiment of this luffing jib crane which has been described above, by way of example; on the contrary, it embraces all variants of construction and application respecting the same principle. In particular, we would not depart from the scope of the invention:
- By making the connection of the platform of the mechanisms with the rotating pivot by lights made on the rotating pivot instead of the platform of the mechanisms, or by any other functionally equivalent slide device;
- by modifying the shape of the connecting axes of the platform of the mechanisms with the rotating pivot;
- by modifying the positions of the joints such as 40 and 43, which can be higher or lower and more or less advanced;
- by using the same boom deflection device for lifting devices other than lifting jib cranes, in particular mobile cranes on wheels or on crawlers.

Claims (9)

1. Lifting jib crane with jib return device comprising a rotary pivot (5) surmounting a support structure such as a vertical tower (1), an arrow carrier (6) integral with the rotary pivot (5) and inclined towards the rear, a platform of mechanisms (7) connected to the rear of the rotary pivot (5) on which is mounted rolling a counterweight (8) movable from front to back and vice versa, a lifting jib (9) articulated at its base (in 19) on the rotary pivot (5), boom lifting means (20) and load lifting (24), and a device causing the movement of the counterweight (8) along the platform mechanisms (7), inclined slightly forward, by means of one or more cables (31) connecting said counterweight (8) to the base (17) of the boom (9), characterized in that the platform of the mechanisms (7) is suspended from the arrow holder (6), in its rear part, by means of tie rods (14), and in its p front part, by means of a linkage (15) belonging to an arrow return device (16) further comprising pushers (37) bearing on the linkage (15) and kept at rest in position on the arrowhead (6) by means of support brackets (45), and is provided in its front part with means (12) forming substantially vertical slides for horizontal connecting axes (13) with the rotary pivot (5), or vice versa, and in that the jib foot (17) carries support means (54) cooperating with the free end (56, 57) of the pushers (37) when the jib (9) is in the raised position. 2. Lifting jib crane according to claim 1, characterized in that the connecting rod assembly (15) of the jib return device (16) consists of a rigid assembly (38) of two connecting rods (39) forming an isosceles trapezoid triangulated whose small base is articulated (at 40) under the arrowhead (6) at intermediate height, and two other connecting rods (41) articulated (at 42) at their first end to the large base of the rigid assembly ( 38) forming a trapezoid and at their other end (at 43) to two supports (44) symmetrically fixed on either side on the front part of the platform of the mechanisms (7), and is assembled in such a way that in position normal working, all of said connecting rod assembly (15) is planar. 3. Lifting jib crane according to claim 2, characterized in that the pushers (37) of the jib return device (16) are articulated at their first end on the hinge pins (42) connecting the two parts (38 , 41) of the connecting rod assembly (15). 4. Lifting jib crane according to any one of Claims 1 to 3, characterized in that at least one of the pushers (37) is adjustable in length. 5. Lifting jib crane according to any one of claims 1 to 4, characterized in that the support means (54) of the jib foot (17) cooperating with the free ends (56,57) of the pushers (37 ) form a guide funnel (58). 6. Lifting jib crane according to any one of claims l to 5, characterized in that the means forming substantially vertical slides, for the connecting pins (13) of the platform of the mechanisms (7) with the rotary pivot (5 ), consist of vertical lights (12). 7. Crane with lifting boom according to claim 6, characterized in that the connection of the front part of the platform of the mechanisms (7) with the rotary pivot (5) consists of two sets of clevis (46) and tenon (11 ) arranged symmetrically on either side of the rotating part (4) of the crane, the ends of the side members (10) of the platform of the mechanisms (7) forming the studs (11) while the recovery elements on the pivot turning (5) form the yokes (46), each assembly with yoke (46) and tenon (11) being connected by an axis (13) of two diameters, with a part of larger diameter (47) constituting the central part of the axis (13) which also has two large flats (48) with parallel faces over its entire length and is arranged in the slot (12) formed in the stud (11), while the second diameter smaller than the spacing of the flats (48) is that of the two end parts (49) of the axis (13) which are m have in the two branches (50,51) of the yoke (46), with the interposition of rings (52) of diameter at least equal to that of the central part (47). 8. Crane with lifting boom according to claim 7, characterized in that the lights (12) of the lugs (11) of the platform of the mechanisms (7) are double and rectangular in shape and are each provided with two sliding pads (53 ) of greater thickness in their central part, which are arranged vertically inside and on either side of said lights (12) so that they provide between them a space of constant width equal to the spacing (d) flats (48) of the connecting axes (13). 9. Crane with lifting boom according to any one of claims 1 to 8, characterized in that the device for moving the counterweight (8) along the platform of the mechanisms (7) inclined towards the front consists of two cables (31) arranged symmetrically on one side and on the other side of the platform of the mechanisms (7), fixed (at 32) on the counterweight element (18) located closest to the tower (1) and (at 33) on the upper members (34) of the foot of the lifting jib (9) passing successively over pulleys (35) arranged at the rear of the platform of the mechanisms (7) and over pulleys (36) disposed at intermediate height on the rear link rods (14).

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