KR930000711B1 - Jib stretching and folding device for crane - Google Patents

Abstract

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Description

Jib extension and folding device for crane

1 is a side view of a jib in a folded state according to a first embodiment of the present invention.

2 is a side view of the jib under suspension in the jib expansion action.

3 is a side view of the jib at an intermediate position during the jib torsion phase in the jib expansion action.

4 is a side view of the jib at the end of the jib torsion step.

5 is a fourth front view.

FIG. 6 is a front view of the jib rising vertically from the position shown in FIG.

7 is a side view of the jib in an expanded state.

8 is an enlarged perspective view of the main part of FIG.

9 is a partial cross-sectional enlarged side view of the main part of FIG. 2;

10 is an enlarged exploded view of a portion of a connecting rod formed from a torsion guide groove.

11 is a view similar to that of FIG. 2, showing a second embodiment;

FIG. 12 is a view similar to FIG. 10 showing a second embodiment.

FIG. 13 is a view similar to FIG. 9, showing the third embodiment;

14 is an enlarged cross-sectional view taken along the line Y-Y of FIG.

Fig. 15 is a side view of the main part of the fourth embodiment.

FIG. 16 is a view similar to FIG. 2 showing a fifth embodiment;

FIG. 17 is a view similar to FIG. 4 showing a fifth embodiment.

* Explanation of symbols for main parts of the drawings

1: boolean 2: jib

3: auxiliary connector 4: twist guide groove

11,12: jib mounting shaft 21,22: jib leg

32 housing 33 connecting rod

41: spiral groove portion 42,43: straight groove portion

The present invention relates to a jib expansion and folding device in wheel type cranes such as truck cranes and rough terrain cranes for expanding and folding the jib in a so-called jib torsion manner in which the jib is twisted.

Such jib expansion and folding apparatuses employing the jib torsion method are disclosed, for example, in Japanese Patent Application No. 63-3827 and Japanese Patent Application No. 63-173185.

In this conventional arrangement, the jib is folded vertically and placed next to the side of the pour.

The jib expansion action is carried out by suspending the jib from the above-mentioned folding position and twisting about 270 ° with respect to the vertical axis.

Then ascend the jib and finally extend the jib from the front of the end of the pour. In contrast, the jib folding action is performed by the step of lowering the jib from the extended position and twisting the jib and attracting the jib to the side of the pour.

However, in the conventional apparatus as disclosed in the above-mentioned publication, the jib twisting step in the expanding or folding action is performed manually. Thus, in the case of large jibs used in huge cranes, the torsional action of the jibs is difficult. Moreover, the manual action of twisting the jib is necessary during the process of the jib expansion or folding action, and the expansion or folding action is not continuous.

An object of the present invention is to provide a jib expansion and folding device for a crane that can automatically twist the jib.

According to the present invention, a buoy having a front end having first and second jib mounting shafts projecting in opposite directions from opposite sides of the front end; A jib having a base end portion having first and second jib legs adapted to be detachably connected to the first and second jib mounting shafts, respectively; A cylindrical housing fixed to the bottom surface of the jib and the connecting rod movable along the axis of the connecting rod and supporting the housing in a rotatable manner with respect to the axis of the connecting rod parallel to the bottom surface of the jib. An auxiliary connector provided on the lower surface of the jib in the vicinity of the base end of the jib under a jib folded state; A spiral groove portion and a jib rise formed in one of the housing and the connecting rod of the auxiliary connector and formed in the circumferential angle range corresponding to the jib torsion angle in the jib torsion step and extending in a direction corresponding to the jib torsion direction. A torsion guide groove composed of a straight groove portion having a length corresponding to each of the ascending and descending amounts of the jib in a step and a jib descending step; An engagement protrusion provided in the other of the housing and the connecting rod to engage the torsion guide groove; And a jib elevating member for raising and lowering the jib in the jib twisting step to move the engagement protrusion in the torsion guide groove. Wherein, when the jib is in the folded state, the jib lies on one side of the surfaces of the buoy with the first jib leg positioned under the second jib leg, while the jib is extended When in the state, the jib extends forward from the front end of the buoy with the first and second jib legs connected to the first and second jib tongue axes, respectively, and the jib is extended Connecting the connecting rod to the first jib mounting shaft to which the first jib leg is connected, suspending the jib from a connection point between the connecting rod and the first jib mounting shaft, and at a predetermined twist angle. Twist the jib with respect to the axis of the connecting rod in a first direction, and angle the first and second jib legs to the first and second jib mounting shafts; The jib folded state is lowered to separate the first and second jib legs from the first and second jib mounting shafts, respectively, and the predetermined angle is obtained. Providing a jib expansion and folding device for a crane obtained by twisting the jib with respect to the axis of the connecting rod in a second direction opposite to the first direction, and attracting the jib to the surface of the buoy. have.

With this structure, the jib expansion and folding device includes an auxiliary connector installed on the bottom surface of the jib near the base end of the jib in the jib folded state. The auxiliary connector includes a cylindrical housing fixed to the bottom surface of the jib and a connecting rod that supports the housing in a rotatable manner about an axis of the connecting rod that is movable along the axis of the connecting rod and is substantially parallel to the bottom surface of the jib. . The jib is twisted about the axis of the connecting rod to effect the jib expansion and folding action. The torsion guide groove is formed in one of the connecting rods of the housing and the auxiliary connector, and the engagement protrusion is provided in the other of the housing and the connecting rod to engage the torsion guide groove. When the jib is raised or lowered by the jib elevating member, the engagement protrusion moves in the torsion guide groove to generate the jib torsion. And, the jib automatically twists in jib expansion or folding. Thus, the workload of the operator extending and folding the jib is reduced. Moreover, the action is continuous so that the efficiency of jib expansion and folding action is increased.

According to another aspect of the invention, one of the connecting rods of the housing or of the auxiliary connector is provided with an arched guide plate with the torsional guide groove and the other of the housing and the connecting rod is provided with the engagement protrusion. Equipped and provided.

With such a structure, the arched guide plate can be easily formed by forming a torsion guide groove to cut the flat plate to be an arched curved flat plate. Thus, the formation of the torsion guide groove is made easier as compared to the case where the torsion guide groove is formed on the cylindrical body (connecting rod or cylindrical housing).

According to another aspect of the invention, in the structure employing the arched guide plate, the auxiliary connector is a structure of a cylindrical cylinder having a cylindrical tube as the housing and a piston rod as the connecting rod, and the jib elevating member is the cylindrical cylinder. Is the structure.

With this structure, the auxiliary connector acts as a jib elevating member, so that the jib elevating force is applied on the axis of the auxiliary connector. Therefore, compared with the case where the winding rope is used as the jib elevating member, the jib can be raised more smoothly and safely.

Other objects and features of the present invention will become more fully understood from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings.

With reference to the drawings will be described a preferred embodiment of the present invention.

[(1) First Preferred Embodiment (FIGS. 1 to 10)]

Reference numerals 1 and 2 denote telescopic pours and jibs, respectively.

The buoy 1 usually consists of a base buoy and a multiple movable buoy. For better understanding, the buoy 1 is shown as a double buoy consisting of a base buoy (1A) pivotally supported on the body of the crane and a single movable buoy (1B) telescopically supported on the base buoy (1A). have.

As is well known, the jib 2 has an inclined ladder structure composed of left and right beams 2a and 2b and a plurality of crossbars 2c connected to the beams 2a and 2b (hereinafter left and right are jibs). This direction is specified from the cab in the extended state.

The movable buoy 1B is provided at the front end with the left and right jib mounting shafts 11 and 12 projecting horizontally.

The left jib mounting shaft 11 is composed of a main mounting portion 11a having the same length as that of the right jib mounting shaft 12 and an auxiliary mounting portion 11b extending integrally from the main mounting portion 11a. (See also 5, 6 and 8).

The front end of the movable buoy 1B is provided with an idler pulley 13, a main pulley 14, and an auxiliary pulley 15 installed through the auxiliary pulley bracket 15a at the front end of the movable buoy 1B. have.

As shown in detail in FIGS. 8 and 9, a pair of left and right fork jib legs 21 and 22 are fixed to the base ends of the left and right beams 2a and 2b of the jib 2, respectively. The jib legs 21 and 22 are formed with pin fixing holes 21a and 22a, respectively, for inserting and fixing pins (not shown).

In the use state of the jib 2, as shown in FIG. 7, the jib legs 21 and 22 are engaged with the jib installation shafts 11 and 12, respectively, and the jib 2 is located in front of the movable pour 1B. It is arranged to extend from the end.

On the other hand, as shown in FIG. 1, in the unused state of the jib 2, the jib 2 is arranged to extend along the left side of the pour 1 in a vertical state, so that the left beam 2a and the left jib are The leg 21 is located below the right beam 2b and the right jib leg 22, and the jib 2 is fixed by a known fixing member (not shown).

In the folded state of the jib 2, as shown in FIG. 1, the auxiliary connector 3 is fixed to the lower surface of the left (lower) beam 2a of the jib 2 at a position near the base end. .

The auxiliary connector 3 is composed of a cylindrical housing 32 fixed to the left beam 2a via a bracket 31 and a connecting rod 33 inserted axially through the housing 32.

The connecting rod 33 is disposed below the left beam 2a in a parallel relationship under the jib folded state, and is slidably along the axis X and the axis X of the rod 33 (see also FIGS. 2 and 9). Is supported on the housing 32 in a rotatable manner.

The connecting rod 33 is provided at one end corresponding to the front end of the jib 2 by connecting the connecting member 34 with the jib legs 21 and 22, and the stopper 35 is also provided at the other end. .

When the stopper 35 is joined to the end face of the housing 32 at the opposite surface of the connecting member 34, the connecting rod 33 protrudes toward the base end of the jib 2 to the maximum (this state is described below). Called advance status).

When the connecting rod 33 slides from this advanced state toward the base end of the jib 2, the contracted state of the connecting rod 33 is obtained. Under the advanced state, the connecting member 34 is disposed at a position protruding from the left (lower) jib leg 21 to the left as shown in FIG. 1, and the auxiliary mounting portion of the left jib mounting shaft 11 ( 11b) can be engaged.

As shown in FIG. 8, the connecting member 34 is formed in a branched portion with a pair of pin holes 34a for inserting the fixing pin 6 therein.

As shown in FIGS. 8 and 7, the torsion guide groove 4 is formed on the outer peripheral surface of the connecting rod 33, and the guide pin 5 forms the cylindrical wall of the housing 32. It is inserted into the housing and is fixedly mounted to the housing 32 in such a manner that its inner end is engaged with the torsion guide groove 4.

As shown in FIG. 10, the torsion guide groove 4 spirals to the outer circumferential surface of the connecting rod 33 at a predetermined circumferential jib torsion angle (α: about 270 °) in the jib expansion and jib folding action. It is composed of first and second straight groove parts 42 and 43 continuous in the axial direction of the connecting rod 33 from opposite ends of the formed spiral groove part 41 and the spiral groove part 41. .

The operation of the first preferred embodiment will be described below.

(I) Jib expansion action

The jib 2 extends from the folded state shown in FIG. 1 to the expanded state shown in FIG. 7 through the following steps.

(I) -1 Preparation

As shown in FIG. 1, the pour 1 is fully deflated and actually lies horizontally.

In this state, the connecting rod 33 advances so that the connecting member 34 meshes with the auxiliary mounting portion 11b of the left jib mounting shaft 11. And the fixing pin 6 is inserted into the pin hole 34a of the connecting member 34 so that the connecting member 34 is detachably and rotatably connected with respect to the pin.

At this time, the guide pin 5 is located at the closed end of the first straight groove portion 42 of the torsion guide groove 4 as shown by the solid line in FIG. 10.

(I) -2 jib suspension stage

As shown in FIG. 2, the buoy 1 rises so as to suspend the jib 2 from the connection point between the connecting member 34 and the left jib mounting shaft 11.

This jib suspension step is automatically performed by a combination of the guiding action of the known jib guide mechanism and the expanding action of the buoy 1, for example, as disclosed in the above-mentioned Japanese Patent Application No. 63-3827.

As disclosed below, the jib attracting step in the jib folding action is also automatically performed by the combination of the guiding action of the jib guiding mechanism mentioned above and the contracting action of the pour 1.

(I) -3 jib torsion stage

After the jib suspension step, the crane-operated winding rope R, which is previously drawn from the winch (not shown) and wound on the auxiliary pulley 15, is wound on the guide pulley 23 installed at the front end of the jib 2 , The hook F fixed to the end of the winding rope R is engaged with the front end of the jib 2.

In winding the winding rope R on the guide pulley 23, the winding rope R is turned to the rear side of the jib 2 as shown in FIG. 2, so that the jib 2 is shown in FIG. As shown, after the completion of the jib torsion step, it is placed on the front side of the jib.

Then, the winding rope R is wound (or the pour 1 is usually extended under the fixed state of the winding rope R).

As a result, the jib 2 rises by the hoisting force of the winding rope R. As shown in FIG. Thus, the housing 32 of the auxiliary connector 3 integrated with the jib 2 has the guide pin 5 as shown by the dashed-dotted line A in FIG. 10 from the first straight groove portion 42. As shown by the double-dotted chain line B of FIG. 10 through the first connection point between the first straight groove portion 42 and the spiral groove portion 41 as shown in FIG. It rises as a result of movement to the second connection point between the second straight groove portion 43 (ie, the connecting rod 33 is relatively retracted).

This movement of the guide pin 5 guided by the helical groove part 41 is simultaneously with the rise of the jib 2 with respect to the axis of the connecting rod 33 in the direction shown by the arrow P in FIG. 2. It causes a twist of about 270 ° jib.

2 shows the state before the jib 2 is twisted; 3 shows a state in which the jib is twisted 180 degrees from the second degree state; 4 and 5 show a state in which the jib 2 is twisted about 90 degrees further from the state of FIG. 3, and the jib legs 21 and 22 are located just below the jib installation shafts 11 and 12, respectively.

(I) -4 jib ascending stage

After the jib torsion step, the jib 2 has a left jib leg 21 engaged with the main mounting portion 11a of the left jib mounting shaft 11, and the right jib leg 22 is shown in FIG. It further rises by winding the winding rope R until it engages with the right jib mounting shaft 12. In this ascending step, the guide pin 5 is removed from the connection point between the helical groove portion 41 and the second straight groove portion 43 as shown by the dashed-dotted line B in FIG. As shown by the dashed-dotted line C at 10 degrees, it moves to the near end of the guy 2nd straight groove part 43. As shown in FIG.

This has a length in which the second straight groove portion 43 corresponds to the amount of rise of the jib 2 in the jib raising step.

(I) -5 jib swing-up stage

After the jib ascending step, the winding rope R is further wound up to swing up the jib 2 with respect to the jib mounting shafts 11 and 12, while at the same time the pour 1 is actually obtained to obtain the state shown in FIG. Lower to the horizontal position.

Under this condition, the jib legs 21 and 22 are fixed to the jib installation shafts 11 and 12 by inserting fixing pins (not shown) into the pin holes 21a and 22a of the jib legs 21 and 22, respectively. . Moreover, the suspension rod S is provided between the jib 2 and the front end of the buoy 1 as shown by the dashed-dotted line in FIG.

Therefore, the expanding action of the jib 2 is completed.

(Ⅱ) Jib folding action

The folding action of the jib 2 is performed inversely to the procedure of the expansion action mentioned above. This first swings the jib 2 from the position shown in FIG. 7 to the position shown in FIG. 6 (the jib swing-down step).

And the jib 2 descends to the position shown in FIG. 4 and FIG. 5 (jib lowering step). And the jib 2 is twisted about 270 ° in the direction opposite to the expanding action to obtain the state shown in FIG. 2 (the jib twisting step).

Finally, the jib 2 is drawn to a position opposite to the side of the pour 1 (jib attracting step). Therefore, the jib 2 is folded on the side of the boolean 1.

In the folding action performed by unwinding the winding rope R, in the jib twisting step and the jib downward step, the guide pin 5 is a helical groove of the twisting guide groove 4 from the second straight groove part 43. By moving through the part 41, automatic torsion of the jib 2 is executed.

Since the guide pin 5 is located in the first straight groove portion 42 of the torsion guide groove 4 after the jib torsion step, there is no possibility that the jib 2 is twisted in the jib attraction step.

[(2) Second Preferred Embodiment (FIGS. 11 and 12)]

In the structure of the first preferred embodiment in which the jib 2 is twisted about 270 °, the jib 2 is likely to be damaged by the winding rope R because the winding rope R is wound in the torsion stage shown in FIG. There is this.

Moreover, the helical groove portion 41 of the torsion guide groove 4 is formed in an angular range of about 270 ° (3/4 of the circumference of the connecting rod 33), and the spiral of the helical groove portion 41 The angle must be large enough to reduce the torsional resistance.

Therefore, the length of the connecting rod 33 on which the torsion guide groove 4 is formed increases, resulting in an increase in cost and weight.

In order to overcome this, the second preferred embodiment is that the helical groove portion 41 of the torsion guide groove 4 is formed in the circumferential angle range of about 90 ° (α = 90 °) as shown in FIG. The jib 2 has a structure that twists about 90 ° in the direction shown by the arrow Q in FIG. 11 to the jib expansion action in the direction opposite to the torsional direction in the first preferred embodiment. The other structure is the same as that of the first preferred embodiment.

With this structure, the winding rope R is wound directly on the guide pulley 23 provided at the front end of the jib 2 without turning to the rear side of the jib 2.

Therefore, there is no possibility that the jib 2 is damaged by the winding rope R in the jib twisting step. Moreover, since the angular range α of the torsion guide groove 4 is reduced to one third of the range in the first preferred embodiment, the length of the connecting rod 33 is reduced.

Thus, the weight of the connecting rod 33 can be reduced.

[(3) Third Preferred Embodiment (FIGS. 13 and 14)]

The formation of the torsion guide grooves 4 on the outer circumferential surface (cylindrical surface) of the connecting rod 33 is more cumbersome, as in the first and second preferred embodiments, and the formation of the torsion guide grooves through a flat plate. Formation costs more expensive processing.

Moreover, the diameter of the connecting rod 33 is increased to compensate for the reduced length due to the formation of the groove 4. As a result, the weight of the connecting rod 33 increases.

To overcome this, the third preferred embodiment is a torsionally fixed on the outer circumferential surface of the housing 32 in a manner extending upwardly from the housing 32 towards the connecting member 34 as shown in FIG. It consists of an arch-shaped guide plate 7 formed with the guide groove 4 and a guide pin 5 engaging with the torsion guide groove 4 protruding from the outer circumferential surface of the connecting rod 33 at the top.

As shown in FIG. 14, the torsion guide groove 4 is formed in an angle range of about 90 degrees, and the arch guide plate 7 has an arch angle of about 90 degrees.

In the case of forming the groove 4 in the angle range of about 270 °, the arched angle of the arched guide plate 7 is set to about 270 °.

The other structure is the same as in the first preferred embodiment.

With this structure, the arched guide plate 7 is formed by cutting to form the guide groove 4 and bending the flat plate in an arch form.

Therefore, the formation of the grooves 4 is easily performed to reduce the processing cost. Furthermore, compared with the case where the guide groove 4 is formed on the outer circumferential surface of the connecting rod 33, it is not necessary to increase the diameter of the connecting rod 33, so that the weight of the rod 33 can be reduced. .

As an alternative, the guide plate 7 can be fixed to the connecting member 34 in a manner extending downward from the connecting member 34 toward the housing 32, with the guide pin 5 at the upper end of the housing 32. Protrude into the outer circumferential surface of the.

[(4) Fourth preferred embodiment (FIG. 15)]

In each of the above preferred embodiments, the jib 2 is raised by winding the winding rope R. As shown in FIG. However, if the axis of the winding rope R does not coincide with the axis of the auxiliary connector 3, the torque is applied to the jib 2 in the jib ascending step to make the lifting action of the jib 2 unstable.

In order to overcome this, the fourth preferred embodiment has a structure in which the hydraulic cylinder 81 is used to form the auxiliary connector 8 serving as the jib elevating member of the present invention.

More specifically, the hydraulic cylinder 81 is composed of a cylindrical tube 81a as a housing of the present invention installed through the bracket 82 on the piston rod 81 b and the jib 2 as the connecting rod of the present invention.

The connecting member 83 is connected to the end of the piston rod 81b.

The arched guide plate 7 with a torsion guide groove (4: formed in an angle range of about 90 ° or about 270 °) extends downwardly from the connecting member 83 to the cylindrical tube 81a. 83) It is fixedly installed.

Guide pins 5 engaging the torsion guide grooves 4 protrude from the outer circumferential surface of the cylindrical tube 81a at the upper end.

Therefore, the torsion step and the lifting step of the jib 2 are performed by the expansion / contraction action of the hydraulic cylinder 81.

The other structure is the same as in the first preferred embodiment.

With this structure, the jib lifting force is applied on the axis of the auxiliary connector 8, and the synergism of the jib 2 can be made smoother and safer than when using the winding roller R for the jib elevating member.

[(5) Fifth Preferred Embodiment (FIGS. 16 and 17)]

In the fifth preferred embodiment, the suspension rope 9 is used as the jib elevating member of the present invention, unlike the wire rope R.

The suspension rope 9 is wound on an arch-type rope guide member (G; replaceable by a pulley installed at the front end of the movable beam 1B), and one end is fixed to the front end of the base pour 1A, and an auxiliary connector The other end is fixed to the housing 32 of (3).

The other structure is the same as in the first preferred embodiment.

With this structure, when the pour 1 extends in the jib expansion action, or when the pour 1 expands in the extended state in the jib folding action, the jib raising or lowering force is applied to the housing 32 through the suspension rope 9. This is applied to the jib 2 and automatically rubs the jib 2 while raising or lowering.

Like the fourth embodiment, in the fifth preferred embodiment, the swing-up or swing-down step of the jib 2 is carried out by the winding rope R and the hook F as in the first preferred embodiment. .

The fifth preferred embodiment exhibits effects which are essentially similar to the effects of the first preferred embodiment.

Although the torsion guide groove is formed on the outer circumferential surface of the connecting rod 33 in the fifth preferred embodiment as similar to the first and second preferred embodiments, the arched guide plate 7 is provided with the third and fourth. As mentioned in the preferred embodiment, it is used in the fifth preferred embodiment.

(6) other modifications

(a) As a modification of the first and second preferred embodiments, the guide pin 5 (engaging projection) is provided on the connecting rod 33, and the torsion guide groove 4 is formed on the housing 32.

(b) In the preferred embodiments mentioned above the first straight groove portion 42 is arranged such that the torsion guide groove 4 prevents the torsion of the jib 2 in the jib attraction step after the jib torsion step in the folding action. Even if equipped, the first straight groove portion 42 is removable.

Even in such a case, the object of the present invention is satisfactorily achieved.

(c) Although the branched connecting members 34 and 83 are used as members for connecting the ends of the connecting rod 33 (piston rod 81b) to the jib installation shaft 11, the connecting rod 33 (piston rod ( 81b)) is appropriately shaped to be detachably connected to the jib mounting shaft 11.

While the invention has been disclosed with reference to specific embodiments, the description is for purposes of illustration and is not intended to limit the scope of the invention.

Those skilled in the art may make various modifications and changes without departing from the scope and spirit of the invention as defined by the appended claims.

Claims (18)

A jib expansion and folding device for cranes, comprising: a buoy having a front end having first and second jib mounting shafts projecting in opposite directions from opposite sides of the front end; A jib having a base end portion having first and second jib legs adapted to be detachably connected to the first and second jib mounting shafts, respectively; A cylindrical housing fixed to the bottom surface of the jib and the connecting rod movable along the axis of the connecting rod and supporting the housing in a rotatable manner with respect to the axis of the connecting rod parallel to the bottom surface of the jib. An auxiliary connector provided on a lower surface of the jib near the base end of the jib under a jib folded state; A spiral groove portion and a jib raising step formed in one of the housing and the connecting rod of the auxiliary connector and formed in a circumferential angle range corresponding to the jib torsion angle in the jib torsion step and extending in a direction corresponding to the jib torsion direction A torsion guide groove composed of a straight groove portion having a length corresponding to the rising amount and the falling amount of the jib in the and jib falling steps, respectively; An engagement protrusion provided in the other of the housing and the connecting rod to engage the torsion guide groove; And a jib elevating member for raising and lowering the jib in the jib twisting step to move the engagement protrusion in the torsion guide groove. Wherein, when the jib is in the folded state, the jib is placed on one side of the surfaces of the pour while the first jib leg is positioned under the second jib leg, while the jib is in an extended state. The jib extends forwardly from the front end of the buoy with the first and second jib legs connected to the first and second jib mounting shafts, respectively, The connecting rod is connected to the first jib mounting shaft to which the first jib leg is connected, and the suspension is suspended from a connection point between the connecting rod and the first jib mounting shaft, and the first jib is connected at a predetermined torsion angle. Twist the jib with respect to the axis of the connecting rod in one direction, and the first and second jib legs on the first and second jib mounting shafts The jib folded state is lowered to separate the first and second jib legs from the first and second jib mounting shafts, respectively, and the predetermined angle is obtained. A jib extension and folding for crane, characterized by twisting the jib with respect to the axis of the connecting rod in a second direction as opposed to the first direction, and attracting the jib to the surface of the buoy. Device. The method of claim 1, wherein one of the connecting rod or the housing of the auxiliary connector is provided in an arched guide plate with the torsional guide groove, and the other of the connecting rod and the housing is provided in the engagement protrusion. Jib expansion and folding device, characterized in that. The jib expansion and folding device according to claim 2, wherein the auxiliary connector is a structure of a cylindrical cylinder having a cylindrical tube as the housing and a piston rod as the connecting rod, and the jib elevating member is a structure of the cylindrical cylinder. . The torsion guide groove is formed on the outer circumferential surface of the connecting rod, and the engaging projection is fixedly installed to the housing in such a manner that it is inserted through the cylindrical wall of the housing. Jib expansion and folding device. The helical groove portion of claim 1, wherein the helical groove portion is formed in a circumferential angle range of about 270 °, wherein the straight groove portion is comprised of first and second straight portions extending continuously from opposite ends of the helical groove portion. And when the jib is expanded, the jib is twisted about 270 ° in the first direction in the jib twisting step, while the jib is twisted about 270 ° in the second direction in the jib twisting step when the jib is folded. Jib expansion and folding device. 2. The helical groove portion of claim 1, wherein the helical groove portion is formed in a circumferential angle range of about 90 [deg.], And the straight groove portion consists of first and second straight portions extending continuously from opposite ends of the helical groove portion. And when the jib is expanded, the jib is twisted about 90 ° in the second direction in the jib twisting step, while the jib is twisted about 90 ° in the first direction in the jib twisting step when the jib is folded. Jib expansion and folding device. 3. The method of claim 2, wherein the arched guide plate is secured to the outer circumferential surface of the housing in a manner extending toward the end of the connecting rod, wherein the engaging projection is an outer circumference of the connecting rod at a position near the connecting rod. Jib expansion and folding device, characterized in that protrudes from the surface. 3. The arch guide of claim 2 wherein the arched guide plate has an arched angle of about 90 [deg.] Wherein the helical groove portion is formed in a circumferential angle range of about 90 [deg.] And the straight groove portion is the helical groove portion. And the first and second straight portions extending continuously from opposite ends of the jib, when the jib is expanded, the jib is twisted about 90 ° in the second direction in the jib twisting step, and the jib when the jib is folded Jib expansion and folding device, characterized in that twisted about 90 ° in the first direction in the torsion step. 3. The arch guide plate of claim 2, wherein the arch guide plate has an arch angle of about 270 degrees, the spiral groove portion being formed in a circumferential angle range of about 270 degrees, and the straight groove portion is the spiral groove portion. And the first and second straight portions extending continuously from opposite ends of the jib, when the jib is expanded, the jib is twisted about 270 ° in the first direction in the jib twisting step, and the jib when the jib is folded Jib expansion and folding device, characterized in that the twisting step in the second direction about 270 °. 3. The jib expansion and folding device according to claim 2, wherein the arched guide plate is formed by cutting the flat plate to form the torsion guide groove and to deflect the flat plate into an arch shape. 4. The connecting rod according to claim 3, further comprising a connecting member adapted to be connected to the first jib mounting shaft and fixed to the end of the piston rod, wherein the arched guide plate extends toward the cylinder tube. And the engaging projection protrudes from an outer circumferential surface of the cylinder tube at a position near the right end of the cylinder tube on the connecting member side. 4. The helical guide plate of claim 3 wherein the arched guide plate has an arched angle of about 90 [deg.], Wherein the helical groove portion is formed in a circumferential angle range of about 90 [deg.] And the straight groove portion is the helical groove portion. The jib is twisted about 90 ° in the second direction in the jib torsion step when the jib is expanded, and the jib when the jib is folded Jib expansion and folding device, characterized in that twisted about 90 ° in the first direction in the torsion step. 4. The helical guide plate of claim 3 wherein the arched guide plate has an arched angle of about 270 °, wherein the helical groove portion is formed in a circumferential angle range of about 270 °, and the straight groove portion is the helical groove portion. And the first and second straight portions extending continuously from opposite ends of the jib, when the jib is expanded, the jib is twisted about 270 ° in the first direction in the jib twisting step, and the jib when the jib is folded Jib expansion and folding device, characterized in that twisted about 270 ° in the second direction in the torsion step. The jib extension and folding device according to claim 1, wherein the jib elevating member is configured by a winding rope connected at one end to a winch and at the other end to a front end of the jib. According to claim 1, wherein the buoy consists of a base buoyant pivotally supported from the base to the body of the crane and a movable buoy telescopically supported on the base buoy, the jib elevating member is one end of the base Jib expansion and folding device connected to the front end of the buoy, the other end consisting of a suspension rope connected to the housing of the auxiliary connector. The jib expansion and folding device according to claim 1, wherein the housing is integrally fixed to the lower surface of the jib through a bracket, and the connecting rod is inserted through the housing in an axial direction. 2. The method of claim 1, wherein the branched connecting member is adapted to be connected to the first jib mounting shaft and fixed to one end of the connecting rod, and is in contact with the end surface of the housing and is connected to the other end of the connecting rod. Jib expansion and folding device further comprises a fixed stopper. 18. The jib according to claim 17, wherein the branched connecting member has a pair of pin holes formed therein for inserting a fixing pin to connect the connecting member to the first jib mounting shaft in a rotatable and detachable manner. Extension and folding device.

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