JP2001278582A - Boom extension mechanism for moving crane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily release a fixing pin of fixed booms in emergency, and to prevent the interference of a member facing to the fixing pin without increasing the cross sectional area of both the booms. SOLUTION: This boom extension mechanism is provided with a one-stage double action hydraulic cylinder built in a multistage telescopic boom, a cylinder and boom connecting means 8 for selectively connecting a rod side end of a cylinder tube 7B of the one-stage double action hydraulic cylinder and a base end of each stage intermediate boom, and a boom-to-boom connecting and disconnecting means 9 for selectively fixing and releasing both the booms. The boom-to-boom connecting and disconnecting means can be advanced and retreated outward the boom, and provided with a pair of fixing pins 9a in right and left capable of connecting adjacent booms to each other, and a ball lock mechanism 14 for hindering the slide of the fixing pins 9A in the condition of both the booms connected to each other for fixation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom extending and retracting device for a mobile crane, and more particularly to a mechanism for fixing adjacent booms which are extended and retracted by using a single hydraulic cylinder.

[0002]

2. Description of the Related Art As is well known, in a boom extension / retraction mechanism used in a truck crane or the like, a hydraulic cylinder is provided for each of the booms to be extended / contracted, and each stage of the boom is extended and retracted in accordance with the extension / contraction operation of each hydraulic cylinder. There is a mechanism to expand and contract. The boom extension and contraction mechanism having the above configuration has a problem that the number of hydraulic cylinders is increased. Instead, a configuration in which a single hydraulic cylinder is used to perform extension and contraction operations of a plurality of stages of booms has been proposed (for example, JP-A-7-267584
No.). In addition to the configuration disclosed in the above-mentioned publication, it is necessary for the expanded and contracted booms to be connected to an adjacent boom and so-called fixed in order to prevent slipping. Conventionally, the configuration of the inter-boom fixing means used for fixing the booms has the following configuration. A boom provided with a fixing pin provided with a habit of protruding from one of the adjacent booms to the other boom by a spring, and a driving device for pulling out the fixing pin from the other boom in opposition to the habit; When fixing the booms together, the fixing pins are protruded using the habit of the spring, and when the booms are unlocked, the drive unit is driven to connect the ends to the drive unit and the fixing pins. The fixing pin is pulled out from the other of the adjacent booms against the behavior of the spring through the swing lever provided. (For example, EP0943580A2).

[0003]

However, the above-described structure for fixing the booms has the following problems. The fixing pin provided in the inter-boom fixing means has a habit of always protruding toward the other boom by the bias of the spring. Moreover, the protruding amount due to the habit is regulated by the swinging lever connected to the driving device, and is always maintained at a constant amount unless the driving device is operated and the fixing pin is pulled from the other boom. . For this reason, for example, in the event of a failure of a hydraulic cylinder used as a driving device or an abnormality in a piping route or an electrical wiring route for driving the same, the fixing pin of the driving device is not used. Pulling out becomes impossible, and it becomes impossible to release the fixing between the booms. Therefore, in order to cope with such an unexpected situation, it is conceivable to provide a special mechanism for releasing the fixing between the booms. However, providing such a configuration not only complicates the structure, The procedure also becomes complicated.

[0004] Since the fixing pin is maintained in a protruding state by the step provided on the fixing pin abutting against the inner wall of the boom, the step comes into contact with the inner wall of the boom. It is not possible to move outward from the position where it is. For this reason, if the positions of the engaging portion on the driving device side for pulling out the fixing pin and the end portion of the fixing pin are slightly irregular between the respective booms, the engaging portion on the driving device side will There is a risk of interference with the end of the fixing pin. As a result, it is necessary to provide a large gap between the adjacent booms so that even when the ends of the fixing pins are not aligned, the engaging portion of the driving device does not interfere near the end when the engaging portion of the driving device passes. Increasing the cross-sectional area of the boom will lead to increased weight and material consumption.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with the conventional boom extension device for a mobile crane, an object of the present invention is to make it possible to easily release the fixing pins of the booms that are fixed in an unforeseen situation, and to set the booms together. It is an object of the present invention to provide a mobile crane boom extension device having a configuration capable of preventing interference of members facing the fixing pin without increasing the cross-sectional area of the boom.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of intermediate booms and a top boom are sequentially inserted into the base boom so as to extend and contract, respectively. A multi-stage telescopic boom, a single-stage double-acting hydraulic cylinder housed in the multi-stage telescopic boom and having a rod end pivotally supported at the base end of the base boom, and a rod-side end of a cylinder tube in the single-stage double-acting hydraulic cylinder. Boom extension / retraction of a mobile crane comprising cylinder / boom coupling means for selectively coupling the base end of each stage intermediate boom, and boom indirect disconnection means capable of selectively fixing and releasing the booms. In the mechanism, the boom indirect disconnecting means includes a pair of left and right fixing pins capable of connecting adjacent booms, and a ball lock machine for preventing sliding of the fixing pins. And provided, the locking pin is characterized by being provided to be retractable toward the outside of the boom, the sliding by said ball-lock mechanism when the fixed state of connecting the boom to each other is prevented.

According to a second aspect of the present invention, in the boom extension and contraction device for a mobile crane according to the first aspect, the boom indirect disconnecting means includes a double-acting hydraulic cylinder disposed orthogonal to the single-stage double-acting hydraulic cylinder. And a pair of drive levers, one end of which is connected and driven to both ends of the drive device, and the other end of which is removably disposed on the inner end of the fixing pin. It is characterized by:

According to a third aspect of the present invention, in the boom extending and retracting device for a mobile crane according to the first aspect, the fixing pin is formed by a concave portion having an inclined surface against which a ball provided in the ball lock mechanism is pressed. Characterized in that a fitting portion is provided.

[0009]

According to the first aspect of the present invention, the fixing pin provided in the boom indirect cutting means is maintained in a fixed state in which the booms are connected to each other by the ball lock mechanism. For this reason,
The sliding prevention state by the ball lock mechanism can be released by externally pressing the fixing pin in a state where the booms are connected and fixed. Thus, the connected and fixed state of the booms can be released by a simple operation of simply pressing from the outside without requiring a special slide prevention release mechanism or the like.

According to the second aspect of the present invention, there is provided a pair of drive levers, one end of which is disposed at both ends of the drive device, and the other end of which is connected to the boom end of the fixing pin. Therefore, it is possible to drive the fixing pins located on both sides by using the output necessary to operate one fixing pin. Thus, it is only necessary to prepare a drive device having an output intended for a single fixing pin, so that the drive device can be small.

According to the third aspect of the present invention, since the fitting portion formed on the fixing pin has the inclined surface against which the ball of the ball lock mechanism is pressed, the fixing pin is pressed against the inclined surface. By pushing the moving ball in the direction opposite to the pressing direction, the ball can slide slightly. As a result, even if the end on the fixing pin side is not aligned between the booms, the pulling means is pushed when it interferes when moving, so that the fixing pin slides in a direction that does not hinder the movement of the pulling means. it can.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial sectional view in a side view for explaining a boom extension mechanism having six stages of extension booms including a top boom and a base boom. , Four intermediate booms 2, 3, 4, and 5 are telescopically inserted, and among these intermediate booms, a top boom 6 is sequentially telescopically inserted into the intermediate boom 5 located at the most distal end side. ing.
Inside the boom, a single one-stage reciprocating hydraulic cylinder 7 for moving the telescopic boom is arranged. 1
The step-return hydraulic cylinder 7 has an end of a piston rod 7A fixed to a base end of the base boom 1 and a piston rod 7A.
The cylinder tube 7B in which A is inserted is adapted to extend and contract using the piston rod 7A as a guide, and a cylinder / boom connecting means 8 described later is provided at the rod-side end of the cylinder tube 7B. .

The cylinder / boom connecting means 8 includes connecting pins 8A which can be connected to engaging holes 2A, 3A, 4A, 5A and 6A formed on both sides at the base end of each step boom except the base boom 1. (See FIG. 2), the details of which are shown in FIGS. 2 and 3. FIG. 2 shows that the connecting pin 8A of the cylinder / boom connecting means 8 is connected to the engaging hole 2A.
A to 6A are shown in FIG.
Conversely, connecting pin 8A of cylinder / boom connecting means 8
Are inserted into the engagement holes 2A to 6A and connected. 2 and 3, an engagement hole 6A is shown for the top boom 6 and the intermediate boom 5 adjacent thereto. 2 and 3, the cylinder / boom connecting means 8 includes a one-stage reverse hydraulic cylinder 7.
By moving together with the cylinder tube 7B, the boom can be moved in the expansion and contraction direction of the boom. Cylinder·
The boom connecting means 8 includes a pair of connecting pins 8A which are provided so as to be able to reciprocate in the horizontal direction in the radial direction of the one-stage backward moving hydraulic cylinder 7 and which can be inserted into and removed from the engaging holes 2A to 6A. A movable end and a fixed end are disposed between a pair of swingable link members 8B supported by the support bracket 50 via a support shaft 8B1 and the link members 8B. A double-acting hydraulic cylinder 8C corresponding to a connection pin driving device which is connected to a pair of link members 8B via an expansion / contraction rod 8C1 and an interlocking member 8C2 is provided on the upper side.

In FIG. 2, cylinder / boom connecting means 8
Is provided near the rod-side end of the cylinder tube 7B, and is used for gripping of the intermediate boom selected at the time of expansion and contraction and expansion and contraction movement of the selected intermediate boom or top boom. When the expanding / contracting rod 8C1 of the driving cylinder 8C is expanded, the link member 8B is swung outward in the radial direction of the cylinder tube 7B, and the connecting pin 8A is gripped or expanded and contracted among the bosses 2A to 6A. The boom or top boom is adapted to enter and engage with the engagement hole. FIG. 3 showing a state in which the connection pin 8A is inserted into the engagement hole, shows a state in which the connection pin 8A is inserted into the engagement hole 6A for the top boom 6 adjacent to the intermediate boom 5. ing.

The boom indirect disconnecting means 9 is used when the selected boom is gripped by the cylinder / boom connecting means 8 and when the telescopic operation is not performed.
And it is used as a means for fixing and releasing the adjacent booms 3 to 6 at each stage. Boom indirect disconnection means 9
As shown in FIG. 1 to FIG. 3, holes 1B to 6B formed on the base end portion of the base boom 1 and the intermediate booms 3 to 6 of each stage and both side walls of the boom at appropriate positions are provided.
B, a pair of fixing pins 9A, a driving device 9B for the fixing pins 9A, and a pair of link members 9 for transmitting the driving force of the driving devices 9B to the fixing pins 9A.
C and 9D.

Holes 2B-5B at intermediate booms 2-5 at each stage
The hole 1B of the base boom 1 is formed at a position different from the connecting pin 8A of the cylinder / boom connecting means 8 so as to penetrate in the same direction as the engaging holes 2A to 6A into which the connecting pin 8A fits. The fixing pin 9 can advance and retreat toward the outside of the boom similarly to the connecting pin 8A, and the holes 2B to 5
Advance to and from B. FIG. 4 is a plan view showing a sliding mechanism of the fixing pin 9A. In FIG. 4, a double-acting hydraulic cylinder having an expansion / contraction rod 9B1 and an interlocking member 9B2 is used as a driving device 9B used for the sliding mechanism. Have been.
A pair of swing link members 9C and 9D are connected to the expansion / contraction rod 9B1 and the interlocking member 9B2, respectively. One of these rocking links 9C and 9D, with a pivot 51A provided on the support bracket 51 as a fulcrum, is connected to the expansion / contraction rod 9B1 and the interlocking member 9B2, and the other rocking end is a pair of rocking links. It can be inserted into the fixing operation control members 10 and 11 provided on the fixing pin 9A. As shown in FIGS. 2 to 4, the fixing operation control members 10 and 11 each include a receiving portion formed of a hollow member connected to an end of the fixing pin 9 </ b> A on the boom side. The surfaces facing each other in the sliding direction of 9A are formed as guide surfaces 10A and 11A whose central portions in the direction orthogonal to the sliding direction are bulged.

In FIG. 4, the boom indirect disconnecting means 9 can swing the link members 9C and 9D outward in the radial direction of the cylinder tube 7B when the expanding and contracting rod 9B1 of the driving device 9B is contracted. As a result, the fixing pin 9A is a hole in the boom, and in FIG.
, And conversely, when the expansion rod 9B1 of the driving device 9B expands, the intermediate boom 5
From the hole 5B.

The fixing operation control member 1 on the fixing pin 9A side
A coupling operation control member 13 is provided on the cylinder / boom coupling means 8 side facing 0 and 11. 2 and 3, a linking operation control member 13 is disposed on a link member 8B of the cylinder / boom connecting means 8 at a swinging end opposite to the boom indirect disconnecting means 9. The coupling operation control member 13 has a substantially rectangular shape in plan view fixed to a support bracket 13A provided at a swing end of the link member 8B that is opposed to the fixed operation control members 10 and 11 among the swing ends. (See FIG. 4). Since the support bracket 13A can move up and down in response to the swing of the link member 8B, the connection operation control member 1
3 functions as a member for moving up and down. The linking operation control member 13 formed of a block body is a member that enters or is prevented from entering between the opposing surfaces of the fixing operation control members 10 and 11 whose intervals change according to the sliding position of the fixing pin 9A. . For example, as shown by reference numeral L1 in FIG. 2, when the fixing pin 9A slides toward the hole 5B, the distance between the opposing surfaces of the fixing operation control members 10 and 11 becomes large. The connection operation control member 13 can enter the gap. On the contrary, as shown by reference numeral L2 in FIG. 3, when the fixing pin 9A slides in a direction to come out of the hole 5B, the fixing operation control member 1
If the distance between the opposing surfaces 0 and 11 becomes narrow unlike the case shown in FIG. 2, the connection operation control member 13 cannot enter between the opposing surfaces.

The fixed operation control members 10 and 11 and the connection operation control member 13 are connected to a drive unit 9B on the boom indirect disconnection means 9 side.
And the cylinder and the boom selected by the cylinder / boom connecting means 8 are directly connected to each other in the path where the driving force from the driving device 8C on the side of the cylinder / boom connecting means 8 is transmitted. 7B
An interlock mechanism serving as a relative locking mechanism is configured in accordance with the connection state between the booms and the connection and fixing state of the booms by the boom indirect disconnecting means 9.

On the other hand, near the fixing pin 9A, a ball lock mechanism 14 for preventing sliding when the booms are connected and fixed is arranged to face each other. In FIG. 4, the ball lock mechanism 14 has a tubular casing 14A.
The piston member 14C is disposed inside and is urged toward the fixing pin 9A side by the spring 14B, and the movement of the piston member 14C to the fixing pin 9A side is provided by contacting the head of the piston member 14C. Ball 14D.
On the peripheral surface of the fixing pin 9A of the ball lock mechanism 14 against which the ball 14D is pressed, there is provided a fitting portion 9A1 composed of a concave portion having an inclined surface against which the ball 14D is pressed. In FIG. 4, for convenience, the reference numeral of only the fitting portion is shown for one ball lock mechanism 14, and the reference numerals of the components are separately shown for the other ball lock mechanism 14.

The fitting portion 9A1 is a portion that can guide the ball 14D in the direction of moving outward from the fitting portion 9A1 by its inclined surface. For this reason, the fitting portion 9A1
The ball lock mechanism 14, which has entered the inside and prevents the sliding of the fixing pin 9A, is pressed in a direction in which the fixing pin 9A comes out of the hole 5B by an external force equal to or greater than the pressing force acting on the fitting portion 9A1. Then, the ball 14D is pushed into the casing 14A side, and the fixing pin 9A can be slid in the axial direction. At this time, the sliding amount is the spring 14B.
Due to the increase in the reaction force due to the increase in the amount of compression, there is not so much, but as will be described later, the end of the fixing pin and the swing end of the link members 9C and 9D of the boom indirect disconnecting means 9 will be described. This is an amount that can eliminate the displacement.

The inclined surface of the fitting portion 9A1 is the ball 1
Since the fixing pin 9A is allowed to slide against the pressing force acting on the 4D, for example, when the boom indirect disconnecting means 9 moves, the other swing of the link members 9C and 9D is performed. When the facing positions of the ends and the fixed operation control members 10 and 11 are not aligned, the positions of the fixed operation control members 10 and 11 can be slid in a direction to align with the positions of the link members 9C and 9D. In this case, for example, when the positional relationship between the two is shifted in the direction in which the fixing pin 9A is pulled out from the hole 5B, and when the positional relationship is shifted in the opposite direction, the fixing pin 9A is Need to move towards. Therefore, in the present embodiment, in FIG. 4, the fitting portion is located at a position where a space S can be set between the hole 5B and the step formed near the distal end portion of the fixing pin 9A that enters the hole 5B. 9A1 is provided. As a result, even in the state where the sliding is prevented by the ball lock mechanism 14, the fixing pin 9A is directed toward the hole 5B or the hole 5B.
It can slide slightly in any direction away from B.

Since the present embodiment has the above configuration,
When the selected boom is gripped by the cylinder / boom connecting means 8, the state in which the booms are connected and fixed by the boom indirect disconnecting means 9 is maintained, and the connecting pin 8A on the cylinder / boom connecting means 8 side engages the boom. It is pulled out from the hole.

When the fixing pin 9A is engaged with the hole of the adjacent boom by the boom indirect disconnecting means 9, the state of the fixing pin 9A is maintained by the ball lock mechanism 14, and the sliding is prevented. When the fixing pin 9A engages with the hole of the boom, the distance between the opposing surfaces of the fixing operation control members 10, 11 integral with the fixing pin 9A increases in the state shown in FIG. Therefore,
When the connecting pin 8A is slid in the direction of pulling out from the engagement hole on the cylinder / boom connecting means 8 side, the connecting operation control member 13 is fixedly controlled in conjunction with the swinging movement of the link member 8B in the direction approaching each other. It rises toward the gap between the opposing surfaces of the members 10 and 11 and enters the gap. As a result, the fixing pin 9A of the boom indirect disconnecting means 9 does not fall out of the hole, and the boom can be prevented from slipping down when the cylinder / boom connecting means 8 changes the boom. Even if any failure occurs in the drive device provided in the boom indirect disconnecting means 9 and the cylinder / boom connecting means 8, regardless of this, the fixed operation control member 10,
11 and the connection operation control member 13 directly act on each other to set a relative engagement relationship, so that an interlock operation can be reliably exhibited.

The fixing pin 9A of the boom indirect disconnecting means 9 is prevented from sliding in the fixed state by the ball lock mechanism 14. Occurs, and when the fixing by the boom indirect disconnecting means 9 cannot be released, the fixing pin 9A is simply pressed from the outside by the force against the pressing force acting on the ball 14D of the ball lock mechanism 14. The fixing pin 9A can be slid. Thereby, even if an unexpected situation occurs, for example, the movement of the boom by the cylinder / boom connecting means 8 becomes possible.

When the cylinder / boom connecting means 8 re-grips the boom, the connecting and fixing of the booms which had been connected and fixed until then is released, and the boom is selected in accordance with the movement of the cylinder / boom connecting means 8. The boom expands and contracts. At this time, the fixing pin 9 of the boom to be released from the connection fixing is pulled out from the hole by the boom indirect disconnecting means 9.

When the booms are unlocked,
The link members 9C and 9D of the boom indirect disconnecting means 9 are fitted to the fixing operation control members 10 and 11 integrated with the fixing pins 9A which are maintained in a state where they do not come out of the holes by the ball lock mechanism 14. . At this time, if the positions of the fixed operation control members 10, 11 and the link members 9C, 9D are slightly shifted, the link members 9C, 9D
Faces the guide surfaces 10A, 11A located inside the fixed operation control members 10, 11, and pushes the fixed operation control members 10, 11 in the sliding direction in accordance with the amount of displacement. For this reason, the fixing pin 9A can push and move the ball 14D of the ball lock mechanism 14 from the fitting portion 9A1 toward the radial outside of the fixing pin 9A along the inclined surface of the fitting portion 9A1. The pin 9A slides by an amount corresponding to the displacement amount.

When the fixing pin 9A can be slightly slid,
The positional relationship between the boom indirect disconnecting means 9 and the fixing pin 9A is optimized, in particular, the swing ends of the link members 9C and 9D are positioned on the axis of the fixing pin 9A, and the link members 9C and 9D are adjusted.
This can prevent the fixing pin 9A from skewing in the hole when swings. Also, when fixing the booms, the boom indirect disconnecting means 9 causes the link members 9C and 9d to enter the fixing operation control members 10 and 11 and fixes the link members 9C and 9D to the fixing pins as in the case described above. 9A swings in the direction of sliding toward the hole. The position of the fixing pin 9A engaged with the hole is maintained by the ball lock mechanism 14.

In the above-described embodiment, the fixing pin 9A in the connected and fixed state is configured to be prevented from sliding by the ball lock mechanism 14.
In addition, it is also possible to maintain the habit of engaging the fixing pin 9A with the hole by using the urging force of an elastic body such as a spring.

[0030]

According to the first aspect of the present invention, the fixing pin provided in the boom indirect disconnecting means is maintained in a fixed state in which the booms are connected to each other by the ball lock mechanism.
For this reason, the sliding prevention state by the ball lock mechanism can be released by externally pressing the fixing pin in a state where the booms are connected and fixed. This allows the booms to be released from the fixed connection state by a simple operation of simply pressing from the outside without the need for a special slide prevention release mechanism, etc. The movement of the boom using the means becomes possible.

According to the second aspect of the present invention, there is provided a pair of drive levers, one end of which is disposed at both ends of the drive device, and one end of which is connected to the boom-side end of the fixing pin. Therefore, the fixing pins located on both sides can be driven using the output necessary to operate one fixing pin. Thus, it is only necessary to prepare a drive device having an output intended for a single fixing pin, so that the drive device can be small and the device can be simplified and the cost can be reduced.

According to the third aspect of the present invention, since the fitting portion formed on the fixing pin has the inclined surface against which the ball of the ball lock mechanism is pressed, the fixing pin is provided on the inclined surface. By pushing and moving the pressed ball in a direction opposite to the pressing direction, the ball can slide even slightly. As a result, even if the ends of the fixing pins are not aligned between the booms, they are pushed when the pulling means interferes when moving, so that the fixing pins slide in a direction that does not hinder the movement of the pulling means. It is possible to make it easier to optimize the positional relationship with the extracting means.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main configuration of a boom extension device of a mobile crane according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the boom extension device shown in FIG.

FIG. 3 is a cross-sectional view showing one embodiment of the boom extension device shown in FIG.

FIG. 4 is a partial plan view for explaining a configuration of a boom indirect cutting means used in the boom extension device shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Base boom 2-5 Intermediate boom 6 Top boom 2A-6A Engagement hole 7 Single-stage double-acting hydraulic cylinder 7A Piston rod 7B Cylinder tube 8 Cylinder / boom connecting means 8A Connecting pin 8B Link member 8C Double-acting hydraulic pressure equivalent to a driving device Cylinder 9 Boom indirect disconnection means 9A Fixing pin 9A1 Fitting part 10, 11 Fixing operation control member 10A, 11A Guide surface 13 Connection operation control member 14 Ball lock mechanism 14D Ball

Claims (3)

[Claims] 1. A multi-stage telescopic boom in which a plurality of intermediate booms are inserted into a base boom and a top boom is sequentially inserted into and retracted from the intermediate boom, and a multi-stage telescopic boom is provided in the base boom base end. A single-stage double-acting hydraulic cylinder having a rod end pivotally supported, and cylinder-boom connecting means for selectively connecting a rod-side end of a cylinder tube and a base end of each intermediate boom in the single-stage double-acting hydraulic cylinder And a boom extension and contraction mechanism for a mobile crane, comprising: a boom indirect disconnection means capable of selectively fixing and releasing the booms, wherein the boom indirect disconnection means is capable of connecting adjacent booms to each other. A pair of fixing pins, and a ball lock mechanism for preventing sliding of the fixing pins, wherein the fixing pins can move forward and backward toward the outside of the boom. Vignetting, boom extension device of a mobile crane, characterized in that sliding is blocked by the ball-lock mechanism when the fixed state of connecting the boom to each other. 2. The boom extension and contraction device for a mobile crane according to claim 1, wherein the boom indirect disconnecting means includes a drive device including a double-acting hydraulic cylinder disposed orthogonal to the single-stage double-acting hydraulic cylinder. One end of the driving device is connected to and driven by both ends of the driving device, and the other end is provided with a pair of driving levers which are detachably disposed on the inner end of the fixing pin. Boom telescopic device 3. The boom extending and retracting device for a mobile crane according to claim 1, wherein the fixing pin is provided with a fitting portion including a concave portion having an inclined surface with which a ball of the ball lock mechanism comes into pressure contact. A boom telescopic device for a mobile crane, wherein the boom is extended.