Telescopic boom

Abstract

To provide a light-weight and a high rigidity telescopic boom suppressing a distortion during manufacturing.SOLUTION: A telescopic boom 13 forms a telescopic constructed by multiple booms, and has a boom fixing mechanism 15 to fix a top boom 21 placed relatively inside with respect to a first intermediate boom 22 placed relatively outside to a prescribed position. The boom fixing mechanism 15 comprises a boom fixing pin 26 provided on the top boom 21 and advancing / retreating against the first intermediate boom 22, a fixing boss 32 provided on the first intermediate boom 22 and into / from which the boom fixing pin 26 is inserted / removed, and a gap maintaining member 90 provided on the fixing boss 32 and protruding outward, and to maintain between the gap maintaining member and a second intermediate boom 23 placed further outside the first intermediate boom 22.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a structure of a telescopic boom mounted on a mobile crane. [Background technology]

[0002] Mobile cranes, such as rough terrain cranes, generally have telescopic booms. These telescopic booms are constructed by assembling multiple booms in a so-called nested configuration, with an inner boom, which has a smaller outer diameter, inserted inside an outer boom, which has a larger outer diameter. A predetermined gap is provided between the two, and when the telescopic booms are extended or retracted, the inner boom slides relative to the outer boom and protrudes from the outer boom.

[0003] Patent Document 1 discloses a connection structure for connecting an inner boom to an outer boom adjacent to the inner boom. In this connection structure, a boom fixing pin provided on the inner boom is fitted into a fixing boss attached to the outer boom. Specifically, the inner boom and the outer boom are connected by inserting the boom fixing pin into a fixing hole provided in the fixing boss. This allows the inner boom and the outer boom to slide together. The connection between the inner boom and the outer boom is released by removing the boom fixing pin from the fixing hole.

[0004] The telescopic boom disclosed in Patent Document 2 is provided with a slide plate between the inner boom and the outer boom. When the inner boom is displaced relative to the outer boom, the slide plate comes into contact with the adjacent boom. This maintains the predetermined gap and prevents direct contact between the outer surface of the inner boom and the inner surface of the outer boom. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4709415 [Patent Document 2] Japanese Patent Application Publication No. 2018-80020 Summary of the Invention [Problem to be solved by the invention]

[0006] Each boom that makes up a telescopic boom is made of a steel plate formed into a cylindrical shape, but it is required to be lightweight and highly rigid. Therefore, each boom is designed to be thin and have a large external size (thin wall and large cross section). In other words, a telescopic boom is designed to be compact, with a large external size for each boom and small gaps between the booms. On the other hand, the fixed bosses and slide plates are provided on each boom that makes up the telescopic boom, and are generally welded from the viewpoints of strength and attachment method.

[0007] When the fixing bosses and the like are welded to thin steel plates, the booms are prone to distortion. This distortion makes it impossible to ensure the required clearance. This not only makes assembling the booms difficult, but also makes the booms' design incompatible with the requirements, creating serious problems in the manufacture of telescopic booms.

[0008] The present invention has been made in light of the above background, and an object of the present invention is to provide a lightweight, highly rigid telescopic boom that is less susceptible to distortion during manufacturing. [Means for solving the problem]

[0009] (1) A telescopic boom according to the present invention has a plurality of telescopic booms and a boom fixing mechanism that fixes a boom arranged relatively inwardly in a predetermined position relative to a boom arranged relatively outwardly. The boom fixing mechanism includes a boom fixing pin provided on the inner boom and adapted to move forward and backward relative to the outer boom, a fixing boss provided on the outer boom and into which the boom fixing pin is inserted and removed, and a gap maintaining member provided on the fixing boss that protrudes outward and maintains a gap between the outer boom and a boom arranged further outwardly.

[0010] According to this configuration, the clearance maintaining member is attached to the fixed boss rather than being welded directly to the boom. This reduces the amount of welding to the boom, thereby suppressing welding distortion that occurs during boom manufacturing. This allows for a thinner boom design and a smaller gap between the booms, enabling a more compact and lightweight telescopic boom design. Furthermore, compared to when the fixed boss and the clearance maintaining member are welded separately to the boom, this reduces the space required for the gap between the booms, enabling optimal boom design. Furthermore, by attaching the clearance maintaining member to the fixed boss, the clearance maintaining member is located near the location where the boom fixing pin is inserted and removed. Therefore, the clearance between adjacent booms is reliably maintained at the location where the boom fixing pin operates.

[0011] (2) The fixing boss has a rectangular shape extending in the longitudinal direction and the up-down direction of the boom, and includes a central plate portion into which the boom fixing pin is inserted and removed, a pair of horizontal bulges continuing from both sides of the central plate portion in the longitudinal direction and bulging smoothly outward, and a vertical bulge portion continuing from at least one of the upper end or lower end of the central plate portion and bulging smoothly. The clearance maintaining member is provided on the vertical bulge portion so as to protrude toward the boom side arranged relatively outward.

[0012] In this configuration, the horizontal bulges smoothly connect to both sides of the central plate located relatively centrally, and the vertical bulges smoothly connect to the upper part of the central plate. That is, the fixing boss is a flat plate-shaped member whose outer periphery forms a smooth closed curve. Therefore, when an external force is applied to the fixing boss, stress concentration at a specific point is alleviated, ensuring sufficient mechanical strength for the fixing boss and enabling a lightweight design.

[0013] Furthermore, the clearance maintaining member is provided on the vertical bulge portion, so that when the clearance maintaining member comes into contact with an adjacent boom (a boom arranged further outward), the impact of the contact, etc., can be reduced from affecting the central plate portion and horizontal bulge portion of the fixed boss.

[0014] (3) The fixing boss is rectangular and extends in the longitudinal and vertical directions of the boom, and includes a central plate portion through which the boom fixing pin is inserted and removed, and a pair of lateral bulges that are continuous with both sides of the central plate portion in the longitudinal direction and bulge symmetrically outward, and it is preferable that the gap maintaining member is provided on the central plate portion or the lateral bulges and has a rectangular shape that protrudes toward the boom side, which is positioned relatively outward.

[0015] In this configuration, the lateral bulges smoothly connect to both sides of the central plate, which is located relatively centrally. In other words, the fixing boss is a flat plate-shaped member, and its outer periphery forms a smooth closed curve. Therefore, when an external force acts on the fixing boss, stress concentration at a specific point is alleviated, ensuring sufficient mechanical strength for the fixing boss. Additionally, the fixing boss has a simple shape, allowing for a lighter design.

[0016] (4) It is preferable that the gap maintaining member is detachably attached to the fixed boss by a fastening member.

[0017] According to this configuration, the gap maintaining member is a consumable item and can be easily replaced.

[0018] (5) The hardness of the gap maintaining member is lower than the hardness of the boom.

[0019] According to this configuration, when the gap maintaining member comes into contact with the boom, the gap maintaining member with low hardness wears, thereby preventing wear on the boom.

[0020] (6) Preferably, the boom is made of a steel material, and the gap maintaining member is made of a copper alloy.

[0021] (7) The gap maintaining member may be welded to the fixing boss.

[0022] With this configuration, the gap maintaining member can be firmly attached to the fixing boss. [Effects of the Invention]

[0023] According to the present invention, a lightweight and highly rigid telescopic boom is provided that is free from distortion during manufacturing. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a left side view of a mobile crane employing a telescopic boom according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the structure of a telescopic boom according to one embodiment of the present invention. [Figure 3] FIG. 3 is a vertical cross-sectional view of a telescopic boom according to one embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of a telescopic boom according to one embodiment of the present invention. [Figure 5] FIG. 5 is a perspective view of a fixing boss according to one embodiment of the present invention. [Figure 6] FIG. 6 is a perspective view of a fixing boss according to one embodiment of the present invention. [Figure 7] FIG. 7 is an enlarged view of the part surrounded by the dashed line in FIG. [Figure 8] FIG. 8 is an enlarged cross-sectional view of a main part showing a mounting structure for a gap maintaining member according to a modified example of one embodiment of the present invention. [Figure 9] FIG. 9 is a perspective view showing the structure of a fixing boss according to a modified example of one embodiment of the present invention. [Figure 10] FIG. 10 is a perspective view showing the structure of a fixing boss according to a modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] A preferred embodiment of the present invention will be described below with reference to the drawings. Note that this embodiment is merely one aspect of the telescopic boom according to the present invention, and it goes without saying that the implementation may be changed without departing from the spirit and scope of the present invention.

[0026] FIG. 1 is a left side view of a mobile crane 10 employing a telescopic boom 13 according to one embodiment of the present invention.

[0027] As shown in FIG. 1, the crane 10 includes a traveling body 111, a boom device 112, a cabin 113, and a winch 139.

[0028] The running vehicle 111 includes a body 120 and wheels 121. The body 120 has axles (not shown), which are arranged at the front and rear of the body 120. Wheels 121 are provided at both ends of each axle. The axles and wheels 121 are rotated by an engine (not shown), which causes the running vehicle 111 to run.

[0029] The boom device 112 includes a swivel base 11, a swivel motor (not shown), a telescopic boom 13, and a hoisting cylinder 136.

[0030] The swivel base 11 is supported by the vehicle body 120. The swivel base is supported so as to be rotatable about a rotation axis extending in the vertical direction. The swivel base 11 is rotated by a rotation motor. The telescopic boom 13 is supported by the swivel base 11. The telescopic boom 13 can rotate together with the swivel base 11.

[0031] The telescopic boom 13 is raised and lowered between a lowered position and an erected position around the hoisting central shaft 12 by extension and contraction of the hoisting cylinder 136. The hoisting central shaft 12 extends in the width direction 102 (see FIG. 2: the direction perpendicular to the paper surface in FIG. 1). In FIG. 1, the telescopic boom 13 in the lowered position is shown by a solid line, and the telescopic boom 13 in the erected position is shown by a dashed line.

[0032] As shown in Figure 2, the telescopic boom 13 includes multiple cylindrical booms (a base boom 20, a top boom 21, and intermediate booms 22 to 25, which will be described later), which are telescopic. Each of the booms 20 to 25 is made of, for example, steel. The configuration of the telescopic boom 13 will be described in detail later.

[0033] The cabin 113 is mounted on the swivel base 11. The cabin 113 has a seat for the operator, a driving device used to drive the running body 111, and a control device used to operate the boom device 112. The crane 10 is a so-called rough terrain crane, and the operator drives the running body 111 and controls the boom device 112 from within the single cabin 113. However, the crane 10 may be an all-terrain crane equipped with two cabins: one with the driving device and the other with the control device. The driving device includes a steering wheel for steering the wheels 121, an accelerator pedal, a brake pedal, a shift lever, etc. The operator uses the driving device to drive the running body 111. The control device includes multiple levers for driving the swing motor, the telescopic cylinder, the hoisting cylinder 136, a winch motor (not shown), etc. The operator uses the control device to operate the boom device 112.

[0034] The winch 139 has a rotatably driven drum 141, a wire rope 142, and a suspension hook 140. The drum 141 is rotatably supported on the swivel base 11.

[0035] The drum 141 is rotated by a winch motor. The wire rope 142 is wound around the drum 141, and is unwound from or wound onto the drum 141 as the drum 141 rotates. The suspension hook 140 is connected to the wire rope 142.

[0036] The wire rope 142 is wound from the drum 141 onto a wire sheave 144 provided at the base end of the telescopic boom 13 and is stretched along the telescopic boom 13. The wire rope 142 is wound onto a wire sheave 143 provided at the tip end of the telescopic boom 13 and hangs down.

[0037] The hoisting hook 140 is connected to the tip of a wire rope 142. The hoisting hook 140 is suspended by the wire rope 142 from the tip of the telescopic boom 13. The hoisting hook 140 rises and falls as the drum 141 rotates.

[0038] FIG. 2 is a schematic diagram showing the structure of the telescopic boom 13.

[0039] In addition to the above-mentioned swivel base 11, swivel motor, telescopic boom 13, and derrick cylinder 136, the boom device 112 also includes a telescopic cylinder 14, a boom fixing mechanism 15, a cylinder-boom connecting mechanism 16, and a drive mechanism (not shown), as shown in the figure.

[0040] The telescopic cylinder 14 extends and retracts the telescopic boom 13. The boom fixing mechanism 15 connects adjacent booms among the multiple booms that make up the telescopic boom 13. The cylinder-to-boom connection mechanism 16 connects the telescopic cylinder 14 to a predetermined part of the telescopic boom 13. The drive mechanism drives the boom fixing mechanism 15 and the cylinder-to-boom connection mechanism 16. Note that a known configuration can be used for the drive mechanism, so a detailed description thereof will be omitted.

[0041] The telescopic boom 13 includes a base boom 20, a top boom 21, and four intermediate booms 22 to 25 disposed between them. The intermediate booms 22 to 25 are referred to as the first intermediate boom 22, the second intermediate boom 23, the third intermediate boom 24, and the fourth intermediate boom 25, in order from the one adjacent to the top boom 21. That is, in this embodiment, the telescopic boom 13 is formed into six sections. Each of the booms 21 to 25 is assembled so as to slide in the longitudinal direction 38 relative to the base boom 20.

[0042] The telescopic boom 13 is telescopic. That is, the fourth intermediate boom 25 is disposed within the base boom 20 and is slidable relative to the base boom 20. The third intermediate boom 24 is disposed within the fourth intermediate boom 25 and is slidable relative to the fourth intermediate boom 25. The second intermediate boom 23 is disposed within the third intermediate boom 24 and is slidable relative to the third intermediate boom 24. The first intermediate boom 22 is disposed within the second intermediate boom 23 and is slidable relative to the second intermediate boom 23. The top boom 21 is disposed within the first intermediate boom 22 and is slidable relative to the first intermediate boom 22.

[0043] It should be noted that the telescopic boom 13 does not need to be a six-stage formation, and the number of intermediate booms is not particularly limited.

[0044] The telescopic cylinder 14 is built into the telescopic boom 13. The telescopic cylinder 14 is a hydraulic double-acting cylinder. The tip of the cylinder rod 39 is connected to the base end of the base boom 20. The telescopic cylinder 14 is arranged along the longitudinal direction 38 of the telescopic boom 13, and the cylinder tube 36 is arranged inside the top boom 21 in the state shown in Figure 2. When the telescopic cylinder 14 extends and retracts, the telescopic boom 13 extends and retracts as described below.

[0045] 2 shows the telescopic boom 13 in a fully retracted state. In this state, adjacent booms are always connected to each other by a boom fixing mechanism 15.

[0046] Figures 3 and 4 are a longitudinal cross-sectional view and a transverse cross-sectional view, respectively, of the telescopic boom 13, and Figure 4 is a cross-sectional view taken along plane IV-IV in Figure 3. These figures schematically show the structures of the boom fixing mechanism 15 and the cylinder-boom connection mechanism 16. Note that Figure 4 only shows the top boom 21, first intermediate boom 22, and second intermediate boom 23, and does not show the third intermediate boom 24, fourth intermediate boom 25, and base boom 20.

[0047] 2, 3, and 4, the boom fixing mechanism 15 includes five boom fixing pins (hereinafter referred to as "B pins") 26-30, a hydraulic cylinder 31 that drives the B pins 26-30, and fixing bosses 32 and 33. The B pins 26-30 pass through the fixing bosses 32 and 33. Note that the fixing bosses 32 and 33 are not shown in FIG. 1.

[0048] 2, the B pin 26 is supported by the top boom 21. The B pins 27 to 30 are supported by the first intermediate boom 22, the second intermediate boom 23, the third intermediate boom 24, and the fourth intermediate boom 25, respectively. The base boom 20, which is located outermost, does not have a B pin.

[0049] The B pin 26 moves forward and backward relative to the boom (the boom arranged outside) adjacent to the boom (the boom arranged inside) supporting the B pin 26, thereby penetrating the outer boom or moving away from the outer boom. The same applies to the B pins 27 to 30. The B pin 26 penetrates the first intermediate boom 22, thereby fixing the top boom 21 to a predetermined position on the first intermediate boom 22. Similarly, the B pins 27 to 30 each penetrate the booms (the third intermediate boom 24, the fourth intermediate boom 25, and the base boom 26) arranged relatively outside, thereby fixing the outer booms to predetermined positions on the booms (the second intermediate boom 22, the third intermediate boom 23, and the fourth intermediate boom 25) arranged relatively inside. The B pins 26 to 30 are normally biased toward the outer booms by springs (not shown).

[0050] B pins 26-30 pass through the base and tip ends of the booms (the third intermediate boom 24, the fourth intermediate boom 25, and the base boom 26) that are positioned relatively outward. Fixing bosses 32, 33 are provided at the locations where the B pins 26-30 pass through. The B pins 26-30 pass through the fixing bosses 32, 33 provided on the first intermediate boom 22, the fixing bosses 32, 33 provided on the second intermediate boom 23, the fixing bosses 32, 33 provided on the third intermediate boom 24, the fixing bosses 32, 33 provided on the fourth intermediate boom 25, and the fixing bosses 32, 33 provided on the base boom 20, respectively. Note that the top boom 21, which is located innermost, does not have fixing bosses 32, 33.

[0051] The following describes the structure of the fixed boss 32. Note that the fixed boss 33 has the same structure as the fixed boss 32, so a description of the structure of the fixed boss 33 will be omitted.

[0052] Fig. 5 is a perspective view of the fixed boss 32. Fig. 6 is a perspective view of the fixed boss 32 as seen from the opposite side to that of Fig. 5.

[0053] 5 and 6, the fixing boss 32 is a plate-shaped member having a predetermined thickness, and is typically made of steel.

[0054] As shown in FIG. 5 , the fixing boss 32 includes a central plate portion 51, a pair of horizontal bulges 52, and an upper bulge portion 53 (corresponding to the "vertical bulge portion" in the claims). The central plate portion 51, the pair of horizontal bulges 52, and the upper bulge portion 53 are integrally formed, and as shown in the figure, the outer periphery of the fixing boss 32 forms a smooth closed curve. In this embodiment, the upper bulge portion 53 is continuous with the upper side of the central plate portion 51, but the upper bulge portion 53 may also be continuous with the lower side of the central plate portion 51. However, the upper bulge portion 53 may also be continuous with the top and bottom of the central plate portion 51. Note that in FIG. 5 , the central plate portion 51, the pair of horizontal bulges 52, and the upper bulge portion 53 are separated by imaginary dashed lines.

[0055] In the following description, each direction is defined assuming that the fixed boss 32 is attached to each of the booms 20, 22 to 25. The central plate portion 51 has a rectangular shape extending in the longitudinal direction 38 and the up-down direction 101. Here, the up-down direction 101 is a direction perpendicular to the longitudinal direction 38 of the boom (see FIG. 1) and the width direction 102 of the boom (see FIG. 2).

[0056] The pair of lateral bulges 52 are provided on both sides of the central plate portion 51 in the longitudinal direction 38. The pair of lateral bulges 52 are positioned so as to sandwich the central plate portion 51 in the longitudinal direction 38. The pair of lateral bulges 52 are continuous with both sides of the central plate portion 51 in the longitudinal direction 38, and bulge smoothly outward. The edge surfaces 81 of each lateral bulge 52 (surfaces forming the outer ends of each lateral bulge 52 in the longitudinal direction 38) are curved so as to protrude outward in the longitudinal direction 38.

[0057] The upper bulge 53 protrudes upward from the upper end of the central plate 51. The upper bulge 53 is continuous with the upper end of the central plate 51 and bulges outward (upward) smoothly. An edge surface 82 of the upper bulge 53 is curved.

[0058] As shown in FIG. 6, a thick portion 84 is formed on the first surface 83 of the fixing boss 32. The thick portion 84 is formed by the first surface 83 bulging in the thickness direction. Therefore, the thickness dimension of the thick portion 84 is greater than the thickness dimension of the remaining portion. The thick portion 84 is formed in a portion excluding the central plate portion 51, the edge portions 85 of the lateral bulging portions 52, and the upper bulging portion 53. The side surface 86 of the thick portion 84 is inclined. In other words, the periphery of the thick portion 84 is chamfered. As a result, the thick portion 84 is tapered.

[0059] As shown in FIGS. 5 and 6 , the fixing boss 32 has a through hole 87. The through hole 87 penetrates the thick-walled portion 84 of the fixing boss 32 in the thickness direction. The through hole 87 penetrates the fixing boss 32 from the first surface 83 to the second surface 88 (the back surface of the first surface 83). As will be described later, the B pins 26 to 30 penetrate through the through hole 87. In this embodiment, the through hole 87 is provided so as to penetrate the central plate portion 51 and one of the pair of lateral bulges 52, but the position of the through hole 87 is not limited to the position shown in FIGS. 5 and 6 . For example, the through hole 87 may not be formed in the pair of lateral bulges 52, but may be formed only in the central plate portion 51. The size and shape of the through hole 87 only need to correspond to the size and shape of the B pins 26 to 30, and are not limited to the size and shape shown in FIGS. 5 and 6 .

[0060] A gap maintaining member 90 is welded to the second surface 88 side of the upper bulging portion 53. The gap maintaining member 90 has a rectangular prism shape and protrudes from the second surface 88. The cross section of the gap maintaining member 90 is trapezoidal. The upper and lower bases of this trapezoidal shape extend in the longitudinal direction 38, with the upper base being shorter than the lower base.

[0061] The gap maintaining member 90 is made of a material that is lower in hardness than the base boom 20, the top boom 21, and the intermediate booms 22 to 25. In this embodiment, the gap maintaining member 90 is made of gunmetal (copper alloy).

[0062] Note that the fixing boss 32 is not limited to the shape and size shown in Figures 5 and 6 as long as it has a through hole 87 and has a gap maintaining member 90 attached thereto. The shape and size of the gap maintaining member 90 are not limited to the shape and size shown in Figures 5 and 6, and various shapes such as a circle, a rectangle, an ellipse, etc. may be used.

[0063] FIG. 7 is an enlarged view of the part surrounded by the dashed line in FIG.

[0064] This figure shows the fixed boss 32 attached to the first intermediate boom 22. Note that the state in which the fixed boss 33 is attached to the first intermediate boom 22 and the state in which the fixed bosses 32, 33 are attached to the second intermediate boom 23, third intermediate boom 24, fourth intermediate boom 25 and base boom 20 are the same as the state in which the fixed boss 32 is attached to the first intermediate boom 22, and therefore descriptions thereof will be omitted.

[0065] As shown in Fig. 2, the first intermediate boom 22 has through holes at its front end and rear end (portion through which the B pin 26 passes). As shown in Fig. 7, the fixing boss 32 is attached to the first intermediate boom 22 from the outside of the base end of the first intermediate boom 22. In detail, the fixing boss 32 is welded to the first intermediate boom 22 with the thick portion 84 of the fixing boss 32 inserted into the through hole.

[0066] 7 also shows the second intermediate boom 23 and the fixed boss 32 attached to the second intermediate boom 23.

[0067] When the fixed boss 32 is welded to the first intermediate boom 22, a portion of the thick portion 84 of the fixed boss 32 protrudes inward from the first intermediate boom 22. However, that portion of the thick portion 84 does not have to protrude inward from the first intermediate boom 22. Meanwhile, the portion of the fixed boss 32 other than the thick portion 84 abuts against the outer surface 72 of the first intermediate boom 22 from the outside. In this state, the second surface 88 of the fixed boss 32 is located outward from the outer surface 72 of the first intermediate boom 22 (toward the second intermediate boom 23). The gap maintaining member 90 is located in a position protruding outward from the fixed boss 32 (toward the second intermediate boom 23). In this case, the first intermediate boom 22 corresponds to the "boom located outward" recited in the claims, and the second intermediate boom 23 corresponds to the "boom located further outward" recited in the claims.

[0068] In the figure, the distance between the outer surface 72 of the first intermediate boom 22 and the inner surface 73 of the second intermediate boom 23 is indicated by reference symbol L1. The distance between the second surface 88 of the fixed boss 32 welded to the first intermediate boom 22 and the thick portion 84 of the fixed boss 32 welded to the second intermediate boom 23 is indicated by reference symbol L2. The distance between the gap maintaining member 90 provided on the first intermediate boom 22 side and the inner surface 73 of the second intermediate boom 23 is indicated by reference symbol L3. The distance L3 is smaller than the distances L1 and L2. As a result, even if the first intermediate boom 22 shifts position and the outer surface 72 of the first intermediate boom 22 approaches the inner surface 73 of the second intermediate boom 23, for example, when the first intermediate boom 22 slides relative to the second intermediate boom 23, the gap maintaining member 90 abuts against the inner surface 73, preventing the fixed boss 32 and the first intermediate boom 22 from contacting the second intermediate boom 23. In other words, the gap maintaining member 90 maintains the gap between the first intermediate boom 22 and the second intermediate boom 23.

[0069] The advancement and retreat of the B pin 26 relative to the fixed bosses 32 and 33 will be described below.

[0070] 2, the B pin 26 passes through the base end and tip end of the first intermediate boom 22. Fixed bosses 32, 33, through which the B pin 26 is inserted, are provided at the base end and tip end. The location where the fixed boss 32 is provided is the position where the B pin 26 faces when the top boom 21 is fully retracted relative to the first intermediate boom 22. The location where the fixed boss 33 is provided is the position where the B pin 26 faces when the top boom 21 is fully extended relative to the first intermediate boom 22.

[0071] The B pin 26 is normally biased toward the first intermediate boom 22 by a spring (not shown).

[0072] As shown in Figure 7, the B pin 26 passes through the through hole 87 of the fixing boss 32, so that the top boom 21 is connected and fixed to the first intermediate boom 22 in a fully contracted state (see Figure 4(B)). On the other hand, the B pin 26 passes through the through hole 87 of the fixing boss 33, so that the top boom 21 is connected and fixed to the first intermediate boom 22 in a fully extended state.

[0073] 4(A), when the hydraulic cylinder 31 is actuated, the B pin 26 is pulled out of the fixed bosses 32, 33 provided on the first intermediate boom 22. This allows the top boom 21 to slide relatively with respect to the first intermediate boom 22.

[0074] In this case, the top boom 21 corresponds to the "inner boom" described in the claims, and the first intermediate boom 22 corresponds to the "outer boom" described in the claims.

[0075] The B-pins 27 to 30 also move forward and backward relative to the fixed bosses 32 and 33 in the same manner as the B-pin 26.

[0076] 2, 3, and 4, the cylinder-boom connection mechanism 16 includes a cylinder connecting pin (hereinafter referred to as "C-pin") 34 and a hydraulic cylinder 35 that drives it. The C-pin 34 is provided on the cylinder tube 36 side of the telescopic cylinder 14, and in the state shown in FIG. 2, it is fitted to the top boom 21.

[0077] 4, the hydraulic cylinder 35 includes a link mechanism 40. The link mechanism 40 slides the C-pin 34 in the width direction 102 when the hydraulic cylinder 35 is actuated.

[0078] The C-pin 34 is normally biased toward the top boom 21 by a spring (not shown).

[0079] As shown in Fig. 2, a fixed boss 37 is provided at the base end of the top boom 21. As shown in Figs. 2 and 4, the C-pin 34 fits into the fixed boss 37. When the hydraulic cylinder 35 is actuated, the C-pin 34 is pulled towards the telescopic cylinder 14 via the link mechanism 40. When the C-pin 34 is pulled out of the fixed boss 37, the telescopic cylinder 14 is mechanically separated from the top boom 21. The telescopic cylinder 14 is normally connected to the top boom 21, and when the hydraulic cylinder 35 is actuated, the telescopic cylinder 14 can slide relative to the telescopic boom 13. A fixed boss 37 is also provided at the base end of each of the intermediate booms 22 to 25, and the C-pin 34 can be selectively connected to each of the intermediate booms 22 to 25 in a manner described below.

[0080] Figure 4(A) shows a state in which the B pin 26 has been pulled out from the first intermediate boom 22 and the C pin 34 has been connected to the top boom 21, and Figure 4(B) shows a state in which the B pin 26 has been connected to the first intermediate boom 22 and the C pin 34 has been pulled out from the top boom 21.

[0081] When the telescopic cylinder 14 is extended from the state shown in FIG. 4(A), as shown in FIG. 2, the top boom 21, together with the cylinder tube 36 of the telescopic cylinder 14, slides leftward in the longitudinal direction 38 relative to the first intermediate boom 22. When the telescopic cylinder 14 is extended to a position where the B-pin 26 faces the fixed boss 33, the operation of the hydraulic cylinder 31 is stopped, and the B-pin 26 returns to the first intermediate boom 22 side by the spring and engages with the fixed boss 33. As a result, the top boom 21 and the first intermediate boom 22 are fixed in their fully extended state. Next, as shown in FIG. 4(B), the hydraulic cylinder 35 is actuated, and the C-pin 34 is disconnected from the top boom 21 via the link mechanism 40. In other words, the C-pin 34 is pulled out of the fixed boss 37 of the top boom 21. When the telescopic cylinder 14 is retracted in this state, only the cylinder tube 36 moves toward the base end of the base boom 20 (to the right in FIG. 2).

[0082] During this time, the hydraulic cylinder 35 remains activated, and the C-pin 34 remains in the position shown in Figure 4(B). When the telescopic cylinder 14 retracts and the C-pin 34 reaches the position of the fixed boss 37 on the first intermediate boom 22, the retraction of the telescopic cylinder 14 is stopped and the operation of the hydraulic cylinder 35 is stopped, and the C-pin 34 is connected to the fixed boss 37 of the first intermediate boom 22, as shown in Figure 4(A). When the second intermediate boom 23 is extended, the same operations as when the top boom 21 is extended are performed, and the second intermediate boom 23, third intermediate boom 24, and fourth intermediate boom 25 are extended in that order. When the telescopic boom 13 is retracted, the reverse operations to those described above are performed.

[0083] [Effects of the embodiment]

[0084] According to this embodiment, because the gap maintaining members 90 are attached to the fixed bosses 32, 33, the gap maintaining members 90 are not welded directly to the boom. In other words, of the fixed bosses 32, 33 and the gap maintaining members 90, only the fixed bosses 32, 33 are welded to the boom. This reduces the amount of welding to the boom, and reduces welding distortion that occurs during boom manufacturing. As a result, the boom can be made even thinner, and space between the booms can be saved, enabling optimal boom design. Furthermore, by attaching the gap maintaining members 90 to the fixed bosses 32, 33, the gap maintaining members 90 are positioned near the locations where the B pins 26-30 are inserted and removed. Therefore, the gap between the booms is reliably maintained at the locations where the B pins 26-30 operate.

[0085] According to this embodiment, the outer edge of the fixing boss 32 forms a smooth closed curve. That is, the pair of lateral bulges 52 and the upper bulge 53 are smoothly connected to the central plate 51, which alleviates stress concentration at specific locations. This allows the fixing boss 32 to have sufficient mechanical strength and also allows for a lightweight design.

[0086] According to this embodiment, the gap maintaining member 90 is provided on the upper bulge 53. Therefore, when the gap maintaining member 90 provided on the boom arranged on the outside comes into contact with a boom arranged further outward, it is possible to reduce the influence of the impact at the time of contact on the central plate 51 and the lateral bulge 52 of the fixing bosses 32, 33.

[0087] According to this embodiment, the gap maintaining member 90 is a quadrangular prism with a trapezoidal cross section, and therefore the gap maintaining member 90 can be made smaller by the amount that the upper base is shorter than the lower base.

[0088] According to this embodiment, when the gap maintaining member 90 comes into contact with the boom, the gap maintaining member 90, which has low hardness, wears, so that it is possible to prevent the boom from wearing.

[0089] According to this embodiment, the gap maintaining members 90 are welded to the fixing bosses 32, 33, so that the gap maintaining members 90 can be firmly attached to the fixing bosses 32, 33.

[0090] [Variations]

[0091] In the above embodiment, the gap maintaining member 90 is made of gunmetal, but the gap maintaining member 90 may be made of a material other than gunmetal. In this case, the gap maintaining member 90 is preferably made of a copper alloy other than gunmetal, but may be made of a material other than a copper alloy. For example, the gap maintaining member 90 may be made of the same material as the fixing boss 32, or a resin may be used.

[0092] The position at which the gap maintaining member 90 is attached to the fixing boss 32 is not limited to the upper bulge 53. For example, the gap maintaining member 90 may be attached to the right or left of the through-hole 87 shown in Fig. 5. Multiple gap maintaining members 90 may be attached to the fixing boss 32. For example, the gap maintaining member 90 may be attached below the through-hole 87 in addition to the position shown in Fig. 5.

[0093] The gap maintaining member 90 may be attached to the fixed boss 32 by means other than welding, for example, by fitting or adhesive. The gap maintaining member 90 may be provided on the fixed boss 32 by being formed integrally with the fixed boss 32.

[0094] FIG. 8 is an enlarged cross-sectional view of a main part showing the mounting structure of a gap maintaining member 90 according to a modified example of this embodiment.

[0095] As shown in the figure, the gap maintaining member 90 may be attached to the fixed boss 32 by a bolt 89 (corresponding to the "fastening member" in the claims). In this modification, the gap maintaining member 90 is fastened to the upper bulge 53 of the fixed boss 32 via a seat member 91. The gap maintaining member 90 has a stepped hole 92 as shown in the figure. The bolt 89 is inserted through this stepped hole 92 and threadedly engages with the upper bulge 53.

[0096] Since the gap maintaining member 90 is fixed by the bolt 89 in this manner, the gap maintaining member 90 is detachable from the fixing boss 32. This has the advantage that the gap maintaining member 90 is a consumable item and can be easily replaced.

[0097] 9 and 10 are perspective views showing the structure of a fixed boss 60 according to a modified example of this embodiment.

[0098] This fixing boss 60 differs from the fixing boss 32 according to the above embodiment (see FIGS. 5 and 6) in that the fixing boss 60 does not have the upper bulge 53 that the fixing boss 32 has, that the central plate portion 61 is a substantially square rectangle, that the lateral bulges 62 are a substantially semicircular shape, that the shape of the thick portion 64 has been changed correspondingly, and that the gap maintaining member 62 is a rectangular parallelepiped. The other configurations of the fixing boss 60 are the same as those of the fixing boss 32, and the same reference numerals are used.

[0099] 9 and 10, the fixing boss 60 includes a central plate portion 61 and a pair of lateral bulges 62. Similar to the fixing boss 32, the central plate portion 61 and the pair of lateral bulges 62 are integrally formed. The central plate portion 61 has a rectangular shape extending in the longitudinal direction 38 and the up-down direction 101. In this modified example, the central plate portion 61 is square. However, the shape of the central plate portion 61 is not limited to a square, and may be any rectangular shape.

[0100] In this modified example, the pair of lateral bulges 62 are semicircular in shape. They are continuous on both sides of the central plate portion 61 in the longitudinal direction 38 and are arranged symmetrically. However, the shape of the lateral bulges 62 is not limited to semicircular, and may be any shape that smoothly bulges outward from the central plate portion 61 in the longitudinal direction 38. The edge surface 81 of each lateral bulge 62 is curved so as to protrude outward in the longitudinal direction 38. The lateral bulge 62 may also be rectangular. In this case, the central plate portion 61 and the lateral bulge 62 as a whole have a rectangular shape.

[0101] 10, the thick portion 84 formed on the first surface 83 of the fixing boss 60 is formed in a portion excluding the central plate portion 60 and the edge portion 85 of the lateral bulge portion 62. A side surface 86 of this thick portion 64 is inclined, similar to the thick portion 84 of the fixing boss 32 (see FIG. 6). The fixing boss 60 has a through hole 87, which, similar to the fixing boss 32, penetrates the fixing boss 60 from the first surface 83 to the second surface 88 (the back surface of the first surface 83). The size and shape of this through hole 87 are not particularly limited, and may be any size and shape that corresponds to the size and shape of the B pins 26 to 30.

[0102] The gap maintaining member 63 is welded to the central plate portion 61. In this modified example, the gap maintaining member 63 has a rectangular parallelepiped shape and is provided on the second surface 88. The gap maintaining member 62 is disposed at the boundary between the central plate portion 61 and the lateral bulging portion 62. However, the gap maintaining member 62 may be disposed so as to bridge between the central plate portion 61 and the lateral bulging portion 62, or may be disposed on the lateral bulging portion 62. The gap maintaining member 62 is preferably disposed near the through hole 87, and for example, as shown in FIG. 9, the distance 65 from the edge of the through hole 87 to the edge of the gap maintaining member 62 is preferably set to 5 mm to 20 mm.

[0103] However, the shape of the gap maintaining member 63 is not limited to a rectangular parallelepiped, and the cross section may be a columnar shape such as a circle, ellipse, or polygon. The shape of the gap maintaining member 63 may also correspond to the outer shape of the fixed boss 60. That is, the outer shape of the gap maintaining member 63 may correspond to the central plate portion 61 and the lateral bulge portion 62. In this case, a through hole similar to the through hole 87 is provided in the gap maintaining member 63. In this modification, the material constituting the gap maintaining member 63 is typically gunmetal (copper alloy), and a material with a lower hardness than that of the base boom 20, the top boom 21, and the intermediate booms 22 to 25 may be used. The gap maintaining member 63 may also be made of resin.

[0104] The fixing boss 60 according to this modification has a simple shape, and has the advantage that it can be designed to be even lighter than the fixing boss 32 according to the above embodiment. [Explanation of symbols]

[0105] 10. Crane 11. Swivel table 12...Center axis of relief 13. Telescopic boom 14 Telescopic cylinder 15. Boom fixing mechanism 16 Cylinder boom connection mechanism 20···Base boom (boom) 21. Top Boom (Boom) 22. First intermediate boom (boom) 23. Second intermediate boom (boom) 24. Third intermediate boom (boom) 25···Fourth intermediate boom (boom) 26 Boom fixing pin 27 Boom fixing pin 28 Boom fixing pin 29 Boom fixing pin 30 Boom fixing pin 31 Hydraulic cylinder 32 Fixed boss 33 Fixed boss 34 Cylinder connecting pin 35 Hydraulic cylinder 36···Cylinder tube 37 Fixed boss 38 Longitudinal direction 39 Cylinder rod 40 Link mechanism 51...Central plate part 52...lateral bulge 53...superior bulge 60 Fixed boss 61...Central plate part 62...lateral bulge 63 Gap maintaining member 64...Thick part 72...External surface 73...Inside 81 Edge surface 82 Edge surface 83...Front page 84...Thick part 85···Edge 86...Side 87...Through hole 88...2nd page 89 volts 90 Gap maintaining member 101...Up and down direction 102...width direction 111...Traveling body 112 Boom device 113···Cabin 120...Body 121...Wheel 136···Deepening cylinder 139···Winch 140···Hanging hook 141...Drums 142 Wire rope 143 Wire sheave 144 Wire sheave

Claims

1. A telescopic boom has a plurality of booms that are telescopic, and has a boom fixing mechanism that fixes a boom that is disposed relatively inward to a boom that is disposed relatively outward in a predetermined position, The boom fixing mechanism is a boom fixing pin provided on the inner boom and adapted to advance and retreat relative to the outer boom; a fixing boss provided on the outer boom and into which the boom fixing pin is inserted and removed; a gap maintaining member that is provided on the fixed boss and protrudes outward to maintain a gap between the boom arranged outward and a boom arranged further outward, The fixed bosses mentioned above are: a central plate portion having a rectangular shape extending in the longitudinal direction and the up-down direction of the boom, into which the boom fixing pin is inserted and removed; a pair of lateral bulging portions each continuing from both sides of the central plate portion in the longitudinal direction and bulging smoothly outward; a vertical bulge portion that bulges smoothly and continuously from at least one of the upper end and the lower end of the central plate portion, The gap maintaining member is provided on the vertical bulging portion so as to protrude toward the boom side arranged relatively outward.

2. A telescopic boom having a plurality of telescopic booms and a boom fixing mechanism for fixing a boom arranged relatively inwardly to a boom arranged relatively outwardly in a predetermined position, The boom fixing mechanism is a boom fixing pin provided on the inner boom and adapted to advance and retreat relative to the outer boom; a fixing boss provided on the outer boom and into which the boom fixing pin is inserted and removed; a gap maintaining member that is provided on the fixed boss and protrudes outward to maintain a gap between the boom arranged outward and a boom arranged further outward, The fixed bosses mentioned above are: a central plate portion having a rectangular shape extending in the longitudinal direction and the up-down direction of the boom, into which the boom fixing pin is inserted and removed; a pair of lateral bulging portions that are continuous with both sides of the central plate portion in the longitudinal direction and bulge symmetrically outward, 2. The telescopic boom according to claim 1, wherein the gap maintaining member is provided on the central plate portion or the lateral bulging portion and has a rectangular parallelepiped shape protruding toward the boom side disposed relatively outward.

3. 3. The telescopic boom according to claim 1, wherein the gap maintaining member is detachably attached to the fixed boss by a fastening member.

4. 4. The telescopic boom according to claim 1, wherein the hardness of the gap maintaining member is lower than the hardness of the boom.

5. 5. The telescopic boom according to claim 4, wherein the boom is made of a steel material, and the gap maintaining member is made of a copper alloy.

6. 6. The telescopic boom according to claim 1, wherein the gap maintaining member is welded to the fixing boss.

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