Retractable boom

Abstract

The present invention provides a lightweight and highly rigid telescopic boom that can suppress deformation during manufacturing. The telescopic boom (13) has a telescopic structure formed by a plurality of booms and includes a boom fixing mechanism (15) that fixes the top boom (21) disposed on the relatively inner side to a predetermined position with respect to the first intermediate boom (22) disposed on the relatively outer side. The boom fixing mechanism (15) includes: a boom fixing pin (26) that is provided on the top boom (21) and advances and retreats with respect to the first intermediate boom (22); a fixing boss (32) that is provided on the first intermediate boom (22) and into which the boom fixing pin (26) is inserted and withdrawn; and a clearance maintaining member (90) that is provided on the fixing boss (32) and projects outward to maintain the clearance between the first intermediate boom (22) and the second intermediate boom (23) disposed on the further outer side.

Description

Technical Field

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

[0002] Mobile cranes such as rough terrain cranes generally have a telescopic boom for forming a telescopic structure. This telescopic boom is assembled by nesting a plurality of booms. A smaller inner boom is inserted inside a larger outer boom. A prescribed gap is provided between the two. When the telescopic boom expands and contracts, 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 adjacent outer boom. In this connection structure, a boom fixing pin provided on the inner boom is fitted into a fixing boss installed on the outer boom. Specifically, by inserting the boom fixing pin into a fixing hole provided in the fixing boss, the inner boom and the outer boom can be connected. Thus, the inner boom and the outer boom slide integrally. By pulling out the boom fixing pin from the fixing hole, the connection between the inner boom and the outer boom can be released.

[0004] The telescopic boom disclosed in Patent Document 2 has a sliding plate between the inner boom and the outer boom. When the inner boom is displaced relative to the outer boom, the sliding plate contacts the adjacent boom. Thus, the prescribed gap can be maintained and direct contact between the outer surface of the inner boom and the inner surface of the outer boom can be prevented.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 4709415 Gazette

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2018-80020 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] However, each boom constituting the telescopic boom is formed into a cylindrical shape from a steel plate, and lightweight and high rigidity are required. Therefore, each boom is designed to have a thin wall thickness and a large outer dimension (thin wall and large cross section). That is, the telescopic boom has been designed to be compact by increasing the outer dimensions of each boom and reducing the gap between the booms. On the other hand, the fixing boss and the sliding plate are provided on each boom constituting the telescopic boom, and are generally welded from the viewpoints of strength and installation method.

[0011] In the case where the above-mentioned fixing bosses and the like are welded to the thin steel plate, the above-mentioned boom arms are liable to be deformed. When such deformation occurs, the above-mentioned specified gap cannot be ensured. As a result, not only is it difficult to assemble the boom arms, but also the design of each boom arm cannot meet the above requirements at all, and serious problems will occur in the manufacturing process of the telescopic boom.

[0012] The present invention has been completed in view of this background, and an object thereof is to provide a lightweight and highly rigid telescopic boom that can suppress deformation during manufacturing.

[0013] Means for Solving the Problem

[0014] (1) The telescopic boom of the present invention is formed of a plurality of boom arms to form a telescopic structure, and has a boom fixing mechanism that fixes the boom arm disposed on the relatively inner side to a specified position with respect to the boom arm disposed on the relatively outer side. The boom fixing mechanism includes: a boom fixing pin that is provided on the boom arm disposed on the inner side and moves forward and backward with respect to the boom arm disposed on the outer side; a fixing boss that is provided on the boom arm disposed on the outer side for inserting and removing the boom fixing pin; and a gap maintaining member that is provided on the fixing boss and protrudes outward to maintain a gap between the boom arm disposed on the outer side and the boom arm disposed on the more outer side.

[0015] According to this structure, the gap maintaining member is not directly welded to the boom arm, but is provided on the fixing boss. Therefore, the amount of welding to the boom arm is reduced, and as a result, the welding deformation generated during the manufacture of the boom arm can be suppressed. Thereby, a design in which the wall thickness of the boom arm can be made thinner and the gap between the boom arms can be made smaller can be achieved, and a compact design and a lightweight design of the telescopic boom can be achieved. In addition, compared with the case where the above-mentioned fixing boss and the gap maintaining member are respectively welded to the boom arm, the space of the above-mentioned gap between the boom arms can be saved, and an optimal design of the boom arm can be achieved. And, by providing the above-mentioned gap maintaining member on the above-mentioned fixing boss, the gap maintaining member is disposed near the portion where the above-mentioned boom fixing pin is inserted and removed. Therefore, the gap between adjacent boom arms can be reliably maintained at the portion where the above-mentioned boom fixing pin operates.

[0016] (2) The fixing boss includes: a central plate portion that is rectangular and extends in the longitudinal direction and the up-and-down direction of the boom arm for inserting and removing the boom fixing pin; a pair of lateral bulging portions that are respectively continuous with both sides in the longitudinal direction of the central plate portion and smoothly bulge outward; and a longitudinal bulging portion that is continuous with at least one of the upper end or the lower end of the central plate portion and smoothly bulges. The gap maintaining member is provided on the longitudinal bulging portion so as to protrude toward the boom arm disposed on the relatively outer side.

[0017] In this structure, the lateral bulging portion is smoothly continuous with both sides of the central plate portion disposed at the relative central portion, and the longitudinal bulging portion is smoothly continuous with the upper side of the central plate portion. That is, the fixing boss is a flat plate-like member, and its outer peripheral edge depicts a smooth closed curve. Therefore, when an external force acts on the fixing boss, stress concentration on a specific part can be alleviated. Thus, the fixing boss can ensure sufficient mechanical strength and can also achieve a lightweight design.

[0018] In addition, a gap maintaining member is disposed on the longitudinal bulging portion. Therefore, when this gap maintaining member comes into contact with an adjacent boom (a boom disposed on the outermost side), the impact and other effects on the central plate portion and the lateral bulging portion of the fixing boss during contact can be reduced.

[0019] (3) Preferably, the fixing boss includes: a central plate portion which is rectangular and extends in the longitudinal direction and the up-and-down direction of the boom, for inserting and removing the boom fixing pin; and a pair of lateral bulging portions which are respectively continuous with both sides of the central plate portion in the longitudinal direction and bulge out symmetrically to the outside. The gap maintaining member is disposed on the central plate portion or the lateral bulging portion and is in the shape of a cuboid protruding toward the boom side disposed on the relatively outer side.

[0020] In this structure, the lateral bulging portion is smoothly continuous with both sides of the central plate portion disposed at the relative central portion. That is, the fixing boss is a flat plate-like member, and its outer peripheral edge depicts a smooth closed curve. Therefore, when an external force acts on the fixing boss, stress concentration on a specific part can be alleviated. Thus, the fixing boss can ensure sufficient mechanical strength. In addition, the shape of the fixing boss is simple, and further lightweight design can be achieved.

[0021] (4) Preferably, the gap maintaining member is detachably disposed on the fixing boss through a fastening member.

[0022] According to this structure, the gap maintaining member can be easily replaced as a consumable.

[0023] (5) The hardness of the gap maintaining member is lower than that of the boom.

[0024] According to this structure, when the gap maintaining member comes into contact with the boom, the low-hardness gap maintaining member will wear, so that the boom can be prevented from wearing.

[0025] (6) Preferably, the boom is made of a steel material, and the gap maintaining member is made of a copper alloy.

[0026] (7) The gap maintaining member can also be welded to the fixing boss.

[0027] According to this structure, the clearance maintaining member can be firmly mounted on the fixed boss.

[0028] Effect of the Invention

[0029] According to the present invention, there is provided a lightweight and highly rigid telescopic boom capable of suppressing deformation during manufacturing. Description of the Drawings

[0030] Figure 1 is a left view of a mobile crane 10 with a telescopic boom 13 according to an embodiment of the present invention.

[0031] Figure 2 is a schematic cross-sectional view showing the structure of a telescopic boom according to an embodiment of the present invention.

[0032] Figure 3 is a longitudinal sectional view of a telescopic boom according to an embodiment of the present invention.

[0033] Figure 4 is a cross-sectional view of a telescopic boom according to an embodiment of the present invention.

[0034] Figure 5 is a perspective view of a fixed boss according to an embodiment of the present invention.

[0035] Figure 6 is a perspective view of a fixed boss according to an embodiment of the present invention.

[0036] Figure 7 is Figure 4 an enlarged view of the portion surrounded by the dotted line in

[0037] Figure 8 is a main part enlarged cross-sectional view showing the mounting structure of a clearance maintaining member according to a modification of an embodiment of the present invention.

[0038] Figure 9 is a perspective view showing the structure of a fixed boss according to a modification of an embodiment of the present invention.

[0039] Figure 10 is a perspective view showing the structure of a fixed boss according to a modification of an embodiment of the present invention. Detailed Description of the Invention

[0040] Hereinafter, preferred embodiments of the present invention will be described with appropriate reference to the drawings. In addition, this embodiment is merely one mode of the telescopic boom of the present invention, and of course, the embodiment can be changed within the scope of not changing the gist of the present invention.

[0041] Figure 1 is a left view of a mobile crane 10 with a telescopic boom 13 according to an embodiment of the present invention.

[0042] As Figure 1 shown, the crane 10 includes a traveling body 111, a boom device 112, a cab 113, and a winch 139.

[0043] The traveling body 111 includes a vehicle body 120 and wheels 121. The vehicle body 120 has axles (not shown), and the axles are arranged at the front and rear of the vehicle body 120. The wheels 121 are provided at both ends of each axle. The axles and the wheels 121 are rotationally driven by an engine (not shown), so that the traveling body 111 travels.

[0044] The boom device 112 includes a slewing platform 11, a slewing motor (not shown), a telescopic boom 13, and a hoisting cylinder 136.

[0045] The slewing platform 11 is supported by the vehicle body 120. The slewing platform is rotatably supported about a rotation axis extending in the vertical direction. The slewing platform 11 is rotated by the slewing motor. The telescopic boom 13 is supported by the slewing platform 11. The telescopic boom 13 can rotate together with the slewing platform 11.

[0046] The telescopic boom 13 expands and contracts by the hoisting cylinder 136, and rises and falls about the hoisting center axis 12 between the stowed position and the upright position. The hoisting center axis 12 extends in the width direction 102 (refer to Figure 2 : the direction perpendicular to the paper surface in Figure 1 ). In Figure 1 the telescopic boom 13 in the stowed position is shown by a solid line, and the telescopic boom 13 in the upright position is shown by a dashed line.

[0047] As Figure 2 shown, the telescopic boom 13 includes a plurality of cylindrical booms (the base boom 20, the top boom 21, and the intermediate booms 22 to 25 described later), which form a telescopic structure. Each boom 20 to 25 is made of, for example, a steel material. The structure of the telescopic boom 13 will be described in detail later.

[0048] The cab 113 is mounted on the slewing platform 11. The cab 113 has a seat for the operator to sit on, a driving device for driving the traveling body 111, and a control device for operating the boom device 112. The crane 10 is a so-called rough-terrain crane, and the operator drives the traveling body 111 and operates the boom device 112 in one cab 113. However, the crane 10 may also be an all-terrain crane having two cabs, one cab having a driving device and the other cab having a control device. The driving device has a steering wheel for steering the wheels 121, an accelerator pedal, a brake pedal, a gearshift lever, etc. The operator uses the driving device to drive the traveling body 111. The control device has a plurality of levers for driving the slewing motor, the telescopic cylinder, the hoisting cylinder 136, the winch motor (not shown), etc. The operator uses the control device to operate the boom device 112.

[0049] The winch 139 has a drum 141 that is rotationally driven, a wire rope 142, and a hook 140. The drum 141 is rotatably supported by the slewing platform 11.

[0050] The drum 141 rotates by a winch motor. The wire rope 142 is wound around the drum 141 and is fed out from or wound around the drum 141 as the drum 141 rotates. The hook 140 is connected to the wire rope 142.

[0051] The wire rope 142 is wound from the drum 141 around a wire rope pulley 144 provided at the base end portion of the telescopic boom 13 and is installed along the telescopic boom 13. The wire rope 142 is wound around a wire rope pulley 143 provided at the front end portion of the telescopic boom 13 and hangs down.

[0052] The hook 140 is connected to the front end of the wire rope 142. The hook 140 hangs down from the front end portion of the telescopic boom 13 through the wire rope 142. The hook 140 moves up and down as the drum 141 rotates.

[0053] Figure 2 It is a schematic diagram showing the structure of the telescopic boom 13.

[0054] In addition to the above-described slewing platform 11, slewing motor, telescopic boom 13, and hoisting cylinder 136, as shown in this figure, the boom device 112 further includes a telescopic cylinder 14, a boom fixing mechanism 15, a cylinder-boom connecting mechanism 16, and a drive mechanism (not shown).

[0055] The telescopic cylinder 14 extends and retracts the telescopic boom 13. The boom fixing mechanism 15 connects adjacent booms among the plurality of booms constituting the telescopic boom 13 to each other. The cylinder-boom connecting mechanism 16 connects the telescopic cylinder 14 to a specified portion of the telescopic boom 13. The drive mechanism drives the boom fixing mechanism 15 and the cylinder-boom connecting mechanism 16. In addition, since the above-described drive mechanism can adopt a known structure, its detailed description is omitted.

[0056] The telescopic boom 13 includes a base boom 20, a top boom 21, and four intermediate booms 22 to 25 disposed therebetween. The intermediate booms 22 to 25 are sequentially referred to as the first intermediate boom 22, the second intermediate boom 23, the third intermediate boom 24, and the fourth intermediate boom 25 starting from the boom adjacent to the top boom 21. That is, in the present embodiment, the telescopic boom 13 is a six-section assembly. Each of the booms 21 to 25 is assembled so as to slide in the length direction 38 with respect to the base boom 20.

[0057] The telescopic boom 13 forms a telescopic structure. That is, the fourth intermediate boom 25 is disposed within the base boom 20 and is capable of sliding relative to the base boom 20. The third intermediate boom 24 is disposed within the fourth intermediate boom 25 and is capable of sliding relative to the fourth intermediate boom 25. The second intermediate boom 23 is disposed within the third intermediate boom 24 and is capable of sliding relative to the third intermediate boom 24. The first intermediate boom 22 is disposed within the second intermediate boom 23 and is capable of sliding relative to the second intermediate boom 23. The top boom 21 is disposed within the first intermediate boom 22 and is capable of sliding relative to the first intermediate boom 22.

[0058] In addition, the telescopic boom 13 does not have to be a six-section assembly, and the number of intermediate booms is not particularly limited.

[0059] The telescopic cylinder 14 is built into the telescopic boom 13. The telescopic cylinder 14 is a hydraulic double-acting cylinder. The front end of the piston rod 39 is connected to the proximal end of the base boom 20. The telescopic cylinder 14 is arranged along the longitudinal direction 38 of the telescopic boom 13, and in Figure 2 this state, the cylinder barrel 36 is disposed inside the top boom 21. Through the telescopic movement of the telescopic cylinder 14, as described later, the telescopic boom 13 expands and contracts.

[0060] Figure 2 Fig. shows the telescopic boom 13 in a fully retracted state. In this state, the adjacent booms are usually connected by the boom fixing mechanism 15.

[0061] Figure 3 and Figure 4 are respectively the longitudinal sectional view and the transverse sectional view of the telescopic boom 13, Figure 4 is Figure 3 the sectional view taken along the IV-IV plane in Figure 4 . These figures schematically show the structures of the boom fixing mechanism 15 and the cylinder boom connecting mechanism 16. In addition, in Figure 4 , only the top boom 21, the first intermediate boom 22, and the second intermediate boom 23 are shown, and the illustration of the third intermediate boom 24, the fourth intermediate boom 25, and the base boom 20 is omitted.

[0062] As Figure 2 , Figure 3 and Figure 4 show, the boom fixing mechanism 15 includes five boom fixing pins (hereinafter referred to as "B pins") 26 to 30, a hydraulic cylinder 31 for driving the B pins 26 to 30, and fixing bosses 32, 33. The B pins 26 to 30 penetrate through the fixing bosses 32, 33. In addition, in Figure 1 , the illustration of the fixing bosses 32, 33 is omitted.

[0063] As Figure 2As shown, the B pin 26 is supported by the top boom 21. The B pins 27 to 30 are respectively supported by the first intermediate boom 22, the second intermediate boom 23, the third intermediate boom 24, and the fourth intermediate boom 25. In addition, the outermost base boom 20 does not have a B pin.

[0064] The B pin 26 moves forward and backward with respect to the boom adjacent to the outside of the boom (the inner - arranged boom) that supports the B pin 26, so as to penetrate through the boom arranged on the outside or separate from the boom arranged on the outside. The same applies to the B pins 27 to 30. The B pin 26 penetrates through the first intermediate boom 22 to fix the top boom 21 at a specified position on the first intermediate boom 22. Similarly, the B pins 27 to 30 respectively penetrate through the booms arranged on the relatively outside (the second intermediate boom 23, the third intermediate boom 24, the fourth intermediate boom 25, and the base boom 20), so as to fix the boom arranged on the outside at a specified position on the boom arranged on the relatively inside (the first intermediate boom 22, the second intermediate boom 23, the third intermediate boom 24, and the fourth intermediate boom 25). Under normal circumstances, the B pins 26 to 30 are biased by a spring (not shown) toward the boom arranged on the relatively outside.

[0065] The B pins 26 to 30 penetrate through the base ends and the front ends of the booms arranged on the relatively outside (the first intermediate boom 22, the second intermediate boom 23, the third intermediate boom 24, the fourth intermediate boom 25, and the base boom 20). Fixing bosses 32 and 33 are provided at the positions where the B pins 26 to 30 penetrate. The B pins 26 to 30 respectively penetrate through the fixing bosses 32 and 33 provided on the first intermediate boom 22, the fixing bosses 32 and 33 provided on the second intermediate boom 23, the fixing bosses 32 and 33 provided on the third intermediate boom 24, the fixing bosses 32 and 33 provided on the fourth intermediate boom 25, and the fixing bosses 32 and 33 provided on the base boom 20. In addition, the innermost top boom 21 does not have the fixing bosses 32 and 33.

[0066] Hereinafter, the structure of the fixing boss 32 will be described. In addition, since the fixing boss 33 has the same structure as the fixing boss 32, the description of the structure of the fixing boss 33 will be omitted.

[0067] Figure 5 is a perspective view of the fixing boss 32. Figure 6 is from the side opposite to Figure 5 is a perspective view of the fixing boss 32 observed from the opposite side.

[0068] As Figure 5 and Figure 6 shown, the fixing boss 32 is a plate - shaped component with a specified wall thickness. Typically, the fixing boss 32 is made of steel material.

[0069] As Figure 5As shown, the fixed boss 32 includes a central plate portion 51, a pair of lateral bulging portions 52, and an upper bulging portion 53 (corresponding to the "longitudinal bulging portion" described in the claims). The central plate portion 51, the pair of lateral bulging portions 52, and the upper bulging portion 53 are integrally formed. As shown in this figure, the outer peripheral edge of the fixed boss 32 depicts a smooth closed curve. In the present embodiment, the upper bulging portion 53 is continuous with the upper side of the central plate portion 51, but the upper bulging portion 53 may also be continuous with the lower side of the central plate portion 51. Of course, the upper bulging portion 53 may also be continuous with both the upper and lower sides of the central plate portion 51. Additionally, in Figure 5 the central plate portion 51 is divided from the pair of lateral bulging portions 52 and the upper bulging portion 53 by the hypothetically marked dashed lines.

[0070] In the following description, each direction is defined in the state where the fixed boss 32 is mounted on each of the booms 20, 22 to 25. The central plate portion 51 is a rectangle that extends in the length direction 38 and the up-and-down direction 101. Here, the up-and-down direction 101 is a direction orthogonal to the length direction 38 of the boom (refer to Figure 1 ) and the width direction 102 of the boom (refer to Figure 2 ).

[0071] The pair of lateral bulging portions 52 are disposed on both sides in the length direction 38 with respect to the central plate portion 51. The pair of lateral bulging portions 52 are located at positions sandwiching the central plate portion 51 in the length direction 38. The pair of lateral bulging portions 52 are respectively continuous with both sides of the central plate portion 51 in the length direction 38 and bulge outward smoothly. The edge surface 81 of each lateral bulging portion 52 (the surface forming the outer end of each lateral bulging portion 52 in the length direction 38) is curved so as to protrude outward in the length direction 38.

[0072] The upper bulging portion 53 protrudes upward from the upper end of the central plate portion 51. The upper bulging portion 53 is continuous with the upper end of the central plate portion 51 and bulges outward (upward) smoothly. The edge surface 82 of the upper bulging portion 53 is curved.

[0073] As Figure 6 shown, a thick wall portion 84 is formed on the first surface 83 of the fixed boss 32. The thick wall portion 84 is formed by bulging from the first surface 83 in the thickness direction. Therefore, the wall thickness dimension of the thick wall portion 84 is larger than the wall thickness dimensions of the other parts. The thick wall portion 84 is formed in a part excluding the edge portion 85 of the central plate portion 51 and the lateral bulging portions 52 and the upper bulging portion 53. The side surface 86 of the thick wall portion 84 is inclined. That is, the periphery of the thick wall portion 84 is chamfered. Thereby, the front end of the thick wall portion 84 becomes tapered.

[0074] As Figure 5 and Figure 6As shown, the fixing boss 32 has a through-hole 87. The through-hole 87 penetrates the thick-wall 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 the through-hole 87. In the present embodiment, the through-hole 87 is provided so as to penetrate one of the central plate portion 51 and the pair of laterally bulging portions 52, but the position of the through-hole 87 is not limited to Figure 5 and Figure 6 the positions shown. For example, the through-hole 87 may be formed only in the central plate portion 51 instead of being formed on the pair of laterally bulging portions 52. 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 Figure 5 and Figure 6 the size and shape shown.

[0075] The clearance maintaining member 90 is welded to the second surface 88 side of the upper bulging portion 53. The clearance maintaining member 90 is in the shape of a quadrangular prism and protrudes from the second surface 88. The cross-sectional shape of the clearance maintaining member 90 is trapezoidal. The upper base and the lower base of the trapezoidal shape extend in the longitudinal direction 38, and the upper base is shorter than the lower base.

[0076] The clearance maintaining member 90 is made of a material having a hardness lower than that of the base boom 20, the top boom 21, and the intermediate booms 22 to 25. In the present embodiment, the clearance maintaining member 90 is made of gunmetal (copper alloy).

[0077] In addition, the fixing boss 32 only needs to have the through-hole 87 and the clearance maintaining member 90 mounted thereon, and is not limited to Figure 5 and Figure 6 the shape and size shown. The clearance maintaining member 90 is not limited to Figure 5 and Figure 6 the shape and size shown, and various shapes such as circular, rectangular, and elliptical can be adopted.

[0078] Figure 7 is Figure 4 an enlarged view of the portion surrounded by the dotted line in

[0079] This figure shows the state in which the fixing boss 32 is mounted on the first intermediate boom 22. In addition, the state in which the fixing boss 33 is mounted on the first intermediate boom 22, and the states in which the fixing bosses 32 and 33 are mounted on the second intermediate boom 23, the third intermediate boom 24, the fourth intermediate boom 25, and the base boom 20 are the same as the state in which the fixing boss 32 is mounted on the first intermediate boom 22, and thus the description thereof is omitted.

[0080] As Figure 2 shown, the front end portion and the rear end portion (the portion through which the B pin 26 penetrates) of the first intermediate boom 22 have through-holes. AsFigure 7 As shown, the fixed boss 32 is mounted on the first intermediate boom 22 from the outside of the base end portion of the first intermediate boom 22. Specifically, in a state where the thick wall portion 84 of the fixed boss 32 is inserted through the through hole, the fixed boss 32 is welded to the first intermediate boom 22.

[0081] In addition, Figure 7 The second intermediate boom 23 and the fixed boss 32 mounted on the second intermediate boom 23 are also shown.

[0082] In a state where the fixed boss 32 is welded to the first intermediate boom 22, a part of the thick wall portion 84 of the fixed boss 32 protrudes inward from the first intermediate boom 22. Of course, a part of the thick wall portion 84 may not protrude inward from the first intermediate boom 22. On the other hand, a portion other than the thick wall portion 84 of the fixed boss 32 abuts against the outer surface 72 of the first intermediate boom 22 from the outside. At this time, the second surface 88 of the fixed boss 32 is located on the outer side (the second intermediate boom 23 side) with respect to the outer surface 72 of the first intermediate boom 22. The clearance maintaining member 90 is located at a position protruding outward (the second intermediate boom 23 side) with respect to the fixed boss 32. In this case, the first intermediate boom 22 corresponds to the "outer boom arranged" described in the claims, and the second intermediate boom 23 corresponds to the "outer boom arranged more outside" described in the claims.

[0083] In this figure, the interval 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 the symbol L1. The interval between the second surface 88 of the fixed boss 32 welded to the first intermediate boom 22 and the thick wall portion 84 of the fixed boss 32 welded to the second intermediate boom 23 is indicated by the symbol L2. The interval between the clearance 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 the symbol L3. The interval L3 is smaller than the intervals L1 and L2. Thus, in the case where the first intermediate boom 22 slides relative to the second intermediate boom 23 or the like, even if the position of the first intermediate boom 22 is shifted and the outer surface 72 of the first intermediate boom 22 approaches the inner surface 73 of the second intermediate boom 23, the contact between the fixed boss 32, the first intermediate boom 22 and the second intermediate boom 23 is prevented because the clearance maintaining member 90 abuts against the inner surface 73. That is, the clearance maintaining member 90 maintains the clearance between the first intermediate boom 22 and the second intermediate boom 23.

[0084] Hereinafter, the advancing and retracting movements of the B pin 26 with respect to the fixed bosses 32 and 33 will be described.

[0085] As Figure 2As shown, the B pin 26 penetrates through the base end portion and the front end portion of the first intermediate boom 22. Fixed bosses 32 and 33 through which the B pin 26 is inserted are provided at the base end portion and the front end portion. The position where the fixed boss 32 is provided is the position opposed to the B pin 26 when the top boom 21 is in a fully retracted state relative to the first intermediate boom 22. The position where the fixed boss 33 is provided is the position opposed to the B pin 26 when the top boom 21 is in a fully extended state relative to the first intermediate boom 22.

[0086] Normally, the B pin 26 is biased toward the first intermediate boom 22 by a spring (not shown).

[0087] As Figure 7 shown, through the through-hole 87 of the fixed boss 32 penetrated by the B pin 26, the top boom 21 is connected and fixed to the first intermediate boom 22 in a fully retracted state (see Figure 4 (B)). On the other hand, through the through-hole 87 of the fixed boss 33 penetrated by the B pin 26, the top boom 21 is connected and fixed to the first intermediate boom 22 in a fully extended state.

[0088] As Figure 4 (A) shown, by operating the hydraulic cylinder 31, the B pin 26 is pulled out from the fixed bosses 32 and 33 provided on the first intermediate boom 22. Thereby, the top boom 21 can slide relative to the first intermediate boom 22.

[0089] 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.

[0090] In addition, regarding the B pins 27 to 30, their advancing and retreating movements relative to the fixed bosses 32 and 33 are the same as those of the B pin 26.

[0091] As Figure 2 , Figure 3 and Figure 4 shown, the cylinder boom connecting mechanism 16 includes a cylinder connecting pin (hereinafter referred to as "C pin") 34 and a hydraulic cylinder 35 for driving the same. The C pin 34 is provided on the cylinder barrel 36 side of the telescopic cylinder 14 and is engaged with the top boom 21 in the state shown in Figure 2 .

[0092] As Figure 4 shown, the hydraulic cylinder 35 includes a link mechanism 40. By operating the hydraulic cylinder 35, the link mechanism 40 slides the C pin 34 in the width direction 102.

[0093] Normally, the C pin 34 is biased toward the top boom 21 by a spring (not shown).

[0094] AsFigure 2 As shown, a fixing boss 37 is provided at the base end portion of the top boom 21. As Figure 2 and Figure 4 shown, the C pin 34 is fitted with the fixing boss 37. By operating the hydraulic cylinder 35, the C pin 34 is pulled toward the telescopic cylinder 14 side via the link mechanism 40. When the C pin 34 is pulled out from the fixing boss 37, the telescopic cylinder 14 is mechanically separated from the top boom 21. Under normal circumstances, the telescopic cylinder 14 is connected to the top boom 21, and when the hydraulic cylinder 35 operates, the telescopic cylinder 14 can slide relative to the telescopic boom 13. Fixing bosses 37 are also provided at the base end portions of the intermediate booms 22 to 25, and the C pin 34 can be selectively connected to the intermediate booms 22 to 25 according to the key points described below.

[0095] Figure 4 (A) shows a state where the B pin 26 is pulled out from the first intermediate boom 22 and the C pin 34 is connected to the top boom 21, Figure 4 (B) shows a state where the B pin 26 is connected to the first intermediate boom 22 and the C pin 34 is pulled out from the top boom 21.

[0096] When the telescopic cylinder 14 extends from the Figure 4 (A) state, as Figure 2 shown, the top boom 21 and the cylinder barrel 36 of the telescopic cylinder 14 slide relative to the first intermediate boom 22 in the left direction of the longitudinal direction 38. When the telescopic cylinder 14 extends to a position where the B pin 26 faces the fixing boss 33, the operation of the hydraulic cylinder 31 stops, and the B pin 26 is reset toward the first intermediate boom 22 side by the above-mentioned spring and is fitted with the fixing boss 33. Thus, the top boom 21 and the first intermediate boom 22 are fixed in a fully extended state relative to each other. Next, as Figure 4 (B) shown, the hydraulic cylinder 35 is operated to release the connection between the C pin 34 and the top boom 21 via the link mechanism 40. That is, the C pin 34 is pulled out from the fixing boss 37 of the top boom 21. In this state, when the telescopic cylinder 14 contracts, only the cylinder barrel 36 moves toward the base end side of the base boom 20 (to the right side in Figure 2 ).

[0097] During this period, the hydraulic cylinder 35 remains in operation, and the C pin 34 remains in the Figure 4 (B) state. When the telescopic cylinder 14 contracts and the C pin 34 moves to the position of the fixing boss 37 provided on the first intermediate boom 22, the contraction operation of the telescopic cylinder 14 stops, and the operation of the hydraulic cylinder 35 stops, as Figure 4As shown in (A), the C pin 34 is connected to the fixing boss 37 of the first intermediate boom 22. When the second intermediate boom 23 is to be extended, the same operation as the extension of the top boom 21 is performed, and the second intermediate boom 23, the third intermediate boom 24, and the fourth intermediate boom 25 are extended in sequence. In addition, when the telescopic boom 13 is to be retracted, the reverse operation is performed.

[0098] [Function and Effect of Embodiment]

[0099] According to the present embodiment, the clearance maintaining member 90 is provided on the fixing bosses 32 and 33, so the clearance maintaining member 90 is not directly welded to the boom. That is, among the fixing bosses 32 and 33 and the clearance maintaining member 90, only the fixing bosses 32 and 33 are welded to the boom. Therefore, the welding amount to the boom is reduced, and the welding deformation generated during the manufacture of the boom can be reduced. As a result, further thinning of the boom can be achieved, the space for the clearance between the booms can be saved, and the optimal design of the boom can be realized. And, by providing the clearance maintaining member 90 on the fixing bosses 32 and 33, the clearance maintaining member 90 is arranged near the portion where the B pins 26 to 30 are inserted and removed. Therefore, the clearance between the booms can be reliably maintained at the portion where the B pins 26 to 30 act.

[0100] According to the present embodiment, the outer edge of the fixing boss 32 is a smooth closed curve. That is, the pair of lateral bulging portions 52 and the upper bulging portion 53 are smoothly continuous with respect to the central plate portion 51, so the stress concentration on a specific portion can be alleviated. Thereby, the fixing boss 32 can ensure sufficient mechanical strength and can also achieve a lightweight design.

[0101] According to the present embodiment, the clearance maintaining member 90 is provided on the upper bulging portion 53. Therefore, when the clearance maintaining member 90 provided on the outer boom comes into contact with the more outer boom, the influence such as impact on the central plate portion 51 and the lateral bulging portion 52 of the fixing bosses 32 and 33 can be reduced during the contact.

[0102] According to the present embodiment, the clearance maintaining member 90 is a quadrangular prism with a trapezoidal cross-sectional shape. Therefore, the clearance maintaining member 90 can be miniaturized corresponding to the amount that the upper base is smaller than the lower base.

[0103] According to the present embodiment, when the clearance maintaining member 90 comes into contact with the boom, the low-hardness clearance maintaining member 90 will be worn, so the wear of the boom can be prevented.

[0104] According to the present embodiment, by welding the clearance maintaining member 90 to the fixing bosses 32 and 33, the clearance maintaining member 90 can be firmly mounted on the fixing bosses 32 and 33.

[0105] [Modification Example]

[0106] In the above-described embodiment, the clearance maintaining member 90 is made of gunmetal, but the clearance maintaining member 90 may also be made of a material other than gunmetal. In this case, the clearance maintaining member 90 is preferably made of a copper alloy other than gunmetal, but may also be made of an alloy other than copper alloy. For example, the clearance maintaining member 90 may be made of the same material as the fixed boss 32, or may be made of resin.

[0107] The position where the clearance maintaining member 90 is installed on the fixed boss 32 is not limited to the portion of the upper bulging portion 53. For example, the clearance maintaining member 90 may also be installed on Figure 5 the right side or the left side of the through hole 87 shown. Multiple clearance maintaining members 90 may also be installed on the fixed boss 32. For example, in addition to being installed at the Figure 5 position shown, the clearance maintaining member 90 may also be installed below the through hole 87.

[0108] The clearance maintaining member 90 may also be installed on the fixed boss 32 by means other than welding, for example, by fitting or bonding. The clearance maintaining member 90 may also be provided on the fixed boss 32 by being integrally formed with the fixed boss 32.

[0109] Figure 8 FIG. is a main part enlarged sectional view showing the mounting structure of the clearance maintaining member 90 which is a modification of the present embodiment.

[0110] As shown in this figure, the clearance maintaining member 90 may also be installed on the fixed boss 32 by a bolt 89 (corresponding to the "fastening member" described in the claims). In this modification, the clearance maintaining member 90 is fastened to the upper bulging portion 53 of the fixed boss 32 via a base member 91. The clearance maintaining member 90 has a stepped hole 92 as shown in this figure. The bolt 89 is inserted through the stepped hole 92 and is screwed with the above-described upper bulging portion 53.

[0111] In this way, since the clearance maintaining member 90 is fixed by the bolt 89, the clearance maintaining member 90 can be disassembled and assembled relative to the fixed boss 32. Therefore, it has the advantage that the clearance maintaining member 90 can be easily replaced as a consumable.

[0112] Figure 9 and Figure 10 FIG. is a perspective view showing the structure of the fixed boss 60 which is a modification of the present embodiment.

[0113] This fixed boss 60 is the same as the fixed boss 32 of the above-described embodiment (refer to Figure 5 and Figure 6) The differences are as follows: The fixed boss 60 does not have the upper bulging portion 53 that the fixed boss 32 has. The central plate portion 61 is a rectangle that is substantially square, and the lateral bulging portion 62 is substantially semicircular. The shape of the thick wall portion 64 also changes accordingly, and the clearance maintaining member 63 is in the shape of a rectangular parallelepiped. In addition, other structures of the fixed boss 60 are the same as those of the fixed boss 32, and the same reference numerals are used.

[0114] As Figure 9 and Figure 10 shown, the fixed boss 60 includes a central plate portion 61 and a pair of lateral bulging portions 62. Similar to the above-mentioned fixed boss 32, the central plate portion 61 and the pair of lateral bulging portions 62 are integrally formed. The central plate portion 61 is a rectangle that extends in the longitudinal direction 38 and the vertical direction 101. In this modified example, the central plate portion 61 is square. Of course, the shape of the central plate portion 61 is not limited to square, as long as it is a rectangle.

[0115] In this modified example, the shape of the pair of lateral bulging portions 62 is semicircular. They are continuous with both sides of the central plate portion 61 in the longitudinal direction 38 and are symmetrically arranged. Of course, the shape of the lateral bulging portion 62 is not limited to semicircular, as long as it is a shape that smoothly bulges outward from the central plate portion 61 in the longitudinal direction 38. The edge surface 81 of each lateral bulging portion 62 is curved so as to protrude outward in the longitudinal direction 38. In addition, the lateral bulging portion 62 can also be rectangular. In this case, the central plate portion 61 and the lateral bulging portion 62 as a whole are rectangular.

[0116] As Figure 10 shown, the thick wall portion 84 formed on the first surface 83 of the fixed boss 60 is formed in a portion other than the edge portion 85 of the central plate portion 61 and the lateral bulging portion 62. The side surface 86 of this thick wall portion 64 is inclined in the same manner as the thick wall portion 84 of the fixed boss 32 (refer to Figure 6 ). The fixed boss 60 has a through hole 87, which, similar to the fixed boss 32, penetrates the fixed 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, as long as they correspond to the size and shape of the B pins 26 - 30.

[0117] The clearance maintaining member 63 is welded to the central plate portion 61. In this modified example, the shape of the clearance maintaining member 63 is a rectangular parallelepiped and is provided on the second surface 88. The clearance maintaining member 63 is disposed at the boundary between the central plate portion 61 and the lateral bulging portion 62. Of course, the clearance maintaining member 63 can also be arranged so as to span the central plate portion 61 and the lateral bulging portion 62, or can also be arranged on the lateral bulging portion 62. The clearance maintaining member 63 is preferably arranged near the through hole 87. For example, as Figure 9As shown, the distance 65 from the edge of the through-hole 87 to the edge of the gap maintaining member 63 is preferably set to 5 mm to 20 mm.

[0118] Of course, the shape of the gap maintaining member 63 is not limited to a rectangular parallelepiped, and it can also be a columnar shape with a circular, elliptical, polygonal, etc. cross-sectional shape. In addition, the shape of the gap maintaining member 63 can also correspond to the outer shape of the fixed boss 60. That is, the outer shape of the gap maintaining member 63 can also correspond to the above-mentioned central plate portion 61 and the laterally bulging portion 62. In this case, a through-hole identical to the above-mentioned through-hole 87 is provided in the gap maintaining member 63. In this modified example, the material constituting the gap maintaining member 63 is typically gunmetal (copper alloy), and a material with a hardness lower than that of the base boom 20, the top boom 21, and the intermediate booms 22 to 25 can be used. Additionally, the gap maintaining member 63 can also be made of resin.

[0119] The fixed boss 60 of this modified example has the advantages of a simple shape and being able to achieve further weight reduction design compared to the fixed boss 32 of the above-described embodiment.

[0120] Explanation of Reference Numerals

[0121] 10: Crane

[0122] 11: Slewing platform

[0123] 12: Luffing center axis

[0124] 13: Telescopic boom

[0125] 14: Telescopic cylinder

[0126] 15: Boom fixing mechanism

[0127] 16: Cylinder-boom connection mechanism

[0128] 20: Base boom (boom)

[0129] 21: Top boom (boom)

[0130] 22: First intermediate boom (boom)

[0131] 23: Second intermediate boom (boom)

[0132] 24: Third intermediate boom (boom)

[0133] 25: Fourth intermediate boom (boom)

[0134] 26: Boom fixing pin

[0135] 27: Boom fixing pin

[0136] 28: Boom fixing pin

[0137] 29: Boom fixing pin,

[0138] 30: Boom fixing pin,

[0139] 31: Hydraulic cylinder,

[0140] 32: Fixed boss,

[0141] 33: Fixed boss,

[0142] 34: Cylinder connecting pin,

[0143] 35: Hydraulic cylinder,

[0144] 36: Cylinder barrel,

[0145] 37: Fixed boss,

[0146] 38: Length direction,

[0147] 39: Piston rod,

[0148] 40: Link mechanism,

[0149] 51: Central plate part,

[0150] 52: Transverse bulging part,

[0151] 53: Upper bulging part,

[0152] 60: Fixed boss,

[0153] 61: Central plate part,

[0154] 62: Transverse bulging part,

[0155] 63: Gap maintaining component,

[0156] 64: Thick wall part,

[0157] 72: Outer surface,

[0158] 73: Inner surface,

[0159] 81: Edge surface,

[0160] 82: Edge surface,

[0161] 83: First surface,

[0162] 84: Thick wall part,

[0163] 85: Rim part,

[0164] 86: Side surface,

[0165] 87: Through hole,

[0166] 88: Second surface,

[0167] 89: Bolt,

[0168] 90: Clearance maintaining member,

[0169] 101: Vertical direction,

[0170] 102: Width direction,

[0171] 111: Traveling body,

[0172] 112: Boom device,

[0173] 113: Cab,

[0174] 120: Vehicle body,

[0175] 121: Wheel,

[0176] 136: Luffing cylinder,

[0177] 139: Winch,

[0178] 140: Hook,

[0179] 141: Drum,

[0180] 142: Steel wire rope,

[0181] 143: Steel wire rope pulley,

[0182] 144: Steel wire rope pulley.

Claims

1. A telescopic boom, which is formed by a plurality of booms to form a telescopic structure and has a boom fixing mechanism that fixes the boom disposed on the relatively inner side to a specified position with respect to the boom disposed on the relatively outer side. Among them, the boom fixing mechanism includes: a boom fixing pin, which is provided on the boom disposed on the inner side and advances and retreats with respect to the boom disposed on the outer side; a fixing boss, which is provided on the boom disposed on the outer side for inserting and removing the boom fixing pin; and a gap maintaining member, which is provided on the fixing boss and protrudes outward to maintain the gap between the boom disposed on the outer side and the boom disposed on the further outer side.

2. The telescopic boom according to claim 1, wherein the fixing boss includes: a central plate portion, which is rectangular and extends in the longitudinal direction and the up-and-down direction of the boom, for inserting and removing the boom fixing pin; a pair of laterally bulging portions, which are respectively continuous with both sides in the longitudinal direction of the central plate portion and smoothly bulge outward; and a longitudinally bulging portion, which is continuous with at least one of the upper end or the lower end of the central plate portion and smoothly bulges, the gap maintaining member is provided on the longitudinally bulging portion so as to protrude toward the boom disposed on the relatively outer side.

3. The telescopic boom according to claim 1, wherein the fixing boss includes: a central plate portion, which is rectangular and extends in the longitudinal direction and the up-and-down direction of the boom, for inserting and removing the boom fixing pin; and a pair of laterally bulging portions, which are respectively continuous with both sides in the longitudinal direction of the central plate portion and symmetrically bulge outward, the gap maintaining member is provided on the central plate portion or the laterally bulging portion and is in the shape of a cuboid protruding toward the boom disposed on the relatively outer side.

4. The telescopic boom according to any one of claims 1 to 3, wherein the gap maintaining member is detachably provided on the fixing boss by a fastening member.

5. The telescopic boom according to any one of claims 1 to 4, wherein the hardness of the gap maintaining member is lower than the hardness of the boom.

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

7. The telescopic boom according to any one of claims 1 to 6, wherein the gap maintaining member is welded to the fixing boss.

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