JP2011084350A - Boom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve buckling characteristics in a side plate, without causing a complicated manufacturing process nor a large weight increase. <P>SOLUTION: A side part sliding pad 51 is arranged along an inside boom 10 (of side plates 12 and 13) on an inner surface of two side plates 31 (32 and 33) of an outside boom 30. Thus, buckling of a side plate 11 of the inside boom 10 is restrained. The two side plates 31 are respectively formed in a straight line shape. Thus, the side plates 31 can be easily formed compared to a case of forming the side plates 31 in a complicated cross-sectional shape such as a curve and a broken line. The side part sliding pad 51 is arranged on the lower side than a bending neutral shaft N of the outside boom 30, and is arranged on the upper side than the upper end 42u of a lower sliding pad 42. Thus, the buckling of the side plate 11 of the inside boom 10 can be further surely restrained more than when the side part sliding pad 51 is not arranged in this range. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a boom of a work vehicle or a crane (nested box boom).

  Conventionally, various shapes of boom sections of work vehicles or cranes are known (for example, Patent Documents 1 to 8). Many of them are intended to improve the buckling characteristics of the bottom plate (bottom plate) and side plates of the boom.

  Methods for improving the buckling characteristics can be roughly divided into two. One is to form various shapes of the lower plate and the side plate where buckling is a concern. For example, buckling characteristics and fatigue characteristics are improved by forming the cross section into a shape having a curved surface or a broken line and forming a boom by butt welding. The other is to increase the thickness of the lower and side plates of the boom (increase the thickness).

  As shown in Patent Documents 1, 2, and 4, in a telescopic boom, a sliding pad is installed on the inner boom support portion on the inner surface of the outer boom.

Japanese Utility Model 55795 ACT 6-80784 Reality 2-11431 JP 2000-143163 A JP-A-2005-112514 JP2000-16673 JP 52-105451 A JP 52-55158

  However, the boom using only the above-described two methods has problems such as a complicated manufacturing process, deterioration of deflection characteristics, and an increase in weight. In particular, if the cross section of the lower plate or side plate is made complicated, such as a curved surface or a polygonal line, the manufacturing process becomes complicated and the deflection characteristics deteriorate (the second moment of section is smaller than that of a rectangular cross section of the same size). ). In particular, when the thickness of the lower plate or the side plate is increased, the weight increases.

  The objective of this invention is providing the boom which can improve the buckling characteristic of a side plate, without requiring a complicated manufacturing process and a big increase in weight.

  A boom according to a first aspect of the present invention is a telescoping box-type boom including an outer boom and an inner boom accommodated in the outer boom, wherein the outer boom is a cross section viewed from the axial direction of the outer boom. In the cross section, two side plates formed in a straight line, an upper plate arranged so as to connect the upper ends of the two side plates in the cross section, and arranged so as to connect the lower ends of the two side plates in the cross section. A lower plate formed in a U-shape, a lower sliding pad installed on the inner surface of the front end portion in the axial direction of the lower plate so as to support the inner boom, and inner surfaces of the two side plates A side sliding pad installed along the inner boom, and the side sliding pad is installed below the bending neutral axis of the outer boom. And, wherein the the upper end of the lower sliding pad disposed on the upper side.

  In this boom, in a cross section viewed from the axial direction of the outer boom, the side sliding pads are installed on the inner surfaces of the two side plates of the outer boom along the inner boom. Here, when the boom receives a bending load, the side plate of the inner boom tends to be deformed to the outside of the cross section. This deformation is pressed inside the cross section by the side sliding pad of the outer boom. Therefore, buckling of the side plate of the inner boom is suppressed. Therefore, the buckling characteristic of the side plate of the boom can be improved.

  Further, the buckling characteristics of the side plates of the boom are improved as described above. That is, it is not necessary to increase the thickness of the boom in order to improve the buckling characteristics. Therefore, the boom can be made lighter than when the buckling characteristic is improved only by increasing the thickness of the boom. In other words, the buckling characteristics of the side plates of the boom can be improved without requiring a significant increase in weight.

  In the cross section, the two side plates of the outer boom are each formed in a straight line. Therefore, the side plate can be easily formed as compared with a case where the side plate has a complicated cross-sectional shape such as a curve or a broken line. Therefore, the boom can be manufactured without requiring a complicated manufacturing process.

  The side sliding pad is installed below the bending neutral axis of the outer boom, and is installed above the upper end of the lower sliding pad. Therefore, the buckling of the side plate of the inner boom can be more reliably suppressed than in the case where the side sliding pad is not installed in this range (described later). Further, when the side sliding pad is installed only in this range, the outer boom can be made lighter than when the side sliding pad is installed in a range wider than this range.

  2nd invention is a boom which concerns on 1st invention, Comprising: The said side part sliding pad is installed in the back side rather than the said axial direction front side front-end | tip part of the said outside boom, The said side sliding pad of the said The amount of offset from the tip in the axial direction is within 100% of the height of the side plate in the cross section.

  In this boom, the offset amount of the side sliding pad from the distal end portion of the outer boom is within 100% of the height of the side plate of the outer boom in the cross section. Therefore, compared to the case where the offset amount is not within this range, the buckling of the side plate of the inner boom is more reliably suppressed (described later). Therefore, the buckling characteristic of the side plate of the boom can be further improved.

  As described in the above description, according to the present invention, the following effects can be obtained. In particular, the configuration in which the side sliding pads are installed on the inner surfaces of the two side plates of the outer boom can reliably improve the buckling characteristics of the boom side plate without requiring a significant increase in weight. Further, since the two side plates of the outer boom are each formed in a straight line shape, the boom can be manufactured without requiring a complicated manufacturing process.

It is sectional drawing of the boom which concerns on 1st Embodiment. It is a side view of the boom shown in FIG. It is sectional drawing (partial drawing) of the boom used for a bending analysis. 4 is a partial view showing a boom according to case 1. FIG. 7 is a partial view showing a boom according to case 2. FIG. 7 is a partial view showing a boom according to case 3. FIG. 7 is a partial view showing a boom according to case 4. FIG. 7 is a partial view showing a boom according to case 5. FIG. It is a graph which shows the load displacement curve of cases 1-5. It is a side view of the boom concerning a 2nd embodiment. It is the figure which looked at the clearance gap adjustment mechanism shown in FIG. 10 from the axial direction of the boom. It is a fragmentary figure which shows the boom which concerns on case 3-1. It is a fragmentary figure which shows the boom which concerns on case 3-2. It is a fragmentary figure which shows the boom which concerns on case 3-3. It is a graph which shows the relationship between the offset amount of a side part sliding pad, and an additional effect.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a boom according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of a boom. 1 is a cross-sectional view taken along arrow F1-F1 shown in FIG. FIG. 2 is a side view of the boom shown in FIG. Hereinafter, the configuration of the boom 1 will be described in detail with reference to FIGS. 1 and 2.

  The boom 1 is a telescoping box boom (expandable boom) used for a work vehicle or a crane. For example, it is attached to an upper swing body of a crane so as to be able to undulate. A plurality of (for example, seven, see FIG. 10) booms are nested to form the boom 1. Here, one of the plurality of booms (excluding the innermost boom) is defined as the outer boom 30. The boom accommodated in the outer boom 30 is referred to as the inner boom 10. More specifically, the boom arranged on the outermost side among the plural (or one) booms arranged inside the outer boom 30 is referred to as the inner boom 10.

  The outer boom 30 is one of a plurality of booms constituting the boom 1 (excluding the innermost boom). The outer boom 30 is configured as follows. In the cross section viewed from the axial direction of the outer boom 30 (that is, as shown in FIG. 1), the overall shape is a vertically long and substantially rectangular shape, and each of the two side plates 31 (32 and 33) that are straight and the upper end of the side plate 31 are The upper plate 34 to be connected and the U-shaped lower plate 37 to connect the lower ends of the side plates 31 form a substantially rectangular shape. Further, two upper sliding pads 41 (41R and 41L), a lower sliding pad 42, and two side sliding pads 51 (52 and 53) are installed on the inner surface.

  Here, the direction in which the two side plates 31 face each other is defined as the X direction, and the direction from the one side plate 33 toward the other side plate 32 (right direction in FIG. 1) is referred to as “X1 direction” or the like, and vice versa (left direction in FIG. 1). ) Is called "X2 direction". The direction in which the lower plate 37 and the upper plate 34 face each other is referred to as the Z direction, and the direction from the lower plate 37 toward the upper plate 34 (upward in FIG. 1) is referred to as “Z1 direction” or the like, and vice versa (in FIG. 1). (Downward) is called "Z2 direction". 2, the axial direction of the outer boom 30 is also referred to as the Y direction, and the side on which the inner boom is inserted (the left side in FIG. 2) is referred to as the front side or the “Y2 side”, and vice versa ( The right side in FIG. 2 is referred to as the rear side or “Y1 side”.

  As shown in FIG. 1, the side plates 31 are two (two) plates constituting the side surface of the boom 1. The two side plates 31 are each formed in a straight line shape when viewed from the axial direction (Y direction) of the outer boom 30, and are arranged in parallel along the Z direction. Further, the two side plates 31 are constituted by a side plate 32 disposed on the X1 side and a side plate 33 disposed on the X2 side.

The side plate 32 has a thin portion 32a on the Z1 side and a thick portion 32b on the Z2 side. This thick portion 32b, together with a lower plate 37 described later, is intended to improve the buckling characteristics of the lower portion (Z2 side portion) of the boom 1 that is particularly easily buckled. For example, after the thin part 32a and the thick part 32b are formed separately, the side plate 32 is formed by butt welding them.
The side plate 33 has a thin portion 33a and a thick portion 33b. These are formed in the same manner as the thin portion 32a and the thick portion 32b of the side plate 32.

  The upper plate 34 is a plate disposed so as to connect the upper ends (ends on the Z1 side) of the two side plates 31. The upper plate 34 includes a straight portion 35 arranged along the X direction, and two curved portions 36 (curved portions 36R on the X1 side) formed to bend from both ends in the X direction of the straight portion 35 to the Z2 side. And the curved portion 36L on the X2 side). The buckling characteristic is improved by forming the curved portion 36 (described later).

  The lower plate 37 is a plate arranged so as to connect the lower ends (ends on the Z2 side) of the two side plates 31. The lower plate 37 is formed in a U shape. The “U-shape” is an arc or a smooth curved shape of an arc shape, or a polygonal line shape connecting three or more points on the curve (the lower plate 37 of the arc is shown in FIG. 1). By forming the lower plate 37 in such a shape, the buckling characteristics of the lower portion (the Z2 side portion) of the boom 1 where buckling is particularly likely to occur are improved. That is, when the side plate and the lower plate are arranged vertically and these joints are fillet welded, stress concentrates on the joint. On the other hand, since the stress concentration does not occur in the U-shaped lower plate 37, the buckling characteristics can be improved. The curved portion 36 of the upper plate 34 can improve the buckling characteristics in the same manner.

  Next, the outline of the sliding pads (21, 22, 41, 42, 51) attached to the outer boom 30 and the inner boom 10 shown in FIG. 2 will be described.

  An outline of the positions of the plurality of sliding pads (21, 22, 41, 42, 51) will be described. As shown in FIG. 2, an upper sliding pad 41, a lower sliding pad 42, and a side sliding pad 51 are installed on the inner surface of the front end portion (Y2 side) of the outer boom 30. An upper sliding pad 21 and a lower sliding pad 22 are installed on the outer surface of the rear side (Y1 side) end of the inner boom 10.

  An outline of the functions of these sliding pads (21, 22, 41, 42, 51) will be described. The sliding pads (21, 22, 41, 42, 51) facilitate sliding between the inner boom 10 and the outer boom 30. Further, when a load (suspending load in the direction of arrow B) is applied to the boom 1 (on the inner boom 10), the inner boom 10 is supported by the lower sliding pad 42 and the upper sliding pad 21. Further, when a load is applied to the inner boom 10, the side plate 11 of the inner boom 10 attempts to open outward (outside of the cross section viewed from the Y direction), but this is pressed inward by the side sliding pad 51. Further, the upper sliding pad 41 and the lower sliding pad 22 fill a gap between the outer boom 30 and the inner boom 10 and suppress vibrations when the boom 1 is extended and contracted.

  These sliding pads (21, 22, 41, 42, 51) are made of, for example, a metal whose surface is coated with a lubricant such as grease. For example, it is resin. Hereinafter, these sliding pads will be further described.

  The upper sliding pad 41 is provided in order to facilitate sliding between the inner boom 10 and the outer boom 30 and to eliminate vibrations during expansion and contraction of the boom 1 by eliminating these gaps. The upper sliding pad 41 is provided as follows. Explaining the position, it is installed at the front end (Y2 side) tip of the outer boom 30. Moreover, as shown in FIG. 1, two are installed so that the two curved parts 36 (36R and 36L) of the upper board 34 may be met. That is, the upper sliding pad 41R on the X1 side and the upper sliding pad 41L on the X2 side are installed. Explaining the shape, it is formed in an arc shape when viewed from the Y direction. Moreover, as shown in FIG. 2, it forms in a rectangular shape seeing from the X direction. That is, the rectangular parallelepiped plate is bent along the inner surface of the curved portion 36 of the upper plate 34. Further, the thickness is formed such that the gap with the inner boom 10 (curved portion 16) is almost filled (a minute gap is opened). Note that the size of the gap can be adjusted by providing a gap adjusting mechanism 238 (see FIGS. 10 and 11) described later.

  The lower sliding pad 42 facilitates sliding between the inner boom 10 and the outer boom 30 and also supports the inner boom 10 when a load (in the direction of arrow B) is applied to the boom 1 (inner boom 10). Provide to do. The lower sliding pad 42 is provided as follows. Explaining the position, it is installed on the inner surface of the front end portion (Y2 side) in the axial direction (Y direction) of the lower plate 37 of the outer boom 30. In other words, it is installed on the nesting support portion on the front side of the outer boom 30. Moreover, as shown in FIG. 1, it installs along the inner surface of the U-shaped lower plate 37 (so as to cover the entire inner surface). For example, the upper end 42u of the lower sliding pad 42 and the upper end of the lower plate 37 (the boundary between the lower plate 37 and the side plate 31. Note that the symbol H in FIG. 1 is the range of the side plate 31) are aligned in the Z direction. To place. Explaining the shape, it is formed in a U shape when viewed from the Y direction. Moreover, as shown in FIG. 2, it forms in a rectangular shape seeing from the X direction. That is, the rectangular parallelepiped plate is bent along the U-shape of the lower plate 37. Further, the thickness is formed so as to be in contact with the outer surface of the lower plate 17 of the inner boom 10 (that is, to support the inner boom 10).

  The side sliding pad 51 facilitates sliding between the inner boom 10 and the outer boom 30, and when the load is applied to the boom 1 (inner boom 10), the side plate 11 of the inner boom 10 is outer (Y). It opens to the outside of the cross section seen from the direction), but is provided to hold it inward. The side sliding pad 51 is provided as follows. Explaining the position, it is installed on the inner surface (inner wall) of the front end (Y2 side) tip of the side plate 31 of the outer boom 30 in the axial direction (Y direction). As shown in FIG. 1, a side sliding pad 52 is installed on the inner surface (X2 side surface) of the side plate 32, and a side sliding pad 53 is installed on the inner surface (X1 side surface) of the side plate 33. The position of the side sliding pad 51 in the Z direction will be described later. The shape of each of the two side sliding pads 51 is a rectangular parallelepiped plate having a thickness direction in the X direction. That is, it is rectangular when viewed from the Y direction and the X direction (as shown in FIGS. 1 and 2). Moreover, as shown in FIG. 1, each thickness is a thickness along the side plate 31 of the inner boom 10 (along a minute gap). Next, the position of the side sliding pad 51 (52 and 53) in the Z direction will be described.

  The side sliding pad 51 is installed at a central portion (near the center) in the Z direction of the side plate 31. More specifically, the side sliding pad 52 is installed on the lower side (Z2 side) than the bending neutral axis N of the outer boom 30 (a line in which no axial force is generated during bending deformation, indicated by a one-dot chain line in FIG. 1). In addition, the lower sliding pad 42 is installed above the upper end 42u (Z1 side). Furthermore, the distance Oz (interval (offset) in the Z direction) between the lower end 52b of the side sliding pad 52 and the upper end 42u of the lower sliding pad 42 is 10 mm or more. Further, the upper end 52t of the side sliding pad 52 coincides with the bending neutral axis N in the Z direction. For example, the lower end 52b is disposed above the thick part 32b of the side plate 32, that is, in the thin part 32a.

  Since the side sliding pad 53 is symmetrical with the side sliding pad 52 in the X direction, the description is omitted.

  As shown in FIG. 2, the upper sliding pad 21 is installed on the outer surface of the rear end (Y1 side) of the inner boom 10 in the Y direction. It is provided to facilitate sliding between the inner boom 10 and the outer boom 30 and to support the inner boom 10 when a load is applied to the boom 1. The upper sliding pad 21 has the same shape (two arcs) as the upper sliding pad 41 of the outer boom 30 shown in FIG. 1 when viewed from the Y direction.

  As shown in FIG. 2, the lower sliding pad 22 is installed on the outer surface of the inner boom 10 at the rear end (Y1 side) in the Y direction. The inner boom 10 and the outer boom 30 are provided for facilitating sliding, and for eliminating vibrations during expansion and contraction of the boom 1 by eliminating these gaps. When viewed from the Y direction, the lower sliding pad 22 has the same shape (U-shape) as the lower sliding pad 42 of the outer boom 30 shown in FIG.

(Bending analysis 1)
Bending analysis was performed on various booms including the boom 1 according to the present invention. That is, for the inner boom having the dimensions shown in FIG. 3, the deformation and load of the boom when the inner boom support method (sliding pad installation position and range) was changed in various ways were examined. It should be noted that the analysis was performed at a portion on the X2 side from the center in the X direction when the inner boom is viewed from the Y direction (that is, the left half portion as shown in FIG. 3). Further, the analysis was performed on the boom from which the sliding pads that do not contribute to the support of the inner boom (the upper sliding pad 41 and the lower sliding pad 22 in the boom 1 shown in FIG. 2) were removed. As models for this bending analysis, the models of cases 1 to 5 shown in FIGS. 4A to 8A were used.

  As shown in FIG. 4A, the case 1 corresponds to the sliding pad 140C1 (the lower sliding pad 42 of the present invention) along the lower plate 37 (see FIG. 1) having a U-shaped cross section viewed from the Y direction. ). That is, this is a model in which the side sliding pad 51 is removed from the outer boom 30 of the present invention. 4 to 8 do not show the outer boom.

  As shown in FIG. 5A, the case 2 is a model in which a sliding pad 140C2a is added so as to be adjacent to the upper end of the sliding pad 140C1 of the case 1 (the reference numeral of these sliding pads is 140C2. ). That is, it is a model without the interval Oz shown in FIG. The Z-direction width of the added sliding pad was 150 mm.

  The case 3 is a model according to the boom 1 of the present invention, as shown in FIG. That is, this is a model in which a side sliding pad 51 is installed at the center of the side plate 31 (see FIG. 1). The width of the side sliding pad 51 in the Z direction was 150 mm.

  As shown in FIG. 7A, the case 4 is a model in which a sliding pad 140C4 is installed so as to go around the inner surface of an outer boom (not shown) like a headband. In other words, this is a case where the sliding pad is supported by the entire circumference of the inner boom.

  The case 5 is a model in which a portion along the upper plate 34 (see FIG. 1) is removed from the sliding pad 140C4 (see FIG. 7A) of the case 4 as shown in FIG. The sign of the sliding pad is 140C5). That is, the difference from the present invention is that the sliding pad is installed not only in the central portion of the side plate 31 (see FIG. 1) but also in the Z direction of the side plate 31.

  Next, the analysis result will be described. The deformation | transformation figure of a boom at the time of applying a suspension load to the boom which concerns on cases 1-5 is shown in FIG.4 (b)-FIG.8 (b). In addition, the character of “outside” in the drawing indicates deformation of the outer surface of the inner boom 10 toward the outside of the cross section, and the character of “inside” indicates deformation toward the inside. Further, the thicker the line in the figure, the larger the deformation to the outside, and the thinner the line, the larger the deformation to the inside.

In case 1, as shown in FIG. 4B, a large one-wave outer deformation (wave W <b> 1) occurred in the inner boom 10 with the maximum deformation point directly above the upper end of the sliding pad 140 </ b> C <b> 1. This waveform will be further described.
In order to make the boom lighter and more rigid, as shown in FIG. 1, the upper plate 14 and the upper plate 14 are located far away from the boom bending center (not shown) in the cross section viewed from the boom axis direction (Y direction). It is necessary to arrange the lower plate 17. In other words, it is necessary to make the cross section longitudinally long and to increase the cross section secondary moment. With such an arrangement (cross-sectional shape), as a result, the side plate 11 has a wide surface in the vertical direction (Z direction), and the side plate 11 is likely to buckle. Therefore, when a suspension load is applied to the boom, the large outer deformation (wave W1) as described above occurs in the inner boom 10.
Further, the maximum deformation point is directly above the upper end of the sliding pad 140C1. This indicates that local compression buckling due to the reaction force of the sliding pad 140C1 is outstanding.

  In case 2, as shown in FIG. 5B, deformation (wave W2) close to the deformation mode of case 1 occurred. It is presumed that the effect obtained by adding the sliding pad is not obtained as compared with case 3 described later.

  In the case 3 (the case according to the present invention), as shown in FIG. 6 (b), the wave W3-1 that deforms inward of the boom with the periphery of the side sliding pad 53 as the maximum deformation point, and its neighbor (FIG. 2). Two waves of the wave W3-2 deforming outward are generated on the Y1 side). This waveform is not an elliptical waveform (see FIGS. 4B and 5B) along the axial direction (Y direction in FIG. 2) of the inner boom 10 as appeared in cases 1 and 2. The waveform is an elliptical shape that is oblique to the Y direction (more specifically, an elliptical shape in which the long side of the ellipse is inclined with respect to the axial direction). This is thought to be a waveform that results from excellent shear buckling.

  In cases 4 and 5, the same waveform as in case 3 was generated. That is, in case 4, as shown in FIG. 7B, two waves of the wave W4-1 deforming inward and the wave W4-2 deforming outward are generated. In case 5, as shown in FIG. 8B, two waves of a wave W5-1 deforming inward and a wave W5-2 deforming outward were generated.

FIG. 9 shows a load displacement curve of each case. The displacement is the displacement at the tip of the boom (see the mounting portion 202 in FIG. 10). The vertical axis represents the load, and the horizontal axis represents the displacement of the boom tip. Moreover, the increase rate of the maximum load of each case with respect to the maximum load of case 1 is shown in the box in the graph of FIG.
As shown in this result, the case 4 (see FIG. 7) in which the sliding pad 140C4 is installed over the entire outer surface of the inner boom 10 and the Z of the side plate 31 as well as the central portion of the side plate 31 (see FIG. 1). It can be seen that an effect equivalent to that of the case 5 (see FIG. 8) installed in the whole direction is obtained in the case 3 (see FIG. 6) in which the side sliding pad 51 having a slight width is installed.

(Features of the boom according to the first embodiment)
In the boom 1 according to the present embodiment, as shown in FIG. 1, the side sliding pad 51 is connected to the two side plates 31 (32 and 32) of the outer boom 30 in a cross section viewed from the axial direction (Y direction) of the outer boom 30. 33) on the inner surface of the inner boom 10 (side plates 12 and 13 thereof). Here, when the boom 1 (inner boom 10) receives a bending load (when receiving a suspension load in the direction of arrow B in FIG. 2), the side plates 11 (12 and 13) of the inner boom 10 are outside the cross section ( The side plate 12 tends to be deformed to the X1 side and the side plate 13 is the X2 side. This deformation is pressed inside the cross section by the side sliding pad 51 of the outer boom 30 (the side plate 12 is pressed to the X2 side by the side sliding pad 52. The side plate 13 is pressed to the X1 side by the side sliding pad 53. ). Therefore, buckling of the side plate 11 of the inner boom 10 is suppressed. Therefore, the buckling characteristic of the side plate (side plate 11) of the boom 1 can be improved.

  Moreover, the buckling characteristic of the side plate (side plate 11) of the boom 1 is improved as described above. That is, it is not necessary to increase the thickness of the boom 1 in order to improve the buckling characteristics. Therefore, the boom 1 can be made lighter than when the buckling characteristic is improved only by increasing the thickness of the boom 1. In other words, the buckling characteristics of the side plate of the boom 1 can be improved without requiring a significant increase in weight.

  Moreover, in the cross section (the cross section viewed from the Y direction), the two side plates 31 of the outer boom 30 are each formed in a straight line shape. Therefore, the side plate 31 can be easily formed as compared with the case where the side plate 31 has a complicated sectional shape such as a curve or a broken line. Therefore, the boom 1 can be manufactured without requiring a complicated manufacturing process.

  Further, the side sliding pad 51 is installed below the bending neutral axis N of the outer boom 30 and is installed above the upper end 42 u of the lower sliding pad 42. Therefore, the buckling of the side plate 11 of the inner boom 10 can be more reliably suppressed as compared to the case where the side sliding pad 51 is not installed in this range (see bending analysis 1). Further, when the side sliding pad 51 is installed only in this range, the outer boom 30 can be made lighter than when the side sliding pad 51 is installed in a range wider than this range.

  Note that since the boom 1 is nested, the outer boom 30 also has the inner boom 10 (excluding the inner boom 10 disposed on the innermost side among the plurality of booms constituting the boom 1). Moreover, the feature which the inner side boom 10 has also has the outer side boom 30 (except the outer side boom 30 arrange | positioned on the outermost side).

(Second Embodiment)
FIG. 10 is a side view of the boom according to the second embodiment (near the front end when the telescoping boom is most contracted). 11 is a cross-sectional view in the vicinity of the boom clearance adjustment mechanism 238 shown in FIG. 10, and is a cross-sectional view taken along arrow F11-F11 shown in FIG. In the first embodiment, as shown in FIG. 2, the side sliding pad 51 is installed at the front end (Y2 side) front end of the outer boom 30 in the axial direction (Y direction). In the second embodiment, as shown in FIG. 10, the side sliding pad 51 is installed on the rear side (Y1 side) of the front end portion 230T in the axial direction (Y direction) front side (Y2 side) of the outer boom 230. The Hereinafter, the configuration of the boom 201 according to the second embodiment will be described with reference to FIGS. 10 and 11. In addition, about the part same as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

First, as shown in FIG. 10, it will be described that the side sliding pad 51 is installed closer to the Y1 side than the Y2 side distal end portion 230T of the outer boom 230.
The boom 201 is nested, and includes seven booms. Among these seven booms, a clearance adjustment mechanism 238 is attached to each of the booms excluding the innermost boom (that is, a boom that can be an outer boom). In order to arrange the gap adjusting mechanism 238, the end portion on the Y2 side of each boom is offset to the Y1 side (details will be described later). In such a boom (outer boom 230) having an offset end, it is difficult to install the side sliding pad 51 directly above the lower sliding pad 42 (Z1 side). Accordingly, the side sliding pad 51 is installed on the rear side (Y1 side) from the front end portion (T2 side) in the axial direction (Y direction) so as to follow the shape of the end portion of the outer boom 230 (Y1 side). Offset). A mounting portion 202 to which various attachments are attached is attached to the innermost boom among the seven booms. Hereinafter, each component will be described.

  As shown in FIG. 11, the clearance adjustment mechanism 238 is a device that adjusts the amount of clearance between the upper sliding pad 41 (41L) and the inner boom 10 (curved portion 16). The gap adjustment mechanism 238 includes an L-shaped bracket 238a attached to the outer side (X1 and Z1 side) of the upper sliding pad 41 (41R) of the outer boom 230, and an outer frame disposed outside the L-shaped bracket 238a. 238b and a pressing bolt 238c attached to the outer frame 238b. Then, the L-shaped bracket 238a and the upper sliding pad 41 are moved in the same direction by moving the pressing bolt 238c in and out (moving) in the X direction and the Z direction. Thereby, the clearance gap between the upper sliding pad 41 and the curved part 16 of the upper board 14 of the inner boom 10 is adjusted. A similar clearance adjustment mechanism (not shown) is installed not only on the upper sliding pad 41L but also on the upper sliding pad 41R.

  The upper part (Z1 side portion) of the axial end (Y direction) front side (Y2 side) end portion of the outer boom 230 is offset to the rear side (Y1 side) as shown in FIG. More specifically, the Y2 side end portion of the outer boom 230 is not linear along the Z direction, the lower portion 230c (Z2 side portion) is linear along the Z direction, and the intermediate portion 230b is inclined with respect to the Z direction. The upper portion 230a (Z1 side portion) is linear along the Z direction. And the upper part 230a is formed in the back side (Y1 side) rather than the lower part 230c. That is, the front end portion (Y2 side) distal end portion 230T of the outer boom 230 as a whole is a portion of the lower portion 230c. The reason for this shape is that the gap adjusting mechanism 238 is installed as described above (and the mounting portion 202 has the protruding portion 202a).

  The side sliding pad 51 is installed on the rear side (Y1 side) of the front end portion 230T (230c) of the outer boom 230 in the axial direction (Y direction) front side (Y2 side). More specifically, it is installed as follows. The distance from the front end portion 230T (230c) in the Y direction of the side sliding pad 51 is defined as an offset amount Oa. This offset amount Oa is the distance in the Y direction between the center of the lower sliding pad 42 in the Y direction and the center of the side sliding pad 51 in the Y direction. The offset amount Oa is within 100% of the height H (see FIG. 1) of the side plate 31 in the cross section viewed from the Y direction. Further, the side sliding pad 51 is installed at an intermediate portion 230b (inclined portion) at the front side (Y2 side) end of the outer boom 230. Further, for example, when viewed from the X direction, the side sliding pad 51 is disposed such that the longitudinal direction of the side sliding pad 51 is along the inclination direction of the intermediate portion 230b.

(Bending analysis 2)
Bending analysis was performed on various booms including the boom 201 according to the present invention (Embodiment 2). That is, the deformation and load of the boom when the offset amount Oa of the side sliding pad 51 was changed variously based on the model of the case 3 according to the bending analysis 1 (see FIG. 6A) was examined. Cases 3-1, 3-2, and 3-3 in which the offset amount Oa was 200 mm, 400 mm, and 800 mm were used as models for this bending analysis (shown in FIGS. 12A to 14A). .

Next, the analysis result will be described. The deformation | transformation figure of a boom at the time of applying a suspension load to the boom which concerns on cases 3-1 to 3-3 is shown in FIG.12 (b)-FIG.14 (b).
From these figures, from the deformation modes observed in case 3 (deformation of two waves, see FIG. 6B) as the offset amount Oa is increased in the order of cases 3-1, 3-2, and 3-3. It is shown that the buckling waveform shifts to the deformation mode observed in case 1 (deformation of one large wave, see FIG. 4B). Specifically: In case 3-1, as shown in FIG. 12B, two waves of a wave W3-1-1 deforming inward and a wave W3-1-2 deforming outward were generated. In cases 3-2 and 3-3, as shown in FIGS. 13 (b) and 14 (b), waves W3-2-1 and W3-3-1 that are deformed inward are generated. Compared to 1-1, the inward deformation was small. On the other hand, in these cases, a large wave W3-2-2 and a wave W3-3-2 along the boom axis direction were generated as in the wave W1 observed in the case 1 (see FIG. 4B).

  FIG. 15 shows the relationship between the offset amount Oa (see FIG. 10) of the side sliding pad 51 and the additional effect. More specifically, the vertical axis represents the maximum load of each case with respect to case 1 (additional effect of side sliding pad 51). The maximum load of case 1 is 100%. Further, the horizontal axis shows the offset amount Oa (see FIG. 10) with respect to the height H (see FIG. 1) of the side plate 31. The height H is 100%. The reason why the height H (see FIG. 1) of the side plate 31 is compared with the offset amount Oa (see FIG. 10) is as follows. The deformation mode when the side sliding pad 51 is installed (added) (see FIGS. 12B to 14B) is the deformation mode of the side plate when the side sliding pad 51 is not provided (case 1, FIG. 3). It is considered that the effect of improving the maximum load is smaller as it is closer to (b). Here, the deformation mode of the case 1 does not depend on the dimension of the side plate (the side plates 11 and 31; see FIG. 2 and the like) in the axial direction (Y direction) of the boom, and is the vertical dimension (height H) of the side plate. It is thought that it depends. This is because the dimension of the side plate in the axial direction is sufficiently larger than the height H. Therefore, it can be assumed that the presence or absence of the effect of improving the maximum load does not depend on the dimension of the side plate in the axial direction but depends on the height H. Therefore, as shown in FIG. 15, the range in which the same effect can be obtained is arranged by the ratio of the offset amount Oa to the height H.

  This graph shows that the additional effect of the side sliding pad 51 decreases as the offset amount Oa increases. It is shown that the effect is particularly reduced when the offset amount Oa is greater than 100% with respect to the height H (note that even in this case, the effect is not completely eliminated).

(Features of the boom according to the second embodiment)
In this boom 201, the offset amount Oa from the distal end portion 230T of the outer boom 230 of the side sliding pad 51 shown in FIG. 10 is the outer boom in a cross section viewed from the axial direction of the outer boom 230 (cross section viewed from the Y direction). It is within 100% of the height H (see FIG. 1) of the side plate 31 of 230. Therefore, compared to the case where the offset amount Oa is not within this range, the buckling of the side plate 31 of the inner boom 10 is more reliably suppressed (see bending analysis 2). Therefore, the buckling characteristic of the side plate (side plate 11) of the boom 201 can be further improved.

  As mentioned above, although embodiment of this invention was described based on drawing, a specific structure is not restricted to these embodiment, It can change in the range which does not deviate from the summary of invention.

  For example, although the side sliding pad 51 is installed below the bending neutral axis N in the above-described embodiment, the position of the side sliding pad 51 is set, for example, below the center in the Z direction of the side plate 31. The present invention can be applied even if it is changed.

1,201 Boom 10 Inner boom 30, 230 Outer boom 31 Side plate 34 Upper plate 37 Lower plate 42 Lower sliding pad 42u Upper end 51 Side sliding pad 230T Tip H Height N Bending neutral shaft Oa Offset amount

Claims (2)

In a telescoping box-type boom comprising an outer boom and an inner boom housed in the outer boom,
The outer boom is
In the cross section seen from the axial direction of the outer boom, two side plates each formed in a straight line,
In the cross section, an upper plate disposed so as to connect the upper ends of the two side plates;
In the cross section, the lower plate is disposed so as to connect the lower ends of the two side plates, and is formed in a U shape,
A lower sliding pad installed on the inner surface of the front end portion in the axial direction of the lower plate so as to support the inner boom;
A side sliding pad installed along the inner boom on the inner surface of the two side plates,
The boom, wherein the side sliding pad is installed below the bending neutral axis of the outer boom and is installed above the upper end of the lower sliding pad. The side sliding pad is installed on the rear side of the front end portion in the axial direction of the outer boom,
The boom according to claim 1, wherein an offset amount of the side sliding pad from the tip end in the axial direction is within 100% of a height of the side plate in the cross section.

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