EP2261166B1

EP2261166B1 - Boom and sliding support member for the boom

Info

Publication number: EP2261166B1
Application number: EP20100164702
Authority: EP
Inventors: Isao Motoyama; Shunsuke Yokoyama; Hiroki Nakayama
Original assignee: Kobelco Cranes Co Ltd
Current assignee: Kobelco Cranes Co Ltd
Priority date: 2009-06-09
Filing date: 2010-06-02
Publication date: 2012-10-10
Anticipated expiration: 2030-06-02
Also published as: JP4760960B2; EP2261166A1; JP2010285224A

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a telescoping boom used for a construction machine such as a crane. More specifically, the present invention relates to a sliding support member for the boom provided between inner and outer boom members constituting this boom for supporting the inner boom member slidably.

2. Description of Related Art

The related art will be described with taking a four-step (three-step telescoping) boom as an example. As shown in Fig. 7, this boom is extendable and stowable, and fourth-step tubular boom members 1 to 4 are telescopically inserted into each other. A first-step boom member is the boom whose base portion is attached to a base machine.
Boom members each having a sectional shape in which a lower portion is curved in a downward convex shape (a substantially U shape) when a boom is in a horizontal state as shown in Fig. 8 are used as one type of the boom members 1 to 4 constituting this telescoping boom due to their excellent strength. Hereinafter, the boom members with the curved lower portions are called the curved boom members, and the boom in which these boom members are used is called the curved boom. Top walls serving as upper portions of the boom members 1 to 4 when the boom is in a horizontal state and both side walls extending downward from these top walls are both in a flat (flat plate) shape. Meanwhile, the lower portions ranging from the both side walls to bottom walls are in a curved shape as described above. Strictly speaking, the lower portions of the curved boom members 1 to 4 are formed into a polygonal shape by plurally bending flat plates so as to be seen as a curved shape in a macroscopic view.
For reducing the sliding resistance (friction) between the inner and outer boom members particularly when a load is imposed on them, a pad 5 is provided between adjacently inner and outer boom members in this curved boom as well as other telescoping booms. In general, this pad 5 is formed in a curved band shape in conformity with the boom members as shown in the figure. This pad 5 is attached over a circumferentially fixed range of an inner peripheral surface of the lower portion of a front end of the outer boom member onto which a heavy load is imposed particularly when something is hung from the boom.
However, such integral pad 5 has disadvantages of mass-productivity and cost, since multiple kinds of pads having different curved shapes (curvature radiuses) should be prepared for respective sectional shapes of the boom members.
Meanwhile, as means to solve this problem, there is such a known technique in which unit pads (divided pads) formed by boom-circumferentially dividing the integral pad into plural pads are used, and the pads are circumferentially attached to an inner peripheral surface of an outer boom member, as shown in Japanese Patent Laid-Open No. 2005-255337 (hereinafter, referred to as the first known technique).
Japanese Patent Laid-Open No. 2008-265980 shows, as an improved technique of the integral type, a technique in which a plurality of bending grooves extending in the boom length direction is provided on an upper surface of a band-shaped pad (a surface facing an inner boom member) at circumferentially fixed intervals in order to help the pad to be bent into a curved shape, and the entire pad can be bent in conformity with a sectional shape of the boom member by these bending grooves (hereinafter, referred to as the second known technique).
However, in the first known technique, when the positions of the unit pads are fixed on the inner peripheral surface of the outer boom member in the boom circumferential direction and in the boom length direction, there is the following problem: the individually fixing method makes the work extremely troublesome. Alternatively, when the pads are collectively fixed, the pads are not fixed but in unstable state until fixing members on both sides of the pads are installed. Therefore, the work efficiency is deteriorated after all.
Meanwhile, in the second known technique, since the pad is in a continuously integral band shape, the thickness of the pad is constant over the entire length (the length in the boom circumferential direction). However, as a realistic problem, a gap between the boom members may be different in parts in the boom circumferential direction in some booms (for example, the gap may be relatively wide on the both sides in the circumferential direction and narrow in the middle). Alternatively, even in case of a boom manufactured to have a constant gap between boom members in the circumferential direction, the gap may vary due to errors in the manufacture of the inner and outer boom members, or the like. Based on these, there is a fear that the pad might not be fitted to an outer peripheral surface of the inner boom member in the second known technique.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a boom capable of improving the efficiency in work of assembling pads to boom members. It is another object of the present invention to provide a boom in which even when there are circumferential changes or variation of a gap between boom members, pads can be surely fitted to an outer peripheral surface of an inner boom member.
The present invention relates to a sliding support member used for a telescoping boom in which a plurality of boom members are telescopically inserted into each other, lower portions of the boom members being curved in a downward convex shape when the boom is in a horizontal state. The sliding support member of the present invention includes a plurality of pads in contact with an outer peripheral surface of the inner boom member for supporting this boom member slidably, and a band-shape pad holder attached to an inner peripheral surface of at least the lower portion of the outer boom member inserted into the inner boom member over a fixed range in the boom circumferential direction. A plurality of bending grooves extending in the boom length direction and opening upward is provided on an upper surface of this pad holder facing the inner boom member at intervals in the boom circumferential direction as a means for helping the pad holder to be bent into a curved shape. A plurality of concave portions opening upward is provided in parts between these bending grooves. The pads are fitted into the concave portions respectively so as to fix a position of the boom in the circumferential direction and in the length direction.
In the boom and the sliding support member for the boom of the present invention, a plurality of the pads is fitted into the concave portions of the band-shaped pad holder so as to be aligned in the boom circumferential direction. Firstly, positions of all the pads can be fixed at the same time by fixing only a position of the pad holder on the outer boom member by means of holder fixing means in the boom circumferential direction and in the length direction. Therefore, the work of assembling the pads is easily performed. Secondly, since the pads are fitted into the concave portions, there is no fear that the pads are dropped due to the sliding resistance with the inner boom member. Thirdly, the thickness of the pads can be freely and individually selected for each of the pads. Thus, even in the case where gaps between the boom members are different in parts in the boom circumferential direction or where the gaps vary due to errors in manufacture of the inner and outer boom members, or the like, a pad having the thickness suitable for the gap can be selected. Therefore, it is possible to fit all the pads to the outer peripheral surface of the inner boom member.
Based on these, it is possible to obtain at the same time both the workability in assembling of the pads and the improvement in pad performance of helping the sliding of the boom members.
Preferred embodiments of the present invention will be described. An auxiliary bending groove opening downward and extending in the boom length direction may be provided at a position corresponding to each of the bending grooves on a lower surface of the pad holder. Since the grooves are provided also on the lower surface of the pad holder in this case, the pad holder is more easily bent and fitted to the inner peripheral surface of the outer boom member, especially when the bending grooves are made shallow in order to prevent a decrease of the strength, than the case where these auxiliary bending grooves are not provided.
The pad holder and the pads may be made of different synthetic resin materials from each other. Further, the pads may have a smaller dynamic friction coefficient, a smaller difference between a static friction coefficient and the dynamic friction coefficient, or the higher abrasion resistance, than the pad holder. For example, the pads satisfying a condition that the static friction coefficient is approximately 0.15 and the dynamic friction coefficient is approximately 0.1 with surface pressure of the pads in a range from 90 kg/cm² to 180 kgf/cm² are preferable. The pads may be made of a synthetic oleoresin material.
In this case, since the pad holder and the pads are made of different synthetic resin materials from each other, proper materials can be used depending on respective roles.
That is, the pads serve as sliding members for helping the sliding of the inner boom member. Therefore, the pads can be made of a synthetic resin material excellent in sliding performance (including the abrasion resistance for maintaining constant sliding performance for a long time) in comparison with the pad holder only for holding the pads. According to experiments of the present inventor, the pads satisfying the surface pressure, the static friction coefficient and the dynamic friction coefficient described above are preferable for ensuring favorable sliding performance. Specifically, synthetic oleoresin excellent in lubrication, particularly polyamide oleoresin or polyacetal oleoresin is preferable.
Meanwhile, the pad holder desirably has the strength and the hardness which are sufficient for supporting a load received through the pads, the bending easiness (the flexibility) and the toughness for preventing breaking at the time of bending. Further, a synthetic resin material which is as inexpensive as possible is desirably used, even if it has low sliding performance.
It should be noted that when a synthetic resin material having a small dynamic friction coefficient of the pads and a small difference between the static friction coefficient and the dynamic friction coefficient is used for the pads, the boom member starts to move smoothly, without being stuck to move intermittently, at the beginning of the telescoping of the boom.
Another preferred embodiment of the present invention will be described. A thermoplastic resin material may be used for the pad holder and preliminarily hot-formed into a curved shape corresponding to the inner peripheral surface of the outer boom member.
The pad holder in the present invention is formed by bending a band-shaped flat plate material into a curved shape in conformity with a sectional shape of the boom member. There are two specific patterns of this bending. The first pattern is a pattern in which bending grooves are made shallow for preventing the decrease of the strength of the pad holder, and the pad holder that is made flexible by heating is bent. The second pattern is a pattern in which the bending grooves are made deep for permitting the bending in non-heated state, and the pad holder is bent at the normal temperature.
Among the patterns, the first pattern is suitable for the case where the pad holder is bent into a curved shape at a manufacturing stage, the curved shape corresponding to the inner peripheral surface of the outer boom member to which the pad holder is attached. The adjustment bending can also be performed at a stage assembling to the boom under the condition that heating is performed by a simple heating means such as blowing of hot air. Therefore, the requirement of the first pattern is that the pad holder is made of thermoplastic resin. That is, in case of using the thermoplastic resin, while grooves are made shallow for maintaining the strength of the pad holder, the efficiency is improved both in the bending at the manufacturing stage, and in the bending for adjusting a curving degree in conformity with a sectional shape of an actual boom member at the assembling stage, under the condition of the heating during the bending operations. Meanwhile, the second pattern is disadvantageous in the view of the strength, whereas the pad holder made of a material other than the thermoplastic resin can be used and the substantial bending can also be performed at the assembling stage.
Further preferred embodiment of the present invention will be described. The pads may be detachably fitted into the concave portions of the pad holder respectively. Further, a pad removing hole may be provided through a bottom surface of each of the concave portions of the pad holder in the thickness direction of the pad holder. In this case, since the pads are detachably fitted into the concave portions of the pad holder, the pads are easily replaced at the time of abrasion and damage. The pads are desirably pressed to be fitted into the concave portions so that the pads are not easily dropped and the positions of the pads are surely fixed in the boom circumferential direction and in the length direction. In this case, however, there is a fear that the removal of the pads is difficult at the time of replacement. In this respect, when the pad removing holes are provided, a pushing rod can be inserted into the pad removing holes from the back side so as to easily push out the pads.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of a boom and a sliding support member according to an embodiment of the present invention;
Fig. 2 is an enlarged perspective view of the sliding support member before assembling;
Fig. 3 is a perspective view of the sliding support member in an assembled state;
Fig. 4 is a partially sectional view of a state that the sliding support member is assembled to the boom;
Fig. 5 is a partially enlarged view of Fig. 4;
Fig. 6 is a sectional view along the line VI-VI of Fig. 5;
Fig. 7 is a side view of a boom to which the present invention is applied; and
Fig. 8 is a sectional view of a conventional boom with a sliding support member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described with Figs. 1 to 6.
A sliding support member of the present invention can be provided between all the adjacent boom members (an inner peripheral surface of a front end of the outer boom member) in a telescoping curved boom.
In this embodiment, a case is used as an example for the explanation, where a sliding support member 11 is provided between a first-step boom member (the outer boom member) 1 and a second-step boom member 2 (the inner boom member, However it is the outer boom member relative to a third-step boom member 3.) in a four-step boom shown in Figs. 7, 8 and at a lower portion of the front end of the first-step boom member 1.
The sliding support member 11 is provided with a band-shaped pad holder 12 attached to an inner peripheral surface of a lower portion of the first-step (outer) boom member 1 over a fixed range in the boom circumferential direction, and a plurality of pads 13 attached to this pad holder 12 for supporting the second-step (inner) boom member 2 slidably.
The pad holder 12 is formed by bending a band-shaped flat plate material into a curved shape so as to fit to the inner peripheral surface of the first-step boom member 1. A plurality of bending grooves 14 opening upward and extending in the boom length direction is provided on an upper surface of the pad holder 12 facing the second-step boom member 2 at intervals in the boom circumferential direction. The curved-shaped pad holder 12 is formed by curving the flat plate material so that openings of the bending grooves 14 are closed.
In this case, the deeper bending grooves 14 permit the easier bending, whereas the shallower ones make the bending more difficult. However, the deeper ones decrease the strength of the pad holder 12 whereas the shallower ones can prevent the decrease of the strength. Therefore, it is possible to select one of the following two patterns regarding what type of material is used to form the pad holder 12 and at which stage the pad holder is bent.

(1) The first pattern, where the pad holder 12 (the flat plate material) is formed from thermoplastic resin that is softened by heating to be easily bent, and the bending grooves 14 are made shallow, so that the bending is performed at a manufacturing stage.
(2) The second pattern, where the bending grooves 14 are made deep for enhancing a bending property, so that the bending is performed at a normal temperature.

The pattern (1) is suitable for the case where the pad holder is bent (substantially bent) so as to almost fit to a sectional shape of the first-step boom member 1 at the manufacturing stage, and the pad holder is bent for adjusting a curving degree so as to fit to a sectional shape of the actual boom member 1, if necessary at an assembling stage where the pad holder 12 is assembled to the inner peripheral surface of the first-step boom member 1. The efficiency in bending work is excellent in both the substantial bending and the adjustment bending.
Meanwhile, the pattern (2) is disadvantageous in terms of the strength due to the deeper bending grooves 14, whereas the pad holder made of a material other than the thermoplastic resin can be used and the substantial bending can be performed also at the assembling stage.
The pad holder 12 desirably has the strength and the hardness which are sufficient for supporting a load received through the pads 13, the bending easiness (the flexibility) and the toughness for preventing breaking at the time of bending. Further, a synthetic resin material which is as inexpensive as possible is desirably used, even if it has low sliding performance. As a material satisfying the above conditions, polyamide resin is preferable.
An auxiliary bending groove 15 opening downward and extending in the boom length direction is provided at a position corresponding to each of the bending grooves 14 on a lower surface of the pad holder 12. Since the grooves (the auxiliary bending grooves opening downward) 15 are provided also on the lower surface as described above, the pad holder 12 is more easily bent and fitted to the inner peripheral surface of the first-step boom member 1, particularly when the bending grooves 14 are made shallow in order to prevent the decrease of the strength, than the case where these auxiliary bending grooves 15 are not provided.
Further, a plurality of concave portions 16 opening upward with four closing sides is provided in parts between the bending grooves 14 on the upper surface of the pad holder 12. The pads 13 are detachably fitted into these concave portions 16 respectively.
A position of this pad holder 12 is fixed, in the boom circumferential direction and in the length direction, at an outer peripheral surface of a front end of the first-step boom member 1 by holder fixing means. As shown in Figs. 1, 4 to 6, the holder fixing means includes a front fixing member 17, a rear fixing member 18 and a circumferential fixing member 19. The front fixing member 17 is detachably attached to the front end of the first-step boom member 1 so as to hold the pad holder 12 from the front. The rear fixing member 18 is attached, at a plurality of points in the boom circumferential direction, to the inner peripheral surface of the outer boom member so as to hold the pad holder 12 from the rear. The circumferential fixing members 19 are attached to the inner peripheral surface of the outer boom member so as to hold the pad holder 12 from the both sides in the boom circumferential direction.
As shown in Fig. 6, the front fixing member 17 is formed in a band plate curved into a semi-spherical shape. The front fixing member 17 is attached to a lower front surface of a flange 1a provided in the front end of the first-step boom member 1 by a plurality of bolts 20 so as to be in contact with a front surface of the pad holder 12.
It should be noted that Fig. 1 shows a case as an example where the semi-spherical front fixing member 17 is formed by a plurality of divided pieces 17a. However, the member 17 may be formed into a continuously integral body.
As shown in Figs. 1, 6, each rear fixing member 18 is formed into a square plate. The rear fixing members 18 are attached by welding or the like to the inner peripheral surface of the first-step boom member at a plurality of points in the circumferential direction where the rear fixing members are abutted with a rear surface of the pad holder 12 through a protection plate 21.
The protection plate 21 is to prevent damage on the rear surface of the holder due to direct contact between the rear fixing member 18 and the pad holder 12. The protection plate is attached to the rear surface of the pad holder 12 by a bolt 22. It should be noted that the protection plate 21 may be provided for each of rear fixing members 18 or the protection plate 21 may be provided across plural or all the rear fixing members 18.
As shown in Fig. 4, each circumferential fixing member 19 is formed in a plate which is thinner than the pad holder 12. The circumferential fixing members 19 are attached to the inner peripheral surface of the first-step boom member 1 by welding or the like at positions where the circumferential fixing members hold the pad holder 12 from the both sides in the circumferential direction so as to fix its position in the circumferential direction.
Each pad 13 is made of a synthetic resin material which is different from the material of the pad holder 12 and formed in a rectangle flat plate. When the pads 13 are fitted into the concave portions 16 of the pad holder 12, upper surfaces of the pads 13 protrude from the concave portions 16 and are contacted with an outer peripheral surface of the second-step boom member 2 so as to function a sliding support. When each pad 13 is fitted into each concave portion 16 of the pad holder 12, the position of the pad is fixed in the boom circumferential direction and in the length direction by four side walls of the concave portion.
Since the pad holder 12 is fixed in the boom circumferential direction and in the length direction by the holder fixing means as described above, the positions of the pads 13 are fixed to the inner peripheral surface of the front end of the first-step boom member 1 in the boom circumferential direction and in the length direction.
These pads 13 serve as slide members for helping the sliding of the second-step boom member 2. Therefore, the pads are desirably made of a synthetic resin material excellent in sliding performance (including the abrasion resistance for maintaining constant sliding performance for a long time) in comparison with the pad holder 12 only for holding these pads 13. That is, it is preferable to use the synthetic resin material satisfying at least one of the following conditions:

(i) a dynamic friction coefficient is smaller;
(ii) a difference between a static friction coefficient and the dynamic friction coefficient is smaller; and
(iii) abrasion resistance is higher,

pad holder

When a synthetic resin material satisfying the conditions (i), (ii), the second-step boom member 2 starts to move smoothly, without being stuck to move intermittently, especially at the beginning of the telescoping of the boom.
According to experiments by the inventor regarding the sliding performance of the pads 13, pads satisfying a condition that the static friction coefficient is approximately 0.15 and the dynamic friction coefficient is approximately 0.1 (the difference between both the coefficients is 0.05) with surface pressure serving as a use environment of the pads in the boom for a crane in a range from 90 kg/cm² to 180 kgf/cm² (limit value) are preferable in order to ensure favorable sliding performance including the starting performance.
As a specific material, synthetic oleoresin excellent in lubricity, particularly polyamide oleoresin or polyacetal oleoresin is preferable.
Since the pads 13 are only fitted into the concave portions 16 of the pad holder 12, they are detachable. Therefore, the pads are desirably pressed to be fitted into the concave portions 16 so as not to be easily dropped. In this case, however, there is a fear that the removal of the pads 13 is difficult at the time of replacement due to damage and abrasion.
Thus, a pad removing hole 23 is provided through a bottom surface of each of the concave portions 16 of the pad holder 12 in the thickness direction of the holder, and a pushing rod 24 (shown in Fig. 6) is inserted into the pad removing hole 23 from the back so as to easily push out the pad 13 upward. The pad removing holes 23 may be provided at both the front and rear of the bottom surface of each concave portion as shown in the figure, or may be provided only at the center.
Fig. 4 shows a state where the sliding support members 11 are attached to the inner peripheral surface of the first-step boom member 1, and shows only a left/right half of the state. It should be noted that the other half is symmetrically attached relative to Fig. 4. The figure shows, as an example, a case where two sliding support members 11, 11 are adjacently provided in the boom circumferential direction so that their end surfaces in the boom circumferential direction are in contact with each other. However, the entire inner peripheral surface of the lower portion of the first-step boom member 1 may be covered by a single wide sliding support member 11.
It should be noted that the sliding support member 11 according to the present embodiment may be used together with known sliding support members including those of the first and second known techniques (one or both of the sliding support members of the first and second known techniques) inside one boom member. Fig. 4 shows, as an example, a case where known pads 25 are used on side walls of the boom member 1.
The boom is assembled in the following order including assembling of the sliding support member 11.

I. The rear and circumferential fixing members 18, 19 among the holder fixing means are attached to the first-step boom member 1.
II. The pad holder 12 is attached.
III. The pads 13 are fitted into the concave portions 16 of the pad holder 12.
IV. The front fixing member 17 is attached.
V. The second-step boom member 2 is inserted.

The bending grooves 14 are provided on the upper surface of the pad holder 12 and the auxiliary bending grooves 15 are provided on the lower surface. Therefore, it is possible to easily bend the pad holder 12 in conformity with the inner peripheral surface of the first-step boom member 1 and surely fit it on the surface in either of the following cases:

(1) the case where the pad holder 12 is preliminarily bent into a curved shape at the manufacturing stage and the adjustment bending is performed at the assembling stage; or
(2) the case where the pad holder 12 is substantially bent from a flat plate into a curved shape and also the adjustment bending is performed at the assembling stage.

A plurality of the pads 13 is fitted into the concave portions 16 of the band-shape pad holder 12 so as to be aligned in the boom circumferential direction. Thus, firstly, the positions of all the pads 13 are fixed at the same time by fixing only the position of the pad holder 12 on the first-step boom member 1 by means of the holder fixing means in the boom circumferential direction and in the length direction. Therefore, the work of assembling the pads is easily performed in comparison with the first known technique. Secondly, since the pads 13 are fitted into the concave portions 16 of the pad holder 12, there is no fear that the pads 13 are dropped due to the sliding resistance with the second-stage boom member 2. Thirdly, the thickness of the pads can be freely and individually selected for each of the pads unlike the second known technique. Thus, even in such a case as where a gap between the boom members 1 and 2 is different in parts in the boom circumferential direction or where the gap varies due to errors in manufacture of both the boom members 1, 2, a pad 13 having the thickness suitable for the gap can be selected. Therefore, it is possible to fit all the pads 13 to the outer peripheral surface of the second-stage boom member 2.
That is, it is possible to obtain at the same time both the workability in assembling of the pads and the improvement in pad performance of helping the sliding of the second-stage boom member 2.

Other Embodiments

(1) The auxiliary bending grooves 15 of the pad holder 12 are desirably provided. However, even in the case where these are not provided, the bending grooves 14 enhance, as their fundamental effects, the bending property of the holder 12 and the fitting property to the inner peripheral surface of the first-step boom member.
(2) The pad holder 12 and the pads 13 are desirably made of different synthetic resin materials having respective characteristics suitable for the pad holder and the pads as in the above embodiment. However, the both may be made of an identical synthetic resin material under the condition that favorable sliding performance of the pads 13 can be at least ensured.
(3) It is desirable that the pads 13 are detachably fitted into the concave portions 16 of the pad holder 12. However, when the pads are replaced together with the pad holder, the pads may be fixed by adhesive or the like after the pads are fitted into the concave portions 16 for strengthening the force of fixing the pads.

Claims

A sliding support member (11) used for a telescoping boom in which a plurality of boom members (1, 2, 3, 4) are telescopically inserted into each other, lower portions of the boom members being curved in a downward convex shape when the boom is in a horizontal state, comprising:
a plurality of pads (13) in contact with an outer peripheral surface of the inner boom member (2) for supporting the inner boom member (2) slidably; and

a pad holder (12) attached to an inner peripheral surface of at least the lower portion of the outer boom member (1) inserted into the inner boom member (2) over a fixed range in the boom circumferential direction,
characterized in that:
said pad holder (12) is in a band shape,

a plurality of bending grooves (14) extending in the boom length direction and opening upward is provided on an upper surface of said pad holder (12) facing the inner boom member (2) at intervals in the boom circumferential direction as a means for helping said pad holder to be bent into a curved shape,

a plurality of concave portions (16) opening upward is provided between said bending grooves (14) respectively, and

said pads (13) are fitted into said concave portions (16) respectively so as to fix a position of the boom in the circumferential direction and in the length direction.
The sliding support member for the boom according to claim 1, wherein
an auxiliary bending groove (15) opening downward and extending in the boom length direction is provided at a position corresponding to each of said bending grooves (14) on a lower surface of said pad holder (12).
The sliding support member for the boom according to claim 1 or 2, wherein
said pad holder (12) and said pads (13) are made of different synthetic resin materials from each other.
The sliding support member for the boom according to claim 3, wherein
said pads (13) satisfy at least one of the following conditions:
(i) a dynamic friction coefficient is smaller;

(ii) a difference between a static friction coefficient and the dynamic friction coefficient is smaller; and

(iii) the abrasion resistance is higher,
than conditions of said pad holder (12).
The sliding support member for the boom according to claim 4, wherein
said pads (13) satisfy a condition that the static friction coefficient is approximately 0.15 and the dynamic friction coefficient is approximately 0.1 with surface pressure in a range from 90 kg/cm² to 180 kgf/cm².
The sliding support member for the boom according to any of claims 3 to 5, wherein
said pads (13) are made of a synthetic oleoresin material.
The sliding support member for the boom according to any of claims 1 to 6, wherein
said pad holder (12) is preliminarily hot-formed from a thermoplastic resin material into a curved shape corresponding to the inner peripheral surface of the outer boom member (1).
The sliding support member for the boom according to any of claims 1 to 7, wherein
said pads (13) are detachably fitted into said concave portions (16) of said pad holder respectively.
The sliding support member for the boom according to claim 8, wherein
a pad removing hole (23) is provided through a bottom surface of each of said concave portions (16) of said pad holder in the thickness direction of said pad holder (12).
A boom provided with the sliding support member according to any of claims 1 to 9, wherein
holder fixing means (17, 18, 19) for fixing said pad holder (12) of the sliding support member in the boom circumferential direction and in the boom length direction are provided.
The boom according to claim 10, wherein
said holder fixing means include a front fixing member (17) detachably attached to a front end of an outer boom member so as to hold said pad holder (12) from the front, rear fixing members (18) attached to an inner peripheral surface of the outer boom member so as to hold said pad holder (12), at a plurality of points in the boom circumferential direction, from the rear, and circumferential fixing members (19) attached to the inner peripheral surface of the outer boom member so as to hold said pad holder (12) from both sides in the boom circumferential direction.