Vibratory compaction working machine

Abstract: A vibratory compaction working machine (50, 50 a , 50 b ) has a lower travel structure (51) and an upper swing structure (52) mounted on the lower travel structure. The upper swing structure has a boom mounted thereon for pivotal movement by a first hydraulic cylinder (54), an arm (20, 20 a ) mounted on the boom at its forward end for pivotal movement by a second hydraulic cylinder (57), and vibratory plate compactor (60, 60 a ) mounted on the arm at its forward and for pivotal movement by a third hydraulic cylinder (62). The arm is in the form of an extension arm (20, 20 a ) having a first arm element (21, 71) and a second arm element (22, 73) mounted for linear movement relative to the first arm element by a fourth hydraulic cylinder (26, 72). The first arm element is attached at the forward end of the boom (53) for pivotal movement by the second hydraulic cylinder (57), and the second arm element has the vibratory plate compactor (60, 60 a ) attached to the forward end thereof for pivotal movement by the third hydraulic cylinder (62).

Description: BACKGROUND OF THE INVENTION The present invention principally relates to a vibratory compaction working machine to be used for compaction of backfilling soil of an excavated ditch formed below the ground surface level, and more specifically, relates to such machine to be used for compaction of soil placed around and above pipes for water supply and drainage, water waste, electric cables, city gas, etc. which have been laid on the bottom of the excavated ditch. There has hitherto been known (c.f. US-A-3 909 149) a vibratory compaction working machine of the type employing a hydraulic excavator as base machine, as shown in Fig. 1. The machine includes a lower travel structure 1 on which an upper swing structure 2 is mounted, the upper swing structure having a boom 3 mounted thereon for pivotal movement about a pin 5 by a hydraulic boom cylinder 4, and an arm 6 mounted on the forward end of the boom 3 for pivotal movement about a further pin 8 by a hydraulic arm cylinder 7. when it is desired to use the machine as a usual hydraulic excavator, the upper structure further has an excavating bucket mounted on the forward end of the arm 6 for pivotal movement, while when it is desired to use it as a compaction working machine, a vibratory plate compactor 11 is mounted by means of a pin 9 applied through the fixing holes for bucket. This vibratory plate compactor 11 comprises a support bracket 13 connected via the above pin 9 to the arm 6 and connected through a further pin 10 to links 33 connected to a hydraulic bucket cylinder 12, a vibrating unit 14 attached to the bracket 13 through vibration damping and force transmitting rubber members 15, and a compacting plate 16 attached underneath the vibrating unit 14. As shown in Fig. 2, the vibratory unit 14 includes a hydraulic motor 14a and a pair of eccentric weights 14b to be driven by the motor 14a. The vibratory compaction working machine of the conventional design as constructed above is operated as follows. Suppose that a concrete pipe 18 of a relatively large diameter (e.g. 1 to 5 m) is laid on the bottom of a ditch 17 defined below the ground surface level (see Fig. 1). As shown in Fig. 3, a distributor 30 with a double chute 34 is operated to distribute soil 19 over at both sides of the pipe 18. Then, the boom cylinder 4, arm cylinder 7 and bucket cylinder 12 of the working machine are actuated to carry out a compaction by the compacting plate 16 of the vibratory plate compactor 11 to form a compacted soil zone of a unit thickness t measured from the bottom of the excavated ditch 17 (this unit thickness t is to be determined according to the compacting strength provided by the machine) and of a width corresponding to the width W of the compacting plate 16 (See Fig. 2B). Subsequently, the vibratory plate compactor 11 is slightly raised and the machine body (the lower travel structure and upper swing structure) is shifted a distance corresponding to the width W . The same step of compaction is effected once again to form a further compacted soil zone with a width of W and a thickness of t , so that backfilling and compaction of a layer A is eventually performed. In this manner, similar operations are repeated for a number of layers B , C , D ... in sequence until the combined thickness of those layers completely cover the top of the concrete pipe 18. In this operation, there is a risk of the bucket cylinder 12 or the vibratory plate compactor 11 striking against the concrete pipe 18 when a first compaction of the layer A shown in Fig. 1 by the width W of the compacting plate 16 is completed and the vibratory plate compactor 11 is slightly raised from the layer A by slightly lifting the boom 3 by extending the boom cylinder 4. In order to avoid the risk, it will be necessary that while the boom 3 is raised as shown by an arrow a in Fig. 1 by extending the boom cylinder 4, the arm 6 is pivotally moved in a direction b by extending the arm cylinder 7. Also after the machine body is shifted a distance corresponding to the unit width W , and when the plate compactor 11 is lowered to set in a second compacting position, it will be necessary to set the plate compactor 11 in an initial position while avoiding engagement with the ditch 17 or pipe 18 by the reverse combined operation of retracting the boom cylinder 4 and the arm cylinder 7. This operation in fact is so complicated that the operator of the machine overstrains his nerves. This complicated combined operation is also necessary when the plate compactor 11 is lowered in response to or following a reduction of the soil thickness 19 or sinking of the soil that may result from the weight of the upper swing structure 2 applied to the plate compactor 11 as a downwardly-directed working forces during the compacting operation. It is noted that the unit thickness t after the sinking of each layer is several tens % less than the original thickness before compaction. There may be involved a further problem caused from the fact that depending on the hardness of the soil material, the excavated ditch 17 may be steep or gentle in respect of its inclination and accordingly the ditch varies in width (the greater the pipe 18 becomes in diameter, this variation becomes the greater). As shown in Fig. 4, wherein a number of working positions assumed by the machine are illustrated, a width W ₁ which is a maximum reach of the plate compactor 11 as indicated by K, is determinable solely by the type of machine in use. Accordingly, even when backfilling and compacting an excavated ditch 17 of the same depth is performed, there is the necessity of having several machines of different capacities e.g., with shorter booms 3 and arms 6 and longer booms and arms, available for selective use. Further, even in case the excavated ditch 17 is of a constant width, it may possibly happen that as the operation proceeds from the layer A to the layer D toward the ground surface level, the plate compactor 11 can hardly make contact with the soil adjacent the machine body because of the boom 3 and arm 6 being excessively lengthy (in Fig. 4, j indicates a working position in which the plate compactor 11 is closest to the machine body. Therefore, the zone E adjacent the upper swing structure 2 is left intact or untreated ( F shows a processible zone). Accordingly, this raises a further problem in that it is necessary to employ a different machine with shorter boom 3 and arm 6, or alternatively to move the machine body rearwardly or to the left as viewed in Fig. 4 prior to resumption of the operation. Still further, the conventional vibratory plate compactor 11, as shown in Fig. 2, includes vibration damping and force transmitting rubber members 15 mounted between the support bracket 13 and the vibrating unit 14, three on each side, fore and aft, with their axes extending perpendicularly of the axes of the pins 9,10. When the working force is applied through the pin 10 of the link 33 as shown in Fig. 2(A), it is those members 15 situated on the right side, as viewed in the drawing, that largely resist this force, the left-hand rubber members escaping in the upward direction. Hence, the right-hand rubber members 15 deflect showing shearing and bending resistances in the vertical direction against the working force, and accordingly, the support bracket 13 is also lowered of its right-hand side toward the vibrating unit 14, so that the magnitude of the working force to be transmitted to the unit 14 as a compacting force is reduced while the compacting force tends to be exerted on the right-hand part of the compacting plate 16. This again raises the problem of difficulties in attainment of effective compaction. When, on the other hand, the boom cylinder 4 is contracted in an attempt to exert the working force upon the plate compactor 11 through the pin 9, the circumstance will be the same as that described above in that because of those rubber members 15 on the left side mainly resisting the working force, those left-hand members would deflect so that only a small magnitude of compacting force is exerted upon the compacting plate. Meanwhile, it is duly conceived that with the left side part of the compactor 11 being lowered preliminarily through the pin 9 by extending the arm cylinder 7, the working force is applied on the side of the pin 10 at the tip end of the link. Nevertheless, this will also result in a decrease in the working force transmitted to the vibrating unit 14 as a compacting force because of the right-hand rubber members being deflected. Yet further, the vibratory compaction working machine involves another problem that follows. When the distributor 30 is actuated to spread out soil 19 as shown in Fig. 3, such soil would be placed in the area between the periphery of the pipe 18 and the side wall of the excavated ditch 17, or somewhat closer to the periphery of the pipe 18. However, there usually is formed a vacant space X immediately below the pipe and a pile of soil as spreaded because the soil can not enter underneath the pipe 18 where load from the pipe 18 be essentially borne. Accordingly, it is necessary to force a volume of soil into the vacant space X underneath the pipe 18 and level off the piled soil surfaces prior to carrying out the compaction work by means of the compacting plate 11. To this end, it has been common practice that with a compacting plate 16 in the form of a flat board, the compactor 11 is pivotally moved about the pin 9 in a snap action by contracting the cylinder 12, thereby forcing a volume of soil 19 into underneath the pipe 18 by means of the compacting plate 16 and then the volume of soil thus pushed in is compacted. However, this operation by use of the flat compacting plate 16 proved unsatisfactory in that it is still difficult to push in the soil as described since that soil being pushed in tends to be compacted earlier prior to being pushed in mainly because of the inclination of the plate 16 with respect to the horizontal surface being small. The object of the invention is to provide a vibratory compaction working machine of the type which is capable of performing effective compaction in a simplified operating manner while being available for common use to excavated ditches of different widths, and which is capable of performing the same while maintaining the distance between the main structure of the machine and the excavated ditch unaltered even when the position to be compacted proceeds in sequence upwardly of the ditch. This object will be solved by the features of claim 1. Dependent claims are directed on features of preferred embodiments of the invention. SUMMARY OF THE INVENTION The advantages of the present invention will be summerized below. The vibratory compacting working machine according to the invention has an extension arm mounted for pivotal movement on the forward end of the boom pivotally attached on the upper swing structure, the compactor being pivotally mounted on the forward end of the extension arm, with this construction, therefore, the invention is capable of linearly raising and lowering the compactor between the ditch wall and the embedded pipe through rather simplified manipulation of extending and contracting the extension arm in contrast to the conventional complicated combined operation of the boom and arm. The operation of compaction thus can be carried out effectively yet without any risk of the moving parts such as hydraulic cylinder, arm or compactor striking against the ditch wall or the pipe. The operator of the machine can raise or lower the compactor with simple manipulation, and therefore his labors are reduced and this enables unskilled operators to operate the machine. In addition, the extension of the extension arm makes it possible to practice the compacting operation for the depth of the ditch far greater than the maximum depth attainable by the conventional machine. In case, further, the compacting operation is conducted for the area adjacent the machine body or remote therefrom, the extension of the extension arm also makes it possible to reach the compactor to the respective desired positions, thereby enabling the operation effected over a range broader than before. And yet, since there will be eliminated any zone adjacent the machine where the compacting operation is impracticable, the use of a single machine is enough to practice the compacting operation against a variety of ditch from narrow to broad or laid pipes of various diameters. There is no necessity to use a plurality of machines having booms and arms of different lengths, so that the operation will be economized by the application of the invention. Further, even when the surface level of soil being compacted is elevated as the operation proceeds, it is possible, by the manipulation of the extension arm, to set the compactor at any desired place without moving the machine apart from the excavated ditch. This operation is quite efficient and again does not need any substitution by a machine of the type having shorter booms and arms. According to a preferred embodiment, the vibratory plate compactor includes a vibrating unit, a support bracket connected through pin to the slide arm, and vibration damping and force transmitting rubber members disposed between said vibrating unit and said support bracket with their axes directed parallel to the axis of the above pin. With this arrangement, therefore, when a working force is applied through the pin for compacting operation, there occur vertically directed shearing and bending resistances, as well as horizontaly directed shearing resistance in the rubber members, resulting in an increase in the total resisting force, and therefore it is possible to transmit a greater compacting force that acts concentratedly upon the central portion of the compacting plate. This can assure highly efficient operation of compaction. According to a further embodiment, the compactor attached at the forward end of the arm releasably attaches a compacting plate with a compacting surface of V-shaped cross-Section. This arrangement facilitates the forcing-in and compacting of soil underneath the pipe by virtue of a greater inclination angle of the compacting surface relative to the horizontal surface. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view schematically showing a convential vibratory compaction working machine in its operating condition; Fig. 2(A) and Fig. 2(B), respectively, show a side view and a front view of a vibratory plate compactor incorporated in the conventional machine shown in Fig. 1; Fig. 3 is a side view schematically showing a soil distributor for backfilling in its operating condition; Fig. 4 is a partly cut side view schematically showing the operating range of the conventional machine shown in Fig. 1; Fig. 5 is a side view showing a vibratory compaction working machine according to a first embodiment of the invention in its operating condition; Fig. 6 is a side view showing a detail of the construction of an extension arm incorporated in the machine shown in Fig. 5; Fig. 7 is a cross-sectional view taken along the line VII-VII of Fig. 6; Fig. 8(A) and Fig. 8(B), respectively, show a side view and a front view of the vibratory plate compactor incorporated in the machine shown in Fig. 5; Fig. 9 is a sectional view showing a rotation lock unit incorporated in the vibratory plate compactor shown in Fig. 8; Fig. 10 is a partly cut side view schematically showing the operating range of the machine shown in Fig. 5; Fig. 11 is a side view showing an altered embodiment of the extension arm incorporated in the machine shown in Fig 5; Fig. 12 is a side view showing a vibratory compaction working machine according to another embodiment of the invention in its operating condition; Fig. 13(A) and Fig. 13(B), respectively, show a side view and a front view of the vibratory plate compactor incorporated in the machine shown in Fig. 12. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the invention will now be described with reference to the accompanying drawings. In Fig. 5, there is shown a vibratory compaction working machine generally denoted by the reference numeral 50, which employs a hydraulic excavator as a base machine. Thus, the machine 50 includes a lower travel structure 51 and an upper swing structure 52 mounted on the lower structure 51. The upper swing structure 52, however, has a particular seat frame 52 a modified to protrude more forwardly than the ordinary hydraulic excavator so as to enable an operator to command a view of the whole operating conditions. The upper swing structure 52 has a boom 53 mounted thereon for pivotal movement about a pin 55 by means of a hydraulic cylinder 54. The boom 53 is provided at its forward end with an extension arm 20, which in turn is provided at its forward end a vibratory plate compactor 60. The extension arm 20 includes a base arm 21 attached to the forward end of the boom 53 for pivotal movement about a further pin 58 by means of a further hydraulic cylinder 57, and a slide arm 22 attached for slidable movement relative to the base arm 21. As shown in Figs. 6 and 7, in the extension arm 20, the base arm 21 is of U-shaped cross-section having opposed side portions on which guide members 23 each having a guide groove 23a are mounted in front and in rear (or in the middle and in front, or over the entire length) thereof by bolts 24, and the slide arm 22 is of a rectangular shaped cross-section having opposed side rails each received in a corresponding one of the guide grooves 23a. A hydraulic arm extension cylinder 26 is connected at its head side end through a pin 28 to a bracket 27 provided on the lower side of the end of the slide arm 22, and is connected at its end of the side of a piston rod 26a to the rear end of the base arm 21 through another pin 29, so that the extension and contraction of the cylinder 26 can cause the slide arm 22 to move forward and backward along the base arm 21. The hydraulic cylinder 26 is disposed inwardly of the U-shaped base arm 21, and the slide arm 22 has its rear end positioned to protrude toward the side of the boom beyond the rear end of the base arm 21. The vibratory plate compactor 60 includes a support bracket 65 connected through a pin 61 to the forward end of the extension arm 20 i.e. the slide arm 22 while being connected through a linkage 63 and pin 64 to a hydraulic cylinder 62, a vibrating unit 67 connected to the bracket 65 through vibration damping and force transmitting rubber members 66, and a compacting plate 68 attached to the vibrating unit 67. The compacting plate 68 is detachably mounted on a fixing plate 35 of the vibrating unit 67 by means of fastening bolts 32 (See Fig. 8). The vibrating unit 67 includes hydraulic motor 67 a and a pair of eccentric weights 67 b driven by the motor 67 a . The linkage 63 which provides for power amplification is not necessarily required, and thus the piston rod of the hydraulic cylinder 62 may be connected directly to the support bracket 65 through the pin 64. For vibration damping and force transmitting the rubber members 66 are mounted with their axes oriented in the same direction as the axes of the pins 61, 64, the number of the rubber members being eight in all, comprised of two upper ones and two lower ones on each side. The support bracket 65 of the vibratory plate compactor 60 includes an upper stationary frame 65 a connected to the slide arm 22 and the linkage 63, a lower movable frame 65 b rotatably connected to the upper stationary frame 65 a , and a lock unit 78 provided between the two frames 65 a and 65 b for selectively restraining the lower movable frame 65 b from rotating relative to the upper stationary frame 65 a . As shown in Fig. 9, the upper stationary frame 65 a has a stationary flange 69 attached to its bottom end, and a holder shaft 70 is fixed in the central portion of the flange 64 by a fastening nut 71. The lower movable frame 65 b has a movable flange 72 attached to its top end. The lock unit 78 includes a lock piston 73 situated between the movable flange 72 and the holder shaft 70. This lock piston 73 is fixed to the movable flange 72 and is made sealingly rotatable relative to the holder shaft 70, with a hydraulic chamber 74 being defined between the lock piston 73 and the holder shaft 70. The movable flange 72 and lock piston 73 are dimensioned such that when a hydraulic fluid is not supplied to the chamber 74, a small clearance is left between them and the stationary flange 69, thereby permitting the lower movable frame 65 b to rotate along with the lock piston 73 about the holder shaft 70 relative to the upper stationary frame 65 a . Within the holder shaft 70 and lock piston 73 are formed a pair of hydraulic passages 75, 76, with the hydraulic chamber 74 forming part of the hydraulic passage 75. The hydraulic passage 75 has an inlet port 75 a leading to a hydraulic fluid source, not shown, and an outlet port 75 b leading to the hydraulic motor 67 a , while the oil passage 76 has an inlet port 76a leading to the hydraulic motor 67 a and an outlet port 76 b leading to a reservoir, not shown. The holder shaft 70 is connected at its bottom to a valve unit 77 including a check valve 77 a and a relief valve 77 b . When the vibrating unit 67 is operated, a hydraulic fluid is supplied to the hydraulic motor 67 a -(See Fig. 8) through the passage 75, and returns therefrom through the passage 76 to the reservoir. When the hydraulic fluid flows through the passage 75, this fluid is also fed in the chamber 74 to thereby lift the lock piston 73 upwardly causing the movable flange 72 to engage the stationary flange 69. The lower movable frame 65 b thus is locked from rotation relative to the upper stationary frame. In this manner, the lock unit 78 acts as an automatic lock operative in response to the operation of the vibrating unit 67. It is to be noted that the lock unit 78 alternatively may be of the remote control type operated independently of the vibrating unit 67. The vibratory compaction working machine embodied according to the invention as described in the foregoing will now be described of its operation by reference back to Fig. 5. When the first step of compacting the layer A has been completed, the extension cylinder 26 for arm 20 is operated to contact to some extent so as to slightly raise the slide arm 22 along the base arm 21 in the direction of C , however with the boom 53 being not operated. Subsequently, the machine is travelled a distance corresponding to the width W of the compacting plate 68 (See Fig. 8 B ), and then the extension cylinder 26 is operated to extend to lower the slide arm 22 along the base arm 21, so that the compacting plate is caused to contact the layer surface, thereby attaining movement of the compacting position. In this operation, there is no risk of the cylinder 62, arm 20 or compactor 60 striking against the excavated ditch 17 or the pipe 18, and therefore it is secured to proceed with the shifting of the compacting position with ease and high efficiency. In the compacting operation after the machine once has moved a distance of W , the process of applying a working force can be performed only by maintaining the compacting plate 68 in a horizontal posture and by extending the cylinder 26. The manipulation involved thus will be significantly simplified. Further, it can be appreciated that the extension of the arm 20 makes it possible to provide a depth h ₂ of a compacted soil as shown in Fig. 10, much greater than the maximum height h ₁, provided by the conventional machine shown in Fig. 4. Also, when it is desired to perform compaction either in a zone remote from the machine or adjacent the machine, the compactor 60 can be placed at a desired position as shown in Fig. 10 at l and m by extending of the arm 20. Thus, as compared with the operating range provided by the conventional machine as indicated at W ₁ in Fig. 4, it is possible to provide a broader range of compaction operation as indicated at W ₂ in Fig. 10. And further, it is possible to eliminate such zone adjacent the machine that cannot be compacted as indicated at E in Fig. 4. This provides for a broad range of compacting operation covering from a narrower ditch to a wider ditch or pipes 18 of varying diameters. Still further, even if the surface level of soil layer being compacted is raised as the compacting operation proceeds, it is possible to place the compactor 60 at any desired position by extending and contracting the arm 20 while moving the machine adjacent the edge of the ditch 17, i.e., without the necessity of moving the machine far away from the ditch 17. This secures efficient operations and eliminates the necessity of replacement by another machine of the type having a shorter boom 3 and arm 6. As mentioned with reference to Fig. 6, furthermore, the hydraulic cylinder 26 for moving the slide arm 22 is disposed within the base arm 21, and the rear end of the slide arm 22 is positioned to protrude toward the side of the boom 3 beyond the rear end of the base arm 21 when the slide arm 22 is in its most retracted position. This provides a prolonged length of stroke for the slide arm 22 i.e. the extension arm 20 such that the length in the retracted position is about a half of that in the extended position, thereby increasing the operating range. In the illustrated embodiment, also, as shown in Fig. 8 in enlargement, the compactor 60 has the vibration damping and force transmitting rubber members 66 mounted with their axes oriented in the same direction as the axis of the pin 61 or 65. Accordingly, when a working force is applied from the side of the pin 61 for compacting operation by manipulating the extension cylinder 26 or boom cylinder 54, as shown by the dotted lines in Fig. 8-(A), all the eight rubber members 66 serve to provide shearing and bending resistances in the vertical direction as well as shearing resistance in the horizontal direction so that resistance forces of the rubber members 66 become greater. In consequence, a greater working force can be transmitted to the vibrating unit 67 before the left side portion of the support bracket 65, as viewed in Fig. 8(A), sinks as indicated by the dotted lines, and also an additional thrust can be transmitted through the right-hand rubber members 66, and this enables the resultant compacting force to be concentratedly exerted around the central portion of the compacting plate 68. Also, if the working force is applied with the right-hand of the support bracket being sunk by extending the hydraulic cylinder 62, in anticipation of the sinking of the left-hand portion of the bracket shown in Fig. 8(A), then there can be provided a still greater working force to be transmitted to the compacting plate. Further, it is possible to further increase the resistance of the rubber members against the working force applied from above by increasing the pitch L between the vertically aligned rubber members 66 as shown in Fig. 8(B). Thus, the efficient compacting operation can be performed. In the embodiment illustrated, the support bracket 65 of the compactor 60 is divided into the upper stationary frame 65 a and the lower movable frame 65 b rotatable relative thereto, the lock unit 78 being provided therebetween for selectively restraining the two frames from relative rotational movement. With this construction, it will be appreciated that when the compactor 60 is brought into and out of the ditch 17 or when the compactor 60 is lifted after completion of the compaction and then the machine is moved to the next position where the compactor 60 is once again lowered into a set position, the lower portion of the compactor below the lower movable frame 65 b is free to swing away from the pipe 18 or ditch 17 even if the compacting plate 68 of the compactor 60 should strike against the ditch 17 or pipe 18, thus avoiding the risks of the pipe 18 being damaged. Further, it is advantageously possible to adjust the compacting plate 68 maintained at all times parallel to the pipe 18, thus facilitating the compacting operation. In the above-described embodiment, the mounting of the extension cylinder 26 in the extension arm 20 has been described as such that the head side of the cylinder is connected to the slide arm 22 and the piston rod 26 a to the base arm 21. However, this may alternatively be such that as shown in Fig. 11, the head side of the cylinder is connected through a pin 29 a to the forward end of the base arm 21 and the end of the piston rod 26 a is connected through a pin 28 a to the bracket 27 a provided at the lower side of the slide arm 22. With this alternative arrangement, the piping for the cylinder can advantageously be mounted with significant ease since the piping for the extension cylinder 26 is kept stationary while the cylinder 26 operates. Additionally, there is provided a further advantage that the cylinder rod 26 a is not subjected to compressive forces when a working force is applied to the compactor 60 through the hydraulic cylinder 26. The invention will now be described of its another embodiment with reference to Figs. 12 and 13. In Figs. 12 and 13, the same parts as those shown in Figs. 5 and 8 are designated by the same reference numerals as used in the latter figures. A vibratory compaction working machine 50 a embodied according to the invention, as shown in Fig. 12, includes a vibratory plate compactor 60 a with a vibrating unit 67 having a compacting plate 65 a of V-shaped cross-section bolted at 32 to the mounting plate 35 in a detachable manner. This type of compactor is particularly adapted to use for forcing-in of soil under the pipe 18 and compacting thereof in the earlier stage of backfilling the excavated ditch 17. That is, as shown in Fig. 3, when the distributor 30 spreaded soil 19 around the bottom of the ditch 17, there usually occurs a vacant space X under the pipe 18 while the spreaded soil presents mountain-shaped. Under these conditions, the cylinder 62 is contracted to swing the compactor 60 a about the pin 61 in a snap action, so that the compacting plate 68 a can force the spreaded soil 19 to be compacted into the vacant space X while leveling off the mountain-shaped soil. In this operation, as the compacting plate 68 a has a V-shaped compacting surface, it is possible to make the forcing-in and compaction of soil underneath the pipe with quite ease since the compacting surface forms a greater angle of inclination ϑ with respect to the horizontal surface, as shown in Fig. 13. Further, it will be appreciated that in the process of forcing soil in underneath the pipe and compacting it through the snap action of the compactor, there can advantageously be provided a unitary movement effected by both of the support bracket 65 and the V-shaped compacting plate 68 a due to the featured arrangement that the elastic means 66 of the compactor 60 a are directed parallel to the axis of the pin 61 and are mounted vertically in two stages as upper and lower rubber members. Upon completion of this operation, the compacting plate 68 a is removed and the ordinary compacting plate 68 described in the previous embodiment is attached to the compactor to thereby allow the ordinary compacting operation to be performed in a manner explained previously. Such operations are continued until there will be no vacant space underneath the pipe when soil is distributed into the ditch 17. In the above-described embodiment, the extension arm 20 is constructed such that it comprises the base arm 21 and the slide arm 22 mounted on the upper sides of the base arms 21 for slidable movement therealong by means of the hydraulic cylinder 26. This, however, may be embodied otherwise, provided that the extension arm 20 essentially comprises a first arm element and a second arm element mounted for linear movement relative to each other by means of a hydraulic cylinder. Nevertheless, the extension arm 20 of the type above-described as having the base arm 21 and the slide arm 22 is duly considered to be most preferred since it attains not only fundamental advantageous effect to satisfy the object of the invention, but also the other unique advantages as follows. (a) Since the slide arm 22 is mounted on the upper surface of the base arm 21 for slidable movement therealong, the base arm 21 can have only to be long enough to mount the paired guides 23 and thus may be substantially shorter than the slide arm in length, while the slide arm may have any desired shape or length suited to provide a necessary strength. Accordingly, as compared with an extension arm of the telescopic type, for instance, in which two tubular arm elements are telescopically extensible relative to each other, the present construction ensures cutdown in weight, reduction of the manufacturing cost and improvement on the operating stability. (b) Since the slide arm 22 is supported for slidable movement by a pair of guides 23 attached on the base arm 21, the distance between the fulcrums for support of the slide arm 22 (a distance between the guides 23) remains constant no matter how the slide arm 22 is extended. Therefore, as compared with the above quoted telescopic type extension arm in which as the lower arm element is extended, the distance between the fulcrums on the upper arm element becomes small, the present construction will provide consistent stability secured through the entire compacting operation. (c) Since the base arm 21 can be substantially shortened more than the slide arm 22 as mentioned in the above a , the extension arm can be shortened accordingly when it is in the most retracted position. Therefore, as compared with the above quoted telescopic type extension arm in which the length of the arm in a most retracted position is determined by the length of the one of the two tubular arm elements that has a longer length, the present construction offers a superior workability in that the machine can cover a wide range of performance from the bottom to the top of the ditch and from a greater width to a smaller width of the ditch. (d) As shown in Figs. 6 and 7, the guide groove 23 a , the slide surfaces of the side rails 25 and the hydraulic cylinder 26 for extension of the arm are exposed outwardly or disposed to permit easy access by the operator. Thus, as compared with the above quoted telescopic type extension arm in which the slide surfaces and the extension cylinder are consealed within the tubular arms, the present construction provides easy maintenance to the slide surfaces and cylinder.

Claims: A vibratory compaction working machine for compacting of backfilled soil of an excavated ditch below the ground surface level, comprising a lower travel structure (51) and an upper swing structure (52) mounted on the lower travel structure (51), said upper swing structure (52) having a boom (53) mounted thereon for pivotal movement by means of a first hydraulic cylinder (54), an arm (20) mounted on the forward end of said boom for pivotal movement by means of a second hydraulic cylinder (57) and a vibratory plate compactor (60, 60a) mounted on the forward end of said arm (20) for pivotal movement by means of a third hydraulic cylinder (62), characterized in that: said arm (20) is formed as an extension arm (20) having a base arm (21) mounted on said boom (53) at a forward end thereof for pivotal movement by means of said second hydraulic cylinder (57) and a slide arm (22) supported by guide means (23) mounted on said base arm (21) for linear slidable movement along the upper side of said base arm outside thereof by means of a fourth hydraulic cylinder (26), said slide arm (22) having a length such that the rear end of the slide arm (22) is Positioned to protrude toward the side of said boom (53) beyond the rear end of said base arm (21) when said slide arm (22) is in its most retracted position, and said vibratory plate compactor (60, 60a) is attached at the forward end of said slide arm (22) for pivotal movement by means of said third hydraulic cylinder (62). A vibratory compaction working machine according to Claim 1, characterized in that said vibratory plate compactor (60, 60a) includes a vibrating unit (67), a support bracket (65) connected to the forward end of said slide arm (22) by pin means (61), and vibration damping and force transmitting elastic means (66) disposed between said vibrating unit (67) and said support bracket (65) and connected thereto, said elastic means (66) being disposed with the axes thereof oriented in the same direction as the axis of said pin means (61). A vibratory compaction working machine according to Claim 1, characterized in that said vibratory plate compactor (60, 60a) includes a support bracket (65) connected to a vibrating unit (67) through vibration damping and force transmitting elastic means (66), said support bracket (65) having an upper stationary frame (65a) connected to said slide arm (22), a lower movable frame (65b) rotatably connected to said upper stationary frame (65a) and carrying said vibrating unit (67) through said elastic means (66), and lock means (78) disposed between said upper stationary frame (65a) and said lower movable frame (65b) for selectively restraining the lower movable frame (65b) from rotating relative to the upper stationary frame (65a). A vibratory compaction working machine according to Claim 3, characterized in that said lock means (78) includes a hydraulically operated lock piston (73) and said vibrating unit (67) includes eccentric weights (67b) rotatably driven by a hydraulic motor (67a), said lock piston (73) being operative in response to the operation of said hydraulic motor (67a) to provide an automatic lock. A vibratory compaction working machine according to Claim 1, characterized in that said vibratory plate compactor (60a) includes a vibrating unit (67) and a compacting plate (68a) removably attached to said vibrating unit (67), said compacting plate (68a) having a compacting surface of a V-shaped cross-section. A vibratory compaction working machine according to Claim 1, characterized in that said fourth hydraulic cylinder (26) has a head side end thereof fixed at the forward end of said base arm (21) and a rod side end thereof fixed to said slide arm (22).

Inventors: IKEDA YUTAKA, ISHIKAWA YASUAKI, ITOU YOSHIFUMI, KOMA HIROSHI, MIYAGAWA HIROKAZU, MURAKAMI SHIRO, IKEDA, YUTAKA, ISHIKAWA, YASUAKI, ITOU, YOSHIFUMI, KOMA, HIROSHI, MIYAGAWA, HIROKAZU, MURAKAMI, SHIRO
Applicants: HITACHI CONSTRUCTION MACHINERY, HITACHI CONSTRUCTION MACHINERY CO., LTD.
Application year: 1986
Main classification: E02D3
IPC codes: E02D3