Patent Application
20070248413
The present subject matter relates to compaction systems including rotating compaction wheels.
Compaction wheels are frequently used in conjunction with installation of various sorts of lines below grade. Lines may comprise sewer pipes, water pipes, power lines and communications lines. Trenches are cut in soil for the purpose of laying a line below grade, i.e., beneath ground level. After laying of the line is completed, the trench must be backfilled. Typically, soil piled to the sides of the trench during excavation will be pushed back into the trench with a backhoe or the like. The backfilled soil must be compacted to avoid adverse effects.
An adverse effect commonly addressed by the prior art is the resulting surface contour above the line. If the is trench is backfilled only to grade level without compacting, the soil will later settle. A depression will form along the line of the underground installation. Such a depression causes water to stand along the trench. Where the lines are communication lines, the possibility of damage to a cable at the bottom of the trench due to moisture is increased. Standing water that seeps into a trench can form ice in winter. Ice expands and causes potholes. Vehicles traveling along or across the trench can be damaged by traversing a depressed area. Where the depression crosses a footpath, people and animals may be injured if they do not see the depression. If additional soil is placed over the line to prevent later formation of a depression, a mound of soil will remain over the trench. The mound may impede travel or present an obstacle to construction over the trench.
Another important aspect of completing the backfilling process is stabilization of bedding surrounding the line. If the backfill surrounding the pipe or other line shifts due, for example, to settling, support of the line is compromised. This can lead to application of varying forces to successive segments of the line. Joint failure may ultimately result. There are several construction specifications which provide standards to assure adequate support of below grade lines. An exemplary specification is Trenching, Backfilling and Compacting (Society for Maintenance and Reliability professionals, Knoxville, Tenn. 2004). Section 3.7.1 states, “BACKFILL AT PIPE ZONE shall be placed on both sides of pipe in 4″ lifts and compacted either by hand or by mechanical tamper to an elevation 1′ above the pipe. Compaction shall be at least 90% of maximum dry density . . .” Contractors face growing safety concerns over “men in the trench” regulations. Even when expensive, mandatory procedures are followed, workers in trenches still face risk of injury in trenches. Therefore, hand tamping is undesirable.
An alternative that will provide sufficient density without tamping and which meets many standard specifications is the use of a “low sack” concrete mix. One form of such a mix comprises three sacks of cement per cubic yard of sand. The cement consolidates a mixture of sand and water, providing a stable support for the line. While effective, this solution adds significant expense to a construction project.
Prior art compaction wheel units have been suited for compacting soil at grade level. An example of a trench compaction device is illustrated in U.S. Pat. No. 4,610,567. In use, the machine straddles the trench and three compaction wheels on one axle rotate to compact the soil as the machine moves. The compaction wheels are in fixed axial positions and spaced from one another. Continuous adjustment of spacing between wheels in order to provide spacing of wheels to straddle a pipe cannot be provided.
U.S. Pat. No. 5,526,590 discloses and compaction wheel which can be positioned laterally at a preselected position along the width of a driving vehicle. However, a single wheel is provided. Width of a compaction track is not adjustable.
Briefly stated, in accordance with embodiments of the present invention a compaction wheel system and a method are provided suitable for providing compaction for earth surrounding below grade lines. A support frame supports system components and can be coupled to a driver. At least first and second compaction wheels are each mounted in a separate axle assembly. The axle assemblies are each mounted to the support frame on linkages which vary the distance between the compaction wheels with angular displacement. Additionally, each linkage maintains its respective compaction wheel at an angle to continue compacting operations. An adjuster is provided to set the angular position of each linkage. Consequently the distance between the wheels is set.
In a method, earth in filled to a preselected height next to a below grade line. A compaction wheel unit is provided, and the wheels are spaced apart to straddle the line. One ore more passes of the compaction unit along a selected linear extent of the pipe may be made.
The invention may be further understood by reference to the following description taken in connection with the following drawings.
The driver 1 in the present illustration moves the compaction wheel system 20 over soil 10 in a trench 12.
Further details are described with additional reference to
The compaction wheel 32 is constructed with dimensions useful for soil compacting. In one embodiment, the compaction wheel is solid steel with a diameter of 3 feet and a thickness of 3 inches. The compaction wheel has a compacting surface 33. Similarly, the compaction wheel 42 has a compacting surface 43. The compacting surface is the surface that is applied to the soil to be compacted, and will generally correspond to an outer diameter of the compaction wheel 32. In the illustrated embodiment, the compacting surface 33 is a flat outer diameter. However, the compaction wheels 32 and 42 could comprise sheep-foot wheels or pad-foot wheels, having circumferentially spaced, radial projections.
The compaction wheel 32 is mounted to an axle 34. In one preferred form, the axle 34 is welded to the compaction wheel 32. This construction will often be most cost-effective. However, it is possible to provide an arrangement in which the compaction wheel 32 rotates on the axle 34. The axle 34 is journaled in mounting brackets 35 and 36 of an axle support platform 37. The axle support platform 37 is pivotally supported to the linkage assembly 30 as further described below. Similarly, the compaction wheel 42 is journaled in mounting brackets 45 and 46 of an axle support platform 47. Each axle support platform 37 or 47 supports a corresponding compaction wheel in a compacting orientation. A compacting orientation is one in which the compacting wheel 32 or 42 will rotate and in which the compacting surface 33 or 43 engages the soil 10. The compaction wheel system 20 permits convenient adjustment of the distance between the compaction wheels 32 and 42 while maintaining them each in a compacting orientation.
In one preferred form, when the linkage assemblies 30 and 40 are vertically disposed, the compaction wheels 32 and 42 are in a first position, which is their closest spacing. The linkage assemblies 30 and 40 are operated by a displacement adjuster 52 to select a distance to be maintained between the first and second compaction wheels 32 and 42 and maintain the first and second compaction wheels 32 and 42 in a compacting orientation.
The structure of the linkage assemblies 30 and 40 and cooperating structures are described with respect to
In a like manner, the linkage assembly 40 comprises a forward linkage 80 and a rear linkage 90. Each of the linkages 80 and 90 comprises a parallelogram linkage. The forward linkage 80 comprises first and second arms 82 and 84. The arm 82 is pivoted at upper and lower pivot joints 85 and 86 to the support frame 26 and the support platform 47 respectively. The arm 84 is pivoted at upper and lower pivot joints 87 and 88 to the support frame 26 and the support platform 47 respectively. Similarly, the rear linkage 90 comprises first and second arms 92 and 94. The arm 92 is pivoted at upper and lower pivot joints 95 and 96 to the support frame 26 and the support platform 47 respectively. The arm 94 is pivoted at upper and lower pivot joints 97 and 98 to the support frame 26 and the support platform 47 respectively.
Within the linkage assembly 30, the linkages 60 and 70 are joined by a bar 110. Within the linkage assembly 40, the linkages 80 and 90 are joined by a bar 112. Opposite ends of the displacement adjuster 52 are coupled to the bars 110 and 112. The displacement adjuster 52 in one preferred form may comprise a hydraulic actuator 120. Another form of displacement adjuster is further described below with respect to
As the linkages 30 and 40 move angularly, the vertical distance from the compaction wheels 32 and 42 to the support frame 26 decreases. The position of the stick 4 of the excavator 2 (
The hydraulic actuator 126 is self-adjusting to provide equal and simultaneous angular displacement of the linkage assemblies 30 and 40. As the hydraulic actuator 126 lengthens, the linkage assemblies 30 and 40 are angularly displaced. A relative displacement between the first and second compaction wheels 32 and 42 to define a second position is selected. The first and second compaction wheels 32 and 42 are maintained in the second position. The compaction wheel 32 rotates about the pivot points in the linkages 60 and 70, while the compaction wheel 42 rotates about the pivot points in the linkages 80 and 90. The compaction wheels 32 and 42 are maintained in the compaction orientation.
In the embodiment of
The compaction wheel system 20 is lowered in the trench 182 to the surface of the backfill 184. The excavator 2 (
Embodiments of the present invention provide for a compaction wheel system with continuously adjustable width of a compacting path and a method for selection of a width of the compacting path. The present subject matter being thus described, it will be apparent that the same may be modified or varied in many ways. Such modifications and variations are not to be regarded as a departure from the spirit and scope of the present subject matter, and all such modifications are intended to be included within the scope of the following claims.
