CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of provisional patent application Ser. No. 61/770,024, filed on Feb. 27, 2013, the entire contents of which are incorporated herein by reference.
The present invention relates generally to the field of utility installation and in particular to the use of plows for the installation of underground utilities.
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The present invention is directed to a system for installing a utility underground. The system comprises a mobile power source comprising a work machine frame and a plow assembly connected to the power source. The plow assembly comprises an arm pivotally connected to the work machine frame at a first end of the arm, a shaker box connected to a second end of the arm, a plow blade connected to the shaker box, and a pivotal sod cutting member supported by the arm between the first end of the arm and the second end of the arm ahead of the plow blade. The sod cutting member has a cutting length less than a length of the plow blade and pivots when the sod cutting member engages an underground obstruction. A biasing member is connected to the sod cutting member and the arm to bias the sod cutting member into the ground.
BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1 is a diagrammatic representation of a vibratory plow and sod cutter.
FIG. 2 is a diagrammatic representation of a sod cutter of the present invention.
FIG. 3 is a diagrammatic representation of an alternative sod cutter of the present invention.
FIG. 1 illustrates a vibratory plow machine 10 used for the installation of slender underground utilities (cables, small pipes, etc.). These machines typically have a power unit 14 on wheels 16 or tracks (not shown) for moving the unit. The power unit 14 pulls a plow unit 18 that has a vibratory shaker box 20 and plow blade 22. The vibratory shaker box 20 will typically feature a set of internal rotating eccentric weights (not shown) that cause a vibratory motion of the shaker box as the weights are rapidly rotated. The shaker box 20 connects to the plow blade 22 extending into the soil 24 which creates a narrow slot in the ground as the machine 14 advances forward. Typically, the utility service is fed into the narrow slot in the ground right behind the plow blade 22.
In many instances, this type of machine is used to install services in nicely landscaped areas with established turf. In these instances, the vibratory plow machines 10 commonly run a sod cutter 26 in front of the plow blade 22 to pre-cut the sod 28 in front of the plow blade to minimize the turf damage done as the vibratory plow machine operates. The sod cutter 26 provides a clean cut in Bermuda grass or similar grasses with rhizomes, or “runners” that spread out on the surface of the ground and helps to prevent a pulling and uprooting of the grass as the blade passes. Sod cutter types that have been used include a narrow fixed blade or a rolling disc to cut the sod.
One problem that can be encountered with the current sod cutters is when an obstacle 30 such as a stone or tree root exists at or close to the surface of the ground. This type of obstacle can damage the sod cutter 26, and/or cause the shaker box 20 to be lifted up as the sod cutter passes over the obstacle, resulting in an inconsistent burial depth for the installed utility.
Turning to FIG. 2, the sod cutter 32 of the present invention is shown mounted on the lower arm 34 of a vibrator plow assembly 18. The sod cutter 32 is pinned in place at the pinned pivot location 36 instead of the rolling disc shown in FIG. 1.
In use, the device functions as follows. The sod cutter 32 extends into the surface of the ground 28 (typically about 3″-6″) and cuts the sod in front of plow blade 22. Springs 38 are attached to a device frame 40 and to an attachment point 42 above the pinned pivot 36 on the blade 32. In this configuration, the spring 38 provides a measure of preload on the blade 32 to keep it from freely pivoting and moving backward. The preload on the blade 32 is sufficient to allow the blade to cut through normal sod and vegetation as is found in an established lawn without pivoting backward. When an obstacle of sufficient size, such as a large stone or tree root is encountered, the preload on the blade 32 is overcome and the blade may pivot back allowing the sod cutter to pass over the obstacle without damage and without causing the shaker box to be lifted up relative to the ground surface. After passing over the obstacle 30 (FIG. 1), the preload of the spring(s) 38 on the blade causes the sod cutter blade 32 to once again extend into the surface of the ground and continue cutting the vegetation as the machine 14 is advanced forward.
Continuing with FIG. 2, a generalized form of the spring-loaded sod cutter for a vibratory plow is shown. The version illustrated in FIG. 2 is shown on a frame 40 which may be added or removed from the vibratory plow assembly 18. Alternatively, the spring loaded sod cutter 32 can be an integral part of the plow assembly 18. The sod cutter would be mounted on the lower arm 34 of the vibratory plow attachment 18. The sod cutter 32 is free to pivot about its attachment point 36 as illustrated in FIG. 2. A mechanical stop (not shown) may be used to limit the amount of forward rotation of the sod cutter in order to maintain pre-load on the spring 38 used to bias the sod cutter. Spring 38 may be a tension spring The spring may be made from steel. Alternatively, the spring 38 could be an elastomer like rubber or urethane, or a gas filled spring. By altering the geometry slightly, a compression spring made of steel, elastomer, or of a gas-charged design could be used to maintain preload on the blade 32. Alternatively, a torsion spring could be adapted to provide the necessary preload to hold the sod cutter in its forward position when an obstacle is not encountered.
The leading edge 44 of the sod cutter 32 will have a semi-sharpened leading edge comparable to a knife blade, and the toe 46, or leading point, of the sod cutter will extend forward of the pivot point 36 as shown in FIG. 2.
FIG. 3 illustrates an alternative embodiment of the spring-loaded sod cutter. In this embodiment, a rolling disk 26, “pizza-cutter” style sod cutter illustrated in FIG. 1 is utilized. However, instead of a fixed mounting as shown in FIG. 1, the rolling disk cutter 26 is mounted on an arm 46 which may pivot to allow the sod cutter 26 to float up out of the way of an obstacle 30 (FIG. 1). As illustrated in FIG. 3, a compression spring 48 is used to maintain a preload on the pivoting arm 46 to hold the rolling disk cutter 26 in the ground 28 when an obstacle 30 (FIG. 1) is not encountered. The spring 48 could be made of steel, and elastomer, or of a gas-charged design. It will be appreciated that by altering the geometry of the arm 46 and pivot point 50 slightly, a tension spring or a torsion spring could be used to maintain the preload on this style of cutter.
The present invention is also directed to a method of using the above described devices to cut a trench in the Earth and install a utility.
Various modifications can be made in the design and operation of the present invention without departing from the spirit thereof Thus, while the principal preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, which have been illustrated and described, it should be understood that the invention may be practiced otherwise than as specifically illustrated and described.