Trench excavation for purposes of installing an underground utility infrastructure is an essential and common activity of any ground development work. The common applications are for various kinds of piping, communications, energy etc. There are different types of digging equipment, and each has its advantages and disadvantages. The common denominator with all equipment manufacturers of mechanical digging equipment is the search for solutions that enable more efficient digging and reduction of the limitations connected with ground hardness.
There are two types of equipment in use today, excavators and trenchers. Excavators have a jointed arm powered hydraulically, with a digging tool at one end. The advantage of these machines lies in the fact that they are universal and flexible in the type of digging they can achieve. However, they are not efficient as they do not operate continuousiy, and require three movements, a first movement for digging, a second for removing the soil from the trench and dumping it along the sides of the trench, and a third for returning to the trench for digging. Thus, the effective digging time is approximately only 30% of working time.
Additionally, these machines do not move while digging. At the end of a digging cycle, depending on the length of the arm, they must be re-positioned. For this reason, the total effective digging time is reduced below 30% of the working time.
An additional limitation of these machines is the ground cutting speed of the digging tool. The speed is very low and thus the digging tool requires a large force to split the ground, and must be very heavy. For these reasons, these machines have difficulty digging into hard and rocky ground.
It is possible to equip excavators with a hydraulic hammer to break the rocks, after which another pass is required to clean the trench. Clearly, these extra operations greatly increase the excavation cost.
Trenchers operate in continuous fashion, thus saving valuable working time. The major disadvantages of these machines are that the digging systems are assembled from a large number of moving parts and chains including a separate soil removal system. Multiplication of systems and moving parts reduces the efficiency and technical reliability, while increasing the price. Further, since trenchers have a large contact area with the ground, and cut on a diagonal, they require large amounts of power, force and weight for digging operations.
Other types of trenchers include those having a large digging wheel with cutting teeth. These machines are limited in their cutting depth which is always less than the wheel radius. This type of trencher also has a large contact area with the ground, and since the wheel is driven from its center, large amounts of power and large moments of force are required for digging operations. An additional soil removal system is required.
Examples of patents disclosing trench excavation equipment include Japanese Patent No. 60-25-129 to Miwa, in which a drum-shaped cutter is pivotally supported on the front of a traveler with a conveyer to carry excavated soil to the rear.
Russian Patent 457777 to Kudra discloses a trench excavator device having inclined knives attached to a screw conveyor, facing the spiral direction to improve operation.
French Patent 2,566,024 to Corneille discloses a narrow trench digger with vertical rotating auger, with a parallel partition behind, equipped with soil loosening tools, such as vibrating vertical toothed bars, teeth on the auger spirals, or vertical rotary cutters.
Belgian Patent 902104 to Durieux discloses a trench cutting machine having a rotating tool comprising a pipe on which a flat is spiral wound or threaded with cutting or abrasive pieces. The trench cutting machine propels itself along the ground via a winch. Belgian Patent 1005788 to Durieux discloses a rotary trench cutter with a detachable vertical partition, to produce trenches of different sizes.
Therefore, it would be desirable to provide a trencher for excavating various size trenches, which operates at a high speed with increased capability for use on hard and rocky ground.