Boring or penetrating the earth – Boring without earth removal
Patent
1987-12-11
1988-11-22
Novosad, Stephen J.
Boring or penetrating the earth
Boring without earth removal
173 91, 175296, E21B 1102, E21B 726
Patent
active
047858982
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to pneumatic percussion-type devices used in construction and more particularly to devices for making holes in soil.
The present invention may be most advantageously utilized in devices intended for making holes in compacted soils when a trenchless (subsurface) method of laying underground service lines under roads, embankments and other structures is employed.
Self-propelled pneumatic machines of a percussion type, viz. pneumatic percussion-type devices are now widely used for making holes in compacted soils. A working member of the pneumatic percussion-type device is essentially a cylindrical body provided with an internal space. The body space internally accommodates a percussion member and an air distributing sleeve. In the pneumatic percussion device of this type the air distributing sleeve is connected to the cylindrical body by means of a threaded bushing.
When the machine is operating the percussion member actuated by compressed air delivered in the working chambers through the air distributing sleeve reciprocates axially and strikes blows at a front portion of the cylindrical body during each working cycle. Under the action of blows the cylindrical body is driven in the soil, thereby forming a hole with compacted walls. The hole diameter is practically equal to the diameter of the pneumatic percussion-type device body. In the process of operation of this pneumatic percussion-type device the cylindrical body-to-threaded bushing joint needs tightening.
BACKGROUND OF THE INVENTION
Known in the prior art is a percussion-type device for making holes in soil (cf. Pneumatic Percussion-Type Devices and Machines for Driving Light Construction Elements in Soil by Kostylev A. D., Gurkov K. S., Smolyanitsky B. N., Novosibirsk, 1980, Publishing House "Nauka", p. 9), comprising a body, a percussion member and an air distributing sleeve. The air distributing sleeve is connected to the body by means of a threaded bushing with a lock washer. In the process of operation of this device, it becomes necessary to disassemble the body-to-threaded bushing joint (for maintenance, repair, etc.); as a result, the lock washer gets out of order after two-three disassembly operations.
Also known to the prior art is a percussion-type device for making holes in soil (cf. Pneumatic Percussion-Type Devices and Machines for Driving Light Construction Elements in Soil by Kostylev A. D., Gurkov K. S., Smolyanitsky B. N., Novosibirsk, 1980, Publishing House "Nauka", p. 10), comprising a body, a percussion member and an air distributing sleeve. The air distributing sleeve is connected to the body by means of a threaded bushing. The body-to-threaded bushing joint is fixed by mating of conical surfaces of the body and threaded bushing.
In the service period this device operates in a percussion-vibration mode due to which the threaded joint works loose and operates for some time in the loosened condition which leads to failure of the thread.
Besides, substantial radial forces are developed in the body portion where the cone is made which cause destruction of the body.
In addition this device features a low operating reliability as unscrewing of the threaded bushing during operation of the device causes axial displacement of the air distributing sleeve which disturbs the operating cycle of the device. Axial displacement of the air distributing sleeve (rearwards) causes an advanced exhaust of compressed air into the front chamber of the device. This air brakes the percussion member before it strikes a blow which reduces the energy of the blow and consequently decreases the capacity of the device. During the return motion of the percussion member the front chamber of the device is kept longer under the pressure (the front edge of the air distributing sleeve is displaced rearwards). Therefore, a greater quantity of the kinetic energy is imparted to the percussion member and after the retarded exhaust of compressed air from the front chamber (the rear edge of the air distributing sleeve is also
REFERENCES:
patent: 2695673 (1954-11-01), Coyle
patent: 3708023 (1973-01-01), Nazarov et al.
patent: 3756328 (1973-09-01), Sudnishnikov et al.
patent: 4171727 (1979-10-01), Tkach et al.
patent: 4708211 (1987-11-01), Shemyakin et al.
"Pneumatic Percussion-Type Devices and Machines for Driving Light Construction Elements in Soil", Kostylev et al., Nov. 1980.
Kostylev Alexandr D.
Plavskikh Vladimir D.
Skachkov Konstantin B.
Terskov Alexei D.
Bagnell David J.
Institut Gornogo Dela SO AN SSSR
Novosad Stephen J.
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