US 6,499,239 B1
Method for extracting and grading sand
Hendrikus Van Berk,
Bunnik (Netherlands);
and Sjerp Zeldenrust,
Winsum (Netherlands)
Assigned to De Groot Nijkerk Machinefabriek BV,
Nijkerk (Netherlands)
Filed on 28-Feb-2001, as Appl. No. De Groot Nijkerk Machinefabriek BV,
Nijkerk (Netherlands)
Int. Cl.7E02F 1/00
US 6,499,239 B1
Method for extracting and grading sand
Hendrikus Van Berk,
Bunnik (Netherlands);
and Sjerp Zeldenrust,
Winsum (Netherlands)
Assigned to De Groot Nijkerk Machinefabriek BV,
Nijkerk (Netherlands)
Appl. No. 9/554,551PCT Filed Nov. 17, 1998, PCT No. PCT/NL98/00661PCT Pub. No. WO99/25932, PCT Pub. Date May 27, 1999.
Claims priority of application No. 1007551 (NL), filed on Nov. 17, 1997.
Int. Cl.7E02F 1/00
U.S. Cl. 378212;314
3 Claims
1. A method for extracting and grading or sizing sand, gravel or a mixture thereof, from a pit formed in untouched ground,
comprising spraying a liquid into the ground, resulting in a fluidized state in the said ground, in which state sand or gravel
with a relatively high relative density and/or relatively large dimensions moves downwards, and sand or gravel material with
a relatively low relative density and/or relatively small dimensions moves upwards, in which a pit is formed in the ground
which contains fluidized sand or gravel, in such a manner that a layered state is obtained, sucking out the layer of sand
or gravel with a specific relative density and/or size, while the remaining fluidized material remains behind in order to
stabilize the wall of the pit, and feeding the material which has been sucked out to a grading device or sizing device.