Pole hole digger with percussive core drilling

• US 4,671,367 A
• Filed: 12/05/1985
• Issued: 06/09/1987
• Est. Priority Date: 12/05/1985
• Status: Expired due to Fees

• Current Assignee: Electric Power Research Institute Incorporated
• Original Assignee: Electric Power Research Institute Incorporated
• Inventors: Spector, Joseph, Tallone, Thomas, Brunsing, Thomas P., Fisk, Allan T.
• Primary Examiner(s): Leppink, James A.
• Assistant Examiner(s): MELIUS, TERRY L
• Application Number:
  US06/805,499
• Time in Patent Office: 551 Days
• Field of Search: 175/20, 175/58, 175/92, 175/95, 175/96, 175/107, 175/113, 175/246, 175/249, 175/253, 175/258, 175/293, 175/296, 175/220, 173/32, 173/50, 173/73, 173/74, 173/145, 299/15, 299/62
• US Class Current: 175/58
• CPC Class Codes: E02D 27/42 Foundations for poles, masts or chimneys sockets or holders for poles or masts per se E04H12/22
• CPC Class Codes: E21B 10/02 Core bits characterised by wear resisting parts E21B10/48
• CPC Class Codes: E21B 10/04 with core destroying means
• CPC Class Codes: E21B 25/10 Formed core retaining or severing means E21B25/06, E21B25/08 take precedence
• CPC Class Codes: E21B 6/00 Drives for drilling with combined rotary and percussive action
• CPC Class Codes: E21B 7/002 Drilling with diversely driven shafts extending into the borehole ⁠ E21B7/001 takes precedence

Abstract

A drilling attachment for a utility truck designed for digging pole holes for ordinary utility and telephone poles is disclosed herein. The attachment is intended to replace the auger portion of a conventional auger digger when it is necessary to drill through rock or other hard materials. The excavating method contemplated employs a three step process. First, a deep kerf is cut into the rock by a plurality of drill bits that are independently driven in a rotary/percussive manner while being rotated about the circumference of the kerf. The dust and rock fragments generated by this process are removed from the kerf by an air flushing/vacuum system, that also serves to cool the drill bits. Second, a hydraulic piston is inserted into the kerf and expanded, thereby applying a lateral force to the base of the resultant core causing it to break away from the surrounding rock. Finally an expandable plug is inserted into a pilot hole located at the center of the core. The plug is then engaged and lifted, thereby removing the core.

Claims

1. A method of digging a vertically downward hole through the above ground surface of hard material, especially where the above ground surface is at an incline, utilizing a drilling apparatus including a coring sleeve having a bottom end and a longitudinal axis, a first drill bit and a second drill bit, said drill bits extending through the wall of said coring sleeve so as to be positioned at the bottom of the latter, said method comprising the steps of:

(a) independently driving said first and second drill bits in a rotary/percussive manner while rotating said coring sleeve in one direction 360°

about its longitudinal axis in order to cause said drilling apparatus to move axially downward and cut a deep kerf, whereby to define a core of material to be removed, the core having a base end;

(b) providing said drilling apparatus with a centering pin assembly including a centering pin located along the longitudinal axis of said coring sleeve and pin connecting means connected with said sleeve for axial downward movement with the sleeve, said pin connecting means supporting said pin in its longitudinal position along the axis of said sleeve but movable axially relative to said pin along with said sleeve, whereby said pin connecting means moves downward with said sleeve relative to said pin;

(c) prior to cutting said kerf, drilling a vertically extending pilot hole into said hard material from its above ground surface;

(d) inserting said centering pin into said pilot hole for preventing said drilling apparatus from slipping laterally while said kerf is being cut, and causing said coring sleeve and pin connecting means to move downward to a limited extent relative to said centering pin while the latter remains stationary as said kerf is being cut;

(e) after said kerf has been cut, breaking the core of material defined by said kerf at its base end; and

(f) removing said core of material.

2. A method according to claim 1 including only two drill bits.

3. An apparatus for digging a vertically downward hole through the above ground surface of hard material, especially where the above ground surface is at an incline, comprising:

(a) a coring sleeve having a bottom end and a longitudinal axis;

(b) first and second drill bits extending through the wall of said coring sleeve so as to be positioned at the bottom of the latter;

(c) means for independently driving said drill bits in a rotary/percussive manner while rotating said coring sleeve in one direction 360°

about its longitudinal axis in order to cause said coring sleeve to move axially downward and cut a deep kerf whereby to define a core of material to be removed, the core having a base end;

(d) a centering pin assembly including a centering pin located along the longitudinal axis of said coring sleeve and pin connecting means connected with said sleeve for axial downward movement with said sleeve, said pin connecting means supporting said pin in its longitudinal position along the axis of said sleeve but movable axially relative to said pin, whereby said pin connecting means moves downward with said sleeve relative to said pin when said pin is inserted into a preprepared pilot hole and as the coring sleeve moves axially downward to cut said deep kerf;

(e) means for breaking the core of material defined by said kerf at its base end; and

(f) means for removing said core material.

4. An apparatus according to claim 3 including only two drill bits.