EARTH BORING MACHINE WITH TANDEM THRUST CYLINDERS
United States Patent 3780816
Rotary drilling means are mounted for travel along the support frames of a raise drill. At least one tandem thrust cylinder system provides the force for moving the rotary drilling means along the support frame. The tandem thrust cylinder system includes a first thrust cylinder and two second thrust cylinders mounted so that the thrust force and movement of said first thrust cylinder is directly opposed to the thrust forces and movements of said two second thrust cylinders. The combined cross sectional area of said two second thrust cylinders is substantially equal to the cross sectional area of said first thrust cylinder thereby maintaining constant force throughout the stroke of the tandem thrust cylinder system. The cylinders are manifolded so that fluid enters one port and is routed to all of the cylinders to equalize the rate of travel and the forces exerted.
US Patent References:
RAISE DRILLING APPARATUS
Millsapps - August 1969 - 3460638
Hydraulic press apparatus
Rowles et al. - May 1961 - 2984981
DRILLING MACHINE
Poage - July 1969 - 3454114
Drilling mechanism
Osgood - December 1929 - 1740701
RAISE DRILLING APPARATUS
Millsapps - August 1969 - 3460638
Hydraulic press apparatus
Rowles et al. - May 1961 - 2984981
DRILLING MACHINE
Poage - July 1969 - 3454114
Drilling mechanism
Osgood - December 1929 - 1740701
Inventors:
Arrington, Thomas L. (Beaumont, TX)
Dyer, Norman D. (Beaumont, TX)
Dyer, Norman D. (Beaumont, TX)
Application Number:
05/234528
Publication Date:
12/25/1973
Filing Date:
03/14/1972
View Patent Images:
Export Citation:
Assignee:
Dresser Industries, Inc. (Dallas, TX)
Primary Class:
Other Classes:
173/39
International Classes:
E21B7/02; E21B19/086; E21B19/00; E21C5/11
Field of Search:
173/22,28,152,39 175/85 91/411B 92/146
Primary Examiner:
Novosad, Stephen J.
Assistant Examiner:
Pate III, William F.
Claims:
The embodiments of an invention in which an exclusive property or privilege is claimed are defined as follows
1. An earth boring machine, comprising:
2. The earth boring machine of claim 1 wherein said first fluid actuated thrust means includes at least one first hydraulic cylinder having a first piston with a first piston head and said second fluid actuated thrust means includes at least one second hydraulic cylinder having a second piston with a second piston head and wherein said first hydraulic cylinder and said second hydraulic cylinder are connected together so that the thrust forces and movements of said first cylinder are directly opposed to the thrust forces and movements of said second cylinder.
3. The earth boring machine of claim 2 wherein said means for delivering actuating fluid includes selectively usable means for simultaneously delivering actuating fluid between one end of said first cylinder and said first piston head and between one end of said second cylinder and said second piston head to move said drilling means in one direction along said support frame with a constant force, and selectively usable means for simultaneously delivering actuating fluid between the other end of said first cylinder and said first piston head and between the other end of said second cylinder and said second piston head to move said drilling means in the other direction along said support frame with a constant force.
4. In an earth boring machine including a support frame adapted to be positioned at a drill site and traveling rotary drilling means mounted for travel along said support frame for forming an earth borehole by supplying drilling forces to a rotary drill string, the improvement comprising:
5. The earth boring machine of claim 4 wherein said first cylinder means includes first piston means with a first piston head means and wherein said second cylinder means includes second piston means with a second piston head means.
6. The earth boring machine of claim 5 including selectively usable means for simultaneously delivering a motive fluid to one side of said first piston head means to move said first piston means and to one side of said second piston head means to move said second piston means thereby causing said drilling means to travel along said support frame in one direction with a constant force, and selectively usable means for simultaneously delivering a motive fluid to the other side of said first piston head means to move said first piston means and to the other side of said second piston head means to move said second piston means thereby causing said drilling means to travel along said support frame in the other direction with a constant force.
7. The earth boring machine of claim 6 wherein said first cylinder means and said second cylinder means are connected together so that the thrust forces and movements of said first cylinder means are directly opposed to the thrust forces and movements of said second cylinder means.
1. An earth boring machine, comprising:
2. The earth boring machine of claim 1 wherein said first fluid actuated thrust means includes at least one first hydraulic cylinder having a first piston with a first piston head and said second fluid actuated thrust means includes at least one second hydraulic cylinder having a second piston with a second piston head and wherein said first hydraulic cylinder and said second hydraulic cylinder are connected together so that the thrust forces and movements of said first cylinder are directly opposed to the thrust forces and movements of said second cylinder.
3. The earth boring machine of claim 2 wherein said means for delivering actuating fluid includes selectively usable means for simultaneously delivering actuating fluid between one end of said first cylinder and said first piston head and between one end of said second cylinder and said second piston head to move said drilling means in one direction along said support frame with a constant force, and selectively usable means for simultaneously delivering actuating fluid between the other end of said first cylinder and said first piston head and between the other end of said second cylinder and said second piston head to move said drilling means in the other direction along said support frame with a constant force.
4. In an earth boring machine including a support frame adapted to be positioned at a drill site and traveling rotary drilling means mounted for travel along said support frame for forming an earth borehole by supplying drilling forces to a rotary drill string, the improvement comprising:
5. The earth boring machine of claim 4 wherein said first cylinder means includes first piston means with a first piston head means and wherein said second cylinder means includes second piston means with a second piston head means.
6. The earth boring machine of claim 5 including selectively usable means for simultaneously delivering a motive fluid to one side of said first piston head means to move said first piston means and to one side of said second piston head means to move said second piston means thereby causing said drilling means to travel along said support frame in one direction with a constant force, and selectively usable means for simultaneously delivering a motive fluid to the other side of said first piston head means to move said first piston means and to the other side of said second piston head means to move said second piston means thereby causing said drilling means to travel along said support frame in the other direction with a constant force.
7. The earth boring machine of claim 6 wherein said first cylinder means and said second cylinder means are connected together so that the thrust forces and movements of said first cylinder means are directly opposed to the thrust forces and movements of said second cylinder means.
Description:
BACKGROUND OF THE INVENTION
The present invention relates to the art of earth boring and, more particularly, to an earth boring machine with an improved thrust cylinder system.
An earth boring machine should be as compact as possible and at the same time include the longest possible drilling stroke. For example, some earth boring machines must be moved through relatively small tunnels and elevators before reaching the drill site and be able to produce a maximum output during the drilling operation. It is therefore desirable for the overall collapsed height of an earth boring machine to be a minimum and for the drill head to be able to travel a maximum distance during the drilling operation.
Hydraulic thrust cylinders are generally used on earth boring machines to move the drill head relative to the support structure. The thrust cylinders should maintain a constant force throughout their stroke for optimum drilling efficiency. If the thrust force is not maintained at a constant rate during the drilling cycle, the earth boring system will not be operating at peak efficiency.
A need clearly exists for a compact and reliable earth boring machine with a maximum capability of drilling performance. For example, such a machine could be applied to mine rescue in order to supply food, water, air and communications. The earth boring machine would have to be capable of being transported to the site without being disassembled, it would have to be able to be moved into a drilling position without delay and it would have to be able to drill as rapidly as possible. This would mean that a maximum possible drilling stroke would have to be provided in a machine with a minimum collapsed height. Such a machine could also be advantageously applied to other operations such as gas probe and relief wherein it would provide exploration of potentially hazardous ground. It could be used for ventilation wherein it would drill both a small diameter and large diameter hole between mine levels and to the earth's surface. Such a machine is also suitable for stress relieving to prevent rock burst and to control rock strain and the machine could be easily applied to raise drilling, core drilling and other types of conventional drilling.
BRIEF DESCRIPTION OF THE PRIOR ART
A general summary of raise drilling is described in U.S. Pat. No. 3,220,494 to R. E. Cannon et al. patented Nov. 30, 1965.
In U.S. Pat. No. 3,460,638 to S. C. Millsapps, Jr., an extremely bulky raise drilling apparatus is shown. This raise drilling apparatus includes a multiplicity of cylinders that are used to move a drilling carriage within a support cage.
U.S. Pat. No. 3,454,114 to L. B. Poage shows a drilling machine with a traveling frame and equipment carried thereby that is moved up and down by thrust ram means comprising a downwardly opening, upwardly projecting piston chamber having a lower mounting portion rigidly secured to the traveling frame and a downwardly directed piston having a lower mounted portion secured to the base frame.
SUMMARY OF THE INVENTION
The present invention provides an earth boring machine including a support frame adapted to be positioned at the drill site with traveling rotary drilling means mounted for travel along said support frame. A tandem thrust cylinder system is mounted between the traveling rotary drilling means and the support frame to provide the force for moving the traveling rotary drilling means along said support frame. The tandem thrust cylinder system includes first and second thrust cylinder means with the cross sectional areas of said first and second thrust cylinder means being substantially equal thereby providing a constant force during the drilling cycle.
It is therefore an object of the present invention to provide an earth boring machine with tandem thrust cylinders.
It is a further object of the present invention to provide an earth boring machine with a thrust cylinder system that maintains constant force throughout the drilling cycle.
It is a still further object of the present invention to provide an earth boring machine with tandem thrust cylinders including a multiplicity of thrust cylinders.
The above and other objects and advantages of the present invention will become apparent from a consideration of the following detailed description of the invention when taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an earth boring machine including a tandem thrust cylinder system constructed in accordance with the present invention.
FIG. 2 illustrates another embodiment of the present invention.
FIG. 3 illustrates a third embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings and in particular to FIG. 1, an earth boring machine generally indicated by the reference numeral 10 is shown anchored to the ground by base elements 11 and 12. A support column 13 is connected to the base elements 11 and 12 by a pair of hinges 14 and 15 that allow the support column 13 to pivot. A brace 16 extends between the support column 13 and a frame connecting the base elements 11 and 12.
It can be appreciated that the length of the brace 16 determines the angle the support column 13 makes with the horizontal and consequently the drilling angle. It is therefore possible to adjust the suppport column angle and the drilling angle for various drilling operations by replacing brace 16 with a brace of a different length or by adjusting the length of brace 16.
A rotary drilling means, generally designated by the reference number 17, is mounted for travel along the support column 13 for providing rotary drilling forces to a rotary drill column (not shown). The rotary drilling means includes a power unit 18 adapted to rotate a drill rod chuck 19. The rotary drill column is connected to the drill rod chuck 19 during the drilling operation. A base plate 20 is connected to the support column 13 and plate 20 is adapted to pivot about hinges 14 and 15 in conjunction with support column 13. A pair of tandem thrust cylinder systems 21 and 22 are mounted between the base plate 20 and rotary drilling means 17.
The tandem thrust cylinder system 21 includes a first thrust cylinder 23 with a downwardly directed piston rod 24. The outer end of piston rod 24 is affixed to base plate 20. A pair of second thrust cylinders 25 and 26 are connected to the first thrust cylinder 23 by a lower connecting frame 27 and an upper connecting frame (not shown). The piston rods (not shown) of the second thrust cylinders 25 and 26 are affixed to the rotary drilling means 17. The thrust cylinders 23, 25 and 26 are double acting thrust cylinders that provide force in both directions. The combined cross sectional area of thrust cylinders 25 and 26 is substantially equal to the cross sectional area of thrust cylinder 23. The force supplied by the tandem thrust cylinder system 21 will therefore be constant throughout its stroke and the collapsed height of the earth boring machine 10 is less than the collapsed height of the comparable prior art earth boring meachines.
The tandem thrust cylinder system 22 includes a first thrust cylinder 28 with a downwardly directed piston rod 29. The outer end of piston rod 29 is affixed to base plate 20. A pair of second thrust cylinders 30 and 31 are connected to the first thrust cylinder 28 by a lower connecting frame 32 and an upper connecting frame 33. Thrust cylinder 30 includes an upwardly directed piston rod 34 that is affixed to the rotary drilling means 17 and thrust cylinder 31 includes an upwardly directed piston rod 35 that is affixed to the rotary drilling means 17. The thrust cylinders 28, 30 and 31 are double acting thrust cylinders that provide force in both directions. The combined cross sectional area of thrust cylinders 30 and 31 is substantially equal to the cross sectional area of thrust cylinder 28. The force supplied by the tandem thrust cylinder system 22 will therefore be constant throughout its stroke and the collapsed height of the earth boring machine 10 is less than the collapsed height of comparable prior art earth boring machines.
The structural details of an earth boring machine constructed in accordance with the present invention having been described, the operation of the machine will now be considered. The machine 10 is transported to the drill site in a collapsed position. The tandem thrust cylinder systems 21 and 22 are moved to a retracted position lowering the rotary drilling means 17 to its lowest position. The earth boring machine may then be moved through relatively small tunnels and passages. The earth boring machine 10 can be made even more compact by reducing the length of brace 16 until the support column is substantially parallel to the base elements 11 and 12. Once the earth boring machine 10 arrives at the drill site, the base elements 11 and 12 are firmly affixed to the floor. The position of the support column and the length of brace 16 are adjusted for the proper drilling angle.
An actuating fluid is delivered to the tandem thrust cylinder systems 21 and 22 and the piston rods 24, 29, 34 and 35 are moved outward. The rotary drilling means is moved to its uppermost position. Since the first thrust cylinder 23 overlaps the pair of second thrust cylinders 25 and 26 and the first thrust cylinder 28 overlaps the pair of second thrust cylinders 30 and 31, the stroke of the tandem thrust cylinder systems 21 and 22 is a maximum for their collapsed height. A section of drill rod is connected to the drill rod chuck 19 and the earth boring machine 10 is ready for operation. A rotary rock bit is connected to the drill rod and the bit is rotated and moved through the formations. An actuating fluid is applied to the tandem thrust cylinder systems 21 and 22 moving the piston rods 24, 29, 34 and 35 toward the retracted position and applying a thrust force to the drill string. Additional drill rods are added to the drill string during the drilling operation thereby requiring repeated up and down travel of the rotary drilling means 17.
In a raise drilling operation, the above-mentioned procedure is continued until a small diameter pilot hole has been completed to another level of the mine. The small diameter pilot bit is removed and a large diameter raise bit is connected to the drill string. The raise bit is then moved through the formations along the pilot hole to form the large diameter raise hole. Actuating fluid is delivered to the tandem thrust cylinder systems 21 and 22 moving the piston rods 24, 29, 34 and 35 toward the extended position thereby applying a thrust force to the raise bit.
Referring now to FIG. 2, another embodiment of a tandem thrust cylinder system constructed in accordance with the present invention is shown. The thrust cylinder system, generally designated by the reference number 36, is connected between the support frame 37 and the traveling drilling means 38 of an earth boring machine.
A pair of first hydraulic cylinders 39 and 40 are affixed to the support frame 37. The hydraulic cylinders 39 and 40 are double acting in that they supply force for both up and down movement. Hydraulic cylinder 39 includes a piston 41 with a piston head 42 and a piston rod 43. The outer end of piston rod 43 is connected to a frame 44. Hydraulic cylinder 40 includes a piston 45 with a piston head 46 and a piston rod 47. The outer end of piston rod 47 is connected to frame 44.
A second double acting hydraulic cylinder 48 is affixed to the traveling drilling means 38. Hydraulic cylinder 48 includes a piston 49 with a piston head 50 and a piston rod 51. The outer end of piston rod 51 is connected to frame 44.
The hydraulic cylinders 39, 40 and 48 are connected together by frame 44 in such a manner that the thrust forces and movements of hydraulic cylinders 39 and 40 are directly opposed to the thrust force and movement of hydraulic cylinder 48. The combined cross sectional area of hydraulic cylinders 39 and 40 are substantially equal to the cross sectional area of hydraulic cylinders. This insures that the force applied to move the traveling drilling means 38 in either the up or down direction will be constant throughout the stroke of the thrust cylinder system.
Referring now to FIG. 3, a third embodiment of the tandem thrust cylinder system of the present invention is shown. The tandem thrust cylinder system, generally designated by the reference number 52, is mounted between the support frame 53 and the traveling drilling means 54 of an earth boring machine.
A pair of first thrust cylinders 55 and 56 are connected to the traveling drilling means 54 to provide force to move the traveling drilling means relative to the support frame 53. Thrust cylinder 55 includes a piston 57 with a piston head 58 and a piston rod 59. The lower end of the piston rod 59 is connected to a cross frame 60. Thrust cylinder 56 includes a piston 61 with a piston head 62 and a piston rod 63. The lower end of the piston rod 63 is connected to cross frame 60.
A second thrust cylinder 64 is connected to the support frame 53 and the cross frame 60. The second thrust cylinder 64 includes a piston 65 with a piston head 66 and a piston rod 67. The lower end of the piston rod 67 is affixed to support frame 53.
The drilling means 54 is moved relative to the support frame 53 by applying an actuating fluid to the thrust cylinders 55, 56 and 64. The actuating fluid is delivered between the outer ends of hydraulic cylinders 55, 56 and 64 and the upper surfaces of piston heads 58, 62 and 66 when the drilling means 54 is being moved upward. When the drilling means 54 is being moved downward, the actuating fluid is delivered between the lower portions of hydraulic cylinders 55, 56 and 64 and the lower surfaces of piston heads 58, 62 and 66. Since the combined cross sectional area of hydraulic cylinders 55 and 56 is substantially equal to the cross sectional are of hydraulic cylinder 64, the force applied by the thrust cylinder system 52 in either the up or down direction will be constant.
The present invention relates to the art of earth boring and, more particularly, to an earth boring machine with an improved thrust cylinder system.
An earth boring machine should be as compact as possible and at the same time include the longest possible drilling stroke. For example, some earth boring machines must be moved through relatively small tunnels and elevators before reaching the drill site and be able to produce a maximum output during the drilling operation. It is therefore desirable for the overall collapsed height of an earth boring machine to be a minimum and for the drill head to be able to travel a maximum distance during the drilling operation.
Hydraulic thrust cylinders are generally used on earth boring machines to move the drill head relative to the support structure. The thrust cylinders should maintain a constant force throughout their stroke for optimum drilling efficiency. If the thrust force is not maintained at a constant rate during the drilling cycle, the earth boring system will not be operating at peak efficiency.
A need clearly exists for a compact and reliable earth boring machine with a maximum capability of drilling performance. For example, such a machine could be applied to mine rescue in order to supply food, water, air and communications. The earth boring machine would have to be capable of being transported to the site without being disassembled, it would have to be able to be moved into a drilling position without delay and it would have to be able to drill as rapidly as possible. This would mean that a maximum possible drilling stroke would have to be provided in a machine with a minimum collapsed height. Such a machine could also be advantageously applied to other operations such as gas probe and relief wherein it would provide exploration of potentially hazardous ground. It could be used for ventilation wherein it would drill both a small diameter and large diameter hole between mine levels and to the earth's surface. Such a machine is also suitable for stress relieving to prevent rock burst and to control rock strain and the machine could be easily applied to raise drilling, core drilling and other types of conventional drilling.
BRIEF DESCRIPTION OF THE PRIOR ART
A general summary of raise drilling is described in U.S. Pat. No. 3,220,494 to R. E. Cannon et al. patented Nov. 30, 1965.
In U.S. Pat. No. 3,460,638 to S. C. Millsapps, Jr., an extremely bulky raise drilling apparatus is shown. This raise drilling apparatus includes a multiplicity of cylinders that are used to move a drilling carriage within a support cage.
U.S. Pat. No. 3,454,114 to L. B. Poage shows a drilling machine with a traveling frame and equipment carried thereby that is moved up and down by thrust ram means comprising a downwardly opening, upwardly projecting piston chamber having a lower mounting portion rigidly secured to the traveling frame and a downwardly directed piston having a lower mounted portion secured to the base frame.
SUMMARY OF THE INVENTION
The present invention provides an earth boring machine including a support frame adapted to be positioned at the drill site with traveling rotary drilling means mounted for travel along said support frame. A tandem thrust cylinder system is mounted between the traveling rotary drilling means and the support frame to provide the force for moving the traveling rotary drilling means along said support frame. The tandem thrust cylinder system includes first and second thrust cylinder means with the cross sectional areas of said first and second thrust cylinder means being substantially equal thereby providing a constant force during the drilling cycle.
It is therefore an object of the present invention to provide an earth boring machine with tandem thrust cylinders.
It is a further object of the present invention to provide an earth boring machine with a thrust cylinder system that maintains constant force throughout the drilling cycle.
It is a still further object of the present invention to provide an earth boring machine with tandem thrust cylinders including a multiplicity of thrust cylinders.
The above and other objects and advantages of the present invention will become apparent from a consideration of the following detailed description of the invention when taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an earth boring machine including a tandem thrust cylinder system constructed in accordance with the present invention.
FIG. 2 illustrates another embodiment of the present invention.
FIG. 3 illustrates a third embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings and in particular to FIG. 1, an earth boring machine generally indicated by the reference numeral 10 is shown anchored to the ground by base elements 11 and 12. A support column 13 is connected to the base elements 11 and 12 by a pair of hinges 14 and 15 that allow the support column 13 to pivot. A brace 16 extends between the support column 13 and a frame connecting the base elements 11 and 12.
It can be appreciated that the length of the brace 16 determines the angle the support column 13 makes with the horizontal and consequently the drilling angle. It is therefore possible to adjust the suppport column angle and the drilling angle for various drilling operations by replacing brace 16 with a brace of a different length or by adjusting the length of brace 16.
A rotary drilling means, generally designated by the reference number 17, is mounted for travel along the support column 13 for providing rotary drilling forces to a rotary drill column (not shown). The rotary drilling means includes a power unit 18 adapted to rotate a drill rod chuck 19. The rotary drill column is connected to the drill rod chuck 19 during the drilling operation. A base plate 20 is connected to the support column 13 and plate 20 is adapted to pivot about hinges 14 and 15 in conjunction with support column 13. A pair of tandem thrust cylinder systems 21 and 22 are mounted between the base plate 20 and rotary drilling means 17.
The tandem thrust cylinder system 21 includes a first thrust cylinder 23 with a downwardly directed piston rod 24. The outer end of piston rod 24 is affixed to base plate 20. A pair of second thrust cylinders 25 and 26 are connected to the first thrust cylinder 23 by a lower connecting frame 27 and an upper connecting frame (not shown). The piston rods (not shown) of the second thrust cylinders 25 and 26 are affixed to the rotary drilling means 17. The thrust cylinders 23, 25 and 26 are double acting thrust cylinders that provide force in both directions. The combined cross sectional area of thrust cylinders 25 and 26 is substantially equal to the cross sectional area of thrust cylinder 23. The force supplied by the tandem thrust cylinder system 21 will therefore be constant throughout its stroke and the collapsed height of the earth boring machine 10 is less than the collapsed height of the comparable prior art earth boring meachines.
The tandem thrust cylinder system 22 includes a first thrust cylinder 28 with a downwardly directed piston rod 29. The outer end of piston rod 29 is affixed to base plate 20. A pair of second thrust cylinders 30 and 31 are connected to the first thrust cylinder 28 by a lower connecting frame 32 and an upper connecting frame 33. Thrust cylinder 30 includes an upwardly directed piston rod 34 that is affixed to the rotary drilling means 17 and thrust cylinder 31 includes an upwardly directed piston rod 35 that is affixed to the rotary drilling means 17. The thrust cylinders 28, 30 and 31 are double acting thrust cylinders that provide force in both directions. The combined cross sectional area of thrust cylinders 30 and 31 is substantially equal to the cross sectional area of thrust cylinder 28. The force supplied by the tandem thrust cylinder system 22 will therefore be constant throughout its stroke and the collapsed height of the earth boring machine 10 is less than the collapsed height of comparable prior art earth boring machines.
The structural details of an earth boring machine constructed in accordance with the present invention having been described, the operation of the machine will now be considered. The machine 10 is transported to the drill site in a collapsed position. The tandem thrust cylinder systems 21 and 22 are moved to a retracted position lowering the rotary drilling means 17 to its lowest position. The earth boring machine may then be moved through relatively small tunnels and passages. The earth boring machine 10 can be made even more compact by reducing the length of brace 16 until the support column is substantially parallel to the base elements 11 and 12. Once the earth boring machine 10 arrives at the drill site, the base elements 11 and 12 are firmly affixed to the floor. The position of the support column and the length of brace 16 are adjusted for the proper drilling angle.
An actuating fluid is delivered to the tandem thrust cylinder systems 21 and 22 and the piston rods 24, 29, 34 and 35 are moved outward. The rotary drilling means is moved to its uppermost position. Since the first thrust cylinder 23 overlaps the pair of second thrust cylinders 25 and 26 and the first thrust cylinder 28 overlaps the pair of second thrust cylinders 30 and 31, the stroke of the tandem thrust cylinder systems 21 and 22 is a maximum for their collapsed height. A section of drill rod is connected to the drill rod chuck 19 and the earth boring machine 10 is ready for operation. A rotary rock bit is connected to the drill rod and the bit is rotated and moved through the formations. An actuating fluid is applied to the tandem thrust cylinder systems 21 and 22 moving the piston rods 24, 29, 34 and 35 toward the retracted position and applying a thrust force to the drill string. Additional drill rods are added to the drill string during the drilling operation thereby requiring repeated up and down travel of the rotary drilling means 17.
In a raise drilling operation, the above-mentioned procedure is continued until a small diameter pilot hole has been completed to another level of the mine. The small diameter pilot bit is removed and a large diameter raise bit is connected to the drill string. The raise bit is then moved through the formations along the pilot hole to form the large diameter raise hole. Actuating fluid is delivered to the tandem thrust cylinder systems 21 and 22 moving the piston rods 24, 29, 34 and 35 toward the extended position thereby applying a thrust force to the raise bit.
Referring now to FIG. 2, another embodiment of a tandem thrust cylinder system constructed in accordance with the present invention is shown. The thrust cylinder system, generally designated by the reference number 36, is connected between the support frame 37 and the traveling drilling means 38 of an earth boring machine.
A pair of first hydraulic cylinders 39 and 40 are affixed to the support frame 37. The hydraulic cylinders 39 and 40 are double acting in that they supply force for both up and down movement. Hydraulic cylinder 39 includes a piston 41 with a piston head 42 and a piston rod 43. The outer end of piston rod 43 is connected to a frame 44. Hydraulic cylinder 40 includes a piston 45 with a piston head 46 and a piston rod 47. The outer end of piston rod 47 is connected to frame 44.
A second double acting hydraulic cylinder 48 is affixed to the traveling drilling means 38. Hydraulic cylinder 48 includes a piston 49 with a piston head 50 and a piston rod 51. The outer end of piston rod 51 is connected to frame 44.
The hydraulic cylinders 39, 40 and 48 are connected together by frame 44 in such a manner that the thrust forces and movements of hydraulic cylinders 39 and 40 are directly opposed to the thrust force and movement of hydraulic cylinder 48. The combined cross sectional area of hydraulic cylinders 39 and 40 are substantially equal to the cross sectional area of hydraulic cylinders. This insures that the force applied to move the traveling drilling means 38 in either the up or down direction will be constant throughout the stroke of the thrust cylinder system.
Referring now to FIG. 3, a third embodiment of the tandem thrust cylinder system of the present invention is shown. The tandem thrust cylinder system, generally designated by the reference number 52, is mounted between the support frame 53 and the traveling drilling means 54 of an earth boring machine.
A pair of first thrust cylinders 55 and 56 are connected to the traveling drilling means 54 to provide force to move the traveling drilling means relative to the support frame 53. Thrust cylinder 55 includes a piston 57 with a piston head 58 and a piston rod 59. The lower end of the piston rod 59 is connected to a cross frame 60. Thrust cylinder 56 includes a piston 61 with a piston head 62 and a piston rod 63. The lower end of the piston rod 63 is connected to cross frame 60.
A second thrust cylinder 64 is connected to the support frame 53 and the cross frame 60. The second thrust cylinder 64 includes a piston 65 with a piston head 66 and a piston rod 67. The lower end of the piston rod 67 is affixed to support frame 53.
The drilling means 54 is moved relative to the support frame 53 by applying an actuating fluid to the thrust cylinders 55, 56 and 64. The actuating fluid is delivered between the outer ends of hydraulic cylinders 55, 56 and 64 and the upper surfaces of piston heads 58, 62 and 66 when the drilling means 54 is being moved upward. When the drilling means 54 is being moved downward, the actuating fluid is delivered between the lower portions of hydraulic cylinders 55, 56 and 64 and the lower surfaces of piston heads 58, 62 and 66. Since the combined cross sectional area of hydraulic cylinders 55 and 56 is substantially equal to the cross sectional are of hydraulic cylinder 64, the force applied by the thrust cylinder system 52 in either the up or down direction will be constant.