Steel pipe coupling device for steel pipes

1. A steel pipe coupling device for connecting opposed ends of two steel pipes to each other, the steel pipe coupling device comprising:

a male coupling and a female coupling which are tubular in shape and configured to be welded to the respective steel pipes, the male and female couplings being further configured to be fitted to and mesh with each other in a direction of a common axis of the male and female couplings so as to be integrally rotatable about the common axis;

wherein the male and female couplings have, respectively, circumferential grooves in peripheral surfaces thereof configured to be opposed to each other when the male and female couplings are fitted together such that the circumferential grooves of the male and female couplings are radially opposed to each other when the male and female couplings are fitted together;

an engaging member configured to be fitted in both of the circumferential grooves of the male and female couplings so as to be movable radially with respect to the male and female couplings when the circumferential grooves of the male and female couplings are radially opposed to each other;

wherein the male and female couplings are configured to be fitted to and mesh with each other with the female coupling located outside the male coupling, and the female coupling has through holes extending from an outer surface of the female coupling to the circumferential groove of the female coupling; and

push sticks each having a distal end thereof fixed to the engaging member, and each of the push sticks extending through a respective one of the through holes such that a proximal end thereof is positioned at or adjacent to the outer surface of the female coupling while a medial portion thereof extends across the circumferential groove of the female coupling;

wherein the male coupling is configured to be inserted into the female coupling by pulling out the push sticks until the engaging member is retracted into the circumferential groove of the female coupling, and when the male and female couplings are fitted together, the male and female couplings are configured to be coupled together so as to be inseparable in the direction of the common axis by pushing in the push sticks until the engaging member is fitted into both of the circumferential grooves of the male and female couplings, and until heads of the push sticks are completely retracted into the respective through holes; and

wherein the head of each of the push sticks has an engaged portion configured to be hooked from a retracted position to an extended position by an extraction tool from outside the female coupling with the male and female couplings fitted together and meshing with each other.

2. The steel pipe coupling device of claim 1 , wherein the engaging member extends around an entire circumference of the male coupling, and is circumferentially divided into divided engaging pieces;

wherein each of the through holes is located at a position corresponding to a respective one of the divided engaging pieces;

wherein the distal end of each of the push sticks is fixed to a respective one of the divided engaging pieces; and

wherein the male coupling is configured to be inserted into the female coupling by pulling out the push sticks until the divided engaging pieces are retracted into the circumferential groove of the female coupling, and when the male and female couplings are fitted together, the male and female couplings are configured to be coupled together so as to be inseparable in the direction of the common axis by pushing in the push sticks until the divided engaging pieces are fitted into both of the circumferential grooves of the male and female couplings, and until the heads of the push sticks are completely retracted into the respective through holes.

3. The steel pipe coupling device of claim 2 , wherein springs are disposed on both sides of a fixed portion where the distal end of each of the push sticks is fixed to one of the divided engaging pieces at equal distances from the fixed portion, and between an outer surface of the one of the divided engaging pieces and a deeper inner surface of the circumferential groove of the female coupling, the springs being configured to press the one of the divided engaging pieces toward the male coupling.

4. The steel pipe coupling device of claim 3 , wherein the male coupling has a first abutment edge, and each of the divided engaging pieces has a second abutment edge configured to abut the first abutment edge, wherein at least one of the first and second abutment edges has a chamfer.

5. The steel pipe coupling device of claim 2 , wherein the male coupling has a first abutment edge, and each of the divided engaging pieces has a second abutment edge configured to abut the first abutment edge, wherein at least one of the first and second abutment edges has a chamfer.

6. The steel pipe coupling device of claim 1 , wherein the male coupling has a first abutment edge, and the engaging member has a second abutment edge configured to abut the first abutment edge, wherein at least one of the first and second abutment edges has a chamfer.

7. A steel pipe coupling device for connecting opposed ends of two steel pipes to each other, the steel pipe coupling device comprising:

a male coupling and a female coupling which are tubular in shape and configured to be welded to the respective steel pipes, the male and female couplings being further configured to be fitted to and mesh with each other in a direction of a common axis of the male and female couplings so as to be integrally rotatable about the common axis;

wherein the male and female couplings have, respectively, circumferential grooves in peripheral surfaces thereof configured to be opposed to each other when the male and female couplings are fitted together such that the circumferential grooves of the male and female couplings are radially opposed to each other when the male and female couplings are fitted together;

an engaging member configured to be fitted in both of the circumferential grooves of the male and female couplings so as to be movable radially with respect to the male and female couplings when the circumferential grooves of the male and female couplings are radially opposed to each other, wherein the engaging member extends around an entire circumference of the male coupling, and is circumferentially divided into divided engaging pieces;

wherein the male and female couplings are configured to be fitted to and mesh with each other with the female coupling located outside the male coupling, and the female coupling has through holes each located at a position corresponding to a respective one of the divided engaging pieces, and extending from an outer surface of the female coupling to the circumferential groove of the female coupling; and

push sticks each having a distal end thereof fixed to a respective one of the divided engaging pieces, and each of the push sticks extending through a respective one of the through holes such that a proximal end thereof is positioned at or adjacent to the outer surface of the female coupling while a medial portion thereof extends across the circumferential groove of the female coupling;

wherein the male coupling is configured to be inserted into the female coupling by pulling out the push sticks until the divided engaging pieces are retracted into the circumferential groove of the female coupling, and when the male and female couplings are fitted together, the male and female couplings are configured to be coupled together so as to be inseparable in the direction of the common axis by pushing in the push sticks until the divided engaging pieces are fitted into both of the circumferential grooves of the male and female couplings, and until heads of the push sticks are completely retracted into the respective through holes; and

wherein springs are disposed on both sides of a fixed portion where the distal end of each of the push sticks is fixed to one of the divided engaging pieces at equal distances from the fixed portion, and between an outer surface of the one of the divided engaging pieces and a deeper inner surface of the circumferential groove of the female coupling, the springs being configured to press the one of the divided engaging pieces toward the male coupling.

8. The steel pipe coupling device of claim 7 , wherein the male coupling has a first abutment edge, and each of the divided engaging pieces has a second abutment edge configured to abut the first abutment edge, wherein at least one of the first and second abutment edges has a chamfer.

9. A steel pipe coupling device for connecting opposed ends of two steel pipes to each other, the steel pipe coupling device comprising:

a male coupling and a female coupling which are tubular in shape and configured to be welded to the respective steel pipes, the male and female couplings being further configured to be fitted to and engage each other in a direction of a common axis of the male and female couplings so as to be integrally rotatable about the common axis;

wherein the male and female couplings have, respectively, circumferential grooves in peripheral surfaces thereof configured to be opposed to each other when the male and female couplings are fitted together such that the circumferential grooves of the male and female couplings are radially opposed to each other when the male and female couplings are fitted together;

an engaging member configured to be fitted in both of the circumferential grooves of the male and female couplings so as to be movable radially with respect to the male and female couplings when the circumferential grooves of the male and female couplings are radially opposed to each other, wherein the engaging member extends around an entire circumference of the male coupling, and is circumferentially divided into divided engaging pieces;

wherein the male and female couplings are configured to be fitted to and mesh with each other with the female coupling located outside the male coupling, and the female coupling has through holes each located at a position corresponding to a respective one of the divided engaging pieces, and extending from an outer surface of the female coupling to the circumferential groove of the female coupling;

push sticks each having a distal end thereof fixed to a respective one of the divided engaging pieces, and each of the push sticks extending through a respective one of the through holes such that a proximal end thereof is positioned at or adjacent to the outer surface of the female coupling while a medial portion thereof extends across the circumferential groove of the female coupling;

wherein the male coupling is configured to be inserted into the female coupling by pulling out the push sticks until the divided engaging pieces are retracted into the circumferential groove of the female coupling, and when the male and female couplings are fitted together, the male and female couplings are configured to be coupled together so as to be inseparable in the direction of the common axis by pushing in the push sticks until the divided engaging pieces are fitted into both of the circumferential grooves of the male and female couplings, and until heads of the push sticks are completely retracted into the respective through holes; and

screws configured to be screwed into the female coupling from the outer surface of the female coupling to press ends of the divided engaging pieces that define boundaries between the adjacent divided engaging pieces so as to press the divided engaging pieces against an inner surface of the circumferential groove of the male coupling.

10. The steel pipe coupling device of claim 9 , wherein springs are disposed on both sides of a fixed portion where the distal end of each of the push sticks is fixed to one of the divided engaging pieces at equal distances from the fixed portion, and between an outer surface of the one of the divided engaging pieces and a deeper inner surface of the circumferential groove of the female coupling, the springs being configured to press the one of the divided engaging pieces toward the male coupling.

11. The steel pipe coupling device of claim 10 , wherein the male coupling has a first abutment edge, and each of the divided engaging pieces has a second abutment edge configured to abut the first abutment edge, wherein at least one of the first and second abutment edges has a chamfer.

12. The steel pipe coupling device of claim 9 , wherein the male coupling has a first abutment edge, and each of the divided engaging pieces has a second abutment edge configured to abut the first abutment edge, wherein at least one of the first and second abutment edges has a chamfer.