Pipe coupling

1. A female pipe coupling member detachably couplable to an associated male pipe coupling member, the female pipe coupling member comprising:

a coupling body having a cylindrical peripheral wall portion configured to receive the male pipe coupling member, the coupling body further having a locking element retaining hole radially extending through the cylindrical peripheral wall portion;

a locking element disposed in the locking element retaining hole, the locking element being displaceable between a locking position where the locking element partly projects inward from the cylindrical peripheral wall portion to lock the male pipe coupling member received in the cylindrical peripheral wall portion and an unlocking position where the locking element is located outward of the locking position to unlock the male pipe coupling member and where the locking element partly projects outward from the cylindrical peripheral wall portion; and

a sleeve having an inner peripheral surface and an outer peripheral surface, the sleeve being disposed to circumferentially surround the cylindrical peripheral wall portion and displaceable along an outer peripheral surface of the cylindrical peripheral wall portion, the sleeve having a locking element receiving hole extending through the sleeve from the inner peripheral surface to the outer peripheral surface, the locking element receiving hole having an inner opening peripheral edge portion opening on the inner peripheral surface, an outer opening peripheral edge portion opening on the outer peripheral surface, and a hole inner peripheral surface extending between the inner opening peripheral edge portion and the outer opening peripheral edge portion, the sleeve being displaceable between a locking element releasing position where the locking element receiving hole radially aligns with the locking element retaining hole to receive a part of the locking element projecting outward from the cylindrical peripheral wall portion, thereby allowing the locking element to assume the unlocking position, and a locking element holding position where the locking element receiving hole does not radially align with the locking element retaining hole and where the inner peripheral surface of the sleeve holds the locking element in the locking position, wherein when the sleeve is in the locking element releasing position, one selected from a group of the inner opening peripheral edge portion, outer opening peripheral edge portion and hole inner peripheral surface of the locking element receiving hole engages the locking element to block the locking element from passing through the sleeve radially outward.

2. The female pipe coupling member of claim 1 , wherein the locking element is a spherical member, and the locking element receiving hole is a circular hole having a diameter smaller than that of the locking element.

3. The female pipe coupling member of claim 2 , wherein the inner peripheral surface of the sleeve has a recess formed thereon, and the inner opening peripheral edge portion of the locking element receiving hole opens into the recess and is thus located away from an outer peripheral surface of the coupling body, the inner opening peripheral edge portion engaging the locking element when the sleeve is in the locking element releasing position.

4. The female pipe coupling member of claim 2 , wherein when the locking element is in the unlocking position, a radial top of the locking element is substantially flush with the outer peripheral surface of the sleeve.

5. The female pipe coupling member of claim 1 , wherein the inner peripheral surface of the sleeve has a recess formed thereon, and the inner opening peripheral edge portion of the locking element receiving hole opens into the recess and is thus located away from an outer peripheral surface of the coupling body, the inner opening peripheral edge portion engaging the locking element when the sleeve is in the locking element releasing position.

6. The female pipe coupling member of claim 5 , wherein when the locking element is in the unlocking position, a radial top of the locking element is substantially flush with the outer peripheral surface of the sleeve.

7. The female pipe coupling member of claim 6 further comprising:

a first guide part provided on the coupling body; and

a second guide part provided on the sleeve;

wherein when the sleeve is displaced from the locking element holding position to the locking element releasing position, the first guide part and the second guide part engage each other to guide the sleeve toward the locking element holding position.

8. The female pipe coupling member of claim 1 , wherein when the locking element is in the unlocking position, a radial top of the locking element is substantially flush with the outer peripheral surface of the sleeve.

9. The female pipe coupling member of claim 1 , further comprising:

a first guide part provided on the coupling body; and

a second guide part provided on the sleeve;

wherein when the sleeve is displaced from the locking element releasing position to the locking element holding position, the first guide part and the second guide part engage each other to guide the sleeve toward the locking element holding position.

10. A pipe coupling comprising:

the female pipe coupling member of claim 1 ; and

a male pipe coupling member detachably couplable to the female pipe coupling member.