Exchangeable cylinder lock assembly

1. An exchangeable cylinder lock that can be mounted removably in a lock housing, comprising:

an outer shell having a plug shell defining a cylindrical hole, and a pin chest connected to said plug shell, said pin chest including a first pin hole and a second pin hole, both of which extend along a radial direction of said cylindrical hole;

a plug disposed inside said cylindrical hole, and having a third pin hole that can be aligned with said second pin hole;

first and second tumbler pins respectively disposed in said second and third pin holes;

a cover plate disposed on said pin chest to cover said first and second pin holes, said cover plate having an aperture aligned with said first pin hole;

a locking pin disposed in said first pin hole and biased to protrude out of said aperture for engaging the lock housing, said locking pin being depressable to retract for disengaging from the lock housing; and

a locking ring disposed around said plug proximate to said first pin hole and rotatable together with said plug, said locking ring having an inner periphery engaging said plug, and an outer periphery capable of abutting against said locking pin, said outer periphery having at least one indentation;

wherein, when said plug is rotated using a right key, said locking ring can be moved to a non-blocking position, in which said indentation is aligned with said locking pin to permit depression of said locking pin, or to a blocking position, in which said indentation is moved away from said locking pin to prevent depression of said locking pin.

2. The exchangeable cylinder lock of claim 1 , further comprising a biasing spring disposed around said locking pin within said first pin hole.

3. The exchangeable cylinder lock of claim 2 , wherein said first pin hole has a first hole section, a second hole section larger in cross section than said first hole section, and a hole shoulder face between said stepped and having a pin shoulder face, said biasing spring being disposed in said second hole section between said hole shoulder face and said pin shoulder face.

4. The exchangeable cylinder lock of claim 3 , wherein said first hole section is proximate to said locking ring, said second hole section being proximate to said cover plate, said aperture being smaller in cross section than said second hole section.

5. The exchangeable cylinder lock of claim 4 , wherein said locking pin has first, second, and third pin sections, said second pin section being intermediate between and larger in cross section than said first and third pin sections, said first pin section partially extending into said first hole section, said pin shoulder face being formed between said first and second pin sections, said second and third pin sections being disposed in said second hole section, said biasing spring being disposed around said first pin section.

6. The exchangeable cylinder lock of claim 1 , wherein said indentation is disposed at a position which is spaced apart from said third pin hole in a circumferential direction by an angle of about 90°.

7. The exchangeable cylinder lock of claim 1 , wherein said plug has at least one engaging groove that is indented from an outer circumferential surface of said plug, said inner periphery of said locking ring having an engaging part engaged in said engaging groove.

8. The exchangeable cylinder lock of claim 1 , wherein said plug has two diametrically opposite engaging grooves that are indented from an outer circumferential surface of said plug, said inner periphery of said locking ring having two diametrically opposite engaging parts respectively engaged in said engaging grooves.

9. The exchangeable cylinder lock of claim 8 , wherein said locking ring is formed as a substantially c-shape, and has two opposite end sections, and an intermediate section between said end sections, said inner periphery of said locking ring having said engaging parts formed at said end sections, respectively, said outer periphery of said locking ring being convex at said intermediate section and having said indentations formed at said end sections, respectively.

10. The exchangeable cylinder lock of claim 9 , wherein each of said engaging parts has a substantially straight edge, each of said engaging grooves having a substantially flat groove bottom to abut against said straight edge.

11. An exchangeable lock assembly comprising:

a plug shell having a cylindrical hole;

a pin chest connected to said plug shell and including a first pin hole and a second pin hole, both of which extend along a radial direction of said cylindrical hole;

a plug disposed in said cylindrical hole, and having a third pin hole that can be aligned with said second pin hole;

first and second tumbler pins respectively disposed in said second and third pin holes;

a cover plate disposed on said pin chest to cover said first and second pin holes, said cover plate having an aperture aligned with said first pin hole;

a lock housing receiving said plug shell and said pin chest, and having a slot aligned with said aperture;

a locking pin disposed in said first pin hole and biased to protrude out of said aperture for engagement with said slot of said lock housing, said locking pin being depressable to retract for disengaging from said lock housing; and

a locking ring disposed around said plug proximate to said first pin hole and rotatable together with said plug, said locking ring having an inner periphery engaging said plug, and an outer periphery capable of abutting against said locking pin, said outer periphery having at least one indentation;

wherein, when said plug is rotated using a right key, said locking ring can be moved to a non-blocking position, in which said indentation is aligned with said locking pin to permit depression of said locking pin, or to a blocking position, in which said indentation is moved away from said locking pin to prevent depression of said locking pin.

12. An exchangeable cylinder lock that can be mounted removably in a lock housing, comprising:

an outer shell adapted to be disposed inside said lock housing, and including a cylindrical hole, and a first pin hole spaced apart from said cylindrical hole;

a plug disposed rotatably in said cylindrical hole;

a locking pin disposed in said first pin hole and extending substantially in a radial direction of said plug, said locking pin having one end biased to protrude out of said first pin hole for engagement with the lock housing, said locking pin being depressable to retract and disengage from said lock housing; and

a locking ring disposed around said plug and rotatable together with said plug, said locking ring having an inner periphery engaging said plug, and an outer periphery capable of abutting against another end of said locking pin, said outer periphery having at least one indentation,

wherein, when said plug is rotated using a right key, said locking ring can be moved to a non-blocking position, in which said indentation is aligned with said locking pin to permit depression of said locking pin, or to a blocking position, in which said indentation is moved away from said locking pin to prevent depression of said locking pin, and

wherein said plug has an engaging groove that is indented from an outer circumferential surface of said plug and that has a flat groove bottom, and said inner periphery of said locking ring is a substantially straight engaging part extending into said engaging groove and abutting against said flat groove bottom.

13. The exchangeable cylinder lock of claim 12 , wherein said locking ring is formed as a substantially C-shape, and has two opposite end sections, and an intermediate section between said end sections, said inner periphery of said locking ring having two said engaging parts formed at said end sections, respectively.

14. The exchangeable cylinder lock of claim 13 , wherein, said outer periphery of said locking ring is convex at said intermediate section and has two said indentations formed at said end sections, respectively.