Patent ID: 7975518
Filing Date: 2011-07-12
Classification: E05B,Y10T

Abstract:
1. A cylinder lock that can be re-keyed using a replacement key to replace an old key, said cylinder lock comprising: a lock housing having a plug hole, and at least one first engaging element; a plug inserted into said plug hole, and having an axially extending key hole, and a plurality of radial holes connected to said key hole, one of said radial holes being located at a predetermined depth of said key hole; a plurality of tumbler pieces inserted into said radial holes except said one of said radial holes and each having a toothed part; a re-keying unit disposed within said plug hole adjacent said plug, said re-keying unit being movable relative to said plug between a first position in which said re-keying unit engages said toothed parts of said tumbler pieces to position said tumbler pieces, and a second position in which said re-keying unit disengages from said toothed parts to permit said tumbler pieces to change in position; and a limit unit inserted into said one of said radial holes and having at least one second engaging element; said first engaging element being engageable with said second engaging element when said re-keying unit in said second position so that said plug is prevented from rotating when the replacement key which is inserted into said key hole for re-keying does not reach the predetermined depth of said key hole, wherein said first engaging element is provided on an inner surface of said housing, said one of said radial holes and said first engaging element being disposed on two opposite sides of said key hole, said limit unit being normally biased to move toward said first engaging element so that said second engaging element engages said first engaging element, and wherein said limit unit is slidable radially in said one of said radial holes and said key hole, said limit unit having a middle part, two opposite legs projecting from said middle part and defining a key passage therebetween, a key contact side disposed on said middle part adjacent said key passage, and a biasing spring biasing said middle part, said limit unit including a pair of said second engaging elements provided on said legs, respectively.