Lock

Claim 2

A lock comprising a housing, key plug means movably mounted in said housing, first tumbler means carried by said housing and key plug means for controlling movement of said key plug means, a first key for insertion in said key plug means for moving same, trapping means cooperating with said key plug means for slectively arresting movement of said key plug means at a partially moved position, control means cooperating with said trapping means for setting said trapping means to a first nonarresting position and to a second arresting position, said key plug means preventing withdrawal of said first key when said key plug means is arrested in said partially moved position, and a second key for operating said control means.

Claim 3

A lock as claimed in claim 1 and including second tumbler means cooperating between said control means and said key plug means for actuation by said second key.

Claim 4

A lock as claimed in claim 2 wherein said key plug means includes override means acted on by said second tumbler means for preventing operation of said trapping means, and further including a third key for operating said first and second tumbler means regardless of the position of said trapping means.

Claim 5

A lock as claimed in claim 2 and further including selection means carried by said housing for preventing operation of said trapping means regardless of the position of said trapping means.

Claim 6

A lock as claimed in claim 3 wherein said key plug means includes a trapping plug having recessed surfaces and said trapping means includes a trapping pin having a trapping finger thereon adapted for engagement with said recessed surfaces.

Claim 7

A lock as claimed in claim 5 wherein said control means includes a control cam, said trapping pin having a control finger thereon in operative engagement with said control cam.

Claim 8

A lock as claimed in claim 6 wherein said trapping pin includes a blocking arm in operative engagement with said override means.

Claim 9

A lock as claimed in claim 2 wherein said first key includes first tumbler operating means for operating said first tumbler means and said second key includes second tumbler operating means for operating said second tumbler means.

Claim 10

A lock as claimed in claim 8 wherein said first key includes a stem and said second key includes a stem receiving slot whereby to permit utilization of said second tumbler operating means when withdrawal of said first key is prevented by said key plug means.

Claim 11

A lock as claimed in claim 7 and including a third key having first tumbler operating means for operating said first tumbler means and second tumbler operating means for operating said second tumbler means.

Claim 12

A lock as claimed in claim 1 wherein said first key has a substantially cylindrical stem and a plurality of radially directed dimples for operating said first tumbler means.

Claim 13

A lock as claimed in claim 2 wherein said second key includes a plurality of parallel prongs for operating said second tumbler means.

Claim 14

A lock as claimed in claim 10 wherein said third key has a substantially cylindrical stem and a plurality of radially directed dimples for operating said first tumbler means and a plurality of parallel prongs having axes parallel to the longitudinal axis of said cylindrical stem for operating said second tumbler means.

Claim 15

A lock as claimed in claim 2 wherein said key plug is generally cylindrical and has a longitudinal axis, said first tumbler means extending generally perpendicular to said longitudinal axis and said second tumbler means extending generally parallel to said longitudinal axis.

Claim 16

A lock as claimed in claim 14 wherein said second tumbler means are circumferentially spaced with respect to the longitudinal axis of said key plug.

Claim 17

A lock as claimed in claim 11 wherein said dimples are coded whereby to identify the individual to whom a first key has been issued.

Claim 18

A lock comprising a housing, key plug means movably mounted in said housing, first tumbler means carried by said housing and key plug means for controlling movement of said key plug means, a first key for insertion in said key plug means for moving same, lock opening preventing means cooperating with said key plug means for preventing operation of said lock to an unlocked position, control means cooperating with said lock opening preventing means for setting said lock opening preventing means to a first position permitting operation of said lock to an unlocked position and to a second position preventing operation of said lock to an unlocked position, a second key for operating said control means, and means carried by said first key for identification of said first key at least when operation of said lock to an unlocked position is prevented.

Claim 19

A lock comprising a housing, key plug means movably mounted in said housing, first tumbler means carried by said housing and key plug means for controlling movement of said key plug means, a first key for insertion in said key plug means for moving same, lock opening preventing means cooperating with said key plug means for preventing operation of said lock to an unlocked position, control means cooperating with said lock opening preventing means for setting said lock opening preventing means to a first position permitting operation of said lock to an unlocked position and to a second position preventing operation of said lock to an unlocked position, a second key for operating said control means, and means carried by said first key for identification of said first key at least when operation of said lock to an unlocked position is prevented.

Claim 20

A lock as claimed in claim 17 and further including selection means carried by said housing for preventing operation of said lock opening preventing means regardless of the position of said lock opening preventing means.

Claim 21

A lock as claimed in claim 17 wherein a plurality of first keys are provided, each of said first keys carrying a different identification means as compared with others of said first keys whereby to identify the individual to whom a first key has been issued.