Locking mechanism

Claim 1

IN A DEVICE FOR RETAINING TWO SLIDING WINDOW SASHES IN CLOSED POSITIONS WHEREIN THE WINDOW SASHES ARE FORMED WITH ALIGNABLE APERTURES, THE COMBINATION OF A KEEPER PLATE ADAPTED TO BE MOUNTED ON ONE OF THE SASHES AND FORMED WITH A FIRST APETURE IN ALIGNMENT WITH THE APERTURES OF THE SASHES WHEN THE SASHES ARE CLOSED, SAID KEEPER PLATE HAVING A SECOND APERTURE SPACED FROM SAID FIRST APERTURE, SAID SECOND APERTURE INCLUDING A RECTANGULAR PORTION AND A CIRCULAR PORTION, A BOLT INSERTABLE IN SAID FIRST APERTURE AND ADAPTED TO EXTEND INTO THE APERTURES OF THE SASHES TO PREVENT THE SASHES FROM BEING OPENED, KEY OPERATED LOCK MEANS INCLUDING A RECTANGULAR LOCKING MEMBER INSERTABLE THROUGH SAID RECTANGULAR APERTURE PORTION, SAID LOCKING MEMBER BEING ROTATABLE WITHIN SAID CIRCULAR PORTION AND ENGAGEABLE WITH SAID KEEPER PLATE TO PREVENT SAID LOCKING MEANS FROM BEING REMOVED EXCEPT UPON OPERATION OF A PROPER KEY, AND A COVER PLATE AFFIXED TO SAID LOCKING MEANS AND SAID BOLT TO PREVENT SAID BOLT FROM BEING WITHDRAWN FROM SAID FIRST APERATURE EXCEPT UPON REMOVAL OF SAID LOCKING MEANS FROM SAID SECOND APERTURE.