U.S. Pat.  No.  4,083,589 for a Vehicle Security System to Palmerino discloses a vehicle security system where the user pushes a push button to overcome a spring bias.  This causes a piece monolithically integrated with the push button to translate in the same direction as the push button.  An inclined surface on the monolithic piece of the push button, in contact with a second member, slides the second member by camming action, in a direction perpendicular to the direction of travel of the push button. 
U.S. Pat.  No.  2,648,561 for a Push Button Latch to Landon discloses a similar device as the one depicted in Palmerino.  In Landon, a button is pushed, overcoming the resilient force of a spring bias, causing a member monolithically integrated to the push button to translate in the same direction as the push button causing an inclined plane located on the monolithic push button piece to move in the same direction as the push button.  This inclined plane remains in contact with a second member, causing, by camming action, the second member to translate in a direction perpendicular to the first member and against a spring bias on the second member.  The translation in the second member caused by the depression of the button on the first member frees a latch monolithically integrated on the second member from an aperture in a chassis part, allowing for the disassembly of the chassis. 
U.S. Pat.  No.  1,944,450 for a Sash Control for Sliding Windows to Myers describes a window sash control.  In Myers, a push button is depressed, causing a monolithically integrated member to cam with a latch bar forcing the latch bar to pivot downward in a direction perpendicular to the push button motion and opposite the spring bias on the latch bar.  By forcing the latch bar to pivot downward, a layer of weatherstripping is disengaged. 
U.S. Pat.  No.  2,221,095 for a Door Locking and Latching Mechanism to Jacobi describes a door locking and latching mechanism.  In Jacobi, a push button feature is disclosed.  When the push button is depressed, the member monolithically integrated with the push button travels in the same direction as the push button.  A rotatable latch, in contact with the push button member, is rotated against a spring bias because of the force of the push button member.  This rotation of the latch member against spring bias causes a hook, monolithically integrated to the pivotable latch member, to rotate out from an aperture of the structure allowing for the door to open. 
U.S. Pat.  No.  5,321,962 for an Injector/Ejector Latch Lock Mechanism to Ferchau et al.  illustrates a sliding safety mechanism that prevents the operation of an unlatching mechanism on a computer console.  A security lock prevents a trigger from rotating preventing a handle pivotably mounted on the chassis from unlatching the chassis parts preventing the disassembly of the chassis. 
U.S. Pat.  No.  2,893,773 for a Latch and Detent Assembly to Clifton describes a latch with a detent assembly for a door.  The detent prevents the unauthorized unlatching of the door. 
U.S. Pat.  No.  5,213,382 for a Locking Mechanism for Refuse Container to Dawdy et al.  discloses a locking mechanism where a control bar is pivotably mounted and contains a tab section having an aperture.  A locking bar also contains a tab with an aperture.  When the control bar is rotated to the latched position, the tabs of the control bar and the locking bar as well as the respective apertures align.  A padlock may be inserted through the two holes when aligned preventing the subsequent unlatching of the container. 
The above button operated latches have not been used in computer cases because of the availability of a less expensive alternatives, such as using screws.  In the past, it was generally a service technician, rather than an operator, that opened computer cases.  As a service technician would work on many computer cases in a single day, the service technician was equipped with specialized equipment to open and close a computer case and to fix the equipment.  Today, it is more common for an operator to be required to open and close a computer case.  Since an operator opens a computer case only occasionally, it is much more cumbersome for the operator to possess and use tools to accomplish this task.  Thus, the latch mechanism would facilitate the opening and closing of the computer case for such an operator.