See,if we think that screen locks automatically then that's not the case. First decrease your screen timeout timing and set your desired screen time out..now go to lock screen and select secure lock settings, here enter your pin..now select first setting I.e lock automatically, click on it and select the first option i. e lock immediately, after this select second setting inside the secure lock settings i. e lock instantly with the power key..
After this whenever you tap on power key, screen gets instantly locked(even if you are using any flip cover or something).
