div.patent-fix-menu li ul {
    -webkit-transition: opacity 0.3s ease 0.3s;
    opacity: 0;
    transition: opacity 0.3s ease 0.3s;
}

    div.patent-fix-menu li:hover ul, .patent-fix-menu li ul.menu-visible {
        opacity: 1;
    }

div.patent-fix-menu li:focus-within ul {
    opacity: 1;
}