Patent ID: 7580652

Claim:
A laser beam printer apparatus comprising: a rear door configured to be openable/closable around a rotational axis that is an axis extending in a width direction of its base portion; a cylindrical photosensitive drum; a cylindrical transfer roller fixed to said rear door, the transfer roller being disposed to be contactable with said photosensitive drum in a line when said rear door is closed; a holding member including a guide groove extending toward a backside; and a hook for restraining said rear door in a closed state, wherein said rear door includes: a rear latch engaging said hook when said rear door is closed; and a boss configured to be partially inserted into said guide groove when said rear door is being closed, said holding member has a hole that is circular in shape in a plan view at a bottom of said guide groove in a position where said boss is disposed when said rear door is closed, said boss includes: a cylindrical case that opens at one end portion at one boss end facing said guide groove; a cylindrical abutting portion disposed within said case, the abutting portion being disposed to abut said guide groove; an anchoring lug extending from said abutting portion toward another boss end opposite said one boss end, the anchoring lug configured to catch an end portion of said case at said other boss end; and a coil spring disposed within said case for biasing said abutting portion toward said one boss end, said guide groove is formed along a path along which said boss is moved as said rear door is opened/closed, said abutting portion has a spherical tip abutting said guide groove, said hole has a diameter in a plan view that is smaller than that of said abutting portion, when said rear door is closed, said rear latch engages said hook to restrain said rear door in a closed state, when said rear door is being closed, part of said boss is inserted into said guide groove, and said tip fits into said hole such that a closed position of said rear door is fixed.