Patent ID: 8044987

Claim:
A printer comprising: a platen roller including a pair of roller shafts; a frame including a pair of lateral plates opposite to each other and defining upper open grooves for supporting the roller shafts of the platen roller and shaft holes; a rotation shaft axially inserted through the shaft holes of the frame; a print head that is rotatably supported by the rotation shaft; a first spring that urges the print head to come into pressure contact with the platen roller; a motor capable of rotatably driving the platen roller; a lock lever member comprising a pair of lock levers and a joint member joined to the pair of lock levers, where the lock lever member is rotatably supported by the rotation shaft; and a second spring that urges the lock lever member to come into pressure contact with the roller shafts of the platen roller, wherein the pressure contact between the print head and the platen roller is adjustable by the first spring, the pressure contact between the lock lever member and the roller shafts of the platen roller being adjustable by the second spring independent of the pressure contact between the print head and the platen roller; wherein the lock levers are provided with locking projections each including a slope guiding portion and a slope locking portion, when the platen roller is mounted in the upper open grooves, the roller shafts of the platen roller being guided by the slope guiding portion toward the slope locking portion and into the upper open grooves such that the slope locking portion contacts an outer periphery of the roller shaft and such that the slope locking portion and the lateral plates of the frame jointly lock the roller shafts between the slope locking portion and the lateral plates of the frame, the slope guiding portion being disposed above the roller shafts of the platen roller to partially close the upper open grooves so as to control a position of the open side of the roller shaft, when the platen roller is moved out of the upper open grooves, the roller shafts pushing the slope locking portion against an urging force of the second spring and being guided by the slope locking portion toward the slope guiding portion.