Disc cartridge having annular shaped mating projections

A disc cartridge comprising:

• a disc recording medium in which a data signal is recorded;
• a cartridge body exhibiting a rectangular shape formed by mating and joining upper and lower halves at circumferential edges of which are formed rising circumferential walls which are mated to each other to constitute circumferential side walls and accommodating portion walls which are mated to each other at mating inner surfaces to constitute a recording medium accommodating portion in which the disc recording medium is accommodated, the circumferential side walls connecting with the accommodating portion walls in a connecting area;
• an opening for recording and reproduction which is formed in upper and lower surfaces of the cartridge body over an area from the vicinity of the center of the cartridge body to a front side of the cartridge body;
• a shutter member which is provided with a shutter portion for opening or closing the opening and which is attached to the cartridge body so that it can move along a front surface of the cartridge body;
• recess portions for preventing erroneous loading formed on both sides of the cartridge body on the lower half from the front side to the middle toward the back side;
• and
• a plurality of fusing portions for mating and fusing together the upper and lower halves at facing surfaces of said upper and lower halves, wherein each of said fusing portions is provided with a mating projection cylindrically formed at one of said upper and lower halves and a mating projection cylindrically formed at another of said upper and lower halves;
• wherein
• the mating projections formed at said another of said upper and lower halves include a flat annular end surface, and the mating projections formed at said one of said upper and lower halves include an annular end surface to be connected to said flat annular end surface and a projection which has a semicircular shape along a part of said annular end surface and which is formed on said annular end surface on said rising circumferential wall side to be fused together with said flat annular end surface to connect the upper and lower halves, wherein
• said mating projections including said semicircular shaped projections are provided at positions adjacent to where said rising circumferential walls and said walls forming said recording medium accommodating portion intersect and
• one of said fusing portions for mating and fusing said upper and lower halves is provided at a thin portion having a thickness less than that of said cartridge body formed by mating of said upper and lower halves at a front side of said opening formed in said cartridge body and at substantially a center of said cartridge body and
• another plurality of said mating projections including complete annular shaped projections are formed at one of said upper and lower halves at positions corresponding to the corners of the cartridge body, wherein
• at least one pair of fusing portions is provided positioned at the two sides of said cartridge body at which said recess portions are formed.