Ribbon cassette with ink ribbon slack prevention mechanism

A ribbon cassette, comprising:

• a ribbon supply spool;
• a ribbon take up spool that takes up an ink ribbon from said ribbon supply spool by rotating in a first rotation direction, said ribbon take up spool being provided with an engaging portion;
• and
• an engaging member that resiliently engages with said engaging portion to prevent said ribbon take up spool from rotating in a second rotation direction opposite to said first rotation direction, said engaging member coming off from said engaging portion when said ribbon take up spool rotates in said first direction, wherein
• said engaging portion includes first and second walls arranged in said second rotation direction in this order, said engaging member engaging with said engaging portion by dropping into a space defined between said first and second walls, said first wall being defined along a plane including a rotation axis of said ribbon take up spools,
• said second wall is formed so as to allow said engaging member to come off from said engaging portion by sliding along said second wall when said ribbon take up spool is rotated in said first rotation direction, and
• said second wall is inclined to face outside said ribbon take up spool.

A ribbon cassette, comprising:

• a ribbon supply spool;
• a ribbon take up spool that takes up an ink ribbon from said ribbon supply spool by rotating in a first rotation direction, said ribbon take up spool being provided with an engaging portion;
• and
• an engaging member that resiliently engages with said engaging portion to prevent said ribbon take up spool from rotating in a second rotation direction opposite to said first rotation direction, said engaging member coming off from said engaging portion when said ribbon take up spool rotates in said first direction,
• wherein said ribbon take up spool has substantially a cylindrical wall,
• wherein said engaging portion is a slit formed through said cylindrical wall, and
• wherein said cylindrical wall is provided with a plurality of said slits arranged in a circumferential direction of said cylindrical wall.

A ribbon cassette, comprising:

• a ribbon supply spool;
• a ribbon take up spool that takes up an ink ribbon from said ribbon supply spool by rotating in a first rotation direction, said ribbon take up spool being provided with an engaging portion;
• an engaging member that resiliently engage with said engaging portion to prevent said ribbon take up spool from rotating in a second rotation direction opposite to said first rotation direction, said engaging member coming off from said engaging portion when said ribbon take up spools rotates in a said first direction;
• and
• a cassette case that accommodates said ribbon supply spool and said ribbon take up spool, said engaging member being held by said cassette case and thereby prevented from rotating together with said ribbon take up spool,
• wherein said engaging member is a single wire rod including:
• an arc portion that extends along a circumferential wall of said ribbon take up spool;
• a linear portion formed at one end of said wire rod;
• and
• a bent portion defined between said arc portion and said linear portion so as to allow said linear portion to extend in substantially a radial direction of said ribbon take up spool,
• wherein said engaging member engages with said engaging portion at said bent portion and is supported by said cassette case at said linear portion so as not to rotate together with said ribbon take up spool.