Ribbon spool, ribbon cassette, and printing apparatus

Abstract

A ribbon spool is detachably attached to a printing apparatus for forming an image on a recording medium by using an ink ribbon. The printing apparatus has an engaging member including an engaging convex portion for engaging the ribbon spool. The ribbon spool includes a ribbon retaining portion for retaining the ink ribbon, and an engaging portion provided at one lateral side end of the ribbon spool for engaging the engaging convex portion and having a plurality of inclined grooves. The grooves have a different inclination angle from that of a lateral side face of the engaging convex portion. At least one of the grooves of the engaging portion has a point contact with the engaging convex portion at two points to engage the engaging convex portion.

1 . A ribbon spool for detachably attaching to a printing apparatus for forming an image on a recording medium by an ink ribbon, said printing apparatus having an engaging member including an engaging convex portion, comprising:
 a ribbon retaining portion for retaining the ink ribbon; and   an engaging portion provided at one lateral side end of the ribbon spool for engaging the engaging convex portion and having a plurality of inclined grooves,   wherein the grooves have an inclination angle different from that of a lateral side face of the engaging convex portion, at least one of the grooves of the engaging portion having a point contact with the engaging convex portion at two points to engage the engaging convex portion.   
     
     
         2 . A ribbon spool according to  claim 1 , wherein the grooves of the engaging portion have convex portions in a shape different from a shape of the engaging convex portion. 
     
     
         3 . A ribbon spool according to  claim 1 , wherein in case the grooves of the engaging portion have an inclination angle α and the lateral side face of the engaging convex portion has an inclination angle β, when α is 0°<α<90° (wherein α<β), the two points correspond to inclined surface of the convex portion of the engaging portion and vertex of the engaging convex portion, and wherein, when α is 90°≦α<180° (wherein β<90°), the two points correspond to vertexe of the convex portion of the engaging portion and lateral side face of the engaging convex portion. 
     
     
         4 . A ribbon spool according to  claim 1 , wherein the ribbon retaining portion has a flange for regulating a position of the ink ribbon in an axial direction, and the engaging portion is adjacent to the flange. 
     
     
         5 . A ribbon cassette, comprising:
 a supply spool for supplying an ink ribbon;   a winder spool around which the ink ribbon is wound; and   a case for rotatably storing the supply spool and the winder spool;   wherein at least one of the supply spool and the winder spool is the ribbon spool according to  claim 1 .   
     
     
         6 . A ribbon cassette, comprising:
 a supply spool for supplying the ink ribbon;   a winder spool around which the ink ribbon is wound; and   a case for rotatably storing the supply spool and the winder spool;   wherein at least one of the supply spool and the winder spool is the ribbon spool according to  claim 2 .   
     
     
         7 . A ribbon cassette, comprising:
 a supply spool for supplying the ink ribbon;   a winder spool around which the ink ribbon is wound; and   a case for rotatably storing the supply spool and the winder spool;   wherein at least one of the supply spool and the winder spool is the ribbon spool according to  claim 3 .   
     
     
         8 . A ribbon cassette, comprising:
 a supply spool for supplying the ink ribbon;   a winder spool around which the ink ribbon is wound; and   a case for rotatably storing the supply spool and the winder spool;   wherein at least one of the supply spool and the winder spool is the ribbon spool according to  claim 4 .   
     
     
         9 . A printing apparatus for forming an image on a recording medium by an ink ribbon situated in a ribbon spool having a ribbon retaining portion for retaining the ink ribbon, and an engaging portion provided at one lateral side end and having a plurality of inclined grooves, comprising:
 an engaging member for engaging the engaging portion of the ribbon spool, said engaging member having an engaging convex portion for engaging at least one of the grooves of the engaging portion,   wherein the engaging convex portion for engaging the engaging portion has a lateral side face with inclination angle different from that of the grooves of the engaging portion, and the engaging convex portion has a point contact with the at least one groove at two points.   
     
     
         10 . A printing apparatus according to  claim 9 , wherein the engaging convex portion has a shape different from those of the convex portions of the engaging portion. 
     
     
         11 . A printing apparatus according to  claim 9 , wherein in case the grooves of the engaging portion have an inclination angle α, and the lateral side face of the engaging convex portion has an inclination angle β, when α is 0°<α<90° (wherein α<β), the two points correspond to an inclined surface of the convex portions of the engaging portion and vertex of the engaging convex portion, and wherein when α is 90°≦α<180° (wherein β<90°), the two points correspond to vertex of the convex portions of the engaging portion and a side face of the engaging convex portion. 
     
     
         12 . A printing apparatus according to  claim 9 , wherein the engaging member has biasing means for biasing the ribbon spool, and the biasing means biases the engaging convex portion toward the engaging portion. 
     
     
         13 . A printing apparatus according to  claim 9 , further comprising an encoder connected to the engaging member for detecting a rotation amount of the ribbon spool. 
     
     
         14 . A combination of a ribbon spool and a printing apparatus for forming an image on a recording medium by an ink ribbon,
 wherein said printing apparatus includes an engaging member having an engaging convex portion, and   wherein said ribbon spool includes a ribbon retaining portion for retaining the ink ribbon; and   an engaging portion provided at one lateral side end of the ribbon spool for engaging the engaging convex portion and having a plurality of inclined grooves,   wherein the grooves have an inclination angle different from that of a lateral side face of the engaging convex portion, at least one of the grooves of the engaging portion having a point contact with the engaging convex portion at two points to engage the engaging convex portion.   
     
     
         15 . A combination according to  claim 14 , wherein the grooves of the engaging portion have convex portions in a shape different from a shape of the engaging convex portion. 
     
     
         16 . A combination according to  claim 14 , wherein in case the grooves of the engaging portion have an inclination angle α and the lateral side face of the engaging convex portion has an inclination angle β, when α is 0°<α<90° (wherein α<β), the two points correspond to inclined surface of the convex portion of the engaging portion and vertex of the engaging convex portion, and wherein when α is 90°≦α<180° (wherein β<90°), the two points correspond to vertexe of the convex portion of the engaging portion and lateral side face of the engaging convex portion. 
     
     
         17 . A combination according to  claim 14 , wherein the ribbon retaining portion has a flange for regulating a position of the ink ribbon in an axial direction, and the engaging portion is adjacent to the flange.