Figures 11,12 and 13 show the meshi

Figures 11,12 and 13 show the meshing of the tooth profiles of teeth when the limit section is selected on the end portion of tooth trace of the diaphragm. Figure 11 shows the meshing thereof on the section of rotation at the opening, Figure 12 shows the meshing on the central section of rotation of tooth trace, and Figure 13 shows that on the section of the end of tooth trace of the diaphragm. When viewed along the tooth trace direction, the portion of the composite curve defined by the envelope from the apex thereof corresponds to the meshing or contact of the teeth form the opening of the flexible external gear to the end portion of the diaphragm side or to the limit section in the vicinity of outside of the end portion, while the remaining portion of the composite curve corresponds to a continuous contact of the tooth profiles within the limit section. However, if the limit section is settled in the vicinity of outside of the end portion of the diaphragm side, no actual teeth exist on this section and therefore the meshing or contact of the teeth within this limit section is a imaginary one. Although, the meshing of the tooth portions located on the end portion of the diaphragm side can be regarded as like as that on the limit section. As seen from the drawings, according to the example of the present invention, in the sections shown in Figures 11 and 12, a part of the continuous contact of the teeth can be realized in accordance with a degree of contact between the envelope and the moving locus of the shown section, and in Figure 13, a continuous contact of the toot profiles within the section can be realized.