Abstract: A spindle head structure rotatable in A/B axes is provided, comprising: a spindle support, an intermediate support, a base support, an upper telescopic strut and a lower telescopic strut. The spindle support may be adapted to be fixed with a spindle. The intermediate support may be connected with the spindle support via two coaxial upper revolute pairs. The base support may be connected with the intermediate support via two coaxial lower revolute pairs. The upper telescopic strut may be connected between the spindle support and the intermediate support. And the lower telescopic strut may be connected between the intermediate support and the base support.

Abstract: A spindle head structure rotatable in A/B axes is provided, comprising: a spindle support, an intermediate support, a base support, an upper telescopic strut and a lower telescopic strut. The spindle support may be adapted to be fixed with a spindle. The intermediate support may be connected with the spindle support via two coaxial upper revolute pairs. The base support may be connected with the intermediate support via two coaxial lower revolute pairs. The upper telescopic strut may be connected between the spindle support and the intermediate support. And the lower telescopic strut may be connected between the intermediate support and the base support.

Abstract: A propelling pencil has a writing core which can be fed out and drawn back controllably and freely. The front portion of the propelling pencil is inserted in the lower end of the shaft of the propelling pencil. The inner surface of the shaft has several ridges which together act as longitudinal guides for the writing core holder. A helical wire, controlling the core holder movement, is formed by winding a flat metal wire. The core holder is made of an elastic material and has a hole therein which has a large diameter at each end thereof and a relatively small diameter at its central region. The core holder is also provided with longitudinal ridges in its lower portion to prevent rotation of the writing core held therein.