This invention relates generally to writing implements such as ball point pens and mechanical pencils and more particularly to a writing unit locking mechanism in a multiple-point writing implement including a mechanical pencil unit.
More specifically, the invention relates to a writing unit locking device in a multiple-point writing implement comprising a mechanical pencil unit in which a chuck connectable with a unit cylinder travels along the axis of the unit cylinder thereby to feed a pencil lead out of the unit cylinder, at least one other writing unit such as, for example, a ball point pen unit, a single holder cylinder for accommodating the pencil unit and the other writing unit, and a writing unit selection member for selecting any of the writing units as desired.
A great problem encountered in the design of a multiple-point writing implement of this kind has been the provision, together with a simple and expedient mechanism for selecting writing units, of a simple and convenient mechanism for locking each of the writing units in its writing position in relation with the writing unit selection mechanism. Particularly in the case of a mechanical pencil, a requirement is that, when it is in its writing position and it is necessary to feed pencil lead out of it, it must remain in its writing position. For this reason, the provision of a simple and convenient locking mechanism has been desired.
Another requirement in a mechanical pencil unit of the instant kind is that the force with which the chuck part holds the pencil lead be increased in order to resist the writing force imparted to the pencil lead. Accordingly, a simple and convenient solution for this requirement is also desired.