The present invention relates to an automatic pencil device which can be releasably mounted in an automatic drafting or writing machine, more particularly, to such a device which has an automatic lead advancing mechanism.
An automatic pencil device with a lead advancing mechanism have been devised, particularly for mounting on automatic drafting, writing or recording machines. Such a pencil device generally comprises an axially movable clamping member to clamp a lead in position during the writing process and a lead guide tube having a lead brake and the tube being axially movable and projecting outwardly of the pencil casing in the rest position. The pencil device is generally mounted in a bracket in such a manner that the device can be mechanically brought into the working or rest positions. Such a writing instrument is disclosed, for example, in DE-OS No. 30 13 973. However, this device has the disadvantage that it has a very complicated and expensive clamping and control mechanism as well as a force applying system several springs required to actuate the lead feed. In addition, this writing instrument does not provide for any automatic follow-up of successive leads after the lead in the writing position is used up.
In addition to the foregoing disadvantages, this prior art instrument has the individual components mounted in several separate mountings so that for example a change to another lead diameter or to another lead color is very difficult and use in another recording mechanism is practically impossible.
Other automatic pencil devices are known from U.S. Pat. Nos. 4,091,393, 4,015,269 and 3,345,640. These pencil devices have a somewhat more simplified construction but still have essentially the same disadvantages as described above. In particular, there is no automatic lead follow-up and replacement leads cannot be introduced. As a result, the recording process must be interrupted to replace leads. In addition, special actuating mechanisms are continuously required on the recording mechanism.
It is therefore the principal object of the present invention to provide a novel and improved automatic pencil device which is particularly adapted for an automatic drafting or writing machine and the like.
It is another object of the present invention to provide such an automatic pencil device which not only automatically advances the lead during use, but also provides for the follow-up of successive leads.
It is a further object of the present invention to provide such an automatic pencil device which is simple in construction, inexpensive to fabricate, and reliable in operation.
It is an additional object of the present invention to provide such an automatic pencil device which can be readily and easily replaced and can be used in virtually all recording machines without the necessity of providing for a special control mechanism.