Patent ID: 7165905

Claim:
An auto-control pencil suitable for pen leads of different sizes comprising: a pen tube having an inner recess at a front inner side thereof; a guide tube having a trench at a lateral side thereof; the guide tube being formed of an extension bar and a connecting unit; two buckles being installed between the connection of the extension bars and the connecting unit; the buckles can be buckled to the recess of the pen tube; a side of the connecting unit near the extension bar being an enlarged portion; the connecting unit having a fixing hole; a push rod having an opening at a front end thereof for receiving pencil lead of different sizes; a rear end of the push rod having a block; when the push rod is placed within the guide tube, the block protruding out of the trench of the guide tube; a front end of the connecting unit having two confining projections which is embedded into two notches of the inner head; a spring being installed to the extension bar of the guide tube; one end of the spring resisting against the enlarged portion of the guide tube; the pen tube being installed at an outer side of the spring; the inner recess of the pen tube being engaged to the buckles of the guide tube; a rotary head installed at a rear end of the pen tube; a front end of the rotary head having a sheet for fixing one end of the spring; and an inner head having the two notches; the inner head having at least two presses at a front end thereof; a front ring being installed at a front end of the presses and a rear ring being installed at a rear end of the presses; a tip recess being formed at the front ends of the presses; a middle section of a stop ring having the two notches; a rear end of the inner head being extended with a buckling ring; when the inner head being combined to the guide tube, the buckling ring will be placed into the fixing hole of the connecting unit; the two notches serving for receiving the two confining projections of the connecting unit; and an outer head installed at an outer side of the inner head, an inner side of the outer head being annularly formed with an annular ring for resisting against the stop ring of the inner head; the front ring and rear ring being in contact to the inclined surface of the outer head for reducing friction force; wherein when the inner head is pressed downwards along the outer head, the presses at the front end of the inner head will reduce inwards so that one end of the pen lead resists against the opening at the front end of the push rod and moreover another end thereof is clamped by the presses so that the two ends of the pen leads are fixed.