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We, Dai Nihon Bungu Kabushiki Kaisha, a body corporate organised under the laws of Japan, of No. 12, 2-Chome, Koami-cho, Nihonbashi, Chuo-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: —

This invention relates to a mechanical pencil having a guard sleeve for covering and uncovering a lead guide tube at the tip of the mechanical pencil.

As a result of recent developments in the manufacture of lead for the mechanical pencils, the pencils using leads of 0.3 mm to 0.5 mm diameter have become [sic] to be widely used. In order to protect such fine leads from fracture, the tips of the pencils are provided with guide tubes through which the leads protrude. The more the leads become smaller in diameter, the more the guide tubes become narrow, so that a pencil having such a guide tube may be deformed, for example, by falling while not in use. A deformed guide tube cannot guide the lead.

An object of the present invention is to provide a mechanical pencil having a guard sleeve which is advanced along a straight line and without itself rotating, by rotating a cylindrical cover in either direction.

According to the present invention there is provided a mechanical pencil comprising a barrel, a lead guide tube at the tip of said pencil, a guard sleeve at the front end portion of the barrel, said guard sleeve having a knob, and means for advancing and retracting the knob in the lengthwise direction of the barrel whereby the guard sleeve is advanced to conceal the guide tube and is retracted to conceal [the author means reveal] the guide tube.

In the accompanying drawings:

Fig. 1

Fig. 1 is a side view of a push-type propelling pencil constructed according to an embodiment of the invention, and including a fine lead guide tube as well as a ferrule exposed outside a barrel;

Fig. 2 is a perspective view of an outer cylindrical cam member of the same embodiment,

Fig. 2		Fig. 3

Fig. 3 is a perspective. view of an inner cylindrical cam member of the same embodiment; and

Figure 4

Fig. 4 is a partially sectioned side view showing only the assembly of a guard sleeve of the pencil according to the same embodiment of the invention.

The pencil illustrated in Fig. 1 has a ferrule 1, a fine lead guide tube 2 protruding through the tip of the ferrule 1. A barrel 3 is reduced in diameter at its front portion 4 and has an end cap 6 protruding through a rear opening of the barrel 3. A mechanism for ejecting a lead 5 through the guide tube 2 is same as the conventional one. Such mechanism is not described herein as it does not constitute a part of the present invention.

At the from portion 4 of the barrel 3, an inner cylindrical cam member 9 is fixed to the barrel at the point 12 (Fig. 4). The inner cylindrical cam member 9 has a straight slot 10 extending lengthwise of the pencil and an annular collar 11 at the front end. An outer cylindrical cam member 7 having a helical slot 8 surrounds the outer surface of the inner cylindrical cam member 9. Inside the inner cylindrical cam member 9 a guard sleeve 13 is fitted. The guard sleeve 13 with a reduced front end portion has a knob 14 at its rear end, the knob 14 extending through the straight slot 10 of the inner cylindrical cam member 9 and being partially inserted into the helical slot 8 of the outer cylindrical cam member. The outer cylindrical cam member 7 is disposed between the collar 11 of the inner cylindrical cam member 9 and a ring 16 fitted to the front portion of the barrel 3 so that the outer cylindrical cam member 7 is prevented from sliding in the lengthwise direction. The outer surface of the outer cylindrical cam member 7 is surrounded by a cylindrical cover sleeve 15.

When the cylindrical cover sleeve 15 is rotated as much as one rotation, for example, by fingers of a user, the helical slot 8 of the outer cylindrical cam member 7 also rotates and the knob 14 is thereby advanced along the straight slot 10 of the inner cylindrical cam member 9, which makes the guard sleeve 13 advance to conceal the guide tube 2. Reference numeral 14a shows the knob in the advanced position and a dotted line in Fig. 4 shows the guard sleeve 13 in the advanced position.

The pencil of this second embodiment of the invention is so constructed that one rotation of the cylindrical cover sleeve 15 straightly advances the guard sleeve 13 from inside of the cover pipe 15 and one rotation of the cylindrical cover sleeve 15 in the opposite direction straightly retracts the guard sleeve 13 into inside of the cover pipe.

1. A mechanical pencil comprising a barrel, a lead guide tube at the tip of said pencil, a guard sleeve at the front end portion of the barrel, said guard sleeve having a knob, and means for advancing and retracting the knob in the lengthwise direction of the barrel whereby the guard sleeve is advanced to conceal the guide tube and is retracted to conceal [the patent attorney is a moron, as should be quite evident by now, and means reveal again] the guide tube.

2. A mechanical pencil as claimed in claim 1, wherein said means comprises an inner cylindrical cam member around the guard sleeve, said cam member having a straight lot through which the knob projects, an outer cylindrical cam member covering over the inner cylindrical cam member, said outer cam member having a helical slot through which the knob is inserted, and a cylindrical cover member fitted to the outer surface of the outer cylindrical cam member whereby the guard sleeve is straightly advanced from inside of the cover member to cover the guide tube by rotation of the cover member and outer cylindrical cam member in one direction and is straightly retracted into inside of the cover member by rotation in the opposite direction.

3. A mechanical pencil substantially as described with reference to the accompanying drawings.

Elkington and Fife,
Chartered Patent Agents,
High Holborn House, 52/54
High Holborn, London, WC1V 6SH.
Agents for the Applicants.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1972. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.