Boring
Welcome | What’s New?
Site Map | Usage Note

Become a Contributor
Really Boring
What is a Leadholder?
Leadholder History
Leadholder Mechanics
Leadholder Database
Yawn
References
Contributors
Leadholder Links
Contact D. B. Smith

United States Patent 3,713,745
“Push-Type Mechanical Pencil”, 1968–1973

date of earliest application
date granted
inventor
assignee


patent holder country

primary examiner
1968 July 11 (Japan)
1973 January 30
Yuko Horie
Dai Nihon Bungu Kabushiki Kaisha
(aka The Japan Stationery Co., Ltd.)
[later known as Pentel]
Chuo-ku, Tokyo, Japan

Charles Lawrence
patent employed on Pentel PSD5
Pentel PSD5
references cited
United States patents:
261,455   July 1882   Hoffman
3,153,479   October 1964   Hultgren
270,567   January 1883   Hoffman
1,355,026   October 1920   Austin
2,649,074   August 1953   Burchett

Abstract

A pushing force applied to an end cap of a push-type mechanical pencil compresses initially a first spring to expose a guide tube at the tip of an inner casing to the outside of a barrel. Then, the stronger pushing force applied successively to the end cap compresses a second spring to eject a lead through the guide tube by means of a lead ejecting means.

Claims

1. A mechanical pencil comprising a barrel opened at both ends, an inner hollow casing disposed inside of said barrel, lead advancing means having a first spring inside of said inner casing, and an end cap projecting through the rear end opening of said barrel, the improvement of said mechanical pencil comprising a fine lead guide tube at the tip of said inner casing which is slidable relative to said barrel, a first projection provided at the outer surface near the front end of said inner casing, a tubular member disposed between said barrel and said inner casing and having a hooked slot through which said first projection is guided and caught at its hooked portion, a second spring provided around the rear cylindrical surface of said inner casing but inside of said barrel, said second spring expanding between said tubular member and a second projection provided at the rear portion of said inner casing and urging said inner casing to the rearward direction of said barrel, and means for transmitting a pushing force applied to said end cap to said second spring, wherein said second spring is weaker in expansion force than the first spring, whereby the inner casing is advanced initially outside of the fore end opening of said barrel and then a lead is ejected through said lead guide tube.

Description

This invention relates to a push-type mechanical pencil.

The lead for use in mechanical pencils has recently been improved and thin leads have been developed. Mechanical pencils now are adapted to use leads of 0.3 mm to 0.5mm in diameter. Such thin leads are widely used for drafting and for conventional writing. In order to protect such a fine lead from breaking, mechanical pencils have a guide tube through which the lead protrudes. The guide tube is provided at the tip of a ferrule of the mechanical pencil. As finer leads are used, i.e., more narrow than 0.5 mm in diameter, the diameter of their guide tubes is likewise reduced. Consequently a mechanical pencil having such a fine guide tube may be dangerous or may be deformed, for example, by falling. Once the guide tube is deformed, it cannot guide the lead.

An objective of the present invention is to provide a push-type mechanical pencil in which a fine lead guide tube is exposed from and concealed into a barrel by simple operations.

Another objective of the present invention is to provide a push-type mechanical pencil in which the fine lead guide tube is exposed outside of the barrel and a lead is ejected through the guide tube in turn by pushing operations of different strength.

Other objectives and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings, in which:

US 3,713,745 Figure 1
Fig. 1

FIG. 1 is a side view of a push-type mechanical pencil incorporating an embodiment of the invention, showing a fine lead guide tube as well as ferrule exposed outside of a barrel;

US 3,713,745 Figure 2
Fig. 2

FIG. 2 is a side view of the push-type mechanical pencil of FIG. 1, showing the concealed position of the guide tube;

US 3,713,745 Figure 3 US 3,713,745 Figure 4
Fig. 3 Fig. 4

FIG. 3 is a partially sectioned enlarged side view showing the fore portion of the push-type mechanical pencil of FIGS. 1 and 2; and

FIG. 4 is a partially sectioned enlarged side view of the center portion of the push-type mechanical pencil of FIGS. 1, 2 and 3;

US 3,713,745 Figure 5
Fig. 5

FIG. 5 is a top plan view of a portion of the inner cylindrical tubular member showing its slot.

An embodiment of the push-type mechanical pencil according to the present invention shall be described with the help of Figures.

In FIG. 1 the mechanical pencil includes a ferrule 1, with a fine lead guide tube 2 protruding through tip of the ferrule 1. A fore end portion of an inner casing 5 is fixed upon, or formed integral with, the rear open end of the ferrule 1. These parts are exposed outside of a frust-conical fore end portion 4 of a barrel 3. The mechanical pencil is of the push-type and its guide tube 2 is in the exposed portion. An end cap 6 protrudes through the rear opening of the barrel 3. In FIG. 2 the guide tube 2, as well as the ferrule 1, is concealed in the barrel 3. As the mechanical pencil is in its concealed position, the end cap 6 is longer than its position shown in FIG. 1. The added length of cap 6 is the same length as the retracted portions (ferrule 1, guide tube 2 and casing 5).

The inner casing 5 is fixed to the rear open end of the ferrule 1, in any convenient manner, or may be formed integral therewith. As shown in FIG. 3, the rear inner end portion of the ferrule 1 and the fore inner end portion of the inner casing 5 are connected together by means of a first spring-receiving bushing member 42, the connections being at 43 and 45. A helical coil spring 8, which serves to eject a lead 11 through the guide tube 2, is provided between the first spring receiving member 42 and a second spring receiving member 18 (see FIG. 4). Spring receiving member 18 is connected to the rear end of a lead guide member 19, the fore portion of which comprises a chuck member 9 and a ring 10. A lead storing housing 7 is fixed at its fore end to the second spring-receiving member 18 and connected at its rear end (not shown) to the end cap 6. As shown in FIG. 5, a cylindrical tubular member 15 has a slot 14 which is hooked at its fore end. Member 15 is positioned between the barrel 3 and the inner casing 5 so as not to move relative to the barrel. A projection 12 is formed integral with the inner casing 5 near its front end. Projection 12 is fitted in the slot 14 so that the inner casing 5 is slidable relative to the barrel 3 and to the cylindrical member 15 along the lengthwise direction of the mechanical pencil. Another spring 16, which serves to advance and retract the inner casing 5 along the slot 14, is provided between the rear end of the cylindrical member 15 and another projection 17 formed at the rear end of the inner casing 5.

When the spring 16 is weaker in expansion force than the other spring 8 (adapted for the push-type mechanical pencil of this embodiment), the inner casing 5 is advanced initially to expose the guide tube 2 as well as the ferrule 1 to the outside of the barrel 3 as described hereinafter. When a pushing force strong enough to compress the spring 16, but not strong enough to compress the spring 8, is applied forwardly to the end cap 6 of the mechanical pencil in the concealed position in FIG. 2, it compresses the spring 16, as the force is transmitted to the rear projection 17 by way of the housing 7, second spring-receiving member 18, spring 8, first spring-receiving member 42 and inner casing 5. Therefore, the inner casing 5 slides forwardly relative to the barrel 3 and the fine lead guid tube 2 is exposed outside of the barrel 1. Reference numeral 12a in FIGS. 4 and 5 shows the position of the fore projection before moving. When fore projection 12 is advanced along the hooked slot 14, it comes to the fore end of the slot 14 and is turned to enter into its hook portion 13, thereby the guide tube 2 is maintained in the exposed position as shown in FIG. 1.

Further, when the pushing force strong enough to compress the spring 8 is successively applied in the same way, as mentioned above, the lead 11 is ejected by way of a bore 20, guide member 19, chuck member 9 and ring 10. As far as the lead ejecting means comprising the guide member 19, chuck member and the ring 10 is concerned, the push-type mechanical pencil of the embodiment of the invention utilizes conventional structure.

By rotating slightly the end cap 6 so that the projection 12 may be disengaged from the hook portion 13, the guide tube 2 in the exposed position can be retracted in the barrel 3 as shown in FIG. 2. When the projection 12 is disengaged from the hook portion 13, the inner casing 5 is retracted by means of the spring 16 to conceal the guide tube 2 in the barrel 3.

The spring 8 serves to eject the lead 11 through the guide tube and spring 16 serves to advance and retract the inner casing. If the spring 16 is stronger in expansion force than the spring 8, the inner casing 5 is advanced after the lead ejecting operation has been performed.

In the above-mentioned embodiment the cylindrical member 15 having the elongated slot 14 is provided apart from the barrel 3. But they may be formed integral with each other.

The push-type mechanical pencil of the embodiment of the invention is so constructed that the exposing of the fine lead guide tube 2 and the ejecting of the lead 11 through the guide tube 2 can be made respectively in turn by simply pushing the end cap 6. The retracting of the inner casing 5 to conceal the guide tube into the barrel 3 is obtained by slightly rotating the end cap 6.