US3899256A

US3899256A - Mechanical pencil

Info

Publication number: US3899256A
Application number: US459854A
Authority: US
Inventors: Yoshihide Mitsuya
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-04-10
Filing date: 1974-04-10
Publication date: 1975-08-12
Anticipated expiration: 1992-08-12
Also published as: AU485791B2; GB1456115A; DE2420448C3; DE2420448A1; DE2420448B2; AU6770674A; FR2268650A1; FR2268650B1

Abstract

A mechanical pencil has at the forward tip portion thereof a movable cylinder made up of a lead-protecting tube and an outside tube covering the lead-protecting tube. Lead extends through the lead-protecting tube and further through a chuck provided above the movable cylinder. A ring is provided for applying a load to the movable cylinder to add to its plunging movement for withdrawing into the pencil proper, the pencil proper having the forward tip directed upward at this time. The ring is the outside of the lead-protecting tube leaving a clearance between the ring and the lead-protecting tube. The outside tube is expanded at the bottom thereof so as to retain the ring therewith at the time of withdrawing the lead into the pencil proper.

Description

1 Aug. 12, 1975 O United States Patent Mitsuya 1 MECHANICAL PENCIL [76] Inventor: Yoshihide Mitsuya, 1,3-chome,

Higashi Nagata, Jhoto-ku, Osaka, Japan [22] Filed: Apr. 10, 1974 [21] Appl. No.: 459,854

[52] US. Cl. 401/65 [51] Int. Cl 843k 21/16 [58] Field of Search 401/65-67, 40l/9294 [56] References Cited UNITED STATES PATENTS 2,385,329 9/1945 Buchanan 401/65 2,532,748 12/1950 Votruba 401/65 3,537,799 11/1970 Sakamoto 401/67 3,804,536 4/1974 Torii et a1. 401/65 Primary ExaminerLawrence Charles Attorney, Agent, or FirmWenderoth, Lind & Ponack 57 1 ABSTRACT A mechanical pencil has at the forward tip portion thereof a movable cylinder made up of a leadprotecting tube and an outside tube covering the leadprotecting tube. Lead extends through the leadprotecting tube and further through a chuck provided above the movable cylinder. A ring is provided for applying a load to the movable cylinder to add to its plunging movement for withdrawing into the pencil proper, the pencil proper having the forward tip directed upward at this time. The ring is the outside of the lead-protecting tube leaving a clearance between the ring and the lead-protecting tube. The outside tube is expanded at the bottom thereof so as to retain the ring therewith at the time of withdrawing the lead into the pencil proper.

1 Claim, 5 Drawing Figures PATENTEU AUG 1 2 I975 SHEET FIG.1

PATENTED AUG 1 2 I975 SHEET FIG.3

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MECHANICAL PENCIL The present invention relates to a mechanical pencil provided with an improvement in the reciprocating movement of lead in and out of the mechanical pencil proper.

In a conventional mechanical pencil having a movable cylinder at its forward tip with a lead-protecting tube fixed therein, the lead-protecting tube is likely to break when the pencil with the lead-protector projected therefrom accidentally hits the ground or any other solid object. Also, a mechanical pencil having such a mechanism as above mentioned usually retracts the lead by pushing a push button attached to the pencil to loosen a lead-trapping chuck, thereby allowing the lead to be pushed into the pencil directly by a finger and the like. Such action very often causes the lead to break.

As a countermeasure, a method has been tried which withdraws the lead-protector into the pencil by taking advantage of the gravity of the lead-protector itself, however this method has proven defective in that regard because when the lead-protector has a weight heavy enough to allow itself and the lead to retract into the pencil without any pressure thereto from the outside, the lead is likely to break under the impact coming from the lead-protector when the pencil accidentally hits the ground or any other solid object described hereinbefore. The present invention adopts a leadapplying ring fixed outside the lead-protector, thereby keeping a space between the ring and the leadprotector. Said ring has the function of giving a load to the movable cylinder, thereby allowing the leadprotector to return into the pencil when the pencil is held vertically with the lead-protector directed upward. The ring is further situated so as not to collide with the lead-protector even when the pencil is dropped on a solid item.

The above-mentioned object of the present invention can be accomplished by the improvement, combination and operation of every part constituting the present invention, the preferred embodiment of which will be described in detail in relation with the annexed drawing as follows.

FIG. 1 is a longitudinal section ofa mechanical pencil in the present invention showing its lower portion organization.

FIG. 2 is an upside-down longitudinal view of FIG. 1 when withdrawing a lead and leadprotector into the pencil proper.

FIG. 3 and FIG. 4 are magnified longitudinal sections of integral parts of the mechanical pencil shown in FIG. 1.

FIG. 5 is a longitudinal section of a movable cylinder of the present invention showing the second embodi ment.

In FIG. 1, the mechanical pencil 12 has a forward tip portion 11, said forward tip portion 11 has therein a movable cylinder S. Said movable cylinder S, in the first embodiment shown in FIG. 1 and 2, comprises a lead-protector 13 made of stainless steel and the like, over which is firmly fitted an outside tube 26 made of elastic material such as rubber and the like, said outside tube 26 having an enlarged outside diameter portion 15 at the bottom thereof and having at the upper inside terminal thereof a projection 27 covering said leadportector 13 all around the periphery thereof. Said projection 27 is smaller in inside diameter than the diameter of lead 28 held in the lead-protector 13 so as to give a suitable friction between the lead and the inside of the elastic projection 27.

In a space provided at the forward tip portion 11 as mentioned above, a ring 17 is adapted to fit outside said lead-protector 13, thereby providing a clearance between said ring 17 and said lead-protector l3. Said ring 17 is situated between the bottom of the outside tube 26 and the bottom 16 of the. inside surface 18 of the forward tip 11.

As shown in FIG. 3, the clearance (a) between the inside surface of the ring 17 and the outside surface of the protector 13 is larger than the clearance (b) between the outside surface of the ring 17 and the inside surface 18 of the forward tip portion 11.

A guide tube 19 is adapted at the lower terminal of a lead-container (not shown), and a chuck 20 is provided at the lower terminal of said guide tube 19. An outer tube 21 is provided within the pencil 12 at the lower terminal portion 22 thereof, said outer tube 21 playing the role of tightening said chuck 20. Said chuck 20 has elasticity, enabling it to close when it is contained within said outer tube 21 and to open when located out of said outer tube 21.

A male screw of said cylindrical portion 22 at its outside screws into a female screw adapted at the forward tip portion 11 at the inside upper terminal thereof, thereby connecting said forward tip 11 to the pencil 12.

The forward tip portion 1 1 at the inside periphery 23 thereof below said female screw is smaller in diameter than the outer diameter of said outer tube 21 and larger than the outer diameter of said chuck 20 in the opened state.

In the forward tip portion 11 between said inside periphery 23 and the inside periphery 18, there is fixed a ring 25 which is smaller in inside diameter than the diameter of said movable cylinder S at the expanded part 15 thereof and bigger than the outer diameter of said outside tube 26. Also, in between the lead-container (not shown), positioned at the upper terminal of said guide tube 19 and a retaining portion 29 at the lower terminal of said pencil 12, there is a spring 30 which sustains said guide tube 19 together with said leadcontainer (not shown) upward.

In FIG. 5 showing the second embodiment of the movable cylinder S, said outside tube 26 covering said lead-protector 13 and said projection 27 are formed separately but are firmly fixed with each other.

Besides the foregoing embodiments, in said movable cylinder S said outside tube 26 and said projection 27 can be eliminated by providing only the enlargeddiameter portions 15 outside said lead-protector 13 and means for holding the lead 28 unslidably inside the lead-protector 13 by providing a friction between the lead 28 and the lead-protector 13 at the inside surface thereof, thereby attaining the same effect as the said projection 27 for retaining the lead 28.

The function of the mechanical pencil in the present invention as described heretofore is given below.

When a push button (not shown), attached on the pencil 12 at the upper terminal thereof, is pushed, the lead-container (not shown) and the guide tube 19 come down toward the forward tip of the pencil and at the same time force the spring 30 downward, thereby causing the outer tube 21 to tighten the chuck 20, thus enabling it to grip the lead 28 therein and plunge downward together. Said chuck continues to move downward after said outer tube 21 comes to a stop after hitting the inside periphery 23 at the upper terminal thereof, and said chuck 20 opens as it goes out of the outer tube 21 and releases the lead from its grip.

When the push button is released, the chuck 20 in the opened state rises until it reaches the outer tube 21 and then closes, thereby holding the lead 28 therein again.

The lead 28 advances forward at a predetermined pace per each operation of the push button as described above, thus reaching a desired position for writing by way of repeating said operation. Needless to mention, it is desirable to start writing with the lead 28 projecting slightly out of the lead-protector 13 when said lead-protector 13 reaches the lowest position in the pencil 12.

When returning this mechanical pencil to the unused state, i.e., withdrawing the lead into the pencil, the pencil is held vertically so that the forward tip directs upward, as shown in FIG. 2. The chuck 20 is then opened by pushing said push button, resulting in the release of the lead 28 from said chuck 20. After releasing said push button, the lead 28 and the movable cylinder S fall together under the effect of the friction between the projection 27 and the lead 28. At this time, said ring 17 works to give a load to the movable cylinder S, thereby helping the movable cylinder S to fall into the pencil 12 by gravity.

Said ring 17, as described above, makes easier the withdrawal of said movable cylinder S into the pencil 12 at a reduced weight of said movable cylinder compared to convention pencil of this kind, thereby reducing the possiblity of breaking the lead under the impact of said movable cylinder when the pencil 12 is dropped or knocked against the ground and the like.

Also, with the clearance (a) between the leadprotecting tube 13 and the inside surface of said ring 17 being larger than the clearance (b) between the ring 17 and said inside surface 18, said ring 17 will not hit the lead-protecting tube 13 and accordingly will never break the lead 28 by its own impact even in the case of such accidents as described above.

I claim:

1. In a mechanical lead pencil having a forward tip with a cavity therein for containing a movable cylinder portion comprised of a lead-protecting tube extending through and beyond said tip and an outside tube covering within said cavity for surrounding a portion of the end of said lead-protecting tube within said cavity, and a push button controlled chuck located above said movable cylinder when said forward tip is pointed downward for holding and controlling the movement of lead in said pencil through said lead-protecting tube in response to depressing the push button, the improvement comprising:

a ring located around said lead-protecting tube immediately below said outside tube covering within said cavity when the forward tip is pointed downward, said ring having an inside radius sufficiently large that the difference between the inside radius of said ring and the radius of said lead-protecting tube is greater than the difference between the outside radius of the ring and the radius of the cavity in which said ring is located, thereby preventing said ring from contacting said lead-protecting tube at any point; and

an enlarged portion at the bottom of said outside tube covering immediately above said ring when said forward tip is pointed downward for preventing said ring from sliding over said outside tube covering when said forward tip is pointed upward, whereby pointing the forward tip upward and releasing said chuck surrounding the lead causes the lead and the lead-protecting tube to fall into the tip of the pencil under their own weight and under the force of the weight of the ring exerted against the enlarged portion of the outside tube.

Claims

1. In a mechanical lead pencil having a forward tip with a cavity therein for containing a movable cylinder portion comprised of a lead-protecting tube extending through and beyond said tip and an outside tube covering within said cavity for surrounding a portion of the end of said lead-protecting tube within said cavity, and a push button controlled chuck located above said movable cylinder when said forward tip is pointed downward for holding and controlling the movement of lead in said pencil through said lead-protecting tube in response to depressing the push button, the improvement comprising: a ring located around said lead-protecting tube immediately below said outside tube covering within said cavity when the forward tip is pointed downward, said ring having an inside radius sufficiently large that the difference between the inside radius of said ring and the radius of said leadprotecting tube is greater than the difference between the outside radius of the ring and the radius of the cavity in which said ring is located, thereby preventing said ring from contacting said lead-protecting tube at any point; and an enlarged portion at the bottom of said outside tube covering immediately above said ring when said forward tip is pointed downward for preventing said ring from sliding over said outside tube covering when said forward tip is pointed upward, whereby pointing the forward tip upward and releasing said chuck surrounding the lead causes the lead and the leadprotecting tube to fall into the tip of the pencil under their own weight and under the force of the weight of the ring exerted against the enlarged portion of the outside tube.