EP1018441A1

EP1018441A1 - Autommatic mechanical pencil

Info

Publication number: EP1018441A1
Application number: EP99123938A
Authority: EP
Inventors: Kazuo Micro Co. Ltd. Aizu Factory Nagamine
Original assignee: Micro Co Ltd
Current assignee: Micro Co Ltd
Priority date: 1999-01-08
Filing date: 1999-12-03
Publication date: 2000-07-12
Also published as: JP2000198293A; JP3493638B2

Abstract

In an automatic mechanical pencil, breakage of a lead can be prevented and a lead protruded from a slider (4) can be housed in the slider. At the frond portion of a mouthpiece, the slider is disposed movably in an axial direction. Within the mouthpiece (2), a chuck and a chuck ring (8) are provided so that an advancing movement of the lead is permitted, but a retracting movement of the lead is prevented. Between the slider and the chuck, a lead supply spring (19) is provided. The chuck ring is disposed movably in an axial direction in the mouthpiece and pressed in an axially forward direction by a writing pressure spring (24). At the rear portion of the chuck, a chuck stopper (23) is provided with a distance (22) from the rear end of the chuck. After the chuck retracts in a predetermined distance, it is stopped by a chuck stopper. Even if the retracting movement of the chuck is stopped, the slider and the lead can be housed in the mouthpiece since the chuck ring can retract by being pressed by the slider.

Description

Field of the Invention

The present invention relates to a mechanical pencil, and more particular to an automatic mechanical pencil for feeding out a lead automatically during the writing.

Background Information

Various types of automatic mechanical pencils which feed out a lead automatically during the writing are well known. The basic construction of such mechanical pencils comprises, as indicated in , for example, U.S. Patent 5,236,271, a slider which is disposed at the front portion of a mouthpiece shiftably in an axial direction, and frictionally holds a lead; a spring which elastically biases the slider to the front portion; and a chuck device which grips the lead releasably so that it allows the advancing movement of the lead toward the front end of the mouthpiece, and to prevent the retracting movement of the lead. During the writing, the front end of the slider is made to abut against a paper surface and the slider is retracted, and when the front end of the slider is released from the paper surface, the slider is advanced by the action of the spring to feed out the lead automatically.
In the above automatic mechanical pencil, since the retracting movement of the lead is prevented by the chuck device fixed within a main body, if excessive writing pressure larger than normal is applied, the lead may sometimes be broken at the chuck portion. Further, when the lead happens to overly protrude from the front end of the slider by any reason, the lead cannot be housed, which results in any damage to the body or in snap or breakage of the lead.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an automatic mechanical pencil as described above, wherein when excessive writing pressure is applied, a lead is not broken, and when the lead protrudes from a front end of the slider, the lead can be housed easily.
Further, another object of the present invention is to provide an automatic mechanical pencil, by which the prevention of damages of the lead and the operation of housing the protruded lead can be made easily by pressing the tip or the front end of the lead in the axial direction.
The above objects can be accomplished by an automatic mechanical pencil which comprises a mouthpiece; a slider which is disposed at a front portion of the mouthpiece movably in an axial direction and frictionally holds a lead; a chuck ring which is disposed in the mouthpiece movably in the axial direction and has a tapered face on its inner face; a chuck which is inserted into the chuck ring and grips the lead so that the chuck loosens the grip and releases the lead when the lead moves in the axially forward direction and is tightened by the chuck ring to grip the lead when the lead is pressed backwardly; a lead supply spring which biases the slider in an axially forward direction and biases the chuck in an axially backward direction; a writing pressure spring which biases the chuck ring in an axially forward direction ; and a chuck stopper which is disposed away from a rear end of the chuck with a distance for buffering so that the chuck abuts on the chuck stopper.
According to the present invention, since the chuck ring is disposed shiftably or movably in the axial direction and the chuck ring is biased in the axially forward direction by the writing pressure spring, if excessive writing pressure larger than normal is exerted to the lead, the chuck moves together with the chuck ring in the axially backward direction, whereby the breakage of the lead can be prevented and the objects of the present invention can be accomplished.
Further, according to the present invention, since the chuck stopper is disposed away from the rear end of the chuck ring with a distance for buffering so that the chuck will abut against the chuck stopper, when the lead is pressed in the axially backward direction with a force larger than the load by the spring, the chuck and the chuck ring retract together in the axially backward direction, and then only the chuck is prevented from retracting movement by the chuck stopper, whereby the lead-holding force is lost or removed and the lead can be retracted into the slider, and the above objects can be accomplished.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partial vertical sectional front view showing an example of the present invention.
Fig. 2 is a partial vertical sectional front view showing another example of the present invention.
Fig. 3 is a partial vertical sectional front view showing an example wherein a main body is combined with the example as shown in Fig. 2.
Fig. 4 is a partial vertical sectional front view showing a combination of a chuck and a chuck ring.
Fig. 5 is a partial front view showing an example of a rear portion of a connecting pipe.
Fig. 6 is a front view showing an example of a chuck stopper.
Fig. 7 is a partial front view showing a state when a connecting pipe and the chuck stopper are connected.
Fig. 8 is a partial front view showing another example of the state when the chuck stopper and the connecting pipe are connected.
Fig. 9 is a partial sectional view showing a connecting portion of a main body and an eraser holder.
Fig. 10 is a partial vertical sectional front view showing a state when a lead protrudes from a slider.
Fig. 11 is a partial vertical sectional front view showing a state wherein a chuck ring and a chuck retract under the state of Fig. 10.
Fig. 12 is a partial vertical sectional front view showing a state when the lead is housed in a slider under the state of Fig. 11.
Fig. 13 is a partial vertical sectional front view showing a state when the slider is housed in a mouthpiece under the state of Fig. 12.

DETAILED DESCRPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 shows an example of the preset invention. In this figure, at the forward end of a main body 1, a mouthpiece 2 is provided, and at the rear portion of the mouthpiece 2, a connecting pipe 3 for installing it to the main body 1 is formed. At the front portion of the mouthpiece 2, a slider 4 is disposed movably in the axial direction. Inside the slider 4, a holding portion for frictionally holding a lead 5 is provided. In the example as shown in Fig. 1, an elastic piece 6 separately made of an elastic material is attached thereto. However, as shown in Fig. 2, the slider 4 may be made of a synthetic resin material and have an elastic clamping piece 7 formed on its inside so as to frictionally hold the lead. The mouthpiece 2 is connected to the main body by an appropriate method such as screw coupling or fitting-in coupling. The mouthpiece may be attached directly to the main body and the connecting pipe may be omitted.
Inside the mouthpiece 2, a chuck ring 8 is axially movably provided. The chuck ring 8 has an outer periphery 9 which is in slidably contact with the inner face of the connecting pipe 3, and an inner face on which an axially forwardly widened and backwardly narrowed tapered face 10 is formed. Further, a front end 11 of the chuck ring 8 faces a rear end 12 of the slider 4, and when the slide 4 is housed in the mouthpiece, the front end 11 abuts on the rear end 12 of the slider 4, as described below. When the connecting pipe is omitted or removed, the chuck ring may suitably be constructed so as to move slidably on the inner face of the main body.
Inside the chuck ring 8, a chuck 13 is inserted, whose rear end 14 projects backwardly from the chuck ring preferably. However, the rear end 14 of the chuck 13 may be constructed so that it would not project from the rear end of the chuck ring. The chuck 13 is constructed in such a manner that when the lead 5 moves in the axially forward direction, the gripping of the lead is released, and when the lead is pressed backwardly, the chuck 13 is tightened by the chuck ring 8 to grip the load. In the figures, the chuck 13 is constituted of one obtained by dividing a pipe-Like member axially into plural parts, for example, in the example as shown inthe figures, chuck elements 13a, 13b having a shape divided into halves, and these chuck elements 13a, 13b are complimentarily combined, balls 16 are seated in a concave portion 15 formed on the outer face of the chuck element, and the chuck elements are inserted into the chuck ring 8 so that balls 16 would be received by the tapered face 10 of the chuck ring 8. The chuck may be constructed in such a collet chuck style that slits are provided at the front end of a pipe-like member and the slit portion has an opening and closing action so as to grip the lead releasably (not shown).
In the case where the chuck is constituted by the above chuck elements, as shown in Fig. 4, when the complimentarily arranged chuck elements are inserted from the forward portion of the chuck ring 8, the rear ends 14 of the chuck elements 13a, 13b are arranged to projects backwardly from the chuck ring 8 and an outward projection 17 formed at the rear end abuts on a rear end 18 of the chuck ring 8, the chuck and the chuck ring are not separated as in the assembled state, whereby the fabrication is made easily. The size of the projection 17 may be at such a level that when the combined chuck elements are forcedly pressed backwardly from the front portion of the chuck ring, the projection 17 can project backwardly from the rear end 18 of the chuck ring 8. Such a construction can be practiced easily by preparing the chuck elements and the chuck ring with a synthetic resin material.
Between the slider 4 and the chuck 13, is disposed a lead supply spring 19 which simultaneously biases the slider 4 in the axially forward direction and the chuck 13 backwardly. The lead supply spring is adjusted to apply a load lower than the usual writing pressure. By this lead supply spring 19, the slider 4 is advanced until a stepped portion 21 abuts on a shoulder portion 20 for the slider disposed within the mouthpiece 2. The chuck 13 is moved in the axially toward a chuck stopper 23. The chuck stopper 23 is disposed with a distance 22 for buffering from the rear end 14 of the chuck 13 to prevent the breakage of the lead.
The chuck ring 8 is biased by a writing pressure spring 24 in the axially forward direction, and advanced to the position at which the front end 11 abuts on a shoulder portion 25 for the chuck ring disposed within the mouthpiece. The load of the writing pressure spring 24 is adjusted at such a level to withstand the usual writing pressure and is larger than the load of the lead supply spring 19 so that the front end would be stopped at this predetermined position in usual writing conditions.
The chuck stopper 23 is fixed to the rear end of the connecting pipe 3 and a large diameter portion 26 is fitted to the connecting pipe 3, and at the forward end of a small diameter portion 27 provided at the forward portion of the large diameter portion 26, a stopper face 28 is formed. The writing pressure spring 24 is provided between the rear end 18 of the chuck ring 8 and a shoulder portion 29 formed between the small diameter portion 27 and the large diameter portion 26. The small diameter portion 27 is constructed so that the rear end 18 of the chuck ring would not abut thereon. Accordingly, the chuck 13 and the chuck ring 8 move together in the axially backward direction, but the movement of the chuck 13 stops at the position where the chuck 13 abuts on the stopper face 28 of the chuck stopper 23, and the chuck ring 8 can move further backwardly. When the mouthpiece is directly attached to the main body by omitting the connecting pipe, a stepped portion may suitably be disposed in the main body so as to fix the chuck stopper within the main body (not shown).
In order to fix the chuck stopper 23 to the connecting pipe 3, an appropriate fixing means such as screw coupling or press fitting, may be employed. In the figures, as shown in Figs. 5 to 7, at the rear portion of the connecting pipe 3, an engagement groove 31 which has an engagement stepped portion 30 and opens backwardly, is provided, and at the outer periphery of the large diameter portion 26 of the chuck stopper 23, an engagement hook 33 having an engagement edge 32 is provided so that the chuck stopper 23 is inserted from the rear portion of the connecting pipe 3 and the engagement hook 33 is inserted into the engagement groove 31 to engage the engagement edge 32 with the engagement stepped portion 30. Further, as shown in Fig. 8, an engagement window 34 may be formed on the connecting pipe 3 and an engagement projection 35 may be provided on the outer periphery of the large diameter portion 26 of the chuck stopper 23 so that the engagement projection 35 would be engaged with the engagement window 34.
At the rear end of the main body 1, an eraser is often provided. The eraser may be directly fitted in the rear end of the main body. It is preferred that as shown in Fig. 3, an eraser holder 36 is attached to the rear end of the main body 1 and an eraser 37 is fitted in the eraser holder 36. The eraser holder 36 is attached, as shown in Fig. 9, by inserting a hollow axis portion 39 of the eraser holder 36 into a fitting portion 38 formed at the rear portion of the main body 1, forming a slit 40 at the front end of the axis portion 39 so that the front end part may be deflected radially, and engaging an engagement edge 41 formed on the outer periphery at the front end with a shoulder portion 42 provided within the main body 1 so as to detachably attach the eraser holder. Further, so as not to permit the eraser holder 36 to rotate easily, the engagement portion 38 of the main body and the axis portion 39 of the eraser holder may be formed into a polygonal shape, or projections such as ribs may be provided on the outer periphery of the axis portion of the eraser holder and the projections may be pressedly fitted in the fitting portion of the main body, to prevent easy rotation (not shown).
Accordingly, writing can be made in such a condition that the slider 4 projects from the mouth piece 2 as shown in Fig. 1. During the writing, the slider 4 retracts into the mouthpiece, but when the front end of the slider is released from a paper face 43, the slider 4 is advanced by the lead supply spring 19 while the slider 4 holds the lead, and the lead can be fed out automatically. When excessive writing pressure larger than normal is applied to the lead, the chuck 13 and the chuck ring 8 move together backwardly or retract against the writing pressure spring 24, whereby no breakage of the lead is caused at the chuck portion. When the excessive writing pressure is removed, the slider, chuck ring, etc. are returned to the advanced position by means of the spring, and the writing can be continued.
If the lead overly protrudes from the front end of the slider as shown in Fig. 10 by any reason, this mechanical pencil may suitably be operated as follows. Firstly, under the state as shown in Fig. 10, if a large force is applied axially to the lead by pressing the lead 5 against the paper surface 43, the slider 4, the chuck 13 and the chuck ring 8 retract together with the lead 5 as described above, and during the retracting movement, the rear end 14 of the chuck 13 abuts on the stopper face 28 of the chuck stopper 23 and the chuck 13 is stopped (Fig. 11).
With respect to the lead-holding force by the chuck 13, the rear end 14 of the chuck abuts on the chuck stopper 23 to prevent the chuck from moving backwardly, whereby only the force generated by the load of the writing pressure spring 24 which biases the chuck ring 8 to the direction of the slider, is exerted. Accordingly, if a force larger than this load is exerted , the lead-holding force of the chuck can no longer withstand, the slippage of the lead starts and the lead is housed in the slider 4 (Fig. 12).
Under the state as shown in Fig. 12, if a stronger force is exerted, the slider 4 retracts or moves backwardly, the rear end 12 of the slider 4 abuts on the front end 11 of the chuck ring 8, by which the chuck ring 8 moves backwardly and the holding force by the writing pressure spring 24 is lost, whereby the slider 4 can be housed easily in the mouthpiece 2 as well (Fig. 13). Then, when the front end of the slider is released from the paper surface, the chuck ring 8 and the slider 4 are returned to the state as shown in Fig. 1 while holding the lead with the writing pressure spring 24 and the lead supply spring 19, and writing can be continued.
The present invention is constituted as mentioned above and comprises a slider movable in the axial direction, a chuck and a chuck ring arranged so that the retracting movement of the lead can be prevented, but the advancing movement of the lead can be permitted, and a lead supply spring provided between the slider and the chuck, wherein the slider is moved backwardly during the writing like the usual automatic mechanical pencil, and when the writing is stopped and the slider is released from the paper surface, the slider is advanced so as to feed out the lead automatically. Then, the chuck ring is axially movably disposed, and the chuck ring is biased in the axially forward direction by the writing pressure spring, whereby when excessive writing pressure larger than a required writing pressure is exerted to the lead, the chuck and the chuck ring move together in the axially backward direction, and the breakage of the lead can be prevented.
Further, since a chuck stopper on which the chuck abuts, is disposed with a distance from the rear end of the chuck for buffering, when the lead projects from the front end of the slider by any reason, if the lead is pressed in the axially backward direction by a force larger than the load of the writing pressure spring, the chuck and the chuck ring move backwardly together in the axially backward direction, and then only the chuck is prevented from moving further backwardly by the chuck stopper. As a result, the lead-holding force is removed and the lead can be retracted into the slider, and at the same time, the lead and the slider can be housed into the mouth piece easily, and then, by removing the pressing force to the lead, the slider is projected from the front portion of the mouthpiece under the state such that the front end of the lead and the front end of the slider are of the same level.

Claims

An automatic mechanical pencil which comprises a mouthpiece; a slider which is disposed at a front portion of the mouthpiece movably in an axial direction and frictionally holds a lead; a chuck ring which is disposed in the mouthpiece movably in the axial direction and has a tapered face on its inner face; a chuck which is inserted into the chuck ring and grips the lead so that the chuck loosens the grip and releases the lead when the lead moves in the axially forward direction and the chuck is tightened by the chuck ring to grip the lead when the lead is pressed backwardly; a lead supply spring which biases the slider in an axially forward direction and biases the chuck in an axially backward direction; a writing pressure spring which biases the chuck ring in an axially forward direction; and a chuck stopper which is disposed away from a rear end of the chuck with a distance for buffering so that the chuck abuts on the chucck stopper.
An automatic mechanical pencil according to Claim 1, wherein the slider is disposed so that when the chuck and the chuck ring move in the axially backward direction, the rear end of the slider abuts on a front end of the chuck ring after the rear end of the chuck abuts on the chuck stopper.
An automatic mechanical pencil according to Claim 1, wherein the chuck is formed by combining complimentarily arranged plural chuck elements, balls are seated on the outer faces of the chuck elements, balls are received on the tapered face of the chuck ring, a rear end of each of the chuck elements protrudes backwadly from a rear end of the chuck ring and has a projection which abuts on the rear end of the chuck ring.
An automatic mechanical pencil according to Claim 1, wherein the mouthpiece has a connecting pipe, the chuck ring slidably moves in the connecting pipe, the chuck stopper is fixed to the connecting pipe, and the writing pressure spring is disposed between the rear end of the chuck ring and a shoulder portion formed on the chuck stopper.