EP0213275B1

EP0213275B1 - Automatic mechanical pencil

Info

Publication number: EP0213275B1
Application number: EP86106534A
Authority: EP
Inventors: Gouji Sakaoka
Original assignee: Micro Co Ltd
Current assignee: Micro Co Ltd
Priority date: 1985-08-10
Filing date: 1986-05-14
Publication date: 1990-03-07
Anticipated expiration: 2006-05-14
Also published as: KR870001945A; DE3669281D1; JPH0460440B2; JPS6235896A; EP0213275A1; KR890001645B1

Description

The invention refers to an automatic mechanical pencil.
DE-A 3 229 448 discloses an automatic mechanical pencil comprising a main body having a tip, a mouth piece connected to the tip of the main body, a connecting pipe provided at a rear portion of the mouth piece and inserted into an inner portion of the main body, a slider shiftably inserted in a front portion of the mouth piece and having an elastic piece, which frictionally holds a lead, further a chuck, whose chuck elements surround the periphery of the lead and are movably provided in the connecting pipe to be slightly shiftable in the radial direction, wherein balls and a chuck ring are positioned in the connecting pipe around the outer periphery of said chuck so as to wedge the chuck element upon the writing pressure and to release the wedge effect of the writing pressure, when said writing pressure disappears. In this known embodiment a spring is provided between the chuck and a pressure member, which abuts on extensions of the chuck elements in the resting position of the pencil in such a way that the chuck elements are slightly moved in radial direction so as to release the lead. An extension of the slider abuts on this pressure member during writing, so that the chuck elements are biased by the spring to clamp to lead. The structure of this known pencil is rather complicated and some parts are provided so that such a pencil cannot be produced economically.
Similar mechanical pencils are known from DE-A 2 153 400 and US-A 3 864 046.
It is the object of the invention to provide an automatic mechanical pencil for automatically feeding out the lead, which pencil has a simple structure and can be produced economically.
This object is achieved according to the invention by the features in claim 1. Owing to the fact that the spring is provided between slider and chuck in such a way that the chuck elements are always biased by the spring, only a few parts can be provided so that the structure can be produced economically and can be incorporated in the mouth piece, whereas the lead is fed out by the slider motion without the necessity to positively open the chuck as it is the case in the known embodiments.
The invention is described in more detail in connection with the drawing.

Fig. 1 is a vertical sectional view of an automatic mechanical pencil according to this invention, schematically showing a portion of the main body.
Fig. 2 is an enlarged sectional view of the mouth piece portion of the mechanical pencil according to this invention, under the state that the lead is not supplied.
Fig. 3 is a front view of an automatic mechanical pencil according to this invention in case a push button for advancing a chuck is provided, showing a half sectional portion of the pencil along its axial direction.
Fig. 4 is a perspective view of the push button shown in Fig. 3.

In the drawing, a mouth piece (2) connected to a main body (1) has a connecting pipe (3) on its rear portion, and a male screw provided on the outer periphery of the connecting pipe is screw clamped with a female screw provided on the main body, thus connecting the mouth piece to the main body. The connecting may be effected with a fitting-in and other suitable means instead of the screw clamping. In the tip portion of the mouth piece, a slider (4) is inserted shiftably in an axial direction. The slider (4) is fitted with an elastic piece (6) so as to elastically hold a lead (5) by the frictional action at the rear portion, while at the front end a lead guide (7) made of the plastic material having a small frictional action is provided. As the plastic material, polyacetal, polyamide, fluororesin and other thermoplastic materials having a low coefficient of the friction are used. For the pipe, metallic pipe such as a stainless pipe can be used, but when it is made of the plastic material, i.e., polyacetal and polyamide whose coefficient of the friction is about 0.15 - 0.2, as shown in the drawing, the friction may be made extremely small. Further, in the drawing, the slider is integrally formed with the plastic material including the guide pipe. However, the pipe may be separately made and then be combined. The pipe (7) is preferably provided with a taper (8) at its front end and is slidably inserted in a bore (9) provided in the mouth piece. On the intermediate portion of the slider (4), a flange (10) is provided, and the slider can advance until the flange (10) abuts against a shoulder (11) of the mouth piece. And the mouth piece (2) may preferably be made of the plastic material, such as polyacetal and polyamide, having the similar effect to that of the guide pipe.
Facing the rear portion of the slider (4), there are provided with a chuck (13) and a chuck ring (17), among which the former (13) is formed so that it can grip the lead by combining complementarily plural chuck elements (12), (12) (two of them are shown in the drawing) and the latter (17) is put on an outer periphery of the chuck elements (12) and is formed to have a tapered face (16) internally so as to receive balls (15) seated on a concave (14) of the outer face of the chuck elements (12). The chuck elements have such shapes as to devide the cylinder into nearly halves, having a lead gripping portion (18) with a suitable rough face internally; and the front and rear parts of the gripping portion are made so that they form a space having slightly larger diameter, adjacent to a slant, than outside diameter of the lead to combine two chuck elements facing each other. On the rear portion of the chuck, a flange (19) is so provided that it abuts against a rear end (20) of the chuck ring (17) to prevent the chuck and balls from falling out forwardly; however, the flange (19) is not always necessary. The chuck ring (17) is provided with a shoulder (21) rearwardly to form into smaller diameter (22) and is pressed in a bore (23) of the connecting pipe (3) under either state of an idle fitting or a light press fitting. Under this state, the tip of the chuck ring abuts on a slant (24) adjacent to the bore (23); and in the smaller diameter portion (22) at the rear portion, an inner projection (25) of the connecting pipe (3) comes in, and the rear end (20) of the chuck ring projects slightly backward. Since the chuck is formed as mentioned above, when it is shifted backwardly, the balls roll into the narrow portion of the tapered face and the chuck elements are tightened to grip the lead. On the other hand, when the chuck shifts forwardly, the balls roll into the wider portion of the tapered face, so that the gripping force by means of balls and the chuck ring will vanish, and the chuck elements will part from each other to allow the advance movement of the lead.
Between the flange (10) of the slider (4) and a tip portion (26) of the chuck (13), a spring (27) is provided so as to project the front end of the guide pipe (7) of the slider (4) from the tip of the mouth piece (2) and to urge the chuck (13) backwardly.
To assmeble each portion, the slider (4) is inserted from the rear of the mouth piece; the spring (27) is inserted; the chuck elements (12), (12) are combined; balls (15) are put in and under such a state, the chuck ring (17) is fitted in, and these portions may be forcibly pushed in from the rear portion of the connecting pipe (3) over the inner projection (25). Thereafter, by the fact that the flange (10) abuts on the shoulder (11), and the balls are pushed by the tapered portion (16) of the chuck ring (17), both of the slider and the chuck would never drop out from the mouth piece.
Into the mouth piece (2) assembled as mentioned above, the lead (5) is pushed from the rear of the chuck (13), and by the tip of the lead, the chuck (13) is advanced. When the chuck is advanced, the gripping force by means of the balls (15) and the chuck ring (17) will vanish and the lead will pass through the gripping portion of the chuck, the front end of the lead advances until it becomes flush with the tip of the guide pipe (7) of the slider (4). When the lead is pushed backward under this state, the chuck shifts backward, thus an action of the gripping force prevents the lead from retracting. Further, on the rear end of the lead, preferably, plastic foam (28) of a shape as approximately conforming to the inner wall of the main body is put on, and by the plastic foam, the shock in case of dropping of the pencil is softened, thus the breakage of the lead may be prevented. When the main body is formed transparent, the length of the residue lead may be seen through.
In case that the mouth piece (2) is connected to the main body (1), the rear end (20) of the chuck ring (17) abuts on a shoulder (29) of the main body (1) facing to the rear end of the connecting pipe.
Since the lead is gripped by the chuck not to retract backward, the writing may be effected and the writing pressure will be received by the shoulder (29) of the main body via the chuck, balls, and the chuck ring. Further, when the inner projection (25) of the connecting pipe is made strong, the writing pressure may be received by the projection. By the writing, the slider (4) will retract against the spring (27) with the wear of the lead. However, when the writing is stopped and the writing pressure is removed, the slider is advanced by the spring, and the lead kept by the elastic piece (6) will be fed out together. When the lead advances, the chuck will also advance to release the gripping action by the balls and the chuck ring, so that the advance of the lead is not checked. Thereafter, the chuck returns backward by the spring (27), and the gripping action by the balls and the chuck ring is restored to check the retraction of the lead.
When the lead is consumed, the mouth piece may be taken off from the main body and the new lead may be supplied from the rear portion of the chuck. Even through the removal of the mouth piece, the chuck will never be separated from the mouth piece.
When the slider (4) itself is abutted on the edge of a ruler, the slider will retract. As the result thereof, the lead will project forward from the tip of the guide pipe (7), but in such a case, an example for effecting the retraction of the lead is shown in Fig. 3.
In Fig. 3, the same reference number as in Fig. 1 is used in the similar elements. In this figure, a slant (30) is provided on the rear end of the chuck (13), and a push button (32) having a slant 31) engaging with the slant (30) is provided on the side of the main body (1) so that the button can freely go in and out. The button (32) is normally put under the state that the slant would not be operated by the elastic legs (33). As shown in Fig. 3, when the lead is put under the projected state, by pushing the push button (32), the chuck (13) is advanced via the slant (30), (31) and the gripping action of the chuck may be made to vanish, so that when the tip of the lead is pushed on a paper face, the tip of the lead will become flush with the guide pipe of the slider, thus the lead can be restored. Further, the mouth piece may be provided with a cap, and the supply mechanism for the lead may be provided within the main body.
As mentioned above, in this invention, the formation thereof is simple, comprising a small number of parts, so that it may be made economically and used conveniently with few troubles.

Claims

1. An automatic mechanical pencil comprising: a main body (1) having a tip;

a mouth piece (2) connected to the tip of the main body;

a connecting pipe (3) provided at a rear portion of the mouth piece (2) and inserted into an inner portion of the main body (1);

a slider (4) shiftably inserted in a front portion of the mouth piece (2) and having an elastic piece (6) which frictionally holds a lead (5);

a chuck (13) comprised of two radially divided chuck elements (12) complementarily combined with each other to surround the periphery of the lead (5), said chuck elements being movably provided in the connecting pipe (3) to be shiftable slightly in the radial direction independently of each other;

balls (15) and a chuck ring (17) positioned in the connecting pipe (3) around the outer periphery of said chuck (13) so as to wedge the chuck elements (12) upon the writing pressure, and to release the wedge effect of the writing pressure when said writing pressure disappears; and

a spring (27) provided between said slider (4) and said chuck (13) to project a tip of said slider (4) from a front portion of the mouth piece (2) and to always urge and shift said chuck (13) backwardly; said spring (27) retracting said chuck elements (12) to enable the same to always hold the lead (5) not only during the writing period but also during the non- writing period, said spring (27) coacting with the slider (4) to advance the lead (5) due to the resilient force of the elastic piece (6) in spite of the holding force of the chuck (13) when the slider (4) advances.

2. An automatic mechanical pencil according to claim 1, wherein said chuck elements (12) are shaped such that a cylindrical body is divided into halves and the two chuck elements (12) are combined facing each other to form the chuck (13).

3. An automatic mechanical pencil according to claim 1, wherein said slider (4) has a guide pipe (7) projecting from the tip of the mouth piece (2), and said guide pipe (7) is made from thermoplastic material having a low coefficient of friction.

4. An automatic mechanical pencil according to claim 1, wherein a push button (32) is provided so as to engage with the rear end of said chuck (13), and by pushing said push button (32), said chuck (13) may be shifted.