AUTOMATIC MECHANICAL PENCIL

Abstract: An automatic mechanical pencil provided with a chuck (13) which will grip a lead (5) to allow the advance of the same, wherein the lead is kept prevented from retraction when it is pushed back by writing pressure, while the advance movement of the lead is allowed when it is to be advanced. On the tip portion of a mouth piece (2), a slider (4) provided with an elastic piece (6) to hold the lead by a frictional action is shiftably inserted. The chuck is provided on the rear portion of the mouth piece. Between the chuck and the slider, a spring (27) is provided so as to urge the slider forward as well as to urge the chuck backward. The advance of the lead is effected by the forward movement of the slider owing to the spring.

Description: Background of the invention 1. Field of the invention: This invention relates to a machanical pencil, in particular to an automatic mechanical pencil feeding out the lead, which is formed in such a manner that when the lead is consumed by the writing, the lead is automatically fed out by releasing the writing tip from the paper surface. 2. Description of the related art: Various types of mechanical pencils feeding out the lead automatically are well known, and most of them are so formed that when the writing stops, the lead will be fed out. However many of them are complicated in construction and have a lot of parts and cannot be economically obtained. Generally, in the usual automatic mechanical pencil feeding out the lead automatically, there is provided with a device which will automatically supply a new lead by a knocking operation, when one lead is completely consumed by the writing. When such a device is provided within a main body, the construction will become complicated inevitably, and the production costs will become higher. Summary of the invention One of the objects of this invention is to obtain an automatic mechanical pencil feeding out the lead automatically, without providing the usual lead supply mechanism for a new lead by the knocking operation in case the lead has completely been consumed, and the whole body is simply formed. Another object of this invention is to obtain an automatic mechanical pencil, wherein an automatic feed out mechanism of the lead is provided within a mouth piece to be connected to the main body, and when the mouth piece is detached from the main body, the lead can be directly supplied by hand to the automatic feed out mechanism of the lead. According to this invention, an automatic mechanical pencil having a chuck mechanism which allows only an advance motion of the lead and a slider mechanism which takes out the lead forward, are provided within the mouth piece to be connected to the main body. Other objects and features of this invention will become apparent from the following detailed description with reference to the accompanying drawings. Brief description of 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. Description of the preferred embodiments 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 mouth piece connected to the tip of a main body; and a chuck and slider provided within said mouth piece, wherein said chuck prevents backward movement of the lead due to the writing pressure, but allows forward movement thereof, said slider elastically grips the lead and moves backward as the lead wears, and when the writing pressure is removed, said slider is urged to advance carrying the lead therewith. 2. An automatic mechanical pencil having a main body and a mouth piece connected to said main body comprising: a slider shiftably inserted in the front portion of the mouth piece, having an elastic piece which holds the lead by the frictional action; a chuck formed so that plural chuck elements are complementarily combined to grip the lead and are shiftably provided; balls and a chuck ring positioned on the outer periphery of said chuck so as to tighten said chuck, when said chusk is shifted backward; and a spring provided between the slider and said chuck to project the tip of said slider from the front portion of the mouth piece as well as to urge shifting said chuck backwardly. 3. An automatic mechanical pencil according to claim 2, wherein said chuck elements are shaped such that a cylindrical body is divided into halves, and two chuck elements are combined facing each other to form a chuck. 4. An automatic mechanical pencil according to claim 2, wherein said mouth piece has a connecting pipe for connecting to the main body at its rear portion, and said chuck, balls and chuck ring are provided within said connecting pipe. 5. An automatic mechanical pencil according to claim 2, wherein said slider has a guide pipe projecting from the tip of the mouth piece, and said guide pipe is formed with the thermoplastic material having the low coefficient of the friction. 6. An automatic mechanical pencil according to claim 2, wherein a push button is provided so as to engage with the rear end of said chuck, and by pushing said push button, said chuck may be shifted irrespective with the movement of said slider.

Inventors: SAKAOKA, GOUJI
Applicants: MICRO CO., LTD.
Application year: 1986
Main classification: B43K21
IPC codes: B43K21