Writing instrument

Abstract: A writing instrument comprising a tubular member (7) having a spiral groove (7a), an eraser guide member (8) having longitudinal guide grooves (8a), and an eraser holder (11) having projections (11a) slidably arranged in the guide grooves of the eraser guide member, and an eraser grip portion (11b) of the eraser holder. The eraser grip portion is capable of protruding beyond the rear end of the writing instrument when the eraser holder is at the most retreated position thereof so that an eraser can be projected from a rear end of the writing instrument.

Description: The present invention relates to a writing instrument which is capable of pushing out, as much as required, an elongated eraser through the rear end thereof, and more specifically, relates to a writing instrument of the type described above, which is convenient to use and which requires no complicated construction, a writing instrument excellent in productivity and capable of being produced at a low cost. In order to increase a usable portion of an eraser mounted on a writing instrument, various attempts have been made on the structure of a writing instrument of the type that contains an elongate eraser which can be pushed out as much as required. For example, Japanese Utility Model Publication (Unexamined) No.57-132598(1982) discloses a structure in which a spiral groove formed on the inner surface of the rear barrel is engaged with projections of an approximately cylindrical eraser holder. The projections protrude through a slit provided in the lead container, the eraser being pushed out by rotating the rear barrel. Further, Japanese Utility Model Publication No. 62-27438(1987) discloses a writing instrument structure enabling the eraser to be pushed out in the same manner as disclosed in the above-described publication No.57-132598 except that it utilizes the spiral groove of an elastic member in the form of a spiral tube and a longitudinal groove formed in the rear barrel. WO-A-86/03658 and US-A-3124245 show similar spiral arrangements to those discussed above, but in these references the advancing and retracting of lipsticks is involved. A principal object of the present invention is to provide a writing instrument which requires no complicated structure, and which excels in productivity and can be produced at low cost. According to the present invention there is provided a writing instrument comprising a tubular member having a spiral groove, an eraser guide member having at least one longitudinal guide groove, said tubular member being rotatable with respect to said eraser guide member, and an eraser holder having a projection slidably arranged in the or each guide groove of said eraser guide member, characterised in that the guide groove or guide grooves of the eraser guide member are closed at the ends thereof, that the guide member comprises a flange and an engagement shoulder formed thereon, and that a deformable securing member engages with said engagement shoulder of the guide member and an engagement flange of said tubular member. The invention also provides a writing instrument comprising a tubular member having a spiral groove, an eraser guide member having at least one longitudinal guide groove, said tubular member being rotatable with respect to said eraser guide member, and an eraser holder having a projection slidably arranged in the or each guide groove of said eraser guide member, characterised in that the guide groove or guide grooves of the eraser guide member are closed at the ends thereof, that the tubular member comprises a flange and an engagement shoulder formed thereon, and that a deformable securing member engages with said engagement shoulder of the tubular member and an engagement flange of said guide member. Preferred embodiments of the invention are described below with reference to the drawings, in which: Fig. 1-A is a sectional view of a writing instrument according to a first embodiment of the present invention; Fig. 1-B is a sectional view of the securing member of the embodiment shown in Fig. 1-A; Fig 2 is a sectional view illustrating the deforming operation of the eraser guide member; Fig. 3 is a sectional view of an embodiment employing a securing member which has elasticity in the longitudinal direction; Figs. 4-A and 5-A are sectional views illustrating embodiments employing the securing members shown in Figs. 4-B and 5-B, respectively; Fig. 6 is a sectional view showing a ring provided for the purpose of preventing the securing member from being detached; and Figs. 7-A and 7-B are schematic views showing modifications of the essential parts of the securing member. Fig. 1-A shows a writing instrument according to a first embodiment of the present invention. A front metal section 43 having a well-known lead detent member 42 is screwed on the front portion of the barrel 41. Inside the barrel 41 is provided a lead container 45 including an adjacent chuck 44 at the front end portion thereof. A spiral spring S is provided between the lead container 45 and the barrel 41, and a chuck ring 46 is slidably fitted over the front portion of the chuck 44. A tubular member 47 having a spiral groove 47a is held between a rear end flange 48b of an eraser guide member 48 and a securing member 50. The eraser guide member 48 has longitudinal guide grooves 48a and is irrotatably arranged between the barrel 41 and the lead container 45. The rear end flange 48b serves to prevent an eraser holder 51, which is to be described later, from being broken. The securing member 50 is composed of a deformable C-ring (see Fig. 1-B) engaged with an engagement shoulder 49 of an eraser guide member 48 and a flange 49A of the tubular member 47, and has a cutout. The section of the ring may be circular or polygonal, and the cutout may not be provided if the securing member itself has elasticity in the radial direction. The tubular member 47 is rotatably arranged with respect to the eraser guide member 48. The flange 48b may be formed as a member independent of the eraser guide member 48. The flange 48b and the engagement shoulder 49 may be provided in the tubular member, with the flange 49A being on the eraser guide member 48 (see Fig. 5-A). An eraser holder 51 is adapted to secure the eraser 10, and projections 51a of the eraser holder 51 protrude through the guide grooves 48a of the eraser guide member 48 and engage with the spiral groove 47a of the tubular member 47. The assembly method will now be explained with respect to the above-described construction. Fig. 1-A shows a push-type mechanical pencil, in which the mechanism of the mechanical pencil in the front section is separated from the eraser pushing-out mechanism in the rear section. The front section has a known mechanical pencil mechanism, so that only the rear section, i.e. the eraser pushing-out mechanism, will be described. First, the eraser holder 51 is inserted through the guide groove 48a of the eraser guide member 48 and slidably arranged with respect to the eraser guide member 48. If the guide groove 48a is formed integrally with the flange 48b (see Fig. 2), a desirable effect may be obtained in that the eraser holder is kept from being detached and the number of parts and elements can be reduced. If the portion of the guide member 48 in the vicinity of the guide groove 48a is deformable, insertion of the eraser holder 51 is facilitated. A further desirable effect may be obtained by effecting chamfering or the like at the portion near where the guide groove 48a is in contact with the eraser holder 51. Subsequently, the tubular member 47 is inserted into the eraser guide member 48 at the front end thereof until it abuts the flange 48b. After that, the securing member 50 is engaged from the front end of the eraser guide member 48. It is secured when returning to its normal state. Finally, the eraser 10 is press-fitted into the eraser holder 51. The eraser pushing out operation will now be explained with respect to the above-described structure. When the tubular member 47 is rotated with respect to the barrel 41, the projections 51a of the eraser holder 51 protruding beyond the guide grooves 48a of the eraser guide member 48, which is irrotatably arranged to the barrel 41, move along the spiral groove 47a of the tubular member 47. This movement causes the projections 51a to move backward along the guide grooves 48a. In other words, the eraser holder 51 carrying the eraser 10 moves backwards, causing the eraser 10 to protrude beyond the rear end of the mechanical pencil. It is desirable, that, as shown in Fig. 3, a member which has elasticity in the longitudinal direction, for example, a coil spring, a one-turn spring (Fig. 3), or a ring having a plurality of flanges 50a (Fig. 4-B) or claws (Fig. 5-B) be adopted as the securing member 50. By using the securing member 50 as described, any clearance generated between the flange 48b and the tubular member 47 held between the flange 48b and the securing member 50 by errors during production can then be prevented from causing looseness as much as possible since the elasticity of the securing member 50 will allow the tubular member 47 to always abut against the flange. Further, the setting of the rotational loads, which has been conventionally effected by friction, can then be conducted by adjusting the elasticity of the securing member, so that stable rotational loads can be obtained. Further, it is desirable to fix a ring 55 restraining the radial movement of the fixed securing member 50, as shown in Fig. 6, because this prevents the securing member from being detached. Further, if, as shown in Fig. 7-A, continuous recesses 53a and projections 53b are provided in the tubular member 47 engaged with the securing member 50 and the engagement shoulder 49 or the opposing shoulder of the eraser guide member 48, respectively, it becomes possible to effect an appropriate resistance when rotating the tubular member 47, so that any unnecessary rotation during the eraser projection operation can be prevented as possible. The number of the recesses 53a and the projections 53b may be one or more for each. Furthermore, by adjusting the configuration and the number of the recesses 53a and projections 53b and the configuration of the securing member (for example, projections 54 may be provided in a ring 50, as shown in Fig. 7-B), a click-clack sound will be given during the rotation, thus providing an excellent feel in using. Further, a similar effect can also be obtained when the recesses and the projections are formed by the combination of flange 48b of the eraser guide member 48 and a part of the tubular member 47 abutting the flange 48b. Thus, the above-described writing instrument has a simple construction in which a flange and an engagement shoulder are formed in either the tubular member or the eraser guide member, and the tubular member is rotatably secured to the eraser guide member by merely engaging a deformable securing member with the engagement shoulder. Thus, the tubular member is then held between the flange and the securing member. Accordingly, the writing instrument of the present invention is easily assembled. Moreover, since the securing member is positively engaged with the engagement shoulder, securing reliability can be maintained for a long period of time. While the above-described writing instruments are of the type in which the tubular member having a spiral groove is provided exteriorly and the eraser guide member having guide grooves is provided interiorly, the eraser guide member may, as to the case with the prior art shown, be provided exteriorly (the guide grooves are then formed into longitudinal grooves, instead of slit-like ones) and the tubular member having a spiral groove may be provided interiorly. The spiral groove can then be a spiral tube. However, it is more desirable to form the longitudinal guide grooves of the eraser guide member shown in Fig. 2 into spiral grooves so that any looseness in using the eraser may be avoided.

Claims: A writing instrument comprising a tubular member (47) having a spiral groove (47a), an eraser guide member (48) having at least one longitudinal guide groove (48a), said tubular member (47) being rotatable with respect to said eraser guide member (48), and an eraser holder (51) having a projection (51a) slidably arranged in the or each guide groove (48a) of said eraser guide member (48), characterised in that the guide groove or guide grooves (48a) of the eraser guide member are closed at the ends thereof, that the guide member (48) comprises a flange (48b) and an engagement shoulder (49) formed thereon, and that a deformable securing member (50) engages with said engagement shoulder (49) of the guide member (48) and an engagement flange (49A) of said tubular member (47). A writing instrument comprising a tubular member (47) having a spiral groove (47a), an eraser guide member (48) having at least one longitudinal guide groove (48a), said tubular member (47) being rotatable with respect to said eraser guide member (48), and an eraser holder (51) having a projection (51a) slidably arranged in the or each guide groove (48a) of said eraser guide member (48), characterised in that the guide groove or guide grooves (48a) of the eraser guide member are closed at the ends thereof, that the tubular member (47) comprises a flange (48b) and an engagement shoulder (49) formed thereon, and that a deformable securing member (50) engages with said engagement shoulder (49) of the tubular member (47) and an engagement flange (49A) of said guide member (48). A writing instrument according to claim 1 or 2, wherein the securing member (50) has elasticity in the longitudinal direction. A writing instrument as claimed in claim 1 or 2, wherein the portion of the eraser guide member (48) in the vicinity of the guide grooves (48a) thereof or the portion of the tubular member (47) in the vicinity of the spiral groove (47a) thereof is deformable.

Inventors: NAKAJIMA KAZUMI, NAKAJIMA, KAZUMI
Applicants: PENTEL KK, PENTEL KABUSHIKI KAISHA
Application year: 1988
Main classification: B43K29
IPC codes: B43K21, B43L19, B43K29, B43K24