JP3602213B2 - Double writing instrument - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to the provision of a double-type writing instrument in which the tips of three types of writing objects are made to be able to come and go alternately at a tip end of a front shaft, and an eraser is made to come and go through a rear end hole of a crown.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an example of a double writing instrument, as shown in Japanese Utility Model Application Laid-Open No. 64-3491 by the same applicant, a guide having a sliding groove for guiding two writing bodies and being fixed to a front shaft is described. At the front end, a cam and a cam slope contacting a sliding piece attached to two writing bodies fitted to the guide cylinder are provided, and the rear end forms a knocking part and is movable in the axial direction with respect to the cap. And a cylindrical cam mounted so that the rotation in the circumferential direction is integrated, and the two writing bodies can be selectively protruded and retracted at the front end of the front shaft by rotating the cap with respect to the front shaft. There is a writing implement. Further, as a conventional example of the present application, as shown in Japanese Utility Model Application Laid-Open No. 60-120889 by the present applicant, there is a double writing instrument in which a crown protruding from a rear end of a cap is rotated to make an eraser appear and disappear. . Also, when three types of cursive characters can be selected in the conventional example, the first and third cursive characters are clearly positioned by the rotation restriction of the cylindrical cam, but the second cursive character is selected. The positioning becomes ambiguous and it is troublesome to consciously position.
[0003]
[Problems to be solved by the invention]
The above conventional example has a problem that metal parts are used in many parts, the structure is complicated, the number of parts increases, and the cost increases. In addition, there is a difficulty in design flexibility because the cap is long with respect to the front shaft, and the rotation operation is performed by gripping the shaft tip with one hand and the rear end of the shaft with the other hand by the operation of writing and retracting cursive writing Therefore, there is a disadvantage that the usability is poor.
Furthermore, the purpose of the present application is to make it possible to select three more convenient types of writing, and to make it possible to select the more frequently used first and second types of writing by clearly controlling the rotation of the cylindrical cam. The third object is to enable easy selection of the third cursive if necessary.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the dual writing instrument of the present invention has a guide portion which is fixed to a front end of a resin shaft and a front end of a resin center shaft so as to be non-rotatable and non-removable, and integrated with the center shaft. In each of the three guide grooves, three types of writing bodies are fitted in such a way that they can move back and forth by urging a return spring between the guide part and the sliding piece, and the cam slope displaced in the axial direction is a front end part. The cylindrical cam provided in a circumferential shape is rotatably retained with respect to the central shaft, and each sliding piece is alternately moved back and forth by rotation of the cylindrical cam with respect to the front shaft or the central shaft by contacting the sliding piece with the cam slope, In a double-type writing instrument in which the tip of each writing body can be selectively protruded and retracted from a tip end of a front shaft, an eraser feeding device integrally connected in the axial direction behind a cylindrical cam is provided, and a cylindrical cam and an eraser are provided. Cover the feeding device and make the rear shaft made of resin The rear end of the eraser feeding device is appropriately projected from the rear shaft rear end hole, and the cylindrical cam is integrally formed with the rear shaft in the rotation direction. The sliding shaft is moved back and forth alternately by the rotation of the rear shaft with respect to the center shaft, so that the tip of each writing body can be projected from the front shaft front end opening, and the rear end of the eraser feeding device with respect to the rear shaft is rotated. Is configured so that the eraser can appear and disappear,
[0005]
With the rotation of the cylindrical cam with respect to the central shaft, a projection provided on the outer peripheral side surface of the cylindrical cam fits into a peripheral groove formed on the outer peripheral side surface of the central shaft so that the cylindrical cam is prevented from coming off with respect to the central shaft and the tip of the cylindrical cam. A circumferential groove is formed so that each writing body projects from the front end of the front shaft in a range of approximately 240 degrees, and a rear wall of the circumferential groove is formed at a position where the second writing body projects, that is, at a position of approximately 120 degrees. A step is formed on the step, and the projection abuts on the step to prevent rotation of the cylindrical cam. When the cylindrical cam is shifted in a predetermined range in conjunction with the rear shaft, the contact is released. A double writing implement characterized in that the cylindrical cam is rotatable by approximately 120 degrees and the third writing body can be protruded.
[0006]
As described above, the composite writing instrument of the present invention has a simple structure with a reduced number of parts, and therefore can be easily assembled and cost can be reduced. In addition, since the length of the rear shaft (cap) can be set to an appropriate length, there is flexibility in design, and the rotation operation is facilitated.
In addition, the first and second writing bodies, which are more frequently used, can be clearly selected by restricting the rotation of the cylindrical cam, and the third writing body can be easily selected if necessary.
[0007]
【Example】
First, FIGS. 1 to 6 show an embodiment of the present invention, and FIG. 1 shows a first embodiment. The compound writing instrument according to the first embodiment includes a center shaft 1, a front shaft 3, a cylindrical cam 5, a pair of sliding pieces 6a, 6b, 6c (not shown) integrally provided with a guide cylinder 2, a mechanical pencil writing body. 7, writing elements 8a and 8b such as a ballpoint pen, an inner cylinder 34, an eraser holder 40, and an eraser 45 are main components. First, the center shaft 1 is made of resin, and as shown in FIGS. 1 and 4, axially long guide grooves 9a, 9b, 9c which are opened from the center to the rear end are located at 120 degrees in the circumferential direction. And a guide cylinder 2 is provided. The front half of the guide cylinder 2 is provided with a cylinder part 10 having a partition part 16 having holes 32a, 32b, 32c (not shown) communicating with the respective guide grooves 9a, 9b, 9c and having an open front end. A stepped portion 31 is formed at the rear end of the cylindrical portion 10, and a bulging engagement portion 13 is formed on a front outer peripheral portion of the stepped portion 31. In addition, it is also possible to form a guide part for guiding the sliding piece by integrally forming a rib or a partition part on the inner periphery of the center shaft 1.
It is also possible to provide a guide cylinder separately from the center shaft 1 and fix them together.
[0008]
On the rear side surface of the center shaft 1, as shown in FIG. 3, a vertical groove 18 is connected to the circumferential groove 19 via the inclined surface 50, and a substantially L-shaped window is formed. Have been. As will be described later, the projection 17 of the cylindrical cam 5 is inserted from the vertical groove 18, and the projection 17 elastically expands the inclined surface 50, passes through the narrow portion 51, and enters the circumferential groove 19. The cylindrical cam 5 rotates approximately 240 degrees while the projection 17 abuts on the rear wall in the circumferential direction of the circumferential groove 19, and the writing portions of the writing materials 8a and 8b such as the mechanical pencil 7 and the ballpoint pen alternately extend from the front end of the front shaft. Will be haunted. The circumferential groove 19 is provided with a wide groove 52 so that the cylindrical cam 5 can move axially at the position of the projection 17 when the mechanical pencil 7 protrudes. , 8b protrudes, the front wall 55 restricts the axial transition by the narrow grooves 53a, 53b.
A step 54b is formed at the connection between the rear walls 54a and 54c so that the side surface of the projection 17 abuts so that the cylindrical cam 5 is prevented from rotating at the position of the projection 17 when the ballpoint pen 8a projects. . The rotation range of the cylindrical cam 5 up to the step 54b is approximately 120 degrees.
[0009]
The front end of the tip shaft 3 is tapered, and has a step 27 at the tip of the inner hole. In the rear end hole, an engagement groove 12 is provided which engages with an engagement portion 13 provided on an outer peripheral portion of the cylindrical portion 10 of the guide cylinder, and prevents the cylindrical portion 10 from slipping out and rotating. . The cylindrical portion 10 and the front shaft 3 are detachably fixed by an appropriate force. (Same as the configuration of the front shaft in Japanese Utility Model Laid-Open No. 64-3491) The connection between the front shaft 3 and the center shaft 1 may be a screw connection.
[0010]
The cylindrical cam 5 has a cylindrical shape, and has a cam slope 14 that is displaced circumferentially back and forth at the front end edge, and a notch 15 is formed at the foremost end of the cam slope 14. On the side surface of the cylindrical cam 5, there is formed a projection 17 which is inserted into the vertical groove 18 of the center shaft 1 and elastically fits into the circumferential groove 19 to rotate and prevent it from falling within a certain range (approximately 240 degrees). .
The cylindrical cam 5 has a cylindrical portion 20 extending behind the step portion 20a, and a spiral groove 33 is formed in an inner hole of the cylindrical portion 20.
[0011]
The sliding piece 6a has a projection 22a on the outer surface, a central portion protruding from the rear end surface of the projection 22a, and both sides thereof have a cam slope having substantially the same slope as the cam slope 14 of the cylindrical cam 5 described above. are doing. Further, a hole is provided which is in contact with the flange portion 24 of the core pipe 23 to protrude and fit the rear of the core pipe 23 long. The sliding piece 6b has a projection 22b and a cam slope like the sliding piece 6a, and has a locking portion 26 at its tip for fixing the rear end of the writing body 8a such as a ball-point pen. Incidentally, the engaging portion may be formed in a pipe shape and the rear end of the writing body may be fitted. A sliding piece 6c (not shown) is formed in the same manner as the sliding piece 6b, and a writing body 8b such as a ballpoint pen is connected.
[0012]
The mechanical pencil 7 has a built-in general chuck mechanism, is joined to the core pipe 23 via a joint 29 connected to the chuck mechanism at the rear end, and comes into contact with a flange portion 24 provided behind the core pipe 23. The sliding piece 6a is fitted to the sliding piece 6a, and the rear end hole of the core pipe 23 projecting from the rear end of the sliding piece 6a is closed by a tail plug 25 or the like. The leading of the lead is performed by moving the chuck by the axial movement of the sliding piece 6 a in a state where the step 28 at the tip of the mechanical pencil 7 is in contact with the inner step 27 of the front shaft 3.
[0013]
Meanwhile, in the center shaft 1, a circumferential flange 1a is formed on a front side of the circumferential groove 19 as appropriate, and a protruding locking portion 1b is formed near the rear of the flange 1a. A circumferential groove-shaped engaging portion 4c is formed in a front end inner hole of the rear shaft 4, and a step portion 4b and an axial rib 4a are formed in the rear inner hole. A flange 20b is formed on the peripheral surface of the cylindrical portion 20 of the cylindrical cam, and an axial groove 21 is formed behind the flange 20b. The rear shaft 4 is fitted so as to cover the cylindrical portion 20, the rib 4a is fitted into the groove 21, the step portion 4b is substantially in contact with the flange portion 20b, and the locking portion 4c is It elastically engages with the locking portion 1b. As described above, the rear shaft 4 can be axially shifted with respect to the center shaft 1 within a range where the front end of the rear shaft 4 abuts on the flange portion 1a. The rotation is stopped.
[0014]
The inner cylinder 34 is a cylindrical body made of resin, has a flange-shaped crown 35 at the rear end, and has a bottom 37 at the front and a locking portion 38 at the tip. A pair of opposed slits 36 are formed in the side surface of the cylindrical portion connecting the crown 35 and the bottom 37. An eraser holder 40 having an eraser 45 fixed to the rear end is mounted in the inner cylinder. The eraser holder 40 is formed with a pair of elastic pieces 43 that sandwich the eraser 45 at the rear, and has an engaging projection 44 on the inner surface of the elastic piece 43. A projection 42 is formed on the outer periphery of the front tubular portion 41. The eraser holder 40 has the projection 42 and the elastic piece 43 fitted in the slit 36 of the inner cylinder portion, and is disposed on the inner cylinder 34 with the projection 42 further fitted in the spiral groove 33.
[0015]
As described above, the inner cylinder 34 is fitted to the cylindrical section 20 of the cylindrical cam while appropriately rotating the projection 42 of the eraser holder so as to engage with the spiral groove 33 of the cylindrical section 20, and the crown 35 is attached to the cylindrical section 20. Abuts on the rear end of the inner cylinder 34, and the engaging portion 38 of the inner cylinder is engaged with a step 39 provided in front of the inner hole of the cylinder 20, so that the inner cylinder 34 is prevented from coming off only in rotation with respect to the cylinder 20. You. As described above, when the crown 35 is rotated with respect to the rear shaft 4, the eraser holder 40 moves back and forth, so that the eraser 45 can protrude and retract from the rear end hole 35a of the crown.
[0016]
Next, a description will be given in assembling order. In the drawing body 7 such as the mechanical pencil 7 and the writing bodies 8a and 8b such as a ball-point pen, the respective sliding pieces 6a, 6b and 6c are connected to the rear end, and each of the guide shafts 2 of the above-mentioned center shaft is connected. A return spring fitted movably in the guide grooves 9a, 9b, 9c and interposed between the front end faces of the sliding pieces 6a, 6b, 6c and the partition portions 16 on the front surfaces of the guide grooves 9a, 9b, 9c. It is urged rearward by 30a, 30b, 30c. Subsequently, the cylindrical cam 5 is inserted into the rear end hole of the center shaft 1 so that the projection 17 is elastically fitted into the circumferential groove 19, and is rotatable at approximately 240 degrees in the circumferential direction with respect to the center shaft 1 and is prevented from falling off. It is fixed. Further, with the mechanical pencil 7 protruding, the cylindrical cam 5 can be moved back and forth with respect to the center shaft 1 by the stroke required for centering, so that the cylindrical cam 5 can be moved when the writing body is stored or the writing body 8a, 8b such as a ball-point pen. It moves back and forth slightly in a protruding state.
Also, since the sliding pieces 6a, 6b, 6c are constantly urged rearward by the return springs 30a, 30b, 30c, the cam slopes of the projections 22a, 22b, 22c are always applied to the cam slope 14 of the cylindrical cam 5. Maintains contact.
[0017]
Also, with the rear end surface of the front shaft 3 in contact with the front surface of the step portion 31 of the center shaft 1, the engaging portion 13 of the cylindrical portion 10 is elastically fitted into the engaging groove 12 of the front shaft 3. The shaft 3 and the center shaft 1 are fixed in a state where they are stopped and prevented from coming off. The tip shaft 3 is detachable with an appropriate force. In this state, when the cylindrical cam 5 is rotated in one direction with respect to the front shaft 3 or the center shaft 1, the sliding piece 6a moves forward and the notch 15 at the foremost end of the cam slope 14 of the cylindrical cam 5 becomes one of the mechanical pencils. 7 is locked to the projection 22a of the sliding piece 6a, and the writing tip projects from the tip end of the front shaft. When the cylindrical cam 5 is rotated in the other direction with respect to the front shaft 3 or the center shaft 1, the sliding piece 6a is retracted so that the writing tip of the mechanical pencil 7 penetrates from the tip of the front shaft and the sliding piece is moved. 6b advances, and the writing tip of the first writing body 8a such as a ballpoint pen projects from the tip end of the front shaft. At that time, the projection 17 of the cylindrical cam comes into contact with the step 54b of the circumferential groove 19 as described above. In this state, when the rear shaft 4 is advanced with respect to the center shaft 1 and the front end is brought into contact with the flange 1a of the center shaft, the contact between the projection 17 and the step portion 54b is released, and the cylindrical cam is rotated as it is. Then, the sliding piece 6b is retracted, the writing tip of the writing body 8a such as a ball-point pen is immersed from the tip end of the tip shaft, and the sliding piece 6c is advanced and the writing tip of the second writing body 8b such as a ball-point pen is moved. Protrudes from the tip end of the front shaft.
[0018]
Next, the rear shaft 4 is fixed to the center shaft 1 in a state where the rear shaft 4 is in contact with the flange portion 1a of the center shaft 1 while covering the cylindrical portion 20 behind the cylindrical cam. In this state, the rear cam rib 4a of the cylindrical cam 20 is fitted in the groove 21 of the cylindrical shaft, and the cylindrical cam 5 is stopped from rotating with respect to the rear shaft 4 so that it can only move forward and backward. The means for stopping the rotation of the rear shaft 4 and the cylindrical cam 5 can be provided in addition to the above for convenience of design.
On the other hand, the eraser holder 40 with the eraser 45 fixed thereto is inserted into the inner cylinder 34 while being rotated while being rotated from the rear end of the cylindrical section 20 of the cylindrical cam, and the front end of the crown 35 is In a state of being in contact with the rear end, it is fixed to the cylindrical portion 20 so as to be able to rotate only in the rotation direction. As described above, when the crown 35 is rotated left and right with respect to the rear shaft 4, the eraser 45 protrudes and retracts from the rear end hole 35a of the crown.
[0019]
FIGS. 5 and 6 show another example of the engagement state between the projection 17 of the cylindrical cam and the center shaft 1 #. In this case, as a means for fitting the protrusion 17 into the circumferential groove 60, a partition wall 62 having an inclined surface 63 is provided on the upper wall of the guide groove 61 for fitting the protrusion 17 from the rear end of the central shaft 1 #. . The reason for providing the partition wall 62 is to enhance the rigidity of the center shaft 1 ° at the engaging portion.
[0020]
FIG. 2 shows a second embodiment of the present invention, which is basically the same as the first embodiment. Hereinafter, only the differences will be outlined.
First, a spiral groove 76 is formed in a tube portion inner hole in front of the inner tube 75. A shaft portion 71 is provided on the outer periphery of the substantially central portion of the cylindrical cam 70 in the longitudinal direction, and the inner hole of the rear shaft 74 and the shaft portion 71 for stopping the rotation so as to allow only the forward and backward movement. Between the shaft portion 71 and the inner hole of the rear shaft 74, engagement between a rib and a groove, a modified cross-sectional shape, or the like is performed. (Not shown)
Further, a locking portion 72 is formed near the rear end of the shaft portion 71, and a tubular portion having a slit 73 formed further extends rearward.
The inner cylinder 75 is provided with a locking portion 78 which is fitted to the cylindrical portion of the cylindrical cam having a slit and is locked to the locking portion 72 of the cylindrical cam so as to be rotatable only in the rotation direction. Is projected from the rear end of the rear shaft 74.
As described above, when the crown 77 is rotated right and left with respect to the rear shaft 74, the eraser can be protruded and retracted from the rear end hole.
[0021]
By the way, the mechanical pencil 7 is a first script, a pen such as a ballpoint pen 8a is a second script, and a pen 8b such as a ballpoint pen is a third script.
In addition, according to the specification, three kinds of cursive writing materials such as three kinds of mechanical pencils with different core diameters and core colors, three kinds of ballistic pens with different ball diameters and ink colors, according to the specifications, Alternatively, it is provided with three kinds of cursive characters combining a cursive character such as a mechanical pencil and a ballpoint pen.
[0022]
[Action]
First, in the first embodiment, when the rear shaft 4 is rotated in one direction with respect to the front shaft 3 or the center shaft 1, the notch 15 provided at the tip of the cam slope 14 of the cylindrical cam 5 as shown in FIG. The writing tip of the mechanical pencil 7 is engaged with the sliding piece 6a of the writing instrument 7 to protrude from the tip end of the front shaft. At this time, the protrusion 17 of the cylindrical cam 5 is located in the wide groove 52 in the circumferential groove 19 of the center shaft 1. In this state, when the rear end of the crown 35 is knocked and the cylindrical cam 5 is moved axially, the operation is transmitted to the sliding piece 6a, the core pipe 23, and the mechanical pencil 7, and the step 28 of the writing tip is moved. From the state of contact with the inner step portion 27 of the front shaft 3, the chuck and the joint 29 are axially moved and the lead is fed out. When the rear shaft 4 is rotated in the other direction with respect to the front shaft 3 or the center shaft 1, the mechanical pencil writing body 7 is retracted, and the writing tip of the writing body 8a such as a ball-point pen protrudes from the front shaft tip opening. At this time, the projection 17 of the cylindrical cam comes into contact with the step 54b of the circumferential groove, so that the positioning is clearly performed. Further, from this state, when the front end of the rear shaft 4 is brought into contact with the flange portion 1a of the center shaft and further rotated, the writing body 8a such as a ball-point pen retreats. Protrude.
[0023]
Next, when the crown 35 is rotated left and right with respect to the rear shaft 4, the eraser holder 40 moves back and forth, and the eraser 45 comes out and retracts from the rear end hole 35a.
Further, the second embodiment is the same as the first embodiment, and the description thereof will be omitted.
[0024]
【The invention's effect】
As described above, the present invention is different from the conventional example in that metal is replaced with resin, the number of parts is omitted, the structure is simplified, and assembling is facilitated and cost reduction can be achieved. In addition, since the length of the rear shaft (cap) can be set to an appropriate length, there is flexibility in design, and the rotation operation is facilitated.
Further, more convenient three types of writings can be selected, and the first and second writings, which are frequently used, can be clearly selected by restricting the rotation of the cylindrical cam. 3 can be easily selected.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional longitudinal sectional view showing the entire first embodiment of the present invention.
FIG. 2 is a partial cross-sectional longitudinal sectional view showing the entire second embodiment of the present invention.
FIG. 3 is an explanatory view showing an engagement state between a projection of a cylindrical cam and a peripheral groove of a center shaft.
FIG. 4 is a cross-sectional view of a guide cylinder.
FIG. 5 is an explanatory view showing another example of the state of engagement between the projection of the cylindrical cam and the peripheral groove of the center shaft.
FIG. 6 is a cross-sectional view of a main part of an engaging portion in FIG.
[Explanation of symbols]
Reference Signs List 1 center shaft 1ａ center shaft 1a flange portion 1b locking portion 2 guide cylinder 3 front shaft 4 rear shaft 4a rib 4b step portion 4c locking portion 5 cylindrical cam 6a sliding piece 6b sliding piece 6c sliding piece 7 Mechanical pencil pencil 8a Writing body such as a ballpoint pen 8b Writing body such as a ballpoint pen 9a Guide groove 9b Guide groove 9c Guide groove 10 Cylindrical part 11 Knock spring 12 Engagement groove 13 Engagement part 14 Cam slope 15 Notch 16 Partition part 17 Projection 18 Vertical groove 19 Peripheral groove 20 Tube 20a Step 20b Flange 21 Groove 22a Projection 22b Projection 22c Projection 23 Core pipe 24 Flange 25 Tail plug 26 Locking part 27 Inner step 28 Step 29 Joint 30a Return spring 30b Return spring 30c Return spring 31 Step 32a hole 32b hole 32c hole 33 spiral groove 34 inner cylinder 35 crown 35a rear end hole 36 slit 37 bottom 3 Locking portion 39 step portion 40 eraser holder 41 cylindrical portion 42 projection 43 elastic piece 44 locking protrusion 45 eraser 50 inclined surface 51 narrow portion 52 wide portion 53a narrow groove 53b narrow groove 54a rear wall 54b step 54c rear Wall 55 Front wall 60 Peripheral groove 61 Guide groove 62 Partition wall 63 Inclined surface 70 Cylindrical cam 71 Shaft portion 72 Locking portion 73 Slit 74 Rear shaft 75 Inner tube 76 Spiral groove 77 Crown 78 Locking portion

Claims (6)

The front end of the resin-made front shaft and the front end of the resin-made middle shaft are fixed to each other so as to be non-rotatable and non-removable, and three types of writing bodies are slid in the three guide grooves of the guide portion integrated with the middle shaft. A return spring is urged between the moving piece and it is fitted so that it can move back and forth, and a cylindrical cam that has a cam slope that displaces in the axial direction at the front end is prevented from coming off rotatably with respect to the center shaft. By making each sliding piece abut on the cam slope, the cylindrical cam is rotated back and forth alternately with respect to the front shaft or the center shaft, so that the tip of each writing body can be selectively protruded and retracted from the front end of the front shaft. In the compound writing instrument, an eraser feeding device integrally connected in the axial direction is provided behind the cylindrical cam, and a resin rear shaft covering the cylindrical cam and the eraser feeding device is provided at a predetermined position behind the center shaft. It is fixed so that it can rotate with the axis change of the range The rear end of the eraser feeding device protrudes from the rear shaft rear end hole as appropriate, and the cylindrical cam is integrally formed in the rotation direction with respect to the rear shaft. By moving, the tip of each writing body can be protruded from the tip end of the front shaft, and the eraser can be extended and retracted by rotating the rear end of the eraser feeding device with respect to the rear shaft. Double writing instrument. The three types of cursives include three types of mechanical pencils with different core diameters or core colors, three types of ballistics such as ballpoint pens with different ball diameters or ink colors, or three types of mechanical typefaces such as mechanical pencils and ballpoint pens. The double-type writing instrument according to claim 1, wherein the writing instrument is composed of three kinds of writing objects combined. 2. The dual writing implement according to claim 1, wherein at least when the mechanical pencil is selected, the cylindrical cam is shifted with respect to the center axis and the rear axis so that the core can be extended. With the rotation of the cylindrical cam with respect to the central shaft, a projection provided on the outer peripheral side surface of the cylindrical cam fits into a peripheral groove formed on the outer peripheral side surface of the central shaft so that the cylindrical cam is prevented from coming off with respect to the central shaft and the tip of the cylindrical cam. A circumferential groove is formed so that each writing body projects from the front end of the front shaft, and rotates at approximately 240 degrees, and the rear wall of the circumferential groove extends at a position where the second writing body projects, that is, at approximately 120 degrees. A step is formed on the step, and the projection abuts on the step to prevent rotation of the cylindrical cam. When the cylindrical cam is shifted in a predetermined range in conjunction with the rear shaft, the contact is released. 2. The dual writing implement according to claim 1, wherein the cylindrical cam is rotatable by approximately 120 degrees so that the third writing body can be protruded. In the above-mentioned eraser feeding device, a spiral groove is formed in a cylindrical portion inner hole portion behind the cylindrical cam, and an inner cylinder having a long slit extending from a front end to a rear end crown is fitted in the cylindrical portion, and a rear portion of the cylindrical portion is formed. The crown is abutted on the end and it is locked so that it can only rotate with respect to the cylinder, and the inner cylinder has an elastic part that sandwiches the eraser backward and an eraser holder with a projection on the front cylinder. The projection according to claim 1, wherein the projection is mounted in a state of being fitted into the slit and the spiral groove, and the eraser is configured to be able to protrude and retract from the rear end hole of the crown by rotating the crown with respect to the rear shaft. 4. The double-type writing implement according to 4. In the above-mentioned eraser feeding device, a slit is provided in a cylindrical portion extending rearward of the cylindrical cam, and an eraser holder having an eraser fixed to the rear of the cylindrical portion fits a projection provided on an outer periphery thereof into the slit of the cylindrical portion. A resin inner cylinder with a spiral groove in the inner hole is fitted around the outer periphery of the cylindrical part, and it is locked on the outer periphery of the cylindrical part so that it can only rotate. The rear end of the inner cylinder is protruded from the rear end of the rear shaft as appropriate, and a crown is provided. The rotation of the crown with respect to the rear shaft allows the eraser to protrude and retract from the rear end hole of the inner cylinder. The compound writing implement according to claim 1, wherein

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