Drawing device for use in drafting machine

Abstract: A drawing device for use in a drafting machine comprising:- a length of casing (5); a lead guide (20) fixedly secured to a leading end of the casing; a pipe member (6) inserted from an other end of the casing into the same in such a manner as to be axially slidably movable freely; a chuck ring (29) fixedly secured to the interior of a leading end portion of the pipe member; a sleeve (7) fitted closely over and fixedly secured to the outer peripheral surface of an other end side portion of the pipe member; a lead stock (8) inserted from the other end side of the pipe member into the same in such a manner as to be slidably moved freely; and a lead chuck (30) fixedly secured to a leading end portion of the lead stock in such a manner that its leading end side portion may be radially deformed or expanded and contracted in cooperation with the chuck ring, and being characterized in that it further comprises : a regulating piece (9) fitted over a rear end of the lead stock in such a manner as to be slidably movable freely by a predetermined stroke; and an auxiliary compression coiled spring (11) mounted between the regulating piece and the sleeve so as to normally bias the regulating piece towards the longitudinal rear end side of the lead stock.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a drawing device for use in a drafting machine, and more particularly to a drawing device arranged such that a lead can be thrust out continuously and sequentially and drawing operation can be conducted with a sufficient drawing pencil depressing pressure. 2. Description of the Prior Art. Drawing devices for use in drafting machines adapted to thrust a pencil lead automatically and sequentially are known, for example, from Japanese Patent Publication NO. SHO 57-36879. DE-A-3 013 973 describes a drawing device for use in a drafting machine, in which a first solenoid moves a lead stock downwards relative to a pipe member against the force of a first compression spring, so that a lead chuck expands and releases the lead, which moves slidably downwards by gravity, to a lead guide. A second solenoid releases a coupling between the pipe member and a holder unit so that the pipe member together with the lead stock may move downwards under the force of a further compression spring. A third solenoid effects retraction of the pipe member to an upper position. This arrangement has the disadvantage that it is somewhat complicated. Our own EP-0 213 621-A1 discloses a drawing device for use in a drafting machine comprising:- a base movable to any desired position; at least one holder unit mounted integrally on the base; at least one drawing pencil fixedly mounted on the holder unit; a driving arrangement capable of moving part of the drawing pencil longitudinally thereof relative to said base; stopper means adapted to limit the upward movement of movable component parts of said drawing pencil relative to the base; a casing fixedly secured to said holder unit; a lead guide fixedly secured to a lower end of the casing; a pipe member slidably mounted in said casing; a chuck ring fixedly secured to a lower end of the pipe member; a sleeve tightly fitted and fixedly secured to the outer peripheral surface of an upper part of the pipe member and connected to said driving arrangement; a lead stock slidably mounted in said pipe member and having a space for the leads and a lead insertion hole formed or perforated longitudinally in an upper part and a lower part, respectively; a lead chuck fixedly secured to a lower end of the lead stock and having a longitudinally extending lead insertion hole which communicates rectilinearly with the lead insertion hole in said lead stock, said lead chuck being capable of deforming or expanding and contracting radially so as to achieve its lead holding function in cooperation with said chuck ring; a first coiled spring mounted between said chuck ring and said lead stock so as to bias normally upwards the lead stock and the lead chuck relative to said pipe member and said chuck ring; and means for radially contracting the lead chuck to enable the lead to be held by the lead chuck when the latter is biased upwards by the resilient force of the first coiled spring relative to the chuck ring, characterised in that said lead guide has a large diameter hole, a small diameter hole, and a lead insertion hole formed continuously, concentrically and sequentially from the upper part to the lower part, said lead guide comprising: a holding cylinder tightly fitted in and fixedly secured to said large diameter hole; a lead holder bushing inserted in the holding cylinder and the small diameter hole so as to be moved up and down freely and having a large diameter outer peripheral portion kept in sliding contact with the inner peripheral surface of the holding cylinder on the side of the latter, an outer peripheral portion kept in sliding contact with the small diameter hole on the side of the latter, and a lead insertion hole formed in the central part thereof, said lead holder bushing being capable of slightly expanding and contracting in the radial direction; and a second coiled spring mounted between the annular lower surface of the large diameter outer peripheral portion of the lead holder bushing and the bottom surface of said large diameter hole so as to bias normally the lead holder bushing upwards, wherein the lead holding force afforded by the lead holding bushing is of a sufficient magnitude not only to prevent the lead from dropping by its own weight in the course of downwards movement of the lead, but also to enable the lead chuck with the lead held thereby to be moved upwards through the lead against the resilient force of the first coiled spring in the course of upward movement of the lead holder bushing by the resilient force of the second coiled spring, whilst with regard to the upward movement of the lead, in case the pipe member is moved upwards under the condition the lead is held, the lead holding force afforded by the lead holder bushing surpasses that given by the lead chuck so that the lead holding effect given by the lead chuck may be released or eliminated. Since such prior art drawing devices for use in drafting machines are not provided with any special mechanism to expel or remove the residual lead, it is necessary to conduct normal lead thrusting operations repeatedly to enable the residual lead to be pushed out by the next new lead. Therefore, the residual lead expelling operation per se is troublesome and takes a long time. As a drawing device for a drafting machine which solves such a disadvantage, there is proposed an arrangement shown in Japanese Utility Model Laid-open Publication NO. SHO 62-41585. This drafting device is arranged as shown in Fig. 6 such that a casing "b" provided at its leading end with a lead guide "a" is mounted on a base "c"; a pipe member "e" having on the leading end side thereof a chuck ring "d" fixedly secured thereto is inserted in the casing "b" so as to be vertically slidably movable freely. A lead stock "g" provided at a leading end with a lead chuck "f" is inserted in the pipe member "e" so as to be slidably movable freely; a coiled spring "h" is mounted between the lead stock "g" and the chuck ring "d" so as to bias and hold the lead chuck "f" at a position where it is radially deformed or contracted by the chuck ring "d". The base "c" is provided with a driving arrangement "i" for vertically moving the pipe member "e" and a stopper "j" for controlling the upward movement of the lead stock "g", the arrangement being made such that when the pipe member "e" is moved up and down by means of the driving arrangement "i" the lead can be thrust out sequentially, and when the pipe member "e" is moved further above a position where the lead stock "g" is abutted against the stopper "j" the lead chuck "f" is deformed so as to expand radially to thereby enable the next new lead to drop from the lead stock "g" and to abut against the residual lead. In such a drawing device for use in a drafting machine, since the lead thrusting operation is conducted by lowering the pipe member "e" so as to thrust a lead held by the lead chuck "f" out from the lead guide "a", and then raising the pipe member "e" to allow the lead chuck "f" to release the lead while the lead is held by the lead guide "a", if the lead holding force of the lead stock "f" is increased, that is the resilient force of the coiled spring is increased, then upon upward movement of the pipe member "e", the lead chuck "f" does not release the lead and is moved upwards together with the lead held thereby, thereby rendering it unable to thrust the lead out. Therefore, the lead holding force of the lead chuck "f" is set to be somewhat weak. Therefore, if lead powder deposits form on the lead chuck "f" or the diameter of the lead is thinner than a predetermined value, there is a tendency for the lead to move upwards relative to the lead chuck "f" by the action of the drawing pencil depressing pressure exerted on a drawing paper when drawing operation is conducted, thus rendering it unable to provide a sufficient drawing pencil depressing pressure. SUMMARY OF THE INVENTION The present invention has been contemplated in view of the above-mentioned circumstances and for eliminating the disadvantages in the prior art, and its object is to provide a drawing device for use in a drafting machine arranged such that the lead of a drawing pencil can be thrust out continuously and sequentially and drawing operation can be conducted with a satisfactory drawing pencil depressing pressure. To achieve the above-mentioned object, according to the present invention, there is provided a drawing device for use in a drafting machine comprising:- a length of casing fixedly secured to a base serving as a holder; a lead guide fixedly secured to a leading end of the casing; a pipe member inserted from an other end of the casing into the same in such a manner as to be axially slidably movable freely; a chuck ring fixedly secured to the interior of the leading end portion of the pipe member; a sleeve fitted closely over and fixedly secured to the outer peripheral surface of the other end portion of the pipe member, the sleeve being connected to a driving arrangement; a lead stock whose leading end is inserted from the other end of the pipe member into the same in such a manner as to be slidably movable freely and in opposed relationship to the rear end of the chuck ring, the lead stock having a central and axially extending lead insertion hole formed in the leading end side thereof, and also a lead stock space formed therein so as to extend axially from the lead insertion hole to the rear end of the lead stock; a lead chuck fixedly secured to the leading end portion of the lead stock in such a manner that its leading end portion may be radially deformed or expanded and contracted in cooperation with the chuck ring, the lead chuck having a centrally extending lead insertion hole formed therein and in aligned relationship with the lead insertion hole in the lead stock; a compression coiled spring mounted between the chuck ring and the lead stock so as to bias normally the lead stock and the lead chuck to the rear end side in the longitudinal direction relative to the pipe member and the chuck ring; and means for radially deforming or contracting the lead chuck to enable the lead chuck to hold a lead firmly when the lead chuck is biased to the rear end side relative to the chuck ring by the resilient force of the coiled spring, the drawing device being characterized in that it further comprises a regulating piece fitted over the rear end of the lead stock in such a manner as to be slidably movable freely by a predetermined stroke; an auxiliary compression coiled spring mounted between the regulating piece and the sleeve so as to normally bias the regulating piece towards the longitudinal rear end side of the lead stock; and a knocker movable up and down provided above said regulating piece so as to move the same down. As is apparent from the above-mentioned aspect, the drawing device for use in a drafting machine according to the present invention comprises a regulating piece mounted on an upper part of the lead stock so as to be slidably movable freely by a predetermined stroke, an auxiliary coiled spring mounted between the regulating piece and the upper end of the pipe member so as to bias the regulating piece upwards beyond the predetermined stroke, and a knocker for lowering the regulating piece, and is arranged such that when drawing operation is made the knocker is moved upwards away from the regulating piece so that the resilient force of the auxiliary coiled spring can be used as the lead holding force of the lead chuck, whilst when the lead is thrust out the regulating piece is moved downwards by means of the knocker so that the resilient force of the auxiliary coiled spring cannot be utilised as the lead holding force of the lead chuck. The above-mentioned and other objects, aspects and advantages of the present invention will become apparent to those skilled in the art when reference is made to the following description and accompanying drawings in which preferred embodiments incorporating the principles of the present invention are shown by way of example only. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a longitudinal sectional view showing a first embodiment of the present invention; Figs. 2, 3 and 4 are explanatory views showing operations of the first embodiment; Fig. 5 is a longitudinal sectional view showing a second embodiment of the present invention; and Fig. 6 is a longitudinal sectional view of a prior art example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail hereinbelow by way of several embodiments thereof with reference to the accompanying drawings. Referring to Fig. 1 which is a longitudinal sectional view of a drawing device for use in a drafting machine according to the present invention, the drawing device comprises a base 1 which serves as a holder movable by a moving arrangement, not shown, in any desired direction parallel to a drawing paper, and which has mounted thereon a drawing pencil 2, a driving arrangement 3, and a knocker 4. The drawing pencil 2 has a cylindrical casing 5 in which a pipe member 6 is slidably inserted. The upper, outer peripheral portion of the pipe member 6 projecting from the casing 5 has a sleeve member 7 integrally mounted thereon. Further, a lead stock 8 is slidably inserted in the inner periphery of the pipe member 6. Still further, a cylindrical regulating piece 9 is slidably fitted over the outer peripheral surface of the upper part of the lead stock 8, and a stopper 10 is fitted in and fixedly secured to the inner peripheral surface of the uppermost end of the lead stock 8. An auxiliary compression coiled spring 11 is provided between the sleeve member 7 and the regulating piece 9 in such a way as to bias the regulating piece 9 upwards until it is abutted against the stopper 10. The stopper 10 is accommodated in an upper recess 9a of the regulating piece 9. Located above the regulating piece 9 is said knocker 4 which is adapted to be moved up and down by means of, for example, a rotary solenoid or an air cylinder, not shown. The casing 5 is held by the base 1 through a holder 12 fixedly secured to the latter. The driving arrangement 3 is a two-forked member which is movable up and down by a driver unit, not shown, and which is connected to said sleeve 7. In the next place, the details of the drawing pencil 2 will be described. Mounted on a leading end of the cylindrical casing 5 is a lead guide 20, which has a large diameter hole 22, a small diameter hole 23, and a lead insertion hole 24 formed continuously and concentrically therein. A holder cylinder 25 is tightly fitted in and fixedly secured to the large diameter hole 22. A bushing 26 is vertically, movably inserted in both the holder cylinder 25 and the small diameter hole 23. The bushing 26 has an upper hole 26a having a large diameter and in which a lead holder bushing 27 made of rubber is fitted. The lead holder bushing 27 has a hole 27a formed therein concentrically with a lead inlet 25a formed in the holder cylinder 25. Both the lead inlet 25a and the hole 27a are upwardly enlarged or divergent, funnel-shaped to facilitate insertion of the lead. The bushing 26 is biased by the resilient force of a compression coiled spring 28 at its upper position where it is abutted against the upper portion of the holder cylinder 25, and is also adapted to be moved to its lower position against the biasing force of the coiled spring 28 to thereby enable it to abut against the bottom of the small diameter hole 23. Fitted in and fixedly secured to a lower part of the pipe member 6 slidably inserted in the casing 5 is a chuck ring 29 whose inner peripheral surface 29a is of a downwardly enlarged or divergent configuration. Steel balls 31 fitted in the outer peripheral surface of a lower part of a lead chuck 30 are held in pressure contact with the inner peripheral surface 29a of the chuck ring. The lead chuck 30 has an open slit 32 formed in the lower part thereof so as to permit its diametral deformation, i.e., expansion and contraction. The upper part of the lead chuck 30 is fitted in and fixedly secured to the bottom 8a of the cylindrical lead stock 8 slidably inserted in an upper part of the pipe member 6. A lead insertion hole 33 provided in the bottom portion 8a of the lead stock 8 is open concentrically with the lead chuck 30. Further, a coiled spring 34 is mounted between the chuck ring 29 and the lower end surface of the lead stock 8. The lead chuck 30 is biased upwards relative to the chuck ring 29 by the resilient forces of the compression coiled spring 34 and the auxiliary compression coiled spring 11. Stating in brief, since the lead stock 8 is biased upwards relative to the pipe member 6 by the resilient forces of the auxiliary coiled spring 11 and the coiled spring 34, the lead chuck 30 fitted in and fixedly secured to the lead stock 8 is biased upwards relative to the chuck ring 30 fitted in and fixedly secured to the pipe member 6. As a result, the steel balls 31 are urged in contact with the inner peripheral surface 29a of the chuck ring 29 so that the lead chuck 30 may deform or contract diametrally to hold the lead firmly thus increasing the lead holding force of the lead chuck 30. A second lead guide 35 is fitted over the upper part of the lead chuck 30 and serves to guide a pencil lead which drops from the lead insertion hole 33 to ensure that it drops towards the inlet 25a for a lead formed in the holder cylinder 25. The casing 5 is a cylindrical member comprising a lower portion 5a having a small inside diameter, and an upper portion 5b having a large inside diameter. The lower portion of the pipe member 6 is slidably inserted in the small diameter lower portion 5a, whilst an annular space 36 is defined between the large diameter upper portion 5b and the pipe member 6. Further, a ring-shaped engaging piece 37 fixedly secured to the outer peripheral surface of an approximately intermediate portion of the pipe member 6 is arranged to be slidably movable in and along the annular space 37. The engaging piece 37 is biased upwards by the resilient force of the compression coiled spring 38 so as to abut against a ring shaped stopper 39 fixedly secured by screwing-in or press fitting to the open end of the large diameter upper portion 5b. Thus, a sleeve position keeping arrangement is provided for holding the sleeve 7 fixedly secured to the outer peripheral surface of the pipe member 6 projecting from the casing 5 such that it may always assume a predetermined and fixed position. In the next place, the operation of the above-mentioned drawing device is described below. During drawing operation, as shown in Fig. 2, the knocker 4 is moved upwards away from the regulating piece 9, and the base 1 is moved towards a drawing paper B in such a way as to press a lead A against it. Reference character C denotes a spare lead. At that time, since the lead chuck 30 is biased upwards relative to the chuck ring 29 by the resilient forces of the coiled spring 34 and the auxiliary coiled spring 11, the lead holding force of the lead chuck 30 is increased so that a sufficient drawing pencil depressing pressure can be obtained without any upward sliding movement of the lead A relative to the lead chuck 30 due to the drawing pencil depressing pressure which occurs when drawing operation is conducted. When it is desired to conduct lead thrusting operation, as shown in Fig. 3, the knocker 4 is moved down to move the regulating piece 9 down relative to the pipe member 6 to thereby keep the regulating piece 9 away from the stopper 10. Consequently, the resilient force of the auxiliary coiled spring 11 is supported by the knocker 4 through the regulating piece 9 and is not exerted on the lead stock 8, with the result that the lead chuck 30 is biased upwards relative to the chuck ring 29 only by the resilient force of the coiled spring 34. As a result, the lead holding force of the lead chuck 30 becomes weaker than that when the drawing operation is conducted, so that the lead A can be thrust down in the same manner as in the prior art example by moving the pipe member 6 down by means of the driving arrangement 3 through the sleeve 7 by a predetermined stroke. When it is desired to supplement or supply the spare lead C, as shown in Fig. 4, the knocker 4 is moved down further so as to push the stopper 10 down to thereby move the lead stock 8 down relative to the pipe member 6. This causes the lead chuck 30 to be moved downwards relative to the chuck ring 29 to disengage the steel balls 31 from the inner peripheral surface 29a of the chuck ring 29 thereby radially expanding the lead chuck 30 so that the spare lead C in the lead stock 8 may drop until it is abutted against the top end of the residual lead A′ in the same manner as in the prior art example to thereby enable the residual lead A′ to be expelled and drawing operation to be conducted with the spare lead C. While in the above-mentioned embodiment the engaging piece 37, the coiled spring 38 and the stopper 39 are provided, an alternative arrangement as shown in Fig. 5 wherein such component parts are omitted can be made. As described in detail hereinabove, according to the present invention, when drawing operation is made, the knocker 4 is moved upwards away from the regulating piece 9 so that the lead chuck 30 fixedly secured to the lead stock 8 is biased upwards relative to the chuck ring 29 fixedly secured to the pipe member 6 by the resilient forces of the coiled spring 34 and the auxiliary coiled spring 11, thus increasing the lead holding force of the lead chuck 30 so as to provide a sufficient drawing pencil depressing force during the drawing operation. However, when it is desired to thrust the lead, the knocker 4 is moved down to move the regulating piece 9 down towards the lead chuck 30 so that the resilient force of the auxiliary coiled spring 11 becomes supported by the knocker and is not transmitted to the lead chuck 30, thus reducing the lead holding force of the lead chuck 30. As a result, the lead can be thrust out by moving the pipe member 6 down and up. It is to be understood that the foregoing description is merely illustrative of preferred embodiments of the present invention, and that the scope of the present invention is not to be limited thereto, but is to be determined by the scope of the appended claims.

Claims: A drawing device for use in a drafting machine, said drawing device comprising:- a length of casing (5) fixedly secured to a base (1) serving as a holder; a lead guide (20) fixedly secured to a leading end of said casing (5); a pipe member (6) inserted from the other end of said casing (5) into the same in such a manner as to be axially slidably movable freely; a chuck ring (29) fixedly secured to the interior of the leading end portion of said pipe member (6); a sleeve (7) fitted closely over and fixedly secured to the outer peripheral surface of the other end portion of said pipe member (6), said sleeve (7) being connected to a driving arrangement ( 3 ); a lead stock (8) whose lead end (8a) is inserted from the other end of said pipe member (6) into the same in such a manner as to be slidably movable freely and in,opposed relationship to the rear end of said chuck ring (29), said lead stock (8) having a central and axially extending lead insertion hole (33) formed in the leading end side (8a) thereof, and also a lead stock space formed therein so as to extend axially from the lead insertion hole (33) to the rear end of said lead stock (8); a lead chuck (30) fixedly secured to the leading end portion of said lead stock (8) in such a manner that its leading end portion may be radially deformed, or expanded and contracted, in cooperation with said chuck ring (29), said lead chuck (30) having a centrally extending lead insertion hole (32) formed therein and in aligned relationship with the lead insertion hole (33) in the lead stock (8); a compression coiled spring (34) mounted between said chuck ring (29) and said lead stock (8) so as to bias normally said lead stock (8) and said lead chuck (30) to the rear end side in the longitudinal direction relative to said pipe member and said chuck ring (29); and means for radially deforming or contacting the lead chuck (30) to enable the lead stock to hold a lead firmly when said lead chuck (30) is biased to the rear end side relative to said chuck ring (29) by the resilient force of the coiled spring (34), said drawing device being characterised in that it further comprises a regulating piece (9) fitted over the rear end of said lead stock (8) in such a manner as to be slidably movable freely by a predetermined stroke; an auxiliary compression coiled spring (11) mounted between said regulating piece (9) and said sleeve (7) so as to normally bias the regulating piece (9) towards the longitudinal rear end side of said lead stock (8); and a knocker (4) movable up and down provided above said regulating piece (9) so as to move the same down. A drawing device for use in a drafting machine according to claim 1, further characterised in that:- the inner peripheral surface of said casing (5) is divided into a leading end side portion (5a) having a small diameter and a rear end side portion (5b) having a large diameter, which are bounded by a stepped portion formed on the approximately intermediate part thereof; in that the leading end portion of said pipe member (6) is slidably inserted in the small diameter portion (5a), whilst an annular space (36) is defined between the inner peripheral surface of said large diameter portion (5b) and the outer peripheral surface of said pipe member (6); and in that a sleeve position keeping arrangement is formed in said annular space (36) and comprises:- a ring-shaped engaging piece (37) fixedly secured to the outer periphery of the approximately intermediary part of said pipe member (6) and arranged to be moved freely together with the pipe member in said annular space (36) in the longitudinal direction of the pipe member; a stopper (39) fixedly secured to the end of the opening of said large diameter portion (5b) so as to block said annular space (36); and a compression coiled spring (38) mounted between said ring-shaped engaging piece (37) and the stepped portion formed in said casing (5) to bias said ring-shaped engaging piece (37) so as to abut against said stopper (39).

Inventors: IAI KENICHIRO, IAI, KENICHIRO
Applicants: YOSHIDA KOGYO KK, YOSHIDA KOGYO K.K.
Application year: 1991
Main classification: B43L13
IPC codes: B43K21, B43L13