Reciprocating drafting pen
This invention relates to hand-held ink marking devices, and is more particularly directed to drafting instruments, such as technical pens and the like for use in illustrating and in drafting mechanical drawings. 
     In the art of the mechanical drawing, and in other related arts, ink is applied to the draft paper with a technical pen. Where cross hatching, shading, dot lines, dash lines, stippling or any line other than a solid line is desired, it is necessary to lift the technical pen manually from the drawing surface and replace the pen intermittently. If there is any more than a minimal amount of cross hatching, dotting, or other type of intermittent lining to be done, the process becomes tiresome and must be done slowly. Consequently, if large areas of a drawing to be inked include a significant amount of such intermittent lining, the quality of the work can suffer. 
     Accordingly, it is an object of this invention to provide a technical pen device which automatically lifts and drops the nib of a technical pen as it is run across a drafting medium to produce an intermittent line, which line can be applied relatively rapidly and without tiring the draftsman. 
     It is another object of this invention to provide such a technical pen device which can be hand held and which is easily portable. 
     It is still another object of this invention to provide such a technical pen device in which a technical pen, including a pen nib and an ink reservoir, are driven reciprocally by means of an electromechanical device such that the nib of the pen is regularly lifted from and then brought into contact with the drafting medium. 
     It is yet a further object of this invention to provide such a technical pen device in which current or voltage supplied to the electromechanical device is regulated to control both the length of the time that the nib is on the drafting medium and also the frequency at which it is alternately lifted from and applied to the drafting medium, thereby affording the user a vast repertoire of intermittent lines, including dots, dashes, chain lines, and many other types of lines. 
     In accordance with an object of this invention, reciprocating drafting pen apparatus are provided for drawing interrupted lines. Such apparatus can comprise a cylindrical housing, or barrel, with a cylindrical piston disposed within the barrel and longitudinally movable with respect to it. A drafting pen or technical pen, including an ink reservoir and a pen nib, is held onto the piston such that the pen nib extends out one end of the barrel for applying ink to the drafting medium when the nib is in contact with it. A guide foot, which in one favorable embodiment can be a J-shaped member, is adjustably connected to the pen-nib end of the barrel and serves to maintain a desired standoff between the barrel and the drafting medium when the drafting pen apparatus is in use. Electromechanical drive means within the barrel move the piston longitudinally in response to an electric drive signal applied to it so that the piston, and with it the pen are reciprocated. Accordingly, the nib is alternately brought into contact and out of contact with the medium. The guide foot can also be a straight member, a knobbed-end rod, or other suitable shape adapted to the type of drawing to be done 
     Adjustable piston stops are preferably included to limit the stroke length of the piston, and their positions in the barrel can be selectively set to achieve optimum results. 
     In one favorable embodiment, the drive means can include a solenoid and plunger for actuating the piston. In another favorable embodiment, the drive means can include a piezoelectric leaf having one end fixed relative to the barrel, and a free end biasing the piston. In this embodiment, voltage pulses applied to the piezoelectric leaf bend the latter so as to reciprocate the drafting pen. 
     In several preferred embodiments, the electric drive signal supply means can be an external supply coupled by means of a cable to the drafting pen apparatus. In other favorable embodiments, the drafting pen apparatus can be completely self-contained, with dry cells in the barrel supplying electricity to actuate the electro-mechanical drive means. 
     The above combination of features, including the barrel, the electro-mechanically reciprocating nib, and the guide foot, provide many advantages not available using conventional techniques. The guide foot serves to keep the nib off the surface of the drafting medium. Because the guide foot is adjustable, the drafting pen apparatus of this invention can be used at many different angles according to the particular needs and desires of the individual draftsman. Of course, the guide foot also provides the draftsman with an accurate indication of where the pen nib is going to touch down to apply ink to the surface of the drafting medium. 
     Moreover, the drafting pen apparatus of this invention is constructed to operate with any of a variety of technical pens, so that the color of ink and the breath of the line can be changed rapidly, simply by replacing the reservoir, nib, or both of the technical pen held within the piston. 
    
    
     The above, and many further objects, features, and advantages of this invention will be more fully appreciated from the ensuing description of several preferred embodiments, which is to be considered in connection with the accompanying drawings, in which 
     FIG. 1 shows generally a reciprocating drafting pen apparatus according to an embodiment of this invention, including also a drive current supply; 
     FIG. 1A is an elevational view of the control panel of the drive current supply; 
     FIGS. 2, 3, and 4 illustrate the operation of the reciprocating pen apparatus of FIG. 1; 
     FIGS. 5, 6, and 7 show intermittent lines of the type which can be drawn with the reciprocating pen device of this invention; 
     FIGS. 8 and 9 are cross sectional views of the reciprocating pen apparatus of one embodiment of this invention; 
     FIG. 10 is an exploded view of the reciprocating pen apparatus of FIGS. 8 and 9; 
     FIGS. 11 and 12 illustrate a reciprocating pen apparatus according to another embodiment of this invention; 
     FIGS. 13 and 14 are a longitudinal cross section and a partial plan view, respectively, of a reciprocating pen according to another embodiment of this invention; 
     FIG. 15 shows an intermittent line as drawn with the apparatus of FIGS. 13 and 14; 
     FIG. 16 is an illustration of another embodiment of the pen of this invention, here itself drawn with a pen according to this invention to show the stippling effect possible with pens of this invention; and 
     FIG. 17 is a cross section of a portion of another pen according to this invention. 
    
    
     With reference to the drawings, and initially to FIGS. 1 and 1A thereof, one embodiment of the reciprocating pen apparatus of this invention includes a reciprocating pen device 10 and an external pulse power supply 12 connected thereto by means of a cord 14. 
     As shown in FIG. 1A, the control panel of the pulse power supply includes an on/off switch 121, a pilot lamp 122, a voltage control knob 123, which can be coupled to a potentiometer or variable transformer, and timer controls 124 and 125, for respectively controlling the periods for which the pulse power signal is high and low. These controls 124 and 125, in effect, control the time that the pen contained within the device 10 is lifted off drafting paper P and is returned into contact therewith. A jack 126 in the control panel serves as a receptacle for plugging in one end of the cord 14. 
     As shown in FIG. 1, the pen device 10 has a guide foot 16 adjustably mounted on one end of a cylindrical pen barrel 18. This guide foot 16 is J-shaped with the curved end disposed outwardly for conforming with the finger of a draftsman. A technical pen 20 is disposed at least partially within the barrel 18 and has a pen nib 22 protruding from the lower end of the barrel 18. 
     As shown in FIG. 1, the guide foot 16 can be held against a straight edge 24 while the pen device 10 is moved laterally across a sheet of drafting paper P or other drafting medium. The guide foot 16 establishes a standoff distance between the paper P and the barrel 18 to conform with the draftsman&#39;s preference, so that the intermittent line that is drawn with the pen device 10 is reliable and uniform. 
     As shown in FIG. 2, the shank of the J-shaped guide foot is releasably held in a mounting device 26 at the lower end of the barrel 18. Accordingly, the standoff provided by the guide foot 16 can be adjusted by moving the guide foot 16 longitudinally with respect to the mounting 26. When the position of the guide foot corresponds to the desired standoff, the guide foot 16 can be secured in the mounting 26, by means of a set screw or the like. 
     If the pen device 10 is moved laterally while the guide foot 16 is kept against the straight edge 24, the technical pen 20 within the barrel 18 will be reciprocated downwardly and upwardly, respectively, as shown in FIGS. 3 and 4. Following a down stroke (FIG. 3) the pen nib 22 is maintained in contact with the drafting paper P, thereby yeilding a solid line segment 28 as shown in FIG. 5. Subsequently, after an up stroke (FIG. 4), the nib 22 is held away from the drafting paper P, thereby yielding a blank space 30 between the line segment 28, as is also shown in FIG. 5. Accordingly, if the apparatus 10 is moved at a steady rate across the paper P while the technical pen 20 is stroked alternately upwards and downwards, a broken line will result as is shown in FIG. 5. 
     As shown illustratively in FIGS. 6 and 7, respectively, a dashed line 32 can be obtained if the down stroke period is longer than the upstroke period, and a series of closely-spaced short segments 32&#39; can be obtained by keeping the upstroke period and downstroke period both relatively short. 
     While not specifically shown, many other desired types of broken or intermittent lines can be drawn using the device of this invention; for example, dot lines and chain lines can be obtained by varying the down periods and up periods in appropriate fashions. 
     The first embodiment of the reciprocating pen device of this invention is shown in cross section in FIGS. 8 and 9, and in exploded form in FIG. 10. Within the generally cylindrical barrel 18 of this embodiment there is a reciprocating, electro-mechanically driven piston arrangement for moving the technical pen 20. This piston device is formed generally as described below. 
     A generally cylindrical pen holder 34 constitutes a front end of the piston arrangement and is threadably connected to an ink reservoir 36 forming a part of the technical pen 20 together with the nib 22. The nib 22 extends out the front or distal end of the barrel 18. Behind the holder 34 is an adjustable piston stop 38 which can be formed as a machined or molded plug secured by a hold-down screw 40 extending through a longitudinal slot 42 in the barrel 18. The slot 42 need not be straight, but can, e.g., be helical, so long as it is elongated, with a longitudinal component. A helical spring 44 has one end biasing against the stop 38. A piston dasher 46 threadably connected to the rear end of the pen holder 34 has a head 48 biased against the other end of the spring 44. A piston shaft 50, in which a central portion 52 thereof is formed of ferromagnetic material and serves as a plunger, has a piston head 54 at the rear end thereof, and extends through a solenoid 56. When the solenoid 56 is energized, the plunger portion 52 is drawin in and urges the dasher head 48 forward. The solenoid 56 is held in place within the barrel 18 by means of a hold-down screw 58 longitudinally fixed on the barrel 18. 
     A rear piston stop 60 is disposed behind the piston head 54 and establishes the rearmost limit of its piston stroke. This stop 60 is maintained in a selected longitudinal location by means of a hold-down screw 62 extending through a longitudinal slot 64 in the barrel 18. Finally, a jack 66 is mounted at the rear or proximal end of the barrel 18; a plug 68 on the cord 14 from the supply 12 is plugged into this jack 66. 
     Although not shown, the jack 66 is connected by wire leads to the solenoid 56. 
     Whenever the drive signal from the pulse power supply 12 is low, the solenoid 56 remains unenergized, and the spring 44 biases the piston arrangement, and thus the pen nib 22, proximally, and thus away from the paper, as shown in FIG. 8. However, when the drive signal from the supply 12 is high, current flows through the solenoid 56 thereby driving the piston arrangement forward to the limit of its stroke as established by the position of the front piston stop 38. This brings the pen nib 22 into contact with the drafting medium, as shown in FIG. 9. 
     FIGS. 11 and 12 illustrate another embodiment of this invention, in which also shown in FIGS. 8 to 10 elements are identified with the same reference characters, but primed, and for which a detailed description will be omitted. In this embodiment, a piezoelectric drive mechanism 70 imparts a stroke to the technical pen 20&#39; disposed within the generally cylindrical barrel 18&#39;. The term piezoelectric drive leaf is here used to mean any type of mechanism that bends when an electrical potential is applied to it. This of course, includes known piezoelectric devices, such as bimorph leaves and piezo ceramic benders, as well as many other piezoelectric devices. In this device 10&#39;, the drive piston includes a pen holder 34&#39;, a piston shaft 46&#39;, and a head 48&#39; thereof, with a spring 44&#39; biasing the piston head 48&#39; rearwardly relative to an adjustable piston stop 38&#39;. 
     The piezoelectric drive mechanism 70 includes a housing 72 attached to the proximal end of the barrel 18&#39;. A piezoelectric leaf 74 has one end 76 affixed to the housing. A finger 78 mounted on the free end of the leaf 74 pushes against the piston head 48&#39;. Here, leads of the cord 14&#39; are coupled from a drive signal voltage source to the piezoelectric leaf 74 to apply a potential thereacross. 
     When the applied drive signal voltage is low, the leaf 74 is bent proximally (FIG. 11) so that the pen nib 22&#39; is retracted. However, when the applied drive signal voltage is high, the leaf 74 bends forward (FIG. 12) extending the nib 22&#39; distally against the drafting medium P. 
     One advantage of the piezoelectric drive of this embodiment is that considerably less power is required than in the solenoid-driven embodiment. Thus, this embodiment can be constructed with an internal power supply, for example, driven by small dry cells, so that the pen can be made completely portable and self contained. 
     FIGS. 13 and 14 illustrate yet another embodiment of this invention, in which elements shown in either of the first two embodiments are identified with the same reference characters, but double primed. 
     In this embodiment, the barrel 18&#34; is enlarged somewhat to accomodate an electric-motor driven displacing device and a pair of dry cells, so that the pen device 10&#34; is completely self-contained. 
     Here, the technical pen 20&#34; is held in a pen holder 34&#34;, the latter being formed as a bushing slidably mounted within the barrel 18&#34;. The spring 44&#34; biases the bushing 34&#34; distally away from a trasverse wall 38&#34;. 
     The drive mechanism for imparting a stroke to the bushing 34&#34; includes a cam follower 80 extending radially from the proximal end of the bushing 34&#34; and engaging a cam surface of a cam wheel 82. The latter is turned by a spur gear 84, engaged by a pinion 86 that is a driven by a small DC motor 88. 
     A battery compartment 90 in the proximal end of the barrel 18&#34; contains a pair of AA dry cells 92 and 94, which supply drive current to the motor 88. A switch 96 having a switch button 98 extending outwardly through the barrel 18&#34; controls the actuation of the motor 88. 
     Normally, the follower 80 engages a circular portion 82a of the cam wheel 82, and the pen 20&#34; is distally disposed within the barrel 18&#34;. Thus, when the switch 96 is not actuated, the device of this embodiment can be used as a standard technical pen. However, when the button 98 is depressed, the cam wheel 82 rotates. Whenever a protuberance 82b thereon engages the follower 80, the pen 20&#34; is moved proximally, and is lifted off the drafting paper P. Thus, when the button 98 is depressed while the device is moved transversely, a dashed line, such as that shown in FIG. 15, will result. 
     The device of this embodiment is self-contained, and can be held comfortably in the hand. It is portable, and not cumbersome to hold. Therefore, the reciprocating pen device of this embodiment is particularly suitable for a draftsman who must prepare or amend drawings out of the office. 
     FIG. 16 shows yet another embodiment of this invention, here with a reciprocating pen device 10a held in a draftsman&#39;s or artist&#39;s hand and a pulse power supply 12a connected thereto by a cord 14a. In this embodiment, the controls 124a and 125a for controlling stroke duration are located directly on the pen barrel to facilitate fingertip control. This particular drawing is of special interest as it not only shows a pen device 10a being used for stippling a drawing D, but FIG. 16 itself was drawn using a technical pen device of this invention set into a stippling mode. As is apparent, the quality of the stippling is excellent, yet the drawing can be done with significantly less effort and fatigue than is possible using conventional techniques. 
     In the illustrated embodiments of this invention, especially in that shown in FIGS. 8-10, the changing of the technical pen can be facilitated by moving the front piston stop 38 to its extreme forward position Then the pen 20, 20&#39;, or 20&#34; protrudes sufficiently so that the pen, including the ink reservoir 36, 36&#39;, or 36&#34; can be unscrewed from its associated holder 34, 34&#39;, or 34&#34;. In accordance with this feature, the forward stop 38 can be formed with a ball and socket detent arrangement (FIG. 17), in which a ball 140 and a spring 142 are situated in a bore 144 in the stop member 138. A radial projection 146 on the member 138 is slidably situated in a longitudinal guide recess 148 on the inner surface of the barrel 18, and the detent ball 140 snaps into a corresponding recess 150 on the barrel 18 to hold the stop member 138 in its rearward position for a drawing mode. If it is desired to change nibs or reservoirs, the detent 140, 150 can be easily released, and the stop member 138 urged forward to the front of the guide recess 148 so that the pen nib and reservoir can be removed from the piston pen holder. 
     The term &#34;technical pen&#34; as used hereinabove is intended to cover all possible equivalents to the drafting instrument shown above, including felt tip markers, which, of course, can be of any convenient size or ink color. In the case of a felt tip marker, the &#34;nib&#34; would be the felt tip which applies the ink to paper. 
     Although the present invention has been described with reference to particular preferred embodiments, it is to be understood that the invention is not limited to those embodiments, but that many modifications and variations thereof will be apparant to those of ordinary skill, without departing from the scope and spirit of this invention, as defined in the appended claims.