Abstract:
A freehand writing instrument will hold a writing tip. The instrument can draw the writing tip across a writing surface in one or more strokes. The instrument has a case sized to be handheld and has a longitudinal axis extending between a distal and proximal end of the case. Also included is a motor mounted at the case. The writing instrument also has an arm mounted at the proximal end of the case. The arm is driven by the motor to move periodically about a predetermined center, reaching a maximum transverse displacement from the center. With the distal end of the case defined as a vertex, this maximum transverse displacement is sized to subtend a displacement angle with respect to the longitudinal axis. The arm has a holder adapted to transversely hold the writing tip at an orientation displaced from parallel to the longitudinal axis no more than the displacement angle. The arm can produce a periodic pattern on the writing surface during the strokes. The arm has clearance to permit the writing tip to write with the case held at varying angles of inclination within a range of angles relative to the writing surface. This angle of inclination is adjustable to alter the periodic pattern.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to freehand writing instruments, and in particular, to instruments that are motorized to alter the writing. 
     2. Description of Related Art 
     For a freehand writing instrument to maintain a comfortable feel, the angular orientation of the writing tip should be parallel or close to parallel to the centerline or longitudinal axis of the instrument. The tolerable amount of angular displacement from parallel depends on whether the writing tip lies on the centerline (longitudinal axis) of the writing instrument, or whether the writing tip is offset from this centerline (asymmetrical placement). For an asymmetrically placed writing tip, greater angular displacement of the writing tip is tolerable since the asymmetrical offset itself creates an inherent angular offset that can be compensated somewhat by tilting the writing tip. The tolerable angular displacement of the writing tip is a function of the inherent angle between the centerline (longitudinal axis) of the writing instrument and a line originating on the instrument&#39;s centerline at the upper (distal) end of the writing instrument and running to the lower (proximal) end of the instrument, terminating at a distance from the centerline representing the asymmetrical offset of the writing tip from this centerline. In effect, asymmetrical writing instruments having a greater asymmetrical offset can tolerate a writing tip with a greater tilting from an orientation parallel to this centerline (longitudinal axis) of the writing instrument. 
     Writing instruments have been designed to alter the appearance of a writer&#39;s normal strokes. Such devices have been designed purely for entertainment or to produce special effects needed for specialized drawings. 
     In U.S. Pat. No. 3,997,972 a writing instrument 17 is connected to a spinning shaft 11 a  by a flexible coupler 18. In the examples of FIGS. 2 and 3, special effects are produced by pressing the spinning tip of the writing instrument 17 so it rolls or “walks” back and forth across the writing surface (parallel strokes of FIGS. 7 and 12). Alternatively, the writing instrument can be held upright as shown in FIG. 4 so that the tip of the writing instrument can roll along a somewhat erratic spiral path, as shown in FIGS. 8-11. In any event, the speed of the writing tip is disadvantageously determined by the rolling properties of the tip. Also, “walking” the spinning writing tip in this way quickly wears the tip. 
     For the embodiments of FIGS. 5 and 6 of U.S. Pat. No. 3,997,972, the writing tip follows a conical orbit, staying essentially aligned as a conical ray (subject to some skewing due to flexing of coupler 18). (FIG. 6 may be deemed a cone with a zero conical angle.) When the barrel is tilted in a natural way as shown, the writing pressure varies orbitally. A problem with this design is that the angle of the writing tip 17 is quite different from the angle of the barrel 10. Consequently, the feel of the writing tip is changed by the canting of the tip 17 relative to the barrel 10. If however, the angle between the writing tip 17 and barrel 10 were to be kept small, the amplitude of oscillations of the tip will remain too small. 
     In U.S. Pat. No. 5,752,870 a toy moves along a surface to drive a wheel, while pens are thereby rotated to draw a pattern on the surface. The pens are held in a turret 57 (FIG. 6) and rotate about a shaft 51. This arrangement requires the wheels and other rollers to remain on the writing surface, so that the assembly maintains a constant parallel orientation to the writing surface. Thus, this device cannot be used like a simple freehand writing instrument. This apparatus lacks a free expressive quality, and must be moved about with a limited motion, much like a scrub brush. See also U.S. Pat. No. 3,638,319 for a wheel-driven toy where the writing instruments are held on the toy, but not mechanically rotated. 
     In U.S. Pat. No. 4,835,874 a marking device attached to a ring gear can orbit inside a handheld device as it slides across a drawing surface. This assembly must remain flat on the writing surface and is pushed around that surface with a scrubbing motion. Thus, this reference does not allow the expressive strokes possible with a freehand writing instrument. 
     In U.S. Pat. Nos. 3,390,460; 5,208,987; and 5,433,642 an eccentric weight is spun in the upper end of a writing instrument to cause oscillations about the writer&#39;s fingers. These spinning mechanisms must generate substantial force to overcome the writer&#39;s grip. Consequently, a substantial mass must be placed at the end of the writing instrument, which will tend to produce an off-balanced feel. Also, since the vibrations must necessarily be transferred through the writer&#39;s fingertips, this device will quickly become uncomfortable and have a tendency to numb the writer&#39;s fingertips. 
     SUMMARY OF THE INVENTION 
     In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a freehand writing instrument for holding a writing tip. The instrument is operable to draw the writing tip across a writing surface in one or more strokes. The instrument has a case sized to be handheld and has a longitudinal axis extending between a distal and proximal end of the case. Also included is a motor mounted at the case. The writing instrument also has an element mounted at the proximal end of the case. The element is driven by the motor to move periodically about a predetermined center reaching a maximum transverse displacement from the center. With the distal end of the case defined as a vertex, this maximum transverse displacement is sized to subtend a displacement angle with respect to the longitudinal axis. The element has a holder adapted to transversely hold the writing tip at an orientation displaced from parallel to the longitudinal axis no more than the displacement angle. The element is operable to produce a periodic pattern on the writing surface during the strokes. The element has clearance to permit the writing tip to write with the case held at varying angles of inclination within a range of angles relative to the writing surface. The angle of inclination is adjustable to alter the periodic pattern. 
     By employing apparatus of the foregoing type, an improved writing instrument is achieved. In a preferred embodiment a cylindrical case contains a battery and a motor driven by the battery. A motor-driven shaft extending from the case supports a claw-like arm that is connected, preferably, at right angles to the motor shaft. A pen, pencil or other writing tip can be held in the arm substantially parallel to the shaft and the longitudinal axis of the case. This orientation gives the writing instrument an overall proper feel. 
     By pressing a pushbutton on the case the motor can spin the arm, preferably, in a plane perpendicular to the motor shaft. Depending upon the angle of inclination of the writing instrument, the writing tip can write connected loops or successive disconnected marks. In some embodiments the writing tip may be allowed to wobble slightly in which case the writing pattern can be more complex and somewhat chaotic or random. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a freehand writing instrument in accordance with principles of the present invention, including an angularly displaced view of the instrument shown in phantom; 
     FIG. 2 is a side view, partially in section, of the instrument of FIG. 1; 
     FIGS. 3A-3D are elevational views of the holder arm of FIG. 1 shown normally and with various angular adjustments; 
     FIG. 4 is a perspective view of a holder arm that is an alternate to that shown in FIG. 1; 
     FIGS. 5-7 are elevational views of a holder arm that is an alternate to that shown in FIG. 1; 
     FIGS. 8A-8C are plan views of various writings produced by the instrument of FIG. 1, which writings vary depending upon the handling of the writing instrument and the nature of the writing hardware. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a freehand writing instrument is shown as a case  10  with a motor shaft  12  extending from the case along longitudinal axis  14  (axis  14  is also referred to as a centerline or central axis). An element  16  is shown as an arm attached to the distal end of motor shaft  12 . Arm  16  has a forked distal end  17  acting as a holder or receptacle for holding pencil  18  (pencil  18  and other writing devices are generally referred to as a writing tip). 
     The illustrated writing instrument is a freehand instrument in that the device is supported by the writer&#39;s hand and the angle of inclination of longitudinal axis  14  can be freely changed, as illustrated by the phantom view of the instrument, which is shown tilted along axis  14 ′. 
     As explained further hereinafter, shaft  12  is spun by a motor (illustrated hereinafter) inside case  10 . This motor is activated by depressing pushbutton  20 . For the embodiment of FIG. 1, the arm will rotate along a plane perpendicular to the longitudinal axis  14 . 
     Referring to FIG. 2, case  20  is shown composed of two cylindrical halves  20 A and  20 B, which are screwed together at threaded joint  20 C. Motor  22  is shown installed in the casing half  20 B. Motor  22  drives motor shaft  12  to spin arm  16 . Battery  24  is shown installed in casing half  20 A. The end of battery  24  adjacent to motor  22  connects to the motor&#39;s battery contact  23 . The motor&#39;s other contact  28  is normally open and is adjacent to leg  26 A of spring contact  26 , which connects to the far end of battery  24 . Leg  26 A can be pressed against motor contact  28  by depressing push button  20  in order to start motor  22 . 
     Referring to FIGS. 3A and 3B, previously mentioned arm  16  is shown with pencil  18  installed in the arm&#39;s forked holder  17 . It will be appreciated that instead of a pencil, a pen, a marker or any other type of writing tip can be placed in the forked end of arm  16 . While writing tip  18  may be held perpendicularly to arm  16 , this view illustrates how writing tip  18  can be swung to either side of perpendicular. In general, writing tip  18  can fall within a solid or conical angle centered on axis  21 , which is parallel to longitudinal axis  14 . A diverging tip position is shown in full, while a converging position  18 ′ is shown in phantom. 
     The holder of arm  16  can either hold writing tip  18  at a fixed angle or can hold the tip loosely, allowing the angle of tip  18  to wobble and change in response to writing pressure and kinematics. In any event, the writing tip will be held within a predetermined acute angle relative to the longitudinal axis (axis  14  of FIG.  1 ). Consequently, arm  16  will be held at an angle in excess of this predetermined acute angle. 
     Referring to FIG. 3B, holder  17  of arm  16  follows a circular path, although other paths may be followed in different embodiments. In these embodiments the holder end  17  of arm  16  will move periodically about a predetermined center (in the illustrated embodiment this center lies on the longitudinal axis  14 ). The maximum transverse displacement is shown herein as the radial distance  19  from the longitudinal axis  14  to the center line  21  of the holder  17 . For non-circular paths such as an elliptical path, the maximum transverse displacement will be the distance from the center of the ellipse along its major axis. For other paths that may not have mathematically defined centers, the center may be deemed to be a predetermined point at a central location within or adjacent to the borders of the path. 
     A displacement angle d is defined herein by axis  15  relative to the longitudinal axis  14 , with the vertex of the angle being defined as the distal end  23  of case  10  at the longitudinal axis  14 . Axis  15  extends between vertex  23  to the holder end  17  of arm  16  (that is, at the intersection between center line  21  and arm  16 ). 
     Referring again to FIG. 3A, writing tip  18  may be displaced somewhat from an orientation parallel to the longitudinal axis  14 . It is desirable to keep writing tip  18  parallel or close to parallel to axis  14 , taking into account the magnitude of the transverse displacement  19 . For arms  16  offering a relatively large transverse displacement  19 , the angular displacement of writing tip  18  can be somewhat larger. In particular, it is desirable to limit the angular displacement of writing tip  18  relative to center line  21  (line  21  is parallel to longitudinal axis  14 ). Specifically, this angular displacement relative to center line  21  ought to be no more than previously mentioned displacement angle d (FIG.  3 B). 
     Referring to FIG. 3C, previously mentioned motor shaft  12  is shown fitted with an arm  216  that is identical to the previously illustrated arm (arm  16 ), except that arm  216  has an elevated distal end so that the arm will trace out a conical path (apex down). The diametrically opposite position of arm  216  is shown in phantom as arm  216 ′. 
     Referring to FIG. 3D, motor shaft  12  is shown fitted with an arm  316  that is identical to the previously illustrated arm (arm  16 ), except that arm  316  has an lowered distal end so that the arm will trace out a conical path (apex up). The diametrically opposite position of arm  316  is shown in phantom as arm  316 ′. It will be appreciated that the writing tips installed in the arms of FIGS. 3B and 3C can be tilted in a fashion similar to that shown in FIG.  3 A. 
     Referring to FIG. 4, previously mentioned motor shaft  12  is fitted with an alternate arm  30 . A holder at the distal end of arm  30  is shown as a cylindrical sleeve  32  extending above and below arm  30 . A writing tip  18  (shown in phantom) may be secured in sleeve  32  by means of set screw  34 . In this embodiment writing tip is rigidly held parallel to shaft  12 . 
     Referring to FIG. 5, previously mentioned motor shaft  12  is shown fitted with alternate arm  36 . The distal end of arm  36  has a holder for holding writing tip  38 . Tip  38  may be a pencil lead, a marker tip, or any other type of writing device. Tip  38  may be secured in a hole or in a gripping fork (not shown). In some embodiments, tip  38  may be permanently embedded in arm  36  at the time of manufacture. In such cases, arm  36  and tip  38  may be removed, discarded, and replaced when the tip  38  is depleted. 
     Arm  36  is elastomeric and is shown deflecting in response to downward pressure applied by a writer through case  10 . In other embodiments arm  36  will be more rigid and will not flex as illustrated. In still other embodiments arm  36  may be relatively rigid and may have the illustrated crooked profile in order to produce specific writing effects. 
     Referring to FIG. 6, previously mentioned arm  16  is shown attached to an alternate shaft  212 . Shaft  212  is flexible and is shown deflecting in response to downward pressure applied by a writer. In other embodiments shaft  212  may be relatively rigid and may have the illustrated crooked profile in order to produce specific writing effects. 
     Referring to FIG. 7, previously mentioned motor shaft  12  is shown attached to the hub  42  of alternate arm  40 . A holder at the distal end of arm  40  supports a stub  44  containing an ink reservoir. A ball point writing tip  46  is shown attached to the distal end of stub  44 . 
     To facilitate an understanding of the principles associated with the foregoing apparatus, the operation of the embodiment of FIGS. 1 and 2 will be briefly described first. The embodiments of FIGS. 4 and 7 will operate similarly, but will employ different hardware to produce similar effects. 
     A writer can install pencil  18  in the jaws of forked holder  17 . The tines of holder  17  have a limited amount of flexibility and can tightly grip pencil  18 . Instead of a pencil  18 , a writer may install a pen, a felt marker, or other writing tip. 
     The writer may hold the writing instrument by gripping case  10  and simultaneously depressing pushbutton  20  while pressing the point of pencil  18  against writing surface S. Leg  26 A will be pressed against contact  28  so that motor  22  will be powered by battery  24 . In response, motor shaft  12  will rotate arm  16  to orbit holder  17  and pencil  18 . Preferably, arm  16  will rotate about 200 rpm, although in other embodiments arm  16  may rotate between 30 to 400 rpm. The specific speed may be selected depending on the writer&#39;s preference, the effect desired, the tolerable vibration, etc. In some embodiments the angular speed of motor  22  can be altered by employing a gear reducer (not shown) to reduce the speed and increase the torque of motor shaft  12 . 
     For the relatively steep angle of inclination shown in full in FIG. 1 (longitudinal axis  14 ), the point of pencil  18  will remain on writing surface S. In this embodiment contact with the writing surface S is enhanced by making arm  16  of a flexible plastic that can deflect as the arm rotates. Also the pencil  18  is allowed to wobble slightly in forked holder  17 . 
     For embodiments where it is desirable for the tip of pencil  18  to break contact with writing surface S, arm  16  can be relatively rigid and can hold pencil  18  rigidly to prevent wobbling. Also, the angular speed of shaft  12  can be increased to prevent axial oscillation of case  10  that might otherwise increase the percentage of time that the tip of pencil  18  remains in contact with writing surface S. 
     When the tip of pencil  18  remains in contact with writing surface S as the writing instrument is moved across the surface S, a continuous loop is drawn as shown in FIG.  8 A. 
     The writer can change the pattern produced by the writing instrument without changing the motor speed or the hardware of the writing instrument. For example, the writer may press harder to keep the tip of pencil  18  in contact with writing surface S for a greater percentage of time, or vice versa. Also, the writer may reduce the contact with writing surface S by changing the angle of inclination to that shown in phantom in FIG. 1 (inclination along axis  14 ′). At this shallower angle, the elevation of the distal end of arm  16  will change more dramatically during each revolution of shaft  12 . Consequently, the writing instrument will produce a number of interrupted lines as shown in FIG.  8 B. 
     For embodiments where arm  16  is flexible and pencil  18  is allowed to wobble somewhat in holder  17 , the angular orientation of pencil  18  can vary dramatically with the angle of inclination of axis  14 , the downward pressure of the writer, the phase of arm  16 , etc. In such a dynamic system the motion of pencil  18  will be chaotic. Accordingly, the pattern produced by pencil  18  can appear random, as shown in FIG.  8 C. 
     For the embodiments of FIGS. 3C and 3D arms  216  and  316  can form an acute or obtuse angle, respectively, with shaft  12 . In these embodiments writing tip  18  and shaft  12  remain in the same plane, although in other embodiments the writing tip can be skewed from such a common plane. For the embodiment of FIG. 3C the upper end of pencil  18  points toward the distal end of case  10  while the lower end of pencil  18  converges outwardly to produce a more exaggerated writing. For the embodiment of FIG. 3D the lower end of pencil  18  points inwardly to create a more compact and intricate pattern. 
     For the embodiments of FIGS. 5 and 6, downward pressure by the writer flexes arm  36  (FIG. 5) or shaft  212  (FIG.  6 ). Thus, the writer can change the angle of divergence of the writing tip by modulating downward pressure. 
     It is appreciated that various modifications may be implemented with respect to the above described, preferred embodiments. The illustrated case can be shape differently and may be produced indifferent proportions depending upon the desired weight, gripping style, writer preference, writing application, etc. The illustrated arms and motor shafts can be sized and portioned differently depending on the desired strength, speed, holding power, etc. Some embodiments may employ a pair of spaced arms to reduce any tendency of the writing tip to wobble. Instead of a rotating arm, some embodiments may provide a reciprocating element that can follow and retrace a predetermined path. In such cases the motion may be produced by cranks, levers, etc. Instead of a rotary motor, some embodiments may incorporate a solenoid that is periodically actuated to provide a reciprocating linear movement. In still other embodiments the upper end of a writing tip may be held in a ball joint while the lower portion of the writing tip is subjected to periodic motion. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.