Abstract:
A piston converter for a fountain pen that permits a user to selectively engage the drive mechanism to the converter is disclosed. The converter has a hollow body fluidly connected to a nib of the pen at one end and a plunger assembly slidably disposed therein. The plunger assembly is engaged to a hollow drive rod. An engagement rod with a first end and an engagement end extends into the drive rod. The drive rod has an internal cavity configured to engage the engagement end of the engagement rod. The engagement end of the engagement rod can be selectively moved into or out of the engagement cavity, thereby permitting selective engagement of the drive mechanism for the piston converter.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to fountain pens and more specifically to the refillable ink cartridges used in fountain pens. 
     BACKGROUND OF THE INVENTION 
     In general there are three methods of supplying ink to a fountain pen: (1) dipping the nib directly into an ink well to coat the same with ink; (2) providing a disposable ink cartridge that is inserted into the body of the pen such that fluid communication is established between the ink cartridge and the nib to supply the same with ink; and (3) providing a refillable ink cartridge that is either removable from or integral with the body of the pen and such that fluid communication is established between the ink cartridge and the nib. The refillable ink cartridges are often referred to as piston converters by the skilled artisan. A piston converter, in general, is a hollow body with a plunger slidably disposed therein. The hollow body is fluidly connected at one end to the nib of a fountain pen. In order to fill a piston converter with ink, the plunger is pushed forward into the hollow body, the nib of the pen is substantially submerged into a well of ink (in the case of a removable type converter, an end of the hollow body is inserted into the well of ink), and the plunger is withdrawn, thereby drawing ink into the hollow body; the operation is analogous to drawing fluid into a syringe. The plunger remains in the hollow body, thereby sealing one end of the hollow body. The second end of the hollow body, as mentioned above, is in fluid communication with the nib. After filling the piston converter the pen can be used until the ink runs dry, after which the process is repeated to fill the piston converter with ink again. In some cases a removable piston converter can be replaced by a disposable cartridge if the user prefers disposable cartridges over piston converters. 
     In one prior art piston converter the plunger is moved within the hollow body by a drive mechanism. The general concept of the drive mechanism uses a plunger shaft connected to the plunger and a drive member fixed relative to the hollow body and engaged with the plunger shaft. The plunger shaft has either external or internal threads, and the drive member has threads that mate with the threads of the plunger shaft. Because the drive member is fixed relative to the hollow body, turning the drive member causes its threads to rotate, which causes the plunger shaft to move longitudinally relative to the hollow body. Thus, turning the drive member moves the plunger within the hollow body permitting a user to draw ink into the hollow body. 
     One disadvantage to using this drive mechanism for piston converters is that the drive member is often inadvertently rotated, thereby causing a relatively large quantity of ink to discharge out of the nib. This inadvertent ink discharge can stain clothes, hands, fingers, it can ruin documents and virtually anything else it contacts. Likewise, inadvertently rotating the drive knob may cause air to be drawn into the hollow body, thereby affecting the performance of the pen. Thus, there is a need in the art for a piston converter with a drive mechanism that a user selectively activates, which, among other things, will substantially prevent the accidental discharge of ink from a fountain pen. 
     SUMMARY OF THE INVENTION 
     A preferred embodiment of a piston converter in accordance with the present invention includes a hollow body having a distal end and a proximal end, a plunger assembly, a metering knob, a drive rod, and an engagement rod. The distal end of the hollow body provides fluid communication between the hollow body and a nib of a fountain pen. The plunger assembly, preferably a plunger attached to a plunger rod, is slidably disposed in the hollow body. The metering knob is configured to engage the plunger assembly, preferably the plunger rod, to advance or withdraw said plunger within said hollow body. The drive rod is configured to engage the metering knob such that turning the drive rod will turn the metering knob, which will advance or withdraw the plunger assembly. An engagement end of the engagement rod is configured to selectively engage the drive rod, preferably by drawing or pushing the engagement end into or out of a cavity within the drive rod configured to engage the engagement end, such that when in the engaged position turning the engagement rod will cause the drive rod to turn which will cause said metering knob to advance or withdraw said plunger within said hollow body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross-sectional view of a fountain pen with a piston converter in accordance with an embodiment of the present invention; 
     FIG. 2A is an enlarged partial cross-sectional view of the top half of the fountain pen and piston converter of FIG. 1; 
     FIG. 2B is a cross-sectional view of a drive knob from the fountain pen in FIGS. 1 and 2A; 
     FIG. 3 is a cross-sectional view of a hollow body from the fountain pen and piston converter of FIGS. 1 and 2A; 
     FIG. 4 is a cross-sectional view of a drive rod from the piston converter depicted in FIGS. 1 and 2. 
     FIG. 5 is a three-dimensional view of an engagement rod from the fountain pen and piston converter of FIGS. 1 and 2A; 
     FIG. 6 is a cross-sectional view of a drawer from the fountain pen and piston converter of FIGS. 1 and 2A; 
     FIG. 7 is a cutaway three-dimensional view of a sleeve from the fountain pen and piston converter of FIGS. 1 and 2A; and 
     FIG. 8 is a three-dimensional view of a sleeve from the fountain pen and piston converter of FIGS.  1  and  2 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2 there is shown a fountain pen  2  with piston converter  4  in accordance with an embodiment of the present invention. Piston converter  4  has a hollow body  6 , a plunger  8 , a plunger rod  10 , a metering knob  12 , a drive rod  14 , an engagement rod  16 , and a drive knob  18 . 
     Referring to FIGS. 1-3, plunger  8  is slidably disposed in hollow body  6 . Plunger rod is attached to plunger  8  and has external threads  20 . Metering knob  12  is preferably a hollow cylinder with internal threads  22  configured to engage external threads  20  of plunger rod  10 . In an alternative embodiment the metering knob has external threads that engage internal threads in a hollow plunger rod. A skilled artisan will readily recognize that other means of engagement between metering knob  12  and plunger rod  10  may be used without departing from the scope of the present invention. Metering knob  12  abuts proximal end  24  of hollow body  6 , and is fixed relative thereto, for example, by crown  26 . Cover  28  is affixed to distal end  30  of hollow body  6  and has an orifice (not shown) therethrough to provide fluid communication between hollow body  6  and tube  32  and to provide fluid communication from hollow body  6  to a nib (not shown) of fountain pen  2 . 
     Referring to FIGS. 1,  2 , and  4 , drive rod  14  is preferably a hollow cylinder. Externally, drive rod  14  has ridge  34  towards its proximal end  36 , followed by a narrower straight cylindrical region  38  and then by circular barb  40  at its proximal end  36 . Drive rod  14  has teeth  42  at its distal end  44  that engage similarly shaped teeth  46  on proximal end  48  of metering knob  12  (the latter is best shown in FIG.  3 ). A skilled artisan will readily recognize that other alternatives for this engagement may be used, including without limitation, permanently joining the two pieces. Internally, drive rod  14 , towards proximal end  36 , has nut cavity  50  configured to engage with nut  52  on distal end  54  of engagement rod  16  (the latter is best shown in FIG.  5 ), which is described in more detail below. 
     Referring to FIGS. 1-3, and  6 - 8 , piston converter  4  is secured in pen  2  by drawer  56 , sleeve  58 , cap  60 , and cylindrical collar  62 . Drawer  56  (best shown in FIG. 6) is half of a hollow cylinder with distal band  64  and proximal band  66 . Distal band  64  receives cover  28  of hollow body  6 . Proximal band  66  secures cylindrical collar  62  to drawer  56 . Cylindrical collar  62  receives sleeve  58  therethrough. Referring to FIGS. 6 and 7, sleeve  58  is a hollow cylinder. Internally, sleeve  58  has ridge  68  configured to abut ridge  34  of drive rod  14  (the latter is best shown in FIGS. 2A and 4) when the two pieces are mated together, as more fully described below. Externally, sleeve  58  has abutment  72  towards its distal end  74 , shelf  76  towards its proximal end  78  followed by rim  80 , followed by indentation  82  and then by flared rim  84  that preferably has a slightly smaller outer diameter than rim  80 . 
     Proximal end  78  of sleeve  58  slides into and through collar  62  and is snap fit into cap  60  such that rim  80  snaps over the top of concentric ring  86  of cap  60 , and such that shelf  76  of sleeve  58  abuts distal side  88  of concentric ring  86 . Additionally, when sleeve  58  is snap fit into cap  60 , flared rim  84  extends through hole  90  and into cylindrical cavity  92  of cap  60 . In this manner drawer  56  and sleeve  58  are affixed to cap  60 , because abutment  72  prevents collar  62  from passing over distal end  74  of sleeve  58 , and sleeve  58  is fixed into cap  60  by rim  80 , as previously described. The octagonal shape  94  of the central portion of sleeve  58  (best shown in FIG. 7) is configured to mate with a similarly shaped surface (not shown) inside of cap  60 , thus preventing rotation of sleeve  58  within cap  60 . 
     Referring to FIGS. 1 and 2, proximal end  36  of drive rod  14  is slid into distal end  74  of sleeve  58  such that circular barb  40  snap fits over flared rim  84  of sleeve  58  and such that drive rod  14  may rotate with respect to sleeve  58 . Proximal end  96  of engagement rod  16  extends out of proximal end  36  of drive rod  14  and drive knob  18  is fixed thereto by adhesive and threads. The skilled artisan will recognize many other ways of fixing drive knob  18  to engagement rod  16 , such as and without limitation, press fitting, locking threads, or pins. 
     Referring to FIG. 2B, drive knob  18  has internal cavity  98  with groove  100  around the inside wall thereof, and cylindrical ring  102  at distal end  104  of drive knob  18 . Cylindrical ring  102  has a smaller outside diameter than the inside diameter of cylindrical cavity  92  of cap  60 . When drive knob  18  is pushed in the distal direction into the unengaged position flared rim  84  of sleeve  58  removably snap fits into groove  100 . When in the unengaged position, drive knob  18  may preferably rotate about its central axis. When drive knob  18  is pulled in the proximal direction into the engaged position, drive knob  18  snaps out of its unengaged position such that the top of flared rim  84  rests against cylindrical ring  102 , which prevents drive knob  18  from returning to the disengaged position unless the user snaps it back into the disengaged position. 
     Referring to FIGS. 4 and 5, distal end  54  of engagement rod  16  is shaped as nut  52 . Nut  52  may have an approximate shape selected from a group consisting of an eight-sided nut, a seven-sided nut, a six-sided nut, or a five-sided nut. When engagement rod  16  is moved in the proximal direction, by unsnapping drive knob  18  into the engaged position, nut  52  engages with nut cavity  50 , such that rotation of drive knob  18  causes drive rod  14  to rotate. When engagement rod  16  is moved in the distal direction, by snapping drive knob  18  into the unengaged position, nut  52  disengages from nut cavity  50 , such that rotation of drive knob  18  will not cause drive rod  14  to rotate. The specific hex-nut configuration of the preferred embodiment is not necessarily required. The skilled artisan will readily recognize that engagement rod  16  may selectively engage drive rod  14  externally rather than internally, and that selective engagement may be achieved using any number of other alternatives, including without limitation having selective engagement between drive knob  18  and proximal end  96  of engagement rod  16  or drive rod  14 . Additionally, the skilled artisan will readily recognize that many alternatives may be used to engage drive rod  14  with engagement rod  16 , such as and without limitation shapes with more or less than eight sides may be use, tapered shapes may be used, threads may be used, or teeth may be used. 
     To use piston converter  4  a user snaps drive knob  18  into the engaged position and rotates it, which rotates drive rod  14 , which rotates metering knob  12 , which, through engagement of external threads  20  of plunger rod  10  with internal threads  22  of metering knob  12 , causes plunger  8  to advance or withdraw within hollow body  6 . When the user has drawn ink into hollow body  6 , the drive knob is snapped into the disengaged position such that rotation of drive knob  18  will not advance or withdraw plunger  8 . 
     Although various embodiments of the present invention have been described, the descriptions are intended to be merely illustrative. Thus, it will be apparent to the skilled artisan that modifications may be made to the embodiments as described without departing from the scope of the claims set forth below.