Patent Publication Number: US-6905268-B1

Title: Clutch mechanism with one piece plastic spool

Description:
This application is a continuation-in-part of application Ser. No. 09/995,353 filed Nov. 27, 2001. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to an ink ribbon cartridge for use in a recording device, and more specifically to a take-up spool for ink ribbon cartridges including a tube and clutch mechanism. 
   In a thermal ink ribbon cartridge, an ink ribbon is wound around a supply spool tube and extends to a take-up spool tube. An ink layer is formed on one surface of the ink ribbon. A spindle without a gear is provided at one end of each of the supply tube and the take-up tube while a spindle with a gear is provided at the other end of the supply tube and take-up tube. The spindles are selectively removable from the supply and take-up tubes. 
   At the time of ink ribbon replacement, each of the spindles is removed from a snap fit engagement with a corresponding hole in the housing of the ink ribbon cartridge. Then, the spindles are removed from their corresponding ends of the supply and take-up tubes. Replacement tubes with ink ribbon are installed onto the take-up and supply spindles and are reattached to the ink ribbon cartridge housing. Subsequently, the ink ribbon cartridge is mounted in a printer or facsimile system. If an ink ribbon is improperly mounted or the direction of winding is reversed from the proper direction, the ink ribbon cannot be wound up thus resulting in a failure in printing. 
   Existing cartridges use a clutching mechanism for an ink ribbon take-up tube which has three separate components, in addition to the tube, namely a gear, a hub and a tube insert. As shown in  FIG. 1A , a take-up tube  10  has an opening  12  extending therethrough and one or two slots  14  in each end of the tube. The tube  10 , which is made of cardboard, receives a plastic insert  20  which is inserted into the end of the tube and has tabs (not shown) which engage the slots  14  and snap the insert into place within the tube opening. The insert remains as part of the take-up tube. The insert has a lip  22  which engages an end surface of the cardboard tube. The insert has an opening  24  extending therethrough. Referring to  FIG. 1B , at an end  26  of the insert, which is opposite the end with lip  22  are a series of drive surfaces  28  and slip surfaces  30  formed by angled slots  32  formed at equally spaced apart areas along a perimeter of the insert. The drive and slip surfaces extend axially inwardly from end surface  26  of the insert  20 . The drive surfaces are substantially radial edges which form an abutment shoulder for drivingly engaging with a drive lug of a drive gear. The slip surfaces are smooth, tapered surfaces or slopes which have a chord component which allows the drive lug to slip along the surfaces. 
   A hub  40  is snap fit onto a drive gear assembly  50 . The hub has several prongs  42  which extend axially from a flat disk surface  44  and extend into matching slots  52  in the drive gear. The prongs are then locked into place within the gear and attach the hub to the gear. The hub further comprises a central portion  46  having an opening  47  therethrough and an end portion  48  with a slot  49  therethrough. The drive gear assembly includes an elongated leg portion  54  which extends through the opening in the central portion of the hub. Portion  54  includes a cantilever member  56  which is formed between grooves in the leg portion. The cantilever member includes a drive lug  58  formed at an end thereof. The cantilever drive lug extends through opening  47  of the hub and protrudes through slot  49 . The drive lug is formed of a resilient material and can be depressed radially inwardly toward the hub center as the hub and drive gear are installed together. Once the drive lug is fully received in the hub, it extends radially outwardly through the slot of the hub and is locked within the slot. 
   The drive gear and hub assembly are then inserted into the plastic insert  20  in the cardboard tube. The drive lug is again depressed radially inwardly as the hub is axially inserted through the opening  24  in the insert  20  until the lug reaches the drive and slip surfaces at the end of the insert. The lug remains depressed inwardly by the slip surfaces  30  and does not allow the cardboard tube to rotate with the drive gear. That is, the drive lug allows the drive gear and hub to rotate counter-clockwise (see  FIG. 1B ) with respect to the slip surfaces but does not engage or lock to the insert. The drive gear and hub rotate counter-clockwise with respect to the slip surfaces and do not engage the insert thus not rotating the cardboard tube. 
   However, if the hub and drive gear are rotated in the opposite direction, i.e. clockwise, the drive lug extends through one of the slots of the insert and engages one of the drive surfaces  28  thus rotating the insert and the cardboard tube in a clockwise manner in  FIG. 1B . Thus, the cardboard tube and the take-up spool can only rotate in one direction as driven by the drive gear. 
   A problem with this existing design is that the end of the cardboard tube with the plastic insert can only accommodate the drive gear with the hub and drive lug. This end is not compatible with any of the spindles or other drive gear arrangements. Further, the design requires four parts and is structurally complex and expensive. 
   Thus, a one piece tube which accomplishes the same function of permitting rotation of the take-up tube in only one direction would be desirable. This tube would also be compatible with other drive gears and supply spindles. Furthermore, no separate insert would be required in the tube and the hub component can be eliminated. Accordingly, it is desirable to provide a new and improved take-up spool for an ink ribbon cartridge which would meet the above stated needs and others and provide better, more advantageous overall results. 
   SUMMARY OF THE INVENTION 
   Generally speaking, the present invention relates to a take-up spool for an ink ribbon cartridge which uses a clutch mechanism which prevents improper winding of the take-up spool thus preventing failure in printing. 
   More particularly, the invention relates to an ink ribbon cartridge spool comprising a one piece plastic tube which is structured to provide a clutch mechanism with a gear spindle. The take-up spool tube is preferably made of plastic and has an opening for receiving hub and cantilevered members of a drive gear spindle. The cantilevered member contacts drive and clutch components in the spool opening and either drives the spool or slips and does not drive the spool while the cantilevered member is rotated. Thus, the drive gear can only rotate the spool in one direction and cannot rotate it in the opposite direction. 
   This is accomplished by including a plurality of drive surfaces and slip surfaces generally equally spaced apart within the plastic tube. The cantilever member of the drive gear has a tab which engages the drive surfaces and slip surfaces. The cantilevered member is deflected inwardly when the tab is pushed against the slip surfaces in the plastic tube while being rotated in one direction. When rotated in the opposite direction, the cantilevered member end engages one of the drive surfaces and provides a positive drive when rotated against the plastic tube thus rotating the take-up spool with the drive gear. 
   In particular, the present invention relates to an ink ribbon cartridge, having a housing, an ink ribbon wound about the tube of a supply spool and the tube of a take-up spool for holding the ribbon. Each spool tube has a first and second end with an opening. Each spool is also removably mounted in the housing. The first and second end of the supply spool tube and the first end of the take-up spool tube each have at least one slot formed in the end. A second end of the take-up spool tube has an opening having a plurality of notches or recesses therein each including a drive surface and a slip surface. The take-up spool tube is preferably of a one-piece construction. 
   A first spindle with a cantilever member and a tab extending therefrom is mounted on the second end of the take-up spool tube. When the drive surface engages the tab on the cantilever member of the spindle, rotation of the spindle rotates the take-up spool tube and thus the take-up spool. When one of the slip surfaces engages the tab, rotation of the spindle does not rotate the take-up spool tube. Rather, the tab slides along the slip surface and is deflected inwardly toward the center of the spool tube. Thus, the take-up spool tube and spindle act as a clutch mechanism. 
   Second and third spindles are mounted on the first and second ends of the supply spool tube and a fourth spindle is mounted on the first end of the take-up spool tube. The fourth spindle engages a slot in the second end of the take-up spool tube, and the second and third spindles each engage one of the slots in the first and second ends of the supply spool tube. Each spindle has a disk portion and a tab which engages one of the slots of the spool tubes. The first and third spindles each further have a gear section. The fourth spindle can also have a cantilever member with a tab which is received by a slot in the first end of the take-up spool tube. 
   One advantage of the present invention is the provision of a clutch mechanism which uses a one-piece spool tube which provides drive surfaces and slip surfaces for allowing or preventing rotation of the spool tube with respect to a drive gear. 
   Another advantage of the present invention is the provision of a spool which does not require a separate insert to be inserted in one end of the spool tube, thus allowing each end of the spool tube to receive take-up or supply spindles. 
   Yet another advantage of the present invention is the provision of a take-up spool structure which minimizes the number of parts and is easy to manufacture. 
   Still other aspects and advantages of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take form in certain components and structures, a preferred embodiment of which will be illustrated in the accompanying drawings wherein: 
       FIG. 1A  is an exploded elevational view in partial cross section illustrating a cardboard tube, a plastic tube insert, a hub, and a drive gear of a take-up spool according to a prior art design; 
       FIG. 1B  is an end view of the insert of  FIG. 1A  looking in the direction of line A—A; 
       FIG. 2  is a perspective view of an ink ribbon cartridge in accordance with the present invention; 
       FIG. 3  is a perspective view of the underside of the ink ribbon cartridge of  FIG. 2 ; 
       FIG. 4  is an exploded side elevational view, partially in section, illustrating the component parts of a take-up spool in accordance with a preferred embodiment; 
       FIG. 5  is a side elevational view, partially in section, of the assembled parts of the spool illustrated in  FIG. 4 ; and, 
       FIG. 6  is a cross-sectional elevational view of the take-up spool looking in the direction of line  6 — 6  in  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, wherein the showings are for purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting same,  FIGS. 2 and 3  show an ink ribbon cartridge in accordance with a preferred embodiment of the present invention. 
   More particularly, an ink ribbon cartridge A comprises a housing  100 , a first wall  102 , a second wall  104 , a third wall  106 , and a fourth wall  108 . First and second walls  102 ,  104  form connection members which extend between and connect the third wall to the fourth wall. The first and second walls are spaced apart and generally parallel to each other. Similarly, the third and fourth walls are spaced apart and are generally parallel to each other. The third wall  106  comprises wall sections  110 ,  112  which extend from the ends of the wall. Each wall  110 ,  112  has an opening for receiving a spindle attached to a spool tube which extends between the walls  110 ,  112 . Wall  106  partially covers the spool and is generally parallel thereto. Preferably, wall  106  has a flat surface extending between the walls  110 ,  112 . Wall  106  further comprises a series of spaced apart slots or openings  116  which are used to grasp the ribbon cartridge by a user&#39;s fingers and to lift and install the ink ribbon cartridge into a printer. 
   Wall  108  has a generally semi-cylindrical shape and extends between sides  102 ,  104 . Wall  108  further comprises wall portions  120 ,  122  which extend downwardly from a top surface of wall  108 , as shown in  FIG. 2 . Sections  120 ,  122  each comprise an opening for receiving a spindle attached to the spool tube of the spool which extends between the two sections. 
   A take-up spool  130  extends between walls  110 ,  112 . The take-up spool includes a one-piece spool tube  132  and is preferably made of plastic, although other materials may be used without departing from the scope of the invention. Spindles  140 ,  142  are attached to opposite ends of the spool tube. Spindle  140  has a gear section  144 . Spindle  142  does not have a gear. Each spindle is preferably molded of a resin material; however, other materials may be used without departing from the scope of the invention. Each spindle  140 ,  142  comprises a cylindrical portion  146 ,  148 , respectively, and a flat disk section  150 ,  152 , respectively, adjacent gear  140  and cylindrical portion  148 . 
   A supply spool  160  extends between walls  120 ,  122 . Spool  160  includes a spool tube which is preferably made of cardboard but may be formed of an alternative material. A spindle  162  is attached to one end of the spool tube and a spindle  164  is attached at the other end of the tube. Spindle  162  has a gear section  166 , but spindle  164  does not have such a gear section. Each spindle comprises a cylindrical portion  168 ,  170 , and a flat disk portion  172 ,  174 , respectively. An ink ribbon  180  extends between and is connected onto take-up spool  130  and supply spool  160 . The ink ribbon has an ink layer on one side. The ink ribbon is formed with a broad width resin film and has an ink surface onto which the ink layer is formed. Spindles  142 ,  164  are received in semi-circular notches or cut-outs  182 ,  184  in the walls  112 ,  122  of the cartridge. Similarly, the gear spindles  140 ,  162  are received in semi-circular notches (not shown) in walls  110 ,  120 . Each end of the tube of spool  160  has one or two slots, preferably 180 degrees apart, which receive tabs extending from one of the ends of each spindle. 
   Referring to  FIGS. 4 ,  5  and  6 , take-up spool  130  has an axis  190  and as set forth above, comprises a spool tube  132  to which gear spindle  140  is attached. More particularly, gear spindle  140  has a hub  192  which is received in opening  194  in one end of spool tube  132 . Opening  194  has an axially outer surface portion  194   a  which is circular in cross-section, an axially inner surface portion  194   b , and a radially outwardly extending shoulder  194   c  therebetween and transverse to axis  190 . Hub  192  is tubular, is rotatably supported by outer surface portion  194   a  and has a cantilever member  196  which is between and defined by slots  196   a  through the wall of the hub. At the axially inner end of the cantilever member is a drive lug  198  which extends beyond the inner end of hub  192  and shoulder  194   c  as seen in  FIG. 5 . Plastic spool tube  132  further has a plurality of recesses  199  in inner surface portion  194   b  which are equally spaced apart about axis  190  and extend axially from shoulder  194   c . Each recess  199  includes a drive surface  200 , a slip surface  202  circumferentially spaced therefrom, a bottom surface  204  between the drive and slip surfaces, and an arcuate surface  206  defined by a portion of inner surface  194   b  which extends from the radially inner end of drive surface  200  of one recess to the radially inner end of the circumferentially adjacent recess. 
   Gear spindle  140  is mounted on tube  132  by inserting hub  192  into the tube until the cantilever member  196  extends past shoulder  194   c  into the portion of the tube which has recesses  199  therein. More particularly, drive lug  198  of the cantilever member has a tapered cam surface  208  on the axially inner end thereof and a locking shoulder  210  therebehind, as best seen in  FIG. 5 , and as best seen in  FIG. 6 , circumferentially spaced driving and sliding faces  212  and  214 , respectively, extending axially between the cam surface and locking shoulder. During assembly, cam surface  208  engages the outer end of opening portion  194   a  and deflects cantilever member  196  radially inwardly of hub  192  until drive lug shoulder  210  passes shoulder  194   c  of opening  194 . At that time, the cantilever member moves radially outwardly and upon rotation of spindle  140  relative to tube  132 , drive lug  198  moves into alignment with one of the recesses  199 , whereupon the cantilever arm moves radially outwardly to its initial position. In this position, shoulder  210  faces shoulder  194   c  and precludes axial separation of the spindle from tube  132 . Referring to  FIG. 6 , if gear spindle  140  is rotated in a counter clockwise direction, drive surface  200  of notch  199  is engaged by driving surface  212  of drive lug  198  and provides a positive drive causing spool tube  132  to also rotate in a clockwise direction. If the gear spindle is rotated in a clockwise direction, again referring to  FIG. 6 , the sliding face  214  of drive lug  198  engages the slip surface  202  of the recess and slides along the surface and deflects the cantilever member inwardly, thus preventing rotation of spool tube  132  with the drive gear. Thus, the one-piece spool tube and spindle arrangement acts as a one-way clutch mechanism. It will be noted that when face  214  engages with slip surface  202  and, ultimately, with arcuate surface  203  between adjacent recesses  199 , locking shoulder  210  remains radially outwardly of surface  194   a  so as to engage shoulder  194   c  and preclude removal of the spindle from the tube. The plastic spool tube can be used with either supply spools or take-up spools and, importantly, the plastic spool tube eliminates the need for the separate hub and insert components heretofore used with a cardboard spool tube. Advantageously, the plastic spool tube according to the present invention is also compatible with a two-piece gear hub as shown in  FIG. 1 . 
   The invention has been described with reference to a preferred embodiment. Obviously, alterations and modifications will occur to others upon a reading and understanding of this specification. The specification is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.