Abstract:
A printer ribbon spool comprising an integral element, molded in one piece from a durable plastic composition, such as of nylon, has an elongate cylindrical ribbon support shaft of substantially uniform, relatively small diameter. One end of the support shaft functions as a first rotation bearing member for the spool, and the other end of the shaft is integral with a narrow, relatively large diameter gear having on the opposed surface thereof a second cylindrical rotation bearing member having a larger diameter than the diameter of the ribbon support shaft and of the first rotation bearing portion thereof.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a ribbon supply spool for an apparatus for feeding ribbon to a print station and is directed to features which enable the ribbon supply spool and ribbon take-up spool to be simpler to make and use, and to contain an increased length of ribbon.  
           [0003]    2. Background Information  
           [0004]    A first general problem with handling ink ribbons is that they are dirty to handle when the ribbon is to be changed frequently for a printer, for example. A second problem with ribbons relates to those which first must be mounted on a core. Such cores have an axial bore or passage and are designed to be assembled over and keyed to the supply shaft and to carry a length of the ribbon. The core must be sufficiently thick radially so as to have the necessary strength and dimensional stability to resist warping or contraction so that the axial bore or passage retains an inner diameter which enables it to be slipped over the outer diameter surface of the shaft of the supply spool during assembly.  
           [0005]    State of the Art:  
           [0006]    It is known in U.S. Pat. No. 5,374,007 to provide a two-piece ribbon supply/take-up spool having a molded tubular, ribbon-carrying core member and a molded hollow shaft member onto which the core member is designed to be mounted and locked against relative rotation. The molded core member has a central bore containing an annular slot or recess which receives a detent member on the outer surface of the shaft member, and also contains a plurality of teeth which mesh with a plurality of teeth on the outer surface of the shaft member to prevent relative rotation of the core member and the shaft member.  
           [0007]    The need for molding the two pieces, namely the tubular core member and the hollow shaft member, with the annular slot, detent member and the cooperating engagement teeth, substantially increases the cost of the ribbon supply/take-up spool. Moreover, the necessary radial thickness of the tubular core, coupled with the diameter of the hollow shaft member, substantially reduces or limits the diameter of the ribbon which can be wound thereon, and the length thereof, to preclude interference of the wound ribbon with elements of the printer apparatus such as the dancer arm, ribbon driving gears and other elements which may be present, depending upon the particular printing apparatus used.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides a novel, one-piece or unitary ribbon supply/take-up spool for a printing apparatus, such as disclosed in U.S. Pat. No. 5,374,007 and similar apparatuses, which is relatively simple and inexpensive to produce, which avoids the need for and disadvantages of separate ribbon-supporting cores and for any means for preventing relative rotation between the mounted ribbon and the ribbon-support shaft, and which enables the winding thereon of a substantially increased length of printing ribbon without any interference with the frame of the apparatus or with the dancer arm or other elements of the particular apparatus, and without extending beyond the diameter of the large gear of the ribbon spool which functions as a driving gear when the spool is positioned as a supply spool and functions as a braking gear when the spool is positioned as a take-up spool.  
           [0009]    The present ribbon spool is an integral element, molded in one piece -from a durable plastic composition, such as of nylon, comprising an elongate cylindrical ribbon support shaft of substantially uniform, relatively small diameter. One end of the support shaft functions as a first rotation bearing member for the spool, and the other end thereof is integral with a narrow, relatively large diameter gear having on the opposed surface thereof a second cylindrical rotation bearing member having a larger diameter than the diameter of the ribbon support shaft and of the first rotation bearing portion thereof. 
       
    
    
     THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an isometric view of a printing apparatus containing the novel ribbon spools of the present invention, one installed and oriented as a ribbon-supply spool and a second installed and oriented as a ribbon take-up spool, both shown without the presence of wound ribbon for purposes of illustration, and  
         [0011]    [0011]FIG. 2 is side view of the integral ribbon spool of the present invention, and  
         [0012]    [0012]FIG. 3 is an isometric view of the ribbon supply spool of FIG. 2, without the ribbon.  
     
    
     DETAILED DESCRIPTION  
       [0013]    [0013]FIG. 1 shows a ribbon supply printing apparatus which is designated generally as apparatus  10  and which accommodates the novel ribbon supply and take-up spools of the present invention. The apparatus  10  includes a support  12  which includes first and second side frames  12 - 1  and  12 - 2 . The apparatus  10  may be used in a business machine such as an encoder which is used to print or encode data on a document  14 . The document  14  is moved in a document track  16 , in a downstream direction, as shown by the direction of arrow  18 , by a document transport  20 , as is done conventionally. The document track  16  has upstanding side walls  16 - 1  and  16 - 2  and a track bottom.  
         [0014]    The apparatus  10  includes a ribbon supply spool  22  and a ribbon take-up spool  24 . Ribbon from the supply spool  22  is fed to the print station where a printer is used to print data on the document  14 , such as in the form of magnetically-readable images. In the embodiment described, the printer selected to portray the invention includes a type drum and a plurality of hammers, although other types of printers, such as thermal printers, could be used. The type drum includes a plurality of type wheels, with one hammer being provided for each type wheel included in the type drum. The upstanding sides  16 - 1  and  16 - 2  have suitable openings therein to enable the hammers to impact the document  14  and the ribbon against the type drum as is conventionally done. There are the usual motor timing circuits to control the data which is printed on the document  14 , as disclosed in U.S. Pat. No. 5,374,007.  
         [0015]    The ribbon supply/take-up spool  22 , is shown in more detail in FIGS. 2 and 3.  
         [0016]    The ribbon spool  22  has a generally cylindrical elongate shaft member  54  which has a large bearing or support portion  58  at one end thereof and a small bearing or support portion  60  at the remaining end thereof, as shown best in FIG. 2. The first side frame  12 - 1  has a first slot or wide slot  62  (FIG. 1) to receive and rotatably support the large bearing portion  58  and also has a second or narrow slot  64  to receive and rotatably-support the small bearing portion  60 . This construction ensures that the ribbon supply spool  22  is loaded correctly in the support  12 . The first and second side frames  12 - 1  and  12 - 2  are spaced apart so as to enable a ribbon  26  on the ribbon supply spool  22  to abut the first side frame  12 - 1  and to abut the second side frame  12 - 2  so as to restrain the ribbon supply spool  22  against axial movement within the support  12 . The first and second bearing slots  62  and  64  are positioned at an angle of  60  degrees relative to a horizontal line (as shown by double arrow  70  in FIG. 1); this type of construction enables the ribbon supply spool  22 , with a supply of ribbon  26  thereon, to be expended to its operating position shown in FIG. 1 without interfering with other elements in the machine in which the apparatus  10  is located. The fresh ribbon  26  which is used in the apparatus  10  is wound on the supply spool shaft  54  when received at the apparatus  10 .  
         [0017]    The ribbon supply spool  22 , shown in FIGS.  1  to  3 , has an external gear  72  located adjacent one end of shaft  54 . When the ribbon supply spool  22  is in the operating position shown in FIG. 1, the external gear  72  meshes with a braking gear  74 . The braking gear  74  is coupled to a braking motor  76 , which is controlled by the controller, as will be described hereinafter. Essentially, the breaking gear  74  and the braking motor  76  keep the ribbon supply spool  22  from rotating.  
         [0018]    Naturally, the bottoms of the bearing slots  62  and  64 , shown in FIG. 1, are arcuately shaped to rotatably support the large bearing portion  58  and the small bearing portion  60  and to maintain the longitudinal axis of the ribbon supply spool  22  in a horizontal position in the embodiment described. The ribbon supply spool  22 , with a supply of ribbon thereon, is maintained in the position shown in FIG. 1 by gravity and a spring clip which is shown, schematically, as a spring loaded wire  96 . The wire  96  biases the ribbon supply spool  22  in a downward direction, as viewed in FIG. 1. The wire  96  contacts the bearing portion  60  of the ribbon supply spool  22 . There is a similar spring loaded wire  96  (not shown) contacting the support portion  58  of the ribbon supply spool  22 . The ribbon take-up spool  24  has similar spring loaded wires (not shown) at support portions  58  and  60 .  
         [0019]    While this discussion has proceeded with respect to the ribbon supply spool  22 , the ribbon take-up spool  24  is identical to the ribbon supply spool  22 ; consequently, a detailed discussion of the take-up spool  24  is not deemed necessary. An important difference relates to the way that the ribbon take-up spool  24  is oriented and positioned in the support  12 . In this regard, the large bearing portion  58  of the take-up spool  24  is mounted in a slot in the second side frame  12 - 2  and the small bearing portion  60  is mounted in a slot in the side frame  12 - 1 , as shown in FIG. 1. The external gear  72  of the take-up spool  24  is in mesh with a driving gear  102  which is rotated by a drive motor  104  which is controlled by a controller (not shown). The external gears  72  of the ribbon supply spool  22  and the ribbon take-up spool  24  are located on opposed sides of the support  12  when properly oriented and positioned in the support  12  as shown in FIG. 1.  
         [0020]    The ribbon  26  is wound on the tubular core member  54  so that the ribbon  26  is drawn or dispensed from the ribbon supply spool  22  in the proper direction. The ribbon  26  rides over rollers at the print station to provide some clearance for the type drum to rotate without contacting the ribbon  26  until actual printing takes place by energizing the print hammers. An idler roller is used to route the ribbon  26  from the print station to a metering roller, and thereafter, the ribbon  26  is wound or collected on the shaft  54  of the take-up spool  24 . The general function of the metering roller is to cooperate with the drive motor  104  to ensure that a prescribed amount of ribbon  26  is supplied to the print station for each cycle of printing which is effected. Because this aspect is not important to an understanding of this invention, it need not be discussed in any further detail.  
         [0021]    The overall operation of the ribbon supply printing apparatus  10  is as follows. The apparatus  10  includes a dancer arm (not shown) which has one end pivotally mounted in the support  12  and the remaining end thereof pivotally supporting a roller. The roller has an axial length which supports the entire width of the ribbon  26 . When a fresh supply of ribbon  26  is to be supplied to the print station, the controller, through its associated software will “unlock” the braking motor  76 , permitting the dancer arm to be pivoted in a clockwise direction to unwind some ribbon  26  from the ribbon supply spool  22 . As the dancer arm pivots in a clockwise direction it approaches a positional sensor which is coupled to the controller via the interfaces, and the controller actuates the braking motor  76  which prevents further rotation of the ribbon supply spool  22 . Thereafter, the controller energizes the drive motor  104  to feed the necessary amount of ribbon  26  to the print station as required by the printing demands. As the ribbon  26  is fed to the print station, the dancer arm pivots in a counterclockwise direction against the bias of the tension spring until the dancer arm approaches a positional sensor which is coupled to the controller via the interfaces. The controller then deenergizes the braking motor  76 , permitting the tension spring to withdraw a new length of ribbon as described. The disclosure of U.S. Pat. No. 5,374,004 is incorporated herein with respect to the printing apparatus  10  and its elements and operation.  
         [0022]    When the ribbon  26  from the supply spool  22  is exhausted, the supply spool  22  is removed from the position shown in FIG. 1. A new supply spool  22  with a new supply of ribbon thereon, is inserted. The used ribbon  26  is then removed from the ribbon take-up spool  24  and discarded, and a new “empty” ribbon supply spool  22  is then mounted as the ribbon take-up spool  24 , in the apparatus  10 .  
         [0023]    It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.