Patent Publication Number: US-6666597-B1

Title: Geared drive hub assembly for a printer cartridge

Description:
FIELD OF THE INVENTION 
     A geared drive hub assembly for a printer cartridge containing a geared hub drive removably engaged with a spool. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 6,161,972 of Kameyama Yoshikatsu discloses an ink ribbon cartridge having a particular spool and spindle arrangement. The spindles used in the device of this patent each have one end which includes a disk shaped section, and a spindle portion 64 which includes projections 65 and 66 disposed 150 degrees apart from each other (see FIGS. 11 and 12). 
     The spindles disclosed in U.S. Pat. No. 6,161,972, although they have some limited utility when used with the spools disclosed in such patent, cannot readily be used with other spools. Furthermore, they tend to fail when more than a minimal amount of shear force is applied to the projections 65 and 66 and, in general, have inferior mechanical properties. 
     It is an object of this invention to provide a novel spindle which can be used with many different spools and which has improved mechanical properties. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, there is provided a geared drive hub assembly removably engaged with a spool. The drive hub contains a gear integrally connected to a spindle assembly. The spindle assembly contains three stepped splines integrally connected to each other and to a base; and the spool is comprised of means for removably engaging each of the three stepped splines. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described by reference to the following drawings, in which like numerals refer to like elements, and in which: 
     FIG. 1 is a perspective view of a printer cartridge comprised of the geared drive hub of this invention. 
     FIG. 2A is a side view of the geared hub drive of FIG. 1 engaged a spool; 
     FIG. 2B is a first end view of the assembly of FIG. 2A; 
     FIG. 2C is a partial sectional view of the assembly of FIG. 2A; 
     FIG. 2D is a partial sectional view of the assembly of FIG. 2A; 
     FIG. 2E is a sectional view of the assembly of FIG. 2A; 
     FIGS. 3A to  3 F each present a schematic representation of how the geared drive hub depicted in FIG. 2A may be used with different spools to produce different assemblies; and 
     FIG. 4 is a front view of the geared drive hub depicted in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view of a printer cartridge  10  comprising gear drive hub  12  operatively connected to a spool  16  The gear drive hub  12  is comprised of a gear  14  which, when the cartridge  10  is disposed within a printer, is engaged by another gear (not shown) and caused to rotate. 
     In recent years, printers have become faster and faster, in response to consumer demand. The faster the printer, the faster gear  14  must turn, and the more torque that is applied to such gear  14 , its component parts, and the spool  16  with which it is operatively engaged. The geared drive hub  12  is well suited to cope with the increased stresses and strains imposed by the use of modern printers. 
     In the preferred embodiment depicted in FIG. 1, the spool  16  is preferably constructed from a plastic material. The use of such a plastic spool eliminates the possibility of contaminating the printer ribbon (not shown) with particles of cardboard material from the cardboard spool commonly used in prior art devices. 
     In one embodiment, spool  16  consists essentially of plastic material. One may use plastics such as, e.g., acrylonititrile/butadiene/styrene (ABS), polystyrene, “DELRIN” (an acetal resin manufactured by the Du Pont de Nemours E.I. &amp; Company of Wilmington, Del.), and the like. 
     FIG. 2A is a side view of one preferred geared drive hub  12  of the invention. Referring to FIG. 2A, and in the preferred embodiment depicted therein, it will be seen that gear drive hub  12  is comprised of gear  14  which is connected by means of shaft  17  to the base  18  of the gear drive hub  12 . 
     Connected to base  18 , and preferable integrally connected to base  18 , is splined section  20 . Splined section  20  is preferable comprised of a multiplicity of stepped splines. 
     As is known to those skilled in the art, a spline is a device which permits the transmission of rotation or translatory motion along the axis of a shaft. Reference may be had, e.g., to U.S. Pat. Nos. 6,152,913, 5,620,427, 4,688,478, 4,237,750, and the like. The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     The splined section  20  preferable contains three stepped splines. Without wishing to be abound to any particular theory, applicants believe that the use of such three stepped splines affords their claimed structure umproved stability, better concentricity around the rotational axis of the gear splined hub, better distribution of torque, and better accuracy. With the high-speed printers commonly in use today, these features are especially important. 
     Referring again to FIG. 2A, one of the stepped splines, stepped spline  22 , is shown on the gear splined hub  12 . As will be apparent, stepped spline  22  is comprised of a lower section  24  communicating with an upper section  26 . 
     FIG. 2B is an end view of geared drive hub  12 , taken facing upper section  26  (see FIG. 2A) and illustrating splined assembly  20  and the stepped splines  22 ,  28 , and  30  which comprise such splined assembly  20 . This Figure is not to scale, having been enlarged for the sake of simplicity of representation. 
     As will be apparent, and in the preferred embodiment depicted in FIGS. 2A and 2B, stepped splines  22 ,  28 , and  30  are integrally connected to a central portion  32  to provide one integral assembly. 
     In the preferred embodiment depicted in FIG. 2B, arcuate sections  34 ,  36 , and  38  are disposed, respectively, between stepped splines  22  and  28 ,  28  and  30 , and  30  and  22 , respectively. These arcuate sections are commonly referred to as fillets. 
     Without wishing to be bound to any particular theory, applicants believe that the use of fillets  34 ,  36 , and  38  provide a stronger splined assembly  20 . 
     FIG. 2C is a sectional view of a spool  16  which may be used with the geared drive hub  12  depicted in FIGS. 2A and 2B. The upper section  26  of gear drive hub  12  (see FIG. 2A) is inserted into end  40  of spool  16  and, in particular, is disposed within receptacle  42  in which the stepped splines  22 ,  28 , and  30  (see FIG. 2C) are engaged within such receptacle  42 . 
     FIG. 2D is an end view of the spool  16 , indicating the cross-sectional shape of one embodiment of the receptacle  42  with which the splines  22 ,  28 , and  30  engage. 
     FIG. 2E is a sectional view of the gear drive hub  12  disposed within the spool  16 . 
     The stepped spline structure depicted in FIG. 2B preferably has stepped splines  22 ,  28 , and  30  disposed equidistantly about centerpoint  33 , located about 120 degrees from each other. This preferred stepped spline structure not only is capable of engaging the cross-sectional shape of receptacle  42 , but it is also capable of engaging with the cross sectional shapes depicted in FIG. 3 and, in particular, FIGS. 3A,  3 B,  3 C,  3 D,  3 E, and  3 F. Other cross-sectional shapes with which such splines may engage will be apparent to those skilled in the art. 
     FIG. 4 is a sectional view of one preferred embodiment of geared drive hub  12 . In the preferred embodiment depicted in FIG. 4, it will be seen that gear  14  has a thickness  50  of 0.16 inches, base  18  has a diameter  52  of 0.7 inches and a thickness  53  of 0.04 inches, the overall length  54  of geared drive hub  12  is 1.485 inches, the distance  56  between end  27  of the geared hub drive  12  and the top surface  29  of base  18  is 0.545 inches, and the distance  58  between the bottom surface  31  of the base  18  and the end  33  of upper spline section  36  is 0.5 inches. 
     It is to be understood that the aforementioned description is illustrative only and that changes can be made in the apparatus, in the ingredients and their proportions, and in the sequence of combinations and process steps, as well as in other aspects of the invention discussed herein, without departing from the scope of the invention as defined in the following claims.