Abstract:
A heater including a plurality of first dielectric vanes and a plurality of second dielectric vanes arranged about a longitudinal axis, each first dielectric vane and second dielectric vane having a plurality of wire guiding grooves, a heater wire structure wound around the first and second dielectric vanes in wire guiding grooves, and wherein the heater wire structure substantially avoids contact with bottoms of the wire guiding grooves of the second dielectric vanes.

Description:
BACKGROUND  
       [0001]     The subject disclosure is generally directed to a heater that can be employed in printing apparatus such as printers, photocopiers, and multi-function devices.  
         [0002]     Some printing technologies employ one or more heaters, for example to heat a print drum or a platen. As a specific example, a solid ink jet printing apparatus can include a heated print drum on which an image is formed pursuant to fluid drop jetting. The image is then transferred to an output print medium such as paper.  
         [0003]     It can be difficult to implement a heater that is reliable. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0004]      FIG. 1  is a schematic block diagram of an embodiment of a solid ink printing apparatus.  
         [0005]      FIG. 2  is a schematic isometric view of an embodiment of a print drum heater.  
         [0006]      FIG. 3  is a schematic isometric view of an embodiment of an expandable frame portion of the print drum heater of  FIG. 2 .  
         [0007]      FIG. 4  is a schematic isometric view of the expandable frame portion of the print drum of  FIG. 2  with a wire structure wound around the expandable frame portion.  
         [0008]      FIG. 5  is an elevational view of an embodiment of an inner panel of an end cap structure of the print drum heater of  FIG. 2 .  
         [0009]      FIG. 6  is an elevational view of an embodiment of an intermediate panel of an end cap structure of the print drum heater of  FIG. 2 .  
         [0010]      FIG. 7  is an elevational view of an embodiment of an outer panel of an end cap structure of the print drum heater of  FIG. 2 .  
         [0011]      FIG. 8  illustrates a use of the print drum heater of  FIG. 2  in the printing apparatus of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0012]      FIG. 1  is a schematic block diagram of an embodiment of a printing apparatus  10  in which a disclosed heater can be employed. The printing apparatus includes a printhead  11  that is appropriately supported for stationary or moving utilization to emit drops  13  of ink onto an intermediate transfer surface  12  applied to a supporting surface of a print drum  14 . The ink can be melted solid or phase change ink, for example. The intermediate transfer surface  12  can be a liquid layer such as a functional oil that can be applied by contact with an applicator such as a roller  16 A of an applicator assembly  16 . By way of illustrative example, the applicator assembly  16  can include a metering blade  16 B and a reservoir  16 C. The applicator assembly  16  can be configured for selective engagement with the print drum  14 .  
         [0013]     The printing apparatus  10  further includes a substrate guide  20  and a media preheater  27  that guides a print media substrate  21 , such as paper, through a nip  22  formed between opposing acutated surfaces of a roller  23  and the intermediate transfer surface  12  supported by the print drum  14 . Stripper fingers  24  can be pivotally mounted to assist in removing the print medium substrate  21  from the intermediate transfer surface  12  after an image  26  comprising deposited ink drops is transferred to the print medium substrate  21 .  
         [0014]      FIGS. 2-7  schematically depict an embodiment of a heater that can be used to heat the print drum  14  of the printing apparatus  10  of  FIG. 1 . The drum heater can comprise a plurality of longitudinally extending dielectric wire guiding vanes  36 ,  37  angularly distributed about a central longitudinal axis CA, wherein each dielectric vane is positioned such that its transverse or width dimension extends radially relative to the central longitudinal axis. Each dielectric vane includes, for example, wire guiding grooves  39  along longitudinal edges that are radially furthest from the central axis CA. A wire structure comprising for example two side by side heater wires  62 ,  64  is spirally wound around the vanes  36 ,  37  such that the heater wires are generally between sides of the wire guiding grooves  39 . Depending upon implementation, the heater wires  62 ,  64  can be of different diameters and/or resistivities, for example. The drum heater further includes wire retaining dielectric panels  67  attached to the dielectric vanes  36  adjacent the grooves  39 , and end cap structures  70 .  
         [0015]     By way of illustrative example, the dielectric vanes  36  can be connected to each other in the vicinity of the central axis CA and form a cross in cross-section, such that the dielectric vanes can be angularly located about the central axis CA at about 90 degree intervals. The dielectric vanes  37  can be panels that are not fixedly connected to any other dielectric vane, and can be angularly located about the central axis at about 90 degree intervals. The dielectric vanes  36 ,  37  and the wire retaining dielectric panels  39  are held together by the end cap structures  70  which engage longitudinally separated end portions or tabs  36 A of the dielectric vanes  36 , longitudinally separated end portions or tabs  37 A of the dielectric vanes  37 , and longitudinally separated end portions  67 A of the wire retaining dielectric panels  67 , as well as by attachment of the wire retaining dielectric panels  67  to associated dielectric vanes  36 ,  37 . The end tabs  36 A of the vanes  36  can comprise for example integral tabs that are shared by radially opposed vanes  36 .  
         [0016]     Each end cap structure  70  can comprise a plurality of panels, for example, and  FIG. 5  schematically illustrates an embodiment of inner panel  71  of the end cap structure  70 .  FIG. 6  schematically illustrates an embodiment of an intermediate  72  panel of the end cap structure  70 , and  FIG. 7  schematically illustrates an embodiment of an outer panel  73  of the end cap structure  70 .  
         [0017]     Each inner panel  71  includes crossed slots  136  generally centered on the central axis CA for radially and angularly capturing the tabs  36 A so that the dielectric vanes  36  are at 90 degree angular spacing. Each inner panel  71  further includes slots  137  for angularly capturing the tabs  37 A such that each of the dielectric vanes  37  is angularly positioned between adjacent vanes  36 , for example. The slots  137  have a radial extent that is greater than the radial extent of the tabs  37 A, which allows the dielectric vanes  37  to be displaced radially while the intermediate and outer panels  72 ,  73  are not engaged with the tabs  36 A,  37 A,  67 A. The intermediate panels  72  generally function to axially secure the inner panels  71  and the intermediate panels  72  onto the tabs  36 A, and to generally locate the tabs  37 A in their innermost radial position such that the dielectric vanes  37  are generally in their innermost radial position. The intermediate panels  72  further engage the tabs  67 A of the wire retaining dielectric panels  67 . The outer panels  73  also support and locate the end tabs  67 A of the wire restraining dielectric panels  67 , and axially secure the inner panels  71 , the intermediate panels  72  and the outer panels  73  onto the tabs  36 A. By way of illustrative example, the intermediate and outer panels  72 ,  73  are configured to be axially slipped over the tabs  36 A and twisted to engage radial notches formed in the tabs  36 A. The wire restraining dielectric panels  67  are attached to the protruding tabs of the dielectric vanes  36 ,  37  after the intermediate and outer panels are meshed and twisted onto the tabs  36 A. The dielectric wire restraining panels  67  assist in maintaining the vanes  37  in a radially inward position when attached thereto.  
         [0018]     Referring more particularly to  FIG. 3 , the dielectric vanes  36 ,  37  and the inner end panels  71  comprise an expandable frame wherein at least some of the dielectric vanes can be selectively displaced radially outwardly, for example by engagement of the tabs  37 A with clamps  81 ,  83  that respectively include concial ramps  81 A,  83 A for pushing the tabs  37 A outwardly.  
         [0019]     By way of illustrative example, the dielectric vanes  36 ,  37  and the inner end panels  71  can be configured such that when the dielectric vanes  37  are in an outermost radial or expanded position, the bottoms of the wire guiding grooves  39  of the dielectric vanes  37  are further from the central axis than the bottoms of the wire guiding grooves of the dielectric vanes  36 , and such that when the dielectric vanes  37  are in a radially innermost or retracted position, the bottoms of the wire guiding grooves of the dielectric vanes  37  are at substantially the same distance from the central axis CA as the bottoms of the wire guiding grooves  39  of the dielectric vanes  36 . By way of specific example, the dielectric vanes  37  and the inner panels  71  can be configured such that the bottoms of the wire guiding grooves  39  of all of the dielectric vanes  36 ,  37  are substantially on an imaginary cylinder substantially centered on the central axis CA when the vanes  37  are in an innermost or retracted radial position, for example as determined by the slots  137  of the inner end panels  71  and such that the bottoms of the wire guiding grooves  39  of the dielectric vanes  37  are outside of such imaginary cylinder when the vanes  37  are in an outermost or expanded radial position, for as determined by the slots  137  of the inner end panels  71 .  
         [0020]     Alternatively, the dielectric vanes  36 ,  37  and the inner end panels  71  can be configured such that when the dielectric vanes  37  are in an outermost radial or expanded position, the bottoms of the wire guiding grooves  39  of the dielectric vanes  37  are at substantially the same distance from the central axis CA as the bottoms of the wire guiding grooves  39  of the dielectric vanes  36 , and such that when the dielectric vanes  37  are in a radially innermost or retracted position, the bottoms of the wire guiding grooves  39  of the dielectric vanes  37  are closer to the central axis CA than the bottoms of the wire guiding grooves  39  of the dielectric vanes  36 . By way of specific example, the dielectric vanes  36 ,  37  and the inner panels  71  can be configured such that the bottoms of the wire guiding grooves  39  of all of the dielectric vanes  36 ,  37  are substantially on an imaginary cylinder substantially centered on the central axis CA when the vanes  37  are in an outermost or expanded radial position, for example as determined by the slots  137  of the inner end panels  71  and such that the bottoms of the wire guiding grooves  39  of the dielectric vanes  37  are inside of such imaginary cylinder when the vanes  37  are in an innermost or retracted radial position, for as determined by the slots  137  of the inner end panels  71 .  
         [0021]     In manufacture, the dielectric vanes  36 ,  37  and the inner end panels  71  are assembled as an expandable frame that can be mounted in a coiling fixture that pushes on the tabs  37 A to move the dielectric vanes  37  radially outwardly, for example to an outermost radial position as determined by the slots  137  of the inner end panels  71 . Heater wire is then coiled into the wire guiding grooves  39  of the expanded frame such that the heater wire contacts substantially all of the bottoms of the wire guiding grooves  39 , and the ends of the wire or wires are suitably secured to brackets attached to one or more of the dielectric vanes  36 , for example. This generally fixes the shape of the wire structure. After removal of the coiled frame from the coiling fixture, the dielectric vanes  37  are retracted radially inwardly, for example to an innermost radial position as determined by the slots  137  of the inner end panels  71 , and the wire retaining dielectric panels  67 , the intermediate panels  72  and outer panels  73  are assembled with the coiled frame. The wire retaining panels  67  can then be attached to associated dielectric vanes  36 ,  37 , which will prevent unlocking rotation of the intermediate and outer panels  72 ,  73 .  
         [0022]     Thus, in the assembled print drum heater, the dielectric vanes are in a radially retracted position and the bottoms of the wire guide grooves  39  of the dielectric vanes  37  are displaced from the coiled heater wire structure. This allows the heater wires  62 ,  64  to substantially avoid contact with bottoms of the wire guiding grooves of the dielectric vanes  37 .  
         [0023]      FIG. 8  illustrates a use of the heater of  FIG. 2  in the print drum  14  of the printing apparatus of  FIG. 1 .  
         [0024]     The disclosed heater structure can be reliable as a result of reduced contact between the heater wire structure and the dielectric vanes, which can allow the heater wire structure to be generally unconstrained and able to move, lengthen and/or shorten pursuant to heating and cooling with reduced loading on the dielectric vanes. Also, the reduced contact between the heater wire structure and the dielectric vanes can reduce cold spots that can be detrimental to heater life.  
         [0025]     The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.