Patent Grant
7918618
1. Field of the Invention
The present invention is related to printers and more particularly print head assemblies of printers.
2. Description of Related Art
Controlling printing quality often requires proper, accurate registration between a print head and the underlying printer media. Such registration can be difficult to maintain with variations in printer media, including the thickness of the printer ribbon and printer label or paper stock.
A conventional printer 10, such as shown in
As shown in
The print head assembly 14 of the conventional printer 10 also includes the pressure spring 21 that has a V-shape, as shown in
Although helping the ceramic base 19 to maintain contact with the printer media and platen roller 18, the V-shaped pressure spring can interfere with passage of the media. Also, improvements in the ability of the print head assembly 14 to track the media are always desired.
Therefore, it would be advantageous to have a printer assembly that provides clearance for passage of media in a printer but still follows the media with accuracy for overall improved printing capability.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
The above needs are met and other advantages achieved by a printer assembly for printing on a supply of media traveling in a media direction of the present invention. The printer generally includes a platen assembly, a print head assembly and a pivot member. The pivot member provides for pivoting of the print head assembly relative to the platen assembly to adjust for variations in the media as it passes therebetween. Advantageously, the pivot member may be supported directly by the platen assembly, such as by bearing supports of the platen assembly, to reduce positioning error from intervening components. Preferably, the pivot member is positioned upstream of the print head assembly. Also, a pair of pivot members may each be supported at the ends of an angulation arm which is coupled to the print head assembly for angulation in the media direction but is uncoupled in the cross-media direction.
In one embodiment, the present invention includes a printer assembly for printing on a supply of media traveling in a media direction. The print head assembly includes a platen assembly configured to support the media. A print head assembly including a print line configured to print on the media as it passes between the print line and the platen. A biasing device of the printer assembly is configured to bias the print head assembly against the media supported by the platen. At least one pivot member is coupled to the print head assembly and pivotally supported relative to the print assembly. In this manner, the print line pivots about the pivot member in the media direction as the media travels between the print head assembly and the platen so as to adjust to variations in the media.
The pivot member may be supported directly by the platen assembly. For example, the print head assembly may be elongated and have a pair of opposite ends each supporting one of the pivot members. A pair of bearing supports rotatably support ends of the platen wherein each of the pivot members is supported by a respective one of the bearing supports. In this manner, the platen is configured to rotate on an axis and the pivot members are supported by a surface fixed relative to the axis.
In another aspect, the pivot members may be supported at ends of an angulation arm and the angulation arm is coupled to the print head assembly for pivoting in the media direction, but is uncoupled with respect to pivoting of the print head assembly across the media direction. For example, the angulation arm may have a coupling positioned midway between its ends that couples it to the print head assembly. The coupling may be a single post extending generally in the media direction from the angulation arm into an opening defined in the print head assembly, or vice versa. This allows the print head to follow the media in the cross-media direction.
The pivot member preferably defines a pivot surface approximating a point. For example, the pivot member may include a cone with a pointed free end defining a pivot surface. These cone pivot members can be supported at the ends of the angulation arm.
Portions of a printer 30 of one embodiment of the present invention are shown in
It should be noted that although the illustrated printer 30 prints using a ribbon and thermal print head, the invention could be useful in any type of printer wherein a printer head needs to follow printer media, such as thermal transfer printing or a direct thermal printing on heat-sensitive media.
The media supply 31, as shown in
The ribbon supply 32 includes a ribbon supply frame 37, a ribbon supply spool 38, a ribbon take-up spool 39 and a ribbon guide structure 40. The ribbon supply frame 37 includes two spaced walls positioned on opposite sides of the media supply path. Generally, each of the spaced walls includes two lobes 41 that extend upward away from the media path. A furthest upstream pair of the lobes spaced across the media supply path rotatably support the ribbon supply spool 38. Further downstream, and approximately above the print head assembly 34, a second spaced pair of lobes 41 rotatably supports the ribbon take-up spool 39.
Also supported by the ribbon supply frame 37 is the ribbon guide structure 40 which extends between the walls of the supply frame and has an edge positioned downstream and adjacent the ribbon take-up spool 39, as shown in
Parts of the ribbon supply frame 37 could also be considered to be ribbon guide structure 40 and vice versa. Regardless, it should be noted that the ribbon supply 32 could have different configurations for supplying ribbon, or not be present at all where a ribbon supply is not required, and still be within the purview of the present invention. Further, the ribbon supply 32 might even include thermal transfer ribbon supply features when the print head assembly of the present invention is used in a thermal transfer printer.
The platen assembly 33, as shown in
The support portion 45 preferably has an outer surface configured to grip and move the printer media past the print head assembly 34. A shaft 44 of the platen roller 42 has a relatively smaller cylindrical diameter than the support portion 45 and extends from ends of the support portion. The ends of the shaft 44 extend through the pair of bearing supports 43 and into a lower frame 46 of the printer 30 where they are rotatably mounted, as shown in
Each of the bearing supports 43, which may also be considered part of the print head assembly 34, have an overall semicircular disc shape defining a central opening 47, a heat sink support surface 48, a pivot support surface 49, a downstream notch 50 and a frame snap 51.
The central opening 47 allows passage of the shaft 44 of the platen roller 42 therethrough and into the lower frame 46 of the printer 30. In addition, the central opening 47 may also be configured to receive a bearing for rotatably supporting the shaft 44. The bearing supports, as shown in
The frame snap 51 is positioned upstream and defines a notch configured to grip a portion of the lower frame 46 of the printer 30. This connection inhibits rotational motion of the bearing supports 43 with respect to the lower frame 46. In addition, the frame snap 51 is positioned at the end of an arc-shaped arm that is free to flex under the forces of the passing media and movement of the platen roller 42. This facilitates the angulation of the print head 54 during printing.
The heat sink support surface 48 is defined by a flange positioned downstream and extending from a top edge of the bearing supports 43. This flange extends generally perpendicularly away from the media path and the heat sink support surface 48 accordingly extends at a right angle to the top edge of the bearing supports 43. The pivot support surface 49 extends parallel to the top edge and generally parallel to the media supply path. A plateau of each of the bearing supports 34 defines the pivot support surface 49 at a position upstream of the heat sink support surface 48.
As will be shown below, the bearing supports 43, and their respective heat sink and pivot support surfaces 48, 49 provide direct or near-direct reference points for the angulation of the print head. This is in contrast to conventional printers in which the angulation of the print head relative to the platen is controlled by several components, or there are several intervening components (e.g., V-shaped pressure spring 21, heat sink 20, bracket 22 and printer frame 11) between it and the platen.
The print head assembly 34 includes a spring housing 52, a heat sink 53, a print head 54 and an angulation arm 55, as shown in
Although there are five springs 57 in the illustrated embodiment, this number may vary, such as by using more springs for a greater cumulative bias, or allowing the use of lesser-biased springs, or less springs for less bias. The use of coil springs is advantageous in that they are generally more cost effective than other springs, such as the V-shaped spring 23, but other types of springs could also be employed, such as leaf springs, as long as some bias is imparted on the print head 54 in the direction of the printer media. The use of less expensive springs is facilitated by the pivoting action of the print head assembly 34 of the present invention which does not require any precisely defined spring behavior to cause angulation.
The spring housing 52 also includes a post 59 that ends in a flange 60. The post has a cylindrical shape and extends upstream, generally parallel with the path of the media and from a center position on the spring housing 52. The post 59 provides a rotatable mounting for the angulation arm 55, as shown in
The heat sink 53 also extends across the media path to the top edges of the two bearing supports 43. The heat sink 53 is preferably constructed by extrusion and has various structures that advantageously eliminate the need for an intervening bracket between the print head 54 and the media and platen assembly 33. The illustrated heat sink 53, for example, includes a base wall 61, an upstream wall 62, a downstream wall 63 and a bull nose 64 that all extend continuously along its length, due to its extruded manufacture. Notably, however, the heat sink 53 could also be constructed using other methods and still have similar structural characteristics. Preferably, the heat sink is made of a metal or other material that conducts heat away from the print head 54 and this function is facilitated by the aforementioned wall structure.
The base wall 61 is planar and extends (except for the tilt when following the media) generally parallel to and in the direction of media flow. The base wall 61 has an upstream free edge and downstream supports the upstream wall 62 and downstream wall 63 that extend perpendicularly therefrom. The walls 62, 63 are spaced apart so as to provide a slot for holding the spring housing 52 therebetween. In this manner, the spring housing 52 and the heat sink 53 are fixed with respect to each other. Extending from the intersection of the downstream wall 63 and the base wall 61 is the bull nose 64.
The bull nose 64, as shown in
The print head 54 is positioned at the media interface of the outside surface of the base wall 61. The print head includes a burn line that extends across the media path and is controlled and energized by a multiple pin connector 65 that extends along the base wall 61 and past the free edge of the base wall in the upstream direction as shown in
The angulation arm 55 includes a crossbar 66, a pair of legs 67 and a post grip 68, as shown in
One of a pair of pivot points 35 is supported by the end of each of the legs 67. The term “pivot point” as used herein refers to a relatively small-area which supports pivoting of the print head assembly 34 relative to the platen assembly 33. For example, as shown in
During operation of the printer 30, the media, such as label or card stock, is dispensed from the media supply receptacle 36 downstream toward the platen assembly 33 and the print head assembly 34. At the same time, the ribbon media extends off of the ribbon supply spool 38 toward the platen assembly 33 and the print head assembly 34. The printer ribbon extends over bull nose 64 of the heat sink 53 and over the burn line of the print head 54 and onto the ribbon take-up spool 39. The printer media extends over the outer surface of the support portion 45 of the platen roller 42 and is urged downstream by the driving of the platen roller. Variations in the printer media and ribbon media urge the print head 54, heat sink 53 and spring housing 52 toward the spring compression members 58, thereby compressing the springs 57 and angling the print head 54 to rotate about the pivot points 35. The pivot points 35 tilt and/or slip against the pivot support surface 49 of the bearing supports 43, thereby controlling the amount of tilt with respect to the platen roller 42. Thus, a torque resisting the tilt and causing the print head 54 to follow the media surface is generated and without the use of an expensive custom spring.
In another embodiment, the present invention includes a variation in the bearing supports 43, as shown in
The present invention has many advantages. The use of the print head locating features, such as the heat sink support surface 48 and the pivot support surface 49, reduces tolerance stack up when compared to conventional printers. The springs need not generate a torque or precise placement and therefore can be less expensive coil springs. The extruded heat sink 53 has components such as the bull nose 64 and base wall 61 supporting the print head 54 directly, that improves precision location of the print head 54 and eliminates an intervening bracket.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
This application claims priority from U.S. Provisional Application No. 60/781,011, filed Mar. 10, 2006, which is hereby incorporated herein in its entirety by reference.
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|---|---|---|---|
| 5528277 | Nardone et al. | Jun 1996 | A |
| 5746519 | Ricketts | May 1998 | A |
| 6068420 | Austin et al. | May 2000 | A |
| 20020135659 | Sato | Sep 2002 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20070212142 A1 | Sep 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60781011 | Mar 2006 | US |
