Solid ink stick

Abstract: An ink stick (10) for use in a printer is disclosed, the ink stick having, in combination: (a) a top surface (12) and an opposing bottom surface (14), the bottom surface not being superimposable on the top surface; and (b) at least a first side and at least an opposing second side connecting the top surface and the opposing bottom surface at junctions, the at least first side and at least opposing second side being shaped so that a plane taken vertically through the top and opposing bottom surface does not create mirror images that are superimposable and the at least first side and at least opposing second side further being at least partly angled from a vertical line through at least one of the junctions such that one area intermediate the top surface and the bottom surface is a greater distance from the vertical line than at least one of the junctions; the ink stick (10) comprising a colorant and an ink carrier composition which comprises at least one of a urethane resin, a urea resin, a mixed urethane/urea resin or mixtures thereof and, optionally, a monoamide.

Description: This invention relates generally to color printer inks and, more specifically, to the particular shape of the solid phase change ink sticks that may be used in the ink feed chutes of a phase change ink color printer. The number of specific ink stick shapes that may be employed to minimize the sticking of the solid ink sticks to the sides of the feed chutes as they are fed down the feed chutes to melt plates is increased. The ink sticks are melted by the melt plates and stored in the reservoir area in liquid form for ejection by the print head onto a receiving medium. Solid ink jet printers were first offered commercially in the mid-1980's. One of the first such printers was offered by Howtek Inc. and used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings that fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends with separate rounded, five, six, and seven sided shapes each corresponding to a particular color. Later more successful solid ink printers, such as the Tektronix Phaser® III and the Jolt printer offered by Dataproducts Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed chute and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. As phase change ink color printers increase their printing speed there is the need to provide larger sized ink sticks so that refill of the ink reservoir in the print head is less frequent and more output or prints can be produced between refills. Also, as the number of phase change ink printers increase it is desirable to use different shaped ink sticks with each model of printer that employs different ink formulations to minimize the potential for the inadvertent use of the incorrect ink in a particular printer since the inks and the printers are customized and made for each to optimize printer output. Current ink sticks employ shapes that have two mirror planes of symmetry. European Patent EP 0703085 A2 discloses an ink stick shape for use in a printer ink stick feed chute wherein the opposing sides of the ink stick are tapered or angled from the horizontal so that at least one area intermediate the top and the bottom of the ink stick is a greater distance from the horizontal than the junction of the side walls and the bottom of the ink stick. The ink stick shape or geometry may be keyed to a particular color. Also, in printer designs where there is not a steep or generally vertical feed path to the heater plate, some provisions must be made to prevent the solid masses of shaped ink from sticking to the sides of the feed chutes so that regardless of the ink stick shapes employed an unrestricted feed of ink sticks proceeds down into the heater plate for melting. The melted ink then fills the individual colored ink reservoirs that are usually located within the print head. Larger sized ink sticks especially have the tendency to hang up or catch within the feed chutes when there is not a steep feed path to the melt plate, especially because of the sticky nature of the ink sticks' waxy exterior surfaces. It is the object of the present invention to improve the shape of an ink stick for a printer, to achieve a higher reliability of its functions. This object is achieved by an ink stick for use in a printer according to claim 1. It is an aspect of the present invention to provide a solid ink stick of a drafted or tapered chiral design that presents only a small surface area for the ink stick to contact the adjacent wall of the feed chute. The opposing sides of the ink sticks extend between the top and the bottom surfaces at an angle. It is a further aspect of the present invention to provide a solid ink stick shape that introduces elements of asymmetry to solid ink stick shapes while maintaining a minimum surface area for contact with the sides of the solid stick ink feed chute. It is another aspect of the present invention to provide a solid ink stick shape that is not superimposable on its mirror image. It is a further aspect of the present invention to provide a solid ink stick shape that does not employ an internal mirror plane or internal mirror planes. It is a feature of the present invention that the solid ink sticks of the present invention may possess an inversion center when viewed from a top plan view. It is another feature of the present invention that the solid ink sticks of the present invention are tapered with non-superimposable mirror images or planes and are otherwise chiral in shape. It is still another feature of the present invention that the solid ink sticks of the present invention are asymmetric when viewed from planes perpendicular and parallel to the top surface. It is an advantage of the present invention that upside down loading of solid ink stick shapes into a ink stick feed chute of a printer is not possible. It is another advantage of the present invention that an increased number of useful ink stick shapes is obtained for a possible design. These and other aspects, features and advantages are obtained by the use of a solid ink stick that utilizes a tapered or drafted design on the opposing sides from the top surface to the bottom surface in combination with the absence of internal mirror planes to form a chiral design. Preferably the solid ink sticks of the present invention comprise a colorant and an ink carrier composition. The colorant may be a dye or a coloured resin or any other coloured material suitable for use in hot melt jet ink printing. The ink carrier composition preferably comprises at least one of a urethane resin, a urea resin, a mixed urethane/urea resin or mixtures thereof and, optionally, a monoamide. Most preferably the ink carrier composition comprises a urethane resin and a mixed urethane/urea resin. Suitable ink carrier compositions are described in European Applications Nos 97304735, 97304731, 97304729, 97304727, 97304701 and 97304730. The use of the ink sticks described herein is particularly advantageous when the printers into which they are to be loaded have ink stick feed chutes that are shaped so as to allow entry of specifically shaped ink sticks only, ie black ink sticks may only be inserted into the feed chute leading to the reservoir for black ink, etc. Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a top plan view of an ink stick shape illustrative of the present invention showing the location of the inversion center and the absence of internal mirror planes; Fig. 2 is a view of a prior art solid ink stick showing internal mirror planes or planes of symmetry taken vertically through the inversion center of the top surface; Fig. 3 is a top plan view of an ink stick shape illustrative of the present invention; Fig. 4 is a side perspective view of the ink stick of Fig. 3 that is illustrative of the design of the present invention; and Fig. 5 an end elevational view of the ink stick of Fig. 3 that is illustrative of the present invention showing the tapering of the ink stick from top to bottom. As discussed hereafter in the context of the present invention, a plane of symmetry shall be understood to be a plane passing through an object such that the part on one side of the plane is the exact reflection of the part on the other side of the plane. The property of an object not being superimposable upon its mirror image shall define a chiral design. In other words, if a design is not superimposable on its mirror image, it is chiral. Chiral designs are asymmetric with respect to mirror planes taken through the ink stick in either the horizontal or vertical direction. Fig. 1 shows a top plan view of a representative solid ink stick shape configuration indicated generally by the numeral 10 that when combined with a taper from top to bottom creates a shape that is not superimposable on its mirror images. Fig. 1 shows an ink stick design that is asymmetric with respect to mirror planes when the planes are taken horizontally or vertically through the object. The inversion center of the top surface of the object is shown as 11 and can be defined as having the characteristic that each and every point in the plane can be taken through the inversion center an equal distance to obtain exactly the same surface. In other words, the inversion center is that point through which a line is passed and along which there exists two points topologically equivalent and equidistant from the inversion center. Ink stick 10 has two opposing ends 12 and 14 and opposing sides 15, 16, 18, 19, 20 and 21. Ink stick 10 has no internal mirror image planes. Fig. 2 in contrast shows a prior art ink stick design with the internal mirror planes shown created by the two planes of symmetry 35 and 36 taken through the axis of symmetry 38 that passes through the inversion center 39 for the top surface. Fig. 3 shows a top plan view of a representative solid ink stick configuration indicated generally by the numeral 22. Ink stick 22 has a front end 24 and an opposing rear end 25. Ink stick 22 has an illustrative design with a first side 27 formed by tapered or angled from the vertical side portions 26, 28, 29 and a second opposing side 33 formed by tapered or angled from the vertical side portions 30, 31 and 32. The taper of the opposing sides 26, 28 and 29, and 30, 31 and 32 is best seen in the end view Fig. 5 as they taper from the top 23 to the opposing bottom 34. The opposing sides can be flat, arcuate or have portions that are any combination thereof as illustrated by ink stick 22 to achieve the desired aesthetic appearance. For example, side portions 28, 29, 31 and 32 are flat and individually or collectively portions 28 and 29, as well as portions 31 and 32 can comprise less than about 50% of the length of the ink stick. Side portions 26 and 30 are arcuate. When employed in a chiral shaped ink stick, the tapering of the opposing sides from the top to the bottom prevents the mirror planes in the horizontal direction from being superimposable. The vertical plane asymmetry of the ink stick, when coupled with the tapering between the top and bottom surfaces, prevents the superimposability of the design. EXAMPLE 1 Preparation of Chiral Ink Sticks About 70 grams of the reaction product urethane material from Example 5 of EP 97304727, about 70 grams of the reaction product urethane/urea mixture material from Example 6 of EP 97304727, about 110 grams of Witco S-180 stearyl stearamide 1 and about 0.5 grams of Uniroyal Naugard 445 antioxidant 2 were combined in a stainless steel beaker. The materials were melted together at a temperature of about 140°C in an oven, then blended by stirring in a temperature controlled mantle at about 115°C for about half an hour. To this mixture was added about 5 grams of Solvent Blue 44. After stirring for about half an hour, the cyan ink was filtered through a heated Mott apparatus (available from Mott Metallurgical) using #3 Whatman filter paper and a pressure of about 15 psi. The filtered phase change ink was poured into appropriate moulds and allowed to solidify to form ink sticks having the shape shown in Figures 3, 4 and 5. While the invention has been described above with reference to specific embodiments thereof, it is apparent that many changes, modifications and variations in the materials, arrangements of parts and steps can be made without departing from the inventive concept disclosed herein. For example, in employing the solid ink stick configuration or shape of the present invention, it should be noted that the ink sticks 10 or 22 can be formed by any suitable process such as molding, extruding, or pouring into a container for shipping in which the ink cools and solidifies. The opposing top and bottom planar surfaces 23 and 33 can be of any shape, such as rounded or pointed, as well as the preferred generally planar shown.

Claims: An ink stick for use in a printer comprising, a colorant and an ink carrier composition which comprises at least one of a urethane resin, a urea resin, a mixed urethane/urea resin or mixtures thereof and optionally, a monoamide,with the outer shape of the ink stick having in combination: a top surface (23) and an opposing bottom surface (34), the bottom surface not being superimposable on the top surface; a front end surface (24) and a rear end surface (25) opposing the front end surface; and a first side (27) and an opposing second side (33) each of which adjoin to the front end surface, the rear end surface, the top surface and the bottom surface and are formed by at least one first portion (26, 30) which is arcuated and by at least one second portion (29,32) which is flat, the first portion and the second portion being tapered from the top to the bottom and adjoining at least the top surface and the bottom surface, characterised in that : the first side and the opposing second side are shaped by their portions (26,29) and (30,32) respectively, such that none of the mirror images of one of the first side and the second side is superimposable with the shaped portions of the other side, the mirror images being created by an arbitrary plane taken vertically through the top surface and the opposing bottom surface. An ink stick as claimed in claim 1, wherein the ink stick has a length defined between the front end surface and the opposing rear end surface and the at least one second portion (29,32) comprises less than about 50% of the length of the ink stick. An ink stick as claimed in any one of claims 1 to 2, wherein the top surface of the ink stick has an inversion center. A printer having printer ink feed chutes accommodating the ink stick according to any one of the claims 1 to 3, whereby the shape of the ink stick prevents upside down loading of the solid ink stick into printer ink feed chutes. The printer according to claim 4, wherein the printer ink feed chutes are shaped so as to allow entry of specifically shaped ink sticks only.

Inventors: MEINHARDT MICHAEL B, MEINHARDT, MICHAEL B.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1998
Main classification: B41J2
IPC codes: B41J2, C09D11