GB1570545A - Ink roller reservoir - Google Patents

Description

(54) INK ROLLER RESERVOIR (71) We, DYMO INDUSTRIES INC., a corporation organised under the laws of the State of California, with principal place of business at One Embarcadero Center, San Francisco, California, United States of America, 94111, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to inking of printing characters and particularly to inking rollers therefor.

In recent developments in the printing arts, the standard inking arrangement which includes an ink supply roller partially immersed in ink has been replaced by a hollow ink supply roller which is filled with ink.These hollow ink supply rollers are generally pre vided with holes spaced about the circumference thereof, and an exterior, permeable coating which limits the ink flow to the exterior and provides a smooth ink transfer to a transfer roller or to the indicia characters directly. These rollers are also provided with a vent arrangement which permits air to enter the roller and replace the ink as it is used.

These hollow ink supply rollers have suffered from significant drawbacks which have severely limited their usefulness. A material which provides consistent print density during repeated use will usually become saturated during prolonged periods of non-use. Using the roller again after such a period of non-use will result in severely over- inked images and blotching. Also, convene tional vented rollers have a tendency to leak through their vent holes during prolonged rest periods.

Furthermore, these rollers exhibit a gradual decline in the print density over their useful life, so that the print image gradually degrades and becomes more and more difficult to read Although human readers can usually adjust to the degraded image, machine readers, such as Optical Character Recognition (OCR) devices usually cannot. Thus the point at which the machine reader begins to misread the fading images is difficult to determine until significant errors have occurred.

To overcome the venting problem, sintered plastics rollers, spongy openecelled rubber rollers, and the like have been proposed.

These constructions exhibit the same print density degradation as noted above. Further more, many of teem still leak or cause blotching.

According to the invention there is vided an inking roller assembly, including a hollow cylinder having a microporous wall, means for closing the ends of the cylinder to form a chamber therein, a reservoir of ink of selected viscosity disposed within the chamber and a resilient microporous sleeve secured about the cylinder for transferring the ink from the surface of the cylinder to a printing device.

A printing character can be inked by cornpressing a portion of the sleeve against the outer surface of the microporous wall of the hollow cylinder to take up ink from the microporous wall, allowing said portion of the sleeve to expand to create a partial vacuum within the microporous wall and draw a portion of the ink from the reservoir into the micropoxfoqls wall, and thereafter allowing ambient air to infiltrate into the reservoir through the microporous wall to replace said portion of the ink.

Such an inking roller assembly having an ink supply reservoir therein, can provide a uniform print density over its useful life without causing blotching or over-inking after rest periods. It need have no vent hole to leak and it is not subject to seepage during normal changes in ambient or atmospheric pressure The hollow cylinder is preferably fabricated of sintered, ultra-high molecular weight polyethylene or similar organic or inorganic material and is hermetically sealed at both ends.

The cylinder contains an ink supply of selected viscosity which is drawn through the microporous wall by capillary action of the micropores in the wall. As the ink is removed from the microporous wall in use, ink flows from the reservoir by capillary action to replace the used ink. Removal of ink from the reservoir results in a slight pressure drop, with the result that outside air will be drawn through the micropores of the microporous wall in order to return the system to a condition of equilibrium.

The hollow cylinder can be formed of sintered material having a porosity of 2770 microns and comprising one of the following materials: sintered polyolefins; low and high density polyethylenes, polypropylene, polyolefin blends, sintered nylons, sintered fluorocarbons, sintered PVC, sintered thermoseting plastic and sintered metals.

In use, print characters impinge on the sleeve directly, compressing a portion of its resilient material. As the compressed area expands after contact, it draws ink out of the microporous wall to replace the ink just removed. Ink is drawn out of the reservoir by the capillary action of the micropores in the wail, and the system returns to equilibrium as the decreased pressure of the reservoir drawn air into the reservoir. Since a transfer roller to ink the print characters is not required, there is no requirement for initial cycling to bring a transfer roller up to uniform inking.

The cost of a transfer roller is also eliminated entirely.

The invention is diagrammatically illus trated by way of example in the accompanying drawings, in which: Figure 1 is a perspective view of an inking roller assembly according to the invention; and Figures 2--5 are a sequence of cross sectional views of the inking roller assembly shown in Figure 1, the sequence depicting the function during an inking cycle.

As shown in Figure 1, an inking roller assembly 11, to provide ink directly to indicia forming print characters, includes a hollow cylinder 12 fabricated of a micro-porous mat erial such as sintered, ultrahigh molecular weight polyethylene. Other microporous mat erials of natal or other materials might be used. The thickness of the cylinder wall where the material is polyethylene is approximately 0.( > 65 inches (1.65 mm), and the micropore diameter is uniform, ranging between 2 and 70 microns. If metal is used, the wall thickness may be as low as about 0.010 inches, with the naicrope diameters being about 10 microns. For softer materials, the wall thick-.

ness might be in excess of .070 inches, and the micropore diameters over 40 microns. The ends of the cylinder 12 are closed to provide a chamber therein, such as by the use of end caps 13. Each end cap is provided with an axially disposed, outwardly extending shaft 14 which engages roller carrier arms 16 normally provided in a printing device.

Disposed within the cylinder 12 is a reservoir of printing ink, the ink having a viscosity at 70"F of approximately 1000 cps and a range of 100--5000 cps, depending on the nature of the microporous material. Disposed about the cylinder 12 is a sleeve 18 formed of a resilient microporous material, such as elastomer or rubber. The sleeve is preferably formed of microporous elastomer material having a durometer reading range of 5745 and a wall thickness of approximately 0.040 inches (1.03 mm), the porosity being so selected that the ink may pass therethrough. The sleeve preferably extends in the axial direction less than the length of the cylinder to expose a portion of the cylinder director to ambient air, and in use can impinge directly on an indicia forming print character.

As shown in Figures 2 and 3, as a print head 23 translates tangentially with respect to the roller assembly 11, the print characters 21 impinge on the sleeve 18 of the roller, and are thus inked. The tangential velocity of the print head imparts a rotational motion to the roller assembly 11, and the radial component of the print head velocity compresses a portion 22 of the sleeve 18 which has contacted the print characters.

As the compressed portion 22 expands and returns to its original shape by natural resilience, the suction created thereby draws ink out of the wall of the cylinder 12. This ink is replaced in the wall by capillary action of the micropores in the wall. As many printing cycles are completed, this removal of the ink from the interior of the cylinder 12 creates a decrease in the pressure inside the cylinder.

When the decrease in pressure becomes sufficient to overcome the resistance of the ink in the wall of the cylinder 12, air is drawn into the cylinder through its sintered wall until the pressure equilibrium is re-established.

Also, tests have shown that the roller assembly 11 exhibits a marked drop-off in print intensity at the end of its useful life, while maintaining a constant print intensity prior to that time. For example, inking roller assemblies according to the invention have successfully completed more than 140,000 print cycles yielding uniform print intensity, and then have failed within the next 5000 print cycles to the point of illegibility. This rapid drop.off makes it very easy to ascertain when roller replacement is required.

Another advantage of the construction of the roller assembly 1,1 is that the micropores of the sleeve 18 and the wall of the cylinder 12 are saturated with ink, and are always ready to print. Also, no transfer roller is required to apply the ink to the print characters. Thus no "warm-up time" is needed to bring the inking system using the roller assembly 11 to the point where the print density is uniform. Even after an extended rest period, the roller assembly 11 will create a dense printed character, without blotching or overinking.

WHAT WE CLAIM IS: 1. An inking roller assembly, including a hollow cylinder having a microporous wall, means for closing the ends of the cylinder to form a chamber therein, a charge of ink of selected viscosity disposed within the chamber and a resilient, microporous sleeve secured about the cylinder for transferring the ink from the surface of the cylinde- to a printing device.

2. An inking roller assembly according to claim 1, wherein the wall of the cylinder has a porosity in the range of 2-70 microns.

3. An inking roller assembly according to claim 1 or claim 2, wherein the ink has a viscosity in the range of 100 5000 cps at 70 F.

4. An inking roller assembly according to any one of claims 1 to 3, wherein the sleeve is formed of microporous elastomer material having a durometer reading range of 5-45.

5. An inking roller assembly according to any one of claims 1 to 4, wherein the sleeve extends in the axial direction less than the length of the cylinder to expose a portion of the cylinder directly to ambient air.

6. An inking roller assembly according to claim 1, wherein the hollow cylinder is formed of sintered material having a porosity d 2-70 microns and comprising one of the following materials: sintered polyolefins; low and high density polyethylenes, polypropylene, polyolefin blends, sintered nylons, sintered fluorocabons, sintered PVC, sintered thernoseting plastic, and sintered metals.

7. A method of inking a printing character using an inking roller assembly according to any one of claims 1 to 6, comprising the steps of compressing a portion of the sleeve against the outer surface of the microporous wall of the hollow cylinder to take up ink from the microporous wall, allowing said portion ot the sleeve to expand to create a partial vacuum within the microporous wall and draw a portion of the ink from the reservoir into the microporous wall, and thereafter allowing ambient air to infiltrate into the reservoir through the microporous wall to replace said portion of the ink.

8. An inking roller assembly, including a hollow cylinder formed of a microporous material having a porosity in the range of 2-70 microns; the cylinder having a single, axially extending general cylindrical chamber therein; means closing the ends of said cylinder to close said chamber; a charge d liquid ink disposed within said chamber and having a viscosity in the range of 1005000 cps at 70 F; and a resilient, microporous sleeve secured about said cylinder, for tssinsferring said ink from the outer surface of said cylinder to a printing device in metered fashion, said sleeve being formed of a microporous elastomer material having a Shore D durometer reading in the range of 5745.

9. An inking roller assembly substantially as hereinbefore described and illustrated with reference to the accompanying drawing.

10. A method of inking a printing chaeeceer as claimed in claim 7 and substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. point where the print density is uniform. Even after an extended rest period, the roller assembly 11 will create a dense printed character, without blotching or overinking. WHAT WE CLAIM IS:

1. An inking roller assembly, including a hollow cylinder having a microporous wall, means for closing the ends of the cylinder to form a chamber therein, a charge of ink of selected viscosity disposed within the chamber and a resilient, microporous sleeve secured about the cylinder for transferring the ink from the surface of the cylinde- to a printing device.

2. An inking roller assembly according to claim 1, wherein the wall of the cylinder has a porosity in the range of 2-70 microns.

3. An inking roller assembly according to claim 1 or claim 2, wherein the ink has a viscosity in the range of 100 5000 cps at 70 F.

4. An inking roller assembly according to any one of claims 1 to 3, wherein the sleeve is formed of microporous elastomer material having a durometer reading range of 5-45.

5. An inking roller assembly according to any one of claims 1 to 4, wherein the sleeve extends in the axial direction less than the length of the cylinder to expose a portion of the cylinder directly to ambient air.

6. An inking roller assembly according to claim 1, wherein the hollow cylinder is formed of sintered material having a porosity d 2-70 microns and comprising one of the following materials: sintered polyolefins; low and high density polyethylenes, polypropylene, polyolefin blends, sintered nylons, sintered fluorocabons, sintered PVC, sintered thernoseting plastic, and sintered metals.

7. A method of inking a printing character using an inking roller assembly according to any one of claims 1 to 6, comprising the steps of compressing a portion of the sleeve against the outer surface of the microporous wall of the hollow cylinder to take up ink from the microporous wall, allowing said portion ot the sleeve to expand to create a partial vacuum within the microporous wall and draw a portion of the ink from the reservoir into the microporous wall, and thereafter allowing ambient air to infiltrate into the reservoir through the microporous wall to replace said portion of the ink.

8. An inking roller assembly, including a hollow cylinder formed of a microporous material having a porosity in the range of 2-70 microns; the cylinder having a single, axially extending general cylindrical chamber therein; means closing the ends of said cylinder to close said chamber; a charge d liquid ink disposed within said chamber and having a viscosity in the range of 1005000 cps at 70 F; and a resilient, microporous sleeve secured about said cylinder, for tssinsferring said ink from the outer surface of said cylinder to a printing device in metered fashion, said sleeve being formed of a microporous elastomer material having a Shore D durometer reading in the range of 5745.

9. An inking roller assembly substantially as hereinbefore described and illustrated with reference to the accompanying drawing.

10. A method of inking a printing chaeeceer as claimed in claim 7 and substantially as hereinbefore described.