WO1999062714A1

WO1999062714A1 - Printhead attachment structure and method

Info

Publication number: WO1999062714A1
Application number: PCT/US1999/012296
Authority: WO
Inventors: Michael David Lattuca; Darrin Wayne Oliver
Original assignee: Lexmark International, Inc.
Priority date: 1998-06-03
Filing date: 1999-06-03
Publication date: 1999-12-09
Also published as: AU4414699A

Abstract

The invention described in the specification relates to a multi-functional device for a printhead of an ink jet printer and a means (38, 32) for attaching the device to an ink cartridge body (12). The device is comprised of a substrate holder (10) or carrier containing one or more substrate locator wells (16, 18, 20) for mounting semiconductor substrates (17) thereon. The substrate holder has a top surface and at least two alignment devices (28) attached adjacent at least one of the side walls for precisely positioning and attaching the substrate holder adjacent to an ink reservoir (12). The alignment devices are of a size and shape that facilitates easy connection between the carrier and cartridge body and provides a means for aligning the body to the carrier once the connection is made.

Description

PRINTHEAD ATTACHMENT STRUCTURE AND METHOD

FIELD OF THE INVENTION

The invention relates to a multi-functional device for a printhead of an ink jet printer and a means for attaching the device to an ink cartridge body.

BACKGROUND OF THE INVENTION Thermal ink jet printers use printheads containing heating elements on a semiconductor substrate for heating ink so that the ink is imparted with sufficient energy to cause the ink to be ejected through a nozzle hole in a nozzle plate attached adjacent to the substrate. The nozzle plate typically consists of a plurality of spaced nozzle holes which cooperate with individual heater elements on the substrate to eject ink from the printhead toward the print media. The number, spacing and size of the nozzle holes influences the print quality. Increasing the number of nozzle holes on a printhead typically increases the print speed without necessarily sacrificing print quality. However, there is a practical limit to nozzle hole or orifice size and to the size of the semiconductor substrate which can be produced economically in high yield. Thus, there is a practical limit to the number of corresponding nozzle holes which can be provided in a nozzle plate for a printhead.

For color printing applications, the three primary colors of cyan, magenta and yellow are used to create a pallet of colors. Typically, each color is associated with a separate nozzle plate and semiconductor substrate specifically designed or tuned to give optimal performance with the associated color. Such nozzle plates are typically attached to separate printheads so that the number of nozzle holes per color is maximized for high quality, high speed printing. However, it is extremely difficult to maintain an alignment tolerance of a few microns between the printheads when using separate printheads.

Using a single substrate containing separate heating elements for each color reduces the alignment problem associated with using separate printheads but reduces the number of nozzle holes and thus the print speed because of the practical limit to substrate size. In order to obtain suitable substrate production yields, the substrates or chips are not large enough to contain the same number of energy imparting devices as would be located on individual substrates attached to separate printhheads.

While locating multiple individual substrates of a conventional size on the same printhead allows relatively faster printing rates. Such a design contributes to significantly increasing the printhead temperature because of the greater number of energy imparting devices located on the printhead and the desire to eject the ink from the printhead at a faster rate. An increased printhead temperature causes problems with ink ejection due to viscosity changes in the ink resulting in oversize ink droplets and well as untimely ejection of ink from a nozzle hole. Higher temperatures may also contribute to plugging of the nozzle holes by a build up of ink decomposition products adjacent the nozzle holes. Furthermore, without adequate temperature control, dimensional changes in the printhead dimensions are not predictable making it difficult to achieve the desired dot placement thus adversely affecting print quality.

Various materials and methods have been proposed for removing heat from the printhead substrates. For example, U.S. 5,084,713 to Wong describes flowing ink from the reservoir through a support panel for the heater substrate to cool the printhead. Such a design requires an adequate flow of ink to the printhead in order to remove sufficient heat therefrom.

U.S. Patent 5,066,964 to Fukuda et al. describes the use of flowing ink in combination with a heat capacity member to remove ink from the printhead in order to cool the printhead. U.S. Patent 5,657,061 to Seccombe et al. describes the use of a heat exchanger in the ink flow path to cool the ink and thus cool the printhead as the ink flow to the substrate. Other methods of removing heat include the use of a heat pipe and blower as described in U.S. Patent 5,451,989 to Kadowaki et al. Conventionally, materials which exhibit a low thermal expansion coefficient have been used to provide suitable heat removal without sacrificing print quality. Materials having low thermal expansion coefficients do not typically expand or contract a sufficient amount to affect printer operation and thus print quality. The materials also enable easier and cheaper printhead fabrication techniques since expansion and/or contraction of the components and electrical connections therebetween is minimized. However, such materials are typically made from exotic composite materials such as metal-ceramic mixtures, carbon fiber, or graphite composites which are costly to make and use in such applications.

An object of the invention is to provide an improved printhead structure.

Another object of the invention is to provide a method for attaching a printhead structure to an ink cartridge body, Still another object of the invention is to provide an improved connection between a cartridge body and a printhead structure.

A further object is to provide a multi-color printhead for thermal ink jet printer which provides improved print quality at a relatively lower cost than conventional printheads. Still another object of the invention is to provide a multi-function printhead structure which may be easily attached to an ink cartridge body.

SUMMARY OF THE INVENTION

With regard to the above and other advantages, the invention provides an ink jet printhead structure including a substrate holder containing one or more substrate locator wells for receiving semiconductor substrates thereon, the substrate holder having a top surface and side walls attached to the top surface along the perimeter thereof providing an open cavity opposite the top surface and at least two alignment devices attached adjacent at least one of the side walls for precisely maintaining the substrate holder adjacent to an ink reservoir. It is preferred that the substrate holder be molded, cast or machined for precision and it is particularly preferred that the substrate holder be made completely or substantially of metal.

In another aspect, the invention provides a method for attaching a substrate carrier to an ink cartridge body. The method includes providing a multifunction substrate carrier, the substrate carrier having a top surface containing one or more substrate locator wells, side walls attached to the top surface along the perimeter thereof and substantially perpendicular thereto providing an open cavity opposite the top surface and an alignment device containing a slot or hole, at least one alignment device being adjacent opposing side walls of the carrier for precisely aligning and attaching the substrate carrier to an ink cartridge body containing at least one upstanding alignment tab pending from each of two opposing cartridge body walls, engaging the tabs with the slots and deforming the tabs to fixedly attach the carrier to the cartridge body. The apparatus and method of the invention provide a cost effective substrate carrier and ink cartridge body for use with ink jet printers. The substrate carrier has the added advantage of being made from a material which more effectively conducts heat away from the semiconductor substrates attached to the carrier as compared to materials conventionally used for ink jet cartridges and printheads so that multiple substrates can be mounted on a single carrier and the printhead can be driven harder to eject ink at a faster rate thereby improving, the speed, quality and reliability of the printer.

By providing a separate nosepiece or substrate carrier and an alignment and attachment structure for readily attaching the substrate carrier to a separate ink cartridge body with sufficient accuracy to assure proper alignment of the printhead relative to a printer carriage, materials having more effective heat removal than plastic may be used for the nosepiece. Because the cartridge body and carrier are separate structures, the carrier can be made of materials which include exotic composite materials such as materials containing a high content of carbon fibers or graphite and metal-ceramic materials and relatively inexpensive metals such as aluminum, zinc and copper possessing relatively high thermal conductivities and having relatively high thermal expansion coefficients in contrast to the cartridge body which may be made from inexpensive plastic materials. Conventional ink cartridges are unitary constructions which are usually completely made of plastic or polymeric materials.

Furthermore, the nosepiece and cartridge body can be manufactured separately and assembled in a separate step after the acceptability of each part is determined rather than producing a unitary structure that may or may not meet manufacturing tolerances. Thus, the yield of useable product is effectively increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the following drawings, which are not to scale so as to better show the detail, in which like reference numerals denote like elements throughout the several views, and wherein:

Figs. 1 is a perspective view of the method for attaching a substrate carrier according to the invention to an ink jet printer cartridge;

Fig. 2 is an enlarged perspective view of one of a tab used for aligning and attaching a substrate carrier to an ink cartridge body for an ink jet printer cartridge; and

Fig. 3 is a perspective view of a fully mated substrate carrier and ink cartridge according to the invention.

DETAILED DESCRIPTION OF THE INVENTION With reference now to Figs. 1 and 2 there is shown, in perspective views, a substrate carrier 10 and an ink cartridge holder 12 according to the invention. The substrate carrier 10 is preferably of a one-piece construction made of a cast, machined or molded material having a top surface 14 containing one or more substrate locator wells 16, 18 and 20. The wells 16, 18 and 20 are precisely located on the top surface 14 of the carrier 10 to provide accurate placement of two or more semiconductor substrates 17 on the carrier for producing a multi- carrier printhead. For the carrier 10 shown in Fig. 1, the wells 16, 18 and 20 contain semiconductor devices 17 and nozzle plates for the primary ink colors of cyan, yellow and magenta or for black, cyan and magenta ink colors.

The carrier 10 also preferably contains side walls such as walls 22 and 24 which are adjacent and preferably attached to the top surface 14 along the perimeter thereof providing an open cavity opposite the top surface 14. The carrier 10 may be made of a variety of materials including composite materials made of carbon fibers, graphite, metal-ceramic materials and metals. The preferred material for the substrate carrier 10 is a metal material selected from aluminum, beryllium, copper, gold, silver zinc and tungsten and alloys of two or more of the foregoing metals.

The size of each well 16, 18 and 20 is preferably such that each well can accommodate one semiconductor chip 17 ranging in size from about ! inch to about Vi inch long and about 2 to 4 millimeters wide. Each well 16, 18 and 20 contains apertures or ink feed slots 26 in the bottom or base of the wells which enable ink from an ink reservoir to flow to the energy imparting areas of the chips or substrates either around the edges of the chips or through generally centrally located vias in the chips. The energy imparting areas of the chips may be provided as by resistive or heating elements which heat the ink or piezoelectric devices which induce pressure pulses to the ink in response to a signal from a printer controller.

The carrier 10 is preferably a shaped, molded or machined device which may contain cooling fins 27 and 29 along one or more side walls 22 and 24 thereof for convective cooling of the carrier 10. The cooling fins 27 and 29 can have a variety of shapes and orientations and are preferably machined, molded or cast into the carrier 10. Separate cooling fin structures may also be fixedly attached to one or more of the side walls 22 and 24 as by use of heat conductive adhesives, solder and the like. Each well 16, 18 and 20 is associated with a corresponding chamber on the opposing side of the carrier for directing ink from an ink cartridge to the corresponding semiconductor substrate.

An improved printhead according to the invention includes carrier 10 attached to an ink cartridge or cartridge holder 12 which contains an ink supply source for feed of ink to substrates in the wells 16, 18 and 20 of the carrier 10. In order to precisely control the location of the ink drop placement on a printed media, the carrier should be mounted on the ink cartridge or cartridge holder body 12 within a tolerance of from about ± 0.01 to about ± 0.05 millimeters. Accordingly, the carrier is provided with alignment devices 28 containing slots or holes 30 which correspond to alignment tabs 32 pending from the cartridge body 12. At least one alignment device 28 containing a hole or slot 30 is positioned on each of opposing side walls of the carrier 10 preferably toward the lower end of the side walls opposite the end of the side walls attached to the top surface 14 of the carrier 10.

In Fig. 1, carrier 10 contains two alignment devices 28 on side wall 22. The opposing side wall from wall 22 also preferably contains two alignment devices 28. Likewise side wall 24 and the opposing side wall from side wall 24 may contain one or more alignment devices 28. Other projections, marks or slots may be used to align the carrier 10 and cartridge body 12 relative to one another.

The cartridge body or ink cartridge holder 12 is preferably made of a thermoplastic material such as high or low density polypropylene, polyethylene and the like. The body 12 has at least one open end wherein the body is attached to the carrier and may contain ink in liquid form or contain an ink saturated foam insert. The body 12 may have two open ends, one open end attached to the carrier 10 and an opposing open end for inserting into the body cavity 34 one or more ink cartridges, each of the cartridges containing ink or an ink saturated foam and being provided for supplying ink to each of the substrates in the ink wells 18, 16 and 20 of the carrier 10. The slots or holes 30 are precisely made in the alignment devices 28 of the carrier 10 to align with tabs or projections 32 which are adjacent the top perimeter 36 of the cartridge body walls 38, 40 and 42, and 44, the tabs 32 being preferably made of the same material as the holder 12. The tabs 32 are shown on the perimeter of three side walls 38, 40 and 42 of the cartridge holder 12 but may be on all four side walls or only on two opposing side walls along the top perimeter 36 of the cartridge body 12. It is preferred that the slots or holes 30 be somewhat larger than the tabs or projections 32 in order to allow for adjustment of the carrier 10 relative to the body 12. The shape of the tabs 32 and slots 30 is not critical to the invention provided mating shapes are used for both the tabs and the slots. Accordingly, the tabs and slots may be circular, oval, round, square, rectangular, triangular, tapered, or any other suitable shape. In Fig. 2, alignment tab 32 is shown as a rectangular tab. When rectangular tabs are used, it is preferred to have the slots 30 slightly oversize in only one dimension and relatively the same size as the tabs in the other dimension so that tab 32 can only move in one direction in slot 30 and is relatively immovable in the other direction. For example slot 30 may have a length x and a width y and tab 32 may have a length (x-z) and a width y which is substantially the same as width y of slot 30. In this example, tab 32 may move in slot 30 relative to the x dimension thereof and is substantially restrained from moving relative to the y dimension thereof. By providing multiple alignment devices 28 adjacent at least two opposing side walls of the carrier 10 and multiple tabs 32 along the perimeter 36 of the holder 12 corresponding to the alignment devices, precise alignment of the carrier 10 to the cartridge body 12 may be obtained.

The tabs 32 are preferably made of the same material as the body 12, most preferably a thermoplastic material, and each tab 32 preferably has a length L which is sufficient to allow a portion of the tab to extend above the alignment device 28 when tab 32 is fully mated with its corresponding slot 30 and the carrier 10 is adjacent the perimeter 36 of the body 12. Once the carrier 10 is precisely aligned to the body 12, the ends of the tabs 32 are deformed as by melting to fixedly attach the carrier 10 to the body 12 as shown in Fig. 3. The tabs 32 may be melted by using a heat stake, hot upset tooling or hot air-cold stake tooling which is positioned adjacent the sides of the carrier 10 containing the alignment devices 28. Once the tabs 32 are melted, a substantially permanent connection is made between the carrier 10 and cartridge holder 12.

Other means for fixedly attaching the carrier 10 to the cartridge body 12 may be used in lieu of or in addition to the alignment devices 28 and tabs 32 described above. Such other means include adhesives and fasteners such as bolts and screws. However, regardless of the attachment means, it is preferred to have a plurality of alignment devices 28 on the carrier 10 and a plurality of tabs 32 on the body 12 so that precise alignment between the parts can be obtained.

Another feature of the carrier 10 according to the invention is the carriage positioning devices 46 attached to the carrier 10 adjacent at least one side 24 thereof (Figs. 1 and 3). The carriage positioning devices 46 accurately align the substrate carrier 10 to the printer carriage thus effectively aligning the substrates which are attached to the carrier with the printer carriage so that the precise location of each nozzle hole in nozzle plates attached to the substrates is maintained as the carrier 10 and cartridge body 12 are attached and removed from the printer carriage. The printer carriage functions to move the printhead structure in a desired manner across the paper as ink is ejected from the printhead. Accordingly, proper alignment of the printhead structure relative to the printer carriage is important for high quality printing of images on a print media.

Having described various aspects and embodiments of the invention and several advantages thereof, it will be recognized that the invention by those of ordinary skills susceptible to various modifications, substitutions and revisions within the spirit and scope of the appended claims.

Claims

1. An ink jet printhead structure comprising a substrate holder containing one or more substrate locator wells for receiving semiconductor substrates thereon, the substrate holder having a top surface and side walls attached to the top surface along the perimeter thereof providing an open cavity opposite the top surface and at least two alignment devices attached adjacent at least one of the side walls for precisely maintaining the substrate holder adjacent to an ink reservoir.

2. The structure of Claim 1 wherein the substrate holder comprises a cast, molded or machined metal selected from the group consisting of aluminum, beryllium copper, gold, silver, zinc, tungsten and alloys of two or more of the foregoing metals.

3. The structure of Claim 1 wherein the substrate holder is comprised substantially of aluminum.

4. The structure of Claim 1 wherein the substrate holder is comprised of a material containing a high content of carbon fibers or graphite.

5. The structure of Claim 1 wherein the substrate holder is comprised of a metal-ceramic composite.

6. The structure of Claim 1 further comprising an ink reservoir or ink cartridge body positioned adjacent to the substrate holder using the alignment devices.

7. The structure of Claim 6 wherein the alignment devices comprise holes which are mated to tabs attached to the cartridge body containing cartridge body walls on a top perimeter of the body walls.

8. The structure of Claim 7 wherein the ink cartridge body is fixedly attached to the substrate holder by melted tabs.

9. The structure of Claim 1 further comprising one or more carriage positioning devices adjacent one of the side walls of the substrate holder.

10. The structure of Claim 1 wherein the alignment devices comprise holes which are mated to tabs attached to the cartridge containing cartridge body walls on a top perimeter of the body walls.

11. A method for attaching a substrate carrier to an ink cartridge body which comprises providing a multi-function substrate carrier, the substrate carrier having a top surface containing one or more substrate locator wells, side walls attached to the top surface along the perimeter thereof and substantially pe╧åendicular thereto providing an open cavity opposite the top surface and an alignment device containing a slot or hole, at least one alignment device being adjacent opposing side walls of the carrier for precisely aligning and attaching the substrate carrier to an ink cartridge body containing at least one upstanding alignment tab pending from each of two opposing upper cartridge body walls, engaging the tabs with the slots and deforming the tabs to fixedly attach the carrier to the cartridge body.

12. The method of Claim 11 wherein carrier is comprised of a cast, molded or machined metal selected from the group consisting of aluminum, beryllium copper, gold, silver, zinc, tungsten and alloys of two or more of the foregoing metals.

13. The method of Claim 11 wherein the carrier is comprised substantially of aluminum.

14. The method of Claim 11 wherein the carrier is comprised of a material containing a high content of carbon fibers or graphite.

15. The method of Claim 11 wherein the carrier is comprised of a metal-ceramic composite.

16. The method of Claim 13 further comprising one or more carriage positioning devices adjacent one of the side walls of the carrier.

17. The method of Claim 13 wherein the cartridge body and tabs are comprised of a thermoplastic material.

18. The method of Claim 17 wherein the tabs are deformed by melting thereby fixedly attaching the ink cartridge body to the carrier.

19. The method of Claim 13 wherein the tabs and holes have a rectangular shape.

20. The method of Claim 19 wherein the tabs are slightly smaller than the holes so that the tabs can be moved along only one axis to align the carrier to the cartridge body.