Interconnect circuit

An ink jet print cartridge having a compact electrical interconnect structure that includes a plurality of pairs of columnar arrays of electrical contact areas disposed on a front wall of the print cartridge.

BACKGROUND OF THE INVENTION

The disclosed invention relates generally to fluid ejecting devices, and more particularly to a flexible interconnect circuit for a fluid ejecting device.

An ink jet printer forms a printed image by printing a pattern of individual dots at particular locations of an array defined for the printing medium. The locations are conveniently visualized as being small dots in a rectilinear array. The locations are sometimes called “dot locations,” “dot positions,” or “pixels”. Thus, the printing operation can be viewed as the filling of a pattern of dot locations with dots of ink.

Ink jet printers print dots by ejecting very small drops of ink onto the print medium, and typically include a movable print carriage that supports one or more print cartridges each having ink ejecting nozzles. The print carriage traverses back and forth over the surface of the print medium, and the nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to the pattern of pixels of the image being printed. Typically, a plurality of rows of pixels are printed in each traverse or scan of the print carriage. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using thermal printhead or piezoelectric technology. For instance, two earlier thermal ink jet ejection mechanisms are shown in commonly assigned U.S. Pat. Nos. 5,278,584 and 4,683,481. In a thermal system, an ink barrier layer containing ink channels and ink vaporization chambers is disposed between a nozzle orifice plate and a thin film substrate. The thin film substrate typically includes arrays of heater elements such as thin film resistors which are selectively energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized heater element. By selectively energizing heater elements as the printhead moves across the print medium, ink drops are ejected onto the print medium in a pattern to form the desired image.

Certain ink jet printers employ disposable print cartridges that are replaced when empty, and a consideration with such printers is the need for a reliable electrical interface between a print cartridge and the printer in which it is installed.

DETAILED DESCRIPTION OF THE DISCLOSURE

In the following detailed description and in the several figures of the drawing, like elements are identified with like reference numerals.

Referring now toFIG. 1, schematically depicted therein is an ink jet printer114partially cut away and with its front loading door removed. The printer includes a case or housing115and carriage drive motor116mounted on a chassis. The motor drives a belt118back and forth as the drive motor reverses direction. The drive belt118is attached to a print carriage119that scans laterally back and forth along a carriage scan axis CA from left to right and right to left. The print carriage119contains one or more externally similar thermal ink jet print cartridges11located side by side. For example, one print cartridge contains black ink while another has three ink chambers containing magenta, yellow and cyan inks. The horizontal scanning motion of the print carriage119is guided by a slider rod121. Located in the rear of the carriage119is an encoder, not shown, that reads a position encoder strip122and provides information of the location of the print carriage119along the carriage axis CA.

The print carriage119includes a cartridge latching system that consistently and accurately positions the print cartridges11relative to an orthogonal coordinate system shown inFIGS. 2 and 10. The X axis is parallel to the carriage scan axis. The Y axis is parallel to and opposite a paper advance path which for example extends horizontally out of the printer114, such that the X and Y axes define a horizontal plane. The Z axis extends vertically, orthogonal to the XY plane.

Referring now toFIGS. 2-4, the print cartridge11more particularly includes a print cartridge body comprised of a rear wall24, a left side wall25, a right side wall26, a front wall27, and a bottom wall28that includes a snout section28athat supports an ink jet printhead15. A top wall or lid31is attached to the upper edges of the front, side, and rear walls, and includes margins or lips29that extend beyond the front and side walls. A latch catch or feature50is disposed on the lid31close to the top boundary of the rear wall24. The latch feature50extends upwardly from the top wall31and includes a front latch surface50aand a rearwardly extending surface50cthat intersects the top of the front latch surface50at an edge surface50b. By way of illustrative example, the front latch surface50ais perpendicular to the lid31while the rearwardly extending surface50cis a ramped surface that extends downwardly and rearwardly from the top of the front latch surface50a. Alternatively, the rearwardly extending surface of the latch feature can comprise a horizontal surface50c′ as illustrated in FIG.3. As described further herein, a latch pushes on a top portion of the latch feature50. Depending upon implementation that top portion is the edge surface50bor the horizontal surface50c′.

Located in the vicinity of the intersection of the left side wall25, rear wall24and snout28aare a printhead cartridge X axis datum PX1, a first printhead cartridge Y axis datum PY1, and a first printhead cartridge Z axis datum PZ1. Located in the vicinity of the intersection of the right side wall26, rear wall24and snout28aare a second printhead cartridge Y axis datum PY2and a second printhead cartridge Z axis datum PZ2. A third printhead cartridge Y axis datum PY3is located in the upper portion of the rear wall24. The print cartridge Y axis datums generally comprise lands that are configured to be generally orthogonal to the Y axis when the cartridge is installed in the print carriage40. The print cartridge Z axis datums comprise lands that are configured to be generally orthogonal to the Z axis when the print cartridge is installed in the print carriage119. The print cartridge X axis datum comprises a land that is configured to be generally orthogonal to the X axis when the print cartridge is installed in the print carriage119. As described further herein, the datums of the cartridge engage corresponding datums in the carriage.

Disposed on the rear wall24and on the snout section28aof the bottom wall28is a flexible circuit33that wraps around the intersection of such walls and provides electrical interconnection between the printer and the printhead15.

FIG. 5is a schematic depiction of an implementation of the flexible circuit33which includes an array70of contact areas71that are contactively engageable from the near side of the flexible circuit33which is the side that is away from the cartridge body. The side of the flexible circuit33that is against the cartridge body is called the far side. The contact areas71are disposed on a portion of the flexible circuit33that is located on the rear wall24, and comprise electrically conductive areas that are contactively engageable with corresponding contact bumps139on a resilient contact circuit137(FIG. 13) located in the print carriage119(FIG.1). By way of illustrative example, the flexible circuit is formed of a flexible substrate such as polyimide having a conductive pattern formed on the far side thereof and openings formed in the substrate so that portions of the conductive pattern can be contacted from the near side of the flexible circuit. In such implementation, the contact areas71comprise conductive areas exposed by openings in the flexible substrate. The contact areas71can be circular, octagonal, square, square with rounded or beveled corners, or some other shape.

The contact areas71are more particularly arranged in a plurality of side by side, transversely separated columnar arrays73of contact areas71. Each columnar array73includes a lower contact area that is closest to the bottom wall of the print cartridge and is also identified by the reference designation71′ for ease of reference. By way of illustrative example, the columnar arrays73can be substantially linear. The columnar arrays73in turn are arranged in side by side pairs or groups75a,75b,75cof columnar arrays73. As shown, there can be three pairs75a,75b,75cof columnar arrays73so as to have six columnar arrays73of contact areas. The pairs75a,75cof columnar arrays73comprise outboard pairs, while the pair75bcomprises an inboard pair. Each pair of columnar arrays includes two columnar arrays73that diverge from each other in the direction toward the bottom wall of the cartridge.

The outermost transversely separated columnar arrays are also identified with the reference designation73′ for ease of reference. Such outermost transversely separated columnar arrays73′ can have fewer contact areas71than the columnar-arrays73between such outermost transversely separated columnar arrays. By way of illustrative example, each outermost columnar array73′ includes five contact areas71, and each of the other columnar arrays73includes at least six contact areas71. By way of specific example, as shown inFIG. 5, a columnar array73adjacent one outermost columnar array73′ includes six contact areas while each of the other columnar arrays73between the outermost arrays73′ includes seven contact areas. Additionally, the outermost transversely separated columnar arrays73′ can have more contact areas71than the columnar arrays73between such outermost transversely separated columnar arrays. Also, the outermost transversely separated columnar arrays73′ can have the same number of contact areas71as the columnar arrays73between such outermost transversely separated columnar arrays.

Each columnar array73spans at least 70% of the height H of the smallest rectangle R that encloses the array of contact areas71and defines a region occupied by the contact areas71. The height H is generally vertical. By way of specific example, the smallest rectangle R has a height H in the range of about 10 to 14 millimeters and a width W in the range of about 15 to 18 millimeters. The height to width ratio can be in range of about 0.6 to about 0.9.

The contact areas71of the outermost transversely separated columnar arrays73′ can spaced center to center at about 2 millimeters from an adjacent contact area in its columnar array, for example. The contact areas71of the outermost transversely separated columnar arrays73′ can also be spaced center to center at less than or greater than about 2 millimeters from an adjacent contact area in its columnar array. The contact areas71of each of the remaining columnar arrays73can be spaced no closer center to center than about 1.7 millimeters from any other contact area in its columnar array, for example. Alternatively, the contact areas71of each of the remaining columnar arrays73can be spaced center to center closer than about 1.7 millimeters from any other contact area in its columnar array. A contact area71in any columnar array can be spaced no closer center to center than about 1.7 millimeters from a contact area in an adjacent columnar array, for example. Also, a contact area71in any columnar array can be spaced center to center closer than about 1.7 millimeters from a contact area in an adjacent columnar array. The lower contact areas71′ of adjacent pairs of columnar arrays73can be separated by at least about 2.8 millimeters center to center. Alternatively, the lower contact areas71′ of adjacent pairs of columnar arrays73can be separated by less than about 2.8 millimeters center to center. The lower contact areas71′ of the columnar arrays73between the outermost transversely separated columnar arrays73′ can be further from the bottom wall than the lower contact areas71′ of the outermost transversely separated columnar arrays73′. Alternatively, the lower contact areas71′ can be at the same distance from the bottom wall, or they can be at different distances from the bottom wall.

Depending upon implementation, some or all of the contact areas71,71′ are electrically connected to the printhead by conductive traces generally indicated by the reference designation77. The conductive traces are preferably disposed on the far side of the flexible circuit33, which is the side against the cartridge body, and lead to bond pads74on the printhead15(FIG.4).

InFIG. 5, the contact areas include primitive select contact areas P1-P16, address signal contact areas A1-A13, enable signal contact areas E1-E2, a temperature sense resistor contact area TSR, an identification bit contact area ID, and ground line contact areas TG1, TG2, BG1, BG2.

Each of the outermost transversely separated arrays73′ can include a ground contact area (TG1, TG2), while each of the columnar arrays73of the inboard pair75bcan include a ground contact area (BG1, BG2). The ground contact area BG1in a columnar array73of the inboard pair75bcan be electrically connected to the ground contact area TG1in the closest outermost columnar array73′ by a ground conductive trace79that is routed close to the columnar arrays so as to be only on the portion of the flexible circuit that is on the rear wall of the print cartridge body. Similarly, the ground contact area BG2in the other columnar array73of the inboard pair75bcan be electrically connected to the ground contact area TG2in the closest outermost columnar array73′ by a ground conductive trace79that is close to the columnar arrays so as to be only on the portion of the flexible circuit that is on the rear wall of the print cartridge.

FIG. 5Aillustrates a contact array similar to that inFIG. 5, but with different routing of the conductive traces77and wherein all of the ground contact areas TG1, BG1, BG2, TG2are interconnected by ground traces79that are on the flexible circuit. Such ground traces can more particularly be located close to the columnar arrays so as to be only on the portion of the flexible circuit that is on the rear wall of the print cartridge body.

FIG. 6shows a contact array similar to that inFIG. 5but wherein four contact areas labeled NC are not used. Also, the contact array ofFIG. 6includes twelve primitive select contact areas P1-P12, instead of sixteen, that are in different locations. The ground contact areas TG1, TG2, BG1, BG2are electrically interconnected by ground traces79that are routed close to the columnar arrays so as to be only on the portion of the flexible circuit that is on the rear wall of the print cartridge body.

The ground contact areas TG1, TG2, BG1, BG2of the flexible interconnect circuits ofFIGS. 5,5A,6can be in different locations, and can be interconnected by conductive ground traces that are disposed only on the portion of the flexible circuit that is on the rear wall of the print cartridge body, for example.

Referring now toFIG. 7, set forth therein is a schematic plan view of a printhead15that can be employed with the flexible circuits ofFIGS. 5 and 5A. The printhead includes a plurality of ink drop generators40arranged in a plurality of columnar arrays61. Each columnar array is arranged in a plurality of primitive groups such that all of the arrays are arranged in primitive groups PG1-PG16, for example. Each ink drop generator comprises for example a thermal ink drop generator formed of a nozzle, an ink chamber, a heater resistor, and drive circuitry. By way of illustrative example, the ink drop generators40receive ink via ink feed slots71located adjacent the columnar arrays61of ink drop generators.

The ink drop generators in one of the primitive groups are switchably coupled in parallel to a respective primitive select signal (FIG. 8, P(1-16)) via an associated primitive select contact area (P1-P16) of the flexible circuit. One outboard columnar array61contains primitive groups PG1, PG3, PG5, PG7, while the other outboard columnar array61contains primitive groups PG10, PG12, PG14, PG16. One inboard columnar array includes primitive groups PG2, PG4, PG6, PG8, while another inboard columnar array contains primitive groups PG9, PG11, PG15, PG13.

FIG. 8more particularly sets forth a simplified electrical block diagram illustrating the electrical connection provided by the flexible circuit33between the printer and the printhead. The printer includes a print control device43having a source of drive current, an address generator, and an enable generator. The source of drive current, the address generator, and the enable generator provide drive current, address signals, and enable signals to the printhead via the contact bumps139of the resilient contact circuit137(FIG. 13) that are contactively engaged with the contact areas71of the flexible circuit33.

For the particular example of a printhead having sixteen primitive groups PG1-PG16, sixteen separate drive current signals or primitive select signals P(1-16) are respectively provided via the primitive select contact areas P1-P16to the primitive groups PG1-PG16. Thirteen separate address signals A(1-13) are provided via the address contact areas A1-A13, while two enable signals E(1-2) are provided via the enable contact areas E1-E2.

More particularly as to electrical connections between the flexible circuit ofFIGS. 5or5A and the printhead ofFIG. 7, primitive select contact areas P1, P3, P7, P5in the outboard pair75cof columnar arrays are electrically connected to the outboard primitive groups PG1, PG3, PG7, PG5. Primitive select contact areas P10, P12, P14, P16in the outboard pair75aof columnar arrays are electrically connected to the outboard primitive groups PG10, PG12, PG14, PG16. Primitive select contact areas P2, P4, P9, P11in the outboard pair75aare connected to inboard primitive groups PG2, PG4, PG9, PG11. Primitive select contact areas P6, P8, P13, P15of the inboard pair75bare connected to inboard primitive groups PG6, PG8, PG13, PG15.

Referring now toFIG. 9, set forth therein is a schematic plan view of a printhead15that can be employed with the flexible circuit of FIG.6. The printhead includes a plurality of ink drop generators40arranged in three columnar arrays61. Each columnar array is arranged in a plurality of primitive groups such that all of the arrays are arranged in primitive groups PG1-PG12, for example. Each ink drop generator comprises for example a thermal ink drop generator formed of a nozzle, an ink chamber, a heater resistor and drive circuitry. By way of illustrative example, the ink drop generators40receive ink via ink feed slots71located adjacent the columnar arrays61of ink drop generators.

The printhead ofFIG. 9is electrically connected to the printer via the flexible circuit ofFIG. 6in a manner similar to that shown in and described with respect toFIG. 7, but with twelve primitive select signals P(1-12) for the primitive groups PG1-PG12.

The ink drop generators in one of the primitive groups (PG1-PG12) are thus switchably coupled in parallel to a respective primitive select signal P(1-12) via an associated primitive select contact area (P1-P12) of the flexible circuit of FIG.6. One outboard columnar array61of the printhead ofFIG. 9contains primitive groups PG1-PG4, while the other outboard columnar array61contains primitive groups PG9-PG12. The inboard columnar array includes primitive groups PG5-PG8.

More particularly as to the electrical connections between the flexible circuit of FIG.6and the printhead ofFIG. 9, primitive select contact areas P1-P4in the outboard pair75cof columnar arrays are electrically connected to the outboard primitive groups PG1-PG4. Primitive select contact areas P9-P12in the outboard pair75aof columnar arrays are electrically connected to the outboard primitive groups PG9-PG12. Primitive select contact areas P5, P6in the outboard pair75aare connected to inboard primitive groups PG5, PG6, while primitive select contact areas P7, P8in the inboard pair75bare connected to inboard primitive groups PG7, PG8.

Thus, in general as to the flexible circuits ofFIGS. 5,5A and6, and the printheads ofFIGS. 8 and 9, a first outboard pair of columnar arrays of contact areas includes primitive select contact areas electrically connected to a first set of outboard primitive groups, a second outboard pair of columnar arrays of contact areas includes primitive select contact areas electrically connected to a second set of outboard primitive groups and to a set of inboard primitive groups, and an inboard pair of columnar arrays of contact areas includes primitive select contact areas electrically connected to another set of inboard primitive groups.

Referring now toFIGS. 10-17, the print carriage119more particularly includes a base126that supports the structure, and two C-shaped bearings128located at the ends of the base126. These C-shaped bearings128slidably support the print carriage119on the slider rod121. The print carriage119further includes two chutes131that each receive, hold, and align an ink jet print cartridge11. Both chutes are constructed and operate similarly. Each chute includes a rear wall135that comprises for example a portion of the base126, a left side wall133that extends from the rear wall135, and a right side wall134that extends from the rear wall135and is generally parallel to the left side wall133.

Carriage datums CY1, CZ1and CX1formed for example as part of the base126are located at the bottom of the chute131in the vicinity of the intersection of the left side wall133the rear wall135, while carriage datums CY2and CZ2for example as part of the base126are located at the bottom of the chute131in the vicinity of the intersection of the right side wall134and the rear wall135. A carriage datum CY3is located on the rear wall135.

A resilient contact circuit137is located on the rear wall135of the chute and contains electrical contacts that are urged against corresponding contacts on the flex circuit33of the print cartridge11. The resilient contact circuit137further functions as a resilient element that urges the print cartridge datums PY1, PY2against carriage datums CY1, CY2when the print cartridge11is installed. By way of illustrative example, the resilient contact circuit137comprises a flexible circuit and resilient pad located between the flexible circuit and the rear wall135.

A cantilever spring146is located adjacent the right side wall134, and functions to urge the print cartridge away from the right side wall134along the X-axis, so that the print cartridge datum PX1is snugly engaged against the carriage datum CX1(as shown in FIG.16).

Located in each side wall133,134is a shaped guide channel140. The guide channels140engage lips29of the lid31of the print cartridge11, and guide the cartridge at an appropriate elevation and pitch (or rotation) of the cartridge about the X axis as the cartridge is inserted, so as to guide the cartridge into the general vicinity of the carriage datums. By way of illustrative example, each guide channel comprises upper and lower rails140a,140bor a recessed slot having appropriate sides.

A cross bar179(seeFIG. 10) spans the upper part of the front portion of chute131and is located above the guide channels140. The cross bar prevents insertion of the cartridge from above, and further prevents spreading of the side walls in the event the cartridge is forced too low in the chute.

Located at the top of each chute131is a hinged latch assembly150(FIG.10andFIG. 14) that includes a latch support arm151that is pivotally attached by a hinge153to the top of the rear wall135so as to be hingably rotatable about a hinge axis that is parallel to the X-axis. The latch support arm151is generally L-shaped having a first leg151athat extends from the hinge153and a second leg151bthat extends generally downwardly from the distal end of the first leg151a. Latch hooks155are located at the ends of the second leg151bfor engaging latch tabs157disposed at the front of the side walls133,134.

A pivoting biased clamp lever159is pivotally attached to the lower side of the latch arm151by a pivoting clamp hinge161that is displaced from the latch arm hinge153and parallel thereto so as to be pivotable about a pivoting clamp hinge axis that is parallel to the X axis. The clamp lever159extends generally toward the chute rear wall135when the latch is closed, and forms an acute angle with an imaginary line that extends between the latch arm hinge axis and the pivoting clamp hinge axis. The clamp lever159is biased by a spring163to pivot away from the latch arm151. Stops165on either side of the clamp lever159limit the rotation of the track lever away from the latch arm151.

A land167is disposed at the distal portion of the pivoting clamp159for pushing down on the top portion (50b,50c′) of the latch feature50of the print cartridge11. Extending beyond the land167is an extension169that prevents the clamp159from jamming on the front latch surface50aof the latch feature50.

The pivoting clamp lever159further includes tracks171in which a sliding clamp arm173is slidably located for movement generally orthogonally to the pivoting clamp hinge axis. The sliding clamp arm173is biased by a spring175to slide along the pivoting clamp lever159away from the pivoting latch hinge161. Stops175limit the displacement of the sliding clamp173. A sliding clamp land177is disposed at the distal end of the sliding clamp173adjacent the pivoting clamp land167.

In use, the cartridge11is inserted generally horizontally into the chute131. The guide channels140control the elevation and the pitch about the X axis of the cartridge11as it is inserted into the chute131, such that print cartridge datums PY1, PY2move over the corresponding carriage datums CY1, CY2. The latch arm151is then pivoted downwardly which causes the sliding clamp land177and the pivoting clamp land167to eventually engage the front latch surface50aand top portion (50b,50c′) of the latch feature50on the top of the cartridge. Continued displacement of the latch arm151causes the sliding clamp173to resiliently push on the latch feature generally along the Y axis, and further causes the pivoting clamp159to push on the latch feature generally along the Z axis. The push generally along the Y axis is independent of the push generally along the Z axis. The push along the Z axis causes the print cartridge datums PZ1, PZ2to snugly seat against the carriage datums CZ1, CZ2. The push along the Y axis causes the print cartridge to pivot about the X axis so that the print cartridge datum PY3snugly seats against the carriage datum CY3. The resilient contact circuit137is located so as to cause the print cartridge datums PY1, PY2to seat snugly against the carriage datum CY1, CY2when the print cartridge datums PZ1, PZ2are engaged with the carriage datums CZ1, CZ2, and the print cartridge datum PY3is engaged with the carriage datum CY3.

The latch arm151is further displaced to engage the latch hooks155with the latch tabs157, which allows the sliding clamp land177and the pivoting clamp land167to continually press against the front surface50aand the top portion (50b,50c′) of the latch feature50along the Y and Z axes so that the print cartridge datums PY1, PY2, PY3, PZ1, PZ2are continually engaged with the corresponding carriage datums CY1, CY2, CY3, CZ1, CZ2. The wire spring146pushes the cartridge generally along the X axis so that the print cartridge datum PX1is snugly engaged with the carriage datum CX1.

Although the foregoing has been a description and illustration of specific embodiments of the invention, various modifications and changes thereto can be made by persons skilled in the art without departing from the scope and spirit of the invention as defined by the following claims.