USRE37671E1 - Printhead-carriage alignment and electrical interconnect lock-in mechanism - Google Patents

Abstract

A printhead cartridge and carriage assembly (10) is provided comprising: a carriage (12); a snap-spring (62) for securing a printing cartridge (14) in postion on the carriage; and an interconnect strip (16) for supplying electrical signals to the cartridge, including a force loading spring pad (24) for urging a portion of the interconnect strip against a portion of the cartridge. The cartridge has top (32), bottom (34), sides (36, 38), front (40) and rear (42) surfaces and includes a printhead (44) on the bottom surface, an electrical contact strip (46) on the back surface connected to the printhead, referencing pads (56) on the side surface, and a lip (64) on the back surface for accepting the snap-spring. Referencing surface (60) are provided for receiving the referencing pads on the cartridge. The spring pad urges the interconnect strip against the electrical contact of the cartridge. The printhead cartridge/carriage assembly of the invention requires only one hand of the operator to both insert and lock the cartridge in position. Further, the cartridge/carriage assembly provides simultaneous alignment of the printhead in the X, Y, and Z directions. Finally, contact between the printhead and the interconnect strip is reliably made each time the cartridge is inserted and locked in position, thereby ensuring proper nozzle firing each time.

Description

The present application is a continuation of application Ser. No. 07/113,101 filed on Oct. 23, 1987, entitled “Printhead-Carriage Alignment and Electrical Interconnect Lock-In Mechanism,” now abandoned.

TECHNICAL FIELD

The present invention relates to ink-jet printers, and, more particularly, to alignment of the printhead and carriage and an electrical interconnect lock-in mechanism for controlling the printhead.

BACKGROUND ART

In ink-jet printing technology, a printhead, comprising a plurality of nozzles in a nozzle plate, is fluidically associated with a reservoir of ink. The printhead is mounted on one end of a print cartridge and the reservoir is provided inside the cartridge. Reference is made to U.S. Pat. No. 4,755,836, issued to Ta et al. on Jul. 5, 1988, and assigned to Hewlett-Packard Company.

An interconnect means is provided, which carries electrical signals from a microprocessor in the printer to the printhead. For thermal ink-jet printers, these signals provide a current to resistors associated with the nozzles and thus control the heating of specific resistors, which in turn form droplets of ink. The droplets of ink are expelled through the nozzles toward a print medium, such as paper. The particular pattern of resistor heating controls the pattern of characters formed on the print medium.

The print cartridge is supported in a carriage, which is adapted to move bidirectionally, normal to the movement of the print medium through the printer. The carriage movement is controlled by a motor and an associated belt drive, with the motor controlled by the microprocessor.

Insertion of an ink-jet cartridge into the carriage often necessitates use of two hands or two operations. Further, many cartridge/carriage configurations do not provide simultaneous alignment of the nozzle plate in the X, Y, and Z directions. Finally, contact between the printhead and the interconnect means must be reliably made, in order to ensure proper nozzle firing.

Accordingly, it is desired to provide a cartridge/carriage assembly that includes the foregoing advantages without the limitations of the prior art.

DISCLOSURE OF INVENTION

In accordance with the invention, a printhead cartridge and carriage assembly is provided comprising:

(a) a carriage;

(b) means for securing a printing cartridge in position in the carriage; and

(c) interconnect means for supplying electrical signals to the cartridge, including force loading means for urging the interconnect means against the cartridge.

The cartridge has top, bottom, sides, front and rear surfaces and includes a printhead on the bottom surface, a contact on the back surface connected to the printhead, referencing pads on the side surfaces, and a lip on the back surface for accepting a snap spring for locking the cartridge in position in the carriage. The securing means includes the snap spring and means for receiving the referencing pads on the cartridge. The force loading means urge the interconnect means against the contact of the cartridge.

The printhead cartridge/carriage assembly of the invention requires only one hand of the operator to both insert and lock the cartridge in position. Further, the cartridge/carriage assembly provides simultaneous alignment of the nozzle plate in the X, Y, and Z directions. Finally, contact between the printhead and the interconnect means is reliably made each time the cartridge is inserted and locked in position, thereby ensuring proper nozzle firing each time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an assembled carriage/cartridge assembly, together with electrical interconnect thereto;

FIG. 2 is an exploded side elevational view showing the assembly of the electrical interconnect and an elastomeric support in the cartridge;

FIG. 3 is a perspective view, partly cut-away, of the elastomeric support;

FIG. 4 is a front elevational view of the carriage;

FIG. 5 is a side elevational view of the carriage, without the cartridge;

FIG. 6a is a cross-sectional view of the assembly depicted in FIG. 5, showing the cartridge inserted into the carriage, but not locked into place;

FIG. 6b is a view similar to that of FIG. 6a, but showing the cartridge locked in position;

FIG. 7 is a view similar to that of FIG. 6b, but showing a greatly enlarged view of the electrical interconnect and elastomeric support assembled in the carriage;

FIG. 8 is a side elevational view similar to that of FIG. 4, but with the cartridge chute removed in order to show the positioning of the electrical interconnect in the carriage; and

FIG. 9 is a perspective view of the cartridge, showing the printhead electrical contact, which provides electrical connection to the resistors in the printhead, and the reference pads.

BEST MODES OF CARRYING OUT THE INVENTION

Referring now to the drawings wherein like numerals of reference designate like elements throughout, a print cartridge/carriage assembly, denoted generally at10, is shown in FIG.1. Theassembly10 comprises acarriage12 in which aprint cartridge14 is depicted, locked into position. Aninterconnect strip16 provides electrical signals from a microprocessor (not shown) to thecartridge14, as discussed more fully below.

As shown in FIG. 2, thecarriage12 comprises abase support18 and achute20 affixed thereto by fastening means22. Thecarriage12 advantageously comprises a glass-filled, carbon-filled, polytetrafluoroethylene-filled, silicon-filled polycarbonate.

Theinterconnect strip16 and aspring pad24 are sandwiched by thesupport18 and achute20. Thespring pad24 comprises a resilient, elastomeric material and, as seen in FIG. 3, comprises a plurality ofresilient bumps26. Thespring pad24 is seated in a depression25 (shown in FIG. 4) in thecarriage base support18, behind a portion of theinterconnect strip16, as described more fully below.

Thebase support18 andchute20 are aligned in proper relationship by molded-in features such aspips27, which engage through corresponding openings in theinterconnect strip16 into opposed openings in the other member.

Theinterconnect strip16 comprises a strip of flexible dielectric material, carrying a plurality of electrically conductinglines28, as seen more clearly in FIG.8. The conductinglines28 terminate in convex contact bumps ordimples30, which are configured in a particular pattern.

Thebumps26 on thespring pad24 are configured in the same pattern as the contact dimples30 on theinterconnect strip16. As seen in FIG. 7, thespring pad bumps26 provide a force loading means against the contact dimples30 to urge them against thecartridge14.

Thecartridge14 comprises top32,bottom34,sides36,38,front40 and back42 surfaces. Thecartridge14 advantageously comprises a modified polyphenylene oxide.

Aprinthead44 is provided on thebottom surface34. Theprinthead44 comprises a plurality of resistors (not shown) associated with a plurality of nozzles (not shown) formed in a nozzle plate (not shown). Ink (not shown) is stored in a reservoir interior thecartridge14.

Thecartridge14 also includes acontact strip46 on theback surface42, which wraps around to thebottom surface34 to provide a plurality of conducting paths or traces to the resistors. In particular, each resistor is supplied by an electrical signal along a unique conducting path. Thecontact strip46 includes a plurality ofconcave contact pads48, which are arranged in the same pattern as the convex contact dimples30 on theinterconnect strip16. Locking of thecartridge14 in thecarriage12, as described in greater detail below, matches up the contact dimples30 with thecontact pads48, to provide an electrical path from the microprocessor to each of the resistors in theprinthead44.

Thecontact strip46 comprises a flexible material having a plurality of electrical traces thereon. Preferably, a tape automated bond (TAB) circuit of the type manufactured and sold by 3M Company (Minneapolis, MN) is employed.

Thetop surface32 of thecartridge14 is provided with a pair offinger grips50a,50b. Thelarger finger grip50a terminates in a V-shapedmember52a, which may be provided with an arrowhead insignia to denote the proper direction of orientation of thecartridge14. When thecartridge14 is locked in thecarriage12, the cartridge is received by a similarly shaped surface on the carriage to provide a visual reference for proper orientation. Lock-outears54 further act to prevent mis-orientation of thecartridge14 in thecarriage12.

Reference pads56, seen more clearly in FIG. 9, are provided on thecartridge14 near the base thereof. In particular, two sets of reference pads56 are provided; these comprise sculpted surfaces that align the nozzle plate in the X, Y and Z directions. TheX reference pad56x is a surface parallel to theside surface38. (There is only oneX reference pad56x, since thecarriage12 is provided with aside spring58 which urges against theopposite side surface36 to force the cartridge against one side of thechute20.) The Y reference pad comprises pads comprise the upper vertical surface surfaces56y of the sculpted surface surfaces. The Z reference pad comprises pads comprise the inner horizontal surface surfaces56z of the sculpted surface surfaces. The junction of56y and56z comprises a pivot orrotation point56r, about which thecartridge14 rotates during the lock-in operation.

Downwardly depending L-shapedmembers60a, b on thesupport base18 each cooperatively engage one of the reference pads56 in mating association. A snap-spring62 in the upper portion of thechute20 engages aledge member64 on theback surface42 of thecartridge14.

The L-shapedmembers60a, b provide reference surface against which the reference pads56 of the cartridge bear. In particular,reference pad56x bears againstreference surface60x onmember60a (the member on the opposite side of the side spring58).Reference pads56y push back againstreference surfaces60y (shown in FIG.2).Reference pads56z bear down onreference surfaces60z.

The snap-spring62 is housed in a molded-infeature66 of thecartridge support base18. Amating housing67, which sits above the snap-spring62 when thebase18 andchute20 are assembled, includes an inward V-shaped surface66a, which receives the similarly-shapedsurface52a of thecartridge14. The rear of thehousing66 comprises afinger grip68. The front of thecartridge chute20 is also provided with afinger grip20b.

Thesupport18 of thecarriage12 includes abearing70, which is associated with a carriage rod (not shown). The carriage rod is positioned substantially parallel with the paper drive axis (not shown), and permits bidirectional movement of thecarriage12 therealong. Thecarriage12 is moved by a belt (not shown), attached to the carriage by abelt attachment72. The belt is attached to a carriage drive motor (not shown), which is controlled by the microprocessor.

A reference means, or slider bump,74 rides on the surface of acarriage guide76. The weight of thecarriage12 preloads theslider bump74 against thecarriage guide12, thereby making constant contact. Theslider bump74 comprises a low-friction, long wearing material and may be a separate piece or a molded-in feature of thecarriage12. Theslider bump74 serves to maintain the printhead44 a constant, fixed distance from the print medium.

Thecarriage base18 also includes aninterposer arm78 secured in ashaft80. The function of the interposer arm is related to mechanically triggering certain features in the service station where theassembly10 resides in between printing operations, and is not relevant to the invention herein.

The printhead lock-in mechanism is considered unique, since it simultaneously aligns the nozzle plate in the X, Y, and Z directions and aligns, wipes, and loads the contact pads of theelectrical interconnect strip16. This is accomplished with no additional bail, latch or lever arm, as seen on other ink-jet printers. The alignment of the nozzle plate and the loading of theinterconnect strip16 occurs when the user rotates thecartridge14 in the direction of the arrow74 (FIG.6a), about thepivot point56r. The user does this by squeezing thecartridge thumbhold50a and the carriage finger hold68 between the thumb and forefinger.

Before the user can squeeze thecartridge14 into its locked-in position, the user must be able to easily drop the cartridge into thecarriage chute20. Thesprings58,62 which align thecartridge14 do not apply any force to the cartridge until the cartridge begins to rotate into the locked-in position (shown in FIG.6b). This leaves an unobstructed path for the user to easily drop thecartridge14 into the pre-rotation position, depicted in FIG.6a. However, the side-kicker spring20 applies light force when inserting thecartridge14.

Thecartridge14 rotates about the reference pads56, specifically,point56r. As the user rotates thecartridge14, the alignment functions are performed before theelectrical interconnect strip16 is loaded. First, oneside36 of thecartridge14 engages the molded-incarriage side spring58. Thisspring58 references thecartridge14 in the X direction by pushing the cartridge sideways until theX reference pad56x is touching theX reference pad60x on the cartridge. The result is an accurate, no slop alignment of the nozzle plate in the X direction.

The next action to occur is the alignment in the Z direction. As therear ledge64 of thecartridge14 encounters the rear metal snap-spring62, the spring pushes the cartridge in the Z direction until theZ reference pads56z are in contact with theZ reference pads60z on thecarriage12. The result is an accurate, no slop registration of both theelectrical interconnect16 and the nozzle plate in the Z direction.

As thecartridge14 continues to rotate about therotation point56r into position, the electrical interconnectconcave contact pads48 on thecartridge contact46 get wiped slightly by the convex contact dimples30 on thecarriage interconnect strip16. This offers improved reliability over the dimpled interconnect on prior art printers, because the oxides and contamination are wiped off thecontacts30 and48 before theinterconnect16 is loaded.

The wiping action is followed by the alignment of the cartridgeelectrical contact pads48 in the X direction. This occurs when the cartridge's outer rear heel lock tabs84a, c engage thesides86a, c of theheel lock slot86 on thecarriage12. Theinterconnect strip16 on thecarriage12 is referenced accurately to theheel lock slot86 bypins27, thereby providing the required alignment of the interconnect strip to the cartridge'selectrical contact pads48. Thecontact strip46 is fastened, such as by glue or adhesive, to thecartridge14 and is referenced by an assembly machine.

Finally, thecartridge14 is aligned accurately in the Y direction. The electrical interconnect'srubber spring pad24 on thecarriage12 must be deflected the proper distance in the Y direction in order to maintain the required contact force. In theback42 of thecartridge14, therubber spring24 pushes back against theelectrical contacts30 and48 so that theY reference pads56y on the cartridge contact theY reference pads60y on the carriage. This maintains the necessary force on thecontact pads48 located on thecontact strip46, on therear surface42 of thecartridge14. This also provides an accurate Y registration of the nozzle plate as well as controlling the rotational alignment of the nozzles.

At the top32 of thecartridge14, the required contact force in the Y and Z directions is maintained by the rear snap-spring62. As thecartridge14 rotates into the locked-in position, therear lip64 of thecartridge14 deflects the rear spring-snap62 and passes over anover-center point62a (FIG. 6a) on the snap-spring. The snap-spring62 is designed to apply about 70% of its force in the Y direction. This is the force required to maintain theelectrical interconnect16 in the rear42 of thecartridge14.

As thecartridge14 passes theover-center point62a on the rear snap-spring62, the cartridge makes an audible “snap”, signalling to the user that the cartridge is in the proper locked-in position. The force of the rubberinterconnect spring pad24 is adequate to hold the cartridge into its accurately aligned position under the large accelerations and shock loads the cartridge encounters in normal printing operations.

To remove thecartridge14 from thecarriage12, the user simply rotates the cartridge by squeezing thecartridge finger hold50b and thecartridge thumb hold20b between the thumb and forefinger. Therear ledge64 on thecarriage14 deflects the rear snap-spring62 until the cartridge over-centers into the unlocked position. There is an audible “snap” which tells the user that thecartridge14 can now be lifted out of thecarriage12 for disposal.

INDUSTRIAL APPLICABILITY

The print cartridge/carriage assembly disclosed herein is suitably employed in ink-jet printers, particularly thermal ink-jet printers.

Thus, there has been disclosed an ink-jet print cartridge/carriage assembly which is easily assembled and disassembled, with reproducibly accurate registration of the cartridge in the carriage. Various changes and modifications of an obvious nature will be readily apparent to those of ordinary skill in this art, and all such changes and modifications are considered to fall within the scope of the invention, as defined by the appended claims.

Claims (11)

What is claimed is:

1. A printhead carriage lock-in assembly (10) for use with a cartridge (14) in a printer, for printing on a print medium, comprising:

a. carriage means (12);

b. said carriage means including base support means (18) for receiving the cartridge;

c. said base support means depending into referencing means (60a,60b), for aligning the cartridge in proper printing position along at least two directions;

d. said base support means further including retention means (62) for causing the cartridge to be locked in position relative to said carriage means;

e. electrical interconnect means (16,24,46), for supplying control signals to the carriage;

f. the cartridge including a reference system (56) corresponding to, and generally coordinating with, said referencing system of said base support means, for providing proper alignment to the cartridge during its positioning relative to said carriage means, and for causing the cartridge to be retained in position during the printing operation;

g. said referencing means including a pair of downwardly depending, spaced-apart, generally oppositely disposed L-shaped members (60a,60b), for engaging said reference system of the cartridge;

h. the cartridge including a rear ledge (64), and said retention means including spring means (62) for engaging said rear ledge in order to retain the cartridge in a locked position;

i. the cartridge further including a top portion (32), a bottom portion (34), and printhead means (44) generally secured to said bottom portion; and

j. said reference system (56) of the cartridge including two sets of similar pads (56x,56y,56z), generally disposed near said bottom portion in a substantially symmetrical relationship relative to said printhead means;

k. said reference pads pad (56x) abutting one of said L-shaped members (60a);

l. said reference pads (56y) abutting the other both L-shaped member members (60a,60b); and

m. the cartridge further including lock-out ear means (54), slightly protruding outwardly from said top portion (32), for enhancing the orientation of the cartridge inside said carriage means.

2. A printhead carriage lock-in assembly for receiving a cartridge having electrical contacts (46,48) a contact strip (46), electrically conducting pads(48), a reference system (56) and a plurality of print elements, the print elements being disposed out of the plane of the electrical contacts electrically conducting contact pads (48), the printhead carriage lock-in assembly comprising:

a. carriage means;

b. said carriage means including base support means for receiving the cartridge;

c. said base support means depending into referencing means (60a,60b), for aligning the cartridge into a proper printing position along at least two directions (x,y);

d. said referncing referencing means generally coordinating with the reference system of the cartridge, for providing proper alignment to the cartridge during its positioning relative to said carriage means, and for causing the cartridge to be retained in position during the printing operation;

e. electrical interconnect means, for supplying control signals to the cartridge electrical contacts electrically conducting contact pads of the cartridge; and

f. said electrical interconnect means being disposed out of the plane of the cartridge electrical contacts print elements to avoid obstructing the firing path of the print elements onto a print medium, to minimize contamination of said electrical interconnect means resulting from the firing of the print elements, and to allow for a desirable relatively close spacing between the print elements and the print medium.

3. The assembly as defined inclaim 2, wherein said referencing means includes a pair of downwardly depending, spaced-apart, generally oppositely disposed L-shaped members (60a,60b), for engaging said reference system of the cartridge.

4. The assembly as defined inclaim 3, further including retention means (62) for causing the cartridge to be locked in position relative to said carriage means; and

wherein the cartridge includes a rear ledge (64), and wherein said retention means includes spring means (62) for engaging said rear ledge in order to retain the cartridge in a locked position.

5. The assembly as defined inclaim 4, wherein said carriage means further includes chute means (20), secured to said base support means (18), for helping guide the cartridge in position.

6. The assembly as defined inclaim 4, wherein the cartridge further includes a top portion (32), a bottom portion (34), and printhead means (44) generally secured to said bottom portion;

wherein said reference system (56) of the cartridge includes two sets of similar pads (56x,56y,56z), generally disposed near said bottom portion in a substantially symmetrical relationship relative to said printhead means;

wherein said reference pads pad (56x) abut abuts one of said L-shaped members (60a); and

wherein said reference pads (56y) abut the other both L-shaped member members (60a,60b).

7. The assembly as defined inclaim 5, wherein said electrical interconnect means includes an interconnect strip (16), disposed intermediate said base support means and the cartridge, and terminating in a plurality of dimples (30) disposed in a predetermined arrangement, for effecting electrical contact with the cartridge.

8. The assembly as defined inclaim 7, wherein the cartridge contacts include a contact strip (46) having a plurality of electrically conducting pads (48) are disposed in a predetermined array on the contact strip (46) for effecting electrical contact with said interconnect strip (16);

wherein said contact strip (46) provides a plurality of conducting paths to said resistors generally terminating in said conducting pads.

9. The assembly as defined inclaim 8, further including spring pad means (24) disposed intermediate said base support means (18) and said interconnect strip (16), for forcing said interconnect strip against the cartridge, in order to maintain a good electrical interconnection therebetween.

10. The assembly as defined inclaim 9, wherein said spring pad means includes a plurality of externally protruding bumps (26); and

wherein said bumps are disposed in a generally similar arrangement to that of said dimples (30) and said conducting pads (48) and in registration therewith, such that said bumps force said dimples against said conducting pads, in order to maintain a good electrical contact between said interconnect strip and the cartridge.

11. A printhead carriage lock-in assembly (10) for use with a cartridge (14) in a printer, for printing on a print medium, comprising:

a. carriage means (12);

b. said carriage means including base support means (18) for receiving the cartridge;

c. said base support means depending into referencing means (60a,60b), for aligning the cartridge in proper printing position along at least two directions;

d. said base support means further including retention means (62) for causing the cartridge to be locked in position relative to said carriage means;

e. electrical interconnect means (16,24,46), for supplying control signals to the carriage;

f. the cartridge including a reference system (56) corresponding to, and generally coordinating with, said referencing system of said base support means, for providing proper alignment to the cartridge during its positioning relative to said carriage means, and for causing the cartridge to be retained in position during the printing operation;

g. said referencing means including a pair of downwardly depending, spaced-apart, generally oppositely disposed L-shaped members (60a,60b), for engaging said reference system of the cartridge;

h. the cartridge including a rear ledge (64), and said retention means including spring means (62) for engaging said rear ledge in order to retain the cartridge in a locked position;

i. said carriage means further including chute means (20) secured to said base support means (18), for helping guide the cartridge in position; and said chute means including spring means (58) for applying a relatively light force against the cartridge, to help guide its alignment and positioning inside said chute means.

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