[0001] Ink jet printers have multiple electrical connection points and provide a means whereby
the user can change the replaceable ink holding component in an out of a cartridge.
The cartridge in tun provides a means to align with the electrical connections of
the ink holding component and to provide contact pressures for electrical connectivity
between the contact locations of the ink holding component and the "cartridge that
supports and locates this ink holding component."
[0002] This invention generally relates to cartridge-type inkjet printheads of the type
formed by the combination of an ink cartridge and a mounting assembly, and is particularly
concerned with a mounting assembly which consistently and reliably applies a conductively
engaging force between electrical contacts on the ink cartridge and control circuitry
carried within the mounting assembly.
[0003] Cartridge-type inkjet printheads are known in the prior art. Such printheads are
formed by the combination of an ink cartridge and mounting assembly. The ink cartridge
includes a row of inkjet nozzles on its bottom surface, and an array of electrical
contact pads on this surface for conducting printer control signals to each of the
various inkjet nozzles. The mounting assemblies for such printheads are provided with
a control circuit having a plurality of contact buttons registrable with the contact
pads of the cartridge which transmit printer control signals. Such mounting assemblies
further include a mechanism for detachably securing the ink cartridge within the assembly
in a position such that the electrical pads of the cartridge are in registry with
the contact buttons of the printer control circuit.
[0004] Such cartridge-type inkjet printheads are particularly adapted for use with document
scanners which optically scan the printed information on documents, and convert the
written information into digital form. In such an application, the printheads are
used to print an identifying number on each of the documents being scanned. The printhead
number allows the user of the scanner to identify the image scanned in case a rescan
is necessary due to poor or missing image information. It is important that the printhead
be easily mountable on and removable from the scanner or other device as the ink cartridge
must be periodically replaced due to exhaustion of its ink reservoir. For the same
reason, the ink cartridge should be easily installable in and removable from the mounting
assembly. Additionally, when the printhead is installed in the scanner, the inkjets
present on the bottom surface of the cartridge must align properly with the documents
fed through a paper transport device in the scanner in order to insure that the index
number printed on the documents is in a desired location. Finally, whenever a new
cartridge is installed in the mounting assembly, some sort of alignment mechanism
must be present to insure registry between the contact pads and buttons. Additionally,
some sort of resilient means must be provided to insure that an electrically-conductive
engagement is reliably created between the contact pads of the ink cartridge and the
contact buttons of the control circuitry present within the mounting assembly.
[0005] In prior art mounting assemblies, the necessary alignment between the contact pads
of the ink cartridge and the contact buttons of the control circuitry is achieved
through a plurality of assembled parts. Additionally, the pressure to form the necessary
electrical engagement between these contacts is generated by a single compliant, elastomeric
pad that has a series of projections or springs that press the contact pads and buttons
together.
[0006] While such prior art mounting assemblies are capable of performing their intended
functions, the inventors have observed a number of shortcomings associated with the
design of such assemblies. The multi-part aspect of such designs adds unwanted cumulative
tolerances to the assembled printhead which can provide non-optimal alignment between
the cartridge contact pads and circuit buttons. Such multi-part designs are also relatively
expensive to manufacture due to the cost of fabricating the individual pieces, as
well as the assembly time and labor necessary to put them together. The use of a single,
elastomeric pad to generate the necessary engagement force between the contact pads
and buttons creates unwanted non-uniformities in the pressures generated between adjacent
pairs of pads and buttons due to the fact that when any one of the pressure-focusing
projections or nubs on the pad is above or below the plane of the others, it will
experience more or less pressure, which is in turn transferred to the neighboring
projections through the beam strength of the pad. The end result is that the projections
or nubs on such pads can create unequal contact pressure which in turn can interfere
with the reliability of the electrical connection made between the contact pads and
buttons of the ink cartridge and control circuitry, respectively. In addition to the
potential for unequal pressures, the dimensional molding accuracy of such elastomeric
pads is not as precise as that of a straight injection molded plastic. When this factor
is added to the placement accuracy of aligning the pad to the support structure, the
ability to apply even pressures exactly where they are needed for good electrical
contact is further diminished. The end result of the cumulative tolerances necessitated
by multi-part construction and the uneven contact pressures generated by the use of
elastomeric pads is that the engagement force necessary to conduct electricity between
the contact pads and buttons of the ink cartridge and control circuitry may not be
reliably generated. These problems are further compounded over the life time of the
printhead, where dried ink deposits can further cause non-uniformities in the thicknesses
and planarity of the circuit board substrates supported the contact pads of the ink
cartridge, and the flexible circuit board material that carries the contact buttons
of the control circuitry.
[0007] Clearly, what is needed is a printhead cartridge having a mounting assembly formed
from a small number of easily assembled parts to reduce the problems associated with
the cumulative tolerances and the expenses associated with multi-part construction.
Ideally, such a mounting assembly should have a plurality of mechanically independent
spring members for generating the necessary contact pressure between the pads of the
ink cartridge and the buttons of the control circuitry to insure that the necessary
contact pressure is consistently and reliably generated, despite any misalignments
and non-uniformities and planarities caused by cumulative tolerances and dried ink
deposits.
[0008] Generally speaking, the invention is an inkjet printhead that eliminates or ameliorates
all of the aforementioned problems associated with the prior art. To this end, the
inkjet printhead comprises an ink cartridge having a plurality of inkjet nozzles,
and a plurality of electrical contacts for conducting control signals to the nozzles,
and a mounting assembly having a retainer for releasably securing the ink cartridge,
and a plurality of mechanically independent spring members for pressing electrical
contacts of a printer control circuit into conductive engagement with the contacts
of the ink cartridge. Each of the independent spring members is preferably independently
cantilevered from a wall of the mounting assembly. Each spring member may have a proximal
end that is integrally connected to the wall of the mounting assembly, and a distal
end that includes a projecting nub for engaging one of the printer control circuit
contacts. The wall of the mounting assembly is preferably formed from an injection
moldable plastic material, and the integral connection and formation of the cantilevered
spring members with the wall advantageously provides a design that is easily accurately
manufactured, and which provides uniform engagement pressures between the contacts.
[0009] The retainer of the mounting assembly includes at least one locking member for engaging
the contacts of the ink cartridge against the contacts of the circuit when the retainer
secures the ink cartridge in the mounting assembly. The retainer may include a pair
of leg members pivotally mounted in side walls of the mounting assembly, and locking
lugs at each end of each leg for applying an engagement force against lock flanges
provided on the ink cartridge. To insure proper registration between the contacts
of the ink cartridge and the control circuit of the mounting assembly, the mounting
assembly and the cartridge include interfitting members such as pegs and holes for
creating the desired alignment. An alignment means for the control circuit captured
within the mounting assembly is also provided which may take the form of registry
holes in the control circuit through which alignment pegs of a circuit retainer are
inserted during the construction of the mounting assembly.
[0010] The mounting assembly may further include a mechanism for detachably connecting the
printhead to a printer. The mounting assembly may take the form of resilient fingers
which snap-fit into opposing slots provided in a printer well of the printer, in combination
with alignment ribs which are insertable into a selected one of a plurality of slots
in the printer well. Such a structure allows the position of the printhead on the
printer to be adjusted so that the position of the printed index number or other image
may be adjusted on the paper fed through the printer.
[0011] The invention and its objects and advantages will become more apparent in the detailed
description of the preferred embodiment presented below.
Figure 1 is a side view of the scanner printer that the printhead of the invention
may be used in combination with;
Figures 2A and 2B are perspective views of the printer of the invention, illustrating
how it can be removed from the printer for cartridge replacement or other servicing;
Figure 3 is a perspective bottom view of the printhead of the invention as seen along
line 3-3 in Figure 2B;
Figure 4 is a perspective, exploded view of the printhead, illustrating in particular
the components of the mounting assembly of the invention;
Figure 5 is a perspective, plan view of the mounting assembly along the line 5-5 in
Figure 4, and
Figure 6 is a bottom, perspective view of the ink cartridge.
[0012] With reference now to Figures 1, 2A, and 2B, the printhead assembly 1 of the invention
is particularly adapted for use in a scanner 2 that scans documents and converts the
printed information thereon into digitized form. In such an application, the printer
assembly 1 prints an identifying number on documents fed through the scanner 2, which
number is also incorporated into the digitized, electronic document created by the
CCD module of the scanner 2. As is best seen in Figures 2A and 2B, the printhead assembly
1 is detachably mounted to a printer well 3 that is likewise detachably mounted on
the exterior surface of a semi-cylindrical paper guide 4. As is best seen in Figure
1, the scanner 2 includes a plurality of rollers 6 for conveying documents around
the semi-circular path defined by the paper guide 4. A paper sensor 8 is provided
on the exterior of the guide 4 for actuating the printer assembly 1. Together, the
printhead assembly 1, we113, paper guide 4, rollers 6, and paper sensor 8 form a printer
9 for the scanner 2. A camera assembly 10 is disposed within the semi-cylindrical
paper guide 4 for optically reading the printed information on the documents fed through
the paper guide 4. The camera assembly 10 includes a housing 12 and the previously
mentioned CCD module 14. A plurality of mirrors 16 allows the CCD module to detect
light reflected from documents circulating around the paper guide 4 through a slide
18 provided in an inner guide member 20. With the exception of the printhead assembly
1 and well 3, the various components of the scanner 2 are conventional, and form no
part of the instant invention.
[0013] With reference to Figures 3, 4, and 5, the printhead assembly 1 is formed from the
combination of a mounting assembly 25, and an ink cartridge 27. As will be seen hereinafter
more clearly, the principal purposes of the mounting assembly 25 are (1) to establish
secure electrical connections between the printer circuit board in the ink cartridge
27 and the control circuitry of the printer; (2) to provide a means whereby the printhead
assembly 1 may be easily installed and removed from the printer well 3 via a snap-fit
arrangement, and (3) to provide a means for the ink cartridge to be easily secured
into and removed from the mounting assembly for replacement or maintenance.
[0014] To the first of these ends, the mounting assembly 25 includes a bottom wall 30 over
which the ink cartridge 27 is mountable. Bottom wall 30 includes a plurality of cantilevered
spring members 31. As is best seen in Figure 5, each of these cantilevered spring
members 31 terminates in a projecting nub 33. As will be described in more detail
hereinafter, the integral, cantilevered structure of the spring members 31 in combination
with the projecting nubs 33, form independent, spring-loaded members which are responsible
for securing electrical connection between contact pads of ink cartridge 25 and the
contact buttons of a printer control circuit. Bottom wall 30 also includes inner alignment
holes 34a,b and outer alignment holes 35a,b which cooperate with similar alignment
holes in the circuit assembly 60 of the printer to align button contacts present in
this circuit with the aforementioned, spring-loaded nubs 33.
[0015] The mounting assembly 25 further includes a pair of opposing side walls 36a,b. Each
of these side walls includes a resilient retaining fingers 37a,b. These fingers, 37a,b,
are insertable into complementary slots 37c,d present in the printer well 3 in order
to detachably connect the printer assembly 1 via a snap-fit mechanism (as is indicated
in Figure 2B). Each of the side walls 36a,b further includes an alignment rib 38a,b
which is insertable into a selected one of several vertically-oriented slots 38c,d
in the printer well 3. The various pairs of vertically-oriented slots 38c,d allow
the position of the printhead 1 to be adjusted relative to the documents fed through
the paper guide 4. A pair of axle holes 39a,b is also present in each of the side
walls 36a,b for a purpose which will become clear presently. Mounting assembly 25
also has a back wall 40 integrally connected to the bottom wall 30 and side walls
36a,b. Back wall 40 includes, near its upper end, a circuit admission slot 42 for
receiving the flexible circuit assembly of the printer 1. A pair of retaining clips
44a,b project from the back side of the wall 40 for securing the connector terminal
of the circuit assembly.
[0016] As is best seen in Figure 4, the mounting assembly 25 has a cartridge retainer 46
formed from a handle 48 and two opposing legs 50a,b. Stub axles 52a,b project from
each of the legs 50a,b and are snap-fittable into the axle holes 39a,b due to the
resiliency of the plastic or other material forming the retainer. Each of the legs
50a,b has a longitudinally-shaped locking recess 53a,b at its lower end. These recesses
cooperate with the inner side of each of the previously discussed retaining fingers
37a,b present in side walls 36a,b to help secure the cartridge retainer 36 in a cartridge-retaining
position when the retainer 46 is pivoted into the position illustrated in Figures
2B and 3. A pair of locking cams 54a,b are defined by the flat bottom surfaces of
each of the legs 50a,b of the retainer 46. Finally, flat portions projecting from
the front of the legs 50a,b form stop portions 56a,b which abut the back wall 40 of
the mounting assembly 25 when the retainer 46 is pivoted into a cartridge-retaining
position.
[0017] With reference again to Figure 4, the printer assembly 1 further has a flexible circuit
assembly 60. The circuit assembly 60 includes a foot portion 62 having an array of
contact buttons 64. Each of these contact buttons 64 is registrable with a contact
pad located on the bottom wall of the ink cartridge 27. Disposed outside of the contact
buttons 64 are two pairs of alignment holes 66a,b. The circuit assembly 60 further
includes, on its opposite end, a connector terminal 68 which snap-fits into position
behind the upper portion of back wall 40 of the mounting assembly 25 via retaining
clips 44a,b. As is also best seen in Figure 4, a circuit retainer 70 is provided for
securing the central portion of the flexible circuit assembly 60 to the back wall
40 of the mounting assembly 25. The circuit retainer 70 has a pair of retaining feet
72a,b, as shown. These feet 72a,b include alignment pegs 74a,b which are registrable
with the alignment holes 66a,b present in the foot portion 62 of the circuit assembly
60. The circuit retainer 70 also has a retaining wall 76 integrally connected to the
retaining feet 72 for capturing and pressing the central portion of the circuit assembly
60 against the back wall 40 of the mounting assembly 25. Finally, at its upper end,
the retainer 70 is provided with a pair of opposing, resilient fingers 78a,b which
snap-fit into opposing sides of the circuit admission slot 42 of back wall 40 in order
to secure the retainer 70 onto the mounting assembly 25.
[0018] With reference to Figure 6, the ink cartridge 27 of the printer assembly 1 includes
an ink reservoir 80 for storing a supply of ink. A handle 82 extends from the side
of the ink reservoir 80 to facilitate the insertion and removal of the cartridge 27
from the mounting assembly 25. The base 84 of the ink cartridge 27 is provided with
a pair of alignment pegs 86a,b which are registrable in and insertable into outer
alignment holes 35a,b located on the bottom wall 30 of the mounting assembly 25. Centrally
disposed on the bottom of the base 84 is a circuit board 88 having a plurality of
contact pads 90. Each of the contact pads 90 controls one of the plurality of printing
orifices 92 present on the printer face 94. Finally, the base 84 of the ink cartridge
27 includes a pair of opposing retaining flanges for a purpose which will become evident
shortly.
[0019] In operation, the mounting assembly 25 of the printhead 1 is first mounted by extending
the foot portion 62 of the flexible circuit assembly 60 through the back of the admission
slot 42 of the back wall 40. The alignment holes 66 of the foot portion 52 are next
placed into registry with the inner alignment holes 34a,b present on the bottom wall
30, as is partly shown in Figure 5. The alignment pegs 74a,b of the circuit retainer
70 are next inserted through the registered alignment holes 66a,b and 34a,b and the
resilient fingers 78a,b are snapped into the ends of the slot 42 of back wall 40.
Terminal connector 68 is then attached to the upper rear portion of the back wall
40 via retaining clips 44a,b. When the mounting assembly 25 is so assembled, the projecting
nubs 33 of each of the cantilevered spring members 31 will be applying pressure beneath
each one of the contact buttons 64 on circuit foot portion 62.
[0020] To install an ink cartridge 27, the handle 48 of the cartridge retainer 46 is pivoted
against the back wall 40 in the direction indicated by the arrow in Figure 3. The
ink cartridge 27 is then slid over the bottom wall 30 of the mounting assembly 25
until the alignment pegs 86a,b are aligned and inserted into the outer alignment holes
35a,b of the bottom wall 30. The handle 48 of the cartridge retainer 46 is then pivoted
away from the back wall 40 in the direction opposite from that indicated by the arrow
in Figure 3. When this occurs, the locking cams 54a,b located on the bottom of the
cartridge retainer 46 forcefully engage the retaining flanges 96a,b on the base 84
of the ink cartridge 27 downwardly to press the contact pads 90 of the cartridge 27
against contact buttons 64. Moreover, the legs 50a,b of the cartridge retainer 46
are snap-fitted into this cartridge locking position by the action of the resilient
retaining fingers 37a,b snapping into the locking recesses 53a,b on the bottom portion
of the legs of cartridge retainer 46. The registration and insertion of the alignment
pegs 86a,b of the ink cartridge 27 with the outer alignment holes 35a,b of bottom
wall 30 insures the registration of the contact buttons 64 of the flexible circuit
assembly 60 with the contact pads 90 of the ink cartridge 27. The upward spring pressure
that the nubs 33 on the ends of the cantilevered spring members 31 apply to the contact
buttons 64, in combination with the downward pressure that the locking cams 54a,b
of the cartridge retainer 46 apply to the base of the ink cartridge 27 insures that
a reliable electrical connection is made between the contact buttons 64 and the contact
pads 90. Moreover, the independent resiliency of each of the spring members 31 achieved
by virtue of the independently cantilevered structure of these members insures that
a sufficient electrical contact pressure will be applied to each of the contact buttons
64 regardless of misalignments, variations in the thicknesses of the buttons 64, or
pads 90, or irregularities in the planarity or thicknesses of the circuit foot portion
62 or cartridge circuit board 88 caused by deposits of dried ink.
1. An inkjet printhead, comprising:
an ink cartridge having a plurality of inkjet nozzles, and a plurality of electrical
contacts for conducting control signals to said nozzles, and
a mounting assembly having a retainer for releasably securing said ink cartridge,
and a plurality of mechanically independent spring members for pressing electrical
contacts of a printer control circuit into conductive engagement with said contacts
of said ink cartridge.
2. The inkjet printhead defined in claim 1, wherein each of said independent spring members
is a cantilevered spring member.
3. The inkjet printhead defined in claim 2, wherein each spring member is cantilevered
from a wall of said mounting assembly.
4. The inkjet printhead defined in claim 3, wherein each spring member has a proximal
end that is integrally connected to said wall of said mounting assembly.
5. The inkjet printhead defined in claim 1, wherein each spring member includes a projecting
nub for engaging one of said contact buttons.
6. The inkjet printhead defined in claim 4, wherein each spring member has a distal end
that includes a projecting nub for engaging one of said circuit contacts.
7. The inkjet printhead defined in claim 1, wherein said retainer includes at least one
locking member for engaging said contacts of said ink cartridge against said contacts
of said circuit when said retainer secures said ink cartridge.
8. The inkjet printhead defined in claim 7, wherein said retainer includes a pair of
leg members pivotally mounted in side walls of said mounting assembly, and locking
lugs at an end of each leg for applying force against said ink cartridge.
9. The inkjet printhead defined in claim 1, wherein said mounting assembly and said cartridge
include interfitting members for aligning said contacts of said cartridge and said
assembly.
10. The inkjet printhead defined in claim 1, wherein said mounting assembly includes means
for aligning said circuit contacts with said plurality of spring members.