Print head cartridge and method of making a print head...

Details Print head cartridge and method of making a print head... Print head cartridge and method of making a print head...

1995-05-12

2001-06-05

Le, N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Fluid or fluid source handling means

Reexamination Certificate

active

06243117

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cartridges for ink jet print heads of the type wherein the ink reservoir is bounded by two thin films and a rigid frame. The invention provides novel cartridges made by a process wherein the frame is formed in a one-shot plastic injection molding step and the thin films are attached to the frame by adhesive bonding.
2. Prior Art
High capacity color ink jet printers configured around independent single color pens are currently commercially available. Typical pens or cartridges of the type suitable for use in such printers are shown in U.S. Pat. Nos. 5,280,300 and 5,325,119 and EP published applications 0 561 051 and 0 583 153.
As shown in
FIG. 5
a typical prior art print head cartridge includes a frame
10
having a flexible ink-impervious thin membrane
12
and a side cover
14
disposed on one side. A second membrane and a second side cover (not shown) are disposed on the opposite side of frame
10
. The frame
10
is formed by a two-shot plastic injection molding process. A rigid outer frame
16
(
FIG. 6
) of high melt temperature plastic is formed in a first mold during a first injection molding step. The rigid outer frame
16
is then placed in a second mold and a low melt temperature rubber-like plastic is injected into the mold. The rubber-like plastic forms an inner frame
18
molded onto outer frame
16
, the inner and outer frames forming the frame
10
as shown in FIG.
7
.
As shown in
FIGS. 7 and 8
, the inner frame
18
has oppositely facing flat side surfaces
20
,
20
′ which extend around the entire periphery of the inner frame
18
. The ink-impervious thin membranes
12
and
12
′ (
FIG. 8
) are heat staked to the surfaces
20
and
20
′ thereby forming a chamber or ink reservoir
22
bounded on opposite sides by the thin membranes and bounded around its periphery by the inner surface
24
of the inner frame
18
.
The outer frame
16
is molded to have a downwardly extending nose portion
16
A (
FIG. 6
) having therein a standpipe
26
as shown in FIG.
6
. The standpipe
26
has an ink flow channel
28
which extends through the standpipe and outer frame
16
to the bottom surface
30
of the nose. The inner frame
18
is molded around the standpipe
26
so that the opening into channel
28
is not closed as the inner frame
18
is molded onto outer frame
16
. This permits ink to flow from reservoir
22
through the channel
28
to the bottom surface of the nose from whence it may be ejected through a nozzle plate (not shown).
The prior art print head cartridges shown in
FIGS. 5-8
has a disadvantage in that the frame requires two separate and distinct molding steps thus making the frame
10
almost twice as expensive to manufacture as a similar frame formed in a single molding step. The device cannot be formed in a single molding step because different materials are required for the inner frame
18
and outer frame
16
. The requirement that the impervious films
12
,
12
′ be heat staked to the inner frame
16
dictates that the material used in forming the inner frame be a low melt temperature, rubber-like material. That is, the material comprising the inner frame must have a melt temperature less than that of the membrane material to prevent tear or damage to the membrane during the staking process and so that it melts to form a bond with the membranes
12
,
12
′ during the heat staking of the membranes. Since the inner frame material is somewhat flexible, the rigid outer frame must be made of a stiff material in order to support the flexible ink reservoir.
As discussed in EP published application 0 561 051, print head cartridges made by the two-shot molding process have a further disadvantage in that the ink reservoir may leak where the inner frame
18
is molded around the standpipe
24
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of making a print head cartridge, the method requiring only one plastic injection molding step.
A further object of the invention is to provide a method of making a print head cartridge having an ink reservoir therein bounded by first and second flexible films and a frame member, the films being secured to the frame by an adhesive bonding material.
According to the invention, a print head cartridge having an ink reservoir therein is made by (1) forming, in a single plastic injection molding step, a rigid monolithic frame having an interior surface facing an opening which extends through the frame from a first side to a second side, the interior surface comprising a peripheral wall of the ink reservoir when the opening is closed, the exterior surface of the frame comprising the peripheral exterior surface of the print head and the frame having first and second bonding surfaces spaced from each other and surround the opening, the bonding surfaces facing the first and second sides, respectively; (2) applying an adhesive bonding material to the first and second surfaces; and (3) securing first and second flexible films to the first and second bonding surfaces to thereby close the opening.
The adhesive material may be a hot melt adhesive such as ethylene vinyl acetate or a dry film adhesive pre-formed to the shapes of the bonding surfaces. When using one of these adhesives the flexible films are secured to the bonding surfaces by heat sealing or staking without melting the material of the frame.
The flexible films may each comprise a laminated polymeric film and may include a surface ply of a higher melt temperature polymer such as polyethylene terephthalate to prevent sticking of the low melt temperature polymer to the heat sealing tool.
In a further embodiment, the flexible films may be polyethylene terephthalate and the adhesive bonding material may cartridge be a liquid epoxy.
Another object of the invention is to provide a print head cartridge made by a process as described above.
Other objects and advantages of the invention will become evident upon consideration of the following description and the accompanying drawings.


REFERENCES:
patent: 5157421 (1992-10-01), Kitahara
patent: 5280300 (1994-01-01), Fong et al.
patent: 5325119 (1994-06-01), Fong
patent: 5448818 (1995-09-01), Scheffelin et al.
patent: 0561051 (1993-09-01), None
patent: 0583153 (1994-02-01), None
Webster's Ninth New Collegiate Dictionary, 1990, p. 768.

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