Note: Descriptions are shown in the official language in which they were submitted.
1 ~
1 BACKGROUND OF THE INVENTION
2 This invention relates to apparatus wherein
3 droplets of ink are ejected from an orifice of an ink
4 jet, and more particularly, to the manner in which the
transducers which control the ejectîon of droplets
6 from an orifice are supported
7 SUMMAR~ OF rrHE INVENTIO~
8 It is an object of this invention to provide
9 improved transducer support in an ink jet array.
It is a more ~pecific ob~ect of this
11 invention to provide improved transducer support such
12 that crosstalk between ink jets in an array may be
13 minimized~
14 In accordance with the present invention,
there is thus provided an ink jet array comprising a
16 plurality of chambers having ink jet droplet ejection
17 orifices therein. A plurality of elongated transdu-
18 cers are respectively coupled to the chambers for
19 expanding and contracting the transducers in response
to energization thereof, the transducers having one
21 end juxtaposed to the chambers and another end
22 opposite therefrom. A transducer supporting means is
23 provided comprising a rigid portion and a compliant
24 clamping portion between the rigid portion and the
transducers in an area along the axis of elongation of
26 the transducers for precluding contact between the
27 rigid portion and the opposite end of the transducers
28 in the area of the clamping portion.
29 According to a preferred embodimenk of the
invention, the compliant clamping portion comprises
31 an elastomeric material. Silicone rubber has been
32 found to be particularly suitable.
~2~
1 According to another preferred embodiment
2 of the invention, the ink jet array further com~rises
3 compliant electrical connections to the transducers~
4 The electrical connections may comprise flexible wires
or a flexible printed circuit.
6 According to a further preferred embodiment
7 of the invention, the compliant clamping means may
substantially surround a transverse cross section of
9 the transducers. As an alternative, the compliant
clamping portion may only partially surround a trans-
11 verse cross-section of the transducers.
12 BRIEF DESCRIPTIO~ OF THE DRAWINGS
13 Fig. 1 is a sectional view of the ink jet
14 apparatus constructed in accordance with the principles
of this invention,
16 Fig. la is an enlarged view of a portion
17 of the ink jet apparatus of Fig. 1,
18 Fig. 2 is a top view of the ink jet apparatus
19 shown in Fig. 1 taken along line 2-2,
Fig. 3 is a sectional view of the apparatus
21 shown in Fig. 2 taken along line 3-3,
22 Fig. 4 is a ~iew comparable to the view of
23 Fig. 2 of another embodiment of the invention;
24 Fig. 5 is a view comparable to Fig. 2 of
another embodiment of the invention, and
26 Fig. 6 is a sectional view of the apparatus
27 shown in FigO 5 taken along 6-6.
28 DETAILED DESCRIPTIO~ OF THE PREFERRED E_BODIME~NTS
29 Referring to Figs. 1-3, an ink jet apparatus
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1 comprises a plurality o chambers 200 having orifices
2 202 and an orifice plate 218 for ejecting droplets of
3 ink in response to the state of energization of the
4 transducers 204. The transducers 204 which are rectang-
ular in cross-section transverse to the axis of elonga-
6 tion expand and contract along the axis of elongation
7 as depicted by the arrowheads shown in Yig. la. The
8 resulting move~ent of the transducers 204 along the axis
9 of elongation is coupled into the chamber 200 by coupl-
ing means 205 including a foot 207, a viscoelastic
11 material 208 juxtaposed to the foot 207 and a diaphragm
12 210 which is preloaded to a position best shown in Fig.
13 la.
14 Ink flows into the chamber 200 from a reser-
voir 212 through a restricted inlet means provided by a
16 restricted opening 214 best shown in Fig. 3. The
17 opening 214 is located in a restrictor plate 216 best
18 shown in Fig. 2.
19 The reservoir 212 is formed by a concave
region in a chamber plate 220 which is covered by the
21 restrictor plate 216 so as to form an acute angle along
22 one side of the reservoir 212 leading to the inlet 214.
23 A feeder input tube 223 communicates with the reservoir
24 212 at one end thereof as shown in Fig. 1. A heater
assembly 225 is also shown in Fig. 1.
26 ~ach of the transducers 204 are supported at
27 the extremities thereof with intermediate portions being
2~ essentially unsupported as best shown in Fig. 1. ~ore
29 specifically, Fig 1 discloses a tran.sducer support
means including a plate 226 and a plate 228. The plate
31 226 of the transducer support means includes bearing
32 means in the form of a hole 224 which receives the foot
33 207 attached to an extremity of the transducer 204.
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1 It will be appreciated that the foot 207 is free to move
2 longitudinally within the hole 22~ thereby permitting
3 longitudinal motion of the transducer along the axis of
4 elongation of the transducer while substantially pre-
venting lateral motion of the transducer.
6 Mounting means for the transducer 204 provided
7 by the plate 228 includes slots 232 best shown in Fig.
8 2. In accordance with this invention, compliant mount-
g ing means 230 as shown in Figs. 2 and 3 clamp the
transducers 204 adjacent the extremities of the trans-
11 ducers 20~ remote from the chambers 200. It will be
12 appreciated that the compliant mounting means 230
3 provides a shear bond with the transducer 204.
14 In accordance with this invention, the com-
pliant mounting means 230 provide a sufficient clamping
16 action with respect to the transducers 204 so as to
17 substantially prevent any longitudinal motion of the
1~ transducers along the axis of elongation at the com-
19 pliant clamping means 230 such that expansion and
contraction of the transducer 204 is translated along
21 the transducer 204 and into the movernent of the foot 207
22 through the bearing holes 224 in the p~ate 226. At the
23 same time~ the compliant mounting means 230 has a
24 sufficient stiffness in the direction of elongation
of the transducers 204 so as to achieve substantial
26 movement in the direction of expansion and contraction.
27 The low mechanical stiffness minimizes the reaction
28 force that one transducer 204 transmits to other trans-
29 ducers 204 in the array when driven or energized.
The plate 228 includes a recessed area 229
31 shown in Fig. 1 below the slots 232 which is spaced from
32 the transducers 204. Thus, there is no contact along
33 the area 229. Moreover, it will be appreciated that
1 portions of the plate 228 including the slots 232 in
2 conjunction with the area 229 and the portion of the
3 plate 226 extending toward the holes 224 forms a C-shape
4 cross-section designated with broken lines identified
with the character C where the region 229 forms the
6 center of the C. Note that ~he space between ~he region
7 229 and the transducer permits the transducer to have a
8 substantially larger dimension than the foot 207 while
9 still avoiding contact with the plate 228. Moreover,
the foot 207 extends sufficiently far upwardly toward
11 the slots 232 so as to assure that the transducer 204
12 may expand and contract without con~acting any portion
13 of the plate 226. Thus, the transducer 204 may be
14 rec~angular in cross-section having a substantially
greater dimension in the direction shown in the plane of
16 Fig. 1 as compared with the direction shown in the
17 plane of Fig. 2.
18 As shown in Fig. 1, the overall leng~h of the
19 longitudinal bearing surface represented by the hole 224
in the direction of the axis of elongation of the
21 transducer 204 is substantially less than the overall
22 length of the transducer 204 along that axis. Prefer-
23 ably, the overall length of the bearing surface 224
24 along the axis is less than twice the maximum cross-
sectional dimension of the transducer as also shown in
26 Fig, 1.
27 Referring to Figs. 1-3, it will be observed
28 that the compliant material 230 surround all four sides
29 of the transducers 204 and the slots 232. However, it
will be appreciated that the compliant material 230
31 need not surround all four sides. In the embodiment as
32 shown in Fig. 4, the compliant material 330 is located
33 between a single side of the transducers 204 in one wall
34 of the slots 232. It will be appreciated that any
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1 number of walls of the transducers 204 may be surrounded
2 by the compliant material. Therefore, lt will be
3 appreciated that regardless of the amount of compliant
4 material utilized to clamp the transducers 204 in place,
the magnitude of the mechanical disturbance from one
6 transducer to another is substantially minirnized. As a
7 consequence, the erroneous ejection of a droplet from
8 a nei3hboring channel or ink jet chamber is minimized.
9 In accordance with another important aspect of
the invention, coMpliance is also provided in the
11 electrical connection to electrodes 236 and 238 of the
12 transducers 204 as shown in Figs. 2 and 3. This com-
13 pliant electrical coupling is provided by flexible wire
14 leads 240 and 242. The wire leads 240 and 242 are
connected to pins 250 extending into a planar insulator
16 244 extending across the top of the plate 228. Each of
17 the pins 250 is capable of coupling an electrical signal
18 to a particular transducer 204 for selectively ejecting
19 a droplet on demand. The flexible wire leads 242 are
connected to a bus 248 which in turn is connected to
21 ground as shown in Fig. 2.
22 It will be appreciated that the compliant
23 electrical connection to the transducer 204 minimizes
24 the possibility of any mechanical disturbances being
transmitted from one channel or one chamber to another
26 channel or chamber by means of ~he electrical connection
27 ~herefore, compliance is provided in both the mechanical
28 mounting through means of the compliant ma~erial 230 as
29 well as the electrical connection by means of the
fle~ible or compliant leads 240 and 242. It will be
31 appreciated that various types of electrical connections
32 may be made at the electrodes 236 and 238 as well as at
33 the pins 250 as shown in Figs. 2, 3 and 4, e.g., solder.
34 The same compliant electrical connection is achieved in
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1 the embodimen~ of Fig. ~ utilizing flexible wire leads
2 240 and 242.
3 Referring now to Figs. 5 and 6, an embodiment
4 of the invention is shown wherein another compliant
electrical connection is utilized. More specifically,
6 in this connection, a flexible prin~ed circuit board
7 having a flexible substrate 300 is unsecured and free to
8 move with respect to the top of the plate 2280 The
9 substrate 300 includes a series oE slots 302 which
generally correspond and are aligned with the slots
11 232 in the plate 228 which are filled with the compliant
12 material 230. The printed circuit board also includes
13 planar conductive portions 304 mounted on the substrate
14 300 which are coupled to the electrodes 23~ of the
transducers 204 by solder points 308. These planar
16 conductive members 304 are selectively energized so as
17 to produce ~rops on demand from the various chambers
18 associated with the ink jets. Additional planar con-
19 ductive members 306 are connected to the electrodes
238 and a flexible ground bus bar 24~ by solder points
21 308 to complete the electrical connection between the
22 planar conductive members 304 and 306 and the electrodes
23 236 and 238. Other techniques may be employed to
24 minimize cross-talk including the slitting of the
substrate 300 between transducers. It may also be
26 desirable to employ other conductive patterns so as to
27 permit a planar ground bus bar to be utilized.
28 It will be appreciated that the compliant
~9 clamping material may comprise a variety of elastomeric
3~ materials. For example, silicone rubber has been found
31 to be particularly suitable for use. Other elastomeric
32 materials suitable for use include latex and Neoprene.
33 In general, it is desirable to have a compliant material
34 characterized by a stiffness at least in order of
9~3~
l magnitude less than the compressive stiffness of the
2 transducer along the transducer axis.
3 As described in the foregoinq, the electrical
4 coupling may comprise wire leads or a flexible printed
circuit board. In ~eneral, flexible leads having a
6 lesser diameter than the thickness of the transducers
7 204 (e.g., less than .25 mm) have been found to provide
8 the necessary compliance. The thickness of the flexible
9 circuit board substrate 300 should also be less than the
13 thickness of the transducers 204 (eOg., less than .25 mm).
11 Although a particular embodiment of the
12 invention has been shown and described t it will be
13 appreciated that other embodiments and modifications
14 will fall within the true spirit and scope of the
invention as set forth in the appended claims.
