CA1055558A - Apparatus for applying liquid droplets to a surface by using a high speed laminar air flow to accelerate the same - Google Patents
Apparatus for applying liquid droplets to a surface by using a high speed laminar air flow to accelerate the sameInfo
- Publication number
- CA1055558A CA1055558A CA236,172A CA236172A CA1055558A CA 1055558 A CA1055558 A CA 1055558A CA 236172 A CA236172 A CA 236172A CA 1055558 A CA1055558 A CA 1055558A
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- discharge channel
- chamber
- channel
- droplets
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 93
- 230000003068 static effect Effects 0.000 claims description 8
- 230000008021 deposition Effects 0.000 abstract description 2
- 230000000737 periodic effect Effects 0.000 abstract 1
- 230000007246 mechanism Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000012530 fluid Substances 0.000 description 6
- 239000012528 membrane Substances 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000002657 fibrous material Substances 0.000 description 2
- 208000036366 Sensation of pressure Diseases 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 229910052573 porcelain Inorganic materials 0.000 description 1
- 239000005373 porous glass Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2202/00—Embodiments of or processes related to ink-jet or thermal heads
- B41J2202/01—Embodiments of or processes related to ink-jet heads
- B41J2202/02—Air-assisted ejection
Landscapes
- Nozzles (AREA)
- Special Spraying Apparatus (AREA)
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
- Coating Apparatus (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Apparatus for applying droplets of colored liquid to a surface includes a chamber divided into a liquid chamber portion and an air chamber portion. The liquid chamber portion includes an intake channel connected to a liquid supply container and a discharge channel through which the liquid is discharged for deposition on the surface. A pressure producing means is in contact with the liquid chamber portion to produce periodic pressure increases in the liquid in the chamber portion to eject it through the discharge channel to the atmosphere in a series of droplets. The air chamber portion includes an intake channel connected to a source of pressurized air and a discharge channel axially aligned with the discharge channel of the liquid chamber portion to allow the air to be discharged therethrough to the atmosphere at a high speed. The liquid droplets are thus dis-charged through the two axially aligned discharged channels and accelerated by the stream of air along their passage to the sur-face.
Apparatus for applying droplets of colored liquid to a surface includes a chamber divided into a liquid chamber portion and an air chamber portion. The liquid chamber portion includes an intake channel connected to a liquid supply container and a discharge channel through which the liquid is discharged for deposition on the surface. A pressure producing means is in contact with the liquid chamber portion to produce periodic pressure increases in the liquid in the chamber portion to eject it through the discharge channel to the atmosphere in a series of droplets. The air chamber portion includes an intake channel connected to a source of pressurized air and a discharge channel axially aligned with the discharge channel of the liquid chamber portion to allow the air to be discharged therethrough to the atmosphere at a high speed. The liquid droplets are thus dis-charged through the two axially aligned discharged channels and accelerated by the stream of air along their passage to the sur-face.
Description
The present invention relates to apparatus for applying fluid droplets to a writing surface, and more particularly to improvement to a mechanism for writing on paper with an ejected colored liquid.
The speed of recording data on paper in, for example, a data processing system is limited for one thing by the capa-bility of the writing mechanism, which in many cases is substan-tially less than that of the data processing system.
Because of the high speed capability of the ink ejec-tion type writing mechanism, many proposals have been made inwhich the liquid is discharged onto the paper by application of electrical pulses, the liquid being ejected in a series of pulsed droplets. The speed of the writing mechanism is in turn largely determined by the capability of the liquid responding to the rapidly occurring electrical pulses. However, the voltage of the electrical pulses must be high enough to overcome the resistance offerred by the liquid due to its surface tension and viscosity.
The range of voltage necessary for driving the writing unit (dynamic range of a writing mechanism) is therefore determined by the resistance of the liquid to the applied pulses. Prior art writing mechanisms have a narrow dynamic range. This resulted in liquid droplets of comparatively large size and therefore satisfactory gradation of image cannot be obtained on the writing surface.
Because of the high operating speed of the writing mechanism, the liquid droplets are ejected onto a sheet of paper which is wrapped around a roller revolving at a high speed.
Since a series of droplets is formed upon ejection in response to a single electrical pulse, they tend to land on different localities of the writing surface, thus causing a blur on the image. Furthermore, the high speed revolution of the roller creates a whirl of wind at the surface which would cause disper-sion of the ejected droplets.
Therefore, an object ofthe present invention is to provide an improved liquid applying apparatus which assures a wider dynamic range than is available by the prior art apparatus to thereby decrease the size of droplets to be deposited on the writing surface.
Another object is to provide an improved liquid apply-ing apparatus in which liquid droplets ejected in response to a single pulse are accelerated by a stream of air so that they land on the writing surface at substantially the same instant of time.
A specific object of the invention is to provide a liquid applying apparatus having a pneumatic chamber connected to a source of pressurized air and an improved 105555~3 arrangement for connecting a liquid supply container with the source of pressurized air.
~ ccording to the present invention there is provided an apparatus for applying liquid droplets to a surface comprising, a housing including a first liquid chamber for containing a liquid to be applied to a surface and having an associated piezoelectric device for generating short-duration rises of the pressure of liquid in the first liquid chamber, a second liquid chamber communicating with the first liquid chamber through a connecting channel and having a first dis-charge channel for droplets of said liquid to leave the apparatus, the first discharge channel being in alignment with the connecting channel and in close proximity thereto so that a short-duration pressure rise in the first liquid chamber causes a series of liquid droplets to be expelled through the first discharge channel, the second liquid chamber having a first intake channel connected to a liquid supply source, a pneumatic chamber substantially divided into an inner, disc-like portion formed with a second discharge channel and an outer, annular portion formed with a second intake channel connected to a source of pressurized air, the second discharge channel being in alignment with the first discharge channel and in close proximity thereto, and means for providing communication for the liquid supply source with the air supply source to increase the static pressure in the liquid in the liquid supply source to such a degree that the static pressure in the first discharge channel is substantially equal to the static pressure in the space between the first and second discharge channels.
The cross-sectional area of the air discharge channels is preferably selected in relation to the cross-sectional area of the liauid di~charge channel in order that a laminar air flow iY
formed at the exit thereofO
The ~ource of pre~urized air i9 in communication with the liquid supply container to increa~e the pres-sure in the liquid in relation to the air pre~sure.
Thi~ prevents the intru~ion of air into the liquid chamber portion.
The present invention will be under~tood from the following description when read in conjunction with the accompanying drawing~, in which;
Fig. 1 is a cro~s-~ectional view of one embodiment of li4uid applying apparatus according to the pre~ent invention;
Fig. 2 i8 a cros~-sectional view of one embodiment f liquid applying apparatUJ according to the invention ~howing a connection of an air intske channel to the pneumatic chamber portion;
~ig. 3 is a cross-sectional view taken along the line~ 3-3 of Fig. 2;
Fig. 4 is a -~chematic functional block diagram of a Yource of pres~urized air employed in the embodi-ment of Fig. 1;
Fig. 5 i~ a cross-sectional view of one embodiment of a humidifier of Fig. 4;
Fig. 6 is a cro~s-sectional view of another embodiment of the humidifier of ~ig. 4;
Fig. 7 i~ a graph ahowing a relation between the diameter of liquid di~charge channel and the air pressure;
Fig~ 8 is a graph showing a relation between the diameters of liquid and air di~charge channelY;
Fig. 9 is a graph ~howing a relation between the thicknes~ of diqc-like chamber and the optical density of an image produced on the ~urface; and Figo 10 is a cross-sectional view qhowing the flow of air from the disc-like chamber to the atmosphere.
Referring now to Fig. 1 apparatus of the present invention is qhown and compriqe~ generally a liquid applying unit 10, a liquid supply container 11 and a pneumatic pressure producing mean~ 12. The liquid applying unit 10 compri~es an outer chamber portion 14 an inner chamber portion 15 and a pneumatic chamber portion which include~ an intake channel 13 connected to the pressure producing means 12 via a conduit 26, an annular chamber portion 13' and a disc-like chamber portion 13" which is in communication with the atmosphere via a diqcharge channel 19. The thickness of the disc-like chamber portion 13" is substantially smaller than the depth, or axial dimengion of the annular chamber portion 13'. The outer and inner chamber-q 14 and 15 are in communication through a connecting channel 16 which is provided in a dividing plate 17 situated between and forming the ~eparation of the liquid chamber into the chamber portions 14 and 15. The con-necting channel 16 i~ positioned in the dividing plate17 so that it is directly opposite to and axially aligned with a discharge channel 18 which is provided at the outer end of the outer liquid chamber 14 and opens to the atmo~phere from the outer chamber portion 14 through the dischar$e channel 19. The discharge channel 19 is axially aligned with the discharge channel 18. A circular metal plate or membrane 20 i~
fastened to the wall 15' of the inner chamber portion 15. The dividing plate 17 has an intake channel 21 which opens into the outer liquid chamber 14 and i4 in communication with the fluid container 11 via a conduit 22. The container may be disposed at a lower level than the discharge channel 18 becau~e of the capillary forces existing in the channel~ communicat-ing with the outer chamber portion 14. A piezoelectriccrystal 23 i~ attached to the metal membrane 20 in any conventional manner. Conductive wires 24 are provided, one being electrically connected to the metal membrane 20 and the other to the piezoelectric crystal 23. The wires 24 supply control pulses to the crystal 23. The Inner liquid chamber portion 15 has its one end oppo~ite to the outer chamber portion 14 a larger diameter portion 15" which i~ in contact with the metal membrane 20. The cros~-sectional area of the discharge channel 18 is substantially 9maller than the cro~s-~ectional area of the larger diameter portion 15", and slightly smaller than the cross-sectional area of the di~charge channel 19.
When the cry~tal 23 i~ activated by a pulse, fluid i~ discharged from the inner chamber portin 15 through the connecting channel 16, through the fluid layer in the outer chamber portion 14 and further through the di~charge channel~ 18 and 19 whereupon it is applied to a writing ~urface. When the voltage pulse drops to zero the direction of the fluid stream in the connect-ing channel 16 i8 reversed and fluid is now sucked in through the outer chamber portion 14 from the container 11 via the intake channel 21.
On the other hand, a stream of air is supplied by constant pre~sure from the pressure producing means 12 to the annular chamber portion 13' through the intake channel 13. The air stream diverges as it flows through the annular path of the chamber portion 13' and converges a~ it flows into the disc-like chamber portion 13" and then escapes through the di.~charge channel 19 at a high speed. The pre~4ure at which the air is supplied is adjusted such that the pre~sure in the di~c-like chamber portion 13"
equal~ the pressure in the liquid in the di~charge channel 18 to permit the liquid to be sucked out there-from overcoming the surface tension and visco~ity associated with the liquid (Fig. 10) and that the velocity of the air at the exit of the discharge channel ~9 i9 greater than the speed at which the liquid is discharged ~o that the discharged liquid i~ accelerated by the air stream. Since the liquid breaks up into a serie~ of droplets of decreasing qize upon di~charge, the droplets of smaller size are accelerated at a higher ~peed than the droplets of larger ~ize ~o that they land on the writing surface at sub~tantially the same inAtant of time.
The axial direction of the intake channel 13 may preferably be tangential to the periphery of the anllu]ar chamber portion 13' aY illu~trated in FigY. 2 and 3 90 that a circular flow of air i9 formed in the annular chamber portion 13' a~ indicated by the arrow in ~ig. 3 and that the air flow~ into the di~c-like chamber portion 13" in a spiral form radially inwardly toward the discharge channel 19.
Exemplary dimen~ion~ of the liquid applying unit _ g _ lO which provide~ a laminar flow at the outlet of the discharge channel 19 are as follows:
Outer diameter of annular chamber portion 13' ...... 20 mm Width of annular chamber portion 13' (W) ..... 1 - 4 mm Depth of annular chamber portion 13' (D) ..... 0.5 - 2 mm Thickness (T) of disc-like chamber portion 13" ..... 10 - 100 ~m Diameter of discharge channel 18 ..... 40 ~m Diameter of discharge channel 19 ..... 100 - 150 ~m Pneumatic pressure in disc-like chamber portion ...... 100 - 1000 mm Aq Hecause there i-q no axial component in the spiral air flow in the disc-like chamber portion 13", the air may be sucked into the outer chamber portion 14 and further into the inner chamber portion 15 through the discharge channel 18 from the disc-like chamber portion 13" and prevents Yati~factory ejection of liquid. In order to prevent 4uch air intruYion, the liquid con-tainer 11 i~ communicated with the pre~sure producing means 12 via a conduit 27.
The preYsure producing mean~ 12 compri~e~, a~
-- 10 _ ~hown in Fig. 4, a pump 30, an air filter 31 connected to the outlet of` the pump unit 30 to filter out any foreign particles and to dampen oscillations of air flow which might be generated from the pump 30. The outlet of the filter 31 is preferably connected to a humidifier 32 to impart moisture to the air to be supplied to the liquid applying unit 10. The outlet of the humidifier 32 iJ also connected to a pressure regulating means such as a valve 33, the outlet of the valve 33 being connected to the liquid supply container S~ j G
11 via the conduit 27. The~pressure in the liquid in 5~ c the container 11, and hence the\pre~sure in the liquid in the discharge channel 18, are thereby increased, and regulated manually by the valve means 33 such that the pressure in the liquid in the discharge channel 18 eqllal J the presAure in the air chamber 13~.
During the intervals when the control pulses are not Yupplied to the crystal 23, the surface area of the liquid in the discharge channel 18 is likely to be dried up to thereby increase its visco~ity. The humidifier 32 keeps it~ liquidity by providing moi~ture to the air stream. A~ illustrated in Fig. 5, the humidifier 32 compri~es a housing 34, a porous member 3; ~uch as ~ponge or fibrous material which divides the interior of the housing into an inlet chamber 36 and nn outlet chamber 37. A water supply pipe 38 is connected to the side wall of the housing 34 to fill a lower portion of the housing 34 with water. The lower part of the porous member 35 i~ immersed in the water so that water permeates throughout the porous material by absorption. The inlet chamber 36 is in communication by a conduit 39 with the filter 31 and the outlet chamber 37 ia connected by a conduit 40 to the intake channel 13 of the liquid applying unit 10.
The pressuri~ed air is admitted into the inlet chamber 36 from the filter 31 and moiAture laden air emerges from the outlet chamber 37.
An alternative arrangement of the humidifier 32 i9 illustrated in Fig. 6. The housing 41 is partially filled with water supplied from pipe 42. A porous porcelain or porous glass member 43 i9 disposed at the lower part of the housing spaced from its bottom wall 41a defining a lower chamber 45. A porous member 44 such aA sponge or fibrous material is preferably provided in a position above the surface of` the water defining an upper chamber 46. The lower chamber 45 is connected to the fulter 31 through conduits 47 and 48 and the upper chamber 46 is connected to the intake channel 13 of the unit 10 via conduit and f`urther con-nected to the presYure regulating means 33 via a conduit ~(). When air is admitted into the lower chamber 45 rrom filter 31, the air will be forced into the water through the porous glasY 43 and emerges as air bubble~
which float upward to the surface. The porous member 44 ab~orb~ the Yplashe~ cauYed by the upward flow of tlle bubble~, but admit~ moi~ture laden air to pass therethrough to the outlet chamber 46.
Experiments were conducted to aqYure ~ati~factory operation of the liquid applying unit of the inventinn.
In Fig. 7 the relation between the air pres~ure and the diameter (d) of diYcharge channel 18 is il-illu~trated. In thi~ experiment, it wa~ assumed that the diameter of discharge channel 19 iY approximately 2d + 20~m and the thicknes~ of the disc-like chamber 13" i~ 20 ~m. The lower limit of the air pressure required to provide a laminar flow at the exit of di~charge channel 19 follow~ the curve which decays in a manner similar to an exponential curve with the increa~e in the diameter of di~charge channel, 18.
Fig. ô ~hows the relation between the diameters of discharge channels 18 and 19, and indicates that a wider range of diameters iY available for the outer discharge channel 19 when the inner discharge channel 1~ has a smaller diameter than when it ha~ a larger diameter.
Fig. 9 shows the relation between optical density and the thickness of disc-like chamber 13" and indicates that at a smaller thickness value the optical density of the image produced on the writing surface by deposition of droplets is smaller than at a larger thickness value. Good gradation of images was ob-tained for the thickness value ranging from 10 to 20 ~m. The thickness value in the range from 40 to 100 ~m was found suitable for two-valued image reproduction, such as black-and-white docu-ments.
By formation of a high speed laminar air flow at the exit of the liquid discharge channel 18, the following advantages are provided:
1) A series of droplets of decreasing size is acceler-ated by the air stream so that the droplets of smaller size are accelerated at a higher speed because of their small inertia than the droplets of larger size. They land on the writing surface substantially at the same instant of time on substantially the same locality of the surface. This increases the resolution of the image produced.
The speed of recording data on paper in, for example, a data processing system is limited for one thing by the capa-bility of the writing mechanism, which in many cases is substan-tially less than that of the data processing system.
Because of the high speed capability of the ink ejec-tion type writing mechanism, many proposals have been made inwhich the liquid is discharged onto the paper by application of electrical pulses, the liquid being ejected in a series of pulsed droplets. The speed of the writing mechanism is in turn largely determined by the capability of the liquid responding to the rapidly occurring electrical pulses. However, the voltage of the electrical pulses must be high enough to overcome the resistance offerred by the liquid due to its surface tension and viscosity.
The range of voltage necessary for driving the writing unit (dynamic range of a writing mechanism) is therefore determined by the resistance of the liquid to the applied pulses. Prior art writing mechanisms have a narrow dynamic range. This resulted in liquid droplets of comparatively large size and therefore satisfactory gradation of image cannot be obtained on the writing surface.
Because of the high operating speed of the writing mechanism, the liquid droplets are ejected onto a sheet of paper which is wrapped around a roller revolving at a high speed.
Since a series of droplets is formed upon ejection in response to a single electrical pulse, they tend to land on different localities of the writing surface, thus causing a blur on the image. Furthermore, the high speed revolution of the roller creates a whirl of wind at the surface which would cause disper-sion of the ejected droplets.
Therefore, an object ofthe present invention is to provide an improved liquid applying apparatus which assures a wider dynamic range than is available by the prior art apparatus to thereby decrease the size of droplets to be deposited on the writing surface.
Another object is to provide an improved liquid apply-ing apparatus in which liquid droplets ejected in response to a single pulse are accelerated by a stream of air so that they land on the writing surface at substantially the same instant of time.
A specific object of the invention is to provide a liquid applying apparatus having a pneumatic chamber connected to a source of pressurized air and an improved 105555~3 arrangement for connecting a liquid supply container with the source of pressurized air.
~ ccording to the present invention there is provided an apparatus for applying liquid droplets to a surface comprising, a housing including a first liquid chamber for containing a liquid to be applied to a surface and having an associated piezoelectric device for generating short-duration rises of the pressure of liquid in the first liquid chamber, a second liquid chamber communicating with the first liquid chamber through a connecting channel and having a first dis-charge channel for droplets of said liquid to leave the apparatus, the first discharge channel being in alignment with the connecting channel and in close proximity thereto so that a short-duration pressure rise in the first liquid chamber causes a series of liquid droplets to be expelled through the first discharge channel, the second liquid chamber having a first intake channel connected to a liquid supply source, a pneumatic chamber substantially divided into an inner, disc-like portion formed with a second discharge channel and an outer, annular portion formed with a second intake channel connected to a source of pressurized air, the second discharge channel being in alignment with the first discharge channel and in close proximity thereto, and means for providing communication for the liquid supply source with the air supply source to increase the static pressure in the liquid in the liquid supply source to such a degree that the static pressure in the first discharge channel is substantially equal to the static pressure in the space between the first and second discharge channels.
The cross-sectional area of the air discharge channels is preferably selected in relation to the cross-sectional area of the liauid di~charge channel in order that a laminar air flow iY
formed at the exit thereofO
The ~ource of pre~urized air i9 in communication with the liquid supply container to increa~e the pres-sure in the liquid in relation to the air pre~sure.
Thi~ prevents the intru~ion of air into the liquid chamber portion.
The present invention will be under~tood from the following description when read in conjunction with the accompanying drawing~, in which;
Fig. 1 is a cro~s-~ectional view of one embodiment of li4uid applying apparatus according to the pre~ent invention;
Fig. 2 i8 a cros~-sectional view of one embodiment f liquid applying apparatUJ according to the invention ~howing a connection of an air intske channel to the pneumatic chamber portion;
~ig. 3 is a cross-sectional view taken along the line~ 3-3 of Fig. 2;
Fig. 4 is a -~chematic functional block diagram of a Yource of pres~urized air employed in the embodi-ment of Fig. 1;
Fig. 5 i~ a cross-sectional view of one embodiment of a humidifier of Fig. 4;
Fig. 6 is a cro~s-sectional view of another embodiment of the humidifier of ~ig. 4;
Fig. 7 i~ a graph ahowing a relation between the diameter of liquid di~charge channel and the air pressure;
Fig~ 8 is a graph showing a relation between the diameters of liquid and air di~charge channelY;
Fig. 9 is a graph ~howing a relation between the thicknes~ of diqc-like chamber and the optical density of an image produced on the ~urface; and Figo 10 is a cross-sectional view qhowing the flow of air from the disc-like chamber to the atmosphere.
Referring now to Fig. 1 apparatus of the present invention is qhown and compriqe~ generally a liquid applying unit 10, a liquid supply container 11 and a pneumatic pressure producing mean~ 12. The liquid applying unit 10 compri~es an outer chamber portion 14 an inner chamber portion 15 and a pneumatic chamber portion which include~ an intake channel 13 connected to the pressure producing means 12 via a conduit 26, an annular chamber portion 13' and a disc-like chamber portion 13" which is in communication with the atmosphere via a diqcharge channel 19. The thickness of the disc-like chamber portion 13" is substantially smaller than the depth, or axial dimengion of the annular chamber portion 13'. The outer and inner chamber-q 14 and 15 are in communication through a connecting channel 16 which is provided in a dividing plate 17 situated between and forming the ~eparation of the liquid chamber into the chamber portions 14 and 15. The con-necting channel 16 i~ positioned in the dividing plate17 so that it is directly opposite to and axially aligned with a discharge channel 18 which is provided at the outer end of the outer liquid chamber 14 and opens to the atmo~phere from the outer chamber portion 14 through the dischar$e channel 19. The discharge channel 19 is axially aligned with the discharge channel 18. A circular metal plate or membrane 20 i~
fastened to the wall 15' of the inner chamber portion 15. The dividing plate 17 has an intake channel 21 which opens into the outer liquid chamber 14 and i4 in communication with the fluid container 11 via a conduit 22. The container may be disposed at a lower level than the discharge channel 18 becau~e of the capillary forces existing in the channel~ communicat-ing with the outer chamber portion 14. A piezoelectriccrystal 23 i~ attached to the metal membrane 20 in any conventional manner. Conductive wires 24 are provided, one being electrically connected to the metal membrane 20 and the other to the piezoelectric crystal 23. The wires 24 supply control pulses to the crystal 23. The Inner liquid chamber portion 15 has its one end oppo~ite to the outer chamber portion 14 a larger diameter portion 15" which i~ in contact with the metal membrane 20. The cros~-sectional area of the discharge channel 18 is substantially 9maller than the cro~s-~ectional area of the larger diameter portion 15", and slightly smaller than the cross-sectional area of the di~charge channel 19.
When the cry~tal 23 i~ activated by a pulse, fluid i~ discharged from the inner chamber portin 15 through the connecting channel 16, through the fluid layer in the outer chamber portion 14 and further through the di~charge channel~ 18 and 19 whereupon it is applied to a writing ~urface. When the voltage pulse drops to zero the direction of the fluid stream in the connect-ing channel 16 i8 reversed and fluid is now sucked in through the outer chamber portion 14 from the container 11 via the intake channel 21.
On the other hand, a stream of air is supplied by constant pre~sure from the pressure producing means 12 to the annular chamber portion 13' through the intake channel 13. The air stream diverges as it flows through the annular path of the chamber portion 13' and converges a~ it flows into the disc-like chamber portion 13" and then escapes through the di.~charge channel 19 at a high speed. The pre~4ure at which the air is supplied is adjusted such that the pre~sure in the di~c-like chamber portion 13"
equal~ the pressure in the liquid in the di~charge channel 18 to permit the liquid to be sucked out there-from overcoming the surface tension and visco~ity associated with the liquid (Fig. 10) and that the velocity of the air at the exit of the discharge channel ~9 i9 greater than the speed at which the liquid is discharged ~o that the discharged liquid i~ accelerated by the air stream. Since the liquid breaks up into a serie~ of droplets of decreasing qize upon di~charge, the droplets of smaller size are accelerated at a higher ~peed than the droplets of larger ~ize ~o that they land on the writing surface at sub~tantially the same inAtant of time.
The axial direction of the intake channel 13 may preferably be tangential to the periphery of the anllu]ar chamber portion 13' aY illu~trated in FigY. 2 and 3 90 that a circular flow of air i9 formed in the annular chamber portion 13' a~ indicated by the arrow in ~ig. 3 and that the air flow~ into the di~c-like chamber portion 13" in a spiral form radially inwardly toward the discharge channel 19.
Exemplary dimen~ion~ of the liquid applying unit _ g _ lO which provide~ a laminar flow at the outlet of the discharge channel 19 are as follows:
Outer diameter of annular chamber portion 13' ...... 20 mm Width of annular chamber portion 13' (W) ..... 1 - 4 mm Depth of annular chamber portion 13' (D) ..... 0.5 - 2 mm Thickness (T) of disc-like chamber portion 13" ..... 10 - 100 ~m Diameter of discharge channel 18 ..... 40 ~m Diameter of discharge channel 19 ..... 100 - 150 ~m Pneumatic pressure in disc-like chamber portion ...... 100 - 1000 mm Aq Hecause there i-q no axial component in the spiral air flow in the disc-like chamber portion 13", the air may be sucked into the outer chamber portion 14 and further into the inner chamber portion 15 through the discharge channel 18 from the disc-like chamber portion 13" and prevents Yati~factory ejection of liquid. In order to prevent 4uch air intruYion, the liquid con-tainer 11 i~ communicated with the pre~sure producing means 12 via a conduit 27.
The preYsure producing mean~ 12 compri~e~, a~
-- 10 _ ~hown in Fig. 4, a pump 30, an air filter 31 connected to the outlet of` the pump unit 30 to filter out any foreign particles and to dampen oscillations of air flow which might be generated from the pump 30. The outlet of the filter 31 is preferably connected to a humidifier 32 to impart moisture to the air to be supplied to the liquid applying unit 10. The outlet of the humidifier 32 iJ also connected to a pressure regulating means such as a valve 33, the outlet of the valve 33 being connected to the liquid supply container S~ j G
11 via the conduit 27. The~pressure in the liquid in 5~ c the container 11, and hence the\pre~sure in the liquid in the discharge channel 18, are thereby increased, and regulated manually by the valve means 33 such that the pressure in the liquid in the discharge channel 18 eqllal J the presAure in the air chamber 13~.
During the intervals when the control pulses are not Yupplied to the crystal 23, the surface area of the liquid in the discharge channel 18 is likely to be dried up to thereby increase its visco~ity. The humidifier 32 keeps it~ liquidity by providing moi~ture to the air stream. A~ illustrated in Fig. 5, the humidifier 32 compri~es a housing 34, a porous member 3; ~uch as ~ponge or fibrous material which divides the interior of the housing into an inlet chamber 36 and nn outlet chamber 37. A water supply pipe 38 is connected to the side wall of the housing 34 to fill a lower portion of the housing 34 with water. The lower part of the porous member 35 i~ immersed in the water so that water permeates throughout the porous material by absorption. The inlet chamber 36 is in communication by a conduit 39 with the filter 31 and the outlet chamber 37 ia connected by a conduit 40 to the intake channel 13 of the liquid applying unit 10.
The pressuri~ed air is admitted into the inlet chamber 36 from the filter 31 and moiAture laden air emerges from the outlet chamber 37.
An alternative arrangement of the humidifier 32 i9 illustrated in Fig. 6. The housing 41 is partially filled with water supplied from pipe 42. A porous porcelain or porous glass member 43 i9 disposed at the lower part of the housing spaced from its bottom wall 41a defining a lower chamber 45. A porous member 44 such aA sponge or fibrous material is preferably provided in a position above the surface of` the water defining an upper chamber 46. The lower chamber 45 is connected to the fulter 31 through conduits 47 and 48 and the upper chamber 46 is connected to the intake channel 13 of the unit 10 via conduit and f`urther con-nected to the presYure regulating means 33 via a conduit ~(). When air is admitted into the lower chamber 45 rrom filter 31, the air will be forced into the water through the porous glasY 43 and emerges as air bubble~
which float upward to the surface. The porous member 44 ab~orb~ the Yplashe~ cauYed by the upward flow of tlle bubble~, but admit~ moi~ture laden air to pass therethrough to the outlet chamber 46.
Experiments were conducted to aqYure ~ati~factory operation of the liquid applying unit of the inventinn.
In Fig. 7 the relation between the air pres~ure and the diameter (d) of diYcharge channel 18 is il-illu~trated. In thi~ experiment, it wa~ assumed that the diameter of discharge channel 19 iY approximately 2d + 20~m and the thicknes~ of the disc-like chamber 13" i~ 20 ~m. The lower limit of the air pressure required to provide a laminar flow at the exit of di~charge channel 19 follow~ the curve which decays in a manner similar to an exponential curve with the increa~e in the diameter of di~charge channel, 18.
Fig. ô ~hows the relation between the diameters of discharge channels 18 and 19, and indicates that a wider range of diameters iY available for the outer discharge channel 19 when the inner discharge channel 1~ has a smaller diameter than when it ha~ a larger diameter.
Fig. 9 shows the relation between optical density and the thickness of disc-like chamber 13" and indicates that at a smaller thickness value the optical density of the image produced on the writing surface by deposition of droplets is smaller than at a larger thickness value. Good gradation of images was ob-tained for the thickness value ranging from 10 to 20 ~m. The thickness value in the range from 40 to 100 ~m was found suitable for two-valued image reproduction, such as black-and-white docu-ments.
By formation of a high speed laminar air flow at the exit of the liquid discharge channel 18, the following advantages are provided:
1) A series of droplets of decreasing size is acceler-ated by the air stream so that the droplets of smaller size are accelerated at a higher speed because of their small inertia than the droplets of larger size. They land on the writing surface substantially at the same instant of time on substantially the same locality of the surface. This increases the resolution of the image produced.
2) The liquid in the inner discharge channel 18 is prevented from being dried because of the moisture provided by the humidifier.
3) Because the static pressure at the exit side of the discharge channel 18 is balanced against the static pressure in the liquid, -~
this contributes to the lowering of surface tension of the boundary surface layer of the liauid in the discharge channel 18 and as a result facilitates the ejection of li~uid droplets to the atmosphere. Therefore, the threshold value at which the droplets of the smallest size are ejected is lowered.
this contributes to the lowering of surface tension of the boundary surface layer of the liauid in the discharge channel 18 and as a result facilitates the ejection of li~uid droplets to the atmosphere. Therefore, the threshold value at which the droplets of the smallest size are ejected is lowered.
4) The air stream serves to avoid objectionable effect caused by high speed rotation of a paper drum or roller by guiding the discharged droplets to the paper surface at a high speed which in some cases reaches 80 meters per second.
5) Because the discharged liquid droplets are guided by the air stream, the distance travelled by the droplets can be increased to advantage to allow the spacing between the li~uid ejection apparatus and the writing surface.
?~
?~
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for applying liquid droplets to a surface comprising, a housing including a first liquid chamber for containing a liquid to be applied to a surface and having an associated piezoelectric device for generating short-duration rises of the pressure of liquid in the first liquid chamber, a second liquid chamber communicating with the first liquid chamber through a connecting channel and having a first dis-charge channel for droplets of said liquid to leave the apparatus, the first discharge channel being in alignment with the connecting channel and in close proximity thereto so that a short-duration pressure rise in the first liquid chamber causes a series of liquid droplets to be expelled through the first discharge channel, the second liquid chamber having a first intake channel connected to a liquid supply source, a pneumatic chamber substantially divided into an inner, disc-like portion formed with a second discharge channel and an outer, annular portion formed with a second intake channel connected to a source of pressurized air, the second discharge channel being in alignment with the first discharge channel and in close proximity thereto, and means for providing communication for the liquid supply source with the air supply source to increase the static pressure in the liquid in the liquid supply source to such a degree that the static pressure in the first discharge channel is substantially equal to the static pressure in the space between the first and second discharge channels.
2. Apparatus for applying liquid droplets to a surface as claimed in claim 1, wherein the ratio of the diameter of the first discharge channel to that of the second discharge channel is in a range substantially from 2:5 to 4:15.
3. Apparatus for applying liquid droplets to a surface as claimed in claim 2, wherein the diameter of said first discharge channel is 40 micrometers.
4. Apparatus for applying liquid droplets to a surface as claimed in claim 2, wherein the ratio of the diameter of said first discharge channel to the axial dimension of said disc-like chamber portion is substantially 1:less than 2.5.
5. Apparatus for applying liquid droplets to a surface as claimed in claim 4, wherein the axial dimension of said disc-like chamber portion ranges from 10 to 100 micrometers.
6. Apparatus for applying liquid droplets to a surface as claimed in one of claims 1 to 3, further comprising means for humidifying the air in said pneumatic chamber to maintain the liquidity of the liquid in the first discharge channel.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP49111279A JPS5137541A (en) | 1974-09-26 | 1974-09-26 | Inkujetsutokirokusochi |
| JP50034109A JPS51109738A (en) | 1975-03-20 | 1975-03-20 | Inkujetsutokirokusochi |
| JP50072555A JPS51147917A (en) | 1975-06-13 | 1975-06-13 | Ink jet head |
| JP50073469A JPS51149029A (en) | 1975-06-16 | 1975-06-16 | Ink jet recording apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1055558A true CA1055558A (en) | 1979-05-29 |
Family
ID=27459893
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA236,172A Expired CA1055558A (en) | 1974-09-26 | 1975-09-23 | Apparatus for applying liquid droplets to a surface by using a high speed laminar air flow to accelerate the same |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1055558A (en) |
| DE (1) | DE2543038B2 (en) |
| FR (1) | FR2285928A1 (en) |
| GB (1) | GB1483571A (en) |
| IT (1) | IT1047509B (en) |
| SE (2) | SE414238B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54123950A (en) * | 1978-03-17 | 1979-09-26 | Matsushita Electric Ind Co Ltd | Ink jet recorder |
| DE2831855C2 (en) * | 1978-07-20 | 1983-10-27 | NCR Corp., 45479 Dayton, Ohio | Inkjet printing system |
| GB2040819B (en) * | 1979-01-19 | 1983-02-09 | Matsushita Electric Industrial Co Ltd | Ink ejection apparatus |
| DE3051102C2 (en) * | 1979-02-14 | 1995-07-27 | Canon Kk | Ink drop recording device for HF signals |
| US4317124A (en) * | 1979-02-14 | 1982-02-23 | Canon Kabushiki Kaisha | Ink jet recording apparatus |
| EP0063853B1 (en) * | 1981-01-21 | 1986-03-12 | Matsushita Electric Industrial Co., Ltd. | Ink jet printing head utilizing pressure and potential gradients |
| US4403228A (en) * | 1981-03-19 | 1983-09-06 | Matsushita Electric Industrial Company, Limited | Ink jet printing head having a plurality of nozzles |
| DE3523428A1 (en) * | 1985-06-29 | 1987-01-02 | Philips Patentverwaltung | Ink jet print head |
| EP0376922B1 (en) * | 1985-08-13 | 1993-07-28 | Matsushita Electric Industrial Co., Ltd. | Ink jet recording apparatus |
| DE19522593C2 (en) * | 1995-06-19 | 1999-06-10 | Francotyp Postalia Gmbh | Device for keeping the nozzles of an ink print head clean |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3596275A (en) * | 1964-03-25 | 1971-07-27 | Richard G Sweet | Fluid droplet recorder |
| US3334351A (en) * | 1965-06-16 | 1967-08-01 | Honeywell Inc | Ink droplet recorder with plural nozzle-vibrators |
| US3708798A (en) * | 1971-12-23 | 1973-01-02 | Ibm | Ink distribution for non-impact printing recorder |
| US3839721A (en) * | 1973-06-27 | 1974-10-01 | Ibm | Device for retention of ink jet nozzle clogging and ink spraying |
| GB1450340A (en) * | 1973-08-16 | 1976-09-22 | Matsushita Electric Ind Co Ld | Arrangements for applying liquid droplets to a surface |
-
1975
- 1975-09-23 SE SE7510644A patent/SE414238B/en not_active IP Right Cessation
- 1975-09-23 CA CA236,172A patent/CA1055558A/en not_active Expired
- 1975-09-24 IT IT7551477A patent/IT1047509B/en active
- 1975-09-25 FR FR7529399A patent/FR2285928A1/en active Granted
- 1975-09-26 GB GB39597/75A patent/GB1483571A/en not_active Expired
- 1975-09-26 DE DE2543038A patent/DE2543038B2/en active Granted
-
1978
- 1978-09-12 SE SE7809571A patent/SE438284B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2285928B1 (en) | 1980-08-01 |
| FR2285928A1 (en) | 1976-04-23 |
| DE2543038C3 (en) | 1981-04-30 |
| SE7809571L (en) | 1978-09-12 |
| DE2543038B2 (en) | 1980-07-17 |
| SE438284B (en) | 1985-04-15 |
| GB1483571A (en) | 1977-08-24 |
| DE2543038A1 (en) | 1976-04-15 |
| SE414238B (en) | 1980-07-14 |
| IT1047509B (en) | 1980-10-20 |
| SE7510644L (en) | 1976-03-29 |
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