EP0037624B1 - A head for an ink jet printer - Google Patents
A head for an ink jet printer Download PDFInfo
- Publication number
- EP0037624B1 EP0037624B1 EP81300577A EP81300577A EP0037624B1 EP 0037624 B1 EP0037624 B1 EP 0037624B1 EP 81300577 A EP81300577 A EP 81300577A EP 81300577 A EP81300577 A EP 81300577A EP 0037624 B1 EP0037624 B1 EP 0037624B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- head
- pressure chambers
- ink
- nozzles
- intermediate plate
- 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
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Images
Classifications
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- 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
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1623—Manufacturing processes bonding and adhesion
-
- 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
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14201—Structure of print heads with piezoelectric elements
- B41J2/14233—Structure of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
-
- 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
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1607—Production of print heads with piezoelectric elements
- B41J2/161—Production of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
-
- 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
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1626—Manufacturing processes etching
-
- 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
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1631—Manufacturing processes photolithography
-
- 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
- B41J2/135—Nozzles
- B41J2/16—Production of nozzles
- B41J2/1621—Manufacturing processes
- B41J2/1632—Manufacturing processes machining
-
- 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
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2002/14379—Edge shooter
Definitions
- This invention relates to heads for ink jet printers of the ink-on-demand type
- a head for an ink jet printer comprising an intermediate plate having a plurality of first pressure chambers and first nozzles connected therewith recessed in one surface thereof, a plurality of second pressure chambers and second nozzles connected therewith recessed in the opposite surface thereof, the intermediate plate being disposed between two vibration plates, electromechanical transducer means located on the vibration plates for ejecting ink from said pressure chambers through said nozzles during a printing operation, ink reservoir means and a feed channel extending between the ink reservoir means and each pressure chamber.
- Such ink jet printers of the ink-on-demand type are known e.g. from DE-A-.L-2 233 469 ( Figure 4) and DE-A-2 918 737 ( Figure 10).
- fluidic diodes are provided in the feed channels between the ink reservoir means and the pressure chambers. These diodes generate different flow impedance between flow towards the nozzles and flow towards the ink reservoir means. This changes the uniform flow of ink and generates a portion through which ink flows at relatively slow speed. Thus it is difficult to dislodge an air bubble located in this portion and consequently such air bubbles cannot be ejected through the nozzles.
- the present invention has as its principal object to purge air bubbles collected in the pressure chambers of an ink jet printer of the type indicated above.
- an island is disposed in a portion of each pressure chamber which portion gradually widens from an inlet thereof.
- ink flows around the islands at uniform speed and there are no portions where there is low speed ink flow in which air bubbles become lodged.
- the air bubbles can therefore be smoothly discharged through the nozzles with the ink.
- the islands have no fluid diode effect and DE-A-2 918 737 in no way approaches a solution to the problem which the present invention senks to solve and in fact aggravates the problem.
- each outer plate is common to the plurality of pressure chambers on the respective adjacent surface of the intermediate plate.
- the first pressure chambers preferably are offset relative to the second pressure chambers.
- the head may include a high impedance element disposed in each feed channel.
- An island may be disposed adjacent an outlet of each pressure chamber.
- An island may be disposed in each feed channel.
- the feed channels each have substantially the same length.
- the outer plates and said intermediate plates may be bonded together.
- the ink reservoir means is constituted at least in part by said intermediate plate.
- the head includes a further channel between each pressure chamber and the respective nozzle, the nozzle having a depth in the direction of thickness of the intermediate plate which is less than the corresponding depth of the further feed channel.
- all the feed channels have substantially the same impedance.
- a head of one conventional ink jet printer which is advanced during a printing operation in the direction of an arrow A.
- the head has a plurality of nozzles 1 through which ink is ejected during a printing operation, the nozzles being spaced apart by distance a.
- the head is inclined to direction A, so that the spacing of the dots is b.
- the conventional head is used in printing apparatus such as a typewriter, for example, while a nozzle 1a is being used to form dots of a first character, a nozzle 1b is being used to form the dots of a second adjacent character.
- FIG. 2 Another conventional head for an ink jet printer is illustrated in Figure 2.
- This conventional head has a plurality of nozzles 4 each connected to a pressure chamber (not shown).
- the nozzles 4 are formed on a plate 3.
- Piezo-electric elements 6 are fixed in positions corresponding to the respective pressure chambers on a vibration plate 5 fixed to the plate 3.
- the conventional head of Figure 2 also has a plurality of nozzles 4' each connected to a respective pressure chamber (not shown).
- the nozzles 4' are formed in a plate 3'.
- Piezo-electric elements 6' are fixed in positions corresponding to the respective pressure chambers on a vibration plate 5' fixed to the plate 3' so that the piezo-electric elements 6, 6' are adjacent to one another.
- the nozzles 4 and nozzles 4' are offset by one half pitch in the vertical direction.
- This conventional head has the advantage that its area can be reduced and made as small as possible.
- the distance between the nozzles 4 and the nozzles 4' is limited by the thickness of the vibration plates 5, 5' and the thickness of the piezo-electric elements 6, 6'.
- the conventional printer of Figure 1 while one character is being printed by the nozzles 4, another character is printed by the nozzles 4'.
- delicate adjustment is necessary in order to ensure that the nozzles 4 are exactly offset from the nozzles 4' by just one half pitch. This means that the conventional head of Figure 2 is expensive to manufacture.
- FIG. 3 One embodiment of an intermediate plate of a head according to the present invention for an ink jet printer is illustrated in Figures 3 and 4.
- the intermediate plate 11 has a plurality of pressure chambers 12, each with a depth of several tens to several hundreds of microns formed on one surface thereof by chemical etching.
- a nozzle 13 is connected to each pressure chamber 12.
- the pressure chambers communicate with the preliminary feed chamber 14 via feed channels 15.
- a further plurality of pressure chambers 16 ( Figure 4) are formed, the pressure chambers 16 being identical to the pressure chambers 12 but offset relative thereto.
- Each pressure chamber 16 communicates with a nozzle 17, the nozzles 17 being offset from the nozzles 13 by one half pitch.
- Ink is supplied to the head by feed pipe 25, the ink being drawn into the pressure chambers 12, 16 by capillary action as ink is ejected from the nozzles 13, 17.
- the intermediate plate 11 is sandwiched between two outer vibration plates 21, 22 to which respective piezo-electric elements 23, 24 are fixed.
- the head shown in Figures 3,4 and 9 will now be described.
- the head is moved in the direction of an arrow B ( Figure 9) by a mechanism (not illustrated) of a printing apparatus and the piezo-electric elements 23, 24 are energised by control signals from control circuitry (not shown).
- the capacity of the pressure chambers 12, 16 suddenly changes corresponding to the control signals applied to the respective piezo-electric elements and ink is ejected from the nozzles on to a printing medium to form dots of the desired character.
- the distance between the nozzles 13, 17 is indicated by c.
- the distance c is the determining factor in deciding whether timing of printing of the dots should be made with a built-in delay or the head should be made to move by the distance c from the start. If the distance c is less than a distance e between adjacent characters ( Figure 10) the head is not required to print two adjacent characters at the same time and so the control circuitry of the printing apparatus in which the head is incorporated is relatively simple compared with control circuitry for printing apparatus in which the conventional heads of Figures 1 and 2 are incorporated.
- the volume and speed of ejection of ink from the nozzles 13, 17 is dependent, inter alia, upon the cross-sectional area of the respective pressure chambers 12, 16 and the length of the feed channels 15.
- the control signals In order to obtain a high quality printing, it is necessary to ensure that the control signals have a constant voltage, constant current and constant phase so that the volume and speed of ejection of ink remains constant. This can be achieved by arranging the length of each of the feed channels 15 connecting the pressure chambers 12, 16 to the preliminary feed chamber 14 to be the same and/or providing a high impedance element 31 where each feed channel 15 communicates with the respective pressure chamber 12, 16.
- the distances between the nozzles 13, 17 and the respective pressure chambers 12, 16 may be made the same for the same purpose but this is difficult to achieve in view of the fact that the nozzles are so closely spaced.
- the pressure chambers 12, 16 are offset, a high density of printing can be realised.
- the length of each of the feed channels 15 is constant to make their impedance the same.
- Figure 8 shows the relationship between driving voltage and volume of ink ejected where the distance between the pressure chambers 12, 16 and the respective nozzles 13, 17 is constant and the length of the feed channel 15 is changed.
- the length of the feed channel 15 in line A is 8 millimetres and in line B is 2 millimetres.
- some air enters the nozzles 13, 17, the amount being dependent, inter alia, upon the surface tension of the ink.
- the ink is subject to different pressures during ejection and during restoration, and the quantity of ink ejected from each nozzle and the time for restoration is made constant for all the nozzles by dimensioning the feed channels 15 suitably to take account of the viscosity of the ink and the impedance of the feed channels.
- Ink is more easily ejected from the nozzles when the pressure chambers 12,16 are smoothly connected to the nozzles 13, 17 respectively and the impedance is low. Thus it is better to increase the width of the feed channels to equalise the impedance of the feed channels. Further, as the piezo-electric elements 23, 24 are circular, it is desirable to make the pressure chambers 12, 16 substantially circular.
- FIG. 6 Another embodiment of an intermediate plate 11 for a head according to the present invention of an ink jet printer is shown in Figure 6 and has a first island 36 and a second island 35.
- Each island 35 is disposed in a portion of the respective pressure chamber which portion gradually widens from an inlet thereof.
- the pressure chamber 12 is substantially circular, high frequency vibration is generated and the pressure within the chamber 12 does not increase uniformly when a control signal is applied to the respective piezo-electric element.
- the first island 36 and the second island 35 prevent the generation of these high frequency vibrations even if the shape of the pressure chambers deviates from circular. It is thus possible to eject the same volume of ink from each of the nozzles.
- an island 37 is disposed within each feed channel in order to increase the impedance thereof and again to prevent high frequency vibrations.
- ink is ejected through the nozzles by applying pressure from the preliminary feed chamber 14, but since the width of the pressure chambers 12,16 is several times that of the feed channels 15 and the other channels, only air bubbles in the neighbourhood of the centre of the pressure chambers 12 will be ejected through the nozzles 13 and air bubbles adjacent the circumference of the pressure chambers will remain.
- the second islands 35 are provided to ensure that all the air bubbles in the pressure chambers will be ejected through the nozzles.
- the depth D 2 of the nozzle 13 is made less than the depth D 1 of a channel 45 connecting a nozzle to respective pressure chambers.
- efficiency of ejection of ink and response frequency can be improved.
- the depth D 2 of each nozzle is 40-50 pm
- the length L is 50-300 pm
- the depth D 1 of the channel 45 is 70-150 pm in order to achieve the response frequency of about 2 KHz.
- the required length L of the nozzles has a close relationship with the quantity of air entering the nozzle when ink has been ejected and during restoration.
- the amount of air entering through the nozzle is exactly the same as the amount of ink that has just been ejected and it is necessary to prevent boundaries between the air and the ink reaching the channel 45. If this occurs, because some ink still adheres to the opposite side walls of the nozzle, the pressure balance may be changed, even though only slightly, and the ink on one side wall of the nozzle may coalesce with the ink on the opposite side wall and so form an air bubble in the channel 45.
- the thickness of the intermediate plate 11 has been found to be very important in practice. If the total thickness of the outer vibration plate 21 and the piezo-electric element 23 is equal to the thickness of the intermediate plate 11, which itself is relatively thin since it is made by an etching technique, pressure will increase by only a half. Further, pressure in one pressure chamber will be transmitted to an adjacent pressure chamber on the opposite side of the intermediate plate. As a result, the volume and speed of ejection of ink will vary depending upon whether the adjacent pressure chambers on opposite sides of the intermediate plate are driven at the same time or not. As a result, the quality of printing is reduced. Therefore, it is necessary to prevent adjacent pressure chambers on opposite sides of the intermediate plate influencing each other or to make the influence so small that it may be disregarded.
- the thickness of the intermediate plate should be 0.95 millimetres.
- the thickness of the intermediate plate may be reduced to some extent. If the pressure chambers are etched to a depth of, for example, 70 pm, the thickness of the intermediate plate is given by: ⁇
- chrome and gold layers are deposited on to a plate made of a material which is not affected by ink, for example, borosilicate glass.
- a resist is formed on both sides of the plate and is exposed to light using a photo mask so as to form the pattern, for example, in Figure 3.
- the plate is etched by, for example, hydrofluoric acid to form the channels in the pressure chambers.
- a spacer 38 having almost the same thickness as that of the intermediate plate is disposed at one side of where the preliminary feed chamber 14 is to be formed, and then the intermediate plate so formed is sandwiched between the outer vibration plates 21, 22 held by a jig, and put into a furnace at 550° to 700°C. thus the intermediate plate, the spacer 38 and the vibration plates are bonded together.
- An electrically conductive film for example, of NESA (Trade Mark) or ln 2 0 3 is formed on the outer vibration plates 21, 22 to act as a transparent electrode. The conductive film may be formed before or after bonding of the intermediate plate and the vibration plates.
- the intermediate plate and the outer vibration plates are transparent, the channels and pressure chambers are visible but if this is not required, the outer vibration plates and intermediate plates may be made opaque.
- Figure 13a shows the intermediate plate 11 and the spacer 38 of Figure 3 disposed between the two outer vibration plates 21, 22 to form a space which defines the preliminary feed chamber 14.
- the preliminary feed chamber 14 has an ink inlet 33a and an ink outlet 33b.
- a feed pipe 25 of stainless steel is secured by binder material 34 to each of the ink inlet 33a and the ink outlet 33b.
- Figure 13b shows a head for an ink jet printer incorporating the intermediate plate of Figure 5 showing an ink reservoir 39 made, for example, of plastics material.
- Figure 13c shows a head for an ink jet printer incorporating the intermediate plate of Figure 6, the preliminary feed chamber 14 being formed by etching on the intermediate plate with the pressure chambers 12.
- the ink outlet 33b for the preliminary feed chamber 14 is not essential but when an air bubble, for example, enters the preliminary feed chamber, if ink is circulated therethrough the air bubble can be removed without having to push it through the pressure chambers and nozzles etc.
- the shape of the nozzle shown in Figure 11 can be produced by a double etching technique.
- a locating plate 40 ( Figure 7) for determining the position of the piezo-electric elements, is fixed in position by a bonding tag 42 and correctly located by a cross- shaped recess 47 engaging correspondingly shaped projections on the respective outer vibration plates.
- the plate 40 has twelve holes 41 each somewhat larger than. the piezo-electric element to be located therein and with a depth of the same as that of the piezo-electric element to be located therein. If the plate 40 is made of metal, it can be used to form electrodes of the piezo-electric elements. A piezo-electric element is put into each.
- each piezo-electric element is wired to control circuitry of the printing apparatus.
- the wiring is sealed by a soft electrically non-conductive material, such as silicon resin.
- a coating may be formed on the plate 40.
- the piezo-electric elements may be wired by various methods, such as soldering, electric bonding, wire bonding, or connecting using electric gum, metal etc.
- soldering electric bonding
- wire bonding or connecting using electric gum, metal etc.
- the wall between one feed channel and the adjacent feed channel preferably has a width of more than 50 pm since it is necessary for the wall to have sufficient strength not to be broken if the ink freezes. It has been found that if the wall between adjacent feed channels has a width of 100 pm, it does not break even when the ink is frozen at -40°C.
- borosilicate glass is preferably used for the intermediate plate and the outer vibration plates due to the ease of etching. However, instead of being etched, the borosilicate glass could be moulded into the desired configuration at high temperature.
- a head according to the present invention of ink jet printer may be disposed as shown in Figure 12 and inclined at an angle of 8° to the plane of printing so that a distance f between adjacent dots formed on printing medium is less than the distance d between corresponding adjacent nozzles, i.e.: As a result high density printing will be obtained.
- a head according to the present invention for an ink jet printer may be employed by typewriters, copying presses or facsimile machines etc.
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- Manufacturing & Machinery (AREA)
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Description
- This invention relates to heads for ink jet printers of the ink-on-demand type comprising a head for an ink jet printer comprising an intermediate plate having a plurality of first pressure chambers and first nozzles connected therewith recessed in one surface thereof, a plurality of second pressure chambers and second nozzles connected therewith recessed in the opposite surface thereof, the intermediate plate being disposed between two vibration plates, electromechanical transducer means located on the vibration plates for ejecting ink from said pressure chambers through said nozzles during a printing operation, ink reservoir means and a feed channel extending between the ink reservoir means and each pressure chamber.
- Such ink jet printers of the ink-on-demand type are known e.g. from DE-A-.L-2 233 469 (Figure 4) and DE-A-2 918 737 (Figure 10). In the printer of the latter document fluidic diodes are provided in the feed channels between the ink reservoir means and the pressure chambers. These diodes generate different flow impedance between flow towards the nozzles and flow towards the ink reservoir means. This changes the uniform flow of ink and generates a portion through which ink flows at relatively slow speed. Thus it is difficult to dislodge an air bubble located in this portion and consequently such air bubbles cannot be ejected through the nozzles.
- The present invention has as its principal object to purge air bubbles collected in the pressure chambers of an ink jet printer of the type indicated above.
- In the present invention, in order to eject air bubbles adjacent the circumference of the pressure chambers through said nozzles, an island is disposed in a portion of each pressure chamber which portion gradually widens from an inlet thereof. Thus ink flows around the islands at uniform speed and there are no portions where there is low speed ink flow in which air bubbles become lodged. The air bubbles can therefore be smoothly discharged through the nozzles with the ink. Thus the islands have no fluid diode effect and DE-A-2 918 737 in no way approaches a solution to the problem which the present invention senks to solve and in fact aggravates the problem.
- Preferably each outer plate is common to the plurality of pressure chambers on the respective adjacent surface of the intermediate plate.
- The first pressure chambers preferably are offset relative to the second pressure chambers.
- The head may include a high impedance element disposed in each feed channel.
- An island may be disposed adjacent an outlet of each pressure chamber.
- An island may be disposed in each feed channel.
- In one embodiment the feed channels each have substantially the same length.
- The outer plates and said intermediate plates may be bonded together.
- In one embodiment the ink reservoir means is constituted at least in part by said intermediate plate.
- Preferably the head includes a further channel between each pressure chamber and the respective nozzle, the nozzle having a depth in the direction of thickness of the intermediate plate which is less than the corresponding depth of the further feed channel.
- Preferably all the feed channels have substantially the same impedance.
- The invention is illustrated, merely by way of example, in the accompanying drawings, in which:-
- Figure 1 is a front view of one embodiment of a conventional head for an ink jet printer;
- Figure 2 is a front view of another embodiment of a conventional head for an ink jet printer;
- Figure 3 is a plan view of one embodiment of an intermediate plate of a head according to the present invention for an ink jet printer;
- Figure 4 shows part of the intermediate plate of Figure 3 in greater detail;
- Figure 5 is a plan view of another embodiment of an intermediate plate of a head according to the present invention for an ink jet printer;
- Figure 6 is a plan view of a further embodiment of an intermediate plate of a head according to the present invention for an ink jet printer;
- Figure 7 is a plan view of a locating plate of a head according to the present invention for an ink jet printer;
- Figure 8 illustrates graphically operation of a head according to the present invention for an ink jet printer;
- Figure 9 is a front view of a head according to the present invention for an ink jet printer;
- Figure 10 illustrates printing produced by the head of Figure 9;
- Figure 11 is a cross-section of a nozzle of a head according to the present invention for an ink jet printer;
- Figure 12 shows, schematically, the disposition of a head according to the present invention for an ink jet printer in printing apparatus; and
- Figure 13, consisting of Figures 13a, 13b, 13c shows, in perspective, heads according to the present invention for ink jet printers and including the intermediate plates of Figure 3, 5 and 6 respectively.
- Referring to Figure 1, there is shown a head of one conventional ink jet printer which is advanced during a printing operation in the direction of an arrow A. The head has a plurality of
nozzles 1 through which ink is ejected during a printing operation, the nozzles being spaced apart by distance a. To reduce the vertical spacing of dots formed on a printing medium by ink ejected through thenozzles 1, the head is inclined to direction A, so that the spacing of the dots is b. However, when the conventional head is used in printing apparatus such as a typewriter, for example, while anozzle 1a is being used to form dots of a first character, anozzle 1b is being used to form the dots of a second adjacent character. Thus different characters may be printed at the same time and so, as a result, it is necessary to increase the number of character generators or memory circuits, and this complicates control circuitry of the printing apparatus. On the other hand, if characters are printed one-by-one, for example, using input keys of the printing apparatus, the head has to be back-spaced after it has printed one character in order to prepare for printing the next character. Thus the conventional head shown in Figure 1 is somewhat inconvenient and requires relatively complex control circuitry. Moreover, energy consumption, vibration, etc., is increased caused by the need to back-space the head. Furthermore, there are problems associated with the fact that the head occupies a considerable space. - Another conventional head for an ink jet printer is illustrated in Figure 2. This conventional head has a plurality of
nozzles 4 each connected to a pressure chamber (not shown). Thenozzles 4 are formed on aplate 3. Piezo-electric elements 6 are fixed in positions corresponding to the respective pressure chambers on avibration plate 5 fixed to theplate 3. - The conventional head of Figure 2 also has a plurality of nozzles 4' each connected to a respective pressure chamber (not shown). The nozzles 4' are formed in a plate 3'. Piezo-electric elements 6' are fixed in positions corresponding to the respective pressure chambers on a vibration plate 5' fixed to the plate 3' so that the piezo-
electric elements 6, 6' are adjacent to one another. - As shown in Figure 2, the
nozzles 4 and nozzles 4' are offset by one half pitch in the vertical direction. This conventional head has the advantage that its area can be reduced and made as small as possible. However, the distance between thenozzles 4 and the nozzles 4' is limited by the thickness of thevibration plates 5, 5' and the thickness of the piezo-electric elements 6, 6'. Thus, as with the conventional printer of Figure 1, while one character is being printed by thenozzles 4, another character is printed by the nozzles 4'. Moreover, delicate adjustment is necessary in order to ensure that thenozzles 4 are exactly offset from the nozzles 4' by just one half pitch. This means that the conventional head of Figure 2 is expensive to manufacture. - One embodiment of an intermediate plate of a head according to the present invention for an ink jet printer is illustrated in Figures 3 and 4. The
intermediate plate 11 has a plurality ofpressure chambers 12, each with a depth of several tens to several hundreds of microns formed on one surface thereof by chemical etching. Anozzle 13 is connected to eachpressure chamber 12. The pressure chambers communicate with thepreliminary feed chamber 14 viafeed channels 15. On the other surface of the intermediate plate, a further plurality of pressure chambers 16 (Figure 4) are formed, thepressure chambers 16 being identical to thepressure chambers 12 but offset relative thereto. Eachpressure chamber 16 communicates with anozzle 17, thenozzles 17 being offset from thenozzles 13 by one half pitch. Ink is supplied to the head byfeed pipe 25, the ink being drawn into thepressure chambers nozzles - As shown in Figure 9, the
intermediate plate 11 is sandwiched between twoouter vibration plates electric elements - The operation of the head shown in Figures 3,4 and 9 will now be described. During a printing operation, the head is moved in the direction of an arrow B (Figure 9) by a mechanism (not illustrated) of a printing apparatus and the piezo-
electric elements pressure chambers nozzles - The volume and speed of ejection of ink from the
nozzles respective pressure chambers feed channels 15. In order to obtain a high quality printing, it is necessary to ensure that the control signals have a constant voltage, constant current and constant phase so that the volume and speed of ejection of ink remains constant. This can be achieved by arranging the length of each of thefeed channels 15 connecting thepressure chambers preliminary feed chamber 14 to be the same and/or providing ahigh impedance element 31 where eachfeed channel 15 communicates with therespective pressure chamber nozzles respective pressure chambers pressure chambers feed channels 15 is constant to make their impedance the same. However, it is also possible to make the impedance of the feed channels the same, even if they have different lengths, by suitably arranging the width and/or depth of the feed channels. - Figure 8 shows the relationship between driving voltage and volume of ink ejected where the distance between the
pressure chambers respective nozzles feed channel 15 is changed. In Figure 8, the length of thefeed channel 15 in line A is 8 millimetres and in line B is 2 millimetres. Generally, the higher the impedance of thefeed channel 15, the greater the volume of ink ejected by thenozzles nozzles feed channels 15 suitably to take account of the viscosity of the ink and the impedance of the feed channels. - Ink is more easily ejected from the nozzles when the
pressure chambers nozzles electric elements pressure chambers - Another embodiment of an
intermediate plate 11 for a head according to the present invention of an ink jet printer is shown in Figure 6 and has afirst island 36 and asecond island 35. Eachisland 35 is disposed in a portion of the respective pressure chamber which portion gradually widens from an inlet thereof. Unless thepressure chamber 12 is substantially circular, high frequency vibration is generated and the pressure within thechamber 12 does not increase uniformly when a control signal is applied to the respective piezo-electric element. As a result, the ejected ink separates into droplets so that the quality of printing deteriorates. However, thefirst island 36 and thesecond island 35 prevent the generation of these high frequency vibrations even if the shape of the pressure chambers deviates from circular. It is thus possible to eject the same volume of ink from each of the nozzles. When the width offeed channels 15 is relatively broad, anisland 37 is disposed within each feed channel in order to increase the impedance thereof and again to prevent high frequency vibrations. - In a head for an ink jet printer, it is an essential requirement that no air bubbles occur in the feed channels, pressure chambers, etc., in order to obtain good quality printing. However, there is a considerable risk of generating such air bubbles, for example, air dissolved in the ink may form an air bubble, an air bubble may flow from the preliminary ink chamber, air may enter through the nozzles and form an air bubble, etc. If an air bubble appears within the head the easiest way to remove it is to allow it to escape through the nozzles. To this end, ink is ejected through the nozzles by applying pressure from the
preliminary feed chamber 14, but since the width of thepressure chambers feed channels 15 and the other channels, only air bubbles in the neighbourhood of the centre of thepressure chambers 12 will be ejected through thenozzles 13 and air bubbles adjacent the circumference of the pressure chambers will remain. To overcome this, thesecond islands 35 are provided to ensure that all the air bubbles in the pressure chambers will be ejected through the nozzles. - If the depth of the
feed channels 15 is made constant by an etching technique, ejection of ink is somewhat inferior as shown by line C in Figure 8. Further, the time for restoration after ejection of ink becomes relatively long. In order to overcome this, as shown in Figure 11, the depth D2 of the nozzle 13 (and the nozzle 17) is made less than the depth D1 of achannel 45 connecting a nozzle to respective pressure chambers. Thus efficiency of ejection of ink and response frequency can be improved. In one embodiment of the present invention, the depth D2 of each nozzle is 40-50 pm, the length L is 50-300 pm and the depth D1 of thechannel 45 is 70-150 pm in order to achieve the response frequency of about 2 KHz. The required length L of the nozzles has a close relationship with the quantity of air entering the nozzle when ink has been ejected and during restoration. The amount of air entering through the nozzle is exactly the same as the amount of ink that has just been ejected and it is necessary to prevent boundaries between the air and the ink reaching thechannel 45. If this occurs, because some ink still adheres to the opposite side walls of the nozzle, the pressure balance may be changed, even though only slightly, and the ink on one side wall of the nozzle may coalesce with the ink on the opposite side wall and so form an air bubble in thechannel 45. - The thickness of the
intermediate plate 11 has been found to be very important in practice. If the total thickness of theouter vibration plate 21 and the piezo-electric element 23 is equal to the thickness of theintermediate plate 11, which itself is relatively thin since it is made by an etching technique, pressure will increase by only a half. Further, pressure in one pressure chamber will be transmitted to an adjacent pressure chamber on the opposite side of the intermediate plate. As a result, the volume and speed of ejection of ink will vary depending upon whether the adjacent pressure chambers on opposite sides of the intermediate plate are driven at the same time or not. As a result, the quality of printing is reduced. Therefore, it is necessary to prevent adjacent pressure chambers on opposite sides of the intermediate plate influencing each other or to make the influence so small that it may be disregarded. As the influence between adjacent pressure chambers on opposite sides of the intermediate plate is inversely proportional to the square of the thickness of the intermediate plate, in order to control this influence the latter should be preferably about 3.2 times the combined thickness of theouter vibration plate 21 and the piezo-electric elements 23 (or theouter vibration plate 22 and the piezo-electric elements 24). If theouter vibration plate 21 is 0.15 millimetres in thickness and the piezo-electric elements - 0.95-(0.15+0.15+0.07)=0.58 millimetres.
- One method of manufacturing the printing head of Figure 9 will now be described. First, chrome and gold layers are deposited on to a plate made of a material which is not affected by ink, for example, borosilicate glass. A resist is formed on both sides of the plate and is exposed to light using a photo mask so as to form the pattern, for example, in Figure 3. After that, the plate is etched by, for example, hydrofluoric acid to form the channels in the pressure chambers. The gold and chrome layers are removed, a
spacer 38 having almost the same thickness as that of the intermediate plate is disposed at one side of where thepreliminary feed chamber 14 is to be formed, and then the intermediate plate so formed is sandwiched between theouter vibration plates spacer 38 and the vibration plates are bonded together. An electrically conductive film, for example, of NESA (Trade Mark) orln 203 is formed on theouter vibration plates - Figure 13a shows the
intermediate plate 11 and thespacer 38 of Figure 3 disposed between the twoouter vibration plates preliminary feed chamber 14. Thepreliminary feed chamber 14 has anink inlet 33a and anink outlet 33b. Afeed pipe 25 of stainless steel is secured bybinder material 34 to each of theink inlet 33a and theink outlet 33b. (Figure 3). - Figure 13b shows a head for an ink jet printer incorporating the intermediate plate of Figure 5 showing an
ink reservoir 39 made, for example, of plastics material. - Figure 13c shows a head for an ink jet printer incorporating the intermediate plate of Figure 6, the
preliminary feed chamber 14 being formed by etching on the intermediate plate with thepressure chambers 12. - The
ink outlet 33b for thepreliminary feed chamber 14 is not essential but when an air bubble, for example, enters the preliminary feed chamber, if ink is circulated therethrough the air bubble can be removed without having to push it through the pressure chambers and nozzles etc. - The shape of the nozzle shown in Figure 11 can be produced by a double etching technique.
- After the intermediate plates and outer vibration plates have been bonded, a locating plate 40 (Figure 7) for determining the position of the piezo-electric elements, is fixed in position by a
bonding tag 42 and correctly located by a cross- shapedrecess 47 engaging correspondingly shaped projections on the respective outer vibration plates. Theplate 40 has twelveholes 41 each somewhat larger than. the piezo-electric element to be located therein and with a depth of the same as that of the piezo-electric element to be located therein. If theplate 40 is made of metal, it can be used to form electrodes of the piezo-electric elements. A piezo-electric element is put into each. of theholes 41 and fixed therein by means, of, for example an epoxy resin or a metal solder, such as a gold-tin solder. Then each piezo-electric element is wired to control circuitry of the printing apparatus. In order to improve insulation properties, the wiring is sealed by a soft electrically non-conductive material, such as silicon resin. In order to increase resistance to damage due, for example, to external shock, a coating may be formed on theplate 40. The piezo-electric elements may be wired by various methods, such as soldering, electric bonding, wire bonding, or connecting using electric gum, metal etc. Thus a highly integrated head for an ink jet printer can be made. Moreover the surface on which the nozzles debouch may be cut by a diamond cutter or polished to make it smooth. - The wall between one feed channel and the adjacent feed channel preferably has a width of more than 50 pm since it is necessary for the wall to have sufficient strength not to be broken if the ink freezes. It has been found that if the wall between adjacent feed channels has a width of 100 pm, it does not break even when the ink is frozen at -40°C. As mentioned above, borosilicate glass is preferably used for the intermediate plate and the outer vibration plates due to the ease of etching. However, instead of being etched, the borosilicate glass could be moulded into the desired configuration at high temperature.
- A head according to the present invention of ink jet printer may be disposed as shown in Figure 12 and inclined at an angle of 8° to the plane of printing so that a distance f between adjacent dots formed on printing medium is less than the distance d between corresponding adjacent nozzles, i.e.:
- A head according to the present invention for an ink jet printer may be employed by typewriters, copying presses or facsimile machines etc.
By disposing the pressure chambers offset with respect to each other, the influence between adjacent pressure chambers on opposite sides of the intermediate plate can be reduced to 0.6 per cent and this can be ignored. Further, as the intermediate plate can be made relatively thin, the distance c between adjacent nozzles is reduced so that the space e between adjacent characters, when a printing operation is performed, as shown in Figure 10, can be reduced.
Claims (11)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3596480A JPH0234781B2 (en) | 1980-03-21 | 1980-03-21 | INKUJETSUTOKIROKUYOHETSUDO |
JP35964/80 | 1980-03-21 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0037624A1 EP0037624A1 (en) | 1981-10-14 |
EP0037624B1 true EP0037624B1 (en) | 1985-06-19 |
Family
ID=12456636
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81300577A Expired EP0037624B1 (en) | 1980-03-21 | 1981-02-12 | A head for an ink jet printer |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0037624B1 (en) |
JP (1) | JPH0234781B2 (en) |
DE (1) | DE3170973D1 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4611219A (en) * | 1981-12-29 | 1986-09-09 | Canon Kabushiki Kaisha | Liquid-jetting head |
JPS60166462A (en) * | 1984-02-10 | 1985-08-29 | Fujitsu Ltd | Ink jet head |
NL8903025A (en) * | 1989-12-08 | 1991-07-01 | Oce Nederland Bv | STACKABLE DROP GENERATOR FOR AN INK-JET PRINTER. |
WO1992010367A1 (en) * | 1990-12-06 | 1992-06-25 | Markpoint Development Ab | Drop-on-demand liquid ejector arrangement |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1416980A (en) * | 1973-04-25 | 1975-12-10 | Original Odhner Ab | Printing head |
DE2429232A1 (en) * | 1974-06-18 | 1976-01-08 | Olympia Werke Ag | Mosaic printing head with underlining facility - has additional mosaic element which operates beyond limits of main printing head |
US4005440A (en) * | 1974-03-12 | 1977-01-25 | Facit Aktiebolag | Printing head for ink jet printer |
DE2918737A1 (en) * | 1978-05-10 | 1979-11-15 | Hitachi Ltd | NOZZLE HEAD DEVICE FOR A COLOR JET PRINTING DEVICE |
EP0013095A1 (en) * | 1978-12-23 | 1980-07-09 | Epson Corporation | A head for an ink jet printer |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2233469C2 (en) * | 1972-07-07 | 1974-02-28 | Olympia Werke Ag, 2940 Wilhelmshaven | Print head for an inkjet writing mechanism |
-
1980
- 1980-03-21 JP JP3596480A patent/JPH0234781B2/en not_active Expired - Lifetime
-
1981
- 1981-02-12 EP EP81300577A patent/EP0037624B1/en not_active Expired
- 1981-02-12 DE DE8181300577T patent/DE3170973D1/en not_active Expired
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1416980A (en) * | 1973-04-25 | 1975-12-10 | Original Odhner Ab | Printing head |
US4005440A (en) * | 1974-03-12 | 1977-01-25 | Facit Aktiebolag | Printing head for ink jet printer |
DE2429232A1 (en) * | 1974-06-18 | 1976-01-08 | Olympia Werke Ag | Mosaic printing head with underlining facility - has additional mosaic element which operates beyond limits of main printing head |
DE2918737A1 (en) * | 1978-05-10 | 1979-11-15 | Hitachi Ltd | NOZZLE HEAD DEVICE FOR A COLOR JET PRINTING DEVICE |
EP0013095A1 (en) * | 1978-12-23 | 1980-07-09 | Epson Corporation | A head for an ink jet printer |
Also Published As
Publication number | Publication date |
---|---|
JPS56133171A (en) | 1981-10-19 |
DE3170973D1 (en) | 1985-07-25 |
EP0037624A1 (en) | 1981-10-14 |
JPH0234781B2 (en) | 1990-08-06 |
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