CA1192083A - Ink jet printer drive mechanism - Google Patents
Ink jet printer drive mechanismInfo
- Publication number
- CA1192083A CA1192083A CA000397809A CA397809A CA1192083A CA 1192083 A CA1192083 A CA 1192083A CA 000397809 A CA000397809 A CA 000397809A CA 397809 A CA397809 A CA 397809A CA 1192083 A CA1192083 A CA 1192083A
- Authority
- CA
- Canada
- Prior art keywords
- print head
- leaf spring
- record media
- movement
- ink jet
- 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
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
- B41J25/00—Actions or mechanisms not otherwise provided for
- B41J25/001—Mechanisms for bodily moving print heads or carriages parallel to the paper surface
- B41J25/006—Mechanisms for bodily moving print heads or carriages parallel to the paper surface for oscillating, e.g. page-width print heads provided with counter-balancing means or shock absorbers
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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
- B41J19/00—Character- or line-spacing mechanisms
- B41J19/18—Character-spacing or back-spacing mechanisms; Carriage return or release devices therefor
- B41J19/20—Positive-feed character-spacing mechanisms
Landscapes
- Character Spaces And Line Spaces In Printers (AREA)
Abstract
INK JET PRINTER DRIVE MECHANISM
Abstract of the Disclosure Mechanism for producing horizontal and ver-tical movement wherein one or more ink jet print heads are positioned adjacent the paper or like record media and are carried on a support member mounted on the free end of leaf springs. The leaf springs are set into oscillation or swinging movement by a drive system and the springs operate in their natural frequency to drive the print heads in the horizontal direction and to feed the paper in the vertical direction.
Abstract of the Disclosure Mechanism for producing horizontal and ver-tical movement wherein one or more ink jet print heads are positioned adjacent the paper or like record media and are carried on a support member mounted on the free end of leaf springs. The leaf springs are set into oscillation or swinging movement by a drive system and the springs operate in their natural frequency to drive the print heads in the horizontal direction and to feed the paper in the vertical direction.
Description
`3~3 INK JET_N ER DRIVE 1`9ECHAN_SM
Background of the Invention In the field of non-impact printing, the most common types of printers have been the thermal printer and the ink jet printer. When the performance of a non-impact printer is compared with that of an impact print-er, one o the problems in the non-impact machine has heen the control of the printing operation. As is well known, the impact operation depends upon the movement of impact members such as wires or the like and which are typically moved by means of an electromechanical system which is believed to enable a more precise control of the impact members.
The advent of non-impact printing, as in the case of thermal printing, brought out the fact that the heating cycle must be controlled in a manner to obtain maximum repeated operations. Likewise, the control of ink ~et printing in at least one form thereof must deal with rapid starting and stopping movement of the ink fluid from a supply of the fluid. In each case of non impact printing, the precise control of the thermal elements and of the ink droplets is necessary to provide for both correct and high-speed printing.
In the matter of ink jet printing, it is extremely important that the control of the ink droplets be precise and accurate from the time of formation of the droplets to the depositing of such droplets on the paper or like record media, and to make certain that a clean printed character results from the ink droplets.
While the method of printing with ink may be performed in continuous~manner or in demand pulse manner, the latter type method and operation is preferred in the present application as applying the features of the present invention. The drive means for the ink droplets is usually in the form of a crystal element to provide the high-speed operation for ejecting the ink through the nozzle while allowiny time between droplets for proper operation. The time allowed between the ink droplets is effected by means for damping the oscil-lations ~f the pressure waves generated during the printing operation.
In the ink jet printer the print head struc-ture may be a multiple nozzle type with the nozzles aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner.
Alternatively, the printer structure may include a plurality of equally-spaced, horizontally aligned single nozzle print heads which are caused to be moved in back-and-forth manner to print successive lines of dots in making up the lines of characters.
There have been various ways and means devised for precisely controlling the deceleration and ac-celeration of the ink jet prin~ head wherein large amounts of energy are used in the printing operation.
It is well-known that a print head carriage may be con-nected with a pulley and cable arrangement and driven by a separate motor for causing transverse movement of the carriage during printing operations. Another driving system utilizes a lead screw connected with the carriage and-driven by a separate motor for back-and-forth move ment of the carriage. A disadvantage of the rnotor driven carriage is the high cost of both the e~uipment and its operation.
It is therefore proposed to provide drive mechanism which has means inherent therein for driving the print head in an oscillating manner in a horizontal direction~
Representative prior art in the field of means for driving a print carriage in oscillating manner includes German Specification No. 2,646,740 on the application of A~ Watanabe et al., and opened to the public on April 20, 1978. This publication discloses a ~ -~3~ ~3 printer havin~ electromagnets mounted on a carriage plate. The plate is mounted on the free ends of the central legs of two cone like leaf springs while the corresponding ends of two other legs are fixed to the frame of the printerO The reciprocating motion of the carriage plate is performed by a crank drive. The special structure and arrangement of the leaf springs bearing the carriage plate provides for parallel movement of the plate relative to the platen during the back-and-forth motion.
United States Patent No7 4,227 t 455 issued to W~ B. Pennebaker on October 14, 1~80t discloses a suspension arrangement for a body oscillating or vibrating at resonance to provide linear motion for a short distance. The body has two portions connected by leaf springs to separate frames, in turn, connected by leaf springs to a main frame suspended by leaf springs from a support.
The present invention relates to ink jet printersD and more particularly to mechanism for driving the carriage of an ink jet print head in a horizontal direction~ A plurality of print heads are supported from a plate secured to the free ends of a pair of leaf springs which are set into oscillation or swinging movement by an electrodynamic drive system.
The print head carriage is caused to be msved in the horizontal direction by the spring structure which i5 oscillating at a natural frequency, Drive means is also connected with the horizontal drive mechanism for moving the paper or other record media in a vertical direction~
In accordance with the present invention~
there is provided apparatus for producing horizontal movement of an ink jet print head for printing in dot matrix manner on record media comprising support -3a-means, leaf spring means having one end thereof secured to said support means and the other end thereof secured to and carrying said print head, electromagnetic means connected with said leaf spring means for initiating swinging movement thereof in side-to-side direction, and circuit means operably associated with the electromagnetic means for damping the leaf spring means and causing oscillating motion thereof in a frequency corresponding to its natural frequency.
In view of the above discussion, the principal object of the present invention is to provide means for moving a print head in a manner to reduce the costs of manufacturing and of operating the printer.
Another object of the present invention is to provide a non-impact printer having a low-energy and substantially noiseless mechanism for moving the print head in a horizontal clirection.
An additional object of the present invention is to provide means for moving an ink jet print head in a manner for reducing the energy required for accel-eration and deceleration of the print head.
A Eurther object of the present invention is to provide a drive system for enabling movement of an ink jet print head wherein the system operates in an oscillating manner at a natural frequency.
Additional advantages and features of the present invention will become apparent and fully under-stood from a reading of the following description taken together with the annexed drawing.
Brief Description of the Draw ng Fig. 1 is a diagrammatic view of spring means for causing horizontal movement of a print head;
F;g. lA is a circuit diagram of a drive for the spring meansi Fig. 2 is a diagrammatic view of a plurality of print heads on a support plate which is caused to be moved by spring means in a horizontal direction;
Fig. 3 is a view similar to portions of Fig. 1 and including circuit means for compensating the damping of the oscillating system;
Figs. 4A and 4B show a timing diagram of the voltage and deflection relationship;
Fig. 5 shows the current pulse through the drive circuit of Fig. 3;
Fig. 6 is a view of ratchet means rotatable by horizontal movement of the print head carriage;
Fig. 7 is a view of drive means driven by the ratchet means of Fig. 6 for enabling vertical motion of the record media;
Fig. 8 is a diagrammatic view of a modified arrangement of spring means for causing horizontal movement o the print head;
~5--Fiy. 9 is a diagrammatic view showing the com-bin~tion of horizontal oscillation of the print head and vertical movement of the record media;
Fig. 10 is a view showing another arrangement S of spring means for causing horizontal movement of the print head, having straight line guide means with horizontal oscillating coil spriny elements;
Fig. 11 shows still another arrangement of such spring means with the use of bent leaf springs performing the function of guide or bearing means along with the function of an oscillating drive;
Figs. 12A, 12B and 12C are diagrammatic show-ings of different arrangements employing a leaf spring in providing the vertical oscillating mechanism for record media movement;
Fig. 13 shows a scanning arrangement for measuring the instantaneous speed of the oscillating print head;
Fig. 14 is a diagrammatic view of a still further spring means arrangement showing a bent leaf spring drive mechanism and a nozzle bar driven in oscil-lating manner;
Fig~ 15 shows the use of a linear motor along with spring means for driving a print head in horizontal oscillating manner, and Fig. 16 is a circuit diagram of the linear motor.
Detailed Description of the Invention Fig. 1 is a diagrammatic view showing an ink jet print head 10 supported from the ree end 12 of a leaf spring 14. The other end 16 of the leaf spring is secured to a fixed frame member 18. The prin~ head 10 has a nozzle 20 for ejecting an ink droplet 22 therefrom in performing a printing operation. An electrodynamic drive system 24 for initiating or setting the leaf spring 14 into oscillation or swinging movement includes a permanent ~agnet 26 operable with an armature 28 over-lying a central core portion 30 of the magnet and wound with a drive coil 32. The drive coil 32 is energized by pulses amplified by a power transistor 31, as illus-trated in Fig. lA. The armature 28 has a couplingmember 34 in the form of a rod fixed thereto at one end and secured at the other end to the leaf spring 14 near the center thereof. The leaf spring 14 operates with a natural frequency wherein the ink jet print head 10 is swinging freely and no electrical power is required for acceleration and deceleration of the head 10. In this manner, the consumed electrical power is only that power which is converted into frictional work. A pulse is applied once for each forth movement of the leaf spring 14 in its back and forth movement and with the pulse frequency being equal to the frequency of spring oscil-lation.
Fig. 2 illustrates a plurality of ink jet print heads 40 carried on a support member 42 which, in turn, is supported from the free ends of a pair of leaf springs 44 and 46. The other ends of the leaf springs 44, 46 are secured to a frame member 48. The print heads 40 are positioned to print on paper 50 or like record media which is caused to be trained around a platen 52. The driving or transporting of the paper 50 in a vertical direction past the line of printing is performed by means to be described later. A dr:ive module 54, similar in form to the electrodynamic drive system 24 of Fig. 1, is used to set the leaf springs 44 and 46 into oscillation with a natural frequency through a coupling member 56. It can be readily seen that the printing width is increased by a factor corresponding to the number of ink jet print heads 40 mounted on the support member 42.
Fig. 3 is a feed-back circuit for compensating the damping of the mechanically oscillating system of Fig. 1 wherein the ink jet print head 10 is supported from the free end 12 of the leaf spring 14 secured at its other end to the frame member 18. The armature 2ff is secured to the leaf spring 14 by the coupling member 34 and includes the drive coil 32 wound on the armature and connected to ground potential. The feed-back cir-cuit includes an operational amplifier 60 having compo-nents wired for use as an integrator and connected in series with a power amplifier 62 which energizes the drive coil 32~ The operational amplifier 60 acts as an integrating element by reason of its feedback capacity to effect a phase shift by ninety degrees so that energy is supplied in phase to the drive coil 32 by the power amplifier 62. A measuring or sensing winding 64 is dis-posed around the drive coil 32 and is connected at one end to the operational amplifier 60 with the other end thereof connected to ground potential. The positive feed-back compensates the damping so that the mechanical spring system oscillates with its natural frequency. The damping compensation is required to maintain the oscil-lation at a constant amplitude wherein the natural fre-quency of spring oscillation is determined by the char-ac~eristics of the spring, such as mass, material, dimensions and design.
Figs. 4A, 4B and 5 show a timing relationship between the pulsa-ting electrical energization of the drive system ~4 of Fig. l and the mechanical oscillation of the spring 14. The relationship of Figs. 4A and 4B
is shown by the formula V=-dD. The induced voltage V
is proportional to the spee~ of oscillation and the de1ection D is shown in time relation for a range of positive or plus current pulse and for a range of negative or minus current pulse. The pulses of Fig. 5 are initiated at predetermined times which are not precisely fixed so that, for certain times or instants during the forward oscillating phase, an electrical pulse must be applied wherein the movement of the free mass spring oscillator is sustained by the electrical energization. More particularly, the pulses are applied, ~L ~ 4 ~ r~
as indicated in Figs. 4A and 5, immediately after the maximum amplitude at a freq~ency equalling the natural frequency of oscillation. Pulses of opposite polarity are applied wherein the polarity corresponds to the respective direction of movement. Generally, the drive system 24 is pulsed or energized once for each cycle of printi~g.
A simple drive means for performing vertical movement of the paper to be printed is possible through use of a simple low power motor which is continuously energized in order to produce a constant paper speed.
It is also a simple matter to change the paper speed by using different means for operating the motor in order to perform a maximum paper feed condition whenever required. To overcome the need for such a separate drive, Figs. 6 and 7 illustrate means for obtaining a vertical drive for the paper from the longitudinal movement of the ink jet print head, wherein a ratchet gear 70 is positioned adjacent the platen 52 around which the paper 50 is trained in a path past the line of printing. An oscillating horizontal push rod 72, suit-ably connected to the leaf spring 14, drives a feed rod 74 against the teeth of the ratchet gear 70 and operates with a ratchet pawl 76 secured to a frame member 78 and engaging with the teeth of the gear 70. The ratchet gear 70 is carried on a shaft 75 along with a gear 77 which meshes with a gear 79 on the end of a worm gear 80 which, in turn, meshes with and drives a drive gear 82 for rotating the platen 52. The stepping mechanism enables driving the paper 50 by using the horizontal drive motion of the ink jet print head drive means and thereby eliminates the use o an electric motor.
Fig. 8 shows an ink jet print head 86 sup-ported in stationary manner from a member 88 for print~
ing on the paper 50 trained around the platen 52. The platen 52 is supported for rotation on a shaft 90 which is slidably journaled for axial movement in bearing blocks 92 and 94 and which has a small plate 96 secured at the right end thereof associated with the armature 28 and the drive coil 32. ~ coil spring 98 is placed on the shaft 90 between the plate 96 and the block 94. In this arrangement, the print head 86 is stationary and the platen 52 along with the paper 5~ is caused to be moved by action of the spring 98 in a horizontal oscil-lating direction as shown by the arrow.
A single print head 40 is illustrated in Fig.
9 as being carried on the support member 42 and oscil-lating in the horizontal direction, as in the mannerillustrated in Fig. 2~ At the same time, the paper 50 around the platen 52 is caused to be regularly moved in incremental manner in a vertical direction. In this combined horizontal oscillating and vertical incrementing drive arrangement the most advantageous operating point is at the resonance of the spring mass system.
Fig. 10 illustrates a straight line guide ar-rangement for an ink jet print head 100 supported from a shaft 102 slidably journaled in bearing blocks 104 and 20 106 on a frame member 108. The shaft 102 has a small plate 110 secured at the left end and a small plate 112 secured at the right end thereof. The plate 110 is drivingly associated with the armature 28 and the drive coil 32. A coil spring 114 is placed on the shaft 102 25 between the plate 110 and the block 104 and a coil spring 116 is placed on the shaft between the plate 112 and the block 106 to provide horizontal oscillation of the print head 100.
In Fig. 11 there is shown another arrangement 30 wherein a pair of print heads 120 and 122, similar to the previously mentioned print heads 10, 40 and 86, are carried on a support member 124 having plates 126 and 128 at the ends thereof. A pair of bent or folded leaf springs 130 and 132 are operably connected with the 35 plates 126 and 128 in a manner to provide guide means as well as horizontal oscillation of the print heads 120 and 122. In like manner, the plate 126 is connected to the armature 28, drive coil 32 assembly through a shaft or rod 131. The outer leg or portion of each spring is fixed or secured to a support member, as 133 for spring 13~.
Figs. 12A, 12B and 12C show different ar-rangements of using a leaf spring for the verticaloscillating mechanism employed in transporting or driving the paper. In Fig. 12A~ the paper 50 is trans-ported and trained around a stationar-y roller 134, a pair of movable rollers 136 and 138 and then around a stationary roller 140. A leaf spring 142 is secured at one end and is connected with a member 144 coupling the movable rollers 136 and 138 to provide the vertical movement for the paper, Fig. 12B has the paper 50 trained around a stationary roller 146, a movable roller 148 and then around a stationary roller 150. A leaf spring 152 is secured at one end and is connected to the movable roller 148 for vertical movement thereof in relation to the print head 154. In each case the leaf spring performs the function of the spring member as well as the bearing or guide function. Fig. 12C sho~s a leaf spring 156 secured at one end and connected to a movable roller 158 for vertical movement. A pair of guide members 160 and 162 are provided to be slidable or displaceable along a horizontal path to and from the roller 158 so as to allow changing the natural frequency of the spring 156.
Fig. 13 shows the armature 2B, as illustrated in FigsO 1 and 3, with the drive coil or operating winding 32 and with the addition of the sensor winding 64 which is within the magnetic field in similar man-ner as is shown in Fig. 3. The sensor winding is used for ascertaining the instantaneous speed of the oscil-lating ink jet print head. It should be here noted that the natural frequency of the spring mass oscillating system is very stable so that no accurate determination of the position of the ink droplets is required. It is only necessary that once for each oscillating period a simple synchronization of the ink jet with the mechan-f~3 -lL
i~al movement should be performed. 'l'his synchronization can be performed by the use of known position detectors, such as by optical scanning of the locating marks by capacitive measurement of an air gap wherein the capaci-tance is changed, or by the magnetic detection of .healteration of the rnagnetic flux. An electrodynamic scanning arrangement for such synchronization in the present invention is provided by use o the sensor winding shown in Fig. 13 as a measuring element for the speed of movement of the print head. The voltage, having a magnitude which is proportional to the speed of the plunger or armature, is induced in the second or sensor winding 64 as a result of the movement. Since a fixe~ phase relationship exists between the displacement and the speed of movement for a sine-shaped wave move-ment, a synchronizing signal may be derived from the speed measuring signal by means o a zero voltage detec-tor and this synchronizing signal can be applied to an assoclated electronic control unit.
Fig. 14 illustrates the use of a nozzle bar 166 having a plurality of ink jet nozzles 168 and car-ried on a support member 170 which has end plates 172 and 174 operably connected with bent or folded leaf springs 176 and 178. The spring 176 is fixed or secured at the left side and the spring 17~ is fi-xed or secured at the right side. The spring 176 has an aperture 181 through which a coupling member 180 is movable and having one end secured to the end plate 172 and being connected at the other end to the oscillating assembly or electrodynamic drive system 24, similar to the unit shown in Fig. 1D It is here noted that the width of an area to be printed is generally defined by the amplitude of the oscillation in connection with the number of ink nozzles so tha~ it is possible to reduce the oscillating amplitude by increasing the number of nozzles. The limiting case is to provide as many ink nozzles as there are ink spots or dots required to print one line on the paper, thus making a horizontal drive not required or necessary in such case. Another arrangement is to pro vide as many nozzles as there are characters to be printed on a line with one nozzle assigned only for the width of each character so that the horizontal oscilla~
tion does not cover the spaces between the characters.
A smaller amplitude of oscillation along with the same oscillation frequency results in a lower acceleration which is favorable for longer life of the print head.
Figs. 15 and 16 illustrate an arrangement wherein the amplit~de of the horizontal drive is in-creased or is larger as a result of the decreased number of nozzles, as may be the case in a cost reduction scheme for the ink jet print heads. If the amplitude of the oscillatLon exceeds 2 centimeters, it is reasonable to use a magnet distributed over the entire length of oscillation and a meander-shaped coil arranged on a circuit board. Fig. 15 shows a nozzle bar 182 having three ink nozzles 184 spaced at a distance apart and carried on the shaft 102 which is slidably journaled in 20 bearing blocks 104 and 106 on the frame member 10~, all in the manner as previously shown in Fig. 10. Shaft 102 has the small plates 110 and 112 secured at the ends thereof along with the coil springs 114 and 116 to provide horizontal oscillation. The magnet and coil arrangement of Fig. 15 is known in the art as a linear motor and limitations in the amplitude of the horizontal oscillation for this type of drive are not an i~portant concern. The linear motor 186 is diagrammatically shown with a magnetic field 188 and current flow to the line 30 190. Fig. 16 shows the linear motor 186 in more de-tailed form with the magnetic field 188 along with current flow in the several lines 190. The horizontal drive is in the direction of the arrow. The drive or the energization can be realized by the above described electrodynamic principle and also by means of a simple electromagnet. This type of drive requires a stroke~
like energization in the proper time relationship with respect to the mechanical oscillation~
Since the use oE a linear motor enables large amplitudes of oscillation, it must be taken into con-sideration that for utilizing such a spring mass system the spring used as the energy storage means likewise has to be capable of a large amplitude of movement.
One solution for enabling a larye amplitude involves the use of a conical spiral spring which has advantages for the present invention, since a spiral spring has a good working volume relationship whereln the volume of the extended spring is contrasted with the volume of the compressed spring. The use of a spiral spring makes it possible to construct a long stroke oscillator in small installations~
If the amplitude of the oscillation of the horizon~al oscillation is large, it may be possible that the oscillation oE the vertical drive alone or by itself is insufficien~ to achieve a satisfactory print quality.
In this case it may be useful to perform the vertical oscillation along the width of the paper in a dephased manner or where the vertical oscillation is combined with the feed movement of the paper. The electro-magnetic exitation of two vertical oscillators is in phase opposition wherein the vertical movement at one side of the paper is downward and the vertical movement - 25 at the other side of the paper is upward~ A tilting oscillation of the paper feeding is accomplished which in combination with the horizontal oscillation produces a satisfactory print pattern.
It is thus seen that herein shown and de-scribed is mechanism for driving an ink jet print head wherein leaf springs are used for supporting the print head and for oscillating the print head in a natural frequency of movement. The apparatus of the present invention enables the accomplishment of the objects and advantages mentioned above, and while a preferred em-bodiment and several modifications thereof have been disclosed herein, other modifications may occur to those ~¢~
skilled in the art. It is contemplated that all such modifications and variations not departing from the spirit and scope of the invention hereof are to be construed in accordance with the followiny claims.
Background of the Invention In the field of non-impact printing, the most common types of printers have been the thermal printer and the ink jet printer. When the performance of a non-impact printer is compared with that of an impact print-er, one o the problems in the non-impact machine has heen the control of the printing operation. As is well known, the impact operation depends upon the movement of impact members such as wires or the like and which are typically moved by means of an electromechanical system which is believed to enable a more precise control of the impact members.
The advent of non-impact printing, as in the case of thermal printing, brought out the fact that the heating cycle must be controlled in a manner to obtain maximum repeated operations. Likewise, the control of ink ~et printing in at least one form thereof must deal with rapid starting and stopping movement of the ink fluid from a supply of the fluid. In each case of non impact printing, the precise control of the thermal elements and of the ink droplets is necessary to provide for both correct and high-speed printing.
In the matter of ink jet printing, it is extremely important that the control of the ink droplets be precise and accurate from the time of formation of the droplets to the depositing of such droplets on the paper or like record media, and to make certain that a clean printed character results from the ink droplets.
While the method of printing with ink may be performed in continuous~manner or in demand pulse manner, the latter type method and operation is preferred in the present application as applying the features of the present invention. The drive means for the ink droplets is usually in the form of a crystal element to provide the high-speed operation for ejecting the ink through the nozzle while allowiny time between droplets for proper operation. The time allowed between the ink droplets is effected by means for damping the oscil-lations ~f the pressure waves generated during the printing operation.
In the ink jet printer the print head struc-ture may be a multiple nozzle type with the nozzles aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner.
Alternatively, the printer structure may include a plurality of equally-spaced, horizontally aligned single nozzle print heads which are caused to be moved in back-and-forth manner to print successive lines of dots in making up the lines of characters.
There have been various ways and means devised for precisely controlling the deceleration and ac-celeration of the ink jet prin~ head wherein large amounts of energy are used in the printing operation.
It is well-known that a print head carriage may be con-nected with a pulley and cable arrangement and driven by a separate motor for causing transverse movement of the carriage during printing operations. Another driving system utilizes a lead screw connected with the carriage and-driven by a separate motor for back-and-forth move ment of the carriage. A disadvantage of the rnotor driven carriage is the high cost of both the e~uipment and its operation.
It is therefore proposed to provide drive mechanism which has means inherent therein for driving the print head in an oscillating manner in a horizontal direction~
Representative prior art in the field of means for driving a print carriage in oscillating manner includes German Specification No. 2,646,740 on the application of A~ Watanabe et al., and opened to the public on April 20, 1978. This publication discloses a ~ -~3~ ~3 printer havin~ electromagnets mounted on a carriage plate. The plate is mounted on the free ends of the central legs of two cone like leaf springs while the corresponding ends of two other legs are fixed to the frame of the printerO The reciprocating motion of the carriage plate is performed by a crank drive. The special structure and arrangement of the leaf springs bearing the carriage plate provides for parallel movement of the plate relative to the platen during the back-and-forth motion.
United States Patent No7 4,227 t 455 issued to W~ B. Pennebaker on October 14, 1~80t discloses a suspension arrangement for a body oscillating or vibrating at resonance to provide linear motion for a short distance. The body has two portions connected by leaf springs to separate frames, in turn, connected by leaf springs to a main frame suspended by leaf springs from a support.
The present invention relates to ink jet printersD and more particularly to mechanism for driving the carriage of an ink jet print head in a horizontal direction~ A plurality of print heads are supported from a plate secured to the free ends of a pair of leaf springs which are set into oscillation or swinging movement by an electrodynamic drive system.
The print head carriage is caused to be msved in the horizontal direction by the spring structure which i5 oscillating at a natural frequency, Drive means is also connected with the horizontal drive mechanism for moving the paper or other record media in a vertical direction~
In accordance with the present invention~
there is provided apparatus for producing horizontal movement of an ink jet print head for printing in dot matrix manner on record media comprising support -3a-means, leaf spring means having one end thereof secured to said support means and the other end thereof secured to and carrying said print head, electromagnetic means connected with said leaf spring means for initiating swinging movement thereof in side-to-side direction, and circuit means operably associated with the electromagnetic means for damping the leaf spring means and causing oscillating motion thereof in a frequency corresponding to its natural frequency.
In view of the above discussion, the principal object of the present invention is to provide means for moving a print head in a manner to reduce the costs of manufacturing and of operating the printer.
Another object of the present invention is to provide a non-impact printer having a low-energy and substantially noiseless mechanism for moving the print head in a horizontal clirection.
An additional object of the present invention is to provide means for moving an ink jet print head in a manner for reducing the energy required for accel-eration and deceleration of the print head.
A Eurther object of the present invention is to provide a drive system for enabling movement of an ink jet print head wherein the system operates in an oscillating manner at a natural frequency.
Additional advantages and features of the present invention will become apparent and fully under-stood from a reading of the following description taken together with the annexed drawing.
Brief Description of the Draw ng Fig. 1 is a diagrammatic view of spring means for causing horizontal movement of a print head;
F;g. lA is a circuit diagram of a drive for the spring meansi Fig. 2 is a diagrammatic view of a plurality of print heads on a support plate which is caused to be moved by spring means in a horizontal direction;
Fig. 3 is a view similar to portions of Fig. 1 and including circuit means for compensating the damping of the oscillating system;
Figs. 4A and 4B show a timing diagram of the voltage and deflection relationship;
Fig. 5 shows the current pulse through the drive circuit of Fig. 3;
Fig. 6 is a view of ratchet means rotatable by horizontal movement of the print head carriage;
Fig. 7 is a view of drive means driven by the ratchet means of Fig. 6 for enabling vertical motion of the record media;
Fig. 8 is a diagrammatic view of a modified arrangement of spring means for causing horizontal movement o the print head;
~5--Fiy. 9 is a diagrammatic view showing the com-bin~tion of horizontal oscillation of the print head and vertical movement of the record media;
Fig. 10 is a view showing another arrangement S of spring means for causing horizontal movement of the print head, having straight line guide means with horizontal oscillating coil spriny elements;
Fig. 11 shows still another arrangement of such spring means with the use of bent leaf springs performing the function of guide or bearing means along with the function of an oscillating drive;
Figs. 12A, 12B and 12C are diagrammatic show-ings of different arrangements employing a leaf spring in providing the vertical oscillating mechanism for record media movement;
Fig. 13 shows a scanning arrangement for measuring the instantaneous speed of the oscillating print head;
Fig. 14 is a diagrammatic view of a still further spring means arrangement showing a bent leaf spring drive mechanism and a nozzle bar driven in oscil-lating manner;
Fig~ 15 shows the use of a linear motor along with spring means for driving a print head in horizontal oscillating manner, and Fig. 16 is a circuit diagram of the linear motor.
Detailed Description of the Invention Fig. 1 is a diagrammatic view showing an ink jet print head 10 supported from the ree end 12 of a leaf spring 14. The other end 16 of the leaf spring is secured to a fixed frame member 18. The prin~ head 10 has a nozzle 20 for ejecting an ink droplet 22 therefrom in performing a printing operation. An electrodynamic drive system 24 for initiating or setting the leaf spring 14 into oscillation or swinging movement includes a permanent ~agnet 26 operable with an armature 28 over-lying a central core portion 30 of the magnet and wound with a drive coil 32. The drive coil 32 is energized by pulses amplified by a power transistor 31, as illus-trated in Fig. lA. The armature 28 has a couplingmember 34 in the form of a rod fixed thereto at one end and secured at the other end to the leaf spring 14 near the center thereof. The leaf spring 14 operates with a natural frequency wherein the ink jet print head 10 is swinging freely and no electrical power is required for acceleration and deceleration of the head 10. In this manner, the consumed electrical power is only that power which is converted into frictional work. A pulse is applied once for each forth movement of the leaf spring 14 in its back and forth movement and with the pulse frequency being equal to the frequency of spring oscil-lation.
Fig. 2 illustrates a plurality of ink jet print heads 40 carried on a support member 42 which, in turn, is supported from the free ends of a pair of leaf springs 44 and 46. The other ends of the leaf springs 44, 46 are secured to a frame member 48. The print heads 40 are positioned to print on paper 50 or like record media which is caused to be trained around a platen 52. The driving or transporting of the paper 50 in a vertical direction past the line of printing is performed by means to be described later. A dr:ive module 54, similar in form to the electrodynamic drive system 24 of Fig. 1, is used to set the leaf springs 44 and 46 into oscillation with a natural frequency through a coupling member 56. It can be readily seen that the printing width is increased by a factor corresponding to the number of ink jet print heads 40 mounted on the support member 42.
Fig. 3 is a feed-back circuit for compensating the damping of the mechanically oscillating system of Fig. 1 wherein the ink jet print head 10 is supported from the free end 12 of the leaf spring 14 secured at its other end to the frame member 18. The armature 2ff is secured to the leaf spring 14 by the coupling member 34 and includes the drive coil 32 wound on the armature and connected to ground potential. The feed-back cir-cuit includes an operational amplifier 60 having compo-nents wired for use as an integrator and connected in series with a power amplifier 62 which energizes the drive coil 32~ The operational amplifier 60 acts as an integrating element by reason of its feedback capacity to effect a phase shift by ninety degrees so that energy is supplied in phase to the drive coil 32 by the power amplifier 62. A measuring or sensing winding 64 is dis-posed around the drive coil 32 and is connected at one end to the operational amplifier 60 with the other end thereof connected to ground potential. The positive feed-back compensates the damping so that the mechanical spring system oscillates with its natural frequency. The damping compensation is required to maintain the oscil-lation at a constant amplitude wherein the natural fre-quency of spring oscillation is determined by the char-ac~eristics of the spring, such as mass, material, dimensions and design.
Figs. 4A, 4B and 5 show a timing relationship between the pulsa-ting electrical energization of the drive system ~4 of Fig. l and the mechanical oscillation of the spring 14. The relationship of Figs. 4A and 4B
is shown by the formula V=-dD. The induced voltage V
is proportional to the spee~ of oscillation and the de1ection D is shown in time relation for a range of positive or plus current pulse and for a range of negative or minus current pulse. The pulses of Fig. 5 are initiated at predetermined times which are not precisely fixed so that, for certain times or instants during the forward oscillating phase, an electrical pulse must be applied wherein the movement of the free mass spring oscillator is sustained by the electrical energization. More particularly, the pulses are applied, ~L ~ 4 ~ r~
as indicated in Figs. 4A and 5, immediately after the maximum amplitude at a freq~ency equalling the natural frequency of oscillation. Pulses of opposite polarity are applied wherein the polarity corresponds to the respective direction of movement. Generally, the drive system 24 is pulsed or energized once for each cycle of printi~g.
A simple drive means for performing vertical movement of the paper to be printed is possible through use of a simple low power motor which is continuously energized in order to produce a constant paper speed.
It is also a simple matter to change the paper speed by using different means for operating the motor in order to perform a maximum paper feed condition whenever required. To overcome the need for such a separate drive, Figs. 6 and 7 illustrate means for obtaining a vertical drive for the paper from the longitudinal movement of the ink jet print head, wherein a ratchet gear 70 is positioned adjacent the platen 52 around which the paper 50 is trained in a path past the line of printing. An oscillating horizontal push rod 72, suit-ably connected to the leaf spring 14, drives a feed rod 74 against the teeth of the ratchet gear 70 and operates with a ratchet pawl 76 secured to a frame member 78 and engaging with the teeth of the gear 70. The ratchet gear 70 is carried on a shaft 75 along with a gear 77 which meshes with a gear 79 on the end of a worm gear 80 which, in turn, meshes with and drives a drive gear 82 for rotating the platen 52. The stepping mechanism enables driving the paper 50 by using the horizontal drive motion of the ink jet print head drive means and thereby eliminates the use o an electric motor.
Fig. 8 shows an ink jet print head 86 sup-ported in stationary manner from a member 88 for print~
ing on the paper 50 trained around the platen 52. The platen 52 is supported for rotation on a shaft 90 which is slidably journaled for axial movement in bearing blocks 92 and 94 and which has a small plate 96 secured at the right end thereof associated with the armature 28 and the drive coil 32. ~ coil spring 98 is placed on the shaft 90 between the plate 96 and the block 94. In this arrangement, the print head 86 is stationary and the platen 52 along with the paper 5~ is caused to be moved by action of the spring 98 in a horizontal oscil-lating direction as shown by the arrow.
A single print head 40 is illustrated in Fig.
9 as being carried on the support member 42 and oscil-lating in the horizontal direction, as in the mannerillustrated in Fig. 2~ At the same time, the paper 50 around the platen 52 is caused to be regularly moved in incremental manner in a vertical direction. In this combined horizontal oscillating and vertical incrementing drive arrangement the most advantageous operating point is at the resonance of the spring mass system.
Fig. 10 illustrates a straight line guide ar-rangement for an ink jet print head 100 supported from a shaft 102 slidably journaled in bearing blocks 104 and 20 106 on a frame member 108. The shaft 102 has a small plate 110 secured at the left end and a small plate 112 secured at the right end thereof. The plate 110 is drivingly associated with the armature 28 and the drive coil 32. A coil spring 114 is placed on the shaft 102 25 between the plate 110 and the block 104 and a coil spring 116 is placed on the shaft between the plate 112 and the block 106 to provide horizontal oscillation of the print head 100.
In Fig. 11 there is shown another arrangement 30 wherein a pair of print heads 120 and 122, similar to the previously mentioned print heads 10, 40 and 86, are carried on a support member 124 having plates 126 and 128 at the ends thereof. A pair of bent or folded leaf springs 130 and 132 are operably connected with the 35 plates 126 and 128 in a manner to provide guide means as well as horizontal oscillation of the print heads 120 and 122. In like manner, the plate 126 is connected to the armature 28, drive coil 32 assembly through a shaft or rod 131. The outer leg or portion of each spring is fixed or secured to a support member, as 133 for spring 13~.
Figs. 12A, 12B and 12C show different ar-rangements of using a leaf spring for the verticaloscillating mechanism employed in transporting or driving the paper. In Fig. 12A~ the paper 50 is trans-ported and trained around a stationar-y roller 134, a pair of movable rollers 136 and 138 and then around a stationary roller 140. A leaf spring 142 is secured at one end and is connected with a member 144 coupling the movable rollers 136 and 138 to provide the vertical movement for the paper, Fig. 12B has the paper 50 trained around a stationary roller 146, a movable roller 148 and then around a stationary roller 150. A leaf spring 152 is secured at one end and is connected to the movable roller 148 for vertical movement thereof in relation to the print head 154. In each case the leaf spring performs the function of the spring member as well as the bearing or guide function. Fig. 12C sho~s a leaf spring 156 secured at one end and connected to a movable roller 158 for vertical movement. A pair of guide members 160 and 162 are provided to be slidable or displaceable along a horizontal path to and from the roller 158 so as to allow changing the natural frequency of the spring 156.
Fig. 13 shows the armature 2B, as illustrated in FigsO 1 and 3, with the drive coil or operating winding 32 and with the addition of the sensor winding 64 which is within the magnetic field in similar man-ner as is shown in Fig. 3. The sensor winding is used for ascertaining the instantaneous speed of the oscil-lating ink jet print head. It should be here noted that the natural frequency of the spring mass oscillating system is very stable so that no accurate determination of the position of the ink droplets is required. It is only necessary that once for each oscillating period a simple synchronization of the ink jet with the mechan-f~3 -lL
i~al movement should be performed. 'l'his synchronization can be performed by the use of known position detectors, such as by optical scanning of the locating marks by capacitive measurement of an air gap wherein the capaci-tance is changed, or by the magnetic detection of .healteration of the rnagnetic flux. An electrodynamic scanning arrangement for such synchronization in the present invention is provided by use o the sensor winding shown in Fig. 13 as a measuring element for the speed of movement of the print head. The voltage, having a magnitude which is proportional to the speed of the plunger or armature, is induced in the second or sensor winding 64 as a result of the movement. Since a fixe~ phase relationship exists between the displacement and the speed of movement for a sine-shaped wave move-ment, a synchronizing signal may be derived from the speed measuring signal by means o a zero voltage detec-tor and this synchronizing signal can be applied to an assoclated electronic control unit.
Fig. 14 illustrates the use of a nozzle bar 166 having a plurality of ink jet nozzles 168 and car-ried on a support member 170 which has end plates 172 and 174 operably connected with bent or folded leaf springs 176 and 178. The spring 176 is fixed or secured at the left side and the spring 17~ is fi-xed or secured at the right side. The spring 176 has an aperture 181 through which a coupling member 180 is movable and having one end secured to the end plate 172 and being connected at the other end to the oscillating assembly or electrodynamic drive system 24, similar to the unit shown in Fig. 1D It is here noted that the width of an area to be printed is generally defined by the amplitude of the oscillation in connection with the number of ink nozzles so tha~ it is possible to reduce the oscillating amplitude by increasing the number of nozzles. The limiting case is to provide as many ink nozzles as there are ink spots or dots required to print one line on the paper, thus making a horizontal drive not required or necessary in such case. Another arrangement is to pro vide as many nozzles as there are characters to be printed on a line with one nozzle assigned only for the width of each character so that the horizontal oscilla~
tion does not cover the spaces between the characters.
A smaller amplitude of oscillation along with the same oscillation frequency results in a lower acceleration which is favorable for longer life of the print head.
Figs. 15 and 16 illustrate an arrangement wherein the amplit~de of the horizontal drive is in-creased or is larger as a result of the decreased number of nozzles, as may be the case in a cost reduction scheme for the ink jet print heads. If the amplitude of the oscillatLon exceeds 2 centimeters, it is reasonable to use a magnet distributed over the entire length of oscillation and a meander-shaped coil arranged on a circuit board. Fig. 15 shows a nozzle bar 182 having three ink nozzles 184 spaced at a distance apart and carried on the shaft 102 which is slidably journaled in 20 bearing blocks 104 and 106 on the frame member 10~, all in the manner as previously shown in Fig. 10. Shaft 102 has the small plates 110 and 112 secured at the ends thereof along with the coil springs 114 and 116 to provide horizontal oscillation. The magnet and coil arrangement of Fig. 15 is known in the art as a linear motor and limitations in the amplitude of the horizontal oscillation for this type of drive are not an i~portant concern. The linear motor 186 is diagrammatically shown with a magnetic field 188 and current flow to the line 30 190. Fig. 16 shows the linear motor 186 in more de-tailed form with the magnetic field 188 along with current flow in the several lines 190. The horizontal drive is in the direction of the arrow. The drive or the energization can be realized by the above described electrodynamic principle and also by means of a simple electromagnet. This type of drive requires a stroke~
like energization in the proper time relationship with respect to the mechanical oscillation~
Since the use oE a linear motor enables large amplitudes of oscillation, it must be taken into con-sideration that for utilizing such a spring mass system the spring used as the energy storage means likewise has to be capable of a large amplitude of movement.
One solution for enabling a larye amplitude involves the use of a conical spiral spring which has advantages for the present invention, since a spiral spring has a good working volume relationship whereln the volume of the extended spring is contrasted with the volume of the compressed spring. The use of a spiral spring makes it possible to construct a long stroke oscillator in small installations~
If the amplitude of the oscillation of the horizon~al oscillation is large, it may be possible that the oscillation oE the vertical drive alone or by itself is insufficien~ to achieve a satisfactory print quality.
In this case it may be useful to perform the vertical oscillation along the width of the paper in a dephased manner or where the vertical oscillation is combined with the feed movement of the paper. The electro-magnetic exitation of two vertical oscillators is in phase opposition wherein the vertical movement at one side of the paper is downward and the vertical movement - 25 at the other side of the paper is upward~ A tilting oscillation of the paper feeding is accomplished which in combination with the horizontal oscillation produces a satisfactory print pattern.
It is thus seen that herein shown and de-scribed is mechanism for driving an ink jet print head wherein leaf springs are used for supporting the print head and for oscillating the print head in a natural frequency of movement. The apparatus of the present invention enables the accomplishment of the objects and advantages mentioned above, and while a preferred em-bodiment and several modifications thereof have been disclosed herein, other modifications may occur to those ~¢~
skilled in the art. It is contemplated that all such modifications and variations not departing from the spirit and scope of the invention hereof are to be construed in accordance with the followiny claims.
Claims (8)
1. Apparatus for producing horizontal movement of at least one ink jet print head for print-ing in dot matrix manner on record media comprising support means, leaf spring means having one end there-of secured to said support means and the other end thereof secured to and carrying said print head, electromagnetic means connected with said leaf spring means and having drive coil means for initiating swinging movement of the leaf spring means in side-to-side direction, and circuit means including a sensing winding disposed around the drive coil means and an amplifier operably associated with the electromagnetic means for compensating the damping of the leaf spring means and maintaining oscillating motion thereof at a constant amplitude in a frequency corresponding to its natural frequency.
2. The apparatus of claim 1 including ratchet means connected with said leaf spring means for causing incremental vertical movement of said record media past said print head.
3. The apparatus of claim 1 including a plurality of print heads carried by said support means and movable a predetermined distance in relation to said record media for printing a greater width there-across.
4. A dot matrix printer for printing on record media movable past a line of printing compris-ing at least one ink jet print head adjacent said line of printing, support means, spring means having one end thereof secured to said support means and utiliz-?
ing the other end thereof for carrying the print head in free swinging manner, electromagnetic means con-nected with said spring means and having drive coil means for initiating swinging movement of the spring means in side-to-side direction, and feedback circuit means including an operational amplifier and a sensing winding disposed around the drive coil means and operably associated with said electromagnetic means for compensating the damping of said spring means and enabling oscillating motion thereof at a constant amplitude and in a frequency corresponding with its natural frequency.
ing the other end thereof for carrying the print head in free swinging manner, electromagnetic means con-nected with said spring means and having drive coil means for initiating swinging movement of the spring means in side-to-side direction, and feedback circuit means including an operational amplifier and a sensing winding disposed around the drive coil means and operably associated with said electromagnetic means for compensating the damping of said spring means and enabling oscillating motion thereof at a constant amplitude and in a frequency corresponding with its natural frequency.
5. The printer of claim 4 including ratchet means connected with said spring means for causing incremental vertical movement of said record media past said print head.
6. The printer of claim 4 including a plurality of print heads carried by said support means and movable a predetermined distance in relation to said record media for printing a greater width there-across.
7. An ink jet printer comprising a platen around which record media is trained, at least one print head adjacent said platen for printing on the record media, support means, a leaf spring having one end thereof secured to said support means and having the other end carrying said print head in free swing-ing movement, electromagnetic means coupled with said leaf spring and having drive coil means for initiating said free swinging movement in side-to-side direction, and feedback circuit means including an amplifier and a sensing winding disposed around the drive coil means and operably associated with the electromagnetic means for compensating the damping of said leaf spring and enabling oscillating motion thereof at a constant amplitude and in a frequency corresponding with its natural frequency.
8. The printer of claim 7 including pawl and ratchet means connected with said leaf spring for causing incremental vertical movement of said record media past said print head.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US24199881A | 1981-03-09 | 1981-03-09 | |
| US241,998 | 1981-03-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1192083A true CA1192083A (en) | 1985-08-20 |
Family
ID=22913065
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000397809A Expired CA1192083A (en) | 1981-03-09 | 1982-03-08 | Ink jet printer drive mechanism |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0073810A1 (en) |
| JP (1) | JPS58500243A (en) |
| CA (1) | CA1192083A (en) |
| WO (1) | WO1982003123A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0109329A3 (en) * | 1982-11-03 | 1986-06-11 | GENICOM Corporation | Balanced print head drive mechanism |
| IT1187967B (en) * | 1986-03-10 | 1987-12-23 | Olivetti & Co Spa | APPARATUS FOR DIGITAL COLOR REPRODUCTION OF DOCUMENTS |
| JPH0614567A (en) * | 1992-06-29 | 1994-01-21 | Canon Inc | Oscillation linear driver and printer employing linear driver |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH375027A (en) * | 1961-04-14 | 1964-02-15 | Paillard Sa | Writing process and machine for implementing this process |
| FR2085784B2 (en) * | 1970-04-02 | 1973-01-12 | Hertz Carl |
-
1982
- 1982-02-19 EP EP19820901066 patent/EP0073810A1/en not_active Withdrawn
- 1982-02-19 WO PCT/US1982/000207 patent/WO1982003123A1/en not_active Application Discontinuation
- 1982-02-19 JP JP50108982A patent/JPS58500243A/en active Pending
- 1982-03-08 CA CA000397809A patent/CA1192083A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0073810A1 (en) | 1983-03-16 |
| WO1982003123A1 (en) | 1982-09-16 |
| JPS58500243A (en) | 1983-02-17 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |