EP0154648A4

EP0154648A4 - Ink jet printing system.

Info

Publication number: EP0154648A4
Application number: EP19840903326
Authority: EP
Inventors: Howard H Barney
Original assignee: Diagraph Corp
Current assignee: Diagraph Corp
Priority date: 1983-08-29
Filing date: 1984-08-27
Publication date: 1985-12-30
Also published as: EP0154648A1; WO1985001104A1

Abstract

A ink jet printing system (5) comprising a plurality of ink jet printheads (7) each having a matrix of ink jets (J), each jet having a nozzle (9) constituting a valve seat at its outlet end, the seat having an orifice (21) for ejection of drops of ink, a solenoid-actuated valve member (33) engageable with and disengageable from the seat to close and open the orifice, a controller (93) for each printhead comprising a microcomputer (95) for processing data for actuating the solenoids (71) to print messages and storing the data, a console (99) for all the printheads having a microcomputer (101) for processing data for delivery to the printheads and operable to store data for a plurality of messages, and a terminal (109) for generating data for messages for delivery to the console or, alternately, directly to the printhead controllers for a minimum system.

Description

INK JET PRINTING SYSTEM Background of the Invention

This invention relates to ink jet printing systems, and more particularly to computer-controlled systems of this class . The invention is concerned with an ink jet printing system for printing on moving surfaces, such as on cartons or boxes being fed forward by a conveyor, and is in the same gen¬ eral field as the systems shown in U.S. patents 4,002,230 and 4,378,564.

Summary of the Invention

Among the several objects of this invention, may be noted the provision of an improved ink jet printing system of the class described better adapted for use in different types of installations and better adapted, once installed, to chang- ing needs; the provision of such a system which is relatively easy to set up, operate and service? the provision of a mul¬ ti-tasking system of the class described, adapted to include as many as eight printheads, for example, with some acting to print on objects (e.g., cartons or boxes) moving one way or the other with respect to the associated printhead or print- heads; the provision of such a system enabling control over the printing in accordance with the speed of the objects being fed past the printheads and selection of the location of a printed message on the objects; and the provision of a print- ^■ head with a fast-acting anti -clogging ink ejection system operable with precise ink drop formation for optimizing print quality and also for minimizing waste of ink.

In general, a system of this invention is adapted for ink jet printing of messages on objects such as cartons or boxes being fed forward one after another in a predetermined path. It comprises a plurality of ink jet printheads posi¬ tioned adjacent to said path to print the messages on the ob¬ jects as they travel forward in said path. Each printhead comprises a plurality of ink jets arranged in a matrix and adapted for ejection o f drops of ink acr oss a gap to a sur face of an object travelling by the printhead to pr int dots on said surface in patterns forming selected characters such as let¬ ters and numerals for said messages . Means is provided for supplying ink to the jets , also a plurality of electr ically actuated valve means , one for each jet, each adapted for electr ical operation for ejection of a drop of ink from the r espective jet. The system fur ther compr ises a terminal in¬ cluding a keyboard for entering message data, a message bank having a microcomputer interconnected with the terminal for processing data received from the terminal and stor ing the data for a plurality o f messages , and a plurality of control¬ lers , one for each pr inthead , each including a microcomputer interconnected with the bank for processing data for a selec- ted message received from the bank and stor ing the data. The bank has means for effecting transfer of data for a selected message from s torage therein to a selected controller for storage in that controller . Each controller has an output circuit in terconnected with the microcomputer thereof and with the respective pr inthead for receiving output of data for the ' selected message from that microcomputer and conver ting the data to dr iving signals for the pr inthead valve means for actuating the latter to pr int the selected message .

In another aspect , each jet compr ises an elongate tubular member hav ing an outlet nozzle consti tuting a valve seat at one end thereof , said seat having an or ifice for ejec¬ tion of drops of ink , said tubular member having an ink cham¬ ber therein for holding ink under pressure for delivery through the orifice , said chamber being defined by the valve seat and by means in the tubular member spaced from the seat . sealing against escape of ink from the chamber. A valve stem extends longi tudinally in said tubular member having a valve member at its end toward the seat engageable with the seat to block flow of ink through the or ifice in the seat. The valve s tem is movable longi tudinally in said tubular jet member for closing the valve member against the seat and for opening it for ejection of a drop of ink through the orifice. And a solenoid is provided for each jet, each solenoid being con¬ nected to a respective valve stem for actuating the latter. Other objects and features will be in part apparent and in part pointed out hereinafter.

Brief Description of the Drawings

Fig. 1 is a semi -diagrammatic view of an ink jet printing system of this invention; Pig. 2 is a perspective of a printhead of the system;

Fig. 3 is a view illustrating a matrix of ink jets of the printhead and pattern of dots printed thereby;

Fig. 4 is a view with parts broken. away and shown in section of an ink manifold of the printhead and associated ink jets and valve actuating means;

Fig. 5 is an enlargement of a fragment of Fig. 4 with parts shown in section;

Fig. 6 is a block diagram showing an installation of the system with four printheads for printing on objects moving from left to right with respect to these four printheads and three printheads for printing on objects moving from right to left with respect to these printheads, and showing the cir¬ cuitry for the system; and

Fig. 7 is a front elevation of a controller for a printhead.

Corresponding reference characters indicate corre¬ sponding parts throughout the several views of the drawings.

Description of the Preferred Embodiment

Referring to Fig. 1, there is indicated at 1 a con- veyor for feeding forward one after another at spaced inter¬ vals a succession of objects 3, such as cartons or boxes, on which messages are to be printed by means of the ink jet printing system of this invention designated in its entirety by the reference numeral 5. The term "message" is intended to cover any item of information, such as a product code.

The ink jet p inting system 5 of this invention is shown in Fig. 1 to comprise a plurality of ink jet printheads each designated 7 positioned alongside and adjacent the path of the objects to print the messages on the objects as they travel forward along said path (left to right as viewed in Fig. 1) past the printheads. Three printheads 7 are shown in Fig. 1 by way of example, arranged to print three different messages on three different lines- Each comprises a plurality of ink jets each generally denoted by the reference character J and each including an outlet nozzle 9, these jets being ar¬ ranged in a matrix and adapted for ejection of drops of ink across a gap between them and an object 3 travelling past them to a surface S of the object (one side of a carton) to print dots on said surface in patterns forming selected characters such as letters, numerals and other symbols for said mes¬ sages. As shown in Figs. 2 and 3, there are nine ink jets and hence nine nozzles 9 arranged in two side-by-side closely adjacent columns of five nozzles and four nozzles, respective¬ ly, the four nozzles in the four-nozzle column being staggered with respect to the five nozzles in the five-nozzle column. With this nozzle arrangement, various patterns of dots may be printed on surface S. Fig. 3 shows a pattern of dots for the characters "Al" in what is called a "bold" font (large charac¬ ter printing) in which each vertical dot column is doubled. At 11 is generally indicated means for supplying ink to the nozzle. A plurality of electrically actuated valve means, one for each jet J, and each designated 13, is provided in each printhead. Two such valve means 13 are shown in Fig. 4 (one • in Fig. 5). It will be understood that for the nine jets of each printhead 7, there are nine such valve means 13, one for each jet. Each said valve means 13 is adapted for relatively momentary operation electrically for ejection of a drop of ink from the respective jet nozzle 9 (i.e., the nozzle associated therewith) .

As shown more particularly in Figs. 4 and 5, each of the printheads 7 comprises means indicated generally at 15 mounting the jets J in the stated matrix for the non-contact printing of patterns of dots to form characters including let¬ ters, numerals and other symbols on the target surface S of the objects 3 moving relative to the jets past the jets, by the selective squirting of ink from the jets on the target surface. Each jet comprises an elongate tubular member 17 . having an ink chamber 19 therein for retaining ink under pres¬ sure. Secured in one end of this tubular member constituting the outlet end thereof is the aforesaid nozzle 9. The nozzle, per se, is a circular jewel, preferably sapphire, having a relatively small circular central orifice 21 with a tapered or countersunk (conical) opening 23 at the inside thereof in com¬ munication with (leading to) the central orifice. The sap¬ phire nozzle constitutes a valve seat of the respective valve means 13, being mounted in the outlet end of the tubular jet member 17 in engagement with an internal annular shoulder 25 in member 17 and held therein by peening over the end of the tubular jet member as indicated at 27. A valve stem or rod 31 extending longitudinally in the tubular jet member 17 has a ball valve member 33 secured on its end toward the outlet end of the tubular member engageable with the tapered or conical valve seat surface of the nozzle or seat 9 in the opening 23 to block flow of ink through the orifice 21 in the seat. The ball valve member may be a carbide ball or a spherical jewel, and is preferably a spherical ruby. The stem 31 is movable longitudinally in the tubular jet member 17 for closing the ball valve member 33 against the valve seat 9 and for opening it for a relatively brief interval for ejection (squirting) of a drop of ink through the orifice 21. The means 15 mounting the jets J, more par ticularly the tubular jet member s 17 , in the stated matr ix (the five plus four matr ix) cons ti tutes an ink manifold for holding ink under pressure. This manifold compr ises a front par t and a back part , the front part compr ising a fr ont wall 37 , which is the wall facing the objects 3 , having a rearwardly extending peripheral flange 39 , and the back part compr is ing a back wall 41 having a forwardly extending per ipheral flange 43. These parts are assembled with the flanges in butting engagement and sealed by an O-ring as indicated ^' at 45, the flanges spacing the walls from each other and thereby defining a manifold chamber 47 for holding ink under pr essur e. The par ts are suitably secured together with the seal 45 under compr ession by means such as screws (not shown) . The walls 37 and 41 have a plurality o f holes as indicated at 49 receiving the tubular jet member s 17 with these members extending from the front wall 37 back across the manifold chamber 47 and out through the back wall 41 as shown in Figs . 4 and 5. Each tubular jet member 17 is sealed in the walls 37 and 41 as indicated at 51 and has later al por ts 53 in communication with the manifold chamber 47 for feeding ink from the manifold chamber to the ink chamber 19 in the tubular jet member 17 .

Each of the tubular je t members 17 extends forward through the manifold 15 from an elongate tubular body member 55, member 17 being threaded at 57 in the forward end of the body member 55. The valve s tem or rod 31 extends rearward from the guide member in to the body member 55. The ink cham¬ ber 19 in the tubular jet member 15 is cons tituted by the space therein rearward of -the nozzle 9 at the forward end of member 17. The body member 55 has an annular flange 61 there¬ in against the rear face of wh ich a flexible resilient dia¬ phragm 63 is held by means of an annular thr ust member 65 and

-OMPI a retainer 67 threaded in the rearward end of the body mem¬ ber. The diaphragm, which may be made of EPR rubber, for ex¬ ample, has an axial tubular coupler or sleeve 69 bonded there¬ in extending forward and rearward. The valve stem or rod 31 is secured at its rearward end in this coupler. A solenoid 71 for operating the valve stem or rod 31 is mounted on the rear¬ ward end of a solenoid support tube 73 which extends rearward from the body member 55. This tube 73 has an adaptor 74 at its forward end threaded in the rearward end of the body mem- ber 55. A flexible drive wire 75 secured to the plunger 77 of the solenoid extends through a metal capillary tube sheath 79 in the support tube 73 and is secured at its forward end in the coupler 69, the latter thus serving to couple wire 75 and the valve stem or rod 31. The forward end of the sheath 79 is fitted in an annular spacer 81 in the forward end of the sup¬ port tube 73 within the adapter 74, and the space within the tube 73 around the sheath has a suitable plastic spacer means therein.

As diagrammed in Fig. 4, the solenoid 71 has spring means 85 biasing its plunger 77 in forward direction to bias the drive wire 75 and the valve stem 31 (which are coupled together by the coupler 69) forward so as to bias the valve ball 33 to its closed position illustrated in Fig. 5 against the nozzle or valve seat 9. The diaphragm 63 serves not only to seal the body 55 against leakage of such ink but also to bias the valve stem or rod 31 in the forward direction for nozzle .closure. The arrangement is such that, on energization for a brief interval of the solenoid 71, the armature 77 is driven rearward to pull the drive wire 75 and rod 31 rearward to move the ball 33 away from the valve seat or nozzle 9 for ejection of a drop of ink from the nozzle, and on deenergiza- tion of the solenoid, the ball 33 is biased back to closed position engaging the seat to cut off the ink. The ink jets J are relatively small and closely spaced, and the solenoid support tubes 73, of which there are nine, one for each jet, are bent or flared so that the rear¬ ward ends of the tubes are sufficiently spaced to provide room for the solenoids. The manifold 15, jets J, body members 55, support tubes 73 and solenoids 71 form an assembly which is housed in a printhead housing 87, with the front wall 37 of the manifold and the forward ends of the jets J in the holes 49 in the front wall 37, and with nozzles 9 at the forward ends of the jets, facing the outside through a rectangular window opening 89 at the forward end 91 of the housing 87. As appears in Fig. 2, the housing 87 is enlarged back from its forward end to accomodate the flaring of solenoid support tubes 73. Again referring to Fig. 1, the ink jet printing system 5 is shown further to comprise a plurality of control modules, one for each printhead 7, each such module being designated 93. These control modules may also be referred to as the printhead controllers. As shown in Fig. 6, each con- tr oiler 93 includes a microcomputer 95 for processing data for actuating the solenoids 71 of the several valve means 13 of the respective printhead 7 to print a message, storing the data for a message and delivering signals for actuating the solenoids for opening the ball valves 33 of the nine valve means 13 at the proper times and in the proper sequence for ejection of drops of ink from the nozzles 9 in the pattern to print the message. Each printhead controller microcomputer 95 contains a CPU chip, ROM's, RAM's, a UART, counter/ timer chips, interface chips, and support chips such as a crystal controlled clock, buffers, and drivers for various signals. - The microcomputer 95 communicates with the console 99 or terminal 109 using a RS-422 se ial interface at 38,000 Baud. Information is tranomitted in both directions in ASCII for¬ mat. Message data Is converted from ASCII to a particular font by the printhead controller microcomputer 95 and other fonts can be sent from the console 99 and s ored in RAM. Since several printhead controllers 93 can be daisy-chained together on a single cable from the console, the operating system uses a pollins protocol when communicating with the printhead controllers. Each printhead microcomputer 95 has on it an array of eight small switches which can be set to var¬ ious combinations for setting options. Four of the switches are used to select an identification number or address so that the console 109 can communicate with the appropriate printhead by sending out its identification number at the beginning of a sequence. Up to 16' different addresses are possible and no two printheads on one daisy chain can have the same identifi¬ cation number. Each printhead controller 93 also includes an ouput circuit or driver means 97 which receives output signals jfrom the microcomputer and converts them to variable pulse length actuating power signals for the solenoids 71 for actua¬ ting the valve means 13 in accordance with the signals.

A master controller 99 for the several printhead controllers 93 has a microcomp ter 101 for processing data for delivery to the printhead controllers 93, and is operable to store data for a large number of different messages to be printed, e.g., messages totalling up to 1000 characters, in a non-volatile memory immune to power loss. Typically, the memory is configured as 25 message lines of 40 characters each. The master controller 99 contains a power supply, microp ocessor, ROM, RAM, EEPROM and its special write circui¬ try, clock/ calen ar chip with battery backup, line drivers, receivers, UARTs, support and interface circuitry. The master controller 99, which may also be referred to as the console or message data bank or base, has a plurality of message routing ^• switch units each designated 103, one for each printhead 7, each adapted to route a selected message from the console 99 to the corresponding printhead 7. For eight printheads, there are eight such units, each comprising, for example, a pair of thumbwheel switches 105 and 107. One of these thumbwheel

OMPI switches sets tens and. the other sets ones for a message code number. For example, setting the numeral 1 on the first switch and 5 on the second switch of the first pair 103, this being the pair for routing a message to the first printhead, results in transmission of data for the message identified by code number 15.

Associated with the console 99 is a terminal 109 for entering data for the messages. ^' This has a keyboard indicated at 111 for typing messages, a display 113, e.g., a liquid cry- stal display, for displaying the ^'"typed, material for review and editing, and a microprocessor 115 and support circuits for processing the message data and transferring it to the console for storage in the memory of the console. The terminal 109 is interconnected with the console 99 as indicated at 117. Mes- sages stored in the console 99 may be fed back to the terminal 109 via 117 and displayed on the display 113. The display may also be used to display information on the operating status of the system, e.g., a count of the number of objects marked by each printhead since the last message was routed to it (or since the last reset), low ink warnings, error conditions, etc. As illustrated in Fig. 1, the console 99 is housed in a case 119 (e.g., a high impact aluminum case) having a hinged lid 121 adapted to be locked in place. The terminal 109 is removably nested in the lid. Typically, the terminal has 59 color-coded keys, divided into 44 upper and lower case character keys and 15 function keys, organized in standard typewriter style layout. A plug-in power supply for the con¬ sole and terminal is indicated at 123.

The console is illustrated in Fig. 6 as having four ports designated P1-P4 for inte connection with up to eight printhead controllers 93 for eight printheads 7, for example, with the printheads arranged in any manner to serve up to four different conveyors. As illustrated in Fig. 6, port PI is interconnected by an interconnect bus cable 125 with four con- trollers for four printheads 7 serving a first conveyor 1A, and port P3 is interconnected by an interconnect bus cable 127 with three controllers 93 for three printheads 7 serving a second conveyor IB. Each bus cable contains a plurality of pairs of conductors (e.g., six pairs) for servicing a plural- ity of printhead controllers (e.g., six printhead controllers), The ink supply means 11 comprises an ink station 129 including a tray 131 for holding a bottle of ink 133 with an air pressure inputindicated at 135 in Fig. 6 for pressurizing ink in the bottle, this system including a pressure regulator 137. A reserve bottle 139 is shown in the tray in Fig. 1. An ink supply means 11 is provided for each set of printheads 7 for each conveyor. Thus, two ink supply means 11 are shown in Fig. 6. Each ink supply bottle 133 is connected to the ink manifolds 15 of the set of printheads 7 serving the respective conveyor as indicated at 141. A low ink level sensor 143 is provided in the ink supply bottle. The ink station is also a power station for the printheads 7 associated therewith , hav¬ ing a power supply unit 145 for supplying power to the print¬ head controllers 93. This unit has an AC power input 147 and an output bus cable 149 interconnected with the respective bus cable 125 for interconnection with the microcomputers 95 of the printhead controllers 93 for the set of printheads 7 serv¬ ing the respective conveyor (e.g., 1A) . The sensor 143 is interconnected with the bus cable 149 as indicated at 151 for transmitting a low ink level signal back to a warning means (e.g., a warning lamp) associated with the console 93. A warning lamp may also be provided at the ink station.

The microcomputer 95 of each printhead controller 93 is responsive to the speed of feed of the objects or targets 3 past the respective set of printheads 7, i.e, the speed of the respective conveyor (e.g., 1A) , for properly timing the ejec¬ tion of drops of ink from the nozzles 9 for properly printing the message on each object or target 3 as it travels past the printhead at that speed. For this purpose, a speed sensor 155 is provided for sensing the speed of the conveyor and tr ans¬ mitting data corrsponding to the speed to the associated con¬ tr oller s 93 for varying the timing of operation o f the sole¬ noids 71 for operating the valve means 13 in accordance with the speed. As illus trated , the speed sensor is a rotary en¬ coder wh ich gener ates pulses at a rate in accordance with the conveyor speed and tr ansmits the pulses v ia a line 157 to the cable 149 for being multiplexed out to the associated print¬ head controllers 93. The microcomputer 95 of- each controller 93 is also r esponsive to the location of each object or target 3 relative to each pr inthead 7 to control the star t of pr inting so as to select the location of the pr inted message on the object or target, i .e . , to control the spacing of the message on the side target faces of the object or target from the leading face of the object or target. For this purpose, a photocell 159 is provided at one side of the conveyor adapted to receive a beam of light r ejected from a reflector 161 at the other side of the conveyor. As each object or target is fed for- ward, it is regis tered by the photocell 159 and the latter thereupon tr ansmits a start signal v ia a line 163 to the cable . 149 for being multiplexed out to the associated controllers 93. The microcomputer 95 of each of the controller s 93 in¬ cludes a var iable delay circuit for delaying the star t of operation of the valve means 13 for a predetermined interval after receipt of the start signal generated by the photocell 159. The contr oller 93 has a set of thumbwheel switches for setting this delay. As shown in Fig. 7 , there are thr ee such switches TI, T2 and T3 , the first being calibrated in tens of inches , the second in inches and the third in tenths of in¬ ches , to enable setting to with in a tenth of an inch the dis¬ tance from the leading face L of an object 3 back to the point where pr inting begins .

Each pr inthead controller 93 also has a run/stop switch 165 ( illustrated as a toggle switch) for activating or deactivating it and the respective printhead and a direction switch 167 (illustrated as a toggle switch) interconnected with the microcomputer 95 of the controller 93 adapted to be set in a first position for controlling said microcomputer for printing on objects 3 moving from left to right past the re¬ spective printhead 7, and in a second position for controlling said microcomputer for printing on objects moving from right to left past the respective printhead. The controller 93 also has a reset switch 169 (illustrated as a push-button switch) for the usual reset purposes, and. may have light-emitting drodes such as indicated at 171 which light up in various pat¬ terns as part of self -testing procedures programmed in the microcomputer 95. The controller 93 may also have internal controls for the driver circuit 97 for controlling dot size by varying the length of pulses for actuating the solenoids 71. The console 99 is shown as configured for reception of data storage means, e.g., a software cartridge 173 con¬ taining a chip, pre-p ogrammed with data for a plurality of messages, e.g., twenty-five messages, for increasing (e.g., up to fifty) the number of messages stored in the console. The latter is shown as having a slot 175 for insertion of the cartridge. It may also have a clock/calendar for computing the time and the date for a long span of years. The cartridge may have a non-volatile EEPROM chip therein, like the console, and may be programmed from the console 99 via keyboard 111. In a typical mode of use of the ink jet printing system of this invention, messages to be printed are entered in the system by typing on the portable terminal 109, displayed on the display 113 of the terminal and edited, and the message data is transmitted via line 117 from the terminal to the con¬ sole or message bank 99 and stored in the memory of the micro¬ computer of the latter. Data for up to twenty-five message lines of forty characters each, for example, may be stored in the console. The number of stored messages may be augmented by use of a cartridge 173. The printhead controller 93 for each printhead 7 which is to p int a message on the objects 3 being fed forward by the conveyor is programmed for control¬ ling the respective printhead to print that message by routing the data for that message from the console or message bank 99 to the microcomputer of the printhead controller by means of the appropriate set 103 of thumbwheel switches 105 and 107 and storing it in memory in the printhead controller.

Each printhead controller 93 is set for the direc¬ tion of feed of the objects 3 by the conveyor (left to right or right to left past the respective printhead) by means of the direction switch 167. It is also set for the desired spacing of the message from the leading end of the objects 3 by means of the delay-setting switches T1-T3, and set to run by means of the switch 165. As each object 3 travelling for- ward is perceived by the photocell 159, and after the time delay interval interposed by the setting of switches T1-T3, output signals from the microcomputer 95 of the printhead con¬ troller 93 via the output circuit 97 effects the relatively momentary energization of the solenoids 71 of the respective printhead 7 relatively momentarily to open the nozzles 9 for ejection of drops of ink on the moving target surface S of each object in a sequence to print the pattern of dots for the programmed message.

In another type of ins allation, referred to as a stand-alone installation, the console 99 is not used, the terminal 109 being di ect -connected to a printhead controller 93 as indicated at 177 in Fig. 6. In this type of installa¬ tion, the message to be printed by the so-connected printhead 7 is entered directly in the printhead controller 93 from the terminal 109, the latter may then be unplugged and removed, and the printhead will continue to print the same message un¬ til a new message is substituted.

Of special importance is the structuring of each jet J as an elongate tubular member 15 with the nozzle 9 constitu- ting a valve seat at the outlet end thereof and with the ball valve member 33 on the end of the solenoid-actuated valve stem or rod 31 engageable with the seat, as distinguished from a system such as shown in the aforesaid U.S. patent 4,378,564 wherein the jet valve is upstream from the jet nozzle, there may be a tendency for development of reflective pressure pul¬ ses in the ink passage from the valve to the nozzle, with con¬ sequent ejection of individual drops (which are sometimes referred to as "satellite" drops) on each pulse, resulting in spattered printing. This pressure pulsing and consequent spattering is avoided by the present invention wherein the nozzle is the valve seat and is located at the outlet end of the jet, so that there is no passage wherein reflective pres¬ sure pulses may develop between a valve seat and a nozzle. In view of the above, it will be seen that the several objects of the invention are achieved and other advan¬ tageous results attained.

As various changes could be made in the above con¬ structions without departing from the scope of the invention, it is intended that all matter contained in the above descrip- tion or shown in the accompanying drawings shall be interpre¬ ted as illustrative and not in a limiting sense.

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Claims

Claims 16

WHAT IS CLAIMED IS:

1. A system for ink jet printing of messages on objects being fed forward one after another in a predetermined path, said system comprising:

a plurality of ink jet printheads positioned adjacent said path to print the messages on the articles as they travel for¬ ward in said path;

each printhead comprising a plurality of ink jets arranged in a matrix and adapted for ejection of drops of ink across a gap to a surface of an object travelling by the printhead to print dots on said surface in patterns forming selected characters for said messages;

means for supplying ink to the jets;

a pluralit of electrically actuated valve means, one for each jet, each adapted for electrical operation for ejection of a drop of ink from the respective nozzle,

a terminal including a keyboard for entering message data,

a message bank having a microcomputer interconnected with the terminal for processing data received from the terminal and storing the data for a plurality of messages,

a plurality of controllers, one for each printhead, each in- eluding a microcomputer interconnected with the bank for pro¬ cessing data for a selected message received from the bank and storing the data,

-_OMPI_ means for effecting transfer of data for a selected message from the bank to a selected controller for storage in that controller ,

each controller having an output circuit interconnected with the microcomputer thereof and with the respective printhead for receiving output of data for the selected message from that microcomputer and converting the data to driving signals for the printhead valve means for actuating the latter to print the selected message.

2. A system as set forth in claim 1 wherein each jet comprises:

an elongate tubular member having an outlet nozzle constitu¬ ting a valve seat at one end thereof, said seat having an ori- fice for ejection of drops of ink,

said tubular member having an ink chamber therein for holding ink under pressure for delivery through the orifice, said chamber being defined by the valve seat and by means sealing against escape of ink from the chamber,

a valve stem extending longitudinally in said tubular member having a valve member at its end toward the seat engageable with the seat to block flow of ink through the orifice in the seat,

the valve stem being movable longitudinally in said tubular jet member for closing the valve member against the seat and for opening it for ejection of a drop of ink through the ori¬ fice. said ink supply means supplying the ink chambers of said tubu¬ lar jet members with ink under pressure,

and a plur ality of solenoids , one for each jet, each connected to a respective valve stem for actuating the latter .

3. A system as set forth in claim 2 having mount¬ ing means for the tubular jet members comprising an ink mani¬ fold for holding ink under pressure, said manifold having a front wall and a back wall spaced from each other and defining therebetween a manifold chamber for holding ink under pres- ^' sure, said walls having a plurality of holes receiving the tubular jet members with the latter extending through the holes in the back wall across the manifold chamber into the . holes in the front wall,

each tubular jet member being sealed in the holes and having a lateral port in communication with the manifold chamber for feeding ink from the manifold chamber to the ink chamber in the tubular jet member .

4. A system as set forth in claim 3 wherein each tubular member extends into the respective hole in the front wall with the valve seat at the said one end of the tubular member generally at the front end of that hole .

5. A system as set forth in claim 1 having means for sensing the speed of the objects , and means interconnec¬ ting said speed sensing means with the microcomputers of the printhead controllers with these microcomputers responsive to the speed to control the actuation of the valve means in ac¬ cordance with the speed.

' 3RSX⁴ _ι

OMPI 6. A system as set forth in claim 1 having means for sensing the passage of each object past a predetermined point in said path and means in erconnecting said object pas¬ sage sensing means with the microcomp ers of the printhead controllers for transmission of a start signal to each control module, said microcomputers imposing a time delay between the start signal input and the output oϊ data from said microcom¬ puters for controlling the spacing of the start of printing from the leading side of the object.

7. A system as set forth in claim 1 wherein the microcomputer of each printhead controller is operable to transmit the data for the message stored therein for printing either on objects moving from right to left relative to the respective printhead or from left to right relative to the respective printhead.

8. A system as set forth in claim 1 for serving a plurality of conveyors each having one or more printheads as¬ sociated therewith wherein the message bank has a plurality of ports each connectable to one or more printhead controllers for one or more printheads.

9. A system as set forth in claim 1 wherein the message bank is adapted to receive data storage means in which data for a plurality of messages is stored in addition to data for messages received from the terminal for selective trans¬ mission to the printhead controllers for programming the printheads.

10. A system as set forth in claim 1 wherein the ink supply means includes means for sensing depletion of the ink supply interconnected with signal means at the message bank or the terminal for signalling depletion of ink. ₁1. A sys tem as set for th in claim 10 wherein the ink depletion sensing means transmits a signal to the signal means via the interconnection between the printhead control¬ lers and the message bank .

12. Ink jet printing apparatus comprising:

a plurality of ink jets; .

means mounting the jets in a matr-ix for non-contact printing of patterns of dots to form characters on a target surface moving past the jets , by selective squirting of drops of ink from the jets ,

each jet comprising an elongate tubular member having an out¬ let nozzle constituting a valve seat at one end thereof , said seat having an orifice for ejection of drops of ink ,

said tubular member having an ink chamber therein for holding ink under pressure for delivery through the orifice , said chamber being defined by the valve seat and by means sealing against escape of ink from the chamber ,

the valve stem being movable longitudinally in said tubular jet member for closing the valve member against the seat and for opening it for ejection of a drop of ink through the or i¬ fice, means for supplying the ink chambers of said tubular jet mem- . bers with ink under pressure,

and a plurality of solenoids, one for each jet, each connected to a respective valve stem for actuating the latter.

13. Ink jet printing apparatus as set forth in claim 12 wherein the mounting means for the jets comprises an ink manifold for holding ink under pressure, said manifold having a front wall and a back wall spaced from each other and defining therebetween a manifold chamber for holding ink under pressure, said walls having a plurality of holes receiving the tubular jet members with the latter extending through the holes in the back wall across the manifold chamber into the holes in the front wall,

14. Ink jet printing apparatus as set forth in claim 13 wherein each tubular member extends into the respec¬ tive hole in the front wall with the valve seat at the said one end of the tubular member generally at the front end of that hole.

15. Ink jet printing apparatus as set forth in claim 13 wherein each tubular jet member has a tubular body member at its other end, constituting its rearward end, a resilient diaphragm in said body member having a central coup- ler extending forward and rearward, the valve stem being secured at its rearward end to the coupler, the solenoid for operating the valve stem being mounted on the rearward end of

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OMPI _ a solenoid support tube extending rearward from the body mem¬ ber, the solenoid having plunger and interconnected with the coupler at the rearward end of the latter via a drive wire estending through the support tube.

16. Ink jet printing apparatus as set forth in claim 15 wherein the drive wire is flexible and at least some of the tubes are bent to flare outwardly.