Pressurizing System For Ink Jet Printing Apparatus

Abstract

A pressurizing system for an ink jet printer is described that is mounted on a movable carrier, the carrier having an associated nozzle, charge ring, and deflection plates for generating information on a character-by-character basis or on a line-by-line basis, the carrier further including an ink supply reservoir and the entire assembly constituting an efficient structure operable at high speeds.

Description

REFERENCES OF INTEREST

The following IBM Customer Engineering Manuals are of interest:

"Selectric Printer Instruction Manual", January, 1966, Form No. 241-5032-2.

"Selectric" Typewriter, November, 1970, Form No. 241-5615-0.

"Selectric" Typewriter Service Manual Supplement, Form No. 241-5615-0 (Supplement).

BACKGROUND OF THE INVENTION AND PRIOR ART

Ink jet printing apparatus prior to this time has ordinarily incorporated nozzle assemblies and pumping and ink supply members as completely separate and independent structures. This has required the use of lengthy conduits or hoses, additional hardware, and more careful control of parameters such as pressure, temperature, and the like.

SUMMARY OF THE INVENTION

In accordance with the present case, an ink jet printing apparatus has a nozzle assembly mounted on a carrier for relative movement in relation to a document to be printed. Integrally formed with the carrier are a pump and ink supply that are relatively movable along with the nozzle assembly. The arrangement results in a compact, efficient structure and provides for required adjustments such as those pertaining to the jet stream itself and the relationship of the pressurizing system to the charging coil and deflection plates as well as adjustment of stream angle relative to the paper. This insures improved print quality and reduces maintenance requirements. Other aspects of the system are the elimination of flexible hose connctions, facilitation of automatic cleaning of the nozzle orifice and ink pressure chamber without contamination or dilution of ink in the supply tubes, and ability to cut the ink jet stream off and on automatially at the end of each line or after any character in a line, if a delay in printing is expected. An ability to cap and uncap the ink jet nozzle may be provided. The elimination of ink at relatively high pressure in flexible tubes reduces greatly the possibility of ink being sprayed on the operator of the apparatus. It also establishes a more constant pressure since flexible hoses required to flex during carrier movement lead to pressure fluctuations. These in turn affect printing quality.

OBJECTS

A primary object of the present invention is to provide a pressurizing system for an ink jet printing apparatus in which all elements of the system are integrated with the ink jet nozzle for a more efficient and reliable operation.

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings.

DRAWINGS

In the Drawings:

FIG. 1 is a block diagram of an ink jet printing apparatus incorporating pressurizing systems in accordance with the present invention.

FIG. 2 is a perspective view of an ink jet printer incorporating the pressurizing and printing systems on a movable carrier.

FIGS. 3a and 3b when combined as shown in FIG. 3 represent an exploded view of the pump and ink supply structures previously discussed in connection with FIGS. 1 and 2.

FIGS. 4a and 4b respectively represent a top elevation and a side elevation of the nozzle, ink supply, and pressurizing systems in relation to a document platen in the printer of FIG. 2.

FIGS. 5a, 5b, and 5c are elevational views of various kinds, illustrating electromagnetic actuating means and associated linkages for controlling the pumping structures of FIGS. 3a, 3b, 4a, and 4b.

DETAILED DESCRIPTION

Various elements concerned with the pressurizing system including the pump, ink supply, and nozzzle structures are designated by reference numerals 1-176 in the detailed drawings of FIGS. 3a, 3b, 4a, 4b, 5a-5c. For this reason, reference numerals in FIGS. 1 and 2 are predominately in the "200" Series.

FIG. 1 is a block diagram of an ink jet printing apparatus incorporating a nozzzle assembly 201, a crystal 105, nozzle 115, charge electrode 135, deflection plates 205a and 205b, and having an associated ink supply 55 with pump 208. Nozzle assembly 201 is positioned for formation, propulsion, charging, and deflection of drops in a stream 210 toward a document 212 to be printed. As is known in the art, drops are formed by vibration of crystal 105 under control of crystal driver 213 and are propelled from nozzle 201. Drops are variably charged by charge electrode 135 under control of charge electrode driver 214 which in turn is controlled by the sync control box 216 in accordance with characters from character generator 218. Other elements of the system include the master clock 220 that provides master pulses for determining machine operation, and a machine logic block 221 for controlling the various processes of the apparatus. Following charging of individual drops, they are deflected by means of a potential from terminal 222 applied across plates 205a and 205b in accordance with the strength of the charge placed on the drops by electrode 135. Any drops not required for printing such as drops 210b are directed to a gutter 165. Other drops, such as drops 210a required for printing are directed along various paths to document 212. Drops landing in gutter 165 are returned to ink supply 55 and conduit 227 for recirculation through the system.

If desired, currents generated in gutter 165 as a result of the drops passing therethrough can be used to determine synchronization following amplification by amplifier 230 comparision by comparator circuit 231 with a reference voltage from source 232 and application of a correction signal on line 233 to sync control 216.

A printer unit 235 shown in more detail in FIG. 2 includes the customary keyboard 236 and various other controls found in a printer such as the IBM "Selectric" printer described in the various customer engineering manuals referred to previously. Nozzle assembly 201 is mounted adjacent a platen 242 on which document 212 is positioned for printing. Nozzle assembly 201 is fastened to a carrier 9 that is slidably movable on shaft 241 adjacent to document 212 for printing of information on a character-by-character or line-by-line basis. Also positioned on carrier 9 are the pump structures 243 that are shown in greater detail in the other figures such as FIGS. 3a, 3b, 4a, 4b, 5a-c. Printer unit 235 includes a left margin switch 246 and a right margin switch 247 that are activated when the carrier reaches those respective locations to indicate the beginning and end of lines on document 212. Printer 235 may be activated from a data source, not shown, that may be any of various known types, such as a computer, a communication network, a magnetic card reader/recorder, a magnetic tape reader/recorder, etc.

DETAILS OF INK SUPPLY, PUMP, AND NOZZLE ASSEMBLIES

Reference is made to FIGS. 3a, 3b, 4a, 4b, and 5a-5c. Only so many of the reference numerals as are believed necessary to facilitate an understanding of the elevational views in FIGS. 4a, 4b, and 5a-5c are incorporated in those figures.

Carrier 9 is mounted in the "Selectric" printer frame similarly to a type head carrier. Print shaft 1, in addition to supporting carrier 9, provides the rotating motion to pump charging cam 3 via sleeve 2 which is free to traverse the distance between the side frames of the support casting with carrier 9 but which also rotates with print shaft 1 upon command to refill the pump with ink. Cam 3 and sleeve 2 are rotated by print shaft 1 via key 4. A partial rotation of cam 3 fills the pump by rotating rocker arm 6 clockwise about shaft 7. The clockwise rotation of arm 6 stretches springs 16 and 17 via arms 10 and 11 and set screws 12 and 13 and adjusting nuts 14 and 15. Set screws 12 and 13 press on ears 6a and 6b of bellcrank 6 and also provide a means of adjusting the force that springs 16 and 17 can exert on the pump. Springs 16 and 17 are hooked to bar 18 which is mounted to carrier 9 in slots 19. See FIG. 3b.

A bellows pump is described. Diaphragm and piston type pumps may be used instead. Rotating bellcrank 6 clockwise stretches bellows 28 that has its peripheral left hand flange clamped between flanges 27a and 35a of housings 27 and 35. The stretching force is translated from bellcrank 6 to bellows 28 by adjustable nut 25 and plunger shaft 26 whose flange is attached to bellows 28 and whose shaft portion is guided in housing 27. Housings 27 and 35 are attached via screws 29, only one being shown. Typically, in subsequent discussion, only one screw of each set is shown.

When bellows 28 is elongated, valve 60 is closed by force of spring 59 and vacuum created by the pump action, and valve 37 opens compressing spring 38.

Ink is drawn into pump chamber in housing 35. The ink is drawn from reservoir 55 thru filter 52 support screen 51 (that are mounted to tank 55 via flange 54 and screws 53) and thru hose 50 and filter 44 and support screen 42. The above filter and screen and valve 37 with its spring 38 are attached to housing 35 and sealed via seal 39, spacer 40, flange 46 and screws 48.

During the pump charge cycle described above a stream of ink under pressure continues to flow out of nozzle 115 to the gutter 165 and back to reservoir 55 thru hole 166. The continuing stream is accomplished as follows: The reserve or capacitance bellows 121 and its spring 123 are compressed when the pump is pressurized by force exerted by springs 16 and 17 and valve 60 is open and valve 37 closed. This action is initiated by turning cam 3 a partial turn so that cam follower portion of bellcrank 6 drops off the high point of cam 3. The pump is in this condition during a print cycle.

During the recharge, cycle valve 60 is closed, the energy stored in spring 123 and bellows 121 is sufficient to maintain a stream of ink thru the bolt 95, nozzle 115, charge ring 135 to the gutter 165. Capacitance or reserve bellows 121 with its spring 123 and plunger 122 are mounted to housing 62 and supported by housings 120 and 125 and screws 128. Nut 126 is used to adjust maximum downstroke of the bellows.

Bolt 95 is attached to strap 100 via tensioning nut 96. Nut 96 is torqued the proper amount to provide correct compressive pressure on piezoelectric crystal 105 which is captured between shoulder of bolt 95 and strap 100. The assembly just described is mounted to ears of bracket 88 by screws 106. Washer 90 and "0" ring 89 seal the ink path from bracket 62 to bolt 95. The right hand tennon of nozzle 115 fits into end of bolt 95. It is sealed to bolt 95 by nut 116. Housing 62 is attached to housing 35 and sealed to it by "0" ring 61. Valve 60 seats in housing 35 and is forced into its seat by spring 59 which seats in housing 62 thus providing a valved ink path from pump reservoir in housings 27 and 35 out thru nozzle 115.

The above described assembly is attached by screws through slots 35b in housing 35 to tapped holes 91 in bracket 88. Bracket 88 is mounted by four screws that extend thru slots 109 into tapped holes 110 of carrier 9. The function of valve 69 whose seat 68 is in housing 62 is to close off the ink flow from the pump and capacitance chambers thru the nozzle any time the machine is shut down or there is a power failure. The valve when closed also provides a by-pass so pressure level in bolt and nozzle is immediately reduced to atmospheric pressure "thereby preventing nozzle from dribbling." Valve 69 also provides a by-pass from pump chamber to capacitance chamber to provide for equalizing pressure in the two chambers when valve 69 is closed and a pump stroke is initiated.

The valve unit parts are mounted and are operated as follows: Solenoid 87 pulls link 86 which rotates bellcrank 85 clockwise, FIG. 3a. The forked portion 85a of bellcrank 85 presses on disc 80 which is attached to valve stem 73. This action opens valve 69, compresses spring 81 and causes the lower portion of valve 69 to seal against pliable valve seat 75 which is supported and mounted to housing 62. This prevents ink under pressure from pump chamber and capacitance chamber from bleeding out through port 74 and hollow valve stem 73 and tubing 47 to ink reservoir 55 during a print cycle or when ink is going to gutter during non-print but non-shutdown time. When the machine is shut down either intentionally or due to a power failure, spring 81 pressing on disc 80 actuates valves stem 73 and valve 69 upwardly so valve 69 is seated at 68.

Due to passage 70 and port 74 the ink pressure in nozzle 115 and bolt 95 can immediately bleed off to reservoir 55 and stabilize at atmospheric pressure. If pressure in the pump chamber is greater than pressure in the capacitance chamber it can equalize via by-pass 71.

With current connected to piezoelectric crystal 105 it stretches bolt 95 and then contracts forcing bolt 95 to stretch and contract with the crystal which shakes nozzle 115 transversely with respect to its axis. This breaks the stream of ink being ejected from nozzle 115 into drops so that they can be charged by charge ring 135 and deflected by deflection plates 205 away from gutter 165 to form characters on paper dependent on the amount of charge placed on each drop and the speed of carrier 9 as it moves to the right during a print cycle.

The design shown has adjustments for many parameters. An example is spacing between deflection plate and base plate. The charge, deflection and gutter system consists of parts and assemblies as follows:

Charge ring 135 is mounted in bracket 137 which carries tennons 136. Bracket 137 is mounted on bracket 138 with the center hole of charge ring 135 circumferentially aligned with stream of ink drops ejected from nozzle 115. The assembly is held together with screws 139. Base plate 145, which acts to direct zero charged droplets from charge ring to gutter, is mounted to bracket 140 via screws 146. Adjustment is provided to permit changing the surface of base plate 145 relative to the ink stream. Deflection plate 152 is mounted on the lower angular or curved surface of bracket 150 which in turn is attached to bracket 140 via screws 151. Adjustment is provided to permit changing the surface of deflection plates 205 relative to the ink stream.

The assembly consisting of brackets 140, 145 and 150 is snapped on to bracket 137 with forks 141 and 142 fitting about tennons 136 and the inside "U" portion of bracket 140 encapsulating the spherical portion of bracket 137.

The whole assembly is mounted to bracket 138 and is adjustable relative to charge ring 135, by manipulation of mounting screw-spring pairs 155-156, 157-158. Bracket 138 is now adjustably mounted to bracket 88 with screws thru slots 175 in 138 and tapped holes 176 in bracket 88. This adjustment permits setting charge ring 135 the proper distance from the end of nozzle 115. Gutter 165 collects all drops of ink that are not deflected to print characters on the paper. This ink is fed thru tube 165 into reservoir 55 thru hole 166. Gutter 165 is mounted in bracket 160. The gutter height can be adjusted relative to the stream of ink drops by set screw 167. The assembly is mounted by screws 161 to tapped holes 162 in bracket 138.

Reservoir 55 is filled thru cap 57. Baffles, such as baffle 56, retard sloshing of ink as carrier 9 traverses machine along shaft 241.

VARIANT OF VALVE AND SOLENOID FOR SHUTDOWN

A variation of the valve, solenoid, and associated structures operable during shutdown is illustrated in FIGS. 5a, 5b, and 5c. Solenoid 87a is mounted in a bracket assembly 250 fixedly mounted at 251. Solenoid 87a has an associated armature 252 with customary pivoting action at 253. Extremity 252a of armature 252 is movable from a deactivated position represented by the dashed line 254 to the solid line condition shown in FIG. 5b. Positioned for actuation by armature 252 is a bellcrank 260 pivotally mounted at 262. Bracket 264 is secured onto frame member 265 and supports bellcrank 260 for rotating action about pivot point 262. Also supported for pivoting action is a rotatable forked member 267 pivotally mounted at 268. Member 267 comprises a first forked portion 267a shown in FIG. 5a and a second forked portion 267b seen more clearly in FIG. 5b. Forked portion 267b is positioned for actuation of a disc 80a associated with valve 69 by means of the valve stem 73a. Energization of solenoid 87a, rotation of armature 252 and rotation of the members 260 and 267 effect opening and closing of valve 69 in a manner analagous to that previously described.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made without departure from the spirit and scope of the invention.

Claims

What is claimed is:

1. A pressurizing system for an ink jet printer having facilities for printing information on a document, comprising:

a carrier assembly, said carrier assembly incorporating a nozzle assembly for forming, propelling and deflecting a stream of ink drops toward said document in order to form information on said document;

a platen assembly for retaining and positioning said document during formation of information thereon;

means for relatively moving said carrier assembly and said platen assembly during formation of information;

ink supply means integrally mounted on said carrier assembly for supplying ink to said nozzle assembly as required during formation of information;

pump means interconnected between said ink supply means and said nozzle assembly, said pump means being operable to provide ink from said ink supply means to said nozzle assembly in predetermined quantities and at a predetermined pressure level; and

a capacitance bellows assembly interconnected with said pump means and operable in between refill operations to maintain a desired pressure level for ink supplied to said nozzle assembly.

2. A pressurizing system for an ink jet printer having facilities for printing information on a document, comprising:

a carrier assembly, said carrier assembly incorporating a nozzle assembly for forming, propelling and deflecting a stream of ink drops toward said document in order to form information on said document;

a platen assembly for retaining and positioning said document during formation of information thereon;

means for relatively moving said carrier assembly and said platen assembly during formation of information;

ink supply means integrally mounted on said carrier assembly for supplying ink to said nozzle assembly as required during formation of information;

pump means interconnected between said ink supply means and said nozzle assembly, said pump means being operable to provide ink from said ink supply means to said nozzle assembly in predetermined quantities and at a predetermined pressure level;

means for sensing machine shutdown, power failure, or other condition requiring standby of said printer apparatus; and

valve means interconnected with said pump means and operable to close off ink supply from said pump means to said nozzle assembly during said standby condition.

3. The apparatus of claim 2 wherein said valve means serves to equalize pressure in the system during refill operations.

4. The apparatus of claim 2, further comprising:

solenoid means interconnected with said valve means and operable to actuate said valve means to provide ink from said pump means to said nozzle assembly, as required during printing operations.

5. The apparatus of claim 2 wherein said pump means includes a pump chamber, and further comprising:

a capacitance bellows incorporating a capacitance chamber; and

means positioning said valve means between said pump chamber and said capacitance chamber to equalize pressure between said chambers during a refill operation, said valve means further serving to prevent ink under pressure from bleeding from said system during any print cycle or during non-printing intervals, and said valve means further serving to prevent supply to said nozzle assembly during shutdown.

6. The apparatus of claim 5 wherein said valve means incorporates at least a passage for said ink supply and an associated port enabling stabilization of ink pressure at atmospheric pressure, and said valve means further incorporating a by-pass enabling equalization of pressure in said pump means when it is greater than pressure in said capacitance bellows.