US 3787883 A
There is disclosed a jet drop recorder which generates and switches two parallel rows of jets. The drops from the two rows of jets are selectively charged by two corresponding rows of charge rings and then pass on opposite sides of an electrically conductive strip which in cooperation with other elements of the generator provides an electrostatic deflecting field to deflect charged drops into one or another of a pair of drop catchers. The electrically conductive strip is relatively thin and is maintained in a straight, non-deformed configuration by taut stretching between the catchers.
Description (OCR text may contain errors)
United States Patent [191 Cassill *Jan. 22, 1974 DEFLECTION ELECTRODE ASSEMBLY FOR A JET DROP RECORDER  Inventor: William Guy Cassill, McArthur,
 Assignee: The Mead Corporation, Dayton,
The portion of the term of this patent subsequent to Oct. 31, 1989', has been disclaimed.
 Filed: Dec. 20, 1972 ] App]. No.: 317,074
52] U.S. c1. 346/75, 317/3  Int. Cl. G0ld 15/18  Field of Search 346/75; 239/3, 15; 317/3  References Cited UNITED STATES PATENTS Houser 346/75 X Mathis 346/75 Lyon et a] 346/75 X Primary Examiner.loseph W. Hartary Attorney, Agent, or Firm-Lawrence B. Biebel et al.
[ 5 7] ABSTRACT There is disclosed a jet drop recorder which generates and switches two parallel rows of jets. The drops from the two rows of jets are'selectively charged by two corresponding rows of charge rings and then pass on opposite sides of an electrically conductive strip which in cooperation with other elements of the generator provides an electrostatic deflecting field to deflect charged drops into one or another of a pair of drop catchers. The electrically conductive strip is relatively thin and is maintained in a straight, non-deformed configuration by taut stretching between the catchers.
8 Claims, 5 Drawing Figures DEFLECTION ELECTRODE ASSEMBLY FOR A JET DROP RECORDER BACKGROUND OF THE INVENTION This invention relates generally to the field of fluid drop generation and the application thereof tov jet drop recorders of the type shown in Mathis US. Pat. No. 3,701,998. In recorders of this type there are a pair of rows of orifices which receive an electrically conductive recording fluid, such as for instance a water base ink from a pressurized fluid manifold, and eject the fluid in two rows of parallel streams. These recorders accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and thereafter depositing at least some of the drops on a moving web of paper or other material.
The above mentioned charging is accomplished by application of binary or ON/OFF charge control signals to charging electrodes positioned near each of the streams. As the drops separate from their parent fluid filaments they carry with them charges which are in effect samples of the charge control signals. Thereafter the drops pass through electrostatic fields which have no effect upon the uncharged drops but which cause the charged drops to be deflected for catching by one or the other of a pair of catchers which service the two rows of streams.
In order to accomplish such drop deflection in the limited space available in a compactly designed print head, it is necessary to provide a very straight and very thin deflection strip running the length of the active printing area and placed between the two catchers. Any irregularity or misalignment of the deflection strip will disturb the electrostatic fields present on both sides of the strip and interfere with the proper catching of the charged drops.
SUMMARY OF THE INVENTION In accordance with the practice of the present invention there is provided a very thin electrically conductive deflection strip which is aligned between the above mentioned catchers and placed under tension to avoid any disfiguration thereof. Preferably the deflection strip is stretched between a pair of catcher holders with one end of the strip being grasped by one of the catcher holders and the other end of the strip being grasped by a tightening block having a pair of screws passing therethrough. The screws extend in a direction parallel to the deflection strip for contact with a face of the second catcher holder. The deflection strip maybe positioned between the catcher holders in a slack condition and then drawn into a taut condition by adjustment of the tightening screws.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a recording head assembly;
FIG. 1a is a perspective view of a portion of the assembly of FIG. 1;
FIG. 2 is a cross section view through the assembly of FIG. 1;
FIG. 3 is a somewhat schematic representation of a preferred embodiment of an electrical circuit for the deflection strip; and
FIG. 4 is an enlarged and partially cut away view of a portion of one end of a recording head assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1 of the drawings it will be seen that the various elements of a head assembly 10 are assembled for support by a support bar 12. Assembly thereto is accomplished by attaching the elements by means of machine screws (not shown) to a clamp bar 14 which is in turn connected to the support bar 12 by means of clamp rods 16.
The recording head comprises an orifice plate 18 soldered, welded or otherwise bonded to fluid supply manifold 20 with a pair of wedge-shaped acoustical dampers 22 therebetween. Orifice plate 18 is preferably formed of a relatively stiff material such as stainless steel or nickel coated beryllium-copper but is relatively thin to provide the required flexibility for direct contact stimulation. Preferably dampers 22 are cast in place by pouring polyurethane rubber or other suitable damping material through openings 24 while tilting manifold 20 (orifice plate 18 being attached) at an appropriate angle from the vertical. This is a two step operation as dampers 22 require tilting in opposite directions (See FIG. l-A).
Orifice plate 18 contains two rows of orifices 26 and is preferably stimulated by a stimulator 28 which is threaded into clamp bar 14 to carry a stimulation probe 30 through the manifold 20 and into direct contact with plate 18. Orifice plate 18, manifold 20, clamp bar 14 together with a filter plate 32 and O rings 34, 36, and 38 (see also FIG. 2) comprise a clean package which may be preassembled and kept closed to prevent dirt or foreign material from reaching and clogging orifices 26. Conduit 40 may be provided for flushing of the clean package. Service connections for the recording head include a coating fluid supply tube 42, air exhaust and inlet tubes 44 and 46, and a tube 48 for connection to a pressure transducer (not shown).
Other major elements comprising the recording head are a charge ring plate 50, an electrically conductive deflection ribbon 52 and a pair of catchers 54. Catchers 54 are supported by holders 56 which are fastened directly to fluid supply manifold 20. Spacers 58 and 60 reach through apertures 62 and 64, respectively in charge ring plate 50 to support holders 56 without stressing or constraining charge ring plate 50. Deflection ribbon 52 is also supported by holders 56 and is stretched tightly therebetween by means of tightening block 66. Ribbon 52 extends longitudinally between catchers 54 as best shown in FIG. 2.
Catchers 54 are laterally adjustable relative to ribbon 52. This adjustability is accomplished by assembling the head with catchers 54 resting in slots 68 of holders 56, and urging them mutually inward with a pair of elastic bands 70. Adjusting blocks 72 are inserted upwardly through recesses 74 and 76 to bear against faces 78 of catchers 54, and adjusting screws 80 are provided to drive adjusting blocks 72 and catchers 54 outwardly against elastic bands 70. Holders 56 are made of insulative material which may be any available reinforced plastic board.
The fully assembled recording head is shown in cross section in FIG. 2. As therein illustrated coating fluid 82 flows downwardly through orifices 26 forming two rows of streams which break up into two curtains of drops 84. Drops 84 then pass through two rows of charge rings 86 in charge ring plate 50 and thence into one of the catchers 54 or onto the moving web of paper 88.'Switching of drops between catch and deposit trajectories is accomplished by electrostatic charging and deflection as hereinafter described. Coordinated printing capability isachieved by staggering the two .rows of streams in accordance with the teachings of Taylor et al U.S. Pat. No. 3,560,641. As taught in that patent, the drops in the forward row of streams (i.e. the row most advanced in the direction of web movement) are switched in a time reference frame delayed from that of the rear row by a time d/V where d is the row cation of a constant frequency, controlled amplitude,
stimulating disturbance to each of the fluid streams emanating from orifice plate 18. Disturbances for this purpose may be set up by operating transducer 28 to vibrate probe 30 at constant amplitude and frequency against plate 18. This causes a continuing series of bending waves to travel the length of'plate 18; each wave producing a drop stimulating disturbance each time it passes one of the orifices 26. Dampers 22 prevent reflection and repropagation of these waves. Accordingly each stream comprises an unbroken fluid filament and a series of uniformly sized and reqularly spaced drops all in accordance with the well known Rayleigh jet break-up phenomenon.
As each drop 84 is formed it is exposed to the charging influence of one of the charge rings 86. If the drop is to be deflected and caught, an electrical charge is applied to the associated charge ring 86 during the instant of drop formation. This causes an electrical charge to be induced in the tip of the fluid filament and carried away by the drop. As the drop traverses the deflecting field set up between ribbon 52 and the face of the adjacent catcher it is deflected to strike and run down the face of the catcher, where it is ingested, and carried off. Drop ingestion may be promoted by application of a suitable vacuum to the ends 90 of catchers 54. When drops which are to deposit on the web 88, no electrical charge is applied to the associated charge rings.
Appropriate charges for accomplishment of the above mentioned drop charging are induced by setting up an electrical potential difference between orifice plate 18 (or any other conductive structure in electrical contact with the coating fluid Supply) and each appropriate charge ring 86. These potential differences are created by grounding plate 18 and applying appropriately timed voltage pulses to wires 92 in connectors 94 (only one connector illustrated). Connectors 94 are plugged into receptacles 96 at the edge of charge ring plate 50 and deliver the mentioned voltage pulses over printed circuit lines 98 to charge rings 86.
Charge ring plate 50 is fabricated from insulative material and charge rings 86 are merely coating of conductive material lining the surfaces of orifices in the charge ring plate. Voltage pulses for the above purpose may be generated by circuits of the type disclosed in Taylor et al, and wires 92 receiving these pulses may be matched with charge rings 86 on a one-to-one basis. Al-
ternatively the voltage pulses may be multiplexed to de- 6 Deflection of those drops 84 which are to be caught is accomplished by setting up appropriate electrical fields between deflection ribbon 52 and each of the catchers 54. The preferred arrangement for this function is shown in FIG. 3 wherein catchers 54 and one side of an electrical potential source 51 are all connected to a common ground. The other side of source 51 is connected to deflection ribbon 52 thereby setting up a pair of equal strength, oppositely directed electrical deflection fields. As illustrated in FIG. 3 with the ground at the positive side of source 51, it is necessary that drops 84 be charged negatively in order to be caught. However, it is also possible to obtain mutual outwarddeflection of the two curtains of drops 84 by charging the drops positively and reversing the terminals on source 51.
It will be appreciated that deflection ribbon 52 must be very thin, and straight for proper operation in a compactly arranged head. Moreover the deflection ribbon must be relatively tough and electrically conductive. Thus in preferred embodiment the deflection ribbon is fabricated from stainless steel about 0.010 inches thick. However, even stainless steel is flexible and readily deformable at such thicknesses, and therefore a special arrangement is employed to meet geometrical design requirements for the deflection ribbon. Accordingly deflection ribbon 52 is provided with an enlarged head 69 at each end and is stretched between catcher holders 56 as above mentioned. One of the heads 69 is grasped by the left hand holder as viewed in FIG. 1, and the other head 69 is grasped by tightening block 66. A lead wire 53 is soldered to one of the heads 69 as illustrated.
The operation of tightening block 66 is best illustrated in FIG. 4 wherein it may be seen that screws 67 extend through the tightening block to bear against a face of catcher holder 56. Deflection ribbon 52 extends through a slot in tightening block 66 so that its enlarged head 69 may rest against the tightening block face. Thus screws 67 may be initially adjusted so that there is sufficient slack in deflection ribbon 52 for ease of head assembly. Later after catcher holders 56 are mounted in place with deflection ribbon 52 extending therebetween, screws 67 may be tightened to draw the deflection ribbon longitudinally and stretch it to a taut condition.
While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention.
What is claimed is:
1. In a twin row drop generator comprising means for generating two parallel curtains of drop streams, means for selective charging of the drops in said streams, and a pair of opposed catchers for catching of drops so charged; a deflection electrode assembly comprising:
an electrically conductive deflection ribbon oriented parallel to said curtains of drops and extending therebetween,
means for grasping said deflection ribbon at two spaced support points along the extent thereof and supporting said deflection ribbon in spaced relation to said catchers, and means for adjusting said grasping means to extend the distance between said support points and stretch said deflection ribbon to a taut condition. 2. Apparatus according to claim 1 said deflection ribbon being positioned midway between said catchers.
3. Apparatus according to claim 1 wherein said catchers are supported by a pair of catcher holders and said grasping means comprises a tightening block and for selective charging of the drops in said streams, and a pair of opposed catchers for catching the drops so charged; a deflection electrode assembly comprising;
an electrically conductive deflection ribbon oriented parallel to said curtains of drops and extending therebetween along a line midway between said catchers,
means for grasping and supporting one end of said ribbon, and
means for grasping the other end of said ribbon and stretching it to a taut condition.
7. Apparatus according to claim 6 said last named means being longitudinally adjustable for assembling said drop generator with said deflection ribbon in a slack condition and thereafter adjusting the deflection ribbon to said taut condition.
8. Apparatus according to claim 7 said deflection ribbon comprising a stainless steel strip approximately 0.010 inch thick and provided with an enlarged head at each end thereof.