CA1078666A - Lithographic moisture system and method - Google Patents
Lithographic moisture system and methodInfo
- Publication number
- CA1078666A CA1078666A CA277,095A CA277095A CA1078666A CA 1078666 A CA1078666 A CA 1078666A CA 277095 A CA277095 A CA 277095A CA 1078666 A CA1078666 A CA 1078666A
- Authority
- CA
- Canada
- Prior art keywords
- roll
- moisture
- ink
- transfer roll
- receptive
- 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
- B41F—PRINTING MACHINES OR PRESSES
- B41F7/00—Rotary lithographic machines
- B41F7/20—Details
- B41F7/24—Damping devices
- B41F7/26—Damping devices using transfer rollers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41L—APPARATUS OR DEVICES FOR MANIFOLDING, DUPLICATING OR PRINTING FOR OFFICE OR OTHER COMMERCIAL PURPOSES; ADDRESSING MACHINES OR LIKE SERIES-PRINTING MACHINES
- B41L25/00—Devices for damping printing surfaces, e.g. moistening printing surfaces in connection with lithographic printing
- B41L25/02—Devices for damping printing surfaces, e.g. moistening printing surfaces in connection with lithographic printing using friction rollers
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Rotary Presses (AREA)
- Inking, Control Or Cleaning Of Printing Machines (AREA)
Abstract
Case No. 1-750110(2) Applicant: Saied Abd-Elrahman Mabrouk Title: LITHOGRAPHIC MOISTURE SYSTEM AND METHOD
ABSTRACT OF THE DISCLOSURE
A lithographic duplicator is provided with a moisture train which has self-balancing properties and embodies the formation of a nip between an ink covered roll and a hydrophilic moisture transfer roll with the latter feeding moisture to the surface of the ink covered roll, the ink covered roll being driven in time with the printing cylinder and the moisture covered hydrophilic roll being driven solely by its contact with the ink covered roll.
ABSTRACT OF THE DISCLOSURE
A lithographic duplicator is provided with a moisture train which has self-balancing properties and embodies the formation of a nip between an ink covered roll and a hydrophilic moisture transfer roll with the latter feeding moisture to the surface of the ink covered roll, the ink covered roll being driven in time with the printing cylinder and the moisture covered hydrophilic roll being driven solely by its contact with the ink covered roll.
Description
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BACKGROUhlD OF T}IE INVL~NTION
This invention relates to lithographic duplicating and especially to the control of mois~ure application to ~he master during printing.
The problem of moisture control has been a persistent one, and many different types of moisture application systems have been developed with varying degrees of success. One fairly standard construction elnploys molleton covered rolls which are moisture absorptive and provide a reservoir situation which proves rather effective under the control of a trained operator, but in the hands of untrained people can be difficult to manage. For example, a slightly low moisture setting will eventually cause the molletons to dry out and ultimately ink up which requires a complex molleton changing procedureg and excessi~ely high moisture setting, on the other hand, will eventually cause the molletons to become over-wet and neces-sitates delaying printing opera~ions until they can be dri~d ou~ sufficiently to proceed. In addition9 of course, molleton covers present the familiar built-in problems of lint pro-duction and a tendency to irregularity of the roll surface.
A number of moisture sys~ems which are free of molleton coverings ~and of the attendant reservoir effects) have been develop~d, and while they escap~-~he above-mentioned dra~backs, they are still significantly reliant upon trained operator control because of their sensitivîty. That is to say, very slight changes in adjustment, or changes in moisture demand ~y the master environmental conditions of humidity, run length, ink temperature or conditlon due $o previous running or non-running, can cause the moisture situation to shift qllickly
BACKGROUhlD OF T}IE INVL~NTION
This invention relates to lithographic duplicating and especially to the control of mois~ure application to ~he master during printing.
The problem of moisture control has been a persistent one, and many different types of moisture application systems have been developed with varying degrees of success. One fairly standard construction elnploys molleton covered rolls which are moisture absorptive and provide a reservoir situation which proves rather effective under the control of a trained operator, but in the hands of untrained people can be difficult to manage. For example, a slightly low moisture setting will eventually cause the molletons to dry out and ultimately ink up which requires a complex molleton changing procedureg and excessi~ely high moisture setting, on the other hand, will eventually cause the molletons to become over-wet and neces-sitates delaying printing opera~ions until they can be dri~d ou~ sufficiently to proceed. In addition9 of course, molleton covers present the familiar built-in problems of lint pro-duction and a tendency to irregularity of the roll surface.
A number of moisture sys~ems which are free of molleton coverings ~and of the attendant reservoir effects) have been develop~d, and while they escap~-~he above-mentioned dra~backs, they are still significantly reliant upon trained operator control because of their sensitivîty. That is to say, very slight changes in adjustment, or changes in moisture demand ~y the master environmental conditions of humidity, run length, ink temperature or conditlon due $o previous running or non-running, can cause the moisture situation to shift qllickly
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either to a low moisture or to an over-wet condition with the result that copies are damaged and time can be lost in restabili~ing the system, unless a skilled alert operator is available to prevent the condition from maturing unduly, or to reestablish correct operating conditions quickly once the aberration is recognized.
The present invention has as its object the provision of a moisture control arrangement which will avoid the drawbacks of the previously mentioned molleton and non-molleton systems, and which will have an inbuilt degree of stability tending to keep the moisture forwarding effect of the system at a value suited to the particular conditions currently existing.
This na~ural stability should be such that within a reasonable range of conditions, the system will be self-adapting for fairly extended periods so as to feed slightly more or slightly less moisture to the master as the occasion demands, without operator intervention, and thereby to permit successful operation of lithographic duplicators who are not highly ex-perienced.
According to the invention, there is provided a moisture system for a lithographic duplicator including a rotary master cylinder adapted to carry a master, said system comprising: an ink-receptive roll having a surface and being adjacently positioned in a substantially fixed axial relationship with the master cylinder for transferring moisture from its surface to ~he surface of the master; means for maintaining on the surface of said ink-receptive roll a continuous film of lithographic ink; means for positively driving said ink-receptive roll in time with the master cylinder; a moisture ~-transfer roll with a hydrophilic surface for transferring moisture from its surface to the ink film on the surface of said ink-receptive roll, said isture transfer roll being solely driven in a rotary direction by nip forming surface contact with the combination of th0 moisture layers and ink layer between said moisture transfer roll and said ink-receptive roll;
means for presenting an adjustably determinable supply of moisture to the ambit of said moisture transfer roll surface; and means for applying to said ~ -moisture transfer roll a preselected retarding torque whose value varies ~ _3_ . . ......................... . : . . ~. : :-: .
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~'78~66 monotonically with the rotary surface speed of said transfer roll; said transfer roll being responsive to the combination of the preselected retard-ing torque of said applying means and the magnitude of the driving effect :~
of the nip contact of said ink recep~ive roll with said transfer roll for -developing a surface speed during normal printing operation of between 10 per-cent and 50 percent of the surface speed of said ink-receptive roll; said surface speed of said moisture transfer roll varying as an inverse function of the thickness of the moisture on said transfer roll such that said transfer roll rotates more rapidly to transfer more moisture to said i.nk-receptive roll as more moisture is required by the master from said ink-receptive roll and less rapidly to transfer less moisture to said ink-receptive roll as less moisture is required by the master from said ink-receptive roll.
The method of the invention for providing moisture to a master cylinder of a lithographic duplicator comprises the steps of providing, at least as part of a roll train having contact with the master surface, a roll with an ink-receptive surface and positively driving the same in time with :
the master cylinder; placing a hydrophilic transfer roll in drlven, nip forming, surface contact with moisture and ink layers lying between the hydroph}lic transfer roll and the ink-receptive roll to transfer moisture from : ~ its surface to the surface of the ink receptive roll so that the ink-recept-ive roll acts by way of the moisture and ink layers as the sole driving ~:~
:. :,, -influence on the transfer roll; maintaining on the surface of said ink- ::
receptive roll a continuous film of lithographic ink; making available to . the ambit of the transfer roll surface an adjustably determinable supply of moisture; applying to the transfer roll a retarding torque whose value ~ ~
varies monotonically with:the speed of rotation of the transfer roll and : : -controlling the driving effect of the nip contact between the transfer roll and ink-receptive roll, and the retarding effect of said retarding torque so ~ -as to have a combined effect resulting in a transfer roll surface speed during normal printing operation of between 10 percent and 50 percent of the surface speed of the ink-receptive roll and further causing the surface speed :
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of the transfer roll to vary as an inverse function of the moisture on the transfer roll such th~t the transfer roll rotates more rapidly as more moisture is required by the master and less rapidly as less moisture is required by the master.
The moisture train described herein includes a roll which is oleophilic and which receives and maintains on its surface a thin film of lithographic ink by reasons of direct or indirect contact with the master surface. This roll is power driven in time with the master cylinder, by which is meant that its rotation rate is directly linked mechanically to that -3b- : :
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of the master cylinder, ei~her at the same surface speed or at some otll~r ~urface spee(l having a specified substantially constant relationship thereto. This oleophilic roll is also made to run in contact with a moisture transfer roll whose surface is primarily hydrophilic, and which is driven s.olely by a nominal or non-film-control pressure contact between its surface and that of the ink covered roll via the shear resistance offered by the intervening layers of ink and moisture. Moisture is fed to the transfer roll by any suitable moisture supply 10 system which will carry an adequate moisture flow, allowing the transfer roll to accept from the system any amount of moisture ~hich is currently being required by its speed of rotation, and in which the speed of ro~ation of the transfer roll is gov-erned by mechanism applying a restraining torque to the rotation o~ the transfer roll, which mechanism is characterized by exe~ting a restraining efect which increases monotonically as the speed of the transfer roll rotation increases.
It has been discovered that under these circumstances the transfer roll will take on~ to a certain degree 9 the character of a self-balancing device and will tend to rotate more rapidly as more moisture is required by the master and less rapidly as less moisture is required by the master~ thereby forwarding more or less moisture respectively to the ink covered roll and thus to the master surface, In this fashion the transfer roll tends to remain centered at a speed providing a balanced condition such that the moisture being supplied to the master remains substantially equal to that being re~uired by the master at the momen~, and such that the speed of rotation can shift through a certain range of speeds as slight changes in moisture requirement occur, regardless of the reason.
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In the drawings: ~
Figure 1 is a vertical elevation, partly in section of a portion ~ -of a lithographic duplicator showing especially the master cylinder and the ink and moisture trains cooperating therewith; and showing one position of the moisture ductor in broken lines, and another in solid lines;
Figure 2 is a fragmentary elevation showing one type of drive for the fountain roll; and Figure 3 is a longitudinal section to a larger scale of an exemplary conventional arrangement for providing an axially reciprocatory motion for a moisture roller.
Referring to the drawing, the master cylinder 10 is served by a conventional ink train 12 and a moisture system 14.
The moisture system 14 includes a fountain 16 receiving a fountain roll 18 having a hydrophilic surface, a ductor roll 20 mounted on an oscillating arm 22, and a moisture transfer roll 24 which has a hydrophilic surface. The transfer roll is in contact with the surface of a moisture form roll 26 having an oleophilic surface which runs in contact with a master ;
M on the surface of the master cylinder 10. A reciprocating distributor soll 28, likewise oleophilic, rides in contact with the moisture form roll 26 and by an inte m al cam mechanism shifts axially back and forth to level the ink layer and moisture deposit on the surface of the form roll 26 in a :~..
known manner. One conventional form of cam mechanism which will serve for this purpose is illustrated in Figure 3 wherein roller 28 is shown as mounted by bearings 60 on a nonrotary shaft 62 to~which is pinned a barrel cam 64 with a double reverse helix groove 66. A sleeve 68 is integral with the roll 24 -~
and rockably retains a dog 70 ;~
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:~786~;6 which has a tip riding in ~he groove 66. Members 72 affixed to the ends of the shaft 62 engage loosely in any suitable mating grooves or aperatures on the frame and consti~u~e one of several conventional means -for preventing rotation of the shaft 62 without influencing its ~ertical location.
For convenient reference the moisture system is divided into the moisture supply module 14A and the moisture flow control module 14B, and it is with the latter that the present invention is primarily concerned.
Referring to the moisture supply module 14A which is essentially conventional, the surface of the foun~ain roll is hydrophilic. Usually this roll is of metal, e.gO aluminum with a ma~te surface, or has a tin-nickel plating or chrome plating on an a~uminum or s~eel support. However, other hydrophilic materials, including nonmetallic compositions~ can be used as the surfacing material for the fountain roll In many conventional systems the ductor roll 20 is covered with a molleton cloth which has certain moisture reser~oir properties, and such a roll is not altogether unsuit-able for the purposes o~ the present invention However, the preferred arrangement employs at this location a roll of ` synthetic elastomeric composition in which has been dispersed a high percentage of short fibers of suitahle composition such as regenerated cellulose, and which presents a matte surface tha~, while not significantly water absorptive, is adequakely hydrophilic and oleophobic when wet and exhibits signiicant moisture attracting and carrying properties.
As is customary, the foun~ain roll 18 is stepped by a ; suitable ratchet mechanism in ~ime with the rotation of the .
; - 6 -~786G6 master cylinder at a rate (smoothed or average rate, that is) which is a~justable, say between 0 RPM and 30 RPM, to provide for increase or decrease in the amount of moisture being forwarded by the system. A setting of perhaps 10 to 20 RPM is representative for moderate circumstances at currently customary machine speeds.
As shown in Fig~ 1, the fountain roll 18 is stepped in a rotary direction opposite in sense to that of the transfer roll 24. Therefore, as the ductor roll 20 swings back and forth it is driven in opposite directions, first in one direction (counterclockwise as seen in Fig. 1) by its contact with the fountaln roller, and then in the opposite direction ~clockwise as seen in Fig. 1) by its contact with the\transfer roller 24.
~ ~ig. 2 illustrates such a conventional adjustable drive .; mechanism wherein the fountain roll 18 (not shown in this view) is drivingly connected to the ratchet wheel 40 which is stepped in the customary fashion by an oscillating drive link 42 carrying a drive pawl 44 meshab:Le with the teeth of the ratchet ` and urged towards the same by a spring (not shown~. The link 42 is powered by any suitable rotary machine element 46 through a connecting link 48 to reciprocate~ for example, at about 7 cycles per second. In order to manually adjus~ the amount of rotation derived from each stroke of the pawl 44, a cam or shroud 50 is arranged to coact with a follower pin 52 on the pawl ~o prevent its meshing with.~the ratchet except where the sur~ace of the cam is relieved , as at 54, to permit sueh ; contact. The point of first contact of the pawl with the ~ .
ratchet can be determined by the angular setting of the cam S0 and this is controlled by the handle 56, the cam setting being held by a suitable detent mechanism 580 While the conventional type of drive for the fountain ~ roll has been described it will be understood that other ; arrangements will work equally well, and one alternative that ~7~36~6 suggests itself is an arrangement for continuously rotating the ~ountain roll by means of a separate variable speed electric motor powering the shaft of the fountain roll 18, with suitable manual speed setting control for the motor.
The oscillating motion of the arm 22 which carries the ductor roll 20 is also caused by a conventional drive from the duplicator mechanism, the arm oscilla~ing at a fairly high rate, for example about 2.8 cycles per master revolution or about 7 cycles per second for machine speeds currently in common use.
Turning now to the moisture flow control module 14B, the moisture form roll 26 is smooth sur~aced and of a rubbery material, preferably a synthetic elasomer o durometer in the range of 20 to 40 on the Shore A scale. The roll 26 is driYen by conventional gear.ingl preferably at the same surface speed as the master cylinder 10. Running in friction contact wi~h the form roll 26 is a distributor roll 28 of material similar to that used for the roll 26. Before the duplica~or is put in operation~
light films of ink 30, 32 are placed on the rolls 26 and 28, and these rolls, being oleophilic, remain inked up at all times 20 when the machine is operating 9 since the roll 26 runs in contact with the master which continually rèceives an ink supply from the ink train 12. As previously no~ed the roll 28 has a cam - inspired axially reciprocating movement to maintain the ink film at a uniform thickness at all times.
2S The transfer roll 24 is constructed of a material pro-viding a suitahle hydrophilic surface as discussed above for the hydrophilic fountain roll 18, and is driven only by the influence it receives from the roll 26 via the nip between ; itself and the roll 26 which experiences only nominal or non-30 film-control pressure. In normal operation the roll 24 carries a ~78666 film of mois~ure on i~s surface as shown at 34. This moisture is supplied and continuously replenished by the moisture su~ply module 14A and as the roll 24 rotates, it transfers portions of this film, via the ink layer 3n, to the surface of a master M on the master cylinder 10, which captures the moisture and carries it away as rapidly as the background areas of the master require added moisture. It is thought that the transferred moisture perhaps in part forms an emulsion with at least the surface of the ink layer 30 and in part supplies a water film 36 overlying the ink layer. Whatever the exac~ mechanism~ however, moisture is indeed carried to the surface of the ma~ster by this composite layer of ink and moisture. While not necessarily required, the preferred arrangement provides a roll 24 which is equipped with a cam for axial reciprocation to improve the levelling action of the mo~sture deposit on roll 24, which arrangement may be, for example, identical with that shown in Pigo 3 for distribution ~oll 28.
It has been discovered in connection with the present in-~ention that the roll 24 does not necessarily rotate at a constant surface speed in spite of the fact that roll 26 is driven at a substantially constant speed for an~ giYen speed setting of the duplicator, and that this variation in speed does indeed per~orm an important function in relation to the improved operation of the system.
It appears likedly that the thickness of the moisture film 34 (indicated as t in Fig. 1) particularly its thickness at the nip of the rolls 24 and 269 lS what controls this speed, and that as t increases the torque necessar~ to generate shearing action in the film 34 decreases so that the drive becomes less ; 30 positive and the roll 24 tends to exhibit increased slip and to turn more slowly. On the other hand, as t decreases, it appears that the torque necessary to generate shearing action in the g ~ 7 8~
film 34 increases so that the drive becomes more positive and roll 24 tends to exhibit decreased slip and thus to speed up.
In fact if the roll 24 dries out completely so as to receive its drive directly through the film of tacky lithographic ink 30 on the roll 26~ its surface speed becomes substan~ially identical to that of the roll 26. As the postulated thickness t of the moisture layer is gradually increased, this results in progressively slower rotation of the hydrophilic transfer roll 24, which appears to be directly responsive to this thickness.
As can be seen from the foregoing dis~ussion, the pressure between the rolls 24 and 30 is quite light since it in no sense controls the moisture film thickness or interferes materially with the changes in thickness above-described. It is merel~
sufficient to insure the possibility of an effective drive at virtually equal surface speeds of the two rolls 24 and 26 if the moisture film were not present. As such, the pressure in question is herein iden~ified as nominal or "non-film~control pressure".
In order for the roll 24 to slow down promptly as t in-creases and driving torque decreases 9 there must of course be certain retarding factors, and these are found to act most effectively when they are of such character that their torque value increases monotonically as the speed of the transfer roll 26 increases (or, conversely, decreases as the speed of the roll 25 decreases). While this would undoubtedly be very efective i~
the increase were directly proportional to speed, this is not seen as a requirement, and any arrangement showing significant increase in retarding torque with increase in the speed of ~7 ~ ~ 6 roll 24 is thou~ht ko give an effective and fully operative result in terms of causing the speed of roll 24 to approximate proportionality to the wa~er film thickness in an inverse re-lationship. It is note~, however~ that conventional bearing friction loadings and the like, customarily present in machinery of this sort, normally provide a restraining torque answering the above description.
In the particular arrangement shown, retarding torque is applied in various ways. For one, the bearings of the shaft supporting ~he trunnions of the roll 24 present a signifi-cant retarding friction. Primarily, however, the ductor roll 20 which is periodically in contact with the roll 24 is so adjusted that its arc of motion will tend to carry it slightly beyond the point of surface contact with the roll 24 and thereby place a momen~ary interference pressure on the transfer roll. Other frictional components may enter into the picture as well, such as the friction in the standard cam dri~e arrangement i the roll 24 is caused to reciprocate axiall~ as above-described, plus the ~iscous resistance generated with the composite layer when thus reciprocated. The combined effects of these ~arious loadings respond to the above descrip*ion and pro~ide the type o re-s~rainin~ torque preferred. Certain of these retarding e~ec~s, particularl~ that o the ductor contact 9 can be arranged to be mechanically adjustable b~ conYentional means 50 as to provide for initial set-up of ~he system to optlmum restraining values.
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It will be understood, of course, that other types of mechanisms for generating the requisite type of restraining torque are also contemplated, for example, fluid dynamic braking means applied to the shaft of the roll 24, electromagnetic braking, and any other sort of restraint torque generating device providing the properties described above will serve the purpose.
To illustrate generally how a system is set up to operate in accordance with the invention, the means, whatever it may be, for applying restraining torque to the ~ransfer roller 24, is adjusted by the assembler or serviceman to provide, in normal : operation, a load sufficient to significantly reduce its surface speed below that of the ink carrying roll with which it is in contact and by which it is dri~en. This restraint might be lS stated i~ terms of torque values, but since these are extremely difficult to measure, interpret and apply, it is deemed more effective to identify the load in practical mechanical terms.
For example, the transfer roll should normally run in a range ; of between about 10~ and about 50% of the surface speed of the 20 inked roll. This can be readily determined by actually measur- :
ing the RPM of each~ converting to surface speed and comparing~
As a practical matter, however, m the construction shown, the transfer roll 24 and the distributor roll 28 are about the same diameter and are in sufficiently close proximity that the .
2S assembler or service technician can readily make a visual comparison of their speeds and determine that the speed re-lationship is well within the range indicatedO The effective moisture supply setting of the handle 56 will depend~ of course, ; on the particular location of the speed ratio within this range ~1378~ 6 of speed ratios, but assuming that l~he proper complementary moisture supply setting is identified in each case, the operatlon at one speed ratio is altogether as effective as at any o~her within the range, The normal speed ratios referred to are, of course, under circumstances of normal stable state running while producing copies of acceptable quality.
In practice, of course, the appropriate loading adjust-ments are predetermined by laboratory tests and specified in terms of adjustment set~ings for the particular design of equipment under considerationO Such specified settings are effective, because the range of permissiblè loading values has very substantial latitude allowing for any reasonable degree of variation in the equipment, To summarize the operation briefly, the device of the `~ 15 inventi~n will be understood as providing an improved type of moisture application for lithographic duplicators which avoids the overrun problems assignable to molleton or other reservoir type systems, and on the other hand provides a quick response device which9 nevertheless, avoids undue sensitivity ~nd affords operating latitude sufficient in amount that moisture settings can be easily made without undue demands on the skill of the o~erator.
The control which the operator exerts on the moisture supply in a system of this type normally relates to the speed - 25 of rotation of the fountain roll 18. The conventional ratchet mechanism heretofore described can be S8t, US ing the handle 56, to step the roll at a wide range of speeds, forwarding more or less moisture along the moisture train, If the setting made by the operator corresponds exactly to the amount of moisture bein~
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taken up by the surface of the master under the prevailing conditions J then there is proper operation and no flooding or starving occurs. Consequently, properly printed copies issue continuously from the duplicator. However, with the usual moisture system which is devoid of reservoir properties (i.e.
the usual non-molleton system) any deviation from the proper setting quickly shows up as flooding and weakening of the image if too high, or starvation and the appearance of spreading, plugging and background if too ].ow, so that the operator must be aler~ to keep the system in proper balance, and adjust it periodically to accommodate changing conditions.
While the system as above-described does not totally relieve the operator of the necessity for making moisture control settings, the requirement placed on the operator is merely that he find an adjustment for the speed of the fountain roll ~or the output of some other moisture supplying module) so that at least sufficient moisture is being made available to the roll 24 to meet the needs of the master, plus ~n extra safety margin of a small amount to remove any possibility of tempor~ry moisture starvation, When a sett.ing such as the foregoing is achieved, the system 14B of Fig. 1 will exert the requisite control as fol~ows.
1. If conditions should change slightly so that the master is dsmanding and taking slightly less moisture 9 the thickness t of the moisture film 34 on the roll 24 ':
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will slightly increase. This causes the speed of ~he roll to slightly diminish. Due to its diminished speed the roll 24 will take slightly less moisture per unit timc of contact from the surface of the ductor roll 20, and will pass slightly less moisture per unit time to the surace of the form roll 26.
2. Conversely if the conditions should change so that the master requires and takes more moistuTe, the thickness t of the moisture film 34 on the roll 24 will slightly decrease. This causes the speed of the roll to slightly increaseO Due to its increased speed the roll 24 will withdraw slightly more moisture per unit time of contact from the surface of the ductor rQ~l 20, and will pass slightly more moisture per unit time to thc surface of the form roll 26, It will be understood that if the setting of th moisture supply being provided by the module 14A is totally ou~ of scale in either direction with the requirements of the master under the existing humidity, ink temperature and ink working conditions, then the balancing action proYided by the module 14B
will probably be unable to compensate for this discrepancy with sufficien~ alacrity to be functional. However, so long as the 1 setting of the moisture supply is a reasonable approximation of ; the requirements at the master, the accommodation will be substantially complete, and further attention to the moisture adjustment will be required only as a gross change in conditions occurs.
~7~666 The signi-fican~e of the foregoing paragraph is illustrated by the fact that it has been found possible to operate with the system illustrated and described under circumstances such that, with fairly continuous running, a duplicator will frequently 5 run all day long without adjustment of the moisture system ex-cept for a few settings to gradually increase the moisture sup~ly during the initial warm-up period. It has even occurred that with a fortuitous high limit setting at the outset, a single additional increased setting of the moisture system after partial warm-up was all that was required during a day of fairly continuous running.
The latitude provided by this invention is indeed suf-ficient that the instruction manual for the operator can provide a table of settings for the moisture supply module based on relative humidity, ambient temperature running condition (e.g.
start-up, 300 to 1000 copiesl over 1000 copies, etc.), and these settings will normally proYide a sufficiently accurate guide that, if carefully applied will make refinements in the setting on the basîs of observed operation virtually unnecessary.
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Since one o the most troublesome responsibilities for the operator of a lithographic duplicator is the monitoring of the moisture system9 and because the failure to successfully execute this responsibility is-so costly in lost time and copy paper, it can be understood that this invention provides an important advantage to the operator, and opens up the use of the lithographic duplicator, on a practical basis to operators of much less skill than heretofore required.
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In the non-molleton form of the presen~ invention, the benefit common to such non-molleton, fast response systems, namely the quick transition from dry condition to print-ready condition, ~requiring perhaps 15 ~o 20 revolutions) 9 is presen~
here. The fast response, however, is obtained without incurring highly objectionable sensitivity which is so characteristic of systems of this character.
An additional benefit is the manner in which the system identifies itself to the operator as being substantially in proper running condition. At the start of operation, or if there should be an interruption for any reason~ such as a paper jam, the operator can merely direct his attention to the hydrophilic roll 24 upon starting up. I the system is in an excessively dry condition, ink deposits will appear on the roll surface When adequate moisture has been moved to the nip the deposit~ will promptly disappear and paper feed can be started.
On the other hand, if aberrant operation has somehow flooded the system, the roll 24 will have stopped turning or will be turning very slowly, in which case the operator merely waits until the roll 24 attains substantial speed and then is free to start the paper feed.
~ hile the foregoing description has proceeded on the basis of employing a special inked up roll 26 as being the moisture form roll, it is important to understand that this particular arrangement is not essential to the operativeness o the invention. The hydrophilic transfer roll may make contact with any ink covered roll, for example with the form roll forming a portion of the ink train, or with one of the o~her ink covered rolls of the ink train9 and such an arrangement is to be considered as the full equivalent of that described herein.
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either to a low moisture or to an over-wet condition with the result that copies are damaged and time can be lost in restabili~ing the system, unless a skilled alert operator is available to prevent the condition from maturing unduly, or to reestablish correct operating conditions quickly once the aberration is recognized.
The present invention has as its object the provision of a moisture control arrangement which will avoid the drawbacks of the previously mentioned molleton and non-molleton systems, and which will have an inbuilt degree of stability tending to keep the moisture forwarding effect of the system at a value suited to the particular conditions currently existing.
This na~ural stability should be such that within a reasonable range of conditions, the system will be self-adapting for fairly extended periods so as to feed slightly more or slightly less moisture to the master as the occasion demands, without operator intervention, and thereby to permit successful operation of lithographic duplicators who are not highly ex-perienced.
According to the invention, there is provided a moisture system for a lithographic duplicator including a rotary master cylinder adapted to carry a master, said system comprising: an ink-receptive roll having a surface and being adjacently positioned in a substantially fixed axial relationship with the master cylinder for transferring moisture from its surface to ~he surface of the master; means for maintaining on the surface of said ink-receptive roll a continuous film of lithographic ink; means for positively driving said ink-receptive roll in time with the master cylinder; a moisture ~-transfer roll with a hydrophilic surface for transferring moisture from its surface to the ink film on the surface of said ink-receptive roll, said isture transfer roll being solely driven in a rotary direction by nip forming surface contact with the combination of th0 moisture layers and ink layer between said moisture transfer roll and said ink-receptive roll;
means for presenting an adjustably determinable supply of moisture to the ambit of said moisture transfer roll surface; and means for applying to said ~ -moisture transfer roll a preselected retarding torque whose value varies ~ _3_ . . ......................... . : . . ~. : :-: .
. : . ~ .
.. . . , . ~. , , ... .~ .
~'78~66 monotonically with the rotary surface speed of said transfer roll; said transfer roll being responsive to the combination of the preselected retard-ing torque of said applying means and the magnitude of the driving effect :~
of the nip contact of said ink recep~ive roll with said transfer roll for -developing a surface speed during normal printing operation of between 10 per-cent and 50 percent of the surface speed of said ink-receptive roll; said surface speed of said moisture transfer roll varying as an inverse function of the thickness of the moisture on said transfer roll such that said transfer roll rotates more rapidly to transfer more moisture to said i.nk-receptive roll as more moisture is required by the master from said ink-receptive roll and less rapidly to transfer less moisture to said ink-receptive roll as less moisture is required by the master from said ink-receptive roll.
The method of the invention for providing moisture to a master cylinder of a lithographic duplicator comprises the steps of providing, at least as part of a roll train having contact with the master surface, a roll with an ink-receptive surface and positively driving the same in time with :
the master cylinder; placing a hydrophilic transfer roll in drlven, nip forming, surface contact with moisture and ink layers lying between the hydroph}lic transfer roll and the ink-receptive roll to transfer moisture from : ~ its surface to the surface of the ink receptive roll so that the ink-recept-ive roll acts by way of the moisture and ink layers as the sole driving ~:~
:. :,, -influence on the transfer roll; maintaining on the surface of said ink- ::
receptive roll a continuous film of lithographic ink; making available to . the ambit of the transfer roll surface an adjustably determinable supply of moisture; applying to the transfer roll a retarding torque whose value ~ ~
varies monotonically with:the speed of rotation of the transfer roll and : : -controlling the driving effect of the nip contact between the transfer roll and ink-receptive roll, and the retarding effect of said retarding torque so ~ -as to have a combined effect resulting in a transfer roll surface speed during normal printing operation of between 10 percent and 50 percent of the surface speed of the ink-receptive roll and further causing the surface speed :
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of the transfer roll to vary as an inverse function of the moisture on the transfer roll such th~t the transfer roll rotates more rapidly as more moisture is required by the master and less rapidly as less moisture is required by the master.
The moisture train described herein includes a roll which is oleophilic and which receives and maintains on its surface a thin film of lithographic ink by reasons of direct or indirect contact with the master surface. This roll is power driven in time with the master cylinder, by which is meant that its rotation rate is directly linked mechanically to that -3b- : :
. . .
. . . - -. . ~ ~ , . . ..
.. . . ..
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of the master cylinder, ei~her at the same surface speed or at some otll~r ~urface spee(l having a specified substantially constant relationship thereto. This oleophilic roll is also made to run in contact with a moisture transfer roll whose surface is primarily hydrophilic, and which is driven s.olely by a nominal or non-film-control pressure contact between its surface and that of the ink covered roll via the shear resistance offered by the intervening layers of ink and moisture. Moisture is fed to the transfer roll by any suitable moisture supply 10 system which will carry an adequate moisture flow, allowing the transfer roll to accept from the system any amount of moisture ~hich is currently being required by its speed of rotation, and in which the speed of ro~ation of the transfer roll is gov-erned by mechanism applying a restraining torque to the rotation o~ the transfer roll, which mechanism is characterized by exe~ting a restraining efect which increases monotonically as the speed of the transfer roll rotation increases.
It has been discovered that under these circumstances the transfer roll will take on~ to a certain degree 9 the character of a self-balancing device and will tend to rotate more rapidly as more moisture is required by the master and less rapidly as less moisture is required by the master~ thereby forwarding more or less moisture respectively to the ink covered roll and thus to the master surface, In this fashion the transfer roll tends to remain centered at a speed providing a balanced condition such that the moisture being supplied to the master remains substantially equal to that being re~uired by the master at the momen~, and such that the speed of rotation can shift through a certain range of speeds as slight changes in moisture requirement occur, regardless of the reason.
1~7~
In the drawings: ~
Figure 1 is a vertical elevation, partly in section of a portion ~ -of a lithographic duplicator showing especially the master cylinder and the ink and moisture trains cooperating therewith; and showing one position of the moisture ductor in broken lines, and another in solid lines;
Figure 2 is a fragmentary elevation showing one type of drive for the fountain roll; and Figure 3 is a longitudinal section to a larger scale of an exemplary conventional arrangement for providing an axially reciprocatory motion for a moisture roller.
Referring to the drawing, the master cylinder 10 is served by a conventional ink train 12 and a moisture system 14.
The moisture system 14 includes a fountain 16 receiving a fountain roll 18 having a hydrophilic surface, a ductor roll 20 mounted on an oscillating arm 22, and a moisture transfer roll 24 which has a hydrophilic surface. The transfer roll is in contact with the surface of a moisture form roll 26 having an oleophilic surface which runs in contact with a master ;
M on the surface of the master cylinder 10. A reciprocating distributor soll 28, likewise oleophilic, rides in contact with the moisture form roll 26 and by an inte m al cam mechanism shifts axially back and forth to level the ink layer and moisture deposit on the surface of the form roll 26 in a :~..
known manner. One conventional form of cam mechanism which will serve for this purpose is illustrated in Figure 3 wherein roller 28 is shown as mounted by bearings 60 on a nonrotary shaft 62 to~which is pinned a barrel cam 64 with a double reverse helix groove 66. A sleeve 68 is integral with the roll 24 -~
and rockably retains a dog 70 ;~
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:~786~;6 which has a tip riding in ~he groove 66. Members 72 affixed to the ends of the shaft 62 engage loosely in any suitable mating grooves or aperatures on the frame and consti~u~e one of several conventional means -for preventing rotation of the shaft 62 without influencing its ~ertical location.
For convenient reference the moisture system is divided into the moisture supply module 14A and the moisture flow control module 14B, and it is with the latter that the present invention is primarily concerned.
Referring to the moisture supply module 14A which is essentially conventional, the surface of the foun~ain roll is hydrophilic. Usually this roll is of metal, e.gO aluminum with a ma~te surface, or has a tin-nickel plating or chrome plating on an a~uminum or s~eel support. However, other hydrophilic materials, including nonmetallic compositions~ can be used as the surfacing material for the fountain roll In many conventional systems the ductor roll 20 is covered with a molleton cloth which has certain moisture reser~oir properties, and such a roll is not altogether unsuit-able for the purposes o~ the present invention However, the preferred arrangement employs at this location a roll of ` synthetic elastomeric composition in which has been dispersed a high percentage of short fibers of suitahle composition such as regenerated cellulose, and which presents a matte surface tha~, while not significantly water absorptive, is adequakely hydrophilic and oleophobic when wet and exhibits signiicant moisture attracting and carrying properties.
As is customary, the foun~ain roll 18 is stepped by a ; suitable ratchet mechanism in ~ime with the rotation of the .
; - 6 -~786G6 master cylinder at a rate (smoothed or average rate, that is) which is a~justable, say between 0 RPM and 30 RPM, to provide for increase or decrease in the amount of moisture being forwarded by the system. A setting of perhaps 10 to 20 RPM is representative for moderate circumstances at currently customary machine speeds.
As shown in Fig~ 1, the fountain roll 18 is stepped in a rotary direction opposite in sense to that of the transfer roll 24. Therefore, as the ductor roll 20 swings back and forth it is driven in opposite directions, first in one direction (counterclockwise as seen in Fig. 1) by its contact with the fountaln roller, and then in the opposite direction ~clockwise as seen in Fig. 1) by its contact with the\transfer roller 24.
~ ~ig. 2 illustrates such a conventional adjustable drive .; mechanism wherein the fountain roll 18 (not shown in this view) is drivingly connected to the ratchet wheel 40 which is stepped in the customary fashion by an oscillating drive link 42 carrying a drive pawl 44 meshab:Le with the teeth of the ratchet ` and urged towards the same by a spring (not shown~. The link 42 is powered by any suitable rotary machine element 46 through a connecting link 48 to reciprocate~ for example, at about 7 cycles per second. In order to manually adjus~ the amount of rotation derived from each stroke of the pawl 44, a cam or shroud 50 is arranged to coact with a follower pin 52 on the pawl ~o prevent its meshing with.~the ratchet except where the sur~ace of the cam is relieved , as at 54, to permit sueh ; contact. The point of first contact of the pawl with the ~ .
ratchet can be determined by the angular setting of the cam S0 and this is controlled by the handle 56, the cam setting being held by a suitable detent mechanism 580 While the conventional type of drive for the fountain ~ roll has been described it will be understood that other ; arrangements will work equally well, and one alternative that ~7~36~6 suggests itself is an arrangement for continuously rotating the ~ountain roll by means of a separate variable speed electric motor powering the shaft of the fountain roll 18, with suitable manual speed setting control for the motor.
The oscillating motion of the arm 22 which carries the ductor roll 20 is also caused by a conventional drive from the duplicator mechanism, the arm oscilla~ing at a fairly high rate, for example about 2.8 cycles per master revolution or about 7 cycles per second for machine speeds currently in common use.
Turning now to the moisture flow control module 14B, the moisture form roll 26 is smooth sur~aced and of a rubbery material, preferably a synthetic elasomer o durometer in the range of 20 to 40 on the Shore A scale. The roll 26 is driYen by conventional gear.ingl preferably at the same surface speed as the master cylinder 10. Running in friction contact wi~h the form roll 26 is a distributor roll 28 of material similar to that used for the roll 26. Before the duplica~or is put in operation~
light films of ink 30, 32 are placed on the rolls 26 and 28, and these rolls, being oleophilic, remain inked up at all times 20 when the machine is operating 9 since the roll 26 runs in contact with the master which continually rèceives an ink supply from the ink train 12. As previously no~ed the roll 28 has a cam - inspired axially reciprocating movement to maintain the ink film at a uniform thickness at all times.
2S The transfer roll 24 is constructed of a material pro-viding a suitahle hydrophilic surface as discussed above for the hydrophilic fountain roll 18, and is driven only by the influence it receives from the roll 26 via the nip between ; itself and the roll 26 which experiences only nominal or non-30 film-control pressure. In normal operation the roll 24 carries a ~78666 film of mois~ure on i~s surface as shown at 34. This moisture is supplied and continuously replenished by the moisture su~ply module 14A and as the roll 24 rotates, it transfers portions of this film, via the ink layer 3n, to the surface of a master M on the master cylinder 10, which captures the moisture and carries it away as rapidly as the background areas of the master require added moisture. It is thought that the transferred moisture perhaps in part forms an emulsion with at least the surface of the ink layer 30 and in part supplies a water film 36 overlying the ink layer. Whatever the exac~ mechanism~ however, moisture is indeed carried to the surface of the ma~ster by this composite layer of ink and moisture. While not necessarily required, the preferred arrangement provides a roll 24 which is equipped with a cam for axial reciprocation to improve the levelling action of the mo~sture deposit on roll 24, which arrangement may be, for example, identical with that shown in Pigo 3 for distribution ~oll 28.
It has been discovered in connection with the present in-~ention that the roll 24 does not necessarily rotate at a constant surface speed in spite of the fact that roll 26 is driven at a substantially constant speed for an~ giYen speed setting of the duplicator, and that this variation in speed does indeed per~orm an important function in relation to the improved operation of the system.
It appears likedly that the thickness of the moisture film 34 (indicated as t in Fig. 1) particularly its thickness at the nip of the rolls 24 and 269 lS what controls this speed, and that as t increases the torque necessar~ to generate shearing action in the film 34 decreases so that the drive becomes less ; 30 positive and the roll 24 tends to exhibit increased slip and to turn more slowly. On the other hand, as t decreases, it appears that the torque necessary to generate shearing action in the g ~ 7 8~
film 34 increases so that the drive becomes more positive and roll 24 tends to exhibit decreased slip and thus to speed up.
In fact if the roll 24 dries out completely so as to receive its drive directly through the film of tacky lithographic ink 30 on the roll 26~ its surface speed becomes substan~ially identical to that of the roll 26. As the postulated thickness t of the moisture layer is gradually increased, this results in progressively slower rotation of the hydrophilic transfer roll 24, which appears to be directly responsive to this thickness.
As can be seen from the foregoing dis~ussion, the pressure between the rolls 24 and 30 is quite light since it in no sense controls the moisture film thickness or interferes materially with the changes in thickness above-described. It is merel~
sufficient to insure the possibility of an effective drive at virtually equal surface speeds of the two rolls 24 and 26 if the moisture film were not present. As such, the pressure in question is herein iden~ified as nominal or "non-film~control pressure".
In order for the roll 24 to slow down promptly as t in-creases and driving torque decreases 9 there must of course be certain retarding factors, and these are found to act most effectively when they are of such character that their torque value increases monotonically as the speed of the transfer roll 26 increases (or, conversely, decreases as the speed of the roll 25 decreases). While this would undoubtedly be very efective i~
the increase were directly proportional to speed, this is not seen as a requirement, and any arrangement showing significant increase in retarding torque with increase in the speed of ~7 ~ ~ 6 roll 24 is thou~ht ko give an effective and fully operative result in terms of causing the speed of roll 24 to approximate proportionality to the wa~er film thickness in an inverse re-lationship. It is note~, however~ that conventional bearing friction loadings and the like, customarily present in machinery of this sort, normally provide a restraining torque answering the above description.
In the particular arrangement shown, retarding torque is applied in various ways. For one, the bearings of the shaft supporting ~he trunnions of the roll 24 present a signifi-cant retarding friction. Primarily, however, the ductor roll 20 which is periodically in contact with the roll 24 is so adjusted that its arc of motion will tend to carry it slightly beyond the point of surface contact with the roll 24 and thereby place a momen~ary interference pressure on the transfer roll. Other frictional components may enter into the picture as well, such as the friction in the standard cam dri~e arrangement i the roll 24 is caused to reciprocate axiall~ as above-described, plus the ~iscous resistance generated with the composite layer when thus reciprocated. The combined effects of these ~arious loadings respond to the above descrip*ion and pro~ide the type o re-s~rainin~ torque preferred. Certain of these retarding e~ec~s, particularl~ that o the ductor contact 9 can be arranged to be mechanically adjustable b~ conYentional means 50 as to provide for initial set-up of ~he system to optlmum restraining values.
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It will be understood, of course, that other types of mechanisms for generating the requisite type of restraining torque are also contemplated, for example, fluid dynamic braking means applied to the shaft of the roll 24, electromagnetic braking, and any other sort of restraint torque generating device providing the properties described above will serve the purpose.
To illustrate generally how a system is set up to operate in accordance with the invention, the means, whatever it may be, for applying restraining torque to the ~ransfer roller 24, is adjusted by the assembler or serviceman to provide, in normal : operation, a load sufficient to significantly reduce its surface speed below that of the ink carrying roll with which it is in contact and by which it is dri~en. This restraint might be lS stated i~ terms of torque values, but since these are extremely difficult to measure, interpret and apply, it is deemed more effective to identify the load in practical mechanical terms.
For example, the transfer roll should normally run in a range ; of between about 10~ and about 50% of the surface speed of the 20 inked roll. This can be readily determined by actually measur- :
ing the RPM of each~ converting to surface speed and comparing~
As a practical matter, however, m the construction shown, the transfer roll 24 and the distributor roll 28 are about the same diameter and are in sufficiently close proximity that the .
2S assembler or service technician can readily make a visual comparison of their speeds and determine that the speed re-lationship is well within the range indicatedO The effective moisture supply setting of the handle 56 will depend~ of course, ; on the particular location of the speed ratio within this range ~1378~ 6 of speed ratios, but assuming that l~he proper complementary moisture supply setting is identified in each case, the operatlon at one speed ratio is altogether as effective as at any o~her within the range, The normal speed ratios referred to are, of course, under circumstances of normal stable state running while producing copies of acceptable quality.
In practice, of course, the appropriate loading adjust-ments are predetermined by laboratory tests and specified in terms of adjustment set~ings for the particular design of equipment under considerationO Such specified settings are effective, because the range of permissiblè loading values has very substantial latitude allowing for any reasonable degree of variation in the equipment, To summarize the operation briefly, the device of the `~ 15 inventi~n will be understood as providing an improved type of moisture application for lithographic duplicators which avoids the overrun problems assignable to molleton or other reservoir type systems, and on the other hand provides a quick response device which9 nevertheless, avoids undue sensitivity ~nd affords operating latitude sufficient in amount that moisture settings can be easily made without undue demands on the skill of the o~erator.
The control which the operator exerts on the moisture supply in a system of this type normally relates to the speed - 25 of rotation of the fountain roll 18. The conventional ratchet mechanism heretofore described can be S8t, US ing the handle 56, to step the roll at a wide range of speeds, forwarding more or less moisture along the moisture train, If the setting made by the operator corresponds exactly to the amount of moisture bein~
~ 6 ~
taken up by the surface of the master under the prevailing conditions J then there is proper operation and no flooding or starving occurs. Consequently, properly printed copies issue continuously from the duplicator. However, with the usual moisture system which is devoid of reservoir properties (i.e.
the usual non-molleton system) any deviation from the proper setting quickly shows up as flooding and weakening of the image if too high, or starvation and the appearance of spreading, plugging and background if too ].ow, so that the operator must be aler~ to keep the system in proper balance, and adjust it periodically to accommodate changing conditions.
While the system as above-described does not totally relieve the operator of the necessity for making moisture control settings, the requirement placed on the operator is merely that he find an adjustment for the speed of the fountain roll ~or the output of some other moisture supplying module) so that at least sufficient moisture is being made available to the roll 24 to meet the needs of the master, plus ~n extra safety margin of a small amount to remove any possibility of tempor~ry moisture starvation, When a sett.ing such as the foregoing is achieved, the system 14B of Fig. 1 will exert the requisite control as fol~ows.
1. If conditions should change slightly so that the master is dsmanding and taking slightly less moisture 9 the thickness t of the moisture film 34 on the roll 24 ':
1~7 ~
will slightly increase. This causes the speed of ~he roll to slightly diminish. Due to its diminished speed the roll 24 will take slightly less moisture per unit timc of contact from the surface of the ductor roll 20, and will pass slightly less moisture per unit time to the surace of the form roll 26.
2. Conversely if the conditions should change so that the master requires and takes more moistuTe, the thickness t of the moisture film 34 on the roll 24 will slightly decrease. This causes the speed of the roll to slightly increaseO Due to its increased speed the roll 24 will withdraw slightly more moisture per unit time of contact from the surface of the ductor rQ~l 20, and will pass slightly more moisture per unit time to thc surface of the form roll 26, It will be understood that if the setting of th moisture supply being provided by the module 14A is totally ou~ of scale in either direction with the requirements of the master under the existing humidity, ink temperature and ink working conditions, then the balancing action proYided by the module 14B
will probably be unable to compensate for this discrepancy with sufficien~ alacrity to be functional. However, so long as the 1 setting of the moisture supply is a reasonable approximation of ; the requirements at the master, the accommodation will be substantially complete, and further attention to the moisture adjustment will be required only as a gross change in conditions occurs.
~7~666 The signi-fican~e of the foregoing paragraph is illustrated by the fact that it has been found possible to operate with the system illustrated and described under circumstances such that, with fairly continuous running, a duplicator will frequently 5 run all day long without adjustment of the moisture system ex-cept for a few settings to gradually increase the moisture sup~ly during the initial warm-up period. It has even occurred that with a fortuitous high limit setting at the outset, a single additional increased setting of the moisture system after partial warm-up was all that was required during a day of fairly continuous running.
The latitude provided by this invention is indeed suf-ficient that the instruction manual for the operator can provide a table of settings for the moisture supply module based on relative humidity, ambient temperature running condition (e.g.
start-up, 300 to 1000 copiesl over 1000 copies, etc.), and these settings will normally proYide a sufficiently accurate guide that, if carefully applied will make refinements in the setting on the basîs of observed operation virtually unnecessary.
.
Since one o the most troublesome responsibilities for the operator of a lithographic duplicator is the monitoring of the moisture system9 and because the failure to successfully execute this responsibility is-so costly in lost time and copy paper, it can be understood that this invention provides an important advantage to the operator, and opens up the use of the lithographic duplicator, on a practical basis to operators of much less skill than heretofore required.
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~7 ~ ~ 6 ~
In the non-molleton form of the presen~ invention, the benefit common to such non-molleton, fast response systems, namely the quick transition from dry condition to print-ready condition, ~requiring perhaps 15 ~o 20 revolutions) 9 is presen~
here. The fast response, however, is obtained without incurring highly objectionable sensitivity which is so characteristic of systems of this character.
An additional benefit is the manner in which the system identifies itself to the operator as being substantially in proper running condition. At the start of operation, or if there should be an interruption for any reason~ such as a paper jam, the operator can merely direct his attention to the hydrophilic roll 24 upon starting up. I the system is in an excessively dry condition, ink deposits will appear on the roll surface When adequate moisture has been moved to the nip the deposit~ will promptly disappear and paper feed can be started.
On the other hand, if aberrant operation has somehow flooded the system, the roll 24 will have stopped turning or will be turning very slowly, in which case the operator merely waits until the roll 24 attains substantial speed and then is free to start the paper feed.
~ hile the foregoing description has proceeded on the basis of employing a special inked up roll 26 as being the moisture form roll, it is important to understand that this particular arrangement is not essential to the operativeness o the invention. The hydrophilic transfer roll may make contact with any ink covered roll, for example with the form roll forming a portion of the ink train, or with one of the o~her ink covered rolls of the ink train9 and such an arrangement is to be considered as the full equivalent of that described herein.
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Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A moisture system for a lithographic duplicator including a rotary master cylinder adapted to carry a master, said system comprising: an ink-receptive roll having a surface and being adjacently positioned in a sub-stantially fixed axial relationship with the master cylinder for transferring moisture from its surface to the surface of the master; means for maintain-ing on the surface of said ink-receptive roll a continuous film of litho-graphic ink; means for positively driving said ink-receptive roll in time with the master cylinder; a moisture transfer roll with a hydrophilic surface for transferring moisture from its surface to the ink film on the surface of said ink-receptive roll, said moisture transfer roll being solely driven in a rotary direction by nip forming surface contact with the combination of the moisture layers and ink layer between said moisture transfer roll and said ink-receptive roll; means for presenting an adjustably determinable supply of moisture to the ambit of said moisture transfer roll surface; and means for applying to said moisture transfer roll a preselected retarding torque whose value varies monotonically with the rotary surface speed of said transfer roll; said transfer roll being responsive to the combination of the preselected retarding torque of said applying means and the magni-tude of the driving effect of the nip contact of said ink-receptive roll with said transfer roll for developing a surface speed during normal print-ing operation of between 10 percent and 50 percent of the surface speed of said ink-receptive roll; said surface speed of said moisture transfer roll varying as an inverse function of the thickness of the moisture on said transfer roll such that said transfer roll rotates more rapidly to transfer more moisture to said ink-receptive roll as more moisture is required by the master from said in-receptive roll and less rapidly to transfer less moisture to said ink-receptive roll as less moisture is required by the master from said ink-receptive roll.
2. A moisture system as set forth in claim 1 which further includes, in rolling contact with said ink-receptive roll, an axially reciprocating distributor roll whose surface is also ink-receptive.
3. A moisture system as set forth in claim 1 in which means is pro-vided for causing axial reciprocation of said moisture transfer roll.
4. A moisture system as set forth in claim 2 in which means is pro-vided for causing axial reciprocation of said moisture transfer roll.
5. A moisture system as set forth in claim 1 in which there is pro-vided adjustable means for exerting on said moisture transfer roll a con-trolled retarding torque which varies as a direct function of the speed of rotation of said transfer roll.
6. A moisture system as set forth in claim 1 wherein said means for presenting moisture to said transfer roll surface comprises: a moisture fountain; a rotatable fountain roll running in contact with the liquid in said fountain; a freely rotating ductor roll and means for oscillating said ductor roll to alternately contact said fountain roll and said transfer roll;
means for rotating said fountain roll; and means for adjusting the operation of said rotating means to control the speed of rotation of said fountain roll.
means for rotating said fountain roll; and means for adjusting the operation of said rotating means to control the speed of rotation of said fountain roll.
7. A moisture system as set forth in claim 6 in which there is pro-vided adjustable means for exerting on said moisture transfer roll a con-trolled retarding torque which increases and decreases with the speed of rotation of said transfer roll.
8. A moisture system as set forth in claim 6 in which said fountain roll rotates in a direction opposite in sense to that of said moisture transfer roll.
9. A moisture system as set forth in claim 1 wherein the driving effect of the nip contact is due in part to force means acting on the rolls to urge them towards contact, and wherein said force means is arranged to urge said moisture transfer roll and said ink-receptive roll into nip contact with a value of force which results in the combination of the moisture and ink layers between said rolls substantially determining the spacing between said rolls.
10. A method for providing moisture to a master on the master cylinder of a lithographic duplicator comprising the steps of: providing, at least as part of a roll train having contact with the master surface, a roll with an ink-receptive surface and positively driving the same in time with the master cylinder; placing a hydrophilic transfer roll in driven, nip forming, surface contact with moisture and ink layers lying between the hydrophilic transfer roll and the ink-receptive roll to transfer moisture from its sur-face to the surface of the ink-receptive roll so that the ink-receptive roll acts by way of the moisture and ink layers as the sole driving influence on the transfer roll; maintaining on the surface of said ink-receptive roll a continuous film of lithographic ink; making available to the ambit of the transfer roll surface an adjustably determinable supply of moisture;
applying to the transfer roll a retarding torque whose value varies monotoni-cally with the speed of rotation of the transfer roll; and controlling the driving effect of the nip contact between the transfer roll and ink-recept-ive roll, and the retarding effect of said retarding torque so as to have a combined effect resulting in a transfer roll surface speed during normal printing operation of between 10 percent and 50 percent of the surface of the ink-receptive roll and further causing the surface speed of the transfer roll to vary as an inverse function of the moisture on the transfer roll such that the transfer roll such that the transfer roll rotates more rapidly as more moisture is required by the master and less rapidly as less moisture is required by the master.
applying to the transfer roll a retarding torque whose value varies monotoni-cally with the speed of rotation of the transfer roll; and controlling the driving effect of the nip contact between the transfer roll and ink-recept-ive roll, and the retarding effect of said retarding torque so as to have a combined effect resulting in a transfer roll surface speed during normal printing operation of between 10 percent and 50 percent of the surface of the ink-receptive roll and further causing the surface speed of the transfer roll to vary as an inverse function of the moisture on the transfer roll such that the transfer roll such that the transfer roll rotates more rapidly as more moisture is required by the master and less rapidly as less moisture is required by the master.
11. A method as set forth in claim 10 wherein the driving effect of the nip contact is due in part to the exerting of force upon the rolls to urge them towards contact, and which includes the step of maintaining said force at a value which results in the combination of moisture and ink layers be-tween said rolls substantially determining the spacing between said rolls.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US68285576A | 1976-05-03 | 1976-05-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078666A true CA1078666A (en) | 1980-06-03 |
Family
ID=24741465
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA277,095A Expired CA1078666A (en) | 1976-05-03 | 1977-04-27 | Lithographic moisture system and method |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS53709A (en) |
| CA (1) | CA1078666A (en) |
| DE (1) | DE2719758A1 (en) |
| FR (1) | FR2350203A1 (en) |
| GB (1) | GB1585510A (en) |
| NL (1) | NL7704849A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2846701A1 (en) * | 1978-10-26 | 1980-04-30 | Rotaprint Gmbh | INK AND DAMPING UNIT FOR A SMALL ROTATIONAL OFFSET PRINTING MACHINE |
| JPS5766969A (en) * | 1980-10-15 | 1982-04-23 | Dainippon Printing Co Ltd | Apparatus for oscillating chromium roler in dampening water-supplier |
| DE3146223C2 (en) * | 1981-11-21 | 1985-03-21 | Heidelberger Druckmaschinen Ag, 6900 Heidelberg | Moist inking unit for offset printing machines |
| DE3644982A1 (en) * | 1986-07-12 | 1988-11-03 | Miller Johannisberg Druckmasch | Damping unit for offset printing machines |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2102641A (en) * | 1934-11-22 | 1937-12-21 | Addressograph Multigraph | Method of and apparatus for planographic printing |
| US3259062A (en) * | 1964-11-30 | 1966-07-05 | Harold P Dahlgren | Process for applying a water-soluble organic dampening fluid |
| US3412677A (en) * | 1965-09-17 | 1968-11-26 | Kantor Press Kontrols Inc | Dampening control means for photooffset lithography press |
| FR93677E (en) * | 1967-05-22 | 1969-05-02 | Etudes De Machines Speciales | Wetting device, in particular for a rotary offset type printing machine. |
| US3937141A (en) * | 1974-06-17 | 1976-02-10 | Dahlgren Harold P | Dampener for lithographic printing plates |
-
1977
- 1977-04-26 GB GB1745477A patent/GB1585510A/en not_active Expired
- 1977-04-27 CA CA277,095A patent/CA1078666A/en not_active Expired
- 1977-05-02 JP JP5001977A patent/JPS53709A/en active Pending
- 1977-05-03 NL NL7704849A patent/NL7704849A/en not_active Application Discontinuation
- 1977-05-03 DE DE19772719758 patent/DE2719758A1/en not_active Withdrawn
- 1977-05-03 FR FR7713404A patent/FR2350203A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| NL7704849A (en) | 1977-11-07 |
| GB1585510A (en) | 1981-03-04 |
| FR2350203A1 (en) | 1977-12-02 |
| DE2719758A1 (en) | 1977-11-24 |
| JPS53709A (en) | 1978-01-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |