US3625147A

US3625147A - Apparatus for contact printing

Info

Publication number: US3625147A
Application number: US864676A
Authority: US
Inventors: Robert Aron Rubenstein
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1969-10-08
Filing date: 1969-10-08
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07

Abstract

A continuously rotating roller transporting a printing master and an idler roller transporting a recording medium are engaged for printing transfer when the idler roller has zero angular velocity but is being driven about the surface of the continuously rotating roller at the latter''s angular velocity. As there is no difference in surface speed between the printing master and recording medium at the area they make contact, smudging is prevented.

Description

United States Patent 10l/228X 101/D1G.13 101/D1G. 13 101/228 101/228 101/228 10l/D1G. 13 10l/D1G.13

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References Cited UNITED STATES PATENTS 8/1914 Cornwall......................

ANGULAR VELOCITY 0F ROLLER-46 [54] APPARATUS FOR CONTACT PRINTING 13 Claims, 3 Drawing Figs.

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W/////// /L ////j 1 al 8% B INVliN'IOR Robert A. Rubenstein A TTORNE Y APPARATUS FOR CONTACT PRINTING BACKGROUND OF THE INVENTION In the printing industry there is a need for apparatus for transferring infonnation from a continuously moving master to a recording medium web which may be moving intermittently or at some average velocity other than that at which the master is moving. The master may, for example, be a multilith master or a ditto master on a revolving roller, In high-speed data processing printers, the master could be an electrofax master belt transported on a drive roller. In each of the above-described examples, when it is desired to transfer infon-nation from the continuously moving master to the recording medium, apparatus must be devised to engage the master and recording medium in such a way as to prevent misregistration and smudging due to differing velocity of master and recording medium at the time of engagement. It is an object of the present invention to provide improved apparatus to meet the need discussed above.

BRIEF SUMMARY OF THE INVENTION A driven roller and an idler roller are in spaced relationship. Means are provided for reciprocating one roller relative to the axis of the other at a varying speed which is equal during at least one point in time to the angular velocity of the driven roller. Further means cause the driven and idler rollers to engage when their relative velocity at their area of contact is zero.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic diagram of a system employing the apparatus of the invention;

FIG. 2 is a perspective view of a major portion of the apparatus with the elements separated for clarity; and

FIG. 3 is a timing diagram of the various mechanisms of FIG. 2.

DETAILED DESCRIPTION FIG. I shows a system embodying the apparatus of the invention in a book printing application. Supply spool 100 supplies a continuous strip of recording medium 52 such as paper which ultimately is cut into consecutive pages for a book. The recording medium is transported through a supply buffer station 102, a print transfer apparatus 104a embodying the invention and through an extractor buffer station 106 (which may include a drying or fixing apparatus, not shown) which combination permits printing alternate pages (such as the odd numbered pages) on one side ofrecording medium 52.

The recording medium is turned over in the vicinity of loop 108 and passes though a second supply buffer station 102a, print transfer apparatus l04b and a second extractor bulTer station 106a, terminating on a takeup reel 110. This part of the system prints the alternate remaining pages such as the consecutive even numbered pages.

A writing station 114, which may comprise a cathode-ray tube being fed signals from a computer (not shown) produces charge patterns of consecutive pages of the book on an endless electrostatic master belt 112. The writing station also includes means for supplying a charge attracting material such as an electroscopic powder particle mixture with pigments, commonly referred to as toner, to the belt to form the printed indicia on the belt. The endless belt and method for applying toner thereto is described in US Pat. No. 3,168,857 issued to E. Hutto, Jr. The toner is transferred from the printing master 1 I2 to one side of the previously charged recording medium at print station 104a and to the other side at l04b. The toner is then caused to permanently adhere to recording medium in a drying operation (not shown). The printing master, containing indicia of consecutively numbered pages on one surface, is transported on driven roller in the direction shown by arrow I at a constant surface velocity, V.

Since the information for consecutive numbered pages will be transferred to opposite sides of the recording medium, for a given number of pages, only half the length is required on the recording medium 52 as is required on the printing master 1 l2. Stated another way, the recording medium need be going at an average surface velocity half that of the printing master to permit transfer of all the information contained on the printing master to the recording medium in identical scale and format (i.e., a velocity V/2). Pinch rollers 116 a, b, c, d are driven at a surface velocity V/2 to accomplish this. When print transfer is occurring at either print station 104a or l04b roller 46 urges the recording medium into engagement with the printing master, Since the printing master is traveling with a velocity, V, during print transfer, the portion of the recording medium in contact with the printing master must of necessity also be moving with the same surface velocity, V i.e., twice its average velocity V/2). If' this condition is not met, smudging will occur on the recording medium. Conversely, when no print transfer is occurring such as when information for odd numbered pages is passing print station 1041] or information for even numbered pages is passing print station 1040, the recording medium must be moving at elfectively zero velocity so as to maintain the average velocity, V/2, at which it is supplied to and taken away from the vicinity of the print transfer apparatus. The print transfer apparatus 104, which contains the elements for causing the necessary recording medium velocity changes, will be fully explained later in the description.

The supply and

takeup buffer stations

102, 102a, 106, 106a, respectively are provided to permit local changes in velocity of the recording medium even though it is delivered and taken up at a velocity V/2 established by pinch rollers 116a, b, c, d. Tension, or takeup, rollers 122, 124 coupled respectively to a base by springs 126, 128 permit loops of the recording medium 129, 131 to become longer or shorter as the local tape speed varies. Further, the springs in combination with

guide rollers

150, 152 respectively keep the recording medium taught against roller 46 at all times.

Print transfer apparatus 104a and its associated supply means and takeup means are illustrated at a time when printing is about to begin. Since the recording medium has been effectively stopped for some time, a large length of web is present in the supply buffer while essentially all web has been removed from the extractor buffer. As print transfer of the next page is in progress, the recording medium is removed twice as fast from the supply buffer (velocity V) as it is being supplied to the supply buffer (V/2). Conversely, the recording medium is being supplied to the extractor buffer twice as fast as it is being removed. Buffer stations 102a and 1060 are illustrated at a point in time when printing has just ceased and all excess recording medium has been transferred to the extractor bufier.

An understanding of the operation of a print transfer apparatus 104 will be gained by referring to FIG. 2 where only the left half of the mechanism is shown, the right half being similarly configured. A driven first roller 10 is continuously rotated in the direction of arrow 12 by a drive means not shown. Roller 10 may be transporting a printing master such as, for example, a multilith master or an endless electrostatic master belt such as shown as element 112, FIG. 1. Drive roller 10 is connected through clutch 14 to shaft 16. The axes of rotation of roller 10 and shaft 16 coincide.

Clutch 14 may have predetermined speed changing means such as gears or belts and pulleys for causing the angular velocity of roller 10 and shaft 16 to be in other than a one-toone ratio. Also, a source (not shown) may apply command signals to clutch 14 for causing shaft 16 to be disconnected from roller 10 and thus to stop as roller 10 continues rotating.

Gear 20, secured to shaft 16, is adapted to drive a first cam 22 through the series of gears 24 and 26. Gear 20 rotating in the direction shown by arrow 28, engages gear 24 which is rotatable about shaft 30. Gear 24 engages idler gear 26, which is secured to shaft 32. Gear 26 in turn engages the gear portion 34 of cam 22. Cam 22, rotatable about shaft 16, is driven in the direction shown by arrow 36 (i.e., a direction opposite that of gear 20).

Parallel shafts

16, 30 and 32 are rotatably supported in a frame 70, only a portion of which is shown. The combination of gears is such that cam 22 revolves at an angular velocity one-half that of drive gear 20.

A raised portion 40 of cam 22 forming an arc of approximately 180, cooperates with a first cam follower 42. The latter is rotatable about the shaft extension 460 of idler second roller 46. The function of the cam 22 is to raise and lower roller 42 and other components attached thereto, as cam 22 rotates.

The idler roller 46 may be adapted to transport a recording medium 52 from a supply buffer station 102 to an extractor buffer station 106, such as illustrated schematically in FIG. 1. The supply and extractor buffers contain a sufficient number of guide rollers to insure that recording medium 52 maintains slip-free contact with roller 46, as already discussed. A means for urging roller 46 into engagement with roller 10 comprises a compression spring 54, shown in phantom, acting on bushing 56 in which shaft 460 is rotatably mounted. (It should be noted that both in the description and in the claims a recording medium and printing master may be between

rollers

10 and 46 when the rollers are said to be in contact or engagement.) Bushing 56 is mounted in an elongated slot 58 in arm 60 and does not rotate. Spring 54 is mounted in a recess in the arm. It can thus be seen that the raised portion 40 of cam 22 will act to force roller 46 and recording medium 52 away from drive roller 10 for one-half revolution of cam 22. During the other one-half revolution of cam 22, spring 54 acts to urge roller 46 into contact with roller 10.

Also mounted on arm 60 is a means 50 for preventing rotation of roller 46 when in the raised position. This, for example, may be a strip of material, having a high coefficient of friction, which engages shaft 46a in the raised position. Altemately, a unidirectional clutch constrained to permit only counterclockwise movement of roller 46 (viewed from the left in FIG. 2) may be employed. If a unidirection clutch is used, spring 126 (FIG. 1) must have a larger spring constant than spring 128 to prevent unwanted movement of recording medium 52 such as could occur in the situation illustrated at 102, 106.

Circular eccentric second cam 61 with eccentricity e is secured to shaft 16 and thus is driven in the same direction and at the same angular velocity as gear 20. Cam 61, through series of elements to be described, serves as a means to cause arm 60 to reciprocate as cam 61 rotates, with shaft 16 serving as the pivot.

The above is accomplished as follows. As cam 61 rotates, a second cam follower 62 reciprocates back and forth in the direction of arrows 64, a direction normal to a plane through the axes of

shafts

16 and 30. Cam follower 62 is constrained to a linear movement by guideways 66 and 68 (shown partially broken away) secured to frame 70. Gear rack 72 portion of cam follower 62 engages segment gear 74 which is secured to shaft 30. As gear 74 reciprocates, segment gear 76, also secured to shaft 30, reciprocates. Gear 76, in engagement with a gear segment portion 78 of arm 60, causes arm 60, which is rotatable about shaft 16, to reciprocate back and forth about the shaft. Its excursion limits are denoted by centerlines 80 and 81.

As can be seen in FIG. 2, arm 60 transporting roller 46 will cause the roller and recording medium 52 to reciprocate about the surface of roller 10. Contact between

rollers

10 and 46 is detennined by whether or not the raised portion 40 of cam 22 is in contact with cam follower 42. Arm 60 travels with an angular velocity varying between zero at its travel limits (center lines 80 and 81) and some maximum value half way between these limits. Due to the circular shape of cam 61 and the constant speed of rotation of shaft 16, the velocity of cam follower 62 is expressed by the formula V =e-w cos (l) where e is the eccentricity (i.e., the distance between the center of the cam and the center of shaft 16) of the cam, w is the angular velocity of the cam, and 0 is the angle between a line drawn through the cam center and shaft 16 center and a plane through the axes of

shafts

16 and 30.

From formula (l) it can be seen that the maximum velocity of cam follower 62 occurs when cos 6 is a maximum value, one, or when 0 is zero (i.e., when cam follower 62 and arm 60 are at their travel midpoints). Then From an examination of FIG. 2, it can be seen that the maximum velocity of arm 60 and its travel limit may vary over wide ranges depending on the various gear parameters, eccentricity e of cam 61 and angular velocity in of the cam. One particularly useful set of parameters (as will become apparent as the operation of the apparatus is described) is to have e=r, where r is the radius of roller 10, (DE-(0D, where o) is the angular velocity of the driven roller 10, and to have 1:1 ratio between cam follower 62 and arm 60. In a 1:1 ratio, as cam follower moves 22 equal to 2r, the diameter of roller 10, arm 60 moves through an angle of 2 radians. Stated another way, as cam follower 62 moves 22, a point 83 on arm 60 which is at a distance r from the axis of shaft 16 will traverse a distance 2r. (This is true because of the definition of a radian, a unit of measurement equal to an angle at the center of a circle enclosed by an are equal in length to the radius.) Point 83 located on an extension of the surface of roller 10, will reach a maximum velocity, V exactly equal to the surface velocity of roller 10 which is In summary, in the so called 1:1 case, as cam 61 rotates, arm 60 travels a total arc of 2 radians, reaching its maximum angular velocity when it is half way between the limits of its travel, which is exactly equal to the angular velocity of roller 10.

The operation of the apparatus will be explained with the use of timing diagrams of FIG. 3 and with the following assumptions:

1. The velocity of driven roller 10 remains constant at an, angular velocity and V surface velocity.

2. Shaft 16 is operating at the same angular velocity, w as roller 10. That is (o to 3. The radius r of roller 10 the radius of roller 46 one unit of length. Therefore substituting R=l into formula (3) the magnitude of surface velocity of roller 10, V,,, will equal the magnitude of its angular velocity, m,,, or V,,= u,,=V. None of these assumptions is necessary to the operation of the apparatus but serve to aid the explanation. FIG. 3, in four superimposed waveshapes, shows:

1. The angular velocity of roller 10 about shaft 16.

2. The angular velocity of arm 60 about shaft 16.

3. The angular velocity of roller 46 about its own axis.

4. The surface velocity of recording medium 52 taken normal to a plane between the axes of rollers 10 and 46 (shown slightly displaced for drawing clarity) which is the difference between

curves

2 and 3. The waveshapes are plotted along the horizontal axis as a function of rotational position of roller 10 in radians (which is the same as plotting against time since roller 10 is rotating at a constant angular velocity).

Below the timing diagram at eight key points in time, numbered 0 to 7, the positional relationship among cam 22, cam follower 42 and arm 60 (in phantom) is illustrated. The arrow on cam follower 42 shows the direction it is about to go. An arbitrary reference point (a small black triangle) shows the position of roller 10 (which is hidden) in each of the time periods. The eight times represent two revolutions of roller 10.

At time 0, roller 46 is in the full counterclockwise position as viewed from the left in FIG. 2. From the timing diagram, it is seen that at this time roller 10 is rotating at constant angular and surface velocity V while the recording medium 52, arm 60, and idler roller 46 are all at zero velocity.

Between time 0 and time 1 roller 10 rotates 1r/2 radians arm 60 moves halfway through its travel l radian) and at time 1 is moving with a maximum velocity V a velocity just equal to the velocity of roller 10. Furthermore, it is moving at zero rate of change of velocity (no acceleration). Roller 46 is still rotationally at zero velocity, any tendancy to move being restrained by element 50 (FIG. 2). Finally, recording medium 52 is also moving at velocity V. This is thus the ideal time for the recording medium to be urged into contact with roller 10 to prevent speed mismatch between the recording medium 52 and roller 10 (and coincidentally the printing master contained thereon). From FIG. 3 it can be seen that the raised portion of cam 22 has just rotated beyond engagement with cam follower 42 allowing the recording medium and roller 10 to engage. Even if element tolerances are such that engagement does not occur precisely at time 1, since arm 60 is moving at or near zero acceleration a slight error in the timing of engagement is not likely to produce noticable smudging.

Between time 1 and time 2, arm 60 decelerates to zero while the angular velocity of roller 46 about its axis accelerates to a velocity, V, in a smooth sinusoidal manner. Thus, even if roller 46 is of large mass it will accelerate smoothly insuring that the recording medium remains in contact with roller 10 and moving at speed V.

When arm 60 again reaches the vertical position (time 3), it is traveling in a counterclockwise direction with a negative velocity V while roller 46 is rotating about its own axis at a velocity 2V. Meanwhile roller 10 has rotated 317/2 radians since time or 11' radians 180) since printing began.

As arm 60 approaches the full counterclockwise position at time 4 a decision must be reached on whether printing is to continue. If it is to continue, appropriate signals must be transmitted to clutch 14 to disconnect shaft 16 from driven roller 10 at time 4. With shaft 16 stopped, arm 60 is at rest in the counterclockwise position and the raised portion of cam 22 is out of engagement with cam follower 42 (i.e.,

rollers

10 and 46 remain in engagement). In this condition time 4 properly illustrates the relationship among the elements.

If printing is to cease after one revolution of roller 10, as in the printing of alternate book pages, no signal is applied to clutch 14 and arm 60 rotates to the vertical position at time 5. At this time it is again traveling an angular velocity V while roller 46 is at zero rotational velocity, the ideal time to separate recording medium from roller 10. Raised portion 40 or cam 22 which is rotating at angular velocity V/2 has rotated into the proper position to accomplish this. The raised portion engages cam follower 42 raising roller 46 and thus recording medium 52 from contact with roller 10. Roller 10 has rotated 21: radians (360) since printing began thus transferring information to the recording medium equal in length to the circumference of the roller 10, termed a page. While roller 46 is raised from contact with roller 10 element 50 restrains the roller from rotation. Since recording medium 52 is held in frictional engagement with roller 46 by other rollers and elements such as guide rollers 150, 152 (FIG. 1), proper registration between recording medium and roller 10 will be insured when printing resumes.

Between time 5 and time 7 while arm 60 recycles to its starting point and while roller 10 is completing its second revolution, a decision must be reached whether the apparatus is to remain in the nonprint condition. If so, appropriate signals are sent to clutch 14 (FIG. 2) to disengage shaft 16 at a time 0. If printing is to resume, as in printing alternate book pages, clutch 14 is not activated and the apparatus completes another cycle as above described.

It should be noted that from time 1 to time 5, the recording medium is traveling at velocity V. During the interval between time 5 and the next time 1, the recording medium is traveling at an average velocity of zero since it positive and negative excursions about zero velocity are equal. Thus, if clutch 14 remains engaged, as times 1-5 and 5-1 represent equal time intervals, the average velocity of the recording medium is V/2.

As an understanding of the operation of the apparatus is gained, it is seen that a key feature is that arm 60, during some portion of its travel, be going the same angular velocity as roller 10 to permit engagement of recording medium and printing master when the two have relative velocity of zero.

As mentioned before, the three assumptions made at the start of the explanation are only for purposes of illustration. For example, driven roller 10 need not rotate at a constant velocity since all other rotating elements are geared to it. The radius of roller 46 need not equal that of roller 10 and in fact would usually be smaller as illustrated in FIG. 1. Finally, shaft 16 need not operate at the same speed as roller 10 unless it is always desired to print on a length of recording medium equal to the circumference of roller 10. If, for example, it is desired to use the apparatus in the book printing application above described, printing will occur during alternate revolutions of roller 10, since its circumference is made equal to the length of a book page. If, however, it is desired to transfer a smaller amount of information than contained on the entire circumference of roller 10, this may also be accomplished. Clutch 14 is prepared to operate shaft 16 faster than roller 10 so that w w The gearing arrangement shown will still cause the appropriate 2:1 ratio to be maintained between the angular velocity of cams 61 and 22. By appropriate change in the gear ratio between cam 61 and arm 60, the arm can still be made to reach a maximum angular velocity of (u the velocity of roller 10. This will be accomplished by having arm 60 rotate through a smaller angle than two radians and thus less than a full revolution will occur during one back and forth cycle of arm 60. For example, with w =4w arm 60 will traverse a total of one-half radian (2radians/4) clockwise and one-half radian counterclockwise during the time roller 10 revolves onefourth revolution. Or, stated another way, only one-fourth the circumference of roller 10 need be transferred during one print cycle. If more than one-fourth page is to be transferred, speed change clutch 14 would be energized at time 4 FIG. 3 and printing would continue indefinitely. w zm ratios of 20 or higher may be employed for some applications for transferring information from as little as 18 or less of roller 10. Ratios higher than 121 are limited only be design, workmanship and materials, not be the mechanism.

Also, less time in terms of angle of rotation of roller 10 is involved in recycling the arm back to the start (clockwise) position, once printing has terminated. The non-print time is, of course, equal to the print time in the absence of signals to clutch 14 disengaging cam 61, either while printing is in progress or stopped.

Should it be desired to print more than the circumferential length of roller 10 in one print cycle without disengaging clutch 14, cam 61 can be slowed down relative to roller 10. However, unlike the speedup, which is limited only by the strength of the various elements, the slowdown is limited by the mechanism. The limit is such that arm 60 travels a length of 31r/4 radians (l35) each side of a centerline. As can be seen from time 2, FIG. 3, for example, travel beyond this point would cause the raised portion of cam 22 to raise roller 46 at an inappropriate time.

FIG. 2 illustrates only one of the many embodiments of the apparatus to achieve the results of the invention. For example, a single contelevered arm 60 could be used rather than the two required by the design of FIG. 2. This arrangement permits the recording medium to be inserted into the apparatus from one side rather than be threaded between

rollers

46 and 10 which would be required if arms on each side of the rollers are employed. Clutch 14 may be omitted entirely if the device is to be used solely for the printing of alternate pages of any size up to four-thirds the circumference of roller 10. Then shaft 16 would merely be an extension of roller 10. Many other physical changes in the mechanism may be made as required by the constraints of the system and are still to be considered within the scope of the claims set forth below.

What is claimed is:

1. In combination:

a driven first roller;

an arm rotatable about said first roller, for movement about the axis of rotation of said first roller in a plane perpendicular to said axis;

an idler second roller rotatably mounted on said arm with its axis of rotation lying in a plane which passes through the axis of rotation of said first roller;

means coupled to said first roller for oscillating said arm through an angle whose origin is said axis of rotation of said first roller at a velocity such that the surface velocity of the portion of the surface of said second roller nearest said first roller equals the surface velocity of said first roller at least once each cycle of the arm; and

means for urging said second roller into contact with said first roller when the surface velocities of the two rollers are equal.

2. The combination as claimed in claim 1, further including means for separating said second roller from said first roller when the angular velocities of the first roller and arm are equal.

3. The combination as claimed in claim 2, wherein said means for oscillating said arm comprises means for oscillating said arm at an angular velocity relative to time which is sinusoidally shaped.

4. The combination as claimed in claim 3, wherein the means for oscillating said arm comprises further means for causing the maximum velocity of said arm to equal that of said first roller.

5. In combination:

a driven first roller;

a second roller rotatably mounted on said arm with its axis of rotation lying in a plane which passes through the axis of rotation of said first roller;

means coupled to said first roller for oscillating said arm through an angle whose origin is said axis of rotation of said first roller at a velocity having a maximum value equal to the angular velocity of said first roller comprising an eccentric first cam coupled to said first roller and rotating in synchronism with said roller and further comprises a first cam follower constrained to move in only a single axis, said axis being perpendicular to the axis of rotation of said cam coupled to said arm and cooperating with said eccentric cam for oscillating the arm about its point of origin; and

means for urging said second roller into contact with said first roller when the angular velocities of the first roller and arm are equal.

6. In combination:

a driven first roller;

means coupled to said first roller for oscillating said arm through an angle whose origin is said axis of rotation of said first roller at a velocity equal, during at least one point on its travel, to the angular velocity of said first roller;

means for urging said second roller into contact with said first roller when the angular velocities of the first roller and arm are equal; and

means for separating said second roller from said firstroller when the angular velocities of the first roller and arm are equal, comprising a cam driven in synchronism with said first roller, said cam having a raised portion thereon, and a cam follower rotatably mounted on said second roller, said raised portion cooperating with said cam follower for maintaining the second roller separated from said first roller.

7. The combination as claimed in claim 6, wherein said means for oscillating said arm comprises an additional cam driven in synchronism with said first roller and further including energy transfer means to rotate said cam at an angular velocity one-half that of said additional cam.

8. The combination as claimed in claim 7, further including a clutch means coupling said driven first roller to said cam and said additional cam for disengaging said cams from said first roller when the angular velocity of arm is zero.

9. In combination:

a continuously driven first roller;

an idler second roller;

a recording medium passing over and in contact with said second roller and driven in the direction of the length of the recording medium, whereby the idler second roller is driven by said recording medium;

means for oscillating said second roller about the axis of said first roller at a speed such that the surface speed of said second roller on the portion of the surface nearest said first roller equals that of said first roller at least once each cycle of back and forth movement of said second roller; and

means for moving one of said rollers toward the other for causing engagement of said recording medium between said rollers at the time the surface speeds of the two rollers are equal.

10. In combination:

a driven first roller;

a second roller having an axis which lies in a plane passing through the axis of said first roller;

a recording medium passing between said first and second rollers and transported by said second roller;

means coupled between said rollers for oscillating one about the other at a velocity such that the surface velocities of the first roller and recording medium are equal during at least one point in the relative motion of the two rollers; and

means for moving the two rollers together when the speed of the recording medium and that of the first roller are equal.

1 1. In combination:

a continuously driven first roller;

a printing master, at least a portion of which is in engagement with said first roller and driven by said first roller;

an idler second roller;

a recording medium, passing between said second roller and said printing master, guided by said second roller;

means coupled between the rollers for oscillating one about the other and concurrently oscillating the portion of the recording medium in the vicinity of said second roller relative to the printing master while the two are separated at a rate such that the velocities of the recording medium and printing master are equal during at least one point during the oscillation of the rollers; and

means for engaging the printing master and recording medium when their velocities are equal to permit information transfer from the former to the latter.

12. The combination as claimed in claim 11, wherein the means for oscillating the recording medium relative to the printing master comprises an arm coupled between the rollers for oscillating the second roller relative to the first roller while maintaining their axes of rotation equidistant.

13. The combination as claimed in claim 12, further including clutch means coupled between said first roller and said arm for disengaging said arm from said roller when said recording medium is traveling with zero velocity.

Claims

1. In combination: a driven first roller; an arm rotatable about said first roller, for movement about the axis of rotation of said first roller in a plane perpendicular to said axis; an idler second roller rotatably mounted on said arm with its axis of rotation lying in a plane which passes through the axis of rotation of said first roller; means coupled to said first roller for oscillating said arm through an angle whose origin is said axis of rotation of said first roller at a velocity such that the surface velocity of the portion of the surface of said second roller nearest said first roller equals the surface velocity of said first roller at least once each cycle of the arm; and means for urging said second roller into contact with said first roller when the surface velocities of the two rollers are equal.

5. In combination: a driven first roller; an arm rotatable about said first roller, for movement about the axis of rotation of said first roller in a plane perpendicular to said axis; a second roller rotatably mounted on said arm with its axis of rotation lying in a plane which passes through the axis of rotation of said first roller; means coupled to said first roller for oscillating said arm through an angle whose origin is said axis of rotation of said first roller at a velocity having a maximum value equal to the angular velocity of said first roller comprising an eccentric first cam coupled to said first roller and rotating in synchronism with said roller and further comprises a first cam follower constrained to move in only a single axis, said axis being perpendicular to the axis of rotation of said cam coupled to said arm and cooperating with said eccentric cam for oscillating the arm about its point of origin; and means for urging said second roller into contact with said first roller when the angular velocities of the first roller and arm are equal.

6. In combination: a driven first roller; an arm rotatable about said first roller, for movement about the axis of rotation of said first roller in a plane perpendicular to said axis; a second roller rotatably mounted on said arm with its axis of rotation lying in a plane which passes through the axis of rotation of said first roller; means coupled to said first roller for oscillating said arm through an angle whose origin is said axis of rotation of said first roller at a velocity equal, during at least one point on its travel, to the angular velocity of said first roller; means for urging said second roller into contact with said first roller when the angular velocities of the first roller and arm are equal; and means for separating said second roller from said first roller when the angular velocities of the first roller and arm are equal, comprising a cam driven in synchronism with said first roller, said cam having a raised portion thereon, and a cam follower rotatably mounted on said second roller, said raised portion cooperating with said cam follower for maintaining the second roller separated from said first roller.

8. The combination as claimed in claim 7, further including a clutch means coupling said driven first roller to said cam and said additional cam for disengaging said cams from said first roller when the angular velocity of said arm is zero.

9. In combination: a continuously driven first roller; an idler second roller; a recording medium passing over and in contact with said second roller and driven in the direction of the length of the recording medium, whereby the idler second roller is driven by said recording medium; means for oscillating said second roller about the axis of said first roller at a speed such that the surface speed of said second roller on the portion of the surface nearest said first roller equals that of said first roller at least once each cycle of back and forth movement of said second roller; and means for moving one of said rollers toward the other for causing engagement of said recording medium between said rollers at the time the surface speeds of the two rollers are equal.

10. In combination: a driven first roller; a second roller having an axis which lies in a plane passIng through the axis of said first roller; a recording medium passing between said first and second rollers and transported by said second roller; means coupled between said rollers for oscillating one about the other at a velocity such that the surface velocities of the first roller and recording medium are equal during at least one point in the relative motion of the two rollers; and means for moving the two rollers together when the speed of the recording medium and that of the first roller are equal.

11. In combination: a continuously driven first roller; a printing master, at least a portion of which is in engagement with said first roller and driven by said first roller; an idler second roller; a recording medium, passing between said second roller and said printing master, guided by said second roller; means coupled between the rollers for oscillating one about the other and concurrently oscillating the portion of the recording medium in the vicinity of said second roller relative to the printing master while the two are separated at a rate such that the velocities of the recording medium and printing master are equal during at least one point during the oscillation of the rollers; and means for engaging the printing master and recording medium when their velocities are equal to permit information transfer from the former to the latter.