US3283710A

US3283710A - Periodic registration mechanism for duplicators

Info

Publication number: US3283710A
Application number: US370028A
Authority: US
Inventors: George J Zahradnik; Fred S Golden
Original assignee: AB Dick Co
Current assignee: AB Dick Co
Priority date: 1964-05-25
Filing date: 1964-05-25
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08

Description

Nov. 8, 1966 G. J. ZAHRADNIK ET AL 3,283,710

PERIODIC REGISTRATION MECHANISM FOR DUPLICATORS Filed May 25, 1964 4 Sheets-Sheet l Fla 1 INVENTORS George JZaftradrzik and Fred 5. Golden 9 Fin. 2

dtlys Nov. 8, 1966 3,283,710

PERIODIC REGISTRATION MECHANISM FOR DUPLICATORS Filed May 25, 1964 G. J. ZAHRADNIK ET AL 4 Sheets-Sheet 2 .WHHU

m mwg J. zahmg k Nov. 8, 1966 G. J. ZAHRADNIK ET AL 3,283,710 7 PERIODIC REGISTRATION MECHANISM FOR DUPLICATORS Filed May 25, 1964 4 Sheets-Sheet s /N VEN 7025 George J. Zahradnlk and Fred 5 G0 .aen

NOV. 8, 1966 ZAHRADNIK ET AL 3,283,710

PERIODIC REGISTRATION MECHANISM FOR DUPLIGATORS 4 Sheets-Sheet 4 Filed May 25, 1964 FIG. 15

FIG. 13

United States Patent 3,283,710 PERIODIC REGISTRATION MECHANISM FOR DUPLICATOR George J. Zahradnik, North Riverside, and Fred S.

Golden, Chicago, Ill., assignors to A. B. Dick Company, Niles, 11]., a corporation of Illinois Filed May 25, 1964, Ser. No. 370,028

- 12 Claims. (Cl. 101-248) This invention relates particularly to stencil duplicators but is also applicable to other types of printing presses or the like.

One object of the present invention is to provide a new and improved duplicator in which the impression cylinder is periodically brought into exact registration with the adjacent main cylinder, at one point in the cycle of the main cylinder, and then is allowed to float relative to the main cylinder so that the impression cylinder will be frictionally driven by the main cylinder. The momentary registration of the impression cylinder makes it possible to insure exact registration between the copy sheets and the main cylinder. The impression cylinder is frictionally driven while the copy sheets are being printed so as to obviate any tendency toward slippage between the impression cylinder and the main cylinder. In the case of a stencil duplicator, such tendency toward slippage may cause stretching or wrinkling of the stencil.

A further object is to provide a new and improved duplicator in which the impression cylinder is driven by a registration mechanism which provides a positive drive at one point in the cycle of the main cylinder, the mechanism being adapted to introduce a variable amount of slack into the drive during the remainder of the cycle. Because of this slack, the impression cylinder is actually propelled by the frictional driving action of the main cylinder while the copy sheets are being printed.

It is a further object to provide a new and improved duplicator in which the successive copy sheets are carried between the main cylinder and the impression cylinder by a gripper bar which is supported and advanced by a pair of endless chains, the impression cylinder being formed with a notch for receiving the gripper bar and being driven by a registration mechanism which momentarily synchronizes the impression cylinder with the gripper chains, so that the notch will register with the gripper bar. After the gripper bar has passed the impression cylinder, slack is introduced into the drive for the impression cylinder so that it will 'be frictionally driven by the main cylinder during the actual printing operation. It this way, the impression cylinder will not exert any drag or any pull on the main cylinder, so that there will be no tendency either to stretch or wrinkle the stencil or other printing sheet on the main cylinder.

In general, it is an object of the present invention to provide a registration mechanism which periodically registers or synchronizes the cylinder or other printing member with a positive drive, and then introduces more or less slack into the drive so that the cylinder can run either slightly ahead or slightly behind its positive drive.

A more specific object is to provide a registration mechanism in which the slack in the drive is changed by the rotation of a cam or eccentric which has a cycle corresponding to the cycle of the main cylinder or other printing member with which the impression cylinder is to be registered.

Another object is to provide such a registration mechanism in which the variable slack is produced between a pair of eccentric cams, which are different in phase by 180, and a pair of arms on a forked drive member.

A further object is to provide such a registration mechanism in which the eccentrices or cams are rotated by a planetary gear which is carried by the impression cylinder and is driven 'by a stationary pinion disposed along the aXis of thecylinder. In one preferred arrangement, the planetary gear is rotated at one-half the rotary speed of the impression cylinder, so that the impression cylinder is registered once for every two revolutions thereof. This arrangement is adapted for use with a machine in which the diameter of the impression cylinder is onehalf the diameter of the main cylinder, so that the main cylinder rotates at one-half the rotary speed of the impression cylinder.

Another object is to provide various modified registratio-n mechanisms in which the variable slack is produced between a drive pin and a tapered notch in a forked drive member which is movable toward and away from the pin.

A further object is to provide such registration mechanisms in which the forked drive member is moved into and out of engagement with the pin by a cam or eccentric.

It is a further object to provide such registration mechanisms in which the cam or eccentric is provided with a separate drive gear, sprocket or the like.

Further objects and advantages of the present invention will appear from the following description, taken with the accompanying drawings, in which:

FIG. 1 is a diagrammatic elevational view showing a duplicating machine which is equipped with a registration mechanism for periodically registering the impression cylinder with a gripper bar carried by endless drive chains.

FIG. 2 is an enlarged elevational section taken through the impression cylinder and the gripper bar to show various details of the registration mechanism, the view being taken generally along the line 22 in FIG. 3.

FIG. 3 is a fragmentary enlarged sectional plan view taken generally along the broken lines 3-3 in FIG. 1.

FIG. 4 is a sectional view taken generally along the line 44 in FIG. 3.

FIG. 5 is a diagrammatic elevational section showing the manner in which the main cylinder is driven by one of the gripper chains, the view being taken generally along the line 5-5 in FIG. 3.

FIG. 6 is a fragmentary enlarged section taken generally along the line 6-6 in FIG. 5.

FIG. 7 is a fragmentary plan view showing the manner in which the gripper bar is attached to the gripper chains.

FIG. 8 is a diagrammatic elevational section showing a modified registration mechanism, the view being taken generally along the line 88 in FIG. 9.

FIG. 9 is a fragmentary sectional plan view taken generally along the line 9-9 in FIG. 8.

FIG. 10 is a view similar to FIG. 8 but showing another modified registration mechanism, the view being taken generally along the line 1010 in FIG. 11.

FIG. 11 is a fragmentary section taken generally along the line 11111 in FIG. 10.

FIG. 12 is a view similar to FIG. 8 but showing still another modified construction, the view being taken generally along the line 1212 in FIG. 13.

FIG. 13 is a fragmentary section taken generally along the line 13-13 in FIG. 12.

FIG. 14 is a sectional view similar to FIG. 8 but showing still another modified registration mechanism, the view being taken generally along the line 14-14 in FIG. 15.

FIG. 15 is a fragmentary section taken generally along the line 15--15 in FIG. 14.

As already indicated, the invention is illustrated in FIG. 1 in connection with a duplicator or printing press 20, which preferably is a stencil-type duplicator. As shown, the duplicator 20 comprises a main. cylinder 22 which is adapted to hold a stencil or other member from which a printed impression can be made on paper or other copy sheets. An impression cylinder 24 is provided 3 to press the copy sheets against the main cylinder or drum 22.

A feed mechanism 26 is preferably provided to feed the successive copy sheets 28 between the main cylinder 22 and the impression cylinder 24. In this case, a stack 30 of the copy sheets 28 is supported on a feed table 32. A rotatable feed roller 34 is adapted to engage the top of the stack 30 so as to feed the topmost sheet therefrom, into a chute or opening 36 between upper and

lower guide plates

38 and 40. Corner separators 42 may be employed adjacent the rear comers of the stack 30 to insure that only a single sheet will be fed from the top of the stack by the roller 34. g

The

guide plates

38 and 40 direct each sheet between upper and

lower forwarding rollers

44 and 46 which are rotated in timed relation to the feed roller 34 so as to propel the sheets toward the main cylinder 22.

In the illustrated duplicating machine 20, each of the sheets is taken from the

forwarding rollers

44 and 46 and is carried between the

cylinders

22 and 24 by a set of grippers or clamping fingers 48 which are movably mounted on a gripper bar and are adapted to clamp the leading edge of each copy sheet against the bar 50. As shown, the gripper bar Si} is carried and propelled by a pair of endless gripper chains 52 which are strung around

sprockets

54 and 56. However, it will be understood that the invention is also applicable to machines in which the grippers are carried by the impression cylinder. One of the illustrated sprockets, preferably the sprocket 54, is continuously driven so that the chains will be advanced at a constant speed corresponding to the surface speed of the main cylinder 22. In fact, the main cylinder 22 is preferably fitted with a sprocket 58 (FIGS. and 6) which meshes with and is driven by one of the gripper chains 52.

Just beyond the forwarding rollers 4-4 and 46, the grippers 48 pass under a guide plate or member 60 which guides the leading end of each paper sheet into the grippers, which are opened at this point by a cam, not shown, in the usual manner. The gripper bar 50 travels in a generally horizontal direction between the two

sprockets

54 and 56 so that the sheets are carried horizontally between cylinders 22 and 24-. The grippers 48 insure that each sheet is precisely registered with the main cylinder 22, so that the imprint of the stencil will be accurately located on the sheet. The grippers 48 continue to propel and control the sheets after they pass between the

cylinders

22 and 24. Thus, the grippers overcome the tendency of the sheets to stick to the inked stencil on the main cylinder 22. As the grippers pass around the sprocket 56 they are opened by another cam, not shown, in the usual manner, so that each sheet is ejected from the grippers and is directed into a receiving tray 62. If desired, a delivery system or conveyor may be employed to carry the sheets to the receiving tray 62.

A longitudinal notch or groove 64 is formed in the impression cylinder 24 in order that the gripper bar 50 may pass between the main cylinder 22 and the impression cylinder 24 without interference. As shown to best advantage in FIG. 2, the gripper bar 50 is adapted to be received in the notch 64.

A registration mechanism 66 is provided to drive the impression cylinder 24 in such a manner that the notch 64 will register with the gripper bar 50. Of course, this in itself could be achieved simply by providing a positive gear or chain drive for the impression cylinder 24, so as to rotate the impression cylinder in timed relation to the gripper chains 52. However, the present registering mechanism 66 operates in a periodical manner so as to provide a positive drive at only one point in the cycle of the mechanism, when the gripper bar 50 is passing the impression cylinder 24 and is to be received in the notch 64. After the gripper bar 50 is past the impression cylinder 24, the registration mechanism 66 introduces a substantial slack or free play into the drive for the impression cylinder 24 so that the cylinder is actually frictionally driven by the main cylinder 22 during the printing operation, in which one of the copy sheets is being pressed between the main cylinder and the impression cylinder. The impositiveness of the drive and the resulting frictional propulsion of the impression cylinder 24 obviates any tendency of the impression cylinder to exert a drag or pull upon the stencil on the main cylinder 22. If the impression cylinder 24 were positively driven at all times, its surface would tend to run slightly faster or slower than the surface of the stencil on the main cylinder 22, in most cases, due to slight variations in the effective printing radius of the stencil. The printing radius is affected by the thickness of the stencil, the thickness of the ink pad or the like under the stencil, and the initial tension in the stencil. If the printing radius is slightly greater than nominal value, the surface speed of the stencil is greater than normal. In this case, the impression cylinder 24 would run behind the stencil and would tend to exert a drag on the stencil so that the impression cylinder would tend to stretch the stencil. In extreme cases, actual slippage might result between the cylinders. If the printing radius is slightly smaller than the nominal value, the stencil runs slower than the normal speed. In this case, the impression cylinder, if positively driven, would tend to exert a pull on the stencil, so that there would be a tendency for the impression roller to wrinkle the stencil. The registration mechanism 66 obviates these difficulties by providing for the frictional propulsion of the impression roller 24 during the printing operation, so that the impression roller runs at the exact speed of the stencil. The registration mechanism affords suificient slack in the drive to the impression cylinder to enable the impression roller to run either ahead of or behind the drive so as to compensate for the usual variations in the printing radius. Thus, the registration mechanism 66 provides a drive which is positive at one point in the cycle and is impositive in the following portions of the cycle during which the actual printmg operation is carried out.

The details of the registration mechanism 66 are shown to best advantage in FIGS. 2, 3 and 4. In accordance with the usual practice, the impression cylinder 24 is movably mounted so that it may be separated from the main cylinder 22 when paper sheets are not being fed between the cylinders. This separation prevents the imprint of the stencil from being applied to the impression cylinder. It will be seen that the cylinder 24 is supported by a pair of generally horizontal arms 68 which are swingable about a shaft 7%. This is the same shaft on which the sprockets 54 for the gripper chains 52 are mounted. The arms 68 are biased upwardly or counterclockwise by springs 72 which are effective to apply pressure between the impression cylinder 24 and the main cylinder 22 during the printing operation. The impression cylinder 24 is rotatably supported between the outer ends of the arms 66. One of the arms 68 and the rotatable support for one end of the cylinder 24 is shown in detail in FIG. 3. It will be seen that a shaft or trunnion 74 is secured to the arm 63 and projects inwardly therefrom. The cylinder 24 is rotatably supported by a ball bearing 76, or other antifriction hearing, which is mounted between the shaft 74 and an end plate or disc '78 secured within the end of the cylinder. A second ball bearing 89 is mounted between the shaft '74 and a plate 82 which is connected to the end plate 78 by pillars or pins 84.

In this case, the drive for the impression cylinder 24 utilizes a chain 86 which is strung around

sprockets

88 and 90, and also a toothless idler sprocket 9 2. The sprocket 88 is secured to the shaft 7% and thus rotates with the sprockets 54 for the gripper chains 52. The sprocket 90 is rotatably mounted on the shaft 74. As shown to best advantage in FIG. 4, the idler sprocket 92 outer end of an arm 96, swingable about the shaft '70 adjacent the arm 68. The chain is tensioned by a spring 98 which is connected between the pin 94 and a pin 1110 on the adjacent arm 68. Thus, the spring 8 pulls the idler sprocket 92 downwardly against the upper flight of the chain 36. The pin 94 passes through a clearance slot 182 in the arm 65.

The sprocket 94 rotates at the same speed as the shaft 711 and is adapted to drive the impression cylinder 24 when the periodic registration mechanism 66 forms a positive connection between the sprocket and the cylinder. In this case, the sprocket 913 is formed with three arms 104 which are arranged in the manner of a spider. A plate or member 106 is connected to the arms 104 by means of posts or pillars 108 which pass through clearance openings 116 in the end plate 78. The plate 106 is connected to a central hub or bushing 112 which is rotatably mounted on the shaft 74. It will be evident that the plate 106 rotates with the sprocket 90.

As shown to advantage in FIG.. 2, the plate 106 is forked and is formed with two arms or

prongs

114 and 116 which straddle a pair of eccentrics or other cams 118 and 1211 which are connected together en-d-toend for common rotation about a shaft or pin 122. It will be seen from FIG. 3 that the pin 122 is similar to the pillars 84 in that it extends between the end plate 78 and the plate 82.

Blocks

124 and 126 are mounted on the

arms

114 and 116 for engagement with the

eccentrics

118 and 120, respectively. While the illustrated cams are in the form of eccentrics, it will be understood that a variety of other cam shapes may be employed.

The rotation of the

eccentrics

118 and 120 is adapted to provide a variable amount of slack or play between the forked drive plate 106 and the impression cylinder 24, the slack being variable from zero to a maximum value, according to the position of the eccentrics 118 and 121). In the position shown in FIG. 2, the slack is zero, in that the eccentric 11%; engages the block 124, while the eccentric 12!) engages the block 126. This is the point at which positive registration is provided between the drive sprocket 90 and the impression cylinder 24 so that the notch 64 in the impression cylinder is accurately and positively registered with the gripper bar 50. It will be observed that the point of maximum throw on the eccentric 118 is engaging the block 124, while the point of maximum throw on the eccentric 120 is engaging the block 126.

When the

eccentrics

118 and 120 are rotated, they recede from the

block

124 and 126 so that there is definite clearance between the blocks and the eccentrics. This clearance or slack permits the impression cylinder 24 to follow the frictional drive of the main cylinder 22.

In this case, the

eccentrics

118 and 120 are adapted to be rotated by a planetary gear 128 which is solidly secured to the eccentrics and is rotatable about the pin or shaft 122. The eccentrics 113 and 120 and the gear 128 may conveniently be molded in one piece from resinous plastic material, preferably a material such as nylon, for example, which affords low friction, high strength and great resistance to wear. The planetary gear 128 meshes with a pinion 131 which in this case is stationary and is solidly secured to the stationary shaft or trunnion 74. It will be,,observed that the pinion 130 is disposed along the axis of the impression cylinder 24 so that the planetary gear 128 rolls around the pinion when the impression cylinder 24 is rotated. The pinion 134) is one-half the size of the planetary gear 128, so that the gear 128 rotates at one-half the rotary speed of the impression cylinder 24. Thus, the rotation of the planetary gear 128 produces positive registration between the impression cylinder 24 and the drive sprocket 90 at one point for every two revolutions of the impression cylinder. At this point, the gripper bar 50 is passing between the

cylinders

22 and 24 and is received in the notch 64. The cycle of the periodic registration mechanism corresponds to each revolution of the main cylinder 22 which rotates at one-half the rotary speed of the impression cylinder 24. The cycle of the periodic registration mechanism also corresponds to the cycle of the gripper bar 50* which is carried once around its complete circuit by the chains 52 for each revolution of the main cylinder 22.

The sprocket and the spider arms 104 may also be conveniently molded in one piece from a resinous plastic material which affords low friction, high strength and great resistance to wear. The hub or bearing 112 may also be made of such plastic material.

It may be helpful to summarize the operation of the embodiment shown in FIGS. 1-7. During the operation of the machine, the gripper chains 52 are continuously advanced and are effective to produce continuous rotation of the main cylinder 22, due to the meshing of the main cylinder sprocket 58 with one of the chains 52. For each revolution of the main cylinder 22, the feed roller 34 engages the topmost copy sheet 28 in the stack 30 and propels the sheet past the corner separators 42 and between the

guide plates

38 and 46 into the nip between the forwarding

rollers

44 and 46. The timed rotation of the forwarding

rollers

44 and 46 advances the sheet into the grippers 48 on the gripper bar 50, so that the leading end of the sheet is gripped between the grippers; and the gripper bar. The movement of the gripper bar 50 carries the sheet between the main cylinder 22 and the impression cylinder 24, so that the sheet receives an imprint from the stencil on the main cylinder 22. The control afforded by the gripper bar 541 prevents the sheet from sticking to the main cylinder. The gripper bar carries the sheet beyond the

cylinders

22 and 24 until the sheet is discharged from the grippers and deposited in the receiving tray 62. The provision of the grippers 48 and the gripper bar 50 make it unnecessary to provide strippers to peel the sheet from the main cylinder. In this way, it is possible to print upon the marginal portions of the sheet which are normally left free of any imprint for engagement by the strip pers. The grippers also provide accurate and positive registration between the sheet and the stencil on the main cylinder 22.

As the gripper bar 50 passes the impression cylinder 24, the gripper bar is received in the notch 64 in the cylinder. During this portion of the cycle, the cylinder 24 is posi tively driven so that it is synchronized with the movement of the gripper bar 50. The rotatable eccentrics 118 and 121) cooperate with the forked plate 106 to form a positive driving connection between the drive sprocket 90, which is positively driven at all times, and the impression cylinder 24. At this point in the cycle, the

eccentrics

118 and 126 positively engage the follower blocks 124 and 126 on the

arms

114 and 116 of the forked plate 106.

' As the cycle of the machine progresses, the rotation of the impression cylinder 24 causes rotation of the planetary gear 128 which rotates the

eccentrics

118 and 120, so that definite slack or clearance is provided between the eccentries and the follower blocks 124 and 126. This slack renders the drive impositive so that the impression cylinder 24 is free to follow or float with the frictional drive provided by the main cylinder 22 during the passage of the paper sheet between the main cylinder and the impression cylinder. Thus, the impression cylinder does not exert any appreciable drag or pull on the stencil, even if the printing radius of the stencil is slightly greater or less than the nominal value. The maximum slack between

eccentrics

118 and 120 and the follower blocks 124 and 126 is developed'afte-r the eccentrics have rotated through one-half revolution. By this time, the impression roller 24 is rotated through one full revolution so that the printing operation has been completed. The continued rotation of the eccentrics 118 and 121i progressively reduces the slack so that a positive drive is again. momentarily provided after the impression cylinder has rotated through another revolution. By this time, the gripper bar 50 is again passing between the

cylinders

22 and 24. The periodic registration mechanism insures that the notch 64 in the cylinder 24 will accurately register with the gripper bar 50.

FIGS. 8-14 illustrate four periodic registration mechanisms of modified construction. Any of these mechanisms may be substituted for the periodic registration mechanism 66 of FIGS. 17. In each of the modified mechanisms, the variable slack is developed between a cylindrical pin 1411 and a tapered notch or slot 142 in a movable member 144. The notch 142 is formed by a pair of converging edges or surfaces 146 which are engageable with the pin 140. In each case, the pin 146 is secured to the impression cylinder 24, while the member 144 is continuously rotated. When the converging surfaces 146 of the notch 142 are fully engaged with the pin 140, the cylinder 24 is positively driven and is accurately registered with the gripper bar 511. This condition of full registration occurs at one point in the cycle of the registration mechanism, when the gripper bar is passing the impression cylinder 24. Throughout the remainder of the cycle, the member 144 is shifted so that the converging surfaces 146 are withdrawn to a greater or lesser extent from the pin 141). The clearance between the converging surfaces 146 and the pin 140 provides slack in the drive so that the impression cylinder 24 is free to follow the frictional drive of the main cylinder 22.

In the registration mechanism 148 of FIGS. 8 and 9, the member 144 is slidably mounted on a sprocket 150 which is continuously driven by a chain 152, corresponding to the chain 86 of FIG. 3. Thus, the sprocket 1511 is continuously driven in timed relation to the main cylinder 22 and the gripper chains 52. The pin 140 extends through a clearance slot 154 in the sprocket 15d.

It will be seen that the sprocket 154 has a hub 156 which is slidably received in an elongated guide slot 158 formed in the member 144. A pin 16% is mounted on the member 144 and extends through a guide slot 162 in the sprocket 156. Thus, the member 144 is slidable laterally along the sprocket 150 so that the relationship between the pin 1411 and the tapered slot 142 may be changed.

This relationship is changed in a periodic manner by an internal eccentric or other cam 164 which is rotatable about a shaft 166, about which the sprocket 156 is also rotatable. In this case, the cam 164 is continuously driven by a chain 168- which is threaded around a sprocket 170 formed on or connected to the cam 164. Like the chain 152, the chain 163 is synchronized with the main cylinder 22 and the gripper chains 52, but is adapted to drive the sprocket 17 at one-half the rotary speed of the sprocket 150, so that the cam 164 will be rotated once for every two revolutions of the impression cylinder 24.

The member 144 is fitted with a follower roller 172 which may be rotatably mounted on the pin 160. Springs 174 are connected between the member 144 and the sprocket 150 to bias the roller 172 against the internal eccentric or cam 164. Thus, the rotation of the cam 164 reciprocates the member 144 on the sprocket 150 so as to move the converging surfaces 146 into and out of engagement with the pin 140. Full engagement between the surfaces 146 and the pin 140 occurs once for every two revolutions of the impressions cylinder 24. At this point in the cycle, the impression cylinder 24 is positively registered with the main cylinder 22 and the gripper bar 50. At other points in the cycle, the registration is impositive so that the impression roller is free to follow the frictional drive of the main cylinder.

In the modified registration mechanism 180 of FIGS. and 11, the member 144 and the sprocket 150 are retained but are changed in shape and will be designated 144a and 1511a. The member 144a is guided for lateral movement on the sprocket 150a by

guide pins

182, 184 and 186 which extend through

guide slots

188, 190 and .192.

The internal eccentric or cam 164 is also retained but is of different shape and will be designated 16411. As before, the cam 164a is continuously driven at one-half the rotary speed of the sprocket 150a. However, in this case, the cam 164a is fitted with a gear 194 which may be driven by an idler gear 196 which is synchronized with the rotation of the main cylinder 22 and the movement of the gripper bar 50. The follower roller 172 is retained but is arranged differently and is designated 172a. In this case, the follower roller 172a is rather large and is rotatably mounted on a hollow cylindrical journal 198 formed on the member 144a. Springs 174a are connected between the member 144a and the sprocket 150a to bias the roller 172a against the cam 164a. In this way, the converging edges 146 of the V-shaped notch 142 are moved into and out of engagement with the pin 140 so as to afford a clearance or slack which is substantial during most of the cycle but which becomes zero at the point of positive registration, so that the cylinder 24 will be accurately registeredwith the gripper bar 51).

In the modified registration mechanism 210 of FIGS. 12 and 13, the internal cam 164 is replaced with an external cam 16% which is engageable with the follower roller 1721) on the slidable member 1441). In this case, the sprocket 151) is replaced with a 'gear 1519b which is continuously driven by an idler gear 212. As shown in FIG. 12, the idler gear 212 is driven by a gear 214 which may be mounted on the shaft which carries the gripper sprockets 54. Springs 174% are connected between the member 14% and the gear 15011 to bias the roller ,172b against the cam 16412.

The sprocket 170 is replaced with a gear 17Gb which is connected to or formed integrally with the cam 16412. The gear 1711b is driven by an idler gear 216, but at onehalf the rotary speed of the gear 15Gb. Thus, the converging surfaces 146 are moved into positive engagement with the pin for a brief interval during every two revolutions of the impression cylinder 24. Other corresponding components are given the same reference characters as in FIGS. 8 and 9, with the addition of the sufliX b.

FIGS. 14 and 15 illustrate still another modified registration mechanism 220, in which the sprocket is replaced with a gear 15110 which may be driven in the manner shown in FIG. 12. The member 144 is replaced with a modified member 1440 having a pair of arms or fingers 222 which are slidably guided between a pair of spaced blocks or lugs 224 formed on the gear 150C. The blocks 224 engage the fingers 222 and cause the member 1440 to rotate with the gear 1500.

In this case, the cam 164 is replaced with an eccentric 164c which is formed on a gear e, corresponding to to the sprocket 17 0. The gear 1706 may be driven in the manner shown in FIGS. 12 and 13 at one-half the rotary speed of the gear 1500.

The member 1440 is fitted with a bushing 226 which is rotatably mounted on the eccentric 164a and is adapted to travel with the ecccentric. Thus, the rotation of the eccentric 1640 causes combined reciprocation and rocking movement of the member 1440, relative to the gear 1500. In this way, the converging surfaces 146 on the member 1440 are moved toward and away from the pin 140. When the surfaces 146 engage the pin 140, the impression cylinder 24 is positively driven and is accurately registered with the main cylinder and the gripper chains.

In all of the described embodiments, the periodic registration mechanism is employed to control the registration of the impression cylinder so that it will be accurately registered at one point in the cycle of the machine. Such registration is normally timed to occur as each of the copy sheets is fed between the main cylinder and the impression cylinder. During the remainder of the cycle, the registration becomes impositive so that the impression cylinder may be frictionally driven by the copy sheet which is traveling between the impression cylinder and the main cylinder. However, it will be understood that the present invention may be applied to other printing cylinders or members so as to achieve periodic registration.

When applied to the impression cylinder of a stencil duplicator, the periodic registration insures that the impression cylinder will be registered with the main cylinder and will be driven at substantially the surface speed of the main cylinder when each copy sheet is fed between the cylinders. The stencil is never required to accelerate the impression cylinder to any appreciable extent. Thus, the periodic registration mechanism obviates the stretching of the stencil which is frictionally experienced in the usual stencil duplicator having a free running impression roller. Such a free running roller is not registered and is driven solely by frictional engagement with the stencil and the main cylinder. When such a machine is started, or when the speed of the machine is changed abruptly, the stencil is required to accelerate the impression roller. The force required to produce such acceleration often tends to stretch the stencil.

The periodic registration mechanism of the present invention has the efifect of registering the impression cylinder and driving it at substantially the speed of the main cylinder, at the point in the cycle when the head or leading end of the stencil is engaging the leading end of the copy sheet. This is the point in the cycle at which the stretching of the stencil is most apt to occur in a conventional machine having a free running impression roller. The periodic registration mechanism obviates any tendency to stretch the stencil at this point in the cycle.

The periodic registration mechanism is also superior to a positive drive that will produce continuously positive registration of the impression cylinder. With a positive drive, slight differences tend to develop between the surface speeds of the stencil and the impression cylinder, due to variations in the thickness of the stencil and the ink pad. These speed dilferences tend to cause stretching or wrinkling of the stencil. With the periodic registration, the impression cylinder is positively registered at the beginning of the cycle but thereafter is frictionally driven by the stencil cylinder so that the surface speed of the impression cylinder will be exactly the same as the surface speed of the stencil.

Various other modifications, alternative constructions and equivalents may be employed without departing from the true sprit and scope of the invention, as exemplified in the foregoing description and defined in the following claims.

We claim:

1. In a duplicator, the combination comprising a ro tatable main cylinder for holding a printing member, a rotatable impression cylinder engageable with said main cylinder, a movable gripper bar having grippers thereon for carrying successive copy sheets between said cylinders, a pair of endless chains supporting the opposite ends of said gripper bar, means for supporting and driving said endless chains, means for driving said main cylinder in timed relation to said chains, said impression cylinder having a notch therein for receiving said gripper bar to provide for the movement of said gripper bar between said cylinders, means forming a driving connection between said chains and said impression cylinder, means providing a variable play in said driving connection, andmeans connected between said chains and said last mentioned means for reducing said play to a minimum condition when said gripper bar passes between said cylinders while increasing said play after passage of said gripper bar therebetween so that said impression cylinder will be frictionally driven by said main cylinder during the printing of the copy sheets.

2. In a registration mechanism, the combination comprising a rotatable cylinder, a rotatable drive member adjacent and coaxial with said cylinder, means for rotating said member, a stationary pinion adjacent and coaxial with said cylinder, a planetary gear rotatably mounted on said cylinder for rotation relative thereto and meshing with said pinion, a pair of opposed arms on said memher, and a pair of eccentric cams connected to said planetary gear and rotatable therewith between said arms to 'form therewith a drive between said drive member and said cylinder, said drive alfording minimum play between said eccentric cams and said arms at one point in the cycle of said eccentric cams and affording progressively variable play therebetween during the remainder of such cycle.

3. In a registration mechanism for a printing press, the combination comprising a rotatable press member, a rotatable drive member coaxial with and adjacent said press member, means for rotating said drive member, a stationary pinion coaxial with said press member, a planetary gear rotatably mounted on said press member and meshing with said pinion, a pair of spaced elements on said drive member, and rotatable camming means connected to said planetary gear and rotatable therewith be tween said elements between a positive registration position in which said carnming means have minimum play with both of said elements and an impositive registration position in which said camming means are receded from said elements to provide substantial play between said camming means and said elements, said camming means thereby affording variable play in the drive of said press member.

4. In a registration mechanism for a printing press, the combination comprising a rotatable press member, a rotatable drive member adjacent and coaxial with said press member, means for rotating said drive member, a pair of spaced driving elements on said drive member and adjacent said press member, camrning means rotatably mounted on said press member and disposed between said spaced elements to form therewith a driving connection between said drive member and said press member, and means for rotating said camming means between a position in which said camming means have minimum play with both of said elements and a position in which said camming means are receded from said elements to afford substantial play between said camming means and said elements.

5. In a registration mechanism for a printing press, the combination comprising a rotatable press member, a rotatable driving member adjacent and coaxial with said press member, first and second driving elements on said driving and press members and forming a driving connection therebetween, and means for moving one of said elements relative to the other element between a position in which said elements are fully engaged with minimum play therebetween and another position in which said one element is receded from the other element to afford substantial play therebetween.

6. In a registration mechanism, the combination comprising a rotatable cylinder, a rotatable drive member adjacent and coaxial with said cylinder, driving means for rotating said drive member, a movable element mounted on said drive member for movement relative thereto and having converging surfaces forming a tapered notch, a drive pin mounted on said cylinder and received in said notch, and camming means operable by said driving means for moving said element between a positive registration position in which said converging surfaces engage said pin and an impositive registration position in which said converging surfaces are receded from said pin to provide substantial play between said element and said pin.

7. In a registration mechanism for a printing press, the combination comprising a rotatable press member, a ro-. tatable driving member adjacent and coaxial with said press member, first and second driving elements on said driving and press members and forming a driving connection therebetween, one of said elements having con- .verging surfaces forming a tapered opening, the other of said elements comprising a pin received in said tapered opening, and means for moving one of said elements relative to the other element between a positive registration position in which said pin and said converging surfaces are fully engaged and an impositive registration position in which said pin is spaced from said converging surfaces to atford substantial play between said pin and said converging surfaces.

8. In a registration mechanism, the combination comprising a rotatable press member, a rotatable driving member adjacent and coaxial with said press member, first and second driving elements on said driving and press members and forming a driving connection therebetween, one of said elements comprising camming means, the other of said elements comprising follower means engageable with said camming means, and means for moving one of said elements relative to the other element between positions of minimum and maximum spacing between said camming means and said follower means to afford variable play therebetween.

9. In a duplicator, the combination comprising a rotatable main cylinder for holding a printing member, a rotatable impression cylinder engageable with said main cylinder, a movable gripper bar having grippers thereon for carrying successive copy sheets between said cylinders, a pair of endless chains supporting the ends of said gripper bar, means for supporting and driving said chains, means for driving said main cylinder in timed relation to said chains, said impression cylinder having a recess therein for receiving said gripper bar to provide for the movement of said gripper bar between said cylinders, and a periodic registration mechanism connected between said chains and said impression cylinder and including means forming a driving connection with variable play therein between said chains and said impression cylinder, and means connected to said last-mentioned means and opetrable in timed relation to said chains for periodically reducing said play to a minimum value when said gripper bar is passing between said cylinders and thereafter increasing said play to allow for frictional drive of said impression cylinder by said main cylinder during the printing of the copy sheets.

10. In a duplicator, the combination comprising a rotatable main cylinder for holding a printing mem- 12 ber, a rot atableimpression cylinder engageable with said main cylinder, a movable gripper bar having grippers thereon for carrying successive copy sheet-s between said cylinders, a pair of endless chains supporting the ends of said gripper bars, means for supporting and driving said chains, means for driving said main cylinder in timed relation to said chains, said impression cylinder having a recess therein for receiving said gripper bar to provide for the movement of said gripper bar between said cylinders, a rotatable drive member adjacent said impression cylinder, means for driving said drive member in timed relation to said chains, first and second driving elements on said drive member and said impression cylinder and forming a driving connection therebetween, one of said elements being movable relative to the other of said elements to vary the play therebe'tween, and means operable in timed relation to said chains for moving said one element to reduce said play to a minimum value when said gripper bar is passing between said cylinders and thereafter to increase said play to allow for frictional drive of said impression cylinder b-y said main cylinder during the printing of the copy sheets.

11. The combination of claim 10, in which one of said driving elements comprises a pair of converging surfaces forming a tapered opening and the other of said driving elements comprises a pin received in said tapered opening.

12. The combination of claim 10, in which one of said driving elements comprises rotatable camming means, and the other of said driving elements comprises a pair of spaced followers on opposite sides of said camming means with variable play between said followers and said camming means, said camming means being rotatable in timed relation to said chains.

References Cited by the Examiner UNITED STATES PATENTS 1,867,529 7/1932 Jones 101-248 2,406,205 8/1946 Davidson et al 101-232 2,551,060 5/1951 Simmons 101-232 2,794,390 6/1957 Burke 101-232 2,887,046 5/1959 Knops et al 101248 ROBERT E. PULFREY, Primary Examiner.

P. R. WOODS, Assistant Examiner.

Claims

5. IN A REGISTRATION MECHANISM FOR A PRINTING PRESS, THE COMBINATION COMPRISING A ROTATABLE PRESS MEMBER, A ROTATABLE DRIVING MEMBER ADJACENT AND COAXIAL WITH SAID PRESS MEMBER, FIRST AND SECOND DRIVING ELEMENTS ON SAID DRIVING AND PRESS MEMBERS AND FORMING A DRIVING CONNECTION THEREBETWEEN, AND MEANS FOR MOVING ONE OF SAID ELEMENTS RELATIVE TO THE OTHER ELEMENT BETWEEN A POSITION IN WHICH SAID ELEMENTS ARE FULLY ENGAGED WITH MINUMUM PLAY THEREBETWEEN AND ANOTHER POSITION IN WHICH SAID ONE ELEMENT IS RECEDED FROM THE OTHER ELEMENT TO AFFORD SUBSTANTIAL PLAY THEREBETWEEN.