US2546372A

US2546372A - Web tensioning mechanism for printing presses

Info

Publication number: US2546372A
Application number: US685473A
Authority: US
Inventors: Carl W Pinckert
Original assignee: Bemis Brothers Bag Co
Current assignee: Bemis Brothers Bag Co
Priority date: 1946-07-22
Filing date: 1946-07-22
Publication date: 1951-03-27
Anticipated expiration: 1968-03-27

Description

1951 cf. w; PINCKERT March 27;

WEB TENSIONING MECHANISM FOR PRINTING PRESSES 5 Sheets-Sheet 1 Filed July 22, 1946 March 27, 1951 c. w. PINCKERT WEB TENSIONING MECHANISM FOR PRINTING PRESSES 5 Sheets-Sheet 2 Filed July 22, 1946 m n y a u a I mdx 1 \Q MN mm L t a N lbw aw Q T kr no 7 M I w Am\ n Q m mnNmm mm Mm March 27, 1951 c. w. PlNcKERT I WEB TENSIONING MECHANISM FOR PRINTING PRESSES 5 Sheets-Sheet 3 Filed July 22, 1946 c. w. PINCKERT March 27, 1951 WEB TENSIONING MECHANISM FOR PRINTING PRESSES -5 Sheets-Sheet 4 Filed July 22, 1946 March 27, 1951 c. w. PJNCKERT 2,545,372

WEB TENSIDNING MECHANISM FOR PRINTING PRESSES Filed July 22, 1946 -5 Sheets-Sheet 5 s: 2 llll f. 7

Patented Mar. 27, 1951 WEB TENSIONING MECHANISM FOR PRINTING PRESSES Carl W. Pinckert, St. Louis, Mo., assignor to Bemis Bro. Bag Company, St; Louis, Mo., a corpora- UNITED STATES PATENT OFFICE tion of Missouri Application July 22, 1946, Serial No. 685,473

be noted the provision of an improved tensioning mechanism adapted to maintain proper tension on a web of material being fed through a rotary offset printing press wherein brand impressions are printed on the web at spaced intervals corresponding to certain lengths; the, provision of 1 a tensioning mechanism of this class permitting operation of the press so as'to print a wide range of said lengths; and the provision of a tensioning mechanism of this class adapted to permit printing of lengths shorter than, equal to, or longer than the circumference of the plate cylinders or printing rolls of the press. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims. In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

Fig. 1 is a diagrammatic side elevation of a rotary offset printing press embodying the improved tensioning mechanism of this invention;

Fig. 2 is an enlarged partial side elevation of the press with the tensioning mechanism set to permit printing of bag lengths shorter than the circumference of the plate cylinders;

Fig. 3 is an enlarged partial side elevation of the press with the tensioning mechanism set to permit printing of bag lengths longer than the circumference of the plate cylinders;

Fig. 4 is an enlarged end view of the web-feeding device for the press, as viewed from line 4-4 in Fig. 1;-

Fig. 5 is a right side elevation of Fig. 4;

Fig. 6 is a view partly in section on line 6-6 of Fig. 2;

Fig. 7 is a section taken on line l---'! of Fig. 2; and, 1

Fig. 8 isa section taken on line 8-8 of Fig. 3.

Similar reference characters indicate corresponding parts throughout the several views of the drawings. V

This, invention constitutes an improvement 11 Claims. (Cl. 101-228) over the tensioning mechanism for printing presses disclosed in the Belcher Patent No. 1,978,073. The tensioning mechanism disclosed in this patent is adapted only to permit operation of the press to print bag lengths which are shorter than or, at most, equal to the circumference of the plate cylinders or printing rolls designated 7 in the Belcher patent. The web to be printed is fed by web-feed rolls between an impression cylinder and a printing cylinder.

This occurs at a linear speed less than the peripheral speed of the cylinders. The web is intermittently gripped between a raised printing surface on the impression cylinder and the printing cylinder and fed forward at the higher peripheral speed of the cylinders. ,To compensate for the difference in web speeds, a tensioning mechanism is provided for supplying additional web to the cylinders and for taking up the slack issuing during such operation. The tensioning mechanism is adapted 'for operation only when the linear speed of the web, as determined by the speed of the web-feed rolls, is less than the peripheral speed of the impression and printing cylinders. This limits the press of the Belcher patent to printing bag lengths shorter than or,

at most, equal to the circumference of the plate cylinders.

The present invention extends the range of the press to include the printing not only of lengths which are shorter than or equal to the circumference of the plate cylinders but also to include the printing of lengths longer than the circumference of the plate cylinders; As illustrated in Fig. 1 herein, the tensioning mechanism, of the present invention is employed in connection with a rotary offset printing press including a main frame I I wherein are journalled an impression or blanket cylinder [3, plate cylinders or printing rolls I5, and a printing cylinder IT. The plate cylinders, as is conventional, receive supplies of ink from suitable inking rollers (not shown), and transfer an ink impression of a brand to a raised blanket or printing surface 19 on the impression cylinder I3. The impression cylinder 1 3 and the printing cylinder I! have the same ,surface speeds. The raised surface [9 is adapted to engage the printing cylinder 11 to grip the web W to be printed therebetween. When the web is thus gripped it is positively fed forward at the peripheral a supply roll 2I supported in roll holder 23. The web is positively fed from the supply roll to the press by a web-feed roll 25, being guided around and pressed against this feed roll by presser r0115 21. Printed web is fed from the press to a suitable winder (not shown) by a web-feed roll 29-, being guidedaround this roll by guide rolls 3I. The web-

feed rolls

25 and 29 are of the same diameter and are connected by a chain and sprocket drive, as indicated at. 33, to rotate at the same speed (Figs. 4 and 5).

The press cylinders and the web-feedrolls are driven from a drive shaft 35 journalled in the feed roll frame. This shaft is driven throu h a belt and pulley drive from a motor (not shown). The shaft 35 has a pulley 31 on one end for the belts 39 of this drive. Onthe same end of the shaft is a sprocket M of a sprocket and chain drive, generally designated 43, for driv-- ing the press cylinders, On the other end of the shaft 35- is a gear 45v which drives the webfeed roll 25 through a change gear drive, generally designated 51-. By means of the change gear drive, the web-

feed rolls

25 and 29* may be driven to feed the web at a speed either slower, equal to, or faster than the surface speeds of the impression or printing cylinders I3 and I1.

The improved tension mechanism of this invention is supported in a frame 55 disposed between the web-feeding means 2529 and. the main press frame II. The tensioning mechanism includes two tension rolls 51 and 59.journalled in an oscillating tension frame. generally designated 6!. Frame BI comprises a pair of arms 63 centrally connectedby a tubular member 65. The arms are secured in alignment on the respective ends of the connecting member by being bolted to flanges 61 welded on the connecting member. The tension rolls 51 and 59 are rotatably supported at the opposite ends of the arms by anti-friction bearings 59 mounted upon studs 11 secured in the ends of the arms. The frame 6| is pivotally supported for oscillation in frame 55 on pivot studs 13 extending from the frame 55.. into the ends of the tubular connecting member 65. Anti-friction bearings 15 are provided between the studs 13 and tubular member 55. The tension rolls 51 and 59- and the arms 53 arepreferably made of light weight material such as an aluminum alloy.

Idler guide rollers 11 and 19 journalled in the frame 55 cooperate with the upper tension roll 51 to form a loop ill in the web between the web-feed roll 25 and the press cylinders. Web issuing from the loop is guided by the idler 19 between the impression and printing cylinders l3 and I1. The tension of the web in the loop BI tends to bias the tension roll 51 to the right and to pivot the tension frame 6| clockwise (Figs. 1, 2 and 3). Idler guide rolls 83 and 85 cooperate with the lower tension roll 59 to form a second loop 81 in the web between the press cylinders and the printed web-feed rolls 29. The tension of the web in the loop 81 tends to bias the tension roll 59 to the right and to pivot the tension frame 6| counterclockwise.

As illustrated in Fig. 2, the tension frame El is biased to. pivot counterclo'ckwise'by spring devices,v generally designated 9!, connected to the frame at opposite sides thereof. There are two spring, devices 9! and each includes a chain 93 removably fastened at one end 95 to the upper side of a collar 91.- The two collars 91 aresecured to the arms 63' by the bolts which connect the arms and flanges I51.v The chains 93 are guided around rollers 99 and their other ends are connected to tension springs IBI, as indicated at I03. Chains I05 are connected to the other ends of the springs, as indicated at I91. Each chain I05 is attached to a take-up pulley I99 on a shaft III which may be rotated and locked inanadjusted position by a pawl and ratchet device M3 for adjustably tensioning the springs I OI. Ends of chains 93 may be detached from the upper sides of collars 91 and secured to .the lower sides of the collars, as indicated at H5 in Fig. 3, so that the spring devices 9| bias the tension frame 6I to pivot clockwise, for a purpose to be mentioned.

When the ends95 of the chains 93 are attached to the upper sides of the collars 91, as shown in Fig.2,- the tension frame BI is biased counterclockwise by the spring devices 9I toward the solid-line positionwherein the lower portions of the arms 63:engage stop H1. These stops are formed on. the ends of the arms II9 of bell-'cranklevers fixed on a rock shaft Ill. The other arms I23 .of the. bell-crank levers are dis posed between spaced. fixed stops I25 and I21. These stops'limitthe' oscillation of rock shaft I2! and stops II1 thereon. Stops II1 function to limit pivotal movementoftension frame GI in'counterclockwise direction, as viewed in Fig. 2. The lower ends ofthe-ar-ms 63 of the. tension frame engage the stops H1 and rock the shaft I2I- until bell-crank arms I23 engage the lower fixed stop I21-.- Stops H1 also function as kickers to kick the-lower ends of arms 53 to the left in a manner to be described. The stops II1 are preferably provided with suitable yieldable' elements I29, of rubber or the like, to cushion the impact.

Clockwise pivotal movement of the tension frame BI from the solid-line position of Fig. 2 is .limitedby bumpers I3'I'. adjustably mounted on the inside of the side members at the top of frame 55.. As, illustratedmore particularly in Fig. '7, each bumper comprises a bracket I33 having spaced bearing. members I35. and. I31 thereon. Aebumpertrod I39. having a cushioned bumper head, Ml. is .disposedfor sliding movementin thebearing members. A. compression spring I43 reacting betweenthe bearing member I35 and a collar. I45- on. the bumper rod biases the rod and head MI toward the tension frame. The. collar limitsthe sliding movement of the=bumper rod.-

Each side-memberofframe 55 hasan arcuate slot I41-therein.- Arcuate racks I49 (not shown in the diagrammatic'Fig l). are secured on the outside of the sideframemembers adjacent the slots. Each bumper bracket I33 has a pair of studs I5I: and l53i.ithei*e.on extending through the corresponding s10t-;l41.: A hand wheel I55 having a pinion I-51; meshing with rack I49 is rotatably mounted 'on.-stud. I5I on the outside of the side frame members. The hand wheel and pinion are removablys retained on the stud I5! by a nut I59 threaded on the outer end. of the stud. The bracket .133 .is clamped in adjusted positionon the. sideframe member by a nut ISI threaded on the end of stud I53 extending through the slot I41: intorengagement with the side frame member. Adjustment of the bumper may be effected even while the press is running by loosening nut I6I and rotating the hand wheel I55 :and pinion. I51, then tightening nut IBI to clamp the bumper bracket in place. The bumpers may. be entirely removed fromithe; side frame members by removing nuts I59 and-I6I and the hand Wheel and pinion.

As illustrated in Fig. 3,;the tension frame 9| is biased by the spring devices 9| to rotate clockwise to the solid-line position of this figure, wherein the lower portions of the arms 63 engage stops I61. These stops are formed on the ends of the arms I69 of bell-crank levers fixed on a rock shaft I1I parallel to and spaced from the rock shaft I25. The other arms I13 of these bell-crank levers are disposed between an upper fixed stop I15 and a lower resilient stop I11. These stops limit the oscillation of rock shaft HI and stop I 61 thereon. Stops I61 function to limit pivotal movement of tension frame BI in clockwise direction, as viewed in, Fig. 3. The lower ends of arms 63 of the tension frame engage. the stops I61 and rock the shaft I1I until bell-crank arms I13 engage the lower resilient stop I11. St0ps I61 also function as kickers to kick the lower ends of arms 63 to the right ina manner to be described. The stops I61 are preferably provided with suitable yieldable'elements I19, of rubber or the like, to cushion the impact of arms 93.

The lower stops I11 are resilient to absorb the shock or sen-crank arms m in the event of breakage of the web. If the web should break when the tensionfframe is, for example, in the dotted-line position" of Fig. 3, the spring devices "9I' wo'uld rapidly pivot the tension frame 6 clockwise. and the lower ends of arms 63 would.strike the stops I 61 with impact. This impact {would be transferred through the bellcrahk lever-to the. lower stop. As shown more particularly in Fig. 8, the lower resilient stop I11 comprises a bumperrod I8I having a bumper head I83 at the upper end thereof. The bumper rod is slidably disposed in a bracket I85. A compression spring I81 reacting between one end-of the bracketand a collar I89 on the bumper rod biases the bumper head I83 to a normal stop position. The spring I81 is sufficiently strong so that the bumper head I83 is substantially immovable under ordinaryimpact of the bell cr'ank arm I13 thereon.

.When the spring devices 9| are connected to the lower sides of the collars 91 to bias the tension frame BI clockwise, bumpers I3I are removed from the position shown in Fig. 2 and mounted upon the side members of, frame in the adjusted position indicated in Fig. 3 to limit pivotal counterclockwise movement of the tension frame. In effecting this transfer, the bumper on the right-hand side of the frame is transferred to the left-hand side of the frame and, similarly, the bumper on the left-hand side of the frame is transferredto the right-hand side.

Means is provided for selectively operating either of the two sets of stops H1 and I61 in timed relation to the printing operation as kickers, dependent upon whether the tension frameis biased to pivot counterclockwise (Fig. 2) or clockwise (Fig. 3). This means includes tation to prevent a rebound of oscillating tena rock shaft 2I3I parallel to and intermediate 1 the rock shafts IZI and I'll. Rock shaft ml is braked'bya conventional band brake 293 at one end thereof. Shaft 29I is periodically rocked is pivoted on the frame II below the impression cylinder. A guide 2I5 is formed at the end of one of the arms of the bell crank. A connecting rod 2I1 pivoted at 2I9 to the link 201 extends through the guide 2I5. Compression spring 229, reactin between the guide 2I5 and .a nut 22I threaded on the end of the connecting rod, provides a lost-motion connection between the connecting rod and the bell crank. A connecting rod 223 links the other arm of the bell crank and an arm 225 secured to the rock shaft'20I.

The cam 295 is phased to lift the cam follower 2 just before the instant when the raised blanket surface I9 on the impression cylinder l3 engages the printing cylinder I1 to feed the web therebetween at the peripheral speed of the cylinders. This actuates the cam-operated linkage quickly to rotate the rock shaft 20I counterclockwise, as viewed in Figs. 2 and 3. When the cam 205 rotates out of engagement with the follower 2, the cam-operated linkage returns to its original position and the rock shaftZOI is thereby rotated clockwise back to its original position.

A bell-crank

lever having arms

221 and 229 is fixed on the end of rock shaft 20I. As illustrated in Fig. 2, the arm 221 is linked to an arm 23I on rock shaft IZI' by a connecting rod 233. With this setup of the tension mechanism no connection is established between the rock shaft 2! and the rock shaft "I. As illustrated'in Fig. 3, arm 229 of the bell crank may be connected to an arm 235 on the rock shaft I'II by a removable pin 231 extending through an elongate slot 239 in arm 229. With this setup of the tension mechanism, there is no connection between the bell-crank arm 221 and the arm 23! on rock shaft IZI. With the connecting rod 233 linking the arms 221 and 23L .as illustrated in Fig. 2, the aforementioned rapid counterclockwise rotation of the rock shaft 29I effects a corresponding rapid counterclockwise rotation of the stops H1 on rock shaft I2I. of the stops II1 effects the striking of a sharp blow upon the lower ends of the arms 93 and to the right, as viewed in Fig. 3. With either of V the above setups,'the brake 293 for the rock shaft 2! functions temporarily to retain the shaft 29'! atthe limit of its counterclockwiserotion frame 6| as it completes a cycle.

Brakes 24I are provided frictionally to retain the tension frame 6| in the solid-line position of Fig. 3 when the spring devices 9| are connected to bias the frame clockwise. These brakes are provided to prevent the tension frame BI from being pivoted counterclockwise away from the initialposition against stops I61 by the tension of the web in loop 81 acting on tension roll 59. f Each brake comprises a detent 243 pivoted on the frame 55, as indicated at 2 55. Each detent has a friction-surfaced detent notch 246 wherein the lower end of an arm 63 is adapted to engage. The detents are biased by adjustably tensioned springs 241 into engagement with the lower ends of the arms. Springs 241 are connected between the ends of the arms 249 on the detents and threaded rods25l'. Rods 25I' extend Such rotation 7 through guides 253 015 the frame 55. The tension of springs-24.? may be varied by adjusting nuts zefithreaded on th'e ends of the rods. Pivotal.-'m'ovement of thedetents is limited by ad- .iu'stablelimit screws 251 threaded througnthe frame55 into engagement iwitharms .259 on the detent. Limit screws 25.? may be adjusted to move the detent 2&3 completely out of engagement with the lower ends of arms 83, as'in Fig.2.

Operation is as follows:

Forprintin-g' lengths shorter than the circumference of the plate cylinders. t5, the elements of the tension mechanism are connected and adjusted a's'illustrated in Fig. 2. The chains es of the spring :devices 9| are connected to the upper sidesof collars -97, .so that the tension frame 6! is normally biasedcounterclockwise.by'the spring devices, to the'solid-line position of Fig.2 Wherein "the lower ends of arms 53 engage stops 1 i1. Bumpers [3| are adjusted in slot M! to permit tension frame 6| to :pivot clockwise from its normalsposition against stops Ill an amount determined by thearcuate length of the raised :printing surface I9 on the impression cylinder fl. This adjustment issuch that the upper ends of arms 63 of the tension frame 6! engage the bumpers :1 35 when the trailing edge of the raised printing surface i-Sl moves out of feeding contact with the web between the impression and printing cylinders. Rod 233 is connected between arms 22? and 23'! on rock shafts 261 and 12!, respectively. The pin 23-? is removed so that there is no connection between rock shafts 2M and l-il. Limiting screws 25? are adjusted to move detents 243 to a position wherein they cannot engage arms 6-3. The change gear drive for the web-feed rolls 25 and 29 has appropriate change gears connected therein for driving the feed rolls at a peripheral speed less than the surface speeds of the impression and printing cylinders.

During a part of each revolution or cycle of the impression cylinder 13, the web is gripped between and fed forward by the raised printing surface l9 thereon and the printing cylinder ll, and the ink impression is transferred from the surface 19 to the web. The web is positively fed forward during this intermittent printing interval at the surface speeds of the cylinders 13 and I1. During the remainder of each cycle of the impression cylinder i3, the web slips between the cylinders 13 and H at the lower speed of travel imparted theretoby the web-feed rolls 25 and '29. The length of web fed forward at the higherspeed during the printing interval is determined by the arcuate length of the raised printing'surface 19.

When the leading edge of the raised 'printing surface I9 engages the web at the beginning of the printing interval, the Web is accelerated and moved faster thanit is supplied by the web-feed roll '25 to the cylinders l3 and H. Just before this occurs, however, the cam 2G5 engages follower '2l| to actuate the cam-operated linkage 201, 2H, 2|3 etc., rapidly to rotate the rock "shaft 20I counterclockwise. Such rotation of rock shaft 2M is transmitted to rock shaft I'2l through the linkage comprising arm 221, rod 233 and arm 23! rapidly to rotate shaft I2! counterclockwise. Upon rotation of shaft l'2l, stops H1 are rapidly rotated, to kick the lower ends of arms 63 to the left and thus to pivot tension frame -5I clockwise. This relieves the tension in the web in loop 8| substantially at the instant when the web is accelerated so as to prevent undue tensioning of the web between web-feed roll 25 and cylinders l3 and '11. Immediately thereafter the loop '81 tightens around the upper tension-roll 51, and

i the increased tension in 'the loop caused by the differential in the peripheral speeds "of web-feed roll '25 and cylinders 13 and 'l-lswi'ngs tension frame 61 --clockwise until it engages bumpers 13 I. This engagement occurs when the trailing edge of the raised-printingsurface l9 moves out of contact with the web. During such clockwise pivoting of-the'tension framefi I, the spring devices 9| are tensioned. When the trailing edge of raised printing surface I'Q'moves out'of contact "with'the web at the end of the printing interval, the web is decelerateithe "tension of the web in loop '81 decreases, "and the-'tensioned spring devices 9| pivot the tension frame 6| back to its normal position'against stops I 'l 1.

During the printing interval, the web is fed forward 'by the impression and printing cylinders faster than it 'is fed by the printed Webfeed roll 29. The accumulating slack between the cylinders and feed roll 29 is taken up in the loop 81 which is enlarged as the lower tension roll 59 moves to the left upon clockwise pivoting of frame 6|. This maintains proper tension in the web between the cylinders and feed roll 29. When'the webdecelerates at the end of the printing interval, the tension frame pivots counterclockwise back to its normal position and the original size of loop 81'is restored.

For printing lengths equal to the circumference of the plate cylinders" l 5, the elements .of the tension mechanism may remain'in the. connected and adjusted positions 'indicated'in Fig. 2, except that link 233 is removed 'so that there is no .kicking action. The change gear drive fo the web-feed rolls 2'5 and 29, however, is varied to drive the feed rolls at'surface speeds equal to the surface speeds of impression .and printing cylinders l3 and IT. This is done by substituting the appropriate change gears therein. This results in the speed of the web feed being equal to the peripheral'speed of the cylinders and consequently there is no acceleration of the speed of the web during the printing'interval. The tension frame therefore remains stationary and the web is fed through the press at constant uniform speed.

For printing bag lengths longer than the circumference of the plate cylinders, the elements of the tension mechanism are connected and adjusted as illustrated in Fig.3. The chains 93 of the spring devices 9i are connected to the lower sides of the collars 97 so that the tension frame 61 is normally biased clockwise by the spring devices to the solid-line position of Fig. 3 wherein the lower ends of the arms 63 engage stops .I SI. Bumpers I31 are placed at the other ends of the slots [41, with respect to their Fig. 2 position.

The bumpers are positioned to permit tension frame BI to pivot counterclockwise from its normal position against stops I6! an amount determined by the arcuate length of the raised printing surface [9 on the impression cylinder IT. This position is such that the upper ends of arms 63 engage the bumpers I3! when the trailing edge of the raised printing surface l9 moves out of feeding contact with the web. Pin 23'! is inserted through the slot 239 in arm 229 and fastened to arm 235 to connect rock shafts 2M and HI. Rod 233 is removed so that there is no connection between rock shafts 20l and IN. Limiting screws 25'! are adjusted to permit springs 2t! to raise detents 243 to a positionwherein they frictionally latch the tension :frame Bl in the solid-line position of Fig. 3. The change gear drive for the web-feed rolls has appropriate change gears connected therein for driving the web-feed rolls at a peripheral speed higher than the peripheral speed of the impression and printing cylinders. V i

During the printing interval, the web is gripped between" and fed forward by the raised printing surface [Ben the impression cylinder and the printing cylinder at the peripheral speed of these cylinders. This speed is lower than the normal web speed as determined by .the'web-feed rolls 25 and 29. During the remainder of a cycle of the impression cylinder, the web slips'between the cylinders l3 and I! at the higher normal web speed. The length of web fed forward at the lower speed during the printing interval'isdetermined by th e; ,arcuate length of the raised printing surfac When the leading edge of the raised printing surface l9 engages the web at the beginning of the printing interval, the web is decelerated and moved by the cylinders l3 and I! slower than it is supplied thereto by web-feed roll 25 and slower than it is pulled therefrom by web-feed roll 29. Just before this occurs, however, the cam 205 engages follower 2| l to actuate the cam-operated

linkage

201, 211, 2 I3, etc., to rotate the rock shaft rapidly counterclockwise; Such rotation of rock shaft 20l is transmitted to rock shaft I'H through arm 229, pin 23'! and arm 235 to rotate rock shaft HI rapidly clockwise. I Upon such ro-' tation of shaft Ill, stops I61 are rapidly rotated clockwise to kick the lower ends of arms 63 to the right out of the detent notches 246 and thus to" pivot tension frame 'Bl counterclockwise. This relieves the tension in the web in loop 81 substantially at the instant when the web is decelerated, so as to prevent undue tensioning of the wise pivoting of the tension frame 6|, the spring devices 91 are tensioned. When the trailing edge of the raised printing surface I9 moves out of engagement with the web at the end of the printing interval, the web is accelerated, the tension of the web in loop 87 decreases, and the tensioned Spring devices pivot the tension frame 6| back to its normal position against stops I61 with the lower ends of arm 63 engaged in detent notches 246.

During the printing interval, the web is fed forward faster by feed roll than it is taken up by the cylinders l3 and I1. The slack accumulating between the feed roll 25 and cylinders 13 and I! is taken up in the loop 8] which enlarges as the uppertension roll 51 moves to the left upon When the web mechanism is set for printing lengths shorter? 8| in the web from which slack is supplied to the" impression and printing cylinders during the printing interval. The lower tension roll 59 functions 'as a guide to form the loop 81 in the web to take up slack between these cylinders and the printed web-feed roll 29. When the tension mechanism is set for printing bag lengths longer than the circumference of the plate cylinders: (Fig. 3), these functions are reversed; The upper tension roll 5'! forms loop 8| to take up slack in the web between unprinted Web-feed roll 25. and cylinders l3 and Il, this slack resulting because roll 25 is feeding the web forward faster than it is being fed by the cylinders. The lower tension roll 59 forms loop 81 to supply slack to the printed web-feed roll 29. In view of the above, it will be seen that the several objects of the invention are achieved'andj other advantageous results attained,

As many changes could be made in the above, constructions without departing from the scope; of the invention, it is intended that all matter, contained in the above description or shown 'in'. the accompanying drawings shall be interpreted. as illustrative and not in a limiting sense.

I claim: i 1. A tension mechanism for rotary printing; presses comprising a tension frame having a 'tension roll in each end thereof, said frame being pivoted for oscillation about an axis'intermediatesaidj tension rolls, said frame being swingable'aboutl. said axis in onedirection to one initial"p'ositionfagainst one stop or in the opposite-direction to?) another initial position against another stop, a, spring biasing device detachably connected to the frame for biasing said frame to one' of said initial positions, said device being alternatively connect: able to said frame for biasing it to the other of said initial positions, a friction brake device; adapted frictionally to retain said frame in one of said positions when it is biased to that position, and mechanism whereby said brake device may be held out of engagement with said frame when it is biased into the other of said positions.'

2. A tension mechanism for rotary printing presses comprising a tension frame having a ten-J sion roll in each end thereof, said frame being pivoted for oscillation about an axis intermediate said tension rolls, said frame being swingable about said axis in one direction to one initial position against one stop or in the opposite direction to another initial position against another stop, biasing mechanism for selectively biasing said frame to one or the other of said initial positions, said stops being movable, and mechanism for selectively actuating said stops to kick the frame away from the stop against which it is biased. t

3. A tension mechanism for rotary printing presses comprising a tension frame having a tension roll in each end thereof, said frame being pivoted for oscillation about an axis intermediate biasing mechanism for selectively biasing said frame to one or the other of said initial positions,

said stops being movable, mechanism for selectively actuating said stops to kick the frame awayfrom thestop against which it is biased, and

spaced stops for limiting movement of saidmovashram able stops,. one of said spacedstops comprising.

a bumper to cushion impactof a movable stop againstit .4, A tension mechanism for rotary printing pressescomprising a tension. frame having atension roll in each end thereof, said frame being pivoted for, oscillation about an axis intermediate said. tension rolls, said frame being. swingable aboutsaidaxis. in one direction to one initial. positionagainst one stopor in the opposite direction to. another initial position against another stop, biasing 'mechanism for selectively biasing said frame to one or the other of said initial positions, bumpers, for selectively limiting oscillation of said framein one direction. from one of said initial positions or for limiting oscillation of said frame inlthe other direction fromthe other initial position,.said. stops. being movable, mechanism for selectively actuating said stops tokick the-frame away'from, thestop against which it is biased, anda-detent for frictionally retaining .said frame in one of said initialpcsitions.

5, A rotary printing press having impression and printing, cylinders adapted intermittently to printaweb fed therebetween, means. for. feeding said. web betweensaid. cylinders. at a predetermined. speed', a tensi'oning mechanism for tensioning the web entering and'leaving saidcylinders comprising a pair of conjointly movableweb guideeior guidingthe web toforma first. loop in the web; entering the cylinders and to form a second loop in the web leaving the cylinders, a.

pair of. stops spaced inthe path of movement of the. tensioningmechanismand engageable thereby, one of said stops determining. a first initial position; of? the guides wherein said first loopis extendedand from which said guides are movable in one direction to supply slack from said first loop to said cylinders and to take up slack in said second loop,the other stop determining a second initial position of the. guides wherein said second loop is extended and from which said guides are.

movablein the opposite direction to take up slack in the firstloop and tosupply slack from said secondloop to said web. feed .means, biasing mechaanismalternately connectable to said tensioning mechanism for selectively yieldingly biasing said guidestoward oneor the other of saidstops, said stops being movable, and mechanism operating in. timedrelation With the cylinders for selectively. actuating said stops substantially at. the beginning. of a. printing operation to move the tensioning mechanism away from the stop with which it is engaged to relieve the web of undue tension at the beginning. of the printing operation.

6,.A rotary printing press having impression andrprinting cylinders adapted intermittently to print .aweb fed therebetween, means for feeding saidwehbetween said cylinders at a predetermined speed, a tensioning mechanism for tensioning the-wehentering and leaving said cylinders comprising a pair. of conjointly movable web guides: forguiding the web to form a first loop in the. web entering, the cylinders. and toform a sec- OIldilOOPJ-il'l the webleavingthecylinders, a-pair of stops.- spacedinthe path. of movement-of the tensioning mechanism and engageable thereby, one of said-stops determining a first initial position of the guides. wherein said first loop isextended-and from which said guides are movable-in one direction tosupply slack from said first loop to said.cylinders and to take up slackin said second loop, the other stop determining a'second initial position of, the guideswherein said second 1 2 loopis-extended:and-from which said guides are movable-in the oppositezdirectionto take up slack in the first loop andtosupply slack. from said second loop to saidweb feed. means; biasing mechanism alternately connectable to said tensioning mechanism for selectively yieldingly biasing said guides toward one or the other of. said at the beginning of the printing'operation, said linkage being selectively connectable to actuate one or the other of said stops.

7. A. rotary printing press having impression and; printingv cylinders adapted intermittently to print. a web fed therebetween, means-for feeding said web between said cylinders at a, predetermined speed, a tensioning mechanism for tensioning. the web entering and leaving said cylinders comprising a pair of conjointly movableweb guides for guiding the web to form afirst. loop in the webentering the cylindersand to form a second. loop in the web-leaving the cylinders, a pair of stops spaced in the path of movement of theitensioning mechanism and engageable thereby, one-of saidstops determining a. first initial position ofthe' guides wherein said first loop. is.

extendedand from. which said. guides. aremovable inv one direction to supply slack. from said first loop to said cylinders and to .take up slack in said second loop, the other stop determining. a second initial position of. the guides wherein. said second loop is extended, and. from which said guides are movable in the opposite direction to take up slack in the first loop. and. to supply slack. from said second loop to said web feed means, biasing mechanism alternately connectable to said tensioningmechanism for selectively yieldinglybiasing said guides toward one or the other of said stops, a friction brake device engageable with the tensioning mechanism for frictionally retaining the guides in their said second initial position, and mechansm whereby said brake device may be held out of engagement with the tensioning mechanism when the biasing mechanism is connected to bias the guides toward their said first initial position.

8..A rotary printing press having impression and printing cylinders adapted intermittently to print. a web fed therebetween, means for feeding said web between said cylinders at a predetermined. speed, a tensioning mechanism for tensioning the web entering andleaving said cylinders comprising a pivoted tension frame having tension rolls therein for guiding the web to form a first loop-in the web entering the cylinders and.

to iormasecondloopin theweb leaving the cylinders, a pair. ofstopsspaced in the path. of swinging movementwoi the frame. and. en ageable thereby,. one of said stops determining a first initiaLpcsition of the frame wherein said first loop is extended and from which the frame is swingable in one direction to supply slack from said first loop to said cylinders and to take up slack in said second loop, the other stop determining asecond initial position of the frame wherein said second loop is extended and from which the frame is swingable in. the opposite di- 13. rection to take up slack in said first loop and to supply slack from said second loop, biasing mechanism detachably connected to said frame for yieldingly biasing it toward one of said stops, said biasing mechanism being alternatively connectable to said frame for yieldingly biasing it toward the other stop, said stops being movable, and mechanism operating in timed relation with the cylinders for selectively actuating said stops substantially at the beginning of a printing operation to move the frame away from the stop with which it is engaged, to relieve the web of undue tension at the beginning of the printing operation.

9. A rotary printing press having impression and printing cylinders adapted intermittently to print a web fed therebetween, means for feeding said web between said cylinders at a predetermined speed, a tensioning mechanism for tensioning the web entering and leaving said cylinders comprising a pivoted tension frame having tension rolls therein for guiding the web to form a first loop in the Web entering the cylinders and to form a second loop in the web leaving the cylinders, a pair of stops spaced in the path of swinging movement of the frame and engageable thereby, one of said stops determining a first initial position of the frame wherein said first loop is extended and from which the frame is swingable in one direction to supply slack from said first loop to said cylinders and to take up slack in said second loop, the other stop determining a second initial position of the frame wherein said second loop is extended and from which the frame is swingable in the opposite direction to take up slack in said first loopand to supply slack from said second loop, biasing mechanism detachably connected to said frame for yieldingly biasing it toward one of said stops, said biasing mechanism being alternatively connectable to said frame for yieldingly biasing it toward the other stop, said stops being movable, and mechanism operating in timed relation with the cylinders for selectively actuating said stops sub-' stantially at the beginning of a printing operation to move the frameaway from the stop with which it is engaged to relieve the web of undue "tension at the beginning of the printing operation, said stop-actuating mechanism comprising a cam on the impression cylinder and a linkage operable by the cam substantially at the beginning of the printing operation, said linkage being selectively connectable to actuate one or the other of said stops.

10. A rotary printing press having impression and printing cylinders adapted intermittently to print a web fed therebetween, means for feeding said web between said cylinders at a predetermined speed, a tensioning mechanism for tensioning the web entering and leaving said cylinders comprising a pivoted tension frame having tension rolls therein for guiding the Web to form a first loop in the web entering the cylinders and to form a second loop in the web leaving the cylinders, a pair of stops spaced in the path of swinging movement of the frame and engageable thereby, one of said stops determining a first initial position of the frame wherein said first loop is extended and from which the frame is swingable in one direction to supply slack from said first loop to said cylinders and to take up slack in said second loop, the other stop determining a second initial position of the frame wherein said second loop is extended and from which the frame is swingable in the opposite direction to take up slack in said first loop and to supply slack from said second loop, biasing mechanism detachably connected to said frame for yieldingly biasing it toward one of said stops, said biasing mechanism being alternatively connectable to said frame for yieldingly biasing it toward the other stop, and a detent engageable with the tensioning mechanism for frictionally retaining the frame in its said second initial position.

11. A rotary printing press having impression and printing cylinders adapted intermittently to printa web fed therebetween, means for feeding said ,web between said cylinders at a predetermined speed, a tensioning mechanism for'tenders comprising a pivoted tension frame having tension rolls therein for guiding the web to form a first loop in the web entering the cylinders and to form a second loop in the web leaving the cylinders, a pair of stops spaced in the path of swinging movement of the frame and engageable thereby, one of said stops determining a first initial position of the frame wherein said first loop is extended and from which the frame is swingable in one direction to supply slack from said first loop to said cylinders and to take up slack in said second loop, the other stop determining a second initial position of the frame wherein said second loop is extended and from which the frame is'swingable in the opposite direction to take up slack in said first loop and to supply slack from said second loop, biasing mechanism detachably connected to said frame for yieldingly biasing it toward one of said stops, said biasing mechanism being alternatively connectable to said frame for yieldingly biasing it toward the other stop, a friction brake device engageable with the tensioning mechanism for frictionally retaining the frame in its said second initial position, and mechanism whereby said brake device may be held out of engagement with the tensioning mechanism when the biasing mechanism is connected to bias the frame toward its said first initial position.

CARL W. PINCKERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number