US2735677A - Automatic loop control mechanism - Google Patents

Description

o. SANDVIK ET AL 2,735,677

AUTOMATIC LOOP CONTROL MECHANISM Feb. 21, 19 56 2 Sheets-Sheet 1 Filed Dec. 24, 1952 Fig.2

INVENTORS' BYM M W A TTORA/EYS WA 0 M 8 m T 0 JASPER S. CHANDLER Feb. 1956 o. SANDVIK ETAL 2,735,677

AUTOMATIC LOOP CONTROL MECHANISM 2 Sheets-Sheet 2 Filed Dec. 24, 1952 Fig.4

0 TTO SAND V/K JASPER S. CHANDLER INVENTORS K BY A TTOR/VEYS United States Patent 2,735,677 AUTOMATIC LOOP CONTROL MECHANISM Otto Sandvik and Jasper S. Chandler, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application December 24, 1952, Serial No. 327,832 7 Claims. (Cl. 271-23) The present invention relates to web-feeding apparatus, and particularly to an automatic loop control for main taining a substantially constant size loopin advance of a particular web-feeding means which requires such a loop for its operation.

In many different types of apparatus having a means for feeding a web at a known rate, it is desirable or necessary to maintain a free loop in the web in advance of such feeding mechanism. Specific examples of such apparatus are those involving the intermittent feed of the web at a given point, such as motion-picture cameras and projectors, motion-picture film perforators and choppers, etc. where the film is intermittently fed past a gate, through a perforating station, or past a chopping knife, respectively. Many loop control arrangements for this purpose have been proposed in the past but, to our knowledge, they have been too'sluggish in response for use in apparatus involving high-speed movement of the web, have been too complicated, expensive or cumbersome to be entirely practical, or have placed too great a physical strain on the web itself in order to operate.

One object of the present invention is to provide in a web-handling apparatus having a web-feeding means which requires a free loop in advance thereof a loopcontrol arrangement which (1) automatically maintains a substantially constant size loop in the web in advance of said feeding means, (2) is capable of operation with a web moving at any speed whatsoever, (3) is compact and inexpensive in construction, (4) places no deleterious physical strain on the web, and (5) does not damage the surface of the web.

The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its methods of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings in which:

Fig. 1 is a side elevational view of a preferred embodiment of the present invention disclosed in association with an intermittent film-feeding means which may constitute a part of a film perforator;

Fig. 2 is a top plan view of the loop-control arrangement shown in Fig. l and with the film strip shown only in section relative to the film-engaging portions thereof;

Fig. 3 is a vertical sectional view'taken substantially on line 3-3 of Fig. 1;

Fig. 4 is a side elevational detail of a safety switch which automatically stops the apparatus when the film loop becomes lost for any reason;

Fig. 5 is an end elevational view of the safety switch showing its manner of mounting; and

Fig. 6 is a schematic elevational view of another embodiment of loop-control arrangement which operates on substantially the same principle as the preferred embodiment, but dilfers therefrom in structure. v

Briefly, our invention consists in feeding the web into the loop by means of a smooth driving drum onto the surface of which it is selectively pressed by a pivoted presser roller normally moved to a position to ress the web onto the surface of the drum with sufficient pressure so that appreciably no slippage occurs between the web and drum. In order to maintain a substantially constant size loop between this driving drum and the succeeding web transport mechanism, two conditions must be fulfilled: (1) the peripheral speed of the driving drum must be sufiiciently great to cause the size of the loop to increase if there is no slippage on the driving drum, and (2) some means must be provided to allow the web to slip back when the loop reaches a certain size. In accordance with the present invention, the web loop is confined between a fixed guide member and a movable guide member which approach one another at an acute angle and are adapted to engage opposite reaches of the loop. The movable guide member is normally moved toward the film loop with such force that, when the web exerts a small force thereagainst, the length of the loop will increase and its average position will move toward the angle of the two guide members. In so doing, more and more force is required to bend the web into a smaller radius and a greater and greater force is exerted by theweb against the movable guide member until said guide member finally moves in a direction away from the stationary guide member or away from the loop. The movable guide member is so connected to the presser roller supporting means that such movement of the guide member causes the roller to be moved away from the driving drum whereupon a slippage between the web and drum occurs and the loop contracts in size due to the fact that the web is being taken away from the loop faster than it is being fed thereinto by the drum. As soon as the loop has contracted to its desired size, the movable guide member returns to its normal position and, accordingly, allows the presser roller to again press the web onto the driving drum. This fluctuation in size of the film loop between narrow limits takes place repeatedly during the web movement, and the sensitivity of the change in drive produced by the cooperation between the presser roller and the driving drum is so great that it is difficult to see this presser roller move when high web speeds are used.

Referring now to the drawings, an automatic loop control constructed in accordance with the present invention will be described in connection with a filmperforating apparatus wherein the film is intermittently fed to the perforating station by means of the claw or shuttle mechanism. t is pointed out, however, that this loop control is not limited to use on such apparatus or to use in combination with an intermittent feed of the type disclosed, but could be used in any apparatus having a web-feeding mechanism operating at a known rate and which might require a free loop in advance of such feeding mechanism. As shown in Fig. l, a motionpicture film F is fed vertically downward from a supply roll 10 over a free running guide roller 11 mounted on a mechanism plate 12. The film then passes in wrapped relation with a smooth driving drum 13 and into a free loop L from which it is pulled vertically upward past a perforating station, not shown, by means of a shuttle mechanism consisting of a driving cam 14 which is con stantly driven at a known rate and engages a V-shaped follower 15 having a claw 16 which engages perforations made in the margins of the film to move the film through the gate 17. The V-shaped follower 15 is pivoted at 18 to one end of arm 19 which is in turn oscillatably mounted on a fixed pivot 20. A spring 21 wrapped around the fixed pivot 20 normally tends to force the two arms of the follower into engagement with spaced portions of the cam 14. This particular shuttle mechanism is disclosed and claimed in U. S. Patent 2,611,292 to which reference can be had for a more specific description of its construction and operation. Since the present invention is not limited to the use of this particular type of shuttle mechanism, it will suffice herein to point out that in advancing the film, the cam 14- rotates counterclockwise and positively drives the claw upwardly and out of engagement with the film perforation of the advancing stroke, while spring 21 provides the power to return the claw to the bottom of its stroke and then back into engagement with the successive film penoration. As is customary in all operations of shuttle mechanisms of this type, the cam will be driven at a constant uniform rate so that the film is advanced at a known uniform rate from the film loop.

Coming now to the loop-control arrangement per se, the periphery of the driving drum 13 is smooth and friction between the web and the drum periphery is relied upon for feeding the film into the loop. In order to protect the film from abrasion to the picture area thereof, the periphery of the driving drum is provided with a relatively narrow film engaging surface 22 which engages only the margin of the film and the remainder of the periphery of the drum is cut away so as not to engage the film. The inner margin of the film is supported at its extreme edge by the upmost portion of a taper 23 formed on the drum periphery immediately adjacent one of the edge-guiding flanges 24. The filming is adapted to be held in wrapped relation with the drivng drum 13 by means of a presser roller 25 which is of such width as to extend inside the guide flanges 24 of the driving drum, as clearly shown in Fig. 2. The center portion of this presser roll is cut away to be free from engagement with the major portion of the film surface and only the extreme outer edges of this presser roll are provided with a smooth periphery 26, which edges aline with the filmengaging portion 22 of the driving drum to press the film into engagement with this portion of the drum.

The driving drum 13 must be driven at such a rate that its peripheral speed will feed the film strip into the loop L at a rate greater than the rate at which the shuttle mechanism pulls the film from this loop when no appreciable slippage between the film and drum occurs. While any suitable driving means may be provided for drum 13, I have shown this drum mounted on a shaft 27 extending through and journalled in the mechanism plate 12 and the end of said shaft being provided with a pulley 28 engaged by a belt 29 which in turn is connected with the prime mover of the apparatus. The presser roller 25 must be mounted so that it can move between an operative position, wherein it presses the film against the driving drum with sufficient pressure so that no appreciable slippage occurs between the film and the drum, and an inoperative position wherein it is moved slightly away from the film and drum so as to permit a slippage between the film and drum. To this end, the presser roller is rotatably mounted on a shaft 30 fixed to a lever 31 which is in turn oscillatably mounted on a shaft 32 rotatably carried by an arm 33 journalled on a shaft 34 fixed to the mechanism plate 12 and extending parallel to the axis of the driving drum. An examination of Figs. 1 and 3 will show that there is a slight eccentricity between the axis A of the shaft 32 on which the lever 31 is pivoted and the axis B of the shaft 30 upon which the presser roller is mounted. As a result of this eccentricity, the spring 84 fastened at one end 35 to the lever 31 and at the other end 36 to a lug 37 fixed to the mechanism plate acts to swing the presser roller into its operative position relative to the film and driving drum and in which position the roller presses the film onto the drum with such force that no appreciable slippage occurs between the film and the drum. Under these conditions, the film will be fed into the loop L faster than it is withdrawn therefrom by the shuttle mechanism.

The film loop is confined by a stationary guide member 38, fixed to the mechanism plate 12 by bolts 39, which engages the vertical reach of the loop and a movable guide 40 which is fastened to an upturned end 41 on lever 31 by bolts 42 and engages the other reach of the loop. Each of these film guide members is slightly concave in cross section so as to engage the surface of the film only at its edges. The movable film guide 40 is inclined relative to the stationary film guide so as to form an acute angle into which the loop extends. As the film loop starts to increase in size, the movable film offers a slight amount of resistance and causes the loop to contract and extend deeper into the acute angle formed by the guides to a position indicated by the dotted line in Fig. 1. As the loop increases in size and is forced into the acute angle between the guide members, it is constantly bent into a smaller radius and the pressure between the film loop and the movable guide builds up to a point at which the tension in the spring 84 is overcome and the guide is moved in a counterclockwire direction about the axis A. When this occurs, the presser roller is moved slightly away from the driving drum and permits a slippage between the film and the drum so that the shuttle mechanism takes film away from the loop faster than the drum feeds it thereinto. As soon as the loop returns to its desired size, the force between the loop and movable guide member decreases to a point where the spring 84 can again move the presser roller to its operative position and the film is fed into the loop without slippage. This movement of the presser roller to and from its operative position occurs repeatedly during the time the film is being fed, with the result that the film loop L floats between relatively narrow limits as to size and the presser roller is continually oscillating between its two positions. In order to obtain the fairly critical balance required between the tension of spring 84 and the pressure required of the film loop to overcome this spring in moving the movable guide member, the fixed end of spring 84 is adjustably mounted on mechanism plate 12 by means of a slotted bracket 43 engaged by a pair of screws 44 threaded into the mechanism plate.

It is desirable to permit the presser roller to be moved completely away from the periphery of the driving drum in order to permit threading of the film between these two members. This can be accomplished by gripping the end of arm 33 and swinging the same clockwise about its pivotal shaft 34. Such movement will carry the presser roller 25 along with the lever 31 and movable guide 40 away from the periphery of the drum since all of these parts are oscillatably mounted on shaft 32 carried by this arm. The entire assembly including arm 33 is normally returned to an operative position by means of spring 46 fastened at one end to the arm 33 and at the other end to a stud 47 fixed to the mechanism plate. The arm 33 is located in its operative position so that the spring 46 does not assist spring 84 in moving the presser roller to its operative position by means of an adjustable stop screw 48 threaded through the arm 33 adapted to engage a locating stop 49 fixed to the mechanism plate, see Fig. 1.

As an added safety feature to this automatic loopcontrol, means may be provided whereby the power to the film-feeding drum and shuttle mechanism may be automatically cut off when the film loop becomes lost by excessive foreshortening for some reason or other. As disclosed, this may be accomplished by mounting a safety switch and operating mechanism therefor indicated generally as 50 within the loop and at a point where it will be engaged by the loop only when the loop is foreshortened by an excessive amount. As most clearly shown in Figs. 4 and 5, this safety switch may include a switch block 51 fastened to the mechanism plate by means of bolts 52 and including enclosed contacts which are normally closed and connected in series with the line going to the prime mover (or to a relay controlling said line) of the apparaarea-67.7

.tus bymeans of apigtail wire.53, one-lead.of which .iscon- :nected to a terminal .54 and thetother lead of which is .connected to terminal 55 on the switch block. ,As .pointedout before, \thecontacts of this-switch are adapted to be normallyclosedand are opened by depressionof an operating plunger56extending to the outside .ofrthe switch block.

.Pivoted tothe switch block at 57 is a generally elliptical switch-operating member 58 which is ,adapted to .engage and depress theswitch plunger 56 to open the switch when moved in aelockwise directionfrom the position shown in .Fig. 4 but which is normally moved to the inoperative position shown in Fig. 4 either by means of gravity orbymeans .of .a'spring. The lower end of this elliptical switch-operating member 58 is arranged to be engaged .by the film loop if and when saidloop becomes foreshortenedbeyond a certainamount and to bemoved by further-foreshortening of the film loop to an operaby means of-any suitable feeding mechanism, not-shown,

the'film in turn being fed into the loop by means of a driving drum 1-3 having a smooth periphery as before and ,pulling filmvertically downward from any source of supply so thatthe film isin wrapped relation with the "drum. The film is selectively j pressed into contact with the periphery ofthe drum 13-by means of a presser roller rotatably mounted on the end of an arm 75 pivotally mounted on.a stud 7.6 fastened to the'mechanism plate,-not shown. .Alever 77 is mounted in face-to-face relation with the .arm 75by means of a clamping screw 78, and this lever has a nose portion 79 which extends along the inclined reach of the film loop. This lever has two upstanding lugsl8i) which are tapped to receive set'screws 81 adapted to engage the shaft 76 at circumferentiallyspaced points. By adjustment of these set screws-when the clamping screw 78 is in a loosened condition, the relative position between the lever 77 and arm 75 can be readily adjusted for purposes of adjusting the operating position of arm 94. After the setscrews are adjusted to properly position the lever77 relative to the arm 75, the clamping screw 781is-tightened to hold these two members in fixed relation. 'While they thensconstitute in effect a singlemember, it is advantageous to make up this assemblage in two parts rather than as asingle part so that the desired operating position can ,be obtained without having to rely upon manufacturing tolerances which would be impractical to maintain.

The .presser roller isnormally moved to an operative position where it presses the film against the periphery of the driving drum by means of a tension spring 82 which is connected at one end to the arm 75 and at the other end to astationary part 83 such as the mechanism plate. The vertical reach of the film loop is confined, as before, by a stationaryfilm guide 38 and the other reach of the loop is confined by -amovable film guide 94 pivoted to the mechanism p1ate'at 85 and inclined relative to the stationaryguide to form an acute angle therewith. As the film'loop increasesin size and moves to the dotted line position, it is bent .at a shorter radius and during this transitiona force is ultimately produced on the end of the movable' guide member '94 above. its pivot point 85 which tends toswin-g .this guide in a counterclockwise direction so that a roller 86 on theother end thereof presses against the nose portion 79 ofthe lever 77 and overcomes spring 82-to-move the presser roller to an inoperative position where: it allows a certain amount of slippage between the filmand the drum. A spring 87, connected at one end to the movablemember and at the other endto a fixed lug 88, tends to assist the film loop in swinging the movable 6 ,guidein a direction .to overcome spring 8 2.and move the ,presser roller ,to an inoperative :position. By proper ad- .justmentofthetension,in;the springs 82 and 87, thelength .of the lloop will .be maintained between narrow limits.

For .the purpose .of obtaining this critical adjustment of thetension in springs87 and 82, the fixed ends 88 and-83 :canbeadjustably clamped to the frame by means not shown. Forthreading purposes, .theextreme end 89.0f .arm 75 can be manually grasped to swing the arm and presser roller in a clockwise direction about shaft 76 to a threading position.

From the .above description, it is believed that it will be readily understood that .a loop-control mechanism, :constructedin accordance with the present invention, is capable of operation fWitllOllt subjecting the film to any :damaging 'physical strength. The arrangement is very sensitive .in response and can be adjusted without difficulty to maintain a free loop within very narrow limits. A very slight movement ofthe presser roll relative to the driving drum will suffice to shift the film drive from a nonslipping condition to a slipping condition so that the mechanism will function regardless of 'the speed at which the film is being fed. In fact, We have operated a loop-control mechanism, constructedin accordance with each of these embodiments, in apparatus wherein the film is moved as fast as 90 feet per-minute and, at this speed, the-film loopis-maintained in'a constantly fluctuating condition by means of'repeatedimovement of the presser roll between its operative and inoperative positions which .is hardly .discernable to the naked eye.

Although-we have shown-,and-described certain specific embodiments-of our invention, we are fully aware that manymodifications thereof are possible. Our invention, therefore, is not to be limited to the precise details of construction shown and described, and is intended to cover all modifications coming within the scope of the appended claims.

Having thus described our invention, what we claim is new and desire'tosecure by Letters Patent of the United States is:

1. automaticloop control for maintaining a free loop of film in front of a film strip feeding means which withdraws-film fromsaid loop at a given rate, and. comprising in combination a smooth film driving drum for feedingrfilm into saidloop; means for holding the film in wrapped relation with the periphery of said drum, includingqa pivoted; guide member, a presser roll carried bysaid guide member tomove between an operative position, wherein it presses said film onto the periphery of said drum with :sufiicient pressure that the drum feeds the film withno appreciable slippage, and an inoperative position, wherein it allows slippage between the film and drum; means "for rotating said drum at such a rate that when no slippage occursbetween the film and its periphery it will feed the film into said loop at a rate in excess of that at which said feeding means draws film from said loop; a spring acting on said guide member to normally move said presserrol-ler to its operative position; means for directlymoving said presser roll to its inoperative position against the action of said spring when said loop expands-beyonda given size, andcomprising a loop confining means, including a movable loop-confining member directly connected to said guide member and normally moved by saidspring to a position to confine a reach of the loopof film to aloop of given size and adapted to be engaged and moved bysaid reach to counteract the force of said spring when said loop expands beyond said given size.

2. An automatic loop control for maintaining a free loop of film in front of a film strip feeding means which Withdraws film from said loop at a given rate, and comprising in combination a smooth film driving drum for feeding film into said loop; means for holding the film in wrapped relation Withthe periphery of said drum, including a presser roll pivoted to move between an operative 7 position, wherein it presses said film onto the periphery of said drum with sufiicient pressure that the drum feeds the film with no appreciable slippage, and an inoperative position, wherein it allows slippage between the film and drum; means for rotating said drum at such a rate that when no slippage occurs between the film and its periphery, it will feed the film into said loop at a rate in excess of that at which said feeding means draws film from said group; a spring normally moving said presser roll to its operative position; means for moving said presser roll to its inoperative position when said loop expands beyond a given size and comprising a fixed loop-confining member; a movable loop-confining member spaced from said fixed member and inclined relative thereto to form a V-shaped trap into which said loop is forced as it increases in size; means normally moving said movable member toward said fixed member and adapted to be overcome by the expanding force of the loop of film as it expands into said V-shaped trap; and a connection between said movable member and said presser roll causing said presser roll to move toward said drum when the film loop is equal to or less than said given size and to be moved away from said drum when the loop increases beyond said given size.

3. An automatic loop control according to claim 2, characterized by the inclusion of means for automatically stopping said film driving drum when said free loop becomes lost.

4. An automatic loop control for maintaining a free loop of film in front of a film strip feeding means which withdraws film from said loop at a given rate, and comprising in combination a smooth film driving drum for feeding film into said loop; means for holding the film in wrapped relation with the periphery of said drum, and including a presser roll pivoted to move between an operative position, wherein it presses said film onto the periphery of said drum with sufficient pressure that the drum feeds the film with no appreciable slippage, and an inoperative position, wherein it allows slippage between the film and drum; means for rotating said drum at such a rate that when no slippage occurs between the film and its periphery it will feed the film into said loop at a rate in excess of that at which said feeding means draws film from said loop; a spring normally moving said presser roll to its operative position; means for moving said presser roll to its inoperative position when said loop expands beyond a given size; said last-mentioned means including a fixed loop-confining member; a movable loop-confining member spaced from, and inclined relative to, said fixed loop confining member to form a V-shaped trap into which said loop is forced and is compressed as it increases in size and movable from an inoperative position to an operative position by the expanding force of said loop as it expands into said trap and is increasingly restricted by the narrowing end thereof; a connection between said movable member and said presser roller causing said presser roller to be moved to its inoperative position when said movable member is moved to its operative position and allowing said presser roller to return to its operative position when said movable member returns to its inoperative position; and means for manually moving said presser roller through its inoperative position and completely away from said drum for purposes of threading a film between the two.

5. An automatic loop control for maintaining a free loop of film in front of a film strip feeding means which withdraws film from said loop at a given rate, and comprising in combination a smooth film driving drum for feeding film into said loop; means for rotating said drum at such a rate that when appreciably no slippage occurs between the film and drum it will feed the film into said loop at a rate in excess of that at which said feeding means draws film therefrom; means for holding the film in wrapped relation with the periphery of said drum, and including a presser roller mounted to move between an operative position, wherein it presses the film onto the periphery of said drum with sufiicient pressure that the drum feeds the film with no appreciable slippage, and an inoperative position, wherein it allows slippage between the film and the drum; means for mounting said presser roller to move between its two positions including a lever carrying said roller and pivotally mounted on an axis eccentric to said roller axis, a spring acting on said lever to pivot the same in a direction, and to an extent, to move said roller to its operative position; and means for pivoting said lever in a direction in opposition to said spring to move said roller to its inoperative position, and including a fixed guide for engaging and confining one reach of said film loop; a second movable film guide fixed to said lever for engaging the other reach of said film loop and inclined relative to said fixed guide to form therewith a V-shaped trap into which the loop extends and becomes more contracted as it increases in size, thus building up a pressure tending to move said movable guide and said lever to move said presser roller to its inoperative position when said loop exceeds a given size.

6. An automatic loop control according to claim 5, characterized by the fact that said lever is pivotally mounted on a manually manipulatable arm which is in turn pivoted to swing said presser roller and lever assembly away from said drum for purposes of threading a film between the roller and said drum; a spring normally acting on said arm to move the same toward said drum; and an adjustable stop for limiting movement of said arm due to the influence of said spring.

7. An automatic loop control for maintaining a free loop of film in front of a film strip feeding means which withdraws film from said loop at a given rate, and comprising in combination a smooth film driving drum for feeding film into said loop; means for rotating said drum at such rate that when appreciably no slippage occurs between the film and drum it will feed the film into said loop at a rate in excess of that at which said feeding means draws film therefrom; means for holding the film in wrapped relation with the periphery of said drum, and including a presser roller mounted to move between an operative position, wherein it presses the film onto the periphery of said drum with sufficient pressure that the drum feeds the film with no appreciable slippage, and an inoperative position, wherein it allows slippage between the film and the drum; means for mounting said presser roller to move between its two positions including an arm rotatably supporting said presser roller and pivotally mounted to permit movement of said roller between its two positions relative to said drum; a spring normally forcing said arm toward said drum and the presser roller thereon into its operative position; means for moving said presser roll to its inoperative position when said loop expands beyond a given size and comprising a fixed film guide engaging and confining one reach of said film loop; a pivoted guide member spaced from, and inclined toward, said fixed guide to engage the other reach of said loop and in combination with said fixed guide forming a V-shaped trap into which the film loop extends as it expands and by which it is contracted to build up an increasing pressure on one end of said pivoted guide tending to swing said member about its pivot; a roller on the other end of said guide member engaging said arm, whereby the spring acting on said arm tends to pivot the other end of said guide member toward said film loop; and a second spring connected to said guide member to oppose movement of said member under the action of said first spring; said two springs being balanced so that a slight increase in loop size beyond said given value will cause a movement of said presser roller to its inoperative position and a decrease in loop size to said given value will cause a return of said presser roller to its operative position, whereby the size of the loop is maintained within narrow limits.

References Cited in the file of this patent UNITED STATES PATENTS 1,115,828 Johnston Nov. 3, 1914 10 Swab June 1, 1926 La Bombard et a1 Sept. 3, 1929 Moore Dec. 24, 1935 Simpson Aug. 30, 1949 Cumfer Dec. 26, 1950

Images