BACKGROUND OF THE INVENTION 
     This invention relates generally to a system for storing a quantity of continuous strip material such as tape or film. More particularly, the invention describes a method and apparatus for continuously storing motion picture film on edge on a flat rotating platter, as part of an endless loop film projection system. 
     It has long been recognized in motion picture projection that an endless loop system is desirable, in order to eliminate the need for manual rewinding and rethreading of film in repeated renditions of a program. A number of attempts have been made to provide for storing the film in a coil on a rotating turntable or platter in such a way as to minimize relative longitudinal movement between adjacent film layers in the coil, and yet permit, during each platter revolution, a predetermined length of film to be withdrawn from the center of the coil while the identical length of film is being added to the outside of the coil. The prior systems produce a series of angularly spaced, inwardly directed rounded cusps in the film coil, and are exemplified by the two U.S. Pat. Nos. 4,066,221 and 4,186,891, to Johnson the U.S. Pat. No. 4,208,018 to Wilkinson, and the U.S. Pat. No. 4,504,025 to Potts. These patents, in common with other prior include an application apparatus for incoming film which feeds or applies the incoming film to the rotating platter and means for shaping the film in the coil into a number of spaced inwardly directed cusps. 
     In another apparatus, the strip or film is transported from the edge of the platter toward the center of the coil by the tension of the strip in the outer layers. A cam is carried for rotation with the platter, with the cam having alternating sections of greater distance and lesser distance from the center, typically comprising arcuate sections and chord sections, respectively. The strip is applied to the outer periphery of the coil by a mechanism which includes a cam follower riding on the cam track as the platter rotats. This apparatus provides the desired cusps in the coil of film, but also involves an undesired tensioning of the film with a resultant rubbing of one layer of film against the adjacent layer. This operation is illustrated in FIG. 14. A white chalk line 20 was applied as a straight line or radius on a coil 21 of film resting on a platter 22. This line 20 was extended to the outer periphery of the coil and an index line 23 was applied at the edge of the platter 22 aligned with the line 20. The apparatus was then operated in the normal manner for ten minutes resulting in application of additional film indicated at 24. The slippage of one layer of the film strip relative to the next during the film application is demonstrated by the curve in the line 20. 
     Accordingly, it is an object of the present invention to provide a new and improved method and apparatus for continuously storing a strip of material in a coil and incorporating the advantages of the prior cam and cam follower system, while overcoming the disadvantages thereof. A particular object of the invention is to provide such a method and apparatus including means for relieving tension in the applied strip, as by addition of a pressure roller at a fixed radius for contacting the arcuate periphery of the coil and urging it inward. 
     It is a further object of the invention to provide an improvement in film handling systems by controlling the friction of the coil on the platter and more particularly by providing a continuous friction producing surface on the platter at the arcuate sections thereby facilitating cusp formation and enhancement. 
     Another problem encountered with prior art systems is the positioning of the strip at the center of the coil during takeoff, and control of the strip immediately after its removal from the center of the coil. In prior art configurations, the takeoff guide, typically a takeoff roller or set of rollers, is positioned at the center of the coil and limits the motion of the strip during takeoff. It is an object of the present invention to provide an improvement on this configuration and in particular, to position a takeoff roller assembly above and spaced from the coil thereby doing away with restrictions on strip movement. 
     These and other objects, advantages, features and results will more fully appear in the course of the following description. 
     SUMMARY OF THE INVENTION 
     Apparatus and method for continuously storing a strip of material in a coil on a flat platter having a cam mounted for rotation with the platter, with the cam having a cam track with alternating sections of greater and lesser distance from the center. Means for applying the incoming strip to the periphery of the coil and including a cam follower for engaging the cam track and varying the distance from the center to the point of application of the strip, and an additional roller mounted in a fixed location adjacent the platter for engaging the coil only at the outer peripheral sections thereof for urging the coil inward toward the center and relieving tension in the strip. 
     A friction producing surface on the platter continuously covering that portion of the platter over the cam track sections of greater distance from the center, which friction producing surface extends from adjacent the periphery of the platter at least part way to the center. 
     A strip takeoff roller assembly positioned between the coil of the strip at the center of the platter and the projector or other strip use device, with the assembly positioned above the platter and spaced from the coil and thereby providing for freedom of motion of the strip during takeoff. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a conventional film winding machine with the system of the present invention mounted on the uppermost of the three turntables. 
     FIG. 2 is a top plan view of the major components of an endless loop system embodying the present invention, including the platter and the film application roller assembly and, diagrammatically shown, the film path to and from a film projector; on the platter in dotted outline is shown the approximate contour of the innermost layer of the film winding when the platter is substantially fully loaded. 
     FIG. 3 is a fragmentary plan view on an enlarged scale of the upper portion of the platter as seen in FIG. 2, showing one of the inwardly directed cusps formed in the film winding, the film being shown substantially fully loaded on the platter. 
     FIG. 4 is a fragmentary view on an enlarged scale of the lower left portion of FIG. 2, showing details of the film application arm and tension relieving roller and their interengagement with the platter and film. 
     FIG. 5 is a fragmentary view on an enlarged scale of the distal portion of the film application arm, showing the path of film immediately before it reaches the application roller, and including an illustrative fail-safe mechanism of the system. 
     FIG. 6 is a sectional view taken on arrows VI--VI of FIG. 5 showing details of the drive mechanism for the metering sprocket gear. 
     FIG. 7 is a sectional view on a greatly enlarged scale taken on arrows VII--VII of FIG. 4. 
     FIG. 8 is a fragmentary view taken on arrows VIII--VIII of FIG. 5 showing details of the fail-safe mechanism in its normal operating condition. 
     FIG. 9 is a view similar to FIG. 8 except showing the fail-safe mechanism when it has been actuated by a defect or break in the film. 
     FIG. 10 is a perspective view of a set of template blocks used to assist in shaping successive film layers during the process of loading or make-up in accordance with the present invention. 
     FIG. 11 is a plan view of the platter of the present system with the first layer of film in place, in condition for the commencement of the loading or make-up process. 
     FIG. 12 is a plan view similar to FIG. 11 showing the platter as make-up is virtually complete. 
     FIG. 13 is an enlarged plan view of the takeoff roller assembly of FIG. 1. 
     FIG. 14 is an diagram drawn from a photograph illustrating the operation of the prior art mechanism, and FIG. 15 is a similar diagram illustrating the operation of the apparatus of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings, FIG. 1 shows a film winding machine of generally conventional construction, modified to embody a system of the present invention. The machine includes a rigid support structure indicated generally at 20 including a pair of lower support legs 22, 24 forming a V with the vertex 26 at the left, resting on the floor 28. From the vertex 26 an upright post 30 extends upwardly. Support arms 32 and 34 are fixed to post 30 and project horizontally, each supporting a rotatable turntable 33 and 35 respectively on which a film is stored, on edge, in use. 
     A third support arm 40 extends horizontally between the other arms and carries a rotatable turntable 42. Attached to the upper side of turntable 42 is a platter indicated generally at 46 on which a quantity of film indicated generally at 48 is supported on its edge. The film path during operation includes an upwardly inclined exiting film portion 49 extending from the center of the platter to a guide roller 50 mounted on the post 30. 
     FIG. 2 shows the exiting film portion 49 passing over guide roller 50, and as diagrammatically shown, over guide rollers 51, 52 and 53 to a film projector 54. The film return path from the projector passes over guide rollers 55, 56, 57 and 58, the latter roller being carried at the outer end of a speed control arm 60. The latter arm extends radially beneath the turntable to a speed control means 62 which controls the speed of rotation of the turntable 42. As diagrammatically indicated at 64, the outer end of speed control arm 60 is biased in a clockwise direction by a spring 61 as seen in FIG. 2, in order to maintain a desired tension on the film entering and existing the guide roller 58. The speed control means may be one of those presently in use on endless loop film handling systems. 
     From guide roller 58 the exiting film moves via guide rollers 66 and 67 to the film application arm indicated generally at 70; the film path there will be described in detail in connection with FIGS. 4 and 5. 
     With continued reference to FIG. 2, it will be seen that the contour of the periphery of platter 46 includes a plurality of arcuate sections alternating with straight sections, there being three of each of the two types of sections in the preferred form of the invention illustrated. Thus arcuate sections 72, 74 and 76 alternate with straight sections 78, 80 and 82. Recessed inwardly from the periphery of the platter, and seen in dotted outline in FIG. 2 is the contour of a cam track, geometrically similar to the periphery of the platter, and including arcuate sections 73, 75 and 77, alternating with straight sections 79, 81 and 83. As shown, the periphery of the platter projects beyond the periphery of the cam track, forming an annular projection of substantially uniform equal width immediately inwardly of the platter rim. This annular projection prevents the possibility that, during the winding operation, one or more of the outer layers of film might fall off the edge of the platform. As will be later understood, it is the contour of the periphery of the cam track which is important in the operation of the present invention. This aspect is emphasized in FIG. 3, showing a portion of the platter almost fully loaded with film. 
     The outermost layer of film 48, as it is being wound onto the platter, is vertically aligned with the cam track. The layers applied earlier to the platter will have been incrementally forced inwardly successively as each new outer layer of film is continuously applied in alignment with the cam track. The earlier applied layers of film are thus shaped into a plurality of inwardly directed rounded cusps, one cusp opposite each of the flats or straight sections of the cam track. 
     Thus cusp 85 is located radially inward of straight section 81 of the cam track, and similar cusps partially seen at 86 and 87 are located radially inward of the other two straight sections of the cam track. For proper shaping of the cusps, each of the straight sections and the arcuate sections of the cam track c subtends an angle of about 60° at the center of the turntable. 
     With reference to FIG. 4, metering and application roller arm 70 is pivotally mounted at 90 to a bracket 92 fixed to vertical post 30. Resilient means such as spring 93 urge arm 70 counterclockwise toward the platter 46. Incoming film 95 moves past guide rollers 66 and 67, then past guide rollers 96, 97 and 98, film sprocket 99, and around fail-safe roller 100 to the film application roller 104, which applies the film to become the outermost layer of the coil of film 48 on the platter 46. 
     Fail-safe means are provided to sense the continuous running of the film and to detect any break in the film, particularly a longitudinal split. One embodiment is shown in FIGS. 4, 5, 8 and 9, where a sensor arm 106 is pivotally mounted at 107 to a microswitch unit 108, and is biased lightly counterclockwise. The distal tip 110 of arm 106 continuously senses the existence of the moving film on roller 100. Operation of the device is described with reference to FIGS. 8 and 9. In FIG. 8 the sensor tip 110 lightly contacts film 112 during operation. In FIG. 9 the film 112 is no longer present, as would occur in the event of a film break, and the sensor tip is biased into a groove 114 formed in the roller 100. This movement, in known manner, actuates a microswitch in unit 108, thus stopping the projector and other moving parts of the system. A second microswitch may be symmetrically disposed to sense the film near the outer edge of roller 100. In an alternative embodiment, an all electronic design can be used. 
     In FIG. 7 are shown details of construction of the film metering and application roller assembly. Near the distal end of pivotal arm 70 is journaled a vertical shaft 120. On its upper portion the film application roller 104 is freely journaled. About midway of its length shaft 120 has fixedly mounted thereon a gear 124 and a cam follower disk 126. The disk is in contact with straight section 83 of the platter cam track. Gear 124 is in mesh with gear belt 128, which is partially recessed in a peripheral groove 130 formed in the platter cam track. The gear belt is continuous around the periphery of the cam track. 
     The lower end of shaft 120 has fixedly mounted thereon a spur gear 132 whose pitch diameter is equal to the diameter of disk 126, and gear 132 drives a smaller gear 134 fixed on the lower end of a countershaft 136, on the upper end of which is fixedly mounted sprocket 99. 
     It will thus be seen that during rotation of the platter 46, shaft 120 and countershaft 136, and thus film sprocket 99 are all moved at speeds exactly proportional to and synchronized with the linear speed of the cam track. 
     FIG. 6 shows the relationship and functioning of sprocket 99, and fail-safe roller 100, and their associated parts. A film retainer pad or keeper 138 is carried on an arm 140, with the pad serving to urge the film against the sprocket 99. The arm 140 is slidable between the solid line position with the pad engaging the film, and the phantom line position with clearance between the pad and sprocket for insertion or removal of film. In an alternate configuration, the arm may be pivoted rather than sliding. 
     FIGS. 10 and 11 show the use of template means to assist in the original loading or make-up of a filmed program which is to become part of an endless loop in accordance with the invention. FIG. 10 shows the template means proper, indicated generally at 150 and including a central template block 152 and a pair of laterally spaced blocks or wings 154, 156, the three blocks being joined together to form a set by a strip 160 attached to the blocks. The width of the strip and the height of the template blocks is generally similar to the width of the film being stored. The strip is stiff enough to assume and initially retain its original position seen in FIG. 10, with the strip 160 in an arcuate shape, as seen in FIG. 11, substantially congruent with a portion of the outer circumference of the coil of film to be stored. Other forms and constructions may be utilized for the template means, if desired. By way of example, an elongate sandbag is used in one embodiment. 
     As appears in FIG. 11, one template set 150 is provided for each of the three arcuate sections of the coil being formed. At the beginning of loading or make-up the leading end of the film may be attached to one of the template blocks. 
     The wing blocks resist breakdown of the ends of the arcuate film sections until a sufficient number of layers of film have been applied to the coil to give the coil stability. As stability is attained the flexibility of the template strip 160 permits it to bend, and thus to allow the template wing blocks 154, 156 to move radially inwardly toward their final positions seen in FIG. 12. With make-up thus completed, the leading end of the film is detached from the template block, all template sets are removed, and the leading end of the film is threaded through the film path previously described, to be spliced to the tail end of the film program to form the endless loop. Rendition of the program can then be repeated as many times as desired without further attention by the operator. 
     As best seen in FIG. 11, one or more elongated skid strips may be provided, on the upper surface of the platter to assist the portions of film forming the cusps to move smoothly toward the center of the platter during operation. Thus, with continued reference to FIG. 11, extending radially upwardly from the center of each of the chord portions or straight section of the platter is a strip 180, by preference made of teflon or similar material of low friction. As will be understood, this provides a skid surface for the lower edge of the film as each layer moves inwardly during operation. Additional flanking strips 182 and 184 may be provided to increase the assistance given to the film layers in their inward movement. 
     The parts thus far described are conventional and known in the art. The apparatus of the present invention, to be now described, may be incorporated into existing non-endless loop film handling systems as a retrofit, or may be utilized in a new endless loop film handling system. 
     As seen in FIGS. 2 and 4, a roller 111 is mounted on a plate 113 which in turn is carried on a bar 115 attached to the upright post 30. In operation, the roller 111 is maintained in a fixed position with respect to the center of rotation of the platter. However, the roller position may be adjusted, as by having the plate 113 pivot about a pin 116 on the bar 115, with a bolt 117 passing through a slot in the plate 113 and threaded into the bar 115 for locking the plate and hence the roller in a desired location. 
     A takeoff roller assembly 121 is supported on the arm 34 in a position aove and spaced upward from the platter or turntable 42, as is shown in FIG. 1. The roller assembly 121 may be conventional in construction, such as that shown in U.S. Pat. No. 4,144,991, and is shown in better detail in FIG. 13. Rollers 125, 127 and 129 are carried on a plate 131 in spaced relation. The roller 127 is directly mounted on the plate, while roller 125 is carried on a link 133 pivoting on the plate 131, and roller 129 is carried on a similar link 135. The links are urged toward each other by a spring 137 thereby urging each of the rollers 125 and 129 toward the roller 127. The strip of film 49 passes between the rollers 127 and 129, around the roller 127, and between the rollers 127 and 125. 
     As an aid in obtaining the shape of the arcuate sections of the coil, an anchor pad 170 has been provided on the surface of the platter beneath the initial position of each of the arcuate sections of the coil, as shown in FIG. 11. Typically these pads are made of a material such as a rubbery substance having a high coefficient of friction. Preferably the pads extend from the periphery inward toward the center for about one quarter of the radius. 
     In operation without the pusher roller 111, tension is built up in the film strip as the circumference of the film on the coil increases to the point where the circumference is greater than than permitted by the metering sprocket. At this point, the tension in the outer windings causes the preceding layers of film to progress toward the center of the coil. This action aids in forming the cusps because the resistance of the film to form loops is least at the flats or straight sections. 
     A disadvantage of this mode of operation is the cinching motion of the outer layers of the film which, while aiding in producing the desired cusps, also produces rubbing of one layer of film against the next layer. This action is illustrated in FIG. 14. 
     Incorporation of the pusher roller 111 into the device acts to reduce or eliminate the tension and the resultant cinching action. As best seen in FIG. 2, the roller 111 is positioned to contact the outer layer of the film in the arcuate sections. By precisely positioning the roller, the roller functions to push the film inward an amount about equal to the thickness of the film as each arcuate section passes the roller. This action moves the film inward to the same degree that the cinching action of the prior art device moved the film inward, but eliminates the cinching action and the accompanying rubbing of one layer of film against the next. 
     This action is illustrated in the diagram of FIG. 15 which illustrates the operation of the apparatus used for producing the diagram of FIG. 14, but with the addition of the pressure roller 111. The white line 20 was applied to the film coil 21, and the apparatus was then operated for ten minutes. The illustration of FIG. 15 shows that substantially no cinching action occurred during the application of the film. The operation of the apparatus was otherwise the same as that for the result illustrated in FIG. 14. 
     Another problem encountered with the prior art configuration is that the film being taken off from the center of the coil is not always the same length as that which is being applied at the outer periphery. Film can change length considerably due to changes in humidity or temperature and to the heating effect of the projector lamp. Also, some films have different sprocket hole spacing or have been stretched. As a result, the film being taken off at the center of the coil will change phase and come off at a different angular position than where it was taken off initially. At times, this change in takeoff location is sufficient to cause the film to wrap around the center takeoff plate and cause damage to the film. One approach to overcoming this problem is provision of a film accumulator on the support post, as is done in some prior art devices. However the capacity of such film accumulators is limited and the action of the accumulator can only be adjusted manually by an operator. Also, when the film is initially loaded on the platter and the head end of the film is to be joined to the tail end, a favorable takeoff angle for the film entering the takeoff roller assembly is not always possible. This means that the operator must either cut some of the film to shorten it or add some leader to lengthen it. Both of these options are undesirable. 
     The present invention provides a solution for these problems without encountering the objections of the prior solutions. In the present invention, the takeoff roller assembly is positioned above the film platter and spaced from the film platter as shown in FIG. 1, preferably being supported on an arm from the upright post. This provides a space between the takeoff roller assembly and the film coil wherein the film can move in any direction. This configuration makes the machine insensitive to the phase angle of the film takeoff point and also does away with the requirement for the film accumulator. It also eliminates the possibility of the film loops pinching off film between a loop and the takeoff roller assembly. 
     The friction pads 170 positioned at the arcuate portions of the platter provide a continuous resistance surface at the arcuate sections for aid in cusp formation. These continuous pads provide improved control of the film and positive loop formation with substantially with all types of film and film condition. In the prior art apparatus which relies on film tension for the cinching action, the utilization of a continuous friction surface would not be possible because the continuous friction surface would substantially increase the tension required to move the film inward. However, with the pusher roller of the present invention, the increase in resistance to film movement is not a factor. 
     The pads 170 could extend substantially to the center of the platter, but are not of as great importance at the inner portions of the platter. Hence the preferred configuration is to have the continuous pads 170 extend from the periphery inward for about 1/4 of the radius.
An apparatus and method for continuously storing a strip of material in a coil, such as a multi-hour motion picture theatre film. The apparatus includes a flat platter with drive means for rotating the platter, a cam mounted for rotation with the platter and having a cam track with alternating sections of greater distance and lesser distance from the center of the platter, and means for applying the incoming strip to the periphery of the coil on the platter. The applying means includes a cam follower for engaging the cam track to position the strip in a coil on the platter having inwardly directed rounded cusps with arcuate outer peripheries therebetween. In order to produce or eliminate tension in the strip, a fixed roller is positioned at the arcuate outer periphery for urging the coil inward as the roller contacts the arcuate periphery. Further improvements include provision of a friction surface on the platter for enhancing cusp formation, and a takeoff roller assembly positioned above the platter for improved strip takeoff operation.