METHOD AND APPARATUS FOR SPLICING CUBE CORNER RETROREFLECTIVE SHEETING

Abstract: A method and device for splicing, i.e., laminating in juxtaposed position, retroreflective cube corner sheeting during lamination comprises a roll applicator apparatus suitable for mounting a plurality of rolls of sheeting, a mechanism for dispensing sheeting from the rolls, and a shim mechanism for maintaining constant separation between sheeting on adjacent rolls. The invention permits simultaneous lamination of the sheetings onto a substrate in side by side spliced or juxtaposed relation with a constant separation distance along the length of the splice and with independent rotation of each roll.

Description: METHOD AND APPARATUS FOR SPLICING CUBE CORNER RETROREFLECTIVE SHEETING 5 Field of the Invention The invention relates to joining retroreflective cube corner sheeting. More particularly, a splicing apparatus and method permits simultaneous side by side splicing of retroreflective 10 cube corner sheeting during lamination. Background of the Invention The manufacture of durable traffic control signs and other signage for use in work zones or other 15 traffic areas utilizes many different types of material. A preferred material comprises fluorescent retroreflective cube corner sheeting, also known in some instances as diamond grade sheeting. The sheeting consists generally of prismatic lenses formed in a 20 transparent synthetic resin which is sealed and backed with a pressure sensitive adhesive and polyethylene liner. The sheeting is then applied to a substrate and then sized according to the particular application. Certain types and sizes of retroreflective cube corner 25 sheeting are required for use in specific applications. For example, in a construction work zone it is preferable to have very large signage faces, and therefore it is necessary to combine more than one standard sheet of sign material in order to manufacture 30 large size sign configurations. Current work zone requirements in many countries include signs with face dimensions of up to approximately 48 inches (122 centimeters) per side. When manufacturing very large signs, it is 35 normally necessary to use more than one roll of sheeting material. This is due to manufacturing and optical limitations that have prevented production of certain retroreflective cube corner sheetings at sizes greater than 36 inches (92 centimeters) wide. Therefore, it has been necessary to hand splice two retroreflective cube corner sheets together in order to achieve the large size signage faces. This typically requires use of a hand squeeze roller and adhesive tape. When manufacturing these signs by hand it is typical to have a low production rate, for example, of approximately 10 signs per hour. .Another method of manufacturing large size signs is to use a motorized apparatus known as a laminator or a motorized squeeze roll applicator, such as a 3M Brand Interstate Squeeze Roll Applicator. Use of a motorized squeeze roll applicator currently requires a purposeful overlap of adjacent sheets, and then use of a straight edge to remove the overlap and to create a region of intentional separation between the two sheets. It is important to precisely manufacture this separation distance in order to permit normal shrinkage or expansion when the product is in use, while at the same time minimizing any apparent optical separation to a viewer of the sign. Summary of the Invention In all embodiments, the invention is a method and a device for splicing retroreflective cube corner sheeting during lamination. In a first embodiment, the device comprises a roll applicator apparatus, engaging means, brake arms, and axial spacers. The roll applicator apparatus comprises a main shaft suitable for supporting and dispensing a plurality of rolls of retroreflective cube corner sheeting. The engaging means engages and removes the sheeting from the rolls. The brake arms each have a first end movably linked to the roll applicator apparatus and a second end which rides on a roll of the sheeting to regulate the rotation of the roll during dispensing. The axial spacers are positioned along the main shaft adjacent the rolls to axially fix the location of each roll along the shaft and to fix a separation distance between the rolls. This permits sheeting on adjacent rolls to be simultaneously laminated onto a substrate in side by side spliced relation with a constant separation distance along the length of the splice, and it allows independent rotation of each roll. It will be understood that "spliced relation" is used herein to mean the sheetings are placed in a juxtaposed, i.e., side by side, position rather than an overlapping position. Similarly a "splice" as used herein refers to lamination of a plurality retroreflective sheetings in such a position. In another embodiment, the invention comprises a roll applicator apparatus having a rotatable main shaft and an auxiliary shaft. The main shaft is suitable for supporting and dispensing a first roll of retroreflective cube corner sheeting, and the auxiliary shaft is suitable for supporting and dispensing a second roll of retroreflective cube corner sheeting. In cooperation with shim means for maintaining optimal separation distance between sheetings, the two rolls dispense sheeting so that a signage product is produced using a side by side spliced lamination method. Brief Description of the Drawings Figure 1 is a perspective view of a representative motorized squeeze roll applicator including one embodiment of the present invention. Figure la is a side sectional view through the shaft, sleeve, core, and sheeting material, taken along line la-la in Figure 1. Figure 2 is a simplified side elevation schematic view of the brake and shim rudder features of one embodiment of the invention. Figure 3 is a side elevation view of a brake arm according to one embodiment of the invention. Figure 3a is a section view of a brake arm first end comprising a hinged clamp assembly for linking a brake arm onto a roll applicator apparatus. Figure 4 is a side view of a shim rudder according to the invention. Figure 5 is a rear elevation view of a roll applicator apparatus according to the invention. Figure 6 is an enlarged sectional view of a roll applicator apparatus according to the invention using a shim rudder to maintain optimal separation between adjacent sheets of material. Figure 7 is an alternate embodiment depiction of a roll applicator apparatus illustrating use of a removable and adjustable auxiliary shaft subsystem suitable for supporting a second roll of sheeting. Figure 8 is a side section view of a brake tensioner unit for use in applying adjustable braking tension to an auxiliary shaft, taken along line 8-8 in Figure 7. Figure 9 is a front elevation view of an alternate embodiment auxiliary shaft subsystem, with parts cut away. Figure 10 is a perspective view of an alternate embodiment roll applicator apparatus using a removable and adjustable auxiliary shaft subsystem, with alternate positions for the auxiliary shaft subsystem shown in shadow lines. Detailed Description of the Invention Use of retroreflective cube corner sheeting, such as SCOTCHLITE™ Durable Fluorescent Diamond Grade Sheeting 3924F/G Orange, manufactured by 3M Company, has greatly improved the recognition of signage at construction work zones as well as in other traffic control applications. The retroreflective cube corner material is normally pre-coated with a pressure sensitive adhesive for application to a sign backing substrate. Currently there is great demand for signs having dimensions of about 48 inches (122 centimeters) per side. However, due to manufacturing and optical restrictions, retroreflective cube corner, sheeting is only manufactured in dimensions up to a maximum of about 36 inches (92 centimeters) in width. Accordingly, it is necessary to combine a plurality of sheets to manufacture signage of greater dimensions per side. This has normally been accomplished through use of the techniques described above which include a manual lamination process or a motorized squeeze roll lamination process. In a manual process, problems exist with respect to a very low through-put or productivity of workers. In addition, the labor rate of workers may vary widely, as well as training and availability of the workers to assemble the sheetings into signage. Use of motorized squeeze roll applicators also has undesirable characteristics in that intentional overlap of adjacent sheetings occurs. This creates unnecessary waste of valuable retroreflective sheeting material. However, the overlap is necessary in order to overcome equipment and roll sizing imprecisions. In both the manual as well as the motorized lamination processes for assembly of a plurality of sheetings, it is necessary to maintain a separation distance between the adjacent sheetings of about 1/16 inch to about 1/32 inch (1.58 to 0.79 millimeters) . This is due to the shrinkage and expansion of the materials caused by weathering of the signage. Due to the replacement rate required to maintain optical standards, even for the best quality signs, it is desired to provide increased productivity in the manufacture of the signs as well as to improve the precision in the separation distance between sheetings. These improvements will minimize rejects and reduce costs. Figure 1 illustrates, in part, a motorized roll applicator apparatus 10, similar to a 3M brand Interstate Squeeze Roll Applicator, which is representative of such motorized roll applicator apparati known in the art. Using known technology, roll applicator apparatus 10 enables sign shops to fabricate signs by mounting a roll 14 of retroreflective cube corner sheeting 16 onto a main shaft 20, also referred to as a spindle or mandrel. Shaft 20 is designed for mounting within side walls 23 and for rotating in a manner suitable to dispense sheeting material 16. Engaging means 25, which may comprise nibs or laminating rollers, engages and removes sheeting 16 from roll 14. Sheeting 16 is then applied by adhesive lamination or other means to a signage substrate 28, which is often a metallic sheet. In this manner, conventional sign sheeting material is manufactured using a motorized system. Figure 1 also discloses features of the present invention which permits use of existing motorized roller applicator apparati to provide simultaneous side by side splicing of a plurality of rolls during a lamination process. For example, as shown in Figure 1, main shaft 20 also provides support for roll 34 of retroreflective cube corner sheeting 16. Roll 34 may be of any desired length, however a length of either 12 inches, 24 inches, or 36 inches, or similar normal increments according to local standards, is preferable. Axial spacers 40 are positioned along main shaft 20, and are preferably linked to the roll applicator apparatus at the main shaft. For example, as shown in Figure 1, axial spacers 40 are substantially linked to main shaft 20 by compressed positioning between roll 16 and clamp means 42, which functions as a locking collar type of mechanism. Axial spacers 40 preferably are positioned along the shaft to prevent axial movement of any sheeting roll spinning about the shaft. The spacers also fix a separation distance 45 between rolls 14, 34, so that sheeting 16 on adjacent rolls is simultaneously laminated in a side by side relationship onto a substrate 28 with a constant separation distance along the length of the splice. The width of axial spacers may vary, and the spacers may be coated with a friction reducing coating. In one embodiment, a teflon coated surface is applied to or used with axial spacers 40. The embodiment of the invention depicted in Figure 1 comprises a plurality of rolls of sheeting material positioned on a single shaft. However, due to the relatively different consistency between rolls of sheeting material 16, the rate of rotation of the rolls may differ slightly, which greatly effects the quality and precision of the final product. Accordingly, each of the rolls 14, 34, have at least one cylindrical sleeve 48 placed around the length of the shaft 20 between each roll and the shaft. Use of sleeves 20 permits independent rotation of each roll according to the consistency of the material on the roll. However, in order to prevent improper rates of rotation of each roll, one or more brake arms 50 are used. Each brake arm 50 comprises a first end 52 which is movably linked to roll applicator apparatus 10, such as at spindle 54 in Figure 1. A brake arm second end 56 presses against and rides on a roll of the sheeting in order to regulate the rotation of the roll during dispensing. Additional details of one embodiment of brake arm 50 are disclosed below. Figure la is a section view depicting retroreflective cube corner sheeting 16 mounted on a spool or core 60, which is frequently a cardboard material. Region 63 comprises a clearance area between core 60 and cylindrical sleeve 46. As described above, cylindrical sleeve 48 is positioned around shaft 20 to permit independent rotation of each roll, and to provide some reduction in the radial distance between core 60 and cylindrical sleeve 48. This promotes more uniform dispensing of sheeting 16, although it is recognized that a shim or a reduction in the size of .core 60 may also provide means for reducing the clearance region. It is also recognized that bearing means of another type of manufacture may be built directly into either main shaft 20 or into core 60 in order to permit independent rotation of a plurality of rolls on a single shaft. Although it is expected that manufacturing costs limit such embodiments, they are nevertheless likely to provide similar advantages as the embodiment depicted in Figures 1 and la. Figure 2 illustrates a side view of brake arm 50 resting on a roll of sheeting. Figure 1 and Figure 2 each depict a shim rudder 66 having a first end 68 movably linked to roll applicator apparatus 10 and a second end 70 preferably comprising a shim 72. Shim 72 is preferably constructed with a width suitable for placing the shim between each roll of sheeting to further maintain optimal separation distance of the sheeting on adjacent rolls at a location just prior to the point of lamination of sheeting 16 onto substrate 28. Figure 3 is a side view of brake arm 50 depicting brake arm second end 56. Counterweight 75 is provided to ensure that brake arm 50 is maintained in a resting position on a sheeting roll. Counterweight 75 may comprise weighted material of varying weights depending on the size and thickness of the particular sheeting roll. Brake arm 50 further comprises felt pad 77, or similar soft material, for engaging sheeting 16 in a non-damaging manner. A pad flange 78 is also disclosed in this embodiment to provide means for mounting and retaining felt pad 77, which may comprise a replaceable felt pad. Figure 3a discloses an optional embodiment of brake arm 50 in which brake arm first end 52 comprises rapid action clamp means 80. Clamp means 80 may comprise a hinged clamp, with easily operated pin or screw means 82 for securing and releasing clamp means 80. The embodiment of Figure 3a permits easy replacement and reconfiguration of brake arm 50 along any part of a suitable mounting portion of apparatus 10. Figure 4 is an enlarged view of one embodiment of shim means, here depicted as shim rudder 66, which is used to maintain a constant separation distance between adjacent sheetings. Rudder arm 84 comprises a shim holder clamp 86 for holding one or more shims 72. Shim rudder clamp 90 is preferably arranged for secure, but readily removable, attachment to a mounting portion of apparatus 10. It is recognized that certain other types of shim means may also be used within the scope of this invention. Figure 5 depicts a rear view of a portion of apparatus 10. In particular, Figure 5 illustrates that differently sized rolls may be used in combination with this invention to create side by side spliced retroreflective cube corner sheeting. This feature is shown by comparing the length LI of roll 14 and length L2 of roll 34. Figure 5 also depicts use of brake arm 50 in one or more locations along a spindle 54. Shim rudder 66 is shown as an optional feature in this depiction. Referring to Figure 6, shim rudder 66 is depicted in use positioned between sheeting 16 to provide precise separation between the adjacent sheetings. It is also noted in Figure 6 that sheeting 16 from each roll is of equal length L3. Figures 1-6 also disclose one embodiment of a method for splicing retroreflective cube corner sheeting, or other sheeting of variable caliper and sensitive optical construction, during lamination. Such a method includes, for example, splicing in side by side or butt-like relation a plurality of sheetings during lamination. The method comprises providing a roll applicator apparatus comprising a rotatab],e main shaft suitable for supporting and dispensing a plurality of rolls of retroreflective sheeting. Then, engaging means for engaging and removing the sheeting from the rolls is configured to bring the sheeting into contact with a substrate material. Brake arms are positioned so that a first end is movably linked to a roll applicator apparatus, and so that a second end rides on a roll of the sheeting to regulate the rotation of the roll during dispensing. Axial spacers are positioned along the main shaft adjacent the rolls to axially fix the location of each roll along the shaft and to fix a separation distance between the rolls. This permits the sheeting on adjacent rolls to be simultaneously laminated onto the substrate in side by side spliced relation with a constant separation distance along the length of the splice. The method may further comprise the step of placing at least one cylindrical sleeve around the length of the main shaft between each roll and the main shaft. Yet another optional step comprises using a shim rudder, as described above, to further maintain optimal separation distance of the sheeting on adjacent rolls at a location prior to the point of lamination of the sheeting onto the substrate. A preferred separation distance is achieved along a length of the splice in consistent manner so that the separation distance is within a range of between about 1/16 inch (1.58 mm) and 1/32 inch (0.79 mm). Achievement of this level of precision in a high through-put manufacturing process, as disclosed and taught in this invention, provides great advantage in the manufacture of large area retroreflective cube corner signs. Sheeting material manufactured using the splicing method described above is quite useful and is manufactured with lower cost than previous techniques. A preferred retroreflective sheeting material manufactured using the splicing method disclosed above comprises a fluorescent retroreflective material manufactured for use as a traffic control sign. Figure 7 discloses an alternate embodiment device for splicing retroreflective cube corner sheeting during lamination. Figure 7 depicts, in perspective view, a roll applicator apparatus 100 which comprises a rotatable main shaft 103 suitable for supporting and dispensing a first roll 107 of retroreflective cube corner sheeting, and an auxiliary shaft 110 suitable for supporting and dispensing a second roll 113 of retroreflective cube corner sheeting. Apparatus 100 comprises elements of a conventional roll applicator apparatus similar to that depicted representatively in Figure 1. However, the embodiment of Figure 7 comprises the auxiliary shaft 110 and its related components in a manner which permits adding on the auxiliary shaft in a relatively simple manner to an existing machine having only a main shaft. In the embodiment depicted in Figure 7, main shaft 103 rotates at a desired speed, and is controlled using tensioned movement as determined by brake adjustment mechanism 116. Main shaft 103 traverse adjustment mechanism 118 is also provided. Axial spacer 40 is optionally used along with clamp means 42, which may comprise a tapered collar or spool clamp of various sizes or shapes. In essence, it is only necessary to fix the axial location of roll 107 with whatever means necessary and convenient. Auxiliary shaft 110, and related components, preferably comprise a subsystem mounting bracket 122 (shown in this embodiment as an angled base) , a spindle or shaft bearing 124 which acts as a thrust bearing mechanism to regulate axial movement of the shaft, a brake mechanism 128, and a snap collar mechanism 131. The relatively few parts involved in adding on the auxiliary shaft and related components, as depicted in Figure 7, provides great advantage to this embodiment. In particular, this embodiment permits modification of pre-existing machines of various design with a relatively simple addition of an application kit comprising ergonomic and user friendly components which permit rapid addition of a second roll of retroreflective cube corner sheeting for use in a unique side by side splicing process during lamination. Figure 8 is a side section view along lines 8- 8 of Figure 7 depicting one representative example of a tensioner or brake mechanism 128 designed for applying an adjustable tension means or braking force to independently adjust the braking tension applied to auxiliary shaft 110. In this embodiment, adjustable handle 134 permits easy adjustment of the tension applied to shaft 110, depending on the particular characteristics of the material on roll 113 and the speed of rotation of shaft 103. Figure 9 is a side partial cutaway view of auxiliary shaft 110 and related components, including a roll 113 positioned about the shaft. Figure 9 more clearly illustrates snap collar 131, which preferably comprises a sturdy collar mechanism having a threaded screw adjustment for tightly connecting the collar to auxiliary shaft 110, but with means for rapid removal and replacement of the collar during replacement of rolls 113. Core engaging means 140 is provided to engage and lock the core of roll 113. This prevents independent spinning of the roll, which could cause improper configuration or dispensing of the sheeting from the roll. In the representative embodiment shown in Figure 9, core engaging means 140 comprises a split lock chuck having locking elements 143 for engaging and locking a core. Both Figures 7 and 9 illustrate preferred mounting means 144 for easy, rapid, and sturdy connection of angled base 122 to a side portion 146 of the roll applicator apparatus. Figure 10 depicts an alternate embodiment dual shaft roll applicator apparatus 200 which functions substantially similar to that disclosed in the embodiment of Figure 7. However, the embqdiment of Figure 10 comprises a dovetail slide adjustment mechanism 204 for axially adjusting auxiliary shaft 110 and roll 113. In addition, support arm 210 is pivotable on base plate 214 about swing axis 218. In a lowered position, shown in shadow lines 220, support arm 210 permits movement of auxiliary shaft 110 and related components out of the way of main shaft 103 and roll 107. This is particularly useful during replacement of roll 107. In all of the above devices and methods using the above embodiments, the finished signage product comprises a side by side spliced retroreflective cube corner laminate sheeting with consistent separation distance between the adjacent sheetings. This results in enhanced performance of the sheeting, as well as a product that has been previously unknown and therefore unavailable.

Claims: CLAIMS : 1. A device for laminating a plurality of retroreflective cube corner sheetings in juxtaposed position on a substrate, characterized in that said device comprises: a) a roll applicator apparatus comprising a main shaft suitable for supporting and dispensing a plurality of rolls of retroreflective cube corner sheeting; b) engaging means for engaging and removing the sheeting from the rolls; c) brake arms each having a first end movably linked to the roll applicator apparatus and a second end which rides on a roll of the sheeting to regulate the rotation of the roll during dispensing; and d) axial spacers positioned along the main shaft adjacent the rolls to axially fix the location of each roll along the shaft and to fix a separation distance between the rolls so that the sheeting on adjacent rolls is simultaneously laminated onto a substrate in desired juxtaposed relation with a constant separation distance and to allow independent rotation of each roll. 2. The device of claim 1 further characterized in that said device further comprises at least one cylindrical sleeve placed around a length of the main shaft between each roll and the main shaft. 3. The device of claim 1 further characterized in that said device further comprises a shim rudder having a first end movably linked to the roll applicator apparatus and a second end which comprises a shim for placement between each roll to further maintain optimal separation distance of the sheeting on adjacent rolls at a location prior to the point of lamination of the sheeting onto the substrate. 4. The device of claim 1 further characterized in that the roll applicator apparatus further comprises adjustable tension means to adjust a braking tension applied to the main shaft. 5. The device of claim 1 further characterized in at least one of the following: a) the axial spacers comprise circular shaped spacers with friction reducing coated surfaces; b) the axial spacers comprise different width axial spacers; or c) at least one brake arm comprises a brake pad made of a material which is softer than the remainder of the brake arm, and which is designed to rest against the sheeting on a roll without damaging the sheeting; or d) the axial spacers permit constant separation distance along the length of the splice to within a range of between about 0.79 millimeter and 1.58 millimeter. 6. A method for laminating a plurality of retroreflective cube corner sheetings in desired juxtaposed position, characterized in that said method comprises: a) providing a roll applicator apparatus comprising a main shaft suitable for supporting and dispensing a plurality of rolls of retroreflective cube corner sheeting; b) configuring engaging means for engaging and removing the sheeting from the rolls; c) positioning brake arms so that a first end of each arm is movably linked to the roll applicator apparatus, and so that a second end of each arm rides on a roll of the sheeting to regulate the rotation of the roll during dispensing; and d) positioning axial spacers along the main shaft adjacent the rolls to axially fix the location of each roll along the shaft and to fix a separation distance between the rolls so that the sheeting on adjacent rolls is simultaneously laminated onto a substrate in desired juxtaposed relation with a constant separation distance and to allow independent rotation of each roll. 7. The method of claim 6, further characterized in that said method further comprises the step of placing at least one cylindrical sleeve around a length of the main shaft between each roll and the main shaft. 8. The method of claim 7, further characterized in that said method further comprises the step of using a shim rudder having a first end movably linked to the roll applicator apparatus and a second end which comprises a shim for placement between each roll to further maintain optimal separation distance of the sheeting on adjacent rolls at a location prior to the point of lamination of the sheeting onto the substrate. 9. The method of claim 6 further characterized in that the step of positioning the axial spacers permits constant separation distance along the length of the splice to within a range of between about 0.79 millimeter and 1.58 millimeter. 10. A device for laminating a plurality of retroreflective cube corner sheetings in desired juxtaposed position, characterized in that said device comprises: a) a roll applicator apparatus comprising a rotatable main shaft suitable for supporting and dispensing a first roll of retroreflective cube corner sheeting, and an auxiliary shaft suitable for supporting and dispensing a second roll of retroreflective cube corner sheeting; b) engaging means for engaging and removing the sheeting from the rolls; and c) shim means for maintaining a separation distance between the rolls, the shim means having a first end movably linked to the roll applicator apparatus and a second end which comprises a shim for placement between each roll so that the sheeting on adjacent rolls is simultaneously laminated onto a substrate in desired juxtaposed relation with a constant separation distance. 11. The device of claim 10, further characterized in at least one of the following: a) the roll applicator apparatus comprises adjustable tension means to independently adjust a braking tension applied to each of the shafts; or b) the axial spacers permit constant separation distance along the length of the splice to within a range of between about 0.79 millimeter and 1.58 millimeter; or c) the auxiliary shaft is removable from the roll applicator apparatus and adjustable relative to a normal operating location. 12. A method for laminating a plurality of retroreflective cube corner sheetings in desired juxtaposed position, characterized in that said method comprises: a) providing a roll applicator apparatus comprising a rotatable main shaft suitable for supporting and dispensing a first roll of retroreflective cube corner sheeting, and an auxiliary shaft suitable for supporting and dispensing a second roll of retroreflective cube corner sheeting; b) configuring engaging means for engaging and removing the sheeting from the rolls; and c) positioning shim means for maintaining a separation distance between the rolls so that a shim means first end is movably linked to the roll applicator apparatus and a second end comprises a shim that is placed between each roll, the shim means is positioned so that the sheeting on adjacent rolls is simultaneously laminated onto a substrate in side by side spliced relation with a constant separation distance along the length of the splice.

Inventors: BOYD WILLIAM C, BOYD, WILLIAM, C.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1993
Main classification: B32B31
IPC codes: B32B37, G02B5, G09F3