Abstract:
An improved web-winding means with a durable thermoplastic polyester resin or polyester resin blend support structure and web capture slot (gate) formed in an interior portion of the support structure. The interior portion is joined to an inner annular surface that has increased lubricity, toughness and creep resistance resulting in decreased debris generation plus increased structural integrity and dimensional stability.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is related to U.S. Ser. No. 10/719,120, filed concurrently herewith, of Michael R. McGovern and Edgar G. Earnhart, entitled “A Web-Winding Means”, and 
   U.S. Ser. No. 10/719,578, filed concurrently herewith, of Michael R. McGovern and Edgar G. Earnhart, entitled “Method Of Manufacturing A Web-Winding Device”. 
   FIELD OF THE INVENTION 
   The invention relates generally to the field of web-winding devices. More particularly, the invention concerns a web-winding means particularly well suited for photographic film material based on silver halide technology. 
   BACKGROUND OF THE INVENTION 
   Traditionally, motion picture film stock cores, such as those defined by the Society of Motion Picture and Television Engineers (SMPTE) standard ANSI-SMPTE 37M or ISO 1039-1995, have been injection molded from thermoplastic high impact polystyrene (HIPS) molding compounds. The HIPS resin has been the material of choice mostly driven by cost, ease of injection molding, and suitability for the state of motion picture film production and cinema projection technology. Cores produced from HIPS resins have been used to produce motion picture cores from multi-cavity tools or molds now for over forty years. 
   Over time the total amount (as measured in length) of motion picture film and the tightness of wrap (with a resultant hoop stress on the core) has increased. The spooling process (manufacturing and printing) has evolved into a high-speed process where motion picture film is spooled at a speed of thousands of meters per minute to achieve greater productivity rates. A result of these improvements is a finished core product with a much greater weight and stress but with no change in the basic design of the motion picture core to compensate. Moreover, the demands of cinematographers for low light sensitive films and the demands from consumers for high-quality theatre experience have increased demands for film cleanliness in raw stock and printing production. The high speed of the spooling process combined with the poor overall wear property of the current thermoplastic HIPS resin result in the generation of a tremendous amount of HIPS dust and debris at the mounting interface of the core with the winding machine spindle. The generation of this level of debris creates high production losses and nightmarish housekeeping issues. The present invention resolves all of these issues plus creates an opportunity of reuse of cores which was never done with the HIPS resins due to the potential of damage from handling, transportation and use. Core crush, a form of permanent deformation, is exemplary of the damage from handling where a fully spooled motion picture core sustains sufficient impact energy to literally crush the core resulting in complete failure of the part. Needless to say, this form of damage is particularly costly and frustrating to motion picture printing customers because: 1) film telescopes and comes off of whatever is left of the damaged core; and/or 2) the core cannot be installed onto the winding spindle. 
   There have been several attempts in the art to solve aspects of the above problems. In U.S. Pat. No. 4,042,399 by Kiesslich teaches the disclosure of a photographic element having improved slip. However, a shortcoming of this development is that the surface of the photographic element is required to be coated with a polyester film to improve slip. 
   Another prior art film transport development is described in U.S. Pat. No. 5,694,629 by Stephenson, III et al. The transport mechanism of Stephenson uses slip clutches made of polycarbonate to improve slip. 
   In U.S. Pat. No. 4,049,861 by Nozari a web-winding device is disclosed that requires the use of abrasion resistant coatings including polyesters and polycarbonates to reduce web slippage. 
   Therefore, a need persists in the art for a web-winding means that has a mounting surface with substantially reduced friction, is substantially damage resistant, and does not generate deleterious debris during typical web-winding and unwinding operations. 
   SUMMARY OF THE INVENTION 
   It is, therefore, one object of the invention to provide a web-winding means that is far more durable and less debris generating than existing developments. 
   Another object of the invention is to provide a web-winding means that have far superior mechanical integrity than prior art models. 
   Yet another object of the invention is to provide a method of making a web-winding means that is far more durable and generates less debris than existing devices. 
   The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a web-winding device has a generally cylindrical support structure having an outer web wrapping surface for receiving at least one convolution of a web, an inner annular surface joined to said support structure for mating with a web-winding machine, wherein said inner annular surface has a wear rate coefficient of less than about 3.0×10 −7  m 3 /Nm. 
   The web-winding means of the present invention has numerous advantages over prior developments, including: substantially improved overall mechanical properties; a stronger core to withstand the higher hoop stress and resist core crush; lower friction and wear which results in a significant reduction in airborne debris that results in product contamination issues and ability to reuse cores; and an enhancement in the surface finish of the working surface of the core that comes into contact with the film which facilitates the cinching of the leader portion of the film. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein: 
       FIG. 1  is an isometric view of the web-winding means of the invention with cinch attachment of web to winding means; 
       FIG. 2  is an isometric view of the web-winding means of the invention for photographic web as described by ANSI-SMPTE 37 M or ISO 1039-1995 with cinch attachment of web to winding device; 
       FIG. 3  is an isometric view of the web-winding means of the invention with a web capture gate attachment to the winding device; 
       FIG. 4  is chart of a qualitative assessment of debris accumulation for various materials; 
       FIGS. 5(   a ) and  5 ( b ) are charts of a quantitative assessment of debris generated from film cores of various materials; 
       FIG. 6  is a chart of static coefficient of friction of the emulsion side of a photographic web against a PBT sample with various surface textures; 
       FIG. 7  is a chart of mechanical property comparison between HIPS and PBT; and 
       FIG. 8  is an isometric view of the preferred embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings, and particularly to  FIG. 1 , the web-winding means  10  of the invention is illustrated. According to  FIG. 1 , the web-winding means  10 , broadly defined, includes a generally cylindrical support structure  12 . The support structure  12  has an outer web wrapping surface  14  with surface texture  15  for receiving by cinching overlap  26  at least one convolution of a web  1 . Skilled artisans will appreciate that web  1  has an interior surface  2 , an exterior surface  3 , a web end  4 , and an annular portion  16  for mounting onto a web-winding machine spindle  6 . A keyway  18  is provided in the annular portion  16  to engage spindle key  7  of the web-winding means for transmitting applied torque  21  generated by the web-winding means and spindle rotation speed  32 . It is well known that cinching attachment of the web to the winding means is a function of the cinching force  24  and the static coefficient of friction for interior surface of web to web wrapping surface  22 . It is also well known that the static coefficient of friction  22  for interior surface of web to web wrapping surface is a function of the material of the web-winding means  10 , the material of the web  1 , and texture of web wrapping surface  15 . 
   Referring again to  FIG. 1 , failure to cinch occurs when the static coefficient of friction for interior surface of web to web wrapping surface  22  is less than the static coefficient of friction for interior surface of web to exterior surface of web  23 . 
   Referring again to  FIG. 1 , deleterious particles  28  are generated from the annular portion surface by the abrasion of the annular portion surface  17  against the spindle surface  8  and the web winding machine spindle key surfaces  9  are against the key way surface  19 . The abrasion results from minute movements of web-winding device  10  relative to the spindle  6  due to the dynamics of the web-winding process. The deleterious particles  28  are predominantly generated from but not limited to the web-winding device  10  being typically composed of a material with a lower abrasion resistance than that of the spindle  6 . Web- winding machine spindle  6  is typically composed of AISI type  316  Stainless Steel in photographic web applications. 
   Referring again to  FIG. 1 , failure of the web-winding means  10  occurs when: a) web-winding means  10  cannot be removed from web-winding machine spindle  6  after web-winding process or, b) web-winding means cannot be reinstalled on a web-winding machine spindle  6  set to run in reverse direction to unwind web for use of web in subsequent process. At the end of the web-winding process, the trailing web end is secured in place typically with a piece of tape. Thus retaining at least partial web tension  20  and resulting cinching force  24 . The resulting compressive stresses in the web device support structure  12  results in a reduction in the size of the annular portion  16  as a function of the geometry and elastic modulus properties of the material composed in the support structure  12 . In the case of a web-winding device  10  composed of plastic materials, the size of the annular portion  16  becomes even smaller with time after completion of web-winding process due to plastic creep under said compressive stresses. Mechanical failure of the web-winding means  10  may also occur due to the said compressive stresses. Therefore it is obvious that the geometry of the support structure  12  as well as the elastic modulus, and compressive strength are important factors in consideration of the design of a web-winding means. 
   Referring to  FIG. 2 , a further embodiment of the web-winding means of  FIG. 1  is illustrated where the material being wound is any photographic web  1 ′ with an emulsion layer side and a support layer side. Of particular note, in this embodiment, is that the interior surface of web  2  is an emulsion side surface  2 ′ and the exterior surface of web  3  is a support side surface  3 ′. 
   Referring to  FIG. 3 , in yet another embodiment of the invention shown in  FIGS. 1 and 2 , an alternate means of attaching the web  1  to the web-winding means  10  is depicted. In this embodiment, the web-winding means  10  comprises a web capture gate  30  formed in an interior portion of the support structure  12  secures a web end portion  5  of the web  1  in the support structure  12  prior to the web  1  being wrapped along the outer web wrapping surface  14 . The web end  4  is then further secured by at least 1 convolution of web  1  thus transmitting the web machine applied torque  21 . 
   It is apparent that the solution to the current problems associated with a web-winding device  10  as described in the previous Figures requires a material with: a) static coefficient of friction between web-winding device surface and inner web surface comparable to current developments; b) lower deleterious particle generation between annular portion surface and web-winding machine spindle surface than current developments; c) higher elastic modulus than current developments; and d) lower plastic creep than current developments. 
     FIG. 4  depicts an example of quantitative experimental results of a study of deleterious particle generation or volume loss of photographic film cores produced of various materials against an AISI type  316  stainless steel block. According to  FIG. 4 , a web-winding device composed of PBT material had substantially less deleterious particle generation (volume loss) than the current development. 
   Referring to  FIGS. 5(   a ) and  5 ( b ), examples are shown of quantitative experimental results of studies of volume loss of various materials from web-winding means  10  (as shown in  FIG. 1)  against AISI type  316  stainless steel balls used to represent spindle  6 . According to  FIG. 5(   a ), a web-winding device composed of PBT material had substantially less deleterious particle generation (volume loss) than prior art developments. According to  FIG. 5(   b ), the same web-winding device above had substantially less deleterious particle generation (volume loss) than prior art development when a series of different semi-crystalline polyester and polyester blends, including lubricants and fillers, are used to produce web-winding means  10 . 
   Referring to Table I below, wear rate coefficients are calculated based on the volume loss measurements discussed in  FIG. 5(   b ). Therefore, wear rate coefficient k=V/(F*s), where (V) is volume loss, F is force applied against the steel balls (spindle  6 ) and (s) is the stroke of motion of steel balls. The results show that the wear rate coefficient k for the preferred materials in  FIG. 5(   b ) are at least a factor of two less than that of the prior art developments. 
   
     
       
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Wear Rate Coefficient Test Results 
             
           
        
         
             
                 
                 
                 
                 
               Wear Rate 
             
             
                 
               Volume Loss 
               Force 
               Stroke 
               Coefficient 
             
             
                 
               V 
               F 
               s 
               k 
             
             
               Core Material 
               m 3   
               N 
               m 
               m 3 /Nm 
             
             
                 
             
             
               ECP Check Core (HIPS) 
               2.240E−06 
                 
                 
               4.497E−05 
             
             
               NOVA 5104 HIPS 
               2.060E−06 
                 
                 
               4.136E−05 
             
             
               BASF Ultradur B4520 PBT 
               1.200E−09 
                 
                 
               2.409E−08 
             
             
               BASF Ultradur 4300 
               0.000E+00 
               1.961 
               0.0254 
               0.000E+00 
             
             
               K4 20% G.B. PBT 
             
             
               GE Lexan WR-2210 
               0.000E+00 
                 
                 
               0.000E+00 
             
             
               PC + Lube 
             
             
               GE Valox 325 PBT 
               1.100E−08 
                 
                 
               2.208E−07 
             
             
               BASF Ultradur B4500 PBT 
               1.100E−08 
                 
                 
               2.208E−07 
             
             
                 
             
             
               K = V/(F · s) 
             
           
        
       
     
   
   Referring to  FIG. 6 , experimental results are illustrated of a study of the coefficient of friction of photographic web emulsion side against unfilled polybutylene terphthalate (PBT) with various surface textures. According to  FIG. 6  the static coefficient of friction is inversely related to the coarseness of the surface texture with the highest values obtained as the surface finish approaches a mirror finish. 
   Referring to  FIG. 7 , comparative mechanical property data is depicted between an unfilled high impact polystyrene (Nova “5104”) and an unfilled polybutylene terphthalate (GE “Valox 325”). The data clearly indicates that the PBT material has higher stress yield and lower plastic creep properties than HIPS. 
   Referring to  FIG. 8 , web-winding means  10 ′ has a support structure  12  injection molded preferably from a family of thermoplastic injection molding grades of polyester or polyester blends. In particular advantages are identified with the use of semi-crystalline thermoplastic polyester or polyester blends that will result in reduced debris generation, lower deleterious particle generation for a molded motion picture film core exhibiting less plastic creep and higher toughness. As a further refinement of this invention, it is noted that in particular, a semi-crystalline thermoplastic polyester resin in the polybutylene terphthalate (PBT) family has yielded the best overall advantages detailed in previous sections of this application. One example of such a PBT thermoplastic semi-crystalline resin is the General Electric polyester product family listed under the trade name of “Valox”. Further still, the authors identify that the neat or unfilled General Electric PBT semi-crystalline thermoplastic resin grade of “Valox 325” natural is a prime candidate for this injection molded motion picture core application. The General Electric line of the “Valox PBT” resins offers good dimensional stability, good chemical resistance, high surface gloss if desired, good fatigue endurance and excellent lubricity. 
   Injection molded motion picture cores formed from the materials above will be produced from semi-crystalline PBT resin with a typical specific gravity (solid) of 1.31 grams per cubic centimeter with an intrinsic viscosity between 5000 to 6000 poise. 
   The antioxidant (AO) package that is very common for PBT resins is a typical combination of a primary AO such as a sterically hindered phenol (2,6-Di-tert. butyl-p-cresol from the alkylidene-bisphenols family) in conjunction with a secondary AO component such as from the phosphite or phosphonite group both of which are short-chained organics. Typical levels of the AO package range from 0.20% to 1.0% by weight with a preferred aim weight percent of 0.5. 
   Described film cores have a generally cylindrical support structure having an outer web wrapping surface for receiving at least one convolution of a web; an annular portion with a keyway for mounting a core onto a film winding machine and transmitting torque thru the core to the film for wind tension; a support structure a web capture slot (gate) for securing a portion of the web in said support structure prior to the web being wrapped along the web wrapping surface; sensible features in the support structure for determination of orientation when mounting on a film winding machine for the purpose of correct web capture slot orientation; and a web wrapping surface capable of providing a cinch wrap engagement of the film to the web wrapping surface that allows winding of film to the core without use of the web capture slot. 
   EXAMPLES 
   The following are exemplary of the web-winding means of the invention composing a 0.5% by weight AO modified PBT resin formulations. 
   In accordance with Example 1, web-winding means  10  is composed of 4,4′-Di-tert-octyldiphenylamine. 
   In accordance with Example 2, web-winding means  10  of the invention is composed of pentaerythrityl tetrakis-3-(3,5-Di-tert-butyl-4-hydroxyphenyl)-proprionate. 
   In accordance with Example 3, web-winding means  10  of the invention is composed of pentaerythrityl tetrakis-3-(3,5- Di-tert-butyl-4-hydroxyphenyl)-propionate with N,N′-hexamethylenebis-3-(3,5-Di-tert-butyl-4-hydroxyphenyl)-propionamide. 
   In each of the above examples, typical mechanical properties for this PBT grade resin include: 
   (1) tensile strength at break (Type I) at 3.2 mm thick tensile bar is about 50 Mega Pascals per ASTM D 638; 
   (2) tensile elongation at yield (Type I) at 3.2 mm thick tensile bar is about 200 percent per ASTM D 638; 
   (3) flexural strength at break at 3.2 mm is about 12,000 psi (80 Mega Pascals) per ASTM D 790; 
   (4) flexural modulus at 3.2 mm is about 2,300 Mega Pascals per ASTM D 790; and, 
   (5) Rockwell (R scale) hardness is about 117 per the ASTM D 785. 
   Alternative suitable materials for an injection molded web-winding device  10  of the invention include: 
   (1) Polybutylene terphthalate/polycarbonate (PBT/PC) blends. Examples are: GE Plastics “Xenoy 5200” and “Xenoy 1200”; 
   (2) Polybutylene terphthalate/polycarbonate-silicone copolymers. 
   Example  
   GE Plastics “LEXAN EXL”; and 
   (3) PTFE filled polycarbonate (amorphous polyester). 
   Examples  
   GE Plastics “LEXAN WR2210” with 15 percent by weight PTFE. 
   Referring to  FIG. 8 , the preferred embodiment of this invention comprises an injection molded web-winding means  10 ′ for a photographic web  1 ′ comprised of a plurality of cored segments  40  forming an outer web-winding surface wall thickness  44 , an inner annular portion wall thickness  42 , and a plurality of support ribs  46 , and a outer web-winding surface to inner annular portion surface connecting portion  48  with a wall thickness  49 . The web-winding means  10  preferably conforms to dimensions per ISO international standard ISO 1039 “Cinematography—Cores for Motion-Picture And Magnetic Film Rolls—Dimensions” and the equivalent standard ANSI/SPTME 37M “SMPTE Standard for Motion-Picture Equipment—Raw Stock Cores”. In particular the preferred embodiment for the invention is a 35 mm×75 mm motion-picture raw stock core. Outer web-winding surface wall thickness  44 , the inner annular portion surface wall thickness  42  and the connecting portion wall thickness  49  are substantially identical with a value of about 3.6 mm. The preferred thickness of support rib  46  is about 2.9 mm. 
   Referring again to  FIG. 8 , the preferred embodiment of the invention comprises a said injection molded web-winding device for a photographic web  1 ′ comprised of neat or unfilled natural GE Plastics “Valox  325 ” semi-crystalline thermoplastic polybutylene terphthalate (PBT), and texture  15  of web-winding surface  14  has a maximum value of 0.03 micron Ra with a lay parallel to the wrapping direction of the web. 
   Referring yet again to  FIG. 8 , the preferred embodiment of the invention comprises a said injection molded web-winding means  10 ′ for a photographic web  1 ′ comprising a web capture gate. The web capture gate  30  is about 1.3 mm wide by about 6.6 mm deep with an angle of incidence of about 45 degrees to the web wrapping surface  14 . 
   Referring again to  FIG. 8 , the preferred embodiment of the invention comprises an injection molded web-winding means  10 ′ for a photographic web  1 ′ comprising a plurality of sensible features  50  to ensure proper orientation of film capture gate to web-winding machine mounting direction  52  in darkroom operations. Each sensible feature  50  is comprised of a protrusion about 2.3 mm diameter by 3.2 mm high. 
   The invention has been described with reference to a preferred embodiment; however, it will be appreciated that a person of ordinary skill in the art can effect variations and modifications without departing from the scope of the invention. 
   PARTS LIST  
   
       
         1  Web 
         1 ′ Photographic Web 
         2  Interior surface of web 
         21  Emulsion side surface 
         3  Exterior surface of web 
         3 ′ Support side surface 
         4  Web end 
         5  Web end portion 
         6  Web-winding machine spindle 
         7  Web-winding machine spindle keyway 
         8  Web-winding machine spindle surface 
         9  Web-winding machine spindle key surfaces 
         10  Web-winding means 
         10 ′ Injection molded web-winding means 
         12  Support structure 
         14  Outer web wrapping surface 
         15  Texture of web wrapping surface  14   
         16  Annular portion 
         17  Annular portion surface 
         18  Keyway 
         19  Keyway surface 
         20  Web tension 
         21  Web-winding machine applied torque 
         22  Static coefficient of friction for interior surface of web to web wrapping surface 
         23  Static coefficient of friction for interior surface of web to exterior surface of web 
         24  Cinching force 
         26  Cinching overlap 
         28  Deleterious particles 
         30  Web capture gate 
         32  Spindle rotation speed (w) 
         33  Web-winding speed (v) 
         40  Cored segment 
         42  Wall thickness, web wrapping surface 
         44  Wall thickness, annular portion surface 
         46  Support ribs 
         48  Support web 
         49  Wall thickness 
         50  Sensible feature 
         52  Web-winding machine mounting direction