Method for severing tubular film
United States Patent 1 1 Martinek [45] Apr.-  
 [ .METHOD FOR SEVERING TUBULAR FILM [75] lnventor: Harold H. Martinek, Danville. Ill.  
 [73] Assignee: Tee-Pak, Inc., Chicago. Ill.  
 [22] Filed: Nov. 30, 1973 [21] Appl. No.: 420,471  
 [52] [1.8. CI 225/1: 225/935 [51] Int. Cl .1 326i 3/00 [58] Field of Search 225/1. 93.5  
 [56] References Cited UNITED STATES PATENTS 2.956 7 17 10/1960 Schurf 225/1 3,27 .493 9/1966 Bergc&#39; 264/143 Primary .E,\&#39;m1iner-Andrew- R. .luhasz Assistant Eramingn-Leon Gilden Attorney. Agelmor Firm -Russell L. Brewer; Neal J,&#39;  
 Mosely 15 1 ABSTRACT v A tubular flexible film or filament is severed along a pre-determined locus&#39;by cooling the film or filament at said pre-determined locus until the film becomesbrittle and striking the film at said predetermined locus thereby severing one portion of the filmtrom another. The method preferably contemplates severing a shirred artificial sausage casing byjdirecting a spray of cold gas against the predetermined locus of the casing. Cooling of the casing and the striking thereof for severing the casing is accomplished substantially simultaneously by the cold gas impinging on the casing. v l  
 7 Claims, 4 Dravving Figures PATENTEBA RZ B 3. 878.878 SHEET 2 115 g 1 METHOD FOR SEVERING TUBULAR FILM DESCRIPTION OF THE PRIOR ART In the past, the severing of tubular films, e.g., shirred artificial sausage casings, often has been accomplished by passing a knife through the casing or passing a heated wire through the casing. However, these methods were not well suited to the severing of shirred artificial sausage casings. What generally happened in those cases was the formation of a tab-like end on the shirred casing. This tablike end often interfered with the performance of the shirred sausage casing, particularly in terms of its ability to fit over a stuffing horn.  
 SUMMARY OF THE INVENTION This invention relates to a method for severing flexible tubular films and filaments capable of flexing at least 90 by cooling the tubular film or filament at a predetermined locus until the material becomes brittle, e.g., incapable of flexing more than about without breaking, and striking the film at the predetermined locus, thereby causing one portion of the tubular film or filament to sever from another portion.  
  In a preferred aspect of the invention, a shirred artifieial sausage casing is severed from the unshirred inflated casing stock by directing a spray of cold liquified gas against the peripheral surface of the unshirred easing stock adjacent to the shirred casing.  
  The advantages of this invention include: the ability to sever a tubular film or filament in a simple, fast, and easy manner; the ability to sever tubular films and filments with equipment requiring little if any maintenance; the ability to sever films and filaments without actual physical contact as is normally encountered with a mechanical apparatus; the ability to sever films positioned over a support e.g., a mandrel; the ability to produce shirred artificial sausage casings having a substantially uniform surface and configuration; the ability to sever shirred artificial sausage casings from unshirred casing without forming a tab-like end resulting from conventional severing methods.  
 DRAWINGS FIG. 1 is a view in front elevation showing the severance of a filment employing one spray nozzle.  
  FIG. 2 is an isometric view showing an arrangement of three nozzle sections for severing a tubular film.  
  FIG. 3 is an isometric view showing an annular ring cut-off for severing shirred artificial sausage casing.  
  FIG. 4 is an isometric view of a cut-off mechanism using spray nozzles positioned at the shirring head. I  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS casing. This resulted in the formation of a tab-like end on the shirred casing.  
  In general, the invention is applicable to the severing of any flexible thermoplastic polymeric tubular films and filaments which cannot be severed by simple bending. Polymeric materials which are particularly&#39;adapted to this invention include: polyethylene, polypropylene, regenerated cellulose, amylose, cellulose acetate, szu ran, cellulose nitrate, alginates, vinyl chloride, vinyl acetate, styrene, polyvinyl alcohol, and the like. i  
  The polymeric materials normally are formed into shaped articles, i.e., tubular films which can subsequently be severed. The tubular films which are particularly adapted to the invention have a wall thickness of from about 0.0005 to 0.010 inches and the filaments a diameter of from about 0.0005 to 0.010 inches.  
  Typically, the tubular film or filament is cooled by spraying a cold fluid, preferably a gas obtained from a liquified gas source such as carbon dioxide, nitrogen, oxygen, helium, argon, and the like, through a spray nozzle or annular ring. By appropriate placement of spray emitting apparatus, e.g., a nozzle of annular ring, severance of the tubular film or filament can be conducted at a predetermined locus. As the cold fluid is passed through the spray emitting apparatus, e.g., an annular ring or nozzle, it cools the immediatesurroundings and the tubular film or filament.  
  The polymeric materials, usually cellulose, in the instance of artificial sausage casings, are cooled to a point where the material becomes extremely brittle, e.g., for cellulose to a temperature of about 50F. or below. Any of these cold fluids, obtained from liquified gases, when sprayed through a nozzle or annular ring is capable of cooling these polymeric materials to an embrittling temperature.  
  The conditions for cooling the tubular film or file ment to the brittle&#34; temperature varies with the temperature of the gas, the nozzle opening or orifice open ing in the annular ring, the exposure time, etc. These conditions can be regulated as desired. Generally, it is desired to employ nozzles or annular rings having a plurality of small orifices (three tosix), having an opening of about 0.005 to 0.250 inches in diameter, so that the impingement of the gas can be limited to a predetermined locus or defined area on&#39;the film or filament.  
  Carbon dioxide is a preferred liquified gas for cooling and severing the casing. It normally is maintained at a temperature from about 0 to 68F. and at a pressure from about 325 to 920 psig. On release, the CO is ejected at high velocity at the sublimation temperature, i.e., -l09F. With this CO gas the exposure time for cooling and severing a cellulosic film having a wall thickness of from about 0.0005 to 0.010 inch generally is from about 0.1 to 5.0 seconds when the gas is sprayed through nozzles as described. The exposure timemay be slightly longer for some polymeric materials or shorter for others, but the time can be varied as desired. Accordingly, exposure times can be regulated as desired when using colder gases, e.g., liquid nitrogen.  
  After the tubular film or filamient has been cooled to the point, such that it is very brittle, the film or filament can be severed by any flexing movement. One advantage of spraying a&#39;coldgas from a liquified gas source through a nozzle or annular ring is. that the impingement of the gas against the surface of the film usually is sufficient to flex and sever the film. Further, where the spraying is conducted in an atmosphere having a relative humidity of from&#39;about&#39;30% to 99% at a temperature of from about -8l0 F. ice crystals are formed bythe spraying of such coldgas through the nozzle and the ice crystals along with the gas flex the tubular film or filament to sever it. Carbondioxide is unique in that in addition to the formation of ice crystals which effect a striking of the casing, solid dry ice particles are formed when the liquified CO is sprayed. These= small particulates of CO and H act in the same manner as a sand blast unit and provide for a smoothing of the shattered, severed end of the tubular shirred sausage casing.  
  By the term strikirig as used herein it is meant to refer to a force causing movement or flexing of the cooled brittle film or&#39;filamen&#39;t at the predetermined locus. For example, a striking force can simply be the movement of the shirred casing causing flexing of the casing at the predeterminedlocus. It canalso be a mechanical rubbing, striking, twisting, etc. as applied to the casing or it can be the force of an impinging gas or particulate matter against the predetermined locus.  
  In the accompanying drawings, several embodiments are presented for showing methods by which tubular film&#39;s-and&#39;filaments of polymeric materials and particularly shirred artificial sausagecasings made of regenerated cellulose&#39; can be severed.  
  In FIG. 1, a solidtubular filament 2 of polyethylene having a diameter of about 1.5 mils is placed about 1 inch from spray nozzle 3 through which cold CO from a liquified CO source is sprayed. The CO is supplied to spray nozzle 3 through supply line 4 at a pressure of &#39;generallyfrorri about 920 psig and a :temperature of about. 68F. As the CO leaves-the nozzle, it is vaporizediinstantaneously, and converted to CO gas and CO solid particles at the sublimation temperature. Severance of the :filament at predetermined locus 5 is effected by the cooling of the filament from the sprayed CO and the striking of the cold filamentat predetermined locus 5 by C0 gas, solid CO particles and ice crystals formed by the rapid cooling of the immediate surroundings. A=-spray period of about 0.5 second usual ly-isgsufficient to sever the filament. In FIG. 2 a tubular film 12 of vinyl chloride having a wallthickness of about 2.0 mils and a diameter of about 5 inches has positioned about it spray nozzles 13, 14&#39;,&#34; and 15. These are substantially. equidistant and equiangularly spaced about tubular film 12 for defining a predetermined locus 16 about which the tubular flim can be severed. Liquid nitrogen is vaporized to nozzles .13, l41and through supplylines 17, 18, and 19, respectively; With the nozzle having an opening of about 0.10 inches&#39;in diameter, a spray period of from 0.3-0.6 seconds generally is sufficient when using a cold nitrogen jet to sever the-film.  
  FIG. 3 is a viewof a means for severing artificial sausage casings, suitably of a cellulosic or collagen material, immediately after it has been shirred. In referring to FIG. 3, shirring wheels .31 and 32 are supportably mounted on shafts 33 and 34 and disposed about a sausagecasing 35 having a shirred portion 36. Actually, there are three. shirring wheels in the arrangement; howevery&#39;for convenience this does not showthe third whe&#39;el. In severing the shirred portion 36 of the artificial sausage casings from the unshirred portion, the shirred .portion 36 is pulled away from the shirring Wheels 31 and 32 and the unshirred portion35. An annular ring 37 is disposed about the artificial sausage casing immediately at the point where the shirred portion 36 ends. The annular ring 37 has four orifices, 38,  
 39, 4O and4l eachhaving a diameter of about 0.10 inches. Supply line 42 communicates with the annular ring 37 for supplying liquified CO under pressure thereto. The CO is emitted from the orifices 38, 39, 40 and 41 to define a spray pattern about the sausage casing. As the CO is sprayed from these orifices (and evaporates to form CO gas and particles of solid CO the casing is cooled and the force (impingement) of the CO gas and particles against the casing severs the shirred portion 36 from the unshirred sausage casing 35. A relatively smooth end is produced on compression of the shirred portion 36. The tab-like end normally encountered where the casing is severed with a knife or hot wire on this is not present.  
  In FIG. 4 a view of severing artificial sausage casings by means of spray nozzles is shown. Shirring wheels 50, 51, and 52 are disposed about a tubular casing of regenerated cellulose having a wall thickness of about 1.0 mil and a diameter of about 1.0 inches. The tubular casing 53 has a shirred portion 54. Spray nozzles 55, 56, and 57 are disposed equiangularly about the sausage casing 53 and equidistant, i.e., about 0.50 inches from the casing. The spray nozzles 55, 56, and 57 each have an annular orifice of about 0.20 inches in diameter. Mandrel 58 is disposed inside the bore of tubular casing 53. Mandrel 58 can be removed or left inside the casing during the severance of the casing.  
  The shirred portion of the casing is severed from the unshirred portion as follows. Liquified carbon dioxide stored at a pressure of about 325 psig and having a temperature of 0 F. is supplied to nozzles 55, 56 and 57 through supply lines not shown and is thereby directed against the end of the shirred portion 54 of the artificial sausage casing. The casing is severed by the substantially simultaneous cooling of the casing and impingement of the gas, the solid CO particles, and ice crystals formed by the spraying of the gas through the nozzle. A spray period of 0.5 seconds generally is sufficient to sever the shirred portion of the casing from the non-shirred portion. A smooth end is provided on the shirred casing stick.  
  The views in FIGS. 3 and 4 are illustrative of those views taken of the severing mechanism positioned on conventional shirring machines adjacent to the shirring wheels. The severing apparatus can be adapted to any of the conventional shirring machines for severing the casing. It is particularly adapted to those shirring machines shown in US. Pat. Nos. 3,454,982; 3,454,981, 3,1 15,669; and 3,456,286. Such description of shirring machines is incorporated by reference.  
 What is claimed is:  
  l. A method for severing a flexible tubular film of polymeric material which comprises the steps of cooling the tubular film by impingement of a cold fluid at a predetermined locus continuously until the material becomes extremely brittle and said fluid flexes the tubular, film to sever it.  
 . 2. The method of claim 1 wherein the method is for severing a tubular film and said cooling of said tubular film is accomplished by impinging a cold gas vaporized from a liquified gas against the surface of said tubular film.  
  3. The method of claim 2 wherein tubular film is a shirred artificial sausage casing and the spraying of said cold gas against the surface of the tubular film is per- 6. The method of claim 5 wherein the cold CO gas and solid particles from said carbon dioxide is sprayed for a period of from about 0.l to 5 seconds against the tubular film.  
  7. The method of claim 2 in which said liquified gas is nitrogen.