Patent GB-1185736-A (GB)
Title: Tubular Casings
Inventor: HAMLYN MAXWELL CHARLES
IPC: B29C48/10
Filed: 1967-07-14
Abstract: 1,185,736. Tubular collagen casings; extruding tubes. UNILEVER Ltd. 10 June, 1968 [14 July, 1967], No. 32451/67. Headings B5A and B5B. An extruder for the preparation of tubular collagen casing comprises inner 4 and outer 1 members defining an annular extrusion nozzle, the inner member 4 having an axial bore 14 of sufficient size to allow passage of a former 15 conforming in external dimensions substantially to the desired dimensions of the casing. A suitable former is an erected flexible tubular body, suitably, a tubular plastics film of e.g. nylon-11 inflated by air or other gas contained in a flexible lining tube within the former; alternatively the former may be erected by means of a flexible, elastic polymer foam. In the preparation of tubular casings from collagen dough, the casing is received on to the former, and extrusion takes place into a bath of setting solution surrounding the nozzle. A preferred collagen dough contains 4% to 7% solids by weight, especially 4À5% to 6%, and a preferred setting bath is saturated brine, the casing being dried to strengthen it after leaving the setting bath, and after drying being washed to remove material taken up in the setting bath and then dried again, the casing finally being removed from the former by shirring. Desirably the casing is subjected to the action of the setting solution on both sides before being received on to the former. As shown, the casing may be formed by a contra-rotating head extruder, suitably of the contra-rotating cone type, a suitable gap between the cones being 0À25 to 0À60 mm., and the cones suitably rotating at 60 to 120 r.p.m., there being a difference of 10 to 15 r.p.m. between the speed of rotation of the cones. Suitably, the former is passed through the nozzle at a rate of 2À5 to 50 cms. sec., but especially at not greater than 25 cms. sec., and the collagen dough is desirably fed to the extrusion nozzle under a pressure of 5À5 to 8À5 kg/sq. cm. Alternative setting solutions include ammonium sulphate solution and methanol/ammonia solution. In a preferred method, a former consisting of inflated tubing, referred to below as a templet is used, suitably in lengths of about 7À5 m; the plant can however be designed to handle the tubing, with the easing on it, continuously until the easing is finished and can be shirred off in convenient lengths. The pressure in the templet tubing when it is used as such over the lining tube, is suitably from 30 to 50 cms. water gauge. The pre-drying and subsequent steps may be done over any convenient period, e.g. a day pre-drying in still air, 5 or 10 minutes washing with water sprays to remove most of the salt still in the easing when a brine setting bath is used, and drying for a further day. If forced-draught drying is used air at 40 to 50 C. is satisfactory and 20 mins. or less for each drying stage may be adequate. After the second drying if necessary the easing is conditioned under controlled relative humidity at ambient temperature, and then shirred. In the extruder of Fig. 1, the setting solution is fed partly by the action of moving templet tubing and partly by a low hydrostatic head, through a U-tube 18, and setting solution is pumped also to surround the outside of the casing. Fig. 2 shows a plant incorporating the extruder. In use the inflated templet tubing is fed to the nozzle and emerges from it carrying a continuous extruded easing, which is set in bath 102. The tubing is pulled through the nozzle by vertical driving chain 103 to which it is attached automatically by means of connectors which join individual lengths of inflated tubing together. When a length of tubing reaches the top of the vertical conveyer it is picked up on a horizontal intermittent conveyer 104. Just before the length of tubing reaches the vertical conveyer an intermittent steam jet travelling with the conveyer severs the extruded easing surrounding the connection with the next length, to facilitate removal. After removal, setting fluid from inside and outside the casing drains off and the completed lengths pass through drying, washing and redrying cabinets to firm the casing, the templets being held for the purpose between the horizontal conveyer, and a bottom conveyer 105 having slots which engage automatically with the connectors at the bottom ends of the templets. Forced-draught drying with warm air is employed. After controlled rehumidification the finished casing is removed from the templets by shaped rubber pads on a vertical-chain shirring device 106 operating during a dwell in the conveyer movement, and the templets then pass, still on conveyer 104 to an automatic release device which causes them to drop into slotted storage shoot 107. Here they are held, hanging vertically with the connectors engaged in the slot, to await reconnection at 108 for a further passage through the extrusion nozzle. Figs. 3a and 3b (not shown) show the construction of the templet connectors (201) for the leading end of a length of tubing and (202) for the bottom end.