Patent GB-1325869-A (GB)
Title: Production of heat seals
IPC: B29C65/00
Filed: 1969-12-15
Abstract: 1325869 Seaming non-metallic sheet material RWP FLEXIBLE PACKAGING Ltd 14 Dec 1970 [15 Dec 1969] 61057/69 Heading B5K Apparatus for heating sealing sheet materials comprises a pair of co-operating heat sealing elements 12, 14 rotatably mounted to a frame 10 about separate relatively radially displaceable axes 16, 20 and which are arranged so that on rotation they pass opposite each other in heat sealing relationship, variable speed drive means for rotating the elements 12, 14 about their axes at a predetermined speed, variable temperature control means for maintaining the elements 12, 14 at a predetermined temperature and variable loading means for opposing displacement of the axes away from each other. Each element 12, 14 comprises an electrically heated bar fast with a shaft 16, 20 journalled through ball bearings 18, 22 to the frame 10 and a pair of arms 24, respectively. The arms 24 are pivoted at 26 to side plates 28 of the frame 10. Each element 12, 14 is provided with a fast response temperature sensing probe and has a working face 30 divided into two parallel regions by a recessed portion 32. The faces 30 are transversely ribbed so that the peaks and troughs of the ribs of one element exactly match the troughs and peaks of the ribs of the second element to provide crimped seals. The shaft 16 is rotated by an electric motor 54 through a belt 52 and a gear-box 50 and the shaft 20 is driven thereform by intermeshing gear-wheels 56, 58. Universal joints 34, 37, 46 ensure that vibration from the drive means does not upset the register of the elements 12, 14. The shaft 36 extending from the joint 34 in which the shaft 20 terminates is arranged within a sleeve 38 to allow displacement of the shaft 20 without effecting the intermeshing of the wheels 56, 58. Each shaft 16, 20 is provided with electrical brush gear 60, 62 and four slip rings by means of two of which electricity is supplied to heat the elements 12, 14 and two of which provide means for feeding the control signal from the temperature sensing probes to temperature controllers. Movable plungers 66 of hydraulic jacks 64 engage identical places on the arms 24 to urge the shaft 20 towards the shaft 16. Probes 70 of gauges 68 engage identical places on the arms 24 and the displacement of each arm 24 is measured on a dial 74. Bolts 76 having adjustable lock nuts 80 act as a stop to provide a minimum limit to the distance between the shafts 16, 20. Bolts 84 having lock nuts 88 provide a maximum limit to the distance between the shafts 16, 20. The bolts 76, 84 can be used to lock the arms 24 in any desired position. A protective shroud (94), Fig. 3 (not shown), is hinged between the plates 28 and, if lifted slightly, causes the shafts 16, 20 to cease rotation by means of an electrical contact. A separate unit, Fig. 3 (not shown), houses the hydraulic and electric controls which comprise separate temperature controls for the elements 12, 14, separate on/off switches for the electric power and the motor 54, a variable speed control for the motor 54 together with a meter which indicates the speed of rotation of the shafts 16, 20 and an electrically operated hydraulic pump whose pressure is varied by rotation of a control knob and indicated by a gauge calibrated to read directly the seal bars loading reacting against the material to be sealed. The apparatus is used to produce a seal the effectiveness of which can be tested after the material has emerged from the elements 12, 14.