Electric heating element for sterilely cutting and welding together thermoplastic tubes

In an apparatus for forming a sterile connection between two thermoplastic tubes which comprises a heatable cutting means, a pair of mounting blocks adapted to receive and hold the two tubes, means to provide movement between said blocks and said cutting means to a position such that the cutting means is between said blocks and traversing where the blocks are adapted to receive tubes, means adapted to realign said blocks to a position where two different tube ends are aligned with and facing each other, and means to separate said blocks and said cutting means while urging said blocks together;

• the improvement comprising that the cutting means is a heating element consisting essentially of, as an outer layer, a folded sheet of a metal having a thermal conductivity of at least about 173 watts/m .degree.K. at a 0.10mm thickness and a tensile yield strength of at least about 34.times.10.sup.4 kPa at a 0.10 mm thickness, a resistor disposed inside the fold of said folded sheet of metal;
• and a layer of dielectric adhesive, stable to about 260.degree. C., between inner surfaces of said folded sheet of metal and surfaces of said resistor, thereby electrically insulating the resistor from the folded sheet and bonding the resulting structure together;
• said resistor having exposed terminals for reception of an electrical current and the folded edge of said metal sheet being the melting edge of the heating element.