Method and apparatus for sealing centrifuge tubes

A method for closing a filler neck protruding from the opening in the end of a substantially closed centrifuge tube, the filler neck being formed of a heat fusible plastic material and having a filler passage along the axis of said neck for delivery of liquid into the centrifuge tube, comprising:

• supporting said centrifuge tube in an upright position with said filler neck protruding upwardly;
• placing a heat conductive cap over the open end portion of said neck, said cap having an inner cavity closely confining the outer surface of the end portion of said neck therein;
• applying heat to said heat conductive cap sufficient to melt the plastic material forming the confined end portion of said neck;
• applying pressure to said cap moving said cap in a direction along the longitudinal axis of said neck thereby causing progressive portions of said neck to melt and fold inwardly to form a mass of plastic material in said filler passage;
• supporting said neck at some position above the centrifuge tube while said heat and pressure are applied to said neck above such position in order to maintain said neck oriented in an upward direction;
• removing said heat and pressure from said cap so that said cap cools and said mass of melted plastic material in said filler passage solidified therein completely closing said filler passage;
• and
• removing said cap from said neck.

A method for closing a filler neck protruding from the opening in the end of a substantially closed centrifuge tube, the neck being formed of a heat fusible plastic material and having a filler passage along the axis of said neck for delivery of liquid into the centrifuge tube, comprising:

• supporting said centrifuge tube in an upright position;
• applying a clamping means to support said filler neck at a predetermined position above said centrifuge tube thereby maintaining said neck in a substantially upright position;
• placing a heat conductive cap over the open end portion of said neck, said cap having an inner cavity closely confining the outer surface of the end position of said neck therein;
• applying heat to said heat conductive cap sufficient to melt the confined end portion of said neck;
• applying pressure to said cap moving said cap in a direction along the longitudinal axis of said neck thereby causing progressive portions of said neck to melt and fold inwardly to form a mass of plastic material closing said filler passage, said pressure forcing said cap along said neck until lower portions thereof abut against said clamping means;
• removing said heat and pressure from said cap so that said cap cools and said mass of plastic material in said filler passage solidifies to close said filler passage;
• and
• removing said cap and said clamping means from said neck.

Apparatus for closing a passage formed in a filler neck protruding from the opening in the end of a substantially closed centrifuge tube after said tube has been filled with sample, the neck being formed of a heat fusible material, comprising:

• means adapted to engage the outer surface of said centrifuge tube for supporting said centrifuge tube in an upright position with said filler neck protruding upwardly;
• a cap formed of a high heat conductivity material having a cavity adapted to closely fit the circumference of said filler neck, said cap adapted to be positioned over the end portion of said filler neck to confine said end portion of said neck within said cavity;
• means for applying heat to said cap member for raising the temperature thereof to the fusion temperature of said material forming said neck;
• pressure applying means movable upwardly and downwardly in a direction subsantially along the axis of said filler passage, said pressure applying means adapted to apply pressure downwardly against said cap so that, when said cap is heated to the fusion temperature of said neck, progressive portions of said neck melt and said cap is forced downwardly so that the sidewalls of said filler neck fold inwardly into said filler passage and form a molten mass closing said filler passage;
• clamping means adapted to grasp said neck at some predetermined position above the upper end of said centrifuge tube to maintain said neck in a substantially upright position as pressure and heat are applied to said cap;
• and
• means for retracting said pressure applying means and interrupting said heat applying means thereby permitting said cap to cool and said molten mass to solidify within the filler passage of said neck of said centrifuge tube.

Apparatus for closing a passage formed in a filler neck protruding from the opening in the end of a substantially closed centrifuge tube after said tube has been filled with sample, the neck being formed of a heat fusible material, comprising:

• means adapted to engage the outer surface of said centrifuge tube for supporting said centrifuge tube in an upright position with said filler neck protruding upwardly;
• a cap formed of high heat conductivity material having a cavity adapted to closely fit the circumference of said filler neck, said cap adapted to be positioned over the end portion of said filler neck to confine said end portion of said neck within said cavity;
• means for applying heat to said cap member for raising the temperature thereof to the fusion temperature of said material forming said neck;
• pressure applying means movable upwardly and downwardly in a direction substantially along the axis of said filler passage said pressure applying means adapted to apply pressure downwardly against said cap so that, when said cap is heated to the fusion temperature of said neck, progressive portions of said neck melt and as said cap is forced downwardly the side-walls of said filler neck fold inwardly into said filler passage and form a molten mass closing said filler passage,
• clamping means adapted to grasp said neck at some predetermined position above the upper end of said centrifuge tube to maintain said neck in a substantially upright position as pressure and heat are applied to said cap;
• means for retracting said pressure applying means and interrupting said heat applying means from said cap;
• and
• cooling means movable into contact with said cap for rapidly cooling said cap and permitting said molten mass to solidify thereby closing the filler passage in said neck of said centrifuge tube.