Apparatus and method for making bag assembly

1. A method of forming a bag assembly comprising a bag and a tube providing fluid communication with an interior of the bag, the method comprising:

forming a subassembly by positioning at least a portion of the tube between a pair of opposed sheets,

placing the subassembly between a first die member and a second die member opposing said first die member,

pressing the subassembly with the first and second die members,

applying an electric field between the first and second die members by supplying a single radiofrequency current to the first and second die members in a first location for heating the pair of sheets along a path to weld the pair of sheets together to define a perimeter of the bag and in a second location for welding the tube to the pair of sheets,

increasing the spacing between portions of the opposing first and second die members in the first location to reduce the heating of the pair of sheets at the first location while portions of the first and second die members at the second location are at a spacing that causes continued welding at the second location, and

decreasing without completely eliminating the electric field after said step of increasing the spacing.

2. A method of forming a bag assembly as set forth in claim 1 wherein said step of pressing the subassembly comprises using a press to force one of the first and second die members toward the other of said first and second die member.

3. A method of forming a bag assembly as set forth in claim 1 wherein the step of applying an electrical field includes simultaneously forming a perimeter-weld of the bag and a tube-weld between the pair of sheets and tube, the perimeter and tube welds defining a continuous weld on the bag assembly.

4. A method of forming a bag assembly as set forth in claim 1 wherein the tube includes a resiliently deformable insert, and wherein said step of pressing the subassembly comprises flattening the tube and the tubular insert.

5. A method of forming a bag assembly as set forth in claim 4 further comprising stopping the step of pressing of the subassembly with the first and second die members, the tubular insert having a resiliency permitting reconfiguring the tubular insert and the tube to an open configuration.

6. A method of forming a bag assembly as set forth in claim 5 wherein the tubular insert when reconfigured to the open configuration has an elliptical cross section having a major axis disposed generally parallel to a plane of the pair of sheets.

7. A method of forming a bag assembly as set forth in claim 6 wherein the tubular insert is unaffected by the applied electric field.

8. A method of forming a bag assembly as set forth in claim 7 wherein the tubular insert is press-fitted in the tube.

9. A method of forming a bag assembly as set forth in claim 7 wherein the tubular insert is adhered to an inside of the tube.

10. An apparatus for forming a bag assembly including a bag formed from opposing sheets welded together along a perimeter-weld and a tube welded to the opposing sheets along a tube-weld for providing fluid communication with an interior of the bag, the apparatus comprising:

a die including a first die member and a second die member opposing the first die member, the first die member and the second die member having opposing tube-welding portions for welding the opposing sheets to the tube, and opposing perimeter-welding portions for welding the opposing sheets together to define the bag, the first die member and second die member being disposed for relative movement toward one another to press the opposing sheets and tube and away from one another, the perimeter-welding portion of the first die member being movable relative to the tube-welding portion of the first die member when the first die member and the second die member press the opposing sheets and tube to permit an increase in spacing between the perimeter-welding portion of the first die member and the perimeter-welding portion of the second die member so that welding of the opposing sheets by the perimeter-welding portions is suspended while welding by the tube-welding portions continues; and

a source of radiofrequency current electrically connected to at least one of the first and second die members for applying a radiofrequency electric field to the opposing sheets and tube when the first and second die members press the opposing sheets and tube for welding the opposing sheets and the tube;

a retaining device for retaining the spacing of the tube-welding portion of the first die member and the tube-welding portion of the second die member as the spacing between the perimeter-welding portion of the first die member and the perimeter-welding portion of the second die member is increased, wherein said retaining device exerts a force on the tube-welding portion of the first die member independent from the perimeter-welding portion of the first die member to retain the spacing of the tube-welding portion of the first die member and the tube-welding portion of the second die member as the spacing between the perimeter-welding portion of the first die member and the perimeter-welding of the second die member is increased;

a press device engaged with at least one of the first and second die members for bringing the first and second die members together and for increasing the spacing between the perimeter-welding portion of the first die member and the perimeter-welding portion of the second die member while allowing the retaining device to retain the spacing of the tube-welding portion of the first die member and the tube-welding portion of the second die member; and

a controller configured to automatically decrease without eliminating an output of the source of radiofrequency energy after the perimeter-welding portion of the first die member is moved away from the perimeter-welding potion of the second die member.

11. An apparatus for forming a bag assembly as set forth in claim 10 wherein the first and second die members are connected in series to the source of radiofrequency energy.

12. An apparatus for forming a bag assembly as set forth in claim 10 wherein each tube-welding portion of the first die member and the second die member includes a tube-welding electrode having a low-profile arcuate surface for at least partially flattening the tube and a resiliently deformable insert in the tube during welding.

13. An apparatus for forming a bag assembly as set forth in claim 10 wherein the tube-welding portion of the first die member is slidably engaged with the perimeter-welding portion of the first die member.

14. An apparatus for forming a bag assembly as set forth in claim 13 wherein the tube-welding portion of the first die member includes at least one tab extending laterally therefrom that is received in a slot of the perimeter-welding portion of the first die member.

15. An apparatus for forming a bag assembly as set forth in claim 14 wherein perimeter-welding portion of the first die member includes a recess defined by sidewalls, the tube-welding portion of the first die member being received in the recess.

16. An apparatus for forming a bag assembly as set forth in claim 14 wherein the retaining device comprises at least one spring.