Abstract
A Thermal Bonding Method and Apparatus to thermally bond sheets of fill in a cooling tower fill pack. The apparatus creates a hemispherical joint extending through two fill sheets to provide a substantial joint between said sheets.
Claims
1. A thermal bonding method comprising: placing alternating film fill sheets on a stack; heating a hemispherical bonding tip to a melting point of said alternating film fill sheets; plunging the bonding tip vertically onto a bond site on a selected one of said alternating film fill sheets; allowing the tip to melt into the stack of alternating film fill sheets to a predetermined depth; providing a pulse of air through the bonding tip that pushes the melted film fill sheets together; and removing the bonding tip from the bond site.
2. The method of claim 1 wherein some steps occur simultaneously.
3. The method of claim 1 wherein a sufficient pressure and duration of air pulse is provided through the tip to cause the bond site to form into a partial bubble shape as air is injected into the bond site.
4. The method of claim 3, wherein the partial bubble shape of the bond site is larger at a bottom, inhibiting separation of bonded sheets.
Description
DESCRIPTION OF THE DRAWINGS
(1) The subsequent description of the preferred embodiments of the present invention refers to the attached drawings, wherein:
(2) FIG. 1 is a schematic showing the major components of a fill bonding apparatus according to an embodiment of the invention.
(3) FIG. 2 shows a cross-sectional view of the thermal bonding tip according to an embodiment of the invention.
(4) FIG. 3 shows an outside perspective view of the thermal bonding tip according to an embodiment of the invention.
(5) FIGS. 4a through 4i show the sequence of operation for placing fill sheets and creating the bond according to an embodiment of the invention.
(6) FIGS. 5a through 5e show the sequence of operation for the bonding tip according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
(7) FIG. 1 shows the major components of the fill bonding apparatus. Two different sheet types, Type A and Type B, are loaded onto feeder trays 1 and 2, respectively. Gantry 3 moves horizontally to pick and place sheets type A and B, alternately, on the fill stack 4. Vacuum chucks 5 and 6 remove the sheets from the stacks 1 and 2. Arrays of thermal bonding tips 7 weld the sheets together when they are placed on the fill stack 4.
(8) FIG. 2 illustrates the main parts of the thermal bonding device. Hemispherical tip 10 extends through insulator and holding bushing 20. Heater block 30 provides heat to the tip 10. Air passage 40 extends through heater block 30 and rod 50 to provide a conduit for pressurized air to the tip 10. Rod 50 extends vertically through slide bushing 60 to allow vertical movement of the heater block, tip, and rod. Spring 70 provides vertical force resistance to movement of tip 10. Collar 80 is fixed to tip 10 and provides a positive vertical stop to the motion of the tip. Heat sensing device 90 provides feedback to control the temperature of the tip 10.
(9) FIG. 3 illustrates an isometric view of the thermal bonding apparatus.
(10) FIG. 4a is an elevation view of the fill bonding apparatus illustrating the starting position in the sequence of operation with parts labeled as in FIG. 1.
(11) FIG. 4b illustrates simultaneously raising the stacking tray 4 and the sheet type A feeder tray 1. Sheet type A is loaded into the gantry 3 and held in place by the vacuum chuck 5.
(12) FIG. 4c illustrates simultaneously lowering the sheet type A feeder tray 1 and stacking tray 4 while sheet type A is in the loaded position.
(13) FIG. 4d illustrates moving the gantry 3 to the sheet type B loading position and sheet type A stack placing position.
(14) FIG. 4e illustrates simultaneously raising the stacking tray 4 and sheet type B feeder tray 2. Sheet type B is loaded into the gantry 3 and held in place by the vacuum chuck 5. Sheet type A is released by the vacuum chuck and placed on the stacking tray 4.
(15) FIG. 4f illustrates simultaneously lowering the sheet type B feeder tray 2 and stacking tray 4 while sheet type B is in the loaded position.
(16) FIG. 4g illustrates moving the gantry 3 to the sheet type A bonding position and sheet type B stack placing position
(17) FIG. 4h illustrates simultaneously raising the stacking tray 4 and sheet type A feeder tray 1. Sheet type A is loaded into the gantry 3 and held in place by the vacuum chuck 5. Sheet type A and sheet type B are bonded together on the stacking tray 4. This is the same position shown in FIG. 4b except bonding is being performed.
(18) FIG. 4i illustrates returning the sheet type A feeder and stacking tray to the start position as illustrated in FIG. 4c which shows the gantry 3 loaded with sheet type A.
(19) FIG. 5a illustrates the bonding tip just contacting the fill stack as the fill stack moves up. The bond tip heated. This occurs in position 8 of the machine.
(20) FIG. 5b illustrates the bonding tip being pushed up as the fill stack continues to move up. This compresses the spring and puts downward pressure on the bonding tip
(21) FIG. 5c illustrates the heated bonding tip extending down into the fill stack bond point as the sheets are heated. The spring decompresses partially during this step as the tip melts down into the bond site, still keeping pressure on the bond. The holding bushing 20 prevents the bonding tip from pushing too far into the fill stack.
(22) FIG. 5d illustrates the end of the bond heating cycle. At this point, the bond is melted together. As the fill stack is lowered, a burst of air is injected through the tip which pushes the sheets together and improves the bond strength. This air burst also helps eject the tip from the bond site without sticking A bubbled-out joint can also be provided to enhance the bond, in which the melted bond site is blown into a partial bubble shape as air is injected. The bubble is a larger on the bottom of the joint, which keeps it from pulling out. Some instantaneous cooling may also occur, solidifying the joint.
(23) FIG. 5e is the last step and corresponds to position 1 of the machine cycle. The tip has been completely removed from the bond site, and the site is allowed to cool.
