Method and apparatus for corrugating filter media

1. A method of corrugating filter media, the method comprising:

transporting a sheet of filter media along a feed path in a feed direction using an upstream roller and a downstream roller, wherein exterior surfaces of the respective upstream and downstream rollers engage the sheet of filter media during said transporting, wherein the exterior surface of at least the upstream roller has a corrugating pattern defining circumferential channels, wherein at least the upstream roller is free from association with another roller such that at an instantaneous time during said transporting, an upstream portion of the sheet of filter media that is engaging the upstream roller is free from engagement with another roller;

rotating the upstream roller at a first rotational speed to move the filter media at the upstream roller at a first feed speed;

rotating the downstream roller at a second rotational speed to move the filter media at the downstream roller at a second feed speed that is greater than the first feed speed;

heating the filter media so that the upstream portion of the sheet of filter media is within its elastic temperature range when the upstream portion of the sheet of filter media engages the upstream roller; and

drawing the heated upstream portion of the sheet of filter media engaging the upstream roller at least partially into the circumferential channels of the corrugating pattern on the upstream roller as the upstream portion of the sheet of filter media engages the upstream roller, wherein during said drawing, the entire upstream portion engaging the upstream roller and entering, at least partially, the circumferential channels of the corrugating pattern is free from engagement with another roller.

2. The method of corrugating filter media set forth in claim 1 , wherein the sheet of filter media comprises a nonwoven fabric layer.

3. The method of corrugating filter media set forth in claim 2 , wherein the nonwoven fabric layer constitutes a base media substrate, the sheet of filter media further comprising a nanofiber layer deposited on at least a first side of the nonwoven fabric layer.

4. The method of corrugating filter media set forth in claim 3 , wherein the nonwoven fabric layer comprises a thermoplastic polymer.

5. The method of corrugating filter media set forth in claim 3 , wherein the nonwoven fabric layer comprises a thermosetting polymer.

6. The method of corrugating filter media set forth in claim 2 , wherein the nonwoven fabric layer comprises bicomponent fibers having core-sheath structures, wherein sheaths of the core-sheath structures have lower melting temperatures than cores of the bicomponent fibers.

7. The method of corrugating filter media set forth in claim 1 , further comprising detecting the temperature of the filter media at the upstream roller using a temperature sensor.

8. The method of corrugating filter media set forth in claim 7 , further comprising:

receiving temperature signals, using a controller, from the temperature sensor detecting the temperature of the filter media at the upstream roller; and

controlling an output of a heater, based on the received temperature signals, using the controller to heat the filter media within its elastic temperature range when the filter media engages the upstream roller.

9. The method of corrugating filter media set forth in claim 7 , further comprising detecting the rotational speeds of the upstream and downstream rollers using at least one rotational speed detector.

10. The method of corrugating filter media set forth in claim 9 , further comprising:

receiving rotational speed signals, using a controller, from the rotational speed sensor detecting the rotational speeds of the upstream and downstream rollers; and

controlling an output of at least one motor driving the upstream and downstream rollers, based on the received rotational speed signals, using the controller to drive rotation of the upstream and downstream rollers at the respective first and second rotational speeds.

11. The method of corrugating filter media set forth in claim 1 , further comprising:

transporting the sheet of filter media along the feed path in the feed direction using a second downstream roller, wherein an exterior surface of the second downstream rollers engages the sheet of filter media during said transporting, wherein the exterior surface of the second downstream roller has a corrugating pattern defining circumferential channels, wherein at least the second downstream roller is free from association with another roller such that at an instantaneous time during said transporting, a downstream portion of the sheet of filter media that is engaging the second downstream roller is free from engagement with another roller;

rotating the second downstream roller at a third rotational speed to move the filter media at the second downstream roller at a third feed speed that is greater than the first and second feed speeds;

heating the filter media so that the filter media is within its elastic temperature range when the filter media engages the second downstream roller; and

drawing the portion heated filter media engaging the second downstream roller at least partially into the circumferential channels of the corrugating pattern on the second downstream roller as the portion of filter media engages the second downstream roller, wherein during said drawing, the entire downstream portion engaging the second downstream roller and entering, at least partially, the circumferential channels of the corrugating pattern of the second downstream roller is free from engagement with another roller.

12. The method of corrugating filter media set forth in claim 1 , further comprising cooling the filter media, after said heating the filter media so that the filter media is within its elastic temperature range when the filter media engages the upstream roller, to a temperature below its elastic temperature range to thermally set a corrugation pattern formed on the filter media.