Folding air filter assemblies

1. A collapsible air-filter assembly comprising:

a filter medium element; and

a frame comprising a top shell and a bottom shell, wherein the frame is positioned to at least partially surround the filter medium element,

wherein the filter medium element and the frame each include a plurality of areas separated by at least one engineered fold line;

wherein the frame and the filter medium element are configured to vary in at least one dimension by folding or unfolding;

wherein the assembly is operable to move from a folded position to an unfolded position along the at least one engineered fold line; and

wherein, when the assembly is in the unfolded position, the filter medium element is configured to expand volumetrically from a flattened configuration to a standing configuration.

2. The assembly of claim 1 , wherein the filter medium element is rectangular pleated or trapezoidal pleated.

3. The assembly of claim 1 , wherein the filter medium element is pleated, wherein the pleats are generally rounded.

4. The assembly of claim 1 , wherein, in a configuration expanded by area and volume, the filter medium element has rectangular channels extending from end to end.

5. The assembly of claim 4 , further comprising edge treatments nestled with the filter medium element.

6. The assembly of claim 4 , wherein channel sidewalls unfold upward from a flattened configuration to a standing configuration when the air-filter assembly is volumetrically expanded.

7. The assembly of claim 1 , wherein, when twice folded in two dimensions, the air-filter assembly is halved in length and halved in width.

8. A variable filter assembly comprising:

a filter medium element; and

a frame comprising a top shell and a bottom shell, wherein the frame is positioned to at least partially surround the filter medium element,

wherein the frame and filter media element are configured to be reducible in at least one dimension via a non-planar action, wherein the non-planar action includes folding;

wherein the assembly is operable to move from a folded position to an unfolded position; and

wherein, when the assembly is in the unfolded position, the filter medium element is configured to expand volumetrically from a flattened configuration to a standing configuration.

9. The variable filter assembly according to claim 8 , wherein the filter medium element is pleated, wherein the pleats are generally rectangular.

10. The variable filter assembly according to claim 8 , wherein the filter medium element is pleated, wherein the pleats are generally trapezoidal.

11. The variable filter assembly according to claim 8 , wherein the filter medium element is pleated, wherein the pleats are generally rounded.

12. The variable filter assembly according to claim 8 , wherein the filter medium element is pleated, wherein edge treatments assist in expansion of the pleats.

13. The variable filter assembly according to claim 8 , further comprising a scrim layer extending approximately parallel to a major plane of the filter medium element and contacting the filter medium element, wherein the scrim layer comprises a flat top layer and bottom layer.

14. The variable filter assembly according to claim 13 , wherein the filter medium element is pleated, wherein the scrim layer is configured to have a tensile and bending stiffness such that the pleats are encouraged to rebound to an original shape profile in an expanded configuration of the variable filter assembly.

15. The variable filter assembly according to claim 8 , further comprising a frame wrap surrounding edges of the frame.

16. The variable filter assembly according to claim 15 , wherein the filter medium element is pleated, wherein the frame wrap is configured to seal the ends of a pleated portion of the filter medium element.

17. The variable filter assembly according to claim 15 , wherein the frame wrap is configured to reduce noise associated with the filter moving when airflow is turned on or off.

18. A collapsible air filter including:

a filter medium element; and

a frame;

wherein the frame includes a top shell and a bottom shell, wherein the frame is positioned to

at least partially surround the filter medium element,

wherein the collapsible air filter is operable to move from a collapsed configuration to an expanded configuration along at least one engineered fold line,

wherein, when in the collapsed configuration, the air filter is reduced in the dimension predominantly parallel to the direction of air flow;

wherein, when in the expanded configuration, the collapsible air filter is increased in the dimension predominantly parallel to the direction of air flow; and

wherein switching from the collapsed configuration to the expanded configuration, the filter media element of the collapsible air filter is expanded thus increasing the effective filter media element volume.

19. A collapsible air filter according to claim 18 , wherein the filter medium element includes a series of pleats, wherein a perforated or otherwise open sheet of resilient material laminated to the filter media element assists in the expansion of the pleats.

20. The collapsible air filter according to claim 1 , wherein the filter medium element further includes a plurality of channels, wherein the plurality of channels extend from a first end of the filter medium element to a second end of the filter medium element, wherein the first end of the filter medium element and the second end of the filter medium element are on opposite sides of the filter medium element.