Air filter

An air filter, comprising:

• a filter element of fibrous material;
• and
• a frame for supporting said filter element at its marginal edges;
• said frame comprising a strip of stiff paper scored along two spaced longitudinal lines and folded away from said longitudinal lines to form a trough for receiving said filter element, said strip also being folded transversely to form a closed configuration surrounding said filter element to receive said marginal edges of said filter element in said trough;
• said frame including an outer wall, a first side wall extending perpendicularly inward from said outer wall toward said filter element, and a second side wall extending inward from said outer wall toward said filter element and sloping toward said first side wall;
• said second side wall terminating in a flange disposed in a parallel relationship with said first side wall, said flange being secured to said first side wall with said filter element compressed therebetween to hold said frame and said filter element together.

An air filter of quadrangular shape, comprising:

• a filter element of fibrous material having a quadrangular shape;
• a porous backing sheet of quadrangular shape located adjacent to said filter element;
• and
• a frame surrounding said filter element and backing sheet for supporting said filter element and backing sheet adjacent to the marginal edges thereof;
• said frame comprising an elongated strip of stiff paper scored along two spaced longitudinal lines on the same side of said strip and folded away from said longitudinal lines to form a trough for receiving said filter element and also folded transversely at predetermined spaced locations to form a closed, quadrangular configuration which surrounds said filter element and backing sheet and receives said marginal edges of said filter element and backing sheet in said trough;
• said frame including an outer wall, a first side wall extending inwardly at right angles to said outer wall from said filter element, and a second side wall extending inwardly from said outer wall and sloping toward said first side wall;
• said strip being scored along an additional longitudinal line on its opposite side and folded away from said additional longitudinal line to provide a flange on said second side wall disposed at right angles to said outer wall, said flange being secured to said first side wall with said filter element compressed therebetween to hold said frame, filter element and backing sheet together.

An air filter of generally rectangular shape, comprising:

• a filter element of fibrous material having a generally rectangular shape;
• a frame surrounding said filter element and supporting said filter element adjacent to its marginal edges;
• and
• a generally rectangular backing sheet for said filter element including a plurality of air flow openings;
• said frame comprising an elongated strip of stiff paper scored along two spaced longitudinal lines on the same side of said strip and folded away from said longitudinal lines to form a trough for receiving said filter element, said strip also being scored along transverse lines at predetermined spaced locations on the same side of said strip and folded away from said transverse lines to form a closed, rectangular configuration which surrounds said filter element and receives said marginal edges of said filter element in said trough;
• said frame being substantially a right triangle in cross section and including an outer wall, a rear wall extending inwardly at right angles to said outer wall toward said filter element, and a front wall extending inwardly from said outer wall and sloping toward said rear wall, said backing sheet being located between said filter element and said rear wall of said frame;
• said strip being scored along an additional longitudinal line on its opposite side and folded away from said additional longitudinal line to provide a flange on said front wall disposed in a parallel relationship with said rear wall, said flange being secured to said rear wall with said filter element compressed therebetween to hold said frame, filter element, and backing sheet together.

An air filter of generally rectangular shape, comprising:

• a filter element of fibrous material having a generally rectangular shape and a substantially uniform thickness;
• a frame surrounding said filter element and supporting said filter element adjacent to its marginal edges;
• and
• a generally rectangular backing sheet for said filter element including a plurality of air flow openings;
• said frame comprising an elongated strip of stiff paper scored along two spaced longitudinal lines on the same side of said strip and folded away from said longitudinal lines to form a trough for receiving said filter element, said strip also being scored along transverse lines at predetermined spaced locations on the same side of said strip and folded away from said transverse lines to form four frame sections into a closed, rectangular configuration which surrounds said filter element and receives said marginal edges of said filter element in said trough;
• each frame section being a right triangle in cross section and having an outer wall substantially equal in width to the thickness of said filter element, a rear wall extending inwardly at right angles to said outer wall toward said filter element, and a front wall extending inwardly from said outer wall toward said filter element and sloping toward said rear wall, said backing sheet being located between said filter element and said rear wall of said frame;
• said strip being scored along an additional longitudinal line on its opposite side and folded away from said additional longitudinal line to provide a flange on said front wall disposed at right angles to said outer wall, said flange being adhesively secured to said rear wall with said filter element compressed therebetween to hold said frame, filter element, and backing sheet together.

An air filter of generally rectangular shape, comprising:

• a filter element of fibrous material having a generally rectangular shape;
• a frame surrounding said filter element and supporting said filter element adjacent to its marginal edges;
• and
• a generally rectangular backing sheet for said filter element including a plurality of air flow openings;
• said frame comprising an elongated strip of stiff paper scored along two spaced longitudinal lines on the same side of said strip and folded away from said longitudinal lines to form a trough for receiving said filter element, said strip also being folded transversely at predetermined spaced locations to form a closed, rectangular configuration which surrounds said filter element and receives said marginal edges of said filter element in said trough;
• said frame being triangular in cross section and including an outer wall, a rear wall extending inwardly at an obtuse angle to said outer wall toward said filter element, and a front wall extending inwardly from said outer wall and sloping toward said rear wall, said backing sheet being located between said filter element and said rear wall of said frame;
• said front wall terminating in a flange disposed in a parallel relationship with said rear wall, said flange being secured to said rear wall with said filter element compressed therebetween to hold said frame, filter element, and backing sheet together.