Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1995-06-12
1997-10-21
Lee, Helen
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428233, 428256, B32B 2714
Patent
active
056794410
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a porous sintered laminate comprising a mesh of metal wires to which a non-woven web of metal fibers is bonded by a sintering operation. It relates also to a method for manufacturing this laminate.
Porous sintered metal fiber laminates reinforced with one or more metal wire meshes are generally known. U.S. Pat. No. 3,437,457, for example, relates to a layered porous structure in which a metal fiber web is bonded by sintering on at least one of its flat sides to a woven wire mesh. To accomplish this, the metal fiber web is pressed against the wire mesh under low pressure and heated so that diffusion bonds are formed in the mutual contact points of the fibers with one another and with the net. A sintered filter structure with homogenous porosity is known from German patent application 2,720,278. To produce it, woven and/or non-woven layers of thin stainless steel fibers possessing a polygonal cross-section are laid on top of one another and then sintered to one another by the simultaneous application of pressure and heat in an oven. These porous laminates are intended especially for use as depth filters, and therefore the percentage content of fibers in them is quite high. U.S. Pat. No. 4,126,560 can also be referred to as an example of the current state of the art.
It is an object of the invention to provide porous laminates that have a relatively low porosity combined with a satisfactory filtering capacity. In particular, the invention can provide such porous laminates in which the percentage content of fiber is relatively small compared to the space occupied by the metal wire mesh and whereby yet a sufficient filtering capacity is maintained. In this case this means that despite a relatively low fiber weight per m.sup.2, sufficiently low porosities and suitable air permeabilities can nevertheless be achieved, particularly in the filter surface zones facing the wire mesh openings.
Another object of the invention is to provide filter laminates containing metal fiber, and relatively thin filter laminates in particular, which are capable of resisting high pressure drops and especially pressure pulses.
It is also the intention to provide filter laminates in which the bonding between fibers and wire mesh is so strong that the fiber layers can in fact no longer be pulled apart from the mesh.
Next, and in contrast to the continuous sintering process in ovens according to the state of the art, it is an object of the invention to provide a specific continuous sintering process that does not require the use of an oven. In particular, with this specific continuous sintering method it is an object of the invention to provide a universal, economical and flexible manufacturing method, which in principle makes it possible to utilize simpler and less expensive sintering installations. More in particular, this new continuous method should enable the realization of new specific filter structures with special filtering characteristics, including the laminates containing metal fibers which are intended by the present invention.
According to the present invention, these objectives are fulfilled by a porous laminate comprising a metal wire mesh consisting of mutually crossing wires upon which a non-woven web of metal fibers sintered to one another under pressure is attached, in which the porosity of the web in the region of the mesh junction points is at most 40%--and preferably not more than 25%--of that in the central zones of the mesh openings between the aforementioned junction points. For particular applications, a porosity ratio of even lower than 15% can be selected.
The economical method of producing the porous laminate envisaged by the invention works as follows: a metal wire mesh together with a metal fiber web laid on top of it is advanced continuously between rotating pressure rollers which are charged with different electrical potentials such that an electrical current flows through the cross-section of the laminate in the zone of contact with the rollers in view of sintering the fibers to
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patent: 4312670 (1982-01-01), Colucci
De Bruyne Roger
Losfeld Ronny
Saelens Johan
Lee Helen
N.V. Bekaert S.A.
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