Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
112 words
A sifting screen comprising a frame; a first woven cloth of hard wearing metal wire, stretched across the frame and secured thereto; and a second woven cloth having a coarser mesh than the first cloth and being woven from an elongate material of greater cross-section than the first and which is also stretched, across the frame, and secured thereto, below the first cloth, to support the latter against sagging; wherein the rigidity of the frame is selected so as to restrict overall flexure of the woven cloths so as to reduce fatigue producing movement of the cloths and extend the life of the screen before material fatigue damages either of the cloths.
Claim 2
Dependent Claim
112 words
A sifting screen comprising a frame; a first woven cloth of hard wearing metal wire, stretched across the frame and secured thereto; and a second woven cloth having a coarser mesh than the first cloth and being woven from an elongate material of greater cross-section than the first and which is also stretched, across the frame, and secured thereto, below the first cloth, to support the latter against sagging; wherein the rigidity of the frame is selected so as to restrict overall flexure of the woven cloths so as to reduce fatigue producing movement of the cloths and extend the life of the screen before material fatigue damages either of the cloths.
Claim 3
Dependent Claim
17 words
A sifting screen according to claim 1, wherein the screen frame is constructed from heavy gauge steel.
Claim 4
Dependent Claim
28 words
A sifting screen according to claim 1, wherein the frame is formed from glass reinforced gas blown polypropylene and is reinforced by elongate metal reinforcing elements or rods.
Claim 5
Dependent Claim
14 words
A sifting screen according to claim 1, wherein the screen includes structural support members.
Claim 6
Dependent Claim
72 words
A sifting screen according to claim 1, wherein the cross-section of the materials from which the cloths are woven and the shape and size of unsupported areas of screen cloths are selected having due regard to the nature of solids materials to be transported over the resulting screen and to the maximum force acting on the screen in a downward sense due to the weight of solids materials heaped thereon during use.
Claim 7
Dependent Claim
87 words
A sifting screen according to claim 1, wherein the lengths of elongate material extending across the unsupported regions of the cloths and the tensions in those lengths of material are selected having regard to the frequency at which the screen is to be vibrated when in use so as to ensure that the natural resonant frequency of the lengths of material making up the warp and weft of each cloth is not capable of being activated into resonance or any harmonic or sub-harmonic of its resonant frequency.
Claim 8
Dependent Claim
34 words
A sifting screen according to claim 6, wherein different tensions are imparted to the warps and wefts of each cloth so that whatever the natural frequency in one direction, it is different in another.
Claim 9
Dependent Claim
19 words
A sifting screen according to claim 1, in which both cloths are tensioned before being secured to the frame.
Claim 10
Dependent Claim
28 words
A sifting screen according to claim 8, wherein the tension in the material forming the upper cloth is different from that in the material forming the lower cloth.
Claim 11
Dependent Claim
16 words
A sifting screen according to claim 1, when fitted in a vibratory cradle of shale shaker.