Weighing device for movable conveyors

Claim 2

A weighing device comprising a belt conveyor; rollers extending beneath and supporting said belt conveyor; supports for said rollers at opposite sides of the conveyor; vertically movable platform means carrying the supports for said rollers; a fixed support beneath the movable platform; a fixed member above the platform; spring means between the movable platform and the fixed support to resiliently separate the said movable platform and the fixed support; spring means between the movable platform and the fixed member above the platform to resiliently separate the movable platform and the fixed member above the platform, said spring means having a different spring rate that that of the spring means between the movable platform and the fixed support; a metallic member fixed to the bottom of the movable platform; and a sensing means spaced from said metallic member beneath said movable platform and arranged to have a flux output within which said metallic member moves upon movement of the movable platform and to supply a signal to an output meter indicative of the position of the metallic member as a function of load placed on the belt conveyor and passing over the said movable platform.

Claim 3

A weighing device as in claim 1, wherein the spring means are each Vlier springs.

Claim 4

A weighing device as in claim 1, further including rigid means fixed to the movable platform for engaging the fixed support before the metallic member can contact the sensing means.

Claim 5

A weighing device as in claim 1, wherein the sensing means includes a magnetic steel housing; a first stainless steel membrane brazed to one end of the housing; said housing and said first membrane having been heat treated together, such that central portions of a said membrane have become more non-magnetic and a peripheral portion has become more magnetic, whereby lines of flux are focused through said central portion; an impedance circuit in said housing, said circuit including substantially identical measuring and reference coils forming legs of a bridge, the other legs of which are formed by the coils of an AC transformer, and wherein said reference and measuring coils are axially aligned within the housing such that the measuring coil is adjacent to the first membrane; a second non-magnetic membrane stretched across the inside of the housing and dividing the housing substantially centrally thereof, said second membrane being spaced from the reference coil a distance corresponding to the distance the said first membrane is spaced from the said measuring coil; a plug of insulating material substantially filling a portion of the housing at the side of the second membrane opposite said reference coil; lead wires to said coils passing through said second membrane and said insulating plug, and being embedded in said plug; cap means for securing said plug in place in said housing; and means, including said lead wires and said transformer, for translating differential impedance changes in the reference and measuring coils into a signal indicative of a sensed characteristic of a material crossing the lines of flux generated by the measuring coil and passing through the first membrane.

Claim 6

A weighing device as in claim 4, wherein the sensing means further includes means for further collimating lines of flux passed through the said first membrane, said means comprising at least one non-ferrous, metallic shield member overlying and covering all but a limited central portion of a face of the first membrane.

Claim 7

A weighing device as in claim 4, wherein the spring means are Vlier springs.

Claim 8

A weighing device as in claim 6, further including rigid means fixed to the movable platform for engaging the fixed support before the magnetic member can contact the sensing means.