Acoustical sensing curtain

Claim 2

An acoustical sensing curtain, comprising: means for generating a collimated acoustical beam; a plurality of acoustical reflectors mutually arranged so as to successively reflect said collimated beam back and forth along non-coaxial parallel paths in an area between said reflectors so that substantially no portion of said area is not transversed by said beam whereby a substantially continuous curtain is thereby established over said area; and acoustically sensitive means operatively disposed in the terminal portion of said beam traveL for sensing any interruption in the propagation of said beam by the penetration of said curtain by an object to be sensed.

Claim 3

Apparatus as defined by claim 1 wherein said generating means includes a whistle, and said sensing means includes a flow mode device.

Claim 4

Apparatus as defined by claim 1 wherein the effective cross sectional area of the object to be sensed is greater than one half of the cross sectional area of said collimated beam.

Claim 5

Apparatus as defined by claim 1 wherein said reflectors are disposed in two opposed and mutually facing rows.

Claim 6

Apparatus as defined by claim 4 wherein at least some of the reflectors in each of said rows are disposed at substantially 90* to their respective adjacent reflectors.

Claim 7

An acoustical sensing curtain: comprising means for generating a collimated acoustical beam; acoustical sensing means adapted to be controlled by said beam; and a plurality of acoustical reflecting means disposed so as to successively intercept and redirect said beam through non-coaxial parallel paths in moving from said generating means to said sensing means so that there is an area adjacent said reflecting means in which there is substantially no portion that is not transversed by said beam, said area thus effectively defining an acoustical curtain whereby when an object to be sensed penetrates said curtain said beam will be interrupted and a signal will be generated by said sensing means indicating the presence of said object.

Claim 8

An acoustical sensing curtain: comprising means for generating a collimated acoustical beam; acoustical sensing means adapted to be controlled by said beam; and a plurality of acoustical reflecting means disposed so as to successively intercept and redirect said beam through non-coaxial parallel paths in moving from said generating means to said sensing means so that there is an area adjacent said reflecting means in which there is substantially no portion that is not transversed by said beam, said area thus effectively defining an acoustical curtain whereby when an object to be sensed penetrates said curtain said beam will be interrupted and a signal will be generated by said sensing means indicating the presence of said object.

Claim 9

Apparatus as defined by claim 6 wherein said reflecting means includes two opposed and facing rows of acoustical reflectors, the reflectors in each row being mutually disposed at substantially 90* with respect to one another; the first operative reflector being disposed at an angle of substantially 45* with respect to the initial portion of said collimated beam.

Claim 10

Apparatus as defined by claim 6 wherein said generating means includes a whistle.

Claim 11

Apparatus as defined by claim 6 wherein said sensing means includes a fluidic flow mode device.