Multiple sheet detecting apparatus

Claim 2

Apparatus for detecting the presence of multiple sheets moving along a predetermined path, comprising: a. means for producing a first time varying electrical signal; b. first transducer means disposed on one side of the path and responsive to said first time varying signal for producing a time varying ultrasonic signal which impinges upon sheet(s) at a first position along the path; c. second transducer means disposed on the opposite side of the sheet path and aligned with said first transducer means to receive at least a portion of the ultrasonic wave which impinged upon said sheet(s) for producing a second time varying electrical signal; and d. phase comparison means responsive to said first and second time varying electrical signals for comparing their phase relationship and producing an output signal when such phase relationship indicates a multiple sheet feed condition has occurred.

Claim 3

The invention as set forth in claim 1 wherein said phase comparison means includes: i. a first zero crossing comparator responsive to said second time varying signal for producing a first square wave-type output; ii. phase detector means responsive to said first square wave signal and said first time varying signal for producing a pulse-type signal, the width of which is a function of the phase difference between said first and second time varying signals; iii. a low-pass filter connected to said phase detector means; and iv. output comparator means connected to said low-pass filter for providing an indication when a multiple sheet feed condition has occurred.

Claim 4

The invention as set forth in claim 2 wherein said output comparator means includes an adjustable reference voltage source.

Claim 5

Apparatus for detecting the presence of multiple sheets moving along a predetermined path, comprising: a. means for producing a first time varying electrical signal; b. first transducer means disposed on one side of the path and responsive to said first time varying signal for producing a time varying ultrasonic signal which impinges upon sheet(s) at a first position along the path; c. second transducer means disposed on the opposite side of the sheet path and aligned with said first transducer means to receive at least a portion of the ultrasonic wave which impinged upon said sheet(s) for producing a second time varying electrical signal; d. means responsive to said first and second time varying signals for producing a third electrical signal having a parameter which is a function of the difference between the phases of such first and second signals; e. means for producing a reference signal having a parameter which defines a range of parameters for the parameter of said third signal so that the third signal parameter will be within such range when a multiple sheet condition has occurred; and f. comparison means for comparing such third electrical signal and reference signal parameters for producing an output indicating that a multiple sheet condition has occurred when the third parameter is within such reference signal parameter range.

Claim 6

Apparatus for detecting the presence of multiple sheets moving along a predetermined path, comprising: a. means for producing a first time varying electrical signal; b. first transducer means disposed on one side of the path and responsive to said first time varying signal for producing a time varying ultrasonic signal which impinges upon sheet(s) at a first position along the path; c. second transducer means disposed on the opposite side of the sheet path and aligned with said first transducer means to receive at least a portion of the ultrasonic wave which impinged upon said sheet(s) for producing a second time varying electrical signal; d. means responsive to said first and second time varying signals for producing a third electrical signal having a parameter which is a function of the difference between the phases of such first and second signals; e. means for producing a reference signal having a parameter which defines a range of parameters for the parameter of said third signal so that the third signal parameter will be within such range when a multiple sheet condition has occurred; and f. comparison means for comparing such third electrical signal and reference signal parameters for producing an output indicating that a multiple sheet condition has occurred when the third parameter is within such reference signal parameter range.

Claim 7

Method for detecting a multiple sheet feed condition comprising: a. producing a time varying ultrasonic signal which impinges upon sheet(s) at a first position along a predetermined sheet feeding path; b. receiving a portion of the ultrasonic wave which impinged upon such sheet(s) and, in response thereto, producing a first time varying electrical signal; and c. providing an output when the phase of such first time varying electrical signal indicates a multiple sheet feed condition has occurred.

Claim 8

Method for detecting a multiple sheet feed condition comprising: a. producing a time varying ultrasonic signal which impinges upon sheet(s) at a first position along a predetermined sheet feeding path; b. receiving a portion of the ultrasonic wave which impinged upon such sheet(s) and, in response thereto, producing a first time varying electrical signal; and c. providing an output when the phase of such first time varying electrical signal indicates a multiple sheet feed condition has occurred.

Claim 9

Method for detecting a multiple sheet feed condition comprising: a. producing a first time varying electrical signal at a predetermined frequency; b. producing a time varying ultrasonic signal at such predetermined frequency which impinges sheet(s) at a position along a predetermined path; c. receiving a portion of said ultrasonic signal which impinged upon said sheet(s) and, in response thereto, producing a second time varying electrical signal; and d. comparing such first and second electrical signals and producing an output when the phase difference between said signals indicates that a multiple sheet feed condition has occurred.

Claim 10

Method for detecting a multiple sheet feed condition comprising: a. producing a first time varying electrical signal at a predetermined frequency; b. producing a time varying ultrasonic signal at such predetermined frequency which impinges sheet(s) at a position along a predetermined path; c. receiving a portion of said ultrasonic signal which impinged upon said sheet(s) and, in response thereto, producing a second time varying electrical signal; and d. comparing such first and second electrical signals and producing an output when the phase difference between said signals indicates that a multiple sheet feed condition has occurred.

Claim 11

Method for determining the presence or absence of a sheet at a predetermined position comprising: a. directing a time varying ultrasonic signal to said predetermined position; b. receiving a portion of the ultrasonic signal coming from said predetermined position; c. comparing the phase of the directed and received ultrasonic signals; and d. producing an indication of the presence or absence of a sheet at said predetermined position in accordance with the differences in phase of said directed and received ultrasonic signals.

Claim 12

Method for determining the presence or absence of a sheet at a predetermined position comprising: a. directing a time varying ultrasonic signal to said predetermined position; b. receiving a portion of the ultrasonic signal coming from said predetermined position; c. comparing the phase of the directed and received ultrasonic signals; and d. producing an indication of the presence or absence of a sheet at said predetermined position in accordance with the differences in phase of said directed and received ultrasonic signals.

Claim 13

Method for determining whether or not a sheet is disposed at a predetermined position along a path comprising: a. producing a first time varying electrical signal at a predetermined frequency; b. producing a time varying ultrasonic signal having a frequency and phase which corresponds to that of said first signal; c. directing said ultrasonic signal to impinge upon a sheet if it were disposed at said predetermined position; d. receiving at least a portion of the ultrasonic signal at said predetermined position and, in response thereto, producing a second time varying electrical signal having a frequency and phase corresponding to said received ultrasonic signal; and e. comparing the phase relationship between the first and second electrical signals and in response thereto producing a manifestation of whether or not a sheet is disposed at the predetermined position.

Claim 14

Method for determining whether or not a sheet is disposed at a predetermined position along a path comprising: a. producing a first time varying electrical signal at a predetermined frequency; b. producing a time varying ultrasonic signal having a frequency and phase which corresponds to that of said first signal; c. directing said ultrasonic signal to impinge upon a sheet if it were disposed at said predetermined position; d. receiving at least a portion of the ultrasonic signal at said predetermined position and, in response thereto, producing a second time varying electrical signal having a frequency and phase corresponding to said received ultrasonic signal; and e. comparing the phase relationship between the first and second electrical signals and in response thereto producing a manifestation of whether or not a sheet is disposed at the predetermined position.