Scanning system using radioactive radiation in cigarette rod making machine

Claim 2

A scanning system for a cigarette making machine or other continuous rod making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the rod and into an ionisation chamber having positive and negative electrodes, the positive electrode being a rod lying substantially along the axis of a surrounding tubular member which acts as the negative electrode, the transverse crosssectional dimension of the rod in every direction being small compared with the internal diameter of the tubular member acting as the negative electrode, a balance unit comprising a radiation source arranged to pass a radiation beam into an ionisation chamber having electrodes of which one is electrically connected to one of the electrodes of the scanning unit and is so polarized as to produce an output current which opposes the output current from the ionisation chamber of the scanning unit, and means for reducing the noise components in the output current from the balance unit comprising a high-value resistor connected to said one electrode of said balance unit.

Claim 3

A scanning system according to claim 1 in which the radiation beam is directed into the ionisation chamber substantially along the axis of the tubular member.

Claim 4

A scanning system according to claim 1 including an adjustable control member which partially interrupts the beam from the radiation source of the balance unit.

Claim 5

A scanning system according to claim 1 in which the high-value resistor is of the order of 2 X 1010 ohms.

Claim 6

A scanning system according to claim 1 in which the output currents from the scanning unit and balance unit pass to an output terminal via a fast-response amplifier having negative feedback and a high gain.

Claim 7

A scanning system according to claim 5 in which the output signal transmitted from the output terminal is arranged in a cigarette making machine to control the amount of tobacco going into the continuous cigarette rod and is also used to eject individual cigarettes which are inadequately filled with tobacco.

Claim 8

A scanning system according to claim 1 in which the scanning unit includes a guide tube for guiding the continuous rod, the guide tube being formed with a window defining the outline of the beam which passes into the ionisation chamber.

Claim 9

A scanning system according to claim 7 for a cigarette making machine, in which the dimensions of the window are such that the beam has a width, measured in the direction of the cigarette rod axis, of approximately 5 mm at the center of the rod.

Claim 10

A scanning system according to claim 1 in which the positive electrode of the scanning unit is at a voltage of the order of 1000 volts.

Claim 11

A scanning system according to claim 1 in which the ionisation chamber is filled with Krypton gas.

Claim 12

A scanning system according to claim 10 in which the Krypton gas is at a pressure of approximately 2 to 2.5 atmospheres.

Claim 13

A scanning system according to claim 1 including a response correction circuit to compensate for the slow response of the part of the output signal contributed by the ions in the ionisation chamber of the scanning unit, the response circuit comprising a first resistor connected between the ionisation chamber and an output terminal, a second resistor connected between the output terminal and ground, and a capacitor connected across the first resistor, the value of the second resistor in relation to the sum of the resistors being in a proportion substantially equal to the proportion of the output signal due to the electrons in the ionisation chamber.

Claim 14

A scanning system for a cigarette making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the continuous cigarette rod and into an ionisation chamber including positive and negative electrodes so arranged that the field strength is greater near the positive electrode or electrodes than it is near the negative electrode or electrodes, so that a major proportion of the output current is due to the movement of electrons in the ionisation chamber, and including a response correction circuit comprising a first resistor connected between the ionisation chamber and an output terminal, a second resistor connected between the output terminal and ground, and a capacitor connected across the first resistor, the value of the second resistor in relation to the sum of the resistors being in a proportion substantially equal to the proportion of the output signal due to the electrons in the ionisation chamber.

Claim 15

A scanning system for a cigarette making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the continuous cigarette rod and into an ionisation chamber including positive and negative electrodes so arranged that the field strength is greater near the positive electrode or electrodes than it is near the negative electrode or electrodes, so that a major proportion of the output current is due to the movement of electrons in the ionisation chamber, and including a response correction circuit comprising a first resistor connected between the ionisation chamber and an output terminal, a second resistor connected between the output terminal and ground, and a capacitor connected across the first resistor, the value of the second resistor in relation to the sum of the resistors being in a proportion substantially equal to the proportion of the output signal due to the electrons in the ionisation chamber.

Claim 16

A scanning system according to claim 13 in which the capacitor is of a value such that it discharges at a rate correSponding substantially to the build-up of the current due to the ions in the ionisation chamber.

Claim 17

A scanning system for a cigarette making machine or other continuous rod making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the rod and into an ionisation chamber having a positive rod electrode mounted substantially along the axis of a surrounding tubular member which acts as the negative electrode; a balance unit comprising a radiation source arranged to pass a radiation beam into an ionisation chamber having electrodes of which one is electrically connected to one of the electrodes of the scanning unit and is so polarised as to produce an output current which opposes the output current from the ionisation chamber of the scanning unit; and a response correction circuit to compensate for the slow response of the part of the output signal contributed by the ions in the ionisation chamber of the scanning unit, the response circuit comprising a first resistor connected between the ionisation chamber and an output terminal, a second resistor connected between the output terminal and ground, and a capacitor connected across the first resistor, the value of the second resistor in relation to the sum of the resistors being in a proportion substantially equal to the proportion of the output signal due to the electrons in the ionisation chamber, the capacitor being of a value such that it discharges at a rate corresponding substantially to the build-up of the current due to the ions in the ionisation chamber.

Claim 18

A scanning system for a cigarette making machine or other continuous rod making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the rod and into an ionisation chamber having a positive rod electrode mounted substantially along the axis of a surrounding tubular member which acts as the negative electrode; a balance unit comprising a radiation source arranged to pass a radiation beam into an ionisation chamber having electrodes of which one is electrically connected to one of the electrodes of the scanning unit and is so polarised as to produce an output current which opposes the output current from the ionisation chamber of the scanning unit; and a response correction circuit to compensate for the slow response of the part of the output signal contributed by the ions in the ionisation chamber of the scanning unit, the response circuit comprising a first resistor connected between the ionisation chamber and an output terminal, a second resistor connected between the output terminal and ground, and a capacitor connected across the first resistor, the value of the second resistor in relation to the sum of the resistors being in a proportion substantially equal to the proportion of the output signal due to the electrons in the ionisation chamber, the capacitor being of a value such that it discharges at a rate corresponding substantially to the build-up of the current due to the ions in the ionisation chamber.

Claim 19

A scanning system for a cigarette making machine or other continuous rod making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the rod and into an ionisation chamber having a positive rod electrode mounted substantially along the axis of a surrounding tubular member which acts as the negative electrode; and a balance unit comprising a radiation source arranged to pass a radiation beam into an ionisation chamber having at least one positive plate electrode and at least one negative plate electrode, and being electrically connected to the scanning unit so as to produce an output current which opposes the output current from the ionisation chamber of the scanning unit.

Claim 20

A scanning system for a cigarette making machine or other continuous rod making machine, including a scanning unit comprising a radiation source for passing a radiation beam through the rod and into an ionisation chamber having a positive rod electrode mounted substantially along the axis of a surrounding tubular member which acts as the negative electrode; and a balance unit comprising a radiation source arranged to pass a radiation beam into an ionisation chamber having at least one positive plate electrode and at least one negative plate electrode, and being electrically connected to the scanning unit so as to produce an output current which opposes the output current from the ionisation chamber of the scanning unit.

Claim 21

A scanning system according to claim 16 in which the balance unit comprises a single centrally mounted negative plate electrode and two positive plate electrodes disposed parallel to and on opposite sides of the negative plate electrode.

Claim 22

A scanning system according to claim 16, including a response correction circuit to compensate for the slow response of the part of the output signal contributed by the ions in the ionisation chamber of the scanning unit, the response circuit comprising a first resistor connected between the ionisation chamber and an output terminal, a second resistor connected between the output terminal and earth, and a capacitor connected across the first resistor, the value of the second resistor in relation to the sum of the resistors being in a proportion substantially equal to the proportion of the output signal due to the electrons in the ionisation chamber.

Claim 23

A scanning system according to claim 7 for a cigarette making machine, in which the dimensions of the window are such that the beam has a width, in the direction of the cigarette rod axis, which is smaller than the diameter of the cigarette rod.