Positioning device for the radiation absorber of thickness measuring devices

Claim 2

In a thickness measuring device of the type having a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, radiation-absorbing means intended to be positioned in the radiation path and a positioning device for positioning this radiation-absorbing means in the radiation path, the positioning device comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the radiation-absorbing means, and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; the improvement comprising: threshold switching means, controlled by the difference between the reference signal and the test signal, for actuating said drive means only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiationabsorbing means at a second, lower speed until the radiationabsorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position.

Claim 3

In a thickness measuring device of the type having a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, and radiation absorbing means intended to be positioned in the radiation path and further including a positioning device for positioning the radiation-absorbing means in the radiation path, comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the radiation-absorbing means, and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; the improvement comprising threshold switching means controlled by the difference between the reference signal and the test signal for actuating said drive means only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiation-absorbing means at a second, lower speed until the radiation-absorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position, and wherein said means for generating the analog test signal comprises two branches of a four-branch bridge circuit, said two branches being arranged potentiometrically with their junction point connected to said radiation-absorbing means for movement therewith; said means for generating the analog reference signal comprises the other two branches of the bridge circuit, which other two branches are also arranged potentiometrically, with their junction point being presettable for predetermining approximately the desired position of the radiation-absorbing means, and said threshold switch is connected across the diagonal of the bridge circuit.

Claim 4

In a thickness measuring device of the type having a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, and radiation absorbing means intended to be positioned in the radiation path and further including a positioning device for positioning the radiation-absorbing means in the radiation path, comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the radiation-absorbing means, and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; the improvement comprising threshold switching means controlled by the difference between the reference signal and the test signal for actuating said drive means only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiation-absorbing means at a second, lower speed until the radiation-absorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position, and wherein said means for generating the analog test signal comprises two branches of a four-branch bridge circuit, said two branches being arranged potentiometrically with their junction point connected to said radiation-absorbing means for movement therewith; said means for generating the analog reference signal comprises the other two branches of the bridge circuit, which other two branches are also arranged potentiometrically, with their junction point being presettable for predetermining approximately the desired position of the radiation-absorbing means, and said threshold switch is connected across the diagonal of the bridge circuit.

Claim 5

A positioning device according to claim 2, wherein said threshold switching means comprises a Schmitt trigger controlled by the bridge diagonal voltage and a relay controlled by the Schmitt trigger and controlling the drive means.

Claim 6

In a thickness measuring device of the type having radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, and radiation-absorbing means intended to be positioned in the radiation path, and further including a positioning device for positioning the radiation-absorbing means in the radiation path, comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the radiation-absorbing means, and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; wherein the improvement comprises threshold switching means controlled by the difference between the reference signal and the test signal for actuating said drive means, only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiation-absorbing means at a second, lower speed until the radiation-absorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position, and wherein said drive means include an electric motor and a first, higher, voltage source and a second, lower, voltage source, said threshold switching means actuating said drive means at the higher speed by connecting the motor to the higher voltage source and at the lower speed by connecting the motor to the lower voltage source.

Claim 7

In a thickness measuring device of the type having radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, and radiation-absorbing means intended to be positioned in the radiation path, and further including a positioning device for positioning the radiation-absorbing means in the radiation path, comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the radiation-absorbing means, and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; wherein the improvement comprises threshold switching means controlled by the difference between the reference signal and the test signal for actuating said drive means, only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiation-absorbing means at a second, lower speed until the radiation-absorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position, and wherein said drive means include an electric motor and a first, higher, voltage source and a second, lower, voltage source, said threshold switching means actuating said drive means at the higher speed by connecting the motor to the higher voltage source and at the lower speed by connecting the motor to the lower voltage source.

Claim 8

A positioning device according to claim 1, wherein said drive means includes an intermediate shaft driven by a motor for transmitting rotary movement to the radiation-absorbing means, said intermediate shaft carrying an actuating member for controlling said fine switching means in accordance with the position of said radiation-absorbing means.

Claim 9

In a thickness measuring device of the type having a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, and radiation-absorbing means intended to be positioned in the radiation path and further including a positioning device for positioning the radiation-absorbing means in the radiation path comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the absorbing means and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; the improvement comprising threshold switching means controlled by the difference between the reference signal and the test signal for actuating said drive means, only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiation-absorbing means at a second, lower speed until the radiation-absorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position, and wherein said drive means includes an intermediate shaft driven by a motor for transmitting rotary movement to the radiation-absorbing means, said intermediate shaft carrying an actuating member for controlling said fine switching means in accordance with the position of said radiation-absorbing means, and wherein said actuating member comprises a cam which operates said fine switching means to stop the drive means when said radiation-absorbing means reaches its predetermined position.

Claim 10

In a thickness measuring device of the type having a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the irradiated object, and radiation-absorbing means intended to be positioned in the radiation path and further including a positioning device for positioning the radiation-absorbing means in the radiation path comprising drive means for driving the radiation-absorbing means in order to change its position, means for generating an analog test signal representative of the position of the absorbing means and means for generating an analog reference signal approximately representative of the desired position of the radiation-absorbing means; the improvement comprising threshold switching means controlled by the difference between the reference signal and the test signal for actuating said drive means, only when said difference exceeds the threshold of the threshold switching means to drive the radiation-absorbing means at a first, higher speed in the direction which reduces said difference, and fine switching means controlled by the position of the radiation-absorbing means for actuating said drive means when said difference is within said threshold to drive the radiation-absorbing means at a second, lower speed until the radiation-absorbing means reaches its predetermined desired position, and for stopping said drive means when said radiation-absorbing means reaches its predetermined desired position, and wherein said drive means includes an intermediate shaft driven by a motor for transmitting rotary movement to the radiation-absorbing means, said intermediate shaft carrying an actuating member for controlling said fine switching means in accordance with the position of said radiation-absorbing means, and wherein said actuating member comprises a cam which operates said fine switching means to stop the drive means when said radiation-absorbing means reaches its predetermined position.

Claim 11

A thickness measuring device comprising: a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the object, a disk having a plurality of radiation absorbers of different absorbing power disposed around its circumference, said disk being rotatable so that any one of the radiation absorbers can be brought into the radiation path, an electric motor geared to the disk via an intermediate shaft, for driving the disk in rotation, a four-branch bridge circuit having a voltage source across one diagonal, this bridge circuit comprising two branches in the form of a potentiometer having an intermediate tap which divides the two branches, this intermediate tap being connected to the intermediate shaft so that the position of the intermediate tap is a function of the position of the disk, the other two branches of the bridge circuit also being in the form of a potentiometer having an intermediate tap which divides them, the position of this latter intermediate tap being selectable to set approximately the desired position of the disk, a Schmitt trigger controlled by the voltage across the other diagonal of the bridge circuit, said Schmitt trigger assuming a first state when this latter voltage exceeds a certain threshold and a second state when this voltage falls within the threshold, a relay controlled by said Schmitt trigger for connecting said electric motor to a first, higher, voltage source when said Schmitt trigger is in its first state and for disconnecting said electric motor from said first higher voltage source when said Schmitt trigger is in its second state, and a cam mounted on said intermediate shaft for operating a further switch which is normally in a first state, for putting it into a second state when the disk reaches its desired position, said further switch, in its first state, causing a further relay to connect said motor to a second, lower voltage, and in its second state, causing said further relay to disconnect said motor from said second lower voltage.

Claim 12

A thickness measuring device comprising: a radiation source for irradiating an object whose thickness is to be measured, a radiation detector for detecting the radiation transmitted by the object, a disk having a plurality of radiation absorbers of different absorbing power disposed around its circumference, said disk being rotatable so that any one of the radiation absorbers can be brought into the radiation path, an electric motor geared to the disk via an intermediate shaft, for driving the disk in rotation, a four-branch bridge circuit having a voltage source across one diagonal, this bridge circuit comprising two branches in the form of a potentiometer having an intermediate tap which divides the two branches, this intermediate tap being connected to the intermediate shaft so that the position of the intermediate tap is a function of the position of the disk, the other two branches of the bridge circuit also being in the form of a potentiometer having an intermediate tap which divides them, the position of this latter intermediate tap being selectable to set approximately the desired position of the disk, a Schmitt trigger controlled by the voltage across the other diagonal of the bridge circuit, said Schmitt trigger assuming a first state when this latter voltage exceeds a certain threshold and a second state when this voltage falls within the threshold, a relay controlled by said Schmitt trigger for connecting said electric motor to a first, higher, voltage source when said Schmitt trigger is in its first state and for disconnecting said electric motor from said first higher voltage source when said Schmitt trigger is in its second state, and a cam mounted on said intermediate shaft for operating a further switch which is normally in a first state, for putting it into a second state when the disk reaches its desired position, said further switch, in its first state, causing a further relay to connect said motor to a second, lower voltage, and in its second state, causing said further relay to disconnect said motor from said second lower voltage.