GB2124386A

GB2124386A - Dynamic measuring system

Info

Publication number: GB2124386A
Application number: GB08317116A
Authority: GB
Inventors: Derek Harry Graddon Redman
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-06-26
Filing date: 1983-06-23
Publication date: 1984-02-15
Also published as: GB8317116D0; GB2124386B

Abstract

The measuring system comprises a movable machine tool table (16), a machine tool (12) (such as a grinding wheel), positioned at a location above the table, a non-contact sensor (18) of the electromagnetic or capacitive type positioned above the table at a second location spaced from the machine tool, the sensor measuring the thickness of the workpiece W as it passes under the sensor, and a sample and hold circuit operable to compare a signal from the sensor (18) indicative of workpiece dimension with a signal representative of the required dimension and provided from datum block (19). <IMAGE>

Description

SPECIFICATION Dynamic measuring system This invention relates to a dynamic measuring system and is particularly applicable to accurate measurement of workpieces on a moving machine tool table.

According to the invention, there is provided a dynamic measuring system comprising a movable machine tool table, a machine tool positioned at one location above the table, a non-contact sensor positioned above the table at a second location spaced from said first location, the sensor being able to detect or measure a dimension of a workpiece on the table as it passes under the sensor, and a sample and hold circuit operable to sample and hold a signal from the sensor indicative of the workpiece dimension.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of a grinding machine incorporating a dynamic measuring system according to the present invention, and Figure 2 is an electrical circuit diagram of the measuring system of Figure 1.

Referring to the drawings, a conventional grinding machine 10 includes a grinding wheel 12 rotating about a horizontal axis, a horizontally movable table 14 and an upper table 16 carried by table 14 and rotatable about the vertical axis.

Workpieces W to be ground to a given thickness are secured to the upper surface of table 16 and are brought into engagement with grinding wheel 12 by the rotational movement of table 1 6 and the horizontal movement of table 14.

Positioned above the table 1 6 at a location A diametrically opposite the grinding wheel is a measuring sensor 1 8 of the non-contact type such as an electromagnetic or capacitive sensor having a highly stable output and giving an output representative of the distance between the sensor face and an upper face of a workpiece as it passes beneath the sensor and of a datum block 19 of required thickness.

Also positioned at location A are two trigger sensors 20, 22, the purpose of which will become apparent in the following description of the electrical circuit of the present system. Associated with the trigger 20 is a magnet 24, and a magnet 26 is positioned alongside one of the workpieces to be measured on the table and is positioned to pass under trigger 22.

Referring to the electrical circuit of Figure 2, two sample and hold amplifiers 28, 30 are each fed at one of their inputs with the output of the measuring sensor 1 8, the other input of amplifier 28 being fed with the output of sensor 20, and that of amplifier 30 being fed with the output of sensor 22. Power for the sensor is provided from supply 32.

As the datum block passes the measuring sensor 18, magnet 24 triggers sensor 20 which causes amplifier 28 to sample the output of sensor 1 8 and to display the output on indicative 34. Similarly,-as workpiece W passes the measuring sensor 18, magnet 26 triggers sensor 22 which causes amplifier 30 to sample the output of sensor 1 8 and to display the output on indicator 36.

The outputs of the amplifiers are compared in scanning amplifier 38 which when the inputs are substantially equal is operative to actuate relay 40 to stop the grinding machine.

In a modification, sensor 20, magnet 24 and datum block 1 9 are omitted and are replaced by a signal producing means (not shown) which provides a signal representative of desired workpiece thickness and compared with the signal output of amplifier 30.

It will be appreciated that the above system enables workpieces to be measured dynamically while the machine tool is in operation, which operation is not terminated until the workpieces are-of the desired thickness.

In a further modification, only one sample and hold amplifier is provided which holds the most recent signal from the sensor 18, the amplifier output being displayed on indicator 36.

Claims

1. A dynamic measuring system for measuring a workpiece dimension whilst the workpieces are moving on a machine tool table, the system comprising a movable table, a machine tool positioned at one location above the table, a noncontact sensor positioned above the table at a second location spaced from said first location, the sensor being able to detect or measure a dimension of a workpiece on the table as it passes under the sensor, and a sample and hold circuit operable to sample and hold a signal from the sensor indicative of the workpiece dimension.

2. The system of Claim 1, including a trigger sensor positioned at the second location and operable to cause an amplifier of the sample and hold circuit to sample the output of the noncontact sensor, and to cause an indicator to display the sensor output.

3. The system of Claim 2, including a summing amplifier for comparing the non-contact sensor output with a required dimension signal and operable to stop the machine tool when the sensor output and required dimension signal are equal.

4. The system of any one of the preceding Claims, wherein the required dimension signal is provided by a datum block positioned on the table.

5. The system of Claim 4, including a second trigger sensor positioned at the second location and operable to cause a second amplifier of the sample and hold circuit to sample the output of the second non-contact sensor as the datum block passes underneath.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Dynamic measuring system This invention relates to a dynamic measuring system and is particularly applicable to accurate measurement of workpieces on a moving machine tool table. According to the invention, there is provided a dynamic measuring system comprising a movable machine tool table, a machine tool positioned at one location above the table, a non-contact sensor positioned above the table at a second location spaced from said first location, the sensor being able to detect or measure a dimension of a workpiece on the table as it passes under the sensor, and a sample and hold circuit operable to sample and hold a signal from the sensor indicative of the workpiece dimension. An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of a grinding machine incorporating a dynamic measuring system according to the present invention, and Figure 2 is an electrical circuit diagram of the measuring system of Figure 1. Referring to the drawings, a conventional grinding machine 10 includes a grinding wheel 12 rotating about a horizontal axis, a horizontally movable table 14 and an upper table 16 carried by table 14 and rotatable about the vertical axis. Workpieces W to be ground to a given thickness are secured to the upper surface of table 16 and are brought into engagement with grinding wheel 12 by the rotational movement of table 1 6 and the horizontal movement of table 14. Positioned above the table 1 6 at a location A diametrically opposite the grinding wheel is a measuring sensor 1 8 of the non-contact type such as an electromagnetic or capacitive sensor having a highly stable output and giving an output representative of the distance between the sensor face and an upper face of a workpiece as it passes beneath the sensor and of a datum block 19 of required thickness. Also positioned at location A are two trigger sensors 20, 22, the purpose of which will become apparent in the following description of the electrical circuit of the present system. Associated with the trigger 20 is a magnet 24, and a magnet 26 is positioned alongside one of the workpieces to be measured on the table and is positioned to pass under trigger 22. Referring to the electrical circuit of Figure 2, two sample and hold amplifiers 28, 30 are each fed at one of their inputs with the output of the measuring sensor 1 8, the other input of amplifier 28 being fed with the output of sensor 20, and that of amplifier 30 being fed with the output of sensor 22. Power for the sensor is provided from supply 32. As the datum block passes the measuring sensor 18, magnet 24 triggers sensor 20 which causes amplifier 28 to sample the output of sensor 1 8 and to display the output on indicative 34. Similarly,-as workpiece W passes the measuring sensor 18, magnet 26 triggers sensor 22 which causes amplifier 30 to sample the output of sensor 1 8 and to display the output on indicator 36. The outputs of the amplifiers are compared in scanning amplifier 38 which when the inputs are substantially equal is operative to actuate relay 40 to stop the grinding machine. In a modification, sensor 20, magnet 24 and datum block 1 9 are omitted and are replaced by a signal producing means (not shown) which provides a signal representative of desired workpiece thickness and compared with the signal output of amplifier 30. It will be appreciated that the above system enables workpieces to be measured dynamically while the machine tool is in operation, which operation is not terminated until the workpieces are-of the desired thickness. In a further modification, only one sample and hold amplifier is provided which holds the most recent signal from the sensor 18, the amplifier output being displayed on indicator 36. Claims

6. The system of Claim 5, including a second indicator to display the output of the second sensor.

7. A dynamic measuring system substantially as herein described with reference to the accompanying drawings.