GB1601571A

GB1601571A - Measuring apparatus for use in a machine tool

Info

Publication number: GB1601571A
Application number: GB1335177A
Authority: GB
Original assignee: HERBERT Ltd ALFRED
Current assignee: HERBERT Ltd ALFRED
Priority date: 1978-03-30
Filing date: 1978-03-30
Publication date: 1981-10-28

Description

(54) MEASURING APPARATUS FOR USE IN A MACHINE TOOL (71) We, ALFRED HERBERT LIMITED, a British Company of P.O Box 30, Edgwick Works, Coventry, CV6 5GT, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of and an apparatus for the measurement in a machine tool of the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position, such method and apparatus being particularly but not exclusively applicable to the in-process measurement of the diameter of a workpiece being machined, such as a roll being ground.

It is a requirement of some machining sequences in machine tools to obtain continuous information about the position of the component relative to a given reference and to provide an absolute measurement of a diameter relative to the machining operation. Very heavy workpieces are usually supported, during machining, on support blocks. Wear of the blocks can lead to gradual displacement of the workpiece and consequent change in the position thereof and this creates a problem in effecting in-process diameter measurement. An object of the invention is to overcome this problem.

According to one aspect of the invention a method of measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position, comprises the steps of supporting the component at a location diametrically opposed to a working location on the component, sensing the positions of two circumferentially spaced points on the surface and obtaining an output representing deviation of said points from a predetermined fixed reference line passing through the rotational axis of the machine and perpendicular to a further line joining the support engagement point on the component and said working location, effecting a cyclic correcting movement of said support in a direction towards or away from said location to maintain the centre of the component in a substantially constant horizontal position, sensing the position of the component in a sense perpendicular to said direction by means of a further probe engaging said surface at a point substantially perpendicular to said direction, and providing, in a fixed time relationship to said cyclic correcting movement, a representation of the position of the component as sensed by all of said probes to provide a component diameter measurement.

According to another aspect of the invention, an apparatus, for measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant-horizontal position, comprises a transverse support engaging the component at a location diametrically opposed to a working location on the component, a pair of probes sensing the positions of two circumferentially spaced points on the surface and providing an output representing deviation of said points from a predetermined fixed reference line passing through the rotational axis of the machine and perpendicular to a further line joining the support engagement point on the component and said working location, means responsive to the output from the probes and operable to effect a cyclic correcting movement of said support in a direction towards or away from said location, to maintain the centre of the component in a substantially constant horizontal position a further probe engaging said surface at a point substantially perpendicular to said direction and arranged to sense the position of the component in a sense perpendicular to said direction, and means for providing in a fixed time relationship to said cyclic correcting movement, a representation of the position of the component as sensed by all of said probes to provide a component diameter measurement.

In one convenient arrangement, the further probe engages the component at a lowermost region of its circumference. With such an arrangement, the probes may, if desired, be housed within an enclosure which may be pressurised to minimise ingress of foreign material, such as coolant and grit. The probes are delicate mechanisms and protection thereof in the aforesaid manner is very desirable.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a component supported for machining and associated with the measuring apparatus of the invention; Figure 2 is an end elevation of the arrangement shown in Figure 1, and Figure 3 is a cross sectional view along the line 3-3 of Figure 1.

Referring to the drawings, these show a component in the form of a roll 1 having an outer cylindrical surface 2 mounted on lower vertically adjustable support blocks 3 and constrained in a horizontal direction by horizontally adjustable support blocks 4.

The roll is rotated for mac ining by means (not shown) engaging one or both of its end portions 5.

A pair of probes 6 and 7 are mounted so as to engage the cylindrical surface 2 of the roll at circumferentially spaced locations, being urged continuously into engagement with the roll surface by suitable resilient or fluid pressure-operated means 6a, 7a. Any tendency for the roll to move off centre in a direction to the right as seen in Figures 2 and 3 is counteracted by inclined surfaces 3a of the blocks 3 and by the anti-clockwise rotation of the roll, i.e. in a direction towards the block 4, as indicated by the arrow A. Movement of the roll to either the left or right, as seen in Figures 2 and 3, is detected by the probes 6 and 7 which actuate respective measuring devices 8 and 9. These in turn give rise to an error signal which is used to produce appropriate corrective movement of the block 4 to maintain the centre of the component in a substantially constant horizontal position.

In a particularly convenient arrangement, the measuring devices produce electrical outputs which are fed to a Wheatstone Bridge and the error signal occurs as a positive or negative voltage, which after any necessary amplification, is supplied to suitable motive means, such as an electric motor for effecting said block corrective movement.

A further probe 10 is arranged beneath the component 1 and engages the component at a lowermost region of its circumference. This further probe provides a third positional reading, which, together with the positions sensed by the probes 6 and 7, will define the position and diameter of the circle represented by the circumference of the roll 1. It will be appreciated that three points in a plane geometrically define the radius of a circle and the position of the centre and this information, when fed to a computer, will provide an immediate indication of the diameter of the component at any instant.

As a practical matter, it is convenient to produce the indication when the roll is correctly centred, i.e. when the reading on the Wheatstone Bridge is zero and no correction is being effected by the block 4.

Means are therefore provided to ensure that, in practice, a diameter reading is obtainable when the Wheatstone Bridge reading is zero. However, since the correcting movement provided by the block 4 is of a cyclic nature, it is only essential to ensure that the diameter reading is given in any fixed time relationship to the cyclic correcting movement.

By using the apparatus of the invention in conjunction with the computer of a numerically controlled machine tool such as a roll grinder, it is possible to obtain extremely accurate in-process correction of any drift occuring in the transverse position of the component. It will be appreciated that wear of the supporting block 3 means that the position of the centre of the component will gradually fall, but the system of invention enables the necessary transverse correction of the component centre to be effected and the component diameter measured irrespective of vertical variation in its position.

The delicate nature of the probes and measuring devices make it desirable to house them in an enclosure such as that shown at 11 and the provision of suitable seals at 1 lea against the outer surface of the component enables the enclosure to be pressurized to discourage ingress of foreign material such as coolant and grit.

WHAT WE CLAIM IS- 1. A method of measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position, said method comprising the steps of supporting the component at a location diametrically opposed to a working location on the component, sensing the positions of two

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. direction, and means for providing in a fixed time relationship to said cyclic correcting movement, a representation of the position of the component as sensed by all of said probes to provide a component diameter measurement. In one convenient arrangement, the further probe engages the component at a lowermost region of its circumference. With such an arrangement, the probes may, if desired, be housed within an enclosure which may be pressurised to minimise ingress of foreign material, such as coolant and grit. The probes are delicate mechanisms and protection thereof in the aforesaid manner is very desirable. The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a component supported for machining and associated with the measuring apparatus of the invention; Figure 2 is an end elevation of the arrangement shown in Figure 1, and Figure 3 is a cross sectional view along the line 3-3 of Figure 1. Referring to the drawings, these show a component in the form of a roll 1 having an outer cylindrical surface 2 mounted on lower vertically adjustable support blocks 3 and constrained in a horizontal direction by horizontally adjustable support blocks 4. The roll is rotated for mac ining by means (not shown) engaging one or both of its end portions 5. A pair of probes 6 and 7 are mounted so as to engage the cylindrical surface 2 of the roll at circumferentially spaced locations, being urged continuously into engagement with the roll surface by suitable resilient or fluid pressure-operated means 6a, 7a. Any tendency for the roll to move off centre in a direction to the right as seen in Figures 2 and 3 is counteracted by inclined surfaces 3a of the blocks 3 and by the anti-clockwise rotation of the roll, i.e. in a direction towards the block 4, as indicated by the arrow A. Movement of the roll to either the left or right, as seen in Figures 2 and 3, is detected by the probes 6 and 7 which actuate respective measuring devices 8 and 9. These in turn give rise to an error signal which is used to produce appropriate corrective movement of the block 4 to maintain the centre of the component in a substantially constant horizontal position. In a particularly convenient arrangement, the measuring devices produce electrical outputs which are fed to a Wheatstone Bridge and the error signal occurs as a positive or negative voltage, which after any necessary amplification, is supplied to suitable motive means, such as an electric motor for effecting said block corrective movement. A further probe 10 is arranged beneath the component 1 and engages the component at a lowermost region of its circumference. This further probe provides a third positional reading, which, together with the positions sensed by the probes 6 and 7, will define the position and diameter of the circle represented by the circumference of the roll 1. It will be appreciated that three points in a plane geometrically define the radius of a circle and the position of the centre and this information, when fed to a computer, will provide an immediate indication of the diameter of the component at any instant. As a practical matter, it is convenient to produce the indication when the roll is correctly centred, i.e. when the reading on the Wheatstone Bridge is zero and no correction is being effected by the block 4. Means are therefore provided to ensure that, in practice, a diameter reading is obtainable when the Wheatstone Bridge reading is zero. However, since the correcting movement provided by the block 4 is of a cyclic nature, it is only essential to ensure that the diameter reading is given in any fixed time relationship to the cyclic correcting movement. By using the apparatus of the invention in conjunction with the computer of a numerically controlled machine tool such as a roll grinder, it is possible to obtain extremely accurate in-process correction of any drift occuring in the transverse position of the component. It will be appreciated that wear of the supporting block 3 means that the position of the centre of the component will gradually fall, but the system of invention enables the necessary transverse correction of the component centre to be effected and the component diameter measured irrespective of vertical variation in its position. The delicate nature of the probes and measuring devices make it desirable to house them in an enclosure such as that shown at 11 and the provision of suitable seals at 1 lea against the outer surface of the component enables the enclosure to be pressurized to discourage ingress of foreign material such as coolant and grit. WHAT WE CLAIM IS-

1. A method of measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position, said method comprising the steps of supporting the component at a location diametrically opposed to a working location on the component, sensing the positions of two

circumferentially spaced points on the surface and obtaining an output representing deviation of said points from a predetermined fixed reference line passing through the rotational axis of the machine and perpendicular to a further line joining the support engagement point on the component and said working location, effecting a cyclic correcting movement of said support in a direction towards or away from said location to maintain the centre of the component in a substantially constant horizontal position, sensing the position of the component in a sense perpendicular to said direction by means of a further probe engaging said surface at a point substantially perpendicular to said direction, and providing, in a fixed time relationship to said cyclic correcting movement, a representation of the position of the component as sensed by all of said probes to provide a component diameter measurement.

2. A method of measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position, substantially as hereinbefore described with reference to the accompanying drawings.

3. An apparatus for measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position, said apparatus comprising a transverse support for engaging the component at a location diametrically opposed to a working location on the component, a pair of probes for sensing the positions of two circumferentially spaced points on the surface and providing an output representing deviation of said points from a predetermined fixed reference line passing through the rotational axis of the machine and perpendicular to a further line joining the support engagement point on the component and said working location, means responsive to the output from the probes and operable to effect a cyclic correcting movement of said support in a direction towards or away from said location, to maintain the centre of the component in a substantially constant horizontal position, a further probe engaging said surface at a point substantially perpendicular to said direction and arranged to sense the position of the component in a sense perpendicular to said direction, and means for providing, in a fixed time relationship to said cyclic correcting movement, a representation of the position of the component as sensed by all of said probes to provide a component diameter measurement.

4. An apparatus according to Claim 3 wherein the further probe engages the component at a lowermost region of its circumference.

5. An apparatus according to Claim 4, wherein all of said probes are housed within an enclosure adapted to be pressurised to minimise ingress of foreign material.

6. An apparatus according to any one of Claims 3 to 5 wherein said transverse support is a horizontally adjustable block.

7. An apparatus according to any one of Claim 3 to 6, wherein displacement of said pair of probes gives rise to an electrical output which is applied to effect said correcting movement of the transverse support.

8. An apparatus for measuring in a machine tool the diameter of a component having a cylindrical surface and for maintaining said component in a substantially constant horizontal position; substantially as hereinbefore described with reference to the accompanying drawings.