US4027245A — Numerically controlled machine tool

Claim 1

Independent Claim 414 words

A process of machining a three-dimensional surface of a workpiece driven in rotation about a first axis and displaced in translation along a second axis substantially parallel to the first, with respect to a tool, so that all the points of the surface of the said workpiece can be presented successively to the said tool, the distance between the tool and the workpiece being variable by relative displacement in a direction distinct from that defined by the two said axes, the process being effected by a numerically controlled machine tool comprising a computer having in store data permitting the surface to be machined to be defined by calculation, in which the speed of rotation of the said workpiece about the said first axis is controlled independently of the speed of displacement, of the workpiece along the said second axis, which is itself independently adjustable, in which the relative position of the workpiece and tool is numerically controlled in the said direction as a function of the rotary speed and angular position of the workpiece relative to the first axis and its speed and position along the second axis in such a manner that the tool machines the desired surface, and in which the instruction for relatively positioning the workpiece and the tool is given in the form of a sum of a profile function and an ovalisation function, the profile function providing the dimension difference, measured perpendicularly to the said axis, between the profile of the said workpiece in a selected profile plane of the said workpiece, the plane passing through the first axis, and the generatrix contained in this same plane of the section of the basic body of revolution co-axial with the said first axis and circumscribed on the said workpiece in such a manner as to have in common with it at least one point on their respective surfaces, the said selected profile plane being chosen in such a manner as to contain the said point, and the ovalisation function being the dimension difference between the outline of the said workpiece in a section through a plane perpendicular to the first axis and a circle in this plane with its centre on the said first axis, the said circle being circumscribed on and tangent to at least one point on the said outline in the said section, the said difference of dimension being measured along a radius passing through the said first axis, in the sectional plane through the first axis.

Claim 2

Dependent Claim 414 words

A process of machining a three-dimensional surface of a workpiece driven in rotation about a first axis and displaced in translation along a second axis substantially parallel to the first, with respect to a tool, so that all the points of the surface of the said workpiece can be presented successively to the said tool, the distance between the tool and the workpiece being variable by relative displacement in a direction distinct from that defined by the two said axes, the process being effected by a numerically controlled machine tool comprising a computer having in store data permitting the surface to be machined to be defined by calculation, in which the speed of rotation of the said workpiece about the said first axis is controlled independently of the speed of displacement, of the workpiece along the said second axis, which is itself independently adjustable, in which the relative position of the workpiece and tool is numerically controlled in the said direction as a function of the rotary speed and angular position of the workpiece relative to the first axis and its speed and position along the second axis in such a manner that the tool machines the desired surface, and in which the instruction for relatively positioning the workpiece and the tool is given in the form of a sum of a profile function and an ovalisation function, the profile function providing the dimension difference, measured perpendicularly to the said axis, between the profile of the said workpiece in a selected profile plane of the said workpiece, the plane passing through the first axis, and the generatrix contained in this same plane of the section of the basic body of revolution co-axial with the said first axis and circumscribed on the said workpiece in such a manner as to have in common with it at least one point on their respective surfaces, the said selected profile plane being chosen in such a manner as to contain the said point, and the ovalisation function being the dimension difference between the outline of the said workpiece in a section through a plane perpendicular to the first axis and a circle in this plane with its centre on the said first axis, the said circle being circumscribed on and tangent to at least one point on the said outline in the said section, the said difference of dimension being measured along a radius passing through the said first axis, in the sectional plane through the first axis.

Claim 3

Dependent Claim 98 words

A method according to claim 1, in which the dimensional difference in the selected profile plane is that between the profile of the said workpiece and the generatrix of the body of revolution circumscribed in a small number of privileged profile sections perpendicular to the first axis, the said dimensional difference in any other standard section perpendicular to the first axis being obtained by linear interpolation of the dimensional differences in the privileged profile sections enclosing the standard plane and as a function of the distance of the standard section from the privileged profile sections which enclose it.

Claim 4

Dependent Claim 49 words

A process according to claim 2, in which the ovalisation function in a small number of sections perpendicular to the first axis, known as privileged sections of ovalisation, is defined by the coefficients of the first n harmonics, n being comprised between 1 and 20, of a Fourier series.

Claim 5

Dependent Claim 66 words

A method of numerical control according to claim 3, in which the ovalisation function in any section perpendicular to the first axis is defined by the coefficients of the first n harmonics of a Fourier series, the said coefficients being derived by interpolation of the coefficients of the harmonics of equal order of the ovalisation functions of two privileged sections enclosing the said chosen perpendicular plane.

Claim 6

Dependent Claim 36 words

A process according to claim 4, in which the said interpolation is linear as a function of the distance of the said chosen perpendicular section from the two privileged ovalisation sections enclosing the said chosen section.

Claim 7

Dependent Claim 118 words

A process of machining according to claim 1, in which the angular position of the workpiece about the said first axis and its position along the said second axis are measured by means of incremental pulse coders, and in which the wavefront of one pulse in p pulses emitted by the coder indexing the position of the workpiece about its first axis is used to synchronise the calculation of the distance between the workpiece and tool, the value of p being defined in such a manner that the maximum duration of a calculation of the relative distance between the tool and workpiece is less than p times the duration separating two pulses from the said workpiece position coder.

Claim 8

Dependent Claim 103 words

A process of machining according to claim 1, in which the angular position of the workpiece about the said first axis and its position along the said second axis are measured by means of incremental pulse coders, and in which the wavefront of each of the pulses emitted by the coder indexing the position of the workpiece about the first axis is used to start the continuous transmission of at least one analogue signal which forms the instruction for the relative position of the workpiece and tool which has been calculated at the time of the preceding computation of the relative workpiece-tool distance.

Claim 9

Dependent Claim 102 words

A method of machining according to claim 1, in which the angular position of the workpiece about the said first axis and its position along the said second axis is measured by means of incremental pulse coders, and in which each pulse transmitted by the coders indexing the position of the workpiece about the first axis and along the second axis is used to increment counters provided in the control computer, the values of the numbers contained in the said counters representing the angular position of the workpiece about the said first axis and its axial position along the said second axis.

Claim 10

Dependent Claim 135 words

A process according to claim 1, in which the algebraic sum of the ovalisation function and of the profile function developed by the command calculator and depending only on the angle of reference of the workpiece about the first axis and its position along the second axis, is incremented at each machining pass by a certain amount corresponding to the thickness of each desired machining pass, before being applied to a positioning servo system controlling the position of the workpiece with respect to the tool, the value of the said amount and the number of passes being capable of being modified by the machine operator without effect on the values developed by the computer or on the given geometric data arranged in the store of the said computer which defines the surface to be produced.

Claim 11

Dependent Claim 28 words

A process according to claim 6, in which the calculation of the workpiece-tool distance is offset by at least two pulses in advance of the actual tool-workpiece position.

Claim 12

Dependent Claim 72 words

A process according to claim 3, in which the coefficient of each of the harmonics of the Fourier series defining the ovalisation function in the command computer of the machine is multiplied by a constant coefficient for each of the harmonics, the said coefficient being determined in such a manner as to correct the errors due to the transfer function of the servo controlling the relative position of the workpiece and tool.

Claim 13

Dependent Claim 87 words

A process according to claim 7, in which, from the command computer of the said machine, at each wavefront of the position coder synchronising pulses corresponding to the position of the workpiece about its first axis, there are transmitted a signal representing the workpiece-tool position corresponding to the said pulse wavefront and another signal corresponding to the value of the difference between this position and the workpiece-tool position which must be achieved at the following pulse wavefront, the said two values being transmitted to a smoothing interpolator.

Claim 14

Dependent Claim 67 words

A process according to claim 12, in which in turn there is transmitted by the said smoothing interpolator to the servo controlling the relative positions of the workpiece and tool, an analogue signal without discontinuity varying linearly with time and which is equal at each pulse wavefront to the value corresponding to the workpiece-tool dimension corresponding to each of the angular positions at the said pulse wavefronts.

Claim 15

Dependent Claim 202 words

In a numerically controlled machine tool system for machining the three-dimensional surface of a workpiece, including a tool for machining the workpiece in a number of machining passes, a workpiece support mounted for pivotal motion about an axis, means for rotating the workpiece about an axis parallel to the said axis of pivotal motion, and a table which supports the pivoting support, mounted for displacement in a direction parallel to the first axis, means for adjusting the workpiece-tool distance by pivoting the said support, the said distance-adjusting means comprising: coding means for generating coder signals corresponding to pivotal movement of the workpiece about the said first axis and movement of the workpiece in the said direction parallel to the first axis; a computer receiving the coder signals; a positioning servo for positioning the pivoting support, the positioning servo having a first loop including an electro-dynamic motor, a second loop connecting to the servo system a workpiece speed pick-off, and a third loop connecting to the servo system a workpiece position pick-off; a smoothing interpolator connected to the output of said computer; and a pass-control system controlling the said machining passes and connecting the output of said smoothing interpolator to the servo system.

Claim 16

Dependent Claim 202 words

In a numerically controlled machine tool system for machining the three-dimensional surface of a workpiece, including a tool for machining the workpiece in a number of machining passes, a workpiece support mounted for pivotal motion about an axis, means for rotating the workpiece about an axis parallel to the said axis of pivotal motion, and a table which supports the pivoting support, mounted for displacement in a direction parallel to the first axis, means for adjusting the workpiece-tool distance by pivoting the said support, the said distance-adjusting means comprising: coding means for generating coder signals corresponding to pivotal movement of the workpiece about the said first axis and movement of the workpiece in the said direction parallel to the first axis; a computer receiving the coder signals; a positioning servo for positioning the pivoting support, the positioning servo having a first loop including an electro-dynamic motor, a second loop connecting to the servo system a workpiece speed pick-off, and a third loop connecting to the servo system a workpiece position pick-off; a smoothing interpolator connected to the output of said computer; and a pass-control system controlling the said machining passes and connecting the output of said smoothing interpolator to the servo system.

Claim 17

Dependent Claim 39 words

A machine tool according to claim 14, in which the smoothing interpolator comprises a zero resetting monostable circuit, an integrator having a first output connected to an anti-saturation device and a second output connected to a first analogue added.

Claim 18

Dependent Claim 65 words

A machine tool according to claim 15, in which the integrator comprises, in parallel, a capacitor, a first transistor, and a series chain of a second transistor with two diodes mounted in opposite orientations, an input of the integrator being constituted by the input electrode of the first transistor and an output of the integrator being constituted by the input electrode of the second transistor.

Claim 19

Dependent Claim 101 words

A machine tool according to claim 16, in which the pass system comprises: analogue multipliers providing the product of the depth of pass and the number of passes respectively in rough machining, in semi-finishing and in finishing; a second analogue adder connected in parallel with the outputs of the analogue multipliers; a third analogue adder connected to the output of the second adder as well as to an input providing a predetermined parameter and a fourth analogue adder connected to the output of the third adder as well as to the output of the first adder contained in the smoothing interpolator.

Claim 20

Dependent Claim 49 words

A machine tool according to claim 17, in which the pass system comprises in addition a logic unit with permanent store connected to the inputs of the analogue multipliers and additionally receiving the pass decrementation instructions and acting through its outputs on the operation of the said analogue multipliers.

Claim 21

Dependent Claim 244 words

In a process of machining a three-dimensional surface of a workpiece which is rotated about a first axis and displaced along a second axis substantially parallel to the first, with respect to a tool, the distance of which from the workpiece is variable, the speed of rotation of the workpiece and the speed of displacement of the workpiece along the second axis being independently adjustable, the process being effected by numerical control as a function of the angular position of the workpiece about the first axis and its position along the second axis, the steps of: entering into a store data permitting the definition, by calculation, of the surface to be obtained by machining; and deriving a control instruction for relatively positioning the workpiece and the tool in the form of the sum of a profile function and an ovalisation function; said profile function providing the dimensional difference, measured perpendicularly to the first axis, between the radius of a circle circumscribed in a selected plane on the outline of the said workpiece and centred on the said first axis, and the generatrix, contained in the same plane, of the section of the body of revolution co-axial with the first axis and circumscribed on the said workpiece; said ovalisation function being the dimensional difference, measured along a line radial to the first axis, between the outline of the workpiece in the said plane and the said circle in this plane circumscribed on the workpiece outline.

Claim 22

Dependent Claim 244 words

In a process of machining a three-dimensional surface of a workpiece which is rotated about a first axis and displaced along a second axis substantially parallel to the first, with respect to a tool, the distance of which from the workpiece is variable, the speed of rotation of the workpiece and the speed of displacement of the workpiece along the second axis being independently adjustable, the process being effected by numerical control as a function of the angular position of the workpiece about the first axis and its position along the second axis, the steps of: entering into a store data permitting the definition, by calculation, of the surface to be obtained by machining; and deriving a control instruction for relatively positioning the workpiece and the tool in the form of the sum of a profile function and an ovalisation function; said profile function providing the dimensional difference, measured perpendicularly to the first axis, between the radius of a circle circumscribed in a selected plane on the outline of the said workpiece and centred on the said first axis, and the generatrix, contained in the same plane, of the section of the body of revolution co-axial with the first axis and circumscribed on the said workpiece; said ovalisation function being the dimensional difference, measured along a line radial to the first axis, between the outline of the workpiece in the said plane and the said circle in this plane circumscribed on the workpiece outline.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1980-05-30	1980-11-29	1981-05-31	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1984-05-30	1984-11-29	1985-05-31	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1988-05-30	1988-11-29	1989-05-31	$7700.00	Window Closed / Lapsed

Numerically controlled machine tool

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