Imbalance determining apparatus and method

Abstract

Apparatus for determining the amount and location of imbalance in an article which is to be balanced about its axis includes a table for receiving the article and for positioning its axis. The table is supported upon a base for substantially free tilting movement generally about a point on a vertically extending axis defined by the base. A number of proximity transducers for sensing the orientation of the table relative to the base are provided. A pair of force coils positioned in quadrature about the axis between the base and the table are responsive to the proximity transducers to apply forces between the table and the base to bring the table and the article which rests thereon into a substantially neutral orientation with respect to the base. The method of the present invention comprises the steps of placing the article on the table with the article axis at a predetermined position thereon. Forces are then applied to the table at one or more predetermined locations to bring the table and the article positioned thereon into a neutral orientation. The amount and location of the applied force are determined to ascertain the amount and location of imbalance existing in the article.

What is claimed is: .[.1. Apparatus for determining the amount of location of imbalance in an article to be balanced about an axis thereof comprising means for receiving the article and for positioning its axis, a base, means for substantially freely movably supporting the article receiving means relative to said base, means for sensing the orientation of the article receiving means relative to the base and for producing at least one electrical output signal related to the sensed orientation, and means for applying a force to the article receiving means at at least one selected location about the axis to bring the article receiving means into a substantially neutral orientation, said force applying means being responsive to signals related to said electrical output signals for acting between the article receiving means and said base..]. .[.2. Apparatus according to claim 1 wherein the article receiving means comprises a table having an upwardly facing surface and a fixture for positioning the axis of the article at a preselected location on the table..]. .[.3. Apparatus according to claim 2 wherein the upwardly facing surface of the table is in a plane perpendicular to the direction of gravitational attraction when the table is in its neutral orientation with the centers of mass of the table and fixture lying along a line extending in the direction of gravitational attraction..]. .[.4. The invention of claim 1 wherein the article is to be balanced about an axis of rotation..]. .[.5. The invention of claim 4 wherein the receiving means comprises a chuck and spindle..]. .[.6. The invention of claim 1 wherein the means for sensing the orientation of the article receiving means comprises at least first and second indicator means for generating first and second signals representative of the orientation of the article receiving means relative to the base, the indicator means being positioned 90° apart about the axis, the article receiving means having a downwardly facing surface and the base having an upwardly facing surface, the indicator means being positioned between the downwardly facing surface and the upwardly facing surface..]. .[.7. The invention of claim 6 wherein the indicator means are equidistant from the axis..]. .[.8. The invention of claim 1 wherein the means for sensing the orientation of the article receiving means comprises four proximity transducers for generating four separate signals representative of the orientation of the article receiving means relative to the base, the four proximity transducers being positioned at 90° intervals about the axis..]. .[.9. The invention of claim 8 wherein the four proximity transducers are equidistant from the axis..]. .[.10. The invention of claim 1 wherein the force applying means comprises a first force coil apparatus for exerting a first and neutralizing force between the article receiving means and base to bring the article receiving means to the neutral position..]. .[.11. The invention of claim 1 wherein electric circuit means are provided for applying the force in response to the output signal of the orientation sensing means..]. .[.12. The invention of claim 11 wherein the orientation sensing means comprises at least first and second indicator means, the indicator means being spaced 90° apart about the axis..]. .[.13. The invention of claim 12 wherein the orientation sensing means comprises four proximity transducers spaced 90° apart about the axis and equidistantly therefrom..]. .[.14. Apparatus for determining the amount of location of imbalance in an article to be balanced about an axis thereof comprising means for receiving the article and for positioning its axis, a base, means for substantially freely movably supporting the article receiving means relative to said base, means for sensing the orientation of the article receiving means relative to the base, and means for applying a force to the article receiving means at at least one selected location about the axis to bring the article receiving means into a substantially neutral orientation, said force applying means acting between the article receiving means and said base, the force applying means comprising first and second force coils for exerting first and second neutralizing forces, respectively, between the article receiving means and base, the second force coil being positioned 90° away from the first force coil about the axis..]. .[.15. Apparatus for determining the amount and location of imbalance in an article to be balanced about an axis thereof comprising means for receiving the article and for positioning its axis, a base, means for substantially freely movably supporting the article receiving means relative to said base, means for sensing the orientation of the article receiving means relative to the base, and means for applying a force to the article receiving means at at least one selected location about the axis to bring the article receiving means into a substantially neutral orientation, said force applying means acting between the article receiving means and said base, the orientation sensing means comprising four proximity transducers spaced 90° apart about the axis and equidistantly therefrom, and the force applying means comprising first and second force coils responsive to the outputs of the proximity transducers for exerting first and second orienting forces, the first and second force coils being spaced 90° apart about the axis between the article receiving means and the base..]. .[.16. The invention of claim 15 wherein electric circuit means are provided for producing first and second force-representative outputs, the first and second force-representative outputs controlling current flow through the first and second force coils, respectively..]. .[.17. The invention of claim 16 and further comprising means for combining the first and second force-representative outputs to generate an output signal representative of a force at a selected angle with respect to a reference axis extending 
     
        through the axis of the article..]. 18. A method for determining the amount and location of imbalance in an article having an axis about which it is to be balanced comprising the steps of positioning the article on an article receiving means with the axis at a predetermined location thereon, applying at least first and second forces to the article receiving means at at least first and second locations about the axis to bring the article reveiving means into a neutral orientation, and determining the amount and location of the force required to bring the article receiving means into neutral orientation, the determining step comprising the steps of generating outputs representative of the amount and location of each applied force and combining these force-representative outputs into an output representative of a composite force at a single location.Iadd., the first and second forces being applied to the article receiving means substantially 90° apart about the axis at substantially equal distances from the axis, the step of combining the force-representative outputs comprises the steps of squaring the magnitudes of the first and second force-representative outputs, summing the squares of the magnitudes, taking the square root of the sum, determining which of the first and second force-representative outputs is smaller, and dividing the smaller force-representative output by the square root of the 
     
     
        sum..Iaddend. .[.19.  The method of claim 18 in which the first and second forces are applied to the article receiving means substantially 90° apart about the axis..]. .[.20. The method of claim 19 in which the first and second forces are applied at substantially equal distances from the axis..]. .[.21. The method of claim 20 in which the step of combining the force-representative outputs comprises the steps of squaring the magnitudes of the first and second force-representative outputs, summing the squares of the magnitudes, and taking the square root of the sum..]. .[.22. The method of claim 21 in which the step of combining the force-representative outputs comprises the steps of determining which of the first and second force-representative outputs is smaller and dividing the smaller force-representative output by the square root of the sum..]. 
     
     
         3. The method of claim .[.22.]. .Iadd.18 .Iaddend.in which the step of combining the force-representative outputs comprises the steps of assigning signs to the directions in which the first and second forces are applied and comparing the signs to determine in which quadrant the 
     
     
        location of imbalance lies. 24. The method of claim 23 in which the step of combining the force-representative outputs comprises the step of comparing the magnitudes of the first and second force-representative 
     
     
        outputs to determine in which octant the location of imbalance lies. 25. The method of claim 18 and further comprising the steps of sensing the displacement of the article receiving means from its neutral orientation and producing at least first and second signals representative of this displacement, the first and second forces being applied in response to the first and second signals, respectively. .[.26. A method for determining the amount and location of imbalance in an article which is to be balanced about an axis comprising the steps of positioning the article on an article receiving means with the axis at a predetermined location thereon, measuring the displacement of the article receiving means from a neutral orientation, generating at least first and second signals in response to such displacement, applying at least first and second forces to the article receiving means at at least first and second locations about the axis in response to the first and second signals, respectively, to bring the article receiving means to neutral orientation, and determining the amount and location of the force required to bring the article receiving means to neutral orientation, the determining step comprising the steps of generating signals representative of the amount and location of each applied force, combining the signals representative of the applied forces, and generating a signal representative of a signal composite force at a single location..]. .[.27. Apparatus comprising a base defining a generally vertically extending axis, a table, means for supporting the table for substantially free tilting movement about the axis relative to the base, means for indicating displacement of the table relative to the base, means for applying force to the table to hold it in a substantially neutral position, the indicating means and force applying means providing outputs representing, respectively, displacement and force, and means for computing the amount and location of imbalance of an article placed on the table, the computing means being connected to, and responsive to, the indicating means output..]. .[.28. Apparatus for determining the amount and location of imbalance in an article to be balanced about an axis thereof comprising a base, a table defining a vertical axis, the table holding the article and positioning the axis of the article to coincide with the table axis, means for supporting the table for substantially free tilting movement on the base, at least a pair for indicating the position of the table relative to the base, the indicating means having an electrical output representative of table displacement, the indicating means being spaced about the table axis, at least one means for applying a force to the table to hold the table in a substantially neutral orientation of the base, the force applying means having an electrical output representative of the force necessary to hold the table in the neutral position, and means for combining the displacement outputs of the indicating means to register the amount and location of the imbalance..]. .Iadd. 29. Apparatus for determining the amount and location of imbalance in an article having an axis about which it is to be balanced comprising means for receiving the article, means for positioning the article on the article receiving means with its axis at a predetermined location thereon, means for applying at least first and second forces to the article receiving means at at least first and second locations about the axis to bring the article receiving means into a neutral orientation, and means for determining the amount and location of the force required to bring the article receiving means into neutral orientation, the determining means comprising means for generating outputs representative of the amount and location of each applied force and means for combining these force-representative outputs into an output representative of a composite force at a single location, the first and second force-applying means being positioned substantially 90° apart about the axis at substantially equal distances from the axis, the means for combining the force-representative outputs including means for squaring the magnitudes of the first and second force-representative outputs, means for summing the squares of the magnitudes, means for taking the square root of the sum, means for determining which of the first and second force-representative outputs is smaller, and means for dividing the smaller force-representative output by the square root of the sum. .Iaddend..Iadd. 30. The apparatus of claim 29 in which the means for combining the force-representative outputs comprises means for assigning signals to the directions in which the first and second forces are applied and for comparing the signs to determine in which quadrant the location of imbalance lies. .Iaddend..Iadd. 31. The apparatus of claim 30 in which the means for combining the force-representative outputs comprises means for comparing the magnitudes of the first and second force-representative outputs to determine in which octant the location of imbalance lies. .Iaddend..Iadd. 32. The apparatus of claim 29 and further comprising means for sensing the displacement of the article receiving means from its neutral orientation and for producing at least first and second signals representative of this displacement, the first and second forces being applied in response to the first and second signals, respectively. .Iaddend..Iadd. 33. Apparatus for determining the amount and location of imbalance in an article having an axis about which it is to be balanced comprising means for receiving the article, means for positioning the article on the article receiving means with its axis at a predetermined location thereon, means for applying at least first and second forces to the article receiving means at at least first and second locations about the axis to bring the article receiving means into a neutral orientation, and means for determining the amount and location of the force required to bring the article receiving means into neutral orientation, the determining means comprising means for generating outputs representative of the amount and location of each applied force and means for combining these force-representative outputs into an output representative of a composite force at a single location, the first and second force-applying means being positioned substantially 90° apart about the axis at substantially equal distances from the axis, the means for combining the force-representative outputs including means for assigning signs to the directions in which the first and second forces are applied, means for comparing the signs to determine in which quadrant the location of imbalance lies and means for comparing the magnitudes of the first and second force-representative outputs to determine in which octant the location of imbalance lies. .Iaddend..Iadd. 34. The apparatus of claim 33 and further comprising means for sensing the displacement of the article receiving means from its neutral orientation and for producing at least first and second signals representative of this displacement, the first and second forces being applied in response to the first and second signals, respectively. .Iaddend..Iadd. 35. A method for determining the amount and location of imbalance in an article having an axis about which it is to be balanced comprising the steps of positioning the article on an article receiving means with the axis at a predetermined location thereon, applying at least first and second forces to the article receiving means at at least first and second locations about the axis to bring the article receiving means into a neutral orientation, and determining the amount and location of the force required to bring the article receiving means into neutral orientation, the determining step comprising the steps of generating outputs representative of the amount and location of each applied force and combining these force-representative outputs into an output representative of a composite force at a single location, the first and second forces being applied to the article receiving means substantially 90° apart about the axis at substantially equal distances from the axis, the step of combining the force-representative outputs comprising the steps of assigning signs to the directions in which the first and second forces are applied and comparing the signs to determine in which quadrant the location of imbalance lies, and the step of comparing the magnitudes of the first and second force-representative outputs to determine in which octant the location of imbalance lies. .Iaddend..Iadd. 36. The method of claim 35 and further comprising the step of sensing the displacement of the article receiving means from its neutral orientation and producing at least first and second signals representative of this displacement, the first and second forces being applied in response to the first and second signals, respectively. .Iaddend.