Determining cutting tool force by measuring electrical resistance of a bearing

Claim 2

In a machine having a rotating means supported by bearings against which force is applied when said machine iS required to do work, which force related to the force used in doing said work, means for measuring the force used in doing said work, comprising a source of current, means for causing current to flow from said source through said bearings, and means for detecting the voltage across said bearings established by the force applied against said rotating means when said machine is doing work whereby said voltage is an indication of the force used in said work.

Claim 3

In a machine as recited in claim 1 wherein there is included: means for establishing a signal representative of a desired force for doing said work, means for comparing said signal with the voltage detected across said bearings and producing a resultant signal, and means for controlling said machine responsive to said resultant signal for nullifying said resultant signal.

Claim 4

In a machine as recited in claim 1 wherein said machine is a machine tool, said bearings are in a spindle housing and hold a spindle, said spindle holds a collet which holds a tool, said machine tool has a table, a workpiece is mounted on said table, said table includes means for moving said table relative to said tool to cause said tool to engage said workpiece and apply force thereagainst.

Claim 5

In a machine tool having a spindle held by bearings in a spindle housing, said spindle having a collet which holds a tool, said machine tool having a table which supports a workpiece, said machine tool having means for moving said table relative to said tool to cause said tool to engage said workpiece; means for determining the side thrust force against said tool comprising: means for causing a current to flow through said bearings, and means for determining the voltage existing across said bearings as a result of said side thrust force whereby said voltage represents said side thrust force against said tool.

Claim 6

In a machine tool having a spindle held by bearings in a spindle housing, said spindle having a collet which holds a tool, said machine tool having a table which supports a workpiece, said machine tool having means for moving said table relative to said tool to cause said tool to engage said workpiece; means for determining the side thrust force against said tool comprising: means for causing a current to flow through said bearings, and means for determining the voltage existing across said bearings as a result of said side thrust force whereby said voltage represents said side thrust force against said tool.

Claim 7

In a machine tool as recited in claim 4 wherein said means for causing a current to flow through said bearings includes: a source of potential having two output terminals, means for connecting one of said output terminals to said spindle housing, and means for connecting the other of said output terminals to said spindle.

Claim 8

In a machine tool having a spindle held by bearings in a spindle housing, said spindle having a collet which holds a tool, said machine tool having a table which supports a workpiece, said machine tool having means for moving said table relative to said tool to cause said tool to engage said workpiece; means for establishing a desired side thrust force against said tool comprising: a resistor, means connecting said resistor to said bearings, means for causing a current to flow through said bearings and said resistor to establish a voltage drop across said resistor that varies as a function of the side thrust force on said bearings caused by the side thrust force against said tool, means for establishing a reference voltage representative of a desired side thrust force against said tool, means for comparing said voltage drop and said reference voltage to establish an error voltage as a result of said comparison, and means for utilizing said error voltage to control said means for moving said table relative to said tool to reduce said error voltage to a minimum value.

Claim 9

In a machine tool having a spindle held by bearings in a spindle housing, said spindle having a collet which holds a tool, said machine tool having a table which supports a workpiece, said machine tool having means for moving said table relative to said tool to cause said tool to engage said workpiece; means for establishing a desired side thrust force against said tool comprising: a resistor, means connecting said resistor to said bearings, means for causing a current to flow through said bearings and said resistor to establish a voltage drop across said resistor that varies as a function of the side thrust force on said bearings caused by the side thrust force against said tool, means for establishing a reference voltage representative of a desired side thrust force against said tool, means for comparing said voltage drop and said reference voltage to establish an error voltage as a result of said comparison, and means for utilizing said error voltage to control said means for moving said table relative to said tool to reduce said error voltage to a minimum value.