Gear grinder with digital control

Claim 2

A machine tool comprising a workpiece support which can be displaced about a first axis, a tool support which can be oscillated about a second axis and which is constructed to support an annular tool for rotation about a third axis spaced from the second axis so that a supported tool will not only rotate about its own axis but will also oscillate on an arcuate path about the second axis, and a control system comprising: two signal generating means for coupling to respective ones of said workpiece support and said tool support of the machine to produce signals indicative of the angular movements of the respective supports; a comparator for comparing the signals and issuing an error signal if the comparision indicates that said signals do not have a predetermined correspondence; and processing means interposed between the comparator and at least one of said generating means to modify the signal of the at least one generating means so that said signals will have said correspondence at said comparator when said supports are moving a desired relative manner.

Claim 3

A machine tool according to claim 1, wherein the signal generating means are pulse generating means coupled to the supports so that the control system produces oscillation of both supports about the first and second axes respectively, the comparator is a pulse comparator, and the control system further comprising means for temporarily bringing the tool support to rest after a number of cycles of oscillation of the tool support, and electrical indexing means operable when the tool support is staionary between oscillations, to introduce into the control system pulses equivalent to a predetermined angular movement of the workpiece support to cause indexing of the workpiece support by the amount of said angular movement. 3.. A machine tool as claimed in claim 1, wherein there are electrical indexing means for introducing into the control system when the tool support is stationary a signal equivalent to a predetermined angular movement of the workpiece support to index the workpiece support.

Claim 4

A machine tool as claimed in claim 2, wherein the indexing means comprises means for supplying additional pulses to the pulse comparator.

Claim 5

A machine tool as claimed in claim 1 and having means for modifying the operation of the control system in dependence upon the movement of one of the supports to achieve a workpiece profile defined by the modifying means.

Claim 6

A machine tool as claimed in claim 2 and having means for modifying the operation of the servo system in dependence upon the movement of one of the supports to achieve a workpiece profile defined by the modifying means, and wherein the modifying means is operable to supply additional pulses to the comparator.

Claim 7

A machine tool as claimed in claim 6, wherein the modifying means comprises cam means coupled to the workpiece support and pulse generating means coupled to the cam means to supply pulses in dependence upon the profile of the cam means.

Claim 8

A machine tool comprising a workpiece support which can be displaced about a first axis, a tool support which can be oscillated about a second axis and which is constructed to support an annular tool for rotation about a third axis spaced from the second axis so that a supported tool will not only rotate about its own axis but will also oscillate on an arcuate path about the second axis, and a control system comprising: two signal generating means coupled to respective ones of said workpiece support and said tool support of the machine to produce signals indicative of the angular movements oF the respective supports; a comparator for comparing the signals and issuing an error signal if the comparison indicates that said signals do not have a predetermined correspondence; processing means interposed between the comparator and at least one of said generating means to modify the signal of the at least one generating means so that said signals will have said correspondence at said comparator when said supports are moving in a desired relative manner; and means for modifying the data compared by the comparator during the machining of a tooth of a workpiece to provide at least one of tip and root relief of the tooth.

Claim 9

A machine tool comprising a workpiece support which can be displaced about a first axis, a tool support which can be oscillated about a second axis and which is constructed to support an annular tool for rotation about a third axis spaced from the second axis so that a supported tool will not only rotate about its own axis but will also oscillate on an arcuate path about the second axis, and a control system comprising: two signal generating means coupled to respective ones of said workpiece support and said tool support of the machine to produce signals indicative of the angular movements oF the respective supports; a comparator for comparing the signals and issuing an error signal if the comparison indicates that said signals do not have a predetermined correspondence; processing means interposed between the comparator and at least one of said generating means to modify the signal of the at least one generating means so that said signals will have said correspondence at said comparator when said supports are moving in a desired relative manner; and means for modifying the data compared by the comparator during the machining of a tooth of a workpiece to provide at least one of tip and root relief of the tooth.

Claim 10

A machine tool as claimed in claim 8, wherein said modifying means are operable to act to vary at least one of the signals supplied to the comparator as a function of the movement of one of the supports of the machine tool.

Claim 11

A machine tool as claimed in claim 9, wherein the signal generating means are pulse generating means and the comparator is a pulse comparator.

Claim 12

A machine tool as claimed in claim 10, wherein the modifying means are operable to supply additional pulses to the comparator.

Claim 13

A machine tool as claimed in claim 9, wherein the modifying means comprises means coupled to the processing means to modify the signal supplied by that processing means to the comparator in dependence upon the movement of one of the supports.

Claim 14

A machine tool as claimed in claim 12, wherein said means coupled to the processing means are responsive to one of said signals indicative of the angular movements of the supports.

Claim 15

A machine tool as claimed in claim 8, wherein the modifying means comprises cam means coupled to the tool support and third signal generating means for producing, in response to rotation of the cam means, a signal for modifying the action of the control system to provide at least one of tip and root relief of a tooth of a workpiece in dependence upon the form of the cam means.

Claim 16

A machine tool as claimed in claim 14, wherein the cam means are a cam and cam follower, and the third signal generating means comprises first means providing a pattern and second means to scan the pattern, the first and second means being arranged to be driven into relative motion by the movement of the cam follower.

Claim 17

A machine tool as claimed in claim 14, wherein the third signal generating means has its output connected to supply its output signal together with one of said signals indicative of angular position to the comparator.

Claim 18

A machine tool as claimed in claim 11, wherein the modifying means also comprises a cam means coupled to the tool support and third pulse generating means for producing, in response to rotation of the cam means, a pulse signal for modifying the action of the control system to provide at least one of tip and root relief of a tooth of a workpiece independence upon the form of the cam means.

Claim 19

A machine tool as claimed in claim 8, wherein the modifying means comprises said generating means for coupling to the tool support, that generating means comprising an arcuate portion for rotation with the tool support and scanning means for scanning a region of that portion, the arcuate portion being adjustable so that its centre of radius can be spaced from its axis of rotation to achieve at least one of tip and root relief of a tooth of a workpiece.

Claim 20

A machine tool as claimed in claim 12, wherein the modifying means additionally comprises said generating means coupled to the tool support, that generating means comprising an arcuate portion for rotation with the tool support and scanning means for scanning a region of that portion, the arcuate portion being adjustable so that its centre of radius can be spaced from its axis of rotation to achieve at least one of tip and root relief of a tooth of a workpiece.