Apparatus and method for machining valve seats in an engine cylinder head

A method for centering a machining tool for machining a valve seat in an engine cylinder head having a height and having a plurality of valve seats disposed within said engine cylinder head at a plurality of different locations within an horizontal plane and having a plurality of angular displacements from a vertical line, the method comprising:

• providing a work surface lying in a first plane parallel to the horizontal plane;
• disposing a base on said work surface;
• disposing a stage on said work surface for holding said engine cylinder head;
• moving one of said base and said stage on a first bearing surface to provide coarse movement parallel to said first plane;
• shifting a distal end of a pantograph having a pair of arms, each arm of the pair having a distal end pivotally attached to said base so that said pair of arms pivots along a vertical plane perpendicular to said first plane up and down to provide coarse movement along a vertical plane;
• pivotally attaching a head portion to a proximal end of each said arm of said pantograph, said head portion having a support frame, wherein the support frame remains parallel to said first plane when the distal ends of said pair of arms of said pantograph are raised and lowered within the vertical plane;
• disposing a spindle for holding said machining tool in a spherical housing having a centroid, an upper portion and a neck portion, said spherical housing being pivotable around the centroid to provide angular displacement of said spindle, wherein the spherical housing is supported by an upper and a lower sphere seat fixedly attached to each other, said lower sphere seat being supported by and movable parallel to said first plane with respect to said support frame;
• moving said lower sphere seat with respect to said support frame to provide fine movement parallel to said first plane;
• translating said spindle along a vertical feed/retraction line to provide fine movement within said vertical plane;
• moving at least three retractable bearing surfaces disposed within said lower sphere seat into contact with said spherical housing;
• and
• pivoting said spherical housing around said centroid.

A system for machining a workpiece having a height and a plurality of work sites located on a surface lying substantially in a common plane, the system being positioned upon a work surface in a horizontal plane, the system comprising:

• a support means for retaining said workpiece in a fixed relation with respect to said work surface so that said common plane is substantially parallel to said horizontal plane;
• a base disposed on said work surface, said base being movable within a first limited range along said horizontal plane with respect to said support means;
• a support frame attached to said base, said support frame being movable with respect to said base in a generally vertical plane, said support frame having a bottom edge, wherein the bottom edge remains parallel to said work surface;
• a plurality of retractable bearing surfaces mounted on said support frame, said plurality of bearing surfaces being movable within a second limited range with respect to said support frame parallel to said horizontal plane, said second limited range being smaller than said first limited range;
• a spherical housing supported within said support frame so that said spherical housing can be pivoted around a centroid of said spherical housing;
• a spindle at least partially retained within said support frame, said spindle being rotatable within said support frame and translatable along a vertical feed/retraction line running longitudinally through said spindle;
• a cutting tool attached to and extending from said spindle generally concentric with said vertical feed/retraction, said cutting tool adapted to rotate with said spindle;
• a translational means for translating said spindle along the vertical feed/retraction line within said spherical housing;
• and
• a drive motor linked to said spindle for providing rotational force for rotating said spindle;
• wherein said machining tool is positioned for machining said workpiece by first moving said base with respect to said work surface to provide coarse movement parallel to said horizontal plane so that said spindle is generally positioned over one work site of said plurality of work sites and by second moving said support frame with respect to said base to provide fine movement parallel to said horizontal plane so that said spindle is centered over said one work site, and translating said spindle along said vertical feed/retraction line to provide movement generally within said vertical plane.

In a system for machining a workpiece having a plurality of work sites located on a surface lying substantially in a common plane, the system being positioned upon a work surface generally in a horizontal plane, and comprising a stage for retaining the workpiece;

• a base disposed on the work surface, one of the stage and the base being disposed in a fixed relationship with the work surface and the other of the stage and the base being movable within a first limited range with respect to the work surface;
• a support frame attached to the base, the support frame being movable with respect to the base in a generally vertical plane, the support frame having a bottom edge, wherein the bottom edge remains generally parallel to the work surface;
• a plurality of retractable bearing surfaces mounted on the support frame;
• a spherical housing supported within the support frame on the plurality of retractable bearing surfaces so that the spherical housing can be pivoted around a centroid of the spherical housing;
• a spindle rotatably retained within the spherical housing;
• a vertical translator attached to the spindle for translating said spindle within the spherical housing along a vertical feed/retraction line;
• a cutting tool extending from the spindle;
• and a drive motor connected to the spindle for providing rotational force to the spindle;
• the improvement comprising:
• the plurality of bearing surfaces being adapted to be movable within a second limited range with respect to the support frame parallel to the work surface, the second limited range being much smaller than the first limited range, wherein the machining tool is positioned for machining the workpiece by first moving one of the stage and the base with respect to the work surface to provide coarse movement parallel to the work surface so that the spindle is generally positioned over one work site of the plurality of work sites and by second moving the plurality of bearing surfaces with respect to the support frame to provide fine movement parallel to the work surface so that the spindle is centered over the one work site, and translating the spindle along the vertical feed/retraction line to provide movement generally within the vertical plane.

In a system for machining a workpiece having a plurality of work sites located on a surface lying substantially in a common plane, the system being positioned upon a work surface generally in a horizontal plane, and comprising a support means for retaining the workpiece in a fixed relationship with respect to the work surface;

• a base disposed on the work surface, the base being movable within a first limited range with respect to the support means;
• a support frame attached to the base, the support frame being movable with respect to the base in a generally vertical plane, the support frame having a bottom edge, wherein the bottom edge remains generally parallel to the work surface;
• a plurality of retractable bearing surfaces mounted on the support frame;
• a spherical housing supported within the support frame on the plurality of retractable bearing surfaces so that the spherical housing can be pivoted around a centroid of the spherical housing;
• a spindle rotatably retained within the spherical housing;
• a translational means attached to the spindle for translating said spindle within the spherical housing along a vertical feed/retraction line;
• a cutting tool extending from the spindle;
• and a drive motor linked to the spindle for providing rotational force to the spindle;
• the improvement comprising:
• a transmission linkage for linking said drive motor which is located within said base to said spindle, said transmission linkage having at least one universal joint disposed adjacent a first end and a first pinion disposed at a second end;
• and
• a second pinion disposed on said spindle, said second pinion cooperating with said first pinion for so that, when said first pinion rotates, said second pinion causes said spindle to rotate.

In a system for machining a workpiece having a plurality of work sites located on a surface lying substantially in a common plane, the system being positioned upon a work surface generally in a horizontal plane, and comprising a support means for retaining the workpiece in a fixed relationship with respect to the work surface;

• a base disposed on the work surface, the base being movable within a first limited range with respect to the support means;
• a support frame attached to the base, the support frame being movable with respect to the base in a generally vertical plane, the support frame having a bottom edge, wherein the bottom edge remains generally parallel to the work surface;
• a plurality of retractable bearing surfaces mounted on the support frame;
• a spherical housing supported within the support frame on the plurality of retractable bearing surfaces so that the spherical housing can be pivoted around a centroid of the spherical housing;
• a spindle rotatably retained within the spherical housing;
• a translational means attached to the spindle for translating said spindle within the spherical housing along a vertical feed/retraction line;
• a cutting tool extending from the spindle;
• and a drive motor linked to the spindle for providing rotational force to the spindle;
• the improvement comprising:
• a pantograph having a first pair of pantograph arms and a second pair of pantograph arms disposed below said first pair of pantograph arms, one of each pair of pantograph arms being disposed on opposing sides of said base, each pantograph arm being pivotably connected at a first end to said base and at a second end to said support frame, each of said second pair of pantograph arms further having a plurality of lugs for cooperating with a first arcuate channel disposed in said base and at least one second arcuate channel disposed in said support frame so that the bottom edge of said support frame remains parallel to the work surface when said support frame is moved along a z-axis.