Apparatus For Cutting Valve Seats In Engine Castings

Abstract

A valve seat is cut in a cylinder head or other engine cast-ing in concentric relation to a valve stem opening therein. A boring head, driven from outside the cylinder head, rotates on a cylindrical arbor concentrically mounted in the valve stem opening. Three tool bits are precisely positioned on the boring head so as to make a three face cut having the exact profile desired with reference to the axis of the valve stem.

Description

BACKGROUND OF THE INVENTION

In the reworking of automotive engines it is often necessary or desirable to reform that surface of the cylinder head or engine block which actually contacts the engine valve as the valve travels between open and closed conditions. This surface is herein referred to as the valve seat working face. This reworking can be done by further removal of metal in the cylinder head or block or by the replacement of an entire valve seat insert with subsequent removal of new metal to form the desired valve seat profile. In addition to the valve seat working fact itself, it is often necessary or desirable to perform an upper clearance cut by removing material between the valve seat working face and the outside of the cylinder head and a lower clearance cut by removing material on the side of the valve seat working face opposite the outside of the cylinder head. Thus the complete valve seat will define three conical concentric surfaces and have a three face transverse profile.

In order to insure proper functioning of the reassembled valve with respect to the valve seat, it is imperative that the new valve seat working face be in precise concentric alignment with the opening in the cylinder head for the steam of the valve which is to operate against the seat.

This has been done by supporting a single tool bit in a boring bar mounted on a machine tool for rotation about the boring bar axis, then attempting to exactly align the boring bar axis with the valve stem opening axis, and next causing the machine tool to rotate the boring bar and to move the bit down into contact with the cylinder head to cut the desired valve seat working face. When this has been accomplished, another tool bit can be supported in a boring bar in the same machine tool with the same alignment of parts, and this tool bit can be used to make the lower clearance cut, for example. Yet another tool bit can be utilized similarly to make the upper clearance cut.

This method has a number of obvious disadvantages including the difficult of getting the proper instrumentation into the valve seat opening on the cylinder head in order to determine if and when the desired valve seat profile has been obtained. Similarly, it is extremely difficult to know when to stop and upper and lower clearance cuts to leave exactly the desired length of the profile of the valve seat working face and the exact desired relationship of the valve seat to the axis of the valve stem opening situated down below in the cylinder head. Obviously the accurate alignment from outside the cylinder head of the perhaps slightly worn valve stem opening with the axis of the boring bar is virtually impossible or, at the very best, takes a long time.

It is also known to support arbors in valve stem openings in engine castings and to mount grinding wheels to rotate on the valve stem axis on such arbors. These grinding wheels, however, must be carefully dressed to attempt to provide precisely the desired face profile of the clearance or relief cuts and of the valve sea working face cut. The flat angles used in making these cuts, however, present difficulties when using grinding wheels, as the wheels tend to seize or grab in the cylinder head or other engine casting, thus often causing extensive damage to the valve seat under formation. A further difficulty with grinders is, of course, that of keeping the grinding faces constantly dressed so as to be of precisely the proper shapes. Also, because of the sophistication of these shapes, it is necessary to employ three separate grinding wheels consecutively to obtain the desired three face profile.

As suggested above, all of the methods employed to accomplish the desired results have, before the present invention, required that measurements be attempted inside of the cylinder head not only to verify the shape obtained after the fact, but in order to set up the tools properly for performing the operation and also to check the progress of the operation while it is happening.

BRIEF SUMMARY OF THE INVENTION

The method and apparatus for cutting valve seats in automotive engine castings such as cylinder heads and engine blocks as disclosed herein has been developed to overcome the difficulties in the prior art. This method includes precisely positioning three tool bits in a boring head. The boring head is then rotatably mounted on a cylindrical arbor positioned in the opening in the cylinder head (for example) for the stem of the valve which is to be seated. The boring head is then rotated by external means. The tool bits sweep out a path defining the desired three face valve seat profile including a valve seat working face, an upper clearance face and a lower clearance face.

Apparatus to accomplish the precise positioning of the tool bits in the boring head includes a tool setting fixture having a cylindrical arbor opening therethrough and a tool setting arbor in that opening. This arbor has an outer cylindrical surface to support the aforementioned boring head. A tool setting stop is supported on the fixture and defines a plane face which exactly duplicates the desired profile of the valve seat working face. This tool setting stop is fixedly positioned on the fixture to precisely relate the plane stop face to the fixture arbor axis exactly as the profile of the desired valve seat working face is to relate to the valve stem axis.

The boring head is situated on the fixture arbor in such a manner as to permit rotative movement with respect to the arbor as desired, but to limit any longitudinal movement along the arbor axis. The arbor itself is initially adjustable longitudinally with respect to the fixture, however. A first of the tool bits is locked in the boring head to position its cutting edge in precise flush alignment with the plane face of the tool setting stop while said cutting edge lies in a plane coincident with the arbor axis. A second tool bit is next positioned with its cutting edge in that plane and in contact with a first corner of the plane stop face and is locked in position, and a third tool bit is similarly positioned against a second corner of the plane face and is locked into place.

The boring head is then removed from the fixture arbor and is positioned on the arbor which is concentrically mounted in the valve stem opening, and a drive means is aligned with the axis of that arbor and affixed to the boring head from above. This driving means then rotates the boring head and forces it down into the automotive cylinder head toward the valve stem opening to cause the desired cuts to be made. This process is continued until such time as precisely the desired valve seat profile has been cut out.

Because the exact dimensions of the valve seat profile have been set by the positioning of the tool bits before the boring head is placed in boring position with respect to the cylinder head, and because the boring head is mounted concentrically with and in the valve stem opening, the only measurement which need be made of the valve seat working face inside of the cylinder head is to determine whether or not the longitudinal spacing of the new valve seat working face with respect to a reference point on the cylinder head is within the desired limits. The completeness of the upper and lower clearance face cuts can be determined by visual inspection, and any other measurements down inside of the engine head as to angle, length, shape and concentricity of the valve seat working face with the valve stem opening are merely for the purpose of checking the accuracy of work. If the method of the invention has been accurately adhered to, such measurements will not reveal any discrepancies or inaccuracies.

In the drawings:

FIG. 1 is a vertical cross sectional view of a fragment of an automotive cylinder head showing a boring head and tool bits of the invention rotatably mounted on a cylindrical arbor which is positioned in exact concentric alignment with a valve stem opening in that cylinder head, and showing driving means for rotating the boring head;

FIG. 2 is an enlarged horizontal sectional view taken on the line 2--2 in FIG. 1;

FIG. 3 is an enlarged fragmentary view of the boring head and cylinder head as seen in FIG. 1 but showing a first tool bit in its relationship to the cylinder head as it cuts the valve seat working face;

FIG. 4 is a fragmentary view of the parts as seen in FIG. 3 but showing a second tool bit in its relationship to the cylinder head as the tool bit makes an upper clearance cut;

FIG. 5 is a fragmentary view of the parts as seen in FIGS. 3 and 4 but showing a third tool bit in its relationship to the cylinder head as the tool bit makes a lower clearance cut;

FIG. 6 is a top plan view of a tool setting fixture according to the present invention with a tool setting fixture arbor and with the boring head of the invention installed thereon;

FIG. 7 is a front elevational view of the tool setting fixture and parts as seen in FIG. 6;

FIG. 8 is a fragmentary view of the fixture and parts as seen in FIG. 6 but showing the relationship of the first tool bit to a tool setting stop having a plane corner face shaped to simulate the profile of the desired valve seat working face;

FIG. 9 is a fragmentary view of the fixture and parts as seen in FIG. 8 but showing the relationship of the second tool bit to a lower corner of the plane face on the tool setting stop;

FIG. 10 is a fragmentary view of the parts as seen in FIGS. 8 and 9 but showing the relationship of a third tool bit to an upper corner of the plane stop face on the tool setting stop; and

FIG. 11 is a top plan view in reduced scale showing the tool setting fixture, the boring bar and tool setting fixture arbor in relationship to a micrometer permanently attached to the tool setting fixture to accurately determine the positioning of the tool setting stop with respect to the axis of said arbor.

DESCRIPTION OF THE PREFERRED EMBODIMENT

I. Method and Apparatus for Performing Cuts

A boring head assembly 10 includes a boring head 12, first tool bit 14, second tool bit 16, and a third tool bit 18, together with means, indicated generally at 11, for rigidly and adjustably attaching the tool bits to the boring head. The boring head 12 is provided with a cylindrical arbor opening 19 extending therethrough. A part spherical knob 21 is integral with and forms the drive end of the boring head 12. Drive pins 23,23 extend outwardly from this spherical knob, but do not extend into the cylindrical wall of the arbor opening 19.

An arbor 20 is mounted, as best seen in FIG. 1, in a valve stem opening 22 of an automotive engine cylinder head 24 on tapered splines 25, or in any usual or preferred manner. This mounting means, per se, forms no part of the invention.

A machine tool 26, somewhat in the nature of a drill press, has a bed, not shown, which is positioned above the cylinder head 24. This machine tool includes a rotatable spindle 28 which may be raised or lowered through the instrumentality of an arm 29 in any usual or preferred manner. The spindle is rotatably powered through a pulley 30 from a power source (not shown). A conical drive cap 27 is fastened up inside of the spindle 28 by means of pins 31, and a drive pin 33 connects the drive cap 27 for rotation with the driven spindle 28. This conical drive cap is provided with a cylindrical sleeve 32 integral therewith and extending downwardly herefrom. This sleeve is provided with a pair of slots 35,35 (one is shown) which loosely fit over the drive pins 23 of the part spherical knob 21.

The axis of the rotatable spindle 28 is precisely aligned with the axis of the spline mounted arbor 20 in any usual or preferred manner forming no part of the invention.

In order to have control over the descent of the boring head assembly including the bits 14, 16 and 18 toward a valve seat region 37 of the cylinder head 24, a compression coil spring 38 is situated around the arbor 20 between cylinder head 24 and boring head 12. Thus, as the spindle 28 of the machine tool 26 is rotated at a speed suitable to perform the cuts in the cylinder head, the arm 29 is operated to force the spindle and the boring head down against the action of the spring 38 and into cutting contact with the engine head casting.

Assuming that there are three tool bits precisely positioned around the boring head, a cut will be made in the cylinder head in the valve seat region 37 to form a valve seat working face and to form upper and lower clearance faces exactly as desired. As soon as the boring head assembly can be seen cutting into the cylinder head for the full width of the desired valve seat working face, the downward pressure on the spindle 28 can be eliminated, and the desired valve seat has been achieved.

II. Apparatus for Setting Boring Head Assembly.

In order to precisely position the three tool bits in the boring head, a tool setting fixture 40 is provided. This fixture includes a main casting 41 in which there is mounted a tool setting arbor 42 having an outwardly extending cylindrical first shank 44 of the same diameter as the spline mounted arbor 20, and having a second shank 45 of larger diameter extending through an arbor opening provided in the casting 41. A set screw 43 is rotatably mounted on the casting 41 to temporarily fixedly position the tool setting arbor 42 after the desired longitudinal adjustment of this arbor with respect to the opening in the casting 41 has been made.

The outer end of the cylindrical shank 44 is provided with screw threads 46. The length of this shank is such that the boring head assembly can be positioned on it and a butterfly nut 47 can be screwed down against the knob 21 of the boring head, forcing the opposite end of the boring head to bottom against enlarged shank 45, to temporarily fixedly position the boring head on the arbor.

As probably best seen in FIGS. 2 and 7, the cutting edges 17 of each of the tool bits positioned in the boring head lie in a plane coincident with the axis of the boring head. In order to precisely position each of these cutting edges, it is necessary that the measurement be ascertained in such a plane, which, when the boring head is in the tool fitting arbor 42, is coincident with the axis of that arbor. In the form of the invention shown, a flat horizontal surface 49 is provided on the top of the main casting 41 in a plane just slightly below a horizontal plane passing through and coincident with the tool setting arbor axis. Adjacent to this flat surface 49 along a line perpendicular to the arbor axis is a slightly raised portion 50 of the casting 41, this portion having indicia 51 along the edge thereof adjacent the flat surface 49.

A tool setting stop 54 is constituted here as a plate, is slideably situated in contact with the surface 49 and is provided with a slot 55 in which a threaded stud is situated. This stud is integral with and extends upwardly from the casting 41 through the surface 49. The stop plate is slideable along the surface 49 in direction at right angles to the axis of the tool setting arbor 42. A butterfly nut 57 is provided on the threaded stud 56 and is for the purpose of locking the stop 54 in position after said position is determined and achieved.

As perhaps best seen in FIGS. 8, 9 and 10, the lower right hand edge corner of the tool setting stop (as seen in those figures) is cut off or truncated. This defines a plane stop face 59 situated at 45.degree. to both the edge of the stop parallel to the axis of the arbor and also to the edge of the stop perpendicular to the axis of the arbor. This plane face 59 will be constituted as having exactly the length of the desired transverse profile of the valve seat working face, and the tool setting stop 54 will be positioned so that the relationship of this plane stop face 59 to the axis of the arbor 42 will be exactly identical to the desired relationship of the valve seat working face to the axis of the valve stem in the cylinder head.

While a plane face 59 having an axis of 45.degree. to a plane perpendicular to the axis of the arbor is shown, it is to be understood that a plurality of tool setting stops 54 can be provided, each having a corresponding truncated plate face such as 59 in the angular relationship specified by the engine manufacturer for his valve seat working face with respect to a plane perpendicular to the axis of his valve and valve stem. For example, the tool setting stop having one edge cut off at an angle of 45.degree. with a face one-sixteenth inch long and and the other edge being cut off at an angle of 45.degree. and having a face 3/32 inch long together with a second stop having a face at an angle of 30.degree. with respect to a plane perpendicular to the arbor axis, that face being one-sixteenth inch long and a second corner of the second stop being cut off to provide a 30.degree. face 3/32 inch long would take care of all of the great bulk of the valve seat working face dimensions being specified by manufacturers of automotive engines today.

In order to properly position the plane face 59 of the stop 54, the indicia 51 on raised portion 50 of the fixture 40 and an index edge 52 of stop plate 54 are related in terms of the positioning of a right edge 53 of the stop plate as seen in FIGS. 6 through 11 with respect to the axis of the boring head and the arbor 42. As shown, this index reads on the indicia in inches of diameter. Assuming by way of example that the valve seat working face is to be conical with the interior edge thereof 13/8 inches in diameter and that the profile is to be one-sixteenth inch long, stop plate 54 will be positioned as seen in FIG. 6, and the butterfly nut 57 will be used to temporarily fasten it in that position.

In order to even more accurately position the parts, a micrometer 60 is mounted on a shaft 61 extending outwardly from the main casting 41 and on a bar 62 fastened to that shaft. The micrometer is calibrated so that an end surface 63 thereof bears against the tool setting stop 54 to exactly position the plane stop face 59 with respect to the axis of the arbor 42.

In the setting of the first tool bit 14, it is important, as pointed out above, that the cutting edge 17 thereof is positioned in a plane coincident with the arbor axis. This is done by providing a lap block 70 in sliding relationship with respect to a groove 72 in the main casting 41 of the tool setting fixture 40. The bottom of this groove is constituted as a plane in exact parallel relationship to the horizontal surface 49 of the main casting, and the block 70 is slideable on that surface into and out of clearing relationship with respect to the tool bits. As best seen in FIG. 7, with the butterfly nut 47 loosened, the boring head 12 will be rotated to bring the bottom surface of the tool bit 14 against the top surface of the block 70, thus (as seen in FIG. 7) positioning the upper left hand corner or cutting edge 17 of that bit in exact horizontal alignment with the axis of the boring head 12 and the arbor 40. This positioning of parts is also seen in FIG. 8. The fastening means 11 will be loosened to allow the first tool bit 14 to be moved in this horizontal plane with respect to the boring head 12, and the cutting edge 17 thereof will be brought into flush relationship to the plane face 59 as seen in FIG. 8. The fastening means 11 will then be utilized to lock the bit in the boring head in that position.

Next as seen in FIG. 7, the block 70 will be temporarily moved to the left and the boring head will be rotated in a counterclockwise direction to allow the passage of the first tool bit in downward direction and the block 70 will be put back into position so that the second tool bit 16 will come to rest on top of it. This positioning of the parts is seen in FIG. 9. The second tool bit will then be slid with respect to the boring head 12 until it contacts the lower left hand corner of the plane face 59 as seen in FIG. 9, and the parts locked to each other.

The same procedure will be utilized to position the third tool bit 18 against the upper corner of the plane stop face 59 as seen in FIG. 10.

With the boring head assembly 10 thus positioned to perform a valve seat cut having the desired profile, the boring head will be removed from the arbor 42, the compression coil spring 38 will be placed over the arbor 20 to rest against the cylinder head and the boring head will be mounted on that arbor.

The outside drive means will be connected up as explained above, the spindle 28 will be power rotated and the arm 29 depressed to cause the boring head assembly to move down into cutting relationship with respect to the valve seat region 37 of the cylinder head 24.

The positioning of each of the first, second and third tool bits on the engine block at the point where the valve seat has just been completed is shown in FIGS. 3, 4 and 5 respectively. As clearly shown in FIG. 3, the first tool bit 14 has just completed cutting the valve seat working face which lies, as shown, at 45.degree. with a plane perpendicular to the boring head axis. The second tool bit 16 has completed its clearance cut, and this is shown in FIG. 4. The angle of that clearance cut, as shown, is 15.degree., and this can clearly be seen from the construction lines in FIG. 3.

FIG. 5 discloses the positioning of third tool bit 15 with respect to the lower clearance cut, and the 60.degree. angular relationship of this cut with respect to a plane perpendicular to the boring head axis is best seen from the construction lines in FIG. 3. Thus it is apparent that the loci of the three tool bits, operating in concentric relationship to the valve stem opening, and against the cylinder head forms a profile defined by a valve working face situated at 45.degree. to the reference plane, and an upper clearance face at 15.degree. to this plane, and a lower clearance fact at 60.degree. thereto. It is to be understood that any one or all of these faces could be at other angles in accordance with the needed clearance and in accordance with the design of the valve with which the tool seat working face is to cooperate.

The invention herein is not limited to use of a flat plate positioned on the tool setting fixture. As long as the proper relationship of a simulated valve seat working face to the boring bar arbor is achieved, tool setting stops of any suitable form can be fixedly positioned with respect to the tool setting fixture. For example, such stops could be constituted as rings simulating all or a portion of the desired valve seat working face and can be, as such, positioned in planes perpendicular to the arbor axis. A rod defining a proper plane stop face can be positioned on, or in an opening provided in, the tool setting fixture.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for cutting a plural face annular valve seat of predetermined transverse profile into a cylinder head or other engine casting in concentric relation to an elongated valve guide opening in said head, said apparatus including:

A. a boring head having a cylindrical arbor opening passing therethrough;

B. a plurality of tool bits, each having a cutting edge of configuration to cut one of the plural faces;

C. means to position and fasten the tool bits in the boring head in location so that rotation of the boring head on the axis of its cylindrical arbor will cause the loci of the surfaces swept out by said cutting edges of said bits to include a shape having said predetermined transverse profile;

D. a cylindrical arbor adapted to be mounted on said cylinder head, said arbor being of size to rotatably support said boring head with respect to said cylinder head when situated in its cylindrical arbor opening, said arbor being supported on said cylinder head to have its axis in concentric relation to said elongated valve guide opening;

E. means to rotate said boring head on said arbor;

F. means to move said boring head longitudinally in said arbor in direction toward said cylinder head; and

G. a compression coil spring adapted to be situated around the arbor and between the cylinder head and the boring head in position to resiliently urge the boring head to move longitudinally of the arbor in direction away from the cylinder head and against the action of the longitudinally acting moving means when the arbor is mounted in concentric relation to said elongated valve opening; the improvement wherein said means to rotate said boring head includes:

A. a part spherical knob constituted as an end portion of said boring head;

B. at least one drive pin extending outwardly from said knob in generally radial and perpendicular relation to the axis of the boring head;

C. a machine tool having a power driven rotatable spindle adjacent said boring head and having its axis aligned with the axis of the boring head;

D. a drive cap on said spindle, said drive cap having an annular sleeve extending downwardly therefrom to be in surrounding, contacting relation to at least a portion of said knob; and

E. said sleeve being provided with at least one slot to drivingly receive said drive pin.