US3674375A - Valve-guide coring tool - Google Patents

Abstract

THE INVENTION CONTEMPLATES A PORTABLE JIG HAVING MEANS FOR ESTABLISHING A REBORING, REAMING OR CORING AXIS FOR THE VALVE-STEM GUIDE BORE OF A WORE VALVE STRUCTURE, BY PRIME RELIANCE ON SEPARATE CENTERING TECHNIQUES AT BOTH THE SEAT AND ACTUATING ENDS OF THE AXIS OF THE VALVE, TO REESTABLISH THE AXIS OF THE VALVE THROUGH THE CENTER OF THE SEAT, EVEN THOUGH THE WORN-SEAT AXIS AT THE TIME MAY BE SLIGHTLY OFFSET FROM ITS ORIGINAL ORIENTATION. ONCE THE AXIS TO BE CORED HAS BEEN THUS ESTABLISHED, CLAMP MEANS OF THE INVENTION RETAINS THE REFERENCE AND ALSO POSITIONS GUIDE MEANS FOR THE CORING TOOL. AFTER FINISHING THE EXPANDED VALVE-STEM GUIDE BORE, BASED ON THE NEW REFERENCE AXIS, A VALVE-STEM GUIDE INSERT IN INSTALLED, AND THE SEAT IS FINISHMACHINED IN THE CUSTOMARY MANNER, WITH MINIMUM REMOVAL OF SEAT MATERIAL.

Description

July 4, 1972 E. E. REED ET AL 3,674,375

VALVE-GUIDE CORING TOOL Filed April 7 1971 INVENT RS EE'ETT EED United States Patent US. Cl. 408-103 9 Claims ABSTRACT OF THE DISCLOSURE The invention contemplates a portable jig having means for establishing a reboring, reaming or coring axis for the valve-stem guide bore of a worn valve structure, by prime reliance on separate centering techniques at both the seat and actuating ends of the axis of the valve, to reestablish the axis of the valve through the center of the seat, even though the worn-seat axis at the time may be slightly offset from its original orientation. Once the axis to be cored has been thus established, clamp means of the invention retains the reference and also positions guide means for the coring tool. After finishing the expanded valve-stem guide bore, based on the new referenceaxis, a valve-stem guide insert is installed, and the seat is finishmachined in the customary manner, with minimum removal of seat material.

This invention relates to a portable jig, particularly adapted to guide a drilling, reaming or the like tool, for reconditioning a worn valve-stem guide, as in a cylinder head or the like body for valve mechanism.

Internal-combustion engines may initially have valve seats which are perfectly concentrically and coaxially aligned with their associated valve-stem guide bores, but wear, however slight, eventually takes its toll, resulting in poorly seating valves, with attendant loss of power, and pollution of the atmosphere by excessive release of unburned hydrocarbons. Such losses are particularly severe for the modern high-compression engine, and the poor seating is frequently attributable to the eccentricities or other misalignments which have progressively formed in the contour of the bore of the valve-stem guide. Angularity of actuating contact by an over-head rocker arm or cam shaft system is among the causes of such uneven Wear. And having thus eccentrically worn the valve-stem guide, it follows that the valve seat itself may have Worn into a displaced shape in which the predominant central axis is no longer the same as it once was but is, on the other hand, olfset angularly and/ or radially with respect thereto. A conventional method of reconditioning such valvestem guide bores is to employ large, expensive and bulky drill-press machines, arbitrarily set to core out or rebore the valve-stem bores to what is hopefully the prior alignment. The expensive and cumbersome nature of such an operation-precludes its use by the ordinary mechanic, and limits use to the sophisticated specialty shop. Moreover, subsequent valve-seat grinding operations may be unduly excessive, due to the fact that an arbitrarily assumed newly cored axis has no particular relation to the currently worn status of the valve seat, particularly the axis orientation thereof.

It is, accordingly, an object of the invention to provide an improved means and method for coring, drilling or reaming valve-stem guides, particularly worn guides of the character indicated.

Another object is to meet said object with means which takes its basic alignment reference from the existing valve seat and from the other end of the valve-stem guide bore.

A further object is to provide such a means and method Patented July 4, 1972 which are basically simple, utilize portable equipment, and are well within the reach of the individual mechanic, in business for himself.

Still another object is to provide a tool meeting the above objects and readily adaptable to a wide variety of valve body configurations, spring-seat orientations, and valve seat and guide sizes.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification, in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, a preferred form of the invention;

FIG. 1 is a view in elevation of a valve-stem coring jig of the invention, shown in application to a cylinder head, the latter being shown as a fragment, in section along one of the valve-stem bores thereof;

FIG. 2 is an exploded fragmentary view in elevation to show separable adapter parts of the jig of (FIG. 1; and

FIG. 3 is a fragmentary view of another part usable in setting the jig of FIG. 1.

Briefly, the invention contemplates a portable jig having means for establishing a reboring, reaming or coring axis for the valve-stem guide bore of a worn valve structure, by prime reliance on separate centering techniques at both the seat and actuating ends of the axis of the valve, to re-establish the axis of the valve through the center of the seat, even though the worn-seat axis at the time may be slightly offset from its original orientation. Once the axis to be cored has been thus established, clamp 'means of the invention retains the reference and also positions guide means for the coring tool. After finishing the expanded valve-stem guide bore, based on the new reference axis, a valve-stem guide insert is installed, and the seat is finish-machined in the customary manner, with minimum removal of seat material.

In FIG. 1, the invention is shown in application to one of the valve-stem guide bores 10 of an automotive cylinder head 11. The bore 10 is seen to extend through solid cast metal, from its opening at the manifold passage 12 (near the region of valve seat 13) to the spring-pad region, comprising an annular and axially outward projection or spring-guide portion 14 and an adjacent annular spring.- seat region 15. In the initial manufacture of the cylinder head 11, all guide bores will have been precision-bored in large special floor-mounted machines, and such operation will have unquestionably established the necessary concentric and coaxial relation of the conical flare of seat 13 with respect to the axis of the bore 10. The new engine, thus fabricated, is well sealed to operate with high-compression and to achieve its designed high-efficiency performance.

The problem solved by the invention is presented by a worn cylinder head 11, that is, by a head in which the valve stem guide bore(s) 10 and/or the valve seat(s) 13 are worn, to the extent that the guide bore 10 is no longer able to assure purely axial guidance of the valve stem and accurate seating of the valve face at 13. For example, the wear in bore 10, due to slight angularity or offset in valve-actuating thrust by a rocker arm or by overhead cam, may have developed an eccentricity in the bore, and such eccentricity may be of different magnitude and at different angle about the original valve-stem guide axis, as a function of position along the valve-stem guide axis. At the same time, the valve face or its seat 13 may have asymmetrically worn, with resulting adaptation to a slightly eccentrically or otherwise ofiset relation to the original valve-stem guide axis.

The jig of the invention is primarily an elongated guide 16 for a rotatable coring tool 17, of size selected to rebore, core or otherwise refinish the bore 10 to accept a valve-stem guide insert or sleeve (not shown). The guide member 16 is provided with an elongated guide bore 18 for the tool 17, a preference being indicated for the provision of sleeve inserts 19-20 at the respective ends of bore 18. The inserts 19-20 may be of suitable hard material, such as high-speed steel, precision-finished at their respective bores 21-22, to a diameter which establishes a close but free guided orientation of the coring axis of the tool 17 inserted therein.

To establish the desired coaxial reference to the worn valve seat 13, the front or work-engaging end of the guide member 16 is precision-finished with a tapered convex surface 23, truly concentric to the tool-guide axis established by bores 21-22. The taper at the front surface 23 is selected according to the design taper of the valve seat 13. To make the guide member 16 more universally applicable to various engine designs, the tapered front surface 23 is formed on a first part or adapter 24, and the precision tool-guide elements 19-20 are parts of a second part or body 25. A reduced cylindrical forward surface 26 on body 25 establishes a shoulder 27, and a correctly tapered selected adapter 24 is appropriately bored and counterbored (at 28) to achieve firm axial and coaxial reference to the body guides 19-20, upon detachable telescoped assembly thereto.

To further establish the axis of the tool (element 16) and to resist the tendency of surface 23 to dislodge from seated relation at 13 in the course of cutting with tool 17, the invention provides means whereby a centering reference may be taken for the remote end of the bore 10, and whereby the guide element 16 may be positively held or clamped in its correct orientation. Such clamp structure relies upon a centering pin 29 (FIG. 3) of diameter larger than bore and having a conical tip 29; and the clamp structure may comprise a rigid frame 30 with spaced arms 31-32 sized to span the largest of the anticipated valve-body or cylinder-head structures to be cored. The described tool-guide member 16 may be viewed as valve-seat engaging means carried by one of these arms (31); and further work-engaging means, accommodating pin 29 and including prefrably another removable adapter part 33 is carried by the other of these arms (32). As shown, the adapter 33 is axially insertable in and removable from the counterbore 34 of an elongated rugged tubular member 35, carried by the arm 32.

In the form shown, adapter 33 includes a cylindrical skirt 36 projecting toward the work 11 and counterbored at 37 to a depth and diameter which allows relatively great axial and radial clearance with the projection 14 which forms part of the valve-spring support. Adapter 33 further includes a body integral with the base of skirt 36 and with a guide bore 38, of diameter exceeding that of the alignment pin 29. The adapter body is externally contoured to provide a reduced neck 39, projecting loosely within the counterbore 34 and externally grooved to carry friction means, such as an elastomeric O-ring 40, for yieldable friction engagement with the counterbore 34. Finally, a truncated convex spherical surface 41 completes the outer profile of adapter 33, accounting for the bulge from neck 39 to skirt 36.

The convex spherical surface 41 interferes with the adjacent end of the tubular support member 35, at a concave spherical flare at the end of counterbore 34. The spherical centers of these convex and concave surfaces should be the same, the convex surface 41 being on the axis of guide bore 38, and the mating concave surface of member 35 being on the axis of bore 42 and counterbore 34 thereof. The bore 42, unlike the bore 38, has a diameter to closely match the diameter of pin 29, thus aligning the same, for centering reference of the tool axis at the adjacent end of bore 10.

Having established means whereby the desired seataxis reference may be taken at one end of bore 10 and work-engagement and axis centering may be achieved at .4 the other end of the valve-stem guide bore, means is provided whereby the frame 30 is utilized to clamp both work-engaging means 16-33, in secure axial compression. This may be done using a jack between telescoped, mutually guided halves of the frame 30; alternatively, a jack mechanism may be interposed between one of the arms 31-32 and the related one of the work-engaging means (16, and 33-35, respectively). The form shown adopts the latter of these alternatives. Thus, the seat-engaging means 16 is adjustably fixed, at set screw 43 in the collared end 44 of arm 31; set screw 43 preferably seats in the bottom of a keyway 45 in the cylindrical periphery of body 26, which otherwise receives extensive support at the bore of collared end 44. Preferably, the bottom of keyway 45 is a ramp, sloping from a shallow end near fitting 23, to a greater radial depth at the end remote from valve-seat engagement; thus, a clamped setting of screw 43 strongly resists dislodgment, however strong the axial force of clamping. The end 46 of the other arm 32 is similarly collared, and a set screw 47 locates in a keyway 48 in the tubular support member 35; the key fit at 47-48 should, however, be loose, to afford longitudinally jacked displacement of member 35, by selective manipulation of a nut 49 on the threaded portion 50 of member 35. Preferably, a lock nut 51 secures screw 47 in such keyin g position.

In use, a valve-seat-engaging adapter 24 is first selected, depending upon the particular seat configuration of the head 11. The selected adapter 24 is telescopically assembled to the reduced end 26 of body 25, and set screw 43 is clamped, as the span for the worn block 11 may dictate. An appropriate self-aligning Work-engaging means or adapter 33 is also selected for the particular design of head 11, and it is assembled with friction fit to counterbore 34. The jig, thus assembled, is applied to span the work (11), with adapter surface 23 firmly planted at the seat 13. Next, nut 49 is manipulated to project adapter skirt 36 into light contact with the work (11) at 15. The alignment pin 29 (FIG. 3) with cylindrical contour sized for precise guidance by the bore 42, is inserted in the tail end of bore 42, until its tapered front end 29' engages and determines its centering reference from the bore 10, as shown by phantom outline in FIG. 1 at 29'; a light hammer tap on the projecting end of pin 29 will assure that it positively references to the bore 10 and thus assures final determination of the tool axis. The nut 49 is then tightened, by wrench or spanner means, to establish a secure, compressionally loaded hold of the now located guide member 16, seated and oriented as well as is possible, at 13; in this clamping process, the self-aligning feature at 41 has enabled the work reference to adapt to various orientations of the spring-pad surface 15. Pin 29 can be removed, and drilling, reaming and the like coring can then proceed, using a portable drill to which the tool 17 has been chucked. Having finished the enlarged bore 10 to the necessary enlarged diameter (and possibly slightly reoriented axis), the tool 17 and jig are removed, and a valve-stem guide sleeve insert is installed. Finally, the valve seat 13 is ground, using the bore of the new insert as the basic reference.

The described embodiment of the invention will be seen to have achieved the stated objects with a basically simple but highly accurate tool which is portable and adaptable to various valve-body, cylinder head, and like configurations in which a guide is to be cored. The clearances in the counterbore 37 and bore 38 of adapter 33 permit the greatest freedom for seat 13 to adapt to the particular orientation of spring seat 15; this feature is so significant in the use of the tool that I have called adapter 33 a spring-seat avoider, or spring-seat compensator.

While the invention has been described in detail for the preferred forms shown, it will be understood that modifications may be made without departing from the scope of the invention.

We claim:

1. A work-mounted rotary-tool jig for use in reconditioning a worn valve assembly, comprising a rigid frame with spaced arms adapted to span a valve body having a valve-stem guide bore and a tapered concave valve-disc seat at one end of the bore, valve-seat engaging means carried by one of said arms and having a tapered convex surface facing the other of said arms and conforming to and adapted to locate on said seat, said valve-seat engaging means having an elongated bore open at both ends and finished at least at two spaced axial regions thereof to provide an accurate cylindrical tool-support guide on an axis that is strictly concentric with that of said tapered convex surface, and work-engaging means on the other of said arms and having an elongated alignment bore aligned with the axis of said valve-seat engaging means, said workengaging means including self-aligning connecting means, said connecting-means being distributed about the axis of the alignment bore and in clearance relation with said valve-stem guide bore, said connecting means having a bore of larger diameter than that of said alignment bore, elongated centering means guided by said alignment bore and projecting through said connecting means for centering engagement with the valve-stem guide bore, and adjustable means for selectively relatively axially spacing said seat-engaging means and said work-engaging means, whereby upon axially adjusting said last-defined means for compressional embrace of the valve body at the seat and valve-stem guide bore thereof, said valve-seat engaging means will be accurately and concentrically referenced, to the center of the seat and to the center of the remote end of the valve-stem guide bore, so that a rotary tool may be guided via the bore of said valve-seat engaging means, to enlarge and possibly offset the prior-existing valve-stem guide axis, thereby conditioning the enlarged bore to receive a valve-stem guide insert.

2. The jig of claim 1, in which said work-engaging means is generally annular with a bore diameter exceeding the bore diameter of said cylindrical tool-support guide, whereby the rotary tool will assuredly clear the bore of said work-engaging means, upon emergence through the work.

3. The jig of claim 2, in which said self-aligning connecting-means includes a truncated convex spherical formation on said work-engaging means and concentric with the bore thereof.

4. The jig of claim 1, in which said centering means includes an element that is selectively removable through the bore of said self-aligning connecting means.

5. The jig of claim 3, in which said work-engaging means includes a reduced neck projecting axially beyond the region of said truncated spherical formation and a tubular member carried by said other arm and having a bore in which said neck is insertable, and yieldable friction means carried by said neck for selective engagement with and retention by the bore of said tubular member.

6. The jig of claim 1, in which said adjustable means includes a lead-screw and nut connection between said self-aligning connecting-means and said other arm.

7. The jig of claim 1, in which said valve-seat engaging means includes concentric head and body elements having a selectively engageable telescopic fit, said body element having the bore with the cylindrical tool-support guide, and said head element having said tapered convex surface and being annular, with a bore diameter exceeding that of said cylindrical tool-support guide.

8. The jig of claim 1, in which said elongated centering means is a rod guided by said alignment bore and having a conical end for work engagement.

9. A work-mounted rotary-tool. jig for use in reconditioning a worn valve assembly, comprising a rigid frame with spaced arms adapted to span a valve body having a valve-stem guide bore and a tapered concave valve-disc seat at one end of the bore, self-centering valve-seat engaging means carried by one of said arms and adapted to locate on said seat, said valve-seat engaging means having an elongated central bore open at both ends and finished at least at two spaced axial regions thereof to provide an accurate cylindrical tool-support guide on an axis that is strictly concentric with that established by self-centering action upon valve-seat engagement by said valve-seat engaging means, and work-engaging means on the other of said arms and having an elongated alignment bore aligned with the axis of said valve-seat engaging means, said workengaging means including self-aligning connecting means, said connecting means being distributed about the axis of the alignment bore and in clearance relation with said valve-stem guide means, said connecting means having a bore of larger diameter than that of said alignment bore, elongated centering means guided by said alignment bore and projecting through said connecting means for centering engagement with the valve-stern guide bore, and adjustable means for selectively relatively axially spacing said seat-engaging means and said work-engaging means, whereby upon axially adjusting said last-defined means for compressional embrace of the valve body at the seat and valve-stem guide bore thereof, said valve-seat engaging means will be accurately and concentrically referenced, to the center of the seat and to the center of the remote end of the valve-stem guide bore, so that a rotary tool may be guided via the bore of said valve-seat engaging means, to enlarge and possibly offset the prior-existing valve-stern guide axis, thereby conditioning the enlarged bore to receive a valve-stem guide insert.

References Cited UNITED STATES PATENTS 3,352,'1 82 11/1967 Norum 408-97 3,333,487 8/1967 Parry 408-97 2,864,268 12/ 1958 Anderson 408-415 2,834,233 5/1958 Anderson 4081 15 GIL WEIDENEELD, Primary Examiner US. Cl. X.R. 408-75, 115, 709

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