US1975985A - Method and apparatus for grinding valve seats - Google Patents

Description

METHOD AND APPARATUS FOR GRINDING VALVE SEATS Filed Feb. 10-, 1934 BYROME 3T0 wk,

ATTORNEYS Patented Oct; 9, 1934 I r UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR GRINDING VALVE SEATS Byron F. Stowell, Springfield, Mass, assignor to t Van Norman Machine Tool Company, Springfield, Masa, a corporation of Massachusetts Application February 10, 1934, Serial No. 710,646

Many attempts have hitherto been made in which I believe the device to operate. It should the field of refacing the valve seats of internal be understood, however, that while these undercombustion motors to grindthe seats directly lying principles are thought to be correct, they by a formed grinding wheel so that they may fit are merely my explanations of why the device 5 the previously ground valves without the necesoperates as it does. However the device may be sity of grinding the valve and seat together. explained, the fact remains that in operation it Such an operation would obviously be much acts in a manner wholly different from previmore rapid and accurate than the use of tapered ously known devices for similar purposes. reamers such as arev now currently employed. It willbe clearer to explain the principle of 10' In spite of the apparent advantages and of long the device after the preferred form of the device continued experimentation, grinding the valve itself has been considered. This will be done seats with formed cutters has not hitherto been with reference to the accompanying drawing,

. found practicable due to the tendency of the in which:

grinding wheelto chatter. chattering of the Fig. 1 is a side elevation of a device embodying 5 wheel shows itself both in roughness of the my invention, the driving member being shown ground valve seat and in extremely rapid deterias tilted at an angle in order to indicate its oration of the formed surface of the cutter. If flexibility of operation;

a mechanical feed of the cutter be provided and Fig. 2 is a central section through the device, the advance made sufilciently slow the chatterwith the driving member shown in axial align- 20 ing can be avoided, but the mechanical comment with the grinding wheel; .plexities and the slowness of the grinding opcra- Fig. 3 is a detail plan of a flexible driving tion have resulted in making such devices imcollar; practicable. Fig. 4 is a section on line 4-4 of Fig. 3; and

In accordance with the present invention, a Fig. 5 is a section on line 5-5 of Fig. 2.

5 conical or flat surface such as a valve seat can The engine block which is to have its valve be ground without the use of a regulable feed, seats ground is shown at 10, with the valve port the grinding wheel being held directly against indicated at 11 and a valve seat at 12. This seat the work, and without any chattering, roughis shown as conical, but it will be understood that ening of the valve seat, or excessive wear of its form will vary with different motors, some 30 the formed surface of the cutter. I have found of which have horizontal annular seats instead that the chattering of the wheel can be conof conical ones. Below the valve seat is a guide siderably reduced if the wheel is rotatably 13 in which the valve stem runs. In the best mounted on a pilot rigidly secured in the valve motor reconditioning practice the valve is shaped stem guide, and the wheel driven solely by a accurately with reference to its stem and the 5 flexible connection with a suitable source of seat is correspondingly shaped with reference to power such as an electric drill head. A grinding the stern guide 13. To secure a bearing upon wheel so driven will avoid much of the chatterwhich the grinding Wheel may turn in accurate ing of the valve grinding wheels as formerly alignment with the guide, an expansible pilot proposed; but I have found that it is possible, is provided, which may be of any desired type 4 by a further improvement, to eliminate the as its only function is to serve as a stationary chattering entirely and also to change comarbor for the wheel mounting. A standard form pletely the finish given to the valve seat by of pilot has been shown, comprising an arbor the wheel. This novel effect is produced by 15 split at 16 at its lower end, and a rod 17 applying to the wheel an eccentric load, prefwith a conical lower end 18 adapted to be drawn 45 erably in such a manner as to shift its point of upwardly by a cap 19 threaded onto the upper application progressively around the circumend of the rod. As the rod is drawn up its ference of the wheel. The difference in operation conical end expands the split lower end of the due to the presence of this eccentric load is very arbor l5, clamping it firmly in place in the valve marked, both in reducing the wear on the stem guide, the middle portion of the arbor being 50 grinding wheel and in improving the quality centered by a conical portion 20. The arbor is of the ground surface. The fundamental theory thus accurately aligned with respect to the guide. upon which this remarkable change in operation Upon the upper portion of the stationary shaft is based is not entirely clear, but in order to thus secured a sleeve 25 is freely rotatable, facilitate an understanding of the invention I preferably with no more clearance than is re- 5 will state as far as I can the principles upon quired for a free running fit. The lower end 26 "member 39. The yielding of this sleeve is threaded to receive the similarly threaded bore of a. hub 28. To this hub is secured in any suitable way a grinding wheel 30. By this construction, the grinding wheel can be removed at any time for replacement or dressing.

Above the grinding wheel the sleeve is provided with a ,stepped cylindrical bearing surface 35, 36 bounded at one side by a flange 3'1. The cylindrical portion 36 of lesser diameter-bears a washer 38, preferably of metal and fitting against the shoulder between the stepped cylindrical portions, ably of leather. The washer and the driving member are held against rotation on the sleeve bra key 40, and are held against longitudinal movement by a fiber washer 41 and a nut 42 which is threaded onto the sleeve. The washer 38 and the flange 37 serve as end guides for a disk 43 which freely rotates upon the sleeve and is arranged to furnish an eccentric load, shiftable' with respect to the wheel as the latter rotates. For this purpose the disk is hollowed out to form opposite compartments 44 and 45 separated by a partition'46. One of these compartments is filled with lead'47 and the other is left empty, the whole being closed by a cover 48 made with a press fit or soldered or welded in place. The disk 43 is free to rotate -relatively to the sleeve 25 and the grinding wheel and when the sleeve 'is rotating the disk will be turned by the friction between it and the sleeve at an indeterminate and varying speed. It will be clear that as the disk rotates the lead 4'! will act to produce an unbalanced sideways thrust on the sleeve and grinding wheel due to the centrifugal force of its rotation. If the grinding wheel turns at a constant rate the eccentric disk will be carried around at the same speed, but the inertia of the disk will cause it to tend to maintain a steady speed when the inevitable changes in wheel speed occur during the grinding operation. This will caus'e an angular shift of the disk relative to the: wheel so that it does not remain permanently in one position. Excessive wear on any portion of the wheel is thus avoided without any additional mechanism for that purpose. The grinding wheel does not vary widely in its speed as the grinding operation progresses, so that the speed of rotation of the disk is always of the same order of magnitude as that of the wheel, although their relative angular relationship is frequently shifted.

The driving member 39 has a plurality of notches 50 in its periphery, and is preferably beveled on its outer surface as at 51. Cooperating with this member is a driving socket 52 having teeth 53 at its lower edge cooperating with the notches 50 in the driving collar. A stud 54 secured to the upper end of the driving member is adapted to be received in the chuck of an ordinary electric drill. A spring 55, having a strength on the order of 3 or 4 pounds for the compression permitted, is located between the nut 42 and the upper end of the socket, the socket being retained in position by a guard 56 having an inturned lower end underlying the driving connection provided by the member 39 and the socket 52 affects the operation of the device in two ways. In the first place, due to the flexibility of the connection and the large size of the socket compared with the upper end of the sleeve 25, a large range of relative angular positions is permitted to the driving member and the sleeve. This is of particular utility incases where the and a driving member 39 prefer"- valve seats are to be ground with the motor block in place on the car, as the operating space is frequently somewhat cramped. In the second place, the flexibility of the member 39, which is the sole connection between the sleeve and the power source, acts to prevent the transmission of vibrations from the power source to the grinding wheel and to dampen vibrations arising in the grinding system itself. Another function performed by the coil spring is to permit a smooth variation in the pressure of the wheel against the work. When the spring is compressecLthe pressure of the wheel against the work is relatively large, with no danger of binding or of temporary excessive load, whereas when the spring is more nearly in its uncompressed state a lighter pressure suitable for polishing is produced.

It is my belief that the use of an unbalanced rotating weight acts in several distinct ways to improve the operation of the grinding wheel. The grinding system, including the pilot, sleeve, grinding wheel, and drive, has a tendency to vibrate or chatter with a frequency dependent upon the physical dimensions and properties of the several parts. The weight of the loaded disk exerts a very considerable effect upon the natural period of the system and apparently re- .moves this period so far from that of the external forces tending to create the vibrations that'thes are practically damped out. This damping is carried to a point of practical extinction of the vibrations by the eccentric position of the center of gravity, which causes forced vibrations in the system so far off the natural period of the chattering vibrations that the latter are-completely nullified. The variations in pressure of the grinding wheel on the work, and the almost imperceptible lateral shift of the grinding wheel under the unbalanced load have a still further apparent effect in facilitating the clearance of ground particles from between the grinding surfaces, and in preventing the formation of ring marks on the ground surface.

All of the above effects are rendered more uniform by the loose mounting of the weighted disk on the sleeve. Were the disk to be fixed the chatter would be reduced, but the pressure of the grinding wheel would be concentrated at one point on its periphery, resulting in excessive wear at that place. By permitting the disk to slip relative to the sleeve it is allowed to change its position, lagging behind or leading the grinding wheel in the inevitably non-uniform rotation of the latter. Thus the zone of highest pressure is shifted around the periphery of the wheel by an extremely simple mechanical expedient. I

The spring 55 is useful in permitting a very easy control of the amount of pressure between the grinding wheel and the valve seat, without in any way preventing free change in the angular position of the socket with respect to the sleeve. The socket is held central, so that no binding will occur, both by the tapered outer surface 51 of the member 39 and by the fiber washer 41. If the device be rotated without any compression of the spring a light pressure between the grinding wheel and the valve seat results, which gives a polishing effect. A heavier pressure can easily be had for faster cutting when desired. In either condition the eccentric load shifts the point of application of the presface, supporting the wheel for'aligned rotation with respect to the seat, rotating the wheel at grinding speed about the common axis of the wheel and the seat, and applying to the rotating wheel an eccentric load varying in direction progressively around the circumference of the seat at a rate differing from the rate of rotationof the wheel. o I

2. A grinding device for annular valve seats and the like which comprises a grinding wheel formed to the shape desired for the seat, means for supporting the wheel for rotation upon an axis substantially coincident with that of the seat and with the wheel in full circular contact with the seat, means for rotating the wheel upon said axle-and an eccentric weight coupled to the wheel for rotation upon said axis to exert by its rotation an unbalanced rotating lateral thrust upon the wheel.

3. A grinding device for annular valve seats and the like which comprises a, grinding wheel formed to the shape desired for; the seat, means for rotating the wheel uponan axis substantially coaxial with the seat, and means adjacent the wheel for dampingout vibrations of the wheel.

4. A grinding device for annular valve seats and the like which comprises a grinding wheel formed to theshape desired for the seat, means for rotating the wheel upon an axis substantially coaxial with the seat and with the wheel in substantiallyunrestrained full contact with the seat, and meansadjacent the wheel and rotatable therewith for damping out the vibrations of the wheel. 7.

5. A grinding device for annular valve seats and the like which comprises a grinding wheel formed to the shape desired for the seat, means for rotating the wheel upon an axis substantially coaxial with the seat and with the'wheel in substantially unrestrained full contact with the seat, and an eccentric weight coupled to the wheel for rotation about said axis.

6. A grinding device for annular valve seats and the, like'which comprises a grinding wheel formed to'the shape desired for the seat, means for rotating the wheel upon an axis substantially coaxial with the seat and with the wheel in substantially unrestrained full contact with the seat, and an eccentric weight coupled to the wheel for rotation relative thereto about said axis.

7. A grinding device for annular valve seats and the like which comprises a pilot secured to the valve stem guide of the valve seat to be ground, a sleeve rotatable on the pilot, means for rotating the sleeve, a grinding wheel secured to the sleeve, and an eccentrically weighted member rotatably mounted on the sleeve.

8. A grinding device for annular valve seats and the like which comprises a pilot secured to the valve stem guide of the valve seat to be ground, a sleeve rotatable on the pilot, means for rotating the sleeve including a flexible vioration-damping coupling comprising the sine connection between the sleeve and the power source, a grinding wheel secured to the sleeve; and an eccentrically weighted'member rotatably mounted on the sleeve.

9. A grinding device for annular valve seats and the like which comprises a pilot secured to the valve stem guide of the valve seat to be ground, a sleeve rotatable on the pilot, means for rotating the sleeve including a flexible notched, disk and a driving member including a socket fitting loosely over the exposed end of the sleeve and having projections engageable in said notches, a grinding wheel secured to the sleeve, and an eccentrically weighted member rotatably mounted on the sleeve.

10. A grinding device for annular valve seats and the like which comprises a pilot secured to the valve stem guide of the valve seat to be ground, a sleeve rotatable on the pilot, a grinding wheel carried by the sleeve, and means for rotating the sleeve including a flexible notched disk, a driving member including a socket fitting loosely over the exposed end of the sleeve and having projections engaged in said notches, a spring forcing the disk and the socket apart, and means for holding the socket and the disk in assembled relation.

11. A grinding device for annular valve seats disk, a driving member including a socket fitting loosely over the exposed end of the sleeve and having projections engaged in said notches, a spring forcing the disk and the socket apart, and means for holding the socket and the disk in assembled relation, and an eccentrically weighted disk freely rotatable on the sleeve.

12. A grinding device for annular valve seats and the like, which comprises a pilot secured to the valve stem guide of the valve seat to be ground, a sleeve rotatable on the pilot, a grinding wheel carried by the sleeve, an eccentrically weighted disk freely rotatable on the sleeve adjacent to the grinding wheel, a flexible notched disk secured to the sleeve above the weighted disk, a socket fitting loosely over the exposed end of the sleeve and having projections engaged in said notches, a spring forcing the disk and the socket apart, a guard secured to the socket and engageable beneath the notched disk, and means for maintaining substantially centralized engagement between the socket and the notched disk.

13. A grinding device for annular valve seats and the like which comprises a pilot secured to the valve stem guide of the valve seat to be ground, a sleeve rotatable on the pilot, a grind-' ing wheel carried by the sleeve, a driving member for rotating the sleeve, a spring forming a thrust connection between the driver and the sleeve and adapted to permit a smoothly varying application of grinding pressure to the grinding wheel so that the latter can be pressed against the valve seat with any desired degree of force, and a flexible, non-metallic cushioning element forming a driving connection between the driving member and the sleeve.

14. A method of grinding a conical seat which comprises placing in full circular contact with the seat a grinding wheel having a conical surface formed to the shape desired for the seat, supporting the wheel for rotation with its axis substantially coincident with the axis of the seat, rotating the wheel at grinding speed about the common axis of the wheel and the seat, and applying to the rotating wheel a radial with that of the seat, means for rotating the wheel upon said axis, and an eccentrically loaded disk freely journaled upon the wheel mounting for rotation thereon, said disk being rotated solely by frictional contact with the wheel mounting and being shifted in its angular position with respect to the wheel by reason or changes in the speed of the wheel, the disk tending to resist speed changes because of itsown inertia.

BYRON F. STOWELL.

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