US2036656A - Valve seat cutter - Google Patents

Description

Ap 1936- B. F. -STOWELL in AL 2,036,555

VALVE SEAT CUTTER Filed June 8, 1932 INVENTORS A" gym! ESTdIp/ELL Y ATTORNEYS Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE VALVE SEAT CUTTER. Byron F. Stowell and Roger 8. Pym, Springfield,

Mass assignors to Van Norman Machine Tool Company, Springfield, Mara, a corporation of Massachusetts Application June s, 1932, Serial No. 015,912 1 Claim. (01. 29-10:)

a cutter at a marketable price, to lower the grade of steel below what would be theoretically desirable. Attempts have also been made to secure the advantages of high grade steel without a prohibitive cost by using cutters of the inserted blade type. The forms of inserted blade cutters heretofore proposed for this purpose have not been entirely satisfactory, and it is the" general object of the present invention to improve upon them in several particulars.

One object of the invention is to produce a cutter which will hold its cutting edge without resharpening for a longer time than was possible with prior cutters. A further object is to provide a superior cutter at a lower manufacturing cost. A further object is to produce a cutter which will be free from chatter during operation. A further object is to provide an'inserted blade cutter which may be used upon a tapered pilot or arbor. A further object is to provide a cutter which will leave a more perfect finish on the valve seat than has heretofore been possible. Additional objects will appear from the following description and Referring to the drawing:

Fig. 1 is a perspective view of a valve seat cutter embodying our invention;

Fig. 2 is a bottom view thereof;

Fig. 3 is a section on line 3-3 of Fig. 2;

Fig.4 is a side elevation of a central bushing forming a part of the completed cutter;

Fig. 5 is a top plan view of the bushing shown in Fig. 4;

Fig. 6 is a detail, on an enlarged scale, of one form of cutting blade;

Fig. '1 is a view of the blade shown in Fig. 6, looking from the left in that figure; I

I ig.8isaviewsimilarto1 'ig.6showlngadifferent form of cutting blade;

Fig. 9 is a'similar view showing a still different form of blade; and Fig. 10 is-a view similar to Fig. 3. showing a modified form of cutter.

The cutter comprises a body portion I l preferably of a hard zinc alloy, and bears series of blades II, II, and it, formed of high grade steel and permanently united to the base at the time the latter is cast. The center of the cutter is preferably formed by a bushing ll made of a hard material such as steel, having its outer surface formed with circumferential grooves I! and peripheral knurlings or fiutings I. This bushing is also permanently united to the body II at the time the latter is cast, the fiutings and 10 grooves preventing any possibility of shift after the material of the base has hardened. The interlor ll of the sleeve is preferably tapered so that the cutter may be mounted without further interconnection upon a tapered arbor or pilot of 1 the usual type. If desired, however, the bushing ll may be omitted and the interior of the central hole in the cutter left cylindrical as in Fig. 10. In this case the body of the cutter is formed with lug engaging portions it or similar devices by which the cutter may be rotated by an arbor or pilot having suitable lugs or dogs thereon.

The blades are, as stated above, preferably of three kinds in order to secure the advantages present in one aspect of the invention. Each kind is made of a'high grade tool steel, preferably of a tungsten alloy, and is heat treated so as to render it suitable for cutting. The special manner of heat treatment will depend upon the particular alloy used, as .is'well understood in the art. Each blade is provided with some means for causing it to become permanently located in the cast base when the latter has become solidified, so that the blades will not become loose under the strains of use. shown the means chosen comprises a series of flutings or depressions i9 adjacent what is to become the inner edge of the blade, the fiutings being indented from opposite sides of the blade In the embodiment and preferably tapering from a point 2| to the inner blade edge. By reason of this tapering and the raised character of the fiutings when considered in relation to the general plane of the side of the blade, the blades will be anchored firmly in place against a force tending to dislodge them in any direction when the matrix of cast material in which they are set has hardened.

Each of the blade types may, if desired, be beveled as at 2| on one corner, so that when the blades are mounted in the body these beveled ally similar to each other, having notches I! cut in their edges. ."The notches are preierablydiiierently positioned in the two cases, however, so that they will out of line when assembled in the cutter. The blades l2 and II are preferably alternated around the cutter, as shown in Fig. 2;; the notches breaking step as is customary, in nicked tooth cutters so that the two setsof blades taken together cover the entire surface of the valve seat being worked on. Que or more plain blades II are interposed between adiacent nicked blades, as is also shown in Fig. 2; resulting in a very smooth finish being givento the valve seat while retaining the added speed of out due to the nicking ofthe teeth. It will be observed from Fig Z that adjacent blades are unevenly spaced around the base i0. Preferably this unevenness of spacing is such that no blade is opposite any other blade and no two blades are spaced. similarly. This can be worked out in many ways, depending on the number of blades used. Using twelve blades, a suitable angular spacing of the blades is 27%;, 33, 34, 27, 23 375?, 31%, 34%2 23 38, The angles are measured between adjacent blades, which converge towards the axis of the cutter, and are given consecutively around the cutter. It desired, the plain blades maybe used instead of notched blades, as it has been found that a outfar of this type with plain blades cuts valve seat scale satisfactorily. The use of notched blades does, however, add somewhat to the speed oi. cutting.

Gne relation between the steel blades and the alloy base is of importance in making possible the production 01' this type of cutter. As is known in the heat treatment of alloy steels, the metal when once hardened and then drawn to a predetermined temperature can subsequently be reheated to a lower temperature without destroying the properties given to it by its heat treatment. The casting temperature of the alloy chosen is lower than the drawing temperature aosaeoa of the steel by an amount sumcient to prevent any accidental impairment oi the hardnessgoi' the blades. It will thus be seen that blades can be hardened and suitably: tempered, subsequently placed in a mold or die, and the molten alloy for the base poured in place without injuring the blades.

One type of alloy which is suitable for the body II is a standard one used in die casting and having 88% fzinc, 4% aluminum, 3% copper, and 5% magnesium. This alloy, which is given as illustrative only, has a'melting'point of 750 degrees and? a pouring temperature in the neighborhood of 380 degrees. contrasted withf this is the tempering heat of a timsten steel aJoy blade of 1056 degrees. It is obvious that ii metals of substantially these characteristics are used, the already tempered steel blades may be cast in place without danger of injuring them.

What we claim is:

An inserted blade cutter comprising a relatively soft body of cast metal, a relatively'fhard metal sleeve centrally located in the body and shaped externally to provide a anchorage with the body, said sleeve being iormed with a central bore whereby the cutter may be detachably supported on an arbor, and a plurality of tempered sheet metal blades set into the body and having their extreme inner edges laterally distorted with corrugations diminishing in size a they extend into the bodies oi the blades, whereby the extreme inner edge of each blade is of substantially greater thicniess than the body of the blade, and a bonding anchorage is provided with the cast metal body, the metal of which the body is formed being of such a composition that its moulding temperature is substantially below that at which the blades are tempered.

BYRON 1". S'I'OWEIL.

ROGER S. PYNE.

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