US 1421202 A
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Description (OCR text may contain errors)
.Il wl PISTON RING.
APPUCATWN FILED IAN. 8, |917.
Patented June 27, V1922.
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UNITED STATES PATENT OFFICE.
JOHN W; FORD, OF ST. LOUIS, lVIISSOI-TRI, ASSIGNOR, BY M ESNE ASSIGNMENTS, TO
SPYROSEAL MANUFACTURING COMPANY, OF ST. LOUIS, MISSOURI, A. CORPO- RATION OF MISSOURI.
Specification of Letters Patent. Patented June 2*?, 1922.
Application filed January 8, 191'?. SeriaI No. 141,110.
T 0 all whom t may concern.'
Be it known that I, JOHN W. FORD, a citizen of the United States, and residing at St. Louis, Missouri, have invented the new and useful Improvement in Piston Rings, of which the following is a specication.
This invention relates to piston rings.
Piston rings are almost universally constructed of cast iron, as this metal gives the greatest wearing qualities under the peculiar conditions of its operation. `Such a ring must, however, be expansible, and in orderv to provide for eXpansion'it is necessary to split the ring and overlap the ends in order to close the gap formed between the ends of the ring. Where, however, the ends overlap, and more particularly where they overlap for an extended part of the ring circumference, then it is diflicult to maintain the ends in overlapping engagement, for the reason that the tool employed to split the ring is necessarily of appreciable thickness. It is, of course, possible for short laps to form the ends by machining, but itis diiiicult to obtain a good joint, even in such a lap, withoutA considerable hand work. Where, ofcourse, the ends overlap for a considerable distance, then the only practical way of obtaining such overlapping is to split the ring for a part of its circumference. This means, however, that the ends are now sprung `apart axially of the ring.
Now it is very important that the over lapping ends of a long lap ring be in. substantially-mutual engagement throughout their parting; if this is not the case then carbon is liable to collect in the parting slot to such an extent, as to not only effect its engagement with the cylinder', but to even cause the ring to wedge in the piston; moreover the rapid movement of the piston intl-1e cylinder is liable to cause Vibration of the necessarily thinpends, so as to cause Crystallization of the cast iron.
It would seem that the spaced overlapping ends could be brought into engagement by mere inversion, i. e., by springing one end over the other and then applying pressure. This is, however, impractical for the following reason: In order to obtain elasticity and wearing qualities in a cast iron piston ring, it is necessary to select a hard close-grained iron. The elastic limit of such an iron is, however, very low, and the iron is, therefore,
so brittle that mere inversion of the ends of the ring, or hammering after inversion, will not set the cast iron in inverted position, but the iron will break before any suchset can be given. l
One of the ob]- ects of this invention, therefore, is to provide a long lap piston ring, that is, one in which the ends Overlap for an extended part of the ring circumference.
Another object is to provide an integral cast iron long lap ring in which the overlap` ping ends are in substantially mutual engagement throughout their parting.
Another object is to construct a piston ring in such a manner that the overlapping ends are held together by the resiliency imparted tothe metal.
Further objects will appear from the detail description taken in connection with the accompanying drawing, in which: l
Figure l is a side view of the ring after it is cut from the tub, and after the dividing slot has been cut therein;
Figure 2 is a similar view, showing the ends cut through to the slot;
Figure 3 is an end view of Figure 2;
Figure 4 is a View showing the ring with the overlapping ends inverted.
Figure 5 is a view showing the ring after treatment, with the ends reinverted;
Figure 6 is a side View showing the finished ring; and, A
Figure 7 is a perspective view of the iinished ring.
Referring to the accompanying drawing, l designates a ring having overlapping ends 2 and 3, the ends being cut on a helix or tonded part of, and in the particular embodi-v ment illustrated, for about one-'half of the circumference of the ring. The overlapping ends lie or are positioned, one within a recess in the other, to that the tips thereof can be and are blunt, as shown at 4, as this avoids breakage of the cast iron ends, and in order to bring about this condition the ring body is cut to form shoulders 5. Gaps 6 are formed between the ends l and the shoulders 5, so as to permit contraction of the ring when placed in the cylinder.
lt will therefore, be seen that in this ring the ends overlap for an extended part of the ring circumference, ,as distinguished from the ordinary short lap ring, in which the lap `is merel sufficient to provide a seal; in this` particulyar embodiment the lapextends practically half way around the ring, the overlapping ends engaging along the line 8 which forms the parting.
AThe method of making this ring will now be described. A casting in the form of a drum and known as a tubf is-bored and turned down in the usual way, and the rings are cut off by suitable cutting tools. The ring is now placed ina -milling machine and the cut c made helically and about half way around the ring, as shown in Figure l; this is accomplished by an ordinary saw cutter, the Iring being clamped between two plates in a rotatable head or work support. The gaps: b are now cut in a miller, so as to split the ring, as-shown in Figures 2 and 3. This, of course, leaves a gap a extend-ingl circumferentially of the ring, and which would render the ring leaky and unfit for use.
In accordance with this invention the ring isnow inverted, i. e., the-end 2 is sprung over on the other side of the end 3, thereby placing the ring under tension and the metal in the ring under strain, as show-n in Figure 4. The ring is now placed in anoven and heated to a cherry red (80() degrees E), the ring being kept at such a cherry red for a few minutes. This heat treatment sets'the ring with thebres in position. When the ring is inverted the molecules or fibres of the iron are placed under strains, and when the ring is heated to redness the strains are relieved and the molecules or fibres are rearranged sothat the iron sets in that position. After the ring has been so heated, it is removed from the oven and allowed to cool in thel air. The cool ring, therefore, has set so that any movement of the overlapping ends from theinverted position shown in Figure 4, even baekto their original positions, will place these ends under strain. In accordance with this invention, therefore, the ring is reinverted, as shown in Figure 5, i. e., the ends 2 and 3 are sprung back over one an` other, so as to place them in their original position. This, of course, places the ends under strain and results in the maintenance of the overlapping ends in close contact along the line 8 -by the resiliency of the metal.
Due to the fact that the parting slot a has been taken up and closed, it is, of course, necessary to finish ofrn the sides of the ring, and this is accomplished in the usual way by placing thering in a chuck and Vfacing and grindingthe end faces ofthe ring with the ring closed to normal diameter. The rings' vare now placed inside of a drum, which is slightly oversize, clamped between two flanges, removed fromy the drum, and ground to size on a cylindrical grinder.
The result is, therefore, a ring `which possesses all of the desirable features of the ideal piston ring. The parting slot is substanti ally closed, even where the overlapping ends extend half way around the circumference of the ring. Moreover, these overlapping ends are held in close contact due to the resiliency of the metal, brought about by this treatment. The operation of inversion and heating causes-a uniform setting of the ring in such a position, and this, together with the dividing of the ring by .a single cutter or saw, so as to form parallelelined Walls of the cut, causes substantially perfect contact of the overlapping ends throughout their length. f
ln accordance with this invention, there is provided aV practical long lap pistonyring, that is one in which the ends thereofoverlap for an extended part of the ring circumfen ence, as .distinguished'from ordinary piston rings in which the ends overlap only sufficiently to form a gas seal between the free ends; in along lap ring,however-,the overlapping ends engage the cylinder-wallsffor extended parts circuinferentially, and, therefore, secure a more uniform engagement and a better gas tight joint betweenthe cylinder and the piston. This is further enhanced by the ring structure, since a body of ring Width is provided, so as to secure a sufficiently stiff juncture between the necessarily thin overlapping ends in order to obtain!therequired tension; and this is still further enhanced by providing a body of ring widthforun eX tended part of the ring circumference. The ring is of cast iron, as required inpractice, and it is an integral and, therefore, a onepiece structure, so as to avoid the use of frail pieces of cast iron which are easilybroken. The ends are moreover blunt-tipped and, therefore, breakageA in this respect isavoided, as would be the case if the end tips came to feather edges.
In accordance with; this invention, the eX- tended overlapping ends are in mut-ual engagement throughout their parting; accordingly ventrance of carbon and other-matter between these ends is avoided, and moreover vibration of the necessarily thin overlapping ends is infevented. AThe treatment produ-ces a ring in which these long' overlapping ends are not only in substantially mutual engagement throughout their parting, but-this engagement is a uniform one, as the straining and setting has been uniform from-the center of each ring half to its-tip, and not a strain or set for a short lengthof a thin end. Moreover the fact that the straining Was that of abeain of the circumferential length of the ring vfrom one tip to the other, breakage and undue strain during straining is reduced to a minimum. Moreover, sincethe setting is of a uniformly strained structure, and ina manner to avoid rupture of the cast' iron,` the resultant set will be a permanent one. The resultant ring, therefore, has the characteristic of elasticity and permanency.
It is obvious that various changes may be made in the details without departing from the spirit of this invention. It is, therefore, to be understood that this invention is not to be limited to the specific details described and shown.
Having thus described the invention what is claimed is:
l. A split piston ring having its ends overlapping for about one half of its circumference and sprung together, the overlapping portions being pressed together by the resiliency of the metal.
2. A piston ring having its opposite sides notched at diametrically opposite points, and its half circumference split on a spiral curve intersecting said notches, thereby forming tapered ends overlapping for about on half of its circumference, said split ring being twisted between its extremities to cause said ends to spring together.
3. A split piston ring having its opposite sides notched at diametrically opposite points, and its ends overlapping for about one half of its circumference and sprung together, the width of the overlapping ends gradually increasing from their extremities to the notches.
4. A metal piston ring having one half of its circumference split on a spiral curve and impressed with internal strains whereby the overlapping portions thereof are pressed together by the resiliency of the metal.
5. A metal piston ring having a substantial portion of its circumference split on a spiral curve and impressed with internal strains whereby the overlapping portions thereof are pressed together throughout their length by the resiliency of the metal.
6. A split piston' ring having its ends lapped lengthwise, said lapped ends being held together sidewise throughout their length by the resiliency of the metal.
7. A split piston ring having its ends tapered and lapped lengthwise, said lapped ends being held together sidewise throughout their length by the vresiliency of the metal.
8. An integral cast iron long lap piston ring having its ends overlapping for an extended part of its circumference and in substantially mutual engagement throughout their parting.
9. An integral cast iron long lap piston ring having its ends overlapping for an extended part of its circumference, positioned one within a recess in the other, and in substantially mutual engagement' throughout their parting.
l0. An integral cast iron long lap piston ring having a body of ring width provided with ends which overlap for an extended part of the ring circumference and in substantially mutual engagement throughout their parting.
11. An integral cast iron long lap piston ring having a body of ring width for an extended part of its circumference, said body being provided with ends which overlap for an extended part of the ring circumference and in substantially mutual engagement throughout their parting.
In testimony whereof I aiiix my signature this 8th day of December, 1916.
JOHN W. FORD.