US1772103A - Piston for engines - Google Patents

Description

Aug. 5, 1930. c. A. MARlEN PISTON FOR ENGINES Filed Aug. 22. 1927 //vv5/vroR.- CHARLES A. MAR/5N. W.

8 A A i/ JQTTOENA'K Patented Aug. 5, 1930 V UNITED STATES CHARLES A. 'IABIEN, OF ST. LOUIS, MISSOURI PISTON Ion nNenrEs a ucaaon'mea August 22, 1927. swarm. 214,723.

My invention has relation to improvements in pistons for engines and cons1sts in the novel features of construction more fully set forth in the specification and pointed out in 5 the claims. The invention is particularly applicable to alldy pistons, that is, pistons that are made of an alloy of aluminium or some other metal which have recently come into very extensive use. 4

At the present time it is the practice in fitting pistons of this type for proper opera tion in the cylinders, to give the piston considerable clearance at the head, approximately twelve one-thousandths of an inch, and decrease this clearance downwardly to- I Ward the skirt of the piston at the lower end of which a clearance of erhaps two onethousandths would be cient. 'In pistons of the typehavinga split skirt, the clearance is generally limited to theupper part of the piston, the expansion of the lower part being compensated for by the contractability of the split skirt. In fitting alloy pistons, great care must be exercised 1n grinding them to provide the proper clearance because differ ent clearances are required for different makes of engines, and even for different engines of the same make. Consequentl it is only a fortuitous circumstance when t e pistons are so ground as to fit the cylinders with the utmost precision.

It is the object of the present invention to provide a .piston that will not require accurate grinding to insure the properamount of clearance in the cylinder, but one that has its outer surface prepared in a manner that will enable the piston to work itself to a proper fit in the cylinder during the operation of the engine. This ob'ect is accomplished in the present case by ormin on the outer surface of the piston a series 0 ribs or alternate ridges and grooves, the ridges extending annularl around the piston wall and being substantia y Vshaped so as to present 'sharp edges outwardly similar to threads. These'formations extend from'the head of the piston downwardly as far as the slots-in the case of a slotted piston, or in the case of a solid piston they may extend only down to the bottom of the skirt or to any intermediate point. The manner in which this ribbed surface accomplishes the above object, as well as its other advantages, will be better apparent from a detailied description of the invention in connection with the accompanying drawings, in which: Figure 1 represents a section of the engine cylinder with my improved piston positloned therein; Figure 2 is an enlarged longitudinal section through the head of the piston showing the shape of the ribs on the piston wall; and Figure 3 is a section similar to that shown in Figure 2, but of a modified shape of rib. 1

Referring to the drawings, P represents 5 my improved piston adapted for operation inthe cylinder C, said piston being provided with the usual piston rings, 1, 1, 1 positioned in the ring grooves 2, 2, 2. In the present instance, the sln'rt 3 of the piston is split or divided by cross slots 4 and longitudinal slots 5 as well understood in the art. The function of the slots is to enable the skirt to be contracted asthe piston expands under the heat of operation and enables the "skirt of I the piston to fit the cylinder walls snugly under practically all conditions ,of operation, as

above pointed out, without specially providing for clearance. However, the upper part of the piston, that is the ring- lands 6, 6, 6, and the intermediate portion '7 of the piston immediately below the bottom groove 2, must be provided with clearance, as above pointed out, in order that the piston may neither bind as it expands under severe operating condi: tions nor wabble in the cylinder under other conditions. Under present practice, in order to make certain that the piston will not hang up, sufficient clearance is provided for, with the result that this clearance is very often too much for the ideal operation of the'Ipiston, and a piston slap is introduced. overcome these difiiculties, as well as simplify very greatly the fitting of the piston, by providing the outer surface of the piston with the ribbed formations or alternate ridges 8 and grooves 9. The entire surface of each of the ring-lands 6 is ribbed as well as the surface of the piston below the bottom ring works back and forth in the groove during 55 si'st The shape of the ridges preferably follows that of an acute angle so that they may be suificiently thin to wear down by contact with 'the. cylinder wall. Obviously, the rooves 9 must be of such depth asto allow t e ridges to wear down the full extent required for the piston to fit the cylinder with the proper amount of clearance for correct operation.

, When the pistons are fitted into the cylin-. 10 ders, the ribs present sharp edges e to the cylinder wall (as shown dotted in Fig. 2), but after the engine has been operated, these sharp edges are-worn off and. the diameter'of the contacting parts 6' of thepiston reduced 5 (Fig. 2), until ultimately, with a continued" operation of-the engine, there has been 'suflicient metal worn from the edges to'allow the piston to operate freely in the cylinder with the ideal clearance for the most efiective peraq formance. That part of the piston which undergoes the greatest expansion in the operation' of the engine will, obviously, wear the most so that the entire piston will finally have the ideal amount of clearance within the cylinder. Thus, the proper amount of clearance'for the piston in any particular type of engine does not have to be precalcu-' lated, but will result inevitably from the operation of. the piston.

It is a matter ofacommonknowledge that the piston rings are not always effective to prevent oil from working up into the combustion chamber as the oil occasionally will find its way around a ring; that is, as the ring the operation of the piston, the oil will enter the ring groove and pass behind the ring, ultimately being deposited on the top of the piston where it carbonizes Tlieoil may thus 40 find its way into the combustion chamber at but a'single point, as shown by the arrows! the upper part thereof, and ring lands boundit is worked free would not score the cylinder because the material worn off would merely enter a groove 9 and not be ground over the cylinder. wall. Preferably the ring grooves 2 haveadja-' cent to them grooves 9 and not ribs,$ so that the material that is worn from the edges e as the piston is ground in will not burr over into the ring grooves. This shown clearly in Figure 2.

Having described my invention, I claim:

1. In combination with a cylinder of an engine, .a piston fitted therein with negligible clearance, said piston havin suitable formations on that' part of its sur ace which is subjected tothe greatest expansion in operation, said formations being adapted to wear to provide the proper clearance for working conditions.

2. A piston provided with ring grooves on the upper part thereof, and ring lands bounding said grooves, alternate grooves and ridges formed onthe periphery of the lands. 3. A piston provided with ring grooves on ing saidgrooves, alternate grooves and ridges formed on the periphery of the lands, 531d. ridges presenting sharp edges outwardly.

4. In combination with the cylinder of an engine, a'piston of softer metal than the cylinder operable therein, said piston being provided with grooves on the upper partthereof, and ring lands bounding said grooves,

suitable formations on the ring lands, said formations being adapted to wear to provide the proper clearance of the piston in the cylinder for wor conditions.

' In testimony whereof I hereunto aflix my signature.

inthe drawings, (Fig. 1). In the case of a smoothly "finished piston, the oil will travel .very readilyover the piston surface after 45 having once passed the rings; but in a piston that is grooved as herein described, the oil will encounter'the grooves 9 and instead of travelling upwardly over the piston surface in the shortest line, it will spreadinto' the i 50, groove 9 where it Wlll be held. together by its e own cohesion, which resists a further upward travel. In cases where there is but aslight pumping. of oil, the ca the particles will he s ciently strong to reexpulsion'of the oil from the -groove 9 v V and to this extentseal the leak.

In Figure 31 show a modified form of ribs 8, said rib's'being 'extendedtherein for a con siderable distance inwardly from their outer floyedges e". By making the ribs in this-form,

- obviously, they will wear down much more geadily than they would if they were more unt.

' Even though the-piston should bind somewhat, the material worn from the piston as illary attraction of s L.MARIEN. 05

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