US2041567A - Engine piston - Google Patents

Description

May 19 1936. E. NELSON 4 ,5

ENGINE PISTON Filed Aug. 27, 1954 2 Sheets-Sheet l Ema/mm Emil-M31801,

19, 1936. Y E NELSON 2,041,567

' ENGINE PISTON Filed Aug. 27, 1954 2 Sheets-Sheet 2 Jim-11:1lvzez mp,

Patented May 19, 1936 STT S EAENT GFFIE Application August 27,

2 Claims.

This invention relates particularly to pistons of the internal-combustion-engine type.

It is an object of the invention to provide improved means to compensate for wear and to avoid piston slap. For this purpose, the invention provides rigid detachable auxiliary skirts for the piston that may be adjusted at right angles to the axis thereof. With skirts of the form and arrangement provided by the invention, use of piston-skirt expanders and pistonring expanders with their attendant disadvantages is avoided.

Heretofore, springs have been used to urge shoes or other piston-skirt parts, and in some instances packing-rings, against the cylinder-wall, but springs have been found initially to be not suf-, ficiently resistive to thrust pressure and power stroke, they become weakened during use under the high temperatures to which subjected, and. oftentimes they break. A piston that includes spring elements is not suitable for internal-combustion engines.

The skirt of a piston is a guide for its head, which carries the rings, and the rings should contact squarely against the cylinder-wall to function properly. A piston-skirt having elements urged laterally by springs against the cylinderwall may not slap under thrust pressure, but it has such give as causes the rings to break their seal with the cylinder-wall, the rings wear round on their faces, and the ring-grooves become worn.

In order that rings and piston can function properly, the piston head and skirt together must be rigid, as loose skirts and those that include spring action result in impairment and eventual elimination of sealing of the rings with the cylinder-wall.

Some prior art forms of pistons are susceptible to bending in the median portion of the skirt and liable to breakage at that place; and, when bending occurs, the head rocks, ring seal is broken, the ring-faces wear round, and the ring-grooves also wear.

With some forms of pistons having laterallyurging springs, the piston slap the springs are intended to obviate is accentuated in some circumstances; and, if the springs are strong enough to withstand thrust pressure, they exert such outward pressure against the cylinder-wall that lubricant film is wiped off with the result that there is too much friction, the resultant temperature breaks down lubricant, and piston drag occurs that materially decreases the efficiency of the engine.

Therefore, in order to avoid diificulties and de- 1934, Serial No. 741,672

fects such as the foregoing, the invention provides a skirted piston, diametrically adjustable in its skirt, that is as rigid as if cast as a. single piece.

When considered with the description herein, the characteristics of the invention are apparent from the accompanying drawings, forming part hereof, wherein there is exemplified, for purposes of illustration, an embodiment of the invention now deemed to be a preferable one.

Like reference-characters refer to corresponding parts in the views of the drawings, of which- Fig. 1 is an elevational View of the piston;

Fig. 2 is an elevational View of another side of the piston;

Fig. 3 is a sectional view on the line 33, Fig. 2;

Fig. 4. is a bottom view of the piston;

Fig. 5 is a view of the piston in a lathe;

Fig. 6 is an elevational view of a shim;

Fig. 7 is a plan view of a shim;

Fig. 8 is a sectional view on the line 88, Fig.

Fig. 9 is an elevational view of a piston with removable skirts;

Fig. 10 is an elevational view of another side of the piston with removable skirts;

Fig. 11 is a bottom view of a piston with removable skirts;

Fig. 12 is a bottom view of a removable skirt;

Fig. 13 is a top view of that skirt;

Fig. 14 is an elevational view thereof;

Fig. 15 is a sectional view on the line l5-l5, Fig. 14.

The upper portion of the piston, including its head I6, circumferential grooves I! containing packing-rings l8, and wrist-pin bearings or bosses I9, is of conventional form.

The piston-skirt 20, which is formed integrally and rigidly with the head, is of less diameter than the head and the cylinder in which it is to work. At diametrically opposite places in a line at right angles to the axis of the wrist-pin bosses, the skirt is flattened exteriorly from top to bottom, as shown at 21, but elsewhere its outer surface is arcuate and concentric with the piston axis.

The wall of the skirt is cut away at the bottom, as shown at 22 and 23, to enable it to take the chuck of a lathe, as shown by Fig. 5.

The skirt is formed with holes 24 to accommodate fastem'ngs, to which reference hereinafter is made.

Two transversely arcuate rigid auxiliary skirts 25 are provided for removable attachment to the integral piston-skirt proper. Each of them is formed with a thickened longitudinal portion 26 having a flattened inside surface corresponding in area to, and arranged to seat against, a flattened part 2i of the integral skirt. The interior contour of the auxiliary skirt corresponds exactly to that of the outside surface of the integral skirt against which it is to abut. Each of the auxiliary skirts has holes 21 and countersinks 23 in its portion 26 to accommodate, respectively, the shanks 29 and heads 30 of bolts 3| by which it is secured to the integral skirt. The bolts extend through the parts, and they are held fast by nuts 32 on their inner ends. The nuts are tightened to draw and hold the auxiliary skirts rigidly against the integral skirts. The countersinks are sufficiently deep to house the bolt-heads inside of the outer periphery, in order to avoid contact of the heads with, and scoring of, the cylinder-Wall.

The auxiliary skirts are of such thickness and exterior contour when new that they have normal working contact with the cylinder-wall when they are on the integral skirt.

When, during use, the auxiliary skirts become worn to the extent that they no longer function efficiently as guides that prevent the piston-head from tilting, the piston from slapping, and the rings from wearing round, one or more thin shims 33, such as shown by Figs. 6 and 7, are placed inside of them, and the auxiliary skirts are replaced on and reattached to the integral skirt. Each of the shims is of a shape and size to seat against a side of the integral skirt such as shown by Fig. l, and it has holes 34 to accommodate the fastenings.

At first, after wear, the number of shims (one or more) required to extend the outer surfaces of the auxiliary skirts to normal working contact with the cylinder-wall are used. Subsequently, additional shims may be inserted from time to time, until the auxiliary skirts have become so worn that it is necessary to discard them, when new auxiliary skirts may be brought into use.

When the removable auxiliary skirts are incorporated into the piston structure, either without or with shims, they are rigid and substantially integral parts thereof. Thus they are guides for the piston-head that do not give at all as do spring-urged and similar elements that permit rocking and/or slapping of the piston under the stresses to which it is subjected.

The auxiliary skirts and replaceable packingrings, as renewable elements of a piston structure, may prolong indefinitely the life of the integral parts of the structure.

If desired, the auxiliary skirts may be strengthened by a lower marginal rib 35.

What I claim as new, and desire to secure by Letters Patent, is

1. A piston comprising a head, an integral skirt of less diameter than and connected directly to said head and extending to the other end of the piston structure and flattened exteriorly at opposite places, and rigidly and non-yieldingly secured to each side of said skirt a removable auxiliary skirt of substantially the same exterior diameter as said head, said two auxiliary skirts interiorly conforming in contour to the flattened and arcuate surfaces of said integral skirt, and said surfaces abutting substantially the entire area of said auxiliary skirt.

2. A piston comprising a head, an integral skirt of less diameter than and connected directly to said head extending to the other end of the piston structure and flattened exteriorly at opposite places, and rigidly and non-yieldingly secured to each side of said skirt a removable auxiliary skirt of substantially the same exterior diameter as said head, each of said auxiliary skirts having in its median portion a thickened part presenting a flat inner surface conforming to and seated against a fiat of said integral skirt, said two auxiliary skirts interiorly conforming in their arcuate portions to the arcuate surfaces of said integral skirt, and said latter surfaces abutting substantially the entire arcuate area of said auxiliary skirts.

- EMIL NELSON.

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