US2397067A - Cylinder and piston and method of producing a working seal therebetween - Google Patents

Description

March 1946. J. WILLIAMS CYLINDER AND PISTON AND METHOD OF FRODUCING A WORKING SEAL THEREBETWEEN Flled May 9 1941 Mum;

- J v Eh-men t oflw l Patented Mar. 19, 1946 "i a is CYLINDER AND PISTON AND METHOD OF PRODUCING A WORKING SEAL THERE- BETWEEN Judson Williams, Philadelphia, Pa.

Application May v9, 1941, Serial No. 392,796

4 Claims.

This invention relates to internal combustion engines and mor particularly to an improved cylinder and piston and method of producing a working seal therebetween.

In recent years, so-called toy motors or model motors have come into quite wide use and the demand for a practical motor of the kind at low cost is at present quite great, due to the constantly spreading interest in toy motor-driven automobiles, boats and aeroplanes.

As will be appreciated, such motors are small, say for the most part, of a cylinder bore ranging from half an inch to an inch, more or less. The partsof such an engine are thus all little, which fact has made it difficult, at low production cost, to equip such a tiny piston with rings or to lap the cylinder in an endeavor to obtain the necessary working seal between the piston and cylinder, the lapping operation almost precluding a low cost motor.

Experience in manufacturing a very large number of toy motors has also shown that even though all the pistons are machined and even though all the cylinders are bored by a tool on th same spindle, no one piston will fit all cylinders. Some of the pistons may be slightly larger than others and some of the cylinders may be slightly smaller than others with the result that it is, in the course of assembly, often necessary to hunt through a pile of cylinders and a pile of pistons in order to find a matching cylinder for a particular piston and vice versa. This matching involves delay and expense.

It is therefore an object of th present invention to provide a working seal between the piston and cylinder without the use of rings on the piston. l I

A further object of the invention is to provide sealing rings on the cylinder to coact with the piston for providing a working seal between the piston and cylinder.

Another object is to provide a construction whereby the necessity for the matching of pistons and cylinders; incident to assembly, will be eliminated.

Still another object is to provide a construction wherein the cylinder rings will be indented from the wall of the cylinder, and wherein the coacting piston will shape the rings to a working fit, so that all pistons will have an effective working seal with all pistons.

And the invention seeks, as a still further object, to provide a construction and method which although primarily intended for use in conjunction with toy motors, may, nevertheless, also be advantageously employed in the fabrication of large'motors, such for example as automobile engines, or in the repair of such large motors for overcoming piston slap, the necessity for reboring or the installation of new pistons and rings.

Other and incidental objects of the invention will appear during the course of the following description, and in the drawing:

Figur l is a perspective view showing a toy motor on substantially full scale and illustrating the smal1 size of the engine.

Figure 2 is an enlarged transverse vertical sectional view on the line 2-2 of Figure 1 and particularly showing the cylinder and piston.

Figure 3 is a fragmentary vertical sectional View on a greatly enlarged scale and showing the cylinder rings before being broken in by the piston, the heat radiating fins being omitted.

Figure 4 is a view similar to Figure 3 and showing oneway in which the cylinder rings may be indented in the cylinder wall.

Figure 5 is a View similar to Figure 3 and showing the cylinder ringsafter being broken in by the piston.

Referring now more particularly to the drawing, I have shown a toy two-cycle engine embodying a crank case i6, cylinder H, and piston i2. The'crank pin of the crank shaft is indicated at l3, and coacting with said pin is a connecting rod M coupled with the piston by a wrist pin i5. In Figure l, the engin is shown substantially full size so as to illustrate the inherent smallness of the parts. However, as the present invention concerns the piston and cylinder only, a detailed description of the construction of the entire engine or the operation thereof is unnecessary.

Asin most engines of the present character, the cylinder H and pistonlZ are preferably of a suitable aluminum alloy, although other suitable materials may be employed, and in carrying the invention into effect, the cylinder H is provided on the inside, near the upper end thereof, with one or more internal rings l6 preferably each convex in cross section. .Any suitablenumber of rings may be employed, as deemed expedient, and also, the rings may be spaced apart as desired. A single wide ring'may' be found sufficient, .but in the present instance'I have shown the use of three rings. 'As will be observed,

the top ring is disposed below the upper'end of" the piston when the piston is at top center and likewise, the bottom ring is disposed below the upper end of the piston when'the piston is at bottom center for isolating the combustion chamber above the piston.

In Figure 3 of the drawing, 1 have shown the rings l6 as initially fashioned. These rings may be formed in any one of a number of different ways. For instance, a suitable indenting tool may be inserted between adjacent heat fins of the cylinder, when the cylinder may be suitably rotated for indenting the wall of the cylinder at the outside thereof and producing an embossed ring on the inside of the cylinder. In Figure 4 of the drawing, I have shown another way of forming the rings It. In this instance, male and 7 female rollers or dies [1 and 18 are employed and the cylinder wall inserted therebetween. As will be perceived, rotation of the rollers or dies will produce the three rings simultaneously. Other expedients may be found advantageous;

The piston I2 is without rings and presents a smooth, cylindrical surface. In this surface are provided, preferably, one or more annular oil grooves l 9. In the present disclosure I have shown two such grooves, one above and one below the wrist pin 15.

After the engine has been assembled, incident to the manufacture thereof, it is then placed upon a suitable test stand when, preferably, the engine is operated under its own power for breaking in the engine. Thus, the piston I2 will be caused to rub across the rings [6 for shaping said rings at the crowns thereof. As initially fashioned, the internal diameter of each of the rings at its crown is somewhat less than the diameter of the piston so that mutilation of the rings will take place as the engine is broken in, and as the piston is causing the mutilation, the crowns of the rings will be shapedby the piston to exactly fit the periphery thereof uniformly and providea tight working seal between the piston and cylinder throughout the periphery of the piston for retaining the explosive charge above the piston in the firing chamber of the cylinder. Tests have shown that the compression pressure is high for any given volume of firing chamber.

It is to be understood that the-rings Is, as initially formed, arenot so pronounced as to block the movement of the piston when initially inserted in the cylinder and it is not intended that Figure 3 of the drawing shall be so construed. As a matter of actual practice, the piston is machined and thecy linder is bored to receive the piston with a close working fit. However, as .compared with standard practice, the bore of the cylinder is a little larger and the diameter of the piston is a little smaller, either or both, while standard tolerances are preserved. Thus, all pistons will fit all cylinders while, however, perceptible looseness in the fit between the parts is not present.

It will accordingly be realized that in initially forming the rings l6, itis only necessary to make them high enough, or as may perhaps be more accurately stated, of a minimum innerdiameter sufiicient to take up or compensate for the. extra clearance provided between piston andcylinder, plus a slight additional height to present a wear surface to the piston. At best, therefore, the maximum initial height of the rings will be measured in terms of ten-thousandths of an inch but as it is impossible to show such minute differentiations on the drawing, Figures 2, 3, 4 and have been greatly enlarged and exaggerated to present amoregraphic showing. When initially installed, the piston may be said to. fit the rings extremely tight, as suggested in Figure 3. After the engine isbroken in,the.pistonmaybesaidtofitthe rings.-

tight, as suggested in Figure 5. As will be observed, the crowns of the rings have been shaped by the piston to fit the piston uniformly.

As previously indicated, experience gained in manufacturing engines of the present disclosure has shown that, under the usual clearance in the fit between piston and cylinder, all pistons will not fit all cylinders, even though all pistons are machined the same and all cylinders are bored 10 by a tool on the same spindle. An uncontrollable variation in the exact size of the two parts seems to be inherent. Thus, therefore, it has been necessary heretofore tomatch a particular piston with aparticular cylinder, which manual operation involves loss-of time and consequent increased expense, or else resort to the expedient of lapping the cylinder. However, the operation of lapping so small a cylinder has proven of greater expense than the whole cost of manufacturing the engine otherwise. I have accordingly evolved the use of a, greater clearance in the fit between pistonand cylinder, to eliminate matching, and the provision of the rings it to, eliminate expensive ringson, the piston and still provide an effective working seal between piston and cylinder.

As will be appreciated, engines of thepresent character are not especially designed for long life, to use the popular term. Toy boats not infrequently capsize, toy automobiles travel fast and upset or are wrecked, and toy aeroplanes are oftenv lost or are not infrequently smashed in landing. Thus, the working seal providedbetween thepise ton and cylinder in the present instance has been found entirely adequate in duration. However, f experiment has shown that the same seal may be. employed in repairing large sized motors, -such as automobile motors for instance. It has been found that as the piston reciprocates across the rings id, as initially formed, the mutilation of. the rings is very fast. It has also been found, however, that after the rings have been shapeddown to the exact contour of the periphery of the piston, appreciable mutilation'of the rings ceases, after which the rings will function, subject to average wear such as experienced in connection with usual piston rings, ,to provide a prolonged, effec: tive seal between the piston and cylinder.

The advantage of the construction in this connection will, therefore, be at once apparent. Assume that a piston has been worn out-of-round andthat the cylinder is indented to provide the rings [6. When, under such conditions, the engine is broken in anew, the out-of-round piston will mutilate the rings only to the out-of-round contour of the piston to ultimately provide a tight, uniform working seal throughout the-periphery of the piston. The necessity and expense of reboring the cylinder and installing'new pistons will thus be obviated. v

Having thus described my invention, what I claim is: p

1. In an internal combustion engine, the combination of a cylinder having its wall indented externally to form therefrom a'permanent internal, ring on said wall jutting into the cylinder and shaped to provide a convex surface at; its inner periphery, and'a pistonassembled withtlie-cyl-i inder' to reciprocate therein as a component part, of the engineand being ofgadiameter reater: than the inner diameter of said ring, the piston. being moveable as the engine isbroken in to mutilate and re-shape the convex surfacenf 'said ring to conform to the individual peripheralgsurface, contour; of the piston and; form. a working: seal; between thepistonand-cylinder; I

2. The method of producing a working seal between a cylinder and coacting piston of an engine which includes the steps of tooling the cylinder externally to indent the wall thereof and form therefrom a permanent internal ring on said wall jutting at its inner peripheral surface into the cylinder, forming the piston to mate with said cylinder but without correction in the peripheral contour thereof to fit the cylinder, and mutilating the inner peripheral surface of said ring by the piston to conform to the individual peripheral shape of said piston and form a working seal between the piston and cylinder as the engine is broken in.

3. In an internal combustion engine, the combination of a cylinder and ringless piston reciprocal in the cylinder, the cylinder having a bore slightly oversize for the piston to provide clearance aifording free movement of the piston in the cylinder and the parts both being of aluminum to afford similar expansion of the material and preserve the free movement of the piston when the parts are hot as well as prevent rubbing of the piston against the cylinder wall, and a ring integral with the cylinder projecting into said bore to coact with the piston and formed by a displaced portion of the cylinder wall extending into said bore, said ring being initially of a height equal to said clearance plus a slight additional height providing excess thickness projecting into the path of the upper end of the piston, whereby upon the initial upward movement of the piston the upper end thereof will out through the excess thickness of said ring and stamp the inner periphery thereof to the exact peripheral shape of the piston fitting the piston uninterruptedly throughout the circumference thereof to form an unbroken working seal between the piston and cylinder.

4. The method of producing a working seal between an aluminum piston and cylinder which includes forming the bore of the cylinder oversize to provide excess clearance for the piston and prevent rubbing of the piston against the cylinder wall when the parts are hot, bending the wall of the cylinder inwardly to produce an internal ring projecting at its inner peripheral margin slightly into the path of the upper end of the piston, and stamping the inner peripheral margin of said ring by the upper end of the piston to fit the individual shape of the piston throughout the circumference thereof when the piston is initially moved upwardly in the cylinder.

JUDSON WILLIAMS.

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