US2358271A

US2358271A - Cylinder and piston and method of producing a working seal therebetween

Info

Publication number: US2358271A
Application number: US429914A
Authority: US
Inventors: Williams Judson
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-02-07
Filing date: 1942-02-07
Publication date: 1944-09-12
Anticipated expiration: 1961-09-12

Description

J. WILLIAMS 2,358,271 STON AND METHOD OF PRODUCING 7 Sept. 12, 1944.

CYLINDER AND PI WORKING SEALS THEREBET-WEEN Filed Feb. 7,

j showing a miniature engine embodying the .presentimprovements; u j

Patented Sept. 12, 1944 CYLINDER AND -PISTON AND METHOD OF PRODUCING A WORKING SEAL THERE- BETWEEN Judson Williams, Philadelphia, Pa. Application February '7, 1942, Serial No. 429,914 2 Claims. (chaos-20 This invention relates to an improved cylinder and piston and method of producing a working seal therebetween, being more particularly con cerned with certain improvements and developments arising out of the practice of the invention disclosed in my copending'application' filed May 9, 1941, Serial No. 392,796 and bearing the same title.

Under the disclosure in my copending application above identified, the cylinder is first indented externally to provide one or more internal rings on the cylinder wall, when the piston is used to broach said rings to form a working seal with the piston. It has been discovered, however, that a working seal may be provided between the piston and cylinder without first indenting the cylinder wall.

An object of the presentinvention, therefore, is to provide a working seal between the piston and cylinder without the use of rings on the piston and without indenting the cylinder wall to form rings. p

A further object of the invention is to provide a construction wherein the cylinder wall will ;be formed by the piston with an annular, burnished" area to coact with the piston and provide a working seal therewith, and wherein said area will be of a width substantially equal to the stroke of the piston so that the workingseal betweenpiston and cylinder will be continuous throughout the stroke of the piston. I

Another object of the invention is to provide a construction wherein the piston will be em ployed to firstbroach the cylinder wall at the provide a distinctly defined, circular shearing edge at the upper end of the piston so that the piston will adequately serve as a broach for shaping the cylinder wall to the contour of the piston.

Other and incidental objects of the invention will appearduring the course of the following description, and. in the drawing:

Figure 1 is a transverse vertical sectional view parts as are pertinent.

Figure 2 is an'enlarged vertical section showing the cylinder before being broached.

Figure 3 is an enlarged fragmentary section showing the piston near bottom center and on the up-stroke. 1

Figure 4 is a view similar to Figure 3 but showing the piston further up in the cylinder. Figure 5 is an enlarged fragmentary section showing the burnished sealing area formed by thepis ton. a 7

Referring now more particularly to the drawing, it will be seen that I have shown the present improvements in conjunction with a miniature motor as used upon miniature aeroplanes, miniature motor boats and miniature automobiles as well as for miniature power units, as said imlarger size, such as automobile engines, as well as other adaptations, such as the injector pumps of Diesel engines and, accordingly, all such variations are to be" considered within the spirit and scope of the invention.

As the construction and operation of the engine as a whole is unnecessary to an understanding of the present invention, 1 have shown only such The engine is of twocycle design and includes a cylinder H) and crank case I l.

' on therear end of which is a disk !2 carrying a crank pin [3, and reciprocable'in the cylinder is a piston l4 having a wrist pin l5 journaling a connecting rod l6 engaged with the crank pin l3. At the upper endof the cylinder is an appropriate firing chamber H.

The cylinder IE! is preferably of a suitable aluminum alloy as is also the piston it. Other suitable materialsmay be employed but it has been found important, however; that the piston and cylinder have the same coeiiioient of expansion. For this reason, the piston should be of the same 7 aluminum alloy as the cylinder, or other material peripheral oil grooves l 8. In the present instance,

I have shown a' groove above and a groove below,

As particularly chosen. As will be observed, the piston is without rings but maybe provided with one or more the wrist pin I 5.

drawing, the wall of the cylinder ill is initially thicker towardthe upper"endofthe cylinder so j that, internallyythe cylinder is more or less-of I The crank case journals a crank shaft. 7

brought out in-Figure 2 of-the 1 the periphery of the firing, chamber 11.

Formed within the cylinder Iii at its upper end is a counterbored wall-surface 19. See Figures 3, 4 and 5 of the drawing. After being fashioned with a tapered bore, the upper end portion of the cylinder is, as seen in Figures 1, 3, 4 and 5 of the drawing, then preferably machined internally to define the wall surface l9 which forms Thus, the wall of the firing chamber is straight so that the volume of said chamber will not be reduced by the original taper of the cylinder bore. If deemed necessary, the counterbored firing chamber may in the finished engine be slightly larger in diameter than the bore of the cylinder at the lower limit of said chamber or the chamber may be so formed as to be of the same diameter as the bore of the cylinder after being broached by the piston, as will be later explained.

At the lower end portion of the cylinder, the bore thereof may, as suggested in Figure 2, be

' more or less uniform to' initially receive the pissembled with any one cylinder without the necessity of matching, as it has been found extremely difucult, in making pistons and cylinders of miniature engines, to fashion the parts of exactly uniform size. a r a As compared wtih the wall of the cylinder 10, the piston I4 is hardened in anypreferred manner so that as the engine is broken in, the piston will effectively provide a broach for shaping said wall. "he piston is of substantially uniform diameter from end to end and the peripheral surface thereof is smooth while the piston is machined so that the upper end thereof or, at least, the peripheral margin of the upper end of the piston is square with said surface; A distinctly defined, circular shearing edge is thus provided at the upper end of the piston for initially broaching the cylinder wall. 7

It is to be understood that Figures 2, 3, 4 and 5 of the drawing have been greatly exaggerated and it is not intended that the showing shall creis but one way of initially forming the cylinder; If preferred, the lower end portion of the cylinder may be of one uniform internal diameter to receive the piston [4 with a close working fit, and the upper. end portion of the cylinder of a -slightly smaller initial, internal diameter, the

junction between the two being. gradually merged.

7 As thepiston is to act as a broach while the engine is being broken in,the lower end porjtion of the bore of the cylinder must, of course, be

- fashioned to a'close working fit with the piston" expensive.

in order that the piston may be initially installed. However, in any event, it is intended that the internal contour of the wall of the cylinder will initiallybe such that said wall will be broached by the piston, as the engine is broken in, for substantially the full length of the stroke of the piston.

Assuming now that the piston [4 has been initially installed in the cylinder l0 and the engine is to be broken in, it has been found that this may be accomplished by operating the engine under its own power. As the piston moves upwardly inthe cylinder, the shearing edge 20 of the piston will function to broach the wall of the cylinder tothe exact peripheral contour of the piston sothat, after a very short time, the piston will reciprocate without broaching effect and the engine will operate freely. The period of time required to break in the engine has been found to be'very short, after which the broaching effect of the piston on the cylinder wall ceases and said wall is subjected by the piston only to a burnishing action. t

Figure 3 of the drawing shows the piston I 4 near the beginning of its upward stroke while Figure 4 shows the piston further up in the cylinder. As will be appreciated, the piston will, as the engine is broken in, broach the cylinder wall substantially throughout the full stroke of the piston, after'which the broached band will be burnished by the piston to provide, as seen in Figure 5, a highly polished, annular sealing area 2| to coact with the piston and provide a working seal therewith.

It is to be noted that since the cylinder wall is broached by the 'piston, the sealing area 2| will exactly conform to the contour of the piston throughout the periphery thereof so that a working seal between piston and cylinder will be provided throughout the circumference of the piston. As is well known,-such a circle-seal may not be completely gained by the use of piston rings and, moreover, since in the present instance the use of rings on the piston is eliminated, the frictional drag of such rings is avoided. Fmthermore, it is to be noted that the sealingsurface 2| will exert no resilient, gripping drag on the piston or, at least, no appreciable drag in any way comparable to the drag exerted by resilient rings eitheron the piston or on the cylinder wall. This factor has been found of great'gain in a miniature engine while, also, the necessity for lapping the cylinder and piston is avoided.

Experience in the manufacture'of miniature engines hasshown that it is difiicult to produce such small pistons exactly round and maintain low-cost production. Also, the'small rings required for such a piston have been found to be However,-by utilizing the piston to broach the cylinder wall, the sealing surface 2| will fit the piston even though the piston may be slightly out-of-round while, also, a more effective working seal :will be had between piston and cylinder than if rings were employed on the piston. In adapting the invention to Diesel injector pumps, however, or in other similar adaptations, it may be necessary to fashion the piston exactly round as, for certain of the pumps noted,.the piston must be rotated as well as reciprocated while, also, the circle-seal between piston and cylinder must still be maintained.

bination of a cylinder having a'roughly finished V bore the lower end portion of which is of uniform diameter and the upper end portion of which is tapered toward the upper end of the cylinder,

and a piston reciprocal in said cylinder to form a working part of the engine and of uniform diameter to freely fit in the lower end portion of said bore, the piston having an individual rough- 1y finished peripheral contour untreated to match the lower end portion of the bore of the cylinder t 2. The method of forming a working seal between a cylinder and coacting piston unfinished to match each other which includes the steps of forming the bore of the cylinder straight at its lower end portion and tapered at its upper end portion toward the upper end of the cylinder,

forming the piston with a roughly finished in-V dividual peripheral contour to freely fit in the straight portion of said bore, treating the piston to render the same harder than the material of the cyliridenfinishing the upper end of the piston to define a hardened peripheral cutting edge, and cutting the tapered portion-0f the bore of said cylinder by said" edge as the engine is broken in to the exact roughly finished peripheral contour of the piston and establishing a close-fitting working seal between the piston and cylinder.

i JUDSON WILLIAMS.