US2802707A - Piston - Google Patents

Description

Aug. 13, 1957 5, DAY 2,802,707

PISTON Filed Aug. 10, 1954 2 Sheets-Sheet l N INVENTOR.

Aug. 13, 5 Y PISTON Filed Aug. 10 1954 2 Sheets-Sheet z v INVENTOR.

United States Patent 7' PISTON Ray E. Day, Grosse Pointe Park, Mich.

Application August 10, 1954, Serial No. 448,933

10 Claims. (Cl. 309-12) This invention relates to pistons for internal combustion engines and particularly, although not exclusively, to pistons which may be formed from aluminum alloys.

An important object of the present invention is to provide a flexible skirt piston having skirt or slipper sections separated from the piston head and flexibly joined in such improved manner to the piston pin bosses as to afford substantially uniform pressure and bearing engagement throughout the skirt bearing areas, reduce skirt friction and avoid any appreciable scoring at the localities of the upper and lower edges of the skirt sections.

Heretofore, in the solution of problems encountered in connection .with the use of flexible skirt pistons, efforts have been directed principally toward constructing the piston so that the skirt sections will yield sufliciently to compensate for expansion conditions and avoid seizing while at the same time rendering the skirt sections stiff enough to withstand the side thrusts imposed by the motion of the connecting rod. Various methods have been employed to deal with the problem of undue skirt friction under various operating conditions. Cam grinding the skirt to oval shape is commonly employed with the view to enabling the skirt bearing surfaces to progressively conform to the shape of the cylinder wall consequent to thermal expansion of the skirt.

I have found that optimum piston operation without undue friction at localized areas of the skirt or undesirable distortion of the skirt consequent to loads imposed thereon generally is not achieved by a compromise between skirt stiffness and flexibility, or by cam grinding the skirt to oval shape, with the, view to minimizing seizing under expansion conditions While at the same time introducing suflicient stiffness into the skirt to withstand loads imposed by connecting rod side thrust. I have found that in high speed engines the pistons are subjected to such severe rocking forces that as a result thereof problems are encountered which are as serious or more so than the problems incident to connecting rod side thrust. These rocking forces, which develop during high speed engine operation, are concentrated largely at the localities of the top and bottom of the skirt and it is important that they be compensaed for without, however, undesirably affecting the flexibility factor of the piston predetermined for efficient control of side thrust forces. If, however, in attempting to compensate for rocking forces the skirt of the piston is made stiff enough to withstand these forces then frequentlythis results in the skirt being stiffer than necessaryto compensate for side thrust forces, resulting in creating excessive friction between the skirt and cylinder wall.

The present invention has for one of its chief purposes the. provision of a flexible skirt or slipper type piston supported from the piston pin bosses in improved manner so as to effectively resist rocking forces directed at the top, and bottom of'the skirt yet capable of withstanding side thrust forces with less skirt friction and with a minimum of skirtdistortion. lustrated embodiment of the invention the skirt or slipper In accordance with the il- 2,802,707 Patented Aug. 13, 1957 ice sections are separated from each other and from the piston head and each skirt section is supported at opposite sides from the piston pin bosses by means of two pairs of reversely curved upper and lower struts in the nature of spring bows which are capable of yielding to the desired degree when the skirt sections are subjected to cylinder wall pressures. The upper strut of each pair is joined to the outer edge of the skirt section at the upper end thereof and extends therefrom angularly and downwardly so as to join the outer edge of the piston pin boss ata locality well below the top of the skirt. The lower strut of each pair extends from the boss support laterally and joins the skirt at the lower end thereof. The upper and lower struts at each side of the skirt section are separated over the major length thereof so that as a consequence each skirt section is supported from the boss mainly at the 10- calities of the top and bottom thereof with the central portion of the skirt between the struts virtually unsupported from the boss. The upper and lower struts at each side of each skirt section are thus closer together in a vertical direction at the ends thereof joining the boss than at the ends thereof joining the skirt.

The foregoing construction achieves important advantages. The yieldable struts extending to the supper and lower ends of the skirt afford the requisite resistance to rocking forces while permitting suflicient yield to prevent scoring. The skirt area between the struts, even though unsupported from the boss, will hold its shape satisfactorily without distortion under side thrust loads. Less skirt friction results. The skirt sections may be finished round and will have substantially full bearing surfaces under all conditions of operation, whether cold or hot, thereby enhancing piston life and oil control and reducing piston slap.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

7 Fig. 1 is a side elevation of a piston embodying the present invention, this view being taken in the direction of one of the skirt sections.

Fig. 2 is also a side elevation of the piston shown in Fig. 1 looking in the direction of one of the piston pin bosses.

Fig. 3 is a vertical section taken substantially through lines 3-3 of Fig. 2 looking in the direction of the arrows.

Fig. 4 is a vertical section taken substantially through lines 44 of Fig. 1 looking in the direction of the arrows.

Fig. 5 is a bottom plan view of the piston taken in the direction of the arrow 5 in Fig. l.

Fig. 6 is a section taken substantially through lines 66 of Fig. 1 looking in the direction of the arrows.

Fig. 7 is a view generally similar to Fig. 2 but illustrating a modification.

Before explaining in detail the present invention it is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of parts illustrated in the accompanying drawings,.

bodying the present invention comprises an annular head 10 provided with ring grooves 11 for the reception of the customary piston rings. Depending integrally from the head 10 at opposite sides thereof are a pair of bosssupports or hanger members 12 carrying pin bosses or bearings 13. Each depending boss support 12 is reinforced or stiffened by means of an outer pair of downwardly converging ribs 14 and a central vertical rib 15. These ribs, as illustrated in Figs. 3 and 4, extend at their upper ends into the head and terminate at their lower ends substantially at the bosses 13.

The piston skirt in the present embodiments of the invention is shown, by way of example, as" comprising a pair of arcuate skirt sections" or thrust bearing slipper members 16. As illustrated in Figs. 1, 2 and 4 each skirt section 16 is separated from the head by means of a through slot 17, thereby providinga construction in which the skirt sections-are arranged at opposite sides of the bosses in separated relation to each other and to the head and, as a consequence; being supported only from the depending boss supports 12.

The supporting means for each skirt or slipper section 16 comprises an upper pair of spring-bow struts 1'8 and a similar lower pair of spring-bow struts 19. As illustrated in Figs. 5 and 6, the struts are reversely curved and in effect provide a goose neck construction. It will be seen that one end of eachupper strut 18 originates at the adjacent outer edge of the skirt section at the top or upper end thereof and at this locality the end of the strut lines at least in part above the boss. Each upper strut from this point of origin at'the top edge portion of the skirt angles or slants inwardly and downwardly toward the center of the boss support, as shown in Fig. 4; and at this locality the end of the strut integrally joins the boss support in an area well below the opposite upper end of the strut. From this construction it will be seen that the opposed skirt sections are joined at each side to one of the bosses by means of downwardly converging struts 18 which join the edges of the skirt sections at the extreme upper ends thereof. The upper struts 18 for each skirt section, as particularly shown in Fig. 6, comprise similar inwardly curving and converging relatively short portions 18a extending from the opposite edges of the skirt section. These struts also comprise outwardly directly relatively long diverging portions 18b joined at their ends to the bosses. The reversely curved portions 18a and 18b of each upper strut are joined by means of a curved bend or bowed portion 180 which is preferably disposed substantially opposite the inner end of the adjacent piston pin boss. The lower struts 19 are substantially similar to the upper struts 18 in longitudinal section. Thus, as shown in Fig. 5 the lower struts for each skirt section have inwardly converging relatively short portions 19a joined to the opposite edges of the skirt section and outwardly directed longer diverging portions 1912 joined at their ends to the piston pin bosses. The portions 19a and 19b of each lower strut are joined by a curved bend or bowed portion 19c.

As illustrated in Figs. 2, 3 and 4 it will be observed that one end of each lower strut 19 originates at the outer edge of the skirt section close to the bottom or lower end thereof and at this locality the end of the strut preferably lies entirely below the bosses. The strut 19 from this point of origin at the lower end of the skirt angles or slants inwardly and upwardly toward the boss support and at this locality the end of the strut 19 integrally joins the lower end 12a of the boss support below the boss. Thus, in the embodiment of Figs. 1 to 6 inclusive the lower struts 19 at each side of the bosses are angularly disposed in an upwardly converging manner and support the lower ends of the skirt sections from the boss supports. On the other hand, the upper struts 18 at each side of the bosses support the upper ends of the skirt sections at points well below the head as well as the upper ends of the skirt sections.

The upper struts 18 are separated from the head as well as the boss supports 12 by means of angularly related downwardly converging slots 20. Also it will be seen that the struts 18 and 19 of each pair are separated throughout their major length by means of relatively 1 large openings 21 which are produced during the casting operation.

In the embodiment illustrated in Fig. 7 the construction of the piston is substantially the same as that shown in Figs. 1 to 6 inclusive excepting that the lower struts extend substantially horizontally from the lower ends of extended boss supports 12b. In this embodiment, however, the lower struts 190 are joined to the lower ends of the skirt sections in the same manner as the previous embodiment. The struts 190 are substantially the same in longitudinal section as the struts 19 and are separated from the upper struts 18 by means of relatively large openings 210.

In the operation of the. present piston it is important to note that by joining the skirt sections to the bosses by means of the upper and lower yieldable bowed struts 18 and 19 effective resistance to rocking forces, concentrated principally at the upper and lower edges of the skirt sections, is achieved. The areas of the skirt sections between the struts, which are free of direct support from the bosses, will satisfactorily hold their shape and will not appreciably distort under side thrust loads. The slanting or angling of the upper struts to points well down on the boss supports achieves a further important advantage in that less heat is transferred from the piston head by way of the boss supports to the upper struts thereby reducing thermal expansion. of the skirt sections.

I claim:

1. A piston comprising a head, a pair of opposite boss carrying supports. depending from the head, a pair of opposed skirt sections separated from each other and from said head, and. strut means supporting the skirt sections from the boss supports at each side thereof and including a pair of struts each joined at one end to the upper end of a skirt section. and extending therefrom angularly and downwardly and joined at its opposite end to the adjacent boss support, said struts being reversely bent intermediate. their ends to form spring bows and the localities of juncture thereof with the boss supports being below the localities of juncture thereof with the skirt sections.

2. A piston comprising a head, a pair of opposite boss carrying supports depending from the head, a pair of opposed skirt sections separated from each other and from said head, and strut means supporting the skirt sections from the boss supports at each side thereof and including a pair of struts spaced inwardly from the bearing surfaces of the skirt sections, said struts extending from the upper edge portions of the skirt sections downwardly in converging relation and being joined to the outer edges of the boss supports.

3. A piston comprising a head, a pair ofv opposite boss carrying supports depending from the head, a pair of opposed skirt sections separated from each other and from said head, and strut means supporting the skirt sections from the boss supports at each side thereof and including a pair of struts, said struts being reversely bent intermediate their ends to form spring bows and joined at said ends to the outer edges of the adjacent skirt section and said boss supports, the upper and lower edges of each strut being inclined downwardly from the skirt section in the direction of the boss support.

4. A piston comprising a head, a pair of opposite boss carrying supports depending from the head, a pair of opposed skirt sections separated from each other and from said head, and strut means supporting each skirt section from the boss supports and including an upper pair of struts and a lower pair of struts, the struts of the upper pair being inclined upwardly in diverging relation from the boss supports to the upper end of the skirt section and the struts of the lower pair extending from the boss supports to the lower part ofv the skirtv section, the upper struts being spaced in a vertical direction from the lower struts.

5. A piston comprising a head, a pair of opposite boss carrying supports depending from the head, a pair of opposed skirt sections separated from each other and from said head, and strut means supporting each skirt section from the boss supports and including an upper pair of bowed struts and a lower pair of bowed struts, the struts of the upper pair being inclined upwardly in diverging relation from the boss supports to the upper end of the skirt section and the struts of the lower pair extending from the boss supports to the lower part of the skirt section, the upper struts being spaced in a vertical direction from the lower struts thereby providing an intermediate area of each skirt section free of connection with the bosses.

6. A piston comprising a head, a pair of opposite boss carrying supports depending from the head, a pair of opposed skirt sections separated from each other and from said head, and strut means supporting the skirt sections from the boss supports at each side thereof and including an upper pair of struts and a lower pair of struts, the struts of each upper pair being inclined upwardly in diverging relation from the boss supports to the upper end of the skirt section and the struts of each lower pair extending from the boss supports in a downwardly inclined direction to the lower part of the skirt section, the upper struts being spaced from the lower struts between their junctures with the skirt sections.

7. A piston comprising a head, a pair of opposite boss carrying supports depending from the head, a pair of opposed skirt sections separated from each other and from said head, and strut means supporting the skirt sections from the boss supports at each side thereof and including an upper pair of struts and a lower pair of struts, the struts of each upper pair being inclined upwardly in diverging relation from the boss supports to the upper end of the skirt section and the struts of each lower pair extending from the boss supports to the lower part of the skirt section, the upper inclined edges of the upper struts being spaced from the head and boss supports and the lower inclined edges of the upper struts being spaced in a vertical direction from the lower struts thereby providing unsupported areas of the skirt sections intermediate the pairs of struts.

8. A piston comprising a head, a pair of boss supports depending from opposite sides thereof, a pair of skirt sections separated from the head, an upper pair of bowed from the outer edges thereof upwardly in inclined manner and joined to the upper edge portions of a skirt section, and a lower pair of bowed struts at each side of the boss supports extending integrally from the outer edges thereof downwardly in inclined manner and joined to the lower part of the skirt section at localities spaced below the localities of juncture of the upper struts with the skirt section.

9. A piston comprising a head, a pair of boss supports depending from opposite sides thereof, a pair of skirt sections separated from the head, an upper pair of bowed struts at each side of the boss supports extending integrally from the outer edges thereof upwardly in inclined manner and joined to the upper edge portions of a skirt section, and a lower pair of bowed struts at each side of the boss supports extending integrally from the outer edges thereof and joined to the lower part of the skirt section at localities spaced below the localities of juncture of the upper struts with the skirt section.

10. A piston comprising a head, a pair of boss supports depending from opposite sides thereof, a pair of skirt sections separated from the head, an upper pair of bowed struts at each side of the boss supports extending integrally from the outer edges thereof upwardly in inclined manner and joined to the upper edge portions of a skirt section, and a lower pair of bowed struts at each side of the boss supports extending integrally from the outer edges thereof downwardly in inclined manner and joined to the lower part of the skirt section at localities spaced below the localities of juncture of the upper struts with the skirt sections, said skirt sections being unsupported from the boss supports in the areas intermediate the localities of juncture of the upper and lower struts therewith.

References Cited in the file of this patent UNITED STATES PATENTS 1,294,833 Ricardo Feb. 18, 1919 1,730,885 Hartog Oct. 8, 1929 1,774,396 Noble Aug. 26, 1930 2,032,849 Nelson Mar. 3, 1936 FOREIGN PATENTS 686,497 Germany Dec. 14, 1939

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