US1852602A - Piston for internal combustion engines and the like - Google Patents

Description

April 1932- H M. BRAMBERRY 1,352,602

PISTON FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Filed Sept. 20, 1930 5 orcfrr E7177 firaiizeri 10 5 M mim q g y I Patented Apr. 5, 1932 UNITED STATES PATENT OFFICE I HARRY ML'IBRAMBERRY, OF NEWCASTLE, IN'DIANA, ASSIGNOR TO THE PERFECT CIRCLE COMPANY, OFHAGERSTOWN, INDIANA, A CORPORATION OF INDIANA PISTON FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Application filed September 20, 1980. Serial No. 483,186.

This invention relates to pistons for internal combustion engines and the like.

The principal object of the inventlon is to providea-piston which is especially designed to maintain an eflicient and uniform clearance between the skirt portion and the cylinder wall throughout the entire operating temperature range of the engine. More particularly, 'provlde a piston in WlllCh' there is approximately ideal functional coordination between the head and the skirt so that the higher thermal expansion of the head will not distort. or change the shape of the skirt under operatin conditions and the most eflicient clearance getween the skirt and cylinder is uniformly maintained to obtain lmproved oil control and eliminate piston slap, blow-by, excessive friction scoring and 8XC8S1V6. wear.

More specifically my invention is an 1mrovement on the so-called Nelson Invargtrut aluminum piston which is now inextensive commercial use and is of the type illustrated in the Nelson Patents Nos. ,1,681,-

621 and 1,7 31,904.

Further objects and advantages of my 1nvention will appear from the followmg description taken in connection with the accompanying drawings in which;

Fig, 1 is a side elevation of a piston embodying my invention; 7

Fig. 2 is a side elevation taken at 9 0 to Fig. 1 and showing the piston partly in section ason the line 22 of Fig. 1;

Fig. 3 is a bottom plan view of my plston;

Fig. 4 is a vertical section taken on the line 4-4 of Fig. 2;

Fig.5 is a reduced side elevatlon of a Nelson Invar-Strut piston and Fig. 6 is a reduced side elevation of the Nelson piston taken at 90 to Fig. 1 and showing the piston partially in section as on the line 6-6 of Fig. 5.

Referring first to Figs. 5 and 6, the Nelson Invar-Strut piston which is formed of an aluminum alloy comprises a head 7, a skirt 8 consisting of cross-head slippers 9 and a lower circular guide and oil control portion 10, webs 11 depending from the head, provided with piston pin bosses 12 and rlgidly connected below the bosses directly to the circular portion 10 by integral portions 13, and Invar-Struts 14 which extend transversely of the webs 11 and connect or tie the adjacent sldes of the slippers 9 to the webs 11. The upper ends of the cross-head slippers 9 are separated from the lower edge of the head by circumferential slots 16. The skirt is provided with the vertical slot 17 extending upwardly from the lower edge thereof to near the upper end of one of the cross-head slippers.

With the Nelson piston, as just described, the diameter across the cross-head slippers 9, is fitted to the cylinder with very close clearance, since the normal expansion of aluminurn as the temperature increases, during operation of the engine, is compensated for by the Invar-Struts 14, which are formed of material, such as steel, which is relatively inexpansible as compared with the aluminum alloy. The lower circular portion 10 of the skirt, however, is permitted to expand at the normal rate of aluminum alloy, as this portion is below the Invar-Struts and not materially affected thereby. As the lower ends of the webs 11 are directly and rigidly connected to the circular portion 10 on opposite sides, it will he manifest that as the head expands the outward movement of the webs in opposite directions, expands and distorts the circular position; the expansion of the head being greater than the normal expansion of the skirt because of the greater temperatures to which the head is subject. The additional expansion of the skirt, due to the expansion of the head must be compensated for by the vertical slot 17. The circular portion 10 of the skirt is ordinarily fitted with a closer clearance than advisable in order that the piston will not slap whenthe engine is cold and to obtain better oil control.

' This close fit, however, results in high friction especially under maximum power and high speed conditions, due largely to the distortion of the skirt portion 10 by the ex- 1 tendant defects in operation. The long slot 17 reduces the strength of the cross-head slipper into which the slot extends to an extent insuflicient to withstand the outward move ment of the webs 11 and-the InvarStruts,

so that the slippers tend to flatten out and their diameter at the slot 17 is reduced. This together with the distortion of the circular portion 10 due to the expansion of the head causes high pressure areas, indicated by the dotted lines 18 and 19 in Fig. 5. As thesepressure areas wear the piston becomes loose in the cylinder which results in poor oil control, piston rocking, etc. Fitting the piston still more snugly cannot be-employed satisfactorily to overcome this defect, since scoring would result.

I overcome the above mentioned disadvantages by theimprovement embodying my invention which I will now describe in connection with Figs. 1 to 4. I have used in these figures, as far as applicable, the same reference numerals employed in the above description to designate corresponding parts, and therefore it will be but necessary now to describe in detail the features of my invention.

It will be observed that the heads, skirts, webs and bosses of the two pistons are very similar in general design, the two most es-v sential difl'erences being that the lower ends of the webs 11 in my piston are integrally connected to flexible arcuate cross struts 20 instead of being directly connected to the upper edges of the circular section 10 as in the Nelson p1ston,'and the slot 17 in my piston is relativel short compared with Nel-L sons long slot 1 I also prefer to strengthen the upper ends of'the slippers 9 by providing internal ridges 22 (Fig. 4) The struts 20, which are cast integra with the piston are oppositely curved and preferably, though not necessarily, the radius of each is larger than that of the piston. They extend transversely of the bosses and are preferably connected at their ends only to the circular portion 10.

The radius struts 20 operate at a slightly higher temperature and expand linearly to a greater degree than the skirt section 10, since the struts 20 are connected to the webs I 11 to which heat is transmitted from the high temperature head. As the head expands the accompanyin outward movements of the webs 11, axia (lay of the piston pin, are taken up by the ra ius struts 20 without being transmitted to the lower skirt portion '10 due to the flexing and linear 'ex ansion o the radius struts 20. As a resu t the mechanical distortion of the circular portion of the skirt by reason of the thermal expansion of the head is practically liminated. The slot 17 may thus be made relatively short so that the portion of the cross-head slipper above the slot, is relatively stronger and rocking of the piston is ehminated. Since the struts 20 support the circular portion 10, the cross-head Way, they strengthen the skirt where the slot 17 tends to weaken it.

It is anifest that since the lower skirt portion of my piston is not distorted by the high expansion of the head and this lower portion and the cross-head slipper, receiving the slot 17, are made relatively stronger, the

.skirt may have a close and uniform clearanoe throughout the operating range resulting in minimum friction, absence of piston slap, excellent oil control and long life. The

pressure and clearance being .umform; the lower ortion of the skirt properly meters the oil Elm to the usual oil control ring which is highly desirable.

If desirable, two slots 17, diametrically positioned may be provided in which case the slot-length in still furtherreduced and they do not extend up so far into the respective cross-head slippers.

I claim:

1. A piston having a head, a skirt oomprisin a lower circular portion and crosshead s ippers separated from the head webs depending from the head and provided with piston pin bosses between said cross-head slippers, and cross struts connected at their opposite ends to the circular ortion and connected to the lower ends of t e respective webs, the struts bein curved outwardly from their ends towar the adjacent surface of .the lower circular portion and of greater radius than that of the piston and the sln'rt being provided with a slot extending from its lower edge part way into one of said cross-head slippers. 7

2. A piston having a head, a skirt comprising a lower circular portion and crosshead s ippers separated from the head webs depending from the head and provided with piston pin bosses between said cross-head slippers, flexible arcuate cross struts within and connected at their ends to the circular portion and connected to the lower ends of said webs, the skirt being provided with a slot extending from its lower edge into one of said cross-head slippers, and relativel inexpansible cross struts between the we s and the cross-head slippers on each side of thepiston.

3. A piston having a head, a skirt comprising a lower circular portion and upwardly extending cross-head slippers separated at their upper ends from the head, the skirt being provided with a slot extending from its lower edge into one of said cross-head slippers, webs depending from said head and spaced from said skirt, piston in bosses on said webs, outwardly curved exible struts having a radius greater than that of the piston and having their ends integral with the circular portion, the distance between the adjacent ends of the struts being less than the length of the struts, and the struts beifi formed to compensate for the movement the webs due to the ex ansion of the head so that the skirt is not istorted by such expension, and relatively inexpansible crossstruts connecting each web with the adjacent sides of the cross-head slippers.

In testimony whereof, I have subscribed my name.

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