US1712591A - Piston for internal-combustion engines - Google Patents

Description

May 14, 1929. TAYLOR 1,712,591

PISTON FOR INTERNAL COMBUSTION ENGINES Filed Jan. 26, 1923 ff 5 ll 21gfig-24 WWW PATENT OFFICE;

, GEORGE A. TAYLOR, OF BOSTON, MASSACHUSETTS.

PISTON FOR INTERNAL-COMBUSTION ENGINES.

Application filed January 26, 1923. Serial No. 615,114.

My invention relates to pistons for internal combustion engines. The piston embodying my invention comprises a head and a skirt, cast in one piece, but separated from each other in part by circumferential slots, the skirt being rendered compressible and resilient by a vertical slot, and the whole being constructed and arranged as will be described. By the head is meant not only that portion of a one-piece or unitary piston which forms the upper end of the body, but also which has the grooves for the piston rings. The skirt is that portion of the piston below the head and is of generally cylindrical shape. i

As is well known to those skilled in the art, pistons for internal combustion engines, and particularly aluminum pistons, wear rapidly and when Worn permit oil to pass from the crank case to the combustion space of the cylinders Wear also causes loss of compression, loss of 'power, and noises known as slap. Furthermore, newpistons have always been --given a considerable clearance varying in amount about oneonethousandth of an inch for cast iron each inch of diameter, the amount depending upon the conditions under which the piston is to be used and the materials of which it and the cylinders are made. In general practice, about double the clearance is provided for aluminum pistons as for cast iron pistons,

owing to the higher coefficient of expansion of aluminumand its alloys, and therefore more (lifiiculty from loss of compression, oil pumping, and slapping has been experienced with aluminum pistons than with cast Iron pistons. Furthermore, aluminum wears more rapidly than cast iron, increasing the clearance on one side of ,the piston and accentuating the difiiculties.

The piston embodying my invention 1s made with a maximum normal diameter greater than that of the cylinder in which it is to be inserted and is believed to be the first piston which is made in this manner. In practice, I make the entire skirt compressible by slotting it, and grind, or otherwise form, the skirt with a taper, the greatest diameter being at the bottom and being greater than the diameter of the cylinder, while the least diameter of the skirt is at the junction of the skirt with the head and when cold is slightly less than the diameter of the cylinder. \Vhen the piston is forced into the cylinder, the skirt is compressed circumferentially and the lower edge contacts with the inside of the cylinder wall, leaving a clearance of increasing amount above the line of contact extending to the top of the skirt. This is the situation when the. parts are cold, but it will be understood that when hot, the exterior of the iston skirt and the interior of the cylinder con- .form more closely in size and she; e. The

result is that the piston, having w en cold only a small area of contact with the cylinder wears in rapidly, adapts itself quickly to the slight variations from a true circle, which always exist in the cylinder of an internal combustion engine, and soon forms a practically tight oi-nt therewith. In practice, the lower edge of the piston acts as an oil scraping edge. a

To produce a better contact with the cylinder walls, the skirt is partly severed from the. head by three circumferential slots intersected by longitudinal slots in the skirt, these slots forming I resilient areas or tongues. Between the circumferential slots are unsevered portions, two of which are located above the wrist pin bosses, forming an integral three-point connection between the head and skirt.

To improve the wearing qualities of the piston, particularly when the same is made of aluminum, I rovide around the bottom of the skirt an inlay of cast iron or other suitable material, which forms a wearing surface of the best possible character. I am aware that piston rings on the bottom of a piston have heretofore been used, but I believe myself to be the first to employ an inlay of cast iron or other suitable metal, that is, an area, the metal of which is practically integralwith the adjacent metal, but is of a different kind and has a surface which is flush with the remainder of the peripheral surface of the cylinder. A con venient method of producing such an inlay is to cut a groove in the surface of the iston, place therein a ring of cast iron or ot ier suitable metal, then drive the ring forcibly into the groove, and finally machine or grind the entire surface of the piston to render the adjacent surfaces flush with each other.

Other novel features of my invention will appear hereafter.

The invention will be fully understood from the following description when taken in connection with the accompanying drawings, and the novel features thereof will be pointed out and clearly defined in the claims at the close of this specification.

In the drawings:

Fig. 1- shows, in section, a portion of a cylinder having therein a piston, the piston being shown in elevation.

Fig. 2 is a view of the piston before the finishingcut is taken or the grinding operation performed. I

Fig. 3'is a similar view after the above operations have been performed.

Fig. 4 is a view showing the opposite side of the finished piston.

Fig. 5 is a section on line 55 of Fig. 3,

.the scale being reduced".

Referring now to the drawings, at A is shown a portion of the cylinder in which the piston is -tobe used. This is designed to be a true .cylinder, that is, is of uniform diameter throughout its entire length and conforms thereto as closely as the processes of manufacture will permit. The piston embodying my invention has a skirt B and head C WhlCh are integral, ring grooves being formed at D to receive piston rings E,

F and G. The lands H between the ring grooves do not contact with the cylinder wall being of a diameter less than that of the cylinder, and in this respect being ofthe well-known construction.

The skirt B is partly severed. from the head by a series of clrcumferential slots, three in number. One of these slots, 11, is located on the so-called compression side of the piston, that is, on the side opposite to that on which the reaction, due to the explosion, exerts pressure and extends-from one piston pin boss 12 to the other boss '13. This slot 11 is intercepted by'a substantially vertical slot 14, extending upward from the bottom of the skirt'and thereby renderingthe skirt compressible. On the explosion side of the piston are two circumferential slots 15 and 16 separated by an unsevered or integral portion 17. These two slots extend from the unsevered portion to points about adjacent the piston pin bosses 12 and 13. The head C is, therefore, connected to the skirt B at three points, which will clearly be seen in-Figure 5, in which they are designated respectively 17, 18 and 19. This construction supports the head firmly on the skirt so that there is ample strength to withstand the shock of the explosion and at the same time permits the skirt to be compressed circumferentially and to carry off the heat to which the head is subjected. All of the circumferential slots 11, 15 and 16. are preferably located in the bottom of the lower piston ring groove G. Surrounding each of the pin bosses 12 and 13 on the outside of the iston is a relieved area 30 which hasa slight y reduced diameter and does not contact with the cylinder wall.

Adjacent the edges of the relieved area on the explosion side of the piston are two substantially vertical closed end slots 20 and 21 whichintercept the circumferential slots 15 and 16. T1115 construction leaves two areas or tongues 22 which are relatively freely ielding, while the area below the unsevered ortion 17 is relatively unyielding andrigid The piston, therefore, has ample bearin surface on the explosion pressure side w ile, at the same time means is rovided 'by which the iston rapidly ad usts itself to the shape of the cylinder an the tendency to slap is reduced.

' In the referred form of my invention, I make the ody of the piston of aluminum and place near the bottom edge an inlay 24 of cast iron. In practice, I cut a groove in the peripheral surface of the skirt and then force into it a ring 24 of cast iron, which has been split to permit it to snap over the bottom of the iston. Thereafter, the rin is driven forcibly into the groove and wedged tightly therein by an suitable method, as, for instance, by ro ling. This secures the inlay in place permanently. Next I turn down and rind the surface both of the piston and 0% the ring so that the will be flush, and the inlay will form, to a l intents and purposes, a portion of the skirt in the piston. In practice, the slot 14 is not'sawn until after the surface of the skirt and the inlay has -been finished. While I have shown in the drawin s the inlay as in the shape of a ring force into a groove, I do not limit myself to this construction, since the inlay may be made of any desired shape and may be made of other suitable metals, as, for instance, of soft bronze or babbitt.

As previously stated, the skirt of the piston is tapered, the skirt bein larger at the bottom than it is adjacent tfie head. Furthermore, the bottom of the skirt is larger than the bore of the cylinder in which it is to be used, while the top of the skirt is smaller. For instance, the diameter at the bottom of the skirt, as indicated .in the drawings, may be .005 of an inch larger, while the top may be made .002 of an inch smaller than the cylinder in which it is to be used. It will be understood, of course, that the head is considerably smaller than the diameter of the cylinder and the piston 'is therefore insertable in the cylinder in the ordinary way. In ractice, the piston is driven or otherwise orced into the cylinder, and this compresses the skirt.

When in glace in the cylinder and the parts are col the bottom edge of the skirt rests against the cylinder wall, and there is a clearance of increasing amount all the way up the skirt to the head. Since the skirt is somewhat elastic and, theoretically I tween the piston and cylinder is very small. In practice also the two areas or tongues 22 spring outwardly and contact with the wall, serving to steady "the piston. When the parts are hot, as is the case in use, and the piston, constructed as described, is run in the bottom edge wears so that the area oi contact between the cylinder wall and the piston increases or widens and extends u wardly until it includes the surface of t e inlay wholly or in part. The rapidity'with which the bottom edge of the piston wears in produces a tight ]oint between the piston and cylinder immediately, and the piston adapts itself almost instantly to the variations from the cylindrical which always exist in engine cylinders.

I find in actual practice that pistons made as described are tight from the beginning and that engines fitted with new pistons, the cylinders having been worn somewhat out of round can be used at once without lapping in the piston.

While I have described herein the preferred embodiment of my invention as comprising an aluminum piston'having a cast iron inlay, it is to 'be noted thatQI do not.

limit myself tothe use ofthese particular materials except in so far as the materials are s ecificallyclaimed hereafter.

at I claim is- 1. A one-piece piston having a skirt :and piston pin bearings, said skirt having relieved areas surrounding said hearings to form segmental bearing portions between them and an annular bearing rtion below them at the lower end of the s "rt, the normal diameter of said annular portion being greater than that of said segmental portions, one of saidsegmental portions being slotted to render said skirt compressible, and the other of said segmental portions being sepa rated from said relieved areas.

2. A piston having adjacent the head a circumferential slot on the compression side and on the explosion pressure side two circumferential slots separated b an integral area connecting the skirt and ead.

3. A iston havin on the explosion ressure si e two resihent' areas forme by closed circumferential and longitudinal slots separated by an integral area connecting the skirt and head, said piston having on the compression side two resilient areas formed by a closed circumferential slot and a longitudinal slot extending to the edge of the skirt.

4. The unitary piston the skirt of which is separated from the head by slots, except at three points, two of which are located above the piston pin bosses and the third of which is on the explosion pressure side.

5. The unitary piston for internal combustion engines having an integral head and skirt separated from each other by. slots except at three points, two of said oints being over the piston in bosses and the third being on the exp osion pressure side of the piston, the explosion pressure side being relativel non-resilient and the oppositeside being re atively resilient. v

6. The improved piston for internal combustion engines com osed of a body of aluminum or an alloy t ereof and havin near the bottom a ring of cast iron inlaid 1n the peripheral surface and flush with it, the skirt of said piston being compressible and the diameter at the bottom being slightly greater than that of the cylinder in which 1t is to be used.

'7. A piston for internal combustion engines having a head and a skirt separated from said head except at three places two o fiwhich are over the re ective piston pin bearings and the third 0 which is on the explosion pressure side.

8. The improved piston for internal combustiomeng'ines, comprising a head and a skirt, said skirt being separated from the head except in three places, two of which I are over t e respective pin bearings and the third being midway circumferentially of the piston pin bearings.

In testimony whereof I afiix my signature.

GEORGE A. TAYLOR.

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