USRE16273E - A corpora - Google Patents

Description

R. M. HOWDESHELL PISTON FOR ENGINE CYLINDERS Feb. 23' 1926. Re. 16,273

Original FiledMay 22, 1920 2 Sheets-Sheet 1 I NVEN TOR Rouwn MJiowa'eanu l.

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Feb. 23 1926.

R. M. HOWDESHELL PISTON FOR ENGINE CYLINDERS Original Filed May 22, 1920 2 Sheets-Sheet 2 I N VEM 7 02 POL Mm M howozsasu ternal combustion engines.

Reissued Feb. 23. 1926.

.UNITED STATES 'nonann m'. nownEsnELL, or ELSBERRY,

- Re. 16,273 PATENT OFFICE.

MISSOURI, ASSIGNOR, IBY MESNE ASSIGN- MEN'IS, TO THE CLEVELAND TRUST CQMPANY, 0? CLEVELAND, OHIO, A CORPORA- men or 01110.

rrsron FOB ENG'Iim CYLINDERS.

Original in. 1,473,233, date November e, 1923, Serial No. 383,519, filed m '22, 920. Application mreissue filed August 20,

To all whom it may concern: Be it'known that I, ROLAND M. Home SHELL, a citizen of the .United States, formerly ofSt. Louis, Missouri, and now residing at Elsberry, Missouri, have invented certain new and useful Improvements in Pistons for Engine Cylinders, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part hereof.

The present invention is directed to improvements in piston construction, and particularly to pistons intended for use 111'111- One of the objects sought is to make use of pistons cast from aluminum or its alloys to secure-light ness, and at the same time secure a fit between the piston andwall's of the cylinder that will not only arrest or prevent sideslapping of the piston but will ensure against the passage of any oil. past the piston into the combustion chamber of the engine. As well understood in the art, aluminum (and its alloys) has a comparatively high coefficient of expansion, so that. an aluminum piston in an internal combustion engine must, when cold, fit with considerable looseness in the cylinder to allow for subsequent expansion by the heat of the gases to which the piston is exposed while the engine is running. When operating at a hightemperature .(as a result of high speed) the piston by reason of expansion may of course maintain proper contact with the walls of the cylinder; but when the tempera-' ture drops (as when running at low speed) the contraction of the piston allows so much clearance between it and the cylinder, walls as not only to cause side-slapping but at fere with the "free operationof the engine.

\Vith my improvement I not only avoid -sideslapping of the piston but ensure against the passage of oil into the combustion chamber under all working conditions by providing the piston with a. skirt so slit and with the sections between the slits so bonded or tied as to permit the skirt to yield circum- 1925. Serial No. 51,529.

ferentially while expandin radially under Y packing ringscarried thereby, against the walls of the cylinder. The improved piston contains further and other features, the advantages of which will be apparent from the following detailed description in connection with the accompanying drawings in which- Figure 1 represents a middle longitudinal section through the cylinder and crank-case ofan internal combustion engine, showing my invention appliedthereto; Fig. 2 is an elevation of the piston detached, looking a bottom plan of the p ston; Fig. 4-is' a middle longitudinal section on the'lin'e 4-4 of Fig. 3; Fig. 5 is a middle longitudinal sec-' rential toward the hollow wrist-pin boss; Fig. 3 1s one of the slits of the'skirtfFig. 9 is an inner face view of the bridge members spanning a slit of the skirt; Fig. 10 is a perspective showing the formation of the br dge members spanning'a slit of-the skirt; and Fig. 11 is a section-similar to Fig. 8 'showing a modified form of bridge member. the same time to permit a flow of oil past Referring to the drawings, and for the present to Figs. 1 to 10 inclusive, C, represents the cylinder, C, the crank-case, P, the piston-head, P, the skirt ofv the piston, R, the connecting rod coupling the iston to the crank-arms A of the crank s aft, the piston-head being equipped with' the usual complement of split metal piston rings 1 as well understood in the art. In the present embodiment of my invention the skirt P is slit in four places, the slits, 8, being open at both ends of the skirt and preferably inclined to the axis ofthe piston and alternately converging toward the piston'head and toward the free end of the skirt, the

walls of the slits being parallel, and inclined to the radius of the piston (Flg. As well understood in the art, the end of the -piston facing the combustion U amber E of the'engine is exposed to the greatest heat, and for this reason the head P is finished to a slightly smaller diameter than that of the skirt P, soas to leave the head free to expand toward the walls of the cylinder. In the prevailing constructions of pistons the greatest expansion would obviously be permanently confined to the end of the piston head adjacent the combustion chamber, the expansion progressively decreasing toward the skirt, the heat from the hottest endof the piston being conducted to the cooler portions farthest removed from the combustion chamber. It is obvious of course that until the entire piston was heated to an even temperature the greatest expansion would be at the end facing or nearest the combustion chamber. For this reason, and to allow for the initial increased expansion of the end of the piston facing said chamber, the piston head in prevailing forms of pistons must be finished with a slight taper toward the end coming in contact with the burning gases; otherwise, and unless a sufiicient clearance was allowed for between the cylinder walls and this end of the piston when cold, the increased expansion of the piston at this point of greatest heat would not only cause the piston to bind but would destroy the desired uniformity of expansion to which the piston head should be subjected, to pro-' duce an ideal piston. In my invention a substantially uniform expansion of the piston-head under working conditions 'is assured by preventing the heat imparted there to by the combustion gases from being conducted to the skirt, this ensuring a quick heating of the piston-head to an even temperature and hence efieeting an even exansion throughout. In the present emodiment of my, invention the assage of the heat from the piston-head to te skirt is prevented by a circumferential air gap, a, (or its equivalent) by means of which the skirt is spaced or insulated from the 'head,

the onl connection being by way of the webs or bri ge-pieces 2 leading from the hollow wrist-pin bosses 3, which span said gap at points diametrically o posite one another, the body ortions oft e webs clearing the inner' we s of both the piston head and skirt (Fig.' 5), the webs being connected to the end wall of the head by the stiffening ribs 419 shown. It is apparent that while some of the heat will be conducted from the headto the skirt through the webs 2, it willthe piston head by the air gap, a, with only.

two of the sections connected to the head by the webs 2, some provision must be made to hold the skirt sections together without impairing the resilience which the skirt must the piston and spanning the slits, s, the

arches spanning any slit being disposed about a common axis parallel to the axis of the piston, that is to say, arallel to 'the elements of the cylinder ormed by the peripheral walls of the pistons. The bridge memberstiare thinnest at the crown of the arch so as to be comparatively resilient or yielding, the said members allowing the skirt sections to yield circumferentially, and radially inward and outward, and causing the sections when expanding under the heat in the cylinder to adjust themselves circumferentially to the cylinder walls, the bridge members exercising a sort of control over the skirt sections and arresting the latter while expanding under the heat of the gases, against an undue radial expansion, and thereby preventing the cutting and scoring of the cylinder walls which would inevitably result were the skirt sections free to expand radially outward their full limit and without restraint. strain the skirt sections in that regard so that the skirt while resiliently hugging the cylinder walls to prevent side-slapping does not cut or score said walls. In ractice, the piston is cast sli htly oversize, that is to say, slightly larger t an the bore of the cylinder, after which the skirt is slit as indicated, thereby imparting to the skirt sections between the slits a resiliency which a skirt without the slits does not possess. After the skirt is slit, the sections are slightly sprung inward and held in this position by a suitable jig or band and the piston placed in a lathe and turned true and finished,

smooth on the outside; When the skirt is released, the parts spring outward so that when the piston is inserted into the cylinder the skirt hugs the walls thereof throughout its full len th with a resilient contact, preventing si e-slapping or knocking when in service. It will be observed that the walls of the skirt are considerably thinner than those of the piston head, this arrangement not onlyfensuring resiliency for the skirt, but permitting the larger mass of metal in the head to absorb the bulk oftheheat units communicated thereto by the gases, the gap,

a, intercepting the passage of this heat to the skirt.

Toprovide a slit or divided piston skirt which will resiliently engage the walls of the cylinder so as not only prevent sideslapping of the piston, but retard the flow of oil sufliciently to prevent undesirable quantities entering the combustion chamber, is the main object of the present invention in addition to employing a piston of light material for that purpose. I need falling within the purview of the skilled mechanic. From the foregoing it is apparent that it is not necessary to impart a taper to the piston-head, since, being subjected substantially to an even temperature and expansion throu hout when in service, its expension will e along theelements of a cylinder or along lines parallel to the elements of the inner walls of the cylinder in which the piston operates. The invention is of course not to be restricted in its applica-.

tion to any particular kind of engine; and while primarily designed for internal 'combustion engines it is not limited thereto. The heat non-conducting air gap, a, may of course have substituted therefor an equiva,

lent nonconductor of heat such as mineral wool, asbestos, and the like, or any material which will not cut the Walls of the cylinder. I do not wish to be limited to'the' number of slits in the skirt, the four slit-s here shown being merely by way of example. Features shown but not alluded to are well understood in the art and require no description in the present connectio I V Having described my invention what I claim is:

1 A piston of the class described including' a head comprising an end portion and wall portion, a sectional skirt portion, hood members connecting the sections of said skirt portion, and rib members integrally connecting the sections of the skirt with the end of the head member.

2. A piston structure comprising a head, a pair of opposed wrist pin bosses, ribs supporting the wrist pinbosses from the'head,

said ribs being disposed'in planes substantially parallel with the axis of the wrist, pin bosses, and a skirt structure formed of a plurality of sections capable of moving toward each other solely supported from the wrist pin bosses in the longitudinal zone of the wrist pin bosses, the upper marginal edge portion of the skirt structure being free and unattached to other portions of the piston in order that temperature distortions of v the head ma be transmitted to the skirt structure sole y through the wrist pin bosses. 3. A piston structure comprising a head, a'pair of wrist. pin bosses supported from the head by connectors including a plurality of ribs extending transversely'of the head and disposed in planes substantially, parallel to the axis of the wrist pin bosses, said ribs constituting a major reinforcement for said head extending generally in the direction of the axis of thewrist pin bosses, and a skirt structure comprising a plurality of resilient- 1y related sections supported solely from said-bosses and having no other connection with said head. x I 4. A one-piece piston comprisin a head, wrist pin bosses connected to sai head, a skirt structure embodying a plurality of sections capable of moving toward each other,-

and resilient connecting means between said sectionspf the skirt, said skirt structure being supported solely from said bosses.

5. A one-piece piston comprising a head, askirt structure formedof a plurality of resili'cntlyrelated. sections, said skirt structure being circumferentially separated from the head throughout its upper peripheral marginal edge, resilient bridges constituting the sole connecting means between the sections of the skirt structure, wrist pin bosses carried by oppositely positioned sections of the skirt structure and connecting means extending from the head to theboss and skirt structure in the zone of each wrist pin boss.

6. A piston comprising a head, a skirt structure having longitudinal slits, and resilient bridges spanning said slits over materially less than their entire length adapted to permit the circumferential contraction and expansion of the skirt throughout its length, said bridge members being of greatly reduced thickness at the, crown of the arch of the bridge andterminating in widely separated thickened base portions.

7. A piston comprising a head, a skirt structure connected thereto having a longitudinally arranged slit disposed in angular relation to the axis of the piston, an arched resilient bridge element spanning said slit to thereby resiliently connect adjacent setions of the skirt, the axis of said bridge element being parallel to the axis of the piston.

8. A' piston comprising a head, a skirt structure supported therefrom. having a longitudinally arranged slit'dis'pos'ed in angular relation to the axis of the piston, and

a plurality of spaced resilient bridge elements spanning the slit of the skirt to thereby resiliently connect adjacent" skirt parts,

said bridge elements being arranged in alignment with each other and in parallelrelation with the axisofthe piston.

9. A' piston comprising a head, a skirt structure having a slit therein and a resilient bridge spanning said slit, said bridge being adapted to control relative movement of the connected portions of the skirt structure, said bridge being of greatly reduced thickness at the crown of the arch of the bridge] and terminating in widely separated thickened base. portions.

a skirt connected thereto 10.-A piston structure com rising a head,

through its walls disposed in angular relation to the axis of the piston, an arched resilient bridge element spanning said slit to thereby resiliently connect adjacent sections'of the skirt, said bridge element beingof substantially uniform thickness and curvature between enlarged base portions, the

substantially that of the width of the arch.

13. A piston structure comprising a pair of movably related pa'rtsfand a flexible bridge connecting said parts having an arcuately formed flexible portion of sub stantially uniform thickness and uniform flexibility.

14. A piston structure. comprising mov ablv related portions separated by a slit,

and a resilient bridge spanning said slit and .yieldingly connecting said portions, said bridge having its base portions spaced :1

materially greater distance than'the width of saidslit.

15. In a piston having a' skirt of resilient material provided with a normally open space into and out of "which the portions of the skirt adjacent the opening may move when the piston, is expanded and contracted by heating and cooling and means to limit ,the movement of such portions to said spaceto maintain the shape of the skirt true to its design during heating and cooling, and a .head forsaid piston separated circumferentially from said skirt.

16. In a piston for an internal-combustion engine, the combination. of a cup-shaped head grooved on the outside for piston rings, a skirt divided into segments by openings extending through the walls of the skirt,

means located well within the walls of the skirt, and {extending part way only along saidopenings, connected at'itsends tothe aving a slit.

inner face of said walls on opposite sides of said openings and joining said wall segments together, said skirt segments being separated at all points about the periphery from said head by an opening extending through the walls of said skirt, connectors located well within the periphery of the skirt unitin certain of said segments and said head, an

wrist pin bosses connected to said connectors.

17. In a piston for-an internal combustion. engine, the combination ofla cup-shaped head grooved on the outside for piston rings, and a skirt divided into segments by openings extending through the walls of the skirt, bridge members located within the walls of the skirt and respectively connected at their ends to the inner face of said walls on opposite sides of said openings to join said wall segments. together, said skirt segments being separated from said head by an opening extending through the walls of saidskirt, connectors located well within the periphery of the skirt uniting said skirt segments and said head,- and wrist pin bosses connected to said connectors.

18. A piston structure comprising ahead, a pair of wrist pin bosses, a pair of bosscarrying webs depending from the head, each web being connected to a boss adjacent the innermost end of the boss, and a skirt structure comprising bodily movable bear.-

ing faces solely supported through relative lyyielding connections by the boss-carrying webs.

19. A piston structure comprising a cupshaped head grooved on the outside for pis 'ton rings, a pair ofwrist-pin bosses, means located well within the walls of the skirt connecting said wrist pinbosses vwith the head, a skirt structure having a bodily movable section carried by said wrist pin bosses, and connecting means disposed within the Y sidewalls of said skirt adapted to support said bodily movable skirt section from said bosses.

QO VA piston structure for an internal combustion engine, comprising a cup-shaped head having its side' wall grooved on the outside for piston rings, a pair of wrist pin bosses each connected to the head by an integrally formed segmental web which" extends inwardly'from the'side wall of saidcup-shaped head and then downwardly to the adjacent boss, a rib integrally formed with said cupshaped head in a plane transverse to said segmental webs extending downwardly from the inside ofsaid cupshapedheadand connected with the adjacent web, and a skirt structure having its upper marginal edge free and-unattached to other portions of the piston, said skirt structure embodying yieldingly related por-' tions connected inside the walls of 'the skirt 1 y by resilient bridge elements.

21'. A piston for an internal combustion engine comprising a cup-shaped head having a depending side wall 'rooved on the outside for piston rin s, am? having an inner face of cylindrical? form, a skirt having bearing surfaces formed thereon adapted to provide a substantially continuous annular wall of the head, and connections between said webs and the skirt adapted to support the skirt with its upper marginal edge free and unattached to the head intermediate the wrist pin bosses, said wrist pin bosses being unconnected except through said head and said skirt. l

22. A piston for an internal combustion engine comprising a cup-shaped head hav ing a depending side wall grooved on the outside for piston rings, opposed wrist pin bosses each connected to said head by structure'including a web extending inwardly from the depending side wall of the head in a plane substantially parallel to the plane of the head and a reinforcing rib integral with the head and the adjacent web and disposed substantially at right angles relative thereto, and a skirt having bearing surfaces formed thereon adapted to provide asubstantially continuous annular bearing surface adjacent the open end of the skirt, portions of the skirt being yieldingly connected inside the walls of the skirt, the uppermarginal edge of the skirt being free and unattached to the head intermediate the wrist pin bosses and said skirt being supported from said web and rib elements well below the upper marginal edge portion of the skirt in order that temperature dis tortions of the head may be transmitted to the skirt structure well below the lower edge of the head.

23. A piston for an internal combustion engine comprising a cup-shaped head having a closed end portion and depending side walls grooved on the outside for piston rings, opposed wrist pin bosses each separately connected to said head by integral structure overlying the bosses including a web extending inwardly from the inner face of the side wall of the head in spaced relation to the closed end portion of the head and a reinforcing rib disposed substantially at right angles to the web, and a skirt supported by said structure embodying yieldingly related port-ions connected inside the walls of the skirt by bridge members.

ROLAND M. HOlVDESHELL.

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