US1436130A - Two-stroke-cycle internal-combustion engine - Google Patents

Description

C. WEBB.

TWO-STROKE CYCLE INTERNAL COMBUSTiON ENGINE APPLICATION FILED-JAN. 27, 1920.

1,436, 1 30 I Patented Nov. 21, 1922.

2 SHEETS-SHEET 2.

F .2, V] V2 I l s PI 7 w W 21 72 asses.

Patented Nov. 21, 1922:

, Lean CECIL WEBB, F LISBUBIN, IRELAND.

.TWo-sT EokE-oYoLE INTERNAL-COMBUSTION ENGINE.

Apfineatibn fiiea J uars; 2?, 1920. ,jserieu No. $54,476.

' T 'azzw'hmamg/ esteem: E

7 Be itknoy'vn thatI, C'E IL WEBB, a sub- Ij'e'ct of thef'Kingof Great Britain and Ireland, residing at ll lislourn county Antriin, Ireland, have inventedcertain new and usej l Improyemehts in; TweStr'oke-Cyde Internal-Combusti on Engines, of which the 'follbwing is specificati'cin. I I This invention relates to internal combustion engines'fof the tvvo-strok e cycle type; in

which three or multiples of three COmPOund cylinders'are fitted 'eachwah a differential piston acting on a common crank shaft'ivith a distribution j of 1'20 reund the cranked fcleandjinvvhich e larg r diameter of each 1' an" pistoiiectsasa pump to deliver e sq i b6. E E E "d ameter .Q' en ete e y' y e wh it is] compressed, ignited and expanded, I v doesiiot fpply'toengi'nes \vhich new ys e ,Qfjflii 'W f E E E 1 Th e e'e ei e hv hti 1 ie p ee impi dvements engines ofthekind referred to, with a vievv'to obtaining effective lead' ee e e fnumfiifi f e au ing, eeei fee fii n e p eie p pi gxie as to" combine" the advantageous Qsca'venging and high volumetric eflicienc'y, which may be attained by means of -differential pistons, ivith the excellent torque ofa two-strokec yCle ngine having .three cylinder distribution 'o f crank efio'rt; -ai1d to do this in such a manner as'to achieve aiargepower output by iiiaintenance'of a rateof revolution. "The highest d gree of yommet'ric'efli- "satay-"and "advantageous scavenging in eng nres of this type," agaseous mixture, is (")btaif ed when the displacement volume of the pump portion is equalto the total volume of the firingportioh of the compound cylinder, and when theyvholeofthe gas in the pump can be ti'ansfer "ed to the firing chamber Without loss. A high rate ofr'ev'oliition with large peeve bee -m, can be obtai'ned' only when the area of the exhaust 'pbi -tsi's siifiiciefit to allow of very rapid e5:-

messing. y E e E E Tbbbtatin these resultsI arrange an efiective system offleads as above stated. EBy theexpressiah'f1iaaa as between pumping and exhaust I mean not onlythatthe pump shall have moved through awlarge portion of its delivery streke, and therefore that the pressureof the gas inside the pump has been raised considerably before i the E exhaust portsopened,butthat'this'hifih pressure ibiis'tible'mi'xture to the'jsinallei' shall not have been impaired because of leaka e.

'By the expression lead as-between coinpressing and pumping I mean that the exhaust ports shall have closed, and compres- V sion shall have commenced, before the pump has completed its delivery stroke.

The object of my invention is secured in a manner now to be described With reference to the annexed drawings Whereon I have shown, forthe purpose of illustration, preferred embodiments of the invention Fig.1 is a cross section through one of the cylinders of an engine embodying iny im- 7 provement's, I l Fig. '2 is a longitudinal section through the engine to a smaller scale. p 1

3 Figs. 3, 4: and 5 are diagrammatic views hereinafter specifically referred to. a

the drawings the same reference letters and numerals Wherever occurring indicate the same or similar} arts. p

To cause each pump 0 "move through a large. portion of its delivery stroke before the exhaust'portsin the cylinder to which 'thejpuinpdelivers are opened I make the ratio of thelongitudinal dimension of the exhaust ports very small with regard to the piston stroke. This is made practically possible by the insertion in each cylinder of a liner The function and advantages of this liner he more fully described When dealin -with the question of lead as between compressing and pumping. lVhen a pressure considerably above atmospheric is obtained in the pump cylinder leal'rage may occur between the piston and cylinder Walls Whenthe'piston rings have moved above the level of thee'z'zhaust ports and I prevent this inserting in each cylinder a ring: or rings shown at C. The contract upon the sides of thepistons which move in relation to them; E

volume'of feach pump equals the total volume of the firing: cylinder to which it delivers and the pump has som plet edits delivery stroke before the exhaust ports the firing cylinder are closed. a portion of the gas delivered will escape through the eirhaustports, and the volumetric efliciency ofthe engine will be greatly reduced. This condition is inevitable when the piston is used as a valfve'to open and close the inlet if the dis 'laeemrit or transfer "p'o'rtsf as well as the exhaust ports, becausethelatter must open first and closela'st I therefore direct the gas from castings.

the pump through a check or transfer valve to the head of the firing cylinder;

l urthermore, if the area of the pump annulus were equal to the area of cross section of the firing cylinder, it would be necessary that the exhaust ports should close when the a pump and firing portions of pistons were in the positions shown at Fig. in which P represents position of pump and C the position in firing cylinder.

But since the area of the annulus is greater than the area of the cross section otthe firing cylinder in the same ratio as the total volume of firing cylinder is to displacement volume 01": the piston of the same cylinder, therefore the exhaust ports may close slightly later, in order to exhaust an additional volume of the spent gases, equivalent to the clearance space of the explosion cylinder, andstill avoid waste'of fresh gases, so that I close the exhaust ports as shown at Fig. 4, P. being pump and C being firing portion ofpistons. i i i C In Fig. 4: the exhaust ports shown 1-2 have a ratioof .12 to the length of stroke shown 13. Thisis a very considerable restriction of port dimension measured longi tudinally of the cylinder, and this necessitates great increase of circumferential di mension, unlessthe port area be very small with consequent low power output.

When however. the circumferential dimensions are greatly increased the strength of the cylinder to resist longitudinal stress is greatly reduced, and in any case there 7 are serious constructional difiiculties when the exhaust ports are formed in the cylinder A Each liner L has exhaust ports E cut in it. As the liner is not subjectto longitudinal stress. the ports E may be cut throughout a very large portion of its circumfer ence, leaving only such solid metal as is required to prevent piston .rings from be- The provision of this ample port area, with but a small. longitudinal dimension,

v enables me to secure the leads desired,

namely :-The pumphasuobtained a considerable compression before the exhaust ports are openecl ,.,consequently a rapid transfer of gas takes place, and the exhaust ports have closed considerably before the pump has completed its delivery, thus securing the highest volumetric efficiency.

. Other ,advag itages also accrue from. the use of this liner, namely S1mpl1ficat1on of construction in thematter of coring and casting, and ease ofrenewal after cylinder wear; also if the engine is water cooled the water-jacket can be carried down around the exhaust chamber, cooling and reduc- .ing the pressure of exhaust gases, and assis t ing rapid discharge; also if it is desired to an outer case 1 attached to thepump cylinder, and a rotating tube 2 which hasapertures cutin it so asto allow: gas tolpass through ports into the pump cylinders in proper sequence. A carburettor or other gas supply is attached to one endand it is actuated by a suitable gear atthe other end. The. gearis driven .from the engine crank:

.In engines of "the typepwhieh', has been defined it has" been; the] common practice to admit' gas to "the pump cylinder through a ,valve which is held open during the; suction stroke iby thei pressure of]. the flowing gas. .By the improvement I here defined there is 'no restriction to the flow of gas, and it will'continue to flow into the pump cylinder until the,;momentum of the gas has been expendedin veryfully charging the pump, hence materially contribr utes-to volumetric efiiciency.v 1 v Gaseous mixture is transffrred from the pump .P, to the firingcylinder F,;thrjongh a check valve V i 1. m.

In like .manner gaseous mixture is.tra nsferredby way of transfer ports similar to T (Fig, 1.) from .P, to F through valve V and from 1?, to F through valve V 3. shows the compression leadinthe pump when the exhaust ports are open,-P

being-position of pump .pistonhand E'the position i of, piston head in. a firing cylinder at momentwhen, exhaust. ports rare being opened.. The cornpressionin: the pump is thus: about 28 ,lbsgper square inch at this time travelling very fast, high pressure is maintained making rapid transfer ellective. J g

P in Fig.= 4 is the position of the pump moment, and,- as, the pump ,pistonis" atthis n piston when the exhaust ports in the cyl- ,inder to which it deliversiare closing; and

the ratio of exhaust port to piston stroke is shown as the ratio of the; distances 1-2 to 1 -:3, that-is\about.12; i

Having. now fully described invenr' tion what I; claim and desire to.secure by Letters Patent is-:-. j '7 1. In an internal combustionfengine, of the type referred to, the combination of three cylinders having explosion; and. pumping chambers, a crank-shaft having cranks distributed at 120 around the crank circle, liners in said explosion chambers having exhaust ports therein, differential pistons in said cylinders, packing rings in said liners to prevent leakage from pumping to explosion chambers, means for admitting gas to the pumping chambers of the cylinders and means for admitting gas from the pumping chamber of one cylinder to the explosion chamber of another cylinder.

2. In an internal combustion engine, of the type referred to, the combination of three cylinders having explosion and pumping chambers, a crank shaft having cranks distributed at 120 around the crank circle, liners in said explosion chambers having exhaust ports therein, differential pistons in said cylinders, packing rings in said liners to prevent leakage from pumplng to explosion chambers, a rotary distributor for admitting gas to the pumping chambers of the cylinders and means for admitting gas from the pumping chamber of one cylinder to the explosion chamber of another 3. In an internal combustion engine, 0t

the type referred to, the combination of three cylinders having explosion and pump ing chambers, a crank shaft having cranks distributed at 120 around the crank circle, liners in said explosion chambers having exhaust ports therein, differential pistons in said cylinders, packing rings in said liners to prevent leakage from pumping to explosion chambers, means for admitting gas to the pumping chambers of the cylinders and means for admitting gas from the pumping chamber of one cylinder to the explosion chamber of another cylinder.

In testimony whereof I aflix my signature in presence of two Witnesses.

oEo L WEBB.

Witnesses:

ANDREW HAMILTON, HARRY WALTER ALLsor.

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