US3771503A

US3771503A - Two-stroke internal combustion engines

Info

Publication number: US3771503A
Application number: US00229317A
Authority: US
Inventors: J Pirault
Original assignee: Vandervell Products Ltd
Current assignee: Federal Mogul Shoreham Ltd
Priority date: 1971-05-26
Filing date: 1972-02-25
Publication date: 1973-11-13
Anticipated expiration: 1990-11-13
Also published as: IT956216B; JPS5333688B1; GB1337474A

Abstract

The specification discloses a two cylinder two stroke engine in which the cylinders are arranged in V-formation. The cylinders contain pistons connected to a crankshaft located in a crankcase and fuel-air mixture in pre-compressed in the crankcase prior to admission to the cylinders. The crankcase is divided into two separate pre-compression chambers, are for each cylinder, by a sealing disc rotatably mounted on the crankshaft and in sealing engagement around its periphery with the crankcase.

Description

United States Patent Pirault 1 Nov. 13, 1973 [5 TWO-STROKE INTERNAL COMBUSTION 1,336,232 4/1920 Isliker 123/73 A ENGINES 2,265,677 12 1941 Straub 123/55 R [75] Inventor: Jean-Pierre Pirault, Maidenhead,

g and Primary Examiner-Laurence M. Goodridge [73] Assignee: Vandervell Products Limited, Assistant g z g g f Tom Maidenhead, Berkshire, England aw [22] Filed: Feb. 25, 1972 [21] Appl. No.: 229,317 [57] ABSTRACT The specification discloses a two cylinder two stroke [30] Foreign Applicam": Priority Data engine in which the cylinders are arranged in V- May 26, 1971 Great Bfllaln 17,305/71 f ti The ylinderscontain pistons connected to a crankshaft located in a crankcase and fuel-air mix- Us. Cl. R, A t r i pre compressed in the crankcase prior to ad- [51] Int. Cl. F02b 33/04 mission to the cylinders The crankcase is divided into [58] Field of Search 123/73 R1 73 73 two separate pre-compression chambers, are for each 123/73 197 A 55 57 56 56 B cylinder, by a sealing disc rotatably mounted on the crankshaft and in sealing engagement around its pe- [56] References Cited riphery with the crankcase.

UNITED STATES PATENTS 11/1910 Akerman 123/56 BA 7 Claims, 3 Drawing Figures TWO-STROKE INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to two-stroke internal combustion engines of the kind having at least two mutually angled cylinders containing pistons, a crankcase in which mixture is compressed before admission to the cylinders for combustion, and a crankshaft in the crankcase to which the pistons are connected.

It is usual in engines of the above kind to connect the pistons to separate crank pins of the crankshaft and to support the crankshaft in a main bearing between the crank pins. Thus the main bearing separates the crankcase into two chambers, one for each cylinder, in which mixture is pre-compressed prior to admission to the cylinders.

It is a disadvantage of this construction that the length of the engine has to be increased to accommodate the main bearing for supporting the crankshaft between the crank pins.

SUMMARY OF THE INVENTION The invention provides a two-stroke internal combustion engine having at least two mutually angled cylinders containing pistons, a crankcase in which mixture is compressed before admission to the cylinders for combustion, and a crankshaft in the crankcase to which the pistons are connected characterised in that the two pistons are connected to a common crankpin of the crankshaft, a disc is rotatably mounted on the crank pin between the two connections andmeans are provided for sealing the periphery of the disc to the crankcase and permitting relative rotation of the disc with the crankshaft about the axis of the crankshaft with respect to the crankcase.

It will be appreciated that the arrangement referred to above obviates the necessity of a main bearing supporting the crankshaft between the connections of the two pistons to the crankshaft to provide a seal between the portions of the crank casing in communication with the two cylinders.

Said sealing means may comprise an annular inwardly facing channel around the crankcase in which the periphery of the disc engages and the disc may be arranged to be axially slidable on the crankshaft between the connections to the pistons so that the periphery of the disc may sealably engage one or the other side of the annular channel according to the difference in pressure in the crankcase on either side of the disc.

The outer periphery of the disc and the inner periphery of the disc around the crankshaft may be formed from a polymeric material.

In the latter arrangement the whole disc may be formed from polymeric material.

Alternatively the remainder of the disc may be formed from metal.

The polymeric material oroethylene.

Preferably the cylinders of the engine are arranged in V-formation.

The engine may have several cylinders in which case each pair of pistons is connected to a common crankpin of the crankshaft and a disc is provided on the crankpin between each pair of connections.

may be polytetraflu- BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a part-section, part-elevation view through a two-stroke internal combustion engine;

FIG. 2 is a view looking in the direction of the arrow A on FIG. 1; and

FIG. 3 is a detailed view of part of the crankshaft of the engine.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 of the drawings shows a V twin twostroke engine having mutually inclined cylinders 10 and 11 containing

pistons

12 and 13. The cylinders are connected to a common crankcase 14 in which a crankshaft 15 is rotatably mounted. The pistons 1 2, 13 are connected by connecting

rods

16, 17 respectively to a common crankpin 18 of the crankshaft. A metal disc 19 is rotatably mounted on the crankpin 18 between the connecting

rods

16, 17 and the periphery of the disc engages in an annular channel 20 formed around the crankcase. The outer periphery of the disc is coated with polytetrafluoroethylene as indicated at and the inner periphery of the disc is also coated with polytetrafluoroethylene as indicated at 19b. As best seen in FIG. 3 of the drawings there is limited clearance indicated at 21 between the disc 19 and crankpin 18 to permit the disc to slide along the crankpin 18 for the purpose described below. The disc 19 divided the crankcase 14 into two compartments in communication with the cylinders 10, 11 respectively below the

pistons

12, 13. Fuel air mixture is drawn into the chambers in succession as the

pistons

12, 13 rise in their respective cylinders and is then compressed as the pistons fall and are delivered into the combustion chambers above the pistons through

passageways

22, 23 cut in the cylinder walls 10, 11 respectively.

Since the cylinders 10, 11 are arranged in V- formation the

pistons

12, 13 will be out of phase with one another so that the pressure cycles in the mixture on either side of the disc will also be out of phase with one another. Thus the disc 19 will be forced along the crankpin 18 to seal with one side of the annular channel 20 or the opposite side according to which of the chambers is at the highest pressure.

It will be appreciated that this arrangement obviates the necessity of a separate main bearing for the crankshaft between the connections of the

pistons

12, 13 to the crankshaft so that the engine can be made shorter than would have been possible than if an additional main bearing had been used.

Although the engine described above has only two cylinders the invention is equally applicable to engines having three or more cylinders in which case at least one pair and preferably each pair of pistons is connected to a common crankpin in the crankshaft and a disc is provided on the crankshaft between each pair of connections. I claim:

1. A two strgke internal cornbustion engine having at least two mutually angled cylinders 'cd'iiaifiifigisis tons, a crank case in which mixture is compressed before admission to the cylinders for combustion, a crank shaft located in the crank case, said crank shaft having a crank pin to which both said pistons are connected, a disc rotatably mounted on and axially slidable along said crank pin between said connections, and means to seal the periphery of the disc with the crank case comprising an annular inwardly facing channel encircling the crank case, said periphery of the disc engaging in the channel whereby a difference in pressure on either side of the disc forces the periphery of the disc against one or the other side of the channel to form a seal therewith.

2. An engine as claimed in claim 1 wherein at least the outer periphery of the disc and the iner periphery of the disc around the crankshaft are formed from a polymeric material.

3. An engine as claimed in claim 2 wherein the whole disc is formed from the polymeric material.

4. An engine as claimed in claim 2 wherein the remainder of the disc is formed from metal.

5. An engine as claimed in claim 2 wherein the polymeric material is polytetrafluoroethylene.

6. An engine as claimed in claim 1 wherein cylinders of the engine are arranged in V-formation.

7. A two stroke internal combustion engine having at least two mutually angled cylinders containing pistons, a crank case in which mixture is compressed before admission to the cylinders for combustion, a crank shaft located in the crank case, said crank shaft having a crank pin to which both said pistons are connected, a disc rotatably mounted on and axially slidable along the crank pin between said connections and means to seal the periphery of the disc to the crank case while permitting the disc to rotate with the crank pin with respect to the crank shaft.

Claims

1. A two stroke internal combustion engine having at least two mutually angled cylinders containing pistons, a crank case in which mixture is compressed before admission to the cylinders for combustion, a crank shaft located in the crank case, said crank shaft having a crank pin to which both said pistons are connected, a disc rotatably mounted on and axially slidable along said crank pin between said connections, and means to seal the periphery of the disc with the crank case comprising an annular inwardly facing channel encircling the crank case, said periphery of the disc engaging in the channel whereby a difference in pressure on either side of the disc forces the periphery of the disc against one or the other side of the channel to form a seal therewith.

7. A two stroke internal combustion engine having at least two mutually angled cylinders containing pistons, a crank case in which mixture is compressed before admission to the cylinders for combustion, a crank shaft located in the crank case, said crank shaft having a crank pin to which both said pistons are connected, a disc rotatably mounted on and axially slidable along the crank pin between said connections and means to seal the periphery of the disc to the crank case whilst permitting the disc to rotate with respect to the crank case.